Power converter and control method for power converter

Abstract

To provide a power conversion device that can charge multiple power storage devices according to the required power without using a switcher, and a control method of the power conversion device.SOLUTION: A power conversion device (127) includes: multiple converter units (116) that charge multiple power storage devices, input AC power and output DC power; and a bidirectional DC / DC converter (160) connected between two DC outputs of the multiple DC outputs of the multiple converter units. The bidirectional DC / DC converter transmits at least a portion of the output power of the converter unit in one DC output from the one DC output to the other DC output of the two DC outputs in accordance with the required power of the multiple power storage devices.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power converter having multiple outputs, and to a method for controlling such a power converter. [Background technology]

[0002] With the increasing adoption of renewable energy sources in power grids and the development of electric vehicle charging infrastructure, medium- and high-voltage isolated AC / DC converters are becoming commonly used as power conversion devices that interconnect high-voltage AC power sources and low-voltage DC buses.

[0003] When an isolated AC / DC converter outputs DC power to multiple loads (for example, an electric vehicle), it is composed of multiple converter cells, each having an isolated AC / DC converter circuit. A prior art technique relating to such an isolated AC / DC converter is described in Patent Document 1.

[0004] In the technology described in Patent Document 1, the AC inputs of multiple converter cells, each having an isolated AC / DC converter circuit, are connected in series with each other. The AC inputs connected in series are directly connected to a high-voltage AC power system without the need for a transformer.

[0005] Each converter cell comprises an AC / DC conversion circuit having an AC input, a smoothing capacitor connected to the DC side of the AC / DC conversion circuit, a DC / AC conversion circuit whose AC side is connected to the DC side of the AC / DC conversion circuit, a high-frequency transformer whose primary winding is connected to the AC side of the DC / AC conversion circuit, and an AC / DC conversion circuit whose AC side is connected to the secondary winding of the high-frequency transformer and which has a DC output.

[0006] The DC outputs of multiple converter cells are connected to multiple input ports of a switch. In the switch, switches are connected in a matrix between the multiple input ports and multiple output ports. Therefore, by operating the switches, the DC output of each converter cell can be connected to any output port. Also, depending on the power required by the load, any number of input ports can be connected to the output port to which the load is connected. Each converter cell supplies DC power to the battery of an electric vehicle, which is the load connected to its output port, and charges the battery. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2019 / 234988 [Overview of the project] [Problems that the invention aims to solve]

[0008] The conventional technology described above has the problem that it requires installation space for a switch where the switches are connected in a matrix, and that power loss increases due to the operating power of the switch.

[0009] Therefore, the present invention provides a power conversion device that can charge multiple energy storage devices according to the required power without using a switch, and a control method for this power conversion device. [Means for solving the problem]

[0010] To solve the above problems, the power conversion device according to the present invention charges multiple energy storage devices and comprises multiple converter units that input AC power and output DC power, and a bidirectional DC / DC converter connected between two of the multiple DC outputs of the multiple converter units. Multiple DC outputs are connected to multiple energy storage devices.The bidirectional DC / DC converter transmits at least a part of the output power of the converter unit in one DC output from one of the two DC outputs to the other DC output according to the required power of a plurality of power storage devices. The system has N converter units (N≧3), and N-1 bidirectional DC / DC converters, with a portion of the output power being transmitted by multiple bidirectional DC / DC converters among the N-1 bidirectional DC / DC converters.

[0011] In order to solve the above problems, a method for controlling a power conversion device according to the present invention is a method for controlling a power conversion device that charges a plurality of power storage devices. The power conversion device includes a plurality of converter units that input AC power and output DC power, and a bidirectional DC / DC converter connected between two of the plurality of DC outputs of the plurality of converter units. It has N converter units (N≧3), N-1 bidirectional DC / DC converters, and multiple energy storage devices are connected to multiple DC outputs. Calculate the average value of the required power of the plurality of power storage devices, control the output power of the plurality of power storage devices based on this average value, and control the output power of the bidirectional DC / DC converter based on the required power and the average value. In response to the power requirements of multiple energy storage devices, at least a portion of the output power of the converter unit at one of the two DC outputs is transmitted from one DC output to the other DC output by multiple bidirectional DC / DC converters among the N-1 bidirectional DC / DC converters.

Effect of the Invention

[0012] According to the present invention, by providing a bidirectional DC / DC converter, a plurality of power storage devices can be charged according to the required power.

