CLOSED-LOOP CONTROL DEVICE FOR CLOSED-LOOP CONTROL OF A POWER ASSEMBLY INCLUDING AN INTERNAL COMBUSTION ENGINE AND A GENERATOR HAVING AN OPERATIVE DRIVE CONNECTION TO THE INTERNAL COMBUSTION ENGINE, CLOSED-LOOP CONTROL ARRANGEMENT HAVING SUCH A CLOSED-LOOP CONTROL DEVICE, POWER ASSEMBLY AND METHOD FOR CLOSED-LOOP CONTROL OF A POWER ASSEMBLY

Abstract

A closed-loop control device, for closed-loop control of a power assembly including an internal combustion engine and a generator having an operative drive connection to the internal combustion engine, includes: the closed-loop control device which is configured for: detecting a generator power (P.sub.G) of the generator as a controlled variable; determining a control deviation (e.sub.P) as a difference between the generator power (P.sub.G) which is detected and a target generator power (P.sub.soll); determining a target speed (n.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.P); using a control rule for determining the target speed (n.sub.soll); and being operatively connected to an open-loop control device of the internal combustion engine in such a way that the target speed (n.sub.soll) can be transmitted by the closed-loop control device to the open-loop control device.

Claims

1. A closed-loop control device for closed-loop control of a power assembly including an internal combustion engine and a generator having an operative drive connection to the internal combustion engine, the closed-loop control device comprising: the closed-loop control device which is configured for: detecting a generator power (P.sub.G) of the generator as a controlled variable; determining a control deviation (e.sub.P) as a difference between the generator power (P.sub.G) which is detected and a target generator power (P.sub.soll); determining a target speed (n.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.P); using a control rule for determining the target speed (n.sub.soll); and being operatively connected to an open-loop control device of the internal combustion engine in such a way that the target speed (n.sub.soll) can be transmitted by the closed-loop control device to the open-loop control device.

2. The closed-loop control device according to claim 1, wherein the closed-loop control device is configured for adapting the control rule used to determine the target speed (n.sub.soll) as a function of at least one adaptation variable, and wherein the at least one adaptation variable is selected from a group consisting of: the generator power (P.sub.G) that is detected; a generator frequency (f.sub.G); a droop variable (d); and at least one target torque variable.

3. The closed-loop control device according to claim 2, wherein the at least one target torque variable is calculated by the open-loop control device of the internal combustion engine.

4. The closed-loop control device according to claim 2, wherein the closed-loop control device is configured for adapting the control rule by determining a proportional coefficient (k.sub.p.sup.P) of the control rule in such a way that a predetermined loop gain (v.sup.p) of an open control loop is constant.

5. The closed-loop control device according to claim 4, wherein the closed-loop control device is configured for calculating the proportional coefficient (k.sub.p.sup.P) as a function of the generator power (P.sub.G), the generator frequency (f.sub.G), the droop variable (d), and the at least one target torque variable.

6. The closed-loop control device according to claim 4, wherein the closed-loop control device is configured for calculating the proportional coefficient (k.sub.p.sup.P) as a function of: (a) the generator power (P.sub.G), the droop variable (d), and the at least one target torque variable; (b) the generator power (P.sub.G) and the generator frequency (f.sub.G); (c) only the generator power (P.sub.G); or (d) the droop variable (d) and the at least one target torque variable.

7. The closed-loop control device according to claim 4, wherein the closed-loop control device (3) is configured for calculating the proportional coefficient (k.sub.p.sup.P) as a function of: (a) the generator power (P.sub.G), the droop variable (d), and the at least one target torque variable, wherein the generator frequency (f.sub.G) is set so as to be constant; (b) the generator power (P.sub.G) and the generator frequency (f.sub.G); (c) only the generator power (P.sub.G), wherein the generator frequency (f.sub.G) is set so as to be constant; or (d) the droop variable (d) and the at least one target torque variable.

8. The closed-loop control device according to claim 1, wherein the closed-loop control device is configured for filtering an actual power (P.sub.ist)which is instantaneousof the generator and for using the actual power (P.sub.ist)which is filteredas the generator power (P.sub.G) that is detected.

