DE102022109257B3 - Modular multilevel converter for multiphase drives with compensation of capacitor voltages - Google Patents

Abstract

The present invention relates to a modular multilevel converter in which each module (110, 120, 130, 580) has a respective phase associated output to a respective winding (591, 592, 593, 598) of a multiphase machine (590). The proposed modular multilevel converter makes use of an intrinsic coupling between windings in the multiphase machine, is simple and efficient, and offers itself as a distributed highly integrated system for electrified vehicle powertrains. Furthermore, a corresponding overall system is claimed together with a controller.

Description

The present invention relates to a modular multilevel converter, in which each module has an output to a multiphase machine, associated with a respective phase. The proposed modular multilevel converter makes use of an intrinsic coupling between windings in the multiphase machine, is simple and efficient, and offers itself as a distributed highly integrated system for electrified vehicle powertrains.

The increase in electrical machines in a wide range of industrial production can be supplemented by targeted selection of the properties of these machines. Electrical multi-phase machines or multi-phase drives with more than three phases have advantages, such as power distribution over a number of phases or lower torque ripple.

On the other hand, since the power is distributed over more than the usual three phases, multi-phase machines require lower input voltages than, for example, three-phase machines for the same nominal power. It is therefore essential to use a DC-DC converter or a comparable topology to reduce the amplitude of the available multi-phase voltages.

The Chinese print CN 105720853B discloses power electronics for a three-phase electrical machine, the power electronics having three H-bridge circuits, each of which includes a multiplicity of semiconductor switches and two series-connected capacitors. The three H-bridge circuits provide a three-phase AC output with a common neutral.

In the pamphlet DE 10 2016 201 283 A1 discloses power electronics for a three-phase electrical machine, the power electronics having three H-bridge circuits, each of which includes four semiconductor switches and a capacitor. The three H-bridge circuits are electrically connected in parallel with respect to a DC voltage source.

The US publication US 9,973,110 B2 describes an electrical circuit architecture for converting DC voltage into AC voltage and vice versa, in which H-bridges are arranged in parallel-connected branches. A control unit is assigned to each H-bridge.

Other important publications in the field of multilevel converters are U.S. 9,496,799 B2 , U.S. 10,473,728 B2 , U.S. 10,442,309 B2 and U.S. 10,700,587 B2 to call.

However, all of these multilevel converters and module typologies mentioned above have the limitation that they cannot feed multiphase machines or multiphase drives. In addition, they are purely DC-based on a module level.

However, there is generally no corresponding multi-phase network available for a multi-level converter designed for multiple phases, which is why control by power electronics is necessary. In contrast to the relatively trivial topological conversion of a three-phase power converter into a multi-phase converter by continuing or copying the switching elements for each phase, a simple extension of a respective control architecture is not always feasible.

In the pamphlet U.S. 9,876,456 B2 a bridge converter has several bridge cells connected in series, each provided with a controller. The bridge converter includes a sensor that provides a commutation signal to at least one controller.

The pamphlet DE 10 2014 212 934 A1 relates to a device for equalizing the state of charge with at least two submodules, each of which has an energy storage module and a voltage converter module. The at least two submodules are connected to an electrical machine and a control device. The control device is designed to control an electrical energy flow between at least one of the submodules and the electrical machine.

The pamphlet " A. RUSELER, et.al: Modular inverter topology with full-bridge submodules for open-end split winding three-phase induction motor drive; In: 2015 IEEE International Conference on Industrial Technology (ICIT); Year: 2015, Conference Paper, Publisher: IEEE “ discloses a modular inverter topology with full bridge submodules for an electric machine. A number of inverters per phase are coupled to a number of pole pairs in the electric machine.

Against this background, it is an object of the present invention to provide a polyphase multilevel converter that offers simple implementation both in terms of the number of phase currents provided and in their respective control. Changes in the connection of different-phase multi-phase machines should be easy to implement and do not require a redesign of the control topology.

A modular multilevel converter is proposed to solve the above task, the modular multilevel converter having a controller and a number N of modules, each module having a plurality of switches, an input connection and an output connection and at least one capacitor connected between the input connection and the output connection wherein the modules are connected in series with each other, the first module being connected at its input terminal to a positive terminal of a voltage source and the Nth module being connected at its output terminal to a negative terminal of the voltage source, and each module being configured to have a provide the respective phase current for a respective winding of an N-phase multiphase machine, whereby during operation of the N-phase multiphase machine, respective windings exchange energy through electromagnetic coupling between the respective capacitors of the corresponding modules and the respective capacitor voltages of the respective capacitors are adjusted to a mean value from all capacitor voltages .

A topology of the modular multilevel converter according to the invention, also abbreviated as MMC, advantageously has a particularly low complexity of the modules or the switches and capacitors arranged in the modules, as is also evident from the reduced number of arranged compared to solutions from the prior art electronic components (see also 1 ). The number N of modules corresponds to the number of phases of the supplied multiphase machine, which is why the modular multilevel converter according to the invention can also be called a multiport MMC for short.

