DE102019201630A1 - Highly efficient power converter for single-phase and three-phase systems - Google Patents

Abstract

Converter circuit with two parallel arms parallel to the intermediate circuit, each having two series-connected first arm half-bridges each with at least one lower power semiconductor and one upper power semiconductor, the center point of the upper arm half-bridge being connected to an upper filter inductance, the center point the lower arm half-bridge is connected to a lower filter inductance and the potential point between the capacitors is connected to the potential point between the arm half-bridges, as well as to a filter circuit with two series-connected filter capacitors, the potential point between the two filter capacitors is connected to the center point, an upper connection of the filter circuit is connected to the upper filter inductances and a lower connection of the filter circuit is connected to the lower filter inductances, furthermore to an output half-bridge whose center point is an alternating voltage An upper potential point of the output half-bridge is connected to the upper connection of the filter circuit and a lower potential point of the output half-bridge is connected to the lower connection of the filter circuit and with a control device that is designed to control the power semiconductors of the two To control the arms out of phase with each other in order to achieve operation in interleaved mode.

Description

The invention relates to a circuit for a converter for single-phase and multi-phase systems and to a method for interconnecting a direct voltage system with an alternating voltage system with at least one such circuit.

Such a circuit is used, for example, in an inverter for use in photovoltaics. The inverters used there take on the power conversion for an entire photovoltaic system, for a string, i.e. a number of solar panels in the facility. Other fields of application for power converters are, for example, electric vehicles, hybrid vehicles, vehicles for rail transport and also charging stations for electric vehicles. Furthermore, power converters are used in energy storage applications, for example in the field of renewable energies or in auxiliary voltage supplies and in power supplies.

An arrangement for converting one type of electrical current into another is referred to as a converter. Such a converter is preferably used when interconnecting a direct voltage system, for example with a direct voltage of 450 V, with an alternating voltage system, for example with an alternating voltage of 230 V, the converter being operated as an inverter or as a rectifier depending on the direction of power flow. An inverter is an electrical device that converts DC voltage into AC voltage. A rectifier is an electrical device that converts AC voltage into DC voltage. The converter can be used here both as a rectifier and as an inverter. A single-phase system has a phase conductor and a neutral conductor, the neutral conductor preferably being grounded. Another embodiment is a so-called single-phase three-wire network or in English “split-phase” or “single-phase three-wire” system, which is preferably used in the United States of America for single-family households and small businesses. The single-phase three-wire network is based on a single-phase system, with the help of a transformer, which preferably has a center tap on the secondary side for the neutral phase, two signals in antiphase, i.e. with a 180 ° phase offset, are generated on two conductors.

From the EP 2 136 465 A1 an inverter for feeding power from a direct voltage source, in particular a photovoltaic generator, into an alternating voltage network with an asymmetrically clocked bridge circuit with at least two first switches clocked with the network frequency and with at least two second switches clocked with a higher clock frequency is known.

In the WO 2016/146171 A1 a converter circuit for single-phase systems is proposed which has a 3-point converter and a downstream 2-point converter.

From the EP 2 306 629 A1 a 5-point converter circuit for three-phase systems is known which combines three half bridges and an AC switch.

From the DE 10 2014 113 306 A1 a power converter with an inverter consisting of two subcircuits, a pole reverser and interconnected chokes is known, the subcircuits each comprising two parallel line branches, the first of which comprises a series of a MOSFET and a diode and the second a series of a diode and an IGBT comprises and wherein the center point of the two line branches is coupled via a further throttle.

The invention is based on the object of specifying a converter circuit which, compared to known converter circuits, has improved properties in terms of heat dissipation and structural size.

According to the invention, this object is achieved by a converter circuit having the features of claim 1. The converter circuit comprises connection contacts for connection to a DC voltage, between which an intermediate circuit with a series connection of two capacitors is arranged, the intermediate circuit being designed as a divided intermediate circuit to produce a midpoint of an intermediate circuit voltage at the point located between the capacitors.

Furthermore, the converter circuit comprises a first arm parallel to the intermediate circuit, which has two series-connected first arm half-bridges each with at least one lower power semiconductor and one upper power semiconductor, the center point of the upper first arm half-bridge being connected to an upper first filter inductance , the midpoint of the lower first arm half-bridge is connected to a lower first filter inductance and the potential point between the capacitors is connected to the potential point between the first arm half-bridges.

In parallel to the intermediate circuit and to the first arm, there is a second arm, which has two second arm half-bridges connected in series, each with at least one lower power semiconductor and one upper power semiconductor, the The midpoint of the upper second arm half-bridge is connected to an upper second filter inductance, the midpoint of the lower second arm half-bridge is connected to a lower second filter inductance and the potential point between the capacitors is connected to the potential point between the second arm half-bridges.

The converter circuit further comprises a filter circuit with two series-connected filter capacitors, the potential point between the two filter capacitors being connected to the center point, an upper connection of the filter circuit being connected to the upper filter inductances and a lower connection of the filter circuit being connected to the lower filter inductances, and an output half-bridge, the center of which forms an AC voltage output, an upper potential point of the output half-bridge being connected to the upper connection of the filter circuit and a lower potential point of the output half-bridge being connected to the lower connection of the filter circuit .

Finally, the converter circuit has a control device which is designed to control the power semiconductors of the two arms in a phase-shifted manner in order to achieve operation in what is known as the interleaved mode.

