基于有功自适应调整的光伏电站无功电压控制策略

Voltage/var Control Strategy of PV Plant Based on Adaptive Adjustment of Active Power

光伏逆变器的无功电压控制在解决并网光伏发电系统电压越限问题时取得了很好的效果,但目前为了保证光伏的消纳能力,相关研究主要集中在单一的无功电压控制方面,无法满足电网出现较大无功缺额时的安全稳定运行需求。因此,根据光伏逆变器输出无功和有功的关系,提出一种基于有功自适应调整的无功电压控制策略。光伏逆变器正常工作在最大功率点跟踪控制模式下,若并网点电压越限,考虑各个光伏集群无功调压能力的差异性,采用无功变下垂控制为电网提供相应的无功功率,实现各个光伏集群无功分配的协调控制。在逆变器的无功容量不足时,根据优先级削减部分光伏输出的有功功率,以满足系统的无功需求。在夜晚或系统无功缺额较严重时,光伏逆变器作为静止同步补偿器(static synchronous compensator,STATCOM)运行。最后,在PSCAD/EMTDC仿真平台上,搭建并网光伏发电系统的模型,验证所提策略的有效性。

The reactive power and voltage control of photovoltaic inverters achieves good results in solving the voltage violation problems of grid-connected photovoltaic power generation system. However, in order to ensure renewable energy accommodation, relevant researches mainly focus on simple voltage/var control, which cannot meet the requirements of safe and stable operation for power grid when a large reactive power vacancy occurs. Therefore, based on the relationship between reactive power and active power of PV inverter, this paper proposes a voltage/var control strategy of PV inverter based on adaptive adjustment of active power. Normally, PV inverter operates in maximum power point tracking(MPPT) control mode. Variable droop control for reactive power is adopted to provide corresponding reactive power when voltage at grid-connection point is beyond limit, during which the difference of reactive power and voltage capabilities for PV cluster is taken into consideration. When the reactive power capacity of PV inverter is insufficient, the active power output of PV is adjusted adaptively to meet the reactive power demand of the system. The PV inverter operates as static synchronous compensator(STATCOM) at night or when the problem of reactive power vacancy is severe. The results of simulation carried out on PSCAD/EMTDC demonstrate validity of the proposed control strategy.