DE102018222819B4 - combined heat and power plant (CHP) - Google Patents

Abstract

combined heat and power plant (1),
- with an internal combustion engine (2) having an exhaust system (16) and an output shaft (3),
- with a heating circuit (4) to which at least one thermal consumer (20) can be coupled and which is thermally connected to the exhaust system (16) of the internal combustion engine (2) via a (first) heat exchanger (5a),
- with a cooling circuit (6) for cooling the internal combustion engine (2), wherein the cooling circuit (6) is thermally connected to the heating circuit (4) by means of a second heat exchanger (5b),
- with a first electric generator (7a) and with a second electric generator (7b), which are galvanically separated from each other and can be driven or are driven by the internal combustion engine (2),
- wherein the first generator (7a) is designed for electrical connection to a public power grid (15) and the second generator (7b) is designed for electrical connection to a self-supply power grid (14) which is galvanically separated from the public power grid (15), wherein the first electrical generator (7a) and the second electrical generator (7b) are each designed to generate alternating electrical current.

Description

The invention relates to a combined heat and power plant (CHP).

The principle of combined heat and power (CHP) can be implemented using many different technologies. It is based on the simultaneous provision of heat and electricity. A motor-driven CHP plant is also known as a combined heat and power plant (CHP). Combined heat and power plants that are powered by natural gas, hydrogen, mine gas, liquefied petroleum gas, biogas, wood gas, sewage gas, alcohols, heating oil, heavy oil and vegetable oils are now used in a wide range of decentralized energy supply applications.

In a combined heat and power plant, an internal combustion engine, which is typically implemented as a so-called piston engine, drives an electric generator, which in turn can be implemented as a synchronous machine. The waste heat generated in the internal combustion engine is taken from the cooling water circuit of the internal combustion engine, which is used to cool the cylinders, from an oil cooling circuit for cooling the engine oil used by the internal combustion engine, and from the exhaust system for removing exhaust gas from the internal combustion engine, and transferred to a thermal consumer.

The electrical energy generated by the electrical generator is typically either fed into a public power grid or used by the operator of the cogeneration plant in a so-called self-supply power grid - often also referred to as an "electrical island network" - for self-supply. In the case of so-called dual use of the electricity generated, i.e. a combination of feeding into the public grid and self-supply - this is also called parallel grid operation - the electrical generator of the cogeneration plant is electrically connected to the public power grid. There is therefore no galvanic separation between the public power grid and the self-supply power grid. This most common embodiment does enable independent use of the waste heat and electricity provided simultaneously in the cogeneration plant.

The disadvantage here is that in this case there is always an electrical connection between the private self-supply power grid and the public power grid, which can cause disruptive effects such as voltage fluctuations etc. in the public power grid to be transferred to the private self-supply power grid, and vice versa. In addition, legal provisions can prohibit such an electrical connection between the self-supply power grid and the public power grid, only allow it under strict conditions and - regardless of this - make it subject to the payment of high fees, which can significantly reduce the profitability of the cogeneration plant for the operator.

One way to avoid such problems is to not implement an electrical connection between the self-supply power grid and the public grid in a so-called “island operation” of the cogeneration plant.

In the case of such an “island operation” that is electrically independent of the public power grid, the generator of the cogeneration plant is connected exclusively to the above-mentioned self-supply power grid of the CHP operator, which in turn has no electrical connection to the public power grid.

The electrical energy generated by the electric generator can therefore only be used for self-supply. However, this requires what is known as "current-controlled" operation of the cogeneration plant, i.e. the drive power generated by the internal combustion engine must be adjusted so that the electrical energy generated by the electric generator corresponds to the current demand of the self-supply power grid. In this case, however, there is no guarantee that the waste heat generated by the internal combustion engine is sufficient to supply the thermal consumer coupled to the cogeneration plant with the required thermal energy.

In addition, for technical reasons, the drive power generated by the internal combustion engine cannot be below a specified minimum value at which the internal combustion engine is in so-called partial load operation. If the self-supply power grid requires less electrical energy than is generated by the electrical generator in partial load operation of the internal combustion engine, the self-supply power grid must be provided with internal redundancy, for example in the form of a separate battery system or a photovoltaic system, when electricity demand occurs below partial load operation. This entails additional costs.

EP 2 661 549 B1 , DE 600 35 020 T2 , US 2010/ 0 230 966 A1 and DE 102 57 943 A1 each disclose a device with features of claim 1.

It is therefore an object of the present invention to provide an improved embodiment for a cogeneration plant in which in particular, the disadvantages explained above have been largely or even completely eliminated.

This object is solved by the subject matter of claim 1. Preferred embodiments are the subject matter of the dependent patent claims.

The basic idea of the invention is therefore to couple the internal combustion engine of a combined heat and power plant with two electrical generators that are galvanically separated from one another. This allows one of the two electrical generators - this is referred to below as the "first generator" - to be electrically connected to a public electrical power grid, whereas the other of the two electrical generators - referred to below as the "second generator" - can be connected to the self-supply power grid of the combined heat and power plant operator. Since no electrical connection can be created between the self-supply power grid and the public power grid due to the galvanic separation of the two electrical generators of the combined heat and power plant, which is essential to the invention, the self-supply power grid cannot be disrupted by the public power grid, and vice versa. In addition, any fees that may be incurred due to legal regulations for an electrical connection of the self-supply power grid to the public grid are waived. A key advantage of the solution presented here of a combined heat and power plant with two electrically isolated generators is that the drive power generated by the internal combustion engine can be used extremely flexibly by the two electrical generators to generate electrical energy. Since the electrical energy generated by the combined heat and power plant is not fed exclusively into the public power grid or the self-supply power grid - as is the case with conventional combined heat and power plants with just a single electrical generator - but can be distributed between both power grids, the drive power generated by the internal combustion engine to generate waste heat for the thermal consumer can be used extremely effectively to generate electrical energy. The provision of a backup system for the self-supply power grid - for example in the form of an additional battery system - mentioned above is not necessary.

