Proposed Modulation Method Research Articles

A Discontinuous Modulation Method with Variable Clamping Interval Width of the Modular Multilevel Converter

The modular multilevel converter (MMC) has been widely used because of the advantages of easier expansion, lower harmonic distortion and higher output voltage level. If the MMC is adapted to high voltage application, more submodules need to be connected in series in each arm. Thus, the switching loss needs to be considered a key issue. A discontinuous modulation method with variable clamping interval width is proposed in this paper in order to reduce the switching loss under variable power factor conditions. Different widths of the clamping interval can be selected according to the requirements of the system. Meanwhile, the capacitor voltage ripple of the submodules can also be reduced. The feasibility and effectiveness of the proposed modulation method are verified under a RT-LAB rapid control prototype based MMC system.

Laser wireless power transfer and thermal regulation method driven by transient laser grating

Wireless power transfer (WPT) technology uses non-conductive-wire methods to realize power transmission from the power-supply side to the load side, which is an advantageous energy supply method in long-distance, non-contact scenarios. Based on the photovoltaic (PV) effect, traditional laser WPT (LWPT) has the advantage of high transmission power. However, the cooling requirements of PV modules introduce additional structural composition and operating energy. In this paper, an LWPT (BeE-LWPT) technology based on the Seebeck effect is proposed, and a brand-new energy conversion mode is designed. Aiming at the limited hot area of the thermoelectric element periodically heated using the expanded beam laser, the improvement effect of the transient laser grating thermal regulation mechanism on BeE-LWPT is studied. Multiphysics simulations of the temperature response of the hot end of the copper plate modulated by the laser beam spot are carried out with commercial finite-element software. Compared with the traditional beam expansion method for temperature control, the proposed modulation method based on the transient laser grating has a more stable temperature response and a more uniform heating area, which means better thermal regulation effect.

Constant-Current and Constant-Voltage Output Using Hybrid Compensated Single-Stage Resonant Converter for Wireless Power Transfer

At present, single-stage wireless power transfer (WPT) resonant converter with boost bridgeless power-factor-correction (PFC) rectifier has not been promoted due to the rising voltage of dc-link and unstable output voltage of the converter. The compensation network with load-independent constant current output (CCO) and constant voltage output (CVO) characteristics cannot be analyzed in this converter due to the above problems. In order to solve these problems, a new asymmetric modulation method and the corresponding compensation network design method for single-stage WPT converter are proposed in this article. The proposed modulation method makes the voltage of dc link and the output voltage of single-stage WPT converter constant. Based on the new modulation method, the design method of the compensation network and the implementation of zero-voltage switching (ZVS) in single-stage WPT converter are proposed and analyzed in this article. Compared with the other WPT converters, the proposed scheme has advantages in efficiency and cost. Finally, the superiorities of the proposed circuit are verified by experiments.

A PWM Method of H-Bridge Converter With Temperature Rise Balancing and Minimization Based on Periodically Alternating Employment of Power Devices

Aiming at the temperature rise and thermal control issues of power devices in H-bridge converters under conventional pulsewidth modulation (PWM) methods, a novel PWM method of H-bridge converter with temperature rise balancing and minimization based on periodically alternating employment of power devices is proposed. In the proposed method, two novel operation mechanisms of power devices are alternately applied into the eight regions with the identical and opposite polarities of reference voltage and input current, which are composed of two fundamental frequency periods. All active switches and antiparallel diodes in H-bridge converters are made to work alternately in these eight regions, each of them is designed to keep in <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -state in one region, operate in switching state in another two regions, and inactive in the left other five regions. This way, the power dissipation and temperature rise of all the devices are balanced and minimized, and H-bridge converters no longer suffer from the dead-time effect on current quality and dc-bus voltage utilization. The implementation strategy of the proposed modulation method is discussed in detail. Simulation and experimental results are presented that verify the effectiveness of the proposed method and the corresponding implementation strategy at different operating points.

