Phase-shift Control Research Articles

A Voltage Spike Suppression Strategy Based on De-Re-Coupling Idea for the Three-Phase High-Frequency Isolated Matrix-Type Inverter

In order to solve the problem of high voltage spikes on the secondary side of the high-frequency transformer when the three-phase high-frequency isolated matrix inverter (HFIMI) operates under the conventional modulation strategies, a new modulation strategy is proposed without introducing an auxiliary circuit. In the proposed scheme, the H-bridge inverter adopts phase-shift control. The matrix converter (MC) adopts the voltage-type de- and recoupling idea, and the decoupled positive and negative group inverters are, respectively, applied with a modified Space vector pulse width modulation (SVPWM) strategy to operate synchronously with the H-bridge inverter. When the H-bridge inverter is in dead-zone mode, the switching tubes of MC are all turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> to provide continuous flow paths for leakage inductance and output filter inductance current and suppress high voltage spikes. The operating mode of the three-phase HFIMI under the proposed modulation strategy is analyzed in detail, the realization conditions for soft switching are designed, and the soft-switching ranges are also discussed. The feasibility and validity of the voltage spike suppression strategy are verified by building a 3-kW principle prototype. The experimental results show that the voltage spikes are effectively suppressed, all switches achieve zero-voltage soft-switching, and the peak efficiency of the three-phase HFIMI can reach 95.2%.

A new detailed loss model and design approach for LLC resonant converter with phase shift control to overall optimization of converter loss at whole battery charging process

AbstractThis paper proposes a new loss modeling and design method for phase shift controlled resonant LLC converter with optimization applied to minimize the overall loss during the whole battery charging process. In this work, the loss model has been formulated more accurately for phase shift controlled LLC converter. One of the contributions in accurate loss modeling is all switching modes of power switches have been investigated in detail in the aspect of zero voltage switching (ZVS) and ZCS occurrence and their related dynamic loss are updated in loss calculation during the whole charging process. In addition, to optimize the copper and core losses of high‐frequency transformer and resonant inductor, a design trend is included in optimization process to calculate the best physical dimensions and winding parameters of magnetic components. A genetic algorithm has been employed for the optimization during the charging process. In this work, the first harmonic approximation (FHA) model was developed and solved by nonlinear Newton–Raphson method in any operating point along one complete charging process. The target of optimization was designing a wall mounted type level 2 battery charger (7.4 kw/32A) for charging a battery pack with specs according to the Nissan Leaf 2011 electric vehicle. For verification of the proposed method, simulation results are provided and also experimental results for a low‐scale prototype are proposed. In this study, the average efficiency along the overall charging process obtained up to 95% in simulation and 84% in experiments.

A Novel Topology for Solar PV Inverter Based on an LLC Resonant Converter With Optimal Frequency and Phase-Shift Control

In this article, a new topology for a grid-connected solar photovoltaic inverter for the direct connection to the medium-voltage grid is proposed. This topology employs an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter with a high-frequency (HF) isolation transformer in the dc–dc stage. The output of the dc–dc stage is a rectified sine wave voltage and current at the line frequency. An unfolder inverter interfaces between this dc stage and the grid. A combined phase-shift and frequency control method is used to control the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter. The phase-shift angle and switching frequency values of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter are regulated to track the reference current signal for the whole operation range. The Lagrange multiplier method is applied to find the optimal trajectory to calculate the optimal phase-shift angle and switching frequency pairs for any operation condition by considering power converter and HF transformer losses to achieve the highest efficiency at a varying current. The transformer leakage and magnetization inductances are properly designed to provide a zero-voltage switching (ZVS) for a wide operation area, and additional resonant inductor requirement is removed. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter operates in a ZVS region except in a narrow band around the zero-current crossings of the inverter output. Using an HF transformer in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter, a bulky line frequency transformer requirement is eliminated, and thus, a more compact and efficient design is obtained. The proposed topology is validated by the simulation and experimental results.

