Step Change In Voltage Research Articles

Advanced Multi-Sampling PWM Technique for Single-Inductor MIMO DC-DC Converter in Electric Vehicles

Amongst the various topologies of multi-input multi-output (MIMO) DC-DC converters, single-inductor MIMO (SI-MIMO) converters have the advantages of a reduced component count, a simpler structure, and low cost. These converters are suitable in electric vehicle (EV) applications involving variable ports, essential for performing different functions. Digital control in SI-MIMO converters is promising for enhancing transient performance due to its numerous benefits. However, delays in digital control, particularly computational and pulse width modulation (PWM) delays, can negatively impact the performance of DC-DC converters. Multi-sampling and double PWM update methods can mitigate these control delays, but they often necessitate complex control schemes, adding computational burden. In this work, an advanced multi-sampling PWM technique, integrating sample shift and multi-sampling, is proposed while employing a simple digital PID control scheme. The proposed method was tested for a shared-switch SI-MIMO converter with battery discharging and charging modes in the MATLAB/Simulink environment and compared with the conventional single- and multi-sampling PWM methods. The results demonstrated that the proposed method significantly improved the converter performance, surpassing the conventional single- and multi-sampling PWM methods. In the battery discharging mode, utilizing the proposed method, the output voltage achieved a settling time of 0.075 s in response to a step change in its reference, significantly outperforming multi-sampling, which yielded a settling time of 0.124 s, and single sampling, which exhibited an even longer settling time of 0.898 s. It also demonstrated a minimal overshoot of 0.06 volts compared to 1.5 volts with multi-sampling during the step change in the input voltage. Similarly, in the battery charging mode, upon a step change in the reference output voltage, the proposed method effectively minimized the overshoot of the output voltage to 0.845 volts compared to 1.175 volts with multi-sampling, and it decreased the inductor current settling time to 0.296 s from 0.330 s recorded under multi-sampling. These findings underscore the potential of the proposed method in enhancing the digital control performance of SI-MIMO DC-DC converters in electric vehicles.

Dynamic ancillary services: From grid codes to transfer function-based converter control

Conventional grid-code specifications for dynamic ancillary services provision such as fast frequency and voltage regulation are typically defined by means of piece-wise linear step-response capability curves in the time domain. However, although the specification of such time-domain curves is straightforward, their practical implementation in a converter-based generation system is not immediate, and no customary methods have been developed yet. In this paper, we thus propose a systematic approach for the practical implementation of piece-wise linear time-domain curves to provide dynamic ancillary services by converter-based generation systems, while ensuring grid-code and device-level requirements to be reliably satisfied. Namely, we translate the piece-wise linear time-domain curves for active and reactive power provision in response to a frequency and voltage step change into a desired rational parametric transfer function in the frequency domain, which defines a dynamic response behavior to be realized by the converter. The obtained transfer function can be easily implemented e.g. via a proportional-integral (PI)-based matching control in the power loop of standard converter control architectures. We demonstrate the performance of our method in numerical grid-code compliance tests, and reveal its superiority over classical droop and virtual inertia schemes which may not satisfy the grid codes due to their structural limitations.

A Frequency Domain Controller Design for Quadratic Boost Converter using Direct Synthesis Approach

ABSTRACT This paper presents a frequency domain based controller design method for the output voltage regulation of quadratic boost converter exhibiting non-minimum phase behaviour. Two approaches of the controller design have been proposed: (1) to achieve desired set-point response and (2) to obtain necessary load disturbance rejection performance. The controller design methods are based on direct synthesis approach in frequency domain. The design approaches do not necessitate model order reduction (since the order of the QBC model is four). To analyse the effectiveness of the proposed control schemes simulation as well as hardware results have been carried out under, that is, step change in input voltage, load resistance, duty cycle disturbance and reference change. The robustness of the proposed controllers has been evaluated by considering 20% perturbation in L and C using Nyquist curve and is also validated experimentally.

Analytical deconvolution of smearing effect for inversion of scanning mobility particle sizer data

The scanning mobility particle sizer (SMPS) is a key instrument for aerosol studies that enables rapid measurement of particle size distribution. When SMPS data are inverted, the smearing effect needs to be considered. Previous studies used numerical methods to deconvolute the smearing effect. In this paper, to reduce the complexity of SMPS data inversion, we derive an analytical formula for de-smearing, and include our de-smearing formula into a full SMPS data inversion scheme. We also propose the voltage step change experiment to characterize the smearing effect of an SMPS. The effectiveness and robustness of our de-smearing approach were demonstrated using experimental data.

