Power conversion system

Abstract

Regardless of the type of energy storage device installed in the vehicle, power transmission is performed appropriately without the need to select a power converter. [Solution] The power conversion system comprises power conversion devices 130, 140 and relay units 180, 185. Power conversion device 130 has terminals 136, 138 to which high-potential line 162 and low-potential line 164 are connected. Power conversion device 140 has terminals 146, 148 to which high-potential line 172 and low-potential line 174 are connected. Relay unit 180 is provided on the low-potential line 164. Relay unit 185 is provided between terminals 138, 146, branch point BP1, and relay unit 180. Relay unit 185 switches between a first state in which terminal 146 is electrically connected to branch point BP1 through high-potential line 172 and a second state in which terminal 146 is electrically connected to the portion of the low-potential line 164 between relay unit 180 and terminal 138.

Description

Technical Field

[0001] This disclosure relates to a power conversion system.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2013-90459 (Patent Document 1) discloses an electric vehicle. This electric vehicle includes a battery, an AC / DC converter (power conversion device) for charging the battery, and a controller. The AC / DC converter converts AC power supplied from an external power source to the vehicle into DC power and outputs it to the battery. The controller controls the AC / DC converter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a power conversion device is connected to a power storage device, the terminal voltage on the power storage device side of the power conversion device (hereinafter, also simply referred to as "terminal voltage") corresponds to the voltage of the power storage device. When the voltage of the power storage device is low, the current of the power storage device increases, which may cause an overcurrent. On the other hand, when the voltage of the power storage device is high, the power conversion efficiency of the power conversion device may be excessively reduced. For these reasons, it is desired that the voltage of the power storage device be within a predetermined reference voltage range according to the type of the power storage device.

[0005] Since the reference voltage range differs depending on the type of energy storage device, the terminal voltage range must correspond to the reference voltage range. For example, an energy storage device with a high reference voltage range requires a power converter with a high terminal voltage range, and an energy storage device with a low reference voltage range requires a power converter with a low terminal voltage range. Therefore, it is conceivable to appropriately select a suitable power converter from a variety of pre-prepared power converters, having a terminal voltage range corresponding to the reference voltage range, according to the type of energy storage device. In this case, by installing a power conversion system including the selected power converter in a vehicle, the voltage of the energy storage device can be appropriately changed within the reference voltage range, thereby enabling proper power transmission.

[0006] In recent years, the types of energy storage devices have become more diverse. Furthermore, because the reference voltage range differs for each type of energy storage device, the reference voltage range has also diversified along with the variety of energy storage devices. As a result, selecting the appropriate power converter each time, depending on the type of energy storage device installed in a vehicle, requires considerable effort.

[0007] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide a power conversion system that enables proper power transmission without requiring the effort of selecting a power converter, regardless of the type of energy storage device installed in the vehicle. [Means for solving the problem]

[0008] The power conversion system of this disclosure is mounted on a vehicle. The power conversion system comprises a first power converter, a second power converter, a first relay unit, and a second relay unit. The first power converter has a first terminal pair to which a first power line pair connected to the vehicle's inlet is connected, and a second terminal pair to which a second power line pair connected to the vehicle's energy storage device is connected. The second power converter has a third terminal pair to which a third power line pair connected to the inlet is connected, and a fourth terminal pair to which a fourth power line pair branching from the second power line pair is connected. The second terminal pair includes a first terminal to which a first high-potential line, which is a power line from the second power line pair connected to the positive terminal of the energy storage device, is connected, and a second terminal to which a first low-potential line, which is a power line from the second power line pair connected to the negative terminal of the energy storage device, is connected. The fourth terminal pair includes a third terminal to which a second high-potential line branched from the first high-potential line at the first branching point is connected, and a fourth terminal to which a second low-potential line branched from the first low-potential line at the second branching point is connected. The first relay section is provided on the first low-potential line. The second relay section is provided between the second terminal, the third terminal, the first branching point, and the first relay section. The second relay section switches between a first state in which the third terminal is electrically connected to the first branching point through the second high-potential line, and a second state in which the third terminal is electrically connected to the portion of the first low-potential line between the first relay section and the second terminal.

[0009] With the above configuration, the connection state (direct / parallel) between the first and second power converters can be appropriately determined according to the state of the first and second relay sections. This allows for appropriate power transmission by changing the voltage of the energy storage device within the reference voltage range, regardless of the type of energy storage device installed in the vehicle. As a result, there is no need to select a suitable power converter each time depending on the type of energy storage device. Therefore, with the above configuration, power transmission can be appropriately performed without the need to select a power converter, regardless of the type of energy storage device.

[0010] The energy storage device may include a first battery and a second battery. The first battery has a positive electrode connected to a first high-potential line. The second battery has a negative electrode connected to a first low-potential line. The power conversion system may further include a switching device. The switching device switches between connecting the first battery and the second battery in series or in parallel between the first high-potential line and the first low-potential line.

