Impact of Renewable Energy Sources on Power System Operation

Contents

• Renewable Energy

• Intermittency

• Effects of Intermittency on Dispatch Operation

• Effects on Power System Operating Cost & Power Imbalances

• Effects on power quality

• Power Dynamics in Wind Generation

• Accessibility Of Renewable Sources in Power System

• Renewable Energy- Future Prime Mover of Power Generation

Renewable Energy

“Source of energy that comes from resources which are naturally replenished

on a human timescale”

Ex. sunlight, wind, rain, tides and geothermal.

• Characteristics of renewable energy

• Reproducible naturally

• Sustainable resource of energy

• Intermittency

• Need of renewable sources

• Depletion of fossil fuel

• Continuous rise in fuel prices

• Environmental regulation for pollution emission reduction such as Kyoto protocol.

Intermittency

“limited-controllable variability and partial predictability of a generation resource.” Ex. Solar energy • Variability: Variation over time of the availability of generation

resources. Ex. Wind generation

Predictability: Ability to determine ahead of time the availability of a generation resource.

• Intermittent renewables: Generation of electricity from wind and solar resources.

• comprise of uncertainty and variability in load or availability of power.

Effects of Intermittency on Dispatch Operation

Figure 1.Comparison of possible scheduled generation with the corresponding real-time dispatch. The variability of intermittent generation can be mitigated largely with day-ahead scheduling. Additional reserves are dispatched in real-time to mitigate day-ahead forecast errors.

• Issues of Renewable Sources with ED problem Uncertainty and variability in renewable sources

Subjected to weather and geographical condition

Treated as non-dispatch able units

Unreliable system due to random behavior

• How to Mitigate the effects of intermittency in ED Additional reserves to meet out the variation in source or load

Low start-up cost

High ramping rate limits

Better demand response strategy for reducing the reserve requirements.

Effects on Power System Operating Cost & Power Imbalances• Negligible cost at low scale • In large scale generation variation on renewable source

generation affects the operating cost of the system.• Ex. Independent operator and wind or solar farm owner

Case1 If generation is more than scheduled generation, then

operator penalty paid to owner.Case 2 If generation is less than scheduled generation, then

operator has to purchase the power from other vendor.

Effects on Power Quality

• In wind generation• Variable frequency due to intermittency of wind speed• Reactive power problem due to Induction generator • Voltage dips• Low power factor

• In solar generation• Discontinuity in charging or discharging• Poor power quality due to use of controlled power

electronics devices, source of harmonics

Power Dynamics in Wind Generation

• Changes on system’s operating points , when subjected to disturbances• Factors affecting the dynamics of the system• Induction Generator • Generator with power electronics devices

• Factors affected by the wind generation• stability• Small signal dynamics• Transient dynamics

Accessibility of Renewable Sources in Power System

• Forecasting methods• Long term forecasting• Day-ahead schedule

• Short-term forecasting• Minute to hour schedule

• Analysis Methods • Time-series method• ANN (artificial neural network)

Renewable Energy- Future Prime Mover of Power Generation• Reasons

Emission less and Environmentally friendly Low capital investment, no running cost Easily established , less construction is required Outage of these source less affects the system operation

• Limitations Intermittent in nature Sustainable source of energy, but not reliable source of power Penetration levels is limited, higher penetration, affects the

stability, makes less reliable system Unpredictable with high variability

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