Maximum Power Capability Research Articles

Enhancing the Grid Support From DFIG-Based Wind Farms During Voltage Events

With the increasing penetration of renewable energy generators, the world is positively progressing toward the goal of sustainable development. However, the grid strength and inertia are decreasing due to the associated technological limitations. To this end, this research paper proposes a novel approach to enhance the support from DFIG-based wind farms with their existing capacity during critical events like voltage-ride-through. The effectiveness of the method is tested with a reactive power-prioritizing grid code of India. The proposed optimization framework achieves this objective in three stages. The first stage maximizes the wind farm's reactive power reserve in maximum power and de-loaded modes. The second stage uniquely distributes the control references to achieve minimal transitional pitch action between these modes for reduced wear and tear while honoring the maximum reactive power capability. The third stage generates lookup tables of control limits for maximal active power support within the grid code and the system constraints. The optimization is a one-time process for a specified farm geometry. Since the method is lookup table-based, the mode transitions are real-time feasible. The simulation test cases with the benchmark model demonstrate the efficacy of the proposed strategy, especially when the Wake Effect is prominent.

Surface Permanent Magnet Synchronous Machines: High Speed Design and Limits

Surface permanent magnet synchronous machines are one of the most widely adopted machine topologies in high-speed applications where efficiency and power factor cannot be compromised. Although the design of such machine type has been extensively investigated in both industry and academia, this work aims at addressing its limitations when applied in high-speed applications. First, this paper proposes an accurate design methodology for continuous-duty high-speed surface-mounted permanent magnets synchronous machines, capable of accounting for the rise of the speed-dependent losses and structural needs with a limited impact on the computational burden. The outlined approach can be used to speed-up the initial design stage as it allows to reduce the number of solutions to evaluate before commencing the refinement stages required before the definition of the final design. Indeed, the introduced design approach is used to systematically assess the maximum power capability as function of the maximum speed and the airgap thickness for a given outer envelope and cooling system. The influence of the high-speed limiting factors is deeply investigated also considering their effects on the machine geometries providing the highest torque. The selection of the final design is discussed and justified. Experimental results of the 4.2kW-80kprm prototype validate the design methodology.

Optimized Power Distribution Technology for Fast Frequency Response in Photovoltaic Power Stations

The fast frequency response (FFR) function in renewable energy source (RES)-based power stations has proved to be able to improve the frequency stability of power systems with high RES penetration significantly. However, most current FFR functions in photovoltaic (PV) power stations typically show power response deviations and unnecessary power loss issues that are caused by inadequate station power distribution strategies. This is particularly important in cases where the power must be increased when the system frequency shows a downward disturbance. This paper proposes a new distribution strategy for FFR in PV power stations and studies related distribution strategies, system structures, calculation algorithms, function execution effect, and active power regulation technology. The proposed approach uses a proportional distribution strategy based on an evaluation of the real-time potential maximum power capability values of the subarrays or generation regions, which are evaluated using a few reference inverters located in every subarray or region. Real-site deployments and tests have been completed in PV power stations to verify the effectiveness of this new distribution strategy, and the proposed FFR solution using this distribution strategy has demonstrated strong performance and potential for wider application scenarios.

A Hierarchical Voltage Control Scheme for Wind Power Plants Through Enhanced Reactive Power Support

To maximize reactive power support from a wind power plant (WPP) and maintain power factor at the point of interconnection (POI) within acceptable limits, a novel hierarchical voltage control scheme consisting of a central WPP controller and a local wind turbine generator (WTG) controller is proposed in this article, and both controllers are operated in voltage control mode. When a voltage deviation is detected, if it is within the normal range, the central WPP controller turns on the integrated power factor controller to regulate the power factor at the POI. If the voltage deviation exceeds the normal range, the local WTG controller relies on the adaptive droop coefficient and the adaptive proportional setpoint weight-based rotor side converter controller to push the WTG toward its maximum reactive power limit to provide reactive power compensation during contingencies. For accurate estimation of the maximum reactive power capability of a WTG, a comprehensive model with various limiting factors is used. The proposed controllers are equipped with a memory, which ensures continuous operation during a communication failure. The proposed control scheme is validated by case and sensitivity studies using a practical WPP currently in operation in Newfoundland, Canada. It shows excellent performance when compared with the two existing methods.

