DE10051156B4 - Method and converter circuit for medium-frequency transformatory energy transmission - Google Patents

Abstract

method for medium-frequency transformatory energy transmission by means of a primary and secondary side transformer connected to power electronic converters, primary and / or secondary side at least two independently controllable, each with a partial winding (2.1, 2.2, 2.3, 3.1, 3.2, 3.3) of a mononuclear one Transformers (1) connected converters (4.1, 4.2, 4.3, 5.1, 5.2, 5.3), characterized in that the power converters clocked in the Zertmultiplexverfehren so that to each Time per winding side (primary or secondary) of the transformer (1) only one power converter is current-carrying.

Description

The The invention relates to a method for medium-frequency transformatory Energy transfer by means of one primary and one secondary transformer connected to power electronic converters, being primary and / or secondary side at least two independently controllable, each with a partial winding of a mononuclear transformer connected power converters be used.

The The invention also relates to a converter circuit for carrying out the Process.

A power transmission by means of transformers with a voltage well above the mains frequency Operating frequency has so far been mainly with so-called switching power supplies with relatively low insulation requirements and low power.

Furthermore are so-called medium-frequency transformers in conjunction with power electronic converters as a replacement for conventional power transformers known. The generated by the power electronic converters, essentially over The mains frequency operating frequency allows in principle considerable Weight and volume savings of transformers. The performance of such However, units have been severely limited so far.

Around the conventional power transformers on electric traction vehicles however, are becoming transferable Services in the range of several hundred kilowatts needed. Around to meet these requirements are in the youngest Time various efforts have been made.

So is from H. Reinold, M. Steiner: "Characterization of Semiconductor Losses Series Resonant DC-DC Converters for High Power Applications using Transformers with Low Leakage Inductance ", EPE 1999, Lausanne, an IGBT series resonant converter known.

In M. Kunz, F. Hörl, T. Klockow: "Development of a low-energy energy supply for electric traction vehicles ", ZEV-DET glass. Ann. 123, 11/12, pp. 423-426, 1999, an arrangement with an input-side and an output-side Four-quadrant described. The four-quadrant manufacturers exist from several subcircuits in cascade arrangement, each subcommander a partial winding of a medium-frequency transformer supplied.

Four-quadrant in cascade arrangement are also the subject of the publication Schibili, N., Rufer, A .: "Single and three-phase multilevel converters for traction systems 50 Hz / 16 2/3 Hz ", Proceedings, 7th European Conference on Power Electronics and Applications (EPE), vol. 4, pp. 210-215, Trondheim, 1997.

From the DE 198 17 752 A1 a method of the type mentioned for medium-frequency transformatory energy transfer is known. In this case, both the primary side and the secondary side power converter are provided, which are independently controllable and are each connected to a partial winding of a mononuclear transformer. The block width of the control of the power converters can be set individually, so that in terms of timing these converters can be alternately clocked.

conditioned by limiting the switching frequency and the associated however, the maximum transformer operating frequency still exists size Disadvantages regarding transformer weight, volume and efficiency.

task The invention is a technically and economically advantageous implementation option for power electronic Converters with high transmission power and high inverter intermediate circuit voltage at transformer Specify potential separation.

The The object is achieved in that in the method for medium-frequency transformatory energy transmission the power converters are clocked in a time division multiplex method, that at each time per winding side (primary or secondary) of the transformer only one power converter is current-carrying. Regarding one Converter circuit for implementation of the method is the object by the features of the claim 7 solved. Advantageous embodiments are the subject of the dependent claims.

After that are primarily and / or secondary side at least two independently controllable, each with a partial winding of a mononuclear transformer connected alternator alternately clocked, either successively bipolar voltage pulses or alternately generate unipolar voltage pulses of opposite polarity.

