Search

The diode bridge submodule (SM) is one of the basic units of a hybrid high-voltage dc circuit breaker. This article works on the low inductance design of a single SM and series SMs. For the layout design of a single SM, this article proposes a simple and clear +-shaped SM layout, the low inductance design is simplified to the optimization of two laminated busbars with a simple structure. Based on the +-shaped SM layout, this article further proposes an SM structure with holes in diodes region, the stray inductance is further reduced, and only one integrated laminated busbar is needed in a single SM. For the layout design of series SMs, this article makes full use of the layout of a single SM and the mutual inductances between the SMs, series SMs are alternately connected in reverse. The single SM layout proposed in this article is effective in reducing the stray inductance. The loop stray inductance in stage II reduced from 148.4 to 72.3 nH, a 51.3% reduction. When the two parallel IGBTs turn off a 6 kA fault current in 2 μs, the voltage spike is reduced from 786.1 to 423.4 V, a 46.1% reduction. And the stray inductance difference of the bidirectional current path is controlled to about 10 nH. The layout of series SMs proposed in this article is effective in reducing the length of the series SMs, the length is reduced by 16.7%. The experimental results show that the SMs layout proposed in this article is effective. [ABSTRACT FROM AUTHOR]

Hybrid circuit breaker (HCB) has shown good performance for interrupting dc fault current. However, a massive number of IGBTs in series is needed. These will lead to high costs and significant difficulty in balancing IGBT dynamic voltage. This paper proposes a bidirectional hybrid circuit breaker based on a cascaded half-bridge submodule structure to reduce the overall costs and implementation difficulty of HCB. The number of IGBTs is reduced by 50%, and the operating speed is fast enough. A model of a four-terminal modular multilevel converter (MMC) system with a proposed hybrid circuit breaker in different stages is developed to describe the fault blocking process more clearly. The performance of the proposed HCB is validated and compared with other HCB structure through both theoretical derivation and time-domain simulation. [ABSTRACT FROM AUTHOR]

A mechanical switch can be used instead of a power electronic load commutation switch in orderto reduce the losses during normal power flow in standard hybrid DC circuit breakers. The success of current commutation in such hybrid breakers depends on the arc voltage formed across the contacts in the mechanical switch. The behaviour of rapidly elongated, wall constricted arcsgenerated during the opening of an ultra-fast mechanical switch in the air is studied here. The voltage-current characteristics of the generated arcs are obtained for steady state contact opening velocities of 6, 11 and 21 m/s. It is found that the arc voltage at a given current and contact separation increases with the contact opening velocity. It is shown that stationary,zero-contact-velocity characteristics can not be used to accurately quantify the voltage build-up in fast elongating arcs in hybrid breakers. A best-fitting black-box equation for the dynamic arc characteristics is presented for the tested velocities. The obtained voltage-current characteristics are used as input to simulate the current commutation process in a 12 kV hybridDC circuit breaker case-study. Different scenarios of current commutation failure related to the arc voltage build up are identified. It is shown that these failures scenarios can be avoided by increasing the contact opening velocity. [ABSTRACT FROM AUTHOR]

This article presented a new hybrid circuit breaker solution for using in dc microgrids. The proposed solution can offer a high-reliability protection feature for the dc microgrid with low conduction loss, bidirectional current flow, and galvanic isolation function. In the design, it is combined with a group of mechanical switches and semiconductors, where the mechanical switches handle the current conduction during normal operation and the semiconductors handle the breaker response during transient operation. The design fully utilizes the advantage of both types of switches and maximizes the performance and life time of the system. Throughout the design, it maintains only one mechanical switch in series with each power line; thereby, the high conductivity of the circuit breaker is maintained. At the same time, through the hybrid design, the electrical stress applied to the mechanical switch is eliminated. Thus, an effective and high-reliability solution is provided for the design of dc circuit breakers. The operation principle is explained in detail and the design guideline is provided. A 150/380 V and 15 A circuit breaker is successfully implemented, and the performance is experimentally verified, which shows good agreement with the theoretical findings. [ABSTRACT FROM AUTHOR]