In particular, it is possible to control or operate the two generators in such a way that the drive power generated by the internal combustion engine is used to generate electrical energy by means of the second electrical generator, which covers the current requirements of the self-supply power grid. In addition, it is possible to use the first electrical generator to generate electrical energy that is not required for the self-supply power grid and can therefore be fed into the public power grid - usually in return for a fee. It is therefore no longer necessary to operate the cogeneration plant in an electricity-controlled manner - as explained above. Instead, heat-conducting operation of the cogeneration plant is possible, which means that the output power generated by the internal combustion engine is adjusted in such a way that the waste heat generated by the internal combustion engine is coordinated for an optimal supply of heat to the thermal consumer coupled to the heating circuit. The two electrical generators can be controlled in such a way that the energy required by the self-supply power grid is generated by the second generator. The drive power not required to drive the second generator can be used to drive the first generator. The electrical energy generated by the first electrical generator can be fed into the public power grid in return for remuneration.

As a result, the provision of two galvanically separated electrical generators presented here, which is essential to the invention, allows the use of the cogeneration plant according to the invention with only one electrical generator with significantly improved economic efficiency.

The method presented here is used to operate a combined heat and power plant. The combined heat and power plant comprises a first electrical generator and a second electrical generator, which are galvanically separated from one another. The advantages of the combined heat and power plant explained above are therefore also transferred to the method. According to the method, at least one of the two generators is drive-connected to the internal combustion engine. Particularly preferably, both generators are drive-connected to the internal combustion engine. According to the method, the first generator is electrically connected to a public power grid, so that it generates electrical power when it is drive-connected to the internal combustion engine and for this public power grid. According to the method, the second generator is electrically connected to a self-supply power grid that is galvanically separated from the public power grid, so that it generates electrical power when it is drive-connected to the internal combustion engine for this self-supply power grid.

When carrying out the method, the first generator is electrically connected to a public power grid and generates electrical power for this as long as the drive connection of the first generator to the internal combustion engine When carrying out the method, the second generator is also electrically connected to a self-supply power grid that is galvanically separated from the public power grid and generates electrical power for the self-supply power grid as long as the drive connection of the second generator to the internal combustion engine exists.

During implementation of the method, the fuel supply of the internal combustion engine of the combined heat and power plant is adjusted depending on the heating output required for the at least one thermal consumer between a full-load operation, in which the internal combustion engine operates with maximum fuel supply and generates a maximum output torque, and a partial-load operation, in which the fuel supply - and consequently also the output torque - of the internal combustion engine is reduced compared to the full-load operation.

In a preferred embodiment, a speed of the output shaft of the internal combustion engine is regulated to a predetermined speed target value independently of the actual fuel supply. In this way, stable operation of the internal combustion engine is ensured. In particular, it is avoided that the speed of the output shaft falls below a threshold value, below which a malfunction of the internal combustion engine cannot be ruled out for technical reasons.

Preferably, the output power generated by the internal combustion engine during operation is distributed to the two generators as first or second drive power depending on the internal requirements of the internal power supply network.

In a preferred embodiment of the method, the output power of the internal combustion engine is used to drive the second generator, so that the second generator generates the electrical power currently required by the internal power grid. The remaining output power of the internal combustion engine, which is not required to drive the second generator, can thus be used in this embodiment to drive the first generator, so that the first generator generates electrical power to feed into the public power grid.

In a further preferred embodiment, the second generator comprises a first stator with stator windings and at least one second stator with stator windings. In this embodiment, the second stator(s) present can be individually electrically connected to or disconnected from the internal power supply network depending on the current output power of the internal combustion engine and depending on the current demand for electrical power for the internal power supply network. In this embodiment, the second generator can generate more electrical power by "switching on" second stators precisely when this is also required by the internal power supply network.

In a further preferred embodiment, which can be combined in particular with the embodiment explained above, the first generator comprises a first stator with stator windings and at least one second stator with stator windings. In this embodiment too, the second stator(s) present can each be individually electrically connected to or disconnected from the public power grid for generating electricity, depending on the current output power of the internal combustion engine and the current demand for electrical power for the public power grid. In this embodiment, the electrical power that is not required by the internal power grid can be generated by the first generator by "switching on" second stators.

According to an advantageous development, the method is carried out in a control/regulation device which controls the internal combustion engine and the two generators. The control/regulation device can preferably also be used to control the (partial) clutches explained above and the existing electrical switches.

This control/regulation device is expediently designed in such a way that it does not electrically connect the two generators to one another. In this way, the galvanic isolation of the two generators, which is essential to the invention, and the associated separation of the public power grid from the self-supply power grid are ensured.

Preferably, the at least one thermal consumer is thermally coupled to the heating circuit. Of course, two or more such thermal consumers can also be provided.

According to a preferred embodiment, the first generator comprises a first stator and at least one second stator, both of which have stator windings. In this embodiment, the at least one second stator of the first generator can optionally be electrically connected to the first stator or electrically separated from it. This can be done with the aid of a suitable (first) electrical switch arranged between the two stators. In this embodiment, the first stator and the at least one second stator of the first generator particularly expediently form an electrical parallel circuit. Alternatively or additionally, in this embodiment, the second generator comprises a first stator and at least one second stator. In this embodiment, the at least one second stator of the second generator can optionally be electrically connected to the first stator or electrically separated from it. This can be done with the aid of a suitable (second) electrical switch arranged between the two stator windings. In this embodiment, the first stator and the at least one second stator of the second generator particularly expediently form an electrical parallel circuit. In this embodiment, the second generator can generate correspondingly more electrical power by "switching on" the at least one second stator if the internal combustion engine provides corresponding output power at the output shaft because this is required for the internal power supply network. Accordingly, by connecting the at least one second stator of the first generator, additional electrical power can be generated for feeding into the public power grid if corresponding mechanical power is provided by the output shaft.

