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Peak fault current and energy dissipation in high voltage direct current (HVDC) circuit breakers (CBs) are very important parameters that impact dc grid protection development. This paper analyses a hybrid DCCB (HCB) control that reduces peak current and energy dissipation, by regulating the voltage across contacts of the ultra-fast disconnector (UFD). This is achieved by manipulating the number of inserted surge arresters while contacts of the UFD are moving apart. The controller is seamlessly integrated with the current controller of HCBs. Analytical model for current and energy calculation is presented, verified, and employed for parametric studies. PSCAD simulation with 320kV, 16kA test circuit confirms that the proposed voltage control reduces the peak current and energy dissipation by around 20-30%. A 900V, 500A HCB laboratory hardware is described and the experimental results are shown to corroborate simulation conclusions. Index Terms--Dc meshed grids, HVDC protection, HCB, fault current limiting. Dragan Jovcic (S'97-M'00-SM'06) obtained a Diploma Engineer degree in Control Engineering from the University of Belgrade, Serbia in 1993 and a Ph.D. degree in Electrical Engineering from the

/ has previously been proposed as a temperature indicator for Si and SiC devices, however, the evaluation of its viability for GaN devices is challenging as known current sensors introduce significant unwanted parasitic inductance. This work presents a figure-of-eight magnetic field sensor (∞-sensor) that permits, for the first time, highbandwidth floating current sensing, with negligible insertion impedance and influence on switching performance, in highspeed GaN and SiC switching circuits. The pair of coils are connected in a way that the measurement is immune to currents outside of the sensing region. The simulated bandwidth of the sensor, taking into account the loading by the probe connected to its output, is 225 MHz. The insertion inductance is 0.2 nH, and the insertion resistance is 4.2 mΩ at 100 MHz. This sensor is used to investigate the temperature dependency of turn-on di/dt in a 650 V, 52 mΩ GaN device. It is found that both average and peak turn-on di/dt decrease with temperature. Peak di/dt appears to be the preferred temperature indicator due to its high sensitivity and linearity.

Abstract-Peak fault current and energy dissipation in high voltage direct current (HVDC) circuit breakers (CBs) are very important parameters that impact dc grid protection development. This paper analyses a hybrid DCCB (HCB) control that reduces peak current and energy dissipation, by regulating the voltage across contacts of the ultra-fast disconnector (UFD). This is achieved by manipulating the number of inserted surge arresters while contacts of the UFD are moving apart. The controller is seamlessly integrated with the current controller of HCBs. Analytical model for current and energy calculation is presented, verified, and employed for parametric studies. PSCAD simulation with 320kV, 16kA test circuit confirms that the proposed voltage control reduces the peak current and energy dissipation by around 20-30%. A 900V, 500A HCB laboratory hardware is described and the experimental results are shown to corroborate simulation conclusions.

This paper examines two new bidirectional hybrid dc circuit breaker topologies for application in meshed dc grids. The goal is to retain performance of hybrid DC CB with bidirectional current interruption, while reducing semiconductor count, DC CB size and weight. The fault current is routed to the unidirectional internal valve using multiple additional ultrafast disconnectors. Operation of both topologies is studied using a 320 kV, 16 kA simulation model, as well as demonstrated on a 900 V, 500 A lab prototype. The control systems are presented and discussed in detail. The low-voltage hardware prototypes verify performance of several new technical and operating solutions in laboratory conditions. A comparison is made with the existing DC CB topologies and performance and reliability compromises of each topology are assessed. The conclusion is that it might be possible to halve the DC CB semiconductor count while retaining same 2 ms opening speed and bidirectional operation.

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