[0011] By adopting the above configuration, the connection state of the first and second batteries can be appropriately switched between a series connection state and a parallel connection state according to the maximum output voltage of each power converter, thereby enabling proper power transmission without requiring each power converter to have a high voltage resistance. [Effects of the Invention]

[0012] According to this disclosure, power transmission can be properly performed without the need to select a power converter, regardless of the type of energy storage device installed in the vehicle. [Brief explanation of the drawing]

[0013] [Figure 1] This is an overall configuration diagram of a power system including a vehicle equipped with a power conversion system according to an embodiment. [Figure 2] This is a diagram illustrating the relationship between the comparative vehicle, battery voltage, battery current, and power conversion efficiency. [Figure 3] This figure illustrates an example of power flow during external charging in this embodiment. [Figure 4] This figure illustrates another example of the power flow during external charging in this embodiment. [Figure 5] This diagram illustrates the relationship between the battery voltage VB and current in each of the comparative examples and embodiments. [Figure 6] This flowchart shows an example of the process performed by the control device in modified examples 1 to 4. [Figure 7] This is a diagram illustrating the configuration of the relay section in modified example 5. [Figure 8] A flowchart for explaining the procedures for setting and operating the target device in Embodiment 2, and a diagram for explaining the advantages of Embodiment 2. [Figure 9] A diagram for explaining an example of the detailed configuration of the battery and the switching circuit in Embodiment 3. [Figure 10] A diagram showing the relationship between the relay unit, the power conversion device, the states of the first battery and the second battery, the target value of the output power of the entire power conversion device, the maximum output voltage of each power conversion device, and the input voltage of the battery in Embodiment 2. [Figure 11] A flowchart for explaining an example of the procedure for determining the connection state of the first battery and the second battery in Embodiment 2.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals and their descriptions will not be repeated. Each of the embodiments and their modifications may be combined with each other as appropriate.

[0015] [Embodiment 1] FIG. 1 is an overall configuration diagram of a power system including a vehicle on which a power conversion system according to Embodiment 1 is mounted. Referring to FIG. 1, the power system 1 includes a vehicle 10 and a power facility 20.

[0016] The vehicle 10 is a BEV (Battery Electric Vehicle) in this example, but may be other types of electric vehicles such as a plug-in hybrid vehicle (PHEV: Plug-in Hybrid Electric Vehicle).

[0017] Vehicle 10 includes a battery 105, a voltage sensor 110, a temperature sensor 115, a SMR (System Main Relay) 120, an inlet 125, and power conversion devices 130 and 140. Vehicle 10 further includes power line pairs 150, 155, 160, 170, relay units 180, 185, temperature sensors 181, 182, 189, and a control device 190.

[0018] The battery 105 is an example of a power storage device that stores power for the running of the vehicle 10. The battery 105 has a reference voltage range according to its type. This range is appropriately determined in advance by experiments or the like. The voltage sensor 110 detects the voltage VB of the battery 105 and outputs the detected value. The temperature sensor 115 detects the temperature TB of the battery 105 and outputs the detected value.

[0019] The SMR 120 is provided in the power line pair 160 (described later) and is assumed to be in a closed state in Embodiment 1. The inlet 125 is connected to the power cable of the power facility 20 and receives the power (in this example, AC power) supplied from the power facility 20.

[0020] The power conversion device 130 is an insulated converter including a transformer and has terminals 132, 134, 136, 138 and a temperature sensor 139. The terminals 132 and 134 correspond to an example of the "first terminal pair" of the present disclosure, and the power line pair 150 is connected thereto. The power line pair 150 is connected to the inlet 125. The terminals 136 and 138 correspond to an example of the "second terminal pair" of the present disclosure, and the power line pair 160 is connected thereto. The temperature sensor 139 detects the temperature TC1 of the power conversion device 130 and outputs the detected value.

[0021] The power converter 130 operates during power transmission between the vehicle 10 and the power equipment 20 (hereinafter also simply referred to as "power transmission"). Power transmission may be either external charging or external power supply. External charging means charging the battery 105 using the power received by the inlet 125. External power supply means supplying power to external equipment of the vehicle 10 (for example, the power equipment 20 or another household appliance) using the power of the battery 105. During external charging, the power converter 130 converts the voltage between terminals 132 and 134 (terminal voltage V1) and outputs the converted voltage (terminal voltage V2A) between terminals 136 and 138. Terminal voltage V1 corresponds to, for example, the voltage applied from the power equipment 20 to the inlet 125. On the other hand, during external power supply, the power converter 130 converts terminal voltage V2A and outputs terminal voltage V1.

[0022] The power line pair 160 is connected to the battery 105 and includes a high-potential line 162 and a low-potential line 164. One end of the high-potential line 162 is connected to terminal 136 and the other end is connected to the positive terminal of the battery 105. One end of the low-potential line 164 is connected to terminal 138 and the other end is connected to the negative terminal of the battery 105.

[0023] The power converter 140 is an isolated converter including a transformer, and has terminals 142, 144, 146, and 148, and a temperature sensor 149. Terminals 142 and 144 correspond to an example of the “third terminal pair” of this disclosure, and are connected to a power line pair 155. In this example, the power line pair 155 is branched from the power line pair 150, but may also be directly connected to the inlet 125. Terminals 146 and 148 correspond to an example of the “fourth terminal pair” of this disclosure, and are connected to a power line pair 170. The temperature sensor 149 detects the temperature TC2 of the power converter 140 and outputs the detected value.

[0024] The power converter 140 operates during power transmission. For example, during external charging, it converts the voltage between terminals 142 and 144 (terminal voltage V1) and outputs the converted voltage as terminal voltage V2B between terminals 146 and 148. Terminal voltage V2B may be different from terminal voltage V2A, but for the sake of clarity in the following explanation, it will be assumed to be equal to terminal voltage V2A. On the other hand, during external power supply, the power converter 140 converts terminal voltage V2B and outputs the converted voltage as terminal voltage V1.

