EPE Association: EPE 2018 - DS1c: Hard & Soft Switching techniques I

EPE 2018 - DS1c: Hard & Soft Switching techniques I
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 02: Power Converter Topologies and Design > EPE 2018 - DS1c: Hard & Soft Switching techniques I

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   A GaN 500 kHz High Current Active Clamp Phase-Shifted Full-Bridge Converter with Zero-Voltage Switching over the Entire Line and Load Range
By Martin HEINTZE [View]
[Download]

Abstract: A GaN Active Clamp Phase-Shifted Full-bridge (PSFB) is introduced which enables zero-voltageswitching (ZVS) over entire load and voltage range without any additional auxiliary circuit elements.For high load operation ZVS is achieved through a small leakage inductance as in conventional PSFBconverters. To expand the ZVS range to zero load conditions the ripple current of the current doublerinductor in conjunction with an increased magnetizing current of the main transformer is used toobtain ZVS in every operating point. A secondary active clamp circuit limits the over-voltage of thecurrent doubler rectifier. The ZVS mechanism is discussed in detail and some design tradeoffs arehighlighted.The ability of the proposed circuit is demonstrated using a 1.5 kW, 400 V to 12 V DC/DC converterfor automotive application with a wide voltage and power range. The small leakage inductancetogether with the ability to realize soft switching even under low load conditions enables a significantincrease of the switching frequency up to 500 kHz and thus a remarkable increase of power densitywith very high efficiency.

   A Novel Gate Driver Approach Using an Inductive Feed Forward for a Robust Turn-on of GaN Power Transistors with Gate Injection
By Jonathan HACKEL [View]
[Download]

Abstract: Many GaN power transistors contain a PN junction between gate and the channel region close to the source. In order to maintain the on-state, current must continuously be supplied to the junction. Therefore, the commonly recommended approach uses a gate bias voltage of 12\,V to compensate the Miller current through a boost circuit. For the same purpose, a novel gate driving method based on an inductive feed forward has been presented. With this, stable turn-on can be achieved even for a bias voltage of only 5\,V. The effectiveness of this concept is demonstrated by double pulse measurements, switching currents up to 27\,A and a voltage of 400\,V. For both approaches a compact design with low source inductance is characterized. In addition to the significant reduction of the gate bias voltage and peak gate current, the new approach reduces the switching losses for load currents $\textgreater$23\,A.

   DESIGN AND DEVELOPMENT OF HIGH EFFICIENCY ISOLATED BOOST CONVERTER FOR LOW VOLTAGE APPLICATIONS
By Muhammad Sohaib ANWER [View]
[Download]

Abstract: This paper discusses the design of a high efficiency isolated boost converter for low voltage applications, including DC micro grid systems, fuel cell, and battery applications. The AC resistance factor and the leakage inductance of an isolating transformer is improved based on a better core selection. A comparative analysis of copper foil and Litz windings with interleaved configuration is also presented. The integration of copper foil transformer in the converter increases the overall efficiency of the converter. The high efficiency of the converter is further achieved by using repetitive avalanche rated MOSFETs for unclamped switching and Schottky didoes for fast switching action. The experimental results verify the high efficiency of the transformer and the designed converter.

   Experimental Verification of Two-Stage Power Converter With Current-Fed Soft-Switching Front-End for Battery Storage Applications
By Roman KOSENKO [View]
[Download]

Abstract: This paper presents a two-stage power system that consists of a novel bidirectional current-fed DC-DCconverter module for interfacing with lithium iron phosphate battery, followed by a single-buck inverter for grid interface. Additional benefit of the proposed two-stage converter lies in the intermediate DC-link between two stages that allows connection of other energy sources, such as PV. The proposed converter offers galvanic isolation, high voltage step-up factor and power factor correction. The operation principle and control system structure of the case study converter are described. Due to the accommodation of a special phase-shift modulation algorithm, the proposed front-end converter features natural voltage clamping and soft-switching of all semiconductor devices without additional components such as snubbers and clamping circuits. Parameters of the converter were estimated in accordance with residential battery energy storage system requirements. A 500W prototype converter was developed to validate theoretically estimated characteristics of the converter, including the soft-switching range, transfer function and design constraints. Experimental waveforms as well as efficiencyfor both charge and discharge operation modes are presented and analysed.

