Hybrid DC Breaker Research Articles

Application of Surge Arrester in Limiting Voltage Stress at Direct Current Breaker

Hybrid DC circuit breakers combine mechanical switches with a redirecting current path, typically controlled by power electronic devices, to prevent arcing during switch contact separation. The authors’ past work includes a bipolar hybrid DC circuit breaker that effectively redirects the fault current and returns it to the source. This reduces arcing between the mechanical breaker’s contacts and prevents large voltage overshoots across them. However, the breaker’s performance declines as the upstream line inductance increases, causing overvoltage. This work introduces a modification to the originally proposed hybrid DC breaker to make it suitable to use anywhere along DC grid lines. By using a switch-controlled surge arrester in parallel with the DC breaker, part of the arc energy is dissipated in the surge arrester, preventing an overvoltage across the mechanical switches. Based on the experimental results, the proposed method can effectively interrupt the fault current with minimal arcing and reduce the voltage stress across the mechanical switches. To address practical fault currents, tests at high fault currents (900 A) and voltage levels (500 V) are conducted and compared with simulation models and analytical studies. Furthermore, the application of the breaker for the protection of DC distribution grids is illustrated through simulations, and the procedure for designing the breaker components is explained.

A Voltage Full-Waveform Reconstruction Method Based on Radiative Near-Field of Electric Field for the Hybrid DC Breaker of MMC-HVDC

The conventional current or voltage signal-based condition monitoring systems for DC high-voltage equipment have the disadvantages of huge volume, inconvenient operation, and low measurement bandwidth and sampling rate. To overcome these drawbacks, a simplified calculational model of the radiative near-field of the electric field in the circuit breaker valve hall is proposed. This model is based on the analytical model of the finite-length current-carrying linear ideal conductor and reveals the physical mechanism of non-invasive situational awareness based on the transient electric field of electrical devices. Predicated on this model, a reconstruction method for calculating the port transient voltage of the hybrid DC breaker is then established and verified by an artificial short-circuit test in an actual ±200 kV MMC-HVDC system. To the best of the author's knowledge, this is the first pilot short-circuit test in a full-scale MMC-HVDC system involving the hybrid DC breaker. Based on the testing data, the reconstructed and measured voltage show a relatively high degree of consistency both in time and frequency domain. The reconstructed voltage signals based on the radiation near-field not only expose the action time sequence of various electrical equipment with the response time of micro-second order, but also disclose the operation of the key devices and fault types for situational awareness in power system.

Transient Current Balancing of Parallel IGCTs in 10-kV/10-kA Hybrid DC Circuit Breaker

Integrated gate-commutated thyristor (IGCT) is an emerging alternative for hybrid DC breaker (HDCB) to achieve fault current clearance in DC systems. However, the maximum controllable current of present IGCT products cannot cope with high-capacity interruption and IGCTs often need to be paralleled. Unlike insulated-gate bipolar transistor (IGBT) whose parallel methods have been widely studied, there lacks intensive study on the transient current balancing and optimization methods for parallel IGCTs, especially in critical current breaking applications. This paper proposes a practical solution to the transient current balancing of parallel IGCTs in HDCB. Theoretical and mathematical analysis shows that current spike occurs due to anode voltage discrepancy. Although self balancing effect and delayed gate signals can help relieve the current spike, IGCT is still possible to exceed the safe operation area (SOA). An improved topology of parallel IGCTs with bypass capacitors is used to deal with this problem, which is verified by 10 kA turn-off experiment. Successful 10 kA current breaking tests of 10 kV HDCB prototype demonstrate the feasibility and validity of the improved parallel IGCT switch.

