Control method for a modular brake actuator

Abstract

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 (uBR) is generated by means of the at least one submodule (1), wherein the square-wave or trapezoidal voltage (uBR) has an alternating portion (uBR,aDC), which is dimensioned such that the time-averaged electrical energy absorbed by means of the modular brake actuator (1) is converted to heat in the braking resistor (3). The invention also relates to a control device (10) designed for carrying out such a method. The invention further relates to 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), wherein a square-wave or trapezoidal voltage (uBR) can be generated by means of the at least one submodule (1), wherein the modular brake actuator (1) has such a control device (10) for controlling or regulating the at least one submodule (2). The invention further relates to a modular drive unit (20) having a modular multi-level power converter (21) and such a modular brake actuator (1), wherein the modular brake actuator (1) is electrically connected to a DC voltage side of the modular multi-level power converter (21).

Description

[0001]Description Control method for a modular brake actuator The invention relates to a method for operating a modular brake actuator, wherein the modular brake actuator comprises at least one submodule and a braking resistor arranged in a series circuit. The invention further relates to a control device configured to carry out such a method. Furthermore, the invention relates to a modular brake actuator, wherein the modular brake actuator comprises at least one submodule and a braking resistor arranged in a series circuit, wherein the modular brake actuator has such a control device for controlling or regulating the at least one submodule.The invention further relates to a modular drive unit comprising a modular multilevel power converter and such a modular braking controller, wherein the modular braking controller is electrically connected to a DC voltage side of the modular power converter. A modular multilevel power converter is known from DE 10103 031 A1. This power converter, also known as M2C or MMC, has a converter topology which, due to its structure with submodules, is particularly suitable for medium and high voltage applications. The basic structure of the multiphase converter comprises two converter arms per phase, each of which has a series connection of submodules. The two converter arms are connected to one another at the phase connection. The other side of the converter arms is connected to the DC voltage side. The AC voltage side of the modular multilevel power converter is formed by one or more phase connections.In its basic design, the converter can be used to bidirectionally transfer energy between the DC and AC voltage sides or to temporarily store it to a certain extent. To additionally enable targeted energy dissipation, the installation of a braking unit is advisable. A modular braking unit is known from WO 2007 / 023061 A2. The modular braking unit is typically connected to the DC side of the modular multilevel converter, for example, between a DC+ and a DC- connection. The resistance of a braking unit arrangement is often also referred to as a braking resistor, as it is suitable for converting electrical energy from an electrical machine, which is generated during a braking process, into heat. The use of a braking unit is not limited to the application of a braking electric drive.It is not necessarily braking energy that is converted into heat. The braking controller can, for example, also be used to stabilize a power grid by converting electrical energy from the power grid into heat. The term braking resistor was chosen to distinguish the resistor in which a given electrical energy or power is converted into heat or heat per unit time from other resistors. The term “power to be converted into heat” in the following means that the integral of the power over time is converted into heat. In other words, an amount of energy resulting from the power over time is converted into heat. The object of the invention is to improve a modular braking controller.This object is achieved by a method for operating a modular brake actuator, wherein the modular brake actuator comprises at least one submodule and a braking resistor which are arranged in a series circuit, wherein a block-shaped or trapezoidal voltage is generated by means of the at least one submodule, wherein the block-shaped or trapezoidal voltage (e.g. BR ) an alternating portion (u BR,aDC) which is dimensioned such that the electrical energy absorbed on average over time by the modular braking actuator (1) is converted into heat in the braking resistor (3). Furthermore, this object is achieved by a control device which is set up to carry out such a method. This object is further achieved by a modular braking actuator, wherein the modular braking actuator comprises at least one submodule and a braking resistor which are arranged in a series circuit, wherein a block-shaped or trapezoidal voltage can be generated by means of the at least one submodule, wherein the modular braking actuator has such a control device for controlling or regulating the at least one submodule.Furthermore, this object is achieved by a modular drive unit, wherein the modular drive unit has a modular multilevel power converter and such a modular braking controller, wherein the modular braking controller is electrically connected to a DC voltage side of the modular multilevel power converter. Further advantageous embodiments of the invention are specified