Future Grid Design and Operation for high
Penetration with Renewable Energies
Gerd Becker
Munich University of Applied Sciences
Possible Future Generation Structure
In 2010 (electricity)
605 TWh Gross energy
83 % Conventional energy
17 % Renewable energy
In 2050 (electricity)
700 TWh Gross energy
100 % Renewable energy
45 % Wind offshore
13 % Wind onshore
16 % Photovoltaics Szenario 2.1.b
5 % Biomass/Biogas
4 % Hydro
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Actual Load Curve 2013 in Germany
Solar and Wind covering peaks!
Load flow in 110 kV/20 kV Substation (High PV Penetration)
Lower Bavaria
15 min average values and 24 h average values 2009 (blue, light blue) und 2010 (yellow, red)
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Impacts of RE on the Grid and Countermeasures (1)
Fluctuating generation of energy
Generation management
Smart grids
Storage technologies necessary
Self consumption
Rise of voltage in LV (0,4 kV) and MV (20 kV) grid
Inverters feed in reactive power
Adjustable transformers
Grid expansion
Energy is fed from LV (0,4 kV) to MV (20 kV) and from MV
(20 kV) to HV (110 kV)
Grid expansion
Impacts of RE on the Grid and Countermeasures (2)
Behavior in the case of a fault, a RE systems may not
disconnect
Low voltage ride through
Stability of the grid
Reduction of real power depending on the frequency (surplus power, grid
fault)
Rotating mass property
Capability for black start of generation units
Location of generation changes
Improved grid structure, new components, new lines
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Future LV and MV Grid Structure
Power station
400 kV
Special case:
110kV
No load flow in
MV and HV grid 20/10kV certain
components
0,4kV
Households
„Intelligent“ grid infrastructure
with overlay IT Æ Smart Grid
Both directions of load flow are possible
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Voltage Rise
Cable
Consumer with PV
Medium U
voltage grid
Voltage rise
ULV Lenght
Voltage drop
Red line: consumer needs power Æ voltage drop
Green line: energy generated Æ rise in voltage
Blue line: PV system (inverter) feeds in reactive power Æ limited rise
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Self Consumption
Appropriate tariffs
Peak shaving e.g. at 70 % (STC power) by using a battery
1000
1000
800 800
In battery
600
Load
600
400 400
200 PV generation 200 PV generation
0 0
00:00 06:00 12:00 18:00 00:00 00:00 06:00 12:00 18:00 00:00
Storage Technologies
Technologies:
Stationary batteries
Accumulators (Cars)
Pumped storage power stations
Power to Gas
Compressed air storage
Ex: IBC SolStore 6.8 Pb
Question: Centralized or decentralized? Capacity 6,8 kWh
Lead acid
DOD = 50 %
Lifetime 10 years
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Grid services
Low voltage ride through
Frequency dependent reduction of real power
Feed reactive power into the grid
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Measures for improved grid integration ‐ PV
Measure + grid capacity Remark
Feed in reactive power 20 % to max. 100 % Limited costs
Expansion of grid >100 % Costly
Generation management 20 % to 40 % Reduces yield
Adjustable transformers 10 % to 30 % Costly
Self consumption Depending on
Peak shaving using battery percentage Very costly
*Values depending on grid structure
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Future Grid Operation
The future LV and MV grid includes an information network
The electricity price will change in 15‐minute intervals
Smart grids permit the individual operation of appliances
(Washing machines, dishwashers, freezers, air condition,
electrically heated hot water .
Smart grids have to be operated and controlled.
Unit commitment (operation power stations) becomes more
sophisticated
Renewable generation units will be switched off some times, as
there is surplus energy
Operation of the storage technology is an important task
The future grid has more HV, MV and LV lines
Fluctuating generation and consumption Æfluctuating load flows
Monitoring (temperature) of lines
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Summary
There are many impacts of RE on the grid
Fluctuating generation of energy
Rise of voltage in LV and MV grid
Behavior in the case of a fault
Stability of the grid
Location of generation changes
Energy is fed back into the MV and HV grid
Measures
Feed in reactive power
Expansion of the grid
Generation management
Adjustable transformers
Self consumption and peak shaving
However
Conventional (gas fired) power stations needed for reserve and stability (rotating masses)
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