| 1. |
- Biegel, Benjamin, et al.
(författare)
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Distributed Low-Complexity Controller for Wind Power Plant in Derated Operation
- 2013
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Konferensbidrag (refereegranskat)abstract
- We consider a wind power plant of megawatt wind turbines operating in derated mode. When operating in this mode, the wind power plant controller is free to distribute power set-points to the individual turbines, as long as the total power demand is met. In this work, we design a controller that exploits this freedom to reduce the fatigue on the turbines in the wind power plant. We show that the controller can be designed in a decentralized manner, such that each wind turbine is equipped with a local low-complexity controller relying only on few measurements and little communication. As a basis for the controller design, a linear wind turbine model is constructed and verified in an operational wind power plant of megawatt turbines. Due to limitations of the wind power plant available for tests, it is not possible to implement the developed controller; instead the final distributed controller is evaluated via simulations using an industrial wind turbine model. The simulations consistently show fatigue reductions in the magnitude of 15 – 20 %.
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| 2. |
- Kristalny, Maxim, et al.
(författare)
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Decentralized Feedforward Control of Wind Farms: Prospects and Open Problems
- 2011
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Konferensbidrag (refereegranskat)abstract
- The problem of load mitigation in wind turbines located in wind farms is addressed. The benefits of letting turbines communicate with and account for their neighbors are explored. First, the idea of exploiting previewed wind speed measurements is examined. The problem is formulated as an H 2 model matching optimization. The influence of preview length on the performance is analyzed and simulation results are presented. Then, the possibility of cooperation between turbines is studied within a distributed feedforward control scheme. The problem is formulated as a decentralized model matching optimization and several theoretical challenges associated with it are outlined. An approximate frequency domain solution and preliminary simulation results are presented.
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| 3. |
- Kristalny, Maxim, et al.
(författare)
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On Using Wind Speed Preview to Reduce Wind Turbine Tower Oscillations
- 2013
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Ingår i: IEEE Transactions on Control Systems Technology. - 1558-0865. ; 21:4, s. 1191-1198
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the potential of using previewed wind speed measurements for damping wind turbine fore-aft tower oscillations. Using recent results on continuous-time H2 preview control, we develop a numerically efficient framework for the feedforward controller synthesis. One of the major benefits of the proposed framework is that it allows us to account for measurement distortion. This results in a controller that is tailored to the quality of the previewed data. A simple yet meaningful parametric model of the measurement distortion is proposed and used to analyze the effects of distortion characteristics on the achievable performance and on the required length of preview. We demonstrate the importance of accounting for the distortion in the controller synthesis and quantify the potential benefits of using previewed information by means of simulations based on real-world turbine data.
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| 4. |
- Madjidian, Daria
(författare)
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A Decomposition Result in Linear-Quadratic Coordinated Control
- 2014
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Konferensbidrag (refereegranskat)abstract
- Scalability is a fundamental requirement in control design for large-scale systems. Typically, it needs to be considered explicitly at the expense of performance degradation and more complicated design procedures. In this paper, we present a class of large scale systems where scalability is an inherent property of the optimal centralized solution. More specifically, we study a coordination problem where a group of identical subsystems are required to satisfy an equality constraint on the sum of their inputs. We show that the problem can be completely decomposed in terms of the unconstrained problems associated with each subsystem. In particular, the computational effort required to obtain the optimal solution is independent of the number of subsystems and the only global information processing required to execute the optimal control law is a simple summation, which scales well when the number of subsystems grows large.
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| 5. |
- Madjidian, Daria, et al.
(författare)
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A Distributed Power Coordination Scheme for Fatigue Load Reduction in Wind Farms
- 2011
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Ingår i: ; , s. 5219-5224
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Konferensbidrag (refereegranskat)abstract
- Wind turbines operating in wind farms are coupled by the wind flow. This coupling results in increased turbulence levels for downwind turbines, and consequently higher maintenance costs. In this paper, we consider a scenario where a wind farm is asked to produce less than maximum power. The objective is to minimize fatigue loads on the turbines, while maintaining the desired power production. We show how this can be achieved by coordinating neighboring turbines. The result is a control structure where each turbine only need to communicate with a limited set of neighboring turbines. Moreover, the synthesis of the controllers is also distributed.
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| 6. |
- Madjidian, Daria, et al.
(författare)
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A Stationary Turbine Interaction Model for Control of Wind Farms
- 2011
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Konferensbidrag (refereegranskat)abstract
- Turbines operating in wind farms are coupled by the wind flow. This coupling results in limited power production and increased fatigue loads on turbines operating in the wake of other turbines. To operate wind farms cost effectively, it is important to understand and address these effects. In this paper, we derive a stationary model for turbine interaction. The model has a simple intuitive structure, and the parameters a clear interpretation. Moreover, the effect of upwind turbines on a downwind turbine can be completely determined through information from its closest neighbor. This makes the model well suited for distributed control. In an example, we increase total power production in a farm, by coordinating the individual power production of the turbines. The example points to an interesting model property: decreasing power in an upwind turbine can lead to a larger and larger increase in available power downwind.
