Phase-shifted Modulation Technique Research Articles

A single-phase seven-level switched capacitor with common ground inverter and improved phase-shift modulation technique

Lately, transformer-less Researchers in the fields of power electronics and renewable energy have taken notice of photovoltaic inverters because of their great efficiency, low cost, and small size. However, higher efficiency typically results in more components, making the inverter costly and bulky. This article proposes a single-phase seven-level transformer-less with common ground topology. The proposed topology utilizes 10 switches, 4 capacitors and 1 diode. This article also suggests an improved Phase Shift (PS) Modulation Technique which reduces overall losses. When implemented with improved Phase Shift (PS), the total highest attainable efficiency of the proposed topology is 98.05% at 15 W. The THD% of voltage harmonics is reduced to 15.29% from 17.20% and for current harmonics is reduced to 5.07% from 10.15%. The reliability of the proposed inverter has also been analyzed. The simulation as well as hardware results have been presented to validate the performance of the proposed inverter.

A fast and structurally simple control scheme based on a fuzzy supervisory approach for wireless power transfer systems

AbstractWireless power transfer (WPT) is a promising technology and has attracted many researchers’ attention due to its inherent advantages such as reliability, safety, flexibility, and low maintenance costs. For WPT systems, the output voltage varies according to the variable loads and the coupling coefficient conditions, affecting system stability and efficiency. In this regard, this study is concerned with the tracking control problem of WPT systems based on fuzzy supervisory proportional–integral (PI) controller and a phase shift modulation technique, which is for the first time proposed by this paper. By introducing appropriate fuzzy rules, the proposed control scheme not only can track the desired output voltage but also has better robust behaviour to deal with the problem of variations of circuit elements and coupling coefficients. That is, the proposed fuzzy supervisory PI control scheme can perform better than the traditional PI controller. Analysis of the designed control method and simulation results validate the superiority of the proposed method over the traditional PI controller in all conditions, which can make it a suitable choice for the applications of electric vehicle charging systems. The analysis is supported by experimental measurements.

Circuit simulation-based comparison of power electronics devices in a five-level converter for UAV applications

<p>In this paper, the performance of a 5-level cascaded H-bridge inverter in unmanned aerial vehicle (UAV) applications is analized to identify, at the converter design stage, the better device choice depending on different UAV operation scenarios. Considering that regardless of the specific application there are some typical operations, such as take-off, climb, land, cruise, and potential recurring climbs and descents, the results can support the choice by considering the typical working conditions of the specific application where the UAV would be used. The results have been obtained by simulating the H-bridge inverter considering the circuit models of insulated-gate bipolar transistors (IGBTs), GaN high-electron-mobility transistors (HEMTs), and Si and SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) provided by manufacturers. The study has highlighted that the choice of the device depends on the UAV usage, switching frequency, and load conditions. More specifically, considering the typical devices and systems costs in the case of a selective harmonic elimination procedure operating at the fundamental switching frequency, the Si devices should be used. Moreover, the preference for using IGBTs or Si MOSFETs depends on the typical working conditions of the UAV application. In the case of phase-shift carrier modulation technique, at 4 kHz the MOSFET is the best device and the choice between Si and SiC devices depends on the UAV application's main operation scenarios. At 20 kHz the SiC MOSFET is the best device, while at higher frequencies the GaN HEMT cost should be faced to take advantage of its best performance.</p>

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 Novel Hybrid Control Strategy and Dynamic Performance Enhancement of a 3.3 kW GaN–HEMT-Based iL2C Resonant Full-Bridge DC–DC Power Converter Methodology for Electric Vehicle Charging Systems

