Short-circuit Protection Research Articles

A Series Stacked IGBT Switch With Robustness Against Short-Circuit Fault for Pulsed Power Applications

The limited value of the insolated-gate bipolar transistors (IGBTs) blocking voltage is an important issue for applying these devices to the high-voltage power converters. An effective solution is to use a series configuration of these devices in order to achieve higher voltage ratings in addition to save the interesting features such as fast rising time. To reach this goal, acceptable equal voltage sharing for the IGBTs are provided by the series stacking schemes in the normal operation. However, a considerable difference in their voltage level will be occurred in the short-circuit condition. Although the IGBT can withstand the short-circuit current in a defined time, the occurred high voltage stress for the IGBT is fatal in such condition. To solve the mentioned problem, this paper proposes a short-circuit protection system suitable for the series stacked IGBTs. Using this proposal, the safe voltage level for IGBTs as well as the adequate time for the performance of the detection and elimination of the short-circuit fault will be provided. Each IGBT can have a different short-circuit current in the active region since the proposed scheme makes the IGBTs independent in terms of the current in the series structure. An external resistor added to the IGBTs emitter improves the equality of the IGBTs short-circuit currents and consequently their voltage sharing. This resistor controls the system short-circuit current by changing the operating point of IGBTs in active region in the short-circuit fault. The experimental and simulation results show that the safe condition is provided for the IGBTs under the short-circuit fault.

Methodology for Protection Performance Evaluation on Power Transmission Networks

An innovative methodology for protection performance evaluation on transmission networks is presented in this paper. It was developed to overcome difficulties faced by the Brazilian utility Companhia Hidro Eletrica do Sao Francisco (CHESF) during the preparation of short-circuit reports that must be sent to regulatory organizations whenever transmission-line faults occur. In the proposed methodology, a combination of several algorithms is used to extract from oscillographic records relevant information about short circuits and performance of protection functions. Aiming toward practical applications in CHESF, a software named disturbance analysis and protection performance evaluation has been developed in order to execute the proposed methodology functions, providing reports about the short-circuit characteristics and protection operation. To validate the proposed methodology, digital fault simulations in the Alternative Transients Program (ATP) and in Computer-Aided Protection Engineering (CAPE) software were carried out. Furthermore, real-world fault cases were also analyzed by assessing actual oscillographic fault records provided by CHESF. The obtained results show that the proposed methodology is reliable and quite useful for short-circuit analysis and protection performance evaluation procedures.

Short-Circuit Fault Management in DC Electric Ship Propulsion System: Protection Requirements, Review of Existing Technologies and Future Research Trends

Ease of integration of the variable speed diesel generators resulting in substantial reduction of the fuel consumption is the key motivation for the development of the dc shipboard power system (SPS). One of the impediments to the widespread adoption of the dc SPS, however, has been the lack of comprehensive fault management strategies during the short-circuit faults. Such strategies comprise of fault detection, fault isolation, and reconfiguration of dc SPS. In the existing literature, all these aspects of fault management are dealt independently and mostly assuming ideal conditions. All the strategies are of utmost importance and it is needed to study them under a common framework which is the aim of this paper. This paper starts with a brief discussion on the characteristics of dc SPS along with recent modeling techniques. Subsequently, this paper describes the short-circuit fault studies, fault characteristics, and protection requirements. Finally, this paper outlines the working principle, advantages, and limitations of the fault detection, isolation, and reconfiguration strategies developed for the dc power system and analyzes their suitability to the dc SPS. This paper is concluded by identifying the future research trends needed for the development of the short-circuit fault management strategies of dc SPS for critical marine missions.

A New Soft Switching qZSC Converter by Using Coupled Inductor

Solar energy is a very cost efficient energy in terms of construction and maintenance that has no pollution and can be found everywhere. So, various converter topologies are used as an interface converter for solar panels. The boost converter is the conventional converter used in photovoltaic (PV) application. But, it has several problems such as instability in Continuous Conduction Mode (CCM), input inrush currents, short circuit protection and etc. These problems, lead to use Z-Source and quasi Z-Source Converter (qZSC) which have higher gain compared to traditional boost converter, lower current ripple at the input without using any extra filters, buck and boost capability, lower output ripple and higher reliability. In this paper a soft switching technique for qZSC converter with coupled inductor and without any auxiliary switch is proposed for PV application. By adding an auxiliary circuit, which includes a coupled inductor, diode and capacitor, soft switching condition is provided for all semiconductor elements of the proposed converter. The proposed converter is theoretically analyzed and to confirm the validity of the theoretical analysis, it is simulated by ORCAD and a laboratory prototype is built. The proposed converter shows six percent efficiency improvement in comparison with hard switching counterpart.

