Conventional Phase-shift Control Research Articles

A Passive Augmented Circuit for EMI Reductions of Full-Bridge Inverters With Conventional Phase Shift Control in Wireless Power Transfer Systems

A Passive Augmented Circuit for EMI Reductions of Full-Bridge Inverters With Conventional Phase Shift Control in Wireless Power Transfer Systems

Research and Design of Misalignment-Tolerant LCC–LCC Compensated IPT System With Constant-Current and Constant-Voltage Output

It is well known that loads of inductive power transfer systems are often energy storage devices. The major benefit of an LCC–LCC compensation topology is that without the additional compensation elements and control methods, the load-independent constant current (CC) and constant voltage (CV) outputs, required by energy storage load, can be achieved at different resonant frequencies. However, the misalignment between two coils at the transmitting and receiving sides is inevitable and can lead to the variation of the resonant frequency in CC or CV output. Therefore, a unique design approach to the LCC–LCC compensation topology is proposed in this article. With the presented method, the resonant frequency, at which load-independent output characteristics can be also implemented, is constant and unaffected by the coupling coefficient, whether in CC mode or CV mode. Furthermore, the transmission gain, which is only impacted by the coupling coefficient, can be conveniently modified by the conventional phase shift control in two modes. Finally, a 120-W prototype is designed to verify the validity of the theoretical analysis. The output current and output voltage fluctuate by only 2.4% and 1.0% in the coupling coefficient range from 0.23 to 0.3 and the large load range, according to experimental results.

Phase-Duty Modulated Loop Decoupling and Design Optimization for a Triple Active Bridge Converter for Light Electric Vehicle Charging

This article presents a comprehensive generalized harmonics approximation based modeling and design of a triple active bridge (TAB) dc–dc converter topology aimed to facilitate simultaneous—main and auxiliary—battery charging solutions for light electric vehicle charging applications. A three-loop control scheme, incorporating the duty and phase control parameters, is proposed in this article to address the issue of inherent coupling of two output bridges and their control loops (as observed in conventional phase modulation-based voltage control techniques), along with an objective to enhance the operational efficiency of the system, in affiliation with a real-time power flow optimization algorithm. Adhering to the objective of achieving minimized losses, the optimization algorithm provides insightful design limitations in terms of selecting the required leakage inductances to ensure desired power flow at the output bridges. Furthermore, to validate the effectiveness of the proposed three-loop control, a detailed set of simulation and experimental results are presented at various steady state and dynamic load change conditions. A detailed analytical loss model of the TAB topology is also presented along with a comparative study elucidating the effectiveness of the proposed three-loop control over the conventional control schemes. The analyses portray a peak efficiency of 96.24% at the rated load of 300 W, which is 2.94% and 4.97% higher than the decoupled and the conventional phase shift control schemes, respectively.

Exploiting Amplitude Control in Intelligent Reflecting Surface Aided Wireless Communication With Imperfect CSI

Intelligent reflecting surface (IRS) is a promising new paradigm to achieve high spectral and energy efficiency for future wireless networks by reconfiguring the wireless signal propagation via passive reflection. To reap the promising gains of IRS, channel state information (CSI) is essential, whereas channel estimation errors are inevitable in practice due to limited channel training resources. In this paper, in order to optimize the performance of IRS-aided multiuser communications with imperfect CSI, we propose to jointly design the active transmit precoding at the access point (AP) and passive reflection coefficients of the IRS, each consisting of not only the conventional phase shift and also the newly exploited amplitude variation. First, the achievable rate of each user is derived assuming a practical IRS channel estimation method, which shows that the interference due to CSI errors is intricately related to the AP transmit precoders, the channel training power and the IRS reflection coefficients during both channel training and data transmission. Next, for the single-user case, by combining the benefits of the penalty method, Dinkelbach method and block successive upper-bound minimization (BSUM) method, a new penalized Dinkelbach-BSUM algorithm is proposed to optimize the IRS reflection coefficients for maximizing the achievable data transmission rate subjected to CSI errors; while for the multiuser case, a new penalty dual decomposition (PDD)-based algorithm is proposed to maximize the users' weighted sum-rate. Finally, simulation results are presented to validate the effectiveness of our proposed algorithms as compared to benchmark schemes. In particular, useful insights are drawn to characterize the effect of IRS reflection amplitude control (with/without the conventional phase-shift control) on the system performance under imperfect CSI.

