Isolated Cuk Converter with Two Symmetrical Output voltages For SRM Drive

This paper presents a control method for three-phase inverter under grid fault condition based on a novel critical conduction mode (CRM)-based soft-switching modulation. In the soft-switching modulation, one phase is clamped to dc bus, other two phases operate in CRM and discontinuous conduction mode (DCM), respectively. The soft-switching technique with silicon carbide (SiC) power devices allows the inverter to operate at hundreds of kHz with high efficiency by reducing switching loss. In order to extend the modulation scheme to more practical cases, behavior of the inverter under grid fault conditions, specifically voltage sag, is investigated. During voltage sag, the grid voltage becomes unbalanced requiring unbalanced ac current reference for the avoidance of output active power oscillation. With the unbalanced grid voltage and ac current reference, continuous conduction mode (CCM) operation occurs where DCM operation is intended leading to high turn-on loss. To eliminate the CCM operation and reduce the turn-on loss, an improved modulation technique is proposed by using off-time extension concept in CRM phase. In this paper, how the CCM operation appears under grid fault condition, and details of the proposed control are discussed. Performance of the proposed control method is validated experimentally with SiC-based three -phase inverter laboratory prototype.

This paper presents a phase shift H-bridge DC–DC converter for electrical vehicle battery charger application. There are many conventional DC–DC converter topologies. Those are buck converter, boost converter, buck-boost, and Cuk converter. The main drawbacks of this converter are single input and single output, and these converters are not suitable for converting high DC supply to low DC supply. This paper presented a phase shift H-bridge DC–DC converter, and this converter is mainly used in step-down high DC voltage to low DC voltage, and it also provides isolation between input and output. The major applications are server power supply, telecom rectifier, battery charging system, and renewable energy system. The presented topology operated in mainly two modes of operation one is discontinuous conduction mode (DCM) and the second one is continuous conduction mode (CCM). When the battery is charged fully the mode circuit is operated in DCM mode. When the charging across the SOC is very low the circuit will operate in CCM. The simulation results are verified in CCM mode. The closed-loop PI controller is used for controlling battery voltage, current, and SOC.KeywordsElectric vehicleZero voltage switchingDC/DC convertersCharge controllerPI controller

Dual Randomized Pulse Width Modulation (DRPWM) is renowned for its better effectiveness than Simple Randomized Pulse Width Modulation (SRPWM) in reducing conducted Electro-Magnetic Interferences (EMI) in power converters. However, the introduction of low-frequency ripples into the output voltage by dual randomization has not yet been addressed; this effect is investigated in this paper for a buck converter operating in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). First, the modulating principle is presented. Then, a general analytical expression for power spectral density (PSD) of the input current is derived and validated for the proposed DRPWM scheme for both the CCM and DCM. A comparison of the PSDs of the input current for all RPWM schemes in both the CCM and DCM shows the PSD spreading effectiveness of the dual scheme as compared to simple schemes. Finally, the low-frequency output ripple is analysed using the PSD of output voltage. The results reveal that the output voltage ripple is affected by all the randomized schemes in both the CCM and the DCM. Also, the dual scheme (RCFM-RPPM) introduces the highest low-frequency voltage ripple, especially in the CCM and for low duty cycles. In DCM, the RPPM scheme gives the lowest voltage ripple, while the RCFM scheme gives the lowest voltage ripple in the CCM. The results are confirmed by both theory and simulations.

This paper discusses experimental validation of semi-bridgeless boost rectifier (SBBR) operation of continuous conduction mode (CCM) & discontinuous conduction mode (DCM) for power quality improvement in uninterrupted power supply (UPS) system. The double stage conversion in UPS attenuates power quality at the input side and output configuration of the system. Many researchers have proposed the improvement of power quality with CCM and DCM operations for ac-dc conversion stage in bridge and bridgeless rectifier, but there is lack of knowledge about their performance and drawbacks of CCM and DCM operation with SBBR topology. This paper focuses on experimental analysis of SBBR topology operating in CCM and DCM under different load ranges. The performance of power quality factors and efficiency of SBBR operating in CCM and DCM are addressed. To study the stability analysis of SBBR operation in CCM and DCM, a comprehensive small signal model is derived by analyzing the inductor current waveforms. PSCAD simulations have obtained theoretical study of SBBR with CCM and DCM operations and experimental validation is carried out through FPGA Spartan 3A processor.

