The Research Of Restraining Load Current Disturbance Method In Micro-Grid With Multi Parallel Connected Inverters

Distributed generation technology makes power device directly arranged for power generation in load field or adjacent point,which let generation mode becomes more efficient and flexible,and so that the new energy sources has been widely and deeply used. However, distributed generation has some limitations, such as the single equipment costs highly, the connection of power grids will cause certain negative effect on power grid. Micro-grid based on distributed generation technologies integrate the concentration of user demand and random distribution of renewable energy characteristics to well together. That is an important direction of the future development of smart grid technology.Micro-grid power as a locality generation system, which has run the grid-connected and islanded modes. When the micro-grid operating in island mode, the frequent switching of load and connecting nonlinear load lead to the power quality problems like voltage fluctuation and harmonic current increasing in micro-grid. Therefore, the research of restraining method for disturbance of load current is of great significance. The main contents of this paper are presented below:(1) Firstly, the overall framework of micro-grid system is analyzed and developed, and topological structure of single-phase photovoltaic inverter is identified. The droop control method on micro-grid island operation is presented further. Then focus on the analysis of feedback points in LC filter closed-loop control as well as the traditional multi-loop feedback controller. The simulation of traditional control method on the condition of linear and nonlinear load is carried out.(2) Aiming at the disturbance of load current in micro-grid, accuracy reduction of power share between parallel inverters, and the distortion rate raise of voltage, a robust voltage control method of restraining load current disturbance is proposed. Frist, the forward compensation of reference voltage as controller is introduced to realize order reduction of closed-loop control system. Then load current compensation brought in controller slickly, which settles the effect from load current disturbance for closed-loop control system. Meanwhile, the stability of control method this paper proposed is analyzed in frequency domain, and control effects of two voltage compensations are discussed. In the end, the simulation of robust voltage control method of restraining load current disturbance on the condition of linear and non-linear load is verified.(3)The system hardware and software parts are designed. The key components of inverter are introduced in particular for the hardware module and software process. Then the controlled method is tested in experiment, which is matched with the simulating results. The results have verified the robust voltage control method of restraining load current disturbance enhance the micro-grid voltage robustness with traditional method, shorten the transient load switching, reducing the circulation between the inverter, power inverter to achieve exact distribution have a significant effect.