JP6685967B2 - Control device for DC / DC converter - Google Patents

Description

  The present invention relates to a control device for a DC / DC converter.

  2. Description of the Related Art Conventionally, an electric vehicle or a hybrid vehicle has been equipped with a DC / DC converter for performing voltage conversion such as step-up of a voltage supplied from a DC power source.

For such a DC / DC converter, Patent Document 1 discloses a technique for controlling the duty ratio of the DC / DC converter according to the power consumption of the load. In this technique, the DC / DC converter includes two switching elements and a reactor. This technique controls a capacitor for smoothing the output voltage from the reactor, and the detection value v _c of the capacitor voltage is the voltage across the capacitor, a reactor current flowing through the reactor based on the target capacitor voltage v _c ^* A reactor current command value for is calculated.

JP, 2005-76986, A

  In the configuration that calculates the reactor current command value using the detected value of the capacitor voltage like the configuration described in Patent Document 1, if there is a detection error of the capacitor voltage, the reactor current command value cannot be calculated accurately. there is a possibility. If the calculation accuracy of the reactor current command value decreases, the capacitor voltage cannot be accurately controlled according to the target value.

  Further, it is possible to use a duty ratio error due to dead time for generating the reactor current command value. Dead time is the time when two switching elements of a DC / DC converter are simultaneously turned off. On the other hand, in the configuration in which the duty ratio error is used to generate the reactor current command value in this way, when there is a capacitor voltage detection error, the duty ratio error includes the capacitor voltage detection error. The accuracy decreases. Also in this case, the accuracy of calculating the reactor current command value may decrease.

  On the other hand, in the case where the detected value of the capacitor voltage is smaller than the actual voltage, it is conceivable to boost the capacitor voltage higher than the target voltage to obtain the actual voltage. However, in this case, when the inverter is connected to the output side of the DC / DC converter, the switching loss of the DC / DC converter and the inverter increases. Further, when the detected capacitor voltage value is higher than the actual voltage, it is possible to boost the capacitor voltage below the target voltage to obtain the actual voltage. However, in this case, the output voltage limit of the inverter becomes low when the inverter is connected to the DC / DC converter.

  One aspect of the present invention is a DC / DC including a first switching element and a second switching element, and a reactor whose both ends are connected to a connection point of the first switching element and the second switching element and a DC power supply. A control device for controlling a converter, the difference being a duty ratio in the presence or absence of dead time with respect to a duty ratio which is a ratio of an ON time of the first switching element, according to a current state value of the DC / DC converter. An error duty ratio, a capacitor voltage which is a voltage across a capacitor connected to the DC / DC converter and smoothing an output voltage from the reactor, an observer for estimating a capacitor voltage detection error of the capacitor, and the error duty ratio. And a state equation including the detection error of the capacitor voltage A current command generator that calculates a reactor current command value that is a target value for controlling the reactor current flowing through the reactor, and a duty ratio control that controls the duty ratio of the DC / DC converter according to the reactor current command value. And a controller for controlling the DC / DC converter according to the reactor current command value.

  One aspect of the present invention is a DC / DC including a first switching element and a second switching element, and a reactor whose both ends are connected to a connection point of the first switching element and the second switching element and a DC power supply. A control device for controlling a converter, the difference being a duty ratio in the presence or absence of dead time with respect to a duty ratio which is a ratio of an ON time of the first switching element, according to a current state value of the DC / DC converter. An error duty ratio, a capacitor voltage that is a voltage across the capacitor that is connected to the DC / DC converter and that smoothes the output voltage from the reactor, and an observer that estimates a capacitor voltage detection error of the capacitor; From the target capacitor voltage command value, the capacitor A current command for calculating a reactor current command value that is a target value for controlling the reactor current flowing through the reactor by performing a PI operation on the deviation obtained by subtracting the detected value of the pressure and the detection error of the capacitor voltage. A control that includes a generator and a duty ratio controller that controls a duty ratio of the DC / DC converter according to the reactor current command value, and controls the DC / DC converter according to the reactor current command value. It is a device.

  According to the present invention, in a DC / DC converter including two switching elements and a reactor, the reactor current command value can be calculated with high accuracy, so that the DC / DC converter can be controlled with high accuracy.

It is a figure showing the basic composition of the motor drive which contains the control device of the DC / DC converter in the embodiment of the present invention. It is a figure which shows the structure of the control apparatus of the DC / DC converter in embodiment of this invention. It is a figure which shows the observer shown in FIG. It is a figure which shows the structure of the switching part of the observer gain shown in FIG. It is a figure which shows the structure of the control apparatus in another example of embodiment of this invention. It is a figure which shows the structure of the control apparatus in another example of embodiment of this invention. It is a figure which shows the structure of the model prediction controller which comprises the duty ratio controller shown in FIG. It is a figure which shows the structure of the control apparatus in another example of embodiment of this invention. It is a figure which shows the structure of the electric current command generator in another example of embodiment of this invention. FIG. 10 is a diagram showing a capacitor voltage waveform when the duty ratio is fixed in a configuration in which the control device does not include a notch filter, unlike the embodiment shown in FIG. 9. FIG. 10 is a diagram showing control of voltage and current when the capacitor voltage detection error is −10 V in the control device of the first example of the comparative example. It is a figure which shows the control of the voltage and current in case the capacitor voltage detection error is -10V in the control apparatus of the 2nd example of a comparative example. FIG. 10 is a diagram showing voltage and current control when the capacitor voltage detection error is −10 V in the embodiment shown in FIG. 9. It is a figure which shows the structure of the control apparatus in another example of embodiment of this invention. It is a figure which shows the structure of the electric current command generator shown in FIG. In an embodiment of the present invention, it is a figure showing an example of current dependence in the inductance of a reactor.

