Study Of The Electrical Characteristics Of Grid-connected PV Inverter

In recent years, the renewable energy industry is growing up globally. One of the most potential and increasing energy is photovoltaics. Photovoltaic generation plays a key role in the future smart distribution grid. But increasing connection of photovoltaic energy to the grid has significant different impact to the operation of the power grid than the traditional geneation. And it is necessary to research on the features of the grid connected with PV energy system. In the system, the core device is the photovoltaic inverter, which is directly connected to the grid. In this dissert the using of power electronic device with its special control mechanism is considered as the main cause of the new feature of the PV grid-connected inverter, comparing with the traditional rotating generator.In this dissert, the electrical characteristics is researched in theory and practice with the base on the conclusion of the electric topology, power electric device feature, power quality and the control technology of inverter. The main works are as below:1. The application issues of PV generation system in the micro-grid are analyzed in theory and practice. It is indicated that the most electrical characteristics of PV generation system depends on the PV inverter unit. And the interaction features between the PV inverter and the micro-grid are concluded in three aspects: power quality, static grid support and transient stability during grid fault.2. After the analysis of the power factor and harmonics, it is found in the national standard for PV inverter with the deficit in field of the specific features of PV inverter: displacement factor, inter-harmonics and higher frequency harmonics. For the large power grid-connected PV inverter, the fitious grid with assumed impedance is used for measurement of the flicker, instead of small current measurement impedance physical network defined by the normal standard.3. With the measurement of active and reactive power control characteristics, the PV inverter can support the frequency and voltage for the grid. Two main methods are introduced: active power-power factor and remote reactive power control. For the study of transient stability of PV inverter, the process of positive component of voltage, current and power is research during the voltage dip, instead of rotor angle analysis of the traditional generator. A Matlab model is provided for the simulation of the transient electrical characteristics and validated with the measurement data for the purpose of verification of plausibility of the model.With the methods of theory analysis, model simulation and test verification, the practical conclusion is made. And the technical method and conclusion is valuable for improvement of application of PV energy and the PV inverter device, as well as the updated reference of the coming revision of relative standards in our country.