Load Impedance Research Articles

Maximum Power Point Tracking control of a variable speed wind turbine via a T-S fuzzy model-based approach

This paper proposes a multi-objective H2/H ∞ maximum power tracking control of a variable speed wind turbine to minimize the H2 tracking error and ensure the H ∞ model reference-tracking performance, simultaneously. The optimal condition is obtained via a boost converter use, which adapts the load impedance to the wind turbine generator. Thus, based on the fuzzy T-S model, a multi-objective Maximum Power Point Tracking (MPPT) controller is developed, ensuring maximum power transfer, despite wind speed variation and system uncertainty. To specify the optimal trajectory to follow, a TS reference model is proposed taking as input the optimal rectified DC current. The conditions of stability and stabilization are expressed in terms of linear matrix inequality (LMI) for uncertain and disturbed T-S models leading to determining the controller gains. Finally, an example of MPP tracking applied to a Wind Energy Conversion System (WECS) illustrates the effectiveness of the proposed fuzzy control law.

Evaluation of the performance of a 7-T 8 × 2 transceiver array.

The decoupled 8 × 2 transceiver array has been shown to achieve a mean B1 + of 11.7 uT with a coefficient of variation of ~11% over the intracranial brain volume for 7-T MR imaging. However, this array may be thought to give lower signal-to-noise ratio (SNR) and higher g-factors for parallel imaging compared with a radio frequency (RF) receive-only coil due to the latter's higher coil count and use of coil overlap to reduce the mutual impedance. Nonetheless, because the transceiver's highly decoupled design (pertinent for transmission) should also be constructive for reception, we measured the noise correlation, g-factors, and SNR for the decoupled transceiver in comparison with a commercial reference coil. We found that although the transceiver has half the number of receive elements in comparison with the reference coil (16 vs. 32), comparable g-factors and SNR over the head were obtained. From five subjects, the transceiver versus reference coil SNR was 65 ± 10 versus 67 ± 15. The mean noise correlation for all coil pairs was 10% ± 5% and 12% ± 9% (transceiver and reference coil, respectively). As changes in load impedance may alter the S parameters, we also examined the performance of the transceiver with tuned and matched (TM) versus untuned and unmatched (UTM) conditions on five subjects. We found that the noise correlation and SNR are robust to load variation; a noise correlation of 10% ± 5% and 10% ± 6% was determined with TM versus UTM conditions (SNRUTM/SNRTM = 0.97 ± 0.08). Finally, we demonstrate the performance of the array in human brain using T2-weighted turbo spin echo imaging, finding excellent SNR performance in both caudal and rostral brain regions.

Ultra-wideband high gain low group delay variation amplifier for phased-array radar system

This paper describes a ultra-wideband (UWB) three-stage cascaded high gain amplifier with low group delay variation for phased-array radar system. The shunt inductor at the input not only provides an electrostatic discharge (ESD) path to ground, but also introduces a new notch for S11, thus extending the matching bandwidth. Staggered tuning of load impedance peaks at each stage facilitates a balance between flat gain and low group delay variation. The output stage further enhances the overall gain while reinforcing bandwidth and stability through resistive feedback, and employs an adaptive bias circuit for linearity improvement. Implemented in SMIC 40-nm CMOS technology, the proposed amplifier achieves good input impedance matching, flat gain and low group delay variation of ±73.5 ps over 4.7–16 GHz. The whole power consumption is 198.3 mW and the output 1 dB compression point (OP1dB) is greater than 9 dBm. After careful design, the chip size is 0.64 mm2.

An overview on Modulated Scattering Sensors and their applications

Modulated scattering sensors are based on the scattering properties of small antennas. They operate similarly to radio frequency identifier RFIDs but they don't require a radio front-end, and with respect to RFIDs, which are characterized by a limited operative range, MST sensors can theoretically reach any distance up to kilometres. The information is carried on by modulating an impinging/interrogating electromagnetic wave by properly change the load impedance of the antenna sensor, with suitable resistive loads and electronic switches. MST sensors can also operate at microwave frequency bands thanks to the introduction of suitable MEMs switches able to operate up to 100 GHz, moreover they are simple, low invasive and very cheap. In this work the evolution and some recent advancements in the development and application of MST sensors at different engineering scenarios will be reported and commented.