Artificial intelligence based switching frequency regulation with fast terminal sliding mode control for DC–DC step-down converters

Making the best voltage/current regulation against disturbances and uncertainties and, most importantly, to minimize chattering effect in power electronics circuits, the hysteresis modulation based (HM) sliding mode control (SMC) is widely used. There are various research on this subject in the literature. However, the variable switching frequency that HM-SMC brought about has regrettably overlooked in the majority of these research. This problem is addressed in depth in this paper by demonstrating how the switching frequency is affected by various factors. Next, the fuzzy logic control (FLC) is proposed for the first time as a solution for switching frequency regulation in a power electronics circuit. The proposed FLC for switching frequency regulation fortifies the system described in this study and sets it apart from many other HM-SMC studies in the literature with its advantages against the difficulties caused by variable switching frequency such as excessive switching and driver power losses. On the other hand, the fast terminal SMC (FTSMC) which has significantly superior convergence performance than its counterparts, has been recommended for voltage regulation. The proposed FTSMC technique employs only one voltage sensor different from the past literature. This simplifies the proposed control mechanism in practical implementation and also makes the system economical. The two proposed controllers’ compatibility with one another has been tested through experimental tests, including the steady-state condition, variations in switching frequency reference value, step change of load resistance, output voltage reference value variation, and finally step change of input voltage. The outcomes of the experiments demonstrate that the switching frequency and output voltage are successfully regulated with good dynamic and steady state performance. Finally, the proposed techniques have been compared with six recent approaches from the existing literature to highlight their performance.

Unity Power Factor Operation in Microgrid Applications Using Fuzzy Type 2 Nested Controllers

The issue of low-power factor operation microgrids was reported for several layouts. Although numerous power factor improvement strategies have been applied and tested, various concerns remain to be addressed such as transient performance, simplicity of implementation, and satisfying the power-quality standards. The presented research aimed to design and implement controllers that can improve the transient response of microgrids due to changes in the load demand and achieve a near-unity power factor at the AC grid side, to which the DC microgrid is connected. Due to the nonlinear nature of microgrids, as they rely on power electronics converters, a Fuzzy type 2 controller was designed, implemented, and tested. The focus was given to improving the power factor of the DC microgrids. The validation of the proposed technique was verified by comparing its performance with Fuzzy type 1 and autotuned conventional PI controllers. To achieve the set aims, two nested control loops were designed with an inner current loop and an outer voltage loop. Besides MATLAB/Simulink simulations, a 10 kHz-sampling dSPACE platform was used to implement the suggested system. Two operational scenarios were tested: (1) a step change in the DC link voltage and (2) a change in the AC load (increase and decrease) at the output of the power inverter, connected to the DC grid. The simulation and experimental results confirmed that the proposed Fuzzy type 2 controller performed better than the other two techniques regarding the dynamic response, steady-state error, and compliance with power quality standards. Conventional approaches develop controllers using a linearized model, which limits the model accuracy and ignores higher-order variability. The method employs the nonlinear model. Fuzzy type 2 can better approximate high-precision problems than Fuzzy type 1.

Interval Type-2 Fuzzy-Logic-Based Constant Switching Frequency Control of a Sliding-Mode-Controlled DC–DC Boost Converter

The inherent unlimited high switching frequency of the sliding mode controller (SMC) is limited by practical constraints of the hysteresis modulation (HM) technique. The inductor current and output voltage of a converter can be regulated using a combination of HM-SMC. However, HM-SMC results in a variable switching frequency operation, which is not preferred due to Electromagnetic Interference (EMI) issues. In this paper, an interval fuzzy controller is designed and developed as a solution to enable HM-SMC. In addition, a robust sliding surface is proposed, which provides an improved dynamic response. The two proposed controllers’ compatibility with one another has been tested via experiments such as a step change in input voltage, load resistance variation, and finally, a step change in output voltage reference value. The test results validate that while the interval type-2 fuzzy maintains a constant switching frequency with acceptable dynamic responses, it successfully regulates the state variables of the system. A comparison of the performance of the proposed control method with existing techniques in the literature is presented.

Artificial Neural Network-Based Nonlinear Black-Box Modeling of Synchronous Generators

This article deals with the black-box modeling of synchronous generators based on artificial neural networks (ANN). The ANN is applied to define the relationship between the excitation and terminal generator voltage values, and the Levenberg–Marquardt algorithm is used for determining the ANN weight coefficients. The relation is made based on generator response on reference voltage step changes. The proposed approach is checked using the experimental results obtained from the measurements on a real 120 MVA generator from a hydroelectric power plant Piva in Montenegro. Furthermore, a fair comparison of the nonlinear autoregression model with the exogenous input (NARX) and Hammerstein–Wiener model is made. For the validation, different experiments were conducted—different values of step disturbances, other controller parameters, and different rotating speeds. Based on the presented results, it can be noted that the proposed ANN model is very accurate and provides a very high degree of matching with the experimental results and outperforms the other considered nonlinear models. Furthermore, the proposed test procedure and model are easy to implement and do not require disconnection of the generator from the grid or additional equipment for experimental realization. Such obtained models can be used for different testing types related to the excitation system.

