The alternative energy resources, like solar, are always complementary due to envi- ronmental changes. Energy generation with the sources such as solar and wind is gaining importance and of that photovoltaic conversion is the main focus of re- searches due to its promising potential as the electrical source. This paper presents the constant voltage method of control where the output of the converter is main- tained constant irrespective of the variations in the irradiance with the high step-up isolated efficient single switch DC-DC converter for the solar PV systems. Constant voltage method of control uses the array of photovoltaic systems as its energy source. The output of the Solar PV systems is nonlinear and has its dependency on tempera- ture and irradiance by which the panel voltage and current varies with the variation in irradiance. Constant voltage control method always operates in such a way that the converter voltage is tried to be maintained constantly to the reference voltage which is set by the user. The system used here utilizes high step single switch isolated DC-DC converter and monitors the voltage continuously by varying the duty cycle to maintain the converter voltage always constant. As a way of improving the perfor- mance, both the open and closed loop analysis is done where the closed loop analysis uses the PI controller for its performance. The model is implemented in MATLAB and it accepts the irradiance as the input and outputs the constant voltage from the converter and the feasibility of the proposed converter topology is confirmed with experimental results of the prototype model.
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The calibration of the mean and fluctuating voltages from a hot-wire operated in the constant voltage mode in a hypersonic flow is examined. Three approaches to relate the hot- wire measurements to mean and fluctuating mass flux and total temperature are evaluated. The first calibration approach, PDR, is based on the ratio of the power dissipated in the hot-wire and the difference between the hot- and cold-wire resistances. This calibration method implicitly accounts for variations in the fluid temperature. The ratio of the power dissipated in the hot-wire and the difference between the hot- and cold-wire resistances is readily obtained in terms of the CVA’s diagnostic voltages, that is the measured CVA output voltage and the specified hot-wire voltage. This approach yields the mean mass flux values. Included with the PDR method is the calculation of the mean total temperature from the “cold wire” or recovery temperature. Once the temperature coefficient of resistance and recovery factor are known, this approach produces excellent mean total temperature results. The second approach, Mixed Mode method, is based on Morkovin’s generalized expressions for the hot-wire response and yields normalized mean square values of the mass flux and total temperature. The third approach, Semi-Empirical Heat Transfer method, is based on the traditional semi-empirical King’s relation for supersonic/hypersonic flows. This approach yields both mean and mean square values of the mass flux and total temperature.
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In a battery pack, cell-to-cell chemical variation, or the variation in operating conditions, can possibly lead to current imbalance which can accelerate pack ageing. In this paper, the Pseudo-Two- Dimensional(P2D) porous electrode model is extended to a battery pack layout, to predict the overall behaviour and the cell-to-cell variation under constant voltage charging and discharging. The algorithm used in this model offers the ﬂexibility in extending the layout to any number of cells in a pack, which can be of different capacities, chemical characteristics and physical dimensions. The coupled electro- thermal effects such as differential cell ageing, temperature variation, porosity change and their ef- fects on the performance of the pack, can be predicted using this modelling algorithm. The pack charging voltage is found to have an impact on the performance as well as the SEI layer growth. Numerical studies are conducted by keeping the cells at different thermal conditions and the results show the necessity to increase the heat transfer coefﬁcient to cool the pack, compared to single cell. The results show that the thermal imbalance has more impact than the change in inter-connecting resistance on the split current distribution, which accelerates the irreversible porous ﬁlling and ageing.
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Accelerated constant voltage test was conducted in 3.5 wt.% NaCl (CR grade, Tianjin Yongda Chemical) solution at room temperature with 3.5 V applied to the work pieces by CHI 760D electrochemical workstation (CH Instruments, Shanghai, CHINA). The counter and reference electrode were connected together to a graphite electrode with the same dimension as the specimens. The distance between anode and cathode was set as 90 mm. In order to avoid any edge effects, all the edges of each specimen were sealed by wax.
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Abstract— This paper aims at designing of an optimized controller for non-isolated DC-DC Single-Ended Primary- Inductance converter (SEPIC) for constant voltage applications. The SEPIC converter can both step up and step down the input voltage, while maintaining the same polarity and the same ground reference for the input and output. MOSFETs are used as a switching device in low power and high frequency switching applications. It may be noted that, as the turn-on and turn-off time of MOSFETs are lower as compared to other switching devices, which reduces the switching losses. High frequency operation of MOSFET reduced size of filters components. These converters are now being used for various applications, such as Switched Mode Power Supply (SMPS) etc. The paper attempts to present parametric variation analysis of SEPIC converters for constant voltage output
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The Battery Charger Specification presents solution for rechargeable batteries used in portable electronic equipment such as laptop computer systems, cellular telephones and video cameras and the demands for low cost battery chargers are rising these days without give attention for the performance. The goal of the paper was combining high efficiency and versatility with low-cost design and this paper includes the design of the snubber cell, and the components of the current/voltage control charge method. This charger applies a relatively constant current and constant voltage to the battery indefinitely regardless of the AC input rang voltage all the equations described in this paper. The design of pro- totype converter is verified through an experimental result.