Improvement of lower hybrid current drive systems for high-power and long-pulse operation on EAST

Aiming at high-power and long-pulse operation up to 1000 s, some improvements have been made for both 2.45 GHz and 4.6 GHz lower hybrid (LH) systems during the recent 5 years. At first, the guard limiters of the LH antennas with graphite tiles were upgraded to tungsten, the most promising material for plasma facing components in nuclear fusion devices. These new guard limiters can operate at a peak power density of 12.9 MW/m2. Strong hot spots were usually observed on the old graphite limiters when 4.6 GHz system operated with power >2.0 MW [B. N. Wan et al., Nucl. Fusion57(2017) 102019], leading to a reduction of the maximum power capability. With the new limiters, 4.6 GHz LH system, the main current drive (CD) and electron heating tool for EAST, can be operated with power >2.5 MW routinely. Long-pulse operation up to 100 s with 4.6 GHz LH power of 2.4 MW was achieved in 2021 and the maximal temperature on the guard limiters measured by an infrared (IR) camera was about 540 °C, much below the permissible value of tungsten material (∼1200 °C). A discharge with a duration of 1056 s was achieved and the 4.6 GHz LH energy injected into the plasma was up to 1.05 GJ. Secondly, the fully-active-multijunction (FAM) launcher of 2.45 GHz system was upgraded to a passive-active-multijunction (PAM), for which the density of optimum coupling was relatively low (below the cut-off value). Good coupling with reflection coefficient ∼3% has been achieved with plasma-antenna distance up to 11 cm for the new PAM. Finally, in order to eliminate the effect of ion cyclotron range of frequencies (ICRF) wave on 4.6 GHz LH wave coupling, the location of the ICRF launcher was changed to a port that is located 157.5° toroidally from the 4.6 GHz LH system and is not magnetically connected.

Improving Power Density of a Three-Level ANPC Structure Using the Electro-Thermal Model of Inverter and a Modified SPWM Technique

Multilevel inverter structures have become an interesting substitute for the well-known two-level inverters in a variety of applications due to their exceptional characteristics when compared to conventional inverters. One major issue regarding multilevel structures is the unequal junction temperature of the switches which deteriorates the power density and increase the cost of the inverter by reducing the maximum achievable output power with a given thermal model and cooling system. Hence, on account of the aggressive goals of power density and cost in a majority of power electronic applications, this article proposes a new technique for reducing the maximum junction temperature of switches in a three-level active neutral-point clamped (ANPC) inverter based on a junction temperature estimation method and a modified SPWM control scheme. This technique can ensure up to a 12% rise in the power density value when compared to basic SPWM techniques with no loss distribution algorithm. Moreover, the suggested approach can be used as a protection stage in the inverter which protects the inverter in transient loads, while allowing for reaching the maximum power capability of the inverter. Finally, the simulations of the proposed technique are validated with experimental results of a 400 V, 20 kW three-level ANPC inverter, controlled by the conventional and proposed techniques.

Design of High-Power Static Wireless Power Transfer via Magnetic Induction: An Overview

Recent years have witnessed the booming development of wireless power transfer (WPT) via magnetic induction, which has the advantages of convenience, safety, and feasibility to special occasions. WPT can be applied to electric vehicles and ships, where high-power WPT technology is required to shorten the charging time with the increasing battery capacity. This paper reviews the state-of-the-art development of high-power static WPT systems via magnetic induction. Selected prototypes and demos of high-power WPT systems are demonstrated with key transfer characteristics and solutions. Theoretical foundation of magnetically coupled WPT systems is analyzed and the maximum power capability of coils is derived. Compensation topologies suitable for high-power applications are discussed. Four basic planar coils, namely the bipolar coil, the square coil, the circular coil, and the rectangular coil, are simulated and compared. The state-of-the-art silicon carbide MOSFET development is introduced. The power electronics converters with power elevation techniques, including cascading, paralleling and inductive elevation, are investigated. Future development of high-power WPT systems is discussed.

