Power Transfer Capability Research Articles

Two-dimensional polarization doping of GaN heterojunction and its potential for realizing lateral p–n junction devices

In the gallium nitride (GaN) commercial applications such as high-power illumination and portable charging station, bipolar devices are highly demanded because of their superior power transfer capability. Also, in other scenarios of the monolithic integration where high electron mobility transistors (HEMTs) or superlattice-based devices are presented, the peripheral components are preferred to be lateral. However, to realize such a lateral bipolar junction in GaN, high-concentration p-type dopant doping is still challenging and hardly compatible with the HEMT integration. In this work, we proposed a novel strategy to form lateral bipolar GaN p–n junctions, enabled by the two-dimensional polarization doping. The theory and the simulation reveal this strategy features inspiring forwarding, blocking, and switching performance. Given the recent success of the GaN selective area regrowth techniques, the proposed lateral bipolar junction is highly promising in monolithic heterojunction integration in the future.

An Inductive Power Transfer System for Powering Wireless Sensor Nodes in Structural Health Monitoring Applications

Inductive power transfer (IPT) has been extensively used to power the sensor nodes embedded into reinforced concrete structures for structural health monitoring (SHM) applications. Due to high dielectric absorption in concrete and hysteresis loss and eddy current loss in reinforced steel, this approach suffers from heavy attenuation and short transmission distance. To tackle the issue, a multicoil inductive power repeater system is proposed, in which the coil not only performs as a power relay but also supplies energy to the local load. Based on the physical model of multicoil coupling, the equivalent circuit is built. The effect of various design parameters (e.g., operating frequency, concrete strength, moisture, and steel types) on the power transfer capability of the proposed IPT system is investigated. A flexible design method using coupling modulation is proposed to achieve equal power distribution among various power relay circuits. Experimental results show that the proposed method can simultaneously provide equal power of 0.6 W to four local loads embedded into reinforced concrete structures with a power variation of less than 7.2%. The IPT system achieves a long distance of 51.5 cm and an efficiency of 47.7%. The results indicate the feasibility of the proposed design method in SHM applications.

Maximization of Wind Energy Utilization through Facts Devices

This paper proposes a method for maximizing capacity of wind generation by best location of FACTs devices. Initially capacities of the connected wind units are determined by industry. A probabilistic approach is applied for the day – ahead planning. It is used to find the maximum deployable wind sources. So that the prescribed wind spillage is not exceeded. This is done using the optimum power flow. Further it can be improved by installing FACTS devices. FACTS devices are used to enhance AC system controllability, stability and increase power transfer capability. Two ranking list are developed for SVC and TCSC and then they are combined into a unified method.

Modular Transformerless Static Synchronous Series Compensator with Self-Balancing for Ultra High Current Using a Paralleling Scheme

A novel modular Transformerless, Self-balanced, Static Synchronous Series Compensator (TSB-SSSC) capable of delivering ultra-high current, with the objective of dynamically balancing the impedance of the transmission power grid, is proposed. Balancing transmission lines is crucial in power optimization and delivery because it increases the power transfer capability without building new power lines. The transformerless SSSC needs to support and control the line current from a few hundred to several thousand amperes. This paper presents how the ultra-high current architecture of the TSB-SSSC is achieved by operating multiple converters with self-balancing capabilities in parallel. The mechanism of self-balancing is based on the intrinsic physics of the capacitor and is enabled by a passive network of capacitor equalizers that keep the capacitor voltage equal during switching disconnection. The second self-balancing system consists of an inductive component that balances possible differences among delay switching caused by the aging of the multiple IGBTs from the different converters that form the SSSC. This work presents the analytical set of equations that describes the system and a complete set of simulations where the effectiveness of self-balancing paralleling topology is shown.

