| 1. |
- Xun, Boyang, et al.
(författare)
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Thermal Resistance Analysis of Power MOSFETs using Creo/ANSYS Software Versus Physical Measurements
- 2022
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Ingår i: 2022 IEEE 13th International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2022.
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Konferensbidrag (refereegranskat)abstract
- High requirement of power electronic converters in power density makes heat dissipation issue critical caused by the packaging of power electronic devices and modules. Compared with the wire bond process, the clip bond process shows excellent thermal performance, which is widely used in the packaging of power MOSFETs. However, due to the complicated structure of the copper bridge in the clip bond process, the thermal resistance cannot be easily evaluated according to mathematical models. A generic method is proposed to evaluate the thermal resistance of power MOSFETs, which is verified by a PDFN5×6 plastic-packaged power MOSFET. According to the physical structure of the selected MOSFET, the finite element model is established using combined Creo and ANSYS software. The thermal resistance from the PN junction to the case and the one from the junction to the PCB board can be accurately simulated from the developed model. The simulation results show very small errors compared with the physical measurements based on the JESD51 standard. The proposed method can replace the thermal resistance test to some extent, which can save time and cost in the early stage of the design and development of power electronic devices and modules.
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| 2. |
- Guo, Xiaorui, et al.
(författare)
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Event-Triggered Consensus Algorithm for Power Sharing with Abnormal Communication in Microgrids
- 2023
-
Ingår i: IECON Proceedings (Industrial Electronics Conference). - 2162-4704 .- 2577-1647.
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Konferensbidrag (refereegranskat)abstract
- The precision and stability of droop control are easily affected by the difference of feeder impedance values and hardware filters in islanded inverter-based microgrids with distributed generations. To improve the performance of the conventional droop control, a distributed hierarchical control framework is introduced in this paper for reactive power sharing. Due to limited communication and transmission delays, an improved discrete consensus algorithm is proposed to reduce the overshoot and convergence error. Moreover, according to Lyapunov's second theorem, an event-triggered mechanism is adopted to control time instants of iteration calculation for each agent, and therefore to save communication resources. The proposed control scheme is extended to applications for the case of time-varying communication delays to compensate iteration error and negative effect due to delays in a distributed multi-agent system. To verify the feasibility and superiority of the proposed control scheme, simulations are implemented in MATLAB/Simulink. Several case studies and their results show that the proposed method can improve the convergence speed and the dynamic stability.
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| 3. |
- Guo, Xiaorui, et al.
(författare)
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Silicon Carbide Converters and MEMS Devices for High-temperature Power Electronics: A Critical Review
- 2019
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Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 10:6
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Forskningsöversikt (refereegranskat)abstract
- The significant advance of power electronics in today's market is calling for high-performance power conversion systems and MEMS devices that can operate reliably in harsh environments, such as high working temperature. Silicon-carbide (SiC) power electronic devices are featured by the high junction temperature, low power losses, and excellent thermal stability, and thus are attractive to converters and MEMS devices applied in a high-temperature environment. This paper conducts an overview of high-temperature power electronics, with a focus on high-temperature converters and MEMS devices. The critical components, namely SiC power devices and modules, gate drives, and passive components, are introduced and comparatively analyzed regarding composition material, physical structure, and packaging technology. Then, the research and development directions of SiC-based high-temperature converters in the fields of motor drives, rectifier units, DC-DC converters are discussed, as well as MEMS devices. Finally, the existing technical challenges facing high-temperature power electronics are identified, including gate drives, current measurement, parameters matching between each component, and packaging technology.
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| 4. |
- Li, Qiuyu, et al.
(författare)
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Adaptive Power Allocation with Real-Time Monitoring and Optimization for Fuel Cell/Supercapacitor Hybrid Energy Storage Systems
- 2022
-
Ingår i: IECON Proceedings (Industrial Electronics Conference). - 2162-4704 .- 2577-1647. ; 2022-October
-
Konferensbidrag (refereegranskat)abstract
- Electric vehicles powered by hybrid energy storage systems composed of fuel cells and supercapacitors are of great interest. To further improve the efficiency of such hybrid systems, better energy management strategies need to be developed. This paper proposes an adaptive power allocation method with real-time monitoring and optimization for fuel cell/supercapacitor hybrid energy storage systems used in electric vehicles. This method utilizes a low-pass filter to distribute power between fuel cells and supercapacitors. The cut-off frequency of the filter is obtained by splitting the load current spectrum according to the supercapacitor state of charge (SOC). The DC-link voltage fluctuation and the supercapacitor SOC are monitored in a real-time fashion. Consequently, a real-time optimization scheme is developed to reduce the dependence of the proposed algorithm on its initial parameters and enhance the adaptivity of the proposed algorithm. To validate the effectiveness of the proposed method, a Simulink model is developed and two standard drive cycles (i.e., NYCC and US06) are selected. Simulation results show that the DC-link voltage fluctuation drops significantly and the supercapacitor SOC can be effectively controlled.
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| 5. |
- Peng, Zihe, et al.
(författare)
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Crosstalk mechanism and suppression methods for enhancemen t-Mode GaN HEMTs in A phase-leg topology
- 2019
-
Ingår i: PCIM Asia 2019 - International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Proceedings. ; , s. 147-153
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Konferensbidrag (refereegranskat)abstract
- It has been demonstrated that Enhancement-mode GaN HEMT(eGaN HEMT) has lower conduction losses and higher switching speed. However, higher switching speed will cause higher dVDS/dt leading to worse crosstalk problems. This paper analyzes the mechanism of crosstalk for eGaN HEMT first. Then, the mathematical model of crosstalk voltage and its influence factors are given. A double pulse test model is established and three kinds of crosstalk suppression methods without auxiliary circuit are simulated and compared. The simulation results may give a guideline for choosing which method in specific situation.
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| 6. |
- Qin, Haihong, et al.
