A CASCADED MULTILEVEL INVERTER BASED
ON SWITCHED-CAPACITOR FOR HIGH-FREQUENCY
AC
POWER DISTRIBUTION SYSTEM
ABSTRACT
The increase of
transmission frequency reveals more merits than low- or medium-frequency
distribution among different kinds of power applications. High-frequency
inverter serves as source side in high-frequency ac (HFAC) power distribution
system (PDS). However, it is complicated to obtain a high-frequency inverter
with both simple circuit topology and straightforward modulation strategy. A
novel switched-capacitor-based cascaded multilevel inverter is proposed in this
paper, which is constructed by a switched-capacitor frontend and H-Bridge
backend. Through the conversion of series and parallel connections, the
switched capacitor frontend increases the number of voltage levels. The output
harmonics and the component counter can be significantly reduced by the
increasing number of voltage levels. A symmetrical triangular waveform
modulation is proposed with a simple analog implementation and low modulation
frequency comparing with traditional multicarrier modulation
EXISTING SYSTEM
The existing applications can be found in computer
telecom electric vehicle and renewable energy micro grid However, HFACPDS has
to confront the challenges from large power capacity, high electromagnetic
interference (EMI), and severe power losses A traditional HFAC PDS is made up
of a high-frequency (HF) inverter, an HF transmission track, and numerous
voltage-regulation modules (VRM). HF inverter accomplishes the power conversion
to accommodate the requirement of point of load (POL). In order to increase the
power capacity, the most popular method is to connect the inverter output in
series or in parallel. However, it is impractical for HF inverter, because it
is complicated to simultaneously synchronize both amplitude and phase with HF
dynamics. Multilevel inverter is an effective solution to increase power
capacity without synchronization consideration, so the higher power capacity is
easy to be achieved by multilevel inverter with lower switch stress.
PROPOSED SYSTEM
A switched-capacitor (SC) based multilevel circuit
can effectively increase the number of voltage Levels. However, the control
strategy is complex, and EMI issue becomes worse due to the discontinuous input
current. A single-phase five- level pulse width-modulated (PWM) inverter is constituted
by a full bridge of diodes, two capacitors and a switch. However, it only
provides output with five voltage levels, and higher number of voltage levels is
limited by circuit structure An SC-based cascaded inverter was presented with
SC frontend and full bridge backend. However, both complicated control and
increased components limit its application Based on the situation
aforementioned, a novel multilevel inverter and simple modulation strategy are presented to serve
as HF power source.
BLOCK DIAGRAM
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CIRCUIT DIAGRAM
ADVANTAGES
·
The number of voltage levels increases
twice in half cycle of 9-level circuit, and the number of voltage levels
increases three times in half cycle of 13-level circuit. With the exponential increase
in the number of voltage levels, the harmonics are significantly cut down in
staircase output, which is particularly remarkable due to simple and flexible
circuit topology.
·
Meanwhile, the magnitude control can be
accomplished by pulse width regulation of voltage level, so the proposed
multilevel inverter can serve as HF power source with controlled magnitude and
fewer harmonics
APPLICATIONS
·
Generate almost sinusoidal waveform
voltage while only switching one time per fundamental cycle.
·
Dispense with multi-pulse inverters'
transformers used in conventional utility interfaces and static var
compensators.
·
Enables direct parallel or series
transformer-less connection to medium- and high-voltage power systems.
A
High-Efficient Nonisolated Single-Stage On-Board
Battery Charger for Electric
Vehicles
Abstract
The design and
implementation of a high-efficiency non isolated single-stage on-board battery
charger (OBC) for electric vehicles are presented. Reviewing the conventional
topologies, a suitable circuit structure is determined to charge a battery in a
wide spectrum of input and output conditions. Additionally, a suitable strategy
for a highly efficient OBC is presented through the analysis of selected topology.
Existing
system
Nevertheless, a
two-stage structure with transformer has been a common rule in OBC design.
However, there is no such requirement in standards for safety of EVs as
specified in SAE J1772 (from the North American standard for electrical
connectors for EVs maintained by the Society of Automotive Engineers). Furthermore,
there is no electrical reason that the battery should be isolated from ac input
power, because its ground is generally floating with the body ground of the
vehicle. Moreover, other power conversion units connected to the high voltage battery
are deactivated when the OBC transmits power to the battery. In terms of
safety, a relay added on the output can be substituted for the roles of
transformers in isolated topologies. Hence, a high-efficiency nonisolated
single-stage OBC is reasonable. This type of OBC features strong points of
decreasing losses and volume, since the transformer that affects the efficiency
and power density can be removed.