[0025] Power line pair 170 branches off from power line pair 160 and includes a high-potential line 172 and a low-potential line 174. The high-potential line 172 branches off from the high-potential line 162 at branching point BP1, and its end is connected to terminal 146. The low-potential line 174 branches off from the low-potential line 164 at branching point BP2, and its end is connected to terminal 148.

[0026] Relay section 180 corresponds to a contact relay provided on the low-potential line 164. Relay section 185 is provided between the branching point BP1, terminals 138 and 146, and relay section 180, and includes contacts 186, 187, and 188. Contact 186 is provided on the portion of the low-potential line 164 between relay section 180 and terminal 138 (low-potential line 165). Contacts 187 and 188 are provided on the high-potential line 172 between the branching point BP1 and terminal 146. Contact 188 can be connected to either contact 187 or contact 186.

[0027] The state of relay unit 185 when contact 188 is connected to contact 187 is also referred to as "state A". In state A, contacts 187 and 188 constitute contact relay RL, and terminal 146 is electrically connected to branch point BP1 via high-potential line 172. On the other hand, the state of relay unit 185 when contact 188 is connected to contact 186 is also referred to as "state B". In state B, contacts 186 and 188 constitute contact relay RL, and terminal 146 is electrically connected to terminal 138 via low-potential line 165. Relay unit 185 switches between state A and state B.

[0028] Temperature sensor 181 is an ambient temperature sensor that detects the ambient temperature TE of the vehicle 10 and outputs the detected value. Temperature sensor 182 detects the temperature TR1 of the relay unit 180 and outputs the detected value. Temperature sensor 189 detects the temperature TR2 of the relay unit 185 and outputs the detected value. Temperature TR2 is, for example, the temperature of the contact relay RL.

[0029] The control device 190 includes memory and a processor (neither of which are shown). The memory includes ROM (Read Only Memory) and RAM (Random Access Memory). The ROM stores programs executed by the processor. The RAM functions as working memory. The processor is, for example, a CPU (Central Processing Unit) which performs various arithmetic operations according to the above program.

[0030] The control device 190 controls various components of the vehicle 10, such as the SMR110, power converters 130 and 140, and relay units 180 and 185, according to detected values ​​of voltage VB and temperatures TB, TE, TC1, TC2, TR1, and TR2. The control device 190 controls the power converters 130 and 140 so that, for example, output power (i.e., the total output power of the power converters 130 and 140 during power transmission) is supplied from the entire power converters 130 and 140 to the battery 105 during external charging, or from the entire power converters 130 and 140 to the outside of the vehicle 10 during external power supply.

[0031] A voltage sensor 110, a temperature sensor 115, power converters 130, 140, power line pairs 150, 155, 160, 170, relay units 180, 185, temperature sensors 181, 182, 189, and a control device 190 form an example of the “power conversion system” of this disclosure.

[0032] Figure 2 is a diagram illustrating the comparative vehicle and the relationship between voltage VB and the current and power conversion efficiency of battery 105. Referring to Figure 2(A), comparative vehicle 10A differs from vehicle 10 (Figure 1) in that its power conversion system does not include the power converter 140, power line pairs 155, 170, and relay units 180, 185, but is otherwise basically the same as vehicle 10. In the comparative example, the terminal voltage V2A during external charging corresponds to the output voltage VP of the power converter 130. The output voltage VP corresponds to the voltage VB of battery 105.

[0033] Referring to Figure 2(B), line 405 represents the relationship between the current IB and voltage VB (output voltage VP) of battery 105. Line 410 represents the relationship between the power conversion efficiency of power converter 130 and voltage VB.

[0034] The reference voltage range RNG corresponds to the reference voltage range of the battery 105. If the voltage VB is lower than the lower limit voltage LV of the reference voltage range RNG, the magnitude of the current in the battery 105 may exceed the threshold TH, leading to overcurrent (line 405). On the other hand, if the voltage VB is higher than the upper limit voltage UV of the reference voltage range RNG, the power conversion efficiency of the power converter 130 may decrease excessively and fall below a predetermined efficiency eth (line 410). For these reasons, the output voltage VP corresponding to the voltage VB is limited to a specific allowable range within the reference voltage range RNG.

[0035] Since the reference voltage range RNG differs depending on the type of battery 105, the range of the output voltage VP (terminal voltage V2A) must correspond to the reference voltage range RNG. For example, in the comparative example, a battery 105 with a high reference voltage range RNG requires a power converter 130 with a high range of output voltage VP, and a battery 105 with a low reference voltage range RNG requires a power converter 130 with a low range of output voltage VP. Therefore, it is conceivable to appropriately select a suitable power converter 130 having an output voltage VP (terminal voltage V2A) range corresponding to the reference voltage range RNG from among various power converters prepared in advance at a factory or the like, according to the type of battery 105. In this case, by mounting the power conversion system including the selected power converter on the vehicle 10A, the voltage VB can be appropriately changed within the reference voltage range RNG, and power transmission can be properly performed.

