JP5962051B2 - Voltage converter - Google Patents

Description

  The present invention relates to a technical field of a voltage conversion device mounted on, for example, a vehicle.

  2. Description of the Related Art In recent years, as an environmentally-friendly vehicle, an electric vehicle that is mounted with a power storage device (for example, a secondary battery or a capacitor) and travels using driving force generated from electric power stored in the power storage device has attracted attention. Examples of the electric vehicle include an electric vehicle, a hybrid vehicle, and a fuel cell vehicle.

  In these electric vehicles, a motor generator for generating driving force for traveling by receiving electric power from the power storage device when starting or accelerating, and generating electric power by regenerative braking during braking to store electric energy in the power storage device May be provided. Thus, in order to control a motor generator according to a driving | running | working state, an inverter is mounted in an electric vehicle.

  In such a vehicle, a voltage conversion device (converter) may be provided between the power storage device and the inverter in order to stably supply power used by the inverter that varies depending on the vehicle state. With this converter, the inverter input voltage can be made higher than the output voltage of the power storage device to increase the output of the motor and reduce the motor current at the same output, thereby reducing the size and cost of the inverter and motor. Can be achieved.

  The converter is provided with a current sensor for detecting the current value of the current flowing through each part. As the current sensor, for example, a shunt resistor as described in Patent Document 1 can be used. The current value detected by the shunt resistor is output to, for example, a converter control circuit and used for various controls.

  On the other hand, in a converter, for example, it is known that a reactor causes magnetic saturation in a region where a current is relatively high, and an inductance value changes. The change in the inductance value of the reactor greatly affects the operation of the converter. For this reason, for example, Patent Document 2 proposes a technique for determining whether or not time saturation has occurred by obtaining an inductance from a temporal change of the reactor current and a reactor voltage.

JP 2011-038964 A JP 2008-099518 A

  When the shunt resistor described in Patent Document 1 described above is used for the converter, an error corresponding to the time variation of the inductance component and the current is superimposed on the detected value. In order to reduce such an error, for example, a method using a filter circuit can be considered. However, since the effective range of the filter is limited, the current value can be accurately detected in the entire region used for boost control. It is difficult.

  In order to expand the application area of the filter circuit, for example, a method of switching the filter characteristics based on the time change of the reactor current is conceivable. However, magnetic saturation as described in Patent Document 2 described above can be considered. When this occurs, it becomes difficult to calculate the time variation of the reactor current using the inductance value of the reactor, and the filter characteristics cannot be switched properly, resulting in an ineffective filtering process. There is a risk that.

  As described above, there are various practical technical problems in current detection using a shunt resistor.

  This invention is made | formed in view of the problem mentioned above, and makes it a subject to provide the voltage converter which can detect a reactor current correctly using shunt resistance.

In order to solve the above-described problem, a voltage converter according to the present invention detects a reactor, a first switching element and a second switching element connected in series to the reactor, and a first current flowing through the first switching element. The first shunt resistor, the second shunt resistor for detecting the second current flowing in the second switching element, and the detected values of the first current and the second current are each filtered with a predetermined filter characteristic. A filter unit; a current combining unit configured to combine the detected value of the first current and the detected value of the second current subjected to the filtering process into a combined current; and a plurality of different current values of the combined current by detecting the timing, the time variation calculation means for calculating a time change in the current value of the composite current, time variation of the current value is greater than a predetermined threshold value If the filter characteristic of the filter means is changed to the first filter characteristic, and the time change of the current value is less than the predetermined threshold, the filter characteristic of the filter means is different from the first filter characteristic. Filter characteristic changing means for changing to the second filter characteristic .

  The voltage conversion device according to the present invention is a converter mounted on a vehicle, for example, and includes a first switching element and a second switching element that are respectively connected in series to a reactor. As the first switching element and the second switching element, for example, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, or a power bipolar transistor can be used.

  For example, a diode is connected in parallel to each of the first switching element and the second switching element to form a first arm and a second arm, respectively. In other words, the first switching element forms a first arm, and the switching operation of the first arm can be switched on and off. Similarly, the second switching element forms a second arm, and on / off of driving in the second arm can be switched by the switching operation.

