三相光伏并网发电系统无功控制策略研究

Study of reactive power control strategy for three-phase PV grid-connected power system

三相光伏并网发电系统通常采用单位功率因数控制,一般情况下只为电网提供有功功率,并保证其具有较高的功率因数。为了提高光伏并网发电系统故障时的无功电压控制能力,首先在直流电容侧加入DC-Chopper来抑制故障情况下直流母线电压的大幅波动,使光伏逆变器能够工作在安全稳定的范围内,接着采用将无功功率补偿与光伏并网发电相结合的控制方式,使光伏并网发电系统在向电网提供有功功率的同时也能够为电网提供所需的无功功率。然而光伏并网发电系统自身无功补偿能力有限,装设STATCOM将使系统的无功电压控制能力得到了进一步的提高。

Three-phase photovoltaic（PV） grid-connected power system usually use the unit power factor control. In general, PV system provides active power to the grid with a high power factor. In this paper, during the period of grid fault, in order to improve the capability of reactive power and voltage control for PV system, DC-Chopper was used at the side of DC-link first. The DC-Chopper could suppress the DC voltage fluctuation and make PV inverter work in the condition of safety and stability. The control mode of PV system had combined power generation to grid with reactive power compensation. At the same time of providing active power to the grid, PV system could also provide the required reactive power to the grid. However, the capacity of reactive power compensation for PV grid-connection system was limited. Installing STATCOM would further improve the system capability of reactive power and voltage control.