Switching Frequency Of Converter Research Articles

Step Incremental Conductance MPPT for Solar PV System Based on Fuzzy Logic Controller

Due to strong industrial expansion, the need for electrical power has increased in recent years. As more than just a by-product of this increased dependence on fossil fuels, resource depletion occurs, and renewable sources such as solar, wind, and wave energy sources have begun to operate as an electricity source and are now playing a key role. Solar energy has been widely used in power systems, particularly in the form of photovoltaic (PV) generating units. Control scheme is a technique for obtaining electricity from a solar photovoltaic system under changing environmental circumstances. The proposed research compares two control methods: incremental conductance algorithm and fuzzy logic, in order to maximise the efficiency of a solar PV system. The algorithms described above change the switching frequency of the power converter to monitor a solar PV array's global MPP. In MATLAB/Simulink, the simulation is run, and the performance is evaluated. The simulated findings imply that the fuzzy logic controller performs better than the incremental conductance technique.

Latest Advances of Model Predictive Control in Electrical Drives—Part I: Basic Concepts and Advanced Strategies

The application of model predictive control in electrical drives has been studied extensively in the past decade. This article presents what the authors consider the most relevant contributions published in the last years, mainly focusing on three relevant issues: weighting factor calculation when multiple objectives are utilized in the cost function, current/torque harmonic distortion optimization when the power converter switching frequency is reduced, and robustness improvement under parameters uncertainties. Therefore, this article aims to enable readers to have a more precise overview while facilitating their future research work in this exciting area.

Online Efficiency Optimization of a Closed-Loop Controlled SiC-Based Bidirectional Boost Converter

This article presents an online efficiency optimization strategy for a digitally controlled, wide operating range silicon carbide based boost converter with bidirectional power flow. The proposed strategy minimizes switching losses at any given operating point by adjusting the converter switching frequency and dead times to optimally set the peak synchronous rectifier turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> current. This results in the converter achieving zero-voltage switching quasi-square wave (ZVS-QSW) operation with minimum inductor current ripple. The optimal timing parameters are determined online by fit functions based on sensed input/output voltages and inductor current, and applied to the converter in a low-bandwidth feed-forward loop operating in conjunction with closed-loop regulation of the converter output voltage. The fit functions are developed from multivariate curve fitting of the analytical solutions of the minimum-conduction ZVS-QSW state plane over the complete range of operation. The proposed approach enables bidirectional operation with efficiencies greater than 97.5% for input voltages ranging from 200 to 400 V, step-up conversion ratios up to 2.5, and power levels between 2 and 8 kW. The converter also achieves efficiencies greater than 99% over wide power levels at boost conversion ratios lower than 2.

Multirate Finite-Control-Set Model Predictive Control for High Switching Frequency Power Converters

Due to the modulator free structure, the finite-control-setmodel predictive control (FCS-MPC) needs a high sampling frequency/interrupt frequency (20–50 kHz) for power converters application, while the typical converter switching frequency is around 20–25% of the sampling frequency. To obtain a high switching frequency, it is not always practical to increase the sampling rate by considering the computational burden in a digital processor. Therefore, increasing the switching frequency without using a high sampling frequency is a critical task for FCS-MPC, particularly applied to silicon carbide and gallium nitride-based high switching frequency power converters. To solve this problem, this article proposes the multirate FCS-MPC (MRFCS-MPC), where the control frequency is allowed to be higher than the sampling frequency. Consequently, the switching frequency can be significantly increased without changing the sampling frequency. The proposed scheme inherits the ability to handle complex control objectives from the traditional FCS-MPC. The lifting model is built to predict the fast rate information of state variables based on the low sampling output. Then, the fast rate control inputs within one sampling interval are solved efficiently with a good tradeoff between computational burden and optimized system performance. The experimental motor drive system tests are carried out to verify the effectiveness of the proposed MRFCS-MPC.

