ABSTRACT: In conventionalboostconverter like switched capacitor converter, switched inductor converter, cascaded boostconverter maximum voltage gain is limited due to extreme duty cycle. This results in reverse recovery problem at the switches, high conduction losses, high electromagnetic interference. These problems can be overcome by isolated converter such as fly back converter, push –pull converter , forward converter, bridge converter etc., however inclusion of transformer or coupled inductor introduces voltage spike and power loss. This project aims at providing different voltage levels required by the D.C load depending upon the power rating. The primary source of energy for DC micro grid is photovoltaic source. Therefore a very high voltage gain converter is designed which is realized by step up DC- DC converter. Steady state analysis and PWM control strategy is proposed in this paper. The proposed converter is simulated in Matlab.
Recently high voltage step-up converters have been proposed for fuel-cell based DC converter, battery discharged DC converter in UPS system,car auxiliary power supplies, automobile HID headlamps , and medical equipment.The conventionalboostconverter cannot realize high voltage step up due to the narrow allowed duty cycle. If high duty cycle is used in the boostconverter,the nonlinear voltage conversion characteristics due to the parasitic resistance is difficult to regulate the output voltage. Cascade boost converters have proposed for non-isolatedcircuit applications. Therefore the drawback of a conventionalboostconverter can be overcome by these circuit topologies for high voltage step up applications.but the main disadvantages are more components and difficult to control compare with the conventionalboost converter.Generally fig1 shows the conventionalboostconverter circuit.If the switch is in “on” position, then there is a short circuit through the switch.If the load is disconnected during operation, then L continues to push power to the right and very quickly charges C up to a high value.
ABSTRACT: A novel high step-up converter is proposed for a front end photovoltaic system. Through a voltage multiplier module, an asymmetrical interleaved high step-up converter usually high step up gain without act as a function at an extreme duty ratio. The voltage multiplier module is create of a conventionalboostconverter and coupled inductors. An extra conventionalboostconverter is combine into the first phase to achieve a considerably higher voltage conversion ratio. The two-phase configuration not only decreases the current stress through each power switch, but also force to do some thing the input current ripple, which decreases the conduction losses of metal–oxide– semiconductor field-effect transistors (MOSFETs). In addition, the proposed converter functions as an active clamp circuit, which moderate large voltage spikes across the power switches. Thus, the low-voltage-rated MOSFETs can be adopted for reduces of conduction losses and cost. Efficiency improves because the energy stored in leakage inductances is energized to the output terminal. Finally, the prototype circuit with a 40-V input voltage, 380-V output, and 1000- W output power is operated to verify its performance. The highest efficiency is 96.8%.
High gain dc/dc converters are widely used in many industrial applications such as solar, fuel cell, x-rays, laser and high intensity discharge lamp ballasts for automobile headlamps-. Theoretically, a basic boostconverter is capable of providing high conversion ratio, but extremely high duty ratio is required. In practice, extreme duty ratios are not permitted because of the large conduction losses and frequent damage of power switches. Usually it is preferable to use low voltage rated power switches having low on state resistance to reduce the conduction losses, which may not be possible in a conventionalboostconverter. Cascaded boost converters can provide high voltage gain-. But high voltage stress across the switches and poor efficiency are the disadvantages. DC/DC converters using coupled inductors is a good alternative to obtain a high step up gain, provided the leakage inductances are handled properly. Interleaved control is found very useful in reducing the input current ripple of the converter-. Two different boostconverter structures can be combined to produce twice the voltage gain by connecting there inputs in parallel and output in series. The two independent inductors of this combined converter is replaced by two coupled inductors. Connecting the primary windings of coupled inductors in parallel and secondary windings in series a high step up DC/DC converter is derived. An input parallel output series boostconverter with dual coupled inductors can be
The remaining plot in figure 4 and its insert, is most important since it represents the mode where the output conditions are controlled, as is the usual method of using the boostconverter. A region of discontinuous inductor current occurs, for duty cycle values above and below which operation returns to continuous conduction . The two boundary conditions for 0 1 are two of the roots of the cubic (see Appendix for the general expressions for roots of this cubic)
In interleaving technique an interconnection of multiple switching cells is done by synchronizing several frequency sources which helps to increase the effective pulse frequency and operating them with phase shift related to number of switching cells. Interleaving technique saves energy and improves power conversion without affecting conversion efficiency. This converter is consists of two boost conversion units parallely connected, having switches S1 and S2, inductors L1 and L2, diodes D1 and D2, Capacitor C and load resistor RL with common input source (VIN). The Circuit diagram for interleaved dc-dc boostconverter is shown in Fig.7.