in the dependent claims. The invention is based, among other things, on the finding that any operating voltage of the braking controller can be implemented due to the modular design of the modular braking controller. The modular braking controller is typically connected to the intermediate circuit of a power converter in order to be able to convert electrical energy from a drive system or a power supply system into heat. With the modular design, the modular braking controller can be adapted to any desired DC link voltage by using an appropriate number of submodules.All known types of submodules can be used as submodules. These include, for example, half-bridge modules, double half-bridge modules, or even full-bridge modules. The capacitor voltage or the capacitor voltages of the corresponding submodule alone can be used to generate voltages. Alternatively, it is also possible, for example, to use pulse-width modulation to generate a voltage through the submodule that is lower than the capacitor voltage or voltages. Pulse-width modulation has proven advantageous for generating different voltages, particularly when only one submodule is used. Furthermore, the method for operating the modular braking unit enables the power to be converted into heat to be precisely controlled or regulated. The heat is then calculated from the time integral of the power.The method ensures that not the entire intermediate circuit voltage drops across the braking resistor during energy conversion. The advantage lies in the ability to regulate the power converted into heat. At the same time, the energy content of the capacitor(s) of the at least one submodule(s) is regulated. This enables stable operation of the modular braking unit, even over longer operating periods, particularly for continuous operation. The braking resistor can be arranged anywhere in the series circuit. For example, the braking resistor can be arranged between one of the terminals of the modular braking unit and a submodule, or at any point between two submodules.In the event that the modular braking unit is not active, i.e. is not intended to convert electrical energy into heat, the voltage applied across the at least one submodule or the further series connection of submodules is identical to the intermediate circuit voltage, so that no voltage drop occurs across the resistor and therefore no current flows. For control or regulation, a voltage is generated across the at least one submodule or, if several submodules are arranged in a further series connection, across the further series connection of submodules. A DC component of the voltage is provided for the control or regulation of the power to be converted into heat. To regulate the capacitor voltage or the capacitor voltages of the submodule(s), an alternating component is superimposed on the DC component. The superposition of the DC component and the alternating component results in a block-shaped voltage curve.The block-shaped curve, in turn, requires that the voltages across the further series circuit can be changed as quickly as desired. This leads to an infinite voltage gradient. Since these voltages cause corresponding currents, it has proven advantageous to limit the rate of change of the voltage change. Due to the currents associated with the voltage changes, the modular braking unit is also suitable for braking units that have an inductance, for example as a parasitic inductance of the braking resistor. The block-shaped voltage then becomes a trapezoidal voltage. It has proven advantageous that the block-shaped ortrapezoidal voltage at comparatively low amplitudes of voltage across the further series connection of the sub-modules and of the current flowing through the modular braking unit, high energy can be exchanged, since the energy results from the time integral of the current or from the integral of the square of the current. This means that high performance can be achieved. This high performance refers to the power to be converted into heat as well as to the cable used to stabilize the sub-modules. In other words, due to the relatively low amounts of current and voltage, in particular low amplitudes or low maximum values ​​in the current and voltage curves, comparatively high rms values ​​can be achieved, which are decisive for conversion into heat by the braking resistor. Due to the low amplitude and low fluctuation range through the use of the block orDue to the trapezoidal shape of the voltage and the associated currents, the semiconductor switches of the sub-modules can be designed for a lower current load. Alternatively, it is possible to use the modular braking unit to convert higher power into heat. The block-shaped or trapezoidal voltage can be easily generated by a control device that controls the semiconductor switches of the sub-module or the sub-modules of the further series connection. It is particularly advantageous to combine the modular braking unit with the modular multilevel power converter, also known as an M2C power converter, to form a modular drive unit. Identical sub-modules can be used for both the modular multilevel power converter and the modular braking unit. The same hardware can also be used to control the sub-modules.Due to the modular design of both the power converter and the modular braking unit, the modular drive unit can be easily adapted to the required power requirement by selecting an appropriate number of sub-modules in the power converter and the modular braking unit. Due to the identical design of the sub-modules in the modular braking unit and the multi-level power