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The paper deals with some new results on the averaging theory approach for the analysis of feedback controlled pulsewidth modulation power electronic converters. It develops some considerations regarding the averaging approximation of time-variant differential systems proving an analytical relationship between the accuracy with which the solution of the averaged model converges to the solution of the original time-variant model (i.e., the switched model) and the switching frequency of the converters. This relation is valid both for stable and unstable systems. Moreover, this paper confirms, as corollary, that under suitable conditions (verified during the standard operations of the power electronic converters) the averaged model uniformly converges to the switched model. [ABSTRACT FROM AUTHOR]

The modeling and control of a buck–boost and stacked dual half-bridge (DHB) integrated bidirectional dc–dc converter have been studied in this paper. This converter features high-voltage transfer ratio, high efficiency, and the minimum number of switches. In this paper, an extended, continuous, full-order, state-space averaging modeling method is proposed. Compared with existing methods, the proposed method exhibits higher coincidence with the switching circuit simulation, in steady and especially dynamic states. Due to its high dynamic accuracy and low complexity, the proposed modeling method provides a better theoretical analysis and a fast simulation tool for transient process and control design of converters with dual-active-bridge units, especially with DHB units. By using this method, the high-frequency transformer series inductance current is directly divided into a sampled dc component and a fluctuant component. Only the sampled dc one is included into state variables, but both components are considered into state equations. Besides, this method regards the entire converter as a linear superposition of its subsections, which provides a stepwise modeling based on linearization of subsections. Moreover, a decoupled proportional-integral control method is proposed to enhance the stability and dynamic response of the converter. This control method is analyzed by the proposed models, which can be regarded as an application of the proposed modeling method. Simulation and experiments have validated both the proposed modeling and the decoupled control strategy. [ABSTRACT FROM PUBLISHER]

This paper introduces a novel five-level nested neutral point piloted (NNPP) converter and analyzes the operating principle of five-level NNPP converter. This paper presents a novel space vector pulse width modulation (SVPWM) algorithm based on gh coordinate for five-level NNPP converter. First, the common-mode voltage is reduced by choosing the appropriate redundant switching states. After that, the floating-capacitor voltage balance control strategy is presented. The appropriate switch combinations of each phase are determined by the control requirements of floating-capacitor voltages respectively and the hardware mapping method of the switching states is presented. Furthermore, the neutral-point voltage balance control strategy is presented. In order to balance the dc-link capacitor voltages, the seven-segment switching sequence is selected according to the control requirements of dc-link capacitor voltages and the neutral-point voltage regulatory factor is introduced to regulate the durations of the redundant switching states in a switching cycle. Finally, the validity of the novel SVPWM algorithm with decoupling control strategies of floating-capacitor voltages and dc-link capacitor voltages is verified by the experimental results of five-level NNPP converter under steady-state and dynamic conditions. [ABSTRACT FROM AUTHOR]

Magnetically coupled impedance-source (MCIS) networks are recently introduced impedance networks intended for various high-boost applications. It employs coupled magnetic in the circuit to achieve higher voltage gain. Various MCIS networks have been proposed in the literature for myriad applications; however, due to effective role of system modeling in the closed-loop controller design, this paper is allocated to small-signal modeling and analysis of MCIS converters. The modeling is performed by means of the circuit averaging and averaged switch technique. A generalized small-signal derivation is demonstrated for pulse width modulation (PWM) MCIS converters and it is shown that the derived transfer functions can simply be applied to Y-source, Γ-source, and T-source impedance networks. Various transfer functions for capacitor voltage, output voltage, magnetizing current, input and output impedance are derived and have been validated through frequency and dynamic responses of computer simulation results. In addition, a comprehensive analysis has been done for all mentioned PWM MCIS converters regarding their circuit parameters. Furthermore, the effect of considering the equivalent series resistances of capacitor and inductor on the stability margin of MCIS converters is revealed in this paper. Finally, in order to validate the derived transfer functions and to consolidate the perfumed analysis, experimental results are presented for all mentioned MCIS converters. [ABSTRACT FROM PUBLISHER]