solar supply along with additionally offers soft beginning of BLDC motor. The model is ensured study manifold parameter different effects upon the PV array in conjunction with operative temperature along with solar irradiation level. This paper accommodates associate degree analysis concerning the electrical phenomenon system’s interpretation in real time additionally to the issue worrying it such Temperature along with Irradiation. BLDC Motor speed is regulated all the way through electrical converter. The Z-source inverter is regulated via basic frequency shift, escaping the losses because of high-frequency switching; in regulate to reinforce the efficiency of the planned system.
ABSTRACT- An improved analysis of maximum power point tracking with incremental conductance of wind energy system array under partial shaded condition is proposed in this paper. In this paper we use the IC techinque, it is used to track the maximum power point of the PV source. MPPT can minimize the system cost and maximize the array efficiency. The proposed system is simple and cost effective. In this paper, a novel two- stage MPPT method is presented to overcome this drawback. In the first stage, a method is proposed to determine the occurrence of PSC, and in the second stage, using a new algorithm that is based on ramp change of the duty cycle and continuous sampling from the P-V characteristic of the array, global maximum power point of array is reached. Open loop operation of the proposed method makes its implementation cheap and simple. The IC algorithm was designed to control the duty cycle of Buck Boostconverter and to ensure the MPPT work at its maximum efficiency. The method is robust in the face of changing environmental conditions and array characteristics, and has minimum negative impact on the connected power system. By using the simulation results we can analyze the proposed method. Index Terms— DC/DC converter, maximum power point tracking (MPPT), Incremental conductance method, Partial shading condition, wind generation system.
The conventional PI controllers are fixed-gain feedback controllers. Therefore they cannot compensate the parameter variations in the process and cannot adapt changes in the environment. Pi controlled system is less responsive to real and relatively fast alterations in state and so the system will be slower to reach the set point.(24) Therefore the fuzzy control algorithm is capable of improving the tracking performance as compared with the classical methods for both linear and nonlinear loads. Also, fuzzy logic is appropriate for nonlinear control because it does not use complex mathematical equation. The two FLC input variables are the error E and change of error _E. The behavior of a FLC depends on the shape of membership functions of the rule base. In this paper a fuzzy logic control scheme (Fig.4) is proposed for maximum solar power tracking of the PV array with an inverter for supplying isolated loads. They have advantages to be robust and relatively simple to design since they do not require the knowledge of the exact model. On the other hand the designer needs complete knowledge of the hybrid system operation.
Batteries, ultra capacitors, fuel cells and solar arrays are widely used as energy storage units. In the structure of the electric power system of modern EVs/HVs more than one of these units are used to improve the performance and efficiency, therefore multiple input DC-DC converter is inevitable to obtain a regulated bus DC voltage. [5,6] As the available DC voltage sources have different magnitudes, they cannot be connected in parallel. Hence, they are connected in parallel through a series-connected active switch.
ABSTRACT: Solar energy is one of the renewable energies with highest potential. To use the solar energy efficiently, a battery storage system is usually added to balance the power difference between the PV generation and the load. In any PV system output may vary with time. In order to make the output constant, battery storage is added in the system. This paper proposes a new system, consist of two boost converters with a battery storage system for photovoltaic applications. In the two boostconverter one is SISO and other boostconverter is DISO. The proposed system has reduced number of switches. So switching losses reduces. It consists of four operational modes to achieve MPPT, battery charging and load regulation requirements. Experiment results are given to confirm the proposed converter. KEYWORDS: Photo Voltaic system (PV system), Single Input Single Output (SISO), Dual input Single Output (DISO), Maximum Power Point Tracking (MPPT).
