| In recent years,the rapid development of photovoltaic(PV)power generation by virtue of clean,safe,reliable and other advantages,which increases the proportion in the field of energy gradually.However,most of the traditional PV power generation systems are grid-connected for a large number of PV modules,with the maturity of distributed photovoltaic power generation technology,a single family of a single or a small number of photovoltaic panels to achieve grid-connected small power single PV grid-connected system has a lot of room to play.Compared to the commonly used control chips in PV systems such as DSP or MCU,FPGAs break the pattern of sequential execution and can perform more processing tasks in each clock cycle,with fast processing speed and high execution efficiency.A single inverter grid-connected PV system based on FPGA is designed in this paper,which can not only realize the grid-connected power generation of a small number of PV modules,but also realize the MPPT of the PV system,which can promote the miniaturization of the grid-connected PV system.In addition,the push-pull DC converter is selected as the pre-stage DC converter module of this system due to the characteristics of low input DC voltage.Besides,a series of custom IP cores are designed by using Platform Designer tool,just as high-precision adjustable dead time IP core,equal-precision frequency detection IP core,high-precision full-phase phase difference detection IP core,SPWM wave IP core,PWM wave IP core.Every IP core is a function-specific component,they can realize real-time SPWM modulation,high-precision grid voltage frequency and grid current and grid voltage phase difference detection,accurate phase correction and dead time control,etc.To achieve coordination between multiple IP cores and stable regulation of the overall system,a SOPC system based on FPGA embedded with Nios Ⅱ CPU is used in this paper.The system starts with parallel sampling of grid voltage,inverter-side current,DC bus voltage,PV module output voltage and PV module output current through FPGA-controlled A/D converters,and further filtering the signals through digital lowpass filters.The Nios Ⅱ CPU is also used for fast response and coordinated control of the entire grid-connected inverter system through custom SPWM and PWM waves,dead-time generation,phase difference detection,and equal precision frequency measurement IP cores.Those IP cores can be easily hooked up in any SOPC system and the system’s control core is only an FPGA,which does not require additional chips,making the system small in size and simple in structure while ensuring good waveform quality and high system stability,which is suitable for popularizing PV power generation technology among the general public. |
