Phase-shifted Technique Research Articles

Phase-shifted third harmonic modulation technique for induction heating applications to improve soft switching capability

Phase-shifted third harmonic modulation technique for induction heating applications to improve soft switching capability

Sensorless Capacitor Voltage Detection Method of Cascaded H-Bridge STATCOM Based on Special Switching Mode Identification

The cascaded H-bridge (CHB) static synchronous compensator (STATCOM) has been widely used in wind farm and conflux station. As the grid-connected voltage increases, the number of cascaded CHB proportionately increases. In order to achieve the capacitor voltage balance, it is necessary to independently detect the capacitor voltage of all H-bridge cells, which raises the cost of capacitor voltage detection. To solve this problem, the mapping relationship is studied between the converter output voltage and capacitor voltages by analyzing carrier phase-shifted sinusoidal pulse width modulation technique (CPS-SPWM), and special switching mode is firstly found. Based on the above finding, without changing the conventional CHB topology, an improved sensorless detection method is proposed to solve the problems of detection error, large computation burden and the application limitation in existing sensorless detection methods. Compared with conventional sensor detection, this method not only saves DC voltage sensors and data transmission channels but also suppress the third harmonics in the converter current. Finally, the effectiveness of the detection method applied on CHB STATCOM is proved by simulation and experiment.

A Combinational Level-Shifted and Phase-Shifted PWM Technique for Symmetrical Power Distribution in CHB Inverters

In cascaded H-bridge (CHB) multilevel inverters (MLIs), phase-shifted pulse width modulation (PSPWM) and level-shifted pulse width modulation (LSPWM) are the two prominent techniques to attain multilevel and better performance. But both of them have certain drawbacks like in PSPWM the switching loss of all the semiconductors is high, and in LSPWM the power-sharing between the cascaded modules is not identical. These two drawbacks have been addressed in this article by proposing a novel modulation technique, named the phase opposed disposed phase-shifted PWM (PODPSPWM). In this technique, the level-shifted carriers have been rotated in such a way that there should not be any active power loss and simultaneously the carriers are phase-shifted as per the PSPWM technique. A detailed mathematical analysis of switching loss for all three methods has been presented. Moreover, the power-sharing and harmonic spectrum of the proposed PODPSPWM over other PWMs have been discussed. This novel modulation technique has been simulated in the MATLAB/Simulink software to validate the superiority of the operation. The 1.5-kW experimental prototype is developed to validate the performance of the proposed PODPSPWM modulation.

HERIC-Clamped and PN-NPC Inverters With Five-Level Output Voltage and Reduced Grid-Interfaced Filter Size

Transformerless grid-connected inverters with highly efficient and reliable inverter concept (HERIC) and positive-negative neutral point-clamped (PN-NPC) circuit configurations exhibit excellent performance in terms of overall efficiency, common-mode voltage, and alleviated leakage current concern. These inverters are designed to generate only a three-level (3 L) output voltage waveform, thereby reducing the power density of a conversion system. On the other hand, it is well-known that increasing the inverter output voltage levels entails the reduction of the output filter size. In this regard, this article aims to develop a five-level (5 L) inverter output voltage for the improved versions of HERIC-clamped and original PN-NPC inverters. This is achieved with either phase-shifted or level-shifted pulse width modulation technique leading to further quality improvement of ac voltage and current waveforms through increasing the number of output voltage levels. Therefore, a much smaller output filter size can be utilized, while the overall efficiency of the entire system is enhanced. Two laboratory-built SiC-based prototypes for both the proposed HERIC-clamped (1.8 kW) and PN-NPC-5 L (2 kW) inverters have been fabricated to show the feasibility and effectiveness of the proposed solution via experiments.

A Constant-Frequency High-Voltage Gain Resonant Converter Module With Semiactive Phase-Shifted Voltage Multiplier for MVdc Distribution

A constant-frequency step-up LLC resonant converter module that employs a new phase-shifted semiactive voltage multiplier technique is proposed in this article for a medium-voltage dc distribution grid. In the proposed converter, a wide voltage gain for different loading conditions can be realized by adaptively controlling the phase shift of the auxiliary switch in a voltage quadrupler-based semiactive voltage multiplier. Zero-voltage switching turn-on is always achieved for all the primary side switches with a constant-frequency operation. In the proposed semiactive voltage multiplier, zero-current switching (ZCS) turn-on is achieved for the auxiliary switch with ZCS operations provided for all the output diodes over a wide range of voltage gain and loading conditions. The operating principles of the proposed circuit are discussed in this article. Simulation results on a 120-kW, 10-kV output and experimental results on a modular laboratory-scale silicon carbide (SiC)-based 5-kW (per-module), 240–440-V/5-kV prototype are provided to demonstrate the performance of the proposed converter.