The invention also creates a method for interconnecting a DC voltage system with an AC voltage system, in which a previously described converter circuit is used, the converter circuit being operated as a rectifier and / or as an inverter, the power semiconductors of the arms of the converter circuit being out of phase with one another can be controlled in order to achieve operation in interleaved mode.

The converter circuit and the method of the invention are preferably used in network applications, for example photovoltaics, in particular as micro solar inverters for individual solar modules and energy storage applications, as well as in electric vehicles, hybrid vehicles and vehicles for rail traffic. Additional areas of application are auxiliary power supplies and power supplies.

The invention creates a converter circuit with a native sinusoidal output voltage. It is also advantageous that such a converter circuit is readily suitable for a parallel connection with other, for example similar, converter circuits. As a result, the power range that can be achieved with the circuit is significantly expanded - while retaining the components used.

In the converter circuit according to the invention, it is also advantageous that the area of the circuit in which a pulse-width-modulated voltage occurs with high-frequency voltage changes is narrowly limited. The pulse width modulated voltage occurs only in the conductor areas between the filter inductances and the directly connected switches of the first half bridges. This means that the area of the circuit with high EMC emissions is advantageously narrowly limited to two short conductor pieces due to the placement of the internal filter. These can easily be provided with shielding, for example by being arranged in a middle layer in a multi-layer circuit board between shielding metal surfaces.

Furthermore, the topology according to the invention ensures that the switches of the second circuit are not in the range of high switching frequencies. Rather, the voltage is smoothed by the filter circuit before the switches of the second circuit. This reduces the load on the switches in the second circuit and the activation of the switches in the second circuit is simplified.

The circuit can be operated bidirectionally due to the circuit topology according to the invention, that is to say, depending on the power flow, as a rectifier and / or an inverter.

A particular advantage of the converter circuit is that by using an interleaved topology and control, components with a reduced current-carrying capacity can be used with the same load. Furthermore, the losses on each component are reduced, which means that the cost of cooling the power semiconductors is reduced.

Advantageous embodiments of the circuit according to the invention emerge from the claims dependent on claim 1.

• - Die Stromrichter-Schaltung kann wenigstens einen weiteren Arm parallel zum Zwischenkreis umfassen, der zwei in Serie geschaltete weitere Arm-Halbbrücken aufweist, wobei der Mittelpunkt der oberen weiteren Arm-Halbbrücke mit einer oberen weiteren Filterinduktivität verbunden ist, der Mittelpunkt der unteren weiteren Arm-Halbbrücke mit einer unteren weiteren Filterinduktivität verbunden ist und der Potentialpunkt zwischen den Kondensatoren mit dem Potentialpunkt zwischen den weiteren Arm-Halbbrücken verbunden ist und wobei die Steuereinrichtung ausgestaltet ist, alle Arme im Interleaved-Modus zu betreiben. Durch beispielsweise einen oder zwei weitere Arme wird die Stromlast der einzelnen Leistungshalbleiter weiter reduziert.
• - Besonders vorteilhaft ist es, wenn die oberen Filterinduktivitäten der Arme als verkoppelte Induktivität ausgeführt sind und die unteren Filterinduktivitäten der Arme ebenso als verkoppelte Induktivität ausgeführt sind. Die jeweiligen Induktivitäten sind dabei auf einem gemeinsamen Kern derart angeordnet, dass der primäre Stromfluss der erzeugten Halbwelle einander entgegengerichtet ist und sich die entstehenden magnetischen Felder aufheben. Hierdurch ist es möglich, die Größe der Filterinduktivitäten nicht auf die Amplitude der erzeugten Wechselspannung auszurichten, sondern lediglich auf die deutlich kleineren Kreisströme, die zwischen den beiden Armen fließen. Die Filterinduktivitäten können deutlich kleiner ausfallen, wodurch eine erhebliche Einsparung im Bauraum möglich ist.
• - Die beiden in Serie geschalteten Kondensatoren des Zwischenkreises, an denen die Zwischenkreisspannung, beispielsweise 400 V, abfällt, können jeweils auch aus mehreren, beispielsweise in Serie oder parallel geschalteten Kondensatoren, bestehen. Dies kann notwendig sein, wenn es keinen Kondensator gibt, der für den geforderten Strom und/oder die geforderte Spannung spezifiziert ist.