<First Embodiment>
FIG. 1 shows a basic configuration of a motor drive device 100 including a DC / DC converter control device 30 according to the first embodiment. The motor drive device 100 includes a DC power supply 10, a DC / DC converter 11, a low voltage side capacitor 17, a high voltage side capacitor 18, and a load 104. The DC / DC converter 11 includes a reactor 12, a first switching element 14, and a second switching element 16. The first switching element 14 corresponds to the upper switching element, and the second switching element 16 corresponds to the lower switching element. The load 104 includes an inverter 105 and a motor 106 connected to the inverter 105 and driven by the inverter 105. The motor 106 is a three-phase motor driven by U-phase, V-phase, and W-phase three-phase alternating currents.

  One end of the reactor 12 is connected to the positive electrode of the DC power supply 10, and the connection point C of one end of the first switching element 14 and one end of the second switching element 16 is connected to the other end of the reactor 12. The other end of the first switching element 14 is connected to the positive electrode side of the inverter 105 that constitutes the load 104 via the positive electrode bus 19. The other end of the second switching element 16 is connected to the negative electrode of the DC power supply 10 and the negative electrode side of the inverter 105 via the negative electrode bus 20. The low-voltage side capacitor 17 is connected between one end of the reactor 12 and the positive electrode of the DC power supply 10 and the negative electrode bus 20 on the input side of the DC / DC converter 11, and is used to smooth the voltage. The high-voltage side capacitor 18 is connected between the positive electrode bus 19 and the negative electrode bus 20 on the output side of the DC / DC converter 11, and is used to smooth the output voltage from the reactor 12.

  In the embodiment, the first switching element 14 and the second switching element 16 are NPN transistors. The first switching element 14 has a positive electrode bus bar 19 side as a collector and a reactor 12 side as an emitter. The second switching element 16 has a reactor 12 side as a collector and a negative electrode bus 20 side as an emitter. A freewheeling diode is connected in parallel with each of the first switching element 14 and the second switching element 16.

In the DC / DC converter 11, the first switching element 14 is turned off and the second switching element 16 is turned on, so that the reactor current i _L flowing from the positive electrode to the negative electrode of the DC power supply 10 flows through the reactor 12. . As a result, energy is stored in the reactor 12. Next, by turning off the second switching element 16, the reactor current i _L is cut off, and a voltage higher than the voltage of the DC power supply 10 (power supply voltage v _b ) is generated at the end of the reactor 12. Then, a current corresponding thereto flows toward the positive electrode bus 19 to charge the high-voltage side capacitor 18, and the capacitor voltage v _c, which is the voltage across the high-voltage side capacitor 18, rises. This capacitor voltage v _c is applied to the load 104. Further, since the first switching element 14 is turned on, the reactor current i _L flows from the high voltage side capacitor 18 to the positive electrode of the DC power supply 10. This causes the capacitor voltage v _c to drop. The output voltage of the DC / DC converter 11, that is, the capacitor voltage v _c is determined by the duty ratio indicating the ON ratio of the first switching element 14 for one cycle of the carrier signal.

In the DC / DC converter 11, the on / off state of each of the switching elements 14 and 16 is controlled by the control device 30. The current state value of the DC / DC converter 11 is input to the control device 30. The control device 30 controls the DC / DC converter 11 according to the input state value. As the state value, the power supply voltage v _b of the DC power supply 10, the reactor current i _L flowing through the reactor 12, the capacitor voltage v _c of the capacitor 18, the currents i _u and i _w of the motor 106 as a load, and the rotation angle θ of the motor 106 The detected value is input to the control device 30 from the corresponding sensor. For example, the motor drive device 100 includes a reactor current detector 22 that detects the reactor current i _L. Control device 30 calculates the output current i _m of the motor current i _u, i _w and the DC / DC converter 11 from the rotation angle θ of the motor.

  FIG. 2 is a diagram showing a configuration of the control device 30. The control device 30 is configured to include a current command generator (iL command generator) 31, an observer 32, a duty ratio controller 34, and a triangular wave comparator 36.

The capacitor voltage command value v _c ^* and the capacitor voltage detection value v _c are input to the current command generator 31. Further, an estimated value of a reactor current i _L flowing through the reactor 12 from an observer 32 described later, an error duty ratio Δd (= Δd (k)) described later, and an estimated value of the capacitor voltage detection error Δv _c is input to the current command generator 31. To be done. The current command generator 31 generates a command value i _L ^* of the reactor current according to these input values. The reactor current command value i _L ^* is a value that is a target value for controlling the reactor current, and is input to the duty ratio controller 34 described later. The current command generator 31 will be described later in detail. In the following, the estimated value in the figure is shown with a superscript wavy line (tilde).

Observer 32 receives the capacitor voltage v _c, the power supply voltage v _b and the output current i _m, using a state equation of the DC / DC converter 11 from these values, the current error duty ratio Δd (= Δd (k) ) Is calculated and output.

Here, in order to explain the state equation of the DC / DC converter 11, first, a comparative example state equation will be described as a state equation of the comparative example assuming that the detection error Δv _c of the capacitor voltage is not included.

The comparative equation of state is represented by equation (1). Here, the capacitor voltage v _c, the reactor current i _L, the power supply voltage v _b, the output current (load current) i _m, inductance of the reactor 12 is L, and the capacitance of the capacitor 18 C, the resistance value of the reactor 12 Is denoted by R _L and the duty ratio is denoted by d.

If the error duty ratio Δd considering the dead time is incorporated into the equation (1), the state equation shown in the equation (2) is obtained. Here, the error duty ratio is the difference between the duty ratio which is the ratio of the ON time of the first switching element and the duty ratio caused by the presence or absence of dead time.

When the mathematical expression (2) is discretized using the bilinear transformation, the mathematical expression (3) is obtained.

  FIG. 3 is a diagram showing the observer 32 of the embodiment. In the observer 32, the input signal and the output signal are as shown in FIG. In FIG. 3, A is obtained by multiplying the coefficient indicated by the broken line frame α in Expression (3) by the matrix indicated by the broken line frame A1, and is represented by α × A1.

In FIG. 3, B is a product of the coefficient indicated by the broken line frame α of the mathematical expression (3) and the matrix indicated by the broken line frame B1, and is represented by α × B1. C in FIG. 3 is represented by the mathematical expressions (4a) and (4b).

