DE102014110491A1 - Circuit arrangement for a multiphase multipoint inverter with relief network - Google Patents

Abstract

A multiphase multi-point inverter circuit arrangement (1) has a positive pole input terminal and a negative input terminal negative input terminal (uin), a medium voltage center (t) center tap (3), and an output terminal (4) for each phase ) for outputting an output alternating current (iload2, iload2, iload3), two external power switches (13, 23), one of which is connected to one of the two input terminals (11, 21), two internal power switches (14, 24) each on the one hand directly or via a diode (5) to the center tap (3) and on the other hand directly or via a diode (5) to the output terminal (4) are connected, and a discharge network, the two capacitors (15, 25) and four unidirectional Switching elements (17, 18, 27, 28). For each of the two capacitors (15, 25) of the relief network for each phase, there is a charging path between the output terminal (4) and the center tap (3), the respective capacitor (15, 25) in the charging path being connected to one of the switching elements (17, 27) and a throttle (16, 26) is connected in series. Between the output terminal for each phase and each of the input terminals (11, 21), there is a discharge path (20, 30) for each one of the two capacitors (15, 25) of each phase, the discharge path (20, 30) being viewed from the output terminal behind the respective condenser (15, 25) and before the throttle (16, 26) in a branch (35) branches off from the respective charging path (19, 29) and wherein another of the switching elements (18, 28) between the branch (35 ) and the input terminal (21, 11) in the discharge path (20, 30) is arranged. At least the charging paths (19, 29) for all the capacitors (15, 25) provided for switching discharge for those of the power switches (13, 23) connected to the same of the two input terminals (11, 21) together carry one common throttle (16, 26) which is directly connected to the center tap (3).

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a circuit arrangement for a multi-phase multipoint inverter with a discharge network. More particularly, the invention relates to a circuit arrangement having the features of the preamble of independent claim 1.

A multipoint inverter is understood to mean in particular a three-phase inverter in which an output connection via which an output alternating current is output is alternately also connected to a neutral electrical potential in addition to a positive electrical potential and a negative electrical potential in order to form the alternating output current. The multipoint inverter with the relief network can also be a five-point inverter or even a seven-point inverter.

A multiphase multipoint inverter is understood to mean, in particular, a three-phase multipoint inverter which outputs three output alternating currents whose phases are offset by 120 ° from each other. In principle, however, the multiphase multipoint inverter can also have only two or more than three phases, ie. H. output phase-shifted output alternating currents to each other.

STATE OF THE ART

A three-phase inverter called NPC (Neutral Point Clamped) is off Akira Nabae et al., A New Neutral-Point-Clamped PWM Inverter, IEEE Transactions on Industry Applications, Vol. 1A-17, no. 5, September / October 1981, pages 518 to 523 known. Here, four power switches are connected in series between input terminals for one DC input voltage per phase. The center of this series connection leads to an output terminal, via which an output alternating current is output. The intermediate points of the series connection on both sides of the center are each connected via reverse-biased diodes to a center tap of a DC input voltage applied to the input terminals. The center tap is a midpoint of a series connection of DC link capacitors between the input terminals forming a common DC link common to all phases. In order to form an output AC current output at the output terminal for each phase, during each half cycle of an output AC terminal connected to one of the input terminals, one of the outer switches connected to one of the input terminals of the phase associated series circuit is clocked complementary to the inner circuit breaker located on the other side of the output terminal. The lying on the same side of the output terminal inner switch is permanently closed and the outer switch located on the other side of the output terminal permanently open.

Different variants of the three-phase NPC three-level inverter have been developed. These include the BSNPC (Bidirectional Switch Neutral Point Clamped) inverter, see A. Nabae et al .: A New Neutral-Point Clamped PWM Inverter, IEEE Transactions on Industry Applications, Vol. 1A-17, no. 5, September / October 1981 . 10 , In the BSNPC inverter, the outer power switches of each phase connected at one end to the input terminals are connected at the other end thereof directly to the output terminal of the respective phase, while the inner power switches are connected between the center input DC input terminal and the output terminal respective phase are connected in series or in parallel, that with one inner power switch, the current flow in one and with the other inner power switch, the current flow in the other direction between the center tap and the output terminal can be switched off. Thus, a switching device which can be switched separately in both directions is realized between the center tap and the output terminal. The schematic of a BSNPC inverter is basically the same as that described above for an NPC inverter.

A known as ARCP (Auxiliary Resonant Commutation Pole) inverter variant of a single-phase BSNPC inverter is from the US 2004/0246756 A1 known. Here, a throttle between the center tap of the DC input voltage and the output terminal is connected in series with the two inner circuit breakers. In addition, a current flowing through the throttle is detected. Only when a zero current is measured during this detection, the respectively clocked inner circuit breaker is opened. The occurrence of the zero current is ensured by a resonant circuit in which the inductor is arranged as a resonance inductance, and which extends over the center tap to link capacitors of an input side DC link of the ARCP inverter. For the outer circuit breaker of the known ARCP inverter, a parallel-connected capacitor is provided for switching relief.

From the DE 10 2010 008 426 B4 a circuit arrangement for a three-point inverter with a discharge network is known. In a polyphase three-level inverter, this circuit arrangement with its own discharge network for each phase should be present, resulting in a multi-phase three-phase inverter having the features of the preamble of independent claim 1. The respective relief network is formed of at least one coil, two capacitors and a series circuit of four poled in the same direction diodes, of which the two outer diodes are each connected directly to the input terminals for the positive and negative pole of a DC input voltage. The midpoint between the two inner diodes is connected on the one hand via the coil with a center tap of the DC input voltage and on the other hand with a central bridge branch of the circuit arrangement of the three-phase inverter for the respective phase. The two capacitors are each connected on the one hand to an intermediate point between one of the inner and one of the outer diodes and on the other hand to the output terminal for the respective phase. Together with the coil, the capacitors each form a resonant circuit. This resonant circuit is used to charge the respective capacitor to the DC input voltage when the outer circuit breaker opposite it is opened. When closing this external circuit breaker discharges the previously charged capacitor and thus takes over the current flowing through the circuit breaker current and thus provides a switching discharge for this circuit breaker. For complete discharge of the capacitor another, across the output terminal across the throttle formed resonant circuit is used. In this known multi-point inverter, also referred to as the S3L (Soft Switching Three Level) inverter, the pulses of complementary clocking one of the outer circuit breakers with one of the inner circuit breakers may be different from other NPC inverters requiring a dead time between these pulses overlap. However, each current from the center tap to the output terminal of one of the phases forcibly flows through the inductor associated with the phase. Accordingly, each choke of the relief network must be sized for each phase for the maximum current of that current.

