Electric system

Abstract

To flexibly respond to a change of the resonance frequency of an electric circuit including a power storage device and a capacitor and raise the temperature of the power storage device in an effective manner.SOLUTION: An electric system includes an inverter 30, an electric circuit 10, and an ECU 50. The electric circuit 10 includes a battery 12, and a capacitor 16 connected between power lines PL, NL for connecting the battery to the inverter 30. When a temperature rise start condition for starting raising the temperature of the battery 12 is satisfied, the ECU 50 executes frequency control for controlling the inverter 30 so that the current frequency of an AC current generated by the inverter 30 equals a set frequency regarding the resonance frequency of the electric circuit 10. The ECU 50 executes update processing for updating the set frequency so that the ripple of a current flowing in the electric circuit 10 increases when frequency control is executed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an electrical system.

Background Art

[0002] Chinese Patent Application Publication No. 113085659 (Patent Document 1) discloses an electric vehicle. This electric vehicle includes an inverter, a power storage device (battery), and a capacitor. The capacitor is provided between the power storage device and the inverter for current smoothing. In this electric vehicle, by passing a current through the power storage device, the power storage device is heated up due to heat generation caused by the internal resistance of the power storage device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By controlling the inverter so as to forcibly resonate an electric circuit composed of a power storage device and a capacitor, the power storage device can be effectively heated up and its temperature can be raised.

[0005] The resonance frequency of the above electric circuit may change due to changes in the characteristics of the electric circuit (for example, component variations or aging degradation). In this case, when the inverter is controlled as described above to raise the temperature of the power storage device, the amount of heat generated by the power storage device may be less than expected. As a result, the power storage device cannot be effectively heated up.

[0006] The present disclosure has been made to solve the above problems, and its object is to flexibly cope with changes in the resonance frequency of an electric circuit including a power storage device and a capacitor and effectively raise the temperature of the power storage device.

Means for Solving the Problems

[0007] The electrical system of the present disclosure includes an inverter, an electrical circuit, and a control device. The electrical circuit includes a power storage device and a capacitor connected between power line pairs that connect the power storage device to the inverter. When a temperature rise start condition for starting the temperature rise of the power storage device is satisfied, the control device executes frequency control to control the inverter so that the current frequency of the alternating current generated by the inverter becomes a set frequency related to the resonance frequency of the electrical circuit. The control device executes an update process for updating the set frequency so that the ripple of the current flowing through the electrical circuit increases during the execution of the frequency control.

[0008] The larger the ripple, the greater the heat generation amount of the power storage device. As a result, the power storage device can be effectively heated during frequency control. With the above configuration, even when the resonance frequency deviates from the set frequency due to a change in the characteristics (resonance frequency) of the electrical circuit and the heat generation amount of the power storage device during the above frequency control decreases, the set frequency is updated (corrected) so that the above ripple increases. As a result, since the current frequency changes and the ripple increases, the heat generation amount of the power storage device increases. As a result, the power storage device can be effectively heated by flexibly coping with changes in the resonance frequency of the electrical circuit.

Advantages of the Invention

[0009] According to the present disclosure, it is possible to effectively heat the power storage device by flexibly coping with changes in the resonance frequency of the electrical circuit.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0011] 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 description will not be repeated.

[0012] FIG. 1 is an overall configuration diagram of a vehicle equipped with an electric system according to this embodiment. Referring to FIG. 1, vehicle 1 is a battery electric vehicle (BEV), and includes an electric circuit 10, a monitoring device 20, and a voltage sensor 25. Vehicle 1 includes an inverter 30, a motor 40, current sensors 45u to 45w, an inlet 46, a charging relay 48, and an ECU 50.

[0013] The electric circuit 10 includes a battery 12, an SMR (System Main Relay) 14, and a capacitor 16. The battery 12 is a secondary battery such as a lithium-ion battery, and corresponds to an example of the "power storage device" of the present disclosure. The battery 12 can be connected to the capacitor 16 and the inverter 30 (both described later) through the SMR 14. The reactor component, internal resistance, and electromotive force of the battery 12 are also represented as "reactor component Lb", "internal resistance Rb", and "electromotive force Vb", respectively. The direct current output from the battery 12 is also represented as "current Ib". When the temperature Tb of the battery 12 decreases, the performance of the battery 12 deteriorates and the current Ib may decrease. In this case, vehicle 1 may not be able to travel a sufficient distance.

