METHOD FOR MONITORING AND CONTROLLING ELECTRICITY DISTRIBUTION IN A PLANT

Description

Technical field

[0001] The present invention relates generally to the field of electrical engineering, in particular to the area of ​​power electronics and power electronic circuits. Specifically, the present invention relates to a method for monitoring and controlling current distribution in load circuits of a control system of a technical plant. The load circuits comprise at least one load unit (e.g., sensor, actuator, relay, contactor, solenoid valve, servo motor, controller, display unit, etc.). A mostly predetermined and constant output voltage is provided by at least one switched-mode power supply unit and distributed to the load circuits of the control system to power the load units. Furthermore, at least a plurality of the load circuits are protected by a switching unit, which is controlled by a control unit. State of the art

[0002] In many sectors, especially in industrial production and manufacturing, automation technology, etc., complex technical systems and machines are used today. A system is understood to be a planned assembly of components (e.g., machines, devices, and / or apparatus) that are spatially related and functionally, control-wise, and / or safety-wise linked. For the efficient operation of technical systems, system controls are typically employed, which aim to ensure that the system operates as autonomously as possible, independent of human intervention. Since technical systems such as production plants, manufacturing plants, etc., are rarely identical due to differing requirements, each system, or rather its associated system control, comprises a different number and size of consumers or components.Load units - such as actuators, relays, contactors, solenoid valves, servo motors, acoustic and / or optical warning signals, sensors, etc., as well as controllers (e.g. programmable logic controller (PLC), PC-based controller, microcontroller, etc.) for, e.g., evaluation of sensor values ​​and / or control of actuators, etc., and display units.

[0003] In technical systems, several electrical load units of the system control are typically grouped into supply sectors or load circuits, with each load circuit containing at least one load unit (e.g., sensors, actuators, controllers, display units, etc.). To supply power to the load units connected in these load circuits, at least one switched-mode power supply unit (e.g., a switching power supply) is usually used. The switched-mode power supply unit converts an unregulated input voltage—usually an AC voltage—into a constant output voltage, typically with a predefined value (e.g., 24 volts DC). The output voltage or current provided by the switched-mode power supply unit is then distributed to the respective load circuits of the system control.The connected load units may have different power requirements.

[0004] However, malfunctions in load units can have repercussions for the power supply unit. For example, an overload, a short circuit, or a short-circuit-like overcurrent, such as that which occurs when motors start up due to high current demand, can trigger a shutdown of the power supply unit in a load circuit. To prevent a total system failure due to, for example, a power supply unit shutdown, the load circuits are usually protected against overloads or short circuits on the output side of the power supply unit, such as circuit breakers or miniature circuit breakers with specific tripping characteristics. This ensures that an overloaded load circuit is shut down and that the remaining load circuits of the system or system control remain unaffected.However, protective devices such as circuit breakers, which are inexpensive, exhibit large tolerances in their tripping accuracy. In the event of a fault, this can lead to delays (e.g., a few milliseconds) in tripping.

[0005] Therefore, electronic fuses are increasingly used nowadays to protect switched-mode power supply units from feedback effects from load circuits (e.g., defective load unit, short circuit, short-circuit-like overcurrent, overload, etc.). These fuses have an electronic switching unit (e.g., a semiconductor switch) which is controlled by corresponding control signals from a control unit. In the event of a fault, these fuses can intervene quickly and, according to the tripping parameters adjustable via the control unit (e.g., tripping current, maximum permissible duration of an overcurrent, etc.), limit and / or disconnect the current in the corresponding load circuit when an exceedance of one of the adjustable tripping parameters is detected.

[0006] The sizing of the protection for individual load circuits or the connected load units is typically determined during the planning phase of a plant, adjusted during the implementation phase, and can be further modified, for example, during initial commissioning. This adjustment primarily involves correcting undersized or undersized fuses. However, due to time constraints, the tripping parameters of the fuses for the individual load circuits are often not selected appropriately. This means, for example, that the tripping parameters for the fuse or circuit breaker are set too high than would be necessary for the respective load circuit or at least one connected load unit.

[0007] Selective tripping of individual fuses or switchgear units is therefore no longer guaranteed, because in the event of a fault (e.g., short circuit, overload, etc.), the switchgear unit located directly upstream of the affected load circuit—which is oversized—is not activated by the control unit in time to limit and / or interrupt the current. The current can then flow into the affected load circuit and thus into at least one load unit within that circuit, potentially causing significant damage. A backup fuse (e.g., a circuit breaker) may trip with a time delay, unnecessarily de-energizing large sections of the system. In the worst-case scenario, the overload or short-circuit current can exceed the capacity of the power supply unit, causing the entire system to fail because the supplying power supply unit is overloaded by the unexpected additional current demand.

[0008] Document WO 2010 / 018018 A1 discloses a method in which the highest necessary tripping current for a consumer or load unit in a technical system is determined over an observation period in order to adjust it in an adjustable fuse. For this purpose, the current drawn by the consumer is measured by a control unit during several observation intervals. A maximum value of the measured current is determined and stored for each observation interval. From the measured maximum values, which are provided with a safety margin, a static limit value for adjusting the tripping parameter or current is then determined, for example, by slow averaging starting from a default value (e.g., rated current, etc.). In addition to the static limit value for normal operation, a dynamic limit value for switching-on events of the consumer can also be determined.

