Generator sets for generating alternating current

Abstract

The present invention relates to a generator set (1) for generating alternating current, the generator set comprising a primary power unit (2) and an alternating current generator (3) rotatably connected to the primary power unit (2), the alternating current generator being configured to convert primary power provided by the primary power unit (2) into electrical power, and the generator set having an accessible secondary power unit (4), the secondary power unit being configured to increase the power generated by the alternating current generator (3) by connecting to the secondary power unit (4).

Description

Technical Field

[0001] The present invention relates to a generator set for generating alternating current. Background Art

[0002] A conventional generator set is usually composed of an internal combustion engine and a generator, wherein the internal combustion engine is coupled to the generator via a transmission or directly coupled to the generator, and the generator is usually a separately excited synchronous motor.

[0003] In this case, the requirements for the frequency of the AC grid are specified by standards, which also define, for example, the permissible frequency deviations. In an AC grid with multiple sources, the power distribution is regulated by the frequency. The higher the frequency, the higher the contributed power share.

[0004] The goal is usually to keep the relative power contribution of the generator as constant as possible at different operating points. In order that the frequency does not leave the permissible tolerance band even in the event of a sudden increase in power, the internal combustion engine must have a control reserve and rapid control. The mass inertia of the generator set also helps to keep the frequency constant in the event of sudden load changes.

[0005] Internal combustion engines usually lack the necessary control dynamics, so that even when there is a control reserve, a larger motor is used in order to be able to provide the required mass inertia. This results in the use of internal combustion engines whose rated power is significantly higher than the rated power of the generator. As a result, the exhaust gas temperature required for correct exhaust gas aftertreatment is far from being achieved. As a result, maintenance costs increase. In addition, more complex and / or additional exhaust gas purification must be provided. This results in high costs for the internal combustion engine and the exhaust system. Summary of the invention

[0006] Based on the known prior art, the object of the present invention is to provide an improved generator set for generating alternating current.

[0007] The object is achieved by a generator set for generating alternating current having the features described in the exemplary embodiment. Advantageous developments are apparent from the description and the drawings.

[0008] Accordingly, a generator set for generating alternating current is proposed, the generator set comprising a primary power unit and an alternator rotatably coupled to the primary power unit, the alternator being configured to convert primary power provided by the primary power unit into electrical power. The generator set is also characterized in that it has an accessible secondary power unit, the secondary power unit being configured to increase the power generated by the alternator by accessing the secondary power unit.

[0009] Due to the connectable secondary power unit, which is designed to increase the power generated by the alternator by connecting it, it is proposed that additional power requirements that exceed the power that can be increased via the rated power of the internal combustion engine can be temporarily met without having to provide a power reserve in the internal combustion engine, which would, for example, result in the rated power of the internal combustion engine being significantly higher than the rated power of the generator. Instead, the connectable secondary power unit makes it possible to achieve a nearly optimal design of the internal combustion engine and the alternator with respect to each other for continuous operation, in particular when the alternator is operated at its rated power.

[0010] Thus, during the provided continuous operation of the primary power unit, the primary power unit can be operated close to or even at its rated power. The exhaust gas temperature required for the best possible exhaust gas aftertreatment provided for the primary power unit can thus be achieved. The maintenance costs for the primary power unit can thus be kept low. Furthermore, the exhaust gas aftertreatment can be of simple design and / or an additional and / or complex exhaust gas aftertreatment unit that would otherwise be provided can be dispensed with.

[0011] The secondary power unit is preferably designed to be at least temporarily accessible.

[0012] According to a preferred embodiment, the power of the alternator corresponds to the power generated by the primary rated power input supplied to the alternator by the primary power unit. It is thus possible to operate the primary power unit close to its optimum operating point.

[0013] Experiments have shown that it is particularly advantageous if the primary power unit is an internal combustion engine.

[0014] Advantageously, the alternator is a separately excited synchronous machine.

