Showing papers on "Pulse-width modulation published in 2017"
TL;DR: It is shown that both stability analysis methods can effectively determine the stability of the system and that the eigenvalue-based method cannot unambiguously predict sustained harmonic oscillations in voltage source converter (VSC) based high voltage dc (HVdc) systems caused by pulse-width modulation (PWM) switching.
Abstract: This paper investigates the small-signal stability of power electronics-based power systems in frequency domain. A comparison between the impedance-based and the eigenvalue-based stability analysis methods is presented. A relation between the characteristics equation of the eigenvalues and poles and zeros of the minor-loop gain from the impedance-based analysis have been derived analytically. It is shown that both stability analysis methods can effectively determine the stability of the system. In the case of the impedance-based method, a low phase-margin in the Nyquist plot of the minor-loop gain indicates that the system can exhibit harmonic oscillations. A weakness of the impedance method is the limited observability of certain states given its dependence on the definition of local source-load subsystems, which makes it necessary to investigate the stability at different subsystems. To address this limitation, the paper discusses critical locations where the application of the method can reveal the impact of a passive component or a controller gain on the stability. On the other hand, the eigenvalue-based method, being global, can determine the stability of the entire system; however, it cannot unambiguously predict sustained harmonic oscillations in voltage source converter (VSC) based high voltage dc (HVdc) systems caused by pulse-width modulation (PWM) switching. To generalize the observations, the two methods have been applied to dc-dc converters. To illustrate the difference and the relation between the two-methods, the two stability analysis methods are then applied to a two-terminal VSC-based HVdc system as an example of power electronics-based power systems, and the theoretical analysis has been further validated by simulation and experiments.
334 citations
TL;DR: In this article, the effect of the phase lead or lag on the active damping is investigated, and it is revealed that when the resonant frequency drifts away from its nominal value, the phase-lead or lag introduced by the notch filter may make itself fail to damp the resonance.
Abstract: Resonant poles of LCL filters may challenge the entire system stability especially in digital-controlled pulse width modulation (PWM) inverters. In order to tackle the resonance issues, many active damping solutions have been reported. For instance, a notch filter can be employed to damp the resonance, where the notch frequency should be aligned exactly to the resonant frequency of the LCL filter. However, parameter variations of the LCL filter as well as the time delay appearing in digital control systems will induce resonance drifting, and thus break this alignment, possibly deteriorating the original damping. In this paper, the effectiveness of the notch filter-based active damping is first explored, considering the drifts of the resonant frequency. It is revealed that when the resonant frequency drifts away from its nominal value, the phase lead or lag introduced by the notch filter may make itself fail to damp the resonance. Specifically, the phase lag can make the current control stable despite of the resonant frequency drifting, when the grid current is fed back. In contrast, in the case of an inverter current feedback control, the influence of the phase lead or lag on the active damping is dependent on the actual resonant frequency. Accordingly, in this paper, the notch frequency is designed away from the nominal resonant frequency to tolerate the resonance drifting, being the proposed robust active damping. Simulations and experiments performed on a 2.2-kW three-phase grid-connected PWM inverter verify the effectiveness of the proposed design for robust active damping using digital notch filters.
321 citations
TL;DR: In this article, a dual-bridge LLC resonant converter for wide input applications is proposed and the topology is an integration of a half-bridge (HB) LLC circuit and a full-bridge circuit.
Abstract: This paper proposes a dual-bridge (DB) LLC resonant converter for wide input applications. The topology is an integration of a half-bridge (HB) LLC circuit and a full-bridge (FB) LLC circuit. The fixed-frequency pulsewidth-modulated (PWM) control is employed and a range of twice the minimum input voltage can be covered. Compared with the traditional pulse frequency modulation (PFM) controlled HB/FB LLC resonant converter, the voltage gain range is independent of the quality factor, and the magnetizing inductor has little influence on the voltage gain, which can simplify the parameter selection process and benefit the design of magnetic components as well. Over the full load range, zero-voltage switching (ZVS) and zero-current switching (ZCS) can be achieved for primary switches and secondary rectifier diodes, respectively. Detailed analysis on the modulation schedule and operating principle of the proposed converter is presented along with the converter performance. Finally, all theoretical analysis and characteristics are verified by experimental results from a 120-V to 240-V input 24 V/20 A output converter prototype.
