| 1. |
- Boscaglia, Luca, 1991, et al.
(författare)
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Convective Heat Transfer Coefficients and Mechanical Loss Evaluation of Oil Splashing in Direct Cooled Electrically Excited Hairpin Motors
- 2022
-
Ingår i: 2022 International Conference on Electrical Machines, ICEM 2022. ; , s. 496-503
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Konferensbidrag (refereegranskat)abstract
- There in an increasing trend in the use of the direct oil cooling in electric motors for automotive because of the increasing demand of high power/torque density as well as overload capability. One of the most immediate solution is to fill the housing with some oil level and benefit of the heat transfer from the oil splashing. The mechanical losses coming from the rotor rotation are well known and they represent a significant challenge, especially at high speed and high oil level. Therefore, the derivation and prediction of these losses have not been properly investigated leading to a lack in the current literature. Moving Particles Simulation (MPS) method is used in Particleworks to calculate the mechanical losses caused by the oil viscosity and convective heat transfer coefficients (HTC) are extracted for a 250 kW Electrically Excited Synchronous Machine at different speeds and oil levels.
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| 2. |
- Boscaglia, Luca, 1991, et al.
(författare)
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Thermal Modeling and Driving-cycle Critical Temperatures Estimation of Electrically Excited Synchronous Machine for Automotive Traction
- 2023
-
Ingår i: 2023 IEEE Energy Conversion Congress and Exposition, ECCE 2023. ; , s. 4501-4508
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Konferensbidrag (refereegranskat)abstract
- Electrically Excited Synchronous Machines (EESM) has garnered attention due to their outstanding performance characteristics but it presents significant thermal challenges. The rotor is embedded with active conductors resulting in a high loss density and large amount of heat that discourage the adoption of this machine in various applications. This paper investigates into the feasibility of utilizing a 60 kW EESM for a commercial vehicle application, with a specific focus on understanding its thermal behavior. Steady-state 3D Conjugate Heat Transfer (CHT) analysis is conducted to obtain the temperature response of various machine components across the torque-speed map. Based on this analysis, thermal resistances are estimated to construct a simplified Lumped Parameter Thermal Network (LPTN) and predict maximum temperatures along the Worldwide harmonized Light-duty vehicles Test Cycles (WLTC). Simulations in MATLAB Simulink show that the temperatures remain below the limits defined by the winding insulation class throughout the entire driving cycle. This finding assures the reliability and safe operation of the EESM for the considered application.
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| 3. |
- Chen, Hao, 1988, et al.
(författare)
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A Permanent Magnet Brushless Doubly-Fed Electric Machine for Variable-Speed Constant-Frequency Wind Turbines
- 2023
-
Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 70:7, s. 6663-6674
-
Tidskriftsartikel (refereegranskat)abstract
- A permanent magnet brushless doubly-fed electric machine is presented in this paper. This machine is developed for variable-speed constant-frequency wind energy generation applications. Differing from conventional doubly-fed electric machines based on induction machines, a permanent magnet rotor provides the magnetic field excitations for both the control winding and the power winding in the presented machine. The operating principle of the presented machine for the variable-speed constant-frequency operation is revealed in detail. Compared to a counterpart machine, the presented machine exhibits significantly improved back- electromotive force, torque/power density, torque per magnet volume, efficiency, etc. Finally, a proof-of-concept prototype of the presented machine is fabricated, and the corresponding experimental results are provided to verify the fact that the presented machine is capable of achieving the variable-speed constant-frequency function.
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| 4. |
- Chen, Hao, 1988, et al.
(författare)
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Design and Analysis of a Variable-Speed Constant-Amplitude Wind Generator for Stand-Alone DC Power Applications
- 2023
-
Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 70:8, s. 7731-7742
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents the design and analysis of a permanent magnet (PM) wind generator, which consists of two sets of windings, and two rotors. The proposed PM wind generator is designed for variable-speed constant-amplitude voltage operation in dc power applications, in order to maximize the utilization of wind energy and make the electricity more accessible to stand-alone situations, e.g., remote areas and offshore islands. The operating principle of the variable-speed constant-amplitude voltage operation of the proposed PM wind generator is demonstrated in detail. A comparative study is carried out among the proposed generator, a conventional surface-mounted PM synchronous generator, and an existing counterpart generator used for the same application. The results show that compared to the conventional PM synchronous generator and the existing counterpart, the proposed PM wind generator exhibits the advantages of high induced voltage, high torque/power density, high efficiency, etc. Finally, the proposed PM wind generator is prototyped and manufactured. The validity of the variable-speed constant-amplitude operation of the proposed generator under both steady-state and dynamic conditions, is verified by experimental results.
