JPH11225477A - Sine wave converter with filtering function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sine wave converter with filtering function which has a function corresponding to an active filter for normally maintaining the sine wave waveform of a power supply circuit. SOLUTION: A sine wave converter with a filtering function converts a sine wave input from the predetermined AC power supply circuit 1 into a preset DC voltage. In this case, the filtering function is provided also to detect any one of the high frequency harmonic elements or current elements of a delay current element from a load current or both of these current elements and to generate a high frequency harmonic element control signal, corresponding to these current elements, in order to maintain the AC power supply circuit current to the sine wave by adding the high frequency harmonic element to the sine wave converter control signal. This filtering function includes a load current detecting function 21, a harmonic detecting function 22 to detect the harmonic included in the load current detected by the load current detecting function 21 as the harmonic control signal of a predetermined shape an the addition of the harmonic control signal detected by the harmonics detecting function 22 to the sine wave converter control signal as the compensating signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is most suitable for business establishments that use power equipment including a sine wave converter connected to a system power supply as a load, and particularly those that use a load that generates harmonics. The present invention relates to a sine wave converter with a filtering function.

[0002]

2. Description of the Related Art Conventionally, in a system which receives power from a three-phase AC system power supply and supplies it to a predetermined AC load, the system power is converted into DC power by a rectifier circuit of a capacitor input type, and then the AC load is converted by an inverter. Is often converted to AC power corresponding to By the way, in the case of the above-mentioned capacitor input type rectifier circuit, there is a problem that a harmonic current flows out to the system power supply side, distorting a voltage or burning out a capacitor facility. Accordingly, means for converting received AC into DC having a predetermined voltage has been used.

An inverter system provided with a sine wave converter is configured as shown in FIG. 4, for example. 4, reference numeral 1 denotes an AC power supply as a system power supply for supplying a sine wave AC having a predetermined frequency voltage, and reference numeral 30 denotes an AC controlled load and its attached functions. Reference numeral 2A denotes a conventional inverter system with a sine wave converter function, and reference numeral 3 denotes an AC motor having a power load as an AC controlled load. In the inverter system 2A, 4A is an AC reactor, 5 is a switching function circuit of a sine wave converter (hereinafter, referred to as a converter) for converting received AC into DC of a predetermined voltage, and 6 is an AC controlled by a control circuit (not shown). It is a DC → AC conversion function unit as a switching circuit unit of an inverter that converts the AC power supplied to the electric motor 3. Reference numeral 7 denotes a smoothing capacitor, and this DC voltage is detected by a voltage detection function 8.

[0004] Reference numeral 10 denotes a transformer for converting a received voltage to a predetermined voltage suitable for proportional signal processing, and reference numeral 11 denotes a current detecting function such as a current transformer for detecting a converter input current (power supply current). The set value signal indicating the DC voltage to be formed by the converter set by the voltage setting function 12 is input to the comparison function 13 and compared with the output voltage value of the switching function circuit 5 of the converter detected by the voltage detection function 8 described above. Then, the deviation voltage signal is input to the automatic voltage adjustment function 14. The converter operation signal created according to the conditions set in advance in the automatic voltage adjustment function 14 is input to the multiplication function 15 and multiplied by the received voltage detected by the transformer 10 described above. Multiplication function 1
The current command signal obtained in step 5 and synchronized with the receiving voltage to be output is input to the current adjusting function 16. In the current adjustment function 16, the load current signal input from the load current detection function 11 is compared with the current command signal to generate a current operation signal from the deviation value and input to the pulse width modulation function 17.

The carrier generated by the carrier generation function 18 is input to the pulse width modulation function 17, and the current operation signal is pulse width modulated by the carrier to output a PWM signal. 5 is turned on / off, the pulse component is smoothed by the smoothing capacitor 7, and the input AC is converted into the DC voltage set by the voltage setting function 12. This DC voltage is converted into AC by the DC → AC conversion function unit 6 of the inverter, and drives the AC motor 3. In the above example, an example in which an AC motor is driven has been described. However, a DC load may be directly driven by a DC converted by a converter.

