JP2011167011A - Dc-dc converter system - Google Patents

Abstract

In a DCDC converter system, it is possible to follow fluctuations in load power.
A rotating electrical machine drive system includes an inverter device connected to a rotating electrical machine, a power storage device, a DCDC converter main body provided between the power storage device and the inverter device, and a DCDC converter control unit. 40. The DCDC converter control unit 40 divider 68 as an input and a load power values P and V _L to calculate the P / V _L = I _B. I _B is input to the differentiator 70 and dI _B / dt is calculated. Divider 72 is inputted with the inductance L the output voltage command value V _H ^* to calculate the L / V _H ^*. The multiplier 74 inputs L / V _H ^* and dI _B / dt and calculates (L / V _H ^* ) × (dI _B / dt) = duty3. The steady duty ratio duty2 is corrected by this duty3.
[Selection] Figure 1

Description

  The present invention relates to a DCDC converter system, and more particularly to a DCDC converter system that is provided between a power storage device and a load driving device and performs voltage conversion by controlling a duty ratio of a switching element based on an output voltage command value.

  A voltage converter that performs step-up / step-down as a device that supplies power from a power storage device such as a secondary battery to a load drive circuit in a drive state, or conversely supplies power from a load drive circuit in a regeneration state to the power storage device Is used. Since this voltage converter has a function of changing the voltage of DC power, it is also called a DCDC converter.

For example, Patent Document 1 has a dead time T _d required for switching a switching element as a boost converter control device, and when the current path fluctuates, the output voltage fluctuates greatly, exceeding the control range of the inverter. It has been pointed out that there is a problem. Therefore, the output voltage is detected, and the duty ratio is controlled according to the voltage deviation that is the difference between the output voltage and the target voltage, and the inverter output power value is obtained by calculation, and this is calculated by the comparator. It is disclosed that the current path of the converter is determined by comparison, and correction is performed by increasing or decreasing the dead time τ _d = T _d / (T _ON + T _OFF ) from the duty command value according to the direction of current flow. In this way, it is stated that voltage feedback is the basis, and dead time compensation is performed without using a current sensor, so that it is possible to cope with sudden and rapid fluctuations in load such as no load, power running or regenerative operation at high speed. ing.

Patent Document 2 discloses an elevator system using a secondary battery, a step-down chopper circuit, an inverter, and a motor. As a conventional technique, a terminal of an input unit smoothing capacitor of an inverter connected to the motor is disclosed. The gate driver of the step-down chopper circuit so that the inter-terminal voltage V _dc of the input unit smoothing capacitor becomes a predetermined set voltage V _{ref of} V _cn2 or less when the inter-voltage V _dc becomes a certain set level V _cn2 or more A DC reactor control system that performs PWM voltage control is described.

As a content of this conventional PWM voltage control, it is stated that a DC reactor current control system is provided as a minor loop. That is, V _dc is compared with V _ref , the difference is input to the proportional integration element, and the output of the proportional integration element is given an upper limit by the limiter, and the signal control system for the DC reactor of the step-down chopper circuit Current command value. Then, this current command value is compared with the detected current value of the DC reactor, the difference is input to the proportional integration element, and the signal that gives the upper and lower limit limits to the output of the proportional integration element by the limiter is output from the PWM generating means. It is described as an input signal.

JP 2004-120844 A JP 2001-253653 A

  According to the boost converter control device of Patent Document 1, when load power changes slowly and the direction of the current flowing through the reactor changes, the output voltage is controlled to follow the voltage command value by dead time compensation and voltage feedback control. it can. However, when the load power fluctuates greatly, the output voltage may not follow the voltage command value.

  In order for the output voltage to follow the voltage command value even when the load power fluctuates greatly, the voltage feedback gain may be increased. However, this reduces the control stability in the steady state. By providing current feedback control in the minor loop of the voltage feedback loop as in Patent Document 2, it is possible to improve the output stability of the DCDC converter while increasing the gain, but a current sensor is required and the cost increases.

  The objective of this invention is providing the DCDC converter system which can track the fluctuation | variation of load electric power. Another object is to provide a DCDC converter system that can follow fluctuations in load power without using a current sensor. The following means contribute to at least one of these purposes.

  A DCDC converter system according to the present invention is a DCDC converter system that is provided between a power storage device and a load driving device and performs voltage conversion by controlling a duty ratio of a switching element based on an output voltage command value. A steady duty ratio calculation means for calculating a steady duty ratio based on an input voltage value that is a terminal voltage of the device and an output voltage command value, a load power value that is a power value of a load driven by the load driving device, and an input voltage Based on the input voltage detection value that is the detection value of the input voltage detector that detects the value, the means for calculating the input current value, the time differential value of the input current value, the inductance component value, and the output voltage value are detected. Means for calculating a correction duty ratio for fluctuations in load power based on an output voltage detection value that is a detection value of the output voltage detector, and a steady duty cycle The ratio, based on the correction duty ratio to the load power variation, characterized in that it comprises means for setting the duty ratio of the switching element.

  Further, in the DCDC converter system according to the present invention, the means for calculating the correction duty ratio is a detection value of the output voltage detector for detecting the output voltage value by multiplying the time differential value of the input current value by the inductance component value. It is preferable to calculate a correction duty ratio by dividing a certain output voltage detection value.

  In the DCDC converter system according to the present invention, the deviation between the square value of the output voltage detection value, which is the detection value of the output voltage detector for detecting the output voltage value, and the square value of the output voltage command value is calculated as the power deviation. The means for calculating the duty ratio by power feedback according to the power deviation is provided, and the means for setting the duty ratio of the switching element includes a steady duty ratio, a correction duty ratio for load power fluctuations, and a duty ratio by feedback. Based on this, it is preferable to calculate the duty ratio of the switching element.

