| Energy is the basic support element of human survival and development of society. With the development of society and economy, the exploitation of conventional energy is more and more, not only caused the global energy crisis, but also polluted the environment seriously. In recent years, governments are successively devoting to developmenting the new energy, including the solar energy which is renewable, sustainable, easy to get, no pollution, no noise, safe and clean, getting people favour. The scale of solar energy power generation and installed capacity has been increased year by year. With the increase of photovoltaic power generation scale and grid-connected capacity, the influence of pv modules on the user and the electric power system is becoming more and more serious, and requirement of the inverter technology is becoming more and more high. As the conventional inverter for electronic device has high reaction speed and no inertia effect, while a sharp change in light conditions and load fluctuation will cause harm to user and power grid. The power regulation performance of conventional inverter is poor, which cannot provide stable frequency and voltage in isolated net system. To improve the inverter interface features and solve the above problems, this paper uses the virtual synchronous generator(VSG) control strategy, making photovoltaic power generation unit imitate characteristic of synchronous generator. This control strategy not only can maintain the stability of voltage and frequency in isolated net running, also can participate in the performance adjustment in parallel power, meeting the photovoltaic power generation in the reliable operation in above two modes.Firstly this paper introduces the developing situation of the photovoltaic power generation at home and abroad and its future prospect, makes clear the significance of subject research. According to the different operation modes of photovoltaic system, this paper introduces the structure of the corresponding classification. In the comparison of the advantage and disadvantage of several common inverter control methods, on the basis of virtual synchronous generator control technology is introduced. According to the second order equations of synchronous generator, this paper built the simulation model of control strategy, and designed the power-frequency control unit and excitation control unit imitating the speed controller and excitation regulator of synchronous generator.Secondly, according to the structure of photovoltaic power generation,this paper built the simulation model in the MATLAB/simulink software.The simulation experiment firstly verified the effection of the energy storage unit for output power of photovoltaic;Then the experiment carried on the simulation of synchronous generator characteristics respectively, including power-frequency adjustment, excitation adjustment, power-Angle characteristic and the role of rotational inertia introduced; Finally the experiment conducted grid-connected and two virtual synchronous generators in parallel operation simulation, verifying that photovoltaic power generation units and the grid can take on the load power together according to their own capacity and the two virtual synchronous generators automatically assigned load changes in accordance with differential coefficient. The simulation effect is better.Finally, employing DSP320F2812 chip and the IPM device as the main control unit, this paper designed the main circuit and control circuit structure, completing the construction of the experimental hardware platform; This paper designed the main program flow and the function subprogram flow structure, and redacted the control program based on CCS3.3, completing the debugging in the hardware circuit. The experiment results verified the validity and correctness of the virtual synchronous generator.control strategy. |
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