DC Circuit Breaker Research Articles

A nonunit two-stage protection scheme for DC transmission lines in high-voltage DC grids

Nonunit protection is suitable for the primary protection of DC lines in high-voltage DC (HVDC) grids because of its rapidity. However, most existing nonunit protections are not sensitive enough for remote-end high-resistance faults. To solve this problem, a novel nonunit two-stage protection capable of tolerating high-resistance faults is proposed in this paper. First, the propagation process of a traveling wave (TW) generated by the fault is presented, revealing the insufficiency of fault TW-based protections to tolerate remote-end high-resistance faults. Then, the TW generated by the DC circuit breaker (DCCB) located on the opposite end is analyzed, and its characteristic difference between the internal and external faults is discussed. Moreover, the nonunit two-stage protection scheme that contains stage-I and stage-II protections is proposed. Stage-I protection rapidly identifies the closed-end and remote-end low-resistance faults using the fault TW. Stage-II protection identifies the remote-end high-resistance fault using the TW generated by the DCCB, and the fault clearing time is reduced by combining the DCCB operation. The protection criteria, setting principle and operation process of the proposed protection scheme are presented in detail. Finally, a large number of PSCAD/EMTDC simulations validate the excellent performance of the proposed scheme, including a high fault resistance tolerance, quick fault clearing time, and no requirements of excessive sampling frequency and complex mathematical operations.

The Application of Vacuum Interrupters in HVDC Circuit Breakers

It has become necessary to develop high-voltage dc (HVDC) circuit breakers to protect against fault currents that may occur in HVDC grids. One possible HVDC circuit breaker design uses vacuum interrupters as the main dc current path and the dc current interrupter using a counter-pulse system to create an artificial current zero. As the counter-pulse has a relatively high– di / dt, the vacuum arc mode at the current zero is critical when withstanding the resulting transient interruption voltages (TIVs). The fault current in the dc system can also increase rapidly to a very high value. In order to prevent serious damage to the dc grid, it is imperative that the vacuum interrupter open soon after the fault is detected and the counter pulse applied in order to limit its magnitude. This article discusses the vacuum arc modes as the contacts open and the requirements to create a fully developed diffuse vacuum arc at the counter-pulse current zero. The vacuum interrupter also has to develop a large enough contact gap in order to withstand the expected recovery voltages (TIVs). To do this a high-speed opening mechanism is required. Thus, the vacuum interrupter will accelerate faster than it would have experienced in a high-voltage ac (HVAC) vacuum circuit breaker. The article presents the critical design parameters for the vacuum interrupter to operate in a HVDC vacuum circuit breaker and contrast them with vacuum interrupters used in HVAC circuit breakers.

Current Limiting Hybrid High Voltage DC Circuit Breaker With Reclosing Function Limiting

Current Limiting Hybrid High Voltage DC Circuit Breaker With Reclosing Function Limiting

A novel current-limiting method for MMC-HVDC by coordinating virtual impedance control and fault current limiter

The modular multilevel converter (MMC) topology is very suitable for high voltage direct current (HVDC) system to achieve feasible power control, favorable black start capability as well as long-distance power transmission. This paper proposes a novel current-limiting method based on the coordination of virtual impedance control (VIC) and resistive fault current limiter (R-FCL) for MMC-HVDC, and it aims to effectively decrease the DC fault current level and assist the DC circuit breaker (DCCB) to remove the fault reliably and smoothly. Firstly, the MMC-HVDC’s topology and control strategy are expounded, and the modeling method of the VIC and the R-FCL is presented. According to the DC fault evolution, the time sequence coordination scheme of the VIC and the R-FCL for the MMC-HVDC is put forward. Then, considering the introduction of the proposed current-limiting method, the fault characteristics of the MMC-HVDC are theoretically deduced, and the capacity design of the VIC and the R-FCL is conducted. Using MATLAB, a typical ±320 kV MMC-HVDC system with VIC, R-FCL, and DCCB is built, and comparative simulations are performed. The results indicate the proposed approach can strongly limit the DC fault current within the acceptable range, and reduce the electrical stress and thermal stress in the MMC and DCCB. The proposed approach possesses better techno-economics than the R-FCL alone to solve the DC fault problem, and a more efficient protection of the MMC-HVDC is realized.