A novel cascaded transformer coupled multilevel inverter with reduced number of switches for high power applications

PurposeThe purpose of this paper is to design a cascaded Multilevel inverter with reduce number of switches for high power applications. This paper came up with an innovative three-phase multilevel inverter (MLI) topology, which is a cascaded structure based on classical three-legged voltage source inverter (VSI) bridges as an individual module. The prominent advantage of this topology is that it requires only one direct current (DC) link system. The main characteristic of it is that a higher number of voltage levels can be achieved with considerably a smaller number of semiconductor switches, which improves the reliability, power quality, cost and size of the system significantly.Design/methodology/approachThe individual modules are cascaded through three-phase transformers to provide higher voltage at the output with the higher number of voltage levels. In this work, the phase-shifted pulse width modulation technique is implemented to verify the result.FindingsThe proposed topology is compared with three-phase cascaded H-bridge MLI (CHB-MLI) and a modified CHB-MLI topology and found better in many aspects. The proposed MLI can produce a higher number of voltage levels with fewer semiconductor switches and associated triggering circuitry. As the device count in the proposed MLI is less compared to other MLI discussed, it tends to have less switching and conduction loss which increases the efficiency and reliability. As the number of level increases, the voltage profile and the total harmonic distortion of the proposed MLI improves.Originality/valueThis is a transformer-based modular cascaded MLI, which is based on classical VSI bridges. Here in this topology, a single module provides all three phases. So, a single string of cascaded modules is enough for three-phase multilevel voltage generation.

A Novel Multiport DC-DC Converter for Enhancing the Design and Performance of Battery–Supercapacitor Hybrid Energy Storage Systems for Unmanned Aerial Vehicles

This paper proposes an integrated multiport non-isolated DC–DC converter system for integrating battery–supercapacitor hybrid energy storage with photovoltaics for solar-powered unmanned aerial vehicles applications. Compared to the traditional topologies used, the proposed converter allows a size reduction of at least 20% of the supercapacitor by maximizing the utilization of the rated energy capacity. In addition, by proposing to use a phase-shifted carrier modulation technique, the inductors’ current ripple is reduced, which enables a further reduction in the inductor size. These improvements in capability and performance of the proposed topology are experimentally validated on a 500 W PV/battery–supercapacitor integrated power system prototype.

Design of High-Frequency ZVS Full-Bridge Power Converter for Photovoltaic Applications

This paper presents the design of a high-frequency Zero Voltage Switching (ZVS) full-bridge converter with a phase-shifted driving signal for photovoltaic applications. According to the rapid development of power electronics technology, the smart power converter could provide high-power capacity with the high-frequency operation and achieve high energy delivery to the load. This power converter could also reduce the size of the transformer compared to the same power rating. The transformer has been developed using resonant technique and selecting the optimal switching frequency whereby the power converter could reduce switching loss and improve the system efficiency. The phase-shifted modulation switching technique has been selected to drive the power semiconductor switches of a full-bridge power converter based on the switching loss minimization method. The desired output voltage has been controlled using a closed-loop controller under a loop gain stability margin. The simulation results have showed that the output voltage could be controlled to the desired constant when the input voltage has changed from 370 VDC to 400 VDC. The output voltage of the power converter could be controlled at a constant of 24 VDC. Therefore, the proposed study has showed the effectiveness of the phase-shifted ZVS full-bridge power converter for photovoltaic applications such as the battery charging system. This power converter could operate at the desired voltage system and reduce the sizing of the power converter under high-performance efficiency.

Harmonic Suppression Scheme for Multipulse Converter Fed Multilevel Inverter-Based IM Drive

The medium-voltage induction motor drives are regularly utilized for crucial application in enormous industries. It is difficult to design a highly efficient drive system with a satisfactory power quality standard not only at the drive end but also at the grid end. To breakthrough this issue, a 36-pulse ac–dc converter fed seven-level binary cascaded H-bridge multilevel inverter (CHB-MLI) based drive system is presented in this work, where a 36-pulse converter is employed to enhance the power quality at the grid end. For this, the phase-shifted technique is implemented on a multiwinding transformer to eliminate the harmonics injected by the nonlinear diode bridge rectifier toward the grid side. Apart from this, the genetic algorithm selective harmonic elimination (GA-SHE) is applied to a seven-level binary CHB-MLI to diminish lower order (fifth and seventh) harmonics at the drive end. Moreover, a GA is adopted to determine the optimized switching angles by the solution of the nonlinear trigonometric equation of SHE. Furthermore, the GA-SHE-based fundamental frequency modulation scheme is favorable to decrease the switching losses and to enhance the drive end converter efficiency. The performance during the dynamics and steady state of the presented drive system with the indirect field-oriented control is analyzed through simulations and experiments on 298.4 kW and 7.5 kW squirrel-cage induction motors, respectively.

