Temperature raising device

Abstract

Provided is a heating device capable of suppressing generation of unintended resonance current and more efficiently heating a secondary battery. The heating device includes: a parallel circuit including a capacitor connected in parallel to a battery to be heated; and an AC generation circuit connected to the parallel circuit, wherein when an electrostatic capacity of the capacitor is set as Cp, an inductive component of the battery is set as Ls, and a resistive component of the battery is set as Rs, the Cp satisfies formula (1), and an angular frequency ω of the AC generation circuit satisfies formula (2).

Description

Technical Field

[0001] This invention relates to a heating device. Background Technology

[0002] From the perspective of reducing vehicle exhaust emissions and CO2 reduction, there is increased attention on electric vehicles, and the use of lithium-ion secondary batteries for vehicle applications is being researched. Secondary batteries, such as lithium-ion secondary batteries, exhibit improved performance in specific temperature ranges, and there are instances where devices are installed to heat them. For example, there are techniques that connect a coil, a capacitor, and an AC generating circuit in series to the secondary battery, and allow AC current to flow through the secondary battery, thereby heating it (see, for example, Patent Document 1).

[0003] In addition, capacitors are typically placed at the input of the inverter and at the input / output of the converter. When a resonant current is intended to be generated to heat the secondary battery, it is desirable to place the secondary battery near the capacitor.

[0004] However, there are instances where resonant currents are generated unintentionally and accidentally. For example, resonance occurs during normal operation when the frequency of the resonant current is close to the operating frequency of a PCU such as an inverter. There are techniques for using reactors to suppress such resonant currents caused by capacitor and inductor components (see, for example, Patent Document 2).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 4081855

[0008] Patent Document 2: Japanese Patent Application Publication No. 2004-166358 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] In countermeasures such as adding a reactor to increase inductance or increasing the capacitance of the input capacitor, as in Patent Document 2, to address the difference between the resonant frequency and the operating frequency, the resonant frequency decreases, and the ratio of the current flowing through the secondary battery to the input current decreases, thus allowing for improvement in energy efficiency. Therefore, in conventional technologies, there are instances of unintended resonant currents or insufficient heating efficiency.

[0011] This invention was made with such considerations in mind, and one of its objectives is to provide a heating device capable of suppressing the generation of unintended resonant currents and heating a secondary battery more efficiently.

[0012] Solution for solving the problem

[0013] The heating device of the present invention adopts the following structure.

[0014] (1): A heating device according to one aspect of the present invention includes: a parallel circuit comprising a capacitor connected in parallel with a battery to be heated; and an AC generating circuit connected to the parallel circuit, wherein when the capacitance of the capacitor is set to Cp, the inductance of the battery is set to Ls, and the resistance of the battery is set to Rs, Cp satisfies equation (1), and the angular frequency ω of the AC generating circuit satisfies equation (2).

[0015]

[0016]

[0017] (2): Another aspect of the heating device of the present invention includes: a parallel circuit comprising a capacitor connected in parallel with the battery to be heated; and an AC generating circuit connected to the parallel circuit, wherein when the capacitance of the capacitor is set to Cp, the inductance component of the battery is set to Ls, and the resistance component of the battery is set to Rs, Cp satisfies equation (1), and the angular frequency ω of the AC generating circuit satisfies equation (47).

[0018]

[0019]

[0020] (3): Based on the above scheme (1) or (2), the AC generating circuit includes a generating circuit for generating ripple current, and the ripple current generated by the generating circuit flows to the parallel circuit.

[0021] (4): Based on the above (3) scheme, the generating circuit includes: a first rectifier element; a first switching element connected in parallel with the first rectifier element; a second rectifier element connected in series with the first rectifier element; and a second switching element connected in parallel with the second rectifier element.

[0022] (5): Based on the above (4) scheme, the heating device also has an amplitude adjustment circuit for adjusting the amplitude of the ripple current.

[0023] (6): Based on the above (5) scheme, the amplitude adjustment circuit adjusts the amplitude of the ripple current by changing the duty cycle between the first switching element and the second switching element.

[0024] (7): Based on the above (2) scheme, the AC generating circuit includes a generating circuit for generating ripple current, the ripple current generated by the generating circuit flows to the parallel circuit, and the heating device also has an amplitude adjustment circuit for adjusting the amplitude of the ripple current, thereby adjusting the amplitude of the ripple current by changing the frequency of the ripple current.

[0025] (8): Based on any of the above schemes (1) to (7), the battery includes a first battery and a second battery connected in series with the first battery, the capacitor includes: a first capacitor connected in parallel with the first battery; and a second capacitor connected in parallel with the second battery, the AC generating circuit includes: a first generating circuit connected to a first parallel circuit including the first battery and the first capacitor and generating a first ripple current; and a second generating circuit connected to a second parallel circuit including the second battery and the second capacitor and generating a second ripple current, the heating device further includes a phase adjustment circuit that imparts a phase difference between the first ripple current and the second ripple current.

[0026] (9): Based on any of the above schemes (1) to (8), the heating device further comprises: a first current limiting element connected between the battery and the capacitor; and a second current limiting element connected between the capacitor and the AC generating circuit, and having a rated capacity different from that of the first current limiting element.

[0027] (10): Based on any of the above (1) to (9), the heating device further includes a current cutting-off element connected between the battery and the capacitor.

[0028] (11): Based on any of the above schemes (1) to (10), the ratio of the current of the inductor component to the current input from the AC generating circuit to the parallel circuit exceeds 1.

[0029] Invention Effects

[0030] According to the above schemes (1) to (11), the generation of unintended resonant current can be suppressed, and the secondary battery can be heated more efficiently. Attached Figure Description

[0031] Figure 1 This is a diagram illustrating an example of the structure of an electric vehicle equipped with an energy storage system 1 including a heating device.

[0032] Figure 2 This is a diagram showing an example of the general structure of the heating device 60.

[0033] Figure 3This is a flowchart illustrating an example of the processing flow performed by the control unit 106 of the control device 100.

[0034] Figure 4 This is a diagram showing the structure of the heating device 60x of the comparative example.

[0035] Figure 5 This is a diagram showing the equivalent circuit structure of the heating device 60 according to the first embodiment.

[0036] Figure 6 This is a diagram showing the admittance plane.

