JPH01129772A - Controller for pulse width modulation power converter - Google Patents

Abstract

PURPOSE:To prevent an AC input current from becoming an overcurrent by detecting a variation in the inductance of a transformer by using the time change rate of the AC input current of a PWM converter. CONSTITUTION:A pulse width modulation power converter has a transformer MTR for stepping down a trolley voltage, an AC reactor ACL, a DC capacitor DCC, a GTO for forming a main circuit, and a load unit LOAD. Its controller has an average value detector AVE, a voltage regulator AVR, a current regulator ACR, a power factor regulator APR, a coordinates converter CRT, first-second pulse width modulators PWM1-2, and a gate signal converter SGL, etc. When the time change rate of the AC input current exceeds a predetermined value, it is judged that the transformer MTR is saturated due to a DC polarization or the like and switches to a gate signal adapted to the management of the peak value of the DC input current from a normal gate signal.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a control device for a pulse width modulation power converter (hereinafter abbreviated as PWM converter) that converts single-phase alternating current to direct current, and particularly relates to a control device for a pulse width modulation power converter (hereinafter referred to as a PWM converter) that converts single-phase alternating current to direct current. The present invention relates to a control method suitable for overcurrent prevention.

[Conventional technology]

PWM converters are capable of forward and reverse conversion operations with a power factor of approximately 1, and can also reduce generated harmonics, making them ideal control devices for use with microprocessors. 1 For example, JP-A-58-7
An example is the method disclosed in Japanese Patent No. 9478. This method also makes it easy to manage the minimum on/off time of the GTO that constitutes the main circuit.

It is also a method that allows phase difference operation that can effectively reduce high frequencies when multiple PWM comparators are connected.

[Problem that the invention seeks to solve]

When a PWM converter is applied as a power converter on the overhead line side of an AC electric vehicle, in order to make the device smaller and lighter, the leakage inductance of the transformer is made large and the AC reactor is omitted, or the AC reactor is omitted, or the capacity is very small. It is common to provide an auxiliary AC reactor. In such devices, when the transformer becomes saturated due to DC bias, the inductance on the AC side decreases to a fraction of its normal inductance, and in the conventional technology described above, the AC input current of the PWM converter is There were problems that increased and made driving difficult.

An object of the present invention is to provide a control method for a PWM converter that prevents an increase in AC input current and enables continuous operation.

[Means for solving problems]

The above purpose is to detect the change in the inductance of the transformer by the time rate of change of the AC input current of the PWM converter,
This is achieved by switching to a gate signal generating means that can control the peak value of the input current at an instantaneous level when an abnormality occurs.

[Effect]

When the time rate of change of AC input current exceeds a predetermined value, it is determined that the transformer is saturated due to DC bias, etc., and the normal gate signal is switched to a gate signal suitable for managing the peak value of AC input current. . This prevents the AC input current from becoming an overcurrent.

〔Example〕

FIG. 1 shows an embodiment of the present invention in which FDR
is an AC overhead line, PAN is a puncture, MTR is a transformer to step down the overhead line voltage, ACL is an AC reactor, DCC is a DC capacitor for DC voltage smoothing, LOAD is a load device, and 61 to G4 are gates that make up the main circuit. Turn-off thyristors (hereinafter abbreviated as GTO) and D1 to D4 are anti-parallel diodes. Also, AVE is an average value detector, PMS
is an effective value detector, and PDD is a phase detector.

AVR is a voltage regulator that creates an effective value command IS umbrella (input current command) for input current is from the deviation between DC voltage command E- and DC voltage average value E4, which is the output of AVE.
is the AC side terminal voltage 8c of the PWM converter from the deviation between IS・ and the detected effective value Is of is, which is the RMS output.
(hereinafter abbreviated as converter input voltage) puncture voltage ep
The current regulator creates the orthogonal component command value Ec- (imaginary axis component), APR is the power factor angle command value φ fist and the phase detector PDD.
CTR is a power factor regulator that creates the in-phase component Ecr and real axis component of the converter input voltage ec with the puncture voltage ep from the deviation from the detected power factor angle value φ, which is the output of the converter input voltage ec. % and Ec- as amplitude command E on polar coordinates
CS, and a coordinate converter that converts one phase angle command o umbrella, P
WMI is a first pulse width modulator that performs pulse width modulation using Ec* and 0* to create a gate signal. on the other hand,
PWM2 is a second pulse width modulator that performs pulse width modulation from Is・, φ− and the instantaneous value fs of the input current to create a gate signal, and GSL is a gate that switches the gate signal according to the time rate of change of is. It is a signal switch.

Next, the operation will be explained.