Efficiency Improvement of a Cascaded Buck and Boost Converter for Fuel Cell Hybrid Vehicles with Overlapping Input and Output Voltages

Fuel cell hybrid vehicles represent an alternative to battery electric vehicles and will gain importance in the future as they do not need large battery capacities and thus require less critical raw materials. Depending on the electric architecture, the voltage of the fuel cell stack and traction battery may overlap. Accordingly, it is necessary to use a bidirectional DC–DC converter that connects the battery to the DC bus, which supports overlapping input and output voltages. Furthermore, these converters should be non-isolating in terms of compact design. Concerning complexity and controllability, the bidirectional cascaded buck and boost converter is preferable and is the subject of this study. Published literature presents the bidirectional cascaded buck and boost converter with high losses for overlapping input and output voltages, introducing two methods for this operation mode. The method selected for this study, namely buck + boost, uses two switches, whereby one switch has a fixed duty cycle. However, there is no appropriate investigation to determine the impact of this fixed duty cycle on converter efficiency to date. Furthermore, efficiency improvement is possible by switching frequency modulation, but current literature does not address this modulation method for overlapping input and output voltages. Therefore, this paper investigates a non-isolated hard-switched bidirectional cascaded buck and boost converter for fuel cell hybrid vehicles operating with up to 19.8 kW. The study focuses on determining the optimum fixed duty cycle and efficiency optimisation through a novel critical conduction mode with adapted switching frequency by utilising the load-dependent inductance of the inductor with powder cores. Measurements with an experimental setup validate the proposed modulation method with Si-IGBT half-bridge modules. The results demonstrate that a loss reduction of 39% is possible with switching frequency modulation and the optimum duty cycle compared to fixed switching frequency. As a result, the converter achieves high efficiencies of up to 99% and low device junction temperatures.

A Modulation Method for Capacitance Reduction in Active-Clamp Flyback-Based AC–DC Adapters

Recent developments of fast-charging power delivery protocols are driving ac–dc adapters to 100-W power ranges. Conventional solutions in this power range employing a two-stage topology and a big twice-line frequency buffer capacitor are generally costly and bulky. This article presents a patent-pending modulation method for an active-clamp flyback converter, allowing for a single-stage adapter design with reduced capacitance requirements and higher efficiency. This is achieved by exploiting the inherent energy storage capability of the clamping capacitor while turning it into an active power buffer. No hardware modifications are needed, while all salient features of active-clamp flyback converter, i.e., soft switching and leakage recycling, are retained. Operating principles and detailed controller design are discussed, and a 100-W laboratory prototype is built. The prototype achieves 94% peak efficiency and up to 92% size reduction of the buffer capacitor. The experimental evaluation shows that the new single-stage solution enabled by the proposed modulation method is superior to the conventional two-stage and single-stage solutions in terms of cost, conversion efficiency, and power density.

A Generalized Simplified Virtual Vector PWM to Balance the Capacitor Voltages of Multilevel Diode-Clamped Converters

This article presents a generalized simplified virtual vector pulsewidth modulation (SVVPWM) to attain the capacitor voltage balancing of multilevel diode-clamped converter (DCC) for all operational conditions, which is not possible by using conventional space vector pulsewidth modulation (PWM) and carrier-based PWM methods. Virtual vector PWM is a solution presented in the literature to sort out this issue but it becomes more complex for higher level converters. The proposed SVVPWM method is simple and easy to implement for any level converter because it converts the space vector (SV) diagram of any level converter to three-level SV diagram. The SVVPWM assures the natural voltage balancing under steady states and ideal operations. Under dynamic operations, a generalized equation that describes the influence of neutral point currents on dc-link capacitor's voltage has been derived and a general decoupled voltage balancing control for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -level DCC is presented. The proposed modulation method is implemented on five-level and seven-level DCCs to authenticate the effectiveness of decoupled voltage balancing control. Simulation and experimental results demonstrate that the proposed modulation strategy is easy to implement and effectively controls the balance of the capacitor voltages for the whole range of modulation index and load power factor.

High-Frequency-Linked Three-Port Converter With Optimized Control Strategies Based on Power System Load Flow Concepts for PV-Battery Systems

This article proposes an optimized modulation and control strategy for high-frequency-linked three-port converters (HFL-TPCs), which is conceptually derived from the generalized load flow equations of a typical power system. The power system analogy explains why single phase shift (SPS) modulation results in higher reactive currents that reduce the overall converter efficiency. The SPS converter also loses zero-voltage switching (ZVS) at lower power operations. The proposed optimized quintuple phase shift (QPS) modulation method allows dynamic control of duty cycles of the HF square wave voltages that potentially control the real and reactive power flows of the HFL-TPC. The QPS modulation phase variables are applied to derive the generalized models of the HFL-TPC using a harmonic analysis approach. Harmonic analysis and the optimized modulation strategy greatly simplify the theoretical analysis of the HFL-TPC compared to a piecewise time-domain approach. A detailed power loss model of the HFL-TPC is also discussed. To verify the practical feasibility of the proposed optimized modulation strategies, a 60-V, 400-W HFL-TPC is built and tested. Simulation and experimental results show that the proposed modulation method reduces reactive power, improves efficiency, and maintains the ZVS operation over a wide voltage and power range.

