Systems for generating electrical energy are seeing changes as a consequence of considerations relating to environmental policy. The classic energy supply mains with few large central power stations can be in the course of time superseded by a modern power supply mains with which numerous smaller energy suppliers are decentrally connected. The tasks to be solved by the operator of the modern power supply mains are as a result far more complex. The supply of renewable energy by energy suppliers, who utilize wind and solar energy, is in some cases plannable only to a limited extent and is subject to substantial fluctuations. In the immediate future a compound operation therefore may prevail in which compensation for failures of energy supplies of alternative energy suppliers is provided by energy supplies from conventional power stations.
In order to keep the supply of electrical energy delivered by the power stations in balance with the need for electrical energy and to help ensure stability and reliability of the power supply mains the energy suppliers and electricity users connected therewith can be continuously monitored. For that purpose the course of load of the power supply mains can be also monitored so as to determine time zones with higher loading. Based on the determined course of load, static electrical loads are switched off at critical time periods so that a load balance can be achieved over longer periods of time.
The connection and disconnection of loads is traditionally carried out by ripple control. In modern power supply mains, i.e. so-termed ‘smart grids’, ripple control is supplemented by ‘smart meters’, which allow detection of the state of the power supply mains close in time to numerous mains junctions. The communication of the decentral measuring units or ‘smart meters’ with a central station is possibly carried out by way of a network operating according to Internet protocols. A method for short-cyclic data detection and control of measuring points in an intelligent power supply mains, which uses smart metering or smart grid functions, is known, from, for example, WO 2012/055566 A2.
If a difference between the supply of and requirement for energy now arises, the regulating energy or regulating power made available by the energy suppliers is used in order to avoid collapse of the power supply mains in the case of increased need or an energy excess in the case of too-small demand. Compensation for the mentioned differences or fluctuations in the power supply mains is provided by means of the regulating energy.
The available regulating energy is divided into different categories. Regulating energy able to be called up within seconds is termed primary reserve. Regulating energy able to be called up within a minute is termed secondary reserve. Moreover, the regulating energy comprises reserve components which can be called up after quarter of an hour (minute reserve) or after hours (hour reserve).
In the case of overloading of the power supply mains, positive regulating energy or current is stored in the power supply mains. If there is an energy excess, negative regulating energy is taken from the power supply mains. Use of power stations capable of regulation is made for the required adaptations of output, such as rapid-response gas-turbine power stations or pumped-storage power stations. It can be disadvantageous even with fast-start power stations that supply always takes place with a significant delay. A primary reserve, which can be used virtually without delay, is hardly ever available. Moreover, energy from the primary reserve can be expensive.
The regulation of the power supply mains can be even more demanding by energy consumers, such as elevator installations, which draw larger amounts of energy from or feed such back to the power supply mains. Whereas connection or disconnection of apparatus with low energy consumption is usually uniformly distributed due to the high number or is plannable on the basis of experience this is not the case with elevator installations. Dynamic loads, such as elevator installations, can relatively strongly load the power supply mains selectively at any time of day or time of night. To the extent that, for example, a larger travel group enters different hotels at night time when the mains operator does not expect greater loads, several elevator installations can coincidentally be simultaneously actuated whereby a high loading is abruptly triggered. On the other hand, insofar as an energy excess is present and the elevator installations can feed additional energy back to the power supply mains, this equally should be absorbed by the regulation technology of the power supply mains. It is to be noted that primarily expensive primary reserves may be required to provide compensation for these processes.
The presence of larger energy consumers, such as elevator installations possibly with several individual elevator units, may require a high level of availability of the regulating capacities of the power supply mains. In particular, possibly expensive primary reserves may be provided.