WO 2007/042603 PCT/FI2006/000312
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ELEVATOR CONTROL SYSTEM FOR REGENERATIVE POWER
The present invention relates an elevator system, which elevator system
can be used both when the internal electricity network of the building is
connected to the public electricity distribution network and when the
electricity network of the building is connected to a reserve power
appliance, and a method for controlling the elevator motor in the elevator.
In a normal operating situation an elevator is controlled such that each time
it is used the elevator travels the distance between the departure floor and
the destination floor as quickly as possible, taking into account equipment
aspects and passenger comfort aspects. Therefore the aim is to control the
elevator motor in such a way that the acceleration, deceleration and travel
speed of the elevator are as great as possible with regard to the equipment
and passenger comfort. The power transmitted via the motor between the
electrical system and the traction sheave of the elevator varies according to
which direction, at what acceleration or deceleration and with what kind of
load the elevator is driving. Depending on the drive situation the elevator
- motor eitherconverts electrical power into mechanical power, with which
the elevator car and any counterweight and rope is moved, or converts
mechanical power transmitted to the traction sheave from changes in the
potential energy or kinetic energy of the elevator car and counterweight into
electrical energy. Some of the power delivered to the motor is consumed
in motor losses.
A requirement for controlling the elevator in the manner described above is
that the electrical system, to which the elevator drive is connected, is able
to adapt to the power requirement of the elevator motor. This means that
the electrical system must be able if necessary to both supply electrical
power to the motor and to receive electrical power supplied to the electrical
system by the motor. In a normal operating situation the electrical power
supplied towards the motor is received from the public electricity distribution
network. The power supplied towards the electrical system by the motor

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can be converted to heat in a resistor pack connected for this
purpose to the electrical system or the power can be supplied back to the
building's internal or the public electricity distribution network for
consumption by the other loads connected to the same network. Especially
in efficient and fast elevators, in which there is substantial power
transmission from the motor towards the electrical system, it is economical
to supply the electrical power generated back into the electricity network for
utilization in other devices connected to the electricity network. The power
supplied towards the electricity network when driving in the lighter direction
e.g. in a situation in which an elevator equipped with a counterweight
drives at full load and speed downwards or empty upwards, or an elevator
without counterweight drives downwards. The electrical power supplied
back corresponds at its best to 90% of nominal power. For this reason the
motor drives contain a so-called controlled network bridge, which forms
current of the correct frequency, form and voltage.
In an exceptional situation, for instance as a consequence of power cuts,
the connection of the electrical system of the elevator to the public
electricity network can be cut off. As a precaution for these kinds of
situations reserve power appliances have been arranged in many buildings,
by means of which typically only a part of the electrical devices can be
used. In this case also the elevator motor must be able to operate within
the limitations of the electrical system. A reserve power system, in which
the speed of the elevator motor is regulated so that the power taken by the
elevator drive from the network is smaller than an adjustable power limit, is
known from publication EP0794919.
In reserve power use some of the loads of the electricity network of the
building are typically switched out of use. When an elevator system, which
is arranged to supply electrical power back towards the electricity network
when driving in the lighter direction, operates in reserve power use, the
power supplied by the elevator system towards the network can exceed the
load capacity of the electricity network of the building. In this case the

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voltage of the electricity network rises, and the electrical devices
connected to the network can be damaged owing to overvoltage.
According to prior-art it is endeavored to limit the power supplied towards
the network of an elevator system such that a separate load is connected
to the electrical system of the elevator, such as a resistor pack, to which
the power generated when braking or driving in the lighter direction is
supplied. A drawback in the prior-art solution is that providing the
elevator with a separate load that receives power for situations of
disrupted electricity supply increases the costs of the elevator system. A
further drawback in using separate loads that consume power is that
space must be reserved for these in connection with the machinery of the
elevator. Additionally when using a separate load resistance the potential
energy of the elevator and passengers is wastefully consumed. In
systems in which the electrical power generated by the elevator motor in
a normal situation is utilized by supplying it to other loads of the electricity
network, procurement of a resistor pack is only necessary in exceptional
circumstances.
The elevator system according to the invention is characterized by what is
disclosed in the characterization part of claim 1 and the method according
to the invention is characterized by what is disclosed in the
characterization part of claim 6. Other embodiments of the invention are
characterized by what is disclosed in the other claims. Some inventive
embodiments are also presented in the descriptive section of the present
application. The inventive content of the application can also be defined
differently than in the claims presented below. The inventive content may
also consist of several separate inventions, especially if the invention is
considered in the light of expressions or implicit sub-tasks or from the
point of view of advantages or categories of advantages achieved. In this
case, some of the attributes contained in the claims below may be
superfluous from the point of view of separate inventive concepts.