Optimal phase‐shift control of three‐level dual‐active bridge DC–DC converter with minimum reflux power for wide voltage conversion ratio range application

Three-level dual-active bridge (3L-DAB) DC–DC converter under conventional phase-shift (CPS) control would produce large reflux power and current stress, especially when the voltage conversion ratio is varied in a wider range, which will lead to high power loss and low system efficiency. An optimised phase-shift (OPS) control strategy is proposed to control the 3L-DAB operating at the point with minimum reflux power. The power characteristics of 3L-DAB under CPS control are analysed. Then the mathematical model of the reflux power is established, and the relationship equations among the reflux power, phase-shift (PS) ratios, and voltage conversion ratio are deduced. The minimum reflux power and optimal PS ratio are calculated by using the segmentation optimisation algorithm in different ranges of transmission power and voltage conversion ratio. Performance comparative analysis between CPS and OPS controls is carried out later. Adopting the proposed OPS control strategy, the reflux power of 3L-DAB is minimised, as well as reducing the current stress and increasing the efficiency in a wide voltage conversion ratio range. An experimental prototype was developed to verify the effectiveness of the OPS control strategy and the correctness of the theoretical analysis.

Optimised phase shift control to minimise current stress of three‐level dual active bridge DC–DC converter

The current stress of three-level dual active bridge (3L-DAB) converter under the conventional phase shift (CPS) control becomes much high, especially when the voltage conversion ratio is unequal to one, which may bring low efficiency and damage of power devices. An optimised phase shift (OPS) control strategy is presented to address the issue. The OPS control is realised by calculating the optimal operation point with real-time detection of voltages and current. The principle of 3L-DAB under CPS control is presented. The mathematical models of transmission power and current stress are then established. The minimum current stress and the corresponding optimal phase shift ratios are deduced within different ranges of transmission power and voltage conversion ratio, the comparative analysis of current stress and reflux power under OPS and CPS controls have been carried out. The current stress is minimised with any given transmission power and voltage conversion ratio in the whole power range after adopting the OPS control strategy. Moreover, the reflux power is reduced as well within the boundary of voltage conversion range. An experimental prototype was developed to verify the effectiveness of the proposed control strategy and the correctness of the theoretical analysis.

Dynamic Control and Performance of a Dual-Active-Bridge DC–DC Converter

This paper discusses dynamic behavior of a dual-active-bridge (DAB) dc–dc converter. Conventional phase-shift control methods for the DAB converter may cause dc offsets in both inductor current and transformer magnetizing current in transient states. The dc offset in the inductor current would introduce an excessive peak current through the switching devices. The dc offset in the magnetizing current may induce magnetic-flux saturation. Conventional methods simultaneously turn on and off the diagonal switches in each H-bridge converter and produce a square-wave voltage with a 50% duty ratio. In contrast, the proposed method in this paper independently controls each switch to modify the duty ratio in transient states. This paper clearly derives the requirements of each switch to eliminate the dc offsets in both currents with a settling time shorter than half the switching period. Experimental results using a 5-kW 20-kHz system verify the validity of the proposed control method, which is effective not only in a single step change, but also in a continuous change in the phase-shift reference.

Comparative analysis of three‐level dual active bridge DC–DC converter between reflux‐power‐optimised and current‐stress‐optimised phase shift control

The reflux power and current stress of three-level dual active bridge (3L-DAB) become very large under the conventional phase shift (CPS) control, especially when the voltage conversion ratio is unequal to one or working with light load. To improve the performance, reflux-power-optimised (RPO) and current-stress-optimised (CSO) have been investigated in many literatures. However, the current stress variation with RPO control, the reflux power variation with CSO control, and the relations between the two optimal strategies have not been decided yet. Thus, a detailed comparative analysis is presented in this study. The operation principle of 3L-DAB under CPS, RPO and CSO control strategies is briefly described. The reflux power and current stress comparison among the three strategies is performed within different ranges of transmission power and voltage conversion ratio. The RPO and CSO control strategies are approximately equivalent when the voltage conversion ratio is less than 1/4, and they can minimise the reflux power as well as the current stress in the whole power range. An experimental prototype was developed to verify the correctness of the theoretical analysis.