[0036] In recent years, the types of on-board batteries have diversified, and various types of on-board batteries can be installed in a vehicle 10A as battery 105. Furthermore, since the reference voltage range RNG differs for each type of on-board battery, the reference voltage range RNG has also diversified along with the diversification of on-board battery types. As a result, selecting a suitable power converter each time, depending on the type of on-board battery used as battery 105, requires considerable effort.

[0037] In contrast, the power conversion system according to Embodiment 1 has a configuration to address such problems. This will be explained below.

[0038] Figure 3 is a diagram illustrating an example of power flow during external charging in this embodiment 1. Referring to Figure 3, in this example, relay unit 180 is in the closed state and relay unit 185 is in state A (Figure 1). In this case, terminal 146 is connected to branch point BP1 through high-potential line 172, so power converters 130 and 140 are connected in parallel. As a result, the sum of the output currents of power converter 130 and power converter 140 (large current) is supplied to battery 105 through SMR 110 as the total output current of these power converters. The voltage of the total output power of these power converters (output voltage VP) is equal to the terminal voltages V2A and V2B, respectively.

[0039] Figure 4 illustrates another example of the power flow during external charging in this embodiment 1. Referring to Figure 4, in this example, relay unit 180 is in the open state and relay unit 185 is in state B (Figure 1). In this case, terminal 146 is connected to terminal 138 through the high-potential line 172 and the low-potential line 165, so that power converters 130 and 140 are connected in series. As a result, the sum of the terminal voltages V2A and V2B is applied to the battery 105 as the output voltage VP. Note that in this case, the total output current of power converters 130 and 140 is smaller than that of the example in Figure 3 (in one example, it may be half of that of the example in Figure 3).

[0040] In Embodiment 1, for a battery 105 with a relatively low voltage VB (reference voltage range RNG), the power converters 130 and 140 can be connected in parallel by closing the relay unit 180 and setting the relay unit 185 to state A, as shown in Figure 3. This allows the battery 105 to be charged with a large current or the power from the battery 105 to be supplied to external devices. On the other hand, for a battery 105 with a relatively high voltage VB (reference voltage range RNG), the power converters 130 and 140 can be connected in series by opening the relay unit 180 and setting the relay unit 185 to state B, as shown in Figure 4. This allows the voltage VB to be increased to a desired voltage within the reference voltage range RNG or high voltage to be applied from the battery 105 to external devices through the inlet 125, while suppressing a decrease in power conversion efficiency when charging the battery 105 (for example, while avoiding the power conversion efficiency of each power converter falling below the predetermined efficiency eth in Figure 2).

[0041] Thus, in Embodiment 1, the connection state (direct / parallel) between the power converters 130 and 140 can be determined according to the state of the relay units 180 and 185. By appropriately switching this connection state, power transmission such as external charging can be properly carried out as described above. In other words, in order to properly carry out power transmission as described above, it is sufficient to install the power conversion system of Embodiment 1 on the vehicle 10 and determine the state of the relay units 180 and 185 according to the voltage of the battery 105. As a result, it is sufficient to prepare the minimum necessary number of (e.g., a single) types of power conversion systems in the factory, etc., and there is no need to select a suitable power converter each time according to the type of battery 105. Therefore, the number of types of on-board power conversion systems prepared in the factory, etc. can be reduced to the minimum necessary number. From the above, according to Embodiment 1, power transmission can be properly carried out regardless of the type of battery 105, without the need to select a power converter.

[0042] The connection state (direct / parallel) between power converters 130 and 140 is fixed by an operator (e.g., by welding), taking into consideration the reference voltage range RNG of battery 105. In one example, if it is known in advance that the reference voltage range RNG is not very high, the output voltage VP does not need to be high. Therefore, the state of relay units 180 and 185 may be fixed so that power converters 130 and 140 are always connected in parallel and battery 105 is charged (or discharged) with a large current.

[0043] Preferably, the above connection state is switched appropriately by the control device 190 according to the detected voltage VB from the voltage sensor 110. In this case, if the detected voltage VB is lower than a predetermined reference value, the control device 190 controls the relay unit 180 to the closed state and the relay unit 185 to state A, as shown in Figure 3. On the other hand, if the detected voltage VB is equal to or greater than the reference value, the control device 190 controls the relay unit 180 to the open state and the relay unit 185 to state B, as shown in Figure 4.

[0044] With this configuration, if the detected voltage VB exceeds a reference value, the relay unit 180 is automatically switched from a closed state to an open state, and the relay unit 185 is automatically switched from state A to state B by the control device 190. Therefore, with the above configuration, the series / parallel connection of the power converters 130 and 140 is appropriately switched in response to changes in voltage VB. For example, when the voltage VB is low, the power converters 130 and 140 are connected in parallel, so the battery 105 is charged with a large current, and the charging time is appropriately shortened. On the other hand, as external charging progresses and the voltage VB rises, the connection state of these power converters is switched from parallel to series, and the output voltage VP rises. Therefore, the voltage VB can be raised to a desired voltage within the reference voltage range RNG while suppressing a decrease in power conversion efficiency. In this way, the above control by the control device 190 enables appropriate power transmission such as external charging.

[0045] Figure 5(A) is a diagram illustrating the relationship between voltage VB (output voltage VP) and current IB in the comparative example (Figure 2) and Embodiment 1, respectively. Referring to Figure 5, line 510 represents the above relationship in the comparative example. Line 520 represents the above relationship when power converters 130 and 140 are connected in parallel in Embodiment 1 (Figure 3). Line 525 represents the above relationship when power converters 130 and 140 are connected in series in Embodiment 1 (Figure 4).

