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This paper proposes a novel nonisolated single-input dual-output three-level dc–dc converter (SIDO-TLC) appropriate for medium- and high-voltage applications. The SIDO-TLC is an integration of the three-level buck and boost converters, whose output voltages are regulated simultaneously. Reducing voltage stress across semiconductor devices, improving efficiency, and reducing inductors size are among the main merits of the new topology. Moreover, due to the considerably reduced volume of the step-down filter capacitor, a small film capacitor can be used instead, whose advantages are lower equivalent series resistance and a longer lifespan. A closed-loop control system has been designed based on a small-signal model derivation in order to regulate the output voltages along with the capacitors’ voltage balancing. In order to verify the theoretical and simulation results, a 300-W prototype was built and experimented. The results prove the aforementioned advantages of the SIDO-TLC, and the high effectiveness of the balancing control strategy. Furthermore, the converter shows very good stability, even under simultaneous step changes of the loads and input voltage. [ABSTRACT FROM AUTHOR]

In this paper, a three-level quasi-switched boost T-type inverter (3L qSBT2I) is proposed. A new pulse-width modulated (PWM) control method is presented to reduce the inductor current ripple of the qSBT2 I. In the introduced PWM technique, the shoot-through duty cycle is maintained constant to keep the modulation index as high as possible. Then, the only control parameters of the qSBT2I are the duty cycles of the two additional switches. By controlling the duty cycles of the two additional switches, the voltage gain of the proposed qSBT2 I can be improved to a value larger than that of the conventional 3L impedance source inverters. The steady-state analysis, operating principles, and comparisons with the impedance source-based 3L inverters are presented. A 1-kW prototype is constructed to verify the operating principle of the 3L qSBT2I. An indirect dc-link voltage regulator and a capacitor voltage-balance controller are applied to the proposed qSBT2I. Simulation and experimental results are presented. [ABSTRACT FROM AUTHOR]

Single-stage power-factor-corrected (S2PFC) power supplies usually suffer from high voltage stress, due to lack of control on the intermediate bus capacitor voltage. In the past, analysis of such voltage stress was mostly based on steady-state condition without providing sufficient explanation during the transient circuit operation. This paper revisits the problem at circuit level and reports that the root cause is due to the inherent negative current feedback property of the output inductor or the transformer operating in continuous conduction mode (CCM). Based on the finding, this paper further proposes a new approach to reducing the voltage stress by adding an auxiliary circuit branch to existing S2PFC converters. The additional circuit branch limits the effect of negative current feedback by suppressing the change of output current slope due to change of load. This assists the pulsewidth modulation controller to track the change of load better such that the bus capacitor voltage range is reduced through duty cycle control. The auxiliary circuit branch also reduces reverse-recovery-related losses of the converter under CCM operation. A laboratory prototype using the popular boost PFC converter combined flyback dc/dc converter was built and tested to confirm the analysis and effectiveness of the approach. [ABSTRACT FROM AUTHOR]

Connecting legs in parallel in a voltage source inverter is a way to increase the output current and, thus, its rated power. The connection can be made using either coupled or uncoupled inductors, and achieving an even contribution to the output current from all the legs is a crucial issue. Circulating currents produce additional losses and stress to the power devices of the converter. Therefore, they should be controlled and minimized. An efficient technique to attain such balance when coupled inductors are used is presented in this paper. The proposed technique can also be used when the inductors are uncoupled, since it is a particular case where the coupling coefficients are zero. This technique does not include proportional–integral controllers and does not require any parameter tuning either. The exact control action needed to reach current balance is straightforwardly calculated and applied. Experimental results are shown in this paper to verify the efficiency of the proposed balancing method. [ABSTRACT FROM PUBLISHER]