Parameters of DC high-speed circuit-breakers

DC high-speed circuit-breakers (HSCB) are the basic protection to cut off short-circuit and overload currents. People’s and railway infrastructure devices’ safety depend on their reliability and parameters. High-speed circuit-breakers, like any other electrical devices, display several electrical and mechanical characteristic parameters, which in many cases are interconnected. The article features these parameters of DC high-speed circuit-breakers that affect the operation safety of electric traction power supply systems. Moreover, it presents ways of their determination basing on laboratory and operational tests. Furthermore, requirements to be met directly and indirectly by DC high-speed circuit-breakers imposed by legal and standardization documents are described. Correlations between the breakers’ construction and their parameters are outlined. Basing on tests of leading European producers’ breakers, the article presents the impact of parameters of circuit where they are tested as regards HSCB parameters. It also deals with the problem of coordination of short-circuit protection and breaking currents of low values with respect to high-speed circuit-breakers used in Poland.

Analysis and Experiments on a Single-Inductor Half-Bridge LED Driver With Magnetic Control

This paper presents the analysis and experiments of a variable inductor (VI) based LED driver for dc grid lighting applications. The proposed driver requires only a series inductor and a transformer as major components to drive the LED lamp from a half-bridge inverter. By introducing a VI as the series inductor, the LED current can be controlled independently from any other parameter, which makes it possible to drive and regulate several LED branches from the same half-bridge output. Other advantages of the proposed converter include inherent open-circuit and short-circuit protections, zero-voltage switching for the bridge transistor and zero-current switching for the output rectifier diodes, simple dynamics, possibility of analog and pulse width modulation dimming, constant switching frequency operation, and high efficiency. The converter is thoroughly analyzed and modeled for both steady-state and dynamic operation. As another novelty of this paper, the dynamic response of the VI has been studied and taken into account to obtain the complete transfer function of the VI-controlled system. In addition, some housekeeping issues that usually arise when dealing with VI, e.g., how to drive the VI bias winding, are solved in this work. Experimental results provided from a 50 W laboratory prototype demonstrate the correctness of the performed analysis and the good possibilities of the proposed converter.

The design and development of low- and high-voltage ASICs for space-borne CCD cameras

The CCD remains the pre-eminent visible and UV wavelength image sensor in space science, Earth and planetary remote sensing. However, the design of space-qualified CCD readout electronics is a significant challenge with requirements for low-volume, low-mass, low-power, high-reliability and tolerance to space radiation. Space-qualified components are frequently unavailable and up-screened commercial components seldom meet project or international space agency requirements. In this paper, we describe an alternative approach of designing and space-qualifying a series of low- and high-voltage mixed-signal application-specific integrated circuits (ASICs), the ongoing development of two low-voltage ASICs with successful flight heritage, and two new high-voltage designs. A challenging sub-system of any CCD camera is the video processing and digitisation electronics. We describe recent developments to improve performance and tolerance to radiation-induced single event latchup of a CCD video processing ASIC originally developed for NASA’s Solar Terrestrial Relations Observatory and Solar Dynamics Observatory. We also describe a programme to develop two high-voltage ASICs to address the challenges presented with generating a CCD’s bias voltages and drive clocks. A 0.35 μm, 50 V tolerant, CMOS process has been used to combine standard low-voltage 3.3 V transistors with high-voltage 50 V diffused MOSFET transistors that enable output buffers to drive CCD bias drains, gates and clock electrodes directly. We describe a CCD bias voltage generator ASIC that provides 24 independent and programmable 0–32 V outputs. Each channel incorporates a 10-bit digital-to-analogue converter, provides current drive of up to 20 mA into loads of 10 μF, and includes current-limiting and short-circuit protection. An on-chip telemetry system with a 12-bit analogue-to-digital converter enables the outputs and multiple off-chip camera voltages to be monitored. The ASIC can drive one or more CCDs and replaces the many discrete components required in current cameras. We also describe a CCD clock driver ASIC that provides six independent and programmable drivers with high-current capacity. The device enables various CCD clock parameters to be programmed independently, for example the clock-low and clock-high voltage levels, and the clock-rise and clock-fall times, allowing configuration for serial clock frequencies in the range 0.1–2 MHz and image clock frequencies in the range 10–100 kHz. Finally, we demonstrate the impact and importance of this technology for the development of compact, high-performance and low-power integrated focal plane electronics.