converter, a high proportion of identical parts can be achieved. This has a positive effect on the reliability and manufacturing costs of such a drive unit. The modular braking unit can be connected to the DC side of power converters of any design and is not limited to use with a modular multi-level power converter. The block-shaped ortrapezoidal voltage has an alternating component that is dimensioned such that the electrical energy absorbed over time by the modular braking unit is converted into heat in the braking resistor. The alternating component can be used to influence the capacitor voltages of the submodules and to stabilize the modular braking unit. The alternating component of the voltage causes a further alternating component in the current through the modular braking unit by means of a corresponding voltage drop across the braking resistor. Both the alternating component and the further alternating component have a mean value of zero, so that only reactive power is exchanged with the further alternating component of the current and the intermediate circuit voltage or the voltage across the modular braking unit.It has been shown that this portion can be used to exchange energy between the capacitors of the submodules and the resistor. The energy exchange is advantageously controlled or regulated in such a way that the entire active power is converted into heat via the resistor. The electrical energy absorbed by the modular braking unit over time is converted into heat in the braking resistor. The relationship is expressed as an equation. where the current i BR by the braking resistor from the DC component i BR,DC and the alternating share i BR,aDC according to ^^ ^ோ ൌ ^^ ^ோ,^^ ^ ^^ ^ோ,^^^ (3). If equation (3) is inserted into equation (2), the resulting equation can be calculated according to i BR,aDCThe block-shaped or trapezoidal voltage waveform can be taken into account. For the simple and idealized case of a block-shaped voltage and current waveform, the alternating current component is In order to calculate the mean value over time of the current i BR,aDC is zero, over half the time the alternating component is the component with the value according to equation (4) and the other half the corresponding value with a negative sign. The resistance R must be chosen sufficiently small so that equation (4) yields a positive value. To generate this current, the alternating component of the voltage across the further series connection of the submodules is the value To ensure that this voltage is also an alternating component with a time average of zero, the value calculated above is used as the alternating component for half the time and the corresponding negative value for the remaining half. In an advantageous embodiment of the invention, the modular braking unit comprises a plurality of submodules arranged in a further series circuit, wherein the block-shaped or trapezoidal voltage is generated across the further series circuit of the submodules by means of the plurality of submodules. By using a plurality of submodules in the further series circuit, the operating voltage of the modular braking unit can be adapted as required to the intermediate circuit voltage of the power converter. In this case, operating voltages of any desired level, i.e. intermediate circuit voltages in the drive unit, can be realized.In a further advantageous embodiment of the invention, the block-shaped or trapezoidal voltage has a DC component, wherein the DC component is controlled or regulated as a function of the power to be converted into heat by means of the modular braking unit or as a function of the voltage applied to the modular braking unit. The DC component of the voltage can be used to generate a current through the modular braking unit, which current also has a further DC component. This DC component flows through the modular braking unit and thus also the braking resistor. The current flowing through the braking resistor generates electrical losses. These losses are used to specifically convert electrical energy into heat.The amount of power to be converted into heat, i.e. energy per unit of time, can be controlled or regulated by the level of the DC component of the voltage, as this directly determines the voltage drop across the resistor and, in turn, the further DC component of the current through the modular braking controller. It has therefore proven advantageous to control or regulate the DC component as a function of the power to be converted into heat. This power can in turn depend on other variables, such as the voltage of the capacitor in the submodules of a modular multilevel converter. If the modular braking controller is operated on an intermediate circuit with an intermediate circuit capacitor, for example on a 2-point or 3-point converter, it has proven advantageous to control or regulate the DC component as a function of the intermediate circuit voltage.These control structures can be used to implement dynamic controls for converting electrical power into heat, which protect the electric drive unit from overloading due to excessive amounts of energy. These amounts of energy can result, for example, from the braking process of an electrical machine. In a further advantageous embodiment of the invention, the DC component is controlled or regulated in such a way that a current with a further DC component is generated through the modular braking unit, wherein the product of the further DC component and the voltage across the modular braking unit corresponds to a predetermined power to be converted into heat by the modular