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| 5. |
- Chen, Hao, et al.
(författare)
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Electromagnetic Performance Investigation of A Brushless Electrically-Excited Synchronous Machine for Long-Distance Heavy-Duty Electric Vehicles
- 2024
-
Ingår i: IEEE Transactions on Transportation Electrification. - 2332-7782. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- Long-distance heavy-duty electric vehicles, e.g., electric trucks, expect demanding requirements from the electric drive system, including high starting torque, high torque density, high power factor, high efficiency, etc. Permanent magnet synchronous machines (PMSMs) have been widely used for traction applications. However, the high cost and associated environmental issues due to the rare-earth permanent magnet material intensify researchers to explore new solutions. Accordingly, a brushless electrically-excited synchronous machine (EESM) is designed and investigated in this paper. The brushless EESM is also quantitatively compared with a PMSM candidate for the aforementioned application. Differing from conventional EESMs in which the brushes and slip rings are used for rotor field winding excitation, a contactless/brushless rotating transformer is adopted for the presented EESM to feed the rotor field winding. It is shown that the interior PMSM exhibits higher efficiency in low-speed region, but lower efficiency in high-speed region. By contrast, the brushless EESM exhibits lower efficiency in low-speed region, but much higher efficiency in high-speed region. Hence, the EESM is more suitable for long-distance heavy-duty electric vehicle applications where significant highspeed operations are required. Moreover, compared to the PMSM, the EESM is more cost-effective, sustainable, and environmentally friendly due to the absence of the rare-earth permanent magnet material. Both the PMSM and the EESM are prototyped and manufactured. Experimental results are provided to validate the effectiveness of the presented designs.
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| 6. |
- Jiang, Bowen, 1993, et al.
(författare)
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Active Balancing of Reconfigurable Batteries Using Reinforcement Learning Algorithms
- 2023
-
Ingår i: 2023 IEEE Transportation Electrification Conference and Expo, ITEC 2023.
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Konferensbidrag (refereegranskat)abstract
- In reconfigurable batteries, series or parallel connections among cells/modules are able to be actively changed during operations. One big advantage of reconfiguration is to achieve active balancing among cells/modules. Rule-based and greedy algorithms of reconfigurable battery control have problems of being sensitive to battery characteristic variation and requiring a lot of computing resources. Therefore, deep reinforcement learning (DRL) algorithms are used to overcome these difficulties. Very few studies related to this idea have been done previously, and the studied battery reconfiguration topologies are either too simple or too complex. Thus, in this paper, a module-level reconfigurable battery with moderate flexibilities is controlled by DRL algorithms. Two neighboring modules are connected in either parallel or series by following a well-trained optimal policy. Two battery discharging cases, constant power and variable power, are simulated. The final results prove the feasibility and great potential of utilizing DRL algorithms in reconfigurable battery control.
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| 7. |
- Jiang, Bowen, 1993, et al.
(författare)
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Identification of Self and Mutual Inductances of Electrically Excited Synchronous Machines Using Signals in Current Controller without Extra Observer
- 2024
-
Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- Electrically excited synchronous machines (EESMs) have become a promising candidate for electric vehicles due to their high power density without using rare-earth materials. Accurate parameters are essential to achieve high performance dynamic control. However, to precisely identify the parameters of an EESM is more challenging than other machines, since the number of parameters is larger and there are also couplings between the parameters. In this study, a method to identify the apparent and incremental values of self and mutual inductances is proposed. In this method, signals from the current controller are extracted and processed to eliminate the parameter errors, without building any extra observer. The method has been verified in both real-time simulations and experiments. It is shown that parameters are calibrated successfully. By using the identified parameters in the current controller, a fast and smooth current dynamic response is achieved.
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| 8. |
- Jiang, Bowen, 1993, et al.