[0037] Figure 7 This illustrates how the capacitance of the capacitor is reduced in stages during the operation of the coil L. S A graph showing the magnitude of the flowing current.

[0038] Figure 8 It is for capacitor C p The values ​​of capacitance (n = 1, 2, 5, 10) are shown in the graphs of the current waveforms for each part.

[0039] Figure 9 This is a diagram showing a comparison of the impedances of an LC series circuit and an LC parallel circuit.

[0040] Figure 10 This is a diagram comparing the current characteristics of an LC series circuit and an LC parallel circuit.

[0041] Figure 11 This is a diagram illustrating an example of the structure of the first embodiment.

[0042] Figure 12 This is a diagram illustrating an example of the AC equivalent circuit of the first embodiment.

[0043] Figure 13 It is a graph showing the shift of current amplitude in different frequency components when the AC power supply outputs a sinusoidal voltage with an amplitude of 1 [V].

[0044] Figure 14 This is a diagram showing the current waveforms of various parts when an AC voltage of 1 V with an amplitude of 200 kHz is applied from AC power source V1.

[0045] Figure 15 This diagram illustrates the state of a battery where the SOC remains unchanged when it is neither charged nor discharged.

[0046] Figure 16 This is a diagram used to illustrate the effects of the first embodiment.

[0047] Figure 17 This is a diagram illustrating an example of the structure of the second embodiment.

[0048] Figure 18 This is a diagram illustrating a more specific example of the structure of the second embodiment.

[0049] Figure 19 This is a diagram illustrating the frequency characteristics of an example impedance for a single unit.

[0050] Figure 20 This is a diagram showing a portion of the AC equivalent circuit of the second embodiment.

[0051] Figure 21 It is shown Figure 20 A diagram illustrating an example of impedance characteristics in a portion of an AC equivalent circuit.

[0052] Figure 22 This is a diagram illustrating an example of the AC equivalent circuit of the second embodiment.

[0053] Figure 23 It is a diagram showing the timing of the switch, voltage changes, and current changes.

[0054] Figure 24 It is a graph showing the discharge power after passing through, for example, a 1 [kHz] LPF (low-pass filter) and the heat generated by each part.

[0055] Figure 25 This is a diagram used to illustrate amplitude adjustment based on duty cycle.

[0056] Figure 26 This is a characteristic graph showing the THD of the ripple current amplitude, battery AC amplitude, and battery AC current.

[0057] Figure 27 This is a diagram showing various variations of the ripple current generation circuit 65.

[0058] Figure 28 This is a diagram showing various variations of the ripple current generation circuit 65.

[0059] Figure 29 This is a diagram showing various variations of the ripple current generation circuit 65.

[0060] Figure 30 This is a diagram showing various variations of the ripple current generation circuit 65.

[0061] Figure 31 This is a diagram showing various variations of the ripple current generation circuit 65.

[0062] Figure 32 This is a diagram illustrating a first variation of the second embodiment.

[0063] Figure 33This is a diagram illustrating a second variation of the second embodiment.

[0064] Figure 34 This is a diagram illustrating a third variation of the second embodiment.

[0065] Figure 35 This is a diagram (Figure 1) used to illustrate amplitude adjustment based on the frequency of the ripple current.

[0066] Figure 36 This is a diagram (Figure 2) used to illustrate amplitude adjustment based on the frequency of the ripple current.

[0067] Figure 37 This is a diagram (3) used to illustrate amplitude adjustment based on the frequency of the ripple current.

[0068] Figure 38 This is a diagram (4) used to illustrate amplitude adjustment based on the frequency of the ripple current.

[0069] Figure 39 This is a graph showing the amplitude of the battery AC current and the THD of the battery AC current when the frequency of the ripple current is varied while the duty cycle is kept at 50%.

[0070] Figure 40 This graph compares the THD of the battery AC current when the amplitude of the battery AC current is adjusted by the duty cycle and when the amplitude of the battery AC current is adjusted by the ripple frequency.

[0071] Figure 41 This is a diagram illustrating the heating efficiency and heating characteristics of the secondary battery when the amplitude of the alternating current flowing to the secondary battery is adjusted by changing the duty cycle.

[0072] Figure 42 This is a diagram illustrating an example of the structure of the third embodiment.

[0073] Figure 43 The figure shows another example of the structure of the third embodiment.

[0074] Figure 44 This is a diagram illustrating the overall voltage fluctuation of the battery and the heating characteristics of the secondary battery when the amplitude of the alternating current flowing to the secondary battery is adjusted by adjusting the ripple frequency.

[0075] Figure 45 It is in Figure 42 The diagram defines the current and voltage flowing in each part of the circuit.

[0076] Figure 46 It is a diagram showing the waveforms of current and voltage (Figure 1).

[0077] Figure 47 It is a diagram showing the waveforms of current and voltage (Figure 2).

[0078] Figure 48 It is a diagram showing the waveforms of current and voltage (Figure 3).

[0079] Figure 49 It is a diagram showing the waveforms of current and voltage (Figure 4).

[0080] Figure 50 It is a diagram showing the waveforms of current and voltage (Figure 5).

[0081] Figure 51 This is a contour plot of the heat generation (W) of a secondary battery with the duty cycle set as the vertical axis and the ripple frequency set as the horizontal axis.

[0082] Figure 52 It is a contour plot of the heating efficiency (%) with the duty cycle set as the vertical axis and the ripple frequency set as the horizontal axis.

[0083] Figure 53 It is a contour plot of the overall voltage variation (V) of the battery with the duty cycle set as the vertical axis and the ripple frequency set as the horizontal axis. Detailed Implementation

[0084] Hereinafter, embodiments of the heating device of the present invention will be described with reference to the accompanying drawings. In the following description, the heating device is described as a heating device for heating a secondary battery mounted in a vehicle, but it can also be applied to primary batteries, capacitors, fuel cells, and other devices or equipment mounted thereon (or based on this).

[0085] <First Implementation>

[0086] Figure 1 This diagram illustrates an example of the structure of an electric vehicle equipped with an energy storage system 1, including a heating device. The electric vehicle equipped with the energy storage system 1 is, for example, a two-wheeled, three-wheeled, or four-wheeled vehicle, whose drive source is an electric motor, or a combination of an electric motor and an internal combustion engine such as a diesel engine or a gasoline engine. The electric motor operates using the discharged power from a secondary battery. In the following description, as an example, we will illustrate the case of a hybrid electric vehicle that uses an engine or an electric motor as its drive source.

