On power losses in switched supercapacitor circuits

HELIX

Supercapacitor (SC) is an electrical energy storage device that bridges the gap between electrolytic capacitor and rechargeable battery. It can accept and deliver charge much faster than battery as well it has a high power density. This property makes them a good choice to be used in electric vehicles like buses and cars. To recharge the on-board SC module used in electric vehicle in less time, a high amount of power is required. If this power is taken from distribution network, then high magnitude of peak current is absorbed from the supply which can create constraint on power network. To overcome this problem, on-board SC module is charged through fixed SC module which acts as energy buffers through DC-DC converters. In this paper, instead of using boost and buck converter, a double stage conversion technique is proposed for the fast energy exchange between the two energy systems with the help of MATLAB Simulink software and by experimental results.

2015

Supercapacitor is most promising energy storage device. Due to High power, high energy and long- term reliability feature of Supercapacitor, it can be use in various applications as backup power unit, auxiliary power unit, instantaneous power compensation, peak power compensation and energy storage as well. This paper presents the analysis and design of a supercapacitor and also examines the temperature effects on supercapacitors using a constant voltage source . Finally, simulation results are shown and analyzed.This paper presents an overview of supercapacitor showing their advantages as well as their potential applications.

2021

All electrical and electronic devices require access to a suitable energy source. In a portable electronic product, such as a cell phone, an energy storage unit drives a complex array of power conversion stages to generate multiple DC voltage rails required. To optimize the overall end-to-end efficiency, these internal power conversions should waste minimal energy and deliver more to the electronic modules. Capacitors are one of the main component families used in electronics, to store and deliver electric charges. Supercapacitors, so called because they provide over a million-fold increase in capacitance relative to a traditional capacitor of the same volume, are enabling a paradigm shift in the design of power electronic converter circuits. Here we show that supercapacitors could function as a lossless voltage-dropping element in the power conversion stages, thereby significantly increasing the power conversion stage efficiency. This approach has numerous secondary benefits: it im...

The modeling of a supercapacitor by an electrical circuit composed of multiple resistors and variable voltage capacitors is studied. The temporal characterization is performed with a realized test bench with accurate data acquisition for the different charge and discharge protocols. Access resistance and RC branches are identified for the different time windows. The experimental characterization is detailed for the transmission line and for the complementary branches which reproduce redistribution and leakage current. Thereafter, the implementation of the equivalent circuit in the Matlab/Simulink environment is shown, namely the consideration of non-linear behaviors of the capacitances regarding voltage. The found characterized values are entered in the model to simulate charge/discharge of the supercapacitor. Agreement between simulated and experimental results proves the consistency of the time constant determination approach.

Journal of Power Sources, 2007

A simple electrical model has been established to describe supercapacitor behaviour as a function of frequency, voltage and temperature for hybrid vehicle applications. The electrical model consists of 14 RLC elements, which have been determined from experimental data using electrochemical impedance spectroscopy (EIS) applied on a commercial supercapacitor. The frequency analysis has been extended for the first time to the millihertz range to take into account the leakage current and the charge redistribution on the electrode. Simulation and experimental results of supercapacitor charge and discharge have been compared and analysed. A good correlation between the model and the EIS results has been demonstrated from 1 mHz to 1 kHz, from −20 to 60 • C and from 0 to 2.5 V.

2020

In switched capacitor circuits, it is quite common to use MOSFET switches, integrated capacitors (IC) and non-overlapping clocks for carrying out switching operations. MOSFET switches are far from ideal switches mainly when they are operated with small operating voltages. Some investigations have been carried out on the performance of switched capacitor resistors (SCRs) with the switches operated under varied conditions. Further, an attempt has been made to find out how closely SCR represents conventional resistors. It has been found that the SCRs with ideal components satisfy the properties of series and parallel connected conventional resistors. Further, the energy dissipation in SCR is the same as that in conventional resistors when operated under fixed voltage difference. FET based SCRs exhibit higher resistance values, compared to SCRs with ideal switches depending on the operating conditions. When SCRs are loaded with conventional resistors or capacitors, their output is entir...

The main disadvantage of using supercapacitors in the field of energy storage systems is their limited voltage due to technology limits. To resolve this problem, these components are usually applied in series to reach the suitable voltage. However the tolerance in these components' characteristics leads to imbalanced voltage during the chargedischarge cycle. This may influence adversely the supercapacitors lifetime. To avoid this phenomenon, balancing circuits have to be employed. This turned out to be very useful in improving the performance and extending the lifetime of supercapacitors and the reliability of energy storage system as a whole.

Energies

The resistance–capacitance (RC) model is one of the most applicable circuits for modeling the charging and discharging processes of supercapacitors (SCs). Although this circuit is usually used in the electric and thermal investigation of the performance of SCs, it does not include leakage currents. This paper presents exact analytical formulas of leakage-current-based supercapacitor models that can be used in industrial applications, i.e., constant-power-based applications. In the proposed model, current and voltage are represented as a solution of nonlinear equations that are solved using the standard Newton method. The proposed expressions’ accuracy is compared with the results obtained using traditional numerical integration methods with leakage current formulation and other methods, found in the literature, with no leakage current formulation. The results confirm that including leakage current represents a more accurate and realistic manner of modeling SCs. The results show that...

2005

Abstract Switched capacitor converters have become more common in recent years. Crucial to understanding the maximum power throughput and efficiency is a model of the converter's equivalent resistance. A new form for equivalent resistance is derived and discussed in a design context. Quasi-resonant operation is also explored and compared to non-resonant operation. Several capacitor technologies are evaluated and compared

This paper presents the applications of supercapacitor energy storage in hybrid systems with renewable energy sources, as well as with other energy storage technologies. Supercapacitors are capable to compensate the power variations of renewable energy sources due to the stochastic nature of the primary resources. These applications can be used in numerous domains, such as electrical transport, power supply to electronic devices and in combination with renewable energy sources for autonomous power supply in remote areas. The supercapacitors main parameters and equivalent circuits are also presented.