Using Zone Impedance Matching Technique to Improve the Power Transfer Capability of an Inductive Charging System over a Long Distance

In many outdoor inductive charging applications, the objects can move quickly, and the environment can change unpredictably. It is therefore difficult to design a fast controller that tracks the change in mutual coupling between the transmitter and receiver. The diminished power delivery to the objects either leads to incomplete charging or prolongs the charging time. In this paper, the concept of a zone impedance matching technique is proposed. This technique pre-matches the transmitter coil to the desired coupling coefficients. Thus, the power transfer capability of the inductive charger can be maintained at a reasonably high level over a long transmission distance and under a wide receiver misalignment. Based on a three-coil inductive power transfer (IPT) system, the proposed concept is practically implemented with a simple control scheme. The proposed IPT system equips a multi-tap transmitter coil to provide flexibility in selecting different numbers of turns in the transmitter coil. The controller senses the currents of the transmitter coil and the repeater coil to determine the zone of impedance to adapt to the change in mutual coupling of the coils. A mathematical analysis is conducted to formulate the design procedures for the proposed system. Under a wide range of distance and misalignment conditions, practical measurement results verified that the proposed system achieves higher power delivery than an ordinary design.

Analisis Aliran Daya Reconductoring Saluran Transmisi Paiton Kraksaan-Probolinggo 150 kV Terhadap Saluran Yang Terimbas

Provision of quality and sufficient electrical energy is something that must be done by PT. PLN (Persero). Based on data from PT. PLN (Persero), carried out work on replacing conductors on the Paiton – Kraksaan – Probolinggo transmission line from the TACSR 330 mm2 conductor with KHA 1190 A to 2xACCC/TW Copenhagen with KHA 2016 A. Reconductoring work is one of the efforts to uprating the transmission line by considering increasing load requirements. This reconductoring is carried out using the open circuit method or a total blackout in a circuit where the conductor is being replaced by taking into account the stages determined by PT. PLN (Persero). So that the power flow in the system must be considered when these conditions take place for the sake of service reliability or system reliability using a power flow simulator application, namely ETAP software. The simulation voltage tolerance with actual conditions is 5%. Next, analyze the power flow on the affected transmission line which is directly connected to the Kraksaan – Paiton – Probolinggo 150 kV transmission line based on voltage drop, transmission line losses and loading from each stage. As well as calculating the power transfer capability after and before reconductoring. The results of the simulation show that the most significant anomaly (deviation that should not be) is that there is a critical point loading of up to 89.220% on the Probolinggo - Gondangwetan channel when reconductoring has been carried out except for the Paiton - Kraksaan1 transmission line. Meanwhile, the value of power transfer capability increased after reconductoring, where the Paiton-Kraksaan1 and Paiton-Kraksaan2 channels increased by 63.91 MW, the Kraksaan - Probolinggo1 channel increased by 67.95 MW, and the Kraksaan - Probolinggo2 channel increased by 63.461 MW from previously.

Power system static and dynamic security studies for the 1st phase of Crete Island Interconnection

The island of Crete is currently served by an autonomous electrical system being fed by oil-fired (Heavy fuel or light Diesel oil) thermal power plants and renewables (wind and PVs). The peak load and annual electric energy consumption are approximately 600 MW and 3 TWh respectively; wind and photovoltaic parks contribute approximately 20% of the electricity needs of the island. Due to the expensive fuel used, the Cretan power system has very high electric energy generation cost compared to the Greek mainland. On the other side the limited size of the system poses severe limitations to the penetration of renewable energy sources, not allowing to further exploit the high wind and solar potential of the island. According to the Ten Year Network Development Plan (TYNDP) of the Greek TSO (Independent Power Transmission Operator S.A. IPTO S.A.), the interconnection of Crete to the mainland Transmission System of Greece will be realized through two links: A 150 kV HVAC link between the Peloponnese and the Crete (Phase I) and a HVDC link connecting the metropolitan area of Athens with Crete (Phase II). The total length of submarine and underground cable of the HVAC link will be approximately 174km; it is at the limits of the AC technology and the longest and deepest worldwide at 150 kV level. A number of studies have been conducted by a joint group of IPTO and Hellenic Electricity Distribution Network Operator (HEDNO) for the design of this interconnection. This paper presents briefly the power system static and dynamic studies conducted for the design of the AC link and its operation. Firstly, the paper presents the main results of the static security study regarding the calculation of the maximum power transfer capability of the link and the selection of the reactive power compensation scheme of the cable. Results from dynamic security analysis studies are also presented. The small-signal stability analysis concludes that a new (intra-area) electromechanical oscillation is introduced to the National System after the interconnection. The damping of the electromechanical oscillations is sufficient; however the operation of power system stabilizers at power plants located both at the mainland and at Crete power system can increase significantly the damping of important oscillation modes. Finally with respect to the risk of loss of synchronism after a significant disturbance in the system of Crete, such as a three-phase fault (“transient stability”)- enough safety margin is estimated by means of Critical Clearing Time calculations.