Although the accuracy of estimating the reactor current can be increased by using C represented by the formulas (4a) and (4b) as C in FIG. 3, the formula (5) can also be used to reduce the calculation amount. .

Here, in the present embodiment, as the state equation of the DC / DC converter 11, Equation (6) including the error duty ratio Δd and the capacitor voltage detection error Δv _C is defined.

When the formula (6) is discretized using the bilinear transformation, the formula (7) is obtained.

Based on the equation (7), the capacitor voltage estimated value v _c (tilde) (k), which is the estimated value of the voltage of the capacitor 18, and the reactor current estimated value i _L ((tilde), which is the estimated value of the current of the reactor 12, are _calculated. ) (K) can be expressed as in Expression (8). Further, based on the equation (7), the error duty ratio estimated value Δd to (tilde) (k) which is the estimated value of the error duty ratio and the capacitor voltage detection error estimated value Δv _c which is the estimated value of the capacitor voltage detection error. ~ (Tilde) (k) can be expressed as in Expression (8). Here, T is the control cycle, h ₁ to h ₄ is the observer gain. In the following, the tilde symbol ~ (dashed line) representing the estimated value may be omitted.

Observer 32, the capacitor voltage is inputted v _c, the power supply voltage v _b and the output current i _m By substituting the equation (8), the current error duty ratio [Delta] d (= [Delta] d (k)) and the reactor current i _L The estimated value of (= i _L (k)) is calculated. The observer 32 also calculates an estimated value of the capacitor voltage detection error Δv _c (= Δv _c (k)).

The estimated error duty ratio estimated value Δd (tilde), the reactor current estimated value i _L (tilde), and the capacitor voltage detection error estimated value Δv _c (tilde) are the same as k-1 in Equation (8). It can be calculated by rereading and processing. The calculated error duty ratio estimation value Δd (tilde), reactor current estimation value i _L (tilde), and capacitor voltage detection error estimation value Δv _c (tilde) are input to the current command generator 31 (FIG. 2). .

  Note that k indicates the number of times of control. For example, d (k) represents the duty ratio d in the kth control, and d (k + 1) represents the duty ratio d in the (k + 1) th control. The same applies to other state quantities.

Here, in the present embodiment, the observer 32 has the four observer gains h ₁ , h ₂ , h ₃ , and h ₄ of Expression (8). Of these, the values of h ₃ and h ₄ corresponding to the third and fourth lines of the equation (8) are switched depending on whether or not the first switching element 14 is always on. Hereinafter, h ₃ may be referred to as a first observer gain h _3, and h ₄ may be referred to as a second observer gain h ₄ . The observer gains h ₁ , h ₂ , h ₃ and h ₄ correspond to h in FIG.

FIG. 4 is a diagram showing the configuration of the observer gain switching unit 37. The control device 30 has a switching unit 37, and the switching unit 37 switches the values of the first and second observer gains h ₃ and h ₄ depending on whether the first switching element 14 is always on. Specifically, the first observer gain h ₃ is an observer gain for calculating the duty ratio with an error due to dead time. The second observer gain h ₄ is an observer gain for calculating the capacitor voltage detection error.

  In FIG. 4, the ON / OFF state of the first switching element 14 is input to the switching unit 37 as the always-on signal of the upper arm. In FIG. 4, “1” inside the switching unit 37 indicates that the first switching element 14 is always on and the upper arm is always on. At this time, the second switching element 16 is always turned off. Inside the switching unit 37 of FIG. 4, “0” indicates that the first switching element 14 has started switching and that the upper arm is constantly turned off. At this time, the second switching element 16 also starts switching.

The switching unit 37 sets the first observer gain h ₃ to 0 and sets the second observer gain h ₄ to a numerical value C4 other than 0 when the first switching element 14 is constantly turned on. On the other hand, the switching unit 37 sets the second observer gain h ₄ to 0 by giving the first observer gain h ₃ a value other than 0 after the first switching element 14 is normally turned off.

Further, the observer gains h ₁ and h ₂ corresponding to the first and second rows of the equation (8) have numerical values C1 and C2 other than 0 regardless of the always-on state of the first switching element 14. .

As a result, when the first switching element 14 is always turned on, the value corresponding to the capacitor voltage detection error is output corresponding to the second observer gain h ₄ , so that the capacitor voltage detection error can be accurately estimated. Further, when the first switching element 14 is constantly turned off, a value corresponding to the error duty ratio due to the dead time is output corresponding to the first observer gain h ₃ . Thereby, the duty ratio can be accurately calculated using the error duty ratio. In this manner, the observer 32 using the equation (8) can estimate the capacitor voltage detection error, and the estimated value is used in the next control cycle to calculate the capacitor voltage v _c , the reactor current i _L , and the error duty ratio Δd. The estimated value of is estimated.

The observer 32 thus estimates the capacitor voltage v _c , the reactor current i _L , and the capacitor voltage detection error Δv _c . As shown in FIG. 2, the observer 32 outputs the error duty ratio estimated value Δd (tilde) and the capacitor voltage detection error estimated value Δv _c (tilde) as disturbances.

On the other hand, in the current command generator 31, the reactor current command value i _L ^* is calculated by modifying the mathematical expression obtained by discretizing the state equation of the DC / DC converter 11, that is, the mathematical expression (7). In the equation (7), the reactor current command value i _L ^* is Δd, where v _c (k + 1) in the first row on the left side is v _c ^* (k), and i _L (k) on the right side is i _L ^* (k). (K) is replaced with Δd (k) (tilde), and Δv _c is replaced with Δv _c (k) (tilde), and the expansion is performed using the equation (9). The reactor current command value i _L ^* calculated by the current command generator 31 and the current reactor current i _L (actual measurement value) are input to the duty ratio controller 34.

The duty ratio controller 34 performs an operation for obtaining the duty ratio d (k + 1) that is a command value. The duty ratio d (k + 1) that is the command value can be calculated by the mathematical expression (10). The duty ratio controller 34 has a PI calculator and an F / F compensator.