[0013] Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0014] [Figure 1] It is a functional block diagram showing the configuration of a power conversion device for charging an electric vehicle, which is an embodiment. [Figure 2] It is a schematic functional block diagram showing the power flow in the power conversion device of this embodiment. [Figure 3] It is a waveform diagram showing an example of the operating state during charging of the power conversion device 127 according to the embodiment. [Figure 4] It is a circuit diagram showing an example of the AC / DC conversion circuit 109 (FIG. 1). [Figure 5]This is a circuit diagram showing another example of the AC / DC conversion circuit 109 (Figure 1). [Figure 6] This is a circuit diagram showing an example of a DC / DC conversion circuit 112 (Figure 1). [Figure 7] This is a circuit diagram showing another example of the DC / DC conversion circuit 112 (Figure 1). [Figure 8] This is a flowchart showing the charging control operation of the control unit 128 (Figure 1). [Figure 9] This is a schematic functional block diagram showing the power flow in the first operating mode of the power converter 127. [Figure 10] This is a schematic functional block diagram showing the power flow in the second operating mode of the power converter 127. [Figure 11] This is a schematic functional block diagram showing the power flow in the third operating mode of the power converter 127. [Figure 12] This is a schematic functional block diagram showing the power flow in the fourth operating mode of the power converter 127. [Figure 13] This is a schematic functional block diagram showing the power flow in the fifth operating mode of the power converter 127. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the drawings. In each figure, elements with the same reference number represent the same or similar functional elements.

[0016] Figure 1 is a functional block diagram showing the configuration of a power conversion device for charging electric vehicles, which is one embodiment of the present invention. In the following description, "electric vehicle" will be abbreviated as "EV".

[0017] The power conversion device 127 includes a power conversion unit 10 that receives three-phase AC power from a three-phase four-wire AC power supply 100 via a power switch 200 and a three-phase reactor 102 connected in series with each other, and a bidirectional DC / DC converter 160 connected to the output side of the power conversion unit 10.

[0018] The power conversion unit 10 has multiple (N) converter units 116, where "N" is an integer greater than or equal to 2. Each converter unit 116 has three converter cells 108 that receive single-phase AC power from one phase of the AC power supply 100 (i.e., 3 units). Each converter cell 108 consists of an AC / DC conversion circuit 109 that converts single-phase AC power to DC power, and a DC / DC conversion circuit 112 that converts the DC power output by the AC / DC conversion circuit 109 to DC power of a different voltage. The DC output terminal of the AC / DC conversion circuit 109 and the DC input terminal of the DC / DC conversion circuit 112 are connected by DC buses 110a and 110b.

[0019] In multiple (N) converter units 116, the AC input of one phase of the three-phase (three) converter cells 108 in each converter unit 116 is connected in series with each other. That is, the AC inputs 103 and 104 of each of the multiple (N) AC / DC conversion circuits 109 are connected in series with each other. One end (103) and the other end 106 of the series connection of the AC inputs are connected to one phase (e.g., U phase) and the neutral point N of the AC power supply 100, respectively. This allows the input of the converter cell 108 to be directly connected to a high-voltage (e.g., 6.6kV or 11kV) AC power supply 100 without going through a transformer.

[0020] The DC outputs of the three converter cells 108 in each converter unit 116 are connected in parallel. That is, the DC outputs 113 and 114 of the three DC / DC conversion circuits 112 are connected in parallel. This constitutes the DC output of each converter unit 116.

[0021] Each DC output of the multiple (N) converter units 116 is connected via DC buses 115a and 115b to one of the multiple (N pairs: one pair consists of two terminals (positive and negative)) of DC output terminals 150a and 150b. Each of the multiple (N pairs) of DC output terminals 150a and 150b is electrically connected via connection cables 121a and 121b to one of the multiple (N) of EV charging ports 122. Each of the multiple (N) of EV charging ports 122 (charging stations) is connected to an EV 124 via a charging cable 125.

[0022] In this embodiment, if we consider the multiple (N) converter units 116 as the first to N converter units, a bidirectional DC / DC converter 160 is connected between the DC output of the N-1 converter unit and the DC output of the N converter unit. This allows for the transmission of DC power between different DC outputs, as will be described later.

[0023] The control unit 128 generates control command signals 130 for each converter cell 108 and each bidirectional DC / DC converter 160 for controlling the DC output power of each converter cell 108 and the transmission power of each bidirectional DC / DC converter 160, based on voltage and current information 129 from the power converter 127, a voltage or current reference value 131, and EV-side information 133 from multiple (N) EV charging ports 122, i.e., the EV charging port group 132.

[0024] In this embodiment, the voltage and current information 129 is the DC bus voltage and current 117 in the DC buses 110a and 110b that connect the AC / DC conversion circuit 109 and the DC / DC conversion circuit 112 in each converter cell 108, and the DC bus voltage and current 118 in the DC buses 115a and 115b to which the DC output of each converter unit 116 is connected. The voltage and current information 129 are detected by a voltage sensor and a current sensor, respectively.

