Abstract
Australia and most other countries are adopting renewable energy generation as the dominant means of reducing dependence on fossil fuels. This has been made more feasible by the exponential take-up of solar photovoltaic (PV) systems and their concurrent production scale-up and cost decline. Rooftop solar PV, combined with battery storage, seems likely to be the dominant means of providing household electricity needs. In response to the technical challenges from rooftop PV, network utilities have implemented various low cost options to cope with PV’s impact on network voltages. However, if we want this clean energy technology to fully utilise the available roof space and eventually meet residential electricity needs, additional hardware, control and commercial options will need to be adopted by both network utilities and their customers to overcome the technical barriers, especially voltage rise. This paper presents the authors’ evaluations of options to mitigate voltage rise, including operating solar inverters with reactive power absorption (var absorbing), dependent only on solar power output or operating the solar inverters in a volt–var response mode (voltage droop control) where the inverter adjusts its reactive power (Q ) in response to changes in its terminal voltage – Q (V ). This paper also considers the fulltime Q (V ) option, where an inverter’s reactive power capacity is independent of solar conditions – statcom mode. The network utility option of using line drop compensation (LDC – used on long rural MV feeders) on urban MV feeders during daylight hours is assessed to lessen voltage rise on LV feeders with low net loading or reverse power flow due to high solar PV generation. The paper concludes that a combination of solar inverters performing fast fulltime voltage droop control outside a voltage deadband (statcom mode) and HV/MV substation transformers with slow acting daytime LDC mitigates voltage rise, whilst limiting feeder reactive power requirements.
Highlights
It appears increasingly probable, given the declining costs, that most dwellings that can accommodate rooftop photovoltaics (PV) will be fitted with solar panels
Network utilities in Australia have not yet had to modify or augment distribution networks to accommodate the current level of solar PV penetration
Utilities may shift single phase LV prosumer houses experiencing excessive voltages to the phase with the lowest LV voltage, if available. Another possible network utility option, which this paper evaluates, is to program urban HV/MV substation transformers with line drop compensation (LDC) during daylight hours
Summary
Given the declining costs, that most dwellings that can accommodate rooftop photovoltaics (PV) will be fitted with solar panels. Rooftop PV may become the norm, provided technical barriers do not prevent this. Network utilities in Australia have not yet had to modify or augment distribution networks to accommodate the current level of solar PV penetration. To become the social norm, customers with rooftop PV, who both consume and produce electricity – sometimes called prosumers, and utilities may both need to play a role in mitigating the adverse technical effects of rooftop PV saturation. The most prominent of these is voltage rise and this paper considers and assesses options that prosumers and utilities could adopt to prevent voltage rise being the limiting barrier. A basic prosumer option, required by some utilities, is for the solar inverter to have a P(V) characteristic, called a volt–watt response mode, whereby a solar
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