JP7208188B2 - Vehicle-mounted power converter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a power conversion device and a power adjustment circuit, and more particularly to technology for reducing power loss.

Electric vehicles such as hybrid vehicles and electric vehicles are widely used. An electric vehicle is equipped with a battery for supplying electric power to a driving motor. In an electric vehicle, the battery is charged with electric power generated by regenerative braking, and if the electric vehicle has a plug-in function, the battery is charged with electric power supplied from a commercial power supply. Also, in a hybrid vehicle, a battery is charged with electric power generated by driving a generator by an engine. In order to charge the battery, the electric vehicle is equipped with a power conversion device. The power conversion device converts the input voltage into an appropriate voltage and applies it to the battery.

Patent Literature 1 below discloses a power conversion device in which two switching circuits are magnetically coupled by windings connected to each circuit, and power is transmitted between the two switching circuits. Patent Document 2 discloses a power conversion device that controls the output voltage by adjusting the frequencies of the first and second boost converters while improving the power factor by pulse width modulation of the first and second boost converters. It is shown.

Patent Document 3 discloses a power converter in which a first half bridge circuit (switching circuit) that operates as a power factor correction circuit and a second half bridge circuit (switching circuit) that operates as an AC/DC converter are coupled by a transformer. A circuit (power converter) is described. The first half bridge circuit adjusts the power factor of AC power output from the external AC power supply. Power is supplied from the first half bridge circuit to the second half bridge circuit via a transformer, and the second half bridge circuit supplies power to the main battery of the electric vehicle. The power converter further includes a third half-bridge circuit coupled to the second half-bridge circuit by a transformer. Power is supplied from the second half bridge circuit to the third half bridge circuit via a transformer, and the third half bridge circuit operating as an AC/DC converter supplies power to the auxiliary battery of the electric vehicle. Patent Document 4 and Non-Patent Document 1 describe a DC/DC converter in which three switching circuits are mutually coupled by a transformer.

JP 2011-193713 A JP 2010-183726 A JP 2018-14794 A JP 2015-119598 A

C.Zhao, “An Isolated Three-port Bidirectional DC-DC Converter With Decoupled Power Flow Management”, IEEE Transaction on Power Electronics, Volume:23, Issue:5, Sept. 2008

Generally, in an electric vehicle, the output voltage of the auxiliary battery is lower than the output voltage of the main battery. Therefore, in the power conversion device described in Patent Document 3, the number of winding turns of the transformer connected to the third half bridge is greater than the number of winding turns of the transformer connected to the second half bridge. be reduced. However, such a design has the problem that the current flowing through the windings connected to the third half-bridge and the current flowing through the third half-bridge are large, resulting in large power losses.

An object of the present invention is to suppress power loss in a power converter.

The present invention provides a transformer including a primary winding , a first secondary winding and a second secondary winding , a primary switching circuit connected to the primary winding, and a first secondary winding connected to the first secondary winding. a switching circuit, a second secondary switching circuit connected to the second secondary winding, and an intermediate capacitor included in the second secondary switching circuit, wherein switching between the primary switching circuit and the first secondary switching circuit is provided. By the operation, power is output from the primary switching circuit to the main battery connected to the first secondary switching circuit through the transformer, and the switching operations of the primary switching circuit and the second secondary switching circuit cause the primary switching circuit to operate. Power is supplied from the switching circuit to the intermediate capacitor through the transformer, and by switching operations of the first secondary switching circuit and the second secondary switching circuit, power is supplied from the main battery through the first secondary switching circuit and the transformer. power is supplied to the intermediate capacitor through the switching operation of the second secondary switching circuit, and power is output from the intermediate capacitor to the auxiliary battery via the midpoint of the second secondary winding by the switching operation of the second secondary switching circuit. the switching circuit comprises a first switching arm and a second switching arm connected in parallel, each including a first switching element and a second switching element connected in series; The second secondary winding is connected between a connection point of the first switching element and the second switching element in the first switching arm and a connection point of the first switching element and the second switching element in the second switching arm. and the intermediate capacitor is connected between parallel connection points of both ends of the first switching arm and the second switching arm, and the intermediate point of the second secondary winding, the first switching arm and the Power is output to the auxiliary battery from one of parallel connection points on both ends of the second switching arm .

2. The vehicle-mounted power conversion apparatus according to claim 1, preferably comprising a controller for controlling said first secondary switching circuit and said second secondary switching circuit , wherein said second secondary switching circuit is switched according to switching timing of said first secondary switching circuit. According to the phase difference between the phase of the voltage appearing on the first secondary winding and the phase of the voltage appearing on the second secondary winding according to the switching timing of the second secondary switching circuit, the first secondary switching circuit is switched. Power is transferred from the circuit to the second secondary switching circuit, and the controller determines an intermediate voltage target value for the voltage across the intermediate capacitor based on a measurement of the voltage being applied to the main battery, and The first secondary switching circuit and the second secondary switching circuit are controlled based on a phase difference determined based on the difference between the measured voltage across the intermediate capacitor and the target intermediate voltage .

