Method for regulating a power supply system

Abstract

A method provides closed-loop control for an entire power supply system which has three supply levels each considered to be a separate regulatory unit and controlled independently of the other supply levels. An interface between two respective regulatory units is defined by control of the active power and reactive power transmitted between the two regulatory units. Appropriate control of the active power and reactive power transmitted between the regulatory units allows these regulatory units to be isolated from or connected to one another in terms of power. A power supply system is ideally regarded as a chain of separate regulatory units for supplying power. This allows efficient and safe operation and local control of a power supply system to which locally produced power is supplied, for example on different supply levels. In addition, a low number of data items to be interchanged between the supply levels is maintained.

Claims

1. A method for closed-loop control of an entire power grid, the power grid having three voltage supply levels, each of the three voltage supply levels having a predefined voltage range and each of the three voltage supply levels being connected to another one of the three voltage supply levels by at least one interface, the method comprising: independently controlling each of the three voltage supply levels with respect to other ones of the three voltage supply levels by using a primary control, a secondary control, and a tertiary control, wherein the independently controlled three voltage supply levels result in three regulating units that are each controlled independently with respect to other ones of the three regulating units; and defining an interface between two of the three regulating units by control of an active power and a reactive power transmitted between the two regulating units.

2. The method according to claim 1, which comprises maintaining, for each of the three regulating units, a voltage range that is predefined for the respective regulating unit.

3. The method according to claim 1, which comprises exchanging control values via the interface between the two regulating units.

4. The method according to claim 3, wherein the control values are selected from the group consisting of values for the reactive power, the active power, and/or a power factor.

5. The method according to claim 1, which comprises separating the two regulating units by reducing the active power and reactive power transmitted between the two regulating units at the interface thereof.

6. The method according to claim 5, which comprises, for reconnecting the two regulating units, first synchronizing the two regulating units to be connected to one another, and then increasing the active power and reactive power transmitted between the two regulating units to be connected to one another at the interface between the two regulating units to be connected to one another.

7. The method according to claim 1, which comprises defining a first of the three supply levels as a high-voltage or transmission level, a second of the three supply levels as a medium-voltage or primary distribution level, and a third of the three supply levels as a low voltage or secondary distribution level.

8. The method according to claim 7, which comprises operating the regulating unit of the primary distribution level as a stand-alone system by decoupling the primary distribution level from the transmission level and from the secondary distribution level.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will now be explained using examples with reference to the accompanying drawing. The FIGURE schematically illustrates a typical power grid in which the method according to the invention is used to control an entire power grid.

DESCRIPTION OF EMBODIMENTS

(2) The FIGURE of the drawing schematically illustrates a typical power grid EV. This power grid EV has three supply levels VE1, VE2, VE3. A high-voltage transmission level is provided as the topmost or first supply level VE1. A second or middle supply level VE2 is implemented as a medium-voltage distribution level and a low-voltage or secondary distribution level is provided as the third or lowest supply level.

(3) At each of these three supply levels VE1, VE2, VE3, energy is fed into the power grid EV decentrally via respective typical power generators EZ, LZ1, LZ2, LZ3, K1, K2, K3 at the respective supply level VE1, VE2, VE3. At the first supply level, i.e. the transmission level VE1, energy produced by large power generators EZ such as e.g. large hydroelectric power plants, thermal power plants or large wind farms is fed into the power grid. As well as larger consumers (e.g. factories, hospitals, etc.), regional or local power generators LZ1, LZ2, LZ3 such as e.g. small hydroelectric power plants, wind farms, etc. can also be connected to the second supply level or more specifically the primary distribution level. Decentrally generated power is then fed into the power grid by these regional or local power generators LZ1, LZ2, LZ3. Private homes, small industrial facilities, etc. are usually connected to the power grid EV as consumers at the lowest supply level or secondary distribution level VE3. However, energy can also be fed into the power grid EV at the third supply level VE3 by private power generators K1, K2, K3 such as e.g. photovoltaic systems, etc.

(4) Each of the three supply levels VE1, VE2, VE3 is regarded by the method according to the invention as a self-contained regulating unit RE1, RE2, RE3 which is controlled independently. Each regulating unit RE1, RE2, RE3 has the same control scheme R1, R2, R3 and primary control, secondary control and tertiary control are used for controlling the respective regulating unit RE1, RE2, RE3. For the respective regulating unit RE1, RE2, RE3, different objects therefore emerge for R1, R2, R3 control. At the first supply level VE1 constituting a first regulating unit RE1, in particular the large power generators are controlled. At the second supply level VE2 representing a second regulating unit RE2, the object of R2 control, in particular of primary control, are particularly the decentralized (regional and/or local) power generators LZ1, LZ2, LZ3. At the third supply level VE3 constituting a third regulating unit RE3, power is generated and fed in e.g. by private producers K1, K2, K3 whereby these customer systems (e.g. photovoltaics, etc.) must be controlled accordingly at the third supply level VE3.