A novel current-limiting hybrid DC breaker based on thyristors

Since the DC current has no zero-crossing in high-voltage and large-capacity DC scenarios, and the low line impedance results in a large growth rate of fault current, the breaking requirements of DC circuit breakers (DCCB) are further increased. Hybrid circuit breaker (HCB) represent the techniques orientation of high-voltage DC interruptions and the HCB can quickly interrupt fault currents to ensure reliable and safe operation of the grid, which is an indispensable piece of equipment in flexible DC systems. Utilizing the characteristics of thyristor with strong current capacity, low on-state loss and zero-crossing natural turn-off of unidirectional current, this article proposes a hybrid circuit breaker scheme based on forced zero-crossing of thyristors (T-HCB). The proposed T-HCB could achieve arcless breaking of mechanical switch (MS), which improves the service life of the MS. In addition, it has the limiting capability of fault current, which reduces the growth rate and amplitude of the fault current and improves the security level and economics of the system. Firstly, the working principle of the proposed topology is introduced and deduced. Then, the key parameters affecting the commutation capacity and current limiting capacity are analyzed extraordinary. Finally, a comparison of the breaking performance in a 4-terminal DC system with existing fault current limiter (FCL) and ABB hybrid DCCB demonstrates the feasibility and superiority of the proposed topology.

A Bipolar Hybrid Circuit Breaker for Low-Voltage DC Circuits

Presently available dc breakers fall into three categories, mechanical, static, and hybrid dc breakers. With the advent of dc generation, loads, and circuits dc breakers are required for system protection. This paper proposes an alternate method to break dc currents for low-voltage applications. Higher voltages have not been tested due to limited resources and safety concerns; however, the proposed mechanism can potentially be used at higher voltages. The proposed mechanism utilizes two switches along with two diodes, to reverse the direction of the current flow and clear the fault. This is different than the conventional single-switch commute-and-absorb method used in mechanical or static breakers in the sense that it reverses the current direction and delivers part of the fault energy back to the source. It is shown that the proposed method can break the fault current effectively with minimal arc and significantly reduces the voltage stress across the mechanical switches. The initial results of this work have been presented in the ECCE2021. Extended simulation and experimental results are provided to show the efficiency of the proposed dc breaker. In addition, the application of the proposed dc breaker is illustrated for dc distribution system via simulations and the design procedure is explained.

A Novel High-Power Hybrid DC Breaker Based on Compound Power Electronic Switch With Integrated Commutation Ability

Medium voltage dc power system has the characteristics of low line impedance, resulting in high peak and fast rise rate of the fault current. For example, the current in an onboard 10 kV dc grid can rise to more than 40 kA in 3 ms after the failure. Therefore, it is necessary to configure dc circuit breaker with high current breaking capacity. In this letter, a novel high-power hybrid dc breaker based on integrated commutation compound power electronic switch is proposed. By giving full play to the complementary advantages of insulated gate bipolar transistor (IGBT) and integrated gate-commutated thyristor (IGCT), and skillfully integrating the commutation function into the power electronic switch, the proposed dc breaker has the characteristics of low cost, compact, high performance, and can also play a role in current limiting. The working principle of the proposed scheme is described in detail, and a 10-kV prototype with 40 kA current breaking ability is built to verify its feasibility.

Research on DC power flow controllable multi-port DC circuit breaker

For the problem of fault isolation and power flow control in DC grid, this paper proposes a DC power flow controllable multi-port DC circuit breaker. Under the normal operation, this breaker has the function of DC power flow regulation, which is used to regulate the power flow on DC lines. After the DC system fails, this breaker is equivalent to the hybrid DC breaker, which is used to cut off the fault current and isolate the fault line. In the paper, the steady-state power flow regulation mechanism and transient current interrupting mechanism of the breaker are described in detail. Finally, a meshed DC grid is built in PSCAD/ EMTDC simulation platform. The simulation results show that the proposed topology has good performance in power flow control and current interrupting.

Basic Topology, Modeling and Evaluation of a T-Type Hybrid DC Breaker for HVDC Grid

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

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.

