RMS Current Research Articles

A General Analysis of Resonant Switched-Capacitor Converters Using Peak Energy Storage and Switch Stress Including Ripple

This work presents a general analytical framework enabling large-signal characterization of resonant switched-capacitor (ReSC) power converters that accounts for passive component voltage and current ripple, for operation at and above resonance. From this, appropriate phase durations for minimized rms currents are derived, in addition to expressions for total passive component volume using an intuitive peak energy method. An example hardware prototype validates both the derived waveforms and timings—as well as total passive volume—through three comparable hardware configurations, one of which minimizes passive component volume. In addition, the proposed technique formulates analytical expressions for both rms currents and peak blocking voltages, facilitating refined loss estimation and component selection. Subsequent calculation of the large-signal Volt–Amp (VA) switch stress metric allows a more accurately quantified trade-off between active and passive components compared to prior work, which has not fully accounted for ripple. Four common ReSC topologies are exemplified throughout, with topology specific parameters documented for reference.

An enhanced current chopping control strategy for SRM drives using Harris Hawks optimization algorithm

This research proposes an Optimized Current chopping Control (CCC) approach for SRM drives. The goal is to implement a simple SRM drive that can effectively meet electric vehicle requirements, comprising minimized torque ripple to reduce vibrations and acoustic noises, maximized output torque to enhance vehicle acceleration, and improved efficiency, which contributes to extending the EV's battery life. Therefore, an optimization problem is formulated and solved offline, incorporating a CCC-based SRM drive model. The control variables for this optimization problem are the switching angles of the SRM. A multi-objective function is chosen to combine three performance indices: torque ripple, average torque, and efficiency. The Harris Hawks Optimization (HHO) method is utilized in this paper to solve the optimization problem and find the optimal switching angles based on the selected objective function. HHO demonstrates a strong search capability that can effectively handle the nonlinear magnetization characteristics of SRMs. Constraints on the switching angles are also included in the optimization problem to control the phase current's RMS value and power consumption. The optimized switching angles are applied to a current chopping control (CCC) strategy and an asymmetric half-bridge converter to implement the proposed HHO-based CCC drive. Moreover, to demonstrate the effectiveness of the proposed HHO-based CCC drive, a comparative analysis based on simulations and experimental measurements is presented against other CCC approaches for SRM drives, including modified particle swarm algorithm (MPSO)-based CCC drives and analytical-based CCC drives.

Variable Switching Frequency for ZVS over Wide Voltage Range in Dual Active Bridge

The Dual Active Bridge (DAB) converter is known for its advantageous characteristics, including bidirectionality, galvanic isolation, and soft-switching operation. However, achieving Zero Voltage Switching (ZVS) across the complete operation range is not guaranteed, particularly through a wide input–output voltage ratio. This paper explores the integration of the switching frequency as a control variable in the DAB converter to ensure ZVS operation across a wide voltage range, employing Single Phase Shift (SPS) modulation. The study evaluated the RMS and reactive currents under variable switching frequency, presenting the advantages of this approach. Moreover, it includes a design-oriented analysis of the ZVS limits and their relationship with the switching frequency, aiming to ensure ZVS at any operating point. Experimental results validated the theoretical analysis, while presenting the main advantages of variable switching frequency implementation.

Composite Duty Modulation of Dual Active Bridge Converters to Minimize Output Voltage Ripples and Inductor RMS Currents

Composite Duty Modulation of Dual Active Bridge Converters to Minimize Output Voltage Ripples and Inductor RMS Currents

Integrated System of Mechanical Regulator and Electrical Circuitry on Triboelectric Energy Harvesting with Near‐Field Communication for Low Power Consumption

AbstractThis paper presents an integrated power generation, conversion, and storage system with a temperature monitoring system, including passive near‐field communication (PGCS‐TMS‐pNFC), based on triboelectric nanogenerators (TENGs). The system consists of three parts; first, a mechanical regulation system (MRS) with kinematic design and multiphase control; second, a phase control rectifying circuit (PCRC) with a battery charging circuit (BCC); and third, a data processing and communication system (TMS‐pNFC) for low power consumption. The MRS, consisting of a reel spring and gear train, achieves a high‐frequency output exceeding 1000 Hz, and long‐lasting operation. PCRC provides stable and minimizing fluctuated DC output with a ripple effect as RMS voltage and current of 423 V and 46 µA, for 2 s, with a crest factor of 1.15 and 1.08. The PGCS‐TMS‐pNFC, harvesting building energy, such as opening and closing doors, is used to sense and store temperature data for more than 29 min, and the data is transmitted to the receiver via pNFC through smartphone tagging. Additionally, the PGCS with BCC is implemented on a bicycle frame to charge electronic devices while riding. This research underscores the integrated approach and practical applications of TENG technology that contribute to energy efficiency and sustainability in the lives.