Methods implemented in the controller for switching the modules or the switches of the modules can also advantageously be implemented in a simple manner using methods known from the prior art in the modular multilevel converter according to the invention. Various switching methods are available here, such as conventional pulse width modulation (PWM), sinusoidal pulse width modulation (SPWM), space vector modulation (SVM) or space vector pulse width modulation (SVPWM) or any other control method that has been proposed for controlling multi-phase converters. Although different switch topologies of the modules have an influence on an output waveform of the phase currents provided, they do not restrict the choice of switching method. The controller of the modular multilevel converter according to the invention is connected, for example via a bus, to a central controller of an overall system, for example also including the multiphase machine, and receives from this, for example, specifications for a torque to be realized by the multiphase machine. Using generally known equations for electrical machines, these torque specifications can be converted into specifications for phase currents or reference phase currents to be provided by the multilevel converter.

In contrast to the prior art, in which the capacitor voltages of a modular multilevel converter are balanced by means of a separate control, the electromagnetic coupling between the respective windings in the multiphase machine, the respective phases or the respective modules and thus the respective capacitors is advantageously compensated in the modular multilevel converter according to the invention are assigned, exploited. The assignment of the respective windings is relatively free of specifications, which is why, for example, windings that do not necessarily run adjacently in a stator also have to be assigned to adjacent modules. There may even be benefits to avoiding such a neighborhood. Each at least one capacitor of a respective module assigned to a respective turn or supplying this turn with the respective phase current, whose capacitor voltage is lower than the capacitor voltages in the other modules, is automatically charged during operation of the multiphase machine. In this way, energy is transferred from capacitors with a higher capacitor voltage or higher capacitor charge state to capacitors with a lower capacitor voltage or lower capacitor charge state, and the capacitor voltages are advantageously balanced.

The multilevel converter according to the invention thus advantageously combines both a simple implementation of the control of an output power and a balancing of the capacitor voltages, balanced capacitor charge states in turn representing a basis for diverse functionalities of the modular multilevel converter according to the invention for power supply of multiphase machines.

wird intrinsisch die zwischen Eingangsanschluss und Ausgangsanschluss anliegende Klemmenspannung der Spannungsquelle V_dc zwischen allen Modulen und damit allen Phasen gleichförmig aufgeteilt: $$V_1=V_2=\cdots =V_N,$$

wobei gilt, dass $$V_{\text{dc}}={\displaystyle {\sum }_{i=1}^N{V}_i}$$

und damit $$V_i=\frac{1}{N}{V}_{\text{dc}}.$$

The arrangement according to the invention of the modular multilevel converter in modules connected in series and the at least one capacitor of the modules connected in series with it, with a capacitance of the at least one capacitor preferably being the same for all N capacitors, $$C_1=C_2=\cdots =C_N,$$

the terminal voltage of the voltage source V _dc present between the input connection and the output connection is intrinsically divided equally between all modules and thus all phases: $$V_1=V_2=\cdots =V_N,$$

where it holds that $$V_{\text{DC}}={\displaystyle {\sum }_{i=1}^N{V}_i}$$

and thus $$V_i=\frac{1}{N}{V}_{\text{DC}}.$$

As a result, a voltage V _i to be switched in the i-th module is significantly reduced compared to the terminal voltage V _dc , which means that the modular multilevel converter according to the invention is predestined for a high-voltage direct current input and a low multiphase alternating current.

Such a voltage distribution is based on an arrangement of capacitors with the same capacity as well as the same power consumption in each module - otherwise the capacitor voltages would diverge. In fact, even with the same nominal capacity, there are usually - even if only minor - differences in the capacities of the respective capacitors. In addition, the power consumption is different simply due to interference in the multi-phase machine. Therefore, in order to avoid different capacitor voltages of the modules, a continuous equalization of the state of charge of the respective capacitors or its continuous control is unavoidable. The modular multilevel converter according to the invention takes care of this, but the electromagnetic coupling of the windings can only ensure the equalization of capacitor voltages to a certain extent, since the capacitor voltages have residual fluctuations of up to 5% of their value. Depending on the application, it may be necessary to reduce the extent of such fluctuations, for which purpose embodiments of the control of the modular multilevel converter according to the invention are also proposed below.

In one embodiment of the modular multilevel converter according to the invention, the controller is configured to trigger a switch with a predetermined duty cycle in the respective discharge path of the respective capacitor as soon as the respective capacitor voltage of the at least one capacitor of the respective module falls below a predefined threshold voltage. As a result, a further energy outflow from the respective capacitor is reduced in accordance with a smaller duty cycle. The threshold voltage corresponds, for example, to the mean value across all capacitor voltages or is formed, for example, from the mean value multiplied by a predetermined factor of less than one, for example 0.98. Since the mean value is continuously lowered during operation due to a discharge of the voltage source, the threshold value is continuously adjusted. So while the capacitor voltages in the other modules continuously drop due to the power drain to the multiphase machine, the respective capacitor voltage of the respective module remains constant with an interrupted discharge path until it is equal to the threshold voltage or is above the threshold voltage. A completely open switch (duty cycle=0) would then be closed again in the respective discharge path. A reverse procedure is also conceivable in generator operation, in which the respective capacitors are charged from the windings.