braking unit, in particular a predetermined active power to be converted into heat by the modular braking unit.The voltage level of the DC component of the voltage is controlled or regulated in such a way that the further DC component of the current is so large that the product of the DC link voltage and the further DC component corresponds to the value of the power to be converted into heat by the modular braking unit. The power to be converted into heat is energy that is converted into heat in a specific time. The DC link voltage is applied across the modular braking unit, as this is electrically connected to the DC link. The DC link voltage is therefore applied across the series connection of the braking resistor and the further series connection of the sub-modules. Instead of the further series connection of sub-modules, there can alternatively be just one sub-module. The modular braking unit, to which the DC link voltage is applied, thus absorbs the active power ^^. ^ோ ൌ ^^ ^ ∙ ^^ ^ோ,^^(1). The entire active power absorbed by the braking resistor should be converted into heat, since the modular braking controller should not be designed to absorb and store significant amounts of energy. The difference in voltage between the block shape and trapezoidal shape can be controlled, for example, with a PI controller, so that a predeterminable voltage is established on the capacitor or capacitors in the submodules. In other words, a further voltage component can be generated to achieve the block-shaped or trapezoidal voltage depending on the voltage on the capacitor or capacitors of the submodules, which, for example, regulates or controls the voltage on the capacitors of the submodules with the help of a PI controller.Alternatively or additionally, it is also possible to influence the voltage at the capacitors of the submodules using the voltage gradient of the trapezoidal shape and / or the frequency of the trapezoidal or block shape. In a further advantageous embodiment of the invention, the alternating component is used as a manipulated variable for regulating the capacitor voltages of the submodules. In order to compensate for disturbances, it has proven beneficial to use the values ​​of the alternating component determined according to the formulas for pre-control. The voltage at the capacitors is then regulated by means of a control. This allows the modular braking unit to operate stably even in the presence of disturbances. Furthermore, operation is independent of changing variables. For example, a change in the resistance value caused by aging or heating can be easily compensated by the control.In a further advantageous embodiment of the invention, an AC voltage side of the modular multilevel power converter is connected to an energy source, in particular to a power grid or to an electrical machine. By connecting it to an energy source, the modular braking controller can be used to convert excess or unusable energy into heat. The energy source can, for example, be an electrical machine that feeds electrical energy back during a braking process. If this energy can no longer be used, it must be converted into heat using the modular braking controller if a mechanical brake is to be dispensed with. In contrast to a mechanical brake, the conversion of electrical energy into heat is wear-free, so that the use of the modular braking controller is more economical in operation.It is also possible to use the modular multilevel power converter for power transmission. In this case, it may be advisable to provide a modular braking unit in the event that the transmitted power cannot be taken off. This ensures that such a power transmission remains operational even if the power reception is disrupted. The power transmission system can remain in operation during this disruption, reliably avoiding the need for time-consuming shutdown and restart, which could also lead to stability problems in the power supply network. Thus, the modular braking unit also increases the reliability and availability of a modular drive unit designed for power transmission.In a further advantageous embodiment of the invention, the control device of the modular drive unit is configured to determine the power to be converted into heat as a function of the capacitor voltage of the submodules of the modular multilevel power converter. In a modular multilevel power converter, energy stored in the power converter is not necessarily reflected in the intermediate circuit voltage, as is the case, for example, with a 2-point or 3-point power converter. In the modular multilevel power converter, an increased energy content affects the stored energy, i.e., the voltage, of the capacitor(s) in the respective submodules of the modular multilevel power converter.In order to specifically reduce the energy content in the modular multilevel power converter, it has proven advantageous to determine the power to be converted into heat for controlling or regulating the DC component as a function of the voltage of the capacitor of the respective submodules of the modular multilevel power converter. One possible method for operating an electric drive unit with a modular power converter and a proposed modular braking controller regulates or controls the DC component of the voltage across the further series connection of the submodules of the modular braking controller as a function of the voltage of the capacitor or capacitors of the submodules of the modular multilevel power converter. The invention is described and explained in more detail below with reference to the exemplary embodiments