[0014] The electrical circuit 10 has a resonant frequency (natural frequency). This frequency depends on the reactor component Lb and the capacitance of the capacitor 16. This capacitance can decrease with the aging of the capacitor 16. At the above resonant frequency, the energy exchanged between the reactor component Lb and the capacitor 16 is maximized.

[0015] SMR14 is connected to the battery 12. When SMR14 is on, the battery 12 is connected to the capacitor 16 and the inverter 30. The capacitor 16 is connected between the power lines PL, NL (power line pair). The power lines PL, NL are provided to connect the battery 12 to the inverter 30. The capacitor 16 smoothes the current ripple (ripple of the current Ib) superimposed on the power lines PL, NL with the operation of the inverter 30.

[0016] The above frequencies and amplitudes of the ripple are represented as "ripple frequency" and "ripple amplitude La", respectively. The ripple amplitude La is an example of an index representing the magnitude of the ripple, and increases as the ripple frequency approaches the resonant frequency of the electrical circuit 10 (hereinafter, also simply referred to as "resonant frequency"). For example, when the ripple frequency matches the resonant frequency, the ripple amplitude La becomes maximum.

[0017] The monitoring device 20 is provided to monitor the state of the battery 12 and includes a current sensor and a temperature sensor (both not shown). These sensors detect the current Ib and the temperature Tb of the battery 12, respectively. The voltage sensor 25 detects the voltage VH of the capacitor 16. The voltage VH corresponds to the voltage between the power lines PL, NL.

[0018] The inverter 30 includes switching elements Q1 to Q6 and diodes D1 to D6. The switching elements Q1 to Q6 are, for example, IGBTs (insulated-gate bipolar transistors), but may also be MOSFETs (metal-oxide-semiconductor field-effect transistors). The diodes D1 to D6 are provided in antiparallel to the switching elements Q1 to Q6, respectively. The inverter 30 converts the DC current from the electric circuit 10 by switching the switching elements Q1 to Q6 to generate an AC current. The AC current is the U-phase current (current Iu), V-phase current, or W-phase current of the motor 40.

[0019] The motor 40 is a permanent magnet synchronous motor connected to the inverter 30, and can generate a driving force for the vehicle 1 to travel by receiving the AC current from the inverter 30.

[0020] Current sensors 45u, 45v, and 45w detect the U-phase current, V-phase current, and W-phase current of the motor 40, respectively. These currents are collectively referred to as "motor currents". The peak-to-peak value of each motor current is also denoted as "peak-to-peak value Vpp". The peak-to-peak value Vpp is an example of an index representing the magnitude of the motor current. The frequency of the motor current is also denoted as "motor current frequency". Since the AC fluctuation of the motor current appears as a current ripple on the DC side of the inverter 30, the motor current frequency is equal to the ripple frequency of the current Ib.

[0021] The inlet 46 can be connected to the connector 3 of the power facility 2 outside the vehicle 1. The signal PISW is transmitted from the inlet 46 to the ECU 50 (described later) as a signal representing the connection state (connected / not connected) between the inlet 46 and the connector 3. The charging relay 48 is provided in the circuit between the inlet 46 and the SMR 14, and is controlled to be in a closed state during external charging. External charging is to charge the battery 12 using the power supply power supplied from the power facility 2 through the inlet 46, the charging relay 48, and the SMR 14.

[0022] The ECU 50 includes a processor 51, a memory 52, and a communication device 53. The processor 51 is, for example, a CPU (Central Processing Unit) and executes various arithmetic processes. The memory 52 includes a ROM (Read Only Memory) and a RAM (Random Access Memory) (both not shown). The ROM stores programs and various data to be executed by the processor. The data includes information indicating the mileage and years of use of the vehicle 1. The communication device 53 can receive a request RQ from the user terminal 5. The user terminal 5 is, for example, a smartphone and can install an app for remotely operating a door (not shown) of the vehicle 1. The request RQ is transmitted from the user terminal 5 to the vehicle 1 when a user operation for unlocking the door is performed by the user using the app. The request RQ may be automatically transmitted when the distance between the user terminal 5 and the vehicle 1 becomes less than a predetermined distance.

