Phase-shift Control Research Articles

Bidirectional CLLLC Resonant Converter Based on Frequency-Conversion and Phase-Shift Hybrid Control

Due to the symmetrical structure, consistent working characteristics in the forward and reverse operations, and good soft-switching characteristics, bidirectional CLLLC resonant converters are widely used in electric vehicles and other fields. To meet the requirements of the on-board charger, this paper uses a bidirectional CLLLC resonant converter as the rear-stage of the on-board charger. The converter uses a constant voltage and constant current control in the forward operation and voltage and current double-closed-loop control in the reverse operation. Aiming at the problem whereby the voltage gain range of the bidirectional CLLLC resonant converter is relatively narrow under frequency-conversion control, the paper proposed a hybrid control method of frequency conversion and phase shift. Frequency-conversion control is used when the voltage gain is high, and phase-shift control is used when the voltage gain is low. The output voltage range of the converter is effectively broadened, and zero voltage switching and zero current switching can be realized in the full load range to improve operating efficiency. A 3.3 kW bidirectional CLLLC resonant converter simulation system is built in the simulation software. The simulation results verify the correctness and feasibility of the designed circuit and control method.

Soft-switching buck/boost full-bridge three-port converter for DC/DC applications

In this paper, a new structure for a DC-DC full-bridge buck/boost LLC three-port converter (TPC) is proposed. The configuration of the converter is designed using the integration of an asymmetric fixed frequency full-bridge LLC network and the buck/boost circuit. The most important advantages of this structure can be summarized in features like the significant reduction of components, high efficiency, soft switching (ZVS and ZCS) and wide gain. In addition, using fixed frequency makes the design of different parts of the converter easier and more efficient. The proposed TPC integrates an input (source) port, a storage port, and an output port that is appropriate for Photovoltaic (PV)/battery hybrid power applications. The power management between ports is handled through two control variables, the duty cycle managed the power flow between the input and storage port, simultaneously the output voltage is adjusted by the phase shift (PS) Control variable. Finally, a laboratory prototype 48 V/8A output is built and experimental findings support the suggested TPC benefits and performance.

Design of a wireless charging system in DC microgrids with accurate output regulation and optimal efficiency

This paper presents a general circuit and control design method for wireless power transfer (WPT) systems in DC microgrids to achieve optimal power transfer efficiency, while maintain accurate output voltage regulation. An auxiliary inductor is added at the transmitter resonator to form a current sink to ensure zero voltage switching (ZVS) of the primary-side full-bridge inverter with even extreme-light load conditions. Besides, an adaptive proportional-integral (PI) controller is adopted to track the output voltage references by regulating the phase shift angle of the phase shift control for the full-bridge inverter. The coefficients of the adaptive proportional-integral controller are determined by the inductor of the auxiliary inductor. Both simulation and experimental results have validated the effectiveness of the proposed circuit and control design in achieving optimal efficiency and output voltage regulation for wireless power transfer systems in DC microgrids with source and load variations.

LAN Wavelength Division Multiplexer on Silicon-Lithium Niobate Hybrid Integration Platform

We demonstrate an 8-channel LAN wavelength division multiplexer (LWDM) on silicon-lithium niobate (Si-LN) hybrid integration platform. The device consists of three-stage cascaded MZIs. The phase-error corrections and precise wavelength alignment of 4.5 nm channel spacing are achieved by employing the electro-optic tuning effect on bonded LN waveguides on silicon. The proposed hybrid LWDM with controllable phase shifters has potential applications in optical links of ultra-large transmission capacity with integration of hybrid modulators of the same technology.

Efficiency Improvement for Wireless Power Transfer System via a Nonlinear Resistance Matching Network

The primary control is widely adopted to obtain a constant voltage output under a wider load range. However, for traditional full-bridge inverters under phase-shift control, due to the loss of soft switching, the system transmission efficiency will decrease rapidly. This problem can be improved by using a half-bridge inverter; however, the power transferred to receiving devices utilizing a half-bridge inverter is inadequate under a small dc load value. To solve these urge issues, a resistance matching network (RMN), constructed by a resonant inductor and capacitor, is added before the full bridge rectifier part of this paper. Owing to the nonlinear resistance conversion characteristics of the proposed RMN structure, the variation range of the equivalent AC impedance before the rectifier end can be compressed into an optimum range to enhance the poor transmission efficiency during the coils part. Simultaneously, when the DC load is small, the power capability of the whole system can be enhanced by increasing the equivalent ac load value; as a result, the insufficient power capability of the half-bridge inverter can be relieved. Finally, a 36 V output WPT system based on the proposed RMN and phase shift control is constructed. Additionally, the experimental results prove the feasibility of the theoretical analysis results.

