JP2011166852A - Method for controlling ac-dc converter and control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling an AC-DC converter for achieving suppression of fifth harmonic voltage of a power system by outputting the fifth harmonic voltage from a power conversion part; and to provide a control apparatus. <P>SOLUTION: In the method for controlling the AC-DC converter configured by applying a PWM control method, an initial value of a switching angle is computed by inputting a basic wave amplitude command value and a DC voltage into a computing circuit 5 for computing the initial value of the switching angle and outputting it; a change in the switching angle is computed by inputting a command value of amplitude of an odd-symmetrical component of the fifth harmonics and a command value of amplitude of an even-symmetric component of the fifth harmonics, the DC voltage and the basic wave amplitude command value/DC voltage into a computing circuit 7 for computing a change in the switching angle and outputting it, the output initial value of the switching angle and the change in the switching angle are totaled by an adder 24, and low-order harmonics other than the fifth harmonics are not output but only the basic wave and the fifth harmonics are output in accordance with the command value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control method and a control device for an AC / DC converter to which pulse width modulation (PWM) is applied.

  As a PWM control method for the power converter, a low-order harmonic elimination PWM control method and a sine wave / triangular wave comparison PWM control method are known. (Patent Documents 1 to 3, Non-Patent Document 1)

  In the low-order harmonic elimination PWM control method, a switching angle capable of erasing low-order harmonics that are difficult to remove by a filter is calculated offline in advance, the result is stored in a storage device, and an external fundamental wave is stored. In this method, the angle is called from the storage device according to the amplitude command value and the waveform is controlled. Since this method allows switching at an ideal angle determined in advance, there are advantages in that harmonics can be reduced, loss can be reduced by reducing the number of switching times, and the size of the filter can be reduced.

  The sine wave / triangular wave comparison PWM control method is a method of comparing a triangular carrier wave and a modulated wave and creating a PWM waveform with the timing of the intersection as a switching angle.

  In addition, the present applicant creates a PWM waveform by comparing a distorted triangular wave capable of creating a PWM waveform in which low-order harmonics are eliminated by comparison with a sine wave in Patent Document 3 and a modulated wave consisting only of a fundamental wave. And the system which controls an AC / DC converter with this PWM waveform was proposed.

FIG. 14 shows a conventional AC / DC converter using a low-order harmonic elimination PWM control system, in which 1 is a direct current unit, 2 is a power conversion unit that converts direct current to alternating current, 3 is an interconnection reactor, 4 is a filter capacitor, 5 is a PWM waveform calculation circuit, 6 is an initial value of a switching angle calculation circuit, 11 is a first storage device in which the switching angle of a PWM waveform not including low-order harmonics is stored, and 21 is a divider. . In the conventional low-order harmonic elimination PWM control, FIG. 13 is stored in the first storage device 11 of FIG. 14, and ξ ₁ ^* = V ₁ by a divider with respect to the command value V ₁ ^* of the fundamental wave amplitude. ^* / E _dc is calculated, and the switching angle θ _k corresponding to ξ ₁ ^* is read from the first storage device 11 to create a PWM waveform.

JP 2004-064878 A JP 2001-339959 A JP 2009-213255 A

IEEJ Semiconductor Power Conversion Method Research Committee: “Semiconductor Power Conversion Circuit”

  In the low-order harmonic elimination PWM control method, switching can be performed only at the switching angle at which the low-order harmonics obtained in advance are eliminated, and thus the low-order harmonic voltage cannot be output from the power conversion unit. However, the system voltage of the power system includes low-order harmonics, and it is expected to suppress the low-order harmonics using an AC / DC converter connected to the power system. Specifically, in an AC / DC converter connected to the grid, a low-order harmonic voltage at the connection point is detected from the power system toward the AC / DC converter, and a low-order harmonic proportional to the low-order harmonic voltage at the connection point is detected. It is known that a low-order harmonic voltage of a power system can be suppressed by flowing a wave current. For this purpose, it is necessary to output a low-order harmonic voltage necessary for flowing the low-order harmonic current in the power converter of the AC / DC converter. However, since the low-order harmonic elimination PWM control method cannot output the low-order harmonic voltage, it cannot suppress the harmonic voltage of the power system.