  At the time of operation of the voltage converter according to the present invention, for example, switching control signals for switching on and off of each of the first switching element and the second switching element are generated. Specifically, for example, a duty command signal corresponding to the duty ratio of the first switching element and the second switching element and a carrier signal corresponding to the switching frequency of the first switching element and the second switching element are compared with each other. A switching control signal is generated. The generated switching control signal is supplied to the first switching element and the second switching element, whereby the driving of the first arm and the second arm of the voltage converter is controlled.

  The voltage converter according to the present invention includes a first shunt resistor that detects a first current flowing through the first switching element, and a second shunt resistor that detects a second current flowing through the second switching element. . The first shunt resistor and the second shunt resistor are provided, for example, so as to be connected in series with each switching element.

  The current value of the first current detected by the first shunt resistor and the current value of the second current detected by the second shunt resistor are configured as part of a processing unit such as an ECU (Electronic Controlled Unit), for example. In the filter means, a filtering process is performed with a predetermined filter characteristic. Note that the “filtering process” here is for reducing the influence of errors superimposed on the detected values of the first current and the detected values of the second current (for example, errors according to the time variation of the inductance component and the current). For example, a band-pass filter process that allows only a specific frequency band to pass therethrough. In addition, the filter means according to the present invention has at least two filter characteristics, and is configured to be able to change the filter characteristics in accordance with instructions from a filter characteristic changing means described later. However, when different filter means are provided for the current value of the first current and the current value of the second current, only one of them needs to be able to change the filter characteristics.

  The current value of the first current and the current value of the second current that have been subjected to the filtering process are set as a combined current by a current combining unit configured as part of a processing unit such as the ECU described above, for example. Therefore, the combined current is a combination of currents on the first arm side where the first switching element is provided and the second arm side where the second switching element is provided. That is, it can be said that the combined current is a current very close to the current flowing through the reactor connected in series with each of the first switching element and the second switching element (hereinafter, “the combined current” is referred to as “reactor current”). ”).

  Here, in the present invention, in particular, the current value of the combined current is detected (sampled) at a plurality of different timings by a time change calculation unit configured as a part of the processing unit such as the ECU described above. Then, the time change calculating means calculates the time change of the current value of the reactor current (that is, the time differential value of the current value) based on the difference between the current values detected at a plurality of different timings.

  In order to appropriately calculate the time change of the reactor current, it is preferable that the current value sampling by the time change calculating means is performed a plurality of times in a relatively short period. Specifically, it is preferable that the current value is sampled at least twice so as not to cross the on / off switching timing of the first switching element and the second switching element.

  When the time change of the reactor current is calculated, the filter characteristic changing unit performs a filter characteristic changing process based on the calculated time change of the reactor current. For example, the filter characteristic changing means performs a filtering process with one filter characteristic when the time change of the reactor current is equal to or less than a predetermined threshold value, and when the time change of the reactor current exceeds a predetermined threshold value, The filter means is controlled to perform the filtering process with the filter characteristics.

  As described above, if the filter characteristic in the filter means is changed based on the time change of the reactor current, the application area of the filtering process that can obtain an effect only in a certain area can be substantially expanded. It becomes possible to detect the reactor current with high accuracy in all the areas to be used.

  Of the first arm including the first switching element and the second arm including the second switching element, the current flowing through the first arm may vary greatly, but the current flowing through the second arm may vary substantially. There is no. Therefore, as long as the filter characteristic corresponding to the first arm (that is, the current value detected by the first shunt resistor) is changed, it corresponds to the second arm (that is, the current value detected by the second shunt resistor). Appropriate filtering can be performed without changing the filter characteristics. Therefore, if only the filter characteristic corresponding to the detected value of the first current in the filter means is changed based on the portion corresponding to the current flowing to the first arm side in the time variation of the reactor current, the efficiency is improved. Thus, the filter characteristics can be changed.

  The time change of the reactor current can also be estimated based on, for example, the voltage values before and after boosting in the voltage converter, the inductance value of the reactor, and the like. However, when magnetic saturation occurs in the reactor, the inductance value changes greatly, and it becomes difficult to accurately estimate the temporal change in the reactor current.