According to the invention, the controller is configured to modify a respective modulation index of the respective phase provided according to a respective ratio of the respective capacitor voltage and the predefined threshold voltage. As a result, the respective capacitor voltage equalizes towards the threshold voltage. If the respective capacitor voltage is greater than the threshold voltage, the respective modulation index for this respective phase is increased, i. H. there is a stronger discharge of the respective capacitor compared to the capacitors in all other modules. If the respective capacitor voltage is lower than the threshold voltage, the respective modulation index for this respective phase is reduced, i. H. there is less discharge of the respective capacitor compared to the capacitors in all other modules.

According to the invention, a respective first control supplement is inserted into the controller on the respective module, with the respective first control supplement having the respective capacitor voltage and the threshold voltage as input variables and being configured to multiply an analog signal of a pulse duration modulation by a ratio of the respective capacitor voltage and threshold voltage.

In a further refinement of the modular multilevel converter according to the invention, the controller is configured for this purpose as soon as the respective capacitor voltage is below a predefined capacitor reference voltage, according to a requested reference torque formed reference phase current to reduce a current value corresponding to a first difference between the capacitor reference voltage and the respective capacitor voltage. As a result, a lower respective capacitor voltage of the at least one capacitor of the respective module results in a lower respective phase current, which reduces the energy drain from the respective capacitor and the respective capacitor voltage adjusts to the capacitor reference voltage. The capacitor reference voltage is given, for example, by the mean value of all capacitor voltages. The reference phase current is provided to a modulation method implemented in the controller as a basis for generating a respective phase current which produces the requested reference torque.

In a continued further embodiment of the modular multilevel converter according to the invention, a second additional control is inserted into the control. The second control supplement has the capacitor reference voltage and the respective capacitor voltage as input variables and is configured to feed the first difference between the capacitor reference voltage and the respective capacitor voltage to a PID controller and to subtract its output signal from the reference phase current.

In yet another embodiment of the modular multilevel converter according to the invention, the controller is configured to increase a requested reference torque of the respective phase by a torque value corresponding to a second difference between the respective capacitor voltage and the capacitor reference voltage as soon as the respective capacitor voltage is above a predetermined capacitor reference voltage. As a result, a respective capacitor voltage of the at least one capacitor of the respective module that exceeds the capacitor reference voltage results in a higher respective phase torque. The energy drain from the respective capacitor thus increases, while the respectively increased capacitor voltage decreases towards the capacitor reference voltage.

In a still further embodiment of the modular multilevel converter according to the invention, a third additional control is inserted into the control. The third control supplement has the respective capacitor voltage and the capacitor reference voltage as input variables and is configured to feed the second difference between the respective capacitor voltage and the capacitor reference voltage to a PID controller (proportional-integral-derivative controller) and to add its output signal to the reference torque of the respective phase.

In a further refinement of the modular multilevel converter according to the invention, the respective module has four switches. The four switches are arranged in two half-bridges and the two half-bridges are arranged in parallel with the respective capacitor. The respective phase is provided by the center tap on the two half-bridges. However, other circuit topologies with possibly a different number of switches per module are also conceivable without being restricted to the above embodiment. The switches are formed, for example, by field effect transistors (FET).

In an even further developed embodiment of the modular multilevel converter according to the invention, the voltage source is selected from the following list: battery, DC-DC converter connected to the AC power grid, DC-voltage supply.

Furthermore, a multiphase system is claimed, the multiphase system comprising a modular multilevel converter according to the invention and a multiphase machine. The multiphase machine is designed, for example, for traction of a vehicle.

Further advantages and refinements of the invention result from the description and the attached drawing.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

• 1 zeigt ein Schaltschema zu einer Ausgestaltung des erfindungsgemäßen modularen Multilevelkonverters.
• 2 zeigt ein Schema einer Pulsdauermodulation mit einer Ausgestaltung eines ersten einen Modulationsindex variierenden Steuerungszusatzes des erfindungsgemäßen modularen Multilevelkonverters.
• 3 zeigt schematisch eine Ausgestaltung eines zweiten einen Referenzphasenstrom variierenden Steuerungszusatzes des erfindungsgemäßen modularen Multilevelkonverters.
• 4 zeigt schematisch eine Ausgestaltung eines dritten ein Referenzphasendrehmoment variierenden Steuerungszusatzes des erfindungsgemäßen modularen Multilevelkonverters.
• 5 zeigt ein Schaltschema zu einer weiteren Ausgestaltung des erfindungsgemäßen modularen Multilevelkonverters mit einer Steuerung mittels Pulsdauermodulation.
• 6 zeigt ein Schaltschema zu einer noch weiteren Ausgestaltung des erfindungsgemäßen modularen Multilevelkonverters mit einer Regelungsstrecke zur Steuerung.
• 7 zeigt ein Schaltschema zu einer fortgesetzt noch weiteren Ausgestaltung des erfindungsgemäßen modularen Multilevelkonverters mit Steuerungszusätzen zu der Regelungsstrecke.

The figures are described in a coherent and comprehensive manner, and the same reference symbols are assigned to the same components.

