no. 7 alkaline battery.Research on supercapacitor energy storage control technology

　　Supercapacitors have been a research hotspot in new energy devices in recent years. Unlike conventional capacitors, their capacity can reach farad level or even tens of thousands of farads, and they can not be broken down in an overcharged state where the electrode terminal voltage exceeds the rated voltage. As an ideal new energy device, its specific power and specific energy are between those of conventional capacitors and rechargeable batteries, making up for the shortcomings of conventional energy storage devices in many application fields. In addition, it also has unique advantages such as small internal resistance, high charge and discharge efficiency (90% to 95%), long cycle life (tens of thousands to one hundred thousand times), superior low-temperature performance, and no pollution [1]. These advantages make supercapacitors very suitable for applications with short-term high power output.

　　Power systems that pursue stable operation and reliable power supply have also introduced supercapacitors as new energy storage devices in recent years, allowing them to quickly charge and discharge when voltage fluctuations or short-term power supply interruptions occur in the power system, thereby ensuring the safety and reliability of the system. sex. At present, research on the application of supercapacitors in power systems has just started to become an upsurge, and practical supercapacitor charge and discharge control is not yet mature. This article applies the bidirectional DC-DC converter to the charging and discharging process of the supercapacitor, analyzes the bidirectional control model, uses the PWM control strategy, and installs PI and PID compensation links according to different charging and discharging conditions to make the system more stable. It meets most situations where supercapacitors need to be charged and discharged quickly.

　　1 Bidirectional DC-DC converter model

　　The bidirectional DC-DC converter is a periodic on-off switching control device between the DC bus and the supercapacitor. Its function is to change the voltage supplied to the supercapacitor. It actually works as a voltage regulation system.

　　In order to meet the needs of use, the converter used should be a two-quadrant converter with reversible current. When the capacitor is discharged to the outside, the DC-DC converter is in a boost state, and when the capacitor is charged, current feedback and DC-DC conversion The device is in a reduced voltage state.

　　The system design converter can be of half-bridge type, consisting of fully controlled transistors IGBT: S1 and S2, freewheeling diodes D1 and D2, diodes D3 and D4 to protect the supercapacitor, and inductor L, as shown in Figure 1.

　　When S1 is in the working state, S2 is turned off, S1 and D2 form a step-down chopper circuit, and the bidirectional DC-DC converter is in the Buck state at this time. In a switching period Ts, when S1 is closed (i.e. 0

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