According to an advantageous development, the first generator has at least two second stators which are electrically connected to the first stator of the first generator in an independently separable manner, preferably in the form of an electrical parallel connection. Alternatively or additionally, in this development, the second generator has at least two second stators which are electrically connected to the first stator of the second stator in an independently separable manner, preferably in the form of an electrical parallel connection. In this development, the first or second generator can generate correspondingly more electrical power by successively "switching on" individual second stators if the internal combustion engine provides corresponding output power for this on the output shaft.

According to a further preferred embodiment, the first generator for generating electrical power can have a first rotor that magnetically interacts with its stators and has a predetermined first number of first pole pairs made up of magnetic poles. Alternatively or additionally, the second generator for generating electrical power can have a first rotor that magnetically interacts with its stators and has a predetermined first number of first pole pairs made up of magnetic poles.

The first magnetic poles and, alternatively or additionally, the second magnetic poles can expediently be formed by magnets, preferably by permanent magnets, made of a magnetic or magnetized material. This variant is technically simple to implement and therefore particularly reliable. Alternatively, the first and/or second magnetic poles can be formed by rotor windings which, when electrically energized, generate a magnetic field, which can particularly preferably be a magnetic dipole field. This variant implements a so-called excitation machine, which can preferably be designed to be brushless. With this variant, the use of magnetic or magnetized materials, the procurement of which can be associated with relatively high costs, can be dispensed with. A combination of both variants explained above is of course also possible.

Alternatively or additionally, according to this embodiment, the second generator for generating electrical power can have a second rotor which magnetically interacts with the second stator and has a predetermined second number of second pole pairs of magnetic poles.

According to a preferred embodiment, the two generators can be or are drive-connected to the internal combustion engine independently of one another. This embodiment allows variable operation of the two electrical generators. In particular, in this embodiment it is possible to decouple the second electrical generator from the internal combustion engine in terms of drive as long as it is not necessary to generate electrical energy for the internal electrical power grid. This can be the case, for example, if no electrical consumers are active in the internal electrical power grid or if they are temporarily supplied with electrical energy from a local electrical energy storage device, such as a rechargeable electrical battery. Accordingly, it is possible to decouple the first electrical generator from the drive train of the internal combustion engine if the entire output power of the internal combustion engine is to be used exclusively to generate electrical energy for the internal electrical power grid.

For the purpose of a particularly simple and thus cost-effective technical realization of the drive connection of the two electric generators with the internal combustion engine, which is essential to the invention, it is proposed that the two generators generators are connected to the internal combustion engine via a common transmission. Such a transmission can comprise a transmission drive for coupling to the output shaft of the internal combustion engine, a first transmission output for coupling to the first generator and a second transmission output for coupling to the second generator. Such a transmission requires particularly little installation space.

It is particularly preferred that the two generators are drive-connectable or drive-connected to one another, preferably by means of the transmission. Such a drive connection of the two generators to one another - independently of or in addition to the drive connection of the generators to the internal combustion engine - allows emergency operation of the cogeneration plant if the internal combustion engine does not work properly or fails completely due to a technical defect. In this case, one of the two generators - if it is designed as a motor generator - can drive the other generator so that the latter can generate electrical current.

According to an advantageous further development, which is technically particularly simple in design, so that it is accompanied by considerable cost advantages, the second generator can be connected to the output shaft of the internal combustion engine via the first generator, or vice versa. In terms of drive technology, this variant implements a series connection of the two generators behind the output shaft. In particular, this variant eliminates the need for a transfer case.

Particularly preferably, in the above-described development, the two generators can be decoupled and connected to one another by means of a partial coupling. This makes it possible to decouple the downstream of the two generators from the drive train of the internal combustion engine if no electrical energy is to be generated by it. This can be the case in particular if the downstream generator is the first generator and the entire output power of the internal combustion engine is required for the second generator, i.e. for generating electricity for the internal power supply network.

According to an advantageous development, the two generators can be decoupled from the output shaft of the internal combustion engine by means of a common clutch that is arranged between the transfer case and the output shaft. In the event that the internal combustion engine is not ready for use - for example due to a technical defect - it is thus possible to drive one or both electric generators using another suitable drive system in the form of a so-called emergency power operation. This scenario is particularly suitable if one of the two electric generators is designed as a so-called motor generator, which means that this generator can be operated either as a generator for generating electrical energy or as an electric motor for generating mechanical work that is driven electrically.

According to an advantageous development, the first generator is drive-connected to the output shaft of the internal combustion engine by means of a first partial clutch that can be decoupled independently of the second generator. In this development, the second generator is drive-connected to the output shaft of the internal combustion engine by means of a second partial clutch that can be decoupled independently of the first generator. In a simplified variant of this development, only the first or only the second partial clutch is provided.

Particularly preferably, the first generator is connected to the first transmission output of the transfer case via the first partial clutch in a decoupleable manner. In this embodiment, the second generator is connected to the second transmission output of the transfer case via the second partial clutch in a decoupleable manner. The individual generators can thus be decoupled from the drive train as long as they are not intended to generate electrical power, in particular for feeding into the public power grid or the self-supply power grid.

Another preferred embodiment has proven to be particularly simple to implement technically and thus cost-effective to manufacture, in which the two generators are connected to the internal combustion engine via the transfer case without a clutch, i.e. cannot be decoupled. This embodiment is not only cost-effective, but also particularly low-maintenance. In addition, it requires less installation space than embodiments with a clutch.

According to an advantageous development, at least one kinetic energy storage device is arranged between the internal combustion engine and the two generators, which ensures the immediate initiation of emergency operation in the event of a malfunction or failure of the internal combustion engine and thus an uninterrupted power supply, especially for the internal power supply network. In such an emergency operation scenario, the first electric generator works decoupled from the output shaft of the internal combustion engine as an electric motor, which draws electrical energy from the public power grid and supplies it as mechanical drive energy to the second generator of the self-generated power grid.

A particularly preferred embodiment in which the intermediate storage device is designed as a flywheel or comprises such a flywheel has proven to be particularly simple to implement from a technical perspective and is therefore cost-effective.

