The control and performance of a series connected multiterminal HVDC transmission system

A DC fault clearance method for series multiterminal HVDC system

“…The rectifiers other than the rectifier of CST have higher current orders while the inverters have lower current orders. Reference [16] suggested that the CST is determined by the respective summations of rectifier V d -I d characteristics and the inverter V d -I d characteristics. Current control is assumed by a rectifier terminal if the summation of the rectifier voltage characteristics is greater than the corresponding summation of inverter characteristics.…”

“…Furthermore, for series MTDC, a simulator with a digital central controller [15] was used to verify the basic concepts followed by simulator verification in 1975 [16]. In fact, the conventional point to point HVDC is essentially a series connected system and the extension of the point to point HVDC to series connected MTDC is a straightforward evolution [14].…”

“…Besides, the rectifiers at the series MTDC system are usually located at different areas, thus the forced retard operation of several rectifiers need a synchronous mechanism, which relies on the fast and reliable telecommunication among the rectifiers. Reference [16] had reported that without coordination assistance of other terminals, the terminal which is closest to the fault point may not be capable of de-energizing the fault.…”

“…To improve the force retard operation of rectifiers, a DC fault clearance method is proposed by using grounding capacitor to the system at a point or points away from the system ground point [16], as shown in Figure 2. Simulation results in [16] showed that grounding capacitor improves the performance of the corresponding rectifier during DC fault, even if the capacity of the rectifier is small relative to the other terminals.…”

“…Simulation results in [16] showed that grounding capacitor improves the performance of the corresponding rectifier during DC fault, even if the capacity of the rectifier is small relative to the other terminals. If the capacitor is appropriately located and of sufficient size, then a single rectifier may be capable of forcing the current to zero to clear the line fault simply by forced retard of the rectifier and causing the capacitor to discharge through the fault in the opposite direction against the fault current.…”