JP2001091550A - Voltage detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an accurate detecting means by eliminating the inclusion of large errors due to the characteristics of a power element, the effects of a drive circuit, non-linear changes in the rising and falling of an output voltage, etc. SOLUTION: This device 10 for detecting the output voltage of an electric power converting device 1 is provided with a potential divider 2 to divide the potential of the phase output voltage Au of the electric power converting device 1, an integrating circuit 4 to integrate the phase output voltage of which the potential is divided by the potential divider 2, a pulse generating circuit 5 to change pulse width according to the magnitude of the output voltage of the integrating circuit 4 and to output a pulse of changed pulse width as a pulse in synchronization with a phase voltage pulse of an instruction or phase output voltage, a reset circuit 6 to reset the integrating circuit 4 at the time when the phase output voltage becomes zero, and a means 13 to compare the pulse outputted from the pulse generating circuit 5 with the phase voltage pulse 11 of an instruction and to derive the voltage of the difference between both pulses as an output voltage error.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage detector for a power converter.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing a circuit configuration of a conventional example of this kind (conventional example). In all the drawings, the same reference numerals indicate the same or equivalent members.
Is an IGBT (Insulated Gate Bipolar Transi
stor) with an inverter 1 consisting of a bridge configuration
The DC voltage from the DC power supply voltage Vdc is converted into a three-phase AC voltage. For example, a one-phase (u-phase) output phase voltage Vu is taken out from the DC power supply voltage Vdc and a voltage divider (output voltage detection The phase output divided voltage Vin from the second output terminal 2c is introduced into the comparison circuit 8 (comprising the comparator 8a and the comparator 8b), and is compared with the third reference voltage Vref3 and the fourth reference voltage Vref4. The output voltage of the comparator 8a and the output voltage of the comparator 8b are given to the arithmetic circuit 9, where they are added and calculated, and detected as a calculated value of the output voltage of the inverter 1.

In this conventional example, the output voltage is changed using a technique such as PWM (pulse width modulation) in order to control the power converter with high accuracy. In this case, the output voltage waveform of the power conversion device changes in a pulse shape, and the power conversion device aiming at higher accuracy detects the output voltage changing in a pulse shape and reflects it in the control. .
Therefore, the output phase voltage is divided using the voltage divider 2, converted into a voltage level that can be input to the control circuit (comparing circuit 8 / arithmetic circuit 9), and, if necessary, insulated. It must be converted to a form that can be operated on. The simplest way to implement this conventional detection method is to use one comparison circuit (for example, 8a or 8b, not shown) and compare it with a reference voltage having a magnitude of 50% of the output phase voltage. In this method, the output voltage is converted into a pulse and detected. However, this method has a problem that accuracy is not good. Therefore, as shown in FIG.
The output voltage is compared with the third reference voltage Vref3 and the fourth reference voltage Vref4 by the comparison circuit 8 using the two circuits 8b and 8b, and the value is input to the operation circuit 9 to perform the addition operation. At this time, the third reference voltage Vref3 is set to about 10% of the output phase voltage,
By setting the fourth reference voltage Vref4 to be about 90% of the output phase voltage, a trapezoidal approximation of the output phase voltage is performed, and this operation is performed at a high speed by an arithmetic circuit, so that the output phase voltage can be detected with higher accuracy. It has been reported. FIG. 8 is a voltage waveform diagram showing the operation pattern of the conventional example of FIG. 7 over time.

[0004]

However, the rise and fall of the output voltage are not linearly affected by the characteristics of the power element used as the power switch and the drive circuit for driving the power element. Shows different changes for each type. Therefore, in the above-described method of the conventional example, a large error may be included depending on at which level of the output voltage the comparison pulse is output. Furthermore, when insulating this detection unit from the inverter main circuit, it is necessary to use an insulating component such as a photocoupler.
As a result, errors cannot be ignored. Also, the output voltage depends on the DC bus voltage, so that the amplitude varies. This is because the DC bus voltage fluctuates under the influence of the input voltage fluctuation, the capacitance of the DC bus portion, and the load connected to the output. Therefore, if accurate control is to be performed, it is important to accurately detect the output voltage supplied to the load. In order to solve the above-described problem of detecting the output voltage, the present invention integrates the output voltage, outputs a pulse having a pulse length proportional to the output voltage, compares the pulse with the command pulse, and compares the difference between the two. As a detection voltage, and to provide a voltage detection device capable of detecting the output voltage of the power conversion device with high accuracy.

