Search Results (53)

The widespread adoption of photovoltaic systems in residential electrical installations has increased the importance of Automatic Transfer Switches (ATSs) for ensuring power continuity during grid outages. However, many low-cost ATS solutions available on the market prioritize economic efficiency over operational safety, leading to significant risks under fault conditions. This paper investigates a real overvoltage incident in a residential three-phase installation equipped with a photovoltaic inverter and an ATS, which resulted in the failure of multiple electronic loads. The study reconstructs the event and demonstrates that the loss of the neutral conductor during backup operation caused severe phase voltage imbalance, generating overvoltage conditions across lightly loaded phases. A simplified electrical model is used to explain current paths and voltage redistribution under asymmetric loads, highlighting the critical role of correct neutral switching in ATS design. Two commercially available ATS architectures, one based on a changeover-contact mechanism and one employing four-pole miniature circuit breakers, are experimentally evaluated. The evaluation reveals major design deficiencies, including the absence of protective elements for control circuits, reliance on mechanical end-position limiters, and the use of switching devices not intended for frequent source transfer. These shortcomings introduce risks such as uncontrolled actuator operation, overheating, mechanical damage, and potential fire hazards. To overcome these limitations, a new ATS architecture was developed using a phase-monitoring relay, interlocked ABB contactors, and dedicated fuse protection for all control circuits. Detailed laboratory measurements were conducted to characterize contactor switching times and internal relay command delays. By optimizing the command sequence, the proposed ATS achieves predictable, fault-tolerant operation with competitive transfer times, representing a meaningful safety improvement over the evaluated commercial alternatives. The proposed solution is scoped to three-phase residential installations equipped with a hybrid photovoltaic inverter providing a dedicated backup output, operating within TN-S or TN-C-S earthing systems with a maximum grid connection capacity of 21 kW. Full article

The development of high-performance DC circuit breakers (DCCBs) and rapid fault detection schemes is a crucial and challenging part of advancing Modular Multilevel Converter (MMC) HVDC grids. This paper introduces a new current-limiting DCCB that uses the differential discharge times of shunt capacitors to generate artificial current zero-crossings, thus facilitating arc quenching. This mechanism significantly reduces the effect of fault currents on the MMC. The shunt capacitors and arresters in the proposed breaker also offer voltage support during faults, effectively stopping transient traveling waves from spreading to nearby non-fault lines. This feature creates an effective line protection boundary in multi-terminal HVDC systems. Additionally, a fast fault detection scheme with primary and backup protection is proposed. A four-terminal MMC-HVDC (±500 kV) simulation model is built in PSCAD/EMTDC to validate the scheme. The results demonstrate the excellent fault detection performance of the proposed method. The voltage and current behavior during the interruption process of the new DCCB is also analyzed and compared with that of a hybrid DCCB. Full article

The use of advanced switching technologies, including hybrid and fully semiconductor-based circuit breakers, enables a significant reduction in the prospective short-circuit current. This enhances the level of circuit protection by minimizing thermal and electrodynamic stresses. One of the available solutions is a hybrid DC circuit breaker employing the forced commutation method, in which a counter-current generator is incorporated into the auxiliary branch. Increasing requirements not only for short-circuit protection reliability but also for operational flexibility impose the need to configure DC breakers for parallel operation. This paper presents an analysis of the performance of forced-commutation circuit breakers connected in parallel with another identical device, as well as with a conventional fast magnetic blow-out breaker. To prevent unintended and undesired tripping, the influence of counter-current generator parameters on the overcurrent protection response was investigated. In the analyzed configuration, the applied hybrid DC breaker limits the expected short-circuit current from approximately 45 kA to 5 kA within about 2 ms. Full article

