The Research On The Stability Of DC Bus Voltage In AC-DC Hybrid Microgrid

With the development of the global economy, the development and application of renewable energy has become a hot research area in order to solve the problem of energy shortage. Among them, the most representative AC-DC hybrid microgrid is currently the most popular research topic. The stability of AC-DC hybrid microgrid is an important basis to ensure the normal energy exchange and operation control of the whole system. In this paper, the stability of the DC bus voltage of the DC sub network in the hybrid microgrid is mainly aimed at the operation of the islanding mode.This paper proposes the following control strategies according to the stability of the DC bus voltage of AC-DC hybrid microgrid:1. The system is equipped with energy storage unit: Firstly, it is analyzes the mathematical model of battery and draws its working characteristics; Secondly, based on the system equipped with Super Capacitor DC/DC converter of DC bus voltage stability control, it is proposed a based on the power balance with load feedforward battery control strategy. This control strategy assumes that the battery power is kept constant, and as a stable value when the DC bus voltage stabilized instant. According to the principle of conservation of power, the DC bus side capacitor is used as the control object while the load feed forward in order to obtain the DC bus voltage control.2. The system is not equipped with storage unit: Using a voltage droop control method, the reference input current provided by the voltage droop controller and the actual current flows in DC subnet that injected with hysteresis current controller, regulating the duty cycle of the switching signal generated to control the DC voltage.In addition,taking into account the disturbance occurs in the DC subnet, the inverter output power is affected, resulting in deviation from the normal voltage amplitude and frequency. Using an improved V/f control method, this control method can be adjusted to restore normal when the voltage amplitude and frequency deviated.In this paper, the method used is simulated by MATLAB/SIMULINK simulation platform to build the circuit model. The advantages and disadvantages of the method are compared with the simulation results, and the correctness and feasibility of the method are verified.