  However, in the present invention, as described above, the temporal change of the reactor current is estimated from the current value detected using the shunt resistor. That is, the time change of the reactor current is calculated from a value that does not depend on the inductance value. Therefore, it is possible to accurately detect the time change of the reactor current without being affected by magnetic saturation.

  As described above, according to the voltage converter of the present invention, it is possible to accurately detect the reactor current using the shunt resistor.

  The effect | action and other gain of this invention are clarified from the form for implementing invention demonstrated below.

1 is a schematic diagram illustrating an overall configuration of a vehicle on which a voltage conversion device according to an embodiment is mounted. It is a block diagram which shows the structure of ECU. It is a circuit diagram which shows the structure of a filter circuit. It is a flowchart which shows operation | movement of the voltage converter which concerns on embodiment. It is a timing chart which shows the sampling timing of a reactor current. It is a graph which shows an example of filter characteristic A. 6 is a graph showing an example of filter characteristics B. It is a graph which shows the fall of the inductance by magnetic saturation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the overall configuration of a vehicle on which the voltage conversion device according to the present embodiment is mounted will be described with reference to FIG. FIG. 1 is a schematic diagram showing the overall configuration of a vehicle on which the voltage conversion device according to this embodiment is mounted.

  In FIG. 1, a vehicle 100 on which the voltage conversion device according to the present embodiment is mounted is configured as a hybrid vehicle using an engine 40 and motor generators MG1 and MG2 as power sources. However, the configuration of the vehicle 100 is not limited to this, and the vehicle 100 can be applied to a vehicle (for example, an electric vehicle or a fuel cell vehicle) that can be driven by electric power from the power storage device. Moreover, although this embodiment demonstrates the structure by which a voltage converter is mounted in the vehicle 100, if it is an apparatus driven by an alternating current motor other than a vehicle, it is applicable.

  The vehicle 100 includes a DC voltage generator 20, a load device 45, a smoothing capacitor C2, and an ECU 30.

  DC voltage generation unit 20 includes a power storage device 28, system relays SR1 and SR2, a smoothing capacitor C1, and a converter 12.

  The power storage device 28 includes a secondary battery such as nickel hydride or lithium ion, and a power storage device such as an electric double layer capacitor. The DC voltage VL output from the power storage device 28 and the input / output DC current IB are detected by the voltage sensor 10 and the current sensor 11, respectively. Voltage sensor 10 and current sensor 11 output detected values of detected DC voltage VL and DC current IB to ECU 30.

  System relay SR1 is connected between the positive terminal of power storage device 28 and power line PL1, and system relay SR2 is connected between the negative terminal of power storage device 28 and ground line NL. System relays SR <b> 1 and SR <b> 2 are controlled by a signal SE from ECU 30, and switch between supply and interruption of power from power storage device 28 to converter 12.

  Converter 12 is an example of the “voltage converter” of the present invention, and includes a reactor L1, switching elements Q1, Q2, diodes D1, D2, and shunt resistors R1, R2.

  The switching elements Q1 and Q2 are examples of the “first switching element” and the “second switching element” of the present invention, and are connected in series between the power line PL2 and the ground line NL. Switching elements Q1 and Q2 are controlled by a switching control signal PWC from ECU 30.

  As the switching elements Q1 and Q2, for example, an IGBT, a power MOS transistor, a power bipolar transistor, or the like can be used. Anti-parallel diodes D1 and D2 are arranged for switching elements Q1 and Q2. Reactor L1 is provided between a connection node of switching elements Q1 and Q2 and power line PL1. Smoothing capacitor C2 is connected between power line PL2 and ground line NL.

  The shunt resistors R1 and R2 are examples of the “first shunt resistor” and the “second shunt resistor” of the present invention, and are provided as corresponding to the switching elements Q1 and Q2 as resistance elements for detecting current. It has been. That is, the shunt resistor R1 is configured to be able to detect the current Vr1 that flows on the switching element Q1 side. The shunt resistor R2 is configured to be able to detect a current Vr2 flowing to the switching element Q2. The currents Vr1 and Vr2 detected at the shunt resistors R1 and R2 are output to the ECU 30, respectively.