Optimal Phase-Shifted Modulation Method for Suppressing the Current Ripple of Modular Multilevel Converter-Bidirectional DC–DC Converter Under Unbalanced Operation

Modular multilevel converter-bidirectional dc–dc converter (MMC-BDC) can be used in the second generation of vessel integrated power system (IPS) to interconnect the medium-voltage dc (MVdc) bus and distributed energy storage elements (ESEs) for its outstanding characteristics. When MMC-BDC operates with submodule (SM) power well balanced, traditional phase-shifted modulation (TPSM) reduces the current ripple at the MVdc side of MMC-BDC for the frequency multiplication effect. However, when it comes to the unbalanced operation conditions, TPSM can result in large current ripple. In this article, the relationship of the MVdc-side current ripple and the switching signal patterns is revealed. An optimal phase-shifted modulation (OPSM) method based on offline genetic algorithm (GA) is proposed to suppress the MVdc-side current ripple by adjusting the phase-shifted ratios of the driving signals of each SM. Combining the proposed modulation method with a proposed online stepwise energy management strategy, all unbalanced conditions can be covered with limited sets of optimal phase-shifted ratios. Simulation and experiment results show that the MVdc-side current ripple of MMC-BDC is remarkably reduced with the proposed OPSM.

Performance Improvement of Dual-Buck Inverter With Mitigating Reverse Recovery Characteristics and Supporting Reactive Power

This paper proposes a three-level dual-buck inverter (DBI) that reduces reverse recovery current and compensates reactive power. To reduce the reverse recovery problem of main switching diodes in the DBI, the auxiliary circuit consisting of diodes and coupled inductors is adapted. The auxiliary circuit enables zero-current turn-off of the diodes. The coupled inductor design is also conducted considering not only for unity power factor (PF) but also non-unity PF operations. By utilizing the auxiliary circuit, the reverse recovery and the shoot-through problems in silicon devices can be significantly mitigated so that the efficiency and the reliability of the DBI are much improved. Meanwhile, the pulse-width modulation scheme is also proposed to supply reactive power with the DBI which is a unidirectional inverter. In the proposed modulation method, the duty offset is simply added according to the required PF and the operating region of the DBI. By doing so, traditional current control concepts for bidirectional inverters can be directly applied to the DBI without any modification. By utilizing the proposed techniques, the reliability, efficiency, and utilization of the DBI can be significantly improved. The experimental results with a 3 kVA DBI prototype demonstrate the effectiveness of the proposed DBI.

Variable Switching Frequency PWM for Three-Phase Four-Wire Split-Capacitor Inverter Performance Enhancement

Three-phase, four-wire, split-capacitor inverters, thanks to their capability to deal with unbalanced systems, are currently employed in photovoltaic installations, electric vehicles battery chargers, active power filters, and many other grid-tied applications. The minimization of ac output current ripple and switching losses positively impacts the inverter's efficiency, volume, weight, and cost optimization. For this reason, a novel variable switching frequency driving strategy independently tunable on each phase is proposed in this article. Taking advantage of phase current ripple prediction, a proper variable switching frequency strategy is applied for obtaining a flat current ripple profile. Having tuned the driving strategy parameters, it is possible to optimize and compare individual metrics such as the maximum peak-to-peak value of the current ripple, current ripple rms, average switching frequency, and switching losses. By applying the proposed modulation method, a significant inverter performance enhancement has been obtained. Converter efficiency is improved without introducing detrimental effects on the current harmonic quality. Analytical derivations are expressed as a modulating index function and the power factor for balanced and unbalanced systems. All the theoretical developments are verified throughout numerical simulations and experimental tests.

