Control method for a modular brake actuator with at least two brake actuator branches

Abstract

The invention relates to a method for operating a modular brake actuator (1), said modular brake actuator (1) comprising at least two brake actuator branches (15). Each brake actuator branch (15) has at least one sub-module (2) and a brake resistor (3), and the brake actuator branches (15) are arranged in a parallel circuit. At least two of the brake actuator branches (15) generate a voltage (uBR) with an alternating component (uBR,aDC) by means of the corresponding at least one sub-module (2), wherein the alternating components (uBR,aDC) of the individual brake actuator branches (15) have a phase offset of 2π / n relative to one another, wherein n corresponds to the number of voltage-generating brake actuator branches (15), the amplitude of all of the alternating components (uBR,aDC) is the same and is measured such that the electric energy received by the modular brake actuator (1), averaged over time, is converted to heat in the brake resistor (3). The invention also relates to a control device (10) designed to carry out such a method, to a modular brake actuator (1) comprising such a control device, and to a modular drive unit (20) having a modular multilevel converter (21) and such a modular brake actuator (1).

Description

[0001] Description

[0002] Structure and control method for a modular brake controller with at least two brake controller branches

[0003] The invention relates to a method for operating a modular brake controller with at least one submodule and a braking resistor. Furthermore, the invention relates to a control device and a modular brake controller, wherein the modular brake controller comprises at least one submodule and a braking resistor. The invention further relates to a modular drive unit comprising a modular multilevel power converter and such a modular brake controller, wherein the modular brake controller is electrically connected to a DC voltage side of the modular multilevel power converter.

[0004] A modular multilevel power converter is available from the

[0005] DE 10 103 031 A1 . This power converter, also known as M2C or MMC, has a converter topology which, due to its design with submodules, is particularly suitable for medium and high voltage applications. The basic design of the multi-phase converter comprises two converter arms per phase, each with 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 side. The AC side of the modular multilevel power converter is formed by one or more phase connections. In the basic design, the converter can be used to transfer energy bidirectionally between the DC side and the AC side, or to temporarily store it to a certain extent.

[0006] To additionally enable targeted energy dissipation, the installation of a braking controller is advisable. A modular braking controller is known from WO 2007 / 023061 A2. The modular braking controller is typically connected to the DC side of the modular multilevel converter, for example, between a DC+ and a DC- connection.

[0007] The resistance of a brake actuator 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 as a result of a braking process, into heat. The use of a braking actuator is not restricted to the application of a braking electric drive. It does not necessarily have to be braking energy that is converted into heat. The braking controller can, for example, also be used to stabilize a power supply network by converting electrical energy from the power supply network into heat. The term braking resistor was chosen in order to distinguish the resistor in which a given electrical energy or power is converted into heat or heat per unit of time from other resistors.

[0008] The term "power to be converted into heat" refers to the integral of the power over time being converted into heat. In other words, the amount of energy resulting from the power over time is converted into heat.

[0009] The invention is based on the object of improving a modular brake controller.

[0010] This object is achieved by a method for operating a modular brake controller, wherein the modular brake controller has at least two brake controller branches, wherein the brake controller branches each have at least one submodule and a braking resistor which are arranged in a series circuit, wherein the brake controller branches are arranged in a parallel circuit between two terminals of the modular brake controller, wherein at least temporarily at least two of the brake controller branches generate a voltage with an alternating component by means of the corresponding at least one submodule, wherein the alternating component is free of DC components, wherein the alternating component of the individual 2TT brake controller branches have a phase shift of n relative to one another, wherein n corresponds to the number of voltage-generating brake controller branches, wherein the amplitude of all alternating components is the same and is dimensioned such thatthat the electrical energy absorbed on average by the modular brake controller is converted into heat in the braking resistor. This object is further achieved by a control device which is designed to carry out such a method. This object is further achieved by a modular brake controller, wherein the modular brake controller has at least two brake controller branches, wherein the brake controller branches each have at least one submodule and one braking resistor which are arranged in a series circuit, wherein the brake controller branches are arranged in a parallel circuit between two terminals of the modular brake controller, wherein a voltage can be generated by means of the at least one submodule of the respective brake controller branches,The modular brake controller comprises such a control device for controlling or regulating the at least one submodule of the respective brake controller branches. This object is further achieved by a modular drive unit comprising a modular multilevel power converter and such a modular brake controller, the modular brake controller being electrically connected to a DC voltage side of the modular multilevel power converter.

[0011] Further advantageous embodiments of the invention are specified in the dependent claims.