  Load device 45 includes an inverter 23, motor generators MG <b> 1 and MG <b> 2, an engine 40, a power split mechanism 41, and drive wheels 42. Inverter 23 includes an inverter 14 for driving motor generator MG1 and an inverter 22 for driving motor generator MG2. As shown in FIG. 1, it is not essential to provide two sets of inverters and motor generators. For example, only one set of inverter 14 and motor generator MG1 or inverter 22 and motor generator MG2 may be provided.

  Motor generators MG1 and MG2 receive AC power supplied from inverter 23 and generate rotational driving force for vehicle propulsion. Motor generators MG1 and MG2 receive rotational force from the outside, generate AC power according to a regenerative torque command from ECU 30, and generate regenerative braking force in vehicle 100.

  Motor generators MG1 and MG2 are also coupled to engine 40 via power split mechanism 41. Then, the driving force generated by engine 40 and the driving force generated by motor generators MG1, MG2 are controlled to have an optimal ratio. Alternatively, either one of motor generators MG1 and MG2 may function exclusively as an electric motor, and the other motor generator may function exclusively as a generator. In the present embodiment, it is assumed that motor generator MG1 functions as a generator driven by engine 40, and motor generator MG2 functions as an electric motor that drives drive wheels 42.

  For the power split mechanism 41, for example, a planetary gear mechanism (planetary gear) is used in order to distribute the power of the engine 40 to both the drive wheels 42 and the motor generator MG1.

  Inverter 14 receives the boosted voltage from converter 12, and drives motor generator MG1 to start engine 40, for example. Inverter 14 also outputs regenerative power generated by motor generator MG <b> 1 by mechanical power transmitted from engine 40 to converter 12. At this time, converter 12 is controlled by ECU 30 to operate as a step-down circuit.

  Inverter 14 is provided in parallel between power line PL2 and ground line NL, and includes U-phase upper and lower arms 15, V-phase upper and lower arms 16, and W-phase upper and lower arms 17. Each phase upper and lower arm is composed of a switching element connected in series between power line PL2 and ground line NL. For example, the U-phase upper and lower arms 15 are composed of switching elements Q3 and Q4, the V-phase upper and lower arms 16 are composed of switching elements Q5 and Q6, and the W-phase upper and lower arms 17 are composed of switching elements Q7 and Q8. Antiparallel diodes D3 to D8 are connected to switching elements Q3 to Q8, respectively. Switching elements Q3 to Q8 are controlled by a switching control signal PWI from ECU 30.

  For example, motor generator MG1 is a three-phase permanent magnet type synchronous motor, and one end of three coils of U, V, and W phases is commonly connected to a neutral point. Further, the other end of each phase coil is connected to a connection node of switching elements of upper and lower arms 15 to 17 for each phase.

  Inverter 22 is connected to converter 12 in parallel with inverter 14.

  Inverter 22 converts the DC voltage output from converter 12 into three-phase AC and outputs the same to motor generator MG2 that drives drive wheels. Inverter 22 also outputs regenerative power generated by motor generator MG2 to converter 12 along with regenerative braking. At this time, converter 12 is controlled by ECU 30 to operate as a step-down circuit. Although the internal configuration of the inverter 22 is not shown, it is the same as that of the inverter 14 and will not be described in detail.

  Converter 12 is basically controlled such that switching elements Q1 and Q2 are turned on and off in a complementary manner in each switching period. During the boosting operation, converter 12 boosts DC voltage VL supplied from power storage device 28 to DC voltage VH (this DC voltage corresponding to the input voltage to inverter 14 is also referred to as “system voltage” hereinafter). This boosting operation is performed by supplying the electromagnetic energy accumulated in the reactor L1 during the ON period of the switching element Q2 to the power line PL2 via the switching element Q1 and the antiparallel diode D1.

  Converter 12 steps down DC voltage VH to DC voltage VL during the step-down operation. This step-down operation is performed by supplying the electromagnetic energy accumulated in the reactor L1 during the ON period of the switching element Q1 to the ground line NL via the switching element Q2 and the antiparallel diode D2.

  The voltage conversion ratio (the ratio of VH and VL) in these step-up and step-down operations is controlled by the on-period ratio (duty ratio) of the switching elements Q1 and Q2 in the switching period. If switching elements Q1 and Q2 are fixed to ON and OFF, respectively, VH = VL (voltage conversion ratio = 1.0) can be obtained.

