Abstract—A novel high-power modular input-series-input- paralleloutput-series connected DC/DC converter for medium- voltage application is proposed. Emphasis has been placed on power sharing control to compensate parameter mismatches and achieve equal power distribution between modules. Converter control is extended to achieve fault-tolerant operation by exploiting modularity to provide redundancy in the event of any failure. The proposed control scheme is validated through application-level simulations and scaled- down experiments to testify the reliability of the proposed control for ensuring power sharing between modules under a range of operating conditions. The results validate the proposed converter and associated control scheme indicating this to be a promising topology for high-power medium-voltage applications.
In this paper, a high-power modular structure DC/DC converter which is realized by input-series-input-paralleloutput-series (ISIPOS) connection of modules is proposed. Parallel-series architectures can be classified into four categories based on their connection. These categories are inputparalleloutputparallel (IPOP), inputparalleloutputseries (IPOS), inputseriesoutputparallel (ISOP) and inputseriesoutputseries (ISOS) . Currently, the open literature contains no publication in the field of the ISIPOS converter and its control strategy. This structure enables generation of high output voltage with reduced voltage and current stresses at the input side. Moreover, the use of high-frequency (HF)
Abstract: High-power converters for high-voltage direct current transmission systems and collecting networks are attracting increasing interest for application in large offshore wind farms. Offshore wind farms are capable of generating more electric energy at lower cost when compared with onshore wind systems. In this study, DC/DC voltage conversion should be achieved with a power converter that uses readily available semiconductor devices. A modular DC/DC converter can achieve the required system currents and voltages without exceeding semiconductor ratings. In this study, the operation and control strategy for an input-series–input-parallel–output-series (ISIPOS) energy conversion system for wind systems are presented. The ISIPOS system allows the direct connection of wind turbines to the DC grid. In this research, the design process to control the input and output currents and voltages is explained. In addition, a new method to ensure voltage and current sharing between the different modules is presented and explained. The basic structure, control design, and system performance are tested using MATLAB/ SIMULINK. Practical results validate the control design flexibility of the ISIPOS topology when controlled by a TMSF280335 DSP.
Low input voltage and high energy step changes, this paper successfully developed and series' inductor production volumes and parallelinput techniques as high-voltage disidisi Converter has been achieved. And to explore the benefits of the proposed changes is the main theory, a stable condition of the operating principles, and the performance of the main circuit wave is described. The following are some important aspects of the changes proposed: 1) it is receiving excessive voltage increase, and in turn ratio of working in harsh and duty cycle can be avoided; 2) The main key pressure voltage output voltage, which is a quarter of that, are very low, 3) automatically input current can be shared with each stage and low ripple investment currents are obtained; Under N = 1 4) ZCS damage major change has been so reduced that can be turned into the main switch. And 5) leakage inductance diodes current is controlled in the fall, so that recovery diode solve the opposite problem everyday. At the same time, a major weakness of each switch duty cycle 180◦ phase shift control of interleaved with at least 50%.
For increasing the voltage magnitude previously charge pump were introduced. Charge pumps are nothing but circuits that generate output voltage higher than input one. Charge pump also consists of source and capacitors for generating higher voltages.With the advances of power electronics devices multilevel converter topologies came into picture for generating more levels with high output voltage. In this series cascaded hybrid inverter firstly came in which inverter uses several H-bridge connected in series to provide output sinusoidal voltage. But it has more voltage stress on device and more dc sources so diode clamped multilevel inverter came into picture which uses clamping diodes to limit voltage stress on devices. In these series flying capacitors MLI also came into existence for getting higher levels and to overcome the disadvantages of all other MLI. Multilevel inverters using series/ parallel dc voltage sources was also used for getting high multilevel voltage but it was having so many switches and elements so switched capacitor inverter using series/parallel came for overcoming all disadvantages.
A single-phase nine-level inverter for grid- connected photovoltaic systems, with pulse width-modulated (PWM) control scheme is proposed. Three reference signals that are identical to each other with an offset that is equivalent to the amplitude of the triangular carrier signal were used to generate the PWM signals. The inverter is capable of producing nine levels of output-voltage levels from the dc supply voltage. Multilevel inverters offer improved output waveforms and lower THD. A PWM switching scheme for the multilevel inverter is generally preferred. By controlling the modulation index, the desired number of levels of the inverter’s output voltage can be achieved. The DC–DC converters based topology applied for high-voltage and high-power applications were introduced. The converter is configured such that the boost - half-bridge (BHB) cells and voltage doublers are connected in parallel and in series to increase the output voltage and the output power. In addition to reduced device voltage and current ratings by the connection, the converter has the advantages of high-step-up voltage gain with significantly reduced transformer turn ratio, low input current ripple due to interleaving effect, zero- voltage switching turn-ON of switches and zero-current switching turn-OFF of diodes. The converter has reduced volume of input and output filters resulting from the interleaved switching. Another advantage provided by the multiphase converter is output ripple cancellation, which results in increasing the effective output frequency.