• - Die Kondensatoren können gleiche Kapazitätswerte aufweisen. Der durch die Verwendung von gleichen Kapazitätswerten symmetrisch geteilte Zwischenkreis teilt die Zwischenkreisspannung um den Mittelpunkt symmetrisch. Daher können in den ersten und zweiten Halbbrücken die gleichen Leistungshalbleiter verwendet werden, welche gleichmäßig und optimal ausgesteuert werden. Dies erhöht den Wirkungsgrad der Stromrichter-Schaltung und reduziert die Komplexität.
• - Die Steuereinrichtung kann ausgestaltet sein, die Leistungshalbleiter der Arme mit einer Schaltfrequenz im Kilohertz-Bereich oder Megahertz-Bereich zu betreiben. Mit dieser Frequenz wird eine Modulation der Wechselspannung vorgenommen. Die Steuereinrichtung kann ferner ausgestaltet sein, die Leistungshalbleiter der Ausgangs-Halbbrücke mit einer tieferen Grundfrequenz im Hertz-Bereich zu betreiben, beispielsweise mit 50 Hz. Da die Leistungshalbleiter für unterschiedliche Aufgaben bei unterschiedlichen Frequenzen innerhalb der Stromrichter-Schaltung vorgesehen sind, erlaubt die angegebene Schaltungstopologie eine Verwendung von angepassten Leistungshalbleitern. Dies ist vorteilhaft, weil sich durch die Verwendung an die Aufgabe angepasster Leistungshalbleiter der Wirkungsgrad der Stromrichter-Schaltung erhöht.
• - Die Leistungshalbleiter der ersten und zweiten Halbbrücken können hinsichtlich geringer Schaltverluste optimiert sein. Die Leistungshalbleiter der Ausgangs-Halbbrücke können hinsichtlich geringer Durchlassverluste optimiert sein. Ein wesentlicher Faktor zur Begrenzung des erreichbaren Wirkungsgrades liegt in den Verlusten, die in den verwendeten Leistungshalbleitern auftreten. Dabei spielen die Schaltverluste, die im Moment des Öffnens und Schließens des Schalters auftreten und mit der verwendeten Schaltfrequenz ansteigen, sowie die Durchlassverluste, die im leitenden Zustand des Schalters auftreten, eine Rolle. Die Leistungshalbleiter wie beispielsweise MOSFETs, IGBTs oder GaN-HEMT-Schalter weisen bezüglich der Schaltverluste und Durchlassverluste verschiedene Eigenschaften auf. Darüber hinaus gibt es auch innerhalb jedes Typs von Leistungshalbleiter verschiedene Ausprägungen, die sich bezüglich der genannten Eigenschaften unterscheiden. Dabei ist typischerweise eine Optimierung der Schaltverluste nicht gleichzeitig mit einer Optimierung der Durchlassverluste zu erreichen, vielmehr stehen die Ziele im Widerstreit miteinander. Bei bekannten Topologien ist die Auswahl der Leistungshalbleiter daher ein Kompromiss. Hingegen können bei der Stromrichter-Schaltung vorteilhaft die schnell schaltenden Leistungshalbleiter der ersten und zweiten Halbbrücken, die für die Modulation der Wechselspannung vorgesehen sind, hinsichtlich geringer Schaltverluste optimiert sein, während die vergleichsweise langsam schaltenden Leistungshalbleiter der Ausgangs-Halbbrücke, die für eine Taktung mit einer Grundfrequenz vorgesehen sind, hinsichtlich geringer Durchlassverluste optimiert sein. Damit ist trotz des Konflikts zwischen Schaltverlusten und Durchlassverlusten eine optimale Auswahl der Leistungshalbleiter möglich, die bei anderen Topologien nicht getroffen werden kann.
• - Die Leistungshalbleiter der ersten und zweiten Halbbrücken können eine Spannungsfestigkeit aufweisen, die wenigstens der halben Zwischenkreisspannung entspricht. Die Leistungshalbleiter der Ausgangs-Halbbrücke können eine Spannungsfestigkeit aufweisen, die wenigstens der ganzen Zwischenkreisspannung entspricht. Dies wird durch die Schaltungstopologie mit dem geteilten Zwischenkreis ermöglicht, welcher als ein kapazitiver Spannungsteiler wirkt und bei bevorzugt gleichen Kapazitätswerten die Zwischenkreisspannung um den Mittelpunkt symmetrisch teilt. Bei gegebener Schaltfrequenz erzeugen Leistungshalbleiter, die eine höhere Spannungsfestigkeit aufweisen und daher zum Schalten höherer Spannungen geeignet sind, signifikant höhere Schaltverluste als Leistungshalbleiter, welche eine geringere Spannungsfestigkeit aufweisen. Die angegebene Schaltungstopologie erlaubt es, dass die Leistungshalbleiter der ersten Schaltung nur eine Spannungsfestigkeit aufweisen müssen, welche der halben Zwischenkreisspannung entspricht. Da so die angepassten Leistungshalbleiter jeweils optimal eingesetzt werden, ergibt sich ein hoher Wirkungsgrad der Stromrichter-Schaltung.
• - Als Leistungshalbleiter der Arme kommen bevorzugt SiC-Schalter oder GaN-Schalter zum Einsatz. Diese erlauben sehr hohe Schaltgeschwindigkeiten und ermöglichen es daher, die Baugröße der Filterelemente zu verringern. Die Leistungshalbleiter der Arme können insbesondere selbstsperrende Galliumnitrid-Schalter oder Kaskoden mit einem selbstleitenden Galliumnitrid-Schalter sein.
• - Die Leistungshalbleiter der ersten und zweiten Halbbrücken können mit einer Frequenz von mehr als 100 kHz, insbesondere mehr als 300 kHz angesteuert werden. Eine hohe Schaltgeschwindigkeit ermöglicht es, die Baugröße der Filterelemente zu verringern.
• - Der erste Kondensator und die erste und zweite obere Halbbrücke können als eine erste Kommutierungszelle ausgebildet sein; der zweite Kondensator und die erste und zweite untere Halbbrücke können als eine zweite Kommutierungszelle ausgebildet sein. Als Kommutierung bezeichnet man in der Leistungselektronik den Vorgang, bei dem ein Stromfluss von einem Zweig zum anderen übergeht. In der vorliegenden Ausführungsform findet die Kommutierung, beispielsweise im Betrieb als Wechselrichter, vom ersten Kondensator zur parallel dazu geschalteten ersten Halbbrücke und vom zweiten Kondensator zur parallel dazu geschalteten zweiten Halbbrücke statt. Die Ausbildung einer Kommutierungszelle insbesondere durch eine niederinduktive Anordnung der Bauelemente ist vorteilhaft, da so ein sehr gutes Kommutierungsverhalten und Schaltverhalten erreicht wird, was die Effizienz der vorliegenden Schaltung erhöht.
• - Die Leistungshalbleiter der ersten und zweiten Halbbrücken werden bevorzugt mit einer Pulsweiten-Modulation angesteuert und die Leistungshalbleiter der zweiten Schaltung mit einer tieferen Grundfrequenz umgepolt. Für die Pulsweiten-Modulation werden die ersten und zweiten Halbbrücken zweckmäßig stets so geschaltet, dass einer der Leistungshalbleiter eingeschaltet ist, während der andere Leistungshalbleiter ausgeschaltet ist.
• - Die Stromrichter-Schaltung kann eine weitere Ausgangs-Halbbrücke umfassen, die parallel zur Ausgangs-Halbbrücke geschaltet ist und einen weiteren Wechselspannungsanschluss umfasst.
• - Die Leistungshalbleiter innerhalb eines der Arme können derart angesteuert werden, dass sie synchron schalten. Mit anderen Worten passiert ein Umschalten der Leistungshalbleiter der beiden ersten Halbbrücken gleichzeitig. In diesem Betriebsmodus wechselt die Spannung zwischen den Armen und der Filterschaltung daher stets zwischen dem vollen Wert der Zwischenkreisspannung und Null, d.h. einem Zusammenschluss des Mittelpunkts-Potentials. Dabei sind zu einer Zeit entweder die beiden äußeren Leistungshalbleiter der beiden ersten Halbbrücken eingeschaltet oder die beiden inneren Leistungshalbleiter der beiden ersten Halbbrücken eingeschaltet. Durch diesen Schaltbetrieb werden vorteilhaft Gleichtakt-Störungen der Stromrichter-Schaltung stark verringert.
• - Alternativ können Leistungshalbleiter der Arme derart angesteuert werden, dass die Leistungshalbleiter der oberen ersten Halbbrücke im Wechsel mit den Leistungshalbleitern der unteren ersten Halbbrücke schalten. Bei einer Ansteuerung der Leistungshalbleiter mittels Trägersignal kann das beispielsweise durch eine entsprechende Phasenverschiebung des Trägersignals für die untere erste Halbbrücke gegenüber der oberen ersten Halbbrücke erreicht werden. Die am Eingang der Filterschaltung anliegende Spannung wechselt in diesem Schaltmodus zwischen der vollen Zwischenkreisspannung, der halben Zwischenkreisspannung und Null. Die dadurch vorliegende Schaltfrequenz ist gegenüber der Schaltfrequenz bei synchronem Schalten der Halbbrücken verdoppelt. Dadurch kann die Baugröße der in der Filterschaltung verwendeten Filter-Induktivitäten verringert werden, da die Filterwirkung invers proportional mit der Frequenz des Signals zusammenhängt.

