Flexible DC-Link Capacitors for VSC-HVDC Converter Valves

Product Features
General Technical Requirements
Special Technical Requirements
Long service life: Not less than 40 years, and the capacitance change does not exceed 5%;
High reliability requirements: low failure rate, less than 100 FIT
Fire protection requirement: Dry type, oil-free, and meeting UL-94V0 flame retardant grade;
Explosion-proof requirement: Equipped with a pressure relief valve and/or pressure switch.
Special Technical Requirements
High ripple voltage;
Low self-inductance and low equivalent series resistance;
High harmonic current;
Product Dimensions
Customized design is supported according to engineering requirements.

Primary Application:
DC support capacitors for flexible DC transmission constitute one of the critical components of flexible DC transmission systems. Integrated into valve towers alongside switching devices—such as IGBTs and IGCTs—these capacitors form modular units that serve to stabilize the DC bus voltage, absorb ripple currents, and simultaneously safeguard the switching devices (IGBTs, IGCTs, etc.).
Voltage Source Converter High-Voltage Direct Current (VSC-HVDC) transmission is a new type of power transmission method based on Voltage Source Converters (VSC), mainly divided into three topological structures: two-level, three-level, and Modular Multilevel Converter (MMC). MMC has the advantages of low loss, small harmonics, and good scalability, and has become the mainstream technical solution in the field of VSC-HVDC transmission. The MMC converter valve consists of three-phase units, each phase unit is composed of upper and lower bridge arms, and each bridge arm is composed of multiple sub-modules. The DC-link capacitor is an important component of the sub-module. As an energy storage element on the DC side of the converter, it provides DC voltage for the converter, buffers the DC side voltage fluctuation during system faults, reduces the DC side voltage ripple, and provides DC voltage support 
-for the receiving end. The DC-link capacitor is crucial for the safe and stable operation of the converter valve and even the entire power transmission system.

Main Applications:
The DC-link capacitor for VSC-HVDC transmission is one of the key components of VSC-HVDC transmission; it forms a module with converter switching devices, such as IGBT and IGCT, and is applied in the valve tower to support the DC bus voltage, absorb ripple current, and protect the safety of switching devices such as IGBT and IGCT.