225 citations
TL;DR: Analysis of the parameters of LCL-filter design in order to understand its significance in grid-connected applications and results demonstrate the efficacy of the proposed method in terms of total harmonic distortion, harmonic attenuation, and reactive power compensated.
Abstract: LCL -filters are preferred over conventional L -filters for grid-connected voltage-source inverters (VSIs) due to their superior harmonic attenuation and smaller filter size and weight. The LCL -filter design process is complex and takes an iterative approach due to the considerations of resonance damping, reactive power compensation, harmonic attenuation limits, etc. This paper analyses the parameters of LCL -filter design in order to understand its significance in grid-connected applications. Secondly, based on the analysis, relationships between the resonance frequency, attenuation of switching ripple, reactive power production, and the ratio between the grid-side inductor and the inverter-side inductor are used to realize a simple LCL -filter design algorithm. The design considers LCL -filter as a single filtering unit rather than individual filtering contributions from passive components. The design is verified by simulations in MATLAB and validated experimentally via a hardware prototype. Results demonstrate the efficacy of the proposed method in terms of total harmonic distortion, harmonic attenuation, and reactive power compensated.
189 citations
TL;DR: In this paper, a three-phase voltage source inverter (VSI) topology is proposed to reduce the common mode (CM) voltage and electromagnetic interference (EMI) of electric motor drives.
Abstract: This letter presents a three-phase voltage source inverter (VSI) topology to reduce the common mode (CM) voltage and electromagnetic interference (EMI) of electric motor drives. Instead of using filters, active or passive, or specific pulse width modulated (PWM) techniques to reduce the CM voltage, the proposed topology has inherently less CM voltage generation. With the addition of two switches placed in series on the dc lines, this topology effectively reduces the CM voltage during zero switching states by “floating” the inverter from the dc source. This topology can be implemented with any PWM method and does not add any additional complexity to the standard control techniques. The operation and CM reduction capability of the topology is first demonstrated in simulation and then verified with experimental results. A comparison of both common mode voltage and EMI is made to a conventional three-phase VSI to demonstrate the effectiveness of the proposed topology.
167 citations
TL;DR: In this paper, an isolated dc-dc three-port converter (TPC) based on an interleaved-boost full-bridge converter with pulsewidth modulation (PWM) and phase-shift control for hybrid renewable energy systems is presented.
Abstract: This paper presents the design, modeling, and control of an isolated dc-dc three-port converter (TPC) based on an interleaved-boost full-bridge converter with pulsewidth modulation (PWM) and phase-shift control for hybrid renewable energy systems. In the proposed topology, the switches are driven by phase-shifted PWM signals, where both phase angle and duty cycle are the controlled variables. The power flow between the two inputs is controlled through the duty cycle, whereas the output voltage can be regulated effectively through the phase shift. The primary-side MOSFETs can achieve zero-voltage-switching (ZVS) operation without additional circuitry. Additionally, due to the ac output inductor, the secondary-side diodes can operate under zero-current-switching (ZCS) conditions. In this study, the operation principles of the converter are analyzed and the critical design considerations are discussed. The dynamic behavior of the proposed ac-inductor-based TPC is investigated by performing state-space modeling. Moreover, the derived mathematical models are validated by simulation and measurements. In order to verify the validity of the theoretical analysis, design, and power decoupling control scheme, a prototype is constructed and tested under the various modes, depending on the availability of the renewable energy source and the load consumption. The experimental results show that the two decoupled control variables achieve effective regulation of the power flow among the three ports.
166 citations
TL;DR: The proposed PWM technique minimizes the leakage current of the PV array and electromagnetic interference filter requirement in the system without addition of any extra switches.