  Further, since the sine wave / triangular wave comparison PWM control method can output low-order harmonics from the power converter, it is possible to suppress the low-order harmonic voltage of the system voltage. However, compared to the low-order harmonic cancellation PWM control method, the order of unnecessary harmonic components that must be removed by a filter is low, so a larger filter is required than the low-order harmonic cancellation PWM control method. There is the problem of increased space and cost.

  Therefore, the present invention outputs the first storage device in which the switching angle of the PWM waveform not including the low-order harmonics is stored, and outputs only the fifth-order harmonics without outputting the low-order harmonics of other orders. A second storage device storing data of coefficients necessary for calculating a change in switching angle, and a switching angle for outputting only the fifth harmonic without outputting the lower harmonics of other orders. Provided is a control method and a control device for an AC / DC converter that outputs a fifth harmonic voltage from a power converter using a first arithmetic circuit that calculates a change and realizes suppression of the fifth harmonic voltage of the power system. To do.

  The invention according to claim 1 is a control method for an AC / DC converter to which a PWM control system is applied, wherein a fundamental wave amplitude command value and a DC voltage are input to an arithmetic circuit that calculates and outputs an initial value of a switching angle, and the switching angle The command value of the amplitude of the oddly symmetric component of the fifth harmonic and the command value of the amplitude of the even component of the fifth harmonic are output to the arithmetic circuit that calculates and outputs the change of the switching angle. DC voltage and fundamental wave amplitude command value / DC voltage are input to calculate the change in switching angle, and the initial value of the output switching angle and the output change of the switching angle are summed to obtain a low value other than the fifth order. A control method for an AC / DC converter characterized by outputting a fundamental wave and a fifth harmonic without outputting a second harmonic.

  The invention according to claim 2 inputs the fundamental wave amplitude command value and the DC voltage to the first divider, calculates and outputs the fundamental wave amplitude command value / DC voltage, and inputs it to the first storage device. 2. The AC / DC converter control method according to claim 1, wherein an initial value of a switching angle corresponding to the fundamental wave amplitude command value / DC voltage is calculated from one storage device.

  According to the invention of claim 3, the command value of the amplitude of the odd-symmetric component of the fifth harmonic and the DC voltage are inputted to the second divider, and the command value of the amplitude of the odd-symmetric component of the fifth harmonic / DC Calculate the voltage, input the command value of the amplitude of the even harmonic component of the fifth harmonic and the DC voltage to the third divider, and calculate the command value / DC voltage of the amplitude of the even harmonic component of the fifth harmonic. The data of the coefficient necessary to calculate and calculate the change of the switching angle that outputs only the 5th harmonic without outputting the output of the first divider and the lower harmonic of other orders is saved. The coefficient input from the second storage device, the output of the second divider, and the output of the third divider are input to the first arithmetic circuit and determined in advance. Calculate the change in the switching angle that outputs only the 5th harmonic without outputting the low-order harmonics of other orders using the calculated equation. A control method of the AC-DC converter according to claim 2, wherein the door.

  The invention according to claim 4 is a second arithmetic circuit for calculating a fifth harmonic voltage at a connection point between the AC / DC converter and the power system, and a third arithmetic circuit for calculating a fifth harmonic current command value at the connection point. And a fourth arithmetic circuit for calculating the fifth harmonic voltage command value of the power converter, and the output of the fourth arithmetic circuit uses the command value of the amplitude of the odd-symmetric component of the fifth harmonic, 5 The control method for an AC / DC converter according to any one of claims 1 to 3, wherein the command value of the amplitude of the even harmonic component of the second harmonic is used.

  The invention according to claim 5 is characterized in that, in the third arithmetic unit, the fifth harmonic current command value at the connection point is proportional to the fifth harmonic voltage at the connection point. It is a control method.