With the rapid development of DC transmission technology, DC circuit breakers, the key equipment for DC fault handling, have become a research hotspot of scholars. This paper proposes a novel hybrid DC circuit breaker topology to improve the shortcomings of traditional hybrid DC circuit breakers. Traditional hybrid DC circuit breakers use too many IGBTs, which results in a large volume and a high cost. The main innovation of this topology is the use of a mechanical switch in series in a solid-state branch, which withstands most of the voltage. An oscillating circuit is in parallel on the mechanical switch, which can generate reverse current to reduce the current flowing through the mechanical switch to zero, to achieve arc free breaking. The feasibility of the proposed topology is verified based on a PSCAD simulation platform. It should serve as a valuable reference for the design of DC distribution systems and DC breakers. [ABSTRACT FROM AUTHOR]

Hybrid dc circuit breaker (HCB) is an effective device for interrupting dc fault currents in dc grids. Conventional two-port HCB requires too many insulated gate bipolar transistors (IGBTs) in series in its main breaker, resulting in considerable costs. Recently proposed multiport hybrid dc circuit breakers (multiport HCBs, and the number of ports is greater than or equal to 2) interrupt fault currents on multiple lines using only one shared main breaker, significantly reducing the implementation costs but losing some fault handling capabilities. To overcome these obstacles, we propose a novel high-performance economical multiport hybrid dc circuit breaker (MP-HCB) in this article. The topology and its control method are proposed. Due to the designed ring-connection structure, the proposed MP-HCB can avoid dc bus fault, and thus is more reliable. The electrical stresses of the breaker are theoretically analyzed, and the parameters are determined to make the MP-HCB capable of multiple-line faults. Compared with the typical two-port HCB and the existing multiport HCBs, the proposed MP-HCB can achieve full fault current interruption capability with lower costs. To protect a dc node connecting with three lines, the cost of the semiconductors of the proposed MP-HCB is only 1/3 of the typical two-port HCB and 1/2 of the existing multiport HCB. Finally, the performances of the proposed MP-HCB are verified via a four-terminal HVdc system in power systems computer aided design/ electromagnetic transients including DC (PSCAD/EMTDC). [ABSTRACT FROM AUTHOR]

The fast raising nature of DC fault currents and sensitivity of high-voltage DC (HVDC) power converters to DC faults is critical protection issues. On the other hand, DC fault current does not meet zero; which causes DC to fault current breaking process become more challenging. Specifically, to protect HVDC grids against DC fault currents, the development of very fast breakers is crucial. This study proposes a DC fault current limiter and breaker, which is able to protect the HVDC system/grid in a very fast and safe manner. The main goal of this study is to enhance the performance of already in the market hybrid DC circuit breakersincluding the magnitude of fault current and breaker operation speed. In the proposed HVDC fault current limiter and breaker, the fault current is limited in two stages by an inductive and resistive current limiter, which drastically decreases the main breaker dissipated energy. The functionality of the proposed HVDC fault current limiter and breaker is mathematically analysed, and then verified by PSCAD and Matlab/Simulink. Finally, simulation results are validated by scaled-down laboratory examinations. [ABSTRACT FROM AUTHOR]

Hybrid dc circuit breakers (HCBs) usually require a large number of insulated-gate bipolar transistors (IGBTs) with high turn-off capability for series and parallel connections. This requirement entails excessive cost. Compared with IGBTs, integrated gate-commutated thyristors (IGCTs) are another kind of fully controlled power device with high surge current and voltage capability but are low cost. However, the weak turn-off capability of IGCTs hinders their application to high-powered HCBs. On the basis of the complementary advantages of IGBTs and IGCTs, this paper proposes a mixture solid-state switch (MSS) for HCBs that uses the switching action of several IGBTs to create a low-current condition that favors the turning off of large-scale series-connected IGCTs. The MSS topology can significantly reduce cost while maintaining the excellent performance of traditional solid-state switches. This study also introduces two different turn-off modes for MSS, namely, single oscillation and multiple oscillations. Finally, 25 kV/20 kA prototypes in both modes are developed to verify the effectiveness of the MSS topology. [ABSTRACT FROM AUTHOR]