[0009] However, the sum of the set or determined values ​​of the tripping parameters, especially the tripping current at which the individual fuses or switch units for protecting the load circuits trip, is often significantly higher than the capacity of the supplying power supply unit, particularly when, for example, several load units (solenoid valves, actuators, contactor coils, etc.) from multiple load circuits are switched on simultaneously during operation of the system. In the method known from document WO 2010 / 018018 A1, the tripping parameters, especially the value of the tripping current of the individual fuses for protecting the individual loads, are indeed adjusted to the operating conditions of the system. However, this does not take into account the capacity of the power supply unit when supplying several connected loads or load circuits, nor the distribution of the output current to the individual loads or load circuits.Load circuits are hardly taken into account. Furthermore, faulty shutdowns of load circuits or load units can occur, since only the current draw of the individual load circuit or the connected load units determines the current value at which the protective device's switching unit trips. This means that a current drawn by a load circuit is, for example, limited or switched off even though the power supply unit still has sufficient capacity to supply it, or because a tripping value that is too low was determined based on historical maximum values ​​during the observation period. This leads, for example, to unnecessary shutdowns of at least parts of the system. Description of the invention

[0010] The invention is therefore based on the objective of providing a method that is further developed compared to the prior art and which enables, in the ongoing operation of a technical plant, a safe and as error-free as possible functioning of the plant, in particular of load circuits of a plant control system and a power supply unit supplying the load circuits of the plant control system, in a simple manner and with little effort for the design of the plant.

[0011] This problem is solved by a method of the type mentioned at the outset, having the features according to the independent claim. Advantageous embodiments of the present invention are described in the dependent claims.

[0012] According to the invention, the problem is solved by a method for monitoring and controlling the current distribution in load circuits of a control system of a technical plant of the type mentioned above. During a learning phase, the current waveform of the current drawn by each load circuit is measured, at least in those load circuits protected by a switching unit. Then, at least one significant current profile and a tolerance range associated with the current profile are derived from the measured current waveform for each load circuit and assigned to the respective load circuit. During the ongoing operation of the plant, the control unit continuously monitors the current waveform, which is measured at least for those load circuits protected by a switching unit. Furthermore, the control unit checks whether the switching power supply unit has reached or exceeded a performance limit.If the power supply unit reaches or exceeds its capacity limit, the control unit reduces and / or switches off the current drawn by the respective load circuit by activating the switching unit in those load circuits where the current curve measured for the respective load circuit exceeds an upper limit of the tolerance range of the significant current profile assigned to the respective load circuit.

[0013] The main aspect of the solution proposed according to the invention is that the load circuits of the plant control system are supplied with as much current or energy as is required by the respective load circuit or by the at least one load unit belonging to the respective load circuit at any given time during operation, as long as the switched-mode power supply unit does not reach or exceed its capacity limit. If this capacity limit is reached or exceeded, the current in those load circuits that draw current above a normal or usual level, or that exhibit "unusual" current behavior, is reduced and / or switched off by means of appropriate control of the switching units. The normal or usual current requirement of a respective load circuit is determined based on the current profile and associated tolerance range determined for the respective load circuit during the learning phase.It is therefore no longer necessary to determine suitable tripping values ​​for the protective switchgear of the system's load circuits protected by a switch unit, at which the current in the respective load circuit is reduced and / or switched off. Instead, the capacity of the supplying power supply unit is used as the limiting factor. This ideally prevents incorrect settings during system planning or installation, in particular excessively high tripping values ​​of switchgear units functioning as electronic fuses. Furthermore, the static and dynamic current behavior of the load circuits in combination, as well as the distribution of the power supply unit's output current across the individual load circuits and their load units, are taken into account.

[0014] It is advantageous for the control unit to monitor the output voltage of the switched-mode power supply unit or a sum of current measurements from the load circuits to detect when the unit's capacity limit has been reached. In the simplest case, the control unit uses the output voltage of the switched-mode power supply unit—i.e., the supply voltage—as the criterion. It monitors whether the output voltage of the switched-mode power supply unit reaches or falls below a predefined limit (e.g., 20 V). Optionally, if the characteristics of the power supply unit are known, several voltage limits can be defined, each corresponding to current information about the overload state of the power supply unit. The voltage limits can be evaluated in stages.The current output voltage of the power supply unit can be compared to determine the current degree of overload and appropriate measures (e.g., reduction and / or shutdown of current in individual load circuits, in multiple load circuits, etc.).

[0015] Alternatively, the control unit can calculate a current sum value from the current values ​​of the current drawn by the load circuits and use this sum value as a criterion. The control unit then checks whether the respective sum value reaches and / or exceeds a predefined limit. Ideally, the predefined limits for the output voltage or for the current sum value of the currents currently drawn by the load circuits result from the overload capacity of the power supply unit.

[0016] Ideally, a time period can be specified during which the power supply unit's capacity limit may be exceeded by a predetermined amount. This means the power supply unit can provide a predefined overcurrent as an output current for a short, predefined period (e.g., 5 ms), exceeding the normally supplied continuous current. This overload capability can be used to handle dynamic current behavior in the system (e.g., connecting multiple load circuits in parallel, etc.).

