Design Of 1kVA Single-stage Photovoltaic Grid-connected Inverter

With the energy shortage and environmental pollution increase, the development and utilization of renewable energy become a topic of growing concern. The grid-connected photovoltaic power generation that becomes the main way of solar energy exploitation is of hot research gradually. But there are several problems need to be addressed and resolved: ensure the maximum power output of PV(Photovoltaic) arrays, ensure the high-quality sine of grid current, ensure the more efficient of the system.In this paper, the research is about the grid-connected PV inverter. Firstly, this paper analyzes the characteristics of photovoltaic cells and the equivalent model, according to the characteristics of PV cells, it gives three commonly used methods of maximum power point tracking (constant voltage method, perturbation and observation method, conductance increment method) and their Principle. The traditional perturbation method has problems of track speed and track progress and the phenomenon of"misjudgment"that because of the drastic changes light, in order to resolve those problems, an improved method of variable step disturbance observation is proposed, which is realized easily and achieves the MPPT quickly.Secondly, this paper analyzes the operation principle and control method of grid-connected PV inverter. Comparing the characteristics of two unipolar SPWM (Sinusoidal Pulse Width Modulation) control, it'found that under the unipolar double frequency SPWM control the grid-connected current is of low THD. The model of the inverter system is established, using the commonly used double-loop control strategy, this paper gives the detailed design of PI parameters.Finally, this paper designs the entire system of hardware and software in detail. A 1kVA single-stage PV grid-connected inverter has been designed. And the relative experiment results show that the improved variable step disturbance observation can achieve better tracking precision, the utilization of photovoltaic cells has greatly improved, the system can provide a good grid current, and harmonic content, power factor and efficiency can meet the target requirements.