Phase-shifted demodulation technique with additional modulation based on a 3 × 3 coupler and EFA for the interrogation of fiber-optic interferometric sensors.

A phase-shifted demodulation technique with a 3×3 coupler and ellipse fitting algorithm (EFA) for the interrogation of interferometric sensors is proposed. To reduce the error of the EFA as to measure small phase signals, additional phase modulation is introduced. The additional modulation provides a walk of the operating point along the Lissajous ellipse large enough to permit calculation of the ellipse parameters at every moment. Experimental result shows that this technique demonstrates high accuracy and stability for measuring small phase signals. The setting of this technology expands the application of the EFA in fiber-optic phase demodulation technology.

Sequential Phase-Shifted Model Predictive Control for Modular Multilevel Converters

Model predictive control has emerged as a promising approach to govern modular multilevel converters (MMCs), due to its flexibility to include multiple control objectives and simple design process. However, this control scheme presents relevant issues, such as high computational complexity and variable switching frequency. This work proposes a sequential phase-shifted model predictive control (PS-MPC) for MMCs. The key novelty of this proposal lies in the way the predictive control strategy is formulated to fully exploit a phase-shifted pulsewidth modulation technique through an appropriate choice of synchronized average models for each carrier. In this way, the proposed predictive controller obtains independent optimal modulating signals for each carrier in a sequential manner, by solving an optimization problem with reduced computational effort independent of the number of submodules. This sequential optimization allows one to formulate the optimal control problem to achieve multiple control objectives, similarly to the finite-control-set MPC (FCS-MPC). Nevertheless, the MMC governed with the proposed PS-MPC generates an output voltage with fix-spectrum and operates with an even power loss distribution among semiconductors in steady-state, outperforming the standard FCS-MPC strategy. Experimental results are provided to verify the proposed PS-MPC effectiveness when governing a three-phase MMC with four half-bridges per stack.

Single-Wavelength Passive Phase-Shifted Demodulation Technique With the Dual-Cavity and EFA for the Interrogation of EFPI Diaphragm-Based Fiber Sensor

A single-wavelength passive phase-shifted demodulation technique for the interrogation of a diaphragm-based fiber sensor is proposed. It is based on the configuration of the external Fabry–Perot interferometer (EFPI) with dual-cavity (DC) and the ellipse-fitting algorithm (EFA). The technique can address two main concerns: the orthogonality of the DC-EFPI must be matched, the direct current values and fringe visibility of the DC–EFPI must be excluded or normalized. Experiment results show that the proposed technique demonstrates high accuracy amplitude measurement of reflective surface vibration with a high dynamic range over 135 dB and good effectiveness with various initial phase differences apart from two areas around <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</i> rad. It is a successful solution for interrogating of diaphragm-based fiber sensors.

Analysis on three phase cascaded H-bridge multilevel inverter based on sinusoidal and third harmonic injected pulse width modulation via level shifted and phase shifted modulation technique

This work proposes a comparative analysis of sinusoidal and third harmonic injected reference signal modulation accompany with level-shifted PWM technique named as phase disposition (LSPD), phase opposition disposition (LSPOD), and alternate phase opposition disposition (LSAPOD) and phase-shifted PWM technique. Switching pulses from both reference signal and PWM technique have been fed into three phase eleven level cascaded H-bridge multilevel inverter (CHBMLI) fed on a resistive-inductive load with the modulation depth (MD) set to varied from 80% to 100%. For voltage source inverter, total harmonic distortion (THD) content is critical and must be within the allowable range. To prove the feasibility of the reference signal with carrier signal schemes, the entire simulation of the modulation techniques is established and conducted via the Simulink environment. According to the analyzed result, the performance is acceptable in terms of %THDV and %THDI values. Simulation analysis also indicates, at full modulation depth, due to higher fundamental output voltage component produces via the THIPWM modulation technique compared to the SPWM technique, this causes higher %THDV value.