  Further, in the DCDC converter system according to the present invention, means for calculating an input current command value in accordance with a deviation between an output voltage detection value that is a detection value of an output voltage detector that detects the output voltage value and the output voltage command value; Means for calculating a duty ratio by voltage feedback based on a deviation between an input current value which is a detected value of an input current detector for detecting an input current value and an input current command value, and sets a duty ratio of the switching element Preferably, the means for calculating the duty ratio of the switching element based on the steady duty ratio, the correction duty ratio with respect to the load power fluctuation, and the duty ratio by feedback.

  In the DCDC converter system according to the present invention, the switching element includes an upper arm side switching element and a lower arm side switching element connected in series between the positive electrode side bus and the negative electrode side bus, and the upper arm side switching element When there is a dead time that turns off both on and off of the lower arm side switching element, the compensation duty ratio for the dead time is calculated according to the size of the dead time And means for setting the duty ratio of the switching element based on the steady duty ratio, the correction duty ratio with respect to load power fluctuation, the duty ratio by feedback, and the compensation duty ratio with respect to dead time. It is preferable to calculate the ratio.

  Further, in the DCDC converter system according to the present invention, the steady duty ratio calculation means includes a steady duty ratio based on the filtered voltage detection value obtained by performing the low-pass filter processing on the input voltage detection value and the output voltage command value. Is preferably calculated.

  In the DCDC converter system according to the present invention, the load driving device is preferably an inverter device connected to the rotating electrical machine.

  With the above configuration, the DCDC converter system is based on the load power value that is the power value of the load driven by the load driving device and the input voltage detection value that is the detection value of the input voltage detector that detects the input voltage value. Calculates the input current value, and varies the load power based on the time derivative of the calculated input current value, the inductance component value, and the output voltage detection value that is the detection value of the output voltage detector that detects the output voltage value The correction duty ratio for is calculated. In this way, the correction duty ratio is obtained based on the time differential value of the input current value related to the fluctuation of the load power value, and the duty ratio by the steady ratio setting is corrected. In the steady ratio setting, low-pass filter processing is performed to prevent divergence of the setting processing, so that it is difficult to follow sudden load fluctuations. According to the above configuration, the duty ratio by the steady ratio setting can be corrected according to the time differential value of the input current value, so that it is possible to follow the fluctuation of the load power. Further, since the input current value is obtained by calculation, a DCDC converter system capable of following the fluctuations in load power without using a current sensor can be obtained.

  Further, in the DCDC converter system, the corrected duty ratio is obtained by multiplying the time differential value of the input current value by the inductance component value and dividing the output voltage detection value which is the detection value of the output voltage detector for detecting the output voltage value. Is calculated. In this way, the correction duty ratio can be calculated by calculation, and the calculated value can be subtracted from the duty ratio set by the steady ratio setting, for example, to obtain an appropriate duty ratio when the load power changes suddenly.

  Further, in the DCDC converter system, the power deviation is defined as a deviation between the square value of the output voltage detection value that is a detection value of the output voltage detector that detects the output voltage value and the square value of the output voltage command value. Accordingly, the duty ratio by power feedback is calculated. Since voltage feedback is the voltage across the terminals of the smoothing capacitor that holds the output voltage, it is affected by the charge / discharge time of the smoothing capacitor. On the other hand, according to the said structure, since the electric power feedback according to an electric power deviation is used, feedback can be performed more rapidly than voltage feedback.

  Also, in the DCDC converter system, the input current command value is calculated according to the deviation between the output voltage detection value and the output voltage command value, and the duty ratio by voltage feedback is calculated based on the deviation between the input current value and the input current command value. To do. As a result, current feedback can be incorporated into the minor loop of the output voltage feedback control of the DCDC converter system, and the DCDC converter system can improve the stability of the output voltage and the responsiveness when the load power changes suddenly.

  Further, in the DCDC converter system, when a dead time is provided for the switching element, a compensation duty ratio with respect to the dead time is calculated according to the magnitude of the dead time. Thereby, dead time compensation can also be performed.

  In the DCDC converter system, the steady duty ratio is calculated based on the post-filtering voltage detection value obtained by performing the low-pass filter processing on the input voltage detection value and the output voltage command value. If the steady duty ratio is calculated using the input voltage detection value as it is, the steady duty ratio may diverge depending on the case, and there is a possibility that control failure occurs. Stable control can be performed by setting the cut-off frequency low by low-pass filter processing and calculating the steady duty.

  Further, in the DCDC converter system, since the inverter device connected to the rotating electrical machine is used as the load driving device, the input current value is estimated without requiring a current sensor for the DCDC converter system widely connected to the inverter device. Can do.

