Rooftop solar systems shine a light on challenges for Australian grid management

The exponential rise of domestic rooftop solar panels is forcing technologists and regulators to find grid management solutions rapidly, particularly for export and system security.

For an hour on Sunday 11th October 2020, 100% of South Australia’s energy demand was met solely by solar panels. National popularity of solar power has grown exponentially, with Australians currently installing new PV systems at a rate of more than 200,000 per annum across the National Electricity Market.

However, this milestone also brings challenges. When solar power generation exceeds the demand for electricity, the voltage rises close to statutory limits and may even exceed it. Occurring on a regular basis, voltage compliance is no longer an infrequent issue. There is now a clear need for reinforcement of the Australian grid if it is to cope with the continued growth of solar power.

Although not exclusive to South Australia (SA), the technological and regulatory challenges PV systems are presenting to grid operators, distributors and legislators are at their greatest in the region and are where the latest innovations and regulations are focused.

SA’s Distributed Network Service Provider, SAPN, has identified that a multi-solution approach consisting of smart inverters, flexible exports, targeted network investments and the enhanced control of voltage on distribution networks is vital for the successful integration of more DER.

The challenge of voltage control is clearly explained in a blog by Australian domestic solar provider, SolarQuotes. The article summarises and adds insight into a recent conference presentation by SAPN. It claims that, whilst the Distributor intends to continue the export of rooftop solar energy to the grid, a number of measures are required – in particular optimising voltages for network distribution and trialling the use of smart solar inverters for export flexibility.

Smart inverters were also part of this mix and, to that end, the Australian Renewable Energy Agency (ARENA) announced an AS$2.09m (£1.1m) contribution towards the trial of rooftop solar to grid integration using smart inverter technology.

The 12-month project, worth almost AS$5m (£2.7m), will be run by SAPN and will be the first of its kind in Australia and could double the region’s network capacity.  The new technology will enable flexible export limits and will be built into Australian-manufactured inverters for solar PV systems.

The aim is to help system customers overcome the zero/very low export limits that currently apply in the SA and Victoria areas – both parts of the country where the export to the network is seriously constrained by the sheer number of rooftop solar systems.

The smart technology is designed to automatically adjust solar-generated electricity exports to match grid capacity at any time of day or night. It is hoped the trial will lead to national adoption of a solar connection agreement for any compatible inverter with network distributors.

Fundamentals Ltd has also developed solutions to help the challenges posed by solar power.  The company’s Low Voltage Regulator automatically increases or decreases the voltage on LV networks impacted by solar power generation and harmonics without the need for wholesale network reinforcements. 

According to Fundamentals’ recently featured Product Application Engineer, Elizabeth Macharia, the new LVR technology: “provides both network operators and prosumers with steady voltage levels. It’s easy to install and performs voltage regulation without impacting elements such as THD, power factor, impedance or phase angle on the network.”

She continues: “Importantly, this solution is easily applied to existing feeders populated with older generation inverters and provides optimal regulation without the need to upgrade large numbers of customer-owned inverters. It would be particularly requisite in South Australia’s networks where it can reduce maximum voltage levels in areas of high PV penetration levels.”

The new technology and the 12-month ARENA trial are longer-term solutions and the immediate issue of over-capacity has forced the Australian Energy Market Operator (AEMO) to introduce legislation to mitigate system security risks caused by the dramatic increase in PV systems. 

Although entitled Regulatory Changes for Smarter Homes, the regulations in fact apply to residential and commercial PV systems and were implemented at the end of September 2020, apparently with little warning to the industry.

The new rules essentially mandate system installers to:

  • Install low voltage ride-through capability inverters from an approved product list;
  • Ensure system owners appoint a Relevant Agent who can remotely disconnect and reconnect PV system from the grid;
  • Install inverters with internet capability and an onboard communications port.

The Operator revealed that it is developing further regulations, set to be implemented from July 2021, which will require dynamic export control using active control of the inverter.

Given that the number of compliant inverters and installers are currently very limited, and that the SAPN field trails are 12 months from completion, the overwhelming popularity of rooftop PV systems in South Australia appears to have forced the Operator to put the cart before the horse.