When the controlled switch (e.g. MOSFET) ‘S’ is on by by pulse width modulation (PWM), then input voltage appears across the inductor L, filter capacitor, C and load resistor R and current in inductor L increases linearly. In the same cycle the capacitor C is charged. During mode 1, the diode reversed biased and resulted from flowing current, the input provides energy to the load as well as to the inductor.
Examples of the first category are dc motors and filaments for large vacuum tubes. While the starting resistance of these loads is very low compared to the normal operating value, it is not necessary that the power supply be able to deliver this peak current--it is necessary that the supply withstand without damage this initial peak load condition and that it continue to operate through the peak load interval until normal load conditions are established. For such loads Constant Voltage/Constant Current or Constant Voltage/Current Limiting supplies rated for the normal (not the peak) load condition are adequate and, in some cases preferable, since the limited output current can provide protection for the load device during the peak load interval. Peak load demands in excess of the current rating of the power supply will not result in damage to the power supply; the output voltage will merely drop to a slightly lower value. Normal output voltage will be restored automatically by the power supply after the peak or transient load condition has passed.
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for improving the function of MPPT. Accordingly, the dual control loops, an outer voltage control loop, and an inner current control loop are applied to control the DC–DC Boost converter as shown in Fig. 5. Since the output voltage of the DC–DC Boost converter is the DC bus voltage that is controlled to be a constant voltage by the five-level inverter, the outer voltage control loop is used to regulate the output voltage of the solar cell array. The inner current control loop is applied to control the inductor current to approach a constant current to block the ripple voltage of dc bus voltage V dc . The perturbation and observation method is adopted to obtain the function of MPPT, and it is incorporated
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Modeling and simulation results of a pulse skipping modulated buck converter for applications involving a source with widely varying voltage conditions with loads requiring constant voltage from full load down to no load is presented. The pulses applied to the switch are blocked or released on output voltage crossing a predetermined value. The regulator worked satisfactorily over a wide input voltage range with good transient response but with higher ripple content. Input current spectrum indicates a good EMI performance with crowding of components at audio frequency range for the selected switching frequency.
The aim in designing Maximum power point controller is to find the voltage and current at which a Photovoltaic array operates to obtain maximum power under the given temperature and irradiance. Practically we have multiple local maxima, but overall there should be only one true MPP (Maximum power point. To find the optimal point and improve the efficiency of energy conversion we have done a controller design and verified its performance on the MPPT algorithms. The solar energy absorbed by the photovoltaic panel does not always generate a fixed output so a regulator should be connected before charging the battery. A voltage regulator is designed to automatically maintain a constant voltage level.
Current super capacitor conventional charging methods . a) Constant vol- tage charging method: in the charging process, the method of charging voltage is always called the constant voltage charging method. The advantage of this me- thod is that it can avoid the loss of the active material of the plate and the loss of electric energy due to the excessive charging current in the later period of charging. The disadvantage is that the charging current is too large at the begin- ning of charging, which makes it easy to bend the capacitor plate and cause the capacitor to be scrapped. b) Constant-current charging method: in the charging process, the charging current is always the same method called the constant cur- rent charging method. This method makes the capacitor charging time short- ened. In the maximum allowable charging current range, the greater the charg- ing current, the shorter the charging time. However, if the charging current is kept at the same level during the later period of charging, the electrolyte will precipitate excessive bubbles and appear boiling. This not only wastes power, but also easily causes the temperature of the battery to rise too high, causing the sto- rage capacity of the capacitor to decline and be discarded in advance. c) Cur- rent-mode PWM control charging. This kind of charging method increases the terminal voltage of the supercapacitor in real-time and analyzes and processes the PWM signal to change the charging current. It can improve the charging ef- ficiency, but its disadvantage is the need for MCU intervention, and the circuit is complex and costly. Therefore, a simple and practical charging scheme was de- signed for the project.
