Research On Grid-connected Converter System Of Large-scale Photovoltaic Power Station

In the current society human is facing the great crisis of the energy shortage and the environmental deterioration, so human has to explore continuously the new theories and methods of the development and utilization of the green and renewable energy so as to dissolve the crisis. Solar photovoltaic power generation helps ease energy shortage and stop environmental deterioration, so it becomes a top academic research direction of Electrical engineering circles. The development of power electronic technology and the decline of photovoltaic battery production costs may make solar photovoltaic power generation turn supplemental energy into alternative energy. With the rising of the power and the power density, the grid-connected operation will be the main operation mode of the solar photovoltaic power generation. The study object of this paper is the grid-connected converter system of the large-scale solar photovoltaic power station, which has the features of the concentrating power, the grid-connected operation of the higher power and the decoupled control between active power and reactive power.Firstly, through the study of the fundamental theories and the latest theories of the solar photovoltaic power generation’s maximum power point tracking, this paper puts forward a practical maximum power point tracking method, which is based on the average physical characteristic curve of PV cell. Through the study of the fundamental theories and the latest theories of the phase-lock loop, this paper clears the most effective theory and method of the phase-lock loop’s design. Through the study of the fundamental theories and the latest theories of the three-phase voltage source PWM converter’s modeling and control, this paper expounds the converter’s working principle and topological structure, deduces the small signal mathematical model of the link of the SPWM converter’s main switch and analyzes the PWM converter’s double closed loop control scheme which achieves decoupled control between active power and reactive power and is based on dq transformation. Through the study of the principle and the classic formula of the PWM converter’s parameters design, this paper establishes a set of formula of the high power PWM converter’s parameter design.Secondly, based on the study of the theory, this paper designs a high power three-phase voltage source SPWM converter, which has the maximum power point tracking, the anti-islanding and the decoupled control between active power and reactive power. This paper makes simulation research by PSIM and gets better result. Through the contrast with the application of the traditional MPPT, simulation result proves the validity of the MPPT based on the average physical characteristic curve of PV cell.Thirdly, based on the theoretical design, this paper designs the structure of the communication system, control system and main circuit system, designs digital signal processing of the phase-lock loop and control circuit, and designs power circuit, sample circuit, isolating circuit, drive circuit, main circuit.Finally, based on the study of the three-phase voltage source SPWM converter, this paper researches and analyzes the three-phase voltage source SVPWM converter. This paper puts forward an SVPWM control’s application technology through the study of the SVPWM control’s principle, deduces the small signal mathematical model of the link of the SVPWM converter’s main switch and carries out the theoretical design of the three-phase voltage source SVPWM converter. Simulation result shows that the design is reasonable and the SVPWM control’s application technology is useful.