[0012] The invention is based, among other things, on the discovery that the modular design of the modular brake controller allows any operating voltage of the brake controller to be implemented. The modular brake controller is typically connected to the intermediate circuit of a power converter in order to convert electrical energy from a drive system or a power supply system into heat. With its modular design, the modular brake controller can be adapted to any desired intermediate circuit voltage by using an appropriate number of submodules.

[0013] The brake controller design comprises at least two brake controller branches arranged in parallel between the terminals of the modular brake controller, each having a series connection of at least one submodule and one braking resistor. The number of submodules can preferably be selected to be the same in each brake controller branch. This simplifies system control. The resistance value can also be selected to be the same for each brake controller branch.

[0014] All known types of submodules can be used as submodules. These include, for example, half-bridge modules, double half-bridge modules, or 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 by using pulse width modulation, to generate a voltage through the submodule that is lower than the capacitor voltage or capacitor voltages. Pulse width modulation has proven particularly advantageous for generating different voltages when only one submodule is used.

[0015] In addition, 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 all of the intermediate circuit voltage is dropped across the braking resistor during energy conversion. The advantage is that the power to be converted into heat can be controlled. At the same time, the energy content of the capacitor or capacitors of the at least one submodule or submodules is controlled. This enables stable operation of the modular braking unit even over longer operating periods, particularly for continuous operation.

[0016] The braking resistor can be arranged anywhere in the series circuit in the braking controller branch. For example, the braking resistor can be arranged between one of the terminals of the modular braking controller and a submodule, or at any point between two submodules.

[0017] If the modular brake controller is not active, i.e. is not supposed to convert electrical energy into heat, the voltage applied across at least one sub-module of all brake controller branches or the further series connection of sub-modules is identical to the intermediate circuit voltage, so that no voltage drops across the resistor and therefore no current flows. It is possible to operate only some, but at least two, of the brake controller branches by converting electrical energy into heat, while the other brake controller branches are idle and the sub-modules there generate the intermediate circuit voltage and are therefore currentless. The brake controller branches involved in the conversion of electrical energy generate an alternating component and are therefore referred to as voltage-generating brake controller branches.

[0018] For the control or regulation, a voltage is generated across at least one sub-module of the voltage-generating brake controller branches or, if several sub-modules are arranged in a further series connection, across the further series connection of the sub-modules. A DC component of the voltage is provided for the control or regulation of the power to be converted into heat. This DC component generates a current with a further DC component through the modular brake controller. It is irrelevant how the further DC component is distributed among the individual voltage-generating brake controller branches. In order to ensure even utilization of the brake controller branches, it is advantageous for the further DC component to be distributed evenly among the voltage-generating brake controller branches. For this purpose, the DC component of the generated voltage in the voltage-generating brake controller branches is the same.

[0019] To control the capacitor voltage or the capacitor voltages of the submodule(s), an alternating component is superimposed on the DC component.

[0020] In this case, an alternating component is generated in each of the voltage-generating brake controller branches. The amplitude of the alternating component is the same in the different voltage-generating brake controller branches. The phase position differs. The alternating component of the different voltage-generating brake controller branches has a 2TT

[0021] Phase difference of — to each other on . Here, nn corresponds to the number of voltage-generating brake controller branches . This ensures that the resulting alternating currents only develop within the modular brake controller . This reliably prevents interference with components connected to the brake controller, such as a power converter or a motor .

[0022] It is particularly advantageous to combine the modular brake controller 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 the modular multilevel power converter and the modular brake controller. The same hardware can also be used to control the sub-modules. Thanks to the modular design of both the power converter and the modular brake controller, the modular drive unit can be easily adapted to a required power requirement by selecting an appropriate number of sub-modules in the power converter and the modular brake controller. The identical design of the sub-modules in the modular brake controller and the multilevel power converter means that 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.

[0023] The modular brake controller can be connected to the DC side of converters of any design and is not limited to use with a modular multilevel converter.

[0024] The DC component of the voltage can be used to generate a current through the modular brake resistor, which also has a further DC component. This DC component flows through the modular brake resistor and therefore also the braking resistor. The current flowing through the braking resistor creates electrical losses. These 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 this in turn determines the further DC component of the current through the modular brake resistor.

[0025] The intermediate circuit voltage is applied across the modular brake controller, as it is electrically connected to the intermediate circuit. Thus, the intermediate circuit voltage is applied across the series connection of the brake resistor and the further series connection of the submodules. Instead of the further series connection of submodules, only one submodule can be present. Thus, the modular brake controller, to which the intermediate circuit voltage is applied, absorbs the active power.