Abstract: This paper presents a pulse width modulation (PWM) technique for the minimization of the leakage current in the grid-connected/stand-alone transformerless photovoltaic (PV)-cascaded multilevel inverter (CMLI). The proposed PWM technique is integrated with the MPPT algorithm and is applied to the five-level CMLI. Furthermore, using the proposed PWM technique the high-frequency voltage transitions in the terminal and common mode voltages are minimized. Thus, the proposed PWM technique minimizes the leakage current of the PV array and electromagnetic interference filter requirement in the system without addition of any extra switches. Furthermore, this paper also presents the analysis for the terminal voltage across the PV array and the common mode voltage of the inverter based on the switching function. Using the given analysis, the effect of the PWM technique can be analyzed, as it directly links the switching function with the common mode voltage and leakage current. Also, the proposed PWM technique requires reduced number of carrier waves compared to the conventional sinusoidal pulse width modulation technique for the given CMLI. Complete details of the working principle and analysis with the support of simulation and experimental results of the proposed PWM technique are presented in this paper.
161 citations
TL;DR: In this paper, an improved high-frequency square-wave voltage injection algorithm was proposed, which is robust to voltage errors without any compensations meanwhile has less fluctuation in the position estimation error.
Abstract: Rotor position estimated with high-frequency (HF) voltage injection methods can be distorted by voltage errors due to inverter nonlinearities, motor resistance, and rotational voltage drops, etc. This paper proposes an improved HF square-wave voltage injection algorithm, which is robust to voltage errors without any compensations meanwhile has less fluctuation in the position estimation error. The average position estimation error is investigated based on the analysis of phase harmonic inductances, and deduced in the form of the phase shift of the second-order harmonic inductances to derive its relationship with the magnetic field distortion. Position estimation errors caused by higher order harmonic inductances and voltage harmonics generated by the SVPWM are also discussed. Both simulations and experiments are carried out based on a commercial PMSM to verify the superiority of the proposed method and the investigations in this paper.
159 citations
TL;DR: An open-circuit insulated-gate bipolar transistor fault detection technique for cascaded H-bridge (CHB) multilevel converters is presented in this paper and experimentally obtained data demonstrate the efficacy of the proposed fault detection and isolation technique.
Abstract: An open-circuit insulated-gate bipolar transistor fault detection technique for cascaded H-bridge (CHB) multilevel converters is presented in this paper. This technique, designed to be implemented independently for each CHB leg, utilizes one current sensor and one voltage sensor to monitor a leg's current and output voltage. Measured voltages are compared to expected voltages, and deviations are used to determine open-circuit fault locations based on the deviation's magnitude and current flow direction. Once potential fault locations have been identified, the fault location is systematically isolated and then verified, reducing the possibility of unnecessary corrective actions due to fault misidentification, e.g., an intermittent gate-misfiring fault being classified as an open-circuit fault. The proposed technique can be implemented for any number of cells, is independent of the pulse width modulation strategy used, and can be applied to symmetric and asymmetric CHB converters regardless of the cell input dc-source magnitudes utilized, i.e., cell input voltages are not required to be equal or to exist in specific ratios. For a CHB leg with $M$ cells, the proposed technique identifies and isolates open-circuit switch faults in less than $2M$ measurement (sampling) cycles, and verification is completed in less than one full fundamental cycle. Experimentally obtained data demonstrate the efficacy of the proposed fault detection and isolation technique.
153 citations
TL;DR: In this article, the basic concept of four different types of multilevel converter: the neutral-point clamped, flying capacitor, cascaded H-bridge and modular is presented.
Abstract: The multilevel converter, (MC) had been recommended for high- and medium-level power applications for decades. It is one of the most popular converters due to its ability to decrease the harmonic distortion in the output waveform without decreasing the converter power output. This paper presents the basic concept of four different types of multilevel converter: the neutral-point clamped, flying capacitor, cascaded H-bridge and modular. This paper also reviews five different modulation techniques for multilevel converters: pulse width modulation, space vector pulse width modulation, phase shifted carrier pulse width modulation, sinusoidal pulse width modulation and selective harmonic elimination pulse width modulation. In addition, recent publications regarding developments and improvements of fundamental concern to MCs and modulation techniques are reviewed in this paper. The implementation of MCs within renewable energy systems is also discussed here.
152 citations
TL;DR: A novel three-phase parallel grid-connected multilevel inverter topology with a novel switching strategy is proposed to feed a microgrid from renewable energy sources (RES) to overcome the problem of the polluted sinusoidal output in classical inverters and to reduce component count.
