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 is configured for: detecting a generator frequency of a generator; determining a control deviation as a difference between the detected generator frequency and a target generator frequency; determining a target torque as a manipulated variable for controlling an internal combustion engine as a function of the control deviation; using a control rule for determining the target torque; and adapting the control ruleused to determine the target torqueas a function of an adaptation variable, the adaptation variable being the detected generator frequency, a target torque variable, or a generator power, wherein the closed-loop control device can adapt the control rule by determining a proportional coefficient of the control rule such that a predetermined loop gain (v.sup.f) of an open control loop is constant, the predetermined loop gain (v.sup.f) being: v.sup.f=k.sub.p.sup.f((f.sub.G,stat)(30 M.sub.m,stat)).

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 frequency (f.sub.G) of the generator as a controlled variable; determining a control deviation (e.sub.f) as a difference between the generator frequency (f.sub.G) which is detected and a target generator frequency (f.sub.soll); determining a target torque (M.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.f); using a control rule for determining the target torque (M.sub.soll); and adapting the control rulewhich is used to determine the target torque (M.sub.soll)as a function of at least one adaptation variable, the at least one adaptation variable being selected from a group consisting of the generator frequency (f.sub.G) which is detected, a target torque variable, and a generator power, wherein the closed-loop control device is configured for adapting the control rule by determining a proportional coefficient $\left(k_p^f\right)$ of the control rule in such a way that a predetermined loop gain (v.sup.f) of an open control loop is constant, the predetermined loop gain (v.sup.f) being as follows: $v^f=k_p^f\left(\left(f_{G,\mathrm{stat}}\right)/\left(30M_{m,\mathrm{stat}}\right)\right).$

2. The closed-loop control device according to claim 1, wherein the closed-loop control device is configured for determining the proportional coefficient $\left(k_p^f\right)$ as a function of the generator frequency (f.sub.G) which is detected and the target torque variable.

3. The closed-loop control device according to claim 1, wherein the closed-loop control device is configured for determining the proportional coefficient $\left(k_p^f\right)$ only as a function of the target torque variable and for setting the generator frequency (f.sub.G) to be constant in order to determine the proportional coefficient $\left(k_p^f\right).$

4. The closed-loop control device according to claim 1, wherein the closed-loop control device is configured for determining the proportional coefficient $\left(k_p^f\right)$ as a function of the generator powerwhich is detectedof the generator or by setting the generator frequency (f.sub.G) to be constant in order to determine the proportional coefficient $\left(k_p^f\right).$

5. The closed-loop control device according to claim 1, wherein the closed-loop control device is configured for determining the proportional coefficient $\left(k_p^f\right)$ as a function of the generator powerwhich is detectedof the generator, in addition to the generator frequency (f.sub.G) which is detected, or by setting the generator frequency (f.sub.G) to be constant in order to determine the proportional coefficient $\left(k_p^f\right).$

6. The closed-loop control device according to claim 1, wherein the closed-loop control device is configured for filtering an instantaneous actual frequency of the generator and for using the instantaneous actual frequencywhich is filteredas the generator frequency (f.sub.G) which is detected.

7. The closed-loop control device according to claim 1, wherein the closed-loop control device is formed as a generator controller.

8. The closed-loop control device according to claim 1, wherein the closed-loop control device is formed as a generator controller with an interface to an open-loop control device of the internal combustion engine.

9. The closed-loop control device according to claim 1, wherein the closed-loop control device does not have or generate any subordinate speed control.

10. The closed-loop control device according to claim 9, wherein the closed-loop control device does not have a speed specification for the internal combustion engine.

11. 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 which is formed as a generator controller, is for closed-loop control of the power assembly, and is configured for: detecting a generator frequency (f.sub.G) of the generator (9) as a controlled variable; determining a control deviation (e.sub.f) as a difference between the generator frequency (f.sub.G) which is detected and a target generator frequency (f.sub.soll); determining a target torque (M.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.f); using a control rule for determining the target torque (M.sub.soll); and adapting the control rulewhich is used to determine the target torque (M.sub.soll)as a function of at least one adaptation variable, the at least one adaptation variable being selected from a group consisting of the generator frequency (f.sub.G) which is detected, a target torque variable, and a generator power, wherein the closed-loop control device is configured for adapting the control rule by determining a proportional coefficient $\left(k_p^f\right)$ of the control rule in such a way that a predetermined loop gain (v.sup.f) of an open control loop is constant, the predetermined loop gain (v.sup.f) being as follows: $v^f=k_p^f\left(\left(f_{G,\mathrm{stat}}\right)/\left(30M_{m,\mathrm{stat}}\right)\right);$ and an open-loop control device operatively connected to the closed-loop control device for directly controlling the internal combustion engine, the closed-loop control device being configured for transferring the target torque (M.sub.soll) generated as the manipulated variable to the open-loop control device.

