Research On Active Damping Control Of Boost Coverter With Constant Power Load

An increasing number of converter systems are cascaded by closed-loop feedback DC/DC converters to realize high performance. In the stable operation, the closed-loop DC/DC converter can be seen as a Constant Power Load(CPL), the negative impedance characteristic of CPL will affect the stability of the system. The system stability can be improved by the active damping method, and the system can not be brought additional loss. In this paper, the Boost converter with CPL is taken as research object, and the instability of the system is solved by active damping method.The studied system is composed of two stage cascade converter, a front-end active damping Boost converter load by a Buck converter. The front stage Boost converter is controlled by the active damping method combined with the outer voltage loop control method, and the Buck converter is used as the CPL of system. The Boost converter is modeled and analyzed by using state space averaging method, and the reasons for the instability of the system with CPL are analyzed in detail. By introducing the active damping method, the inductor current is multiplied by a coefficient and is subtracted from the control voltage, the negative impedance characteristic of CPL is compensated by using a virtual resistor in series inductance, and then the control strategy of active damping method combined with outer voltage loop is obtained. The open loop Boost converter was simulated by the MATLAB software. The simulation results show that the active damping method can effectively solve the problem of instability caused by CPL, and the system has good dynamic performance.Finally, a 300W prototype of active damping Boost converter is developed base on DSP2812. At the same time, a closed loop Buck converter based on SG3525AN control is developed as a CPL of the system, the active damping Boost converter system with CPL is composed of the Buck converter and the Boost converter. By testing the system prototype, the active damping Boost converter with CPL is proved to have good stability and dynamic performance.