[0006]

By the way, not only a load circuit having a converter but also a load generating a harmonic component and a load generating a reactive power due to a delay current are connected in parallel to the system power supply circuit. There are cases.

An active filter may be used as a means for absorbing harmonic components and reactive power generated in a power supply circuit as illustrated in FIG. Note that, in the figure, those corresponding to FIG. 4 are denoted by the same reference numerals as those in the figure. In FIG. 3, 1 is a system power supply, and 30 is a power supply in FIG.
2A is an inverter system including a sine wave converter, 3 is a power load such as an AC motor, 31 is a load that generates harmonic noise in the power load.
A to 31N are shown collectively, and 32 also shows loads 32A to 32N that are unlikely to generate harmonic noise in the power load. An active filter 40 is connected to the system power supply, and detects and inputs a harmonic current flowing through the loads 30 and 31 by the current transformer 41. That is, the active filter 40 eliminates harmonic current components flowing to the system power supply. By employing the active filter 40 in this manner, it is possible to maintain the current waveform of the system power supply as a sine wave, but this causes an increase in cost. A compensation function that can be maintained in waves has been desired.

As examples using an active filter, for example, Japanese Patent Application Laid-Open No. 4-334930 and Japanese Patent Application Laid-Open
-75329 and JP-A-8-223804. First, the one disclosed in Japanese Patent Application Laid-Open No. 4-334930 is one in which an active filter is connected in series with a load circuit, and is not always suitable for a large-capacity power load. Also, Japanese Patent Application Laid-Open No. 7-732
The device disclosed in Japanese Patent Publication No. 9 is connected between a single-phase commercial AC power supply and a load, and cannot be used as it is in a three-phase power supply circuit. Further, the one disclosed in Japanese Patent Application Laid-Open No. 8-223804 discloses an active / integrated circuit that calculates the active / sin component from the cos component and sin component of the compensation target harmonic current contained in the compensation target current.
If a command value for a filter is created and a large number of harmonic currents are included, complicated processing may be required. SUMMARY OF THE INVENTION It is an object of the present invention to provide a sine wave converter with a filtering function having a function equivalent to an active filter that can solve the above-mentioned problems (problems) of a conventional device and can maintain a sine wave waveform of a power supply circuit normally. And

[0009]

In order to solve the above problems, a sine wave converter with a filtering function according to the present invention converts a sine wave AC input from a predetermined AC power supply circuit into a set DC voltage. In a sine wave converter, a current component such as a harmonic component and / or a lag current component is detected from a current of a harmonic generation load other than the sine wave converter connected in parallel, and a harmonic control signal corresponding to the current component shape is created. A filtering function for maintaining the AC power supply circuit current in a sine wave form by adding the harmonic control signal to the control signal of the sine wave converter is provided. In this case, the filtering function includes a load current detection function, a harmonic detection function that detects a harmonic component included in the load current detected by the load current detection function as a harmonic control signal having a predetermined shape, It is desirable to add the harmonic control signal detected by the wave detection function as a correction signal to the control signal of the sine wave converter.

The control function of the sine wave converter includes a voltage setting function for setting a DC voltage to be formed by the converter, and a comparison function for comparing a set value set by the voltage setting function with a converter output voltage value. And an automatic voltage adjustment function for creating a converter operation signal from the deviation signal output by the comparison function, and a multiplication function for multiplying the converter operation signal output from the automatic voltage adjustment function by a voltage proportional to the received voltage at a predetermined ratio. Adding the correction signal to the output of the multiplication function to create a current command signal for the converter; adding or subtracting a function corresponding to the positive or negative of the correction signal; the current command signal value of the converter and the sine wave converter Is compared with a current value proportional to the input circuit current at a predetermined ratio. A comparison function to be created, a switching signal creation function to convert the current operation signal into a PWM switching signal by a predetermined carrier, and a conversion function operated by the PWM switching signal to convert and output to DC in synchronization with an input AC power supply. It is desirable to be prepared.