9. A closed-loop control arrangement for closed-loop control of a power assembly including an internal combustion engine and a generator having an operative drive connection to the internal combustion engine, the closed-loop control arrangement comprising: a closed-loop control device for closed-loop control of the power assembly, the closed-loop control device being configured for: detecting a generator power (P.sub.G) of the generator as a controlled variable; determining a control deviation (e.sub.P) as a difference between the generator power (P.sub.G) which is detected and a target generator power (P.sub.soll); determining a target speed (n.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.P); using a control rule for determining the target speed (n.sub.soll); and being operatively connected to an open-loop control device of the internal combustion engine; and the open-loop control device which is operatively connected to the closed-loop control device for direct control of the internal combustion engine, the closed-loop control device being configured for transmitting the target speed (n.sub.soll) to the open-loop control device.

10. The closed-loop control arrangement according to claim 9, wherein the open-loop control device is configured for determining at least one target torque variable and for transmitting the at least one target torque variable to the closed-loop control device, and wherein the closed-loop control device is configured for receiving the at least one target torque variable from the open-loop control device.

11. The closed-loop control arrangement according to claim 10, wherein the open-loop control device is configured for determining, as the at least one target torque variable, a variable which is selected from a group consisting of: a target torque (M.sub.soll) and an integral component (M.sub.soll.sup.l) of a speed controller of the open-loop control device.

12. The closed-loop control arrangement according to claim 11, wherein the target torque (M.sub.soll) is filtered. and

13. A power assembly, comprising: an internal combustion engine; a generator including an operative drive connection to the internal combustion engine; and one of: (a) a closed-loop control device for closed-loop control of the power assembly, the closed-loop control device being configured for: detecting a generator power (P.sub.G) of the generator as a controlled variable; determining a control deviation (e.sub.P) as a difference between the generator power (P.sub.G) which is detected and a target generator power (P.sub.soll); determining a target speed (n.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.P); using a control rule for determining the target speed (n.sub.soll); and being operatively connected to an open-loop control device of the internal combustion engine in such a way that the target speed (n.sub.soll) can be transmitted by the closed-loop control device to the open-loop control device; and (b) a closed-loop control arrangement for closed-loop control of the power assembly, the closed-loop control arrangement including: a closed-loop control device for closed-loop control of the power assembly, the closed-loop control device being configured for: detecting a generator power (P.sub.G) of the generator as a controlled variable; determining a control deviation (e.sub.P) as a difference between the generator power (P.sub.G) which is detected and a target generator power (P.sub.soll); determining a target speed (n.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.P); using a control rule for determining the target speed (n.sub.soll); and being operatively connected to an open-loop control device of the internal combustion engine; and the open-loop control device which is operatively connected to the closed-loop control device for direct control of the internal combustion engine, the closed-loop control device being configured for transmitting the target speed (n.sub.soll) to the open-loop control device; wherein the closed-loop control device or the closed-loop control arrangement is operatively connected to the internal combustion engine and the generator of the power assembly.

14. A method for closed-loop control of a power assembly including an internal combustion engine and a generator having an operative drive connection to the internal combustion engine, the method comprising the steps of: detecting a generator power (P.sub.G) of the generator as a controlled variable; determining a control deviation (e.sub.P) as a difference between the generator power (P.sub.G) which is detected and a target generator power (P.sub.soll); determining a target speed (n.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.P); and determining the target speed (n.sub.soll) based on a control rule.

15. The method according to claim 14, wherein the step of determining the target speed (n.sub.soll) based on the control rule includes calculating the target speed (n.sub.soll) based on the control rule.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0079] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0080] FIG. 1 shows a first schematic representation of an exemplary embodiment of a power assembly with an exemplary embodiment of a control device;

[0081] FIG. 2 shows a second schematic representation of the exemplary embodiment of the power assembly according to FIG. 1;

[0082] FIG. 3 shows a third schematic representation of the exemplary embodiment of the power assembly according to FIG. 1;

[0083] FIG. 4 shows a detailed representation of a power controller;

[0084] FIG. 5 shows a detailed representation of a first embodiment of a method for calculating the proportional coefficient for the power control;

[0085] FIG. 6 shows a detailed representation of a second embodiment of a method for calculating the proportional coefficient for the power control;

[0086] FIG. 7 shows a detailed representation of a third embodiment of a method for calculating the proportional coefficient for the power control;

[0087] FIG. 8 shows a detailed representation of a fourth embodiment of a method for calculating the proportional coefficient for the power control; and

[0088] FIG. 9 shows a schematic, diagrammatic representation of the mode of operation of an embodiment of a method for closed-loop control of a power assembly.

[0089] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplification are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0090] FIG. 1 shows a first schematic representation of an exemplary embodiment of a power assembly 1 with a first exemplary embodiment of a closed-loop control device 3. The power assembly 1 is part of a higher-level network of a multiplicity of power assemblies, of which only the one power assembly 1 considered in greater detail here is shown. In particular, the power assembly 1 is electrically connected to a power grid 4, here specifically to a busbar 6. In particular, the power assembly 1 can be operated in island parallel operation or in mains parallel operation; in particular, the power grid 4 can be a local power grid, in particular an on-board electrical system of a vehicle, for example a ship, or a supra-regional power grid. An external open-loop control unit 8 is assigned to the power grid 4 and distributes a total power P.sub.Schiene requested at the busbar 6, which is also referred to as the total load, across the individual power assemblies 1, in particular by setting a separate target generator power P.sub.soll.sup.1, P.sub.soll.sup.2, P.sub.soll.sup.3, etc. for each power assembly 1. A first target generator power P.sub.soll.sup.1 assigned to the power assembly 1 specifically shown here is referred to in the following as the target generator power P.sub.soll for short for the sake of simplicity.

[0091] The power assembly 1 has an internal combustion engine 5 and a generator 9 which has an operative drive connection to the internal combustion engine 5 via a shaft 7 shown schematically. The closed-loop control device 3 is operatively connected to the internal combustion engine 5 on the one hand and to the generator 9 on the other. In particular, the generator 9 is electrically connected to the busbar 6 in a manner not presented explicitly here.

[0092] In particular, the closed-loop control device 3 is set up for closed-loop control of the power assembly 1, wherein it is set up to detect a generator power P.sub.G of the generator 9 as a controlled variable, to determine a control deviation as the difference between the detected generator power P.sub.G and the target generator power P.sub.soll, and to determine a target speed n.sub.soll as a manipulated variable for controlling the internal combustion engine 5 as a function of the control deviation. The closed-loop control device 3 is also designed to use a control rule for determining the target speed n.sub.soll. The closed-loop control device 3 is designed as a generator controller and is operatively connected to an open-loop control device 11 of the internal combustion engine 5 in such a way that the target speed n.sub.soll can be transmitted by the closed-loop control device 3 to the open-loop control device 11. This also enables, at the same time, particularly robust power control and versatile use of the closed-loop control device 3, in particular with a multiplicity of power assemblies 1.

[0093] The closed-loop control device 3 is optionally set up to adapt the control rule used to determine the target speed n.sub.soll as a function of at least one adaptation variable, wherein the at least one adaptation variable is selected from a group consisting of the detected generator power P.sub.G, a generator frequency f.sub.G, a droop variable d and a target torque variablecalculated in particular by the open-loop control device of the internal combustion engine.

[0094] The closed-loop control device 3 and the open-loop control device 11 together form a closed-loop control arrangement 13 for closed-loop control of the power assembly 1. The open-loop control device 11 is optionally designed as an engine controller, in particular as an engine control unit (ECU).

[0095] In particular, the open-loop control device 11 is set up to calculate the at least one target torque variable and to transmit it to the closed-loop control device 3, wherein the closed-loop control device 3 is set up to receive the at least one target torque variable from the open-loop control device 11.

[0096] In addition, the open-loop control device 11 is optionally set up to determine a variable as the target torque variable which is selected from a group consisting of aoptionally filteredtarget torque M.sub.soll and an integral component of a speed controller 21shown in FIG. 2of the closed-loop control device 11, in particular an integral component M.sub.soll.sup.l of the target torque M.sub.soll.

