Proposed Circuit Breaker Research Articles

Hybrid Z-Source Circuit Breaker with Thomson Coil for MVDC

Hybrid circuit breakers are the most promising circuit breakers among DC circuit breakers. Conventional hybrid circuit breakers complete fault current isolation by converting current to IGBT when fault current occurs. However, in this case, the fault current continues to increase, so the IGBT must be large enough to withstand this current. In addition, in the case of a method of detecting and operating a fault, a delay time of up to hundreds of microseconds occurs, and in a hybrid circuit breaker, this delay time is a very large value. To solve this problem, this paper proposes a hybrid Z-source circuit breaker that operates without delay for low-impedance faults. The proposed breaker is designed to reduce stress on IGBTs and mechanical switches by generating a current zero crossing, as well as to enable the breaker to trip quickly in high-risk cases such as low-impedance fault circuits. Due to the limited environment of the laboratory, we performed 600 V fault isolation experiments. As a result of the experiment, it was confirmed that the proposed circuit breaker successfully isolated the fault within 1.6 ms. The current limiting feature of the Z-source appears to reduce stress on the IGBTs and MOVs used, and it allows for faster fault isolation.

A fuse‐based DC circuit breaker with vacuum interrupter enhanced by an external transverse magnetic field

AbstractDue to the increasing power system capacity, the interruption of large fault currents has gradually become a major challenge in power systems. At the moment, such currents are interrupted mainly via circuit breakers based on the method of active current commutation. However, these types of circuit breakers tend to be costly and oversized. One possible alternative—a fuse‐based circuit breaker with current commutation process enhanced by an external transverse magnetic field (ETMF)—is proposed by the authors. Its main advantage lies in the fast current commutation achieved by an ETMF‐enhanced three‐stage increase of the vacuum arc voltage. The study of the current commutation process is mainly represented by the authors, and the influencing factors of the current commutation—contact opening speed and ETMF current—are discussed. At last, the proposed circuit breaker is verified by an experiment, whose results show that a short‐circuit current of 42 kA can be interrupted within just 2 ms.

Reliability investigation of repeated unclamped inductive switching in a diode-clamped SiC circuit breaker

This paper investigates the reliability of a solid-state circuit breaker with a clamped SiC diode as avalanche voltage after repeated cutoff operations. In solid-state circuit breakers, a clamping element is connected in parallel with a power semiconductor switch to divert the cutoff current. The SiC merged PiN Schottky (MPS) diode is one of the candidates for clamping elements in solid-state circuit breakers because of its high avalanche tolerance and good robustness after the shocks. Reliability tests indicate that no significant electrical characteristics are found for both the SiC MOSFET and the SiC MPS diode in the proposed circuit breaker, even after more than 10,000 unclamped inductive switching (UIS) cycles. These results are based on a 400V, 50A DC distribution system with the UIS condition. The results show that the SiC MPS diode works well as a clamped element for the long-term reliability of the solid-state circuit breaker.

A Bidirectional Efficient Circuit Breaker With Automatic and Controllable Shutoff Functions for DC Distribution Network

Compared with the solid-state circuit breakers based on IGBT and MOSFET, circuit breakers based on thyristor have higher capacity and lower cost, which have been extensively studied. However, the existing circuit breakers based on thyristor cannot achieve fast and reliable shutoff of the fault current. Therefore, a novel efficient bidirectional circuit breaker is proposed in this paper, which has the functions of automatic and controllable shutoff. In any current direction, only one thyristor is conductive, which eliminates the unnecessary power losses. The automatic shutoff function can cut off the fault current independently without detection delay. The controllable shutoff function can isolate the fault reliably without being affected by the line inductance. The proposed topology integrates the advantages of high efficiency, fast reaction and high reliability. Although the existing bidirectional circuit breakers based on thyristor may have one of these advantages, no circuit breaker integrates all of them. Finally, the proposed circuit breaker is verified through simulation and experiment of 1.2kW.

