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DC microgrid systems are increasingly utilized in power systems, and the significance of solid-state circuit breakers (SSCB) is paramount due to the absence of zero-crossing current in DC systems. However, one of the concerns in a DC microgrid is proposing and implementing a new algorithm due to safety concerns and system stability. Properly coordinating a DC microgrid is one of these challenges. Moreover, protecting the system from unpredictable transient overshoot plays a significant role in system stability and SSCB performance. Consequently, the design of a virtual test platform for monitoring the system's behavior in challenging situations holds significant importance. To address these matters, this paper presents an examination of a DC microgrid using a novel, easy-to-implement, and cost-effective controller hardware-in-the-loop (CHIL) test platform. This platform utilizes MATLAB/Simulink software as a simulator and proposes a new communication path between the simulator and real-world controllers. Additionally, a new method to control the system in overshoot situations is proposed. To demonstrate the effectiveness of the proposed CHIL platform, three short-circuit CHIL tests are performed for load#1 to load#3 at 430 A, 300 A, and 180 A fault currents, respectively. To investigate the designed algorithm protection, a complex protection experiment was conducted to evaluate the performance of the designed algorithm under multiple transient overshoot conditions in the current. The extracted CHIL results are also presented as the validation of proposed algorithm.

When ac and dc microgrids get exposed to load power changes or voltage transients, instability could occur owing to constant power loads’ (CPLs) behaviour. CPL has the negative impedance behaviour which is the reason behind such instability. A flexible alternating current transmission system (FACTS) devices are used in ac grid to help improve the power quality under such circumstances. Contrarily, dc networks doesn’t have such devices and suffers under similar situations. In this paper, the T-Type Modular Dc Circuit Breaker (T-Breaker) is proposed to act as a compensator device for dc networks when energy storage is integrated. Its compensation functions in addition to breaking and limiting a system’s current can be achieved using this single device. By implementing the T-Breaker’s shunt (current) and series (voltage) compensations, ride-through of grid transients can be achieved. T-Breaker’s series compensation function and how it can be integrated with the shunt compensation to improve the stability of a dc microgrid is the focus in this paper. In addition to modeling and simulating the system, both small signal and large signal stability are analyzed. Furthermore, a scaled down 270 V 5 kW system is utilized to validate T-Breake’s compensation functions and their influence on a microgrid’s stability.

Characterized by ultra-fast and arc-free fault clearing, solid state circuit breakers (SSCBs) are getting increasing popularity with the latest development of advanced power semiconductor devices, like the silicon carbide (SiC) MOSFETs. On the other hand, the mature and cost-effective thyristor technology exhibits the beneficial features of low conduction losses, high surge current capability, bidirectional voltage blocking capability, etc., making it a very attractive candidate for SSCB development. However, the conventional thyristors (silicon controlled rectifiers) have no current turn-off capability and need some auxiliary circuits (e.g., LC resonant circuit) or special topology (e.g., Z-source breakers) to be applied in SSCBs. Meanwhile, some active turn-off thyristors (like integrated gate-commutated thyristors, emitter turn-off thyristors, etc.) are specially modified to have current turn off capability, and better suitable for SSCBs. This paper reviews and studies the SSCBs based on the conventional or active turn-off thyristors. The design challenges and performance comparison of SSCBs with different thyristor technologies are also discussed.

A new series-type hybrid circuit breaker (S-HCB) concept for dc fault protection is reported that is fundamentally different from other prior-art hybrid circuit breakers (HCB) or solid-state circuit breakers (SSCB) in the literature. The S-HCB conducts its load current through metal wires instead of power semiconductor switches and curtails its fault current to near zero throughout the entire opening process of a series mechanical switch. It offers the low on-resistance of the conventional mechanical contacts for normal operation and µs-scale fault response even faster than the fast-acting SSCBs. A proof-of-concept S-HCB prototype experimentally demonstrates the interruption of a fault current of 30 A within 10 μs at a dc voltage of 600 V. The operating principle, simulation, and experimental results are discussed in this letter. [ABSTRACT FROM AUTHOR]

Due to the interconnected scheme of multiple components, such as distributed generators, storage systems, and loads through converters to a common bus in DC microgrids, the possibility of fault occurrence is increasing significantly. Meanwhile, due to the huge and rapid increase of short-circuit currents, the development of a small- and large-scale DC system requires a reliable and fast protection system to ensure fault clearance and maintain safety for the rest of the system. Thus, fault protection has been focused on as one of the most critical issues in a direct current network. The application of traditional circuit-breakers for DC fault protection has the drawback of slow operation, which requires a high rating power equipment. Recently, the high speed and excellent performance capabilities of semiconductor breakers have attracted a lot of attention and been considered as an optimal solution for fast DC fault interruption. In this study, a bidirectional Insulated-Gate Bipolar Transistor (IGBT) semiconductor breaker, suitable for the fault protection of low-voltage DC networks, is proposed. The operating characteristics of this breaker are based on changes in the circuit current and terminal voltage of IGBTs. It detects the abrupt change of the terminal voltage as an abnormal condition and isolates the faulted branch in a short time to prevent the operation disturbance in the healthy part of the network. Therefore, for the entire protection of a typical 400V DC-microgrid cluster, breakers need to be integrated and examined in each branch and the interconnected lines. The proposed protection method in this study is examined in a Simulink®/MATLAB environment to analyze and assess its operation. [ABSTRACT FROM AUTHOR]