A 60-kW 3-kW/kg Five-Level T-Type SiC PV Inverter With 99.2% Peak Efficiency

A silicon carbide (SiC) T-type LCL inverter can achieve smaller device loss than two-level topology, however, its improvement on power density is limited by current ripple loss on magnetic components as switching frequency increases. This paper presents a five-level T-type (5LT2) photovoltaic (PV) inverter that achieves better utilization of SiC devices than the traditional three-level T-type LCL topology at higher switching frequency. The operation principle of the SiC 5LT2 PV inverter has been presented. The key design aspects including magnetic balancing, short-circuit protection, and digital controller computation time have been discussed and methods are developed. A 60-kW PV converter including boost stage and inverter stage has been built in the laboratory, which achieves a power density of 27 W/in3 and 3 kW/kg, and measured peak efficiency of 99.2%.

Switching Characterization and Short-Circuit Protection of 1200 V SiC MOSFET T-Type Module in PV Inverter Application

In this paper, a 1200 V, 100 A T-type full SiC power module is evaluated in a five-level T-type photovoltaic (PV) inverter. The T-type module is characterized with double pulse test, and based on the results, loss evaluation of the PV inverter is performed. The high power density of 27 W/in3 and 3 kW/kg, and the peak efficiency of 99.2% are achieved for the lab prototype. A de-sat based short-circuit protection scheme using commercial driver chip ACPL339J is presented and experimentally verified on the PV inverter prototype. With the presented circuit, less than 600 ns response time is realized, and a two-stage soft turn-off circuit with gate voltage clamping is implemented. A gate voltage stabilizer circuit without affecting the switching loss is also proposed to prevent false trigger. Experimental results show the superior performance of the T-type module-based PV inverter and demonstrate the effectiveness of the protection scheme.

Short-Circuit Fault Protection of a Low Voltage DC Distribution System using Superimposed Current Components

Low voltage DC (LVDC) distribution systems are gaining attention as customer loads are shifting towards power electronics-based equipment. The DC distribution system has the advantage of supplying power to these power electronic-based loads with high efficiency and without undergoing an energy conversion process. However, the power electronic components used in the LVDC distribution system are vulnerable during short-circuit faults. These components must be protected during the short-circuit faults for a safe and reliable operation. Therefore, this paper proposes a protection technique based on DC short-circuit fault current behavior. The fault is detected via a superposition principle. A fault current limiter (FCL) is used to suppress DC fault strength and reduce the stress from the circuit breaker. Finally, a solid state circuit breaker (SSCB) is used to isolate the fault point. The simulation results show that the proposed protection Scheme operates quickly enough as per expectations to avoid damage to sensitive power electronic devices.

Digital Implementation of Soft Start-Up and Short-Circuit Protection for High-Frequency LLC Converters With Optimal Trajectory Control (OTC)

Achieving soft start-up and short-circuit protection have always been challenging for resonant converters due to severe stresses in the resonant tank. Optimal trajectory control (OTC) has been proven to be the most effective control method to optimize energy delivery with given stresses. This paper proposes a method to implement soft start-up and short-circuit protection for LLC converters by using low-cost microcontrollers (MCUs) with minimum stresses and optimal energy delivery. Our current understanding of the relationship between the switching frequency and the output voltage is based on the state-plane analysis, and the requirement for the controllers is significantly reduced when using the lookup table. Further improvement enables the application of the proposed control method to high-frequency LLC converters without increasing the cost for the controllers. This paper proposes a method to protect the LLC converter from abrupt short-circuit with low-cost MCUs, which improves transient response to short-circuit significantly, and investigates limitations when operating the high-frequency LLC converter under short-circuit conditions. The proposed methods minimize the CPU resource requirement and can be further integrated with other state-trajectory control functions within one MCU. Experimental results are demonstrated on a 500-kHz 1-kW 400-V/12-V LLC converter with 60-MHz MCU TMS320F28027.

