The Direct Power Control Of PWM Reversible Converter In Energy Storage Station

With the progress of social，the demand for energy is increasing while the fossil fuels are dwindling, so the energy storage technology becomes the research hotspot in order to reasonably and efficiently use the energy. So far, the main research about the storage of energy is the storage of power because it is easy to product and transport. The energy storage system is not only able to carry the grid load on the load shifting to stabilize the grid, but also promotes the solar,wind and other renewable energy to the grid in order to make the energy more conveniently and efficiently to use by people. The core part of energy storage system is the PWM converter, whose performance directly determines whether the system operate highly efficiently and stably.The PWM reversible converter of the20KW small storage station is studied and analyzed in this paper. Firstly, the current research status of energy storage station and the development of the PWM inverter converter are introduced. Secondly, it describes that the research on PWM inverter has far-reaching social benefits. The operation works of PWM inverter in the four-quadrant and the topologies and control strategies of the common converter are introduced. Finally,the mathematical model of inverter in three-phase stationary coordinate system, two-phase stationary coordinate system and two-phase rotating coordinate system is established based on the circuit topology of the three-phase voltage-type PWM inverter. On the basis of it, the study of the rectifier and inverter for PWM inverter is discussed in this paper.On the basis of the concept of instantaneous power, the direct power control of PWM inverter is researched and analyzed in this paper.When rectification works, the principle of direct power control strategy and system architecture are discussed, the core of traditional direct power control system is based on the switch tables by using the voltage loop and the structure of the inner power loop to control the power switches of the rectifier, which has the advantage of simple structure and good robust, but the hysteresis comparator and switch tables make the switching frequency not fixed. With the lack of traditional power control, a predictive direct power control strategy that combines SVPWM modulation techniques is designed in this paper, it not only has the advantages of the traditional direct power control, but also achieves a fixed switching frequency. When the inverter works, the control is more advantaged due to the power transmit form the power grid. The mathematical model of direct power control according to the instantaneous power theory is derived.The power controller is designed and the choices of its parameters are detailed to derivate and calculate on the basis of the mathematical model.Besides, the method of power decoupling control is proposed, which combines with the SVPWM modulation to make the direct power control have the advantages of better unity power factor, better sinusoidal of line current and harmonics lower.The control strategy of the rectifier and inverter designed in this paper are respectively simulated and experimented with the software of Matlab and the results are also analyzed. Then, the hardware and software of the control system of the PWM inverter in small20KVA storage is designed to verify the feasibility of the control method.