The five-level active neutral-point-clamped (5L-ANPC) converter has been widely studied for its excellent performance in high-power medium-voltage applications. This paper analyzes the space vector pulse width modulation (SVPWM) strategy of the 5L-ANPC converter in the virtual coordinate, and presents an optimized control strategy which can balance the neutral point (NP) voltage and avoid the dead-time effects for the first time. In this strategy, on one hand, the 125 space vectors are combined by 96 triangles in the seven-segment vector synthesis method, then the triangles are divided into seven categories which have different characteristics of balancing the NP voltage, and every category has its own principles to choose the vector sequence and compute the vector durations. On the other hand, the dead-time effects of the 5L-ANPC converter are studied in detail and the transitions between different switching states are constrained in the optimized control strategy to avoid the dead-time effects that cannot be compensated by traditional pulse-based dead-time compensation methods. Finally, the optimized SVPWM strategy is experimentally verified in this paper. [ABSTRACT FROM AUTHOR]

Variable-speed multiphase (more than three phases) drive systems are seen as serious contenders to the existing three-phase drives due to their distinct advantages. Supply to the multiphase drives is invariably given from a voltage source inverter. However, this paper proposes an alternative solution for supplying multiphase drive system using a direct ac–ac converter called a matrix converter. This paper proposes the pulsewidth modulation (PWM) algorithm for the matrix converter topology with three-phase grid input and five-phase variable-voltage and variable-frequency output. The PWM control technique developed and presented in this paper is based on space vector approach. This paper presents the complete space vector model of the three-to-five-phase matrix converter topology. The space vector model yield 2^15 total switching combinations which reduce to 243 states considering the imposed constraints, out of which 240 are active and 3 are zero vectors. However, for space vector PWM (SVPWM) implementation, only 90 active and 3 zero vectors can be used. The SVPWM algorithm is presented in this paper. The viability of the proposed solution is proved using analytical, simulation, and experimental approaches. [ABSTRACT FROM AUTHOR]

This paper proposes a unified PWM method for matrix converters so as to establish a common platform which can generate various types of PWM methods in real time by adjusting the free parameters in the modulation algorithm. As a foundation for unification, the general form of the modulation functions for matrix converters is derived using geometric transformation approach. All eligible direct modulation matrices are shown to be of indirect form and are expressed in terms of instantaneous phase quantities. This paper also presents a new viewpoint to consider a matrix converter as a generalized three-level inverter and to apply the double-carrier-based dipolar modulation technique of the three-level inverter to the matrix converter. Several concepts of the two-level PWM inverters are then generalized to the matrix converters for better visualization and understanding of the modulation process. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems having rechargeable batteries are prone to be complex and costly because multiple converters are necessary to individually regulate a load, PV panel, and battery. This paper proposes novel nonisolated multiport converters (MPCs) integrating a bidirectional pulsewidth modulation (PWM) converter and phase-shift-switched capacitor converter (PS-SCC) for standalone PV systems. A PWM converter and PS-SCC are integrated by reducing the total switch count, realizing the simplified system and circuit. In the proposed MPCs, two control freedoms of duty cycle and phase shift angle are manipulated to individually regulate the load, PV panel, and/or battery. The detailed operation analysis was performed to mathematically derive gain characteristics and zero voltage switching operation boundaries. For the battery discharging mode, in which the PV panel is not available and the MPC behaves as a single-input–single-output converter with two control freedoms available, the optimized control scheme achieving the lowest rms current is also proposed to maximize power conversion efficiencies. Various kinds of experimental verification tests using a 200-W prototype were performed to verify the theoretical analysis and to demonstrate the performance of the proposed MPC. [ABSTRACT FROM AUTHOR]

Interleaving of voltage-source converter (VSC) legs enables higher output currents per phase, effectively increasing the power rating without increasing semiconductor ratings. However, the interleaved operation results in circulating currents between each phase converter legs as well as a zero-sequence circulating current (ZSCC), which become quite prominent when the converters operate with low switching frequencies. This paper demonstrates the interleaved operation of three-level converters under selective harmonic elimination pulsewidth modulation (SHE-PWM). A controller for the circulating current within the legs of each phase is also proposed. The controller is used in combination with optimally selected SHE-PWM patterns to generate the maximum number of voltage levels and minimize the peak value of the circulating current. Simulation and experimental results show the interleaved operation and the effect of SHE-PWM pattern selection in the overall system. [ABSTRACT FROM PUBLISHER]