Open-Phase-Tolerant Online Current References for Maximum Torque Range and Minimum Loss With Current and Torque-Ripple Limits for n-Phase Nonsalient PMSMs With Nonsinusoidal Back EMF

Multiphase permanent-magnet synchronous machines (PMSMs) with nonsinusoidal back-electromotive force (back-EMF) offer high fault tolerance and torque density for electric vehicles. Most current-reference generation methods either minimize stator copper loss (SCL) or maximize achievable torque. Optimization of both goals is accomplished by full-torque-range minimum-loss (FRML) strategies, but so far just for sinusoidal back-EMF. Thus, FRML for nonsinusoidal back-EMF should be sought. Moreover, many methods are only suitable for healthy conditions or specific machines, harmonics, or open-phase-fault (OPF) scenarios. Additionally, the torque range may be extended by permitting torque ripple or (transiently) greater rms current, but this approach is not general nor FRML yet. This paper proposes online FRML current-reference generation for multiphase PMSMs with nonsinusoidal back-EMF: nonsinusoidal-back-EMF FRML (NSBE-FRML). When the torque reference is feasible, minimum SCL is attained while maximizing the achievable torque (i.e., FRML). For higher torque references, the instantaneous torque deviation is minimized, and the torque reference is saturated in consecutive samples limiting the torque ripple to a pre-specified threshold. Furthermore, the rms current is limited after transient overload by automatically decreasing the torque reference. The NSBE-FRML is suitable for any harmonics, healthy/OPF conditions, and multiphase PMSMs with negligible saliency ratio. Experiments are performed with a six-phase PMSM.

Full power range DAB unified ZVS control strategy based on low current RMS

Inductive current RMS and soft switching are important performance indexes of dual active bridge DC-DC converter (DAB). This paper proposes a new optimal control strategy for the soft switching range based on the optimization of the effective value of the inductor current. This control strategy restricts the inductor current during switch action, ensuring a significant extension of the soft switching range across the entire power range, reducing switch losses, and achieving the accurate effective value of current, thereby further enhancing the efficiency of the DAB converter. Meanwhile, a new modulation method is proposed to achieve thermal balance between bridge arms. Finally, a simulation model is built and verified using Matlab.

Enhancing power quality in vehicle-to-grid (V2G) operations of FCEVs through the integration of real-time digital IIR filters in power calculations

Fuel cell electric vehicles (FCEVs) are estimated as the future's mobile distributed generators with vehicle-to-grid (V2G) functions. Besides, V2G topologies are required to be designed with an appropriate analog filter by accurately measuring the reference current and voltage values of inverters and converters. Thus, the highest accuracy is required in control structures for charging and grid connection of FCEVs to improve the power quality (PQ). In this study, PQ improvement of V2G operation of FCEVs is proposed by considering the developed real-time digital infinite impulse response (IIR) filters in generating reference signals in the power calculation stage. A band-pass digital IIR filter design is realized with the inverter using LabVIEW infrastructure, and reference signals are smoothed by using IIR filters. The performances of developed different IIR filters' results are examined in the study. Developed filters are designed using the order estimation method. Elliptic, Chebyshev, and Butterworth filters are applied to the voltage and current signals, and the best results are obtained in reference power signals with the Butterworth filter. The Butterworth filter maintains stability in current RMS, induces a 0.09 % decrease in voltage RMS, and shows a slight 0.30 % increase in active power. The proposed approach removes distortions in reference power signals by using a designed filter for a reliable V2G operation of FCEVs.