Since the sine wave converter with a filtering function of the present invention is configured as described above, a sine wave converter having a simple circuit configuration and a low-cost filtering function can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a sine wave converter with a filtering function according to the present invention will be described by taking an example of a power load system of a system power supply introduction business office to which the present invention is applied.
This will be described in detail with reference to FIGS. In FIG. 1, components corresponding to those of the related art will be described with the same reference numerals as in FIGS. Also, in the description of the embodiment of the present invention, the case where the AC power supply has three phases is used, but in FIG. 1, the three phases are not shown in detail but are shown in a single line diagram. Element functions and connection lines are also shown in a simplified manner without affecting the description of the present invention. Therefore,
For example, a signal processing function for a three-phase circuit is not particularly described, but is similarly configured with three sets of functions. In addition, illustrations of an inverter for driving a power load such as an AC motor and various circuit breakers, which are unnecessary for the description of the basic functions of the present invention, are omitted.

First Embodiment: A sine wave converter (hereinafter abbreviated as a converter) having a filtering function according to the present invention is configured as shown in FIG. 1, for example. In FIG. 1, reference numeral 1 denotes an AC power supply such as a system power supply that supplies a sine-wave AC having a predetermined frequency voltage, and 2 denotes an inverter that receives power from the AC power supply 1 and converts it into AC corresponding to a power load 3 such as an AC motor and supplies it. System.

In the inverter system 2, reference numeral 20 denotes a converter having the above-mentioned filtering function, which will be described in detail later. Reference numeral 4 denotes a reactor for connecting the system and switching noise generated by the converter to prevent leakage to the system power supply. Power supply filter function. That is, the characteristics of the power supply filter function 4 are set in accordance with the characteristics and functions of the converter described in detail later. Reference numeral 6 denotes a DC → AC conversion function unit of an inverter for converting the DC obtained by the converter 20 into a frequency and a voltage corresponding to the power load 3 such as an AC motor. Since the inverter is not directly related to the present invention, the illustration of the control function is omitted. That is, the direct current obtained by the converter 20 may be supplied directly to the direct current load. In the converter 20, reference numeral 5 denotes a switching function circuit that converts received AC into DC of a predetermined voltage, for example, is configured by bridge-connecting six semiconductor switching function elements such as transistors. Reference numeral 7 denotes a smoothing capacitor that removes a switching component included in DC output from the switching function circuit 5, and the DC voltage is detected by a voltage detection function 8.

Reference numeral 31 denotes a power load for generating a harmonic component applied to the AC power supply 1. A load current including a harmonic component supplied to the power load 31 is detected by a load current detection function 21 including a current transformer or the like. Therefore, the output a of the load current detection function 21 is a current signal including a fundamental component and a harmonic component proportional to the current of each phase supplied to the power load 31 at a predetermined ratio. FIG. 3, which corresponds to the prior art, shows the detection of the harmonic current flowing through the loads 30 and 31 as the detection signal of the active filter. In this case, the load current detection function 21 may be appropriately mounted. A harmonic component is extracted from an output a of the load current detection function 21 by a harmonic detection function 22 and converted into a harmonic control signal b. In the harmonic detection function 22, a fundamental component is extracted from the current signal a by the band-pass filter function 23,
A subtraction function 24 subtracts a current signal a including a fundamental wave component and a harmonic component from the fundamental wave component. Therefore, the harmonic control signal b indicates each instantaneous value in which a waveform proportional to a harmonic component included in the current supplied to the power load 31 at a predetermined ratio is indicated by a negative sign. The harmonic control signal b is input to a first input terminal of a harmonic control signal addition function (hereinafter, referred to as an addition function) 25 formed by an addition function.

That is, the filtering function according to the present embodiment based on the present invention includes a load current detecting function 21
A harmonic control signal of a predetermined shape, that is, a harmonic detection signal 22 for detecting a harmonic component included in the load current detected by the load current detection function 21 as a correction signal, and a harmonic detected by the harmonic detection function 22. The wave control signal is added to a later-described control signal of the sine wave converter by an addition function (harmonic control signal addition function) 25.

Next, the control function of converter 20 will be described. Reference numeral 10 denotes a transformer for converting a received voltage into a predetermined voltage suitable for proportional signal processing. Reference numeral 11 denotes a converter input current detection function, which is constituted by a current transformer for converting the received voltage to a predetermined voltage suitable for signal processing. h is detected and output. As described above, since the received AC is three-phase, the illustration is omitted, but the transformer 10 and the converter input current detection function 11 are appropriately formed so as to detect the voltage / current of each phase.