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The elevator system according to the invention is connected to the
internal electricity distribution network of the building, which can be
further connected either to the public electricity distribution network or to
a reserve power appliance. The elevator system comprises at least one
elevator, an elevator control system, an elevator motor and a frequency
converter fitted to supply the elevator motor. The elevator system can be
used both when the electricity distribution network of the building is
connected to the public electricity distribution network and when the
electricity distribution network of the building is connected to a reserve
power appliance. The elevator system comprises means for controlling
the elevator such that when the electricity network of the building is
connected to a reserve power system the power supplied by the elevator
system towards the electricity network of the building is smaller than the
power limit that can be set for it. The elevator system can be fitted to
operate such that the elevator system does not supply power to the
internal electricity network of the building.
In one embodiment of the invention the elevator system further comprises
means for controlling at least one motor such that the electrical power
generated by the elevator motor is smaller than the power limit that can
be set for generated electrical power. In this case means for consuming
electrical power generated by the motor or for storing energy do not need
to be arranged in the intermediate circuit of the frequency converter fitted
to supply the elevator motor. The power limit can be set to correspond to
e.g. the power consumption of the auxiliary devices and of the control
system. In one embodiment of the invention the system further comprises
means for monitoring the status of the electricity network of the building
and for specifying the power limit.
In the method according to the invention for controlling elevators in an
elevator system, which elevator system is connected to the electricity
distribution network of the building, which can be further connected either
to the public electricity distribution network or to a reserve power

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appliance, and which elevator system comprises at least one
elevator, an elevator motor, a frequency converter fitted to supply the
elevator motor, an elevator control system and the auxiliary devices of the
elevator, and which elevator system can be used both when the electricity
network of the building is connected to the public electricity distribution
network and when the electricity network of the building is connected to a
reserve power appliance, when the electricity network of the building is
connected to the reserve power system the elevators are controlled such
that the power supplied by the elevator system to the electricity network
of the building is smaller than the limit value that can be set for it. In one
embodiment of the invention the speed of at least one elevator motor is
controlled to be such that the electrical power generated by the elevator
motor is smaller than the power limit Pr that can be set for the power
generated. According to the method the power needed by the auxiliary
devices of the elevator and by the control system of the elevator can
further be specified, and the power limit can be set to correspond to the
power required by the auxiliary devices and the control system of the
elevator. The- power limit for power supplied to the network can be
specified e.g. such that it corresponds to the power requirement of other
equipment of the electricity network as well as that of the elevator system
itself.
The elevator system according to the invention can be used both when
the electricity network supplying the elevator is connected to the public
electricity distribution network and when the electricity network is
connected to reserve power. A power limit can be set for the power
supplied by the elevator system towards the network, in which case when
the elevator system is operating connected to the reserve power supply
the power supplied to the electricity network of the system does not
exceed the permitted limit. When the limit is set to be such that the power
supplied does not exceed the power which can be consumed in the loads
of an isolated network, the means for consuming power, such as a