Abstract: In this paper, a novel three-phase parallel grid-connected multilevel inverter topology with a novel switching strategy is proposed. This inverter is intended to feed a microgrid from renewable energy sources (RES) to overcome the problem of the polluted sinusoidal output in classical inverters and to reduce component count, particularly for generating a multilevel waveform with a large number of levels. The proposed power converter consists of $n$ two-level $(n+1)$ phase inverters connected in parallel, where $n$ is the number of RES. The more the number of RES, the more the number of voltage levels, the more faithful is the output sinusoidal waveform. In the proposed topology, both voltage pulse width and height are modulated and precalculated by using a pulse width and height modulation so as to reduce the number of switching states (i.e., switching losses) and the total harmonic distortion. The topology is investigated through simulations and validated experimentally with a laboratory prototype. Compliance with the $\text{IEEE 519-1992}$ and $\text{IEC 61000-3-12}$ standards is presented and an exhaustive comparison of the proposed topology is made against the classical cascaded H-bridge topology.
TL;DR: In this article, a model predictive control (MPC) strategy that combines finite-control-set MPC with selective harmonic elimination (SHE) modulation pattern in its formulation is proposed to govern multilevel power converters.
Abstract: In this study, a model predictive control (MPC) strategy that combines finite-control-set MPC with selective harmonic elimination (SHE) modulation pattern in its formulation is proposed to govern multilevel power converters. Based on a desired operating point for the system state (converter current reference), an associated predefined SHE voltage pattern is obtained as a required steady-state control input reference. Then, the cost function is formulated with the inclusion of both system state and control input references. According with the proposed reference and cost function formulation, the predictive controller prefers to track the converter output current reference in transients, while preserving the SHE voltage pattern in steady state. Hence, as evidenced by experimental results, a fast dynamic response is obtained throughout transients while a predefined voltage and current spectrum with low switching frequency is achieved in steady state.
TL;DR: In this article, an automatic switched-coupling-capacitor equalizer (SCCE) is proposed, which can realize the any-cells-to-any-cells equalization for a battery string.
Abstract: Due to the low cost, small size, and easy control, the switched-capacitor (SC) equalizer is promising among all types of active cell balancing methods. However, the balancing speed is generally slow and the balancing efficiency is seriously low when the SC equalizer is applied into a long battery string. Therefore, an automatic switched-coupling-capacitor equalizer (SCCE) is proposed, which can realize the any-cells-to-any-cells equalization for a battery string. Only two switches and one capacitor are required for each battery cell. All mosfet s are controlled by one pair of complementary pulse width modulation signals, and energy can be automatically and directly delivered from any higher voltage cells to any lower voltage ones without the need of cell monitoring circuits, leading to a high balancing efficiency and speed independent of the cell number and the initial cell voltages. Contrary to the conventional equalizers using additional components for the equalization among modules, the proposed equalizer shares a single converter for the equalization among cells and modules, resulting in smaller size and lower cost. A prototype for four lithium battery cells is implemented, and an experimental comparison between the proposed SCCE and the conventional SC equalizer is presented. Experimental results show the proposed topology exhibits a substantially improved balancing performance, and the measured peak efficiency is 92.7%.
TL;DR: A hybrid control method combining pulse frequency modulation (PFM) and pulse width modulation is proposed to overcome the limited frequency resolution issue and improve voltage regulation performance for LLC resonant converters.
Abstract: High switching frequency is an effective method to improve power density for LLC resonant converters. However, conventional digital controllers, such as general-purpose digital signal processors and microprocessors, have limited frequency resolution, which induces high primary- and secondary-side current variation and leads to poor output voltage regulation. In this paper, a hybrid control method combining pulse frequency modulation (PFM) and pulse width modulation is proposed to overcome the limited frequency resolution issue. The proposed hybrid control method focuses on steady-state operation, and its operating principles are introduced and analyzed. In addition, the proper magnetizing inductance and dead time duration are derived to ensure that the power mosfet s achieve zero voltage switching with the proposed control method. The improved voltage regulation performance is compared with the conventional PFM control and verified through simulation and experimental results using a 240 W prototype converter operating at a switching frequency of 1 MHz.
TL;DR: A novel zero voltage vector sampling method (ZVVSM) is proposed, which can move the current reconstruction dead zones in low modulation region and sector boundary regions toward the outline of the space vector hexagon without modifying PWM signal.