[0046] The voltage range rng1 is the allowable range (limit range) of the output voltage VP of the power converter 130 in the comparative example. In the comparative example, since the output voltage VP is limited to the voltage range rng1 determined based on the reference voltage range RNG, the voltage VB is also limited to the voltage range rng1. As a result, when the voltage VB falls below the lower limit voltage V1a, the current IB is limited, and it is not possible to charge the battery 105 with a current IB greater than the threshold value TH1 (line 510). The threshold value TH1 corresponds, for example, to the magnitude of the allowable upper limit current of the power converter 130. In addition, in the comparative example, if the voltage VB is higher than the upper limit voltage V1b, the power conversion efficiency decreases excessively, making it difficult to raise the voltage VB above the upper limit voltage V1b.

[0047] In contrast, in Embodiment 1, since the connection state (series / parallel) of the power converters 130 and 140 can be switched, the allowable range (limit range) of the output voltage VP from the power converters 130 and 140 as a whole is expressed as a voltage range rng2 that is wider than the voltage range rng1. The voltage range rng2 is determined based on the reference voltage range RNG.

[0048] In Embodiment 1, when the detected voltage VB is less than the reference value RV (e.g., 500V), the relay units 180 and 185 are controlled so that the power converters 130 and 140 are connected in parallel, as shown in Figure 3. This allows each of the power converters 130 and 140 to receive their respective maximum allowable currents, unlike the comparative example where only the power converter 130 can receive its maximum allowable current. As a result, unlike the comparative example, the maximum allowable current does not flow through each power converter unless the output voltage VP falls below the lower limit voltage V2a of the voltage range rng2, so the battery 105 can be charged with a large current (up to the magnitude of the threshold TH2) (line 520).

[0049] On the other hand, if the detected voltage VB exceeds the reference value RV as external charging progresses, the relay units 180 and 185 are controlled so that the power converters 130 and 140 are connected in series, as shown in Figure 4. This is different from the comparative example in which the power conversion efficiency drops excessively when the output voltage VP exceeds the upper limit voltage V1b. In Embodiment 1, even if the output voltage VP exceeds the upper limit voltage V1b, the power conversion efficiency remains within an acceptable range, and the output voltage VP can be increased up to the upper limit voltage V2b (>V1b) of the voltage range rng2 (line 525). Therefore, the battery 105 with a high reference voltage range RNG can be charged while suppressing an excessive drop in power conversion efficiency. In this case, for example, each of the terminal voltages V2A and V2B is lower than the upper limit voltage UV (Figure 2), and the power conversion efficiency of each power converter is prevented from falling below a predetermined efficiency eth.

[0050] Figure 5(B) is a flowchart showing an example of the process performed by the control device 190 in Embodiment 1. This flowchart is executed repeatedly during external charging. Hereinafter, steps will be abbreviated as "S".

[0051] Referring to Figure 5(B), the control device 190 determines whether the detected voltage VB is less than the reference value RV (S105). If the detected voltage VB is less than the reference value RV (YES in S105), the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in parallel as shown in Figure 3. Specifically, the control device 190 controls the relay unit 180 to the closed state and the relay unit 185 to the A state (S110). On the other hand, if the detected voltage VB is greater than or equal to the reference value RV (NO in S105), the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in series as shown in Figure 4. Specifically, the control device 190 controls the relay unit 180 to the open state and the relay unit 185 to the B state (S115). After S110 or S115, the process returns to S105.

[0052] As described above, according to Embodiment 1, regardless of the type of battery 105, power transmission such as external charging can be appropriately performed without the need to select a power conversion device in a factory or the like.

[0053] [Example 1] If the detected voltage VB in S105 (Figure 5) is less than the reference value RV, the control device 190 may control the relay units 180 and 185 according to the detected temperature TB of the battery 105.

[0054] Figure 6(A) is a flowchart showing an example of the process performed by the control device 190 in Modification Example 1. This flowchart is performed in place of S110 (Figure 5).

[0055] Referring to Figure 6(A), the control device 190 determines whether the detected temperature TB is lower than a predetermined value PV1 (S120). When the detected temperature TB is lower than the predetermined value PV1 (YES in S120), charging the battery 105 with a high current will not cause the battery 105 to overheat. Therefore, the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in parallel as shown in Figure 3 (S130). On the other hand, when the detected temperature TB is greater than or equal to the predetermined value PV1 (NO in S120), charging the battery 105 with a high current may cause the battery 105 to overheat. Therefore, the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in series as shown in Figure 4 (S135). After S130 or S135, the process returns to S105 in Figure 5(B).

[0056] According to Modification 1, when the voltage VB is low and the temperature TB is low, the power converters 130 and 140 are connected in parallel. This allows the battery 105 to be charged with a large current and to be effectively warmed. As a result, the time required for power transmission, such as external charging, can be appropriately shortened. On the other hand, when the voltage VB is low and the temperature TB is high, the power converters 130 and 140 are connected in series. This allows power transmission to be performed while effectively avoiding overheating of the battery 105.

[0057] [Differentiation 2] If the detected voltage VB in S105 (Figure 5) is less than the reference value RV, the control device 190 may control the relay units 180 and 185 according to the detected ambient temperature TE.