  According to a sixth aspect of the present invention, there is provided a control device for an AC / DC converter to which a PWM control system is applied, wherein a first storage device and a first divider in which a switching angle of a PWM waveform not including a low-order harmonic is stored are stored. A calculation circuit for calculating and outputting an initial value of a switching angle by inputting an input fundamental wave amplitude command value and a DC voltage, a second divider, a third divider, and other low order orders A second storage device storing data of coefficients necessary for calculating a change in switching angle for outputting only the fifth harmonic without outputting the second harmonic is provided, and the odd harmonic of the fifth harmonic is provided. Component amplitude command value, fifth harmonic even component amplitude command value, DC voltage, and fundamental wave amplitude command value / DC voltage calculated by the first divider are input to determine the switching angle. An arithmetic circuit that calculates and outputs the change, and an output An adder for summing the initial value of the switching angle and the output change of the switching angle is provided, and only the fundamental wave and the fifth harmonic are output according to the command value without outputting the lower harmonics other than the fifth. It is a control apparatus of the AC / DC converter characterized by the above.

  According to a seventh aspect of the present invention, there is provided a first divider that receives a fundamental wave amplitude command value and a DC voltage and calculates and outputs a fundamental wave amplitude command value / DC voltage, and a fundamental that is output from the first divider. 7. An arithmetic circuit for calculating an initial value of a switching angle corresponding to the fundamental wave amplitude command value / DC voltage from a first storage device to which a wave amplitude command value / DC voltage is input. It is a control apparatus of the AC / DC conversion apparatus as described in above.

  The invention of claim 8 inputs the command value and the DC voltage of the odd-symmetric component of the fifth harmonic, and calculates and outputs the command value / DC voltage of the odd-symmetric component of the fifth harmonic. Input the command value and DC voltage of the fifth harmonic even component, and calculate the command value / DC voltage of the fifth harmonic component. The third divider to be output, the coefficient output from the second storage device by the input of the first divider, the output of the second divider, and the output of the third divider are input. And a first arithmetic circuit that calculates a change in switching angle that outputs only the fifth harmonic without outputting the lower harmonic of other orders using a predetermined arithmetic expression. The control device for an AC / DC converter according to claim 7.

  The invention according to claim 9 is a second arithmetic circuit for calculating a fifth harmonic voltage at a connection point between the AC / DC converter and the power system, and a third arithmetic circuit for calculating a fifth harmonic current command value at the connection point. Then, the fifth harmonic voltage command value of the power converter is calculated, and the command value of the amplitude of the odd-symmetric component of the fifth harmonic and the command value of the amplitude of the even-numbered component of the fifth harmonic are output. 9. The control device for an AC / DC converter according to claim 6, further comprising a fourth arithmetic circuit.

  The invention according to claim 10 is characterized in that the third arithmetic unit comprises a proportional device that makes the fifth harmonic current command value at the connection point proportional to the fifth harmonic voltage at the connection point. It is a control apparatus of the AC / DC conversion apparatus.

The present invention has the following effects.
(1) In an AC / DC converter to which the PWM control system of the present invention is applied, unlike a conventional low-order harmonic elimination PWM control system, a harmonic of a specific order is output according to a target value while eliminating a low-order harmonic. can do. For this reason, this control method can also be applied to various devices that require harmonic control, such as active filters, and these devices can be reduced in size by reducing the size of the output filter and switching by reducing the number of switching times. Loss can be reduced.

(2) Unlike the conventional low-order harmonic cancellation PWM control method, the present invention not only suppresses harmonics generated from the AC / DC converter, but also suppresses harmonic voltages of a specific order at the connection point. Can do. For this reason, this control system can suppress harmonics in the power system only by changing the control device of the AC / DC converter to which the existing low-order harmonic elimination PWM control system is applied.