Abstract: For the purpose of reducing cost and volume, techniques of reconstructing three-phase currents through a single current sensor have been reported for permanent magnet synchronous motor vector control system. In existing studies, the reconstruction precision is largely affected by the dead zones in space vector PWM plane, which requires additional efforts to compensate the dead zones either by modifying pulse width modulation (PWM) modulation strategy or by phase-shifting of PWM signal. In this paper, a novel zero voltage vector sampling method (ZVVSM) is proposed, which can move the current reconstruction dead zones in low modulation region and sector boundary regions toward the outline of the space vector hexagon without modifying PWM signal. By arranging the single current sensor at a novel position, the proposed method is able to sample current in two zero voltage vectors (ZVV). ZVVSM avoids the complicated algorithms as well as the increase of the switching times, so that it is beneficial to the PMSM drive performance. The proposed method is validated by both simulation and experiments.
TL;DR: In this article, identical modular magnetic-links are proposed for high-power transmission and isolation between the low and the high voltage sides, which shows better frequency spectra as well as reduced switching loss.
Abstract: The high-frequency common magnetic-link made of amorphous material, as a replacement for common dc-link, has been gaining considerable interest for the development of solar photovoltaic medium-voltage converters. Even though the common magnetic-link can almost maintain identical voltages at the secondary terminals, the power conversion system loses its modularity. Moreover, the development of high-capacity high-frequency inverter and power limit of the common magnetic-link due to leakage inductance are the main challenging issues. In this regard, a new concept of identical modular magnetic-links is proposed for high-power transmission and isolation between the low and the high voltage sides. Third harmonic injected sixty degree bus clamping pulse width modulation and third harmonic injected thirty degree bus clamping pulse width modulation techniques are proposed which show better frequency spectra as well as reduced switching loss. In this paper, precise loss estimation method is used to calculate switching and conduction losses of a modular multilevel cascaded converter. To ensure the feasibility of the new concepts, a reduced size of 5 kVA rating, three-phase, five-level, 1.2 kV converter is designed with two 2.5 kVA identical high-frequency magnetic-links using Metglas magnetic alloy-based cores.
TL;DR: In this article, a modulation method for a full-bridge three-level LLC resonant converter is proposed to enable fixed frequency operation, small resonant inductance ratio and zero-current switching operation of rectifier diodes under wide output-voltage variation.
Abstract: This paper proposes a modulation method for a full-bridge three-level LLC resonant converter The target converter is known to enable fixed frequency operation, small resonant inductance ratio, and zero-current switching operation of rectifier diodes under wide output-voltage variation Therefore, it is suitable for an application such as in battery chargers A new parameter named “master duty,” which determines each voltage-level duty, is introduced to this modulation method It simplifies the modulation method; therefore, a modification of the modulation is easy It also makes possible seamless handling of two-level, three-level, and mixed modes The modulation method is represented by the relationship between the master duty and each gate-pulse edge position This representation can clearly depict a complex modulation such as a combination of pulse-width and phase-shift modulations The voltage gain of the converter is analyzed using the first-harmonic approximation technique The result of the analysis is verified by the circuit simulation The voltage gain is also analyzed using lossy components, which is verified by the experimental result A 385-V input 225- to 378-V/66-kW output prototype converter is fabricated for this verification It shows 9814% peak efficiency, and its power density is 1036 W/L
TL;DR: An improved cascaded multilevel inverter (CMLI) based on a highly efficient and reliable configuration for the minimization of the leakage current and reduction in the size of electromagnetic interference filters is presented.
Abstract: This paper presents an improved cascaded multilevel inverter (CMLI) based on a highly efficient and reliable configuration for the minimization of the leakage current. Apart from a reduced switch count, the proposed scheme has additional features of low switching and conduction losses. The proposed topology with the given pulse width modulation (PWM) technique reduces the high-frequency voltage transitions in the terminal and common-mode voltages. Avoiding high-frequency voltage transitions achieves the minimization of the leakage current and reduction in the size of electromagnetic interference filters. Furthermore, the extension of the proposed CMLI along with the PWM technique for 2 m + 1 levels is also presented, where m represents the number of photovoltaic (PV) sources. The proposed PWM technique requires only a single carrier wave for all 2 m + 1 levels of operation. The total harmonic distortion of the grid current for the proposed CMLI meets the requirements of IEEE 1547 standard. A comparison of the proposed CMLI with the existing PV multilevel inverter topologies is also presented in the paper. Complete details of the analysis of PV terminal and common-mode voltages of the proposed CMLI using switching function concept, simulations, and experimental results are presented in the paper.