Modulated Coupled Inductor for Input-Serial–Output-Parallel Dual-Active-Bridge Converter

In this letter, a solution to achieve changeable inductance without any other auxiliary circuit based on pulsewidth modulation (PWM) for the coupled inductor is proposed to reduce the circulating current at the steady state and limit the inrush current during startup for the input-serial–output-parallel dual-active-bridge converter in the solid-state-transformer applications. By modulating the PWM signals, the equivalent inductance of the coupled inductor can be changed without any other auxiliary circuit. The smaller equivalent inductance is adopted in the steady state to reduce the circulating current and increase the power transfer capability. And the larger equivalent inductance is used to limit the inrush current during the startup. The analysis based on the modulated coupled inductor for the steady state and the startup process is given. The design consideration for the coupling coefficient is introduced according to the optimization of the leakage inductor root-mean-square current, the inrush current, and the filter capacitance. Finally, the comparison of experimental results between the proposed solution and the conventional method for a 1600 W/250 kHz prototype verifies the effectiveness.

Enhancing the Performance of Eskom’s Cahora Bassa HVDC Scheme and Harmonic Distortion Minimization of LCC-HVDC Scheme Using the VSC-HVDC Link

Cahora Bassa, a thyristor-based High Voltage Direct (HVDC) link, transmits 1920 MW of power from a hydro-power plant in Zambezi River, north of Mozambique, to Apollo Substation in Johannesburg, South Africa. The high degree of harmonics distortion that is transferred into the AC side of the transmission network and the continuous increase in the rate at which commutation failure occurs during systems disturbance are both flaws in the utilization of this HVDC converter technology. AC and DC filters with rugged controllers are often used to minimize this effect but are limited in scope. Modern converter technology, such as the Voltage Source Converter (VSC), was proposed in this study to reduce harmonics content level, increase power transfer capabilities, enhance network stability, and reduce the rate of commutation failure occurrence. This paper, therefore, evaluates the performance analysis of the Cahora Bassa HVDC link and its level of harmonic distortion in the line commutated converters. A proposed method of utilizing VSC HVDC is provided as a suitable solution using three modular-level voltage source converter technology. Current and voltage waveform characteristics during a three-phase short circuits fault were analyzed, and the latest developments in the area of VSC HVDC were discussed. The results show a lower total harmonics distortion with the usage of VSC HVDC converter technology at the inverter station. The continuous occurrence of commutation failure was minimized by implementing a new converter architecture. The network simulation and analysis were carried out using the DIgSILENT PowerFactory engineering software tool.

FACTS Devices in Indian Power System

This paper aggressively tells about FACTS (Devices in Indian Power System) study whose full form is Flexible Alternative current Transmission System. FACTS is used as it is the best technology which is growing around to improve power transfer capabilities around us to improve the power transfer. FACT devices has its many benefits which are like if for a given transmission system we use it then it will improve the power transfer capability also enhances reliability, and not only provide security for system but also helps in maintaining the stability with better controlling abilities in power transmission networks with all these benefits it is economical which add an advantage for using this in existing network. After seeing such a growth and advantages of FACTS Devices has been system of attention due to which many developing countries like China, Australia, Brazil, etc. has adopted this technology. India is also one of the developing country whose demand of power is increasing rapidly so to provide that demand more efficiently Indian Power system is installing FACTS devices which is helping with great economy and also improving the transmission system. By this paper we have gone through the different surveys which shows that how India’s state electricity boards has installed and used FACTS devices in detailed manner.