The embodiment according to claim 1 can be combined with the features of one of the subclaims or preferably also with those from several subclaims. Accordingly, the following features can also be provided for the converter circuit:

• The converter circuit can include at least one further arm parallel to the intermediate circuit, which has two further arm half-bridges connected in series, the center point of the upper further arm half-bridge being connected to an upper further filter inductance, the center point of the lower further arm half-bridge Half bridge is connected to a lower further filter inductance and the potential point between the capacitors with the potential point between the further arm Half bridges is connected and wherein the control device is configured to operate all arms in the interleaved mode. For example, one or two additional arms further reduce the current load on the individual power semiconductors.
• It is particularly advantageous if the upper filter inductances of the arms are designed as a coupled inductance and the lower filter inductances of the arms are also designed as a coupled inductance. The respective inductances are arranged on a common core in such a way that the primary current flow of the generated half-wave is directed opposite to one another and the resulting magnetic fields cancel each other out. This makes it possible not to align the size of the filter inductances to the amplitude of the alternating voltage generated, but only to the significantly smaller circular currents that flow between the two arms. The filter inductances can be significantly smaller, which means that considerable savings in installation space are possible.
• The two capacitors of the intermediate circuit connected in series, at which the intermediate circuit voltage, for example 400 V, drops, can each also consist of several capacitors, for example in series or in parallel. This may be necessary if there is no capacitor that is specified for the required current and / or the required voltage.

