为了提高光伏并网系统的低压穿越(Low Voltage Ride Through, LVRT)能力,本文将储能系统(Energy Storage System, ESS)和静止同步补偿器(Static Synchronous Compensator, STATCOM)组成新型功率补偿装置STATCOM/ESS引入光伏并网发电系统。当电网侧发生电压跌落时,STATCOM/ESS不但提供的无功功率可以支撑并网点电压,同时吸收多余的有功功率避免对光伏发电系统的危害,电压恢复后将储存的能量返送回电网,高效利用能源。为便于功率双向流动,STATCOM与ESS之间采用双有源主动桥(Dual Active Bridge, DAB)直流变换器连接。针对DAB变换器,本文提出一种改进的双移相控制策略,来减小DAB变换器的回流功率。仿真结果表明,本文提出的控制策略在一定范围内将回流功率限制为零,显著提升光伏并网系统的低压穿越能力,提高光伏并网系统的稳定性,具有良好的灵活性和优越性。
英文摘要:
In order to improve the low voltage ride through (LVRT) capability of the grid-connected PV system, this paper introduces a novel power compensator STATCOM/ESS which consists of a static synchronous compensator (STATCOM) and an energy storage system (ESS) to the system. When the grid voltage drops, the STATCOM/ESS not only supplies reactive power to support the voltage of grid connection point, but also absorbs active power at the same time to avoid damaging to the PV system. After voltage recovers, it will return energy stored in ESS to system. To achieve power bidirectional flow, a dual active bridge DC/DC converter is used to connect STATCOM and ESS. For the DAB DC/DC converter, an improved double phase shift control strategy is proposed to reduce the backflow power of it. Simulation results show that the control strategy proposed in this paper is able to limit the backflow power to zero, improve the LVRT capability of PV system significantly, contribute to stability of grid and has the feasibility and the superiority.