Series Capacitor Research Articles

Application of Optimization Algorithms to Enhance the Transmission System Performance Using Thyristor Controlled Series Capacitor

Application of Optimization Algorithms to Enhance the Transmission System Performance Using Thyristor Controlled Series Capacitor

The Thyristor Switched Parallel Capacitors (TSPC) Converter for Power Factor Correction in Wind Power Systems

This paper presents a novel power factor correction circuit suitable for low-speed electric generators usually used in direct drive wind turbines. The Thyristor Switched Parallel Capacitors (TSPC) circuit belongs to the Controlled Series Capacitor (CSC) circuits. Those circuits have been used in power transmission lines to correct the power factor and improve the performance of the electrical system. Such a circuit can be used in wind power systems to improve and maximize the efficiency of a wind turbine. A typical direct-drive wind power system employs variable speed electric generators, but the downside is that systems like that suffer from high and variable inductive reactance. In order to correct the power factor and to improve the efficiency of the system, the inductive reactance of the generator must become equal in value to the capacitive reactance. A TSPC circuit uses a set of capacitors, connected in series with anti-parallel thyristors. In every cycle, a controller triggers the appropriate thyristors, allowing the current to pass from the capacitor which then provides the system with the capacitive reactance that matches the generator’s inductor reactance. Therefore, the TSPC circuit is able to counteract for any reactive losses and improve the power factor, as well as, the efficiency. This paper introduces this novel power factor correction circuit that employs capacitors in parallel configuration. This circuit was simulated in PSPICE and was implemented and tested in the lab. Based on the simulation and implementation results, we discuss the benefits as well as the drawbacks of the proposed circuit

Enhancement of Power Quality in Transmission Network Using TCSC

The thyristor-connected series capacitor (TCSC) lowers transmission losses, boosts functional potential, and boosts the transmission community's overall power. In this post, the transmission group of the strength system is equipped with a thyristor switched collection capacitor. The system's performance in the presence of TCSC was investigated using a variety of strength machine fluctuations, such as voltage amplitude variance, weight turning off and on, output and synchronization of the generator with the grid, as well as voltage, energy glide, and impedance are taken as the variables. The tests are checked in the MATLAB/Simulink setting using a review gadget that is integrated with the TCSC. In the proposed method of TCSC the results are demonstrated the usefulness of this proposed TCSC method.

Resonance suppression of LCL filter for shunt active power filter via active damper

Resonance damping of LCL filter has become a crucial concern in the operation of shunt active filter inverters due to its wide control bandwidth. To address the challenges of the resonance issue, this paper proposes a novel damping method for SAPF with an LCL filter to reduce the damping losses without affecting control of SAPF. The proposed approach is based on an auxiliary converter that is connected to the filter capacitor in series. In the auxiliary converter, the resonance current is detected and injected by inverse as a controlled voltage. The stability of the proposed method is carried out by bode diagrams and compared with the conventional method. The performance of the proposed method has been validated under different cases by implementing a laboratory setup. The effectiveness of the proposed method has been validated through the theoretical and experimental results. The switching harmonic components are attenuated by 215 dB and 70 dB ratios at the 10 kHz and 20 kHz via the proposed method. Furthermore, the damping power losses are 1.9% and 0.9% for the conventional method and the proposed method, respectively. As a result, the proposed method has better switching harmonic mitigation with 1% lower damping power losses than the conventional method.

Kinetics of nanoscale probe-based contact electrification between metal and polymethyl methacrylate under bias

Contact electrification (CE) has the potential to be a renewable energy resource, because it converts mechanical energy to electrical energy. The kinetics of probe-based CE between metal and polymeric slab was studied by scanning probe microscopy. The CE static charges were produced on polymethyl methacrylate (PMMA) films by a Pt-coated probe under a bias (VB) and characterized by electrostatic force microscopy. The metal/PMMA CE was attributed to the charge transfer between the Fermi level of the metal (Ef) and the neutral level of the surface states of PMMA (En). The kinetics of the probe-based metal/PMMA CE was described by a saturating exponential function and the saturated charge QS was proportional to the net bias, VB − Vnull, where the nulling bias Vnull = −(En − Ef)/e. The kinetics was regarded as the charging to a conductor–capacitor series circuit. QS established a potential to cancel the net bias and ceased the CE. CE was a reversible process, and its transmission coefficient was asymmetric with the polarity of bias because of the heterogeneous nature of the metal/polymer contact.