According to another advantageous development, the first generator and/or the second generator are connected to the output shaft via a transmission gear, which increases or decreases the speed of the generator rotor compared to the speed of the output shaft. In the event that an optimal adjustment of the number of first and second pole pairs is not possible at a certain target speed of the output shaft and specified grid frequencies for the public grid and the self-supply power grid, it is advisable to implement a drive connection between at least one of the two generators and the output shaft of the internal combustion engine via a transmission gear, which increases or decreases the speed of the rotor of this generator compared to the speed d of the output shaft. Alternatively, such a transmission gear can also be arranged in the output train between the two generators.

According to a preferred embodiment, the second generator is electrically connected or connectable to a - typically private - self-supply electrical power grid, which is galvanically separated from a public power grid. In this way, the electrical power generated by the second electrical generator can be made available for consumption in the self-supply electrical power grid without disrupting the public power grid. In particular, unavoidable frequency fluctuations in the public power grid can be kept away from the self-supply electrical power grid.

According to an advantageous further development, the first electrical generator is not electrically connected or connectable to the (private) electrical self-supply power grid. This variant proves to be particularly advantageous if the first generator can be electrically connected to a public power grid and if legal regulations exist that prohibit an electrical connection of the self-supply power grid to the public power grid.

According to a preferred embodiment, the first generator is or can be electrically connected to a public power grid, which is galvanically separated from the self-supply power grid to which the second generator is or can be electrically connected. The first electrical generator can thus be used to use drive power of the internal combustion engine to generate electrical energy that is not required for the self-supply power grid, so that it can be fed into the public power grid as surplus electrical energy against payment.

According to an advantageous development, the first generator and, alternatively or additionally, the second generator are designed as motor generators. Such a motor generator can be operated in two different operating modes, as is known to those skilled in the art: In a first operating mode, the motor generator works as a conventional generator and converts mechanical energy into electrical energy. In a second operating mode, the motor generator works as an electric motor and converts the electrical energy provided into mechanical energy. The design of the first generator as a motor generator enables the aforementioned implementation of emergency power operation of the cogeneration plant in the event of failure of the internal combustion engine. In this case, the first generator can work as an alternative drive system in accordance with the second operating mode, which draws electrical energy from the public power grid and in this way drives the second generator so that it can generate electrical energy for the self-supply power grid.

It is also conceivable that the second generator could be designed as a motor generator.

According to another preferred embodiment, at least the second generator can be designed as a direct current machine. This variant is suitable if the electrical current generated by the generator to supply the electrical consumer has to be in the form of direct current anyway. This can be the case in various applications. For example, modern data centers are typically supplied with electrical energy in the form of direct current. An unnecessary conversion of electrical current into alternating current generated by an alternating current generator can be eliminated in this way.

The combined heat and power plant expediently has a control/regulation device for controlling/regulating the internal combustion engine and the two generators. The control/regulation device is preferably designed in such a way that it does not electrically connect the two generators to one another. In this way, the The galvanic separation of the two generators, which is essential to the invention, and thus also the galvanic separation of the public power grid from the self-supply power grid is ensured.

The control/regulation device can preferably also be used to control the (partial) clutches explained above as well as the existing electrical switches.

The invention relates to a combined heat and power plant. The combined heat and power plant comprises an internal combustion engine which has an exhaust system and an output shaft. The combined heat and power plant further comprises a heating circuit to which at least one thermal consumer can be or is thermally coupled and which is thermally connected to the exhaust system of the internal combustion engine via a (first) heat exchanger. The combined heat and power plant further comprises a heating circuit for cooling the internal combustion engine, wherein the heating circuit is thermally connected to the heating circuit by means of a second heat exchanger. According to the invention, the combined heat and power plant comprises a first electrical generator and a second electrical generator, which are galvanically separated from one another and can be or are drive-connected to the internal combustion engine. The combined heat and power plant according to the invention also comprises a control/regulation device which is set up/programmed to carry out the method explained above. The advantages of the method explained above are therefore also transferred to the combined heat and power plant according to the invention.

Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures based on the drawings.

It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein like reference numerals refer to like or similar or functionally identical components.

• 1 ein Beispiel eines erfindungsgemäßen Blockheizkraftwerks in schematischer, stark vereinfachter Darstellung,
• 2a,ab das Blockheizkraftwerk der 1 jeweils in einer Detailansicht, in welcher der Aufbau der beiden Generatoren genauer dargestellt ist,
• 3 eine Variante des Beispiels der 1.

They show, each schematically

• 1 an example of a combined heat and power plant according to the invention in a schematic, highly simplified representation,
• 2a ,from the combined heat and power plant of 1 each in a detailed view, in which the structure of the two generators is shown in more detail,
• 3 a variant of the example of 1 .

1 illustrates in a schematic representation an example of a combined heat and power plant 1 according to the invention. The combined heat and power plant 1 comprises an internal combustion engine 2, which in turn has an exhaust line 16 for discharging the exhaust gas A generated in the cylinders (not shown) of the internal combustion engine 2 from the internal combustion engine 2. The internal combustion engine 2 also comprises an output shaft 3, via which the mechanical output power generated by the internal combustion engine 2 is provided. The combined heat and power plant 1 also comprises a heating circuit 4, to which a thermal consumer 20 - in the example of the figures this is shown as a radiator 21 - can be thermally coupled. A heating medium H circulates in the heating circuit 4, which can be heating water, for example. The heating circuit 4 is thermally connected to the exhaust line 16 of the internal combustion engine 2 by means of a first heat exchanger 5a. Furthermore, the cogeneration plant 1 comprises a cooling circuit 6 in which a cooling medium K circulates to cool the cylinders of the internal combustion engine 2.

Accordingly 1 The heating circuit 4 is thermally connected to the heating circuit 4 by means of a second heat exchanger 5b. Furthermore, the combined heat and power plant 1 can also have a 1 not shown in detail for cooling the engine oil required by the internal combustion engine 2. In this case, said oil circuit can also be thermally connected to the heating circuit 4 via a further, third heat exchanger - not shown in the figures. Furthermore, the combined heat and power plant 1 can also have a 1 low-temperature mixture cooling water circuit (not shown in detail) for cooling the fuel mixture compressed before combustion in the internal combustion engine 2.

