JP7159811B2 - converter - Google Patents

Description

This specification discloses a converter in which a first converter circuit and a second converter circuit are connected in parallel to a battery, and power obtained by boosting the output power of the battery is supplied to an electric device.

In order to keep the current flowing through the switching elements of the converter within an allowable range, or to reduce the ripple current generated when the switching elements are controlled, the first converter circuit and the second converter circuit are connected in parallel to operate the converter. may be configured. Each converter circuit has a reactor that generates heat during operation, and it is necessary to prevent the reactor from overheating.

An overheating prevention technique is disclosed in Patent Document 1, and the converter includes a current sensor that detects the current flowing through the reactor and a control section that controls the switching element. The control unit estimates the temperature of the reactor based on the current detected by the current sensor, and when the estimated temperature of the reactor becomes higher than the reference value, shortens the conduction time of the switching element to suppress the current flowing through the reactor. to prevent overheating.

Japanese Patent Application Laid-Open No. 2016-041012

When applying the technique of Patent Document 1 to a converter in which a first converter circuit and a second converter circuit are connected in parallel, it is necessary to apply an overheat prevention technique to each converter circuit, which increases manufacturing costs. This specification discloses a technique for preventing overheating of a converter in which a first converter circuit and a second converter circuit are connected in parallel with a simpler configuration.

In the converter disclosed in this specification, the first converter circuit and the second converter circuit are connected in parallel to the battery, and each converter circuit has a reactor. That is, the converter includes a first converter circuit having a first reactor, and a second converter circuit having a second reactor and connected in parallel to the first converter with respect to the battery. In addition to the above, the converter disclosed in this specification includes a temperature sensor that detects the temperature of the first reactor, and a controller. The first reactor and the second reactor are arranged with the cooler therebetween, and are adjusted so that the temperature of the first reactor is higher than the temperature of the second reactor. The controller uses the detected value of the temperature sensor and the reference value to adjust the magnitude of the current flowing through the first reactor and the second reactor.

The relationship in which the temperature of the first reactor is higher than the temperature of the second reactor can be obtained by various methods. For example, it is possible to use the relationship that the amount of heat generated by the first reactor is greater than or equal to the amount of heat generated by the second reactor when the configurations of the first reactor and the second reactor are changed and the same current value is used. Alternatively, control may be performed so that the current change speed of the first reactor is faster than the current change speed of the second reactor to obtain a relationship in which the temperature of the first reactor is higher than the temperature of the second reactor.

According to the above configuration, the magnitude of the current flowing through the first reactor is adjusted based on the temperature of the first reactor, and overheating of the first reactor can be prevented. The magnitude of the current flowing through the second reactor is adjusted similarly to the first reactor. The temperature of the second reactor is lower than the temperature of the first reactor, and if adjusted in the same manner as the first reactor, overheating of the second reactor can also be prevented. As a result, one overheat prevention technique can protect both the first reactor and the second reactor from overheating.

1 is a block diagram of an electric power system of an electric vehicle equipped with a converter of an embodiment; FIG. It is a figure which shows the relationship between the reactor of the converter of an Example, a temperature sensor, and a cooler. 4 is a graph showing the relationship between an integrated value of current and a temperature rise value;

(First embodiment)
The converter 30 of the first embodiment will be described with reference to FIGS. 1 and 2. FIG. Converter 30 is mounted on electric vehicle 10 such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle. Converter 30 is mounted in power converter 20 that constitutes a power control unit of electric vehicle 10 .

A block diagram of the power system of the electric vehicle 10 will be described with reference to FIG. Electric vehicle 10 includes battery 12 , power converter 20 , and motor 94 . Power converter 20 includes converter 30 , inverter 90 , and smoothing capacitor 92 . Converter 30 boosts the DC power output from battery 12 and outputs the boosted DC power to inverter 90 . The circuit configuration of converter 30 will be described later in detail. The inverter 90 converts the DC power output from the converter 30 into AC power based on a drive signal supplied from a higher control unit (not shown), and outputs the converted AC power to the motor 94 . Since the circuit configuration of the inverter 90 is well known, a detailed circuit diagram and description thereof will be omitted. Motor 94 is rotated by the AC power output from inverter 90 . As a result, the power of the motor 94 is transmitted to the wheels of the electric vehicle 10, and the electric vehicle 10 runs.

