Hybrid DC Circuit Breaker Research Articles

A Multi‐Port Current‐Limiting Hybrid DC Circuit Breaker Based on Thyristors

Multi‐port hybrid DC circuit breakers (MP‐HCBs) are rapidly developing due to their obvious advantages in economy compared to traditional two‐port hybrid circuit breakers (HCBs). However, most of the existing MP‐HCB topologies do not have the current‐limiting capability, and a large number of insulated‐gate bipolar transistors (IGBTs) are still needed in their main breakers. In response to the problems, a multi‐port current‐limiting hybrid DC circuit breaker (MP‐CLHCB) based on thyristors is proposed in this paper. MP‐CLHCB uses low‐cost thyristors instead of IGBTs, and suppresses the rise of fault current through current‐limiting branch. In an attempt to prevent the MP‐CLHCB from reclosing in a permanent fault and causing damage to the DC grid again, an adaptive reclosing scheme is also proposed. In this paper, the topology, operation stages, theoretical derivation, and parameter design of the MP‐CLHCB are provided. Finally, the performance of the MP‐CLHCB is verified and compared through simulations in PSCAD/EMTDC. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Topology optimization and evaluation of multiport hybrid DC circuit breaker based on graph theory

The multiport hybrid dc circuit breaker (M-HCB) is a cost-effective choice for fault blocking in meshed HVDC system. Various M-HCB topologies have been proposed in recent years. However, the topology derivation has randomness and uncertainty. Whether the topology can be improved and how to derive new topology from existing topology has less discussion. In this paper, a topology optimization and evaluation method based on graph theory is proposed to deduce more M-HCB topologies from existing topologies. A series of new topologies is quickly derived from the proposed method, and the performance can be evaluated based on the feasible path calculation. Compared with the existing topology, the derived topologies have the advantages of cost and loss in specific application scenarios. Simulation and experiment results are given to verify the topologies. The comparison between the existing topologies proves the superiority of the deduced topologies and the feasibility of the proposed method.

Analysis for magnetic field disturbance of hybrid DC circuit breaker during breaking

The high current of hybrid DC circuit breaker (HCB) in the process of breaking generates strong transient magnetic field (MF), which may interfere with the normal operation of driver control units (DCUs). Therefore, the analysis for transient MF disturbance is of great significance. Due to the large space scale of HCB, with the large number of power electronic devices, the numerical calculation method has the disadvantages of large consumption of resources and slow calculation speed in solving the transient MF inside the HCB. In this study, the current generation mechanism of a 500 kV HCB is analysed, and the equivalent current path is obtained by considering the skin effect. Combined with the temporal and spatial distribution of transient current, the multi-process transient equivalent model of transient MF calculation is established, and the model has the advantages of high precision and high speed. Then, the breaking experiment of HCB is carried out, and the transient MF near the DCU is measured. The experiment results verify the validity of the model. Furthermore, the disturbance of transient MF at the DCU of the transfer branch during breaking 25 kA current is analysed.

Hybrid DC circuit breaker with fault current suppression capability

Hybrid DC circuit breaker with fault current suppression capability

A modular hybrid DC circuit breaker with fault current self-adaptive control and protection coordination

Hybrid DC circuit breaker (HDCCB) takes advantage of both mechanical and solid-state breakers, the low-loss and fast-breaking characteristics are suitable for MMC-HVDC system. Because the existing DC protection cannot act fast enough, the limitation of fault current based on HDCCB has become an prospective technology. This work proposes a modular hybrid DC circuit breaker (MHDCCB) at first which can self-adaptively control current limiting and current clearing according to the protection action signal after fault. The new topology can be switched to primary current-limiting state and backup current-limiting state, which reserves enough time for fault detection and location. After receiving trip signal, current-limiting reactor can be bypassed to accelerate current clearing speed. Then, the cooperation strategy of protection system and MHDCCB is analyzed. Finally, the simulation cases are carried out to verify the working principle, protection coorperation strategy, and superiorities of the proposed MHDCCB. The technology presented in the paper alleviates the speed limitation of protection and benefits the safty operation after fault in high-voltage and large-capacity MMC-HVDC systems with overhead transmission lines.