It is a figure which shows the structure of the rotary electric machine drive system containing the DCDC converter system of embodiment which concerns on this invention. It is a figure explaining the internal structure of the steady ratio setting device in the DCDC converter system of embodiment which concerns on this invention. It is a figure which shows the structure of another rotary electric machine drive system containing the DCDC converter system of embodiment which concerns on this invention. It is a figure which shows the mode of the variation model of the load used in order to demonstrate the effect | action of the DCDC converter system of embodiment which concerns on this invention. In embodiment which concerns on this invention, it is a figure which shows the simulation result of electric power feedback control. It is a figure which shows the mode of duty2 in the example of FIG. FIG. 6 is a diagram illustrating a state of duty 2 together with an enlarged view of the example of FIG. 5. In embodiment which concerns on this invention, it is a figure which shows the simulation result when duty correction regarding the time differentiation of an input electric current value is performed. It is a figure which shows the mode of duty2 in the example of FIG. FIG. 9 is a diagram illustrating the states of duty 2 and duty 3 together with the enlarged view of the example of FIG. 8. FIG. 10 is a diagram illustrating a simulation result when an inductance error is + 50% in the example of FIG. 8. FIG. 12 is a diagram illustrating the states of duty 2 and duty 3 together with the enlarged view of the example of FIG. FIG. 9 is a diagram illustrating a simulation result when an inductance error is set to + 100% in the example of FIG. 8. It is a figure which shows the mode of duty2 and duty3 together with the enlarged view of the example of FIG. FIG. 9 is a diagram illustrating a simulation result when an inductance error is −34% in the example of FIG. 8. FIG. 16 is a diagram showing the states of duty 2 and duty 3 together with the enlarged view of the example of FIG. 15. In the example of FIG. 8, it is a figure which shows the simulation result when the error of an inductance is made into -50%. It is a figure which matches the state of duty2 and duty3 with the enlarged view of the example of FIG. It is a figure which shows the structure of the other rotary electric machine drive system containing the DCDC converter system of embodiment which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, the inverter device will be described as a load drive circuit connected to the DCDC converter system. However, any drive circuit other than the inverter device may be used as long as it is a drive circuit that exchanges DC power with the power storage device via the DCDC converter system. There may be. For example, a general driver circuit may be used. Further, although a three-phase rotating electrical machine mounted on a vehicle will be described as a load device connected to the load drive circuit, it may be a rotating electrical machine other than the vehicle mounted, or a load device other than the rotating electrical machine, for example, an air conditioner It may be a device, an AV device, a small motor, or the like.

  In the following, a limiter is provided as appropriate, but the limiter may be omitted depending on circumstances.

  Below, the same code | symbol is attached | subjected to the same element in all the drawings, and the overlapping description is abbreviate | omitted. In the description in the text, the symbols described before are used as necessary.

  FIG. 1 is a diagram illustrating a configuration of a rotating electrical machine drive system 10 in which a DCDC converter system is used. The rotating electrical machine drive system 10 is a system that drives a rotating electrical machine 12 mounted on a vehicle. The rotating electrical machine drive system 10 includes an inverter device 14 connected to the rotating electrical machine 12, a power storage device 16, a DCDC converter main body 20 provided between the power storage device 16 and the inverter device 14, and a DCDC converter control unit 40. Consists of. Here, the DCDC converter body 20 and the DCDC converter controller 40 correspond to a DCDC converter system.

  The rotating electrical machine 12 is a motor / generator (MG) mounted on the vehicle. When the vehicle is powered, it receives power from the power storage device 16 via the DCDC converter body 20 and functions as a motor. This is a three-phase synchronous rotating electrical machine that drives an axle, functions as a generator during braking, collects regenerative energy, and supplies it to the power storage device 16 via the DCDC converter main body 20.

  The inverter device 14 corresponds to a load driving device when the rotating electrical machine 12 is used as a load. When the rotating electrical machine 12 functions as a generator, the inverter device 14 converts AC three-phase regenerative power from the rotating electrical machine 12 into DC power, and supplies a charging current to the power storage device 16 side via the DCDC converter body 20. Supply AC / DC conversion function. Further, when the rotating electrical machine 12 functions as a motor, the orthogonal power supplied from the power storage device 16 side via the DCDC converter main body 20 to the alternating current three-phase driving power and supplied to the rotating electrical machine 12 as the driving power is orthogonal. Has a conversion function. As shown in FIG. 1, the inverter device 14 is configured by combining a plurality of switching elements and diodes.

  The power storage device 16 is a DC power source that can be charged and discharged. As the power storage device 16, for example, a lithium ion assembled battery or a nickel hydride assembled battery having a terminal voltage of several hundred volts or a capacitor can be used.

  Since the voltage for operating the inverter device 14 is not necessarily the same as the voltage across the terminals of the power storage device 16, a DCDC converter system is provided to exchange power while performing voltage conversion therebetween. The DCDC converter system includes a DCDC converter body 20 that is disposed and connected between the power storage device 16 and the inverter device 14 and a DCDC converter controller 40 that controls the operation of the DCDC converter body 20.

The DCDC converter system has a function of performing voltage conversion between the voltage on the power storage device 16 side and the voltage on the inverter device 14 side by using the energy storage action of the reactor and controlling the duty ratio of the switching element. For example, the voltage on the power storage device 16 side is set to V _L , the voltage on the inverter device side is set to V _H , and the duty ratio of the switching element is controlled to control the voltage conversion ratio V _H / V _L. .

  Here, regarding the power supply lines of the power storage device 16 and the inverter device 14, when the high voltage side is referred to as a positive side bus and the low voltage side is referred to as a negative side bus, the line connected to the positive terminal of the power storage device 16 is The positive electrode bus on the power storage device 16 side, and the line connected to the negative terminal of the power storage device 16 is the negative electrode bus on the power storage device 16 side. Similarly, the high voltage side power supply line of the inverter device 14 is a positive side bus on the inverter device 14 side, and the low voltage side power supply line is a negative side bus on the inverter device 14 side. As shown in FIG. 1, the negative side bus on the power storage device 16 side and the negative side bus on the inverter device 14 side are connected to each other to form a common negative side bus.

On the power storage device 16 side, the smoothing capacitor 30 provided between the positive-side bus and the negative-side bus is a capacitive element that holds _VL that is the input voltage of the DCDC converter body 20. Similarly, on the inverter device 14 side, the smoothing capacitor 32 provided between the positive side bus and the negative side bus is a capacitive element that holds V _H that is the output voltage of the DCDC converter main body 20.

