JP5904834B2 - Control device, control method, and control program for power converter - Google Patents

Description

  Embodiments of the present invention relate to a control technique for a power converter that converts power between AC and DC.

  A power conversion device that converts power between alternating current and direct current is used in various applications. For example, a three-phase, two-level type has been used as an inverter used for driving a motor by converting direct current to alternating current. The three-phase two-level is a method of converting between direct current and three-phase alternating current by performing switching at two levels such as on / off of six switches.

  A semiconductor element is used as a switching element that performs switching, which is on / off switching. Common switching elements are diodes and IGBТ (Insulated Gate Bipolar Transistor).

  The control method of the three-phase two-level inverter is generally PWM control. PWM control is a method for controlling the magnitude of the output AC voltage by controlling the pulse width. For example, when the input DC voltage is Vdc, switching between binary values of + Vdc / 2 and −Vdc / 2 is performed for each phase at a predetermined timing. Thereby, the output waveform from the three-phase two-level inverter can be a pseudo-generated AC waveform.

  Incidentally, in recent years, there has been an increasing need for large-scale DC power transmission with less power loss compared to AC power transmission. For example, power transmission by submarine cables, conversion of 50 Hz to 60 Hz, and long-distance direct current power transmission from a remote large-scale photovoltaic power generation system to a consumer area are attracting attention.

  In the case of large-scale direct current power transmission, the direct current to be turned on / off becomes an extremely high voltage such as 300 kV. On the other hand, IGBТ used as a switching element has a rating of only about 6500V. In order to cope with this, the voltage applied to each IGBT can be reduced by connecting a number of IGBTs in series.

  As such a power conversion device, for example, a modular multilevel converter (hereinafter referred to as MMC) that converts DC power into AC power has been proposed. This MMC is provided with a plurality of chopper cells in which capacitors as power storage elements are connected in parallel to two switching elements.

  The capacitor in each chopper cell forms an output voltage using the voltage. That is, the chopper cell outputs a voltage corresponding to the capacitor when one switching element is on, and becomes a zero voltage when the other switching element is on.

  The plurality of chopper cells constitute an arm by being connected in multiple stages in series for each phase. The arm is provided on the positive side and the negative side of the direct current, and constitutes a leg by connecting to each other. Between the positive side arm and the negative side arm is an output terminal that outputs a variable frequency AC voltage.

  In such an MMC, by increasing the number of stages of chopper cells, the voltage borne by each chopper cell can be set low while realizing high breakdown voltage as a whole. For this reason, as a switching element, it is possible to apply a self-extinguishing element such as an IGBT which has a relatively low withstand voltage and has been difficult to apply. In addition, it is possible to configure a power conversion device that can be applied to high-voltage applications that cannot be realized with conventional switching elements.

Special table 2010-512134 gazette

  As described above, the capacitor provided in the chopper cell of the MMC is used for shaping the output voltage. For this reason, the capacitor needs to keep a voltage value constant so that charging / discharging is performed appropriately. Therefore, the control device of the MMC performs control to store power by constantly flowing a reflux current that recirculates the DC power source to the leg.

From the above, there are the following two current paths in the MMC.
(1) Current path output from the DC side to the AC side
(2) Current path that circulates between DC positive and negative through the leg

  For the control of (2), the control device calculates an average value in the leg of the capacitor voltage of each chopper cell, and flows a DC circulating current according to the difference between the average value and the chopper cell voltage command value. Thereby, the control device controls the average value of the capacitor voltage of the chopper cell in the leg to a constant value. In the following description, such an average value of the capacitor voltage in the leg is referred to as an in-leg average value.

  Further, the control device manipulates the output voltage of each chopper cell according to the difference between the average value in the leg and the capacitor voltage of each chopper cell. Thereby, the control device balances the capacitor voltage of each chopper cell in the leg. Thus, the control device controls the capacitor voltage of each chopper cell to be constant by using both average value control and balance control.

  However, in such control, balance control is performed on the average value of the capacitor voltage in the leg, and therefore, the operation amount of the balance control may not be canceled in each arm constituting the leg. In this case, a voltage may be generated at the output terminal located between the arm and the reactor.

  This means that the balance control interferes with the output voltage depending on the unbalanced state of the capacitor voltage. In many cases, the capacities of the capacitors constituting each chopper cell differ depending on individual differences. For this reason, each capacitor voltage tends to be unbalanced. Therefore, distortion may occur in the output voltage due to this imbalance, and it becomes difficult to obtain a desired output.

  Embodiments of the present invention have been proposed in order to solve the above-described problems, and an object of the present invention is to configure a chopper cell without interfering with an output voltage in a power conversion device in which chopper cells are connected in multiple stages. The object is to control the voltage of the capacitor to obtain a good output voltage waveform.

In order to solve the above-described problems, a control device for a power conversion device according to an embodiment includes at least one leg including a pair of arms, which are configured by multistage chopper cells including switching elements and capacitors, on a positive side and a negative side. A control device for controlling a power converter having the following configuration.
(1) Voltage command value storage unit for storing a voltage command value for controlling the average value of the capacitor voltage of the chopper cell in the leg to be constant
(2) Based on the externally input capacitor voltage, the average value in the arm, which is the average value of the capacitor voltage in each arm, is calculated for each positive arm and negative arm in the leg. Value calculator
(3) In-arm difference calculation unit for calculating an in-arm difference that is a difference between each capacitor voltage of the positive arm and each capacitor voltage of the negative arm input from the outside and the average value in the arm
(4) Based on the intra-arm difference, an arm that calculates an intra-arm balance operation amount that is an operation amount of a switching element that balances the output voltage of each chopper cell in the arm for each of the positive side arm and the negative side arm Internal balance manipulated variable calculator
(5) An in-arm balance command value calculation unit that calculates an in-arm balance command value that is an output voltage command value of each chopper cell in the arm based on the voltage command value and the in-arm balance operation amount.

