Three-phase arrangement for power generators

Abstract

The three-phase arrangement has an internal combustion engine-driven power generator (5) which provides a three-phase supply for consumers at connection terminals (6) via a primary three-phase winding Wp (8, 8', 8''). The excitation field of the generator, and thus also the output voltage, can be controlled by an actuating device (3). The three-phase generator (5) has an additional secondary winding Ws (7, 7', 7'') which is connected to at least one energy store (10) via a converter (9) in such a way that a control unit (2) can operate the secondary winding with bidirectional power flow. This allows the energy store (10) to be charged and discharged, and the internal combustion engine (4) can be assisted with motor power or loaded with generator power.

Description

[0001] The invention relates to a three-phase arrangement for power generators according to the preamble of claim 1.

[0002] Decentralized, combustion-engine-powered power generators are used in a wide range of applications, especially where no electricity connection is available via existing infrastructure. Typical applications include: • Construction site power generators • Fire brigade and disaster control • Supply of remote buildings or facilities of all kinds in island operation • military power generators • on-board power generators on ships or vehicles

[0003] Conventionally constructed power generators 11 in the embodiment according to Fig.1 are driven by an internal combustion engine 4 and, via a connected three-phase generator 5, which is preferably designed as a synchronous generator, provide a three-phase network 6 with, for example, 400 V AC, which can supply not only three-phase consumers but also single-phase consumers with, for example, 230 V AC. Depending on the grid frequency of 50 or 60 Hz, the internal combustion engine 4 is operated with a four-pole three-phase generator at a fixed speed of 1,500 or 1,800 rpm.

[0004] For the operation of the internal combustion engine at a fixed speed, an engine control unit 1 from the engine manufacturer is used, which is connected to an additional control unit 2 of the generator. The latter takes over the operation of the generator and, in particular, the regulation of the generator output voltage with a field controller 3. The three line voltages U L1 , U L2 and U L3as well as the voltage of the neutral conductor N as reference potential are recorded via measuring transducers and fed to the control unit 2 so that it can regulate the output voltage at the connection terminals 6 to the specified voltage setpoints.

[0005] In separately excited synchronous machines, as in Fig. 1, the excitation current for generating the magnetic field in the synchronous generator is generated in the rotor field winding 16 by means of the field adjuster 3. The control unit of the power generator 2 is connected to the field adjuster 3 via an electrical interface 28, whereby the control unit 2 can influence the excitation current for regulating the generator output voltage at the connection terminals 6. For this purpose, the excitation current is measured and a corresponding current measurement signal, in Fig. 1 as i f referred to, to the control unit 2. Preferably, galvanically isolated current transformers are used for current measurement, as in Fig.1. The field regulator 3 is typically implemented as a controllable voltage source whose output voltage feeds the rotor field winding 16. The electrical interface 28 can be implemented in various ways, in particular as a transmission of an analog or digital voltage setpoint for the field regulator or for the transmission of a pulse-width modulated control level for controlling a clocked voltage source as the field regulator.

[0006] For the entire duration that the voltage supply thus generated is to be available at the terminals of the three-phase network 6, the combustion engine 4 must operate at the set fixed speed, regardless of the actual power required by the consumers. Depending on the load profile, the combustion engine 4 is therefore often operated at very unfavorable operating points at partial load or even completely idle without any load.

[0007] Table 1 provides exemplary manufacturer data for a diesel-powered generator, showing fuel consumption in g / kWh at four characteristic operating points. PRP is the continuous power output at variable load. Table 1 - Fuel consumption of a generator at different operating points Fuel consumption (PRP), 50 Hz / 1500 min -1 Deutz series 2011, F2M 2011 Relation to 75% load Fuel consumption 25% load g / kWh 305 127,62 % Fuel consumption 50% load g / kWh 250 104,60 % Fuel consumption 75% load g / kWh 239 100,00 % Fuel consumption 100% load g / kWh 248 103,77 %

[0008] It can be seen that at 75% load, the generator has the lowest specific fuel consumption. The last column in Table 1 shows the fuel consumption at the other operating points relative to the optimal operating point. It can be seen that between 50% and 100% load, the generator has quite good consumption values, which are close to the optimum. However, at even lower loads, consumption increases significantly.

