ISOLATED WIND HYDRO HYBRID SYSTEM USING …goaltechnologies.in/Power Electronics .pdfISOLATED...

ISOLATED WIND–HYDRO HYBRID SYSTEM USING CAGE GENERATORS AND BATTERY STORAGE

ABSTRACT

This paper deals with a new isolated wind-hydro hybrid generation system employing one squirrel-cage

induction generator (SCIG) driven by a variable-speed wind turbine and another SCIG driven by a

constant-power hydro turbine feeding three-phase four-wire local loads.

The proposed system utilizes two back-to-back-connected pulse width modulation controlled insulated-

gate-bipolar-transistor-based voltage-source converters (VSCs) with a battery energy storage system at

their dc link.

The main objectives of the control algorithm for the VSCs are to achieve maximum power tracking (MPT)

through rotor speed control of a wind-turbine-driven SCIG under varying wind speeds and control of the

magnitude and the frequency of the load voltage.

The proposed wind-hydro hybrid system has a capability of bidirectional active- and reactive-power

flow, by which it controls the magnitude and the frequency of the load voltage.

The proposed electromechanical system using SCIGs, an MPT controller, and a voltage and frequency

controller are modeled and simulated in MATLAB using Simulink and Sim Power System set toolboxes,

and different aspects of the proposed system are studied for various types of linear, nonlinear, and

dynamic loads, and under varying wind-speed conditions.

The performance of the proposed system is presented to demonstrate its capability of MPT, voltage and

frequency control (VFC), harmonic elimination, and load balancing.

TECHNO-ECONOMIC ANALYSIS OF SVC-HVDC TRANSMISSION SYSTEM FOR OFFSHORE WIND

ABSTRACT

One of the trends concerning offshore wind farms is to increase the distance from the wind farm to the

shore, and has to be transported over very long distances to make a connection with the main supply

grid. But placing wind farms offshore rises a lot o challenges related to construction, installation and

nevertheless with the energy transmission.

VSC HVDC is a rather new technology with promising characteristics for offshore wind transmission. And

the techno-economic value analysis for VSC HVDC is necessary as all projects require a maximal effort in

order to make the offshore wind farm viable. The possible structures for offshore wind farm and some

feasible turbine topologies for offshore wind were introduced in the paper.

Based on the grid code requirements, a techno-economic analysis for VSC HVDC with SCIG was

proposed. This HVDC system is compared to the main variable-speed topologies (DFIG and DDPMSG) in

combination with HVAC and a typical wind farm is put upfront to investigate. Result show that the SVC

HVDC transmission system with SCIC could get a cost-efficient.

GRID INTERCONNECTION OF RENEWABLE ENERGY SOURCES AT THE DISTRIBUTION LEVEL WITH POWER-

QUALITY IMPROVEMENT FEATURES

ABSTRACT

Renewable energy resources (RES) are being increasingly connected in distribution systems utilizing

power electronic converters. This paper presents a novel control strategy for achieving maximum

benefits from these grid-interfacing inverters when installed in 3-phase 4-wire distribution systems.

The inverter is controlled to perform as a multi-function device by incorporating active power filter

functionality. The inverter can thus be utilized as: 1) power converter to inject power generated from

RES to the grid, and 2) shunt APF to compensate current unbalance, load current harmonics, load

reactive power demand and load neutral current.

All of these functions may be accomplished either individually or simultaneously. With such a control,

the combination of grid-interfacing inverter and the 3-phase 4-wire linear/non-linear unbalanced load at

point of common coupling appears as balanced linear load to the grid.

This new control concept is demonstrated with extensive MATLAB/Simulink simulation studies and

validated through digital signal processor-based laboratory experimental results.

A NEW APPROACH TO MULTIFUNCTIONAL DYNAMIC VOLTAGE RESTORER IMPLEMENTATION FOR

EMERGENCY CONTROL IN DISTRIBUTION SYSTEMS

ABSTRACT

The dynamic voltage restorer (DVR) is one of the modern devices used in distribution systems to protect

consumers against sudden changes in voltage amplitude. In this paper, emergency control in distribution

systems is discussed by using the proposed multifunctional DVR control strategy.

Also, the multiloop controller using the Posicast and P+Resonant controllers is proposed in order to

improve the transient response and eliminate the steady-state error in DVR response, respectively. The

proposed algorithm is applied to some disturbances in load voltage caused by induction motors starting,

and a three-phase short circuit fault. Also, the capability of the proposed DVR has been tested to limit

the downstream fault current.