(författare)
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A Comparative Study of Freewheeling Methods for eGaN HEMTs in a Phase-leg Configuration
- 2021
-
Ingår i: IEEE Journal of Emerging and Selected Topics in Power Electronics. - 2168-6777 .- 2168-6785. ; 9:3, s. 3657-3670
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Tidskriftsartikel (refereegranskat)abstract
- Enhancement Gallium nitride high-electron mobility transistors (eGaN HEMTs) have been developed with lower conduction losses and higher switching speed compared to MOSFETs. Self-commutated reverse conduction (SCRC) mechanism determines no reverse recovery phenomenon but larger reverse conduction voltage drop of eGaN HEMTs than the body diodes in traditional Si MOSFETs or other freewheeling diodes. To reduce the large reverse conduction loss of eGaN HEMTs, the performance of different freewheeling methods for eGaN HEMTs in a phase-leg configuration is compared in this paper. Firstly, the reverse conduction mechanism and characteristics of eGaN HEMTs are analyzed. Then, four freewheeling ways for eGaN HEMTs are introduced, and the equivalent circuits are also given and analyzed. A double pulse test platform is established to further explore the influence of the freewheeling ways on the conduction and switching characteristics. Finally, the total losses of a phase-leg configuration with different freewheeling ways based on a buck converter is analyzed and compared. The paper aims to give a guidance to properly select freewheeling ways for eGaN HEMTs under different operation conditions.
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| 7. |
- Qin, Haihong, et al.
(författare)
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A digital-controlled SiC-based solid state circuit breaker with soft switch-off method for DC power system
- 2019
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Ingår i: Electronics (Switzerland). - : MDPI AG. - 2079-9292. ; 8:8
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Tidskriftsartikel (refereegranskat)abstract
- Due to the lower on-state resistance, direct current (DC) solid state circuit breakers (SSCBs) based on silicon-carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) can reduce on-state losses and the investment of the cooling system when compared to breakers based on silicon (Si) MOSFETs. However, SiC MOSFETs, with smaller die area and higher current density, lead to weaker short-circuit ability, shorter short-circuit withstand time and higher protection requirements. To improve the reliability and short-circuit capability of SiC-based DC solid state circuit breakers, the short-circuit fault mechanisms of Si MOSFETs and SiC MOSFETs are revealed. Combined with the desaturation detection (DESAT), a “soft turn-off” short-circuit protection method based on source parasitic inductor is proposed. When the DESAT protection is activated, the “soft turn-off” method can protect the MOSFET against short-circuit and overcurrent. The proposed SSCB, combined with the flexibility of the DSP, has the μs-scale ultrafast response time to overcurrent detection. Finally, the effectiveness of the proposed method is validated by the experimental platform. The method can reduce the voltage stress of the power device, and it can also suppress the short-circuit current.
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| 8. |
- Qin, Haihong, et al.
(författare)
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A Novel Adaptive Dead-Time Control Method for GaN-Based Motor Drives
- 2024
-
Ingår i: IEEE Transactions on Energy Conversion. - 1558-0059 .- 0885-8969. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Compared to Si devices, Gallium Nitride (GaN) devices are more suitable for achieving high switching frequency in motor drive applications, thereby improving power density. However, increasing switching frequency can also lead to extra switching losses and poor total harmonic distortion (THD). A smaller dead-time can mitigate these issues, but conventional constant dead-time design methods struggle to ensure optimal performance across all load ranges. This paper proposes a novel adaptive dead-time control method for GaN high electron mobility transistors (HEMTs) in phase-legs to simultaneously enhance the efficiency and THD of motor drives. To achieve this, the detailed switching process of GaN HEMTs in a double-pulse test circuit is modeled and analyzed. The optimization principle of the dead-time setting is revealed, considering the tradeoff effect of dead-time on switching losses and THD. The adaptive dead-time control method dynamically adjusts the dead-time under different load conditions. The effectiveness of the proposed method is verified on a 1kW GaN-based permanent magnet synchronous machine drive platform. Extensive experimental results show that the proposed method can increase efficiency up to 0.85% at full load with a switching frequency of 100 kHz compared to constant dead-time. Meanwhile, THD is reduced by 1.44% under the same condition.
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| 9. |
- Qin, Haihong, et al.
(författare)
-
An optimized parameter design method of SiC/Si hybrid switch considering turn-off current spike
- 2022
-
Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 8, s. 789-797
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Tidskriftsartikel (refereegranskat)abstract
- In order to reduce the switching loss of SiC MOSFET/Si IGBT (SiC/Si) hybrid switch, the switching mode that turn off the Si IGBT prior to the SiC MOSFET is generally adopted to achieved the zero-voltage switching operation of IGBT. The minority carrier in N-base region of the IGBT are recombined in the form of exponential attenuation due to the conductivity modulation effect. When the SiC MOSFET is turned off, if the carrier recombination process of the IGBT is not finished, it needs to bear a large collector–emitter voltage change rate, resulting in apparent current spike. This current spike will increase the current stress of the device and produce additional turn-off loss. The equivalent model of double pulse test circuit of SiC/Si hybrid switch considering parasitic parameters is established, and the turn-off transient process is given analytically. The influence of turn-off delay time, circuit parameters and working conditions on current spike are analysed quantitatively. Combined with the consideration of device stress and comprehensive turn-off loss, an optimized circuit design method of SiC/Si hybrid switch considering turn-off current peak is proposed, which provides theoretical and design guidance for high reliability and high efficiency SiC/Si-based converters.
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| 10. |
- Qin, Haihong, et al.
(författare)
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Analysis the reverse conduction characteristic and influence of anti-parallel SiC SBD of eGaN HEMT
- 2019
-
Ingår i: PCIM Asia 2019 - International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Proceedings. ; , s. 140-146
-
Konferensbidrag (refereegranskat)abstract
- eGaN HEMT has been developed with up to 650V blocking capability with lower conduction losses and higher switching speed compared MOSFET. Self-commutated reverse conduction is a very important characteristic of eGaN HEMT, especially for synchronous rectification topologies. This paper introduces the reverse conduction mechanism and characteristics of eGaN HEMT, and establishes a double pulse test platform to explore the influence of anti-parallel SiC SBD for eGaN HEMT on the reverse conduction characteristic and switching characteristic of eGaN HEMT, which will provide some help for the application of the eGaN HEMT's self-commutated reverse conduction.