[0009] The lower operating point at 25% load is generally also the minimum load specified by the engine manufacturer for continuous operation. If an internal combustion engine is operated continuously at even lower loads, the self-cleaning mechanisms of the engine and exhaust system can fail, leading to engine damage and / or operation with unacceptably high emissions.

[0010] Fig. Figure 2 shows an example of a diesel engine map. The location of the most favorable operating point is found at a fixed speed of 1,500 rpm in the range of 75% load. The relatively flat increase in fuel consumption values ​​in the range from 50 to 100% load is also visible. At low loads, the lines of equal fuel consumption become significantly denser. This means that the specific fuel consumption values ​​increase very rapidly at low loads. It should be noted that the map is Fig.2 ends at an average effective piston pressure of 2 bar, which corresponds approximately to a load of 25% PRP - prime power. At operating points below this, the specific fuel consumption increases rapidly even further and can easily reach values ​​of over 500 g / kWh at loads of 10% of the PRP rated power.

[0011] The unfavorable operating conditions at low loads are a major problem in many applications. The reason for this is that a generator must typically be designed with a considerable power reserve to cover the starting currents of consumers. Machines driven by asynchronous motors, such as pumps, compressors, and fans, in particular, have very high starting currents. For example, in an island power system with a continuous power requirement of 100 kVA, it may be necessary to use a generator with a 150 kVA PRP rating just to provide the mentioned starting currents.

[0012] This example shows that, when taking practical design conditions into account, the usable operating range of the combustion engine with favorable operating points is severely restricted and it is therefore foreseeable that the power generator will very frequently operate at very unfavorable or even inadmissible operating points in the partial load range.

[0013] For the reasons mentioned above, solutions are desired and various technical concepts are known and can also be found in practical applications.

[0014] For large island networks with power requirements in the range above one MW, e.g. on mining facilities, large military camps or real islands, a simple solution, as in Fig. 3, several power generators 11 are used, which operate in parallel.

[0015] During partial load operation, some of the generators 11 are shut down so that the active generators operate at the desired optimal operating points. This concept is simple and easy to implement in such applications, since the output of mobile, transportable generators is limited anyway. Therefore, when the island grid has a high power demand, multiple generators are used for fundamental reasons.

[0016] However, this simple solution becomes increasingly disadvantageous for smaller power requirements of the stand-alone grid, e.g., below 200 kVA, since the entire consumer power in this power range can and should be provided by a single compact power generator. Distributing power generation among an unnecessarily large number of small power generators is then undesirable.

[0017] Another known solution concept that can be used in such applications is to connect the power generator 11, as in Fig. 4, with a storage battery 10, wherein the consumers 15 are supplied from the storage battery 10 via a controlled grid converter 12. In this configuration, for low consumer power levels, the primary power generator 11 with the combustion engine 4 can be switched off. When the storage battery 10 is discharged, the combustion engine 4 is restarted and charges the storage battery 10 via a rectifier 13 and a DC-DC converter 14 for voltage adjustment. The variable power adjustment is thus achieved by periodic on-off operation of the primary power generator 11.

[0018] The advantages of this concept are its temporarily silent operation and the advantageous integration options for renewable energy sources. In particular, feed-in from solar systems can be easily supplemented into the storage battery 10.

[0019] However, the additional functions for the various power conversions in the AC-DC rectifier 13, the grid converter 12, the DC-DC converters 14 and 17, if required, and the energy storage in a storage battery 10 significantly increase the system complexity and acquisition costs. At the same time, the complexity and use of numerous electronic components reduces the system's availability. However, as shown in Fig.4, the primary power generator 11 can continue to be used directly to supply the consumers 15 in emergency operation. It should also be considered that, due to the limited battery life, additional costs for replacement batteries must be planned for over the lifetime of the system, which in turn offset the fuel costs saved by the advantageous operation of the combustion engine.

[0020] Table 1 shows that, in this configuration, optimal operation of a diesel combustion engine with a maximum fuel saving of around 27% is possible, assuming that partial load operation with 25% load would otherwise predominantly occur in an assumed application. However, this is offset by additional losses due to the additional energy converters 12, 13, 14, and 17 and the storage battery 10. For high-quality lithium batteries, a charge-discharge efficiency of 90-95% can be expected. Rectifiers 13, DC-DC converters 14, 17, and grid converter 12 can achieve efficiencies in the range of 96-99%. Overall, however, it can be seen that of the potentially possible fuel saving of 27%, based on the exemplary numerical values ​​from Table 1, a total fuel saving of barely more than 10% can be expected in the overall balance.

