JP2014176186A - Converter controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a converter controller capable of suppressing increase in DC voltage and DC current in the case of power regeneration in a power conversion device.SOLUTION: A converter controller in a device comprising a converter 13 whose AC side is connected to an AC power supply, a DC capacitor 14 connected between positive and negative output terminals of the converter 13, and an inverter whose DC side is connected to the DC capacitor 14 and whose AC side is connected to a load detects DC output voltage Vof the converter 13; and performs feedback control so that the DC detection voltage Vis approximately equal to a DC voltage instruction value V*. The converter controller comprises a control unit which raises a control response of the feedback control in a period when current of the inverter Iis larger than current of the converter I, and lowers the control response of the feedback control in a period when the current of the inverter Iis equal to or smaller than the current of the converter.

Description

  The present invention relates to a converter control device in a power conversion device that regenerates power supplied to a load and power from the load to a power source side.

  FIG. 1 shows an example of a power converter. In FIG. 1, a three-phase AC power supply 11 is connected to a three-phase input side of a converter 13 through a filter circuit 12 including a reactor and a capacitor.

  The converter 13 is configured by connecting semiconductor switching elements such as IGBTs in a three-phase bridge, and a DC capacitor (smoothing capacitor) 14 is connected between the positive and negative terminals.

  Reference numeral 15 denotes an inverter configured by connecting a semiconductor switching element such as an IGBT, for example, in a three-phase bridge. The DC side is connected between both ends of the DC capacitor 14, and the AC side is connected to a load 16 such as an electric motor. Yes.

  In addition, in the power converter device comprised as mentioned above, the method of suppressing the DC output voltage fluctuation | variation of a converter was conventionally proposed, for example in patent documents 1-3.

JP-A-8-223959 JP-A-10-257773 Japanese Patent Laid-Open No. 11-150955

In the power converter configured as shown in FIG. 1, the converter current I _C is controlled so that the voltage V _DC of the DC capacitor 14 is constant. Here, when a load (16) that regenerates energy to the power source side is connected like an electric motor, the energy is temporarily stored in the DC capacitor 14 by the operation of the inverter 15, and then the AC power source by the operation of the converter 13 11 is sent.

At this time, when the rise of the regenerative power is steep and the DC voltage control of the converter 13 is slow, the DC voltage V _DC rises and becomes an overvoltage. If the control response of the DC voltage _VDC is improved, the DC voltage can be prevented from rising to the overvoltage level, but the converter current (current flowing in the direction opposite to the arrow of I _C in FIG. 1) becomes excessive, causing an overvoltage fault. There is a possibility.

  The present invention solves the above problems, and an object of the present invention is to provide a converter control device that can suppress an increase in DC voltage and DC current during power regeneration in the power conversion device.

  The control apparatus for a converter according to claim 1 for solving the above-described problem includes a converter in which an AC side is connected to an AC power source, a smoothing capacitor connected between positive and negative output terminals of the converter, and a DC side in the converter In an apparatus including an inverter connected to a smoothing capacitor and having an AC side connected to a load, a converter that detects a DC output voltage of the converter and performs feedback control so that the DC detection voltage is substantially equal to a DC voltage command value The control device is configured to increase the control response of the feedback control during a period in which the inverter current is larger than the converter current, and to control the feedback control during a period in which the inverter current is equal to or less than the converter current. It is characterized by having a control unit that lowers the response.

  According to a second aspect of the present invention, there is provided the converter control device according to the first aspect, wherein the control unit calculates a proportional term of a current command value based on a deviation between the DC voltage command value of the converter and a DC detection voltage. A term calculation unit, an integration term calculation unit that calculates an integral term of the current command value based on a deviation between the DC voltage command value of the converter and the DC detection voltage, a first gain constant, and the first gain constant And an integral gain changing unit that creates a small second gain constant and changes an integral gain of the integral term computing unit according to the gain constant.

  According to the above configuration, during power regeneration, during the period when the regenerative current rises steeply and the regenerative current of the inverter is larger than the converter current, the control response of the converter control becomes high. Since regeneration can be performed on the AC power supply side, an increase in DC voltage during this period can be suppressed.