  As described above, the DCDC converter main body 20 constitutes a DCDC converter system together with the DCDC converter control unit 40, and includes the reactor 22, two switching elements 24 and 26 connected in series with each other, and two switching elements. Each of the elements 24 and 26 includes diodes 25 and 27 that are reversely connected in parallel.

The reactor 22 is an element having an inductance value L. When the current I flows, the reactor 22 can store (LI ² ) / 2 electromagnetic energy, and can discharge the stored electromagnetic energy. One side terminal of reactor 22 is connected to one side terminal of power storage device 16, and the other side terminal of reactor 22 is connected to a connection point where two switching elements 24 and 26 are connected in series with each other.

  The two switching elements 24 and 26 have a function of exchanging electric power while performing voltage conversion between the power storage device 16 side and the inverter device 14 side by causing the reactor 22 to accumulate or release electromagnetic energy. . One side of the two switching elements 24 is provided between the other side terminal of the reactor 22 and the positive side bus of the inverter device 14, and the other side of the two switching elements 24 is the other side terminal of the reactor 22 and the inverter device. 14 negative electrode buses.

  When the two switching elements 24 and 26 are distinguished, the switching device 24 connected to the positive bus on the inverter device 14 is connected to the switching device 24 on the upper arm side, and the switching device 24 connected to the common negative bus is connected to the lower arm side. It can be called an element. As the switching elements 24 and 26, a high power bipolar transistor or a high power MIS (Metal Insulator Semiconductor) transistor can be used. For example, an n-channel IGBT (Insulating Gate Bipolar Transistor) can be used.

  The two diodes 25 and 27 are rectifying elements reversely connected in parallel to the two switching elements 24 and 26, respectively. The diode 25 is reversely connected in parallel so that the direction in which the current of the switching element 24 on the upper arm side flows is the forward direction of the rectifying element. That is, the diode 25 has a cathode connected to the positive bus of the inverter device 14 and an anode connected to the other terminal of the reactor 22. Similarly, the diode 27 has a cathode connected to the other terminal of the reactor 22 and an anode connected to a common negative bus.

Here, the voltage conversion ratio = V _H / V _L can be controlled by appropriately changing the ON / OFF duty ratio of the switching elements 24 and 26. The switching elements 24 and 26 are turned on and off in a complementary manner in a normal case. Complementary means that when the upper arm side switching element 24 is on, the lower arm side switching element 26 is off, and conversely, when the lower arm side switching element 26 is on, the upper arm side switching element 24 is off. Is off. The duty ratio is given by ON time / (ON time + OFF time). When the switching elements 24 and 26 are complementarily turned ON / OFF, the duty ratio of the switching element 24 = (1−duty of the switching element 26). Ratio).

  Therefore, when the switching elements 24 and 26 are turned on and off in a complementary manner, the entire operation of the switching elements 24 and 26 can be expressed by the duty ratio of either switching element. Therefore, hereinafter, unless otherwise specified, the duty ratio refers to the duty ratio of the switching element 24 on the upper arm side.

In Figure 1, the switching element 24 of the upper arm is on, energy having a V _H the voltage of the smoothing capacitor 32 as V _H is transferred to the reactor 22. Conversely, the switching element 26 of the switching element 24 of the upper arm and the lower arm side when the off is on, energy having a V _L voltage of the smoothing capacitor 30 as V _L is stored in the reactor 22, the following This energy is transferred to the smoothing capacitor 32. Therefore, when the duty ratio of the switching element 24 of the upper arm side is increased, V _H decreases to V _L, conversely, the duty ratio becomes smaller, V _H increases to V _L.

When the complementary ON / OFF is ideally performed and the resistance of the switching elements 24 and 26 and the resistance of the reactor 22 are negligible, the duty ratio of the switching element 26 of the upper arm is (V _L / V _H )}. Given. For example, if V _L = 300V and the duty ratio is 0.5, then V _H = 600V. On the contrary, when V _L = 300V and V _H = 500V, the duty ratio = (300/500) = 0.6, and when V _L = 300V and V _H = 700V, Duty ratio = (300/700) = 0.428.

  In FIG. 2, the power detector 34 has a function of detecting input power to the rotating electrical machine 12, that is, load power viewed from the inverter device 14. Specifically, it has a function of detecting the voltage and current of the three-phase drive signal from the inverter device 14 and converting it to electric power. The power detector 34 can be configured by a voltage sensor, a current sensor, and a calculation unit that converts power from values detected by these sensors. In some cases, the calculation unit may be a function of the DCDC converter control unit 40. The data of the power detector 34 is transmitted as the load power value P to the divider 68 of the DCDC converter control unit 40 via an appropriate signal line or the like.

The voltage sensor 36 provided corresponding to the smoothing capacitor 30 is an output voltage detector having a function of detecting an input voltage of the DCDC converter main body 20 that is a voltage between both terminals of the smoothing capacitor 30. Data detected by the voltage sensor 36 is transmitted to the DCDC converter control unit 40 via an appropriate signal line or the like as the input voltage detection value V _L.

The voltage sensor 38 provided corresponding to the smoothing capacitor 32 is an output voltage detector having a function of detecting the output voltage of the DCDC converter main body 20 which is a voltage between both terminals of the smoothing capacitor 32. Data detected by the voltage sensor 38 is transmitted as an output voltage detection value V _H to the DCDC converter controller 40 via an appropriate signal line or the like.