illustrated in the figures.9 to 11 exemplary embodiments of the modular drive unit. FIG. 1 shows a modular braking unit 1. This has a series connection 4 of at least one submodule 2 and a braking resistor 3. The series connection 4 can have a multiplicity of submodules 2. These are in turn arranged as part of the series connection 4 in a further series connection 41. The modular braking unit 1 is designed to be connected at its connections 11 to an intermediate circuit 9 of a power converter. A voltage u can be generated across the further series connection 41 of the submodules with the aid of a control device 10. BR generate. With the voltage u BR a current can be BR by the modular braking unit 1. The current i BRalso flows through the braking resistor 3 and causes the conversion of electrical energy into heat. The operating voltage U is applied across the modular braking controller 1. DIf the modular braking unit 1 is connected to the intermediate circuit of a power converter, the intermediate circuit voltage is applied to the modular braking unit. In this case, the modular braking unit 1 is said to be connected to the DC voltage side of the power converter. Figures 2 to 4 show exemplary embodiments of submodules 2. All known submodules, in particular the submodules of Figures 2 to 4, are suitable for implementing the proposed method. To avoid repetition, reference is made to the description of FIG. 1 and the reference numerals introduced there. The illustrated exemplary embodiments of the submodules 2 comprise at least two semiconductor switches and at least one capacitor. By switching operations of the semiconductor switches, an output voltage U subare generated at the terminals of submodule 2. A control device 10 transmits the control signals to the semiconductor switches of submodule 2. The control device 10 is preferably arranged outside of submodule 2 and is therefore not part of the submodule. Rather, it has proven advantageous to control all submodules 2 of the modular braking unit 1 with one control device 10. In addition, the control device 10 can perform the calculations required for the control and regulation of the voltages and currents. Thus, the control device 10 can determine the required current through the modular braking unit i from the specified value of the power to be converted into heat. BR To determine this current i BRTo generate a voltage across the submodules of the further series circuit 41, a voltage determined, controlled, or regulated by the control device 10 is generated by appropriate control signals. In the following exemplary embodiments, the control device 10 is not shown for reasons of clarity. Figure 2 shows a so-called half-bridge module. This has two semiconductor switches and a capacitor. The voltage U is applied to the capacitor. C,sub By switching actions of the semiconductor switches, the output voltage U sub of zero or U C,sub at the terminals of submodule 2. Figure 3 shows a so-called double-bridge module. This has four semiconductor switches and two capacitors. The voltage U is applied to each capacitor. C1,sub or U C2,sub By switching operations of the semiconductor switches, the output voltage U subof zero, one of the capacitor voltages U C1,sub , U C2,sub or the sum of the capacitor voltages U C1,sub , U C2,sub generated at the terminals of submodule 2. Figure 4 shows a so-called full-bridge module. This has four semiconductor switches and a capacitor. The voltage U is applied to the capacitor. C,sub By switching actions of the semiconductor switches, the output voltage U sub of zero, the positive or the negative capacitor voltage ±U C,sub generated at the terminals of submodule 2. FIG 5 shows the time course of the voltage u BR across the submodules 2 of the further series circuit 41 for the proposed method. To avoid repetition, reference is made to the description of Figures 1 to 4 and the reference symbols introduced there. The voltage u BR consists of a constant component and BR,DC and an alternating portion u BR,aDCtogether, with the alternating part being increased by the value +û BR,aDC and -û BR,aDC for each half switching period. Thus, the alternating component u BR,aDC no DC component, so it is mean-free. By superimposing the DC component and BR,DC and alternating proportion u BR,aDC the voltage u results BR . Due to a finite voltage gradient of the alternating component, which changes its value in the form of a ramp, a trapezoidal voltage curve results for the voltage u BR . If a high, ideally infinite, edge steepness is assumed, the dashed curve in the transition results and from this a block-shaped voltage waveform of the voltage u BR . Figure 6 shows an example of the current curve i resulting from the voltage curve in Figure 5 BR by the modular brake actuator 1. By the voltage u BRresults in a voltage across the braking resistor 3, which has a current i BR with a further DC component i BR,DC and a further alternating portion i BR,aDC To distinguish it from the DC component or alternating component of the voltage, this DC component or alternating component of the current is referred to as the additional DC component or additional alternating component. During the time in which the voltage across the submodules 2 in the further series circuit 41 is small, a larger voltage drops across the braking resistor 4, so that a larger current i BR by the modular braking unit 1 and vice versa. The current i BR by the braking resistor 3 depending on the height of the alternating component u BR,aDCtemporarily become negative. In other words, depending on the operating point, the amount