Renewable energy technique is gaining more interest due to increasing demand and threat zero carbon foot prints. The energy from wind has a high potential as a source of energy. The growing demand of wind energy tends to produce a quality output power in terms of grid integration. An appropriate controller is required to control the power produce by the wind energy. A decent number of research publications reports had reviewed maximum power point tracking (MPPT), grid side controller (GSC) and machine side controller (MSC) associated with wind energy conversion system (WECS). However survey on pitch angle based control has not been focused exclusively in any such reviews. A concise review of pitch angle controller, maximum power extraction control and grid synchronisation controller is analysed in this paper. Thus, this paper presents a comprehensive review of overall control strategies for wind energy conversion control. The review paper is intended to provide a suitable reference for further research in the field of wind energy.

Recent developments of control strategies for wind energy conversion system

Renewable energy is being embraced globally as a viable alternative to conventional fossil fuels generators. This is in direct response to the challenge of depleting fossil fuel reserves and its impact on environmental pollution. Wind energy has continued to play a significant role and can be regarded as the most deployed renewable energy source, however the efficiency level and cost effectiveness of a wind turbine (WT) system with regards to wind application is very much dependent on its control. This research paper reviews the various control methods associated with wind energy control. More recently there has been an attempt to review these control techniques but the authors have focused more on the maximum power point tracking (MPPT) techniques and pitch angle control of WTs however discussions around stall control of the WT is not presented in these research papers. This review paper presents a detailed review of the various operational control strategies of WTs, the stall control of WTs and the role of power electronics in wind system which have not been documented in previous reviews of WT control. This research aims to serve as a detailed reference for future studies on the control of wind turbine systems.

An overview of control techniques for wind turbine systems

Evaluating peak-regulation capability for power grid with various energy resources in Chinese urban regions via a pragmatic visualization method

In this paper, supplementary excitation damping control (SEDC) and generator terminal subsynchronous damping control (GTSDC) are designed in a coordinated way to solve the multimodal subsynchronous resonance (SSR) problem in series-compensated transmission systems. Firstly, the basic principle of the combined SEDC and GTSDC scheme for SSR mitigation is explained. Then the task of tuning control parameters of SEDC and GTSDC simultaneously is formulated into a constrained nonlinear optimization problem, in which different operating conditions/disturbances and equipment capacities are fully considered. Next the Genetic Algorithm and Simulated Annealing (GASA) are implemented to solve the problem and the optimal parameters are obtained. Finally, based on a practical system, Shangdu series-compensated system, the effectiveness of the coordinated controller is verified by both eigenvalue analysis and electromagnetic simulation. The results have demonstrated that the proposed method is effective and the optimized control parameters can greatly improve the damping of the three torsional modes.

Coordinated parameters design of SEDC and GTSDC for SSR mitigation

In wind energy conversion system the wind turbine captures the kinetic energy associate with the wind for the production of electricity with the help of generator. Performance of a wind turbine is dependent upon its operating conditions such as wind speed as well as its design parameters such as blade radius, blade pitch angle, weight etc. In the present paper, authors have made an attempt to develop a MATLAB/SIMULINK model of wind turbine. Model as developed is suitable to investigate its performance under constant as well as variable speed mode. Simulated results as obtained are found to be useful to predict the effect of wind speed and blade pitch on the performance of wind turbine under two operating modes.

Behaviour of wind turbine under different operating modes

Due to the complexity and non-linearity of the pitch control system, the pitch angle could not be controlled accurately by traditional PI control. To solve the problem, a prediction-correction pitch control strategy is proposed in this paper. The strategy first processes the wind speed by moving average method, and then gets the prediction value of pitch angle by using wind speed-pitch angle curve-fitting method. Based on this, PI control is used to revise the control error further. At last, the performances of the traditional strategy and the improved strategy are compared by simulation. The results show that the improved strategy can decrease the influence of the wind fluctuation on pitch control effectively. So it can improve the performance of wind generator by capturing maximum wind energy in low wind speed and limiting power output of wind generator in high wind speed.

