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In future high-voltage direct current (HVDC) systems, a large number of HVDC breakers will be required. In this paper, the influence of HVDC breakers on the transient performance of point-to-point HVDC links in both asymmetrical and symmetrical monopolar configuration with half-bridge modular multilevel converters is studied with simulations in PSCAD. As HVDC breakers, the active resonant breaker...
An investigation of the voltage imbalance of the two capacitors of the semi-full-bridge submodule is performed. Since the capacitances are not exactly the same, there may be a difference between the capacitor voltages. The resulting current-spike when they are connected in parallel has been analyzed in a full-scale laboratory experiment.
Focus is on the design and development of an auxiliary power supply converter for HVDC and FACTS applications, utilising integrated gate-commutated thyristors. Due to relatively high requirements for gate drive power and operating voltage of 2.8 kV, special measures have to be considered when designing such systems. The tapped-inductor buck converter topology was chosen as the first non-isolated conversion...
A renewed interest for dc breakers has evolved owing to the visions of connecting several HVDC links into a HVDC grid. Several breaker concepts have been presented and some also have been implemented and tested. A new approach is proposed in this paper. The fundamental principle is to take advantage of the fast recovery of the voltage withstand capability in a Vacuum Interrupter (VI) when the current...
In this paper, a comparison of the energy storage requirements is performed for the modular multilevel converter (MMC) with half-bridge and full-bridge submodules as well as for the alternate arm converter (AAC). Concerning the AAC, the operational mode with overlap period is taken into account and an analytical relation between the overlap angle and the modulation index is presented. This ensures...
Modular multilevel converters (M2C) are increasingly used in high voltage direct current (HVDC) systems. The efficiency of M2Cs is highly related to the modulation method which determines the switching frequency and capacitor voltage ripple in the converter station. A new approach to modulation of M2C is presented in this paper. Tolerance-band methods are employed to obtain switching instants, and...
This paper presents a test circuit and methodology suitable for testing high-power half-bridge submodules such as would be used in cascaded converters for high-voltage dc converters. The circuit utilizes a series resonant tank and two half-bridge submodules with voltage and impedance cancellation in order to minimize hardware requirements.
The modular multilevel converter is a suitable converter topology for high-voltage high-power applications and consists of series-connected submodules. Typically, these submodules are half-bridges with dc capacitors. A voltage ripple in the submodule capacitors is inevitable due to the current flowing in the arms. The converter should therefore be controlled in such a way that the capacitor voltages...
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