of the alternating component can be greater than the direct component. When using unipolar submodules that only have one polarity in their output voltage U sub such as half-bridges or double half-bridges, the current i BR by the modular brake controller 1 has a minimum negative value. Figure 7 shows the voltage u BR on the further series connection 41 of the submodules 2 of the modular brake actuator 1 for application in the medium-voltage range. The medium-voltage range begins at a voltage of 1000 V, also referred to as 1 kV. The DC component u shown BR,DC is an alternating portion u BR,aDC superimposed in such a way that the voltage curve of the voltage u BRThe value of the power to be converted into heat changes between times t=0.34s and t=0.36s. In the curve shown, this power is reduced. This value is specified to the modular brake actuator 1 or its control device 10. For example, this value can be derived from the voltage of the intermediate circuit U D to which the modular brake controller is connected or, more generally, which is present at the terminals 11 of the modular brake controller 1. Likewise, the value can also be determined as a function of the voltage at the capacitor or capacitors of the submodules of a modular multilevel power converter connected to the modular brake controller 1. The modular brake controller 1 with the control device 10 reacts by measuring the DC component u BR,DC At the same time, the smaller fluctuation range of the voltage u BR a smaller alternating proportion u BR,aDC. This alternating share u BR,aDC stabilizes the capacitor voltages U C of the capacitors of submodules 2. FIG 8 shows the corresponding current i BR by the modular brake actuator with its additional DC component i BR,DC The reduction in power is evident from the lower current. Furthermore, from time t=0.35s onwards, there is an operating point at which the current i BR temporarily assumes a significantly negative value. At the times before t=0.35s, the current at the minimum is only barely recognizably negative. The time profiles in FIGS. 7 and 8 exhibit such high rates of change that the time profiles can be described as block-shaped time profiles. FIG. 9 shows a modular drive unit 20 with a modular multilevel power converter 21 and a modular braking unit 1. These are connected via the intermediate circuit 9, at which the voltage U Dis applied, are connected to one another. The modular multilevel power converter 21 can, but not necessarily, have the same submodules 2 as the modular braking controller 1. The series connection of the submodules 2 of the modular multilevel power converter 21 also has an inductance 8, which improves the control behavior of the modular multilevel power converter 21. The connections L1, L2, L3 represent the AC voltage side connections or, in short, the AC voltage side of the modular multilevel power converter 21. In this exemplary embodiment, the modular multilevel power converter 21 is designed as a three-phase system. Alternatively, a single-phase version with a neutral conductor or any desired number of phases is possible by providing a corresponding number of phase modules in the modular multilevel power converter 21. FIG. 10 shows an exemplary embodiment of a modular drive unit 20.An energy source 5 is electrically connected to the AC voltage side of the modular multilevel power converter 21. The energy source can be, for example, a power supply network 6 or an electrical machine 7. In the exemplary embodiment in FIG. 11, the modular drive unit 20 has two modular multilevel power converters 21 and a modular braking controller 1, which are electrically connected to one another at the intermediate circuit 9. A first of the two modular multilevel power converters 21 is connected on its AC voltage side to a power supply network 6, and a second of the two modular multilevel power converters 21 is connected on its AC voltage side to an electrical machine 7. The electrical machine 7 can be supplied with electrical energy from the power supply network 6.The modular drive unit 20 also enables energy to be fed back from the electrical machine 7 into the power supply network 6, for example during a braking operation. If the power supply network 6 is not capable of absorbing the energy, the electrical energy generated by the electrical machine 7 can advantageously be converted into heat by means of the modular brake actuator 1. A mechanical brake subject to wear can be dispensed with in this embodiment. 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. To improve the function of the modular brake actuator, it is proposed that a block-shaped or trapezoidal voltage u. BRis generated, whereby the block-shaped or trapezoidal voltage u BR an alternating portion u BR,aDC which is dimensioned such that the electrical energy absorbed over time by the modular brake actuator 1 is converted into heat in the braking resistor 3. Furthermore, the invention relates to a control device 10, configured to carry out such a method. The invention further relates to 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, wherein by means of the at least one submodule 1, a block-shaped or trapezoidal voltage u BRcan be generated, wherein the modular brake actuator 1 has such a control device 10 for controlling or regulating the at least one submodule 2. The invention further relates to a modular drive unit 20, comprising a modular multilevel power converter 21 and such a modular brake actuator 1, wherein the modular brake actuator 1 is electrically connected to a DC voltage side of the modular multilevel power converter 21.

