Intelligent distribution automation of MV/LV transformer stations at LV networks

Advanced Power Quality Management

Unlike passive filters, active filters do not generate connection overvoltages, as the charge is not trapped in capacitors in the same way. The typical structure of active filters comprises an inductor, namely a filter coil, and a power electronic converter, that is, switches and capacitor - based energy storage.

The active filter converter is usually controlled to generate opposite - phase harmonic waveforms, thereby reducing or eliminating harmonic propagation. Besides harmonic filtering, active filters can also be used to correct the power factor. In future functions of active filters, harmonic filtering and power - factor correction could be implemented in the grid - side control of energy storage.

Figure 1 shows the management systems and communication architecture of MV/LV transformer stations with energy storage.

This communication architecture is based on the public internet and consists of Ethernet and IP protocols, transformer centre gateways (GW), and the local IP network within MV/LV transformer stations and control centres. The IP network allows for the use of multiple protocols, which can be applied in areas such as energy trading, storage management configuration, remote control, power quality monitoring, and web - based services.

When traffic is tunneled through the public network, an encrypted virtual private network (VPN) can be employed.
Standard IEC protocols are utilized to govern distributed resources and filters. The intelligent logical device for energy storage can be modeled using the object - oriented structure and architecture specified in IEC 61850 and its subsequent IEC amendments.

The SCADA schematic diagram in Figure 2 depicts an MV/LV transformer station equipped with an active filter. It encompasses symbols for the disconnectors of the ring unit, the disconnectors of the transformer, the transformer itself, the relay of the LV busbar, the fuse - switches of the LV feeders, and the relay of the feeder for the active filter.
Moreover, the active filter (depicted in red) and potential measurement values and indication information are presented.

With SCADA, extensive monitoring of LV processes and PQ indices involves a large number of measurement and calculation points.
The pricing of SCADA products hinges on the number of required points. So far, this has offered a reasonable means for distribution companies, both small and large, to afford SCADA system upgrades. To enable large - scale, multi - parameter LV monitoring, novel pricing models for SCADA and NIS/DMS are required.
A new pricing approach, not reliant on the number of points, could do away with the needless virtual grouping, structures, and compression of LV information. For example, relational databases can handle extremely large databases, and the processing and storage capabilities of information systems have grown exponentially.