(författare)
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Lithium-ion Battery State of Health Estimation with Recurrent Convolution Neural Networks
- 2022
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Ingår i: IET Conference Proceedings. - : Institution of Engineering and Technology. - 2732-4494. ; 2022:4, s. 479-484
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Tidskriftsartikel (refereegranskat)abstract
- State of health (SOH) estimation of lithium-ion batteries is one of the major functions conducted by battery management systems. Machine learning and neural networks become popular for SOH estimation in recent years, especially when huge amounts of battery data from laboratories and end-users are available. This paper proposed a new SOH estimation structure, which combines recurrent neural network and convolution neural network together. Measurements not only from the studied cycle but also from the previous two cycles is used together to estimate the studied cycle SOH. By this way, hidden information of aging trends among cycles is utilized. Furthermore, two-dimensional filters in convolution layers are applied to study features of voltage, current, and temperature during the charging process. Validation results show that the proposed SOH estimation structure can reduce the validation set loss by 31.5% and 18.8% respectively, compared to the long-short-term model and another proposed reference structure that combines recurrent neural network and feedforward neural network together.
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| 9. |
- Lai, Linhua, 2000, et al.
(författare)
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Digital Control Implementation for Coupling Independent IPT Systems without Communication
- 2024
-
Ingår i: 2024 IEEE 10th International Power Electronics and Motion Control Conference, IPEMC 2024 ECCE Asia. ; , s. 3350-3356
-
Konferensbidrag (refereegranskat)abstract
- Inductive Power Transfer (IPT) offers a convenient solution for charging electric vehicles (EVs). By synchronizing the inverter output voltage with current, a parity-time (PT)-symmetric IPT system can operate in the PT-symmetric mode, ensuring that the transfer power and efficiency remain independent of misalignment. However, the inherent propagation delay in the control circuit can lead to synchronization failure, reducing the efficiency of the system. In this article, the influence of propagation delay are analyzed. The results show that propagation delay increases the switching loss of system, causes working frequency and output power drift. To address this issue, a novel digital control scheme is proposed to compensate for propagation delay without requiring any extra component. The theoretical analysis and the feasibility of the compensation control scheme are validated through experiments with an IPT prototype. The results show that the maximum efficiency can be achieved when the system is slightly over-compensated. Within a misalignment range of 0-160 mm, the fully-compensated system maintains nearly constant output power.
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| 10. |
- Liu, Yujing, 1962, et al.
(författare)
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High Frequency Exciter of Electrically Excited Synchronous Motors for Vehicle Applications
- 2016
-
Ingår i: Proceedings - 2016 22nd International Conference on Electrical Machines, ICEM 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509025381 ; , s. 378-383
-
Konferensbidrag (refereegranskat)abstract
- Future electric vehicles requires electric motors with excellent torque-speed characteristics, high efficiency, and low costs. Equipped with controllable rotor flux, electrically excited synchronous motors are able to provide high torque at low speed and high efficiency at high speed. However, brushes and slip rings for field windings need maintenance and may influence reliability. In this paper a brushless power transferring approach through a high frequency rotating exciter is presented. Compared with conventional rotating exciters, the high frequency exciter is much more compact and energy efficient due to high energy conversion frequency. This enables the exciter to be integrated in the rotor and provides opportunities for electrically excited synchronous motors to compete with other motors in vehicle applications. A prototype of the rotating exciters with SiC based converter, Litz wire, and shaft-end mounting structure has been built and measured in standalone tests and combined tests with a synchronous machine.
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| 11. |
- Mademlis, Georgios, 1992, et al.
(författare)
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Performance Evaluation of Electrically Excited Synchronous Machine compared to PMSM for High-Power Traction Drives
- 2020
-
Ingår i: Proceedings - 2020 International Conference on Electrical Machines, ICEM 2020. - 9781728199450 ; , s. 1793-1799
-
Konferensbidrag (refereegranskat)abstract
- The electric drive design for heavy-duty vehicles ischallenging due to special requirements involved, such as highstarting torque and operation at the peak power for a longtime. The electrically excited synchronous machine (EESM) is asuitable machine type for such an application and a potentialalternative to the permanent magnet synchronous machines(PMSM) due to the superior flexibility that the control of thebrushless rotor excitation offers. The direct adjustment of theflux allows also to tune the best efficiency region of the machineclose to the usual operating points of the vehicle achieving at thesame time a better power factor compared to a PMSM, whichcan further increase the efficiency and the power capability ofthe stator inverter. A case-study comparison of a EESM- andPMSM-based drive for electric trucks is presented in this paperwhere Finite-Element-Method and Matlab simulations of thewhole vehicle drivetrain showcase the advantages of the EESM.