Proposed System
The design of a highly efficient
nonisolated single-stage OBC for EVs is presented, and the experimental
verification of the charging performance is provided. A discussion is also presented
for the selection of topology by reviewing the efficiency and power density of
conventional topologies. Based on the results of the review, the structure and
the operational principles of the proposed system are described. Then, the
possible operation modes in the proposed structure are given. By considering available
modes in the input and output conditions for charging a battery, the control
strategies are also provided.
Block Diagram
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Circuit diagram
Advantages
Ø The number of components is less than
conventional OBCs.
Ø High-power density and high efficiency are
obtained by the single-stage structure without the high-frequency transformer
Ø High performance is also attained in the wide
input and output voltage range for charging a battery.
Applications
· Modern energy regeneration applications such
as low-speed wind, wave, electric bikes, and regenerative suspension in
vehicles.
A Bridgeless
Boost Rectifier for Low-Voltage
Energy Harvesting Applications
Abstract
In this paper,
a single-stage ac–dc power electronic converter is proposed to efficiently
manage the energy harvested from electromagnetic microscale and mesoscale generators
with low-voltage outputs. The proposed topology combines a boost converter and
a buck-boost converter to condition the positive and negative half portions of
the input ac voltage, respectively. Only one inductor and capacitor are used in
both circuitries to reduce the size of the converter.
Existing
system
In energy
harvesting systems, power electronic circuit forms the key interface between
transducer and electronic load, which might include a battery. The electrical
and physical characteristics of the power conditioning interfaces determine the
functionality, efficiency, and the size of the integrated systems. The power
electronic circuits are employed to 1) regulate the power delivered to the
load, and 2) actively manage the electrical damping of the transducers so that
maximum power could be transferred to the load. The output voltage level of the
microscale and mesoscale energy harvesting devices is usually in the order of a
few hundred millivolts depending on the topology of device. The output ac
voltage should be rectified, boosted, and regulated by power converters to
fulfill the voltage requirement of the loads. Nonetheless, miniature energy harvesting
systems have rigid requirement on the size and weight of power electronic interfaces.
Conventional ac–dc converters for energy harvesting and conditioning usually
consists of two stages. A diode bridge rectifier typically forms the first
stage, while the second stage is a dc–dc converter to regulate the rectified ac
voltage to a dc voltage. However, the diode bridge would incur considerable
voltage drop, making the low-voltage rectification infeasible.
Proposed system
The boost converter is the common power
conditioning interface due to its simple structure, voltage step-up capability,
and high efficiency. The buck-boost converter has ability to step up the input
voltage with a reverse polarity; hence, it is an appropriate candidate to
condition the negative voltage cycle. Besides, the boost and buck-boost
topologies could share the same inductor and capacitor to meet the miniature
size and weight requirements. A new bridgeless boost rectifier, which is a unique
integration of boost and buck-boost converters, is proposed in this paper. When
the input voltage is positive, S1
is turned ON and D1 is reverse
biased, the circuitry operates in the boost mode. As soon as the input voltage
becomes negative, the buck-boost mode starts with turning ON S2 and reverse biasing D2. MOSFETs with bidirectional
conduction capability work as two-quadrant switches to ensure the circuitry
functionality in both positive and negative voltage cycles. This topology was
introduced for piezoelectric energy harvesting applications
Block Diagram
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Circuit Diagram
Advantages
·
This
employs the minimum number of passive energy storage components, and achieves
the maximum conversion efficiency.
Applications
· Modern energy regeneration applications such
as low-speed wind, wave, electric bikes, and regenerative suspension in
vehicles.
A Bridgeless
Boost Rectifier for Low-Voltage
Energy Harvesting Applications
Abstract
In this paper,
a single-stage ac–dc power electronic converter is proposed to efficiently
manage the energy harvested from electromagnetic microscale and mesoscale generators
with low-voltage outputs. The proposed topology combines a boost converter and
a buck-boost converter to condition the positive and negative half portions of
the input ac voltage, respectively. Only one inductor and capacitor are used in
both circuitries to reduce the size of the converter.
