Hybrid DC Circuit Breaker Research Articles

Resonant Network-Based MVDC Circuit Breaker Topologies With Fast Current Breaking Capability

This paper presents two improved circuit breaker (CB) topologies based on resonant networks for medium voltage DC (MVDC) applications, such as shipboard power distribution and subsea oil and gas production. The topologies feature simple LC resonant networks that efficiently suppress fault current in just a few tens of microseconds, making them suitable for integration with existing solid-state or hybrid DC CB. Moreover, they also help to minimize the CB energy and reduce (if not eliminate) the requirement for protection devices like surge arresters during fault events. The proposed topologies are first tested using Typhoon Hardware-in-the-Loop (HiL) simulations at 1.2 MW (6 kV, 200 A) power levels and thyristor-based solid-state circuit breakers (SSCB). Then, scaled-down laboratory prototypes, also based on thyristor-based SSCB, are experimentally validated. The results show that both topologies quickly bring the current of the CB’s main switch to 0 A. The main circuit pathway requires only a small inductor and switch, resulting in a steady-state efficiency of >99.9%. The resonant network-based design allows for a fast response time of less than 50 μs using a simple and low-cost auxiliary circuit, eliminating the need for complex charging circuitry and protection devices typically used to suppress voltage surges during faults.

Traveling Wave-Based Primary Protection and Fault Localization Scheme for MTDC Grid Considering IEC 61869-9 Measurement Standard

Traveling wave (TW) based protection and fault localization requires high sampling frequency measurements (500 kHz - 1 MHz) and are non-compliant to the IEC 61869-9 measurement standards, which allows maximum sampling frequency of 96 kHz for DC application. This work proposes a novel low sampling frequency (50 kHz) TW based primary protection and real-time DC fault localization technique for multi terminal high voltage DC (MTDC) grid which is compliant with the aforementioned measurement standard. In the proposed MTDC protection scheme, a TW arrival time (TWAT) is estimated under low sampling frequency measurement using cascaded combination of modified mathematical morphology gradient (MMG), sobel operator and linear regression tool. Subsequently, the TWAT information at both DC link terminals is communicated via dedicated communication channel compliant to IEC-61850-9-2 standard. And if the TWAT difference between DC terminals is less than the TW propagation threshold for the protected DC line, then a DC trip signal is issued to the associated hybrid DC circuit breaker (HDCCB). For fast power system restoration, the same TWAT information is also used for real-time fault localization in the faulted DC line, which is also compliant with IEC 61869-9 measurement standards. Finally, the practical feasibility of the proposed algorithm is demonstrated through control hardware-in-loop testing with real-time digital simulation setup and TI TMS320F28379d digital signal processor card.

Low-loss and Compact Hybrid DC Circuit Breaker Scheme Using Self-commutated Semiconductor Switch Module

Low-loss and Compact Hybrid DC Circuit Breaker Scheme Using Self-commutated Semiconductor Switch Module

Reliability modeling of multi-terminal DC circuit breaker and its impact on multi-terminal DC distribution network

In the medium-voltage distribution network, the multi-terminal DC circuit breaker (MTCB) is one of the key pieces of equipment for the connection of multi-terminal converter stations and rapid fault isolation in the future. The reliability level of the multi-terminal DC distribution network is directly impacted by reliability of MTCB. In this paper, the main topological structure and basic working principle of MTCB are systematically analyzed. Then, taking the three-terminal hybrid DC circuit breaker which has been applied in the Zhuhai Tangjiawan “Internet plus” Demonstration Project of China Southern Power Grid (hereafter referred to as Zhuhai Demonstration Project) as an example, the reliability evaluation model of the MTCB is established based on the engineering reliability principle and considering the redundancy level of device. By calculating multi-dimensional reliability index, the reliability of MTCB under different design modes and redundancy levels is analyzed, and the influence of MTCB on the reliability of multi-terminal DC distribution network is further studied based on the minimum cut set method. The influence of the MTCB on the reliability of multi-terminal DC distribution network of Zhuhai Demonstration Project is then studied. Finally, an example of the three-terminal DC distribution network structure of Zhuhai Demonstration Project is analyzed to confirm the accuracy and effectiveness of the proposed model.

Multiport Hybrid DC Circuit Breaker With Current Flow Control for MTDC Grids

The multiterminal dc (MTDC) grid plays an important role in large-scale power transmission and renewable energy integration owing to its excellent performance. However, there are still some problems existing in the MTDC grid, such as difficult fault current interruption and current flow control, which impedes its development. Currently, the mentioned two problems can be separately solved by hybrid dc circuit breaker (HCB) and current flow controller (CFC). However, when configured separately, they are expensive and have large footprints. Therefore, this article proposes a multiport hybrid dc circuit breaker (MHCB) with current flow control capability. The HCBs near the same dc bus are first integrated into a single MHCB and then novel CFCs are embedded into the MHCB to replace the load commutation switches. Compared with the existing MHCBs, the proposed topology shows advantages in the aspects of implementation cost, power loss, and operation speed. The operation principle is analyzed and the basis for parameter design is given in detail. The effectiveness of the proposed topology is verified by extensive simulations and experiments. Besides, the proposed MHCB is compared with the existing solutions.

