DefinePK

Abstract

This paper presents a novel seamless switching technology between different operating conditions of the Unified Power Quality Conditioner (UPQC) with the energy storage system. Frequent start and stop of the series inverter will cause shock and loss under the conventional control method. Moreover, it is a key issue to achieve seamless switching when the UPQC operating condition changes. This paper proposes an improved power angle control (PAC) method to solve these problems. An agile power angle is calculated by this method under stable operating conditions. This feature enables the series inverter to share the load reactive power with the shunt inverter. On the other hand, both the series and shunt inverters are in an easy-to-switch operating state which can help achieve better seamless switching between different operating conditions. Simulation results show the shunt inverter capacity can be reduced up to 47% due to the reactive power sharing by both the inverters which means the reactive power burden of the shunt inverter is great lightened. It is also found that the switching time is about 300μs faster and the maximum voltage fluctuation amplitude is about 90V smaller under improved PAC than the conventional control method.