   Fixed Frequency Predictive MPPT for Phase-shift Modulated LLC resonant Micro-inverter
By Omar ABDELGHAFOUR [View]
[Download]

Abstract: the variability of the environmental conditions tuned the Maximum Power Point Tracking (MPPT) control to be a fundamental technique for Photovoltaic (PV) systems. The majority of the well-known MPPT techniques are good fitting to conventional (PWM) converters; but they are not suitable for resonant converters applications, as its output gain is frequency dependent. In this paper, a fixed frequency predictive phase shift MPPT technique for the LLC resonant converter. A two-stage Micro-inverter is presented, for grid tied PV applications, employing the LLC resonant converter as the first DC/DC stage, due to it's high power density, high efficiency and the possibility to operate at Zero-Voltage Switching (ZVS) or Zero-Current Switching (ZCS). The second stage is formed from traditional H-bridge Inverter. The proposed control is a fixed frequency predictive phase shift MPPT technique for the LLC converter stage with both fixed and variable steps. To demonstrate the proper operation of the proposed MPPT methodology, a 300 W simulation model for the converter is tested. Hardware prototype is being built in the lab and samples of the experimental results are presented that proves the advantage of the proposed control.

   Modified Modulation Signals for GaN-E-HEMTs based HERIC Inverter to Improve Reverse Conduction Performance
By Bilal AHMAD [View]
[Download]

Abstract: This paper presents an application of modified PWM signals to enhance the efficiency of Gallium Nitride (GaN) HEMTs based HERIC inverter. Although application of GaN switches increases the power density and overall efficiency of inverters due to the structure of GaN HEMTs, reverse conduction losses are increased during the second and fourth quadrant operation of the inverter. Hence, control of the inverter requires modifications to tackle additional losses introduced by GaN switches. Conventional PWM signals were designed to suppress the leakage current by keeping the voltage level constant at the switching nodes in all operating modes. However, modified PWM signals not only suppress the leakage current but also reduce the reverse conduction losses in GaN HEMTs. In this paper, proposed theory is validated by simulations based on spice models provided by the manufacturer of switches on LtSpice. Simulation results validated the proposed solution and reported almost 50\% reduction in reverse conduction losses. Practical prototype based on GaN HEMTs was also designed and tested. This study aids understanding the effect of the reverse losses on the device behavior and overall efficiency of the inverter.

   NEW SOFT SWITCHING SYSTEM FOR THREE-PHASE THREE-LEVEL VOLTAGE SOURCE INVERTERS
By Witold MAZGAJ [View]
[Download]

Abstract: The paper deals with a new soft switching system in three-phase three-level voltage source inverters.In the majority of soft switching systems applied until now, additional capacitors are connected inparallel to main transistors and very often special inductors are connected in series to auxiliarytransistors. In cases when disturbances in the control system of the voltage source inverters wouldoccur, the main or auxiliary transistors can be damaged because capacitors can be abrupt dischargedthrough the main conductive transistors or sudden interruption of the inductor current can causeovervoltages which may be dangerous for semiconductor elements. Above mentioned disadvantagesdo not occur in the proposed soft switching system and the control method of the transistor switchingis simpler in comparison to the existing soft switching systems. This paper presents switchingprinciples of all transistor of the three-phase three-level voltage source inverter, and guidelines for theselection of elements of this system are briefly discussed. The working correctness of the new softswitching system was validated during laboratory tests, and attention was also paid to certainlimitations of the control algorithm. The proposed system is recommended for medium and highpower inverters.

