Filter circuit for an electrical drive

Abstract

The invention implements a filter circuit (100) for an electric drive (200), in which the filter circuit (100) comprises an x-type capacitor (CXi), a first y-type capacitor and a second y-type capacitor (CY1i, CY2i). An x-type capacitor (CXi) is coupled between the first filter output terminal pole and the third filter output terminal pole (212, 216) or between the first filter input terminal pole and the third filter input terminal pole (213, 217), and a first y-type capacitor (CY1i) is coupled between the third filter output terminal pole (216) or the third filter input terminal pole (217) and a reference potential or ground. A second y-type capacitor (CY2i) is coupled between the second filter output terminal pole (214) or the second filter input terminal pole (215) and a reference potential or ground.

Description

Technical Field

[0001] The invention relates to a filter circuit for operating an electric drive of a vehicle, a drive train having the circuit and a vehicle having the drive train, as well as a method for operating the circuit, a computer program and a computer-readable storage medium. Background Art

[0002] In the effort to develop more environmentally friendly means of transportation, electromobility forms an important component. However, in order to achieve widespread acceptance of electric vehicles, several prerequisites must be met. In addition to a sufficient driving range of the vehicle, a regional supply of energy sources is required to ensure that the electric vehicle can be charged at any time. In addition, the required charging time must be kept low in order to avoid major delays.

[0003] When an electric vehicle is charged at an alternating voltage (AC) charging station, such as when connected to a public power grid, the alternating voltage is converted into a direct voltage (DC) by a rectifier preferably inside the vehicle. Fast charging stations are distributed more and more, and these fast charging stations directly provide a direct voltage and are characterized by a shorter charging time. An exemplary direct current fast charging station is known from WO 2012 / 038222A3. An inverter is known from WO 2019 / 215128 A1, which is used to convert the electrical energy of a direct voltage source into an alternating voltage for driving an electric motor. In addition, the inverter is set up to increase the charging voltage of the charging device to a higher voltage. If the available charging voltage is less than the required voltage for charging the vehicle battery, this type of step-up chopper is used. The supply of the charging voltage at a voltage level of 400 volts is achieved, for example, by at least one winding of a connected electric motor. In motor operation, generator operation, and also in step-up chopper operation for increasing the charging voltage of, for example, 400 volts to the battery voltage of, for example, 800 volts of the battery or high-voltage battery in charging operation, the power switches of the inverter are operated in a clocked manner to provide the desired voltage at the output or input of the inverter. Electrical common-mode interference parameters and differential-mode interference parameters are formed here. They are usually filtered by HV-filters (high-voltage filters) to reduce EMC interference radiation. In charging operation, the EMC interference radiation in the direction of the power supply network, that is, in the direction of the high-voltage battery or in the direction of the public charging grid, preferably the DC voltage-charging network or the charging pile is minimized by means of a high-voltage filter. In charging operation, once the charging plug is connected to the public charging pile, the limit value of the allowable electromagnetic interference radiation that must be followed on the charging connection line is particularly low. An obvious solution for the filter circuit or HV filter to be used is a symmetrical filter circuit in which all three charging connection lines are filtered with equal intensity, i.e. symmetrically, by means of Y-capacitors with respect to ground or a reference potential, preferably the chassis of the vehicle. An important boundary condition when designing the Y-capacitors is that the sum of the capacitances of all Y-capacitors in the vehicle is limited for safety reasons. Limiting to, for example, 600 nF would mean that in a symmetrical filter, 6 capacitors each with 100 nF could be used, for example 2 capacitors per line, with each line having a total of 200 nF. Therefore, preferably in an electric drive train for a vehicle, there is a need for a solution that has a particularly good reduction in electromagnetic interference radiation with a minimum sum of the capacitances of the Y-capacitors. Summary of the invention

[0004] Based on the knowledge that, in step-up chopper operation for increasing the charging voltage to the battery voltage of the battery in charging operation, significantly lower limit values ​​for permissible electromagnetic interference radiation should be observed than in driving operation, i.e. in motor or generator operation of the electric drive train, the solution particularly takes into account the circuits associated with the step-up chopper operation. The invention realizes a filter circuit having the features of claim 1, a drive train having the features of claim 8, and a vehicle having the features of claim 9.

