Converter and method for controlling an electric motor, as well as working machine

Abstract

A converter for controlling an electric motor, preferably an electric motor of a work machine, is disclosed. The converter comprises at least one converter input (4), one converter output (5), a converter control unit (10), and a converter output stage (9). The converter control unit (10) is designed to generate control signals based on parameterization and to output the control signals to the converter output stage (9). The converter output stage (9) is designed to generate at least one converter output voltage from at least one converter input voltage applied to the converter input (4) based on control signals received from the converter control unit (10), and to output said voltage to the converter output (5) for controlling the electric motor (3).The converter (1) additionally comprises an error handling unit (11) with an error input, wherein an error signal for signaling an error can be input into the error input. The error handling unit (11) is designed to generate an emergency operation parameterization based on a received error signal and to output it to the converter control unit (10). The converter control unit (10) is designed to control the converter output stage (9) based on a received emergency operation parameterization such that the electric motor can continue to be operated in emergency mode. Furthermore, a work machine with such a converter and a corresponding method are disclosed.

Description

[0001] The present disclosure relates to a converter for controlling an electric motor, preferably an electric motor of a work machine. The present disclosure further relates to a work machine having such a converter and a corresponding method.

[0002] Working machines such as pumps, compressors, agitators, hoists, fluid energy machines, conveyor systems, or the like often have an electric motor that drives the working machine. Such electric motors are usually controlled by a converter, which generates one or more alternating voltages with variable amplitude and / or variable frequency and outputs them to the electric motor. In this way, for example, a rotating magnetic field can be generated in a stator of the electric motor, which sets a rotor in motion. By combining an electric motor with a converter, drives are created that can be flexibly controlled and regulated, allowing them to be used in a wide variety of operating situations.

[0003] Such converters typically have a converter input, a converter output, a converter control unit, and a converter output stage. Based on parameterization and, if applicable, other input variables (e.g., measured values, default signals, or setpoints), the converter control unit generates control signals and outputs the control signals to the converter output stage. Using the control signals received from the converter control unit, the converter output stage generates at least one converter output voltage from at least one converter input voltage applied to the converter input and outputs the at least one converter output voltage to the electric motor via the converter output. If there are multiple converter output voltages, these can form a multi-phase voltage system, for example, a three-phase system.The converter output stage usually features several power semiconductors that play a key role in generating the converter output voltage. In at least some converter topologies, the control signals from the converter control unit can be used directly to control the power semiconductors.

[0004] As with any technical system, errors can occur in one or more components of converters. The consequences of some errors can be easily intercepted. For example, to prevent a long-term failure if a converter control unit crashes, a monitoring circuit can monitor the converter control unit and trigger a restart if the converter control unit no longer responds in a predefined manner. This allows the converter control unit to be available again after a short time. If the converter drives a compressor in a refrigeration machine, for example, the failure can even be rectified largely unnoticed or at least without serious consequences.

[0005] Other errors are more critical and can have far-reaching consequences. These include, in particular, errors in which a power semiconductor in the converter output stage can no longer be switched. This error can originate in the periphery of the power semiconductor or in the power semiconductor itself. In the case of a periphery error, for example, a component between the converter control unit and the power semiconductor (e.g. a driver, a filter capacitor or an internal power supply) is defective, meaning that control signals no longer reach the power semiconductor or are significantly corrupted. In the case of a error in the power semiconductor itself, the power semiconductor can, for example, be permanently high-impedance or permanently low-impedance, exhibit undefined switching behavior or no longer respond to incoming control signals.In all of these cases, an affected power semiconductor can no longer fulfill its intended function, which is likely to lead to a deviation of the converter output voltage(s) from the target. This can place significant strain on the electric motor and the entire machine, or even damage it. Therefore, when such a fault is detected, the entire system is regularly shut down in an emergency to prevent damage and unsafe operating conditions.

[0006] The disadvantage of this approach is that an emergency shutdown can have significant consequences. This is particularly critical in safety-relevant scenarios. For example, a switched-off flood pump can cause life-threatening situations because incoming water is no longer pumped out. In water supply or water disposal, a switched-off pump can shut down important infrastructure and lead to massive problems in the supply area. A switched-off pump in cooling systems or a switched-off compressor in systems in the food industry, medical technology, or utility cooling can lead to critical temperatures being reached. Therefore, especially in these scenarios, a fault must be identified quickly and the failed converter repaired promptly. This requires a good monitoring system, appropriate logistics, and the availability of sufficient spare parts and specialists.This entails considerable costs. Moreover, especially in emergency situations such as flooding, there are already bottlenecks, making timely repairs impossible in some cases.

[0007] The invention is based on the object of designing and developing a converter, a working machine and a method in such a way that an emergency shutdown can be avoided at least in the case of individual fault conditions and continued operation in emergency mode is possible.

[0008] This problem is solved by feature combinations of the independent claims. Further embodiments are disclosed in the respective subclaims.

[0009] It should be noted that the features listed individually in the claims can be combined with one another in any technically reasonable manner (even across category boundaries, for example, between methods and devices) and demonstrate further embodiments. The description further characterizes and specifies the invention, particularly in conjunction with the figures.