   Oscillating Power Minimization in Cascaded H-bridge Converter with Phase-Shifted Carrier PWM
By Kevin SUN [View]
[Download]

Abstract: In PWM converters, current ripple is inherently produced by the switching actions. The current ripplewould then introduce oscillating power which reduces the efficiency of the system. This paper proposes a new Phase-Shifted Carrier PWM technique for the Multilevel Cascaded H-bridge converter, which employs Carrier Phase Angle Offset to achieve cancellation in the current harmonics. Thus reducing the oscillating power delivered to the load. The mathematical analysis of the proposed modulation technique is presented and shown to provide an significant improvement over the conventional PSC-PWM. Simulation and experimental results are also provided to verified the theoretical analysis.

   Resonant Switching and Power Control of DC-DC-Converters with a Variable Transmission Path
By Lukas GÖBEL [View]
[Download]

Abstract: A new control strategy for the detection of the resonant frequency of a DC-DC converter with a variabletransmission path is used in this paper. Applying a Second Order Generalized Integrator (SOGI) in combinationwith a Frequency Locked Loop (FLL), the primary current of the transmission path is filteredand the orthogonal signal is determined. With the two outputs the current phase angle can be calculatedand the correct switching time is determined by compensation of the signal propagation delay. Based onthis approach a continuous adaption of the dead time between two complementary control signals for thefull bridge is proposed. The importance of the correct dead time is proven by measurements. Furthermore,a new algorithm for power regulation is introduced. Improving the state-of-the-art energy injectionand free-oscillation method, the power transmission can be enhanced and the switching frequency mightbe reduced for low power.

   Soft-switching characterization of medium voltage IGBT power modules and press-pack diodes in a 1 kHz mega-watt dc/dc resonant converter
By Catalin DINCAN [View]
[Download]

Abstract: 6.5kV IGBT power modules and line frequency press-pack diodes are proposed for a new mega-watt, medium voltage, resonant converter intended for DC wind turbines. The challenge of characterizing losses in softswitching semiconductors - without building the full circuit - is overcome by a proposed test circuit and procedure that minimizes cost and complexity, yet subjects the device under test to similar use as in the target application. The paper describes the test method, and results obtained with it.

   Soft-Switching Range of an Isolated Three-Phase AC/DC Converter for Variable Output Voltage Control
By Takumi HAMAGUCHI [View]
[Download]

Abstract: This paper presents the soft-switching range of an isolated three-phase AC/DC converter for variable output voltage control. The relation between the output voltage and the phase-difference of the transformer voltages for the soft-switching is theoretically derived. The effectiveness of the soft-switching range is verified by experiments.

   Steady-State Analysis of Soft-Switched Three-Phase Grid-Tie DC-AC Converter Isolated by High-Frequency Transformer for High Efficiency and Low THD
By Mahmoud A. Sayed ABDALLAH [View]
[Download]

Abstract: This paper presents a new mathematical model and soft-switching technique for the matrix-based highfrequency link (HFL) DC-AC converters. The converter topology uses an H-bridge converter linked with a single-to-three-phase matrix converter by a high-frequency transformer (HFT). The proposed mathematical model provides the matrix converter switches with the accurate duty cycles by compensating the trapezoidal approximated waveform of the HFT current. Soft-switching of all switches is realized by connecting shunt ceramic capacitor across each switch. This enables, simultaneously, zero-current switching (ZCS) for the OFF-going switches and zero-voltage switching (ZVS) for the ON-coming switches. Also, the proposed control technique regulates the battery DC current to follow the reference value and injects a sinusoidal three-phase current to the grid at unity power factor. In addition, the control technique is able to adapt with severe sudden reduction in the three-phase grid voltages and ensures safe operation of the converter. Compensated duty cycles of the matrix converter reduce the THD of the grid current, whereas the soft-switching enhances the system efficiency. The validity of the system has been verified experimentally using a 200 V/2.0 kW laboratory prototype system.

