JPH1066358A - Controller for sine-wave converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the sizes and the cost of a sine-wave converter by advancing the phase of a line current flowing to a three-phase AC power source from that of a regenerated current outputted from a power rectifier means when regenerated energy is generated. SOLUTION: When regenerative operation is made, the output voltage of a motor 4 is converted into a direct current by means of a reverse-converting circuit 3 and the current is used for charging a smoothing capacitor C0 . As a result, the output voltage of the capacitor C0 is converted into a three-phase AC voltage by means of a power rectifier circuit 2. Then the circuit 2 outputs an output voltage *VCRS and, because of the voltage *VCRS, a regenerated current *IRC which flows to a three-phase AC power source 1 from the circuit 2 flows through a connecting line SR. The current *IRC is divided into a capacitor current *IC and an R-line current *IR and the current *IC flows to a capacitor CR and the current *IR flows to the R-phase of the power source 1. When the regenerated current *IRC flows, in addition, a voltage drop *VLR occurs across a coil LR and the phase of the current *IR advances.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a sine wave converter used for controlling the rotation speed of an electric motor, for example.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a configuration of a conventional control device for a sine wave converter. In this figure, 1
Is a three-phase AC power supply in which the R, S, and T phases are star-connected. Reference numeral 2 denotes a forward conversion circuit that rectifies the three-phase AC supplied from the three-phase AC power supply 1, and includes a power transistor and the like. As the forward conversion circuit 2, a sine wave converter, which has recently attracted attention as a measure against power supply high frequency, is used. Further, the forward conversion circuit 2
At the time of regenerative operation described later, it has a function of inversely converting a DC supplied from the smoothing capacitor Co into a three-phase AC. Further, the forward conversion circuit 2 is controlled by a control device (not shown) to switch between a power operation operation for converting three-phase AC to DC and a regenerative operation for converting DC to three-phase AC.

The forward conversion circuit 2 and the three-phase AC power supply 1
Between them, coils LR, LS and LT corresponding to the R, S and T phases, respectively, are inserted. further,
A smoothing capacitor Co is connected in parallel to the output terminal of the forward conversion circuit 2. Reference numeral 3 denotes an inverse conversion circuit connected in parallel to the smoothing capacitor Co, and converts an input DC into a three-phase AC. In the inverse conversion circuit 3, as an example of the AC voltage control, a well-known PWM (Pulse Width Modula) is used.
tion) control is employed. Reference numeral 4 denotes a motor driven by the output voltage of the inverse conversion circuit 3.

In the above configuration, when the three-phase AC is supplied from the three-phase AC power supply 1 to the forward conversion circuit 2, the three-phase AC is rectified by the forward conversion circuit 2 and further smoothed by the smoothing capacitor Co. As a result, the DC voltage is input to the inverse conversion circuit 3, and the three-phase AC voltage of a predetermined frequency generated by the PWM control is supplied from the inverse conversion circuit 3 to the electric motor 4. Thereby, the electric motor 4 is driven.

[0005] When the frequency of the three-phase AC voltage applied to the motor 4 decreases, the motor 4 continues to rotate due to inertia. That is, the electric motor 4 continues to operate as a generator (hereinafter, referred to as regenerative operation). Therefore, the three-phase AC voltage generated in the electric motor 4 is converted into a DC voltage by the reverse conversion circuit 3 through the operation reverse to the above-described power operation operation, and the smoothing capacitor Co is charged by the DC voltage. Further, a three-phase AC voltage is generated by the forward conversion circuit 2, and the three-phase AC power based on the three-phase AC voltage is regenerated to the three-phase AC power supply 1 via the coils LR, LS, and LT.

FIG. 4 shows the relationship between the voltage vector and the current vector of each part of the control device of the sine wave converter during the regenerative operation described above. FIG. 4 shows a three-phase AC power supply 1
FIG. 5 is a diagram showing voltage and current vectors related to the R phase of FIG. 5. In this diagram, * VCRS (“*” means vector display dots) indicates output voltage of the forward conversion circuit 2 during regenerative operation. , * VLR respectively represent the voltage drop of the coil LR. * VRS is the R of the three-phase AC power supply 1
The line voltage between the phase and the S phase (hereinafter, referred to as an RS line voltage), * IR represents a line current flowing into the R phase (hereinafter, referred to as an R line current), and * VR represents a three-phase alternating current. R-phase voltage of the power supply 1 (hereinafter, referred to as R-phase voltage).

