JP4144942B2 - Power supply voltage estimation device for PWM converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a PWM converter that is controlled without a power supply voltage sensor, and more particularly to a power supply voltage estimation device when a controller is stopped.
[0002]
[Prior art]
FIG. 2 is a diagram showing a main circuit configuration of a PWM converter for converting a polyphase alternating current into a direct current for explaining the conventional technique. In FIG. 2, 1 is a PWM conversion bridge constituting the converter, and 2 is a polyphase An AC power source, 3 is an AC reactor, and 4 is a DC circuit.
The purpose of the converter control is to make the AC current follow a sine wave command value with a predetermined power factor angle shifted from the power supply voltage waveform, and to match the DC voltage with the predetermined voltage command value. Since it is based on the power supply voltage, information on the power supply voltage is indispensable. For this reason, conventionally, the power supply voltage is often directly detected by a detection transformer or the like in hardware.
[0003]
However, since the power supply voltage detector is affected by power supply fluctuations, switching ripples, noise, etc., it requires installation space and is disadvantageous in terms of cost. Therefore, an observer is configured by software, the power supply voltage is estimated, and converter control is performed. A power supply voltage sensorless control method has been devised.
FIG. 3 is a system configuration block diagram in the case of power supply voltage sensorless control. In the figure, 5 is a block representing the converter main circuit of FIG. 2, 6 is a CPU calculation block for controlling the converter, 7 is a DC voltage detector, and 8 is an AC current detector. Reference numeral 9 denotes a controller inside the CPU, which performs a control operation so that an alternating current and a direct current voltage coincide with a predetermined command value, and outputs a switching signal which becomes a gate signal of the converter, thereby fulfilling the control purpose. A power supply voltage observer 10 receives an AC current detection signal, a DC voltage detection signal, and a switching signal output from the controller 9 as inputs, estimates a power supply voltage value from an AC circuit model and observer theory, and provides it to the controller 9.
Since the switching signal of the controller output is required to operate the observer, the observer cannot operate unless the control is started. Conventionally, the initial value of the estimated power supply voltage is set to zero at the start-up, and the observer is Is started simultaneously with the controller. In this case, since the observer's initial error is large, the period until convergence is long. During this time, since the controller cannot obtain accurate power supply voltage information, there is a risk of malfunction resulting in overcurrent and overvoltage.
[0004]
In order to start smoothly, there is also a method of providing a special test operation stage before the normal control operation. In the test operation period, the observer is operated while outputting an appropriate test switching signal to the converter. When the power supply voltage can be estimated to some extent after an appropriate time, the control is switched to the normal control operation. In this case, it is safer than the above-mentioned simultaneous start, but during the test operation, an increase in alternating current is unavoidable, and there is a possibility that overload will occur while the direct current side is charged when there is no load.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned points, and the object of the present invention is to estimate the power supply voltage to some extent before starting, without causing overcurrent and overvoltage, and to start up the above problem. An object of the present invention is to provide an AC power supply voltage estimation device for a PWM converter that performs control smoothly.
[0006]
[Means for Solving the Problems]
That is, in order to achieve the purpose, a PWM converter for converting from AC to DC, a controller for causing the AC / DC control amount of the converter to follow a predetermined command value, an AC current detection signal and a DC voltage detection of the converter In a control device for a PWM converter that is controlled by a power supply voltage sensor, which includes a power supply voltage observer that estimates a power supply voltage value by inputting a signal and a switching signal,
In the gate block state before starting the controller, the first means for obtaining the polarity of each phase alternating current of the PWM converter and the equivalent switching signal for obtaining the equivalent switching signal based on the current polarity obtained by the first means And an equivalent switching signal obtained by the second means is input to a power supply voltage observer to estimate the power supply voltage value.
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a configuration of a power supply voltage estimation device in a gate block according to the present invention. In the figure, 11 is a first means for obtaining the alternating current polarity, and 12 is a second means for obtaining the equivalent switching signal of the conversion bridge based on the current polarity obtained by the first means when the gate is blocked. Yes, 13 is a conventional power supply voltage observer, which estimates the power supply voltage using the input switching signal as the equivalent switching signal obtained by the second means.
