Research On Smooth Switching Control Strategy Of Grid-connection And Stand-alone Operation For Double Modes Inverter

In recent years, renewable energy has become to an important alternative energy which is the driving force to the social sustainable development, diversification of the energy structure and to combat the climate change. As energy shortages became increasingly prominent, renewable energy development and utilization has got more and more attention. The distributed power generation systems based on wind, solar and other renewable energy sources has also become a hot spot of the researches in related fields. If connected in the form of micro-grid access to the large power grid to support each other, the distributed power generation systems can bring a variety of advantages into play more effectively. The micro-grid system has two operation modes, stand-alone and grid-connection. It needs to achieve smooth switching between these two modes, so as to reduce the voltage and current mutations, and ease the damage to the load, grid and inverter.In this paper, the micro-grid technology was the research background, and double modes inverter was the research object. The topology, working status and operation of the single-phase inverter, three-phase inverter system were analyzed. The control strategies for the stand-alone operation and grid-connection operation of the single-phase inverter and three-phase inverter were researched and designed according to the characteristics of their structure. Meanwhile, the differential equations of the important variables in the switching process of the two operating modes were summarized according to the basic circuit schematic. The relationship between the transient component and system related variables was analyzed according to the form of equations solutions in order to summarize the control strategy for the smooth switching of the double-modes operation.In order to verify the theoretical analysis, in this paper, the grid-connection control model and stand-alone control model of single-phase and three-phase inverter, the simulation model of double modes operation were all built in the Matlab/Simulink environment. The simulation results demonstrate the reliability and superiority of the design. In addition, some software programming were designed in the DSP control chip TMS320F2812based on the10kW direct- driven permanent magnet synchronous wind power system converter devices experimental platform according to the design of the control system, and the three-phase inverter experiment was achieved, the experimental waveforms verify the rationality of the design theory.