Reactive Power Optimization Scheme Of Double Fed Wind Power System Based On Indirect Matrix Converter

The two-stage matrix converter has sinusoidal input current and output curren and no intermediate large capacitance,so it is suitable for doubly-fed wind power generation system.In the past,the matrix converter is simply applied to doubly-fed wind power generation system,and the influence of the characteristics of matrix converter on doubly-fed wind power system is seldom discussed.For doubly fed wind power system based on matrix converter,the total reactive power emitted by the system is equal to the sum of input reactive power of matrix converter and stator reactive power.Because the input and output of the matrix converter are directly coupled and the input reactive power of the matrix converter is affected by the output side,so the operation state of the wind power system will also influence input reactive power of the matrix converter.In this paper,the reactive power control range of doubly-fed wind power system based on matrix converter is studied,and the reactive power regulation ability of doubly-fed wind power system is fully excavated,so as to support the grid voltage and improve the power quality.Firstly,the maximum wind energy capture principle of doubly-fed wind power generation system,the working principle and the power relationship under different working conditions are analyzed,and the mathematical model in the two-phase synchronous rotating coordinate system is derived.Based on this model,a double closed loop control system with rotor angle velocity and stator reactive power as outer loop and stator current as inner loop is established by using vector control method of stator voltage orientation.Then,by studying the reactive power characteristics of doubly-fed wind power system based on traditional space vector modulation,it is found that the limit of input reactive power of matrix converter is limited by the range of input power factor angle.The total reactive power output capacity of the system is further limited.In order to solve the above problems,by analyzing the constraint relationship between input reactive power and stator side reactive power of matrix converter,the optimization problem of total reactive power of maximized system is proposed in this paper.Secondly,two-vector modulation strategy and three-vector modulation strategy based on space vector combination are adopted for matrix converter.These two methods can further reasonably plan duty cycle and reduce redundant switching state.It is beneficial to enlarge the input reactive power range of matrix converter.Then,under different power conditions,the stator reactive power and input reactive power of matrix converter are optimally allocated by numerical optimization method,and then the reactive power control range of doubly-fed wind power generation system is extended.Finally,the correctness of the above scheme is verified by simulation.