  The PI calculation unit of the duty ratio controller 34 calculates the second and third terms on the right side of Expression (10). In Expression (10), Kp is a coefficient of the proportional term, and Ki is a coefficient of the integral term.

The F / F compensator of the duty ratio controller 34 receives the capacitor voltage command value v _c ^* and the power supply voltage v _b and calculates the feed forward compensation value. The feed forward compensation value is represented by the first term on the right side of Expression (10). The output value from the PI calculation unit and the output value from the F / F compensation unit are added and output from the duty ratio controller 34 as the duty ratio d (k + 1).

The duty ratio d (k + 1) output from the duty ratio controller 34 is input to the triangular wave comparator 36. The triangular wave comparator 36 compares the value of the triangular wave carrier signal with the duty ratio, generates a switching signal based on the comparison result, and outputs the switching signal to the switching elements 14 and 16 of the DC / DC converter 11. The on / off state of each of the switching elements 14 and 16 is controlled by the switching signal, so that appropriate voltage control is performed. As a result, the DC / DC converter 11 is controlled according to the reactor current command value i _L ^* .

Specifically, the control device 30 controls the ON periods of the first switching element 14 and the second switching element 16 so that the duty ratio d (= d (k + 1)) output from the duty ratio controller 34 is obtained. . As a result, the DC / DC converter 11 controls the capacitor voltage v _c and the reactor current i _L such that the command value is the capacitor voltage command value v _c ^* and the reactor current command value i _L ^* .

  The duty ratio d (k + 1) output from the duty ratio controller 34 can also be input to a limiter (not shown). The limiter receives the duty ratio d (k + 1) output from the duty ratio controller 34, and limits the input duty ratio d (k + 1) so as to be within the optimum duty ratio range DR. The duty ratio d (k + 1) in the optimum range output from the limiter is input to the triangular wave comparator 36. As a result, the control device 30 controls the ON periods of the first switching element 14 and the second switching element 16 so that the duty ratio d (= d (k + 1)) input to the triangular wave comparator 36 is achieved.

According to the control device 30 described above, the current command generator 31 calculates the reactor current command value i _L ^* from the state equation including the error duty ratio and the capacitor voltage detection error. Thus, in the DC / DC converter 11, the reactor current command value i _L ^* can be accurately calculated even if there is a capacitor voltage detection error, and thus the DC / DC converter 11 can be accurately controlled. Therefore, it is not necessary to boost the capacitor voltage higher than the target voltage in consideration of the capacitor voltage detection error, so that the switching loss of the DC / DC converter 11 and the inverter 105 (FIG. 1) can be reduced. Further, since it is not necessary to raise the capacitor voltage below the target voltage in consideration of the capacitor voltage detection error, it is possible to suppress a decrease in the output voltage limit of the inverter 105.

In the above-described first embodiment, the above equation (9) is used to calculate the reactor current instruction value i _L ^{* in} the current instruction generator 31, but as another example of the embodiment, the following equation (11) is used. It may be used to calculate the reactor current command value i _L ^* . Equation (9), the detected capacitor voltage v _c (k) and the capacitor voltage estimated value v _c (k) for (tilde) and are substantially equal, the formula (9) v _c of (k) (tilde) By substituting v _c (k), the formula (11) was obtained.

In addition, as another example of the embodiment, the reactor current command value i _L ^* may be calculated using Expression (12). In Expression (9), the second term on the right side underlined in C2 is sufficiently smaller than the first term on the right side underlined in C1. As a result, the second term on the right side was omitted from the equation (9), and the equation (12) was obtained. This can simplify the calculation.

In addition, as another example of the embodiment, the reactor current command value i _L ^* may be calculated using Expression (13). In the formula (12), the detected capacitor voltage v _c (k) and the capacitor voltage estimated value v _c (k) (tilde) are almost equal, so v _c (k) (tilde) in the formula (12) By substituting v _c (k), the formula (13) was obtained.

In each of the above-described embodiments, the reactor current command value i _L ^* is calculated using any one of the equations (9) and (11) to (13) converted from the state equation of the equation (7). Explained the case. On the other hand, the reactor current command value i _L ^* may be calculated using a mathematical expression converted from the state equation of the above mathematical expression (3). Different from the mathematical expression (7), the mathematical expression (3) does not include a part for calculating Δv _c (k + 1). For example, as another example of the embodiment, the reactor current command value i _L ^* may be calculated using Expression (14). In the formula (14), in the formula (3), the first row v _c (k + 1) on the left side is v _c ^* (k), the i _L (k) on the right side is i _L ^* (k), and Δd (k ) (in k) (tilde), v _c a (k) (v _c (k) the Δd obtained by expanding by replacing (tilde) - [Delta] v _c (k) (tilde)).

In addition, as another example of the embodiment, the reactor current command value i _L ^* may be calculated using Expression (15). Equation (14), the detected capacitor voltage v _c (k) and the capacitor voltage estimated value v _c (k) for (tilde) and are substantially equal, v _c of Equation (14) (k) (tilde) By substituting v _c (k) for, Equation (15) was obtained.

In addition, as another example of the embodiment, the reactor current command value i _L ^* may be calculated using Expression (16). In Expression (14), the second term on the right side is sufficiently smaller than the first term on the right side. As a result, the second term on the right-hand side of the formula (14) was omitted to obtain the formula (16). This can simplify the calculation.

In addition, as another example of the embodiment, the reactor current command value i _L ^* may be calculated using Expression (17). In the formula (16), the detected capacitor voltage v _c (k) and the estimated capacitor voltage v _c (k) (tilde) are almost equal to each other, so that v _c (k) (tilde) in the formula (16) By substituting v _c (k) for, Equation (17) was obtained.

<Second Embodiment>
In the first embodiment shown in FIGS. 1 to 4, the reactor current i _L actually flowing through the reactor 12 is detected by the reactor current detector 22 (FIG. 1), and the duty ratio d is determined based on the reactor current i _L. The configuration of the control device 30 for controlling the above has been described. FIG. 5 shows the configuration of the control device 30a according to the second embodiment. In the second embodiment, the motor drive device does not include a reactor current detector that detects the reactor current i _L. Instead, as shown in FIG. 5, the observer 32 a included in the control device 30 a uses the duty ratio controller 34 to calculate the reactor current estimated value i _L to (tilde) calculated for input to the current command generator 31. Also enter.