[0025] In this embodiment, the EV-side information 133 includes SOC information 123 regarding the charge state (SOC) of the EV's energy storage device (e.g., battery), user-configured information such as the charging speed (slow, medium, fast, ultra-fast), and EV connection information regarding the connection or disconnection of the EV to the EV charging port 122. The SOC information 123 is transmitted to the control unit 128 via the communication lines provided in the charging cable 125 and the EV charging port 122. The user-configured information is set by operating switches or buttons on the EV charging port 122. The EV connection information is detected by the EV charging port 122. The user-configured information and EV connection information are transmitted to the control unit 128 by the EV charging port 122.

[0026] Figure 2 is a schematic functional block diagram showing the power flow in the power conversion device of this embodiment. In Figure 2, the number of outputs of the power conversion unit 10 is "3". That is, the aforementioned "N" is "3".

[0027] In Figure 2, the power requirements for EV124-1, EV124-2, and EV124-3 are denoted as P1, P2, and P3, respectively. Each of the DC outputs 115-1, 115-2, and 115-3 of the power conversion unit 10 outputs the same DC output power P0.

[0028] DC outputs 115-1, 115-2, and 115-3 are connected to EV charging ports 122-1, 122-2, and 122-3, respectively. The DC power output by the power conversion unit 10 is used to charge EVs 124-1, 124-2, and 124-3 via each charging port.

[0029] The total DC output power (3P0) from the power conversion unit 10 supplies the total power requirements (P1+P2+P3) for the three EVs. Therefore, in this embodiment, P0 is set to the average value of the power requirements ((P1+P2+P3) / 3).

[0030] If any of P1, P2, or P3 is greater than P0, at least a portion of the output power from the power conversion unit 10 is transmitted between the DC outputs by either the bidirectional DC / DC converter 160-1 or 160-2 to compensate for the difference in P0 and meet the required power.

[0031] For example, if P1 > P0 and P1 > P2 > P3, the bidirectional DC / DC converter 160-1 outputs DC power P to the DC output 115-1 to satisfy the required power P1. 12 (=P1-P0) is transmitted. Also, to satisfy P2 and P3, DC power P is transmitted to the DC output 115-2 by the bidirectional DC / DC converter 160-2. 23 (=P2-P0+P 11 :P3=P0-P 23 ) transmits.

[0032] As mentioned above, P0,P 12 ,P 23 These are set based on the requested power P1, P2, and P3.

[0033] Depending on the required power P1, P2, and P3, power can be transmitted between DC outputs 115-1 and 115-3 via bidirectional DC / DC converters 160-1 and 160-2 in sequence. Similarly, if the number of DC outputs N is 3 or more, power can be transmitted between DC outputs 115-m and 115-n (where m and n are natural numbers: m,n ≤ N, m ≠ n) via multiple bidirectional DC / DC converters from among the N-1 bidirectional DC / DC converters in sequence.

[0034] Furthermore, depending on P1, P2, and P3, power can be transmitted from DC outputs 115-1 and 115-3 to DC output 115-2 via bidirectional DC / DC converters 160-1 and 160-2, respectively. Similarly, if the number of DC outputs N is 3 or greater, power can be transmitted from DC outputs 115-(n-1) and 115-(n+1) to DC output 115-n (where n is a natural number: 2 ≤ n ≤ N-1) via bidirectional DC / DC converters 160-(n-1) and 160-n, respectively.

[0035] The differences in power requirements for EVs, as described above, correspond to differences in charging speed. Therefore, a bidirectional DC / DC converter connected between the DC outputs of the power converter 127 allows for the simultaneous charging of multiple EVs with different charging speeds.

[0036] Furthermore, if the configurable charging speed consists of multiple stages, including a normal charging speed and a charging speed faster than the normal charging speed, it is preferable that the rated power capacity of the bidirectional DC / DC converter is 50% or more of the amount of energy during normal charging of the EV's energy storage device, i.e., the rated power capacity of the converter unit 116, and smaller than the rated power capacity of the converter unit 116.

[0037] Figure 3 is a waveform diagram showing an example of the operating state of the power converter 127 according to this embodiment shown in Figure 2 during charging.

[0038] In Figure 3, from top to bottom, the values ​​are: voltage at the EV charging ports (122-1, 122-2, 122-3), EV charging current detected at each charging port, phase shift angle of the DC / DC converters (160-1, 160-2), and output current of the DC / DC converters (160-1, 160-2).

[0039] In this embodiment, the DC / DC converters (112 (Figure 1), 160-1, 160-2) have their output power or output current controlled by phase shift control.

[0040] The voltages at EV charging ports 122-1, 122-2, and 122-3 represent the voltages of the energy storage devices in EVs 124-1, 124-2, and 124-3, respectively, and indicate the charging status of each energy storage device.