The DCDC converter control unit 40 calculates the input current value in the DCDC converter body 20 using the load power value P, the input voltage detection value V _L , and the output voltage detection value V _H transmitted as described above, and the load It has a function of calculating duty3 as a correction duty ratio with respect to power fluctuation and correcting duty2, which is a steady duty ratio when there is no feedback. Further, it has a function of performing power feedback and calculating a duty ratio duty1 by the feedback. It should be noted that the relationship between the on / off state of the upper arm side switching element 24 and the on / off state of the lower arm side switching element 26 is not a completely complementary relationship, and a dead time is provided in which both are turned off. In this case, it also has a function of calculating duty4 for dead time compensation.

  The DCDC converter control unit 40 has a function of issuing an on / off command for the switching elements 24 and 26 of the DCDC converter main body 20 based on these duty1, duty2, duty3, and duty4. Each function of the DCDC converter control unit 40 can be realized by software, specifically, by executing a DCDC converter control program. Of course, a part of each function may be realized by hardware.

  As described above, the DCDC converter control unit 40 generates an on / off command to the switching elements 24 and 26 in order to control the operation of the DCDC converter body 20. In FIG. 1, the generation of the on / off command is represented by the generation of the duty ratio dutyA of the upper switching element 24. For example, in the case of an ideal complementary on / off command, the duty ratio of the switching element 26 can be obtained by (1-duty ratio of the switching element 24) as described above.

  As described above, the DCDC converter control unit 40 issues an on / off command for the switching elements 24 and 26 of the DCDC converter main body 20 based on the duty1, duty2, duty3, and duty4. As a control, a flow based on duty 1 and duty 2 will be described first, then a flow considering duty 3 corresponding to a sudden change in load power will be described, and finally a flow considering duty 4 corresponding to dead time compensation will be described. In some cases, duty4 may be omitted.

Here, in FIG. 1, an output voltage command value V _H ^* is a command value of an output voltage given to the DCDC converter system from a rotating electrical machine control unit (not shown). Further, the inductance value L indicates the inductance value of the reactor 22 in the DCDC converter main body 20.

First, the flow of duty 1 and duty 2 as power feedback control will be described.
duty2 is a steady duty ratio when there is no feedback, and duty1 is a duty ratio by power feedback.

In FIG. 1, the part that generates the on / off command signal for the switching elements 24 and 26 of the DCDC converter main body 20 based on V _H ^* and V _L has no feedback of V _{H and} the feedback of the estimated input current. This is the part of the operation control by the steady duty ratio duty2 when there is no. Specifically, duty 2 is calculated by a low-pass filter (LPF) 46 and a steady-state ratio setting unit 48 using V _H ^* and V _L as input data, and the switching element 24, via the limiter 50 and the triangular wave comparator 52, 26 on / off command signals are generated.

The low-pass filter (LPF) 46 is a filter arithmetic unit having a function of performing a low-pass filter process on the input voltage detection value V _L and outputting V _L-LPF as a post-filtering voltage detection value.

The reason why the low-pass filter process is performed is that if the steady duty ratio is calculated using the input voltage detection value as it is, the steady duty ratio may diverge in some cases, resulting in a control failure. By using _VL-LPF obtained by low-pass filter processing with a low cutoff frequency, divergence of the steady duty ratio can be suppressed.

The steady ratio setter 48 is a calculation means having a function of calculating a duty ratio when there is no feedback using V _H ^* and V _L-LPF and setting it as a steady ratio. The steady-state ratio is the duty ratio of the upper arm, and when this is duty2, it is generally given by (V _L / V _H )} as described above. Here, using the V _H to the output voltage command value V _H ^*, also because in using V _L-LPF instead of V _L, it is given by _{duty2 = (V L-LPF /} V H *).

FIG. 2 is a diagram showing an internal configuration of the steady ratio setting unit 48. The steady ratio setting unit 48 includes a divider 80 and a limiter 82. The divider 80 is arithmetic processing means for outputting A / B = (V _L−LPF / V _H ^* ) with V _L−LPF as the input value A and V _H ^* as the input value B. The limiter 82 is an upper / lower limit calculation processing means for setting an upper limit value and a lower limit value for A / B calculated in this way, and adjusting the value to a range suitable for the subsequent processing. Thus, A / B after setting the upper and lower limits is used as duty 2 in the subsequent processing. As an example of the upper and lower limit settings, the upper limit can be 100% and the lower limit can be 25%. Of course, other values can be used as the upper and lower limits.

In Figure 1, using a square value of the V _H ^* as the power value corresponding to the output voltage command value V _H ^*, using the squared value of V _H as the power value corresponding to the output voltage detection value V _H, these differences The portion for performing PI control for setting the power deviation ΔP to zero as the power deviation ΔP is a portion for calculating duty 1 by power feedback.

Specifically, the subtractor 58 for obtaining a squarer 56, V _H ^* power deviation ΔP from squared values of the squared value and the V _H of obtaining the square values of the squarer 54, V _H for obtaining the squared value of the V _H ^*, A PI controller 60 and a limiter 62 are included. The PI controller 60 is a proportional differential control calculation processing means for inputting ΔP, performing a proportional integral calculation on this, and outputting a duty ratio for setting ΔP to zero. The limiter 62 is an upper / lower limit calculation processing means for applying an upper / lower limit to the duty ratio output in this way so as not to exceed the ability of the subtractor 66 or the like for performing the subsequent processing. In this way, the duty after the upper and lower limit settings are made becomes duty1 for adding power feedback correction to duty2.

  Power feedback can be performed more quickly than voltage feedback. In other words, the voltage feedback is the voltage across the terminals of the smoothing capacitor that holds the output voltage, and is therefore affected by the charging / discharging time of the smoothing capacitor. On the other hand, since the power change according to the power deviation is faster than the voltage change of the smoothing capacitor, the power feedback can perform feedback more quickly than the voltage feedback, and therefore the output voltage of the DCDC converter system. The fluctuation can be effectively suppressed.

