Aachen 03/14/2001 - Consumers are happy about the deregulation of the energy supply markets, the utility corporations, however, encounter new challenges. Slogans such as new tariff structure, performance contracts, globalization, forwarding contracts and power stock exchange determine the discussion. The fixed contractual frames the utility corporations had to deal with, are increasingly dissolving. Frequent changes will be going to influence the utility market for still some more time.

This change even influences the technical and operational level, in which new challenges ask for new technical solutions to exist in a dynamic market. To achieve this, existing installations have to be adapted to the modified situation, with as little effort and risk as possible.

The municipal utilities of the City of Viersen have accepted this challenge. However, they do not start a general technical overhaul but optimize existing systems. A system based on a Gesytec embedded PC has been installed for the load management in order to equalize today’s insufficiencies of a reliable system in an efficient manner by adding standard devices without modifying the system itself. An additional load profile generator makes the existing load management system suitable for dynamic energy purchase.

Load Management for Dynamic Requirements

In former times load management systems to avoid load peaks were usually adapted to static tariff structures with parameters for peak and off-peak tariffs but fixed to a maximum purchase from a determined supplier. The extension to a further supplier with settlement by the quarter hour under changing tariffs radically modifies the requirements. Now the task of the load management system is to keep the actual consumption below the amount of the total power purchased resulting from both partial purchases. This means not to exceed a dynamically preset amount of electrical power.

Performance schedules from the supplier reflecting the consumption during fixed periods are the basis for load management under new supply conditions. This information (e.g. 33,64 MW from 08:15 until 08:30 on March 24, 2001) exists as file but cannot be processed by the current load management system. It is, however, equipped with meter pulse inputs for power metering, receiving either consumption or own power generation.

Real-Time Meter Pulse Sequences with Embedded PC

By using Gesytec’s Gipsy Micro Embedded PC the he engineering office EnerOPT has developed a solution converting the performance schedules into meter pulse sequences by using suitable pulse parameters to forward them in real-time to the load management system. Hereby the nominal energy purchase evaluated by the load management system is modified and the system maintains the newly preset dynamic power limit without any changes in its software basis.

The system realized consists of an operator dialog (on a PC) and of a Gipsy Micro. The operator dialog, running under all common Windows operating systems, serves for parameterization, conversion of the performance schedules and operation. It reads in the summary performance schedules, checks their plausibility and converts them into meter pulse sequences. Those compact data are serially transferred to the Gipsy Micro, a Windows CE embedded PC. Operating on one of two selectable pule sequences the Gipsy Micro generates meter pulses on one of its digital outputs feeding them to the load management system. Fitted with current time (radio clock synchronized) and winter time/summer time settings the Micro fulfills its function without connected operating dialog. It is provided with a watchdog output for operation monitoring. Termination of the current meter pulse sequence is signaled in good time via an additional output.

The existing load management system receives the meter pulses generated by Gipsy Micro via one of its pulse input channels. It considers the power input recorded as negative consumption resp. as own generation and hereby is up to a dynamic behavior on both sides, consumption and supplier.

Reliable Solution under Windows

Since last autumn, the system is successfully used at the municipal utilities of the City of Viersen and further partner utilities. This solution is very attractive due to its favorable price/performance ratio. A software upgrade of the load management system integrating the handling of a dynamically preset power purchase would have been far more costly than the Embedded PC and the straightforward programming under Windows of the operator dialog and Gipsy Micro.

Further arguments in favor of the Embedded PC based load profile generator:

  • No modification of running systems
  • Simplicity by limitation to a clear task
  • Maintenance free
  • Easy replacements in case of technical reconstruction in the future

A system improvement connecting it to Ethernet networks is currently being prepared. A modification to another input method of basis data will make the system suitable to handle even spot quantities. The application is not limited to load management but can also be used to support forwarding contracts or similar as well as within simulation studies.