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| 12. |
- Mademlis, Georgios, 1992, et al.
(författare)
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Zero-Sequence Current Reduction Technique for Electrical Machine Emulators With DC Coupling by Regulating the SVM Zero States
- 2022
-
Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 69:11, s. 10947-10957
-
Tidskriftsartikel (refereegranskat)abstract
- In this article, a new zero-sequence current suppression technique for electrical machine emulators with reduced component count is proposed. The proposed control scheme is implemented by properly regulating the zero states in space vector modulation (SVM). It is well known that a machine emulator allows fast experimental validation of the control and design of a drive system without having a physical electrical machine, since the machine is replaced by another voltage-source converter and a three-phase inductor. However, in emulators with a coupled dc link, circulating zero-sequence current is freely developed creating additional load for the power switches. The currently available control methods require additional hardware common-mode filters to effectively reduce this current. Contrarily, the proposed SVM algorithm suppresses the zero-sequence current more effectively via direct compensation of common-mode voltage, and thus, no additional hardware filters are needed. Thus, an electrical machine emulator with less hardware requirements can be developed with the proposed control technique for being utilized in several laboratory test-bench applications. Experimental results on a 60-kW system validate the effectiveness of the proposed SVM algorithm, since the zero-sequence current amplitude has been measured to be 3.7% of the phase current or even less than this.
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| 13. |
- Sharma, Nimananda, 1988, et al.
(författare)
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Evaluation of Operating Range of a Machine Emulator for a Back-to-Back Power-Hardware-in-the-Loop Test Bench
- 2022
-
Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 69:10, s. 9783-9792
-
Tidskriftsartikel (refereegranskat)abstract
- Inverter testing using laboratory test benches with rotating machines can be bulky, complex and maintenance intensive. One solution is to use machine emulator for laboratory testing of inverters. The emulator is controlled in such a way that currents and voltages at the terminals resemble a machine connected to a mechanical load. A machine emulator for a back-to-back power-hardware-in-the-loop (PHIL) test bench is proposed in this study. The PHIL test bench consists of two identical VSCs with three single-phase inductors as coupling network. The two VSCs are connected to the same DC supply. One VSC acts as inverter under test (IUT) while the other is part of machine emulator. Aim of this paper is to analyze the influence of coupling inductance on operating range of the emulator. An analytical method to dimension the coupling inductance is introduced and verified in experiments. The operating range of the emulator is also evaluated. The performance of the IUT when tested with an equivalent PMSM in simulations and that of a prototyped 60-kW rated machine emulator are compared. Sensitivity of emulator control on parameter estimation is discussed. The experimental results show good agreement with simulations in both steady-state and dynamic conditions.
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| 14. |
- Tang, Junfei, 1990, et al.
(författare)
-
Common Mode Power Control of Three-Phase Inverter for Auxiliary Load without Access to Neutral Point
- 2022
-
Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 37:1, s. 221-233
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study is to investigate the potential of obtaining an auxiliary dc output from the common mode switching harmonics of a three-phase inverter without access to the neutral point of the ac load. To achieve this, the control of common mode switching harmonics with space vector modulation is proposed. With this control, common mode switching harmonics can be regulated independently from the differential mode power flow to the main three-phase load. To physically implement the common mode power flow, a harmonic extraction circuit is placed in parallel with the main three-phase load. The extraction circuit is formed by series-connected inductance and capacitance. Due to the LC series resonance and the mutual coupling of the inductance, only common mode switching harmonics can pass through the extraction circuit. The extracted harmonics are then rectified and delivered to the auxiliary dc output. The control and topology are verified in both simulations and experiments. In the end, it is shown in experiments that there is no significant difference of the inverter efficiency after the auxiliary dc load is connected. This method can be used for instance to drive an ac machine while charging a battery or powering a compressor simultaneously.
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| 15. |
- Tang, Junfei, 1990, et al.