Next, duty 3 corresponding to a sudden change in load power will be described. The response to the sudden change in the load power is executed using the duty 3 calculated based on the following idea. That is, the load power value P is divided by the input voltage detection value V _L of the DCDC converter main body 20, and the input current value to the DCDC converter main body 20 that is the output current value of the power storage device 16 corresponding to the load power value P first, calculate the I _B. Here, the acquisition of the input current value I _B, not used a current sensor. Next, the time differential value of the input current value I _B is multiplied by the inductance value L of the reactor 22 to be converted into a voltage value, and the value is divided by the output voltage command value V _H ^* . This division value is duty3.

Specifically, in FIG. 1, the load power values P and V _L are input to the divider 68, and P / V _L = I _B is calculated. Then, I _B is input to the differentiator 70 to calculate dI _B / dt. On the other hand, the inductance value L and the output voltage command value V _H ^* are input to the divider 72 to calculate L / V _H ^* . Then, the calculated L / V _H ^* and dI _B / dt are input to the multiplier 74, and (L / V _H ^* ) × (dI _B / dt) = duty3 is calculated.

Thus, since it is calculated as ^{_{duty3 = (L / V H *}} ) × (dI B / dt), higher inductance value L used in the calculation is small, Duty3 decreases close to when the correction is not performed Become. Here, if correcting the inductance value L using the input current value I _B corresponding to the load power value P, you can reduce the error of inductance values L. As described above, in the divider 68, using a load power value P (P / V _L) = With obtaining the I _B, it is possible to absorb some error of inductance values L. Instead of _VL input to the divider 68, _VL-LPF , which is a value after low-pass filter processing of _VL , may be used.

  When duty1, duty2, and duty3 are respectively calculated in this way, the subtractor 76 calculates (duty2-duty3), and the result is further subtracted by the subtractor 66 from duty1. That is, (duty2-duty3-duty1) is output from the subtractor 66. This value is obtained by subtracting duty 3 which is a correction duty ratio with respect to load power fluctuation, and further subtracting duty 1 due to power feedback from duty 2 which is a steady duty ratio when feedback is not applied.

Next, the duty 4 that is the compensation duty ratio with respect to the dead time will be described. In the above description, it is assumed that the upper arm side switching element 24 and the lower arm side switching element 26 of the DCDC converter main body 20 are turned on and off in a complementary manner. That is, when the upper arm side switching element 24 is on, the lower arm side switching element 26 is turned off. Conversely, when the lower arm side switching element 26 is on, the upper arm side switching element 24 is turned off. Alternatively, a dead time _{Td during} which both the upper arm side switching element 24 and the lower arm side switching element 26 are turned off may be provided.

In the above description, when the upper arm side switching element 24 and the lower arm side switching element 26 of the DCDC converter main body 20 are turned on and off in a complementary manner, the upper arm side switching element 24 depends on the response of the switching element. And the lower arm side switching element 26 can both be turned on. In this case, a through current flows between the positive side bus and the negative side bus. If the dead time _Td is provided, it is possible to prevent such a through current from occurring. However, when the dead time _Td is provided, for example, different on / off control is performed with respect to the steady duty ratio, so it is preferable to compensate the duty ratio. The duty ratio for this compensation is duty4.

As described in Patent Document 1, the duty 4 can be set to T _d / (T _ON + T _OFF ) = duty 4 using the _ON time T _ON and the OFF time T _OFF , but depending on the direction in which the input current flows, the duty 4 The sign of is different. In FIG. 1, duty4 is on the addition side in the subtractor 66, but the sign of duty4 changes depending on the direction in which the input current flows, and may be on the subtraction side.

The sign of duty4 can be determined by detecting the direction of current flow using a sensor that detects the input current. Further, by using voltage detection means for detecting the voltage at the connection point between the switching element 24 and the switching element 26, depending on whether the voltage at the connection point during the dead time period is close to V _H or close to the voltage of the negative side bus, It is also possible to determine the sign of duty4 by judging the direction of current flow. The latter method requires voltage detection but does not require a current sensor, so that the cost can be reduced.

Specifically, in the dead time compensator 64, a compensation duty ratio corresponding to a preset dead time _Td is calculated and output as duty4 whose sign is determined according to the direction in which the input current flows. The By performing the dead time compensation, the voltage control performance of the DCDC converter system can be further improved.

  Thus, when the configuration includes the dead time, the dead time compensator 64 outputs the duty 4 that is the compensation duty ratio with respect to the dead time, and inputs the duty 4 to the subtractor 66. Therefore, when duty4 is used, (duty2-duty3-duty1 + duty4) is output from the subtractor 66.

  These duty1, duty3, and duty4 are used to correct duty2, which is a steady duty ratio. For example, when the steady ratio setting unit 48 sets duty2 = 0.5 and the correction duty ratio with respect to the load power fluctuation is duty3 = + 0.1, the subtractor 76 is duty2-duty3 = 0.5-0. 1 = 0.4 is output.

  Then, if it is calculated that duty1 = −0.2 and the dead time is not set and duty4 = 0, the subtractor 66 uses (duty2−duty3−duty1 + duty4) = 0.4 + 0.2 = 0.6. Is output. This value is dutyA.

  The triangular wave comparator 52 in FIG. 1 is a control signal generator having a function of converting the calculated duty A into an on / off control signal of the switching elements 24 and 26 constituting the DCDC converter main body 20.