The Cascade of High-Voltage Pulsed Current Sources

Currently, pulsed adders are used as pulsed voltage sources maturely. However, their use as pulsed current sources is significantly limited due to circuit impedance and the characteristics of power devices. This paper presents a simple yet effective design for a pulsed current source, incorporating a solid-state Marx pulsed adder as the primary power source and an inductor for energy storage. In the pulsed current source, a Marx pulsed adder produces high voltage to charge the inductor. Then, the stored inductance energy is converted to generate current pulses on the load; the amplitude of the pulsed current is unaffected by the load impedance within a certain range. The pulsed current source can be designed as a standard module, and several modules can form a cascade system for producing current pulses with higher voltage. Finally, a pulsed current source was developed, which can produce adjustable current pulses with high voltage. The design principles, control methods and the effects of the distribution parameters are described. The feasibility of the cascade pulsed power system was validated in experiments. Nine modules were connected to generate pulses of current 10 A on a 15 kΩ resistor.

Realization of an Optimum Load for Wireless Power Transfer System

Wireless power transfer (WPT) system has been an integral part of personal living since its regained interest, especially the magnetic resonance (MR) scheme. MR-WPT scheme suffers, however, change of the coil separation distance and various alignment errors. This paper reports a realization of optimum load for MR-WPT system, which can change the loading impedance accordingly for different coupling coefficients between the Tx and Rx coils. A simple varactor circuit is adopted to realize the optimum load curve. Usefulness of this is demonstrated through both the steady and transient analysis. The proposed realization relies on an open-circuit scheme, and hence it is suitable for scenarios with low-cost and small-size requirements.

Efficient self-powered cathodic corrosion protection system based on multi-layer grid synergistic triboelectric nanogenerator and power management circuits

The last few years have seen a boom in the use of triboelectric nanogenerators (TENGs) for capturing wave energy in the ocean. This work reports a multi-layer grid synergistic triboelectric nanogenerator (MLGS-TENG). In this work, the independent layer triboelectric nanogenerator in the grid format is skillfully employed, and the design of the multi-layer parallel structure can effectively increase the capture rate of blue energy in the ocean. The shell of the triboelectric nanogenerator adopts a gyroscopic structure, which, when combined with its internal architecture, operates effectively on the surface of ocean waves. Moreover, it can be very effective in harvesting low-frequency wave energy in the ocean and converting it into mechanical energy, and then converting it into electrical energy through the friction of the internal self-assembly layer. In low-frequency mechanical tests, when the frequency is about 1 Hz and the load impedance is 400 MΩ, the peak power output of the generator in a single layer can reach 77 mW/m2. Given the excellent energy harvesting performance of MLGS-TENG, it is applied to build a high-efficiency cathodic corrosion protection system in conjunction with a buck rectifier circuit. This work is of great significance for the wide application of triboelectric nanogenerators in the marine environment and provides a feasible way to ensure the long-term stability of offshore platforms.

Time domain modeling of constant power loads for electromagnetic transient simulations

This paper proposes a dynamic constant power load offering constant active and reactive power and constant power factor suitable for electromagnetic transient simulations. The proposed model is agnostic to the frequency components of the system because it is developed in the time domain. The proposed model returns current and voltage quantities imitating the behavior of either inductive or capacitive loads. The model is customized so that it can be solved using readily available numeric solvers, such as branch-and-bound algorithms. The bottleneck of the computational speed depends on the numeric solver that is employed to solve the proposed model and the hardware used to process the computations. Also, convergence to a solution (an issue associated with every solver) is more likely to occur if the optimum initial solution is provided, which is left for future research. The model is validated using constant impedance load data. In this work, 2500 data points were simulated, and the output shows that the proposed model is accurate, and any approximations can be attributed to the adopted numerical differentiation method. The model is computationally exhaustive; thus, its application is limited to small systems.

