JP2008306830A - Harmonic current compensator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform more accurate current control by being able to compensate the current error by the insertion of an AC filter and materializing a stable control system. <P>SOLUTION: The current error is compensated by adding up the output of having performed arithmetic processing, having a transfer function H(s) being gotten beforehand from the circuit constant of an AC filter, to the input of the current command (Iref0) on input side of the AC filter, and the output of having performed arithmetic processing, having a transfer function G(s) being gotten beforehand from the circuit constant of the AC filter, to the input of the voltage (Vload) on output side of the AC filter, thereby making a harmonic compensating current command (Iref1). The voltage drop is compensated by adding up the output of having performed arithmetic processing, having a transfer function sL1, to the input of the current command (Iref0), and the output of having performed arithmetic processing, having a transfer function sL2, to the input of the current command (Iref1), and adding the sum to the reference voltage command of the active filter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention extracts a harmonic current generated by a load connected to a system power supply and compensates a system harmonic component (active filter) or a parallel type sag compensation having an active filter function. The present invention relates to harmonic current compensation control in a device, and more particularly to current control of a device that outputs a harmonic compensation current from an active filter via an AC filter.

  Generally, in an electric power system, an active filter that compensates a harmonic current generated by a load connected to a system power supply, a parallel type voltage sag compensator having an active filter function, and the like are used.

  FIG. 3 shows an example of a main circuit configuration of a parallel type sag compensator having an active filter function. During normal times, power is supplied from the power system to the load via the high-speed switch 10. In this state, the AC / DC bidirectional conversion device 20 constituted by an inverter or the like compensates for the harmonic current generated from the load by the active filter function, and waits for the electric double layer capacitor 30 to be floated or stopped. In addition, the AC / DC bidirectional converter 20 converts the DC power stored in the electric double layer capacitor 30 into AC power when the high-speed switch 10 is disconnected at the time of a power failure of the power system, and power to the load without interruption. Supply. The AC / DC bidirectional converter 20 supplies a harmonic compensation current to the load through the AC filter 40.

  Next, normal active filter function control will be described. FIG. 4 shows a circuit configuration of a control device of a parallel type sag compensator having an active filter function. In normal times, it includes a detecting means for detecting a harmonic current generated by a load, and a self-excited conversion device for extracting a harmonic component and supplying a current for compensating the harmonic component of the system.

  The control device 50 includes detectors 51 to 56 for system voltage Vs, system current Is, load current Iload, load voltage Vload, inverter output current Iinv0, and inverter output current Iinv1. From the detected system voltage Vs, the phase θ of the system power supply is detected by the PLL circuit 57, and a sin θ component and a cos θ component of the phase θ are generated by the sine wave generator 58. The command value creation block 59 creates a command value for the harmonic compensation current from the detected system voltage Vs, system current Is, load current Iload, load voltage Vload, inverter output current Iinv0, and inverter output current Iinv1. Then, the harmonic compensation current command value is PWM-modulated by a pulse width modulation (PWM) 60, and a harmonic compensation current output is obtained by PWM inverter control of the AC / DC bidirectional converter 20. From this PWM control output, the PWM carrier signal component is removed by the AC filter 30.

  As current command generation means (command value creation block 59) for compensating harmonic current generated by a load, there is a compensation method by load current detection type batch harmonic detection, an example of which is shown in the block diagram of FIG. The detected load current Iload is subjected to coordinate conversion to the dq axis by the 3φ / dq coordinate conversion unit 61 using the sin θ component and the cos θ component of the detected power supply phase θ, and the converted d-axis and q-axis components are converted. Then, only the harmonic component is extracted by subtracting the fundamental wave components detected by the low-pass filters 62 and 63, and further the inverse dq coordinate conversion is performed by the dq / 3φ coordinate conversion unit 64, and the charge command value is added thereto. A current command value Iref0 for compensating harmonics is obtained. Then, current control calculation is performed by an ACR (automatic current control) 65 so that the current command value Iref0 coincides with the inverter output current Iinv0, and the reference voltage command value sinθ obtained by the PLL is used as a reference phase with the ACR output as an amplitude. A harmonic compensation current command signal is obtained.