Hybrid AC/DC microgrids (HMGs) are pivotal for integrating renewable resources, yet their stability and resilience are fundamentally constrained by the power electronic converters that interface them. This paper provides a critical review and synthesis of the co-dependent advancements in HMG converter topologies, control strategies, and fault management. Through a systematic analysis of the state of the art, this review examines the evolution from classical control to intelligent, software-defined converter functions. The analysis reveals a fundamental bifurcation in design philosophy between low-voltage (LV) and medium-voltage (MV) systems, driven by a trade-off between power density Gallium Nitride (GaN) and systemic reliability silicon carbide (SiC). Furthermore, it highlights the rise of virtualization, namely virtual Inertia control (VIC) and adaptive virtual impedance control (AVIDC), as a dominant paradigm to compensate for the physical limitations of low-inertia, resistive grids. Finally, this review identifies a critical, synergistic dependency in fault management, where ultra-fast solid-state circuit breakers (SSCBs) guarantee the survivability of vulnerable voltage source converters (VSCs), which in turn enables software-based resilience via fault ride-through (FRT). This synthesis concludes that the converter has become the intelligent nexus of the HMG and identifies the primary barriers to widespread adoption as the computational, economic, and standardization gaps in this new cyber–physical domain. Full article

The growing interest in high-voltage direct current (HVDC) technology and multi-terminal HVDCs (MTDCs) has motivated the evaluation of DC circuit breakers (DCCBs) for increased operational flexibility. While modeling DCCBs remains essential, their complex structures and modeling techniques require careful consideration. In this context, trade-offs in modeling accuracy and complexity of DCCBs are of paramount importance, and hence, benchmarking-based modeling methodology for hybrid and non-hybrid DCCBs is performed in this study. To this end, the performance of different aggregated DCCB technologies, namely hybrid DCCBs, simple DCCBs, and voltage-source DCCBs, is benchmarked for MTDC applications, with the full representation of hybrid DCCBs taken as the baseline for comparison. First, it is shown that the aggregated hybrid DCCB provides an accurate representation of the full hybrid DCCB’s performance. This is followed by an analysis of the parameters for the simple DCCB and voltage-source DCCB (VSCB) that enable their performance to closely match that of the aggregated hybrid DCCB. Finally, the impact of aggregated DCCB models on voltage transients within a test system is analyzed, demonstrating the effectiveness of aggregated modeling across different DCCB technologies. Simulation-based analyses are conducted in PSCAD/EMTDC to compare the performance of different aggregated DCCB models. Full article

The use of vacuum-hybrid DC circuit breaking methods allows the short-circuit current to be switched off in a shorter time, resulting in a reduction in the arc burning time. This requires the use of a drive, such as the Thomson Coil Actuator TCA, capable of providing a short response time for opening the vacuum interrupter VI, regardless of its rated current. The IDD is powered by a pre-charged capacitor, which, together with the drive coil, forms an LC oscillating circuit that, when switched on by a thyristor, generates a current pulse of several kA with a frequency above 1 kHz. The paper investigates the effect of modifying the basic IDD power supply circuit by adding semiconductor diodes to shape the current pulse and improve its performance. The authors also focused on exploring the impact of the connection quality and their length and the associated loss in drive force while proving that a circuit with a reverse diode on the IDD coil is most beneficial and that the effect of the circuit on the front of the current pulse can significantly slow down the drive. Full article

In order to solve the problem of the slow initial speed caused by the large mass of the bistable permanent magnetic actuator (PMA) in the traditional bistable permanent magnetic–electromagnetic repulsion mechanism (PM-ERM), a novel fast contact operating mechanism is proposed by using the flexible spring system (SS) between the PMA and the ERM. The novel structure can separate the mass of the PMA and the ERM at the initial phase of the interrupting process, improve the initial speed of the contact and increase the initial opening distance of the contact. Firstly, the paper conducts an extensive investigation and analysis of the principle of the existing fast operating mechanism and points out the advantages and disadvantages of the existing mechanism. In order to meet the requirement of fast interrupting and improve the service life of the mechanism, a novel mechanism is proposed. And then, the working principle of the novel mechanism is introduced. The cooperative relationship between the ERM and the PMA and the working principle and performance parameter requirements of the ERM, SS and PMA are analyzed and designed. Finally, the feasibility of the novel mechanism is verified by the experiment. The results show that the opening distance of the novel operating mechanism can reach 2.25 mm in 1 ms. Compared with 1.24 mm of the traditional operating mechanism, it improves the initial opening distance of the contact by 81.5% and is conducive to the rapid interruption of the Hybrid DC current-limiting circuit breaker (HDCCLCB). Full article