A Step-Up Reconfigurable Multimode LLC Converter Module With Extended High-Efficiency Range for Wide Voltage Gain Application in Medium Voltage DC Grid Systems

In this article, a newmodular multimode reconfigurable step-up resonant converter that is capable of extending very high efficiency from full load to reduced load conditions is proposed for wide voltage gain application in medium voltage dc (MVdc) grid system. The proposed converter module is able to switch from a hybrid control scheme that consists of variable frequency and phase shift control to pulsewidth modulation (PWM) control in the auxiliary switch of the output voltage quadrupler (VQ). In addition, the input bridge can also be reconfigured to a half-bridge mode to suit high input voltage range while utilizing a hybrid control technique that consists of variable frequency and asymmetrical PWM control. With the proposed approach, the converter module is able to achieve constant output voltage regulation without requiring a wide spectrum of switching frequency or phase shift control. Hence, close-to resonance operation with very high efficiency can be maintained for a wide range of input voltage and loading conditions. Soft switching operations are always guaranteed for all the primary side switches, the output diodes and the auxiliary switch in the VQ. The steady-state and dynamic performance of the proposed modular multimode step-up converter are validated through simulation results on a silicon carbide (SiC) based 360 V–1 kV/16 kV, 80-kW system and experimental results on a proof-of-concept 150–400 V/6.6 kV, 10-kW SiC laboratory prototype. Results confirmed that the efficiency is maintained between 97.8% and 99.1% from full load to at least 20% load condition for the specified input voltage range.

Robust phase-shifted model predictive control for cascaded H-bridge power supplies using linear matrix inequality

Robust phase-shifted model predictive control for cascaded H-bridge power supplies using linear matrix inequality

Duty Cycle Control Strategy for Dual-Side LCC Resonant Converter in Wireless Power Transfer Systems

The dual-side inductor–capacitor–capacitor (LCC) topology circuit has been widely adopted in wireless power transfer (WPT) systems due to its constant output current characteristic. However, most conventional control methods need specific synchronization techniques between the primary and secondary sides to avoid the oscillation in the system, which increases the cost and control complexity. To solve this issue, this article proposes a new duty cycle control (DCC) strategy for a dual-side LCC resonant converter with a semibridgeless active rectifier (SAR). With such a control strategy, gate signals of the primary- and secondary-side circuits do not need to be synchronized, which could reduce the complexity and the cost of the WPT system. Besides, the switching frequency of the secondary side can be decreased significantly. This article first presents the modal analysis of phase shift control (PSC) and DCC. Then, generalized state-space averaging (GSSA) modeling with PSC and the hybrid average modeling with DCC are performed. In addition, controllers’ design for both strategies is conducted to achieve the constant output voltage. Finally, the eigenvalues’ analysis is used to determine the stability region of the WPT system. The theoretical analysis has been validated by both simulation and experimental results.

A Hybrid Control Strategy for Half-bridge Three-level LLC Resonant Converter

The half-bridge three-level LLC resonant converter uses the resonant process of the inductance and the capacitance to transfer energy. It has the advantages of low voltage stress on the switch and high efficiency, but there are problems such as narrow voltage gain range. To widen the voltage gain range of the converter, a hybrid control strategy for a half-bridge three-level LLC resonant converter is proposed in this paper. The voltage gain of the converter is divided into three gain intervals: low, medium and high. Burst control is used in the low gain interval, phase shift control is adopted in the middle gain interval, and frequency modulation control is adopted in the high gain interval. The experiment results show that the proposed control strategy can realize a wide range of output voltage gain of the converter.

Multiresonant-Frequency Filter for an Electrosurgery Inverter.

This paper presents a multi-resonant-frequency (MRF) filter for a high-frequency inverter (HFI) used in electrosurgery. The fundamental (sinusoidal) output frequency of the HFI is 390 kHz and is the same as the switching frequency of the HFI. The MRF is designed to extract the fundamental frequency of the tri-state bipolar waveform, generated by the HFI operating with phase-shift control. The structure and operation of the MRF are outlined. An experimental 300 W GaN-FET-based HFI prototype is developed to validate the feasibility of the proposed MRF under closed-loop control.