Multi-port DC circuit breaker based on dual capacitor current limiting and energy sink

The coupling relationship between the removal of the fault current and the dissipation of the residual energy of the fault line during the fault isolation process of the multi-port capacitive current-limiting DC circuit breaker prolongs the breaking time of the fault to a certain extent. In order to solve the above problems, this paper proposes a multi-port DC circuit breaker based on dual-capacitor current limiting and energy sinking on the premise of decoupling the fault current attenuation and removal process and the fault line residual energy discharge process. Further reduce the fault breaking time and equipment withstand voltage requirements of the DC circuit breaker. Firstly, the topology and working principle of the proposed circuit breaker are analyzed, and then the parameters in the topology are designed. Then a simulation model is built in the PSCAD/EMTDC simulation platform to verify the fault breaking performance and breaking time. The effect of decoupling the fault current clearing process and the fault line residual energy discharge process on the effectiveness of shortening the fault breaking time is verified.

A Modular Bidirectional Solid-State DC Circuit Breaker for LV and MVDC Grid Applications

Direct current (dc) microgrids are increasingly gaining attention in industrial applications due to their simpler and more efficient integration with renewable energy resources and energy storage elements. The dc grid demands a faster, compact, cost-effective, and fault-tolerant protective system for reliable operation. To address the above challenges, this article proposes a bidirectional solid-state dc circuit breaker topology that guarantees reliable operation of dc grids [low voltage dc (LVDC) and medium voltage dc (MVDC)]. A modular extension of the proposed circuit breaker is also presented, resulting in better reliability, scalability, and fault-tolerant operation. The circuit breaker is derived using power semiconductor devices [silicon-controlled rectifiers (SCRs) and insulated-gate bipolar transistors (IGBTs)], with SCR acting as a main power interruption device. Salient features of the proposed topology include modularity, use of low-power rated devices, low-current rated sensors, and pre-fault interruption. A detailed mathematical analysis validating the design and operation of the proposed modular circuit breaker is presented. Moreover, the article also highlights the merits and limitations of the proposed concept. Finally, a laboratory prototype is developed with a system specification of 400 VDC/14 A to validate the performance of the proposed circuit breaker with single and modular operations, which is in line with the obtained simulation results. To verify current sharing between the modules, a few non-ideal conditions such as the use of non-identical main SCRs and turn-on delay are considered and tested on the developed prototype.

A Novel Low-Loss Bidirectional T-Source Circuit Breaker With Physical Isolation for Low-Voltage DC Distribution Network

The development of a low-voltage dc distribution network has advanced the research on dc circuit breakers. Compared with the Z-source circuit breakers, T-source circuit breakers offer more advantages and greater research value. However, the existing bidirectional Z-source and T-source circuit breakers still suffer from limitations, such as high conduction loss, complex topology, and no physical isolation. Therefore, to solve these limitations, in this article, a novel low-loss bidirectional T-source circuit breaker with physical isolation is proposed. The proposed circuit breaker employs mechanical switches to reduce conduction loss, realize physical isolation, and change the power-flow direction. Since mechanical switches do not need to operate in the fault-clearing stage, the novel circuit breaker does not generate a dc arc and retains the fast self-shut <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-off</small> characteristic of T-source circuit breakers. Moreover, soft-starting circuit and manual-tripping circuit are integrated into the proposed circuit breaker. The detailed analysis and design equations of the circuit breaker are provided. Finally, the capabilities of the novel circuit breaker are verified by simulation and experiment.

A current‐limiting DC circuit breaker with power flow control capability

Power flow controller (PFC), fault current limiter (FCL) and DC circuit breaker (DCCB) are important equipment in the DC grid. There are a large number of power electronic components in these equipment, resulting in high cost. In order to reduce the use of additional components, a current-limiting DC circuit breaker with power flow control capability is proposed here, which integrates the PFC, FCL, and DCCB into one equipment. Further, the main breaker in the proposed circuit breaker is shared by all lines connected to a DC bus to reduce cost. The topology and operating principle of the circuit breaker are introduced. Theoretical analysis and parameter design are carried out. Besides, the proposed circuit breaker is verified in PSCAD/EMTDC. Finally, the performance and cost are compared with existing schemes. The simulation results show that the proposed circuit breaker can effectively realize power flow control, current limiting and fault isolation at a lower cost.