[0010] It should also be noted that a conjunction “and / or” used herein between two features and linking them together is always to be interpreted in such a way that in a first embodiment only the first feature is present, in a second embodiment only the second feature is present and in a third embodiment both the first and the second feature are present.

[0011] It has been recognized that not all faults in a converter necessarily lead to the entire converter being shut down, even if the fault cannot be rectified by restarting a system. This is because fault conditions usually only affect a part of the converter, while the "rest" of the converter can still be used. For example, if there is a fault in one branch of a converter bridge, it is often only this branch that is affected, while other branches can continue to be used. The faulty section will usually have an impact on the continued use of other parts of the converter, and emergency operation can negatively impact the service life of the converter, the electric motor, and / or a machine driven by the electric motor.Nevertheless, the consequences of an emergency shutdown can be even more serious, so that suboptimal operation of the electric motor, a reduced service life, increased noise, increased energy consumption, or other adverse effects of emergency operation can be accepted. For example, emergency operation of a flood pump for a few hours can save lives, even if the pump subsequently requires significant maintenance. In a cooling system, emergency operation for a few hours or even days can facilitate the procurement of spare parts and the organization of repairs without damaging the system being cooled due to excessive temperatures.

[0012] This basic idea is implemented in the converter disclosed here in that the converter additionally comprises an error handling unit that is communicatively connected to the converter control unit. The error handling unit has an error input into which an error signal can be input to signal a detected error. It can be advantageous to not only signal the general presence of an error, but also to provide information about a failed component and / or the type of failure. If this information is not available, it can be obtained subsequently if necessary. The error handling unit is designed to generate an emergency operation parameterization based on a received error signal and to output it to the converter control unit.If the inverter control unit receives an emergency operation parameter from the fault handling unit, the inverter control unit controls the inverter output stage in such a way that the electric motor can continue to operate in emergency mode. Typically, this would mean that the inverter control unit completely or partially replaces the existing parameter setting, which describes normal inverter operation, with the received emergency operation parameter. It will not be possible to avoid an emergency shutdown of the inverter in all cases. Nevertheless, in this way, an emergency shutdown and potentially associated safety-critical states can be avoided at least in some fault conditions, and emergency operation can be enabled for at least a limited period of time.

[0013] The present disclosure can be used in connection with a wide variety of work machines and electric motors. The term "work machine" refers to an overall system that may include electrical and mechanical components. The work machine converts input electrical energy into another form of energy, for example, kinetic energy, pressure, etc. Examples of such work machines are pumps, compressors, agitators, hoists, fluid energy machines, conveyor systems, or fans. Examples of possible electric motors are permanent magnet synchronous machines (PMSMs), synchronous reluctance machines (SRMs), permanent magnet synchronous reluctance machines (PMASynRMs), or asynchronous machines (ASMs). These lists are merely exemplary and not exhaustive, and are not intended to limit the present disclosure to these examples.It is important that the electrical energy input to a converter input is transferred through the converter to the electric motor and used to drive the driven machine. However, pumps and compressors are particularly preferred designs for driven machines.

[0014] The term "converter" can, in principle, encompass anything required to generate an inverter output voltage for driving an electric motor from an inverter input voltage. This can include power semiconductors, filters, amplifiers, drivers, and safety circuits, as well as rectifiers, intermediate circuit capacitors, line filters, microprocessors, memory, DC / DC converters for internal power supply, ammeters, voltmeters, input / output interfaces, etc. This list is neither exhaustive nor restrictive.

[0015] In simplified terms, the converter has at least one converter input, one converter output, a converter control unit, and a converter output stage with the functions described above. A converter input voltage can be input to the converter input to supply the converter and the electric motor to be controlled. This "converter input voltage" can be a direct voltage, possibly also from a direct voltage intermediate circuit, or a single- or multi-phase alternating voltage. An example of these multi-phase alternating voltages is three-phase current. The converter output voltage output at the converter output is usually an alternating voltage, which can also be single- or multi-phase. In this context, "alternating voltage" is generally understood to mean a voltage with a non-constant amplitude, which can be unipolar or bipolar, have a variable frequency, and have various voltage waveforms.The alternating voltage can be equivalence-free, but can also have an equivalence non-zero. In some cases, the aim is to generate the inverter output voltage(s) as an approximately sinusoidal alternating voltage. In other cases, the inverter output voltage(s) are generated as a rectangular voltage. However, the inverter output voltage can also be triangular or trapezoidal, to name just a few other conceivable voltage shapes. It goes without saying that the inverter input and output should be matched to the respective inverter input voltage and the respective inverter output voltage. This can also mean that additional circuitry is present at the inverter input or output, for example filters for electromagnetic compatibility, overvoltage protection, or overcurrent protection.

[0016] The converter itself can have a wide variety of topologies. Examples, but not limited to, include dual-level inverters, multi-level inverters, soft-switching topologies with switching points at the voltage zero point (ZVS), or soft-switching topologies with switching points at the current zero point (ZCS). In principle, the present disclosure can be used with all of these and other topologies.