Nowadays high voltage gain DC-DC converters are required in many industrial applications.Photovoltaic energy conversion systems and fuel-cell systems usually need high step up and large input current dc-dc converters to boost low voltage (18-56 V) to high voltage (200- 400 V) for the grid-connected inverters. High-intensity discharge lamp ballasts for automobile headlamps call for high voltage gain DC-DC converters to raise a battery voltage of 12 V up to 100 V at steady operation. Also, the low battery voltage of 48 V needs to be converted to 380 V in the front-end stage in some uninterruptible power supplies and telecommunication systems by high step- up converters. Theoretically, abasic boost converter can provide infinite voltage gain with extremely high duty ratio. In practice, the voltage gain is limited by the parasitic elements of the power devices, inductor and capacitor. Moreover, the extremely high duty cycle operation may induce serious reverse-recovery problem of the rectifier diode and large current ripples, which increase the conduction losses. On the other hand, the input current is usually large in high output voltage and high power conversion, but low-voltage-rated power devices with small on resistances may not be selected since the voltage stress of the main switch and diode is, respectively, equivalent to the output voltage in the conventional boost converter. Many other converter topologies have developed for high step up gain. Here a high gain input-paralleloutput-series DC-DC converter with dual coupled inductors is designed.This configuration inherits the merits of high voltage gain, low output voltage ripple, and low voltage stress across the power switches.Moreover, the converter is able to turn ON the active switches at zero current and alleviate the reverse recovery problem of diodes by reasonable leakage inductances of the coupled inductors [11-12].
voltage gain of conventional three-state switching boost converter is only determined by the duty ratio -. Moreover, the voltage stresses of the power devices are still equivalent to output voltage. Thus, the large duty ratios, high switch voltage stresses and serious output diode reverse recovery problem are still major challenges for high step-up and high power conversion with satisfactory efficiency. To solve above drawbacks, some three-state switching converters with high static gain employing diode-capacitor cells were presented . However, several diode-capacitor cells are required to meet a very high step-up gain. Thus, other topologies using three state switching cell and coupled inductors are investigated in -. Reference  proposes an interleaved boost converter with coupled inductors and a voltage doubler rectifier in order to satisfy the high step-up applications and low input current ripple, in which the secondary sides of two coupled-inductors are connected in series. The winding-cross-coupled inductors and output diode reverse-recovery alleviation techniques are also introduced in an interleaved three-state switching DC– DC converters -, which can get a considerably high voltage conversion ratio and improve the performance of the converter. In , an interleaved fly-back converter based on three-state switching cell for high step up and high power conversion is proposed. Although the converter can eliminate the main limitations of the standard fly-back, this circuit is a little complex and the input current ripples are large from the experimental results.
Figure 4 shows the simulation model of proposed system. The fundamental principle behind the operation of BDHC is based upon the fact that the inverter bridge input must be connected to a positive voltage during the power interval only.This means that the inverter output has to be modulated when vsn ?= 0 andboost operation occurs when vab = 0. The inverter output voltage assumes three different values, and hence, the PWMmodulation strategy used is based upon unipolar sine-PWMscheme, which provides three voltage levels for output. The PWM control scheme for the BDHC is based upon the switching scheme proposed. In this scheme, shown in Fig. 4 the shoot-through is realized by gating-on both the switches of a single leg at the same time. The switching strategy involves turning on only one leg at a time in order to achieve shoot- through. Another alternative is to turn on all the switches during shoot-through. As shown in the figure, turning on all the switches for shoot-through involves more switching during each switching period with their associated losses. The reliability of the circuit also reduces since the time between two successive switching is dependent on tz which can be close to zero. This may be impractical considering minimum switching times for the devices used.
