Parallel Capacitor Research Articles

Dynamic Reactive Power Compensation Optimization Strategy for Distribution Networks with Distributed Generators and Energy Storage Systems

To balance the output and load dynamic changes of distributed power generators (DG) and energy storage systems (ESS), a demand-side response-based dynamic reactive power optimization (RPO) strategy for distribution networks (DN) is proposed. This strategy adopts a phased optimization method to coordinate and optimize different types of reactive variables within the same period. By adjusting the states of parallel capacitor banks (SCBs) on load voltage transformers (OLTC), DGs, and ESS inverters, the RPO of the DN is carried out. Based on the characteristics of the model, an improved particle swarm optimization algorithm (IPSO) is used to solve different types of variables, and an IPSO based on tent chaotic mapping and levy flight strategy is proposed to improve the efficiency of collaborative solving. The simulation results show that the proposed strategy, considering the change of new energy output and demand side response, can reduce the solution scale while obtaining high satisfaction RPO results.

Difference between Charge–Voltage Relations of Ordinary and Fractional Capacitors

In an ordinary time-varying capacitor, there is debate on whether a time-domain multiplication or a time-domain convolution of capacitance and voltage determines charge. The objective of this work is to resolve this question by experiments on a time-varying capacitor in parallel with a resistor. It was implemented by a motor-driven potentiometer and op-amps. The response matched a power-law function over about two decades of time, and not an exponential, for several sets of parameters. This confirms the time-domain multiplication model. This result is the opposite of that obtained for a constant phase element (CPE) in its common time- and frequency-varying capacitor interpretation. This demonstrates that a CPE is fundamentally different from an ordinary time- and frequency-varying capacitor.

Development of equivalent circuit model for thermal runaway in lithium-ion batteries

An integrated equivalent circuit model was developed to analyze thermal runaway in lithium-ion batteries under different conditions. The thermal runaway model was developed by adding various circuit components to a second-order resistor–capacitor circuit, whose values were obtained based on previous experimental studies. First, the characteristics of thermal runaway by electrical abuse were analyzed. When the charge rate was high, the maximum temperature during thermal runaway was high, and the thermal runaway ended fast. At charge rate of 3C, the maximum temperature was 209.4 °C, since a high current generates large heat, and the thermal runaway duration was 1200 s. Next, thermal runaway by mechanical abuse was analyzed by examining the state of charge effect on the maximum temperature. When the state of charge increased from 0.5 to 1, the temperature increased to 470 °C during thermal runaway because a high potential difference arises when the state of charge is high. Lastly, an integrated equivalent circuit model was developed by adding a series of resistors and capacitors in parallel to the conventional battery model. The model showed an accuracy of 87 % compared to previous experimental results. The proposed model can enable the analysis of thermal runaway during fast charge caused by combined abuse factors.

Non-Contact Adaptive Voltage Sensor Based on Electric Field Coupling Principle.

Non-contact voltage sensors based on the principle of electric field coupling have the advantages of simple loading and unloading, high construction safety, and the fact that they are not affected by line insulation. They can accurately measure line voltage without the need to connect to the measured object. Starting from the principle of non-contact voltage measurement, this article abstracts a non-contact voltage measurement model into the principle of capacitive voltage sharing and deduces its transfer relationship. Secondly, it is theoretically inferred that the edge effect of the traditional symmetric structure sensor plate will cause the actual capacitance value between the sensor plates to be greater than the theoretically calculated capacitance value, resulting in a certain measurement error. Therefore, the addition of an equipotential ring structure is proposed to eliminate the edge additional capacitance caused by the edge effect in order to design the sensor structure. In addition, due to the influence of sensor volume, material dielectric constant, and other factors, the capacitance value of the sensor itself is only at pF level, resulting in poor low-frequency performance and imbuing the sensor with a low voltage division ratio. In this regard, this article analyzes the measurement principle of non-contact voltage sensors. By paralleling ceramic capacitors between the two electrode plates of the sensor, the capacitance of the sensor itself is effectively increased, improving the low-frequency performance of the sensor while also increasing the sensor's voltage division ratio. In addition, by introducing a single pole double throw switch to switch parallel capacitors with different capacitance values, the sensor can have different voltage division ratios in different measurement scenarios, giving it a certain degree of adaptability. The final sensor prototype was made, and a high and low voltage experimental platform was built to test the sensor performance. The experimental results showed that the sensor has good linearity and high measurement accuracy, with a ratio error of within ±3%.

