By Helen Roberts-Ferguson, Zinfra Group
With the lure of a green power source and the incentive of government rebates and feed-in tariffs, Australian customers are installing solar photovoltaic panels at an ever increasing rate. While this is positive action for residential customers, it is creating challenges for our electricity networks.
Australia’s electricity networks were designed for electricity to flow one way and with the assumption it will dry up as it goes down the line.
Solar photovoltaic (PV) integration to the network is causing extreme and erratic voltage discrepancies the system is not equipped to deal with. The solar PV panels feed power back into the network during sunlight hours when electricity is not being consumed, leading to an oversupply on the lines.
As a result, United Energy (UE) is trialling an innovative and cost-effective technology that will allow the existing network to accept higher levels of solar generated power and regulate supply.
ZNX Network Services Victoria, a Zinfra Group company and service provider to UE’s northern network in Victoria, is installing low voltage regulators (LVRs) on UE’s metropolitan, interconnected three phase network as part of a six month trial.
The self-automated LVR units solve the common utility problems of flicker and excessive voltage drop.
The power electronics contained in the LVR dynamically regulate voltage flow up or down to within 1 per cent of a programmable set point, in UE’s case, stabilising the voltage to a set point voltage of 230. This precise regulation of voltage ensures grid stability and compliance with appropriate service standards.
The units are produced and sourced from Microplanet, based in Seattle, US. Engineer Greg Wiegand, from Microplanet, visited Australia to provide guidance and technical advice for their use on UE’s networks.
The installation of the units on the pole, currently involves the placement of three units on a pole, one for each three phase wire.
Mr Wiegand explained these units were initially designed for single wire earth return (SWER) networks in Queensland and Microplanet is currently designing a custom three phase integrated unit that will conform to height restriction and other regulations on the UE network.
The new, customised units, known as U3Ps, will consist of one box containing the contents of three of the current LVR units. These units have recently undergone an extensive testing regime at the Queensland University of Technology under the Guided Innovation Alliance (GIA) program.
The GIA is an industry applied research collaboration established in October 2011 to address barriers and shorten the pathway to market for new innovations in the electricity sector.
The GIA program is looking to identify technologies to counter the problems associated with the increasing trend of domestic solar PV installation. It was through this program UE identified the LVR units as a solution to their network difficulties.
ZNX construction supervisor Grant Attewell said the units provide a very economical solution to the problem of voltage regulation.
“The LVR units allow the network to be updated without updating the infrastructure,” he said.
“The traditional solution to this problem would be the installation of a new pole substation and the high voltage lines needed to feed it, which would cost at least three times as much as these LVRs.”
Each LVR can also transmit the activity and performance of the unit. Incoming voltage, output voltage, current and temperature of the unit can be retrieved by downloading it to a laptop via Bluetooth. This can be done from the ground, thereby removing the requirement for a worker to access the unit up on the pole.
Mr Wiegand said Microplanet is currently working on improving the data functionality on future units by installing an SD card that will record data on a minute-by-minute basis and be stored for one year. A wi-fi solution to improve reliability when data gathering is also being added to future models.
The trials are being conducted in known trouble spots on the UE network. Three separate poles will have the units installed on them by mid-May as part of the trial. In some cases, UE will use smart meters on individual premises with known issues to monitor and gauge their effectiveness.
The first trial devices have been installed on the low voltage network of Steven-Woodcrest substation which is a pole-mounted 300kVA transformer located in Vermont, Victoria.
Mr Attewell said he is excited about the potential for the LVRs.
“There are many short-term and long-term benefits associated with this technology. The problem of voltage regulation is addressed with minimal impact on the end customer and they get a more reliable service,” he said.
The pole units are small and it all comes at a fraction of the cost of traditional ways of dealing with these problems.”
When you take into account the short installation time, which is as little as 30 minutes, the immediate increased grid reliability and improved service for utility customers, the potential for this new technology to tackle the issues associated with long runs and the growing use of domestic solar panels looks very promising.
ZNX is proud to be partnering with UE on this innovative initiative, bringing their skill, experience and expertise to the team.
How the LVR works
Microplanet’s LVR combines traditional power electronics with patented technology. The LVR will dynamically raise or lower and balance the incoming voltage to maintain a constant output level. The system consists of:
• An AC-to-AC converter that produces voltage with a varying magnitude. The converter drives the primary of a high-efficiency toroidal transformer.
• A control board with a microprocessor for measuring the output voltage and controlling the AC-to-AC converter to precisely maintain a fixed level set by the customer.
The control board senses line-to-neutral output voltage and compares it to the desired reference. Depending on whether the voltage is too low or too high, the unit decides if it should be raising or lowering the voltage, and how much. Then it controls the AC-to-AC converter to adjust the output voltage to exactly match the reference voltage. The regulator maintains its output (load side) voltage even when the power reverses and is flowing from the customer PV backwards to the utility.
In the event of electronics failure, regulation stops but power is not interrupted. Fault alarms can be sent to a connected network.