大规模光伏电站并网的振荡模式分析

随着光伏电站容量的不断增大,其对于电网稳定性的影响也日趋明显。建立了大规模光伏电站并网系统的等值模型,采用特征值法和时域仿真验证其准确性。基于等值模型采用特征值法分析了大规模光伏电站的振荡模式,并研究了光伏逆变器的控制器参数、光伏阵列结构以及交流系统强弱对振荡模式的影响。仿真结果表明:光伏并网系统中主要包含正阻尼的次同步振荡模式和低频振荡模式,其中次同步振荡模式主要受q轴电流PI参数的影响,低频振荡模式主要受外环电压和d轴电流PI参数的影响;光伏阵列结构的变化对系统振荡模式有影响,会使系统中与直流电压相关的模式由非振荡状态变为振荡状态;交流系统变弱会导致振荡模态阻尼减弱,威胁系统的安全稳定运行。时域仿真验证了特征值分析的正确性。

Analysis on oscillation modes of large-scale grid-connected PV power plant

The impact of PV(PhotoVoltaic) power plant on the stability of power system becomes more obvious along with its increasing capacity. An equivalent model of large-scale grid-connected PV power plant is established and its accuracy is verified by the eigenvalue method and time-domain simulation. Based on the equivalent model, the eigenvalue method is applied to analyze the oscillation modes of large-scale PV power plant and the influences of PV inverter controller parameters, PV array configuration and AC system strength on the oscillation modes are also researched. Simulative results show that, the grid-connected PV system mainly contains the positive-damping sub-synchronous oscillation mode and the low-frequency oscillation mode, the former is mainly affected by the PI parameters of q-axis current and the latter by the PI parameters of outer loop voltage and d-axis current; the change of PV array configuration may convert the nonoscillating state of DC-voltage-related system mode into the oscillating state; the weakened AC system may reduce the damping of oscillation modes, threatening the safe and stable system operation. Time-domain simulation verifies the correctness of eigenvalue analysis.