Modular brake actuator with hybrid design

Abstract

The invention relates to a modular brake actuator (1) having a brake resistor (3) and at least two sub-modules (2), the brake resistor (3) and the sub-modules (2) being arranged in a series circuit (4). In order to improve the modular brake actuator (1), at least one submodule (2) is embodied as a full-bridge module (21) and at least one submodule (2) is embodied as a double-half-bridge module (22), the modular brake actuator (1) having a control device which is configured to generate a voltage (uBR) at the submodules (2) arranged in series, the voltage (uBR) having a direct-current voltage component (uBR, uBR), and the direct-current voltage component (uBR, uBR) having a direct-current voltage component (uBR, uBR). The invention relates to a modular brake actuator (1) comprising a brake resistor (3) and a control device (4) for providing an alternating voltage component (uBR, DC) and an alternating voltage component (uBR, AC), said control device being further configured to provide an open-loop control or a closed-loop control of the alternating voltage component (uBR, AC), in particular in terms of the magnitude of the alternating voltage component, such that energy absorbed averagely by the modular brake actuator (1) over time is converted into heat in the brake resistor (3), said alternating voltage component (uBR, AC) being connected to the brake resistor (3). AC) is at least temporarily greater than the DC voltage component (uBR, DC). The invention also relates to an electric drive (10) having such a modular brake actuator (1) and a power converter (5), the power converter (5) being electrically connected to the modular brake actuator (1) on the DC voltage side. The invention also relates to a method for operating such a modular brake actuator (1) or such an electric drive (10), in which submodules (2) generate such a voltage (uBR) on submodules (2) arranged in series.

Description

Technical Field

[0001] The invention relates to a modular brake actuator having a brake resistor and at least two submodules, wherein the brake resistor and the submodules are arranged in a series circuit. The invention also relates to an electric drive having such a modular brake actuator and a power converter, wherein the power converter is electrically connected to the modular brake actuator on the DC voltage side. The invention also relates to a method for operating such a modular brake actuator or such an electric drive. Background Art

[0002] Modular multi-level power converters are known from DE 10 103 031 A1. This power converter, also called M2C or MMC, has a converter topology that is particularly suitable for medium-voltage and high-voltage applications due to its structure with submodules. The basic structure of a multiphase converter includes two converter arms per phase, each of which has a series circuit of a submodule. 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 multi-level power converter is formed by one or more phase terminals. In the basic structure, energy can be bidirectionally transmitted between the DC voltage side and the AC voltage side or energy can be temporarily stored to a certain extent by means of a converter.

[0003] In order to additionally achieve targeted energy reduction, it is expedient to install a brake actuator. A modular brake actuator is known from WO 2007 / 023061 A2. The modular brake actuator is usually connected to the DC voltage side of a modular multilevel power converter, for example between the DC+ and DC- terminals.

[0004] The resistor of a brake actuator device is often also referred to as a brake resistor, since it is suitable for converting the electrical energy of an electric machine generated by the braking process into heat. The use of brake actuators is not limited to the use of braking electric drives. Therefore, it is not necessarily necessary for the braking energy to be converted into heat. Brake actuators can also be used, for example, to stabilize an energy supply network by converting electrical energy from the energy supply network into heat. The term "brake resistor" was chosen to be able to distinguish resistors in which it is provided that electrical energy or power is converted into heat or heat per unit time from other resistors.

[0005] The term “power converted to heat” means below that the integral of the power converted to heat over time is the integral of the power converted to heat. In other words, the amount of energy generated from the power converted to heat over time. Summary of the invention

[0006] The invention is based on the object of improving a modular brake actuator.