Furthermore, the combined heat and power plant 1 comprises a first electrical generator 7a and a second electrical generator 7b. The two electrical generators 7a, 7b are galvanically separated from one another and can be connected to the output shaft 3 of the internal combustion engine 2. When the internal combustion engine 2 is in operation and the drive connection to the output shaft 3 exists, the two electrical generators 7a, 7b generate electrical energy independently of one another. In the example of the 1 the two generators 7a, 7b are arranged on the same side of the internal combustion engine 2.

According to 1 the two generators 7a, 7b are drive-connected to the internal combustion engine 2 via a common transmission 8, which for this purpose has a transmission drive 9 for coupling to the output shaft 3 of the internal combustion engine 2 and two transmission outputs 10a, 10b for coupling to the first and second generators 7a, 7b, respectively.

In the example of 1 the transmission 8 is designed as a so-called transfer case 11. In order to be able to selectively couple or decouple the two generators 7a, 7b together with the output shaft 3 of the internal combustion engine 2, the drive connection of the transmission 8 to the internal combustion engine 2 is made via a common clutch 12, which is arranged in the drive train of the internal combustion engine 2, between the transmission 8 or the transfer case 11 and the output shaft 3. The clutch 12 can be adjusted between a clutch state in which the transmission 8 is drive-connected to the internal combustion engine 2, and an uncoupled state in which this drive connection is interrupted or canceled.

In the example of 1 the two generators 7a, 7b can also be driven independently of one another with the internal combustion engine 2. For this purpose, the first generator 7a is drivenly connected to the output shaft 3 of the internal combustion engine 2 by means of a first partial clutch 13a, which can be decoupled independently of the second generator 7b. The first generator 7a is drivenly connected to the first transmission output 10a of the transmission or the transfer case 11 via the first partial clutch 13a, which can be decoupled. In a similar way to the clutch 12, the first partial clutch 13a can also be adjusted between a clutch state in which the first generator 7a is drivenly connected to that of the internal combustion engine 2, and a decoupled state in which this drive connection is interrupted or canceled.

The second generator 7b can be electrically connected to a private electrical power grid 14 - known to the relevant expert as a so-called "self-supply power grid" or "island power grid" - which is galvanically separated from a public power grid 15. The electrical energy generated by the second electrical generator 7b can thus be made available to the self-supply power grid 14 without causing disruptions in the public power grid 15. The first generator 7a, on the other hand, is not electrically connected to the private electrical self-supply power grid 14, and is therefore always galvanically separated from it. Instead, the first generator 7a can be electrically connected to the public power grid 15. The first electrical generator 7a can thus be used to use drive power from the internal combustion engine 2 to generate electrical energy that is not required for the self-supply power grid 14. This electrical energy can be fed into the public power grid 15 for a fee. The second generator 7b cannot be connected to the public power grid 15. This proves to be advantageous if there are legal regulations that prohibit an electrical connection of the self-supply power grid 14 to the public power grid 15 or only allow it in connection with the payment of corresponding fees. In a manner analogous to the first generator 7a, the second generator 7b is also drive-connected to the output shaft 3 of the internal combustion engine 2 by means of a second partial clutch 13b that can be decoupled independently of the first generator 7a. The second generator 7b is drive-connected to the second transmission output 10b of the transmission 8 or the transfer case 11 via the second partial clutch 13b that can be decoupled. In a manner analogous to the clutch 12 or the first partial clutch 13a, the second partial clutch 13b can also be adjusted between a clutch state in which the second generator 7b is drive-connected to that of the internal combustion engine 2 and a decoupled state in which this drive connection is interrupted or canceled.

Thus, the two generators 7a, 7b can be individually decoupled from the drive train, for example as long as no electrical energy is to be generated by them, in particular for feeding into the public power grid 15 or the self-supply power grid 14.

A drive connection of the two generators 7a, 7b with each other - with simultaneous decoupling of the two generators 7a, 7b from the output shaft 3 by means of the coupling 12 - allows emergency operation of the combined heat and power plant 1 if the internal combustion engine 2 is not working properly due to a technical defect or has completely failed. In this case, the two generators 7a, 7b are decoupled from the output shaft 3 by means of the coupling 12. Thus, one of the two generators 7a, 7b - if it is designed as a motor generator - can drive the other generator 7b, 7a so that the latter can generate electrical current. For said emergency operation, a kinetic buffer 36 for temporarily storing the kinetic energy generated by the internal combustion engine 2 is arranged between the internal combustion engine 2 and the two generators 7a, 7b, which buffer 36 has a 1 can include the flywheel 37, which is only roughly indicated.

Such an emergency operation can be activated with the aid of the buffer 36 immediately after the failure or malfunction of the internal combustion engine 2 occurs. so that an uninterrupted electrical power supply can be ensured, in particular for the internal power supply network 14. In such an emergency operation, the first electrical generator 7a - decoupled from the output shaft 3 of the internal combustion engine 2 - can work as an electric motor which draws electrical energy from the public power grid and provides this as mechanical work to drive the second generator 7b, which in turn generates electrical energy for the internal power supply network 14.

2a shows the first generator 7a in a detailed view, the 2b analogous to 2a the second generator 7b in a detailed view. According to 2a the first generator 7a comprises a first stator 30a with stator windings 30.1a and a second stator 30b with stator windings 30.1b. For the electrical power generation, the first generator 7a has a first rotor 33a which interacts with its stators 30a and 30b and is rotatably adjustable relative to it and has a predetermined first number n1 of first pole pairs p1 made up of magnetic poles. The electrical power generated in the first stator 30a can be fed into the public power grid 15 via a first electrical supply line 34a. Accordingly, according to 2b the second generator 7b has a stator 31a with stator windings 31.1a and a second stator 31b with stator windings 31.1b. For the generation of electrical power, the second generator 7b has a second rotor 33b which interacts with the existing stators 31a, 31b and has a predetermined second number n2 of second pole pairs p2 of magnetic poles. The electrical power generated in the second stator 30b can be fed into the internal power supply network 14 via a second electrical supply line 34b.