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resistor pack, normally connected for reserve power use in
conjunction with the power supply of an elevator system can be
dispensed with. This achieves both cost savings and saves space in the
building, as the space required by the elevator machinery is smaller.
It is also possible to limit the power generated by the motors of the
elevator system such that it corresponds to the specific power
consumption of the elevator and its auxiliary devices. In this case the
elevator system operates when driving in the lighter direction fully self-
sufficiently, without taking power from the network or supplying power to
the network. The reserve power capacity of the building can in this case
be utilized for other use.
In the following, the invention will be described in more detail by the aid of
a few examples of its embodiments with reference to the attached
drawings, wherein
Fig. 1 illustrates one elevator system according to the invention
connected to the internal electricity, distribution network of the
building
Fig. 2 illustrates another elevator system according to the invention
connected to the internal electricity distribution network of the
building
Fig. 3a illustrates an electricity supply appliance of a prior-art elevator
system
Fig. 3b illustrates an electricity supply appliance of an elevator system
according to the invention
Fig. 1 presents an elevator system according to the invention, in which the
elevator system 24 comprises four elevators 8. In the elevator system
according to Fig. 1 the reserve power machine or reserve power generator
2 in a reserve power situation supplies the power-consuming devices

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connected to the network via the electricity supply network 4. In a
normal operating situation the network 4 is connected via the switch 6 to
the external electricity supply network 7, such as the public electricity
distribution network. Some of the power-consuming devices are the
elevators 8 of the building, of which there are four in this figure, but of
which there can be more, and which can be formed into an elevator group
24 subject to the same group control. Of the elevators 8, only the traction
sheave 29, drive motor 28 and the regulating device for controlling the
motor, such as a frequency converter 26, are presented in Fig. 2. The
number of elevators, their grouping into elevator groups and the control
devices and auxiliary devices vary in practical implementations. It is also
possible that the elevator system comprises its own reserve power source,
such as a UPS appliance, which can be connected e.g. to point A of Fig. 1.
Some of the power-consuming devices are appliances which must be
operational in an emergency, such as emergency lighting 10, fans 12. In
addition the devices in use in the building in a normal situation such as
normal lighting 18 and office machines and other machines 20 are
connected to the network 4 via the switch 16. The reserve power
generator supplies devices which are specified in advance and the others
are switched out of operation. For example the devices behind the switch
16 can be switched off if necessary. Consequently the power
consumption capacity of the internal electricity network of the building in
reserve power use is typically smaller than in a normal operating
situation, in which case the supply is received from the public electricity
distribution network. As a consequence the power generated by the
elevator motors to the electricity network cannot be utilized in reserve
power use in the same way as in normal operating conditions.
In order to avoid a rise in the voltage of the electricity network 4, the
elevator system 24 may not supply more power to the electricity network 4
than what can be consumed in the loads connected to it. When the
elevator system 24 comprises more than one elevator, there is no need to

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limit the power generated in respect of each individual elevator motor 28
in order to limit the power supplied by the elevator system towards the
network. In this case the power generated by one elevator motor can be
utilized to move another elevator car. The elevator system according to the
invention comprises means for controlling the elevators such that the power
supplied by the elevator system towards the network 4 does not exceed the
limit value Pa that can be set for it. The motions of the elevators are
controlled in the manner of the group control or the other control equipment
manner that is in itself prior-art in the directions according to the commands
delivered. The speed of the elevators according to the invention and / or
the power factor of the elevator motor as well as the departure sequences
of the elevators are controlled to be such that the sum of the outputs of the
electric motors remains at any given moment below the power limit Pa that
can be set. The power generated by the motor of an individual elevator 8
can in this case be greater than Pa. It is possible for example that one
elevator starts first to drive in the lighter direction, and after this has started
another elevator is set to drive in the heavier direction such that the speed
of the elevator is adapted to the load of the elevators and the power
generated by the motor of the other elevator to a definite value. If UPS is
used in the system it is possible to drive for a long time such that the
accumulators of the UPS device are not loaded at all. The power supplied
towards the network can be minimized, the limit value Pa can also be set to
zero, in which case the elevator system does not supply any power at all to
the network.
Fig. 2 presents another embodiment of the invention, in which the elevator
system 24 comprises one elevator 8, which is controlled by means of a
frequency converter 26 and an elevator motor 28. The same numbering
has been used in Fig. 2 as in Fig. 1. The operation of the elevator system
according to Fig. 2 is described in more detail in the following with
reference to Figs. 3a and 3b.