[0041] The EV charging current increases in the order of EV charging ports 122-1, 122-2, and 122-3. In other words, the EV charging current increases in the order of EV124-1, 124-2, and 124-3, corresponding to the order of the highest power requirements P1, P2, and P3 (P1>P2>P3) for EV124-1, 124-2, and 124-3.

[0042] The phase shift angle in each DC / DC converter (112 (FIG. 1)) in the power conversion device 127 is set according to the required power P0, where the required power P0 is the average value of the required powers (P1, P2, P3) (P0 (FIG. 2) = (P1 + P2 + P3) / 3). The phase shift angle in the bidirectional DC / DC converter 160-1 is set according to the DC power P 12 (=P1 - P0) transmitted from the DC output 115-2 to the DC output 115-1 so as to satisfy the required power P1. The phase shift angle in the bidirectional DC / DC converter 160-2 is set according to the DC power P 23 (=P2 - P0 + P 11 :P3 = P0 - P 23 ) transmitted from the DC output 115-3 to the DC output 115-2 so as to satisfy P2 and P3.

[0043] As described above, P0, P 12 , P 23 are set based on the required powers P1, P2, and P3. Therefore, each phase shift angle can be set based on the required powers P1, P2, and P3.

[0044] In the bidirectional DC / DC converters 160-1 and 160-2, currents flow according to the respective transmission powers (P 12 , P 23 ), that is, according to the phase shift angles. As shown in FIG. 3, the phase shift angle of the bidirectional DC / DC converter 160-1 is larger than that of the bidirectional DC / DC converter 160-2, and accordingly, a larger current flows through the bidirectional DC / DC converter 160-1 than through the bidirectional DC / DC converter 160-2.

[0045] FIG. 4 is a circuit diagram showing an example of the AC / DC conversion circuit 109 (FIG. 1).

[0046] As shown in Figure 4, the AC / DC conversion circuit 109 is composed of a single-phase full-bridge circuit using a semiconductor device 210 in which a semiconductor switching element (IGBT in Figure 4) and a diode are connected in antiparallel. The series connection points of the two semiconductor devices 210 in each half-bridge circuit are designated as AC inputs 103 and 104. A capacitor 201 is connected in parallel to the two half-bridge circuits which are connected in parallel to each other. The parallel connection points of the two half-bridges and the capacitor 201 are connected to DC buses 110a and 110b as DC outputs.

[0047] The AC power input to AC inputs 103 and 104 is rectified by the diode and converted into DC power. The DC power is used to charge capacitor 201 and is also output to DC buses 110a and 110b.

[0048] The AC / DC conversion circuit 109 uses semiconductor switching elements to convert the DC power input to the DC buses 110a and 110b into AC power, which is then output from the AC inputs 103 and 104. In other words, the AC / DC conversion circuit 109 operates as a bidirectional power conversion circuit.

[0049] Figure 5 is a circuit diagram showing another example of the AC / DC conversion circuit 109 (Figure 1).

[0050] As shown in Figure 5, the AC / DC conversion circuit 109 consists of a parallel connection of a half-bridge circuit using a semiconductor device 210 in which a semiconductor switching element (IGBT in Figure 5) and a diode are connected in antiparallel, and a series connection circuit of capacitors 202 and 203. The series connection points of the two semiconductor devices 210 in the half-bridge circuit and the series connection points of capacitors 202 and 203 are designated as AC inputs 103 and 104, respectively. The parallel connection point between the half-bridge circuit and the series connection circuit of capacitors 202 and 203 is connected to DC buses 110a and 110b as DC outputs.

[0051] The AC power input to AC inputs 103 and 104 is rectified by the diodes and converted into DC power. The DC power is used to alternately charge capacitors 202 and 203 according to the polarity of the AC input voltage.

[0052] The AC / DC conversion circuit 109 shown in Figure 5 uses semiconductor switching elements to convert DC power input to DC buses 110a and 110b into AC power, which is then output from AC inputs 103 and 104. In other words, the AC / DC conversion circuit 109 operates as a bidirectional power conversion circuit.

[0053] Figure 6 is a circuit diagram showing an example of the DC / DC conversion circuit 112 (Figure 1).

[0054] As shown in Figure 6, the DC / DC conversion circuit 112 is isolated and includes a DC / AC conversion circuit 300 and an AC / DC conversion circuit 400 connected to the DC / AC conversion circuit 300 via a high-frequency transformer 310.

[0055] The DC / AC conversion circuit 300 includes a single-phase full-bridge circuit in which a semiconductor device 301 is used, in which a semiconductor switching element (IGBT in Figure 6) and a diode are connected in antiparallel.