  Further, when the inverter current becomes equal to or lower than the converter current, the control response of the converter control is lowered, so that the current flowing from the converter to the AC power supply side can be prevented from being excessive.

  According to a third aspect of the present invention, in the converter control device according to the second aspect, the integral gain changing unit creates the gain constant according to a sign of a deviation between the DC voltage command value of the converter and a DC detection voltage. It is characterized by that.

  According to the above configuration, the regenerative state can be reliably recognized and the level of the control response can be switched by the sign of the deviation between the DC voltage command value of the converter and the DC detection voltage.

(1) According to the first to third aspects of the present invention, it is possible to suppress an increase in DC voltage and DC current during power regeneration, and to prevent occurrence of failure due to overvoltage and overcurrent.
(2) According to the invention described in claim 3, it is possible to reliably recognize the regenerative state and switch the level of the control response.

The circuit diagram which shows an example of the power converter device to which this invention is applied. The control block diagram showing the DC voltage control system in the embodiment of the present invention. The characteristic view which shows the relationship between the regenerative electric power by the conventional control method, the voltage of a converter, and an electric current. The principal part block diagram of the DC voltage control system in the example of embodiment of this invention. The characteristic view which shows the relationship between the regenerative electric power by the control method of the example of embodiment of this invention, the voltage of a converter, and an electric current.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. FIG. 2 is a control block diagram of a DC voltage control system using a converter in an embodiment in which the present invention is applied to the power converter shown in FIG.

In the present embodiment, the DC voltage (voltage of the DC capacitor 14) V _DC of the converter 13 of FIG. 1 is detected, and the control of the present invention is performed so that the _DC voltage V _DC is substantially equal to the DC voltage command value V _DC *. The feedback control is performed by the PI controller 20 as a unit.

The PI controller 20 calculates a proportional term and an integral term of the current command value based on the deviation between the V _DC and V _DC * to obtain a converter current command value I _c *.

A deviation between the converter current I _C and the inverter current I _INV becomes a capacitor current I _DC , and this I _DC indicates that a DC voltage V _DC is generated in the DC capacitor 14 (C _DC ).

DC DC voltage V _DC by the difference current I _C flowing through the DC capacitor 14 from the current I _INV and converter 13 that flows from the capacitor 14 to the load 16 side becomes Equation (1).

  However, t = 0 is set at the start of regeneration.

Here, the converter 13 controls _VDC as shown in FIG. The Figure 2, the PI controller 20 calculates the converter current I _C of the command value I _C *, the DC voltage V _DC is flow I _C so that the command value V _DC *. Here, it is assumed that the converter current I _C is equal to the command value I _C *.

With the above V _DC * constant, the Laplace transform of V _DC * −V _{DC with} respect to I _INV is

The relationship between the converter current I _C and the inverter current I _INV is

  It becomes.

From the relationship between the inverter current I _INV and the converter current I _C , the DC voltage V _DC becomes a set value V _DC * through the following process.

  This is shown in FIG. However, in FIG. 3, the direction of the current is opposite to the arrow in FIG.

(1) DC voltage V _DC increases during I _INV > I _C (2) DC voltage V _DC is maximum when I _INV = I _C (3) DC voltage V _DC decreases during I _INV <I _C where If the difference between I _INV and I _C is small in the period (1), the maximum value of V _DC becomes small and overvoltage can be avoided. Therefore, overvoltage can be avoided by making the converter 13 have a high response.

On the other hand, since the current flowing from the converter 13 to the power supply side becomes the maximum in the period (3), when the converter 13 is adjusted to have a high response in order to avoid an overvoltage, the expression (3) seems to overshoot in the period (3). become. This increases the possibility that the converter current I _C will be excessive and the semiconductor switching element will be damaged.

Therefore, in this embodiment, in order to prevent the DC voltage from becoming overvoltage during the rising period of the regenerative current from the load (the period (1)), the response of the DC voltage control system is increased, and the converter current is excessive. In order to avoid this, the gain of the PI controller 20 is switched when I _INV and I _C become equal (the period (2)), and the response is delayed.

  FIG. 4 shows details of the PI controller 20 in the DC voltage control system of FIG. 2 of the present embodiment, and the same parts as those in FIG. In FIG. 4, reference numeral 21 denotes an integral term calculation unit that calculates the integral term of the current command value, and reference numeral 22 denotes a proportional term calculation unit that calculates the proportional term of the current command value.