• - The capacitors can have the same capacitance values. The intermediate circuit, which is symmetrically divided by using the same capacitance values, divides the intermediate circuit voltage symmetrically around the midpoint. Therefore, the same power semiconductors can be used in the first and second half bridges, which are controlled uniformly and optimally. This increases the efficiency of the converter circuit and reduces the complexity.
• The control device can be designed to operate the power semiconductors of the arms with a switching frequency in the kilohertz range or megahertz range. This frequency is used to modulate the alternating voltage. The control device can also be designed to operate the power semiconductors of the output half-bridge with a lower fundamental frequency in the Hertz range, for example 50 Hz. Since the power semiconductors are intended for different tasks at different frequencies within the converter circuit, the specified circuit topology allows a use of adapted power semiconductors. This is advantageous because the use of power semiconductors adapted to the task increases the efficiency of the converter circuit.
• - The power semiconductors of the first and second half bridges can be optimized with regard to low switching losses. The power semiconductors of the output half-bridge can be optimized with regard to low transmission losses. An essential factor for limiting the achievable efficiency is the losses that occur in the power semiconductors used. The switching losses that occur at the moment of opening and closing of the switch and increase with the switching frequency used, as well as the transmission losses that occur when the switch is conductive, play a role. Power semiconductors such as MOSFETs, IGBTs or GaN-HEMT switches have different properties with regard to switching losses and conduction losses. In addition, there are different versions within each type of power semiconductor that differ with regard to the properties mentioned. Typically, an optimization of the switching losses cannot be achieved at the same time as an optimization of the transmission losses, rather the goals are in conflict with one another. With known topologies, the selection of the power semiconductors is therefore a compromise. In contrast, in the converter circuit, the fast-switching power semiconductors of the first and second half-bridges, which are provided for modulating the AC voltage, can be optimized with regard to low switching losses, while the comparatively slow-switching power semiconductors of the output half-bridge, which are used for clocking with a Base frequency are provided, be optimized with regard to low transmission losses. Despite the conflict between switching losses and conduction losses, an optimal selection of the power semiconductors is possible, which cannot be made with other topologies.
• The power semiconductors of the first and second half bridges can have a dielectric strength which corresponds to at least half the intermediate circuit voltage. The power semiconductors of the output half-bridge can have a dielectric strength which corresponds at least to the entire intermediate circuit voltage. This is made possible by the circuit topology with the divided intermediate circuit, which acts as a capacitive voltage divider and, with preferably the same capacitance values, the intermediate circuit voltage around the center point divides symmetrically. At a given switching frequency, power semiconductors that have a higher dielectric strength and are therefore suitable for switching higher voltages generate significantly higher switching losses than power semiconductors that have a lower dielectric strength. The specified circuit topology allows the power semiconductors of the first circuit to only have a dielectric strength which corresponds to half the intermediate circuit voltage. Since the matched power semiconductors are used optimally in this way, the converter circuit is highly efficient.
• - SiC switches or GaN switches are preferably used as power semiconductors in the arms. These allow very high switching speeds and therefore make it possible to reduce the size of the filter elements. The power semiconductors of the arms can in particular be self-locking gallium nitride switches or cascodes with a self-conducting gallium nitride switch.
• - The power semiconductors of the first and second half bridges can be controlled with a frequency of more than 100 kHz, in particular more than 300 kHz. A high switching speed makes it possible to reduce the size of the filter elements.
• The first capacitor and the first and second upper half-bridges can be designed as a first commutation cell; the second capacitor and the first and second lower half bridges can be designed as a second commutation cell. In power electronics, commutation is the process in which a current flow passes from one branch to the other. In the present embodiment, the commutation takes place, for example in operation as an inverter, from the first capacitor to the first half-bridge connected in parallel and from the second capacitor to the second half-bridge connected in parallel. The formation of a commutation cell, in particular through a low-inductance arrangement of the components, is advantageous because very good commutation behavior and switching behavior are achieved, which increases the efficiency of the present circuit.
• - The power semiconductors of the first and second half bridges are preferably controlled with a pulse width modulation and the polarity of the power semiconductors of the second circuit is reversed with a lower fundamental frequency. For the pulse width modulation, the first and second half bridges are expediently always switched in such a way that one of the power semiconductors is switched on while the other power semiconductor is switched off.
• The converter circuit can comprise a further output half-bridge, which is connected in parallel to the output half-bridge and comprises a further AC voltage connection.
• - The power semiconductors within one of the arms can be controlled in such a way that they switch synchronously. In other words, the power semiconductors of the first two half bridges are switched over at the same time. In this operating mode, the voltage between the arms and the filter circuit therefore always changes between the full value of the intermediate circuit voltage and zero, that is to say a combination of the midpoint potential. In this case, either the two outer power semiconductors of the two first half bridges are switched on at one time or the two inner power semiconductors of the two first half bridges are switched on. This switching operation advantageously greatly reduces common-mode interference in the converter circuit.
• - Alternatively, power semiconductors of the arms can be controlled in such a way that the power semiconductors of the upper first half bridge switch alternately with the power semiconductors of the lower first half bridge. When the power semiconductors are controlled by means of a carrier signal, this can be achieved, for example, by a corresponding phase shift of the carrier signal for the lower first half bridge with respect to the upper first half bridge. The voltage at the input of the filter circuit changes in this switching mode between the full intermediate circuit voltage, half the intermediate circuit voltage and zero. The resulting switching frequency is doubled compared to the switching frequency with synchronous switching of the half bridges. As a result, the size of the filter inductances used in the filter circuit can be reduced, since the filter effect is inversely proportional to the frequency of the signal.

The invention is described and explained in more detail below with reference to the exemplary embodiments shown in the figures.

• 1 einen Schaltplan einer Ausführungsform der erfindungsgemäßen Stromrichter-Schaltung für einphasige Systeme,
• 2 einen Schaltplan einer Ausführungsform der erfindungsgemäßen Stromrichter-Schaltung für dreiphasige Systeme,
• 3 eine Phasenschaltung für die Stromrichter-Schaltung für dreiphasige Systeme,
• 4 bis 7 ein Zeitablaufdiagramm des Schaltzustands für verschiedene Halbbrücken der Stromrichter-Schaltung,
• 8 ein Zeitablaufdiagramm einer innerhalb der Stromrichter-Schaltung erzeugten Spannung.

They show schematically:

• 1 a circuit diagram of an embodiment of the converter circuit according to the invention for single-phase systems,
• 2 a circuit diagram of an embodiment of the converter circuit according to the invention for three-phase systems,
• 3 a phase circuit for the converter circuit for three-phase systems,
• 4th to 7th a timing diagram of the switching state for various half bridges of the converter circuit,
• 8th a timing diagram of a voltage generated within the converter circuit.