(CC) mode and then the transition to constant voltage (CV) is demonstrated. The CCCV control is implemented by choosing the minimal value of two parallel controllers, as it can be seen in Figure 3. At t < 0, the converter operates in CC mode and the output current is limited to 2 A. The load R load = 10 Ω results in an output voltage of U out = 20 V. The voltage limit is set to U max = 24 V. After
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The world is facing energy crisis now a days. Non-renewable energy resources are getting used up very fast. So renewable energy resources are gaining popularity now. The most popular renewable energy resource is solar energy. Photovoltaic cells (PV) are used to harvest solar energy. PV cells convert the solar radiation to DC form of electrical energy. Their output have to be given to the grid. The grid provides a fixed voltage fixed frequency AC power all the time. So the output from the PV cells have to be converted suitably to connect it with the grid. The output from the PV cells varies with climatic and weather conditions. In morning and evening time the solar radiations are very feeble. In night it is almost zero. In noon time the solar radiation is maximum. So we can see that the input to the PV cell is not a constant. So the output also varies. The output voltage from the PV cells will be maximum when the solar radiation is higher and the output will be minimum when the radiation is lower. So the output from the PV cell array have to be made constant so that they can be connected to the grid. Also the output from the PV cell array is a DC value. So the DC voltage have to be converted to AC voltage for connecting it to the grid. So we require a power converter i.e. a DC/AC converter. Also the power have to be modulated. If the output voltage from the converter is less than the grid voltage then it have to be stepped up (boost). If the output voltage from the converter is higher than the grid voltage then it have to be stepped down (buck). So there have to be a power modulator. Conventional power converters have one DC/AC inverter and the AC/AC power modulator. So they require two stage operation.
This is a fixed switching frequency control strategy. The figure above shows the various components of the control scheme. The negative input of the PWM Comparator is fed with a ramp of frequency equal to desired switching frequency. The boost switch is kept on until the ramp voltage equals the error amplifier output voltage. The error amplifier compares the actual inductor current with the reference current. The capacitor Cf will have a value enough to behave as short at switching frequency and hence at switching frequency the amplifier gain will be Rf/R2. In this way the average value of the inductor current will follow the reference current with almost zero tracking error.
UNIT I TRANSISTOR BIAS STABILITY 9 BJT – Need for biasing – Stability factor - Fixed bias circuit, Load line and quiescent point. Variation of quiescent point due to h FE variation within manufacturers tolerance - Stability factors - Different types of biasing circuits - Method of stabilizing the Q point - Advantage of Self bias (voltage divider bias) over other types of biasing, Bias compensation – Diode, Thermister and Sensistor compensations, Biasing the FET and MOSFET.
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A modified BFOA approach for placement of SVC has been designed and presented. A multi-objective function comprising voltage deviation, system overload and real power losses were determined and optimised using modified BFOA. For all the cases, the proposed approach delivered better results like reducing the real power loss, considerable increment in the voltage profile, reducing the overload and limiting the voltage deviation. The results of comparison with other optimisation approaches also testify the suitability of the present approach in identifying the location and size of SVC. The performance of the proposed approach has been compared for cost and reduction in real power loss by taking Neyveli Thermal Power Station (IU-NTPS) case.
In Electrical vehicle Battery is used as a power source for vehicle motor. So Battery has to be recharg regularly. A constant current constant voltage is required for battery charging. In simulation of charging station a constant current and constant voltage is achieved with the use of PI controller.In BLDC drive simulation a hysteresis current control technique is used for a control a applied motor current for control a speed of BLDC motor.
In the pilot cell MPPT algorithm, the constant voltage or current method is used, but the open- circuit voltage or short-circuit current measurements are made on a small solar cell, called a pilot cell, that has the same characteristics as the cells in the larger solar array.13 The pilot cell measurements can be used by the MPPT to operate the main solar array at its MPP, eliminating the loss of PV power during the VOC or ISC measurement. However, the problem of a lack of a constant K value is still present. Also, this method has a logistical drawback in that the solar cell parameters of the pilot cell must be carefully matched to those of the PVarray it represents. Thus, each pilot cell/solar array pair must be calibrated, increasing the energy cost of the system.
Abstract: In todays world, the mobility of goods and people is its peak. To make this happen there are numerous vehicles which can deliver this service. In most recent trends, to avoid damage to the environment Electric Vehicles are extensively used. Tremendous amount of research is going on the field of Electric Vehicle such as Battery Types for improvement in overall performance, inclusion of other factors such as Ultra capacitors for betterment of overall performance, advancement in Brushless DC motors which will be more suitable to use in E- Vehicles. Many of research units have solved the issues related with the above topics. The more focus is to be given on the charging and discharging time for E Vehicles. In this paper, various charging discharging methods used for Lithium ion batteries are discussed. The methods such as constant current (CC) method, constant voltage (CV) method, constant current constant voltage method(CC-CV), constant temperature constant voltage method(CT-CV).Not only the Fast Charging methods will be sufficient to make real change in the Li-ion Batteries but also the materials that are used in these batteries should have the capacity to handle the fast charging. So, according to material properties and specifications the battery needs to be designed and as per fast charging methods suitable fast charging technique can be implemented to it.