The circuit diagram which shows the structural example of the power converter device used as the control object of embodiment The block diagram which shows the control apparatus of the power converter device of 1st Embodiment. The block diagram which shows the control apparatus of the power converter device of 2nd Embodiment. It is a figure which shows the waveform of each part in 2nd Embodiment. It is a figure which shows the waveform of each part in 2nd Embodiment. It is a figure which shows the waveform of each part in 2nd Embodiment. The block diagram which shows the control apparatus of the power converter device of 3rd Embodiment. It is a figure which shows the waveform of each part in 3rd Embodiment. It is a figure which shows the waveform of each part in 3rd Embodiment.

[A. First Embodiment]
[1. Constitution]
[1-1. Power conversion device]
[The entire]
With reference to FIG. 1, the structural example of the power converter device X used as the control object of this embodiment is demonstrated. The power conversion device X is a device that is connected between a DC system and a three-phase AC system and performs conversion between DC and AC. The power conversion device X includes a chopper cell 1, an arm 2 in which a plurality of chopper cells 1 are multistaged, and a leg 4 in which a positive side and a negative side arm 2 are connected via a reactor 3.

[Chopper cell]
Each chopper cell 1 has two switching elements 11a and 11b, diodes 12a and 12b, and a capacitor 13. The switching elements 11a and 11b are elements having self-extinguishing ability connected in series with each other. The switching elements 11a and 11b are, for example, IGBТ. Although not shown, each switching element 11a, 11b is connected to a connection line for inputting an on / off switching control signal.

  The diodes 12a and 12b are rectifying elements connected in antiparallel to the switching elements 11a and 11b. The diodes 12a and 12b are feedback diodes, for example.

  The capacitor 13 is a storage element connected in parallel to the switching elements 11a and 11b connected in series. Although not shown, each capacitor 13 is provided with a voltage detector that detects the capacitor voltage.

[arm]
The arm 2 is formed by connecting n chopper cells 1 in series. It should be noted that n ≧ 2. Hereinafter, the positive arm 2 connected to the positive side (P) as viewed from the DC side is referred to as an upper arm 2a, and the negative arm 2 connected to the negative side (N) is referred to as a lower arm 2b. Further, in the following description, it is synonymous to read “upper arm” as “positive arm” and “lower arm” as “negative arm”.

[Leg]
The leg 4 is obtained by connecting the upper arm 2a and the lower arm 2b of each phase in series. Three legs 4 corresponding to the three phases are connected in parallel between the positive and negative (PN) on the DC side. The connection point between the upper arm 2a and the lower arm 2b is an output terminal and is connected to the AC side.

  Reactors 3 are inserted between the upper arm 2a and the connection point in the leg 4 and between the lower arm 2b and the connection point, respectively. This reactor 3 is connected to restrict an excessive short-circuit current from flowing between the phases. Each leg 4 is provided with a current detector that detects a current value, although not shown.

[1-2. Control device]
Next, the control apparatus 100 of this embodiment is demonstrated with reference to FIG. The control device 100 includes an input unit 200, a calculation unit 300, a storage unit 400, and an output unit 500.

[Input section]
The input unit 200 is a processing unit that inputs information from external devices such as the voltage detector, the current detector, and the host system. That is, the input unit 200 inputs the voltage value of each capacitor 13 from the voltage detector and the circulating current value from the current detector. Further, the input unit 200 inputs an output voltage command value and a direct current (between PN) voltage from a host system.

[Calculator]
The calculation unit 300 includes an in-leg average value control unit 310 and an in-arm balance control unit 320.
(Leg average value controller)
The in-leg average value control unit 310 is a processing unit that controls the output voltage based on the average value of the capacitor voltage in the leg 4. The in-leg average value control unit 310 includes an in-leg average value calculation unit 311, a capacitor voltage command value calculation unit 312, an in-leg difference calculation unit 313, a circulating current command value calculation unit 314, an in-leg average manipulated variable calculation unit 315, a voltage A command value calculation unit 316 is provided.

  The in-leg average value calculation unit 311 is a processing unit that calculates an in-leg average value that is an average value of the capacitor voltage values in each leg 4 based on the capacitor voltage value in each leg 4 input from the input unit 200. It is. The capacitor voltage command value calculation unit 312 is a processing unit that calculates the capacitor voltage command value of each chopper cell 1 based on the output voltage command value input from the outside. The in-leg difference calculation unit 313 is a processing unit that calculates an in-leg difference that is a difference between the in-leg average value and the chopper cell voltage command value.

  The circulating current command value calculation unit 314 is a processing unit that calculates the circulating current command value based on the in-leg difference. The in-leg average manipulated variable calculator 315 is a processor that calculates a voltage manipulated variable that balances the capacitor voltage in the leg 4 based on the difference between the circulating current command value and the circulating current value input from the outside. . The voltage command value calculation unit 316 is a processing unit that calculates a voltage command value for the average in the leg based on the voltage operation amount and the capacitor voltage command value.

(In-arm balance controller)
The in-arm balance control unit 320 is a processing unit that controls the output voltage based on the average value of the capacitor voltage in the arm 2. The in-arm balance control unit 320 includes an in-arm average value calculation unit 321, an in-arm difference calculation unit 322, an in-arm balance operation amount calculation unit 323, and an in-arm balance command value calculation unit 324.