[0021] As a further solution, with the advent of modern power converters, so-called VSCF units (VSCF - Variable Speed ​​- Constant Frequency) were proposed and developed for practical applications. In VSCF units, as in Fig. As shown in Figure 5, the combustion engine 4 is operated at a variable speed depending on the load requirement and the constant mains frequency is in turn provided via a mains converter 12.

[0022] Here, too, the potential for fuel savings in the combustion engine can be expected to be up to 27%, based on Table 1. Similar to the configuration according to Fig. 4 but here again losses occur in the various current transformers 12, 13 and 14.

[0023] In practical operation, however, even with VSCF units, it is not possible to always operate the combustion engine 4 at its optimal operating point, as a so-called "spinning reserve" is required. This means that the combustion engine 4 must always be operated at a certain overspeed to prevent the power generator 11 from stalling during sudden load activation. The "spinning reserve" represents a significant obstacle that significantly limits the practically achievable fuel savings.

[0024] The disadvantages of the VSCF unit are: • High costs due to a powerful mains converter 12, which must also be 100% capable of unbalanced loads and designed to meet the power peaks of the consumers • High electronic expenditure leads to losses in the availability of the system • The fuel saving potential can only be partially realized due to the “spinning reserve” • The power converters 12, 13 and 14 cause energy conversion losses, which further reduce the actual achievable fuel savings

[0025] Due to these disadvantages, VSCF technology has not been widely adopted and remains limited to a few special applications.

[0026] To counteract the disadvantage of the "spinning reserve," various other solutions have been proposed, including the use of batteries or supercapacitors as short-term energy storage devices in EP 0 947 042 B and US 8 987 939 B2, which are intended to prevent the combustion engine 4 from stalling even without a "spinning reserve." However, these approaches further increase the system complexity and system costs of VSCF units, and availability decreases even further. For these reasons, these concepts have not been able to gain widespread acceptance on the market.

[0027] Due to the often still unsatisfactory operating conditions for combustion engine-powered generators, further hybrid concepts have been proposed. For example, DE 10 2014 115 596 B4 proposes a concept in which a conventional combustion engine-powered generator directly supplies large consumers, but also provides the option of supplying smaller consumers during partial load operation via a parallel supply branch from a storage battery with a grid converter. This configuration also allows the combustion engine to operate at favorable operating points, with high loads supplied directly, so that the grid converter and storage battery only need to be dimensioned for smaller partial load requirements, thus saving costs.

[0028] The disadvantage of this concept is the overall high system complexity, with numerous DC-DC converters and power converters, and the complicated switching between the unit's operating modes. In particular, this hybrid unit cannot respond directly and without interruption to large load surges, i.e., the activation of a large load. Instead, the large power ranges at the three-phase output are only available after prior load detection and starting of the combustion engine, and thus with a significant time delay.

[0029] The invention is based on the object of developing a concept for a power generator for the generic three-phase arrangement which achieves a noticeable fuel saving while at the same time maintaining the good basic properties of the unit, in particular a high load switching capability, an uninterrupted load supply and which increases the system complexity as little as possible.

[0030] In addition, electronic power converters should not impede the basic function of the power generator in the event of a failure in order not to limit availability.

[0031] This object is achieved according to the invention in the generic three-phase arrangement with the features of claim 1.

[0032] The three-phase arrangement according to the invention is characterized by the fact that an additional secondary winding is provided in the three-phase generator, which is connected to at least one energy storage device via a power converter. The additional secondary winding makes it possible to support the internal combustion engine when connecting three-phase consumers. This makes it possible to design the internal combustion engine for the continuous load of the consumers rather than for peak loads. This allows the internal combustion engine to be designed compactly. It can be operated at favorable operating points, thereby reducing specific fuel consumption and increasing service life.

[0033] Further features of the invention emerge from the further claims, the description and the drawings.