Observation of negative capacitance in antiferroelectric PbZrO3 Films

Negative capacitance effect in ferroelectric materials provides a solution to the energy dissipation problem induced by Boltzmann distribution of electrons in conventional electronics. Here, we discover that besides ferroelectrics, the antiferroelectrics based on Landau switches also have intrinsic negative capacitance effect. We report both the static and transient negative capacitance effect in antiferroelectric PbZrO3 films and reveal its possible physical origin. The capacitance of the capacitor of the PbZrO3 and paraelectric heterostructure is demonstrated to be larger than that of the isolated paraelectric capacitor at room temperature, indicating the existence of the static negative capacitance. The opposite variation trends of the voltage and charge transients in a circuit of the PbZrO3 capacitor in series with an external resistor demonstrate the existence of transient negative capacitance effect. Strikingly, four negative capacitance effects are observed in the antiferroelectric system during one cycle scan of voltage pulses, different from the ferroelectric counterpart with two negative capacitance effects. The polarization vector mapping, electric field and free energy analysis reveal the rich local regions of negative capacitance effect with the negative dP/dE and (δ2G)⁄(δD2), producing stronger negative capacitance effect. The observation of negative capacitance effect in antiferroelectric films significantly extends the range of its potential application and reduces the power dissipation further.

Compact planar multiple‐input‐multiple‐output antenna with pattern diversity based on the complementary theory

AbstractA three‐port planar multiple‐input‐multiple‐output (MIMO) antenna system with pattern diversity based on the complementary theory is presented in this letter. Three directional antennas without any directors or reflectors are introduced as the radiating elements, which are rotationally symmetrical and sharing a small ground. The unilateral radiation pattern is achieved for each antenna element based on the complementary theory, where an electric dipole and a magnetic dipole are placed orthogonally and excited simultaneously. An inverted L‐shaped stub is used as the electric dipole. A capacitively loaded loop operated on the zeroth‐order resonant mode is applied as the equivalent magnetic dipole. The capacitive loading is realized with six periodical interdigital left‐handed series capacitors. Furthermore, a defected ground structure between each two ports is adopted to further improve the isolation. The operation mechanism of the proposed MIMO antenna is discussed and experimentally verified. The proposed MIMO antenna system has a measured fractional bandwidth of 7.2% (3.33–3.58 GHz) with |S11| < −10 dB. The port isolation is better than 15 dB and the envelope correlation coefficient is less than 0.0234 in the operation band.

Analysis of a Novel Three-phase Asynchronous Generator Based on Graph Theory for Supplying Single-Phase Load

This paper presents a novel three-phase star-connected stand-alone asynchronous generator (SAG) with only two capacitors, connected in series with two stator phase windings, for supplying power to single-phase resistive load. This new scheme has excellent voltage regulation (less than 1.7%) due to the presence of these two series capacitors and does not require any separate voltage regulating device making it very simple and cheaper. The symmetrical component theory has been used to form a simplified equivalent circuit of the scheme. Graph theory has been applied to the equivalent circuit to simplify the process of obtaining two non-linear higher-order equations which are solved using the binary search algorithm (BSA) to obtain the values of per unit frequency and magnetizing reactance. Accordingly, using the magnetization characteristics of the machine and the performance equations, the steady-state performance of the SAG has been obtained. To investigate the behavior of the SAG under transient conditions, such as voltage build-up, load switching and load perturbation, a dynamic model of the generator scheme has been developed on the basis of d-q axes theory in stationary reference frame including the effect of main and cross flux saturation. The simulated results have been validated through experimentation using an induction machine rated as 2 hp, 4-pole, 415 V, 3.5 A, 3-phase, 1440 rpm, 50 Hz. The simulated results closely agree with the experimental results, indicating the efficacy of the proposed approach. This can be a promising single-phase power generation scheme for supplying power in remote rural areas.

