This description of the one used in grid-connected PV systems, the use of three-phase voltage source PWM direct current master grid inverter design process,power inverter, and inverter control strategy were analyzed and seminars, and The Mitsubishi company smart power module IPM50RSA060 with the Texas Instruments (TI) company DSP chip TMS320LF2407 designed the prototype. The final test results show that the the appropriate inverter PWM moderate use of small and medium power PV grid system, and there is widespread use of vision. http://www.gridtieinverter.de/
1 PV Grid
power generation system
grid-connected PV systems important by the solar panels (photovoltaic arrays),Grid tie inverter, and grid-connected inverter, filter reactor and DSP control circuit formation. The structure of the system as a whole is shown in Figure 1.
situation in the power generation, the direct current into grid-connected PV systems use solar panels to convert solar energy into DC energy, re-use grid-controlled current source characteristics of the inverter to control the operation of the inverter can be seen from Figure 1 exchange of electricity to feed the grid.
The transform
the energy of the whole system and the transfer process, the application of IPM module formed the grid inverters road to achieve grid inverter control is the main circuit of the PWM signal to drive through the DSP born.
2 grid inverter dominated principle
basis photovoltaic grid power generation system works shows, is the center of all the grid system install grid-connected inverter, grid inverter function resolution with the functioning of the entire system. For Figure l shown in grid-connected PV system design grid inverter to take a three-phase half-bridge inverter topology structure, its structure is shown in Figure 2.
grid satisfaction following equation for the AC side of the inverter output voltage and current signals
above model L on behalf of the exchange side inductance parameter, R is the parasitic resistance of the inductor, The the inductor equivalent impedance Hongyuan resistor R regulator design influence can neglect the system design process.
according to the three-phase voltage source PWM grid mathematical model of the inverter, known grid inverter to control the output current by controlling the three-phase voltage source inverter leg output voltage control the output current at the same time progress in the photovoltaic grid-connected inverter system generating capacity and adequate application in equivalent a light premise PV array can supply maximum power in the PV grid inverter unit control system, the introduction of the maximum power point tracking (MPPT) skills.
shown in Figure 2 for the grid-connected inverter restraint structure. Figure 2 shows the grid inverter dominated structure of the outer ring power ring to take self-optimizing MPPT algorithm. Calculated by sampling the installation of the current inverter output voltage and current signals from the optimization algorithm of the output power of the current moment, and then figuring out a moment output power comparable to the swap has been based on the size of the output power grid inverter change the operating point, the ultimate make grid-connected inverter operating point along the curve of the maximum power of the PV array. Inverter MPPT algorithm figured out the PV array DC voltage loop command signal, the voltage loop error signal in this power point after PI regulator links output amplitude of the current loop instruction, the amplitude command and grid voltage synchronization signal phase multiplied by the current loop synchronous command signal, the output current of the system by the current error with the inner ring proportion regulator grasp the current loop gain resolution the systems output current is properly tracking the command signal, and decide whether photovoltaic grid system unity power factor to achieve maximum power to the grid.
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