OBJECT OF THE INVENTION

The invention has for its object to provide a circuit arrangement for a particularly cost multi-phase multipoint inverter with relief network.

SOLUTION

The object of the invention is achieved by a circuit arrangement with the features of independent claim 1. Preferred embodiments of the circuit arrangement according to the invention are defined in the dependent claims.

DESCRIPTION OF THE INVENTION

The multi-phase multi-point inverter circuit of the present invention has a positive pole input terminal and a negative input DC terminal input terminal, a DC center voltage center center tap center, and an output terminal output terminal for each phase, two outer power switches, one each is connected to one of the two input terminals, two inner power switches, which are connected on the one hand directly or via a diode to the center tap and on the other hand directly or via a diode to the output terminal, and a discharge network for the outer circuit breaker on. The relief network for each phase comprises two capacitors and four unidirectional switching elements. For each of the two capacitors of the discharge network of the respective phase, a charging path between the output terminal and the center tap, wherein the respective capacitor is connected in series in the Aufladepfad with one of the unidirectional switching elements and a throttle. Between the output terminal of the respective phase and each of the input terminals also extends a discharge path for each one of the two capacitors of the discharge network of the respective phase, said discharge path branches from the output terminal seen behind the respective capacitor and before the throttle in a branch of the respective charging path and wherein another one of the unidirectional switching elements is arranged between the branch and the input terminal in this discharge path and thus not in the charging path. At least the charging paths for all the capacitors provided for switching discharge for those of the power switches connected to the same of the two input terminals together carry a common throttle connected directly to the center tap. This means that the relief networks of all phases share each of the common chokes and, accordingly, the number of common chokes and the cost associated with providing the chokes do not increase with the number of phases.

The fact that the inner circuit breakers of the respective phase are connected directly or via a diode to the center tap or the output terminal means that they are permanently electrically conductively connected to the center tap or dc current of a direction predetermined by the forward direction of the respective diode are connected to the output terminal. This does not exclude that in the respective compound additionally an inductive or resistive component is arranged. With the diode even more diodes of the same forward direction can be connected in parallel or in series.

In the case of the circuit arrangement according to the invention, a common DC voltage intermediate circuit between the two input terminals for the DC input voltage can be provided for all phases. This DC voltage intermediate circuit can be divided, wherein its center forms the center tap for the voltage center of the DC input voltage. The divided DC voltage intermediate circuit can be constructed from two or more DC link capacitors, wherein the center tap, for example, is the center of a series connection of these DC link capacitors.

In the circuit arrangement according to the invention, the relief networks of the various phases, which share at least one common throttle, to decouple, so there is no mutual interference, especially in the form of unwanted short-circuit currents through the discharge networks of several phases. Such short circuit currents may occur when two capacitors serving as a circuit breaker for two external power switches connected to different ones of the two input terminals are charged at the same time or when one of them is charged while discharging the other one. The desired decoupling can be achieved by various measures that can be realized for other reasons, d. H. in a circuit arrangement according to the invention need not necessarily be taken in addition.

Thus, in the case of the circuit arrangement according to the invention, a control can be present which is set up to wait at least one charging time after switching on one of the outer circuit breakers of one of the phases and before another circuit of another of the outer circuit breakers of another of the phases of the one of the outer circuit breaker provided capacitor is charged to substantially double the DC input voltage. After this charging time, the capacitor provided for switching discharge of one of the outer power switches is already substantially fully charged and this charging is no longer disturbed by the switching on of the other of the outer power switches of the other of the phases.

Furthermore, the controller can be set up to wait for at least the charging time even after one of the outer circuit breakers of one of the phases has been switched on and before another of the phases is switched on. Here, by waiting for the charging time, it is ensured that the capacitor provided for switching discharge of the one of the outer power switches of the one phase is not charged by discharging a charged capacitor of the other phase.

Alternatively or additionally, in the circuit arrangement according to the invention for decoupling the discharge networks of the individual phases, the one of the unidirectional switching elements in each charging path can be an actively activatable switching element. With the help of this active controllability z. B., a current flowing in the forward direction of the unidirectional switching element current can be prevented to prevent unwanted charging of each not serving for switching discharge capacitor of the respective phase or to limit charging of each serving for switching discharge capacitor. If only the charging capacitor of the respectively charged capacitor is closed by the actively controllable switching elements in the Aufladepfaden the discharge networks of all phases, there is no mutual interference when charging the individual capacitors. In addition, if it is noted that the respective actively controllable switching element is not yet closed, while discharging a capacitor for switching discharge, from which the discharge can flow on the capacitor to be charged, all other unwanted currents between the capacitors of the individual discharge networks are avoided.