Improved Integrated Hybrid DC Circuit Breaker for MTDC Grid Protection

The current-limiting inductors are usually installed in the multi-terminal dc grid to limit the fault current rising speed. However, they will increase the energy dissipation pressure and fault isolation time of the dc circuit breaker, which puts forward higher requirements on the capacity of arresters in hybrid dc circuit breaker and the heat dissipation of grid equipment. Therefore, an improved integrated hybrid dc circuit breaker is proposed in this brief for applications in the multi-terminal dc grid. Compared with the fault isolation solution based on existing integrated hybrid dc circuit breakers, the proposed breaker has slightly higher cost of semiconductor switches but significantly reduced arrester capacity requirement and faster fault isolation speed by bypassing the inductance components. Extensive electromagnetic simulations and physical experiments verify the effectiveness of the proposed device.

Hybrid DC circuit breaker with current-limiting capability

Hybrid DC circuit breaker with current-limiting capability

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.

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

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.

A Line-Frequency Commutated HV VSC Embedded Modular Multilevel Converter With DC Fault Blocking Capability

Modular multilevel converter (MMC) has become one of the most favored topologies in medium-voltage and high-voltage (HV) applications. However, it still suffers from some drawbacks, including a lot of sizeable capacitors, high conduction losses, and no dc-fault ride-through capability. To circumvent these issues, this article presents a modified MMC, namely hybrid-leg MMC (HL-MMC). HL-MMC integrates a pair of three-phase line-frequency commutated HV voltage source converters (VSC) to replace up to 40% MMC submodules (SMs), leading to lower cost and conduction losses. Due to the ripple energy cancellation in the three-phase HV VSCs, the total energy storage requirement in HL-MMC could be also reduced, leading to up to 30% energy storage capacitance reduction compared with MMC. In addition, by combing the dc hybrid circuit breaker, the HV VSCs in the proposed HL-MMC also help provides the dc fault blocking capability, enabling a dc-fault tolerant HL-MMC without using the full-bridge (FB) MMC SMs. Therefore, a significant device and loss saving can be attained compared with the traditional MMC with FB SMs. The detailed converter operational analysis, control method, high-voltage direct current simulation model, and scale-down prototype are provided to validate the effectiveness of proposed topology.

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.

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.

A Fast Pilot Protection for DC Distribution Networks Considering the Whole Fault Process

To improve the consumption of renewable energy and to meet complex load demands. A model of a multi-terminal flexible DC distribution network with multiple overhead branch lines is constructed. Aiming at frequent non-permanent faults of overhead lines, a fast pilot protection scheme is proposed to cover the whole fault process. Using the hybrid DC circuit breaker (HDCCB) action as the boundary mark, the fast pilot protection can be divided into two phases: post-fault and fault restart. The first phase highlights rapidity, sending a trip command to HDCCB within 1-2 ms after the fault. The second stage emphasizes reliability, and points out that the data of the whole fault process should be fully utilized, and to fully excavate the characteristics of fault current. A multi-time scale and multi-criteria fusion protection scheme is proposed, which can effectively improve the reliability of fault area identification. Finally, a corresponding model was built based on PSCAD, a large number of simulation tests and robustness analysis proved that the proposed fast pilot protection scheme is feasible.

An Adaptive Reclosing Scheme Based on Phase Characteristics for MMC-HVDC Systems

To improve the reliability of power supply, reclosing schemes are required after transient faults, which commonly occur in overhead line based high voltage DC (HVDC) systems. However, in the event of permanent faults, the auto-reclosing scheme may cause a severe strike. To avoid the severe impacts caused by permanent faults, the fault type should be discriminated before activating the reclosing scheme. Therefore, an adaptive reclosing scheme based on phase characteristics is proposed in this paper. Firstly, the modulation of a periodic voltage by actively controlling the hybrid DC circuit breaker (DCCB) is introduced. Then, a cascaded π equivalent model and its decoupling algorithm are presented to analyze the frequency-domain characteristics of the measured impedance of the coupled overhead lines. From the frequency-domain characteristics, the frequency of the periodic detecting voltage is determined to analyze the phase features of the measured impedance at primary frequency. The permanent or transient faults can thus be accurately identified by using these different phase characteristics, with negligible influence on the healthy lines. In addition, the proposed scheme is robust to various fault resistances, leading to improved reliability. The effectiveness of the proposed scheme is verified in PSCAD/EMTDC.