[0056] A capacitor 311 is connected in parallel to two half-bridge circuits that are connected in parallel to each other. The parallel connection point between the two half-bridges and the capacitor 311 is connected to DC buses 110a and 110b as a DC input. The series connection point of the two semiconductor devices 301 in each half-bridge circuit is connected to the primary winding 305 of the high-frequency transformer 310 via a reactor 303 as an AC output.

[0057] The AC / DC conversion circuit 400 includes a single-phase full-bridge circuit in which a semiconductor device 312 is used, in which a semiconductor switching element (IGBT in Figure 6) and a diode are connected in antiparallel.

[0058] The series connection point of the two semiconductor devices 312 in each half-bridge circuit is connected to the secondary winding 308 of the high-frequency transformer 310 as an AC input. A capacitor 313 is connected in parallel to the two half-bridge circuits which are connected in parallel to each other. The parallel connection point between the two half-bridges and the capacitor 313 is connected to the DC buses 115a and 115b as a DC output.

[0059] The DC / AC conversion circuit 300 uses semiconductor switching elements to convert DC power input from DC buses 110a and 110b via capacitor 311 into AC power, which is then output to the primary winding 305 of the high-frequency transformer 310. The high-frequency transformer 310 then takes the AC power received by the primary winding 305, steps down or steps up the AC voltage, and outputs it to the secondary winding 308.

[0060] The AC / DC conversion circuit 400 rectifies the AC power input from the secondary winding 308 using a diode and converts it into DC power. The DC power is used to charge the capacitor 313 and is also output to the DC buses 115a and 115b.

[0061] The AC / DC conversion circuit 400 converts DC power input from DC buses 115a and 115b into AC power using semiconductor switching elements. The DC / AC conversion circuit 300 converts AC power input from the AC / DC conversion circuit 400 via a high-frequency transformer 310 into DC power using diodes. In other words, the DC / DC conversion circuit 112 operates as a bidirectional power conversion circuit.

[0062] The DC / DC conversion circuit 112 shown in Figure 6 employs a so-called DAB (Dual Bridge Converter) type bidirectional DC / DC conversion circuit.

[0063] Furthermore, the DC / DC conversion circuit 112 shown in Figure 6 employs a so-called SST (Solid State Transformer), which transforms the voltage using high-frequency switching of semiconductor switching elements and a high-frequency transformer. This makes it possible to miniaturize the power conversion unit 10, which has multiple converter units 116.

[0064] Figure 7 is a circuit diagram showing another example of the DC / DC conversion circuit 112 (Figure 1).

[0065] As shown in Figure 7, the DC / DC conversion circuit 112 is isolated and includes a DC / AC conversion circuit 300 and an AC / DC conversion circuit 400 connected to the DC / AC conversion circuit 300 via a high-frequency transformer 310.

[0066] The DC / AC conversion circuit 300 consists of a parallel connection circuit of a semiconductor device 301 in which a semiconductor switching element (IGBT in Figure 7) and a diode are connected in antiparallel, and a series connection circuit of capacitors 314 and 315.

[0067] The parallel connection point between the half-bridge circuit and the series connection circuit of capacitors 314 and 315 is connected to DC buses 110a and 110b as a DC input. The series connection point of the two semiconductor devices 301 in the half-bridge circuit and the series connection point of capacitors 314 and 315 are connected to the primary winding 305 of the high-frequency transformer 310 via a reactor 303 as an AC output.

[0068] The AC / DC conversion circuit 400 consists of a single half-bridge circuit using a semiconductor device 312 in which a semiconductor switching element (IGBT in Figure 7) and a diode are connected in antiparallel, and a parallel connection circuit of a series connection circuit of capacitors 316 and 317. Capacitor 318 is connected at the parallel connection point between the half-bridge circuit and the series connection circuit of capacitors 316 and 317.

[0069] The series connection point of the two semiconductor devices 312 in the half-bridge circuit and the series connection point of capacitors 316 and 317 are connected to the secondary winding 308 of the high-frequency transformer 310 as AC inputs. Capacitor 318 is connected to the parallel connection point between the half-bridge circuit and the series connection circuit of capacitors 316 and 317. This parallel connection point is connected to DC buses 115a and 115b as a DC output.

[0070] The DC / AC conversion circuit 300 uses semiconductor switching elements to convert DC power input from DC buses 110a and 110b into AC power and outputs it to the primary winding 305 of the high-frequency transformer 310. The high-frequency transformer 310 takes the AC power received by the primary winding 305, steps down or steps up the AC voltage, and outputs it to the secondary winding 308.

[0071] The AC / DC conversion circuit 400 rectifies the AC power input from the secondary winding 308 using a diode and converts it into DC power. The DC power is used to charge the capacitor 318 and is also output to the DC buses 115a and 115b.

