JP6839687B2 - Boost control device - Google Patents

Description

The present invention relates to, for example, the technical field of a boost control device mounted on a vehicle or the like.

Electric vehicles such as electric vehicles, hybrid vehicles, and fuel cell vehicles are equipped with an inverter to control a motor generator that generates driving force used for traveling and regenerative power used for storage. Since the electric power used by the inverter fluctuates according to the traveling state and the like, a voltage converter may be provided between the power storage device and the inverter.

Then, in order to improve the fuel efficiency of the electric vehicle, it is effective to reduce the loss of the converter. Therefore, for example, Patent Document 1 proposes a technique of switching and driving a boost converter with only one element (hereinafter, appropriately referred to as "single element control"). According to the one-element control, for example, the loss of the converter can be reduced by the amount that the current ripple can be reduced.

In addition, Patent Document 2 proposes a technique for detecting the moment (zero cross) when the current flowing through the reactor becomes near zero as a technique related to the control of the converter.

Japanese Unexamined Patent Publication No. 2011-120329 Japanese Unexamined Patent Publication No. 2005-151606

In single-element control, the relationship between the output current and the duty ratio changes significantly before and after zero cross, so it is preferable to change the control content depending on whether or not there is zero cross. That is, it is preferable that the control for the zero-cross region and the control for the non-zero-cross region can be appropriately switched and executed.

Here, the zero cross can be determined by, for example, monitoring the current flowing through the reactor, the applied voltage, or the like, but in the prior art including the above-mentioned Patent Documents 1 and 2, it is possible to detect the zero cross with high accuracy and without delay. It's not easy. If the zero-cross timing cannot be detected accurately, the duty control cannot be appropriately switched, and as a result, a technical problem that a desired output current cannot be obtained may occur. In particular, it is considered that such a problem occurs remarkably in a state where the frequency is increased.

The present invention has been made in view of the above-mentioned problems, for example, and an object of the present invention is to provide a boost control device capable of accurately determining zero cross during single element control and executing appropriate duty control. To do.

<1>
In order to solve the above problems, the boost control device of the present invention connects only one of the first switching element and the second switching element, which are connected in series with each other and one end of the reactor is connected to each other's connection nodes. A boost control device capable of controlling a single element to be driven, which is a current detecting means for detecting an output current flowing through the reactor and outputting a detected value, and for driving the one during the control of the single element. , if (i) before Kide force current is not near zero, performs a first duty control for calculating the duty command value by a first operation expression including a first control parameter, (ii) the output current is near zero In the case of the control means for performing the second duty control for calculating the duty command value by the second calculation formula including the second control parameter different from the first control parameter, and during the one-element control. Calculate the rate of change, which is the slope as the ratio of the amount of change in the output current based on the output detected value to the amount of change in the duty value based on the duty command value in the first duty control or the second duty control. When the rate of change is less than a predetermined value during the control of the single element and the means for calculating the ratio, it is determined that the output current is near zero, and the second duty is determined regardless of the detected value output. It is provided with a control determining means for controlling the control means so as to perform control.

The boost control device according to the present invention is, for example, a converter mounted on a vehicle, and includes a first switching element and a second switching element, which are connected in series to the reactor, respectively. 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, a power bipolar transistor, or the like can be used. For example, a diode is connected in parallel to each of the first switching element and the second switching element.

In particular, the boost control device according to the present invention can realize single-element control that drives only one of the first switching element and the second switching element. When single-element control is performed, for example, which of the first switching element and the second switching element should be driven to perform single-element control based on the voltage value or current value to be output. It is judged. More specifically, for example, when the motor generator connected to the boost control device performs the regenerative operation, the one-element control by the first switching element is selected, and when the power running operation is performed, the one-element control by the second switching element is selected. Control is selected. In this way, when performing single-element control, single-element control by the first switching element and single-element control by the second switching element are appropriately switched.

During single-element control, different controls are executed depending on whether or not the output current flowing through the reactor is near zero. Specifically, when the output current is not near zero, the first duty control is performed by the first control parameter. On the other hand, when the output current is near zero, the second duty control is performed by the second control parameter. The "duty control" here is a control for changing the duty ratio of the first switching element or the second switching element (that is, the ratio between the on period and the off period), and the control means controls the output current to be output. The duty ratio is controlled according to the value. The "control parameter" may be the duty ratio itself, or may be another parameter that indirectly affects the duty ratio.