Efficiency in a light load dc–dc converter is improved by reducing the switching frequency with the load current. Further, a bifrequency operation (BFO) using pulse train (PT) control can achieve spread spectrum. Using discrete-time models, this paper shows that a stable periodic BFO is generally not achievable in existing PT control methods. Thereafter, a unified multimode digital control technique is proposed, in which a voltage-mode digital pulse-width-modulator (DPWM) is used to control a predefined periodic BFO. Beside the fixed-frequency DPWM, an extra multiplexer is considered for real-time configuration to: 1) bifrequency pulse frequency modulation; 2) PT control; or 3) pulse regulation control; or 4) pulse skipping control with smooth transition. Analysis and design methods are discussed to ensure periodic BFO and to customize the power spectrum with predictable ripple parameters. A buck converter prototype is made, and the proposed control is implemented using an FPGA device. [ABSTRACT FROM PUBLISHER]

This paper presents a buck-boost dc-dc converter for LED drivers capable of delivering an output current ranging from 0.1 to 2 A and a variable output voltage ranging between 2 and 5 V, starting from an input voltage spanning from 2.7 to 5.5 V. The dc-dc converter, realized in a 0.18-μm CMOS technology with 5-V option, occupies an area of 4 mm2 including pads. The circuit features automatic mode switching and dynamic sizing of the power transistors to achieve a peak efficiency of 91%. With a switching frequency of 2.5 MHz, the achieved line regulation is lower than 0.1% V-1 and the output voltage ripple is less than 10 mV. The obtained turn-on and load transient settling time are lower than 40 μs, thus allowing pulsed operation of the LEDs, as well as switching among LEDs of different colors. [ABSTRACT FROM AUTHOR]

Distributed energy resources (DERs) are expected to provide ancillary functions including reactive power generation and harmonics compensation. Meanwhile, multilevel inverters and two-level converters with optimal pulsewidth modulation (OPWM) will be commonly used for DERs at high power levels. The challenge is to realize harmonic compensation with limited switching angles. This paper presents an online solution to realize the selective harmonics compensation (SHC), and power generation with DERs. For harmonics compensation, the selective harmonic components in the load current are detected. Then, the harmonic voltages are provided with DERs to cancel out these detected components. Since the power converter is requested to realize both harmonics filtering and power generation, limitations on harmonics compensation at the given power are discussed. Power hardware-in-the-loop-based online verifications are shown at the end of the paper. [ABSTRACT FROM AUTHOR]

Dynamic voltage restorer (DVR) technology has become a mature power quality product. In high-power applications, DVR using a multilevel converter is commonly used. However, DVR using a multilevel direct pulse width modulation (PWM) ac–ac converter has not been well studied. This paper presents a new DVR topology using a cascaded multilevel direct PWM ac–ac converter. In the proposed scheme, the unit cell of the multilevel converter consists of a single-phase PWM ac-ac converter using switching cell structure with coupled inductors. Therefore, the multilevel converter can be short- and open-circuited without damaging the switching devices. Neither lossy RC snubber nor a dedicated soft commutation strategy is required in the proposed DVR. This improves the reliability of the DVR system. The output voltage levels of the multilevel converter increase with the number of cascaded unit cells, and a high ac output voltage is obtained by using low-voltage-rating switching devices. Furthermore, a phase-shifted PWM technique is applied to significantly reduce the size of the output filter inductor. A 1-kW prototype of single-phase DVR is developed, and its performance is experimentally verified. Finally, the simulation results are shown for a three-phase DVR system. [ABSTRACT FROM AUTHOR]

This paper analyses the natural voltage-balancing characteristic of a three-phase flying capacitor multilevel converter when it is operated under the spectrally optimal Phase Disposition (PD) pulsewidth modulation (PWM) strategy. Using this analysis, it is shown that PD PWM has superior balancing characteristics compared to the phase-shifted carrier PWM strategy, because it places more spectral energy into the differential-mode sideband harmonics that drive the voltage-balancing process. From this understanding, an alternative balance booster filter network connection is proposed that significantly improves the natural balancing response of a flying capacitor converter for either PWM strategy. The analysis is confirmed by extensive simulation and experimental studies. [ABSTRACT FROM AUTHOR]