A review study on various types of circuit breaker and its application

The generation, transmission, distribution, and substation are all parts of the power system. All power system components need appropriate protection devices as part of the protection system to safeguard the system in the event of a failure. The circuit breaker has been chosen as one of the protective devices in many applications in this article. Oil circuit breakers (OCB), air circuit breakers (ACB), sulphur hexafluoride (SF6) circuit breakers, vacuum circuit breakers, and DC breakers (hybrid DC breaker and solid-state DC breaker) are among the circuit breakers discussed in this article. Normally, the failure disrupts or damages the systems or circuits. The kind of faults and causes of faults must be understood in order to install a protective system in the system or circuit. The substation is required to regulate the voltage transferred at high voltage from the producing station in order to deliver the appropriate voltage to the consumer. A substation must also include a protection system.

Backup Protection Algorithm for Failures in Modular DC Circuit Breakers

HVDC grid protection with adequate speed and reliability is required to minimise the impact of DC faults. In particular, fast breaker failure backup protection algorithms are needed to meet the expected reliability requirements of HVDC grids. In this paper, existing breaker failure backup protection algorithms are shown inadequate to detect partial failures like a single module failure of breakers with a modular structure. This paper proposes a backup protection algorithm which rapidly detects a DC breaker failure based on estimating the counter-voltage created by the energy absorption branch during an interruption. The performance of the proposed algorithm is evaluated using a four-terminal test network with both hybrid and mechanical DC breaker technologies. The simulation results show that the proposed algorithm is able to quickly detect both complete and partial failures of the two breaker technologies even considering measurement errors, noise and ageing of the energy absorption components.

Interactions between a half‐bridge MMC and a hybrid DC breaker during fault current interruption compared to a full‐bridge MMC

The large-scale integration of remote renewable energy resources into existing AC grids is one of the main drivers for the construction of multi-terminal direct current (MTDC) systems. Today, a few MTDC systems are already in execution stage or even in operation. However, with a growing number of extended MTDC systems, the probability of high-voltage DC (HVDC) insulation faults is likely to increase and therefore, reliable solutions for handling of such disturbances are crucial in order to maintain high availability. Since most HVDC converters are realised by modular multilevel converters (MMC) converters are based on half-bridge (HB) modules, they lack an inherent capability to control DC fault currents. Therefore, additional equipment like HVDC breakers needs to be installed as well. Among the various breaker types, the so-called ‘hybrid’ DC circuit breaker (DCCB) is considered most popular. This contribution provides a more holistic view on the overall system behaviour, represented AC grid, MMC HVDC converter, DC reactor and DCCB altogether. It discusses the physical interactions of these main components in MTDC systems. In particular, the influence of the electrical parameters of the hybrid DCCB and its required DC reactors on the MMC converter's internal current and voltage conditions is outlined.

HV isolated power supply system for complex multiple electrical potential equipment in 500 kV hybrid DC breaker

High-voltage direct current circuit breakers (HVDC CB) are one of the key technologies of multi-terminal DC systems and DC grids. Different from other equipment that use a large number of power electronic devices, the HVDC CB cannot obtain its power from the primary system at high potential, making the power supply of the complex multiple electrical potential equipment in HVDC CB a challenge. In this study, the authors propose an HV isolated power supply system based on the multi-output high-frequency isolated power supply unit and the cascaded isolation transformer network. This power supply system can support the 500 kV CB to turn-off 25 kA current with 800 kV overvoltage.

Concept design of 100 kA hybrid DC breaker on China fusion engineering test reactor

• High current DC breaker is the key problem of quench protection system design for superconducting Tokamak. • This paper describes a new of hybrid breaker composed of three-levels contacts mechanical switch, and a solid-state switch in parallel. • The new hybrid breaker is more effective to realize high-power DC interruption and fast energy transfer. • A principle prototype experiment was done to verify the conceptual design. China Fusion Engineering Test Reactor (CFETR) is the next device for the Chinese magnetic confinement fusion program, which is now under conceptual design phase. This paper describes the concept design of the high current hybrid breaker for the quench protection of superconducting magnets. The rated currents and maximum reapplied interruption voltages for breaker are 100 kA and 20 kV. The concept solution design of DC breaker is presented, which is mainly composed of a mechanical main switch with three levels contacts for conducting the continuous current, and a solid-state switch in parallel for current transferring. The design principles of each part and the preliminary results are given respectively. Finally, two test platforms were built to verify the calculation and design. Compared with the traditional oscillation zero-point DC breaker, the hybrid breaker topology can improve the dielectric strength recovery speed of mechanical switch and reduce the whole operation time. It is more suitable for fast current interruption at heavy DC current level.

