The fifth element for microgeneration
aksja
Modern power generation requires different approaches and management from those that were in use even a few years ago.

Alongside other breakthrough decisions, Russian power company Rosseti is to be the first to create a controller for low-voltage systems.

     The process of energy transition is proceeding apace the world over.

     On the one hand, multi-resource generating systems are starting to operate using both renewable energy and traditional sources. On the other, energy systems are becoming increasingly differentiated in terms of the scale of use and capacity of the energy they produce.

    Microgeneration is becoming an element in and of itself in the energy sector, living according to its own rules. And within these systems, new active players are emerging – prosumers who at the same time act as consumers and producers of energy.

    The simplest example of such players are the owners of solar panels in rural houses that produce energy for their own needs and – in the event of surpluses – are prepared to supply it to a general grid.

   The inevitable controller

   Maintaining control and ensuring the reliability of such multi-levelled systems has become more and more difficult. And many energy companies are beginning to invest in devising and introducing specialised systems – controllers which unite in one single object the equipment associated with microgeneration – power storage units, prosumers and plain old consumers.

     Modern microgeneration systems simply cannot exist without controllers. That’s the view of the laureate of the 2020 Global Energy award, Nikolaos Hatziargyriou, Director and professor at the National Technical University of Athens.

    “The main distributed renewable energy generators, like photovoltaics and wind turbines need power electronic converters to connect with the power grid,” Hatziargyriou told Global Energy.

    “Batteries also need controllers to connect to the network. Only very old wind turbines can be directly coupled to the network, causing various problems. These are not installed anymore. . So, theoretically some old renewable energy technologies (wind turbines with directly coupled induction machines) might exist without them, but in practice most, e.g. photovoltaics and batteries cannot…”

    Professor Hatziargyriou noted that centrally automated controllers optimising the operation of an electrical grid, are already produced by many companies (Siemens, ABB, SEL) and work  primarily with middle and high-voltage networks.

    . “For sure competition in this field is very, very high. I doubt however, if such technologies have been installed in practice in LV (low voltage) grids beyond the pilot level,” he said.

    “There have been several…R&D efforts in Europe, the U.S. and China and several pilots have been developed.”

    So, are Russia and Rosseti on to a trend?

    A specialised consortium has already been set up for the development of jus such a Russian controller – including the Rosseti R and D centre the “NIR” Fund (National Intellectual Development Fund), and Skoltekh (Skolkovo Institute of Science and Technology). The work is chartered by the Rosseti Centre branch in the southern city of Belgorod, Work is due to be completed late in 2021.

    The system will bring together components of microgeneration, including solar and wind equipment with a capacity of up to 15 KW, energy storage devices, electric vehicles supported by V2G (vehicle to grid) technology and prosumers – active consumers and producers of energy – one and the same people.

    The projects could be designed for remote areas or for any residents of rural homes equipped with solar panels or wind turbines. A mini renewable energy installation will enable the homeowner to supply surplus energy to the main grid.

    The distinguishing feature of most of these electrical systems is the inclusion of an inverter driven by a microprocessor. On the one hand, the inverter provides the required quality supply of power. On the other hand, the pulsed nature of an inverter turns electrical equipment into a source of disturbance and instability in the grid.

    The controller will act at the same time as a means of operating the 0.4 KW unit automatically and as an inverter. It will act as a chain of modules – in fact, the equipment of a substation linked remotely to other devices and counters and also as equipment for measuring of power lines in addition to being linked to the consumer. 

    Initially, a computer model will be used to set down the main principles and methods of managing a low-tension section of the network with the help of a network controller. A programmed system will then be set up, complete with working documentation, including the technical requirements for a tested industrial piece of equipment. If the project proves successful, it can then be adapted for a network of up to 35 KW.

    Development and prospects

    Russia’s scientific community believes this development will fully meet the modern challenges of developing a power system and see it as having a bright future.

    “It is clear that the development of microgeneration based on renewable energy sources requires a modern and, to some extent, a different system of operation from a traditional system. This is linked, to a degree, to the use of an energy storage device. New, completely different tasks become apparent in the development of such systems,” said Konstantin Suslov, head of the Power Supply and Electrical Engineering Department at Irkutsk National Research Technical University.

    “Common world practice now is the intellectualisation of electrical engineering. If you talk about experience throughout the world, such systems abroad, no matter what form they might take, use controllers. Energy systems, even when based on only a small proportion of renewable sources, need them in view of their stochastic nature (randomness).”

    Risks of a glut

       At the same time, the use of such systems is accompanied by a number of risks, says Michael Grätzel, a laureate of the Global Energy Prize and director of the Laboratory of Photonics and Interfaces at the École Polytechnique Fédérale de Lausanne in Switzerland.

      “Broadly speaking, the project is focused on any country house owner, who has photovoltaic panels installed. In the future, the system will be able to transfer all the unused electricity to the common grid, while the owners are on vacation.

    “While this sounds like an interesting approach, it does not address the fundamental problem of grid instability due to large temporal fluctuations of the power input by renewable sources such as solar and wind,” Grätzel said.

    “For example, in Germany during the summer season, solar power provides up to around 10 % additional electricity to the grid, which is already very hard to cope with. Sometimes the German electricity company is obliged to sell the extra power at a loss to neighbouring countries, such as Switzerland. The only solution to this problem is to have individual homes use the solar electricity directly – this could be done without DC-AC conversion – and store the surplus e.g. in a battery. Not surprisingly, individual homes that opt for this solution receive much higher subsidies in Germany than the ones that connect their panels to the grid.”

    Global Energy will keep a close watch on this work.

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