[0034] The invention will be explained in more detail with reference to an embodiment shown in the drawings. Fig.1 a circuit diagram of a three-phase arrangement according to the prior art; Fig. 2 a map of a diesel engine, Fig. 3 a circuit diagram of another three-phase arrangement according to the prior art, Fig. 4 a circuit diagram of another three-phase arrangement according to the prior art, Fig. 5 a circuit diagram of another three-phase arrangement according to the prior art, Fig. 6 a circuit diagram of a three-phase arrangement according to the invention, Fig. 7 the three-phase arrangement according to Fig. 6 with those components that are activated when the combustion engine is stopped and the three-phase system is transferred to the connection terminals, Fig. 8 shows the design of a pulse inverter 9 of the three-phase arrangement according to the invention with semiconductor switches in a half-bridge arrangement,

[0035] Fig.6 shows a three-phase arrangement which, starting from a conventional power generator 11 driven by an internal combustion engine 4, is Fig. 1 has extensions for additional functions.

[0036] The additional features are: • Integration of a secondary winding Ws (7, 7',7'') into the three-phase generator 5 • Use of a storage battery 10 • Use of an inverter 9 for the controllable connection of the secondary winding Ws (7, 7',7'') with the storage battery 10 • Optional detection of the rotor position 27 of the three-phase generator 5, which may be required for some operating modes and control concepts

[0037] In the order pursuant to Fig.6 shows the internal combustion engine 4 with the engine control unit 1. The engine control unit controls the operation of the internal combustion engine 4 and contains functions for speed-controlled operation at the required speed of, for example, 1,500 rpm. The engine control unit 1 is connected to the control unit of the power generator 2 via an electrical interface. The three-phase generator 5 has a first three-phase winding arrangement, referred to below as the primary winding Wp (8, 8', 8''). This generates approximately sinusoidal voltages, which are made available at the connection terminals 6 with a resilient neutral conductor for supplying the consumers. The control unit of the power generator 2 is provided with the measurement signals of the generator output voltage so that the control unit regulates these to the specified target values ​​by controlling the three-phase generator 5.

[0038] Optionally, the generator control unit also has a measurement of the rotor position angle 27.

[0039] Depending on the application, various designs of the three-phase generator 5 are possible. Separately excited synchronous machines are particularly frequently used. This arrangement is shown in Fig. 6. As an alternative, asynchronous generators, especially double-fed asynchronous generators, are also used in certain applications.

[0040] In the new three-phase arrangement, in addition to the primary three-phase winding Wp (8, 8', 8''), there is another secondary winding Ws (7, 7', 7''). Both windings are transformer-coupled via the magnetic circuit of the three-phase generator. The secondary winding Ws (7, 7', 7'') can, as in Fig. 6, galvanically isolated, but can also be designed as a winding tap of the primary winding, according to the principle of an autotransformer.

[0041] The secondary winding Ws (7, 7', 7'') is connected to the three-phase inverter 9 with a DC link. The DC link, in turn, is connected to the storage battery 10. This arrangement allows, by appropriately controlling the inverter 9, to provide approximately sinusoidal voltages at the terminals of the secondary winding Ws (7, 7', 7'') and a correspondingly regulated and also approximately sinusoidal three-phase current that feeds the secondary winding Ws (7, 7', 7'').

[0042] The secondary winding Ws (7, 7',7'') is always supplied with a three-phase current which is synchronized in terms of rotation frequency and direction of rotation with the three-phase output voltage at the connection terminals 6.

[0043] The control and regulation of the pulse-controlled inverter 9 is particularly advantageously implemented by a current control in rotor or field coordinates (Control of Electrical Devices, Werner Leonhard, Springer-Verlag 1996) of the three-phase generator 5, whereby operation with pure active power of the secondary winding Ws is always aimed for. For the corresponding synchronization with the coordinates of the excitation field, knowledge of the rotor position angle 27 is required. This is either measured by a rotor position sensor or calculated from the measured output voltages of the primary winding Wp (8, 8', 8'') of the generator 5.

[0044] When the three-phase system feeding the secondary winding Ws (7, 7', 7'') is synchronized with the direction of rotation and frequency of the synchronous generator 5, the phase position of the three-phase current in the secondary winding Ws (7, 7', 7'') in relation to the voltage induced in the same windings as a result of the circulating excitation field of the synchronous generator remains as a free control variable. Rectified operation results in generator operation of the secondary winding Ws (7, 7', 7''). This means that the rotor shaft of the synchronous generator, driven by the combustion engine 4, is also braked in a generator-like manner by the three-phase current flowing in the secondary winding Ws (7, 7', 7''), and a power flow is established which, via the pulse-controlled inverter 9, leads to charging of the storage battery.