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Fig. 3a presents a prior-art elevator system comprising one elevator
applicable to high-rise buildings, which is designed to be operable both in
reserve power use and when normally connected to the network. Reserve
power means here a situation in which the internal electricity distribution
network of the building, to which the elevator system is connected, is
supplied by a generator, by means of the accumulators of an
uninterruptible power source (UPS) or by another applicable appliance
arranged to supply electrical energy to the network. The elevator car 82 is
moved by the motor 28, which is supplied by a frequency converter 26, via
the hoisting ropes 81 and the traction sheave 29 of the elevator. The
frequency converter 26 comprises two controllable rectifier units 31,32 and
a direct-voltage intermediate circuit 33 between them, to which a resistance
pack 30 is connected. A capacitor can additionally be connected to the
intermediate circuit. The frequency converter is controlled by means of the
elevator control system 34. The elevator system of Figs. 3a and 3b
contains in addition a counterweight 83, the mass of which typically
corresponds to approximately 50% of the mass of the elector car with a
full load. -The-elevator system of Fig; 3a operates as follows, when the
elevator system is connected to the public electricity distribution network.
When the elevator drives in the heavier direction, e.g. when moving an
empty elevator car downwards, power is transmitted from the electricity
network by means of the rectifier units 31 and 32 to the motor 28. When
the elevator is driving in the lighter direction the motor 28 generates
electrical power, which is supplied by means of the frequency converter 26
back to the electricity network for consumption by the devices connected to
the network. When the elevator system is connected to an electricity
network, which receives its supply from reserve power, maximum power is
not necessarily available from the electrical system, in which case it may be
necessary to limit the travel speed of the elevator when driving in the
heavier direction. This type of solution is known from e.g. publication
EP0794920. Owing to the change in the potential energy and kinetic
energy of the elevator car, when driving in the lighter direction the

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generated power can be supplied to the other elevators of the elevator
group or to other electrical devices. If there is a risk that the generated
power exceeds the power requirement of the loads of the electricity
network, the power generated in the electric motor is consumed in the
resistor pack 30 connected to the frequency converter, which can be
connected e.g. by means of the switch 35 of its intermediate circuit 33, i.e.
the electrical energy is converted to heat. In connection with the elevator
groups it is further possible to consume energy supplied to the network by
driving elevators belonging to another group at zero speed, in which case
the elevator motor consumes an amount of power equivalent to its losses,
or by supplying the generated power for driving an elevator of another
elevator group in the heavier direction. In connection with elevator systems
which contain only one elevator this is not, however, possible.
Fig. 3b describes an elevator system according to the invention. In Fig. 3b
the parts of the elevator system are numbered in the same way as in Fig.
3a. The elevator system according to the invention otherwise operates in
the same way as the prior-art elevator system described above, but. in the
elevator system according to the invention the power supplied by the motor
28 towards the network is limited in reserve power use such that the power
generated by the electric motor 28 does not in any operating situation
exceed the load capacity of the other devices 10,12,18,20 connected to the
electricity network. In this case the power generated by the electric motor
can be supplied through the frequency converter 26 back to the electricity
network also in reserve power use, and the resistor pack 30 presented in
Fig. 3a for consuming power or an energy store is not needed in the
intermediate circuit 33 or elsewhere in connection with the electricity supply
system. By dispensing with the resistor pack it is possible to achieve
substantial cost savings in the elevator system, and in addition the space
required in the building by the electricity supply appliances of the elevator
system is smaller.

