HK1111274A - Controlled power consumption of electric drives in machinery - Google Patents

Description

Controlled energy consumption of an electric drive in a machine

Technical Field

The present invention relates to a device for controlling an electric drive in a machine.

Background

Production machines with high-power electric drives in the range of 100KW and above place a considerable load on the ac power grid of the energy supply system, the machines with particularly strong fluctuating loads being particularly high loads of the power grid. The peak load occurring in this case must be correspondingly buffered by the current supply device, i.e. the current supply device of the machine must be designed such that the current supply is ensured even in the case of peak loads. Furthermore, load peaks are reflected in the electricity prices of energy supply companies, since peak loads result in the need for correspondingly expensive infrastructure in order to intercept such peak loads at any time. In particular, companies with a large total amount of mechanical equipment and a correspondingly large number of heavy fluctuating loads must pay correspondingly high electricity charges. However, load peaks occurring in large machines not only represent a large load of the power grid, but also result in the need for a correspondingly large determination of the parameters of the current supply in the machine itself, since all components, such as the power electronics and the intermediate current circuit, must be designed according to the peak load, which occurs, although only briefly. For example, printing presses therefore have a plurality of electric drives, which are usually supplied with power via a dc voltage intermediate circuit. If an electric drive with a high load peak is connected to the dc voltage intermediate circuit, a correspondingly high peak load arises for the dc voltage intermediate circuit, i.e. the dc voltage intermediate circuit must determine the parameters as a function of the high peak load. This makes the costs for determining the parameters of the dc voltage intermediate circuit and for supplying the dc voltage required for this purpose via the rectifier high.

The problem of load peaks has been known for a long time, wherein so-called energy management systems have been developed as an aid. Such an energy management system is known from DE 4421914 a 1. The solution described in DE 4421914 a1 is particularly applicable in a company grid connected to the grid of an energy supply company. The company grid supplies a plurality of machines and thus loads with electrical energy, wherein the individual loads are controlled by means of so-called "power regulators". Such devices are used on the one hand to avoid active power peaks by taking electrical energy from the power grid of the electricity supply company and forwarding it into the energy store during times of low load, for example at night when the electricity prices are low. As energy store, for example, a flywheel energy store can be used. If the load of the company power grid exceeds a predefined limit of the energy supply company, the required energy is no longer taken from the power grid of the energy supply company, but from an energy store in the form of a flywheel. This avoids overloading the power grid of the energy supply company by active power peaks. In addition, a capacitor bank is provided for compensating the reactive power peak, which compensates the reactive power peak. The solution proposed in DE 4421914 a1 does not, however, change the problem that the current supply of the loads 1 to n in the company grid still has to be parameterized according to the load peaks. This design according to the load peaks makes the current supply in the company network and the loads 1 to n significantly expensive.

Disclosure of Invention

The object of the present invention is therefore to provide a device for controlling the energy consumption of an electric drive in a machine, which allows the parameters of the current supply in the machine to be determined from the average power demand.

According to the invention, this object is achieved by the device according to the invention. According to the invention, a device for controlling electric drives in a machine is proposed, wherein an electronic control device is provided for precalculating the electric energy required by the electric drives as a function of a movement pattern of at least one electric drive. According to the invention, a machine for processing printing materials is also proposed, which machine has the device according to the invention.

Advantageous embodiments of the invention are apparent from the following description and the accompanying drawings.

