DE102012220371A1 - Device for charging high voltage battery of electric vehicle from three-phase alternating current voltage source, has switch switched by control device such that current and voltage of source are in phase with each other - Google Patents

Abstract

The device has a converter device (U) connected with a rectifier device (G2), and including a half bridge (H1) of two serially connected switches (S1, S2). An inductor (L1) is connected between a connecting point of the switches and the converter device. One of the switches is switched by a control device (10) such that a current that is withdrawn for charging an electrical energy storage (B), and a voltage of a three-phase alternating current (AC) voltage source (W) are in phase with each other. An electrical chopper device (Z) is connected with another rectifier device (G1). Independent claims are also included for the following: (1) a method for charging an electrical energy storage from a three-phase AC voltage source (2) a computer program product comprising instructions for performing a method for charging an electrical energy storage from a three-phase AC voltage source.

Description

The invention relates to a device for charging an electrical energy store from an AC voltage source. The invention further relates to a method for charging an electrical energy store from an AC voltage source.

DE 195 235 76 A1 discloses a DC power supply and a method of voltage conversion. Described is an AC-to-DC converter in which efficiency of the power supply is improved by providing a flyback converter in which a first semiconductor switch has a lower breakdown voltage than a second semiconductor switch, and by reducing a power component processed in a readjustment device.

Disclosure of the invention

• – eine erste Gleichrichtereinrichtung;
• – eine mit der ersten Gleichrichtereinrichtung verschaltete elektrische Zerhackereinrichtung;
• – eine mit einem Ausgang der Zerhackereinrichtung verschaltete Transformatoreinrichtung;
• – eine mit einer Sekundärseite der Transformatoreinrichtung verschaltete zweite Gleichrichtereinrichtung; und
• – eine mit der zweiten Gleichrichtereinrichtung verschaltete Umrichtereinrichtung mit einer ersten Halbbrücke aus zwei seriell geschalteten Schaltern, wobei eine erste Induktivität zwischen einem Verbindungspunkt der Schalter der ersten Halbbrücke und der zweiten Gleichrichtereinrichtung verschaltet ist, wobei mittels einer Steuerungseinrichtung einer der Schalter der ersten Halbbrücke derart schaltbar ist, dass ein zum Laden des elektrischen Energiespeichers der Wechselspannungsquelle entnommener Strom und eine Spannung der Wechselspannungsquelle im Wesentlichen in Phase sind.

According to a first aspect, the invention provides a device for charging an electrical energy store from an AC voltage source, comprising:

• A first rectifier device;
• - An electrical chopper connected to the first rectifier means;
• A transformer means connected to an output of the chopper means;
• A second rectifier device connected to a secondary side of the transformer device; and
• A converter device connected to the second rectifier device having a first half-bridge of two serially connected switches, wherein a first inductance is connected between a connection point of the switches of the first half-bridge and the second rectifier device, wherein by means of a control device one of the switches of the first half-bridge can be switched in such a way in that a current removed for charging the electrical energy store of the AC voltage source and a voltage of the AC voltage source are substantially in phase.

• – Gleichrichten einer Eingangswechselspannung;
• – Wandeln der gleichgerichteten Eingangswechselspannung in eine hochfrequente Wechselspannung;
• – Transformieren der hochfrequenten Wechselspannung;
• – Gleichrichten der transformierten Wechselspannung; und
• – Generieren einer Gegenspannung zur gleichgerichteten, transformierten Spannung derart, dass eine Spannung der Wechselspannungsquelle und ein Strom, der der Wechselspannungsquelle zum Laden des elektrischen Energiespeichers entnommen wird, im Wesentlichen in Phase sind.

According to a second aspect, the invention provides a method comprising the following steps:

• - rectifying an input AC voltage;
• - converting the rectified input AC voltage into a high frequency AC voltage;
• - transforming the high-frequency AC voltage;
• - rectifying the transformed AC voltage; and
• - Generating a counter voltage to the rectified, transformed voltage such that a voltage of the AC voltage source and a current that is taken from the AC voltage source for charging the electrical energy storage, are substantially in phase.

Preferred developments of the invention are the subject of dependent claims.

