Variable Switching Frequency Research Articles

Design and Implementation of A LED Driver Circuit with Dimming Function without Burst Mode at Constant Switching Frequency

This paper presents a dimmable LED driver with a topology of combination of series and parallel resonant converter. In dimming operation, a variable resonant inductor controlled by a PWM signal at a low frequency, while proving DC output current approaches, switching frequency variation or conventional PWM technique is not used. The proposed technique is performed on a load that consists of 40 one-watt power LEDs connected in series. Switching frequency of circuit is kept constant at 60 kHz. According to experiments results, LEDs can be dimmed to a desired power level linearly within the range of nominal power to very low power without being in burst mode unlike of the conventional PWM technique.

Control tuning methodology for modular multilevel converter‐based STATCOM

SummaryThe application of modular multilevel converters (MMC) in medium voltage static synchronous compensators (STATCOMs) has been investigated in recent years. A huge challenge for MMC‐STATCOM is to compute the gain of the controllers. Therefore, the contribution of this paper is the proposal of a control tuning methodology for MMC‐STATCOM. For this purpose, the control and tuning strategies are presented. Since MMC‐STATCOM can employ different modulation strategies, two distinct modulation strategies are considered: nearest‐level control, with variable switching frequency; and phase‐shifted carrier pulse‐width modulation, with fixed switching frequency. Moreover, the proposal was validated through simulation and an experimental platform. The results indicate that the power response follows the reference, besides supplying the internal losses of the converter. The 10% ripple tolerance of the submodule voltages is respected in steady state for both modulation strategies. Moreover, the 5% total demand distortion (TDD) limit recommended by the Institute of Electrical and Electronics Engineers (IEEE) standard is attended. These results demonstrate the effectiveness of the controls employed.

A new generalized predictive current control algorithm with integration of fractional part function based modulation technique: Single phase self‐balanced type multilevel inverter topologies

SummaryIt is generally impossible to control the inverter output current (IOC) based on operator needs if only pulse width modulation (PWM) techniques are used. Conventionally, authors have reported the finite control set‐based predictive current control algorithm (FCS‐PCCA) to control the IOC with a fast dynamic response. However, this type of algorithm without a PWM stage generates a variable switching frequency (VSF) of operation, and it leads to filter design problems, inequitable thermal stress, and more current distortions that have been presented. To alleviate all these issues, a new generalized PCCA with the integration of a fractional part function‐based single carrier modulation technique (G‐PCCA‐FPF‐SCMT) has been proposed, and it provides constant switching frequency (CSF) of operation. In this technique, the normalized optimum inverter output voltage (N‐O‐IOV) has been fed with FPF‐SCMT. The particular modulation stage implementation is straightforward since even inverter level number increases, the number of references and triangular carrier signals is always only one. The complete control implementation process of the proposed technique is extremely low compared with all traditional CSF‐based PCCAs. To verify the proposed technique experimentally in both steady and transient state operations, one of the conventional five‐level switched capacitor‐based inverter topologies has been considered and elucidated vividly in both open‐loop and closed‐loop operations.

Dynamic Voltage Restorer to Mitigate Voltage Sag/Swell using Black Widow Optimization Technique with FOPID Controller

The efficiency with which electrical equipment use electricity is essential for several reasons. First, superior power quality (PQ) improves efficiency and facilitates peak performance in electronic equipment. This article's goal is to make the advantages of installing a Dynamic Voltage Restorer (DVR) to enhance PQ for energy users clearer. To improve DVR dependability and user friendliness, the suggested technique uses a hysteresis voltage control system that works with variable switching frequency. Simulation findings show that voltage compensation is successful under disturbances when a black widow optimization (BWO) based Factional order proportional derivative (FOPID) controller is used. This paper proposed is to improve PQ using a BWO- FOPID controller and compare the outcomes to those achieved from a previously developed PI controller in a distribution power system using MATLAB.