[0017] The converter output stage can comprise one or more power semiconductors, which can be interconnected in different ways. One or more converter branches can be used as a half-bridge or full-bridge. The power semiconductor(s) can be formed in a variety of ways. Various transistor designs are common, in particular MOSFET (Metal Oxide Semiconductor Field Effect Transistor), IGBT (Insulated Gate Bipolar Transistor), SiC-FET (Silicon Carbide Field Effect Transistor), and GaN-FET (Gallium Nitride Field Effect Transistor). The control of the transistors can also be varied and can be adapted to the type of modulation used. The use of space vector modulation, sine modulation, and discontinuous (flat top) modulation is mentioned purely as examples and is not exhaustive or limiting.It is also possible that different modulation types are used in normal operation and emergency operation, for example, to better cope with a component failure. Depending on the modulation type, the control signals can also look different. In many cases, the control signals for the power semiconductors are likely to be pulse-width modulated signals.

[0018] The "converter control unit" can be designed accordingly in different ways. The converter control unit can be used to control important functions of the converter and / or be part of a control loop. In the latter case, the converter control unit participates directly or indirectly in a control process. The task of the converter control unit is to generate and output control signals that cause the converter output stage to generate and output the converter output voltage. The exact form of the "control signals" depends on various factors. In principle, a control signal can include a specification for a voltage vector, which is then converted accordingly by the converter output stage. The control signals preferably include the signals that can be fed directly to the power semiconductors. Additional processing steps may be required for this, for example using an amplifier or a filter.In one embodiment, the control signals are formed by pulse width modulated signals (PWM signals).

[0019] When generating the control signals, the inverter control unit uses – in addition to any other input variables such as preset signals, measured values, setpoints, or the like – a "parameterization" that defines various framework conditions for generating the control signals. In principle, the parameterization can define everything that directly or indirectly controls the behavior of the inverter. If this is not already specified by the inverter components, the parameterization can, for example, define which modulation type should be used, the basic modulation frequency, the control concept used, the maximum output current, the acceptable voltage deviations from an ideal curve, which subsystem is activated / deactivated, or other framework conditions. How precisely these parameters are defined and used in generating the control signals is not crucial in this case.In one embodiment, the parameterization is defined by a data set that, for example, defines various parameters in a table-like format. In another embodiment, the parameterization is not recognizable as a closed construct, but rather as part of the converter control unit. The respective parameters can be defined by registers or memory contents, which are then read and / or used during processing.

[0020] The "error handling unit" can also operate differently. It is advantageous if the error handling unit has information about how to respond to each error. This can mean that the error handling unit uses a predefined mapping between different error types or different errors to appropriate emergency operation parameters. However, this can also mean that the error handling unit, for example, using artificial intelligence and / or machine learning, generates emergency operation parameterization based on an error signal and any underlying conditions.

[0021] The "error signaling" that can be entered into the "error input" of the error handling unit can have different designs and varying levels of detail. It is important that the error signaling "tells" the error handling unit that an error has occurred and that a response should be made to this error. This can be seen in the form of an electrical signal or an electrical logic level, but also in the form of a logic value or a message with multiple pieces of information, to name just a few conceivable designs. The level of detail of this message and what additional information needs to be obtained is not crucial. In one design, the error signaling simply indicates that there is a general error in the converter or its peripherals. The error handling unit therefore has the additional task of identifying the specific error and responding to it.In another embodiment, the error signaling includes more extensive information about the signaled error. Here, too, the level of detail can vary. For example, it can be indicated that the high-side power semiconductor of phase W can no longer be switched and is permanently high-impedance, which allows the error handling unit to react very specifically to the error. However, it is also conceivable that only a general problem with the power semiconductors is indicated and that the error handling unit must further narrow down the specific type of error. In all cases, it can be provided that the error handling unit uses additional units, for example sensors or the converter control unit. If further information about the existing error needs to be obtained, this additional information can be used when generating the emergency operation parameterization.

[0022] The "emergency operation parameterization" essentially defines how the inverter is to be controlled and / or regulated in emergency operation. With the emergency operation parameterization, the behavior of the inverter components can be adjusted, components can be activated or deactivated, or the inverter can be influenced in other ways. It is conceivable that the emergency operation parameterization can completely replace the parameterization for normal operation. However, the emergency operation parameterization can also include only the parameters that are specifically relevant for emergency operation, replacing only the relevant parts of the parameterization for normal operation. In this way, the emergency operation parameterization can be kept compact.The emergency operation parameterization can define various things, for example which modulation type is used in emergency operation, how the modulation should be adjusted in emergency operation, which control concept is used in emergency operation, which parts of the converter are no longer usable, which parts of the converter are usable, which subsystems of the converter are activated / deactivated, how the control signals are adjusted, which extent of service life reduction per unit of time is acceptable due to emergency operation, which maximum current may flow through the windings of the electric motor, which winding temperatures are permissible, which power should be delivered by the electric motor if possible, and the like.

[0023] In general, the present disclosure can ensure that an emergency shutdown can be avoided at least in some fault cases. The fault handling unit is used for this purpose. Knowledge about recoverable fault conditions can be stored in the fault handling unit – in whatever form. In particular, errors in the controllability of power semiconductors can be effectively handled in this way. Emergency operation may be more or less far removed from ideal operation of the converter, the electric motor, and / or the driven machine. Nevertheless, emergency operation can be more helpful than an emergency shutdown system, at least in individual application scenarios.

