JP3216068B2 - Power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter for converting an AC voltage into a DC voltage or a DC voltage into an AC voltage, and controlling the AC current into a sine wave having a power factor of 1 with respect to the AC voltage. It concerns the device.

[0002]

2. Description of the Related Art FIG. 4 shows the configuration and control method of a sine wave converter as a conventional power converter. In the figure, 1 is an AC power supply, 2 is a converter device, and 3 is a DC load circuit such as an inverter circuit for driving a motor or an uninterruptible power supply, and a storage battery. The converter device 2 includes a converter output unit 4 composed of a semiconductor switching element, a capacitor 5, a reactor 6, a control circuit 7, and a current detector 8. Here, the capacitor 5 and the reactor 6 constitute a filter circuit. The control circuit 7 includes a DC voltage controller 71, a reference sine wave generator 72, a current commander 73, a current controller 74, and a gate amplifier 75.

A DC voltage control unit 71 takes in the DC voltage of the converter device 2 and uses an adder 71a to set a DC voltage setting signal.
A deviation from 71b is obtained, and a voltage control signal is output via a control amplifier 71c. The reference sine wave generation unit 72 outputs a reference sine waveform having a constant amplitude and the same phase as the voltage of the input terminal of the converter device 2. The current command unit 73 is a multiplier 73a
By multiplying the voltage control signal from the DC voltage controller 71 by the reference sine waveform from the reference sine wave generator 72, the phase matches the input terminal voltage of the converter device 2 and the current required by the amplitude is A sine waveform proportional to
This sine waveform is the input current command Id of the converter output unit 4.
* The current control unit 74 includes an adder 74a and a control amplifier 74b.
Consists of Here, the difference between the input current command Id * waveform and the current waveform fetched from the current detector 8 is obtained by the adder 74a, and is sent to the converter output unit 4 via the control amplifier 74b and the gate amplifying unit 75, thereby obtaining the converter output. Control can be performed so that the input current of the unit 4 becomes the same as the input current command Id * waveform.

FIG. 5 shows an equivalent circuit of the relationship between the converter device 2 and the AC power supply in FIG. 4, wherein 1a is an equivalent circuit of the AC power supply 1, 4a is an equivalent circuit of the converter unit 4, and 9 is an AC power supply. 1 is a wiring impedance or a power supply impedance between the power converter 1 and the converter device 2. In FIG.
FIG. 6 is a vector diagram of voltage and current of each unit obtained from the equivalent circuit of FIG. Each symbol in FIG. 6 indicates the symbol shown along with the arrow in FIG. 5 and 6, a solid arrow indicates a current, and a dashed-dotted arrow indicates a voltage. Referring to the voltage Vc of the capacitor 5 which is the input terminal voltage of the converter device 2, a current Ic having a phase leading by 90 degrees from the Vc flows through the capacitor 5.

In FIG. 4, the input current command Id * of the converter output unit 4, which is the output of the multiplier 73a, exactly matches the phase of the voltage Vc of the capacitor 5 as described above. And reactor 6
Has the same phase as the voltage Vc of the capacitor 5.
The current I of the capacitor 5 is supplied to the power source 1a and the reactor 9.
c and the current IL2 of the sum of the current IL4 to the converter output unit 4
Flows. This current IL2 is obtained from the voltage Vc of the capacitor 5.
Due to the component of the current Ic advanced in phase by 90 degrees, the capacitor 5
Is a current having a phase advanced from the voltage Vc. Since the phase difference between the voltage Vc of the capacitor 5 and the electromotive voltage E of the power source 1a is small, the current IL2 flowing through the power source 1a and the reactor 9 such as the wiring is viewed from the electromotive voltage E of the power source 1a as shown in FIG. The phase is advanced.

[0006]

If the power supply has a sufficient margin for the capacity of the converter device, the phase of the current flowing through the power supply does not matter, but the power supply is a generator and the capacity is not sufficient. In this case, when a current flows through the generator, the generator self-excited, increasing the output voltage,
Outputs excessive voltage. The voltage can reach 1.5 times the normal voltage, which can damage the device due to overvoltage. Further, when the power factor of the power supply current is advanced or delayed and the power factor is lower than 1, and reactive power is generated, a large power supply equipment capacity is required, which is uneconomical.

