Control method for modular brake actuator

Abstract

The invention relates to a method for operating a modular brake actuator (1), the modular brake actuator (1) comprising at least one sub-module (2) and a brake resistor (3), which are arranged in a series circuit (4). In order to improve the functionality of the modular brake actuator, it is provided that a square-wave or trapezoidal voltage (uBR) is generated by means of the at least one submodule (1), said square-wave or trapezoidal voltage (uBR) having an alternating component (uBR, aDC) which is dimensioned in such a way that the time-averaged electrical energy absorbed by the modular brake actuator (1) is converted into heat in the brake resistor (3). The invention further relates to a control device (10) which is designed to carry out such a method. The invention further relates to a modular brake actuator (1), the modular brake actuator (1) comprising at least one sub-module (2) and a brake resistor (3) which are arranged in a series circuit (4), a square wave or trapezoidal voltage (uBR) being generated by means of the at least one sub-module (1), the modular brake actuator (1) having a control device (10) of this type, the control device (10) being designed to control the modular brake actuator (1). For open-loop or closed-loop control of at least one sub-module (2). The invention further relates to a modular drive unit (20) having a modular multilevel converter (21) and such a modular brake actuator (1), the modular brake actuator (1) being electrically connected to the DC voltage side of the modular multilevel converter (21).

Description

Technical Field

[0001] The invention relates to a method for operating a modular brake actuator, wherein the modular brake actuator comprises at least one submodule and a brake resistor, which are arranged in a series circuit. The invention also relates to a control device, which is suitable for carrying out such a method. The invention also relates to a modular brake actuator, which comprises at least one submodule and a brake resistor, which are arranged in a series circuit, wherein the modular brake actuator has such a control device for open-loop or closed-loop control of at least one submodule. The invention also relates to a modular drive unit, comprising a modular multilevel rectifier and such a modular brake actuator, wherein the modular brake actuator is electrically connected to the DC voltage side of the modular rectifier. Background Art

[0002] A modular multilevel converter has been disclosed in DE 10103 031A1. This converter, also known as M2C or MMC, has a converter topology that is particularly suitable for medium and high voltage applications because it includes submodules. The basic structure of the multiphase converter includes two converter arms per phase, each converter arm having a series circuit of submodules. Here, the two converter arms are connected to each other at the phase terminals. The other side of the converter arm is connected to the DC voltage side. The AC voltage side of the modular multilevel converter is formed by one or more phase connections. Using the basic structure of the converter, energy can be transmitted bidirectionally between the DC voltage side and the AC voltage side, or partially buffered.

[0003] To further allow for selective energy consumption, it is appropriate to install a brake actuator. A modular brake actuator is disclosed in WO 2007 / 023061 A2. A modular brake actuator is typically connected to the direct voltage side of a modular multilevel converter, for example between the DC+ and DC- terminals.

[0004] The resistor of a brake actuator device is often also called a brake resistor, because it is suitable for converting the electrical energy of the electric motor generated by the braking process into heat. The use of brake actuators is not limited to applications for braking electric drives. In other words, it is not necessarily limited to applications where the braking energy is converted into heat. For example, brake actuators can also convert electrical energy from the energy supply network into heat in order to stabilize the energy supply network. The term brake resistor was chosen in order to distinguish resistors that convert a specific amount of electrical energy or power into heat or heat per unit time from other resistors.

[0005] Hereinafter, the so-called power converted into heat means that the integral of the power over time is converted into heat. In other words, the energy generated by the power over time is converted into heat. Summary of the invention

[0006] The object of the present invention is to improve a modular brake actuator.

[0007] The object is achieved by a method for operating a modular brake actuator, wherein the modular brake actuator comprises at least one submodule and a brake resistor, wherein the submodule and the brake resistor are arranged in a series circuit, and a square wave or trapezoidal voltage is generated by the at least one submodule, wherein the square wave or trapezoidal voltage (u BR ) has an AC component (u BR，aDC ), the AC component being dimensioned such that the time-averaged electrical energy absorbed by the modular brake actuator (1) is converted into heat in the brake resistor (3). The object is also achieved by a control device, which is designed to carry out the method. The object is also achieved by a modular brake actuator, wherein the modular brake actuator comprises at least one submodule and a brake resistor, the submodule and the brake resistor being arranged in a series circuit, wherein a square wave or trapezoidal voltage can be generated by at least one submodule, wherein the brake actuator has such a control device for modular open-loop or closed-loop control of at least one submodule. The object is also achieved by a modular drive unit, wherein the modular drive unit comprises a modular multilevel converter and such a modular brake actuator, wherein the modular brake actuator is electrically connected to the DC voltage side of the modular multilevel converter.

