An Essay on UPS (part 2)

An Essay on UPS (part 2)




System hardware design



The program is designed to use TMS320F28335 microcontroller circuit UPS system control panel. The system is composed of bus voltage detection circuit module, amplitude detection circuit module, peak current protection circuit module, auxiliary power supply monitoring circuit module, open, shut down circuit module, the voltage detection circuit module, PWM generating circuit module, relay control circuit module, external expansion memory modules as well as the peak-ming generating circuit composed of modules.



Bus Voltage Detection Module



Bus voltage detection circuit module shown in Figure 2. Partial pressure + BUS voltage after the RC filter and sent to DSP by the AD converter pin ADCINA2. After partial pressure-BUS voltage through the power inverter, the RC filter sent to the DSP via the AD converter pin ADCINA3.



Amplitude detection circuit module



Amplitude detection circuit shown in Figure 3, it is used power inverter output voltage, mains input voltage, load current amplitude detection. The circuit uses a time when one-way active-precision detector to achieve, using active-precision detector is designed to ensure the output from the detector received unipolar signal amplitude is always associated with sine wave input to the detector the amplitude of the signal maintained a strict linear relationship between the general diode detectors to eliminate the small-signal input non-linear distortion that may arise.



Peak current protection circuit module



Peak current protection circuit shown in Figure 4, the power output of power supply through the UPS board current transformer, with its current size of the form of voltage signals through the signal amplifier to go after the three columns. Amplitude detection circuit all the way through, sent to DSP-ADCINA0 pin; all the way through the current zero-crossing detection circuit, the DSP sent to the GPIO75 pin; the other way through the overload, short circuit protection. When the load overload or short circuit, PWM_OFF into a low-level signals, it will immediately shut down the required two-way inverter PWM wave output, the same time the system switches to bypass DSP mode, play a quick protection.



Results



In the experiment, using the oscilloscope detect steady state inverter output voltage tracking voltage AC power waveform, the results we can see from the inverter system can be basically free of static error tracking. Grid sudden power down, the system switches to protect waveforms, switching time <10ms, indicating that the UPS power grid failure detection speed, switching time is short; the exchange of power grid voltage <190V, when, UPS converts the output from the power grid inverter for the load electrical waveform, switching voltage waveform during the small fluctuation. Inverter output voltage distortion is small, switching time <10ms, UPS output voltage when sudden load increases the dynamic response waveform shows the output voltage fluctuation is small, recovery time <40ms, fast dynamic response to meet the stability and dynamic performance requirements.



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