The present invention relates to a method of operating an observer at that time, because the observer can provide power supply voltage information to the controller at the time of starting the converter, so that the observer is operated even in a gate block state before the operation of the controller. Hereinafter, the observer operating principle at the time of the gate block of the present invention will be described in detail.
[0008]
Before starting the controller, it is normal to turn off the gate signals of the semiconductor switching elements that constitute the conversion bridge, that is, in the gate block state. In this state, the switching element is in a gate-off state, but the converter bridge is a multiphase diode rectifier due to the presence of the converter bridge shown in FIG. 2, that is, the antiparallel diode in the PWM converter 1. Therefore, it can be seen that a small amount of current flows through the AC reactor 3 in FIG. The equivalent switching signal is determined by the polarity of the current. The principle of this will be described below with reference to FIG.
FIG. 4 shows one phase of the multi-phase PWM converter of FIG. 2, in which 2 ′ is an AC power source, 3 ′ is an AC reactor, 4 ′ is a DC load circuit, and 14 and 14 ′. Are upper and lower switches constituting the arms of the PWM converter bridge, and 15 and 15 'are diodes connected in reverse parallel to the switches. Further, i represents an alternating current, and the direction in which it flows through the bridge is assumed to be positive thereafter.
When the current polarity is positive, the current flows through the antiparallel diode 15 of the switch on the arm. This is the same switching effect as when an ON signal is given to the gate of the upper switch and an OFF signal is given to the gate of the lower switch. Therefore, the switching signal u can be regarded as 1 (upper ON, lower OFF) equivalently. For the same reason, when the current polarity is negative, u = 0 (lower ON, upper OFF) equivalently.
[0009]
Utilizing this equivalent phenomenon at the time of the gate block, the present invention provides the first means to obtain the current polarity, and the second means obtains the equivalent switching signal as described above. Then, the observer is operated using the equivalent switching signal obtained by the second means as the switching signal input to the observer, and the power supply voltage is estimated.
Therefore, the power supply voltage can be estimated by operating the observer even when the controller is stopped. Thus, when the controller is activated, accurate power supply information can be obtained from the observer, so that problems such as overcurrent and overvoltage can be avoided.
[0010]
【The invention's effect】
As described above, according to the present invention, in the power supply voltage estimation device for a PWM converter that is controlled without a power supply voltage sensor, the power supply voltage can be estimated even when the controller is in a stopped state. Therefore, the controller can obtain correct power supply voltage information at start-up, can start up smoothly without causing overcurrent, overvoltage, etc., and is extremely useful in practical use.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of the present invention.
FIG. 2 is a diagram showing a main circuit configuration of a three-phase voltage type PWM converter.
FIG. 3 is a power supply voltage sensorless control block diagram for explaining a conventional technique.
FIG. 4 is a diagram showing characteristics at the time of a gate block for explaining the principle of the present invention.
[Explanation of symbols]
1 PWM converter 2, 2 'AC power supply 3, 3' AC reactor 4, 4 'DC circuit 5 Converter main circuit 6 CPU arithmetic block 7 DC voltage detector 8 AC current detector 9 Converter control Operation block 10 Power supply voltage observer operation block 11 First means 12 of the present invention Second means 13 of the present invention 13 Power supply voltage observer 14, 14 'Semiconductor switching element 15, 15' Antiparallel diode i AC current u Switching signal

Claims (1)

A PWM converter that converts AC to DC, a controller that causes the AC control amount of the converter to follow a predetermined command value, an AC current detection signal, a DC voltage detection signal, and a switching signal of the converter as inputs, and a power supply voltage A PWM voltage controller that is controlled by a power source voltage sensor and that is controlled by a power source voltage observer for estimating a value , wherein a DC load connected to the DC side of the PWM converter is always connected. In the control device of the converter device, when the controller is in a gate block state before start-up, the polarity of each phase alternating current is determined using a current signal that flows to a direct current load through an antiparallel diode connected to the switching element of the PWM converter. Based on the first means to be obtained and the current polarity obtained by the first means, equivalent switching A power supply voltage estimation device for a PWM converter, characterized in that a second means for obtaining a signal is provided and the equivalent switching signal obtained by the second means is input to a power supply voltage observer to estimate the power supply voltage value .

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