| With the gradual depletion of fossil fuels and the deteriorating ecological environment, it is a new trend for the development and utilization of non-polluting or less polluting alternative energy sources. Solar energy, as its inexhaustible supply and being almost non-polluting advantage, is receiving worldwide attention and support. There are many ways to use solar energy, among which photovoltaic generation is the mainstream, representing the direction of development of solar energy. This paper focuses on control strategy of DC/DC and DC/AC for single-phase PV inverter system. Detailed analysis and simulation is made on system topology, parameters, MPPT, inverter control and so on.This paper researches on PV system components, classification, main circuit topology, filter and grid-control, emphasizing on two-stage single-phase full-bridge circuit and LCL filter. Particular analysis has been made on MPPT algorithm especially on the incremental conductance (INC) method. Based on the general principle of MPPT, a power-detection adaptive variable step size of INC method is proposed. Simulation results show the correctness and advance of the improved algorithm.Based on internal model principle, the repetitive control method has natural advantage on suppressing periodic interference. Since its gain characteristics of LCL filter itself, the comb filter is generally set to eliminate spikes when designing repetitive controller. By the way of series or parallel of resistance on L or C, the gain characteristic can be improved. But there will undoubtedly be power loss for the extra resistance. This way is especially not applied in high power systems. For this problem, a virtual resistor repetitive control method is proposed. This method simplifies the design of the repetitive controller with adding a PD and a second-order low-pass filter part and no power loss. Through building modules for system simulation, comparing simulation results verify the feasibility of the improved algorithm. |
PDF Full Text Request