The current limitation will restore the point of common coupling (PCC) (the bus to which all feeders

under study are connected) voltage and protect the DVR itself.

The innovation here is that the DVR acts as a virtual impedance with the main aim of protecting the PCC

voltage during downstream fault without any problem in real power injection into the DVR. Simulation

results show the capability of the DVR to control the emergency conditions of the distribution systems.

RESEARCH ON THE WIND FARM REACTIVE POWER COMPENSATION CAPACITY AND CONTROL TARGET

ABSTRACT

Wind generation rapid development has brought challenge to the grid. Reactive voltage is the most

outstanding and one of the most concerned problems.

This paper introduces the concept of wind farms reactive power compensation and wind power grid

code with respect to reactive power regulation all over the world, gives the simplified approach to

estimate reactive power compensation capacity, and validates its efficiency with the case study.

From grid reactive voltage control target and practical operation routine, the paper analyses and

compares the impacts of two reactive power control targets, that is, constant voltage and constant

power factor, on the grid steady-state operation.

The conclusion shows that the reactive power compensation control target of wind farms should be

determined by the robustness of the grid integrated, hierarchical reactive power balance, wind turbines

reactive voltage control characteristic, and the reactive compensation device applied in wind farms.

FLEXIBLE D-STATCOM PERFORMANCE AS A FLEXIBLE DISTRIBUTED GENERATION IN MITIGATING FAULTS

ABSTRACT

This paper proposes a flexible D-STATCOM (Distribution Static COMpensator) and its new controller

system, that be able to both mitigate all types of faults and operate as a Distributed Generation (DG),

when it supplies power to sensitive loads while the main utility source is disconnected (i.e. it is under

islanded operating condition).

Thus D-STATCOM operates same as a flexible DG (FDG) and consequently, it is called Flexible D-

STATCOM (FD-STATCOM). This paper validates the performance of FD-STATCOM system to mitigate

power quality problems and improve distribution system performance under all types of system related

disturbances and system unbalanced faults, such as Line-to-Line (LL) and Double Line to Ground (DLG)

faults and supplies power to sensitive loads under islanding condition.

In this paper, the 12-pulse D-STATCOM configuration with IGBT is designed and the graphic based

models of the D-STATCOM are developed using the PSCAD/EMTDC electromagnetic transient simulation

program.

The reliability and robustness of the control schemes in the system response to the voltage disturbances

caused by LL and DLG faults and islanded operating condition are obviously proved in the simulation

results.

POWER SYSTEM STABILITY ENHANCEMENT USING STATIC SYNCHRONOUS SERIES COMPENSATOR (SSSC)

ABSTRACT

In this study, a static synchronous series compensator (SSSC) is used to investigate the effect of this

device in controlling active and reactive powers as well as damping power system oscillations in

transient mode.

The SSSC equipped with a source of energy in the DC link can supply or absorb the reactive and active

power to or from the line. Simulations have been done in MATLAB/SIMULINK environment.

Simulation results obtained for selected bus-2 in two machine power system shows the efficacy of this

compensator as one of the FACTS devices member in controlling power flows, achieving the desired

value for active and reactive powers, and damping oscillations appropriately.

MATRIX CONVERTER-BASED UNIFIED

POWER-FLOW CONTROLLERS

ADVANCED DIRECT POWER CONTROL METHOD

ABSTRACT

This paper presents a direct power control (DPC) for three-phase matrix converters operating as unified

power flow controllers (UPFCs). Matrix converters (MCs) allow the direct ac/ac power conversion

without dc energy storage links; therefore, the MC-based UPFC (MC-UPFC) has reduced volume and

cost, reduced capacitor power losses, together with higher reliability.

Theoretical principles of direct power control (DPC) based on sliding mode control techniques are

established for an MC-UPFC dynamic model including the input filter. As a result, line active and reactive

power, together with ac supply reactive power, can be directly controlled by selecting an appropriate

matrix converter switching state guaranteeing good steady-state and dynamic responses.

Experimental results of DPC controllers for MC-UPFC show decoupled active and reactive power control,

zero steady-state tracking error, and fast response times.

