Power conversion device

Abstract

Disclosed is a power conversion device that can be commonly used in batteries having different output voltages. A power conversion device for converting an output voltage of a battery to an AC voltage or a DC voltage lower than the output voltage of the battery includes a multi-winding transformer (1), and a first DC / AC converter (11) and a second DC / AC converter (12), the DC side of which is connected to the battery. When the output voltage of the battery is higher than the withstand voltage of the semiconductor switching element, the DC inputs of the first DC / AC converter (11) and the second DC / AC converter (12) are connected in series with each other. When the output voltage of the battery is lower than the withstand voltage, the DC inputs of the first DC / AC converter (11) and the second DC / AC converter (12) are connected in parallel with each other, or one of the DC input of the first DC / AC converter (11) and the DC input of the second DC / AC converter (12) is connected to the battery.

Description

Technical Field

[0001] This invention relates to a power conversion device that converts DC power from an energy storage device into DC power or AC power with a voltage lower than the output voltage of the energy storage device via a transformer. Background Technology

[0002] Electric vehicles and other electric mobility devices have an electric motor drive system consisting of an electric motor, a battery or other energy storage device with a high voltage (e.g., several hundred volts or more), and a power conversion device that converts the output power of the energy storage device into the required power and drives the electric motor with the converted power.

[0003] The electric mobile unit includes a low-voltage energy storage device for its onboard electrical appliances and an AC voltage output unit for equipment operating on AC power frequency. Therefore, a power conversion device is used to step down the output voltage of the high-voltage energy storage device used to drive the electric motor.

[0004] As prior art concerning such power conversion devices, the technology described in Patent Document 1 is known.

[0005] In this prior art, a multi-winding transformer is used. A high-voltage (e.g., 350–500V) main battery is connected to the first winding of the multi-winding transformer via an inverter circuit. The AC voltage output from the inverter circuit is stepped down by the multi-winding transformer, and the stepped-down AC voltage is output from the second and third windings of the multi-winding transformer.

[0006] The AC voltage output from the second winding is converted into a mains frequency AC voltage by the rectifier and inverter circuits. This mains frequency AC voltage is output from the AC output terminal. The AC voltage output from the third winding is converted into a DC voltage by the rectifier circuit. This DC voltage is used to charge the auxiliary equipment battery.

[0007] According to this prior art, the installation space of the power conversion device that converts the DC voltage of the main battery into a low-voltage DC voltage and AC voltage can be reduced.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2008-109754 Summary of the Invention

[0011] The technical problem that the invention aims to solve

[0012] In recent years, there has been progress in increasing the voltage of main batteries to increase their capacity and shorten charging time. Therefore, currently, there is a situation where standard and high-voltage main batteries are used depending on the system model and application. To address this situation, according to the aforementioned prior art, various power conversion devices with different voltage ratings are needed in the inverter circuit connected to the main battery.

[0013] Therefore, the present invention provides a power conversion device that can be used in conjunction with main batteries having different output voltages.

[0014] Technical solutions to the problem

[0015] To address the aforementioned problems, the power conversion device of the present invention converts the battery's output voltage into an AC or DC voltage lower than the battery's output voltage. It includes: a multi-winding transformer having multiple windings, including a first primary winding, a second primary winding, and a secondary winding; a first DC / AC converter whose DC and AC sides are respectively connected to the battery and the first primary winding; a second DC / AC converter whose DC and AC sides are respectively connected to the battery and the second primary winding; and a power converter that converts the AC voltage output from the secondary winding into an AC or DC voltage lower than the battery's output voltage. When the battery's output voltage exceeds the withstand voltage of the multiple semiconductor switching elements in the first and second DC / AC converters, the DC inputs of the first and second DC / AC converters are connected in series, and the two ends of the series-connected DC inputs are connected to the battery. When the battery's output voltage is less than its withstand voltage, the DC inputs of the first DC / AC converter and the second DC / AC converter are connected in parallel, and the two ends of the parallel DC inputs are connected to the battery, or only one of the DC inputs of the first DC / AC converter and the second DC / AC converter is connected to the battery.