It is a circuit diagram of an AC / DC converter which can control a fundamental wave and a harmonic using the table and arithmetic circuit of the switching angle and coefficient of the present invention. It is a circuit diagram of the AC / DC converter which performs suppression control of the 5th harmonic voltage of a system voltage. It is a graph which shows the relationship between the 5th harmonic amplitude and the theoretical value of the change of an angle. It is a graph which shows the relationship between the theoretical value of the change of a 5th harmonic amplitude and an angle among the graphs which show the derivation | leading-out process of the approximate expression of this invention. It is a figure which shows the relationship between the ratio of the component of the even number object of 5th harmonic amplitude, and the change of an angle among the graphs which show the derivation | leading-out process of the approximate expression of this invention. It is a figure which shows the comparison of a theoretical value and an approximate value about the relationship between a 5th harmonic amplitude and the change of an angle among the graphs which show the derivation | leading-out process of the approximate expression of this invention. It is a graph which shows the data of the coefficient for the 5th harmonic control of this invention. It is a graph which shows the harmonic analysis result of the output voltage of a power converter part at the time of deleting a lower order harmonic from a power converter part, and outputting only a fundamental voltage and a 5th harmonic voltage from this invention. It is a circuit diagram of the simulation electric power system containing a harmonic generation source. It is a graph which shows the comparison of a conventional system and an invention system about the waveform of the system voltage at the time of connecting an AC / DC converter to a simulation system | strain, an AC / DC converter part voltage, and the inflow current to an AC / DC converter. It is a graph which shows the comparison of a conventional system and an invention system about the harmonic analysis result of the system voltage at the time of connecting an AC / DC converter to a simulation system, an AC / DC converter part voltage, and the inflow current to an AC / DC converter. This is an output voltage waveform of a three-level inverter with 11 half-cycle pulses. It is a graph which shows the switching angle of the PWM waveform at the time of erasing the low order harmonic except the order of the multiple of 3 to the 31st order used by the conventional low order harmonic elimination PWM control system. It is a circuit diagram of the AC / DC converter used with the conventional low order harmonic elimination PWM control system. It is an example of the detection circuit of the 5th harmonic voltage of an electric power system. It is an example of the arithmetic circuit of the command value of the 5th harmonic voltage of a power converter.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings, taking a system interconnection AC / DC converter as an example.

  In FIG. 1, 1 is a direct current unit, 2 is a power conversion unit that converts direct current to alternating current, 3 is an interconnected reactor, 4 is a filter capacitor, 5 is a PWM waveform arithmetic circuit, and 6 is an initial value of a switching angle arithmetic circuit. , 7 is a calculation circuit for switching angle change, 11 is a first storage device in which the switching angle of the PWM waveform not including the low-order harmonics is stored, and 12 does not output low-order harmonics of other orders. The second storage device 13 stores the coefficient data necessary for calculating the change of the switching angle for outputting only the 5th harmonic in the 5th order without outputting the lower order harmonics of other orders. Arithmetic circuits for calculating the change of the switching angle that outputs only harmonics, 21, 22, 23 are dividers, and 24 is an adder.

In the control of the power conversion unit 2 of FIG. 1, the present invention uses the input of the PWM waveform calculation circuit 5 as the DC voltage E _dc , the fundamental wave amplitude command value V ₁ ^* , the amplitude of the odd component of the fifth harmonic. The command value ΔV _5d , the command value ΔV _5q of the amplitude of the even- _numbered component of the fifth harmonic, and the first storage device 11, the second storage device 12, and the arithmetic circuit 13 are used, and the lower order harmonics are used. And a PWM waveform that outputs only the fifth harmonic is generated.

  To facilitate understanding of the present invention, first, the principle and control method of conventional low-order harmonic PWM control will be described.

As shown in FIG. 12, the phase voltage of the power converter is a waveform having a half-cycle pulse number of 11 pulses and a level number of 3 levels. In this case, ₁ the switching angle of up to 1/4 period _{θ, θ 2, ··· θ 11} , the amplitude of the n-th harmonic at the time of Fourier transform of the waveform in FIG. 12 when the _{V n, V} n / E _dc becomes the following formula.

Since there are 11 θ _{j that} can be set in this equation, the fundamental amplitude can be controlled and 11 harmonics can be eliminated. The switching angles θ ₁ , θ ₂ ,... Θ _{11 at} that time are V ₁ / E _dc = ξ ₁ (ξ ₁ is an arbitrary value) and V _n = 0 (n = 5, 7 in Equation (1)) , 11, 13,..., 29, 31). The solution is shown in FIG.

  Next, a method of creating a PWM waveform that outputs the fifth harmonic will be theoretically described.