(5) According to the inventive method for controlling the power grid EV, an interface between two regulating units RE1, RE2, RE3 is then defined by control of an active power P and a reactive power Q transmitted between said two regulating units RE1, RE2, RE3. In the power grid EV illustrated by way of example, an interface is therefore defined by control of the active power P and reactive power Q between the first and the second regulating unit RE1, RE2—and therefore between the transmission level VE1 and the primary distribution level VE2. In addition, an interface is formed via the control of active power P and reactive power Q between the second and third regulating unit RE2, RE3, i.e. the primary distribution level VE2 and the secondary distribution level VE3. Consequently, the supply levels VE1, VE2, VE3, i.e. the regulating units RE1, RE2, RE3 can interact flexibly as links in a chain by the control of the active power P and reactive power Q at the respective interfaces, wherein the second regulating unit RE2, i.e. the primary distribution level VE2 because of its position—it has interfaces with the two other supply levels VE1, VE2—can be seen as a central, strategic link in the chain. The respective regulating unit RE1, RE2, RE3 thus represents for the other regulating units RE1, RE2, RE3 a so-called “black box” and only a very small amount of data or control values are exchanged across the interface between the regulating units RE1, RE2, RE3. Thus, only values for the reactive power Q and/or the active power P and/or a value for the so-called power factor cos φ are exchanged e.g. between the first regulating unit RE1, i.e. the transmission level VE1, and the second regulating unit RE2, i.e. the primary distribution level VE2, e.g. for maintaining voltage ranges predefined for the supply level VE1, VE2.

(6) In addition, each regulating unit RE1, RE2, RE3, i.e. each supply level VE1, VE2, VE3, can have a predefined voltage range which shall be maintained by the respective regulating unit. The first regulating unit RE1 or rather the transmission level VE1 is operated e.g. in an extra-high-voltage and high-voltage range (e.g. 60 to 380 kV and possibly even higher). In the second regulating unit RE2, i.e. the primary distribution level VE2, a medium-voltage range (e.g. 1 to 60 kV) can be maintained, for example. For fine distribution of energy, the third regulating unit RE3, i.e. the secondary distribution level VE3, can be operated in a low-voltage range e.g. between approx. 230/400 volts.

(7) For voltage transformation of energy between the supply levels VE1, VE2, VE3, appropriate transformation stations T1, T2 are therefore provided. For this purpose the second regulating unit RE2 or rather supply level VE2 has, for example, a first transformation station T1 (e.g. electrical substation, etc.). At the third supply level VE3 or rather in the third regulating unit RE3 a second transformation station T2 (e.g. transformer, etc.) is provided for this purpose.

(8) By controlling the active power P and reactive power Q transmitted between the regulating units RE1, RE2, RE3, so-called microgrids or stand-alone systems can also be very easily created or rather reincorporated into the power grid EV. For example, the second regulating unit RE2, i.e. the second supply level VE2, can be (temporarily) disconnected from the first regulating unit RE1 or rather the transmission level VE1 jointly with the third regulating unit RE3, because sufficient energy is being produced e.g. by the regional or local generators LZ1, LZ2, LZ3 to meet the demand of the second and third supply level VE2, VE3. Transmission of the active power P and the reactive power Q via the interface between the first and the second regulating unit RE1, RE2 is reduced to zero. The first and second supply levels VE1, VE2 are then still synchronized, but no more power P, Q is transmitted between them. Then once the corresponding first transformation station T1 has been disconnected, the two supply levels VE1, VE2 or rather the two regulating units RE1, RE2 are separated from one another. The second regulating unit is then operated as a microgrid or stand-alone network.

(9) For reconnection of the second regulating unit RE2 to the first regulating unit RE1, i.e. to the transmission level VE1, because, for example, the energy demand can no longer be covered locally/regionally, synchronization between the first regulating unit RE1 and the second regulating unit RE2 to be connected is first carried out. The active power P and reactive power Q to be transmitted between the regulating units RE1, RE2 is then increased so that power P, Q can again be exchanged between the regulating units RE1, RE2.

(10) A power grid EV is regarded by the method according to the invention and as a kind of energy supply chain in which the individual regulating units RE1, RE2, RE3 or rather links in the chain can interact with one another in a simple and flexible manner. This enables decentralized power generators LZ1, LZ2, LZ3, K1, K2, K3 to be very easily integrated into an existing power grid EV.