By switching the duty control as described above, it is possible to cope with the change in the relationship between the output current and the duty ratio that occurs when the output current is close to zero. For example, when the relationship between the output current and the duty ratio changes, when the output current is near zero (hereinafter, appropriately referred to as “zero cross”) and when the output current is not near zero (hereinafter, appropriately referred to as “non-zero cross”). (Referred to as) means that different output currents are output even if the duty ratio is the same. Therefore, if the duty control is performed at the time of zero crossing as in the case of non-zero crossing, the output current may not reach a desired value. On the other hand, if different duty controls are performed depending on whether or not the output current is near zero, it is possible to obtain an appropriate output current at each of the zero crossing and the non-zero crossing.

In particular, the present invention includes a ratio calculating means as a means for determining whether or not the output current is near zero. In the ratio calculation means, the change ratio, which is the slope as the ratio of the change amount of the output current to the change amount of the duty value in the first duty control or the second duty control, is calculated .

Here, according to the research by the inventor of the present application, it has been found that at zero crossing, the rate of change, which is the slope as the ratio of the amount of change in output current to the amount of change in duty value, is smaller than that at non-zero crossing. ing. That is, when the duty value is changed by a predetermined amount at the time of zero crossing, the output current changes only slightly, but when the duty value is changed by a predetermined amount at the time of non-zero crossing, the output current changes relatively significantly. I know.

In the present invention, the duty control to be executed is determined by the control determining means by utilizing the above-mentioned characteristics. Specifically, according to the control determination unit, when the rate of change is less than the predetermined value, the second duty control regardless of the detected value (i.e., duty control to be executed when the zero-cross) control to perform the Means are controlled. The "predetermined value" here is a threshold value for determining whether or not the output current is near zero. For example, the above change rate at the time of zero crossing and the above change rate at the time of non-zero crossing are actually measured. It is sufficient to set an appropriate value by measuring to. Further, " regardless of the detected value " means that the control is determined by giving priority to the judgment based on the rate of change rather than the value of the output current actually detected. For example, it is detected by a current sensor or the like. even the value of that output current is not zero the vicinity, when the change rate calculated is less than the predetermined value, the second duty control to be executed when the zero-crossing is performed.

If the duty control is determined according to the rate of change, appropriate duty control can be executed even when the value of the output current cannot be detected accurately, for example. In particular, in single-element control, since the output current fluctuates periodically, it is difficult to directly determine the zero cross from the output value of the current sensor or the like, but by using the above rate of change, the zero cross can be suitably determined. .. Therefore, it is possible to switch the duty control according to the zero cross at an appropriate timing, and as a result, a desired output current can be surely obtained.

As described above, according to the boost control device according to the present invention, since the zero cross can be accurately determined during single element control, it is possible to execute appropriate duty control.

<2>
In one embodiment of the step-up control apparatus of the present invention, the control determination unit, in the piece device control in the case the rate of change is not smaller than the predetermined value, the output current is determined not to be near zero, is the output The control means is controlled so as to perform the first duty control regardless of the detected value.

According to this aspect, when the rate of change is not less than the predetermined value, the first duty control regardless of the detected value is performed. Therefore, even if the non-zero cross cannot be directly determined from the output value of the current sensor or the like, the non-zero cross is determined from the above change rate, and the first duty control to be executed at the non-zero cross is executed at an appropriate timing. It becomes possible.

<3>
In another aspect of the boost control device of the present invention, when the control means switches between the first duty control and the second duty control during the one-element control , the first control parameter and the first control parameter and the second duty control are switched. Transient control is performed to enhance the continuity of the second control parameter.

According to this aspect, due to the low continuity between the first control parameter and the second control parameter, inconvenience may occur when switching between the first duty control and the second duty control. Can be prevented. The process executed as the control for increasing continuity is not particularly limited, and examples thereof include a process for adjusting a value used for feedback control or feedforward control. Further, it is preferable that the continuity is increased as much as possible (that is, the first control parameter and the second control parameter at the time of switching are extremely close values), but if the continuity can be increased to some extent. , The above-mentioned effects can be obtained accordingly.