[0087] like Figure 1 As shown, the energy storage system 1 includes, for example, an engine 10, a motor 20, a PCU (Power Control Unit) 30, a secondary battery 40, a drive wheel 50, a heating device 60, a current sensor 80, a voltage sensor 82, and a control device 100.

[0088] Engine 10 is an internal combustion engine that outputs power by burning fuels such as gasoline. Engine 10 is, for example, a reciprocating engine equipped with cylinders and pistons, intake valves, exhaust valves, a fuel injection device, spark plugs, connecting rods, a crankshaft, etc. Alternatively, engine 10 can also be a rotary engine.

[0089] Motor 20 is, for example, a three-phase alternator. Motor 20 is, for example, an electric motor for driving. Motor 20 uses the supplied electricity to output power to the drive wheels 50. Additionally, motor 20 uses the vehicle's kinetic energy to generate electricity during vehicle deceleration. Motor 20 performs both vehicle driving and regeneration. Regeneration refers to the power generation operation performed by motor 20. It should be noted that motor 20 may also include an electric motor for power generation. This electric motor for power generation, for example, uses power output from engine 10 to generate electricity.

[0090] PCU30, for example, includes a converter 32 and a VCU (Voltage Control Unit) 34. It should be noted that the structure of integrating these components into a single PCU30 is just one example; these components can also be configured separately.

[0091] Converter 32 is, for example, an AC-DC converter. The DC side terminal of converter 32 is connected to VCU34 via DC line DL. Converter 32 converts AC power generated by motor 20 into DC power and outputs it to DC line DL, or converts DC power supplied via DC line DL into AC power and supplies it to motor 20.

[0092] VCU34 is, for example, a DC-DC converter. VCU34 boosts the power supplied from the secondary battery 40 and outputs it to the converter 32.

[0093] The secondary battery 40 is, for example, a lithium-ion battery capable of repeated charging and discharging. The secondary battery 40 is connected to the PCU 30 via power line 70. The secondary battery 40 may include multiple battery cells connected in series. The positive and negative terminals of each battery cell are connected to the PCU 30. It should be noted that the secondary battery 40 may also include a DC-AC converter, DC-DC converter, etc. (not shown).

[0094] A temperature sensor 42 for detecting the temperature of the secondary battery 40 and a current sensor for detecting the current output by the secondary battery 40 are provided in the secondary battery 40 (or the housing containing the secondary battery 40).

[0095] The heating device 60 raises the temperature of the lithium-ion battery. Details of the heating device 60 are described later.

[0096] A current sensor 80 is mounted on the power line 70. The current sensor 80 detects the current at a predetermined measurement point in the power line 70. A voltage sensor 82 detects the voltage between the terminals of the secondary battery 40. For example, the voltage sensor 82 may also include multiple voltage sensors, each detecting the voltage between the terminals of different battery cells.

[0097] The control device 100 includes, for example, an information management unit 102, an information processing unit 104, and a control unit 106. The information management unit 102, information processing unit 104, and control unit 106 are implemented by executing programs (software) stored in a storage device (not shown) using a hardware processor such as a CPU (Central Processing Unit). Furthermore, some or all of these components can be implemented using hardware (including the circuitry) such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), and GPU (Graphics Processing Unit), or through the coordinated operation of software and hardware or a hardware processor. The storage device is implemented, for example, using non-volatile storage devices such as ROM (Read Only Memory), EEPROM (Electrically Erasable and Programmable Read Only Memory), and HDD (Hard Disk Drive), as well as volatile storage devices such as RAM (Random Access Memory) and registers.

[0098] The information management unit 102 acquires the detection results of the current sensor 80, the detection results of the voltage sensor 82, the status of the secondary battery 40, and the detection results of the temperature sensor 42. The information management unit 102 manages the acquired information and the processing results of the device. For example, the information management unit 102 stores the aforementioned information in a storage device.

[0099] Based on the information obtained by the information management unit 102, the information processing unit 104 estimates the SOC (State of Charge) or other states of the secondary battery 40. Other states refer to abnormalities, operating conditions, etc. of the secondary battery 40.

[0100] Based on instructions from the control device 100, the control unit 106 controls the charging circuit (not shown) of the secondary battery 40 to charge the secondary battery 40, or controls the discharging circuit (not shown) of the secondary battery 40 and the load connected to the secondary battery 40 to discharge the secondary battery 40. The control unit 106 controls the heating device 60 based on the temperature or state of charge (SOC) of the secondary battery 40.

[0101] Figure 2 This figure shows an example of the general structure of the heating device 60. The heating device 60, for example, includes a parallel circuit C connected to the two ends of the secondary battery 40 and in parallel with an AC power supply 62 and a capacitor 64. The AC power supply 62, based on the control of the control device 100, sets the AC voltage and AC current, and supplies the set AC voltage and AC current to the capacitor 64 and the secondary battery 40.

[0102] Figure 3 This is a flowchart illustrating an example of the processing flow performed by the control unit 106 of the control device 100. First, the control unit 106 obtains the temperature of the secondary battery 40 from the temperature sensor 42 and determines whether the obtained temperature T1 is below the threshold Th1 (step S100). If the obtained temperature T1 is below the threshold Th1, the control unit 106 obtains the SOC of the secondary battery 40 estimated by the information processing unit 104 and determines whether the obtained SOC is above the threshold Th2 (step S102).

[0103] If the obtained SOC is above the threshold Th2, the control unit 106 activates the heating device 60 (step S104). Activation means supplying power to the capacitor 64 and the secondary battery 40. The method for operating the heating device 60 will be described later.

[0104] If the obtained temperature T1 is not below the threshold Th1 or the obtained SOC is not above the threshold Th2, the control unit 106 does not operate the heating device 60 (step S106). If the heating device 60 is operating, it stops operating.

[0105] As described above, the control unit 106 controls the heating device 60 based on the temperature and SOC of the secondary battery 40.

