Equal Output Voltages Research Articles

Optimal dynamic operation and modeling of parallel connected multi-stacks fuel cells with improved slime mould algorithm

In this article, a comprehensive detailed dynamic representation of multi-stacks fuel cells is addressed. This representation is applied and compromised for parallel connected and operated multi-stacks solid-oxide fuel cells (SOFCs), which is considered a hot topic and research challenge. A proposed control system is presented to manage SOFCs parallel stacks sharing and operation. A part of this technical challenge in regards to the parallel operation is to realize equal output voltages with various current values of each cell. An improved slime mould algorithm (ISMA) is proposed to set the operational parameters of parallel operated SOFCs stacks. Digital simulations have validated the proposed system effectiveness with optimal dynamic parameters under various operating scenarios. These scenarios include step-load changes (increase/decrease) under equal and unequal load sharing's plus emergent fault conditions by short-circuit disturbance and protection tripping. Further validations thru comparisons of ISMA's results with the best results of genetic algorithm (GA) as a well-established benchmark algorithm are emphasized. The simulation results show the efficacy of proposed technique and representation to improve the dynamic performance of the underlined system, for example at a particular scenario. Just to figure out the cropped results, it is noted the ability of proposed technique to realize a very smooth dynamic response (overshoot = 2.30e-5 pu and settling time = 0.054 s) compared to those achieved by GA (overshoot = 4.78e-2 pu and settling time = 0.22 s) under fuel cells different shares' scenarios.

New Four-Channel Resonant Boost DC/DC Converter

Multichannel resonant DC/DC converters have recently been popular in diverse fields, where multiple output voltage levels are required, such as supplying multilevel inverters. This paper is devoted to present the new member of a four-channel resonant DC/DC converter family, having consisted till now of step down as well as step-up/down configurations. The new converter is capable of realizing the power flow amongst the two input and the four output channels in order to maintain the required equal or unequal output voltages. In the meanwhile, it offers the benefits of soft-switching capability, including zero voltage (ZVS) and zero current switching (ZCS), resulting in high efficiency and reduced electromagnetic interference (EMI). The presentation of the new boost converter topology is followed by a detailed steady-state analysis. The focus is on the symmetrical operation of the converter in discontinuous current conduction mode (DCM). Possible sets of control variables are revealed and their effect on the operation, especially on the output voltages and powers is analyzed in detail. A step-by-step calculation procedure is also proposed to determine the circuit parameters. The outcomes of simulations and experiments validate the theoretical results.

Combined use of the nearest vector selecting technique and low-frequency quarter-wave symmetric space vector PWM in control of three-phase multilevel voltage source inverter

The paper offers the problem’s solution of the three-phase multilevel voltage source inverter (MLVSI) control with low dynamic losses in power semiconductor switches. The proposed technique is based on a single approach that operates with values of the integer and fractional parts of the relative values of the reference delta voltages, and it allows combining the use of the space-vector control, choosing the nearest vector (SVC), with the low-frequency space-vector pulse-width modulation with the quarter-wave symmetry of the output voltages (QWS-SVPWM). Depending on the impedance kind of a generalized load, the integrated voltage harmonics factor (weighted THD) of the appropriate order is being minimized by applying one of the two mentioned modulation methods (SVC or QWS-SVPWM) for a current range of voltage amplitude modulation index. Like its components, the combined algorithm is suitable for MLVSI of any circuit configuration and any number of equal output voltage levels.

Trinary Hybrid Cascaded H-Bridge Multilevel Inverter-Based Grid-Connected Solar Power Transfer System Supporting Critical Load

Higher power rating solar photovoltaic systems are emerging in the power system owing to the reduction in the cost of photovoltaic arrays and environmental concerns of the conventional power generation systems. Multilevel inverters are reported at high power levels due to reduced switching frequency and increased efficiency. Cascaded H-bridge (CHB) multilevel inverters have been reported in the literature due to its redundant structure compared to other multilevel topologies. When CHBs with dc sources are in the ratio of 1:3, it is named as a trinary hybrid multilevel inverter, and it generates a maximum number of equal output voltage levels. In this article, a trinary CHB multilevel inverter-based grid-connected solar power transfer system using modified second-order generalized integral control is proposed. A two-stage solar PV system consists of a single-input-multiple-output single-ended primary inductance converter and two CHB structures per phase used to verify the proposed system. A modified second-order generalized integral control is presented for active power control and grid synchronization. The controller is designed to eliminate dc-offset from the sensed load currents and to ensure balanced, sinusoidal, and unity power factor grid currents. Moreover, the shunt-connected system mitigates the reactive power and harmonic demands of the local load, thus maintaining the grid current power quality within the standard prescribed by IEEE-519. The performance of the proposed system is validated with an experimental prototype, and the test results validate the theoretical claims.