[0072] The AC / DC conversion circuit 400 converts DC power input from DC buses 115a and 115b into AC power using semiconductor switching elements. The DC / AC conversion circuit 300 converts AC power input from the AC / DC conversion circuit 400 via a high-frequency transformer 310 into DC power using diodes. In other words, the DC / DC conversion circuit 112 operates as a bidirectional power conversion circuit.

[0073] In the DC / DC conversion circuit 112 shown in Figure 7, a Solid State Transformer (SST) is used, similar to the DC / DC conversion circuit 112 shown in Figure 6. This allows for miniaturization of the power conversion unit 10, which has multiple converter units 116.

[0074] Furthermore, when the converter cell 108 (Figure 1) is constructed using the AC / DC conversion circuit 109 shown in Figure 4 and the DC / DC conversion circuit 112 shown in Figure 6, a common DC link capacitor may be used as capacitor 201 (Figure 4) and capacitor 311 (Figure 6). Also, when the converter cell 108 (Figure 1) is constructed using the AC / DC conversion circuit 109 shown in Figure 5 and the DC / DC conversion circuit 112 shown in Figure 7, a common capacitor two-series connection circuit may be used as the series connection circuit of capacitors 202 and 203 (Figure 5) and the series connection circuit of capacitors 314 and 315 (Figure 7).

[0075] As described above, in this embodiment, an isolated DC / DC conversion circuit 112 is used, so the AC input and DC output of the converter unit 116 are electrically isolated.

[0076] The circuit configuration of the bidirectional DC / DC converter 160 connected between the two different DC outputs of the power conversion unit 10 is the isolated bidirectional DC / DC conversion circuit shown in Figures 6 and 7. In this embodiment, since each output voltage is equal to the others, the transformation ratio of the high-frequency transformer 310 is 1:1. Because the high-frequency transformer 310 electrically isolates the DC outputs, electrical isolation between EVs connected to the EV charging port 122 can be ensured. Furthermore, since power can be transmitted bidirectionally between the two different DC outputs, the power conversion unit 10 according to this embodiment can supply multiple different power requirements simultaneously.

[0077] Figure 8 is a flowchart showing the charging control operation of the control unit 128 (Figure 1). The control unit 128 has a computer system such as a microcomputer, and the control operation is performed by the computer system executing a predetermined program.

[0078] In step S0, the control unit 128 starts the charge control operation.

[0079] Next, in step S1, the control unit 128, based on the EV-side information 133, determines the SOC and required power (P) of each of the multiple (N units) EV charging ports 122 (charging stations) for each EV. n The power (where n is a natural number: 1 ≤ n ≤ N) is obtained. If the EV side information 133 includes the charging speed, the control unit 128 obtains the requested power based on the pre-prepared data corresponding to the charging speed and the requested power.

[0080] Next, in step S2, the control unit 128 uses the output power of each DC output of the power conversion unit 10, that is, the output power of each of the N converter units 116, as the requested power (P) obtained in step S1. n Based on the average power requirement P avg (=(ΣP n Calculate ) / N).

[0081] Next, in step S3, the control unit 128 calculates the average required power P calculated in step S2. avg And the requested power P obtained in step S1. n Based on this, the transmission power, i.e., the output power P, of the bidirectional DC / DC converters 160-1 to 160-(N-1) connected between the DC outputs of the power converter 127. m Calculate (1 ≤ m ≤ N-1).

[0082] After executing step S3, the control unit 128 performs step S5 after a predetermined delay time (step S4). In this embodiment, the delay time is 1 msec or less.

[0083] During the delay period, the control unit 128 will operate as follows: SOC,P avg and P m Accordingly, control command signals 130 (Figure 1) are created and set for each converter unit 116 and the bidirectional DC / DC converters 160-1 to 160-N. Such control command signal creation may also be performed in the charge control operation shown in Figure 8. In that case, step S4 is replaced by the control command signal creation operation.

[0084] In step S5, the control unit 128 causes the converter unit 116 and the bidirectional DC / DC converters 160-1 to 160-N to output DC power in response to the control command signal, thereby initiating charging at the EV charging port 122.

[0085] Next, in step S6, the control unit 128 determines whether it has received a request signal to stop charging and whether the EV's charging power has fallen below a predetermined threshold. If the control unit 128 determines that it has received a request signal or that the charging power has fallen below the threshold (YES in step S6), it then executes step S8. If the control unit 128 determines that it has not received a request signal and that the charging power has not fallen below the threshold (NO in step S6), it then executes step S7. In this case, the control unit 128 continues charging and then executes steps S1 onwards again.

[0086] In this embodiment, the threshold value for charging power is 1kW or less.