[0106] (Comparative Example)

[0107] Figure 4 This diagram illustrates the structure of the comparative example heating device 60x and the secondary battery 40. In the heating device 60x, capacitor Cs, resistor Rs, and coil Ls are connected in series, forming an LC series circuit. Figure 4In such an LC series circuit, the input current Iin, current IC, and current IL are the same. Therefore, in the heating device 60x, an AC generating circuit Vin is needed to make a current of the same amount as the current IL flow. Therefore, when it is desired to increase the current IL to increase the heat generation, the burden on the AC generating circuit Vin increases.

[0108] (Structure of the first embodiment)

[0109] In the first embodiment, a structure is formed where an additional capacitor resonates with the inductance of the secondary battery 40 at high frequencies, thereby obtaining a large alternating current with a small alternating voltage. In this first embodiment, by energizing the circuit at a frequency where the resistive component increases, a large amount of heat can be generated with a small amount of current.

[0110] Figure 5 This diagram illustrates the equivalent circuit structure of the heating device 60 and the secondary battery 40 according to the first embodiment. In the heating device 60, for example, a capacitor Cp is connected in parallel with a resistor Rs and a coil Ls, forming an LC parallel circuit. The resistor Rs and the coil Ls are imaginary components representing the characteristics of the secondary battery to be heated. Figure 5 In the case of such an LC parallel circuit, a larger current IL can be obtained with a smaller input current Iin, but this requires satisfying equation (1).

[0111]

[0112] The condition for the amplitude of current IL to increase compared to the input current Iin (=IL+IC) is that the capacitance Cp of the parallel-connected capacitor is smaller than the values ​​of Rs, which is the series resistance component of the secondary battery, and Ls, which is the series inductance component, as specified by equation (1). The ratio (i.e., the multiple) of current IL to input current Iin is the largest at the angular frequency ω shown in equation (2).

[0113]

[0114] The ratio of current IL to current Iin is expressed as shown in equation (3).

[0115]

[0116] The following is a detailed explanation of the relational expression. Figure 6 This is a diagram showing the admittance plane. The real part of the admittance is the conductance G, and the imaginary part is the capacitive susceptance B and the inductive susceptance B. When based on R... s With L s Let the admittance of the series circuit be Y. LR and will be based on Cp The admittance is set as Y C When they are, they are represented as in equations (4) and (5).

[0117]

[0118] Y C =jωC P …(5)

[0119] The synthesized admittance observed from the ripple power source is Y. LR With Y C The sum of , therefore expressed as in equation (6).

[0120]

[0121] It should be noted that equations (7) to (11) illustrate the derivation process of equations (4) to (6). Here, Z LR For R s With L s The impedance of a series circuit, Z C C p The impedance.

[0122] Z LR =R S +jωL S …(7)

[0123]

[0124]

[0125]

[0126]

[0127] Equation (12) shows the admittance Y LR The square of the absolute value of .

[0128]

[0129] Equation (13) shows the synthetic admittance Y LR +Y C The square of the absolute value of .

[0130]

[0131] Regarding admittance Y LR The square of the absolute value and the composite admittance Y LR +Y C The ratio of the squares of the absolute values ​​of is shown in equations (14) and (15).

[0132]

[0133]

[0134] Here, when 2ω is satisfied 2 CpLs 2 +CpRs 2 When ω = -2Ls = 0 is set to ω0, ω0 2 As shown in equation (16).

[0135]

[0136] According to the relationship in equation (17), in CpRs 2 When the value is greater than 2Ls, equation (18) holds true.

[0137]

[0138]

[0139] In CpRs 2 When ω = 0, equation (19) holds true.

[0140]

[0141] In CpRs 2 In the case of <2Ls, there exists ω that becomes equation (20).

[0142]

[0143] ω0 2 As shown in equation (21).

[0144]

[0145] When ω=ω0, equation (22) becomes an extreme value.

[0146]

[0147] For equation (23) to hold, CpRs needs to be made 2 <2Ls holds true.

[0148]

[0149] Therefore, the capacitor can be selected in the manner of formula (24).

[0150]

[0151] Next, the angular frequency ω 2 As shown in equation (25).

[0152]

[0153]

[0154] C P (R S 2 +ω 2 L S 2 ≤2L S

[0155]

[0156] When ω=ω0, it becomes like equation (26).

[0157]

[0158] Therefore, when ω=ω0, it becomes like equation (27).

[0159]

[0160] Here, we define equation (28).

[0161]

[0162] Capacitor C p As shown in equation (29).

[0163]

[0164] Therefore, equation (30) can be shown.

[0165]

[0166] Similarly, ω0 can also be expressed as in equation (31).

[0167]

[0168] The principle of obtaining n times the current amplitude is explained below. Figure 7 This illustrates the effect of gradually reducing the capacitance of the capacitor in coil L. S A graph showing the magnitude of the flowing current. The vertical axis represents the current [A], and the horizontal axis represents the frequency [Hz]. The resistance component R is also shown. S Set to 0.1 [Ω], and set the inductance component (coil) L S With the input current set to 796 [nH] and the input current Iin set to 1 [A], regarding the capacitor C P The relevant values ​​(n = 1, 2, 5, 10) are respectively in Figure 7 The curves I(L1), I(L2), I(L3), and I(L4) illustrate the application of current to coil L in the frequency range of tens of kHz to 1 MHz. S The magnitude of the flowing current.

[0169] Here, when defined as angular frequency ω 00 =R s / L s At that time, its value was 125.66 k rad / s, and its frequency was f. 00 For ω 00 / 2π=20[kHz]. From equation (33), it can be seen that relative to the frequency f... 00 We obtain approximately n times the current amplitude.

[0170]

[0171]

[0172]

[0173] Specifically, for n = 1, 2, 5, 10, the coil L is obtained as shown in equations (34) to (37). S The ratio relative to the input current Iin.

[0174]

[0175]

[0176]

[0177]

[0178] It should be noted that the angular frequency ω when n=1 is as shown in equation (38), and the angular frequency ω when n=2 is as shown in equation (39).

[0179]

[0180]

[0181] Figure 8 It is for capacitor C p The capacitance values ​​(n = 1, 2, 5, 10) are plotted as the current waveforms for each part. The vertical axis represents current [A], and the horizontal axis represents time [ms]. From Figure 8 The bottom image faces the top image, at C. p =C p At 00 = 79.6 [μF], the current is IL = Iin × 1.15 [A], and the frequency is f = 14.1 [kHz]. At Cp =C p 00 / 2 2 At a current of IL = 19.9 μF, the frequency is f = 37.4 kHz. At C p =C p 00 / 5 2 When the current is IL = 3.18 [μF], the frequency is f = 99.0 [kHz]. At C p =C p 00 / 10 2 When the current is IL = Iin × 10.01 A, the frequency is f = 14.1 kHz.