This paper extends the trans-Z-source concept to ac–ac power conversion and proposes a novel single-phase trans-Z-source ac–ac converter. The proposed converter retains the advantages of its existing Z-source/quasi-Z-source counterparts in which the output voltage can be boosted and in-phase with the input voltage or bucked/boosted and out-of-phase with the input voltage. Meanwhile, a coupled inductor is introduced into the proposed converter, and the turns ratio of the coupled inductor become another control variable beside the duty cycle to obtain extreme voltage gain. Importantly, the input voltage and output voltage share the same ground, and the input current could be continuous, which is a benefit for reducing input current harmonics. Most important of all, the safe-commutation strategy for the proposed converter is deep developed, and analytic expression between the switches state and loop circuit voltage/current condition is derived out. Hence, the current/voltage ripple can be avoided without a loss snubber circuit, which benefits a reduced cost and enhanced reliability. The performance analysis is discussed in consideration of parasitic resistance, and system parameter design is optimized based on theoretic calculation. A laboratory prototype is fabricated, and experiments are performed to verify the validation of the proposed converter. [ABSTRACT FROM PUBLISHER]

The control loop stability in boost converters operating in continuous conduction mode has been restricted due to its nonminimum phase nature: the presence of a positive zero (right-half plane zero) in the control to output voltage transfer function. This paper proposes a method to mitigate the effect of the zero on the control loop by shifting the position of the zero to the left-half plane and hence leading to increased stability for the control loop of the boost converter. Superior performance of the proposed method has been clearly demonstrated using simulation and experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, a new nonisolated high-voltage-gain boost converter is proposed. The proposed converter is constructed by adding an additional inductor to a conventional three-level-boost (TLB) converter. When compared with the conventional boost and TLB converters, the proposed converter can achieve higher voltage conversion ratio with reduced voltage and current stresses in the switches. In particular, the proposed converter can reduce the losses of active devices by reducing the current of the switch compared to conventional converters, thus, can achieve high efficiency. In addition, the proposed converter automatically balances the output voltages for an unbalanced load without the need for any additional control strategy or auxiliary circuit. A 2-kW prototype converter was built and tested to verify performances of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel family of cascade three-level (TL) ac–ac direct converters based on ac switch cells, which transfer unsteady high ac voltage with distortion into regulated sinusoidal voltage with low total harmonic distortion (THD). The topological family includes buck TL–boost, buck–boost TL, and buck TL–boost TL modes. In order to achieve a reliable TL ac–ac conversion, a double transient voltage feedback control strategy of the output voltage and the voltage across the flying capacitor is introduced in this paper. A 500-VA 220-V \pm10% 50-Hz ac/220-V 50-Hz ac prototype is presented with the experimental results to prove that the converters have four improved advantages simultaneously, including lower voltage across power switches, bidirectional power flow, low THD of output voltage, and higher input power factor. [ABSTRACT FROM AUTHOR]

This paper presents a model predictive voltage control (MPVC) method for the single-inductor multiple-output (SIMO) dc–dc converter. The proposed MPVC method is able to solve the cross-regulation problem, which is a critical issue in SIMO dc–dc converters. The design of the proposed method including augmented state-space model, cost function, enumerated algorithm, and constraints for the SIMO dc–dc converter is discussed. Simulation for the influences of predict horizon NP, control horizon NC, and Lagrange multiplier $\lambda$ on the voltage ripple is conducted to guide the control parameters’ setting for hardware implementation. Steady-state operation and dynamic performance of the proposed MPVC method are conducted in simulation and experiment based on the single-inductor dual-output (SIDO) buck converter to verify the proposed MPVC method. In addition, the comparison between the proposed method and state-of-art methods for the SIMO dc–dc converters is presented. Simulation and experimental results demonstrate that the MPVC method guarantees low cross regulation for the SIMO dc–dc converter in continuous-conduction mode (CCM) and has a fast response speed to variations in load and reference. [ABSTRACT FROM PUBLISHER]

