Phase-shift Control Strategy Research Articles

Minimize Current Stress of Dual-Active-Bridge DC-DC Converters for Electric Vehicles Based on Lagrange Multipliers Method

Optimal modulation scheme is proposed for the dual-active-bridge DC-DC converter to minimize current stress of the switching devices. The converter is an ideal alternative for bidirectional power transfer, as an Electric Vehicle charger or a power interface in a micro-grid. A PWM plus phase-shift control strategy is presented, and the working principle is analyzed. The mathematical models of the power and peak current are established, and the method of Lagrange Multipliers is applied to the optimization. Experimental results confirm a considerable decrement of the current stress achieved with the proposed optimal schemes, as compared with traditional single phase shift modulation under light load. The efficiencies are enhanced correspondingly.

Non-isolated stacked bidirectional soft-switching DC-DC converter with PWM plus phase-shift control scheme

In this paper, a non-isolated stacked bidirectional DC-DC converter with zero-voltage-switching (ZVS) is introduced for the high step-up/step-down conversion systems. The extremely narrow turn-on and/or turn-off duty cycle existing in the conventional bidirectional buck-boost converters can be extended due to the stacked module configuration for large voltage conversion ratio applications. Furthermore, the switch voltage stress is halved because of the series connection of half bridge modules. The PWM plus phase-shift control strategy is employed, where the duty cycle is adopted to regulate the voltages between the input and output sides and the phase-shift angle is applied to achieve the power flow regulation. This decoupled control scheme can not only realize seam-less bidirectional transition operation, but also achieve adaptive voltage balance for the power switches. In addition, ZVS soft-switching operation for all active switches is realized to minimize the switching losses. Finally, a prototype of 1 kW operating at 100 kHz is built and tested to demonstrate the effectiveness of the proposed converter and the control strategy.

High step‐up/step‐down non‐isolated BDC with built‐in DC‐transformer for energy storage systems

A non-isolated bidirectional DC-DC converter (BDC) is proposed for high step-up/step-down bidirectional power conversion applications. A DC-transformer is integrated into a conventional non-isolated buck-boost BDC to achieve high-voltage conversion ratio and wide voltage/power range regulation simultaneously. The switches are shared by the buck-boost BDC and the DC-transformer. Voltage stresses of switches are reduced by connecting the input and output of the DC-transformer in-series. The duty cycles of switches are used to make sure that the voltages on the two sides of the DC-transformer are matched. As a result, the DC-transformer always operates under the highest-efficiency condition. The phase-shift angle between the switching bridges is employed to achieve the power flow regulation. Soft-switching of all the switches is achieved by adopting the pulse-width modulation plus phase-shift control strategy. Operation principles, characteristics and design considerations of the proposed BDC are analysed in detail. Experimental results from a 48 V/400 V-1 kW prototype verify the effectiveness of the proposed converter. The efficiency is demonstrated to peak at 96.6% for both the step-up and step-down modes.

Challenges Facing PFC of a Single-Phase On-Board Charger for Electric Vehicles Based on a Current Source Active Rectifier Input Stage

This paper aims to study the power factor (PF) correction scheme for a single-phase on-board charger of electric vehicles. The topology is based on a unidirectional current source active rectifier (CSAR) consisting of four insulated-gate bipolar transistors in series with four diodes followed by a boost converter. Buck-type rectifiers inject low-order input current harmonics into the ac mains. Thus, an inductor–capacitor ( LC ) input filter is employed. The capacitor's reactive energy results in a leading grid current. In order to achieve a unity displacement power factor, a phase shift control is implemented. However, the LC filter is prone to series and parallel resonances coming from the grid disturbances and the converter harmonics, respectively. Therefore, the phase shift control strategy combined with the topology of the CSAR results in a periodical resonance of the input filter. This phenomenon is studied in detail. In order to reduce the grid current's distortion level, an active damping control with resonance frequency tracking that achieves a good PF while meeting the IEC's international standards on harmonic current emissions is presented. An experimental test bench is developed to validate the simulations’ theoretical findings. Compliance with the standards is achieved and system limitations are discussed.

