基于动态相量法的电网换相换流器谐波传递研究

Research on Harmonic Transfer of Line Commutated Converter Based on Dynamic Phasors Method

在高压直流系统中,尤其是电网换相换流器(line commutated converter,LCC)中,由于电力电子器件的非线性特性而产生的丰富谐波,对交直流互联系统的稳定构成了潜在的威胁。首先,在考虑换流变压器连接方式的前提下,通过结合换相过程物理意义进行数学推导,改进电压开关函数,提出一种改进统一的电压电流开关函数,改进后的电压和电流开关函数具有相同的形式,计算时可节约一半的储存空间;然后,基于动态相量使用矩阵运算,提出LCC谐波变换定量分析计算方法,包括LCC特征谐波的计算方法,所提方法可以计算谐波的幅值及谐波的相位,简化计算过程并提高计算精度;最后,将所提方法及相关文献方法的计算结果与PSCAD仿真结果进行比较,证明所提方法有效且精度更高,可作为滤波器设计和谐波传递评估的基础。

The AC-DC interconnection systems face a hidden stability threat, because of the harmonics produced by the power electronics with non-linear characteristics, especially the line commutated converters(LCCs), in the high voltage direct current(HVDC) systems. In this paper, an improved voltage switching function was proposed based on the combination of the physical meaning and mathematical derivation of the commutation process. At the same time, an improved unified voltage and current switching function was proposed with consideration of the connection mode of the converter transformer. Then, a quantitative analysis method was proposed for harmonic transfer of LCC based on the dynamic phasors and matrix calculation. This method can calculate the amplitude and the phase of the harmonics, including the characteristic harmonics. This method not only improves the calculation accuracy but also simplifies the calculation process. Besides, half of the memory storage in the calculation program can be saved due to the unified form of the voltage and current switching function. Finally, the calculation results of this paper and some other related references were together compared with the simulation results of PSCAD. It proves that the method proposed in this paper is effective and more accurate than the others, and thus can be regarded as the foundation of filter design or harmonic transfer estimation.