It is assumed that the phase voltage v _inv of the power conversion unit is a waveform with 11 half-cycle pulses and 3 level levels as shown in FIG. Here, v _inv is the fundamental wave ξ ₁ sin (ωt) · E _dc , fifth harmonic voltage (Δξ _5d sin (5ωt) + Δξ _5q cos (5ωt)) E _dc and It is composed only of unnecessary harmonic components v _err (components of order of multiples of 3 and components of orders higher than 31), and includes low-order harmonics excluding orders of multiples of 3 from 7th to 31st. Suppose not. Δξ _5d E _dc is the amplitude of the odd-symmetric component of the fifth-order harmonic voltage, and Δξ _5q E _dc is the amplitude of the even-symmetric component of the fifth-order harmonic voltage.

  In this case, with respect to the switching angle when the fifth harmonic voltage is zero, the change in the switching angle when the fifth harmonic voltage is output is derived as shown in the equation (2).

  If only the half-wave symmetry (that is, f (θ) = − f (π + θ)) is established in the waveform of FIG. 12, the amplitude of the nth-order harmonic of the phase voltage is expressed by the following equation.

In equation (3), V _inv-nd is an oddly symmetric component, and V _inv-nq is an evenly symmetric component. When a relational expression of dV _inv−n with respect to dθ _{k is obtained} from the expression (3),

  When Equations (4) and (5) are used for degree 1 and n (n = 6 m ± 1 (m = 1, 2,..., 5)), the results are as follows.

Therefore, the switching angle for outputting the voltage of the expression (2) is _obtained by reading the switching angle θ _k (ξ ₁ ) at V ₁ / E _dc = ξ ₁ from FIG. 13, and using this as an initial value, the differential equation of the expression (7) Is obtained by calculating the change Δθ _k of θ _k when the fifth harmonic of amplitudes Δξ _5d E _dc and Δξ _5q E _dc is output. When Ratio = Δξ _5q / Δξ _5d and ξ ₁ = 1.0, −0.1 < Δξ _5d < 0.1, −1 < Ratio < 1, Δθ _k (k = 1) is calculated. It becomes. However, to control the fifth-order harmonic voltage using FIG. 3, it is necessary to prepare a graph similar to FIG. 3 for all ξ ₁ and θ _k , and a very large capacity database is required.

Therefore, an approximate expression is used in the present invention. First, C _k = Δθ _k / Δξ _5d, and the graph of FIG. 4 is created. Next, in Δξ _5d = Δξ _{5d_1} and Δξ _{5d_2} , the relationship between Ratio and C _k is approximated by a linear function as shown in FIG.

Finally, Δξ _5d and C _k are approximated by a linear function within the range of Δξ _5d−1 < Δξ _5d < Δξ _5d2 .

  Substituting Equation (8) and Equation (9) into Equation (10),

It becomes. And the theoretical value of C _k shown in FIG. 4, the comparison of C _k obtained by the approximate expression shown in FIG. In FIG. 6, the theoretical value and the approximate value almost coincide with each other within the approximate range.

Finally, the coefficients a _k , b _k , c _k , and d _k when 0.88 <ξ ₁ <1.12 are shown in FIG.

Note that the present invention can be applied not only to the fifth-order harmonic but also to other lower-order harmonics by performing the same calculation in advance to obtain the coefficients a _k , b _k , c _k , and d _k. is there.

  Next, among the methods of implementing the invention, a method for calculating a PWM waveform will be described.

In FIG. 1, first, the fundamental wave amplitude command value V ₁ ^* and the DC voltage E _dc of the DC unit 1 are input to the arithmetic circuit 6 for the initial value of the switching angle, and ξ ₁ ^* = V ₁ ^* / E by the divider 21. Calculate _dc . Next, ξ ₁ ^* is input to the first storage device 11, and the switching angle θ _k0 of the PWM waveform that does not include low-order harmonics is read from the first storage device 11. This is the initial value of the switching angle.