  The in-arm average value calculation unit 321 is a processing unit that calculates an in-arm average value that is an average value of capacitor voltage values in each arm 2. The arm average value calculator 321 includes an upper arm average value calculator 321a and a lower arm average value calculator 321b.

  The average value calculation unit 321a in the upper arm is a processing unit that calculates the average value in the arm for each upper arm 2a based on the capacitor voltage value of the upper arm 2a in each leg 4 input from the outside. The lower arm average value calculation unit 321b is a processing unit that calculates an arm average value for each lower arm 2b based on the capacitor voltage value of the lower arm 2b in each leg 4 input from the outside.

  The in-arm difference calculation unit 322 is a processing unit that calculates an in-arm difference that is a difference between the capacitor voltage value in each arm 2 and the average value in the arm. The in-arm difference calculation unit 322 includes an upper arm difference calculation unit 322a and a lower arm difference calculation unit 322b.

  The difference calculation unit 322a in the upper arm is a processing unit that calculates the difference in the arm between the average value in the upper arm and the capacitor voltage value in the upper arm 2a input from the outside. The lower arm difference calculation unit 322b is a processing unit that calculates an in-arm difference between the lower arm average value and the capacitor voltage value in the lower arm 2b input from the outside.

  The in-arm balance operation amount calculation unit 323 is a processing unit that calculates an in-arm balance operation amount that balances the capacitor voltage in the arm 2 based on the in-arm difference. The intra-arm balance operation amount calculation unit 323 includes an upper arm balance calculation unit 323a and a lower arm balance calculation unit 323b that calculates a lower arm balance operation amount.

  The upper arm balance calculation unit 323a is a processing unit that calculates the upper arm balance operation amount by multiplying the difference in the upper arm 2a by the gain value. The lower arm balance calculation unit 323b is a processing unit that calculates the lower arm balance operation amount by multiplying the difference in the lower arm 2b by the gain value.

  The in-arm balance command value calculation unit 324 is a processing unit that calculates a voltage command value for balancing the capacitor voltage in the arm 2 by superimposing the in-arm balance operation amount on each chopper cell output voltage command in the arm 2. is there. The in-arm balance command value calculation unit 324 includes an upper arm command value calculation unit 324a and a lower arm command value calculation unit 324b.

  The upper arm command value calculation unit 324a is a processing unit that calculates the voltage command value in the upper arm 2a by superimposing the upper arm balance operation amount on each chopper cell output voltage command in the upper arm 2a. The lower arm command value calculation unit 324b is a processing unit that calculates the voltage command value in the lower arm 2b by superimposing the lower arm balance operation amount on each chopper cell output voltage command in the lower arm 2b.

[Storage unit]
The storage unit 400 is a processing unit that stores various types of information necessary for the processing of the calculation unit 300. These pieces of information include an externally input capacitor voltage value, circulating current value, output voltage command value, direct current (between PN) voltage, and the like. In addition, the storage unit 400 also stores the number of stages of the chopper cell 1, an arithmetic expression, parameters (including gain values), calculation results, and the like. The area storing these pieces of information functions as a storage unit for each piece of information. For example, the area for storing the circulating current command value calculated by the circulating current command value calculation unit 314 can be regarded as the circulating current command value storage unit. Moreover, the area | region which memorize | stores the voltage command value which the voltage command value calculating part 316 computed can be regarded as a voltage command value storage part.

  Accordingly, the circulating current command value and the output voltage command value calculated by the in-leg average value control unit 310 are stored in the storage unit 400, and the in-arm balance control unit 320 is based on the circulating current command value and the output voltage command value. A mode of performing in-arm balance control is also included in the embodiment. An embodiment in which the arm balance control unit 330 described later performs the arm balance control based on the circulating current command value and the output voltage command value is also included in the embodiment.

[Output section]
The output unit 500 is a processing unit that is connected to the switching elements 11a and 11b and outputs an operation signal to the switching elements 11a and 11b. That is, the output unit 500 outputs an operation signal based on the voltage command value calculated by the calculation unit 300 to each of the switching elements 11a and 11b.

[2. Action]
An example of the control process of the present embodiment as described above will be described.
[2-1. Leg average value control]
First, the in-leg average value control by the in-leg average value control unit 310 will be described. As described above, in the current path of the power converter X, the current i _out from the DC PN to the output side shown in FIG. 1 and the DC circulating current i _cir that circulates between the DC PNs via the legs 4 are included. is there. In FIG. 1, each capacitor 13 is indicated by C _{P1 to} C _Pn and C _{N1 to} C _Nn . The number of stages of the chopper cell 1 in the leg 4 is 2n.

  The in-leg average value control is a process of controlling the in-leg average value, which is the average value of the capacitor voltage of the chopper cell 1 in the leg 4 of each phase, to a constant value. In this control, a DC circulating current corresponding to the difference between the average value in the leg and the capacitor voltage command value of the chopper cell 1 is caused to flow so that the average value in the leg follows the capacitor voltage command value.

That is, the in-leg average value calculation unit 311 calculates the in-leg average value V _{cell_ave} . This can be obtained by dividing the sum of the capacitor voltages of all the chopper cells 1 in the leg 4 by the number of stages of the chopper cells 1 in the leg 4 as shown in Equation 1.

In Equation 1, V _CPn is the capacitor voltage of each chopper cell 1 in the upper arm 2a. V _CNn is the capacitor voltage of each chopper cell 1 in the lower arm 2 b in the same leg 4. The number of stages of the chopper cell 1 of the upper arm 2a and the lower arm 2b is equal. For this reason, the number of stages of each chopper cell 1 in the upper arm 2a and the lower arm 2b is n.

