Method for controlling high-voltage systems comprising at least two generators

Abstract

The invention relates to a method for controlling high-voltage systems (10) comprising at least two generators (16, 18) and at least one power electronics system (20, 22, 26, 28), the generators (16, 18) being coupled to one another via the at least one power electronics system (20, 22, 26, 28) and a distributor intermediate circuit (24), wherein the method comprises the following steps: - specifying a global reference target value (S10) for a controlled variable of the at least two generators (16, 18) by means of a global control unit; - measuring the controlled variable for a first generator (S12); - comparing the global reference target value with the measured controlled variable of the first generator (S14); - determining an individual reference target value for the first generator (S16); and - generating a symmetrical load distribution (S18) between the generators (16, 18) by controlling the first generator using the individual reference target value for the first generator.

Description

[0001] Method for controlling high-voltage systems with at least two generators

[0002] Description

[0003] The invention relates to a method for controlling high-voltage systems with multiple generators. Such a high-voltage system could, for example, be an off-road vehicle.

[0004] State of the art

[0005] In electrical engineering, a high-voltage system refers to an electrical system that uses high voltages, typically in the range of several hundred volts to several kilovolts. These systems are widely used in various industrial and infrastructural sectors, including power generation, transmission, and distribution, as well as in specialized applications such as electric mobility and off-road vehicles.

[0006] In such systems, several generators or voltage sources are often connected in parallel to generate and distribute the required electrical power. This presents a number of technical challenges, particularly regarding the synchronization of load distribution across the generators and the stability of the overall system.

[0007] Synchronizing multiple generators is a complex process that must ensure all generators operate at identical frequency, voltage, and phase. This is crucial for the safe and efficient operation of the system. Synchronization is typically achieved through specialized control systems that continuously monitor and adjust the generators' operating parameters.

[0008] A key element in high-voltage systems with multiple power sources is load sharing. This ensures that each power source or generator carries an equal share of the total load to prevent overloads and inefficient operating conditions. This is often achieved through load control systems that use control algorithms to regulate the power output to the generators to optimize load distribution. Uneven load distribution can lead to undesirable effects such as excessive heat generation and increased wear.

[0009] In systems with multiple generators connected to a common DC link via power electronics, the total system power can be distributed approximately evenly among the generators by adjusting the DC link voltage setpoint as needed, depending on the load. This means that when driving, the generators supply energy to the DC link. The generators' power electronics measure the power output and reduce the DC link voltage setpoint accordingly, using a load-dependent factor.

[0010] Due to measurement inaccuracies in the DC link voltage measurement of the power electronics for regulating the generators, an asymmetrical distribution of the generator power can occur despite load-dependent adjustment of the internal DC link voltage setpoint.

[0011] The invention is therefore based on the objective of proposing a method with which an asymmetrical load distribution caused by measurement inaccuracies of the intermediate circuit voltage can be compensated.

[0012] The problem is solved by the subject matter of the independent claims.

[0013] Disclosure of the invention

[0014] According to a first aspect of the invention, this problem is solved by a method for controlling high-voltage systems with at least two generators and at least one power electronics unit, wherein the generators are coupled to each other via the at least one power electronics unit and a distribution intermediate circuit, wherein the method comprises the steps:

[0015] Specifying a global reference setpoint for a controlled variable of at least two generators by a global control unit;

[0016] Measuring the controlled variable for a first generator; comparing the global reference setpoint with the measured controlled variable of the first generator;

[0017] Determining an individual reference setpoint for the first generator, wherein the individual reference setpoint for the first generator is determined based on the difference between the global reference setpoint and the measured controlled variable of the first generator; and

[0018] Creating a symmetrical load distribution between the generators by controlling the first generator with the individual reference setpoint for the first generator.

[0019] To distribute the total system load symmetrically when using multiple voltage sources or generators on a DC link, the setpoint for the DC link voltage control is calculated individually for each voltage source, depending on the load. A higher-level global control unit, which controls all power components, can specify the global reference setpoint for the DC link voltage.

[0020] This global reference setpoint is then compared with the actual controlled variable. From the difference, an individual reference setpoint can be generated for the first generator, which is then used to control it individually. The setpoint for controlling the voltage sources or power components can thus be adjusted individually and depending on the load.