According to the vector diagram shown in FIG. 4, during the regenerative operation, the absolute value of the output voltage * VCRS of the forward conversion circuit 2 becomes larger than the absolute value of the RS line voltage * VRS. Therefore, in order to normally realize regenerative operation,
In the control device of the conventional sine wave converter, a device having a large rated voltage is used as each element of the smoothing capacitor Co and the forward conversion circuit 2 shown in FIG.

[0008]

In the conventional control device for a sine wave converter, a circuit element having a large rated voltage must be used in order to normally perform the regenerative operation as described above. However, there was a drawback that the size became large and the cost was high. The present invention has been made under such a background, and an object of the present invention is to provide a control device for a sine wave converter which is small and inexpensive.

[0009]

According to a first aspect of the present invention, there is provided a three-phase AC power supply, a forward conversion means for converting a three-phase AC supplied from the three-phase AC power supply to a DC, and the three-phase AC power supply. In a control device for a sine wave converter having three coils interposed in each phase between a power supply and the forward converting means, and a regenerative energy generating means connected to the forward converting means and generating regenerative energy, When the energy generation means is generating the regenerative energy, the power generation apparatus further comprises a phase advance means for advancing the phase of a line current flowing into the three-phase AC power supply with respect to a regenerative current output from the forward conversion means. Features.

According to a second aspect of the present invention, in the control device for a sine wave converter according to the first aspect, the regenerative energy generating means reversely converts an output of the forward converting means into a three-phase alternating current. And a driving device driven by the output of the inverse conversion means.

According to a third aspect of the present invention, in the control device for a sine wave converter according to the first or second aspect, the phase advance means includes a control circuit for controlling each of the three-phase AC power supply and the three coils. It is characterized by comprising three capacitors which are star-connected between the phase connection lines.

According to a fourth aspect of the present invention, in the control device for a sine wave converter according to the first or second aspect, the phase advance means includes a control circuit for controlling each of the three-phase AC power supply and the three coils. It is characterized by comprising three capacitors delta-connected between the phase connection lines.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a control device for a sine wave converter according to one embodiment of the present invention. In this figure, parts corresponding to the respective parts in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted. In the control device of the sine wave converter shown in FIG.
R, CS and CT are newly provided.

The capacitor CR is interposed between a connection line SR connecting the R phase of the three-phase AC power supply 1 and the forward conversion circuit 2 and a point a shown in FIG. Capacitor CS
Is inserted between a connection line SS connecting the S-phase of the three-phase AC power supply 1 and the forward conversion circuit 2 and a point a. The capacitor CT is interposed between a connection line ST connecting the T phase of the three-phase AC power supply 1 and the forward conversion circuit 2 and a point a. That is, capacitors CR, CS and C
T has a star connection (a delta connection is also possible).

Next, the operation of the control device of the sine wave converter according to the above-described embodiment during regenerative operation will be described. First, when the regenerative operation described above is performed, the output voltage of the electric motor 4 is converted into DC by the inverse conversion circuit 3, and the DC current is charged in the smoothing capacitor Co. Then, the charge of the smoothing capacitor Co is discharged.

As a result, the output voltage of the smoothing capacitor Co is converted by the forward conversion circuit 2 into a three-phase AC voltage. Here, in order to facilitate understanding, the R of the three-phase AC voltage 1
The operation related to the phase will be described. Then, the output voltage * VCRS is output from the forward conversion circuit 2, whereby
Regenerative current * I flowing from forward conversion circuit 2 to three-phase AC power supply 1
RC flows through the connection line SR. And this regenerative current * IRC
Is divided into a capacitor current * IC and an R-line current * IR, and the capacitor current * IC flows to the capacitor CR, while the R-line current * IR flows to the R phase of the three-phase AC power supply 1. When the regenerative current * IRC flows, the coil LR
Causes a voltage drop * VLR.

