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Hybrid DC circuit breakers (HDCCBs) have excellent performance in terms of breaking speed and low losses and have become the mainstream technology for dc fault isolation in dc grids. However, because of the breaking limitation of the solid-state branch in HdcCBs, the existing HdcCBs are still weak in breaking high current. Although the breaking ability can be improved by series and parallel devices, the cost will increase rapidly, and it is very difficult to share current by paralleling a single type of device. This article proposes a novel HdcCB topology that combines two types of power electronic devices in solid-state branches to meet the requirement of a large breaking capacity in dc grids. The structure and breaking principles of this novel topology, which aims to break high current, are introduced. The design methods of the key parameters are presented. Then, the current breaking ability of the novel topology is verified by developing a prototype completing a 10 kV/60 kA breaking test in 3 ms. Finally, this novel topology is compared with other dc circuit breakers at the same breaking level, which shows that this novel topology has obvious advantages in cost and volume with fewer devices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The reliability of meshed DC grids mainly relies on their ability in DC fault protection and line power flow managing. Multiple DC circuit breakers (DCCB) and current flow controller (CFC) need to be installed, which significantly increases the system cost. A novel current flow controller integrated with hybrid dc circuit breaker (CFC-IHCB) is proposed to significantly reduce the loss and cost of the whole system. Only one unidirectional IGBT string based main breaker branch is needed for n lines, and the CFC function is integrated into the load communication switches (LCSs). The basic working principle of proposed topology is presented and analyzed. The functionality is verified and a comparison of the proposed solution and other DCCB/CFC solutions is given based on a multi-terminal HVDC system case study. [ABSTRACT FROM AUTHOR]

The hybrid dc circuit breaker (HDCCB) is one of the most promising solutions for the dc interruption. But the power electronics-based load commutation switch (LCS) in the main current path causes the high on-state loss and cost, which inhibits the application of the HDCCB. In this paper, a novel hybrid dc circuit breaker is proposed, in which the vacuum interrupter with the external transverse magnetic field (ETMF) is designed to improve the arc voltage and thus enhance the current commutation to power electronics. The ETMF-based vacuum interrupter achieves the fast current commutation instead of the LCS, which realizes the low on-state loss and cost while preserving the short commutation and interruption time. The arc voltage characteristic with ETMF is analyzed, and the influence of the different factors on the commutation time and di/dt before current zero are investigated in detail. Based on the calculation results, a 10 kV dc breaker prototype based on the proposed topology is developed with the breaking current of 15.5 kA. Finally, the application of the proposed scheme in HVdc grids is discussed. [ABSTRACT FROM AUTHOR]

Hybrid dc circuit breakers (HCBs) are recognized as suitable devices for protecting high-voltage direct-current (HVDC) systems, along with other dc circuit breakers (DCCB). However, compared to mechanical circuit breakers, HCBs exhibit higher conduction losses. Such losses are inevitable under no-fault conditions as current may flow through some of the semiconductor switches. An integrated circuit breaker (ICB) minimizing these losses is presented in this paper, and this is achieved by replacing semiconductor switches by mechanical components in the current path. For completeness, the topology design, operating sequence and a mathematical analysis for component sizing of the device are provided. In addition, an estimation of the conduction losses is quantified. It is estimated that the power losses of an ICB are 2 to 30% of an HCB only. The ICB has been implemented in PSCAD/EMTDC to demonstrate its effectiveness for isolating dc faults, with simulations conducted on a three-terminal HVDC grid. [ABSTRACT FROM AUTHOR]