[0024] The converter can be implemented in various ways. In one embodiment, the converter is implemented entirely in hardware. In another embodiment, the converter is implemented using a combination of hardware and software, which makes the response to fault conditions more flexible, in particular. The hardware can comprise power semiconductors, amplifiers, sensors, analog-to-digital converters, filters (e.g., high-pass, low-pass, or band-pass filters), processor(s) (e.g., microcontroller, digital signal processor, or ASIC (Application Specific Integrated Circuit)), and / or a programmable logic circuit (e.g., an FPGA (Field Programmable Gate Array) or CPLD (Complex Programmable Logic Device)). Furthermore, one or more memories can be present, for example, RAM (Random Access Memory), ROM (Read Only Memory), or flash memory, which other hardware components can access.Software can control the individual components of the converter. Depending on the converter's implementation, the various units can also be designed differently. For example, the error detection unit can be implemented as a dedicated electrical unit, such as an integrated circuit, or as a logical function block of a software or logic circuit.

[0025] In one embodiment, the error handling unit is designed to identify faulty control states and / or fault-free control states, wherein the identification of the faulty or fault-free control states is preferably based on a received error signal. This embodiment is particularly helpful when a fault is caused by a power semiconductor of the converter output stage that can no longer be controlled. By knowing the faulty or fault-free control states, the error handling unit can specifically use the still usable control states for emergency operation.

[0026] In one embodiment, the emergency operation parameterization causes the converter control unit to generate adapted control signals for the converter output stage such that only control states of the converter output stage that are recognized as fault-free are used to generate the converter output voltage. By using only control states that are recognized as fault-free, the converter output voltage can still be sufficiently influenced and emergency operation can be enabled. It should be noted that a fault-free control state does not necessarily mean that a fault-free power semiconductor is activated. For example, with a permanently low-resistance power semiconductor, the use of the other power semiconductor in the same branch is excluded, as this would result in a short circuit.For example, if the low-side power semiconductor is permanently low-resistance, the high-side power semiconductor can no longer be used and must remain permanently switched off. Nevertheless, all switching states of the converter can be realized in which the affected low-side power semiconductor is switched on.

[0027] In one embodiment, the converter output stage has a plurality of converter branches, wherein each of the plurality of converter branches comprises at least one switching device. The at least one switching device of the plurality of converter branches is switched based on the control signals, and the converter control unit generates the adapted control signals such that the switching devices are controlled according to a fault-free control state. This creates effective converter bridges. A power semiconductor is preferably used as the switching device.

[0028] In one embodiment, the converter output stage can be controlled by the converter control unit during normal operation such that the at least one converter output voltage comprises an alternating voltage with a variable amplitude and / or variable frequency. This allows a wide variety of electric motors to be controlled.

[0029] In one embodiment, a period of the alternating voltage in emergency operation comprises at least one emergency operation section and one normal operation section, wherein the emergency operation section is disjoint from the normal operation section and wherein the time profile in the emergency operation section differs from that of the alternating voltage in normal operation. Dividing a period of the alternating voltage into a normal operation section and an emergency operation section makes it possible to concentrate an adaptation of the control for emergency operation on the emergency operation section. In the normal operation section, the control of the converter output stage can, in principle, take place as in normal operation. The adaptation of the control can also mean that the converter output stage is not controlled at all.

[0030] In one embodiment, the converter control unit controls the converter output stage before an emergency operating phase in such a way that the output converter output voltage can generate a higher torque in the controlled electric motor than during normal operation. In this way, additional energy can be introduced into the electric motor during the fault-free control phase. This can be achieved, for example, by lengthening the resulting voltage vector during space vector modulation shortly before leaving the normal operating phase, thereby increasing the output power of the converter. In this way, additional kinetic energy is introduced into the electric motor; however, due to the moment of inertia of the rotor and / or components of the driven parts of the work machine, this energy is not significantly expressed in a change in rotational speed.Nevertheless, the additional kinetic energy can contribute to the smoother traversal of the emergency operation section. Leaving a normal operation section or an emergency operation section "before" means that the corresponding measure is initiated a few degrees of electrical rotation before the emergency operation section. The range should not be chosen too small to achieve a sufficient effect. At the same time, the range should not be too large so as not to severely impair the synchronous operation of the electric motor. Therefore, the range before the emergency operation section is between 1° and 15° in one design, and between 5° and 10° in another design. The same applies to the extension of the voltage vector. An extension that is too small has only a minor effect on the additional energy introduced.A voltage vector that is too large can lead to problematic conditions, such as excessive currents through the electric motor. Therefore, the extension of the voltage vector is greater than or equal to 3% of the "normal" length in one embodiment, greater than or equal to 5% in another embodiment, and greater than or equal to 10% in another embodiment. On the other hand, the extension is less than or equal to 30% in one embodiment, less than or equal to 20% in another embodiment, and less than or equal to 15% in another embodiment.