[0058] Figure 6(B) is a flowchart showing an example of the process performed by the control device 190 in the modified example 2. This flowchart is performed in place of S110 (Figure 5).

[0059] Referring to Figure 6(B), the control device 190 determines whether the detected temperature TE is lower than a predetermined value PV2 (S122). When the detected temperature TE is lower than the predetermined value PV2 (YES in S122), the temperature TB of the battery 105 tends to be low. Therefore, in order to appropriately shorten the power transmission time, the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in parallel as shown in Figure 3 (S130). On the other hand, when the detected temperature TE is greater than or equal to the predetermined value PV2 (NO in S122), the temperature TB tends to be high. Therefore, in order to avoid overheating of the battery 105, the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in series as shown in Figure 4 (S135). After S130 or S135, the process returns to S105 in Figure 5(B).

[0060] According to Modification 2, similar to Modification 1, the time required for power transmission can be appropriately shortened while effectively avoiding overheating of the battery 105.

[0061] [Difference 3] If the detected voltage VB in S105 (Figure 5) is less than the reference value RV, the control device 190 may control the relay units 180 and 185 according to the detected temperature TC1 of the power converter 130.

[0062] Figure 6(C) is a flowchart showing an example of the process performed by the control device 190 in Modification Example 3. This flowchart is performed in place of S110 (Figure 5).

[0063] Referring to Figure 6(C), the control device 190 determines whether the detected temperature TC1 is lower than a predetermined value PV3 (S124). When the detected temperature TC1 is lower than the predetermined value PV3 (YES in S124), even if a large current is passed through the battery 105 and the power converter 130, the power converter 130 will not overheat. Therefore, the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in parallel as shown in Figure 3 in order to charge the battery 105 with a large current (S130). On the other hand, when the detected temperature TC1 is greater than or equal to the predetermined value PV3 (NO in S124), passing a large current through the battery 105 and the power converter 130 may cause the power converter 130 to overheat. Therefore, the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in series as shown in Figure 4 (S135). After S130 or S135, the process returns to S105 in Figure 5(B).

[0064] In the determination process of S124, the detected value of the temperature TC1 of the power converter 130 may be replaced by the detected value of the temperature TC2 of the power converter 140.

[0065] According to Modification 3, when the voltage VB is low and the temperature TC1 or TC2 is high, the power converters 130 and 140 are connected in series. This prevents the large currents that would flow through the power converters 130 and 140, as would occur in the example where they are connected in parallel. Therefore, an excessive increase in the amount of heat generated by these power converters is prevented. As a result, power transmission can be performed while adequately protecting the power converters 130 and 140 from overheating.

[0066] [Differentiation Example 4] If the detected voltage VB in S105 (Figure 5) is less than the reference value RV, the control device 190 may control the relay units 180 and 185 according to the detected temperature TR1 of the relay unit 180.

[0067] Figure 6(D) is a flowchart showing an example of the process performed by the control device 190 in Modification 4. This flowchart is performed in place of S110 (Figure 5).

[0068] Referring to Figure 6(D), the control device 190 determines whether the detected temperature TR1 is lower than a predetermined value PV4 (S126). When the detected temperature TR1 is lower than the predetermined value PV4 (YES in S126), even if a large current is passed through the battery 105 and the relay unit 180, it will not cause the relay unit 180 to overheat. Therefore, the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in parallel as shown in Figure 3 in order to charge the battery 105 with a large current (S130). On the other hand, when the detected temperature TR1 is greater than or equal to the predetermined value PV4 (NO in S126), passing a large current through the battery 105 and the relay unit 180 may cause the relay unit 180 to overheat. Therefore, the control device 190 controls the relay units 180 and 185 so that the power converters 130 and 140 are connected in series as shown in Figure 4 (S135).

[0069] In the determination process of S126, the detected temperature TR1 of the relay unit 180 may be replaced by the detected temperature TR2 of the relay unit 185.

[0070] According to Modification 4, when the voltage VB is low and the temperature TR1 or TR2 is high, the power converters 130 and 140 are connected in series. This prevents the large current that would flow through the relay units 180 and 185, as would occur in the example where these power converters are connected in parallel. Therefore, an excessive increase in the amount of heat generated by the relay units 180 and 185 is prevented. As a result, power transmission can be performed while adequately protecting the relay units 180 and 185 from overheating.

[0071] [Difference 5] In the above description, the relay section 185 is assumed to include contacts 186, 187, and 188 (Figure 1), but it may have a different configuration.

[0072] Figure 7 is a diagram illustrating the configuration of the relay unit 185 in Modification 5. Referring to Figure 7, the relay unit 185 of Modification 5 differs from the relay unit 185 of Embodiment 1 and its Modifications 1 to 4 in that it includes contact relays RL1 and RL2 instead of contacts 186, 187, and 188. State A of the relay unit 185 is defined as the state in which contact relay RL1 is closed and contact relay RL2 is open. On the other hand, state B of the relay unit 185 is defined as the state in which contact relay RL1 is open and contact relay RL2 is closed. Thus, states A and B may be defined as shown in Figure 7.

[0073] [Embodiment 2] The control device 190 of Embodiment 2 differs from the control device 190 of Embodiment 1 in that it is capable of operating only one of the power converters 130 and 140. In other words, the control device 190 operates at least one of the power converters 130 and 140 (hereinafter also referred to as the "target device") and controls the target device so that output power (output power of the target device during power transmission) is supplied from the target device to the battery 105 or from the target device to the outside of the vehicle 10.

