HYBRID CONVERTERSNIRAJ MULEY

Contents

Literature survey Recap to dc-dc converters What are Hybrid converters Operation Modifications Applications Some other types References Conclusion

Literature SurveyBoost-Derived Hybrid Converter With Simultaneous DC and

AC Outputs IEEE Transactions on Industry applications, VOL. 50, NO. 2, MARCH/APRIL 2014

•This paper proposes a family of hybrid converter topologies which can supply simultaneous dc and ac loads from a single dc input. The steady-state behavior of the BDHC has been studied in this paper, and it is compared with conventional designs.

Improved Hybrid Converter with Simultaneous DC and AC Outputs, International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064

•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 converter by replacing the controlled switch with voltage source inverter (VSI).

Literature Survey High Gain Buck-Boost Derived Converter for Simultaneous

DC & AC Applications, International Journal of Engineering Research and General Science Volume 3, Issue 4, July-August, 2015 , ISSN 2091-2730.

• The new Hybrid Converter is derived from the single switch controlled high gain Buck-Boost converter 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.

Buck converter

Voltage - step upCurrent - step down

dco VDV

Boost converter

Voltage - Step upVV

DV

V dco 1

Buck-Boost converter

Output voltage either greater than or less than input voltage depending on duty cycleD>0.5- boost operationD<0.5- buck operation

dco VDDV

1

DC as well as AC output

(a)Dedicated power converter approach (b) Hybrid converter approach

Dedicated power converter approach

Cascaded connection

Parallel connection

BDHC (Boost Derived Hybrid Converter)

Switch S is replaced by bridge inverter

Because of same 4 switches to control both ac as well as dc outputs, there are some challenges involved in the operation -

1) Defining duty cycle(D) for boost and Modulation index(Ma) for inverter operation

2) Defining Voltage stresses and currents through different circuit components

3) Control and channelizing of input power to both ac and dc loads

3 distinct switching intervals

1. Shoot through interval- (Q1, Q4) or (Q2,Q3)2. Power interval- (Q1, Q2) or (Q3, Q4)3. Zero interval- (Q1,Q3) or (Q2,Q4)

Shoot through interval

•On switches (Q1,Q4) or (Q2,Q3)

•Any particular leg is shorted

•Diode D is reverse biased

•Time interval defines duty cycle

for boost operation.

•This allows additional switching

states which are strictly forbidden in

VSI

Power interval

•On switches (Q1,Q2) or (Q3,Q4)

•Inverter current enters at switch node s

dcoutsn VV

Zero interval

• This occurs when inverter current circulates in bridge network and is not sourced or sunk

• On switches (Q1,Q2) or (Q3,Q4)

•Diode D conducts

dcoutsn VV

Waveforms -switch node voltage -inductor current -inverter output voltage -diode current -Inverter input current

snV

LiabV

dI

snI

Circuit parameters in different intervals

Steady state observations

Where D is defined as the shoot-through time interval in a switching cycle.we assume that the output dc capacitor voltage and the input inductor current havesmall ripple compared to their dc values.The modulation index, denoted by Ma (0 ≤ Ma ≤ 1), regulates the ac output voltage of the BDHC.The peak output ac voltage is related to the input as,

DVV

dcin

dcout

11

DM

VV a

dcin

dcout

1

The ac gain increases with the increase of modulation index for any fixed value of duty cycle . As the same set ofswitches controls both the dc and ac outputs, there is limitationto the maximum duty cycle or modulation index that can beachieved for this topology. The switching strategy must satisfythe following constraint: + ≤ 1.

At equality condition , maximum ac gain is achieved, where peak value of ac voltage is equal to input voltage

To achieve even more higher voltages, step up transformers can be used.

stD

stDaM

aM

Power expressionsDC power output

AC power output

It can be observed that dc output power depends onlyon duty cycle while ac output power depends upon both and

22

1* stdc

dcindc DR

VP

222

1***5.0

stac

adcinac DR

MVP

stDstD aM

Switch stress

•The input to the inverter bridge equals to vdcout, during both power and zero intervals. Thus, the maximum stress on each switch is equal to vdcout, the dc output voltage, neglecting the voltage drop across the conducting diode D.

•The stress across the diode D is equal to vdcout during the shoot-through interval. Thus, the selection of switch ratings is dependent upon the dc output voltage rather than the input voltage, contrary to the case for a conventional VSI.

Control strategy•The inverter output has to be modulated whenVsn = 0 and boost operation occurs when vab = 0.

•The inverter output voltage assumes three different values, and hence, the PWM modulation strategy used is based upon unipolar sine- PWM scheme, which provides three voltage levels for output.

comparison

Improvements possible•The maximum output-to-input gain achieved by the boost converter is

limited to approximately four due to resistive losses. The higher gains can be achieved by using higher order boost converters such as quadratic BDHC.

•Other dc-dc converters such as buck-boost converter, cuk converter are also being used to derive hybrid converter topologies.

Conclusion• A converter to obtain dc as well as ac outputs from a single dc source of energy is possible by replacing control switch in boost converter (or other dc-dc converters) by an inverter bridge consisting of 4 switches.• The inverter and dc-dc will operate simultaneously according to the PWM method used for the circuit.•Different types of topologies are being evolved incorporating this concept in different types of existing converters.•These type of converters are becoming increasingly popular in nano-grid architectures in modern smart electrical power systems.

References• Olive Ray, Santanu Mishra“Boost-Derived Hybrid Converter With Simultaneous DC and AC Outputs” IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 2, MARCH/APRIL 2014

• Sarath Prasad K S, T Valsalan2 Dr. P Vijayakumar “Improved Hybrid Converter with Simultaneous DC and AC Outputs” International Journal of Science and Research (IJSR) ISSN 2319-7064

•Sarath R and P. Kanakasabapathy, "Switched-capacitor/switched-inductor Ćuk-derived hybrid converter for nanogrid applications", Computation of Power Energy Information and Commuincation (ICCPEIC) 2015 International Conference on, pp. 0430-0435, 2015.

Thank you…Any questions?