Preferably, in the vehicle-mounted power converter according to claim 2, the controller controls the number of turns of the first secondary winding, the number of turns of the second secondary winding, and the number of turns applied to the main battery. The intermediate voltage target value is obtained based on the measured voltage at which the voltage is applied.

Preferably, the first secondary switching circuit is a third switching arm and a fourth switching arm connected in parallel, each including a first switching element and a second switching element connected in series. a fourth switching arm, between a connection point of the first switching element and the second switching element in the third switching arm and a connection point of the first switching element and the second switching element in the fourth switching arm; A first secondary winding is connected, and duty ratios of the first switching arm, the second switching arm, the third switching arm, and the fourth switching arm are equal.

The related art of the present invention also relates to a first switching arm, a second switching arm and a third switching arm connected in parallel, each of which includes a first switching element and a second switching element connected in series. a switching arm, a second switching arm and a third switching arm; a filter and an output capacitor connected between parallel connection points across the first switching arm, the second switching arm and the third switching arm, the filter being connected from a first terminal to the first switching arm; A first capacitor having one end connected to a path leading to a connection point of a first switching element and a second switching element in a switching arm, and a connection from a second terminal to the first switching element and the second switching element in the second switching arm. and a third capacitor having one end connected to a path from the third terminal to the connection point of the first switching element and the second switching element in the third switching arm. , the other ends of the first capacitor, the second capacitor and the third capacitor are commonly connected and grounded, and the first switching arm, the second switching arm and the third switching arm are: A three-phase mode in which a three-phase AC voltage is applied to the first terminal, the second terminal, and the third terminal, or a single phase between the first terminal, the second terminal, and the third terminal It operates in either single-phase mode in which an alternating voltage is applied, and in the three-phase mode, the time waveforms of the voltages at the first terminal, the second terminal, and the third terminal are applied to the first terminal, the A switching operation mode that approximates or matches the time waveforms of currents at the second terminal and the third terminal, and the single-phase mode is a switching operation mode in which the time waveforms of the voltages at the first terminal and the second terminal are matched to the time waveforms of the first terminal. The switching operation mode is characterized in that the time waveforms of the currents flowing through the 1 terminal and the 2nd terminal are approximated or matched.

ADVANTAGE OF THE INVENTION According to this invention, the power loss in a power converter can be suppressed.

It is a figure which shows a vehicle-mounted power conversion system. FIG. 4 is a diagram showing simulation results of voltages between terminals of a first secondary winding and a second secondary winding and currents flowing through switching elements S9 and S10; FIG. 3 is a diagram showing a specific configuration of a power adjustment circuit; FIG. It is a figure which shows the structure of the EMI filter in a three-phase mode. It is a figure which shows the structure of the EMI filter in single phase mode. It is a figure which shows the power conversion system which concerns on an application example.

Each embodiment of the present invention will be described with reference to each drawing. The same reference numerals are given to the same components shown in multiple drawings to simplify the description. Further, the terms "up, down, left, and right" used in the following description indicate the directions of up, down, left, and right in the drawings for convenience of explanation, and do not limit the attitudes when arranging each component.

FIG. 1 shows an in-vehicle power conversion system according to an embodiment of the present invention. The vehicle-mounted power conversion system includes a power adjustment circuit 14, a primary switching circuit 18, a transformer 22, a first secondary switching circuit 30, a second secondary switching circuit 36, and a controller 100, and is mounted on an electric vehicle. The in-vehicle power conversion system supplies power output from AC power source 10 to main battery 34 and auxiliary battery 40 . In addition, the vehicle-mounted power conversion system supplies power from the main battery 34 to the auxiliary battery 40 . The AC power source 10 may be a power supply system by a power supplier, or may be a household power generator.

When the electric vehicle is stopped and the AC power source 10 is used to charge the main battery 34, the AC terminals 12-1 and 12-2 of the power adjustment circuit 14 are connected to the AC power source 10. FIG. A primary switching circuit 18 is connected to the positive terminal 16P and the negative terminal 16N of the power adjustment circuit 14 .

Transformer 22 includes a primary winding 24, a first secondary winding 26 and a second secondary winding 28 that are magnetically coupled together. Both ends of the primary winding 24 are connected to the primary switching circuit 18 . Both ends of the first secondary winding 26 are connected to the first secondary switching circuit 30 and both ends of the second secondary winding 28 are connected to the second secondary switching circuit 36 .

A main battery 34 is connected to the first secondary switching circuit 30 . The main battery 34 supplies power for power running to a motor generator that drives the electric vehicle, and is charged with power generated by regenerative braking of the motor generator. An auxiliary battery 40 is connected to the second secondary switching circuit 36 . Auxiliary battery 40 supplies power to auxiliary devices such as an audio device, an interior light, and an air conditioner mounted on the electric vehicle.

An overview of the operation of the in-vehicle power conversion system will be described. Under the control of controller 100, power conditioning circuit 14, primary switching circuit 18, first secondary switching circuit 30 and second secondary switching circuit 36 operate as follows. Power adjustment circuit 14 adjusts AC terminal 12-1 so that the time waveform of the current flowing through AC terminals 12-1 and 12-2 approximates or matches the time waveform of the AC voltage output from AC power source 10. and 12-2. This improves the power factor of the power input from the AC power source 10 to the power adjustment circuit 14 .