The conventional resonant inductor–inductor–capacitor (L2C) DC–DC converters have the major drawbacks of poor regulation, improper current sharing, load current ripples, conduction losses, and limiting the power levels to operate at higher loads for electric vehicle (EV) charging systems. To address the issues of the L2C converter, this paper proposes an interleaved inductor–inductor–capacitor (iL2C) full-bridge (FB) DC–DC converter as an EV charger with wide input voltage conditions. It comprises two L2C converters operating in parallel on the primary side with 8-GaN switches and maintains the single rectifier circuit on the secondary side as common. Further, it introduces the hybrid control strategy called variable frequency + phase shift modulation (VFPSM) technique for iL2C with a constant voltage charging mode operation. The design requirements, modeling, dynamic responses, and operation of an iL2C converter with a controller are discussed. The analysis of the proposed concept designed and simulated with an input voltage of 400 Vin at a load voltage of 48 V0 presented at different load conditions, i.e., full load (3.3 kW), half load (1.65 kW), and light load (330 W). The dynamic performances of the converter during line and load regulations are presented at assorted input voltages. In addition, to analyze the controller and converter performance, the concept was validated experimentally for wide input voltage applications of 300–500 Vin with a desired output of 48 V0 at full load condition, i.e., 3.3 kW and the practical efficiency of the iL2C converter was 98.2% at full load.

Improved Triple-Phase-Shift Modulation for Bidirectional CLLC Converters

CLLC resonant converters are an attractive option for battery charging applications due to their bidirectional power flow and high efficiency. Pulse frequency modulation (PFM) is the simple method to drive CLLC converters. However, PFM cannot regulate the output voltage under the light-load condition properly, which leads to high switching and core losses. Phase shift modulation techniques like dual-phase shift (DPS) modulation can overcome this challenge. However, more improvements are demanded due to high circulating currents in phase shift modulations. In this paper, an improved modulation technique based on triple-phase shift (TPS) has been applied in CLLC converters to improve the light-load efficiency. TPS modulation like any other phase-shift modulation, keeps the switching frequency of CLLC converters fixed at the resonant frequency under the light-load condition and regulates the output voltage by its three phase shift parameters. The improved TPS modulation has lower circulating current at the same average output current compared to DPS modulation. Therefore, higher efficiency, smaller peak, and RMS current values can be achieved under the light-load condition. In addition, the proposed TPS modulation has a better flexibility in regulating the output voltage under the light-load condition due to an extra phase shift parameter compared to DPS modulation. The proposed TPS modulation has been analyzed thoroughly in this paper and a proper selection of phase shift values has been explained to improve the efficiency of the converter. Finally, advantages of the improved TPS modulation have been validated by simulation and a 1 kW experimental setup.

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.

Comparative analysis of dual active bridge dc–dc converter employing Si, SiC and GaN MOSFETs for G2V and V2G operation

Electric vehicles (EVs) are ideally suited for carbon footprint reduction and energy-efficient transportation. EV battery chargers comprise of cascade connection of ac–dc and dc–dc converters. With the bidirectional dc–dc converters, EV chargers can implement grid-to-vehicle (G2V) and vehicle-to-grid (V2G) functionality. Dual active bridge (DAB) converter is a bidirectional dc–dc converter that can support G2V and V2G operation. DAB converters are operated at high switching frequencies (fsw) leading to higher switching loss. This issue can be addressed by employing SiC and GaN-MOSFETs, which work with lesser switching losses and can operate at much higher fsw. This paper presents a detailed comparative analysis of DAB converter employing Si, SiC and GaN MOSFETs for G2V and V2G operation. The EV charging system with a DAB converter employing V2G and G2V operation is modeled in PSIM software. Single phase shift (SPS) modulation technique is employed for DAB converter. The system operation is analyzed for V2G and G2V operation with the fsw of 20 kHz, 50 kHz, 100 kHz and 200 kHz. The performance comparison reveals that DAB converter with GaN-MOSFETs has the highest operating efficiency. To validate the DAB operation with SPS modulation, experimental studies have been carried out with SPS modulation being implemented on TMS320F28335 DSP using SimCoder Module of PSIM. A step-by-step procedure to implement the modulation technique with SimCoder is also provided.

