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IMPACT OF INCREASED
PENETRATION OF
PHOTOVOLTAICS ON POWER
SYSTEMS
PRESENTED BY:
MUWAFFAQ USMAN
M.TECH POWER SYSTEMS
ROLL N...
OUTLINE
• INTRODUCTION
• WHAT IS PENETRATION?
• VOLTAGE PROFILE
• POWER FACTOR
• HARMONICS
• SYSTEM STABILITY
• PROTECTION...
INTRODUCTION
• A rapid growth is observed in the installation of solar photovoltaic
systems and would increase in the upco...
CONT.
• Many of these grids were designed to operate with conventional
power houses at one end.
• Structural changes in po...
08-04-2016 5
WHAT IS PENETRATION?
• Penetration is defined as the ratio of nameplate PV power rating to
the maximum load seen on the di...
ADVANTAGES OF PV PENETRATION
• Less pollution
• Low maintenance
• Minimization of transmission loss
• Reduce the stress on...
VOLTAGE PROFILE
8
VOLTAGE PROFILE
• In high or low penetration conditions, this results in over voltages and
results in changes in power flo...
VOLTAGE PROFILE WITH AND WIHTOUT PV
10
08-04-2016 11
CONT.
• High penetration of PV can result in voltage instability
• Intermitted nature of PV is the reason for voltage fluc...
VOLTAGE FLUCTUATION
• Voltage quality is affected by intermittency of PV power output in
distribution systems
• Climatic c...
VOLTAGE UNBALANCE
• Voltage unbalance is a consequence of line voltages not being equal.
• Caused by uneven distribution o...
POWER FACTOR
15
POWER FACTOR
• Grid connected PV systems operate at unit power factor & the power
produced by the PV is active power.
• Ac...
CONT.
17
HARMONICS
18
HARMONICS
• Penetration of PV systems into the distribution grid causes harmonic
distortion of current and voltage waves.
...
DC BIAS
• When the inverter is not properly designed, there is a chance that it
will introduce DC bias into the system
• D...
STABILITY
21
SYSTEM STABILITY
• Depending on PV penetration level, a portion of the generation is
transferred to the locations closer t...
STEADY STATE STABILITY
• Ability of the system to maintain a steady state equilibrium while
satisfying system constrains.
...
TRANSIENT STABILITY
• Ability of power system to maintain synchronism during large
disturbances.
• Disturbances range from...
CONT.
• Power system tend to have larger oscillations during post fault
transients when PV systems are present.
• Thus pow...
CONT.
Relative rotor angle of generators with and without PV during fault.
2608-04-2016
CONT.
• Dependent on the weather conditions, the output of PV systems can
fluctuate due to cloud transients etc.
• As the ...
PROTECTION ISSUES
28
PROTECTION ISSUES
• The protection issues of grid integrated solar PV systems are
1. Change of short circuit levels
2. Rev...
1. CHANGE OF SHORT CIRCUIT LEVEL
• High penetration of PV systems result in higher fault current
compared to systems witho...
2. REVERSE POWER FLOW
• Power flow is unidirectional in radial distribution systems, hence the
protection schemes are desi...
3. ISLANDING
• The higher the PV penetration into the distribution grid, the greater
the chances of islanding which the PV...
REMEDIAL MEASURES
33
REMEDIAL MEASURES
• Increased PV penetration has positive and negative effects on the
power system.
• However above a part...
CONT.
• Thus solar PV systems can be operated at safe penetration levels.
• Penetration limit stems from the technical abi...
CONT.
• Penetration limits can be found by simulations.
• At present PV penetration issues are of concern for European nat...
CONCLUSION
37
CONCLUSION
• Use of grid integrated PV systems are increasing rapidly.
• PV penetration can have both positive and negativ...
REFERENCES
1. Eftekharnejad, S; Vittal, V. ; Heydt, G.T. ; Keel, B.Loehr, J., “ Impact of Increased
Penetration of Photovo...