In 1 Figure 3 is a circuit diagram of one embodiment of the power converter circuit of the present invention 20th shown for single-phase systems. The converter circuit 20th is between a DC voltage system 1 and an in 2 AC voltage system, not shown, switched. The converter circuit includes 20th Connection contacts 24a , 24b for connection to the DC voltage system 1 and AC contacts 25a , 25b for connection to the AC voltage system.

The converter circuit 20th comprises two series-connected half bridges with power semiconductors T11 ... T14 in a first arm A1 . The top two power semiconductors T11 , T12 form an upper half-bridge of the first arm A1 off and the lower two power semiconductors T13 , T14 form a lower half-bridge of the first arm A1 out. An intermediate circuit is parallel to the half bridges 27 arranged of a series connection of two capacitors C1 , C2 having. The outer connections of the two half bridges are with the connection contacts 24a , 24b connected and thus form the DC voltage input of the converter circuit 20th . The intermediate circuit 27 is designed as a split intermediate circuit and to create a center point M. an intermediate circuit voltage UCC am between the capacitors C1 , C2 and the half-bridges located potential point is provided. Where is the first capacitor C1 connected in parallel to the upper half bridge and the second capacitor C2 connected in parallel to the lower half bridge. Parallel to the first arm A1 is a second arm A2 connected, which is constructed analogously to the first arm and also two half bridges connected in series with power semiconductors T21 ... T24 includes.

The midpoint of the upper half-bridge of the first arm A1 , i.e. the potential point between the power semiconductors T11 , T12 is with an upper first filter inductance LO1 connected. The midpoint of the upper half-bridge of the second arm A2 , i.e. the potential point between the power semiconductors T21 , T22 is with an upper second filter inductance LO2 connected. The other connections of the upper filter inductances LO1 , LO2 are merged into an upper filter node FO . The midpoint of the lower half-bridge of the first arm A1 , i.e. the potential point between the power semiconductors T13 , T14 is with a lower first filter inductance LU1 connected. The midpoint of the lower half bridge of the second arm A2 , i.e. the potential point between the power semiconductors T23 , T24 is with a lower second filter inductance LU2 connected. The other connections of the lower filter inductances LU1 , LU2 are merged into a lower filter node FU . The two filter nodes FO , FU are connected in series with two filter capacitors 29A , 29B connected. The potential point between the filter capacitors 29A , 29B is with the center M. of the intermediate circuit 27 connected.

In the present exemplary embodiment, the upper filter inductances are LO1 , LO2 , designed as a coupled inductance. Likewise are the lower filter inductances LU1 , LU2 , designed as a coupled inductance. The filter inductances LO1 , LO2 , LU1 , LU2 are each coupled in opposite directions so that the load currents counteract each other.

The converter circuit 20th includes a pole inverter on the output side, the two parallel half bridges made of power semiconductors P1 ... 4th includes. These half bridges are with their upper connection with the upper filter node FO connected and with their lower connection to the lower filter node FU connected. The potential point between the first two power semiconductors P1 , P2 of the pole changer is connected to the first AC voltage contact 25a . The potential point between the second two power semiconductors P3 , P4 of the pole changer is connected to the second AC voltage contact 25b .

The converter circuit 20th works with power electronic switches T11 ... T24 , P1 ... 4th which can be implemented as Insulated Gate Bipolar Transistors (IGBT), metal-oxide-semiconductor field-effect transistors (MOSFET) or gallium nitride-high electron mobility transistors (GaN-HEMT). The switches used can be different T11 ... T24 , P1 ... 4th also differ. In the present embodiment, the power semiconductors T11 ... T24 fast switching GaN switch, while the power semiconductors P1 ... 4th of the reverser are IGBTs.

The power semiconductors T11 ... 24 of the first and second arms A1 , A2 are provided for a modulation, preferably a pulse width modulation, PWM for short, with a clock that has a significantly higher frequency than the basic frequency f _G of the AC voltage network. At this high clock frequency of 10 kHz, 100 kHz or 250 kHz, for example, the switching losses of the power semiconductors are T11 ... 24 dominant over the throughput losses and therefore become such power semiconductors T11 ... 24 used, which are optimized with regard to low switching losses.

The power semiconductors P1 ... 4th of the pole changer are for clocking with the basic frequency f _G intended. Because with this significantly lower switching frequency f _G the conduction losses of the power semiconductors P1 ... 4th such power semiconductors are dominant in comparison to the switching losses P1 ... 4th selected for the pole changer, which are optimized with regard to low throughput losses.

2 shows schematically an embodiment of the converter circuit according to the invention 30th for three-phase systems. The converter circuit 30th is between a DC voltage system 1 and an in 2 AC voltage system, not shown, switched. The converter circuit includes 30th Connection contacts 24a , 24b for connection to the DC voltage system 1 and AC contacts 25 for connection to the AC voltage system.

The converter circuit 30th includes a divided intermediate circuit 27 that of the converter circuit 20th of the 1 corresponds. Parallel to the intermediate circuit 27 but is with the converter circuit 30th a phase connection for each phase 21U , V , W. arranged. The structure of the phase circuits 21U , V , W. is in 3 shown and corresponds to one of the parts of the single-phase converter circuit 20th . The phase connections 21U , V , W. are each on the input side with the DC voltage connections 24a , b and the center M. connected. On the output side, they are connected to an output half-bridge provided for each phase 22U , V , W. . The midpoint of each of the output half bridges 22U , V , W. is with one phase of the AC output 25 connected.

