Transpower

Problem specification

The rapid uptake of distributed solar photovoltaic (PV) generation around the world has created unprecedented challenges for electricity transmission system operators. In response, Transpower is investigating the potential impact of solar PV on the power system. The findings of the MINZ group will inform future work by Transpower and within the New Zealand electricity industry.

Initially, two key problem components will be addressed by the MINZ group:

• Developing a methodology for simulating the spatial aggregation of point-source solar PV sites within regions, to characterise variable power output under all possible weather conditions.
• Stochastically forecasting the potential magnitude of solar PV uptake and allocation between regions, based on available data including observed uptake to date.

The group will then investigate further aspects relating to physical implications for the power system:

• Characterising the transmission network interfaces across boundaries between all 16 council regions. This will be mapped to Transpower’s 14 grid operating zones where necessary. Alternatively, the solution approach can focus on individual grid exit points within regions.
• Defining the probability and magnitude of solar PV induced changes to net transmission flows between regions. This will enable evaluation of the greatest risk inter-region imbalances that could eventuate.
• Carry out additional analysis using initial results, e.g. identify correlation with various other time series data (wind & hydro resource, grid capacity) to draw high-level conclusions about potential impacts.

The problem scope will be refined based on preliminary results and any opportunities identified over the week.

Data available

• Modelled PV generation derived from global horizontal irradiance data:
• Normalised W generated/W installed per 10 minute period
• 16 regional sites over 16 years
• Site geographical co-ordinates
• Census data for population, dwellings and socio-economic indicators
• Transpower network asset maps and grid operating zones boundaries
• Electricity Authority EMI data
• Transpower time series data: historical wind generation, hydro inflows, transmission capacity etc.

All data is publically available or has been procured by Transpower.

Desired outcomes

The study has several primary aims:

• Develop models for understanding and simulating potential distributed PV generation between regions under uncertainty, based on available point-source data and observed PV uptake.
• Produce a statistically robust quantification of potential inter-regional irradiance variability outcomes for future solar PV generation.
• Identify high risk local impacts, in the context of available power system data. Future work will directly reference the results of the study, particularly in regard to:
• Evaluating thermal constraints on the 110 kV transmission network.
• Probability distributions of induced power transmission changes for power flow studies.
• Possible solar PV generation allocations between regions and overall magnitudes.

The final report will cover study assumptions, results and high-level conclusions. Any mathematical models or algorithms developed will be supplied for further studies carried out by Transpower.
No technical power system implications will be inferred, as this is impractical for the MINZ format. However, relevant areas for further study may be identified and highlighted.