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In this article, a novel Z-source dc circuit breaker topology with a Q-shaped impedance network (Q-Z-source circuit breaker) is presented. The new topology has a better performance and is more resilient properties than those of the recently published O-Z-source circuit breaker. The new Q-Z topology provides bidirectional protection but only requires one semiconductor switch in its current path during normal operation, leading to a simpler and smaller physical structure and a lower conduction penalty. It also drastically improves the sensitivity issue on the magnetic coupling coefficient that manifests in the existing O-Z-source circuit breaker. In a realistic, practical application with a nonideal magnetic coupling coefficient, the new topology requires a smaller capacitance that can be translated into lower weight and/or lower cost. Detailed mathematical models are built to analyze and compare the short-circuit fault responses of a variable coupling coefficient. The bidirectional snubber circuit and its connection to the Q-Z topology are discussed for achieving faster fault clearing. Finally, a prototype is built in the laboratory to verify the theoretical analysis and improved performance of the proposed bidirectional Q-Z-source dc circuit breaker. [ABSTRACT FROM AUTHOR]

This article proposes a novel method for detection of open-phase faults, which was specifically designed for usage in low-cost motor drives. The proposed algorithm uses analysis of current signals to detect the failure and it was developed for usage with conventional configuration of motor drives, where phase currents are measured with the shunt sensors placed in motor phases, or dc-link and which signals are corrupted with a noise. The author discusses the specifics of inverter hardware design for low-cost applications and explains why the conventional techniques are not applicable. After that a new method capable of operating at high noise to signal ratio is proposed and implemented. The experimental results verified feasibility of the developed technique and demonstrated its reliable operation under different load conditions. In order to perform comparative analysis, several conventional algorithms were implemented and their performance was compared to the performance of the proposed method. After experimental verification, this algorithm was included into the existing control scheme of commercial permanent magnet synchronous motors, as a part of the safety module. The modified motor drive successfully passed standardization according to UL 60730 safety standards and was put into mass production. [ABSTRACT FROM AUTHOR]

Solid-state dc circuit breaker (SSCB) plays a very important role in the dc system protection against fast rising overload and short-circuit faults. Among various SSCB topologies, z-source dc circuit breakers (ZSCBs) have a great ability to interrupt the fault at a much faster rate, without even using a fault sensing circuit. However, ZSCBs suffer from various issues such as: 1) high starting current in the main thyristor (SCR), 2) unwanted power flow in the load during commissioning and reclosing of ZSCBs, and 3) negative current flow through the load at starting/reclosing of the ZSCB. These problems arise due to the fact that the z-source series capacitor stays charged even after the fault is interrupted or cleared. Unwanted power flow, negative current circulation in the load needs special attention especially in unidirectional loads and also in electromechanical systems. Hence, this article proposes a modified ZSCB to address the aforementioned problems. The proposed topology employs power semiconductor devices such as IGBTs to discharge the capacitor before the next interruption cycle. Initially, a detailed analysis, with simulation and experimental validation showing the issues with the existing ZSCB is presented. Later, a detailed analysis of the proposed modified ZSCB is presented, followed by an extensive simulation and experimental validation on a laboratory scale 120-V/3.5-A (400 W) prototype. [ABSTRACT FROM AUTHOR]

To protect the converters and minimize the power transmission interruption during dc line faults, it is necessary to detect the faults at ultra high speed for the modular multilevel converter (MMC)-based HVdc grids. This article reviews the state-of-the-art of dc fault protection methods of MMC-HVdc grids, and summarizes the underlying principles of each method. On this basis, the dc fault characteristics analysis in terms of modal-domain, time-domain, and frequency-domain are analyzed, which direct the protection design. Typical boundary protection and nonboundary protection schemes are reviewed. The advantages and disadvantages of existing fault protection methods are compared. A two-terminal MMC-HVdc prototype is developed to test the effectiveness of three fault protection methods. Comprehensive quantitative assessments of the protection methods discussed above are carried out in a four-terminal MMC-HVdc grid. Finally, the future trends of the protection schemes are discussed and the findings are concluded. [ABSTRACT FROM AUTHOR]

Although conventional electromechanical circuit breakers have a proven record as effective and reliable devices for circuit protection, emerging power distribution technologies and architectures, such as dc microgrids, require improved interruption performance characteristics (e.g., faster switching speed). The need for faster switching operation, in combination with the latest developments of advanced power semiconductor technologies, has spurred an increase in the research and development in the area of solid-state circuit breakers. This article provides a comprehensive review of various solid-state circuit breaker technologies that have been reported in the literature during recent years. First, we categorize solid-state circuit breakers based on key features and subsystems, including power semiconductor devices, main circuit topologies, voltage clamping methods, gate drivers, fault detection methods, and commutation methods for power semiconductor devices. Second, we discuss the various challenges associated with the design of solid-state circuit breakers from the perspective of generic applications and provide a comparison of several solid-state breaker technologies based on key metrics. Finally, we provide a useful framework and point of reference for future development of solid-state circuit breakers for many emerging power distribution applications. [ABSTRACT FROM AUTHOR]