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.

A Grid-connected Hybrid Renewable Energy System Using High-frequency Multi-winding Transformer and Phase Shift Modulation Technique

This paper presents a topology of multi-port phase-shift converter for integration of a PV system, a wind-turbine generator and a battery to supply a grid-connected domestic load. The main advantage of the topology is using a multi-winding high-frequency transformer to couple the input and outputs of the system. This simplifies the power flow control and provides isolation between the converter ports. Detailed operation of the proposed topology and the control system analysis are discussed. A numerical simulation of the proposed system is carried out to confirm the system operation and control technique.

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.

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.

A phase shifted modular multilevel converter with variable arm inductance

The performance of a modular multilevel converter depends on modulation technique, circuit parameter and harmonic order, etc. This performance can be improved by better modulation technique, proper selection of circuit parameters (arm inductance and capacitance), etc. This paper presents the performance of a modular multilevel converter using a phase shifted and phase disposition modulation technique. It has been observed that the total harmonic distortion of phase shifted modulation technique is better than the total harmonic distortion of phase disposition modulation technique. The paper also shows the analysis of modular multilevel converters using variable arm inductance. A comparative analysis of voltage and current THD has also been shown here. The total harmonic distortion is minimum below 100 μH arm inductance. The THD has been improved at the minimum value of arm inductance for both modulation techniques. This improved THD of MMC is very efficient for wind farm application. All analysis has been done by using MATLAB/Simulink software.

Reduced switch z-source multilevel inverter using constant boost control methods for renewable energy sources

This paper presents single phase seven level Reduced Switch Z-Source Multi-level Inverter (RSZSMLI) for Renewable Energy Sources (RES). The performance ofRSZSMLI topology is analysed using Constant Boost Control (CBC) methodsbased on sine reference and third-harmonic reference Phase Shift Modulation (PSM) techniques. RSZSMLI will have three DC sources, three Z-source networks, ten power switches and ten main diodes. In the suggested RSZSMLI topology, the output voltage is not limited to summation of DC input voltagescompared to traditional Multilevel Inverters (MLIs).The output voltage can be amplified with shoot-through ratio (K) of Z-source network.Hence, additional DC to DC converter is not required and the topology is more immune to short circuit. The RSZSMLIis analysed using two CBC methods with variable shoot-through ratio (K) to gain additional boost capability. The performance of the RSZSMLItopology is validated with simulation results using MATLAB/SIMULINK.

Variable-Angle PS-PWM Technique for Multilevel Cascaded H-Bridge Converters With Large Number of Power Cells

Modular converters such as the multilevel cascaded H-bridge (CHB) are an attractive option for multiple applications mainly because of inherent modularity and fault-tolerant operation. This article is focused on the CHB converter operating with unbalanced conditions (different dc voltages and/or modulation indexes). Under these circumstances, applying the conventional control and modulation strategies, the output voltage harmonic spectrum is degraded. In this article, a generalized variable-angle phase-shifted pulsewidth modulation (PS-PWM) technique for CHB converters with a large number of power modules <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(&gt;\!\!3)$</tex-math></inline-formula> is presented. The method considers all possible cells’ combinations to form groups and assigns the role of each cell in the group. This cell role defines the identifier of the cell in the variable-angle PS-PWM technique. In the steady state, in each group of cells, the harmonic distortion of the CHB output voltage located at twice the carrier frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$f_c$</tex-math></inline-formula> is eliminated, while the distortion at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4f_c$</tex-math></inline-formula> is also diminished. Experimental results show how the proposed technique achieves superior harmonic performance without introducing any significant disadvantage.

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.