[0182] Here, we will explain the concept of higher frequency resonance. In applications such as HEVs (Hybrid Electric Vehicles) and EVs (Electric Vehicles), the characteristics of a secondary battery are that each individual cell has a resistive component of a few mΩ and an inductive component of tens of nH. Within the battery package as a whole, the resistive component is approximately 100 to 500 mΩ, and the inductive component is approximately 1 to 10 μH. The PCU's input capacitor is connected in parallel with the secondary battery and is approximately 100 μF or more. In such applications, there is a strong desire to achieve higher frequency resonance.

[0183] That is, let's call it R. s =100[mΩ], L s =10[uH], C p The resonant frequency under the condition of 100 [uF] is 11.3 [kHz] as shown in Equation (40), and the current multiplier is 1.15 times as shown in Equation (41), which has a smaller effect on increasing the current flowing into the secondary battery relative to the input current.

[0184]

[0185]

[0186]

[0187] Furthermore, the operating frequency of PCUs is mostly above 15 kHz, avoiding the audible range. In the case of the aforementioned resonant frequency, this becomes below the operating frequency, resulting in unintended resonance during normal operation. To suppress this resonant current, increasing the capacitance of the PCU's input capacitor or adding a reactor to increase the inductance is considered, but this lowers the resonant frequency and is therefore not preferred. In other words, when the frequency of the AC current applied to the secondary battery is low, the charging and discharging reactions inside the battery increase. Therefore, from the viewpoint of preventing overcharging and over-discharging of the secondary battery, it is necessary to suppress the current amplitude to reduce the heating effect on the secondary battery.

[0188] Therefore, it is also possible to use a secondary battery that has the characteristic that the resistance component of the secondary battery's impedance decreases as the frequency of the alternating current flowing in the secondary battery increases from a low frequency, and that the resistance component increases further away from the high frequency side where the resistance component is at its minimum, so that an alternating current of a high frequency band higher than the frequency where the resistance component is at its minimum can be introduced into the secondary battery.

[0189] Alternatively, it is preferable to divide the series-connected battery pack into multiple blocks, and use a high-frequency current generation circuit connected to each block to supply high-frequency current to the secondary batteries in each block, making the phase of the high-frequency current in each block different, thereby reducing the overall voltage fluctuation of the battery pack. This will be explained in the third embodiment.

[0190] Thus, by incorporating small-capacity capacitors of a few μF into the secondary batteries of actual HEVs and EVs as described above, resonance can be easily achieved in high frequency bands above 100 kHz.

[0191] Here, we will explain the comparison between LC series resonance and LC parallel resonance. Figure 9 This is a graph comparing the impedances of an LC series circuit and an LC parallel circuit. (Example) Figure 9 As shown in the left figure, in the case of an LC series circuit, the impedance Z = 0 at the resonant frequency. In contrast, as... Figure 9 As shown in the right figure, in the case of a parallel LC circuit, the impedance at the resonant frequency is Z = ∞ (infinity).

[0192] Figure 10 This is a graph comparing the current characteristics of an LC series circuit and an LC parallel circuit. (See figure.) Figure 10 As shown in the left figure, in the case of an LC series circuit, the impedance Z = 0 at the resonant frequency. Since it is a series circuit, the input current is the same as the current flowing in the coil (I(V²)). In contrast, as... Figure 10As shown in the right figure, in the case of a parallel LC circuit, the impedance Z = ∞ (infinity) at the resonant frequency. At the resonant frequency, the input current I(V1) hardly flows, but the currents I(C1) and I(L1) circulate between the coil and the capacitor.

[0193] Figure 11 This diagram illustrates an example of the structure of the first embodiment. If the secondary battery 40 and capacitor 64 are connected in parallel, and ripple is applied to this parallel circuit from an AC power source (also called an "AC generation circuit") 62, a large-amplitude AC current is generated between the secondary battery 40 and capacitor 64 using the small-amplitude ripple current. This large-amplitude AC current can be used to heat the secondary battery 40.

[0194] Figure 12 This is a diagram illustrating an example of the AC equivalent circuit of the first embodiment. Regarding the circuit constants, for example, the series inductance Ls1 of the secondary battery is 200 [nH], the series resistance Rs1 of the secondary battery is 100 [mΩ], the parallel capacitor C1 is 3 [uF], the equivalent series resistance Rc1 of the capacitor is 1 [mΩ], and the output resistance Rv1 of the AC power supply is 100 [mΩ].

[0195] Figure 13 This is a graph showing the shift of current amplitude across different frequency components when the AC power supply outputs a sinusoidal voltage with an amplitude of 1 [V]. For example... Figure 13 As shown, the current flowing through AC power supply V1 is I(Rv1), the current flowing through capacitor C1 is I(Rc1), and the current flowing through coil Ls1 is I(Rs1). Equation (42) shows the resonant frequency in this case.

[0196]

[0197] Figure 14 This is a diagram showing the current waveforms of various parts when an AC voltage of 1 V with an amplitude of 200 kHz is applied from AC power supply V1. It should be noted that the sign of the current is... Figure 12 In the AC equivalent circuit, downward is considered positive. According to... Figure 14 It can be seen that near the resonant frequency, an AC current I(Rs1) larger than the AC current I(Rv1) output by the AC power supply V1 flows to the secondary battery.

[0198] Figure 15 This diagram illustrates the state of a secondary battery where the State of Charge (SOC) remains unchanged when it is neither charged nor discharged. In this state, according to the law of conservation of energy, the sum of the heat generated by the resistive components of each component, W1, is approximately equal to the average electrical power output W2 from the AC power source.