Motor 94 may function as a generator. For example, when the driver depresses the brake pedal while the electric vehicle 10 is running, the motor 94 is rotated by the inertial energy of the electric vehicle 10 to generate electricity. Electric power generated by motor 94 is converted into DC power by inverter 90 , stepped down by converter 30 , and then charged into battery 12 .

A smoothing capacitor 92 is connected in parallel between the converter 30 and the inverter 90 . Smoothing capacitor 92 smoothes the current and voltage flowing between converter 30 and inverter 90 .

Next, converter 30 will be described. Converter 30 is a bi-directional DC-DC converter. Hereinafter, the terminal on the battery 12 side (low voltage side) is referred to as input terminal 32 , and the terminal on the inverter 90 side (high voltage side) is referred to as output terminal 34 . Further, the positive and negative terminals of the input terminal 32 are called an input positive terminal 32a and an input negative terminal 32b, respectively. Also, the positive and negative terminals of the output terminal 34 are referred to as an output positive terminal 34a and an output negative terminal 34b, respectively.

The converter 30 includes a first converter circuit 40 , a second converter circuit 60 , a filter capacitor 80 and a controller 82 . The first converter circuit 40 and the second converter circuit 60 are connected in parallel to the battery 12 between the common inputs 32a, 32b and the common outputs 34a, 34b. The first converter circuit 40 and the second converter circuit 60 have a function of boosting the DC power output from the battery 12 . Also, the first converter circuit 40 and the second converter circuit 60 have a function of stepping down the DC power output from the inverter 90 . A filter capacitor 80 is connected between the input positive terminal 32a and the input negative terminal 32b. Filter capacitor 80 smoothes the current and voltage flowing between converter 30 and battery 12 .

The first converter circuit 40 includes switching elements 42 and 46 , diodes 44 and 48 , a first reactor 50 , a current sensor 52 and a temperature sensor 54 . The switching elements 42 and 46 are, for example, insulated gate bipolar transistors (ie IGBTs) or metal oxide semiconductor field effect transistors (ie MOSFETs). The switching elements 42, 46 are connected in series. One end of the switching element 42 is connected to the output positive terminal 34a. The other end of the switching element 46 is connected to the input negative terminal 32b and the output negative terminal 34b.

A diode 44 is connected in antiparallel to the switching element 42 . A diode 48 is connected in anti-parallel to the switching element 46 . A first reactor 50 is connected to the midpoint between the switching elements 42 and 46 . When current flows through the first reactor 50, the first reactor 50 generates heat. The other end of the first reactor 50 is connected to the current sensor 52 . The other end of the current sensor 52 is connected to the input positive terminal 32a. Current sensor 52 detects the current flowing through first reactor 50 .

Temperature sensor 54 detects the temperature of first reactor 50 . The temperature sensor 54 is, for example, a diode whose resistance value changes according to the ambient temperature. The temperature of first reactor 50 is detected by detecting the resistance value of temperature sensor 54 .

The second converter circuit 60 includes switching elements 62 and 66 , diodes 64 and 68 , a second reactor 70 and a current sensor 72 . The circuit configuration of the switching elements 62 and 66, the diodes 64 and 68, the second reactor 70, and the current sensor 72 is the switching elements 42 and 46, the diodes 44 and 48, and the first reactor 50 of the first converter circuit 40. , and the circuit configuration of the current sensor 52 is the same.

When current flows through the second reactor 70, the second reactor 70 generates heat. The thermal characteristics of second reactor 70 are different from the thermal characteristics of first reactor 50 . When the rate of change of the supplied current is the same, the amount of heat generated by the second reactor 70 is smaller than the amount of heat generated by the first reactor 50 . For example, the number of turns of the winding of the second reactor 70 is less than the number of turns of the winding of the first reactor 50 .

The controller 82 is communicatively connected to the switching elements 42 , 46 , 62 , 66 , the temperature sensor 54 and the current sensors 52 , 72 . In FIG. 1, the connection lines between the control unit 82 and the switching elements 42, 46, 62, 66, the connection lines between the control unit 82 and the temperature sensor 54, and the connection lines between the control unit 82 and the current sensors 52, 72 are arranged at short pitches. is illustrated by the dashed line of Control unit 82 acquires the temperature of first reactor 50 from temperature sensor 54 . Also, the control unit 82 detects the current flowing through the first reactor 50 from the current sensor 52 . Also, the control unit 82 detects the current flowing through the second reactor 70 from the current sensor 72 . Also, the control unit 82 controls the switching elements 42 , 46 , 62 , 66 . That is, the control unit 82 switches the switching elements 42, 46, 62, 66 between the ON state and the OFF state. Also, the control unit 82 controls the switching elements 42 and 62 at the same time, and controls the switching elements 46 and 66 at the same time.

