Abstract
Hybrid high-voltage direct current (HVDC) transmission systems employ a new type of HVDC transmission topology that combines the advantages of the line-commutated converter system and the voltage-source converter system. They can improve the efficiency and reliability of long-distance power transmission. However, realizing alternating-current (AC) grid-fault ride through on the inverter side of a hybrid HVDC transmission system is a challenge considering that a voltage-source converter based HVDC (VSC-HVDC) is used on the inverter side. In this study, a control strategy for an overvoltage fixed trigger angle based on the power-balance method is developed by fully utilizing the operation characteristics of a hybrid HVDC transmission system. The strategy reduces the inverter-side overvoltage of the HVDC system under a fault in the inverter-side AC system. Simulations based on Gezhou Dam are conducted to validate the effectiveness of the proposed strategy.
Highlights
Line-commutated converter based high-voltage direct current (LCC-HVDC), which is based on thyristor technology, has been widely used in remote and large-capacity transmission and asynchronous interconnection but has the problem of commutation failure on the inverter side [1]
4 College of Electrical Engineering, Beijing Jiaotong University, Beijing, China characteristics of the alternating current (AC) system on the VSC side. It is suitable for the construction of the ultra-high voltage direct current (UHVDC) project and the reformation of the LCC-HVDC project and exhibits good potential for engineering applications [4,5,6,7]
The strategy is based on the powerbalance method and reduces the overvoltage of the HVDC system after a fault in the inverter side AC system
Summary
Line-commutated converter based high-voltage direct current (LCC-HVDC), which is based on thyristor technology, has been widely used in remote and large-capacity transmission and asynchronous interconnection but has the problem of commutation failure on the inverter side [1]. In [15], a new control method for LCC-HVDCs was introduced, which can regulate both the direct-current (DC) voltage and the current of an LCCHVDC system to increase the short-term operating margin of DC power transfer and improve the transient responses to DC power references It can be used for reference for hybrid HVDC transmission systems. For multi-terminal VSC-HVDC, if the system adopts voltage-power droop control, the active power input from a non-fault rectifier station decreases to a certain extent with the increase of the DC voltage, whereas that one from a non-fault inverter station decreases with the increase of the DC system voltage after removal This condition is conducive to the stability of the system [16] but is inapplicable for an LCCVSC. Simulations based on Gezhouba Dam are performed to validate the effectiveness of the proposed strategy
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