Enhanced Low-Speed Characteristics With Constant Switching Torque-Controller-Based DTC Technique of Five-Phase Induction Motor Drive With FOPI Control

The Classical hysteresis controller-based DTC (C-DTC) of an induction motor is a simple control scheme with better dynamics and steady-state characteristics when compared with the flux-oriented control (FOC) scheme. The major drawbacks of the C-DTC scheme are variable switching frequency and high average torque ripple under different rotor speeds. In this paper, the two-level five-leg inverter-controlled five-phase induction motor drive with constant switching torque controller-based DTC (PI-CST-DTC) scheme is introduced to improve the steady-state performance with constant switching frequency under various operating speeds. However, the proposed PI-CST-DTC exhibits slower torque and slower speed dynamics w.r.t C-DTC which is due to the periodic occurrence of zero vectors under transients. These slower dynamics are improved with the help of the proposed fractional order PI (FOPI) constant switching torque controller-based DTC (FOPI-CST-DTC) method. With the help of the hardware results, it has been verified that the proposed FOPI-based CST-DTC exhibits improved low-speed steady-state and dynamic performance of the five-phase induction motor drive. The proposed CST-DTC techniques with PI and FOPI controllers are compared with C-DTC for torque ripple reduction and %THD analysis and dynamics through hardware results.

The Impact of Periodic Variable Switching Frequency Modulation on Power Transmission in Dual-Active-Bridge Converter and an Improved Scheme

The Impact of Periodic Variable Switching Frequency Modulation on Power Transmission in Dual-Active-Bridge Converter and an Improved Scheme

Power Quality Improvement Using TID based DVR Controller

The effectiveness of power utilized by electronic devices is crucial for various reasons. Firstly, high-quality power results in better efficiency, allowing devices to operate at optimal energy levels. This article aims to clarify the significance of Power Quality by highlighting the benefits of using a Dynamic Voltage Restorer (DVR) to improve power quality for electricity consumers. The proposed method employs a hysteresis voltage control system that operates with variable switching frequency to enhance DVR reliability and ease of operation. Using a Tilt Integral Derivative (TID) controller, a type of fractional order controller similar to the PID controller, voltage compensation under disturbances is achieved with satisfactory results demonstrated via simulation. The primary objective of this project is to mitigate power quality issues such as voltage swell and sag in a distribution power system by enhancing power quality with a TID controller and comparing the results with those obtained from a previously implemented PID controller, using MATLAB software. Keywords: Dynamic Voltage Restorer (DVR), Tilt Integral Derivative controller (TID), Total Harmonic Distortion, MATLAB software.

A high-efficiency primary-side regulation control strategy for half-bridge LLC resonant converter with wide input voltage range

The requirement of the half-bridge LLC resonant converter with a wide input voltage range is becoming higher in photovoltaic applications because of its simple structure and low switching loss. Conventional frequency modulation (FM) requires a wide switching frequency range and a high-quality factor circuit design, leading to reduced efficiency and large component volumes at light loads. To solve the problems, a high-efficiency control strategy using adaptive pulse-width and frequency modulation (APWFM) is proposed. APWFM adjusts the gain by changing the switching frequency and duty cycle simultaneously. When the output power is below the reference value, the switching frequency decreases linearly as the output power decreases, and the duty cycle is simultaneously modulated to achieve constant output voltage, so the switching frequency variation range is smaller than FM. This results in improved light or medium load efficiency in a limited frequency range while keeping a small volume of magnetic components. Also, the proposed control strategy is realized with primary-side regulation (PSR) to eliminate the optocoupler and simplify the control circuit. Experimental results demonstrate a significant improvement in efficiency at medium and light loads compared to FM, and the average efficiency is improved by 5% based on low cost and simple operation.