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| 11. |
- Qin, Haihong, et al.
(författare)
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Design of overvoltage suppression filter based on high-frequency modeling of cable in SiC based motor drive
- 2022
-
Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 8, s. 822-831
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Tidskriftsartikel (refereegranskat)abstract
- SiC-based motor drives have the advantages of achieving higher efficiency and higher power density than traditional Si-based motor drives, and are gradually being widely used in electric power transmission. Due to different application situations such as oil field and airplane, a long cable is applied between the motor drive and three-phase motor and the distance may exceed hundreds of meters, which will cause serious voltage reflection problem, damaging working life of the motor. Meanwhile, the high slew rate of output voltage created by SiC-based motor drive deteriorates this phenomenon. In order to solve this problem, we first analyze the principle and influencing factors of voltage reflection, and establish the equivalent circuit model of the long cable. Then we put forward design method of LRC passive filter to suppress voltage reflection, and give simulation analysis. At last we built an experimental platform to verify the effectiveness of the LRC passive filter in SiC-based motor drive, and the experimental results show that the LRC passive filter with optimized parameters has good suppression effect of voltage reflection.
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| 12. |
- Qin, Haihong, et al.
(författare)
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Evaluation and Suppression Method of Turn-off Current Spike for SiC/Si Hybrid Switch
- 2023
-
Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 11, s. 26832-26842
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Tidskriftsartikel (refereegranskat)abstract
- SiC MOSFET/Si IGBT (SiC/Si) hybrid switch usually selects the gate control pattern that SiC MOSFET turns on earlier and turns off later than Si IGBT, with the aim of making the hybrid switch show excellent switching characteristics of SiC MOSFET and reduce switching loss. However, when SiC MOSFET turns off, the fast slew rate of drain source voltage causes the current spike in Si IGBT due to the effects of parasitic capacitance charging and carrier recombination, which will produce additional turn-off loss, thus affecting the overall efficiency and temperature rise of the converter. Based on the double pulse test circuit of SiC/Si hybrid switch, the mathematical model of the turn-off transient process is established. The effects of the remnant carrier recombination degree of Si IGBT, the turn-off speed of SiC MOSFET and the working conditions on the turn-off current spike of hybrid switch are evaluated. Although adjusting these parameters can reduce the turn-off current spike somewhat, additional losses will be introduced. Therefore, a new method to suppress the turn-off current spike is proposed to balance the power loss and current stress.
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| 13. |
- Qin, Haihong, et al.
(författare)
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Evaluation of antiparallel SiC Schottky diode in SiC MOSFET phase-leg configuration of synchronous rectifier
- 2023
-
Ingår i: Energy Reports. - 2352-4847. ; 9, s. 337-342
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Tidskriftsartikel (refereegranskat)abstract
- The MOSFET synchronous rectification (SR) is widely used to reduce the conduction loss during the freewheeling period. Due to the wide band gap of silicon carbide (SiC), the intrinsic body diode of SiC MOSFET exhibits a high voltage drop. Therefore, SiC Schottky diodes (SBD) and SiC MOSFETs are usually used in reverse parallel to reduce power loss. However, the increase of equivalent junction capacitance due to the addition of an external SiC SBD could bring larger turn-on current on opposite power transistor of the phase-leg. Furthermore, as the parasitic inductance associated with layout hinders the prompt transfer of current between SiC SBD and body diode, the external SiC SBD cannot be fully utilized, and it may deteriorate the overall performance, especially at heavy load. We comprehensively compare power losses when SiC SBD are antiparallel or not, at different working conditions, including different layout compactness, load current and dead time. It's hard to get the effect of loss reduction loss when add antiparallel SiC SBD due to the parasitic inductance induced by the layout. The results can provide a guidance to properly select SiC SBD in a phase-leg configuration under SR mode for freewheeling during the dead time.
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| 14. |
- Qin, Haihong, et al.
(författare)
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Parameters Design and Optimization of SiC MOSFET Driving Circuit with Consideration of Comprehensive Loss and Voltage Stress
- 2023
-
Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 14:3
-
Tidskriftsartikel (refereegranskat)abstract
- In conventional parameters design, the driving circuit is usually simplified as an RLC second-order circuit, and the switching characteristics are optimized by selecting parameters, but the influence of switching characteristics on the driving circuit is not considered. In this paper, the insight mechanism for the gate-source voltage changed by overshoot and ringing caused by the high switching speed of SiC MOSFET is highlighted, and we propose an optimized design method to obtain optimal parameters of the SiC MOSFET driving circuit with consideration of parasitic parameters. Based on the double-pulse circuit, we evaluated the influence of main parameters on the gate-source voltage, including driving voltage, driving resistance, gate parasitic inductance, and stray inductance of the power circuit. A SiC-based boost PFC is constructed and tested. The test results show that the switching loss can be reduced by 7.282 W by using the proposed parameter optimization method, and the over-voltage stress of SiC MOSFET is avoided.
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| 15. |
- Qin, Haihong, et al.