A preferred embodiment of the device is characterized in that by means of the control device in dependence on a charging current for the electrical energy storage and of the voltage of the AC voltage source, a duty cycle of the switch of the first half-bridge is adjustable. In this way can be advantageously regulated by means of the control device by changing the duty cycle of the switch, a charging current for the energy storage.

A preferred embodiment of the device is characterized in that a second inductance is connected between a second half-bridge of the converter device from two switches connected in series and the second rectifier device. Thereby, an improved utilization of the converter device can be achieved, wherein the individual switches of the converter device are relieved.

A preferred embodiment of the device according to the invention is characterized in that second switches of the two half-bridges are switchable in an overlapping switching operation. This advantageously causes a reduction of a ripple of the charging current (current ripples) due to overlapping interleave switching. Advantageously, this results in reduced harmonic emissions into the AC grid.

A preferred embodiment of the device according to the invention is characterized in that the first inductance is formed as an inductance of windings of a three-phase electric motor, wherein the windings are connected to connection points of switches of three half-bridges of the converter. As a result, advantageously no external coupling inductance is required and it is provided a use of the three-phase windings of the electric machine for the purpose of loading. In this way, an implementation of the harmonic recovery device (English Power Factor Correction) can be provided by the electric motor.

A preferred embodiment of the device according to the invention is characterized in that an additional inductance between the second rectifier device and the Connection point of the two switches of the first half-bridge is connected. As a result, an additional external inductance can advantageously be used if the inductance of the motor windings of the three-phase electric motor is insufficient to build up the required reverse voltage.

A preferred embodiment of the device according to the invention provides that second switches of the two half-bridges are switchable in an overlapping switching operation. This advantageously brings about a reduction of current ripples, moreover, electrical switching energy is distributed over a plurality of switches, which can bring about an increased service life of the switches. Advantageously, the electric motor is thereby exploited also improved by all three phases are used.

A preferred embodiment of the device according to the invention is characterized in that the device is formed in three, wherein the device is connected in each case with a phase of a three-phase system, wherein in each case interconnected a first inductance between each second rectifier means and a connection point of two switches of the half-bridges of the converter wherein, by means of the control device, the switches of the three half-bridges are switchable such that a current removed for charging the electrical energy store of the AC voltage source and a respective phase voltage of the AC voltage sources are substantially in phase. In this way, the converter device advantageously takes over again the functionality of the power factor correction. Advantageously, all half bridges of the converter device can be used, which causes a uniform power distribution to all switches. Due to the threefold configuration of the device, three independent charging current profiles can be simulated and it can thereby advantageously a rapid charging of the electrical energy storage can be achieved.

A preferred embodiment of the device according to the invention is characterized in that the electrical chopper device is designed as a fourth half-bridge with two switches on a primary side of the transformer device, wherein the transformer device has a center tap on the primary side. This advantageously achieves a reduction in a number of semiconductor switches, which means reduced forward and switching losses. In addition, thereby a space gain and a reduced number of drivers for the switches can be achieved. This results in a total advantageous in a cost saving of the entire device.

An advantageous development of the device according to the invention is characterized in that the second rectifier device in each case has a diode at each end section of the secondary side of the transformer device, wherein the secondary side of the transformer device has a center point tap. As a result, a number of semiconductor components of the second rectifier device is advantageously halved, whereby failure rates are advantageously minimized.

Advantages of the invention

Particularly advantageous is considered in the invention that for loading the electrical energy storage in a charging operation of the electric vehicle, an existing converter can be used. Advantageously, a link capacitor, which is used in conventional devices omitted. In addition, the inverter is also used to realize a harmonic improving device, so that the conventional correcting device can be omitted. Advantageously, in this way a charging device according to the invention can be made much simpler and less expensive. In addition, a safety aspect for users can be advantageously increased by means of galvanic isolation by the transformer device.

Further features and advantages of the present invention will be explained below with reference to embodiments with reference to figures. All described or illustrated features, alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency, as well as regardless of their formulation or representation in the description or in the figures. The figures are primarily intended to illustrate the principles essential to the invention and are not necessarily to be understood as detailed circuit diagrams. In the figures, like reference numerals designate the same or functionally identical elements.