A three-phase single-switch discontinuous conduction mode (DCM) boost power factor correction (PFC) converter features zero-current turn on for the switch, no reverse recovery in the diode, a constant-switching-frequency operation, a simple control, and a low cost, which are suitable for low-to-medium-power and cost-sensitive applications. Due to the DCM, the energy transfer does not cover the whole switching cycle, the rms and peak values of the inductor current are large, and those of the switch and the diode are also large. This increases not only the current stress of the power components but also the conduction and switching turn-off losses, which lower the efficiency of the converter. An optimum utilization control of switching cycles is proposed in this paper to increase the critical boost inductance. The rms and peak current values of the main power components are reduced, and the conduction and switching turn-off losses are therefore decreased, leading to higher efficiency. The proposed method also slightly achieves an output voltage ripple reduction, and the input current harmonics comply with the standard of the International Electrotechnical Commission 61000-3-2 Class A. [ABSTRACT FROM AUTHOR]

Carrier-based pulsewidth-modulation (CBPWM) techniques are popular due to their simplicity, and have been widely researched for various three-phase inverter configurations. In this paper, two CBPWM techniques are proposed to reduce the common-mode (CM) voltage generated by the five-phase inverter. The five-phase inverters have more flexibility in reducing the CM voltage than their three-phase counterparts because they have more phase legs, hence finer control over the star-point voltage of the load. Two methods are proposed for the conventional two-level five-phase inverter to reduce the CM voltage; one utilizing adjacent modulating waveforms and the other utilizing nonadjacent modulating waveforms. The coupled inductor inverter (CII) uses coupled inductors to generate multilevel outputs. As the volt-second balance must be maintained across each coupled inductor, direct application of the proposed methods on the CII inverter will result in overcurrents in the coupled inductors. Hence, the proposed methods are further improved to ensure the volt-second integral over each switching period is zero. Moreover, the two proposed methods are designed to reduce switching events and prevent unexpected states occurring during the switching transitions. The performance and the switching strategy of both methods are verified by both simulations and experiments on a prototype of five-phase CII. [ABSTRACT FROM AUTHOR]

This paper presents high step-up dc-to-dc converter for low voltage sources such as solar photovoltaics, fuel cells, and battery banks. To achieve high voltage gain without large duty cycle operation, combination of coupled inductor and switched capacitor voltage doubler cells are used. By incorporating active clamp circuit, voltage spike due to the leakage inductance of the coupled inductor is alleviated and zero-voltage switching turn on of the main and auxiliary switch is obtained. Due to the use of MOSFETs of low voltage rating and soft turn on of the switches, conduction loss and switching losses are reduced. This improves the efficiency and power density of the converter. The proposed converter can achieve high voltage gain with reduced voltage stress on MOSFET switches and output diodes. Design and analysis of the proposed converter is carried out, and finally, a 500-W experimental prototype is built to verify theoretical analysis. [ABSTRACT FROM PUBLISHER]

In this paper, the two-input buck converter is proposed as the dc/dc stage for photovoltaic (PV) cascaded converters. This converter is attractive for this application because it is cost effective and reliable and can achieve dual maximum power point tracking (MPPT) with only one power transistor. However, due to the simplified and integrated structure, the nonlinear characteristics of the converter and the two PV arrays complicate the control. By means of a small-signal modeling, the control theme of the two PV voltages is formulated, and the effect of the nonlinearities is presented. It is shown that, while fast voltage dynamics are achieved for the first input, the second-input voltage response depends on the second-stage converter control. Simulation and experimental results are reported to validate the theoretical analysis, showing the dual MPPT capability. [ABSTRACT FROM PUBLISHER]