This paper presents a multi-cell single-phase high power factor boost rectifier in interleave connection, operating in critical conduction mode, employing a soft-switching technique, and controlled by field programmable gate array (FPGA). The soft-switching technique is based on zero-current-switching (ZCS) cells, providing ZC (zero-current) turn-on and ZCZV (zero-current-zero-voltage) turn-off for the active switches, and ZV (zero-voltage) turn-on and ZC (zero-current) turn-off for the boost diodes. The disadvantages related to reverse recovery effects of boost diodes operated in continuous conduction mode (additional losses, and electromagnetic interference (EMI) problems) are minimized, due to the operation in critical conduction mode. In addition, due to the interleaving technique, the rectifier's features include the reduction in the input current ripple, the reduction in the output voltage ripple, the use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the IEC61000-3-2 standards. The digital controller has been developed using a hardware description language (VHDL) and implemented using a XC2S200E-SpartanII-E/Xilinx FPGA device, performing a true critical conduction operation mode for all interleaved cells, and a closed-loop to provide the output voltage regulation, like as a pre-regulator rectifier. Experimental results are presented for a implemented prototype with two and with four interleaved cells, 400 V nominal output voltage and 220 Vrms nominal input voltage, in order to verify the feasibility and performance of the proposed digital control through the use of a FPGA device

The flyback converter is widely used in modern power conversion systems due to its simple topology, single switch, low component count, and inherent galvanic isolation. This paper investigates the performance characteristics of flyback converters by analyzing their operation in Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM), with particular emphasis on voltage spike behavior. The main contribution of this study is the development of a mathematical model that correlates the operating mode (CCM or DCM) with the voltage spike across the power switch. In addition, the study examines the impact of duty cycle variations on voltage spike behavior. The results show that, for comparable operating conditions and moderate duty cycles, CCM operation generally results in lower voltage spikes than DCM due to reduced peak magnetizing current, while at higher duty cycles and load levels, CCM may exhibit increased voltage stress. The proposed approach was validated through MATLAB/Simulink simulations and a scaled-down experimental prototype. A proportional integral (PI) controller is implemented in simulation to ensure regulated output voltage under practical operating conditions. The results demonstrate that optimizing the duty cycle and accounting for the influence of conduction mode can enhance the reliability of flyback converters, making them suitable for applications requiring galvanic isolation and cost-effective solutions.

The boost converter operates either in discontinuous conduction mode (DCM) or in continuous conduction mode (CCM). The operation mode is determined by the duty ratio, load and parameters of the boost converter. The plant model in DCM and CCM are different in the frequency domain response. Therefore, it will be difficult to design a controller with stable operation and fast transient response for both modes. Moreover, the boost converter will be unstable between DCM and CCM. In this paper, the proposed control strategy can transit between DCM and CCM seamlessly by adding a mode detector, the boost converter can be automatically operated by selecting of control loop in both operation modes. The proposed controller still has a voltage control loop in DCM and current/voltage control loops in CCM. Each controller is designed by considering the stability and response time. The proposed mode detector will be explained with a frequency domain analysis. Due to the wide range operation capability of the proposed control strategy, the proposed control strategy is suitable in the fuel cell portable applications. In addition, smooth operation of the converter will also be beneficial to the fuel cell stack reliability. A 20 W boost converter prototype is used to verify the performance of the proposed control scheme.

Due to the simple structure and low cost, the primary-side-regulation (PSR) flyback converter is widely used in small power applications. As the output voltage is sampled from auxiliary winding in PSR flyback converter, some sampling error exists, especially when continuous conduction mode (CCM) is introduced for higher power. To improve the constant voltage accuracy, a novel digital controlled sampling strategy is proposed. This scheme uses a digital ramp sampling method to sample output voltage in both discontinuous conduction mode (DCM) and CCM, and proposes a voltage adjustment strategy to adjust sampling errors in CCM without weakening the stability in the load-switch process. Finally, the experimental results validate the presented scheme and show that the output voltage error is less than 0.6% in a 20-V, 5-A PSR flyback prototype.

Continuous and discrete-time averaged models are available for pulse width modulated (PWM) converters operating in the continuous conduction mode (CCM). A new discrete-time model for PWM converters operating in the discontinuous conduction mode (DCM) is proposed that leads to the exact discrete-time mathematical representation of the averaged values of the output signal.This model can also provide the averaged values of other internal signals with little increase in simulation time. This model is also used to simulate PWM converters operating in both DCM and CCM when combined with the averaged CCM model in [1]. It is compared to other models with respect to accuracy and simulation speed through a numerical example of boost converter. This method gives the exact values of the one-cycle-average (OCA) values of signals at switching instants. Numerical simulations show the accuracy and speed of the proposed method as well as its advantage in simulating PWM converters operating in both CCM and DCM.

This paper presents efficiency comparison of quadratic boost converter in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). Analytical expression for the DC component and RMS component of currents in CCM and DCM is derived. Total losses incurred in quadratic boost converter are calculated. Discontinuous conduction modes in three cases are discussed. The simulation result in software MATLAB/SIMULINK is presented for validating the results obtained by mathematical theories.