EPE 2018 - DS1c: Hard & Soft Switching techniques I
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 02: Power Converter Topologies and Design > EPE 2018 - DS1c: Hard & Soft Switching techniques I
	[return to parent folder]

	A GaN 500 kHz High Current Active Clamp Phase-Shifted Full-Bridge Converter with Zero-Voltage Switching over the Entire Line and Load Range By Martin HEINTZE	[View] [Download]
Abstract: A GaN Active Clamp Phase-Shifted Full-bridge (PSFB) is introduced which enables zero-voltageswitching (ZVS) over entire load and voltage range without any additional auxiliary circuit elements.For high load operation ZVS is achieved through a small leakage inductance as in conventional PSFBconverters. To expand the ZVS range to zero load conditions the ripple current of the current doublerinductor in conjunction with an increased magnetizing current of the main transformer is used toobtain ZVS in every operating point. A secondary active clamp circuit limits the over-voltage of thecurrent doubler rectifier. The ZVS mechanism is discussed in detail and some design tradeoffs arehighlighted.The ability of the proposed circuit is demonstrated using a 1.5 kW, 400 V to 12 V DC/DC converterfor automotive application with a wide voltage and power range. The small leakage inductancetogether with the ability to realize soft switching even under low load conditions enables a significantincrease of the switching frequency up to 500 kHz and thus a remarkable increase of power densitywith very high efficiency.

	A Novel Gate Driver Approach Using an Inductive Feed Forward for a Robust Turn-on of GaN Power Transistors with Gate Injection By Jonathan HACKEL	[View] [Download]
Abstract: Many GaN power transistors contain a PN junction between gate and the channel region close to the source. In order to maintain the on-state, current must continuously be supplied to the junction. Therefore, the commonly recommended approach uses a gate bias voltage of 12\,V to compensate the Miller current through a boost circuit. For the same purpose, a novel gate driving method based on an inductive feed forward has been presented. With this, stable turn-on can be achieved even for a bias voltage of only 5\,V. The effectiveness of this concept is demonstrated by double pulse measurements, switching currents up to 27\,A and a voltage of 400\,V. For both approaches a compact design with low source inductance is characterized. In addition to the significant reduction of the gate bias voltage and peak gate current, the new approach reduces the switching losses for load currents $\textgreater$23\,A.

	DESIGN AND DEVELOPMENT OF HIGH EFFICIENCY ISOLATED BOOST CONVERTER FOR LOW VOLTAGE APPLICATIONS By Muhammad Sohaib ANWER	[View] [Download]
Abstract: This paper discusses the design of a high efficiency isolated boost converter for low voltage applications, including DC micro grid systems, fuel cell, and battery applications. The AC resistance factor and the leakage inductance of an isolating transformer is improved based on a better core selection. A comparative analysis of copper foil and Litz windings with interleaved configuration is also presented. The integration of copper foil transformer in the converter increases the overall efficiency of the converter. The high efficiency of the converter is further achieved by using repetitive avalanche rated MOSFETs for unclamped switching and Schottky didoes for fast switching action. The experimental results verify the high efficiency of the transformer and the designed converter.

	Experimental Verification of Two-Stage Power Converter With Current-Fed Soft-Switching Front-End for Battery Storage Applications By Roman KOSENKO	[View] [Download]
Abstract: This paper presents a two-stage power system that consists of a novel bidirectional current-fed DC-DCconverter module for interfacing with lithium iron phosphate battery, followed by a single-buck inverter for grid interface. Additional benefit of the proposed two-stage converter lies in the intermediate DC-link between two stages that allows connection of other energy sources, such as PV. The proposed converter offers galvanic isolation, high voltage step-up factor and power factor correction. The operation principle and control system structure of the case study converter are described. Due to the accommodation of a special phase-shift modulation algorithm, the proposed front-end converter features natural voltage clamping and soft-switching of all semiconductor devices without additional components such as snubbers and clamping circuits. Parameters of the converter were estimated in accordance with residential battery energy storage system requirements. A 500W prototype converter was developed to validate theoretically estimated characteristics of the converter, including the soft-switching range, transfer function and design constraints. Experimental waveforms as well as efficiencyfor both charge and discharge operation modes are presented and analysed.

