Research On Grid-connected Bidirectional Inverter In A Wind-solar-diesel Hybrid Power System

The wind-solar-diesel hybrid power system based on AC coupling of parallel technology, which is also called pure AC bus wind-solar-diesel hybrid power system, has many advantages such as all power units adding up their power, simplified operation, higher reliability, easy expandability and so on. It provides a very good solution for the problem of areas which are far from public grid and power instability. Recently, this technology has been applied to products abroad, but at home reseach on the technology and grid-connected bi-directional inverter is in the initial stage.In the wind-solar-diesel hybrid power system, the main fuction of grid-connected bi-directional inverter is battery storage control and charging-discharging maintenance to achieve two-way flow of energy between battery and AC bus and adjust system power balance. As one of important component of the system, its reliable operation has become the key factors that affect the entire system's economy and reliable operation.Firstly, this paper introduces the configuration and features of the wind-solar-diesel hybrid power system based on AC bus. And the two operation modes that are grid-connected and independent operation of grid-connected bi-directional inverte are also introduced. On this basis, according to the function of grid-connected bi-directional inverte and the features of its two operation, the PWM rectifier and DC/DC converter are used as the main circuit of grid-connected bi-directional inverte, and the control strategies in two operation modes have developed. In grid-connected rectifier and inverter control, the fuzzy adaptive PI control has been introduced to suppress grid voltage fluctuation and improve the DC voltage control precision. In independent inverter operation control, the multi-loop control strategy has been used to suppress load and DC voltage disturbance toward the inverter output voltage. Finally, the feasibility and validity of control strategies in two operation mode are verified by simulation. And the main circuit and hardware control circuit have been established with the microchip PIC as the centre process unit of the control system. By programming, the grid-connected bi-directional inverter has realized rectifier and inverter operation in grid-connected mode and inverter operation in independent mode.