Specifically, in each Aufladepfad one actively controllable unidirectional switching element may comprise a non-actively controllable unidirectional switching element, ie a diode, and an actively controllable bidirectional switching element connected in series therewith. The non-actively controllable unidirectional switching element must not be at the same time in the associated discharge path. This also applies to a one-piece, actively activatable unidirectional switching element or, more generally, to that part of the actively activatable unidirectional switching element which makes it unidirectional. Any other part of the actively controllable unidirectional switching element can also be arranged where the charging path and the associated Unloading path coincide. Thus, the actively controllable switching element can also be arranged between the output terminal of the respective phase and the branch of the discharge path of the Aufladepfad. Then, however, it must be closed at the time of the switching relief to be provided with the respective capacitor, provided that it also shuts off a current flow in the discharge direction of the capacitor in the opened state. In the actively controllable switching element means "bidirectional" that it allows a flow of current in both directions, but this can not necessarily switch off in both directions. In concrete terms, the actively controllable bidirectional switching element may be a transistor having an anti-parallel diode, whose forward direction is then aligned opposite to the forward direction of the diode which forms the unidirectional switching element which can not be activated. The antiparallel diode may, for example, be a body diode of the transistor.

The non-actively controllable unidirectional switching element and the actively controllable bidirectional switching element of the actively controllable unidirectional switching element can be connected in the inventive circuit arrangement with interposition of the capacitor and / or the throttle in the Aufladepfad in series. They can also be arranged on the same side of the condenser and / or the throttle.

In the case of the circuit arrangement according to the invention, each discharge path can be connected directly to the respective input connection. The further unidirectional switching element provided in the discharge path between the input terminal and the branch from the charging path is preferably a passive unidirectional switching element, i. H. a diode.

Each charging path and thus also each discharge path is preferably connected directly to the output terminal of the respective phase in the circuit arrangement according to the invention, in order to realize its charging and also discharging for switching discharge independently of the switching position of the inner circuit breaker.

At its other end, each charging path may be directly or through the connection of the internal power switches of the respective phase with the center tap to the center tap. In this case, all the charging paths for all capacitors of all the discharge networks of all phases can lead together via the common choke, which is arranged between a junction where all connections are combined, which connect the two inner circuit breakers one phase to the center tap, and the center tap. This position of a common throttle corresponds to the location of each throttle of each discharge network of each phase of the DE 10 2010 008 426 B4 known circuit arrangement.

In the case of a common choke, the decoupling of the discharge networks of the individual phases of the circuit arrangement according to the invention can also be achieved by a respective auxiliary choke in each of these discharge networks. For this purpose, these auxiliary chokes are each seen from the inner circuit breakers before the common throttle in the not yet merged connections of the two inner circuit breaker of the individual phases to arrange the center tap, in which case the two charging paths of the discharge network of the respective phase lead through its own auxiliary throttle, the is arranged from the inner circuit breakers before merging in the connection of the two inner circuit breakers of the respective phases with the center tap, and thus only in the Aufladepfaden the respective phase. With the auxiliary chokes, the individual discharge networks are passively decoupled.

Even with such additional auxiliary chokes per phase is the cost of all the chokes of the circuit arrangement according to the invention with a common throttle small compared to the cost of the large throttle for each phase of the DE 10 2010 008 426 B4 known circuit arrangement. It should be noted that an inductance of the common throttle is typically at least as large as inductances of the auxiliary throttles. The inductance of the common throttle can also be at least twice, five times or ten times as large as the inductances of the auxiliary throttles. The smaller the relative inductances of the auxiliary inductors, the less they affect the total inductances in the charging path and thus the resonant circuits formed by the respective capacitors and the common inductor as well as the auxiliary inductors also arranged in the charging path. Specifically, the auxiliary throttles can be designed as air throttles.

As an alternative to only one common throttle, in the circuit arrangement according to the invention for those charging paths from which the associated discharge path leads to the same of the two input terminals, a separate common throttle can be arranged in the charging path, as seen from the output terminals of the phases behind the branches of Discharge paths and before connecting these charging paths to a junction of all connections that connect the two inner circuit breakers each one of the phases with the center tap. None these two separate common chokes in the charging path then lie in one of the connections of the inner circuit breakers of any of the phases with the center tap, and the separate common chokes do not therefore have to conduct the current flowing between the center tap and the respective output terminal via the inner circuit breakers. Accordingly, they must be designed only for the current flowing through the charging path.

When charging the individual capacitors assigned to them, the two separate common reactors basically have the same function as the one reactor of the circuit arrangement according to FIG DE 10 2010 008 426 B4 , However, when discharging the capacitors during the switching discharge, the separate common reactors are not involved. The discharge of the capacitors is thus neither via resonant circuits in which the separate common reactors are arranged, nor is a current from the capacitors to the center tap attenuated by the separate common inductors. This must be taken into account in the pulsed control of the middle circuit breakers.

Compared with the effort for the large throttle to be provided for each phase of the DE 10 2010 008 426 B4 known circuitry, the cost of only small separate common chokes this embodiment of the circuit arrangement according to the invention is particularly small. This advantage in the production of a multipoint inverter with relieving network in the circuit arrangement according to the invention is not lost in that in this embodiment of the circuit arrangement according to the invention provided in the respective Aufladepfad a unidirectional switching element is preferably an actively controllable switching element to the individual charging paths also within the relief network every single phase decouple.

If there are separate common chokes for those charging paths from which the associated discharge path leads to the same of the two input terminals, an additional auxiliary throttle may be provided in the mated connection of the two internal circuit breakers of all phases with the center tap to attenuate currents flowing from the each serving for switching discharge, but not completely discharged capacitor can flow when the complemented to the switch-relieved outer circuit breaker inner circuit breaker is closed. Even with such an additional auxiliary throttle, the cost of all the chokes of the circuit arrangement according to the invention with two separate common chokes is particularly small compared to the cost of the large throttle for each phase of the DE 10 2010 008 426 B4 known circuit arrangement. It should be noted that inductances of the two separate common reactors are typically at least as large as an inductance of the auxiliary inductor. The inductances of the two separate common reactors can also be at least twice, five times or ten times as large as an inductance of this auxiliary inductor. The smaller the relative inductance of the auxiliary throttle, the less it affects the total inductance in the Aufladepfaden and thus on the resonant circuits, which are formed by the respective capacitors and the separate common reactors and also arranged in the Aufladepfaden auxiliary throttle. Specifically, the auxiliary throttle can be designed as an air throttle.