	Fixed Frequency Predictive MPPT for Phase-shift Modulated LLC resonant Micro-inverter By Omar ABDELGHAFOUR	[View] [Download]
Abstract: the variability of the environmental conditions tuned the Maximum Power Point Tracking (MPPT) control to be a fundamental technique for Photovoltaic (PV) systems. The majority of the well-known MPPT techniques are good fitting to conventional (PWM) converters; but they are not suitable for resonant converters applications, as its output gain is frequency dependent. In this paper, a fixed frequency predictive phase shift MPPT technique for the LLC resonant converter. A two-stage Micro-inverter is presented, for grid tied PV applications, employing the LLC resonant converter as the first DC/DC stage, due to it's high power density, high efficiency and the possibility to operate at Zero-Voltage Switching (ZVS) or Zero-Current Switching (ZCS). The second stage is formed from traditional H-bridge Inverter. The proposed control is a fixed frequency predictive phase shift MPPT technique for the LLC converter stage with both fixed and variable steps. To demonstrate the proper operation of the proposed MPPT methodology, a 300 W simulation model for the converter is tested. Hardware prototype is being built in the lab and samples of the experimental results are presented that proves the advantage of the proposed control.

	Modified Modulation Signals for GaN-E-HEMTs based HERIC Inverter to Improve Reverse Conduction Performance By Bilal AHMAD	[View] [Download]
Abstract: This paper presents an application of modified PWM signals to enhance the efficiency of Gallium Nitride (GaN) HEMTs based HERIC inverter. Although application of GaN switches increases the power density and overall efficiency of inverters due to the structure of GaN HEMTs, reverse conduction losses are increased during the second and fourth quadrant operation of the inverter. Hence, control of the inverter requires modifications to tackle additional losses introduced by GaN switches. Conventional PWM signals were designed to suppress the leakage current by keeping the voltage level constant at the switching nodes in all operating modes. However, modified PWM signals not only suppress the leakage current but also reduce the reverse conduction losses in GaN HEMTs. In this paper, proposed theory is validated by simulations based on spice models provided by the manufacturer of switches on LtSpice. Simulation results validated the proposed solution and reported almost 50\% reduction in reverse conduction losses. Practical prototype based on GaN HEMTs was also designed and tested. This study aids understanding the effect of the reverse losses on the device behavior and overall efficiency of the inverter.

	NEW SOFT SWITCHING SYSTEM FOR THREE-PHASE THREE-LEVEL VOLTAGE SOURCE INVERTERS By Witold MAZGAJ	[View] [Download]
Abstract: The paper deals with a new soft switching system in three-phase three-level voltage source inverters.In the majority of soft switching systems applied until now, additional capacitors are connected inparallel to main transistors and very often special inductors are connected in series to auxiliarytransistors. In cases when disturbances in the control system of the voltage source inverters wouldoccur, the main or auxiliary transistors can be damaged because capacitors can be abrupt dischargedthrough the main conductive transistors or sudden interruption of the inductor current can causeovervoltages which may be dangerous for semiconductor elements. Above mentioned disadvantagesdo not occur in the proposed soft switching system and the control method of the transistor switchingis simpler in comparison to the existing soft switching systems. This paper presents switchingprinciples of all transistor of the three-phase three-level voltage source inverter, and guidelines for theselection of elements of this system are briefly discussed. The working correctness of the new softswitching system was validated during laboratory tests, and attention was also paid to certainlimitations of the control algorithm. The proposed system is recommended for medium and highpower inverters.

