Switching Frequency Research Articles

Measurement of half-bridge parasitic impedances using a flexible test probe

The use of SiC MOSFETs in power applications allows to increase power density and efficiency because switching frequencies are higher. However, parasitic impedances are responsible for oscillations that can have negative effects. In this paper we analyse the parasitic impedances of a half-bridge formed by a busbar PCB laminated with SiC MOSFETs. Using the distributed parameter approach, we have developed a procedure to characterize the impedance of the switching current loop responsible for the oscillations in the switching. According to the above, the conclusions obtained will be presented.

Cognitive abilities are associated with rapid dynamics of electrophysiological connectome states

Abstract Time-varying changes in whole-brain connectivity patterns, or connectome state dynamics, hold significant implications for cognition. However, connectome dynamics at fast (>1 Hz) timescales highly relevant to cognition are poorly understood due to the dominance of inherently slow fMRI in connectome studies. Here, we investigated the behavioral significance of rapid electrophysiological connectome dynamics using source-localized EEG connectomes during resting state (N = 926, 473 females). We focused on dynamic connectome features pertinent to individual differences, specifically those with established heritability: Fractional Occupancy (i.e., the overall duration spent in each recurrent connectome state) in beta and gamma bands and Transition Probability (i.e., the frequency of state switches) in theta, alpha, beta, and gamma bands. Canonical correlation analysis found a significant relationship between the heritable phenotypes of subsecond connectome dynamics and cognition. Specifically, principal components of Transition Probabilities in alpha (followed by theta and gamma bands) and a cognitive factor representing visuospatial processing (followed by verbal and auditory working memory) most notably contributed to the relationship. We conclude that rapid connectome state transitions shape individuals’ cognitive abilities and traits. Such subsecond connectome dynamics may inform about behavioral function and dysfunction and serve as endophenotypes for cognitive abilities.

Rapid dynamics of electrophysiological connectome states are heritable

Abstract Time-varying changes in whole-brain connectivity patterns, or connectome state dynamics, are a prominent feature of brain activity with broad functional implications. While infraslow (<0.1 Hz) connectome dynamics have been extensively studied with fMRI, rapid dynamics highly relevant for cognition are poorly understood. Here, we asked whether rapid electrophysiological connectome dynamics constitute subject-specific brain traits and to what extent they are under genetic influence. Using source-localized EEG connectomes during resting state (N = 928, 473 females), we quantified the heritability of multivariate (multistate) features describing temporal or spatial characteristics of connectome dynamics. States switched rapidly every ~60–500 ms. Temporal features were heritable, particularly Fractional Occupancy (in theta, alpha, beta, and gamma bands) and Transition Probability (in theta, alpha, and gamma bands), representing the duration spent in each state and the frequency of state switches, respectively. Genetic effects explained a substantial proportion of the phenotypic variance of these features: Fractional Occupancy in beta (44.3%) and gamma (39.8%) bands and Transition Probability in theta (38.4%), alpha (63.3%), beta (22.6%), and gamma (40%) bands. However, we found no evidence for the heritability of dynamic spatial features, specifically states’ Modularity and connectivity pattern. We conclude that genetic effects shape individuals’ connectome dynamics at rapid timescales, specifically states’ overall occurrence and sequencing.

An extendable switched‐capacitor based three‐phase multilevel inverter with boosting capability

AbstractThe increasing demand for integrating renewable energy sources necessitates inverter topologies with boosting capabilities. Using inverters with boosting capability and a low number of components to integrate renewable energy sources can reduce costs. This study describes a three‐phase multilevel inverter based on extendable switching capacitors. The use of voltage‐doubling modules permits the development of the inverter's capability. By increasing the number of doubling modules, the number of output voltage levels and boost factor are increased. Furthermore, the study introduces and implements a line voltage‐based pulse width modulation approach developed for the proposed inverter. The operation of the proposed multilevel inverter, along with the pulse width modulation scheme, common mode voltage, and power loss analysis are thoroughly discussed. Additionally, a comparative analysis is provided; highlighting the advantage of reducing the number of power switches in the proposed three‐phase inverter compared to other existing topologies. Finally, a laboratory prototype is developed, operating at a 4 kHz switching frequency and with a 120 V DC‐link voltage. The experimental results corroborate the efficiency and performance of the proposed multilevel inverter, thereby validating its practical applicability.