Reference numeral 12 denotes a voltage setting function for setting a DC voltage to be formed by the converter. The set value signal c set by the voltage setting function 12 is input to a comparison function 13 and detected by the voltage detection function 8 described above. Converter output voltage value d
Is input to the automatic voltage adjusting function 14. The comparison function 13 is configured by, for example, a subtraction function. The converter operation signal generated from the deviation voltage signal e according to the condition set in advance in the automatic voltage adjustment function 14 is input to the multiplication function 15 and the above-described transformer 1
The received voltage of each phase detected and converted by 0 is multiplied. The multiplication function 15 multiplies the sinusoidal current command signal f of each phase synchronized with the received sine wave voltage to be output by the addition function 2 described above.
5 is input to the second input terminal. Therefore, in the addition function 25, the harmonic control signal (correction signal) b is added to the current command signal f, and the current control signal g of each phase is obtained.

In the above description, the harmonic detection function 22
Has been described so that the addition function 25 adds the harmonic control signal b to the current command signal f under the condition that a harmonic control signal b indicated by a negative sign is obtained as described above. When a positive sign is obtained from the detection function 22 or when the current command signal f has an opposite phase, the addition function 25 may be a subtraction function, and the subsequent functional configuration may be made to correspond to this polarity.

The above-described current control signal g is a current adjustment function 1
Enter 6 In the current adjusting function 16, the current signal h input from the converter input current detecting function 11 is compared with the current control signal g, and a current operation signal is generated from the deviation value in accordance with a preset condition. input. That is, since this function forms a servo system that compares the current command signal and the load current signal and controls the converter based on the deviation value, the current adjustment function 16 includes, for example, a servo amplification function. I have.

The pulse width modulation function 17 has a switching signal generation function, and receives a carrier wave i having a predetermined frequency sufficiently higher than the frequency component of the current operation signal on which the harmonic component generated by the carrier generation function 18 is superimposed. P is turned on / off in correspondence with each semiconductor switching function element forming the switching function circuit 5 of the converter 20 by pulse width modulating the current operation signal by the carrier wave i.
Outputs the WM signal j. The PWM signal j turns on / off each semiconductor switching function element, smoothes a pulse component by a smoothing capacitor 7 and inputs the alternating current to a voltage setting function 1.
Convert to the DC voltage set in step 2. This DC voltage is converted by a DC to AC conversion function unit 6 of the inverter into an AC according to a separately provided control signal, and drives the power load 3 such as an AC motor.

That is, the converter control function includes a voltage setting function 12 for setting a DC voltage to be formed by the converter, a set value signal c set by the voltage setting function 12, and an output voltage value d of the converter. Function 1 to compare
3 and an automatic voltage adjustment function 14 for generating a converter operation signal from the deviation voltage signal e output from the comparison function 13.
A multiplying function 15 for multiplying a converter operation signal output from the automatic voltage adjusting function 14 by a voltage proportional to the received voltage at a predetermined ratio; and a harmonic control signal (correction signal) to the output of the multiplying function 15. The addition (or subtraction) function 25 corresponding to the positive / negative of the above-mentioned harmonic control signal (correction signal) b for creating the current control signal g by adding b, the current control signal g and the input circuit of the sine wave converter A current adjusting function 16 for comparing each value of the current signal h proportional to the current at a predetermined ratio and generating a current operation signal from a deviation value of the comparison result in accordance with a preset condition; A pulse width modulation function 17 for converting the signal into a PWM switching signal, and a converter that is operated by the PWM switching signal and converts and outputs a direct current in synchronism with an input alternating current power supply , I.e., and a switching function circuit 5.

Next, the operation of the harmonic detection function 22 will be described in detail with reference to FIG. The current waveform detected by the load current detection function 21 flowing through the load circuit is, for example, a square wave as shown in FIG. ), The current waveform of the harmonic component to be eliminated superimposed on the sine wave (b) is shown as (c) below. That is, when the fundamental wave component shown in the lower part (e) of the figure is extracted by the band-pass filter function 23 and the detection current a of the load current detecting function 21 is subtracted, as shown in the third part (d) of the figure. As a result, a harmonic control signal (correction signal) b having a negative sign and a shape obtained by inverting the harmonic component is obtained.

