Input Disturbance Suppression for Unidirectional Matrix Converter with a Stability-Enhancing Modulation Scheme

In this article, a band-limited three-level modulation scheme is proposed for a three-phase neutral-point-clamped (NPC) converter with an aim to balance the average capacitor voltages under all operating conditions. When conventional carrier-based pulsewidth modulation is applied, the amplitude of neutral point (NP)-voltage ripple tends to increase under linear imbalances, while the NP voltage can shift, leading to instability in the presence of nonlinear loads. A previously proposed three-level modulation scheme was able to eliminate all low-frequency capacitor voltage ripple by switching a phase between three levels in each switching period. This approach significantly increased the switching loss. The proposed modulation scheme limits the increase in switching loss by employing two operational bands, one fixed band applied to the capacitor voltages and another variable band applied to the phase currents. If the instantaneous capacitor voltages exceed the voltage band, then an appropriate phase-leg is switched in three levels to guarantee that the capacitor voltages cannot diverge further. If the instantaneous capacitor voltages reside within the voltage band, a variable current band is used to regulate switching in three voltage levels in order to obtain lower switching losses as compared to the conventional three-level modulation scheme. Therefore, the proposed modulation scheme presents a tradeoff between switching losses and capacitor voltage ripple. The experimental results are obtained under different loading conditions for validating the performance of the proposed modulation scheme.

In this paper, an improved Space Vector Modulation (SVM) scheme is developed for matrix converter based rectifier. The conditions of using traditional SVM include small current ripple and continuous current operation mode (CCM). Thus the converter requires a very large inductor on DC side. To further reduce the size of converter, Discontinues current mode (DCM) is adopted for high efficiency compact design. The developed the modulation scheme works well with both CCM and DCM. The simulation results show that the line side current THD is further improved with proposed modulation scheme, especially for DCM operation.

Electric vehicles provide portable energy storage that can be used in Vehicle-to-Grid (V2G) applications. In order to source power to the grid, the power electronics on-board these vehicles must be bidirectional. A single stage bidirectional isolated AC-DC converter is discussed. A modulation scheme for this topology is proposed to provide control of real and reactive power. A control scheme is coupled with the modulation and allows the topology to act as an inductive or capacitive or load while sinking or supplying power. The proposed modulation scheme can charge the electric vehicle battery as well as provide ancillary services to the grid. The modulation and control scheme are analyzed and discussed. Simulation and hardware results are presented.

SummaryIn battery energy storage system (BESS) applications, the life of the battery depends on the quality of the charging/discharging current. However, the dual active bridge (DAB) converter, which interfaces BESS with the DC link, suffers from a backflow current in all modulation schemes, degrading the battery's performance. Hence, this paper proposes a particle swarm optimization (PSO) based universal phase shift (UPS) modulation scheme to improve the battery's life. In the proposed modulation scheme, the phase shift ratio of DAB to eliminate the backflow power is estimated using PSO. Also, it is observed that there is an improvement in the zero voltage switching (ZVS) range of the DAB. Hence, the overall efficiency of the DAB converter is increased over a wide operating region. The operating principle of the proposed modulation scheme, steady state analysis of power transmission, and backflow power are reported in this paper. The theoretical performance of the proposed modulation scheme is validated in a 2 kW experimental setup.

We propose the use of time-varying (TV) signaling in modulation schemes to provide multiuser detection and multipath diversity in TV wireless channels. Specifically, we design an orthogonal linear chirp modulation scheme that is based on assigning different users with optimally designed parameters in order to reduce multiple-access interference. We also derive conditions on the parameters of the modulation signals to achieve multipath diversity. Furthermore, we propose the use of TV pilot signals with nonlinear instantaneous frequency and matched time-frequency (TF) techniques to estimate fast-fading channels with unknown state information. The proposed algorithm simplifies to the estimation of the parameters of multiple linear chirps, which we perform using the modified matching pursuit decomposition. We compare our estimation method with the use of pilot signals with linear instantaneous frequency, which we implement using the reassigned spectrogram. The proposed modulation scheme is applied to a frequency-hopped code-division multiple-access system for which we demonstrate improved performance when compared with frequency-shift-keying (FSK) modulation due to the designed multipath diversity and low multiple-access interference. Our simulations also demonstrate the increased estimation performance when pilot signals with nonlinear structures are used instead of linear structured ones to estimate TV channel parameters.

