Research On The Three-phase Photovoltaic Inverter And Islanding Detection Method

Today the petrochemical energy is decreasing and the ecological environment is being destructed. Renewable energy such as solar energy is becoming a hot issue. Photovoltaic (PV) technology has been widely used. This paper focuses on PV grid inverter system and extensively studies some aspects including model and characteristics of PV grid system, topology and control method of PV grid system, detecting method for island condition in PV grid system.Inverters are of great importance to PV grid system. This paper proposes models of PV system which can be used for theoretical analyses. The models provide basis for system design. First, this paper introduces PV grid power system, classification and topology. Then realization of the main circuit of PV system is described. After the introduction of available control schemes, synchronous PI method is adopted. There are international technology standards related to island detection. According to these standards, this paper proposes testing methods for frequency and voltage protection. The pros and cons of passive and active methods for detecting island are introduced in detail. This paper proposes two detection methods for island and simulation is made by MATLAB. Experiments are also made for verifying the performance of these two methods. According to the demand of PV system, this paper designs and makes a PV inverter testbed of with capacity of 100kW. This testbed adopts TI The PWM rectifier provided revolutionary idea and method for the power converter and control technology. The advantages include high power factor, sinusoidal ac current and bidirectional power etc. This paper considers traction power supply, electric drive application, has discussed several kind of advanced controls strategy of the PWM rectifier and its DSP realization.This paper imports the dummy net linkage conception, through voltage, electric current and condition estimate flux linkage. Then dummy linkage direction detection vector control strategy is given, netside voltage sensorless control of PWM rectifier is realized. Control performance has carried on the simulation and the experimental confirms.Meanwhile, a new PWM rectifier control method of 8K electric locomotive inverter experimental system is propounded. The 50kW PWM rectifier ac side is connected the inverter output through the inductance, PWM rectifier dc line output parallel with inverter dc input. The device, using forecasting current arithmetic under a three-phase static coordinate, can accomplish fully loading experiment and over loading, miss phase fault experiment. The device realized energy recyclem, saves lots of experimental energy. This system already through the approval and put into operation in the scene, has the merit of structure simple, free control, energy saving and noise reduction.