[0045] When the phase position of the three-phase current is reversed with respect to the induced voltage in the secondary winding Ws (7, 7', 7''), the secondary winding switches to motor operation and generates an additional driving torque on the rotor shaft, which supports the combustion engine. This results in a power flow through the pulse-controlled inverter 9, which discharges the storage battery 10.

[0046] This bidirectional, controllable power flow enables both charging and discharging of the storage battery 10. This results in a generator load on the combustion engine 4, with the storage battery 10 being charged simultaneously. Alternatively, with the opposite power flow, an additional three-phase motor drive is created, which supports the combustion engine 4, while the storage battery 10 is discharged.

[0047] The reference variable for controlling the power flow is derived, on the one hand, from monitoring the speed of the internal combustion engine 4, in that the secondary winding Ws (7, 7', 7'') switches to motor operation when the consumer loads are high and the speed of the internal combustion engine 4 decreases as a result, and the internal combustion engine 4 is supported as if by an additional three-phase drive.

[0048] In the opposite case, the consumer load is relieved, the speed of the combustion engine 4 will increase beyond the target speed and the secondary winding Ws (7, 7', 7'') will go into generator operation, thus braking the combustion engine 4 and charging the battery 10.

[0049] In order for the control unit of the power generator 2 to be able to take over the corresponding operational management of the power generator and the additional devices, it is connected to the inverter 9 via an electrical interface 29, measures the voltage of the storage battery 10 and at least two of the three phase currents of the inverter 9. In a preferred embodiment, the electrical interface 29 serves to switch 6 semiconductor switches S1 to S6 on and off with pulse-width modulated control signals ( Fig. 8) For this purpose, a pulse-width modulated control signal is generated for each semiconductor switch S1 to S6, which is transmitted to the respective driver circuit D of the semiconductor switch and switches the semiconductor switch on or off depending on the signal level.

[0050] The current measurement of the phase currents of the inverter 9 is preferably carried out via galvanically isolated current transformers, which convert the current measurement signals into Fig.6, designated as I1M and I2M, to control unit 2. Due to the insulated design of the three-phase winding Ws (7, 7', 7''), measuring two phase currents is sufficient. The third phase current can be calculated from the two measured values ​​for I1M and I2M.

[0051] A particularly advantageous feature of this arrangement is that the transformer-coupled primary and secondary windings allow the voltage level of the secondary winding Ws (7, 7', 7'') and the inverter 9 to be adapted to the respective application and the intended voltage of the storage battery 10. This eliminates the need for an otherwise necessary DC-DC converter for adapting different voltage levels of the generator 5 and the storage battery 10.

[0052] For low power levels, batteries with a low DC voltage of, for example, 24 or 42 V can be used, allowing for a pulse-controlled inverter 9 using MOSFET technology with very high efficiency. It is also possible to use only a single storage battery 10 for the power generator, as this can also be used as the starter battery for the combustion engine 4.

[0053] The secondary winding Ws (7, 7', 7'') requires additional winding space in the generator design, so that the stator or slot cross-section must either be adapted or, with a standard lamination section, the available winding cross-section is divided between the primary winding Wp (8, 8', 8'') and the secondary winding Ws (7, 7', 7''). Since the secondary winding Ws (7, 7', 7'') only has a dynamic power-supporting function in the system concept, i.e., only needs to be designed for a fraction of the nominal generator power, these restrictions are minor compared to the cost advantages due to the simple system design and high system flexibility, and only insignificantly reduce the benefits of the system.

[0054] Since the two three-phase windings Wp (8, 8', 8'') and Ws (7, 7', 7'') are coupled via the magnetic circuit of the three-phase generator 5, power and voltage transmission between the primary and secondary windings is also possible independently of the rotor excitation field of the three-phase generator 5. This mode of operation can be used to supply the load with three-phase current via the output terminals 6 even when the combustion engine 4 is switched off. The required three-phase system is generated by the inverter 9 and transmitted via the secondary winding Ws (7, 7', 7'') to the primary winding Wp (8, 8', 8'') to supply the load at the connection terminals 6. The components of the power generator arrangement that are active in this operating mode are shown in Fig. 7 shown.