Adaptive online auto-tuning using Particle Swarm optimized PI controller with time-variant approach for high accuracy and speed in Dual Active Bridge converter

<abstract> <p>Electric vehicles (EVs) are an emerging technology that contribute to reducing air pollution. This paper presents the development of a 200 kW DC charger for the vehicle-to-grid (V2G) application. The bidirectional dual active bridge (DAB) converter was the preferred fit for a high-power DC-DC conversion due its attractive features such as high power density and bidirectional power flow. A particle swarm optimization (PSO) algorithm was used to online auto-tune the optimal proportional gain (<italic>K<sub>P</sub></italic>) and integral gain (<italic>K<sub>I</sub></italic>) value with minimized error voltage. Then, knowing that the controller with fixed gains have limitation in its response during dynamic change, the PSO was improved to allow re-tuning and update the new <italic>K<sub>P</sub></italic> and <italic>K<sub>I</sub></italic> upon step changes or disturbances through a time-variant approach. The proposed controller, online auto-tuned PI using PSO with re-tuning (OPSO-PI-RT) and one-time (OPSO-PI-OT) execution were compared under desired output voltage step changes and load step changes in terms of steady-state error and dynamic performance. The OPSO-PI-RT method was a superior controller with 98.16% accuracy and faster controller with 85.28 s<sup>-1</sup> average speed compared to OPSO-PI-OT using controller hardware-in-the-loop (CHIL) approach.</p> </abstract>

A Direct Actual-Power Control Scheme for Current-Fed Dual-Active-Bridge DC/DC Converter Based on Virtual Impedance Estimation

High dynamic performance is an essential requirement for the dual-active-bridge (DAB) dc/dc converters. As dc voltage sources, they should maintain the desired output voltage instantly under all working conditions. However, the previous literature mainly focus on the dynamic control of the voltage-fed DAB converters, and the existing control schemes for the current-fed DAB converters achieve limited dynamic performance. Aiming at improving the dynamic performance, a direct actual-power control (DAPC) scheme based on virtual impedance estimation (VIE) is proposed for the current-fed DAB converters in this article. The proposed DAPC scheme is based on a parallel structure instead of the series structure of existing control schemes, and it realizes fast dynamic control through combining actual power control with the VIE method. The proposed DAPC scheme can obtain the fastest transient response for the output voltage without voltage overshoot in transient conditions, such as load step change, input voltage fluctuation, and the desired output voltage step change. Besides, a leakage inductor precharging method is integrated into the DAPC scheme to avoid the current mismatching. Finally, the proposed DAPC schemes are compared with two existing control schemes and tested in a scale-down experimental prototype. Experimental results verify the effectiveness of the proposed DAPC scheme.

Performance Analysis of Three Levels Three Switches Vienna-Type Rectifier Based on Direct Power Control

The Vienna-type rectifier is broadly employed in various implementations thanks to realizable three-level operation, simple structure and controllable DC-link voltage. This paper proposes an adaptive proportional integral (PI) with anti-windup based direct power control (DPC) to improve dynamic response during load change, DC-link voltage step change and start up and to reduce current tracking errors. An adaptive PI with anti-windup DC-link voltage control is utilized to enhance dynamic response of the DC-link voltage and the instantaneous power because the PI regulator affected by the load change and system parameter variations. The PI based conventional power control is used to indicate the availability and accuracy of the proposed control strategy. The proposed control strategy performs outstanding performance and copes with vigorous disturbances in contrast to the conventional strategy. A detailed theoretical analysis of the proposed approach has been performed. Extensive case studies carried out by PSIM software are performed to validate the excellent behavior of the proposed control strategy.

Passivity‐based control for a DC/DC high‐gain transformerless boost converter

AbstractIn this work, an adaptive passivity‐based controller for a DC‐DC high‐gain transformerlessdouble‐inductor boost converter is fully detailed. The proposed current‐mode control scheme results in two feedback loops, a current controller for tracking the inductor current considering damping injection and energy shaping, and a voltage loop composed by a proportional‐integral action to guarantee output voltage regulation. Furthermore, a parametric uncertainty estimator using immersion‐invariance approach is designed to improve the robustness of the current loop. As a result, a multi‐loop adaptive nonlinear energy‐based controller, which ensures regional asymptotic stability via Lyapunov analysis is accomplished. In addition, considering practical conditions, real‐time numerical simulations, using a 1 kW case‐study converter, are carried out in order to assess the effectiveness of the proposed control scheme. Results for output voltage regulation, current tracking, and parametric uncertainty estimation under input voltage and load step changes are shown.