Adaptive Tuning of PV Generator Control to Improve Stability Constrained Power Transfer Capability Limit

The stability of power systems can largely limit the power transfer capability limit of transmission lines. The PV generator control is different from synchronous generator control. The impact of PV generator dynamics on the power transfer limit constrained by stability is not well explored in the literature. This paper focuses on improving the stability constrained power transfer capability limit of transmission lines emanating from PV generators. The PV generator is provided with dc link voltage and reactive power control and is equipped with low voltage ride through capability, voltage and frequency support functionalities. In this paper, Lyapunov function analysis based adaptive tuning laws are proposed for PV generator control parameters to improve the power transfer capability limit (constrained by stability) of transmission lines connecting PV generators to grid. The tuning laws are proposed for Phase Locked Loop (PLL), outer and inner control loop parameters. The effectiveness of the proposed method is validated on a Single PV-Synchronous Machine system, modified IEEE-39 and IEEE-118 bus system. Comparison with existing method shows that the proposed tuning method can achieve higher power transfer capability limit considering stability.

A Multi-Load Capacitive Power Relay System With Load-Independent Constant Current Outputs

This article proposes a power relay system to wirelessly power multiple loads via capacitive coupling. The intermediate capacitive relay unit is designed to power the load as well as enhance the power transfer capability, which contains two receiving plates and two transmitting plates. It is proven in this article that the capacitive coupling between the receiving and transmitting plates in the same relay unit can be eliminated by being placed perpendicularly with the help of the proposed split-inductor-based compensation network. A general mathematical model of the multiload capacitive power relay system is established. The <i>L</i> compensation circuits are employed to compensate the first and the last relays, while the <i>LCL</i> compensation circuits are designed to compensate the intermediate relays. Thus, the constant current output can be obtained for each load without affecting each other when neglecting the parasitic resistances. Additionally, the load current and efficiency variations versus the load resistance, coupling coefficient, and quality factor are thoroughly analyzed. Finally, a three-load experimental prototype is constructed to verify the feasibility of the proposed multiload capacitive power transfer relay system. The maximum efficiency can reach 86.1&#x0025; at a power level of 37&#x00A0;W.

Increasing Power Transfer Capability of Transmission Lines Using the Quasi-Dynamic Operation and Monitoring System

One of the key methods for reducing the possible interruptions and the pressures imposed on the operator is to employ the hidden capacity of the transmission lines. The basis of selecting the line capacity is the ability of the operator to preserve the allowed distance between the transmission line and the ground, trees, vehicles, and other obstacles that are directly under the line. One of the methods that increase the capacity of the employed line is the line monitoring equipment and using the dynamic capacity. Although the dynamic capacity method costs less than other options, it might be costly and laborsome. Thus, there should be a tradeoff between the dynamic and static capacity, known as the quasi-dynamic capacity. This term indicates that the dynamic capacity is used in studies for making logical decisions for changing the static capacity or operation of the operator. In many cases, this technology can be implemented temporarily and then removed or displaced for other applications. The purpose of this study is to present a quasi-dynamic method for determining and operating the line capacity to reduce the costs required to determine the complete dynamic capacity and improve the assumptions used in determining the static capacity.

Design and Control of an Off Board Battery Charger for Electric Vehicles

The rise in the penetration of electric vehicles has led to the increased interest in the charging technologies. Controlled charging and vehicle to grid power transfer is being given much importance. This paper proposes an off board charger (three phase) for charging the batteries used in electric vehicles. The proposed charger has a bidirectional power transfer capability so as to transfer power back to the utility grid. The topology proposed is simple and less costly as it has fewer elements. The charger has two converters, a three phase ac-dc converter for conversion of ac into dc and bidirectional dc-dc converter. The technique called Vector control is used to control ac-dc converter which allows controlling of active and reactive power independently. The control strategy proposed here provides a better control and leads to a better performance while maintaining unity power factor at input. The charging algorithm designed is such that it is able to maintain voltage at dc link at desired value. The charging algorithm is designed for lithium ion batteries and the combined Constant Current Constant Voltage (CC-CV) method of charging is used because it is simple and easy to implement. The proposed electric vehicle charger changes the mode of charging with change in State of Charge (SOC). The different modes are switched and the suitable reference is generated based on the different charging characteristics of a battery. The proposed charger is modeled in MATLAB-Simulink. The working operation of both forward and reverse power transfer mode has been analyzed. The proposed charger is able to maintain the unity power factor operation. The simulation results of all modes validate the design and control of the proposed charging topology.