[0021] Since the DC link voltage is regulated depending on the load, measurement inaccuracies in the DC link voltage measurement negatively affect a symmetrical load distribution for each power section. This measurement inaccuracy is compensated for by individually controlling the loads of the individual generators. This step can preferably be performed by the global control unit.

[0022] Thus, the invention fulfills its purpose.

[0023] In one embodiment, the individual reference setpoint for the first generator is equal to the sum of the global reference setpoint and the difference between the global reference setpoint and the measured controlled variable of the first generator. In another embodiment, the first generator is the generator with the lowest controlled variable.

[0024] Advantageously, the generator with the lowest load offers the greatest potential for upward correction of the controlled variable. If the load of other generators were reduced to regulate the controlled variable, the total available load might not be sufficient to maintain the idling process of the entire system. When the entire system is idling and thus at the lower end of its load range, it can be assumed that an increase in load is harmless to the overall system, provided the load distribution is synchronized.

[0025] In one embodiment, the method further comprises:

[0026] Measuring the controlled variable for at least one further generator;

[0027] Comparing the global reference setpoint with the measured control variable of at least one other generator; and

[0028] Determining an individual reference setpoint for the at least one further generator, wherein the individual reference setpoint for the at least one further generator is determined based on the difference between the global reference setpoint and the measured controlled variable of the at least one further generator; and wherein generating a symmetrical load distribution between the generators is further achieved by controlling the at least one further generator with the individual reference setpoint for the at least one further generator.

[0029] In this embodiment, at least two generators are controlled to compensate for measurement inaccuracies. First, the controlled variable for at least one additional generator is determined. The measured controlled variable is then compared to the global reference setpoint, and the difference between the controlled variable of the at least one additional generator and the global reference setpoint is calculated.

[0030] For at least one additional generator, an individual reference setpoint is then generated, which is used to control it. The control is proportional to the determined difference between the measured controlled variable and the global reference value. In one embodiment, the individual reference setpoints are iteratively adjusted for the generator with the lowest load.

[0031] As with the embodiment using only one controlled generator, it is advantageous to always adjust the load of the generator with the lowest load. Furthermore, this iterative approach allows the system to regulate itself slowly and systematically into a state with a symmetrical load distribution. If several generators are controlled simultaneously, the control mechanisms could cancel each other out, resulting in nothing happening in the worst case, or they could add up, causing the system to be overdriven and operating outside of equilibrium.

[0032] In one embodiment, the method is carried out when the high-voltage system is operated at a stable operating point.

[0033] Since the measurement inaccuracy of the controlled variable in the intermediate circuit can change during operation, for example due to temperature effects, the described procedure is applicable during operation. The higher-level control system should be designed to ensure that the generators operate at a stable operating point for the duration of the adjustment. This means that the power output of the generators should be as constant as possible and not subject to fluctuations due to external influences.

[0034] If the high-voltage system is part of a vehicle, the vehicle should move at a constant speed and on a constant incline. The power output should remain constant at least until the adjustment of the individual reference setpoints is complete.

[0035] In one embodiment, the method is executed during an idle phase of the power electronics.

[0036] The idle phase of a high-voltage system is particularly suitable for adjusting the control system, as no active control is required for active processes during this state. For the power electronics, idle operation means that there is no system load, and therefore only losses such as the switching losses of the power output stage occur. The power supply is at a minimum and can be distributed evenly across all generators. Furthermore, the overall system is designed for higher loads, namely when the generators' power is drawn. This allows adjustments to be made without individual reference setpoints for each generator until a symmetrical load distribution is ensured.

[0037] In one embodiment, the method is executed during the system start-up of the high-voltage system.

[0038] System startup is another advantageous way to balance the load distribution. During system startup, clearly defined processes and calibrations of the entire system are performed regularly. This verifies whether the system is functioning nominally in all areas. For these defined processes, it is usually specified what load each generator should have at any given time. This provides each generator with a global reference setpoint that it must reach during the nominal operation check.

[0039] In one embodiment, the controlled variable is the voltage supplied by the generators.

[0040] The voltage supplied by the generators is a preferred control variable because it can be determined directly at the power electronics. Furthermore, voltage is the physical quantity that the generators are designed to produce; that is, it is a directly measurable quantity.

