Single-phase UPS inverter composite control design

1206RGB (single)

Single chip microcomputer STM32L151CCU6

Photocoupler

Overview:
This paper analyzes the output characteristics of pulse width modulation (PWM) single-phase uninterruptible power supply (UPS). An integrated control strategy based on UPS inverter combining repetitive control and fuzzy PI control is proposed. Fuzzy PI control improves the dynamic characteristics of the UPS inverter, and repeats the control to improve the steady-state accuracy of the UPS inverter. Experimental results show that this strategy can obtain waveforms with good dynamic and steady-state characteristics.

1 Introduction
UPS is usually used in places where power quality is critical, such as financial departments, medical centers, communication systems, military equipment, etc. Generally, the output waveform of the UPS is of good quality, fast dynamic response, and strong anti-interference ability. In recent years, Chinese and foreign scholars have developed a variety of inverter power waveform control technologies: PID control, deadbeat control, sliding mode variable structure control, repetitive control, fuzzy control, etc. Various control methods have their own characteristics, showing excellent characteristics and deficiencies. In this paper, the mathematical model of single-phase inverter is established for the problem that the UPS inverter power waveform can not take into account the steady-state effect and dynamic effect. A new control strategy based on the combination of repeated control and fuzzy PI control is proposed. The repetitive control is used to eliminate the periodic interference of the inverter and improve its steady-state accuracy. The fuzzy PI control is used to improve the transient response speed of the inverter to the aperiodic disturbance. The experimental results show that the UPS output waveform quality controlled by the controller is good, the steady state precision is high, and the dynamic response is fast.

2. Single-phase full-bridge PWM inverter structure The main circuit structure of single-phase full-bridge inverter is shown in Figure 1.
In the figure, T1~T4 are IGBT switching devices, E is DC input voltage, filter inductor L and filter capacitor C form a low-pass filter, and resistor r is connected in series with filter inductor L, which provides dead zone effect and loss of each link. A small damping.

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