Phase disposition PWM control topology based: A novel multilevel inverter with reduced switch for power electronics applications

In the field of industrial drive applications, a neutral point clamped multilevel inverter (NPC MLI) is an extensively used option. The NPC MLI architecture involves more number of components for higher level and higher switching frequency operation. In this work paper, a novel three-phase 3-Level MLI is proposed evading the usage of clamping diodes and quadratic switches. Additionally, phase disposition pulse width modulation (PD-PWM) control technique is also employed for the proposed MLI. In comparison to NPC MLI, proposed MLI reduces the voltage switching stress as only one switch is operated per inverter leg. Another feature is that there is a considerable reduction in power losses as the current flows only through fewer elements. The proposed 3L inverter topology is explored thoroughly using the MATLAB simulation model. The evaluation of results is also demonstrated concerning the proposed PD-PWM technique by comparing its performance with the conventional sinusoidal PWM method. The Real-Time hardware-in-loop (HIL) simulator is also used to validate the simulation outcomes of the proposed model.

Design Considerations for Power-Efficient Fully Integrated 3:1 Switched Capacitor DC-DC Converter for PV Modules

This article presents a power-efficient DC-DC converter based on a switched-capacitor (SC) cell in power management systems supplied for fully integrated photovoltaic (PV) modules. These modules shall provide high-performance point-of-load voltage regulation. The primary objective of this study is to better utilize capacitance and switches by selecting a proper SC topology in order to improve the power efficiency of SC converters. A general steady-state performance model is investigated to optimize and compare a variety of SC DC-DC topologies. The investigation method relies on a charge-multiplier approach and considers the impact of area constraint on capacitors. To identify the most suitable topology for a given conversion ratio, the performance-limit metrics of SC converters are calculated. The analysis provides framework to determine optimum switch size and switching frequency for a two-phase 3:1 series–parallel converter for a target load current of 10 mA implemented on a 22 nm process technology. The results shows that a minimum of 250 MHz switching frequency is desirable for achieving a target efficiency greater than 85% while maintaining the minimum output voltage of 0.34 V. The analysis results are verified through MATLAB and PSpice-based simulations.

Evaluation and Implementation of EMI/EMC Compliance for a Proposed Power Electronics-Based Converter Topology for Electric Vehicles

The demand for high-gain, efficient, and cost-effective power converters with simple control mechanisms to connect electric vehicle batteries to the grid is increasing. This study introduces a switched capacitor-based power boost converter circuit to meet these needs. The minimal number of power switches in the circuit simplifies control operations and improves practical applicability. The proposed converter boosts the battery pack voltage by a factor of 5 and 11 for duty ratios of 0.5 and 0.8, respectively, which is significant compared to conventional boost converters. However, designing an electromagnetic interference (EMI) filter is crucial when a power converter board requires the application of a wide range of switching frequencies to enhance electromagnetic compatibility (EMC) immunity. Therefore, as the next step, the EMI/EMC filter design stages were discussed for the proposed converter. For this purpose, 15 printed circuit board (PCB) design rules were checked using the Altium Designer EMI Design Rule Checker, and board EMI/EMC compatibility was analysed. The resonance between the power and ground layers in the PCB was assessed using the plane resonance analyser. The results of simulation and laboratory tests are presented, which confirms the theoretical studies. On the basis of the software results, the points on the electronic board most susceptible to visual interferences have been identified. To minimise these EMI/EMC errors, it is suggested to add electronic components, such as capacitors, at these points according to mathematical and software findings.

