One Cycle Control Research Of Quadratic DC-DC Converter

The post-stage DC-DC converter of new energy systems should accommodate wide voltage input, as the output voltages of such systems as photovoltaic array、wind energy and fuel cell vary in wide range. The cascade DC-DC converter with a single switch achieves the cascade goal without the increase of switches, broadening voltage input range as well as ensuring the efficiency.Also, large range fluctuation of output voltages requires the control strategy has stronger input disturbance rejection capability. By using the nonlinear characteristics and pulse characteristics of switching converter, one cycle control is used to realize the real-time control of the current average value and pulse voltage. It has the characteristics of good robustness, fast response and strong interference rejection of input.With the secondary cascade topology as the research object, this paper has made a discussion on one cycle controlled quadratic Buck converter (OCCQB). Traditional one cycle controlled quadratic Buck converter (TOCCQB) has such shortages as the poor anti-load disturbance ability and the existence of steady-state error and so on, mainly because output feedback is not introduced. Aiming at these shortages of TOCCQB, an improved one cycle controlled quadratic Buck converter (IOCCQB) is proposed. In this method, inductor current is integrated with diode voltage as the feedback of the current inner loop, the output voltage is used as the control variable of the voltage outer loop to form the output feedback, effectively enhancing the load disturbance rejection ability of the TOCCQB. The improved control scheme uses one cycle control circuit to achieve signal current feedback, this distinctive characteristic makes it inherit such advantage as quick transient response speed of the current mode control, while different from current mode control.The operation of IOCCQB is described in detail, the small signal model of IOCCQB is established by using the average method of the state space, and the frequency domain design of the IOCCQB has been carried out. Simulation and experimental results show that, when the load jumps, the IOCCQB recovers quickly, proving its good anti-load disturbance ability; when the input jumps, the IOCCQB has lower overshoot compared with current mode control scheme, verifying good input disturbance rejection performance of the IOCCQB.