In the case of the circuit arrangement according to the invention, the forward directions of the one and the other of the unidirectional switching elements in the charging path and the discharge path for each capacitor are opposite one another, as viewed from the respective output exclusion. In this case, the other of the unidirectional switching elements with respect to the pole of the input voltage to that of the input terminals to which the discharge path is connected, with respect to the pole of the input DC voltage, which is applied to the input terminal, in the reverse direction. The other unidirectional switching elements of the circuit arrangement according to the invention thus largely correspond to the outer diodes of the DE 10 2010 08 426 B4 known circuit arrangement, while the local inner diodes in the circuit arrangement according to the invention can be replaced by actively controllable unidirectional switching elements and parts can also be arranged elsewhere in the respective Aufladepfad.

The circuit arrangement according to the invention can be applied to a large number of multiphase three-point and multipoint inverters. These include NPC inverters, BSNPC inverters, ARCP and S3L inverters.

For timing the power switch and also the actively controllable unidirectional switching elements of certain embodiments of the circuit arrangement according to the invention, a control is provided. In particular, when describing what actions this controller can perform, this implies that the controller is properly set up to perform those same actions. This control can for each phase the actively controllable switching element in the Aufladepfad from which the discharge path leads to the one input terminal, within a time period over which it shunts the outer power switch for each phase connected to the other input terminal in pulses. For this external circuit breaker, the capacitor, for which the charging path is provided, serves as a switching relief. The other capacitor, which is provided as a switching relief for the other external power switch should, as long as the other external circuit breaker is not clocked, not be charged, in particular to cause any unwanted discharge currents. Therefore, the controller keeps open the actively controllable switching element in the Aufladepfad as long as the other outer circuit breaker is not clocked for the respective phase.

Preferably, the control of the circuit arrangement according to the invention for each phase closes the actively controllable switching element only within a sub-period of the period over which it clocks the respective outer circuit breaker, d. H. in pulses closes. This sub-period is characterized in that the magnitude of an instantaneous value of the output alternating current output via the output connection complies with a lower limit value and that the instantaneous value of the output alternating current and an instantaneous value of the output alternating voltage have the same sign. The limit value is to be dimensioned such that the condenser serving for switching discharge is discharged at least substantially completely at each discharge process, and within a short time. This time must remain as a dead time between the pulses, in which the outer circuit breaker and the complementarily clocked inner circuit breaker are closed.

The control of the circuit arrangement according to the invention can close the actively controllable switching element not only once per half cycle of the output AC output current, but also in pulses having the same frequency as the pulses in which it closes the respective circuit breaker. These pulses are preferably completely within the pulses in which the controller closes the outer circuit breaker. Ideally, the pulses for which the actively actuable switching element is closed are synchronized with the pulses in which the controller closes the outer circuit breaker. However, the necessary to decouple the discharge networks of the individual phases necessary waiting for the charging or discharging is maintained. The width of the pulses, for which the actively controllable switching element is closed, can also be influenced by the degree of charging of the circuit breaker that relieves the load on the external circuit breaker. The width of the pulses for which the actively controllable switching element is closed, but can also be constant.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the description are merely exemplary and can take effect alternatively or cumulatively, without the advantages having to be achieved by embodiments according to the invention. Without altering the subject matter of the appended claims, as regards the disclosure content of the original application documents and of the patent, the following applies: Further features can be found in the drawings, in particular the relative arrangement and operative connections of several components. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims. Likewise, in the claims listed features for further embodiments of the invention can be omitted.

The features mentioned in the patent claims and the description are to be understood in terms of their number that exactly this number or a greater number than the said number is present, without requiring an explicit use of the adverb "at least". For example, when talking about an element, it should be understood that there is exactly one element, two elements or more elements. These features may be supplemented by other features or be the only characteristics that make up the product in question.

The reference numerals contained in the claims do not limit the scope of the objects protected by the claims. They are for the sole purpose of making the claims easier to understand.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention will be further explained and described with reference to preferred embodiments shown in the figures.

1 shows a circuit arrangement according to the invention in a first embodiment based on a three-phase S3L inverter.

2 shows the circuit arrangement according to the invention in a second embodiment based on a three-phase S3L inverter.

3 shows the circuit arrangement according to the invention in a further embodiment, also based on a three-phase S3L inverter.

4 shows the circuit arrangement according to the invention in a further embodiment based on a three-phase BSNPC inverter.

5 illustrates the activation of actively controllable unidirectional switching elements of the circuit according to 4 in one embodiment, having a phase angle of zero between output AC output and AC output voltage.

6 illustrates the activation of the actively controllable unidirectional switching elements of the circuit according to 4 in an embodiment with a AC output lagging the AC output voltage.

7 shows the structure of a phase of a circuit arrangement according to the invention in a further embodiment based on an NPC inverter.

8th shows the structure of a phase of a circuit arrangement according to the invention in another embodiment based on a BSNPC inverter; and

9 shows the structure of a phase of a circuit arrangement according to the invention in yet another embodiment based on a BSNPC inverter.

DESCRIPTION OF THE FIGURES

In the 1 illustrated circuit arrangement 1 based on a three-phase S3L inverter. It has two input connections 11 and 21 for a positive and a negative pole of a DC input voltage u _in . The DC input voltage u _in is above a DC voltage intermediate circuit 2 with two DC link capacitors 12 and 22 and a center tap 3 at. Between the input terminals 11 and 21 For each phase, there are two external circuit breakers 13 and 23 connected in series. Between the circuit breakers 13 and 23 There is one output connection in each case 4 , via which an output _alternating current i _load1 , i _load2 or i _{load3 is} output. The output terminal 4 each phase is through series-connected internal circuit breakers 14 and 24 with the center tap 3 connected. The circuit breakers 13 . 14 . 23 and 24 are here each as IGBT with anti-parallel diodes 5 educated. The antiparallel diodes 5 the outer circuit breaker 13 and 23 are with respect to the DC input voltage and oriented _{in the} reverse direction. The antiparallel diodes 5 the inner circuit breaker 14 and 24 have mutually opposing blocking directions.