TL;DR: A single-phase version of SSI with improvements in inverter topology as well as the pulse width modulation (PWM) technique is presented with the merit of simplicity since the control of dc-link voltage and ac output is detached within the single-stage topology.
Abstract: A single-stage topology of a three-phase boost inverter known as split-source inverter (SSI) has recently been introduced in the literature. This topology suffers from high frequency current commutations across two diodes and complicated analysis since the inductor is charged with variable duty cycle. This paper presents a single-phase version of SSI with improvements in inverter topology as well as the pulse width modulation (PWM) technique. An inductor is connected to two MOSFETs operating at fundamental frequency to boost the voltage from input source to dc-link voltage. In the proposed hybrid quasi-sinusoidal and constant PWM, one of the full-bridge legs undergoes constant duty cycle switching while the other one undergoes sinusoidally varying duty cycle switching, with the former is accountable for charging and discharging of inductor while the latter is accountable for producing ac output. Therefore, the proposed topology with hybrid quasi-sinusoidal and constant PWM exhibits the merit of simplicity since the control of dc-link voltage and ac output is detached within the single-stage topology. It is not liable to the undesired high frequency current commutation. In addition, a wide range of ac output voltage is achievable in either buck or boost operation. Theoretical analysis is presented and verified through simulation and experimental results.
TL;DR: In this paper, the second-order torque harmonics produced by dc-capacitor voltage fluctuations are first demonstrated, and a very simple compensation method is presented by introducing a novel nonorthogonal coordinate transformation.
Abstract: As a result of their reduced number of switches, three-phase four-switch (TPFS) inverters are generally applied as cost-reduction topologies for permanent magnet synchronous motor (PMSM) drives. However, the torque ripples of PMSM severely deteriorate the performance and reliability of the entire system. Hence, comprehensive considerations for torque ripple reduction, including high- and low-frequency torque ripples, are elaborated considering TPFS inverter-fed PMSM drives. The second-order torque harmonics produced by dc-capacitor voltage fluctuations are first demonstrated, and a very simple compensation method is presented by introducing a novel nonorthogonal coordinate transformation. Then, to evaluate the effects on the high-frequency torque ripples of space vector modulation (SVM) schemes, three SVM schemes for TPFS inverter-fed PMSM drives are assessed based on the torque ripple root-mean-square value. Consequently, the preferred SVM scheme is obtained for high-frequency torque ripple minimization. Moreover, the linear modulation range of the TPFS inverter-fed PMSM drive is derived considering capacitor voltage fluctuations, therein avoiding the low-frequency torque ripples caused by overmodulation. Meanwhile, an adaptive capacitor voltage offset suppression method is proposed to fully exploit the dc-link voltage. The experimental results demonstrate the validation and effectiveness of the proposed analysis and methods for torque ripple reduction.
TL;DR: The proposed FSP ϕ-OTDR uses optical pulses with linear frequency modulation with higher pulse energy for longer sensing fiber and uses matched filter in the receiver to compress the processed pulse width, so the contradiction between spatial resolution and the working distance in ordinary ϕ -OTDR is relaxed.
Abstract: A high spatial resolution phase-sensitive optical time domain reflectometer (ϕ-OTDR) with an optical frequency-swept pulse (FSP) is proposed, and the experimental results are presented in the Letter. The FSP ϕ-OTDR uses optical pulses with linear frequency modulation with higher pulse energy for longer sensing fiber and uses matched filter in the receiver to compress the processed pulse width. Thus, the contradiction between spatial resolution and the working distance in ordinary ϕ-OTDR is relaxed. A spatial resolution of 30 cm, a sensing distance of 19.8 km, and a signal-to-noise ratio of 10 dB for vibration sensing were obtained experimentally. To our best of our knowledge, this is the first time that a sub-meter spatial resolution over such a long sensing range has been reported in ϕ-OTDR sensors.
