Circuit diagram design of DC DVR device based on supercapacitor energy storage

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Overview:
Voltage sag is one of the most dangerous power quality problems in power systems. Aiming at the voltage sag problem, this paper proposes a DC-based dynamic voltage restorer (DVR) device based on supercapacitor, completes the main circuit of the device and the control method of supercapacitor charge and discharge, and simulates the device. And experimentation. The test proves that the device can effectively support the DC voltage of the sensitive load when the voltage sag occurs in the power grid, and reduce the impact of the voltage sag on the sensitive load.

0 Introduction With the development of science and technology and the expansion of industry scale, the electricity consumption of various sectors of the economy is increasing. More and more users use high-tech equipment with good performance and high efficiency but sensitive to changes in power supply characteristics, such as : Robots, automated production lines, precision CNC machine tools, high-precision measuring instruments and computer information management systems. These systems and equipment are sensitive to various disturbances in the power grid, and any power quality problem can cause significant economic losses and adverse social impacts. In the complaints about users' power quality problems, more than 90% involve voltage sag problems; statistical data and case reports show that most of the factors that cause abnormal operation or power outage of power equipment are also caused by voltage sag. Therefore, this paper mainly studies the voltage sag governance problem. For the sensitive load equipment with rectified inverter structure, a new idea of ​​using supercapacitor to control voltage sag is proposed.

1 Voltage sag Voltage sag refers to the event that the supply voltage suddenly drops in a short time. The International Electrotechnical Commission (IEC) defines voltage sag as the voltage rms value drops to 90% to 1% of the rated value, and the Institute of Electrical and Electronics Engineers (IEEE) defines it as falling to 90% to 10% of the rated value. Its typical duration is 0.5 to 30 cycles. Severe voltage sag will cause the use of electrical equipment to stop working, or the quality of the products produced will be degraded. The severity of the consequences will vary depending on the characteristics of the electrical equipment.

The treatment of voltage sag is a complex project. Usually, the auxiliary equipment is used to make the main equipment load withstand the frequent voltage sag. The super capacitor voltage sag suppression device studied in this paper is such auxiliary equipment. At present, the voltage sag control devices studied at home and abroad mainly include dynamic voltage restorer (DVR) and uninterruptible power supply (UPS) of the AC system. For devices with DC bus, if UPS compensation equipment is installed, the system has low cost performance due to short service life, small discharge current and long charging time. If the DVR and other devices are installed, the main circuit of the system exists. Two inverter circuits not only reduce system efficiency, but also increase costs. For devices with rectified inverter structure, we have developed a DC DVR device based on supercapacitor energy storage. The bidirectional half-bridge DC-DC converter is combined with a supercapacitor to control the charging and discharging of the supercapacitor through a double closed loop method. When the voltage sag occurs in the system, the DC bus voltage supporting the sensitive load reaches the purpose of the control voltage sag (Fig. 1).


Figure 1 The main circuit of the voltage sag governance system

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