Next, the switching angle change calculation circuit 7 is supplied with an amplitude command value ΔV _5d of an odd-symmetric component of the fifth harmonic, an amplitude command value ΔV _{5q of} an even target component of the fifth harmonic, and a DC voltage E. _dc is input, and Δξ _5d ^* and Δξ _5q ^* are calculated in the divider 22 and the divider 23. Also, ξ ₁ ^* calculated by the divider 21 of the arithmetic circuit 6 is input to the second storage device 12, and the lower harmonics of other orders are not output from the second storage device 12, but the fifth order harmonics are not output. The coefficients a _k , b _k , c _k , and d _k necessary for calculating the change in the switching angle that outputs only the wave are read. Then, Δξ _5d ^* , Δξ _5q ^* , a _k , b _k , c _k , and d _k are input to the arithmetic circuit 13, and the arithmetic circuit 13 uses other approximations of lower harmonics according to the approximate expression (11). A change in switching angle Δθ _k that outputs only the fifth harmonic without outputting a wave is calculated.

Finally, the adder 24 adds the initial value θ _k0 of the switching angle and the change Δθ _k of the switching angle, and this is set as the switching angle θ _k of the PWM waveform.

  Next, a method for suppressing the harmonic voltage of the power system of the present invention will be described.

In FIG. 2, first, phase voltages V _Ru , V _Rv , and V _Rw of the power system are detected, and the fifth harmonic voltages V _Rd and V _Rq are calculated by the detection circuit 14 of the fifth harmonic voltage of the power system. . V _Rd is an oddly symmetric component, and V _Rq is an even target component. An example of the fifth-order harmonic voltage detection circuit 14 is shown in FIG.

Next, the command values I _R5d ^* and I of the fifth harmonic current flowing from the power system to the AC / DC converter using the proportional devices 25 and 26 of the command circuit 15 for the fifth harmonic current of the AC / DC converter. Calculate _R5q ^* . I _R5d ^* is an odd-symmetric component, and I _R5q ^* is an even- _numbered component. By flowing a harmonic current having the same phase as the fifth harmonic voltage of the system voltage from the power system toward the AC / DC converter, the fifth harmonic voltage of the system voltage can be suppressed.

Finally, command values ΔV _5d ^* and ΔV _5q ^* of the fifth harmonic voltage of the power converter are calculated using the arithmetic circuit 16 of the command value of the fifth harmonic voltage of the power converter, and this is calculated as a PWM waveform. Input to the arithmetic circuit 5. An example of a calculation circuit for the command value of the fifth harmonic voltage of the power converter is shown in FIG.

  With the above procedure, the power converter can be operated so as to suppress the fifth harmonic voltage of the power system.

  Examples of the present invention will be described below.

  First, the result of controlling to output the fifth harmonic voltage using the PWM waveform calculation circuit 5 is shown.

In FIG. 1, the input of the PWM waveform to the arithmetic circuit 5 is a fundamental amplitude command value V ₁ ^* , a harmonic amplitude command value ΔV _5d ^* , and ΔV _5q ^* . The PWM waveform calculation circuit 5 calculates a switching angle θ _k that outputs only the fifth-order harmonic without outputting the other-order low-order harmonics. Finally, the switching angle θ _k is input to the power conversion unit 2. As a result of the above operation, the power conversion unit 2 eliminates the lower harmonics except the orders of multiples of 3 from the 7th to the 31st, and only the harmonic components of the fundamental wave, the 5th harmonic, and the 33rd and higher harmonics. Is output.

FIG. 8 shows the phase voltage of the power conversion unit when the fundamental wave amplitude command value ξ ₁ ^* = 0.88 and the fifth harmonic command value are ΔV _5d ^* = − 0.05 and ΔV _5q ^* = 0.05. The result of harmonic analysis is shown.

  It can be seen from FIG. 8 that only the fifth harmonic can be output while the lower harmonics from the seventh order to the 31st order are eliminated.

  Next, the result of suppressing the fifth harmonic voltage of the power system is shown.

