Modeling and Simulation of Equivalent Series Resistance for Asymmetrical Supercapacitor

Output capacitor in the voltage regulator (VR) circuit ensures stability especially during fast load transients. However, the capacitor parasitic, namely equivalent series resistance (ESR), may cause unstable VR operation. VR characterization in terms of ESR suggests stable range of capacitor ESR based on the ESR tunnel graph in the VR datasheet. Specifically, the stable ESR range is the critical ESR value, which lies on the failure region boundary of ESR tunnel graph. New or updated ESR tunnel graph through characterization is required for new product development or quality assurance purpose. However, the characterization is typically conducted manually in industry, thereby increases the manufacturing time and cost. Therefore, this work proposed a characterization approach that can reduce the time to determine the ESR tunnel graph based on the hybrid system identification and neural network (SI-NN) approach. This method utilised system identification (SI) to estimate the VR circuit model for certain operating points before predicting the transfer function coefficients for the remaining points using radial basis function neural network (RBFNN). Eventually, the critical ESR of failure region boundary was estimated. This hybrid SI-NN approach able to reduce the number of data that would be acquired manually to 25% compared to manual characterization, while provides critical ESR estimation with error less than 2%.

This paper presents the equivalent series resistance (ESR) modeling method of filter components and its stability impact of LCL filtered grid-connected voltage-source converters (VSCs). First, the time-domain models of filter inductor and capacitor are developed for modeling the ESR effect, which are used in simulations. Then, the current control loop gains of the grid-connected three-phase VSC, which include the ideal LCL filter and the ESR-modeled LCL filter are compared. The result shows that the ESR affects both the resonance peak and the phase characteristic in the frequency domain. Finally, in order to verify accuracy of proposed model, the loop gain is measured by network analyzer in the experimental set up, which shows that the analytical loop gain with proposed ESR modeled inductor agrees very well with experimental value. This verification means that the ESR modeling method is useful for an accurate stability analysis.

Optimizing the capacitance and equivalent series resistance (ESR) has been a key issue in the fabrication of Electric double layer capacitor (EDLC). The typical method used for identifying optimal parameters in the manufacturing process reported in the literature relies on “trial-and-error” method (optimizing one factor at a time), which is ineffective, inaccurate, time consuming and not systematic. Therefore, in this work, the Taguchi technique was applied to identify the most the significant process variables in order to optimize (maximize) capacitance and (minimize) ESR of the supercapacitor device. Design of experiments (DOE) with this method allows multiple parameters to be evaluated with a very small number of experiments. With the use of the Taguchi methodology in this paper the number of experiments can be reduced for three factors at three levels from (33) = 27 experiments to only 9 set of experiments. In terms of the materials, the core supercapacitor materials that have been used in the present study is based on activated carbon (AC) as the active material, carbon black (CB) as the conducting agent and PVDF polymer as the binder material. A total of nine experiments were conducted, where the percentage composition of PVDF and CB were varied for different mixing times in order to find the most significant process parameter affecting the capacitance and the ESR. 1M lithium perchlorate (LiClO 4 ) in acetonitrile was used as the electrolyte. Button shape supercapacitors with a diameter of 13mm have been produced for the present study. The cell capacitance was found to range from 24.91 − 51.23mF, depending on the exact parameters used in the fabrication process. The capacitive properties of the fabricated cells were evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge-discharge measurements using an Autolab (PGSTAT302N) potentiostat. The results indicated that binder percentage and mixing time has greater effect on the capacitance, whereas for the ESR, PVDF and carbon black percentages were found to be more significant.

A capacitor with a suitable equivalent series resistance (ESR) characteristic is typically connected to the output terminal of a voltage regulator. This ESR must be characterized during the manufacturing process to identify the range of ESR values and to stabilize voltage regulator operation. This ESR range is characterized manually in current manufacturing practice. However, it is tedious, time-consuming, and limits manufacturing productivity rate. Therefore, the ESR characterization process should be simplified and its effectiveness enhanced. In line with this objective, this work mainly aims to automate the ESR characterization process of voltage regulators. Simulation was performed as the reference for subsequent ESR characterization experiments. After investigating manual characterization outcomes, automated ESR characterization was conducted. A stepper motor controlled by the microcontroller was used to automatically change the ESR values. Results show that the automated ESR characterization approach is simple and can effectively reduce characterization time.