THANK YOU
40
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Impact of high level penetration of photovoltaics on Power system

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Discusses the impact of high penetration levels of PV system, and its effects on the grid. It has detrimental effects on system stability and cause power quality issues. The remedial measure is discussed

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Impact of high level penetration of photovoltaics on Power system

  1. 1. IMPACT OF INCREASED PENETRATION OF PHOTOVOLTAICS ON POWER SYSTEMS PRESENTED BY: MUWAFFAQ USMAN M.TECH POWER SYSTEMS ROLL N0:6
  2. 2. OUTLINE • INTRODUCTION • WHAT IS PENETRATION? • VOLTAGE PROFILE • POWER FACTOR • HARMONICS • SYSTEM STABILITY • PROTECTION ISSUES • REMEDIAL MEASURES • CONCLUSION 08-04-2016 07EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS 2
  3. 3. INTRODUCTION • A rapid growth is observed in the installation of solar photovoltaic systems and would increase in the upcoming years. • The development of power electronic devices & fast acting controllers made it possible to integrate solar PV systems to existing grids at distribution levels. • With the decreasing prices of PV panels, coupled with government financial incentives, has promoted the used of solar plants. 307EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  4. 4. CONT. • Many of these grids were designed to operate with conventional power houses at one end. • Structural changes in power systems result in new concerns regarding the reliable and secure operation of systems with high penetration of renewable energy. • Integration of Photovoltaics has both positive as well as negative impacts on the power grid. 407EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  5. 5. 08-04-2016 5
  6. 6. WHAT IS PENETRATION? • Penetration is defined as the ratio of nameplate PV power rating to the maximum load seen on the distribution feeder [4]. • PV penetration (%) = 𝑇𝑜𝑡𝑎𝑙 𝑃𝑉 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 (𝑀𝑊) 𝑇𝑜𝑡𝑎𝑙 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 (𝑀𝑊) [1]. 607EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  7. 7. ADVANTAGES OF PV PENETRATION • Less pollution • Low maintenance • Minimization of transmission loss • Reduce the stress on the power system 707EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  8. 8. VOLTAGE PROFILE 8
  9. 9. VOLTAGE PROFILE • In high or low penetration conditions, this results in over voltages and results in changes in power flow. • Increased penetration can cause improper selection of tap setting for the distribution transformer. • Excess power generated by solar PV during low demand period must export the active power to grid which results in over voltages and reverse power flow. 907EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  10. 10. VOLTAGE PROFILE WITH AND WIHTOUT PV 10
  11. 11. 08-04-2016 11
  12. 12. CONT. • High penetration of PV can result in voltage instability • Intermitted nature of PV is the reason for voltage fluctuations in grid connected PV. • Passing of clouds, angle of incidences also play a major role in driving the system to instability by means of voltage fluctuations. • The voltage regulation becomes difficult during high level penetration due to tap setting of the distribution transformer. 1207EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  13. 13. VOLTAGE FLUCTUATION • Voltage quality is affected by intermittency of PV power output in distribution systems • Climatic changes can create irradiance fluctuations either for a short period or long periods. • Voltage problems of system that has solar PV can be characterized as voltage rise, voltage unbalance and flickers in the network. 1307EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  14. 14. VOLTAGE UNBALANCE • Voltage unbalance is a consequence of line voltages not being equal. • Caused by uneven distribution of single-phase loads on a three-phase system. • PV sources also contribute to unbalance as they generate power on only one phase. • Unbalance of 2.5% to 3% or greater is unacceptably high Calculated as: max( , , ) 100 %a b c unb avg dV dV dV V V  1407EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  15. 15. POWER FACTOR 15
  16. 16. POWER FACTOR • Grid connected PV systems operate at unit power factor & the power produced by the PV is active power. • Active power for the demand is provided by PV and reactive power is provided by the grid. • In effect this reduces the power factor, as the grid is then supplying less active power, but the same amount of reactive power. • The PV inverter can be made to provide reactive power, improving the voltage regulation and power factor. Unfortunately this can interfere with most anti islanding schemes. 1607EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  17. 17. CONT. 17
  18. 18. HARMONICS 18
  19. 19. HARMONICS • Penetration of PV systems into the distribution grid causes harmonic distortion of current and voltage waves. • Its due to the conversion of DC current in order to synchronize with the AC supply by utilizing an inverter. • PV inverters are the main source to inject current harmonics to the system. • Produced harmonics can cause series and parallel resonance, overheating equipment, misoperation of protection devices. • Harmonic filters can be used to overcome this. 1907EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  20. 20. DC BIAS • When the inverter is not properly designed, there is a chance that it will introduce DC bias into the system • DC bias will increase transformer core loss as it will cause the heating of windings and saturation of transformer core. 2007EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  21. 21. STABILITY 21