[0031] In one embodiment, the converter control unit controls the converter output stage before a normal operating phase in such a way that a field weakening is induced in the electric motor in order to facilitate the entry of the electric motor's rotor into the normal operating phase. This can be achieved by applying a lead angle to a resulting voltage vector of a space vector modulation. In this way, for example, in a PMSM, the rotor can already be pulled subtly asynchronously in a defined direction. In a field-oriented control, this can mean, for example, that the field-forming current I dbefore leaving the emergency operation section. It may be advisable not to leave the adjustment constant, but to change it depending on the electrical angle of rotation in order to avoid current components adding up to an overcurrent. The "before" a normal operation section means that the corresponding measure is initiated a few degrees of electrical rotation before leaving the emergency operation section. The range selected should not be too small in order to achieve a sufficient effect. At the same time, the range should not be too large in order not to cause an overcurrent. Therefore, the range before the normal operation section is between 1° and 15° in one design, and between 5° and 10° in another design. Here, too, the field weakening should neither be too small nor too large.The degree of field weakening chosen depends on various factors, such as the technology used for the electric motor and the driven machine.

[0032] In one embodiment, the converter additionally has an error detection unit, wherein the error detection unit is connected to the error input of the error handling unit, wherein the error detection unit is designed to monitor at least parts of the converter and / or the electric motor and / or the driven machine and, upon detection of an error, to generate an error signal and to output the error signal to the error input. In this way, a unit can be created that can monitor the operating state of the converter, the electric motor and / or the driven machine, thus avoiding dependence on external error information. The error detection unit can use a wide variety of units, to whose measured values ​​or information the error detection unit may or can generally have access.The fault information can originate from units in the converter, the electric motor, or the working machine. However, sensors dedicated to fault detection can also be provided. Preferably, the fault detection unit accesses information already available in other contexts. This avoids additional costs.

[0033] In one embodiment, the fault detection unit is connected to one or more sensors for monitoring at least parts of the converter, wherein the sensor(s) are designed to detect status values ​​within the converter and / or the electric motor and / or the driven machine, and wherein the sensor(s) are preferably designed to detect a current, a voltage, a temperature, a phase position, a rotor position, a resistance, and / or their temporal progression. By using one or more sensors, information about the converter itself, the electric motor, and / or the driven machine, and their operating states can be obtained in a targeted and reliable manner. Detecting a current, for example at the converter input or at the input of the converter output stage, can identify short circuits, at least temporarily.Detecting a voltage, for example at the converter output, can provide information about the quality of voltage generation. Detecting a temperature, for example of the power semiconductor, can provide information about the usability of the power semiconductor. For example, in a MOSFET, the power loss is particularly high in an undefined switching state, resulting in particularly high heat generation. Detecting a phase position, for example several phases of the converter output voltage against each other, provides information about the quality of the converter output voltage generation. Detecting a rotor position can give an indication of whether the rotor of the electric motor is in a target position at a given time. Detecting a resistance allows you to detect a deviation from a target state.Measuring resistance can also affect the power semiconductor itself, evaluating the resistance in the closed or open state. Analyzing a time profile can provide insights into the function of the power semiconductor.

[0034] If a fault to be detected originates from a power semiconductor that is no longer usable, the identification of usable and / or unusable control states can be done, for example, via a current measurement. If, for example, a high-side power semiconductor has a permanently low resistance, the measured motor current is no longer approximately sinusoidal in the case of flat-top or space vector modulation. If, for example, a low-side power semiconductor has a permanently low resistance, switching the high-side power semiconductor would cause a short circuit and thus an increased current flow into the converter input. If the high-side power semiconductor or the low-side power semiconductor has a permanently high resistance state, the motor current would also no longer be approximately sinusoidal. These fault patterns can also be identified in a similar way via a voltage measurement in the motor phase.

[0035] In one embodiment, the converter output stage is connected to the error input of the error handling unit and is configured to output an error signal to the error input upon detection of an error condition. This allows coupling directly from the converter output stage to the error handling unit and direct utilization of detected errors.

[0036] In one embodiment, the converter further comprises an output interface, wherein the error detection unit is communicatively connected to the output interface and is designed to output an error message via the output interface upon receipt of an error signal. In this way, the converter can immediately communicate the detected error externally upon detection of an error. This allows a faster response to the failure. The output interface can be connected to a communication unit (for example, for a wide-area network such as a cellular network), a relay output, a higher-level control unit, or the like. In this way, the converter can be integrated into an Industry 4.0 environment, which enables immediate initiation of maintenance work and / or immediate response to emergency operation or impending failure.The communicating connection between the error detection unit and the output interface enables direct forwarding of an error message.

[0037] In one embodiment, the converter additionally comprises a memory in which framework conditions characterizing emergency operation are stored, wherein the error handling unit is designed to read at least individual framework conditions from the memory and to take them into account when generating the emergency operation parameterization. In this way, emergency operation can be influenced in a targeted manner. The framework conditions characterizing emergency operation can include, for example, the extent of the deviation from a target curve of the voltage, current and / or torque, the intensity of a vibration of the electric motor during emergency operation, an expected maximum reduction in service life as a result of emergency operation, a maximum permissible current in the motor windings during emergency operation, or the like. It should be noted that this list is merely exemplary and should not be understood as complete or restrictive.Regarding the design of the memory, it may be advisable for the memory to be non-volatile.