Experimental Evaluation of 5 kV, 2 kA, DC Circuit Breaker With Parallel Capacitor

This article describes design, operation and experimental testing of a mechanical DC CB (Circuit Breaker) with parallel capacitors. The topology resembles hybrid DC CB but there are possible advantages in the costs since the main semiconductor valve is replaced with capacitors, and in performance since this breaker inserts counter voltage earlier. A detailed PSCAD model is employed to support DC CB design and to analyse operating principles. A 5 kV, 2 kA hardware demonstrator with 1.5 ms disconnector opening time is developed in the university laboratory. The test results demonstrate successful breaking of DC currents, with the measured time for insertion of capacitor voltage of around 290 μs. Further experimental analysis evaluates stresses on the key components, optimal timing for opening of LCS (Load Commutation Switch) and the margins for successful current interruption.

Modular Bidirectional Solid-State DC Circuit Breaker for Next-Generation Electric Aircrafts

The design of electric power systems (EPSs) for the aviation industry has become a major research area to reduce the global annual CO2 emission caused by the transportation sector. DC power distribution is envisaged to meet the high load demand of more-electric and all-electric aircraft power architectures. Nonetheless, the development of dc distribution is significantly impeded by the challenges associated with dc system protection. Aircraft EPS demands high speed and high current protection. Among various dc circuit breaker (DCCB) technologies, solid-state dc circuit breakers (SSCBs) operate at higher speeds. To make them withstand high current ratings, modular structured DCCBs with the highest power density, reliability, and bidirectional fault interruption capability are presented in this article. The existing DCCBs fail to comply with the design constraints such as faster response, high current breaking, and compact design. This article proposes a coupled inductor-based modular bidirectional SSCB that employs the magnetic coupling principle for counter-current commutation of thyristors. The proposed modular SSCB exhibits a fast fault interruption time of approximately 200 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> . The analysis, design, and experimental validation of the proposed SSCB are presented in detail. Each module in the prototype is designed for a system rating of 270 V/15 A. The performance of this SSCB for single- and two-module operations is experimentally verified for a 270-V/20-A dc system.

Effect Analysis of Change of Turn-Ratio in a Transformer Type Superconducting DC Circuit Breaker

Effect Analysis of Change of Turn-Ratio in a Transformer Type Superconducting DC Circuit Breaker

New thyristor-based hybrid DC circuit breaker with reverse injection of resonant current

New thyristor-based hybrid DC circuit breaker with reverse injection of resonant current

A multi‐port hybrid circuit breaker integrated with power flow control ability

Power flow controllers and DC circuit breakers are compulsory components in a multi-terminal DC grid with overhead lines. They are both composed of similar power electronic devices and thus can be reasonably combined together to realize cost savings. This paper proposes a multi-port circuit breaker integrated with a multi-port power flow controller (M-PFCHCB). The topology structure, operation principles, control strategy and parameter configuration are illustrated in detail. The main breakers are composed of unidirectional power electronic switches, and the selection branch is based on two diode strings, which can significantly save the investment of the breaker. The proposed M-PFCHCB is able to deal with the fault isolation and the ultra-fast disconnector failure with high performance. Besides, the power flow of multiple lines can be simultaneously regulated by the M-PFCHCB without any external power supply. The internal power balance is achieved by controlling the AC circulating current inside the M-PFCHCB. The simulations conducted on PSCAD in a five-terminal DC grid with eight DC lines verify the feasibility of the proposed M-PFCHCB. The technical and economic analysis performed proves that the proposed M-PFCHCB can achieve the comprehensive functions of fault isolation and power flow control with low construction cost.