A new pitch control strategy for variable-speed wind generator

The invention provides an active control method of a doubly-fed wind turbine generator set. The method comprises the following steps that step 1, a wind power plant active control system issues an active power instruction Pgive to the doubly-fed wind turbine generator set; step 2, the actual rotating speed Omega r of the doubly-fed wind turbine generator set is measured, the control modes of the doubly-fed wind turbine generator set are switched, and the active power reference value Pref of the doubly-fed wind turbine generator set is set as different power values according to the control modes; step 3, the maximum operation rotate speed pitch angle control system of the doubly-fed wind turbine generator set is set to adjust the pitch angle based on the comparison value of the actual rotating speed Omega r and the maximum operation rotate speed, and therefore the stable operation of the doubly-fed wind turbine generator set is controlled. Compared with the prior art, the active control method of the doubly-fed wind turbine generator set guarantees flexible switching of the active power control modes of the doubly-fed wind turbine generator set under various wind power input conditions, guarantees stable operation, and plays a pivotal supporting role for the wind power plant to participate in management and running of an electrical power system.

Active control method of doubly-fed wind turbine generator set

Typhoons and other natural disasters affect the normal operation of power systems thus it is an important goal for strong and intelligent power grid construction to improve the ability of power systems to resist typhoons and other natural disasters. Especially, an effective coordinated and optimized dispatching strategy for a multi-source power system is greatly helpful to cope with the impact of typhoons and other natural disasters on power system operation. Given this background, a typhoon wind circle model considering the temporal and spatial distribution of typhoons is established to obtain the input wind speed of the wind farm at first. Second, based on the initial input wind speed of wind farms, a typical scenario set of wind power output is constructed to reflect its fluctuation and uncertainty. Next, an optimal coordinated dispatching model of a multi-source power system with wind, hydro and thermal power based on the conditional value at risk (CVaR) is established with the target of minimizing the total cost of system dispatching, in which a 72 h pre-dispatching mode is studied to optimize the system operation for 72 h on the day before, on and after the typhoon. Finally, a revised 24-node transmission network system in a coastal area with typhoon is served as a case for demonstrating the effectiveness of the proposed model, and the simulation result shows that the proposed model could take the advantages of the coordination and complementarity of multi-sources power system and decrease the total cost of system dispatching and improve the renewable energy consumption level.

Optimal Coordinated Dispatching Strategy of Multi-Sources Power System with Wind, Hydro and Thermal Power Based on CVaR in Typhoon Environment

The integration of large-scale renewable energy has brought great challenges for the control and operation of power systems. In order to accommodate the renewable power as much as possible, the system operators should properly coordinate the conventional generators such hydro and thermal units in the system. In this paper, a peak regulation strategy is proposed for the control of multiple heterogeneous generators to maximize the renewable energy usage ratio in a regional power system. To this end, first the hydro generators is utilized to alleviate the stress for peak regulation due to dramatic fluctuation of the renewable power. Then an optimization model is established with objective function being maximizing the peak regulation capability of the system in a weekly period. The obtained optimal solution of the model can ensure the peak regulation requirement of the system during the whole planning-period while avoiding the frequent switch of on-off operation for the thermal units within the system.

Peak Regulation Strategy of Regional Power Systems for Large-Scale Renewable Generation Accommodation

The invention provides a double-fed wind power plant adaptive reactive power compensation operation method. The method comprises the following steps: the step 1, the reactive power upper limit Qigmax of each wind turbine generator and the reactive power limit Qwfmax of the double-fed wind power plant are acquired; the step 2, the reactive power demand reference value Qdem of the double-fed wind power plant is calculated according to the grid-connected point voltage offset delta U%; the step 3, if the Qdem is less than or equal to the Qwfmax, then the number k of the wind turbine generator subjected to reactive power compensation according to the reactive power demand reference valueQdem, and the reactive power reference value of each wind turbine generator is acquired; the step 4, if the Qdem is greater than the Qwfmax, then the n wind turbine generators are subjected to reactive power compensation at the same time, and the reactive power reference value of each wind turbine generator is acquired; and the step 5, the reactive power reference value is distributed to the wind turbine generator stator side and network side converter respectively to perform reactive power compensation, and then the process returns to the step 1. Compared with the prior art, the double-fed wind power plant adaptive reactive power compensation operation method provided in the invention can be used to reduce the active loss of the wind turbine generators and simplify the power dispatch control system of the wind power plant so as to improve the operation efficiency of the wind power plant.

Dawei Zhao

Papers

A new pitch control strategy for variable-speed wind generator

Active control method of doubly-fed wind turbine generator set

Optimal Coordinated Dispatching Strategy of Multi-Sources Power System with Wind, Hydro and Thermal Power Based on CVaR in Typhoon Environment

Peak Regulation Strategy of Regional Power Systems for Large-Scale Renewable Generation Accommodation

Double-fed wind power plant adaptive reactive power compensation operation method