UNIVERSAL SINGLE-STAGE GRID-CONNECTED INVERTER
Presented by
VINEETH .S
S7 E2
NO:259
College Of Engineering, Trivandrum
2007-11 batch

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Overview
Introduction

Analysis and working of the proposed Topology in various configuration

Shuffling between configurations

Design of L,C Components for the Universal Inverter

Simulation Results and Observations

Experimental Results

Conclusion

References



Introduction
Power Conditioning Unit (PCU)

Acts as an interface between power source and grid

Conditions the source energy appropriately to meet the grid requirements

Specific functions such as Reactive Power control, maximum Power point tracking, boosting, bucking etc




PCUs are of 2 types




Disadvantage of Multistage
Reduces overall efficiency
Reliability & Compactness

So need for integrating various stages of a multistage system into a single stage.

A single stage PCU is essentially a single stage grid connected inverter capable of performing several functions



Works on DCM(Discontinuous current mode)

Controlled using PWM(Pulse width modulation)

3 modes of operation-buck,boost, buck-boost
Analysis &working of the proposed topology

Switching pattern determines mode.











Egk = VmImSin²[k/n]Ts




Buck mode:

S5 is ON, source energises capacitor through inductor.

S5 is OFF, IL free wheels.

Boost mode:

Main switch is ON, inductor is energised and capacitor supplies energy to the load

During OFF output diode is turned off,inductor and source supply energy.


Buck-boost mode:

Main switch is ON – inductor across source

During OFF, inductor transfers energy to load

IL=0 capacitor provides energy

Shuffling between Configurations
Vi > Vm:
Work in either buck or buck boost

Vi < Vm:
Works in boost mode
Design Of LC Components For Universal Inverters
L is chosen so that operation is in DCM

L<Lcrit

Design of Lg & C:

Depends on filtering of inverter output

Simulation Results & Observations
Simulated in MATLAB/SIMULINK for an output=500W

Case 1 :
[Grid voltage 90V @ 50Hz,input=200V dc]

Case 2 :
[Grid voltage 230V,input=100V]

Considering ΔV =50V and fhl =800 Hz for both case 1 and case 2, the values of the filter components, Lg and C, are 10mHand 3.85 μF, respectively; L=0.8mH
OBSERVATION:
1) It is seen that the inductor current is higher in buck–boost(buck) configuration than that in buck configuration(about 50% of the peak value in buck–boost configuration).
2) The reference waveform would just be a rectified sinusoidal waveform in the case of buck–boost configuration, if the grid voltage was sinusoidal.

Experimental Results

Various experiments have been performed on a 500 W laboratory prototype of the proposed topology with a variable dc voltage source (which varies over a range of 100–200 V). All possible tests have been done. The inverter output is tied to a 1 − φ grid ac voltage adjustable with the help of an auto-transformer.
MOSFETs IRFP460 are used as the controllable devices while CSD20060 are used as power diodes.
Input dc voltage is sensed using TI ISO122 chip while the grid voltage is sensed through a step down transformer.

conclusion
A new concept has been proposed in which the system’s configuration can be changed during the operation.

With optimally designed L,C components, this inverter can operate in various configurations and can swiftly and smoothly shuffle between them.

Provides higher boosting and bucking ability, low peak inductor currents, and higher efficiency.

References
[1] S. Rahman and A. D. Castro, “Environmental impacts of electricity generation:A global perspective,” IEEE Trans. Energy Convers., vol. 10,no. 2, pp. 307–313, Jun. 1995.
[2] B. K. Bose, “Energy, environment, and advances in power electronics,”IEEE Trans. Power Electron., vol. 15, no. 4, pp. 688–701, Jul. 2000.
[3] G. K. Andersen, C. Klumpner, S. B. Kjaer, and F. Blaabjerg, “A new green power inverter for fuel cells,” in Proc. IEEE PESC, 2002, pp. 727–733.
[4] B. K. Bose, P. M. Szczesny, and R. L. Steigerwald, “Microcomputer control of a residential photovoltaic power conditioning system,” IEEE Trans. Ind. Appl., vol. IA-21, no. 5, pp. 1182–1191, Sep. 1985.
Thank you