(författare)
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Switching Time Delay Optimization for “SiC+Si” Hybrid Device in a Phase-leg Configuration
- 2021
-
Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 9, s. 37542-37556
-
Tidskriftsartikel (refereegranskat)abstract
- Compared to SiC MOSFET, the switching loss of Si IGBT is much higher due to its slow switching speed and tail current. Si IGBT/SiC MOSFET hybrid switch device can reach to optimal performance with low static and dynamic loss, which can improve the current capacity of SiC devices and reduce the power loss of Si IGBT based converters. With the separated gate control signals, the switching moments of the two devices can be controlled independently to ensure Si IGBT under zero-voltage switching (ZVS) conditions. This measurement tends to reduce the switching loss of Si IGBT. However, the switching time delay between these two devices has significant impacts on its power loss. In this paper, the switching time delay optimization method is proposed to minimize the power loss of the hybrid switch. The static and dynamic characteristics of Si IGBT/SiC MOSFET hybrid-paralleled switch are studied, and a generalized power loss model for hybrid switch is developed. The influence of switching time delay on the characteristics of hybrid switch is analyzed and verified through double pulse tests in a phase-leg configuration. The experimental results show that the optimal turn-on delay time is that the two devices turn on at the same time and the turn-on loss can be reduced by about 73% compared with the solely Si IGBT and by about 52% compared with the solely SiC MOSFET. While the optimal turn-off sequence is that the Si IGBT turns off ahead of the SiC MOSFET. Under the proposed optimal turn-off delay time of the hybrid switch, the turn-off loss is reduced by about 61.4%. This optimization strategy is used in a Buck converter to verify the superiority of the SiC/Si hybrid switch and the optimal switching sequence. Simulation results show that the optimal switching sequence is consistent with theoretical analysis, and the efficiency is improved by 2.5% compared with Buck converter using solely Si IGBT.
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| 16. |
- Xie, Haotian, et al.
(författare)
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A Low-Complexity Gradient Descent Solution with Backtracking Iteration Approach for Finite Control Set Predictive Current Control
- 2022
-
Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 69:5, s. 4522-4533
-
Tidskriftsartikel (refereegranskat)abstract
- Finite control set model predictive control (FCS-MPC) has been widely recognized in the field of electrical drive control during the past decades, due to its merits of quick dynamic response and low switching frequency. However, it is inherently penalized by the high tracking deviations in the steady state as well as exhaustive search among the switching sequences. To cope with this issue, a low-complexity gradient descent based finite control set predictive current control (GD-FCSPCC) combined with backtracking optimized iteration approach is proposed in this paper, aiming to improve the control performance by effectively tracking the reference value. Firstly, FCS-PCC is reformulated as a quadratic programming (QP) problem from a geometric perspective. Consequently, the convexity of QP problem is proved to underlying the gradient descent to minimize the tracking error in an effective manner. Thus, the control objectives are determined by optimizing the deviation between the gradient descent and the stator current derivative in a cascade structure, to reduce the number of enumerated sequences. The procedures are repeated in the iteration periods optimized via a backtracking search method, until the stopping criterion is satisfied. The effectiveness of the proposed GD-FCSPCC is experimentally validated on a 2.2 kW induction machine testbench.
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| 17. |
- Xie, Haotian, et al.
(författare)
-
Iterative Gradient Descent Based Finite Control Set Predictive Current Control with Least Squares Optimized Duty Cycles
- 2022
-
Ingår i: IEEE Journal of Emerging and Selected Topics in Power Electronics. - 2168-6777 .- 2168-6785. ; 10:2, s. 1422-1433
-
Tidskriftsartikel (refereegranskat)abstract
- Finite Control Set Predictive Current Control (FCS-PCC) is widely recognized as a competitive control strategy in the field of electrical drives, due to its superiority of fast dynamic response and low switching frequency. However, FCS-PCC is penalized by its inherent drawback that the discrete nature of switching states leads to relatively high torque and current deviations. In this paper, an iterative gradient descent method combined with least squares optimized duty cycles is presented to improve the steady-state performance of FCS-PCC. Unlike the cost function optimization in the conventional FCS-PCC, the quadratic programming problem is solved from a geometric perspective, by obtaining the gradient descent which minimizes the tracking deviation in the fastest manner. To synthesize the gradient descent, the optimal stator current derivatives in the current and previous iteration are employed, and their duty cycles are determined by the least squares method. The abovementioned procedures are iteratively repeated in the dichotomy-based periods. The experimental performance of the proposed gradient descent based FCS-PCC is verified at a 8 kHz sampling frequency, which is compared with that of conventional and dichotomy-based FCS-PCC. It is validated that the proposed algorithm outperforms the conventional and dichotomy-based FCS-PCC at both the steady-state and transient state.
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| 18. |
- Xie, Haotian, et al.
(författare)
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Robust parallel predictive torque control with model reference adaptive estimator for im drives
- 2020
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Ingår i: Proceedings - 2020 International Conference on Electrical Machines, ICEM 2020. ; 23 August 2020, s. 1219-1224
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Konferensbidrag (refereegranskat)abstract
- This paper presents the robustness improvement for the proposed parallel structure predictive torque control (PPTC) via a MRA-based estimator. Although predictive torque control (PTC) has the merits of lower switching frequency and straightforward implementation, it inevitably suffers from the inherent drawbacks of high torque ripple and inappropriate tuning of the weighting parameter. To solve this issue, the proposed PPTC employs two homogeneous objective terms which are optimized in a parallel strucutre, to bypass the usage of weighting parameters. However, the parameter mismatches in the control plant will lead to the prediction torque and flux error, which further impacts the control behavior of the system. Therefore, this paper evaluates the parameter sensitivity for PPTC, aiming to improve robustness of the proposed algorithm with a MRA-based parameter estimator. Finally, the validity of the proposed scheme is confirmed through an experimental assessment.
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| 19. |
- Xu, Chao, et al.
(författare)
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Loss Minimization Based Energy Management for a Dual Motor Electric Vehicle
- 2022
-
Ingår i: 2022 IEEE Transportation Electrification Conference and Expo, Asia-Pacific, ITEC Asia-Pacific 2022.