[0007]

In order to avoid such a problem, the present invention provides a reference sine wave generator for outputting a reference sine waveform in phase with the voltage of an AC power supply, an output DC voltage and a setting signal. DC voltage control unit that amplifies the deviation of the multiplier, a multiplier that receives the output of the reference sine wave generator and the DC voltage control unit as an input, and a power converter that uses the output of the multiplier as the input current command value of the converter output unit. A sine waveform delayed by 90 degrees and a multiplier output are added to the reference sine waveform, and the output is used as an input current command value of the converter output unit.

Further, a product of a sine waveform delayed by 90 degrees from the reference sine waveform and an AC power supply voltage value and a multiplier output are added, and the output is used as an input current command value of a converter output section. Similarly, the problem can be solved.

[0009]

In this manner, the input current command Id * of the converter output section always has a lag current component that cancels the lead current Ic by the capacitor, and it is possible to prevent the lead current from flowing to the power supply. In addition, the power factor of the power supply current can be set to one.

[0010]

FIG. 1 shows a configuration according to a first embodiment of the present invention. In FIG. 1, 7 'is a control circuit, 76 is a reference sine wave generator,
77 is a current command unit, 77a is a multiplier, 77b is an adder, 77c
Indicates a multiplier. Note that the components denoted by the same reference numerals as those in FIG. 4 indicate the same components. Here, the multiplier 77a is the same as the multiplier 73a of FIG. The difference between the reference sine wave generator 72 and the reference sine wave generator 76 is that the reference sine wave generator 76 outputs a second output, and this output is delayed by 90 degrees from the reference sine wave. This is a point that has a waveform. This waveform can be easily obtained in terms of a circuit by delaying the phase of the reference sine wave by a filter circuit or by shifting the reading point of a data table representing the sine wave by software processing of a microcomputer. In the case of a three-phase AC power supply, for example, a waveform delayed by 90 degrees from the R-phase is obtained by calculating the difference between the S-phase voltage or the reference sine wave and the T-phase voltage or the reference sine wave. Can also be obtained in the circuit.

The difference between the current command unit 73 and the current command unit 77 is that the current command unit 77 includes an adder 77b and a multiplier 77c in addition to the multiplier. The second output of the reference sine wave generator 76 is input to the multiplier 77c, and the output of the multiplier 77c and the output of the multiplier 77a are added by the adder 77b. In this way, the waveform delayed by 90 degrees from the reference sine waveform is multiplied by a coefficient corresponding to the value of the advance current by the capacitor 5 by the multiplier 77c, and the output of the conventional converter output unit 4 is added by the adder 77b. It is added to the input current command Id * to obtain a new input current command I *.

FIG. 2 shows a vector diagram of voltage and current of each section according to the present embodiment. In FIG. 2, the components denoted by the same reference numerals as those in FIG. 6 indicate the same components. In FIG. 2, similarly to the conventional example, the waveform obtained by multiplying the output of the DC voltage controller 71 and the reference sine waveform from the reference sine wave generator 76 by the multiplier 77a has a phase equal to the input terminal voltage. It is a sine waveform that matches and is proportional to the amplitude of the current required for DC voltage control, and the vector of this sine waveform is Id *. This sinusoidal waveform is a purely necessary current component for DC voltage control. The multiplier 77c
The second output waveform of the reference sine wave generating section 76 is a waveform whose phase is delayed by 90 degrees from the reference sine waveform, and has a 180 degree phase opposite to the current Ic of the capacitor 5. The sum of the waveforms ILAG * and Id * obtained by multiplying this waveform by an appropriate coefficient by a multiplier 77c is obtained by an adder 77b, and a new input current command I * for the converter output unit 4 is obtained.

The input current IL4 of the converter output unit 4 according to the input current command I * has the same waveform as I *, and this current is a component IR required for purely controlling the DC voltage.
And a current ILAG having a phase opposite to that of the leading current IC flowing through the capacitor 5. Therefore, ILAG is I
By setting the gain of the multiplier 77c so as to be equal to or slightly larger than c, the input current IL2 of the converter device is made purely a component necessary for DC current control, and the input current IL2 of the converter device is reduced with respect to the input terminal voltage Vc of the device. The phase can be slightly in phase or slightly delayed. FIG. 2 shows an example in which IL2 is slightly delayed with respect to the input terminal voltage Vc of the device.
At this time, since the phase of the power supply current IL2 is delayed with respect to the power supply and the generator, the generator does not cause self-excitation, thereby preventing generation of an excessive voltage.