The processing in the duty ratio controller 34 is the same as that in the first embodiment. At this time, the duty ratio controller 34 uses the reactor current estimated value i _L (tilde) input from the observer 32a as the reactor current i _L in the above formula (10), and the duty ratio d (= d (K + 1)) is calculated. Accordingly, the duty ratio controller 34 controls the duty ratio using the reactor current estimated value i _L (tilde). In the present embodiment, other configurations and operations are similar to those of the first embodiment shown in FIGS. 1 to 4.

<Third Embodiment>
As a duty controller used in the control device 30 in the first embodiment shown in FIGS. 1 to 4, a first model prediction controller (MPC) 50 (FIG. 7) is used instead of the PI calculation unit and the F / F compensation unit. ) May be included. FIG. 6 shows the configuration of the control device 30b according to the third embodiment. Hereinafter, the first model predictive controller 50 may be referred to as the first MPC 50.

The control device 30b includes an observer 32b. Observer 32b, as in the first embodiment, receives the capacitor voltage v _c, the power supply voltage v _b and the output current i _m, the current from these values the error duty ratio Δd (= Δd (k)) , reactor The estimated values of the current i _L and the capacitor voltage detection error Δv _c are calculated and output. The calculated error duty ratio estimated value Δd (tilde) and estimated capacitor voltage detection error value Δv _c (tilde) are input to the current command generator 31 and the first MPC 50. The calculated reactor current estimated value i _L (tilde) is input to the current command generator 31.

The current command generator 31 calculates the reactor current command value i _L ^* as in the first embodiment. The calculated reactor current command value i _L ^* is input to the first MPC 50.

  The first MPC 50 controls the duty ratio using the state equation of the DC / DC converter 11. At this time, the first MPC 50 outputs predicted values for predetermined state values (state quantities) in the DC / DC converter 11 when the duty ratios d of the first and second switching elements 14 and 16 are changed to a plurality of different values. calculate. Then, the first MPC 50 controls the duty ratio d according to the difference between the command value indicating the target of the state value (state amount) and the predicted value.

In the present embodiment, the first MPC 50 calculates the reactor current predicted value i _L ^{^} (hat) which is the predicted value of the current flowing through the reactor 12 as the predetermined state value. Then, the first MPC 50 performs a process of obtaining the duty ratio d that becomes the reactor current predicted value i _L ^{^} (hat) that approaches the reactor current command value i _L ^* .

  FIG. 7 is a diagram showing the configuration of the first MPC 50. As shown in FIG. 7, the first MPC 50 includes an adder 40 (40-2 to 40-129), a prediction calculator 42 (42-1 to 42-129), and an evaluation function calculator 44 (44-1 to 44-). 129) and a minimum value selector 46.

  The adder 40 (40-2 to 40-129) changes the duty ratio d (k) by adding a predetermined value to the current duty ratio d (k), and outputs the duty ratio d (k). In the present embodiment, the duty ratio d (k) is represented in the range of 0 to 1023. That is, it is assumed that the duty ratio d is 0 when the second switching element 16 which is the lower arm is always on and the first switching element 14 which is the upper arm is always off. It is also assumed that the duty ratio d is 1023 when the second switching element 16 which is the lower arm is always off and the first switching element 14 which is the upper arm is always on. The adder 40 gives a change in the range of d (k) ± 64 with the current duty ratio d (k) as the center value, and outputs it. The range of change is preferably set based on the dead time period of the DC / DC converter 11 and the PWM cycle. For example, it is preferable to set the conversion range larger than the value calculated by the numerical range of dead time / PWM cycle × duty ratio d. Specifically, when the dead time is 5 μs and the PWM cycle is 100 μs, when the duty ratio d is expressed in the range of 0 to 1023, a numerical range larger than 5/100 × 1023 = 51 is defined as the change range. Is preferred. On the other hand, in order to reduce the calculation load as much as possible, it is preferable that the range of change is as narrow as possible. Therefore, the present embodiment shows an example in which the range of change is ± 64.

  The adder 40-2 adds 1 to the current duty ratio d (k) and outputs d (k) +1. The adder 40-3 adds 2 to the current duty ratio d (k) and outputs d (k) +2. Similarly, the adders 40-4 to 40-65 add 3 to 64 to the current duty ratio d (k) and output the result. Further, the adder 40-66 subtracts 1 from the current duty ratio d (k) and outputs d (k) -1. The adder 40-67 subtracts 2 from the current duty ratio d (k) and outputs d (k) -2. Similarly, the adders 40-68 to 40-129 subtract 3 to 64 from the current duty ratio d (k) and output the result. The outputs from the adders 40-2 to 40-129 are input to the prediction calculators 42-2 to 42-129, respectively.

Prediction calculator 42, the output capacitor voltage v _c from the adder 40, the reactor current i _L, the power supply voltage v _b, the output current (load current) i _m, error duty ratio Δd~ (= Δd~ (k) ( Tilde)) and the capacitor voltage detection error Δv _c ˜ (= Δv _c ˜ (k) (tilde)) to calculate and output the reactor current prediction value i _L ^{^} (hat). The reactor current predicted value i _L ^{^} (hat) is a predicted value of the current flowing through the reactor 12.

Reactor current predicted value i _L ^{^} (hat), in equation (7), i and developed by replacing the left side of second line i _L a (k + 1) to the ^{_{i L ^ [d (k)}} + a] ( hat) _L ^{^} It is calculated using the arithmetic expression of [d (k) + a] (hat).