Digitally Controlled AC Current Measurement and Protection Techniques

Abstract This paper describes a cost effective AC current measurement method that avoids complex AC to DC current measurements by converting an amplified and rectified AC voltage drop across a shunt resistor to a duty cycle of a PWM signal. The current measurement chain output is fed into a microcontroller unit (MCU) and into a short circuit protection block that inhibits AC load drivers in case of overcurrent or short circuit events, overriding the state set by the MCU control algorithm. The authors present a mathematical model, simulations and a practical evaluation of custom-developed circuits that are capable to reach a convincing level of measurement precision. By counting a given number of consecutive AC periods, the effect of inrush current generated by inductive AC loads is filtered. The proposed solution allows inrush currents up to 3A, fitting the consumption range of AC control elements met in household application circuits, such as relays or solenoid valves.

Protective and control relays as coal-mine power-supply ACS subsystem

The paper presents instantaneous selective short-circuit protection for the cabling of the underground part of a coal mine and central control algorithms as a Coal-Mine Power-Supply ACS Subsystem. In order to improve the reliability of electricity supply and reduce the mining equipment down-time, a dual channel relay protection and central control system is proposed as a subsystem of the coal-mine power-supply automated control system (PS ACS).

Multilevel current source converters for high power medium voltage applications

In medium voltage high power applications, multi-level current source converters (CSCs) are good candidate to increase system power region, reliability, and the quality of output waveforms. Compared with widely researched voltage source multi-level converters (MLCs), the current source MLCs have the advantages of inherent short-circuit protection, high power capability and high quality of output current waveforms. The main features of MLCs include reduced harmonics, lower switching frequency and reduced current stress on each device which is a particularly important for high power application with low voltage and high current requirements. This paper conducts a general review of the current research about MLCs in higher power medium voltage application. The different types of parallel structure based MLCs and the modulation methodologies will be introduced and compared. Specifically, the circuit analysis of the common-mode (CM) loop for parallel structures will be conducted, the common-mode voltage (CMV) and circulating current suppression methods developed on the base of multilevel modulations will be addressed.

Impulse Commutated High-Frequency Soft-Switching Modular Current-Fed Three-Phase DC/DC Converter for Fuel Cell Applications

Current-fed converters offer enormous potential as power conditioning units for fuel cell applications, owing to precise fuel cell stack current control, short-circuit protection, voltage gain, and stiff fuel cell dc current. Aspects such as low current ripple and smaller input current slope ensure energy efficient operation and better fuel utilization, and enhance the lifetime of the fuel cell stack. However, the demerits of turn-off voltage spike across semiconductor devices limits the operating frequency. This paper proposes, analyzes, and implements a simple and cost-effective impulse commutated modular three-phase circuit to eliminate and solve the associated turn-off spike problem. Impulse commutation permits soft turn-off of devices and clamps the device voltage. The converter efficiently handles the variations in the fuel cell stack voltage and current with variable frequency modulation. Detailed steady-state operation, analysis, and performance of the proposed modular converter with impulse commutation are reported. The proposed impulse commutated three-phase circuit is a potential candidate for high-current applications. The validation of the converter operation on a 1-kW proof-of-concept hardware prototype is performed to substantiate the claims.

A High-Voltage Solid-State Switch Based on Series Connection of IGBTs for PEF Applications

Pulsed electric field (PEF) technology is a promising nonthermal processing techniques that can be utilized to inactivate microorganisms in liquid food with high-voltage PEF. Herein, a high-voltage solid-state switch consisting of 64 insulated gate bipolar transistors (IGBTs) connected in series was designed and developed for the PEF treatment. Regarding the unbalanced sharing of voltage in series-connected IGBTs, the resistor–capacitor–diode snubber circuit was specifically used and investigated in terms of model of parameters. Furthermore, using gate drivers and optic fiber, the driving circuit and protection circuit were designed and validated. A 50-kV isolation level power supply was built in order to provide 16 independent IGBT stacks with 24 V of power each. The results show that the developed switch works adequately a delay time of 380 ns with 35.8-kV voltage and 44.8-A current capacity. Moreover, the response time of the short-circuit protection is acceptable as well with a reaction time of under $7~\mu \text{s}$ . In conclusion, the switch designed for PEF treatment of liquid food performs within set parameters and is ready for pilot-scale processing capability.

Microsecond‐scale fast fusing and cutout characteristics of high current fuse

As to the problem that common high current fuses have a long cutout time at ms scale to protect the DC power source, an effective way for fast arc extinction and cutout of fuse is put forward in this study, based on the burst high-pulse current discharge from a parallelly connected filter capacitor. Through increasing the discharge current from the filter capacitor, the total cutout time of fuse can be reduced from ms to 40 μs after the load of the DC800 V power source was shorted in experiment. The method for designing the crucial parameters of the short-circuit fault protection in DC power source is also presented. Experimental results showed that the DC1500V/32A fuse with a single fuse body and solidified filling quartz sand can reduce the time before arc forms (T f) and total cutout time (T e) to 30 and 44 μs, respectively. The effects of the shorted load impedance on the DC power source protection are also studied. It showed that the dynamic short-load impedances formed by the breakdown semiconductor parts in short-circuit faults were <25 mΩ, and the corresponding T e of fuse was compressed in the range between 50 and 90 μs.