[0199] Figure 16 This diagram illustrates the effects of the first embodiment. According to the first embodiment, it includes: a parallel circuit comprising a capacitor 64 connected in parallel with the secondary battery 40 to be heated; and an AC power supply 62 connected to the parallel circuit. When the capacitance of the capacitor 64 is set to Cp, the inductance of the secondary battery 40 is set to Ls, and the resistance of the secondary battery 40 is set to Rs, Cp satisfies equation (1), and the angular frequency ω of the AC generation circuit satisfies equation (2). Therefore, the AC current (IL+IC) is larger than the input current Iin. In other words, a larger IL can be obtained with a smaller Iin. Thus, the secondary battery 40 can be heated using the AC current IL flowing to it. Furthermore, resonance at a higher frequency is possible, thereby suppressing the generation of unintended resonant currents and enabling more efficient heating of the secondary battery 40.

[0200] <Second Implementation Method>

[0201] Figure 17 This diagram illustrates an example of the structure of the second embodiment. The heating device 61 of the second embodiment is connected to a secondary battery 41 having a predetermined impedance characteristic. The heating device 61 includes, for example, a capacitor 64 connected in parallel with the secondary battery 41 and a generating circuit 65 connected in parallel with the capacitor 64 and generating ripple current. The generating circuit 65 generating this ripple current is an example of an "AC generating circuit" in the technical solution. A ripple current flows between the parallel circuit consisting of the secondary battery 41 and the capacitor 64 and the generating circuit 65. Due to this ripple current, an alternating current is generated within the parallel circuit, reciprocating between the secondary battery 41 and the capacitor 64. This alternating current flows to the secondary battery 41, thereby heating the secondary battery 41.

[0202] Figure 18 This is a diagram illustrating a more specific example of the structure of the second embodiment. The ripple current generating circuit 65 includes, for example, a first rectifier element D1, a first switching element S1 connected in parallel with the first rectifier element D1, a second rectifier element D2 connected in series with the first rectifier element D1, and a second switching element S2 connected in parallel with the second rectifier element D2.

[0203] Figure 19 This is a graph illustrating the frequency characteristics of an example impedance for a single unit. Figure 19 In the diagram, characteristic curve Cv1 shows the resistance component, characteristic curve Cv2 shows the amplified resistance component, characteristic curve Cv3 shows the reactance component, and characteristic curve Cv4 shows the amplified reactance component.

[0204] Figure 20This is a diagram showing a portion of the AC equivalent circuit of the second embodiment. Regarding the circuit constants, for example, we assume that the number of individual cells in the secondary battery is 12, the parallel-connected capacitor Cp1 is 3.6 [µF], and the equivalent series resistance Rcp1 of the capacitor is 1 [mΩ]. Figure 21 It is shown Figure 20 A diagram illustrating an example of the impedance characteristics in a portion of the AC equivalent circuit. A resonant point exists near 200 kHz, where the impedance becomes maximum.

[0205] Figure 22 This is a diagram illustrating an example of the AC equivalent circuit of the second embodiment. Regarding the circuit constants, for example, let's assume that the number of individual cells in the secondary battery is 12, the battery voltage is 3.7 × 12 = 44.4 [V], the parallel-connected capacitor Cp1 is 3.6 [uF], the equivalent series resistance Rcp1 of the capacitor is 1 [mΩ], the resistance R1 is 0.1 [Ω], the coil L2 is 3 [uH], the capacitor C2 is 1 [uF], the switching frequency is 200 [kHz], and the switching duty cycle is 50%.

[0206] Figure 23 This diagram illustrates the timing of the switch, voltage changes, and current changes. The current I(R1) of the ripple current generation circuit 65 is a fraction of the battery current I(E1). Therefore, the heat generated by the switching elements S1 and S2 in the generation circuit 65 can be suppressed. The current I(E1) flows back and forth between the parallel-connected capacitor Cp1 and the secondary battery, but no switching element is included in this current path, thus simplifying the structure.

[0207] Figure 24 It is a graph showing the discharge power after passing through, for example, a 1 [kHz] LPF (low-pass filter) and the heat generated by each part. Figure 24 The following graph shows the heat generated by the battery, capacitor, and circuit. The vertical axis represents power [W], and the horizontal axis represents time [ms]. The sum of these values ​​is the "total heat generated". Figure 24 The middle diagram shows the sum of the discharge power and the heat generated. Figure 24 The diagram above shows the value obtained by subtracting the total heat generated from the discharged electricity. According to the law of conservation of energy, the sum of the heat generated by the constituent elements (secondary battery, parallel capacitor, and ripple current generating circuit) is equal to the electricity discharged by the secondary battery when averaged.

[0208] Figure 25This diagram illustrates amplitude adjustment based on duty cycle. In the heating device 61 of the second embodiment, an amplitude adjustment circuit 66 may also be included to adjust the amplitude of the ripple current. The amplitude adjustment circuit 66 may, for example, include a change circuit 67 that alters the duty cycle between the first switching element S1 and the second switching element S2. Figure 25 The left figure shows the case where the change circuit 67 sets the duty cycle between switching element S1 and switching element S2 to 50:50. Figure 25 The middle diagram shows the case where the circuit 67 changes the duty cycle between switching element S1 and switching element S2 to 30:70. Figure 25 The diagram below shows the case where the duty cycle between switching elements S1 and S2 is changed to 10:90 by the circuit 67. When the duty cycle is changed from 50:50 to 10:90, the amplitude of the ripple current changes, and consequently, the amplitude of the battery AC current decreases by d. That is, there is a predetermined relationship between the ripple current and the amplitude of the AC current flowing in the secondary battery. Figure 26 This is a characteristic graph showing the THD of the ripple current amplitude, the battery AC amplitude, and the battery AC current. The ripple current includes many harmonic components; therefore, when the fundamental wave component of the ripple current (200 kHz in this example) is extracted and compared with the fundamental wave component of the battery AC component, as shown... Figure 26 As shown, the two are proportionally related. The extraction of the fundamental wave component can be achieved using Fourier transform or similar methods. Thus, the amplitude of the alternating current flowing through the secondary battery can also be adjusted by regulating the amplitude of the ripple current.

[0209] It should be noted that, as Figure 26 As shown, the total harmonic distortion (THD) of the battery's alternating current is approximately less than 2% and is approximately sinusoidal.

