Commonly used series voltage equalizing circuit for supercapacitors

Supercapacitors commonly used series voltage equalizing circuit?

Supercapacitor series voltage equalization methods can be divided into two categories: one is the way of consuming energy through resistive devices, such as the Zener tube method and the switch resistance method; the other is the way of energy transfer through energy storage devices, such as DC/DC converter method, etc. The Zener tube method and the switched resistance method achieve the voltage balance of the capacitor by consuming energy , which will inevitably reduce the efficiency of the supercapacitor energy storage system, and when the charging current of the supercapacitor is large, it will be difficult to use the Zener tube or the switched resistance method. To meet the requirements of voltage balance, on the one hand, high-power resistive devices increase the volume, which is inconvenient to install, on the other hand, the energy consumption increases, and the high temperature will bring security risks to the energy storage system and reduce the reliability of the system. In addition, the Zener tube method and the switch resistance method can only achieve voltage balance during the charging process, which has certain limitations. The energy transfer voltage equalization method uses energy storage devices for voltage equalization, which is the current development direction of the supercapacitor series voltage equalization technology.

1. Multi-flying capacitor equalizing method

The Duofeidu capacitor voltage equalization method is a voltage equalization method that uses multiple ordinary capacitors with small capacity as intermediate energy storage units to transfer part of the energy in the high-voltage supercapacitor to the low-voltage supercapacitor.

2. Single-flying capacitor voltage equalization method

The single Feidu capacitor voltage equalization method, as the name suggests, is a voltage equalization method that uses an ordinary capacitor with a small capacity as an intermediate energy storage unit to transfer the energy from a high-voltage supercapacitor to a low-voltage supercapacitor.

3. Average value inductance energy storage voltage equalization method

The inductive energy storage voltage equalization method is a voltage equalization method that uses an inductive energy storage device as an energy storage unit. Law.

Topology of bidirectional DC/DC converter

As an energy storage element, it is connected to the grid system through the grid-connected converter. There are two ways for the supercapacitor to connect to the DC bus of the grid-connected converter: one is directly connected to the DC bus of the inverter; the other is through The power converter is connected to the DC bus. Supercapacitors form an energy storage array through series and parallel connection. Since the voltage at both ends of the supercapacitor varies widely during the charging and discharging process, it must be connected to the DC bus through the power converter, so that the grid-connected converter can transmit power to the grid. , the power converter can provide a constant DC bus voltage. Therefore, after connecting to the power converter, the super capacitor has the advantages of low voltage level requirements and high utilization rate. Aiming at the characteristics of supercapacitor energy storage with two-quadrant power flow for energy storage and energy release, the power converter must use a converter that can flow current in two-quadrants—a bidirectional DC/DC converter.

Bidirectional DC/DC converters are divided into two categories according to isolation and non-isolation.

1. Non-isolated half-bridge bidirectional DC/DC converter

The same structure is obtained by changing the power diode of the non-isolated half-bridge bidirectional DC/DC converter into a bidirectional switch to form a non-isolated half-bridge bidirectional DC/DC converter.

2. BUCK-BOOST bidirectional DC/DC converter

The energy of BUCK-BOOST bidirectional DC/DC converter is stored and transferred through the inductor Lsc, which is not suitable for high-power applications. Like the half-bridge bidirectional DC/DC converter, the inductor current can be operated in an intermittent state, but the peak value of the current flowing through the switch tube will become larger, and the advantage is that the structure is simple.

3. Double full-bridge buck-boost bidirectional DC/DC converter

Double full-bridge buck-boost bidirectional DC/DC converter, this circuit is mostly used in high-power occasions where the power supply side is a current source. Due to the full-bridge conversion, the voltage and current stress of each power device is reduced, and the same device It can transmit more power and is suitable for high-power applications.

4. Bidirectional DC/DC converter of double half bridge type buck-boost

Compared with the full-bridge converter, the bidirectional DC/DC converter of double half-bridge type BUCK-BOOST requires a large current capacity of the power device, and its supporting capacitance is relatively high, which is suitable for medium power and high voltage applications.