[0041] In one embodiment, the controlled variable is the power supplied by the generators.

[0042] The power output of the generators is another advantageous control variable that can be used for symmetrical load distribution. While voltage is a quantity generated by the generators, power is the quantity that matters for the working system's operation. This means that measuring power involves considering physical processes that should be carried out as stably as possible. For example, this method can be used to distribute the power load of the generators in a vehicle symmetrically, ensuring the vehicle is driven evenly.

[0043] In another aspect, the invention relates to a computer program with program code for carrying out a method as described above when the computer program is executed on a computer.

[0044] In another aspect, the invention relates to a computer-readable data carrier containing the program code of a computer program for carrying out a method as described above when the computer program is executed on a computer.

[0045] In another aspect, the invention relates to a system for controlling high-voltage systems, wherein the system is configured to execute a method as described above.

[0046] In another aspect, the invention relates to a high-voltage system comprising at least two generators and at least one power electronics unit, wherein the generators are connected to each other by the at least one power electronics unit and a distribution intermediate circuit, wherein the system further comprises a system for controlling high-voltage systems as described above.

[0047] In summary, the present invention provides a method for controlling a high-voltage system, a computer program and a computer-readable data carrier, as well as a system for controlling a high-voltage system and a corresponding high-voltage system.

[0048] The described configurations and training programs can be combined in any way desired.

[0049] Further possible embodiments, developments and implementations of the invention also include combinations of features of the invention described previously or subsequently with regard to the exemplary embodiments that are not explicitly mentioned.

[0050] Brief description of the drawings: The accompanying drawings are intended to provide a further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain the principles and concepts of the invention.

[0051] Other embodiments and many of the aforementioned advantages become apparent with reference to the drawings. The elements depicted in the drawings are not necessarily shown to scale.

[0052] Fig. 1 shows an example of a high-voltage system.

[0053] Fig. 2 shows the flowchart for one embodiment of the proposed method.

[0054] Fig. 3 schematically shows the process of another embodiment.

[0055] In the figures of the drawings, identical reference symbols denote identical or functionally equivalent elements, parts or components, unless otherwise stated.

[0056] Fig. 1 shows a high-voltage system 10 in which the proposed method can be implemented. The high-voltage system comprises an internal combustion engine 12 with which kinetic energy is generated from a fossil fuel. The internal combustion engine 12 is coupled via a transfer case 14 to a first generator 16 and a second generator 18.

[0057] Generators 16 and 18 convert the kinetic energy of the combustion engine 12 into electrical energy, which is modulated and / or transformed by a first power electronics unit 20 and a second power electronics unit 22. The precise processes within the power electronics units are of secondary importance for the processes described here.

[0058] In a distribution intermediate circuit 24, the electrical energy supplied by generators 16 and 18 is balanced between the two electrical circuits. For example, the control variable for generator 16 and / or generator 18 can be determined in the distribution intermediate circuit 24.

[0059] Two further power electronics units 26 and 28 are connected to the distribution intermediate circuit 24, which in turn are coupled to the drives 30 and 32 respectively.

[0060] The high-voltage system 10 shown here can, for example, represent the energy supply and drive of an off-road vehicle, in particular a tracked vehicle, in which each track is driven by one of the drives 30 or 32.

[0061] The load distribution for generators 16 and 18 can be balanced by determining the voltages at the power electronics 20 and 22 in the distribution intermediate circuit. Subsequently, individual reference setpoints are determined for one or both generators 16 and / or 18, which can be used to directly control the power electronics 20 and / or 22 or the generators 16 or 18.

[0062] Preferably, generators 16 and 18 are directly controlled to synchronize the power output and not just the voltages supplied by the power electronics 20 and 22. This allows generators 16 and 18 to operate under the same load, thus distributing wear evenly between them. This can potentially simplify vehicle maintenance, as longer maintenance intervals are possible.

[0063] Fig. 2 shows the flowchart for one embodiment of the invention. In this embodiment, the high-voltage system comprises three generators 34, 36, and 38. Each of the generators provides a voltage that can be manipulated or regulated by downstream power electronics.

[0064] Generator 34 produces a voltage value of 40. Generator 36 produces a voltage value of 42 and generator 38 produces a voltage value of 44.

