JPH05316754A - Power converter having eccentric magnetic field compensation circuit - Google Patents

Abstract

PURPOSE:To compensate a DC component contained on the AC side of a power converter completely and to perform control stably. CONSTITUTION:A saturable reactor 15 and a reactor 16 which causes exciting current proportionate to the number of interlinking magnetic flux to flow, are connected in parallel on the primary side of a transformer 11. When DC voltage is generated in this transformer 11, the DC component, proportionate to the number of the interlinking magnetic flux, of the exciting current flowing through the reactors 15 and 16 is detected by a circuit composed of a resistor 19, a capacitor 20, and an operational amplifier 23, and the zero point of a sine-wave generator 21 is shifted, and the eccentric magnetization of the transformer 11 is completely compensated. Consequently, possibility of an unstable phenomenon by overcompensation becomes very slim, and it is possible to widen the gain tolerance of the control system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device that performs reverse conversion or forward conversion, and relates to a device for compensating for the bias magnetization of a transformer due to the DC component contained in the AC side voltage.

[0002]

2. Description of the Related Art As described in Japanese Patent Application No. 1-128384, a conventional DC component compensating circuit for a power converter is provided with a dead zone formed by a reactor and a diode having a non-linear excitation characteristic to detect a demagnetization. Was there.

[0003]

In the above-mentioned prior art, the bias current is detected by utilizing the saturation characteristic of the reactor. However, the exciting current when the reactor is saturated is more than proportional to the number of flux linkages. Since it increases, there is a problem that the gain of the control system rapidly increases equivalently and overcompensation is likely to occur. Further, since a part of the detected amount of the exciting current is not detected because the dead zone is provided by the diode in the control circuit, the direct current component generated in the power converter cannot be completely compensated.

An object of the present invention is to completely compensate for the direct current component contained in the alternating current side of the power conversion device for reverse conversion or forward conversion and to control it stably.

[0005]

In order to solve the above problems, a plurality of reactors having different magnetic saturation characteristics are connected in series to detect a DC component contained in an AC voltage, and a zero point of a reference signal in a control circuit is detected. It is achieved by shifting.

[0006]

When the DC component is generated on the AC side of the power converter due to the offset in the control circuit or the variation of ON / OFF of the self-arc-extinguishing element in the main circuit, the saturable reactor is saturated, and the flux linkage is further increased. It is possible to detect the amount of eccentricity that is proportional to the amount of magnetic saturation with a reactor that supplies an exciting current that is proportional to the number, and to perform stable control without overcompensation.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The main circuit 100 includes a bridge circuit including self-extinguishing elements 1 to 4 and diodes 5 to 8, a transformer 11, an AC filter including a reactor 12 and a capacitor 13.
The DC voltage source 9 is used to convert DC power into AC power. The control circuit 101 includes a sine wave generator 21, a transformer 14 that detects an AC voltage, a sine wave generator 21, and a transformer 1.
It is composed of a summing amplifier 24 that amplifies the difference of 4 and a comparator 25 that compares the output of the summing amplifier 24 and the output of the triangular wave generator 22, and is output from the PWM signal comparator 25. The gate circuit 26 creates a signal necessary for driving the self-extinguishing elements 1 to 4 from this PWM signal, and the drive circuit 10 drives the self-extinguishing elements 1 to 4.

A series connection of a saturable reactor 15 and a reactor 16 for flowing an exciting current proportional to the number of flux linkages is connected in parallel with a transformer 11, and a current transformer 17 and a resistor 18 are used to connect the reactor 15, The current flowing through 16 is detected. This output is integrated by a circuit composed of the resistor 19, the capacitor 20, and the operational amplifier 23, and is input to the adding amplifier 24.

