Research On Energy Balance Control Strategy Of Chain Energy Storage System

Renewable energy output has the disadvantages of volatility and intermittence,and direct grid connection will have a serious impact on the grid.As an effective way to solve the problem of renewable energy grid connection,cascaded H-bridge(CHB)energy storage system can provide backup capacity to achieve the dynamic power dispatch balance of the grid.However,the DC side of cascaded H-bridge energy storage converter is independent of each other,which is prone to generate the problem of energy imbalance in the storage and release of energy.Therefore,this paper takes the cascade H-bridge energy storage converter based on super capacitor as the research object,and puts forward reasonable grid-connected control strategy and energy balance control strategy for the above-mentioned problems.Aiming at the grid connection control of cascaded H-bridge energy storage converter,this paper first analyzes the working principle of cascaded H-bridge energy storage converter by taking the single-phase equivalent circuit of cascaded H-bridge as an example.The mathematical models in abc,αβ and dq coordinate systems are established,and the expressions in complex domain are derived.On this basis,the proportional complex integral controller is introduced into the grid connected control of cascaded H-bridge energy storage converter,and its control equation in αβ coordinate system is derived.The control effect is compared with PI controller in dq coordinate system.Analysis and simulation results show that the controller has better tracking performance.Aiming at the energy balance control strategy of the energy storage unit of cascade H-bridge energy storage converter,this paper first analyzes the causes of the energy imbalance of the energy storage unit,and then analyzes the traditional energy balance control method.The solution of energy balance problem is obtained.Based on this,an energy balance control strategy with balance coefficient is proposed.The control strategy is studied by taking the inter phase energy balance as an example,and the detailed theoretical derivation and analysis are carried out.The calculation formula of the relevant parameters of the control strategy is given.Finally,compared with the traditional energy balance control strategy,the simulation results show that the control strategy is easy to implement and has short equalization time.Finally,according to the relevant criteria,this paper designs the main power circuit board,sampling circuit board and other parts of the hardware circuit,using RT-LAB as the controller of the system,completed a small experimental prototype.The prototype is used to verify the proposed grid connection control strategy and energy balance control strategy.The experimental results are consistent with the simulation results,which verify the correctness and effectiveness of the proposed control strategy.