[0005]

In order to achieve the above object, according to a first aspect of the present invention, there is provided an apparatus for detecting an output voltage of a power converter, comprising: a voltage divider for dividing a phase output voltage of the power converter; A voltage divider, an integrating circuit that integrates the phase output voltage divided by the voltage divider, and a pulse width that is changed according to the magnitude of the output voltage of the integrating circuit, and that pulse is a commanded phase voltage pulse or the aforementioned A pulse generation circuit that outputs a pulse synchronized with a phase output voltage, a reset circuit that resets an integration circuit when the phase output voltage becomes zero, a pulse output by the pulse generation circuit, and a phase voltage of the command. Means for comparing a pulse with a pulse to derive a difference voltage between the two. Thus, according to the invention of claim 1 of the present invention, in a device for detecting an output voltage of a power conversion device, an error of a temporal voltage change is integrated by integrating an output phase voltage to improve accuracy, A voltage pulse having a pulse length proportional to the magnitude is set, the output phase voltage is adjusted to a voltage form that can be calculated by a control circuit in the subsequent stage, and a voltage pulse having a pulse length proportional to the magnitude and a command voltage pulse are compared. Is used as the feedback control amount, an excellent effect is obtained that an excellent voltage detection device capable of accurately controlling the output voltage of the power converter can be obtained.

According to a second aspect of the present invention, in a device for detecting an output voltage of a power converter, a voltage divider for dividing a phase output voltage of the power converter and a phase output voltage divided by the voltage divider are provided. Is compared with a first reference voltage; an integration circuit that integrates a difference between the divided phase output voltage and a voltage obtained by level-converting the output voltage of the comparator; A level converter to be converted; an output of the comparison circuit; an integrator for integrating a difference between the output of the level converter from the divided phase output voltage; and an output of the integrator and the comparison circuit. In addition to changing the pulse width according to the magnitude obtained by adding the output and the two,
A pulse generation circuit that outputs the pulse as a command phase voltage pulse or a pulse synchronized with the phase output voltage,
A voltage detecting device, comprising: means for comparing a pulse output from the pulse generation circuit with a phase voltage pulse of the command to derive a voltage difference between the two. Thus, according to the invention of claim 2 of the present invention, the bottleneck that the integration circuit in the above-described invention of claim 1 reaches a saturation state and hinders the operation is completely eliminated, and the range of the magnitude of the output phase voltage is reduced. Is remarkably enlarged, a remarkable effect is observed.

According to a third aspect of the present invention, in the device for detecting the output voltage of the power converter according to the second aspect, the first reference voltage of the comparison circuit is divided by the DC bus voltage of the power converter. 3. The voltage detecting device according to claim 2, wherein the voltage detecting device is obtained by applying pressure. Thus, according to the invention of claim 3 of the present invention, the fluctuation of the DC bus voltage of the power converter, which is one of the main causes of the fluctuation of the output voltage, is adopted as the base of the calculation of the detection value. The effectiveness that the output phase voltage of the power converter can be detected more accurately can be exhibited.

[0008]

Embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram showing a circuit configuration of a first embodiment of the present invention, and FIG. 2 is a voltage waveform showing an arithmetic operation of a detected phase voltage with time.・
It is a time chart. In FIG. 1, an inverter 1
The output phase voltage Vu is divided by two voltage dividing resistors 2a and 2b into a voltage Vin, which is converted to a level that can be input to the detection circuit 10. This voltage Vin is input to the integration circuit 4, and the voltage Vin is totally integrated [total area Svin including the shaded portion and the outlined portion in FIG. 2 (a)]. Next, the fully integrated output phase voltage Svin is input to the pulse generation circuit 5, and a pulse Vout having a pulse length [area Svin = α (proportional constant) × tp (pulse width)] proportional to the voltage Svin [FIG. (b), the pulse having a length of tp] is output from the pulse generation circuit 5 in synchronization with a synchronization signal 14 of a pulse [hereinafter simply referred to as “command pulse”] corresponding to the commanded output phase voltage.
Alternatively, the output voltage pulse Vout having the pulse length tp is output from the pulse generation circuit 5 in synchronization with the output phase voltage Au (time t22). The operation pattern at this time is shown in FIG. Depending on the magnitude (pulse length) of the output phase voltage Vout, Δ
t is changed to derive an accurate value, and the difference Δt between the output phase voltage pulse Vout and the command voltage pulse Vc (set value) input to the subtractor 13 is detected in the subtractor 13, and the power conversion is performed as a feedback control amount. Applied to the base drive of the device, high-precision control can be realized.

[Second Embodiment] FIG. 3 shows a second embodiment of the present invention.
FIG. 4 is a voltage waveform / time chart showing the calculation of the detected voltage waveform of the phase voltage with the lapse of time. The second embodiment is configured as follows. That is, the divided voltage Vin converted to a level suitable for the operation in the voltage detection circuit 10 is supplied to the subtracter 14 in the preceding stage of the integration circuit 4 and the comparison circuit 8
To enter. The comparison circuit 8 compares the divided voltage Vin of the input with the first reference voltage Vref1, and outputs the first reference voltage Vref1.
Exceeds the threshold value, the comparison circuit 8 outputs to the pulse generation circuit 5 an output signal of a constant voltage [Sref1 in FIG. 4 (b), and Sref in FIG. 4 (c).
th]. On the other hand, the output signal Sref1 is also supplied to the level conversion circuit 7, which further converts the signal Sref1 to a level suitable for the arithmetic operation and then inputs the signal Sref1 to the subtracter 14, and the divided voltage Vin and the signal Sref1 converted to the level. The difference between the two is input from the subtractor 14 to the integration circuit 4, and the voltage signal integrated by the integration circuit 4 is given as one input [SΔt in FIG. 4 (c)] of the next stage pulse generation circuit 5. Can be In this way, the pulse generation circuit 5 operates at time t41 in FIG.
From time t45 to output phase voltage pulse Vout,
In the subtractor 13, the difference between the command voltage pulse and the command voltage pulse [FIG.
(SΔt) in (c) is detected as an output voltage error.

[Third Embodiment] FIG. 5 shows a third embodiment of the present invention.
FIG. 6 is a voltage waveform / time chart showing the calculation of the detected voltage waveform of the phase voltage with the lapse of time. The circuit of the third embodiment shown in FIG. 5 is the same as that of the second embodiment of FIG. 3 except that the second reference voltage Vref2 of the comparison circuit is formed from the DC bus voltage Vdc. It becomes possible to cope with a sudden change in the output phase voltage. FIG. 6 shows the operation pattern at this time. In the case of the first reference voltage Vref1 where the second reference voltage Vref2 is constant, the intersection with the output phase voltage changes greatly and the output pulse also includes a large error, but the reference voltage is higher than the DC bus voltage Vdc. In the case of the generated second reference voltage Vref2, the detection error is suppressed to a minimum because the second reference voltage Vref2 changes similarly following the output phase voltage. Then, the output phase pulse Vout and the command voltage pulse are compared by the subtractor 13, and the difference between the two is used as a feedback control amount, so that the control system of the power conversion device is controlled, thereby achieving more accurate control.

[0011]

As described above, according to the present invention, in the means for detecting the output voltage of the power converter, the error of the temporal voltage change is integrated by integrating the output phase voltage to improve the accuracy. , A voltage pulse having a pulse length proportional to the magnitude thereof, and adjusting the output phase voltage to a voltage form that can be computed by a computation in a subsequent control circuit, a voltage pulse having a pulse length proportional to the magnitude and a command voltage pulse. By comparing the difference and using the difference as the feedback control amount, it is possible to provide a voltage detection device capable of detecting the output voltage of the power converter with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration according to a first embodiment of the present invention;

FIGS. 2A and 2B are voltage waveforms and time charts showing calculation of a voltage waveform of a detected phase voltage with time in FIG. 1, wherein FIG. 2A is a diagram of an inverter output Au phase voltage, and FIG. The pulse diagram (c) is the diagram of the integrator reset signal. (D) is the diagram of the output voltage pulse by an arbitrary synchronization signal.

