Interleaved high step-up converter for variable load conditions using microcontroller

In this paper, the concept of control circuit for variable load conditions and for small variation in input conditions is derived to generate an improved interleaved high step-up converter for distributed photovoltaic generation applications. The proposed control circuit consists of one micro controller, voltage and current sensing device. The voltage and current sense the the signal in load circuit and send the data to micro controller, which is control the output voltage by changing the gate pulses to MOSFETs. The switch duty cycle and the transformer turns ratio can be employed as two controllable freedoms to lift the voltage ratio flexibly. The power device voltage stress can also be reduced to improve the circuit performance. Furthermore, the active clamp scheme is adopted to recycle the leakage energy, absorb the switch turn-off voltage spikes, and achieve zero-voltage switching (ZVS) operation for all active switches. Meanwhile, the diode reverse recovery problem is alleviated by the leakage inductance of the built-in transformer. All these factors benefit the circuit performance improvements in the high step-up and large current applications. Finally, a 1-kW prototype with 40-250 V conversion is built and tested to demonstrate the effectiveness of the proposed converter.