Abstract
This paper presents a region boundaries determination method for critical commutation failures (CF) in multi-infeed high-voltage direct-current (HVDC) systems under unbalanced short circuit faults. By using the nodal impedance matrix, a calculation approach for the converter extinction angles is deduced. First, the extinction angles under unbalanced short circuit faults are calculated. If the extinction angle of a bus is less than the minimum extinction angle, the bus is a failed bus set. By this means, region boundaries of critical commutation failures are demarcated by examining each bus in the AC system. Finally, the effectiveness of the proposed approach was verified by using a modified IEEE 39-bus system.
Highlights
Multi-infeed high-voltage direct-current (HVDC) is widely used in power grids for its advantages in long-distance power transmission (Yao et al, 2020; Mirsaeidi et al, 2018)
According to the calculation results, when a single line-to-ground fault is applied at Bus 15, commutation failures (CF) fault will occur on three HVDC systems at the same time, the three inverters will be blocked, and their DC powers drop to 0 MW
According to the calculation results, when a double line-to-ground fault is applied at Bus 14, CF fault will occur on three HVDC systems at the same time, the three inverters will be blocked, and their DC powers drop to 0 MW
Summary
Multi-infeed high-voltage direct-current (HVDC) is widely used in power grids for its advantages in long-distance power transmission (Yao et al, 2020; Mirsaeidi et al, 2018). The Extinction Angle of a converter station is calculated when any bus has a two-phase fault and line fault in an AC system. According to (8), when a single-phase to ground short-circuit fault happens, the corresponding converter extinction angle ci reaches the minimum value. Double Line-To-Ground Fault and Line-To-Line Fault The fault conditions for a double line-to-ground fault occurring on phase A and B of Bus j can be written as: FIGURE 1 | AC voltage of converter bus after an unbalanced short circuit. Using the same process as in Single Line-To-Ground Fault, the line-to-line voltage between phase A and phase B can be formulated as Eq 12, and the extinction angle can be formulated by an equation. When the double line-to-line fault or line-to-line fault occurs at bus j, the extinction angle cV1,V4 of the corresponding converter at CB i can be calculated by Eqs. 11–14. This serves as a criterion of CF in detecting the line-toline fault
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