Wielopoziomowe przekształtniki energoelektroniczne – topologie, zasada działania, metody modulacji

In this paper selected issues concerning topological structure, operation and control as well as modulation methods used in multilevel converters are presented. There is reviewed general topologies of multilevel converters, which include Diode-Clamped Converters, Capacitor-Clamped Converters, Cascade Converters and Hybrid Converters. The general structure of a multilevel converter consisting of several stages depending on its application and topology is described. In the structure of operation, the stages of Outer Control Loop, Inner Control Loop, DC voltage stabilization and modulation are specified. Next, the division of modulation methods used in multilevel converters is presented and a detailed description of selected modulation methods is made. In the further part of the article the modulation methods were described in detail, i.e. the Level-Shifted Carrier Modulation Technique and Phase-Shifted Carrier Modulation Technique were used to present the analysis of power losses in multilevel converters.

Adaptive Phase-Shifted PWM based on Particle Swarm Optimization for Cascaded H-Bridge Inverter with Unequal Dc-link Voltages

The cascaded H-Bridge Multilevel Inverter has been found a promising technology in industrial applications because of its higher voltage with less distortion production. Various PWMs techniques have been proposed to push the harmonics frequencies higher than the switching frequency and thus reduces the THD as compared to non-carrier control technique based upon grid frequency. The Phase-Shifted PWM technique has an advantage over others PWM techniques because its harmonics orders are multiples of switching frequency and also depend on the number of levels of the inverter. The phase shifting angle is uniform when the equal voltage sources are adopted. However, in applications where sets of different voltage source levels feed the H-Bridge cells, the Phase Shifted PWM suffers its high order harmonics elimination capability. As a solution to alleviate this problem, an adaptive variable angle approach is proposed in this paper using Particle Swarm Optimization (PSO) algorithm to eliminate desired higher order harmonics. The algorithm is used to minimize the cost function based on high order sideband harmonics elimination equations. The results through MATLAB/Simulink environment shown in this paper confirm the reduction of sideband harmonics of higher orders, and the overall THD.

Cascaded Multilevel Inverter Topology Based on Cascaded H-Bridge Multilevel Inverter

A three-phase multilevel inverter topology for use in various applications is proposed. The present topology introduces a combination of a cascaded H-bridge multilevel inverter with a cascaded three-phase voltage source inverter (three-phase triple voltage source inverter (TVSI)). This combination will increase the number of voltage levels generated when using fewer components compared with the conventional multilevel inverter topologies for the same voltage levels generated. The other advantage gained from the proposed configuration is the assurance of a continuous power supply to the grid in case of failure in one part of the proposed configuration. In addition, the voltage stresses on switches are reduced by half compared if each part in the proposed topology is working independently. The comparison of the proposed topology with some conventional multilevel inverter topologies is presented. The proposed topology is built in the SIMULINK environment and is simulated under various loads in addition to being connected to the grid. Phase-shifted pulse width modulation technique is used to generate the required switching pulses to drive the switches of the proposed topology. The inverter is experimentally implemented in the lab, and the switching pulses are generated with the help of MicroLabBox produced by dSPACE (digital signal processing and control engineering) company. The simulation and experimental results and their comparisons are presented to verify the proposed topology’s effectiveness and reliability.

Dynamic Voltage Restorer Using Switching Cell Structured Multilevel AC–AC Converter

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.

PSPWM based Five-Level Shunt Active Filter for Power Quality Improvement in Power System Network

Power quality is a very important phenomenon in modern days and good power quality indicates efficient performance of a power system network. Presence of non-linear loads in power system network degrades the quality of power being delivered to other sensitive loads connected to the same network. Harmonics is one of the key parameters that power engineers are concerned about and good power quality insists for compensation of harmonics in power system. Active power filters prove to be feasible, valuable and successful custom power devices for harmonic compensation. The operation of a Five-Level Cascaded Inverter driven Shunt Active Power Filter for harmonic elimination and to improve power factor is discussed in this paper. Phase-Shifted carrier PWM technique is implemented for generating the gate drive signals of the inverter. The proposed Active Power Filter model was simulated on MATLAB/ SIMULINK platform and results were presented for a system with balanced linear and balanced non-linear load conditions.

Variable-Angle Phase-Shifted PWM for Multilevel Three-Cell Cascaded H-Bridge Converters

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.

Design of the power supply system for the plasma current modulation on J-TEXT tokamak

In order to further study the influence of current modulation parameters on suppressing tearing instability, the plasma current should be modulated in a wider range. So a modification scheme is designed to improve the performance of ohmic heating power supply system on J-TEXT tokamak. A multilevel cascade circuit with carrier phase-shifted PWM technique has been proposed. Coupled inductors are connected in the form of cyclic symmetry to restrain the circulating current caused by multiple paralleled branches. The simulation proves this proposed current modulation power supply system matches output requirement and achieves good current sharing effect. Finally, a prototype is designed, and the experiment results can verify the correctness of the simulation model well.