This paper proposes a novel modulation scheme for a multilevel Dual Active Bridge (DAB) DC–DC converter with direct power transfer capability in PV applications. The proposed modulation scheme has the ability to shape the high-frequency current waveforms, leading to lower peak/RMS values of current over a wide range of PV voltages. In addition, the multi-level structure allows for the use of low-voltage devices with significantly smaller channel resistance. The power circuit topology is based on a current-fed half-bridge (CF-HB) converter, with a coupled inductor, which facilitates the direct power transfer, resulting in significantly lower conduction losses. In summary, the proposed topology tackles both the conduction and switching losses through a multi-faceted approach by using the novel modulation scheme, the multi-level structure, the direct power transfer, and the inherent soft-switching. Detailed mathematical analysis and extensive experimental results demonstrate the superior performance of the proposed converter.

In body-centric communications, energy efficiency is a critical performance metric, while the achievable data rate is not of primary concern. In this paper we present a novel modulation scheme, which can be efficiently used in body-centric terahertz (THz) nanonetworks. The proposed scheme is a combination of the time-spread On-Off keying (TS–OOK) and the pulse position modulation (PPM) and presents lower energy consumption, compared to other existing methods as TS–OOK, at a minor cost to the data rate. Furthermore, another important aspect is that the proposed modulation scheme can be effectively used to mitigate the impact of the specific kind of noise in THz body-centric communications, thus leading to better error performance. Finally, we present analytical and simulation results in order to compare the new scheme with the existing TS–OOK.

This study focuses on the possibility of modular multilevel converter (MMC) loss optimisation by modulation without any additional circuit, where a common‐mode voltage is injected into a nearest level modulator. Owing to the common‐mode voltage injection, the proposed modulation strategy increases the fundamental voltage. Therefore, for a given voltage, operation is possible with the submodule (SM) voltage of at least one SM inserted each arm. This reduces the number of SMs required, resulting in reduction of conduction losses and leading to significant cost savings and/or returns on investment for facilities. Furthermore, the injection of common‐mode voltage also decreases the total SM transitions, resulting in reduction of switching losses. The proposed modulation strategy is valid under both normal and unbalanced ac fault conditions for MMCs. The common‐mode voltage extraction method is provided and its harmonic components are extracted. Then, the SM saving capability of the injection‐based nearest level modulation is discussed and the SM saving limit is presented in relation with modulation indexes. The optimisation of both conduction losses and switching losses is analysed. The effectiveness of the proposed modulation strategy under both normal and unbalanced ac fault condition is verified by simulations of a 101‐level three‐phase MMC in MATLAB/Simulink.

This paper presents a ground switching load modulation scheme for passive HF RFID transponders. The proposed modulation scheme allows HF transponders to communicate with the reader in the strong field with a higher modulation index using simple RF clamps, compared with conventional resistive and capacitive load modulation schemes. Also presented is a ground-isolated voltage doubler rectifier to eliminate effects of parasitic diodes in CMOS processes, thereby increasing the communication distance. A 13.56-MHz transponder prototype was implemented in a standard CMOS 0.35-process. Measurement results show that the proposed transponder achieves over 35-mV modulation depth for the magnetic field strength from 0.15 to 7.5 A/m.

The increasing popularity of power electronic (PE) converters in different applications has led the research work to obtain higher efficiency and power density of the system. The dual active bridge (DAB) converter becomes very important in the domain of DC-DC isolated converters, due to its several advantages. Multiple research articles have studied the operation procedure of DAB converter, and proposed various modulation techniques for the same. Several phase shift modulation techniques have improved the operation of DAB for wide voltage and power range. However, at low power and wide voltage variation of converter, some limitations of those phase sift modulation techniques can be identified such as, low efficiency, hard switching operation, high peak and rms current of transformer, high computational effort etc. Targeting those issues, a hybrid modulation technique is proposed combining single phase shift and variable phase shift modulation techniques. The proposed modulation scheme a) optimizes the transformer peak current at its minimum value for full range of power, b) provides zero voltage switching (ZVS) operation for all operating conditions, c) ensures minimum voltage stress on switches, d) does not use any current sensor for the optimization process and e) operates with simplified control strategy which results low computational efforts. The optimization of peak current is achieved using two different methods, which are differential method and Lagrangian multiplier method. The optimization process is carried out for full range of voltage and power to ensure the ZVS operation for all operating conditions. All the claimed characteristics of the proposed modulation technique are verified through simulation and the experimental results derived from a hardware prototype.

