Research On Distributed Power Coordinated Control Strategy Based On Power Decision

The distributed power, as an important part of DC micro power grid, its coordinated control strategy plays an important role in improving power quality and economical efficiency of micro grid. Up to now, the control of distributed power sources has been mainly implemented by the voltage signal selecting the operation mode, this control method is hard to keep the system internal power supply and demand balance, causing too big a busbar voltage change. This thesis proposes a method for the system operation mode to be selected based on power signal of each module in the system and a coordinated control strategy of battery charging current control, and the thorough research of them is made. The main research work is as follows:1. A deep research on how to keep the balance of power in DC micro grid is performed, the DC micro grid model is established, and a detection method for each micro-source in DC micro grid system to generate and absorb power is put forward. The correctness of the system model has been proved by analyzing of the output characteristics of the power supply.2. In view of the shortcoming of three-stage charging in distributed power coordinated control strategy, a research on control strategy of photovoltaic cell, battery and fuel cell has been conducted. A battery charging method for choosing appropriate charging current in terms of the system power supply and demand status and real time voltage of the battery, the control photovoltaic battery mode combining the MPPT with constant voltage control, and the fuel cell control strategy based on constant power discharge are put forward. The feasibility of the control method and high efficiency of charging method are verified by simulating all the micro-source control strategy.3. Research on coordinated control strategy of all the distributed power sources is made. Five kinds of operation modes are determined which can better coordinate the output of each microsource. It is shown by simulation that the charging method can keep the bus voltage constant while the system operates, and that the system operation modes can switch rapidly, and the system can run efficiently and steadily under normal circumstances.4. The design of the system hardware and software is completed. Experiments are conducted for some typical operation modes and the control strategy of photovoltaic cells, batteries and fuel cells. The experiment results are well agreement with the theoretical results, which further verifies the feasibility and effectiveness of the method.