JP4264782B2 - Voltage detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage detection device for a power converter.
[0002]
[Prior art]
FIG. 7 is a block diagram showing a circuit configuration of this type of conventional technology example (conventional example). In all of the drawings, the same reference numerals denote the same or equivalent members in the conventional example of FIG. 7, in which a DC voltage from a DC power supply voltage Vdc is converted to a three-phase AC voltage by an inverter 1 having an IGBT (Insulated Gate Bipolar Transistor) bridge configuration. For example, one phase (u phase) of the output phase voltage Vu is taken out, and the phase output voltage division from the output terminal 2c of the voltage divider (output voltage detection) 2 connected in series with the resistors 2a and 2b. The voltage Vin is introduced into the comparator circuit 8 (comprised of the comparator 8a and the comparator 8b), and is compared with the third reference voltage Vref3 and the fourth reference voltage Vref4, and compared with the output voltage of each comparator 8a. The output voltage of the converter 8b is applied to the arithmetic circuit 9, where it is added and calculated to detect the calculated value of the output voltage of the inverter 1.
[0003]
By the way, in this conventional example, in order to control the power converter with high accuracy, the output voltage is changed using a technique such as PWM (pulse width modulation). In this case, the output voltage waveform of the power conversion device changes in a pulse shape, and the power conversion device aimed at higher accuracy detects the output voltage changing in the pulse shape and reflects it in the control. . Therefore, the output phase voltage is divided using the voltage divider 2 and converted to a voltage level that can be input to the control circuit (comparison circuit 8 / arithmetic circuit 9), insulated if necessary, and further the signal is transmitted by the control circuit. It must be converted into a form that can be computed.
The simplest implementation of this conventional detection method is to use one comparator circuit (eg 8a or 8b, not shown) and compare it to a reference voltage having a magnitude of 50% of the output phase voltage. In this method, the output voltage is detected by converting it into a pulse. However, this method has a problem that accuracy is not good.
Therefore, as shown in FIG. 7, the output voltage is compared with the third reference voltage Vref3 and the fourth reference voltage Vref4 by the comparison circuit 8 using the comparator 8a and the comparator 8b. The result is input to the arithmetic circuit 9 to perform an addition operation. At this time, by setting the third reference voltage Vref3 to about 10% of the output phase voltage and the fourth reference voltage Vref4 to about 90% of the output phase voltage, the output phase voltage is approximated to a trapezoid, and this is calculated by an arithmetic circuit. A method has been reported that can perform high-speed computation and detect the output phase voltage with higher accuracy.
FIG. 8 is a voltage waveform diagram showing the operation pattern of the conventional example of FIG. 7 as time elapses.
[0004]
[Problems to be solved by the invention]
However, due to the characteristics of the power element used as the power switch and the influence of the drive circuit that drives it, the rise and fall of the output voltage are not linear changes, and show different changes for each type of power switch.
For this reason, the above-described conventional method may include a large error depending on which level of the output voltage is compared and the pulse is output. Furthermore, when this detector is insulated from the inverter main circuit, it is necessary to use an insulating component such as a photocoupler, and the error cannot be ignored.
Further, since the output voltage depends on the DC bus voltage, the amplitude fluctuates. This is because the DC bus voltage fluctuates under the influence of the input voltage fluctuation, the capacitor capacity of the DC bus section, 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.
Therefore, in order to solve the above-described problem of output voltage detection, the present invention integrates the output voltage, outputs a pulse having a pulse length proportional to the magnitude, compares the pulse with the command pulse, and compares the difference between the two. Is provided as a detection voltage to provide a voltage detection device capable of detecting the output voltage of the power conversion device with high accuracy.
[0005]
[Means for Solving the Problems]
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, a voltage divider for dividing a phase output voltage of the power converter, and a voltage divider using the voltage divider. An integration circuit that integrates the phase output voltage, and the pulse width is changed according to the output voltage of the integration circuit, and the pulse is output as a command phase voltage pulse or a pulse synchronized with the phase output voltage. A pulse generation circuit that performs a comparison, a reset circuit that resets an integration circuit when the phase output voltage becomes zero, a pulse output from the pulse generation circuit, and a phase voltage pulse of the command, A voltage detection apparatus comprising: means for deriving a voltage.