The capacitor voltage command value calculation unit 312 calculates a capacitor voltage command value. This can be obtained as shown in Expression 2 based on the output voltage command value v _out ^* input from the outside.

In Equation 2, v _Pn ^* is a voltage command value of each chopper cell 1 in the upper arm 2a. v _Nn ^* is a voltage command value of each chopper cell 1 in the lower arm 2b. v _out ^* is an AC output voltage command value to be output to the leg 4. V _PN is a voltage between PNs.

The in-leg difference calculation unit 313 calculates an in-leg difference that is a difference between the above-mentioned average value in the leg and the capacitor voltage command value. And circulating current command value calculating part 314 calculates circulating current command value i _pn ^* by a compensator based on the difference in a leg. As the compensator, commonly used ones such as a proportional compensator by P control and a proportional / integral compensator by PI control can be applied.

Then, the in-leg average manipulated variable calculator 315 obtains the voltage manipulated variable by the compensator based on the difference between the circulating current command value i _pn ^* and the circulating current value input from the outside. A compensator similar to the above can be applied.

  Further, the voltage command value calculation unit 316 calculates the voltage command value by the average in the leg by superimposing the voltage operation amount equally on each voltage command value of all the chopper cells 1 in the leg 4.

  The output unit 500 outputs a control signal to each switching element based on the voltage command value based on the average in the leg obtained as described above. Then, voltage control is performed on the entire chopper cell 1 in the leg 4, thereby enabling average value control in the leg by circulating current control that circulates between the DC PNs through the leg 4.

[2-2. In-arm balance control]
Furthermore, in this embodiment, in addition to the above-described average value control in the leg, the in-arm balance control unit 320 performs balance control in the upper and lower arms 2. In-arm balance control is control for converging the capacitor voltage of each chopper cell 1 in each arm 2 to the average value of the capacitor voltage in each arm 2.

  First, the arm average value calculation unit 321 calculates the average value of the capacitor voltage for each arm 2. This arithmetic expression is shown in Expression 3.

That is, the upper arm average value calculation unit 321a calculates the upper arm average value V _{cell_ave_P} that is the average value of the capacitor voltages of all the chopper cells 1 in the upper arm 2a. That is, the average value calculation unit 321a in the upper arm divides the sum of the capacitor voltages in the upper arm 2a by the number n of stages of the chopper cells 1 in the upper arm 2a. The capacitor voltages in the upper arm 2a are V _{CP1 to} V _CPn corresponding to C _{P1 to} C _Pn shown in FIG.

The lower arm average value calculation unit 321b calculates a lower arm average value V _{cell_ave_N} that is an average value of the capacitor voltages of all the chopper cells 1 in the lower arm 2b. That is, the lower arm average value calculation unit 321b divides the sum of the capacitor voltages in the lower arm 2b by the number n of stages of the chopper cells 1 in the lower arm 3. The capacitor voltages in the lower arm 2b are V _{CN1 to} V _CNn corresponding to C _{N1 to} C _Nn shown in FIG.

  Next, the in-arm difference calculation unit 322 calculates the difference between the in-arm average value and the capacitor voltage of each chopper cell 1 in each arm 2. Then, the intra-arm balance operation amount calculation unit 323 calculates the operation amount of the intra-arm balance control by multiplying the difference value obtained by the intra-arm difference calculation unit 322 by the gain value. Such an arithmetic expression is shown in Expression 4.

That is, the upper arm difference calculation unit 322a calculates the difference between the upper arm average value V _{cell_ave_P} and the capacitor voltage V _CPn of each chopper cell 1 in the upper arm 2a. Then, the upper arm balance calculation unit 323a multiplies the difference value of the upper arm 2a by the gain value Karm_blc, respectively. Thereby, the operation amount V _{arm_blc_P} for the arm balance control of the upper arm 2a is calculated.

Further, the lower arm difference calculation unit 322b calculates the difference between the lower arm average value V _{cell_ave_N} and the capacitor voltage V _CNn of each chopper cell 1 in the lower arm 2b. Then, the lower arm balance calculation unit 323b multiplies the difference value of the lower arm 3b by the gain Karm_blc. Accordingly, the operation amount V _{arm_blc_N} for the arm balance control of the lower arm 2b is calculated.

Further, the in-arm balance command value calculation unit 324 superimposes the amount of balance control operation in each arm 2 on the output voltage command value of each chopper cell 1 obtained by the above-described in-leg balance control. That is, the upper arm command value calculation unit 324a _superimposes the balance control operation amount V _{arm_blc_P} in the upper arm 2a on the voltage command value of each chopper cell 1 in the upper arm 2a obtained by the voltage command value calculation unit 316.

The lower arm command value calculation unit 324b _superimposes the balance control operation amount V _{arm_blc_P} in the lower arm 2b on the voltage command value of each chopper cell 1 in the lower arm 2b obtained by the voltage command value calculation unit 316.

  The output unit 500 outputs a control signal to the switching elements 11a and 11b based on the voltage command value generated by superposition. Based on this control signal, the switching elements 11a and 11b operate to execute the arm balance control. Since the value obtained by multiplying the average value of the capacitor voltage in the arm and the difference between the capacitor voltages by the gain is used as the manipulated variable, the variation in the capacitor voltage is offset in each arm 2.