• 1 shows a circuit diagram for an embodiment of the modular multilevel converter according to the invention.
• 2 shows a scheme of a pulse duration modulation with an embodiment of a first control addition varying a modulation index of the modular multilevel converter according to the invention.
• 3 shows a schematic of an embodiment of a second control supplement, which varies a reference phase current, of the modular multilevel converter according to the invention.
• 4 shows schematically an embodiment of a third control supplement, which varies a reference phase torque, of the modular multilevel converter according to the invention.
• 5 shows a circuit diagram for a further embodiment of the modular multilevel converter according to the invention with control using pulse duration modulation.
• 6 shows a circuit diagram for yet another embodiment of the modular multilevel converter according to the invention with a control path for control.
• 7 shows a circuit diagram for a still further embodiment of the modular multilevel converter according to the invention with control add-ons for the controlled system.

In 1 a circuit diagram 100 for an embodiment of the modular multilevel converter according to the invention is shown. A voltage source 101 provides a terminal voltage V _dc 102 which, according to equation (2), is distributed over the modules 110, 120, 130 connected in series. Four switches 111, 112, 113, 114, 121, 122, 123, 124, 131, 132, 133, 134 are arranged in each module 110, 120, 130, each of which forms two half-bridges per module. The switches 111, 112, 113, 114, 121, 122, 123, 124, 131, 132, 133, 134 shown are each an n-channel metal-oxide field effect transistor with an insulated gate, which is driven by a controller of the modular multilevel converter , shown. Respective capacitors 115 , 125 , 135 are connected in parallel with the half-bridges and in series with the arrangement of the modules 110 , 120 , 130 . A respective load is formed by a respective winding 116, 126, 136, for example in a stator of a multi-phase machine. At the same time, this also corresponds to a respective phase, ie the respective module 110, 120, 130 provides the respective phase current flowing in the respective winding 116, 126, 136, which leads to a reference torque provided by the multiphase machine. In the embodiment shown, an interconnection of the windings 116, 126, 136 has no neutral point. Due to an intrinsically given electromagnetic coupling between respective turns running in the stator, for example, there is a transfer of energy from capacitors with higher capacitor voltages to capacitors with lower capacitor voltages.

In 2 a scheme 200 of a pulse duration modulation is shown with an embodiment of a first control supplement 201 of the modular multilevel converter according to the invention, whereby a respective modulation index is varied for a respective phase provided by a respective module. The first control supplement 201 provides a respective ratio of a respective capacitor voltage 211 and a predetermined threshold voltage 212, which are present as input variables in a multiplier 210. In this case, an inverse of the specified threshold voltage 212 is multiplied by the respective capacitor voltage 211 . A result 213 of the multiplier 210 or of the first control supplement 201 is supplied to a pulse duration modulation in the further course of the switching scheme 200 assigned individually to the respective module, ie initially to a further multiplier 220. The multiplier 220 receives a modulation reference signal 221, for example a sine curve, as an additional input signal , and a reference voltage 222 corresponding to a torque to be realized. A comparator 230 compares a result 223 of the multiplier 220 with a carrier signal 231, which is configured as a sawtooth signal, for example. A control signal 232 for the individual switches of the respective module emerges from the comparator 230 . If the respective capacitor voltage 211 is greater than the threshold voltage 212, the respective modulation index for this respective phase is increased, ie the respective capacitor is discharged to a greater extent than the capacitors in all other modules. If the respective capacitor voltage 211 is less than the threshold voltage 212, the respective modulation index for this respective phase is reduced, ie the respective capacitor discharges less than the capacitors in all other modules. As a result, the respective capacitor voltage equalizes towards the threshold voltage.

In 3 an embodiment of a second control supplement 300 of the modular multilevel converter according to the invention, which varies a reference phase current 332, is shown schematically. At a first adder 310, the second control supplement 300 has as input variables a capacitor reference voltage 312 and the respective capacitor voltage 311 provided with a negative sign, so that as a result 313 a first difference between the capacitor reference voltage 312 and the respective capacitor voltage 311 is sent to a PID controller 320 (proportional integral-derivative controller) is supplied. Its output signal 321 is fed to a second adder 330 provided with a negative sign and is subtracted from the reference current 331 so that the second control supplement 300 outputs a reference phase current 332 that varies depending on the capacitor voltage 311 . The second control attachment 300 is included in the control of the modular multilevel converter. One in the controller imple mented modulation method, the reference current 331 is generally available as the basis for generating a respective phase current, which causes the requested reference torque, or is converted to a reference voltage specification, for example, for the pulse duration modulation. A relationship between phase current and torque is given by the equations describing the electric machine. The reference phase current 332 varied according to the invention is thus reduced compared to the reference current 331 by a current value corresponding to the first difference between the capacitor reference voltage 312 and the respective capacitor voltage 311 . As a result, a lower respective capacitor voltage 311 of the at least one capacitor of the respective module results in a lower respective reference phase current 332, which reduces the energy drain from the respective capacitor and the respective capacitor voltage 311 equalizes the capacitor reference voltage 312. The capacitor reference voltage is given, for example, by the mean value of all capacitor voltages.