Forced Oscillation Grid Vulnerability Analysis and Mitigation Using Inverter-Based Resources: Texas Grid Case Study

Forced oscillation events have become a challenging problem with the increasing penetration of renewable and other inverter-based resources (IBRs), especially when the forced oscillation frequency coincides with the dominant natural oscillation frequency. A severe forced oscillation event can deteriorate power system dynamic stability, damage equipment, and limit power transfer capability. This paper proposes a two-dimension scanning forced oscillation grid vulnerability analysis method to identify areas/zones in the system that are critical to forced oscillation. These critical areas/zones can be further considered as effective actuator locations for the deployment of forced oscillation damping controllers. Additionally, active power modulation control through IBRs is also proposed to reduce the forced oscillation impact on the entire grid. The proposed methods are demonstrated through a case study on a synthetic Texas power system model. The simulation results demonstrate that the critical areas/zones of forced oscillation are related to the areas that highly participate in the natural oscillations and the proposed oscillation damping controller through IBRs can effectively reduce the forced oscillation impact in the entire system.

Quasi-oppositional turbulent water flow-based optimization for cascaded short term hydrothermal scheduling with valve-point effects and multiple fuels

In an interconnected power system, short-term hydrothermal scheduling (SHTS) portrays a paramount important task in the economic operation of electric power system. SHTS is discerned as a formidable non-convex constrained optimization problem considering the cascade nature of hydro plants, and valve-point loading (VPL) and multi-fuel sources of thermal plants. In the present study, a novel metaheuristic approach, a quasi-oppositional turbulent water flow-based optimization (QOTWFO) is proposed to solve the SHTS problem. Turbulent water flow-based optimization (TWFO) is evolved by the whirlpool prodigy formed in a turbulent flow of water. QOTWFO is an amended version of TWFO, where the quasi-opposition-based learning is pioneered for population initialization and iteration vaulting. It generates a quasi-oppositional solution which has the highest probability to elicit the global optimum solution than a randomly generated solution. Thus, the global searching ability and computational efficiency of the algorithm is enhanced. A new heuristic constraints handling mechanism is proposed to fulfil the equality constraints notably active power balance and dynamic water flow balance. The cogency of proposed QOTWFO is examined on standard benchmark functions, and multi-reservoir cascaded hydrothermal test systems with the cogitation of VPL effects and multi-fuel sources of thermal plants. Besides, Newton Raphson load flow approach is employed to determine power losses and line flows in a 16-bus, and 35 transmission lines hydrothermal power system. To model a realistic power system model, the maximum power transfer capability of each transmission line is taken into account. Simulation outcomes substantiate that, compared with state-of-the-art heuristic techniques, QOTWFO offers better feasible solutions as well as guarantees the robustness of the algorithm.

Joint Beamforming, Power Allocation, and Splitting Control for SWIPT-Enabled IoT Networks with Deep Reinforcement Learning and Game Theory.

Future wireless networks promise immense increases on data rate and energy efficiency while overcoming the difficulties of charging the wireless stations or devices in the Internet of Things (IoT) with the capability of simultaneous wireless information and power transfer (SWIPT). For such networks, jointly optimizing beamforming, power control, and energy harvesting to enhance the communication performance from the base stations (BSs) (or access points (APs)) to the mobile nodes (MNs) served would be a real challenge. In this work, we formulate the joint optimization as a mixed integer nonlinear programming (MINLP) problem, which can be also realized as a complex multiple resource allocation (MRA) optimization problem subject to different allocation constraints. By means of deep reinforcement learning to estimate future rewards of actions based on the reported information from the users served by the networks, we introduce single-layer MRA algorithms based on deep Q-learning (DQN) and deep deterministic policy gradient (DDPG), respectively, as the basis for the downlink wireless transmissions. Moreover, by incorporating the capability of data-driven DQN technique and the strength of noncooperative game theory model, we propose a two-layer iterative approach to resolve the NP-hard MRA problem, which can further improve the communication performance in terms of data rate, energy harvesting, and power consumption. For the two-layer approach, we also introduce a pricing strategy for BSs or APs to determine their power costs on the basis of social utility maximization to control the transmit power. Finally, with the simulated environment based on realistic wireless networks, our numerical results show that the two-layer MRA algorithm proposed can achieve up to 2.3 times higher value than the single-layer counterparts which represent the data-driven deep reinforcement learning-based algorithms extended to resolve the problem, in terms of the utilities designed to reflect the trade-off among the performance metrics considered.