A high efficiency buck converter based on PLL for frequency stabilization

A high efficiency Buck converter circuit based on Phase-locked loop (PLL) to achieve frequency stabilization is proposed to solve the problems of reduced converter efficiency, unstable output and high electromagnetic interference caused by unstable switching frequency. Since the increase of load current increases the switching frequency in the conventional adaptive on-time (AOT) control, a phase-locked loop is designed to achieve the switching frequency stabilization by forming a negative feedback. In addition, a bootstrap high-voltage gate driver circuit is designed to drive the dual NMOS power tubes in order to achieve high conversion efficiency and optimize the chip area. The proposed Buck circuit is simulated and verified based on SMIC 0.18 μm CMOS 2P4M process, with an input voltage of 2.5V–5.5V, an output voltage of 0.8V–4V, a switching frequency variation rate of only 8.5 kHz/A over the load range of 0.5A–3A, and a peak efficiency of 94.8 % over the full load range is achieved, and the undershoot/overshoot recovery time of the load transient response is only 5.4μs and 6.9μs.

Speed regulator and hysteresis based on artificial intelligence techniques of three-level DTC with 24 sectors for induction machine

Direct torque control (DTC) of induction motor (IM) is important in many applications. In this paper presents a three-level direct torque control with 24 sectors is applied for IM using PI-flou controller and hysteresis regulators based in artificial intelligence techniques. The DTC system is known to offer fast decoupled control between torque and flux via a simple control structure. Nevertheless, DTC system has two major drawbacks, with are the variable inverter switching frequency and high torque output ripple. The validity of the proposed control scheme is verified by simulation tests. The stator flux, torque, and current are determined and compared to the above technique.

Single-Phase Universal-Input PFC Converter Operating at High Frequency

Single-phase ac to dc converters for computers and related applications have requirements that are difficult to meet while achieving both high power density and high efficiency: wide input voltage range, large voltage step down, galvanic isolation, harmonic current limits and hold-up requirements. This work explores a circuit architecture and topology that is structured to facilitate operation at multi-MHz frequencies in order to address this challenge. We present a 250 W, 24 V output, universal input PFC converter prototype that leverages the proposed approach to achieve a power density of 34.9 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> while meeting the 80 PLUS Platinum efficiency standard, EN61000-3-2 line harmonic requirements and half-cycle holdup. The converter operates at variable switching frequencies in the range of 1-4 MHz; the measured efficiency at 230 Vac RMS, 60 Hz input is 95.33% at full load and 84.57% at 8% load.

Optimal Energy Management System Control of Permanent Magnet Direct Drive Linear Generator for Grid-Connected FC-Battery-Wave Energy Conversion

The Wave Energy Conversion System (WECS) control strategy is presented in this study to make sure the system operates at its best under fluctuating wave resource situations. The suggested system consists of a MOPSO based MPC approach, a point absorber WEC oscillating in heave, back-to-back power converter for grid connections, and a linear permanent magnet generator. Despite the benefits of model predictive control, problems including switching frequency variations, steady-state errors, high processing costs, and constrained prediction horizons continue to exist. The article presents a method that incorporates the switching control action into the cost function while maintaining the finite nature of a model predictive control to handle the switching frequency issue. In order to minimise switching frequency variations while also addressing other control goals, such as regulating the direct current linked voltage and controlling the flow of active and reactive power, the switching control weight factors are optimised. In order to increase power quality, a fuel cell-based short-term energy storage system is also included to direct current link between the back-to-back converters.

Modulated model predictive current control technique for single phase nine‐level T‐type packed U‐cell inverter topology

SummaryThis paper proposes a new floor function single carrier‐based modulated model predictive current control technique (FF‐SC‐M2PC2T) by considering conventional nine‐level T‐type packed U‐cell (9L‐TPUC) inverter topology. To get desired peak value of load current with low harmonic distortion, the finite control set‐based model predictive control technique (FCS‐MPCT) has been reported in the literature considering load dynamics and minimization of the cost function. However, inherently it suffers from variable switching frequency (VSF) of operation. To diminish this issue, an M2PC2T has been implemented and it provides a constant switching frequency (CSF) of operation. Especially coming to the modulation stage, most authors generally use level‐shifted pulse width modulation (PWM) techniques which inherently require more carriers, if‐else conditions, and additional logical gate blocks to generate particular level output. Hence, the control complexity increases as going to higher‐level inverter topologies. In this manuscript, a new simple floor function single carrier‐based pulse width modulation (FF‐SC‐PWM) technique has been proposed which applies to any single‐phase switched capacitor type multilevel inverter topology and it can be easily integrated with a predictive control algorithm to regulate the inverter output current (IOC). Finally, to check the effectiveness of the proposed control technique (PCT) in a closed loop, a laboratory prototype has been employed on 9L‐TPUC inverter topology with different static and dynamic case studies considering RL‐Load.