Abstract — The efficiency of the DC-DC converters is an important issue which has received great attention in literature works. Nowadays, step up conversion is widely used in many applications like Electric vehicles, Photovoltaic (PV) system, Uninterruptable power supplies (UPS) and fuel cell system. Frequency dependent boostconverter and interleaved boost DC-DC converters presents a novel two-stage boostconverter with a soft switching operation. The converter units are connected to each other by an inductor known as interleaved inductor as a bridge. This inductor plays an important role in the soft switching operation of the converter by zero-voltage switching. By paralleling the converters, high reliability and efficiency in power electronic systems can be obtained. . Using high frequency converters we can get improved efficiency, reduced ripple voltage, reduced inductor current ripple. Both the converters are simulated using MATLAB/SIMULINK. The converters are tested by varying the frequency with constant duty cycle and varying the duty ratio with constant frequency in Continuous Conduction Mode(CCM). The performance parameters of the converters are compared. A circuit prototype of frequency dependent boostconverter is designed and tested to verify the proof of concept. The hardware realization is done using PIC16F877A controller.
Abstract— Increase in the use of power electronic equipment has resulted in greater need for regulating the harmonic distortion level in the power system. This is satisfied using some form of power factor correction (PFC) circuits to shape the input currents so that they are sinusoidal in nature and total harmonic distortion (THD) remains within the limit specified by 1EEE standard 519. This paper provides a review of the most commonly used active power factor correction (APFC) technique, boost type PWM rectifier for AC-DC converters and their control strategies. Simulation of the converter using APFC circuit is done and the results are analyzed.
to high switching losses and electromagnetic interference (EMI). So, it causes reduced performance and low efficiency. The soft switching (SS) techniques are proposed for resolving all of these adverse effects in interleaved converters [1- 8].The most advanced soft switching techniques are ZVT to turn on and ZCT to turn off. In the traditional ZVT converter, a gate signal is given to the main switch when its voltage falls to zero by means of active snubber cell. Thus, the main switch turns on with ZVT. Therewith, the main diode turns off and the auxiliary switch turns on with ZCS. But turning off of the main switch is not enough good and the auxiliary switch turns off under hard switching (HS) .
As per maximum power transfer theorem, the circuit delivers maximum power to the load when source impedance matches the load impedance. In case of stand-alone solar system dc-dc converter is connected in between PV array and the dc load. Maximum power point tracking (MPPT) system varies the duty cycle of the dc-dc converter in order to match source and load impedance and to deliver maximum power to the load. Various MPPT methods have been reported in the literature. These methods can be classified as: i) methods based on load line adjustment of I-V curve and ii) method based on artificial intelligence (fuzzy logic or neural network based MPPT methods). The MPPT methods viz. perturb and observe (P & O), incremental conductance (INC), voltage feedback (VF) are based on load line adjustment of I-V curve. These methods have been found less suitable under uncertainties due
This paper deals with a three-phase two- stage grid tied SPV (solar photo-voltaic) system. The first stage is a boostconverter, which serves the purpose of MPPT (maximum power point tracking) and feeding the extracted solar energy to the DC link of the PV inverter, whereas the second stage is a two- level VSC (voltage source converter) serving as PV inverter which feeds power from a boostconverter into the grid. The proposed system uses an adaptive DC link voltage which is made adaptive by adjusting reference DC link voltage according to CPI (common point of interconnection) voltage. The adaptive DC link voltage control helps in the reduction of switching power losses. A feed forward term for solar contribution is used to improve the dynamic response. The system is tested considering realistic grid voltage variations for under voltage and over voltage. The performance improvement is verified experimentally. The proposed system is advantageous not only in cases of frequent and sustained under voltage (as in the cases of far radial ends of Indian grid) but also in case of normal voltages at CPI. The THD (total harmonics distortion) of grid current has been found well under the limit of an IEEE-519 standard.