12. The closed-loop control arrangement according to claim 11, wherein the open-loop control device: (a) does not have a speed controller; (b) includes a speed controller which is deactivated; or (c) includes a final idling speed controller which is activated.

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 frequency (f.sub.G) of the generator as a controlled variable; determining a control deviation (e.sub.f) as a difference between the generator frequency (f.sub.G) which is detected and a target generator frequency (f.sub.soll); determining a target torque (M.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.f); using a control rule for determining the target torque (M.sub.soll); and adapting the control rulewhich is used to determine the target torque (M.sub.soll)as a function of at least one adaptation variable, the at least one adaptation variable being selected from a group consisting of the generator frequency (f.sub.G) which is detected, a target torque variable, and a generator power, wherein the closed-loop control device is configured for adapting the control rule by determining a proportional coefficient $\left(k_p^f\right)$ of the control rule in such a way that a predetermined loop gain (v.sup.f) of an open control loop is constant, the predetermined loop gain (v.sup.f) being as follows: $v^f=k_p^f\left(\left(f_{G,\mathrm{stat}}\right)/\left(30M_{m,\mathrm{stat}}\right)\right);$ 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 which is formed as a generator controller, is for closed-loop control of the power assembly, and is configured for: detecting a generator frequency (f.sub.G) of the generator as a controlled variable; determining a control deviation (e.sub.f) as a difference between the generator frequency (f.sub.G) which is detected and a target generator frequency (f.sub.soll); determining a target torque (M.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.f); using a control rule for determining the target torque (M.sub.soll); and adapting the control rulewhich is used to determine the target torque (M.sub.soll)as a function of at least one adaptation variable, the at least one adaptation variable being selected from a group consisting of the generator frequency (f.sub.G) which is detected, a target torque variable, and a generator power, wherein the closed-loop control device is configured for adapting the control rule by determining a proportional coefficient $\left(k_p^f\right)$ of the control rule in such a way that a predetermined loop gain (v.sup.f) of an open control loop is constant, the predetermined loop gain (v.sup.f) being as follows: $v^f=k_p^f\left(\left(f_{G,\mathrm{stat}}\right)/\left(30M_{m,\mathrm{stat}}\right)\right)$ and an open-loop control device operatively connected to the closed-loop control device for directly controlling the internal combustion engine, the closed-loop control device being configured for transferring the target torque (M.sub.soll) generated as the manipulated variable 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, by way of a closed-loop control device, a generator frequency (f.sub.G) of the generator as a controlled variable; determining, by way of the closed-loop control device, a control deviation (e.sub.f) as a difference between the generator frequency (f.sub.G) which is detected and a target generator frequency (f.sub.soll); determining, by way of the closed-loop control device, a target torque (M.sub.soll) as a manipulated variable for controlling the internal combustion engine as a function of the control deviation (e.sub.f); using, by way of the closed-loop control device, a control rule to determine the target torque (M.sub.soll); and adapting, by way of the closed-loop control device, the control rulewhich is used to determine the target torque (M.sub.soll)as a function of at least one adaptation variable, the at least one adaptation variable being selected from a group consisting of the generator frequency (f.sub.G) which is detected, a target torque variable, and a generator power, wherein the closed-loop control device is configured for adapting the control rule by determining a proportional coefficient $\left(k_p^f\right)$ of the control rule in such a way that a predetermined loop gain (v.sup.f) of an open control loop is constant, the predetermined loop gain (v.sup.f) being as follows: $v^f=k_p^f\left(\left(f_{G,\mathrm{stat}}\right)/\left(30M_{m,\mathrm{stat}}\right)\right).$

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0077] 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:

[0078] FIG. 1 shows a schematic representation of a first exemplary embodiment of a power assembly with a first exemplary embodiment of a closed-loop control device;