The power adjustment circuit 14 converts the AC power output from the AC power source 10 into DC power and outputs the DC voltage to the primary switching circuit 18 while executing an operation to improve the power factor. The primary switching circuit 18 outputs an AC voltage to the primary winding 24 by switching to this DC voltage. The first secondary switching circuit 30 outputs AC voltage to the first secondary winding 26 by switching the voltage output by the main battery 34 . A second secondary switching circuit 36 comprises an intermediate capacitor 38 . The second secondary switching circuit 36 charges the intermediate capacitor 38 with power supplied from the primary switching circuit 18 or the first secondary switching circuit 30 via the transformer 22, as will be described later. The second secondary switching circuit 36 outputs an alternating voltage to the second secondary winding 28 by switching the voltage on the intermediate capacitor 38 .

Depending on the difference between the switching timing of the primary switching circuit 18 and the switching timing of the first secondary switching circuit 30, the power adjustment circuit 14, the primary switching circuit 18, the primary winding 24 and the first secondary winding 26 are switched from the AC power source 10. power is transmitted to the first secondary switching circuit 30 via the . The first secondary switching circuit 30 supplies power to the main battery 34 with power transmitted through the first secondary winding 26 . The first secondary switching circuit 30 may supply power to the main battery 34 and output power to a load circuit (not shown) connected to the main battery 34 .

Depending on the difference between the switching timing of the primary switching circuit 18 and the switching timing of the second secondary switching circuit 36, the power adjustment circuit 14, the primary switching circuit 18, the primary winding 24 and the second secondary winding 28 are switched from the AC power source 10. power is transmitted to the second secondary switching circuit 36 via the . The second secondary switching circuit 36 supplies power to the auxiliary battery 40 with power transmitted through the second secondary winding 28 . The second secondary switching circuit 36 may output power to the auxiliary battery 40 and may also output power to an auxiliary device (not shown) connected to the auxiliary battery 40 .

When the electric vehicle is running, the power regulation circuit 14 is disconnected from the AC power source 10, and the power regulation circuit 14 stops switching operation. When the electric vehicle is running, power is supplied from the main battery 34 to the auxiliary battery 40 by the following operation. Depending on the difference between the switching timing of the first secondary switching circuit 30 and the switching timing of the second secondary switching circuit 36 , from the first secondary switching circuit 30 via the first secondary winding 26 and the second secondary winding 28 . Power is transferred to the second secondary switching circuit 36 . The second secondary switching circuit 36 supplies power to the auxiliary battery 40 with power transmitted through the second secondary winding 28 . The second secondary switching circuit 36 may output power to the auxiliary battery 40 and to the auxiliary equipment connected to the auxiliary battery 40 .

Next, detailed configurations and operations of the primary switching circuit 18, the first secondary switching circuit 30, and the second secondary switching circuit 36 will be described. The primary switching circuit 18 comprises switching arm u, switching arm v and buffer capacitor 20 . Switching arm u comprises series-connected switching elements S1 and S2, and switching arm v comprises series-connected switching elements S3 and S4. The switching arms u and v are connected in parallel. A buffer capacitor 20 is also connected in parallel to the switching arms u and v. The upper parallel connection point of the switching arms u, v and the buffer capacitor 20 is connected to the positive terminal 16P of the power conditioning circuit 14, and the lower parallel connection point is connected to the negative terminal 16N of the power conditioning circuit 14. . A primary winding 24 is connected between a connection point of switching elements S1 and S2 and a connection point of switching elements S3 and S4.

The first secondary switching circuit 30 has a switching arm w, a switching arm x and a main machine capacitor 32 . Switching arm w comprises series-connected switching elements S5 and S6 and switching arm x comprises series-connected switching elements S7 and S8. The switching arms w and x are connected in parallel. A main machine capacitor 32 is further connected in parallel to the switching arms w and x. The upper parallel connection points of the switching arms w, x and the main machine capacitor 32 are connected to the positive terminal of the main machine battery 34 , and the lower parallel connection points are connected to the negative terminal of the main machine battery 34 . A first secondary winding 26 is connected between the connection point of the switching elements S5 and S6 and the connection point of the switching elements S7 and S8.

The second secondary switching circuit 36 has a switching arm y, a switching arm z, an intermediate capacitor 38 and an auxiliary capacitor 42 . Switching arm y comprises series-connected switching elements S9 and S10 and switching arm z comprises series-connected switching elements S11 and S12. The switching arms y and z are connected in parallel. An intermediate capacitor 38 is also connected in parallel to the switching arms y and z. A second secondary winding 28 is connected between the connection point of the switching elements S9 and S10 and the connection point of the switching elements S11 and S12. An auxiliary capacitor 42 is connected between the midpoint of the second secondary winding 28 and the lower parallel connection point of the switching arms y, z and the intermediate capacitor 38 . The midpoint of the second secondary winding 28 is connected to the positive terminal of the auxiliary battery 40, and the parallel connection point of the switching arms y, z and the lower side of the intermediate capacitor 38 is connected to the negative terminal of the auxiliary battery 40. It is connected. The midpoint of the second secondary winding 28 refers to the midpoint of the conductor forming the second secondary winding 28 . The midpoint may be a center tap provided at the midpoint of the conductors forming the second secondary winding 28 .