Brief description of the figures

Show it:

1 a schematic block diagram of a battery charger according to the prior art;

2 a schematic block diagram of a first embodiment of a device according to the invention for charging an electrical energy storage device;

2a .. 2f time courses of electrical quantities within the device of 2 ;

3 an electrical equivalent circuit diagram of the device according to the invention;

4 a phasor diagram with voltages and currents within the device according to the invention;

5 a timing diagram with waveforms of currents and voltages within the device according to the invention;

6 a schematic block diagram of a second embodiment of the device according to the invention;

7 a schematic block diagram of a third embodiment of the device according to the invention;

8th a conventional device for three-phase charging of an electrical energy storage device;

9 a schematic block diagram of a fourth embodiment of the device according to the invention;

10 a course diagram with electrical variables within the fourth embodiment of the device according to the invention.

11 a schematic block diagram of a fifth embodiment of the device according to the invention;

12 a schematic block diagram of a sixth embodiment of the device according to the invention; and

13 a schematic flow diagram of an embodiment of the method according to the invention.

Embodiments of the invention

1 shows a schematic block diagram of a conventional device for charging an electrical energy storage B (eg, a high-voltage battery for an electric vehicle) from an AC voltage source W. In this case, a first rectifier device G1 is electrically connected to the AC voltage source W. The AC voltage is converted into a DC voltage by means of the first rectifier device G1 and a DC link capacitor. An electric chopper Z chops the rectified AC voltage to transmit it via a transformer T with a defined winding ratio. After the transformer device T, a second rectifier device G2 rectifies the chopped voltage again. A subsequently connected low-pass filter with an inductance and a capacitor filters residual harmonics from the rectified voltage.

In order to comply with standardized requirements with regard to harmonic emissions in the public alternating voltage network, a correction device K is connected between the first rectifier device G1 and the electric chopper device Z, which essentially ensures that the current drawn from the AC voltage source W is in phase with the AC voltage from the AC voltage source ,

2 shows a block diagram of a first embodiment of the device according to the invention. It can be seen that now the correction device K of the conventional charging device is missing and a converter U (for example, a B6 inverter with three half-bridges H1, H2, H3, each with two series-connected semiconductor switches), which is provided for operation of an electric vehicle, between the second Rectifier device G2 and the electrical energy storage B is connected. In addition, a first inductance L1 is connected between the second rectifier device G2 and the converter device U.

A control device 10 By means of sensors (not shown), measured values of the voltage of the alternating voltage source W and the charging current of the electrical energy store B (for example, before the first inductance L1) are supplied.

By means of the control device 10 a second switch S2 of the first half-bridge H1 is actuated such that a current flows via a freewheeling diode (not shown) connected in parallel with the first switch S1. In this way, by means of the converter device U, an electrical countervoltage is generated after the first inductance L1 in relation to an electrical voltage in front of the first inductance L1. By means of this countervoltage, the charging current for the electrical energy store B is controlled such that it has a substantially sinusoidal profile and a current taken from the AC voltage source is substantially in phase with the AC voltage of the AC voltage source W. The transformer T acts as a low pass for high frequency signals from the inverter U, so that disturbing harmonics can not get into the AC mains.

Multiple diagrams within 2 show time courses of electrical quantities within the device 100 , where the local positions the device at which the respective size occurs, are marked with arrows.

2a shows a time course of the AC voltage of the AC voltage source W.

2 B shows a time course of the rectified AC voltage after the first rectifier device G1.

2c shows a chopped course of the AC voltage after the electric chopper Z.

2d shows a reduced voltage profile of the AC voltage after the second rectifier device G2.

2e shows a profile of said back voltage of the converter U after the first inductor L1.

2f shows a profile of the charging current of the electrical energy storage (battery charging current) B.

3 represents a principal electrical equivalent circuit diagram with electrical quantities in which the electrical isolation by means of the transformer T is not taken into account. It can be seen that the individual electrical voltages: U _AC (voltage of the AC voltage source W), U _R (voltage drop due to ohmic losses), U _L (voltage drop across the first inductance L1) and U _B6 (reverse voltage of the converter U) form a closed voltage mesh form and add up to zero.