This paper presents a complete analysis of studying the impact of interleaving on the ripple current in the dc-side passive components of paralleled three-phase voltage-source converters (VSCs). The analysis considers the effects of different pulsewidth modulation scheme, the modulation index, the interleaving angle, and the power factor or displacement angle. In the analysis, the rms value of the total ripple current in the dc-side is used as figure of merit and calculated in the frequency domain. The results obtained show that all of the factors considered can strongly affect the rms value one way or another. Based on the analysis, the interleaving angle-optimization method is shown to minimize the rms in different cases. The effect of circulating currents on the ripple currents in the dc-side passive components is also taken into consideration to perform a more accurate analysis. All the analysis is based on an example system containing two VSCs, but the proposed analysis method in the frequency domain can be easily expandable for multiple paralleled VSCs. Experimental results are used to verify the analysis conducted. [ABSTRACT FROM AUTHOR]

This paper proposes a bidirectional three-level LLC resonant converter with a new pulse width and amplitude modulation control method. With different control signals, it has three different operation modes with different voltage gains. Therefore, it can achieve wide voltage gain range by switching among these three modes, which is attractive for energy storage system applications needing wide voltage variation. The proposed topology operates with constant switching frequency, which is easy to implement with digital control, and it can achieve soft switching for all the switches and diodes in the circuit as a conventional LLC resonant converter. The performance of the proposed converter is validated by the experimental results from a 1-kW prototype with 20 A maximum output current. [ABSTRACT FROM PUBLISHER]

This paper proposes a simplified space vector modulation (SVM) scheme for multilevel converters. Compared with earlier SVM methods, the proposed scheme simplifies the detection of the nearest three vectors and the generation of switching sequences, and therefore is computationally more efficient. Particularly, for the first time, the proposed scheme achieves the same easy implementation as phase-voltage modulation techniques. Another superior characteristic of the proposed scheme over earlier methods is its potential for multiphase multilevel applications. The proposed scheme also offers the following significant advantages: 1) independence of the level number of the converter; 2) more degrees of freedom, i.e., redundant switching sequences and adjustable duty cycles, to optimize the switching patterns; and 3) no need for lookup tables or coordinate transformations. These advantages make the proposed scheme well suited to large level-number applications, such as modular multilevel converters and high voltage direct current systems. Simulation and experimental results verify this new concept. [ABSTRACT FROM PUBLISHER]

The modular multilevel converter (MMC) has been a subject of increasing importance for medium/high-power energy conversion systems. Over the past few years, significant research has been done to address the technical challenges associated with the operation and control of the MMC. In this paper, a general overview of the basics of operation of the MMC along with its control challenges are discussed, and a review of state-of-the-art control strategies and trends is presented. Finally, the applications of the MMC and their challenges are highlighted. [ABSTRACT FROM AUTHOR]

This paper proposes a novel wide-range soft-switching pulse-width modulation three-level (TL) combined dc-dc converter characterized with no added primary clamping devices and reduced output inductance value. It is well suited for high input voltage dc-dc industrial applications due to following desirable features: all the switches sustain half of the input voltage; off state voltage of the switches is directly clamped by the bulky input capacitors, and no added primary clamping devices such as clamping diodes, flying capacitors, are required; TL waveform before output filter can be achieved, which significantly reduces the value of the output inductance; the modified phase-shift control method can be utilized to achieve wide output range. The converter can obtain zero-voltage switching (ZVS) for all power switches in wide load range; furthermore, less conduction loss is added to achieve ZVS. The operation and theoretical analysis of the proposed converter are presented. Experiments are carried out to validate the proposed converter, and efficiency curves are tested and given. [ABSTRACT FROM AUTHOR]

Hybrid cascade multilevel inverters combine semiconductor devices of different voltage ratings and technologies, which theoretically allow high efficiency to be achieved. The bottlenecks of these topologies are, however, the need for isolated supplies for the cells and the lack of modularity. This paper focuses on the design and control of high-resolution, high-efficiency multilevel inverters with simplified dc power supplies. It introduces several rules for systematically designing the dc voltages of the cells, for which all unsupplied capacitor voltages can be regulated. Six classes of inverters are obtained covering single- and three-phase, staircase and pulsewidth-modulated (PWM) inverters. New configurations of hybrid cascade multilevel inverters are obtained for each class. A double modulation strategy with two different frequencies is proposed that allows switching losses of PWM inverters to be reduced. Decoupled mechanisms are proposed for the total and internal energy balances. It is shown how to make the design robust by taking into account conversion losses and large dc-voltage imbalances in the design and control. An analysis of the maximum voltage utilization and efficiency of the resulting configurations is carried out. The effectiveness of the novel concepts is validated experimentally for two of the proposed topologies. [ABSTRACT FROM PUBLISHER]