• a) geringem Gewicht und Volumen
• b) hoher übertragbarer Leistung
• c) hohem Wirkungsgrad
• d) hoher Isolationsspannung
• e) hoher Stromrichter-Zwischenkreisspannung
• f) reduziertem Materialaufwand (insbesondere weichmagnetisches Material)

auf eine technisch und wirtschaftlich vorteilhafte Art zu erfüllen.With the method and the converter circuit, it is possible to meet the sometimes reluctant demands for:

• a) low weight and volume
• b) high transmittable power
• c) high efficiency
• d) high isolation voltage
• e) high power converter DC link voltage
• f) reduced material costs (in particular soft magnetic material)

to meet in a technically and economically advantageous manner.

With Help of independent converters on the primary or / and secondary side of the Transformers can increase its operating frequency with practically only slightly Inverter losses corresponding to the number of independent converters on the primary or / and secondary side elevated

The Invention will be explained below with reference to exemplary embodiments. In the associated Drawings show

1 the schematic diagram of a converter circuit according to the invention with three primary-side and one secondary-side converter,

2 a converter circuit with three converters each primary and secondary,

3 a converter circuit with two primary-side converters,

4 the principal voltage curve in the process with bipolar voltage pulses,

5 the principal voltage curve in the process with unipolar voltage pulses,

6 the composition of the secondary-side voltage from the voltages of three primary-side converters in bipolar voltage pulses,

7 the composition of the secondary side voltage from the voltages of two primary - side converters with unipolar voltage pulses and

8th an example of a converter circuit with two primary and secondary side power converters as IGBT half-bridges in center circuit.

According to the invention, the transformer consists of at least two windings on the primary and / or secondary side and a corresponding number of independent power converters. 1 shows an example with three primary-side converters 4.1 . 4.2 . 4.3 and a secondary side power converter 5.1 , Each primary-side partial winding 2.1 . 2.2 . 2.3 a transformer 1 is with its own power converter 4.1 . 4.2 . 4.3 connected. Accordingly, each power converter 4.1 . 4.2 . 4.3 independent of the others any voltage at the respective part winding 2.1 . 2.2 . 2.3 memorize.

The operation of the method according to the invention in time-division multiplexing converter 4.1 . 4.2 . 4.3 can be done in two fundamentally different ways, namely by means of bipolar or unipolar voltage pulses.

When using bipolar voltage pulses generate all participating power converters 4.1 . 4.2 . 4.3 Voltage pulses whose basic course in 4 is shown. Each converter generates this 4.1 . 4.2 . 4.3 a bipolar voltage pulse for a period T ₁ . For the subsequent period T ₂ - T ₁ , in each case the other two of the power converters 4.1 . 4.2 . 4.3 generate a bipolar voltage pulse, it goes to the clock lock, which corresponds to a state of "open terminals" on the associated transformer winding, see 4 and 6 , T ₂ represents the duration of the total period of all three input-side converter 4.1 . 4.2 . 4.3 represents. 6 shows the voltage curves for the in 1 shown circuit with three primary-side bipolar voltages U ₂₁ , U ₂₂ , U ₂₃ , which have different phase angles φ ₁ to φ ₃ to the secondary-side bipolar voltage U ₃₁ for the transmission of various services.

The power converter 5.1 on the secondary side of the transformer 1 operates at N times the inverter switching frequency of the converters 4.1 . 4.2 . 4.3 , All power converters 4.1 . 4.2 . 4.3 . 5.1 work as in all examples described in full block operation. The inverter switching losses are limited to a minimum during full block operation. Basically, however, a converter operation is possible in which the inverter can be clocked at a multiple of the fundamental frequency (so-called pulsed operation). With the aid of the phase angles φ ₁ to φ ₃ , the transmitted powers can be set independently, see 6 , The power converter 5.1 transfers the total power of the three primary-side converters 4.1 . 4.2 . 4.3 ; its frequency converter is equal to the transformer operating frequency f ₁ and thus three times as large as that of the converter 4.1 . 4.2 . 4.3 , Accordingly, the inverter frequency of the converter has 4.1 . 4.2 . 4.3 in relation to the transformer operating frequency f ₁ , which results in a significant reduction of the semiconductor losses in the power converters 4.1 . 4.2 . 4.3 means. With the increase of the transformer operating frequency f ₁ is also a reduction of the maximum magnetic flux in the Transforma torkern connected. As a result, the power density of the transformer 1 according to the increase in Transformer operating frequency f ₁ increases. Thus, the above-mentioned requirements a) to f) at constant switching frequency of the power electronic switches in the power converters 4.1 . 4.2 . 4.3 be fulfilled on the primary side.