Global fast terminal sliding mode control with fixed switching frequency for voltage control of DC–DC buck converters

In this study, a global fast terminal sliding-mode control (GFTSMC), which offers a faster convergence performance than its counterparts is constructed for managing the state variables of the DC–DC buck converters. For the first time in this study, the GFTSMC was designed for power electronics circuits based on hysteresis modulation (HM). The HM technique’s variable switching frequency problem is overcome by reusing the GFTSMC structure, which enables the hysteresis band to be changed adaptively, and a fixed switching frequency is obtained. The proposed control scheme uses only one sensor for regulating the output voltage and controlling the switching frequency. Thus, an extremely economical and robust system, which is minimally affected by the negative aspects originating from the sensors, is obtained. Effectiveness of the proposed controller is validated with experimental studies. The experimental results shows that the output voltage and switching frequency are successfully controlled with good dynamic and steady state response. Finally, to validate the experimental feasibility of this paper, a comparison of the proposed method and four existing studies with different control schemes is presented.

A Variable Switching Frequency Multimode Control Scheme for Single-Phase Grid-Tied Multilevel PV Microinverters

Single-phase grid-tied microinverters are required to operate over a wide power range in photovoltaic (PV) applications. It is desirable to improve the efficiency over the entire power range without extra cost. This paper proposes a variable switching frequency (VSF) multimode control scheme to optimize the device losses at each operating point for a single-phase T-type hybrid-bridge inverter. The proposed optimal control scheme is devised based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V-I</i> plane analysis and can therefore be applied in both unity power factor (PF) and non-unity power factor operations. With reasonable simplifications and curve fitting, neither a multi-dimension lookup table nor excessive computational burden is required for the controller. A 1kW prototype is built to verify the proposed optimal VSF scheme and compare it with conventional constant switching frequency (CSF) scheme. The experimental results show that the proposed optimal VSF scheme can achieve higher efficiency than the CSF scheme over a wide power range. The weighted average efficiency of the proposed scheme is improved by a maximum of 1.3% in unity PF operation and 0.63% in non-unity PF operation.

A new floor function single‐carrier‐based modulated model predictive current control technique for single‐phase PUC5 inverter topology

SummaryIn this paper, a new floor function (F2) single‐carrier (SC)‐based modulated model predictive current control technique (M2PC2T) has been proposed by considering the conventional single‐phase five‐level packed U‐cell (PUC5) inverter topology. Generally, to regulate the output current, the finite control set‐based MPC technique without a modulator inherently operates with variable switching frequency, and it is unsuitable for industrial applications. To alleviate this, authors have implemented M2PC2T, which provides constant switching frequency of operation. In this technique, generally, the predictive algorithm has been integrated with any modulation stage. However, while the implementation of pulse width modulation (PWM) techniques, most authors have used conventional PWM techniques which further increases the control complexity as the level number increases. In this manuscript, a simple and generalized F2‐SC‐PWM technique has been proposed and integrated with the predictive algorithm. This PWM technique implementation process is very simple as compared with all conventional PWM techniques since even if the level number increases, the number of modulating and carrier signals is always only one. Finally, the complete closed‐loop control technique is called a generalized F2‐SC‐M2PC2T which is suitable for all stiff direct current (dc) sources and switched capacitor‐type multilevel inverter (MLI) topologies. The proposed control technique (PCT) has been experimentally verified with different transient and steady‐state case studies by considering resistive‐inductive load.