Generation of a Fundamental/Doubled Frequency Phase-Coded Microwave Signal Based on Polarization Multiplexed Technology

Microwave photonic phase-shifting technology can be used to generate high-frequency, broadband, and tunable phase-coded microwave signals, which are helpful in solving the contradiction between the detection range and the range resolution in radar systems. A method for generating a reconfigurable carrier phase-coded signal of a fundamental or doubled carrier frequency, based on polarization multiplexed technology, is proposed and verified by the experiments in this paper. A dual-parallel dual-polarization Mach–Zehnder modulator (DP-DPMZM) and a polarization-dependent phase modulator (PD-PM) were used to load the carrier and the phase-shifting signal, respectively. By reasonably configuring the state of the RF switch and the bias voltages of the sub-DPMZM, the fundamental or doubled carrier frequency can be obtained through photoelectric conversion. The reconfigurable carrier frequency gives the system a wider work bandwidth range and can effectively reduce the frequency requirement for local oscillator (LO) signals. By adjusting the driving voltage, the broadband microwave signal can be phase-shifted within the range of 360°, and when the phase-shifted control signal is a multilevel amplitude signal, it can generate binary, quaternary, or other high-order phase-coded signals, which have high reconfigurable performance and potential application value in multifunctional radar systems. In addition, the scheme has wideband tunability, since no optical filter is involved. The proposed scheme was theoretically analyzed and experimentally verified. Binary, quaternary, and octal phase-coded signals, with fundamental and doubled frequencies centered at 8 GHz and 16 GHz, were successfully generated.

Novel Isolated Multiple-Input, Multiple-Output Multidirectional Converter for Modern Low-Voltage DC Power Distribution Architectures

This work introduces a multiple-input, multiple-output (MIMO) isolated converter for low-power applications involving residential DC nanogrids and nanogrids. The topology has a multiport characteristic that allows for the integration of loads and sources with distinct ratings, e.g., photovoltaic (PV) modules, battery banks, DC loads, and the AC grid. The structure relies on a DC-DC multi-winding multidirectional flyback converter that operates as power interface and can minimize the number of power conversion stages while enabling flexible power flow control. Owing to its multidirectional characteristic, a port can be responsible for supplying or absorbing energy using duty cycle control or phase-shift control, respectively. Since the operating modes of the converter are decoupled, a predictive controller is capable of managing the power flow among the ports independently. Simulation results are presented and discussed to evaluate the control system robustness and its performance in power flow management.

A Coupled-Inductor-Based Bidirectional DC–DC Converter With High Voltage Conversion Ratio and Sensorless Current Balance

In this article, a coupled-inductor (CI)-based bidirectional dc–dc converter with a high voltage conversion ratio (VCR) and low voltage stress is proposed. The topology can achieve high VCR by employing two CIs; moreover, the interleaved technique overcomes the defect of large current ripple in CI. A sensorless current balance between the two CIs is also realized without an auxiliary circuit and complex control method. The pulsewidth modulation plus phase-shift control is employed, where the duty cycle <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> is used to adjust the VCR, and the phase-shift angle <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϕ</i> is used to control the direction and amount of the transferred power. In addition, all switches can achieve soft-switching under a wide operation range. The steady-state analysis of the proposed converter is analyzed in detail, followed by comprehensive experimental verification under a 1-kW prototype.