Compared to an MC-UPFC using active and reactive power linear controllers based on a modified

Venturini high-frequency PWM modulator, the experimental results of the advanced DPC-MC guarantee

faster responses without overshoot and no steady-state error, presenting no cross-coupling in dynamic

and steady-state responses.

MODELING, ANALYSIS, AND CONTROL FOR THE RECTIFIER OF HYBRID HVDC SYSTEMS FOR DFIG-BASED

WIND FARMS

ABSTRACT

In order to improve the dynamic performance of the hybrid HVdc system for doubly fed induction

generator wind farms, this paper presents the modeling, analysis, and control methods for its line-

commutated rectifier.

First, the state variable model of the rectifier subsystem on the reference frame is derived considering

different control modes of the current source inverter subsystem. Then, the ac current dynamic of the

rectifier subsystem is quantitatively analyzed based on the eigenvalue analysis method.

According to the analysis results, a double loop control scheme is designed: the inner loop utilizes the

inverse system control technique plus a switchable phase-lead compensator, and the outer loop

implements an ordinary propotional-integral controller.

Finally, the validity of the quantitative analysis method and the superiority of the proposed control

scheme are verified by Simulink / SimPowerSystems simulations.

PERFORMANCE ANALYSIS OF LCL-T RESONANT CONVERTER WITH FUZZY/PID CONTROLLER USING STATE

SPACE ANALYSIS

ABSTRACT

A closed loop series parallel resonant converter with LCL-T configuration has been simulated and

presented in this paper. The fuzzy/PID controller has been used for closed loop operation and the

performance of proposed converter has been estimated with the closed loop and the open loop

condition.

The mathematical model using state space approach has been developed and simulated using MATLAB.

The performance of the converter has been found to be better when the fuzzy controller has been

considered.

The Harmonic Spectrum and steady state error for various load condition have been obtained to

validate the role of controllers. The proposed approach is expected to provide better voltage regulation

for dynamic load conditions.

AVERAGE CURRENT CONTROLLED SWITCHING REGULATORS WITH CASCADE BOOST CONVERTERS

Power Electronics

ABSTRACT

A controller design methodology for an n-stage cascade boost converter is given using average current-

mode control. This class of converters has n-LC filters; thus, it will exhibit 2n-order characteristic

dynamics.

The proposed scheme employs the inductor current of the input stage and the capacitor voltage of the

output stage; thus, there are (n-1) capacitor voltages and (n-1) inductor currents that are not used for

feedback purposes.

The sensed current can also be used for one-cycle overload protection; therefore the full benefits of

current-mode control are maintained. Owing to the fact that this scheme uses only a reduced set of

variables for feedback, it is important to study the internal stability.

The results given in this study allow the designer to easily pinpoint the control circuit parameters that

optimise the converter-s performance. Experimental results are given for a 100 W switching regulator

where the robustness of the proposed controller is tested under changes in the input voltage and

output load.

ANALYSIS, DESIGN AND CONTROL OF ZERO-VOLTAGE SWITCHING QUASI-RESONANT-POSITIVE OUTPUT

SUPER LIFT LUO CONVERTER

Power Electronics

ABSTRACT

This study presents the analysis, design and voltage regulation of a zero-voltage switching quasi-

resonant-positive output super lift Luo converter with low switching losses for industrial applications

requiring regulated output voltage.

To increase the power packing density, a simple control method using an analogue resonant controller

UC3861 is used to regulate the output voltage against load variation and supply disturbance. The

performance of the controller is verified by developing a prototype model of the converter and

experimental results are presented.

The results reveal the superiority of using a single dedicated IC for voltage regulation. Also it is observed

that the converter provides maximum efficiency of 95% at full load.

NONISOLATED HIGH STEP-UP STACKED CONVERTER BASED ON BOOST-INTEGRATED ISOLATED

CONVERTER

Power Electronics, IEEE Transactions on

ABSTRACT

To obtain a high step-up gain with high efficiency in nonisolated applications, a high step-up technique

based on isolated-type converters is introduced in this paper. By stacking the secondary side of an

isolated converter in addition to its primary side, a high step-up conversion ratio and a distributed

voltage stress can be achieved.

Moreover, a careful choice of an isolated converter can provide zero-voltage switching, continuous input

current, and reduced reverse recovery on diodes.

Based on a conventional voltage-doubler-rectifier boost-integrated half-bridge converter, the derived

converter satisfies all these features, which make it suitable for high step-up applications.