[0023] The ECU 50 controls the inverter 30. Specifically, the ECU 50 generates drive signals S1 to S6 according to the detection results of the monitoring device 20, the voltage sensor 25, and the current sensors 45u, 45v, 45w, and thereby controls the on / off states of the switching elements Q1 to Q6. The drive signal Sk (1 ≤ k ≤ 6) is a signal for driving the switching element Qk and is input to the gate of the switching element Qk (1 ≤ k ≤ 6).

[0024] When a temperature increase start condition for starting the temperature increase of the battery 12 is satisfied, the ECU 50 increases the temperature of the battery 12 by executing frequency control. This frequency control is to control the inverter 30 so that the motor current frequency becomes a set frequency (hereinafter, also simply referred to as "set frequency") with respect to the resonance frequency. From the viewpoint of increasing the temperature of the battery 12, it is preferable that the set frequency is the resonance frequency itself in the following description, but the battery 12 can also be effectively heated even at a frequency near the resonance frequency (for example, a frequency within a predetermined range from the resonance frequency). The temperature increase start condition is, for example, that the connector 3 is connected (inserted) to the inlet 46 and the temperature Tb is lower than a predetermined threshold temperature. The ECU 50 stores in the memory 52 a counter value representing the number of times the temperature increase start condition is satisfied.

[0025] According to the above frequency control, since the motor current frequency approaches (including matching) the resonance frequency, the ripple frequency also approaches the resonance frequency, and thereby the ripple amplitude La increases. As a result, the power loss due to the internal resistance Rb increases, the heat generation amount of the battery 12 increases, and the battery 12 is warmed from the inside. Therefore, it is possible to avoid a decrease in the performance of the battery 12 due to a decrease in the temperature Tb. Hereinafter, the above frequency control is also referred to as "ripple temperature increase control". In the embodiment, the ripple temperature increase control is executed so that the torque of the motor 40 becomes zero (for example, so that the d-axis current of the motor 40 is constant and the q-axis current becomes zero). The set frequency corresponds to the target frequency of the motor current frequency during the ripple temperature increase control.

[0026] The ECU 50 calculates an amplification factor af of the ripple amplitude La with respect to the peak-to-peak value Vpp according to the detection results of the monitoring device 20 and the current sensors 45u, 45v, 45w. The closer the ripple frequency (motor current frequency) is to the resonance frequency, the higher the amplification factor af. For example, when the ripple frequency matches the resonance frequency, the amplification factor af is the highest, and the heat generation amount of the battery 12 during temperature increase becomes the maximum. The amplification factor af will be described in detail later. The electric circuit 10, the inverter 30, and the ECU 50 are an example of the "electrical system" of the present disclosure.

[0027] Figure 2 is a diagram showing the relationship between the heat generation amount of the battery 12 and the ripple frequency during ripple heating control. This relationship is based on the premise that the peak-to-peak value Vpp of the motor current is constant.

[0028] Referring to FIG. 2, line 105 represents the relationship between the heat generation amount and the ripple frequency estimated at the design stage of the vehicle 1. This relationship is determined in advance by pre-evaluation or the like. Line 110 represents the relationship between the heat generation amount and the ripple frequency actually measured after the manufacture of the vehicle 1. This relationship is derived at a predetermined timing after the manufacture of the vehicle 1 (in this example, when the vehicle 1 shifts to its maintenance mode during maintenance at a dealership before delivery to the customer). The shift to the maintenance mode is a procedure performed by an operator such as a dealership mechanic before maintaining the vehicle 1. Line 110 does not coincide with line 105 due to variations in the performance of the components of the electric circuit 10 (in this example, the capacitance of the capacitor 16).

[0029] The reference frequency fr0 is the frequency at which the heat generation amount becomes maximum (Wr0) on line 105 and corresponds to the resonance frequency at the design stage. The reference frequency fr0 is determined at the design stage according to a calculation formula including the design values of the reactor component Lb and the capacitance of the capacitor 16 as parameters in this example, and is stored in the memory 52 as the default value of the aforementioned set frequency. The reference frequency fr1 is the frequency at which the heat generation amount becomes maximum (Wr1) on line 110 and corresponds to, for example, the actual resonance frequency during maintenance of the vehicle 1.