Diodes are connected to the switching elements S1 to S12 with the anode terminals facing the lower ends of the switching elements S1 to S12. IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) may be used for the switching elements S1 to S12.

The controller 100 outputs control signals g1-g12 to the switching elements S1-S12, respectively. Each of the switching elements S1 to S12 is turned on when the control signal is high and turned off when the control signal is low.

When the electric vehicle is stopped and the AC power source 10 is used to charge the main battery 34, the power adjustment circuit 14, the primary switching circuit 18, the first secondary switching circuit 30, and the second secondary switching circuit 36 perform switching operations. do. The power adjustment circuit 14 converts the AC power output by the AC power source 10 into DC power and outputs the DC voltage to the primary switching circuit 18 .

The control signals g1 and g2 that control the switching elements S1 and S2 provided in the switching arm u repeat high and low alternately. That is, the control signal g1 switches from low to high, the control signal g2 switches from high to low, the control signal g1 switches from high to low, and the control signal g2 switches from low to high. As a result, the switching element S1 is switched from off to on, and the switching element S2 is switched from on to off. Then, the switching element S1 is switched from ON to OFF, and the switching element S2 is switched from OFF to ON.

Similar to the switching elements S1 and S2, the control signals g3 and g4 alternately turn on and off the switching elements S3 and S4 of the switching arm v. Control signals g3 and g4 are 180° out of phase with control signals g1 and g2, respectively. That is, the switching phase of the switching arm v (switching elements S3 and S4) lags the switching phase of the switching arm u (switching elements S1 and S2) by 180°. As a result, an AC voltage having a crest value corresponding to the DC voltage output from the power adjustment circuit 14 appears across the primary winding 24 .

The operation of the first secondary switching circuit 30 will be described. Switching elements S5 and S6 provided in switching arm w are alternately turned on and off according to control signals g5 and g6. Switching elements S7 and S8 provided in switching arm x are alternately turned on and off according to control signals g7 and g8. The switching phase difference of the switching arms w and x is 180°. As a result, across the first secondary winding 26, an AC voltage having a crest value corresponding to the voltage across the terminals of the intermediate capacitor 38, that is, the output voltage of the main battery 34 appears.

The operation of the second secondary switching circuit 36 will be described. Switching elements S9 and S10 provided in switching arm y are alternately turned on and off according to control signals g9 and g10. Switching elements S11 and S12 provided in switching arm z are alternately turned on and off according to control signals g11 and g12. The switching phase difference of the switching arms y and z is 180°.

The duty ratio of the switching arm y is the ratio of the time during which the switching element S10 is turned on to the switching period, where one period in which the switching elements S9 and S10 are repeatedly turned on and off is defined as a switching period. In an automotive power conversion system, the switching arms u, v, w, x, y and z switch with the same duty ratio D.

Due to the operation of the second secondary switching circuit 36 , a voltage that is (1−D) times the voltage across the terminals of the intermediate capacitor 38 appears across the auxiliary battery 40 and the auxiliary capacitor 42 . That is, V _dc3 =(1−D)·V _dc,buf where V dc, _buf is the voltage across the terminals of the intermediate capacitor 38 and V _dc3 is the voltage across the auxiliary battery 40 and the auxiliary capacitor 42. Voltage is applied to auxiliary battery 40 and auxiliary capacitor 42 .

The main battery supply power _Pdc2 supplied from the AC power source 10 to the main battery 34 via the power conditioning circuit 14, the primary switching circuit 18 and the first secondary switching circuit 30 is , is adjusted by adjusting the phase difference φ ₂₁ , which is the phase delay of the switching of the switching arms w and x. The controller 100 may obtain the phase difference φ ₂₁ based on the value obtained by proportionally integrating the main machine power error e1 obtained by subtracting the measured value P _dc2 of the main machine battery supply power from the main machine power target value P _dc2 ^* . The main machine power target value _Pdc2 ^* is a target value for the main machine battery supply power _Pdc2 . The controller 100 generates control signals g1 to _g8 based on the phase difference φ21, and controls the on/off of the switching elements S1 to S8.

Note that the controller 100 makes the main battery supply power _Pdc2 negative and the phase difference φ ₂₁ negative, so that the main battery 34 or the load circuit is supplied from the first secondary switching circuit 30, the primary switching circuit 18, and the power adjustment circuit 14. You may transmit electric power to the alternating current power source 10 side via.

The voltage V _dc,buf on the intermediate capacitor 38 in the second secondary switching circuit 36 adjusts the phase difference φ ₃₂ , which is the lag of the phase of switching of switching arms y and z relative to the phase of switching of switching arms w and x. is adjusted by The controller 100 may obtain the phase difference φ ₃₂ based on the value obtained by proportionally integrating the intermediate voltage error e2 obtained by subtracting the intermediate voltage measured value _Vdc, buf from the intermediate voltage target value _Vdc,buf ^* . The intermediate voltage target value _Vdc,buf ^* may be determined, for example, as _Vdc,buf ^* = _Vdc2 /n. Here, _Vdc2 is the voltage across the terminals of the main machine capacitor 32, that is, the output voltage of the main machine battery . n is the ratio of the number of turns of the first secondary winding 26 to the number of turns of the second secondary winding 28 (winding ratio n). The controller 100 generates control signals g5- _g12 based on the phase difference φ32, and controls the on/off of the switching elements S5-S12.

