低压微电网逆变器频率电压协调控制

Improved PV Control of Grid-Connected Inverter in Low Voltage Micro-Grid

近年来,分布式发电(Distributed Generation,DG)技术发展迅猛,DG结合本地负载、储能设备等可构成微电网,微电网能够在并网模式与孤岛模式下运行。并网时,DG输出给定的功率,实现能量管理;孤岛运行时,要求DG维持微电网电压和频率稳定。因而微网中逆变器的控制尤为重要。由于传输线阻抗特性不同,本文在低压系统中应采用PV下垂控制,PV下垂控制能够实现孤岛运行时不同DG均分负载,但它是有差调节,电压和频率会存在较大的偏差。本文提出一种改进的PV下垂控制(NPV):加入电压和频率偏差的前馈调节,可实现电压和频率的二次调节。以微电网脱网运行的稳态以及暂态情况分析为例,通过PSCAD仿真以及实验,验证了NPV不但可以实现并网时的能量管理而且还实现了孤岛运行过程中电压和频率的二次调节。

With the increasing acceptance,micro-grid,combined with distributed generation（DG）,may be operated in grid-connected mode or islanding mode.In grid-connected mode,energy management is the main control objectives.While in islanding mode,to maintain voltage and frequency stable is the key point.Taking line impedance into account,PV droop control should be adapted in low voltage system.The PV droop control can share active and reactive power in islanding mode,but it will bring a great offset in voltage and frequency.The article proposes an improved opposite droop control（NPV）： By adding feed-forward control to given power,secondary regulation of the voltage and frequency can be achieved.The NPV managed to do the job of both energy management in grid-connected mode and the secondary regulation of voltage and frequency in islanding mode.The results have been validated through simulations by PSCAD software and experiments.