[0038] In one embodiment, the converter input voltage comprises a direct voltage or an alternating voltage, and the converter output voltage, during normal operation, comprises a multi-phase alternating voltage system with variable amplitude and / or variable frequency. A supply from a direct voltage offers the advantage of reducing the control effort required for the converter. The direct voltage can also originate from a direct current intermediate circuit, meaning that connection to a three-phase network can also fall under this embodiment. Supplying from an alternating voltage offers the advantage that conventional power supply networks can be used to power the converter. In this case, a direct current intermediate circuit can be part of the converter. Outputting a multi-phase alternating voltage system allows the converter output voltages to be directly coupled into the windings of the electric motor.By changing the amplitude, the torque can be influenced, and by changing the frequency, the speed of the electric motor can be influenced.

[0039] In one embodiment, the electric motor is part of a working machine, the working machine is formed by a pump or a compressor and the converter is designed to control the electric motor of the pump or compressor.

[0040] Pumps and compressors, in particular, are frequently used in safety-critical application scenarios and can particularly benefit from the emergency operation disclosed here. Adapting the converter, particularly with regard to the generated emergency operation parameterization, to a pump or compressor enables an improved response to fault conditions while taking the driven machine into account.

[0041] Further features and advantages of the invention will become apparent from the following description of non-limiting embodiments of the invention, which are explained in more detail below with reference to the drawings. In this drawing, schematically show: Fig. 1 is a block diagram with functional blocks of an embodiment of a converter according to the present disclosure, Fig. 2 a partial circuit diagram of an embodiment of a converter output stage with a full bridge with three converter branches, Fig. 3 a diagram with voltage vectors for a space vector modulation for a normal operation of the converter output stage according to Fig. 3, Fig. 4 a diagram with voltage vectors in a space vector modulation for emergency operation in the event of a fault in a power semiconductor of the converter output stage according to Fig. 3, Fig. 5 is a flowchart showing steps of an embodiment of a method according to the present disclosure and Fig. 6 a flowchart of an embodiment of a method according to the present disclosure for determining an emergency operation parameterization.

[0042] In the different figures, parts that are equivalent in terms of their function are always provided with the same reference symbols, so that they are usually only described once.

[0043] Fig. 1 shows a block diagram with functional blocks of an embodiment of a converter according to the present disclosure. The converter 1 is supplied with a converter input voltage from a power supply network 2 and controls an electric motor 3. The power supply network 2 is designed as a three-phase AC network and is connected to a converter input 4 of the converter 1. The electric motor 3 is connected to a converter output 5 of the converter 1. The converter input voltage input to the converter input 4 is first input to an input stage 6. The input stage 6 comprises line filters, for example, for reducing line harmonics and for protecting the converter 1 from overvoltages and overcurrents, and a rectifier for rectifying the converter input voltage.The output voltage of the input stage 6 is input to an intermediate circuit 7, which, in particular, has an intermediate circuit capacitor for smoothing and buffering the intermediate circuit DC voltage. The intermediate circuit DC voltage at the output of the intermediate circuit 7 is input to the central electronics 8 of the converter 1. The central electronics 8 includes, among other things, a converter output stage 9, a converter control unit 10, and an error handling unit 11.

[0044] In the lower part of the Fig. 1, individual components of the central electronics 8 (outlined with dotted lines) are shown in more detail. The central electronics 8 comprises, in addition to the error handling unit 11, a control signal generator 12, a first filter 13, a driver 14, a second filter 15, safety circuitry 16, power semiconductors 17 (e.g., IGBTs), anti-parallel diodes 18, a switched-mode power supply 19, and a DC / DC converter 20. For example, the error handling unit 11, the control signal generator 12, and other computer-implementable units can be implemented in a microprocessor. The converter output stage 9 and the converter control unit 10 are located in the lower part of the Fig. 1 is not explicitly shown. However, the power semiconductors 17 are an integral part of the converter output stage 9, and the control signal generator 12 is an integral part of the converter control unit 10.

[0045] The task of the control signal generator 12 is to output a control signal that is conditioned by the first filter 13, amplified in the driver 14, and input to the power semiconductors 17 via the second filter 15 and the safety circuit 16. The anti-parallel diodes 18 are each connected in parallel to the power semiconductors 17 and function as freewheeling diodes. The switched-mode power supply 19 generates a supply voltage for the central electronics 8, for example, from the intermediate circuit DC voltage. The DC / DC converter 20 stabilizes the output voltage of the switched-mode power supply 19 and / or generates multiple voltage levels and / or isolates the supply to a secondary side of the driver 14. The error handling unit 11 can monitor various states within the converter 1.Examples include the intermediate circuit DC voltage, the output voltages of the power semiconductors 17, the supply voltage at the output of the DC / DC converter 20 or the status of the control signal generator 12.