The voltage V _dc,buf on the intermediate capacitor 38 may be adjusted by adjusting the phase difference φ ₃₁ , which is the lag of the phase of switching of switching arms y and z with respect to the phase of switching of switching arms u and v. In this case, the controller 100 may obtain the phase difference _φ31 based on the value obtained by proportionally integrating the intermediate voltage error e2. Controller 100 generates control signals g1-g4 and g9-g12 based on phase difference _φ31 , and controls switching elements S1-S4 and S9-12 on and off.

The duty ratio D of each switching arm is a value obtained by proportionally integrating the auxiliary battery voltage error e3 obtained by subtracting the auxiliary battery voltage target value _Vdc3 ^* from the output voltage measurement value _Vdc3 of the auxiliary battery 40. is determined based on the measured value V _dc3 of the output voltage of and the measured value V _dc,buf of the intermediate voltage. That is, the controller 100 obtains the duty ratio D of each switching arm based on the value obtained by adding 1−V _dc3 /V _dc,buf to the proportionally integrated value of the auxiliary battery voltage error e3. The controller 100 generates control signals g1 to g12 based on the duty ratio D in addition to the phase differences described above, and controls the switching elements S1 to S12 on and off.

When the electric vehicle is running, the power regulation circuit 14 is disconnected from the AC power source 10, and the power regulation circuit 14 stops switching operation. Similarly to charging the main battery 34 using the AC power source 10, the first secondary switching circuit 30 and the second secondary switching circuit 36 perform switching operations, power is supplied from the main battery 34 to the auxiliary battery 40, and Auxiliary battery 40 is charged.

FIG. 2(a) shows the on/off timings of the switching elements S6 to S12. The upper part shows the switching timing of the first secondary switching circuit 30 . That is, the upper part shows that the set of switching elements S6 and S7 and the set of switching elements S5 and S8 are alternately turned on and off. The switching timing of the second secondary switching circuit 36 is shown in the lower part. That is, the upper part shows that the set of switching elements S10 and S11 and the set of switching elements S9 and S12 are alternately turned on and off.

FIG. 2B shows simulation results of the voltage _Vwx across the terminals of the first secondary winding 26 and the voltage _Vyz across the terminals of the second secondary winding 28 . The horizontal axis indicates time and the vertical axis indicates voltage value. The inter-terminal voltage _Vwx is the voltage at the connection point of the switching elements S5 and S6 with reference to the potential at the connection point of the switching elements S7 and S8. The inter-terminal voltage _Vwx is the voltage at the connection point of the switching elements S9 and S10 with reference to the potential at the connection point of the switching elements S11 and S12.

FIG. 2(c) shows a current _{i_SW9} flowing through the switching element S9 and the diode connected in parallel with the switching element S9, and a current _{i_SW10} flowing through the switching element S10 and the diode connected in parallel with the switching element S10. there is The horizontal axis indicates time and the vertical axis indicates current value.

In an in-vehicle power conversion system, when power is transmitted from the first secondary switching circuit 30 as the first switching circuit to the second secondary switching circuit 36 as the second switching circuit, the in-vehicle power conversion system includes the following: A power conversion device such as is configured.

That is, a transformer 22 having a first secondary winding 26 as a primary winding and a second secondary winding 28 as a secondary winding, and a first secondary switching circuit 30 connected to the first secondary winding 26. , a power converter comprising a second secondary switching circuit 36 connected to the second secondary winding 28 and an intermediate capacitor 38 included in the second secondary switching circuit 36 .

The second secondary switching circuit 36 comprises switching arms y and z as a first switching arm and a second switching arm. The first secondary switching circuit 30 has switching arms w and z as a third switching arm and a fourth switching arm.

In this power converter, power is supplied from the first secondary switching circuit 30 to the intermediate capacitor 38 in the second secondary switching circuit 36 through the transformer 22 by the switching operations of the first secondary switching circuit 30 and the second secondary switching circuit 36. be done. Further, the switching operation of the second secondary switching circuit 36 outputs power from the intermediate capacitor 38 to the auxiliary battery 40 via the midpoint of the second secondary winding 28 .

The phase of the voltage appearing in the first secondary winding 26 according to the switching timing of the first secondary switching circuit 30 and the phase of the voltage appearing in the second secondary winding 28 according to the switching timing of the second secondary switching circuit 36 Power is transferred from the first secondary switching circuit 30 to the second secondary switching circuit 36 according to the difference.