In principle, it can thus be seen that in the case where U _B6 <U _AC , a current I flows from the AC voltage source W in the direction of the converter device U and thus into the electrical energy store B. The first inductance L1 thus serves as a kind of decoupling between the electrical voltage U _{AC of} the AC voltage source W and the countervoltage U _{B6 of} the converter U.

4 represents a phasor diagram of the equivalent circuit diagram of 3 It can be seen that by means of the countervoltage U _{B6 of} the converter U the current through the converter U and thus the charging current of the electrical energy store B can be controlled such that it is substantially in phase with the _AC input voltage U _AC . In this way, the inverter U is not only used to control a level of the charging current, but also takes over the function of the conventional correction device K.

From the 4 It can be seen that a phase angle φ between the charging current I and the voltage of the AC voltage source U _AC is substantially zero by changing a phase angle α of the countervoltage U _B6 . A maximum value for the charging current is marked with I _Max . U _zk denotes the electrical intermediate circuit voltage or the electrical voltage of the high-voltage battery (HV battery).

5 shows three time courses of electrical variables of the device according to the invention. It can be seen that a charging current I of the electrical energy store B is substantially in phase with the AC voltage U _{AC of} the AC voltage source W and the current I _AC taken during a charging process from the AC voltage source W.

6 shows a schematic block diagram of a second embodiment of the device according to the invention. It can be seen that now unlike the embodiment of 2 a second inductance L2 is connected between the second rectifier device G2 and a connection point of the switches S3 and S4 of a second half-bridge H2 of the converter device U. The second switches S2 and S4 of the first and the second half-bridge H1, H2 are preferably switched overlapping ("interleave switching operation"), so that a ripple of the charging current for the electrical energy storage B is advantageously minimized. In this way, an electrical switching capacity of the switches on two half-bridges H1, H2 of the inverter U is divided, so that the switches can be clocked at a higher frequency.

The current flow is via freewheeling diodes (not shown), which are connected in parallel to the switches S1 and S3.

An electric equivalent circuit and a phasor diagram are the same as those of the first embodiment (see FIG 3 and 4 ).

7 shows a block diagram of a third embodiment of the device according to the invention 100 , In this embodiment, an inductance of motor windings of an electric motor M operated by means of the converter device U is used to build up the countervoltage. For this reason, advantageously no external inductance is required. A current flow through the converter U is indicated in principle by arrows.

For example, only the switches S3 and S4 of the second half-bridge H2 can alternate, whereby the charging current for the electrical energy store B flows through two winding inductances. A used motor inductance therefore corresponds to twice the winding inductance. By this switching, a torque can be generated for a short time at the beginning of the charging process, depending on the position of the rotor of the electric motor M, which leads to a geometric orientation of the rotor. During the further charging process, no further torque is generated.

In an alternative mode of operation of the embodiment of the device according to the invention 100 from 7 is by means of the control device 10 an overlapping switching operation for the switches S4 and S6 is performed. In this way, advantageously, a third winding inductance can be used, wherein the switches for the electrical phases V and W are switched overlapping. As a result, a ripple of the charging current of the electrical energy store B is advantageously reduced. In this case, the entire charging current for the electrical energy store B flows through the electrical phase U.

8th shows a conventional three-phase device for charging the electrical energy storage B. In this case, an input AC voltage from a three-phase AC voltage source W1, W2, W3 rectified via a boost converter HS and raised to a higher voltage level. A DC link capacitor smoothes the DC link DC voltage. A step-down converter TS lowers a voltage level of the intermediate circuit voltage in accordance with the charging requirements of the electrical energy store B. A line filter N prevents the exceeding of harmonic content according to legal standards and regulations.

9 shows a fourth embodiment of the device according to the invention, in which case the device 100 is formed three-phase. It can be seen that the device differs from the basic structure of the device of FIG 2 corresponds, wherein for each phase W1, W2, W3, an output of the second rectifier device G2 is connected to a first inductance L11, L12, L13 to a connection point of a half-bridge H1, H2, H3 of the inverter U. In this way, no DC link capacitor or an additional implementation of a correction device K is also required. A major advantage of the device, in turn, is that the converter device U, which is already present in a system, can be shared for the charging function of the electrical energy store B. The converter U controls the charging current of the battery and also realizes the harmonics improvement functionality without additional components.

