Design Of A Photovoltaic DC/DC Switching Converter Control Module And PC Monitoring Platform

As people increasingly pay attention to pollution caused by fossil fuels, photovoltaic system are used more widely. Whether on-grid PV, or off-grid PV, their topology structures are inseparable from this part of the DC-DC converter. The work of this part is to adjust the characteristic of the power which is exported by PV modules.Such as raising voltage and making it stable,then send it to the subsequent stage including an inverter, the grid with a load or other needs. With the digital electronic controls in industry becomes more sophisticated, the traditional analog control methods are gradually replaced. Similarly, DC / DC switching converters which is widely used in the photovoltaic power generation system are mostly using digital control technology. It uses the DSP chips as the core, data of switching converter circuit of the indicators are sampled and added to the on-chip program PID control algorithm, the final form a closed loop feedback by pulse width modulation method for adjusting the proportion of the switch-off time of one period in order to achieve the purpose of tracking.Hardware design ideas are as follows: Depending on the DC / DC converter circuit topology, you can have a variety of control strategies for these control programs which already have vast amounts of literature for reference. But as long as the control scheme is still the core idea of the frequency of the pulse width modulation and closed-loop feedback, the underlying hardware is required for the issue of input and output signals and a PWM wave samples be supported which remains the same.For the IGBT switch modules of main circuit require a 10 KHz PWM control signal and need of real-time monitoring multi-channel samples, based on DSP core chip TMS320F28335, this paper has designed a complete set of control circuit board which has 8 PWM output channels and 16 signal sampling input channels. Specific method comprising: providing signal conditioning circuit, isolation circuit to protect input and output signals; adding external analog-to-digital conversion module,voltage level conversion module to improve the sampling accuracy; providing complete fault detection and protection circuit to ensure system security.Software design ideas are as follows: Taking into account that the jtag interface debug in high-pressure work environment having huge risk, if the whole framework of the on-chip program changes little, only the specific control strategies of some parameters need to be adjusted, then use this software will be able to reflect the tremendous portability. At the same time since it is possible to make simple configuration via database matching parameters can be achieved in versatility, and added an extra multi-channel analog oscilloscope interface for coarse tracking signal waveform samples, so the debugging functions can be enriched. Although the whole function of the software has much room for improvement, for it is self-designed open-source program, it’s convenient to do futher development in use.Aiming at the monitoring interface’s demand to the stability and real-time of communication, this paper based on. Net framework and serial communication Modbus communication protocol designed a PC monitor interface with real-time monitoring and virtual oscilloscope functions. Specific methods include: programing serial ports setting interface; programing Modbus protocol transceiver function procedures; adding database module which configured to monitor table; set up multi channel virtual oscilloscope module implementation monitoring data curve display.At last, the test varified that the control circuit can achieve the desired results, such as multiple sampling and transmission of 10 KHz control signals, at the same time, stability, real-time, anti noise ability, accuracy and so on have been improved. And the monitoring software is the expected design, it can stablely communicate with the lower machine, and auto refresh and display the date of the control circuit board at least intervals of 100 ms, and depict the waveform of the data of each channel in virtual oscilloscope. The functionality of hardware and software all achieve the desired requirements.