[0008] Further advantageous embodiments of the invention are specified in the dependent claims.

[0009] The invention is based on the recognition that any operating voltage of the brake actuator can be realized by means of a modular construction of a modular brake actuator. Usually, a modular brake actuator is connected to an intermediate circuit of a rectifier in order to convert electrical energy from a drive system or an electrical power supply system into heat. By means of a modular construction, the modular brake actuator can be adapted to any level of intermediate circuit voltage by using a corresponding number of submodules.

[0010] In this case, all known types of submodules can be used as submodules. For example, half-bridge modules, double half-bridge modules or full-bridge modules. To generate the voltage, a capacitor voltage or a plurality of capacitor voltages of the respective submodule can be used alone. Alternatively, it is also possible to generate a voltage that is smaller than the capacitor voltage or the plurality of capacitor voltages, for example by using pulse width modulation. In particular, pulse width modulation has proven to be an advantageous method for generating different voltages when only one submodule is used.

[0011] Furthermore, the method allows precise open-loop or closed-loop control of the power converted into heat in the modular brake actuator. The heat is derived from the time integral of the power. The method provides that not all of the intermediate circuit voltage is consumed in the braking resistor during the energy conversion process. This has the advantage that the power converted into heat can be controlled in a closed-loop manner. At the same time, the energy content of a capacitor or capacitors of at least one submodule or of a plurality of submodules is controlled in a closed-loop manner. As a result, stable operation of the modular brake actuator is possible even over longer operating times, in particular for continuous operation.

[0012] The brake resistor can be arranged at any position in the series circuit. For example, the brake resistor can be arranged between one of the terminals of the modular brake actuator and a submodule, or at any desired position between two submodules.

[0013] When the modular brake actuator is inactive, ie does not need to convert electrical energy into heat, the voltage across at least one submodule or a further series connection of submodules is identical to the intermediate circuit voltage, so that there is no voltage drop across the resistor and no current flows.

[0014] For open-loop or closed-loop control, a voltage is generated on at least one submodule or, if a plurality of submodules are arranged in a series circuit, on a further series circuit of submodules. For open-loop or closed-loop control of the power to be converted into heat, the DC component of the voltage is used for this purpose. For closed-loop control of a capacitor voltage or a plurality of capacitor voltages of one or more submodules, an AC component is superimposed on the DC component. The voltage assumes a square-wave shape due to the superposition of the DC component and the AC component. The square-wave shape in turn requires that the voltage in the further series circuit can change as fast as desired. This results in an unlimited rate of voltage rise. Since these voltages induce corresponding currents, it has proven to be advantageous to limit the speed of the voltage change. Since the voltage change is accompanied by currents, the modular brake actuator is also suitable for brake actuators with inductances, for example parasitic inductances as brake resistors. The square-wave voltage is then transformed into a trapezoidal voltage.

[0015] It has proven to be advantageous that, with relatively small amplitudes of both the voltage on the other series circuit of the submodule and the current flowing through the modular brake actuator, high energy can be exchanged by means of a square wave or trapezoidal voltage, since the energy comes from the time integral of the current, or from the integral of the square of the current. This means that high power can be achieved. This high power is related to the power converted into heat and the power used to stabilize the submodule. In other words, due to the relatively small values ​​of the current and voltage, in particular the small amplitude or small maximum value in the current and voltage waveform, relatively high effective values ​​can be achieved, which are essential for the conversion into heat by the brake resistor. Due to the low amplitude or low fluctuation range caused by the use of square wave or trapezoidal voltage and its associated current, the semiconductor switches of the submodule can be designed to withstand lower current loads. Alternatively, a higher power can be converted into heat with the modular brake actuator.

[0016] A square-wave or trapezoidal voltage can be easily generated by a control device which activates semiconductor switches of submodules or other submodules of a series circuit.

