Abstract
Multi-terminal high voltage DC (MT-HVDC) grid has broad application prospects in connecting different energy sources, asynchronous interconnection of power grids, remote load power supply, and other fields. At present, the key technologies that affect the development of MT-HVDC transmission system include swift fault identification and location in the DC line and its rapid isolation. Traditional fault monitoring relies on line communication, which cannot guarantee the rapidity and reliability of protection; moreover, it may even cause device damage. A fault identification scheme based on a single-terminal transient is presented in this paper. This scheme calculates the line inductance by using the rise rate of fault current at the initial stage of the fault, and determines the occurrence of the fault by comparing the observed line inductance with the set value, which lays a foundation for calculating the location of the fault point using distance protection. A simulation model on the PSCAD/EMTDC platform is built; the simulation example verifies that the proposed scheme can identify faults under dissimilar conditions while maintaining a low error level on the premise of no communication lines so as to meet the protection requirements of the MT-HVDC grid.
Highlights
High voltage DC (HVDC) transmission technology uses voltage source converter (VSC) as its core component and pulse width modulation (PWM) as its basic control theory
Based on the structure and DC fault characteristics of an multi-terminal HVDC (MT-HVDC) power grid, this paper proposes a DC fault detection and discrimination strategy which only considers the single-ended quantity of a DC line as its criterion
In view of the fault characteristics of the MT-HVDC power grid, this paper discusses the DC transmission line fault protection strategy, and proposes a principle of HVDC grid fault monitoring and traveling wave protection based on a single-terminal quantity
Summary
High voltage DC (HVDC) transmission technology uses voltage source converter (VSC) as its core component and pulse width modulation (PWM) as its basic control theory. [9], a differential protection strategy was proposed to realize fault detection and discrimination by extracting current values at both ends of the line; this method too requires communication lines, which sacrifices the rapidity of fault protection. Based on the structure and DC fault characteristics of an MT-HVDC power grid, this paper proposes a DC fault detection and discrimination strategy which only considers the single-ended quantity of a DC line as its criterion. This fault protection scheme uses the rise rate of fault current to calculate the inductance of the circuit in real-time, determines the occurrence of the fault by comparing this real-time inductance value with that observed during normal operation. Through real-time measurement of the rise rate of the current in each line, the event of DC fault occurrence in the system was identified and discriminated
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