23 is a differentiator that differentiates the difference e between the DC voltage command value V _DC * and the DC voltage V _DC , and 24 is a sign determination unit that determines the sign in the regenerative or driving state from the voltage difference e.

  Reference numeral 25 denotes a multiplier that multiplies the output of the differentiator 23 and the output P of the sign determination unit 24. Reference numeral 26 denotes a gain constant of 1 (first gain constant) when the output a of the multiplier 25 is 0 or more. Is a gain constant creating unit that creates a gain constant G (second gain constant) having a value of 0 to 1 when it is less than 0.

The output h of the gain constant creation unit 26 is multiplied by the V _DC * and the deviation e of V _{DC in} the multiplier 27, and the output x of the multiplier 27 is used as the input of the integral term calculation unit 21.

The outputs of the integral term computing unit 21 and the proportional term computing unit 22 are added by an adder 28 to output a current command value I _C * for the converter 13.

  The differentiator 23, the sign determination unit 24, the multipliers 25 and 27, and the gain constant creation unit 26 constitute an integral gain changing unit.

When the inverter current I _INV and the converter current I _C is equal in the period (2), the differential of the deviation e of the V _DC * and V _DC is zero. At this time, the parameter of the PI controller 20 is changed to slow down the control response. In FIG. 4, the state is determined from the sign of the deviation e. When e <0, the derivative of the deviation is 0 or more, and when e> 0, the integral gain of the PI controller 20 is 0 or less. The input of the integral term is multiplied by the gain constant G (0 or more and 1 or less) created by the gain constant creating unit 26 so as to decrease.

FIG. 5 shows the converter voltage and current during regeneration when the control circuit of FIG. 4 is applied. The period (1) has the same voltage and current as in FIG. 3, but the parameter of the PI controller 20 is changed at the time of period (2), and as a result of the slow control response, the converter in period (3) The maximum value of the current I _C is suppressed. However, as a result of the slow control response, the time for the DC voltage to converge to the command value becomes longer.

  As described above, according to the present embodiment, by increasing the response of the DC voltage control system until it becomes oscillating, the regenerative power can be quickly output to the power supply side during the rising period of the regenerative current from the load. An increase in DC voltage can be suppressed. In addition, since the response of the controller (PI controller 20) is delayed when the regenerative power and the output power to the converter power supply become equal, even if the response of the DC voltage control system is increased to vibration, The maximum value of the converter current can be suppressed.

DESCRIPTION OF SYMBOLS 11 ... AC power supply 12 ... Filter circuit 13 ... Converter 14 ... DC capacitor 15 ... Inverter 16 ... Load 20 ... PI controller 21 ... Integral term operation part 22 ... Proportional term operation part 23 ... Differentiator 24 ... Sign determination device 25, 27 ... Multiplier 26 ... Gain constant creation unit 28 ... Adder

Claims (3)

An apparatus comprising a converter having an AC side connected to an AC power source, a smoothing capacitor connected between positive and negative output terminals of the converter, and an inverter having a DC side connected to the smoothing capacitor and an AC side connected to a load In
A converter control device that detects a DC output voltage of the converter and performs feedback control so that the DC detection voltage is substantially equal to a DC voltage command value,
A control unit that increases the control response of the feedback control during a period when the inverter current is larger than the converter current, and lowers the control response of the feedback control during a period when the inverter current is equal to or less than the converter current. A converter control device comprising the converter. The controller is
A proportional term calculation unit that calculates a proportional term of the current command value based on a deviation between the DC voltage command value of the converter and the DC detection voltage;
An integral term computing unit that computes an integral term of the current command value based on the deviation between the DC voltage command value of the converter and the DC detection voltage;
An integral gain changing unit that creates a first gain constant and a second gain constant that is smaller than the first gain constant, and changes the integral gain of the integral term computing unit according to the gain constant; The converter control device according to claim 1.   3. The converter control device according to claim 2, wherein the integral gain changing unit creates the gain constant according to a sign of a deviation between a DC voltage command value of the converter and a DC detection voltage.

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