Family of Multiport Switched-Capacitor Multilevel Inverters for High-Frequency AC Power Distribution

This paper proposes a family of multiport switched-capacitor multilevel inverter (SCMLI) topologies for high-frequency ac power distribution. It employs asymmetric dc voltage sources with a common ground that makes it ideal to be employed in renewable energy farms and modern electric vehicles. The proposed family of step-up SCMLI attains higher number of output voltage steps with optimum component count in comparison to several existing topologies. The problem of capacitor voltage balancing is solved as the capacitors are inherently charged to a finite voltage every half cycle. In-depth study on two staircase modulation strategies, namely, selective harmonic elimination and minimum total harmonic distortion (THD) scheme is presented with study on the variation of switching angles and THD with modulation indices under both schemes. Working principle and analysis are presented for the proposed family of topologies. Simulation outcomes are validated with experimental results under both the aforementioned modulation schemes with equal and unequal output voltage waveform steps.

Power Factor Correction in Cuk–SEPIC-Based Dual-Output-Converter-Fed SRM Drive

In this paper, a power factor correction (PFC)-based switched reluctance motor (SRM) drive is proposed. Generally, the SRM drive is fed with a simple diode bridge rectifier followed by a bulky capacitor, which draws peaky current at low power factor and high-input-current total harmonic distortion (THD). Here, a dual output converter is proposed to control the SRM and to provide power quality improvement as well. This converter is a combination of Cuk and SEPIC converters, which produces two equal output voltages with neutral point N, to feed a midpoint converter of the SRM drive. The converter is designed to operate in discontinuous conduction mode of operation to obtain inherent PFC at supply side. The motor control is attained by regulating dc link voltage over a wide range. Test results on a prototype of the SRM drive demonstrate the excellent performance with high power factor and reduced input current THD. The observed power quality indices depict the improved power quality as per the standard IEC 61000-3-2.

PFC‐based half‐bridge dual‐output converter‐fed four‐phase SRM drive

This study proposes a power factor correction (PFC)-based half-bridge dual-output converter-fed switched reluctance motor (SRM) drive for home appliances. The proposed converter provides two equal output voltages to feed a mid-point converter of a four-phase SRM. An adjustable speed drive is proposed here such that the speed control is obtained by regulating converter output voltage. The converter is operated in discontinuous conduction mode to obtain inherent PFC at supply side. The sensors requirement is reduced by selecting a voltage follower approach. The performance of proposed drive is evaluated for steady-sate and dynamic conditions. The input current total harmonic distortion is reduced below 5% as per an IEC standard.

Fault-Tolerant Operation of Three-Phase Cascaded H-Bridge Converters Using an Auxiliary Module

This paper presents a new fault-tolerant solution for cascaded H-bridge (CHB) converters, which generates equal output voltages in both prefault and single fault conditions. To generate a balanced three-phase voltage with the highest amplitude regardless of the fault location and its type, an auxiliary module is employed in series with the CHB converter. The auxiliary module is a two-level voltage-source inverter with a capacitive dc link. The module is brought to the circuit after fault detection and its capacitor is charged by a novel algorithm to the reference value. Then, using the space vector modulation, the inverter's reference space vector is synthesized and the voltage of auxiliary module is kept constant. The validation of the proposed method is confirmed by simulations and experiments on a three-phase five-level CHB converter.

Minimum required magnetising inductance for multiple‐output flyback DC–DC convertor in CCM

The derivation of the equation for the minimum value of magnetising inductance needed for the multiple-output flyback DC–DC converter to operate in continuous-conduction mode (CCM) is presented. The equation is derived for two outputs and then generalised for multiple outputs. Two design examples are presented, one for equal output voltages and the other for unequal output voltages. Simulation results are presented in order to verify the derived expressions.

