基于虚拟直流发电机的风储直流微电网控制策略研究

Research on Virtual DC Generator-based Control Strategy of DC Microgrid with Wind/Energy Storage

为了提高风储直流微电网的惯性,提出了一种基于虚拟直流发电机的风机后级变换器控制策略,建立了风力发电系统和储能系统小信号模型,得到了风储直流微电网的小信号模型以及蓄电池充、放电模式下的阻抗比表达式。并在转动惯量变化范围内选取典型值代入到阻抗比表达式中进行了计算和分析,揭示了微电网的基本特性及转动惯量对微电网稳定性的影响。以直流母线电压波动范围最小和系统动态响应时间最优为多目标,给出了粒子群优化求解算法及流程,进而求得了系统的最优转动惯量。不同工况下的仿真结果表明,所提控制策略不仅可以在风机最大功率和限功率跟踪模式下提高系统惯性,还可以在负载和风速变化时使母线电压的波动范围达到最小,实现了系统的优化运行,从而验证了所提控制策略的正确性和可行性。

In order to improve the inertia of the DC microgrid with wind/energy storage, the back stage converter control strategy of the wind turbine based on virtual DC generator(VDG) is proposed in this paper. A small-signal model of DC microgrid with wind/energy storage is established and an expression of impedance ratio under the charging and discharging modes of battery is obtained. In the range of the moment changes of inertia, some typical values are substituted into the impedance ratio expression for calculation and analysis to reveal that the basic characteristics of mircogrid and the influence of the moment of inertia on stabilization of DC microgrid. In order to minimize the deviation values of the bus voltage and system dynamic response time, the particle swarm optimization solution algorithm(PSO) and flow chart are proposed, and then the optimal moment of inertia is obtained. Simulation results under different working conditions show that the control strategy in this paper can not only improve the system inertia on maximum power point(MPPT) and load power tracking(LPTC), but also minimize the fluctuation of DC bus voltage when the load and wind speed change and the optimal operation of this system can be realized, thus the correctness and feasibility of the proposed control strategy are verified.