Design and Analysis of Complementary Metal–Oxide–Semiconductor Single-Pole Double-Throw Switches for 28 GHz 5G New Radio

We propose a single-pole double-throw (SPDT) switch with low insertion loss (IL), high isolation, and high linearity for a 28 GHz 5G new radio. The transmit (TX) path is a π-network consisting of a parallel dynamic-threshold metal–oxide–semiconductor (DTMOS) transistor, M1, with large body-floating resistance, RB (DTMOS-R M1), a series one-eighth-wavelength (λ/8) transmission line (TL), and a parallel capacitance, Cant. The series λ/8-TL in conjunction with the parallel Cant and transistors’ capacitance constitute an equivalent λ/4-TL with a characteristic impedance of 50 Ω. This leads to low IL in the TX mode and decent isolation in the receive (RX) mode. The RX path is an L-network constituting a series impedance (of parallel inductance L1 and DTMOS-R M2) and a parallel DTMOS-R M3. This leads to a decent IL in the RX mode and isolation in the TX mode. The first SPDT switch (SPDT SW1) is designed and implemented in a 90 nm complementary metal–oxide–semiconductor (CMOS) with a top metal thickness (TMT) of 3.4 μm. A comparative SPDT switch (SPDT SW2) in a 0.18 μm CMOS with a thinner TMT of 2.34 μm is also designed and implemented. In the TX mode, SPDT SW1 achieves a measured IL of 0.67 dB at 28 GHz and 0.58–1 dB for 17–34.9 GHz and a measured isolation of 44.3 dB at 28 GHz and 25.6–62.3 dB for 17–34.9 GHz, one of the best IL and isolation results ever reported for millimeter-wave CMOS SPDT switches. The measured input 1 dB compression point (P1dB) is 28.5 dBm at 28 GHz. Moreover, in the RX mode, SPDT SW1 attains a measured IL of 1.9 dB at 28 GHz and 1.83–2.1 dB for 25–38.3 GHz and an isolation of 25 dB at 28 GHz and 24.5–27 dB for 25–38.3 GHz. The measured P1dB is 24 dBm at 28 GHz.

Impedance Spectroscopy of Binary Mixtures of Dimethyl Silicone Fluid and Methyl Iso Butyl Ketone

A precision LCR metre was used to measure the parallel resistance (RP) and parallel capacitance (CP) of a capacitive cell filled with samples of binary mixes of methyl isobutyl ketone (MIBK) and dimethyl silicone fluid (DMSF), over the frequency range of 100 Hz to 2 MHz, at a temperature of 303.15 K. Using RP and CP, complex impedance Z*(ω) was computed. A four-element equivalent circuit model was used to fit the complex impedance data. The fitting provided the values of various circuit elements representing various electrical processes occurring in the capacitive measurement cell under the influence of an applied ac field. The Bode plot presentation of the complex impedance data confirmed the values of various circuit elements determined using the fitting process. Complex impedance formalism supports the observation of the electronic double-layer capacitance (EDLC) phenomena and ionic conduction relaxation phenomena.

Floating parallel lossy inductance, parallel lossy capacitance, parallel C‐D, and lossless capacitance multiplier circuits using current feedback operational amplifiers

SummaryA new synthetic floating simulator topology is proposed which realizes lossy parallel inductance (R‐L), lossy parallel capacitance (R‐C), lossy parallel C‐D, and lossless floating capacitance multiplier (FCM) circuits using only three current feedback operational amplifiers (CFOA) as active elements and three impedances. In all the presented circuits, the value of L, C, and D is independently controllable through a single resistance without requiring any matching condition for passive elements. A novel feature of the proposed circuit involves a straightforward adjustment in the CFOA connections, allowing the circuit to function as either a floating lossless immittance simulator or a floating series‐type lossy immittance simulator. Various application examples of the presented circuits such as lead compensator, lag compensator, first‐order high‐pass filter, and fourth‐order Butterworth filter are also given to justify the theoretical analysis. To validate the workability of the proposed circuits, several analyses are conducted, including frequency analysis, transient analysis, Monte‐Carlo analysis, and temperature analysis, using the macro‐model of AD844 in the SPICE simulation tool. Experimental results of the parallel R‐L simulator and application examples are also provided using commercially available IC AD844‐type integrated CFOAs.

Parallel High Capacitance Capacitors Connected With Flexible Electrodes for Enhancement of cECG Signal Quality

Parallel High Capacitance Capacitors Connected With Flexible Electrodes for Enhancement of cECG Signal Quality

The effect of electrical parameters of eddy current sensor on metal film thickness measurement performance and the optimization method.