[3. effect]
In the present embodiment as described above, in addition to the balance control for the average value of the capacitor voltage in the leg, the balance control for the average value in each arm 2 is performed. For this reason, the balance control operation amount is canceled in the upper and lower arms 2a and 2b, and it is possible to prevent a voltage from being generated at the output terminal positioned between the upper and lower arms 2a and 2b and the reactor 3. .

  That is, even if the capacitor voltage is unbalanced due to individual differences in capacitor capacity, the capacitor voltage in each arm 2 can be balanced. For this reason, the balance control does not interfere with the output voltage, the output voltage is prevented from being distorted, and a desired output voltage can be obtained.

[B. Second Embodiment]
[1. Constitution]
The configuration of this embodiment will be described with reference to FIG. This embodiment is basically the same configuration as the first embodiment. However, in the present embodiment, the calculation unit 300 includes the inter-arm balance control unit 330. The arm balance control is control for converging each capacitor voltage to an average value between the upper and lower arms. The inter-arm balance control unit 330 includes an inter-arm difference calculation unit 331, an inter-arm balance operation amount calculation unit 332, and an inter-arm balance command value calculation unit 333.

  The inter-arm difference calculation unit 331 is a processing unit that calculates an inter-arm difference that is a difference between the average value in the arm of the upper arm 2a and the average value in the arm of the lower arm 2b. The inter-arm balance operation amount calculation unit 332 is a processing unit that calculates the operation amount of the switching element that balances the capacitor voltage between the upper and lower arms 2a and 2b based on the inter-arm difference. This operation amount is defined as an arm-to-arm balance operation amount.

  The inter-arm balance command value calculation unit 333 is a processing unit that calculates a command value for inter-arm balance control based on the inter-arm balance operation amount. The inter-arm balance command value calculation unit 333 includes a voltage command value superimposing unit 333a that superimposes the inter-arm balance operation amount on the voltage command value by the intra-arm balance control.

[2. Action]
The balance control between the upper and lower arms according to the present embodiment as described above will be described. The balance control between the upper and lower arms is control for balancing the average value in the arm between the upper arm 2a and the lower arm 2b.

  Note that the processing according to the present embodiment is performed in addition to the in-leg balance control and the in-arm balance control. For this reason, the description of the same processing as in the first embodiment is simplified or omitted.

  First, in the same manner as described above, the arm average value calculation unit 321 calculates the upper arm average value and the lower arm average value. Then, the inter-arm difference calculation unit 331 calculates the difference between the upper arm average value and the lower arm average value. This arithmetic expression is shown in Expression 5.

In Expression 5, V _{cell_ave_P} is an average value in the upper arm, and V _{cell_ave_N} is an average value in the lower arm. The inter-arm difference is V _{cell_ave_PN} .

  The inter-arm balance operation amount calculation unit 332 calculates an operation amount for balance control between the upper and lower arms 2a and 2b. This arithmetic expression is shown in Expression 6.

That is, the inter-arm balance operation amount calculation unit 332 multiplies the inter-arm difference V _{cell_ave_PN} by the gain value K _{PN_arm_blc} and multiplies the output voltage command value V _ref input from the outside.

However, the arm between balanced operation amount calculation unit 332, by multiplying the sign _{(i d),} depending on the polarity of the active current _{i d} of the output current, switching the sign of the manipulated variable _{V ope_PN_blc.} The effective current _id is obtained from the output current by rotational coordinate conversion or the like.

In Expression 6, V _{ope_PN_blc} is an operation amount for balance control between the upper and lower arms 2a, 2b.

The inter-arm balance command value calculation unit 333 calculates a command value based on the inter-arm balance operation amount. That is, the voltage command value superimposing unit 333a superimposes the operation amount V _{ope_PN_blc} on the output voltage command values of all the chopper cells 1 in the leg 4 obtained by the above-described arm balance control.

  The output unit 500 outputs a control signal to the switching elements 11a and 11b based on the voltage command value generated by superposition. Based on this control signal, the switching elements 11a and 11b operate to execute balance control between the upper and lower arms.

The principle of balance control between the upper and lower arms as described above will be described with reference to the waveform diagrams of FIGS. Each waveform in FIGS. 4 to 6 is shown from the top as follows.
(A) Capacitor voltage average value in the upper and lower arms (first stage)
(B) Chopper cell output voltage in the upper and lower arms (second stage above)
(C) Amount of balance control operation between upper and lower arms (bottom of second stage)
(D) Reactor current of the upper and lower arms (third stage)
(E) Instantaneous power of the chopper cell of the upper and lower arms (fourth stage)

FIG. 4 shows a state in which the arm capacitor voltage average value of the lower arm 2b is smaller than the arm capacitor voltage average value of the upper arm 2a, as shown in FIG. For this reason, the inter-arm difference V _{cell_ave_PN} is positive. Then, the balance control operation amount (C) between the upper and lower arms 2a and 2b obtained by Expression 6 becomes positive by superimposing the gain value _{KPN_arm_blc} . For this reason, the balance control operation amount (C) between the upper and lower arms 2a and 2b has a waveform in phase with the output voltage command _Vref .

  The operation amount is superimposed on all the chopper cell output voltage commands in the upper and lower arms 2 a and 2 b in the leg 4. Therefore, as shown in Equation 2, the output voltage amplitude of the chopper cell 1 of the lower arm 2a that outputs the in-phase component with the output voltage command is increased. Further, the output voltage amplitude of the chopper cell 1 of the upper arm 2b that outputs a component opposite to the output voltage command is reduced.