<4>
In the mode of performing the transient control described above, the first arithmetic expression and the second arithmetic expression include an integration term related to proportional integration control, and the control means is (i) during the one-element control. When switching from the first duty control to the second duty control, as the transient control, an arithmetic expression obtained by adding the difference between the first control parameter and the second control parameter to the integration term in the second arithmetic expression. (Ii) When switching from the second duty control to the first duty control during the one-element control, the difference is used as the transient control in the first calculation formula. By calculating the duty command value by the calculation formula added to the integration term, the continuity of the first control parameter and the second control parameter may be enhanced.

In this case, the difference between the first control parameter and the second control parameter at the time of control switching is added to the integration term in the proportional integration control. The value added to the integration term may be the difference itself, or may be a value subjected to some arithmetic processing such as multiplying the difference by a predetermined coefficient. As a result, the continuity of the first control parameter and the second control parameter is enhanced, and the inconvenience that occurs at the time of control switching can be suitably avoided.

<5>
In another aspect of the boost control device of the present invention, the first calculation formula and the second calculation formula include a feedback gain related to feedback control, and the control means is said to have the first calculation during the one-element control . When switching between the 1-duty control and the 2nd-duty control, the feedback gain is switched from the current feedback gain to another feedback gain.

According to this aspect, since the gain of the feedback control is switched to an appropriate value at the time of control switching, the inconvenience caused by the change in responsiveness due to the control switching can be preferably avoided. When switching the gain, a preset gain for the first duty control and a gain for the second duty control may be appropriately switched, or the gain according to the situation is appropriately selected (or calculated). You may do it.

The actions and other gains of the present invention will be apparent from the embodiments for carrying out the invention described below.

It is a schematic block diagram which shows the whole structure of the vehicle which mounts the step-up control device which concerns on embodiment. It is a conceptual diagram which shows the flow of the electric current at the time of controlling a lower element. It is a conceptual diagram which shows the flow of the electric current at the time of controlling the upper element. It is a time chart which shows the fluctuation of the reactor current at the time of one element control. It is a block diagram which shows the specific structure of the ECU which concerns on embodiment. It is a graph which shows the relationship between the duty and the reactor current at the time of zero cross. It is a graph which shows the simulation result of the reactor current which concerns on a comparative example. It is a graph which shows the problem by the deviation of feedforward control. It is a flowchart which shows the switching operation of duty control which concerns on embodiment. It is a graph which shows the change rate of the reactor current with respect to the duty change amount. It is a graph which shows the switching operation of a feedforward term. It is a flowchart which shows the adjustment operation at the time of control switching. It is a graph which shows the simulation result of the reactor current which concerns on embodiment.

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

<Overall configuration>
First, the overall configuration of the vehicle on which the boost control device according to the present embodiment is mounted will be described with reference to FIG. Here, FIG. 1 is a schematic configuration diagram showing an overall configuration of a vehicle equipped with the boost control device according to the present embodiment.

In FIG. 1, the vehicle 100 equipped with the boost control device according to the present embodiment is configured as a hybrid vehicle powered by the engine 40 and the motor generators MG1 and MG2. However, the configuration of the vehicle 100 is not limited to this, and can be applied to a vehicle (for example, an electric vehicle or a fuel cell vehicle) that can travel by electric power from a power storage device. Further, in the present embodiment, the configuration in which the boost control device is mounted on the vehicle 100 will be described, but it can be applied to any device other than the vehicle as long as it is driven by an AC motor.

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

The 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, for example, a secondary battery such as nickel hydrogen or lithium ion, and a power storage device such as an electric double layer capacitor. Further, the DC voltage VL output by the power storage device 28 is detected by the voltage sensor 10. Then, the voltage sensor 10 outputs the detected value of the detected DC voltage VL to the ECU 30.

The system relay SR1 is connected between the positive electrode terminal of the power storage device 28 and the power line PL1, and the system relay SR2 is connected between the negative electrode terminal of the power storage device 28 and the ground line NL. The system relays SR1 and SR2 are controlled by the signal SE from the ECU 30, and switch between supplying and shutting off the power supplied from the power storage device 28 to the converter 12.

The converter 12 includes a reactor L1, switching elements Q1 and Q2, and diodes D1 and D2. 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. The switching elements Q1 and Q2 are controlled by the gate signal PWC from the ECU 30.