In the above-described functional configuration, when the power load 31 is not functioning, the current signal a detected by the load current detecting function 21 does not include a harmonic component. Therefore, since the harmonic control signal b becomes zero, the adding function 25 does not function in the converter 20. Therefore, since converter 20 functions as a normal sine wave converter, the power supply circuit current such as the system power supply forms a normal sine wave.

In the above-described functional configuration, if the power load 31 functions and the detected current a of the load current detecting function 21 includes a harmonic component, the harmonic detecting function 22 detects the harmonic component, and the harmonic component is detected. The harmonic control signal b for canceling the wave current from the power supply circuit is added to the current command signal f which is the control signal of the sine wave converter by the addition function 25, and the current control signal g is obtained. The current control signal g becomes a PWM signal by the pulse width modulation function 17 and operates the control circuit of the switching function circuit 5 forming the servo system. Therefore, the current waveform input to the switching function circuit 5 is as follows.
FIG. 2 shows a combined shape of the sine wave shown in (e) and the inverse waveform of the harmonic component of the current flowing through the power load 31 shown in (d). Therefore, the power supply circuit before the inverter system 2 and the power load 31 are branched, that is, for example, the current waveform flowing from the system power supply includes a harmonic component of the current flowing through the power load 31 and a harmonic component flowing through the inverter system 2. The components cancel each other out, resulting in a normal sine wave.

In the above description, the inverse harmonic signal and the harmonic control signal b with a negative sign are output from the harmonic detection function 22. However, the sine wave of the power supply circuit, which is the fundamental wave of the sine wave converter, is output. And a signal component for canceling a harmonic component flowing through the power load 31 are:
As long as it can be configured as a signal for controlling the switching function circuit 5, it is only necessary that the polarity of the harmonic control signal b output from the harmonic detection function 22 be formed with an appropriate polarity. The amplitude of the harmonic control signal b output from the harmonic detection function 22 is appropriately set so that the harmonic component of the current flowing through the power load 31 and the harmonic component flowing through the inverter system 2 cancel each other. As described above, it is only necessary to appropriately form the performance of the harmonic detection function 22 and the like.

The carrier i created by the carrier creation function 18 flows into the power load 31 and has a frequency sufficiently higher than the harmonic component to be canceled. Naturally, the component passes through the component without distortion, and the harmonic component of the carrier wave i is removed. Further, in the above description, an example is described in which the sine wave converter is configured to be controlled by the PWM signal. Needless to say, it is only necessary to make a filter function or the like correspond.

Second Embodiment In the above description of the first embodiment, the case where the power load flows a current having a harmonic component is described. In the case, the load current detection function 21
As a result, the load current including the delay current is detected, so that the functions and characteristics of the respective element functions forming the converter 20 are formed such that the advance current corresponding to the delay current flows through the converter 20. That is, for example, the slow current detection function is added to the harmonic detection function 22, or the current control of the slow current flowing through the power load 31 and / or the inverse characteristic of the harmonic current is performed as the current detection function of the slow current detection function alone. A signal may be output, and other element functions may be configured according to the signal form.

The above description shows a basic configuration for realizing the technical idea of the present invention. For example, in the above description, an inverted shape signal is output from a current detection function such as the harmonic detection function 22. However, the current component detected from the load circuit is directly compared with the compensation current detected from the output circuit, and the PWM signal corresponding to the above purpose is output from the switching signal generation function by the deviation signal. May be. If the current control signal can be appropriately added to the control signal of the converter, it goes without saying that the present invention can be applied to converter control methods other than those described in the above embodiment. In the above example, an example in which the power load 3 such as an AC motor is driven has been described. However, it is obvious that the present invention may be applied to a system in which a DC load is directly driven by a DC converted by a converter. When one of the above-described inverter control function and converter control function (not shown), or both the inverter control function and the converter control function are configured by a computer, element functions appropriate for software processing are configured in the computer. Then, the power portion and the current transformer detection signals that necessarily require analog processing may be processed by appropriately configuring an A / D converter or a D / A converter. Also, it goes without saying that a dedicated circuit may be appropriately configured. Also, as described above, the three-phase circuit is configured with the circuits necessary for each phase, and a circuit breaker for protecting each circuit and the element functions is inserted, and element functions necessary for a normal AC circuit are arranged. Just set it.