As described above, according to the first aspect of the present invention, in the device for detecting the output voltage of the power converter, the error of the temporal voltage change is integrated by integrating the output phase voltage, thereby improving the accuracy. A voltage pulse with a pulse length proportional to the magnitude is set, and the output phase voltage is adjusted to a voltage form that can be calculated by the control circuit at the subsequent stage, and a voltage pulse with a pulse length proportional to the magnitude is compared with a command voltage pulse. The difference between the two is used as a feedback control amount, so that an excellent voltage detection device capable of accurately controlling the output voltage of the power converter is obtained.
[0006]
According to a second aspect of the present invention, there is provided a device for detecting an output voltage of a power converter, wherein a voltage divider for dividing a phase output voltage of the power converter and a phase output voltage divided by the voltage divider are first. A comparison circuit for comparing with the reference voltage, an integration circuit for integrating the difference between the divided phase output voltage and the voltage obtained by level conversion of the output voltage of the comparator, and the output of the comparison circuit for level conversion. A level conversion circuit ;
The output of the integration circuit and the output of the comparison circuit are introduced, and the pulse width is changed according to the sum of the two, and the pulse is output as a command phase voltage pulse or a pulse synchronized with the phase output voltage. And a means for comparing the pulse output from the pulse generation circuit with the commanded phase voltage pulse and deriving a voltage difference between them. Thus, according to the invention of claim 2 of the present invention, the bottleneck of reaching the saturation state of the integrating circuit in the invention of the preceding claim 1 and hindering the calculation is completely eliminated, and the range of the magnitude of the output phase voltage A remarkable effect is observed when the image is significantly enlarged.
[0007]
According to a third aspect of the present invention, in the apparatus for detecting an output voltage of the power converter according to the second aspect, the first reference voltage of the comparison circuit is obtained by dividing the DC bus voltage of the power converter. The voltage detection device according to claim 2, wherein Thus, according to the invention of claim 3 of the present invention, by adopting 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, as the base of the calculation of the detected value, The effectiveness that the output phase voltage of the power converter can be detected more accurately can be exhibited.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
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 / time chart showing a calculation with the passage of time of a voltage waveform of a detected phase voltage.
In FIG. 1, the output phase voltage Vu of the inverter 1 is divided by two voltage dividing resistors 2 a and 2 b to become 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 integrating circuit 4, and the voltage Vin is totally integrated [total area Svin including the inside of the shaded portion and the white 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) pulse having a length of tp] is output from the pulse generation circuit 5 in synchronization with a synchronizing signal 14 of a pulse corresponding to the commanded output phase voltage [hereinafter simply referred to as “command pulse”]. 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 point t22).
Figure 2 shows the operation pattern at this time. An accurate value is derived by changing Δt according to the magnitude (pulse length) of the output phase voltage Vout, and the subtractor 13 inputs the output phase voltage pulse Vout and the command voltage pulse Vc (set value) The difference Δt is detected and applied as a feedback control amount to the base drive of the power converter, so that highly accurate control can be realized.
[0009]
[Second Embodiment]
FIG. 3 is a block diagram showing the circuit configuration of the second embodiment of the present invention, and FIG. 4 is a voltage waveform / time chart showing the calculation over time of the voltage waveform of the detected phase voltage.
The second embodiment is configured as follows. That is, the divided voltage Vin converted to a level suitable for calculation in the voltage detection circuit 10 is input to the subtracter 14 and the comparison circuit 8 in the previous stage of the integration circuit 4. The comparison circuit 8 compares the input divided voltage Vin with the first reference voltage Vref1. When the comparison voltage exceeds the first reference voltage Vref1, the comparison circuit 8 outputs a constant voltage output signal to the pulse generation circuit 5 [FIG. ) And Sth in FIG. 4 (c)].
On the other hand, this output signal Sref1 is also given to the level conversion circuit 7, and further, the signal Sref1 is converted to a level suitable for calculation and then input to the subtractor 14, and the signal Sref1 converted to the previous divided voltage Vin and level. The difference between the two is input to the integrating circuit 4 from the subtractor 14, and the voltage signal integrated by the integrating circuit 4 is given as one input [SΔt in FIG. 4 (c)] of the pulse generating circuit 5 in the next stage. It is done.
In this way, the pulse generation circuit 5 outputs the output phase voltage pulse Vout from the time t41 to the time t45 in FIG. 4 (c), and the difference between the command voltage pulse and the command voltage pulse in the subtractor 13 [FIG. 4 (c). SΔt] is detected as an output voltage error.
[0010]
[Third Embodiment]
FIG. 5 is a block diagram showing the circuit configuration of the third embodiment of the present invention, and FIG. 6 is a voltage waveform / time chart showing the calculation over time of the voltage waveform of the detected phase voltage.