Tab. 2 , compared with the conventional interleaved DC-DC Boost converter, the proposed converter benefits from higher voltage-gain and lower voltage stress for the power semiconductors. The proposed topology can also achieve a higher voltage-gain than the voltage-gain of the three-level DC-DC Boost converter. In addition, compared with the topology in , the voltage stress for each power semiconductor of the proposed topology is half of the output voltage. Regarding the input current ripple, the converter in  suffers the highest input current ripple among these converters, because its input current is a pulse current which is discontinuous. According to Error! Reference source not found., when these converters have the same parameters, such as the output voltage U o , the duty cycle d, the switching
In comparison with an AC network, a DC collection grid offers a number of potential benefits. The use of DC can better utilise the cable voltage rating and eliminates the charging current associated with long AC cables. These issues may become of increasing importance as the capacity and area of offshore wind farms increase. A medium-voltage DC collection grid also has the potential to reduce losses through the use of medium-voltage converters and better optimisation of conversion stages . Additionally, a DC collection grid may reduce the size and weight of the required plant and power units . Present offshore farms connect to conventional 50 or 60Hz AC systems by employing mains- frequency transformers to step up the generator output voltage to collection network voltage levels. Advances in DC/DC converters, particularly High-Frequency (HF) technologies [2, 3], allow the heavy line-frequency transformer in an AC grid to be replaced by a high- or medium-frequency transformer, leading to significant weight and size savings.
Abstract: Large offshore wind farms require extensive sub-sea cables within the collection network. Present solutions are based around medium-voltage AC collection networks. Recent studies have highlighted the potential benefits of DC collection networks. However, achieving DC/DC conversion at the required voltage and power levels presents a significant challenge for wind-turbine power electronics. This paper proposes an alternative DC collection network based around a modular DC/DC converter with input-paralleloutput-series (IPOS) connection. This modular topology can overcome the limitations imposed by semiconductor voltage ratings and provides fault-tolerant operation. Small-signal analysis of the converter is presented to be used to facilitate controller design for the converter input and output stages. A new master- slave control scheme and distributed voltage sharing controllers are proposed that ensure power sharing under all operating conditions, including during failure of a master module. This control scheme achieves fault-tolerant operation by allowing the status of master module to be reallocated to any healthy module. The proposed control scheme is validated using simulation and experimentation, considering active power sharing between modules with parameter mismatch.
The proposed interleaved boost converter with dual coupled inductor based topology is used to convert the given low input voltage to higher voltage and hence producing high voltage gain. Interleaved converters can improve voltage gain. Here interleaving is done by combing a conventional boost converter and boost converter with diode in the negative dc- link rail. The system also employs a dual couple inductor whose primary is connected in series and output side is connected in parallel (IPOS). IPOS connection has the advantage of having capability of handling high input current and high output voltage. Secondary sides of coupled inductor are connected in series to form a voltage doubler module. This module further doubles the voltage gain. The clamp capacitor and clamp diode in this module also serves as a path to release energy stored due to leakage inductance in coupled inductor.
used for high step up and high power applications. The interleaved control adopted reduces the input current ripple considerably. This configuration inherits the merits of high voltage gain, low voltage stress across the power switches and low output voltage ripple. Also, the converter is capable to turn on the active switches at zero current and hence reduce switching losses.
Lv Xiaopeng et al. (2011) presented a fully on-chip Low Drop-Out (LDO) voltage regulator with 150mA driving capability, which is implemented in 180 nm CMOS technology. This proposed LDO voltage regulator uses paralleled input differential pairs and current amplifiers to provide fast transient response, achieving 1.4μs settling time with transient variation less than 155mV, while consuming 90μA quiescent current . A two stage cascoded operational transconductance amplifier is used to designed error amplifier by Herminio Martinez-Garcia et al. (2012) that achieve high DC gain and PSRR of 34.3 dB at 10 KHz . Leo C. J. et al. (2013) proposed an ultra low power capacitor less low drop out voltage regulator with High PSR of -95dB at 5MHz which is integrated with medical body area network (MBAN) transceiver having drop of 300mV and implemented on 0.13 μm CMOS IP6M process . A slew rate enhancement circuit is proposed (Cheekala Lovaraju et al. (2013)) that improves the transient response and have high loop bandwidth with improvement in settling time by 61% . Fan Yang et al.