[0017] A suitable further development approach stipulates that, in order to detect when the switching power supply unit (SPU) reaches its performance limit, it continuously transmits current load values, or notifications of reaching and / or exceeding the power limit, to the control unit. The SPU can, for example, detect internal thermal conditions (e.g., temperature, degree of heating, etc.), input voltage fluctuations (e.g., voltage spikes, power disturbances, phase failure, etc.), and calculate parameters dependent on the current situation, which reflect the current performance of the SPU. These parameters are then forwarded to the control unit as current load values ​​and can be used by the control unit to monitor the SPU's performance limit.This advantageously takes into account the current state of the power supply unit, such as temperature rise, fluctuations in the input voltage, etc. Furthermore, based on the current load values, it is possible to predict when the power supply unit will need to regulate the output voltage, for example, for self-protection, or when its performance limit will at least be reached.

[0018] Ideally, the control unit is programmed with a sequence for reducing and / or switching off the current in those load circuits where the upper limit of the tolerance range of the significant current profile assigned to the respective load circuit is exceeded. For example, it can be specified that the current drawn is first reduced and / or switched off in those load circuits that place the heaviest load on the power supply unit or that consume the most current. This allows for a simple and rapid way to relieve the load on the power supply unit.

[0019] Furthermore, the control unit advantageously assigns a status marker to those load circuits where the current curve measured for the respective load circuit during operation exceeds the upper limit of the tolerance range of the significant current profile assigned to that load circuit. This allows for the simple identification of load circuits exceeding the tolerance limits, which draw a current above the usual level during operation. If, for example, the current demand of a load circuit decreases—i.e., the currently measured current curve of this load circuit falls back within the tolerance range of the significant current profile assigned to that load circuit—the status marker for this load circuit can be reset.

[0020] It is therefore advantageous if, when the capacity limit of the switched-mode power supply unit is reached and / or exceeded, the control unit uses the status marker currently assigned to the respective load circuit. This allows for the simple and rapid identification of those load circuits in which current reduction and / or shutdown should be implemented in the event of a supply bottleneck or emergency.

[0021] Furthermore, ideally, based on the current profiles of the load circuits monitored by the control unit during operation, an alarm message can be issued for those load circuits where the current profile currently measured for the respective load circuit exceeds the upper limit of the tolerance range of the significant current profile assigned to that load circuit. This alarm message can, for example, be logged or forwarded to a system operator and ideally provides information about "abnormal" current behavior in a load circuit of the system. Furthermore, the alarm messages can be weighted, for example, according to system hazard.The evaluation will determine whether the tolerance range of the associated significant current profile in a load circuit is only slightly and / or briefly exceeded by the current consumed, or whether there is a larger and / or longer-lasting exceedance of the tolerance range of the respective current profile.

[0022] A convenient embodiment of the invention provides that, to reduce the current drawn by the respective load circuit, the switching unit of the respective load circuit is controlled by the control unit in such a way that the current drawn by the respective load circuit is limited in time. That is, in the event of a supply bottleneck or supply emergency, the switching unit protecting the respective load circuit is controlled linearly to maintain the current in the respective load circuit at a predetermined value, regardless of the behavior of the at least one load unit or a nominal load arranged in the load circuit. Alternatively, the switching unit of the respective load circuit can also be controlled by the control unit to reduce the current drawn in the respective load circuit in such a way that the switching unit is switched to pulse operation.In this case, the switching unit is pulsed by the control unit to maintain the current in the respective load circuit at a predetermined value. In the simplest case, the current drawn by the respective load circuit is completely switched off after a predetermined time, for example, with the switching unit protecting the load circuit being controlled accordingly.

[0023] It is also advantageous if the significant current profile of the respective load circuit is derived during the learning phase from the measured current waveform of the respective load circuit using reference data. Ideally, this reference data comprises typical and characteristic current patterns of load units frequently used in load circuits. Such current patterns are, for example, characteristic current waveforms for individual load units. The reference data can include the following exemplary current patterns: a purely resistive profile, which is typical for simple sensors, heating elements, etc.; a capacitive-current-limited profile with a current peak that decays according to an exponential function, and which can be typical for sensor units, for example; an inductive-resistive profile, for example, with a dip, which is typical for solenoid valves, contactors, etc.is; a profile with a current increase, followed by a waiting period and another current increase, which is typically exhibited by controllers during startup; etc. The characteristic current patterns are determined, for example, based on historical current profiles, e.g., on a dedicated computer unit (e.g., PC), and provided to the control unit as target data, e.g., before the learning phase, ideally before the initial commissioning of the system, in order to derive the significant current profiles of the load circuits of the system control more quickly.

[0024] Ideally, a trained neural network is used to derive the significant current profile of each load circuit. Using a trained neural network can significantly accelerate the derivation of the respective significant current profile of the system's load circuits. Training the neural network can be performed, for example, on a dedicated computer, such as a PC, using training data such as typical and characteristic current patterns of load units frequently used in load circuits. Through training, the neural network acquires a collection of weighted decision criteria that allow it to quickly distinguish between different current patterns and recognize rapidly recurring current patterns in measured current profiles of load circuits. The trained neural network is then, for example,After appropriate training and before the learning phase, ideally before the initial commissioning of the system, the information is transferred to the control unit and can significantly accelerate the finding of the current profiles significant for the respective load circuits and the determination of the respective tolerance ranges - i.e., recurring current patterns in current magnitude, duration and shape in the respective current profiles including respective fluctuation ranges - during the learning phase.