Tuning of PID Controller with Differential Evolution Algorithm for LCC Resonant Converter

This paper deals with the optimization of LCC Resonant Converter based on Differential Evolution Algorithm. Closed Loop Analysis of LCC Resonant Converter have been Simulated by tuning PID Controller for different values of Kp, Ki and Kd values. Optimum Values of Kp, Ki and Kd were obtained using Differential Evolution Algorithm and these values were fitted to Obtain Maximum Output Voltage with LCC Resonant Converter. Initially three Variables namely Series Inductance, Series Capacitance and Parallel Capacitance were considered, out of which the Value of Series Capacitance was tuned with Differential Evolution.

A Design of Compact Meta-material CRLH Antenna for Wireless Applications

This article presents a compact design of a composite-right-left-handed (CRLH) antenna for wireless applications. The antenna is fed using a coplanar waveguide (CPW) feed structure. The CRLH-antenna is comprised of one CRLH unit cell. The CRLH unit cell has a series capacitance (interdigital capacitor) and a shunt inductor (stub meander inductor). The antenna achieves compactness with a small size of 16.5 mm × 26 mm × 1.6 mm, thanks to the CRLH features such as nonlinear phase. The proposed antenna achieves a size reduction of better than 50 % with respect to the microstrip patch antenna operated at the same frequency band. The operating frequency band of the proposed antenna is from 5.83GHz to 6.3 GHz for WLAN applications, dedicated short range communications (DSRC), and intelligent transportation systems (ITS). Also, the antenna fulfills a radiation performance of omnidirectional pattern. To confirm the antenna design performances, a prototype is fabricated, and the reflection coefficient and radiation patterns are measured. Furthermore, the measured results have a good match with the simulation results.

A Compact Broadband Phase Shifter Based on HMSIW Evanescent Mode

A compact broadband phase shifter based on the half-mode substrate-integrated waveguide (HMSIW) is proposed in this letter. By etching interdigital capacitor or adding blind holes and patches into the HMSIW, the width of the HMSIW can be reduced. Moreover, based on the complementary phase responses of series capacitance and shunt capacitance loading on the HMSIW, a broadband phase shifter is designed with a small phase deviation. To validate the proposed design approach, two phase shift channels and the reference channel are fabricated and measured. Phase shifts of 86° ± 2.5° (and 43.5° ± 2.5°) with fractional bandwidths of 53.3% (and 35.7%) covering central frequencies of 7.5 GHz (and 8.4 GHz) are achieved. The insertion losses of the three channels are 0.76-1.32, 0.40-0.63, and 0.87-1.40 dB, respectively. Besides, the area of each branch is only 0.343λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ; λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> is the guided wavelength at the center frequency in the dielectric.

Local current-based method for fault identification and location on series capacitor-compensated transmission line with different configurations

This paper proposes a new efficient method for fault detection, faulty phase selection, and fault point identification on series capacitor-compensated transmission line. The method is based on sensing only the three phase current at the relay site. A reverse synchronous reference frame (RSRF) approach is proposed for fast fault detection and classification. Then, an analytical algorithm based on symmetrical components theory is presented for accurate estimation of fault location. Three possible arrangements of the series capacitor bank (SCB) on the line are analyzed. The SCB and the associated protective metal oxide surge arrestor (MOV) are modeled thoroughly to characterize its behavior during fault. In addition to its simplicity and practicality, the proposed scheme is equipped with decaying DC offset removal technique that allows fast extraction of the current phasors within one fundamental cycle. The proposed method works well for all ground and non-ground faults; it does not need pre-fault information; does not require any communication facilities; avoids high voltage measurement; and works smoothly for a wide range of fault resistance values. The efficacy of the proposed method is proved by a large number of simulated cases under a variety of operating conditions.