Design and analysis of hybrid DC circuit breaker for LVDC grid systems

Design and analysis of hybrid DC circuit breaker for LVDC grid systems

Research on Magnetic Field Characteristics in DC Yard of Dinghai Converter Station Under Monopolar Grounding Fault

In Dinghai converter station of Zhoushan VSC-HVDC transmission project, 200 kV hybrid DC circuit breaker is used for the first time to realize DC side fault isolation. When DC side short circuit occurs, its fault current characteristics are different from those of AC substation and HVDC converter station, and the magnetic field interference to secondary equipment in DC yard is still unknown. In this paper, taking the single pole grounding short circuit fault with high probability in flexible DC power grid as an example, the electromagnetic transient simulation model of fault current in Dinghai converter station is established, and the time-domain current waveform is obtained. Then, the magnetic field calculation model of DC circuit breaker and other key electrical equipment is established, and the magnetic field of secondary equipment in DC yard is calculated based on Biot-Savart Law. The results show that the maximum magnetic field strength at the secondary equipment is 59 A/m, the waveform is ms level, and it is aperiodic. The distribution of magnetic field in DC yard varies between 3 and 346 A/m.

A pilot line protection for MT-HVDC grids using similarity of traveling waveforms

Protection of dc line faults is a major challenge for the operation of multi-terminal high-voltage dc (MT-HVDC) grids. To avoid blocking converter and system shutdown, ultra-fast protection is required to detect and isolate line fault with the application of hybrid dc circuit breaker. This paper proposes a pilot protection scheme based on improved Hausdorff distance to detect the overhead line fault for MT-HVDC grid. Compared with literature, this protection method owns higher withstanding ability of noise interference, start-up delay and data anomaly. Moreover, the fault segment can be correctly identified as independent of fault location, and protection sensitivity is maintained even under internal ground fault with high impedance of up to 1000 Ω. The issue of dead zone fault recognition is considered and solved in this paper with reasonable sacrifice in the sampling frequency requirement. Based on Zhangbei HVDC grid in China, a four-terminal dc grid model is developed in PSCAD/EMTDC environment for fault simulation, and the data processing is performed in MATLAB platform. The feasibility and effectiveness of this protection scheme are verified by a simulation study that considers different scenarios.

Impact on Current-Interrupting Characteristic by Parameter Settings of Superconducting Hybrid DC Circuit Breaker

DC faults cause severe disruption in not only the DC system but also the AC system because the fault current is very large and rapidly increases. The DC circuit breaker used to separate the DC faults from the power system is still being researched, but it is very expensive due to the use of multiple power semiconductors to interrupt a large fault current in a short time. However, if the quench characteristic of a superconductor is used, the amplitude of fault current can be reduced. Therefore, it is possible to effectively interrupt a large fault current even if a relatively cheap mechanically passive DC circuit breaker is used. In the current study, a superconducting hybrid DC circuit breaker is proposed, and the limiting characteristics of each element are analyzed. By using two superconducting elements, the quench occurs sequentially twice according to the magnitude of the fault current, and the current-limiting reactor and resistance are used. If a current-limiting reactor is used in the DC system, the fault current rises slowly at the beginning of the fault, and the use of resistance can reduce the magnitude of the fault current. The inductance of the current-limiting reactor and resistance parameter settings of the hybrid DC circuit breaker was analyzed by the step-changing case method, and the interrupting characteristic of the DC circuit breaker was improved.

Capacitor Commutation Method for MVDC Hybrid Circuit Breakers

The medium voltage DC (MVDC) type system can connect multiple terminals to a common MVDC bus, so it is possible to connect several renewable DC power sources to the common MVDC bus, but a DC circuit breaker is needed to isolate short circuit accidents that may occur in the MVDC bus. For this purpose, the concept of a hybrid DC circuit breaker that takes advantage of a low conduction loss contact type switch and an arcless-breaking semiconductor switch has been proposed. During break the hybrid switch, a dedicated current commutation device is required to temporarily bypass the load current flowing through the main switch into a semiconductor switch branch. Existing current commutation methods include a proactive method and a reverse current injection method by a LC (Inductor-capacitor) resonant circuit. This paper proposes a power circuit of a new MVDC hybrid circuit breaker using a low withstanding voltage capacitor branch for commutation and a sequence controller according to it, and verifies its operation through an experiment.

