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Summary: In order to achieve efficiency extremum of power conversion independent of parameter values and operational mode, an adaptive dual‐controller on‐line efficiency optimization method is presented in this paper. Firstly, based on tri‐modal analysis for four‐switch buck‐boost (FSBB) converter, efficiency extremum analysis is given and existed for such this converter. Then, adaptive dual controller on‐line efficiency seeking algorithm is shown to adaptive two variables for efficiency optimization and output voltage regulation. Furthermore, perturb and observe detector is described to realize control variables decoupling of dual‐controller and to prevent the instability of the whole system during the algorithm tuning process and to improve the algorithm speed of the dual controller. The proposed method is model independent and does not depend on the circuit parameter values. The detail implement of algorithm and performance analysis is given, and the experimental platform and experimental results are put forward to verify the effectiveness of the algorithm. [ABSTRACT FROM AUTHOR]

Summary With the characteristics of high efficiency and high power density, the four switch buck–boost (FSBB) converter is widely used in electric vehicles, direct current microgrids, and so forth. However, how to achieve smooth switching between different modes of FSBB has always been a hot issue in the theoretical and engineering fields. In this paper, considering the dynamic performance and output voltage or inductance current deviation, a control algorithm with integrated natural trajectory method is designed to realize the switching of different modes of FSBB converter. The proposed control algorithm is based on the theory of large signal natural locus and average natural locus. The normalized phase locus of inductance current and output voltage divides the phase plane into five regions and performs large signal or average switching operations in different regions. Theoretical analysis shows that the proposed control algorithm can achieve the balance between the dynamic performance and output voltage or inductance current deviation of FSBB converter in different mode switching. Finally, the performance of the proposed control algorithm is verified by experiments results. [ABSTRACT FROM AUTHOR]

Summary: Aiming to the problems of high circulating current and low efficiency caused by the traditional strategy of dual active bridge (DAB) converter under light load, in this paper, simple graphical optimization method (GSO) is proposed to improve the efficiency of dual active bridge converter. Through the contour plot of transmission power and current stress, optimal efficiency point can be obtained by tangent of contour map under condition of constant power, and heavily calculation or complex iterations of existing conventional control strategies are avoided. Moreover, analysis of proposed graphical current stress optimization is addressed, and controller design of proposed method is given and described. Efficiency comparison between traditional modulation strategy and GSO is given to show the advantage of proposed mothed. An experimental prototype is built to verify the analysis. [ABSTRACT FROM AUTHOR]

Summary: Resonant converters have been widely applied in many fields, such as electric vehicles, renewable energy sources, and switch‐mode power supply. Conventional resonant converters generally adopt pulse frequency modulation (PFM), which would cause an extremely wide frequency variation range under wide output applications. However, it would lead to high electromagnetic interference (EMI), low utilization of magnetic components, and loss of soft switching features. For catering to wide output range applications, this paper proposes a self‐adaptive narrow frequency range PFM and asymmetrical voltage‐cancelation hybrid modulation strategy to solve the above problem. The advantages of the proposed strategy include (1) narrow frequency variation range; (2) self‐adaptive shift frequency; and (3) full process achievement of zero voltage switch. The modulation strategy and operational principle and performance analysis of the proposed method are given. Eventually, a series resonant converters–based experimental platform was implemented to verify the proposed strategy. [ABSTRACT FROM AUTHOR]

In order to address the issue of keeping the converter operating at a high efficiency level under different conditions, this paper suggests an adaptive step frequency adjustment online optimization search algorithm, which achieves the goal of fast adjustment and real‐time response to parameter changes. The converter is quickly adjusted to operate at a high efficiency by sampling the input and output current values and modulating the switching frequency utilizing the algorithm. Additionally, the algorithm shifts between two working models to finish the search for the best switching frequency while the converter's characteristics do not change. Moreover, it accomplishes the objective of instantly resynchronizing the algorithm after a change in the converter's parameters and starting a search for the best switching frequency in the new converter state. For various input voltages and output loads, the operating principle, optimal frequency, and efficiency are given. In addition, the principle analysis when the converter parameters are changed is provided, and the choice of two algorithm models is compared. Finally, a prototype buck converter with adjustable input voltage and load is constructed to test the algorithm's efficiency. [ABSTRACT FROM AUTHOR]