Used instead of the circuit of 1 the circuit off 2 with three secondary-side converters 5.1 . 5.2 . 5.3 , can via the common transformer 1 Power in each case from the primary-side converter 4.1 to the power converter 5.1 as well as from the power converter 4.2 to the power converter 5.2 and analag from the power converter 4.3 to the power converter 5.3 be transmitted. These can be between the respective power converters 4.1 . 5.1 ; 4.2 . 5.2 ; 4.3 . 5.3 In turn, the transmitted services are set independently of each other.

• • Bei gleicher Schaltfrequenz der primärseitigen Stromrichter 4.1, 4.2, 4.3 als auch der sekundärseitigen Stromrichter 5.1, 5.2, 5.3 kann die Transformatorbetriebsfrequenz f₁ auf das Dreifache angehoben werden.
• • Gleichzeitig ergibt sich mit der auf das Dreifache angestiegenen Transformatorbetriebsfrequenz f₁ eine deutlich gestiegene Leistungsdichte des Transformators 1.
• • Trotz eines gemeinsamen Transformators 1 können die Leistungen zwischen den Stromrichtern 4.1 und 5.1, 4.2 und 5.2 sowie 4.3 und 5.3 unabhängig voneinander mit Hilfe des erfindungsgemäßen Zeitmultiplexverfahrens übertragen werden.

Due to the magnetic coupling of all partial windings involved, the following advantages result:

• • With the same switching frequency of the primary-side converter 4.1 . 4.2 . 4.3 as well as the secondary-side converter 5.1 . 5.2 . 5.3 The transformer operating frequency f ₁ can be raised to three times.
• • At the same time, the transformer operating frequency f _1, which has increased threefold, results in a significantly increased power density of the transformer 1 ,
• • Despite a common transformer 1 can the power between the power converters 4.1 and 5.1 . 4.2 and 5.2 such as 4.3 and 5.3 be transferred independently of each other using the time division multiplex method according to the invention.

In addition, a power transmission is among the primary-side converters 4.1 . 4.2 . 4.3 as well as the secondary-side converters 5.1 . 5.2 . 5.3 possible. This means, for example, that of the power converter 4.1 transmitted power is not necessarily that of the power converter 5.1 must correspond, because power converters 4.1 also power to the power converter 4.2 or power converter 4.3 and the associated secondary-side converters 5.2 and 5.3 can transfer.

Assuming that the gear ratio of the transformer 1 between all windings is always 1, strong deviations of the DC link voltage z. B. the power converter 4.1 . 4.2 . 4.3 lead to any desired power balancing operations. During these processes, the state of the "open terminals" is sometimes canceled, for example a power converter 4.1 with relatively high DC link voltage during power transmission to the power converter 5.1 at the same time a part of the power to the power converter 4.2 and / or power converters 4.3 transmitted, if they have a lower DC link voltage.

Of the State "open Clamps "can at all converter types are always realized by a separate switch disposed between the power converter and associated transformer winding is, the transformer winding separates from the power converter and thus switches to idle.

Becomes the converter circuit with converters with voltage intermediate circuit built up, the state can be "open Clamps "through the Power converter clock lock up to a voltage that is the DC link voltage corresponds to the respective power converter, be realized. This is sufficient, as long as all power converters have approximately the same the gear ratio of the Transformers have corresponding DC link voltage. On this way can on the otherwise additional required switch between power converter and transformer winding are dispensed with.

When using unipolar voltage pulses, all participating converters generate voltage pulses, the basic course of which in 5 is shown, in which case two primary-side converter 4.1 . 4.2 according to 3 are required. Every power converter 4.1 . 4.2 generates two unipolar voltage pulses over each half of a period T ₁ . Between two voltage pulses of the same polarity the converter goes over a period of (T ₂ - T ₁ ) / 2 in the state "open terminals", the clock lock.

