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In this paper, a single-inductor dual-output (SIDO) dc–dc converter is proposed. The significant feature of the proposed converter is feeding a constant power load in low-voltage side (LVS) port, where even feeding a variable load at LVS does not have any cross regulation to high-voltage side port with the desired approximation. Magnificently, both merits are obtained in open-loop manner, which is an outstanding characteristic in comparison with that of the existed converters. In this paper, soft commutation and soft switching of switches and diodes are investigated along with the aforementioned main novelty. Moreover, detailed theoretical analyses of the proposed SIDO dc–dc converter in continuous conduction mode are presented besides the comparisons with some other structures. Finally, theoretical analyses are verified through a 1500 W experimental prototype results. [ABSTRACT FROM AUTHOR]

Thanks to the favorable advantage of low cost, integrated three-port dc–dc converters with reduced switches have attracted extensive attention. In order to provide more new topologies, this paper aims to propose a programmable topology derivation method, which effectively simplifies the cumbersome process of the conventional combination method. Instead of the manual connection and examination, the proposed alternative can quickly and rigorously derive multiple viable integrated three-port dc–dc topologies from a great number of possible connections with the aid of computer program. Besides, generalized analysis is also accomplished, with which performance characteristics of all derived converters are simultaneously obtained and then a comprehensive comparison can be easily conducted to select a preferred one for the practical application. Finally, an example-specific application with one input and two outputs is given, with topology selection, design, and experimental results demonstrated in detail. [ABSTRACT FROM AUTHOR]

In this paper, performances on two kinds of aggregated flyback microinverters are compared in aspect of harmonic resonances, which are controlled by current feedback control and peak current control. Based on the Norton models of flyback microinverters obtained by a small-signal modeling approach, potential harmonic resonances with the grid are analyzed. Following that, an impedance-based stability criterion is proposed, where the resonance frequency can be calculated and predicted based on the derived Norton models and the system admittance matrix of aggregated microinverters. After comprehensive analysis and comparisons, it is found that the peak-current-control-based flyback microinverters has better performance on damping the harmonic resonances than the current feedback controlled one. Simulations and experiments are carried out for verifying the effectiveness of the presented models and the correctness of the analysis results. [ABSTRACT FROM AUTHOR]

In this paper, the remedial operation of switch faults will be investigated comprehensively for T-type-three-level-inverter-fed dual three-phase motor drives. The open-circuit switch faults in multiple phase legs are discussed at first. The faulty conditions are classified into five categories. Different remedial strategies, namely Type-I to Type-V schemes, are proposed for different faulty conditions. In particular, three kinds of Type-III fault-tolerant control schemes are proposed by using medium-voltage vectors to synthesize small-voltage vectors, in such a way that the mid-point voltage in a dc link can be stabilized well. Then, the short-circuit faults in both clamping switches and half-bridge switches are investigated. By analysis, their operation conditions are equivalent to conditions loss of both P and N voltage levels and open-phase faults, respectively. Thus, the corresponding remedial strategies can be applied accordingly. Particularly, a voltage compensation control method is proposed for conditions, where open-switch faults coexist with open-phase operation induced by short-circuit faults in half-bridge switches. The validity of all of theoretical analysis and the proposed remedial strategies has been verified by experiments. [ABSTRACT FROM PUBLISHER]

This paper proposes a new space-vector pulsewidth modulation (SV-PWM) strategy for a three-level neutral point clamped inverter. The presented SV-PWM strategy makes it possible to control the neutral point voltage by optimum choice of switch sequence for any position and length of output voltage vector. The proposed solution takes into consideration the unbalance of the dc-link voltages. It also analyzes the influence of vector sequences on the predicted unbalance of the dc-link voltage. The solution allows selecting optimum vectors and their on-time durations in order to reduce quickly the dc-link voltage unbalance. The calculation of the space vector area proposed in this paper takes into consideration voltage unbalance and its influence on the length and position of vectors. The proposed approach assures properly generating the voltage output vectors, even in the case of the existing large voltage unbalance in the dc-link. The results of the experimental investigation of the proposed modulation strategy are presented in this paper. [ABSTRACT FROM PUBLISHER]

Multilevel power electronic converters have gained popularity in high-power applications due to their lower switch voltage stress and modularity. Cascaded H-bridge converters are a promising breed of multilevel converters which generally require several separate dc voltage sources. By utilizing the redundant switching states, it is possible to replace the separate dc voltage sources with capacitors and keep only the one with the highest voltage level. Redundancy in the charge and discharge modes of the capacitors is assumed to be adequate for their voltage regulation. However, the effects of the output current of the converter as well as the time duration of the redundant switching states have been neglected. In this paper, the impacts of the connected load to the cascaded H-bridge converter as well as the switching angles on the voltage regulation of the capacitors are studied. This paper proves that voltage regulation is only attainable in a much limited operating conditions that it was originally reported. In addition, based on the analysis of the converter, a simplified formula is found which can be used to find those modulation indices that regulate the voltage of the capacitor. This formula can be used in harmonic minimization problems while capacitor voltage regulation is ensured. Simulation and laboratory results are provided to confirm the analysis. [ABSTRACT FROM PUBLISHER]

Most variable-speed ac generation systems use back-to-back converters to supply electrical energy, with fixed electrical frequency and voltage, to a stand-alone load or grid. Matrix converters (MCs) are a good alternative to back-to-back converters because they have several advantages in terms of size and weight. Therefore, MCs can be advantageously used in any variable-speed generation system where high efficiency, reliability, small size, and low weight are considered important factors. Nevertheless, to interface an MC-based generation system to an unbalanced 3\phi stand-alone load, a four-leg MC is required to provide a path for the zero-sequence load current. Space-vector-modulation (SVM) algorithms for the operation of four-leg MCs have been proposed in the literature. However, these modulation methods have high computational burdens, and they are difficult to implement, even in fast DSP-based control platforms. Therefore, only simulation results have been reported in these publications. In this paper, an SVM algorithm is optimized and experimentally tested. Moreover, the harmonics produced in the input current when a four-leg MC is feeding an unbalanced or nonlinear load are also mathematically analyzed in this paper, with experimental verification being provided. [ABSTRACT FROM AUTHOR]

Improved pulse regulation (IPR) control, a novel control technique for switching dc–dc converters, is proposed and studied in this paper. According to the output voltage and load current of the switching dc–dc converter, IPR control technique achieves output voltage regulation by generating control pulse train made up of some preset control pulses with different duty ratios. IPR control needs only comparators, triggers, and some simple logic devices, without error amplifier and the corresponding compensation circuit of pulse width modulation control scheme, thus IPR control scheme is easy to realize, benefits with excellent transient performance and stability. The principle and operation of IPR control scheme are introduced and illustrated with buck converter operating in discontinuous conduction mode as an example. Simulation and experimental results are presented to show that IPR-controlled converter has much lower output voltage ripple and more accurate output voltage regulation than PR converter. [ABSTRACT FROM PUBLISHER]

This paper presents a sliding mode control for a wound rotor synchronous machine acting as an isolated generator. The standard dq model of the machine is connected to a resistive load. A switching function is defined in order to fulfill control objectives, and the ideal sliding dynamics is proved to be stable. From the desired surface, the standard sliding methodology is applied to obtain a robust and very simple controller. Numerical simulations and experimental results validate the control law and show good performance and a fast response to load and reference changes. [ABSTRACT FROM AUTHOR]

An active-clamp forward (ACF) converter, which is popular in low-to-medium power applications, suffers from the high-voltage stress on switches, i.e., the sum of input voltage and reset capacitor voltage. To relieve this problem, a two-switch (2-SW) ACF converter, where the voltage stresses on the main switches are clamped to either the input voltage or the reset capacitor voltage by simply employing one clamping diode and a delayed turnoff gate signal, is proposed in this paper. Therefore, in view of utilizing high-performance low-voltage switches, the proposed 2-SW ACF converter can be promising for high-input-voltage applications. [ABSTRACT FROM AUTHOR]

A five-level flying-capacitor (FC)-based active-neutral-point-clamped (ANPC) converter is an arrangement of a three-level ANPC converter and a two-level cell. In this paper, a control strategy is proposed to regulate the voltage across the FCs at their respective reference voltage levels by swapping the switching patterns of the switches based on the polarity of the output current, the polarity of the FC voltage, and the polarity of the fundamental line-to-neutral voltage under selective harmonic elimination pulsewidth modulation. The voltage across the FCs and the dc-link capacitors are simultaneously controlled at their reference voltage levels. The proposed control strategy is applied using power system computer aided design/electromagnetic transients including dc on a static synchronous compensator operating under a power-factor-correction mode to verify its performance. Experimental results are also presented for low and high number of angles per quarter period using a low-power laboratory prototype. [ABSTRACT FROM AUTHOR]

With regard to a five-level inverter comprising flying-capacitor asymmetric H-bridge, the impact on the capacitor voltage under conventional modulation approach is analyzed. Since it is sensitive to the fundamental period and the load current, it may introduce undesired low-order harmonics into the output voltage and may even break down the power switches due to the considerable fluctuation of the flying-capacitor voltage. Thus, this paper proposes a novel pulsewidth-modulation scheme with the positive and negative cross carriers, which controls the flying-capacitor voltage by utilizing the redundant switching states of the output voltages. Three modes of precharging the flying capacitor without extra equipments are presented. Moreover, the capacitance of the flying capacitor and the switching frequency of the power switches can be chosen according to the allowable fluctuation of the flying-capacitor voltage and the load current. In order to remove the overlapping of the level layers, the optimization of the line-to-line voltage waveform is proposed to synthesize the reference vector with the “nearest three-vector” approach. The theory is supported by the experimental results from the prototype. [ABSTRACT FROM AUTHOR]