[0016] Invention Effects

[0017] The power conversion device of the present invention can be used in conjunction with main batteries having different output voltages.

[0018] Other technical issues, features, and effects not described above will become clear in the following description of the embodiments. Attached Figure Description

[0019] Figure 1 This is a circuit diagram showing the structure of the power conversion device in Embodiment 1.

[0020] Figure 2 This is a circuit diagram showing the first connection configuration of the main battery on the DC side of a DC / AC conversion circuit.

[0021] Figure 3 This is a circuit diagram showing the second connection configuration of the main battery on the DC side of the DC / AC conversion circuit.

[0022] Figure 4 This is a circuit diagram showing the third connection configuration of the main battery on the DC side of a DC / AC conversion circuit.

[0023] Figure 5 This is a circuit diagram showing the fourth connection configuration of the main battery on the DC side of the DC / AC conversion circuit.

[0024] Figure 6 This is a circuit diagram showing the structure of the power conversion device in Embodiment 2.

[0025] Figure 7 This is a flowchart illustrating the operation of the control unit in Embodiment 2.

[0026] Figure 8 This is a timing diagram showing the ON / OFF state of the drive signal generated by the control unit in Embodiment 2.

[0027] Figure 9 The waveform diagram below shows the time-dependent change in the output current of the DC / AC converter in Example 2.

[0028] Figure 10 This is a circuit diagram showing the structure of the power conversion device in Embodiment 3.

[0029] Figure 11 The waveform diagram below shows the time-dependent change in the output current of the DC / AC converter in Example 3. Detailed Implementation

[0030] Hereinafter, embodiments of the present invention will be described using the accompanying drawings in the following examples 1 to 3.

[0031] In each figure, the parts with the same reference number represent the same constituent element or constituent elements with similar functions.

[0032] Example 1

[0033] Figure 1 This is a circuit diagram illustrating the structure of the power conversion device according to Embodiment 1 of the present invention.

[0034] like Figure 1 As shown, the power conversion device of Embodiment 1 has multiple windings ( Figure 1 The device includes a multi-winding transformer 1 (with four windings) and multiple power converters (11, 12, 21, 22) connected to the multiple windings. This power conversion device is installed in an electric vehicle (not shown).

[0035] In the multi-winding transformer 1, four independent windings are wound on a magnetic core.

[0036] The AC sides of DC / AC converters 11 and 12 (inverters) are connected to the two primary windings N1, respectively. DC / AC converter 11 has DC voltage input terminals T1 and T2 on its DC side. DC / AC converter 12 has DC voltage input terminals T3 and T4 on its DC side. As described later, the main battery is connected to DC / AC converters 11 and 12 at the DC voltage input terminals T1 to T4. Furthermore, the main battery supplies power to the electric motor (main unit) that drives the electric vehicle.

[0037] In the DC / AC converter 11, the semiconductor switching element S 1A S 2A S 3A S 4A This constitutes a single-phase full-bridge circuit. This single-phase full-bridge circuit operates as a DC / AC conversion circuit (inverter circuit). The AC output of the DC / AC conversion circuit is connected to one of the two primary windings N1. The DC input of the DC / AC conversion circuit is connected to the DC voltage input terminals T1 and T2. Electrolytic capacitor C A It is connected to the DC input of the DC / AC conversion circuit. That is, the electrolytic capacitor C A Connect between DC voltage input terminals T1 and T2.

[0038] In Example 1, a MOSFET for power applications is used as the semiconductor switching element S. 1A S 2A S 3A S 4A The body diode of a MOSFET is used as a freewheeling diode.

[0039] In the DC / AC converter 12, the semiconductor switching element S 1B S 2B S 3B S 4B This constitutes a single-phase full-bridge circuit. This single-phase full-bridge circuit operates as a DC / AC conversion circuit (inverter circuit). The AC output of the DC / AC conversion circuit is connected to the other of the two primary windings N1. The DC input of the DC / AC conversion circuit is connected to the DC voltage input terminals T3 and T4. Electrolytic capacitor C B It is connected to the DC input of the DC / AC conversion circuit. That is, the electrolytic capacitor C B Connect between DC voltage input terminals T3 and T4.

