On-grid PV System Inverter Circuit
Author: Source: Datetime: 2016-09-18 07:14:19
DC/DC circuit control principle
Control box DC/DC converter. Here the control circuit is integrated SG3525 core, two 50kHz drive signal to the output of SG3525, the gate driver door push-pull circuit switches SW1 and SW2 on the pole, as shown in Figure 5-6. Force remained stable DCVDC converter output voltage, the detected output voltage and the command voltage is compared to the error after PI regulator controls the duty cycle SG3525 output drive signal. The control circuit also has a limited output overcurrent and overvoltage protection. Upon detection of DC/DC converter output current is too large, SG3525 will reduce the gate pulse width, reduce the output voltage, thereby reducing the output current. When the output voltage is too Gao, stops DC/DC converter work. Solar power portable generator since the push-pull circuit is susceptible to DC bias lead to transformer saturation, therefore, push-pull circuit design difficulty is how to prevent magnetic saturation of the transformer. In this circuit, except to note that the circuit is also designed symmetrical outer magnetic saturation detection circuit, when the push-pull circuit flows through the two branches of the current imbalances will start SG3525 soft start function, so that DC/DC converter again start, transformer reset.
Biasing magnetic detection circuit. Drawn only secondary magnetic ring, the two primary coil connected to the two primary windings of the transformer primary side of the circuit, the current flowing through the two coils to opposite direction. When the transformer magnetic bias occurs, abnormally large current in one direction through the current transformer testing, can generate a voltage across the transformer output resistor R1,solar power generator if the voltage is large enough, you can make the zener diode D5 is turned on, in pressure drop on the potentiometer, the potentiometer value transferred to the appropriate resistance, so that the potential drop on the transistor is greater than the threshold voltage, the transistor is turned on, connected between the chip SG3525 feet 8 and the capacitance to ground discharge, and the constant current source SG3525 charge it, SG3525 restart so that the transformer core reset serve the purpose of preventing magnetic saturation of the transformer.
DC/AC control principle
DC/AC control principle. This is the company's high-performance Texas Instruments DSP chip TMS320F240 employed as the control core, through the input DC voltage and output AC inverter and a series of synthesis performed using computing, then the triangular wave carrier signal synthesizer generates SPWM modulation signal,solar power generation dc voltage inverter PV module array is a stable sine wave AC output. Since this is a mains power grid system, TMS320F240 also increased the electricity grid voltage synchronous tracking signal acquisition process. The grid voltage signal synchronization tracking purpose is to ensure that the voltage waveform alternating current from the grid and on-grid inverter output strictly maintain the same frequency, same phase, purpose of doing so is to make active and maximum net output of the portable solar power generator system, but also to avoid pollution of the public grid electricity, good electromagnetic compatibility.
In order to keep the grid voltage of the same frequency and phase, something must be captured when the grid voltage zero-crossing signal, trigger synchronization interrupt is detected by the DSP over the rising edge of zero signal, this time as a reference time, as a starting point sine wave signal. To get zero voltage signal can be obtained through the grid voltage signal synchronous step-down transformer, and then shaping filter for synchronous square wave signal, sending DSP external interrupt port detects obtained.
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