AC Power Output Research Articles

Voltage Control Principle Analysis of Permanent Magnet Generator

The permanent magnet generator has small size, simple structure, light weight, low cost, simple process, and eliminates the need for rectifier generator excitation windings and easy problems of the collector ring and brush devices, etc, are widely application. In recent years, a variety of good performance permanent magnet generators have been developed, but these generators are AC power output and generally low, when load changes the output voltage changes greater. Through the magnetism of permanent magnet generator, using good performance electronic components, a new type of intelligent electronic controller is developed; using the electronic regulator and the developed generator, the DC electrical power for vehicles required is solved.

Optimal design of a vibration-based energy harvester using magnetostrictive material(MsM)

In this study, an optimal vibration-based energy harvesting system using magnetostrictivematerial (MsM) was designed and tested to enable the powering of a wireless sensor. Inparticular, the conversion efficiency, converting from magnetic to electric energy, isapproximately modeled from the magnetic field induced by the beam vibration. A numberof factors that affect the output power such as the number of MsM layers, coil design andload matching are analyzed and explored in the design optimization. From themeasurements, the open-circuit voltage can reach 1.5 V when the MsM cantilever beamoperates at the second natural frequency 324 Hz. The AC output power is 970 µW, giving a powerdensity of 279 µW cm − 3. The attempt to use electrical reactive components (either inductors or capacitors) toresonate the system at any frequency has also been analyzed and tested experimentally.The results showed that this approach is not feasible to optimize the power. Since the MsMdevice has low output voltage characteristics, a full-wave quadrupler has beendesigned to boost the rectified output voltage. To deliver the maximum outputpower to the load, a complex conjugate impedance matching between the load andthe MsM device is implemented using a discontinuous conduction mode (DCM)buck-boost converter. The DC output power after the voltage quadrupler reaches 705 µW and the correspondingpower density is 202 µW cm − 3. The output power delivered to a lithium rechargeable battery is around 630 µW, independent of the load resistance.

Validated real-time energy models for small-scale grid-connected PV-systems

Abstract This paper presents validated real-time energy models for small-scale grid-connected PV-systems suitable for domestic application. The models were used to predict real-time AC power output from a PV-system in Dublin, Ireland using 30-min intervals of measured performance data between April 2009 and March 2010. Statistical analysis of the predicted results and measured data highlight possible sources of errors and the limitations and/or adequacy of existing models, to describe the temperature and efficiency of PV-cells and consequently, the accuracy of power prediction models. PV-system AC output power predictions using empirical models for PV-cell temperature and efficiency prediction showed lower percentage mean absolute errors (PMAEs) of 7.9–11.7% while non-empirical models had errors of 10.0–12.4%. Cumulative errors for PV-system AC output power predictions were 1.3% for empirical models and 3.3% for non-empirical models. The proposed models are suitable for predicting PV-system AC output power at time intervals suitable for smart metering.

Single-Phase to Single-Phase Full-Bridge Converter Operating With Reduced AC Power in the DC-Link Capacitor

This paper presents a control technique based on input and output AC power synchronization to reduce the low frequency AC power and the DC-link voltage fluctuation of a single-phase full-bridge converter. The control technique is based on a technique in which the load voltage is synchronized with the input grid voltage for both constant (Mode I) and variable (Mode II) phase angle. Such approach allows for a reduction in the capacitor size. A capacitor bank design approach is also proposed. The technique has been achieved for the same input and output converter frequency. Simulated and experimental results are addressed.

Development of Intermediate-Temperature Solid Oxide Fuel Cells Using Doped Lanthanum Gallate Electrolyte

Intermediate-temperature(IT) solid oxide fuel cells(SOFCs) were developed using lanthanum gallate electrolyte, samarium cobaltite cathode and the cermet anode of nickel and ceria. High efficiency operation below 800°C was enabled using planar disk type cells with unique seal less stack design. The first 10 kW-class combined heat and power (CHP) system provided AC output power of 10 kW with electrical and overall efficiency of 41 and 82 %HHV, respectively. Optimization of cell-stack components to increase the output power density is in progress.