In 4 an embodiment of a third control supplement 400 of the modular multilevel converter according to the invention, which varies a reference phase torque 432, is shown schematically. At a third adder 410, the third control supplement 400 has the respective capacitor voltage 411 and the capacitor reference voltage 412 provided with a negative sign as input variables, so that as a result 413 a third difference between the respective capacitor voltage 411 and the capacitor reference voltage 412 is fed to a PID controller 420. Its output signal 421 is added to reference torque 431 by a fourth adder 430 and output as reference phase torque 432 . The third control attachment 400 is included in the control of the modular multilevel converter. A modulation method implemented in the controller is based on a reference torque 431 that is requested (e.g. by a central controller of a vehicle) and is calculated using machine equations (reference number 331 in 3 ) before. The varied reference phase torque 432 according to the invention is thus increased compared to the reference torque 431 by a torque value corresponding to the third difference between the respective capacitor voltage 411 and the capacitor reference voltage 412 (PID output signal 421). As a result, a respective capacitor voltage 411 of the at least one capacitor of the respective module that exceeds the capacitor reference voltage 412 results in a higher respective reference phase torque 432, which increases the energy drain from the respective capacitor and reduces the respective capacitor voltage 411 towards the capacitor reference voltage 412.

aufteilt. Eine geeignete Wechselstromausgabe wird bspw. über die gezeigte Ansteuerung per Pulsdauermodulation 5100, 5200, 5300, 5800 mit jeweiligem sinusförmigen Modulationsreferenzsignal 518, 528, 538, 588, jeweiligem Sägezahn-Trägersignal 519, 529, 539, 589 und Komparator 517, 527, 537, 587 erhalten, wobei die jeweilig erzeugten Steuersignale 516, 526, 536, 586 an die jeweiligen Module 110, 120, 130 bis 580 bzw. deren Schalter 111, 112, 113, 124 bis 581, 582, 583, 584 geleitet werden. Dementsprechend fluktuiert eine jeweilige Phasenspannung auf mehreren Stufen zwischen $-\frac{1}{N}{V}_{\text{dc}}\text{ und }+\frac{1}{N}{V}_{\text{dc}},$

insbesondere wenn eine Topologie mit zusätzlichen Schaltern respektive Halbbrücken ausgestaltet werden würde. Die vom Schaltschema 500 umfasste HV-Spannungsquelle 501 bis 509 und die für eine vergleichsweise niedrigere Betriebsspannung ausgelegte Multiphasenmaschine 590 als Antriebsmaschine sind besonders vorteilhaft in einem Elektrofahrzeug umsetzbar.In 5 a circuit diagram 500 is shown for a further embodiment of the modular multilevel converter according to the invention with control by means of pulse duration modulation. The multilevel converter shown is connected to an N-phase multiphase machine 590, e.g. 130 to 580 are supplied with a respective phase current. Four FET switches 581, 582, 583, 584 are also arranged in the Nth module 580, each of which forms two half-bridges. A row with a number M of DC voltage storage devices 501, 502 to 509, which provide a terminal voltage V _dc 102 in the high-voltage range, are used as the voltage source $\frac{1}{N}{V}_{\text{DC}}$

splits. A suitable AC output is provided, for example, via the illustrated pulse width modulation drive 5100, 5200, 5300, 5800 with respective sinusoidal modulation reference signal 518, 528, 538, 588, respective sawtooth carrier signal 519, 529, 539, 589 and comparator 517, 527, 537, 587, the respectively generated control signals 516, 526, 536, 586 being routed to the respective modules 110, 120, 130 to 580 or their switches 111, 112, 113, 124 to 581, 582, 583, 584. Accordingly, each phase voltage fluctuates at plural levels between $-\frac{1}{N}{V}_{\text{DC}}\text{and}+\frac{1}{N}{V}_{\text{DC}},$

in particular if a topology were to be designed with additional switches or half-bridges. The HV voltage source 501 to 509 included in the circuit diagram 500 and the multiphase machine 590 designed for a comparatively lower operating voltage as a drive machine can be implemented particularly advantageously in an electric vehicle.

661 und eine mit einem negativen Vorzeichen versehene tatsächlich vorliegende Drehfrequenz ω_r 662. Eine dabei gebildete Differenz wird einem ersten PI-Regler 672 zugeführt, welcher ein gefordertes Referenzdrehmoment $T_e^{\ast }$

663 ausgibt. Dieses wird mittels Maschinengleichungen 673 zu einem dq-Referenzstrom $I_{\text{dq}}^{\ast }$

664 umgerechnet. Weiter wird der aktuell in den Modulen 110, 120, 130, 640, 650 fließende Phasenstrom I_abcde 665 mittels dq-Transformation 674 zu einem dq-Strom I_dq 666 umgerechnet, mit einem negativen Vorzeichen versehen in einem sechsten Addierer 675 von dem dq-Referenzstrom $I_{\text{dq}}^{\ast }$