Multifrequency Modulation to Achieve an Individual and Continuous Power Distribution for Simultaneous MR-WPT System With an Inverter

To achieve an individual and continuous power distribution for multireceiver wireless power transfer (WPT) systems, a novel multifrequency modulation method has been proposed. In the proposed method, a look-up table and delta-sigma modulation scheme are introduced to generate a mixed-frequency driving voltage pulse by synthesizing it from the given voltage pulses. The components of synthesized driving voltage pulse have continuously and individually varying amplitudes of multiple specific frequencies. With the proposed modulation method, only a standard full-bridge inverter is employed in the transmitting side to achieve power distribution among receivers, leading to a simple configuration of the transmitting source. Moreover, the proposed method has a small calculation burden and can be easily extended to the system with more receivers. When compared with the existing multifrequency modulation method, a lower switching frequency is obtained in the proposed method. Finally, the effectiveness of the proposed modulation method is verified theoretically and experimentally.

Bin Code: Encoding and Decoding of Picture Embedded Barcodes by Novel Intensity Bin

Objectives: To introduce a new algorithm for embedding pictures into barcodes, thereby facilitating the barcodes to hold the picture about its carrying information. This facilitates easier storage and faster retrieval, thereby avoiding manual errors and time consumption. Methods: The message to be embedded is encoded using Reed Solomon code and then embedded into the image by the proposed modulation method, finally generating a picture embedded barcode. Findings: The image quality and the information embedding capacity achieved by this method are proved to be higher than the previous works. Novelty: This study proposed an encoding/ decoding method for barcodes with pictures with the novel Intensity bins to generate a barcode with maximum visual quality. Keywords: Barcodes; Encoding; Decoding; Modulation; Demodulation

Harmonic Elimination in Uniform Step Nine-Level Inverter Using Differential Evolution: Experimental Validation

This study presents the application of differential evolution algorithm to compute optimal switching angles for a single-phase nine-level inverter to improve the output voltage quality. The topology of the proposed inverter in this article is a simple cascade converter composed of two H-bridge cells with non-equal DC voltage sources in order to generate multiple voltage levels. Selective harmonic elimination pulse width modulation strategy is used to improve the generated AC output voltage waveform. The differential evolution optimization algorithm is used to solve non-linear transcendental equations necessary for the (SHPWM). Computational results obtained from computer simulations presented a good agreement with the theoretical predictions. A laboratory prototype based on STM32F407 microcontroller was built in order to validate the simulation results. The experimental results show the effectiveness of the proposed modulation method.

An SVM Scheme for Three-Level Quasi-Switched Boost T-Type Inverter With Enhanced Voltage Gain and Capacitor Voltage Balance

This article introduces a space vector control method for the three-level quasi-switched boost T-type inverter, which provides some benefits such as: good output voltage quality, high voltage gain, and low voltage stress on power devices. By applying corresponding P-type or N-type small vectors in switching sequence, the neutral-point voltage unbalance problem can be solved easily. The advantage of this modulation solution is that it does not require any extra calculations. The upper-shoot-through and lower-shoot-through states are utilized instead of full-shoot-through, which is usually used in traditional single-stage three-level impedance source inverter, to ensure the boost capability of the inverter. These states are inserted into small vectors in order not to affect the output line-to-line voltage. Some investigations about voltage gain, diode, and switch voltage stress have been conducted to demonstrate the effectiveness of the proposed method. The experimental results are also presented to validate the accuracy of the proposed modulation method. The proposed approach has resulted in efficiency rise by 2% as compared to the conventional PWM scheme.

10-Gsymbol/s IM-based quantum noise encryption system modulated by a dual digital‐to‐analog converter

To attain secure fiber-optic transmissions at a high rate, a realizable scheme is proposed in this paper, that can achieve 10-Gsymbol/s quantum noise encryption based on intensity modulation. Specifically, a dual digital-to-analog converter (DAC) is used to drive a single-drive Mach–Zehnder modulator. Then, to demonstrate the advantage of this scheme, a trial of 10-Gsymbol/s single-channel transmissions over 30 km are confirmed at 4096 intensity levels. Furthermore, specific indicators that affect secure transmissions are analysed, such as the number of modulation levels and noise masking. Finally, experimental results show that a masking number of 370 is achieved to resist direct detection attacks at the 4096 signal levels. Multilevel optical signals are hidden in the quantum noise. It is also apparent that the proposed modulation method realizes highly secure fiber-optic transmission.