Optimized Bidirectional DC-DC Converter Adapted to High Voltage Gain and Wide ZVS Range

As a key component connecting dc microgrid and energy storage system, dual active bridge (DAB) converter has some inherent problems under high gain conditions. To solve the problems, this article proposes a half-bridge cascaded DAB converter with partial switch sharing. The converter combines the advantages of high voltage gain, wide soft switching range and less reactive backflow loss, under a hybrid modulation strategy based on pulsewidth modulation control and phase-shift control. In this article, the output power, soft switching characteristic and reactive backflow loss are analyzed in detail. By using the Karush–Kuhn–Tucker function method to achieve multiobjective optimization, the system can achieve the zero voltage switch (ZVS) turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and reduce the reactive backflow loss. Moreover, the coupled relationships among variables are clarified clearly, and the system can achieve high voltage gain at low turns ratio. A 500 W, 100 kHz experimental prototype is built to verify the correctness of the theoretical analysis.

A Bidirectional Fast EV Charger for Wide Voltage Range Using Three-Level DAB Based on Current and Voltage Stress Optimization

Converter cost is the crucial concern while designing off-board electric vehicle (EV) chargers for high-voltage charging applications using advanced high breakover voltage power semiconductor switches. To solve this problem, multilevel topology is used with the typical dual active bridge (DAB) for the development of high-voltage and high-power EV charging. It offers low cost, compact, less complex control, highly efficient, and reliable development. This article presents the design and development of bidirectional off-board fast EV charger with voltage and current stress optimization for wide voltage range. It is designed with two-stage power conversion. Here, active front-end converter is connected to three phase grid and controlled through synchronous reference frame (SRF) d-q control approach for active rectification. The large range of power and voltage variation in off-board EV charger design makes it challenging to develop a controller that allows the converter to operate inside the zero voltage switching (ZVS) operating region. In this context, a detailed circuit analysis of dc–dc stage with dual phase shift (DPS) control under different operating conditions is presented to identify the coordinates of safe operating region with reduced voltage stress. To select the converter control parameters with optimum current stress in conjunction with reduced voltage stress, particle-swarm-optimization technique is applied to the identified operating regions. This provides a unique selection criterion for both control parameters over wide voltage conversion ratio. A coordinated control is designed based on the identified boundaries for easy implementation and less computation burden on microcontroller units (MCUs). A 7.2-kW system is designed and simulated on MATLAB/Simulink. A 3.3-kW laboratory prototype is designed to validate the identified operating points with wide battery voltage range under varying source and loading scenarios.

Autonomous Input Voltage Sharing Control and Triple Phase Shift Modulation Method for ISOP-DAB Converter in DC Microgrid: A Multiagent Deep Reinforcement Learning-Based Method

This article proposes a multiagent (MA) deep reinforcement learning (DRL) based autonomous input voltage sharing (IVS) control and triple phase shift modulation method for input-series output-parallel (ISOP) dual active bridge (DAB) converters to solve the three challenges: the uncertainties of the dc microgrid, the power balance problem, and the current stress minimization of the converter. Specifically, the control and modulation problem of the ISOP-DAB converter is formed as a Markov game with several DRL agents. Subsequently, the MA twin-delayed deep deterministic policy gradient (MA-TD3) algorithm is applied to train the DRL agents in an offline manner. After the training process, the multiple agents can provide online control decisions for the ISOP-DAB converter to balance the IVS, and minimize the current stress among different submodules. Without accurate model information, the proposed method can adaptively obtain the optimal modulation variable combinations in a stochastic and uncertain environment. Simulation and experimental results verify the effectiveness of the proposed MA-TD3-based algorithm.

Performance Characterization of T-Type Multilevel Dual Active Bridge DC-DC Converter

Conventionally, single phase shift control technique is used for controlling dual active bridge (DAB) performance, which works efficiently at unity voltage conversion ratio and full load. However, when there is mismatch between primary voltage and reflected secondary voltage on primary side at light load, its efficiency reduces because of increased current stress and reactive power. Moreover, due to single control variable, its power flow controllability is confined. In this paper, analysis, implementation and performance characterization of isolated bi-directional T-type multilevel dual active bridge DC-DC converter topology is presented. It has five level voltages on both the primary and secondary side of high frequency transformer, which reduces the current stress and reactive power over wide operating range. It also has five control variables which gives extra edge for enhancing power flow controllability. Comparative analysis reveals that the proposed converter has high efficiency over wide operating range, due to reduced reactive power and current stress. Performance of the proposed T- type multilevel dual active bridge DC-DC converter topology has been verified via simulation and experimental prototype developed in the laboratory.