The invention is suitable above all for use in larger production machines with a power consumption in the range of about 100KW and higher, which is already high-loaded and reaches the capacity limit for a 400 volt three-phase network. Such machines are also used in the printing industry, wherein sheet-fed printing presses and folding machines have drives at this power level. Since the machines installed in the printing plant must be maintained by on-site current supply devices, it is of interest for the operator of the printing machine to: the load characteristic of the installed machine is as problem-free as possible, since he must then take correspondingly few additional precautions for his printing plant power grid and not incur the expensive special electricity prices of the energy supply company. Furthermore, by avoiding overdetermined parameters of the current supply in the printing press itself, the production costs of the machine can be reduced accordingly. According to the invention, the device for controlling the energy consumption of the electric drive has a power electronics which makes it possible to calculate the electrical energy required by the drive motor in advance as a function of the movement pattern of the electric drive. The load peaks occurring in the drive motor are closely related to the working process in the printing press. In the case of printing presses, in particular in the case of the periodic operation of the control motor, certain processes therefore occur, which occur at regular intervals. Other drive motors are only required for a specific control process, the required electrical energy being dependent on the range of the control process itself. According to the invention, the power electronics can calculate the required electrical energy in advance from the movement pattern of the electric drive in the machine, whereby the required electrical energy is known with a high probability for a certain period of time in the future. The electrical energy required for this period of time is compared in the power electronics with the allowable peak load limit. If the load limit is to be exceeded in a pre-calculated time interval, a correspondingly higher electrical energy is drawn from the electrical network and temporarily stored in an energy store beyond the initial requirement of the electric drive, but the electrical energy thus drawn beyond the initial requirement is below the permissible peak load limit. And energy can also be taken before the motor is switched on, so the energy store can also be charged and then the peak load intercepted. The stored electrical energy can then be called out from an energy store in the machine by the electric drive when the peak load limit is exceeded, in order to mask load peaks occurring at short times.

When all electric motors of the machine or at least all powerful electric motors are equipped with the device according to the invention, the device according to the invention makes it possible to calculate the electrical energy requirement of the entire machine beforehand by calculating the electrical energy required for the respective movement pattern beforehand for each electric drive and by calculating the total energy requirement of all electric drives in the machine by means of a superordinate electronic control unit. For this purpose, either a separate electronic control unit can be provided, or one of the electronic control units can be provided for calculating the energy requirement of all other drive units in addition to the energy requirement of the connected drive unit or at least for receiving the calculation results of the other power electronics and taking into account the total requirement. The device according to the invention offers the important advantage that the total electrical energy supply of a machine, which usually has a plurality of electric drives, can be dimensioned according to the maximum average electrical energy requirement, since load peaks occur only in the drive itself, but no longer in the current supply of the machine itself. This maximum average power demand then represents the maximum peak load of the grid and is typically significantly lower than the maximum peak load.

In a first embodiment of the invention, it is provided thatThe power electronics are designed such that they calculate the average electrical power required for the electrical drive over a defined time interval. The defined time interval is expediently selected such that it corresponds to the duration of the movement process of the electric drive. If the movement pattern of the electric drive has a time interval T_nThe interval for calculating the average electrical energy then corresponds to this time interval T_n. The power electronics thus operate for the time interval T by means of the movement pattern_nThe total required electrical energy is determined and can be used for the time interval T_nDivided to calculate the average electrical power required. This required average electrical energy is then taken from the current supply device and used by the electric drive during the course of the movement pattern or already at least partially before the course, wherein load peaks are masked by a corresponding energy store in front of the electric drive. For this purpose, an energy store, which may be, for example, a capacitor or a capacitor bank, is provided between the voltage source and the electric drive. The electrical energy store absorbs the temporarily unneeded average electrical power drawn off, which is then recalled by the electric drive at load peaks during a sport mode start (Abfahren) and smoothes the load peaks accordingly.

It is advantageously provided that the electric drive is supplied with electrical energy via a converter or inverter. Drive motors are usually used in printing presses, which are supplied with current by a voltage controlled in a converter or inverter. A very precise and largely stepless electronic speed regulation of the drive motor can thereby be achieved. The inverter converts the dc voltage applied to its input into an ac voltage controlled by the motor electronics. The use of an inverter offers the advantage that not only can a current flow be achieved from the dc voltage network to the electric drive, but also a feedback flow can be made from the electric drive into the dc voltage network, for example in regenerative braking. In order to subject the electrical network of the machine to as little load as possible, the energy store is arranged directly upstream of the converter or inverter of the electric drive. This has the important advantage that the load peaks occurring due to the electric drive occur only in the drive itself and in the converter or inverter, but the entire network upstream of the energy store is loaded only with the maximum average electrical power of the electric drive. The energy store arranged in this way allows the load peaks that occur to be limited locally narrowly and thus allows the remaining grid parameters of the machine to be determined to a lesser extent from the average electrical power that is tapped. In printing presses, a plurality of drive motors are usually supplied with electrical energy via a dc voltage intermediate circuit. The power electronics, energy store, inverter or converter and electric drive are connected to the direct voltage intermediate circuit. The device according to the invention allows the dc voltage intermediate circuit to be used only for the maximum average power of the connected drive motor for the load.