For example, when dutyA = 0.4 is calculated in the above example, for the switching element 24 on the upper arm side, a pulse with an on-time of 40% and an off-time of 60% with respect to the period T ₀ of the reference triangular wave A signal is output. For the switching element 26 on the lower arm side, a complementary pulse signal is output to the switching element 24. That is, a pulse signal is output so that the switching element 26 is turned off when the switching element 24 is on, and the switching element 26 is turned on when the switching element 24 is off.

  Thus, in the DCDC converter system, it is possible to cope with load power fluctuations without using a current sensor. Moreover, since power feedback is used, output voltage fluctuation can be effectively suppressed. Further, even when the dead time is set, the compensation can be performed.

  In the above description, the number of rotating electric machines is one. However, it is also possible to have two rotating electric machines and one DCDC converter main body for each inverter. FIG. 3 “is a diagram showing a configuration of a rotating electrical machine drive system 11 in which two rotating electrical machines 12 and 13 are mounted on a vehicle and one is used for driving a vehicle and the other is used for a generator.

  In this configuration, the rotating electrical machine 13 is increased as compared with the configuration of FIG. 1, and an inverter device 15 is provided for driving the rotating electrical machine 13. The two inverter devices 14 and 15 are connected to one DCDC converter main body 20.

The power detector 34 is used to detect the load power value P ₁ from the inverter device 14, whereas the power detector 35 is provided to detect the load power value P ₂ from the inverter device 15. . Then, a subtractor 78 is provided in front of the divider 68, (P ₁ −P ₂ ) = P is calculated, and this value is input to the divider 68 as a load power value P. That is, as the load power value P, the difference in the amount of power between the two rotating electrical machines 12 and 13 is used. Since the configuration of the other DCDC converter main body 20 and the configuration of the DCDC converter control unit 40 that controls the configuration are the same as those described with reference to FIG. 1, detailed description thereof is omitted.

  The operation of the above configuration, in particular, the effect on fluctuations in load power will be described with reference to FIGS. 4 to 10, and the influence of the error of the inductance value L will be described with reference to FIGS. These all show the results of simulation.

  FIG. 4 is a diagram schematically showing fluctuations in load power used for the simulation. The horizontal axis in FIG. 4 indicates time, and the vertical axis indicates the magnitude of the load power. Here, the load power suddenly changes from the H level to the L level between the times 0.14 s and 0.15 s.

  FIGS. 5 to 7 illustrate the case where the power feedback control is performed and the duty 3 is not corrected in the configuration of FIG. FIG.

5, the horizontal axis indicates time and the vertical axis is the output voltage command value V _H ^*, the output voltage detection value V _H, the input voltage detection value V _L, the V _L-LPF subjected to low-pass filtering on the V _L It has been taken. FIG. 6 is a diagram showing a time change state of duty 2 calculated by the function of the steady-state ratio setting unit 48 based on V _H ^* and V _L-LPF in FIG. 5, and the horizontal axis is common to FIGS. 4 and 5. Has been taken in time. FIG. 7 is a partially enlarged view of FIG. 5 and also shows how the duty 2 changes.

As can be seen from these figures, when the load power in FIG. 4 fluctuates, the output voltage detection value V _H once deviates from the output voltage command value V _H ^*. However, since duty 2 changes accordingly, V _H again ^* Follows. Out from the V _H ^* of V _H is about 50V at a maximum.

  8 to 10 are the same as FIGS. 5 to 7. Here, in the configuration of FIG. 1, when the power feedback control is performed and the duty 3 is corrected, the load fluctuation of FIG. It is a figure explaining the change of the input voltage and output voltage at a time with the change of duty2 and duty3.

As shown in FIG. 9, correction of duty 3 having a negative magnitude is performed in accordance with the variation in load power in FIG. 4. As a result, as shown in the enlarged view of FIG. 10, out-of-V _H ^* of the V _H is most suppressed to approximately 30 V.

8 to 10 show ideal simulation results on the assumption that there is no error in the inductance value L. FIG. As described in connection with the calculation of duty 3 in FIG. 1, since it is calculated as duty 3 = (L / V _H ^* ) × (dI _B / dt), therefore, if there is an error in the inductance value L, the duty 3 An error occurs in the calculation. For example, the smaller the inductance value L used for this calculation, the smaller the duty 3 becomes, and the closer to the case where correction is not performed. Note that by so as to calculate the input current value I _B with the load power value P, it has already been described that can absorb some of the errors of the inductance value L.

  11 to 18 are diagrams showing the results of simulating the influence of the inductance value L. FIG. 11 and 12 show a case where the inductance value L has an error of + 50%. FIG. 11 corresponds to FIG. 8, and FIG. 12 corresponds to FIG. Similarly, FIGS. 13 and 14 show cases where there is an error of + 100% in the inductance value L, FIG. 13 corresponds to FIGS. 8 and 11, and FIG. 14 corresponds to FIGS. FIGS. 15 and 16 show the case where the inductance value L has an error of −34%. FIG. 15 corresponds to FIGS. 8, 11, and 13, and FIG. 16 corresponds to FIGS. FIG. FIGS. 17 and 18 show the case where there is an error of −50% in the inductance value L. FIG. 17 corresponds to FIGS. 8, 11, 13, and 15. FIG. 18 shows FIGS. FIG. 17 is a diagram corresponding to FIG. 16.

These figures show that the effect of duty 3 decreases as the error of the inductance value L becomes negative. For example, even when the error of the inductance value L is −50%, V _H of V _H It can be seen that deviation from ^* is suppressed as compared with FIG. 7 in which the correction of duty 3 is not performed.

