Dept. of Electrical Drive Systems and Power Electronics · PDF fileDept. of Electrical Drive Systems and Power Electronics ... 7,244 PV modules 80 ... "A review of single-phase grid-connected

Dept. of Electrical Drive Systems and Power Electronics

Prof. Dr. Ing. Ralph Kennel Arcisstr. 21, 80333 Munich

Outline:

Photovoltaic

Photovoltaic Application

Photovoltaic modeling and MPPT

Power Electronics for Photovoltaic

2



Photovoltaic

29.7 GW in 2011---------------------16.8 GW in 2010

21.9 GW in Europe in 2011------------13.4 GW in 2010

9.3 GW in Italy--------------------7.5 GW in Germany

Italy and Germany ---------60%----- 3 million households

2.2 GW China--------------------1.9 GW in USA (2011)

3

Advantages:

Pollution-free energy.Low maintenance cost (no moving/rotating parts). Long life time (> 20 years)

Limitations: Ineffectiveness during the nights or low insolation periods.Partially shading problems.High initial capital cost.



4

Photovoltaic



PV Applications

5



[1] Small-scale Photovoltaic

6

Roof-top mounting:

Feed-in tarif (e.g., Germany) Own supply of electricity

Problems: Partial shading Power losses Snow and ice



[2] Building-integrated Photovoltaic

7

CIS Tower in Manchester, UK(the largest commercial solar facade in Europe)

7,244 PV modules 80 watts each 391 kW peak power

Advantages: Cut-down electricity cost Large facades are already available

Problems: Partial shading



[3] Large-scale Photovoltaic

8

Waldpolenz Solar park, Leipzig, Germany(the world’s largest PV farm, 2008) 52 MW peak power 153,650 PV modules 220 hectares Investment cost 130 M€Advantages: No pollutants Profitable investment? Problems: High power fluctuations Maintenance (ice) Locating a fault



9

Photovoltaic Model

phIDI

CI

CV

CS

0

C0phCC IR)

I

IIIln(

q

nKTV

DphC III

)(eIII C

D

nKT

qV

phC 10

)(eIII C

SCC

nKT

)RIq(V

phC 10

KJ/10*1.38K

C10*1.602q

o23-

19



10

Photovoltaic Maximum power

Voc

IscMaximum

powerMaximum

power

2 W/m200

2 W/m400

2 W/m600

2 W/m800

2 W/m1000

Imp

Vmp

Nonlinear current-voltage (I-V) characteristics



11

PV Direct Connection

A

BProblems:

The operating point dependson the load.

Only one operating pointleads to the maximum power.

DC Load

PV Module

+

-

Maximum power



Power Electronics in Photovoltaic

12

Why?

To track the maximum power from PV (MPPT). To convert the DC power to AC power. To control the voltage level. To interface PV with load (stand-alone or grid-connected).

Power electronics converter Criteria:

Reliability. Achieves MPPT. Inject high quality current, Cost abd efficiency.

T2

T5

T1

T4

T3

T6

C2PV

+

-

To AC Load

or Grid




13

Power Electronic converter topologies:

DC-DC converter modifies the PV voltage and MPPT. Transformer to provide galvanic isolation.

PV Inverters

With DC-DC converter

With isolation(transformer)

On the LF side(grid side)

On the HF side (DC-DC Converter side)

Withoutisolation

Without DC-DC converter

With isolation(transformer)

Withoutisolation




14

Converter Configurations:

DCAC

3-phase connection

DCAC

DCAC

1-phase connection

DCDC

DCDC

DCAC

1 or 3-phase connection

Centralized Technology String Technology Multi-String Technology AC module Technology

DCAC

DCAC

1-phase connection




15

[1] Centralized Converter: (The oldest technology)

Advantages: Few converters are used. Low power losses: small number of power switches. High input voltage.

Disadvantages: High voltage DC-cables between PV and the converter. Power losses: centralized MPPTMismatch losses among PV modules. Not flexible design

DCAC

3-phase connection




16

[2] String Converter: (reduced form of Centralizedconverter)

Advantages: Few converters are used. Low power losses. High input voltage (at sufficient number of PV modules). Allows individual MPPT.Missmatch losses are reduced (still exist). Overall efficiency is improved (> Centralized topology)

Disadvantages: If the input voltage is low, DC-DC converter ortransformer is required.

DCAC

DCAC

1-phase connection




17

[3] Multi-string Converter: (Present day technology)

Advantages: Has the advantages of the two previous topologies. High input voltage. Allows individual MPPT. Higher efficieny. Flexible design. DC

DCDC

DC

DCAC

1 or 3-phase connection

[4] AC Module Topology: ( Future technology)

Each PV module is integrated with itsinverter in single device (plug & play). DC

ACDC

AC

1-phase connection



“Global Market Outlook for Photovolatics until 2016”, EPIA, May 2012.

Kjaer, S.B.; Pedersen, J.K.; Blaabjerg, F., "A review of single-phase grid-connected inverters for photovoltaic modules," Industry Applications, IEEE Transactions on , vol.41, no.5, pp.1292,1306, Sept.-Oct. 2005.

Edwin, F.; Weidong Xiao; Khadkikar, V., "Topology review of single phase grid-connected module integrated converters for PV applications," IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society , vol., no., pp.821,827, 25-28 Oct. 2012.

18

References

Documents

Dept. of Electrical Drive Systems and Power Electronics · PDF fileDept. of Electrical Drive Systems and Power Electronics ... 7,244 PV modules 80 ... "A review of single-phase grid-connected