[0074] Figure 8 is a flowchart illustrating the setup and operation procedures of the target device in Embodiment 2, and a diagram illustrating the advantages of Embodiment 2. Hereinafter, steps will be abbreviated as "S".

[0075] Referring to Figure 8(A), the control device 190 determines whether the above-mentioned target value of output power is greater than a predetermined specified value (S103). This target value is appropriately determined based on the specifications of the power equipment 20 and various conditions such as the voltage and temperature of the battery 105. If the above target value is greater than the specified value, the control device 190 sets both power converters 130 and 140 as target devices and operates them (S104a). The specified value is, for example, the maximum output power value of each power converter. The maximum output voltage corresponds to the maximum values ​​of terminal voltages V2A and V2B in the specifications of power converters 130 and 140. On the other hand, if the target value of output power is less than or equal to the specified value, the control device 190 sets only one of the power converters 130 or 140 as the target device and operates it (S104b). The process then proceeds to S105.

[0076] Referring to Figure 8(B), the relationship between output power and power conversion efficiency in Embodiment 2 and the Comparative Example will be explained. In the Comparative Example, both power converters are always in operation regardless of the target value of the output power. In Embodiment 2, if the target value of the output power is less than a specified value, only one power converter operates and supplies the target value of output power to its destination. As a result, in Embodiment 2, power loss during power conversion is reduced in the low output power range compared to the Comparative Example. Consequently, the power conversion efficiency during power transmission can be appropriately improved according to the output power.

[0077] [Embodiment 3] The power system 1 of Embodiment 3 differs from the power system 1 of Embodiment 1 in that the vehicle 10 further includes a switching circuit connected between the battery 105 and the SMR 120, and the battery 105 includes a first and a second battery. In other respects, the power system 1 of Embodiment 3 is basically the same as the power system 1 of Embodiment 1 or 2.

[0078] Figure 9 is a diagram illustrating an example of the detailed configuration of the battery 105 and switching circuit in Embodiment 3. Referring to Figure 9, the battery 105 includes a first battery 307 and a second battery 309. The first battery 307 has a positive electrode connected to a high-potential line 162 and a negative electrode connected to a switch 314 (described later). The second battery 309 has a positive electrode connected to a switch 312 (described later) and a negative electrode connected to a low-potential line 164.

[0079] The switching circuit 310 includes switches 312, 314, and 316. For example, when switches 312 and 314 are off and switch 316 is on, the negative terminal of the first battery 307 is connected to the positive terminal of the second battery 309. As a result, the first battery 307 and the second battery 309 are electrically connected in series. On the other hand, when switches 312 and 314 are on and switch 316 is off, the negative terminal of the first battery 307 is connected to the low-potential line 164, while the positive terminal of the second battery 309 is connected to the high-potential line 162. As a result, the first battery 307 and the second battery 309 are electrically connected in parallel. The state of each switch may be switched by user operation, automatically switched by the control device 190, or fixed and determined by the user by welding or the like.

[0080] In Embodiment 2, the switches 312, 314, and 316 of the switching circuit 310 can be used to switch between connecting the first battery 307 and the second battery 309 in series or in parallel between the high-potential line 162 and the low-potential line 164. As a result, by appropriately switching the connection state of the first battery 307 and the second battery 309 between a series connection state and a parallel connection state according to the maximum output voltage of the power converters 130 and 140, power transmission can be properly performed without requiring high voltage resistance for each power converter (details will be described later).

[0081] Figure 10 is a diagram showing the relationship between the states of the relay units 180, 185, the power converters 130, 140, the first battery 307, and the second battery 309 in Embodiment 2, the target value of the total output power of the power converters 130, 140, the maximum output voltage of each power converter, and the input voltage of the battery 305.

[0082] Referring to Figure 10, when the maximum output voltage of each power converter is greater than or equal to a predetermined voltage (in this example, Va), the connection state of the first battery 307 and the second battery 309 is set to a series connection state using the switching circuit 310. On the other hand, when the power converters 130 and 140 are connected in parallel and the maximum output voltage is less than a predetermined voltage (in this example, Vb), the connection state of the first battery 307 and the second battery 309 is set to a parallel connection state using the switching circuit 310. In either case, when the target value of the total output power of the power converters 130 and 140 is greater than or equal to the aforementioned specified value (for example, Wa), or when this target value is less than the specified value (for example, Wb), the connection state of the first battery 307 and the second battery 309 is determined as described above. In this example, Va = 800 [V], Vb = 400 [V], and Wa = 2 × Wb [W]. Furthermore, when the power converters 130 and 140 are connected in series, the connection state of the first battery 307 and the second battery 309 is considered to be a series connection state, even when the maximum output voltage is less than a predetermined voltage.

[0083] When power converters 130 and 140, which are the target devices, are connected in parallel, and the first battery 307 and the second battery 309 are connected in series, in order to charge battery 105, the output voltage VP of each power converter must be greater than the sum of the voltages of the first battery 307 and the second battery 309. This requires that each power converter have a high voltage rating.

[0084] Therefore, it is conceivable to charge the battery 105 by switching the relay units 180 and 185 and connecting the power converters 130 and 140 in series, as in Embodiment 1. However, in this case, the output power from all of these power converters (the power used to charge the battery 105) decreases.