In FIG. 2, the fifth harmonic voltage V _R5d and V _R5q of the _system are obtained by the fifth harmonic voltage detection circuit 14 of the power system. Next, the fifth harmonic current command values I _R5d ^* and I _R5q ^* to be flown into the power converter are calculated by the arithmetic circuit 15 for the fifth harmonic current command value of the AC / DC converter. Next, the command values V _5d ^* and V _5q ^* of the fifth harmonic voltage of the power conversion unit necessary for causing the fifth harmonic currents I _R5d ^* and I _R5q ^* to flow into the AC / DC converter are _supplied to the power conversion unit. The calculation circuit 16 of the command value of the fifth harmonic voltage is calculated. Finally, the DC voltage E _dc , the fundamental wave amplitude command value V ₁ ^* , and the fifth harmonic voltage command values ΔV _5d ^* and ΔV _5q ^* are input to the PWM waveform calculation circuit 5, and the switching angle θ _k, that is, the PWM waveform. Get.

  As an example of the case where the harmonic voltage is suppressed, the results when the AC / DC converter is connected to the node 3 in the simulated power system shown in FIG. 9 are shown in FIGS.

As shown in FIGS. 10 and 11, when the conventional low-order harmonic elimination PWM control method is applied, the harmonic voltage of the system voltage is 5.4% of the fifth harmonic ratio and the total harmonic distortion rate. (THD) is 6.6%.

  However, when the harmonic suppression method according to the present invention is applied to the circuit shown in FIG. 2, the fifth harmonic can be suppressed, the fifth harmonic ratio is 2.3%, and the THD is 4.5%. It can be seen that harmonics can be reduced compared to the method.

  The present invention can be applied as follows. According to the output voltage control method of the present invention, in the AC / DC converter connected to the power system, low-order harmonics generated from the AC / DC converter can be effectively removed, and the loss due to the downsizing of the filter and the reduction in the number of switching times. Can be reduced. In addition, it is possible to suppress low-order harmonics of the power system. From this, it can apply to uses, such as a photovoltaic interconnection inverter and the inverter for charging / discharging a storage battery.

  In addition, low-order harmonic cancellation PWM control that cannot control conventional harmonics is applied to DC power transmission and AC / DC converters for BTB (Back to Back) in the power system, assuming that the system voltage is a sine wave. There is also a part that has been done. Therefore, although there is no effect of suppressing harmonics in the power system, the use of the present invention can suppress harmonics in the power system.

DESCRIPTION OF SYMBOLS 1 DC part 2 Power converter 3 which converts direct current into alternating current 3 Reactor 4 Filter capacitor 5 PWM waveform calculation circuit 6 Initial value of switching angle calculation circuit 7 Switching angle change calculation circuit 11 First storage device 12 Second storage device 13 Arithmetic circuit 14 for calculating change in switching angle Detection circuit 15 for fifth-order harmonic voltage of power system 15 Calculation circuit 16 for command value of fifth-order harmonic current of AC / DC converter 16th order of power converter Harmonic voltage command value calculation circuit 21 Divider 22 Divider 23 Divider 24 Adder 25 Proportional device 26 Proportional device

Claims (10)