Comparative study of the two DTC (6S - 12S) approaches applied to PMSM equipped with an IP regulator

Direct torque control was introduced in 1980 for induction machine for torque and flux control and developed for MSAP in 1990. DTC is gaining popularity due to its simple control structure and easy implementation. The principle of direct torque control (DTC) of the asynchronous machine was introduced in 1985 by I. Takahashi as an alternative to flux-directed vector control (FOC). It is thanks to its simple control structure that it gains popularity and its easy implementation that it has opened a new horizon in the field of variable speed control of electric drives. Indeed, direct torque control (DTC) has benefited in recent years from significant methodological advances in operation and technological development following the introduction of power electronics and digital electronics and the implementation of possible and very usable control algorithms. In conjunction with these technological advances, the scientific community has developed several control approaches to control the operation of electrical machines. In this context, this article presents a comparative study of the different direct torque control (DTC) strategies and structures of the permanent magnet synchronous machine (MSAP). We propose the algorithm of this control making it possible to provide solutions to the ripples of the torque and the stator flux in order to reduce them by adopting a method of compensating the effects of progression by passing from the six sector DTC (DTC – 6S: classic and modified) then develop the twelve-sector DTC (DTC-12S) whose purpose is to minimize ripples and control the switching frequency of the inverter. The simulation graphs presented will clearly show the difference between the different controls techniques cited.

Direct Torque Control Space Vector Modulation for Induction Motor Driven by Matrix Converter

This study proposes enhancing induction motor (IM) drive systems by developing a DTC-MC with SVPWM integration to reduce ripple. DTC-MC is effective for precise torque control in AC drives, offering high control accuracy by isolating stator flux and torque. The method excels in sensor-less speed control, maintaining unity input power factor at low speeds, and constant switching frequency for rapid torque adjustments. Combining DTC-MC with SVPWM improves simplicity, dynamic behavior, and torque response. The DTC-SVM approach further refines the torque response by correcting flux and torque discrepancies. MATLAB/SIMULINK simulations validated the approach, showing a robust dynamic response and significantly reduced motor torque ripple and control of speed.

A Decoupled Modulation Strategy for Constant Voltage/Current Wireless Charging System Under High Coils Misalignment

ABSTRACTOutput fluctuation and lower transmission efficiency under load and mutual inductance variation are hot concerned in the wireless charging system for power batteries. In this paper, a decoupled tracking strategy is proposed to realize constant voltage (CV) or current (CC) output and high transmission efficiency. The circuit model of series–series compensation network is built, and corresponding transmission characteristics can be derived. First, the load and mutual inductance value can be estimated by measuring the primary electrical information, including the inverter output voltage, current, and the phase error between them. Then load‐independent voltage or current output characteristics under coils misalignment can be maintained by tracking the optimal switching frequency of inverter part. In addition, the value of output voltage or current can be adjusted flexibly for different operation occasions by the employment of pulse‐width modulation. As a result, the load‐independent output characteristics realization and output adjustment can be decoupled. Based on only the primary measuring information, the CV/CC output can be maintained via the proposed hybrid control strategy when the coils misalignment and load variation happen, increasing the robustness of whole wireless power transfer (WPT) system. Furthermore, the soft switching of all power switches in the inverter part can be realized to reduce the switching loss. Compared with previous research, the proposed wireless charging system has a higher power density and a simplified control strategy. Finally, an experimental platform with 60‐V charging voltage and 3.6‐A charging current is built to verify the feasibility of the proposed sys‐tem and control method.

Optimization Control Strategy for Light Load Efficiency of Four-Switch Buck-Boost Converter

The four-switch buck-boost (FSBB) converter usually adopts a pseudo-continuous conduction mode (PCCM) soft switching (ZVS) control strategy, but there is a problem with the low efficiency of FSBB converters under light loads. Firstly, the constraints that the control variables of the FSBB converter need to satisfy are analyzed, and it is pointed out that the fixed frequency constraint is not necessary. Then, the switching frequency is used to control the degree of freedom, and the quantitative relationship between the FSBB converter loss and the switching frequency is obtained. Finally, for different input voltages and loads, the switching frequency corresponding to the minimum power loss is calculated offline. By optimizing the switching frequency, the light-load efficiency of the FSBB converter is improved. A prototype with an input voltage range of 210 V–330 V, an output voltage of 270 V, and an output power of 3 kW was developed. The loss was reduced by 15% at 20% load, and the peak efficiency of the converter reached 99.23%. The experimental results verified the effectiveness of the proposed control strategy.