Harmonic Oscillation and Stabilization Strategy of Source-Current-Detected Shunt APF Considering Interaction With Nonlinear Load and Grid Impedance

Harmonic Oscillation and Stabilization Strategy of Source-Current-Detected Shunt APF Considering Interaction With Nonlinear Load and Grid Impedance

Optimization of series-series compensated wireless power transfer system using alternative secondary side rectification

This paper focuses on the operational analysis of wireless power transfer (WPT) system, while the topology of the secondary side rectifier represents the main element, for which the properties of WPT system are being investigated. Initially the system description and technical specifications are given. Because WPT systems are designed for a certain type and value of the load (impedance matching) in order to achieve the highest possible efficiency, the definitions for those values are identified for individual topologies of the secondary side rectifiers. Consequently, the results are compared and discussed and followed by the simulation analysis to prove the operational behavior in time-domain for each of investigated alternative of rectifier. Several relationships have been identified in relation to secondary side electrical variables, and discussion for stress-optimization are given as well. The simulation results are verified by the experimental measurements, while individual solutions for secondary side rectifiers are evaluated from efficiency point of view followed by the recommendations of the operational conditions.

Power Distribution Control Method in Communication–Free MIMO–WPT Through Load Impedance and Mutual Inductance Estimation

Power Distribution Control Method in Communication–Free MIMO–WPT Through Load Impedance and Mutual Inductance Estimation

An Adaptive Stabilization Strategy for Harmonic Oscillation of SAPF Interacted With Nonlinear Load and Grid Impedance

An Adaptive Stabilization Strategy for Harmonic Oscillation of SAPF Interacted With Nonlinear Load and Grid Impedance

Passive Islanding Detection Method based on Resultant Sequence Impedance Component and Load Shedding in Islanded Area

Passive Islanding Detection Method based on Resultant Sequence Impedance Component and Load Shedding in Islanded Area

Microgrids control: AC or DC, that is not the question

In these lecture notes, we delve into the models of the most commonly used DC-DC power converters: namely, the buck converter and the boost converter. Furthermore, we derive models for a DC microgrid consisiting of multiple buck and/or boost converters interconnected via (dynamic) resistive-inductive power lines and supplying the so-called ZIP loads, which are characterized by the parallel combination of constant impedance (Z), current (I), and power (P) load components. Furthermore, we introduce the primary control objectives in DC microgrids, focusing on voltage regulation and current sharing. Finally, we explore the most advanced control techniques to achieve these objectives. Importantly, these lecture notes are not intended to advocate total replacement of Alternating Current (AC) power systems with their Direct Current (DC) counterparts, but rather aim to offer a balanced perspective between them, acknowledging the historical dominance of AC power systems while underscoring the contemporary relevance of DC microgrids, which, with their inherent advantages, represent a viable complement to the existing infrastructure, fostering innovation and resilience in modern power networks.

A 43.5dB Gain Unipolar a-IGZO TFT Amplifier with Parallel Bootstrap Capacitor for Bio-signals Sensing Applications.

In this paper, a high gain amplifier with phase compensation loop is presented. A structure of parallel gate cross-coupled transistors to both ends of differential pair drain and source is designed to improves the load impedance, which obtains sufficient gain and further reduces power consumption. A novel capacitor bootstrap load circuit is proposed. The capacitor bootstrap topology is constructed by the drain source resistance of the transistor working in the cut-off region, where the gate source parasitic capacitor of the transistor is in parallel with the bootstrap capacitor rather than the existing series structure, thereby only a small bootstrap capacitor is required. By avoiding the use of large capacitors, chip area can be effectively reduced without compromising performance such as gain and bandwidth. The amplifier is fabricated using 10-μm n-type a-IGZO TFT technology. Measurement results show that the proposed amplifier achieves a voltage gain of 43.5dB and a common mode rejection ratio of 61.2dB while maintaining low power consumption. The amplifier also exhibits a -3dB bandwidth covering 0.4~2.1KHz, encompassing major bioelectric frequency bands. A real-time ECG signal was successfully captured using the fabricated TFT amplifier and gel electrodes. It has great potential in flexible sensing and acquisition applications such as electro cardiogram (ECG), electro encephalogram (EEG), pulse detection, and other wearable applications.

