The Coordinated Control Strategy Of Multivariate Composite Energy Storage System In Micro-grid

In recent years, new energy power generation technology and micro-grid technology have been rapidly developed because of its advantages of full utilization of renewable energy, clean and environmental, economic and efficient.However, the current development of micro-grid technology is not mature and there still exists many technical problems in the aspects of the grid-connected control, switching between island and grid-connected mode, energy storage system and relay protection. It has a great role in the development of the micro-grid technology to study and solve these problems, and what is more, it is of great significance to solving the problem of energy crisis, protecting the ecological environment and maintaining the security and stability of power grid. So the control problem of storage system which is composed of battery and super capacitor in micro-grid is studied in this paper, it proposed a coordinated control strategy of multivariate composite energy storage system. The strategy is helpful to avoid the impact and adverse effects of intermittent power on the main grid, ensuring the operation of micro-grid security, reliability, stability and economic.When micro-grid operates in grid-connected mode, power-current double loop control method is used by battery and super capacitor. Calculate the unbalanced power between load and PV power, and then the unbalanced power is decomposed into high frequency component and low frequency component using a filter. And the two component of power are compensated respectively by super capacitor and battery(main grid). Considering the state of charge and the overcharge and over discharge in energy storage at the same time, it proposed a coordinated control strategy of multivariate composite energy storage system for grid-connected operation mode, the control strategy can not only stabilize the impact of intermittent power on the power grid, ensuring the quality of electric energy, but also help to reduce the battery charge and discharge conversion times and prolong the life of battery and super capacitor.When in island operation mode, the battery adopts voltage-current double loop control and the super capacitor control method does not change. The same as in grid-connected operation mode, calculate unbalanced power and decompose it into high frequency component and low frequency component using the filter.The components are compensated respectively by the super capacitor and thebattery. Considering the state of charge and the overcharge and over discharge in energy storage at the same time, it put forward the coordinated control strategy of multivariate composite energy storage system for island operation mode. The strategy can maintain stable operation of micro-grid, stabilize the intermittent power supply shocks, ensure the power quality in micro-grid, also it reduces the charge and discharge conversion times, avoids overcharge and over discharge, and prolong the energy storage service life.In the island operation mode of micro-grid, it put forward two kinds of methods of starting the motor. One is an improved control method based on inverter and APF, the improved control algorithm is simpler.The other is based on multivariate composite energy storage system, it fully utilizes the characteristics of the energy storage system, introduces no harmonics, adds no equipments, and it helps to increases economic benefits of the micro-grid.Finally, build the simulation models using MATLAB/SIMULINK to verify the proposed control strategy and the motor starting control strategy. The simulation results prove the rationality and validity of the control strategy.