Prediction of grid-photovoltaic system output using three-variate ANN models

This paper presents the prediction of total AC power output from a grid-photovoltaic system using three- variate artificial neural network (ANN) models. In this study, two-hidden layer feedforward ANN models for the prediction of total AC power output from a grid-connected photovoltaic system have been considered. Three different models were configured based on different sets of ANN inputs. In addition, each model utilizes three types of inputs for the prediction. The first model utilizes solar radiation, wind speed and ambient temperature as its inputs while the second model uses solar radiation, wind speed and module temperature as its inputs. The third model uses solar radiation, ambient temperature and module temperature as its inputs. Nevertheless, all the three models employ similar type of output which is the total AC power produced from the grid-connected system. Data filtering process has been introduced to select the quality data patterns for training process, making only the informative features are available. Thus, the regression analysis and root mean square error (RMSE) performance of each model could be enhanced. After the training process is completed, the testing process is performed to decide whether the training process should be repeated or stopped. Besides selecting the best prediction model, this study also exhibits some of the experimental results which illustrate the effectiveness of the data filtering in predicting the total AC power output from a grid- connected system. Each ANN model was tested with Levenberg-Marquardt training algorithm and scaled conjugate gradient training algorithm to select the best training algorithm for each model. Fully trained ANN model should later be able to predict the AC power output from a set of un-seen data patterns.

Voltage Controller of a Single Phase Self-Excited Induction Generator

This paper presents the design of a low cost voltage controller of a single phase Self-Excited Induction Genera- tor (SEIG). The control scheme is based on the measurement of users load voltage and controlling the dump load power using an Analogue Input Power Controller (AIPC). The controller output varies from 2 -10V and it controls the output AC power going to a resistive dump load. A PI type controller is designed to adjust the dump load as the users load varies to maintain a constant voltage across the load. The system voltage regulation is tested by sudden change in the users load. This paper presents the system description, controller design, and test results.

Development of IT-SOFC Based on Lanthanum Gallate Electrolyte

The Kansai Electric Power Company, Inc. and Mitsubishi Materials Corporation started a joint research project for developing intermediate temperature (600{degree sign}C to 800{degree sign}C) solid oxide fuel cells (IT-SOFC) in 2001. High performance disk-type cells with lanthanum gallate-based electrolyte and a seal-less cell-stack design enable high efficiency operation at temperatures below 800{degree sign}C. The development of 10 kW-class CHP system under a project supported by NEDO (New Energy and Industrial Technology Development Organization) was started in FY2004. In 2007, the performance test of the 10 kW-class system using town gas as fuel has been undertaken. In this test, the electrical efficiency of 41%HHV on AC power output of 10 kW and the overall efficiency of 82%HHV by recovering 60åC hot water have been achieved. And the voltage degradation rate per 1,000 hours was 1.08% after 3,000 hours operation has been observed during the field test of the 10 kW-class system. Furthermore, after making some refinements to enhance the performance of 10 kW-class module, the second long-term stability test for 3,000 hours were carried out in 2008. Efforts to enhance cell and module durability have been made with 1 kW-class modules operated for 5,000 hours, and with the cell-stack units operated for 15,000 hours. The voltage degradation rates per 1,000 hours were 0.51 % for the 1 kW-class modules, and 0.23 - 0.48% for the cell-stack units.

Partial Evolutionary ANN for Output Prediction of a Grid-Connected Photovoltaic System

This paper presents the Evolutionary Programming (EP) based technique to optimize the architecture and training parameters of a one-hidden layer backpropagation Artificial Neural Network (ANN) model for the prediction of total AC power output from a grid connected photovoltaic system. A partial Evolutionary Programming-ANN (EPANN) model has been developed for the prediction. It utilizes solar radiation, wind speed and ambient temperature as its inputs while the output is the total AC power produced from the grid connected PV system. EP is used to optimize the regression performance of the ANN model by determining the optimum values for the number of nodes in the hidden layer as well as the optimal momentum rate and learning rate for training. The results obtained from the EPANN have been compared with the results from a classical ANN with similar input and output settings. It is observed that the prediction of total AC power output from a grid connected PV system could be accelerated and simplified using the partial evolutionary ANN model. Index Terms—Artificial neural network (ANN), Correlation coefficient (R), Evolutionary programming-ANN (EPANN), and Photovoltaic (PV).

A capacitive vibration-to-electricity energy converter with integrated mechanical switches

Due to recent advances in low-power VLSI design technology, it has become feasible to power portable or remote electronic devices by scavenging the ambient energy. The design, fabrication and measurement of a capacitive vibration-to-electricity energy converter are presented in this paper. With a device area constraint of 1 cm2 and an auxiliary battery supply of 3.6 V, the device was designed to generate an output power of 31 µW with an output saturation voltage of 40 V. An external mass of 4 g was needed to adjust the device resonance to match the input vibration of 2.25 m s−2 at 120 Hz. Mechanical contact switches were integrated onto the device to provide accurate charge–discharge energy conversion timing. The device was fabricated in SOI (silicon-on-insulator) wafers by deep silicon etching technology. Parasitic capacitance was minimized by partial back side substrate removal. Resonant frequencies of the fabricated device with and without the external mass agreed with the expected values. Without the external mass, the measured ac output power was 1.2 µW with a load of 5 MΩ at 1870 Hz. Detailed circuit modeling and ac output power measurement of the devices with the external mass attached are in progress.