[0030] Thus, since the resonance frequency can change due to component variations of the electric circuit 10 or the like, the actual resonance frequency does not necessarily coincide with the reference frequency fr0 at the design stage. For example, when the ripple heating control is executed with the set frequency as the reference frequency fr0 (heat generation amount: Wra), since the set frequency deviates from the actual resonance frequency (reference frequency fr1), there is a possibility that the battery 12 cannot be effectively heated. As a result, the ripple heating control may be prolonged.

[0031] Therefore, in the present embodiment, the ECU 50 has a configuration for dealing with such problems. Specifically, when executing the ripple temperature rise control, the ECU 50 executes an update process of updating the set frequency so that the ripple of the current flowing through the electric circuit 10 increases (for example, so that the ripple amplitude La increases). In this example, it is preferable that the ECU 50 updates the set frequency from the reference frequency fr0 to the reference frequency fr1.

[0032] The larger the ripple amplitude La is, the larger the heat generation amount of the battery 12 is. As a result, the battery 12 can be effectively heated during the ripple temperature rise control. With the above configuration, the set frequency is updated (corrected) so that the current ripple of the electric circuit 10 during the ripple temperature rise control increases. As a result, the motor current frequency (ripple frequency) during the ripple temperature rise control changes and the ripple amplitude La increases, so that the heat generation amount of the battery 12 increases from Wra to (for example, Wr1). As a result, it is possible to flexibly cope with the change in the resonance frequency and effectively heat the battery 12. Therefore, a situation where the ripple temperature rise control lasts for a long time can be avoided.

[0033] Although it is preferable that the ECU 50 updates the set frequency from the reference frequency fr0 to the reference frequency fr1, the set frequency may be updated to a frequency higher than the reference frequency fr1 and lower than the reference frequency fr0. Even in this case, the heat generation amount can be increased from Wra.

[0034] In the present embodiment, the update process is executed so that the amplification factor af of the ripple amplitude La with respect to the peak-to-peak value Vpp increases.

[0035] As described above, the higher the amplification factor af is, the closer the motor current frequency (ripple frequency) is to the resonance frequency. Therefore, according to the above update process, the ripple frequency approaches the resonance frequency and the ripple amplitude La increases. As a result, the battery 12 can be effectively heated.

[0036] FIG. 3 is a diagram for explaining an example of a method for updating a set frequency. Referring to FIG. 3, the frequency range RNG1 is predetermined by experiments or the like as a range of values that the motor current frequency can take. In this example, it is the range from fa to fb.

[0037] First, the ECU 50 scans (sweeps) the motor current frequency within the frequency range RNG1 by controlling the inverter 30. Specifically, the ECU 50 controls the inverter 30 so that each phase current flows through the motor 40 while changing the motor current frequency at intervals of Δf within the frequency range RNG1.

[0038] By scanning the motor current frequency as described above, the ECU 50 executes a first search process for searching for a reference frequency fr1, which is the motor current frequency at which the amplification factor af is maximized in the frequency range RNG1. Specifically, the ECU 50 calculates the amplification factor af at each of a plurality of frequencies (f1,... fn) within the frequency range RNG1, derives the correspondence relationship (line 205) between the calculation results and these frequencies, and then searches for the reference frequency fr1 from it. The ECU 50 stores the above correspondence relationship in the memory 52 as the resonance characteristics of the electric circuit 10 at the initial stage of the vehicle 1 (for example, during maintenance at a dealer before delivery). The reference amplification factor af1 corresponds to the reference frequency fr1 in line 205. Specifically, it is the amplification factor af that is maximized at the reference frequency fr1 in line 205.

[0039] According to the result of the first search process, the ECU 50 executes a first update process for updating the set frequency at the time of executing the ripple temperature rise control from the reference frequency fr0 (FIG. 2) to the reference frequency fr1 as the above-described update process. The first search process and the first update process are executed, for example, when these processes are instructed during the maintenance mode of the vehicle 1.