[0040] In Example 1, a MOSFET for power applications is used as the semiconductor switching element S. 1B S2B S 3B S 4B The body diode of a MOSFET is used as a freewheeling diode.

[0041] DC / AC converter 11 uses a gate drive circuit (not shown) to drive the semiconductor switching element S 1A S 2A S 3A S 4A ON / OFF control is performed, thereby converting the DC voltage output from the main battery, which is input from the DC voltage input terminals T1 and T2, into AC voltage, and outputting the AC voltage to one of the two primary windings N1.

[0042] DC / AC converter 12 uses a gate drive circuit (not shown) to drive the semiconductor switching element S. 1B S 2B S 3B S 4B ON / OFF control is performed, thereby converting the DC voltage output from the main battery, which is input from the DC voltage input terminals T3 and T4, into AC voltage, and outputting this AC voltage to the other of the two primary windings N1.

[0043] The AC voltage output from the two primary windings N1 of DC / AC converters 11 and 12 is stepped down by multi-winding transformer 1. The stepped-down AC voltage is then output from the secondary windings N2 and N3 of multi-winding transformer 1.

[0044] AC / DC converter 21 (rectifier) ​​is connected to the secondary winding N2. AC / DC converter 21 has a synchronous rectification circuit composed of MOSFETs M1 and M2, and a DC reactor L... dc A smoothing circuit is formed with capacitor C1. The AC voltage output from the secondary winding N2 is rectified by the synchronous rectifier circuit and then smoothed by the smoothing circuit. Therefore, the AC / DC converter 21 outputs a DC voltage lower than the output voltage of the main battery. The DC voltage output by the AC / DC converter 21 is used to power the low-voltage battery Bat. L Charge.

[0045] Low-voltage battery Bat L It is a power supply used for vehicle electrical appliances (auxiliary machines) with a lower voltage than that of an electric motor.

[0046] AC / AC converter 22 is connected to the secondary winding N3. AC / AC converter 22 has a full-bridge rectifier circuit composed of diodes D1 to D4, a smoothing capacitor C2, and a single-phase full-bridge circuit (inverter circuit) composed of MOSFETs Q1 to Q4.

[0047] The AC voltage output from the secondary winding N3 is rectified by the full-bridge rectifier circuit. The full-wave rectified voltage output from the full-bridge rectifier circuit is smoothed by the smoothing capacitor C2, becoming a DC voltage, which is then input to the single-phase full-bridge circuit (inverter circuit). The single-phase full-bridge circuit (inverter circuit) controls the ON / OFF state of MOSFETs Q1 to Q4, thereby converting the input DC voltage into AC voltage.

[0048] The AC output of a single-phase full-bridge circuit (inverter circuit) is transmitted via an AC reactor L that suppresses higher harmonics. ac The capacitor filter circuit (C3-C5) and the common-mode choke coil CMC for noise removal are connected to the vehicle socket SC. Thus, the mains frequency voltage is obtained from the vehicle socket SC. Therefore, electrical appliances operating at mains frequency voltage can be used inside the vehicle.

[0049] Additionally, a control unit (not shown) generates semiconductor switching elements (S) that produce AC voltages of equal magnitude to the output voltages of DC / AC converters 11 and 12. 1A ~S 4A S 1B ~S 4B The drive signal (gate signal) of ).

[0050] Figure 2 This indicates DC / AC converters 11 and 12 ( Figure 1 A circuit diagram showing the first connection configuration of the main battery on the DC side of the circuit. Wherein, a semiconductor switching element (S...) is included. 1A ~S 4A S 1B ~S 4B The withstand voltage is V. DSS At that time, the main battery Bat H1 Output voltage V H1 Greater than V DSS .

[0051] For example, V H1 It's 800V, V DSS It is 650-700V.

[0052] Additionally, Example 1 ( Figure 1 In the figure, capacitor C A C B The electrostatic capacitances are equal. Therefore, the DC voltages input to DC / AC converters 11 and 12 become V. H1 / (Number of DC / AC conversion circuits) is V H1 / 2, they are equal. Therefore, V DSS Greater than V H1 / 2.