Closed Loop Reactive Power Compensation on a Single-Phase Transmission Line

Nowadays the power consumption is increasing significantly. Due to this, the transmission lines are heavily loaded and in turn results in instability of the line. So orderly transmission of power is essential. For the proper operation of the load the voltage has to be maintained within the acceptable limit. Due to the changes in load, the voltage level of the line also changes. The voltage levels can be improved by using the reactive power compensator like capacitor banks, series compensator, STAT COM and svc. Here, we considered the SVC as reactive power compensator. This paper presents the reactive power compensation for a 230v transmission line model with variable inductive load using SVC and designed in Simulink. Here we considered the SVC model which contains of anti-thyristors in series to the inductor and a shunt capacitor. The required reactance is fed from the inductor to the transmission line by changing the gate triggering pulse to the thyristor pair. So, the main disadvantage of the open loop var compensation using svc is the triggering to the thyristor pair has to be changed every time depending on the load. This can overcome by implementing it using the feedback loop. Here for the feedback, we used the PI controller. under The PI controller gives the required gating pulse to the thyristor pair. The performance of this model is studied variable load conditions.

A linearized MOV model-based method for fault location on off-terminal series capacitor bank-compensated transmission line using one-end current

This paper proposes a method for fault location on single and double-circuits series capacitor bank-compensated transmission line (SCTL). A common situation for installing the series capacitor bank (SCB) is to place it some point away from the terminal substations. One-end measurement-based fault locators are favorable for many utilities due to simplicity and less cost especially if they are accurate enough. For impedance-based one-end fault locators on SCTL, the current passing in the SCB is unknown for about 50% of faults. This prevents the prediction of the challenging metal oxide varistor (MOV) behavior that is inevitable for a one-end method. Herein, the nonlinear characteristics of the MOV protecting the SCB are simplified by a linearized simple yet precise model. This makes it possible to express the SCB-MOV characteristics as a linearized function of the far-end current for faults upstream the SCB keeping the nonlinear characteristics of the MOV. This eventually enables to estimate the fault current contribution of the far-end. Hence, an analytical fault distance estimation algorithm is derived for both single and parallel transmission lines using the sequence-networks modeling of the system. Beside simplicity and robustness, the proposed method is found to be accurate enough in locating a big number of faults under a variety of conditions.

Boost Voltage Single Phase Full Bridge Inverter with No Voltage Drop Based on Switched Capacitor

In this paper, a voltage-boost-type non-voltage drop single-phase full-bridge inverter connected to a switched-capacitor structure is proposed. The output voltage of the inverter is controlled by the pulse width modulation of a DSP to control the lead and break of the active switches. The full-bridge switches work at low frequency; the other switches work at high frequency. The inverter uses two capacitor modules to charge and discharge alternately so as to overcome the problem of voltage drop on the output side of the inverter in the transition stage from series capacitor discharge to parallel charge. By analyzing the charge–discharge characteristics of the RC charge–discharge circuit, the capacitor charge–discharge cycle can be adjusted to alter the output voltage within a certain range. The results from the physical construction verify the Simulation results achieved well, which demonstrates satisfactory performance that supports the verification of the above theory.

Cardiovascular disintegration: A conceptual, model-based approach to heart failure hemodynamics.

The current understanding of heart failure (HF) largely centers round left ventricular (LV) function; however, disorders in serial integration of cardiovascular system may cause a hemodynamic picture similar to left-sided HF. Therefore, focusing only on LV function may be a limited and misleading approach. We hypothesized that cardiovascular system has four major integration points, and disintegration in any of these points may produce the hemodynamic picture of HF. We used a computational model in which mechanical properties of each chamber were characterized using time-varying elastance, and vascular beds were modeled by series of capacitances and resistances. The required percent changes in stressed volume (Vstressed) was presented as a measure of congestion susceptibility. As mean systemic pressure is closely correlated with pulmonary capillary wedge pressure (PCWP), arteriovenous disintegration can create a diastolic dysfunction pattern, even without any change in diastolic function. For 10%, 20%, 30%, 40%, and 50% interventricular disintegration, required Vstressed for reaching a PCWP over 20 mmHg was decreased by 42.0%, 31.2%, 22.5%, 15%, and 8.3%, respectively. Systolodiastolic disintegration, namely combined changes in the end-diastolic and systolic pressure-volume curves and ventriculoarterial disintegration significantly decreases the required percent change in Vstressed for generating congestion. Four disintegration points can produce the hemodynamic picture of HF, which indicates that combination of even seemingly mild abnormalities is more important than an isolated abnormality in a single function of a single chamber. Our findings suggest that a "cardiovascular disintegration" perspective may provide a different approach for assessing the HF syndrome.