According to such a configuration, the intermediate capacitor 38 is charged with a voltage obtained by dividing the terminal voltage _Vdc2 of the main machine capacitor 32 by the winding ratio n. Furthermore, the voltage obtained by dividing the intermediate voltage _{Vdc, buf} , which is the voltage across the terminals of the intermediate capacitor 38, by the step-up ratio 1/(1−D) defined by the duty ratio D is applied to the auxiliary battery 40 and the auxiliary capacitor 42. be done. Therefore, the voltage _Vdc2 between the terminals of the main equipment capacitor 32 is stepped down to the intermediate voltage Vdc, _buf , and the intermediate voltage _Vdc,buf is stepped down to the voltage _Vdc3 across the auxiliary battery 40 and the auxiliary equipment capacitor 42. . Such a stepwise step-down reduces the current flowing through the second secondary winding 28 and the switching elements S9 to S12, thereby suppressing the power consumed by the second secondary winding 28 and the second secondary switching circuit 36. .

Further, instead of setting n in advance as described above, the duty ratio is set to D=0.4 or more and 0.6 or less, preferably D=0.5, and auxiliary battery 40 and auxiliary capacitor 42 By setting the winding ratio n so that the voltage V _dc3 across , becomes a desired value, the switching losses generated in the switching elements S1 to S12 are suppressed.

In the vehicle power conversion system, when electric power is transmitted from the primary switching circuit 18 as the first switching circuit to the second secondary switching circuit 36 as the second switching circuit, the power conversion system for vehicle has the following: A power conversion device such as is configured.

That is, a transformer 22 having a primary winding 24 as a primary winding and a second secondary winding 28 as a secondary winding, a primary switching circuit 18 connected to the primary winding 24, and a second secondary winding A power converter is configured comprising a second secondary switching circuit 36 connected to 28 and an intermediate capacitor 38 included in the second secondary switching circuit 36 .

The second secondary switching circuit 36 comprises switching arms y and z as a first switching arm and a second switching arm. The primary switching circuit 18 comprises switching arms u and v as a third switching arm and a fourth switching arm.

In this power converter, power is supplied from the primary switching circuit 18 through the transformer 22 to the intermediate capacitor 38 of the second secondary switching circuit 36 by the switching operations of the primary switching circuit 18 and the second secondary switching circuit 36 . Further, the switching operation of the second secondary switching circuit 36 outputs power from the intermediate capacitor 38 to the auxiliary battery 40 via the midpoint of the second secondary winding 28 .

Depending on the difference between the phase of the voltage appearing in the primary winding 24 according to the switching timing of the primary switching circuit 18 and the phase of the voltage appearing in the second secondary winding 28 according to the switching timing of the second secondary switching circuit 36 , power is transferred from the primary switching circuit 18 to the second secondary switching circuit 36 .

In this configuration, in the primary switching circuit 18 and the second secondary switching circuit 36, the voltage _Vdc1 across the terminals of the buffer capacitor 20 is stepped down to the intermediate voltage Vdc, _buf , and the intermediate voltage _Vdc,buf is reduced to the auxiliary battery 40 and the auxiliary battery 40. The voltage across the machine capacitor 42 is stepped down to the voltage _Vdc3 . Such a stepwise step-down reduces the current flowing through the second secondary winding 28 and the switching elements S9 to S12, thereby suppressing the power consumed by the second secondary winding 28 and the second secondary switching circuit 36. .

FIG. 3 shows a specific configuration of the power adjustment circuit 14. As shown in FIG. The power conditioning circuit 14 includes AC terminals a, b, c, an EMI filter 52, inductors Lα, Lβ, Lγ, switching arms α, β, γ, an output capacitor 56, a positive terminal 16P and a negative terminal 16N. The switching arm α comprises switching elements Q1 and Q2 connected in series. The switching arm β comprises switching elements Q3 and Q4 connected in series. The switching arm γ comprises switching elements Q5 and Q6 connected in series.

The switching arms α, β, γ and the output capacitor 56 are connected in parallel. A parallel connection point of the switching arms α, β, γ and the output capacitor 56 has a positive terminal 16P connected to its upper end and a negative terminal 16N connected to its lower end.

EMI (Electro Magnetic Interference) filters 52 are inserted in a path from the AC terminal a to one end of the inductor Lα, a path from the AC terminal b to one end of the inductor Lβ, and a path from the AC terminal c to one end of the inductor Lγ. ing. The other end of inductor Lα is connected to a connection point between switching elements Q1 and Q2. The other end of inductor Lβ is connected to the connection point between switching elements Q3 and Q4, and the other end of inductor Lγ is connected to the connection point between switching elements Q5 and Q6.

Power conditioning circuit 14 operates in either a three-phase mode or a single-phase mode of operation. In the three-phase mode, the U-phase output terminal, V-phase output terminal and W-phase output terminal of the three-phase AC power source 50 are connected to AC terminals a, b and c, respectively.

Switching arms α, β and γ are controlled by controller 100 . The switching arms α, β, and γ approximate or match the time waveforms of the currents flowing through the AC terminals a, b, and c to the time waveforms of the three-phase AC voltage output by the three-phase AC power source 50. It switches the current through AC terminals a, b and c. This improves the power factor of the power input from the three-phase AC power source 50 to the power adjustment circuit 14 .