A new discrete time state feedback controller is presented, which allows high bandwidth voltage control of a buck converter for any load condition whether it operates in discontinuous conduction mode (DCM), continuous conduction mode (CCM) or in the boundary of these regions. This makes the buck converter applicable for a wide range of applications. For the control design process two large signal models are developed, which represent the buck converter's discrete time dynamics in CCM and DCM. A simple PI regulator is used for the voltage control of the converter. The operation mode is detected and the voltage controller is connected in cascade to a current controller in CCM or to a nonlinear state feedback decoupling structure in DCM. In this work, the modeling and design of the proposed control topology are introduced and its performance is demonstrated in simulation and experiment.

A general discrete formulation procedure for steady-state analysis of switching DC-DC converters is presented. The method provides both sample and average values of the converter state vector in steady state in either of the two conduction modes. In the continuous conduction mode, the technique leads to the same results as the state-space averaging method for the average values. In the discontinuous conduction mode, it leads to the same results as the classical non-systematic analysis of switching DC-DC converters even in the case of high order power stages, thus overcoming the limitations of the state-space averaging method. The procedure can be easily programmed for computer-aided analysis. The Cuk converter operating in the discontinuous conduction mode is used to illustrate its application. >

The overall dynamics of power-factor-correction (PFC) boost converter, including the fast-scale instability, the low-frequency stable periodic operation, the low-frequency bifurcation and chaos, are investigated by using the combined continuous conduction mode (CCM) and discontinuous conduction mode (DCM) model. It is conventionally assumed that the converter operates in CCM in the design and analysis process of a PFC boost converter, which prevents us to understand the overall dynamics of the converter. It has been pointed out that the DCM can occur in the PFC boost converter, especially, in the light load condition. Therefore, the DCM model has to be included to analyze this PFC converter to cover the possible DCM operation. The unified model for describing the overall dynamics of the PFC boost converter is derived, which can be used to analyze the overall dynamics uniformly. By using the proposed combined model, the fast-scale instability can be detected. At the same time, the low-frequency bifurcation diagram is derived by proposed model, which makes the route from period-double bifurcation to chaos clear. The overall dynamics derived from the proposed method is verified by the experimental results

A performance comparison of boundary control with the first-(sigma <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> ) and second-order(sigma <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) switching surfaces for buck converters operating in discontinuous conduction mode (DCM) is presented in this paper. Performance attributes under investigation include the average output voltage, output ripple voltage, switching frequency, parametric sensitivities to the component values, and large signal characteristics. Due to the presence of the output hysteresis band, an additional switching boundary formed by the zero-inductor-current trajectory is created. This phenomenon causes a shift of the operating point in converters with sigma <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> . Conversely, the operating point remains unchanged in converters with sigma <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . As well as in continuous conduction mode (CCM), sigma <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> can make the converter revert to the steady-state in two switching actions in DCM and gives better static and dynamic responses than in both CCM and DCM. Most importantly, its control law and settings are applicable for both modes. Experimental results of a prototype are found to be in good agreement with theoretical predictions.

본 논문에서는 임계전류도통모드로 동작하는 디지털제어 단상 역률개선(PFC; power-factor correction) 컨버터를 제안한다. 제안한 컨버터는 PFC를 위하여 DC-DC 부스트 컨버터 구조를 이용하며 인덕터전류를 임계도통모드로 동작시킨다. 또한 제안한 컨버터는 마이컴을 이용하여 디지털적으로 제어되기 때문에 제어회로는 간단해지고 컨버터는 더욱 효과적으로 동작한다. 본 논문에서는 먼저 제안한 컨버터의 동작원리를 설명하고 회로를 해석한다. 그리고 본 논문은 제안한 컨버터의 구현방법을 소프트웨어와 회로설계 부분으로 구분하여 구체적인 설계예와 함께 설명한다. 또한 설계된 회로파라미터에 의한 프로토타입 컨버터의 실험결과로 제안한 컨버터가 단상 PFC 컨버터로써 좋은 동작 특성을 가지고 있음을 보인다. This paper presents a digital-controlled single-phase power-factor correction (PFC) converter operating in critical current conduction mode. The proposed converter utilizes the DC-DC boost converter topology for the PFC and operates the inductor current in critical conduction mode. Because the proposed converter is controlled digitally using a micom, its control circuit is simplified and the converter operates more effectively. This paper first explains the operational principles of the proposed converter and then analyzes the converter circuit. And this paper explains the implementation method of proposed converter with a detail design example, which is divided into software and circuit design parts. Also, it is shown through the experimental results of the prototype converter by the designed circuit parameters that the proposed converter has good performance as a single-phase PFC converter.