[0055] To prevent torque from being generated in the rotor of the three-phase generator 5 in this operating mode, the excitation current of the field winding 16 must be switchable off by a corresponding switching device. This switching device can be integrated into the field controller 3 or implemented separately.

[0056] With this new three-phase arrangement, diverse and advantageous operating modes are possible for different application scenarios and depending on the system design.

[0057] An important advantage is the low complexity, which means only the smallest possible additional effort with regard to the electronic components, as shown by a comparison with the system concepts proposed according to the state of the art, which usually include several electronic functional modules, such as AC-DC rectifiers, DC-AC inverters and DC-DC converters.

[0058] Regarding the voltage level, the number of turns of the secondary winding Ws (7, 7', 7") is designed so that it remains lower than the minimum expected voltage of the storage battery 10. This allows the pulse inverter 9 to be operated according to the basic principle of a boost converter. The pulse inverter 9 preferably consists of the transistors S1 to S6 as semiconductor switches, which are connected as shown in Fig. 8, are arranged in three half-bridge circuits, each of which has freewheeling diodes connected in antiparallel. Fig. In the embodiment shown in Figure 8, the semiconductor switches S1 to S6 are represented as MOSFET transistors, which have integrated anti-parallel freewheeling diodes and are particularly suitable for applications with low battery voltages.

[0059] During normal operation of the generator, the current control of the secondary winding Ws (7, 7', 7'') is preferably carried out in rotor or field coordinates, as previously explained, whereby the current setpoint is determined by the operating control in the control unit 2 under the following aspects: A) Provision of additional motor drive power when load changes in the consumer power lead to a drop in the engine speed. For this purpose, the control unit 2 measures the rotational frequency and thus the speed of the combustion engine 4 from the measured output voltages 6. If the target speed is undershot, the pulse-controlled inverter 9 is controlled in such a way that the secondary winding Ws (7, 7', 7'') is operated in a motor mode. B) Provision of an additional generator load when the speed of the combustion engine 4 increases due to a reduction in the consumer load. This is again detected by the speed monitoring and, if the target speed is exceeded, triggers the activation of the pulse-controlled inverter 9, which initiates generator operation of the secondary winding Ws (7, 7', 7''). C) A higher-level control level for battery management must ensure that the state of charge of the storage battery 10 is always within a usable range. If the storage battery is completely discharged, then the option of providing additional motor drive power is lost. Conversely, the option of providing a generator load is lost if the storage battery is already fully charged. It is therefore advantageous if the storage battery is at an average state of charge between, for example, 20 and 80%. This is achieved by specifying a state of charge of, for example, 50% as a target value for a battery charge controller integrated in the control unit 2. The actual state of charge can be calculated from the measured battery voltage and, taking into account the current power flow, from a battery model.From the control deviation, the charge controller generates a correction current setpoint of limited magnitude, which is added to the current setpoint in rotor or field coordinates due to the dynamic current control according to control mode A.) or B.) This ensures that the storage battery is maintained at a medium charge level. Use case 1 - Optimized power dimensioning of the combustion engine in consumer networks with high load switching

[0060] Large load connections are only feasible to a limited extent for a combustion engine-driven generator without exceeding the specified voltage tolerances. For this purpose, the loads may have to be divided into several load groups and gradually switched on and off by load management. Such systems require additional effort on the part of the load grid and grid management. Further challenges when dimensioning the generator are loads with high starting currents, such as those found particularly in pumps, fans, compressors, and other machines driven by asynchronous electric motors. In practical applications, the PRP rated power of the generator often has to be selected significantly higher than would actually be necessary for continuous operation of the loads. The surcharge factor for covering dynamic load requirements can easily amount to 30-50%.This in turn means that the internal combustion engine 4 is dimensioned much too large in relation to the continuous power actually required, which in turn leads to an unfavorable underutilization of the internal combustion engine 4 in normal operation with the known risks and problems: There is a risk of damage to the engine or exhaust system, emissions increase and may even exceed the permissible limit values, and the specific fuel consumption increases significantly.