  As a result, as shown in FIG. 4E, in the chopper cell 1 of the lower arm 2b, the positive region of the instantaneous power is expanded, and the capacitor voltage of each chopper cell 1 of the lower arm 2b is increased. On the other hand, in the chopper cell 1 of the upper arm 2a, the negative region of the instantaneous power is expanded, and the capacitor voltage of each chopper cell 1 of the upper arm 2a is decreased. Therefore, the average value of the capacitor voltage in the arm is balanced between the upper and lower arms 2a and 2b.

Contrary to the state of FIG. 4, FIG. 5 is a waveform diagram of each part in a state where the arm capacitor voltage average value of the upper arm 2 a is smaller than the arm capacitor voltage average value of the lower arm 2 b as shown in FIG. It is. In this state, the inter-arm difference V _{cell_ave_PN} is negative. Then, the balance control operation amount (C) between the upper and lower arms obtained by Expression 6 becomes negative by superimposing the gain value _{KPN_arm_blc} . For this reason, the balance control operation amount (C) between the upper and lower arms 2a, 2b has a waveform having a phase opposite to that of the output voltage command _Vref .

  The operation amount is superimposed on all the chopper cell output voltage commands in the upper and lower arms 2 a and 2 b in the leg 4. Therefore, as shown in Expression 2, the output voltage amplitude of the chopper cell 1 of the lower arm 2a that outputs the in-phase component with the output voltage command becomes small. Further, the output voltage amplitude of the chopper cell 1 of the upper arm 2a that outputs a component opposite to the output voltage command is increased.

  As a result, as shown in FIG. 5E, the negative region of the chopper cell instantaneous power of the lower arm 2b is expanded, and the chopper cell capacitor voltage of the lower arm 2b is decreased. On the other hand, in the chopper cell 1 of the upper arm 2a, the positive region of the instantaneous power is enlarged, and the capacitor voltage of each chopper cell 1 of the upper arm 2a is increased. Therefore, even in the state of FIG. 5, the average value of the capacitor voltage in the arm is balanced between the upper and lower arms 2a and 2b. FIG. 6 shows a waveform in which the arm capacitor voltage average value is balanced between the upper and lower arms 2a and 2b through the above processing.

[3. effect]
In the present embodiment as described above, the same value is superimposed on all the arms 2 in the leg 4 as the operation amount for balancing the upper and lower arms 2a, 2b. For this reason, the difference in the capacitor voltage of the chopper cell 1 is canceled between the upper and lower arms 2a and 2b, and the influence on the output voltage can be prevented more reliably.

[C. Third Embodiment]
[1. Constitution]
The configuration of this embodiment will be described with reference to FIG. This embodiment is basically the same configuration as the second embodiment. However, the difference is that the inter-arm balance command value calculation unit 333 includes a circulating current command value superimposing unit 333b. The circulating current command value superimposing unit 333 b is a processing unit that superimposes the inter-arm balance operation amount on the circulating current command value of the leg 4.

  Note that the storage unit 400 stores the circulating current command value calculated by the in-leg average value control unit 310, and the inter-arm balance control unit 330 performs the inter-arm balance control based on the circulating current command value. Included in the embodiment.

[2. Action]
The balance control between the upper and lower arms according to the present embodiment as described above will be described. Note that the processing according to the present embodiment is performed in addition to the in-leg balance control and the in-arm balance control. For this reason, description of processes similar to those of the first embodiment is simplified or omitted.

First, similarly to the above, the in-arm average value calculation unit 321 calculates the upper arm average value V _{cell_ave_P} and the lower arm average value V _{cell_ave_N} . This arithmetic expression is the same as Expression 5 above.

  The inter-arm balance operation amount calculation unit 332 calculates an operation amount for balance control between the upper and lower arms 2a and 2b. This arithmetic expression is shown in Expression 7.

That is, the inter-arm balance operation amount calculation unit 332 multiplies the inter-arm difference V _{cell_ave_PN} by the gain value K _{PN_arm_blc} and multiplies the output voltage command value V _ref input from the outside. In Expression 7, I _{ope_PN_blc} is an operation amount for balance control between the upper and lower arms 2a, 2b.

  The inter-arm balance command value calculation unit 333 calculates a command value based on the inter-arm balance operation amount. That is, the circulating current command value superimposing unit 333b superimposes the inter-arm balance operation amount on the circulating current command value of the circulating current control determined by the above-mentioned average control in the leg.

  The output unit 500 outputs a control signal based on the circulating current command value generated by superposition to the switching elements 11a and 11b. Based on this control signal, the switching elements 11a and 11b operate to execute balance control between the upper and lower arms.

The principle of balance control between the upper and lower arms as described above will be described with reference to FIGS. Each waveform in FIG. 8 and FIG. 9 is shown from the top as follows.
(A) Capacitor voltage average value in the upper and lower arms (first stage)
(B) Chopper cell output voltage in the upper and lower arms (second stage)
(C) Amount of balance control operation between the upper and lower arms (upper third stage)
(D) Reactor current of the upper and lower arms (lower 3rd stage)
(E) Instantaneous power of the chopper cell of the upper and lower arms (fourth stage)

FIG. 8 shows a state in which the arm capacitor voltage average value of the lower arm 2b is smaller than the arm capacitor voltage average value of the upper arm 2a, as shown in FIG. For this reason, the inter-arm difference V _{cell_ave_PN} is positive. Then, the balance control operation amount (C) between the upper and lower arms 2a, 2b obtained by Expression 7 becomes positive by superimposing the gain value _{KPN_arm_blc} . For this reason, the balance control operation amount (C) between the upper and lower arms 2a and 2b has a waveform in phase with the output voltage command _Vref .