  In the above description, power feedback is used, but this can also be voltage feedback. FIG. 19 is a diagram showing a configuration of a rotating electrical machine drive system 17 in which current control is incorporated into a minor loop of voltage feedback to further improve control stability. Here, as with the rotating electrical machine drive system 10 of FIG. 1, only one rotating electrical machine 12 is shown, but this may correspond to the two rotating electrical machines 12 and 13 as shown in FIG.

In the rotating electrical machine drive system 17, a current sensor 90 that detects an input current of the DCDC converter main body 20 is used. Data detected by the current sensor 90 is transmitted as an input current value I _B to the DCDC converter control unit 40 through an appropriate signal line.

In the DCDC converter control unit 40, a subtractor 93 for obtaining a voltage deviation ΔV _H which is a deviation between the output voltage detected value V _H which is a detected value of the voltage sensor 38 and the output voltage command value V _H ^* , and a voltage deviation ΔV _H A PI controller 94 that performs proportional-integral control processing so as to make the value zero, a limiter 96 that outputs an input current command value I _B ^* with upper and lower limits defined for the output of the PI controller 94, and an input current command value a subtracter 98 for calculating the I _B ^* and the input current value current deviation [Delta] I _B is the deviation between I _B, the PI controller 100 that performs proportional integral control process to the current deviation [Delta] I _B to zero, PI control There is provided a limiter 96 for outputting duty 1 as a duty ratio having upper and lower limits defined for the output of the device 100.

With this configuration, a current control minor loop for the input current value I _B can be incorporated in the feedback of the output voltage detection value V _H. In FIG. 19, the input current is detected using the current sensor 90, but the input current can be estimated using an appropriate input current estimation method. In this case, the current sensor 90 can be omitted.

  The DCDC converter system according to the present invention can be used by being connected to an inverter device that drives a rotating electrical machine mounted on a vehicle, for example.

  10, 11, 17 Rotating electrical machine drive system, 12, 13 Rotating electrical machine, 14, 15 Inverter device, 16 Power storage device, 20 DCDC converter body, 22 Reactor, 24, 26 Switching element, 25, 27 Diode, 30, 32 Smoothing Capacitor, 34, 35 Power detector, 36, 38 Voltage sensor, 40 DCDC converter control unit, 48 Steady ratio setter, 50, 62, 82, 96 limiter, 52 Triangular wave comparator, 54, 56 Squarer, 58, 66 76, 78, 93, 98 Subtractor, 60, 94, 100 PI controller, 64 Dead time compensator, 68, 72, 80 Divider, 70 Differentiator, 74 Multiplier, 90 Current sensor.

Claims (7)

A DCDC converter system that is provided between a power storage device and a load driving device and performs voltage conversion by controlling a duty ratio of a switching element based on an output voltage command value,
A steady duty ratio calculating means for calculating a steady duty ratio based on an input voltage value which is a terminal voltage of the power storage device and an output voltage command value;
Means for calculating an input current value based on a load power value that is a power value of a load driven by the load driving device and an input voltage detection value that is a detection value of an input voltage detector that detects the input voltage value; ,
Means for calculating a correction duty ratio with respect to load power fluctuation based on a time differential value of an input current value, an inductance component value, and an output voltage detection value that is a detection value of an output voltage detector that detects an output voltage value;
Means for setting the duty ratio of the switching element based on the steady duty ratio and the correction duty ratio for the load power fluctuation;
A DCDC converter system comprising: The DCDC converter system according to claim 1, wherein
The means for calculating the correction duty ratio is:
The time differential value of the input current value is multiplied by the inductance component value, and the output voltage detection value that is the detection value of the output voltage detector that detects the output voltage value is divided to calculate the correction duty ratio. DCDC converter system. The DCDC converter system according to claim 1, wherein
The deviation between the square value of the output voltage detection value, which is the detection value of the output voltage detector that detects the output voltage value, and the square value of the output voltage command value is defined as the power deviation, and the duty by the power feedback according to the power deviation Means for calculating the ratio,
The DCDC converter system characterized in that the means for setting the duty ratio of the switching element calculates the duty ratio of the switching element based on the steady duty ratio, the correction duty ratio with respect to the load power fluctuation, and the duty ratio by feedback. The DCDC converter system according to claim 1, wherein
Means for calculating an input current command value according to a deviation between an output voltage detection value and an output voltage command value, which is a detection value of an output voltage detector for detecting an output voltage value;
Means for calculating a duty ratio by voltage feedback based on a deviation between an input current value that is a detection value of an input current detector that detects an input current value and an input current command value;
With
The DCDC converter system characterized in that the means for setting the duty ratio of the switching element calculates the duty ratio of the switching element based on the steady duty ratio, the correction duty ratio with respect to the load power fluctuation, and the duty ratio by feedback. The DCDC converter system according to claim 3 or 4,
The switching element includes an upper arm side switching element and a lower arm side switching element connected in series between the positive side bus and the negative side bus,
When there is a dead time between the upper arm side switching element on / off and the lower arm side switching element on / off, depending on the size of the dead time, Means for calculating a compensation duty ratio;
The means for setting the duty ratio of the switching element calculates the duty ratio of the switching element based on the steady duty ratio, the correction duty ratio with respect to load power fluctuation, the duty ratio by feedback, and the compensation duty ratio with respect to dead time. DCDC converter system characterized by the above. The DCDC converter system according to claim 1, wherein
The steady duty ratio calculation means is
A DCDC converter system, wherein a steady duty ratio is calculated based on a post-filtering voltage detection value obtained by performing low-pass filtering on an input voltage detection value and an output voltage command value. The DCDC converter system according to claim 1, wherein
The DC / DC converter system, wherein the load driving device is an inverter device connected to the rotating electrical machine.

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