[0085] In contrast, in Embodiment 2, the power converters 130 and 140 can be operated with the power converters 130 and 140 connected in parallel, and the first battery 307 and the second battery 309 connected in parallel using the switching circuit 310. In this case, in order to charge the battery 105, the output voltage VP does not need to be greater than the sum of the above, but it is sufficient if it is greater than the voltage of the first battery 307 and the second battery 309 individually. Furthermore, since the power converters 130 and 140 operate in a parallel connected state, the output power is twice the power supplied from a single power converter and does not decrease as described above. Therefore, the battery 105 can be charged without increasing the voltage resistance of the power converters 130 and 140 or reducing the output power. For example, if the maximum output voltage of each power converter is Vb(<Va)であっても、Wa(> The output power of Wb can be supplied to the battery 105 as charging power.

[0086] Figure 11 is a flowchart illustrating an example of the procedure for determining the connection state of the first battery 307 and the second battery 309 in Embodiment 2. Referring to Figure 11, if the maximum output voltage of each power converter is greater than or equal to a predetermined voltage (YES in S101), the state of each switch in the switching circuit 310 is determined so that the first battery 307 and the second battery 309 are connected in series (S102a). On the other hand, if the maximum output voltage is less than a predetermined voltage (NO in S101), the state of each switch in the switching circuit 310 is determined so that the first battery 307 and the second battery 309 are connected in parallel (S102b). After S102a or S102b, the process ends. After that, for example, the process in the flowchart of Figure 5(B) or Figure 8(A) is started.

[0087] As described above, in Embodiment 3, the connection state (series / parallel) of the first battery 307 and the second battery 309 can be switched using the switching circuit 310. This makes it possible to properly transmit power without requiring each power converter to have a high voltage rating.

[0088] [Other variations] Although each of the power converters 130 and 140 is assumed to be an isolated converter in the above description, they may be replaced by converters such as a current-reversible boost chopper circuit.

[0089] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0090] 1 Power system, 10, 10A, 100 Vehicle, 20 Power equipment, 105 Battery, 110 Voltage sensor, 115, 139, 149, 181, 182, 189 Temperature sensor, 125 Inlet, 130, 140 Power converter, 180, 185 Relay section, 190 Control device.

Claims

1. A power conversion system installed in a vehicle, A first power converter having a first terminal pair to which a first power line pair connected to the inlet of the vehicle is connected, and a second terminal pair to which a second power line pair connected to the energy storage device of the vehicle is connected, The second power converter comprises a third terminal pair to which a third power line pair connected to the inlet is connected, and a fourth terminal pair to which a fourth power line pair branching from the second power line pair is connected. The second terminal pair includes a first terminal to which a first high-potential line, which is a power line connected to the positive terminal of the energy storage device from the second power line pair, is connected, and a second terminal to which a first low-potential line, which is a power line connected to the negative terminal of the energy storage device from the second power line pair, is connected. The fourth terminal pair includes a third terminal to which a second high-potential line branched off from the first high-potential line at a first branching point is connected, and a fourth terminal to which a second low-potential line branched off from the first low-potential line at a second branching point is connected. The aforementioned power conversion system further, The first relay unit provided on the first low-potential line, The system comprises a second relay unit provided between the second terminal, the third terminal, the first branch point, and the first relay unit, The power conversion system comprises a second relay unit that switches between a first state in which the third terminal is electrically connected to the first branching point through the second high-potential line, and a second state in which the third terminal is electrically connected to the portion of the first low-potential line between the first relay unit and the second terminal.

2. A voltage sensor that outputs a voltage detection value of the aforementioned energy storage device, The system further comprises a control device that controls the first relay unit and the second relay unit according to the voltage detection value, The control device is If the voltage detection value is lower than the reference value, the first relay unit is controlled to a closed state and the second relay unit is controlled to a first state. The power conversion system according to claim 1, wherein if the voltage detection value is equal to or greater than the reference value, the first relay unit is controlled to be in the open state and the second relay unit is controlled to be in the second state.

3. The system further comprises a first temperature sensor that outputs a temperature detection value of the energy storage device, The power conversion system according to claim 2, wherein if the voltage detection value is lower than the reference value, the control device controls the first relay unit to the open state and the second relay unit to the second state if the temperature detection value output from the first temperature sensor is equal to or greater than a first predetermined value.

4. The vehicle further comprises a second temperature sensor that outputs a detected value of the outside air temperature of the vehicle, The power conversion system according to claim 2, wherein if the voltage detection value is lower than the reference value, the control device controls the first relay unit to the open state and the second relay unit to the second state if the temperature detection value output from the second temperature sensor is equal to or greater than a second predetermined value.

5. The system further comprises a third temperature sensor that outputs a temperature detection value of the first power converter or the second power converter, The power conversion system according to claim 2, wherein if the voltage detection value is lower than the reference value, the control device controls the first relay unit to the open state and the second relay unit to the second state if the temperature detection value output from the third temperature sensor is equal to or greater than a third predetermined value.

6. The energy storage device includes a first battery having a positive electrode connected to the first high-potential line and a second battery having a negative electrode connected to the first low-potential line. The power conversion system according to claim 1, further comprising a switching device that switches between connecting the first battery and the second battery in series or in parallel between the first high-potential line and the first low-potential line.

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