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In the elevator system according to the invention the frequency
converter 26 controls the motor 28 in reserve power use such that the
power generated by the motor does not exceed the power limit Pr that can
be set for it. If the elevator system comprises only one elevator, the power
limit Pr can be set also as the power limit Pa of the power supplied by the
elevator system to the network.
When the motor is functioning as a generator the distribution of power
can be expressed with the equation Pm = Pe + Pi, where Pm = mechanical
power on the shaft of the motor, Pe = generated electrical power and Pi =
power loss. The power Pm is proportional to the speed of rotation of the
motor, so the power generated by the motor can be limited in elevator
use e.g. such that the speed of rotation of the motor is limited. In this
case the speed reference, with which the frequency converter drives the
motor, can be formed based on the power limit Pr that can be set and on
the load data. It is further possible to limit the generated power such that
the proportion of the of the shaft power that is the power loss Pi is
increased, e.g. by changing the power factor with which the motor is
supplied. In this case the generated power Pe decreases.
The power limit Pr can be selected e.g. such that the power limit
corresponds to the sum of the power required by the control system 34 and
the auxiliary devices, such as the lighting 10 and the fans 12, if necessary
with the losses of the frequency converter added. In this case the load
capacity of the other devices 18, 20 possibly connected to the electricity
network does not need to be utilized.
It is also possible that the elevator system comprises means, with which
the status of the electricity network can be monitored, in which case by
comparing the reserve power supplied to the electricity network to the
power of the elevator system at the same time it is possible to specify the
electrical power consumed by the other devices 10,12,18,20 connected to
the electricity network, and further to set the power limit Pa and / or Pr such

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that the power limit corresponds to the power required by the devices
connected to the electricity network. The power limits Pa and Pr can also be
specified on another appropriate basis.
In an emergency people are typically leaving the building, in which case
the elevator cars travel downwards loaded and upwards empty, in other
words in the case of an elevator with counterweight they are driven in the
lighter direction when moving both upwards and downwards. In one
preferred embodiment of the invention the power of the electric motors is
limited such that the power generated by the motors corresponds to the
specific power consumption of the elevator system itself and its auxiliary
devices. In this case the elevator system can operate fully self-
sufficiently, without taking power from the network or supplying power to
the network. The elevator system can thus be available for evacuation
drive also in a situation in which the internal electricity network of the
building is completely without a separate power supply, i.e. when the
network has no connection with the public electricity network and the
reserve power appliance is not connected or not available for some other
reason.
If the elevator system includes only one elevator, the generated power
can be consumed in the control system of the elevator and in the auxiliary
devices of the elevator. In an elevator system comprising more than one
elevator it is further possible to supply power also to the other motors of
the elevator system.
The inventive concept also includes a method for controlling the elevators
in an elevator system. The drive directions and destination floors of the
elevators are specified using a method that is in itself prior-art. In
accordance with the invention when the electricity network of the building is
connected to the reserve power supply the departure sequence and travel
speeds of the elevators and/or the power factors of the elevator motors are
controlled such that the power supplied by the elevator system to the

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electricity network does not exceed the power limit that can be set for
it. In an elevator system comprising more than one elevator the power
generated by the motor of an individual elevator can be utilized for use by
another elevator, and the travel speeds of the elevators and / or the
power factors of the motors can be adapted such that the power supplied
by the elevator system towards the network remains below the permitted
limit Pa.
in one embodiment of the invention the speed of at least one elevator
motor is controlled to be such that the electrical power generated by the
elevator motor is smaller than the power limit Pr that can be set for the
generated power. Regulation of the speed of the motor can be
implemented by methods that are in themselves prior-art. The method
can also comprise specification of the power limit Pa and / or Pr itself. For
specifying the power limit it is possible e.g. to specify the power required
by the auxiliary devices, the power required by the control system of the
elevator, and to set a power limit that corresponds to the power required
by the auxiliary devices and the control system. It is further possible to
specify the power supplied by the reserve power appliance to the
electricity network of the building and simultaneously the power taken
from or supplied to the network by the elevator system, and to specify the
power requirement of the other devices connected to the electricity
network of the building by comparing the power supplied by the reserve
power appliance to the network and the power taken or supplied by the
elevator system. The power limit Pa and / or Pr can be set such that it
corresponds to the power requirement of the other devices of the
electricity network as well as of the elevator system itself.
The invention is described above by the aid of some embodiments. The
embodiments are not however to be regarded as restricting the scope of
protection of the patent, but instead the embodiments of the invention
can vary within the scope defined in the claims below.