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Konferensbidrag (refereegranskat)abstract
- The dual-motor electric vehicle has a simple structure, which enables the front and rear wheels to obtain adhesion at the same time. It can improve the acceleration characteristics of the vehicle and achieve high efficiency of the system. To optimize the propulsion efficiency, a power allocation method is designed to determine the torque ratio between the front and rear axle motors. This paper proposes an efficiency-based optimal energy management strategy for dual-motor driven electric vehicles. In this way, the remaining battery state of charge is improved by reducing vehicle power loss. The energy consumption of the vehicle is firstly determined by drive cycles. The optimal distribution factor is calculated to minimize the system loss at each time sample. This determines distributions of the traction, regeneration, and mechanical braking forces between two motors. Simulation analysis is conducted under drive cycles of NEDC and WLTC. Results show that the method can reduce the total energy consumption of the system. With the proposed method, the braking energy recovery rate is improved, which also enhances the economy of the whole vehicle under different driving conditions.
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| 20. |
- Xun, Qian, 1990, et al.
(författare)
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A Comparative Study of Fuel Cell Electric Vehicles Hybridization with Battery or Supercapacitor
- 2018
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Ingår i: SPEEDAM 2018 Proceedings: International Symposium on Power Electronics, Electrical Drives, Automation and Motion. ; , s. 389-394
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the conception and the achievement of a hybrid power source using a fuel cell combined with a battery or a supercapacitor. In which, the fuel cell supplies the main power to the drive system; while the battery or the supercapacitor is used as an auxiliary power source. This gives the benefit that the regenerative energy is stored in battery or supercapacitor during the deceleration and it is transferred back to the drive system during the acceleration when compared to electric vehicles solely powered by a fuel cell. Different energy storage devices, such as fuel cell, battery, and supercapacitor are compared., and then several structures of fuel cell-based electric vehicles are analyzed in the paper. Following that a conventional topology based on fuel cell and battery using a DC/DC converter with the connection between the fuel cell and the inverter, and a floating voltage topology powered by fuel cell and supercapacitor without any DC/DC converters are chosen for the simulation analysis. Simulation results show that power variations of the fuel cell in floating voltage topology can be smoother, and its rated power is downsized, which can extend the fuel cell lifetime and take full advantages of the fuel cell and the supercapacitor.
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| 21. |
- Xun, Qian, 1990, et al.
(författare)
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An adaptive power split strategy with a load disturbance compensator for fuel cell/supercapacitor powertrains
- 2021
-
Ingår i: Journal of Energy Storage. - : Elsevier BV. - 2352-152X. ; 44
-
Tidskriftsartikel (refereegranskat)abstract
- Electric vehicles powered by fuel cell and supercapacitor hybrid power sources are of great interest. However, the power allocation between each power source is challenging and the DC bus voltage fluctuation is relatively significant in cascaded PI control schemes. This paper develops a power control strategy with an adjustable cut-off frequency, using an artificial potential field, to adaptively split the load current between the fuel cell and the supercapacitor under various load conditions. The adaptive cut-off frequency is calculated by cutting the load frequency spectrum with an allocation ratio that changes with the supercapacitor state of charge. Therefore, the relatively lower frequency portion of the load current is provided by the fuel cell and the supercapacitor handles the higher frequency portion. To enhance the control performance of the DC bus voltage regulation against the load disturbance, a load disturbance compensator is introduced to suppress the DC bus voltage fluctuation when the load variation occurs, which is implemented by a feed-forward controller that can compensate the load current variation in advance. The effectiveness of the proposed strategy is validated by extensive experiments.
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| 22. |
- Xun, Qian, 1990, et al.
(författare)
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Chance-constrained robust co-design optimization for fuel cell hybrid electric trucks
- 2022
-
Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 320
-
Tidskriftsartikel (refereegranskat)abstract
- The co-design optimization that simultaneously couples embodiment design and control design is widely applied in fuel cell hybrid electric vehicles. However, due to imperfect manufacture process, modeling simplification and uncertain parameters during vehicle operation, the optimal results obtained from a deterministic co-design optimization might not be robust to variations of parameters and optimization variables. This paper introduces a chance-constrained robust co-design optimization framework, where the chance constraint firstly translates into a deterministic constraint. The robust objective is computed as a function of the second-order approximated mean and inequality constraints are computed by shifting 3 times of their standard deviations inside of deterministic bounds. The vehicle movement in long-haul trucking application is considered as an uncertain parameter and the propagation of uncertainties to state variables are also illustrated with considerations of uncertainties in design decision variables. A deterministic and stochastic co-design problem are formulated and decomposed into two steps, i.e. electric machine sizing and sizing of fuel cell and battery as well as the energy management. A case study of a fuel cell hybrid electric long-haul truck indicates the importance of the robust approach in the joint component sizing and energy management. The uncertainties of the truck movement results in uncertainties of the battery energy and power, leading to a bigger battery capacity. The energy capacity is around 2.34 times higher than that without considering uncertainties.
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| 23. |
- Xun, Qian, 1990, et al.
(författare)
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Commutation Torque-ripple Minimization for Brushless DC Motor Based on Quasi-Z-Source Inverter
- 2018
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Ingår i: Proceedings - 2018 23rd International Conference on Electrical Machines, ICEM 2018. - 9781538624777 ; , s. 1439-1445
-
Konferensbidrag (refereegranskat)abstract
- Conventional brushless DC Motor (BLDCM) drive involves a voltage-source inverter with six-step squarewave control, which can be widely used in automated industrial applications. However, high torque ripple due to different current slew rates during the commutation interval would significantly reduce the performance in the high-precision area. To tackle this problem, the paper proposes a novel strategy to reduce the commutation torque-ripple by using a quasi-Z-source inverter. In which, an impedance network is implemented between the power supply and the voltage-source inverter. This could make the equivalent DC-link voltage boosted during the commutation interval to compensate the current dip of commutation phase, and keep incoming and outgoing phase current changing at the same rate. In Matlab/Simulink environment, proposed scheme is developed and simulated. Finally, the effectiveness of the proposed control strategy is validated, the torque ripple can be greatly reduced and with the increased average torque.