[0053] The high-potential side of the DC voltage input terminals T1 and T2 of the DC / AC converter 11 is connected to the main battery Bat. H1 The positive terminal A is electrically connected. Terminal T2 on the low-potential side is electrically connected to the high-potential terminal T3 of the DC / AC converter 12's DC voltage input terminals T3 and T4. Terminal T4 on the low-potential side is connected to the main battery Bat. H1 The negative terminal B is electrically connected.

[0054] Therefore, as Figure 2 As shown, in the first connection configuration, the DC inputs of DC / AC converters 11 and 12 are connected in series, and the two ends of this series connection are connected to the main battery Bat. H1 Connection. Thus, the power conversion device of Embodiment 1 can be applied to situations where the output voltage of the main battery is greater than the withstand voltage of the semiconductor switching element.

[0055] Figure 3 This indicates DC / AC converters 11 and 12 ( Figure 1 The circuit diagram of the second connection configuration of the main battery on the DC side.

[0056] With the first connection form ( Figure 2 Similarly, the main battery Bat H1 Output voltage V H1 Larger than semiconductor switching elements (S 1A ~S 4A S 1B ~S 4B The withstand voltage V DSS And V DSS Greater than V H1 / 2(V) H1 >V DSS >V H1 / 2).

[0057] The following refers to the connection with the first connection mode ( Figure 2 Explain the differences between them.

[0058] like Figure 3 As shown, the main battery Bat H1 It has an intermediate potential terminal n. It is connected to the first configuration ( Figure 2 Similarly, the DC voltage input terminal T2 of DC / AC converter 11 is electrically connected to the DC voltage input terminal T3 of DC / AC converter 12. Second connection configuration ( Figure 3 Under these conditions, T2 and T3 are also connected to the main battery Bat. H1 The intermediate potential terminal n is electrically connected. Therefore, the DC input voltages of DC / AC converters 11 and 12 are balanced.

[0059] Therefore, the power conversion device of Embodiment 1 can be applied to situations where the output voltage of the main battery is greater than the withstand voltage of the semiconductor switching element.

[0060] Figure 4 This indicates DC / AC converters 11 and 12 ( Figure 1 The circuit diagram of the third connection configuration of the main battery on the DC side.

[0061] Main battery Bat H2 Output voltage V H2 Smaller than the main battery (Bat) H1 ( Figure 3 Output voltage V H1 Semiconductor switching elements (S) 1A ~S 4A S 1B ~S 4B The withstand voltage V DSS Greater than V H2 That is, V H1 >V DSS >V H2 .

[0062] For example, V H1 and V H2 They are 800V and 400V respectively. DSS It is 650-700V.

[0063] The high-potential side of the DC voltage input terminals T1 and T2 of DC / AC converter 11 is electrically connected to the high-potential side of the DC voltage input terminals T3 and T4 of DC / AC converter 12. T1 and T3 are also connected to the main battery Bat. H2 The positive terminal A is electrically connected.

[0064] The low-potential side of the DC voltage input terminals T1 and T2 of DC / AC converter 11 is electrically connected to the low-potential side of the DC voltage input terminals T3 and T4 of DC / AC converter 12. T2 and T4 are also connected to the main battery Bat. H2 The negative terminal B is electrically connected.

[0065] Therefore, as Figure 4 As shown, in the third connection configuration, the DC inputs of DC / AC converters 11 and 12 are connected in parallel, and the two ends of this parallel connection are connected to the main battery Bat. H2 connect.

[0066] Therefore, the power conversion device of Embodiment 1 can be applied to situations where the output voltage of the main battery is less than the withstand voltage of the semiconductor switching element.

[0067] Figure 5 This indicates DC / AC converters 11 and 12 ( Figure 1 The circuit diagram of the fourth connection configuration of the main battery on the DC side.

[0068] Main battery Bat H2 Output voltage V H2 Smaller than the main battery (Bat) H1 ( Figure 3 Output voltage V H1 Semiconductor switching elements (S) 1A ~S 4A S 1B ~S 4B The withstand voltage V DSS Greater than V H2 .