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. Full article

DC circuit breakers (DCCBs) are the key equipment to rapidly interrupt the fault current in high-voltage DC power grids and ensure the safe operation of the system. However, most DCCBs do not take current-limiting measures and rely solely on current-limiting reactors in the system to limit the rate of current rise during the interruption process. The extensive use of fully controlled power electronic devices in circuit breakers (CBs) results in high costs. To address the issues above, this paper proposes a DCCB topology with a current-limiting function based on thyristors and diodes, which can reduce the cost of CB while ensuring reliable interruption. The impact of various parameters on CB performance is analyzed using numerical calculations to optimize the parameters. Then, a simulation model of a 500 kV/16 kA DCCB is built in PSCAD/EMTDC, and the performance of the proposed CB topology is compared with the other CB topologies. By comparison, the proposed DCCB topology can reliably isolate fault currents and reduce the amplitude of fault currents and the cost of CBs. Significantly, the energy absorbed by the metal oxide varistor (MOV) during the interruption process decreases by 64.2%, reducing the cost and volume of the MOV. Finally, the feasibility of the CB is further verified in the ±500 kV 4-terminal high-voltage DC power grid simulation model. The results show that the proposed DCCB topology can limit the fault current rise rate, interrupt and isolate the fault reliably, and reduce the cost. Full article

The interline power flow controller (IPFC) based on a modular multilevel converter with a half-bridge configuration can control the active and reactive power flows of multiple alternating current (AC) lines. However, it forms a multiterminal system on the direct current (DC) side, which leads to DC faults. To reduce the protection and clearance requirements on the DC side of IPFCs, this paper proposes a hybrid current limiter topology suitable for generating a DC-side fault ride-through scheme. The current limiter employs a low-loss branch in steady-state conditions; when the fault occurs, a commutation capacitor and controllable power electronic devices are used to transfer the fault current to the current-limiting branch. To clarify the operating principles of the current limiter, the working states of each stage and electrical stress of each device are analyzed. Different components with varying limiter parameters are also discussed, and optimal parameters to achieve the best limitation effect are discussed. PSCAD simulations show that the proposed limiter can limit the overcurrent effectively, and DC-side fault clearance can be achieved easily with this fault ride-through strategy. Full article

Hybrid circuit breakers are the most promising circuit breakers among DC circuit breakers. Conventional hybrid circuit breakers complete fault current isolation by converting current to IGBT when fault current occurs. However, in this case, the fault current continues to increase, so the IGBT must be large enough to withstand this current. In addition, in the case of a method of detecting and operating a fault, a delay time of up to hundreds of microseconds occurs, and in a hybrid circuit breaker, this delay time is a very large value. To solve this problem, this paper proposes a hybrid Z-source circuit breaker that operates without delay for low-impedance faults. The proposed breaker is designed to reduce stress on IGBTs and mechanical switches by generating a current zero crossing, as well as to enable the breaker to trip quickly in high-risk cases such as low-impedance fault circuits. Due to the limited environment of the laboratory, we performed 600 V fault isolation experiments. As a result of the experiment, it was confirmed that the proposed circuit breaker successfully isolated the fault within 1.6 ms. The current limiting feature of the Z-source appears to reduce stress on the IGBTs and MOVs used, and it allows for faster fault isolation. Full article

