背靠背变流系统中优化前馈控制策略的研究

在背靠背变流系统中,直流母线电压受负载和电网等因素的影响而上下波动,这极大影响了系统的安全可靠运行。为了抑制直流母线电压的波动,提高系统动态响应能力,文中采用小信号模型的分析方法,分析了传统前馈控制策略提高母线电压动态响应的原理以及优缺点,提出了一种优化的前馈控制策略,不仅抑制了由负载和电网变化引起的母线电压波动,使系统的动态响应能力得到了提高,而且应用状态观测器取代电流传感器对负载电流进行测量,降低了成本并解决了电流传感器给系统带来的各种问题,提高了系统的稳定性。最后,仿真结果和基于4kVA实验平台的试验结果都证明了该控制策略的有效性。

Study of the Optimum Feed-forward Control Strategy in Back-to-back Converter System

In back-to-back converter system, dc-bus voltage usually fluctuates as the variation of motor speed and grid voltage, which makes it impossible for system to run safely and sysbly. In order to restrain dc-bus voltage fluctuation and improve system transient response, the principle of the conventional power feed-forward control strategy on improving dc-bus voltage transient response is analyzed, and points out advantages and disadvantages of this control strategy by using the technology of small-signal model. Then, an optimum feed-forward control strategy is presented. By using this control strategy, dc-bus voltage is immunized from not only variation of motor speed but also variation of grid voltage, and the transient response of system is improved. In addition, this control strategy replaces a current sensor with the state observer to measure load current, which saves system cost and solves many problems produced by current sensor and increases the stability of system. Finally, it is verified by both simulated results and experimental results in a 4kVA laboratory prototype system.