[0040] When the motor current frequency is the resonance frequency, the amplification factor af is maximum and the ripple amplitude La is maximum. Therefore, the reference frequency fr1 corresponds to the actual resonance frequency of the electrical circuit 10 during the maintenance of the vehicle 1. According to the first search process and the first update process, when the set frequency deviates from the actual resonance frequency due to component variations etc. of the electrical circuit 10 (for example, when the set frequency is the reference frequency fr0 even though the actual resonance frequency is the reference frequency fr1), the reference frequency fr1 is surely searched as the resonance frequency, and the set frequency is updated to this frequency. Thereby, surely, the amplification factor af becomes maximum and the ripple amplitude La becomes maximum during the ripple temperature rise control. Therefore, the power storage device can surely be heated effectively.

[0041] After the set frequency is updated to the reference frequency fr1 by the first update process, if the capacitance etc. of the capacitor 16 decreases due to the aging deterioration of the electrical circuit 10, the resonance frequency may further change. Therefore, if the set frequency remains at the reference frequency fr1 for a long period, there is a possibility that the resonance frequency further changes from the reference frequency fr1 and the ripple temperature rise control cannot be effectively executed. Therefore, it is preferable that the set frequency is further updated at a specific timing after the first update process.

[0042] After the set frequency is once updated by the first update process, the resonance frequency is unlikely to change greatly from the reference frequency fr1 in a short period. Therefore, in many cases, it is not so far from the reference frequency fr1. Therefore, if the first search process within the frequency range RNG1 is always executed for updating the set frequency, the time required for searching the resonance frequency may increase unnecessarily.

[0043] FIG. 4 is a diagram for explaining a method of searching the resonance frequency in a short time and updating the set frequency. Referring to FIG. 4(A), the line 205 is the same as that shown in FIG. 3.

[0044] In the embodiment, after the first search process and the first update process, the ECU 50 executes a second search process and a second update process. The second search process is a process of searching for a reference frequency fr2, which is a motor current frequency at which the amplification factor af is maximized in the frequency range RNG2, by scanning the motor current frequency within the frequency range RNG2. The frequency range RNG2 is a frequency range near the reference frequency fr1, specifically, a range that includes the reference frequency fr1 and is narrower than the frequency range RNG1. Since the frequency range RNG2 is narrower than the frequency range RNG1, the execution time of the second search process is shorter than the execution time of the first search process (Figure 3).

[0045] In the second search process, the ECU 50 calculates the amplification factor af for each of a plurality of frequencies within the frequency range RNG2, derives a correspondence relationship (line 210) between the calculation results and these frequencies, and searches for the reference frequency fr2 therefrom. The ECU 50 stores the above correspondence relationship in the memory 52 as the resonance characteristics after the deterioration of the electric circuit 10. The reference amplification factor af2 corresponds to the reference frequency fr2 in the line 210, specifically, the amplification factor af that is maximized at the reference frequency fr2 in the line 210. The reference amplification factor af2 is lower than the reference amplification factor af1 by Δaf. The line 211 represents the actual resonance characteristics after the deterioration of the electric circuit 10 within the frequency range RNG1.

[0046] After the second search process, the ECU 50 executes the second update process of updating the set frequency from the reference frequency fr1 to the reference frequency fr2 so that the ripple amplitude La during the ripple temperature rise control increases (becomes maximum in this example) as the above-described update process.

[0047] According to the second search process and the second update process, after the set frequency is updated to the reference frequency fr1 by the first update process, the reference frequency fr2 is searched within the frequency range RNG2, and the set frequency is updated to the frequency. Thereby, even when the resonance frequency changes from the reference frequency fr1 due to the aging deterioration of the electric circuit 10 after the first update process, the reference frequency fr2 is accurately searched as the resonance frequency after the aging deterioration of the electric circuit 10 in a short time, and the battery 12 can be appropriately heated by the ripple heating control.

[0048] Thereafter, the ECU 50 periodically executes the search for the resonance frequency and the update of the set frequency. For example, when the above counter value reaches the threshold value after the second search process and the second update process, the ECU 50 searches for the resonance frequency again and updates the set frequency to the searched frequency. Thereby, even when the resonance frequency changes from the reference frequency fr2 to another frequency, it is possible to flexibly cope with the change in the resonance frequency and effectively heat the battery 12 during the ripple heating control. The above threshold value can be set as appropriate.

[0049] Hereinafter, the specific procedure of the second search process will be described. Also in this example, it is assumed that while the resonance frequency has changed from the reference frequency fr1 to the reference frequency fr2 due to the aging deterioration of the electric circuit 10 after the first update process, the set frequency remains the reference frequency fr1.