[0097] Optionally, another input variable of the closed-loop control device 3 is the droop variable d.

[0098] The open-loop control device 11 also has the target speed n.sub.soll and a detected speed n.sub.ist as input variables. From this, the open-loop control device 11 calculates a speed control deviation. Lastly, the open-loop control device 11 uses this speed control deviation to calculate an energization duration BD for controlling the fuel injection valves of the internal combustion engine 5. Optionally, the open-loop control device 11 first calculates the target torque M.sub.soll from the speed control deviation and, from this, in turn, the energization duration BD.

[0099] FIG. 2 shows a second schematic representation of the exemplary embodiment of the power assembly 1 according to FIG. 1, in particular in the form of a block diagram.

[0100] Like and functionally similar elements are provided with the same reference signs in all figures, and therefore reference is made to the previous description in each case.

[0101] Optionally, an actual power P.sub.ist detected at the generator 9 is filtered in a power filter 15, and the filtered actual power P.sub.ist is used as the detected generator power P.sub.G. The power filter 15 is optionally a PT.sub.1 filter or a mean value filter. The power filter 15 is optionally part of the closed-loop control device 3, which also has a power controller 17 that calculates the target speed n.sub.soll from the control deviation e.sub.p as the difference between the target generator power P.sub.soll and the detected generator power P.sub.G.

[0102] The open-loop control device 11 has a speed filter 19, which is optionally designed as a PT.sub.1 filter or mean value filter. A measured speed n.sub.mess, optionally used to calculate a speed control deviation e.sub.n, is obtained by filtering the actual speed n.sub.ist measured directly at the internal combustion engine 5 using the speed filter 19. The open-loop control device 11 also has the speed controller 21, which calculates the target torque M.sub.soll from the speed control deviation e.sub.n and optionally, from this,in a manner not shownthe energization duration BD. A controlled system 23 of the speed control loop assigned to the speed controller 21 includes the internal combustion engine 5, the shaft 7 and the generator 9.

[0103] In the text which follows, the meaning of the droop variable d will be explained in more detail:

[0104] The droop variable d is optionally used to calculate a differential speed ?n, wherein an effective target speed n.sub.eff is calculated by adding the differential speed ?n to the target speed n.sub.soll. The effective target speed n.sub.eff is used to calculate the speed control deviation e.sub.n by subtracting the measured speed n.sub.mess from the effective target speed n.sub.eff. The differential speed ?n is calculated in a calculation block 25. The input variables of the calculation block 25 are the integral component M.sub.soll.sup.l, calculated by the speed controller 21, of the target torque M.sub.soll, the droop variable d, a full-load torque M.sub.V, and a nominal speed n.sub.N for the internal combustion engine 5, wherein the nominal speed n.sub.N can be 1500 min.sup.?1, for example. The differential speed ?n is optionally calculated according to the following equation:

[00020]$\begin{array}{cc}?n=n_{N}d\frac{M_V-M_{\mathrm{soll}}^I}{M_V}.& \left(24\right)\end{array}$

[0105] The droop variable d is optionally set to a finite value, in particular in the single-digit percentage range, optionally to a maximum of 8%, optionally to 4%. The droop variable d can be preset, i.e., in particular parameterized, by a user of the power assembly 1 or the closed-loop control device 3. The droop variable d can also be set to zero, in this case both in the closed-loop control device 3 and in the open-loop control device 11. If the droop variable d is zero, the differential speed ?n also vanishes, so that the effective target speed n.sub.eff is then equal to the target speed n.sub.soll.

[0106] If the droop variable d is different from zero, the result is as follows: If the internal combustion engine 5 is running at full load, the integral component M.sub.soll.sup.l of the target torque M.sub.soll is equal to the full-load torque M.sub.V, so that the differential speed ?n is zero. If, on the other hand, the internal combustion engine 5 is idling, the integral component M.sub.soll.sup.l is zero and the differential speed ?n is equal to the percentage of the nominal speed n.sub.N determined by the droop variable d. If the nominal speed n.sub.N is 1500 min.sup.?1 and the droop variable d is 4%, the value of the differential speed ?n therefore varies between 0 min.sup.?1 at full load and 60 min.sup.?1 at idling speed.