[0005] Therefore, the present invention relates to a filter circuit for an electric drive. The filter circuit comprises a three-pole filter input connection on the input side. Preferably, the filter input connection is a DC voltage connection, to which a DC voltage source or a DC voltage sink is connected, preferably a battery and / or an external charging voltage. The filter circuit comprises a three-pole filter output connection on the output side. Preferably, the filter output connection is a DC voltage connection, to which a DC voltage source or a DC voltage sink is connected, preferably a DC voltage input of an inverter or a winding connection point of a winding of an electric motor. The three-pole filter input connection on the input side is thus designed to be connected to the positive pole of a high-voltage battery at a first filter input connection pole, to the negative pole of the high-voltage battery and the negative pole of the charging voltage at a second filter input connection pole, and to the positive pole of the charging voltage at a third filter input connection pole. Preferably, the charging voltage is significantly lower than the battery voltage, so that the charging voltage is first increased in order to charge the high-voltage battery. Preferably, the power switching elements of the inverter and the windings of the electric motor are used to increase the charging voltage. The three-pole filter output connector on the output side is designed to be connected to the positive input connector of the preferred DC voltage side of the inverter at the first filter output connector pole, connected to the negative input connector of the preferred DC voltage side of the inverter at the second filter output connector pole, and connected to the winding connector of the motor connected to the inverter at the third filter output connector pole. The filter circuit is characterized in that it includes an x-type capacitor, a first y-type capacitor and a second y-type capacitor. The x-type capacitor is connected between the first filter output connector pole and the third filter output connector pole or the first filter input connector pole and the third filter input connector pole. The first y-type capacitor is connected between the third filter output connector pole or the third filter input connector pole and a reference potential or ground. The second y-type capacitor is connected between the second filter output connector pole or the second filter input connector pole and a reference potential or ground.

[0006] Since only the x-type capacitor is connected to the first filter input connection pole or the first filter output connection pole, the filter circuit is constructed asymmetrically in terms of the common mode suppression performed by means of the y-type capacitor. Through the resulting filter circuit, only the values ​​of the first y-type capacitor and the second y-type capacitor connected to the second filter input connection pole or the third filter input connection pole or the first filter output connection pole need to be added up when considering the limit value for the permitted electromagnetic interference radiation. Advantageously, compared with when the third y-type capacitor for filtering the line between the first filter input connection pole and the filter output connection pole is also considered, the first y-type capacitor and the second y-type capacitor can be designed to be larger. Since the line between the first filter input connection pole and the filter output connection pole is not required when the step-up chopper is running, the topology does not require a y-type capacitor here. The specified x-type capacitor is sufficient for the relevant driving operation or charging operation. According to the above numerical example, the y-type capacitor can now be implemented as 4×150nF (instead of 100nF respectively). Therefore, the line through which the charging voltage to be increased flows will be particularly strongly filtered. Preferably, when the y-type capacitor limit value is exhausted Afterwards, the necessary filter attenuation can only be set by the common mode choke (CMC) between the y-type capacitors. Advantageously, in the case of such asymmetric filters, a smaller CMC can be used for design-critical operations with a charging voltage to be increased. This again brings advantages in terms of smaller required structural space and the lower weight associated with this. In summary, asymmetric filters are smaller, lighter and more cost-effective. In order to achieve a slightly reduced filtering effect compared to the line filtered by means of a y-type capacitor on the line between the first filter input connection pole and the first filter output connection pole, an x-type capacitor is used to capacitively contact the y-type capacitor on the line between the third filter input connection pole and the first filter output connection pole. Instead of the third y-type capacitor, this x-type capacitor is arranged on the line between the first filter input connection pole and the first filter output connection pole. In the case of a symmetrical filter, a corresponding third y-type capacitor will be arranged. Advantageously, the sum of the capacitances of the preferred y-type capacitors remains the same. Preferably, the x-type capacitor does not require a y safety classification and therefore behaves smaller, lighter and more cheaply.