The operational principle and characteristics of the proposed converter are presented, and verified

experimentally with a 135-W, 24-V input, 250-V output prototype converter for a LED driver.

SOFT-SWITCHING TECHNIQUES FOR EFFICIENCY GAINS IN FULL-BRIDGE FUEL CELL POWER CONVERSION


ABSTRACT

This paper presents a set of novel soft-switching techniques to increase the power conversion efficiency

in fuel cell (FC) systems using a full-bridge topology. For this purpose, a special right-aligned modulation

sequence is developed to minimize conduction losses while maintaining soft-switching characteristics in

the MOSFETs.

Traditional auxiliary elements in the primary, such as series inductors that are impractical for realizing

due to the extreme input current, are avoided and reflected to the output of the rectifier to minimize

circulating current and generate soft transitions in the output diodes.

As a result, the proposed combined techniques successfully reduce conduction losses, minimize reverse-

recovery losses in the output rectifiers, minimize transformer ringing, and ensure low stress in all the

switches. The high efficiency is maintained in the entire range of loading conditions (0%-100%) while

taking into consideration remarkable challenges associated with FC power conversion: high input

current, low voltage and poor regulation, and wide range of loading conditions.

A detailed analysis of the techniques for efficiency gains are presented and a phase-shift zero-voltage

switching topology is employed as a reference topology to highlight the mechanisms for performance

enhancement and the advantages in the use of the special modulation.

Experimental results of a 1-kW power converter are presented to validate the efficiency gains, illustrate

the benefits of the special modulation, and demonstrate the soft-switching transitions.

INTERLEAVED ACTIVE-CLAMPING CONVERTER WITH ZVS/ZCS FEATURES


ABSTRACT

In this paper, an interleaved soft-switching dc-to-dc converter configuration is proposed. It consists of

two parts: the primary side is a constant-frequency asymmetrical converter with active-clamp feature

and the secondary side is a series-resonant tank circuit.

The active-clamp circuit recycles the energy stored in the magnetizing inductance of transformer to

allow main/auxiliary switches turn-ON at zero-voltage switching and clamps the voltage stress of the

main switches. Series-resonant tank circuit employs the transformer leakage inductance and secondary

resonant capacitance to achieve zero-current switching of the output diodes.

The circuit features constant-frequency operation and soft switching for both the transistors and the

diodes. Interleaving operation of this configuration combines the aforementioned benefits and small

output capacitor.

Theoretical analysis and computer simulation of the converter were given. An 80-KHz 500-W

experimental circuit of the proposed converter was demonstrated.

INHERENT CLAMP FLYBACK–BUCK CONVERTER WITH WINDING CROSS-COUPLED INDUCTORS

Power Electronics, IET

ABSTRACT

An isolated interleaved buck-type converter is deduced by inserting a third winding of the coupled

inductor to each phase of the interleaved flyback converter.

By making some topology modifications and adding one small clamp capacitor, the existed power

switches of the derived flyback-buck converter can serve as the clamp switches for the interleaved

phase to absorb the leakage energy of the coupled inductor and to reduce the switch turn-off voltage

stress, which simplifies the circuit configuration and improves the circuit reliability.

Furthermore, the current falling rate of the output diodes is limited by the leakage inductance to

alleviate the output diode reverse-recovery problem. Finally, a 160-W 200-V-input 15-V-output

prototype is built and tested to verify the improved performance of the proposed converter.

A NOVEL CONTROL SCHEME OF SYNCHRONOUS BUCK CONVERTER FOR ZVS IN LIGHT-LOAD CONDITION


ABSTRACT

This paper proposes a new control technology that enables a synchronous rectifier (SR) buck converter

to realize zero voltage switching (ZVS) in light load condition. The SR control technique is applicable to

DC low voltage output because the replacement of output rectifier diode by MOSFET can minimize

conduction losses and increase the efficiency of the whole circuit.

However, the technique cannot achieve good efficiency in light load condition. The control technique

introduced in this paper enables a SR buck converter to carry out ZVS in light load condition to increase

efficiency. No extra auxiliary switches or RLC passive components are required; thus, it is low cost and

easy to control.

The output of buck converter with 5V/25W featured by SR is developed in this paper; the availability of

the technique introduced herein is also proven. The experimental results are satisfactory.