Improvement of the Source Current Quality for a Shunt Active Power Filter Operating Using Hysteresis Technique with Stabilized Switching Frequency

Determining the current reference for a shunt active power filter (SAPF) can be carried out in many ways. Once the reference is determined, it can be shaped by SAPF switches with the use of pulse width modulation (PWM)/hysteresis control techniques. There are many variants of shaping the compensation waveform using these techniques. Nevertheless, regardless of the PWM/hysteresis technique adopted, a switching frequency current component appears in the system. It acts as a carrier used to inject a compensating current into the grid. Once the compensating current has been entered into the grid, the switching component should be reduced in it. This can be performed using RLC passive filters in various variants. The article discusses a variable/stabilized frequency hysteresis current control technique adapted for SAPF regulation with the use of current closed-loop control (source current direct control). For this technique, the passive filter should be placed outside the current control loop. The article focuses on examining the effectiveness of the interaction of the RLC filter with SAPF acting with such a control technique.

Research on a Thirteen-Level Switched Capacitor Inverter with Low Switching Loss

This paper presents a 13-level switched capacitor inverter with a novel modulation method designed to minimize the number of switches and significantly reduce switching losses. The inverter stands out for its simplicity, requiring only ten semiconductor switches to generate 13 levels. A key feature is the inherent self-voltage balancing of the capacitors, which eliminates the need for additional control mechanisms. The inverter’s unique architecture, comprising high-voltage and low-voltage modules, enables modulation using a hybrid PWM approach that combines step waveform modulation with level-shifted PWM (LS-PWM). This innovative technique dramatically lowers the switching frequency of the high-voltage module’s switches, independent of the carrier frequency, thereby limiting the number of switches in high-frequency operation and achieving substantial reductions in switching losses. This paper provides a detailed analysis of the inverter’s operating modes, voltage-balancing mechanisms, and parameter calculations. The advantages of the topology presented in this paper are demonstrated by comparison. Finally, the simulation and experimental results confirm the practicality and effectiveness of the proposed inverter and its modulation strategy.

Harmonics Measurement Errors in Grids with High Presence of Power Electronics Converters

The article presents field results and discusses the harmonic measurement errors of power quality analyzers (PQA) due to sampling aliasing of currents and voltages in grids with the presence of power electronics converters (PEC). The PQA may imply non-existing harmonic components incorrectly depending on the sampling rate of the PQA and the switching frequency of the PEC. Such phenomenon is prone to become more common and unpredictable due to the amplification of high-frequency components in voltages and currents due to interactions between PEC, loads, and grid elements. The conclusion is that PQAs, as required by standards in use currently, are not prepared to identify and quantify, when necessary and correctly, the high-frequency components that are present in modern electric networks with multiple PECs.

High efficiency AOT-controlled boost converter with pseudo-constant switching frequency

An on-time generator for boost converters is proposed to achieve an adaptive on-time (AOT) control with pseudo-constant frequency in continuous conduction mode (CCM). Since the first-order parasitic effect of the components and devices is considered in the design of the on-time generator, the switching frequency (fsw) variation of the boost converter in CCM can be better suppressed with the load current (ILOAD), input voltage (VIN) and output voltage (VOUT) changes, which can effectively solve the EMI noise problem. In addition, the idea of capacitor pre-charging is applied to simplifying circuit complexity. Meanwhile, an on-demand modulation strategy is applied to improve the conversion efficiency. Simulation results show that the boost converter based on the proposed on-time generator can realize the fsw variation of 0.4 % in case of 200 mA ILOAD change. Moreover, the VIN may range from 0.8 to 1.5 V, the VOUT is set to 1.8 V, and the peak efficiency of the simulation is 96.9 %.

ISOS-SAB DC/DC Converter for Large-Capacity Offshore Wind Turbine

This study offers a modular isolated grid-connected DC/DC medium-voltage DC aggregation converter to support offshore full DC wind farms’ need for lightweight and highly efficient power aggregation and transmission. The converter can simultaneously have a smaller transformer size and lower switching frequency during operation through the dual-voltage stabilization three-loop control strategy and phase-shift modulation strategy, which greatly reduces the space occupied by the converter and lowers the switching loss, Additionally, the use of a two-level structure at a lower switching frequency has lower loss, which effectively reduces the cost of the power device compared with the commonly used three-level converter. The input series output series connection between the converter sub-modules effectively lowers the voltage stress on each power switching device and facilitates expansion into a multi-module structure, expanding its application in high-voltage and large-capacity environments. This study analyzes the two working modes of the DC/DC converter and its control approach, in addition to providing a detailed introduction to the application scenarios of this converter. Ultimately, the efficacy and practicability of the suggested topology and control scheme are confirmed by simulations and experiments.