In the control method of the AC / DC converter using the PWM control method,
Calculate the initial value of the switching angle by inputting the fundamental wave amplitude command value and the DC voltage to the arithmetic circuit that calculates and outputs the initial value of the switching angle.
The arithmetic circuit that calculates and outputs the change of the switching angle includes the command value of the amplitude of the oddly symmetric component of the fifth harmonic, the command value of the amplitude of the even component of the fifth harmonic, the DC voltage, and the fundamental wave. Input the amplitude command value / DC voltage and calculate the change of the switching angle.
The AC-DC conversion is characterized in that the initial value of the output switching angle and the change of the output switching angle are summed, and the fundamental wave and the fifth harmonic are output without outputting the lower harmonics other than the fifth. Control method of the device.   The fundamental wave amplitude command value and DC voltage are input to the first divider, the fundamental wave amplitude command value / DC voltage is calculated and output, input to the first memory device, and the fundamental wave from the first memory device. 2. The control method for an AC / DC converter according to claim 1, wherein an initial value of a switching angle corresponding to the amplitude command value / DC voltage is calculated. The command value and DC voltage of the odd harmonic component of the fifth harmonic are input to the second divider to calculate the command value / DC voltage of the odd harmonic component of the fifth harmonic,
Input the command value of the amplitude of the even harmonic component of the fifth harmonic and the DC voltage to the third divider to calculate the command value / DC voltage of the amplitude of the even harmonic component of the fifth harmonic,
The second data in which the coefficient necessary for calculating the change of the switching angle for outputting only the fifth harmonic without outputting the low-order harmonic of the other order is outputted as the output of the first divider is stored. To the storage device,
The coefficient output from the second storage device, the output of the second divider, and the output of the third divider are input to the first arithmetic circuit, and another order is determined using a predetermined arithmetic expression. The method of controlling an AC / DC converter according to claim 2, wherein a change in switching angle at which only the fifth harmonic is output without outputting the lower harmonic is calculated. A second arithmetic circuit for calculating the fifth harmonic voltage at the connection point of the AC / DC converter and the power system, a third arithmetic circuit for calculating the fifth harmonic current command value at the connection point, and 5 of the power conversion unit A fourth arithmetic circuit for calculating a second harmonic voltage command value,
The output of the fourth arithmetic circuit is set as a command value of the amplitude of the odd-symmetric component of the fifth harmonic, and a command value of the amplitude of the even-numbered component of the fifth harmonic. The control method of the AC / DC converter in any one of.   5. The method of controlling an AC / DC converter according to claim 4, wherein in the third computing unit, the fifth harmonic current command value at the connection point is proportional to the fifth harmonic voltage at the connection point. In the control device of the AC / DC converter using the PWM control method,
A first storage device storing a switching angle of a PWM waveform that does not include low-order harmonics and a first divider are provided, and an input fundamental wave amplitude command value and a direct-current voltage are input to initialize the switching angle. An arithmetic circuit that calculates and outputs a value;
The second divider, the third divider, and other low-order harmonics are not output, but only the fifth harmonic is output, and the coefficient data necessary to calculate the change in the switching angle is stored. The second storage device is provided, and the command value of the amplitude of the odd-symmetric component of the fifth harmonic, the command value of the amplitude of the even-numbered component of the fifth harmonic, the DC voltage, and the first divider An arithmetic circuit that receives the calculated fundamental wave amplitude command value / DC voltage and calculates and outputs a change in switching angle; and
An adder that adds the initial value of the output switching angle and the change in the output switching angle is provided, and only the fundamental and fifth harmonics are output as command values without outputting the lower harmonics other than the fifth. A control device for an AC / DC converter, characterized in that the output is output.   A first divider for calculating and outputting a fundamental wave amplitude command value / DC voltage by inputting a fundamental wave amplitude command value and a DC voltage, and a fundamental wave amplitude command value / DC voltage output from the first divider. 7. The control of the AC / DC converter according to claim 6, further comprising an arithmetic circuit that calculates an initial value of a switching angle corresponding to the fundamental wave amplitude command value / DC voltage from the first storage device to which is input. apparatus. A second divider for inputting the command value and the DC voltage of the odd-symmetric component of the fifth harmonic and calculating and outputting the command value / DC voltage of the odd-symmetric component of the fifth harmonic; ,
A third divider for inputting a command value and a DC voltage of the amplitude of the even harmonic component of the fifth harmonic and calculating and outputting a command value / DC voltage of the amplitude of the even harmonic component of the fifth harmonic; ,
The coefficient outputted from the second storage device when the output of the first divider is inputted, the output of the second divider, and the output of the third divider are inputted and a predetermined arithmetic expression is used. 8. The AC / DC conversion according to claim 7, further comprising a first arithmetic circuit that calculates a change in switching angle that outputs only the fifth harmonic without outputting the lower harmonic of other orders. Control device for the device.   A second arithmetic circuit for calculating the fifth harmonic voltage at the connection point of the AC / DC converter and the power system, a third arithmetic circuit for calculating the fifth harmonic current command value at the connection point, and 5 of the power conversion unit A fourth arithmetic circuit that calculates a second harmonic voltage command value and outputs a command value of the amplitude of the odd-symmetric component of the fifth harmonic and a command value of the amplitude of the even-numbered component of the fifth harmonic; The control device for an AC / DC converter according to claim 6, wherein the controller is provided.   10. The control device for an AC / DC converter according to claim 9, wherein the third arithmetic unit includes a proportional device that makes the fifth harmonic current command value at the connection point proportional to the fifth harmonic voltage at the connection point. .