A PWM Plus Phase-Shift Controlled Interleaved Isolated Boost Converter Based on Semiactive Quadrupler Rectifier for High Step-Up Applications

Semiactive quadrupler rectifiers (SAQRs) are proposed in this paper to serve as the secondary rectification circuits, which make the secondary-side voltages to be controllable and help reduce current stress and conduction losses. An interleaved isolated boost converter is developed based on the proposed SAQRs. By utilizing the pulse-width modulation (PWM) plus phase-shift (PPS) control strategy, the primary- and secondary-side voltages are well matched to reduce the current values and circulating conduction losses. With the proposed SAQRs, the voltage gain is extended and the voltage stresses on power devices and passive components used in rectification circuits are reduced to the half of the high output voltage. Hence, the efficiency is improved by using a transformer with a smaller turns ratio and reduced parasitic parameters, and by employing low-voltage rating devices with better switching and conduction performance. With optimal design, lower voltage, and current stresses on the primary-side switches, minimized input current ripple can be realized. Moreover, the zero-voltage turn on switching of the active switches and the zero-current turn off switching of the diodes can be achieved over a wide load and voltage range by the proposed SAQR-based converter and the control strategy. Meanwhile, the higher voltage gain, the lower voltage, and the current stresses on power devices can be obtained with the proposed SAQR-based converter compared with passive quadrupler rectifier-based converter. The feasibility and effectiveness of the proposed SAQRs and the derived converter are verified by a 380-V output prototype.

Comparative Study of Hard and Soft Switched Full Bridge DC-DC Converter for Photovoltaic Application

This paper aims to compare the performance of two control schemes viz. hard switched and phase shifted control scheme for full bridge DC-DC converter used in photovoltaic application .The proposed converters are designed for 650W photovoltaic input power. Voltage and current waveforms at various test points like across IGBT, transformer primary and secondary, output etc. are compared and results are presented. From results it can be seen that in phase shift control simultaneous transition of voltage across IGBT and current through IGBT is avoided hence reduction in switching losses , dv/dt, di/dt effects and EMI effects can be achieved. At higher switching frequencies phase shift control scheme is meritorious over hard switched control scheme.

Phase-Shift-Controlled Isolated Buck-Boost Converter With Active-Clamped Three-Level Rectifier (AC-TLR) Featuring Soft-Switching Within Wide Operation Range

An active-clamped three-level rectifier (AC-TLR) is derived from the diode-clamped three-level inverter, by replacing the active switches and the diodes in the three-level inverter with the diodes and active switches, respectively. Novel isolated buck-boost converters, featuring single-stage conversion and soft-switching within wide operation range, are developed based on the proposed AC-TLR. By utilizing the AC-TLR, the voltage stress on the power devices and passive components, including the rectifying diodes, the active-clamping switches, the flying capacitor, and output filter capacitors, is reduced to the half of the output voltage. Low-voltage rating switching devices with better switching and conduction performances and a transformer with reduced turns ratio and parasitic parameters are used to enhance the efficiency. The full-bridge isolated buck-boost converter with the proposed AC-TLR is analyzed in detail as an example. An optimized phase-shift control strategy is employed to realize isolated buck and boost conversion. Soft switching of all of the switching devices in both the primary- and secondary-side circuits is achieved within the whole operation range by using the proposed AC-TLR and the phase-shift control strategy. Experimental results on a prototype with 380-V output verify the effectiveness of the proposed AC-TLR and its derived isolated buck-boost converters.

Secondary-Side Phase-Shift-Controlled Dual-Transformer-Based Asymmetrical Dual-Bridge Converter With Wide Voltage Gain

A novel dual-transformer-based asymmetrical dual-bridge (DT-ADB) converter with secondary-side phase-shift control strategy is proposed. The primary side of the DT-ADB converter is a fully active full bridge, and the secondary side is a semiactive bridge comprising of one active leg and two passive legs. The current and power of the two transformers in the converter are shared automatically by adopting primary-side-series and secondary-side-parallel configuration, and the turns ratio of the transformer is reduced by employing two transformers. The high-frequency-link inductor is reduced because the voltage applied on the inductor is reduced compared to previous converters, and hence the efficiency and power density can be improved. Zero-voltage turn-on of all the active switches and zero-current turn-off of all the diodes are achieved in a wide operation range. Furthermore, the turn-off losses of the secondary-side active switches are reduced because only half of the output current flows through the switches. Moreover, the proposed topology offers several other advantages including continuous output current and smaller output filter requirement. The operation principle is analyzed and experimental results are provided to verify the effectiveness and advantages of the proposed converter.