[0107] FIG. 3 shows a third schematic representation of the power assembly 1 according to FIG. 1, in this case as a linearized block diagram. The individual controllers are represented by transfer blocks with correspondingly assigned transfer functions. In contrast to FIG. 2, the controlled system 23 in FIG. 3 is shown divided into two transfer blocks, namely a transfer block assigned to the internal combustion engine 5, characterized by the transfer function G.sub.s.sup.n(s), with the target torque M.sub.soll as the input variable and the actual speed n.sub.ist as the output variable, and a transfer block assigned to the generator 9, characterized by the transfer function G.sub.s.sup.p(s), with the same input variable, namely the target torque M.sub.soll, and the actual power P.sub.ist as output variable. The speed controller 21 is represented by a first multiplication element 27 for calculating a proportional component M.sub.soll.sup.p of the target torque M.sub.soll by multiplication with the speed proportional coefficient k.sub.p.sup.n and a first integration element 29 for calculating the integral component M.sub.soll.sup.l of the target torque M.sub.soll by multiplication with a term

[00021]$\frac{1}{{?}_n^{n}s},$

with the reset time ?.sub.n.sup.n in and the complex variable s. Thus, the speed controller 21 has a PI transmission behavior here, since the first multiplication element 27 has a proportional transmission behavior and the first integration element 29 has an integral transmission behavior. The calculation block 25 is given a negative sign by the linearization here, so that the differential speed ?n calculated in the calculation block 25 is now subtracted from the target speed n.sub.soll. Due to the linearization, the differential speed ?n is calculated in the calculation block 25 according to the following modified equation:

[00022]$\begin{array}{cc}?n=n_{N}d\frac{M_{\mathrm{soll}}^I}{M_V}.& \left(25\right)\end{array}$

[0108] FIG. 4 shows a schematic representation of a power controller 17 according to FIG. 3, which is optionally implemented as a PI controller. The control deviation e.sub.p is first multiplied by the proportional coefficient k.sub.p.sup.P so that a proportional component k.sub.p.sup.P for the target speed n.sub.soll is obtained. In a second integration element 31, the proportional component n.sub.soll.sup.p, by division by the product of the reset time ?.sub.n.sup.p with the complex variable s, calculates an integral component n.sub.soll.sup.l for the target speed n.sub.soll, which is then added to the proportional component n.sub.soll.sup.p. This results in the target speed n.sub.soll as output variable. The transfer function of the power controller 17 is therefore given by:

[00023]$\begin{array}{cc}{G}_r^P\left(s\right)=k_p^P\left(1+\frac{1}{{?}_n^{P}s}\right).& \left(26\right)\end{array}$

[0109] The calculation of the proportional coefficient k.sub.p.sup.P is optionally calculated according to equation (1).

[0110] The control rule is adapted here in particular by determining the proportional coefficient k.sub.p.sup.P in such a way that the predetermined loop gain v.sup.p is constant, in particular remains constant.

[0111] FIG. 5 shows a detailed representation of a first embodiment of a method for calculating the proportional coefficient k.sub.p.sup.P for the power control according to equation (1). For this purpose, the predetermined loop gain v.sup.p is multiplied in a second multiplication element 33 by the factor 450, the generator frequency f.sub.G,stat, the reciprocal of the generator power P.sub.G,stat, and an output of a summation element 35. The proportional coefficient k.sub.p.sup.P is obtained as the output of the second multiplication element 33. In the summation element 35, the number 1 is added to the output of a third multiplication element 37. In the third multiplication element 37, the droop variable d is multiplied by the torque M.sub.stat and the reciprocal value of the full-load torque M.sub.V. The reciprocal value of the full-load torque M.sub.V is formed from the full-load torque M.sub.V in a first reciprocal value element 39.