In order to break limited step-down ratio range and poor regulation capacity in the conventional resonant switched-capacitor converters for rectifier application, a single-stage ac/dc rectifier based on the dual-resonance switched-capacitor converter is proposed in this article. Through utilizing a dual-resonant structure and nonoverlapping strategy to realize wide continuous voltage gain of the proposed converter, high power factor (PF) and low total harmonic distortion (THD) based on the narrow dead zone are guaranteed by operating at high step-down conversion ratio in this converter topology. Moreover, the voltage gain is concentrated between resonant frequency and double resonant frequency to achieve a narrow switching frequency range for rectifier application. Furthermore, operating at flat voltage stress curves to obtain low voltage stress character. Comprehensive mode analysis, input PF and THD, and stress analysis are given, and analysis results indicate that the proposed power factor correction converter can work with soft turn on and zero-current turn off; high efficiency is realized. Finally, an experimental prototype with 85–130 Vac input and 47 Vdc/44 W output is built and tested for verifying the operation modes and PFC performance, and the comparison between different rectifiers and the proposed one is provided. [ABSTRACT FROM AUTHOR]

Dual active converter (DAB) can achieve high efficiency when the voltage ratio (the ratio of the input voltage to the output voltage equivalent to the primary side) is one, but when the voltage ratio is not one, the light-load efficiency drops sharply. Based on the realization logic of DAB light-load, this article proposes a modulation method with asymmetric compression duty cycle, which only increases one degree of freedom and does not need additional components to significantly improve the light-load efficiency. First, this article introduces the existing problems and solutions of the traditional scheme and puts forward a new modulation strategy. Then, the operating modes and power characteristics are analyzed. Then, the influence of duty cycle compression on reflux power and current stress is analyzed. Finally, a prototype with an input voltage of 100–200V, an output voltage of 50 V, and a full load power of 300–600 W is built to verify the analysis. [ABSTRACT FROM AUTHOR]

In the application of bipolar DC bus configuration in the DC nanogrid, the unbalanced voltage of two outputs in bipolar DC bus, due to the unbalanced conditions of loads and/or energy sources, will cause deterioration of the power quality of the bus and may damage the switch, affecting the stability and safety of the system. In order to solve the problem of unbalanced voltage of two outputs, interleaved series capacitor based dual‐output converter with a high conversion ratio is presented in this paper. By applying negative current mode (NCM) to the main inductor, the character of two‐output self‐balancing and zero voltage switching (ZVS) of all switches for such this topology configuration is achieved. In the NCM mode, the parallel diodes of main switches are not conducted during dead time and guarantee the flowing path to load side. Thus, based on this condition, volt‐second balance of main inductor is obtained to get the character of two‐output self‐balancing. Furthermore, by adopting series capacitor in the proposed topology and based on the charge‐balance of the intermediate block capacitor, inductor current existed in the two phase could be auto‐sharing. Comprehensive operational principle analysis, loss analysis, and efficiency of the proposed converter under different load conditions have been given, and the comparison analysis of three operation modes and selection of negative current mode is clarified. Small signal model of the proposed converter is described to convenient for the controller design. Finally, simulation results and a 20–220 V prototype are built to verify the character analysis of the proposed converter. [ABSTRACT FROM AUTHOR]

Aim to improve the power efficiency of the dual-active-bridge (DAB) dc–dc converter, an efficiency optimization scheme with triple-phase-shift (TPS) modulation using reinforcement learning (RL) is proposed in this article. More specifically, the Q-learning algorithm, as a typical algorithm of the RL, is applied to train an agent offline to obtain an optimized modulation strategy, and then the trained agent provides control decisions online in a real-time manner for the DAB dc–dc converter according to the current operating environment. The main objective is to obtain the optimal phase-shift angles for the DAB dc–dc converter, which can achieve the maximum power efficiency by reducing the power losses. Moreover, all possible operation modes of the TPS modulation are considered during the offline training process of the Q-learning algorithm. Thus, the cumbersome process for selecting the optimal operation mode in the conventional schemes can be circumvented successfully. Based on these merits, the proposed efficiency optimization scheme using the RL can realize the excellent performances for the whole load conditions and voltage conversion ratios. Finally, a 1.2-KW prototyped is built, and the simulation and the experimental results demonstrate that the power efficiency can be improved by using the optimization scheme based on the RL. [ABSTRACT FROM AUTHOR]

This article proposed a current sharing strategy for three-phase series capacitor boost converter for continuous conduction mode operation. The phase current can be automatically balanced based on the charge-balance principle, without any additional sensors or devices. And a uniform output voltage expression in full duty ratio range can be obtained. The mechanism of unbalanced current is disclosed. A current sharing strategy is proposed by adjusting the duty ratio in adjacent phase. The selection of capacitor and inductor is discussed via the analysis of topological operation and current deviation. The related characteristics are presented, including uniform output expression, continuous duty ratio operation, insensitivity to inductor parameters, loos analysis, and device stress. Experimental results on 100-W prototype are provided to confirm the feasibility of the proposed strategy. [ABSTRACT FROM AUTHOR]