Eddy current sensors have been widely used in the field of micro- and nano-measurements. The detection circuit is a key part of eddy current sensors. In particular, the electrical parameters in the signal conversion circuit have an important effect on the measurement performance. It is necessary to study the effect of the electrical parameters on the measurement performance and propose an optimization method. In this study, a simulation model of the eddy current sensor is established by coupling a magnetic field and a circuit field. The circuits include the LC parallel resonance, the AC bridge, and three combination circuits of the LC resonant and AC bridge. The output voltage variation with the thickness of copper film is calculated, and the effect of the electrical parameters on sensitivity Ki is obtained. In the LC parallel resonant circuit, it' is revealed that K1 is maximum when the parallel capacitance CP is equal to the resonant capacitance C0. An optimization method of adjusting resistance RS in different thickness intervals is proposed. In the AC bridge circuit, it' is revealed that there exists an optimal RS, which makes K2 maximum. In three combination circuits, K3, K4, and K5 are the maximum when the capacitances (C1, C2, and C3) reach the resonant capacitance C0. In addition, the sensitivity of each combination circuit is improved compared with that of the AC bridge. The relevant analysis results are further verified by a series of experiments. According to the calculation results and the experimental analysis, the optimization method for electrical parameters is further proposed.

Mutual Inductance and Load Identification of LCC-S IPT System Considering Equivalent Inductance of Rectifier Load

The variation of mutual inductance and load parameters will affect the transmission power and efficiency of the inductive power transfer (IPT) system. The identification of mutual inductance and load parameters is an essential part of establishing a stable and reliable IPT system. This paper presents a joint identification method of load and mutual inductance for the LCC-S IPT system, which does not require the establishment of primary and secondary communication and related control. Firstly, the resistance-inductance characteristics of the equivalent load of the rectifier are analyzed by simulation, and then the rectifier and system load are equivalent to the circuit model of resistance and inductance in series. Secondly, the characteristics of the reflected impedance are analyzed, and the functional relationship between the transmitter impedance and the rectifier impedance is established by using the ratio of the real part to the imaginary part of the reflected impedance, which realizes the decoupling of the load and the mutual inductance. Thirdly, the functional relationship between the equivalent impedance of the rectifier and the load resistance of the system is obtained by data fitting. Then, the equations of the above two functional relationships are combined. By measuring the voltage of the parallel compensation capacitor at the transmitting side, the current of the transmitting coil and the phase difference between the two, the battery load can be solved first, and then the mutual inductance can be calculated, so that the high-precision identification of the load and mutual inductance can be realized. Finally, an experimental platform of the LCC-S IPT system is built for experimental verification. The experimental results show that the maximum identification errors of mutual inductance and load are 5.20% and 5.53%, respectively, which proves that the proposed identification method can achieve high precision identification.

Design and analysis of quasi-resonant high-gain impedance source DC–DC converter for DC microgrid

ABSTRACT This paper presents a quasi-resonant, isolated, high-gain, Y-source, DC/DC converter for a DC microgrid. Here, quasi-resonance is obtained by the LC tank during the shoot through period, resulting in natural commutation at the turn-off instant of the MOSFETs. The LC tank is formed by an additional parallel capacitor and transformer leakage inductance. The high voltage gain is obtained by including an isolation transformer with lower turns ratio, coupled inductor and voltage doubler. Here, frequency is modulated to regulate the output voltage with ON period constant. This converter’s zero current switching feature allows it to operate at a higher switching frequency and thus enhances the power density and efficiency. This converter’s continuous input current feature is an added advantage. The proposed converter inherits all the benefits of traditional impedance source converters. Finally, a 250 W hardware prototype is developed, and its performance is tested in the laboratory.

Investigation of Soft-Switching QSW Technique in DC/DC SiC-Based Flying Capacitor Converter With Q2L Control

This paper investigates the soft-switching quasi-square-wave (QSW) technique in DC/DC SiC-based flying capacitor converter with quasi-two-level (Q2L) control establishing design guidelines for constructing high-efficiency soft-switched bidirectional converters with low-voltage power transistors. The general idea behind the soft-switching in the proposed system is based on near-CRM (critical conduction mode) operation using TCM (triangular current mode) and Q2L control with the addition of auxiliary transistor capacitances. The soft-switching process is based on a resonance between the capacitances in parallel to each transistor, and the main inductor - ZVS at turn-on is ensured through proper modulation pattern according to TCM-Q2L control, and the turn-off soft-switching mechanism is assured through the novelty in the form of adding auxiliary capacitance in parallel to each of the SiC power MOSFETs according to QSW operation. Thus, the converter can reach very high efficiency (peak at 99.5%), maintaining soft-switching for a wide operating range, using only small auxiliary SMD capacitors and a low-volume flying capacitor, leading to high power density. The presented study is based on experimental tests using a 1.5 kV model at up to 15 kW and includes the impact of various auxiliary capacitance values and optimal capacitor value selection for maximizing the converter efficiency.