This paper analyzes the interleaved boost with coupled inductors (IBCI) converter, which is an isolated topology that is suitable for high step-up applications. Two main contributions are given: an exhaustive steady-state analysis and an accurate small-signal model. The former allows for deriving a closed-form noniterative design procedure for the power-stage active and passive components. In addition, it reveals an interesting equivalence with an apparently different converter, i.e., the single active bridge. Subsequently, the IBCI converter dynamic behavior is investigated, deriving a nonlinear average model that, under small-signal approximation, can be linearized around a given operating point and used for feedback controller design. A single photovoltaic module interface converter, rated for 300-W output power, is considered as a case study to validate the analysis outcome and the design procedure. Both are fully validated by measurements taken on the laboratory prototype. [ABSTRACT FROM PUBLISHER]

This paper proposes the pulsewidth modulation (PWM) strategy of Z-source inverters (ZSIs) with minimum inductor current ripple. In existing PWM strategy with single-phase shoot-through, the shoot-through time interval is divided into six equal parts, therefore the three phase legs bear the equal shoot-through time interval. In this manner, the allotment and arrangement of the shoot-through state is easy to realize, but the inductor current ripple is not optimized. This causes to use relatively large inductors. In the proposed PWM strategy, the shoot-through time intervals of three phase legs are calculated and rearranged according to the active state and zero state time intervals to achieve the minimum current ripple across the Z-source inductor, while maintaining the same total shoot-through time interval. The principle of the proposed PWM strategy is analyzed in detail, and the comparison of current ripple under the traditional and proposed PWM strategy is given. Simulation and experimental results on the series ZSI are shown to verify the analysis. [ABSTRACT FROM PUBLISHER]

The pulse-train (PT) control technique for switching dc–dc converters is simple to design and benefits from excellent control performance. Up to now, almost all of the works on PT control are focused on switching dc–dc converters operating in discontinuous conduction mode, with few works reported on PT control of switching dc–dc converters operating in continuous conduction mode (CCM). In this paper, a PT-controlled CCM buck converter is studied and a unique low-frequency oscillation phenomenon is revealed, which results in large undesired inductor-current and output-voltage variations. The effect of equivalent series resistance (ESR) output-capacitor on the low-frequency oscillation is examined. The results indicate that such oscillation occurs when the ESR output-capacitor is relatively small and disappears when it is relatively large. However, a larger ESR will result in a large output-voltage ripple. In order to avoid the low-frequency oscillation and, at the same time, to ensure a small output-voltage ripple, the ICRIF circuit is applied. In this way, a small ESR output-capacitor can be used to decrease the output-voltage ripple. Simulation and experimental results are provided to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

A novel pseudo-continuous conduction mode (PCCM) boost power-factor-correction (PFC) converter and its corresponding control strategy are proposed in this paper. Connecting a power switch in parallel with the inductor makes the boost converter operate in PCCM, which provides an additional degree of control freedom to realize PFC control. Therefore, a simple and fast voltage control loop of the PCCM boost PFC converter can be designed to realize output-voltage regulation. The additional degree of control freedom introduced by inductor current freewheeling operation of the PCCM boost PFC converter has been exploited through the dead-zone control technique, which can be dynamically adjusted in accordance with the output-voltage ripple. Compared with continuous conduction mode (CCM) boost PFC converter, the controller of the proposed PCCM boost PFC converter is much simpler. Moreover, the PCCM boost PFC converter benefits with reduced inductor-current ripple and improved power factor compared with boost PFC converter operating in discontinuous conduction mode (DCM). Analysis, simulation, and a 400-W prototype of the PCCM boost PFC converter have been presented and compared with those of boost PFC converters operating in conventional CCM and DCM. The results show that the dynamic response of the PCCM boost PFC converter is significantly faster than the existing boost PFC converter. [ABSTRACT FROM AUTHOR]

A simple current-sharing control technique for the switching power supply is presented herein, which is based on the concept of the differential-mode transformer and which makes the load current evenly shared well among phases all over the line voltage and load current ranges. This current-sharing structure is very simple, and it makes the efficiency relatively high at light load, which is quite suitable for industrial applications with standby power considered. In this circuit, a synchronously rectified switch is used to further upgrade the efficiency, and the coupling output inductors in copolarity are utilized to decrease the phase current ripples. In this paper, the detailed basic operating principles, together with mathematical deductions, are first described, and second, some simulated and experimental results are provided to demonstrate the proposed control strategy. [ABSTRACT FROM AUTHOR]