The need to increase the efficiency and reduce the operating cost of shipboard dc power distribution networks results in a desire to increase the operating voltage of such installations to the medium-voltage levels. Devices, such as solid state bus-tie switches, are an essential component of such systems, as they allow for system reconfigurations and prevent fault propagation across different sections of the system. This article presents a scalable solid-state bus-tie switch topology designed initially for low-voltage power-distribution networks, but easily scalable in terms of voltage and current. The use of a single active device greatly increases simplicity and reliability of the solution. The ability to extend the current and voltage ratings has been verified on the prototypes through extensive experimental tests in parallel and series connection, respectively. Several methods for fault detection are discussed and further verified experimentally. [ABSTRACT FROM AUTHOR]

Low-voltage dc (LVdc) microgrids emerge as a viable alternative to ac microgrids. A large research interest is noted toward fast and selective protection of dc grids, typically focusing on hybrid or full solid-state solutions. In this article, the use of fuses as short-circuit protection in low-voltage dc microgrids is evaluated. The main advantage of fuses is that they are simple, cheap, standardized, and have low steady-state losses. A theoretical basis is formed to model dc short-circuit currents in grids with a limited short-circuit availability. The outcomes are applied to evaluate the possibilities of fuse protection in LVdc grids. It was found that fuses are an effective means of protection, although the required amount of capacitance at the output of the voltage balancing converter can be high, which impacts the total system cost. A fuse-based protection strategy is presented that highlights the need for additional capacitance to clear faults compared to the necessary capacitance for system stability. An experimental setup was built to validate the claims. [ABSTRACT FROM AUTHOR]

This article is an extension of our research, which was presented at the PCIM Europe conference in Nuremberg 2019. After proving the potential of the two-dimensional (2-D) short circuit detection method for SiC mosfets in the preceding work Hofstetter et al., this article presents the use of the protection system in an urban rail transit application. This introduces many challenges. It is shown how to calibrate the detection system when facing the challenge of different Miller plateaus due to temperature and dc-link voltage ranges and charge carrier trapping effects. Additionally, the effects due to parallelization are examined. False detections due to drain current oscillation are prevented with a simple additional circuit, which is used to suppress the oscillation from the detection circuit. This method leads to a minor increase in current until detection in a short circuit type 2 event. All the techniques and circuitry are experimentally verified and validate the 2-D short-circuit protection as a perfect candidate for the use in urban rail transit application. [ABSTRACT FROM AUTHOR]

This paper proposes a new device by combining features of an interline dual H-bridge current flow controller with the core idea of a hybrid HVdc circuit breaker for meshed HVdc grid application. The proposed device can substitute two dc circuit breakers at a dc bus with at least two adjacent transmission lines. In addition to the current interruption action, the current in one of the adjacent lines can be controlled by the embedded current flow controller. The system-level behavior of the proposed current flow controlling hybrid dc circuit breaker is similar to that of the typical hybrid dc circuit breaker and the interline dual H-bridge current flow controller. The operation principles of the proposed device are introduced and analyzed in this work. The component ratings are compared to the existing solution, and the functionality of the proposed device is verified by simulation. [ABSTRACT FROM AUTHOR]

In order to eliminate power conversion steps, future microgrids with renewable energy sources are being visualized as dc power systems. System components such as sources (solar panels, fuels cells, etc.) loads, and power conversion have been identified and are readily available. However, when it comes to dc circuit breakers, many designs are still in the experimental phase. The main limitation is that interrupting a current which does not have a zero crossing will sustain an arc. This paper introduces a new type of dc circuit breaker. It uses a short conduction path between the breaker and load as well as mutual coupling to automatically and rapidly switch Off in response to a fault. The proposed breaker also can have a crowbar type switch at the output so that it can be used as a dc switch. Mathematical analysis, detailed simulation, and laboratory measurements of the new dc switch are included. [ABSTRACT FROM AUTHOR]

Current fed parallel resonant electronic ballast (PREB) dominates the applications for the T8 fluorescent lamp in North America for its advantage of low cost, flexibility and high reliability. At fault condition, a PREB generates much heat externally, and it is difficult to provide fault protection with traditional approaches. In this paper, a digital solution is presented to detect universal fault condition in PREB without sacrificing its other advantages. Operational principal of PREB is explored to show that the load impedance disturbance in PREB leads to frequency perturbation of the inverter, which can be detected with a very simple and low cost digital device for fault detection. Experiments show that this frequency diagnostic provides very sensitive and reliable fault detection for PREB. With both end-of-life lamp and anti-arcing protections implemented with one algorithm, this technology provides a superior fault protection to one of the most widely used ballast topologies and extends the potential applications of PREB in modern lighting industry. [ABSTRACT FROM AUTHOR]