Generalized Harmonic Control for CHB Converters With Unbalanced Cells Operation

Multilevel cascaded H-bridge (CHB) converters are an attractive solution for multiple applications like flexible ac transmission systems and solid-state smart transformers, among others. This article is focused on a CHB working with unbalanced conditions per cell (different cell dc voltages and/or cell voltage references). In this scenario, the phase-shifted pulsewidth modulation (PS-PWM) technique produces a harmonic distortion around twice the carrier frequency and its multiples in the CHB output voltage. In this article, a generalized variable-angle PS-PWM method is presented in order to mitigate this drawback improving the CHB output voltage harmonic spectrum. The proposed method is based on applying a mathematical search algorithm to determine the phase displacement angles to be applied to the PS-PWM technique. Experimental results show how this objective is achieved without introducing any disadvantage in the CHB operation. The method can be applied to CHB with any number of cells.

Hybrid Multi-Carrier PWM Technique Based on Carrier Reconstruction for Cascaded H-bridge Inverter

In response to the deficiencies that the Carrier Phase Shift (CPS-PWM) and Carrier In-Phase Disposition (IPD-PWM) modulation techniques are applied to Cascaded H-bridge (CHB) multilevel inverters, combined with the advantages of the two techniques, a Hybrid Multi-carrier PWM technique based on carrier reconstruction is proposed. The aforementioned technique uses the carrier segment in the half carrier period of the IPD-PWM technique as the basic unit and optimizes the modulation performance by periodically adjusting its arrangement in the vertical direction. When CHB multilevel inverter adopts Hybrid Multi-carrier PWM technique, as with CPS-PWM technique, the output power balance between the cascaded H-bridge cells is achieved naturally; at the same time, the harmonic spectrum of the output voltage is identical with that of the IPD-PWM technique, that is to say, the harmonic characteristics of the output line voltage of the inverters are effectively improved. In this paper, the CHB seven-level inverter is taken as an example, and the correctness of the relevant conclusions is verified by simulation and experimental results.

Low-load Efficiency Improvement of a Three-Phase Bidirectional Isolated DC-DC Converter (3P-BIDC) Via Enhanced Switching Strategy

This paper presents the system design, operation and enhanced switching strategy of a three-phase bidirectional isolated dc-dc converter (3P-BIDC). The paper discusses the operating modes of the 3P-BIDC using phase-shift modulation (PSM), with analysis on its soft-switching characteristics. The phase-shift modulation is the simplest modulation technique that can be applied to the 3P-BIDC. However, it comes with the consequences of low efficiency performance in the low-load conditions. Therefore, this paper investigates the improvement in efficiency of the 3P-BIDC during low-load condition using an enhanced switching strategy combining burst-mode switching and phase-shift modulation. The model of a 700-V, 100-kW, 20-kHz 3P-BIDC and the enhanced switching strategy are verified via simulation using PSCAD. The simulation results shows that the combination of burst-mode and phase-shift modulation technique improves the efficiency of the 3P-BIDC at low-load conditions.

Analysis and Design of a Wide-Range Soft-Switching High-Efficiency High-Frequency-Link Inverter With Dual-Phase-Shift Modulation

A wide-range soft-switching high-efficiency cycloconverter-type high-frequency-link inverter with dual-phase-shift modulation strategy is proposed in this paper. By adding an auxiliary inductor in primary-side full bridge circuit and adopting center-tapped four-winding transformer structure, the soft-switching range for primary-side switches has been extended. The secondary-side active clamper network is designed to recycle leakage inductor energy, and suppress voltage spikes caused by the resonance of the leakage inductor and the parasitic capacitance of switches. One feature of the proposed inverter is that both the primary-side full-bridge and active clamper network employ phase-shift modulation technique where all switches are driven with nearly 50% duty cycle square signals, hence a simple and reliable transformer-isolated gate drive circuit with small transmission delay is presented. Moreover, all switches in the proposed inverter achieve zero voltage switching, which contributes to higher conversion efficiency as well as higher switching frequency. Analysis, design, and implementation of the proposed inverter are discussed in detail. A 200-kHz laboratory prototype for the high-voltage audio amplifier application is developed and the experimental results are presented to validate the analysis and performance of the proposed inverter.