[0030]

According to the present invention, the sine wave converter with the filtering function to which the present invention is applied has the following excellent effects. Since the filtering function can be integrated into the sine-wave converter, a normal sine-wave-shaped current can be passed also to an AC power supply connected to a power load for passing a current including a harmonic component and a lag current. Since the filtering function could be integrated into the sine wave converter, the above effects were obtained with a simple circuit configuration. Therefore, the object can be achieved at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram of a schematic configuration showing a basic configuration for explaining a control function of a sine wave converter with a filtering function according to the present invention.

FIG. 2 is a schematic AC waveform diagram illustrating a basic function of a filtering function according to the present invention.

FIG. 3 is a schematic configuration block diagram illustrating a configuration in which a conventional sine wave converter and an active filter are connected, corresponding to a case where a load circuit through which a harmonic current flows is connected.

FIG. 4 is a schematic block diagram illustrating a basic configuration for explaining a control function of a conventional sine wave converter.

[Explanation of symbols]

 1: AC power supply (AC power supply circuit) 2: Inverter system 3: AC motor (power load) 4: Power supply filter function 5: Switching function circuit 6: DC to AC conversion function part of inverter 7: Smoothing capacitor 8: Voltage detection function 10: Transformer 11: Converter input current detection function 12: Voltage setting function 13: Comparison function (subtraction function) 14: Automatic voltage adjustment function 15: Multiplication function 16: Current adjustment function 17: Pulse width modulation function 18: Carrier wave generation function 20: Sine wave converter with filtering function 21: Load current detection function 22: Harmonic detection function 23: Band pass filter function 24: Subtraction function 25: Harmonic control signal addition function (addition function) 31: Harmonic generation load (power) load)

Claims (3)

[Claims] 1. A sine wave converter for converting a sine wave AC input from a predetermined AC power supply circuit into a set DC voltage, wherein a harmonic component or a delay is determined based on a current of a harmonic generation load other than the load connected in parallel. One of the current components or a current component of both the harmonic component and the lag current is detected, a correction signal corresponding to the shape of the current component is created, and the correction signal is controlled by the sine wave converter. A sine wave converter with a filtering function, characterized by having a filtering function of maintaining the AC power supply circuit current in a sine wave shape by adding to a signal. 2. A filtering function provided in a sine wave converter with a filtering function includes a load current detecting function for detecting a load current including a harmonic component, and a harmonic component included in the load current detected by the load current detecting function. A harmonic detection function of detecting as a harmonic control signal of a predetermined shape,
2. A sine wave converter with a filtering function according to claim 1, wherein a harmonic control signal detected by said harmonic detection function is added as said correction signal to a control signal of said sine wave converter. 3. A control function of the sine wave converter includes a voltage setting function for setting a DC voltage to be formed by the converter, and a comparison function for comparing a set value set by the voltage setting function with a converter output voltage value. An automatic voltage adjustment function for creating a converter operation signal from the deviation signal output by the comparison function; and a multiplication function for multiplying the converter operation signal output from the automatic voltage adjustment function by a voltage proportional to the received voltage at a predetermined ratio. An addition or subtraction function corresponding to the positive or negative of the correction signal for generating the load current command signal by adding the correction signal to the output of the multiplication function; the load current command signal value and the input circuit current of the sine wave converter; A comparison function of comparing a current value proportional to a predetermined ratio to a current ratio, and generating a current operation signal according to a preset condition from a deviation value of the comparison result,
A switching signal generating function of converting the current operation signal into a PWM switching signal by a predetermined carrier;
A sine wave converter with a filtering function, the sine wave converter being operated by a switching signal and converting and outputting a direct current in synchronization with the input alternating current power supply.