(författare)
-
Comparison of copper loss minimization and field current minimization for Electrically Excited Synchronous Motor in mild hybrid drives
- 2017
-
Ingår i: 2017 19th European Conference on Power Electronics and Applications (EPE'17 ECCE Europe). - 2325-0313. - 9789075815276 ; 2017-January
-
Konferensbidrag (refereegranskat)abstract
- Electrically Excited Synchronous Motor (EESM) serves as an option on hybrid vehicle applications. An EESM for mild hybrid application is designed in this study. Copper loss minimization and field current minimization are analyzed for current control strategies of EESM. Both of the current control strategies are applied and comparisons between the two are made thereafter. In both of the strategies, high efficiency is achieved in the high speed region whereas high power factor is achieved in the high torque region. Copper loss minimization gives a larger operation area of high efficiency and high power factor, whereas the rotor heat generation can be reduced when field current minimization is applied.
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| 16. |
- Tang, Junfei, 1990, et al.
(författare)
-
Comprehensive Dynamic Current Control of Electrically Excited Synchronous Machines With Magnetic Mutual Couplings
- 2024
-
Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; In press
-
Tidskriftsartikel (refereegranskat)abstract
- Electrically excited synchronous machines have become an attractive solution to electric vehicles. The excitation of the machine is controllable by adjusting the field current. However, due to the magnetic mutual couplings between stator and rotor windings, a voltage will be induced in the stator winding in case of a current rise in the field winding and vice-versa. In this article, a dynamic current control algorithm is proposed in which magnetic mutual couplings are comprehensively taken into consideration. To achieve this, first, the expected current derivatives are determined according to the error. Then, the voltages across all self- and mutual inductances are calculated correspondingly. In the end, the resistive voltages, inductive voltages, and the cross-coupling terms are summed up to construct the total controller output. To make sure that the control still works when the voltage output limit is reached, an antiwindup algorithm with adaptive bandwidth is proposed to cooperate with the dynamic current control algorithm. The results from simulations and experiments show that smoother responses can be achieved with the proposed control method.
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| 17. |
- Tang, Junfei, 1990
(författare)
-
Design and Control of Electrically Excited Synchronous Machines for Vehicle Applications
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrically excited synchronous machines (EESMs) are becoming an alternative to permanent magnet synchronous machines (PMSMs) in electric vehicles (EVs). This mainly attributes to the zero usage of rare-earth materials, as well as the ability to achieve high starting torque, the effectiveness to do field weakening and the flexibility to adjust power factor provided by EESMs. Furthermore, in case of converter failure at high speed, safety can be improved by shutting down the field current in EESMs. The purpose of this study is to investigate the potential application of EESMs in EVs. To achieve this aim, several topics are covered in this study. These topics are studied to confront the challenges before EESMs could become prevalent and to maximumly use the advantages of EESMs for EV applications. In control strategies, the challenge is to properly adjust the combination of stator and field currents so that high power factor and minimum copper losses can be achieved. To tackle this, control strategies are proposed so that reactive power consumption and total copper losses are minimized. With the proposed strategies, the output power is maximized along the torque-speed envelope and high efficiency in field-weakening is achieved. In dynamic current control, due to the magnetic couplings between field winding and stator winding, a current rise in one winding would induce an electromagnetic force (EMF) in the other. This introduces disturbances in dynamic current control. In this study, a current control algorithm is proposed to cancel the induced EMF and the disturbances are mitigated. In machine design, high starting torque and effective field weakening are expected to be achieved in the same EESM design. To realize this, some criteria need to be satisfied. These criteria are derived and integrated into the design procedure including multi-objective optimizations. A 48 V EESM is prototyped during the study. In experimental verification, a torque density of 10 N·m/L is achieved including cooling jacket. In field excitation, a contactless excitation technology is adopted, which leads to inaccessibility of the field winding. To realize precise control of field current in a closed loop, an estimation method of field current is proposed. Based on the estimation, closed-loop field current control is established. The field current reference is tracked within an error of 2% in experimental verifications. The cost of an EESM drive increases because of the additional converter used for field excitation. A technique is proposed in which the switching harmonics are extracted for field excitation. With this technique, both stator and field windings can be powered using only one inverter. From all the challenges tackled in this study, it can be concluded that the application of EESMs in EVs is feasible.
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| 18. |
- Tang, Junfei, 1990, et al.