The prediction calculator 42-1 sets i in the arithmetic expression of i _L ^{^} [d (k) + a] (hat) to 0 and calculates and outputs i _L ^{^} [d (k)] (hat). Prediction calculator ^{_{42-2, i L ^ [d (k}} ) + a] ( hat) i _L ^{^} a a calculation formula as 1 [d (k) +1] calculates and outputs the (hat). Similarly, the prediction calculator 42-3～ prediction calculator 42-65 is, i _L ^{^} as 2 to 64 of a respective [d (k) + a] calculates and outputs the (hat). Prediction calculator 42-66 ^{_{is, i L ^ [d (k}} ) + a] ( hat) arithmetic expression of a i as ^{_{-1 L ^ [d (k)}} -1] calculates and outputs the (hat) . Prediction calculator 42-67 ^{_{is, i L ^ [d (k}} ) + a] ( hat) arithmetic expression of a i as ^{_{-2 L ^ [d (k)}} -2] calculates and outputs the (hat) . Similarly, the prediction calculator 42-68～ prediction calculator 42-129 is, i _L as -3 to 64 a respective ^{^ [d (k) + a} ] calculates and outputs the (hat). The outputs of the prediction calculators 42-1 to 32-129 are input to the evaluation function calculators 44-1 to 44-129, respectively.

The evaluation function calculator 44 has a capacitor voltage command value v _c ^* , a reactor current prediction value i _L ^{^} (hat) input from the prediction calculator 42, and a reactor current command value i _L ^* input from the current command generator 41 ^. The evaluation function J is calculated based on the above, and the calculation result is output. The evaluation function J is represented by Expression (18).

  The evaluation function calculator 44-1 calculates J [d (k)] by setting a in Expression (18) to 0 and outputs it. The evaluation function calculator 44-2 calculates J [d (k) +1] by setting a in Expression (18) to 1 and outputs it. Similarly, the evaluation function calculator 44-3 to the evaluation function calculator 44-65 calculate and output J [d (k) + a] with a set to 2 to 64, respectively. The evaluation function calculators 44-66 calculate and output J [d (k) -1] by setting a in Expression (18) to -1. The evaluation function calculators 44-67 calculate J [d (k) -2] by setting a of the formula (18) to -2 and output it. Similarly, the evaluation function calculators 44-68 to 44-129 calculate and output J [d (k) + a] with a set to -3 to -64. The outputs of the evaluation function calculators 44-1 to 44-129 are input to the minimum value selector 46.

The evaluation function J may be the mathematical expression (19). Also in this case, the evaluation function calculator 44-1 to the evaluation function calculator 44-129 respectively have J [d (k)], J [d (k) +1] ... J [d (k) -64]. Is calculated and output.

The minimum value selector 46 has J [d (k)], J [d (k) +1] ... J [d (calculated by the evaluation function calculators 44-1 to 44-129. k) -64] is selected. The minimum value selector 46 outputs d (k) + a that minimizes the evaluation function J to the triangular wave comparator 36 as the duty ratio d (k + 1) for the next control. As a result, the duty ratio controller 34 controls the duty ratio d (k + 1) so that the reactor current estimated value i _L (tilde) becomes the reactor current command value i _L ^* . In the present embodiment, other configurations and operations are similar to those of the first embodiment shown in FIGS. 1 to 4.

As another example of the third embodiment, the configuration of the first MPC 50 in the third embodiment may be changed to the second model predictive controller. Hereinafter, description will be given with reference to FIGS. The second model predictive controller may be referred to as the second MPC. In another example of the third embodiment, the second MPC transforms the state equation of the DC / DC converter 11 into a quadratic equation for the duty ratio d of the first switching element 14 and the second switching element 16, and equations observer 32b error duty ratio estimate calculated in (Fig. 6) Δd~ (= Δd~ (k ) ( tilde)) and capacitor voltage detection errors _{Δv c ~ (= Δv c ~} (k) ( tilde)) By introducing, that is, applying, the duty ratio d is calculated and controlled. The control device controls the DC / DC converter 11 using the calculated duty ratio d.

The second line i _L (k + 1) on the left side of Expression (7) is i _L ^* (k), Δd (k) on the right side is Δd to (k) (tilde), and Δv _c (k) is Δv _c to (k. ) (Tilde) and changed to a quadratic equation for the duty ratio d (k), formula (20) is obtained.

When the quadratic equation of Expression (20) is solved for the duty ratio d (k + 1), it is expressed by Expression (21).

The second MPC outputs the calculated duty ratio d (k + 1) to the triangular wave comparator 36 with or without a limiter. As a result, the control device controls the ON periods of the first switching element 14 and the second switching element 16 so that the duty ratio d (= d (k + 1)) input to the triangular wave comparator 36 is achieved. Therefore, the DC / DC converter 11 controls the capacitor voltage v _c and the reactor current i _L such that the command value is the capacitor voltage command value v _c ^* and the reactor current command value i _L ^* .

<Fourth Embodiment>
FIG. 8 shows the configuration of the control device 30c according to the fourth embodiment. The motor drive device of this embodiment does not include a reactor current detector for measuring the reactor current i _L flowing through the reactor 12. Instead, as shown in FIG. 8, the controller 30c includes an observer 32c. The observer 32c also inputs the reactor current estimated value i _L (tilde) calculated for input to the current command generator 31 to the duty ratio controller 34a.

The processing in the duty ratio controller 34a is the same as that in the third embodiment shown in FIGS. 6 and 7. At this time, the duty ratio control unit 34a, as reactor current i _L, reactor current estimated value i _L ~ input from the observer 32c using (tilde), calculates the duty ratio d (= d (k + 1 )). Accordingly, the duty ratio controller 34a controls the duty ratio using the reactor current estimated value i _L (tilde). In the present embodiment, other configurations and operations are the same as those of the first embodiment shown in FIGS. 1 to 4 or the third embodiment shown in FIGS. 6 and 7.

<Fifth Embodiment>
FIG. 9 is a diagram showing the configuration of the current command generator 31a in the fifth embodiment. The controller in the fifth embodiment includes a current command generator 31a and a center frequency calculator 39 instead of the current command generator 31 (FIG. 2) in the first embodiment shown in FIGS. 1 to 4. Is included. The current command generator 31a has a current command calculator (iL command calculator) 38a and a notch filter 38b.