Bypass Inductor Type LCL Filter Parameter Optimization for Three-Level Grid-Connected Converter

In the application of the three-level grid-connected system, passive damping is the most common method to keep the LCL filter working stably. However, in the case of high power density, the low switching frequency of the grid-connected converter results in the complexity of filter parameter design, and the increase in passive components leads to lower equipment utilization efficiency. To solve the above problems, based on the optimization of resonant frequency and system loss, this study proposes a set of LCL filter parameter design processes of a three-level neutral point clamped (NPC) converter, which can switch components freely and is easy to achieve. This study explores the theoretical evidence and application value of the proposed design, considering the influence of the current ripple and the reactive power limit. The design adopts the improved passive damping method to select the appropriate inductance ratio and impedance ratio to make the resonance frequency of the whole system and the extra loss of the system smaller. The simulation and experiments show that compared with the conventional method, the improved design method reduces the current THD of the grid side by 1.5% and the damping resistance loss by 0.17%.

A High-Efficiency Dynamic Inverter Dead-Time Adjustment Method Based on an Improved GaN HEMTs Switching Model

Benefited from the fast switching speed, Gallium nitride (GaN) high electron mobility transistors (HEMTs) have been widely used in high switching frequency converters. However, due to the significant correlation between the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> time and operating conditions (more than 20 times difference of the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> time between the high load current and small load current for GaN HEMTs), using a fixed dead time will introduce extra dead-time (DT) losses in inverters where the output voltage and current are constantly varying. Therefore, this article proposes a high-efficiency adaptive method to dynamically adjust the GaN-inverter DT with operating conditions. An improved transient model including the parasitic inductance and output voltage with bidirectional solution flow has been proposed for GaN HEMTs to increase the accuracy of DT adjustment. Based on this model, the dynamic DT adjustment can be realized without extra sensors for GaN-inverters. Using the dynamic DT adjustment, the experimental results show a peak efficiency of 98.25% in a 1200 W inverter with triangular current mode modulation. Compared with using the fixed DT, the dynamic DT method can reduce the power loss by 26.7% under full load and 49.14% under light load.

New FOM-Based Performance Evaluation of 600/650 V SiC and GaN Semiconductors for Next-Generation EV Drives

The drive inverter represents a central component of an electric vehicle (EV) drive train, being responsible for the DC/AC power conversion between the battery and the electrical machine. In this context, novel converter topologies adopting modern 600/650V wide bandgap (WBG) semiconductor devices will play a crucial role in improving the performance of next-generation drive inverters. In fact, WBG devices theoretically allow to achieve both higher inverter power density and higher conversion efficiency with respect to conventional silicon (Si) IGBT based solutions. Even though silicon carbide (SiC) devices are already well established in the automotive industry, high-voltage gallium nitride (GaN) devices are rapidly entering the market, promising higher theoretical performance but featuring a lower degree of maturity. As a consequence, it is currently not clear which semiconductor technology is most suited for future EV drive inverters. Therefore, this paper aims to address this gap providing a comparative performance evaluation of state-of-the-art SiC and GaN 600/650V active switches. In particular, a novel figure-of-merit (FOM) representing the minimum theoretical semiconductor losses under hard-switching operation is introduced. Remarkably, this FOM enables a fair and accurate performance comparison among semiconductor devices, allowing to clearly determine the best performing technology for a given set of application-specific conditions. The results of the comparative assessment show that currently available SiC and GaN active switch technologies can outperform each other depending on the semiconductor operating temperature and the converter switching frequency.

Experimental study on vibration and noise of the ROEWE electric vehicle

In order to control the vibration and noise of the ROEWE electric vehicle, it is necessary to carry out the experimental study on the vibration and noise of the electric motor. Firstly, two acoustic sensors are arranged on both sides of the road to measure the pass-by noise of the electric vehicle and to analyze the influence of motor noise on the passing noise. Then, several acoustic sensors are arranged in the vehicle to measure the noise signal in the vehicle, and to analyze the characteristics of interior noise. At the same time, one acoustic sensor and three vibration acceleration sensors are arranged in the vehicle power cabin to measure the vibration signal, and measure the signals of the upper and lower vibration acceleration sensors of the powertrain mount, and analyze the vibration and noise characteristics of the motor and the vibration isolation rate of the powertrain mount. The experimental results show that the vibration of the ROEWE motor has obvious order characteristics, which is mainly composed of order components of order 8, order 16, order 24, order 40, order 48 and order 72 based on the motor output shaft speed and frequency converter switching frequency components concentrating on 10000Hz and 20000Hz. Therefore, to reduce vehicle vibration and noise from the perspective of optimizing motor vibration, the impact of cogging torque on motor vibration should be mainly considered.

