Studies on Characteristics of Power System Composed of Various Power Sources with Electronic Power Conversion

1. 如果逆变器的容量与电力系统的容量相比不能小到不可忽略的程度，逆变电源会影响互联电力系统的动态性能。假设一个由同步发电机和容量相当的逆变电源组成的供电系统，通过计算机仿真和仿真实验，研究了在直流输出功率变化和负载变化情况下，系统的频率变化和电压变化等动态性能。仿真和实验结果表明，同步发电机的频率控制机构（调速器）和逆变器的电压、相角控制方案主要决定了同步发电机的动态性能。如果一个地区的电力主要由逆变电源供电，在与主电力系统断开的情况下，可以继续供电。为了使无同步发电机的逆变器组成的孤岛电网运行，需要开发一种新的逆变器频率控制和负荷分担方案。在本研究中，提出了一种用于此目的的控制算法，并通过瞬态仿真验证了其有效性。结果表明，只要控制系统设计合理，在负荷变化和区域断开等瞬态情况下，频率和负荷分担都能得到很好的控制。

1. Inverter power sources can affect the dynamic performance of the interconnected power system, if the capacity of inverters is not negligibly small compared with that of the power system. A power supplying system composed of a synchronous generator and an inverter power source of comparable capacity was assumed, and examined was its dynamic performance such as frequency variation and voltage variation in case of dc output power change and load change via computer simulations and simulated experiments. From the results of simulations and experiments, it was found that the dynamic performance is mainly governed by the frequency control mechanism (governor) of the synchronous generator and the voltage and phase angle control scheme of the inverter.2. If an area is largely supplied electric power by inverter power sources, power supply can be continued in case of disconnection from the main power system. For the operation of islanded power network composed of inverters without a synchronous generator, a new frequency control and load sharing schemes for the inverters should be developed. In the present study, a control algorithm for that purpose was proposed, and its validity was examined via transient simulations. From their results it was found that the frequency and load sharing are adequately controlled under transients such as load change and area disconnection, if the control system is designed rightly.