3 shows a phase connection 21U , V , W. in detail. The phase connection 21U , V , W. comprises two series-connected half bridges with power semiconductors T11 ... T14 in a first arm A1 . The top two power semiconductors T11 , T12 form an upper half-bridge of the first arm A1 off and the lower two power semiconductors T13 , T14 form a lower half-bridge of the first arm A1 out. The outer connections of the two half bridges are with outer input nodes 23a , c connected. The potential point between the two half bridges is with a middle input node 23b connected. Parallel to the first arm A1 is a second arm A2 connected, which is constructed analogously to the first arm and also two half bridges connected in series with power semiconductors T21 ... T24 includes and analogous to the first arm with the input node 23a ... c connected is.

The midpoint of the upper half-bridge of the first arm A1 , i.e. the potential point between the power semiconductors T11 , 12th is with an upper first filter inductance LO1 connected. The midpoint of the upper half-bridge of the second arm A2 , i.e. the potential point between the power semiconductors T21 , 22nd is with an upper second filter inductance LO2 connected. The other connections of the upper filter inductances LO1 , LO2 are merged into an upper filter node FO . The midpoint of the lower half-bridge of the first arm A1 , i.e. the potential point between the power semiconductors T13 , 14th is with a lower first filter inductance LU1 connected. The midpoint of the lower half bridge of the second arm A2 , i.e. the potential point between the power semiconductors T23 , 24 is with a lower second filter inductance LU2 connected. The other connections of the lower filter inductances LU1 , LU2 are merged into a lower filter node FU . The two filter nodes FO , FU are connected in series with two filter capacitors 29A , 29B connected. The potential point between the filter capacitors 29A , 29B is with the middle input node 23b connected. The top filter node FO is with a top exit node 23d connected while the lower filter node FU with a lower exit node 23e connected is.

The 4th to 7th show the sequence of the switching states of the half bridges of the first arm A1 as well as the half bridges of the pole changer over a period of time that is one period of the fundamental frequency f _G corresponds to, ie 20 µs at a basic frequency of 50 Hz. The half bridges of the first arm A1 are according to 4th and 5 operated with a PWM, the frequency of which is only 4 kHz for better representation. The 4th to 7th show a corresponding time axis in the horizontal direction Z . There is a normalized axis in the vertical direction S. , which indicates the switching status of the respective half bridge. The switching state includes the state of the two power semiconductors T11 ... 24 , P1 ... 4th the respective half-bridge, whereby from the power semiconductors T11 ... 24 , P1 ... 4th of a half bridge, one is switched on and the other is switched off.

In the 4th and 5 it can be seen that the half bridges of the first arm A1 always switch in the same mode, i.e. synchronously, and in opposite directions. The resulting voltage difference at the outputs of the half bridges therefore either corresponds to the intermediate circuit voltage UCC or zero (short-circuited outputs). With the filter capacitors 29A , B. , so from the point of view of the half bridges behind the filter inductances LO1 , LO2 , LU1 , LU2 this results in a smoothed voltage curve which corresponds to a rectified sinusoidal alternating voltage, ie a sequence of positive half-waves. This voltage curve is standardized Shape in 8th shown. 8th uses the same time axis Z as the 4th to 7th . The PWM used is designed in such a way that a sequence of half-waves remains after filtering high frequencies. It therefore differs somewhat in terms of its exact course from a PWM for generating a complete sine curve.

The power semiconductors T21 ... 24 of the second arm A2 switch in the same way as power semiconductors T11 ... 14th of the first arm A1 , however, switch out of phase with these, for example 90 ° out of phase. This results in an operating mode that is referred to as interleaved. The current is divided equally between the power semiconductors that are analogous to one another T11 ... 14th , T21 ... 24 of the two arms A1 , A2 on, whereby the losses in the respective power semiconductors T11 ... 14th , T21 ... 24 be reduced.

In the 6 and 7th it can be seen that the half-bridges of the pole changer or, in the case of the three-phase circuit, the output half-bridges with the fundamental frequency f _G be reversed, ie with a relatively low frequency of 50 Hz, for example. As a result, every second of the positive half-waves in the voltage curve of the filter capacitors 29A , B. folded over and thus a complete sine wave is generated as the output voltage. The polarity reversal of the half bridges also takes place synchronously and the half bridges are of course always switched in phase opposition.

The high-frequency voltage changes that are generated by reversing the polarity of the half-bridges of the arms are limited in the topology shown to the areas between the power semiconductors T11 ... 24 the arms and the respective filter inductance LO1 , LO2 , LU1 , LU2 . When realizing the converter circuit 20th , 30th the conductor pieces that correspond to these areas can be kept very short. A shield to reduce emissions, ie to improve the EMC properties of the converter circuit 20th , 30th , can therefore be designed with little structural effort. Will the power converter circuit 20th , 30th built up in a multi-layer circuit board, the conductor pieces corresponding to the areas can be arranged, for example, in a middle layer. Layers above and / or below can then either be other parts of the converter circuit suitable for shielding 20th , 30th or have specially provided metallic surfaces. As a result, the housing of the converter circuit can in turn 20th , 30th be constructed in a simplified manner, for example as a plastic housing instead of a metal housing, since the housing has to fulfill fewer or no shielding tasks.