A new single modulating and single carrier‐based predictive current control technique for single‐phase quadruple boost multilevel inverter topology

SummaryA new floor function single carrier‐based modulated model predictive current control (F2‐SCM2PC2) technique has been proposed in this paper by considering traditional single‐phase quadruple boost switched capacitor‐based multilevel inverter (QB‐SCMLI) topology. Conventionally, the implementation process of single modulating and single carrier‐based pulse width modulation (PWM) techniques are very much complex and finite control set‐based model predictive control (FCS‐MPC) technique inherently operates with variable switching frequency (VSF) operation, which is not suitable for industrial applications. To alleviate the aforementioned issues, a new generalized closed‐loop F2‐SCM2PC2 technique has been proposed. It consists of a simple PWM implementation process and can easily be integrated with a predictive algorithm, thereby providing a constant switching frequency (CSF) of operation. The particular single modulating and single carrier‐based PWM technique with floor function is also suitable for low and high switching frequency (LSF‐HSF) operations. The validation of floor function‐based PWM technique in open‐loop and closed‐loop F2‐SCM2PC2 techniques has been effectively verified through experimentation on QB‐SCMLI topology with consideration of resistive–inductive load.

Simple Predictive Current Control of Asymmetrical Six-Phase Induction Motor With Improved Performance

Despite the intensive research work on the application of model predictive control (MPC) for multi-phase machines, there are many challenges still to be handled such as high circulating currents, variable switching frequency, and high computation burden. This paper proposes a simple, yet efficient predictive current control (PCC) for six-phase induction motor (IM) that reduces considerably circulating current, computation cost, and switching frequency. In the proposed method, a group of four candidate voltage vectors (VVs) is formed in each control sample. Unlike similar methods reported in literature, these candidate vectors are generated based on a simple lookup table and the previous optimal VV. The lookup table is designed such that it allows only one commutation in each control sample. The performance of the proposed method is assessed experimentally using a one kW asymmetrical six-phase induction motor (A6PIM). Different performance indices are investigated to compare the proposed method against two different PCC methods in literature at different operating conditions. The experimental results confirm that about 50% reduction in average switching frequency and 15% in current total harmonic distortion at different speed ranges are observed with the proposed method compared to the conventional one.

On Single-Input Dual-Output (SIDO) DC/DC Multi-Port Converters for DC Microgrid Applications

This paper proposes the use of linear-assisted switching power converters in the context of single-inductor dual-output (SIDO) for microgrids (MG) applications. By combining a DC/DC ripple-controlled switching power converter with the respective voltage linear regulators at each output, improved performance in terms of load and line regulations is obtained. To achieve that aim, a current-steering switching policy is proposed, together with a resource-aware circuit implementation. The ripple-based hysteretic control results in variable switching frequency to guarantee critical conduction mode (boundary of CCM and DCM).

Application of a novel metaheuristic algorithm based two-fold hysteresis current controller for a grid connected PV system using real time OPAL-RT based simulator

Grid connected photovoltaic (GCPV) rooftop systems have been considered as fast development and promising renewable energy sources due to low maintenance cost, secure investment, noise-free and do not require additional space for installation. Various factors considered for the installation of GCPV are mathematical models of PV module, sizing methods based on techno-economic objectives, PV panels and configurations, selection of the final optimum configuration and environmental criteria. Selection of appropriate controller and its optimal design for power electronic based converters also plays a crucial role in the performance of GCPV. Therefore in this article, a two-fold hysteresis current controller (TFHCC) based on an Improved Arithmetic Optimization Algorithm (IAOA) is introduced and investigated for the first time, for a GCPV system to minimize the switching loss and total harmonic distortion (THD). A novel multi-objective function considering switching frequency and current error is proposed by assigning appropriate weights to obtain the optimal values of duty cycle and hysteresis bands using IAOA, AOA, Forensic Based Investigation (FBI), Differential Evolution (DE) and Particle Swarm Optimization (PSO) algorithms. TFHCC utilizes zero level of the inverter by properly switching it on for a half cycle only and either on or off for the other cycle. Comparative performance analysis of the optimal TFHCC obtained with different algorithms is presented and it is proved that IAOA based TFHCC exhibits substantial reductions in variation and magnitude of the average switching frequency by 2.82 kHz and THD by 0.65%. Initially, the study is carried out with MATLAB Simulink environment and then experimentally validated with real time simulator based on OPAL-RT 4510.