Four-Frequency Small-Signal Model for High-Bandwidth Voltage Regulator With Current-Mode Control

High-bandwidth buck voltage regulator with peak current-mode control is a commonly-used scheme, especially for CPU power applications. However, the conventional single-frequency and three-frequency models are inaccurate in modeling the loop gain stability when the control bandwidth is close or higher than one-third of the converter switching frequency. A more accurate four-frequency small-signal model for a high-bandwidth buck converter with peak current-mode control is proposed in the present paper. The describing function approach is used to model the duty-cycle modulator. The effects of the four-frequency components, including the modulating frequency, the two sideband harmonics, and the switching frequency, are considered. Simulations and experiments verified the results.

Modeling of Power Electronics Systems and PWM Modulators in Harmonic-State Space

Modeling and simulation of the converter dominated systems have recently emerged as a monumental challenge. These simulations are useful for predicting instability and system's harmonic content, consequently assisting in developing better control and filters. But, as more and more converters are incorporated into the system, time-domain simulation models have a tradeoff of either limited accuracy or fewer simulated converters. On the contrary, frequency-domain modeling methods like linear time-invariant models cannot capture the system's time-varying nature and complex converter interactions. The recently developed harmonic state space (HSS) modeling approach has emerged to provide an alternate avenue to model and simulate these converter-dominated systems. HSS models, while accurate, until recently have not been able to reliably model the non-linear pulse width modulator. This paper solves this challenge and develops a new modulator model for harmonic domain models, including HSS. The proposed large-signal modulator is computationally less demanding and can reliably capture the harmonic spectrum of complex multi-converter systems till converter switching frequencies. Several optimization methods are introduced to utilize the unique multi-harmonic nature of HSS, making simulations faster than conventional time-domain methods. Results are verified with extensive simulations and experiments. The application, challenges, and future scope for this method are also highlighted.

Design and Optimization Approach for the Magnetic Components of a Five-Level Current Source Rectifier

This work presents a design and optimization method of the five-level current source converter magnetics components, this is a contribution of this work, since the magnetics volume information of this topology lacks in the literature. The magnetics components are: the interphase transformers, the input and the output filter inductors. The converter volume is minimized when the magnetic components multi-domain optimization is done. The inductance values are defined with given constraints such as Electromagnetic Compatibility standards for differential mode filters, conduction and switching losses of the semiconductors and maximum current variation. This optimization is shown for two different converter switching frequencies: 45 kHz and 150 kHz. The copper losses, iron losses and temperature rise are calculated and used for selecting the smallest volume of each magnetic component with given specifications. A 6-kW prototype with the optimized magnetics was constructed

Effect of Semiconductor Parasitic Capacitances on Ground Leakage Current in Three-Phase Current Source Inverters

This paper investigates the influence of power semiconductor parasitic components on the ground leakage current in the three-phase Current Source Inverter topology, in the literature called H7 or CSI7. This topology allows reducing converter conduction losses with respect to the classic CSI, but at the same time makes the topology more susceptible to the parasitic capacitances of the semiconductors devices. In the present work, a grid-connected converter for photovoltaic power systems is considered as a case study, to investigate the equivalent circuit for ground leakage current. The same analysis can be extended to applications regarding electric drives, since the HF model of electric machines is characterized by stray capacitance between windings and the stator slots/motor frame. Simulation results proved the correctness of the proposed simplified common-mode circuit and highlighted the need of an additional common-mode inductor filter in case of resonance frequencies of the common-mode circuit close to harmonics of the power converter switching frequency. Experimental results are in agreement with the theoretical analysis.