The circuit of the third embodiment shown in FIG. 5 is the same as the second embodiment of FIG. 3, except that the second reference voltage Vref2 of the comparison circuit is made from the DC bus voltage Vdc. It will be possible to cope with sudden fluctuations in the output phase voltage.
Figure 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 contains a large error, but the reference voltage is higher than the DC bus voltage Vdc. In the case of the produced second reference voltage Vref2, the detection error is suppressed to the minimum because it changes in the same manner following the output phase voltage.
Then, the output phase pulse Vout and the command voltage pulse are compared by the subtractor 13, and the control system of the power converter is controlled using the difference between the two as a feedback control amount, thereby realizing further highly accurate control.
[0011]
【The invention's effect】
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, and the accuracy is increased. A voltage pulse with a proportional pulse length is set, and the output phase voltage is adjusted to a voltage form that can be calculated by calculation in the control circuit at the subsequent stage.The voltage pulse with a pulse length proportional to this magnitude is compared with the command voltage pulse, Since the difference is used as the feedback control amount, a voltage detection device that can detect the output voltage of the power converter with high accuracy can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a circuit configuration according to a first embodiment of the present invention. FIG. 2 is a voltage waveform / time chart showing calculation over time of a voltage waveform of a detected phase voltage in FIG.
(a) is the inverter output Au phase voltage
(b) is a pulse generator circuit output voltage pulse diagram
(c) Diagram of integration circuit reset signal
FIG. 3 is a block diagram showing a circuit configuration in the second embodiment of the present invention. FIG. 4 is a voltage waveform of a detected phase voltage in FIG. In the voltage waveform and time chart showing the calculation over time,
(a) is the inverter output Au phase voltage
(b) Diagram of comparator output pulse
(c) is a pulse generator circuit output voltage pulse diagram
FIG. 5D is a block diagram showing a circuit configuration in the third embodiment of the present invention. FIG. 6 is a block diagram showing the circuit waveform in the third embodiment of the present invention. FIG. In the voltage waveform and time chart showing the accompanying calculations,
(a) is the inverter output Au phase voltage
(b) Diagram of comparator output pulse
(c) is a pulse generator circuit output voltage pulse diagram
(d) is a diagram of an integration circuit reset signal. FIG. 7 is a block diagram showing a circuit configuration of a conventional example. FIG. 8 is a voltage waveform and time chart showing calculation over time of the voltage waveform of the detected phase voltage in FIG. In the chart
(a) is the inverter output Au phase voltage
(b) is the calculated output voltage [Explanation of symbols]
1 Inverter 2, 3 Voltage divider
2a, 2b.3a, 3b Resistor 4 Integration circuit 5 Pulse generation circuit 6 Reset circuit 7 Level conversion circuit 8 Comparison circuit
8a, 8b Comparator 9 Arithmetic circuit
10 Voltage detection circuit
11 Command voltage pulse
12 Sync signal
13,14 subtractor
15 Inverter output terminal Vdc DC bus voltage Vin Input voltage Vout after voltage division Output voltage Vout of pulse generator circuit First reference voltage Vref2 Second reference voltage Vref3 Third reference voltage Vref4 Fourth Reference voltage

Claims (3)

In the device for detecting the output voltage of the power converter,
A voltage divider for dividing the 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 a pulse width according to the magnitude of the output voltage of the integration circuit and outputs the pulse as a command phase voltage pulse or a pulse synchronized with the phase output voltage;
A reset circuit that resets the integration circuit when the phase output voltage becomes zero;
A voltage detection apparatus comprising: means for comparing a pulse output from the pulse generation circuit with the commanded phase voltage pulse and deriving a voltage difference between the two. In the device for detecting the output voltage of the power converter,
A voltage divider for dividing the phase output voltage of the power converter;
A comparison circuit for comparing the phase output voltage divided by the voltage divider with the first reference voltage;
An integrating 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 conversion circuit for level conversion of the output of the comparison circuit;
The output of the integration circuit and the output of the comparison circuit are introduced, and the pulse width is changed according to the sum of the two, and the pulse is output as a command phase voltage pulse or a pulse synchronized with the phase output voltage. And a means for comparing the pulse output from the pulse generation circuit with the commanded phase voltage pulse and deriving a voltage difference between them. In the apparatus which detects the output voltage of the power converter device of Claim 2,
The voltage detection device 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.

Images