Due to the galvanic isolation by means of the transformer device T, it is possible to design a charging concept such that the charging of the battery is always possible independently of voltage levels of the battery voltage or the mains voltage. This makes it possible to realize a charging concept which can be used worldwide. In order to increase the efficiency of the concept, passive components of the second rectifier device G2 can be replaced by active switches.

A time course of electrical quantities within the device 100 corresponds to the courses of the 2a to 2f , The AC voltage source W provides three voltages (with the phases W1, W2, W3), each with 120 ° phase shift to each other. Each of the three first rectifier devices G11, G12, G13 rectifies one of the phase voltages. The electric chopper device Z1, Z2, Z3 then chops the respective intermediate circuit voltage in order to transmit it at high clock frequency via the transformer T1, T2, T3. A high clock frequency of the chopper Z1, Z2, Z3 makes it possible to form transformer devices T1, T2, T3 with a small size. After the transformer devices T1, T2, T3, the chopped intermediate circuit voltages are rectified again by means of second rectifier devices G21, G22 and G23. The converter device U forms at the first inductors L11, L12, L13 each have an electrical counter-voltage, wherein the charging current for the electrical energy storage B can be adjusted with a height of the respective counter-voltage.

An equivalent circuit and a phasor diagram are the same as those of the first embodiment.

10 shows time courses of electrical quantities within the device 100 from 9 , It can be seen that in the uppermost figure, the three charging currents i ₁ , i ₂ , i ₃ , result in a total current through the first inductors L 11, L 12 and L 13, which is substantially less harmonic and has substantially fewer ripples. It can be seen from the middle representation that the named currents i ₁ , i ₂ , i ₃ are substantially in phase with the currents i _N1 , i _N2 , i _N3 from the three phase voltages. In the bottom diagram, a basic curve of one of the mains voltages is shown, which in this case represents the voltage u _{N2 of} the second phase W2 of the three-phase AC voltage source.

11 shows a fifth embodiment of the inventive device for charging a battery from an AC voltage source. In this variant, the transformer device T has a symmetrical center point tap on the primary side, switches S7 and S8 being electrically connected to one end section of the primary winding of the transformer device T in each case. in the In contrast to the preceding embodiments, in this embodiment the electrical chopper device Z is thus realized by the two switches S7, S8 on the primary side of the transformer device T. This advantageously means a reduction of a number of switches of the chopper Z with resulting space or space gain and thus a cost-effective implementation of the device according to the invention. The operation is otherwise the same as previously described and will therefore not be explained again.

12 shows a sixth embodiment of the device according to the invention. In contrast to the fifth embodiment of 11 is now the second rectifier device G2 realized by means of two diodes D1, D2 on a secondary side of the transformer device T. The transformer T has a secondary point on the secondary side. As a result, this means for the second rectifier device G2 a reduction of a diode number from four to two. This advantageously means a reduction of wiring complexity, driver software, logic circuits, etc., which advantageously also means a reduction of failure rates, so that even with this variant, a more cost-effective implementation of the device according to the invention is possible. The operation is otherwise the same as previously described and will therefore not be explained again here.

13 shows a basic sequence of an embodiment of the method according to the invention.

In one step 101 the input AC voltage is rectified. In one step 201 there is a conversion of the rectified input AC voltage into a high-frequency AC voltage. In one step 301 the high-frequency AC voltage is transformed. In one step 401 a rectification of the transformed AC voltage is performed. Finally, in one step 501 a counter voltage to the rectified, transformed voltage is generated such that a voltage of the AC voltage source and a current that is taken from the AC voltage source for charging the electrical energy storage, are substantially in phase In summary, the present invention, an apparatus and a method are proposed, with which It is advantageously possible to use an existing converter or inverter in a charging operation for charging a battery. By means of a controlled actuation of switches of the converter device, an ohmic behavior between current and voltage of the AC voltage source is forced. In this way, a functionality of a harmonic improving device is shifted into the inverter, so that overall a more cost-effective implementation of the charging device is made possible. As a result, it is advantageously also possible for the converter to assume a functionality of the conventional correction device, so that predefined standards with respect to the public power supply network can be maintained in this way.

