Load Current Variation Research Articles

Fuzzy Logic based Control Strategies for Proton Exchange Membrane Fuel Cell System

In this work, new fuzzy logic-based control strategies have been proposed to improve the performance of the non-linear Proton Exchange Membrane Fuel Cell (PEMFC) system. This paper considers the empirical approach to designing the controller. This allows the controller’s design to be straightforward, and the controller can be fine-tuned as and when necessary. Three control strategies have been proposed in this paper, viz. Fuzzy feedforward control strategy (Strategy 1), Fuzzy feedforward controller with a feedback loop (Strategy 2), and Fuzzy feedforward controller with a feedback loop and conditional switch (Strategy 3) are proposed. The performance comparison of the proposed strategies is evaluated in terms of performance indicators such as the integral square error (ISE), integral absolute error (IAE), and total variation (TV) of the closed-loop control system. Furthermore, the proposed strategies keep the voltage at a given setpoint under load current variation. Finally, Strategy 3 is used to regulate the oxygen excess ratio (OER) at a reasonable value under load current variation to avoid oxygen starvation and keep the voltage at a defined point of a PEM fuel cell system. The results show that Strategy 3 provides better performance than other strategies

Buck-boost switched control without polarity reversal to regulate the production of direct current (DC-DC) in hybrid cars

The biggest problem that electric or hybrid vehicles present today are the amount of time required to recharge their energy, hence the importance of ensuring that the charge is not lost quickly and reducing the recharging time. We propose a more efficient energy production model to maintain the charge of the battery banks in hybrid and electric vehicles so that the autonomy time increases. A direct current to direct current (DC-DC) converter was modeled, in a buck-boost configuration that can keep the voltage constant of 50VDC powering the battery bank, with input voltages ranging between 35 and 70VDC with a fixed charging current of 4A. To automatically determine the values of the discrete components of the power filter, a MATLAB® script was developed. The transfer function of the power filter controller was calculated and simulated in open and closed loops to analyze the converter's stability. The complete circuit was tested for possible variations in voltage and load current using a Pulse-Width Modulation (PWM), with a time base of 2.4 kHz. To demonstrate the ability to perform the same function of the converter in a more stable way, digital control by PWM was implemented on a Nexys 4 development board (FPGA, Field Programmable Gate Arrays). In addition, with the advantage of reducing the variations inherent in using discrete components in an electronic circuit.Herein we disclose 1. a high-level language computer program to estimate the value of the components of the power filter that performs the energy conversion; 2. the transfer functions of the system modules; 3. the simulation of the buck-boost DC-DC converter control system without polarity inversion; and 4. the simulation of the system in digital form implemented on an FPGA.

Identification of Inter-Turn Short-Circuits in Induction Motor Stator Winding Using Simulated Annealing

This paper presents a method of inter-turn short-circuit identification in induction motors during load current variations based on a hybrid analytic approach that combines the genetic algorithm and simulated annealing. With this approach, the essence of the method relies on determining the reference matrices and calculating the distance between the reference matric values and the test matrix. As a whole, it is a novel approach to the process of identifying faults in induction motors. Moreover, applying a discrete optimization algorithm to search for alternative solutions makes it possible to obtain the true minimal values of the matrices in the identification process. The effectiveness of the applied method in the monitoring and identification processes of the inter-turn short-circuit in the early stage of its creation was confirmed in tests carried out for several significant state variables describing physical magnitudes of the selected induction motor model. The need for identification of a particular fault is related to a gradual increase in its magnitude in the process of the induction motor’s exploitation. The occurrence of short-circuits complicates the dynamic properties of the measured diagnostic signals of the system to a great extent.