[0007] The object is achieved by a modular brake actuator, wherein the modular brake actuator has a brake resistor and at least two submodules, wherein the brake resistor and the submodules are arranged in a series circuit, wherein at least one submodule is implemented as a full-bridge module and at least one submodule is implemented as a double half-bridge module, wherein the modular brake actuator has a control device, which is configured to: generate a voltage across the submodules arranged in series, wherein the voltage has a DC voltage component and an AC voltage component, wherein the control device is further configured to: open-loop control or closed-loop control of the AC voltage component, in particular with respect to the amplitude of the AC voltage component, so that the energy absorbed by the modular brake actuator over time is converted into heat in the brake resistor, wherein the amplitude of the AC voltage component is at least temporarily greater than the DC voltage component. In addition, the object is achieved by an electric drive, wherein the electric drive has such a modular brake actuator and a power converter, wherein the power converter is electrically connected to the modular brake actuator on the DC voltage side. The object is also achieved by a method for operating such a modular brake actuator or such an electric drive, wherein the submodules generate a voltage across the submodules arranged in series, wherein the voltage has a DC voltage component (u BR,DC ) and AC voltage component (u BR,AC ), wherein the control device is further configured to: perform open-loop control or closed-loop control of the AC voltage component so that the energy absorbed by the modular brake actuator on average over time is converted into heat in the brake resistor, wherein the amplitude of the AC voltage component is at least temporarily greater than the DC voltage component.

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

[0009] The invention includes, but is not limited to, the following knowledge: The combination of at least one full-bridge module and a double half-bridge module allows: A negative voltage to be applied to the series circuit of the submodules. The negative voltage is oriented such that the voltage applied to the brake resistor is greater than the DC line voltage applied to the terminals of the modular brake actuator. By increasing the voltage at the brake resistor, higher power can be converted into heat by the modular brake actuator. Here, the heat corresponds to the power integrated over time.

[0010] The braking resistor can be arranged at any position in the series circuit. For example, the braking resistor can be arranged at any position between one of the terminals of the modular brake actuator and a submodule or between two submodules. The braking resistor can also be obtained from the sum of a plurality of partial resistors arranged in series. The partial resistors that can be arranged at different positions in the series circuit cooperate like a braking resistor in the series circuit.

[0011] By means of a plurality of submodules, the modular brake actuator can be advantageously adapted to the DC link voltage of a power converter, so that the modular brake actuator can be connected to any power converter, in particular to a modular multi-level power converter. For expansion to higher voltages and for operation at different operating points, any number of full-bridge modules, half-bridge modules and resistors can be arranged or connected in series in any order.

[0012] With the aid of semiconductor switches arranged in the submodules, different voltages can be generated at the terminals of the corresponding submodules. In the case of a full-bridge module, voltages with different signs (+ / -) can also be generated. In the case of a double half-bridge module, four defined switching states can be generated in active operation: zero voltage, a first capacitor voltage, a second capacitor voltage, or the sum of the first and second capacitor voltages. Similarly, four switching states can be achieved with the aid of a full-bridge module, wherein two of the switching states produce zero voltage at the terminals of the switch module. In addition, a positive capacitor voltage and a negative capacitor voltage can be generated at the terminals of the submodule. The above-mentioned switching states of the double half-bridge module and the full-bridge module are independent of the flow direction of the current flowing through the corresponding submodule. For medium-voltage and high-voltage applications, IGBT modules with anti-parallel diodes are usually used as semiconductor switches for their cut-off capabilities.

[0013] From observation of the switching states it can be seen that by using a dual half-bridge module the voltage range of the modular brake actuator can be expanded approximately twice compared to a full-bridge module, since in one of the switching states of the dual half-bridge module the voltages at the two capacitors are added to the output voltage.

[0014] The current flowing through the brake resistor is open-loop controlled or closed-loop controlled by means of the voltage on the series circuit of the submodules. The current has a DC component and an AC component. The AC component has a periodic trend and an average value of zero. The power to be converted into heat by the modular brake actuator is open-loop controlled or closed-loop controlled by means of the DC component, and the AC component is used to maintain the energy balance in the submodule and thus to stabilize the operation of the modular brake actuator. Here, the voltage on the series circuit of the submodules and the magnitude of the AC component of the current flowing through the modular brake actuator include but are not limited to being related to the resistance value of the brake resistor. By using full-bridge modules, negative voltages can also be generated on the series circuit of the submodules. Thereby, operation can also be achieved in which the amplitude of the AC component exceeds the DC component. This increases the power range of the modular brake actuator under the condition of a given resistance. The more full-bridge modules are used, the greater the absolute value of the negative voltage generated on the series circuit of the submodules.