DC fault current-limiting method based on dual-loop active control for modular multilevel converters

PurposeIn the event of a DC short-circuit fault in a flexible DC power grid, the high peak value of the fault current puts forward more stringent requirements on the DC circuit breaker. The existing fault current cutoff mainly focuses on changing the topology structure. To suppress the development of fault current and reduce the investment cost of the DC grid, this paper aims to propose a dual-loop active current-limiting control based on energy difference.Design/methodology/approachFirstly, the equivalent circuit at fault is established, and the parameters related to the fault current are analyzed. Then, the relationship between the output voltage change of the bridge arm and the difference between the AC and DC energy is deduced. Finally, the experimental results are discussed on the real-time simulation platform Opal-RT.FindingsThe proposed current-limiting measures can greatly reduce the fault current, reduce the breaking current of the circuit breaker and increase the capacitor voltage during the fault period, which is beneficial to the stability of the AC system. It is verified that the proposed method is also applicable to a certain high-resistance fault.Originality/valueThis paper applies the method of AC fault to DC fault and deduces the relationship between energy difference and voltage variation corresponding to different step lengths based on digital simulation. In addition, two variables are used as control structure parameters to reduce the probability of system misoperation.

DC Circuit Breakers: A Technology Development Status Survey

DC circuit breakers (DCCBs) play a significant role in obtaining the reliability and stability of DC power systems. Selective and fast isolating of faults minimizes the power supply outages to end electricity users and protects the power converters implemented in the DC system. During the last decades, DCCBs have been deeply investigated in industry and academia. There has been impressive progress in terms of efficiency, response time, power-density, lifetime, and electrical operating ratings. Introducing wide bandgap (WBG) devices further has motivated researchers to propose more efficient and novel topologies. This paper provides a point of reference and a background review for DCCBs from novel aspects, fulfilling absent parts in the literature. The elaborated subjects include current commutation circuitry, DCCBs trip-curves developments, newly added functions to DCCBs, as well as marketing analysis. The advancements of DCCBs are surveyed and development needs are recognized. This paper aims to identify the future research needs of DCCBs for emerging DC power systems.

Modular DC Circuit Breaker With Master−Slave Concept for Gate Driver Simplification: Topology and Implementation

DC circuit breaker is the key equipment to deal with the interruption of short-circuit current. Compared with the mechanical switch, the solid circuit breaker and the hybrid circuit breaker using the semiconductor device to interrupt the short-circuit current exhibit superiorities in response duration and arc-less characteristics. Massive power devices controlled by corresponding gate drivers which make the semiconductors-based dc circuit breaker bulky and costly are required to withstand the high dc-bus voltage. In this article, the master−slave concept based modular circuit breaker is proposed to simplify the gate driver topology. Only one single gate driver is required to control highly compact modular submodules consisting of power devices, passive components, and diodes. Moreover, the proposed topology can be easily implemented with high flexibility and low cost. Specifically, the gate control function and voltage equalization for series-connected devices can be realized reliably. The master−slave concept and operation principle of the proposed topology are elaborated and the effectiveness has been demonstrated by both simulation and experimental test.

Comparison and Analysis of Impedance According to the Winding Method of Superconducting Element Connected to DC Circuit Breaker

DC Interruption technology is essentially required as DC systems and microgrids have increased. The Interruption technology also includes current limiting technology. Until now, many hybrid Interruption technologies have been proposed in which a semiconductor element or a superconducting element is combined with a mechanical DC circuit breaker. In this paper, an interrupting test was performed by combining a superconductor and a DC circuit breaker. The advantage of circuit breakers combined with superconducting elements is that they do not cause losses and effectively limit the fault current. When the fault occurs, if the fault current exceeds the critical value of the superconducting material, resistance occurs in the superconducting element. The fault current is limited by the resistance generated during quenching and resonates due to the LC divergence oscillation circuit. The current flowing through the mechanical circuit breaker reaches zero-point by resonance. After that, the mechanical breaker is completely opened, and the fault current is interrupted. Superconducting elements exhibit different characteristics depending on their winding method, material, and length. The purpose of this study is to comparatively analyze solenoid and toroid coil type superconducting elements. Both types are made with the same number of turns, permeability, and length. As a result of the experiment, the toroid coil has generated more impedance than the solenoid coil.