Power adjustment circuit 14 converts the three-phase AC power output from three-phase AC power source 50 into DC power, charges output capacitor 56, and outputs the DC voltage to the positive terminal while performing an operation to improve the power factor. 16P and the negative terminal 16N.

In the single-phase mode, the positive phase terminal L of the AC power source 10 (single-phase AC power source) is connected to the AC terminals a and b, and the negative phase terminal N is connected to the AC terminal c. The switching arms .alpha., .beta. and .gamma. It switches the current flowing through the terminals a and b and the AC terminal c. This improves the power factor of the power input from the AC power source 10 to the power adjustment circuit 14 .

Power adjustment circuit 14 converts the AC power output from AC power source 10 into DC power while performing an operation to improve the power factor, charges output capacitor 56, and applies the DC voltage to positive terminal 16P and negative terminal 16P. Output from 16N.

FIG. 4 shows the configuration of the EMI filter 52 in 3-phase mode. Two common-mode conductors (a three-phase line consisting of a U-phase line, a V-phase line, and a W-phase line) from AC terminals a, b, and c to inductors Lα, Lβ, and Lγ have two common mode Choke coils 60 and 62 are inserted. Three Y-connected capacitors C1 to C3 are connected to the three-phase line between the three-phase AC power source 50 and the common mode choke coil 60 shown on the left side of FIG. One end of each of the Y-connected capacitors C1, C2 and C3 is connected to the U, V and W phase lines. The other ends of Y-connected capacitors C1, C2 and C3 are commonly connected. The capacitance of the three Y-connected capacitors C1-C3 may be the same.

Three Y-connected capacitors CU, CV and CW are connected between the phases of the three-phase line between the common mode choke coil 60 shown on the left and the common mode choke coil 62 shown on the right. One end of each of the Y-connected capacitors CU, CV and CW is connected to the U-phase line, the V-phase line and the W-phase line. The other ends of Y-connected capacitors CU, CV and CW are connected in common and grounded. Three Y-connected capacitors C4 to C6 are connected to the three-phase line between the common mode choke coil 62 shown on the right side of FIG. 4 and the inductors Lα, Lβ and Lγ. One end of each of Y-connected capacitors C4, C5 and C6 is connected to the U, V and W phase lines. The other ends of Y-connected capacitors C4, C5 and C6 are commonly connected. The capacitance of the three Y-connected capacitors C4-C6 may be the same. The EMI filter 52 suppresses common mode noise generated in the 3-phase line and differential mode noise generated between the phases of the 3-phase line.

FIG. 5 shows the configuration of the EMI filter 52 in single-phase mode. Two conductors from AC terminals a and b to inductors Lα and Lβ serve as one transmission line for AC power source 10, and one conductor from inductor Lγ to AC terminal c serves as an AC power source. 10 is the other transmission line.

By appropriately setting the capacities of the Y-connected capacitors CU, CV, and CW, common mode noise and differential noise appearing in each conductor can be suppressed. At least one of Y-connected capacitors CU, CV and CW may be a variable capacitor.

Thus, the power regulation circuit 14 comprises switching arms α, β and γ as the first switching arm, the second switching arm and the third switching arm connected in parallel. Each switching arm each includes a first switching element and a second switching element connected in series. Switching elements Q1, Q3 and Q5 correspond to the first switching element, and switching elements Q2, Q4 and Q6 correspond to the second switching element.

The power adjustment circuit 14 has inductors Lα, Lβ and Lγ at the connection points of the first switching elements (Q1, Q3, Q5) and the second switching elements (Q2, Q4, Q6) in the switching arms α, β and γ, respectively. and an output capacitor 56 connected between the parallel connection points at both ends of each switching arm.

The EMI filter 52 includes a first capacitor (C1, CU, C4) whose one end is connected to a path from the AC terminal a (first terminal) to the connection point of the switching elements Q1 and Q2 in the switching arm α, and the AC terminal b A second capacitor (C2, CV, C5) whose one end is connected to a path from (second terminal) to a connection point of switching elements Q3 and Q4 in switching arm β, and AC terminal c (third terminal) to switching arm and a third capacitor (C3, CW, C6) one end of which is connected to a path leading to a connection point of switching elements Q5 and Q6 at γ. The other ends of the first, second and third capacitors are commonly connected. Furthermore, the other ends of capacitors CU, CV and CW are grounded.

The switching arms .alpha., .beta. and .gamma. Operates in either single-phase mode where voltage is applied.

FIG. 6(a) shows a power conversion system according to an application. The power conversion system includes batteries 70-1 through 70-N, switching circuits 72-1 through 72-N, removable windings 74-1 through 74-N and core 66. FIG. Each positive terminal and each negative terminal of batteries 70-1 to 70-N are connected to switching circuits 72-1 to 72-N, respectively. A load circuit may be connected to any one of the batteries 70-1 to 70-N. Both ends of the detachable windings 74-1 to 74-N are connected to switching circuits 72-1 to 72-N, respectively. Each detachable winding 74-1 to 74-N is detachable with respect to core 66, and magnetically couples to other detachable windings when fixed to core 66. FIG.