[0050] Referring to FIG. 4(B), the ECU 50 first controls the inverter 30 to change the motor current frequency from the reference frequency fr1 (= f(j)). The ECU 50, for example, decreases the motor current frequency from f(j) to f(j - 1). The ECU 50 determines that the amplification factor af has increased from af1a, and thereby further decreases the motor current frequency from f(j - 1) to f(j - 2). Thereafter, the ECU 50 repeats the same process and continues to decrease the motor current frequency by the interval Δf as long as the amplification factor af increases.

[0051] Incidentally, the ECU 50 may first increase the motor current frequency from f(j) to f(j + 1). In this case, the ECU 50 determines that the amplification factor af has decreased from af1a, and thereby reverses the frequency change direction and changes the motor current frequency from f(j + 1) to f(j - 1). The subsequent processing is as described above.

[0052] Referring to FIG. 4(C), the ECU 50 decreases the motor current frequency from f(k + 1) (<f(j - 2))) to f(k) and determines that the amplification factor af has increased. Next, the ECU 50 decreases the motor current frequency from f(k) to f(k - 1) and determines that the amplification factor af has decreased. Thereby, the ECU 50 determines that the positive / negative of the change rate of the amplification factor af has reversed before and after f(k). The ECU 50 determines, according to the result of this determination, that the amplification factor af is maximum at f(k), and determines that the resonance frequency after the aging deterioration of the electric circuit 10 is f(k). The ECU 50 ends the second search process with f(k) determined as the resonance frequency as the reference frequency fr2. Note that the method of the resonance frequency search process executed after the second search process is also the same as the methods in FIGS. 4(B) and 4(C).

[0053] In the above, although the interval between each frequency is assumed to be equal to the interval Δf (FIG. 3), it may be different from the interval Δf.

[0054] FIG. 5 is a flowchart showing the processing executed by the ECU 50. Hereinafter, the steps are abbreviated as "S".

[0055] Referring to FIG. 5(A), this flowchart starts when the mode of the vehicle 1 shifts to the maintenance mode. The ECU 50 scans the motor current frequency within the frequency range RNG1 (S105), thereby searching for the reference frequency fr1 (S115). The ECU 50 updates the set frequency during the ripple temperature rise control from the reference frequency fr0 to the reference frequency fr1 (S120). The ECU 50 initializes the aforementioned counter value (S125). Thereafter, the processing ends.

[0056] Referring to FIG. 5(B), this flowchart starts after S125 when the temperature increase start condition is satisfied. The ECU 50 increments the counter value (S205) and determines whether the counter value has reached a threshold (S210). If the counter value has not yet reached the threshold (NO in S210), the process proceeds to S235. If the counter value has reached the threshold (YES in S210), the process proceeds to S215.

[0057] The ECU 50 scans the motor current frequency within a frequency range near the current set frequency (S215). This frequency range is, for example, the frequency range RNG2. The ECU 50 searches for the motor current frequency at which the amplification factor af is maximized within the above-mentioned near frequency range as the current resonance frequency (S220). This frequency is, for example, the reference frequency fr2. The ECU 50 updates the set frequency to the searched frequency (S225) and initializes the counter value (S230). Thereafter, the ECU 50 executes ripple temperature increase control (S235). Then, the process ends.

[0058] As described above, according to the embodiment, even when the resonance frequency deviates from the current set frequency due to a change in the characteristics of the electric circuit 10 (for example, component variation or aging deterioration), the set frequency is updated (corrected) so that the amplification factor af increases. As a result, since the ripple frequency approaches the resonance frequency, the ripple amplitude La increases and the heat generation amount of the battery 12 increases. Consequently, it is possible to effectively heat the battery 12 by flexibly coping with the change in the resonance frequency. Therefore, it is possible to avoid a situation where the ripple temperature increase control continues for a long time.

[0059] [Modification Example 1] FIG. 6 is a diagram for explaining the overall configuration of the vehicle in this Modification Example 1. Referring to FIG. 6, the vehicle 1A is different from the vehicle 1 (FIG. 1) in that it includes an electric circuit 10A instead of the electric circuit 10, but is basically the same as the vehicle 1 in other respects. The electric circuit 10A is different from the electric circuit 10 in that it further includes a circuit element 17.

