阻抗隔离型中压并联式UPS控制策略研究

UPS作为高敏感、大容量负荷的电力保障设备，能在电网受到扰动或发生故障时为负荷提供安全可靠的供电。提出了一种适用于并联连接至中压配电网的阻抗隔离型UPS的控制设计思路。为使UPS外部输出特性兼具响应速度和抗扰性能，内部三相逆变器采用了基于电压控制型虚拟同步发电机技术的功率控制及电压电流双闭环控制，配合电网电压和频率偏差响应，保证负载电压稳定，并实现网侧接近单位功率因数运行；设计了电网故障的隔离及故障恢复后的准同步并网控制策略，实现UPS系统离并网过程的无缝切换。最后在PSCAD/EMTDC上搭建了UPS系统运行的仿真模型，验证了所研究拓扑及控制策略的有效性和可行性。

Control Strategy for Impedance Isolated Medium Voltage Parallel UPS

UPS is the facility for power supply of highly sensitive and large capacity load and can provide safe and reliable power supply when disturbance or fault occurs in power grid. The paper proposes an idea of control design for impedance isolated UPS connected in parallel to medium-voltage distribution network. In order to make the UPS external output characteristics have both response speed and anti-interference performance， power control and voltage and current double closed-loop control based on the control technology of voltage controlled virtual synchronous generator is adopted in the internal three-phase inverter， cooperating with the grid voltage and frequency deviation response， ensuring the load voltage stability， and achieving the operation close to unit power factor on the grid side. In addition， the paper proposes the control strategy for the grid fault isolation and quasi-synchronous grid connection after the fault recovery to realize the seamless switching control of the UPS system between off-grid mode and grid-connected mode. Finally， the simulation model of the UPS system is established based on PSCAD/EMTDC to verify the effectiveness and feasibility of the topology and control strategy.