[0087] In step S8, the control unit 128, as in step S1, checks the SOC and required power P of each EV. n In addition to reconfirming this, as in step S2, the average required power P is taken as the output power of each converter unit 116. avg Recalculate the output power P of the bidirectional DC / DC converters 160-1 to 160-(N-1) as in step S3. m Recalculate.

[0088] Next, in step S9, the control unit 128 stops charging the EV that has received a charge stop request, and the P recalculated in step S8 avg ,P m Based on this, the charging operation is initiated by the updated control command signal 130. After the control unit 128 executes step S9, it repeats steps S1 onwards.

[0089] The various operating modes of the EV charging power converter 127 (Figure 1) in this embodiment will be described below with reference to Figures 9 to 13. In each figure, the number of outputs of the power converter unit 10 is "3," as in Figure 2 mentioned above. Also, in each figure, the flow of power is indicated by arrows.

[0090] Figure 9 is a schematic functional block diagram showing the power flow in the first operating mode of the power converter 127.

[0091] In this operating mode, the power requirements of EV124-1, 124-2, and 124-3 are equal (P1=P2=P3), and only the output power (P0) of the DC outputs 115-1, 115-2, and 115-3 of the power conversion unit 10 is used to charge the energy storage devices of EV124-1, 124-2, and 124-3, respectively. Therefore, the power transmitted by the bidirectional DC / DC converters 160-1 and 160-2 (P 12 ,P 23 ) is zero.

[0092] Figure 10 is a schematic functional block diagram showing the power flow in the second operating mode of the power converter 127.

[0093] In this operating mode, the power requirements of EV124-1, 124-2, and 124-3 are not equal. Therefore, the bidirectional DC / DC converters 160-1 and 160-2 are used to transfer power (P) between the two outputs of the power conversion unit 10. 12 ,P 23 ) is transmitted.

[0094] The bidirectional DC / DC converters 160-1 and 160-2, connected between the two DC outputs of the power conversion unit 10, transmit power from one DC output to the other, or vice versa, depending on the power requirements. Additionally, depending on the power requirements, power is transmitted between the two outputs of the power conversion unit 10 (between DC outputs 115-1 and 115-3 in Figure 10) via multiple bidirectional DC / DC converters (two in Figure 10 (160-1 and 160-2)).

[0095] This second operating mode allows multiple battery storage devices in multiple electric vehicles to be charged at different charging speeds.

[0096] Figure 11 is a schematic functional block diagram showing the power flow in the third operating mode of the power converter 127.

[0097] In this operating mode, EV124-1 is not connected to EV charging port 122-1. Therefore, the required power P1 is zero. Consequently, all power (P0) output from DC output 115-1 is transmitted from DC output 115-1 to DC output 115-2 by the bidirectional DC / DC converter 160-1 connected to DC output 115-1.

[0098] Figure 12 is a schematic functional block diagram showing the power flow in the fourth operating mode of the power converter 127.

[0099] In this operating mode, power is exchanged only between the energy storage units of EV124-1, 124-2, and 124-3. Power discharged from any of the energy storage units of EV124-1, 124-2, or 124-3 is used by the bidirectional DC / DC converters 160-1 and 160-2 to charge the energy storage unit of any of the other EVs.

[0100] Furthermore, the power switch 200 is turned off, and the power conversion unit 10 is in a stopped state. Therefore, the output power of the multiple DC outputs 115-1, 115-2, and 115-3 of the power conversion unit 10 is zero (P0=0).

[0101] Thus, according to the fourth operating mode, multiple energy storage devices in multiple electric vehicles can charge and discharge each other using bidirectional converters.

[0102] Figure 13 is a schematic functional block diagram showing the power flow in the fifth operating mode of the power converter 127.

[0103] In this operating mode, the DC power (P1, P2, P3) discharged from the EV124-1, 124-2, and 124-3 energy storage devices is converted into AC power P by the multiple converter units 116 (Figure 1) provided in the power conversion unit 10. AC It is converted and output to AC power supply 100, i.e., the AC power grid side. Note that the transmission power by bidirectional DC / DC converters 160-1 and 160-2 is zero (P 12 =P 23 =0).

[0104] Thus, according to the fifth operating mode, the power from multiple energy storage devices of multiple electric vehicles is supplied to the AC power supply side via the power conversion unit 10, that is, via multiple converter units 116 (Figure 1).

[0105] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to add, delete, or replace some of the configurations of the embodiments with other configurations.

[0106] The energy storage device installed in an EV may be a battery or a capacitor. Furthermore, the device to be charged is not limited to the energy storage device installed in the EV; it may also be an energy storage device installed in other devices, or even an energy storage device on its own.

[0107] A converter module may be used as each of the bidirectional DC / DC converters 160-1 to 160-(N-1).