The operation of the bias compensating circuit shown in FIG. 1 will be described in detail with reference to FIGS. 2 (1) is the excitation characteristics of the saturable reactor 15 and the reactor 16, FIG. 2 (2) is the excitation characteristic of the saturable reactor 15 and the reactor 16 connected in series, and FIG. 2 (3) is the saturable reactor for the transformer 11. 15 shows the excitation characteristics of the reactor 15 and the reactor 16. As shown in FIG. 2 (1), saturable reactor 15 is saturated by the number of interlinked magnetic fluxes .PHI ₁ or more, the reactor 16 is the number of interlinked magnetic fluxes .PHI ₃
Does not saturate until. By connecting two reactors having different characteristics in series, the characteristics as shown in FIG. 2 (2) can be obtained. Further, as shown in FIG. 2C, the transformer 11 has a characteristic larger than Φ ₁ and saturated between Φ ₁ and Φ ₃ . That is, the reactor 16 has a characteristic that is slightly larger than the value of the number of flux linkages that the transformer 11 saturates, so that the exciting current increases in proportion to the number of flux linkages in the saturation region of the saturable reactor 15. Therefore, if this is detected, an amount proportional to the amount of magnetic bias of the transformer 11 can be detected.

FIG. 3 shows the excitation characteristics of the saturable reactor 15 and the reactor 16 connected in series when the primary side AC voltage of the transformer does not include a DC component. FIG. 4 shows the excitation characteristics of the saturable reactor 15 and the reactor 16 connected in series when a DC component is included. In FIG. 3, positive and negative symmetrical currents flow in the reactors 15 and 16, and the output of the operational amplifier 23 in FIG. 1 does not generate a DC component. However, when a DC voltage is included on the primary side of the transformer 11 as shown in FIG. 4, the excitation characteristic of the series connection of the saturable reactor 15 and the reactor 16 is such that the magnetic flux is biased in the positive direction. Then, the currents of the reactors 15 and 16 are asymmetrical in positive and negative, and a DC component proportional to the number of interlinkage magnetic flux is generated in the output of the operational amplifier 23. By inputting this DC component to the summing amplifier 24, the zero point of the reference voltage can be shifted to completely compensate the DC component generated in the transformer 11.

Although FIG. 1 shows the embodiment applied to a single-phase inverter, the present invention can also be applied to a three-phase inverter. FIG. 5 shows a main circuit and a DC correction value generation circuit. The three-phase PWM inverter 28 receives the DC voltage source 27 as an input and connects a transformer 29 to the output. As in the case of the single phase, the saturable reactors 30 to 32 and the reactors 33 to 35 that flow an exciting current proportional to the number of flux linkages are connected in series and are connected in parallel with the transformer 29. This exciting current is detected by the current transformers 36 to 38 and the resistors 39 to 41, integrated by a circuit including the resistors 42 to 44, the capacitors 45 to 47, and the operational amplifiers 48 to 50, and the exciting currents of the respective phases are detected. DC component is detected. This operational amplifier 48-50
Is used as a correction value to shift the zero point of the reference voltage of each phase in the PWM generation circuit 51. With the above configuration, the three-phase PW
The DC component generated in each phase of the M inverter 28 is corrected to prevent the transformer 29 from being magnetized.

Further, the present invention is not limited to the inverse conversion device,
It can also be applied to a forward conversion device. FIG. 6 shows an embodiment applied to the converter. The main circuit includes a bridge circuit including a reactor 54, diodes 55 to 58, and self-extinguishing elements 59 to 62, a capacitor 63, a load 64, and an AC voltage source 52. The control circuit performs the following control in order to make the input current a sine wave having the same phase as the input voltage. The transformer 53 detects the input voltage, and the current reference sine wave generator 72 generates a current command value in phase with the input voltage. Then, the input current value is changed to the current transformer 68 and the resistor 70.
Detected by and the input current and the current command value are detected by the operational amplifier 77.
Calculate with. A comparator 78 compares this output with the output of the triangular wave generator 73 to generate a PWM signal. This PWM
The gate circuit 79 creates from the signals the signals needed to drive the self-turn-off elements, and the drive circuit 80 drives the self-turn-off elements 59-62.