Although the present invention has been described in terms of preferred embodiments, it is not limited thereto. The person skilled in the art will thus be able to modify or combine the described features of the invention without departing from the essence of the invention.

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

• DE 19523576 A1 [0002]

Claims (12)

Contraption ( 100 ) for charging an electrical energy store (B) from an AC voltage source (W), comprising: - a first rectifier device (G1); - An electrical chopper device (Z) connected to the first rectifier device (G1); A transformer device (T) connected to an output of the chopper device (Z); A second rectifier device (G2) connected to a secondary side of the transformer device (T); and - a converter device (U) connected to the second rectifier device (G2), having a first half-bridge (H1) of two serially connected switches (S1, S2), a first inductor (L1) being connected between a connection point of the switches (S1, S2) the first half-bridge (H1) and the second rectifier device (G2) is connected, wherein by means of a control device ( 10 ) one of the switches (S1, S2) of the first half-bridge (H1) is switchable such that for charging the electrical energy store (B) of the AC voltage source (W) removed current and a voltage (U _AC ) of the AC voltage source (W) substantially are in phase. Apparatus according to claim 1, characterized in that by means of the control device ( 10 ) in dependence on a charging current for the electrical energy store (B) and of the voltage of the AC voltage source (W), a duty cycle of the switch (S2) of the first half-bridge (H1) is adjustable. Apparatus according to claim 1 or 2, characterized in that a second inductance (L2) between a second half-bridge (H2) of the converter device (U) of two series-connected switches (S3, S4) and the second rectifier device (G2) is connected. Apparatus according to claim 3, characterized in that second switches (S2, S4) of the two half-bridges (H1, H2) are switchable in an overlapping switching operation. Device according to claim 1, characterized in that the first inductance (L1) is formed as an inductance of windings of a three-phase electric motor (M), the windings being connected to connection points of switches (S1 ... S6) of three half-bridges (H1, H2 , H3) of the converter (U) are interconnected. Apparatus according to claim 5, characterized in that an additional inductance between the second rectifier means (G2) and the connection point of the two switches (S1, S2) of the first half-bridge (H1) is connected. Apparatus according to claim 6, characterized in that second switches (S4, S6) of the two half-bridges (H2, H3) are switchable in an overlapping switching operation. Apparatus according to claim 1, characterized in that the device is formed in three, wherein the device is connected in each case with a phase of a three-phase system, wherein in each case a first inductance (L11, L12, L13) between in each case a second rectifier means (G2) and a connection point two switches (S1, S2, S3, S4, S5, S6) of the half-bridges (H1, H2, H3) of the converter device (U) is connected, wherein by means of the control device ( 10 ) the switches (S1 ... S6) of the three half-bridges (H1, H2, H3) are switchable in such a way that a current taken to charge the electrical energy store (B) of the alternating voltage source (W) and a respective phase voltage of the alternating voltage sources (W1, W2, W3) are substantially in phase. Apparatus according to claim 1, characterized in that the electrical chopper device (Z) as a fourth half-bridge (H4) with two switches (S7, S8) on a primary side of the transformer device (T) is formed, wherein the transformer means (T) on the primary side has a center tap. Apparatus according to claim 9, characterized in that the second rectifier means (G2) each comprise a diode (D1, D2) at each end portion of the secondary side of the transformer means (T), the secondary side of the transformer means (T) having a center tap. A method of charging an electrical energy store (B) from an AC source (W), comprising the steps of: - rectifying an AC input voltage; - converting the rectified input AC voltage into a high frequency AC voltage; - transforming the high-frequency AC voltage; - rectifying the transformed AC voltage; and generating a counter voltage to the rectified, transformed voltage such that a voltage (U _AC ) of the AC voltage source (W) and a current taken from the AC voltage source (W) for charging the electrical energy store (B) are substantially in phase , Computer program product with program code means for carrying out the method according to Claim 11 when on an electronic control device ( 10 ) or stored on a computer-readable medium.

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