[0108] The semiconductor switching elements constituting the AC / DC conversion circuit 109, the DC / DC conversion circuit 112, and the bidirectional DC / DC converters 160-1 to 160-(N-1) are not limited to IGBTs, but may also be MOSFETs, junction bipolar transistors, etc. Furthermore, the semiconductor materials constituting the semiconductor switching elements and diodes are not limited to Si, but may also be wide-bandgap semiconductors such as SiC or GaN. [Explanation of symbols]

[0109] 10 Power conversion units 100 AC power supply 102 Three-phase reactor 103,104 AC input 108 Converter Cells 109 AC / DC Conversion Circuit 110a, 110b DC bus 112 DC / DC Conversion Circuit 113,114 DC output 115a, 115b DC bus 115-1, 115-2, 115-3 DC output 116 Converter Unit 117,118 DC bus voltage / current 121a, 121b Connection Cable 122 EV charging ports 123 SOC information 124, 124-1, 124-2, 124-3 EV 125 Charging Cable 127 Power converter 128 Control Unit 129 Voltage and Current Information 130 Control command signal 131 Voltage or current reference value 132 EV charging ports 133 EV-side information 150a, 150b DC output terminals 160, 160-1, 160-2 Bidirectional DC / DC Converter 200 Power switch 201, 202, 203 Capacitors 210 Semiconductor equipment 300 DC / AC Conversion Circuit 301 Semiconductor Equipment 305 Primary winding 308 Secondary winding 310 High-Frequency Transformer 311 Capacitors 312 Semiconductor equipment 313, 314, 315, 316, 317, 318 Capacitors 400 AC / DC Conversion Circuit

Claims

1. In a power conversion device that charges multiple energy storage devices, Multiple converter units that take AC power as input and output DC power, A bidirectional DC / DC converter connected between two of the DC outputs of the plurality of converter units, Equipped with, The plurality of DC outputs are connected to the plurality of energy storage devices. The bidirectional DC / DC converter transmits at least a portion of the output power of the converter unit at one of the DC outputs from one of the two DC outputs to the other DC output, in accordance with the power requirements of the plurality of energy storage devices. The system has N units (N≧3) of the aforementioned converter unit, and N-1 units of the aforementioned bidirectional DC / DC converter. A power conversion device characterized in that a portion of the output power is transmitted by a plurality of the bidirectional DC / DC converters among the N-1 bidirectional DC / DC converters.

2. In the power conversion device described in claim 1, A power conversion device characterized in that the output power from each of the plurality of DC outputs is equal.

3. In the power conversion device described in claim 2, A power conversion device characterized in that the output power value is the average value of the required power of the plurality of energy storage devices.

4. In the power conversion device described in claim 3, A power conversion device characterized in that the value of the required power of the energy storage device connected to the other DC output is greater than the average value.

5. In the power conversion device described in claim 2, A power conversion device characterized in that the rated power capacity of the bidirectional DC / DC converter is 50% or more of the rated power capacity of the converter unit, and is smaller than the rated power capacity of the converter unit.

6. In the power conversion device described in claim 1, The power conversion device is characterized in that the bidirectional DC / DC converter is of the isolated type.

7. In the power conversion device described in claim 1, The AC inputs of the aforementioned plurality of converter units are connected in series with each other. The power conversion device is characterized in that the plurality of converter units are electrically isolated from the AC input and the DC output.

8. In the power conversion device described in claim 1, The power conversion device is characterized in that the multiple energy storage devices are charged at different charging speeds.

9. In the power conversion device described in claim 1, Furthermore, the power conversion device is characterized in that the plurality of energy storage devices are charged and discharged from each other by the bidirectional DC / DC converter.

10. In the power conversion device described in claim 1, Furthermore, the power conversion device is characterized in that the DC power from the plurality of energy storage devices is supplied to the power source that supplies the AC power via the plurality of converter units.

11. In a control method for a power converter that charges multiple energy storage devices, The aforementioned power converter is Multiple converter units that take AC power as input and output DC power, A bidirectional DC / DC converter connected between two of the DC outputs of the plurality of converter units, Equipped with, The system has N units (N≧3) of the aforementioned converter unit, and N-1 units of the aforementioned bidirectional DC / DC converter. The plurality of DC outputs are connected to the plurality of energy storage devices. The average value of the power requirements of the aforementioned multiple energy storage devices is calculated, Based on the average value, the output power of the multiple energy storage devices is controlled, and based on the requested power and the average value, the output power of the bidirectional DC / DC converter is controlled. A control method for a power conversion device, characterized in that, in accordance with the power requirements of the plurality of energy storage devices, at least a portion of the output power of the converter unit at one of the DC outputs is transmitted from one of the two DC outputs to the other DC output by a plurality of the bidirectional DC / DC converters among the N-1 bidirectional DC / DC converters.

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