PWM-Based Predictive Direct Torque Control of Switched Reluctance Machine for Accurate Torque Tracking with Minimization of Phase RMS Currents

PWM-Based Predictive Direct Torque Control of Switched Reluctance Machine for Accurate Torque Tracking with Minimization of Phase RMS Currents

Experimental analysis of the air- and water-based cooling solution for the three-phase line choke

Modern power systems are affected by current harmonics. The high-order harmonics may result in overheating of the power system and lifetime reduction. Hence, the most novel power systems are equipped with three-phase line chokes. However, power losses generated in three-phase chokes result in a temperature increase within the choke. Most of the commercially available three-phase chokes are equipped with a passive air-based cooling solution. Such a solution results in an increase in the overall size of the device as well as an increase in the manufacturing costs. The water-cooling plates were installed in the commercial three-phase and the cooling performance of the air- and water-based cooling systems were experimentally compared. The chokes were analyzed at the RMS currents that corresponded to 100%, 75% and 50% of the nominal losses of the device. The temperature of the chokes was monitored with the thermocouples and precise IR camera. The comparison of the thermal results showed that the water-cooled choke outperformed the air-cooled unit. The core temperature of the device was reduced from approximately 110 °C to approximately 26 °C for the water-cooled solution compared to the air-cooled one. The temperature distribution in the windings was comparable for both solutions. The highest measured temperature exceeded 100 °C for both cooling solutions. The experimental results presented in this study can be used for further modification of the water-cooling system. Especially, in terms of the water panels’ shape, position and water inlet configuration. Such modifications should lead to further reduction of the device temperature, material and manufacturing costs.

Power Boundary Controlled Single-Stage LLC Power Factor Correction Converter and Its Optimal Parameter Design

The time-domain analysis on single-stage LLC power factor correction (PFC) converter is performed in this paper, which reveals that PON mode may occur around the peak point of instantaneous input power and cause instability issue. In order avoid PON mode, the power boundary between PO and PON mode is calculated. For the common design methods of LLC PFC converter with average mode control strategy, the power boundary requires to be higher than the instantaneous input power at its worst point. However, higher power boundary brings higher RMS value of resonant current, and causes higher reactive power loss. Therefore, it is a wasteful designing methodology, as the other points of instantaneous input power don't need such high power boundary. In order to improve the efficiency, a power boundary control strategy is proposed in this paper. By controlling the input current to make the instantaneous input power follow the power boundary, PON mode is eliminated. Consequently, the required power boundary is overall reduced, and the minimal RMS current of resonant tank can be achieved. Furthermore, the optimal parameter design is also presented. A 90∼240VAC input and 250W/48V output experimental prototype has been built to verify the analysis results.

Simulation of Energy Dissipation in BLDC Motor and Analysis of Speed-Acoustic Characteristics

The hybrid electric vehicle combines dual propulsion systems: one employs the traditional internal combustion engine, while the other utilizes a PMDC or BLDC motor. Generally, BLDC motors exhibit an efficiency of 85% to 90%. Conversely, the PMDC motor inherently achieves an efficiency of 88% under optimal running conditions. Moreover, improving the efficiency of both motors is impeded by their design constraints. Power losses in these motors primarily stem from factors such as heat generation in the rotor (I²R losses), bearing friction, vibrations, and noise. This paper aims to investigate energy loss in a 4 kW BLDC motor manufactured by Bosch, attributable to speed-induced acoustic noise effects. Harmonic analysis of the phase current reveals the presence of odd-order harmonics, specifically those below the 11th order, resulting in current ripples. These dominant harmonic frequencies interact, ultimately generating noise and consuming a certain amount of power. These predominant frequencies correlate with fundamental electrical parameters: current frequency (Hz), RMS current (A), and threshold (%r), all associated with the motor's input power source. The 'K' factor, a parameter dependent on these three electrical factors, is calculated to determine harmonic stability. Variations in stable speeds (ranging from 1280 to 7500 RPM) are used to record 'K' factor readings. Based on IEEE Standard 85-1980 guidelines, motors are classified as either acceptable (OK) or not acceptable (not OK) according to their harmonic stability 'K' factor. Readings for each speed step are captured at a specific predominant frequency, facilitating subsequent comparisons. To validate the experimental findings, MATLAB/Simulink and a Fluke scope meter are employed to conduct power analyses for each motor, thus assessing energy loss attributed to noise. The waveform of the phase current proves instrumental in quantifying energy consumption in the BLDC motor. Notably, higher-frequency noise waves with shorter wavelengths entail greater energy consumption. Evaluating energy loss significantly contributes to the analysis of BLDC motor speed acoustics, serving to inform the design of energy-efficient hybrid electric vehicle models powered by BLDC motors, which are intended for customer service.

