Output Power Control Research Articles

Lossless Multiway Power Combining and Outphasing for High-Frequency Resonant Inverters

A lossless multi-way power combining and outphasing system have recently been proposed for high-frequency inverters and power amplifiers that offers major performance advantages over traditional approaches. This paper presents outphasing control strategies for the proposed power combining system that enable output power control through effective load modulation of the inverters. It describes a straightforward power combiner design methodology and enumerates various possible topological combiner implementations. Moreover, this study presents the first-ever experimental demonstration of the proposed outphasing system. The design of a 27.12 MHz, four-way power combining and outphasing system is described and used to experimentally verify the power combiner's characteristics. The proposed outphasing law is shown to be effective in controlling the output power over a 10-100 W (10:1) power range.

Proposed Control Method of Doubly Fed Induction Generator Rotor Side Converter Based on System Frequency Regulation

With the more penetration of wind power based on the DFIG wind turbine to the grid, there is increasing significance for controlling output power in order to meet power system requirements and to participate the frequency regulation in the power grid. This paper is presented proposed control method of DFIG implemented in the RSC using system frequency coordinated control. In this study, the GSC is controlled by using modified vector control method while the RSC is controlled by adjusting the rotor dq-axis currents. The quadrature axis current controls by using the active power generating from the frequency deviation and DFIG store kinetic energy, whereas the direct axis current is controlled by using grid reactive power. Moreover, this power is also used as a main parameter besides rotor speed to control the pitch angle blade in the turbine side. To confirm this method study, the system operation is conducted at steady state and transient modes, and the simulation results were carried out using PSCAD software program. The simulation results show that the voltage of DFIG is very stable, and the system frequency response has been improved. Furthermore, this study realized a full rated value of rotor speed and stable operation of DFIG active power at a steady state besides a good transient response. Moreover, the pitch angle control provided adequate control action at dynamic mode to decrease turbine torque hence to lead to safety transient mode operation.

배터리 충전을 위한 소형풍력 발전 시스템의 한계 풍속에 관한 연구

Three phase PWM(Pulse Width Modulation) converter of the small-scale wind power system is able to charge battery under the rated wind speed regions. However, it is impossible to control output power of converter at the over win speed region because back-EMF(Electro Motive Force) of PMSG(Permanent Magnet Synchronous Generator) is higher than the battery terminal voltage of PMSG is reduced. However, the cut-off wind speed exists although battery charging algorithm is implemented by flux weakening control method. Therefore, this paper performs analysis of other factors which affects limitation wind speed. The validity of the analysis are verified through simulation.

Numerical Optimization and Power Output Control of a Hot Thermal Battery with Phase Change Material

Numerical simulations were conducted to investigate the release of heat from a thermal storage unit, which we refer to as a hot thermal battery. The battery is composed of a hexagonal arrangement of parallel tubes through which a heat absorbing fluid flows, surrounded by phase change material (PCM) that fills spaces between adjacent tubes. The simulations implemented, aimed to optimize the battery such that it meets a total volume constraint while ensuring a critical power output before the phase change fronts of the PCM surrounding two adjacent heat transfer tubes merge—indicating the PCM is completely solidified—after which, only sensible heat can be released by the battery. It was found that the PCM latent heat has negligible impact on the optimal heat exchanger (HEx) design. In comparison, increasing either the flow velocity of the heat transfer fluid in the tubes or PCM thermal conductivity can significantly reduce the needed volume of heat exchanger. Additionally, a novel closed loop control modeling approach is proposed to dynamically tune the heat transfer fluid flow rate such that the thermal battery yields a constant power output. The flow tuning results indicate the optimal dynamic HTF velocity curve shape, obtained from closed-loop method, is unique and this optimal flow velocity is dependent on the location of the phase change front. Numerical results were also compared against hot battery discharge experiments, using both constant and dynamically tuned flow rates, indicating a good agreement for both cases.

A Digital Polar CMOS Power Amplifier With a 102-dB Power Dynamic Range Using a Digitally Controlled Bias Generator

A digitally modulated CMOS power amplifier (DPA) for a polar transmitter with a high dynamic range is presented. To improve local oscillator (LO) leakage, which limits the minimum output power of the DPA, the unit amplifier cell of the DPA employs a balanced mixer-type LO canceller at the power stage and a virtual ground is introduced in the layout of the output-power combining networks. A high dynamic range of the output power is simply achieved by adjusting gate-bias voltage of a cascode transistor in each power amplifier (PA) cell using a digitally controlled bias generator. This architecture allows a few-mA drain current at a low Tx power level without degrading the linearity. An array of unit PA cells is segmented to have a 10-bit amplitude resolution, and the bias generator is designed to have 8-bit control of the average output power. The peak output power is 24.4 dBm with an overall efficiency of 43% at 800 MHz. The total output dynamic range is 102.8 dB. A simple static pre-distortion helps the DPA achieve an average efficiency of 35% with a root mean square error vector magnitude of 3.59% while delivering linear output power of 22 dBm for WCDMA. The range of the digital transmit-power control for the WCDMA signal is 49.7 dB. This chip is fabricated in a 65-nm RF CMOS process.