Current-Fed Multilevel Converters: An Overview of Circuit Topologies, Modulation Techniques, and Applications

Multilevel converters (MLCs) have emerged as standard power electronic converters in high power as well as quality demanding applications. They are classified into current-fed MLCs and voltage-fed MLCs. Voltage-fed MLCs have widely researched whereas the current-fed MLCs are the recent topic of research. Based on the principle of duality between voltage and current sources, several current-fed MLCs analogous to voltage-fed MLCs have been identified. Current-fed MLCs offer several advantages in terms of high power capability, transformerless operation, short-circuit protection, and excellent quality of output current waveform. The goal of this paper is: 1) to present review of circuit topologies, modulation schemes, and applications of current-fed MLCs; and 2) to review an emerging low-device switching frequency modulation technique known as synchronous optimal pulsewidth modulation for current-fed MLCs. The circuit configuration and advantages of each topology along with various modulation techniques are discussed in detail. Compared to voltage-fed MLCs, the operation of current-fed MLCs need to satisfy additional switching constraints. A survey of classical methods for realization of these operational constraints has been done and a new generalized method has been proposed. Finally, future scope of research has been presented to encourage further development of topologies and modulation techniques for current-fed MLCs.

A Medium-Voltage Medium-Frequency Isolated DC–DC Converter Based on 15-kV SiC MOSFETs

In this paper, a novel isolated dc-dc converter topology for medium-voltage (MV) applications is proposed by combining the advantages of resonant converters and dual active bridge (DAB) converters. In normal load scenario, this converter operates in an open loop resonant mode with a fixed switching frequency equals to the resonant frequency of the series resonant tank. Thus, zero voltage turn on at primary side and zero current turn off at secondary side are secured from zero to full load. When overload happens, the resonant capacitors will be clamped to the output voltage by the additional paralleled diodes. The proposed converter automatically switches to resonant and DAB mixed operation mode; therefore, the resonant current is naturedly limited. With zero to full load range soft switching and fast overload protection, the proposed topology is especially suitable for MV medium frequency applications utilizing high-voltage SiC MOSFETs. The converter operation modes are analyzed using time-domain waveforms and graphical state trajectory to derive the quantitative relationship between duty cycle, output voltage, and the overload current. Based on these relationships, a predictive duty cycle control is proposed to further limit the overload current of the resonant tank by sensing the output voltage. Combing the proposed topology and the predictive control, cycle-by-cycle overload and short-circuit protections are achieved. To fully utilize the capability of the 15-kV SiC MOSFET, magnetizing inductance, dead time, MV transformer, and resonant components are optimized with the operating range of 6-12 kV and 20-100 kHz. An experimental prototype running at 6 kV and 40 kHz is successfully tested with peak efficiency exceeding 98%. Test waveforms at no load and 10-kW full load validate the zero to full load range soft switching capability. Short circuit protection test demonstrates a 25-us overload protection speed.

Future Shipboard MVdc System Protection Requirements and Solid-State Protective Device Topological Tradeoffs

The search for the optimum architecture for shipboard medium voltage dc integrated power systems must take into account the short-circuit protection in addition to overarching goals of efficiency, survivability, reliability of power, and cost effectiveness. Presently, accepted approaches to protection are “unit-based,” which means the power converter(s) feeding the bus coordinate with no-load electromechanical switches to isolate faulted portions of the bus. However, “breaker-based” approaches, which rely upon solid-state circuit breakers for fault mitigation, can result in higher reliability of power and potentially higher survivability. The inherent speed of operation of solid-state protective devices will also play a role in fault isolation, hence reducing stress level on all system components. A comparison study is performed of protective device topologies that are suitable for shipboard distribution systems rated between 4 and 30 kVdc from the perspectives of size and number of passive components required to manage the commutation energy during sudden fault events and packaging scalability to higher current and voltage systems. The implementation assumes a multichip silicon carbide (SiC) 10-kV, 240-A MOSFET/junction barrier Schottkey (JBS) diode module.