For the switching elements Q1 and Q2, for example, an IGBT, a MOS transistor for electric power, a bipolar transistor for electric power, or the like can be used. The antiparallel diodes D1 and D2 are arranged with respect to the switching elements Q1 and Q2. The reactor L1 is provided between the connection node of the switching elements Q1 and Q2 and the power line PL1. Further, the smoothing capacitor C2 is connected between the power line PL2 and the ground line NL.

The current sensor 18 detects the reactor current flowing through the reactor L1 and outputs the detected value IL to the ECU 30. The reactor current IL is an example of the "output current" of the present invention.

The load device 45 includes an inverter 23, motor generators MG1 and MG2, an engine 40, a power split mechanism 41, and a drive wheel 42. Further, the inverter 23 includes an inverter 14 for driving the motor generator MG1 and an inverter 22 for driving the motor generator MG2. It should be noted that it is not essential to include two sets of the inverter and the motor generator as shown in FIG. 1, and for example, only one set of the inverter 14 and the motor generator MG1 or the inverter 22 and the motor generator MG2 may be provided.

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

Further, the motor generators MG1 and MG2 are also connected to the engine 40 via the power split mechanism 41. Then, the driving force generated by the engine 40 and the driving force generated by the motor generators MG1 and MG2 are controlled to be in an optimum ratio. Further, either one of the motor generators MG1 and MG2 may be made to function exclusively as an electric motor, and the other motor generator may be made to function exclusively as a generator. In the present embodiment, the motor generator MG1 is made to function as a generator driven by the engine 40, and the motor generator MG2 is made to function as an electric motor for driving the drive wheels 42.

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

The inverter 14 receives the boosted voltage from the converter 12 and drives, for example, the motor generator MG1 to start the engine 40. Further, the inverter 14 outputs the regenerative power generated by the motor generator MG1 to the converter 12 by the mechanical power transmitted from the engine 40. At this time, the converter 12 is controlled by the ECU 30 so as to operate as a step-down circuit.

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

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

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

The inverter 22 converts the DC voltage output by the converter 12 into a three-phase alternating current and outputs it to the motor generator MG2 that drives the drive wheels 42. Further, the inverter 22 outputs the regenerative power generated by the motor generator MG2 to the converter 12 in accordance with the regenerative braking. At this time, the converter 12 is controlled by the ECU 30 so as to operate as a step-down circuit. Although not shown, the internal configuration of the inverter 22 is the same as that of the inverter 14, and detailed description thereof will be omitted.

The converter 12 is basically controlled so that the switching elements Q1 and Q2 are complementarily and alternately turned on and off within each switching cycle. At the time of boosting operation, the converter 12 boosts the DC voltage VL supplied from the power storage device 28 to the DC voltage VH (this DC voltage corresponding to the input voltage to the inverter 14 is also referred to as “system voltage” below). This boosting operation is performed by supplying the electromagnetic energy stored 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.

Further, the converter 12 lowers the DC voltage VH to the DC voltage VL during the step-down operation. This step-down operation is performed by supplying the electromagnetic energy stored 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 (ratio of VH and VL) in these step-up operations and step-down operations is controlled by the on-period ratio (duty ratio) of the switching elements Q1 and Q2 in the switching cycle. If the switching elements Q1 and Q2 are fixed on and off, respectively, VH = VL (voltage conversion ratio = 1.0) can be set.

The smoothing capacitor C2 smoothes the DC voltage from the converter 12 and supplies the smoothed DC voltage to the 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 the motor generator MG1 is positive (TR1> 0), the inverter 14 of the switching elements Q3 to Q8 responds to the gate signal PWI1 from the ECU 30 when a DC voltage is supplied from the smoothing capacitor C2. The motor generator MG1 is driven so as to convert a DC voltage into an AC voltage by a switching operation and output a positive torque. Further, when the torque command value of the motor generator MG1 is zero (TR1 = 0), the inverter 14 converts the DC voltage into an AC voltage by the switching operation in response to the gate signal PWI1 so that the torque becomes zero. Drives the motor generator MG1. As a result, the motor generator MG1 is driven to generate zero or positive torque specified by the torque command value TR1.

Further, at the time of regenerative braking of the vehicle 100, the torque command value TR1 of the motor generator MG1 is set to a negative value (TR1 <0). In this case, the inverter 14 converts the AC voltage generated by the motor generator MG1 into a DC voltage by the switching operation in response to the gate signal PWI1, and the converted DC voltage (system voltage) is passed through the smoothing capacitor C2. Is supplied to the converter 12. Regenerative braking here refers to braking that involves regenerative power generation when the driver who drives the electric vehicle operates the foot brake, or regenerative braking by turning off the accelerator pedal while driving, although the foot brake is not operated. This includes decelerating (or stopping acceleration) the vehicle while generating electricity.