The switching circuits 72-1 to 72-N may have the same configuration as either the first secondary switching circuit 30 or the second secondary switching circuit 36 shown in FIG. The switching circuits other than the switching circuit 72-3 shown in FIG. 6(a) have the same configuration as the first secondary switching circuit 30, as shown in FIG. 6(b). The switching circuit 72-3 has the same configuration as the second secondary switching circuit 36, as shown in FIG. 6(c).

As for the switching circuit having the same configuration as the first secondary switching circuit 30 , a battery is connected to a location corresponding to the location where the main battery 34 was connected in the first secondary switching circuit 30 . As for the switching circuit having the same configuration as that of the second secondary switching circuit 36 , a battery is connected to a location corresponding to the location where the auxiliary battery 40 was connected in the second secondary switching circuit 36 .

In the power conversion system, according to the difference between the switching phase of one switching circuit and the switching phase of the other switching circuit, each switching circuit is connected between the switching circuit and the other switching circuit. Electric power is transferred through the detachable winding. That is, power is transferred between the switching circuits 72-1 to 72-N according to the mutual switching phase difference of the switching circuits 72-1 to 72-N.

In such a configuration, the removable winding is removable from core 66 . Therefore, the number of switching circuits used can be easily increased or decreased. Further, by adopting the same circuit configuration as the second secondary switching circuit 36, power loss in the windings and switching circuit is suppressed.

10 AC power source, 12-1, 12-2, a, b, c AC terminals, 14 Power adjustment circuit, 16P Positive terminal, 16N Negative terminal, 18 Primary switching circuit, 20 Buffer capacitor, 22 Transformer, 24 Primary winding , 26 first secondary winding, 28 second secondary winding, 30 first secondary switching circuit, 32 main capacitor, 34 main battery, 36 second secondary switching circuit, 38 intermediate capacitor, 40 auxiliary battery, 42 auxiliary capacitor , 50 three-phase AC power source, 52 EMI filter, 56 output capacitor, 60, 62 common mode choke coil, 70-1 to 70-N battery, 72-1 to 72-N switching circuit, 74-1 to 74-N Detachable winding, 100 controller, S1-S12, Q1-Q6 switching element, u, v, w, x, y, z, α, β, γ switching arm.

Claims (4)

a transformer comprising a primary winding , a first secondary winding and a second secondary winding;
a primary switching circuit connected to the primary winding;
a first secondary switching circuit connected to the first secondary winding;
a second secondary switching circuit connected to the second secondary winding;
an intermediate capacitor included in the second secondary switching circuit;
By switching operations of the primary switching circuit and the first secondary switching circuit, power is output from the primary switching circuit through the transformer to a main battery connected to the first secondary switching circuit,
Power is supplied from the primary switching circuit to the intermediate capacitor through the transformer by switching operations of the primary switching circuit and the second secondary switching circuit,
Power is supplied from the main battery to the intermediate capacitor through the first secondary switching circuit and the transformer by switching operations of the first secondary switching circuit and the second secondary switching circuit,
A switching operation of the second secondary switching circuit outputs electric power from the intermediate capacitor to the auxiliary battery via the midpoint of the second secondary winding ,
The second secondary switching circuit,
a first switching arm and a second switching arm connected in parallel, each including a first switching element and a second switching element connected in series;
The second secondary winding is connected between a connection point of the first switching element and the second switching element in the first switching arm and a connection point of the first switching element and the second switching element in the second switching arm. has been
The intermediate capacitor is connected between parallel connection points at both ends of the first switching arm and the second switching arm,
Power is output to the auxiliary battery from between a midpoint of the second secondary winding and one of parallel connection points at both ends of the first switching arm and the second switching arm. Vehicle-mounted power converter. The vehicle-mounted power converter according to claim 1, further comprising a controller that controls the first secondary switching circuit and the second secondary switching circuit ,
The phase of the voltage appearing in the first secondary winding according to the switching timing of the first secondary switching circuit and the phase of the voltage appearing in the second secondary winding according to the switching timing of the second secondary switching circuit power is transmitted from the first secondary switching circuit to the second secondary switching circuit according to the phase difference , which is the difference ;
The controller is
Obtaining an intermediate voltage target value for the voltage across the intermediate capacitor based on the measured value of the voltage applied to the main battery,
controlling the first secondary switching circuit and the second secondary switching circuit based on the phase difference obtained based on the difference between the voltage measured across the intermediate capacitor and the intermediate voltage target value; A vehicle-mounted power conversion device characterized by: In the vehicle-mounted power converter according to claim 2,
The controller is
The intermediate voltage target value is obtained based on the number of turns of the first secondary winding, the number of turns of the second secondary winding, and a measured value of the voltage applied to the main battery. A vehicle-mounted power conversion device. In the vehicle-mounted power converter according to any one of claims 1 to 3,
The first secondary switching circuit,
a third switching arm and a fourth switching arm connected in parallel, each including a first switching element and a second switching element connected in series;
The first secondary winding is connected between a connection point of the first switching element and the second switching element in the third switching arm and a connection point of the first switching element and the second switching element in the fourth switching arm. has been
A vehicle-mounted power converter, wherein duty ratios of the first switching arm, the second switching arm, the third switching arm, and the fourth switching arm are equal.

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