12-kV 1-kA Breaking Capable Modular Power Electronic Interrupter With Staged Turn-off Strategy for Medium-Voltage DC Hybrid Circuit Breaker

The dc circuit breaker plays an important protection role in the dc distribution systems. Hybrid dc circuit breaker (HCB) offers low conduction losses and reasonably fast response times. In this article, a high power density, modular, and scalable power electronic interrupter (PEI) design is introduced for medium-voltage (MV) HCB platforms. Following this concept, the single low-voltage module is first investigated in terms of the high pulse current ratio and the voltage clamping circuit. After the comparison and test among different devices, a compact module with 1.7-kV discrete IGBTs are selected as main switches. While the voltage clamping circuit is carefully designed to guarantee no tail current bump and sufficient turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> voltage margin. Next the whole system with series modules is optimized on the aspects of the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> strategy, power supply structure, and layout of modules. An improved staged turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> scheme is proposed, which can not only reduce the peak current and total metal oxide varistor (MOV) energy, but also help balance the MOV energy distribution. A 12-kV and 1-kV breaking capable PEI was demonstrated based on the proposed PEI design, achieving a peak power density of 7.4 kW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , much higher than the IGBT module-based solution. The breaking capability and effectiveness of the modular PEI is demonstrated in a 6-kV MVDC HCB device.

Interruption Characteristics of Transformer-Type Superconducting DC Circuit Breaker According to Transformer Turn-Ratio

Series and parallel connection of each superconducting element is required to solve the capacitance problem of the superconducting element. However, unbalanced quench of the superconducting element may occur due to the difference in critical current of a single element. We intended to add a neutral line to the secondary of the transformer of the transformer-type superconducting DC circuit breaker among the interruption technologies proposed. This way has the advantage that the transformer-type superconducting element reduces the fault current through the quenching, and the DC circuit breaker interrupts the fault current by creating an artificial zero-point. In addition, the neutral line solves the unbalanced quench of the superconducting element. In this paper, we compared and analyzed the operating characteristics of the transformer-type superconducting DC circuit breaker by changing the turn-ratio of the transformer from 1:1. As a result, we confirmed that the efficiency of the transformer-type superconducting DC circuit breaker was the best when the turn-ratio of the transformer was 1.1:1.

Resistive SFCL Integrated Ultrafast DC Hybrid Circuit Breaker for Subsea HVDC Transmission Systems

High voltage direct current (HVdc) power transmission systems do not encounter any natural zero crossing unlike the ac systems, and hence, the dc circuit breakers employed should be fast-acting and reliable to ensure safe operation. Circuit breakers (CBs) that have fast response time with lower energy loss dissipation are required for subsea HVdc transmission systems. This article investigates the performance of various CB topologies, including ultrafast coupled inductor hybrid CB (CIHCB) topology without and with the integration of resistive-type superconducting fault current limiter (R-SFCL) for a 100-kV, 100-MW HVdc transmission systems. It is found that the addition of R-SFCL with 1.7-ms response time decreases the peak current through the breaker and, hence, the power dissipated in the CB during short-circuit fault conditions. Thus, the rating of CB can be significantly decreased with the proposed topology. Furthermore, a comparison of power loss in CIHCB with the existing topologies, such as mechanical CB, resonant CB, and HVdc-hybrid CB, are also presented in this article.