Similarly, the inverter 22 receives the gate signal PWI2 from the ECU 30 corresponding to the torque command value of the motor generator MG2, and converts the DC voltage into an AC voltage by the switching operation in response to the gate signal PWI2 so as to obtain a predetermined torque. Drives the motor generator MG2.

The current sensors 24 and 25 detect the motor currents MCRT1 and MCRT2 flowing through the motor generators MG1 and MG2, and output the detected motor currents to the 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 so as to detect the motor currents of the two phases as shown in FIG. All you need is.

The rotation angle sensors (resolvers) 26 and 27 detect the rotation angles θ1 and θ2 of the motor generators MG1 and MG2, and send the detected rotation angles θ1 and θ2 to the ECU 30. The ECU 30 can calculate the rotation speeds MRN1 and MRN2 and the angular velocities ω1 and ω2 (rad / s) of the motor generators MG1 and MG2 based on the rotation angles θ1 and θ2. 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 by the ECU 30.

The ECU 30 is an example of the "boost control device" of the present invention, and includes, for example, a CPU (Central Processing Unit), a storage device, and an input / output buffer, and controls each device of the vehicle 100. 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). The specific configuration and operation of the ECU will be described in detail later.

<Single element control>
Next, the one-element control of the converter 12 will be described with reference to FIGS. 2 to 4. Here, FIG. 2 is a conceptual diagram showing the current flow when the lower element is controlled, and FIG. 3 is a conceptual diagram showing the current flow when the upper element is controlled. Further, FIG. 4 is a time chart showing fluctuations in the reactor current during single-element control.

In FIGS. 2 and 3, the converter 12 according to the present embodiment has one of the switching elements Q1 and Q2 in addition to the normal control (that is, the control in which both the switching elements Q1 and Q2 are turned on alternately). It is possible to realize single-element control that turns on only. Specifically, during power running, lower element control is performed in which only the switching element Q2 is turned on. In this case, as shown in FIG. 2, the current flowing on the switching element Q1 side flows through the diode D1, and the current flowing on the switching element Q2 side flows through the switching element Q2. On the other hand, during regeneration, lower element control is performed in which only the switching element Q2 is turned on. In this case, as shown in FIG. 3, the current flowing on the switching element Q1 side flows through the switching element Q1, and the current flowing on the switching element Q2 side flows through the diode D2.

According to the one-element control, since only one of the switching elements Q1 and Q2 is turned on, the dead time set to prevent the switching elements Q1 and Q2 from being short-circuited becomes unnecessary. Therefore, for example, even when a higher frequency is required due to the miniaturization of the apparatus, it is possible to prevent the boosting performance of the converter 12 from deteriorating. Further, in the single element control, it is possible to avoid the gate interference of the switching element and reduce the boost loss.

As shown in FIG. 4, in the one-element control, either one of PWC1 which is a gate signal for switching on / off of the switching element Q1 and PWC2 which is a gate signal for switching on / off of the switching element Q2 is selectively supplied. As a result, the value of the reactor current IL is controlled.

Specifically, during power running when the lower element is controlled (that is, when the reactor current IL is positive), PWC1 which is a gate signal for switching on / off of the switching element Q1 is not supplied, and the switching element Q2 is turned on / off. Only PWC2, which is a gate signal for switching between, is supplied. Further, at the time of regeneration in which the upper element control is performed (that is, when the reactor current IL is negative), only PWC1 which is a gate signal for switching on / off of the switching element Q1 is supplied, and a gate signal for switching on / off of the switching element Q2 is supplied. PWC2 is not supplied.

<ECU configuration>
Next, a specific configuration of the ECU 30 which is an example of the boost control device according to the present embodiment will be described with reference to FIG. Here, FIG. 5 is a block diagram showing a specific configuration of the ECU according to the embodiment. Note that, for convenience of explanation, FIG. 5 shows only the parts closely related to the present embodiment among the parts provided in the ECU 30, and the other detailed parts are not shown as appropriate.