[0026] PßR = D ■ IßR,DC = U D ■ n - ißR'Dc on . The entire active power absorbed by the braking resistor should be converted into heat, since the modular braking resistor should not be designed to absorb and store significant amounts of energy. Here, n again corresponds to the number of voltage-generating braking resistor branches.

[0027] The alternating component of the individual voltage-generating brake controller branches is dimensioned in such a way that the electrical energy absorbed over time by the modular brake controller is converted into heat in the braking resistor. The alternating component can be used to influence the capacitor voltages of the sub-modules and to stabilize the modular brake controller. The alternating component of the voltage causes a corresponding voltage drop across the braking resistor of the respective brake controller branches, a further alternating component in the current inside the modular brake controller that does not flow via the connections of the modular brake controller. The generated alternating components only circulate within the modular brake controller and are not visible from the outside.

[0028] 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 brake resistor. The alternating component is therefore free of direct component. It has been shown that this component 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 across the resistor. The electrical energy absorbed on average by the modular brake resistor is converted into heat in the brake resistor. Formulated as an equation, this results in the relationship where the current 1 BR by the braking resistance of the respective brake actuator branch consists of the direct component 1 BR, DC and the alternating component i BR , aD c according to lBR = l BR,DC + l BR,aDC. From this, the alternating component can be determined depending on the voltage waveform that influences the effective value.

[0029] Conventional resistors with a sufficiently high parasitic inductance are preferably used as braking resistors. If this is too low, additional inductances can optionally be installed in series with the submodules or resistors in the braking resistor branches. Circulating currents can be specifically impressed and regulated via the modulated voltage drop across the parasitic and / or integrated inductances.

[0030] When using the proposed method, the converters connected to a DC voltage network or intermediate circuit of a drive system do not need to be specially designed for brake controller operation or have their functions expanded, even with higher brake controller power. This means that with conventional converters used in combination with cell-based brake choppers, the components only need to be dimensioned and considered for stable converter operation. Furthermore, the proposed method and the corresponding devices also enable operation with passive converters, such as diode rectifiers. This was not possible until now, since the circulating current cannot be closed via the diode rectifier.The proposed design enables completely autonomous braking unit operation, which can also be installed as a protective component at any location within a DC voltage network or transmission link. In an advantageous embodiment of the invention, the braking unit branches each comprise a large number of sub-modules arranged in a further series connection, wherein the voltage generated by the large number of sub-modules is applied across the further series connection of the sub-modules. By using a large number of sub-modules in the further series connection, 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 implemented.

[0031] It has proven advantageous to select the same number of submodules in the individual brake controller branches. This makes control and regulation particularly simple, as the energy balance is particularly easy to achieve, particularly with regard to the energy stored in the capacitors of the submodules. This enables stable operation of the complex structure.

[0032] In a further advantageous embodiment of the invention, the voltage generated by the voltage-generating brake controller branches 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 brake controller or as a function of the voltage applied to the modular brake controller. The power to be converted into heat or the voltage applied to the modular brake controller is predetermined, for example, by means of a setpoint. By comparing the setpoint with the actual value, control can be carried out in a simple manner, for example by means of a PI 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 sub-modules of a modular multilevel power 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 overload caused by excessive amounts of energy. This energy can result, for example, from the braking process of an electrical machine.

[0033] It has proven advantageous to generate the DC components of all voltage-generating brake controller branches at the same level. This also distributes the remaining DC component of the current evenly among the individual voltage-generating brake controller branches. This leads to a uniform load on the individual brake controller branches and thus to uniform aging. This results in a long service life for the modular brake controller.

[0034] In a further advantageous embodiment of the invention, the DC component is controlled or regulated in such a way that currents with a further DC component are generated through the modular brake controller, the product of the further DC component of all voltage-generating brake controller branches and the voltage across the modular brake controller corresponding to a predetermined power to be converted into heat by the modular brake controller, in particular a predetermined active power to be converted into heat by the modular brake controller. 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 intermediate circuit voltage and the further DC component of all brake controller branches corresponds to the value of the power to be converted into heat by the modular brake controller.The power to be converted into heat is the energy that is converted into heat within a specific time. Alternatively, it is possible to specify an active power as the power to be converted into heat.