[0017] It is particularly advantageous to combine a modular brake actuator with a modular multilevel rectifier (also called M2C rectifier) ​​to form a modular drive unit. For the modular multilevel rectifier and the modular brake actuator, identically constructed submodules can be used. The same hardware can also be used for the control of the submodules. Due to the modular construction of the rectifier and the modular brake actuator, the modular drive unit can be easily adjusted to the required power requirements by selecting a corresponding number of submodules in the rectifier and the modular brake actuator. Due to the identical design of the submodules in the modular brake actuator and the multilevel rectifier, a high proportion of common components can be achieved. This has a positive effect on the reliability and manufacturing costs of such a drive unit.

[0018] The modular brake actuator can be connected to the DC voltage side of a rectifier of any structure and is not limited to application with modular multilevel rectifiers.

[0019] In this case, the square wave or trapezoidal voltage has an AC component whose size is set so that the time-averaged electrical energy absorbed by the modular brake actuator is converted into heat in the braking resistor. The AC component can be used to influence the capacitor voltage of the submodule and stabilize the modular brake actuator. The AC component of the voltage causes a further AC component of the current in the modular brake actuator via a corresponding voltage drop across the braking resistor. In this case, the average values ​​of the AC component and the further AC component are both zero, so that only reactive power is exchanged via the further AC component of the current and the intermediate circuit voltage or the voltage across the modular brake actuator. It is advantageously shown that this part can be used to exchange energy between the capacitor and the resistor of the submodule. In this case, the energy exchange is controlled in an open-loop or closed-loop manner in an advantageous manner, so that the total effective power across the resistor is converted into heat. In this case, the time-averaged electrical energy absorbed by the modular brake actuator is converted into heat in the braking resistor. In this case, the relationship expressed in the equation is given,

[0020]

[0021] Among them, the current i passing through the braking resistor BR The DC component i BR，DC and AC component i BR，aDC Composition, according to

[0022] i BR =i BR,DC +i BR,aDC (3).

[0023] If we substitute equation (3) into equation (2), we can solve the resulting equation with respect to i BR，aDC The square wave or trapezoidal voltage waveform can be considered as follows. For the simple and idealized case of square wave voltage and current form, the AC component of the current is given by

[0024]

[0025] In order to make the current i BR，aDC The time average value of is zero, and in half the time the AC component is the component with the value of equation (4), and in the other half of the time it is the value corresponding to the negative operator. The resistance R must be correspondingly small enough so that equation (4) yields a positive value.

[0026] In order to generate this current, the AC component of the voltage of the other series circuit of the submodule has a value

[0027]

[0028] In order for the AC component to have a zero mean value over time at this voltage, the value calculated above is set to the AC component for half of the time and to the corresponding negative value for the remaining time.

[0029] In an advantageous embodiment of the invention, the modular brake actuator comprises a plurality of submodules which are arranged in a further series circuit, and a square wave or trapezoidal voltage is generated by the plurality of submodules in the further series circuit of the submodules. By using a plurality of submodules in the further series circuit, the operating voltage of the modular brake actuator can be adjusted as desired to the intermediate circuit voltage of the rectifier. In the drive unit, any desired level of operating voltage, i.e., intermediate circuit voltage, can be achieved.

[0030] In a further preferred embodiment of the invention, the square wave or trapezoidal voltage has a DC component which is controlled in an open-loop or closed-loop manner depending on the power that the modular brake actuator converts into heat or depending on the voltage applied to the modular brake actuator. By means of the DC component of the voltage, a current can be generated by the modular brake actuator, which current also has a further DC component. This DC component flows through the modular brake actuator and thus also through the brake resistor. In this case, the current flowing through the brake resistor generates electrical losses. These losses are used to purposefully convert electrical energy into heat. The power to be converted into heat, i.e. the energy per unit time, can be controlled in an open-loop or closed-loop manner by the size of the DC component of the voltage, since this directly determines the voltage drop across the resistor, thereby further determining the further DC component of the current through the modular brake actuator. Therefore, it has proven to be advantageous to control the DC component in an open-loop or closed-loop manner depending on the power to be converted into heat. In this case, the power can also depend on other variables, such as the voltage of the submodule capacitors of the modular multilevel converter. If the modular brake actuator is operated in an intermediate circuit with an intermediate circuit capacitor, for example in a two-position or three-position rectifier, it has proven to be advantageous to control the DC component in an open-loop or closed-loop manner, depending on the intermediate circuit voltage. Using such a closed-loop control structure, a dynamic control of the conversion of electrical power into heat can be achieved, thereby protecting the electric drive unit from overload caused by excess energy. This energy can be generated, for example, by a braking process of the electric machine.