A Review of Smart Energy Metering System Projects

The rule of thumb dictates that for any country to have a stable and sufficient power supply, there must be at least a thousand Megawatts of electricity for every one million population. However, many developing countries generate far less than the population demand. Despite not generating enough, enormous electrical power loss, energy theft, and unpaid bills are major problems bedeviling the power distribution companies. A fundamental process in the electricity cycle is energy metering from power generation to distribution and consumption. For decades now, manual (or conventional) energy meters are used to estimate every end-user's energy consumption. But there are lots of setbacks to these meters. These meters were unable to solve the problems of power loss and theft, giving necessity to developing a metering system that will serve as a solution to all issues emanating from the consumer end. The past decade saw many developments of such meters, where all are based on the internet of things (IoT) technology. Such meters are called – by the early developers – a smart energy metering system (SEMS), or simply, a Smart Meter. While there have been several reviews on SEMS, most were found to be based on the instant billing capabilities of SEMS, system development, and the wireless communication protocols of the systems. This review focuses on individual components of SEMS with particular attention to the different types and modes of sensors used for other applications. It analyzes various SEMS designs, microcontrollers, sensors, modules, transducers, communication protocols, data storage accuracy, and maximum power capability. Also discussed are the achievements and weaknesses of the designs, some future research challenges, and open issues in the implementation of SEMS.

Optimized EPS Control to Achieve Full Load Range ZVS With Seamless Transition for Dual Active Bridge Converters

Dual active bridge (DAB) converters are widely studied for applications requiring isolation, bidirectional power flow and high efficiency. To solve the problem of limited zero voltage switching (ZVS) range and achieve seamless transition for extended-phase-shift (EPS) control, the magnetizing current is utilized and an optimized control law is proposed in this article. With the injection of magnetizing current, the two ZVS regions under EPS control will be creatively intersected with a large region, instead of disconnected or just intersected at a particular point as in previous studies. The ZVS model considering switch junction capacitors, ZVS region analysis with magnetizing current injection and power transfer characteristics are analyzed. Based on these analyses, the optimized EPS control is proposed to achieve full load range ZVS, low root-mean-square current and maximum transmission power capability. A 250 kHz, 500 W GaN-based DAB prototype is built to verify the effectiveness of the proposed solution.

Behavior Study of Permanent Magnet Synchronous Machines Based on a New Normalized Model

Permanent magnet synchronous machines (PMSMs) are widely used in many applications. The performance of the PMSM is highly dependent on the motor parameters. Many research studies have been done to evaluate the PMSM performances in terms of maximum torque capability, power capability, and field-weakening capability. This paper proposes a new normalized PMSM model and uses two parameters, characteristic current and saliency ratio, to uniquely define the motor characteristic. Based on this normalized model, the full map motor behaviors, including torque capability, power capability, torque/power-speed characteristics, and power factor behaviors, are studied parametrically. A new unitless metric, i.e., copper loss factor, is introduced to evaluate the copper loss variation of PMSMs. The saturation effect on the motor behavior is studied based on the 2004 Prius traction motor, which confirms that the field-weakening characteristic can be well predicted using the linearized model. A new design flow for traction PMSMs, which requires wide-speed operation, is proposed based on the full map motor behavior study, and a prototype machine is designed accordingly. The behavior study and the effectiveness of the traction motor design flow are validated experimentally by the prototype.

Model migration based battery power capability evaluation considering uncertainties of temperature and aging

Uncertainties of cell temperature and aging are two challenges for the power management of battery-integrated systems. To evaluate the maximum power capability of batteries with uncertain degree of degradation and internal temperature, a temperature-compensated battery model is first established as a base model in this paper. Then the linear migration with particle filtering is employed to adjust the developed base model so that the migrated model can be adaptive to the uncertainties of aging and internal temperature. Moreover, a numerical seeking method is proposed for state of power (SoP) calculation to avoid direct handling of the complex, highly nonlinear battery model. After that, the multiple constraints such as current, state of charge (SoC), and voltage limitations are considered for SoP estimation. Experimental results show that for the cases of capacity degradation up to 15%, temperature variation up to 40 °C, and the root-mean-square error (RMSE) of the voltage measurement noise up to 50 mV, the RMSE of the voltage tracking for SoP calculation can still be limited to 8.4 mV, and the RMSE of the SoC estimation is better than 1.64%. In addition, the computational efficiency of the proposed seeking algorithm is stable with particle filters using different configurations.