[0015] According to another preferred embodiment, the secondary power unit has an electric motor, preferably an asynchronous motor or a reluctance motor or a "switched reluctance motor" (SRM); and a secondary energy storage device in contact with the electric motor, preferably a battery, in particular a lithium-ion battery, or a capacitor, in particular an electrolytic capacitor or a supercapacitor, wherein the electric motor is preferably rotationally coupled to the input shaft of the alternator. The electric motor makes it possible to provide additional mechanical power, in particular an additional torque, at the alternator in addition to the power provided via the primary power unit. It has been found that the electric motor has a particularly good overload capacity and very good control dynamics, especially if it is designed as an asynchronous motor or a reluctance motor. In addition, the electric motor, in particular an electric motor designed as an asynchronous motor or a reluctance motor, has low losses during standby operation, which are generally negligible. Alternatively, if permanently occurring iron losses can be tolerated, the electric motor can also be designed in the form of a permanently excited synchronous motor.

[0016] The electrical contact between the electric motor and the secondary energy storage device may include a converter, preferably a frequency converter, wherein the converter acts as an adapter element between the secondary energy storage device and the electric motor so that the energy provided by the secondary energy storage device is rectified or converted into a form suitable for operation of the electric motor in its corresponding embodiment.

[0017] According to another preferred embodiment, the output shaft of the primary power unit is directly connected to the input shaft of the alternator in rotation. Alternatively, the output shaft of the primary power unit can be connected to the input shaft of the alternator in rotation via a transmission.

[0018] According to another preferred embodiment, the output shaft of the secondary power unit is directly connected to the input shaft of the alternator in rotation. Alternatively, the output shaft of the secondary power unit can be connected to the input shaft of the alternator in rotation via a transmission.

[0019] Preferably, the secondary power unit can be decoupled from the AC generator and / or the secondary power unit can be designed to be torque-free switchable.

[0020] The secondary power unit can preferably be designed such that the electric motor of the secondary power unit is designed such that it can be operated as a generator. The energy storage of the secondary power unit can thus be charged by the generator operation of the electric motor of the secondary power unit. For this purpose, the torque required for the generator operation can also be provided by the primary power unit and transmitted via the alternator or via a continuous input shaft of the alternator.

[0021] Furthermore, the converter of the electrical contact is designed so that the energy generated by the electric motor in generator operation can be converted into a form suitable for charging the secondary energy storage of the secondary power unit. In other words, the converter or transformer can be designed to work bidirectionally. Alternatively, another converter can also be provided in the electrical contact for this purpose and / or another converter, preferably a rectifier, can be provided independently of the electrical contact.

[0022] The electric motor of the secondary power unit can be designed to be switchable without torque. The electric motor of the secondary power unit can be switched without torque as long as the primary power unit can meet the power demand itself, which is called up by the generator set, for example by electrical loads.

[0023] In particular, taking into account the desired torque addition of the torque provided by the primary power unit and the torque provided by the secondary power unit, it has proven to be advantageous, with respect to the AC generator, to arrange the primary power unit on a first side of the AC generator and to arrange the secondary power unit on a second side of the AC generator situated above the first side.

[0024] Alternatively, the primary power unit and the secondary power unit can also be arranged together on one side of the alternator, if the output shafts of the primary power unit and of the secondary power unit allow for the addition of torques.

[0025] According to a further preferred embodiment, the primary power unit has a speed controller and / or the secondary power unit has a speed controller.

[0026] In order to enable a simple decentralized control / regulation of the secondary electric machine, the activity of the secondary power unit can also be determined by its own tolerance range.

[0027] Accordingly, the behavior of the primary power unit can also be determined by its own tolerance band.

[0028] According to a preferred improvement, a desired value, i.e. a desired speed, is provided to the speed regulator of the secondary power unit, which is lower, preferably slightly lower, than the desired value or desired speed of the primary power unit. Preferably, the desired value of the secondary power unit is within a tolerance band predefined for the secondary power unit.

[0029] Preferably, the control structure of the primary power unit and / or the secondary power unit is designed in two stages, wherein preferably an internal torque regulator is subordinate to an external speed regulator. In this case, the speed regulator can provide a preset value for the torque regulator, wherein the preset value is preferably limited to a positive torque value. This makes it possible for the secondary power unit to not normally work in opposition to the speed regulator of the primary power unit.

[0030] According to another preferred embodiment, different speed threshold values ​​are preset for the primary power unit and the secondary power unit, thereby providing the primary power unit and the secondary power unit with a hysteresis effect that can reduce or even completely eliminate the occurrence of speed oscillations at a desired speed, which speed oscillations can occur as a result of switching on and / or switching off a torque provided via the secondary power unit.

[0031] It has been shown that additional safety can be achieved with the optional use of a pure P-type amplifier. Providing a P-type amplifier can achieve that the set torque increases with the control deviation, ie the closer the speed is to the desired value of the secondary power unit, the lower the torque.

[0032] According to another preferred embodiment, the primary power unit comprises a speed regulator with a negative torque that can be switched on and off, and / or the secondary power unit comprises a speed regulator with a negative torque that can be switched on and off. It is preferably proposed that the switching on or off of the negative torque is controlled / regulated as a function of the energy content of the energy storage of the secondary power unit.

[0033] In particular, in the case where the energy storage of the secondary power unit has a small capacity, so that the voltage changes significantly when the secondary motor or the secondary power unit is used, the voltage can be used as a criterion for activating or deactivating the negative torque. Preferably, the negative torque is only released when the voltage of the energy storage falls below a first limit value determined for this purpose. Furthermore, the release of the negative torque can be withdrawn again if a further limit value is exceeded that is greater than the first limit value. Thus, a hysteresis can be provided, which can achieve a stability with respect to the charging function of the storage.

[0034] According to a preferred alternative design, the control / regulation of switching on or off the negative torque can also be based on another variable, preferably the charge of the energy storage device. This can be particularly advantageous if the capacity of the energy storage device is so large that the voltage does not show a significant change during the power output. In order to use the charge as a variable for control / regulation, the storage current can be integrated over time. Similar to the control / regulation with the aid of the voltage of the energy storage device, when the charge of the energy storage device is used as the control / regulation variable, the negative torque can be released or switched on when it falls below a preset value, for example, below the integral value of the storage current, and the negative torque can be switched off again when a further preset value, which is higher than the first preset value mentioned above, is exceeded.

[0035] Preferably, a further regulator can be provided for controlling / regulating the voltage amplitude. This can be done, optionally by tracking excitation, when using a separately excited synchronous generator.

[0036] According to another preferred embodiment, the secondary power unit, preferably the electric motor of the secondary power unit, is designed so that its torque, preferably its rated torque, is greater than the starting torque of the primary power unit, preferably greater than the starting torque plus the mechanical losses present in the given system. In other words, the secondary power unit can be designed to provide a torque that is greater than the starting torque and the mechanical losses of the generator set. This makes it possible to start the generator set by the secondary power unit or at least to assist in starting the generator set by means of a starter.

[0037] According to another preferred embodiment, the secondary power unit comprises: a secondary energy storage, preferably a battery, in particular a lithium-ion battery, or a capacitor, in particular an electrolytic capacitor or a supercapacitor; and an inverter, preferably an externally guided inverter. Preferably, the output lines of the alternator and the output lines of the inverter are connected to each other, preferably in a switchable and switchable manner. Thus, by switching in the secondary power unit, additional power can be supplied directly from the energy storage via the inverter to the power generated by the alternator. As a result, the primary power unit can be relieved of load and can continue to operate at its design point.

[0038] According to another preferred embodiment, the inverter of the secondary power unit is a bidirectional converter. Thus, in normal operation, energy for (re)charging the secondary energy store can be provided by the alternator and supplied to the secondary energy store via the bidirectional converter. Alternatively, it can also be provided that an additional rectifier is provided, via which the secondary energy store can be charged with the aid of the alternating current generated by the alternator.