The first magnetic poles or pole pairs p1 and, alternatively or additionally, the second magnetic poles or pole pairs p2 can expediently be formed by magnets, preferably by permanent magnets, made of a magnetic or magnetized material. Alternatively, the first and/or second magnetic poles or pole pairs p1, p2 can be formed by rotor windings which, when electrically energized, generate a magnetic field which can particularly preferably be a magnetic dipole field. A combination of both variants explained above is also conceivable.

The number n1 of first pole pairs p1 influences - together with the speed d of the output shaft 3 in heat-controlled operation of the internal combustion engine 2 - the frequency of the alternating current generated by the first generator 7a. The number n1 is ideally set such that the frequency of the alternating current generated by the first generator 7a corresponds to the grid frequency required for feeding into the public power grid 15. The same applies to the number n2 of second pole pairs p2 of the second generator 7b. It is understood that the self-supply power grid 14 can be designed for a different alternating current frequency than the public power grid 15, so that the number n1 of first pole pairs p1 can be selected to be different from the number of second pole pairs n2.

Typically, the public power grid has a grid frequency of 50 Hz. The self-supply power grid 14 of private households also generally has a grid frequency of 50 Hz. In certain cases, particularly when electrical power is to be generated with increased power quality, the self-supply power grid 14 can be operated with a higher grid frequency, for example 400 Hz.

The second stator 30b of the first generator 7a can be electrically connected in parallel to the first stator 30a or electrically separated from it by means of a first electrical switch 35a. The first generator 7a has in the example of the 2 i.e. two cascaded stators 30a, 30b. In a further development of the example, a larger number of stators can also be provided, which can be electrically connected in parallel with or separated from the other stators of the first generator via one or more electrical switches or in another suitable manner (in 1 not shown for the sake of clarity). The electrical current generated in the stators 30a, 30b of the first generator 7a can be fed into the public power grid 15 via a first electrical supply line 34a. Depending on how much electrical power is to be generated by the first generator 7a and fed into the public power grid 15, the individual stators 30a, 30b can be electrically connected in parallel to one another.

The second generator 7b with its stators 31a, 31b, each having stator windings 31.1a and 31.1b, which can be electrically connected in parallel to one another or electrically separated from one another by means of the second electrical switch 35b, is constructed in a similar manner to the first generator 7a. The electrical current generated in the second stator 31 can - as in 1 shown - fed into the self-supply power grid 14 via a second electrical supply line 34b.

The combined heat and power plant 1 has a control/regulation device 40 for controlling ung/regulation of the internal combustion engine 2 and the two generators 7a, 7b. The method can be carried out by means of the control/regulation device 40. The control/regulation device 40 controls the internal combustion engine 2 and the two generators 7a, 7b. For this purpose, suitable electrical control lines (in the 1 only roughly indicated) between the control/regulation device 40 and the internal combustion engine 2 as well as the two generators 7a, 7b. To carry out the method, the control/regulation device 40 can have a control unit and a memory unit, in which the latter can be stored computer program code which is executed by the control unit. The control/regulation device 40 is designed in such a way that it does not electrically connect the two generators 7a, 7b to one another. In this way, the galvanic separation of the two generators 7a, 7b, which is essential to the invention, and thus also the galvanic separation of the public power grid 15 from the internal power grid 14 is ensured. In the course of carrying out the method, one of the two generators 7a, 7b is drive-connected to the internal combustion engine 2. According to the method, the first generator 7a is electrically connected to the public power grid 15 and generates electrical current for it. According to the method, the second generator 7b is electrically connected to a self-supply power grid 14 that is galvanically separated from the public power grid 15 and generates electrical power for this.

The combined heat and power plant 1 is expediently operated in a so-called heat-controlled operating mode, in which the actual output power of the internal combustion engine 2 is at least 50% of the maximum possible output power. This is achieved by a corresponding adjustment of the fuel supply to the internal combustion engine 2. This adjustment takes place in such a way that the waste heat generated by the internal combustion engine 2 is sufficient to supply the thermal consumer 20 with the required amount of thermal energy. At the maximum possible output power, the internal combustion engine operates in what is known as full-load operation; at a reduced output power compared to the maximum possible output power, the internal combustion engine operates in what is known as partial-load operation.

When the internal combustion engine 2 is operating, a speed d of the output shaft 3 of the internal combustion engine 2 is regulated to a predetermined speed target value d _target . By regulating the speed d in this way, it is prevented that it falls below a minimum permissible threshold value, below which the proper functioning of the internal combustion engine 2 and thus of the entire cogeneration plant 1 can no longer be guaranteed for technical reasons. Above all, compliance with the minimum permissible threshold value should ensure complete and clean combustion of the fuel mixture introduced into the internal combustion engine 2 so that the legally applicable emission limits are adhered to. The output power in partial load operation of the internal combustion engine must also not fall below a permissible threshold value which no longer guarantees the proper functioning of the internal combustion engine 2 and thus of the entire cogeneration plant 1 for technical reasons. In particular, by complying with the minimum permissible threshold value of the output power of the internal combustion engine 2, an insufficient piston expansion of the movable pistons of the internal combustion engine 2 is to be avoided, so that an associated, undesirable entry of lubricating oil into the combustion chamber of a respective cylinder is prevented.

In addition, with a suitable or adapted definition of the pole pairs p1, p2 in the two generators 7a, 7b explained above, the regulation of the speed d ensures that the alternating electrical current generated by the two generators 7a, 7b has the grid frequency f1 or f2 required for feeding into the public grid 15 or into the internal power grid 14. The following relationship, known to the relevant expert, applies here: d _soll = f1/p1 or d _soll = f2/p2. Typically, the grid frequency f of the public power grid is 50 Hz. This results in various combinations of the required speed d of the output shaft 3 and the number of pole pairs p1 of the first rotor 33a of the first generator 7a, according to the so-called 50 Hz rule. For example, it is possible to operate the internal combustion engine 2 with two first pole pairs p1 and at a speed d = 1500 revolutions/minute. Alternatively, the internal combustion engine 2 can be operated with four first pole pairs p1 at a speed d = 750 revolutions/minute. For the internal power supply network 14, the network frequency f2 can be 400 Hz, for example. In this case, it is advisable to equip the rotor 33a of the second generator 7b with p2 = 16 pole pairs if the output shaft 3 is to be operated at a target speed d _target = 1500 revolutions/minute.