Organic Solar Cells: An Analysis of AC and DC Electrical Properties

In this paper, AC and DC electrical properties of organic solar cells based on P3HT:PCBM active layer have been investigated. The performance of such solar cell has demonstrated the efficiency of 2.31% corresponding with short-circuit current density of 6.08 mA ⋅ cm[Formula: see text], open circuit voltage of 0.64 V and fill factor of 60%. The equivalent circuit and the properties of the supposed interfaces between the layers in the P3HT:PCBM-based solar cell have been estimated. AC properties have demonstrated series capacitance increasing with increasing frequencies, which means series capacitance saves charges and parallel capacitance has decreased with increasing of frequency work as discharge part of charges stored in series capacitance. Also, equivalent series and parallel resistances have demonstrated a decrease from 7 [Formula: see text] and 120 k[Formula: see text] at low frequency to 1 [Formula: see text] and 43 k[Formula: see text] at high frequencies, respectively.

Analysis of a DC converter working on a plasma arc

Introduction. The article is devoted to the analysis of a stabilized direct current converter operating on a plasma arc. Electroplasma technologies of the new generation cause the need to design workable systems that provide control of technological processes and their dynamic optimization in real time. The improvement of any electroplasma technology begins with the improvement of the operating parameters of the main element of plasma installations - the power source. Goal is to build and study a continuous model of a pulsed source of secondary power supply, which works on an electric welding and plasma arc. Methodology. In the work, a mathematical description of the converter was performed. The continuous model of the system is substantiated, taking into account its features, namely, the load (gas-discharge gap) is a source of voltage and dynamic resistance. The parameters of the constant part during circuit synthesis are determined: the components of the gain of the constant part, the relative signal coefficient of the current sensor and the PWM gain. Studies of the open system «power source - arc» have been carried out. Results. MATLAB objects were created - continuous mathematical models of the object in the form of transfer functions. The obtained transient characteristics for different options: «arc current - control signal» and « inductor current - control signal» showed that open systems are unstable. It was found that in the case of instability, the filling frequency of self-oscillations occurring in the linear mode is close to the frequency of natural oscillations of the circuit. The dependence of the module and the argument of the input resistance of the power part of the pulsed power supply with parallel capacitance to the electric arc and without it, which have matching frequency characteristics, is established. The circuit considered with the initial data adopted in this article has a frequency transfer coefficient of the same type as the first-order non-minimum-phase (phase-shifting) link. Frequency response graphs for the output impedance of the power unit show that this power unit is a broadband frequency-selective system with a bandwidth of B0.707 = 100 kHz. Originality. Expressions for the frequency transfer function, input and output resistance of the pulse voltage converter operating on an arc load were obtained by the method of averaging and linearization. The frequency amplitude and phase characteristics for the pulse voltage converter with an LC filter and the output according to the arc current and the choke current were studied. The transfer functions of the continuous model in terms of arc current and choke current at the specified parameters are the same, which must be taken into account when designing regulators. Practical significance. The frequency characteristics of the input and output resistances and transfer functions can be used when forming a technical task for designing a power source to assess the stability of the «pulse converter - arc» system and rational calculation of input filters.

Digital equipment and algorithms for determining the basic parameters of piezoelectric elements in pulsed excitation mode

A method for measuring the spectrum of complex admittance of piezoelectric elements in the pulsed excitation mode and its digital implementation is proposed. The method reduces the duration of measurements, and the processing algorithm increases the accuracy of the estimated parameters. To determine the characteristic frequencies, Q-factor and parallel capacitance, an algorithm of fractional-rational approximation of the frequency dependence of the complex admittance in the resonant frequency range is used.

A Dual-Band Composite Frequency Selective Rasorber With Broadband Absorption Performance

In this paper, a dual-band frequency selective rasorber(FSR) is proposed based on a composite absorption structure. The FSR is a three-tier structure composed of lossy layer I, lossy layer II and a dual-band frequency selective surface (FSS). The lossy layer I is composed of a lossy cross-shaped structure in which, dual-passband resonators are added and constructed by parallel interdigital capacitors and meandering strip inductors(PLC). The lossy layer II is composed of a hybrid circular strip resonator loaded with lossy elements. FSS is implemented in two Jerusalem slots. By combining the lossy layers I and II as a composite lossy structure, the absorption bands of lossy layers I and II are successfully connected in the frequency response, and the bandwidth of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> under -10dB is extended from 3.1 to 20.6GHz. The proposed FSR integrate dual-band, dual-polarized, and broadband absorption performance simultaneously. Finally, a prototype of the composite FSR is fabricated to validate the simulated results.

