Research On Three-level Bidirectional Inverter In A Wind-solar-diesel Hybrid Power System

For human survival and development is confronted with a serious environmental crisis, the Low-carbon Economy is growing stronger as a promotional resources protection and comprehensive utilization of renewable energy of the important measures to get the support of all over the world. The wind-solar-diesel hybrid power system is built up basing on the complementary property of solar and wind energy in space and time. This system provides a good approach to resolve the problem of energy supply problems in remote and border areas.The bi-directional inverter is mainly used for the battery charger, discharge control, to achieve two-way flow of energy of the pure AC bus wind-solar-diesel hybrid power system. As an indispensable part of the whole power generation system, the bi-directional inverter has a direct impact on the stability of the system, it needs not only based on the systematic operational state of DC side voltage control, also requires the power factor close to one in the process of energy flow, and try to reduce the current harmonic content. This thesis studies that three level bi-directional inverter can effectively reduce the power switch tube voltage stress, and extend the service life of the switch tube. The increase in level can make AC side current is more close to the sine wave, under the same switching frequency, the current harmonic total aberrations rate is far less than the two level structure of the bi-directional inverter.This thesis introduced the structure and feature of wind-solar-diesel hybrid power system based on pure AC bus,and the operational mode of three-level bi-directional inverter in the system is also described. On this basis, according to the function and operational characteristics of the three-level inverter, the structure of the main circuit is determined. And the double loop control strategy, which consists of outer voltage loop and inner current loop. In order to improve the dynamic response speed and robustness of the system, adaptive hysteresis control algorithm is introduced. Finally, the effectiveness and feasibility of the control strategy are verified by simulation. The main circuit and hardware circuit of the control system based on dsPIC microchip are established. And the charge and discharge control of the batteries by the three-level bi-directional inverter is implemented by using software.