INTERLEAVED FOUR-PHASE BUCK-BASED CURRENT SOURCE WITH CENTER-TAPPED ENERGY-RECOVERY

SCHEME FOR ELECTRICAL DISCHARGE MACHINING


ABSTRACT

This paper proposes a center-tapped energy-recovery scheme used in the interleaved four-phase buck-

based current source in continuous-conduction mode for electrical discharge machining (EDM).

A pulse-machining current with high-slew rate is required for the EDM. Using the interleaving technique,

the output-current slew rate of the buck-based current source can be improved because of the

paralleled inductors at the start of discharge.

The proposed center-tapped energy-recovery scheme provides a major path for the inductor to release

its stored energy to avoid high-voltage stress in the output terminal when the gap is in the high-

impedance state.

The energy stored in the inductor is recovered to the input capacitor, and can be reused for machining.

The experimental results are provided as the verification of the high-output-current slew rate and the

energy recovery when the gap is in high-impedance state.

A SERIES-TUNED INDUCTIVE-POWER-TRANSFER PICKUP WITH A CONTROLLABLE AC-VOLTAGE OUTPUT


ABSTRACT

This paper presents a new type of series ac-processing pickup used in inductive-power-transfer

applications. The proposed pickup uses an ac switch operating under zero-current-switching conditions

in series with a resonant network to produce a controllable ac voltage source suitable for driving

incandescent lights. When a rectifier is cascaded onto this pickup, it can also produce a precisely

controlled dc voltage.

This topology eliminates the need to use an extra buck converter after the traditional series pickup for

controlling the output load voltage to a desired value, which may be different from the induced voltage

of the pickup.

Furthermore, this pickup has the ability to control the inductor current directly, and hence, eliminate

the transient inrush current at startup for the series-tuned resonant tank. The circuit is analytically

analyzed and the maximum efficiency for a 1.2-kW prototype is measured to be 93%.

BRIDGELESS HIGH-POWER-FACTOR BUCK CONVERTER


ABSTRACT

A bridgeless buck power factor correction rectifier that substantially improves efficiency at low line of

the universal-line range is introduced. By eliminating input bridge diodes, the proposed rectifier's

efficiency is further improved.

Moreover, the rectifier doubles its output voltage, which extends useable energy of the bulk capacitor

after a dropout of the line voltage. The operation and performance of the proposed circuit was verified

on a 700-W, universal-line experimental prototype operating at 65 kHz.

The measured efficiencies at 50% load from 115 and 230 V line are both close to 96.4%. The efficiency

difference between low line and high line is less than 0.5% at full load. A second-stage half-bridge

converter was also included to show that the combined power stages easily meet Climate Saver

Computing Initiative Gold Standard.

A NEW STRATEGY FOR CONDITION MONITORING OF ADJUSTABLE SPEED INDUCTION MACHINE DRIVE

SYSTEMS


ABSTRACT

A new strategy for monitoring the condition of adjustable speed induction machine drive systems is

presented in this paper. The main concept of the new method is to use the inverter to perform off-line

tests for quality assessment of the vulnerable components in the inverter, cable, and induction motor

automatically whenever the motor is stopped.

This new approach is suitable for monitoring system components that deteriorate gradually to failure, if

the degradation is observable. Off-line test methods for monitoring the quality of the 1) dc-link

aluminum electrolytic capacitor; 2) electrical connections; 3) cable and stator winding insulation; 4)

stator core; and 5) rotor bar are presented along with a summary of the failure mechanism and existing

test methods.

It will be shown that the new strategy can be implemented with minimal hardware requirements, and

that it has many advantages over existing off-line and on-line tests.

An experimental study performed under simulated fault conditions for each component shows that the

method provides a reliable and sensitive indication of drive system problems for reliable, efficient, and

safe operation.

A NEW SINGLE-PHASE TO THREE-PHASE CONVERTER USING QUASI Z-SOURCE NETWORK

Applied Power Electronics

ABSTRACT

This paper introduces a new cost effective structure of a 4-switch single-phase to three-phase converter

using a Quasi Z-source (QZs) network for induction motor drive applications.

In comparison to the traditional 6-switch structure, the proposed circuit reduces the cost of the system,

switching losses and the complexity of the control method as well as the interface circuits used to make

the trigger signals.

In addition, The Quasi Z-Source network, similar to the Z-Source network uses a unique LC network with

added advantages, such as; lower component ratings, reduced source stress, reduced component count

and simplified control strategies for Adjustable Motor Drives (ASD) which require large range of gain.