  Since the manipulated value is superimposed on the circulating current command value, a component in phase with the output voltage command is added to the circulating current. Therefore, as shown in Equation 2, the average value of the instantaneous power of the chopper cell 1 of the lower arm 2b that outputs the in-phase component with the output voltage command increases. On the other hand, the average value of the instantaneous power of the chopper cell 1 of the upper arm 2a that outputs the reverse phase component decreases.

  As a result, the capacitor voltage of each chopper cell 1 of the lower arm 2b increases. On the other hand, the capacitor voltage of each chopper cell 1 of the upper arm 2a falls. Therefore, the average value of the capacitor voltage in the arm is balanced between the upper and lower arms 2a and 2b.

Contrary to the state of FIG. 8, FIG. 9 shows waveforms of respective parts in a state in which the arm capacitor voltage average value of the upper arm 2 a is smaller than the arm capacitor voltage average value of the lower arm 2 b as shown in FIG. . In this state, the inter-arm difference V _{cell_ave_PN} is negative. Then, the balance control operation amount (C) between the upper and lower arms 2a and 2b obtained by Expression 6 becomes negative by superimposing the gain value _{KPN_arm_blc} . For this reason, the balance control operation amount (C) between the upper and lower arms 2a, 2b has a waveform having a phase opposite to that of the output voltage command _Vref .

  Since the manipulated value is superimposed on the circulating current command value, a component having a phase opposite to that of the output voltage command is added to the circulating current. Therefore, as shown in Equation 2, the average value of the instantaneous power of the chopper cell 1 of the lower arm 2b that outputs the output voltage command and the opposite phase component decreases. On the other hand, the average value of the instantaneous power of the chopper cell 1 of the upper arm 2a that outputs the in-phase component with the output voltage command increases.

  As a result, the capacitor voltage of each chopper cell 1 of the lower arm 2b falls. On the other hand, the capacitor voltage of each chopper cell 1 of the upper arm 2a rises. Therefore, even in the state of FIG. 9, the average value of the capacitor voltage in the arm is balanced between the upper and lower arms 2a and 2b.

[3. effect]
In the present embodiment as described above, the operation amount that balances between the upper and lower arms 2a, 2b is superimposed on the circulating current command value of the leg 4, so that it does not interfere with the output current. Therefore, the influence on the output voltage can be prevented more reliably.

[D. Other Embodiments]
(1) In the above embodiment, in-leg balance control and inter-arm balance control are performed in addition to the in-leg average value control by the in-leg average value control unit. However, it is also possible to omit the in-leg average value control unit and perform control by the in-arm balance control unit and the inter-arm balance control unit. In this case, the arm balance command value calculation unit superimposes the upper and lower arm balance operation amounts on the value obtained by equally dividing the output voltage command value input from the outside into all the chopper cells in the leg.

  Further, the voltage command value superimposing unit of the inter-arm balance command value calculating unit superimposes the inter-arm balance operation amount on the upper and lower arm balance command values. Alternatively, the circulating current command value superimposing unit of the inter-arm balance command value calculating unit superimposes the inter-arm balance operation amount on the circulating current command value input from the outside of the host system or the like.

  Thereby, the balance between the upper and lower arms and the balance between the upper and lower arms are controlled while reducing the amount of calculation, and the balance control can be prevented from interfering with the output voltage.

(2) The control device can be realized by controlling the computer with a predetermined program or by a dedicated electronic circuit. The program in this case implements the processing of each of the above units by physically utilizing computer hardware. A method, a program, and a recording medium that records the program for executing the processing of each unit described above are also one aspect of the embodiment. Moreover, how to set the range processed by hardware and the range processed by software including a program is not limited to a specific mode.

(3) The storage unit can typically be configured by various built-in or externally connected memories, a hard disk, an optical disk, or the like, but any storage medium that can be used now or in the future can be used. A register, a memory, and the like used for calculation can also be regarded as a storage unit. Therefore, even a storage area temporarily stored for the arithmetic processing of each unit described above can be regarded as a storage unit.

(4) Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Chopper cell 2 ... Arm 2a ... Upper arm 2b ... Lower arm 3 ... Reactor 4 ... Leg 11a, 11b ... Switching element 12a, 12b ... Diode 13 ... Capacitor 100 ... Control device 200 ... Input part 300 ... Calculation part 310 ... In leg Average value control unit 311 ... In-leg average value calculation unit 312 ... Capacitor voltage command value calculation unit 313 ... In-leg difference calculation unit 314 ... Circulating current command value calculation unit 315 ... In-leg average manipulated variable calculation unit 316 ... Voltage command value calculation Unit 320 ... Intra-arm balance control unit 321 ... In-arm average value calculator 321a ... Upper arm average value calculator 321b ... Lower arm average value calculator 322 ... In-arm difference calculator 322a ... Upper arm difference calculator 322b ... Lower arm difference calculation unit 323 ... In-arm balance operation amount calculation unit 323a ... Upper arm balance calculation unit 3 3b: Lower arm balance calculation unit 324 ... In-arm balance command value calculation unit 324a ... Upper arm command value calculation unit 324b ... Lower arm command value calculation unit 330 ... Inter-arm balance control unit 331 ... Inter-arm difference calculation unit 332 ... Inter-arm balance operation amount calculation unit 333 ... Inter-arm balance command value calculation unit 333a ... Voltage command value superimposition unit 333b ... Circulating current command value superimposition unit 400 ... Storage unit 500 ... Output unit

Claims (8)