A travelling wave based primary and backup protection for MMC-MTDC transmission system using morphological un-decimated wavelet scheme

The primary protection speed requirement for the HVDC grid is much faster as compared to the conventional HVAC grid. This research article proposes a travelling wave-based primary and backup protection scheme for the multi terminal HVDC transmission system using the morphological un-decimated wavelet decomposition signal processing technique. Depending on the polarity and arrival time information of the first incident travelling wave at both DC transmission line terminals, the fault is identified to be either in the internal zone, forward external zone, or backward external zone of the DC transmission line. Each DC transmission line is covered by its own internal zone as well as forward & backward external zone of its neighbouring line. The internal zone fault identification of the protection scheme sends the primary relay trip signals to associated hybrid DC circuit breakers. But if the primary protection relay fails, then the neighbouring DC substation protection system identifies the fault either in forward external or backward external zone. Then it sends a remote backup trip signal to the DC circuit breaker in the forward or backward external direction with a coordinated time delay.

An adaptive reclosing strategy for high-voltage DC grids with mechanical DC circuit breakers

After fault isolation, the timely reclosure of DC circuit breakers (DCCBs) can improve the reliability of high-voltage DC (HVDC) grids. In previous studies, many adaptive reclosing strategies have been proposed to reclose hybrid DCCBs without a second fault shock. However, the reclosure of mechanical DCCBs is much different from that of hybrid DCCBs and has only received little attention. During permanent faults, further research is needed to make full use of the internal capacitor of a mechanical DCCB to suppress the second fault shock. In this paper, an adaptive reclosing strategy is proposed for a mechanical DCCB, which has the following merits: 1) the second fault shock is effectively suppressed during permanent faults; and 2) the power transmission is restored without significant voltage oscillations during temporary faults. In the preparation stage, the internal capacitor is discharged to a high residual voltage. The HVDC grid injects a traveling wave (TW) into the isolated line through the internal capacitor, and the permanent and temporary faults are distinguished using the TW characteristic. The adaptive reclosing strategy is presented in detail and compared with several existing strategies. Finally, the proposed strategy is validated using PSCAD/EMTDC simulations.

Reduced-Time Finite Element Model for Thomson Coil Actuator

With the rapid development of DC systems and the increasing demand for DC circuit breakers, electromagnetic repulsive drive-based Thomson coil actuators (TCAs) are widely investigated to provide high-speed actuating required for ultra-fast mechanical switches, especially used in hybrid DC circuit breakers. The actuating mechanism is required to be fast, reliable, and economic. This also creates the need to perform fast highly accurate modeling, simulation, and optimization to investigate the operating mechanism performance. In this study, the fast-operating mechanism-based Thomson coil repulsive drive actuator modeling is investigated. Two simulation methods, equivalent-circuit method (ECM), and finite element method (FEM) are performed for analyzing the TCA performance. In the ECM simulation, Newton’s equation of motion is solved together with the circuit equations of the coils. On the other hand, the electrical, magnetic, and mechanical coupling is solved by FEM simulation. A sliding mesh technique is introduced to reduce the computational cost. The two developed solutions were then compared with the experiment for model verification. Results showed that the presented mesh technique was able to significantly reduce the simulation time, and results were in good agreement with the experiment compared to ECM.

An integrated multi-port hybrid DC circuit breaker for VSC-based DC grids

DC circuit breakers are of great significance for the reliable and flexible operation of VSC-based DC grids. The hybrid DC circuit breaker (HDCB) combines the advantages of low on-state loss of the mechanical DC circuit breaker and fast breaking speed of the solid-state DC circuit breaker, showing excellent application prospects. However, the cluster of two or more HDCBs connected to the same DC bus could significantly increase the total project investment. At present, the solution based on multiport HDCB (M-HDCB) has been proposed to practically reduce the construction cost, but the power transmission among adjacent healthy DC lines will also be interrupted after the isolation of DC bus fault, which is still a challenging problem. Therefore, in order to solve this problem, a novel integrated multiport HDCB (IM-HDCB) is proposed in this paper. In addition to the shared transfer and energy dissipation branches, the key auxiliary units composed of diode-stacks and thyristor-stacks are also integrated into the IM-HDCB to enhance the overall performance. Compared with existing solutions, it is shown that the proposed IM-HDCB has more excellent performance. Finally, the capabilities of the proposed novel IM-HDCB are validated by simulations in PSCAD/EMTDC.

A Review on Thomson Coil Actuators in Fast Mechanical Switching

With the rapid development of DC power systems and the increasing demand for DC circuit breakers, electromagnetic repulsive drives-based Thomson coil actuators (TCA) are widely investigated to provide the high-speed actuating required for ultra-fast mechanical switches, especially those used in hybrid DC circuit breakers. The actuating mechanism is required to be fast, reliable, and economic. This article summarizes the development of Thomson coil actuators in circuit breakers in recent years, further illustrating the basic principles and the actuator topology. In addition, it discusses the various structural components of TCA and describes the utilized modeling and simulation methods. The main objective was to provide a comprehensive overview of the TCA field.