组合式三相逆变器软硬件限流保护策略

A Hardware and Software Current Limit Protection Strategy for the Combined Three-Phase Inverter

针对中低压大电流应用场合,提出了组合式三相逆变器的拓扑结构,并建立了旋转坐标系(简称dq坐标系)下的模型。对常用几种限制电流方法进行了对比分析,提出了一种基于电流瞬时值的硬件电路封锁和基于电流平均值的软件限流相结合的限流策略。利用硬件电路动作快,迅速将电流降到一定的范围,再在TMS320LF2407控制芯片上实现软件限流。由于软件限流中前后几个基波周期的电流误差大小不同,采用分段调节,更好地保证其快速性。考虑在过载的极端即短路情况下,在400kVA/50Hz的样机上进行了实验。实验结果表明该方法保证安全运行的同时,又改善了波形动态性能和减小了波形的畸变。

For the medium or low voltage and high-current applications, the topology of combined three-phase inverter is presented and its mathematical model in rotate dq coordinate system is built. Several current-limiting methods that used commonly are compared and analyzed, and then the hardware blockade current-limiting strategy based on temporary current combined with software current-limiting strategy based on average current is put forward . Using fast response of hardware circuit, the current is reduced fast to a certain scope. Then, software current-limiting is working by TMS320LF2407 DSP control chip. Because of the differences between the current error values in first and last several fundamental cycles when using software current-limiting, parted adjustment is employed to ensure well fast response speed. Considering the extreme overloaded circumstances ---short-circuit, experiments are carried out on the 400kVA/50Hz experimental machine. The experimental results show that the method not only ensures safe operation, but also improves dynamic performance and reduces the distortion of the waveform.