[0007] Connecting and disconnecting or decoupling or connected and disconnected are used synonymously with electrically connecting and disconnecting.

[0008] In other designs, the first y-type capacitor and the second y-type capacitor have the same capacitance value. Thus, the common-mode interference on the line between the third filter output connection pole and the third filter input connection pole and the line between the second filter output connection pole and the second filter input connection pole is suppressed with the same intensity. On the line between the first filter output connection pole and the first filter input connection pole, preferably due to the lack of the y-type capacitor between the first filter output connection pole and the first filter input connection pole, the common-mode interference is significantly weaker suppressed. Preferably, only the common-mode interference on the line between the first filter output connection pole and the first filter input connection pole is suppressed by means of capacitive coupling by combining the first y-type capacitor with the x-type capacitor.

[0009] Advantageously, a dimensioning of the capacitance value of the filter circuit is provided which ensures effective filtering for both charging operation and driving operation.

[0010] In other refinements, the x-type capacitor in combination with the first y-type capacitor at least partially suppresses common-mode interference on the line between the first filter output terminal and the first filter input terminal.

[0011] Advantageously, a circuit topology is provided which, instead of the third Y-capacitor, enables common-mode suppression on the line between the first filter output terminal and the first filter input terminal.

[0012] In one configuration, an x-type capacitor is arranged instead of the third y-type capacitor between the first filter output terminal or the first filter input terminal and a reference potential or ground.

[0013] Advantageously, a possible solution for reducing the resulting sum of the capacitance values ​​of the y-capacitors is provided.

[0014] In one design solution, the filter circuit is implemented in 1 stage, 2 stages, 3 stages, 5 stages or multiple stages. Each line of the first stage of the filter circuit, preferably of the high-voltage filter or the DC voltage-high-voltage filter, includes a capacitor preferably for reducing common-mode interference. In the case of a two-stage filter, each line is additionally provided with a longitudinal choke, preferably a common mode choke (CMC), preferably for reducing common-mode interference. In the case of a three-stage filter, an additional first stage is added to the filter circuit of the two-stage filter. In the case of a four-stage filter, an additional second stage is added to the filter circuit of the three-stage filter. The corresponding situation applies to filters of even higher orders. Preferably, the filter circuit is constructed as a 1st order (1st stage), 2nd order (2nd stage), 3rd order (3rd stage) or nth order (multiple stages) filter circuit, wherein (n is an element from natural numbers).

[0015] Advantageously, a possible solution for forming a multi-stage filter circuit is provided.

[0016] In one configuration, the voltage at the positive pole of the high-voltage battery is at least 1.2 times the voltage at the positive pole of the charging voltage.

[0017] Advantageously, a filter circuit is provided for filtering common-mode interference occurring during charging operation, in which the inverter is operated as a step-up converter in combination with the windings of the electric machine.

[0018] In one embodiment, the electric drive is preferably designed for operating a vehicle. The electric drive includes an inverter and a multi-phase electric machine. The inverter includes a positive input connection and a negative input connection on the input side for connecting to a first filter output connection pole and a second filter output connection pole. The inverter includes a multi-phase connection, preferably an AC voltage connection, for connecting to the multi-phase electric machine on the output side. The inverter is configured to supply electrical energy to the electric machine in motor operation and absorb electrical energy from the electric machine in generator operation, wherein at least one of the windings of the multi-phase electric machine includes a winding connection that can be connected to the positive pole of the charging voltage.

[0019] "Connectable" means that the winding connection is electrically connected to the positive pole of the charging voltage by means of a switch during charging operation and is disconnected by means of a switch during driving operation. The windings of the multi-phase electric machine are preferably connected in a star connection; a delta connection is also possible. The winding connection is a contact of at least one winding. Preferably, the star point is designed as a winding connection.

[0020] Advantageously, a filter circuit for an electric drive is provided, wherein, for an efficient filter circuit and taking into account a predetermined limit value for the sum of the capacitances of the Y-capacitors, the first Y-capacitor and the second Y-capacitor can be designed to be larger than when a third Y-capacitor for filtering the line between the first filter input terminal and the filter output terminal is also taken into account.

