Low voltage ride-through control method of permanent magnetic direct drive wind power system under unbalanced network voltage

Abstract

The invention relates to a low voltage ride-through control method of a permanent magnetic direct drive wind power system under unbalanced network voltage. The control method includes the concrete steps that first, the phase theta and the phase theta<n> of positive and negative sequence voltages are acquired; second, through the positive and negative sequence voltage phases, voltages and currents of a three-phase network are converted in a dq coordinate system, and positive and negative sequence voltages and currents in the dq coordinate system are obtained; third, through the positive and negative sequence network currents and parameters of a network connection reactor, the active power consumption direct current component deltaP<0>, the cosine component deltaP<c2> and the sine component deltaP<s2> on the network connection reactor are calculated; fourth, the reference value of the direct current component of active power output by an inverter and the reference value of the direct current component of reactive power output by the inverter are acquired; fifth, through the obtained reference values of power, the positive and negative sequence components of the output current of the inverter are calculated; sixth, switching signals are obtained through the positive and negative sequence components of the output current, and the output current and the output power of the inverter are controlled through the switching signals. Compared with the prior art, the low voltage ride-through control method of the permanent magnetic direct drive wind power system under unbalanced network voltage has the advantages of being efficient, easy and convenient to operate and the like.

Description

technical field [0001] The invention relates to a control method of a wind power system, in particular to a low voltage ride-through control method of a permanent magnet direct drive wind power system under an unbalanced grid voltage. Background technique [0002] As the power of wind farms connected to the grid continues to increase, the interaction between wind farms and the grid is increasing. In order to improve the stability and power quality of the grid, the grid puts forward a series of requirements for the grid connection of wind farms, including Low voltage ride through requirements. [0003] The permanent magnet direct drive synchronous wind turbine with full power converter connected to the grid realizes the complete decoupling of the wind turbine from the power grid, flexible control, and the low voltage ride-through ability can be greatly improved through reasonable control. [0004] Unbalanced grid voltage can be caused by unbalanced grid faults or loads, non-...

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Problems solved by technology

But for megawatt-class wind turbines, the switching frequency of the full power converter is low (about 2kHz), and the inductance value of the grid-connected reactor is relatively large, so ignoring the power fluctuation on the grid-connected reactor will have a negative impact on the control effect. to adversely affect

Yongsug Suh introduced the network side change in "Control scheme in hybrid synchronous stationary frame for PWM AC-DC converter under generalized unbalanced operating conditions" and "Modeling and Analysis of Instantaneous Active and Reactive Power for PWM AC / DCConverter Under Generalized Unbalanced Network" respectively. Although the output voltage variable of the bridge arm of the converter can eliminate the double frequency component of the DC terminal, the control system is complicated

Liao Yong, Zhuang Kai, and Yao Jun proposed a control strategy that considers the power fluctuation on the grid-connected reactor and introduces feedforward into the voltage outer loop in "Control Strategy of Full-power Wind Power Grid-connected Converter When Grid Voltage is Unbalanced" , but the calculation process is complicated

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