Analysis and Design of LCCL Resonant Converter Based on Time-Domain Model for Bidirectional Onboard Charger Applications

A novel bidirectional LCCL resonant dc-dc converter is proposed in this paper. By substituting the magnetizing inductance of CLLC with a parallel resonant capacitor, the LCCL resonant converter obtains enhanced voltage gain regulation capability compared to CLLC while maintaining zero-voltage switching for the inverting side and zero-current switching for the rectifier side during bidirectional power flow. The state of the isolated bidirectional dc-dc converters is thoroughly reviewed in this study. The operating principle and gain characteristic of LCCL under bidirectional power flow are explored in detail adopting time domain model (TDM), which effectively overcomes the drawback of the lower accuracy of the first harmonic approximation (FHA) in wide voltage range applications and guarantees the achievement of ZVS in time-domain accuracy. A parameters optimization method of LCCL is provided to address the wide voltage range of battery applications, which is capable of achieving the required bidirectional voltage gain and ZVS operation over the designed frequency range under the desired load conditions while minimizing reactive power. Finally, a laboratory prototype rated at 1kW is developed to convert between 400V and 250V∼450V bidirectional. The experimental results confirm the feasibility of the proposed LCCL topology and the validity of the corresponding parameters optimization method.

A Modification in Thyristor-Based Hybrid DC Circuit Breaker for DC-Side Fault Identification in Auto-Reclosing of MMC-HVDC Systems

Safe reclosing of high voltage direct current (HVDC) systems after DC-side fault current interruption is essential. Otherwise, a second strike can endanger the components of DC circuit breakers (DCCBs) and modular multilevel converters (MMCs). Thus, it is necessary to identify the fault type prior to auto-reclosing of MMC-HVDC systems. This paper proposes a method that enables an MMC-HVDC system equipped with the thyristor-based hybrid DCCB introduced by Alstom to identify and localize the DC-side fault. In the proposed method, adding some capacitors with low capacitance parallel to the thyristors in one part of an auxiliary branch enables the hybrid DCCB to inject active pulses. To clarify, by turning a specified number of the thyristors on, a desirable number of capacitors parallel with the off thyristors are applied, and a second-order circuit is formed, resulting in the injection of active pulses with controllable amplitude and width. According to the traveling wave theory, the difference in the reflection of the injected pulse determines whether the fault is permanent or temporary. The efficacy of the proposed method is validated by an MMC-HVDC test system built in PSCAD/EMTDC platform. Furthermore, generating active pulses with the modified hybrid DCCB is verified by a scaled-down prototype.

Electrochemical Impedance Spectroscopy‐Based Dynamic Modeling of Lithium‐Ion Batteries Using a Simple Equivalent Circuit Model

As one of the most commonly used models for describing the dynamic voltage response of lithium‐ion batteries (LIBs), the equivalent circuit model (ECM) is routinely parameterized using the time–domain experimental data from some dynamic tests. One downside of this time–domain approach is a lack of credible physical interpretation about the model parameters. In this article, a genuine electrochemical impedance spectroscopy (EIS)‐based dynamic modeling approach for LIBs is developed, which only uses low‐frequency EIS data in parameterization of the ECM. The EIS‐based modeling method combines simplicity, high accuracy, and clear physical interpretation. With the EIS‐based modeling method, a simple ECM, namely, a serial connection of a resistance (), describing Ohmic polarization and interfacial reactions, and an resistance–capacitance parallel branch (), describing diffusion polarization, suffice to accurately capture LIB dynamics in most applications.

Dielectric spectroscopy of a ferroelectric nematic liquid crystal and the effect of the sample thickness

The recently discovered ferroelectric nematic liquid crystals have been reported to exhibit very large dielectric permittivity values. Here, we report a systematic investigation of the dielectric behavior of a prototypical ferroelectric nematogen by varying the thickness of the parallel capacitor measuring cell. While in the non-polar high temperature nematic phase results show only slight differences due to slight variations of the alignment, the measured permittivity values in the ferroelectric nematic phase show a linear dependence on the cell thickness. It is also shown that the characteristic relaxation frequency decreases inversely proportionally to the thickness. The results are discussed in terms of three different available models based on different underlying mechanisms, accounting for cancellation of the probe electric fields by polarization reorientation or by ionic charges, or based on a recently proposed continuous phenomenological model.