[0021] The invention further relates to a drive train with the described filter circuit. The drive train comprises a filter circuit and an inverter, a multiphase electric machine and / or a high-voltage battery. Advantageously, a drive train with a filter circuit is provided, wherein the first y-capacitor and the second y-capacitor can be designed to be larger than when a third y-capacitor for filtering the line between the first filter input terminal and the filter output terminal is also taken into account.

[0022] Furthermore, the invention relates to a vehicle having a drive train. Advantageously, a vehicle having a filter circuit is provided, which enables reliable operation of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] in:

[0024] Figure 1 shows a first schematic block diagram of an electric drive having a filter circuit;

[0025] Figure 2 A schematic diagram of a vehicle having an electric drive train with a filter circuit is shown.

[0026] In the figures, identical elements or elements with the same function are provided with the same reference symbols. DETAILED DESCRIPTION

[0027] Figure 1A schematic block diagram of a filter circuit 100 for an electric drive 200 is shown. The electric drive 200 is preferably designed for operating a vehicle 400. The electric drive 200 includes an inverter 210 and a multi-phase motor 220. The inverter 210 includes a positive input connection and a negative input connection for connecting the filter circuit 100 on the input side. Preferably, the inverter 210 includes a capacitor 242, preferably an intermediate circuit capacitor, on the input side. The inverter 210 includes a multi-phase connection 240 on the output side for connecting the multi-phase motor 220, preferably for connecting to the phase connections of the individual phases or windings of the motor 220. The inverter 210 is set up to supply electrical energy to the motor 220 in motor operation and absorb electrical energy from the motor 220 in generator operation. Preferably, the power switching elements shown in the inverter 210 are controlled accordingly. Preferably, three half-bridges preferably connected in parallel are constructed by means of the power switching elements, which are connected to a DC voltage at the ends. Preferably, the center tap of each half bridge is connected to a phase connection for connecting one of the windings of the motor 220. The windings 222, 224, 226 of the multi-phase motor 220 are connected in a star-shaped manner as an example. A connection of the windings in a triangle is also possible. The winding connection 228 of the motor 220, preferably the contact at the winding, is preferably connected to the switching element 229. The winding connection is preferably a phase connection of the motor. However, contacts at other locations of the winding, preferably within the winding or at other ends of the winding, between multiple windings of the motor 220, preferably at the star point of the motor 220, can also serve as winding connections. The filter circuit 100 includes three-pole filter input connections 213, 215, 217 on the input side and three-pole filter output connections 212, 214, 216 on the output side. The three-pole filter input connection on the input side is designed to be connected to the positive pole of the high-voltage battery 230 at the first filter input connection pole 213, to the negative pole of the high-voltage battery 230 and the negative pole 232 of the charging voltage at the second filter input connection pole 215, and to the positive pole 234 of the charging voltage at the third filter input connection pole 217. The three-pole filter output connection on the output side is designed to be connected to the positive input connection of the inverter 210 at the first filter output connection pole 212, to the negative input connection of the inverter 210 at the second filter output connection pole 214, and to the winding connection 228 of the motor 220 connected to the inverter 210 at the third filter output connection pole 216. Preferably, the third filter output connection pole 216 is switchably connected to the winding connection 228 via a switching element 229. The filter circuit 100 includes an x-type capacitor CX_i, a first y-type capacitor, and a second y-type capacitor CY1_i, CY2_i.The x-type capacitor CX_i is connected between the first filter output connection pole and the third filter output connection pole 212, 216 or the first filter input connection pole and the third filter input connection pole 213, 217. The first y-type capacitor CY1_i is connected between the third filter output connection pole 216 or the third filter input connection pole 217 and the reference potential or grounding portion. The second y-type capacitor CY2_i is connected between the second filter output connection pole 214 or the second filter input connection pole 215 and the reference potential or grounding portion. Preferably, in the case of a two-stage filter, coils 142, 144, 146, i.e., chokes or longitudinal chokes are arranged respectively between the first filter input connection pole and the first filter output connection pole, between the second filter input connection pole and the second filter output connection pole, and between the third filter input connection pole and the third filter output connection pole, and the filter input connection pole and the filter output connection pole are connected. Preferably, in the case of a three-stage filter, again, such as. Figure 1As shown in , another x-type capacitor CX_i, another first and another second y-type capacitor CY1_i, CY2_i are connected in parallel with the previous x-type capacitor CX_i, the previous first y-type capacitor and the second y-type capacitor CY1_i, CY2_i. Preferably, in the case of a multi-stage filter, the number of x-type and y-type capacitors connected in parallel is increased, and coils are added between each capacitor. Preferably, after the y-type capacitor limit value is exhausted, the necessary filter attenuation can only be set by the common mode choke (CMC) between the coils 142, 144, 146, i.e., the choke valve, the longitudinal choke or the y-type capacitor. Advantageously, in the case of such asymmetric filters, smaller common mode chokes 142, 144, 146 can be used for design-critical operations with a charging voltage to be increased. Preferably, the second capacitor 244 is arranged between the second filter output connection pole and the third filter output connection pole 214, 216. The second capacitor 244 preferably filters the voltage ripples that occur between the second filter output connection pole and the third filter output connection pole 214, 216 due to the alternating opening and closing of the power switching element during charging operation. Preferably, the switching element 229 is connected to the motor connection 228 on the one hand and can be connected to the positive pole 234 of the charging voltage through the third filter output connection pole 216 and the third filter input connection pole 217 on the other hand. Preferably, the negative pole 232 of the charging voltage can be connected to the second filter input connection pole 215. Preferably, the positive and negative poles 234, 232 of the charging voltage are set up for connecting to the charging energy source for charging operation for charging the energy source 230. Preferably, the circuit 100 is arranged in a common housing with the inverter 210 and / or the motor 220. Alternatively, the circuit 100 can be arranged in a separate housing and connected to the corresponding connections and connections relative to the motor 220, the inverter 210, the energy source 230 and the positive and negative poles 234, 232 of the charging voltage by means of lines.