[0031] In another preferred embodiment of the present invention, the DC component is controlled in an open-loop or closed-loop manner so that a current having an additional DC component is generated through the modular brake actuator, wherein the product of the additional DC component and the voltage on the modular brake actuator corresponds to a predetermined power converted into heat by means of the modular brake actuator, in particular a predetermined effective power converted into heat by means of the modular brake actuator. In this case, the DC component of the voltage is controlled in an open-loop or closed-loop manner in a voltage amplitude so that the additional DC component of the current is large enough so that the product of the intermediate circuit voltage and the additional DC component is equal to the power value converted into heat by the modular brake actuator. The power to be converted into heat is the energy converted into heat within a specified time. The intermediate circuit voltage is applied to the modular brake actuator because it is electrically connected to the intermediate circuit. Therefore, the intermediate circuit voltage is applied to the series circuit consisting of a brake resistor and an additional series circuit of a submodule. As an alternative to the additional series circuit of the submodule, it is also possible for only one submodule to be present. Therefore, the modular brake actuator to which the intermediate circuit voltage is applied absorbs effective power.

[0032] P BR =U D ·i BR,DC (1).

[0033] The entire effective power absorbed by the brake resistor should be converted into heat, since the modular brake actuator should not be designed to absorb and store significant energy. For example, the voltage difference between the square wave or trapezoidal wave can be controlled in a closed-loop manner using a PI controller in order to establish a predeterminable voltage across a capacitor or capacitors in the submodule. In other words, a further voltage component can be generated from the voltage at the capacitor or capacitors of the submodule to achieve a square wave or trapezoidal voltage, which voltage component can control the voltage across the capacitor in the submodule in a closed-loop or open-loop manner by means of a PI controller. Alternatively or in addition, the voltage steepness of the trapezoidal wave and / or the frequency of the trapezoidal wave or square wave can also be used to influence the voltage across the capacitor in the submodule.

[0034] In a further advantageous embodiment of the invention, the AC component is used as a control variable for the submodule capacitor voltage control. In order to be able to eliminate interference, it has proven effective to use the AC component value determined according to the formula for feedforward control. The voltage on the capacitor is then controlled in a closed-loop manner by means of closed-loop control. As a result, the modular brake actuator can operate stably even in the presence of interference quantities. In addition, the operation is not affected by the change quantity. For example, changes in the resistance value caused by aging or heating can be easily compensated by the control.

[0035] In a further advantageous embodiment of the invention, the AC voltage side of the modular multilevel converter is connected to an energy source, in particular to an energy supply network or an electric machine. The modular brake actuator can convert excess or unusable energy into heat by connecting to the energy source. The energy source can be, for example, an electric machine that feeds back electrical energy during the braking process. If this energy cannot be used further, it must be converted into heat by the modular brake actuator so that the mechanical brake is not used. Compared to mechanical brakes, the process of converting electrical energy into heat is wear-free, so that the use of modular brake actuators is more economical in operation.

[0036] Modular multilevel rectifiers can also be used for energy transmission. In this case, it may be wise to provide modular brake actuators if the transmitted energy cannot be received. This ensures that the energy transmission can continue to operate even when the energy reception is interrupted. The energy transmission system can continue to operate during such interruptions, thus reliably avoiding expensive shutdowns and restarts, which can also lead to stability problems for the energy supply network. Modular brake actuators thus also increase the reliability and availability of modular drive units for energy transmission.

[0037] In a further advantageous embodiment of the invention, the control device of the modular drive unit is designed to determine the power to be converted into heat as a function of the voltage of the capacitor of the modular multilevel converter submodule. In a modular multilevel converter, the energy stored in the converter is not necessarily represented by the intermediate circuit voltage as in a two-level or three-level converter. In a modular multilevel converter, an increased energy content influences the stored energy, i.e. the capacitor or the voltage of the capacitor in each submodule of the modular multilevel converter. In order to selectively reduce the energy content in the modular multilevel converter, it has proven to be advantageous to determine the power conversion of the DC component into heat for open-loop or closed-loop control as a function of the voltage of the capacitor of each submodule of the modular multilevel converter. A possible method for operating an electric drive unit with a modular converter and a proposed modular brake actuator controls the DC component of the voltage on the other series circuit of the submodules of the modular brake actuator in a closed-loop or open-loop manner, depending on the voltage of one or more capacitors of the submodule of the modular multilevel current converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be described and explained in detail below based on the embodiments shown in the figures.