[0079] FIG. 2 shows a schematic representation of a second exemplary embodiment of a power assembly with a first exemplary embodiment of a closed-loop control arrangement and a second exemplary embodiment of a closed-loop control device;

[0080] FIG. 3 shows a detailed representation of a control loop for frequency control with a frequency controller;

[0081] FIG. 4 shows a detailed representation of a frequency controller;

[0082] FIG. 5 shows a detailed representation of a first embodiment of a method for calculating the proportional coefficient for the frequency control;

[0083] FIG. 6 shows a detailed representation of a second embodiment of a method for calculating the proportional coefficient for the frequency control;

[0084] FIG. 7 shows a detailed representation of a third embodiment of a method for calculating the proportional coefficient for the frequency control;

[0085] FIG. 8 shows a detailed representation of a fourth embodiment of a method for calculating the proportional coefficient for the frequency control; and

[0086] FIG. 9 shows a schematic, diagrammatic representation of the mode of operation of a method for closed-loop control of a power assembly.

[0087] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0088] FIG. 1 shows a schematic representation of a first exemplary embodiment of a power assembly 1 with a first exemplary embodiment of a closed-loop control device 3. 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. 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.

[0089] 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 frequency f.sub.G of the generator 9 as a controlled variable, to determine a control deviation as the difference between the detected generator frequency f.sub.G and the target generator frequency f.sub.soll, and to determine a target torque M.sub.soll as a manipulated variable for controlling the internal combustion engine 5 as a function of the control deviation, and to adapt a control rule, used for determining the target torque M.sub.soll, as a function of at least one adaptation variable. The adaptation variable is selected here from a group consisting of the detected generator frequency f.sub.G, a target torque variable, and a generator power of the generator 9.

[0090] In the first exemplary embodiment shown here, the closed-loop control device 3 is designed as an open-loop control device 15, in particular an engine controller, for direct, in particular immediate control of the internal combustion engine 5.

[0091] In addition to the generator frequency, the closed-loop control device 3 optionally has other input variables that are not explicitly shown here: a target generator frequency, a target power for the generator 9, a measured generator power of the generator 9, and optionally other variables.

[0092] In particular, the closed-loop control device 3 is set up to calculate an energization duration BD for controlling the injectors of the internal combustion engine 5 from the control deviation and the target torque M.sub.soll determined therefrom. In this arrangement, the generator frequency f.sub.G is the controlled variable, and the target torque M.sub.soll calculated in the open-loop control device 15 is the manipulated variable of the frequency control loop.

[0093] FIG. 2 shows a schematic representation of a second exemplary embodiment of a power assembly 1 with a first exemplary embodiment of a closed-loop control arrangement 11 and a second exemplary embodiment of a closed-loop control device 3.

[0094] 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.

[0095] In the second exemplary embodiment, the closed-loop control device 3 is designed as a higher-level generator controller 13. In particular, the generator controller 13 has an interface to an open-loop control device 15 of the internal combustion engine 5.

[0096] In addition to the generator frequency, the generator controller 13 also has other input variables: the target generator frequency f.sub.soll, a target power P.sub.soll for the generator 9, a measured generator power P.sub.mess of the generator 9, and optionally other variables not explicitly shown here. The generator controller 13 again uses the target generator frequency f.sub.soll and the detected generator frequency f.sub.G to calculate the target torque M.sub.soll, which represents the manipulated variable of the frequency control loop and is transmitted to the open-loop control device 15. The open-loop control device 15 in turn uses the target torque M.sub.soll to calculate the energization duration BD as a control signal for the injectors of the internal combustion engine 5.

[0097] A speed controller of the open-loop control device 15 is optionally deactivated here. Optionally, a final idling speed controller of the open-loop control device 15 is activated. This controls the engine speed if a lower speed limit n.sub.Leer is undershot or an upper speed limit n.sub.End is exceeded by an instantaneous speed n.sub.m,ist of the internal combustion engine 5. Between these speed limits, a target torque calculated in the open-loop control device 15 is equal to the target torque M.sub.soll specified by the generator controller 13. In particular, a torque specification is activated in the open-loop control device 15.

[0098] Optionally, the closed-loop control device 3 has no subordinate speed control, in particular no speed specification for the internal combustion engine 5. In particular, the closed-loop control device 3 does not generate any subordinate speed control, in particular no speed specification for the internal combustion engine 5.