Direct AC–AC Resonant Boost Converter for Efficient Domestic Induction Heating Applications

Domestic induction heating (IH) is currently the technology of choice in modern domestic applications due to its advantages regarding fast heating time, efficiency, and improved control. New design trends pursue the implementation of new cost-effective topologies with higher efficiency levels. In order to achieve this aim, a direct ac-ac boost resonant converter is proposed in this paper. The main features of this proposal are the improved efficiency, reduced component count, and proper output power control. A detailed analytical model leading to closed-form expressions of the main magnitudes is presented, and a converter design procedure is proposed. In addition, an experimental prototype has been designed and built to prove the expected converter performance and the accurateness of the analytical model. The experimental results are in good agreement with the analytical ones and prove the feasibility of the proposed converter for the IH application.

고역률을 갖는 단일 전력변환 AC-DC 컨버터

This paper proposes a single power-conversion ac-dc converter with a dc-link capacitor-less and high power factor. The proposed converter is derived by integrating a full-bridge diode rectifier and a series-resonant active-clamp dc-dc converter. To obtain a high power factor without a power factor correction circuit, this paper proposes a suitable control algorithm for the proposed converter. The proposed converter provides single power-conversion by using the proposed control algorithm for both power factor correction and output control. Also, the active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. Moreover, it provides zero-voltage turn-on switching of the switches. Also, a series-resonant circuit of the output-voltage doubler removes the reverse-recovery problem of the output diodes. The proposed converter provides maximum power factor of 0.995 and maximum efficiency of 95.1% at the full-load. The operation principle of the converter is analyzed and verified. Experimental results for a 400W ac-dc converter at a constant switching frequency of 50kHz are obtained to show the performance of the proposed converter.

Control Strategies for AC Fault Ride Through in Multiterminal HVDC Grids

A fully operational multiterminal dc (MTDC) grid will play a strategic role for mainland ac systems interconnection and to integrate offshore wind farms. The importance of such infrastructure requires its compliance with fault ride through (FRT) capability in case of mainland ac faults. In order to provide FRT capability in MTDC grids, communication-free advanced control functionalities exploiting a set of local control rules at the converter stations and wind turbines are identified. The proposed control functionalities are responsible for mitigating the dc voltage rise effect resulting from the reduction of active power injection into onshore ac systems during grid faults. The proposed strategies envision a fast control of the wind turbine active power output as a function of the dc grid voltage rise and constitute alternative options in order to avoid the use of classical solutions based on the installation of chopper resistors in the MTDC grid. The feasibility and robustness of the proposed strategies are demonstrated and discussed in the paper under different circumstances.

Automatic power controlled, load compensated magnetic resonant wireless power transmitter

As compared to other wireless transfer mechanism, like the inductive coupling method, magnetic resonance-based wireless power transfer can achieve power transfer over a larger distance. However, as the transmission range increases, the change in the load impedance lowers the transmission efficiency in the currently available magnetic resonance-based wireless power transmitters. This article presents a CMOS transmitter for magnetic resonant wireless battery charging system. A class-E power amplifier (PA) with an automatic power control loop and load compensation circuit is proposed to improve the power efficiency. The transmitted power is controlled by adjusting the signal applied to the gate of the power control transistor. In addition, a parallel capacitor is also controlled to enhance the efficiency and compensate for the load variation. The proposed design is implemented using 0.35 μm BCD technology with an active area of around 5 mm × 2.5 mm. The transmitter provides an output power control range of 9–30.2 dBm. The measured maximum power efficiency of the PA is 70.2%.

Fuzzy Predictive Control of a Boiler–Turbine System Based on a Hybrid Model System

This paper proposes a fuzzy predictive control scheme for controlling power output of a boiler–turbine system in the presence of disturbances and uncertainties. A new model of the boiler–turbine system is introduced based on the modeling approaches of hybrid systems, namely, the mixed logical dynamical modeling approach. Nonlinear parts of the system are linearized using the piecewise affine approach. To overcome the deficiency of the model predictive control in presence of disturbance and uncertainty, a fuzzy predictive control scheme is proposed in which a fuzzy supervisor is utilized to adjust the main predictive controller. The proposed fuzzy predictive control scheme has advantages such as simplicity and efficiency in nominal conditions and strong robustness in the presence of disturbances and uncertainties. Simulation results demonstrate the effectiveness and superiority of the method.