664 abgezogen und ein Ergebnis einem zweiten PI-Regler 676 zugeleitet. Eine dabei ermittelte dq-Referenzspannung $V_{\text{dq}}^{\ast }$

wird mittels dq-Rücktransformation 677 zu den Referenzspannungen V_a,ref 681, V_b,ref 682, V_c,ref 683, V_d,ref 684, V_e,ref 685 für die Pulsdauermodulation umgerechnet. Das gezeigte Schaltschema 600 ist als eine allgemeine Ausgestaltung des erfindungsgemäßen modularen Multilevelkonverters zu verstehen und ist für alle Multiphasenmaschinen einsetzbar.In 6 a circuit diagram 600 is shown for yet another embodiment of the modular multilevel converter according to the invention with a control path 670 for control by means of pulse duration modulation. In this still further refinement, the modular multilevel converter has five modules 110, 120, 130, 640, 650 for supplying a five-phase electrical machine 690 with windings 691, 692, 693, 694, 695. To control the respective switches 111, 112, 113, 114, 121, 122, 123, 124, 131, 132, 133, 134, 641, 642, 643, 644, 651, 652, 653, 654, the control system 670 with respective Pulse width modulation units 6100, 6200, 6300, 6400, 6500 connected. In addition to those that can now be defined as a five-fold multiport MMC Modulation reference signals with V _m sin(ωt) 618, V _m sin(ωt - 2π/5) 628, V _m sin(ωt - 4π/5) 638 (voltage amplitude V _m of the modulation reference signal), also receives the fourth module 640 and the fifth Module 650 control signals 646, 656 from respective pulse width modulation 6400, 6500 with respective sinusoidal modulation reference signal V _m sin(ωt - 6π/5) 648, V _m sin(ωt - 8π/5) 658, respective sawtooth carrier signal 649, 659 and comparator 647, 657 to connect the respective capacitor 645, 655. This also requires a multiplication 6110, 6210, 6310, 6410, 6510 with a reference voltage V _a,ref 681, V _b,ref 682, V _c,ref 683, V _d,ref 684, V _e,ref 685, which is the control path 670 can be provided. The control system 670 receives a rotational frequency requested (for example by the central controller) as an input variable to a fifth adder 671 ${\omega }_{\mathrm{right}}^{\ast }$

661 and an actual rotational frequency ω _r 662 provided with a negative sign $T_e^{\ast }$

663 outputs. This becomes a dq reference current using machine equations 673 $I_{\text{dq}}^{\ast }$

664 converted. Furthermore, the phase current I _abcde 665 currently flowing in the modules 110, 120, 130, 640, 650 is converted to a dq current I _dq 666 by means of dq transformation 674, provided with a negative sign in a sixth adder 675 from the dq reference current $I_{\text{dq}}^{\ast }$

664 and a result is sent to a second PI controller 676. A dq reference voltage determined in the process $V_{\text{dq}}^{\ast }$

is converted by means of dq inverse transformation 677 to the reference voltages V _a,ref 681, V _b,ref 682, V _c,ref 683, V _d,ref 684, V _e,ref 685 for the pulse width modulation. The circuit diagram 600 shown is to be understood as a general embodiment of the modular multilevel converter according to the invention and can be used for all multiphase machines.

In 7 a circuit diagram 700 for a continued further embodiment of the modular multilevel converter according to the invention with control add-ons 7111, 7211, 7311, 7411, 7511, 778, 779 for the control path 770 is shown. While in the further development of the modular multilevel converter according to the invention in 6 only the intrinsically given electromagnetic coupling between respective windings 691, 692, 693, 694, 695 in the stator of the electric multiphase machine 690 for a compensation of capacitor voltages of the capacitors 115, 125, 135, 645, 655 provides, can by implementing in the 2 , 3 and 4 With the control add-ons 201, 300 and 400 shown, the balancing of the capacitor voltages must be strictly observed. So the first control option 201 becomes off 2 as the respective control supplement M1 7111, 7211, 7311, 7411, 7511 on the respective pulse duration modulation 7100, 7200, 7400, 7500 of the five modules 110, 120, 130, 640, 650 arranged for an amplitude of the reference voltage 681, 682, 683 , 684, 685 to be modified depending on the capacitor voltage. The second control add-on 300 off 3 is arranged as a control supplement M2 778 in the controlled system 770 for modifying the reference current 664. The third control add-on 400 off 4 is arranged as a control supplement M3 779 in the controlled system 770 for modifying the reference torque 663.