(författare)
-
Design and Experimental Verification of a 48 V 20 kW Electrically Excited Synchronous Machine for Mild Hybrid Vehicles
- 2018
-
Ingår i: International Conference on Electrical Machines. - 2381-4802. - 9781538624777
-
Konferensbidrag (refereegranskat)abstract
- Electrically Excited Synchronous Machines (EESM) have become an attractive solution to Electric Vehicles (EV). This work aims to develop a 48 V 20 kW EESM for mild hybrid vehicles (MHV), which prioritizes torque production ability during start-up. An H-bridge converter including an H-bridge inverter, a rotating transformer and a diode rectifier is employed for magnetic field excitation on the rotor side. Efforts have been made to maximize torque production and to estimate field current and field winding temperature without physical contact. The EESM is manufactured after having been designed with the help of FEM, and then verified by practical experiments. The back-EMF waveforms, flux linkage distributions and the produced torque levels from the experiments are compared with the FEM results. Field current estimation by DC-link current of the excitation H-bridge converter is developed, and solutions for field winding temperature estimation have been investigated as well.
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| 19. |
- Tang, Junfei, 1990, et al.
(författare)
-
Design of Electrically Excited Synchronous Machines to Achieve Unity Power Factor in Field Weakening for Long-Haul Electric Trucks
- 2020
-
Ingår i: Proceedings - 2020 International Conference on Electrical Machines, ICEM 2020. ; 23 August 2020, s. 422-428
-
Konferensbidrag (refereegranskat)abstract
- Electrically excited synchronous machines are a promising candidate for long-haul electric trucks due to excellent capability in field weakening. This study aims at concluding a structural design process of the machine for long-haul electric trucks. A criterion of machine design to achieve unity power factor in field-weakening is derived. With this criterion, a minimum level of field current is decided in the design process. Parametric sweeps are applied to decide the optimum slot geometries for stator and rotor. The optimization of slot geometries is multi-objective. In this study, it is to maximize the peak torque while minimize iron-core losses simultaneously. Pareto frontier is used to identify the optimum solutions. The performance of the finalized design is then evaluated. The high efficiency area is located at high-speed low-torque region which is preferable for long-haul electric trucks. Balance is achieved between copper and iron-core losses during steady-speed intervals of the test cycles which leads to minimum losses in total.
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| 20. |
- Tang, Junfei, 1990, et al.
(författare)
-
Dynamic Current Control to Compensate for Magnetic Mutual Coupling in Electrically Excited Synchronous Machines
- 2020
-
Ingår i: Proceedings - 2020 International Conference on Electrical Machines, ICEM 2020. ; 23 August 2020, s. 1779-1785
-
Konferensbidrag (refereegranskat)abstract
- Electrically excited synchronous machines have become an attractive solution to electric vehicles. Equipped with a field winding in the rotor, the excitation of the machine is controllable. However, due to the magnetic mutual coupling between the stator and rotor windings, a voltage will be induced in the field winding in case of a current rise in the stator winding and vice versa. In this study, a dynamic current control algorithm with compensation for magnetic mutual coupling is proposed. A first-order response of current rise is expected. To achieve this, the controller consists of three parts. The first part is the feed forward of cross-coupling terms due to Park transform. The second part takes care of the resistances and selfinductances. The third part takes care of the mutual inductances. Finally, the outputs from the three parts are summed up to be the total output from the controller.
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| 21. |
- Tang, Junfei, 1990, et al.
(författare)
-
Dynamic Current Reference Determination of Electrically Excited Synchronous Machines Based on Torque Gradients of Copper Losses
- 2024
-
Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 39:6, s. 7423-7433
-
Tidskriftsartikel (refereegranskat)abstract
- Electrically excited synchronous machines (EESMs) have become an attractive solution to electric vehicles. The excitation of the machine can be regulated by adjusting field current. This introduces one additional degree of control freedom. The control of armature current in stator and field current in rotor is expected to not only reduce the total losses, but also dynamically redistribute the load on both windings so that neither of them overheats. To realize this function, an algorithm is proposed in this study to dynamically determine the current references in EESM torque control. A cost function is introduced by placing weights on stator and rotor copper losses separately. The weights can be adjusted dynamically. The cost function is minimized by moving the current reference vector. The moving of the vector is orthogonally decomposed into a torque-related component and a cost-related component. When current or voltage limits are reached, a cancellation technique is activated to constrain the reference vector. It is shown in experimental results that expected performance is achieved in all operating conditions.
