小容量同步发电机组谐波特性分析

Analysis of the Harmonics Characteristic of the Synchronous Generator in Short-Capacity System

相对于大电网,小容量系统惯性小、承受扰动的能力弱,因此小容量同步发电机组受谐波影响较大。为揭示谐波的作用机理,从注入谐波电流后电机内部的电磁关系变化入手,描述了谐波电流形成的旋转磁场与基波磁场叠加后的形态。进而分析了谐波电流对发电机输出电压的影响,并运用瞬时功率理论推导了谐波转矩的解析式,指出了发电机组转轴机械振动的原因。进行了柴油发电机组带非线性负载的实验,观察了机组在谐波影响下的运行状态,实验结果与理论分析一致。

Compared with the power grid, the short-capacity system has smaller inertia and weaker resistance to disturbances. As a resuh, the synchronous generator in the short-capacity system can be severely influenced by harmonies. To reveal how harmonics influence the generator, this paper begins with studying the change of electromagnetic relations of the generator with injection of the harmonic current, and depicts the rotating track of the magnetic field when the harmonic current is superposed to the fundamental current. On this basis, it studies how the harmonic current affects the output voltage. Furthermore, it deduces a formula that can describe the electromagnetic torque pulsation by the theory of Instantaneous Power which explains why the generator shaft vibrates. Finally, an experiment is made on the diesel generating unit with the non-liner load. The conclusion from the experimental resuhs is consistent with the theoretical analysis.