  22. 22. SYSTEM STABILITY • Depending on PV penetration level, a portion of the generation is transferred to the locations closer to the loads which may alter the amount of reactive power supplied to the load. • High PV penetration results in replacing large scale generating units with the PV systems can limit the availability of reactive power. • This is because most of the PV systems provide active power only. • Increased PV penetration will also result in reduced inertia within the system which can cause potential rotor angle stability problems. 2207EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  23. 23. STEADY STATE STABILITY • Ability of the system to maintain a steady state equilibrium while satisfying system constrains. • High PV penetration levels can result in variations of bus voltage magnitudes. • Steady state voltages increases as the PV penetration increases. • Increase in PV penetration, reactive power export decreases while reactive power generated by the generators increase. 2307EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  24. 24. TRANSIENT STABILITY • Ability of power system to maintain synchronism during large disturbances. • Disturbances range from equipment, line outages to could cover incase of PV systems. • System inertia plays a key role in transient stability. • High PV penetration results in low inertia of system and can lead to potential transient stability issues. 2407EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  25. 25. CONT. • Power system tend to have larger oscillations during post fault transients when PV systems are present. • Thus power system is more perturbed with higher PV penetration levels. • Power systems employed with PV shows increased voltage dips during the transients. 2507EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  26. 26. CONT. Relative rotor angle of generators with and without PV during fault. 2608-04-2016
  27. 27. CONT. • Dependent on the weather conditions, the output of PV systems can fluctuate due to cloud transients etc. • As the amount of PV penetration increases the voltage fluctuations increase. • DG solar PV systems can trip simultaneously due to a single system event such as extreme voltage dip condition. • Modern PV inverters are equipped with Low Voltage Ride Through Capability (LVRT) which improves transient stability. 2707EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  28. 28. PROTECTION ISSUES 28
  29. 29. PROTECTION ISSUES • The protection issues of grid integrated solar PV systems are 1. Change of short circuit levels 2. Reverse power flow 3. Islanding 2907EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  30. 30. 1. CHANGE OF SHORT CIRCUIT LEVEL • High penetration of PV systems result in higher fault current compared to systems without PV. • This is because during a fault PV systems continue to inject current into the feeder until islanding condition is detected and breakers are open. • This leads to further damage of the grid causing conductor damage or damage to transformer. 3007EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  31. 31. 2. REVERSE POWER FLOW • Power flow is unidirectional in radial distribution systems, hence the protection schemes are designed accordingly. • DG connected can cause alteration in the coordination of the relay due to reversal in power. • This is also explained in the voltage profile. 3107EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  32. 32. 3. ISLANDING • The higher the PV penetration into the distribution grid, the greater the chances of islanding which the PV continues to supply local loads even after supply loads even after utility fault. • If the protection relays do not detect islanding, then the inverters may remain online and pose a serious threat to equipment and service personnel. 3207EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  33. 33. REMEDIAL MEASURES 33
  34. 34. REMEDIAL MEASURES • Increased PV penetration has positive and negative effects on the power system. • However above a particular level of penetration its observed to have significant detrimental effects on the power system. • Higher PV penetration causes voltage rise, stability, harmonics, poor power factor and protection issues. • These effects are not significant for lower penetration levels. 3408-04-2016 07EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS
  35. 35. CONT. • Thus solar PV systems can be operated at safe penetration levels. • Penetration limit stems from the technical ability of the grid to reliability integrate distributed solar capacity. • At present there is no perfect rule for determining the penetration limits. • Penetration limit is dependent on factors 1. Load 2. Consumer behavior 3. Climate etc. 3507EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  36. 36. CONT. • Penetration limits can be found by simulations. • At present PV penetration issues are of concern for European nations like Germany, Italy, Greece and others. • Penetration level varies from region to region. • In India CEA has approved for a penetration level of 10-15%. 3607EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  37. 37. CONCLUSION 37
  38. 38. CONCLUSION • Use of grid integrated PV systems are increasing rapidly. • PV penetration can have both positive and negative effects on the grid. • The detrimental effects of grid integration can be avoided limiting the penetration levels within safe limits. • There is no definite rule to determine the safe penetration level. • Safe penetration level is dependent on many factors of the grid and varies from region to region. 3807EE6264 SEMINAR: IMPACT OF INCREASED PENETRATION OF PV ON POWER SYSTEMS08-04-2016
  39. 39. REFERENCES 1. Eftekharnejad, S; Vittal, V. ; Heydt, G.T. ; Keel, B.Loehr, J., “ Impact of Increased Penetration of Photovoltaic Generation on Power Systems” IEEE transactions on power system, May 2015, pages 893-901 2. Hasheminamin, M. Agelidis, V.G. ; Salehi, V. ; Teodorescu, R.Agelidis, V.G. ; Salehi, V. ; Teodorescu, R. ; Hredzak, B.; “ Index-Based Assessment of Voltage Rise and Reverse Power Flow Phenomenon in Distribution Feeder Under High PV Penetration ” IEEE Journal of photovoltaics, June 2015, pages 1158-1168 3. Cheng, D.; Mather, B.A. ; Seguin, R. ; Hambrick, J. Mather, B.A. ; Seguin, R. ; Hambrick, J. ; Broadwater, R.P ; “ Photovoltaic (PV) Impact Assessment for Very High Penetration Levels “ IEEE Journal of photovoltaics, October 2015, pages 295- 300 4. Baran, M.E.Hooshyar, H. ; Zhan Shen ; Huang, A. “Accommodating High PV Penetration on Distribution Feeders” IEEE transactions on smart grid , June 2014, pages 1039-1046 5. Shichao Liu, P. X. Liu , Xiaoyu Wang “Stochastic Small-signal stability Analysis of grid connected photovoltaic systems ” IEEE transactions of industrial electronics, January 2016 39
  40. 40. THANK YOU 40

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