The circuit breakers 13 . 14 . 23 and 24 be in the circuit 1 Just as controlled as with a conventional three-phase S3L inverter. For switching discharge of the outer circuit breaker 13 and 23 is a relief network for each phase 6 provided that two capacitors 15 and 25 and four unidirectional switching elements 17 . 18 . 27 . 28 having. Together, the relief networks 6 all phases a common throttle 16 on. In each case one of the capacitors 15 and 25 with one of the unidirectional switching elements 17 and 27 and the common throttle 16 in a charging path 19 respectively. 29 connected in series. This charging path 19 respectively. 29 is with a capacitor end to the output terminal 4 connected and with a throttle end with the center tap 3 , This leads to the charging paths 19 and 29 in connections 8th the series connection of the internal circuit breakers 14 and 24 with the center tap 3 one and the common throttle is between a merge 9 the connections 8th and the center tap 3 , From each of the discharge paths 19 and 29 branches between the respective capacitor 15 respectively. 25 and the respective throttle 16 respectively. 26 a discharge path 20 respectively. 30 in a turnoff 35 from. From the output terminal 4 to the branches 35 are the discharge paths 20 and 30 identical to the charging paths 19 and 29 , Beyond the branches 35 are the discharge paths 20 and 30 over the other unidirectional switching elements 18 and 28 to the input terminals 21 respectively. 11 connected. For the other unidirectional switching elements 18 and 28 these are diodes 7 , with the unidirectional switching elements 17 and 27 around diodes 10 , From the output terminal 4 via the charging paths 19 and 29 and the discharge paths 20 and 30 From the perspective view, the forward directions of the diodes are 7 and 10 the unidirectional switching elements 17 and 18 on the one hand, and 27 and 28 on the other hand in opposite directions. Between the input terminals 11 and 21 are all diodes 7 and 10 a phase connected in series, with their focus on the connection 8th falls and their intermediate points on each side of the midpoint on the junctions 35 and where all diodes 7 and 10 u are aligned _{in the} reverse direction with respect to the input DC voltage.

In every relief network 6 is the capacitor 15 for switching discharge of the external circuit breaker 13 and the capacitor 25 for switching discharge of the external circuit breaker 23 intended. The following is an example of charging and discharging one of the capacitors 15 described. Charging and discharging the capacitors 25 takes place accordingly. With the circuit breaker closed 13 and at the same time closed MOSFET 9 of the switching element 17 a current i _{13 flows} through the circuit breaker 13 not just as at the output port 4 issued output _AC current i _load1 , i _load2 or i _load3 to a connected, but not shown here load, but temporarily partly through the Aufladepfad 19 to the capacitor 15 and from there via the switching element 17 and through the throttle 16 to the center tap 3 , The fact that a current must flow here temporarily results from the fact that the current is above the DC link capacitor 12 decreasing half DC input voltage u _in / 2 across the mesh, passing through the circuit breaker 13 and via the charging path 19 to the center tap 3 extends, must completely fall off. Actually, the capacitor becomes 15 but not just charged to half the DC input voltage u _in / 2, because the choke 16 the current initially flowing through it continues to maintain until a charge of the capacitor is reached on the full DC input voltage u _in . A subsequent discharge of the capacitor 15 is through the in the charging path 19 lying diode 10 prevented.

In other words, the capacitor forms 15 with the throttle 16 a series resonant circuit in which the through the charging path 19 until charging the capacitor 15 on u _in / 2 flowing during a first quarter of a resonant period current, the throttle 16 energized, then their energy during a second quarter of the resonance period of the series resonant circuit with further charging of the capacitor 15 on u _in again. Through the diode 10 in the series resonant circuit, however, the resonant oscillation is subsequently terminated, so that the capacitor 15 not under renewed energization of the throttle 16 can discharge. The discharge of the capacitor 15 rather happens when the circuit breaker 13 is opened so that the current i ₁₃ can no longer flow. By the capacitor 15 by discharging the output _ac current i _load takes over, the diode 7 in his unloading path 20 becomes conductive, it prevents a sudden rise of the over the circuit breaker 13 decreasing voltage u ₁₃ . This voltage u ₁₃ is the sum of the input DC voltage u _in and over the capacitor 15 decreasing voltage u ₁₅ . Because the capacitor 15 has been charged to u _in , the voltage is u ₁₃ across the circuit breaker 13 therefore initially zero and increases only with the u u _in falling voltage u _{15 of} the capacitor 15 at. In this way, a switching discharge by de-energized switching of the circuit breaker 13 realized.

This place of common thrush 16 in the circuit arrangement 1 according to 1 corresponds in principle to the one from the DE 10 2010 008 426 B4 known circuit arrangement. Deviating from the DE 10 2010 008 426 B4 However, in the circuit arrangement according to the invention 1 only one throttle 16 available for all three phases. It comes even when using only this one throttle 16 to no mutual interference between the relief networks 6 of the individual phases when switching the circuit breaker 13 . 14 . 23 and 24 All phases are coordinated so that no currents between the capacitors 15 . 25 flow. For this it suffices, after closing one of the outer circuit breakers 13 or 23 and before a next closing of one of the outer circuit breakers 13 respectively. 23 or an internal circuit breaker 24 respectively. 14 wait at least one recharge time for another phase, in which the one to the circuit breaker of the outer circuit breaker 13 or 23 provided capacitor 15 respectively. 25 is charged to twice the input DC voltage u _in .