[0015] Therefore, the hybrid structure of the modular brake actuator has proven to be particularly positive, wherein the number of full-bridge modules is derived from the requirement for the absolute value of the negative voltage amount on the series circuit of the submodules to generate a correspondingly high current flowing through the full-bridge module. At the same time, a high operating voltage of the modular brake actuator is achieved by using double-bridge modules. The two types of submodules, namely full-bridge modules and double half-bridge modules, occupy almost the same structural space due to the same number of semiconductors and the control circuits associated therewith. As a result, the mechanical frame for accommodating the submodules of the modular brake actuator can be filled with double half-bridge modules and full-bridge modules in a simple manner. The corresponding installation space for the submodules can be designed identically and thus suitable for accommodating double half-bridge modules. As a result, a modular brake actuator with high performance and high operating voltage can be constructed modularly and thus simply and cost-effectively in a particularly advantageous manner. Likewise, the same control circuit can be used to control the double half-bridge module and the full-bridge module, because both types of modules have the same number of semiconductor switches (4 semiconductor switches). As a result, the hybrid structure of the modular brake actuator can be produced simply and cost-effectively and covers a wide range of performance and operating voltages.

[0016] The modular brake actuator is usually advantageously operated in combination with a power converter. The modular brake actuator is thus part of a drive system in which energy that cannot be recovered (e.g. from the electric machine) is converted into heat during the braking process. Compared to braking with a mechanical brake, the process is wear-free.

[0017] In the method according to the invention, in which the submodule generates a voltage across the submodules arranged in series, which voltage at least temporarily includes a negative voltage range and a positive voltage range, the negative voltage across the submodules arranged in series is generated at least temporarily by the self-module. This is done in order to generate a current through the modular brake actuator which is greater than the current that can be generated when the DC line voltage of the electric drive or the operating voltage of the modular brake actuator is applied to the brake resistor.

[0018] In an advantageous embodiment of the invention, at least one of the submodules, in particular all of the submodules, each has a bypass switch which is configured to short-circuit the terminals of the respective submodule. In order to be able to continue operating even in the event of a submodule failure, it has proven to be advantageous to create redundancy. In this case, not all submodules contribute to being able to generate a DC line voltage across the series circuit of the submodules. In the event of a submodule failure, the corresponding submodule can then be bridged by means of the bypass switch, so that the operation of the modular brake actuator is not disrupted.

[0019] In another advantageous design of the present invention, the power converter is implemented as a modular multi-level power converter. It is particularly advantageous to combine a modular brake actuator with a modular multi-level power converter (also called an M2C power converter) to form an electric drive. Here, submodules with the same structure can be used for the modular multi-level power converter and the modular brake actuator. Here, the modular multi-level power converter can be constructed by a double half-bridge module, a full-bridge module or a combination of these two types of submodules. The same hardware can also be used to control the submodules. Due to the modular structure of the power converter and the modular brake actuator, both adopt a modular design. By selecting a corresponding number of submodules in the power converter and the modular brake actuator, the electric drive can be simply adapted to the required power requirements. Since the implementation structure of the submodules in the modular brake actuator and the multi-level power converter is the same, a high-component identical component can be achieved. This has a positive effect on the reliability and manufacturing cost of such a drive unit.

[0020] The modular brake actuator can be connected to the DC voltage side of a power converter having any configuration and is not limited to use with modular multi-level power converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Below, the present invention is described and explained in more detail based on the embodiments shown in the accompanying drawings. The accompanying drawings show:

[0022] Figure 1 and Figure 2 shows an embodiment of a modular brake actuator,

[0023] Figure 3 The submodules are shown as full-bridge modules,

[0024] Figure 4 The submodule is shown as a dual half-bridge module,

[0025] Figure 5 and Figure 6 shows an embodiment of the proposed electric drive,

[0026] Figure 7 shows the time course of the electrical variables, and

[0027] Figure 8 Shows the operating range of the modular brake actuator. DETAILED DESCRIPTION

[0028] Figure 11 shows a modular brake actuator 1. The modular brake actuator has a series circuit 4 of at least two submodules 2 and a brake resistor 3. In this case, the series circuit 4 also includes a series circuit of submodules 2. For the submodules 2, at least one submodule 2 is implemented as a full-bridge module 21 and one submodule 2 is implemented as a double half-bridge module 22. The modular brake actuator can also have a plurality of submodules 2, such as Figure 2 Here, the submodule 2 can be a full-bridge module 21 and a double half-bridge module 22. Of course, it is also possible to use all other known submodules 2. The modular brake actuator 1 is configured to be connected to the DC line 9 of the power converter 5, 51 at its terminal 11.