[0099] FIG. 3 shows a detailed representation of a control loop for frequency control with the closed-loop control device 3 as frequency controller 17. This representation is independent of whether the closed-loop control device 3 is designed as an open-loop control device 15, in particular an engine controller, or as a higher-level generator controller 13. In particular, the frequency controller 17 shown can be implemented in the open-loop control device 15 or in the generator controller 13. Accordingly, a conversion element 19, which is also shown, is either implemented in the open-loop control device 15 together with the frequency controller 17, or it is implemented in the open-loop control device 15 on its own if the frequency controller 17 is implemented in the generator controller 13.

[0100] The internal combustion engine 5 and the generator 9 are shown here together as controlled system 21.

[0101] FIG. 3 shows in particular the closed frequency control loop. The frequency controller 17 has the control deviation e.sub.f resulting from the difference between the detected generator frequency f.sub.G and the target generator frequency f.sub.soll as an input variable, and the target torque M.sub.soll as an output variable. The frequency controller 17 is optionallyas shown in FIG. 3implemented as a PI algorithm; however, it can also be implemented in another optional embodiment as a PI(DT.sub.1) algorithm. The transfer function of the PI frequency controller is as follows:

[00039]$\begin{array}{cc}{G}_r^f\left(s\right)=k_p^f\left(1+\frac{1}{T_n^{f}s}\right)=\frac{M_{\mathrm{soll}}\left(s\right)}{e_f\left(s\right)},& \left(33\right)\end{array}$

with the proportional coefficient

[00040]$k_p^f$

and the reset time

[00041]$T_n^f.$

[0102] In the exemplary embodiment shown here, an instantaneous actual frequency f.sub.ist of the generator 9 is filtered in a first filter 18, and the filtered actual frequency f.sub.ist is used as detected generator frequency f.sub.G. However, an embodiment is also possible in which the instantaneous actual frequency f.sub.ist of the generator 9 is used directly as detected generator frequency f.sub.G.

[0103] The target torque M.sub.soll resulting as the output variable of the frequency controller 17 is fed to the conversion element 19 as an input variable. The conversion element 19 uses this to calculate the energization duration BD for the injectors of the internal combustion engine 5.

[0104] FIG. 4 shows a schematic representation of a detail of the frequency controller 17 according to FIG. 3, whichas describedis optionally implemented as a PI controller. The control deviation e.sub.f is first multiplied here by the proportional coefficient

[00042]$k_p^f$

so that a proportional component

[00043]$M_{\mathrm{soll}}^P$

is obtained. In an integration element 23, the proportional component

[00044]$M_{\mathrm{soll}}^P,$

by division by the product of the reset time

[00045]$T_n^f$

with the complex variable s, calculates an integral component

[00046]$M_{\mathrm{soll}}^I,$

which is then added to the proportional component

[00047]$M_{\mathrm{soll}}^P.$

This results in the target torque M.sub.soll as output variable. The transfer function G(s) of the frequency controller 17 is therefore given by:

[00048]$\begin{array}{cc}G\left(s\right)=k_p^f\left(1+\frac{1}{T_n^{f}S}\right).& \left(34\right)\end{array}$

[0105] The calculation of the proportional coefficient

[00049]$k_p^f$

is optionally calculated according to equation (3). This is obtained by modeling the controlled system, consisting of the internal combustion engine 5, the shaft 7 and the generator 9, as presented above.

[0106] The control rule is adapted here in particular by determining the proportional coefficient

[00050]$k_p^f$

in such a way that the predetermined loop gain v.sup.f is constant, in particular remains constant.

[0107] FIG. 5 shows a first option for calculating the proportional coefficient

[00051]$k_p^f.$

The proportional coefficient

[00052]$k_p^f$

is calculated here strictly according to equation (3) by multiplying the predetermined and in particular predefinable, i.e. optionally parameterizable, loop gain v.sup.f in a first multiplication element 25 by the factor 30 and the torque M.sub.m,stat as a target torque variable. The resulting product is multiplied at a first multiplication point 27 by the reciprocal value of the generator frequency f.sub.G,stat formed in a first reciprocal value element 29, i.e., the result is divided by the generator frequency f.sub.G,stat. The torque M.sub.m,stat can be determined in two different ways:

[0108] According to a first embodiment, it is determined from the integral component

[00053]$M_{\mathrm{soll}}^I$

delayed by one sampling step .sub.a, which is then limited downward in a first limiting element 31 to a predetermined torque limit value

[00054]$M_{\mathrm{soll}}^{\min },$

for example 100 Nm. In this case, a switch 33 provided for switching between the two calculation types is arranged in the upper switch position according to FIG. 5.