TL;DR: In this article, a single-phase, single-stage buck-boost inverter for photovoltaic (PV) systems is proposed, which eliminates common mode leakage current problem in the grid-connected PV applications.
Abstract: This paper proposes a single-phase, single-stage buck–boost inverter for photovoltaic (PV) systems. The presented topology has one common terminal in input and output ports which eliminates common mode leakage current problem in the grid-connected PV applications. Although it uses four switches, its operation is bimodal and only two switches receive high-frequency pulse width modulation signals in each mode. Its principle of operation is described in detail with the help of equivalent circuits. Its dynamic model is presented, based on which a bimodal controller is designed. Experimental results, in stand-alone and grid-connected mode, obtained with a 300-W laboratory prototype are presented to validate its performance.
TL;DR: A fast detection period and negligible current spikes are benefits for the drive using the same square-wave injection voltage for both the polarity detection and position estimation, and a smooth operation between two estimation methods is proposed.
Abstract: This paper aims to improve the full speed sensorless drive for permanent-magnet (PM) synchronous machines on the region of initial zero speed and the region of medium speed. At zero and low speed, the saliency-based drive using the square-wave voltage injection has demonstrated the comparable performance to the sensor-based drive using the encoder with hundreds of pulses per revolution. For PM machines at initial state, the magnet polarity is typically identified based on the injection of voltage pulses before the saliency-based drive. Instead of pulses injection, this paper directly adds the polarity detection capability in the saliency-based drive by superimposing the same square-wave voltage. A fast detection period and negligible current spikes are benefits for the drive using the same square-wave injection voltage for both the polarity detection and position estimation. At medium speed, electromotive force voltage can be estimated to replace the saliency for the sensorless drive. To achieve a smooth operation between two estimation methods, a transition algorithm is also proposed based on a single-phase-lock loop by blending two feedback position signals. According to the experimental evaluation, the reduced power consumption as well as the smooth switch between two different drives is achieved. All the sensorless methods are verified by an interior PM machine with a saliency ratio of 1.37 ( $L_{q}/ L_{d}\,= \,1.37$ ).
TL;DR: In this paper, a new module for multilevel inverters with reduced components is presented, which produces 25 levels using four asymmetrical DC voltage sources (two 1V DC and two 5V DC sources) and 10 semiconductor switches.
Abstract: This study presents a new module for multilevel inverters with reduced components Each module produces 25 levels using four asymmetrical DC voltage sources (two 1V DC and two 5V DC sources) and 10 semiconductor switches A significant advantage of the suggested module is its potentiality in producing voltage levels with negative polarity without any end side H-bridge inverter Therefore, switches with lower voltage ratings are used in its structure Series connection of the proposed structure leads to a modular topology which produces more voltage levels using reasonable number of switches, gate driver circuits, power diodes and less DC voltage sources These advantages are analysed by comparing this structure with other state-of-the-art topologies Selective harmonic elimination pulse width modulation (SHE-PWM) scheme is used to achieve output voltage with high quality To produce all voltage levels, two algorithms are proposed to determine DC voltage sources magnitude The accuracy of the suggested module performance in producing all voltage levels is verified by simulation and experimental results
TL;DR: This paper suggests another candidate for isolated/bidirectional dc/dc converter in electric vehicle on-board charger based on PWM resonant converter (RC) by analysis of the gain characteristics and the feasibility of bidirectional PWM-RC is verified.
Abstract: This paper suggests another candidate for isolated/bidirectional dc/dc converter in electric vehicle on-board charger based on PWM resonant converter (RC). The PWM-RC has good switching characteristics but it is not adequate for bidirectional applications because it is always operated under “buck type” operation regardless of power flow directions. This problem can be solved by structure change method, which increases the converter gain into double. Also, additional technique to increase the converter gain during discharging operation is suggested by analysis of the gain characteristics. The feasibility of bidirectional PWM-RC is verified with a 6.6-kW prototype charger.
TL;DR: In this paper, the Particle Swarm Optimization (PSO) approach is used to select and generate an optimal duty cycle which varies with photovoltaic parameters in order to extract the maximum power.