Next, the step-up operation and step-down operation of converter 30 will be described. The switching elements 46, 66 are involved in the boost operation. When a driving signal having a predetermined duty ratio is supplied from the control unit 82 to the switching elements 46 and 66, the switching elements 46 and 66 are switched between an ON state and an OFF state at the predetermined duty ratio. As a result, the DC voltage output from the battery 12 is boosted.

In step-down operation, switching elements 42, 62 are involved. When a driving signal having a predetermined duty ratio is supplied from the control unit 82 to the switching elements 42 and 62, the switching elements 42 and 62 are switched between an ON state and an OFF state at the predetermined duty ratio. As a result, the DC voltage output from inverter 90 is stepped down.

Next, the hardware configuration of power converter 20 will be described with reference to FIG. Power converter 20 further includes cooler 100 . Cooler 100 is, for example, a case or the like that accommodates power converter 20 . Cooler 100 is made from a metallic material. As shown in FIG. 2, the cooler 100 has a channel 102 inside. In FIG. 2, only hatches showing the cross section of the cooler 100 are shown. A liquid coolant supplied from a coolant supply device (not shown) passes through the flow path 102 . Note that, in a modified example, cooling air may pass through the flow path 102 .

The first reactor 50 is mounted on the cooler 100 via a heat radiation sheet (not shown). The heat of the first reactor 50 is transferred to the liquid refrigerant passing through the flow path 102 via the cooler 100 . Thereby, the first reactor 50 is cooled. The second reactor 70 is mounted on the cooler 100 via a heat radiation sheet (not shown) on the surface opposite to the surface on which the first reactor 50 is mounted. First reactor 50 and second reactor 70 are arranged with cooler 100 interposed therebetween. The heat of the second reactor 70 is transferred to the liquid refrigerant passing through the flow path 102 via the cooler 100 . Thereby, the second reactor 70 is cooled. Also, the cooling efficiency of the second reactor 70 by the cooler 100 is equivalent to the cooling efficiency of the first reactor 50 by the cooler 100 .

A temperature sensor 54 is mounted on the first reactor 50 . Note that, in a modified example, the temperature sensor 54 may be arranged inside the first reactor 50 .

Next, a method of adjusting currents flowing through the first reactor 50 and the second reactor 70 using the temperature detected by the temperature sensor 54 will be described. The control unit 82 supplies drive signals to the switching elements 42 , 46 , 62 , 66 . The control unit 82 simultaneously switches the switching elements 42 and 62 to the ON state and simultaneously switches them to the OFF state. In addition, the control unit 82 simultaneously switches the switching elements 46 and 66 to the ON state and simultaneously switches them to the OFF state. In this case, the amount of heat generated by the first reactor 50 is greater than that of the second reactor 70 due to the difference in thermal characteristics between the first reactor 50 and the second reactor 70 . Therefore, the temperature of first reactor 50 becomes higher than the temperature of second reactor 70 .

The control unit 82 continues to acquire the temperature of the first reactor 50 detected by the temperature sensor 54 . The control unit 82 continues to compare the obtained temperature of the first reactor 50 with the reference value. The reference value is a temperature at which overheating of the first reactor 50 can be prevented, and is specified in advance by experiments. The reference value is stored in the control section 82 in advance.

When the acquired temperature of the first reactor 50 is lower than the reference value, the control unit 82 continues to supply normal drive signals to the switching elements 42 , 46 , 62 , 66 . On the other hand, when the obtained temperature of the first reactor 50 is higher than the reference value, the control unit 82 controls the switching elements 42, 46, 62, 66 to reduce the currents flowing through the first reactor 50 and the second reactor 70. adjusts the duty ratio of the drive signal supplied to the In this case, the drive signal supplied to the inverter 90 and the torque of the motor 94 are adjusted by the host controller.