[0065] In this embodiment, generator 34 is an actively controlled generator in which the generated voltage corresponds to the setpoint. The reference setpoints of the other voltages for generators 36 and 38 are adjusted according to the invention to create a symmetrical load on the generators.

[0066] Since generator 34 is actively controlled, the voltage it generates can be used as a reference setpoint. It is compared with the voltages 42 and 44 of generators 36 and 38. Individual reference setpoints for generators 36 and 38 are generated from the difference between voltages 40 and 42 and 40 and 44, respectively. Based on these individual reference setpoints, adjustments 46 and 48 can be determined to compensate for the voltage differences between generators 34, 36, and 38.

[0067] After balancing, the voltages 50 and 52 of generators 36 and 38 should correspond to the global reference setpoint, so that the load is evenly distributed on generators 34, 36 and 38.

[0068] An example can illustrate this. Generator 34 is specified with a reference setpoint of 700 V. The voltage 40 supplied by generator 34 corresponds to the reference setpoint and is also 700 V.

[0069] The internal measured value for generator 36, that is, the voltage 42, is 701 V. The difference of 700 V minus 701 V results in a new, individual reference setpoint of 699 V for generator 36. This means the setpoint for voltage 42 is adjusted by -1 V, so that voltage 50 is ultimately 700 V.

[0070] The voltage 44 supplied by generator 38, however, is 699 V. The difference of 700 V minus 699 V results in an individual reference setpoint of 701 V for generator 38, thus compensating for the insufficient voltage 44. The voltage 52 supplied by generator 38 therefore corresponds to the global reference setpoint of 700 V.

[0071] The generators can be controlled by a global controller or by several individual controllers. In the embodiment with multiple individual controllers, they are communicatively coupled and communicate with each other, thus functioning as a global controller. Fig. 3 schematically illustrates the process according to one embodiment of the proposed method.

[0072] In step S10, a global control unit specifies a global reference value. The global control unit is the unit that controls the high-voltage system. It can consist of a single device or a combination or network of devices. Using the global reference setpoint, the global control unit defines a value for the controlled variable of the high-voltage system's generators. This value specifies the power or voltage that the generators and the downstream power electronics should provide.

[0073] The generators are operated using the global reference setpoint as the controlled variable. In step S12, the controlled variable is measured for all generators, including the first one. The first generator does not need to be explicitly named as such at this point. For example, the generator with the lowest controlled variable could be designated as the first generator.

[0074] Alternatively, the first generator can be specified in step S12. This can be achieved by setting up continuous monitoring of the generators' control variables. Other criteria, such as naming based on external circumstances, can also be used to distinguish the first generator from the others.

[0075] Furthermore, the first generator need not differ technically from the subsequent generators. On the contrary, identical generators are preferably used to achieve a symmetrical load distribution.

[0076] However, it is also conceivable that a first generator is designed to deliver a specific power output and that a second generator is designed to deliver a fraction of this specific power output. In this case, the reference setpoint for the second generator can correspond to the fraction of the specified power output. For example, generator 1 might be designed to generate 1,000 V, while generator 2 is designed to generate 750 V. The global reference setpoint is determined by the respective scaled control variable. In other words, the global reference setpoint is a voltage of 1,000 V for generator 1 and a voltage of 750 V for generator 2.

[0077] In step S14, the measured controlled variable of the first generator is compared with the global reference setpoint. The comparison can be designed, for example, to determine the difference between the values. It is of secondary importance whether the measured controlled variable is subtracted from the global reference setpoint or vice versa, as long as the sequence is used consistently for all measurements and control operations.

[0078] In some embodiments, the amount of the difference can also be used, in which case it must be determined in which direction the generator is to be controlled, upwards or downwards.

[0079] In step S16, an individual reference value for the first generator is determined from the comparison result. This reference setpoint can be used for control until a new reference setpoint is provided. Finally, in step S18, the first generator can be controlled with this individual reference setpoint to compensate for measurement uncertainties during generator operation.

[0080] For example, the first generator may have a global reference value of 700 V. This means that the generator should produce a voltage of 700 V, for example, when idling or in another constant operating phase. However, due to internal inaccuracies, whether in the measuring electronics, the construction, or the non-constant drive, the generator does not produce exactly 700 V, but a slightly higher or lower voltage. The voltage produced by the generator is determined as the controlled variable.