List of reference symbols

1

DC voltage

20.30

Converter circuit

21U, V, W

Phase connection

22U, V, W

Exit half-bridge

23a, b, c

Input node

23d, e

Exit node

24a, b

Connection contacts

25,25a, b

AC voltage connections

27

Intermediate circuit

29A, 29B

Filter capacitors

A1, A2

poor

T11 ... 24

Power semiconductors

P1 ... 4

Power semiconductors

C1, C2

Capacitors

LO1, LO2

Upper filter inductances

LU1, LU2

Lower filter inductances

M.

Focus

FU, FO

Filter node

UCC

DC link voltage

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• EP 2136465 A1 [0004]
• WO 2016/146171 A1 [0005]
• EP 2306629 A1 [0006]
• DE 102014113306 A1 [0007]

Claims (11)

Power converter circuit (20, 30) comprising - Connection contacts (24a, 24b) for connection to a direct voltage (1), between which an intermediate circuit (27) with a series connection of two capacitors (C1, C2) is arranged, the intermediate circuit (27) being designed as a divided intermediate circuit for production a midpoint (M) of an intermediate circuit voltage (UZK) at the point between the capacitors (C1, C2), - A first arm (A1) parallel to the intermediate circuit (27), which has two series-connected first arm half-bridges, each with at least one lower power semiconductor (T12, T14) and one upper power semiconductor (T11, T13), the center of the upper one first arm half-bridge is connected to an upper first filter inductance (LO1), the midpoint of the lower first arm half-bridge is connected to a lower first filter inductance (LU1) and the potential point (M) between the capacitors (C1, C2) is connected to the potential point is connected between the first arm half bridges, - A second arm (A2) parallel to the intermediate circuit (27), which has two series-connected second arm half-bridges each with at least one lower power semiconductor (T22, T24) and one upper power semiconductor (T21, T23), the center of the upper second arm half-bridge is connected to an upper second filter inductance (LO2), the midpoint of the lower second arm half-bridge is connected to a lower second filter inductance (LU2) and the potential point (M) between the capacitors (C1, C2) is connected to the potential point is connected between the second arm half bridges, - A filter circuit with two filter capacitors (29a, 29b) connected in series, the potential point between the two filter capacitors (29a, 29b) being connected to the center point (M), an upper connection of the filter circuit to the upper filter inductances ( LO1, LO2) is connected and a lower connection of the filter circuit is connected to the lower filter inductances (LU1, LU2), - An output half-bridge (22U, V, W), the center of which forms an alternating voltage output (25, 25a, 25b), an upper potential point of the output half-bridge (22U, V, W) being connected to the upper connection of the filter circuit and a lower potential point of the output half-bridge (22U, V, W) is connected to the lower connection of the filter circuit, - A control device which is designed to control the power semiconductors (T11 ... T14, T21 ... 24) of the two arms (A1, A2) out of phase with one another in order to achieve operation in the interleaved mode. Converter circuit (20, 30) according to Claim 1 with at least one further arm parallel to the intermediate circuit (27), which has two further arm half-bridges connected in series, the center point of the upper further arm half-bridge being connected to an upper further filter inductance, the center point of the lower further arm half-bridge being connected to a The lower further filter inductance is connected and the potential point (M) between the capacitors (C1, C2) is connected to the potential point between the further arm half-bridges and the control device is designed to operate all arms (A1, A2) in interleaved mode . Converter circuit (20, 30) according to Claim 1 or 2 , in which the upper filter inductances (L01, LO2) of the arms (A1, A2) are designed as coupled inductances and in which the lower filter inductances (LU1, LU2) of the arms are designed as coupled inductances Converter circuit (20, 30) according to one of the preceding claims, in which the capacitors (C1, C2) of the intermediate circuit (27) have the same capacitance values. Converter circuit (20, 30) according to one of the preceding claims, in which the control device is designed to switch the power semiconductors (T11 ... T14, T21 ... 24) of the first and second half bridges with a switching frequency in the kilohertz range or megahertz -Operate area. Converter circuit (20, 30) according to one of the preceding claims, in which the control device is designed to operate the power semiconductors (P1 ... 4) of the output half-bridge (22U, V, W) with a switching frequency in the Hertz range . Converter circuit (20, 30) according to one of the preceding claims, in which the power semiconductors (T11 ... T14, T21 ... 24) of the first and second half bridges are optimized with regard to low switching losses and the power semiconductors (T5 ... 8 ) of the output half-bridge (22U, V, W) are optimized with regard to low transmission losses. Converter circuit (20, 30) according to one of the preceding claims, in which the power semiconductors (T11 ... T14, T21 ... 24) of the first and second half bridges are designed as silicon carbide switches or as gallium nitride switches, in particular as self-locking gallium nitride switches or as a cascode with a self-conducting gallium nitride switch. A method for interconnecting a DC voltage system (1) with an AC voltage system, in which a converter circuit (20, 30) according to one of the preceding claims is used, the converter circuit (20, 30) being operated as a rectifier and / or as an inverter , whereby the power semiconductors (T11 ... T14, T21 ... 24) of the arms (A1, A2) of the Converter circuit (20, 30) are controlled out of phase with one another in order to achieve operation in the interleaved mode. Procedure according to Claim 9 , in which the power semiconductors (T11 ... T14, T21 ... 24) of the first and second half bridges are controlled with pulse width modulation in the kilohertz or megahertz range and the power semiconductors (P1 ... 4) are the output - Half-bridge (22U, V, W) with a fundamental frequency in the Hertz range. Photovoltaic system with at least one solar module and at least one converter circuit (20, 30) according to one of the Claims 1 to 8th .

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