[0210] Figures 27 to 31 This is a diagram illustrating various variations of the ripple current generation circuit 65. (To be continued) Figure 18 The explanation will focus on the differences in the structures shown. Figure 27 In a modified example, coil 68 is connected in series with capacitor 69, and then connected in parallel with switching element S1. Figure 28 In a modified example, coil 68 is connected in series with capacitor 69 and in parallel with rectifier element D1, and the connection point of coil 68 and capacitor 69 is connected to one end of capacitor 64. Figure 29 In a modified example, the two terminals of capacitor 64 are connected in parallel with the two terminals of rectifier element D2 via coil 68. Figure 30In a modified example, coil 68 is connected in series with capacitor 69, and then connected in parallel with switching element S2. Figure 31 In a modified example, coil 68 is connected in series with capacitor 69 and in parallel with rectifier element D2, and the connection point of coil 68 and capacitor 69 is connected to one end of capacitor 64.

[0211] Figure 32 This diagram illustrates a first variation of the second embodiment. In the structure of the second embodiment, the first variation includes, for example, a first current limiting element fs1 connected between the secondary battery 41 and the capacitor 64, and a second current limiting element fs2 connected between the capacitor 64 and the ripple current generating circuit (AC generation circuit) 65. In this first variation, the rated capacity of the first current limiting element fs1 and the rated capacity of the second current limiting element fs2 may be different. Specifically, the rated capacity of the first current limiting element fs1 may be larger than the rated capacity of the second current limiting element fs2. The first current limiting element fs1 and the second current limiting element fs2 may also be fuses or PTC (Positive Temperature Coefficient) components.

[0212] Figure 33 This diagram illustrates a second variation of the second embodiment. In the structure of the second embodiment, the second variation includes, for example, a current-cutting element SW1 connected between the negative terminal of the secondary battery 41 and the capacitor 64. The current-cutting element SW1 maintains its open state when heating of the secondary battery 41 is not required. According to the second variation, when heating of the secondary battery 41 is not required, it is possible to prevent the generation of unnecessary resonant currents due to noise interference, etc.

[0213] Figure 34 This diagram illustrates a third variation of the second embodiment. In the structure of the second embodiment, the third variation includes, for example, a current-cutting element SW2 connected between the positive terminal of the secondary battery 41 and the capacitor 64. The current-cutting element SW2 maintains its open state when heating of the secondary battery 41 is not required. According to the third variation, when heating of the secondary battery 41 is not required, it is possible to prevent the generation of unnecessary resonant currents due to noise interference, etc.

[0214] The fourth variation of the second embodiment will now be described. The amplitude adjustment circuit 66 can also adjust the amplitude of the ripple current without adjusting the duty cycle, but by adjusting the frequency of the ripple current while maintaining, for example, a 50% duty cycle. This reduces the THD of the battery AC current when the amplitude is controlled to be small.

[0215] As a performance requirement of the heating device 61, it is desirable that the current gain (the aforementioned multiplier) is greater than 1. According to... Figure 6 To make the current gain greater than 1, it is necessary to have |Y LR |>|Y LR +YC|。 That is, the current gain is greater than 1 when equation (43) is satisfied.

[0216]

[0217]

[0218]

[0219]

[0220] Here, when ω for the current gain to be 1 is set as ω1, equation (44) holds. The current gain to be the maximum ω0 is represented by equation (45). Since ω1 = ω0 × √2, the range of ω for the current gain to be greater than 1 is represented by equation (46).

[0221]

[0222]

[0223]

[0224] Figures 35-38 These are diagrams used to illustrate amplitude adjustment based on the frequency of the ripple current. These diagrams show the amplitude adjustment relative to setting the frequency of the ripple current to 200 kHz. Figure 23 The waveforms at various frequencies are obtained by varying the frequency of the ripple current while maintaining a 50% duty cycle. It can be seen that by varying the frequency from 200 kHz upwards or downwards, the amplitude of the battery AC current is suppressed.

[0225] Figure 39 This is a graph showing the amplitude of the battery AC current and the THD of the battery AC current when the frequency of the ripple current is varied while maintaining a 50% duty cycle. Additionally, Figure 40This graph compares the THD of the battery AC current when the amplitude is adjusted by the duty cycle and when it is adjusted by the ripple frequency. It shows that adjusting the ripple frequency further reduces the THD of the battery AC current compared to adjusting by the duty cycle. Furthermore, Figure 41 This diagram illustrates the heating efficiency and heating characteristics of the secondary battery when the amplitude of the alternating current flowing to the secondary battery is adjusted by changing the duty cycle. Heating efficiency is the ratio of the secondary battery's heating output to its discharge capacity. The heating output of the secondary battery is adjusted by changing the duty cycle, and the change in heating efficiency is relatively small. At the ripple frequency close to the resonant frequency, the heating efficiency is high, and the heating output of the secondary battery is also large. When the ripple frequency is far from the resonant frequency, both the heating efficiency and the heating output of the secondary battery decrease, but even when the ripple frequency is far from the resonant frequency, the change in heating efficiency caused by adjusting the duty cycle is small.

[0226] <Third Implementation Method>

[0227] In the third embodiment, the description will focus on the differences from the second embodiment. Figure 42 This diagram illustrates an example of the structure of the third embodiment. The secondary battery of the third embodiment includes, for example, a first battery 41-1 and a second battery 41-2 connected in series with the first battery 41-1. The capacitor of the third embodiment includes, for example, a first capacitor 64-1 connected in parallel with the first battery 41-1 and a second capacitor 64-2 connected in parallel with the second battery 41-2. The AC generating circuit of the third embodiment includes, for example, a first generating circuit 65-1 connected to a first parallel circuit including the first battery 41-1 and the first capacitor 64-1 and generating a first ripple current, and a second generating circuit 65-2 connected to a second parallel circuit including the second battery 41-2 and the second capacitor 64-2 and generating a second ripple current. Furthermore, the structure of the third embodiment includes a phase adjustment circuit 71 that imparts a phase difference between the first ripple current and the second ripple current.

[0228] Phase adjustment circuit 71 in such Figure 42 In the case where two battery modules (41-1, 41-2) are connected in series as in the example, a phase difference of 180 degrees is given between the first ripple current from the first generation circuit 65-1 and the second ripple current from the second generation circuit 65-2.