An Interleaved Bidirectional Coupled-Inductor Based DC–DC Converter With High Conversion Ratio for Energy Storage System

In this article, an interleaved coupled-inductor (CI) based bidirectional dc–dc converter (BDC) is proposed with a higher voltage conversion ratio (VCR). In this proposed interleave CI-based BDC (ICI-BDC), the CIs can operate as both a filter inductor and a transformer simultaneously, so that the power density is improved. Moreover, as a transformer, the turns ratio of CIs is used to improve the VCR with a voltage stress reduction purpose. Furthermore, the interleaved technique can well achieve the low current ripple and reduced current stress in this topology. To control ICI-BDC, the pulsewidth modulation plus phase-shift (PPS) control is employed, where the duty cycle is used to match the two side voltages, and the phase-shift angle is used to control the amount and direction of power flow. Uniquely, a difference value is set between the two side duty cycles, and the duty cycle of the high voltage side is smaller than that of the low voltage side by a fixed value. In this proposed control method, all the switches can achieve soft-switching even at light load condition, which can improve transmission efficiency. Experimental results obtained from a 1-kW prototype show a nearly high efficiency under all loading conditions, validating the viability of the proposed ICI-BDC topology and control method.

Optimal control strategy of global return power based on soft switching under triple phase-shift control

Return power and soft switching are important performance indicators for dual active bridge DC-DC converters (DAB). Aiming at the problem that the DAB converter has a large return power under the traditional control strategy, a control strategy that optimizes the return power in the full power range is proposed, and on this basis, the soft switching range of the switching device is increased. The control strategy not only ensures the minimum return power in the entire power range, but also increases the soft switching range, reduces the switching loss, and further improves the efficiency. Finally, an experimental platform is built for verification, and the experimental results verify the validity of the theoretical analysis.

Coordinated Control of ALFC-AVR in Multiarea Multisource Systems Integrated with VRFB and TCPS Using CFPDN-PIDN Controller

The article discusses the coordinated effect of the vanadium redox flow battery (VRFB) and thyristor control phase shifter (TCPS) on combined automatic load frequency control and automatic voltage regulator of three area hydrothermal systems incorporating renewable sources. Solar thermal power plant, dish-Stirling solar thermal system, and geothermal power plant are integrated into Area-I, Area-II, and Area-III, respectively. Suitable generation rate constraint and governor dead-band are considered for both thermal and hydro plants. A new fuzzy logic-based cascaded controller named fuzzy proportional-derivative with filter coefficient cascaded with proportional-integral-derivative with filter coefficient (CFPDN-PIDN) is proposed as a secondary controller and its performance is compared with the PIDN and CPDN-PIDN controllers. Various controller parameters are optimized by the artificial flora algorithm. Simulation results reveal that the CFPDN-PIDN controller outperforms the PIDN and CPDN-PIDN controllers. Two types of control schemes are used to regulate the TCPS's phase angle variation: Type-I is a first-order lag transfer function, while Type-II includes a washout filter and lead-lag compensator along with Type-I. Analysis shows that the Type-I control strategy is better than Type-II. VRFB charging/discharging is regulated using high-pass filter (HPF) and dead-band (DB) control schemes. Investigation reveals that the BD scheme provided better system dynamics than the HPF scheme. Moreover, the system performance degrades with very high or low state-of-charge values. Further, using the best control schemes for both VRFB and TCPS, the system's dynamic performance was superior to that of the individual one. Finally, the robustness of the proposed control approach is validated through sensitivity analysis.

Spin-Electric Coupling with Anisotropy-Induced Vanishment and Enhancement in Molecular Ferroelectrics.