Reliability and Performance Improvement of PUC Converter Using a New Single-Carrier Sensor-Less PWM Method With Pseudo Reference Functions

A new single-carrier sensor-less pulsewidth modulation (PWM) method using suggested pseudo reference functions is proposed for packed U-cell (PUC) converter to improve performance and reliability of the PUC converter. It is composed of one PWM carrier signal and two suggested pseudo reference functions. By employing the proposed modulation method, the PUC dc capacitor voltage ripple is substantially decreased, and faster sensor-less capacitor voltage balancing is obtained. Moreover, the power losses are evenly distributed among all power switches. Consequently, notable reduction of the PUC dc capacitor voltage ripple and even distribution of the power loss among switches enhance the PUC converter's reliability and lifetime. In addition, odd multiples of the switching harmonic clusters are eliminated from the output voltage; thus, the values of output passive filter components are halved. Hence, applying the proposed single-carrier sensor-less PWM method remarkably improves the performance, power density, reliability, and lifetime of the PUC converter and notably simplifies implementation of the switching pattern. Provided experimental results and comparisons as well as reliability analysis verify the viability and effectiveness of the proposed PWM method.

Carrier-Based Generalized Discontinuous PWM Strategy for Single-Phase Three-Legs Active Power Decoupling Converters

Three-legs active power decoupling (APD) converters are widely studied in the single-phase grid-connected systems to enhance the circuit lifetime by creating an alternative path for the typical existing dc-side power pulsating ripple. Therefore, this reduces the requirement of smoothing dc capacitors allowing compact designs even with the implementation of long life metalized film technology. In this article, to allow enhancement of the system power density by improving power conversion efficiency and thus reducing the requirement of thermal management of the semiconductors, a carrier-based generalized discontinuous PWM strategy is proposed. This method detects the converter ac currents and ac reference voltages to determine the optimum clamped duration in each one of the three bridge-legs, which will minimize the converter overall switching losses. The proposed modulation method is analyzed and validated on a PLECS simulation and a 2 kVA single-phase three-legs APD converter.

Minimum Switching Losses Discontinuous PWM Strategy for Bidirectional Single-Phase AC–DC Converter With Active Power Decoupling Circuit

Active power decoupling circuits are used in bidirectional single-phase grid-connected systems to enhance the circuit lifetime by creating an alternative path for the typical dc-side power pulsating ripple. Therefore, this reduces the requirement of smoothing dc capacitors allowing compact designs even with the implementation of long life metalized film technology. However, with the necessary addition of auxiliary components, extra power losses in the added switching devices and passive components will be introduced, which will inevitably reduce the system power conversion efficiency. To relieve this issue, a new discontinuous pulsewidth modulation (PWM) strategy with minimum switching losses is proposed in this article. This method detects the converter current and reference voltages synchronously to determine the optimum clamped duration of each circuit phase-leg. With such a characteristic, the proposed strategy can realize the minimum switching losses at any instant, thus improving the power conversion efficiency and potentially the power density of the converter. The proposed modulation method is described, analyzed, validated, and compared with different PWM methods on a 2-kVA bidirectional single-phase ac–dc converter with active power decoupling circuit.

Simultaneous Switching Loss Reduction and Neutral-Point Voltage Balance Scheme for Single-Phase Three-Level T-Type Inverter

Single-phase three-level T-type inverter (3LT <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> I) has revealed superior performances in many applications. However, it inevitably faces the challenge of high switching loss and imbalanced neutral-point voltage with conventional carrier based pulsewidth modulation (CBPWM). To address these issues, an improved CBPWM strategy with maximum offset voltage injection is proposed to reduce the switching loss and balance the neutral voltage simultaneously. Neutral-point voltage balance is maintained by selecting P-type or N-type switching sequence, which depends on the sign of offset voltage. Also, switching loss is mitigated by reducing the number of total switching commutation. First, the restriction of injected offset voltage is investigated and when the offset voltage is maximum, the switching commutation is reduced. Then, to further reduce the number of switching commutation, a new set of carrier signals are proposed to realize zero switching commutation between P-type and N-type switching sequences. After the analysis, the proposed modulation method also has better common-mode voltage restriction and faster response of neutral-point voltage balance. Simulation and experiment have been conducted to verify the theoretical analysis.