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| 24. |
- Xun, Qian, 1990
(författare)
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Control and Optimization of Fuel Cell Based Powertrain for Automotive Applications
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fuel cell powered electric vehicles, with fast-refueling time, high energy density, and zero CO2 emissions, are becoming a promising solution for future fossil-free transportation. However, the relatively slow dynamic response and the inability of recovering the regenerative energy make vehicles solely powered by fuel cells not an immediately attractive solution. Instead, hybrid vehicles powered by fuel cells combined with energy buffers such as batteries and supercapacitors could be of more interest. Due to the unique characteristics of each energy buffer, the vehicle performance may vary with the hybrid energy storage system configuration. This thesis performs a comprehensive study on various energy storage configurations for applications in fuel cell hybrid electric vehicles. This thesis first examines the fuel cell/supercapacitor passive hybrid configuration where the fuel cell and supercapacitor share the same DC-link voltage. The power distribution between them is inherently determined by their internal resistances. Therefore, the DC-link voltage varies and depends on the vehicle power demand. In this work, a fuel cell/supercapacitor passive hybrid powertrain is first modeled and evaluated. Simulation results show that the energy efficiency is 53%–71% during propulsion and 84%–94% during braking, respectively. Moreover, a 3 kW lab-scale fuel cell/supercapacitor passive hybrid system is designed and investigated. Experimental results show that the fuel cell takes time to respond to a load change, while the supercapacitor provides the transient power, which makes it possible to downsize the fuel cell. Since the passive configuration loses the active controllability, this thesis further considers a fully-active fuel cell/supercapacitor system to improve the controllability of the power distribution. This configuration requires a boost converter for the fuel cell and a buck-boost converter for the supercapacitor. In this work, an adaptive power split method is used to smooth the fuel cell current and prevent the supercapacitor from exceeding its lower and upper charge limits. The cut-off frequency of the low-pass filter is adaptively controlled by the spectrum area ratio. Experimental results show that the supercapacitor state-of-charge is effectively controlled within the desired range. Moreover, a load disturbance compensator is proposed and demonstrated to improve the control performance such that the DC-link voltage fluctuation caused by the load current variation is significantly reduced. This thesis also investigates the cost-effectiveness of different energy buffers hybridized with fuel cells in various trucking applications. First, a chance-constraint co-design optimization problem is formulated. Convex modeling steps are presented to show that the problem can be decomposed and solved using convex programming. Results show that the power rating of the electric machine can be dramatically reduced when the delivered power is satisfied in a probabilistic sense. Moreover, the hybridization of fuel cells with lithium-ion batteries results in the lowest cost while the vehicle using lithium-ion capacitors as the energy buffer can carry the heaviest payload. This work also develops a robust co-design optimization framework considering the uncertainties in parameters (e.g., vehicle movement) and design decision variables (e.g., scaling factors of fuel cells and batteries). Results show that these uncertainties might propagate to uncertainties in state variables (e.g., battery energy) and optimization variables (e.g., battery power), leading to a larger battery capacity and therefore a higher total cost in robust optimal solutions. In summary, this thesis performs a comprehensive study on control and optimization of fuel cell based powertrains for automotive applications. This will provide a guidance on component selection and sizing, as well as powertrain system configuration and optimization for design of fuel cell powered electric vehicles.
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| 25. |
- Xun, Qian, 1990, et al.
(författare)
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Design and experimental verification of a fuel cell/supercapacitor passive configuration for a light vehicle
- 2021
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Ingår i: Journal of Energy Storage. - : Elsevier BV. - 2352-152X. ; 33
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Tidskriftsartikel (refereegranskat)abstract
- The fuel cell/supercapacitor passive configuration without using any DC/DC converters is promising in auto-motive applications as it can downsize the fuel cell stack, maintain the peak power capability, improve the system efficiency, and remove the need of additional control. This paper presents the design and characterization of a fuel cell/supercapacitor passive hybrid system for a 60 V light vehicle. A detailed design procedure for the passive hybrid test platform is presented with each component modelled and experimentally verified. The voltage error of the fuel cell and the supercapacitor model in the steady state is within 2% and 3%, respectively. Experimental results also validate the function of the passive configuration under conditions of a step load and a drive cycle. The simulation model of the passive hybrid system matches the measurements when a step load current is applied. The supercapacitor provides the transient current due to its smaller resistance while the fuel cell handles the steady state current, which makes it possible to downsize the fuel cell stack. For the drive cycle examined in this paper, the fuel cell stack can be downsized to one third of the load peak power.
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| 26. |
- Xun, Qian, 1990, et al.
(författare)
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Drive Cycle Energy Efficiency of Fuel Cell/Supercapacitor Passive Hybrid Vehicle System
- 2021
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Ingår i: IEEE Transactions on Industry Applications. - 0093-9994 .- 1939-9367. ; 57:1, s. 894-903
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Tidskriftsartikel (refereegranskat)abstract
- The electric vehicle with passive hybridization of fuel cells and supercapacitors leads to lower cost and compactness due to the absence of DC/DC converters. This paper models such a vehicle and evaluates the energy efficiency of its powertrain system. The powertrain component losses, as functions of electric machine torque, speed and DC-link voltage, are modelled with a high level of detail which are verified against available test data. Compared to a pure fuel cell system, the fuel cell efficiency is higher when supercapacitors are introduced under pulse current load, and it is higher at lower current amplitude. As the pulse current frequency increases, the fuel cell efficiency also increases due to higher proportional current from the high-efficiency supercapacitors. A multiplicity of drive cycles is selected, divided into a low, middle, and high speed category to analyze the powertrain efficiency. The total powertrain energy efficiency varies between 53%-71% during propulsion for the studied drive cycles, whereas it is higher during braking ranging from 84% to 94%. The differences are closely related to the speed, acceleration, and DC-link voltage levels. The lower powertrain efficiency causes higher hydrogen consumption, leading to a reduced fuel cell efficiency at high speed, high acceleration and low DC-link voltage.
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| 27. |
- Xun, Qian, 1990, et al.
(författare)
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Energy Efficiency Comparison of Hybrid Powertrain Systems for Fuel-Cell-Based Electric Vehicles
- 2020
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Ingår i: ITEC 2019 - 2019 IEEE Transportation Electrification Conference and Expo.