In this study, a wide load range zero‐voltage zero‐current switching (ZVZCS) dual‐active‐bridge DC–DC converter using auxiliary parallel networks is proposed. The outstanding feature of the proposed converter is that all of the switches are allowed to operate with zero‐voltage switching while four of the switches are allowed to operate with zero‐current switching, due to the use of two auxiliary parallel networks, which were paralleled to two active bridges, respectively. Furthermore, the circulating current losses can be reduced significantly by using unified boundary trapezoidal modulation method. Based on these merits, the proposed converter has some advantages for the wide range load variation applications with less circulating current losses. The operation principles, soft‐switching conditions and loss analyses comparison are given in this study. These benefits and characteristics mentioned above are verified from the experimental results by using a 1 kW prototype. [ABSTRACT FROM AUTHOR]

In this paper, a series-capacitor-based interleaving buck power factor correction (PFC) converter is proposed, the intermediate energy storage capacitance of which is operated at discontinuous capacitor voltage mode (DCVM), and automatic power factor (PF) correction for this converter is obtained. Moreover, the voltage across the series capacitor of the proposed PFC converter is clamped at the input voltage, and thus peak voltage stress existed in the traditional DCVM buck PFC could be relieved. By effectively regulating the charge/discharge time for the series capacitor, ultrahigh step-down conversion ratio of the proposed converter is achieved, the conversion ratio of which is independent of the duty cycle and only related to the switching frequency and circuit parameters. Therefore, high PF can be obtained due to very narrow deadtime of the input current. Meanwhile, the proposed PFC converter can realize the soft turn-on of part power switch and soft turn-off of part power diodes. In addition, comparing with the traditional discontinuous inductor current mode PFC, the input current of the proposed PFC converter is continuous so that the peak value and root-mean-square value of input current can be reduced. The operational principle, performance analysis, and parameter design principle are given in this paper. The analysis results show that the PF and total harmonic distortion are also independent of the duty cycle. Finally, a 220-Vac input, 60 W/15 V output experimental prototype is built to verify the validity of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Compared with constant duty cycle-controlled discontinuous conduction mode (DCM) boost power factor (PF) correction (PFC) converter, constant duty cycle-controlled quadratic DCM–DCM boost PFC converter features with much lower second-order line frequency output voltage ripple, and however, it suffers from low PF. To increase PF of quadratic DCM–DCM boost PFC converter, a variable duty cycle control technique for quadratic DCM–DCM boost PFC converter is presented in this paper. An approximation equivalent for the variable duty cycle is employed to simplify the implementation circuit. The corresponding expressions of PF and output voltage ripple are analyzed. For input voltage range of 100–240 Vac, quadratic DCM–DCM boost PFC converter with variable duty cycle control benefits with very high PF, and tradeoff between PF and output voltage ripple of this converter is analyzed. Experimental results from 100-W prototypes are given to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

A single-inductor dual-output (SIDO) buck–boost power factor correction (PFC) converter operating in critical conduction mode is proposed in this paper. By multiplexing a single inductor, each output of the SIDO buck–boost converter can be regulated independently. Compared with a conventional two-stage multiple-output converter, the SIDO buck–boost PFC converter benefits from significant overall cost saving, small size, and light weight. Moreover, the efficiency of the SIDO buck–boost PFC converter can be improved due to single-stage power conversion. The control strategy and characteristics of the proposed converter are analyzed. The efficiency, power factor, total harmonic distortion, and output accuracy are verified using the experimental results. [ABSTRACT FROM PUBLISHER]

A novel high‐efficiency high step‐up pulse‐width modulation (PWM) resonant converter is proposed. It achieves high‐voltage step‐up by connecting the outputs of the boost converter cell and the isolated single‐ended PWM resonant converter cell in series, and high efficiency by zero current switching for the diode on the secondary side of the transformer of the single‐ended PWM resonant converter cell. The boost converter cell in the proposed converter can not only step‐up voltage, but also absorbs the leakage inductor energy during the turn‐off interval of the power switch to improve power conversion efficiency. Experimental results of a 100 W 35 V/200 V prototype are presented to verify the analysis results of the proposed converter. [ABSTRACT FROM AUTHOR]

An improved Harris corner detection algorithm is proposed based on Barron operator, since Harris corner detection algorithm has a poor accuracy in positioning complex corner detection and may miss certain real corners. Firstly, the image gradient is calculated by using Barron operator to reduce the calculation errors from Prewitt operator or Sobel operator. Secondly, the centre B-spline function is used to smooth image, filter noise, and retain the corners information better. Thirdly, a non-maximal inhibition and corners sieving method is used to determine whether the detected corners are real corners or not. A square window is centered at the pixel and eliminate the corner if the value of the corner response function is non-maximal in the window. And then divide the test image into several blocks so as to process each block independently, and use a cyclic iterative method to determine the threshold value to make sure that the real corners are accurately selected. Finally, experiments indicate the algorithm has relatively great noise proof ability and is able to extract complex corners effectively. [ABSTRACT FROM AUTHOR]