This paper proposes a time-domain method to calculate the fault response in multiterminal dc (MTdc) grids and the performance of hybrid dc breakers. The proposed method, based on traveling waves: 1) provides a sound representation of fault performance by considering all created traveling waves; 2) introduces a new approach to estimate the reflection coefficients; and 3) provides an approximation of the worst case fault location. Then, based on the analytical results, three parameters of the hybrid dc circuit breaker, i.e., current limiting reactor, arrester rated voltage, and time delay are optimally selected with respect to maximum overcurrent, maximum overvoltage, fault clearance time, and energy absorption in arresters through multiobjective optimization. Accuracy and performance of the proposed method are evaluated and verified by time-domain simulation studies in the power systems computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) environment using frequency-dependent models. The results confirm reasonable accuracy of the proposed fault performance calculation and represent a further step towards optimized design of hybrid dc circuit breakers. [ABSTRACT FROM AUTHOR]

This paper proposes a coupled inductor-based hybrid dc circuit breaker topology with zero current switching for fast fault interruption in dc systems. A series resonant circuit comprising of the secondary winding of a two-winding coupled inductor and a charged capacitor (commutation capacitor) is switched on during fault to inject a counter-current pulse, and, consequently, force a zero crossing of fault current. Proposed solution facilitates arcless breaking for a mechanical circuit breaker due to zero current turn-off. The proposed circuit breaker exhibits fast fault response ($\sim$ 30  $\mu$ s), and the response time is programmable based on the design of the coupled inductor and commutation capacitor. Furthermore, presented solution mitigates the requirement of energy-absorbing elements for demagnetizing the dc network following fault interruption, in contrast to conventional dc breakers. The paper also presents two modified circuit-breaker topologies to achieve unipolar voltage profile on the capacitor, which will enable the use of electrolytic capacitors for commutation so that the capacitor stack size is reduced in high-voltage applications. Detailed analysis and design equations are presented to explain the operation of the proposed topologies. Functionality of the proposed circuit breakers is verified through simulation, and experimental results are based on two laboratory prototypes. [ABSTRACT FROM AUTHOR]

Highlights • The proposed method can significantly improve the system operation reliability. • The proposed method is insensitive to fault locations, fault types, etc.. • The proposed method can determine the permanent fault location precisely. • There is no impact on the MTDC grid when the method is performed. Abstract In order to ensure that the healthy lines continue to operate after the line fault, the multi-terminal high voltage direct current (MTDC) grid based on half-bridge modular multilevel converter (HB-MMC) prefers to isolate the fault line using DC circuit breakers (DCCBs). Since most of overhead (OH) line faults are instantaneous faults, after the fault line is isolated, usually the DCCB will reclose with a certain delay to improve system stability. For fear of reclosing to permanent fault, this paper proposes a fault property identification (FPI) method suitable for MTDC grids with hybrid DCCBs (HDCCBs), which can distinguish between instantaneous and permanent faults. The method is based on the characteristic signal injected by the HDCCB with the auxiliary circuit. Besides, once a permanent fault has been determined, the method can also locate the fault position accurately. The effectiveness of the proposed FPI method is verified by extensive simulations in PSCAD/EMTDC platform. [ABSTRACT FROM AUTHOR]

• The steady state availability of hybrid DC circuit breakers is relatively high, but the failure rate is much higher than AC circuit breakers. • The reliability of hybrid DC circuit breaker is mainly affected by IGBT valve block. • Passive redundancy performs better in reliability improving of hybrid DC circuit breaker. Natural commutation hybrid DC circuit breakers integrate the low loss of mechanical circuit breakers and the fast switching speed of solid-state circuit breakers. Its overall reliability determines the success or failure of the control of the current distribution of the DC distribution network. In this paper, the Fault Tree was used to analyze the basic components that caused the circuit breaker to fail, based on the topology of hybrid DC circuit breaker. The Markov model is introduced into the reliability modeling of hybrid DC circuit breaker to calculate steady state availability, failure rate and mean time between failures. On this basis, k/n(G) model and Gamma distribution are used to analyze the redundancy of weak components in hybrid DC circuit breakers. Finally, the influence of different redundancy components and different redundancy modes of weak components on the reliability of hybrid DC circuit breakers is analyzed quantitatively. The analysis methods and results can provide a reference for reliability prediction and design of hybrid DC circuit breakers. [ABSTRACT FROM AUTHOR]