Solid-State DC Circuit Breakers and Their Comparison in Modular Multilevel Converter Based-HVDC Transmission System

This paper proposes a new and surge-less solid-state direct current (DC) circuit breaker in a high-voltage direct current (HVDC) transmission system to clear the short-circuit fault. The main purpose is the fast interruption and surge-voltage and over-current suppression capability analysis of the breaker during the fault. The breaker is equipped with series insulated-gate bipolar transistor (IGBT) switches to mitigate the stress of high voltage on the switches. Instead of conventional metal oxide varistor (MOV), the resistance–capacitance freewheeling diodes branch is used to bypass the high fault current and repress the over-voltage across the circuit breaker. The topology and different operation modes of the proposed breaker are discussed. In addition, to verify the effectiveness of the proposed circuit breaker, it is compared with two other types of surge-less solid-state DC circuit breakers in terms of surge-voltage and over-current suppression. For this purpose, MATLAB Simulink simulation software is used. The system is designed for the transmission of 20 MW power over a 120 km distance where the voltage of the transmission line is 220 kV. The results show that the fault current is interrupted in a very short time and the surge-voltage and over-current across the proposed breaker are considerably reduced compared to other topologies.

An Integral Fault Location Algorithm Based on a Modified T-Source Circuit Breaker for Flexible DC Distribution Networks

Flexible DC distribution networks have been widely developed because of their advantages of high efficiency, low cost, and easy access to renewable energy. However, as distribution networks have more ends than the two-terminal transmission line, it is more challenging to protect them and locate their faults. Therefore, this paper proposes a modified T-source circuit breaker to protect against DC faults. Based on the proposed circuit breaker, an integral fault location method using double-terminal asynchronous data is proposed. The accuracy of the algorithm is not affected by the fault resistance. There are no differential terms in the algorithm, which greatly reduces the sensitivity to noise. The integral algorithm can remain steady when the voltage and current are zero in oscillation and attenuation periods. This constitutes the main contribution of this paper. Finally, it is verified by simulation and experiment that the proposed circuit breaker can isolate the power source within a short time in the typical DC distribution network. Under a noise of 30 dB for simulation, the location error of the proposed algorithm is <0.4% when the fault resistance is 0.5 Ω–500 Ω.

A Resonant Hybrid DC Circuit Breaker for Multi-Terminal HVDC Systems

High-voltage direct current (DC) transmission systems and multi-terminal direct current transmission systems are attracting attention for expanding the grid to promote introduction of renewable energy. Fault clearing in DC systems is difficult because there is no zero point of current. Hybrid circuit breakers are suitable for fault clearing in DC systems. Conventional hybrid circuit breakers have a hard-switching path that damages the switch. Hard switching damages the device and produces emissions due to harmonic noise. A novel resonant hybrid DC circuit breaker is proposed in this paper. The proposed circuit breaker reduces the damage to the switching device using soft switching due to the current zero point. The proposed circuit breaker is compared with conventional hybrid circuit breakers using numerical simulations. Interruption times and switching types of circuit breakers were compared. The simulation results of the fault clearing characteristics of the proposed breakers show that the proposed breakers have sufficient performance and are capable of stable reconnections in multi-terminal direct current transmission systems.

Performance Evaluation of a Modified Bidirectional Z-Source Breaker

An optimized configuration of bidirectional Z-source circuit breaker using a coupled inductor is introduced for the fault isolation in low-voltage dc microgrid. The proposed circuit breaker is designed to operate with a single coupled inductor for bidirectional power flow. Use of the single coupled inductor for the power flow in both the directions reduces the component count. In this article, the operating principle of the breaker is explained for a short-circuit fault condition and breaker design criteria are derived. The performance of the circuit breaker is evaluated by carrying out a MATLAB simulation study. The functional prototype is developed to validate the breaker capabilities. Experimental results show that the fault is cleared within few microseconds. Additionally, the breaker is tested under the step load change condition for a current five times the steady-state rated current of the breaker and results are satisfactory.

Coupled Inductor-Based Zero Current Switching Hybrid DC Circuit Breaker Topologies

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.