	Oscillating Power Minimization in Cascaded H-bridge Converter with Phase-Shifted Carrier PWM By Kevin SUN	[View] [Download]
Abstract: In PWM converters, current ripple is inherently produced by the switching actions. The current ripplewould then introduce oscillating power which reduces the efficiency of the system. This paper proposes a new Phase-Shifted Carrier PWM technique for the Multilevel Cascaded H-bridge converter, which employs Carrier Phase Angle Offset to achieve cancellation in the current harmonics. Thus reducing the oscillating power delivered to the load. The mathematical analysis of the proposed modulation technique is presented and shown to provide an significant improvement over the conventional PSC-PWM. Simulation and experimental results are also provided to verified the theoretical analysis.

	Resonant Switching and Power Control of DC-DC-Converters with a Variable Transmission Path By Lukas GÖBEL	[View] [Download]
Abstract: A new control strategy for the detection of the resonant frequency of a DC-DC converter with a variabletransmission path is used in this paper. Applying a Second Order Generalized Integrator (SOGI) in combinationwith a Frequency Locked Loop (FLL), the primary current of the transmission path is filteredand the orthogonal signal is determined. With the two outputs the current phase angle can be calculatedand the correct switching time is determined by compensation of the signal propagation delay. Based onthis approach a continuous adaption of the dead time between two complementary control signals for thefull bridge is proposed. The importance of the correct dead time is proven by measurements. Furthermore,a new algorithm for power regulation is introduced. Improving the state-of-the-art energy injectionand free-oscillation method, the power transmission can be enhanced and the switching frequency mightbe reduced for low power.

	Soft-switching characterization of medium voltage IGBT power modules and press-pack diodes in a 1 kHz mega-watt dc/dc resonant converter By Catalin DINCAN	[View] [Download]
Abstract: 6.5kV IGBT power modules and line frequency press-pack diodes are proposed for a new mega-watt, medium voltage, resonant converter intended for DC wind turbines. The challenge of characterizing losses in softswitching semiconductors - without building the full circuit - is overcome by a proposed test circuit and procedure that minimizes cost and complexity, yet subjects the device under test to similar use as in the target application. The paper describes the test method, and results obtained with it.

	Soft-Switching Range of an Isolated Three-Phase AC/DC Converter for Variable Output Voltage Control By Takumi HAMAGUCHI	[View] [Download]
Abstract: This paper presents the soft-switching range of an isolated three-phase AC/DC converter for variable output voltage control. The relation between the output voltage and the phase-difference of the transformer voltages for the soft-switching is theoretically derived. The effectiveness of the soft-switching range is verified by experiments.

	Steady-State Analysis of Soft-Switched Three-Phase Grid-Tie DC-AC Converter Isolated by High-Frequency Transformer for High Efficiency and Low THD By Mahmoud A. Sayed ABDALLAH	[View] [Download]
Abstract: This paper presents a new mathematical model and soft-switching technique for the matrix-based highfrequency link (HFL) DC-AC converters. The converter topology uses an H-bridge converter linked with a single-to-three-phase matrix converter by a high-frequency transformer (HFT). The proposed mathematical model provides the matrix converter switches with the accurate duty cycles by compensating the trapezoidal approximated waveform of the HFT current. Soft-switching of all switches is realized by connecting shunt ceramic capacitor across each switch. This enables, simultaneously, zero-current switching (ZCS) for the OFF-going switches and zero-voltage switching (ZVS) for the ON-coming switches. Also, the proposed control technique regulates the battery DC current to follow the reference value and injects a sinusoidal three-phase current to the grid at unity power factor. In addition, the control technique is able to adapt with severe sudden reduction in the three-phase grid voltages and ensures safe operation of the converter. Compensated duty cycles of the matrix converter reduce the THD of the grid current, whereas the soft-switching enhances the system efficiency. The validity of the system has been verified experimentally using a 200 V/2.0 kW laboratory prototype system.