[0025] A preferred embodiment of the invention provides that a minimum duration is specified for the learning phase, in which a significant current profile for a given load circuit is derived from a current waveform measured for that load circuit. The minimum duration of the learning phase ensures, at least, that for each load circuit at least two typical, recurring current patterns are found in the current waveform measured for that load circuit, so that, based on these at least two typical, recurring current patterns, a significant current profile and at least a rough tolerance range for this current profile can be determined.

[0026] In the best-case scenario, the learning phase can encompass the entire lifespan of the system. This means that even during operation, the current profiles measured for the load circuits are checked for typical current patterns in order to continuously refine and improve the assigned, significant current profile and the associated tolerance range of the respective load circuit. Furthermore, a change in a significant current profile (e.g., in magnitude, duration, and / or shape) can indicate aging or an impending malfunction of a load unit in the corresponding load circuit. The control unit can easily detect such changes.

[0027] For example, the current profile measured for an affected load circuit during plant operation may permanently exceed or fall below the tolerance range of the significant current profile assigned to that load circuit. The affected load circuit can be reported to the plant operator, for example, by means of an alarm message. Before the alarm message is sent, a relevance check can be performed, whereby deviations from the significant current profile, or exceeding or falling below the associated tolerance range, are only reported if a predefined minimum deviation of, for example, the current magnitude and / or the shape of the significant current profile is reached.

[0028] Furthermore, repeated deviations from the significant current profile, or repeated exceedances or falls below the associated tolerance range, can lead to a corresponding adjustment of the significant current profile of a load circuit or its associated tolerance range, provided predefined criteria are met. One possible criterion is, for example, that the deviations from the current profile, or repeated exceedances or falls below the associated tolerance range, occur regularly or consistently. This allows, for example, the assumption that they correspond to a "normal" current profile in the affected load circuit. The adjustment of the significant current profile of the affected load circuit, or its associated tolerance range, can be performed automatically. However, it can also be stipulated that an operator of the system must confirm such an adjustment.The operator can, for example, ensure beforehand that no obvious defects or unusual operating behavior has occurred in the affected load circuit.

[0029] Since at least a majority of the load circuits in the system control are protected by a switching unit that acts as an electronic fuse, a safety limit is ideally defined for each load circuit protected by a switching unit. If this limit is reached and / or exceeded, the current drawn by the respective load circuit is always switched off. This safety limit, which should ideally be above the upper limit of the tolerance range of the significant current profile assigned to the respective load circuit, represents a maximum value for the load circuit current. The safety limit is set to comply with fire protection regulations and, in the worst-case scenario of a defective load unit in a load circuit, to prevent a fire.

[0030] Furthermore, it is advantageous to provide an additional protective device, for example, to meet fire protection requirements. The switch unit that protects the respective load circuit is, for example, preceded by this additional protective device (e.g., circuit breaker, fuse, etc.), which will trip in any case if the switch unit fails. The protective device can be selected, for example, to allow only current levels or waveforms that protect the cable and at least one load unit in the load circuit from damage and / or fire.

[0031] A favorable embodiment of the invention provides for the use of a power transistor or a microelectronic-mechanical system (MEMS) as the switching unit. Both power transistors and MEMS constitute electronic switches that can be easily controlled by a control unit to limit current. Furthermore, the current can be easily interrupted by appropriate control of a power transistor or MEMS as a switching unit. MEMS are typically tiny semiconductor devices that ideally combine logic elements and micromechanical structures (e.g., armatures moved by electrostatic forces) in a single component. Brief description of the drawing

[0032] The invention is explained below by way of example with reference to the accompanying figures. These show: Figure 1a schematic and exemplary arrangement for carrying out the inventive method for monitoring and controlling a current distribution in load circuits in a technical plant; Figure 2 An exemplary sequence of the inventive method for monitoring and controlling a power distribution in load circuits in a technical plant. Implementation of the invention

[0033] Figure 1Figure 1 schematically shows an exemplary arrangement SV for the power supply of a plant control system in a technical plant. This exemplary arrangement SV allows for the monitoring and control of power distribution in load circuits L1, L2, and L3 of the plant control system. For this purpose, the arrangement SV includes a switched-mode power supply unit NG, such as a switching power supply, which is fed by a mains voltage UN – for example, a DC voltage, a single-phase AC voltage, or a three-phase AC voltage. The switched-mode power supply unit NG is connected to a reference potential BP (e.g., 0 volts) and provides an output voltage UA with a regulated and usually predefined value (e.g., 24 volts) and an output current IA. Furthermore, if configured accordingly, the power supply unit NG can continuously transmit current load values ​​AW to a control unit SE.

[0034] Furthermore, at least one load circuit L1, L2, L3 is provided for the system control. However, a system control system usually has several load circuits L1, L2, L3. Each load circuit L1, L2, L3 contains at least one load unit, such as a sensor, actuator, relay, contactor, solenoid valve, drive unit for a motor, servo motor, controller, display unit, etc. The load circuits L1, L2, L3 are connected to the reference potential. Additionally, for power supply to the load units, the load circuits L1, L2, L3 are connected via branches A1, A2, A3 to the switched-mode power supply unit NG. The output voltage UA or output current IA provided by the power supply unit NG is distributed to the respective load circuits L1, L2, L3.