An empirical model for voltage and equivalent series resistance (ESR) has been developed for lead acid batteries used as a pulsed power source. During the design of the battery upgraded supply (BUS) for Eglin Air Force Base, the Center for Electromechanics at the University of Texas at Austin (CEM-UT) developed a model for the batteries to be used in this system. BUS is a 5 MA, 500 MJ inductive power supply charged by batteries for use as a railgun power supply. A series of tests was performed to determine the driving voltage and ESR of the batteries for discharge times from 2 to 10 s and current levels from 500 to 2500 A. A model for voltage and ESR was obtained from these tests. The methods used and sample data from the tests are presented. The main factors affecting battery voltage and ESR are discussed, and the models developed for the batteries tested are described. It is concluded that the proposed empirical model can be used to predict the performance of Pulsar batteries as long as the currents are around 500 to 2500 A and the timeframes are from 2 to 10 s. >

A simple equivalent series inductance (ESL) and equivalent series resistance (ESR) measurement technique for capacitors is presented. A low-cost square waveform voltage source coupled with a reference resistor can be used to measure the ESL, ESR and capacitance of an electrolytic capacitor. By connecting a capacitor in series with a reference resistor, the equivalent output step response of the capacitor voltage reveals the ESL and ESR of the capacitor. To effectively capture the output step response, a square input waveform is used instead. The square waveform voltage source can easily be realised using a DC voltage source and simple switching devices. Experimental results are included to demonstrate the effectiveness of the proposed scheme.

Being one of the most used passive components in power electronics, electrolytic capacitors have the shortest life span due to their wear-out failure which is mainly caused by vaporization and deterioration of capacitor electrolyte. Knowing these two phenomena increase Equivalent Series Resistance (ESR) of the capacitor, tracking ESR value over the system operating time can be a good indicator for state of health of an electrolytic capacitor. In order to set the maintenance schedule, various ESR monitoring algorithms computing remaining time before failure have been investigated in literature. These real-time algorithms use classical models for ESR and life-time estimation which are not precise enough and leads the maintenance program to be either risky if the prediction is more than the actual life-time or more expensive if it is much less than the actual life span. This paper presents a generalized equivalent model using fractional order element for electrolytic capacitor to estimate the ESR and impedance of faultless running capacitor. Unlike other existing fractional order models, proposed model considers a fractional order dynamic only in the dielectric losses and the terminal capacitor remains integer order as observed in actual capacitor’s behavior. Furthermore, a novel failure predictive model using Mittage-Leffler function is proposed to track the ESR increment due to aging of the capacitor and estimate the failure time based on the information which are provided through ESR monitoring system. Using this model increase the life-time prediction accuracy. Hence the predictive maintenance of the system with capacitors nearing their failure time can be set more precisely. These two fractional order models are compared against classical ESR and life-time prediction models to illustrate the enhanced performances of the proposed models.

We propose an adjustment strategy for time-varying equivalent serial resistance (ESR) of the decoupling capacitor to minimize the worst-case voltage noise of power distribution network (PDN). Previous works mainly focus on how to find the optimum equivalent serial resistance to obtain the minimum voltage noise, where ESR is constant. In this paper, we first derive the closed-form expressions for the voltage response of RLC tank with the constant ESR, and analyze the conditions for input load current to create the worst-case peak voltage noise of RLC tank with the time-varying ESR. We then propose our adjustment strategy for the time-varying ESR. Experimental results show that the worst-case voltage responses generated by our method can be decreased by 30%, compared to that with the constant ESR.

Aluminium Electrolytic Capacitors (AEC) are indispensable in applications where high capacitance per unit volume and low cost are preferred. However, it is also one of the most failure-prone components in a power converter system. As AEC is an electrochemical device, which follows Arrhenius law, the most important life-deciding factor of an AEC is its operating temperature [1]. In this paper, a condition monitoring system for AECs is proposed based on the accurate estimation of equivalent series resistance (ESR) and operating temperature. Operating temperature is estimated using the thermal impedance model based on improved power loss calculation methodology. The proposed method computes power loss using the capacitor voltage and current in contrast to the existing methods [4] - [7] which uses capacitor current and ESR to estimate the power loss. Thereby, it avoids the issue of ESR variation with ageing and temperature which may give erroneous results with ageing in case of stored look-up tables for ESR. ESR estimation is based on the method proposed in [14]. As ESR is the most widely used degradation indicator, the ESR and operating temperature can be used to estimate the present health status of an AEC.