[0029] A voltage U can be generated across the series connection of the submodules 2 BR With the help of voltage U BR can cause a current i to flow through the modular brake actuator 1 BR The current flowing through the braking resistor 3 causes the electrical energy to be converted into heat energy. D Applied at the modular brake actuator 1. If the modular brake actuator 1 is connected to the DC line of a power converter, the DC line voltage is applied at the modular brake actuator. In this case, the modular brake actuator 1 is connected to the DC voltage side of the power converter.

[0030] Figure 3 and Figure 4 An embodiment of the submodule 2 is shown. Here, Figure 3 The full bridge module 21 is shown and Figure 4 A double half-bridge module is shown. The full-bridge module and the double half-bridge module are part of the proposed design. Furthermore, the modular brake actuator 1 can be expanded with known submodules 2. To avoid repetitions, reference is made to Figure 1 and Figure 2 Description of and reference numerals introduced therein.

[0031] The illustrated exemplary embodiment of the submodule 2, 21, 22 comprises four semiconductor switches and at least one capacitor. An output voltage U 21 can be generated at the terminals of the submodule 2 by switching the semiconductor switches. sub In this case, the trigger circuit transmits the trigger signal to the semiconductor switch of the submodule 2. In order to bridge the corresponding submodule 2, a bypass switch 6 can optionally be provided in the submodule 2.

[0032] Figure 3 A so-called full-bridge module is shown. This full-bridge module has four semiconductor switches and a capacitor. The voltage U c,sub Applied at the capacitor. By switching operation of the semiconductor switch, a zero, positive or negative capacitor voltage ±U can be generated at the terminal 11 of the submodule 2 C,sub The output voltage Usub .

[0033] Figure 4 A so-called double bridge module is shown. This double bridge module has four semiconductor switches and two capacitors. The voltage U C1,sub or U C2,sub By switching the semiconductor switch, a capacitor voltage U of zero can be generated at the terminal 11 of the submodule 2. C1,sub , U C2,sub One of the capacitor voltages U C1,sub , U C2,sub The sum of the output voltage U sub .

[0034] exist Figure 5 1 shows an exemplary embodiment of an electric drive 10. In this case, the electric device 7 is electrically connected to the AC voltage side of the power converter 5. The modular brake actuator 1 is connected to the DC voltage side of the power converter 5 via a DC line 9. The electric device 7 can be, for example, a power supply network or an electric machine.

[0035] Figure 6 The electric drive 10 is shown, in which the power converter 5 is designed as a modular multi-level power converter 51. The modular brake actuator 1 and the modular multi-level power converter 51 are connected to each other via a DC line 9, the voltage U D Applied at the DC line. Here, the modular multilevel power converter 51 can (but not necessarily) have a submodule 2 that is the same as the submodule 2 of the modular brake actuator 1, i.e. a full-bridge module 21 and / or a double half-bridge module 22. In addition, the series circuit of the submodules 2 of the modular multilevel power converter 51 also has an inductor 8, which improves the closed-loop control behavior of the modular multilevel power converter 51. Terminals L1, L2, L3 represent terminals on the AC voltage side of the modular multilevel power converter 51, or simply the AC voltage side. In this embodiment, the modular multilevel power converter 51 is implemented as a three-phase. Alternatively, by providing a corresponding number of phase modules in the modular multilevel power converter 51, a single-phase implementation or any number of phases with a neutral conductor is also feasible.