Constant Current Output Control Based on Cross-Coupling Compensation in Multireceiver WPT System Using Active Rectifier

Multireceiver wireless power transfer (multi-Rx WPT) technology is a promising method for charging multiple electronic devices simultaneously. However, the cross-coupling effect between Rxs not only leads to the correlation of output characteristics of each load, but also reduces the power transfer capability and efficiency of WPT systems. This article proposes a method to achieve constant current (CC) output with cross-coupling compensation in multi-Rx WPT systems, thus avoiding tedious parameter measurement and communication between Rxs. The cross-coupling can be compensated adaptively, and the output can be controlled independently and not affected by the fluctuation of system parameters. A closed-loop control strategy based on the phase shift control method of an active rectifier is carried out, which can continuously regulate the load current while maintaining cross-coupling compensation. An optimized phase synchronization auxiliary circuit for multi-Rx WPT systems is presented, which shares the power transfer coils and is not affected by the cross-coupling effect. A 70-W two-load experimental prototype is built to verify the theoretical analysis, and the maximum efficiency reaches 88.1%.

Design and Control of a Novel Wireless Energy Router With Independent Power Transmission Channels

Energy routers are intelligent power electronic systems that enable energy sharing and flexible power flow regulation among various distributed energy sources. Combining the excellent feature of wireless power transfer technology for contactless transmission of electrical energy, this article proposes a novel wireless energy router to realize the power exchange of multiple energy storage devices, such as various mobile electronics, electric vehicles, and energy storage stations. Independent power transmission channels with specific operating frequencies are built between any two of the power-exchanging units. The multiple resonating decoupling compensations are designed and implemented, which offer each power-exchanging unit and various resonate operating frequencies while suppressing the frequency components from irrelevant channels. Moreover, through generation by the bidirectional multilevel converter, the drive voltage of each unit can naturally realize the synthesis of multiple-frequency voltage components. In addition, the decoupled dual-side phase-shift control with capacitor voltage balancing strategy is proposed to regulate the power flow in each power channel. As a result, simultaneous energy sharing among power storage devices can be achieved. And the power flows can be adjusted independently without cross interference. Finally, both simulation and experimental results are presented to verify the effectiveness of the proposed wireless energy router.

A Phase-Shift Control Method of Triple-Active-Bridge Converter for Reducing Power Loss Under Light Load Condition

This paper presents a phase-shift control method of a triple-active-bridge converter for distributed power supply systems with multiple batteries. The experimental results show that the reactive power through the transformer can be suppressed under a wide range of conditions. The proposed phase-shift control method improves the light load loss at 500W by approximately 30% compared to the conventional method. In addition, according to the power-transmission characteristics of the proposed method, for applications in which a voltage source connected to an input port is attached and detached, the power supply and demand can be adjusted between each output port while gradually lowering the charge of the input port by utilizing the characteristics of the charging operation. Therefore, the converter can continue to operate regardless of the attachment and detachment of the input port-voltage source.

소형풍력발전을 위한 3상 단일전력단 교류-직류 컨버터

This paper proposes a three-phase single-stage AC-DC converter for the small wind generation system. Input power factor improvement and insulated output can be implemented with the proposed three-phase single-stage AC-DC converter under the wide power generation voltage (80-260 Vac) and frequency (10-42 Hz) in a small wind power generation (WPG) system. The proposed converter is also capable of zero-voltage switching in the primary-side switches and zero-current switching in the secondary-side diodes by phase-shift control at a fixed switching frequency. In addition, it is possible to control a wide output voltage (Vo: 39 VDC-60 VDC) by varying the link voltage and improving the input power factor (PF) and the total harmonic distortion factor (THDi). Simulation and experimental results verified the validity of the proposed converter.