TL;DR: An improved virtual space vector modulation (IVSVM) scheme for a three-level active neutral-point-clamped (3L-ANPC) inverter to balanceneutral-point potential (NP), reduce switching loss, and suppress common mode voltage (CMV).
Abstract: This paper presents an improved virtual space vector modulation (IVSVM) scheme for a three-level active neutral-point-clamped (3L-ANPC) inverter to balance neutral-point potential (NP), reduce switching loss, and suppress common mode voltage (CMV). In the IVSVM scheme, an improved virtual medium vector (VMV) is synthesized by the original medium vector and the adjacent two pairs of the small vectors since there are always two pairs of the small vectors in any regions of the new space vector diagram. The improved VMV provides the flexibility to control the NP balancing under any modulation indexes and power factors in one switching cycle while achieving SL reduction and CMV suppression. This is achieved by the proper selection of two pairs of small vectors in terms of NP charge and the pulse sequence. The experimental platform based on a 3L-ANPC inverter is established and results obtained to verify the effectiveness of the IVSVM control strategy.
TL;DR: A modification of this conventional modulation method using variable shift angles between the power cells is introduced, which leads to the elimination of harmonic distortion of low-order harmonics due to the switching (triangular carrier frequency and its multiples) even under unbalanced operational conditions.
Abstract: Multilevel cascaded H-bridge converters have become a mature technology for applications where high-power medium ac voltages are required. Normal operation of multilevel cascaded H-bridge converters assumes that all power cells have the same dc voltage, and each power cell generates the same voltage averaged over a sampling period using a conventional phase-shifted pulse width modulation (PWM) technique. However, this modulation method does not achieve good results under unbalanced operation per H-bridge in the power converter, which may happen in grid-connected applications such as photovoltaic or battery energy storage systems. In the paper, a simplified mathematical analysis of the phase-shifted PWM technique is presented. In addition, a modification of this conventional modulation method using variable shift angles between the power cells is introduced. This modification leads to the elimination of harmonic distortion of low-order harmonics due to the switching (triangular carrier frequency and its multiples) even under unbalanced operational conditions. The analysis is particularized for a three-cell cascaded H-bridge converter, and experimental results are presented to demonstrate the good performance of the proposed modulation method.
TL;DR: In this article, a three-level space vector modulation (SVM) scheme was proposed for a system with two paralleled voltage-source converters (VSCs) with common-mode inductor (CMI) or single-phase inductors.
Abstract: For high-power applications, paralleling converters is a popular approach to increase the power capacity of the system. Circulating current has been a major concern for the implementation of paralleled converters. This paper proposes a three-level space vector modulation (SVM) scheme for a system with two paralleled voltage-source converters (VSCs) with common-mode inductor (CMI) or single-phase inductors. The proposed scheme aims to reduce the zero-sequence circulating current (ZSCC) and the magnitude of common-mode voltage (CMV) of the system simultaneously. The ZSCC patterns with respect to modulation schemes are first analyzed to provide a clear understanding of the generation of ZSCC. Based on the analysis, the proposed three-level modulation scheme is introduced. Furthermore, performance regarding the ZSCC peak value, impact on the common-mode current (CMC), CMI scaling analysis, and switching losses are analyzed and compared with the existing methods. The proposed method has been verified in both simulation and experiment.
TL;DR: In this article, a high step-up pulse width modulation dc-dc converter integrating coupled-induction and switched-capacitor (SC) techniques is presented, which consists of a synchronous rectification Boost unit and multiple coupled-Induction-SC units.
Abstract: In this paper, a novel high step-up pulse width modulation dc–dc converter integrating coupled-inductor and switched-capacitor (SC) techniques is presented. The proposed converter consists of a synchronous rectification Boost unit and multiple coupled-inductor-SC units. Its structure can therefore be easily extended for ultrahigh voltage gain. The diodes employed in the proposed converter can operate under soft-switching condition by utilizing leakage inductance of the coupled inductor. Low-voltage-rated transistors can be used to improve the efficiency as the voltage stress on the main switches of the proposed converter is reduced. The feasibility of the proposed converter is experimentally demonstrated by a 200 W prototype converter.