[0028] Preferably, in another embodiment, the three-pole filter input connection on the input side is designed to be connected to the negative pole of the high-voltage battery 230 at the first filter input connection pole 213, to the positive pole of the high-voltage battery 230 and the positive pole 232 of the charging voltage at the second filter input connection pole 215, and to the negative pole 234 of the charging voltage at the third filter input connection pole 217. The three-pole filter output connection on the output side is designed to be connected to the negative input connection of the inverter 210 at the first filter output connection pole 212, to the positive input connection of the inverter 210 at the second filter output connection pole 214, and to the winding connection 228 of the electric machine 220 connected to the inverter 210 at the third filter output connection pole 216.

[0029] Figure 2A schematic diagram of a vehicle 400 having an electric drive train 300 and a circuit 100 is shown. The vehicle 400 preferably includes four wheels 402, wherein preferably at least one wheel is driven by means of an electric motor 220. This diagram only shows one possible embodiment of the vehicle 400. Preferably, the vehicle is any vehicle on water, on land or in the air. The drive train 300 includes a filter circuit 100 and an inverter 210, a multi-phase motor 220 and / or an energy source 230. Preferably, the electric energy source 230 is connected to the power switching element of the inverter 210 via the filter circuit 100. The charging connector, i.e., the negative pole 232 of the charging voltage and the positive pole 234 of the charging voltage, is configured to be connected to a charging energy source (not shown) during charging operation for charging the energy source 230.