For the method with unipolar voltage pulses, it is necessary that an even number of converters always participate in the generation of the multiplex signal, since one converter of one converter pair always has to generate positive voltage pulses and the other converter always has to generate negative voltage pulses ( 5 ).

The principal voltage curves of the circuit with unipolar voltage pulses may be next to it 7 are removed, in which case again a circuit according to 3 This means that the secondary-side voltage U _{31 is} generated from two primary-side unipolar voltages U ₂₁ , U ₂₂ , which have different phase angles φ ₁ , φ ₂ for the transmission of different powers

Also in this circuit, the power converters 4.1 and 4.2 independent power to the power converter 5.1 transfer. This is done via the free adjustment of the phase angles φ ₁ and φ ₂ . The advantage of this circuit over the converter circuit of 1 in that with a 2-quadrant operation the power converter 4.1 and 4.2 Power can be transmitted from the primary side to the secondary side as well as in the opposite direction.

Otherwise Operation with unipolar voltage pulses has the same characteristic Features such as operation with bipolar voltage pulses.

In addition to the operation of the power converter on its own DC link, as is the case in the above examples, the operation of power converters on a common DC link is conceivable. So z. B. the primary-side converter after 2 have separate DC link, the secondary-side converter 5.1 . 5.2 but have a common two-circle. But there are also combinations of common and separate DC links on the primary or the secondary side of the transformer conceivable.

Finally, it is still in 8th an example of a converter circuit shown. power converters 4.1 . 4.2 . 5.1 and 5.2 are designed in this circuit as IGBT half-bridges in center circuit.

Claims (9)

Method for medium-frequency transformatory energy transmission by means of a transformer connected on the primary and secondary side with power electronic converters, at least two mutually independently controllable primary and / or secondary side, each having a partial winding ( 2.1 . 2.2 . 2.3 ; 3.1 . 3.2 . 3.3 ) of a mononuclear transformer ( 1 ) connected converters ( 4.1 . 4.2 . 4.3 ; 5.1 . 5.2 . 5.3 ), characterized in that the converters are clocked in Zertmultiplexverfehren so that at each time per winding side (primary or secondary) of the transformer ( 1 ) only one power converter is current-carrying. Method according to Claim 1, characterized in that the power converters ( 4.1 . 4.2 . 4.3 ; 5.1 . 5.2 . 5.3 ) generate successive bipolar voltage pulses. A method according to claim 1, characterized in that an even number of power converters ( 4.1 . 4.2 ; 5.1 . 5.2 ) alternately produces unipolar voltage pulses of opposite polarity in pairs. Method according to one of the preceding claims, characterized in that the power converters ( 4.1 . 4.2 . 4.3 ; 5.1 . 5.2 . 5.3 ) work in full block mode. Method according to one of the preceding claims, characterized in that the power converters ( 4.1 . 4.2 . 4.3 ; 5.1 . 5.2 . 5.3 ) of the associated partial windings ( 2.1 . 2.2 . 2.3 ; 3.1 . 3.2 . 3.3 ) are separated by separate switches. Method according to one of the preceding claims, characterized in that a partial energy transfer in each case within the primary and / or secondary-side partial windings ( 2.1 . 2.2 ; 2.3 ; 3.1 . 3.2 . 3.3 ) he follows. Converter circuit for carrying out the method according to one of the preceding claims, characterized in that primary and / or secondary side at least two independently controllable power converters ( 4.1 . 4.2 . 4.3 ; 5.1 . 5.2 . 5.3 ) each with a partial winding ( 2.1 . 2.2 . 2.3 ; 3.1 . 3.2 . 3.3 ) of the transformer ( 1 ) are connected and all windings are magnetically coupled via a common core. Converter circuit according to claim 7, characterized in that the power converters ( 4.1 . 4.2 . 4.3 ; 5.1 . 5.2 . 5.3 ) are formed as half bridges in center circuit. Converter circuit according to claim 7 , characterized in that the power converters ( 4.1 . 4.2 . 4.3 ; 5.1 . 5.2 . 5.3 ) are designed as working in two-quadrant half bridges without center circuit.