The Research Of Charging And Discharging System Based On PWM Rectifier Technology

With the development of society, the battery has been wildly applied in recent years.Battery and charge-discharge technology are inseparable. The traditional charge-dischargesystems are generally implemented by using thyristor and resistance. Though it is usedcompletely technique and low price,it also has many disadvantages. For example,there arelow input power factor,large in size,and only one-way ransformation of energy. And thischarging and discharging system will generate a large number ofharmonics. Harmonics willaffect the power generation equipment, the relay in the power grid, communication systemsand electrical equipment in the same grid.These questions need to be resolved. With thepower electronics technology and the development of power devices, PWM rectifiertechnology appear which has the advantages of bidirectional power flow, unit power factor.These benefits can solve the problem of the traditional charge-discharge systems.In this thesis, a battery charge and discharge system was designed based on PWMrectifier technology and bi-directional buck-boost DC chopper. This thesis introduces theclassification of the PWM rectifier topology.Through theanalysis of the characteristics of avariety of topologies and their performance, this thesis and ultimately select the three-phasevoltage source PWM rectifier system of the former class. This thesis analyzes the PWMrectifier topology, working principle and control strategy. And its mathematical models werepresented in the three-phase stationary coordinate system, two-phase stationary coordinatesystem and two-phase rotating coordinate system. And the design method of system controlstrategy parameter was given. This thesis also analyzed DC-DC converter topology, operatedprinciple and control strategy, summed up the design method of DC-DC converter systemparameters and control parameters. Based on the above work, the three-phase voltage-typePWM rectifier and DC-DC converter was simulated, but also charge and discharge systemwas simulated in the matlab environment,. The results of the simulation show this system hashigh power factor, and sinusoidal current of AC side. The software PLL based on PI was usedin three-phase voltage-type PWM rectifier to solve the problem of uneven frequency whichused hardware PLL. DC-DC converter used parallel independent current closed-loop andvoltage closed-loop control, so current and voltage can be independently controlled.This thesis designed a three-phase voltage-type PWM rectifier experimental prototype.The SVPWM was used in the experimental prototype. Prototype implements two-way flowof energy and grid-side current sinusoidal.The software PLL had a good performance, can stabilize the tracking phase. In the experimental electricity can flow in both directions. Thecurrent of grid side is sine wave,and the power factor close to1, and reduces the harmoniccontent of the system.Battery charge and discharge experiments has been done based on thebi-directional DC-DC converter prototype.The experiment can be completed properly.Experiment results demonstrate that the theory algorithms and design methods for this systemare effective.