[0069] With the third connection form ( Figure 4 Similarly, the main battery Bat H2 Output voltage V H2 Smaller than the main battery (Bat) H1 ( Figure 3 Output voltage V H1 Semiconductor switching element (S 1A ~S 4A S 1B ~S 4B The withstand voltage V DSS Greater than V H2 .

[0070] like Figure 5 As shown, in the fourth connection configuration, only one of the DC / AC converters 11 and 12 ( Figure 5 The middle part is the DC input terminal of the DC / AC converter 11. Figure 5 (T1, T2) and the main battery Bat H2 Electrical connection.

[0071] Therefore, the power conversion device of Embodiment 1 can be applied to situations where the output voltage of the main battery is less than the withstand voltage of the semiconductor switching element. Furthermore, depending on the power supplied by the power converter connected to the secondary winding of the multi-winding transformer 1, either the third or fourth connection configuration can be used.

[0072] As described above, according to Embodiment 1, the power conversion device can be shared with a main battery having different output voltages.

[0073] In addition, the primary winding of the multi-winding transformer 1 and the DC / AC converter connected to the primary winding can be two or more.

[0074] Example 2

[0075] As described below, the power conversion device of Embodiment 2 has a unit for suppressing circulating currents between multiple DC / AC converters connected to multiple primary windings of the multi-winding transformer 1.

[0076] Figure 6 This is a circuit diagram illustrating the structure of the power conversion device according to Embodiment 2 of the present invention.

[0077] The differences from Example 1 will be explained below.

[0078] In Example 2, the above-mentioned Figure 2 The first connection configuration shown is for DC / AC converters 11 and 12 ( Figure 1 The connection configuration of the main battery on the DC side.

[0079] The main circuit structure and embodiment 1 include a multi-winding transformer 1, DC / AC converters 11 and 12, AC / DC converter 21 and AC / AC converter 22. Figure 1 )same.

[0080] When there is a phase difference in the AC voltage output from the primary windings N1 of DC / AC converters 11 and 12, power is transferred between DC / AC converters 11 and 12 via the multi-winding transformer 1, generating an output current I. A I B The imbalance, i.e., circulating current (cross-current). Such a phase difference may affect the switching characteristics of semiconductor switching elements, wiring inductance (e.g., Ls). A 、Ls B The size of the value is generated when there is an error between DC / AC converters 11 and 12.

[0081] Therefore, in Embodiment 2, in order to reduce the phase difference of the AC voltage output from the primary winding N1 of each pair of DC / AC converters 11 and 12, the semiconductor switching element (S) is controlled. 1A ~S 4A S 1B ~S 4B The ON / OFF drive of the circuit suppresses the circulating current.

[0082] Figure 6 The control unit shown generates semiconductor switching elements (S) that produce AC voltages of the same magnitude at the outputs of DC / AC converters 11 and 12. 1A ~S 4A S 1B ~S 4B The drive signal (SIG) 1A ~SIG 4A SIG 1B ~SIG 4B Additionally, the control unit is based on capacitor C.A voltage V A and capacitor C B voltage V B The detected value generates a drive signal (SIG) to reduce the phase difference of the AC voltage output by DC / AC converters 11 and 12. 1A ~SIG 4A SIG 1B ~SIG 4B ).

[0083] I A I B When an imbalance occurs, V A V B An imbalance also occurs. Therefore, the control unit in Example 2 is based on V, which can be detected relatively easily. A V B Control semiconductor switching elements (S 1A ~S 4A S 1B ~S 4B The ON / OFF drive of the DC / AC converters 11 and 12 is used to reduce the phase difference of the AC voltage output.

[0084] Figure 7 This is a flowchart illustrating the operation of the control unit in Embodiment 2. See also: Figure 6 .

[0085] In addition, in Embodiment 2, the control unit has a computer system such as a microcomputer, and runs a prescribed program using the computer system to control the DC / AC converters 11 and 12.

[0086] In step S1, the control unit drives the inverter on the primary side of the DC / AC converters 11 and 12, i.e., the multi-winding transformer 1, using a so-called phase-shifting method (hereinafter referred to as "primary side INV").