Furthermore, the power electronics arranged at the higher level can additionally coordinate the power requirements of the drive motors in order to further reduce the maximum average electrical power occurring in the dc voltage intermediate circuit, for example, by avoiding simultaneous operation of all drive motors on the dc voltage intermediate circuit. For this purpose, the power electronics of the electric motors can communicate with one another and exchange their power calculation results, either directly or via a computer, for example a machine control device, so that the energy requirements can be coordinated with one another. When the maximum peak power is reached in the direct voltage intermediate circuit, the electric drive with the low priority is never switched on first. Furthermore, the power consumption of the individual drives can also be limited in order to reduce the overall demand. The dc voltage intermediate circuit can in turn be connected to an ac voltage network via a rectifier. In the printing machine, this network connection is the connection of the machine to a 400 volt three-phase network. By using the device according to the invention, a relatively uniform electrical power is obtained from the 400 volt three-phase network, which electrical power in particular does not have load peaks above the maximum average power.

It is also advantageously provided that sensors are provided for detecting the motor current and/or the motor voltage, which sensors feed the motor current and/or the motor voltage to the power electronics in order to calculate the electrical energy requirement of the electric motor. In this way, the power electronics can also take into account the actual value of the motor current and the actual value of the motor voltage and adjust for possible deviations from the pre-calculated setpoint values of the motor current and of the motor voltage. This prevents the motor current and the motor voltage from reaching values which would increase the average electric power beyond a predefined power limit. This is important because the electrical power drawn by the drive motor is not constant over the life even when the movement pattern is uniform. Therefore, the motor becomes easy to rotate or difficult to rotate over time due to the wear phenomenon, which causes the power consumption to increase or decrease accordingly. And there may be a jamming of the movable part, as a result of which the power consumption of the electric drive is also increased at least temporarily. All this can be determined by the detection of the motor current and the motor voltage by the power electronics and taken into account accordingly. In this way, if the power consumption is no longer compensated for by the existing energy store, the power electronics can also switch off the electric drive or reduce its power consumption if necessary. This also avoids a maximum average power consumption being exceeded by the electric drive.

It is advantageously provided that the power electronics have an electronic memory for storing a movement pattern of the electric drive. Depending on the task of the electric drive in the printing press, this drive has a typical movement pattern. In particular, in feeders of printing presses, the electric drive is operated at periodic intervals, wherein the power consumption fluctuates strongly during the period, but this can be taken into account correspondingly from the power electronics in the case of known movement patterns. According to the invention, the periodic movement pattern on the feeder is stored in a memory component of the power electronics. Once the printing press is put into operation, the power electronics can calculate the average electrical power required by the feeder drive motor using the machine speed selected by the operator and the stored movement pattern and charge the energy store accordingly. The periodic load peaks occurring during operation of the feeder are then captured by the energy store and do not cause the direct voltage intermediate circuit of the printing press to be loaded. The invention is therefore particularly applicable to: in the case of a periodic movement pattern of the electric drive, the peak load is homogenized and the maximum peak power drawn is limited to the average power during a period.

The electronic control unit is advantageously designed such that it calculates the average electrical power required for the electric drive during a specific time interval.

The electronic control unit is advantageously designed such that it calculates an arithmetic mean value of the power requirement of the electric drive as a function of the movement pattern to be periodically implemented.

Advantageously, an electrical energy store is provided between the voltage source and the at least one electric drive, and the electronic control device is provided in combination with the electrical energy store for: a largely constant electrical power is drawn from the upstream current supply at least for a time period, although the electric drive does not have a constant power consumption during this time period.

Advantageously, a converter or inverter is connected between the energy store and the electric drive.

Advantageously, the electronic control device is connected to a dc voltage intermediate circuit.

Advantageously, at least one dc load is connected to the dc voltage intermediate circuit.

Advantageously, the flow of electrical energy from the electronic control device to the electric drive is adjustable.

Advantageously, the energy flow from the electric drive to the electronic control device is adjustable.

Advantageously, the energy flow from the electronic control device to the electric drive and vice versa is adjustable.

Advantageously, the electronic control device has an electronic memory for storing the movement pattern of the electric drive.

Drawings

The invention is illustrated and described in detail below with the aid of several figures. The attached drawings show that:

fig. 1 shows a direct voltage intermediate circuit of a printing press with a device according to the invention, for supplying an electric drive with current,

the current characteristic in the direct voltage intermediate circuit of figure 1a,

figure 1b shows a current characteristic curve over a current transformer of an electric drive,

figure 2 is a flow of calculation of the average electric power,

figure 3a circuit according to the invention for constant power consumption in the case where the movement mode for driving the motor is purely electric,

FIG. 3b is a circuit for constant power consumption in the case where the motion mode of the drive motor is the generator only mode, according to the present invention, an

Fig. 3c shows a circuit according to the invention for constant power consumption in the case of generator mode and motor mode of the motion mode for driving the motor.

Detailed Description

The printing press 1 in fig. 1 has a plurality of consumers 3, one of which is illustrated in detail as an electric motor 2. The other dc loads 3 can also be electric motors. The dc load 3 and the electric motor 2 are connected to a dc voltage intermediate circuit 12 of the printing press 1. The dc voltage intermediate circuit 12 represents the highest voltage supply stage of the printing press 1. The printing press 1 is connected to a 400 volt triple via a rectifier 5And the phase grid 6. The rectifier 5 takes care of the intermediate circuit voltage U in the dc voltage intermediate circuit 12 which is as constant as possible_ZWK. The electric motor 2 in fig. 1 is an electronically regulated drive, wherein the current supply of the electric motor 2 is effected via an inverter 4 for the four-quadrant operating mode. The rotational speed and the torque of the electric motor 2 can be adjusted steplessly by means of the inverter 4. The actual invention consists in an energy management system 7, which is connected upstream of the inverter 4 of the electric motor 2. The energy management system 7 connects the inverter 4 to the dc voltage intermediate circuit 12 and is responsible for: only the maximum permissible electrical power is taken from the direct-voltage intermediate circuit 12 by the electric motor 2. For this purpose, the energy management system 7 has an electronic control device 8, which is composed of a power electronics and a computer, which calculates the power requirement of the electric motor 2 in advance. Furthermore, the energy management system 7 has an energy store 9, which is composed of one or more capacitors. The energy store 9 is provided for: the power peak of the motor 2 is intercepted. Furthermore, a movement pattern of the electric motor 2 is stored in the electronic control device 8, which can be used, for example, to drive a beam arrangement or a sheet brake in the printing press 1. Both the beam arrangement and the sheet brake cause a periodically strongly fluctuating movement pattern. Furthermore, fig. 1 shows sensors 13 which detect the motor voltage U at the inverter 4_PWRAnd motor current I_PWRAnd transmits them to the electronic control device 8. The electronic control unit 8 can thus take into account the motor current I_PWRAnd motor voltage U_PWRAnd if necessary, a setpoint-actual value regulation. The dc load 3, which is not shown in detail in fig. 1, can be constructed in common with the electric motor 2, together with the inverter 4 and the energy management system 7 connected upstream. This enables these dc loads 3 to also draw the maximum permissible input dc current I from the dc voltage intermediate circuit 12_EistAnd thus does not exceed the maximum allowed average power. An important advantage of the invention is that the direct voltage intermediate circuit 12 has to be designed only on the basis of the maximum permitted average power and not the power peak. The power peak being only localizedThe direct presence of these power peaks on the electric motor 2 is limited, since these power peaks are correspondingly intercepted by the energy management system 7, which is composed of the electronic control device 8 and the energy store 9. The reduced parameters of the dc voltage intermediate circuit 12 in turn lead to the parameters of the rectifier 5 being able to be determined to be smaller, since the rectifier also does not have to carry a strongly fluctuating peak load, but only has to output the maximum permissible average power. As a further consequence, the 400-volt three-phase network 6 is also accordingly not loaded with strongly fluctuating power and in particular not with high peak loads.