[0036] Figure 7 The voltage U across the series circuit of the submodule 2 is shown. BR and the associated current i flowing through the modular brake actuator 1 BR To avoid repetition, refer to Figures 1 to 6, and the reference numerals introduced therein. The proposed design can be used with various methods for operating the modular brake actuator 1. One possibility is to carry out active current and voltage modulation with the aid of the modular brake actuator 1. The submodules 2 can be considered in general as controllable voltage sources. In simple terms, the modular brake actuator 1 modulates the voltage U across the series connection of the submodules 2. BR , so that the modular brake actuator 1 generates a current i BR Here, the current i BR With DC component i BR,DC and AC component i BR,AC Here, the voltage u BR With DC voltage component u BR,DC and the AC voltage component u BR,AC , which generates a DC component and an AC component in the current flowing through the brake actuator. It has been shown that if the voltage u applied to the submodule is BR Taking a negative value can improve the dynamic and operating range of the brake actuator. BR Perform open-loop control or closed-loop control so that the AC voltage component U BR,AC The amplitude is greater than the DC voltage component u BR,DC In order to be able to operate the brake actuator stably at this operating point, a full-bridge module is provided in the series circuit. The freely selectable voltage amplitude ensures an energy balance of the capacitors of the individual submodules, even if its value exceeds the DC voltage component. This makes it possible for the modular brake actuator to be operated stably with a current flowing through the brake actuator, wherein the current can assume different polarities. In addition to stable operation, this also ensures high utilization of the operating range of the brake resistor.

[0037] The main task of the modular brake actuator 1 is to convert the power limited over time in the braking resistor 3 or the sum of all braking resistors arranged in series into heat. The power converted into heat is transferred via a DC component i BR,DC To ensure the energy balance and stability of the modular brake actuator 1, the current i flowing through the modular brake actuator BR With AC component i BR,AC Current i BR The amplitude of the AC component is expressed as express.

[0038] With the aid of a monopole module (ie, for example, a half-bridge module or a double half-bridge module 22), no negative voltage can be generated. Figure 7 The voltage u shown in BR A time curve with a value of less than zero presupposes the use of two-pole modules, ie, for example, full-bridge modules 21 .

[0039] Operation at higher powers increases the proportion of the modulated negative voltage across the series connection of the submodules 2, which necessitates the use of an additional full-bridge module 21. The realization of higher powers also leads to a reduction in the modulated negative current flowing through the modular brake actuator. Since the monopole submodules can only provide positive terminal voltages, a negative proportion of the current flowing through the modular brake actuator is required to maintain the energy balance. This limits the use of monopole submodules. The possible operating range of the modular brake actuator 1 can be determined by means of the specific resistance R spec and the current i flowing through the modular brake actuator BR The DC component i BR,DC The operating range is Figure 8 Specific resistance R spec is related to the DC line voltage U D , that is, the resistance value R of the modular brake actuator 1 related to the operating voltage. Under a given system configuration, the current i flowing through the modular brake actuator 1 is BR The DC component i BR,DC Equivalent to the power converted by the modular brake actuator 1 .

[0040] The brake actuator variant equipped with only unipolar submodules can only be operated in the shaded operating range marked with I. Only in this range does the voltage U generated across the series connection of the submodule 2 BR For example, if the system is equipped with a specific resistance R spec =0.5Ω / kV, the maximum DC component i can be achieved with this design BR,DC =0.5I Nom Here, I Nom describes the nominal current of the semiconductor switches used. The proposed modular brake actuator 1 can also be operated in this operating range. If higher powers are to be achieved, i.e. with i BR,DC >0.5I Nom A negative voltage u must be generated in the series circuit of submodule 2. BR . This is characterized by an operating range II, in which the proposed modular brake actuator 1 can also be operated. Compared to operating range I with only unipolar submodule types, the proposed modular brake controller 1 doubles the performance of the proposed modular brake actuator. Operating range III can only be used with designs with only full-bridge modules 21. Due to the lower voltage that a full-bridge module 21 can generate compared to a dual half-bridge module 22, a design of a modular brake actuator 1 with submodules 2 of the full-bridge module 21 type has proven to be uneconomical. In comparison, the proposed modular brake actuator 1 provides a significantly cheaper and more economical solution.