Two key challenges in meshed multi-terminal dc (MTdc) grids are line power flow management and fault current interruption, which can be solved by current flow controllers (CFCs) and hybrid dc circuit breakers (HCBs), respectively. However, the power losses and the implementation costs of CFCs and HCBs are relatively high. In order to overcome these drawbacks, a combined HCB (CHCB) is proposed in this article by fully utilizing the core ideas of the interline dual H-bridge CFC and the HCB. The proposed device can substitute multiple HCBs at a dc bus with greatly reduced cost. In addition to the fault current interruption capability, the current flows in the adjacent lines can be controlled by the embedded multi-line CFC in the CHCB expanded from the existing interline dual H-bridge CFC. The system-level behavior of the proposed CHCB is similar to the separate solution of the typical HCB and the multi-line CFC. Extensive simulations and experiments verify the effectiveness of the proposed device. Besides, a comparison of the proposed CHCB and the separate solution is presented. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Extraction of the current commutation loop (CCL) inductance is necessary for the overvoltage analysis of power devices. In general, each transient process of a converter corresponds to a specific CCL. However, there is no such single CCL in the full-bridge module in hybrid dc circuit breakers during the turn-off transient. First, this article proposes a coupled inductance model of full-bridge modules. The model has less number of inductance compared to the traditional partial inductance model. Second, this article proposes the extraction method of inductances that can be easily obtained by both simulation and measurement. Moreover, the measured overvoltage waveforms of insulated gate bipolar translators (IGBTs) in the full-bridge module agree with the simulation results. Third, we propose an equivalent circuit of the series full-bridge modules in a 500 kV hybrid circuit breaker based on the proposed coupled inductance model. The mutual inductances among different modules are considered due to the compact structure of the series modules. The measured results show that the overvoltage of the IGBT in the series module could be well-predicted by the proposed equivalent circuit. [ABSTRACT FROM AUTHOR]

In recent years, dc distribution grids have become increasingly popular because of the interest in the diffusion of distributed renewable energy. In this scenario, dc distribution grids are also favored because of the increased use of batteries and power electronic loads. The main limit to the spread of dc grids is their protection devices, which still present several problems. At present, protection devices are represented by traditional mechanical breakers or static electronic components. The first, which interrupt dc currents, have good reliability but need maintenance and have long intervention periods. In contrast, electronic switches are fast and reliable, but they reduce the efficiency because of their voltage drop. In this scenario, some hybrid breakers have been proposed to obtain the advantages of both devices. The previous solutions of hybrid breakers still suffer several critical issues and, usually, are not capable of protecting a system from short circuits without significantly reducing their lifetime. In this paper, a new low-voltage hybrid circuit breaker topology is proposed. The procedure to dimension all of the active and passive components in the device is analyzed, and the effectiveness of the proposed solution is proven by means of experimental results obtained using a prototype. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic dielectric recovery synergy (DDRS) of hybrid circuit breakers (HCBs) with CO2 gas and vacuum gaps in series. The interaction between the vacuum arc and CO2 gas arc is simulated by the continuous transient arc model and Mayr arc model. The simulation results indicate that the extra methods, for example, dividing capacitors, are needed to obtain optimal DDRS of HCB. The prototype of HCB and the test circuit are established. The influence of the coordination of arcing time, dividing capacitors, and the CO2 gas pressures on the transient recovery voltage (TRV) distribution and the breaking capacity is investigated. The differences of HCBs with SF6 gas and CO2 gas are also compared. According to the results, favorable DDRS in HCB can be obtained in the condition that the vacuum gap endures the initial TRV while the following major TRV distribution is mainly depended on the dynamic dielectric in CO2 gas gap. However, the dynamic dielectric recovery of CO2 gas gap is limited by the structure of rotating arc CO2 gas interrupter in this paper. In the future, the interruption capacity of HCB based on CO2 gas can be improved by synergy control, as the development of CO2 gas circuit breakers. [ABSTRACT FROM PUBLISHER]

This paper presents the design and experimental results of a Thomson coil-based fast mechanical switch for hybrid ac and dc circuit breakers rated at 30-kV voltage and 630-A current. The compact design with optimized circuit parameters and geometric dimensions of components targets 2-mm travel within 1 ms when driven by a 2-mF capacitor bank precharged to 500 V. The use and design of a disc spring as the damping and holding mechanism is presented. Structural design of a complete switch assembly rather than just the actuator is given. Experimental results show that the switch can travel 1.3 mm in the first 1 ms and 3.1 mm in the first 2 ms when driven by a 360-V 2-mF capacitor bank. Such fast mechanical switches facilitate hybrid circuit breaker interruptions within 2 or 3 ms for ultra-fast and highly efficient protections in 5–35 kV medium-voltage dc as well as ac systems. [ABSTRACT FROM PUBLISHER]