Evaluation of the Optional Wideband Accuracy of Inductive Current Transformers in Accordance with the Standard IEC 61869-1 Ed.2

This paper presents the evaluation of tested inductive CTs’ accuracy for distorted current harmonics in accordance with the optional accuracy class WB1 introduced by the new edition of the standard IEC 61869-1 published in the year 2023. The tests were performed in compliance with the interpretation sheet IEC 61869-2:2012/ISH1:2022. Therefore, the resistive and the resistive–inductive loads of the secondary winding of tested inductive CTs were used, as this was required for the given test conditions. The results indicate that the units designed for the transformation of a sinusoidal current of a frequency of 50 Hz ensure the high wideband transformation accuracy of the distorted current harmonics, as demanded by the power quality monitoring and distorted electrical power and energy requirements. The key to this is proper design using modern magnetic material(s) for the magnetic core and its oversizing in relation to the requirements for a given accuracy class defined for the transformation of sinusoidal currents with a rated frequency. Both tested inductive CTs with a rated primary current RMS value equal to 300 A, class 0.2 and 0.5, ensured compliance with the requirements of the WB1 wideband accuracy class.

LLC Resonant Converters as Isolated Power Factor Corrector Pre-Regulators—Analysis and Performance Evaluation

The power supply of many applications running off the power line is made up of an isolated dc-dc converter powered by a front-end power factor corrector (PFC) stage. The PFC stage ensures compliance with the electromagnetic compatibility regulations but does not usually provide safety isolation since it is typically implemented with a boost converter. Lately, the increase in multi-output power supplies, especially in lighting and USB Power Delivery applications, has raised the need for an isolated PFC at power levels where currently there is not an industry standard solution. This isolated PFC is intended to power one or more non-isolated post-regulators to enable a substantial simplification of the overall architecture and a cost reduction. The usage of an LLC resonant converter as an isolated PFC has been considered and demonstrated only quite recently, raising the industry’s attention due to the favorable converter’s characteristics that have led to its success as a dc-dc converter. This paper provides two significant contributions. Firstly, it provides a quantitative assessment of the difference in the results obtained by designing an LLC-based PFC converter based on the first harmonic approximation analysis or the time-domain analysis by applying them to the design of the same converter. Secondly, it demonstrates that designing an LLC-based PFC converter to work also in the above-resonance region optimizes its performance by reducing the (magnetizing) reactive current in the resonant tank and, therefore, the rms currents on both the input and the output side and the related power loss.

Experimental Analysis of Fluke 345 Measurement Instrument Laboratory: Unloaded and Loaded Engines Case Studies

This scientific initiative project was carried out using the resources available in the laboratories of the Federal Universityof Tocantins (UFT), focusing on the Fluke 345 measuring equipment. The experiment presented in this paper involved two differentapproaches: one with an unloaded engine and another with a load consisting of a DC generator, both powered by a 60-volt supply. TheFluke 345 measures the voltage RMS, current RMS, and power factors and plots them along with the harmonic analyzes. The experimentshowed that no harmonics were detected at no load, while harmonics occurred under load. The data collected validates the theoreticalconcepts through practical application. This study provides valuable insights for power engineering, especially regarding the performanceof the devices under different conditions.

A Nonisolated Wide-Range Resonant Converter for LED Driver Applications

In this article, a non-isolated resonant light-emitting diode (LED) driver based on the LCLC resonant network is presented. The adopted LCLC network can provide load-independent current for LED string, also, the soft switching range and the semiconductor devices RMS current can be optimized within the entire range of the input and output voltage using the LCLC network parameters. A single auxiliary switch is employed for regulating the output current within a wide input voltage range using PWM control. In addition, the employed auxiliary switch can provide PWM dimming and open-load protection features. Detailed theoretical analysis including the operating modes and soft switching conditions of the proposed LED driver is presented, and the impact of the auxiliary switch snubber capacitor on the load-independent output current characteristic is analyzed. To verify the analysis and effectiveness of the proposed topology operation, a 40 W laboratory prototype with the input voltage range of 80 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 230 V is designed and implemented which delivers 0.5 A current to a high-brightness light-emitting diode (HB-LED) string.