[0081] If, for example, the global reference setpoint is 701 V, there is a difference of 1 V between the global reference setpoint and the measured controlled variable. In this case, an individual reference setpoint is specified for the generator, which is 1 V below the global reference setpoint. This means the generator is controlled to produce a voltage of 699 V. However, since it previously produced 1 V more, the generator can now actually produce 700 V due to the reduction of the reference setpoint, which corresponds to its original specification by the global reference setpoint. In the illustrated embodiment, further generators are provided that can be controlled. In step S20, the controlled variable is also determined for at least one additional generator.

[0082] Besides the first generator and at least one other generator, there can be further generators. Preferably, only one generator is controlled at a time to reduce the complexity of the control system and avoid overdriving.

[0083] The measured control variable of at least one additional generator is compared with the global reference setpoint in step S22. Similar to the first generator, an individual reference setpoint for at least one additional generator is determined from this in step S24.

[0084] The process then returns to step S18 and thus to the control of the high-voltage system. In step S18, at least one additional generator is now controlled. Preferably, only one generator is controlled at any given time to avoid overloading. During the control process in step S18, the individual reference setpoints for generators can be adjusted iteratively to gradually achieve a symmetrical load distribution across all participating and / or controllable generators.

Claims

Claims 1. Method for controlling high-voltage systems (10) with at least two generators (16, 18) and at least one power electronics unit (20, 22, 26, 28), wherein the generators (16, 18) are coupled to each other via the at least one power electronics unit (20, 22, 26, 28) and a distribution intermediate circuit (24), wherein the method comprises the steps: Setting a global reference setpoint (S10) for a controlled variable of at least two generators (16, 18) by a global control unit; Measuring the controlled variable for a first generator (S12); Comparing the global reference setpoint with the measured control variable of the first generator (S14); Determining an individual reference setpoint for the first generator (S16), wherein the individual reference setpoint for the first generator is determined based on the difference between the global reference setpoint and the measured controlled variable of the first generator; and Generating a symmetrical load distribution (S18) between the generators (16, 18) by controlling the first generator with the individual reference setpoint for the first generator.

2. Method according to claim 1, wherein the first generator is the generator (16, 18) with the lowest controlled variable.

3. A method according to any of the preceding claims, wherein the method further comprises: Measuring the controlled variable for at least one additional generator (S20); Comparing the global reference setpoint with the measured control variable of at least one other generator (S22); and Determining an individual reference setpoint for the at least one additional generator (S24), wherein the individual reference setpoint for the at least one additional generator is determined based on the difference between the global reference setpoint and the measured controlled variable of the at least one additional generator; and wherein generating a symmetrical load distribution between the generators (16, 18) furthermore by rules of at least one further generator with the individual reference setpoint for the at least one further generator.

4. Method according to one of the preceding claims, wherein the individual reference setpoints are iteratively adjusted for the generator (16, 18) with the lowest load.

5. Method according to any of the preceding claims, wherein the method is carried out when the high-voltage system (10) is operated at a stable operating point.

6. Method according to one of the preceding claims, wherein the method is carried out in an idle phase of the power electronics (20, 22, 26, 28).

7. Method according to any one of claims 1 to 5, wherein the method is carried out at the system start-up of the high-voltage system (10).

8. Method according to any of the preceding claims, wherein the controlled variable is the voltage provided by the generators (16, 18).

9. Method according to any one of claims 1 to 8, wherein the controlled variable is the power provided by the generators (16, 18).

10. Computer program with program code for executing a method according to any of the preceding claims when the computer program is executed on a computer.

11. Computer-readable data carrier containing program code of a computer program for executing a method according to any one of claims 1 to 9 when the computer program is executed on a computer.

12. System for controlling high-voltage systems (10), wherein the system is configured to perform a method according to any one of claims 1 to 9.

13. High-voltage system (10) comprising at least two generators (16, 18) and at least one power electronics unit (20, 22, 26, 28), wherein the generators (16, 18) are connected to each other by the at least one power electronics unit (20, 22, 26, 28) and a distribution intermediate circuit (24), wherein the system further comprises a system for controlling high-voltage systems (19) according to claim 12.

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