  Smoothing capacitor C <b> 2 smoothes the DC voltage from converter 12 and supplies the smoothed DC voltage to inverter 23. The voltage sensor 13 detects the voltage across the smoothing capacitor C2, that is, the system voltage VH, and outputs the detected value to the ECU 30.

  When the torque command value of motor generator MG1 is positive (TR1> 0), inverter 14 responds to switching control signal PWI1 from ECU 30 when a DC voltage is supplied from smoothing capacitor C2, and switching elements Q3-Q8 The motor generator MG1 is driven so as to convert a DC voltage into an AC voltage and output a positive torque by the switching operation. Further, when the torque command value of motor generator MG1 is zero (TR1 = 0), inverter 14 converts the DC voltage into the AC voltage and the torque becomes zero by the switching operation in response to switching control signal PWI1. In this manner, motor generator MG1 is driven. Thus, motor generator MG1 is driven to generate zero or positive torque designated by torque command value TR1.

  Furthermore, during regenerative braking of vehicle 100, torque command value TR1 of motor generator MG1 is set negative (TR1 <0). In this case, inverter 14 converts the AC voltage generated by motor generator MG1 into a DC voltage by a switching operation in response to switching control signal PWI1, and converts the converted DC voltage (system voltage) to smoothing capacitor C2. To the converter 12. The regenerative braking here refers to braking with regenerative power generation when the driver operating the electric vehicle performs a footbrake operation, or regenerative braking by turning off the accelerator pedal while driving, although the footbrake is not operated. This includes decelerating (or stopping acceleration) the vehicle while generating electricity.

  Similarly, inverter 22 receives switching control signal PWI2 from ECU 30 corresponding to the torque command value of motor generator MG2, receives a switching control signal PWI2, and converts the DC voltage into an AC voltage to a predetermined torque by a switching operation. The motor generator MG2 is driven so that

  Current sensors 24 and 25 detect motor currents MCRT1 and MCRT2 flowing through motor generators MG1 and MG2, and output the detected motor currents to ECU 30. Since the sum of the instantaneous values of the currents of the U-phase, V-phase, and W-phase is zero, the current sensors 24 and 25 are arranged to detect the motor current for two phases as shown in FIG. All you need is enough.

  Rotation angle sensors (resolvers) 26 and 27 detect rotation angles θ1 and θ2 of motor generators MG1 and MG2, and send the detected rotation angles θ1 and θ2 to ECU 30. ECU 30 can calculate rotational speeds MRN1, MRN2 and angular speeds ω1, ω2 (rad / s) of motor generators MG1, MG2 based on rotational angles θ1, θ2. Note that the rotation angle sensors 26 and 27 may not be arranged by directly calculating the rotation angles θ1 and θ2 from the motor voltage and current in the ECU 30.

  ECU 30 includes a CPU (Central Processing Unit), a storage device, and an input / output buffer, and controls each device of vehicle 100. Note that the control performed by the ECU 30 is not limited to processing by software, and can be constructed and processed by dedicated hardware (electronic circuit).

  As representative functions, the ECU 30 includes the input torque command values TR1 and TR2, the DC voltage VL detected by the voltage sensor 10, the DC current IB detected by the current sensor 11, and the system voltage detected by the voltage sensor 13. Based on VH and motor currents MCRT1 and MCRT2 from current sensors 24 and 25, rotation angles θ1 and θ2 from rotation angle sensors 26 and 27, motor generators MG1 and MG2 generate torques according to torque command values TR1 and TR2. The operations of the converter 12 and the inverter 23 are controlled so as to output. That is, switching control signals PWC, PWI1, and PWI2 for controlling converter 12 and inverter 23 as described above are generated and output to converter 12 and inverter 23, respectively.

  During the boost operation of converter 12, ECU 30 feedback-controls system voltage VH, and generates switching control signal PWC so that system voltage VH matches the voltage command value.

  Further, when vehicle 100 enters the regenerative braking mode, ECU 30 generates switching control signals PWI1 and PWI2 so as to convert the AC voltage generated by motor generators MG1 and MG2 into a DC voltage, and outputs it to inverter 23. Thus, inverter 23 converts the AC voltage generated by motor generators MG1 and MG2 into a DC voltage and supplies it to converter 12.