Design, Fabrication, and Test of a 5-kWh/100-kW Flywheel Energy Storage Utilizing a High-Temperature Superconducting Bearing

The Boeing team has designed, fabricated, and is currently testing a 5-kWh/100-kW flywheel energy-storage system (FESS) utilizing a high-temperature superconducting (HTS) bearing suspension/damping system. Primary design features include: a robust rotor design utilizing a composite rim combined with a metallic hub to create a 164-kg rotor assembly without critical resonances within the normal operating range, a closed-loop passive HTS bearing suspension/damping system, and a brushless 100-kW motor/generator. The Boeing FESS provides true isolation for the critical load as the 3-phase 480-V AC input power is converted to 600-V DC and re-inverted to clean, 3-phase 480-V AC output power by the inverter power electronics. When fully charged, the system is capable of responding within 4 ms for the uninterruptible protection of critical digital loads. Low losses and stable operation were demonstrated at rotational speeds exceeding 15,000 rpm.

Modeling of Wind Turbine Driving Permanent Magnet Generator with Maximum Power Point Tracking System

This paper elaborates on the analysis and simulation of 15 kW Wind Turbine Generator (WTG) driving low speed Permanent Magnet Synchronous Generator (PMSG) using PSIM computer simulation program. The system consists of wind turbine, permanent magnet generator, three-phase diode rectifier, boost converter, and voltage source inverter models. In the WTG model, the best performance coefficient has been determined according to the wind and rotational speed. The low speed PMSG has been used to eliminate gearbox to achieve high efficiency. The ac power output from PMSG is fed to a three-phase diode bridge forward by boost converter to effectively control the dc voltage level. The voltage source PWM inverter is used to interface the system with the electrical utility. The modulation index of the PWM inverter has been controlled to enhance the stability of the dc bus voltage. Simulation results show the superior stable control system and high efficiency.

Analysis of power output for piezoelectric energy harvesting systems

Power harvesting refers to the practice of acquiring energy from the environment whichwould be otherwise wasted and converting it into usable electric energy. Much work hasbeen done on studying the optimal AC power output, while little has considered theAC–DC output. This article investigates the optimal AC–DC power generation for arectified piezoelectric device. In contrast with estimates based on various degrees ofapproximation in the recent literature, an analytic expression for the AC–DC power outputis derived under steady-state operation. It shows that the harvested power depends on theinput vibration characteristics (frequency and acceleration), the mass of the generator,the electrical load, the natural frequency, the mechanical damping ratio and theelectromechanical coupling coefficient of the system. An effective power normalizationscheme is provided to compare the relative performance and efficiency of devices. Thetheoretical predictions are validated and found to be in good agreement withboth experimental observations and numerical simulations. Finally, several designguidelines are suggested for devices with large coupling coefficient and qualityfactor.

Inverter sizing of grid-connected photovoltaic systems in the light of local solar resource distribution characteristics and temperature

Inverter sizing strategies for grid-connected photovoltaic (PV) systems often do not take into account site-dependent peculiarities of ambient temperature, inverter operating temperature and solar irradiation distribution characteristics. The operating temperature affects PV modules and inverters in different ways and PV systems will hardly ever have a DC output equal to or above their STC-rated nominal power. Inverters are usually sized with a nominal AC output power some 30% (sometimes even more) below the PV array nominal power. In this paper, we show that this practice might lead to considerable energy losses, especially in the case of PV technologies with high temperature coefficients of power operating at sites with cold climates and of PV technologies with low temperature coefficients of power operating at sites with warm climates and an energy distribution of sunlight shifted to higher irradiation levels. In energy markets where PV kW h’s are paid premium tariffs, like in Germany, energy yield optimization might result in a favorable payback of the extra capital invested in a larger inverter. This paper discusses how the time resolution of solar radiation data influences the correct sizing of PV plants. We demonstrate that using instant (10 s) irradiation values instead of average hourly irradiation values leads to considerable differences in optimum inverter sizing. When calculating inverter yearly efficiency values using both, hourly averages and 1-min averages, we can show that with increased time resolution of solar irradiation data there are higher calculated losses due to inverter undersizing. This reveals that hourly averages hide important irradiation peaks that need to be considered. We performed these calculations for data sets from pyranometer readings from Freiburg (48°N, Germany) and Florianopolis (27°S, Brazil) to further show the peculiarities of the site-dependent distribution of irradiation levels and its effects on inverter sizing.