[0109] Alternatively, the torque M.sub.m,stat in accordance with a second embodiment can be calculated from the target torque M.sub.soll calculated by the frequency controller 17. This is also initially delayed by a sampling step .sub.a, then filtered by a second filter 35, wherein the second filter 35 is optionally a PT.sub.1 filter or a mean value filter, and finally also limited downward to the predetermined torque limit value

[00055]$M_{\mathrm{soll}}^{\min }$

in the first limiting element 31. This calculation is active when the switch 33 is in the lower switch position according to FIG. 5.

[0110] The generator frequency f.sub.G,stat is calculated from the detected generator frequency f.sub.G, wherein this is limited downward to a predetermined frequency limit value f.sup.min in a second limiting element 37.

[0111] Since the generator frequency f.sub.G,stat varies only slightly during generator operation, the control rule of the frequency controller 17 can be simplified by assuming that the generator frequency f.sub.G,stat is constant, optionally at 50 Hz or 60 Hz, depending on the application. This is advantageous because the calculation of the proportional coefficient

[00056]$k_p^f$

depends only on the exclusively calculated value of the torque M.sub.m,stat and not on a sensor signal. This makes the calculation of the proportional coefficient

[00057]$k_p^f$

as robust as possible. In particular, this procedure means that the proportional coefficient

[00058]$k_p^f$

is only determined as a function of the target torque variable, in this case the torque M.sub.m,stat, wherein the generator frequency is set to be constant for the purpose of determining the proportional coefficient

[00059]$k_p^f,$

in particular is set to a predetermined standard frequency value.

[0112] FIG. 6 shows a further embodiment of the calculation of the proportional coefficient

[00060]$k_p^f:$

Here, this is determined as a function of a detected generator power P.sub.stat, optionally additionally as a function of the detected generator frequency, in particular the generator frequency f.sub.G,stat.

[0113] The detected generator power P.sub.stat results here from a measured and optionally filtered power P.sub.mess of the generator 9, which is limited downward to a predetermined power limit value P.sub.min by a third limiting element 39. The detected generator frequency f.sub.G is in turn limited downward to the predetermined frequency limit value f.sup.min by the second limiting element 37.

[0114] In a second multiplication element 41, the limited generator power P.sub.stat is multiplied by the predetermined loop gain v.sup.f and a factor of 30,000, divided by , and the proportional coefficient

[00061]$k_p^f$

is obtained by dividing the resulting product by the square of the generator frequency f.sub.G,stat. In particular, the square of the generator frequency f.sub.G,stat is first formed in a squaring element 43, then its reciprocal value is formed in a second reciprocal element 45, and this in turn is multiplied at a second multiplication point 47 by the output of the second multiplication element 41.

[0115] The proportional coefficient

[00062]$k_p^f$

is thus calculated in particular according to the following equation:

[00063]$\begin{array}{cc}{k}_p^f=\frac{3.Math.{10}^4{P}_{\mathrm{stat}}{v}^f}{f_{G,\mathrm{stat}}^2}.& \left(35\right)\end{array}$

[0116] Equation (35) can be derived as follows: The following applies for the detected generator power in unitless representation:

[00064]$\begin{array}{cc}{P}_{\mathrm{stat}}=\frac{}{3.Math.{10}^4}{M}_{m,\mathrm{stat}}{n}_{\mathrm{stat}},& \left(36\right)\end{array}$

with the speed n.sub.stat. Because of

[00065]$\begin{array}{cc}{f}_{G,\mathrm{stat}}=\frac{n_{\mathrm{stat}}}{30}& \left(37\right)\end{array}$

then the following also applies

[00066]$\begin{array}{cc}{P}_{\mathrm{stat}}=\frac{}{{10}^3}{M}_{m,\mathrm{stat}}{f}_{G,\mathrm{stat}}.& \left(38\right)\end{array}$

and after reshaping:

[00067]$\begin{array}{cc}{M}_{m,\mathrm{stat}}=\frac{{10}^3{P}_{\mathrm{stat}}}{f_{G,\mathrm{stat}}}.& \left(39\right)\end{array}$

[0117] Inserting equation (39) into equation (3) directly gives equation (35).