FIG. 3 shows a second embodiment of the present invention. FIG.
In the figure, 7 "is a control circuit, 79 is a power supply voltage value detector for detecting the magnitude of the power supply voltage. Here, the multiplier 77c in FIG. Is multiplied by the output of the power supply voltage value detector 79. That is, the magnification of the multiplier 77c is made variable to be proportional to the power supply voltage value. The multiplier 78a is the same as the multiplier 73a and the multiplier 77a.

In the first embodiment, the delay current command ILAG for canceling the advance current Ic by the capacitor 5 is set.
* Was constant. However, the advance current Ic by the capacitor 5 changes in proportion to the magnitude of the power supply voltage Vc. Therefore, in the state of the power supply voltage where the delay current command ILAG * is constant, the lead current and the delay current I
LAG just cancels out, and the power supply current IL2 has the same phase as the power supply voltage. I can't keep one. In particular, when the power supply voltage Vc increases and the advance current of the capacitor 5 increases, the power supply current IL2 advances with respect to the power supply voltage Vc, and the above-described problem occurs. Also, when the delay current command ILAG * is set to be large so that the power supply current IL2 becomes a delay current with respect to the power supply voltage Vc even for the maximum power supply voltage, the power supply current IL2 at the normal power supply voltage is reduced from the power supply voltage Vc. The delay is increased, the power supply power factor is reduced, and a large power supply capacity is required. In order to solve such a problem, in the second embodiment, the delay current command ILAG * is changed in proportion to the magnitude of the power supply voltage, and the delay current command ILAG * in FIG.
LAG is always controlled to a level that just cancels out the advance current Ic by the capacitor 5. Thus, the power supply current IL2 can always be in phase with the power supply voltage Vc.

[0016]

As described above, according to the present invention, in addition to a current command in phase with a power supply voltage required for DC voltage control, a delay current component for canceling a lead current of a capacitor is used as an offset. By superimposing the converter current command, it is possible to prevent the power supply current from leading the phase, prevent self-excitation of the generator, generate excessive voltage, and damage the converter device and load device. It is possible to provide a power converter that can prevent the power supply from being given and can perform stable operation even in a severe power supply environment. Further, by changing the magnitude of the offset of the delay current component in proportion to the magnitude of the power supply voltage, the power factor of the power supply is always kept at 1 even when the power supply voltage fluctuates, so that the power supply equipment capacity can be effectively used.

[Brief description of the drawings]

FIG. 1 is a circuit configuration showing a first embodiment of the present invention.

FIG. 2 is a vector diagram of each unit according to the first embodiment.

FIG. 3 is a circuit configuration showing a second embodiment of the present invention.

FIG. 4 is an example of a conventional circuit configuration.

FIG. 5 is an equivalent circuit for one phase.

FIG. 6 is a vector diagram of each unit according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 AC power supply 2 Converter device 3 DC load circuit 4 Converter output unit 5 Capacitor 6 Reactor 7 Control circuit 7 'Control circuit 7 "Control circuit 8 Current detector 9 Reactor 71 DC voltage control unit 71a Adder 71b DC voltage setting signal 71c Control Amplifier 72 Reference sine wave generator 73 Current commander 73a Multiplier 74 Current controller 74a Adder 74b Control amplifier 75 Gate amplifier 76 Reference sine wave generator 77 Current commander 77a Multiplier 77b Adder 77c Multiplier 78 Current command Section 78a Multiplier 78b Adder 78d Multiplier 79 Power supply voltage detector

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/155 H02P 9/00

Claims (2)

(57) [Claims] 1. A reference sine wave generator for outputting a reference sine waveform in phase with a voltage of an AC power supply, a DC voltage controller for amplifying a deviation between an output DC voltage and a setting signal, a reference sine wave generator and a DC A multiplier that receives the output of the voltage control unit as an input,
In a power conversion device in which an output of the multiplier is used as an input current command value of a converter output unit, a sine waveform delayed by 90 degrees with respect to the reference sine waveform is added to the output of the multiplier, and the output is output from the converter. A power conversion device characterized in that it is configured to be an input current command value of a section. 2. A reference sine wave generator for outputting a reference sine waveform in phase with a voltage of an AC power supply, a DC voltage controller for amplifying a deviation between an output DC voltage and a setting signal, a reference sine wave generator and a DC A multiplier that receives the output of the voltage control unit as an input,
In the power converter, the output of the multiplier is used as an input current command value of a converter output unit, a product of a sine waveform delayed by 90 degrees with respect to the reference sine waveform and an AC power supply voltage value, and the output of the multiplier , And the output is used as the input current command value of the converter output unit.