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 dynamic overmodulation strategy for fast dynamic torque control in direct torque control (DTC)-hysteresis-based induction machine is proposed. The fastest dynamic torque response with a six-step mode can be achieved in the proposed method by switching only the most optimized voltage vector that produces the largest tangential component to the circular flux locus. This paper also discusses the performance of dynamic torque control in basic DTC in order to justify on how the proposed selected voltage vector results in excellent dynamic torque performance. The main benefit of the proposed method is its simplicity, since it only requires a minor modification to the conventional DTC-hysteresis-based structure and does not require a space vector modulator. To verify the feasibility of the proposed dynamic overmodulation strategy, simulation and experimentation, as well as comparison with the conventional DTC scheme, are carried out. Results showed a significant improvement in the dynamic torque response when compared to the conventional DTC-hysteresis-based method. [ABSTRACT FROM PUBLISHER]

This paper presents a flyback switch-mode rectifier (SMR) with spread harmonic spectrum. The SMR switching control is conducted by a charge-regulated pulsewidth modulation (PWM) scheme with constant turn-on period. The inherently stable discontinuous conduction mode operation is preserved to yield good line drawn power quality. In voltage loop, a quantitatively designed PI feedback controller is augmented with a robust error cancellation control scheme. Further improved dc output voltage regulation and input power quality performances are achieved under varied operating conditions. In spread harmonic spectrum control, the harmonic spectral properties of the developed flyback SMR are first analyzed. Then, the dedicated random switching scheme is developed to let its switch current harmonic spectrum be dispersedly distributed. In the proposed random switching scheme, the PWM turn-off period is modulated using 1-b binary sequence, pseudo random binary sequence, and 4-b binary sequences. Under randomized harmonic spectrum, the SMR control performances are not sacrificed. [ABSTRACT FROM PUBLISHER]

This paper suggests an isolated dc/dc converter using an unregulated LLC converter for fuel cell applications. The LLC converter operates as an isolated voltage amplifier with a constant voltage gain, and a nonisolated converter installed in the input stage regulates the output voltage under a wide variation of fuel cell stack voltage. By separating the functions, the unregulated LLC converter can be operated at an optimal switching condition, and the high-frequency operation of 300 kHz can be accomplished without introducing an excessive switching loss. The prototype converter with a 1-kW design (Vin = 24 \sim 48\ \V/Vo = 400\ \V) shows an efficiency of above 90.2% under a 24-V input and full load conditions. [ABSTRACT FROM AUTHOR]

This paper describes a novel switching signal generator for three-phase voltage source inverters. Unlike conventional space-vector pulsewidth modulation (SVPWM) which achieves three-phase input voltage by a combination of the basic space vectors, the proposed scheme produces optimal switching commands to minimize the filtered measure of quantization error. Under specific selections of the filter matrix and the quantization scheme, it is shown that the proposed modulator is equivalent to SVPWM. An experimental platform is built to verify the effectiveness of the proposed scheme. It is shown that the switching number of the proposed method is reduced without sacrificing the harmonic distortion within the input frequency band under various reference signals. [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 novel three-phase diode boost rectifier is proposed in this paper. The core of the proposed topology is a power conversion device [the loss-free transformer (LFT)] with two terminals; one input and one output. The input is parallel-connected with the dc bus capacitor, while the output is connected between the rectifier plus rail and the dc bus plus rail. The LFT is controlled in such a way to control the rectifier current and boost the dc bus voltage. In contrast to the ordinary boost rectifiers, the switches of the new boost rectifier are rated on a fraction of the dc bus voltage and a fraction of the input current. It makes this topology very compact and efficient. Power rating, size, and losses depend strongly on the ratio of the dc bus voltage to rectifier voltage (boosting factor). For example, if the boosting factor is low, below 1.5, the power converter efficiency could be 98–99%. The proposed boost rectifier has been analyzed and experimentally verified on a 5.5-kW prototype. The results are presented and discussed. [ABSTRACT FROM AUTHOR]

Multilevel cascaded H-bridge converters have found industrial application in the medium-voltage high-power range. In this paper, a generalized modulation technique for this type of converter based on a multidimensional control region is presented. Using the multidimensional control region, it is shown that all previous modulation techniques are particularized versions of the proposed method. Several possible solutions to develop a specific implementation of the modulation method are addressed in order to show the potential possibilities and the flexibility of the proposed technique. In addition, a feedforward version of this technique is also introduced to determine the switching sequence and the switching times, avoiding low harmonic distortion with unbalanced dc voltages. Experimental results are shown in order to validate the proposed concepts. [ABSTRACT FROM AUTHOR]

An input filter is necessary for a matrix converter (MC) system to improve the input current quality with low harmonic components, as well as to reduce the input voltage distortion supplied to the MC. However, the input filter's characteristics make the input power factor (IPF) obtained at unity only in the presence of high output loads, and the IPF degrades significantly under light-load conditions. In this paper, we propose a new direct space vector modulation (DSVM) method to achieve the required displacement angle between the input voltage and input current of the MC. A new switching strategy is introduced based on the maximum compensated angle. Then, power factor compensation algorithms using the new DSVM method to achieve the maximum IPF are presented, in which compensation algorithm I is based on using the input filter and power supply parameters to estimate the optimal compensated angle. Compensation algorithm II is subsequently proposed using a proportional–integral controller to overcome drawbacks presented in compensation algorithm I. Simulation and experimental results are shown to validate the effectiveness of the proposed compensation algorithms. [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]