Operating modes and practical power flow analysis of bidirectional isolated power interface for distributed power systems

Due to the intermittent nature of the renewable energy sources including photovoltaic and wind energy, the energy storage systems are essential to stabilize dc bus voltage. Considering the discharge depth of super-capacitors and energy-storage batteries, the bidirectional isolated power interface will operate for a wide range of voltage and power. This study focuses on in-depth analysis of the dual-active-bridge dc–dc converter that is controlled by the dual-phase-shift scheme to improve the conversion efficiency in distributed power system. The power flow of each operating mode with dual-phase-shift control is characterized based on a detailed analysis of the effects of “minor parameters”, including the deadtime and power device voltage drops. The complete output power plane of the dual-active-bridge converter with dual-phase-shift control is obtained and compared with experimental results. The optimal operating mode is determined according to the practical output power range and the power flow characteristics. Experimental evaluation shows the effectiveness of the proposed power flow model with dual-phase-shift control and significant efficiency improvement using the optimal mode of dual-phase-shift compared with the conventional phase shift control.

Dual Active Bridgeを用いた絶縁形DC-DCコンバータの過渡特性の改善

This paper presents dynamic analysis and control of an isolated dual-active-bridge (DAB) dc-dc converter. Conventional control methods for the DAB converter may cause dc offsets in both inductor current and transformer magnetizing current in transient states. The dc offset in the inductor current introduces an excessive peak current through the switching devices. The dc offset in the magnetizing current cannot be neglected and may induce magnetic flux saturation. Conventional phase-shift control methods simultaneously turn on and off the diagonal switches in each H-bridge converter to produce a square-wave voltage with a 50% duty ratio. In contrast, the proposed method independently controls the diagonal switches to modify the duty ratios in transient states. The theoretical analysis derives the requirements of the switching angles for eliminating dc offsets in both inductor and magnetizing currents with a settling time as short as half a switching period. The results of experiments using a 5-kW, 20-kHz experimental system verify the validity of the proposed control method.

Self-Sustained Oscillating Control Technique for Current-Driven Full-Bridge DC/DC Converter

This paper presents a novel control approach for a current-driven full-bridge dc/dc converter, which is able to significantly improve the converter performance over a very wide range of operating conditions. The proposed control approach is based on the self-sustained oscillating control (SSOC) scheme, in order to adaptively change the phase shift and the switching frequency of the converter for different operating points. In this control technique, the timing signal is produced based on the transformer primary current, which is a feedback to the control system to determine the switching instants of the power MOSFETs. Therefore, the control system automatically tunes the control variables for different operating conditions. The comprehensive mathematical analysis of the proposed SSOC scheme is presented in detail. The mathematical analysis is based on the geometric viewpoint of the control system, which provides a very good insight into designing the control system. Experimental results provided from a 3 kW prototype confirm the feasibility of the proposed scheme and prove the superiority of the performance compared to the conventional phase-shift control approach.

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.

Asymmetric Duty Control of a Dual-Half-Bridge DC/DC Converter for Single-Phase Distributed Generators

A dual-half-bridge (DHB) converter is integrated with a half-bridge 60-Hz inverter as a converter/inverter system for a small distributed generator. This topology provides an isolation between the power source and the load with a 100-kHz transformer, and therefore, the system volume is small. On the other hand, it reduces the number of switching devices greatly. However, the half-bridge inverter causes severe capacitor-voltage fluctuations. The unbalanced voltage problem can be solved by controlling the converter switching: In addition to the conventional phase-shift control method, an asymmetric charging method is used that charges the upper and lower secondary capacitors differently. This means that the voltage imbalance is corrected by adjusting the switching time of the secondary switches. Furthermore, a decoupling control algorithm can be derived from this approach. The usefulness of this method is then validated by simulation and experimental results.