Manipulating quantum properties by electric fields using spin-electric coupling (SEC) effects promises spatial addressability. While several studies about inorganic materials showing the SEC functionality have been reported, the vastly tunable crystal structures of molecular ferroelectrics provide a range of rationally designable materials yet to be exploited. In this work, Mn2+-doped molecular ferroelectrics are chosen to experimentally demonstrate the feasibility of achieving the quantum coherent SEC effect in molecular ferroelectrics for the first time. The electric field pulse applied between Hahn-echo pulses in electron paramagnetic resonance (EPR) experiments causes controllable phase shifts via manipulating of the zero-field splitting (ZFS) of the Mn(II) ions. Detailed investigations of the aMn crystal showed unexpected SEC vanishment and enhancement at different crystal orientations, which were elucidated by studying the spin Hamiltonian and magnetic anisotropy. With the enhanced SEC efficiency being achieved (0.68 Hz m/V), this work discovers an emerging material library of molecular ferroelectrics to implement coherent quantum control with selective and tunable SEC effects toward highly scalable quantum gates.

Single-Stage Isolated AC-AC Converter Without Commutation Problem

A single-stage isolated ac–ac converter without the commutation problem is proposed. The proposed converter has the step-up/down function dependence on the phase shift control which provides zero-voltage switching zero-voltage switching (ZVS) for all switches in rated condition. Also, the commutation paths of the secondary side switches are provided for any switching case by adding a single capacitor; originally, a filter capacitor is used for the switching mode power supply input, and in this case, this filter capacitor also solves the primary-side commutation problem. The ZVS and solving the commutation problem increase the power efficiency and reliability. The proposed converter achieves high power quality with a simple control algorithm. A 1 kW/ 220 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> prototype is implemented to verify the theoretical analysis and performance of the proposed converter. The California energy commission efficiency is 97.3%, the total harmonic distortion (THD) of the input current is 2.45% at full load, and the THD of the output voltage is 1.07% at full load.

A Sharing-Branch Modular Multilevel DC Transformer With Wide Voltage Range Regulation for DC Distribution Grids

As the key equipment in dc distribution grids, dc transformer (DCT) suffers from low power density caused by a large number of submodules (SMs). Hence, this article proposes a novel DCT for the interconnection of medium-voltage dc (MVdc) and low-voltage dc (LVdc) distribution grids, which adopts a series-connected half-bridge SM branch (SSB) on MV-side to achieve low voltage stress of devices and reduce the number of SMs. Quasi square wave modulation strategy and phase-shifted control are employed to realize bidirectional power transmission control and zero-voltage switching (ZVS) for all switches. Furthermore, in order to ensure low current stress and ZVS within wide voltage range, a certain number of SMs are constantly inserted or bypassed to achieve voltage matching. Besides, smooth transition control strategy is employed to avoid current spikes caused by abruptly bypassing or inserting SMs. Based on the theoretical analysis, design consideration and control strategy are elaborated. Finally, a 500&#x00A0;kW&#x002F;6&#x2013;12&#x00A0;kV&#x002F;750&#x00A0;V simulation model and a 2&#x00A0;kW prototype are built to verify the proposed DCT.

Decoupled EPS Control Utilizing Magnetizing Current to Achieve Full Load Range ZVS for Dual Active Bridge Converters

A decoupled extended phase shift control is proposed to decrease the control complexity and achieve full load range zero voltage switching (ZVS) for dual active bridge (DAB) dc–dc converters. In the proposed solution, full load range ZVS is achieved by adding an extra small fixed duty cycle and utilizing the magnetizing current. In addition, the two control variables are decoupled, since the control of the duty cycle is only determined by the voltage conversion ratio and is independent of the phase shift angle, which avoids the detection of operation mode and switching of control laws. The ZVS model considering junction capacitors and magnetizing inductance, ZVS region under full load range, and derivation of control law are analyzed in detail. Finally, the effectiveness of the proposed solution is experimentally verified on a 500-W, 250kHz GaN-based prototype.

