| In recent years, the country’s strongly support for distributed photovoltaic power genera-tion pushes sturdily the rapid development of photovoltaic and energy-storage hybrid mi-crogrid(PV/Battery microgrid). PV/Battery microgrid which integrates distributed PV unit, storage unit, load unit and control/protection device, is an autonomous system with self-control, protection and management to overcome the random fluctuations of PV unit output power. As an effective way of stable power supply from distributed photovoltaic, PV/Battery microgrid takes great social and economic significance. However, PV/Battery mi-crogrid’s operation mode is flexible and changeable, and it includes variety of distributed sources with different characteristic, making coordinated control of microgrid complicated. To achieve stable and efficient operation of PV/Battery microgrid and provide high quality power supply services for customers, stable and excellent multi-source coordinated control strategy for PV/Battery microgrid is needed. Therefore, this dissertation researches and developments coordinated control system for PV/Battery microgrid, the main research contents are as fol-lows:1. Based on the analysis of typical structure and operation mode of PV/Battery microgrid, this dissertation studies the operating characteristics of micro-source in microgrid including PV unit and storage unit systematically, summarizes the function orientation and access prin-ciple of the two micro-sources, and points out the energy storage type that suitable for PV/Battery microgrid’s storage power system. In order to reduce the storage cost and improve the cost performance of PV/Battery microgrid, the principle and calculation method for the capacity allocation of energy storage unit is proposed, and a PV/Battery microgrid system suitable for ordinary consumers is designed for specific demonstration project.2. This dissertation analyzes the mathematical models and control strategies of PV unit, lithium battery energy storage unit, load unit in PV/Battery microgrid system, and builds sim-ulation models of these unit on the PSCAD/EMTDC software platform. On this basis, the op-eration model of PV/Battery microgrid system is established. Simulation experiment in two cases of micro-source scheduling and load mutation on PV/Battery microgrid’s grid-connected and island operation mode is conducted, the results shows that the PV/Battery microgrid model can adjust the micro-source output power quickly responding to the com-mands, and withstand a certain range of power fluctuation under the premise of safe and sta-ble running of system.3.Analyzing the advantages and disadvantages of existing coordination control strategy, this dissertation proposes a multi-source coordinated control strategy for PV/Battery mi-crogrid based on the idea of hierarchical control, among which centralized control layer is the core layer to implement coordinated control strategy. According to fragile characteristic of PV/Battery microgrid’s voltage and frequency and its dynamic property, this dissertation pro-poses the voltage/frequency fragmet auto-switch coordinated control strategy. reasonable con-trol strategies is selected on different fragment to achieve rapid control of voltage and fre-quency.4.On this basis of PV/Battery microgrid’s safe and stable operation, coordinated control strategy on grid-connected mode is putted forward to track the power commands from dis-tributed network; coordinated control strategy on island mode based on fuzzy control is putted forward to maintain important load power supply and standard power quality; coordinated control strategy on switch mode is putted forward to achieve smooth switch.5. Using C language to generally program the proposed coordinated control strategy, this dissertation builds a dynamic simulation system for the designed PV/Battery microgrid sys-tem based on C language interface technology of PSCAD/EMTDC. On this basis, the coordi-nated control strategy on grid-connected, island and switch mode is tested by simulation ex-periments. Results show that the proposed coordinated control strategy can effectively guar-antee the PV/Battery microgrid’s safe and stable operation on the grid-connected, island and switch mode and track the distributed network’s power command quickly on the grid-connected mode.6. This dissertation proposes a practical structure to realize coordinated control system for PV/Battery microgrid. Based on the idea of modular design, the hardware and software scheme of microgrid central controller which is the key control device in microgrid system is designed, to realize unification of the micro-source coordinated control and protection in mi-crogrid system with low cost.The research in this dissertation was supported by the national high technology research and development program(863 program, Research on key technology and demonstration project of smart grid on customers’ side based on distributed sources, 2014AA052001). |
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