[0035] Furthermore, at least a majority of the load circuits L1, L2, L3 are protected by a switching unit S1, S2, S3. This means that, for example, individual load circuits L1, L2, L3, which require very little current and / or must be supplied almost constantly (e.g., a load circuit L1, L2, L3 with a controller as the load unit), may not have a switching unit S1, S2, S3 for protection. Ideally, all load circuits L1, L2, L3 are protected by a switching unit S1, S2, S3 – as shown in Figure 1As illustrated by example, the switching unit S1, S2, S3 acts as an electronic and adjustable fuse for the respective load circuit L1, L2, L3. Each switching unit S1, S2, S3 is controlled by corresponding control signals AS1, AS2, AS3 from a control unit SE. This allows the current drawn by the respective load circuit L1, L2, L3, and thus the distribution of the output current IA of the power supply unit NG to the load circuits L1, L2, L3, to be controlled accordingly. A power transistor or a microelectronic-mechanical system (MEMS) can be used as the switching unit S1, S2, S3. Additionally, a further protective device (e.g., circuit breaker, fuse, etc.) can be provided, which is, for example, connected upstream of the respective switching unit S1, S2, S3. The additional protective devices are described in Figure 1 Not shown for the sake of simplicity.

[0036] Furthermore, a measuring unit ME1, ME2, ME3 is provided in a branch A1, A2, A3 of the respective load circuit L1, L2, L3. The measuring unit ME1, ME2, ME3 measures the current waveform i1, i2, i3 of the current drawn by the respective load circuit L1, L2, L3 and forwards it to the control unit SE for monitoring and evaluation.

[0037] A microprocessor, for example, can be used as the control unit SE, from which the switching units S1, S2, S3 are controlled by means of control signals AS1, AS2, AS3 and which monitors the current profiles i1, i2, i3 in the load circuits L1, L2, L3.

[0038] Furthermore, the control unit SE can have at least one memory unit SP, in which, for example, monitoring limits for the output voltage UA of the power supply unit, limits for the sum of the currents in the load circuits L1, L2, L3, and / or adjustable values ​​for the switching units S1, S2, S3 are stored. The memory unit SP of the control unit SE can also contain, for example, a predefinable safety limit for each switching unit SE. At this predefinable safety limit (e.g., maximum permissible load circuit current), the current drawn by the respective load circuit L1, L2, L3 is interrupted by the respective switching unit S1, S2, S3. Furthermore, the memory unit SP can contain predefined data VD (e.g., current patterns, decision criteria for a neural network, etc.).) are stored, which are determined, for example, on an external computer unit PC and are needed for carrying out the procedure to monitor and control the power distribution in the load circuits L1, L2, L3.

[0039] To divide the load units of the plant control system into load circuits L1, L2, L3, the switched-mode power supply unit NG itself can, for example, have at least one or more outputs A1, A2, A3 to which the load circuits L1, L2, L3 are directly connected. Each output A1, A2, A3 is then protected by a switching unit S1, S2, S3 and has a measuring unit ME1, ME2, ME3 for measuring the current waveform i1, i2, i3 in a connected load circuit L1, L2, L3. Furthermore, the control unit SE is integrated into the power supply unit NG. That is, the power supply unit comprises the following: Figure 1 units encompassed by the dashed line and thus corresponds to that in Figure 1Exemplary arrangement SV.

[0040] Alternatively, at least one or more electronic protection modules, such as the Siemens SITOP SEL1200 or SITOP SEL1400 selectivity modules, can be connected downstream of the switched-mode power supply unit NG. In this case, the respective protection module has outputs A1, A2, and A3, to which the load circuits L1, L2, and L3 are connected. The protection module comprises the switching units S1, S2, and S3 for protecting the outputs A1, A2, and A3, respectively, and the connected load circuits L1, L2, and L3; the measuring units ME1, ME2, and ME3 for measuring the current waveforms i1, i2, and i3 in the connected load circuits L1, L2, and L3; and the control unit SE.

[0041] When using multiple fuse modules, the control unit SE can, for example, be divided into several functional units, which are distributed across the respective fuse modules. The fuse modules, or at least one functional unit of the control unit SE arranged on them, are connected, for example, via a data bus. One of the distributed functional units is a so-called master functional unit for higher-level control and monitoring of the load circuits L1, L2, and L3, while the other distributed functional units function as so-called slave functional units for local and rapid control and monitoring of the load circuits L1, L2, and L3 connected to the respective fuse module. Furthermore, a memory unit SP can be provided in each fuse module for the functional units of the control unit SE, in which at least those values ​​(e.g., fuse limits, etc.) are stored.) are stored, which require local control and monitoring of the current in the load circuits L1, L2, L3 connected to the respective fuse module.

[0042] The Figure 2 Figure 1 shows an exemplary sequence of the inventive method for monitoring and controlling the current distribution in the load circuits L1, L2, L3 of a plant control system in a technical plant, as exemplified in Figure 2. Figure 1 depicted.

[0043] During a learning phase, which can be started, for example, with the initial commissioning of the system, the current waveform i1, i2, i3 of the current drawn by each load circuit L1, L2, L3, protected by a switching unit S1, S2, S3, is measured in a measurement step 101. This measurement can be performed, for example, using the measuring unit ME1, ME2, ME3 provided for the respective load circuit. The current waveform i1, i2, i3 measured for the respective load circuit L1, L2, L3 is then forwarded to the control unit SE.