A Voltage-Feed High-Frequency Resonant Inverter With Controlled Current Output as a High-Frequency AC Power Source

A current-based power distribution is presented for the applications of high-frequency ac power distribution system (PDS). Comparing with the traditional voltage-based counterpart, the current-based system can be applied into some specific applications, such as high-voltage gate-driving system, contactless power transmission, etc. A modified resonant topology based on LCL-T tank is proposed to implement high-frequency current source. The effective magnitude control and high conversion efficiency are both achieved. First, the proposed topology is examined with circuit principle, operational cycle analysis, and soft-switching description. Second, the phase-shifted control scheme is explored to calculate the equivalent resonant capacitor of LCL-T resonant tank, as well as the relations between current gain ratio and phase-shifted angle control are discussed in depth. Finally, the simulation model and experiment prototype are implemented with rated peak current of 2 A, rated output frequency of 30 kHz, and rated output power of 50 W. The experimental results in accordance with simulation prove that the constant current characteristics are maintained with high conversion efficiency. Hence, the proposed circuit topology and control scheme are a feasible realization of current source that is used to feed high-frequency PDS.

Decoupling-Controlled Triport Composited DC/DC Converter for Multiple Energy Interface

In this paper, a decoupled controlled triport dc/dc converter is derived by combining two bidirectional single-phase buck–boost converters and one isolated full-bridge converter for multiple input source applications. The power density is improved, and the circuit structure is simplified because the power devices are completely shared in the primary side. Furthermore, the pulsewidth modulation plus phase-shift control strategy is introduced to provide two control freedoms and achieve the decoupled voltage regulation within a certain operating range. The duty cycle of the bidirectional buck–boost converters is adopted to balance the voltage between the two primary input terminals, while their phase angle is applied to regulate the accurate secondary voltage. Furthermore, zero-voltage-switching soft-switching operation is provided for all of the primary power switches due to the inherent phase-shift control scheme. Moreover, the two filter inductors in the bidirectional buck–boost converters and the isolated transformer in the full-bridge topology are integrated and replaced by the winding-cross-coupled inductors to reduce the component numbers and simplify the magnetic structure. Finally, a 1-kW prototype is built to verify all theoretical considerations, and it is shown that the proposed topology is particularly advantageous in the distributed power generation system with multiple energy sources.

A Family of Soft-Switching DC–DC Converters Based on a Phase-Shift-Controlled Active Boost Rectifier

High efficiency and high power density can be achieved with a dc-dc transformer by operating all the switches at a fixed 50% duty cycle. However, the output voltage of the dc-dc transformer cannot be regulated. Novel rectifiers named active boost rectifiers (ABRs) are proposed in this paper. Basically, an ABR is composed of a traditional diode rectifier and a bidirectional switch. By adopting phase-shift control between the primary- and secondary-side switches, the output voltage regulation can be achieved when introducing the ABR to a dc-dc transformer. As a result, a family of novel soft-switching dc-dc converters is harvested. When the proposed converter operates in the soft-switching continuous conduction mode, zero-voltage-switching (ZVS) performance for all the primary- and secondary-side switches is achieved. When the converter operates in the discontinuous conduction mode, zero current switching (ZCS) for the primary-side switches and ZVS for the secondary-side switches are achieved. Furthermore, the diode reverse-recovery problem is alleviated by employing the ABR and phase-shift control scheme. As an example, the full-bridge converter with voltage-doubler ABR is analyzed to verify the proposed ABR concept and converters. The operation principles, voltage conversion ratio, and output characteristics are analyzed in depth. Finally, experimental results are provided to verify the feasibility and effectiveness.

A Modified Dual Active Bridge Converter With Hybrid Phase-Shift Control for Wide Input Voltage Range

By inserting a small inductor between the transformer center tap and the midpoint of two split output capacitors in the dual active bridge (DAB) topology, this paper proposes a modified DAB converter for wide-input applications. A hybrid phase-shift (HPS) control scheme is proposed to allow all power switches to achieve practical ZVS over the full operating range; thereby, significantly minimizing the switching losses and alleviating electromagnetic interference. Moreover, the proposed control scheme does not significantly increase the conduction losses in comparison with the extended phase-shift (EPS) control. Therefore, the modified DAB can operate efficiently. The topology derivation and description are first presented. Then, the EPS and triple phase-shift (TPS) modulations are applied, and the corresponding operating principles and characteristics, including the soft-switching, power transfer, and root-mean-square current, are investigated in detail. To achieve practical ZVS operation of all switches over full operating range, while minimizing the conduction losses, the EPS and TPS are combined, and an HPS control scheme is proposed. Finally, experimental results from a 1.4-kW converter prototype with 200-400-V input and 400-V output are presented to verify the feasibility and advantages of the converter and control.