Parameter Identification and Maximum Power Estimation of Battery/Supercapacitor Hybrid Energy Storage System Based on Cramer–Rao Bound Analysis

This paper presents the analysis, design, and experimental validation of parameter identification of battery/supercapacitor (SC) hybrid energy storage system (HESS) for the purpose of condition monitoring and maximum power estimation. The analytic bounds on the error of battery and SC parameter identification, considering voltage measurement noise, are obtained based on the Fisher information matrix and Cramer–Rao bound analysis. The identification of different parameters requires different signal patterns to ensure high accuracy, rendering tradeoffs in the multiparameter identification process. With an appropriately designed current profile, HESS parameters are identified using recursive least squares with a forgetting factor. The identified parameters are then used to estimate the maximum power capability of the HESS. The maximum power capabilities of the battery and SC are estimated for both 1 and 30 s time horizons. The parameter identification algorithm can be applied to systems including either batteries or SCs when the optimal excitation current can be injected. Experimental validation is conducted on an HESS test-bed, which shows that the proposed algorithm is effective in estimating the HESS maximum power based on appropriate current excitation.

Hybrid Alternate-Common Arm Converter With High Power Capability: Potential and Limitations

This article studies a new hybrid converter that utilizes thyristors and full-bridge (FB) arms for achieving high-power capability with reduced semiconductor power rating compared to the FB modular multilevel converter. The study covers the theoretical analysis of the energy balancing, the dimensioning principles, the maximum power capability, and the limitations imposed by the discontinuous operation of the converter. Based on the analysis of these aspects, the theoretical analysis is concluded by identifying the operational constraints that need to be fulfilled for maximizing the power capability of the converter. It is concluded that the maximum power capability can be achieved for a certain range of modulation indices and is limited by both the commutation time of the thyristors and the power angle. Moreover, the P – Q capability of the hybrid converter is presented and discussed. Finally, simulation and experimental results that confirm the theoretical analysis and the feasibility of the studied converter are presented and discussed.

The Effect of Carbon and Zinc Electrodes Using Sea Water Electrolyte on Air Battery Power

The air-zinc battery uses oxygen from the atmosphere to produce electrochemical energy. After opening the battery into the air, oxygen diffuses into the cell and is used as cathode reagent. The air passes through the cathode to the active surface of the interior cathode in contact with the electrolyte liquid, namely sea water. On the active surface, the air cathode catalytically encourages the reduction of oxygen in the electrolyte liquid. This study aims to determine the effect of zinc anode on air batteries that are in direct contact with activated carbon as a source of electrical energy and find out the influence of electrolyte of seawater as an alternative source of electrical energy in air batteries. The research method uses Volta cells. Other advantages are safety and ecological benefits and low energy costs, as well as maximum power capability on environmentally friendly tolerance. In this study four salinity salinity was used, namely salinity of 3.56%, salinity of 3.99%, salinity 4.60% and salinity 5.02%. The results obtained are the highest voltage 1.144 Volt and the highest current of 4.85 mA is found in salt water salinity 5.02% .

On developing an optimal design procedure for a bimorph piezoelectric cantilever energy harvester under a predefined volume

Abstract A typical vibration harvester is tuned to operate at resonance in order to maximize the power output. There are many design parameter sets for tuning the harvester to a specific frequency, even for simple geometries. This work studies the impact of the geometrical parameters on the harvested power while keeping the resonance frequency constant in order to find the combination of the parameters that optimizes the power under a predefined volume. A bimorph piezoelectric cantilever is considered for the study. It consists of two piezoelectric layers and a middle non-piezoelectric layer and holds a tip mass. A theoretical model was derived to obtain the system parameters and the power as functions of the design parameters. Formulas for the optimal load resistance that provide maximum power capability at resonance and anti-resonance frequency were derived. The influence of the width on the power is studied, considering a constant mass ratio (between the tip mass and the mass of the beam). This keeps the resonance frequency constant while changing the width. The influence of the ratio between the thickness of the middle layer and that of the piezoelectric layer is also studied. It is assumed that the total thickness of the cantilever is constant and the middle layer has the same mechanical properties (elasticity and density) as the piezoelectric layer. This keeps the resonance frequency constant while changing the ratio between the thicknesses. Finally, the influence of increasing the free length as well as of increasing the mass ratio on the power is investigated. This is done by first, increasing each of them individually and secondly, by increasing each of them simultaneously while increasing the total thickness under the condition of maintaining a constant resonance frequency. Based on the analysis of these influences, recommendations as to how to maximize the geometrical parameters within the available volume and mass are presented.