Analysis and design of high-efficiency resonant inverters for domestic induction heating applications

Nowadays, the induction heating market is continuously growing due to its benefits including precise output power control, reduced heating times, and cleanness. The domestic induction heating application, based on the same principle, in- cludes some extra features such as the controlled temperature profiles or over-temperature detection for an outstanding cooking process. Because of the high power density and the reduced cooling capabilities, efficiency becomes critical in this applica- tion. This paper introduces some techniques to improve the efficiency of the induction heating power converters. The proposed converters are analyzed, including the main losses sources, proving that the proposed solution improves the overall efficiency while the component count and cost are keep to reasonable values.

A high efficiency transmitter and receiver for magnetic resonant wireless battery charging system in 0.35 μm BCD

This paper presents a transmitter and receiver for magnetic resonant wireless battery charging system. In the receiver, a wide-input range CMOS multi-mode active rectifier is proposed for a magnetic resonant wireless battery charging system. The configuration is automatically changed with respect to the magnitude of the input AC voltage. The output voltage of the multi-mode rectifier is sensed by a comparator. Furthermore, the configuration of the multi-mode rectifier is automatically selected by switches as original rectifier mode, 1-stage voltage multiplier or 2-stage voltage multiplier mode. As a result, a rectified DC voltage is output from 7.5 to 19 V for an input AC voltage of 5---20 V. In the transmitter, a class-E power amplifier (PA) with an automatic power control loop and load compensation circuit is proposed to improve the power efficiency. The transmitted power is controlled by adjusting the signal applied to the gate of the power control transistor. In addition, a parallel capacitor is also controlled to enhance the efficiency and compensate for the load variation. This chip is implemented using 0.35 μm BCD technology with an active area of around 5,000 × 2,500 μm. When the magnitude of the input AC voltage is 10 V, the power conversion efficiency of the multi-mode active rectifier is about 94 %.The maximum power efficiency of the receiver is about 70 %. The transmitter provides an output power control range of 10---30.2 dBm. The maximum power efficiency of the PA is 71.5 %.

Voltage magnitude and frequency control of three‐phase voltage source inverter for seamless transfer

This study presents voltage magnitude and frequency control of a three-phase voltage source inverter for distributed generations to achieve a seamless transfer between grid-tied mode and intentional islanding mode. When the grid is normal, the inverter works in grid-tied mode. On the contrary, when the grid fault occurs, the breaker connecting the inverter to the grid must be turned off and the inverter just supplies the power for local loads. By varying the frequency and the magnitude of the inverter output voltage, an output power control, with which the output active and reactive power can be precisely controlled, is presented. To improve the transient response, a virtual inductor with high-pass filter in synchronous d-q frame is proposed. The effectiveness of the virtual inductor is explained by the frequency response of the inverter. Finally, experimental results are given to verify the effectiveness of the scheme.

Dynamic Responses Improvement of Grid Connected WPGS Using FLC in High Wind Speeds

Environmental and sustainability concerns are developing the significance of distributed generation (DG) based on renewable energy sources. In this paper, dynamic responses investigation of grid connected wind turbine using permanent magnet synchronous generator (PMSG) under variable wind speeds and load circumstances is carried out. In order to control of turbine output power using Fuzzy Logic controller (FLC) in comparison with PI controller is proposed. Furthermore, the pitch angle based on FLC using wind speed and active power as inputs, can have faster responses, thereby leading to smoother power curves, enhancement of dynamic performance of wind turbine and prevention of mechanical damages to PMSG. Inverter adjusted the DC link voltage and active power is fed by d-axis and reactive power is fed by q-axis (using P-Q control mode). Simulation of wind power generation system (WPGS) is carried out in Matlab/Simulink, and the results verify the correctness and feasibility of control strategy.

Relationship between static postural control and type of muscle power output in middle-aged and older men

Relationship between static postural control and type of muscle power output in middle-aged and older men

Effects of Wind Generation Uncertainty and Volatility on Power System Small Signal Stability

This paper discusses the impacts of large scale grid-connected wind farm equipped with permanent magnet synchronous generator (PMSG) on power system small signal stability (SSS) incorporating wind generation uncertainty and volatility. Firstly, a practical simplified PMSG model with rotor-flux-oriented control strategy applied is derived. In modeling PMSG generator side converter, the generator-voltage-oriented control strategy is utilized to implement the decoupled control of active and reactive power output. In modeling PMSG grid side converter, the grid-voltage-oriented control strategy is applied to realize the control of DC link voltage and the reactive power regulation. Based on the Weibull distribution of wind speed, the Monte Carlo simulation technique based is carried out on the IEEE 16-generator-68-bus test system as benchmark to study the impacts of wind generation uncertainty and volatility on small signal stability. Finally, some preliminary conclusions and comments are given.