Based on the vector El (=ES) of the secondary voltage e3 of the transformer, the input current i3. And, if the fundamental wave vector of converter input voltage ec is Is and Ec, then 1, Es-Ec jωL ωL ωL where, ω: power supply angular frequency L: inductance of ACL Ecr: real axis component of Ec Eci: imaginary of Ec As shown in the above equation for the axis component, in a PWM converter, the converter flow is
In addition, by adjusting the real component Ecr of Ec, the reactive current can be
Each can be controlled independently. Therefore, as shown in Fig. 1, the DC output voltage E- is controlled to a predetermined value by adjusting Ect with a voltage control system consisting of AVR and ACR, and Ecr is adjusted with a power factor control system including APR. By doing so, the power factor can be controlled to approximately 1 (φ=O).

In practice, the converter input voltage ec is regulated by controlling the gate signal applied to the GTO, so a pulse width modulator PWMI is required to generate this gate signal. Figure 2 shows the pulse width modulator PWM shown in Figure 1.
This figure shows an example of the configuration of I. In the same figure, E
CG is a basic sine wave generator, and GPGI is a gate signal generator.

The basic sine wave generator ECG creates the basic sine wave command ec- of ec from the amplitude command Ec* of the converter input voltage ec and the phase angle command 0, and divides this by the DC voltage average value E- to generate a modulated sine wave. Create a wave y. The difference between this modulated sine wave y and the triangular carrier wave yc is taken, and based on the sign, the gate signal generator GPGI gives the gate signal G to the GTO.
Create S1.

On the other hand, when the transformer MTR in Fig. 1 becomes saturated due to the influence of DC bias magnetization, the transformer actance rapidly decreases, and the time rate of change dss/dt of the input current is becomes as shown in Fig. 3 (C). Gate signal switch G
SL detects the magnitude of this time rate of change dzs/dt, and when the value exceeds a predetermined value, the gate signal is changed to GSL.
Switch from GS2 to GS2. Second pulse width modulator PWM2
gives a gate signal to the GTO so that the peak value of the input current is does not exceed the allowable value of the cut-off current of the GTO. FIG. 4 shows an example of the configuration of the second pulse width modulator PWM2. In the same figure, ISO is a basic sine wave generator, AB
S is an absolute value detector, HCM is a comparator with hysteresis characteristics, and GPG2 is a gate signal generator. The basic sine wave generator ISO has an effective value command Is of input current is and a phase angle command φ (φ umbrella = 0° during power running, φ skewer = 180 during regeneration)
°) to the fundamental sine wave command is as shown in Figure 5(a).
Create *. When the difference between this i- and the input current is exceeds the set value, the comparator HCM outputs a signal with the sign shown in FIG. 5 (Q), and the gate signal generator GPG2 Power line/PW by regeneration discrimination signal P/B
The operating mode of the M converter is determined as shown in FIG. 5(d), and a gate signal corresponding to this is created. Furthermore, the fifth
In Figure (d), mode C is a charging mode in which the AC side and DC side of the main circuit are connected, and is a mode in which 01 on, G4 on, 02 on, and 03 on. Mode S is a short-circuit mode in which the AC side and DC side are separated and the AC side is short-circuited, and 01 on, 03 on, or
This is a mode in which G2 is on and 64 is on.

In this way, the input current Ls follows the command value Is'' with a certain width, as shown in FIG. 5(a).

According to this embodiment, even if the transformer becomes saturated due to direct current biased magnetism or the like, no overcurrent occurs and continuous operation is possible.

[Effects of the Invention] According to the present invention, changes in inductance due to transformer saturation can be effectively detected and overcurrent can be prevented.

Continuous operation is possible without stopping the PWM converter.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a control system diagram of the first pulse width modulator in FIG. 1, FIG. 3 is an explanatory diagram of the detection method, and FIG. FIG. 5 is a control system diagram of the second pulse width modulator in the figure, and FIG. 5 is an explanatory diagram of the operation of FIG. 4. PWMI...first pulse width modulator, PWM2...
Second pulse width modulator, GSL...Gate signal control 2nd '$ ≠View 51!1

Claims (1)

[Claims] 1. A self-extinguishing switching element in which diodes are connected in antiparallel is bridge-connected, and its AC side terminal is connected to a single-phase AC power source via an AC reactor and a transformer,
A pulse width modulation power converter is equipped with a DC capacitor on the DC side terminal leg and a load is connected in parallel with the DC capacitor, and the pulse width modulation is performed to maintain the DC output voltage and power factor of the pulse width modulation power converter at predetermined values. A pulse width modulation power converter comprising a control device that performs control, comprising a plurality of means for generating a gate signal, the gate signal being generated in accordance with a time rate of change of an AC input current of the pulse width modulation power converter. 1. A control device for a pulse width modulation power converter, comprising means for switching means for generating.