[0061] With the three-phase arrangement presented, the design of the power generator can now be modified by dimensioning the internal combustion engine 4 only for the required continuous power, while the dynamic load peaks are handled by the additional three-phase arrangement, consisting of the secondary winding Ws (7, 7', 7''), the pulse converter 9, and the storage battery 10. This allows the internal combustion engine 4 to be designed with a smaller size than with a conventional power generator concept, and the internal combustion engine 4 can be operated more frequently in favorable operating ranges with low fuel consumption and low emissions due to the load profile being freed from dynamic load peaks.

[0062] Through suitable battery management, operating points with low consumer power can be used specifically to charge the storage battery 10.

[0063] The design power of the secondary winding Ws (7, 7', 7'') can be 30-50% of the PRP rated power of the combustion engine, depending on the application.

[0064] Since the three-phase arrangement with the secondary winding Ws (7, 7', 7'') represents a parallel arrangement to the primary winding Wp (8, 8', 8''), in the event of a failure of the additional components it is possible to continue to use the generator with limited restrictions on the load connection capacity.

[0065] A comparison of the presented configuration with a VSCF unit according to Fig. 5 shows that with the additional three-phase arrangement at least the same fuel savings can be achieved as with a VSCF unit, because • the combustion engine 4 can be selected with a smaller size and can therefore operate more frequently at favorable operating points • the controllable bidirectional energy flow to the storage battery 10 provides an additional possibility to influence the operating point of the combustion engine 4, whereby its operation can be further optimized

[0066] The arrangement offers the following advantages over a VSCF unit: • The only electronic module that must be used is a pulse inverter 9, which only has to provide a fraction of the power of the power generator and is accordingly cost-effective. • The pulse inverter 9 does not need to be capable of handling unbalanced loads, unlike a grid converter suitable for VSCF units, and can therefore be provided by standard commercially available designs • The transformer-based voltage adjustment across the two stator windings Wp (8, 8', 8") and Ws (7, 7', 7") provides a high degree of flexibility in selecting the voltage level of the storage battery 10, enabling the use of MOSFET pulse converters. This allows for significantly higher pulse converter efficiencies at battery voltages below 100V than with IGBT converters for the otherwise typical mains voltage applications with an intermediate circuit voltage of approximately 750 VDC. • The parallel arrangement of the two stator windings Wp (8, 8', 8'') and Ws (7, 7', 7'') enables an uninterrupted energy flow from the conventional power generator, consisting of the combustion engine 4 and the synchronous generator 5, to the connection terminals 6, even in the event of a failure of the pulse converter 9. The resulting limitations in the load connection capacity can be compensated for by adapted load management. Use case 2 - Dynamization of a power generator driven by a gasoline engine

[0067] Gasoline engines have so far been used less frequently in power generators than combustion engines because they operate at low working pressures and thus have disadvantages compared to diesel engines in terms of torque development. This results in gasoline engines having significantly worse load response than diesel engines. However, interest in the use of gasoline engines is increasing rapidly from the perspective of climate and environmental protection. In particular, natural gas engines operate with comparatively low emissions and low noise levels and offer a promising future for the transition to green hydrogen.

[0068] With the help of the presented three-phase arrangement consisting of • Storage battery 10 • Pulse inverter 9 • Secondary winding Ws (7, 7', 7'') makes it possible to support the weak dynamic load switching capacity of gasoline engines in such a way that the good characteristics of a diesel engine drive are achieved. And as an additional advantage, the gasoline engine only needs to be dimensioned for the continuous consumer load, since dynamic load peaks are covered by the additional three-phase arrangement. Application 3 - Uninterruptible power supply with start-stop operation of the combustion engine

[0069] A major advantage and special feature of the new concept is the ability to ensure uninterrupted power supply at terminals 6, even during start-stop operation of the combustion engine 4. Therefore, if the minimum engine power, usually 25% of the PRP rated power, is undercut for extended periods in an operating scenario, the combustion engine 4 can be shut down. At the same time, the rotor winding 16 must be de-energized, since with the generator shaft stopped, the magnetizing rotating field of the synchronous generator can no longer be provided at the required frequency of, for example, 50 or 60 Hz.

