The Research On Grid-connected Photovoltaic Inverter And Control Method

Development of green energy is one of the human social activities to attract the most attention. With new energy prospects and the incentive policy and demand, the photovoltaic power industry of solar energy is in rapid growth. One of the keys to gain popular use of the photovoltaic power supply is availability of photovoltaic grid-connected inverters. Developing the efficient grid-connected inverter is the important content and the direction of research on the photovoltaic power system. For power supply with photovoltaic grid-connected inverters, this paper focus on analysis of and research on some of key technologies for the inverters, with arriving at the useful methods and the implementation for those inverters. The following aspects of the research work have been conducted and completed in this paper:(1)From based on analysis and study of the mechanism of photovoltaic power generation, with effect of the PN junction built-in electric field on photo-carriers, the physical model of charges output and produced voltage, the photoelectric energy conversion relation, and the photovoltaic power output characteristics are preseted.(2)In terms of the specificity and the technical target of the topic PV system, some of inverter circuits, and operating methods and architectures of the system are analyzed. The operation principle, the built-up structure, and the flyback of forward power reusable in photovoltaic energy delivery are analyzed as well. As followed in the PWM process of single-polarity output with double-polarity modulation, the calculation of the modulation at various input and output voltages is given for later design.(3)As in research on the preset control for MPPT and the current regulating method for the grid-connected inverter, the charge equilibrium principle and its MPP tracking method are explored and preseted, with followed as the result the MPPT control method by the preset from MPP migration due to differential integration of charge flow in disbalance. The control model of the current feedback closed-loop regulator over the F time base (or sinusoidal period) and the modulating switch cycle, the incremental PID algorithm, and the linear-fitted method with least square approach are analyzed, meanwhile their operation flows illustrated. All of those methods are aggregated to result in the total solution to the topic photovoltaic grid-connected inverter system.(4)In this paper, the analyzed design and the calculation methods for the primary circuits of the inverter are put forward along with the basic analysis of inverter efficiency, and the research on the short-circuit protection on basis of the measured current of inverter bridge arms and the modulating phase overlap, and the design method for software control procedures.(5)According to the basics of the power inverter, an one kilowatt of single-phase photovoltaic grid-connected inverter is developed as to demonstrate the effectiveness and workability of the PV inverter to which the outcome of this paper is related. The experimental run shows the performance of the inverter system archieves more than the specifications as designed.