  Further, when vehicle 100 enters the regenerative braking mode, ECU 30 generates a switching control signal PWC so as to step down the DC voltage supplied from inverter 23 and outputs it to converter 12. Thus, the AC voltage generated by motor generators MG1 and MG2 is converted into a DC voltage, and is further stepped down and supplied to power storage device 28.

  Here, a specific configuration of the above-described ECU will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the ECU. In FIG. 2, for convenience of explanation, only the parts deeply related to the present embodiment are shown among the parts provided in the ECU 30, and other detailed parts are appropriately omitted.

  2, the ECU 30 includes a first filter circuit 310, a second filter circuit 320, a current synthesis unit 330, an ADC (Analog to Digital Converter) 340, a time change calculation unit 350, and a filter characteristic change unit 360. , A controller 370, a carrier signal generation unit 380, and a switching signal generation unit 390.

  The first filter circuit 310 and the second filter circuit 320 are examples of the “filter means” of the present invention, and perform filtering processing on the currents Vr1 and Vr2 detected in the shunt resistors R1 and R2 (see FIG. 1), respectively. Apply. The filtering process is, for example, a band pass filter process, and is performed using a predetermined filter characteristic.

  In the present embodiment, in particular, the first filter circuit 310 (that is, the filter circuit to which the current value Vr1 detected by the shunt resistor R1 is input) has a filter characteristic switching function. That is, the first filter circuit 310 is configured to be able to perform filtering processing with a plurality of different filter characteristics. On the other hand, the second filter circuit 320 (that is, the filter circuit to which the current value Vr2 detected by the shunt resistor R2 is input) does not have a filter characteristic switching function.

  Here, a more specific configuration of the first filter circuit 310 will be described with reference to FIG. FIG. 3 is a circuit diagram showing the configuration of the filter circuit.

  In FIG. 3, the first filter circuit 310 includes resistance elements Rf1 and Rf2, changeover switches Sf1 and Sf2, and a capacitor Cf.

  The first filter circuit 310 has a configuration in which the changeover switches Sf1 and Sf2 are switched in accordance with a switching signal supplied from the filter characteristic changing unit 360. When the change-over switches Sf1 and Sf2 are switched, the connection position with respect to the resistance elements Rf1 and Rf2 changes, so that the resistance value also changes. As a result, the filter characteristics in the first filter circuit 310 are switched.

  Returning to FIG. 2, the current synthesis unit 330 is an example of the “current synthesis unit” of the present invention, and the current value Vr1f (that is, the filtered Vr1) filtered by the first filter circuit 310 and the first The current value Vr2f subjected to the filtering process in the two-filter circuit 320 (that is, the filtered Vr2) is combined with each other to obtain a combined current. The combined current becomes equal to the current IL flowing through the reactor L1.

  The ADC 340 samples the value of IL, which is the combined current, at a plurality of different timings for filter characteristic switching processing, and outputs the sampled value to the time change calculation unit 350. Further, ADC 340 samples the value of IL, which is a combined current, for control of converter 12 and outputs the sampled value to controller 370.

  The time change calculation unit 350 calculates the time change (di / dt) of the combined current (that is, the reactor current IL) by using the plurality of detection values sampled for the filter characteristic switching process in the ADC 340. That is, the time change calculation unit 380 here functions as an example of the “time change calculation means” of the present invention together with the ADC 340 described above.

  The filter characteristic changing unit 360 is an example of the “filter characteristic changing unit” of the present invention, and the filter characteristic in the first filter circuit 310 can be switched based on the value of di / dt calculated by the time change calculating unit 350. It is configured. For example, a threshold value for the di / dt value is stored in advance in the filter characteristic changing unit 360, and the filter characteristic in the first filter circuit 310 is switched according to the magnitude of the calculated di / dt value and the threshold value.

  The controller 370 generates the duty signal DUTY based on the control current value among the current values detected by the ADC 340. The duty signal DUTY is a signal indicating the on / off period ratio of the switching elements Q1 and Q2.

  The carrier signal generation unit 380 generates a carrier signal having a predetermined period in order to generate the switching control signal PWC. The carrier signal is output to switching signal generation section 390.

  The switching signal generation unit 390 generates a switching control signal PWC (in other words, a gate signal) that switches on / off of the switching elements Q1 and Q2 by comparing the carrier signal and the duty signal DUTY with each other. The generated switching control signal PWC is supplied to each of the switching elements Q1 and Q2.

  The ECU 30 described above is an integrated electronic control unit configured to include the above-described parts, and all the operations related to the parts are configured to be executed by the ECU 30. However, the physical, mechanical, and electrical configurations of the above-described parts according to the present invention are not limited thereto. For example, each of these means includes various ECUs, various processing units, various controllers, microcomputer devices, and the like. It may be configured as a computer system or the like.

  Next, the operation of the converter 12 which is a voltage converter will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of the voltage conversion apparatus according to this embodiment. In the following, among the operations of the converter 12, operations unique to the present embodiment will be described in detail, and descriptions of other general operations will be omitted as appropriate.

  In FIG. 4, during the operation of the converter 12 according to the present embodiment, first, currents Vr1 and Vr2 are detected in each of the shunt resistors R1 and R2 (step S101). The detected currents Vr1 and Vr2 are output to the ECU 30.

  The detected currents Vr1 and Vr2 are subjected to filtering processing by each of the first filter circuit 310 and the second filter circuit 320 in the ECU 30 (step S102). Thereby, for example, it is possible to reduce the influence of an error that occurs according to the time variation of the inductance component and the current. The first filter circuit 310 performs a filtering process using different filter characteristics according to conditions, and the filter characteristic changing process will be described in detail later.

  The filtered currents Vr1f and Vr2f are combined by the current combining unit 310 in the ECU 30, and thereby the reactor current IL is estimated (step S103).

  When reactor current IL is estimated, ADC 320 samples the value of reactor current IL at a plurality of different timings (step S104). Hereinafter, sampling of the reactor current IL will be described in detail with reference to FIG. FIG. 5 is a timing chart showing the sampling timing of the reactor current.

  As shown in FIG. 5, the ADC 320 samples the value of the reactor current IL that goes up and down by turning on and off the switching elements Q1 and Q2 at the sampling timings ta and tb. Note that the sampling timings ta and tb are set in advance as appropriate timings for calculating the temporal change of the reactor current IL. The sampling timings ta and tb are preferably set so as not to straddle the on / off switching timings of the switching elements Q1 and Q2, as shown in the figure.

  The current value Ia detected at the sampling timing ta and the Ib detected at the sampling timing tb are output to the time change calculation unit 350, respectively.

  Returning to FIG. 4, when the value of the reactor current IL is sampled, the time change calculating unit 350 calculates the time change (di / dt) of the reactor current IL (step S105). For example, di / dt can be calculated using the following mathematical formula (1).

di / dt = (Ib−Ia) / (tb−ta) (1)
The value of di / dt calculated by the time change calculation unit 350 is output to the filter characteristic changing unit 360.

  When di / dt is calculated, the filter characteristic changing unit 360 determines whether the value of di / dt is less than the threshold value α (step S106). Note that the threshold value α is a threshold value used for changing the filter characteristics in the first filter circuit 310 (that is, a threshold value for determining which filter characteristic is used for the filtering process), and is based on the device characteristics and the like. Is preset.

  When the value of di / dt is less than the threshold value α (step S106: YES), the filter characteristic changing unit 360 instructs the first filter circuit 310 to use the filter characteristic A (step S107). On the other hand, when the value of di / dt is equal to or greater than the threshold value α (step S106: NO), the filter characteristic changing unit 360 instructs the first filter circuit 310 to use the filter characteristic B (step S108). ).

  Hereinafter, the filter characteristics A and B will be specifically described with reference to FIGS. 6 and 7. FIG. 6 is a graph showing an example of the filter characteristic A. FIG. 7 is a graph showing an example of the filter characteristic B.

  In FIG. 6, the filter characteristic A shows such a characteristic that the gain is “1” until the value of di / dt exceeds the threshold value α and reaches X1, and then gradually decreases. According to the filter characteristic A, when the value of di / dt is smaller than the threshold value α, the gain is always “1”, so that an appropriate filtering process can be performed. However, when the value of di / dt greatly exceeds the threshold value α (that is, when it exceeds X1), the gain becomes smaller than “1”, so that appropriate filtering processing cannot be performed.