(2014) design LDO that enhance the transient response using active feedback and damping factor control technique which in turn use to drive 50mA load with dropout of 200mV on 65nm CMOS process . Sau Siong Chong et al. (2014) proposed a capacitor-less low drop out regulator which enhance the transient response by using push pull composite power transistor with drop out of 700mV and implemented on UMC 65-nm CMOS technology. It consumes a very low quiescent current of 16.2 μA . Sreehari Rao Patri et al. (2014) presented a stable LDO voltage regulator with a novel Double Recycling Error Amplifier structure which enhance the slew rate and implemented on UMC 180-nm CMOS process . Longjie Du et al. (2014) had make use of shunt feedback as a buffer stage and the LDO regulator becomes stable for all the load conditions. Author also employs a current boosting circuit to reduce the output voltage. This paper achieved a very low quiescent current with low output voltage variation . Chang-Joon Park et al. (2014) introduce the concept of adaptive noise compensation scheme to improve the PSRR at high frequency. This paper also utilizes the concept of replica pass transistor . Seong Jin Yun et al. (2015) presented a capacitor-less low dropout regulator for enhanced power supply rejection. The proposed scheme is implemented with 0.18 μm CMOS technology by an additional capacitor at a gate node of a pass transistor. Simulation results show the optimum value of the capacitor gives a PSR better than -40 dB up to 5 MHz with a 50 mA load current 
The water data provided in the WIOD are used in this paper to calculate, for the first time, the water use, the water footprint and the water trade balance for all the countries reported in the database (for further information see Timmer et al., 2012). From a methodological point of view, water data in the WIOD are estimated by using the concepts of blue, green and grey water as proposed by Hoekstra et al. (2011). In addition, the agricultural water use of the WIOD has been estimated based on data on crop production and livestock provided from FAOSTAT and based on the crop and livestock water intensities proposed by Mekonnen and Hoekstra (2010a; 2010b). Similarly, the water evaporated from artificial reservoirs to produce electricity has been calculated using the world average water use per unit of electricity as estimated by Mekonnen and Hoekstra (2011b) and the hydropower generation from the IEA. The use of water in other economic sectors has been calculated by using the total water use in industry as reported by Mekonnen and Hoekstra (2011a), the shares of water use by industry in the EXIOPOL database, and the sectoral gross output at constant prices from the WIOD. Finally, water use by households is estimated on the basis of the average domestic water supply from Mekonnen and Hoekstra (2011a) and population data from the United Nations.
to search for optimal stabilizer parameters. Different control schemes have been proposed in and tested on a weakly connected power system with different disturbances loading conditions and parameter variations. The problem of poorly damped, low frequency oscillations, associated with the generator rotor swings has been a matter of concern to power engineers for along time. Damping of electro-mechanical oscillations between interconnected synchronous generators is necessary for secure system operation. These problem is improved, in , a fuzzy set theory based algorithms has been suggested for coordinate stabilizers so as to increase the operational dynamic stability margin of power system for TCSC and UPFC in power system environments. A hybrid fuzzy logic algorithm has been proposed for the coordination of FACTS controllers in power system. The coordination method is well suitable to series connected FACTS devices like TCSC, SSSC in damping multi-modal oscillations in multi-machine power systems .
A periodic signal can be represented by the complex exponential form of the Fourier series. When a periodic signal is applied to the input of a filter, each of the harmonic components of the input signal experiences an amplitude and phase change caused by the filter. At the filter output the harmonic components add together to produce the output waveform. The amplitude and phase changes experienced by each of the input components combine to make the output signal different from the input signal in a predictable way.
Conventional BJTs have limited frequency response range. In any amplifier design, it is always necessary to give utmost attention to its frequency response analysis. While applying frequency response for some application it is also important to extend the bandwidth of an amplifier. Increasing the bandwidth means increasing the upper 3 dB frequency and decreasing the lower 3 dB limit. There are several approaches by which this range can be extended  . An extended range allows use of the BJT based system for multiple applications. A simple approach to extend the bandwidth of the BJT amplifier is the use of negative feedback. Such works have already been explored and studied extensively  . Another approach is to combine multiple feedback configurations and derive additional benefits. Here, we discuss such an approach. We have analyzed the detail frequency response provided by composite structures formed using combinations of known feedback topologies. The work includes detailed theoretical analysis of the proposed topology and responses to various parameter variations considered. The theoretical analysis show that the proposed approaches provides considerable improvement in bandwidth expansion and enables multiple frequency dependent applications. Experimental works suggest that cascade topologies provide improved performance. Especially series shunt - shunt shunt topology provides the best bandwidth expansion. Compared to series-shunt topology, the proposed approach provide 30% betterment while in comparison to shunt shunt topology, the improvement is 22%.