The increasing number of decentralized, renewable generation plants has changed the demands on the international power grid. While the grid used to be a one-way street, from the centralized large power plants to the consumers, today, this has changed. Consumers have become so-called prosumers (producers and consumers). Due to the multitude of generation plants, the core task of grid operators - to maintain grid stability - has become more complex. Solar-Log™ always offers the right technical solution for the internationally varying requirements of the grid operators.
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In order to stabilize the power grid even on critical days, there will be new requirements for grid stability in the medium term in all countries that provide larger capacities of decentralized power generation. The Solar-Log™ devices already cover the basic functionalities of feed-in management with the basic firmware. For the full range of PM requirements we offer the PM Pro license. With this license, you will find the right solution for every grid stability requirement.
A central function is the limitation of the feed-in to the grid. In many countries, fixed or dynamic power limits are now prescribed. This limit can be set flexibly for different threshold values. Thus, different requirements (70 % regulation, 50 %, or 60 % regulation for storage promotion, 0 % regulation in Spain, etc...) can be served.
This function offers the possibility to minimize losses caused by x% control. The current consumption is measured for the control. The Solar-Log™ offsets this with the current production of the inverters. Only if the difference between production and consumption exceeds, for example, 70% of the module power, the inverters are regulated accordingly.
For implementation, a meter is required that determines the consumption directly in the consumption branch.
The requirements of the German Renewable Energy Sources Act (EEG) require a "simplified feed-in management" for plants between >30kWp and 100kWp, which is usually implemented via a ripple control receiver.
The simplified feed-in management can also be implemented by the function: "remote controlled with billing of own power consumption". For this, only the momentary own power consumption in the household must be measured by a separate consumption meter.
Feed-in management (with Solar-Log™ PM Pro license)
In Germany, PV plants that are connected to the medium-voltage grid are subject to extended requirements. The different regulations that may be applied in a plant are bundled in the VDE-AR-N-4110 (VDE-4110).
As a rule, in addition to the type of control of the PV system, it is also stipulated that various information about the current status of the PV system must be made available to the energy company.
Communication with the energy company is implemented via telecontrol systems. Signal transmission between the telecontrol system and the Solar-Log™ Base normally takes place via a Modbus/TCP interface, more rarely via the I/O box(es) (analog, digital) included in the PM package. In addition to the control of active power, reactive power control presents a particular technical challenge.
VDE-4110 provides for various voltage - or power-controlled concepts here. The voltage-guided reactive power control requires a measurement at the feed-in point, for this a Solar-Log™ GmbH approved meter (Utility Meter) is required.
Modbus TCP Power Management (PM) Interface
Complex grid operator requirements can be implemented by having the telecontrol systems communicate directly with the Solar-Log™ using the TCP based Modbus protocol. In this case, commands and feedback are exchanged between the telecontrol system and the Solar-Log Base 2000 via protocol, i.e. without the floating and analog interfaces. Through the Modbus interface and a protocol converter, telecontrol protocols such as IEC 60870-C, IEC 61850-5-101 and -104 can be implemented.
Interconnected Control - PM Management with Solar-Log™ Networks
In order to implement feed-in management for plants in the larger plant area, the Solar-Log Base devices are coupled with each other via Ethernet network. Networking allows the control signals of the grid operators to be exchanged with each other.
The signals from the grid operator are received at the Solar-Log Base 2000 (master) and distributed to the connected inverters via the Solar-Log Base 2000 (slaves). For this system architecture, the master can be coupled with up to nine slaves in the network. By networking the Solar-Log™ devices, complex requirements (multiple plant sections, feed-in points, and many different inverter manufacturers) can be implemented.
Through the use of the interconnection control license, it is additionally possible to carry out a plant division for direct marketing. By using slave devices the plant is divided into areas. A separate direct marketer can then be selected for each area. Possible reduction commands of the direct marketers are prioritized with the commands of the energy suppliers and documented accordingly.