Development of an On-line Insulation Degradation Diagnosis Technique for Wind Turbine Generators by Measurement and Analysis of Capacitive Leakage Current for Load Current Variation

Development of an On-line Insulation Degradation Diagnosis Technique for Wind Turbine Generators by Measurement and Analysis of Capacitive Leakage Current for Load Current Variation

An adaptive power split strategy with a load disturbance compensator for fuel cell/supercapacitor powertrains

Electric vehicles powered by fuel cell and supercapacitor hybrid power sources are of great interest. However, the power allocation between each power source is challenging and the DC bus voltage fluctuation is relatively significant in cascaded PI control schemes. This paper develops a power control strategy with an adjustable cut-off frequency, using an artificial potential field, to adaptively split the load current between the fuel cell and the supercapacitor under various load conditions. The adaptive cut-off frequency is calculated by cutting the load frequency spectrum with an allocation ratio that changes with the supercapacitor state of charge. Therefore, the relatively lower frequency portion of the load current is provided by the fuel cell and the supercapacitor handles the higher frequency portion. To enhance the control performance of the DC bus voltage regulation against the load disturbance, a load disturbance compensator is introduced to suppress the DC bus voltage fluctuation when the load variation occurs, which is implemented by a feed-forward controller that can compensate the load current variation in advance. The effectiveness of the proposed strategy is validated by extensive experiments.

Design and Simulation of a Capless Low Drop Out Voltage Regulator

Portable electronic devices mostly used battery as their primary source for operation hence longer running batteries or Power resources or vital for any portable device need for stable voltage supplies have led to the development of low dropout voltage regulators low dropout regulators provide stable regulated output voltage in various operating conditions which makes it useful in portable devices that design of high performance and stable low dropout voltage regulator is a challenge nowadays with decreasing device size and increasing power densities. The proposed circuit used a 5pack architecture of error amplifier. This paper proposes the study of behavior of the LDO voltage regulator with internal capacitors i.e., capless. The regulated voltage of 1.8V is obtained using the typical power supply of 2.2V obtained dropout voltage of 400mv with the delay of 12.77micro sec, power consumed 1.816W. The proposed design produced DC gain of 31.77db,with the load current variation of 0 to 20mA. The capless LDO architecture is verified in the Cadence 180nm technology. The architecture provides a stable gain and plot for both Temperature and Load Variations. The stability issues are overcome using the compensation techniques which uses a current amplifier and a capacitor in the differentiator configuration. The current amplifier implemented uses current mirror with current copying ratio of unity.

Simple temperature modeling of proton exchange membrane fuel cell using load current and ambient temperature variations

ABSTRACT This paper proposes a simplified proton-exchange membrane fuel cell (PEMFC) temperature model for the purpose of estimating PEMFC temperatures with high accuracy using air-cooling systems. Besides knowing that most of the existing models were designed for specific systems, the proposed model also focuses on generalizing the conventional temperature model for easy adoption by other PEMFCs. The proposed model is developed based on the first-order exponential equation to avoid the limitations of complex mechanistic temperature models. The model uses only the information available from typical commercial PEMFCs, the main inputs of which are the current, elapsed time, and ambient temperature. In addition, the PEMFC area, number of cells in the stack, and high/low operating currents were incorporated in the proposed model to ensure its generalizability and applicability to different PEMFC technologies with air-cooling systems under various ambient conditions. The required model parameters were optimized using the Harris hawks optimization method. The proposed model was validated using experiments conducted on the Horizon-500 W and NEXA-1.2 kW PEMFC systems equipped with air-cooling mechanisms under different ambient temperatures and load currents. The root mean square error of all the examined cases was less than 0.5. The proposed model is helpful for simulations, dynamic real-time controllers, and emulators because of its fast response and high accuracy.

An Impedance Adapting Compensation Scheme for High Current NMOS LDO Design

This brief presents a simple and power-efficient impedance adapting compensation scheme for high current NMOS low-dropout regulators (LDOs). By the proposed technique, the low-frequency node impedance retains to high value, while the high-frequency impedance is greatly attenuated. Therefore, both high gain and decent transient response is achieved simultaneously. Besides, the proposed impedance adaption waived the need for a commonly required power-hungry driver circuit, leading to a more simplified and energy-efficient design. In addition, the load-tracking technique is applied to further cancel the effect of load current variations, and helps achieve decent frequency and transient responses over a wide load range. Fabricated in a 0.35 μm CMOS process, the chip regulates an output voltage form 0.8 V to 1.8 V with 6 A current capacity and 114 mV maximum dropout voltage. The measurement results show an over-/undershoot voltages of 35.4 mV and -32.2 mV, respectively, for load transitions between 400 mA and 5A. The load and line regulations are 0.7mV/A and 0.12 mV/V, respectively, and the power supply rejections are -55 dB and -30 dB at 10 KHz and 1 MHz, respectively.