Claims

Patent claims 1. 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), wherein by means of the at least one submodule (1) a block-shaped or trapezoidal voltage (u BR ), whereby the block-shaped or trapezoidal voltage (u BR ) an alternating portion (u BR,aDC ), which is dimensioned such that the electrical energy absorbed over time by the modular brake actuator (1) is converted into heat in the braking resistor (3).

2. Method according to claim 1, wherein the modular brake actuator (1) comprises a plurality of submodules (2) arranged in a further series circuit (41), wherein the block-shaped or trapezoidal voltage (u BR) across the further series circuit (41) of the submodules (2).

3. Method according to one of claims 1 or 2, wherein the block-shaped or trapezoidal voltage (u BR ) a DC component (u BR,DC ), where the DC component (u BR,DC ) depending on the power to be converted into heat by means of the modular brake controller (1) or depending on the voltage (U D ) is controlled or regulated.

4. Method according to claim 3, wherein the DC component (u BR,DC ) is controlled or regulated in such a way as to produce a current (i BR ) with a further DC component (i BR,DC ) by the modular brake actuator (1), whereby the product of the further DC component (i BR,DC ) and the voltage (U D) above the modular brake actuator (1) corresponds to a predetermined power to be converted into heat by the modular brake actuator (1), in particular a predetermined active power to be converted into heat by the modular brake actuator (1).

5. The method according to any one of claims 1 to 4, wherein the alternating portion (u BR,aDC ) as a control variable for the capacitor voltages (U C,sub ) of the submodules (2).

6. Control device (10) configured to carry out a method according to one of claims 1 to 5.

7. Modular brake actuator (1), wherein the modular brake actuator (1) comprises at least one submodule (2) and a braking resistor (3) arranged in a series circuit (4), wherein by means of the at least one submodule (1) a block-shaped or trapezoidal voltage (u BR), wherein for controlling or regulating the at least one submodule (2), the modular brake actuator (1) has a control device (10) according to claim 6.

8. 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 by means of the plurality of submodules (2) a block-shaped or trapezoidal voltage (u BR) can be generated across the further series circuit (41).

9. Modular drive unit (20), comprising a modular multilevel power converter (21) and a modular braking unit (1) according to one of claims 7 or 8, wherein the modular braking unit (1) is electrically connected to a DC voltage side of the modular multilevel power converter (21).

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

11. Modular drive unit (20) according to one of claims 9 or 10, wherein the control device (10) is configured to determine the power to be converted into heat as a function of the voltage of the capacitor of the submodules of the modular multilevel power converter (21).

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