The capacitor command value v _c ^* and the capacitor voltage detection value v _c are input to the current command calculator 38a, as in the current command generator 31 shown in FIG. Further, the estimated values of the reactor current i _L , the error duty ratio Δd, and the capacitor voltage detection error Δv _c are also input from the observer 32 (FIG. 2) to the current command calculation unit 38a. The current command calculation unit 38a uses the formula (9) obtained by modifying the formula (7), which is a discrete formula of the state equation of the DC / DC converter 11, according to these input values to filter the filter. The reactor current command value i _L ^* before processing is calculated. The calculated reactor current command value i _L ^* is input to the notch filter 38b.

  The carrier frequency of the inverter 105 (FIG. 1) to which the output current of the DC / DC converter 11 is input and the carrier frequency of the DC / DC converter 11 are input to the center frequency calculator 39. Based on these input values, the center frequency calculator 39 calculates the absolute value of the value obtained by subtracting the carrier frequency of the DC / DC converter 11 from twice the carrier frequency of the inverter 105 as the center frequency f0. At this time, when the carrier frequency of the inverter 105 is fci and the carrier frequency of the DC / DC converter 11 is fcc, the center frequency f0 is | 2fci-fcc | which is the (absolute value) of (2fci-fcc). expressed. The calculated center frequency f0 is input to the notch filter 38b.

Notch filter 38b is a filter pretreatment reactor current command value i _L ^*, by using the center frequency f0, to remove components of the center frequency f0 from the pre-filtering reactor current command value i _L ^*. Then, the notch filter 38b outputs the filtered reactor current command value i _L ^* to the duty ratio controller 34 (FIG. 2).

According to the fifth embodiment described above, the width of steady-state swing of the reactor current command value i _L ^* , the reactor current i _L and the capacitor voltage v _c can be narrowed, and the control stability can be improved. FIG. 10 is a diagram showing a capacitor voltage waveform when the control device does not include a notch filter and the duty ratio is fixed, unlike the fifth embodiment.

  As shown in FIG. 10, when the notch filter is not included, the capacitor voltage oscillates in a cycle of 1 / (| 2fci-fcc | (absolute value)), and therefore its central value also oscillates in a waveform. According to the fifth embodiment, the vibration component having the cycle of 1 / (| 2fci-fcc | (absolute value)) can be removed.

  11 to 13 are diagrams showing simulation results performed to confirm the effects of the fifth embodiment. FIG. 11 is a diagram showing control of voltage and current when the capacitor voltage detection error is −10 V in the control device of the first example of the comparative example. FIG. 12 is a diagram showing voltage and current control when the capacitor voltage detection error is −10 V in the control device of the second example of the comparative example.

  In the first example of the comparative example in which the control is shown in FIG. 11, in the first embodiment shown in FIGS. 1 to 4, the current command generator is an arithmetic expression modified from the state equation not including the capacitor voltage detection error. It is used to calculate the reactor current command value. Further, in the first comparative example, the notch filter does not remove the component of the center frequency f0 from the calculated reactor current command value. In the second example of the comparative example, in the configuration of the first example of the comparative example, the current command generator has a notch for removing the component of the center frequency f0 from the calculated reactor current command value, as in the fifth embodiment. Contains a filter.

11, FIG. 12, and FIG. 13 described later, in the diagrams showing the control of the capacitor voltage, the capacitor voltage command value v _c ^* is shown by the broken line. Further, in the control of FIGS. 11 to 13, the detection error of the capacitor voltage is set to −10V.

As shown in FIG. 11, in the first comparative example, the oscillation widths of the reactor current command value i _L ^* , the reactor current i _L, and the capacitor voltage v _c were all large. Further, the center value of the waveform of the capacitor voltage v _c is largely offset with respect to the capacitor voltage command value v _c ^* .

As shown in FIG. 12, in the second comparative example, since the notch filter is added to the first comparative example, the reactor current command value i _L ^* , the reactor current i _L and the capacitor voltage v _c The vibration width of was a little smaller. On the other hand, the central value of the waveform of the capacitor voltage v _c is largely offset with respect to the capacitor voltage command value v _c ^* as in the first comparative example.

On the other hand, FIG. 13 is a diagram showing voltage and current control when the capacitor voltage detection error is −10 V in the fifth embodiment. As shown in FIG. 13, in the control of the fifth embodiment, since the reactor current command value is calculated using the estimated value of the capacitor voltage detection error, the reactor current command value is further increased as compared with the second example of the comparative example. The oscillation width of i _L ^* , reactor current i _L and capacitor voltage v _c could be reduced. Further, the central value of the waveform of the capacitor voltage v _c substantially matched the capacitor voltage command value v _c ^* . From this, according to the fifth embodiment, it was confirmed that the capacitor voltage v _c can be controlled almost as the target value.

  In the present embodiment, other configurations and operations are similar to those of the first embodiment shown in FIGS. 1 to 4. Further, the notch filter 38b of this embodiment can be similarly applied to the embodiments of FIGS. 5 to 8 described above.

<Sixth Embodiment>
FIG. 14 is a diagram showing the configuration of the control device 30d in the sixth embodiment. FIG. 15 is a diagram showing the configuration of the current command generator 31b shown in FIG. In the sixth embodiment, the control device 30d in the first embodiment shown in FIGS. 1 to 4 includes a current command generator 31b instead of the current command generator 31 (FIG. 2). The capacitor command value v _c ^* and the capacitor voltage detection value v _c are input to the current command generator 31b. The capacitor voltage detection error estimated value Δv _c (tilde) is input from the observer 32 to the current command generator 31b.

The current command generator 31b has a PI control unit 60, as shown in FIG. The deviation obtained by subtracting the capacitor voltage detection value v _c and the capacitor voltage detection error estimated value Δv _c (tilde) from the capacitor voltage command value v _c ^* is input to the PI control unit 60. The PI control unit 60 calculates the reactor current command value i _L ^* by performing a PI operation on the deviation. The calculated reactor current command value i _L ^* is output to duty ratio controller 34. The duty ratio controller 34 controls the duty ratio d (k + 1) according to the reactor current command value i _L ^* and the reactor current detection value i _L , as in the first embodiment shown in FIGS. 1 to 4. At this time, the reactor current estimation value i _L (tilde) calculated by the observer 32 can be used instead of the reactor current detection value i _L.