Grid-Connected Rectifier Based Dynamic Voltage Restorer To Improve Power Quality By Compensating Voltage Sag And Swell

Voltage sag and voltage swell are frequently occurred power quality problems in present power distribution system, which are cause more problems to avoid these problems and maintain constant voltage at sensitive load during sag and swell Dynamic voltage restorer gives solution .we propose self-supported DVR, to minimize the cost by preventing external dc source in DVR, it is controlled by SRF PI control along with an inner current loop to stabilize the system and outer voltage loop to increase the system robustness. The proposed model provides fast voltage restoration for a short and long duration of voltage sags and swells manage wide load current variation for short and long voltage disturbances. In this paper, we present the effectiveness of the proposed method by using MATLAB/simulation results. A laboratory prototype DVR is modelled and we are using CCS studio to interface DSPTMS320F28027F

A Fast IGBT Junction Temperature Estimation Approach Based on ON-State Voltage Drop

Insulated gate bipolar transistor (IGBT) module is the most widely used power electronic device in converters. Condition monitoring of IGBT is critical for avoiding sudden failures. Health management of converters based on accurate IGBT junction temperature is of great importance to reliable operation. However, the existing monitoring methods have some drawbacks, including low feasibility of online implementation, intrusiveness, and slow response. IGBT junction temperature has a strong influence on IGBT on-state voltage drop. A novel online IGBT junction temperature measurement method based on the on-state voltage drop is proposed in this article. This technique can monitor the on-state voltage drop of IGBT and extract IGBT junction temperature online. Besides, the influences of the measurement circuit temperature variations and IGBT load current variations are considered and compensated based on the off-state stage of the IGBT. Simulation and experimental results validate the feasibility of the proposed technique. The proposed method has advantages of fast response, low cost, and simple circuit structure for noninvasive online IGBT junction temperature monitoring.

Comparative Reliability Analysis for Resonant Converter Operation Under Component Ageing

This article is concerned with reliability analysis in relation to optimal switching of resonant power converters, aimed at minimizing their power loss and operational temperature and, thus, reducing their lifetime degradation. In most cases, high-performance resonant converter control requires a continuous adaptation of the power device switching instances depending on the power input source, load current, or parameter variation in passive components. If the resonant converter is switched before or after the resonant swing ends, more loss is added to the system, with effects in operating temperature rise and reliability deterioration. Even if the switching frequency is adjusted to keep the output voltage constant, it may influence the operational temperature. This article is quantifying this problem with a calculation of the lifetime implication for both cases of zero voltage transition (ZVT) and zero current transition (ZCT) buck converters. A broad range of parameter variation in passive components is considered due to ageing or aggravated stress. A thorough performance (lifetime/reliability) evaluation is achieved through a comparative analysis of results obtained for resonant converters with ideal operation, resonant converters with adjusted timing due to parameter variation, and hard-switched converters without any resonance. Conclusions are formulated in the end. The results reported in this article should be of high interests to the power electronics community, given that resonant converters are used in a wide range of applications due to their ability to reduce power semiconductor losses.

Investigating Conditions for an Unexpected Additional Source of Partial Discharges in DC Cables: Load Power Variations

This paper has the purpose to investigate the variation of electric field inside a HVDC cable insulation, and consequent potentiality of partial discharge inception in a defect upon load current variation. Simulations carried out by COMSOL Multiphysics show that load variations can incept partial discharges during cable operation at a constant voltage, depending on insulating material characteristics, defect size and location, and, in particular, the temperature and field dependence of electrical conductivity. Different values for temperature and field dependency of electrical conductivity, as well as of thermal conductivity and heat capacity are considered and their effect on the field distribution inside cavities near inner and outer semiconducting layer analyzed. For this purpose, a new analytical model to predict the behavior of PD amplitude and repetition rate from cable energization to steady state, including load variation, is introduced. The likelihood of PD inception during load transients, and not only voltage transients as previously demonstrated, poses further attention and constraints to HVDC cable design.