Damping inter‐area oscillation using reinforcement learning controlled TCSC

Inter-area oscillation is a serious problem that threatens a power system. Appropriate damping control of the inter-area oscillation would ensure the grid stability and maintain the tie-line power transfer capability. In this paper, a novel reinforcement learning (RL) based power oscillation damping (POD) controller is proposed that uses Thyristor Controlled Series Compensators (TCSC) to damp inter-area oscillations. By leveraging the unbiased gradient direction estimation of the natural evolution strategy (NES), the power flows on the tie-lines were successfully regulated and inter-area oscillations were damped through dynamically modulating the inserted reactance of the TCSC. Furthermore, parallel computation techniques were adopted to speed up the training process of the NES. The proposed RL-based POD controller has been tested on both two-area four-machine system and North American MinniWECC system. Extensive studies have demonstrated the excellent performance of the proposed RL-based TCSC POD controller in damping inter-area oscillations.

High-Efficiency Module Design of Solid-State Transformers for Railway Vehicles

The solid-state transformer (SST) can be a promising solution to replace the conventional 50- or 60-Hz main transformer (MTr) for railway vehicles. Unlike the existing SST technologies for stationary power applications, the SST applied to railway vehicles requires severe constraint of installation space and intensive management of heat dissipation. To optimally design the SST module applied to the railway vehicles, which is one of the major components in the whole SST system, the optimal magnetic component designs for high-efficiency and thermal stable operations in the confined installation space are proposed in this article. In order to meet the SST system requirements for ac 25-kV-to-dc 1.5-kV power conversion, an overall SST topology and its control schemes are established. Based on the proposed SST topology, considering the operating drive profile of the urban railway vehicles, the operating sequence of the proposed SST is introduced and verified by simulation. By virtue of the proposed magnetic component design, the optimal number of turns for the inductor and transformer in dual-active-bridge converters can be appropriately determined for 50-kV high-voltage insulation and high-efficiency operation when the installation space for the magnetic components is given. For targeting the 3.0-MW maximum power transfer capability of the proposed SST system, the 300-kW SST modules, operating at 500 Hz and 10 kHz for ac/dc converters and dc/dc converters, respectively, were fabricated and verified by experiment. By two experimental SST module sets, the static performance of the power converters in the SST module and the dynamic operating sequence has been successfully implemented. For the 300-kW full-load operation, 99.7% of power transfer efficiency for the proposed magnetic components and 97.2% of total power efficiency were obtained. As a result, the measured temperature characteristics for the proposed SST module, including the magnetic components, were managed below 125 °C under a severe experimental environment.

Single-phase bidirectional AC-AC converter with H-bridge energy buffer for wireless power transfer applications

This paper introduces a single-phase bidirectional AC-AC Matrix type converter for wireless power transfer (WPT) applications. The proposed converter converts mains 50 Hz alternating current (AC) directly to high frequency 85 kHz AC without an intermediate direct current (DC) conversion stage. A minimum cost realization of only two bidirectional AC switches comprised each of two semiconductor device and one gate drive signal is employed. The converter operation modes are quantum energy injection and circulating self-oscillation. Elimination of the DC link introduces a sag in the power transfer during the zero crossing of input AC mains, which is well documented in literature. A novel H-bridge buffer structure is introduced which eliminates the power sag by storing energy during mains peak and delivering energy during the zero-crossing period. The converter operates with inherent zero current switching, thus achieving a low switching loss and electro-magnetic interference. The control feature ensures that the converter can be used for both static and dynamic wireless charging applications. The bidirectional power transfer capability ensures that the system can operate in both grid to vehicle (G2V) and vehicle to grid (V2G) power transfer modes. The proposed converter design is analyzed analytically and verified through thorough simulation study.