In this paper, a soft-switched three-phase resonant converter with a low quality factor (Q) design is proposed for Photovoltaic (PV) energy harvesting systems with a very wide range of operating conditions. Due to the low quality factor (Q ≤ 1), the voltage stress across the capacitors is drastically reduced. However, a major challenge of using a low Q design is the wide switching frequency range required for operation over a wide range of load and input conditions. In order to reduce the switching frequency range, this paper introduces a hybrid modulation technique employing asymmetric pulse width modulation (APWM) along with variable frequency modulation. The proposed modulation scheme also substantially extends the soft-switching range of the converter from full-load upto 10–35% load condition over a wide range of line voltages. To sustain soft-switching in the entire operating region of the converter, the converter is operated in a hybrid structure with single-phase and burst modes at light load conditions. A comprehensive time-domain analysis of the proposed converter is presented, which greatly improves accuracy over conventional frequency-domain modeling. Experimental results from a 1 kW prototype are presented to verify the performance of the converter and validate the theoretical analysis.

Modulation techniques have attracted increasing attention in optical wireless communications. Basic schemes such as on off keying (OOK), pulse amplitude modulation (PAM) and pulse position modulation (PPM) have been validated as suitable for the optical wireless channel. This paper starts from the analysis of these three modulation schemes in terms of their power and bandwidth requirements. As a result, a new tunable hybrid modulation technique is proposed. The proposed modulation scheme takes the real time channel conditions into account, which is different from other schemes. By employing amplitude and position modulation selectively, a guaranteed system performance can be secured, without compromising power and bandwidth efficiency. This is also a new approach to realize reliable optical wireless links.

IEEE 802.22 is the cognitive radio-based first worldwide standard for wireless regional area network (WRAN). The primary objective of this standard is to provide broadband access to remote and rural areas. In these remote areas, a large number of vacant TV channels are available, known as white spaces. This standard allows broadband access to the users using these TV white spaces (TVWS). Also, much analog transmission has been moved towards digital transmission in UHF band so this situation has created a digital divide. In this paper, we proposed a novel scheme of simulation for the physical layer of IEEE 802.22 Wireless Regional Area Network (WRAN) with another cyclic prefix. In this paper, we have also demonstrated the effect of length of cyclic prefix in OFDM symbol on the BER performance of the physical layer of WRAN. We simulated the physical layer of WRAN with cyclic prefix 1/4 and 1/32 between successive OFDM symbols. We used convolution code with code rate 1/2 as FEC and evaluated the performance with BPSK, QPSK, and QAM-19 digital modulation schemes in Rayleigh fading condition in MATLAB. We concluded that the effect of ISI can be mitigated with cyclic prefix 1/32 for all three proposed modulation schemes and found that better BER performance in limited SNR. Also, the performance of BPSK with CP 1/32 is superior to QPSK and QAM-16 for CP of 1/4 as well as 1/32.

Pulse Width Modulated (PWM) inverters produce common mode voltage. The common mode voltage will have adverse effect on the motor bearings. Hence the common mode voltage has to be reduced. This paper presents a modified Sinusoidal Pulse Width Modulation (SPWM) scheme in which two complementary modulating inputs are used to generate the pulses for the switches of a two level, three phase inverter to reduce the common mode voltage. The performance of proposed modulation scheme is evaluated and tested for various switching frequencies. With the proposed modulation scheme the phase voltages appears to be three level voltage which helps in reduction of common mode voltage. A comparative study of common mode voltage with both normal and modified SPWM method is also done and the results are presented in this paper.

Recent years have seen a surge in the usage of optical signals for real-time wireless data transfer in a wide range of underwater applications because of their large bandwidth, higher data rates, low latency, security, power, and cost efficiency. However, underwater optical wireless communication (UOWC) is substantially impaired by absorption, scattering, and turbulence effects that induce scintillations during optical signal propagation. A potential modulation scheme can be a promising solution to overcome such scintillations. The pulse position modulation (PPM) may address the fading and optical irradiance across the underwater channels while providing the power efficiency to the wireless sensor networks (WSNs). To access the link performance under the proposed modulation scheme, the closed-form expressions for outage probability and BER metrics are typically required. Unlike horizontal and single-layered models, this work evaluates the performance of vertical cascaded links in the North and Baltic oceans affected by the combined effects of absorption, scattering, and turbulence by utilizing an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i>-ary PPM scheme. The unified expressions for the probability density function (PDF) and cumulative distribution function (CDF) are obtained by integrating depth-dependent layered Gamma-Gamma (GG) turbulence with absorption- and scattering-based path-loss (PL) attenuations. The closed-form expressions for the outage probability (OP) and the average bit error rate (ABER) are derived by following the derived PDF and CDF to evaluate the end-to-end (E2E) performance under<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i>-ary PPM. The analytical results are validated using experimentally extracted channel parameters and rigorous Monte-Carlo (MC) simulations.