In the embodiment of the circuit arrangement according to the invention for a three-phase multipoint inverter according to 2 are to decouple the individual relief networks 6 auxiliary chokes 39 in the connections 8th the inner circuit breaker 14 and 24 with the center tap 3 from the internal circuit breakers 14 respectively. 24 seen from the throttle 16 and also before the merger 9 arranged. These auxiliary throttles 39 whose inductance is significantly smaller than the inductance of the choke 16 can prevent the flow of currents from a capacitor 15 . 25 a relief network 6 a phase to one of the capacitors 15 . 25 the relief network 6 another phase. This may be due to waiting for a recharge time between turning on various circuit breakers 13 . 14 . 23 . 24 different phases are dispensed with.

3 illustrated like that 1 and 2 a circuit arrangement according to the invention 1 for a three-phase S3L inverter, the build again 1 matches, except that the unidirectional switching elements 17 and 27 in the charging path 19 and 29 for each phase here as actively controllable switching elements 38 are formed. By selective activation, ie switching on the actively controllable switching elements 38 , can the charging paths 19 . 29 be selectively enabled and in this way a mutual interference of the relief networks 6 the individual phases are avoided.

In the 4 illustrated circuit arrangement according to the invention 1 for a three-phase multipoint inverter is a BSNPC inverter, in which compared to the previously shown 3SL inverters as a special feature two common chokes 16 and 26 are provided. These common throttles 16 and 26 lie in each Aufladepfaden 19 respectively. 29 for the capacitors 15 respectively. 25 which are used to relieve the load of all power semiconductor switches 13 respectively. 23 are provided, each with the same of the input terminals 11 and 21 are directly connected. The throttles 16 and 26 lie before the merger 9 the connections 8th that the inner circuit breakers 14 and 24 the individual phases with the center tap 3 connect. Currents flowing through the connections 8th flow, therefore not flow through the chokes 16 and 26 ; the throttles 16 and 26 therefore do not have to be designed for these currents. The throttles 16 and 26 are separate throttles for all charging paths 19 on the one hand and 29 on the other hand, but they are from the relief networks 6 all phases shared. The decoupling of the individual discharge networks 6 takes place here as in the circuit arrangement according to 3 by as actively controllable switching elements 38 trained unidirectional switching elements 17 and 27 in the charging path 19 and 29 ,

So that the capacitors 15 and 25 after the switching discharge caused by it for the respective outer circuit breaker 13 respectively. 23 do not disturb the function of the multipoint inverter, they must discharge as completely as possible during the switching discharge. An unwanted charge in the wrong direction is the antiparallel diode 5 of the other circuit breaker 23 respectively. 13 opposite. A complete discharge, for example, of the capacitor 15 at the circuit discharge of the circuit breaker 13 is reached when at the time of opening the circuit breaker 13 at least one output _alternating current i _load flowing from the capacitor 15 is taken over and unloads it. In 5 are for a phase angle zero between an output AC voltage u _out at one of the output terminals 4 according to 3 or 4 and the output _alternating current i _load1 partial periods 31 and 32 in which the magnitude of an instantaneous value of the output _alternating current i _{load1 exceeds} a limit value i _min . These are part-time periods 31 and 32 the two half-waves of the output AC voltage u _out , across each of which one of the circuit breakers 13 . 23 the respective phase is clocked, namely the circuit breaker 13 at the positive half-wave and the circuit breaker 23 at the negative half wave. About the sub period 31 the positive half-wave is the actively controllable switching element 38 of the unidirectional switching element 17 according to 3 or 4 closed, over the sub period 32 the negative half wave the actively controllable switching element 38 of the unidirectional switching element 27 , By keeping open the actively controllable switching element 38 of the other unidirectional switching element 27 respectively. 17 during the part-time periods 31 and 32 Ensures that the previously charged capacitor 15 or 25 when opening the respective circuit breaker to be relieved 13 respectively. 23 not in part also over the other capacitor 25 respectively. 15 discharges. Such an undesired charged capacitor 25 respectively. 15 would be in the subsequent driving of the complementary to the outer circuit breaker 13 or 23 clocked inner circuit breaker 24 respectively. 14 as short-circuited as a not fully discharged in the discharge of the capacitor 15 respectively. 25 , An open switching element 17 or 27 in the respective charging path 19 respectively. 29 Prevents unwanted charging in the charging path 19 respectively. 29 arranged capacitor 15 respectively. 25 ,

6 illustrates that at one of the _AC output voltage u _{out, the alternating} output _AC current i _{load1 is} the partial time periods 31 and 32 in which the switching elements 17 and 27 be closed within the half-waves of the output _AC voltage u _out only begin when the amount of the instantaneous value of the output _AC current i _{load1 has exceeded} the limit i _min at the same sign of the instantaneous values of the output _AC voltage u _out and the output _AC current i _load1 . The part-time periods 31 and 32 but ends at the latest with the sign change of the output AC voltage u _out , in which when clocking between the external power semiconductor switches 13 and 23 is changed. Next shows 6 on that it is also possible, the switching elements 17 and 27 not for the entire subareas 31 and 32 permanently closed, but only for pulses that are synchronized with the pulses for which the respective external circuit breaker 13 and 23 when the bar is closed. Due to the relative position of the pulses, for which the switching elements 17 and 27 be closed, within the pulses, for which the respective external circuit breaker 13 and 23 is closed, the course of the over the respective switching elements 17 respectively. 27 to the respective capacitor 15 respectively. 25 flowing charging current can be influenced. Preferably, the pulses for which the switching elements 17 and 27 be closed, at least as long as half the resonance period of the series resonant circuit from the capacitor 15 respectively. 25 and the throttle 16 respectively. 26 , By shorter pulses than half the resonance period of the series resonant circuit, the charging of the respective capacitor 15 respectively. 25 even on less than u _in be limited to ensure its discharge even at low output _alternating current i _load . However, then there is no complete switching discharge, ie no completely dead switching of the respective circuit breaker 13 respectively. 23 ,

To the 5 and 6 It should also be noted that the actual output AC voltage u _out , which is a pulse width modulated square wave signal, is not shown here. Rather, it is the desired output AC voltage u _out , ie a specification for the pulse width modulation in the control of the outer circuit breaker 13 and 23 connected to the fundamental of the voltage at the output terminal 4 is in phase.