  In FIG. 7, the filter characteristic B has a gain that increases as the di / dt value approaches X2, and is constant at "1" when the di / dt value is between X2 and X3, and then gradually decreases. It shows such characteristics. As can be seen from the figure, X3 is larger than X1. According to the filter characteristic B, when the value of di / dt is smaller than the threshold value α (more precisely, smaller than X2), the gain is smaller than “1”, so that appropriate filtering processing cannot be performed. However, even if the value of di / dt greatly exceeds the threshold value α (more precisely, if it is smaller than X3), the gain is “1”, so that appropriate filtering processing can be performed.

  As described above, when the value of di / dt is smaller than the threshold value α, the filtering process can be appropriately performed by using the filter characteristic A. Further, when the value of di / dt is equal to or greater than the threshold value α (and less than X3), the filtering process can be appropriately performed by using the filter characteristic B. Therefore, if the filter characteristic is selected by comparing the calculated di / dt value with the threshold value α, an appropriate filtering process can be performed regardless of the di / dt value.

  If the current usage region of the converter 12 exceeds X3 (that is, the upper limit value that allows appropriate filtering processing with the filter characteristic B), the gain is “1” even when the value of di / dt exceeds X3. It is sufficient to use a filter characteristic C such that “ That is, three or more types of filter characteristics that can be switched may be set. In this way, an appropriate filtering process can always be performed regardless of the value of di / dt.

  The filter characteristic switching process described above can be performed appropriately even when magnetic saturation occurs in the reactor L1, for example. Hereinafter, problems caused by magnetic saturation will be described with reference to FIG. FIG. 8 is a graph showing a decrease in inductance due to magnetic saturation.

  In FIG. 8, in a region where the reactor current is extremely large, magnetic saturation occurs, and the inductance value of the reactor L1 that has been constant until then greatly changes. For this reason, for example, in a configuration in which di / dt is calculated based on the inductance value of the reactor L1, it is difficult to calculate an accurate value.

  However, in the present embodiment, as described above, di / dt is estimated from the current values Vr1 and Vr2 detected using the shunt resistors R1 and R2. That is, di / dt is calculated from a value that does not depend on the inductance value of the reactor L. Therefore, it is possible to accurately detect the time change of the reactor current without being affected by magnetic saturation.

  As described above, according to the voltage conversion device according to the present embodiment, the filter characteristic can be changed to an appropriate one using the value of di / dt. Therefore, it is possible to accurately detect the reactor current using the shunt resistor.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 12 ... Converter, 20 ... DC voltage generation part, 22, 23 ... Inverter, 28 ... Power storage device, 30 ... ECU, 40 ... Engine, 41 ... Power split mechanism, 42 ... Drive wheel, 45 ... Load device, 100 ... Vehicle, 310 ... 1st filter circuit, 320 ... 2nd filter circuit, 330 ... Current synthesis part, 340 ... ADC, 350 ... Time change calculation part, 360 ... Filter characteristic change part, 370 ... Controller, 380 ... Carrier signal generation part, 390: Switching signal generator, C2: Smoothing capacitor, D1, D2 ... Diode, IL ... Reactor current, L1 ... Reactor, MG1, MG2 ... Motor generator, PWC ... Switching control signal, Q1, Q2 ... Switching element, SR1, SR2 ... system relay.

Claims (1)

Reactor,
A first switching element and a second switching element respectively connected in series to the reactor;
A first shunt resistor for detecting a first current flowing through the first switching element;
A second shunt resistor for detecting a second current flowing through the second switching element;
Filter means for applying a filtering process to each of the detected values of the first current and the second current with a predetermined filter characteristic;
Current combining means for combining the detected value of the first current and the detected value of the second current subjected to the filtering process into a combined current;
A time change calculating means for calculating a time change of the current value of the combined current by detecting the current value of the combined current at a plurality of different timings;
When the time change of the current value is equal to or greater than a predetermined threshold, the filter characteristic of the filter unit is changed to the first filter characteristic, and when the time change of the current value is less than the predetermined threshold, the filter of the filter unit And a filter characteristic changing means for changing the characteristic to a second filter characteristic different from the first filter characteristic .

Images