According to the sixth embodiment described above, the reactor current command value i _L ^* is calculated using the capacitor voltage detection error estimated value Δv _c (tilde). Thus, as in the first embodiment, the DC / DC converter 11, even if there is a capacitor voltage detection errors Delta] v _c, so the reactor current command value i _L ^* can be accurately calculated, the DC / DC converter 11 Can be controlled accurately. Therefore, it is possible to reduce the switching loss of the DC / DC converter 11 and the inverter 105 (FIG. 1) and suppress the decrease in the output voltage limit of the inverter 105. In the present embodiment, other configurations and operations are similar to those of the first embodiment of FIGS. 1 to 4 or the above-described second embodiment of FIG. In the present embodiment, the duty ratio controller 34 may be configured to include the first MPC or the second MPC as in the embodiments of FIGS. 6 and 7.

[Modification]
In the DC / DC converter, the value of the inductance L of the reactor changes according to the reactor current. Therefore, in the control in each of the above-described embodiments, the inductance L of the reactor 12 is set to be changed in accordance with the reactor current i _L flowing in the reactor 12 or the estimated reactor current i _L ~ (tilde) expected to flow. Is preferred.

  FIG. 16 is a diagram showing a change in the inductance L of the reactor 12 with respect to a current value. In FIG. 16, the current value on the horizontal axis is normalized with the maximum current being 1, and the inductance L of the reactor 12 on the vertical axis is normalized with 1 when the current value is 0.

  Although the observer is the same-dimensional observer in the above embodiment, the minimum-dimensional observer may be applied. Further, although the state equation is discretized by using the bilinear transformation, the present invention is not limited to this, and may be discretized by using the 0th-order hold, the forward difference, and the backward difference.

According to each of the above-described embodiments and its modification, the reactor current command value i _L ^* can be calculated with high accuracy, and thus the DC / DC converter 11 can be controlled with high accuracy.

  10 DC Power Supply, 11 DC / DC Converter, 12 Reactor, 14 First Switching Element, 16 Second Switching Element, 17 Low Voltage Side Capacitor, 18 High Voltage Side Capacitor, 19 Positive Bus, 20 Negative Bus, 22 Reactor Current Detector, 30 , 30a, 30b, 30c, 30d, control device, 31, 31a, 31b current command generator, 32, 32a, 32b, 32c observer, 34, 34a duty ratio controller, 36 triangular wave comparator, 37 switching unit, 38a current Command calculator, 38b notch filter, 39 center frequency calculator, 40 adder, 42 prediction calculator, 44 evaluation function calculator, 46 minimum value selector, 50 first model prediction controller, 60 PI control unit, 100 motor Drive device, 104 load, 105 inverter, 106 m Ta.

Claims (7)

A control device for controlling a DC / DC converter including a first switching element and a second switching element, and a reactor having both ends connected to a connection point of the first switching element and the second switching element and a DC power supply. hand,
Depending on the current state value of the DC / DC converter, an error duty ratio that is the difference between the duty ratio that is the ratio of the ON time of the first switching element and the presence or absence of dead time, A capacitor voltage which is a voltage across the capacitor connected to smooth the output voltage from the reactor, and an observer for estimating a capacitor voltage detection error of the capacitor,
A current command generator that calculates a reactor current command value that is a target value for controlling the reactor current flowing through the reactor from a state equation that includes the error duty ratio and a detection error of the capacitor voltage.
A duty ratio controller for controlling the duty ratio of the DC / DC converter according to the reactor current command value,
A control device that controls the DC / DC converter according to the reactor current command value. The control device according to claim 1,
The observer estimates the error duty ratio and the capacitor voltage detection error by using a power supply voltage of the DC power supply, the capacitor voltage, and an output current of the DC / DC converter. In the control device according to claim 1 or 2,
The observer estimates a reactor current estimation value of the reactor current,
The duty ratio controller controls the duty ratio using the reactor current estimated value. The control device according to any one of claims 1 to 3,
The duty ratio controller,
Using the state equation of the DC / DC converter, a predicted value for a predetermined state value in the DC / DC converter when the duty ratio is changed to a plurality of different values is calculated, and a target of the predetermined state value is indicated. A controller having a first model predictive controller that controls the duty ratio according to a difference between a command value and the predicted value. The control device according to any one of claims 1 to 3,
The duty ratio controller,
A control having a second model predictive controller for controlling the duty ratio by transforming the state equation of the DC / DC converter into a quadratic equation of the duty ratio and introducing the error duty ratio into the quadratic equation. apparatus. The control device according to any one of claims 1 to 5,
The current command generator includes a notch filter into which the reactor current command value before filtering calculated from the state equation is input,
When the carrier frequency of the inverter to which the output current of the DC / DC converter is input is fci and the carrier frequency of the DC / DC converter is fcc, the notch filter uses the reactor current command value before processing ( A controller that removes the component of the center frequency f0 represented by the absolute value of 2 × fci-fcc) and outputs the reactor current command value after the filtering process to the duty ratio controller. A control device for controlling a DC / DC converter including a first switching element and a second switching element, and a reactor having both ends connected to a connection point of the first switching element and the second switching element and a DC power supply. hand,
Depending on the current state value of the DC / DC converter, an error duty ratio that is the difference between the duty ratio that is the ratio of the ON time of the first switching element and the presence or absence of dead time, A capacitor voltage which is a voltage across the capacitor connected to smooth the output voltage from the reactor, and an observer for estimating a capacitor voltage detection error of the capacitor,
The deviation obtained by subtracting the detection value of the capacitor voltage and the detection error of the capacitor voltage from the capacitor voltage command value, which is the target value of the capacitor voltage, is PI-calculated to control the reactor current flowing through the reactor. A current command generator that calculates a reactor current command value that is a target value for
A duty ratio controller for controlling the duty ratio of the DC / DC converter according to the reactor current command value,
A control device that controls the DC / DC converter according to the reactor current command value.