(effect)
This prevents the first reactor 50 from overheating. The temperature of second reactor 70 is lower than the temperature of first reactor 50 . Therefore, if the first reactor 50 does not overheat, the second reactor 70 will not overheat either. As a result, by commonly controlling the first reactor 50 and the second reactor 70 using the temperature of the first reactor 50 detected by one temperature sensor 54, the temperature of the first reactor 50 and the second reactor 70 Protect both from overheating. This simplifies overheat protection techniques.

In the above description, the temperature of the first reactor 50 is higher than the temperature of the second reactor 70 by changing the configurations of the first reactor 50 and the second reactor 70 . However, it is also possible to obtain a relationship in which the temperature of the first reactor 50 is higher than the temperature of the second reactor 70 while the configurations of the first reactor 50 and the second reactor 70 are the same. In this case, (duty ratio of the second reactor 70)=α×(duty ratio of the first reactor 50). Here, α is a constant less than one. Using this relationship, it is also possible to obtain the relationship that the temperature of the first reactor 50 is higher than the temperature of the second reactor 70 . In this case, if the duty ratio of the first reactor 50 is lowered, the duty ratio of the second reactor 70 is also lowered accordingly. As a result, by commonly controlling both the first reactor 50 and the second reactor 70 using one temperature sensor 54, both the first reactor 50 and the second reactor 70 can be protected from overheating. can.

Also, by using the relationship that the gate resistance of the switching elements 42 and 46 is higher than the gate resistance of the switching elements 62 and 66, the relationship that the temperature of the first reactor 50 is higher than the temperature of the second reactor 70 can be obtained. good. Since the switching speed changes depending on the gate resistance, a relationship in which the temperature of the first reactor 50 is higher than the temperature of the second reactor 70 can be obtained. In this case also, one temperature sensor 54 is used to commonly control both the first reactor 50 and the second reactor 70, thereby protecting both the first reactor 50 and the second reactor 70 from overheating. can be done.

(Second embodiment)
In the first embodiment, it is necessary to adjust the relationship such that the temperature of the first reactor 50 is higher than the temperature of the second reactor 70 . The second embodiment is effective when this relationship is not guaranteed. The configuration of FIG. 1 is also common to the second embodiment. That is, only the first converter circuit 40 has the temperature sensor 54 . Temperature sensor 54 detects the temperature of first reactor 50 . The temperature of second reactor 70 is not detected.

The controller 82 uses the temperature of the first reactor 50 detected by the temperature sensor 54 to adjust the duty ratio of the drive signal supplied to the switching elements 42 and 46 . In this case, the drive signal supplied to the inverter 90 and the torque of the motor 94 are adjusted by the host controller.

Further, the control unit 82 uses the temperature of the first reactor 50 detected by the temperature sensor 54 to calculate the temperature of the second reactor 70, and then adjusts the duty ratio of the drive signal supplied to the switching elements 62 and 66. adjust. First, a method for calculating the temperature of the second reactor 70 will be described with reference to FIG. The control unit 82 calculates the temperature of the second reactor 70 using a data map showing the relationship between the current integrated value and the temperature rise value, the first correction coefficient k1, and the second correction coefficient k2. A data map showing the relationship between the current integrated value and the temperature rise value is illustrated as relationship X1 in FIG. Hereinafter, the data map showing the relationship between the current integrated value and the temperature rise value may be referred to as relationship X1. The relationship X1 is specified in advance by experiments. In the relationship X1, the current integrated value and the temperature rise value are in a linear relationship. In the relationship X1, the larger the integrated value of the current, the larger the temperature rise value. Relationship X1 is stored in advance in control unit 82 .

The first correction coefficient k1 is a correction coefficient corresponding to the thermal resistance deterioration rate. The thermal resistance deterioration rate represents the degree to which the heat dissipation of the reactor has changed from the initial state. The first correction coefficient k1 is calculated by the following equation.
First correction coefficient k1=αβD _L1
Here, α is the ratio of the current flowing through the first reactor 50 and the current flowing through the second reactor 70 . β is the ratio of the rate of deterioration of the thermal resistance of the second reactor 70 to the rate of deterioration of the thermal resistance of the first reactor 50 . β is previously specified by experiments. β is stored in the control unit 82 in advance.

_DL1 is the thermal resistance deterioration rate of the first reactor 50; _DL1 is calculated from a data map showing the relationship between the integrated value of current and the thermal resistance deterioration rate of first reactor 50 and the integrated value of current flowing through first reactor 50 . A data map indicating the relationship between the current integrated value and the thermal resistance deterioration rate of the first reactor 50 is specified in advance by experiments. A data map showing the relationship between the current integrated value and the thermal resistance deterioration rate of the first reactor 50 is stored in advance in the controller 82 .