  Here, an LCL type or LC type AC filter 40 is inserted between the inverter and the load in order to remove a carrier component used for PWM modulation. FIG. 6 shows an example of an AC filter having a T-type LCL configuration. When an AC filter is inserted, the inverter output current Iinv1 cannot be set to the current command value Iref due to the influence of the current flowing through the capacitor Cf in the AC filter. As a result, when performing harmonic compensation by the active filter function, there arises a problem that the harmonic compensation rate decreases.

  Therefore, in the following Patent Document 1, a current command value Iref1 is created in consideration of an AC filter. In this control method, the current error between the inverter output current Iinv1 on the load side of the AC filter and the current command value that occurs when the AC filter is installed between the inverter and the load is calculated in advance from the circuit constant of the AC filter. Compensation is performed using a transfer function that removes the influence of the AC filter. AC filter circuit constants are: L1: load side inductance [H] of AC filter, L2: input side inductance [H] of AC filter, Cf: capacitor capacity [F] of AC filter, Rf: resistance value of AC filter [Ω ].

  FIG. 7 shows a block diagram for creating a command value in Patent Document 1. The load voltage detection value Vload and the current command value Iref0 are multiplied by a calculation element 66 having a transfer function G (s) for removing the influence of the AC filter and a calculation element 67 having a transfer function H (s), respectively. The ACR control is performed using this as the current command value Iref1, and the command value is created by adding the reference voltage command value.

Furthermore, in Patent Document 1, assuming that current control is ideal, the inverter current detection value Iinv1 on the load side of the AC filter, the inverter current detection value Iinv0 on the inverter (input) side of the AC filter, and the AC filter A method of compensating for the voltage drop by feedforward using the inductance values L1 and L2 of the above is also proposed. This command value creation block diagram is shown in FIG. The AC filter load-side inverter current detection value Iinv1 is multiplied by a calculation element 68 having a transfer function sL1, and the inverter-side inverter current detection value Iinv0 is multiplied by a calculation element 69 having a transfer function sL2, and feed-forward to obtain a current command value. Add to Iref0 to create a command value.
JP 2004-254429 A

  In Patent Document 1, when an AC filter is inserted between an inverter and a load, an AC filter load-side inverter output current Iinv1 caused by the influence of a current flowing in the capacitor Cf and a current error between the current command values are represented by an AC filter circuit. Compensation is performed using a transfer function calculated in advance from a constant. In this method, the amount of current flowing through the capacitor Cf of the AC filter is compensated.

  Further, in Patent Document 1, a voltage drop is performed in a feedforward manner by using an inverter current detection value Iinv0 on the load side of the AC filter, an inverter current detection value Iinv1 on the inverter side of the AC filter, and inductance values L1 and L2 of the AC filter. Compensate for minutes. This method is established when the current control is in an ideal condition, but in reality, it is affected by a calculation dead time and the like, so that the ideal control becomes difficult.

  Therefore, ACR is performed using the inverter current detection value Iinv0 on the inverter (input) side and the current command value Iref0, and feedforward is performed using the inverter current detection value Iinv1 on the load side and the inverter current detection value Iinv0 on the inverter (input) side. When the voltage drop compensation of L1 and L2 is performed, the control system becomes unstable.

  An object of the present invention is to realize a stable control system capable of compensating a current error due to the insertion of an AC filter in a harmonic current compensator that outputs a harmonic compensation current from an active filter via an AC filter. It is an object of the present invention to provide a harmonic current compensator capable of highly accurate current control.

  According to the present invention, in an apparatus in which an AC filter is inserted between an inverter and a load, a transfer function H (s) obtained in advance from the circuit constant of the AC filter is input to the input of the current command value (Iref0) on the input side of the AC filter. ) And an output processed with a transfer function G (s) obtained in advance from the circuit constant of the AC filter with respect to the input of the voltage (Vload) on the output side of the AC filter. Is added to obtain a harmonic compensation current command value (Iref1), thereby compensating for a current error due to the insertion of an AC filter. Then, an output that has been processed with the transfer function sL1 for the input of the current command value (Iref0), and an output that has been processed with the transfer function sL2 for the input of the current command value (Iref1). By adding and compensating for the voltage drop by adding to the reference voltage command value of the active filter, a stable control system can be realized and more accurate current control can be achieved. To do.