FIG. 3 is a block diagram showing a circuit configuration according to a second embodiment of the present invention;

4A and 4B are voltage waveform and time charts showing the calculation of the voltage waveform of the detected phase voltage over time in FIG. 3, wherein FIG. 4A is a diagram of an inverter output Au phase voltage, and FIG. Figure (c) is a diagram of the output voltage pulse of the pulse generation circuit. (D) is a diagram of the reset signal of the integration circuit.

FIG. 5 is a block diagram showing a circuit configuration according to a third embodiment of the present invention.

FIGS. 6A and 6B are voltage waveform and time charts showing the calculation of the voltage waveform of the detected phase voltage over time in FIG. 5, wherein FIG. 6A is a diagram of an inverter output Au phase voltage, and FIG. Figure (c) is a diagram of the output voltage pulse of the pulse generation circuit. (D) is a diagram of the reset signal of the integration circuit.

FIG. 7 is a block diagram showing a circuit configuration of a conventional example.

8A and 8B are voltage waveforms and time charts showing the calculation of the voltage waveform of the detected phase voltage over time in FIG. 7, wherein FIG. 8A is a diagram of the inverter output Au phase voltage, and FIG. Figure

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter 2-3 Voltage divider 2a, 2b.3a, 3b Resistor 4 Integrator circuit 5 Pulse generator circuit 6 Reset circuit 7 Level conversion circuit 8 Comparison circuit 8a, 8b Comparator 9 Operation circuit 10 Voltage detection circuit 11 Command voltage pulse 12 Synchronization signal 13,14 Subtractor 15 Inverter output terminal Vdc DC bus voltage Vin Input voltage to voltage detector after voltage division Vout Output pulse voltage of pulse generation circuit Vref1 First reference voltage Vref2 Second reference voltage Vref3 Third Reference voltage Vref4 fourth reference voltage

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Eiji Watanabe 2-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu-shi, Fukuoka Prefecture F-term (reference) 2G035 AA26 AB07 AC01 AC15 AD11 AD21 AD23 AD32 AD51 5H007 AA04 AA12 BB02 CB04 CB05 CC23 DA06 DB01 DB02 DC05 EA02

Claims (3)

[Claims] 1. An apparatus for detecting an output voltage of a power converter, comprising: a voltage divider for dividing a phase output voltage of the power converter; an integrating circuit for integrating the phase output voltage divided by the voltage divider; A pulse generation circuit that changes the pulse width according to the magnitude of the output voltage of the integration circuit and outputs the pulse as a commanded phase voltage pulse or a pulse synchronized with the phase output voltage, and the phase output voltage is reduced to zero. A reset circuit that resets the integration circuit when the pulse signal is output, and a unit that compares a pulse output from the pulse generation circuit with the phase voltage pulse of the command and derives a difference voltage between the two. Voltage detector. 2. A device for detecting an output voltage of a power converter, comprising: a voltage divider for dividing a phase output voltage of the power converter, and comparing the phase output voltage divided by the voltage divider with a first reference voltage. A comparing circuit that integrates a difference between the divided phase output voltage and a voltage obtained by level-converting the output voltage of the comparator; and a level converter that converts the output of the comparing circuit into a level. An integrator for integrating the difference between the output of the comparison circuit and the output of the level converter from the divided phase output voltage; introducing the output of the integrator and the output of the comparison circuit; A pulse generation circuit that changes the pulse width according to the magnitude of the pulse, and outputs the pulse as a commanded phase voltage pulse or a pulse synchronized with the phase output voltage, and a pulse output from the pulse generation circuit. Voltage detecting apparatus characterized by comparing the phase voltage pulse of the command and means for deriving a difference between the voltage of both. 3. The apparatus for detecting an output voltage of a power converter according to claim 2, wherein the first reference voltage of the comparison circuit is obtained by dividing a DC bus voltage of the power converter. The voltage detection device according to claim 2.