In the event that an optimal adjustment of the number of first and second pole pairs p1, p2 is not possible at a certain target speed d _target and given grid frequencies f1, f2, it is advisable to put one of the two generators - for example the second generator 7b - into drive connection with the output shaft 3 via a transmission gear, which reduces the speed of the rotor of this generator 7b compared to the speed d of the output shaft 3 is increased or decreased. If the desired grid frequency f1 of the public power grid 15 is f1 = 50 Hz and the grid frequency f2 of the self-supply grid is f2 = f60 Hz, an optimal adjustment can be achieved by selecting the first pole pairs to p1 = 2 and the second pole pairs to p2 = 2 if a transmission gear is provided between the output shaft 3 and the second rotor 33b, which speeds up the speed d of the output shaft 3 by a factor of 1.2. For this purpose, the transmission gear is connected to the output shaft on the input side and in this way a rotor speed of the second rotor 33b is increased by a factor of 1.2 compared to the speed d of the output shaft 3. The speed d of the output shaft, which during operation of the internal combustion engine 2 corresponds to the target speed d _target = 1500 rpm, is present on the input side of the transmission gear and, after being translated by a factor of 1.2, is 1800 rpm on the output side, so that the second rotor 33b rotates at the ideal speed for a mains frequency f2 = 60 Hz.

The output power generated by the internal combustion engine 2 during operation is distributed as first and second drive power P1, P2 to the first and second generators 7a, 7b, respectively, depending on the internal power requirement of the internal power supply network 14. The output power of the internal combustion engine 2 provided on the output shaft 3 is used to drive the second generator 7b in such a way that the latter generates the electrical power currently required by the internal power supply network 14. The remaining output power of the internal combustion engine 2 that is not required to drive the second generator 7b can be used to drive the first generator 7a, so that the latter generates electrical power to feed into the public power grid 15.

For optimized power generation, the existing second stators 31b of the second generator 7b can be individually electrically connected to or disconnected from the internal power grid 14 for power generation depending on the current output power of the internal combustion engine 2 and depending on the current demand for electrical power in the internal power grid 14. Accordingly, the individual second stators 30b of the first generator 7a can be individually electrically connected to or disconnected from the public power grid 15 depending on the available output power. This ensures that the entire output power generated by the internal combustion engine 2 is used for electrical power generation and thus also for feeding the generated electrical power into the internal power grid 14 or into the public power grid 15.

One of the two generators 7a, 7b or both electrical generators 7a, 7b can optionally be designed as a motor generator. Such a motor generator can be operated in two operating modes, as is known to those skilled in the art: In a first operating mode, the motor generator works as a conventional generator and converts mechanical energy into electrical energy. In a second operating mode, the motor generator works as an electric motor and converts the electrical energy provided into mechanical energy. The design of the first generator 7a as a motor generator enables the aforementioned implementation of emergency power operation of the combined heat and power plant 1, in particular in the event of failure of the internal combustion engine 2. In this case, the first generator 7a can work as an alternative drive system in accordance with the second operating mode, which draws electrical energy from the public power grid 15 and in this way drives the second generator 7b so that it can generate electrical energy for the self-supply power grid 14. In principle, however, it is also conceivable for the second generator 7b to be designed as a motor generator. In this case, the electrical energy stored in an electrical energy storage device present in the self-supply power grid 14, for example a rechargeable battery, can be used to drive the first generator 7a and thus generate electrical energy for the public power grid 15.

The variants explained above can be combined with each other where appropriate. In a first simplified variant of the example of 1 The common coupling 12 and, alternatively or additionally, one or both partial couplings 13a, 13b can be dispensed with. In a second simplified variant of the example of the 1 the gearbox 8 can be dispensed with. In this variant, the two generators 7a, 7b can be directly connected to the output shaft 3 of the internal combustion engine 2.

By means of the control/regulation device 40, the (partial) clutches 12, 13a, 13b explained above and the electrical switches 35a, 35b can preferably also be controlled.

3 shows a variant of the example of 1 in a partial view. In the following, only the differences of the example of 3 compared to the example of 1 In the example of 3 The first generator 7a is connected to the output shaft 3 of the internal combustion engine 2 via the second generator 7b. This variant realizes a series connection of the two generators 7a, 7b behind the output shaft 3. In this variant, in particular The provision of a transfer case is omitted. The two generators 7a, 7b can be connected to one another in a decoupleable manner by means of a partial clutch 13a, as shown. This makes it possible to decouple the downstream generator 7a from the output shaft 3 of the internal combustion engine 2 if no electrical energy is to be generated by it. This can be the case, for example, if the entire output power of the internal combustion engine 2 is required for the second generator 7b, i.e. for generating electricity for the internal power supply network 14.