Thermochemical Heat Storage – System Design Issues

Thermochemical materials (TCMs) are a promising solution for seasonal heat storage, providing the possibility to store excess solar energy from the warm season for later use during the cold season, and with that all year long sustainable energy. With our fixed bed, vacuum reactors using zeolite as TCM, we recently demonstrated long-term heat storage with satisfactory output power. For domestic application, however, it will be necessary to considerably increase storage density and to reduce system costs. In this paper, we discuss issues on system, component and material levels for realizing a commercially attractive system. We first discuss a modular, fixed bed concept with a hot water storage. We show that with proper dimensioning of TCM modules and hot water storage, one can obtain a system where daily storage and on-demand heat delivery can be arranged by the hot water storage, while demands on output power, power control and material stability during operation are relaxed as much as possible. We also discuss atmospheric and central reactor concepts, which may provide lower-cost TCS systems. An important issue on component level is the implementation of a low temperature source providing evaporation heat in winter. We discuss several options, including the application of solar collectors in winter. Heat storage density can be increased by an order of magnitude by applying hydration reactions of hygroscopic salts, but this introduces physical and chemical stability issues during repeated cycles of hydration and dehydration. We discuss several of these stability issues as well as possible stabilization in a composite TCM, which should also provide sufficient vapor and heat transport.

Increasing the Efficiency of Grid Tied Micro Wind Turbines in Low Wind Speed Regimes

Major problem with grid tied micro wind turbine is synchronization and wind variability. Due to this problem the stability of available grid gets reduced. The stability can be achieved by output power control of the turbine. Major part of many countries like India, the annual mean wind speed is not high. The rated wind speed of turbine remain around 11 m/s and cut in is around 3.5 m/s. Due to this problem we aimed to develop a sustainable wind energy system that can provide stable power supply even at the locations of low wind speed of 2 - 4 m/s. To address this issue, a momentary impulse or external torque to the rotor by external motor is one of the good options to maintain the momentum of blades and thus provide stability for sufficient time. Various theoretical calculations and experiments are conducted on the above method. This would increase the output power and also the efficiency of wind turbine. We show that Return-On-Investment will be high as compared with other grid connected turbines. Our proposed concept in the present study, if implemented properly, can help the installation of number of wind turbines even at domestic level. It also makes the consumers energy independent and promotes the use of wind as a source of energy and may enter as a rooftop energy supply system similar to solar.

Controlled Soil Warming Powered by Alternative Energy for Remote Field Sites

Experiments using controlled manipulation of climate variables in the field are critical for developing and testing mechanistic models of ecosystem responses to climate change. Despite rapid changes in climate observed in many high latitude and high altitude environments, controlled manipulations in these remote regions have largely been limited to passive experimental methods with variable effects on environmental factors. In this study, we tested a method of controlled soil warming suitable for remote field locations that can be powered using alternative energy sources. The design was tested in high latitude, alpine tundra of southern Yukon Territory, Canada, in 2010 and 2011. Electrical warming probes were inserted vertically in the near-surface soil and powered with photovoltaics attached to a monitoring and control system. The warming manipulation achieved a stable target warming of 1.3 to 2°C in 1 m2 plots while minimizing disturbance to soil and vegetation. Active control of power output in the warming plots allowed the treatment to closely match spatial and temporal variations in soil temperature while optimizing system performance during periods of low power supply. Active soil heating with vertical electric probes powered by alternative energy is a viable option for remote sites and presents a low-disturbance option for soil warming experiments. This active heating design provides a valuable tool for examining the impacts of soil warming on ecosystem processes.

English

The ever increasing energy demand, along with the necessity of cost reduction and higher reliability requirements, are driving the modern power systems towards Distributed Generation (DG) as an alternative to the expansion of the current energy distribution systems. This paper is aimed to introduce the new controller in order to control of output power of one of the most important types of distributed generation namely micro-turbine, during system load variations. Micro-turbine output power should be controlled against the load variations in island mode condition and a controller should be designed for this purpose. Here, the PID controller is used which its coefficients are optimized based on ‘evolutionary programming’ algorithm. Simulation results are done for various loads in time domain, and the results show the efficiency of the proposed controller. Key words: Micro-turbine, evolutionary programming, distributed generation, controller design, optimization.