[0060] Circuit element 17 is electrically connected in parallel to capacitor 16 and includes sub-capacitor 18 and switches 19a, 19b (switch section 19). Only one of these switches may be provided. Sub-capacitor 18 is provided to compensate for excessive capacitance reduction during degradation of capacitor 16. Switches 19a, 19b can switch the connection state (connection / non-connection) between capacitor 16 and sub-capacitor 18.

[0061] FIG. 7 is a diagram for explaining a method of searching for a resonance frequency and updating a set frequency in this first modification. Referring to FIG. 7, this figure is the same as FIG. 4(A) except that line 220 (dashed line) and line 221 are added.

[0062] In this first modification, as long as the magnitude of the difference (for example, Δaf in FIG. 4(A)) between the amplification factor af (in this example, reference amplification factor af2) at the resonance frequency searched this time and the amplification factor af (in this example, reference amplification factor af1) at the resonance frequency searched last time is less than the threshold value, switches 19a, 19b are open. As a result, sub-capacitor 18 is electrically disconnected from capacitor 16. Δaf is related to the capacitance reduction amount of capacitor 16. In this example, it is assumed that the larger Δaf is, the larger the capacitance reduction amount is. The relationship between Δaf and the capacitance reduction amount is determined, for example, by a prior evaluation test as a map and stored in memory 52.

[0063] When Δaf is equal to or greater than the threshold value, the resonance characteristics (line 211) of electric circuit 10 have changed significantly from the characteristics in the initial stage (line 205), for example, due to excessive capacitance reduction of capacitor 16. In this case, even if the set frequency during ripple temperature rise control is updated from reference frequency fr1 to reference frequency fr2 (raising the amplification factor af from af1a to af2) and the heat generation amount of battery 12 becomes maximum, the ripple amplitude La may be small and the heat generation amount of battery 12 may be insufficient. As a result, there is a possibility that battery 12 cannot be heated sufficiently as in the case before the capacitance reduction of capacitor 16 (when the set frequency was reference frequency fr1 in the initial stage).

[0064] The ECU 50 has a configuration for dealing with such problems. Specifically, after the second search process and the second update process, the ECU 50 uses the above-mentioned map to determine the amount of capacitance reduction of the capacitor 16 according to Δaf. When the amount of capacitance reduction is equal to or greater than the reference amount, the ECU 50 controls the switches 19a and 19b to be in the closed state so that the sub-capacitor 18 is electrically connected to the capacitor 16 (switch switching control). Note that when the amount of capacitance reduction is less than the reference amount, the switch switching control is not executed.

[0065] After the switch switching control, the ECU 50 executes a third search process. The third search process is a process of searching for a reference frequency fr3, which is the motor current frequency at which the amplification factor af is maximized in the frequency range RNG3, by scanning the motor current frequency within the frequency range RNG3. The frequency range RNG3 includes the reference frequency fr2 and is a range narrower than the frequency range RNG1 but different from the frequency range RNG2. The method for scanning the motor current frequency is the same as the method described in FIG. 4, whereby the relationship (line 220) between the motor current frequency and the amplification factor af within the frequency range RNG3 is derived. In this modification 1, the reference amplification factor af3, which is the amplification factor af that is maximized at the reference frequency fr3 in the third search process, is higher than the reference amplification factor af2. The ECU 50 executes a third update process of updating the set frequency from the reference frequency fr2 to the reference frequency fr3 as the above-mentioned update process.

[0066] According to the switch switching control, the connection state between the sub-capacitor 18 and the capacitor 16 is switched so that the sub-capacitor 18 is connected in parallel with the capacitor 16. As a result, the resonance characteristics (the relationship between the ripple frequency and the amplification factor af) of the electric circuit 10 change as if the capacitor 16 were replaced by a capacitor having a combined capacitance of the capacitance of the capacitor 16 and the capacitance of the sub-capacitor 18 (as if the capacitance of the capacitor 16 were restored by only the capacitance of the sub-capacitor 18). In this example, the resonance characteristics change from line 210 to line 221. Further, according to the third search process and the third update process, the reference frequency fr3 is searched, and the set frequency is updated to this frequency. As a result, the amplification factor af during the ripple temperature rise control increases from the reference amplification factor af2 to the reference amplification factor af3, and the ripple amplitude La increases. As a result, it is possible to avoid a situation where the battery 12 cannot be effectively heated due to an excessive capacitance decrease of the capacitor 16.