In FIG. 5, the ECU 30 according to the present embodiment includes a change rate calculation unit 310, a zero cross determination unit 320, and a duty control unit 330.

The change rate calculation unit 310 is an example of the "ratio calculation means" of the present invention, and calculates the change rate of the reactor current IL with respect to the change amount of the duty . Change rate detected by the change rate calculating unit 310 is configured to output the zero-crossing decision unit 320.

Zero-crossing decision unit 320 is an example of the "control determination means" of the present invention, based on the change rate detected by the change rate calculating section 310, whether or not the zero-crossing (i.e., near zero reactor current IL Whether or not) is determined. The zero cross determination unit 320 stores, for example, a threshold value for the rate of change, and determines the zero cross by comparing the rate of change and the threshold value with each other. The determination result of the zero cross determination unit 320 is configured to be assigned to the duty control unit 330, respectively.

The duty control unit 330 is an example of the "control means" of the present invention, and controls the on / off of the switching elements Q1 and Q2 by outputting the gate signal PWC. The duty control unit 330 includes, for example, a duty signal generation circuit that generates a duty command signal DUTY and a carrier signal generation circuit that generates a carrier signal CR, and the duty command generated according to a desired duty ratio. The signal duty and the carrier signal CR are compared, and the gate signal PWC obtained as a result of the comparison is output to the switching elements Q1 and Q2, respectively.

<Problems that can occur at zero cross>
Next, problems that may occur when the reactor current IL is near zero will be described in detail with reference to FIGS. 6 to 8. Here, FIG. 6 is a graph showing the relationship between the duty and the reactor current at the time of zero crossing, and FIG. 7 is a graph showing the simulation result of the reactor current according to the comparative example. Further, FIG. 8 is a graph showing problems due to deviation of feedforward control.

As shown in FIG. 6, at the time of non-zero cross, the relationship between the duty and the reactor current IL becomes linear. However, at the time of zero crossing, the reactor current IL cannot change across zero, so that the relationship between the duty and the reactor current IL becomes non-linear. In this way, the relationship between the duty and the reactor current IL changes greatly depending on whether or not the reactor current IL is near zero.

As shown in FIG. 7, if the same control is performed both at the time of zero crossing and at the time of non-zero crossing, the actual reactor current IL is greatly disturbed with respect to the command value of the reactor current IL. That is, if control is performed without considering whether or not the reactor current IL is near zero, there may be a problem that a desired reactor current IL cannot be obtained.

If feedforward control and feedback control are performed when controlling the duty, the above-mentioned inconvenience may be avoided. However, since the feedforward control uses parameters that are liable to fluctuate, such as the inductance of the reactor L1 and the internal resistance of the power storage device 28, there is a high possibility that a deviation will occur. Therefore, even if feedforward control and feedback control are used, the desired reactor current IL is not always obtained.

As shown in FIG. 8, it is assumed that control at point a is currently desired in a situation where the reactor current IL is gradually increased. However, if the feedforward control is deviated, the control at point b is executed. That is, the duty is controlled to be smaller than the appropriate value. In this case, the control is performed at the point c corresponding to the true duty, and the output reactor current IL becomes an extremely high value. If the reactor current IL is output as an unnecessarily large value in this way, the PCU or the like may be destroyed, for example. That is, if the desired reactor current IL cannot be obtained, an unexpected inconvenience may occur.

The boost control device according to the present embodiment is configured to be able to execute the duty control switching operation described below in order to avoid the above-mentioned inconvenience.

<Duty control switching operation>
Hereinafter, the duty control switching operation executed by the ECU 30, which is an example of the boost control device according to the present embodiment, will be described in detail with reference to FIGS. 9 and 10. Here, FIG. 9 is a flowchart showing a duty control switching operation according to the embodiment. Further, FIG. 10 is a graph showing the rate of change of the reactor current with respect to the amount of change in duty.

In FIG. 9, during the duty control switching operation, the change rate calculation unit 310 first calculates the amount of change in duty in duty control (step S101). Further, the change rate calculation unit 310 calculates the amount of change in the reactor current IL in duty control (step S102). That is, the amount of change in the reactor current IL with respect to the amount of duty change calculated in step S101 is calculated.

The change rate calculation unit 310 further calculates the change rate α of the reactor current IL with respect to the duty change amount (step S103). The rate of change α can be calculated by dividing the amount of change in the reactor current IL calculated in step 102 by the amount of change in duty calculated in step S101.