Reference List

100

Circuit diagram multiport MMC

101

voltage source

102

Terminal voltage _Vdc

110

module

111

Top FET switch left H-bridge

112

Lower FET switch left H-bridge

113

Top FET switch right H-bridge

114

Lower right H-bridge FET switch

115

capacitor

116

winding as a load

120

module

121

Top FET switch left H-bridge

122

Lower FET switch left H-bridge

123

Top FET switch right H-bridge

124

Lower right H-bridge FET switch

125

capacitor

126

winding as a load

130

module

131

Top FET switch left H-bridge

132

Lower FET switch left H-bridge

133

Top FET switch right H-bridge

134

Lower right H-bridge FET switch

135

capacitor

136

winding as a load

200

Pulse width modulation control scheme

201

First control addition to the modulation index

210

multiplier

211

capacitor voltage

212

threshold voltage

213

Score first multiplier

220

multiplier

221

modulation reference signal

222

reference voltage

223

Result of second multiplier

230

comparator

231

sawtooth signal

232

control signal

300

Second control addition to reference current

310

Difference formation in the first adder

311

capacitor voltage

312

capacitor reference voltage

313

Result of first adder

320

PID controller

321

Result signal PID controller

330

Difference formation in second adder

331

reference current

332

reference phase current

400

Third control addition to reference torque

410

Difference formation in third adder

411

capacitor voltage

412

capacitor reference voltage

413

Result of third adder

420

PID controller

421

Result signal PID controller

430

Fourth adder

431

reference torque

432

reference phase torque

500

Circuit diagram for control

501

First energy storage unit

502

Second energy storage unit

509

Mth energy storage unit

516

Control signals for first submodule

517

comparator

518

reference signal

519

sawtooth signal

5100

pulse width modulation

526

Control signals for first submodule

527

comparator

528

reference signal

529

sawtooth signal

5200

pulse width modulation

536

Control signals for first submodule

537

comparator

538

reference signal

539

sawtooth signal

5300

pulse width modulation

580

Nth submodule

581

Top FET switch left H-bridge

582

Lower FET switch left H-bridge

583

Top FET switch right H-bridge

584

Lower right H-bridge FET switch

585

capacitor

586

Control signals for the nth submodule

587

comparator

588

reference signal

589

sawtooth signal

5800

pulse width modulation

590

Multiphase machine as N-phase load

591

Winding as a load to the first submodule

592

Winding as a load to the second submodule

593

Winding as a load to the third submodule

598

Winding as a load to the Nth submodule

600

Circuit diagram of a five-phase electric machine

6100

pulse width modulation

6110

multiplier

6200

pulse width modulation

6210

multiplier

618

Reference voltage first phase with V _m sin(ωt)

628

Second phase reference voltage with V _m sin(ωt - 2π/5)

638

Third phase reference voltage with V _m sin(ωt - 4π/5)

6300

pulse width modulation

6310

multiplier

640

fourth submodule

641

Top FET switch left H-bridge

642

Lower FET switch left H-bridge

643

Top FET switch right H-bridge

644

Lower right H-bridge FET switch

645

capacitor

646

Control signals for fourth submodule

647

comparator

648

Reference voltage fourth phase with V _m sin(ωt - 6π/5)

649

sawtooth signal

6400

pulse width modulation

6410

multiplier

650

fifth submodule

651

Top FET switch left H-bridge

652

Lower FET switch left H-bridge

653

Top FET switch right H-bridge

654

Lower right H-bridge FET switch

655

capacitor

656

Control signals for fifth submodule

657

comparator

658

Reference voltage fourth phase with V _m sin(ωt - 8π/5)

659

sawtooth signal

6500

pulse width modulation

6510

multiplier

661

requested rotation frequency

662

current rotation frequency

663

required reference torque T _e *

664

requested reference current I _dq *

665

Phase current I _abcde in the five windings

666

transformed dq current I _dq

667

Reference voltage v _d,q *

670

Control section for control

671

Fifth adder

672

First PI controller

673

machine equations

674

dq transformation

675

Difference formation in sixth adder

676

Second PI controller

677

dq inverse transformation

681

Va _,ref

682

Vb _,ref

683

Vc _,ref

684

Vd _,ref

685

V _e,ref

690

Five-phase electric machine

691

Cable winding as load to the first submodule

692

Cable winding as a load to the second submodule

693

Cable winding as a load to the third submodule

694

Cable winding as a load to the fourth submodule

695

Cable winding as a load to the fifth submodule

700

Second circuit diagram of a five-phase electric machine

7100

modified pulse width modulation

7111

M1

7200

modified pulse width modulation

7211

M1

7300

modified pulse width modulation

7311

M1

7400

modified pulse width modulation

7411

M1

7500

modified pulse width modulation

7511

M1

770

modified control system for control

778

M2

779

M3

Claims (8)

