Research On Vector Control Of The Grid-connected Power Onverter In Wind Power System

Wind power converter as a key component of the wind power system, the controlstrategy is the premise of effective development of wind energy, the use of new energytechnologies. In recent years, with the rise of wind power installed capacity, wind turbineconverter control technology requirements continue to improve. In the doubly-fed windpower systems, wind power converters, including the rotor side converter andgrid-connected power converter can independently control. The doubly-fed wind powersystem low voltage ride through (LVRT) process compared to other types of motor more.Commonly used with rotor crowbar circuit (the crowbar) and in line with the strategy ofdynamic reactive power compensation device (STATCOM) to achieve low voltage ridethrough in double-fed wind power systems. When the Grid is fault, the rotor side converterwill be bypassed by the crowbar circuit, grid-connected power converter can be used as areactive power compensation device to provide reactive power to the grid in order to assistthe recovery of the grid voltage. In this paper, study the vector-oriented control strategyfor three-phase AC system. Study the current decoupling control algorithm of three-phasevoltage source PWM rectifier. When the grid voltage failure, rectifier DC voltage willcontain even-order harmonics, in order to control the stability of the DC voltage. By usingthe method of symmetrical components, analyzed the expression of the active and reactivepower of bridge arm side, deduced a new algorithm for grid current which can be appliedto the extreme unbalance conditions; Rectifier control strategy, in order to improve thebandwidth of current control loop, current loop eliminates the need for positive andnegative sequence power extraction, the current loop controlled by the quasi-resonantregulator and PI regulator with the completion of the DC side voltage loop PI regulator totrack a given voltage. The DC voltage small signal perturbation model is derived by use ofthe mathematical model of the rectifier, and use the bote Figure optimized designparameters of the system regulator. The policy for the control of the grid-connected powerconverter should ensure that the peak amount of current does not lead to false triggering ofprotection devices. At the same time, provide as much as possible reactive power to thegrid. In this paper, given a maximum reactive power algorithm, the maximum peak of the unbalanced current does not exceed the limit value. By injecting the maximum reactivepower to the grid, and ensuring the stability of the DC bus voltage, improved the lowvoltage ride through capability in doubly-fed wind power system. The above controlstrategies have been simulated by using MATLAB / SIMULINK simulation software.Produced a three-phase voltage source PWM rectifier experimental platform basedDSP2812, completed a double-loop control experiment of the rectifier system when thegrid balance, as well as only current-loop control experiments under unbalanced gridcondition. The experiments results verify the correctness of the control algorithm of therectifier control strategy under balanced and unbalanced grid conditions.