This paper presents a unique modulation method for extending the input range of pulse-width modulation (PWM)-integrated resonant converters, such as the isolated boost resonant converter, while maintaining high conversion efficiency. The technique includes primarily the hybridizing of constant-on, constant-off, and fixed-frequency control depending only on the required duty cycle. The modulation scheme reduces core loss and conduction loss dramatically by decreasing the applied volt-seconds at the transformer and improving the switching period utilization. With hybrid-frequency control, the circuit also maintains zero current switching for the output diodes, minimizes switching loss, and eliminates circulating energy at the transformer across the entire operating range. It also allows for a predictable voltage gain, dependent only on duty cycle and transformer turns ratio. A detailed loss analysis is provided and verified against a 180 W experimental prototype, with an input range of 12–48 V and a switching frequency range of 30–70 kHz. Implementation issues are also handled with a variety of solutions for realizing the modulation scheme. Experimental results show greater than 4% weighted efficiency improvement in the prototype using the proposed method. [ABSTRACT FROM AUTHOR]

This paper extends the Z-source concept to matrix converters and explores a family of Z-source matrix converters. Their principles and characteristics are analyzed, and a simplified voltage-fed Z-source matrix converter is used as an example to demonstrate its operation, voltage gain versus modulation index, PWM method, boost control, and implementation of the control. Both simulation and experimental results verify operation of the proposed Z-source matrix converter, analytical results, and control method. The Z-source converters can achieve buck and boost operation with reduced number of switches needed, therefore achieving low cost, high efficiency, and reliability, compared to the traditional matrix converters. [ABSTRACT FROM AUTHOR]

This paper proposes the concept and the synthesis methodology of simplified zero-voltage-transition (ZVT) circuits applied to bidirectional pulsewidth modulation poles. The main goal of simplified ZVT circuits is to make possible the use of conventional modulation schemes to accomplish better converter performance and to eliminate the synchronous-switching requirements imposed by ZVT integrated multipole topologies. To derive the simplified ZVT circuits, a synthesis methodology is proposed based on the generalization of the ZVT technique, where the restrictions to achieve the zero-voltage switching for the main converter switches are identified. Thereafter, a set of simplified semiconductor switches composed by only one high-frequency switch is defined to be used in the simplified ZVT auxiliary circuits. Thus, using the proposed synthesis methodology, any simplified ZVT topology can be derived, whether or not they have appeared in a previous publication. In order to validate the proposed approach, experimental results for a three-phase ZVT inverter, employing the minimum-loss space vector modulation and operating at 1.5 kW and 20 kHz are presented. The prototype presented an efficiency of 98% at full load representing an improvement of 0.5% when compared to its hard-switched counterpart and 1.8% when compared to an integrated ZVT topology. [ABSTRACT FROM AUTHOR]

Rapid voltage and current transitions in switched-mode power converter circuits generate electromagnetic interference (EMI) which may interfere with other electronic systems. High-speed (e.g., wide bandgap) switching devices can improve circuit efficiency and compactness, but may increase the bandwidth of the interference generated. The peak interference is concentrated at harmonics of the fundamental switching frequency, and so may be reduced by modulating the converter switching frequency. However, converter topologies incorporating more than one switching device may not be suited to modulation of the switching frequency, and coordinated modulation of other pulse parameters is required to suppress interference. A relatively simple implementation of a hybrid pulse modulation technique is presented to suppress EMI in a quasi-Z-source converter comprising an impedance-source network and GaN-based H-bridge switching circuit. The technique uses two anharmonically related periodic signals to generate a modulated sawtooth carrier, which in turn generates coordinated switching pulses aperiodically modulated in position and width within a constant switching period. Experimental results demonstrated 10 dB suppression of the peak interference with negligible impact upon the converter's efficiency or output voltage. The proposed pulse modulation technique and its method of implementation are generic, and are expected to be widely applicable to other switched-mode dc–dc power converters. [ABSTRACT FROM AUTHOR]