Secondary-Side-Regulated Soft-Switching Full-Bridge Three-Port Converter Based on Bridgeless Boost Rectifier and Bidirectional Converter For Multiple Energy Interface

A systematic method for deriving soft-switching three-port converters (TPCs), which can interface multiple energy, is proposed in this paper. Novel full-bridge (FB) TPCs featuring single-stage power conversion, reduced conduction loss, and low-voltage stress are derived. Two nonisolated bidirectional power ports and one isolated unidirectional load port are provided by integrating an interleaved bidirectional Buck/Boost converter and a bridgeless Boost rectifier via a high-frequency transformer. The switching bridges on the primary side are shared; hence, the number of active switches is reduced. Primary-side pulse width modulation and secondary-side phase shift control strategy are employed to provide two control freedoms. Voltage and power regulations over two of the three power ports are achieved. Furthermore, the current/voltage ripples on the primary-side power ports are reduced due to the interleaving operation. Zero-voltage switching and zero-current switching are realized for the active switches and diodes, respectively. A typical FB-TPC with voltage-doubler rectifier developed by the proposed method is analyzed in detail. Operation principles, control strategy, and characteristics of the FB-TPC are presented. Experiments have been carried out to demonstrate the feasibility and effectiveness of the proposed topology derivation method.

Analysis and Design of a High-Frequency Isolated Dual-Tank LCL Resonant AC-DC Converter

An integrated single-phase single-stage high-frequency transformer isolated dual-tank LCL-type series resonant ac-dc converter with fixed-frequency phase-shift control strategy is presented. The circuit configuration combines a diode rectifier, a boost converter, and two identical half-bridge dc-dc LCL resonant converters. A high power factor and a low total harmonic distortion are achieved by discontinuous current mode operation of the front-end power factor correction circuit. The output voltage is regulated by the fixed-frequency phase-shift between two identical half-bridge LCL resonant converters. Soft-switching operation is achieved for all of the switches. The operation of intervals and steady-state analysis are presented briefly. A design example of a 100-W proposed converter is given, together with its simulated and experimental results for different input voltages.

Modular Multilevel DC/DC Converters With Phase-Shift Control Scheme for High-Voltage DC-Based Systems

In this paper, by investigating the topology derivation principle of the phase-shift-controlled three-level dc/dc converters, the modular multilevel dc/dc converters, by integrating the full-bridge converters and three-level flying capacitor circuit, are proposed for the high step-down and high power dc-based systems. The high switch voltage stress in the primary side is effectively reduced by the full-bridge modules in series. Therefore, the low-voltage-rated power devices can be employed to obtain the benefits of low conduction losses. More importantly, the voltage autobalance ability among the cascaded modules is achieved by the inherent flying capacitor, which removes the additional possible active components or control loops. In addition, zero-voltage-switching performance for all the active switches can be provided due to the phase-shift control scheme, which can reduce the switching losses. The circuit operation and converter performance are analyzed in detail. Finally, the performance of the presented converter is verified by the simulation and experimental results from a 2-kW prototype.

Analysis, design and implementation of isolated bidirectional converter with winding‐cross‐coupled inductors for high step‐up and high step‐down conversion system

In this study, a zero voltage switching (ZVS) isolated bidirectional DC/DC converter is proposed for high step-up and high step-down conversion systems. In the low voltage side, an interleaved Buck and Boost converter is employed to reduce the current ripple and improve the power level. In the high voltage side, a modified three-level structure is adopted to bring each power switch sustain half of the high bus voltage, which makes the low voltage rated MOSFETs available for the performance improvement. Two coupled inductors are interleaved in the low voltage side and in series in the high voltage side, which can not only serve as the filter inductors for the current ripple cancellation, but also as the transformer for isolation, which is named as winding-cross-coupled inductors. As a result, the magnetic size can be reduced to enhance the power density. ZVS operation is ensured from light load to full load conditions by the advanced pulse width modulation plus phase shift control strategy. The voltage regulation and transferred power are decoupled for easy design and implementation. Finally, a 1.5 kW 48 V/800 V prototype is built to verify the effectiveness of the proposed converter.