Development of a Novel HVdc Circuit Breaker Combining Liquid Metal Load Commutation Switch and Two-Stage Commutation Circuit

The emerging demand on development of high-voltage direct current (HVdc) networks brings about an increasingly urgent need for a fast and reliable HVdc circuit breaker. This paper proposes a novel topology of HVdc circuit breaker combining a liquid metal load commutation switch and a two-stage commutation circuit, which offers an effective solution for isolating faults while preserving larger current breaking capability and lower overvoltage rate of rise. With the topology optimized in terms of circuit parameters for determining their optimum design values, the handling of short-circuit faults for the proposed circuit breaker in HVdc application is predicted theoretically. Finally, preliminary tests from a developed low-power prototype are presented together with a comparative simulation study provided to verify the performance of the proposed HVdc circuit breaker.

A Multiport Circuit Breaker-Based Multiterminal DC System Fault Protection

Although hybrid circuit breaker (HCB) uses a combination of mechanical switch and insulated-gate bipolar transistors (IGBTs) to accommodate HVDC application, it still has a large number of series-connected IGBTs in its main breaker. Besides, in multiterminal HVDC system, three or more HCBs appear in cluster at one node, which worsens the HCBs’ disadvantage in volume. To simplify the breaker cluster’s topology structure and control system as well as increase the compactness, a multiport circuit breaker (MPCB) is proposed in this paper with its control procedure presented. By assembling the HCBs at one node, it can not only cut down the component count for fault interruption remarkably but also reduces the number of control signals. Apart from this, due to a more compact structure, the proposed circuit breaker avoided the use of a dc bus and, hence, dc bus fault which will result in disconnecting the node completely from the system. Hence, regardless of faults and their fault locations, it is always able to connect the remaining healthy ports together. Finally, the effectiveness of the proposed MPCB in different fault scenarios is verified by RTlab.

A new hybrid DC circuit breaker topology

Being advantageous for long-distance power transmission and new energy connection, DC system has wide range of applications in many scenarios. As the capacity of DC power grids increases, the fault current is more difficult to interrupt. And the DC circuit breaker which is very important for protecting DC grid attracts more and more attention of researchers. In this paper, a new hybrid DC circuit breaker topology based on the technique of thyristor forced current zero is proposed. The breaker is able to interrupt the fault current in several milliseconds, and the mechanical switch can be cut off at zero current. In addition, no extra power supply and control devices are needed, the pre-charging capacitor can obtain energy from DC grid directly. Therefore, the control process is simpler and the reliability is greatly improved. The operating principle of the proposed circuit breaker is analyzed in detail, and then the simulation is carried out in PSCAD/EMTDC which verifies the correctness of the theoretical analysis and the feasibility of the breaker.

Novel topology of DC circuit breaker and current interruption in HVDC networks

With the emerging growth of high‐voltage direct current (HVDC) transmission in modern power systems, the HVDC grid has become a hot topic in recent academic research and real projects. In the DC grid, DC faults can have very serious consequences, and so the faulty DC parts need to be rapidly isolated from the system. Compared to the full‐bridge converters for the DC grid, DC circuit breakers are preferred to deal with this problem economically. In this paper, the self‐excited resonant DC circuit breaker is reviewed. Then, a novel scheme of hybrid DC circuit breaker is introduced, and the operation principle of the proposed circuit breaker is described in detail. Finally, a four‐terminal HVDC grid based on a modular multilevel converter (MMC) is used as the DC test system in PSCAD/EMTDC to verify the validity of the proposed DC circuit breaker. From the simulation results, it is seen that the proposed DC circuit breaker has advantages on current interruption time, voltage on DC circuit breaker, investment, etc. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

A Surgeless Solid-State DC Circuit Breaker for Voltage-Source-Converter-Based HVDC Systems

This paper proposes a dc circuit breaker for voltage source converter (VSC) based high-voltage dc transmission (HVDC) systems. Technical challenges for applying dc circuit breakers are to increase blocking voltage and to suppress surge voltage at the current clearing. The proposed dc circuit breaker is a solid-state breaker which consists of a number of semiconductor devices in series. It maintains equal voltage balancing among the devices to apply it to high-voltage applications. Moreover, the surge voltage across the circuit breaker is reduced by employing a freewheeling diode. Considering a system rated at 300 MW in power and 250 kV in dc voltage, the conduction loss of the proposed circuit breaker is estimated to be 0.045% of the rated power. The value is smaller than the power loss of the VSCs. A downscaled HVDC system rated at 10 kW in power and 360 V in dc voltage was built and tested. A series of experimental results demonstrates the dc fault clearing and rapid restoration of power transmission.