A control device for controlling a power conversion device having at least one leg including a pair of arms, which are configured by multistage chopper cells including switching elements and capacitors, on the positive side and the negative side,
A voltage command value storage unit for storing a voltage command value for controlling the average value of the capacitor voltage of the chopper cell in the leg to be constant;
In-arm average value calculation unit that calculates the average value in the arm, which is the average value of the capacitor voltage in each arm, for each of the positive arm and the negative arm in the leg based on the capacitor voltage input from the outside. When,
An intra-arm difference calculation unit for calculating an in-arm difference that is a difference between each capacitor voltage of the positive arm and the capacitor voltage of the negative arm input from the outside and the average value in the arm;
Intra-arm balance operation that calculates an intra-arm balance operation amount that is an operation amount of a switching element that balances the output voltage of each chopper cell in the arm for each of the positive side arm and the negative side arm based on the difference in the arm. A quantity calculation unit;
Based on the voltage command value and the in-arm balance operation amount, an in-arm balance command value calculation unit that calculates an in-arm balance command value that is an output voltage command value of each chopper cell in the arm;
The control apparatus of the power converter device which has. An inter-arm difference calculation unit that calculates an inter-arm difference that is the difference between the average value in the arm of the positive arm in the leg and the average value in the arm of the negative arm;
Inter-arm balance operation amount for calculating an inter-arm balance operation amount that is an operation amount for balancing the output voltage between the positive and negative arms based on the voltage command value input from the outside and the inter-arm difference. An arithmetic unit;
Based on the balance operation amount between the arms, an arm balance command value calculation unit for calculating an arm balance command value for balancing the output voltage between the positive and negative arms,
The control apparatus of the power converter device of Claim 1 which has these.   The control device for a power converter according to claim 2, wherein the inter-arm balance command value calculation unit includes a voltage command value superimposing unit that superimposes the inter-arm balance operation amount on the intra-arm balance command value. . A circulating current command value storage unit for storing a circulating current command value for controlling the average value of the capacitor voltage of the chopper cell in the leg to be constant;
The control device for a power converter according to claim 2, wherein the inter-arm balance command value calculation unit includes a circulating current command value superimposing unit that superimposes the inter-arm balance operation amount on the circulating current command value. A computer or electronic circuit is a control method for controlling a power conversion device having at least one leg including a pair of arms, which are configured by multistage chopper cells including switching elements and capacitors, on the positive side and the negative side,
The computer or electronic circuit is
Voltage command value storage processing for storing a voltage command value for controlling the average value of the capacitor voltage of the chopper cell in the leg to be constant;
In-arm average value calculation processing for calculating the average value in the arm, which is the average value of the capacitor voltage in each arm, for each of the positive side arm and the negative side arm in the leg based on the capacitor voltage input from the outside. When,
Intra-arm difference calculation processing for calculating an intra-arm difference that is a difference between each capacitor voltage of the positive side arm and each capacitor voltage of the negative side arm input from the outside, and the average value in the arm,
Intra-arm balance operation that calculates an intra-arm balance operation amount that is an operation amount of a switching element that balances the output voltage of each chopper cell in the arm for each of the positive side arm and the negative side arm based on the difference in the arm. Quantity calculation processing,
Based on the voltage command value and the arm balance operation amount, an arm balance command value calculation process for calculating an arm balance command value that is an output voltage command value of each chopper cell in the arm;
For controlling the power conversion apparatus. The computer or electronic circuit is
An inter-arm difference calculation process for calculating an inter-arm difference that is a difference between an average value in the arm of the positive arm in the leg and an average value in the arm of the negative arm;
Inter-arm balance operation amount for calculating an inter-arm balance operation amount that is an operation amount for balancing the output voltage between the positive and negative arms based on the voltage command value input from the outside and the inter-arm difference. Arithmetic processing,
Based on the inter-arm balance operation amount, an inter-arm balance command value calculation process for calculating an inter-arm balance command value that balances the output voltage between the positive and negative arms,
The control method of the power converter device of Claim 5 which performs. A control program for causing a computer to control a power conversion device having at least one leg including a pair of arms on the positive side and the negative side, which are configured by multistage chopper cells including switching elements and capacitors,
In the computer,
Voltage command value storage processing for storing a voltage command value for controlling the average value of the capacitor voltage of the chopper cell in the leg to be constant;
In-arm average value calculation processing for calculating the average value in the arm, which is the average value of the capacitor voltage in each arm, for each of the positive side arm and the negative side arm in the leg based on the capacitor voltage input from the outside. When,
Intra-arm difference calculation processing for calculating an intra-arm difference that is a difference between each capacitor voltage of the positive side arm and each capacitor voltage of the negative side arm input from the outside, and the average value in the arm,
Intra-arm balance operation that calculates an intra-arm balance operation amount that is an operation amount of a switching element that balances the output voltage of each chopper cell in the arm for each of the positive side arm and the negative side arm based on the difference in the arm. Quantity calculation processing,
Based on the voltage command value and the arm balance operation amount, an arm balance command value calculation process for calculating an arm balance command value that is an output voltage command value of each chopper cell in the arm;
The control program of the power converter device which performs. In the computer,
An inter-arm difference calculation process for calculating an inter-arm difference that is a difference between an average value in the arm of the positive arm in the leg and an average value in the arm of the negative arm;
Inter-arm balance operation amount for calculating an inter-arm balance operation amount that is an operation amount for balancing the output voltage between the positive and negative arms based on the voltage command value input from the outside and the inter-arm difference. Arithmetic processing,
Based on the inter-arm balance operation amount, an inter-arm balance command value calculation process for calculating an inter-arm balance command value that balances the output voltage between the positive and negative arms,
The control program for the power conversion device according to claim 7, wherein:

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