Microwave Plasma Generation With Resonance Frequency Tracking and Power Regulation

This paper presents a palm-sized power-providing module for microwave plasma generation with resonance-frequency tracking and output-power-regulation schemes. A 2.4-GHz coaxial transmission line resonator is used as a microwave plasma generator. The power module covers the frequency range from 2.3 to 2.5 GHz with the maximum power capability of 24 W. The power module adaptively sets the output frequency so that the forward power to the resonator is minimally reflected in response to the resonance frequency shift due to plasma formation. At a forward input power of 2 W, the resonance frequency shift by plasma formation is 41 MHz. With the proposed adaptive frequency tracking scheme, the power-transfer efficiency improves from 56 to 88 %. In addition, production of $\cdot $ OH radical, which is one of the key species in biomedical applications, increases by 33 % at 2 W. The power regulation function is verified by measuring the plasma gas temperature, which is an important indicator of safety for biomedical applications. With a feedback loop control, the power module stably generates 1 W and maintains a constant plasma gas temperature of 40 °C for 300 s. The measurements reveal that the proposed schemes can improve the power efficiency and controllability of microwave plasma generation, and thereby increase the feasibility of producing a portable low-power microwave bio-plasma device.

A Study on Bandwidth and Performance Limitations of Array Vibration Harvester Configurations

Abstract Many researchers introduced an array of generators for broadband energy harvesting. The array has been studied in comparison to a single element from this array, but never compared to a single reference harvester with same volume as the whole array. This paper presents a theoretical study of evaluating the performance of the array harvester in comparison to the reference harvester. Power from the reference harvester as well as from the array is analytically calculated. The array is compared to the reference harvester when loaded by their optimal resistances which provide maximum power capability. The comparison is divided into two sections: firstly when the elements of the array are tuned to resonate at matching frequencies and secondly when they are tuned to non-matching resonance frequencies. The comparisons lead to two significant limits of the working bandwidth of the array: the lower and the upper limit. Between the two limits, the power produced from the array is less than the reference harvester, but with a small additional bandwidth. Below the lower limit, the array has no advantage over the reference harvester. Above the upper limit, output power of the array is inconsistent. Hence, design guidelines for the array are provided.

Experimental verification of winding switching technique to enhance maximum speed operation of surface mounted permanent magnet machines

Flux weakening is an inevitable requirement in the operation of variable speed permanent magnet (PM) machines for high-speed applications due to inverter voltage limits. A new winding switching technique is experimentally validated in this study that can extend the speed range of such PM machines. A drive topology is proposed that utilises two current regulated voltage source inverters to control the machine in a dual inverter fed configuration before transitioning into an open winding configuration after winding switching. The proposed drive topology extends the constant torque region of the machine and boosts its maximum output power capability. Complete experimental results are provided to demonstrate the effectiveness of the proposed machine drive system for continuous operation over the entire speed range.

On-state voltage drop based derating/uprating on a MW converter to improve reliability

Power semiconductor devices are the most fragile components limiting reliability of power converters, where major stresses are temperature dependent parameters. Typically, the operating virtual maximum junction temperature is specified by a manufacturer for each individual device. The thermal system and operating load are designed based on this number. Online monitoring of an on-state collector–emitter voltage (υce,on) and a junction temperature is necessary to ensure the design performance within a safe limit and also to make this method applicable for derating/uprating power. This paper presents the real time measurement of υce,on and thereby the junction temperature estimation in high power converters. Knowing these parameters online, the maximum power capability can be detected. The operating maximum junction temperature is selected and thereby based on the operating condition the derating of power is shown for a megawatt (MW) converter. An experimental setup including online monitoring is described and the measurement of power derating is presented at the specified conditions.

A Compact Multi-Input Power Conversion System with High Time-Efficiency Inductor–Sharing Technique for Thermoelectric Energy Harvesting Applications

A compact multi-input thermoelectric energy harvesting system implemented in a 0.18[Formula: see text][Formula: see text]m CMOS technology is proposed to extract electrical energy from human body heat. By combining the techniques on inductor sharing and bidirectional power converter, the harvesting- and regulating-stage circuits in conventional energy harvesting system can be merged into a single-stage circuit. With the proposed duty-cycle-based strategy for maximum power extraction and the high-efficiency timing scheme for inductor sharing, the proposed multi-input thermoelectric energy harvesting system can ensure optimal power transfer from each thermoelectric energy source without sacrificing power conversion efficiency (PCE) and maximum output power capability. The peak PCE is achieved at 58.5%, the maximum end-to-end output power is 2.43[Formula: see text]mW, and the maximum output power capability is 32.4[Formula: see text]mW while the storage capacitor is fully charged.