[0087] S in DC / AC converter 11 1A With S 2A The group and S 3A With S 4A A phase shift α is set between the groups. In the DC / AC converter 12, S... 1B With S 2B The group and S 3B With S 4B The same phase shift α is also set between the groups. The same phase shift α is set for DC / AC converters 11 and 12, thereby outputting the same AC voltage.

[0088] In addition, make S 1A With S 2A Complementary ON / OFF. Making S 3AWith S 4A S 1B With S 2B S 3B With S 4B They are also complementary in being ON / OFF.

[0089] Next, in step S2, the control unit detects the DC input voltage of the single-phase full-bridge circuit to the primary side INV, i.e., the voltage of capacitor C. A voltage V A and capacitor C B voltage V B .

[0090] Next, in step S3, the control unit calculates V. A With voltage V B Voltage difference ΔV (=V A -V B ).

[0091] Next, in step S4, the control unit determines whether the value of ΔV obtained in step S3 is negative, zero, or positive. If the value is negative (ΔV<0), zero (ΔV=0), or positive (ΔV>0), the control unit proceeds to steps S5, S6, and S7 respectively.

[0092] In step S5, the control unit sets the hysteresis phase correction amount -δβ for INV12 (DC / AC converter 12).

[0093] ΔV<0 (V A <V B In the case of [missing information], power is transferred from INV11 (DC / AC converter 11) to INV12 (DC / AC converter 12). That is, a circulating current is generated between INV11 (DC / AC converter 11) and INV12 (DC / AC converter 12). At this time, the AC output voltage of INV12 (DC / AC converter 12) leads the AC output voltage of INV11 (DC / AC converter 11) in phase. Therefore, by setting a hysteresis phase correction amount -δβ for INV12 (DC / AC converter 12), the phase difference β between the AC output voltage of INV11 (DC / AC converter 11) and the AC output voltage of INV12 (DC / AC converter 11) is reduced, thereby suppressing the circulating current.

[0094] In step S6, the control unit sets the phase correction amount of INV12 (DC / AC converter 12) to zero.

[0095] When ΔV=0, no circulating current is generated, so the phase difference β between the AC output voltage of INV12 (DC / AC converter 12) and the AC output voltage of INV11 (DC / AC converter 11) does not need to be corrected. Therefore, the phase correction amount of INV12 (DC / AC converter 12) is set to zero.

[0096] In step S7, the control unit sets the lead phase correction amount +δβ for INV12 (DC / AC converter 12).

[0097] ΔV>0 (V A >V B In the case of [missing information], power is transferred from INV12 (DC / AC converter 12) to INV11 (DC / AC converter 11). That is, a circulating current is generated between INV11 (DC / AC converter 11) and INV12 (DC / AC converter 12). At this time, the AC output voltage of INV11 (DC / AC converter 11) leads the phase relative to the AC output voltage of INV12 (DC / AC converter 12). That is, the AC output voltage of INV12 (DC / AC converter 12) lags the phase relative to the AC output voltage of INV11 (DC / AC converter 11). Therefore, by setting a phase lead correction amount +δβ for INV12 (DC / AC converter 12), the phase difference β between the AC output voltages of INV11 (DC / AC converter 11) and INV12 (DC / AC converter 11) is reduced, thereby suppressing the circulating current.

[0098] In addition, in steps S5 to S7, the control unit calculates the phase correction amount based on ΔV, for example using a proportional / integral (PI) controller.

[0099] If the control unit executes any one of steps S5, S6, and S7, then step S8 is executed next.

[0100] In step S8, the control unit generates a drive signal (SIG) based on the phase difference β after correction according to the set phase correction amount. 1A ~SIG 4A SIG 1B ~SIG 4B The generated drive signal drives the semiconductor switching element (S) in INV11 (DC / AC converters 11, 12). 1A ~S 4A S 1B ~S 4B ).

[0101] Based on the corrected phase difference β, the control unit 8 reduces the phase difference β in the SIG. nA With SIG nBA phase difference is set between (n=1,2,3,4). That is, the control unit 8 controls the phase difference by using the semiconductor switching element S in INV11 (DC / AC converter 11). nA With the semiconductor switching element S in INV12 (DC / AC converter 12) nB The switching timing is deviated by n=1,2,3,4 to compensate for the phase deviation between the AC output voltage of INV11 (DC / AC converter 11) and the AC output voltage of INV12 (DC / AC converter 11).