[0118] In another optional embodiment, it is also possible in this case to set the generator frequency f.sub.G,stat as constant for the purpose of determining the proportional coefficient

[00068]$k_p^f$

as constant, which in turn simplifies the calculation and makes it more robust.

[0119] FIG. 7 shows a corresponding variant for 50 Hz, wherein, in contrast to FIG. 6, a factor of 12/ is used here instead of the factor 30,000/ and at the same time as a replacement for the lower branch for calculating the generator frequency f.sub.G,stat.

[0120] FIG. 8 shows a corresponding variant for 60 Hz as a constant value of the generator frequency f.sub.G,stat. Here, the corresponding factor is 25/(3).

[0121] In particular, a method for closed-loop control of the power assembly 1 includes the step of detecting the generator frequency f.sub.G of the generator 9 as a controlled variable, furthermore the step of determining the control deviation e.sub.f as the difference between the detected generator frequency f.sub.G and the target generator frequency f.sub.soll, determining the target torque M.sub.soll as a manipulated variable for controlling the internal combustion engine 5 as a function of the control deviation e.sub.f, and lastly the step of adapting the control rule used to determine the target torque M.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 frequency f.sub.G, the target torque variable and the generator power.

[0122] FIG. 9 shows a schematic, diagrammatic representation of this method. A first time graph a) shows the time curve of the generator power P.sub.G. At a first point in time t.sub.1, this changes abruptly from 0 kW to a specific value P.sub.l, as a load is switched on at this point in time. At a fourth point in time t.sub.4, this load is switched off again, and therefore the generator power P.sub.G again changes abruptly to the value 0 kW.

[0123] A second time graph b) shows the course of the detected generator frequency f.sub.G for the case of speed control as a comparative example, represented by a dashed curve K1, and for the case of frequency control according to the present invention or optionally in accordance with the present inventionrepresented by a solid curve K2.

[0124] In the case of speed control, the generator frequency f.sub.G, starting at the first point in time t.sub.1, drops from the target frequency f.sub.soll and falls by a first differential frequency value f.sub.1 to a first frequency value f.sub.1. The frequency then rises again and is back to the target generator frequency f.sub.soll at a third point in time t.sub.3.

[0125] In the case of frequency control, the generator frequency f.sub.G drops by a second differential frequency value f.sub.2 to a second frequency value f.sub.2 due to the greater dynamics of the frequency control loop. The first differential frequency value f.sub.1 is greater than the second differential frequency value f.sub.2; the first frequency value f.sub.1 is less than the second frequency value f.sub.2. The generator frequency f.sub.G then rises again and has already settled back to the target generator frequency f.sub.soll at a second time t.sub.2before the third point in time t.sub.3. Thus, in the case of frequency control according to the second curve K2, the generator frequency f.sub.G has a frequency dip that is smaller by the comparative difference value (f), which is the difference between the second frequency value f.sub.2 and the first frequency value f.sub.1, and a settling time which is shorter by a first time difference value t.sub.1, which is the difference between the third time point t.sub.3 and the second time point t.sub.2.

[0126] At the fourth time t.sub.4, the generator load is switched off, as already mentioned above. This causes the detected generator frequency f.sub.G to increase by a third differential frequency value f.sub.3 up to a fourth frequency value f.sub.4 in the case of speed control. The frequency then drops and at a sixth point in time t.sub.6 has settled back to the target generator frequency f.sub.soll.

[0127] If frequency control is active, the detected generator frequency f.sub.G increases at the fourth point in time t.sub.4 and only reaches a third frequency value f.sub.3, which is lower than the fourth frequency value f.sub.4, before the generator frequency f.sub.G drops again and returns to the target generator frequency f.sub.soll at an earlier, fifth time t.sub.5.

[0128] In the case of load disconnection, the generator frequency f.sub.G therefore increases by a maximum of a third differential frequency value f.sub.3 when speed control is active, but by a maximum of the smaller, fourth differential frequency value f.sub.4 when frequency control is active. In the case of frequency control, the settling time is lower by the second time difference value t.sub.2, which is the difference between the sixth time t.sub.6 and the fifth time t.sub.5.

[0129] It is thus clear that the frequency control according to the present invention or optionally in accordance with the present invention exhibits better load switching behavior than the speed control used by way of comparative example.

[0130] 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.