基于网压预测的并网换流器前馈控制

Feed-forward control for grid-connected converter based on grid voltage prediction

在换流器控制中,直接电压前馈被广泛用来抑制电网电压畸变.但系统中的延时环节导致前馈电压和实际电压并不同相,严重影响了电压畸变抑制效果.为了减小延时环节对直接电压前馈性能造成的影响,提高抑制电网电压畸变的能力,提出了基于网压预测的前馈控制方法.利用上一周波的电压采样值来预测PWM装载时刻的实际电压值,保证了前馈电压和实际电网电压较好的同相性.仿真和实验结果表明:采用预测电压进行前馈控制,将3、5、7、11次谐波电压抑制能力由94%、84%、72%、42%提高到99%、97%、94%和85%,提高了电网电压畸变时换流器的输出电流质量.

The direct voltage feed-forward control is used in converter control to suppressing the grid voltage distortion. But the delay in the system makes the feed-forward voltage be out of the phase with the actual grid voltage. So the effect of suppressing the voltage distortion is seriously affected. In order to decrease the influence of the delay on the direct voltage feed-forward control,and improve the suppression ability of voltage distortion,the feed-forward control based on grid voltage prediction is proposed aiming at the periodic voltage distortion. The actual grid voltage magnitude at the PWM loading moment is forecasted by using the sampled grid voltage magnitude in previous power frequency periodic,and the better synchronization between the feed-forward voltage and the actual grid voltage is guaranteed. The simulation and experimental results verify that the inhibition rates at frequencies of 3rd,5th,7th,and 11 th voltage harmonics are improved from 94%,84%,72%,42% to 99%,97%,94%,85%,by the feed-forward control based on grid voltage prediction,and the output current of the converter can be improved when the grid voltage is distorted.