Study On The Control Strategy Of The Hybrid Energy System

The distributed generation is intermittent and randomness. So the grid will be incorporated and the bus voltage will be fluctuated in the integration process. Adding the energy storage device is one of the effective ways to solve this problem. The hybrid energy storage system which consists of super capacitors and all vanadium redox flow battery(VRB) can reduce the impact of energy imbalance on the grid. And the hybrid energy storage system has longer life and faster response to power fluctuations.Firstly the paper introduces the works of the photovoltaic cells, super capacitors and all vanadium redox flow battery. And the circuit models of each unit are established. The energy storage system consists of the all vanadium redox flow batteries and super capacitors. The paper discusses several basic parallel topologies and analyzes the characteristics of various topologies for the hybrid energy storage system. And the dispatchable distributed power structure is designed.Secondly, the low-pass filtering with compensation coefficients for power distribution is discussed in the paper. Multi-mode switching control strategy is used to mobilize energy which is based on the different states of charge of the energy storage unit and the DC bus voltage. The terminal voltage pre-control algorithm of super capacitors is added to prevent the transient pulse and the influence on the life of VRB.Finally the compensation filter coefficient low-pass filtering algorithm is simulated and compared with the general filtering algorithm in the paper. The control strategy of the analog multi-mode switching is simulated and verified with the simulink/ stateflow.The simulation results show that low-pass filtering algorithm with the band filter compensation coefficient can follow changes more quickly in the power distribution and shorten the reaction time. Multi-mode switching control strategy can be used to response to fluctuations in load power to achieve energy scheduling and stabilize the DC bus voltage. The paper establishes the dual-loop control system of VRB. And the simulation results show the feasibility of the control method.