A 15-W Quadruple-Mode Reconfigurable Bidirectional Wireless Power Transceiver With 95% System Efficiency for Wireless Charging Applications

In this article, a 15-W quadruple-mode reconfigurable wireless power-receiving unit with high efficiency for Inductive coupling and magnetic resonance-based standards, such as wireless power consortium (WPC), power matters alliance (PMA), alliance for wireless power (A4WP), and magnetic secure transmission (MST) applications is proposed. Quadruple-mode gate controller(QMGC) is proposed in quadruple-mode synchronous rectifier to manage sizes of core and drivers which results in maximum power conversion efficiency (PCE) for each mode based on conduction and switching losses. In QMGC, switchable zero voltage and current sensing block is proposed for WPC/PMA to maximize PCE regardless of load current variations. For A4WP mode, a digitally controlled delay adjustment block is adapted to minimize power consumption while compensating for delay which results in reverse leakage current and power loss. Finally, for MST mode, low power TX (LPTX) block is implemented to minimize current consumption so that burden on battery can be minimized. A high-resolution current sensor is proposed in low-drop out regulator to sense current for overcurrent limit and overcurrent protection. The measured PCE of proposed system at 15 W are 95.3% and 92.3% for WPC/PMA and A4WP mode, respectively. For MST, power consumption is reduced to 35% courtesy LPTX block.

Online Junction Temperature Measurement for SiC MOSFET Based on Dynamic Threshold Voltage Extraction

The online junction temperature monitoring of power devices is a viable technique to ensure the reliable operation of mission-critical power electronic converters. This article provides a potential approach for the junction temperature estimation of SiC MOSFETs based on the dynamic threshold voltage. The proposed method is independent of load current variation, which eliminates the complicated calibration procedure with load current. First, the physical mechanism and the temperature dependence of the dynamic threshold voltage are analyzed. An analytical model for the dynamic threshold voltage is built to investigate the effects of gate loop parameters on the temperature sensitivity and measurement accuracy. Then, the principle of the dynamic threshold voltage measurement circuit is introduced. Finally, the proposed dynamic threshold voltage measurement circuit is experimentally evaluated through the double-pulse tests. The experimental results show that the dynamic threshold voltage of SiC MOSFET has a good linear relationship with junction temperature. The temperature sensitivity of the dynamic threshold voltage of two SiC MOSFETs is approximately 5.2 mV/°C and 19.6 mV/°C, respectively.

An Adaptive Protection Technique for Smart Distribution Network

The future distribution networks (DNs), commonly known as the smart grid is expected to be reliable, efficient, and can accommodate renewable energy resources. The smart distribution network has to withstand the technical challenges related to the integration of distributed generations (DGs). Among these technical challenges, protection malfunctioning with the increased integration of DGs is one of the important issues, which requires a great concern. Thus, a protection philosophy, which can suit the future smart grid requirements with respect to increased integration of DGs, has to be devised. In this paper, an adaptive protection technique, which is based on the characteristics of fault-current and load-current variation, is proposed. In the proposed method, intelligent electronic devices (IEDs) monitor the status of circuit breakers (CBs) and DGs. If any status change occurs, the calculation and relay agents are triggered to update the IEDs. DigSILENT PowerFactory is used to verify the suggested philosophy. Especially DigSILENT Programming Language (DPL) is used to model the adaptive protection. The solar power plant in the Antalya vicinity in Turkey is used to verify the proposed method. The results of the simulation study show the correct operation and effectiveness of the proposed method.

Quantitative Feedback Design-Based Robust PID Control of Voltage Mode Controlled DC-DC Boost Converter

This brief addresses the problem of instability occurring in the voltage control mode of a non-minimum phase (NMP) DC-DC boost converter. To solve this instability issue in the presence of uncertainties and the external disturbances, quantitative feedback theory (QFT) is adapted to systematically design a robust proportional integral derivative (PID) controller, which is realized using only sensed output voltage as feedback. The advantages of the proposed PID design using the QFT are: (i) it eliminates the burden of tedious and ad-hoc tuning of PID gains using the conventional PID design approaches, (ii) current measurement is not required, (iii) disturbance dynamics (input voltage and load current variations) are included in the design stage itself, which further enhances the disturbance rejection performance of the output voltage, and (iv) it allows direct design for the non-minimum phase boost converter despite the bandwidth limitations. Extensive simulations and experiments are carried out to validate the efficacy of the proposed PID controller in the presence of the external disturbances and compared its superiority over a conventional PID controller.

