UHVDC converter valve system is the demarcation point between AC system and DC system, and it mainly includes converter valve, valve control unit (VCU) and valve cooling system. The converter valve, as the core primary equipment of DC transmission system, is comprised of thyristor, radiator,equalizing and damping circuit, reactor, thyristor control unit (TCU) and surge arrester, etc. VCU is the bridge between the control & protection system and the converter valve, and it is responsible for receiving control signals from the control & protection system, and generating trigger pulses through appropriate modulation scheme, then sending the pulses to the converter valve, while receiving the return signals from converter valve, transmitting them to the control & protection system after treatment, and monitoring converter valve‘s states.
By VCU, converter valve could cooperate with the DC control & protection system, and can realize AC/DC power conversion and quickly adjust transmission power. The converter valve system features fast adjust-speed, reliable operation, and it can guarantee stable output under normal conditions, in case of any accident it could provide emergency support. The system is applicable to long-distance DC transmission, back-to-back DC transmission and multi-terminal DC transmission under a variety of voltage level.
Optimized structure design
Based on the small-sized series thyristor modules, adopt U-shaped flat layer structure and include a sunken dedicated maintenance channel.
Compact structure and well integrality, facilitating for modular production, installation and maintenance.
Use suspension insulators for connecting the valve layers, with well shock-resistance.
Adopt single-insulated indirect water-cooling columnar damping resistance, with clear, simple electrical connection and structure.
High reliability and availability
The valve subassembly and the valve tower both adopt water-electricity separation design, avoiding the waterway fault impact on the circuit.
The materials and components used in the valve are self-extinguishing and flame-retardant, which can reach UL94-V0 flame retardant grade.
Low loss and low thermal resistance
Adopt multi-objective constrained damping parameter optimization method, with low valve-loss and small thyristor reverse voltage stress.
Flow-disturbing channel used in radiator, with low thermal resistance and high heat transfer effect.
High performance TCU
Use dual high-potential self-energy technology, with strong low-voltage ride through capability.
Provide the complete thyristor protections, trigger circuit fully installed in the shielded enclosure.
Adopt variable pulse width technology, effectively distinguishing protective IP pulse and normal resend IP pulse, eliminating the risk of tripping under OLT(Open Load Test) operating mode.
High integration VCU
Adopt high performance general hardware platform based on embedded technology, with high integration, fast processing speed and high reliability.
Provide online monitoring and fault alarm functions for the key components of the converter valve.
Fast fault location for the control unit link failure based on the built-in high-speed recording function, easy operation and maintenance.