[0035] In a further advantageous embodiment of the invention, the alternating component is used as a manipulated variable for controlling the capacitor voltages of the submodules. In order to compensate for disturbances, it has proven advantageous to use the values ​​of the alternating component determined according to the formulas for feedforward control. The voltage across the capacitors is then controlled by means of a control system. This allows the modular brake controller 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 for by the control system.

[0036] 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 supply network or to an electrical machine. The modular brake controller can be used by connecting it to an energy source to convert excess or unusable energy into heat. The energy source can be, for example, an electrical machine which feeds electrical energy back during a braking process. If this energy can no longer be used, it must be converted into heat by means of the modular brake controller if a mechanical brake is to be dispensed with. In contrast to a mechanical brake, the electrical energy is converted into heat without wear, so that the use of the modular brake controller is more economical in operation.

[0037] 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 brake controller in the event that the transmitted power cannot be taken off. This ensures that this type of power transmission remains in operation even if the power reception is disrupted. The power transmission system can remain in operation during this disruption, reliably avoiding the need for costly restarts and shutdowns, which can also lead to stability problems in the power supply network. The modular brake controller therefore also increases the reliability and availability of a modular drive unit designed for power transmission.

[0038] 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 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 or capacitors 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 the control or regulation of 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 brake controller regulates or controls the DC component of the voltage across the further series connection of the submodules of the modular brake 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. In the drawings:

[0039] FIG 1 a modular brake controller,

[0040] FIG 2 to FIG 4 examples of the submodule, FIG 5 time curves of voltage and current,

[0041] FIG 6 to FIG 8 are examples of the modular drive unit.

[0042] FIG. 1 shows a modular brake controller 1. This has a plurality of brake controller branches 15 which are arranged in parallel between terminals 11 of the modular brake controller 1. The brake controller branches 15 each have 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. These are in turn arranged as part of the series circuit 4 in a further series circuit 41. The modular brake controller 1 is designed to be connected at its terminals 11 to an intermediate circuit 9 of a power converter.

[0043] Across the further series circuit 41 of the submodules 2, a voltage U B R . With the generated voltage U B R can be a current i BR by the modular brake controller 1. The current i BR also flows through the respective braking resistor 3 and causes the conversion of electrical energy into heat. At the terminals 11, the currents i BR to a total current I BR . Preferably, the currents i BR regulated in such a way that they are the same except for the phase position.

[0044] The operating voltage U is above the modular brake controller 1 DIf the modular brake controller 1 is connected to the intermediate circuit of a power converter, the intermediate circuit voltage is applied to the modular brake controller 1. In this case, the modular brake controller 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 2, in particular the submodules 2 in Figures 2 to 4, are suitable for carrying out the proposed method. To avoid repetition, reference is made to the description of FIG. 1 and the reference symbols introduced there.

[0045] The illustrated 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 SUb are generated at the terminals of the submodule 2. A control device 10 transmits the control signals to the semiconductor switches of the submodule 2. The control device 10 is preferably arranged outside the submodule 2 and is therefore not part of the submodule 2. Rather, it has proven advantageous to control all submodules 2 of the modular brake actuator 1 with one control device 10. In addition, the control device 10 can carry out the calculations required for the control and regulation of the voltages and currents. Thus, the control device 10 can determine the required current 1 from the predetermined value of the power to be converted into heat. B R through the modular brake controller 1. To determine this current i BR, a voltage determined, controlled, or regulated by the control device 10 is generated across the submodules 2 of the further series circuit 41 by means of corresponding control signals. In the following exemplary embodiments, the control device 10 is not shown for reasons of clarity.

[0046] FIG 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 , S ub . By switching operations of the semiconductor switches, the output voltage U SU b of zero or U c , S ub are generated 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 of the capacitors. C i, SU b or U C2,sub. By switching operations of the semiconductor switches, the output voltage U SU b of zero, one of the capacitor voltages U Ci ,sub, U C 2,sub or the sum of the capacitor voltages Uci,sub, U C 2,sub are generated at the terminals of submodule 2.

[0047] FIG 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 , SU b. By switching operations of the semiconductor switches, the output voltage U SU b of zero, the positive or the negative capacitor voltage ± U c , sub are generated at the terminals of submodule 2.

[0048] FIG 5 shows a selection of possible time profiles for the voltages U generated across the further series circuit B R and the current flowing through the modular brake controller 1 i B R . The alternating part uBR , aD c can be sinusoidal. Alternatively, the alternating component u BR , aD c can also be obtained from the superposition of two sine functions with different frequencies. As a further alternative, the voltage waveform and the current waveform of the alternating component u B R, aB c be block-shaped or trapezoidal. All of these designs can be used to control or regulate the modular brake actuator.

