Research On Technology Of Seamless Switch Based On Power Angle Control In UPQC

With the rapid development of the national economy,the requirements for power quality in all walks of life are getting higher and higher.In the case of the increasingly complex power load structure in China,how to ensure the supply of high-quality power to the user side and effectively control the pollution introduced by nonlinear and impact loads has important practical significance.So the Unified Power Quality Conditioner(UPQC)with energy storage device is taken as the research object,and the seamless switching technology between different working conditions is studied.Firstly,in view of the low utilization rate of UPQC series compensator in the traditional control strategy,the agile power angle control method under stable operating conditions is studied.By reasonably distributing the power output of the series and parallel compensators,the series compensator is controlled to share the partial reactive power of the load,and the series compensator function reuse is realized.Thereby making full use of the series compensator capacity,and reducing the reactive load of the parallel compensator to a greater extent.Secondly,in order to realize the seamless switching of UPQC between different operating conditions,a principle of determining the one-half of the agile power angle is proposed.The control string and the parallel compensator are in an easy-to-switch operating state,thereby reducing the shock and loss that the series compensator may accompany during the multiple start and stop processes in the conventional control,and providing a necessary premise for smooth switching between different operating conditions of the device.Furthermore,based on the mathematical model of each unit of the system,based on the principle of the equivalent output capacity of the parallel compensator,the energy coordination control method of UPQC is studied.The coordinated control of the energy storage unit is used to effectively alleviate the energy on the DC bus and in the case of voltage interruption,it can guarantee uninterrupted power supply to the load.Finally,the MATLAB simulation model of the UPQC system with energy storage unit is built,and the compensation effect is simulated and verified under different operating conditions.The simulation results show that the seamless switching strategy based on power angle control proposed in this paper can make greater use of the capacity of the series compensator,and UPQC can achieve smooth and seamless switching between different grid operating conditions.