Analysis Methodology for Differential Mode Interference in Energy Supply System of Hybrid DC Breaker

High di/dt during the close-open operation process of hybrid dc breaker will cause differential mode interference (DMI) in the energy supply system of the breaker's driver units due to their inductive coupling. The generated DMI may lead to false action of the breaker, which is an important issue that should be carefully considered in design stage. A method to analyze DMI based on time-domain wideband circuit simulations is proposed in this article. First, a time-domain waveform expression of DMI voltage source is derived, and then wideband equivalent circuit models of major components in the energy supply system are established. Furthermore, a standardized design methodology to reduce DMI is suggested. Applying the method to a high-frequency energy supply system of a ±200 kV hybrid dc breaker, simulation results show that the DMI level for two DMI mitigation measures is reduced by about 90% and 80% of the initial value, respectively.

DC Fault Current Blocking With the Coordination of Half-Bridge MMC and the Hybrid DC Breaker

In this article, a modified hybrid dc breaker and a half-bridge modular multilevel converter (MMC) are employed to interrupt the dc fault current in a high-voltage direct current transmission system. In the hybrid dc breaker, parallel to the main branch, a series connection of an energy-absorbing capacitor and a Thyristor stack is employed. When a dc fault current is recognized, the Thyristor stack is triggered and the load commutation switch in the main branch is turned off. In addition, in the fault clearing state, the MMC is programmed to generate zero voltages at all arms. Using this mechanism, a second-order RLC circuit with zero input is formed, and the fault current is cleared in a very short time. A freewheeling path is provided to bypass the dc line when the equivalent inductance seen from the dc line is large. In contrast to conventional approaches, the peak of dc fault current is limited to a specific limit and the necessity to ultrafast mechanical switches is avoided. In addition, the amplitude of arms currents and corresponding insulated-gate bipolar transistors are kept in the safe operating area. A detailed circuit analysis of the new method is given and design formulas are extracted. Simulation results are provided in PSCAD/EMTDC environment, and experimental results are presented for a scaled-down prototype.

A Novel Mixture Solid-State Switch Based on IGCT With High Capacity and IGBT With High Turn-off Ability for Hybrid DC Breakers

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

Optimum Selection of Circuit Breaker Parameters Based on Analytical Calculation of Overcurrent and Overvoltage in Multiterminal HVDC Grids

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

Research on Switching Overvoltage of MMC-MTDC System with Hybrid DC Circuit Breaker

The modular multilevel converter based multi-terminal HVDC (MMC-MTDC) system with hybrid DC breakers should consider the influence of the action of the DC breaker on the switching overvoltage, which puts higher requirements on the overvoltage protection of the system. Flexible DC demonstration project in Zhangbei will realize the first engineering application of hybrid DC circuit breaker. Based on this project, an overvoltage protection scheme for MMC-MTDC system is proposed. Firstly, this paper investigates the effect of the operation mode of the DC grid on the switching overvoltage level. Secondly, typical faults and the protection action sequence of various faults are analyzed in detail. The characteristics and laws of various switching overvoltage are deeply studied. Finally, the switching overvoltage of converter station is calculated on the basis of the control and protection system, and the recommended values of the insulation level of converter station equipment for the ±500kV MMC-MTDC system with hybrid DC circuit breaker are given.

DC line soft reclosing sequence for HVDC grid based on hybrid DC breaker

DC line soft reclosing sequence for HVDC grid based on hybrid DC breaker