[0070] During operation with the combustion engine 4 switched off and the rotor winding 16 deactivated, the three-phase generator 5 is used as a passive three-phase transformer, which continues to supply the supply network 6 via the two windings Wp (8, 8', 8'') and Ws (7, 7', 7'') by means of a pulse inverter 9 from the storage battery 10. This operating state is illustrated in Fig. 7, which shows only the components that are active in this operating mode.

[0071] To stop the internal combustion engine 4, coordinated operational control is necessary, which is carried out by the control unit of the power generator 2. In particular, while the internal combustion engine 4 is still running, the rotor winding 16 must first be de-energized and the magnetization of the three-phase generator must be taken over by the correspondingly fed secondary winding Ws (7, 7', 7''). Only then can the internal combustion engine 4 be stopped. When the internal combustion engine 4 is restarted, the process must be reversed, i.e., the internal combustion engine 4 is initially started at idle while the rotor winding 16 is still de-energized. The rotor position 27 is then synchronized with the circulating three-phase voltage system that supplies the secondary winding Ws (7, 7', 7'') and is provided via the pulse-controlled inverter 9 and the control unit 2.The rotor winding 16 is then activated, whereby the mechanical power of the combustion engine 4 is again available to feed the supply network in accordance with the nominal operation of the power generator.

[0072] Depending on the system design, with a sufficiently large storage battery 10, even longer operating times with the combustion engine 4 switched off can be covered. The integration of renewable energy sources, especially PV systems, is possible with minimal effort.

[0073] When the combustion engine 4 is shut down, the control system's operation is fundamentally changed to provide a three-phase voltage system with a frequency of 50 or 60 Hz and an approximately sinusoidal voltage curve at the mains connection terminals 6. The currents of the secondary winding Ws (7, 7', 7'') are monitored, and when the maximum values ​​are reached and / or when the storage battery 10 is discharged, the combustion engine 4 is restarted. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 0 947 042

[0026] US 8 987 939 B2

[0026] DE 10 2014 115 596 B4

[0027]

Claims

[1] Three-phase arrangement of a combustion engine-driven three-phase generator (5), which provides a three-phase supply for consumers (15) at connection terminals (6) via a primary three-phase winding Wp (8, 8', 8'') and whose excitation field and thus also the output voltage can be controlled by an adjusting device (3), characterized by that an additional secondary winding Ws (7, 7', 7'') of the three-phase generator (5) is connected via a power converter (9) to at least one energy store (10) in such a way that a control device (2) can operate the secondary winding with bidirectional power flow, so that the energy store (10) can be charged and discharged and the internal combustion engine (4) can be supported with motor power or loaded with generator power. [2] Three-phase arrangement according to claim 1, characterized bythat the pulse inverter (9) consists of half-bridge circuits of pulse-controlled semiconductor switches (S1 to S6), to which freewheeling diodes are connected in anti-parallel. [3] Three-phase arrangement according to claim 1 or 2, characterized by that the energy storage device (10) is designed as an electrochemical accumulator. [4] Three-phase arrangement according to one of claims 1 to 3, characterized by that a control device (2) is designed simultaneously for the charging and discharging operation of the energy storage device (10) and for the operation of the power generator (11). [5] Three-phase arrangement according to one of claims 1 to 4, characterized by that the windings Wp (8, 8',8'') and Ws (7, 7', 7'') are galvanically isolated. [6] Three-phase arrangement according to one of claims 1 to 5, characterized by that the three-phase connection terminals of the secondary winding Ws (7, 7', 7'') are designed as winding taps of the primary winding Wp (8, 8',8''). [7] Three-phase arrangement according to one of claims 1 to 6, characterized by that the rotor position (27) intended for the current and voltage control of the secondary winding Ws (7, 7', 7'') is not measured, but is calculated from the output voltages measured at the connection terminals (6). [8] Three-phase arrangement according to one of claims 1 to 7, characterized by that the logic of the control unit (2) stops the combustion engine (4) when the load requirements of the consumers are low and the output voltage of the power generator is then continued to be provided without interruption via appropriate control of the secondary winding Ws (7, 7', 7''). [9] Three-phase arrangement according to one of claims 1 to 8, characterized by that the logic of the control unit (2) starts the combustion engine (4) when the load requirements of the consumers are high or when the energy storage device (10) is discharged.

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