Intelligent Photovoltaic Grid-connected Inverter Based On ARM & DSP Architecture

As the global energy crisis becomes more and more serious, the solar photovoltaic grid-connected power generation plays an increasingly important role in the energy structure. However, the performance of the gird-connected inverter, which is the core part of the PV power generation system, has yet to be improved. In order to meet the market's needs of high quality, high performance and intelligent gird-connected inverter, we took the ARM+DSP architecture as the control system of gird-connected inverter. The system integrated the respective powerful functions of ARM and DSP, which improved the level of gird-connected inverter's performance and Intellectualization remarkably. This paper was based on PV Grid-connected Inverter Project of Luneng company, which is the practice base of Shandong University. The prototype machine has been trial-produced. I mainly took charge of the software/hardware design of gird-connected inverter's control system. The main study content of the paper include:1. The grid-connected inverter adopted the inner high-frequency loop inverter technique. The paper analyzed the merit and demerit of this kind of inverter in detail, carried out sufficient system analysis and demonstration.2. The simulation of control algorithms including forestage DC-DC conversion control algorithms and backstage DC-AC inversion control algorithms was carried out by MATLAB/ Simulink software. The designed algorithms' feasibility was validated by simulation, which gave DSP program development well guidance.3. In this paper, we used ARM + DSP architecture as the inverter's control system, and designed the corresponding hardware control system. DSP hardware system contained many circuits such as AD data sampling , hardware current protection, power supply, eCAN bus, SPI bus, PWM output .ARM board hardware system included power supply, SPI bus, RS232 bus, RS485 bus, Ethernet bus, LCD display, real-time clock, keyboard, memory and other hardware circuit.4. This paper designs and realizes two algorithms: power perturbing algorithm and incremental conductance algorithm. Islanding detection used two methods: passive detection and active detection. The passive detection method combined over / under voltage detection with phase jumping detection. The active detection method adopted the frequency drift positive feedback. In order to make the output current of the gird-connected inverter same frequency and same phase with the voltage of the network, we use the software phase-locked loop control technology. This paper presented various flow charts of the above algorithms.5. This article also gave the program flow charts including the AD data sampling, eCAN bus, RS232 bus, RS485 bus, Ethernet bus, PWM output, ,as well as the DSP and ARM communication control SPI program flow chart. It also gave the main program flow charts of the ARM management control system and the DSP control system.6. At last, the experimental result of the gird-connected inverter prototype was analyzed. It shows that the prototype realized the functions proposed by this paper and its performances reached the expected objective.