Radio Frequency 4-Channel 0-360° Range Digitally Controlled Phase Shifter for Telecommunication Systems with Amplitude Modulation of Many Components

Radio Frequency 4-Channel 0-360° Range Digitally Controlled Phase Shifter for Telecommunication Systems with Amplitude Modulation of Many Components

Investigation on Performance of Various Power Control Strategies with Bifilar Coil for Induction Surface Melting Application

In recent years, induction heating applications assisted by electronic power control have been very appealing. For melting applications, induction heating is widely used as it seems to be appropriate and provides higher efficiency, zero pollutants, non-contamination of material, etc. in comparison with conventional heating. The conventional variable frequency control scheme is not sufficient for melting applications because of its high switching loss, low efficiency, and lower heat rate. A superlative control technique is required to control the output power smoothly, for a high heating rate with minimum power loss, and to lower the number of components. In this paper, a capacitorless self-resonating bifilar coil is proposed for induction surface melting applications. The performance of the system in terms of modular losses, heat rate, and efficiency is analyzed for various power methods such as pulse duty cycle control, phase shift control, pulse density modulation control, and asymmetric duty cycle control. An experimental validation is performed for the 1 kW prototype, and the heating rate, efficiency, and modular losses are calculated. The control technique is digitally validated using a PIC16F877A microcontroller with 30 kHz switching frequency. The temperature distribution is analyzed using a FLIR thermal imager. Among the tested methods, pulse density modulation-based control provides smooth and varied power control from 0% to 100% with minimum modular losses. The efficiency of the system is 89% at a rated output power and is greater than 85% for pulse density modulation control with a fast heating rate.

Dual-band composite right/left-handed metamaterial lines with dynamically controllable nonreciprocal phase shift proportional to operating frequency

Abstract Dual-band composite right/left-handed transmission lines with the nonreciprocal phase shift approximately proportional to the operating frequency are proposed and demonstrated by using normally magnetized ferrite microstrip lines. The nonreciprocal phase shift can be dynamically controlled by changing the externally applied dc magnetic field. Dynamic change in the nonreciprocal phase gradient along the line enables us to realize dual-band and unidirectional beam-scanning leaky-wave antennas without suffering from frequency-dependent change in the beam direction. A prototype nonreciprocal metamaterial line using polycrystalline yttrium iron garnet was fabricated and measured for verification of our basic concept.

Soft-Switching Bidirectional Switched-Capacitor DC–DC Converter With Multiple Phase Shift Control Methods

In this article, a bidirectional bridge modular switched-capacitor (BBMSC) dc–dc converter is proposed with soft switching and multiple phase shift control methods, including in-bridge single phase shift (ISPS) control, out-of-bridge single phase shift (OSPS) control, and dual phase shift (DPS) control method. The topology, phase shift control scheme, and operating states are analyzed. Then the circuit characteristics, such as output power and current stress characteristics, are given to analyze and compare the advantages of different phase shift control methods. In addition, the efficiency characteristics of various phase shift control methods are compared and analyzed from the perspective of magnitude of reverse power. A 300-W experimental prototype is constructed to verify the working principle and efficiency characteristic. The comparison of different phase shift control methods is validated by experimental results.

DC-link Voltage Equalization and Output Voltage Stabilization Control of the Medium Voltage High Power Cascaded Converter Source

Nowadays, H-bridge cascaded converter is widely adopted in the field of ship’s shore power supply in ports and quays, new energy grid connection, et al. This paper focuses on the design and key technology of cascaded inverter. According to the design requirements of medium voltage shore power supply, the main circuit voltage, current and other parameters were calculated firstly, and overall design scheme of cascaded H-bridge type converter power supply is designed. And then the specific realization process of the carrier phase-shifted control of each H-bridge module in the cascaded connection converter was analyzed. To solve the problems of unequal capacitor voltages and unstable output voltages caused by power grid fluctuation and variable load, the DC-link voltages equalization and output voltages stabilization control method of the converter power supply without output voltage sensors was proposed. Furthermore, a sliding window iterative DFT algorithm was used to detect current feedback rapidly. Based on the design parameters, the system simulation was built, and the principle prototype was completed. Finally, the simulation and experimental results are compared to verify the design and control method. And the results indicate that the system design scheme proposed in this paper can basically meet the requirements of design indexes, and realize the control of DC-link voltage equalization and output voltage stabilization at the same time. All those certify the control method is correct and effective.