基于电压扰动源的并网逆变器输出阻抗测量方法

Measurement Method of Inverter Output Impedance Based on Voltage Disturbance Source

并网逆变器输出阻抗是判定其并网运行稳定性的重要参数,通常采用谐波电流注入法测量。但由于并网逆变器本身存在背景谐波,会影响测量结果的准确性,采用非整数谐波的偏频电流注入方法能够有效避免该问题。然而,由于实际电网运行频率在一定范围内波动,采用谐波电流源注入非整数次谐波电流时存在难以同步的问题,从而造成测量误差。针对以上问题,该文利用电压扰动与电流扰动两种阻抗测量方法的等效性,提出通过同一台电压扰动源产生基频及非整数次谐波电压进行逆变器阻抗测量的方法,以提高阻抗测量的准确性,最后通过插值获取逆变器全频段阻抗。实时数字仿真结果证明了所提测量方法的有效性和可行性。

The output impedance of a grid-connected inverter is an important parameter to determine the stability of its operation in the grid. It is usually measured by the harmonic current injection method. However, the background harmonics of the inverter may affect the accuracy of measurement results. The non-integer harmonics current injection method can effectively avoid this problem. Since the actual grid operating frequency fluctuates within a certain range, it is difficult to synchronize when using a harmonic current source to inject a non-integer harmonic current, and the method may cause measurement errors. Aiming at the above problems, this paper uses the equivalence of voltage disturbance and current disturbance, and proposes a method to measure the impedance of inverters by a voltage disturbance source. The voltage disturbance source can generate the fundamental frequency and non-integer harmonic voltage to measure the impedance of the inverter, and hence the accuracy of the impedance measurement is improved. The full-band impedance of the inverter is obtained by interpolation. The proposed measurement method is verified by the real-time digital simulation.