[0039] In a further preferred embodiment, it can be provided that the secondary energy store can be charged via connection to an electrical grid. Preferably, for this purpose, the secondary energy store has a corresponding connection unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The preferred further embodiments of the present invention are explained in detail by the following description of the drawings. Here, it is shown:

[0041] Figure 1 Schematically showing a generator set for generating alternating current according to a first embodiment;

[0042] Figure 2 schematically shows a generator set for generating alternating current according to another embodiment; and

[0043] Figure 3 A generator set for generating alternating current according to a further embodiment is schematically shown. DETAILED DESCRIPTION

[0044] Preferred embodiments are described below with reference to the accompanying drawings. In the various drawings, identical, similar or identically acting elements are provided with identical reference numerals, and a repeated description of these elements is partially omitted in order to avoid redundancy.

[0045] Figure 1 A generator set 1 for generating alternating current according to a first embodiment is schematically shown. The generator set 1 comprises: a primary power unit 2 in the form of an internal combustion engine, which is currently a diesel engine; and an alternator 3 rotatably coupled to the primary power unit 2, which is currently in the form of a separately excited synchronous motor and is configured to convert the primary power provided by the primary power unit 2 into electrical power. The generator set 1 also has an accessible secondary power unit 4, which is configured to temporarily increase the power generated by the alternator 3 by connecting the secondary power unit 4.

[0046] In this case, the power of the alternator corresponds to the power generated by the primary rated power input supplied to the alternator by the primary power unit.

[0047] The secondary power unit 4 has an electric motor 40, in the present case an asynchronous motor, and a secondary energy storage 41, for example in the form of a battery, in particular a lithium-ion battery, or in the form of a capacitor, optionally an electrolytic capacitor or a supercapacitor, which is in contact with the electric motor 40. The electrical contact between the electric motor 40 and the secondary energy storage 41 includes a bidirectional converter (not shown) which converts the energy provided by the secondary energy storage 41 into a form suitable for operating the electric motor 40 and vice versa.

[0048] The electric motor 40 is rotationally coupled to the input shaft 30' of the alternator 3. The electric motor 40 makes it possible to provide additional mechanical power, in particular additional torque, at the alternator 3 in addition to the power provided via the primary power unit 2.

[0049] Alternatively, the electric motor 40 can also be designed as a reluctance motor or a “switched reluctance motor” (SRM). Furthermore, the output shaft 42 of the secondary power unit 4 can be rotationally connected to the input shaft 30 ′ of the alternator 3 via a gear (not shown).

[0050] The output shaft 20 of the primary power unit 2 is rotationally connected to the input shaft 30 of the alternator 3 via a transmission 22. Alternatively, the output shaft 20 can also be directly rotationally coupled to the input shaft 30.

[0051] The electric motor 40 is designed to be decoupled from the alternator 3 . Furthermore, if no additional power has to be provided by the secondary power unit 4 , the electric motor 40 can also be operated as a generator in order to be able to charge the secondary energy store 41 .

[0052] The electric motor 40 of the secondary power unit 4 can be switched without torque as long as the primary power unit 2 itself can meet the power demand of the generator set 1 , for example, by electrical consumers, and the secondary energy store 41 does not have to be charged.

[0053] In the present case, with regard to the alternator 3 , the primary power unit 2 is arranged on a first side of the alternator 3 , and the secondary power unit 4 is arranged on a second side of the alternator 3 which is located above the first side.

[0054] Alternatively, the primary power unit 2 and the secondary power unit 4 can also be arranged together on one side of the alternator 3 .

[0055] In the present case, the primary power unit 2 and the secondary power unit 4 each have a speed regulator. The primary power unit 2 and the secondary power unit 4 are also each provided with their own tolerance band.