FIG. 1a shows exemplarily a calculated input current I_EThe input current corresponds to the actual input current I in FIG. 1_Eist. It can be seen that in the ideal case I_EAnd I_EistAt a determined time interval T_nIs kept constant, thereby during the time interval T_nNo load fluctuations occur in the dc voltage intermediate circuit 12 caused by the electric motor 2. In contrast, fig. 1b shows the motor current I at the inverter 4_PWRThe motor current has strong fluctuations corresponding to the movement pattern of the motor 2. The current characteristic curve in fig. 1b represents the operation both in generator mode and in motor mode. But is effected by the energy management system 7 first at a determined period T_nCalculates the required electrical energy and is thus cycled for a time period T_nDivided to calculate the average electrical power required and thereby calculate the average input current I required_E. The input current is then during the period duration T_nConstant in the above view and corresponding to an average strongly fluctuating motor current I_PWR。

FIG. 2 shows a diagram for calculating the average electric power P required for the motor 2_AVThe process of (1). For this purpose, the stored movement pattern is used to input the period duration T of the repetitive movement to the electronic control device 8_nAnd the mode occurring in this case, and the motor voltage U sampled at the inverter 4 as the actual value input_PWRAnd motor current I_PWR. From these data, the electronic control unit 8 passes the data for a given period duration T_nIntegrating to calculate the time T for a predetermined period_nRequired average electric power P_AV. The required average power P thus calculated is calculated in a module 11 of the electronic control device 8 for calculating the current_AVAnd an intermediate circuit voltage U of the direct voltage intermediate circuit 12_ZWKTo calculate a given motor current I_Esoll. The given value I_EsollActual value I of the input current to the energy management system 7 in a current regulator 10_EistA comparison is made in which a deviation I occurs_EdiffAs a difference current is adjusted. In this way, the calculated average electric power P is then calculated_AVFor use in the inverter 4, temporarily unneeded electrical energy is temporarily stored in the energy store 9 and is available for use by the inverter 4 during load peaks. In this way, power peaks are blocked by the energy management system 7 and do not propagate to the dc voltage intermediate circuit 12.

The energy store 9 is designed according to the following criteria. According to the permissible input voltage range U of the inverter 4_PWRThe energy store 9 must be charged to the maximum permissible voltage by the energy management system 7 before or at the start of operation of the electric motor 2. The energy store 9 is dimensioned such that the voltage across the energy store 9 after the periodic power peaks have decayed does not fall below the lower voltage limit of the inverter 4. During the discharging phase or the recuperating phase, for example when the electric motor 2 is braking, the energy store 9 is charged with constant power by the energy management system 7. The supplementary charging current is designed as optimally as possible according to the periodically occurring power peaks of the drive motor 2, so that the next acceleration process of the motor 2 takes place when the maximum charging voltage in the energy store 9 is reached.

Fig. 3a shows an electronic control device 8 connected to an energy store 9, which is designed to compensate for the motor-occurring power peaks of the electric motor 2. However, no feedback is possible with the circuit according to fig. 3a, so that only power peaks during operation in the motor mode can be compensated. In this case, an inverter 4 which allows only motor operation is connected to the energy store 9. In contrast, the circuit according to fig. 3b only allows the connected electric motor 2 to be operated as a generator, which for example continuously operates as a brake drive in the printing press 1. The electronic control device 8 is configured to: the average electrical power, which is as uniform as possible, is fed back from the electric motor 2 via the energy store 9 into the direct-voltage intermediate circuit 12. In this case, the electronic control device 8 is used in conjunction with the energy store 9 for: even during the feedback, no feed peaks occur in the dc voltage intermediate circuit 12. Fig. 3c shows an electronic control device 8 as used in connection with the inverter 4 in fig. 1. In this case, the electric motor 2 can be operated both as a generator and as a motor, wherein the electronic control device 8 ensures, in combination with the energy store 9: only the maximum permitted electrical power is taken from the dc voltage intermediate circuit 12 and is also fed in. The embodiments according to fig. 3a, 3b, 3c are used in accordance with the respective application. The electric motor 2 operated in the four-quadrant operating mode is fed via the circuit according to fig. 3c, while the electric motor 2 operated only in the motor mode or in the generator mode is each coupled to the circuit according to fig. 3a or 3 b. However, all three circuits have in common that the dc voltage intermediate circuit 12 is loaded only with the maximum permissible average electrical power, as a result of which the parameters of the dc voltage intermediate circuit 12 can be correspondingly reduced.