Secondary-Side Phase-Shift-Controlled ZVS DC/DC Converter With Wide Voltage Gain for High Input Voltage Applications

In this paper, a soft-switching dc/dc converter with secondary-side phase-shift control strategy is proposed to improve the conversion efficiency and minimize the primary switch voltage stress in the high input voltage applications. Zero-voltage-switching performance is achieved for both the primary- and secondary-side power devices in a wide load range to reduce the switching losses due to the secondary-side phase-shift control scheme. Furthermore, compared with the conventional phase-shift control mechanism, the circulating current at the freewheeling stage is effectively suppressed as well to minimize the conduction losses. Moreover, the voltage stress of the primary switches is only half of the input voltage by employing the improved three-level structure, which makes the low-voltage rated power devices available to improve the circuit performance. In addition, the converter can work in the buck, balance, and boost modes to achieve a relatively wide input voltage range, which is an expected advantage for the communication power system to minimize the electrolytic capacitors with an acceptable hold-up time. The operation principle is analyzed and experimental results of a 1-kW 100-kHz prototype are provided to verify the effectiveness and the advantages of the proposed converter.

Step-up AC Voltage Regulators with High-Frequency Link

A circuit configuration and a circuit topological family of step-up ac voltage regulators with high-frequency link are proposed. This kind of circuit topology is composed of input LC filter, energy-storage inductor, input cycloconverter, high-frequency transformer, output cycloconverter and output filtering capacitor. The regulators can convert an unstable sinusoidal voltage with high THD to a stable sinusoidal voltage with the same frequency and low distortion. Operating principle, normalized output characteristics, phase-shifting control strategy, methods to suppress magnetic saturation of the energy-storage inductor at start-up, and voltage spike caused by the high-frequency HF transformer leakage inductance are proposed and fully investigated. The results from theoretical analysis and principle experiment indicate that the proposed regulators have advantages of high-frequency galvanic isolation, simple topology, two-stage power conversions, bidirectional power flow, high conversion efficiency, and high reliability during short-circuit conditions of the load.

Optimal Design of a Push-Pull-Forward Half-Bridge (PPFHB) Bidirectional DC–DC Converter With Variable Input Voltage

This paper presents a low-cost bidirectional isolated dc-dc converter, derived from dual-active-bridge converter for the power sources with variable output voltage like super capacitors. The proposed converter consists of push-pull-forward circuit half-bridge circuit (PPFHB) and a high-frequency transformer; this structure minimizes the number of the switching transistors and their associate gate driver components. With phase-shift control strategy, all the switches are operated under zero-voltage switching (ZVS) condition. Furthermore, in order to optimize the converter performance and increase efficiency, optimal design methods and criteria are investigated, including coupled inductors design, bidirectional power flow analysis, harmonics analysis, and ZVS range extension. Based on all the optimal parameters, higher efficiency can be achieved. Finally, prototypes are built in laboratory controlled by digital signal processor for comparison purpose. Detailed test results verify the theoretical analysis and demonstrate the validity of optimization design method.

Cascade Dual Buck Inverter With Phase-Shift Control

This paper presents a new type of cascade inverter based on dual buck topology and phase-shift control scheme. The proposed cascade dual buck inverter with phase-shift control inherits all the merits of dual buck type inverters and overcomes some of their drawbacks. Compared to traditional cascade inverters, it has much enhanced system reliability thanks to no shoot-through problems and lower switching loss with the help of using power MOSFETs. With phase-shift control, it theoretically eliminates the inherent current zero-crossing distortion of the single-unit dual buck type inverter. In addition, phase-shift control and cascade topology can greatly reduce the ripple current or cut down the size of passive components by increasing the equivalent switching frequency. A cascade dual buck inverter has been designed and tested to demonstrate the feasibility and advantages of the system by comparing single-unit dual buck inverter, 2-unit and 3-unit cascade dual buck inverters at the same 1 kW, 120 V ac output conditions.