Research On Battery Equalization Managemnet And Inverter Control Technologies Of Distributed Power System

With the rapid development of the society and economy, the demand of the energy is increasing year by year in our country. The fossil fuel reserve is limited and many countries are faced with the danger of the energy resources crisis. Solar and wind energy are renewable and clean energy resources and are inexhaustible. In order to relieve the energy resources crisis, every country pays more and more attention to the development of renewable energy resources, our country also emphasizes it very much. For the development and utilization of the renewable energy resources, the keys are the energy storage technology and power supply inverter control technology. Aimed at the distributed power supply system in renewable energy resources development, this paper focus on the research of battery management technology of energy storage system and inverter control technology, and the following results have be achieved:(1) Aiming at the switched-resistor and fly-back converter equalization circuit of battery management system, this paper studies the equalization circuit model, then corresponding charge equalization control strategy is proposed. The proposed strategy can not only quickly charge the battery, but also increase the lifecycle of the battery.(2) A method adopting frequency-hopping spread spectrum modulation technology is put forward to suppress the harmonics of single-phase. It expands the frequency spectrum of the conventional inverter from single point to a wider band, and it makes harmonic energy of output voltage extend to a wider area evenly. Consequently, the method can reduce the output harmonic amplitude of the inverter. Then, the EMI of inverter is suppressed.(3) In inverter parallel operating system, the relationship between the inverter power flow and the output voltage and phase of the inverter is systemically studied for the first time in polar coordinate system. It is pointed out that the output power vector is made up of two orthmetric sub-vectors, and the length of these two sub-vectors is controlled independently by the amplitude and phase of the inverter respectively.(4) In two inverter parallel operating system, the relationship between the system circulating current and the differenced of voltage amplitude and phase of two inverter is systemically studied for the first time. It is pointed out that, in polar coordinate system, the system circulating current vector is made up of two orthmetric sub-vectors, and the length of these two sub-vectors is independently controlled by the differences of inverter output voltage amplitude and phase respectively, and the angle of the sub-vectors is decided by the output impedance angle of the inverter. (5) Aimed at single phase inverter parallel operating, a current decoupling control strategy is proposed, which decomposes the output current into active component and reactive component according to the instantaneous reactive power theory. The active and reactive current is decoupled to regulate the amplitude and phase of the output voltage, respectively. By using instantaneous reactive power theory, the proposed decoupling control strategy obtains good transient response performance and has the features of simplified algorithm, fast calculation speed and easy digital processing.(6) A novel constant frequency current hysteresis control strategy for grid-connected inverter based on switch time predication is proposed. The proposed control strategy retains the benefit of fast dynamic response of the conventional current hysteresis control, with constant switch frequency. The proposed current hysteresis control is based on the switch time prediction, with no hysteresis bandwidth is needed, and the circuit design is simplified.