[0102] The control unit repeatedly executes steps S1 to S8 during the operation of the power conversion device.

[0103] Figure 8 This is a timing diagram showing the ON / OFF state of the drive signal generated by the control unit in Embodiment 2.

[0104] like Figure 8 The output current I of the DC / AC converter 11 described in the document is... A and DC / AC converter 12 output current I B As shown, due to the phase difference β between the AC output voltage of DC / AC converter 11 and the AC output voltage of DC / AC converter 12, in I... A with I B A phase difference β is generated in I. Furthermore, with the generation of circulation, in I... A with I B An imbalance has arisen.

[0105] To reduce this phase difference β, the control unit generates, as follows: Figure 8 The drive signal shown (SIG) 1A ~SIG 4A SIG 1B ~SIG 4B That is, the control unit is in SIG. nA With SIG nB A phase difference β is set between (n=1,2,3,4). The control unit sets the corrected β successively, thus enabling precise suppression of circulating current.

[0106] in addition, Figure 8 The phase difference α shown corresponds to the phase shift control in each DC / AC converter. Figure 7 The phase shift α in step S1).

[0107] Figure 9 This represents the output current I of the DC / AC converters 11 and 12 in Embodiment 2. A I B The waveform diagram showing the time-varying changes of I is shown below. It also illustrates the I under the condition of circulation. A IB The waveform diagram (above).

[0108] like Figure 9 As shown, according to Example 2, I A I B The size is balanced, and I A I B Phase alignment.

[0109] As described above, according to Embodiment 2, the circulating current generated among the multiple DC / AC converters 11, 12 connected to the primary side of the multi-winding transformer 1 is suppressed. Therefore, the efficiency of the power conversion device of Embodiment 1 is improved.

[0110] Furthermore, the control unit in Embodiment 2 can also be applied to the second and third connection configurations of the main battery. Figure 3 , Figure 4 (The situation is as follows.)

[0111] Example 3

[0112] As described below, the power conversion device of Embodiment 3 has a unit for suppressing circulating currents between multiple DC / AC converters connected to multiple primary windings of the multi-winding transformer 1.

[0113] Figure 10 This is a circuit diagram illustrating the structure of the power conversion device according to Embodiment 3 of the present invention.

[0114] The following refers to Example 2 ( Figure 6 Explain the differences between them.

[0115] In Example 3, a constant-mode choke coil is used as the unit for suppressing circulating current. Therefore, the control unit only executes... Figure 7 The phase shift control in step S1 of steps S1 to S8 shown.

[0116] In Example 3, the constant-mode choke coil NMC has two windings wound on a ring-shaped magnetic core without an air gap. One winding is electrically connected between one end of the AC output of DC / AC converter 11 and one end of the primary winding N1 to which the AC output of DC / AC converter 11 is connected. The other winding is electrically connected between one end of the AC output of DC / AC converter 12 and one end of the primary winding N1 to which the AC output of DC / AC converter 12 is connected.

[0117] The output current I flowing in the wiring between the DC / AC converter 11 with the primary winding N1 and the winding inserted into one side of NMC. A The direction of the (basic wave component) and the output current I flowing in the wiring between the DC / AC converter 12, which is inserted into one of the windings of NMC, and the primary winding N1. BThe directions of the (fundamental wave components) are the same. Thus, the windings are wound onto the magnetic core in such a way that the magnetic flux generated by the current flowing in each winding cancels each other out when current flows in the same direction in each winding. Therefore, for I... A I B The basic wave components, NMC does not function as an inductor.

[0118] In contrast, I A I B The circulating current flows in opposite directions in the two windings of the NMC. Consequently, the magnetic flux generated by the current flowing in each winding reinforces each other, thus the NMC functions as an inductor. This suppresses the circulating current.