In recent years, dc distribution grids have become increasingly popular because of the interest in the diffusion of distributed renewable energy. In this scenario, dc distribution grids are also favored because of the increased use of batteries and power electronic loads. The main limit to the spread of dc grids is their protection devices, which still present several problems. At present, protection devices are represented by traditional mechanical breakers or static electronic components. The first, which interrupt dc currents, have good reliability but need maintenance and have long intervention periods. In contrast, electronic switches are fast and reliable, but they reduce the efficiency because of their voltage drop. In this scenario, some hybrid breakers have been proposed to obtain the advantages of both devices. The previous solutions of hybrid breakers still suffer several critical issues and, usually, are not capable of protecting a system from short circuits without significantly reducing their lifetime. In this paper, a new low-voltage hybrid circuit breaker topology is proposed. The procedure to dimension all of the active and passive components in the device is analyzed, and the effectiveness of the proposed solution is proven by means of experimental results obtained using a prototype. [ABSTRACT FROM AUTHOR]

The dc fault current has a high amplitude and a fast rising speed, therefore with regard to the hybrid dc circuit breaker, it is hard to meet the requirement of a high breaking capacity while maintaining economically efficient. The SI-SFCL can prevent the speed of the fault current from rising too fast, and ensure the current remains under the interrupting capability of the dc circuit breaker, so the couse of the SI-SFCL and the dc circuit breaker is an effective solution for fault clearing in dc grids. In this paper, the current-limiting requirement of the DCCB is given, and a simplified equivalent circuit of the active SI-SFCL is proposed, based on which the matching between the electrical parameters of the active SI-SFCL and the dc circuit breaker is studied. Parameter constraint and the protection voltage range of the active SI-SFCL are given. Finally, the conclusion on the matching between the electrical parameters of the active SI-SFCL and the DCCB is verified by MATLAB/Simulink. [ABSTRACT FROM AUTHOR]

This technical note presents the conceptual design of bidirectional hybrid dc circuit breaker for quench protection circuit (QPC) of the China fusion engineering test reactor. The rated parameter of bidirectional hybrid dc circuit breaker is up to 70 kA and 15 kV. The novel scheme based on a mechanical breaker and the controlled static circuit breaker (SCB) in parallel is proposed. The mechanical breaker consists of three independent control contacts to realize the rapid transfer of the large current and fast recovery of dielectric strength. The SCB is composed of the insulated-gate bipolar transistors (IGBTs) unit and four diode units in a rectifier scheme for both current directions. Moreover, the feasibility of bidirectional dc circuit breaker, such as the turn-on reliability of IGBTs unit, and voltage sharing and current sharing of each IGBTs are investigated in this technical note, finally, the conceptual design result of the QPC is given. [ABSTRACT FROM AUTHOR]

The direct current circuit breakers are considered a promising option to protect the transmission line against commonly appearing line-to-ground fault. However, the challenges of losses in the nonoperational stage, escalation of response against fault current, and large fault current handling capability remain the debatable issues for direct current circuit breakers. This paper introduces a novel topology of the hybrid circuit breaker with fault-current-limiting characteristics, which contains three branches: the main branch, fault-current-limiting branch, and energy absorption branch. The main branch includes a mechanical switch, breaker impedance, and bidirectional power electronics switches. In the fault-current-limiting branch, a fault-current-limiting circuit is introduced which contains n numbers of bidirectional switches and current-limiting inductors, which are connected in series to make the design modular in nature. During the normal working stage, the current flows through the main branch of the breaker. Once a fault in the system is confirmed, the fault current is transferred to the fault-current-limiting branch. At this stage, the intensity of the fault current is reduced significantly using the fault-current-limiting circuit, and finally, the residual current is shifted to the energy absorption branch. The working principle, design considerations, and parametric analysis concerning the design of hybrid circuit breakers are incorporated in this paper. The performance of the proposed breaker is evaluated using a three-terminal voltage-source converter-based high-voltage direct current transmission network; for this purpose, a PSCAD/EMTDC simulation tool is used. The performance of the proposed breaker is also compared with other topologies. The comparative analysis shows that the proposed breaker is a good alternative considering high fault current interruption requirements, response time against fault current, and power losses. [ABSTRACT FROM AUTHOR]