[0049] FIG 6 shows a modular drive unit 20 with a modular multilevel power converter 21 and a modular brake controller 1. These are connected to one another via the intermediate circuit 9, to which the voltage UD is applied. The modular multilevel power converter 21 can, but not necessarily, have the same submodules 2 as the modular brake 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 LI, 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 of three-phase design.Alternatively, a single-phase version with 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.

[0050] FIG. 7 shows an exemplary embodiment of a modular drive unit 20. A power source 5 is electrically connected to the AC voltage side of the modular multilevel power converter 21. The power source can be, for example, a power grid 6 or an electrical machine 7.

[0051] In the exemplary embodiment in FIG 8, the modular drive unit 20 has two modular multilevel power converters 21 and a modular braking converter 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. Energy can also be fed back into the power supply network 6 from the electrical machine 7, for example during a braking process, using the modular drive unit 20.If the power supply network 6 is not capable of absorbing the energy, the electrical energy generated by the electric machine 7 can be advantageously converted into heat by means of the modular brake controller 1. A mechanical brake subject to wear can be dispensed with in this embodiment.

Claims

Patent claims 1. A method for operating a modular brake controller (1), wherein the modular brake controller (1) has at least two brake controller branches (15), wherein the brake controller branches (15) each have at least one submodule (2) and one braking resistor (3) which are arranged in a series circuit (4), wherein the brake controller branches (15) are arranged in a parallel circuit between two terminals (11) of the modular brake controller (1), wherein at least temporarily at least two of the brake controller branches (15) have a voltage (U B R) with an alternating portion (u B R,aoc), where the alternating component (u BR , aD c) is free of equal components, whereby the alternating component (u BR , aD c) the individual brake positions 2TT brake branches (15) have a phase shift of — n to each other, where n corresponds to the number of voltage-generating brake branches (15), the amplitude of all alternating components (u BRfaDC ) and is dimensioned in such a way that the time-averaged braking force of the modular brake controller (1) absorbed electrical energy is converted into heat in the braking resistor (3).

2. Method according to claim 1, wherein by means of the DC component (U BR ,DC) the power to be converted into heat is controlled or regulated, whereby by means of the alternating component (u BR ,aDc) r which corresponds to the DC component (u BRfDC ) is superimposed, the capacitor voltage or the capacitor voltages of the submodule (2) or the submodules (2) is or are regulated.

3. Method according to one of claims 1 or 2, wherein the brake controller branches (15) each comprise a plurality of submodules (2) which are arranged in a further series circuit (41), wherein by means of the plurality of submodules (2) the generated voltage (u BR ) across the further series connection (41) of the submodules (2).

4. Method according to one of claims 1 to 3, wherein the generated voltage (u BR ) of the voltage-generating brake controller branches (15) have a DC component (U B R, DC ), where the DC component (U B R, 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.

5. The method according to claim 4, wherein the DC component (U B R, DC ) is controlled or regulated in such a way that currents (1 B R) with a further DC component (i BRfDC) by the modular brake controller (1), whereby the product of the further DC component (i BRfDC ) of all voltage-generating brake controller branches (15) and the voltage (U D ) via the modular brake controller (1) corresponds to a predetermined power to be converted into heat by the modular brake controller (1), in particular a predetermined active power to be converted into heat by the modular brake controller (1).

6. The method according to any one of claims 1 to 5, wherein the alternating portion (u B R,aoc) as a control variable for the capacitor voltages (U c , SU b) the submodules (2) are used.

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

8. Modular brake controller (1), wherein the modular brake controller (1) has at least two brake controller branches (15), wherein the brake controller branches (15) each have at least one submodule (2) and one braking resistor (3) which are arranged in a series circuit (4), wherein the brake controller branches (15) are arranged in a parallel circuit between two terminals (11) of the modular brake controller (1), wherein by means of the at least one submodule (2) of the respective brake controller branches (15) a voltage (U B R), wherein for controlling or regulating the at least one Submodule (2) of the respective brake controller branches (15) of the modular brake controller (1) has a control device (10) according to claim 7.

9. Modular brake controller (1) according to claim 8, wherein the brake controller branches (15) comprise a plurality of submodules (2) arranged in a further series circuit (41), wherein by means of the plurality of submodules (2) a generated voltage (U B R) across the further series circuit (41).

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

11. Modular drive unit (20) according to claim 10, 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).

12. Modular drive unit (20) according to one of claims 10 or 11, 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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