In instances where vessels encounter impacts or other factors leading to communication impairments, the status of electrical equipment becomes inaccessible through standard communication lines for the controllers. Consequently, the shipboard power system enters the partial observable state. Failure to timely ascertain and respond to the current state of the shipboard power system with appropriate restorative controls can result in irreversible damages to the electrical infrastructure and potentially precipitate a complete systemic failure. In this paper, an innovative fault-tolerant control and state estimation approach is proposed to address the partial observability problem of shipboard power systems, based on distributed control architecture and hybrid automata modeling, where controllers are unable to fully acquire equipment status due to device failures like sensor malfunctions. This approach infers the overall state of subsystems using data from intact equipment and discrete events from circuit breakers. Through fault-tolerant control techniques, it ensures that the subsystem state avoids invalid regions, effectively preventing the system from entering unhealthy operational states and significantly reducing the risk of performance degradation or systemic collapse due to faults. Simulation results confirm that this approach can quickly and accurately estimate the system’s current state under partial observation, enabling subsequent fault recovery strategies to accurately pinpoint fault locations and identify optimal recovery solutions. Full article

Aimed at the optimization design of the parameters of the commutation circuit of a hybrid DC-current-limiting circuit breaker (HDCCLCB), a parameter selection model considering the short-time withstand of the thyristor and the volume of the commutation circuit is proposed by simplifying the object, and the commutation circuit parameters were preliminarily obtained. In order to verify the correctness of the method of selecting the commutation circuit parameters, the circuit simulation model of the HDCCLCB was built. The experimental platform was built, and the breaking experiment was completed under the fault condition with the current rising rate of 20 A/μs. The correctness of the simulation model and parameter design method was verified by comparing the circuit model simulation results with the experimental results. In order to further optimize the parameters of the commutation circuit, a mathematical model for optimization design was established. Taking the maximum critical breakdown voltage under unit capacitance energy as the objective function, the arcing time before commutating and the current-limiting inductance and capacitance are enumerated to obtain the optimized commutation circuit parameters. By comparing this result with the result of the preliminary design, the objective function is improved by 20.7%, laying a solid foundation for further research and the development of current-limiting circuit breakers for medium-voltage DC systems. Full article

The state of the energy-absorption branch MOV in the hybrid DC circuit breaker (DCCB) has a very important impact on the short fault breaking operation of the circuit breaker. Therefore, it is necessary to evaluate the state of the MOV, which is also called the “sleep component”. Due to DCCB being placed indoors, the aging is mainly caused by short-circuit impulse current. Therefore, this paper mainly focuses on the study of the short-circuit impulse aging characteristics of the energy-absorption branch MOV. The dynamic simulation system of a hybrid DCCB was built to investigate the impulse of short-circuit current on the MOV of the energy-absorption branch during the circuit breaking process. Then, an accelerated impulse aging test platform was built and the accelerated impulse aging tests of the MOV were conducted. The aging characteristics of the MOV were analyzed in detail and detailed analysis was conducted of the macroscopic parameters and microstructure changes. The results indicate that the nonlinear coefficient α could be emphasized as a basis for judging the “sleeping” component states and aging degree of the hybrid DC circuit breaker, and can be expected to be applicable to MOV condition monitoring of BCCB in the future. Full article

While traditional AC mechanical circuit breakers can protect AC circuits, many other DC power distribution technologies, such as DC microgrids (MGs), yield superior disruption performance, e.g., faster and more reliable switching speeds. However, novel DC circuit breaker (DCCB) designs are challenging due to the need to quickly break high currents within milliseconds, caused by the high fault current rise in DC grids compared to AC grids. In DC grids, the circuit breaker must not provide any current crossing and must absorb surges, since the arc is not naturally extinguished by the system. Additionally, the DC breaker must mitigate the magnetic energy stored in the system inductance and withstand residual overvoltages after current interruption. These challenges require a fundamentally different topology for DCCBs, which are typically made using solid-state semiconductor technology, metal oxide varistors (MOVs), and ultra-fast switches. This study aims to provide a comprehensive review of the development, design, and performance of DCCBs and an analysis of internal topology, the energy absorption path, and subcircuits in solid-state (SS)-based DCCBs. The research explores various novel designs that introduce different structures for an energy dissipation solution. The classification of these designs is based on the fundamental principles of surge mitigation and a detailed analysis of the techniques employed in DCCBs. In addition, our framework offers an advantageous reference point for the future evolution of SS circuit breakers in numerous developing power delivery systems. Full article