This paper proposes a coupled inductor based hybrid DC circuit breaker topology with zero current switching (ZCS) for fast fault interruption in DC systems. A series resonant circuit comprising of the secondary winding of a two-winding coupled inductor and a charged capacitor (commutation capacitor) is switched on during fault to inject a counter-current pulse, and, consequently, force a zero crossing of fault current. Proposed solution facilitates arcless breaking for a mechanical circuit breaker due to zero current turn-off. The proposed circuit breaker exhibits fast fault response (~30 μs), and the response time is programmable based on the design of the coupled inductor and commutation capacitor. Furthermore, presented solution mitigates the requirement of energy-absorbing elements for demagnetizing the DC network following fault interruption, in contrast to conventional DC breakers. The paper also presents two modified circuit breaker topologies to achieve unipolar voltage profile on the capacitor, which will enable the use of electrolytic capacitors for commutation so that the capacitor stack size is reduced in high voltage applications. Detailed Analysis and design equations are presented to explain the operation of the proposed topologies. Functionality of the proposed circuit breakers is verified through simulation, and experimental results based on two laboratory prototypes.

The design of electric power systems (EPSs) for the aviation industry has become a major research area to reduce the global annual CO2 emission caused by the transportation sector. DC power distribution is envisaged to meet the high load demand of more-electric and all-electric aircraft power architectures. Nonetheless, the development of dc distribution is significantly impeded by the challenges associated with dc system protection. Aircraft EPS demands high speed and high current protection. Among various dc circuit breaker (DCCB) technologies, solid-state dc circuit breakers (SSCBs) operate at higher speeds. To make them withstand high current ratings, modular structured DCCBs with the highest power density, reliability, and bidirectional fault interruption capability are presented in this article. The existing DCCBs fail to comply with the design constraints such as faster response, high current breaking, and compact design. This article proposes a coupled inductor-based modular bidirectional SSCB that employs the magnetic coupling principle for counter-current commutation of thyristors. The proposed modular SSCB exhibits a fast fault interruption time of approximately 200 $\mu \text{s}$ . The analysis, design, and experimental validation of the proposed SSCB are presented in detail. Each module in the prototype is designed for a system rating of 270 V/15 A. The performance of this SSCB for single- and two-module operations is experimentally verified for a 270-V/20-A dc system.

An isolated multilevel bidirectional dc-dc converter is presented in this paper to interface the low voltage (LV) battery and the high voltage (HV) propulsion inverter in electric vehicles. The proposed topology achieves a high voltage step-up ratio in the motoring mode by reconfiguring two split capacitor half-bridge circuits in series/parallel through the symmetrical modulation of a voltage bidirectional, two quadrant switch. This reconfiguration generates a high-frequency multilevel voltage output at the dc bus side of the inverter, which reduces the output filter volume. The dc bus voltage is regulated by the duty cycle modulation of the intermediary switch in the motoring mode, simplifying the sensing and control. During regenerative braking, the converter is operated with phase shift modulation between the HV half bridges and the LV full bridge to regulate the battery voltage. The presented modulation strategies achieve ZVS for the full bridge devices over a wide load range. A comprehensive analysis of the proposed multilevel converter in motoring and braking modes along with the design constraints and soft switching boundary conditions is presented in this paper. Detailed experimental results on a 1.5 kW laboratory prototype are presented to verify the design approach and illustrate the converter performance.

The increasing demand for the development and utilization of renewable energy resources has lead to a growing interest in the development of LVDC systems. The dc grid provides more flexibility in integrating different forms of renewable energy sources effectively. However, the lack of a reliable protection mechanism remains the main drawback in the growth of dc distribution systems. Unlike ac systems, the absence of a natural zero crossing in dc systems for arc extinction makes the use of a conventional mechanical circuit breaker (MCB) a less reliable solution. The use of a solid-state circuit breaker (SSCB) results in fast fault interruption but reduces the overall efficiency of the system due to the on-state voltage drop of the semiconductor devices. A hybrid circuit breaker (HCB) combining MCB and SSCB yields better static and dynamic performances but the main challenges remains in the demagnetization of the transmission line inductance after a fault interruption and an arc formation between the MCB contacts. This paper proposes a hybrid circuit breaker (HCB) which is suitable for fast fault interruption in low voltage dc (LVDC) systems while alleviating the above issues. Proposed topology employs a semiconductor switch as well as an actively switched capacitor branch in parallel with the main mechanical breaker to facilitate fast current commutation during a fault. The mechanical breaker forming the main branch is turned off at zero voltage. This eliminates the arc formation across the moving contacts of the breaker. Moreover, the fault interruption process does not require a varistor for network demagnetization following the fault current commutation. This paper also presents a discharging mechanism for the capacitor in a practical implementation. Operation of the proposed dc circuit breaker is evaluated through a prototype tested in the laboratory.

Subsea oil and gas (O&G) exploration demands significantly high power to supply the electrical loads for extraction and pumping of the oil and gas. The energy demand is usually met by fossil fuel combustion-based platform generation, which releases a substantial volume of greenhouse gases including carbon dioxide (CO₂) and methane into the atmosphere. The severity of the resulting adverse environmental impact has increased the focus on more sustainable and environment-friendly power processing for deepwater O&G production. The most feasible way toward sustainable power processing lies in the complete electrification of subsea systems. This paper aims to dive deep into the technology trends that enable an all-electric subsea grid and the real-world challenges that hinder the proliferation of these technologies. Two main enabling technologies are the transmission of electrical power from the onshore electrical grid to the subsea petroleum installations or the integration of offshore renewable energy sources to form a microgrid to power the platform-based and subsea loads. This paper reviews the feasible power generation sources for interconnection with subsea oil installations. Next, this interconnection’s possible power transmission and distribution architectures are presented, including auxiliary power processing systems like subsea electric heating. As the electrical fault is one of the major challenges for DC systems, the fault protection topologies for the subsea HVDC architectures are also reviewed. A brief discussion and comparison of the reviewed technologies are presented. Finally, the critical findings are summarized in the conclusion section.

This paper introduces a hybrid DC circuit breaker (DCCB) topology suitable for protection of bidirectional DC systems such as DC micro-grids with energy storage. The proposed DCCB utilizes series resonance of a 3-winding coupled inductor and a charged commutation capacitor to inject reverse current to the fault, thereby forcing a zero crossing in fault current to commutate the series path switch and interrupt fault. The commutation capacitor is actively charged from the DC source through circuit elements. Also, as the series path mechanical switch is turned off at zero current, no arc is formed between separating contacts of the switch. Fault interruption time is programmable based on the choice of passive elements. A modification of the proposed topology using two 2-winding coupled inductors is also explored. Analysis and operation of the proposed circuit breaker topology is illustrated with design equations and its functionality is evaluated through relevant simulation and experimental results.