Modular multilevel converter, wherein the modular multilevel converter comprises a controller (670, 770, 5100, 5200, 5300, 5800, 6100, 6200, 6300, 6400, 6500) and a number N of modules (110, 120, 130, 580, 640, 650 ), wherein a respective module (110, 120, 130, 580, 640, 650) has a plurality of switches (111, 112, 113, 114, 121, 122, 123, 124, 131, 132, 133, 134, 581 , 582, 583, 584, 641, 642, 643, 644, 651, 652, 653, 654) has an input connection and an output connection and at least one capacitor (115, 125, 135, 585, 645, 655 ) with the modules (110, 120, 130, 580, 640, 650) connected in series with the first module (110) being on Nem input connection is connected to a positive pole of a voltage source (101, 501) and the N-th module (580, 650) is connected at its output connection to a negative pole of the voltage source (101, 509), and wherein each module (110, 120, 130, 580, 640, 650) configured to provide a respective phase for a respective winding (591, 592, 593, 598, 691, 692, 693, 694, 695) of an N-phase multiphase machine (590, 690), whereby during operation of the N-phase multiphase machine (590, 690) respective turns (591, 592, 593, 598, 691, 692, 693, 694, 695) are formed by electromagnetic coupling between the respective capacitors (115, 125, 135, 585 , 645, 655) of the corresponding modules (110, 120, 130, 580, 640, 650) exchange energy and the respective capacitor voltages (211, 311, 411) of the respective capacitors (115, 125, 135, 585, 645, 655) thereby aligning a mean value from all capacitor voltages (211, 311, 411), whereby the controller (670, 770, 5100, 5200, 5300, 5800, 6100, 6200, 6300, 6400, 6500, 7100, 7200, 7300, 7400, 750 0 ) is configured to modify a respective modulation index of the provided respective phase according to a respective ratio of the respective capacitor voltage (211) and the threshold voltage (212), whereby the respective capacitor voltage (211) equalizes the threshold voltage (212), wherein in the controller (5100, 5200, 5300, 5800, 6100, 6200, 6300, 6400, 6500, 7100, 7200, 7300, 7400, 7500) on the respective module (110, 120, 130, 580, 640, 650) a respective first Control supplement (201, 7111, 7211, 7311, 7411, 7511) is inserted, the respective first control supplement (201, 7111, 7211, 7311, 7411, 7511) having the respective capacitor voltage (211) and the threshold voltage (212) as input variables and configured to multiply an analog pulse width modulation signal by a ratio of the respective capacitor voltage (211) and threshold voltage (212). Modular multilevel converter according to claim 1 , wherein the controller is configured as soon as the respective capacitor voltage (211, 311, 411) of the at least one capacitor (115, 125, 135, 585, 645, 655) of the respective module (110, 120, 130, 580, 640, 650) falls below a predetermined threshold voltage (212), a switch (111, 112, 113, 114, 121, 122, 123, 124, 131) in the respective discharge path of the respective capacitor (115, 125, 135, 585, 645, 655). , 132, 133, 134, 581, 582, 583, 584, 641, 642, 643, 644, 651, 652, 653, 654) with a predetermined duty cycle, causing a further outflow of energy from the respective capacitor (115, 125 , 135, 585, 645, 655) decreases according to the specified duty cycle. Modular multilevel converter according to one of the preceding claims, wherein the controller (770) is configured to, as soon as the respective capacitor voltage (311) is below a predetermined capacitor reference voltage (312), a reference current (331, 664) formed according to a requested reference torque (663). to reduce a current value (321) corresponding to a first difference between the capacitor reference voltage (312) and the respective capacitor voltage (311), resulting in a lower respective capacitor voltage (311) of the at least one capacitor (115, 125, 135, 585, 645, 655) of the respective Module (110, 120, 130, 580, 640, 650) has a lower respective phase current (332) result, so that the energy drain from the respective capacitor (115, 125, 135, 585, 645, 655) is reduced and the respective capacitor voltage (311) to the capacitor reference voltage (312) is adjusted. Modular multilevel converter according to claim 3 , wherein a second control supplement (300, 778) is inserted into the controller, wherein the second control supplement (300, 778) has the capacitor reference voltage (312) and the respective capacitor voltage (311) as input variables and is configured to calculate the first difference (313 ) from the capacitor reference voltage (312) and the respective capacitor voltage (311) to a PID controller (320) and to subtract its output signal (321) from the reference current (331). Modular multilevel converter according to one of the preceding claims, wherein the controller (770) is configured to, as soon as the respective capacitor voltage (411) is above a predetermined capacitor reference voltage (412), a requested reference torque (431) of the respective phase by a second difference from the respective To increase the torque value (421) corresponding to the capacitor voltage (411) and capacitor reference voltage (412), whereby a capacitor voltage (411) of the at least one capacitor (115, 125, 135, 585, 645, 655) of the respective module that exceeds the capacitor reference voltage (412). (110, 120, 130, 580, 640, 650) results in a higher respective reference phase torque (432), thus increasing the energy drain from the respective capacitor (115, 125, 135, 585, 645, 655) and increasing the respective increased capacitor voltage (411) decreased towards the capacitor reference voltage (412). Modular multilevel converter according to claim 5 , wherein in the controller (770) a third additional control (400, 779) is inserted, wherein the third additional control (400, 779) as input variables, the respective capacitor voltage (411) and the Has capacitor reference voltage (412) and is configured to feed the second difference (413) from the respective capacitor voltage (411) and capacitor reference voltage (412) to a PID controller (420) and to add its output signal (421) to the reference torque (431) of the respective phase . Modular multilevel converter according to one of the preceding claims, wherein the respective module (110, 120, 130, 580, 640, 650) has four switches (111, 112, 113, 114, 121, 122, 123, 124, 131, 132, 133, 134, 581, 582, 583, 584, 641, 642, 643, 644, 651, 652, 653, 654), the four switches (111, 112, 113, 114, 121, 122, 123, 124, 131 , 132, 133, 134, 581, 582, 583, 584, 641, 642, 643, 644, 651, 652, 653, 654) are arranged in two half-bridges and the two half-bridges are parallel to the respective capacitor (115, 125, 135, 585, 645, 655) are arranged, the respective phase being provided by center tapping on the two half-bridges. Multiphase system, the multiphase system having a modular multilevel converter according to one of Claims 1 until 7 and a multi-phase machine (590, 690).

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