Guangfu Tang

Study on the design and equivalence test methods of VSC-HVDC valves

The high voltage direct current transmission technology based on voltage source converter (VSC-HVDC) which employs voltage source converter (VSC), self-turn-off device and pulse-width modulation (PWM) technique. VSC can be categorized into two types as per its topology: one is multi-level converter which consists of series-connected self-turn-off devices, and the other is Modular Multi-level converter (MMC) which is made up of series-connected submodules whose major components are self-turn-off devices. To ensure safe operation, type testing of VSC-HVDC valves is essential before launching them. Substitute equivalence methods are always utilized for valve type tests. For different converter topologies, test objects and test methods are similar. This article begins with the studying of the two kinds of VSC-HVDC valve topologies, and then the electric structures are analyzed. Moreover, corresponding equivalence test methods are investigated, including valve stresses, test requirements, test items, and test methods.

Analysis on voltage distribution performance of HVDC thyristor valves

Analysis and simulation on voltage distribution of HVDC thyristor valves under a variety of voltage stress are performed respectively. The summarized influencing factors on voltage distribution indicate that they are different with frequency. Due to the importance and difficulty in approaching even distribution in high frequency, the voltage distribution with different module structure and different power circuit parameters is also investigated in detail. Equivalent circuits are built and circuit analysis method is applied on the basis of “field-circuit coupled method”. It shows that module structure such as framework and module size, module array etc. influence both stray capacitances and equivalent circuit topology, consequently the voltage distribution performance. Besides some power circuit parameters also take great effect. All these key factors are listed and their influences on transient voltage distribution are generally discussed

Upgrade test capability for ±800kV/6250A and ±1100kV/5454A UHVDC valve

The paper mainly described the upgrade study of UHVDC converter valve type test capability, which will meet all the test requirements of ± 800kV/6250A and ±1100kV/5454A thyristor valves. By optimizing and upgrading rectifier transformer and water-cooled systems, especially that a new synthetic fault test circuit, the operational test capability reaches rated current 7500 A, and fault current peak is 62 kA. In addition, surface electric field intensity on shielding cases of the impulse test equipment is calculated by using Galerkin boundary element method. According to existing conditions, a feasible measure is proposed, which can be employed to decrease electric field dramatically and avoid corona discharge of shielding cases. Another effort in the dielectric test is theoretically analysis and test study for the DC test equipment with rated voltage ±2400kV. Finally, the parameters and results for the ± 800kV/6250A and ±1100kV/5454A prototype will be presented.

Operational tests on thyristor valves for Ningdong-Shandong ±660kV UHVDC project

For purchasing more efficiency, more power transmission capacity, UHVDC projects are employed in the gird of China. Thyristor valves, as one of the key equipments, must pass the operational tests in order to make sure the valve design is proper. In coordinate with IEC60700-1 standards and based on thorough investigation and comparison of exiting operational test circuits, a new operational tests circuit is developed and applied in the Ningdong-Shandong ±660kV UHVDC project. In this paper, the topology and working principle of the test circuit are introduced. Then test parameters and results are presented, showing that development of thyristor valves for Ningdong-Shandong UHVDC project is successful.