By controlling the zero shoot-through duty cycle, the converter can generate any desired output voltage,

even greater than the supply voltage. Consequently, the converter is capable of extending the output

voltage range, improving the power factor and reliability, reduces line harmonics and provides ride-

through ability at the voltage sag interval. Simulation results on the proposed converter have indicated

its efficiency and potential for further development.

OPEN LOOP V/F CONTROL OF INDUCTION MOTOR BASED ON HYBRID PWM WITH REDUCED TORQUE

RIPPLE

ABSTRACT

Voltage source inverter (VSI) fed induction motors are widely used in variable speed applications. Space

Vector Pulse Width Modulation (SVPWM) has become the successful techniques to construct three

phase sine wave Voltage Source Inverter (VSI) parallel to control three-phase induction motor using v/f

control. Because of the low maintenance and robustness induction motors have many applications in

the industries.

The speed control of induction motor is more important to achieve maximum torque and efficiency. VSI

fed induction motor produces a pulsating torque due to the application of non sinusoidal voltages.

Among the various modulation strategies Space Vector pulse width Modulation Technique is the

efficient one because it has better spectral performance and output voltage is more closed to sinusoidal.

Torque pulsation is strongly influenced by PWM technique used. This paper compares the torque ripples

of convectional space vector PWM with hybrid PWM techniques. In hybrid PWM both continuous PWM

and discontinuous PWM techniques are employed.

The open loop V/f control of induction motor with hybrid PWM shows better reduction in torque ripples

when compared with conventional space vector PWM technique. The simulated design is tested using

MATLAB 7.8.

ON DYNAMIC EFFECTS INFLUENCING IGBT LOSSESIN SOFT-SWITCHING CONVERTERSIN SOFT-SWITCHING

CONVERTERS


ABSTRACT

Two different dynamic effects influencing the insulated gate bipolar transistor (IGBT) losses in soft-

switching converters are demonstrated. The first one, the Dynamic tail-charge effect shows that the tail

charge is dependent not only on the absolute value of the current at turn-off, but also on the dynamics

of the current.

This effect may have a significant impact on the optimization of zero-current-switching converters. The

Dynamic conduction losses originate from the conductivity modulation lag of the IGBT. It is shown by

experiments that the on-state losses depend on the operating frequency.

Different methods to accurately determine the on-state losses are evaluated. It was found that the best

method is an indirect measurement, where the stray inductance is identified by the use of an oscillating

circuit. The experiments are performed under a sinusoidal current excitation at a fixed amplitude (150

A) for different frequencies (up to 104 kHz).

The switching devices used are IGBT modules rated 300-400 A/1200 V in a bridge-leg configuration.

From the experiments performed, it is found that IGBTs of a modern punch-though (PT) designs have

the lowest losses in the series-loaded resonant converters studied in this paper.

ASYMMETRIC DUTY CONTROL OF A DUAL-HALF-BRIDGE DC/DC CONVERTER FOR SINGLE-PHASE

DISTRIBUTED GENERATORS


ABSTRACT

A dual-half-bridge (DHB) converter is integrated with a half-bridge 60-Hz inverter as a converter/inverter

system for a small distributed generator. This topology provides an isolation between the power source

and the load with a 100-kHz transformer, and therefore, the system volume is small.

On the other hand, it reduces the number of switching devices greatly. However, the half-bridge inverter

causes severe capacitor-voltage fluctuations.

The unbalanced voltage problem can be solved by controlling the converter switching: In addition to the

conventional phase-shift control method, an asymmetric charging method is used that charges the

upper and lower secondary capacitors differently.

This means that the voltage imbalance is corrected by adjusting the switching time of the secondary

switches. Furthermore, a decoupling control algorithm can be derived from this approach. The

usefulness of this method is then validated by simulation and experimental results

ANALYSIS OF A NEW QUASI RESONANT DC LINK INVERTER

Power Electronics, Drive Systems

ABSTRACT

In this paper a new three phase DC link soft switching inverter is introduced. The auxiliary circuit of the

proposed inverter is composed of two switches beside the DC link switch. All switches in the proposed

inverter are soft switched.

The proposed auxiliary circuit provides zero voltage switching condition for the main inverter switches

independent of the link current direction.

An analysis of this inverter topology is presented and various operating modes are explained in details.