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CLAIMS
1. Elevator system (24), which elevator system (24) is connected to the
electricity distribution network (4) of the building, which can further be
connected either to the public electricity distribution network (7) or to a
reserve power appliance (2), and which elevator system (24)
comprises at least one elevator (8), an elevator control system (34),
an elevator motor (28), a frequency converter (26) fitted to supply the
elevator motor (28), and which elevator system (24) can be used both
when the electricity network (4) of the building is connected to the
public electricity distribution network (7) and when the electricity
network (4) of the building is connected to a reserve power appliance
(2), characterized in that the elevator system (24) comprises means
for controlling the elevators (8) such that when the electricity network
(4) of the building is connected to the reserve power appliance (2) the
power supplied by the elevator system (24) towards the electricity
networkdoes notexceedthe power limit Pa that can be set tor it
2. Elevator system (24) according to claim 1, characterized in that the
elevator system does not supply power to the internal electricity
network (4) of the building.
3. Elevator system according to claim 1 or 2, characterized in that the
elevator system (24) comprises means for controlling at least one
motor (28) such that the electrical power generated by the elevator
motor (28) is smaller than the power limit Pr that can be set for the
generated electrical power.
4. Elevator system according to any of claims 1-3 above, characterized
in that the frequency converter (26) fitted to supply the elevator motor
(28) comprises two controllable rectifier units (31, 32) and a direct-
voltage intermediate circuit (33) between them, and for which

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intermediate circuit (33) no means are arranged for
consuming the electrical power generated by the motor.
5. Elevator system according to any of the claims above, characterized
in that the power limit Pa and / or Pr is set to correspond to the power
consumption of the auxiliary devices (10,12) and of the control system
(34).
6. Elevator system according to any of the claims above, characterized
in that the system further comprises means for monitoring the status
of the electricity network of the building and for specifying the power
limit Pa and / or Pr.
7. Method for controlling elevators (8) in an elevator system (24), which
elevator system (24) is connected to the electricity distribution network
(4) of the building, which can be further connected to the public
electricity distribution network (7) or to a reserve power appliance (2),
and which elevator system (24) comprises at least one elevator (8), an
elevator motor- (28)ra-frequency-converter (26) -fitted to -supply the
elevator motor (28) and an elevator control system (34), and which
elevator system (24) can be used both when the electricity network (4)
of the building is connected to the public electricity distribution network
(7) and when the electricity network (4) of the building is connected to
a reserve power appliance (2), characterized in that the elevators (8)
are controlled such that when the electricity network (4) of the building
is connected to a reserve power system (2) the power supplied by the
elevator system (24) towards the electricity network (4) of the building
is smaller than the power limit Pa that can be set for it.
8. Method according to claim 7, characterized in that the speed of at
least one elevator motor (28) is controlled to be such that the electrical
power generated by the elevator motor (28) is smaller than the power
limit Pr that can be set for the power generated.

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9. Method according to claim 7 or 8, characterized in that the
method further comprises the phases:
- The power required by the auxiliary devices of the elevator is
specified
- The power required by the control system of the elevator is
specified
10. Method according to claim 9, characterized in that the method
further comprises the phase:
- The power limit Pa and / or Pr is set to correspond to the power
required by the auxiliary devices and the control system of the
elevator.

In the invention an elevator
system (24) and a method for controlling
elevators in the elevator system are presented.
The elevator system (24) is connected to
the electricity distribution network (4) of the
building, which can further be connected either
to the public electricity distribution network
(7) or to a reserve power appliance (2). The
elevator system (24) comprises at least one
elevator (8), an elevator control system (34), an
elevator motor (28), and a frequency converter
(26) fitted to supply the elevator motor (28).
The elevator system can be used both when
the electricity network (4) of the building is
connected to the public electricity distribution
network (7) and when the electricity network (4)
of the building is connected to a reserve power
appliance (2), and the elevator system (24)
comprises means for controlling the elevator (8)
such that when the electricity network (4) of the
building is connected to a reserve power system
(2) the power supplied by the elevator system
(24) towards the electricity network does not
exceed the power limit P3 that can be set for it.