Passification-Based Robust Phase-Shift Control for Two-Rotor Vibration Machine

In this paper, the solution to the problem of robust control of the phase shift during rotation at a given speed of the unbalanced rotors for a two-rotor vibratory machine is presented. The solution to this problem is relevant for the development of vibration technologies (for example, a vibro-transportation of bulk materials). The proposed controller includes two proportional-integral (PI) rotor speed controllers with a cross-coupling, which receive signals with opposite signs from the phase shift controller. Unlike previous works, where a PI controller for phase shift control was also taken, including the adaptive controller with an implicit reference model (IRM), in the present paper, a relay-type signal controller with an integral component without a parametric adaptation is used. This approach allows, while maintaining robustness, to increase the operation speed and accuracy of the control process, avoiding at the same time the possible divergence of the tunable parameters due to the influence of noises and disturbances caused, among other things, by vibrations of the setup’s structural elements and measurement errors. For the control law design, the speed-gradient method was employed. For various types of reference phase-shift signals (constant, harmonic, chaotic), the results of extensive experimental studies performed on the mechatronic vibration setup and the simulations accomplished based on the results of identifying the parameters of the stand drive model are presented in the paper. The obtained results confirm the efficiency and robustness of the proposed algorithm and allow one to reveal the system performance properties.

A Study and Implementation of Inductive Power Transfer System Using Hybrid Control Strategy for CC-CV Battery Charging

In this paper, a hybrid control strategy is studied and implemented on an Inductive Power Transfer (IPT) system to simultaneously realize zero-voltage switching (ZVS) and constant current (CC) and constant voltage (CV) battery charging. A steady-state analysis of pulse frequency modulation was conducted, based on the characteristic of voltage gain versus switching frequency, and CC and CV charging modes were promised. The ZVS of the inverter was obtained by satisfying the minimum requirement of full discharge of the junction capacitor on the MOSFETs using a commutation current during the dead-time interval. Two control degrees of freedom are needed to realize the two control targets. This hybrid control strategy adopts a self-oscillating (SO) control to achieve ZVS and phase shift (PS) control and a constant output for the series–series (SS)-compensated IPT system. To validate the hybrid control strategy, a 1.6 kW prototype with 360–440 V input voltage and 250–400 V output voltage was built and the experimental results show that the peak efficiency can reach 96.1%. Compared with the conventional variable frequency (VF) control, the hybrid control method proves that an additional control variable can fulfill the control target in a more flexible manner, which makes the switching frequency close to the resonant frequency during the charging process, minimizing the reactive current in the resonant tank and improving system efficiency.

Integrated Optimization of Dual-Active-Bridge DC–DC Converter With ZVS for Battery Charging Applications

In this article, dual-active-bridge (DAB) dc–dc converter with phase shift control is explored extensively, and optimal performances obtained with different objectives are comparatively analyzed in each mode. First, the principle and operating modes of TPS control are introduced in detail. Second, the electrical characteristics of the converter in each operating mode are systematically derived. Third, resonant commutation in each dead-band is analyzed, and soft-switching areas of the converter are obtained. Then, based on zero-voltage switching (ZVS), peak, and root mean square (rms) of the inductor current, backflow power and operating losses are taken as optimization objectives, and the obtained optimized results are contrastively analyzed. The commonalities of the optimization results with different objectives in modes I–III are revealed, and the differences in optimization characteristic in mode IV are present, as a guidance for practice design and operation. Experiments are performed to demonstrate the theoretical analysis.

Dual-Frequency Retrodirective Antenna Array With Wide Dynamic Range for Wireless Power Transfer

This letter presents a dual-frequency heterodyne retrodirective antenna (RDA) array with relatively large frequency ratio between receiving and transmitting for adaptive tracking in far-field wireless power transfer systems. The proposed RDA consists of an eight-channel radio frequency mixing, amplify chain and two 1 × 8 circularly polarized arrays with different operation frequency and orthogonal polarizations, receiving at 3.8 GHz with right-hand circular polarization and transmitting at 5.8 GHz with left-hand circular polarization, respectively. For received power levels from −80 to −40 dBm, each chain outputs with consistent phase and stable power about 29 dBm brought by automatic gain control and compensation phase shifter. It can transmit reversely along the direction of beacon signal from near to far distance. High system isolation is achieved through inherent isolation of different frequencies and orthogonal polarizations of the T/R arrays. Monostatic and bistatic measurements are taken, and measured results verify that the proposed RDA is of far-field tracking capability to receive and transmit from −40° to 40°.