In the inventive S3L inverters according to the 1 to 3 can be a complete discharge of the respective capacitor 15 . 25 with the switching relief also with the help of a via the respective output terminal 4 away with the common throttle 16 formed resonant circuit can be used.

Below are three variations of the in 4 illustrated three-phase multipoint inverter explained on the basis of the construction of only one phase of this inverter. To supplement the other phases are with the exception of the input terminals 11 . 21 , the DC link 2 with the DC link capacitors 12 . 22 and the center tap 3 as well as the common throttles 25 and 26 all parts shown for each phase added again.

7 shows a phase of a circuit arrangement according to the invention, which starts from an NPC inverter, in which the outer circuit breaker 13 and 23 and the inner circuit breakers 14 and 24 are connected in series, with the midpoint of the series connection the output terminal 4 forms. Lead by intermediate points 33 between the external circuit breakers 13 and 23 and the internal circuit breakers 14 and 24 diodes 34 Which include aligned with respect to the input DC voltage _in reverse direction to the center tap 3 , About these diodes 34 Here are the inner circuit breakers 14 and 24 on the one hand to the center tap 3 On the other hand, they are connected directly to the output terminal 4 are connected. The relief network 6 is basically the same as in 4 , The circuit breakers 13 . 14 . 23 and 24 be in the circuit 1 according to 1 basically the same way as with a conventional NPC inverter.

The embodiment of the circuit arrangement according to the invention, which is based on a phase in 8th is based as that according to 4 on a BSNPC inverter. The following variations are possible 4 Illustrated, which can also be implemented independently. Instead of the inner switching elements 14 and 24 from series-connected transistors with anti-parallel diodes 5 form, wherein the antiparallel diode 5 each one transistor provides for a unidirectional current flow through the other transistor, here are two reverse blocking transistors 36 , ie directly unidirectionally formed switching elements, connected in parallel. Furthermore, the controllable as active switching elements 38 trained unidirectional switching elements 17 and 27 as thyristors 37 concretized.

In the 9 embodiment of the circuit arrangement according to the invention shown by means of a phase 1 deviates from the one according to 4 characterized in that the controllable as active switching elements 38 trained unidirectional switching elements 17 and 27 not just in diodes 10 and further not unidirectionally formed and shown here only schematically switching elements 40 are split, but that these parts 10 and 40 also on different sides of the capacitors 15 and 25 are located. This will be the function of the Relief Network 6 but not fundamentally changed.

LIST OF REFERENCE NUMBERS

1

 circuitry

2

 Dc link

3

 center tap

4

 output port

5

 Antiparallel diode

6

 Relief Network

7

 diode

8th

 connection

9

 together

10

 diode

11

 input port

12

 Link capacitor

13

 breakers

14

 breakers

15

 capacitor

16

 throttle

17

 switching element

18

 switching element

19

 charging path

20

 discharging

21

 input port

22

 Link capacitor

23

 breakers

24

 breakers

25

 capacitor

26

 throttle

27

 switching element

28

 switching element

29

 charging path

30

 discharging

31

 subregion

32

 subregion

33

 intermediate point

34

 diode

35

 diversion

36

 transistor

37

 thyristor

38

 switching element

39

 auxiliary throttle

40

 switching element

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2004/0246756 A1 [0006]
• DE 102010008426 B4 [0007, 0021, 0023, 0025, 0026, 0027, 0050, 0050]
• DE 10201008426 B4 [0028]

Cited non-patent literature

• Akira Nabae et al., A New Neutral-Point-Clamped PWM Inverter, IEEE Transactions on Industry Applications, Vol. 1A-17, no. 5, September / October 1981, pages 518 to 523 [0004]
• A. Nabae et al .: A New Neutral-Point Clamped PWM Inverter, IEEE Transactions on Industry Applications, Vol. 1A-17, no. 5, September / October 1981 [0005]

Claims (14)