(1) Harmonic current generated by the load connected to the system power supply is extracted, and this harmonic current is used as the harmonic compensation current command value of the active filter. From the active filter through the AC filter of T-type LCL configuration In the harmonic current compensator that outputs the harmonic compensation current,
With respect to the input of the current command value (Iref0) on the input side of the AC filter, an output processed with the following transfer function H (s) obtained in advance from the circuit constants of the AC filter, and the output side of the AC filter The harmonic compensation current command value (Iref1) is added to the input of the voltage (Vload) by adding an output having the following transfer function G (s) calculated in advance from the circuit constants of the AC filter and performing the arithmetic processing. Current error compensation means for

However, L1: Load side inductance of AC filter, L2: Input side inductance of AC filter, Cf: Capacitance of AC filter, Rf: Resistance value of AC filter Transfer function sL1 with respect to the input of current command value (Iref0) The voltage drop that is added to the reference voltage command value of the active filter is added to the input of the current command value (Iref1) and the output that is calculated to have the transfer function sL2 to the input of the current command value (Iref1) Compensation means;
It is provided with.

(2) The harmonic current generated by the load connected to the system power supply is extracted, and this harmonic current is used as the harmonic compensation current command value of the active filter, and the active filter is passed through the AC filter of the L-type LC configuration. In the harmonic current compensator that outputs the harmonic compensation current,
For the input of the current command value (Iref0) on the input side of the AC filter, the output having a transfer function sL2 (L2 is the input-side inductance of the AC filter) obtained in advance from the circuit constant of the AC filter is calculated and processed. The voltage drop compensation means for adding to the reference voltage command value of the active filter is provided.

  As described above, according to the present invention, an infinite impulse response filter is created from the transfer function calculated in advance from the AC filter circuit constants, and the IIR created from the respective transfer functions for the load voltage Vload and the current command value Iref0. By applying a filter process to the filter, a current error due to the AC filter insertion is compensated, and the current command value Iref0 and the current command value Iref1 subjected to the IIR filter process are used to feed the inductance components L1, L2 of the AC filter by feedforward. By performing the voltage drop compensation according to the above, a stable control system can be realized and more accurate current control can be performed.

(Embodiment 1)
FIG. 1 is a block diagram of harmonic current compensation command value creation showing an embodiment of the present invention, which is applied to a harmonic current compensator with an AC filter having an LCL configuration. In FIG. 1, 61 to 67 have the same configuration as the block of FIG. 7, and 68 and 69 operation blocks are added to this configuration. Hereinafter, the configuration of the calculation blocks 66 to 69 and the current compensation control will be described.

  The circuit equation of the circuit constants L1, L2, Cf, and Rf of the AC filter having the LCL configuration shown in FIG. 6, the load current Iload, the load voltage Vload, the inverter output current Iinv0, and the inverter output current Iinv1 is as shown in Equation (1). I can express. s is a Laplace operator.

  Here, the coefficients of Iinv1 and Iinv0 are set as shown in equation (2).

  From equations (1) and (2), the load voltage Vload can be expressed as equation (3).

  When equation (3) is solved for Iinv1, it can be expressed as equation (4).

  From the equation (4), the current Iinv1 on the load side and the current Iinv0 on the inverter side are different due to the influence of the AC filter. Linv0 is determined as in the following equation (5) so that the current Iinv0 on the load side becomes the current command value Iref0.

  Next, when the formula (5) is substituted into the formula (4), the formula (6) is obtained, and the inverter output current Iinv1 and the current command value Iref0 can be matched.

  When the current control is ideally performed, the current command value and linv0 coincide with each other. Therefore, the current command value Iref1 considering the input filter may be expressed by the following equation (7).

  Therefore, the transfer function G (s) and the transfer function H (s) of the calculation blocks 66 and 67 are expressed by the following equations (8) and (9), so that the inverter output current on the load side The current error between Iinv1 and the current command value can be compensated.

  Next, in order to perform voltage drop compensation for the inductance values L1 and L2 of the AC filter, the following circuit equation is established.

  From the equations (10) and (11), Vload can be expressed as follows.

  Here, since the current command value Iref1 considering the AC filter is approximated to the inverter-side inverter current Iinv0, and the current command value Iref0 is approximated to the load-side inverter current Iinv1, equation (12) can be expressed as follows. .