List of reference numerals

1 printing machine 12 DC voltage intermediate circuit

2 electric motor 13 sensor

3 DC electrical appliance I_PWRCurrent of motor

4 inverter U_PWRVoltage of motor

5 rectifier I_EistInput direct current

6 net connecting end U_ZWKIntermediate circuit voltage

7 energy management System I_ECalculated input current

8 electronic control device I_EdiffDifference current

9 energy store I_EsollGiven motor current

10 Current regulator P_AVRequired power

11 current calculating means T_nDuration of cycle

Claims (15)

1. Device (7) for controlling an electric drive (2) in a machine (1), characterized in that: an electronic control device (8) is provided for pre-calculating the electrical energy required by the electric drive device (2) on the basis of a movement pattern of at least one electric drive device (2).

2. The device (7) according to claim 1, characterized in that: the electronic control device (8) is designed in such a way that it calculates the time interval (T) between two points_n) Required level of said electric drive (2)Are all electrically powered.

3. The device (7) according to claim 1 or 2, characterized in that: the electronic control device (8) is designed in such a way that it calculates an arithmetic mean of the power requirement of the electric drive (2) as a function of the movement pattern to be periodically implemented.

4. Device (7) according to one of the preceding claims, characterized in that: an electrical energy store (9) is arranged between the voltage source (6) and the at least one electric drive (2) and the electronic control device (8) is arranged in conjunction with the electrical energy store (9) for: at least for a period of time (T)_n) The largely constant electrical power (P) is taken from the upstream current supply device (6, 12)_AV) Although during this time period (T)_n) Wherein the electric drive (2) does not have a constant power consumption.

5. Device (7) according to one of the preceding claims, characterized in that: the electric drive (2) is supplied with electrical energy via a converter or inverter (4).

6. The device (7) according to claim 5, characterized in that: the converter or inverter (4) is connected between the energy store (9) and the electric drive (2).

7. Device (7) according to one of the preceding claims, characterized in that: the electronic control device (8) is connected to a DC voltage intermediate circuit (12).

8. The device (7) according to claim 7, characterized in that: the DC voltage intermediate circuit (12) can be connected to an AC voltage network (6) via a rectifier (5).

9. The device (7) according to claim 7 or 8, characterized in that: at least one direct current consumer (3) is connected to the direct voltage intermediate circuit (12).

10. Device (7) according to one of the preceding claims, characterized in that: provided with means for detecting motor current (I)_PWR) And/or motor voltage (U)_PWR) And sensors (13) which feed the motor current and/or the motor voltage to the electronic control device (8) in order to calculate the electrical energy requirement of the electric motor (2).

11. Device (7) according to one of the preceding claims, characterized in that: the flow of electrical energy from the electronic control device (8) to the electric drive (2) is adjustable.

12. Device (7) according to one of claims 1 to 10, characterized in that: the energy flow from the electric drive (2) to the electronic control device (8) is adjustable.

13. Device (7) according to one of claims 1 to 10, characterized in that: the energy flow from the electronic control device (8) to the electric drive (2) and vice versa is adjustable.

14. The device (7) according to one of claims 1 to 13, characterized in that: the electronic control device (8) has an electronic memory for storing a movement pattern of the electric drive (2).

15. Machine (1) for treating substrates, having a device (7) according to one of claims 1 to 14.