Circuit arrangement ( 1 ) for a multiphase multipoint inverter, - with an input terminal ( 11 ) for a positive pole and an input terminal ( 21 ) for a negative pole of a DC input voltage (u _in ), - with a center tap ( 3 ) for a voltage center of the input DC voltage (u _in ) and - for each phase - with an output terminal ( 4 ) for outputting an output _alternating current (i _load1 , i _load2 , i _load3 ), - with two external circuit breakers ( 13 . 23 ), one of which is connected to one of the two input terminals ( 11 . 21 ), - with two internal circuit breakers ( 14 . 24 ), each on the one hand directly or via a diode ( 5 . 34 ) with the center tap ( 3 ) and on the other hand directly or via a diode ( 5 ) with the output terminal ( 4 ), and - with a relief network ( 6 ) for the external circuit breakers ( 13 . 23 ), the two capacitors ( 15 . 25 ) and four unidirectional switching elements ( 17 . 18 . 27 . 28 ), wherein - for each of the two capacitors ( 15 . 25 ) a charging path ( 19 . 29 ) between the output terminal ( 4 ) and the center tap ( 3 ), wherein the respective capacitor ( 15 . 25 ) in the charging path ( 19 . 29 ) with one of the switching elements ( 17 . 27 ) and a throttle ( 16 . 26 ) is connected in series, and - wherein between the output terminal ( 4 ) and each of the input terminals ( 11 . 21 ) a discharge path ( 20 . 30 ) for each one of the two capacitors ( 15 . 25 ), wherein the discharge path ( 20 . 30 ) from the output terminal ( 4 ) seen from behind the respective capacitor ( 15 . 25 ) and in front of the throttle ( 16 . 26 ) in a branch ( 35 ) from the respective charging path ( 19 . 29 ) and wherein another of the switching elements ( 18 . 28 ) between the branch ( 35 ) and the input terminal ( 21 . 11 ) in the discharge path ( 20 . 30 ), characterized in that at least the charging paths ( 19 . 29 ) for all capacitors ( 15 . 25 ), which are used to relieve the circuit breaker ( 13 . 23 ) provided with the same of the two input terminals ( 11 . 21 ) are connected together via a common throttle ( 16 . 26 ) directly with the center tap ( 3 ) connected is. Circuit arrangement ( 1 ) according to claim 1, characterized in that for all phases a common DC voltage intermediate circuit ( 2 ) between the two input terminals ( 11 . 21 ), the center tap ( 3 ) a center of a series connection of intermediate circuit capacitors ( 12 . 22 ) of the DC intermediate circuit ( 2 ). Circuit arrangement ( 1 ) according to any one of the preceding claims, characterized in that there is a control which is adapted, after switching on one of the outer circuit breakers ( 13 . 23 ) one of the phases and before a next switching on of one of the outer circuit breakers ( 13 . 23 ) wait for at least one recharge time of another of the phases in which the one of the outer circuit breakers ( 13 . 23 ) provided capacitor ( 15 . 25 ) is charged to twice the DC input voltage (u _in ). Circuit arrangement ( 1 ) according to claim 3, characterized in that the controller is also adapted, after switching on one of the outer circuit breaker ( 13 . 23 ) one of the phases and before next turning on one of the inner circuit breakers ( 24 . 14 ) wait for another of the phases at least the recharge time. Circuit arrangement ( 1 ) according to one of the preceding claims, characterized in that the one of the unidirectional switching elements ( 17 . 27 ) in each charging path ( 19 . 29 ) an actively controllable switching element ( 38 ). Circuit arrangement ( 1 ) according to one of the preceding claims, characterized in that the further of the unidirectional switching elements ( 18 . 28 ) in each discharge path ( 20 . 30 ) is a non-actively controllable switching element. Circuit arrangement ( 1 ) according to one of the preceding claims, characterized in that each discharge path ( 20 . 30 ) directly to the respective input terminal ( 21 . 11 ) and / or that each charging path ( 19 . 29 ) directly to the output terminal ( 4 ) is connected to the respective phase. Circuit arrangement ( 1 ) according to one of the preceding claims, characterized in that all the charging paths ( 19 . 29 ) for all capacitors ( 15 . 25 ) together about the common throttle ( 16 ) between a merge ( 9 ) of connections ( 8th ), which are the two inner circuit breakers ( 14 . 24 ) one of the phases with the center tap ( 3 ) and the center tap ( 3 ) is arranged. Circuit arrangement ( 1 ) according to claim 8, characterized in that for each phase its own auxiliary choke ( 39 ), via which the two charging paths ( 19 . 29 ) of the Relief Network ( 6 ) of the respective phase and that of the internal circuit breakers ( 14 . 24 ) seen before the merge ( 9 ) in the compound ( 8th ) of the two inner circuit breakers ( 14 . 24 ) of the respective phases with the center tap ( 3 ) is arranged. Circuit arrangement ( 1 ) according to one of claims 1 to 7, characterized in that for those charging paths ( 19 . 29 ), of which the discharge paths ( 20 . 30 ) to the same of the two input terminals ( 11 . 21 ), a separate common throttle ( 16 . 26 ) from the output terminals ( 4 ) seen from behind the branches ( 35 ) of the discharge paths ( 20 . 30 ) and before connecting these charging paths ( 19 . 29 ) to a merge ( 9 ) of connections ( 8th ) which houses the two inner circuit breakers ( 14 . 24 ) one of the phases with the center tap ( 3 ) connect. Circuit arrangement ( 1 ) according to one of the preceding claims, characterized in that the transmission directions of the one and the other of the unidirectional switching elements ( 17 . 18 . 27 . 28 ) in the charging path ( 19 . 29 ) and the discharge path ( 20 . 30 ) for each capacitor ( 15 . 25 ) from the output terminal ( 4 ) are directed counter to each other, with the other of the unidirectional switching elements ( 18 . 28 ) with respect to the pole of the DC input voltage (u _in ) at that of the input terminals ( 11 . 21 ), with which the discharge path is connected, are aligned in the reverse direction. Circuit arrangement ( 1 ) according to one of the preceding claims, characterized in that the circuit breakers ( 13 . 14 . 23 . 24 ) are connected according to type - of an NPC inverter, - of a BSNPC inverter, - of an ARCP inverter or - of an S3L change-over contactor. Circuit arrangement ( 1 ) according to claim 5 or one of the claims dependent on claim 5, characterized in that there is a control which is set up for each phase of the actively controllable switching element ( 17 . 27 ) in the charging path ( 19 . 29 ) from which the discharge path ( 20 . 30 ) to the one input terminal ( 21 . 11 ) closes within a period of time over which they pass the outer circuit breaker ( 13 . 23 ) for the respective phase in pulses, which is connected to the other input terminal ( 11 . 21 ) connected is. Circuit arrangement ( 1 ) according to any one of the preceding claims, characterized in that there is a control which is arranged to switch one of the inner circuit-breakers for each phase ( 14 . 24 ) with respect to an output AC voltage at the output terminal half-wave close and the other of the inner circuit breaker ( 14 . 24 ) at least temporarily complementary to the respective pulsed outer circuit breaker ( 13 . 23 ) in pulses, with dead times between the pulses of the inner and the outer circuit breaker ( 13 . 23 ) remain, in which the with the outer circuit breaker ( 13 . 23 ) charging capacitor ( 15 . 25 ) of the Relief Network ( 6 ) discharges.

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