[0041] In general, fewer submodules are required for designing modular brake actuators. As can be seen from the curve of the voltage to be generated: a higher proportion of positive voltage must be generated than negative voltage. The double half-bridge module 22 can achieve twice the positive output voltage relative to the full-bridge module 21 using the same amount of material. Another decisive advantage of using a combination of a double half-bridge module 22 and a full-bridge module 21 is the possible mechanical design of these two variants. The same components are required to build the two submodules of the system. Only the busbar connections of the individual modules between the semiconductors and the submodule capacitors are different. However, they provide the same size, cooling water terminals, electrical terminals for the busbars, triggers, etc. For such a system, it is not necessary to adapt the design (i.e., for example, a cabinet system) and the surrounding peripherals to the specific implementation of the submodule. More precisely, the design or cabinet system contains a receiving device that can accommodate full-bridge modules and double half-bridge modules without any changes. Therefore, the number and ratio of the installed full-bridge modules 21 and double half-bridge modules 22 can be freely changed and scaled in the design.

[0042] In summary, the present invention relates to a modular brake actuator 1, which has a brake resistor 3 and at least two submodules 2, wherein the brake resistor 3 and the submodules 2 are arranged in a series circuit 4. In order to improve the modular brake actuator 1, it is proposed that at least one submodule 2 is implemented as a full-bridge module 21 and at least one submodule 2 is implemented as a double half-bridge module 22, wherein the modular brake actuator 1 has a control device, which is configured to generate a voltage u across the submodules 2 arranged in series. BR , where the voltage u BR With DC voltage component u BR,DC and the AC voltage component u BR,AC , wherein the control device is further configured to, for the AC voltage component u BR,AC , in particular, an open-loop control or closed-loop control is provided with respect to the amplitude of the AC voltage component, so that the energy absorbed by the modular brake actuator 1 over time is converted into heat in the brake resistor 3, wherein the AC voltage component u BR,AC The amplitude is at least temporarily greater than the DC voltage component u BR，DC The invention further relates to an electric drive 10 having such a modular brake actuator 1 and a power converter 5, wherein the power converter 5 is electrically connected to the modular brake actuator 1 on the DC voltage side. The invention further relates to a method for operating such a modular brake actuator 1 or such an electric drive 10, wherein the submodules 2 generate such a voltage u across the submodules 2 arranged in series. BR .

Claims

1. A modular brake actuator (1) comprising a brake resistor (3) and at least two submodules (2), wherein: The braking resistor (3) and the submodules (2) are arranged in a series circuit (4), wherein at least one submodule (2) is implemented as a full-bridge module (21) and at least one submodule (2) is implemented as a double half-bridge module (22), wherein the modular brake actuator (1) has a control device configured to generate a voltage (u) across the submodules (2) arranged in series. BR ), wherein the voltage (u BR ) has a DC voltage component (u BR,DC ) and AC voltage component (u BR,AC ), wherein the control device is further configured to provide the AC voltage component (u BR,AC ) in particular with respect to the amplitude of the AC voltage component, so that the energy absorbed by the modular brake actuator (1) averaged over time is converted into heat in the brake resistor (3), wherein the AC voltage component (u BR,AC ) has an amplitude at least temporarily greater than that of the DC voltage component (u BR，DC ).

2. The modular brake actuator (1) according to claim 1, wherein: At least one of the submodules (2), in particular all of the submodules (2), each has a bypass switch (6) which is configured to short-circuit a terminal (25) of the respective submodule (2).

3. An electric drive (10) having a modular brake actuator (1) according to any one of claims 1 or 2 and a power converter (5), wherein: The power converter (5) is electrically connected to the modular brake actuator (1) on the DC voltage side.

4. The electric drive (10) according to claim 3, wherein: The power converter (5) is implemented as a modular multi-level power converter (51).

5. A method for operating a modular brake actuator (1) according to any one of claims 1 or 2 or an electric drive (10) according to any one of claims 3 or 4, wherein: The submodule (2) generates a voltage (U BR ), the voltage at least temporarily includes a negative voltage range and a positive voltage range, wherein the voltage (u BR ) has a DC voltage component (u BR,DC ) and AC voltage component (u BR,AC ), where the AC voltage component (u BR,AC ) performs open-loop control or closed-loop control, so that the energy absorbed by the modular brake actuator (1) over time is converted into heat in the brake resistor (3), wherein the AC voltage component (u BR,AC ) has an amplitude at least temporarily greater than that of the DC voltage component (u BR，DC ).

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