Researchers are running into problems providing short-circuit protection for the development of modern DC micro-grids that have commercially practical hardware and supplies fast operation along with coordination and that is reliable on a constant basis In this paper, issues about short-circuit protection of low voltage DC (LVDC) microgrids are analyzed. A methodology for protection against short-circuiting using the assistance of solid state circuit breakers (SSCB) that offer fault-current limiting (FCL) are assessed. A number of methods for detection of faults related to the design of SSCB are deliberated. Simulation results for a basic 1KV DC micro-grid system displays that SSCB resolutions rooted in integrated, gate-commutated thyristors are practical for low voltage micro-grids but requires many devices to interconnect with them in parallel to open, rapidly increasing fault currents. [ABSTRACT FROM AUTHOR]

Due to the interconnected scheme of multiple components, such as distributed generators, storage systems, and loads through converters to a common bus in DC microgrids, the possibility of fault occurrence is increasing significantly. Meanwhile, due to the huge and rapid increase of short-circuit currents, the development of a small- and large-scale DC system requires a reliable and fast protection system to ensure fault clearance and maintain safety for the rest of the system. Thus, fault protection has been focused on as one of the most critical issues in a direct current network. The application of traditional circuit-breakers for DC fault protection has the drawback of slow operation, which requires a high rating power equipment. Recently, the high speed and excellent performance capabilities of semiconductor breakers have attracted a lot of attention and been considered as an optimal solution for fast DC fault interruption. In this study, a bidirectional Insulated-Gate Bipolar Transistor (IGBT) semiconductor breaker, suitable for the fault protection of low-voltage DC networks, is proposed. The operating characteristics of this breaker are based on changes in the circuit current and terminal voltage of IGBTs. It detects the abrupt change of the terminal voltage as an abnormal condition and isolates the faulted branch in a short time to prevent the operation disturbance in the healthy part of the network. Therefore, for the entire protection of a typical 400V DC-microgrid cluster, breakers need to be integrated and examined in each branch and the interconnected lines. The proposed protection method in this study is examined in a Simulink®/MATLAB environment to analyze and assess its operation.

The development of a large-scale high-voltage direct current (HVDC) power grid requires a reliable, fast, and low-loss circuit breaker. The load commutation switch (LCS) is an essential part of ABB's 1200-MW hybrid HVDC breaker concept, which builds up a low-loss conducting path for the load current. The technical requirements for the LCS are expressed in this paper by studying the operation principle of the hybrid HVDC breaker. The voltage stress over the LCS is determined based on a dc grid with 320 and 2 kA rated voltage and current. A system model of the hybrid HVDC breaker is developed in PSCAD/EMTDC to study the design criteria for snubber circuit and arrester blocks. It is observed that conventional snubber circuits are not suitable for a bidirectional LCS as the current of snubber capacitors prevent the fast interruption action. A modified snubber circuit is proposed in this paper along with two more alternatives for the LCS to overcome this problem. Moreover, the power loss model for a semiconductor device is discussed in this paper based on the 4.5-kV StakPak IGBT. The model is used to calculate the conduction power losses for different LCS topologies. Ultimately, a matrix of 3 $\times$ 3 IGBT modules is selected to provide a reliable LCS design which can handle several internal fault cases with no interruption of operation. A full-scale prototype has been constructed and tested in ABB HVDC Center, Ludvika, Sweden. The experimental test results are also included in the paper in order to verify the calculation and simulation study. [ABSTRACT FROM AUTHOR]

In order to reduce the breaking pressure of solid-state circuit breaker when removing DC fault and improve the ability of restraining fault current, a current limiting solid-state circuit breaker topology is proposed. Compared with the traditional current limiting solid-state circuit breaker, this structure has certain advantages in cutting off the fault line speed and restraining the fault current. It is suitable for DC microgrid with fast development speed and high amplitude of fault current. In this paper, the blocking process of the topology is analyzed theoretically, and the design method of relevant parameters and energy consumption calculation are given. In order to verify the feasibility of the scheme, a simulation model is built in saber software. The simulation results show that the proposed structure can suppress the rise rate of fault current by 53.9%, and shows excellent performance in fault isolation speed. [ABSTRACT FROM AUTHOR]