High demand on voltage regulator (VR) currently requires VR manufacturers to improve their time-to-market, particularly for new product development. To fulfill the output stability requirement, VR manufacturers characterize the VR in terms of the equivalent series resistance (ESR) of the output capacitor because the ESR variation affects the VR output stability. The VR characterization outcome suggests a stable range of ESR, which is indicated in the ESR tunnel graph in the VR datasheet. However, current practice in industry manually characterizes VR, thereby increasing the manufacturing time and cost. Therefore, an efficient method based on multilayer neural network has been developed to obtain the ESR tunnel graph. The results show that this method able to reduce the VR characterization time by approximately 53% and achieved critical ESR prediction error less than 5%. This work demonstrated an efficient and effective approach for VR characterization in terms of ESR.

The operation of a voltage source inverter (VSI) depends on its output LC filter and the PWM modulator delay. The VSI model includes serial equivalent resistance based on the resistances of the active inverter bridge transistors, the filter coil winding, and additional PCB elements, such as traces and connectors, in addition to the large equivalent resistances that result from power losses in the coil core and switches. These dynamic power losses depend on the switching frequency and the inverter load. This paper investigates the change in equivalent serial resistance that occurs if the standard Si-MOSFET switches are replaced with wide bandgap (WBG) transistors with correspondingly lower equivalent serial resistance. The paper further investigates how such a change influences the design of the controller, given that replacement of the switches shifts the roots of the closed-loop characteristic equation. Theoretical analyses of the influence of equivalent serial resistance for a multi-input single-output passivity-based controller and a single-input single-output coefficient diagram method are also presented. These analyses are applied to both types of switches. Two methods are used to measure the serial equivalent resistance for a given VSI using Si and WBG switches. The possibility of replacing switches with WBG technology in existing inverters was assessed, and the corresponding controller adjustment that would be required. The theoretical analysis is verified via the use of an experimental VSI.

A review on selection criteria of aqueous electrolytes performance evaluation for advanced asymmetric supercapacitors

Benchmarking of capacitor power loss calculation methods for wear-out failure prediction in PV inverters

In the high voltage line type pulse modulators, Pulse Forming Network (PFN) capacitors are one of the important components. These capacitors operate at peak kilo ampere current range and at repetition rate in the range of a few hundred hertz. The performance of these capacitors is critical w.r.t. overall system performance, and they are required to operate at high power density and low losses with high reliability. The Equivalent Series Inductance (ESL) and Equivalent Series Resistance (ESR) are two critical parameters that affect the performance of these capacitors. PFN modulator demands a capacitor of very low ESL and ESR for reliable operation and generation of high-voltage pulses. Higher ESR value adversely affects the performance of the capacitor by raising its temperature and thus deteriorating its life. ESL value does not directly affect life, but it affects the quality of high voltage pulse. In RRCAT, the PFN capacitors purchased from Indian manufacturers were showing high-temperature rise and failures. Therefore, new capacitors were designed to have lower ESL and ESR values. Measurement of ESL and ESR is important to evaluate the performance of the capacitors. The low value of these parameters makes their measurement a challenging task and requires special techniques. For low values of ESL and ESR (less than 100 mΩ) measurement, a differential measurement technique was used in which modification and different layouts were explored to improve the repetitive accuracy of the measurements. The differential ESR and ESL measurement techniques with more emphasis on the low-value ESR measurement will be discussed in the paper.

Because of the self-heating effect of InGaN based high power light-emitting diodes (LEDs), the temperature of the LED chip is much higher than the case temperature (TC). The maximum Tj in our experiment is 148K higher above the case temperature. The voltage drops on p-n junction and equivalent series resistance are extracted from the measured I-V curve, and then the values of equivalent series resistance at different forward power are obtained. Due to the self-heating effect, the values of equivalent series resistance show a very strong forward power-dependent characteristics, the maximum equivalent series resistance reported in this paper is about 1.9Ω at high forward power, being more than twice the minimum value. The power dissipation of equivalent series resistance is increased sharply when the forward power is increased, nearly half of the forward electrical power was dissipated on equivalent series resistance at high power, and it becomes the an important factor restraining the lumen efficiency of high power GaN based light emitting diodes.