Claims

1. A filter circuit (100) for an electric drive (200), in, The filter circuit comprises a three-pole filter input connection (213, 215, 217) on the input side and a three-pole filter output connection (212, 214, 216) on the output side, The three-pole filter input connector on the input side is designed to be connected to the positive pole of the high-voltage battery (230) at the first filter input connector pole (213), to the negative pole of the high-voltage battery (230) and the negative pole (232) of the charging voltage at the second filter input connector pole (215), and to the positive pole (234) of the charging voltage at the third filter input connector pole (217), and The three-pole filter output connector on the output side is designed to be connected to a positive input connector of an inverter (210) at a first filter output connector pole (212), to a negative input connector of the inverter (210) at a second filter output connector pole (214), and to a winding connector (228) of a motor (220) connected to the inverter (210) at a third filter output connector pole (216). or The three-pole filter input connector on the input side is designed to be connected to the negative pole of the high-voltage battery (230) at the first filter input connector pole (213), to the positive pole of the high-voltage battery (230) and the positive pole (232) of the charging voltage at the second filter input connector pole (215), and to the negative pole (234) of the charging voltage at the third filter input connector pole (217), and The three-pole filter output connector on the output side is designed to be connected to the negative input connector of the inverter (210) at a first filter output connector pole (212), to the positive input connector of the inverter (210) at a second filter output connector pole (214), and to the winding connector (228) of the motor (220) connected to the inverter (210) at a third filter output connector pole (216). It is characterized in that The filter circuit (100) comprises an x-type capacitor (CX_i), a first y-type capacitor and a second y-type capacitor (CY1_i, CY2_i), wherein the x-type capacitor (CX_i) is connected between the first filter output terminal and the third filter output terminal (212, 216) or the first filter input terminal and the third filter input terminal (213, 217), and the first y-type capacitor (CY1_i) is connected between the third filter output terminal (216) or the third filter input terminal (217) and a reference potential or ground, and The second y-type capacitor (CY2_i) is connected between the second filter output terminal (214) or the second filter input terminal (215) and a reference potential or ground.

2. The filter circuit (100) according to claim 1, in, The first y-type capacitor and the second y-type capacitor (CY1_i, CY2_i) have the same capacitance value, whereby common-mode interference on the line between the third filter output terminal (216) and the third filter input terminal (217) and on the line between the second filter output terminal (214) and the second filter input terminal (215) is suppressed with the same intensity, and common-mode interference on the line between the first filter output terminal (212) and the first filter input terminal (213) is suppressed significantly weaker and in particular is suppressed only by the x-type capacitor (CX_i) in combination with the first y-type capacitor (CY1_i).

3. The filter circuit (100) according to any one of the preceding claims, in, The x-type capacitor (CX_i) in combination with the first y-type capacitor (CY1_i) at least partially suppresses common-mode interference on the line between the first filter output connection pole (212) and the first filter input connection pole (213).

4. The filter circuit (100) according to any one of the preceding claims, in, Instead of the third y-type capacitor (CY3_i), the x-type capacitor (CX_i) is arranged between the first filter output terminal (212) or the first filter input terminal (213) and a reference potential or ground.

5. The filter circuit (100) according to any one of the preceding claims, in, The filter circuit is implemented in one stage, two stages, three stages, five stages or multiple stages.

6. The filter circuit (100) according to any one of the preceding claims, in, The voltage at the positive electrode of the high voltage battery (230) is at least 1.2 times the voltage at the positive electrode (234) of the charging voltage.

7. The filter circuit (100) according to any one of the preceding claims, in, The electric drive (200) is particularly designed for operating a vehicle (400), wherein the electric drive (200) comprises an inverter (210) and a multi-phase electric machine (220), wherein the inverter (210) comprises a positive input connection and a negative input connection on the input side for connecting the first filter output connection pole (212) and the second filter output connection pole (214), and comprises a multi-phase connection (215) on the output side for connecting the multi-phase electric machine (220), wherein the inverter (210) is designed to supply electrical energy to the electric machine (220) in motor operation and to absorb electrical energy from the electric machine (220) in generator operation, wherein at least one of the windings of the multi-phase electric machine (220) comprises a winding connection (228) which can be connected to a positive pole (234) of a charging voltage.

8. A drive train (300) comprising a filter circuit (100) according to any one of claims 1 to 7, in, The drive system (300) includes the filter circuit (100), the inverter (210), the multi-phase motor (220) and / or the energy source (230).

9. A vehicle (400) having a drive train (300) according to claim 8.

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