Demonstration of high efficiency intermediate-temperature solid oxide fuel cell based on lanthanum gallate electrolyte

The Kansai Electric Power Co., Inc. (KEPCO) and Mitsubishi Materials Corporation (MMC) have been jointly developing intermediate-temperature solid oxide fuel cells (SOFCs). The operation temperatures between 600 and 800 °C were set as the target, which enable SOFC to use less expensive metallic separators for cell-stacking and to carry out internal reforming of hydrocarbon fuels. The electrolyte-supported planar-type cells were fabricated using highly conductive lanthanum gallate-based electrolyte, La(Sr)Ga(Mg,Co)O 3− δ , Ni-(CeO 2) 1− x (SmO 1.5) x cermet anode, and Sm(Sr)CoO 3− δ cathode. The 1 kW-class power generation modules were fabricated using a seal-less stack of the cells and metallic separators. The 1 kW-class prototype power generation system with the module was developed with the high performance cell, which showed the thermally self-sustainability. The system included an SOFC module, a dc–ac inverter, a desulfurizer, and a heat recovery unit. It provided stable ac power output of 1 kW with the electrical efficiency of 45% LHV based on ac output by using city gas as a fuel, which was considered to be excellent for such a small power generation system. And the hot water of 90 °C was obtained using high temperature off-gas from SOFC.

Autonomous reluctance generator

A single-phase autonomous reluctance generator is analysed as an oscillator with time-varying parameters. It is shown that the reluctance generator can be modelled by the parametric Hill's equation. The necessary condition for generating AC output power is obtained by using different methods of analysis. Furthermore, when the inductance varies as a square wave, using a piecewise method solves the RG differential equation in an exact manner. In this case, the RG could be driven at a different rotor velocity to elicit the same resonant current and voltage frequency. The analysis is verified by experimental and simulation results.

Portable and stable source of AC voltage, current, and power

This paper describes a portable and stable source of AC voltage, current, and power. It was developed for use with the National Research Council of Canada (NRC) watt-voltampere (W-VA) Transfer Standard to provide high-accuracy on-site calibrations of standards maintained by Canadian electrical utilities in order to establish traceability of these standards to the NRC. The stability of the source monitored over 100 s, a typical measurement cycle of the NRC W-VA Transfer Standard, is better than 10 ppm of full scale for the voltage and current outputs. The stability of its AC power output is better than 20 ppm of full scale at all possible power factor settings. The stable source is needed to minimize test uncertainties during on-site calibrations and to take full advantage of the accuracy of the NRC W-VA Transfer Standard. >

High breakdown voltage InGaAs/InAlAs HFET using In0.5Ga0.5P spacer layer

A highly strained In0.5Ga0.5P spacer is introduced into an HFET grown by MOVPE on InP substrate for the first time. Despite the large lattice mismatch and the group V exchange at the channel-spacer interface the transport data are not affected (µH, 300K = 11 300 cm2/Vs, ns = 2 x 1012 cm-2). However the large bandgap energy of InGaP results in improved gate leakage, drain-conductance and drain breakdown. At VDS = 10 V a voltage gain of vu > 100 is maintained. HFETs with Lg = 0.7µm exhibit gm = 360 mS/mm, ID, max(VDS = 6V) = 550 mA/mm and a cutoff frequency fmax of 150 GHz. At VDS = 5.5V an AC output power of 0.6 W/mm is achieved indicating the capability for high power HFET application on InP substrates.

Simplex Optimization of the Alternating-Current Plasma Detector for Gas Chromatography

Several operating parameters for the alternating-current plasma detector for gas chromatography were optimized on the basis of maximization of the peak area response of the detector towards ethylmerctiry (II) chloride by the modified simplex algorithm. The parameters included in the study were the ac power output, helium make-up flow rate, column flow rate, PMT voltage, and slit width. Univariant values of the optimum were equivalent to most simplex optimum values in this study. Detector evaluation was based on the new optimized response and a new detector interface design and is compared to previous values obtained for this detector. Lower detection limits of 1.10 pg/s were realized, coupled with a relative standard deviation between 1 and 5%. Detector linearity extended over three orders of magnitude.

Simulation of photovoltaic power systems and their performance prediction

A number of photovoltaic (PV) performance-analysis models are tested for their ability to estimate the AC power output and validated against historical observations from a PV test facility. A method to estimate meteorological parameters is developed for use in PV performance models for predicting future AC power output from a PV test site. Twelve such PV performance models are examined, and the PVFORM system analysis program and lifetime cost and performance models are extensively tested. These two models are tested using the typical meteorological year and the VPI model-generated estimates of long-term data. Performance prediction results are compared against actual observations at a 4 kW PV test facility. Results show that the VPI model-generated data, when used with the PVFORM model, provide the best predictions for AC power output from this 4 kW PV test facility. >