[0056] A desired value in the form of a desired rotational speed is provided to the rotational speed controller of the secondary power unit 4 , which desired value is slightly lower than the desired value in the form of a desired rotational speed of the primary power unit 2 , but lies within a tolerance band predefined for the secondary power unit 4 .

[0057] The primary power unit 2 and the secondary power unit 4 each have a two-stage control structure, wherein an inner torque regulator is subordinate to an outer speed regulator. The speed regulator therefore provides a preset value for the torque regulator, wherein the preset value is optionally limited to a positive torque value according to this preferred embodiment.

[0058] Furthermore, different speed threshold values ​​are preset for the primary power unit 2 and the secondary power unit 4. Thus, a hysteresis effect is provided for the primary power unit 2 and the secondary power unit 4, which reduces or even completely eliminates the occurrence of speed oscillations at the desired speed, which speed oscillations may occur from switching on and off the torque provided via the secondary power unit 4.

[0059] For additional safety, a pure P-type amplifier is used.

[0060] The speed controller of the secondary power unit 4 is designed with a negative torque that can be switched on and off. In the present case, the switching on or off of the negative torque is controlled / regulated based on the energy content of the secondary energy storage device 41 .

[0061] The electric motor 40 of the secondary power unit 4 is designed to provide a torque that is greater than the sum of the torques formed by the starting torque of the primary power unit 2 and the mechanical losses of the generator set 1 . The generator set 1 can therefore be started via the secondary power unit 4 .

[0062] Figure 2 A generator set 1 for generating alternating current according to a further embodiment is schematically shown. Figure 2 The generator set 1 in the figure basically corresponds to Figure 1 The generator set in the embodiment of the present invention further comprises a rectifier 43, through which the secondary energy storage 41 can be disconnectably connected to the output line 32 of the alternator 3. Therefore, the secondary energy storage 41 can be charged by converting the AC voltage provided by the alternator 3 into a DC voltage through the rectifier 43.

[0063] exist Figure 3 Schematically shows a generator set 1 for generating alternating current according to another embodiment. The generator set 1 is similar to Figure 1 and 2 The embodiment of has a primary power unit 2 in the form of an internal combustion engine, which is connected to an alternator 3 via a transmission 22 .

[0064] As Figure 1 and Figure 2 An alternative embodiment of the invention is Figure 3The secondary power unit 4 in has a secondary energy store 41 , for example a battery, for example a lithium-ion battery, or a capacitor, for example an electrolytic capacitor or a supercapacitor, and also an inverter 45 , optionally in the form of an externally guided inverter 45 .

[0065] The output line 44 of the inverter 45 is connected to the output line 32 of the alternator 3 in an accessible and disconnectable manner. In order to provide additional power to the output line 32, the output line 44 can be connected to the output line 32. Thus, additional power is provided from the secondary energy storage 41 via the inverter 45.

[0066] Optionally, the inverter 45 can be designed as a bidirectional converter or transformer, so that in normal operation, the secondary energy store 41 can be charged via the power provided by the alternator 3 on the output line 32. Figure 2 The configuration scheme in the embodiment can be provided with a separate rectifier (in Figure 3 ), in order to charge the secondary energy storage 41.

[0067] As far as applicable, all individual features shown in the exemplary embodiments can be combined with one another and / or exchanged without departing from the scope of the present invention.

[0068] List of reference numerals:

[0069] 1 Generator

[0070] 2 Primary power unit

[0071] 20 Output shaft

[0072] 22 Transmission

[0073] 3. Alternator

[0074] 30, 30' input shaft

[0075] 32 output lines

[0076] 4 Secondary power unit

[0077] 40 Electric Motor

[0078] 41 Secondary Energy Storage

[0079] 42 Output shaft

[0080] 43 Rectifier

[0081] 44 Output lines

[0082] 45 Inverter

Claims

1. A generator set (1) for generating alternating current, the generator set comprising a primary power unit (2) and an alternating current generator (3) rotatably coupled to the primary power unit (2), the alternating current generator being configured to convert primary power provided by the primary power unit (2) into electrical power, It is characterized in that A connectable secondary power unit (4) is provided, the secondary power unit being designed to increase the power generated by the alternator (3) by connecting the secondary power unit (4). The secondary power unit (4) comprises an electric motor (40) and a secondary energy storage (41) in contact with the electric motor (40), wherein the electric motor (40) is rotationally coupled to an input shaft (30') of the alternator (3), wherein the primary power unit (2) has a speed regulator and the secondary power unit (4) has a speed regulator, and A desired rotational speed is supplied to the rotational speed regulator of the secondary power unit (4), which desired rotational speed is lower than the desired rotational speed of the primary power unit (2).

2. The generator set (1) according to claim 1, characterized in that: The power of the alternator (3) corresponds to the power generated by the primary rated power input supplied to the alternator (3) by the primary power unit (2).

3. The generator set (1) according to claim 1 or 2, characterized in that: The primary power unit (2) is an internal combustion engine, and / or the alternator (3) is a separately excited synchronous motor.

4. The generator set (1) according to claim 1 or 2, characterized in that: The electric motor (40) is an asynchronous motor or a reluctance motor.

5. The generator set (1) according to claim 1 or 2, characterized in that: The output shaft (20) of the primary power unit (2) is directly rotationally connected to the input shaft (30) of the AC generator (3), or the output shaft (20) of the primary power unit (2) is rotationally connected to the input shaft (30) of the AC generator (3) via a transmission device (22).

6. The generator set (1) according to claim 1 or 2, characterized in that: The output shaft (42) of the secondary power unit (4) is directly rotationally connected to the input shaft (30') of the AC generator (3), or the output shaft (42) of the secondary power unit (4) is rotationally connected to the input shaft (30) of the AC generator (3) via a transmission device.

7. The generator set (1) according to claim 1, characterized in that: The expected value of the secondary power unit (4) lies within a tolerance band predefined for the secondary power unit (4).

8. The generator set (1) according to claim 1 or 2, characterized in that: The control structure of the primary power unit (2) and / or the control structure of the secondary power unit (4) is designed in two stages.

9. The generator set (1) according to claim 1 or 2, characterized in that: Different rotational speed threshold values ​​are predefined for the primary power unit (2) and the secondary power unit (4).

10. The generator set (1) according to claim 1 or 2, characterized in that: The primary power unit (2) comprises a speed regulator with a negative torque that can be switched on and off, and / or the secondary power unit (4) comprises a speed regulator with a negative torque that can be switched on and off.

11. The generator set (1) according to claim 1 or 2, characterized in that: The secondary power unit (4) is designed to provide a torque which is greater than the starting torque of the primary power unit (1) and the mechanical losses of the generator set (1).

12. The generator set (1) according to claim 1 or 2, characterized in that: The secondary power unit (4) comprises a secondary energy storage (41) and an inverter (45).

13. The generator set (1) according to claim 1, characterized in that: The secondary energy storage (41) is a battery.

14. The generator set (1) according to claim 13, characterized in that: The battery is a lithium-ion battery.

15. The generator set (1) according to claim 1, characterized in that: The secondary energy storage (41) is a capacitor.

16. The generator set (1) according to claim 15, characterized in that: The capacitor is an electrolytic capacitor or a supercapacitor.

17. The generator set (1) according to claim 8, characterized in that: The internal torque regulator is subordinate to the external speed regulator.

18. The generator set (1) according to claim 17, characterized in that: The rotation speed regulator provides a preset value for the torque regulator.

19. The generator set (1) according to claim 18, characterized in that: The preset value is limited to a positive torque value.

20. The generator set (1) according to claim 10, characterized in that: The switching on or off of the negative torque is controlled / regulated as a function of the energy content of the secondary energy storage device (41) of the secondary power unit (4).

21. The generator set (1) according to claim 12, characterized in that: The inverter (45) is an externally guided inverter.

Images