[0044] In derivation step 102, which also belongs to the learning phase, a significant current profile with an associated tolerance range is derived from the current waveforms i1, i2, i3 measured for the respective load circuit L1, L2, L3. For this purpose, the current waveforms i1, i2, i3 measured for the respective load circuit L1, L2, L3 are searched for a recurring, characteristic current pattern. Such a current pattern represents a segment of the respective measured current waveform i1, i2, i3 that exhibits approximately the same current amplitude, duration, and / or waveform. In particular, the current patterns should contain the highest instantaneous current values.

[0045] From the recurring current pattern found for each load circuit L1, L2, L3, the significant current profile for that load circuit L1, L2, L3 is derived. Ideally, this profile represents both the static and dynamic current behavior (e.g., the switching behavior) of the respective load circuits L1, L2, L3 during the ongoing operation of the system or the system control. Furthermore, in derivation step 102, a tolerance range corresponding to the significant current profile is determined from the recurring current pattern found for each load circuit L1, L2, L3. This tolerance range results from a drift in, for example, current amplitude, duration, and / or waveform of the recurring current pattern found in the respective current profiles i1, i2, i3 for the respective load circuit L1, L2, L3. The respective tolerance range can optionally be extended with a safety margin.

[0046] To identify the characteristic current patterns in the respective current waveforms i1, i2, i3, predefined data VD, such as current patterns frequently occurring in load circuits and / or current patterns typical for commonly used load units, can be used in derivation step 102. Ideally, the predefined data VD are determined in advance, for example, based on historical current waveforms of load circuits L1, L2, L3 and / or individual load units on the external computer unit PC, and then transferred to the control unit SE before the learning phase and stored there in the storage unit SP.

[0047] To accelerate the detection of current patterns in the respective current waveforms i1, i2, i3, or to derive the significant current profile of the respective load circuit L1, L2, L3 and its associated tolerance range from the current waveform i1, i2, i3 measured for the respective load circuit L1, L2, L3, a trained neural network can be used in derivation step 102. Before the learning phase, the neural network was trained on the external computer PC using training data, such as typical and characteristic current patterns of load units frequently used in load circuits L1, L2, L3, etc., and then transferred to the control unit SE.

[0048] For the learning phase, which includes at least measurement step 101 and derivation step 102, a minimum duration can be specified. Within this minimum duration, at least two characteristic current patterns for the respective load circuit L1, L2, L3 should be found in each measured current waveform i1, i2, i3, in order to derive at least one significant current profile with a rough tolerance range for each load circuit L1, L2, L3. After the specified minimum duration of the learning phase, the system can, for example, transition to continuous operation. In the most extreme case, however, the learning phase can last the entire service life of the system. During this time, the significant current profiles of the load circuits L1, L2, L3 and their associated tolerance ranges can also be adjusted and improved during operation. For example,Minor deviations from the tolerance range of a current profile lead to an adjustment of the respective significant current profile. Larger or significant deviations from the tolerance range, which are detected, for example, based on predefined percentage values ​​for the deviation, can be interpreted as errors in the respective load circuit L1, L2, L3 and may result in an alarm or a message to the system operator.

[0049] During the ongoing operation of the system, the control unit SE continuously monitors the current profile i1, i2, i3 of each load circuit L1, L2, L3, as measured by the respective measuring units ME1, ME2, ME3, in monitoring step 103. The control unit SE can, for example, check whether the current profile i1, i2, i3 currently measured for the respective load circuit L1, L2, L3 exceeds an upper limit of the tolerance range of the significant current profile assigned to that load circuit L1, L2, L3. If such an exceedance is detected, a status marker can be assigned to the respective load circuit L1, L2, L3. This marker remains active until the control unit SE determines that the current profile i1, i2, i3 currently measured for the respective load circuit L1, L2, L3 is again within the tolerance range of the significant current profile assigned to that load circuit L1, L2, L3.Alternatively or additionally, the control unit SE can also issue an alarm message for each load circuit L1, L2, L3, in which the upper limit of the tolerance range of the significant current profile assigned to the respective load circuit L1, L2, L3 is exceeded by the current curve i1, i2, i3 currently measured for the respective load circuit L1, L2, L3.

[0050] Furthermore, in test step 104, which runs more or less in parallel to monitoring step 103, the control unit SE checks whether the clocked power supply unit NG has already reached or exceeded its performance limit. To detect whether the power supply unit NG has reached or, if applicable, exceeded its performance limit in test step 104, the control unit can, for example, monitor the output voltage UA of the power supply unit NG. If the output voltage UA of the power supply unit NG falls below a predefined limit, then the power supply unit NG has at least reached its performance limit.The power supply unit NG can no longer maintain its specified output voltage UA under a current load from the load circuits L1, L2, L3, and the control unit SE begins, in a control step 105, to at least reduce and / or switch off the current drawn in load circuits L1, L2, L3.