[0046] In Fig. 2 shows the interaction of power semiconductor 17 and electric motor 3 in more detail. The power semiconductors 17 are in the Fig. 2, each is designed as a MOSFET. The electric motor 3 has three rotor windings connected in a star configuration, symbolized here as coils L1, L2, and L3, and fed by the phases U, V, and W of the converter. The power semiconductors 17 are connected in a full bridge with three converter branches, with each converter branch comprising a high-side MOSFET and a low-side MOSFET. The MOSFETs are designated according to their function as high-side or low-side MOSFETs, respectively, and assigned to the respective phase, i.e., HSU, LSU, HSV, LSV, HSW, and LSW.

[0047] Fig. Figure 3 shows a diagram with voltage vectors that can be directly controlled by activating one or more power semiconductors 17. When labeling the voltage sectors, a 0 means that the low-side MOSFET is on, and a 1 that the high-side MOSFET is on. The label 010 therefore means that LSW, HSV, and LSU are on, while HSW, LSV, and HSU are off. In this way, the electrical angles 0°, 60°, 120°, 180°, 240°, and 300° can be directly controlled. The zero vector is formed by 000 or 111. Voltage vectors between two directly controllable voltage vectors can be generated by alternating between the directly controllable voltage vectors and the zero vector.

[0048] In Fig. Figure 4 illustrates the consequences of a failure of the high-side MOSFET HSU, where the MOSFET can no longer be controlled and is permanently high-impedance. In this case, all control states in which the high-side MOSFET HSU must be switched are unusable. This means that the electrical angles 0°, 60°, and 300° can no longer be controlled. However, the electrical angles 120°, 180°, and 240° can still be controlled. The zero vector can be controlled by 000. Accordingly, the period of the alternating voltage is divided into an emergency operating section 21 and a normal operating section 22. The vectors in the emergency operating section 21 are shown as dashed lines, while the vectors in the normal operating section 22 are shown as solid lines.Before the change from emergency operation section 21 to normal operation section 22 (for example between 80° and 90°), the entry into the normal operation section can be prepared by field weakening, and before the change from normal operation section 22 to emergency operation section 21 (for example between 260° and 270°), additional energy can be introduced by increasing the voltage vector.

[0049] Fig. 5 shows a flowchart with steps of an embodiment of a method according to the present disclosure. In step S1, the error handling unit 11 receives an error signal via its error input, thereby signaling the presence of an error to the error handling unit. In step S2, the error handling unit 11 generates an emergency operation parameterization based on the error signalization, which is output to the converter control unit 10 in step S3. In step S4, the converter control unit 10 generates control signals for emergency operation based on the emergency operation parameterization. In step S5, the control signals are output by the converter control unit 10 to the converter output stage 9. In this way, the electric motor 3 can continue to be controlled in emergency operation in the event of a fault. The goal here is to continue to use control states that can be used without errors.

[0050] Fig.6 shows the flowchart of an embodiment of a method according to the present disclosure, in which an emergency operation parameterization is to be determined and output to the converter control unit. Step S10 indicates regular operation, in which the electric motor 3 can be operated in normal mode. In step S11, error detection is active, in which the converter 1, the electric motor 3 and / or the driven machine (not shown) are checked for the presence of an error. In step S12, a check is made to determine whether such an error exists. If this is not the case ("n"), the system returns to step S10. If an error has been detected ("y"), the error is identified in more detail in step S13. For this purpose, measured values ​​from sensors, status information from converter units, or other information can be requested and / or used.In step S14, a check is carried out to determine whether the identified fault permits emergency operation and, in particular, whether modulation of the power semiconductors 17 is possible in emergency operation. If this is not the case (“n”), an emergency shutdown of the working machine is initiated in step S15. If emergency operation is possible (“y”), an emergency operation parameterization is created and emergency operation is prepared in step S16. If fault case “A” is detected, the associated emergency operation parameterization is generated in step S17 and output to the converter control unit 10. Generating the emergency operation parameterization can also include loading a predefined parameterization from a memory. If fault case “B” is detected, the associated emergency operation parameterization is generated in step S18, output to the converter control unit, and used there for emergency operation. The same applies to fault case “C” and step S19.

[0051] With regard to further advantageous embodiments, reference is made to the general part of the description and to the appended claims in order to avoid repetition. List of reference symbols 1 inverter 2 Energy supply network 3 electric motor 4 Inverter input 5 Inverter output 6 Rectifier / input filter 7 intermediate circuit 8 central electronics 9 Inverter output stage 10 Inverter control unit 11 Error handling unit 12 Control signal generator 13 first filter 14 drivers 15 second filter 16 Safety circuit 17 power semiconductors 18 antiparallel diodes 19 Switching power supply 20 DC / DC converters 21 Emergency Operation Section 22 Normal operating section