The second correction coefficient k2 is a correction coefficient corresponding to the initial temperature of the second reactor 70 and is calculated by the following equation.
Second correction coefficient k2=T _L1a +(T _L1b -T _L1a )γ
Here, _TL1a is the temperature of the first reactor 50 immediately after the ignition switch of the electric vehicle 10 is turned on. _TL1b is the temperature of the first reactor 50 immediately before the ignition switch of the electric vehicle 10 is turned off. T _L1a and T _L1b are detected by temperature sensor 54 .

γ is a correction coefficient calculated from the ratio of the time constant of the second reactor 70 to the time constant of the first reactor 50 . The time constants of the first reactor 50 and the second reactor 70 are specified in advance by experiments. γ is stored in advance in the control unit 82 .

Next, a method of calculating the temperature of the second reactor 70 using a data map showing the relationship between the integrated current value and the upper temperature value, the first correction coefficient k1, and the second correction coefficient k2 will be described. . First, the control unit 82 multiplies the slope of the straight line representing the relationship X1 by the first correction coefficient k1 to convert the relationship X1 into the relationship X2. In FIG. 3 the relationship X2 is illustrated by a dashed line. Next, a second correction coefficient k2 is added to the initial value of the straight line representing the relationship X2 to convert the relationship X2 into the relationship X3. In FIG. 3 the relationship X3 is illustrated by a dashed line. Next, the control unit 82 calculates the temperature rise value of the second reactor 70 using the integrated value of the current flowing through the second reactor 70 and the relationship X3. Next, the temperature of the second reactor 70 is calculated by adding the temperature rise value of the second reactor 70 to the temperature of the first reactor 50 detected by the temperature sensor 54 . In the above, instead of calculating the temperature of the second reactor 70 using the magnitude of the current detected by the current sensors 52 and 72, the magnitude of the current detected by the current sensors 52 and 72 and the temperature sensor 54 The temperature of the second reactor 70 is calculated using the temperature of the first reactor 50 detected by . Therefore, the calculation accuracy of the temperature of the second reactor 70 is high.

Next, a method of adjusting the duty ratio of the drive signal supplied to the switching elements 62 and 66 will be described. The controller 82 adjusts the duty ratio of the drive signal supplied to the switching elements 62 and 66 based on the calculated temperature of the second reactor 70 and the reference value. Specifically, when the estimated temperature of the second reactor 70 is higher than the reference temperature, the control unit 82 adjusts the duty ratio of the drive signal supplied to the switching elements 62 and 66 so that the current flowing through the second reactor 70 is to be smaller. In this case, the drive signal supplied to the inverter 90 and the torque of the motor 94 are adjusted by the host controller.

(effect)
If the second converter circuit 60 does not have a temperature sensor, the temperature of the second reactor 70 can be accurately calculated using the single temperature sensor 54 of the first converter circuit 40 . As a result, one temperature sensor 54 protects both the first reactor 50 and the second reactor 70 from overheating. This simplifies the overheat protection technique.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or in the drawings exhibit technical utility either singly or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technique illustrated in this specification or drawings can simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

Reference Signs List 10: Electric vehicle 12: Battery 20: Power converter 30: Converter 32: Input end 34: Output end 40: First converter circuits 42, 46, 62, 66: Switching elements 44, 48, 64, 68: Diode 50: First reactors 52, 72: Current sensor 54: Temperature sensor 60: Second converter circuit 70: Second reactor 80: Filter capacitor 82: Control unit 90: Inverter 92: Smoothing capacitor 94: Motor 100: Cooler 102: Current road

Claims (1)

a first converter circuit including a first reactor;
a second converter circuit including a second reactor and connected in parallel to the first converter circuit with respect to the battery;
a temperature sensor that detects the temperature of the first reactor;
Equipped with a control unit,
The first reactor and the second reactor are arranged with a cooler interposed therebetween,
The temperature of the first reactor is higher than the temperature of the second reactor,
The control unit adjusts the magnitude of the current flowing through the first reactor and the second reactor using the detection value and the reference value of the temperature sensor, and the detection value of the temperature sensor is higher than the reference value. A converter that reduces the current flowing through the first reactor and the second reactor when the current is high .

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