[0051] As an alternative to the output voltage UA of the power supply unit NG, the control unit SE can monitor a sum of current measurements of the currents drawn by the load circuits L1, L2, L3. For this purpose, the control unit SE evaluates, for example, the current waveforms i1, i2, i3 of the load circuits L1, L2, L3 currently measured by the measuring units ME1, ME2, ME3, and determines a current sum of the corresponding current measurements. This sum is then compared with a predefined limit value – for example, a known power reserve of the power supply unit NG. If the sum exceeds this predefined limit value, the control unit SE recognizes that the power supply unit NG has at least reached its capacity limit and, in control step 105, begins to at least reduce and / or switch off the current drawn in the load circuits L1, L2, L3.

[0052] However, a short time period (e.g., 5 ms) can be specified within which the power supply unit NG can exceed its capacity limit, at least slightly. The power supply unit NG then briefly delivers an overcurrent as output current IA, which exceeds the output current IA normally supplied as a continuous current. If this specified time period is exceeded, however, the capacity limit of the power supply unit NG is at least reached, and the control unit SE must initiate control step 105 to at least reduce and / or switch off the current drawn in load circuits L1, L2, L3.

[0053] Alternatively, the control unit SE can, for example, derive from the current profiles individually assigned to load circuits L1, L2, L3 how long an overcurrent (e.g., inrush current) will last before the control unit SE begins reducing the current in one or more load circuits L1, L2, L3 in control step 105. The resulting additional current consumption can be compared by the control unit SE with the time-limited overcurrent capability of the power supply unit NG. If this comparison shows that the power supply unit NG can supply the necessary overcurrent for the expected duration (i.e., only slightly exceeding the power limit), then, for example, the supply to load circuits L1, L2, L3 is not yet affected. A reduction and / or shutdown of the current in load circuits L1, L2, L3 only occurs, for example, when it becomes apparent that the significant current profile is not being adhered to.

[0054] Furthermore, the power supply unit NG can continuously transmit current load values ​​AW to the control unit SE. These values, for example, represent parameters reflecting the current situation within the power supply unit NG, such as internal thermal conditions (e.g., temperature, degree of heating, etc.), input voltage fluctuations (e.g., voltage spikes, power disturbances, phase failure, etc.). Based on the current load values ​​AW of the power supply unit NG, the control unit SE can determine the current performance of the power supply unit NG and, for example, predict when and if the power supply unit NG needs to reduce its output voltage UA for self-protection or at least reach its performance limit.

[0055] If the power supply unit NG reaches or exceeds its capacity limit, the control unit SE, in control step 105, begins to reduce and / or switch off the current drawn in those load circuits L1, L2, L3 where the current curve i1, i2, i3 measured for the respective load circuit L1, L2, L3 exceeds an upper limit of the tolerance range of the significant current profile assigned to that load circuit. The control unit SE then activates the respective switching units S1, S2, S3 of these load circuits L1, L2, L3 with control signals AS1, AS2, AS3 to reduce and / or switch off the current in the respective load circuit L1, L2, L3.

[0056] To reduce the current drawn by the respective load circuits L1, L2, L3, the corresponding switching unit S1, S2, S3 can be controlled, for example, by a corresponding control signal AS1, AS2, AS3 such that the current drawn by the respective load circuit (L1, L2, L3) is limited in time. The switching unit S1, S2, S3 can, however, be put into pulse operation by means of a corresponding control signal AS1, AS2, AS3, which, for example, maintains a constant value. Can a reduction in the current in the load circuits L1, L2, L3 exceeding the tolerance – i.e.,If the current current waveform i1, i2, i3 exceeds the upper limit of the tolerance range of the significant current profile assigned to the respective load circuit L1, L2, L3, and the power supply unit NG cannot achieve a reduction below the performance limit, then individual or all load circuits L1, L2, L3 exceeding the tolerance can be switched off by corresponding control signals AS1, AS2, AS3 from the control unit SE to the respective switching units S1, S2, S3.

[0057] To quickly identify load circuits L1, L2, and L3 that exceed the tolerance limits, the control unit SE can access the status markers from monitoring step 103 in control step 105. Status markers were assigned in monitoring step 103 to those load circuits L1, L2, and L3 where the current profile i1, i2, and i3 measured in monitoring step 103 exceeded the upper limit of the tolerance range of the significant current profile assigned to the respective load circuit L1, L2, or L3.

[0058] In control step 105, the control unit SE can also be given a sequence according to which the current in the load circuits L1, L2, L3 exceeding the tolerance is reduced or according to which load circuits L1, L2, L3 exceeding the tolerance are switched off. This predefined sequence can, for example, stipulate that current reduction and / or current shutdown is performed first in those load circuits L1, L2, L3 that most significantly exceed the respective upper limit of the tolerance range of the associated significant current profile. This means that the current in those load circuits L1, L2, L3 exceeding the tolerance that place the greatest load on the power supply unit NG, consume the most current, or are most likely to have a defect, is reduced and / or switched off first.

[0059] Furthermore, it is also possible to reduce and / or disconnect the current drawn by load circuits L1, L2, L3 in other load circuits that do not exceed tolerance limits, if, for example, the current reduction and / or disconnection in the load circuits exceeding tolerance limits is insufficient to restore the performance of the power supply unit NG. The disconnection of the current drawn in load circuits L1, L2, L3 can, for example, be carried out according to a predefined prioritization of the load circuits, so that, for example, important load circuits L1, L2, L3 and the important load units connected to them (e.g., controllers, etc.) are supplied with energy as much as possible and remain available for as long as possible.