Power electronic circuits that convert electrical energy from one type to another form is known as power converter. In power electronic circuit, a converter is an intermediate device between source and load. There are various types converter in these electrical engineering field, which are DC-DC converter, AC-AC converter, DC-AC converter and AC-DC converter . The function of the DC-DC converter is same as the function of transformer. This is because DC-DC function used to convert from one level of current value or voltage value to another level either step up or step down voltage value which is same as the transformer function. In addition, power converter circuits have the options in controlling the output voltage normally. For the linear voltage regulators circuit, it is normally control by transistor. Figure 2.1 shows the basic circuit of the linear regulator on how it is used. However, in power converter circuit, it also have a device to control the circuit which is normally used such as BJT and MOSFET. Therefore, the controller of the circuit or the switching is the main component in order to operate the power converter. Figure 2.2 show the basic switching converter. The comparison between a basic switching converter and a linear voltage regulator shows that basic switching converter is better than linear voltage regulator . This is because it can increase the efficiency of the circuit.
Abstract:- This Paper introduces new hybrid converter topologies which can supply simultaneously AC as well as DC from a single DC source. The new Hybrid Converter is derived from the single switch controlled Boost and Buck-Boostconverter by replacing the controlled switch with voltage source inverter (VSI). This new hybrid converter has the advantages like reduced number of switches as compared with conventional design having separate converter for supplying AC and DC loads, provide DC and AC outputs with an increased reliability, resulting from the inherent shoot through protection in the inverter stage. For controlling switches PWM control, based upon unipolar Sine-PWM is described. Simulink model is used to validate the operation of the converter. The proposed Converter can supply DC and AC loads at 190 V and 48 V (rms) respectively from a 48 V DC source.
Voltage gain of the converter can be increased without increasing the duty cycle of the switch by connecting an intermediate capacitor in series with the inductor [Fig. 2(f)]. The intermediate energy storage capacitor with coupled inductor charges in parallel and discharges in series with the coupled inductor secondary. Various principles discussed in preceding paragraphs have also been used in combinations to achieve high voltage gain and enhanced features. A coupled inductor type boostconverter has been used in association with a passive clamp circuit to achieve high gain and increased efficiency. Converter configurations with coupled inductor in association with a voltage multiplier circuit and/or intermediate capacitor have also been reported to achieve high voltage gain. In recent times, use of coupled inductors along with intermediate capacitors has also become popular. Keeping in mind the merits and demerits of the various schemes described in preceding paragraphs, a novel topology has been proposed in this paper that achieves high voltage through a coupled inductor connected in interleaved manner that charges an intermediate buffer capacitor and a passive clamp network to recover the leakage energy. Coupled inductor leads to the incorporation of 'turn‟s ratio' into the gain expression that leads to high efficiency without increasing the duty ratio. As compared to existing high gain dc-dc converters, the number of passive components used in the proposed converter is less, which reduces the cost and improves the efficiency. Though the proposed converter is applicable to any low voltage source application (e.g. solar PV, Fuel cell stack, battery etc.), this paper focuses only on the solar PV source. All the details of this work are presented in the subsequent sections of the paper.
This topology combines KY converter with a traditional synchronously rectified (SR) buck-boostconverter and a coupled inductor with the turns ratio, which is used to improve the voltage gain. The duty cycle and the turns ratio are independent, which means that tuning the duty cycle does not affect the turns ratio and vice versa. And voltage gain can be determined by adjusting both the duty cycle and the turns ratio . Most of the converter topologies has one Right-Hand Zero (RHZ) in the transfer function under the continuous current mode (CCM) owing to instable operation. This will cause the parameters of the corresponding controller to be difficult to design and the transient load response to be slow.