Hardware implementation of a four-terminal HVDC test-bed

This paper presents the implementation of a scaled 4-terminal high-voltage direct current (HVDC) test-bed. The hardware construction, control scheme and communication architecture are described. The typical scenarios such as system start-up, station online recommission, power variation, online mode transition and station failure are emulated in the test-bed. A dc line current control is proposed to allow online disconnecting dc lines by using HVDC disconnectors with low current interrupting capability instead of the expensive dc circuit breaker. This control can be further utilized for dc line current limiting function. When a dc line is overloaded, the line current control will be automatically activated to regulate current below the allowable maximum value.