Claims

[1] Converter for controlling an electric motor, preferably an electric motor of a working machine, with a converter input (4), a converter output (5), a converter control unit (10) and a converter output stage (9), wherein the converter control unit (10) is designed to generate control signals based on a parameterization and to output the control signals to the converter output stage (9) and wherein the converter output stage (9) is designed to generate at least one converter output voltage from at least one converter input voltage applied to the converter input (4) based on control signals received from the converter control unit (10) and to output it to the converter output (5) for controlling the electric motor (3), characterized bythat the converter (1) additionally comprises an error handling unit (11) with an error input, wherein an error signal for signaling an error can be input into the error input, that the error handling unit (11) is designed to generate an emergency operation parameterization based on a received error signal and to output it to the converter control unit (10), and that the converter control unit (10) is designed to control the converter output stage (9) based on a received emergency operation parameterization in such a way that the electric motor can continue to be operated in emergency operation. [2] Converter according to claim 1, characterized byin that the error handling unit (11) is designed to identify faulty control states and / or fault-free control states, wherein the identification of the faulty or fault-free control states is preferably based on a received error signaling. [3] Converter according to claim 2, characterized by that the emergency operation parameterization causes the converter control unit (10) to generate adapted control signals for the converter output stage (9) in such a way that only control states of the converter output stage recognized as error-free are used when generating the converter output voltage. [4] Converter according to one of claims 1 to 3, characterized bythat the converter output stage (9) has a plurality of converter branches, that each of the plurality of converter branches comprises at least one switching device (HSU, LSU, HSV, LSV, HSW, LSW), that the at least one switching device (HSU, LSU, HSV, LSV, HSW, LSW) of the plurality of converter branches is switched based on the control signals and that the converter control unit (10) generates the adapted control signals such that the switching devices (HSU, LSU, HSV, LSV, HSW, LSW) are controlled which correspond to a fault-free control state. [5] Converter according to one of claims 1 to 4, characterized by in that in the emergency operation, a period of the alternating voltage comprises at least one emergency operation section (21) and one normal operation section (22), wherein the emergency operation section (21) is disjoint from the normal operation section (22) and wherein in the emergency operation section (21) there is a temporal profile which differs from the alternating voltage in a normal operation. [6] Converter according to claim 5, characterized by that the converter control unit (10) controls the converter output stage (9) before an emergency operation section (21) in such a way that the output converter output voltage can generate a torque in the controlled electric motor (3) which is increased compared to normal operation. [7] Converter according to claim 5 or 6, characterized by that the converter control unit (10) controls the converter output stage (9) before a normal operating section (22) in such a way that a field weakening is caused in the electric motor (3) in order to facilitate entry of the rotor of the electric motor (3) into the normal operating section (22). [8] Converter according to one of claims 1 to 7, which additionally has an error detection unit, wherein the error detection unit is connected to the error input of the error handling unit (11), wherein the error detection unit is designed to monitor at least parts of the converter (1) and / or the electric motor and / or the working machine and, upon detection of an error, to generate an error signal and to output the error signal to the error input. [9] Converter according to claim 8, characterized bythat the fault detection unit is connected to one or more sensors for monitoring at least parts of the converter (1), wherein the sensor(s) is / are designed to detect state values ​​within the converter (1) and / or the electric motor and / or the working machine, and wherein the sensor(s) is / are preferably designed to detect a current, a voltage, a temperature, a phase position, a rotor position, a resistance and / or their temporal progression. [10] Converter according to one of claims 1 to 9, characterized by that the converter output stage (9) is connected to the error input of the error handling unit (11) and is designed to output an error signal to the error input upon detection of an error condition. [11] Converter according to one of claims 1 to 10, further comprising an output interface, wherein the error detection unit (11) is communicatively connected to the output interface and is designed to output an error message via the output interface upon receipt of an error signal. [12] Converter according to one of claims 1 to 11, which additionally comprises a memory in which framework conditions characterising the emergency operation are stored, wherein the error handling unit is designed to read at least individual framework conditions from the memory and to take them into account when generating the emergency operation parameterisation. [13] Converter according to one of claims 1 to 12, characterized bythat the converter input voltage comprises a direct voltage or an alternating voltage and the converter output voltage in normal operation comprises a multi-phase alternating voltage system with variable amplitude and / or variable frequency. [14] Converter according to one of claims 1 to 13, characterized by that the electric motor (3) is part of a working machine, that the working machine is formed by a pump or a compressor and that the converter (1) is designed to control the electric motor of the pump or the compressor. [15] Working machine, preferably a pump or a compressor, comprising an electric motor driving the working machine and a converter controlling the electric motor, wherein the converter is designed according to one of claims 1 to 14. [16] Method for controlling an electric motor using a converter, preferably a converter according to one of claims 1 to 14, wherein the converter has a converter control unit and a converter output stage, and wherein the converter output stage, in normal operation, generates at least one converter output voltage from at least one converter input voltage based on control signals received from the converter control unit and outputs it for controlling the electric motor, comprising: Receiving (S1) an error signal by means of an error input of an error handling unit (11), Generating (S2) an emergency operation parameterization based on the error signaling by the error handling unit (11), Output (S3) of the emergency operation parameterization to the converter control unit (10), Generation (S4) of control signals by the converter control unit (10) based on the emergency operation parameterization and Outputting (S5) the control signals to the converter output stage (9) for continued operation of the electric motor (3) in emergency mode, wherein the emergency parameterization is generated and / or used in such a way that switching elements (HSU, LSU, HSV, LSV, HSW, LSW) of the converter output stage (9) are operated in control states that can be used without errors.

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