Digital implementation of sliding-mode current control applied to dc–dc switching converters is analyzed and developed in this paper. It is based on an interpolation predictive strategy that avoids problems associated to continuous sampling process of the controlled variable and minimizes quasi-sliding effects. In addition to inherent advantages of digital implementation, as programmability, flexibility, complex calculation capability and noise immunity, the proposed strategy maintains robustness and has similar behavior than analog sliding-mode current control implementations. In order to obtain output voltage regulation, an outer proportional-integral digital output voltage control loop is added. Simulated and experimental results in a boost converter are in good agreement with the theoretical predictions. [ABSTRACT FROM AUTHOR]

This paper proposes a twin-buck converter with zero-voltage transition (ZVT). The converter comprises two identical buck conversion units employing power MOSFETs as the active power switches with an interleaved inductor. The ZVT is accomplished by resonating the currents between the interleaved inductor and the parasitic capacitances of the power MOSFETs. The detailed circuit operations and analysis are provided. A laboratory circuit rated at 300 W is designed and tested. Experimental results show that the switching losses can be effectively reduced by ZVT of the active power switches, accompanied by the reduced reverse recovery loss of freewheeling diodes. [ABSTRACT FROM AUTHOR]

A discontinuous-current-mode (DCM) boost power factor correction (PFC) converter features zero-current turn-on for the switch, no reverse recovery in diode, and constant–frequency operation. However, the input power factor (PF) is relatively low when the duty cycle is constant in a half line cycle. This paper derives the expressions of the input current and PF of the DCM boost PFC converter, and based on that, variable-duty-cycle control is proposed so as to improve the PF to nearly unity in the whole input–voltage range. A method of fitting the duty cycle is further proposed for simplifying the circuit implementation. Other than a higher PF, the proposed variable-duty-cycle control achieves a lower output–voltage ripple and a higher efficiency over constant-duty-cycle control. The experimental results from a 120-W universal input prototype are presented to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a novel ac automatic voltage regulator (AVR) is proposed. This AVR is configured by an input inductor, an output filter, a small-capacitance dc capacitor, and a three-arm power converter. This three-arm power converter acts as an ac boost converter when the utility voltage is lower than the specified voltage. On the contrary, this three-arm power converter acts as an ac buck converter when the utility voltage is higher than the specified voltage. Hence, the output voltage of the AVR can be maintained at the specified voltage. The salient feature of this AVR is that the power electronic switches of only one arm are switched in high frequency, while those of the other arms are switched in low frequency. Hence, the switching loss of this AVR can be reduced. Moreover, the capacitance of the dc capacitor in the three-arm power converter is very small. Hence, the size and cost can be reduced, while the reliability and power efficiency can be increased. A prototype is developed and tested to verify the performance of the proposed AVR. The experimental results verify that the proposed AVR has the desired performance. [ABSTRACT FROM AUTHOR]

In this paper, a robust digital voltage-mode controller (DVMC) is proposed for a fifth-order boost point-of-load converter. Salient features of the proposed topology are compared with a conventional boost converter. Mathematical models are formulated using a discrete-time modeling technique and then employed in the compensator design, which uses the digital direct design approach. The DVMC is designed to ensure load voltage regulation. Robustness theory is applied directly in the digital domain, and then, various robust stability criteria describing sensitivity functions are formulated. The controller is designed to satisfy robustness criteria and then evaluated over a range of disturbances in spite of the fact that it maintains regulation. To confirm this, design simulations have been carried out on a 25-W 12–36-V converter system. Experimental results are provided to validate the concept and also to verify the range over which the designed controller is robust. [ABSTRACT FROM AUTHOR]