[0112] The torque M.sub.stat can be determined in two different ways: On the one hand, from the integral component M.sub.soll.sup.l delayed by a sampling step ?.sub.a. In this case, a switch 41 provided for switching between the two calculation types is arranged in the upper switch position according to FIG. 5.

[0113] Alternatively, the torque M.sub.stat can be calculated from the target torque M.sub.soll calculated by the open-loop control device 11. This is also first delayed by a sampling step ?.sub.a and then filtered by a torque filter 43, wherein the torque filter 43 is optionally a PT.sub.1 filter or a mean value filter. This calculation is active when the switch 41 is in the lower switch position according to FIG. 5.

[0114] The generator frequency f.sub.G,stat is optionally calculated by filtering an actual frequency f.sub.ist, which is optionally detected at the generator 9, using a frequency filter 45. The frequency filter 45 is not explicitly shown in FIG. 1 for reasons of simplification.

[0115] The generator power P.sub.G,stat is optionally calculated by first filtering the actual power P.sub.ist using the power filter 15 and then limiting it downward to a predetermined power limit value P.sub.min in a limiting element 47. The reciprocal value of the generator power P.sub.G,stat limited in this way is then calculated in a second reciprocal value element 49. The reciprocal value calculated in this way is then fed to the second multiplication element 33. Both the power filter 15 and the limiting element 47 are not explicitly shown in FIG. 1 for reasons of simplification.

[0116] FIG. 6 shows a detailed representation of a second embodiment of a method for calculating the proportional coefficient k.sub.p.sup.P for power control according to equation (21). In the second multiplication element 33, the predetermined loop gain v.sup.p is multiplied here by the factor 45.Math.10.sup.4/? the reciprocal of the torque M.sub.stat, and the output of the summation element 35. The proportional coefficient k.sup.p is again obtained as the output of the second multiplication element 33. The torque M.sub.stat is branched off from the calculation for the third multiplication element 37, and its reciprocal value is formed in a third reciprocal value element 51. Otherwise, the calculation is carried out as described in conjunction with FIG. 5.

[0117] FIG. 7 shows a detailed representation of a third embodiment of a method for calculating the proportional coefficient k.sub.p.sup.P for power control according to equation (19) and thus for a constant generator frequency with a standard frequency value of 50 Hz. In the second multiplication element 33, the predetermined loop gain v.sup.p is multiplied by the factor 22500 and the reciprocal of the generator power P.sub.G,stat. The proportional coefficient k.sub.p.sup.P is again obtained as the output of the second multiplication element 33. The reciprocal value of the generator power P.sub.G,stat is calculated here as described in conjunction with FIG. 5.

[0118] FIG. 8 shows a detailed representation of a fourth embodiment of a method for calculating the proportional coefficient k.sub.p.sup.P for power control according to equation (20) and thus for a constant generator frequency with a standard frequency value of 60 Hz. In the second multiplication element 33, the predetermined loop gain v.sup.p is multiplied by the factor 27000 and the reciprocal of the generator power P.sub.G,stat. The proportional coefficient k.sub.p.sup.P is again obtained as the output of the second multiplication element 33. The reciprocal value of the generator power P.sub.G,stat is calculated here as described in conjunction with FIG. 5.

[0119] Alternatively, the proportional coefficient k.sub.p.sup.P can also optionally be calculated in particular according to one of equations (2), (3), (17) or (18).

[0120] FIG. 9 shows a schematic, diagrammatic representation of the method. A first time graph at a) shows the total power P.sub.Schiene measured on the busbar 6. This is identical to the value 0 kW up to a first point in time t.sub.1. At the first point in time t.sub.1, the total power P.sub.Schiene changes abruptly to a specific value P.sub.L and subsequently remains at this value.