Event-Driven Approach With Time-Scale Hierarchical Automaton for Switching Transient Simulation of SiC-Based High-Frequency Converter

On the emerging development of SiC MOSFET, the switching frequency of power converters has been pushed to the order of hundreds of kilohertz or even megahertz to improve power density. However, the state-of-the-art simulations for such high-frequency power electronics circuits are usually time-consuming, blocking the studies of long dynamics such as several seconds. What’s worse, adopting physical models to simulate the turn-on and turn-off transients leads to high stiffness and therefore convergence problems. In this paper, an event-driven approach is proposed to improve the solving speed and simulation stability of SiC based high-frequency converters. A time-scale hierarchical automaton is proposed to model the system, where piecewise analytical transient model for SiC MOSFET is established as the second layer in the automaton to simulate the switching transients with improved numerical stability. Simulation of the system is driven by discrete events in the automaton. A 3.3 kW 79.1 kHz wireless power transfer system for the wireless charging of electric vehicle is studied. Compared with ideal switch model in Simulink and physical switch model in LTspice, 60-fold and 400-fold increases in terms of simulation speed with same level of accuracy are achieved respectively. The simulated results are also attested to by experimental verifications.

Low-Voltage GaN FETs in Motor Control Application; Issues and Advantages: A Review

The efficiency and power density improvement of power switching converters play a crucial role in energy conversion. In the field of motor control, this requires an increase in the converter switching frequency together with a reduction in the switching legs’ dead time. This target turns out to be complex when using pure silicon switch technologies. Gallium Nitride (GaN) devices have appeared in the switching device arena in recent years and feature much more favorable static and dynamic characteristics compared to pure silicon devices. In the field of motion control, there is a growing use of GaN devices, especially in low voltage applications. This paper provides guidelines for designers on the optimal use of GaN FETs in motor control applications, identifying the advantages and discussing the main issues. In this work, primarily an experimental evaluation of GaN FETs in a low voltage electrical drive is carried out. The experimental investigation is obtained through two different experimental boards to highlight the switching legs’ behavior in several operative conditions and different implementations. In this evaluative approach, the main GaN FETs’ technological aspects and issues are recalled and consequently linked to motion control requirements. The device’s fast switching transients combined with reduced direct resistance contribute to decreased power losses. Thus, in GaN FETs, a high switching frequency with a strong decrease in dead time is achievable. The reduced dead time impact on power loss management and improvement of output waveforms quality is analyzed and discussed in this paper. Furthermore, input filter capacitor design matters correlated with increasing switching frequency are pointed out. Finally, the voltage transients slope effect (dv/dt) is considered and correlated with low voltage motor drives requirements.

Fixed switching frequency scheme for current predictive control of DFIG

This paper suggests a new current predictive control algorithm for the wind-driven doubly-fed induction generator (DFIG) based on space vector modulation (SVM) with fixed switching frequency. Combining the current predictive controller and SVM has the benefits of a predictive controller, and fixing the switching frequency improves the output waveform quality. However, if classical predictive control is used, the computational burden will still be high. The proposed algorithm uses SVM to fix the switching frequency of the rotor side converter. Additionally, by using an incremental algorithm, the proposed technique prevents examining all inputs over the prediction horizon. As a result, in the proposed current predictive algorithm the computational time is significantly reduced. The detailed state-space model of DFIG and rotor side converter are used to execute the predictive algorithm. The proposed algorithm uses the rotor current to predict the next behavior of the DFIG, and then, by using SVM, the duty cycles of 2-level voltage source inverter are obtained. Finally, the proposed controller's responses are compared to those of the SVM-based field-oriented control strategy. Simulation results of the proposed controller on a two-level voltage source inverter under a balanced three-phase power system illustrate the satisfactory active and reactive power tracking and improved quality of the inverter outputs.

Nonparametric Frequency Response Identification for Dc-Dc Converters Based on Spectral Analysis with Automatic Determination of the Perturbation Amplitude.

Digital control for high switching frequency converter enables new features on DC-DC power conversion for a minimum cost. Frequency response identification is one such enabled functionality used in auto tunning, measurement of components to assess the converter’s state of health, or system stability monitoring. High accuracy, flexibility to operate in open or closed loop, and minimum impact in the converter’s regular operation are the frequency response identification system’s goals. We propose in this paper a nonparametric identification system addressing these main goals. First, it can autoadjust the perturbation size to reduce the perturbation’s impact on the converter’s output quantities. Second, as it is based on spectral analysis, it is suitable for open and closed-loop operation. Third, we demonstrate the identification system’s high accuracy, achieving a very low difference between the experimental measurements and the discrete model used as reference.