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Konferensbidrag (refereegranskat)abstract
- Fuel cell electric vehicles have great superiorities in endurance mileage, charging speed and climate tolerance compared to battery electric vehicles. However, a supercapacitor or battery bank is required to maintain a fast-dynamic response, which leads to several hybridization structures for fuel-cell-based electric vehicles due to the unique characteristics of each device, and their performances are also differing. The purpose of this paper is to provide a comprehensive comparison of hybrid powertrain systems for three types of powertrains: fuel cell/supercapacitor passive hybrid, fuel cell/supercapacitor semi-active hybrid, and fuel cell/battery semi-active hybrid. Each powertrain component model is developed from the real components wherever possible, and Honda FCX Clarity fuel cell vehicle is studied as the benchmark. The powertrain energy efficiency under Worldwide harmonized Light vehicles Test Cycle (WLTC) is analyzed and evaluated. The simulation results show that three powertrains have the same energy consumption, and fuel cell/supercapacitor passive hybrid powertrain increases the system efficiency by 2% and 4% in propulsion and regenerative braking, respectively. By contrast, the other two powertrain topologies have similar performance in terms of energy efficiency.
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| 28. |
- Xun, Qian, 1990, et al.
(författare)
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Evaluation of fluctuating voltage topology with fuel cells and supercapacitors for automotive applications
- 2019
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 43:9, s. 4807-4819
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Tidskriftsartikel (refereegranskat)abstract
- To develop a single stage power conversion topology in which energy storage devices can be directly coupled, a fluctuating voltage topology is applied, leading to lower cost and more compactness with the absence of DC/DC converters. This paper investigates such topology for automotive applications where fuel cells are directly connected to the DC bus of the inverter, resulting in fluctuating voltage across the DC bus. Further, a supercapacitor pack is also introduced to maintain power capacity and voltage stability. The hybridization principle and practical application of such a topology are then discussed in the time domain and frequency domain. Furthermore, the transient power requirement is decomposed to design the size of fuel cells and supercapacitors. Simulation results from the modelling of the fuel cell‐supercapacitor powertrain demonstrate the feasibility and effectiveness of this topology. The supercapacitors can serve as a low‐pass filter for the fuel cells. In conclusion, the peak power requirement can be successfully achieved because of the lowered system impedance and the fuel cells only need to supply the average power.
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| 29. |
- Xun, Qian, 1990, et al.
(författare)
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Experimental Characterization of Fuel Cells, Supercapacitors, and Their Passive Connection
- 2022
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Ingår i: 2022 IEEE 13th International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2022.
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Konferensbidrag (refereegranskat)abstract
- This paper investigates a passive hybrid configuration consisting of a fuel cell stack and a supercapacitor bank. In this configuration, the fuel cell and the supercapacitor are directly connected in parallel without the use of any DC/DC converters. Extensive experiments are performed on the fuel cell stack, the supercapacitor bank, and their passive hybrid connection. The internal impedance of the supercapacitor bank is 10 times lower than that of the fuel cell stack. The hybrid system shows a capacitive behavior in the selected frequency range, as given by the electrochemical impedance spectroscopy results. For the fuel cell stack, its voltage response to the step load current shows an inductive behavior, which can be represented by an RL circuit. On the other hand, the dynamics of the supercapacitor bank can be represented by two RC branches. When a step load current is applied, the supercapacitor provides the transient current while the fuel cell provides the steady current.
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| 30. |
- Xun, Qian, 1990, et al.
(författare)
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Intelligent Power Allocation with Load Disturbance Compensator in Fuel Cell/Supercapacitor System for Vehicle Applications
- 2020
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Ingår i: ITEC 2019 - 2019 IEEE Transportation Electrification Conference and Expo. - 9781728146294 ; , s. 489-494
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Konferensbidrag (refereegranskat)abstract
- A fuel cell-based hybrid power system with a supercapacitor can downsize the fuel cell power rating and shows good dynamic characteristics. However, power distribution between fuel cell and supercapacitor is challenging, and inappropriate power allocation strategy will easily cause over-charge or overdischarge of supercapacitor. Also, the DC bus voltage fluctuation is always encountered during the acceleration and deceleration of the vehicle. This paper proposes an intelligent power allocation method based on a low-pass filter. The adaptive cut-off frequency is applied to avoid over-charging and over-discharging the supercapacitor, and the cut-off frequency is calculated by cutting the load spectrum with allocation ratio changing with the state of charge (SoC) of the supercapacitor. A load disturbance compensator is also proposed to suppress the DC bus voltage fluctuation when the load variation occurs. According to the hybrid system model developed with commercially available devices, the feasibility of the strategy is verified by MATLAB/Simulink. The simulation results show that the SoC of the supercapacitor is effectively controlled and the DC bus voltage fluctuation is significantly reduced.
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| 31. |
- Xun, Qian, 1990, et al.
(författare)
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Joint Component Sizing and Energy Management for Fuel Cell Hybrid Electric Trucks
- 2022
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Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 71:5, s. 4863-4878
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a cost-effective way to design and operate fuel cell hybrid electric trucks (FCHETs) where a chance-constrained optimization is formulated. The aim of the introduced problem is to minimize a summation of component cost and operational cost with consideration of fuel cell (FC) degradation and cycle life of energy buffer. We propose to decompose the problem into two sub-problems that are solved by sequential convex programming. The delivered power satisfies a cumulative distribution function of the wheel power demand, while the truck can still traverse driving cycles with a similar speed and travel time without delivering unnecessarily high power. This allows to downsize powertrain components, including electric machine, FC and energy buffer. A case study considering different energy buffer technologies, including supercapacitor (SC), lithium-ion battery (LiB), and lithium-ion capacitor (LiC) is investigated in a set of trucking applications, i.e. urban delivery, regional delivery, construction, and long-haul. Results show that the power rating of the electric machine is drastically reduced when the delivered power is satisfied in a probabilistic sense. Moreover, the configuration with LiB as the energy buffer has the lowest expense but the truck with LiC can carry more payload.