4 MHz Electrosurgical Generator System for Wide Load Impedance Range With SiC-Based Full-Bridge Inverter

A power conversion system to drive a high-frequency electrosurgical generator (ESG) is proposed. The proposed system consists of a 4 MHz full-bridge (FB) inverter capable of ensuring power in a wide load impedance range and implementing energy control functions in accordance with the ESG characteristics. Unlike conventional inverter systems, ESG cannot deliver energy directly to the load, but through an instrument, which makes it difficult to ensure power. Thus, impedance matching is essential to ensure power in ESG. For ensuring power, impedance matching is realized using a resonance filter while considering instrument induced parasitic components that cannot be ignored at high frequencies. The inverter is composed of silicon carbide (SiC) suitable for the MHz switching operation. A prototype is to validate the proposed system. Experimental test of the prototype that it can provide a load power of more than 100 W for a tissue model with impedance range of 5-to-800 Ω.

A 4–22 GHz Ultra-Wideband Low-Noise Amplifier With 0.8–1.5 dB NF and 28–31 dB Gain Enhanced by the Negative Load Impedance

A 4–22 GHz Ultra-Wideband Low-Noise Amplifier With 0.8–1.5 dB NF and 28–31 dB Gain Enhanced by the Negative Load Impedance

An improved impedance space for extended hybrid continuous mode power amplifiers

AbstractExtended hybrid continuous mode expands the design bandwidth of the power amplifier (PA) by sacrificing drain efficiency. To balance the performance of drain efficiency and bandwidth, this letter limits the range of relevant parameters of its impedance space through theoretical analysis. An improved high‐efficiency load impedance space is proposed. Through the improved high‐efficiency impedance space, a PA operating at 0.8–2.2 GHz is designed, with a drain efficiency of more than 55% and an output power of more than 38.2 dBm, which verifies the design goals of broadband and high efficiency.

Incorporating Incremental Conductance MPPT Techniques into Solar Power Extraction

Research into alternative, green energy sources such as solar power has been driven by concerns about environmental sustainability, escalating petroleum costs, and surging energy demand. Solar energy can power the entire world sustainably, since it is abundant and easy to access. Solar radiation, cell temperature, and load impedance all play a part in improving the efficiency of solar energy utilization. In order to maximize solar energy utilization, Maximum Power Point Tracking (MPPT) techniques are used. In order to address factors such as solar effectiveness, dynamic response, convergence speed, complexity, cost, and sensor requirements, different MPPT techniques have been developed. Using Incremental Conductance (INC) as an example, this paper provides a comprehensive overview of MPPT techniques. P&O’s drawback of oscillations around the Maximum Power Point (MPP) is overcome by INC, which minimizes them. The MPP voltage is maintained until the incremental conductance equals zero by comparing the instantaneous conductance of the panel with the incremental conductance. In addition to being easy to implement, INC-based methods offer rapid tracking and efficiency gains. Results from simulations demonstrate INC MPPT’s effectiveness in maximizing power extraction from photovoltaic systems, especially when environmental conditions change rapidly.

Design of Dynamic Voltage Restorer for Power Quality Improvement

Solutions for customers with delicate loads and quick voltage regulation are essential. Protect important loads from supply-side voltage disturbances with a power electronic converter-based Dynamic Voltage Restorer (DVR). In the case of severe sag and swell, DVR is a well-known, low-cost therapy option. On the basis of its maximum voltage injection and active power contribution, a DVR's mitigation ability is determined. Standard DVRs use batteries as their DC input, but batteries are cumbersome, expensive, and hazardous to dispose of after they've been used. This limits compensation for DVRs. It is recommended to increase the DVR's VA rating by 1.5 times by increasing the DC connection voltage to 1.5 times the micro grid voltage regulation and quality improvement methods are proposed in this study. As a series voltage compensator, these solutions incorporate a Dynamic Voltage Restorer (DVR) for regulation, quality improvement, and reduction of harmonic distortion. Continuous adjustment of the DVR output voltage is proposed to reduce harmonic distortions while minimizing network bus voltage changes. As a result of this strategy, the peak demand voltage loss is compensated for. In constant impedance loads, voltage rise reduces network demand, resulting in lower branch currents and losses