Reclosing Strategy of a Hybrid DC Circuit Breaker on Overhead Lines in Half-Bridge MMC-Based DC Grids Considering Fault Type Discrimination

Flexible DC grids with dedicated metallic return (DMR) encounter two major challenges when reclosing hybrid DC circuit breakers (DCCBs): (1) identifying permanent and nonpermanent faults to determine whether DCCBs should be reclosed; and (2) identifying pole-to-ground (P-GND) and pole-to-DMR (P-DMR) faults to determine whether all DC lines should be isolated when a permanent fault occurs. Under a permanent P-DMR fault, all DC transmission lines should be isolated instead of maintaining half of the power transmission. In this study, the equivalent circuits and analytical expressions of the fault currents under the P-GND and P-DMR faults are deduced. On this basis, two different criteria are proposed to discriminate these two faults. Permanent and nonpermanent faults are recognized according to the characteristics of the residual voltage of the DC transmission line. Finally, a comprehensive reclosing strategy considering fault type discrimination for a hybrid DCCB is developed. A simulation model of a four-end flexible HVDC grid with DMR is constructed in PSCAD/EMTDC. The validity of the proposed reclosing strategy is verified through different simulation cases.

Adaptive Threshold-Based Zonal Isolation of Faults in a Multiterminal DC Using Local Measurements

Fast and accurate methods of fault detection and isolation are a pre-emptive measure in multiterminal dc (MTdc) systems. Zonal isolation of faults is necessary to prevent any misopertation of the dc breakers that can lead to a shutdown of the network. Existing techniques require fast-communication or data synchronization methods have their own disadvantages. This article proposes a method for efficient fault zone isolation without the need of a communication link that prevents any misoperation of the dc breakers in a radial MTdc. This method provides individual local measurement-based control to the hybrid dc circuit breakers (dcCB). Faults created outside the zone of protection for a breaker create a change in the rate of change of current or voltage leading to misoperation. To avoid detection using a fixed threshold, an adaptive threshold based approach is suggested that updates the threshold based on the present operating status. Sensitivity analysis by varying the current limiting inductance and fault location is performed. A three terminal radial model of an MTdc is used for zonal isolation using power system computer aided design/electromagnetic transients including dc.

Prototype Current-Limiting Hybrid DC Circuit Breaker Incorporating a Fuse and a Semiconductor Device

Owing to the increased demand for DC interruption, a prototype current-limiting hybrid DC circuit breaker incorporating a fuse and a semiconductor device was developed, based on a completely novel design concept. Recently, hybrid DC breakers have been attracting attention because of their low conduction loss and high-speed current interruption capability. The superiority of this hybrid DC circuit breaker lies in the simultaneous use of the high-speed current-limiting performance of the fuse and the highly reliable current-interruption performance of the semiconductor device. Furthermore, the hybrid DC circuit breaker performs the current interruption without any mechanical contact, thus preventing any delay in operation induced by the mechanical contact. The feasibility of the proposed concept was demonstrated by the successful application of the circuit breaker in a 1 kA fault current interruption procedure. Hence, the current-limiting hybrid DC circuit breaker is suitable for low voltage and medium voltage DC system protection. As the fuses and semiconductor modules progress, the hybrid DC circuit breaker may also adapt to HVDC systems.

DC grids DC fault detection using asymmetric pole inductors

DC fault isolation is recognized as the major obstacle against widespread development of multi-terminal meshed DC grids. To fulfill DC grid protection requirements a fast, discriminative, and seamless DC fault detection and isolation mechanism is needed. This paper presents a DC grid protection system based on using asymmetrical pole inductors (APIs) for fault detection, and hybrid DC circuit breakers (HDCCBs) for fault isolation. The pole inductors are those normally used in series with cable-end HDCCBs to limit rate of fault current development. An intentional mismatch between positive and negative poles’ inductors is proposed for autonomous fault detection using the difference between positive and negative poles’ DC voltage magnitudes measured at all cable-ends. Better accuracy in discriminative symmetrical fault detection, and less sensitivity against fault impedance are achieved using lower series inductors compared to rate of change of voltage (ROCOV) technique as the most effective approach proposed so far. In order to investigate the proposed technique, a 2 GW symmetrical monopole DC grid equipped with proposed protection system is modeled in PSCAD. Simulation results are demonstrated to show the capabilities of the proposed protection system in fast and discriminative DC fault detection.

Fault Location Using the Natural Frequency of Oscillation of Current Discharge in MTdc Networks

This paper discusses a novel fault location approach using single ended measurement. The natural dissipation of the circuit parameters are considered for fault location. A relationship between the damped natural frequency of oscillation of the transmission line current and fault location is established in this paper. The hybrid dc circuit breaker (dcCB) interrupts the fault current and the line current attenuates under the absence of any driving voltage source. The line capacitance discharges into the fault at a specific frequency of oscillation and rate of attenuation. Utilizing this information, the fault location in a multi-terminal direct current (MTdc) network can be predicted. A three terminal radial model of a MTdc is used for performance evaluation of the proposed method using Power System Computer Aided Design (PSCAD)/Electromagnetic Transients including dc (EMTdc).