Design and Implementation of an Analog Controller Based on K-factor Design Method for a Novel Isolated Z-Source DC-DC Converter with High Voltage Gain

In this study, an analog control circuit design and implementation are performed by using the K-factor design method for a novel isolated Z-source dc-dc converter with high voltage gain. The closed loop system created by the control circuit ensures a constant output voltage at the converter output although there is a step change in input voltage and load within certain limits. The K-factor design method used to design the control circuit allows obtaining the design of the feedback circuit with a certain flow of mathematical equations. The mathematical method used to calculate the control circuit elements increases the reliability of the closed loop system. In this study, firstly, theoretical study of a closed loop control of a novel Z-source dc-dc converter topology is completed with K-factor design method. Secondly, the theoretical study results are analyzed by implementing a simulation study in PLECS. Lastly, by conducting an experimental study, simulation results and experimental results are compared. As a result, the verification of the experimental study that results in 1% error margin of the simulation study has formed the basis of a reliable control method for a new generation dc-dc converter.

Modelling and Performance Analysis of Grid Connected PMSG Based Tidal Generation System

Globally, most national grid relies on fossil fuel with consequent economic burdens, environmental pollution and global warming. Hence, Tidal energy possesses the capacity to mitigate the emission of carbon dioxide because it is clean, abundant, less expensive and predictable. However, the power output from Tidal energy generation system (TEGS) fluctuates due to changes in tidal flow whereby causing power instability. This work is geared at fundamentally model, simulate and control TEGS since it encounters problems such as harmonics, frequency fluctuations and voltage sags. These problems are resolved using a nonlinear controller coupled with a high-speed simulation of circuit-oriented electrical and digital electronic systems. The generator power output is optimised by utilising various control methods as proposed to control the voltage and frequency which is a Voltage Oriented Control technique that relies on high level performance 𝑑𝑞‐coordinate controllers. The system simulation is implemented in the MATLAB/Simulink environment. The current controller and DC‐link voltage controller are designed using Internal Model Control method. The simulation results show the system performance in response to the load and dc‐bus voltage step changes while directly running a Simulink model as a controller. The performance and validity of the preferable control method is verified by the simulation results and corresponds to available literature. The simulated results show that the controller can stabilise the constant dc-link voltage under dynamic and steady-state performance of the system.

A Control Strategy for Suppressing Submodule Capacitor Voltage Fluctuation of MMC Based on Circulating Current Voltage Drop Balance

The submodule capacitor voltage fluctuation of the modular multilevel converter (MMC) leads to the increase of the size of the submodule capacitor, the increase of system cost, and the decrease of system reliability and stability. In order to solve the problem, the mathematical model of circulating current voltage drop is derived, and the mechanism of circulating current on the submodule capacitor voltage fluctuation is studied through the submodule switching function. A control strategy for suppressing the submodule capacitor voltage fluctuation is proposed, which is based on circulating current voltage drop balance (CCVDB). The simulation model is built to compare three control strategies for suppressing submodule capacitor voltage fluctuation under the step changes of DC bus voltage and active power, namely, the circulating current is suppressed to zero, the second-order component of the submodule capacitor voltage is suppressed to zero, and the CCVDB strategy. The research results show that the CCVDB strategy can effectively suppress the submodule capacitor voltage fluctuation, reduce the capacitance demand, and reduce the total harmonic distortion (THD) of the submodule capacitor voltage, which verifies the feasibility and effectiveness of the CCVDB strategy.

Power System Impedance Estimation Using a Fast Voltage and Current Changes Measurements

Equivalent power system impedance is an important electrical quantity from many points of view. Areas in which this parameter plays an important role include, in particular: Voltage stability analysis, power quality, or fault condition analysis. Power system impedance estimation in real operation conditions can be performed by one of the non-invasive methods described by different authors. This paper aims to investigate and compare seven different methods for power system impedance estimation based on voltage and current variations measurement. After a brief description of selected methods, these methods were applied for power system impedance estimation in the case of two simple simulation tests and then in the case of three real measured data. Voltage and current changes used for power system impedance estimation in real conditions were measured in high voltage (HV) and medium voltage (MV) substations feeding steel mill with the electric arc furnace (EAF) operation. As the results presented in this paper have shown, not all of the methods analyzed are suitable for determining the power system impedance based on the fast step changes of voltage and current that occur, for example, during an EAF operation. Indeed, some of the tested methods were originally designed to determine the power system impedance from changes in voltages and currents recorded at steady state.