Influence of Parasitic Elements on Flyback Converter at High Switching Frequency Operation: A Comprehensive Analysis

The presence of parasitic elements in the flyback converter amplifies the impact on the converter’s primary current quality, particularly when the converter's switching frequency exceeds its designated operational rate. In this paper, the parasitic and stray elements of the transformer have been comprehensively examined, modelled, and simulated to evaluate their influence on the converter, with specific emphasis on the primary current. The simulation was performed utilising MATLAB SIMULINK software, integrating the authentic critical characteristics of the components, and conducting tests at various switching frequencies. The simulation results indicate that the primary current exhibits pronounced resonance effects at higher switching frequencies. The experimental findings are presented to corroborate the theoretical analysis and simulations pertaining to the impact of parasitic elements on the transformer and its immediate environment.

Comparison of space vector and switching frequency optimal pulse width modulation for diode free F‐type multi level inverter

AbstractThis study presents a comprehensive examination of space vector pulse width modulation (SVPWM) and switching frequency optimal PWM (SFOPWM) for an F‐type multilevel inverter (FTMLI). SVPWM offers a simple, digital implementation for three‐phase, three‐level inverter structures, and carrier‐based SFOPWM allows for maximum use of switching frequency with a simple construction. This approach reveals the underlying relationship between the above two PWM techniques with various amplitude and frequency modulation indices to ensure the performance of FTMLI. A suitable comparative study was carried out to verify the PWM techniques based on the inverter output voltage, total harmonic distortion, switching stress, and filter size. The analytical conclusions are supported by the simulation results and their experimental validation.

Fixed Switching Frequency Model Predictive Control and Passivity Based Control for DC-DC Converter

The DC-DC converter represents a crucial component in the renewable energy sources. The stability and dynamic capability enhancement of the DC/DC converter have emerged as a significant research topic in the current era. Model predictive control (MPC) is particularly prevalent due to its high dynamic response speed, simplicity of the controller design, and capacity for multi-objective optimization. However, the traditional finite control set model predictive control (FCS-MPC) method is suffer to variable switching frequency and vast computing. To improve the dynamic performance of the converter, a novel nonlinear control strategy named fixed switching frequency MPC and passivity-based control (PBC), named FSFPBMPC, is proposed, which could achieve fixed switching frequency and enhance the system's dynamic response speed. Firstly, the Euler-Lagrange (EL) model of the boost converter is established. Secondly, the relationship between duty cycle and MPC is established. Ultimately, the output voltage of PBC is incorporated into the cost function of the FCS-MPC. The characteristics of PBC power shaping and damping injection can enhance the system's immunity to interference, improve the system's dynamic response speed, and thus reinforce the system's stability. Then, depending on MATLAB, the simulation results proved that the proposed strategy has the same effect as we expected.

A novel satisfactory model predictive control based on current variance for high power three‐level‐NPC rectifiers

AbstractHere, a novel satisfactory model predictive control based on current variance (CV‐SMPC) is proposed for three level neutral point clamped (NPC) rectifiers. CV‐SMPC achieves global optimization of multiple control objectives rather than optimal control of a single control objective with the satisfaction interval. The current satisfaction interval is adjusted online based on the current variance in the CV‐SMPC. The relationship between the current total harmonic distortion (THD), switching frequency, and current variance is established through experimental investigation, enhancing the comprehensibility of control effects. In addition, three simplified sets of candidate vectors are proposed based on the voltage satisfaction interval, thereby reducing the computational burden. Furthermore, the control objectives are categorized into three levels and sequentially combined, eliminating the laborious process of adjusting the weighting factors. Finally, the experimental results conclusively demonstrate the exceptional control performance of CV‐SMPC in both steady‐state and dynamic processes.