Research On Three-phase Grid-connected Photovoltaic Inverter With Active Power Filter's Function

With the development of social economy, energy and environment problems have become increasingly prominent. As owing inexhaustible and no pollution advantages, the solar energy is potential renewable energy, then the photovoltaic power generation has been extensively developed. However, the photovoltaic power generation just can work in daytime and be affected by light intensity and temperature with poor system utilization. What's more, as countries to speed up the process of industrialization, the mass nonlinear loads that produce harmonic current are connected to grid. The more requirements of power quality, and more power quality equipment are used for power system. The research combines the photovoltaic power generation and active power filter, which realizes the photovoltaic generation and harmonics control to improve power quality.At first, through analyzing the model of photovoltaic cell, the output characteristic of PV cell is simulated in different light intensity and temperature by MATLAB. Through the comparing the topologies and control methods of three-phase photovoltaic power generation system and parallel active power filter, this paper gets the similarity for unified control in theory, and intends to make the three phase inverter system with the function of active filter. Next, aiming at maximum power point tracking(MPPT), the research proposes an adaptive variable step-size perturbation observation method which quickly gets the maximum power and reduces the oscillation near maximum point. As for the aspect of system debugging, a simple simulation photovoltaic experiment platform is built.Meanwhile, the overall structure of two stage grid-connected photovoltaic generation system with active filter function is analyzed, so as this system control method. The voltage out-loop is applied by PI control to stabilize the dc-link voltage of inverter and get amplitude instruction of active reference current. The decomposition detection algorithm based on harmonic current ip-iq is used for testing particular single or several harmonic directly and compensating these particular harmonics. Regarding of the power capacity constraints of system, a limit method of harmonic current is presented. The harmonic accurate compensation and output of active power become realized by digital deadbeat control. The different output characteristic of system is analyzed in different word modes by using PISM simulation.The keystone of this paper is the inverter prototype development. First, the main circuit structure of system is designed and the power devices of system and their driver circuit are selected. Then the filter inductors and dc-link capacitor are designed further. In the aspect of hardware design, the control system structure based on DSP, external sampling circuit, zero crossing detection electric circuit of voltage, and protection circuit etc. are designed. Afterwards, the software design are introduced, and the experiment which is based on inverter prototype verified the accuracy and efficiency of the methods proposed.