Claims

1. Method for monitoring and controlling a current distribution in load circuits (L1, L2, L3) of an installation control system of a technical installation, wherein a predetermined output voltage (UA) is made available by at least one clocked power supply unit (NG) and distributed for an energy supply to the load circuits (L1, L2, L3), and wherein at least a plurality of the load circuits (L1, L2, L3) are protected by a switch unit (S1, S2, S3) in each case for each of the load circuits, which is actuated by a control unit (SE), characterised in that during a learning phase, at least in the load circuits (L1, L2, L3) which are protected with a switch unit (S1, S2, S3), a current variation (i1, i2, i3) of the current consumed by each load circuit (L1, L2, L3) is measured (101), in that from the current variation (i1, i2, i3) measured for the respective load circuit (L1, L2, L3) at least a significant current profile and an associated tolerance range is derived and associated (102) with the respective load circuit (L1, L2, L3), in that during an ongoing operation of the installation, a current variation (i1, i2, i3) which is presently being measured at least in the load circuits (L1, L2, L3) which are protected with one of the switch units (S1, S2, S3) is continuously monitored (103) by the control unit (SE) and it is checked (104) whether a power capacity limit is at least reached by the clocked power supply unit (NG), and if the power capacity limit is at least reached by the clocked power supply unit (NG), the current consumed by each load circuit (L1, L2, L3) is at least reduced and / or switched off by the control unit (SE) by actuating the respective switch unit (S1, S2, S3) in those load circuits (L1, L2, L3), in which an upper limit of the tolerance range of the current profile associated with the respective load circuit (L1, L2, L3) is exceeded by the current variation (i1, i2, i3) presently being measured for the respective load circuit (L1, L2, L3).

2. Method according to claim 1, characterised in that in order to recognise a reaching of the power capacity limit of the clocked power supply unit (NG), the output voltage (UA) of the clocked power supply unit (NG) or a sum of prevailing current measurement values of the respective currents consumed by the load circuits (L1, L2, L3) is monitored (104) by the control unit (SE).

3. Method according to one of claims 1 to 2, characterised in that a timespan is predetermined during which the power capacity limit of the clocked power supply unit (NG) can be exceeded by a predetermined amount.

4. Method according to one of the preceding claims, characterised in that in order to recognise the reaching of the power capacity limit of the clocked power supply unit (NG), prevailing capacity utilisation values (AW) or a reaching and / or exceeding of the power capacity limit are continuously transferred (104) from the clocked power supply unit (NG) to the control unit (SE).

5. Method according to one of the preceding claims, characterised in that a sequence is specified (105) to the control unit (SE) for a reduction and / or a switching-off of the current in those load circuits (L1, L2, L3) in which the upper limit of the tolerance range of the significant current profile associated with the respective load circuit (L1, L2, L3) is exceeded by the current variation (i1, i2, i3) presently being measured for the respective load circuit.

6. Method according to one of the preceding claims, characterised in that a status marking is assigned (103) to those load circuits (L1, L2, L3) in which the upper limit of the tolerance range of the significant current profile associated with the respective load circuit (L1, L2, L3) is exceeded, during ongoing operation of the installation, by the current variation (i1, i2, i3) presently being measured for the respective load circuit (L1, L2, L3).

7. Method according to claim 6, characterised in that on reaching the power capacity limit by the clocked power supply unit (NG), the status marking that is currently assigned to the respective load circuit (L1, L2, L3) is used (105) by the control unit (SE).

8. Method according to one of the preceding claims, characterised in that an alarm message is output (103) for those load circuits (L1, L2, L3) in which the upper limit of the tolerance range of the significant current profile associated with the respective load circuit (L1, L2, L3) is exceeded, during ongoing operation of the installation, by the current variation (i1, i2, i3) presently being measured for the respective load circuit (L1, L2, L3).

9. Method according to one of the preceding claims, characterised in that for the reduction of the current consumed by the respective load circuit (L1, L2, L3), the switch unit (S1, S2, S3) of the respective load circuit (L1, L2, L3) is actuated (105) by the control unit (SE) such that the current consumed by the respective load circuit (L1, L2, L3) is time-limited and / or the switch unit (S1, S2, S3) is switched into a clocked operation.

10. Method according to one of the preceding claims, characterised in that the significant current profile of the respective load circuit (L1, L2, L3) is derived (102) from the current variation (i1, i2, i3) measured for the respective load circuit (L1, L2, L3) on the basis of preset data (VD).

11. Method according to one of the preceding claims, characterised in that a trained neural network is used (102) for a derivation of the significant current profile of the respective load circuit (L1, L2, L3).

12. Method according to one of the preceding claims, characterised in that a minimum duration is specified for the learning phase.

13. Method according to one of the preceding claims, characterised in that furthermore for each load circuit (L1, L2, L3) protected with a switch unit, a safety limit value is defined, on reaching and / or exceeding which the current consumed by the respective load circuit (L1, L2, L3) is always switched off.

14. Method according to one of the preceding claims, characterised in that an additional protection apparatus is provided in the load circuits (L1, L2, L3).

15. Method according to one of the preceding claims, characterised in that a power transistor or a microelectromechanical system, MEMS for short, is used as the switch unit (S1, S2, S3).