[0067] [Modification Example 2] The electric circuit 10A may include a plurality of circuit elements 17. Each circuit element 17 is provided in parallel with the capacitor 16. The capacitance of the sub-capacitor 18 of each circuit element 17 is smaller than the capacitance of the capacitor 16. The ECU 50 can connect one or more of the plurality of sub-capacitors 18 in parallel to the capacitor 16 by switching the switch unit 19 of each circuit element 17. With such a configuration, the ECU 50 can appropriately change the number of sub-capacitors connected in parallel to the capacitor 16 among the plurality of sub-capacitors 18, and thereby can finely adjust the combined capacitance of the sub-capacitor and the capacitor 16.

[0068] [Other Modification Examples] Although the search process of the resonance frequency after the first update process (for example, the second search process) is assumed to be executed when the counter value reaches the threshold value, for example, it may be executed when the traveling distance of the vehicle 1 reaches a predetermined threshold distance or when the usage year of the vehicle 1 reaches a predetermined threshold year.

[0069] The temperature rise start condition may be that the communication device 53 receives a request RQ from the user terminal 5, or that the key-off boarding of the vehicle 1 is performed. By setting the temperature rise start condition in this way, after appropriately raising the temperature of the battery 12 while the vehicle 1 is parked (external charging is not being executed), the vehicle 1 can start running.

[0070] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0071] 1, 1A Vehicle, 10, 10A Electric Circuit, 12 Battery, 16 Capacitor, 18 Sub-capacitor, 19a, 19b Switch, 30 Inverter, 40 Motor, 50 ECU.

Claims

1. An inverter, an electrical circuit including a power storage device and a capacitor connected between the power storage device and a pair of power lines connecting the power storage device to the inverter, and a control device that executes frequency control to control the inverter such that the current frequency of the alternating current generated by the inverter becomes a set frequency related to the resonance frequency of the electrical circuit when a temperature rise start condition for starting the temperature rise of the power storage device is satisfied. The control device executes an update process for updating the set frequency so that the ripple of the current flowing through the electrical circuit increases during execution of the frequency control. The electrical system.

2. The update process is executed such that an amplification factor of the ripple with respect to the magnitude of the alternating current increases. The electrical system according to claim 1.

3. The control device executes a first search process for searching for a first reference frequency that is the current frequency at which the amplification factor is maximized in the first frequency range by scanning the current frequency within a predetermined first frequency range, and the update process includes a first update process for updating the set frequency to the first reference frequency. The electrical system according to claim 2.

4. After the first update process, the control device executes a second search process for searching for a second reference frequency that is the current frequency at which the amplification factor is maximized in the second frequency range by scanning the current frequency within a second frequency range that includes the first reference frequency and is narrower than the first frequency range, and the update process further includes a second update process for updating the set frequency from the first reference frequency to the second reference frequency. The electrical system according to claim 3.

5. The electrical system further includes a circuit element electrically connected in parallel to the capacitor, wherein the circuit element includes a sub-capacitor and a switch for switching the connection state between the capacitor and the sub-capacitor, wherein the amplification factor includes a first reference amplification factor that is maximized at the first reference frequency in the first search process and a second reference amplification factor that is maximized at the second reference frequency in the second search process, and the second reference amplification factor is lower than the first reference amplification factor, and the control device determines the amount of capacitance reduction of the capacitor according to the magnitude of the difference between the second reference amplification factor and the first reference amplification factor. When the amount of capacity reduction is equal to or greater than the reference amount, the switch is controlled so that the sub-capacitor is connected to the capacitor. After the sub-capacitor is connected to the capacitor, the control device executes a third search process of searching for a third reference frequency, which is the current frequency at which the amplification factor is maximized in the third frequency range, by scanning the current frequency within a third frequency range that includes the second reference frequency and is narrower than the first frequency range. The electrical system according to claim 4, wherein the update process further includes a third update process of updating the set frequency from the second reference frequency to the third reference frequency.

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