  The terms sL1 · Iref0 and sL2 · Iref1 in the equation (13) are obtained by operation blocks 68 and 69 having transfer functions sL1 and sL2, and these are added to the reference voltage command value by feedforward. As the reference voltage command value, a sine wave corresponding to a rated voltage synchronized with the system voltage or a normalized system voltage is used.

  According to this embodiment, in an apparatus in which an AC filter is interposed between an inverter and a load, the inverter output current Iinv1 on the load side of the AC filter and the current command value current are transferred using a transfer function that eliminates the influence of the AC filter. By compensating for the error and compensating the voltage drop of the inductance component of the AC filter by feedforward using the current command values Iref0 and Iref1 instead of the inverter current detection values Iinv0 and Iinv1, a stable control system is realized, and more Highly accurate current control can be performed. Moreover, the non-interference term on the dq axis can be compensated by performing on three phases.

(Embodiment 2)
FIG. 2 is a harmonic current compensation command value creation block diagram showing an embodiment of the present invention, which is applied to a harmonic current compensator having an AC filter as an LC configuration. In the figure, the difference from FIG. 5 is that an arithmetic block 70 is provided.

  When the AC filter has an LC configuration, the circuit equation (1) that is solved to create a current command value considering the AC filter is not satisfied. Therefore, using only the current command value Iref0 on the input side of the AC filter, As shown in the following equation, voltage drop compensation is performed by the input side inductance L2 of the AC filter.

When the AC filter has an LC configuration, a calculation block 70 is provided that adds the term of sL2 · Iref0 in equation (14) to the reference voltage command value by feedforward. For the reference voltage command value, use a sine wave equivalent to the rated voltage synchronized with the system voltage or a normalized system voltage.
According to this embodiment, when the AC filter between the inverter and the load has an LC configuration, the voltage drop compensation of the inductance component of the AC filter is performed by feedforward using the current command value instead of the inverter current detection value. Therefore, a stable control system can be realized, and more accurate current control can be performed.

The harmonic current compensation command value creation block diagram which shows Embodiment 1 of this invention. The harmonic current compensation command value creation block diagram which shows Embodiment 2 of this invention. The main circuit structural example of a parallel type voltage sag compensator. The circuit block diagram of the control apparatus of a parallel type sag compensation apparatus. The conventional command value creation block diagram. An example of an AC filter. The conventional command value creation block diagram. The conventional command value creation block diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 High speed switch 20 AC / DC bidirectional converter 30 Electric double layer capacitor 40 AC filter 50 Control apparatus 61, 64 Coordinate conversion part 62, 63 Low pass filter 65 Automatic current control part (ACR)
66, 67, 68, 69 Transfer function block

Claims (2)

Harmonic current generated by the load connected to the system power supply is extracted, this harmonic current is used as the harmonic compensation current command value of the active filter, and the harmonic compensation from the active filter through the AC filter of T-type LCL configuration In the harmonic current compensator that outputs current,
With respect to the input of the current command value (Iref0) on the input side of the AC filter, an output processed with the following transfer function H (s) obtained in advance from the circuit constants of the AC filter, and the output side of the AC filter The harmonic compensation current command value (Iref1) is added to the input of the voltage (Vload) by adding an output having the following transfer function G (s) calculated in advance from the circuit constants of the AC filter and performing the arithmetic processing. Current error compensation means for

However, L1: Load side inductance of AC filter, L2: Input side inductance of AC filter, Cf: Capacitance of AC filter, Rf: Resistance value of AC filter Transfer function sL1 with respect to the input of current command value (Iref0) The voltage drop that is added to the reference voltage command value of the active filter is added to the input of the current command value (Iref1) and the output that is calculated to have the transfer function sL2 to the input of the current command value (Iref1) Compensation means;
A harmonic current compensator characterized by comprising: Harmonic current generated by the load connected to the system power supply is extracted, this harmonic current is used as the harmonic compensation current command value of the active filter, and harmonic compensation is performed from the active filter via the AC filter of the L-type LC configuration. In the harmonic current compensator that outputs current,
For the input of the current command value (Iref0) on the input side of the AC filter, the output having a transfer function sL2 (L2 is the input-side inductance of the AC filter) obtained in advance from the circuit constant of the AC filter is calculated and processed. A harmonic current compensator comprising voltage drop compensation means for adding to the reference voltage command value of the active filter.

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