Claims (22)

Combined heat and power plant (1), - with an internal combustion engine (2) having an exhaust line (16) and an output shaft (3), - with a heating circuit (4) to which at least one thermal consumer (20) can be coupled and which is thermally connected to the exhaust line (16) of the internal combustion engine (2) via a (first) heat exchanger (5a), - with a cooling circuit (6) for cooling the internal combustion engine (2), wherein the cooling circuit (6) is thermally connected to the heating circuit (4) by means of a second heat exchanger (5b), - with a first electrical generator (7a) and with a second electrical generator (7b), which are galvanically separated from one another and can be driven or are driven by the internal combustion engine (2), - wherein the first generator (7a) is designed for electrical connection to a public power grid (15) and the second generator (7b) is designed for electrical connection to a self-supply power grid (14), which is galvanically separated from the public Power grid (15), wherein the first electrical generator (7a) and the second electrical generator (7b) are each arranged to generate alternating electrical current. combined heat and power plant according to claim 1 , characterized in that the at least one thermal consumer (20) is thermally coupled to the heating circuit (4). combined heat and power plant according to claim 1 or 2 , characterized in that - the first generator (7a) comprises a first stator (30a) and at least one second stator (30b), both of which each have stator windings (30.1a, 30.1b), wherein the at least one second stator (30b), preferably by means of at least one first electrical switch (35a), is optionally electrically connected to the first stator (30a) - preferably in an electrical parallel circuit - or is electrically separated from it; or/and that - the second generator (7b) comprises a first stator (31a) and at least one second stator (31b), both of which each have stator windings (31.1a, 31.1b), wherein the at least one second stator (31b), preferably by means of at least one first electrical switch (35a), is optionally electrically connected in parallel to the first stator (31a) or is electrically separated from it. combined heat and power plant according to claim 3 , characterized in that - the first generator (7a) has at least two second stators (30b) which are electrically connected independently of one another, preferably in a parallel circuit, to the first stator (30a) of the first generator (7a); or and that - the second generator (7b) has at least two second stators (31b) which are electrically connected independently of one another, preferably in a parallel circuit, to the first stator (31a) of the second generator (7b). combined heat and power plant according to claim 3 or4, characterized in that - the first generator (7a) for generating electrical power has a first rotor (33a) which interacts with its stators (30a, 30b) and has a predetermined first number (n1) of first pole pairs (p1) of magnetic poles; or/and - the second generator (7b) for generating electrical power has a second rotor (33b) which interacts with its stators (31a, 31b) and has a predetermined second number (n2) of second pole pairs (p2) of magnetic poles. Combined heat and power plant according to one of the Claims 3 until 5 , characterized in that - the first and/or second magnetic pole pairs (p1, p2) or magnetic poles are formed by magnets, preferably by permanent magnets, made of a magnetic or magnetized material, and/or that - the first and/or second magnetic pole pairs (p1, p2) or pole pairs are formed by rotor windings which generate a magnetic field, preferably a magnetic dipole field, when electrically energized. Combined heat and power plant according to one of the preceding claims, characterized in that the two generators (7a, 7b) are drive-connectable or drive-connected to the internal combustion engine (2) independently of one another. Combined heat and power plant according to one of the preceding claims, characterized in that the two generators (7a, 7b) are connected via a common gear (8) which has a gear drive (9) for coupling to the output shaft (3) of the internal combustion engine (2) and two gear drives (10a, 10b) for coupling to the two generators (7a, 7b), which are drive-connectable or drive-connected to the internal combustion engine (2). Combined heat and power plant according to one of the preceding claims, characterized in that the two generators (7a, 7b) are drive-connectable or drive-connected to one another, preferably by means of the transmission (8). Combined heat and power plant according to one of the preceding claims, characterized in that - the second generator (7b) is drive-connected to the output shaft (3) of the internal combustion engine (2) via the first generator (7a); or that - the first generator (7a) is drive-connected to the output shaft (3) of the internal combustion engine (2) via the second generator (7b); combined heat and power plant according to claim 10 , characterized in that the two generators (7a, 7b) are drive-connected to one another in a decoupleable manner by means of a partial coupling (13a). Combined heat and power plant according to one of the preceding claims, characterized in that the two generators (7a, 7b) can be decoupled from the output shaft (3) of the internal combustion engine (2) by means of a common clutch (12) which is arranged between the transmission (8) and the output shaft (3). Combined heat and power plant according to one of the preceding claims, characterized in that - the first generator (7a) is drive-connected to the output shaft (3) of the internal combustion engine (2) by means of a first partial clutch (13a) such that it can be decoupled independently of the second generator (7b); and that - the second generator (7b) is drive-connected to the output shaft (3) of the internal combustion engine (2) by means of a second partial clutch (13b) such that it can be decoupled independently of the first generator (7a). combined heat and power plant according to claim 13 , characterized in that - the first generator (7a) is drive-connected to the first transmission output (10a) of the transmission (8) via the first partial clutch (13a) in a decoupleable manner; and in that - the second generator (7b) is drive-connected to the second transmission output (10b) of the transmission (8) in a decoupleable manner via the second partial clutch (13b). Combined heat and power plant according to one of the Claims 8 until 14 , characterized in that the two generators (7a, 7b) are drive-connected to the internal combustion engine (2) by means of the transmission (8). Combined heat and power plant according to one of the preceding claims, characterized in that at least one kinetic buffer (36) for temporarily storing the kinetic energy generated by the internal combustion engine (2) is arranged between the internal combustion engine (2) and the two generators (7a, 7b). combined heat and power plant according to claim 16 , characterized in that the kinetic intermediate storage device (36) is designed as a flywheel (37). Combined heat and power plant according to one of the preceding claims, characterized in that the first or second generator (7a, 7b) is drive-connected to the output shaft (3) or, alternatively, to the second or first generator (7b, 7a) via a transmission gear, which increases or decreases the speed of the rotor (33b, 33a) of the generator (7b, 7a) compared to the speed (d) of the output shaft (3). Combined heat and power plant according to one of the preceding claims, characterized in that the second generator (7b) is or can be electrically connected to a (private) electrical self-supply power network (14) which is galvanically isolated from a public power network (15). Combined heat and power plant according to one of the preceding claims, characterized in that the first generator (7a) is not or cannot be electrically connected to the (private) electrical self-supply power grid (14). Combined heat and power plant according to one of the preceding claims, characterized in that the first and/or the second generator (7a, 7b) are designed as a motor generator. Combined heat and power plant according to one of the preceding claims, characterized in that the combined heat and power plant has a control/regulation device (40) for controlling/regulating the internal combustion engine and the two generators (7a, 7b), wherein the control/regulation device (40) is designed such that it does not electrically connect the two generators (7a, 7b) to one another.

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