Modified LQR Technique for Fuel-Cell-Integrated Boost Converter

Fuel cells (FCs) are an alternative source of energy whose by-products are heat, vapor, and water. For medium-power and standalone operation, an FC is integrated with a boost converter, as the required voltage level is higher than the supply. Control of such a converter with a slow dynamic source requires a fast-acting controller, since the demand executed by the controller affects the action taken by the hydrogen valve in FCs. In this article, a linear-quadratic regulator (LQR) is developed to control the power converter. In practical applications, the conventional LQR produces offset in output voltage due to effective series resistance (ESR) of the output capacitor. To make the LQR dynamic with load perturbation, information of inductor reference current is required, which changes with variation in load current. To solve these two problems, two modifications in the classical LQR have been proposed to minimize the impact of ESR (m-LQR) and incorporate control action based on the reference inductor current (M-LQR). The proposed methods are compared with the conventional average current-mode control technique. The M-LQR-based scheme is found to outperform the classical m-LQR technique in terms of improved transient dynamics and reduced offset at the steady state. In addition to numerical simulations, the proposed control techniques have been validated experimentally.

Matching Resonant Switches Operation Using Classical Pulse-Width Modulation Algorithms

This paper presents a new method of controlling resonant switches of a converter, in which the instants of control pulses supply to the main and auxiliary switches of the circuit are strictly synchronized with pulse-width modulation (PWM) logic signals. Any classical options providing the specified quality of the output voltage and current can be used as such signals. The control pulses durations of the main switches have the same time intervals as those of the PWM control signals, since the control pulses are shifted relative to the PWM signals by a constant time delay. The durations of control pulses of auxiliary switches used to activate resonant switching processes are constant and independent of changes of the electric mode parameters of the circuit and the scatter of the parameters of resonant circuit components. The synchronizing mode is shown to be achieved by introducing two additional time intervals into each resonant switching cycle compensating the effect of external and internal factors on the duration of the required control pulses for the main and auxiliary switches of the converter. Such additional time intervals are the duration of free—that is, without significant loss of power—circulation of current (energy) in the inductance of the resonant circuit. In addition, it is shown that the necessary conditions for free circulation are the capability of the main converter switches for bilateral current conductivity and the absence of energy absorption sources in the circulation circuit. The diagrams are presented of switching processes demonstrating the advantages of a new method for controlling resonant switches of the inverter in a wide range of the supply voltage and load current variations of the circuit.

Dual‐input and triple‐output boost hybrid converter suitable for grid‐connected renewable energy sources

In grid-connected distributed energy system, power converters are used to integrate different renewable sources and loads. If the number of sources/loads increases, the number of converters/conversions are required. Because of more conversions and operations, the conversion efficiency decreases, and it is difficult to control load/source parameters independently. In order to overcome the problems associated with the integration of multiple sources and loads, this study proposes a dual-input and triple-output boost hybrid converter (DTBHC) with independent control. The dual input ports of the proposed converter can be used to connect two different dc voltage sources. Triple output ports of the proposed converter can be used to connect ac grid, ac local loads, and dc local loads. These load voltages are regulated by using carrier-based modified sinusoidal pulse-width modulation (CBMSPWM) technique in order to control the dc and the ac loads independently with respect to sources. The DTBHC with CBMSPWM control is simulated using a MATLAB/Simulink validated using FPGA controlled laboratory prototype. The validation of the proposed converter is carried out with variation of load current, different input voltages to generate stable ac output voltages (same as well as different frequencies).

Adaptive Output Feedback Controller of Voltage Source Inverters in Microgrid Connected Mode

Abstract This paper deals with the control of Voltage Source Inverters (VSIs) connected to the main grid. The controller aim is fourfold: i) enforcing the current injected by the VSI to follow a given reference, ii) estimating the grid resistance and inductance, iii) estimating the current load and the grid voltage, iv) assuming an asymptotic stability of the system. To achieve these aims, we designed an adaptive output feedback controller using the backstepping technique and the high gain approach. Moreover, the controller has the ability to compensate the reactive power of the local load. The system stability was analyzed by Lyapunov theory. The controller performances were illustrated by simulations with grid parameter and load current variations.