[0119] Figure 11 This represents the output current I of the DC / AC converters 11 and 12 in Embodiment 3. A I B The waveform diagram showing the time-varying changes of I is shown below. It also illustrates the I under the condition of circulation. A I B The waveform diagram (above).

[0120] like Figure 11 As shown, according to Example 3, I A I B The size is balanced, and I A I B Phase alignment.

[0121] As described above, according to Embodiment 3, the circulating current generated among the multiple DC / AC converters 11, 12 connected to the primary side of the multi-winding transformer 1 is suppressed. Therefore, the efficiency of the power conversion device of Embodiment 1 is improved.

[0122] In addition, the NMC in Example 3 can also be applied to the second and third connection configurations of the main battery. Figure 3 , Figure 4 (The situation is as follows.)

[0123] Furthermore, the present invention is not limited to the above embodiments, but includes various modifications. For example, the above embodiments are described in detail for ease of understanding of the present invention and are not limited to having all the structures described. In addition, for a part of the structure of each embodiment, other structures can be deleted, added, or replaced with other structures.

[0124] For example, the semiconductor switching elements in DC / AC converters 11 and 12 are not limited to MOSFETs, but can also be other semiconductor switching elements such as insulated gate bipolar transistors or bipolar junction transistors.

[0125] In addition, the power conversion devices of Examples 1 to 3 can be applied not only to electric vehicles, but also to electric mobile bodies such as electric ships and electric aircraft.

[0126] Explanation of reference numerals in the attached figures

[0127] 1… Multi-winding transformer, 11… DC / AC converter, 12… DC / AC converter, 21… AC / DC converter, 22… AC / AC converter.

Claims

1. A power conversion device for converting the output voltage of a battery into an AC voltage or DC voltage lower than the output voltage of the battery, characterized in that, include: A multi-winding transformer having multiple windings, wherein the multiple windings include a first primary winding, a second primary winding, and a secondary winding; A first DC / AC converter, wherein its DC side and AC side are respectively connected to the battery and the first primary winding; The second DC / AC converter has its DC side and AC side connected to the battery and the second primary winding, respectively. and A power converter that converts the AC voltage output from the secondary winding into an AC voltage or DC voltage that is lower than the output voltage of the battery. When the output voltage of the battery is higher than the withstand voltage of the plurality of semiconductor switching elements in the first DC / AC converter and the second DC / AC converter, the DC inputs of the first DC / AC converter and the second DC / AC converter are connected in series with each other, and the two ends of the series-connected DC inputs are connected to the battery. When the output voltage of the battery is lower than the withstand voltage, the DC inputs of the first DC / AC converter and the second DC / AC converter are connected in parallel with each other, and the two ends of the parallel-connected DC inputs are connected to the battery, or one of the DC inputs of the first DC / AC converter and the second DC / AC converter is connected to the battery.

2. The power conversion device as described in claim 1, characterized in that: When the output voltage of the battery is higher than the withstand voltage, the withstand voltage is higher than 1 / 2 of the output voltage.

3. The power conversion device as described in claim 1, characterized in that: When the output voltage of the battery is higher than the withstand voltage, the intermediate potential of the battery is connected to the series connection point of the DC input.

4. The power conversion device as described in claim 1, characterized in that: The power converter is an AC / DC converter capable of charging a low-voltage battery whose output voltage is lower than that of the battery.

5. The power conversion device as described in claim 1, characterized in that: The power converter is an AC / AC converter that outputs power frequency AC voltage.

6. The power conversion device as described in claim 1, characterized in that: It has a control unit that generates drive signals for the plurality of semiconductor switching elements capable of suppressing the circulating current between the first DC / AC converter and the second DC / AC converter.

7. The power conversion device as described in claim 6, characterized in that: The control unit sets the phase difference between the drive signal of the semiconductor switching element in the first DC / AC converter and the drive signal of the semiconductor switching element in the second DC / AC converter based on the voltage difference between the DC input voltage of the main circuit of the first DC / AC converter and the DC input voltage of the main circuit of the second DC / AC converter.

8. The power conversion device as described in claim 1, characterized in that: It has a constant-mode choke coil connected between the first DC / AC converter and the first primary winding and between the second DC / AC converter and the second primary winding.

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