[0039] Figure 1 shows a modular brake actuator,

[0040] Figures 2 to 4 shows an embodiment of a submodule,

[0041] Figures 5 to 8 shows the time curves of voltage and current, and

[0042] Figures 9 to 11 An embodiment of a modular drive unit is shown. DETAILED DESCRIPTION

[0043] Figure 1 A modular brake actuator 1 is shown. The modular brake actuator has a series circuit 4 of at least one submodule 2 and a braking resistor 3. The series circuit 4 can have a plurality of submodules 2. The submodules are further arranged as part of the series circuit 4 in a further series circuit 41. The modular brake actuator 1 is provided to be connected via its connection 11 to an intermediate circuit 9 of a rectifier.

[0044] By means of the further series connection 41 of the submodules, a voltage u BR . Through the voltage u BR , which is capable of generating a current i in the modular brake actuator 1 BR Current i BR The operating voltage U is applied to the modular brake actuator 1. D When the modular brake actuator 1 is connected to the intermediate circuit of the rectifier, the intermediate circuit voltage is applied to the modular brake actuator. In this case, the modular brake actuator 1 is said to be connected to the DC voltage side of the rectifier.

[0045] Figures 2 to 4 An embodiment of a submodule 2 is shown. All known submodules, in particular Figures 2 to 4 The submodules of are all suitable for executing the proposed method. To avoid repetition, see Figure 1 Description of and reference symbols introduced therein.

[0046] The exemplary embodiment of the submodule 2 shown comprises at least two semiconductor switches and at least one capacitor. By switching the semiconductor switches, an output voltage U can be generated at the connection of the submodule 2. sub In this case, the control device 10 transmits an activation signal to the semiconductor switch of the submodule 2. The control device 10 is preferably arranged outside the submodule 2 and is therefore not part of it. In practice, it has proven to be advantageous to use the control device 10 to control all submodules 2 of the modular brake actuator 1. In addition, the control device 10 is able to carry out the calculations required for the open-loop or closed-loop control of the voltage and current. Thus, the control device 10 is able to determine the power to be converted into heat by the modular brake actuator 1 according to the predetermined power value to be converted into heat. BR The required current. In order to generate this current i BRThe voltage on the submodule of the other series circuit 41 is controlled or determined by the control device 10 in an open-loop or closed-loop control manner through the corresponding activation signal. In the following embodiments, the display of the control device 10 is omitted for the sake of simplicity.

[0047] Figure 2 A so-called half-bridge module is shown. It has two semiconductor switches and a capacitor. A voltage U C，sub By switching the semiconductor switch, a zero or U can be generated at the connection of the submodule 2. C，sub The output voltage U sub .

[0048] Figure 3 A so-called double bridge module is shown. It has four semiconductor switches and two capacitors. A voltage U C1，sub and U C2，sub By switching the semiconductor switch, an output voltage U can be generated at the connection of the submodule 2. sub , which voltage can be zero, where a capacitor voltage U C1，sub , U C2，sub or capacitor voltage U C1，sub , U C2，sub sum.

[0049] Figure 4 The full-bridge module is shown in Figure 1. It has four semiconductor switches and a capacitor. A voltage U C，sub By switching the semiconductor switch, an output voltage U can be generated at the connection of the submodule 2. sub , which can be zero, a positive capacitor voltage, or a negative capacitor voltage ±U C，sub .

[0050] Figure 5 shows the voltage u across the submodule 2 of the further series circuit 41 in the proposed method. BR To avoid repetition, reference is made to Figures 1 to 4 The voltage u BR By the DC component u BR，DC and the AC component u BR，aDC The AC component is composed of and Therefore, the AC component u BR，aDC There is no DC component, that is, its average value is zero. BR，DC and the AC component u BR，aDC The voltage u is obtained by superposition. BRSince the voltage steepness of the AC component is limited, its value changes in the form of a ramp, so the voltage u BR If a high, ideally infinite edge steepness is assumed, the dotted line represents the change in the transition, resulting in a voltage u BR in the form of a square wave voltage.