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| 22. |
- Tang, Junfei, 1990, et al.
(författare)
-
Estimation Algorithm for Current and Temperature of Field Winding in Electrically Excited Synchronous Machines with High-Frequency Brushless Exciters
- 2021
-
Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 36:3, s. 3512-3523
-
Tidskriftsartikel (refereegranskat)abstract
- Electrically excited synchronous machines (EESMs) have become one of the potential alternatives to permanent magnet synchronous machines (PMSMs) in electric vehicles (EVs) to avoid rare-earth materials. Utilizing high-frequency brushless exciters for rotor excitation is a promising choice to reduce friction losses and maintenance effort and cost. However, with the usage of brushless exciters, the field current and temperature cannot be measured directly. In this paper, an algorithm is proposed to dynamically estimate the field current as well as the field winding temperature. The dc-link current is utilized as a feedback to correct the estimation. The performance of the estimation algorithm is initially evaluated in simulations and then verified by experimental measurements in a prototype. Based on the estimation algorithm, closed-loop control of the field current is developed and verified experimentally.
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| 23. |
- Tang, Junfei, 1990, et al.
(författare)
-
Modeling and Experimental Verification of High-Frequency Inductive Brushless Exciter for Electrically Excited Synchronous Machines
- 2019
-
Ingår i: IEEE Transactions on Industry Applications. - 0093-9994 .- 1939-9367. ; 55:5, s. 4613-4623
-
Tidskriftsartikel (refereegranskat)abstract
- Electrically excited synchronous machines have shown potential to be an alternative to permanent magnet synchronous machines in electromobility and wind power applications. High frequency wireless power transferring technology enables a compact design of brushless exciters for the machine. In this paper, a dynamic model of high frequency brushless exciters is proposed for the purposes of operating condition monitoring and excitation control. The modeling is done by using arithmetic and differential equations, as well as considering different operation modes of the system. The operation modes are defined based on the physical behaviors of the excitation circuit. The model is verified by experiments with variations of different circuit parameters. With the proposed model, further studies, including parameter sensitivity study, component parameter selection and loss analysis are conducted to demonstrate the effectiveness of the model. These studies can be used to assist design and optimization of the brushless excitation system.
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| 24. |
- Tang, Junfei, 1990, et al.
(författare)
-
Observations of Field Current and Field Winding Temperature in Electrically Excited Synchronous Machines with Brushless Excitation
- 2022
-
Ingår i: 2022 International Conference on Electrical Machines, ICEM 2022. ; , s. 841-847
-
Konferensbidrag (refereegranskat)abstract
- Electrically excited synchronous machines have become an alternative in electrification of transportations and renewable power generations. To reduce the extra effort in the maintenance of sliprings and brushes for field excitation, brushless excitation has been developed. However, when brushless excitation is adopted, the field winding becomes physically inaccessible when the machine is rotating. To solve this problem, an algorithm is proposed in this study to observe the field current and field winding temperature of an EESM with brushless excitation. The stator currents are measured and then used to correct the machine state predictor. The correction of the state prediction is interpreted to adjust the field winding resistance and temperature value. The algorithm is evaluated in simulations. The estimations of field current and field winding temperature track the measurements successfully.
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| 25. |
- Tang, Junfei, 1990, et al.
(författare)
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Sensorless control of a PMSM with a transmission system including shunt branches
- 2016
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Ingår i: Proceedings - 2016 22nd International Conference on Electrical Machines, ICEM 2016. Lausanne; Switzerland; 4-7 September 2016. - 9781509025381 ; , s. 1160-1166
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Konferensbidrag (refereegranskat)abstract
- In oil and gas applications, permanent magnet synchronous motors (PMSM) are becoming a preferred choice to drive subsea and submersible pumps to achieve higher efficiency than induction motors. In the drive system, a submersible PMSM is fed through a transmission system by a top-side variable speed drive. Previous studies have included the series impedance of the transmission system but excluded the transformer magnetizing branch and the cable capacitive branches. In this work, both the series impedance and the shunt admittance of the transmission system are considered. The PMSM current controller is restructured to be an inverter current controller. A static estimator is implemented to estimate the PMSM stator voltage and current. Sensorless control is realized by combining the statically compensated voltage model method and the high frequency injection method. The developed controller can successfully start and accelerate the PMSM from standing still up to 6000 rev/min within 5 s.
