More PV and Wind Power with Smart Meter Based Voltage ControlOLOF SAMUELSSON, IEA, LUND UNIVERSITY

Overvoltage from DG

• Low X/R in distribution active power affects voltage• DNO allows DG to raise LV voltage 5%• Case study with Kraftringen with three different LV feeders:

– With symmetric three-phase output, villa-roof-sized PV OK everywhere except in remote rural areas

– With unsymmetric output from DG, network capacity is limited with a factor up to 8 (eight)

• Only symmetric DG output considered in the following

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Voltage Control Challenge

• Stay within upper and lower limits when– DG raises voltage– Load reduces voltage– Transformer tap changer raises or reduces all voltages

• How low is the lowest voltage?

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Voltage reduction at maximum load

Smart Meter-Based Tap Changer Control

• Use voltage reading from smart customer meter– Standards define voltage limits at consumer

• If less than maximum load, substation voltage can be reduced• More room for DG until lower voltage limit is reached

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Voltage reduction at actual load

Local Control of DG unit

• If necessary adjust voltage locally– Draw reactive power – remember loss increase– Curtail (reduce) active power

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Case Study 1 – Simulated MV and LV

• Network data from E.ON– 40 MVA 130/20 kV infeed to 9x20 kV feeders – 1 load,

1 generation, 7 mixed– Residential and some rural LV network

• MV: 38 MW wind power and 16 MW PV, LV: 1 MW PV

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Simulation Results

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Traditional Local DG control Combined control

Case Study 2 – Field Test

• E.ON network– 12 MVA 50/10 kV infeed to 9x10 kV feeders– 0.8 MW WTG on 32 km feeder with 1.1 MW load

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Field Test Results

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% Curtailed wind power

Trad Central Combined

Field Test Meters

• Meters transmit values every 10 s via GPRS or GSM• Lowest voltage captured with two meters 89 % of time

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Conclusions

• Smart Meters a resource for voltage control– Few key points need monitoring– Asynchronous update of data every 10 s works

• Control scheme can be simultaneously applied to MV and LV– No network data needed– Traditional tap changing controller is used

• DG projects need expected curtailment– Matching between load and generation central– Probability replaces worst case

• More details in Ingmar Leisse, PhD thesis 2013Lund University/Industrial Electrical Engineering and Automation 11