Coordination Control of Power Flow Controller and Hybrid DC Circuit Breaker in MVDC Distribution Networks

Coordination Control of Power Flow Controller and Hybrid DC Circuit Breaker in MVDC Distribution Networks

A Current-Commutation DC Circuit Breaker with Adaptive Reclosing Capability

DC faults are critical events in a flexible high-voltage dc (HVDC) grid. Thus, ensuring that the power system returns to normal operation rapidly and reliably after fault isolation is very important. This requires a HVDC breaker. In overhead line systems under temporary faults, reclosing is often required. However, once the dc circuit breaker (DCCB) is reclosed directly, the large second overcurrent may occur which could damage the power electronic devices. To avoid this problem, a current-commutation DC circuit breaker with adaptive reclosing capability is proposed. Compared with the traditional auto-reclosing strategy, the second damage under permanent fault condition can be avoided by the proposed DCCB, which can identify the fault property. Compared with the hybrid DCCB, the power electronic breaking branch composed of lots of IGBTs is replaced by the current-commutation branch, which is employed to interrupt bi-directional dc fault current. Moreover, bypassing branch is configured to reduce the energy dissipation of arrester and shorten the fault isolation time effectively. Finally, simulation cases in PSCAD /EMTDC verify the effectiveness and superiorities of the proposed DCCB.

A Modified Hybrid DC Circuit Breaker With Reduced Arc for Low Voltage DC Grids

The increasing demand for the development and utilization of renewable energy resources has lead to a growing interest in the development of LVDC systems. The dc grid provides more flexibility in integrating different forms of renewable energy sources effectively. However, the lack of a reliable protection mechanism remains the main drawback in the growth of dc distribution systems. Unlike ac systems, the absence of a natural zero crossing in dc systems for arc extinction makes the use of a conventional mechanical circuit breaker (MCB) a less reliable solution. The use of a solid-state circuit breaker (SSCB) results in fast fault interruption but reduces the overall efficiency of the system due to the on-state voltage drop of the semiconductor devices. A hybrid circuit breaker (HCB) combining MCB and SSCB yields better static and dynamic performances but the main challenges remains in the demagnetization of the transmission line inductance after a fault interruption and an arc formation between the MCB contacts. This paper proposes a hybrid circuit breaker (HCB) which is suitable for fast fault interruption in low voltage dc (LVDC) systems while alleviating the above issues. Proposed topology employs a semiconductor switch as well as an actively switched capacitor branch in parallel with the main mechanical breaker to facilitate fast current commutation during a fault. The mechanical breaker forming the main branch is turned off at zero voltage. This eliminates the arc formation across the moving contacts of the breaker. Moreover, the fault interruption process does not require a varistor for network demagnetization following the fault current commutation. This paper also presents a discharging mechanism for the capacitor in a practical implementation. Operation of the proposed dc circuit breaker is evaluated through a prototype tested in the laboratory.

Research on a Low Switching Loss Bidirectional Hybrid DC Circuit Breaker Topology

Research on a Low Switching Loss Bidirectional Hybrid DC Circuit Breaker Topology

Influence of capacitor-buffered hybrid DC circuit breaker on bipolar short circuit fault of three-terminal MMC-HVDC transmission system

The flexible DC transmission system needs a DC circuit breaker to remove and isolate the bipolar short-circuit fault to prevent the excessive short-circuit current from damaging the DC transmission system. In this paper, a comprehensive model of DC circuit breaker and transmission system is established by using PSCAD based on capacitive buffered hybrid DC circuit breaker. The short-circuit current waveform and DC port voltage waveform of the three-terminal ±350 kV flexible DC transmission system under the condition of double-pole short-circuit fault at the DC side of rectifier station are simulated and calculated. The simulation results show that the maximum current and voltage of the capacitor-buffering hybrid DC circuit breaker model is lower than that of the ideal DC circuit breaker model under the condition of bipolar short-circuit fault at the DC side of the rectifier station. The system fault waveform under different parameters of capacitor-buffered hybrid DC circuit breaker is compared and analyzed through simulation, so as to optimize the parameters of circuit breaker. It can be seen that the actual results more in line with the switching process can be obtained by using the capacitor buffer type hybrid DC circuit breaker.