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| 26. |
- Tang, Junfei, 1990, et al.
(författare)
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Study of Voltage Spikes and Temperature Rise in Power Module Based Integrated Converter for 48 V 20 kW Electrically Excited Synchronous Machines
- 2018
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Ingår i: 2018 IEEE Applied Power Electronics Conference and Exposition (APEC). - 2470-6647. - 9781538611807 ; 2018-March, s. 210-217
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Konferensbidrag (refereegranskat)abstract
- Electrically Excited Synchronous Motor (EESM) has become an option for electric vehicles, and in order to drive an EESM, an integrated converter is preferred for its compact design so that the machine and the converter can be combined together as a package to deliver power. Therefore, an integrated converter for driving a 48 V 20 kW EESM in mild hybrid applications is designed and tested. Attention is paid to voltage spikes and temperature rises, which are the challenges for a compact design with low voltage but high current ratings. Results show that the idea of integrated converter for EESM is practical and promising. Several suggestions for integrated converter design are given as well.
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| 27. |
- Tang, Junfei, 1990
(författare)
-
Synchronous Machines with High-Frequency Brushless Excitation for Vehicle Applications
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrically excited synchronous machines (EESM) are becoming an alternative to permanent magnet synchronous machines (PMSM) in electric vehicle (EV) applications. This mainly attributes to the zero usage of rare-earth material as well as the capabilities of high starting torque and good field weakening provided by EESM. EESM also improves safety in case of converter failure at high speed. The prevalence of wireless power transfer (WPT) technologies enables the employment of high frequency brushless excitation in EESM. This reduces the friction loss and maintenance effort compared with traditional excitation through brushes and sliprings. Hence this study aims at investigating the potential of EESM with high frequency brushless excitation in EV applications. Modeling, design and control are the main aspects of interest in this study. Due to the varieties of different vehicle applications, this study covers the developments of three EESM drive systems, one for mild hybrid vehicles, one for electric passenger cars and one for heavy duty vehicles. To achieve a comprehensive understanding of the system, modeling is firstly studied. This includes the modeling of the machine as well as the modeling of the high frequency brushless excitation system. Nonlinear properties of magnetic material are taken into considerations. Based on the machine modeling, the vector loci of current, voltage, torque and power factor in dq-frame as well as the envelop in torque-speed map are derived analytically. One step further, algorithms to achieve unity power factor along with minimizations of copper loss or field current are studied. To achieve unity power factor at high speed, the field excitation needs to be stronger than the armature reaction. The design of the system starts with profiling of the specifications for the three applications. The varieties in specifications lead to the differences in design strategies. This study adopts a general design procedure with interactions of FEM analysis and operation point iterations. Then the design strategies are established based on each set of design specifications to tune the parameters of the machine geometry accordingly. The design for mild hybrid vehicles emphasizes on widening the flux path. In terms of the design for electric passenger cars, a good balance is required between copper area and flux path. Comparisons between open-slot and closed-slot designs bring a trade-off of torque ripples and average torque. Adding ferrite to the top of rotor slots introduces a study of influence from the ferrite pieces to the field excitation. This includes a possible ease of local saturation in rotor and a reduction of copper losses etc. As for the machine design for heavy-duty vehicles, investigations show that, the adjustable field in EESM brings a significant benefit in field weakening operation. A 48 V EESM with high frequency brushless excitation for mild hybrid vehicles is prototyped. The experimental results of both machine and exciter are consistent with the FEM calculation results. This verifies the modeling and the methods that are applied in the design and analysis. One challenge for the prevalence of EESM is the difficulty to access the field winding after assembly. As a solution, an algorithm is developed to estimate the field winding current and temperature. The dc-link current is utilized as a feedback in the algorithm to correct the estimations. The current and temperature variations are tracked quite well. As one step further, a closed-loop field current control is established. The ability to track field current reference is experimental verified as well. This closed-loop field current control enables a complete dynamic closed-loop control of the EESM.
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