As shown in FIG. 10, according to the research by the inventor of the present application, it has been found that the rate of change of the reactor current IL with respect to the amount of change in duty is smaller at zero crossing than at non-zero crossing. Specifically, as can be seen from the figure, even when the duty value is significantly changed at zero crossing, the reactor current IL changes only slightly, but at non-zero crossing, the duty is changed. The reactor current IL changes significantly even when is slightly changed. In the present embodiment, it is determined whether or not the cross is zero by using this characteristic.

Returning to FIG. 9, the zero cross determination unit 320 determines whether or not the calculated change rate α is smaller than the predetermined threshold value β (step S104). The threshold value β is an example of the “predetermined value” of the present invention. For example, an appropriate value can be obtained by actually measuring the rate of change of the output current at the time of zero crossing and the rate of change of the output current at the time of non-zero crossing. You can set it.

When it is determined that the rate of change α is smaller than the predetermined threshold value β (step S104: YES), it is determined that the reactor current IL is near zero, and duty control for zero crossing is executed (step S105). Specifically, the duty control unit 330 performs feedforward control using a feedforward term for zero crossing (hereinafter, appropriately referred to as “FF term”).

On the other hand, when it is determined that the rate of change α is not smaller than the predetermined threshold value β (step S104: NO), it is determined that the reactor current IL is not near zero, and duty control for non-zero cross is executed (step). S106). Specifically, the duty control unit 330 performs feedforward control using the FF term for non-zero cross.

As described above, if the duty control is determined according to the rate of change of the reactor current IL, appropriate duty control can be executed even when the value of the reactor current IL cannot be detected accurately, for example. In particular, in single-element control, since the reactor current IL fluctuates periodically, it is difficult to directly determine the zero cross from the output value of the current sensor or the like. However, in the present embodiment, the zero cross can be suitably determined by using the rate of change of the reactor current IL. Therefore, it is possible to switch the duty control according to the zero cross at an appropriate timing, and as a result, a desired reactor current IL can be surely obtained.

<Adjustment processing when switching duty control>
Hereinafter, the adjustment process executed at the time of switching the duty control described above will be described with reference to FIGS. 11 to 13. Here, FIG. 11 is a graph showing a switching operation of the feedforward term, and FIG. 12 is a flowchart showing an adjustment operation at the time of control switching. Further, FIG. 13 is a graph showing the simulation result of the reactor current according to the embodiment.

In FIG. 11, as described above, when it is determined that the non-zero cross has changed to the zero cross, the FF term is switched from the non-zero cross to the zero cross. At this time, since the continuity of the FF term is lost before and after the switching, there is a possibility that inconvenience may occur simply by switching the FF term. Therefore, in the present embodiment, when the duty control is switched, the adjustment process described in detail below is executed.

In FIG. 12, when the duty control is switched according to the result of the zero cross determination (step S201: YES), the difference between the previous and current FF terms is added to the integration term (step S202). As a result, the continuity before and after the duty control switching is maintained, and the occurrence of inconvenience can be avoided.

Further, when the duty control is switched from the control for non-zero cross to the control for zero cross (step S203: YES), the feedback gain is switched for zero cross. On the other hand, when the duty control is switched from the zero cross control to the non-zero cross control (step S203: NO), the feedback gain is switched to the non-zero cross control. This makes it possible to cope with changes in responsiveness caused by switching duty control.

Specifically, the duty command when the control for non-zero cross is continued is expressed by the following equation (1).

Duty command = FF term at non-zero cross + kp1 x current deviation + ki1 x current deviation + integral term ... (1)

Note that kp1 and ki1 are feedback gains at the time of non-zero cross, respectively, and for example, kp1 = 0.01 and ki1 = 0.1. Further, the "ki1 x current deviation + integral term" here becomes the integral term at the time of the next control.

On the other hand, the duty command when the control is switched from the control for non-zero cross to the control for zero cross is expressed by the following equation (2).

Duty command = FF term at zero cross + kp2 x current deviation + ki2 x current deviation + {integral term + (FF term at non-zero cross-FF term at zero cross)} ... (2)

Note that kp2 and ki2 are feedback gains at the time of zero crossing, respectively, and for example, kp1 = 0.03 and ki1 = 0.3. Further, "ki2 x current deviation + {integral term + (FF term at non-zero cross-FF term at zero cross)}" here becomes the integral term at the time of the next control.