[0051] Figure 6 The current i through the modular brake actuator 1 is shown by way of example BR , the current is given by Figure 5 The voltage curve is generated by the voltage u BR , a voltage is generated on the braking resistor 3, which causes a current i BR With another DC component i BR，DC and the other AC component i BR，aDC In order to distinguish the DC component from the AC component of the voltage, the DC component and the AC component of the current are referred to as an additional DC component and an additional AC component.

[0052] When the voltage across the further series circuit 41 of the submodule 2 is low, the voltage across the braking resistor 4 is high, so that the current i through the modular brake actuator 1 is BR Therefore, the current i through the braking resistor 3 is BR can depend on the AC component u BR，aDC The magnitude of is periodically negative. In other words, depending on the operating point, the amplitude of the AC component may be greater than the DC component. sub When a single-polarity unipolar module is used in the circuit, such as a half-bridge or a double half-bridge, the current i BR The minimum value of the modular brake actuator 1 is a negative value.

[0053] Figure 7 shows the voltage u across the further series circuit 41 of the submodule 2 of the modular brake actuator 1 BR The medium voltage range starts from a voltage of 1000V, also called 1kV. The DC component u BR，DC An AC component u is superimposed BR，aDC , thus obtaining the voltage u BR Voltage waveform. Between the time points t=0.34s and t=0.36s, the value of the power to be converted into heat changes. In the process shown, the power is reduced. This value is preset to the modular brake actuator 1 or its control device 10. For example, this value can be determined by the intermediate circuit U to which the modular brake actuator is connected. DThe voltage of the modular brake actuator 1 is obtained, or more generally, the voltage applied to the connection 11 of the modular brake actuator 1. Similarly, this value can also be determined based on the voltage across a capacitor or capacitors of a submodule of the modular multilevel converter connected to the modular brake actuator 1. The modular brake actuator 1 controls the increase of the DC component u by the control device 10. BR，DC At the same time, it is possible to BR The smaller fluctuation range identifies the smaller AC component u BR，aDC The AC component u BR，aDC Stabilizes the capacitor voltage U of submodule 2 C .

[0054] Figure 8 shows the current i through the modular brake actuator BR The relevant curve and its additional DC component i BR，DC The reduction in power can be detected by the lower current. In addition, starting from the time t = 0.35s, there is an operating point where the current i BR It periodically presents negative values. At the time point before t = 0.35s, the current is almost not obviously negative at the lowest point.

[0055] Figure 7 and Figure 8 The time curve of shows such a high rate of change that the time curve can be described as a block time curve.

[0056] Fig. 9 A modular drive unit 20 is shown with a modular multilevel rectifier 21 and a modular brake actuator 1. These are connected via an intermediate circuit 9, wherein the voltage U D is applied thereto. The modular multilevel converter 21 can (but does not necessarily) have the same submodule 2 as the modular brake actuator 1. The series circuit of the submodules 2 of the modular multilevel converter 21 also has an inductor 8 to improve the control performance of the modular multilevel converter 21. Terminals L1, L2, and L3 represent the AC voltage side terminals of the modular multilevel converter 21, or simply the AC voltage side. In this embodiment, the modular multilevel converter 21 is three-phase. Alternatively, a single-phase or arbitrary phase configuration with a neutral line can be achieved by arranging a corresponding number of phase modules in the modular multilevel converter 21.

[0057] exist Fig.10 , an embodiment of a modular drive unit 20 is shown. Therein, an energy source 5 is electrically connected to the AC voltage side of a modular multilevel converter 21. The energy source can be, for example, an energy supply network 6 or an electric machine 7.

[0058] exist Fig.11In the embodiment of the invention, the modular drive unit 20 has two modular multilevel converters 21 and a modular brake actuator 1, which are electrically connected to each other on the intermediate circuit 9. The first of the two modular multilevel converters 21 is connected to the energy supply network 6 on its AC voltage side, and the second of the two modular multilevel converters 21 is connected to the motor 7 on its AC voltage side. The motor 7 can obtain electrical energy via the energy supply network 6. For example, during braking, the energy of the motor 7 can be fed back into the energy supply network 6 via the modular drive unit 20. If the energy supply network 6 cannot receive it, the electrical energy generated by the motor 7 can be effectively converted into heat via the modular brake actuator 1. In this design, a worn mechanical brake can be omitted.

