Design And Implementation Of Discontinuous Current Type Electronic Load

Nowadays,with the rapid development of science and technology,DC power has been widely used in all fields of our daily life. The energy feedback type DC electronic load is a kind of power electronic device, which is used to test DC power before rollout. It can simulate actual load and feed the power cost by test back to power system. Most research of energy feedback type DC electronic load at home and abroad is based on performing aging test on power, aiming to improve the control method of inverter or focus on digital control research.However, the actual output voltage of DC source is fairly low, some natural energy product such as photovoltaic cell fluctuates due to the change of natural energy. To realize the synchronization, the DC bus voltage must be stabled at around 400V, which can't be satisfied by common boost converter. Moreover, when performing special tests on DC source, the energy input of system maybe cause a big change rate or even interruption, which cause a negative impact on the power grid .The system designed in this paper can solve the problem above well. The main content and results of this research are present as follow:Firstly, the propose system complete all function of common energy feedback type electronic load, for example, simulate actual load, feed the power of testing back to power grid with unity power factor. On that basis, to ensure the power feedback process under low output voltage of DC power or voltage fluctuation situation, we adapt the single power switch cascade type Boost with high set-up ratio in the load simulation section. Since electronic load system is nonlinear, we set the linear dynamic model of the system with state space average method, and then design the controller base on frequency domain method.For another, to buffer the impact caused by power feedback process under discontinuous energy input, we propose a new way that add energy storage section to the energy feedback type electronic load system. Energy storage section is consist of super-capacitor bank and bi-directional DC/DC converter, and we determine the type, parameters and series-parallel connection methods of super-capacitor according to the demand of energy storage. Meanwhile, we determine the main circuit parameters and operating mode under different input state of the system. Similarly, we design the controller of energy storage section base on frequency domain method.At last, we set up simulation model in MATLAB/Simulink environment, carry on the simulation analysis of all conditions, and implement part function of energy feedback electronic load. The experimental result generally can meet simulation result, which indicates the correctness of theoretical analysis and design.