Research And Design Of Household Energy Storage System With Parallel Photovoltaic Inverters

The continuous deepening of the global energy crisis and the deterioration of the environment make the energy field of the reform imminent. During “13th Five-Year” period, our country will propose to establish the strategic plan which is called “global energy Internet”.A number of important initiatives are proposed in the new energy field including the development of distributed energy storage technology. Energy storage system is a power storage link between power system and load, which can solve the contradiction between power supply and demand effectively and improve the reliability and security of power grid. The continuous promotion of household energy storage system also brings new opportunities for the development of new energy photovoltaic industry in many areas of poor transmission difficulties in light. Therefore, it has a good prospect to carry out the discussion of the topic of household energy storage system with multilevel parallel inverters.This thesis focuses on the research and design of the small household energy storage system which is the integration of the inverter and the energy storage. The working principle, device selection and the design of parameters for each part of the household energy storage system are introduced. A robust back stepping sliding mode control strategy is proposed in this paper, aiming at the deficiency of the traditional double closed loop control strategy in the charge and discharge of the lithium iron phosphate battery. A virtual flux linkage direct power control strategy is proposed in operation of inverters. The superiority of the proposed control strategy is proved by the simulation and experiment results.The concrete work is as following:Firstly, the function of energy storage system is expounded in the field of photovoltaic power generation. The practical significance of the development of household energy storage system is introduced. The future development direction and control strategy of multilevel inverter parallel technology are summarized in this paper.Secondly, the overall design scheme of the 3k W household energy storage system is described. The working principle, device selection and parameters of each component of the system are introduced and designed. After analyzing and comparing several different topologies of inverter, the two stage non isolated topology is adopted. The interactive interface of the system is introduced. Three different working modes of the energy storage system are analyzed and compared.Thirdly, considering that the cost of materials, cycle life and other factors, the lithium iron phosphate batteries are selected as the experimental object.The model of constant current / constant voltage charging and discharging device for lithium iron phosphate battery was established, A robust back stepping sliding mode control strategy is proposed for the shortcomings of the traditional double closed loop control strategy in the aspects of dynamic performance, suppression of harmonic suppression and large amplitude disturbance. The principle of robust backstepping sliding mode control system is analyzed and the backstepping sliding mode controller is designed. Experiments and simulations show that the robust backstepping sliding mode control strategy is more efficient than the double closed loop control strategy in the charge discharge performance of the lithium iron phosphate battery.Fourthly, considering the traditional droop control strategy of active power and reactive power detection calculation of complex, dynamic response, poor stability and inhibition of the disadvantage of the inverter current total harmonic effect is not ideal, the virtual flux linkage direct power control is proposed in the control strategy of parallel inverters. Simulation model and vector diagram of grid connected inverter based on VF-DPC are established. Experiments and simulations show that compared with the droop control strategy, the VF-DPC control strategy has obvious advantages in the dynamic response stability control and the total harmonic of the inverter.Fifth, the digital realization process of parallel inverters for small household energy storage system is designed. Hardware: S3C2440 A control chip is selected which is from Samsung. ARM920 T is used as internal control part. At the same time, In order to convert the small power signal into a larger power signal which can drive IGBT, driving circuit is designed. The voltage current detection circuit and over current protection circuit are designed. In order to supply the 12 V power supply to the above circuits, flyback switching power supply was designed, which uses PC40 material core, EC35 framework and DPA425 chip. Software: the paper introduced the software running system environment platform which is called ADS integrated development environment. The software program of the A/D sampling module, PWM generation module, phase-locked loop and MPPT are designed.In the last, the simulation and experiment of the 3kW household energy storage system are carried out. The experimental platform of 3kW energy storage system is built in the laboratory ideal environment. Using outdoor experimental project which comes from Peak valley Energy Storage Technology Research Institute also completed the corresponding comparison. The feasibility of the whole system is verified by experiments. The MPPT experimental platform of photovoltaic array is designed in the laboratory, which is used to look for the MPP position of the 1500 WP solar cell board equipped with the 3k W energy storage system in the natural environment. The charging and discharging status of the lithium iron phosphate battery pack of 51.2V and 100 Ah was tested by the NBT battery test system. The battery test system comes from the Peak valley Energy Storage Technology Research Institute. The test results of the above three groups are in agreement with the theoretical analysis and the experimental results basically meet the expectations.