[0059] In summary, the invention relates to a method for operating a modular brake actuator 1, wherein the modular brake actuator 1 comprises at least one submodule 2 and a braking resistor 3, which are arranged in a series circuit 4. In order to improve the function of the modular brake actuator, it is proposed that a square wave or trapezoidal voltage u is generated by at least one submodule 1. BR , where the square wave or trapezoidal voltage u BR With AC component u BR，aDC , the size of the AC component is set so that the time-averaged electrical energy absorbed by the modular brake actuator 1 is converted into heat in the brake resistor 3. In addition, the invention relates to a control device 10 suitable for performing such a method. The invention also relates to a modular brake actuator 1, wherein the modular brake actuator 1 comprises at least one submodule 2 and a brake resistor 3, which are arranged in a series circuit 4, and a square wave or trapezoidal voltage u can be generated by at least one submodule 1 BR , wherein the modular brake actuator 1 has such a control device 10 for open-loop or closed-loop control of at least one submodule 2. The invention also relates to a modular drive unit 20, comprising a modular multilevel converter 21 and such a modular brake actuator 1, wherein the modular brake actuator 1 is electrically connected to the DC voltage side of the modular multilevel converter 21.

Claims

1. A method for operating a modular brake actuator (1), wherein: The modular brake actuator (1) comprises at least one submodule (2) and a brake resistor (3), wherein the submodule and the brake resistor are arranged in a series circuit (4), wherein a square wave or trapezoidal voltage (u BR ), wherein the square wave or trapezoidal voltage (u BR ) has an AC component (u BR，aDC ), the size of the AC component is set so that the time-averaged electrical energy absorbed by the modular brake actuator (1) is converted into heat in the brake resistor (3).

2. The method according to claim 1, wherein: The modular brake actuator (1) comprises a plurality of submodules (2), which are arranged in a further series circuit (41), wherein the square wave or trapezoidal voltage (u) is generated on the further series circuit (41) of the submodules (2) by means of the plurality of submodules (2). BR ).

3. The method according to claim 1 or 2, wherein: The square wave or trapezoidal voltage (u BR ) has a DC component (u BR，DC ), wherein the DC component (u BR，DC ) according to the power converted into heat by means of the modular brake actuator (1) or according to the voltage (U D ) is controlled in an open-loop or closed-loop manner.

4. The method according to claim 3, wherein: The DC component (u BR，DC ) is controlled in an open-loop or closed-loop manner so that a DC component (i BR，DC ) of the current (i BR ), wherein the additional DC component (i BR，DC ) and the voltage (U D ) corresponds to a predetermined power converted into heat by means of the modular brake actuator (1), in particular a predetermined effective power converted into heat by means of the modular brake actuator (1).

5. The method according to any one of claims 1 to 4, wherein: The AC component (u BR，aDC ) is used as the capacitor voltage (U C，sub ) is the control variable of the closed-loop control.

6. A control device (10) designed to execute the method according to any one of claims 1 to 5.

7. A modular brake actuator (1), wherein: The modular brake actuator (1) comprises at least one submodule (2) and a brake resistor (3), wherein the submodule and the brake resistor are arranged in a series circuit (4), wherein a square wave or trapezoidal voltage (u BR ), wherein, for the open-loop or closed-loop control of at least one of the submodules (2), the modular brake actuator (1) has a control device (10) according to claim 6.

8. The modular brake actuator (1) according to claim 7, wherein: The modular brake actuator (1) comprises a plurality of submodules (2) which are arranged in a further series circuit (41), wherein the square wave or trapezoidal voltage (u BR ).

9. A modular drive unit (20) having a modular multilevel converter (21) and a modular brake actuator (1) according to claim 7 or 8, wherein: The modular brake actuator (1) is electrically connected to the DC voltage side of the modular multi-level converter (21).

10. The modular drive unit (20) according to claim 9, wherein: The AC voltage side of the modular multilevel converter (21) is connected to an energy source (5), in particular to an energy supply network (6) or a motor (7).

11. The modular drive unit (20) according to claim 9 or 10, wherein: The control device (10) is designed to determine the power to be converted into heat as a function of the voltage of the capacitors of the submodules of the modular multilevel converter (21).

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