[0121] A second time graph at b) shows the target generator power P.sub.soll, which is transmitted to the closed-loop control device 3 by the external open-loop control unit 8. Since the target generator power P.sub.soll is calculated in the external open-loop control unit 8, there is a time delay until the target generator power P.sub.soll is available in the closed-loop control device 3. For clarification and concretization, it is assumed here that there is island parallel operation of four identical power assemblies 1, wherein the total power P.sub.Schiene is to be distributed evenly across all four power assemblies 1. For this reason, the target generator power P.sub.soll rises abruptly to a value P.sub.L/4 at a second point in time t.sub.2 and subsequently remains identical to this value. The time delay between the first point in time t.sub.1 and the second point in time t.sub.2 is optionally two sampling steps, i.e., with a sampling time of 5 ms, the total time span is 10 ms.

[0122] A third time graph at c) shows two curves: a first, dashed curve shows the instantaneous actual power P.sub.ist generated by the individual generator 9 of the individual power assembly 1. Since the total power P.sub.Schiene must be provided in equal parts by the generators 9 of the four power assemblies 1, the actual power P.sub.istalso at the first point in time t.sub.1rises abruptly to the value P.sub.L/4. A second, solid curve shows the detected generator power P.sub.G, which is obtained by filtering from the actual power P.sub.ist. As the detected generator power P.sub.G is the output variable of a filter, it increases with a time delaystarting from the first point in time t.sub.1and settles at the value P.sub.L/4 at a third point in time t.sub.3.

[0123] A fourth time graph at d) shows a time curve of the target speed n.sub.soll. A fifth time graph at e) shows a time curve of the integral component M.sub.soll.sup.l for the target torque M.sub.soll. A sixth time graph at f) shows the time curve of the differential speed ?n. The load application shown in the first time graph is an exampleas shown in the second graphof an application of a 50% loadbased on full loadand optionally corresponds to a torque of 5000 Nm. The droop variable d is set to a value of 4% in the exemplary embodiment considered here.

[0124] Up to the first time t.sub.1, the internal combustion engine 5 is in a load-free state, resulting in a value of 60 min.sup.?1 for the differential speed ?nas shown in the sixth time graph. Since a sum of the target speed n.sub.soll and the differential speed ?n at a target frequency for the generator 9 of 50 Hz must result in an effective target speed n.sub.eff of 1500 min.sup.?1the value of the nominal speed n.sub.effthe target speed n.sub.soll up to the first point in time t.sub.1 is 1440 min.sup.?1. The integral component M.sub.soll.sup.l up to the first point in time t.sub.1 is 0 Nm.

[0125] From the first point in time t.sub.1 to the second time t.sub.2, there is a negative control deviation e.sub.p, as the detected generator power P.sub.G assumes larger values than the target generator power P.sub.soll. This results in a decreasing target speed n.sub.soll as a manipulated variable for the power control loop. If the target speed n.sub.soll falls, the effective target speed n.sub.eff, which is not explicitly shown here, also falls at the same time. This results in a negative speed control deviation e.sub.n, whereby the integral component M.sub.soll.sup.l of the speed controller 21 becomes smaller. The decreasing integral component M.sub.soll.sup.l leads to an increase in the differential speed ?n as shown in FIG. 2. This ensures that the effective target speed n.sub.eff returns to the nominal speed n.sub.N.

[0126] At the second point in time t.sub.2, the target generator power P.sub.soll is increased to the value P.sub.L/4. This now results in a positive control deviation e.sub.p. As a result, the target speed n.sub.soll is increased. As the effective target speed n.sub.eff is also increased with the target speed n.sub.soll, this results in a positive speed control deviation e.sub.n, so that the integral component M.sub.soll.sup.l of the speed controller 21 is increased. As a result, the differential speed ?n is reduced. As the target generator power P.sub.soll is increased to 50% of the maximum power, the differential speed ?n drops to the value 30 min.sup.?1 at a value of the droop variable d of 4%. This value is reached at the third point in time t.sub.3. As the effective target speed n.sub.eff is identical to the nominal speed n.sub.N in the steady state, the target speed n.sub.soll increases by 30 min.sup.?1 to the value 1470 min.sup.?1 by the third time t.sub.3. The integral component M.sub.soll.sup.l reaches 50% of the maximum torque at the third time t.sub.3 with the value 5000 Nm. From the third time t.sub.3 the system is in a steady state.

[0127] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.