The inverter simulation is performed to validate the analysis.

MODELING AND ANALYSIS OF GRID HARMONIC DISTORTION IMPACT OF AGGREGATED DG INVERTERS


ABSTRACT

This paper proposes an impedance-based analytical method for modeling and analysis of harmonic

interactions between the grid and aggregated distributed generation (DG) inverters.

The root cause of harmonic interaction/resonance problems is the impedance-network quasi-resonance

between the effective output impedance of the inverter and the equivalent grid impedance at the

connection point. Starting with the output impedance modeling of an inverter, a Norton model of the

inverter is derived. Comparing with the switching model and the average model of the inverter,

simulation results show the effectiveness of the model.

This paper proposes that impedance limits should be specified and used as an extra design constraint for

DG inverters in order to minimize the harmonic distortion impact on the grid.

Assuming the impedance models of individual inverters and local loads within a distribution grid are

known, especially in the case of new grids under construction, harmonic interactions between the grid

and a certain number of DG inverters can be preliminarily estimated.

INTERLEAVED SOFT-SWITCHING BOOST CONVERTER FOR PHOTOVOLTAIC POWER-GENERATION SYSTEM


ABSTRACT

In this paper, a interleaved soft switching boost converter (ISSBC) for a photovoltaic (PV) power-

generation system is proposed. The topology used raises the efficiency for the dc/dc converter of the PV

power conditioning system (PVPCS), and it minimizes switching losses by adopting a resonant soft-

switching method.

A detailed mode analysis of the proposed topology is presented. The feasibility of the proposed

topology is experimentally verified for a 1.2-kW prototype.

The experimental results imply that 97.28% efficiency is achieved under the full-load condition.

Consequently, it is confirmed that the overall efficiency is increased by about 1.5% compared with the

conventional hard switching interleaved boost converter

A SIMPLE DIGITAL POWER-FACTOR CORRECTION RECTIFIER CONTROLLER


ABSTRACT

This paper introduces a single-phase digital power-factor correction (PFC) control approach that requires

no input voltage sensing or explicit current-loop compensation, yet results in low-harmonic operation

over a universal input voltage range and loads ranging from high-power operation in continuous

conduction mode down to the near-zero load.

The controller is based on low-resolution A/D converters and digital pulsewidth modulator, requires no

microcontroller or DSP programming, and is well suited for a simple, low-cost integrated-circuit

realization, or as a hardware description language core suitable for integration with other power control

and power management functions. Experimental verification results are shown for a 300-W boost PFC

rectifier.

A VERY HIGH FREQUENCY DC-DC CONVERTER BASED ON A CLASS PHI-2 RESONANT INVERTER


ABSTRACT

This paper introduces a new dc-dc converter suitable for operation at very high frequencies under on-off

control. The converter power stage is based on a resonant inverter (the 2 inverter) providing low switch

voltage stress and fast settling time compared to other resonant topologies.

A new multi-stage resonant gate driver suited for driving large, high-voltage rf MOSFETS at VHF

frequencies is also introduced.

Experimental results are presented from a prototype dc-dc converter operating at 30 MHz at input

voltages up to 200 V and power levels above 200 W under closed-loop control. These results

demonstrate the high performance achievable with the proposed design

INDIRECT VECTOR CONTROL OF INDUCTION MOTOR USING FUZZY LOGIC CONTROLLER

ABSTRACT

The paper presents a fuzzy logic speed control system based on fuzzy logic approach for an indirect

vector controlled induction motor drive for high performance.

The analysis, design and simulation of the fuzzy logic controller for indirect vector control induction

motor are carried out based on fuzzy set theory. The proposed fuzzy controller is compared with PI

controller with no load and various load condition.

The result demonstrates the robustness and effectiveness of the proposed fuzzy controller for high

performance of induction motor drive system.

PROSPECTS OF THE APPLYING OF UPFC IN MODERN DISTRIBUTION NETWORK

Power and Energy Engineering

ABSTRACT

Taking the unified power flow controller as an example, this paper states the applying foreground of

flexibility AC transmission system technology in distribution systems, which comprise wind power

generators.

As for the impacts of the wind power on the power systems, this paper indicates the deficits of the

unified power flow controller, proposes the idea that integrating the energy storage system into the DC

bus of the unified power flow controller, and the hybrid PCH control method can deal with the hybrid

systems introduced in above

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