A transformer 27, a saturable reactor 65, and a reactor 66 for supplying an exciting current proportional to the number of interlinking magnetic fluxes are connected in parallel with an AC voltage source 52 to detect a direct current component of the exciting current. This exciting current is detected by the current transformer 67 and the resistor 69, integrated by the circuit consisting of the resistor 71, the capacitor 74, and the operational amplifier 75, and this output is added as a compensation value to the current command value by the operational amplifier 76.

This PWM converter device has a power supply voltage V
The voltage difference between s and the converter voltage Vcon is applied to the reactor 54, and the input current is controlled by the magnitude and phase of this voltage.
Here, even if a direct current component is generated in the PWM converter, the direct current component can be compensated by the above configuration, and the magnetic bias of the transformer on the power supply side can be prevented. Although the embodiment of the single-phase converter is shown here, the same effect can be obtained by applying it to the three-phase converter as in the case of the inverter.

[0015]

According to the present invention, in a power converter that performs reverse conversion or forward conversion, by connecting a reactor whose exciting current is proportional to the number of flux linkages and a saturable reactor in series, it is possible to stabilize without overcompensating. Controllable,
Even if there are relatively large variations in the manufacturing of the reactor, the control works well, and the allowable range of the gain of the control system can be made much wider.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment when the present invention is applied to a single-phase inverter.

FIG. 2 is an excitation characteristic diagram of a reactor.

FIG. 3 is a diagram showing an excitation characteristic (when a DC component is not included in a primary side AC voltage of a transformer) due to a series connection of a supersaturated reactor 15 and a reactor 16.

FIG. 4 is a diagram showing an excitation characteristic (when a DC component is included in a primary side AC voltage of a transformer) due to a series connection of a supersaturated reactor 15 and a reactor 16.

FIG. 5 is a diagram showing an embodiment in which the present invention is applied to a three-phase inverter.

FIG. 6 is a diagram showing an embodiment in which the present invention is applied to a converter.

[Explanation of symbols]

1-4, 59-62 ... Self-extinguishing element, 5-8, 55-
58 ... Diode, 9 ... DC voltage source, 10 ... Driving circuit,
11, 14, 29, 53 ... Transformer, 12, 16, 33-
35, 54, 66 ... Reactor, 13, 20, 45-4
7, 63, 74 ... Capacitor, 15, 30-32 ... Saturable reactor, 17, 36-38, 67-68 ... Current transformer, 18-19, 39-44, 67-71 ... Resistor, 2
1 ... Sine wave generator, 22, 73 ... Triangle wave generator, 23,
48 to 50, 75 to 77 ... Operational amplifier, 24 ... Summing amplifier, 25, 78 ... Comparator, 26, 79 ... Gate circuit, 2
7 ... DC voltage source, 28 ... Three-phase PWM inverter, 51 ...
PWM generation circuit, 52 ... AC voltage source, 64 ... Load, 65
... Saturable reactor, 72 ... Current reference sine wave generator, 8
0 ... Drive circuit, 100 ... Main circuit, 101 ... Control circuit.

Claims (3)

[Claims] 1. A signal generator for generating a reference signal wave, a carrier wave generator for generating a carrier wave, a comparator for comparing these two, and an inverse conversion or forward conversion driven by a signal at the output of the comparator. In the power converter, a plurality of reactors having different characteristics are connected in series on the AC side, the current transformer attached to the connection line, the resistor attached to the secondary side of the current transformer, and the resistor A power converter using a bias magnetic compensating circuit, comprising a circuit for integrating a voltage across both ends and a calculator for calculating the integrated value and a reference signal wave. 2. The bias compensating circuit and the power converter using the same according to claim 1, wherein a saturable reactor and a reactor for supplying an exciting current proportional to the number of flux linkages are provided on the AC side. Converter using a bias magnetic compensating circuit. 3. A bias magnetic compensating circuit according to claim 1, and a power converter using the same, wherein a reactor connected to an alternating current side is more likely to be saturated than a transformer connected inside or outside the power converter. And a power converter using a bias magnetic compensating circuit, which is characterized in that the reactor is hard to saturate.