Existing
system
In energy
harvesting systems, power electronic circuit forms the key interface between
transducer and electronic load, which might include a battery. The electrical
and physical characteristics of the power conditioning interfaces determine the
functionality, efficiency, and the size of the integrated systems. The power
electronic circuits are employed to 1) regulate the power delivered to the
load, and 2) actively manage the electrical damping of the transducers so that
maximum power could be transferred to the load. The output voltage level of the
microscale and mesoscale energy harvesting devices is usually in the order of a
few hundred millivolts depending on the topology of device. The output ac
voltage should be rectified, boosted, and regulated by power converters to
fulfill the voltage requirement of the loads. Nonetheless, miniature energy harvesting
systems have rigid requirement on the size and weight of power electronic interfaces.
Conventional ac–dc converters for energy harvesting and conditioning usually
consists of two stages. A diode bridge rectifier typically forms the first
stage, while the second stage is a dc–dc converter to regulate the rectified ac
voltage to a dc voltage. However, the diode bridge would incur considerable
voltage drop, making the low-voltage rectification infeasible.
Proposed system
The boost converter is the common power
conditioning interface due to its simple structure, voltage step-up capability,
and high efficiency. The buck-boost converter has ability to step up the input
voltage with a reverse polarity; hence, it is an appropriate candidate to
condition the negative voltage cycle. Besides, the boost and buck-boost
topologies could share the same inductor and capacitor to meet the miniature
size and weight requirements. A new bridgeless boost rectifier, which is a unique
integration of boost and buck-boost converters, is proposed in this paper. When
the input voltage is positive, S1
is turned ON and D1 is reverse
biased, the circuitry operates in the boost mode. As soon as the input voltage
becomes negative, the buck-boost mode starts with turning ON S2 and reverse biasing D2. MOSFETs with bidirectional
conduction capability work as two-quadrant switches to ensure the circuitry
functionality in both positive and negative voltage cycles. This topology was
introduced for piezoelectric energy harvesting applications
Block Diagram
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|
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Circuit Diagram
Advantages
·
This
employs the minimum number of passive energy storage components, and achieves
the maximum conversion efficiency.
Applications
· Modern energy regeneration applications such
as low-speed wind, wave, electric bikes, and regenerative suspension in
vehicles.
Multi-port
Converters Based on Integration of
Full-Bridge
and Bidirectional DC-DC Topologies for
Renewable Generation Systems
Abstract
A systematic
method for deriving multi-port converters (MPCs) from full-bridge converter
(FBC) and bidirectional DC-DC converters (BDCs) is proposed in this project through
sharing the parasitized switching legs by the BDCs and the FBC. By employing
the proposed method, families of full-bridge and BDC-based MPC (FB-BDC-MPC),
including some existed ones, are developed for renewable generation systems
with the merits of simple topology, reduced devices and single stage power
conversion. Voltage regulations between any two ports can be achieved by
employing pulse width modulation and phase angle shift control scheme. Furthermore,
zero-voltage-switching for all the switches can be realized in the proposed
FB-BDC-MPCs. A typical four-port converter developed by the proposed method,
named Buck/Boost four-port converter (BB-FPC), is analyzed in detail as an
example in terms of operation principles, design considerations and control
strategy.
Existing System
Generally, the MPCs can be classified
into three categories: fully isolated topologies, fully non-isolated topologies
and partly isolated topologies. Fully isolated MPCs are typically derived by
combining full-bridge, half-bridge or series-resonant topologies via magnetic
coupling, e.g. utilizing multi-winding transformers. Isolation, bidirectional
capabilities of all the ports and zero-voltage-switching (ZVS) can be achieved
in these topologies. These MPCs are good candidates for the applications where
isolation and bidirectional conversion are required. However, the major problem
is that too many active switches are used. This results in complicated driving
and control circuitry, which may degrade the reliability and performance of the
integrated converters. Non-isolated MPCs can either be derived by using DC-link
or integration method. These MPCs feature compact design and high-power
density.
Proposed
System
The main focus of this paper is to
propose a systematic method for derivation of MPC topologies from full-bridge converter
and non-isolated BDCs. The derived MPCs, including those proposed provide good
candidates for the applications of renewable power system, such as PV supplied
aerospace power systems, hybrid energy storage systems, fuel-cell and battery
systems and thermoelectric generation systems with battery backup. This paper
is organized as follows. In section II, the derivation methodology of the MPCs
is proposed and families of MPC topologies are derived. In section III, the
Buck/Boost four-port converter (BB-FPC) is analyzed in detail, including
operation principles and design considerations presented. The modulation
scheme, operation mode analysis and power management strategy are presented in
section IV.
Block diagram
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Circuit
Diagram
Advantages
·
Interfacing multiple bidirectional
sources and isolated output load simultaneously.
·
High conversion efficiency
Applications
·
Low power applications
·
Space applications
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