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| 7. |
- Madjidian, Daria, et al.
(författare)
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Distributed Control with Low-Rank Coordination
- 2014
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Ingår i: IEEE Transactions on Control of Network Systems. - 2325-5870. ; 1:1, s. 53-63
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Tidskriftsartikel (refereegranskat)abstract
- A common approach to distributed control design is to impose sparsity constraints on the controller structure. Such constraints, however, may greatly complicate the control design procedure. This paper puts forward an alternative structure, which is not sparse yet might nevertheless be well suited for distributed control purposes. The structure appears as the optimal solution to a class of coordination problems arising in multi-agent applications. The controller comprises a diagonal (decentralized) part, complemented by a rank-one coordination term. Although this term relies on information about all subsystems, its implementation only requires a simple averaging operation.
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| 8. |
- Madjidian, Daria, et al.
(författare)
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Dynamic Power Coordination for Load Reduction in Dispatchable Wind Power Plants
- 2013
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Ingår i: [Host publication title missing]. ; , s. 3554-3559
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Konferensbidrag (refereegranskat)abstract
- In a dispatchable wind power plant, turbines are free to continuously vary their power production as long as the sum of their productions meets the total power demand. Previous research has shown that this freedom can be used to reduce structural loads by allowing turbines in the plant to coordinate their power. This paper explains the mechanisms that make power coordination useful for reducing structural loads on the turbine tower and the low speed shaft. In addition, it assesses the benefits of coordination at different operating points.
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| 9. |
- Madjidian, Daria, et al.
(författare)
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H2 Optimal Coordination of Homogeneous Agents Subject to Limited Information Exchange
- 2017
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Ingår i: IEEE Transactions on Automatic Control. - 0018-9286. ; 62:3, s. 1424-1430
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Tidskriftsartikel (refereegranskat)abstract
- Controllers with a diagonal-plus-low-rank structure constitute a scalable class of controllers for multi-agent systems. Previous research has shown that diagonal-plus-low-rank control laws appear as the optimal solution to a class of multi-agent H2 coordination problems, which arise in the control of wind farms. In this paper we show that this result extends to the case where the information exchange between agents is subject to limitations. We also show that the computational effort required to obtain the optimal controller is independent of the number of agents and provide analytical expressions that quantify the usefulness of information exchange.
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| 10. |
- Madjidian, Daria
(författare)
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Low-Rank Distributed Control with Application to Wind Energy
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis addresses three different topics in wind power plant operation. Most of the research is focused on controlling a wind farm that is required to meet a power set-point. In this mode of operation, the wind turbines are able to vary their power production as long as the total power demand is met. The research investigates how this freedom can be used in order to reduce the fatigue loads experienced by the wind turbines. The problem is studied in a linear-quadratic control setting where the objective is to minimize the total fatigue load experienced by the turbines, while satisfying a requirement on their joint power production. It is shown that, under certain assumptions, the design problem can be drastically simplified. In particular, the computational effort needed to obtain the solution is independent of the number of wind turbines and the only centralized operation required to implement the optimal control law is a single summation. The research also explains the mechanisms that make power allocation schemes useful for load reduction. Part of the research addresses wake effects in wind farms by developing a low-complexity model of the aerodynamic interaction between wind turbines. The model is used in a series of examples, where the wind turbines coordinate their power productions in order to maximize the power production of the wind farm. The examples indicate that the benefit of power coordination increases with the number of turbines in the wind farm. They also identify the underlying mechanisms behind this effect. The last topic of the thesis is to investigate the benefits of using preview of the incoming wind speed in order to reduce structural loads on the wind turbine tower. The main focus is to understand how measurement distortion influences the achievable load reduction as well as the required length of preview. Results from high-fidelity simulations based on real wind turbine measurements indicate that the use of preview can lead to a significant reduction of tower fatigue loads and that the length of preview needed to attain the reduction does not exceed a few seconds.
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| 11. |
- Madjidian, Daria, et al.
(författare)
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Optimal Coordination of Homogeneous Agents Subject to Delayed Information Exchange
- 2014
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Konferensbidrag (refereegranskat)abstract
- We consider a class of large scale linear-quadratic coordination problems where the information exchange is subject to a time-delay. We show that several previously known properties of the optimal solution to the delay-free problem extend to this case. In particular, the optimal control law comprises a diagonal (decentralized) term complemented by a rank-one coordination term, which can be implemented by a simple averaging operation. Moreover, the computational effort required to obtain the controller is independent of the number of subsystems.
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