Design, Modeling and Control of Hybrid DC Circuit Breaker Based on Fast Thyristors

Abstract

This paper presents a systematic study on designing hybrid direct current (DC) circuit breaker (CB) based on fast thyristors. As an illustration, the DC CB main parameters are calculated for a 120kV, 1.5kA test breaker with interrupting current of 10kA. The studies indicate that the opening time of 2.3ms can be achieved only if fast thyristors are employed. It is further illustrated that there is a design tradeoff between minimum interrupting current capability and discharge time for the internal capacitors (reclosing speed). The DC CB control system for opening and closing is presented based on different levels of protection and the self-protection. The DC CB is modelled in PSCAD and simulation results are used to evaluate the breaker performance under different operating conditions. It is concluded that the model represents well the DC CB and can be employed for DC grid protection studies. It is further shown that opening time becomes longer as interrupting current reduces, and it is very long in case of load current interruption.

A Thyristor-Based DC Fault Current Limiter With Inductor Inserting–Bypassing Capability

“…[16] can be only used in medium voltage range and not suitable for HVDC system. In [17], a hybrid DCCB uses fast thyristors to achieve the purpose of fault interruption is proposed. The DCCB structure takes full use of the thyristors and capacitors to transfer the fault currents between adjacent branches, therefore, minimized number of IGBTs are used and the overall cost as well as the power losses are significantly reduced.…”

“…Considering that the investment can be decreased by using FCL, it is worth of further studying the hybrid FCL under various fault and operation conditions. This paper proposes a bidirectional hybrid FCL using fast thyristors and capacitors, compared to the Alstom Grid's hybrid DCCB structure proposed in [17], the technical features of the proposed FCL include:…”

“…• The proposed FCL will respond to a fault earlier than DCCB, thus the peak current of FCL will be less than using a DCCB only, and the voltage levels of these two devices are similar, ,so the required number of thyristors, capacitors, and surge arresters of the FCL are less than the DCCB in [17] • When the companion DCCB of the proposed FCL is interrupting the fault current, the current limiting inductor in the proposed FCL is intentionally bypassed by the inductor bypass branch to accelerate the decay of the fault current, thus enabling faster operation of the DCCBs.…”

“…Ref. [17] uses a structure where the thyristor and capacitor are connected in series. It uses the clamping voltage of the arrester parallel with the capacitor to keep the voltage across the UFD sufficiently small when it is opening.…”

“…2. Note that the surge arresters for the semiconductor devices in the proposed FCL are not shown for simplicity purpose, and their configurations are similar to the hybrid DCCB reported in [17]. The symbols of all the timings during the fault current limiting process are given in Table 1.…”