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| 32. |
- Xun, Qian, 1990, et al.
(författare)
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Modelling and simulation of fuel cell/ supercapacitor passive hybrid vehicle system
- 2019
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Ingår i: 2019 IEEE Energy Conversion Congress and Exposition, ECCE 2019. ; , s. 2690-2696
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Konferensbidrag (refereegranskat)abstract
- The concept of the passive hybrid system is to develop a single-stage power conversion topology in which fuel cell and supercapacitor can be directly coupled, leading to low cost and compactness in the absence of DC/DC converters. The paper deals with the modelling and simulation of such a vehicle system. The powertrain component losses are modelled with a high level of detail, and they are functions of speed, torque and DC-link voltage. Different drive cycles divided into a low, middle, and high-speed category are used to evaluate the performance of the powertrain system. The wheel energy per distance and powertrain efficiency differs between the drive cycles due to the different speed and acceleration levels. Furthermore, the acceleration and WLTC characteristics of the powertrain system show that in the passive hybrid system, the supercapacitors can support fuel cells as a low-pass filter. As a result, the peak power requirement can be successfully achieved due to the lowered system impedance, and the fuel cell only needs to supply the average power during operation. © 2019 IEEE.
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| 33. |
- Xun, Qian, 1990, et al.
(författare)
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Sizing and Management of Fuel Cell Based Powertrains for City Ferry Applications
- 2022
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Ingår i: IECON Proceedings (Industrial Electronics Conference). - 2162-4704 .- 2577-1647. ; 2022-October
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Konferensbidrag (refereegranskat)abstract
- Fuel cell powered ferries with fast refueling time and high energy density are of great interest as they help reduce carbon emissions. This paper considers the sizing and management of fuel cell based powertrains and performs a case study using the real-world data of a city ferry, i.e., Älvsnabben 4. An optimization problem is formulated to minimize the sum of the hydrogen cost and the component costs. Various components of the powertrain are examined: electric machine, fuel cell, and energy buffer. In particular, the fuel cell degradation and the cycle life characteristics of different energy buffer technologies including lithium-ion battery, supercapacitor, and lithium-ion capacitor are taken into account. Results show that the total cost of the hybrid system composed of fuel cell and supercapacitor is the lowest due to the long cycle life and high power density of the supercapacitor technology. Moreover, since the hydrogen cost is the major contributor to the total cost, the variation of the hydrogen unit price can significantly impact the total cost.
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| 34. |
- Yang, Tongguang, et al.
(författare)
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Adaptive Backstepping-based H∞ Robust controller for Photovoltaic Grid-connected Inverter
- 2020
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Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 8, s. 17263-17272
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Tidskriftsartikel (refereegranskat)abstract
- To improve the robustness and stability of the photovoltaic grid-connected inverter system, a nonlinear backstepping-based H∞ controller is proposed. A generic dynamical model of grid-connected inverters is built with the consideration of uncertain parameters and external disturbances that cannot be accurately measured. According to this, the backstepping H∞ controller is designed by combining techniques of adaptive backstepping control and L2-gain robust control. The Lyapunov function is used to design the backstepping controller, and the dissipative inequality is recursively designed. The storage functions of the DC capacitor voltage and grid current are constructed, respectively, and the nonlinear H∞ controller and the parameter update law are obtained. Experimental results show that the proposed controller has the advantage of strong robustness to parameter variations and external disturbances. The proposed controller can also accurately track the references to meet the requirements of high-performance control of grid-connected inverters.
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| 35. |
- Yang, Tongguang, et al.
(författare)
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LSTM-Attention-Embedding Model-Based Day-Ahead Prediction of Photovoltaic Power Output Using Bayesian Optimization
- 2019
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Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 7, s. 171471-171484
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Tidskriftsartikel (refereegranskat)abstract
- Photovoltaic (PV) output is susceptible to meteorological factors, resulting in intermittency and randomness of power generation. Accurate prediction of PV power output can not only reduce the impact of PV power generation on the grid but also provide a reference for grid dispatching. Therefore, this paper proposes an LSTM-attention-embedding model based on Bayesian optimization to predict the day-ahead PV power output. The statistical features at multiple time scales, combined features, time features and wind speed categorical features are explored for PV related meteorological factors. A deep learning model is constructed based on an LSTM block and an embedding block with the connection of a merge layer. The LSTM block is used to memorize and attend the historical information, and the embedding block is used to encode the categorical features. Then, an output block is used to output the prediction results, and a residual connection is also included in the model to mitigate the gradient transfer. Bayesian optimization is used to select the optimal combined features. The effectiveness of the proposed model is verified on two actual PV power plants in one area of China. The comparative experimental results show that the performance of the proposed model has been significantly improved compared to LSTM neural networks, BPNN, SVR model and persistence model.
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| 36. |
- Zhang, Jinyuan, et al.
(författare)
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Bi-level Optimization of Component Sizing and Energy Management in Fuel Cell Hybrid Electric Trucks
- 2023
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Ingår i: 2023 IEEE Energy Conversion Congress and Exposition, ECCE 2023. ; , s. 202-207
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Konferensbidrag (refereegranskat)abstract
- Electric trucks powered by hydrogen fuel cells are a promising electrified transportation technology. To compensate for the relatively slow dynamics of fuel cells, lithium-ion batteries can be incorporated into the hydrogen power systems. This paper proposes a bi-level optimization framework for proper component sizing and energy management in fuel cell hybrid electric trucks. Based on the sizing variables at the upper level, the lower level utilizes convex programming to generate an optimal energy management solution and returns the solution to the upper level. Then, the upper level runs a particle swarm optimization process to determine the optimal sizes of the fuel cells and lithium-ion batteries to minimize the sum of the component costs and operating costs. By conducting a case study using a modified ACEA long-haul drive cycle, this paper demonstrates the effectiveness of the proposed framework.
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