A 2.4–6 GHz Broadband GaN Power Amplifier for 802.11ax Application

This paper presents a 2.4-6 GHz highly integrated broadband GaN power amplifier (PA) with three stages for 2.4-/5-GHz dual-band 802.11ax application. A compact external output matching network is introduced to realize broadband output matching, while reducing the loss of the output matching network and saving the chip area. A novel topology of coupled resonators is exploited for the broadband inter-stage matching to cover the 802.11ax bands from 2.4 to 6 GHz. In the proposed topology, the coupling between the primary and secondary resonators is through a series inductor and a series capacitor. Compared with other conventional coupled resonators, the proposed topology produces an additional complex pole, further extending the bandwidth. The PA was designed and fabricated in Wolfspeed 0.25- μm GaN-on-SiC technology. The implemented PA achieves a saturated output power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> ) of 35.2-36.3 dBm with a maximum power added efficiency (PAE) of 38-53% from 2.4 to 6 GHz. When tested with an 80-MHz, 256-quadratic-amplitude modulation (QAM) 802.11ax signal, the PA delivers an average output power of 27.1 and 25.7-27.2 dBm with a PAE of 20.9% and 18.4-24.6% in the 2.4-GHz and 5-GHz wireless local area network (WLAN) bands, respectively, while meeting the specification of error vector magnitude (EVM) below -32 dB.

Assessment & Alternatives for SSR in a Series Capacitor Wind Farm Employing TCSC

Wind energy systems are going to build their footprint in the electricity grid around the world as one of the most viable renewable and environmentally friendly sources of energy. Keeping this scenario in mind and predicting further growth in installations, power systems should be prepared for the assimilation of such large wind farms. Almost every system has been outfitted with electricity compensation processes to enhance a sustainable transfer of electricity generation.This would have the possibility to trigger SSR difficulties in a variety of power grid circumstances. An analysis and SSR solutions will be discussed and recommendations. SSR inhibition is accomplished via the TCSC that also aids in increasing the transmitting station’s power flow. So if coupled to closed-loop control loops, TCSC dampens SSO. Efficacy is evaluated using SIMULINK studies in the MATLAB environment to results demonstrate the effectiveness of TCSC throughout the SSR damping process.

Component value calculations in a mixed element ladder network containing series capacitors separated by unit elements

SummaryLossless LC ladder networks have many applications. But at high frequencies, inductor‐free designs are preferred since inductors are heavy and have limited values. An additional reason for not using the inductors (at high frequencies) consists in that the values of very small inductors could be quite imprecise. If LC ladder network is high‐pass type, then parallel inductors must be removed. The resulting network will have only series capacitors, which can be combined as a single series capacitor. But if commensurate transmission lines separate the series capacitors, a high‐pass mixed element network is obtained. In this paper, a procedure is proposed to compute the values of series capacitors and characteristic impedances of the transmission lines in the mixed element ladder network. The usage of the procedure is explained by means of the given example.

Neutral-Point Voltage Balance Control of Three-Level Converter Based on Selection Method of Dynamical Adjustment for Small Voltage Vector

The balance control of neutral-point voltage (NPV) is important in the three-level converter. In this paper, this problem is studied by taking the VIENNA circuit as an example. The deviation of NPV is essentially caused by mismatch between the charging and discharging time of two series capacitors by the neutral-point current flowing into or out of the DC side. The unbalanced NPV will lead to unbalanced voltage stress of two capacitors and power switches and may cause overvoltage damage to both and also increase the total harmonic distortion (THD) and harmonic components in the AC current. In this paper, by analyzing the role and effect of a small-voltage vector on NPV, a control strategy based on the selection method of dynamical adjustment for a small vector is proposed. By judging the fluctuation of NPV, different small vectors are dynamically selected to act to adjust the NPV. For verification, the proposed strategy is compared with the traditional zero-sequence voltage injection (ZSV-J) method through simulation and experiment. Compared with ZSV-J, the THD of AC current is decreased by about 27.2%, the efficiency is increased by about 1.66%, and the adjustment speed of NPV is increased by about 50%. Therefore, the feasibility and advantages of the strategy are verified.