Design Robust Self-tuning FPIDF Controller for AVR System

This paper presents the fuzzy PID filter (FPIDF) controller for the automatic voltage regulator (AVR). This controller is used to maintain the generating unit output voltage within allowable limit, and improve the weakness of the conventional controller’s fast response under any sudden changes in operating conditions or any disturbance that affect the voltage stability. Firstly, the PID low pass filter (PIDF) controller initial values are calculated by using teaching-learning based optimization (TLBO) algorithms. After that, we construct the FPIDF for self-tuning the PIDF parameters in real-time to make the controller fast response. The dynamic performance characteristic of the terminal voltage is investigated and analyzed when the system subjected to the different step change in reference voltage from low to high. The performance of FPIDF is compared with PIDF, fuzzy PID (FPID), and classical PID controller. Also, the FPIDF controller performance is compared with other metaheuristics algorithms based on the controller in the latest literature. Moreover, the strengths, robustness, and effectiveness of the FPIDF controller are checked under uncertainties of AVR parameters. The maximum total deviation of the system performance is calculated in different ranges of the system parameter deviations. The results show a small maximum total deviation percentage when using the proposed controller. Finally, we can observe that the FPIDF controller has better dynamic performance than the other controllers, also has strong robustness and fast real-time response under any sudden changes in system operation.

Model Predictive Power Control for Bidirectional Series-Resonant Isolated DC–DC Converters With Fast Dynamic Response in Locomotive Traction System

High-frequency bidirectional dual-bridge series-resonant dc–dc converters have been attracted more attention in power electronic transformer (PET) due to high power density and efficiency. In this article, a model predictive power control method with phase shift modulation is proposed, to improve the dynamic response and robustness of the converter without load current sensor. In addition, the proposed method is insensitive to the resonant parameters in the adopted converter and can keep excellent dynamic characteristics even if the resonant parameter deviates from the desired operating point, which indicates good robustness. Effectiveness of the proposed control is verified on a 400-W scale-down experimental prototype with resistance load and inverter load, respectively. Compared with traditional voltage loop control and model predictive voltage control schemes, the proposed scheme can achieve a faster dynamic response of the output voltage in load and input voltage step change.

Transient Response of Microfluidic Fuel Cell

Diffusion boundary layer on the electrode surface of microfluidic fuel cells limits the mass transfer to the catalyst layer. Thus, investigation of the transient response of microfluidic fuel cell associated with the change in operating condition is not a trivial work. In this paper, transient characteristics of a microfluidic fuel cell upon changes in voltage load is investigated by applying a transient three-dimensional, two-phase and non-isothermal numerical model. Proposed model is developed with COMSOL multi-physics and governing equations are formulated based on the conservation laws for mass, momentum, species and electrical potentials. This model evaluates the effect of a dominant dynamic aspect of MFFC operation (mass transfer effect), accounts for transient convective and diffusive transport, and allows prediction of species concentration. Simulation results show that during step voltage change, the transient current lags behind voltage due to the time constant of reactant species transport. Also, simulation results show that the over/under shot of the current density occurs during the step change in the fuel cell voltage. The limited mass transport in the diffusion boundary layer causes a time delay between the voltage step change and the change of reactant distribution on the electrode surface. During the step voltage decrease/increase, the initial higher/lower reactant concentration on the electrode surface causes the over/under-shoot of current density. Simulation results show that the properties of the current over/undershoot can be varied according to the different values of functional parameters of the fuel cell.

Dynamic behaviors of PEM fuel cells under load changes

In this study, a one-dimensional isothermal single-phase transient model considering the finite-rate water absorption/desorption of membrane was established to study the dynamic behaviors of polymer electrolyte membrane (PEM) fuel cells under different cathode inlet humidity conditions in the presence of voltage step changes. Both the overshoot and undershoot phenomena were observed. Moreover, the distributions of water inside the electrolyte and the influence of that on the response current density of fuel cells were analyzed. When voltage stepped up/down, the water content in anode generally increased/decreased, and the water content in cathode is reversed. If the cathode intake is fully humidified, the water vapor in cathode is always over-saturated causing the change of ionic resistance is determined by that of the water content in anode. If the cathode intake is partially humidified, the change of ionic resistance could maintain within a small range owing to the change of water content in anode can be balanced by that of the water content in cathode.