[0229] Figure 43This is a diagram illustrating another example of the structure of the third embodiment. In another example of the third embodiment, the secondary battery includes, for example, a first battery 41-1, a second battery 41-2 connected in series with the first battery 41-1, and a third battery 41-3 connected in series with the second battery 41-2. The capacitor in the third embodiment includes, for example, a first capacitor 64-1 connected in parallel with the first battery 41-1, a second capacitor 64-2 connected in parallel with the second battery 41-2, and a third capacitor 64-3 connected in parallel with the third battery 41-3. The AC generating circuit in the third embodiment includes, for example, a first generating circuit 65-1 connected to a first parallel circuit including the first battery 41-1 and the first capacitor 64-1 and generating a first ripple current, a second generating circuit 65-2 connected to a second parallel circuit including the second battery 41-2 and the second capacitor 64-2 and generating a second ripple current, and a third generating circuit 65-3 connected to a third parallel circuit including the third battery 41-3 and the third capacitor 64-3 and generating a third ripple current. In the structure of the third embodiment, the phase adjustment circuit 71 imparts a phase difference between the first ripple current, the second ripple current, and the third ripple current.

[0230] Phase adjustment circuit 71 in such Figure 43 In the case where three battery modules (41-1, 41-2, 41-3) are connected in series as in the example, a phase difference of, for example, 120 degrees is assigned between the first ripple current from the first generation circuit 65-1, the second ripple current from the second generation circuit 65-2, and the third ripple current from the third generation circuit 65-3.

[0231] According to the third embodiment, for a battery pack composed of multiple battery modules (41-1, 41-2, ...) connected in series, capacitors (64-1, 64-2, ...) and ripple current generation circuits (65-1, 65-2, ...) are connected in parallel with respect to each battery module, and the phase adjustment circuit 71 adjusts the phase of the multiple ripple currents, thereby suppressing the overall voltage fluctuation of the battery pack.

[0232] In the third embodiment, the first generating circuit 65-1 and the second generating circuit 65-2 can also adjust the amplitude of the ripple current by adjusting the frequency of the ripple current. Figure 44This diagram illustrates an example of the overall battery voltage fluctuation and secondary battery heating characteristics when the amplitude of the alternating current flowing to the secondary battery is adjusted by changing the ripple frequency. The overall battery voltage fluctuation is the amplitude of the voltage variation between the negative terminal of the first battery 41-1 and the positive terminal of the second battery 41-2. Here, the phase difference between the first ripple current from the first generation circuit 65-1 and the second ripple current from the second generation circuit 65-2 is set to 180 degrees. By adjusting the ripple frequency, the heating of the secondary battery is regulated. In particular, when the duty cycle is 50%, the THD is small, so the alternating current flowing to the secondary battery is close to a sine wave, and the two currents flowing with a 180-degree phase difference are suppressed, thus the overall battery voltage fluctuation is kept low. When the duty cycle is far from 50%, the voltage fluctuation increases. There is a tendency for voltage fluctuation to be suppressed when the ripple frequency is adjusted at a high frequency relative to the resonant frequency. Figure 45 That's how it was defined. Figure 42 Given the current and voltage flowing in each part, their waveforms are as follows: Figures 46-50 As shown.

[0233] in addition, Figure 51 This is a contour plot of the heat generation (W) of a secondary battery with the duty cycle set as the vertical axis and the ripple frequency set as the horizontal axis. Figure 52 This is a contour plot of the heating efficiency (%) for the same axis. Figure 53 This is an isograph of the overall voltage variation (V) of the battery along the same axis. Thus, by adjusting the duty cycle and ripple frequency, the heating effect, heating efficiency, and overall voltage variation of the secondary battery can be controlled.

[0234] It should be noted that the number of battery modules mentioned above is not limited to the example of 2 or 3.

Claims

1. A heating device, wherein, The heating device includes: A parallel circuit, comprising a capacitor connected in parallel with the battery of the object being heated; and An AC generating circuit is connected to the parallel circuit. When the capacitance of the capacitor is set to Cp, the inductance of the battery is set to Ls, and the resistance of the battery is set to Rs, The Cp satisfies equation (1), and the angular frequency ω of the AC generating circuit satisfies equation (2). 。 2. A heating device, wherein, The heating device includes: A parallel circuit, comprising a capacitor connected in parallel with the battery of the object being heated; and An AC generating circuit is connected to the parallel circuit. When the capacitance of the capacitor is set to Cp, the inductance of the battery is set to Ls, and the resistance of the battery is set to Rs, The Cp satisfies equation (1), and the angular frequency ω of the AC generating circuit satisfies equation (47). 。 3. The heating device according to claim 1 or 2, wherein, The AC generating circuit includes a ripple current generating circuit, and the ripple current generated by the generating circuit flows to the parallel circuit.

4. The heating device according to claim 3, wherein, The generation circuit includes: First rectifier element; The first switching element is connected in parallel with the first rectifier element; A second rectifier element, which is connected in series with the first rectifier element; and The second switching element is connected in parallel with the second rectifier element.

5. The heating device according to claim 4, wherein, The heating device also includes an amplitude adjustment circuit for adjusting the amplitude of the ripple current.

6. The heating device according to claim 5, wherein, The amplitude adjustment circuit adjusts the amplitude of the ripple current by changing the duty cycle between the first switching element and the second switching element.

7. The heating device according to claim 2, wherein, The AC generating circuit includes a generating circuit for generating ripple current, which flows to the parallel circuit. The heating device also includes an amplitude adjustment circuit for adjusting the amplitude of the ripple current by changing the frequency of the ripple current.

8. The heating device according to claim 1 or 2, wherein, The battery includes a first battery and a second battery connected in series with the first battery. The capacitor comprises: A first capacitor, which is connected in parallel with the first battery; and The second capacitor is connected in parallel with the second battery. The AC generating circuit includes: A first generating circuit is connected to a first parallel circuit including the first battery and the first capacitor and generates a first ripple current; and The second generating circuit is connected to a second parallel circuit including the second battery and the second capacitor, and generates a second ripple current. The heating device also includes a phase adjustment circuit that imparts a phase difference between the first ripple current and the second ripple current.

9. The heating device according to claim 1 or 2, wherein, The heating device also includes: A first current limiting element, connected between the battery and the capacitor; and A second current limiting element is connected between the capacitor and the AC generating circuit, and its rated capacity is different from that of the first current limiting element.

10. The heating device according to claim 1 or 2, wherein, The heating device also includes a current-cutting element connected between the battery and the capacitor.

11. The heating device according to claim 1 or 2, wherein, The ratio of the current in the inductive component to the current input from the AC generating circuit to the parallel circuit exceeds 1.

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