inverter 5kw There’s a lot of fear-mongering about how the rise of renewables threatens our power grids, but a real problem getting real attention from the industry is how voltage rises on our mostly old and inflexible infrastructure stops customers from getting the most out of their solar PV installations.
Anyone who’s trained in this stuff already knows this of course, but I’d guess most consumers don’t realise the relationship between the voltage at the inverter and the voltage on the grid is very important. When things go wrong, the customer gets a bill showing far less electricity shipped to the grid than they expected, and someone – a solar installer, an electricity retailer, or a network – gets an angry phone call.
At a recent Clean Energy Council webinar, all four speakers – the CEC’s James Patterson, Solar Analytics’ Stefan Jarnason, SA Power Networks’ Travis Kausche, and SMA’s Piers Morton – agreed over-voltage problems are a big contributor to consumer complaints that they’re not getting value-for-money out of their grid-connected solar power systems.
The inverter has to be running at a higher voltage than the grid, so it can push power out (current flows from a point of higher voltage towards a point of lower voltage, never the other way around). The problem is every solar installation pushing power into the system lifts the network voltage just a little – and with tens of thousands of systems coming online on SA Power’s network each year, some systems are confronted with a grid with voltage outside inverter tolerance (the AS/NZS 4777.1 standard limits inverter voltage to 255V).
It’s worth noting solar power systems aren’t the only cause of overvoltage issues – as Solar Analytics founder Stefan Jarnason remarked, enough overvoltage issues occur at night-time to prove that.
SA Power Networks strategist Travis Kausche told the webinar the state currently has homes feeding 1 GW into the grid; 163 MW of that came online in 2018, and there’s up to 300 MW in the pipeline for 2019.
Kausche said the growth of solar energy “makes the dynamic range [the difference between the highest and lowest voltages seen on the network – Editor] much greater than if there was only load on the network”.
What happens when the inverter has to back off? The customer starts complaining, usually to their installer, that network feed-in tariff payments are falling short of their expectations.