Integrating Voltage-Source Active Filters Into Grid-Connected Power Converters—Modeling, Control, and Experimental Verification

More demanding harmonic limits of future grid standards are likely to aggravate the disadvantages associated with the use of passive filters in high-power converters. These include substantial additional losses, a large footprint, and a considerable, power factor dependent voltage drop. For this reason, active filters (AFs) are an increasingly attractive alternative for reducing converter-induced harmonics; however, their performance is often subject to a limited frequency range and a frequency-dependent attenuation. To further improve the potential of AFs for use with grid-connected power converters, this article presents a novel control scheme for a parallel voltage-source AF integrated into a high-power main converter. A detailed converter analysis shows that, due to the advantageous converter configuration, the AF requires only fundamental frequency current control to mitigate converter-induced current harmonics. In contrast to conventional AF applications, this avoids tuning to specific frequencies, identification of individual harmonics, and measurement of high-frequency current ripple and high control bandwidth. The control design is carried out with the aim of minimizing the AF current load in steady state and transient operation. As shown by simulation results, the AF thus allows the mitigation of harmonics up to frequencies above the switching frequency of the main converter at only a small share of the total power and with small passive components. Finally, the hybrid converter is compared to LCL-filter based converter systems and the effectiveness of the presented control scheme is verified experimentally using a silicon carbide demonstrator.

Active Power Filtering With a Low Switching Frequency Converter

This paper focuses on the relationship between the controller and the control delay of the low switching frequency converter with active power filtering function. This paper also investigates the effect of the current transformer (CT) probe on the measured signals for a long-distance compensation of the non-linear loads. An one step deadbeat controller under consideration of the CT model is presented to meet the demands with the control delay compensation and the correction of the distorted measured signals. Finally, the laboratory test results will be used to support the aforementioned analysis.

Evaluation of Fuzzy Membership Function Effects for Maximum Power Point Tracking Technique of Photovoltaic System

The photovoltaic generation system (PGS) is considered a potential renewable energy harvesting system. However, the low conversion efficiency of PGS and maximum power point tracking (MPPT) technique are the main challenges that must be solved. In addition, the switching frequency of the converters employed also affects the MPPT system performance. A high gain voltage DC-DC converter is proposed to replace conventional power converter and fuzzy logic controller (FLC) is applied in the MPPT for optimizing solar energy harvesting system. Nevertheless, evaluation of suitable fuzzy membership function is needed for optimal MPPT technique of photovoltaic system. In this paper, FLC of MPPT for photovoltaic application system was built using various membership functions in MATLAB/Simulink environment. The switching frequency of the high gain voltage DC-DC converter is varied to test the robustness of the performance of each FLC membership function. The results showed that the FLC-based MPPT technique for high gain voltage DC-DC converter with GBell membership function type has the capability to track the maximum power point (MPP) accurately and to achieve optimum power conversion. Furthermore, GBell membership showed having stable and consistent performance at various switching frequencies.

Auto-Resonant Detection Method for Optimized ZVS Operation in IPT Systems With Wide Variation of Magnetic Coupling and Load

In wireless charging systems, the H-bridge converter's switching frequency is set close to the system's natural resonance for achieving optimized zero voltage switching (ZVS). Variations to the system's natural resonance are commonly tracked by following the changes in the resonant current's polarity, i.e., current zero-crossings. The main implementation challenge is accounting for the time delay between the real monitored current and the final resulting switches’ commutations. This becomes critical at high switching frequencies, particularly when the magnetic coupling and loading vary widely. This paper proposes an auto-resonant detection method that continuously ensures optimized ZVS turn-on with the minimal circulating current over the operable range of magnetic coupling and load. The suggested implementation provides two split variable references for the resonant frequency detection, which adaptatively compensate for the propagation delay based on the resonant current slope. The auto-resonant scheme is benchmarked against the commonly employed method with fixed current detection references. The results highlight the auto-resonant strategy's advantages, namely extended operable range, wider ZVS turn-on region, ease start-up, and improved DC-to-DC efficiency. The auto-resonant features and functionality are verified experimentally with a 200 W low-voltage e-bike wireless charger. Finally, the benefits of the presented method are analytically explored for high-power applications by considering the H-bridge semiconductor losses of a state-of-art 50 kW wireless charging system.