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Grid voltage rise and solar power systems

If your inverter sees a grid voltage that is likewise high for also long, Australian Standards mandate it disconnects from the grid. Before the voltage is so loftier information technology disconnects, your inverter may likewise reduce its power output in response to high grid voltages.

There's a lot of fright-mongering about how the ascension of renewables threatens our power grids, but a existent problem getting real attending from the industry is how voltage rises on our more often than not one-time and inflexible infrastructure stops customers from getting the most out of their solar PV installations.

Anyone who'south trained in this stuff already knows this of course, but I'd guess most consumers don't realise the human relationship between the voltage at the inverter and the voltage on the filigree is very of import. When things go incorrect, the customer gets a nib showing far less electricity shipped to the grid than they expected, and someone – a solar installer, an electricity retailer, or a network – gets an aroused phone phone call.

At a contempo Clean Energy Council webinar, all 4 speakers – the CEC'due south 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-coin out of their grid-continued solar power systems.

The inverter has to be running at a college voltage than the grid, so information technology can push power out (current flows from a indicate of higher voltage towards a signal of lower voltage, never the other style effectually). The problem is every solar installation pushing power into the system lifts the network voltage but a little – and with tens of thousands of systems coming online on SA Ability's network each twelvemonth, 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 ability systems aren't the only cause of overvoltage problems – as Solar Analytics founder Stefan Jarnason remarked, plenty overvoltage problems occur at dark-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 2022, and there's upward to 300 MW in the pipeline for 2022.

Kausche said the growth of solar free energy "makes the dynamic range [the difference betwixt the highest and lowest voltages seen on the network – Editor] much greater than if there was just load on the network".

What happens when the inverter has to back off? The client starts complaining, usually to their installer, that network feed-in tariff payments are falling short of their expectations.

Voltage rise slide - compliance

Everybody can do the correct affair, but the system doesn't work right (Image: Clean Energy Council seminar)

That tin can be fixed, just it'southward always better to try and avoid issues than to have to rescue the relationship with a cranky customer – and preventative measures, as well equally remediation, were the focus of the webinar.

Scaling The Overvoltage Problem

Solar Analytics' Stefan Jarnason said his company's analysis of 30,000 customers showed 50 per centum of feeders had overvoltage issues fifty times a year or more, when scanned for voltages exceeding 253V for more than 5 minutes (undervoltage was, by comparison, rare, affecting simply 2 percent of customers experiencing 50 or more than events a yr).

The more granular the data-logging, Jarnason showed, the easier to come across the impact on the customer. Solar Analytics' capture at five-second resolution clearly shows an inverter shutting down considering its voltage is too loftier, trying to reconnect, shutting down again, and then on.

grid voltage rise - inverter shutdown graph

The orange line shows a organisation shutting downwards because of voltage rising on the grid, and then trying to restart (Image: Clean Free energy Council seminar)

Fixing The Trouble

The challenge for networks is some of the bachelor fixes are hard to implement on old infrastructure.

Imagine a long feeder serving many customers, significant that to maintain voltage in-tolerance for the last customer, the voltage closest to the transformer will leave the inverter very little headroom.

Equally Kausche explained, the network provider tin only adjust the voltage by changing the tap on the transformer if the transformer is new enough and has lower voltage taps bachelor – but the majority of SA Power Network'due south lxx,000 low voltage transformers don't have that chapters, and transformer upgrades are expensive. Substation transformers are much more capable, simply don't offer granular voltage direction.

"We have these legacy old assets that can't really go down," Kausche said.

The webinar highlighted the role solar installers can play in remediation, with all iii speakers proverb that getting inverter installation and configuration right plays a big office in fugitive complaints.

SA Power Networks has changed its inverter rules to crave all inverters installed on its network have the Volt-VAR setting enabled (listed equally optional in the AS/ NZS 4777.1 standard), and then the inverter is more than responsive to network conditions.

The network is likewise working with other providers to produce a standard ready of solar inverter settings, so at some point OEMs and solar installers have a standard configuration profile Australia-broad.

SA Power Networks is also trying to move more customer loads to the middle of the day. If an off-superlative hot h2o system, for instance, can be remotely configured, adjustment is easy, and from 2022 there will be a "sponge" tariff to encourage consumers to schedule loads such as washers, dishwashers and pool pumps towards the middle of the day.

What Solar Installers Tin can Do

The CEC's Patterson pointed out arrangement design, including cablevision judge, is also of import to manage voltage rising. The CEC surveyed participants to see if they liked the idea of an online calculator tool to aid installers design their solar ability systems – and received a 100 percent "Yeah" vote; so we can probably expect to see that offered adequately soon.

SMA's Piers Morton said the bear upon of voltage rise emphasised the need for remotely-manageable solar inverters, something SMA will be introducing in the near time to come, and said installers can too help past paying more attending to balancing systems across different phases.

If yous are solar power system owner with a voltage rise problem Finn has written a handy troubleshooting guide here.