Further, the duty command when the control for zero cross is continued is expressed by the following equation (3).

Duty command = FF term at zero cross + kp2 x current deviation + ki2 x current deviation + integral term ... (3)

The "ki2 x current deviation + integral term" here becomes the integral term at the time of the next control.

On the other hand, the duty command when the control is switched from the control for zero cross to the control for non-zero cross is expressed by the following equation (4).

Duty command = FF term at non-zero cross + kp1 x current deviation + ki1 x current deviation + {integral term + (FF term at zero cross-FF term at non-zero cross)} ... (4)

The "ki1 x current deviation + {integral term + (FF term at zero cross-FF term at non-zero cross)}" here is the integral term at the time of the next control.

As shown in FIG. 18, if the duty control switching process and the adjustment process described above are implemented, the disturbance of the reactor current IL as shown in FIG. 7 can be suppressed. That is, the deviation between the command value of the reactor current IL and the actual reactor current IL can be reduced. That is, if different duty controls are selectively executed depending on whether or not the duty is zero crossed, the desired reactor current IL can be reliably obtained even when the relationship between the duty and the reactor current IL changes. Obtainable.

As described above, according to the boost control device according to the present embodiment, it is possible to accurately determine the zero cross and preferably execute the duty control.

The present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of claims and within a range not contrary to the gist or idea of the invention that can be read from the entire specification, and the boost control device accompanied by such a modification. Is also included in the technical scope of the present invention.

10 Voltage sensor 12 Converter 13 Voltage sensor 18 Current sensor 20 DC voltage generator 22, 23 Inverter 28 Power storage device 30 ECU
40 Engine 41 Power split mechanism 42 Drive wheel 45 Load device 100 Vehicle 310 Change rate calculation unit 320 Zero cross judgment unit 330 Duty control unit C2 Smoothing capacitor CR Carrier signal D1, D2 Diode IL Reactor current L1 Reactor MG1, MG2 Motor generator PWC1, PWC2 Gate signal Q1, Q2 Switching element SR1, SR2 System relay

Claims (5)

It is a step-up control device capable of realizing single-element control that drives only one of the first switching element and the second switching element, which are connected in series with each other and one end of a reactor is connected to each other's connection node. ,
A current detecting means that detects the output current flowing through the reactor and outputs the detected value,
In the piece element control in order to drive the one, first for computing the duty command value by the case (i) prior Kide force current is not near zero, first arithmetic expression containing a first control parameter A second duty that performs duty control and (ii) calculates the duty command value by a second calculation formula including a second control parameter different from the first control parameter when the output current is near zero. Control means for control and
During the one-element control, the ratio of the change amount of the output current based on the output detected value to the change amount of the duty value based on the duty command value in the first duty control or the second duty control. A rate calculation means for calculating the rate of change, which is the slope, and
During the one-element control, when the change rate is less than a predetermined value, it is determined that the output current is near zero, and the second duty control is performed regardless of the output detected value. A boost control device including a control determination means for controlling the control means. Said control determining means in the piece device control in the case the rate of change is not smaller than the predetermined value, it is determined that the output current is not zero near the first duty control regardless of the outputted detection value The boost control device according to claim 1, wherein the control means is controlled so as to perform the above. The control means is a transient that enhances the continuity of the first control parameter and the second control parameter when switching between the first duty control and the second duty control during the one-element control. The boost control device according to claim 1 or 2, wherein the control is performed. The first arithmetic expression and the second arithmetic expression include an integration term related to proportional integration control.
The control means (i) is a difference between the first control parameter and the second control parameter as the transient control when switching from the first duty control to the second duty control during the one-element control. Is calculated by the calculation formula added to the integration term in the second calculation formula, and (ii) when switching from the second duty control to the first duty control during the one-element control. As the transient control, the duty command value is calculated by the calculation formula obtained by adding the difference to the integration term in the first calculation formula , so that the first control parameter and the second control parameter are continuous. The boost control device according to claim 3, wherein the performance is enhanced. The first calculation formula and the second calculation formula include a feedback gain related to feedback control.
The control means is characterized by switching the feedback gain from the current feedback gain to another feedback gain when the first duty control and the second duty control are switched to each other during the one-element control. The boost control device according to any one of claims 1 to 4.