基于小交流信号注入的接口变换器二次控制方法

The secondary control method for interface converter based on small AC signal injection

在交直流混合微网中,双向接口变换器是连接交流子网和直流子网的桥梁,对系统的安全稳定运行和功率的合理分配起着举足轻重的作用。目前,双向下垂控制方法广泛用于双向接口变换器的控制中,它是通过检测直流母线侧电压和交流母线侧频率来反映直流子网和交流子网的功率需求,进而控制功率的流动。然而,这种方法会使变换器输出的电压和频率存在偏差。在实际中,每个变换器的参数和输出阻抗也不会完全相同,这也会造成功率在并联变换器之间难以精确分配。为了解决以上问题,在双向下垂控制的基础上,提出了小交流信号注入的新型二次控制方法。在该方法中,小交流信号在并联的各变换器之间如同一种通信信号,其频率与接口变换器输出基波电压的下垂偏置成下垂关系,可以使变换器输出的电压和频率恢复到额定值,也可以实现并联变换器之间的功率精确分配。Matlab/Simulink仿真结果验证了所提控制方法的有效性。

In AC/DC hybrid micro-grid,the bidirectional interface converter plays an important role in the stable operation and power distribution of the system as a bridge connecting the AC and DC subnet.At present,the bidirectional droop control method,which uses DC bus voltage and AC bus frequency to measure the power demand of DC and AC micro-grid and control the power flow,is widely used in the control of bidirectional interface converter.However,this method can make the voltage and frequency of the converter output deviate.Meanwhile,the parameters and output impedance of each converter will not be exactly same in practice,which will also cause the power distribution between the parallel converters is not accurate.In order to solve these problems,a second control method by small AC signal injection is proposed.The relationship between the frequency of small AC signal and the droop offset of the fundamental voltage of the interface converter are drooped and the small AC signals are used as communication signals among parallel converters.The method can restore the voltage and frequency of the converter output to the rated value,and the power between the parallel converters can be precisely distributed.Matlab/Simulink simulation results verify the effectiveness of the proposed control method.