Here, the output voltage * VCRS, the regenerative current * IRC, the voltage drop * VLR, and the capacitor current * I
FIG. 2 shows the vector relationship between C, R line current * IR, R phase voltage * VR and RS line voltage * VRS. As shown in FIG. 2, during the above-described regenerative operation, the capacitor current * IC causes a phase difference of θ between the R-line current * IR and the regenerative current * IRC, so that the voltage shown in FIG. The phase of the voltage drop * VLR advances by the phase difference θ from the voltage drop * VLR shown in FIG. Therefore, the output voltage * VCR shown in FIG.
The absolute value of S becomes smaller than the absolute value of the output voltage * VCRS shown in FIG.

That is, according to the control device for the sine wave converter according to the embodiment of the present invention, the output voltage * VCRS of the forward conversion circuit 2 during the regenerative operation becomes smaller than that of the conventional one, Thus, the rated voltage of the circuit element can be reduced. As an example, a capacitor having a smaller rated voltage than the smoothing capacitor Co shown in FIG. 3 is used as the smoothing capacitor Co shown in FIG.
Therefore, according to the control device of the sine wave converter according to the embodiment of the present invention, the rated voltage of the circuit element can be reduced as compared with the conventional device, so that the device can be downsized and the cost can be reduced. Can be obtained at a low price.

As described above, one embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and a design within a range not departing from the gist of the present invention. Modifications and the like are included in the present invention. For example, in the control device of the sine wave converter according to the above-described embodiment, an example in which the inverter 3 and the electric motor 4 are used as the regenerative energy sources has been described. However, the present invention is not limited thereto, and the regenerative energy sources may be used. A solar cell, a fuel cell, or the like may be used.

[0020]

According to the present invention, the phase of the line current advances with respect to the regenerative current by the phase advance means, whereby the phase of the voltage drop of the coil advances as compared with the conventional one. Therefore, according to the present invention, during the regenerative operation, the absolute value of the output voltage of the forward conversion means is smaller than that of the conventional one, so that the rated voltage of the circuit element can be reduced.
The effect that the apparatus can be miniaturized and the cost can be reduced is obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a control device for a sine wave converter according to an embodiment of the present invention.

FIG. 2 is a vector diagram showing a relationship between a current vector and a voltage vector of each unit of the control device of the sine wave converter according to the same embodiment.

FIG. 3 is a circuit diagram showing a configuration of a control device for a conventional sine wave converter.

FIG. 4 is a vector diagram showing a relationship between a current vector and a voltage vector of each unit of a conventional control device for a sine wave converter.

[Explanation of symbols]

 Reference Signs List 1 three-phase AC power supply 2 forward conversion circuit 3 reverse conversion circuit 4 motor Co smoothing capacitor CR, CS, CT capacitor

Claims (4)

[Claims] 1. A three-phase AC power supply, forward conversion means for converting three-phase AC supplied from the three-phase AC power supply to DC, and each phase between the three-phase AC power supply and the forward conversion means. In a control device for a sine wave converter having three interposed coils and a regenerative energy generating means connected to the forward converting means and generating regenerative energy, the regenerative energy generating means generates the regenerative energy. A phase-advance means for advancing the phase of a line current flowing into the three-phase AC power supply with respect to a regenerative current output from the forward conversion means. 2. The regenerative energy generating means includes: an inverting means for inverting an output of the forward converting means into a three-phase alternating current; and a driving machine driven by an output of the inverting means. The control device for a sine wave converter according to claim 1, wherein: 3. The phase-advancing means includes three capacitors connected in a star connection between connection wires of each phase between the three-phase AC power supply and the three coils. The control device for a sine wave converter according to claim 1 or 2, wherein: 4. The method according to claim 1, wherein the phase-advancing means comprises three capacitors which are delta-connected between connection wires of each phase between the three-phase AC power supply and the three coils. The control device for a sine wave converter according to claim 1 or 2, wherein: