# Energy-Feedback Load Simulation Algorithm Based on Fuzzy Control
## 1 Introduction  
Uninterruptible power supply, power battery, and charging pile, such as power equipment in the process of manufacturing, require a series of strict product testing. Load can be traditional and electronic. The energy consumption in the process of load simulation, the output energy by measuring equipment on the load resistance, and power components such as heat dissipation assist the cooling device. The energy-fed electronic load does not have energy dissipation devices, and the test energy is conveyed to the public grid or the input end of the tested equipment through the switching circuit, thus forming an energy loop, which not only completes the load simulation function but also realizes the energy recovery. The front stage of the energy-fed AC electronic load is the load simulation unit, which not only realizes the high-precision load simulation but also undertakes the function of rectifier and voltage boost. The PI parameters of a traditional load simulation PI control algorithm are fixed values, which cannot adapt to complex load simulation conditions [1]. It is easy to cause system overshoot and steady-state errors, and there are certain limitations on the stability and response speed of the system. Therefore, the accuracy of load simulation and steady-state precision of overload are a great test. At the same time, when the load analog boost circuit only adopts the traditional PI control, it cannot give good consideration to the problem of response speed and current overshoot. In order to obtain faster dynamicresponse, the input current overshoot will be larger [2]. In light of this, the over-current protection of the triggered system will lead to the restart of the energy-fed DC electronic load, which will lead to the damage of components and increase the cost of operation and maintenance. Therefore, an efficient and high-precision control algorithm is very important for simulating load cells. The load simulation algorithm in Reference [3] adopts voltage single-closed-loop PI control, compares input voltage with the reference voltage, passes through a PI controller, and finally outputs the control signal used to control the phase-shifted full-bridge load analog circuit. Reference [4] adopted an integrated automatic control single-cycle controller chip and reconfigurable field-programmable analog array. With its simple interface structure, it does not need to adopt DSP to design a control algorithm, which saves the cost of research and development. In Reference [5], the former load analog circuit adopted the repetitive control algorithm based on the internal model principle and improved the robustness of the control system by introducing historical deviation information. The steady-state performance of the system was good. Recent works [6; 7] used the recharging structure of the converter circuit; that is, using the proposed resonant load with a wide variety of speeds and continuous loading function, the feasibility of the tested battery was verified, and the energy recycling was realized in the test process. Aiming at the problem that PI control depends on the system model, a load simulation control strategy was proposed in Reference [8], which combines single-cycle control with PI control. The control algorithm switcher can switch between PI control and single-cycle control according to the given quantity and feedback quantity. Therefore, it has the advantages of the fast dynamic response of single-cycle control and high steady-state precision of PI control. In References [9; 10], a load analog control algorithm of the digital outer loop and analog inner loop was proposed. The given current reference value was obtained by the digital outer loop and then converted to the analog inner loop. The analog inner loop is a special analog control chip for the power circuit. The algorithm has a fast response speed and can realize cycle-by-cycle current control, but there is a temperature drift problem, which affects the control accuracy.