A Fault Detection Scheme in MTDC Systems Using a Superconducting Fault Current Limiter

This article proposes a fault detection scheme for modular multilevel converter-based multiterminal dc (MMC-MTdc) girds based upon a resistive-type superconducting fault current limiter (RSFCL). By analyzing the characteristics of the currents through the faulted and healthy lines in an MMC-MTdc system, the theoretical foundations of the scheme are established. This yields a fault detection scheme with fault identification, fault pole discrimination, and high-resistance tolerance abilities. Extensive simulations confirm that the proposed detection scheme can identify the metallic short circuit fault within 1 ms, with the ability to promptly detect faults with high resistance in less than 3 ms taking the communication delay into consideration. This method does not cause any mal-operation of dc circuit breakers as a result of faults on adjacent lines and power order changes. The proposed scheme has immunity to noise and provides full-length protection of the protected transmission line. Simulation results show significant suppression of both the amplitude and the rate-of-rise of the fault current during the fault detection process, which enhance the reliability and stability of the protected grid.

Measurement of electromagnetic environment of hybrid DC circuit breaker during bipolar short circuit fault

Hybrid DC circuit breakers (DCBs) have recently been used to break short-circuit fault currents to ensure safety in flexible DC transmission projects. However, electromagnetic transients from DCB operation can interfere with the secondary equipment and cause malfunctions. In this paper, the bipolar short-circuit test, which is the first short-circuit test for DC transmission line in flexible DC project in the world, has been carried out in the 200 kV HVDC converter station equipped with two hybrid DCBs. The transient magnetic field near the secondary equipment in the DCB hall were measured, and its characteristics were discussed. Furthermore, the relationships among the space magnetic field, the short-circuit current and the action of the power electronic equipment in the DCB were also analyzed The main findings are as follows. During the bipolar short-circuit process, the maximum space magnetic field intensity near the secondary device is 109 A/m, and the maximum rising rate of the magnetic field waveform is about 350 A/m/ms. The magnetic field strength reached its peak value at the moment when the DCB was blocked, as well as the short-circuit current. It can be indicated that the DCB can cut off the short-circuit fault current accurately and reliably. The results can provide reference for the immunity evaluation and anti-interference protection of secondary equipment, and its optimal arrangement in the DCB hall.

3D transient MHD simulation of DC breaking vacuum arc based on artificial current zero

In the vacuum DC circuit breaker based on the artificial current zero, the change of arc luminosity delays the change of current value significantly in the fast current-zero stage. This phenomenon has impacts on the breaking capacity of the DC vacuum circuit breaker. Therefore, it is necessary to study the dynamic characteristics of the arc plasma under the above condition. In this work, a 3D transient magneto-hydro-dynamic model based on the commercial cup-type axial magnetic field (AMF) contact is established to study this phenomenon. The simulation results show that the fast current-zero stage is too short for the plasma to diffuse. The changes of the physical characteristics of the arc plasma lag the change of current value. Moreover, the magnetic field hysteresis caused by the eddy current on the electrode occurs in this stage, resulting in a continuous stronger AMF. It makes the distributions of the plasma uniform, while the diffusion of the arc plasma reduced at low currents, which is detrimental to the post-arc dielectric recovery stage. In addition, in the fast current-zero stage, the AMF near the contact slot is smaller than in other areas. This indicates that the slotting is effective in suppressing eddy currents and avoiding the negative effect of excessive AMF on plasma diffusion at this stage. The simulation results are consistent with the experimental results.

A New Thyristor-Based DC Circuit Breaker Using Diode Clamping Switching

It has been widely accepted to apply dc circuit breakers (DCCBs) to protect dc grids. Nevertheless, existing DCCBs have one or more following limitations: insulation recovery scheme of mechanical switch, additional precharge power supply, high conduction loss, unreliable current-breaking process, and unidirectional design. In this letter, a new DCCB with low conduction loss, simple precharging scheme, and reliable breaking ability is proposed. The proposed DCCB could break both fault and operating current actively with the same simple operation sequences. Moreover, bidirectional topology possessing all advantages mentioned previously is also presented. Topology introduction, parameters designing, and scaled-down experiment of the proposed DCCB are all presented in the letter.