Non-Isolated Current-Fed Series Resonant Converter with Hybrid Control Algorithms for DC Microgrid

Module-level power electronics can optimize the power generation of photovoltaic panels, which requires a simple topology structure, high power conversion efficiency, and wide voltage gain, corresponding to irradiance variations. This paper proposes a non-isolated current-fed L-C series resonant converter and its control algorithms. The proposed converter can obtain a buck–boost voltage gain with the hybrid control algorithm utilizing the switching frequency modulation and asymmetric pulse width modulation. The proper power stage design can guarantee the soft-switching capability for the entire operating range. Also, the control strategy is designed to obtain a small rms current. The operational principle of proposed converter is analyzed in order to design the resonant tank and control strategy. The performance of designed converter can be verified with the experimental results with a 500 W prototype converter.

Ampacity Decrease in a Three-phase Power Cable Fed by an Uncontrolled Rectifier and Finding a Lower Limit for the Power Cable Loss

23.06.2023 Accepted: 25.07.2023 DOI: 10.55581/ejeas.1293146 Abstract—Rectifiers are the most common nonlinear loads encountered in electrical power systems. Uncontrolled rectifiers are cheaper than synchronous rectifiers and more common than them because of this but the currents drawn by uncontrolled rectifiers contain harmonics. In addition, the amplitude of these harmonics depends on the value of the load power and the rectifier parameters. A 3-phase cable can be used to connect a three-phase rectifier to a 3-phase power system. In this study, the power losses of a 3-phase cable fed by a synchronous rectifier and an uncontrolled rectifier were compared. The electrical equivalent of a power cable is frequency dependent. The analysis performed in this study was made by making some assumptions about the frequency-dependent resistance of the cable and the rectifier currents. The analysis shows that when an uncontrolled rectifier is fed by a power cable, the cable always has more loss and heats up more for the same amount of RMS current.

RMS Current Minimization in a SiC-Based Dual Active Bridge Converter Using Triple-Phase-Shift Modulation

This paper proposes an optimization approach targeting RMS current minimization in a dual active bridge (DAB) converter controlled by triple-phase-shift modulation. The proposed technique overcomes the drawbacks in the existing optimization solutions, namely, the high complexity of the time-domain optimization and low accuracy of the fundamental harmonic minimization. A finite-component harmonic model is employed in the optimization approach to calculate the current harmonic values in the converter. The total RMS current is approximated as the summation of dominant harmonics using the harmonic model. A numerical assessment technique is also proposed in this research that guarantees the accuracy of the adopted harmonic model. The proposed method ensures that the harmonic approximation error is less than a certain level over the operating range. The converter's optimal parameters are calculated through a standard nonlinear optimization procedure. The results are verified in the PLECS simulation environment and experimentally validated on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$5\ kW$</tex-math></inline-formula> DAB converter. The prototype input and output voltage ranges are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$600\ V - 800\ V$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$200\ V - 450\ V$</tex-math></inline-formula> , respectively.

Degradation-Sensitive Control Algorithm Based on Phase Optimization for Interleaved DC–DC Converters

As the use of interleaved DC–DC converters in electric vehicles (EVs) increases, research on reliability improvement is required. In the case of interleaved DC–DC converters, degradation occurs between transistors and capacitors. In particular, transistor degradation imbalances cause an increase in output capacitor RMS current, which increases power loss and accelerates capacitor degradation. This degradation affects system reliability by increasing thermal stress. In this paper, based on a degraded 2-leg interleaved DC–DC boost converter, research to reduce the converter’s output capacitor RMS current was conducted. The output capacitor RMS current according to the transistor degradation imbalance was analyzed. As a result, it was confirmed that the transistor degradation imbalance causes an increase in the capacitor RMS current. To address this issue, a phase optimization algorithm for reducing increased capacitor RMS current is presented in this paper. Next, the phase optimization algorithm is mathematically analyzed. Finally, its efficacy is proved through simulations and experiments.