2014年5月18日星期日

5kW off-grid PV inverter control strategy

SPWM control technology in a wide range of inverter circuit , we use a closed-loop PID control with a combination of negative feedback control of digital control strategy.
Generating a control pulse
This article is based on TI 's main chip , F2812 12 volt inverter There are two event manager EVA and EVB, each of which can generate a pulse output 8-channel , in which three pairs of complementary signal output from the full compare unit , each pair of complementary signals delay from the corresponding dead time timer generated , the event manager using the internal timer , and comparison means generates a corresponding pulse. Man in a pair of complementary output SPWM pulse signal and PWM signal output by one independent EVA, respectively Boost boost control circuit and an inverter circuit .
2 Output frequency calculations
SPWM inverter output frequency of the pulse signal is 50Hz, points SPWM output waveform of each sine wave cycle depends on the carrier frequency and the target output sine wave frequency SPWM pulse waves. As for the carrier frequency SPWM 18kHz, the frequency of the sine wave to be 220v inverters outputted respectively 50Hz, sine table needed for the point N
3 closed-loop negative feedback control
DSP2812 time detection output voltage input , the current value fed to the internal DSP , after the PI regulator to change the parameters associated register , controls the waveform of the drive pulses to achieve real-time closed-loop control , the control system block diagram shown in Figure 6, the system uses two closed loop negative feedback , depending on the feedback signal, the output of real-time adjustment , the output is stable. In addition, when the output current signal suddenly increases to exceed the maximum allowable current when off the PWM output to protect the inverter device from damage.

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