Modeling of dimensionally graded magnetoelectric energy harvester

The magnetoelectric behavior of a dual-phase dimensionally graded magnetostrictive-piezoelectric composite is modeled in this article. The cantilever is formed by piezoelectric macro-fiber composite bonded to a Ni cantilever. Theoretical estimates show a large magnetoelectric voltage coefficient of 100V/(cmOe) at electromechanical resonance frequency. An additive effect was realized when an acceleration and magnetic field was applied to the structure simultaneously. Applied magnetic field of 10Oe and shaker acceleration of 0.02g induce the approximately equal output voltage of 20–35V.

A novel symmetrical microwave power sensor based on GaAs monolithic microwave integrated circuit technology

A novel symmetrical microwave power sensor based on GaAs monolithic microwave integrated circuit (MMIC) technology is presented in this paper. In this power sensor, the left section inputs the microwave power, while the right section inputs the dc power. Because of the symmetrical structure, this power sensor is created to provide more accurate microwave power measurement capability without mismatch uncertainty and restrain temperature drift. The loss model is built and the loss voltage is 0.8 mV at 20 GHz when the input power is 100 mW. This power sensor is designed and fabricated using GaAs MMIC technology. And it is measured in the frequency range up to 20 GHz with the input power in the −20 dBm to 19 dBm range. Over the 19 dBm dynamic range, the sensitivity can achieve about 0.2 mV mW−1. The difference between the input powers in the two sections is below 0.1% for equal output voltages. For an amplitude modulation measurement, the carrier frequency is the main factor to influence the measurement results. In short, the key aspect of this power sensor is that the microwave power measurement can be replaced by a dc power measurement with precise wideband.

A novel symmetrical microwave power sensor based on MEMS technology

A novel symmetrical microwave power sensor based on MEMS technology is presented. In this power sensor, the left section inputs the microwave power, while the right section inputs the DC power. Because of its symmetrical structure, this power sensor provides more accurate microwave power measurement capability without mismatch uncertainty and temperature drift. The loss caused by the microwave signal is simulated in this power sensor. This power sensor is designed and fabricated using GaAs MMIC technology. And it is measured in the frequency range up to 20 GHz with an input power in the 0–80 mW range. Over the 80 mW dynamic range, the sensitivity can achieve about 0.2 mV/mW. The difference between the input power in the two sections is below 0.1% for an equal output voltage. In short, the key aspect of this power sensor is that the microwave power measurement is replaced with a DC power measurement.

A comparison of dissipated power and signal-to-noise ratios in electrical and optical interconnects

A comparison between dissipated power and signal-to-noise ratios (SNR's) in electrical and optical interconnects is performed. It is shown that in the absence of amplification to logic voltage levels the electrical interconnection requires much lower signal powers. However, if the amplification in the receiver is included, comparable total power dissipation and SNR's result under the constraint of equal output voltage.

A Method of a Single Phase PWM for a Utility-connected Power Supply in Photovoltaic Power Generation Systems

We propose a method of a sigle phase PWM for a utility-connected power supply in photovoltaic power generation systems. In this paper, the PWM is derived from camparing levels of signal waves with ones of carrier waves which have bipolar swing different from unipolar one in the conventional PWM, and shifting phase a little at exery on-off time. We can expect that array voltage needed is reduced by about 15% and harmonics content contained in output voltage is reduced by about 24% in this PWM in comparison with the conventional with equal output voltage.

Modular DC–DC convertor for high-output voltage applications

A modular DC–DC convertor for high-output voltage applications is presented. The proposed convertor consists of DC–DC modules whose inputs are connected in parallel and the outputs in series, with a control scheme that ensures input current sharing among the modules and regulated output voltage. Moreover, it utilises single feedback sensing that achieves almost equal output voltage sharing among the modules.

Frequency Independent “RC” Phase Shifter

This is a report of a study of an “RC” Phase Shifting network to develop a constant phase difference over a broad frequency range. Two channels are used which give equal output voltages nearly independent of frequency, while their phase difference is approximately constant over the design range. Some interesting properties of this circuit will be demonstrated.