JP2004187472A - Power converter and its open phase detecting program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for detecting the open phase of a power converter stably by an arrangement of low cost. <P>SOLUTION: A smoothed voltage is detected and two voltage maximal points or voltage minimal points located at adjacent time-positions are determined from the difference of the detected voltage between first and second moments in time and a difference between second and third moments in time. A period or a frequency of a voltage ripple is then determined based on a time interval between two voltage maximal points or voltage minimal points. An open phase is determined by comparing that a period or a frequency with a preset reference period or frequency. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power converter that performs full-wave rectification and smoothing of AC power of a plurality of phases and supplies the smoothed AC power to a load side, and more particularly to a technique of detecting an open phase.
[0002]
[Prior art]
Conventional techniques for detecting phase loss are described in, for example, JP-A-11-215686 (Patent Document 1), JP-A-11-206003 (Patent Document 2), and JP-A-6-276665 (Patent Document 3). There is. Japanese Patent Application Laid-Open No. H11-215686 discloses a configuration in which the amplitude of a ripple voltage in the voltage division of a voltage across a smoothing capacitor connected to the subsequent stage of a forward converter (converter) is detected, and phase loss detection is performed based on the amplitude. Japanese Unexamined Patent Application Publication No. 11-206003 discloses detecting a voltage across an electrolytic capacitor of an inverter device, extracting a ripple component of the detected voltage by a high-pass filter, and measuring a frequency or a repetition period of the ripple component. In JP-A-6-276665, as a frequency protection relay for protecting a power system, current or voltage of a power system is sampled on a predetermined sampling time axis and digitally quantized. The digital data is stored in a time-series data storage circuit while maintaining the time series, and the absolute value of the stored digital data is stored. The sampling time at which the maximum data of the absolute value data is stored is determined, and data having a time-series relationship required for the operation is extracted from the time-series data storage circuit based on the determined sampling time. Is substituted into a predetermined arithmetic expression to calculate the frequency of the power system and detect an open phase.
[0003]
[Patent Document 1]
JP-A-11-215686 [Patent Document 2]
JP-A-11-206003 [Patent Document 3]
JP-A-6-276665
[Problems to be solved by the invention]
Generally, in a power converter, the power supply voltage is often changed in a wide range, for example, about 380 V to 480 V. In the technique described in Japanese Patent Application Laid-Open No. H11-215686, the amplitude of the ripple voltage fluctuates due to a change in the power supply voltage. This may make it difficult to perform stable open phase detection. In the technique described in Japanese Patent Application Laid-Open No. H11-206003, a high-pass filter or the like is required for extracting a ripple component. Further, the technology described in Japanese Patent Application Laid-Open No. 6-276665 requires a digital data storage circuit and a time-series storage circuit, and the past digital data stored in the time-series data storage circuit in a time-series manner according to a predetermined standard. Need to search.
The problems of the present invention are: (1) to enable stable open-phase detection even when the power supply voltage changes greatly; and (2) to cope with low cost by sharing components such as a microcomputer. And so on.
An object of the present invention is to provide a technique capable of solving such a problem.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, in a power converter or a program for detecting an open phase used in the power converter, basically, ripples based on a voltage difference at the time of sampling of a voltage smoothed after full-wave rectification. A cycle or frequency is obtained, and a phase loss is detected from a difference between the frequency at a normal time and a frequency at a phase loss. That is, two voltage maximum points where the voltage difference between the voltage at the first time point and the voltage at the second time point is positive, and the voltage difference between the voltage at the second time point and the voltage at the third time point is negative. Or two voltage minima where the voltage difference between the voltage at the first time and the voltage at the second time is negative and the voltage difference between the voltage at the second time and the voltage at the third time is positive. A point is determined at a time position adjacent to each other, a period or a frequency of a voltage ripple having a period between the two voltage maximum points or the time between the two voltage minimum points as one period is determined, and the period or the frequency is determined. Is compared with a preset reference cycle or reference frequency to determine whether or not the phase is missing. In addition, the determination result is displayed. Specifically, as the power converter, (1) voltage detecting means for detecting a voltage of the smoothed power, a voltage difference between the detected time and a first time point and a second time point, and From the voltage difference between the second time point and the third time point, two voltage maximum points or voltage minimum points at time positions adjacent to each other are obtained, and between the two voltage maximum points or the two voltage minimum points. Calculating means for determining the phase or frequency of the voltage ripple based on the time between the two, and comparing the frequency with a preset reference cycle or reference frequency to determine open phase; and means for displaying the determination result. Configuration. (2) a converter for full-wave rectification of AC power, a smoothing means for smoothing the full-wave rectified power using a smoothing capacitor, a voltage detection means for detecting a voltage across the smoothing capacitor, and The voltage includes a first voltage difference as a difference between a voltage value at a first time point and a voltage value at a second time point, and a second voltage value as a difference between the voltage value at the second time point and the voltage value at a third time point. Means for determining the two voltage differences, wherein the first voltage difference is positive and the second voltage difference is negative, or two voltage maxima, or the first voltage difference is negative and the second voltage difference is negative. Means for determining two voltage minimum points at which the voltage difference is positive at time positions adjacent to each other; and determining the period of the voltage ripple or the period of the voltage ripple based on the time between the two voltage maximum points or between the two voltage minimum points. Means for determining the frequency, and determining the determined cycle or frequency by a preset reference cycle or reference Calculation means comprising a means for determining a phase loss as compared to the wave number, a configuration and means for displaying the determination result. Further, (3) the computer calculates the voltage difference between the first time point and the second time point of the smoothed voltage and the voltage difference between the second time point and the third time point as a program for detecting an open phase. A first procedure and two voltage maxima in which the voltage difference between the first time point and the second time point in the first procedure is positive and the voltage difference between the second time point and the third time point is negative. A point or two voltage minimum points where the voltage difference between the first time point and the second time point is negative and the voltage difference between the second time point and the third time point is positive are located at time positions adjacent to each other. A second procedure for obtaining, a third procedure for obtaining the period or frequency of the voltage ripple from the time between the two voltage maximum points or the time between the two voltage minimum points, and A fourth procedure for determining a phase loss by comparing with a preset reference cycle or reference frequency, and a result of the determination A configuration to execute a fifth step of performing a display instruction.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration example of a power conversion device as an embodiment of the present invention.
In FIG. 1, 1 is a polyphase AC power supply, 2 is a converter for full-wave rectification of the polyphase AC power, 3 is a smoothing capacitor for smoothing the full-wave rectified power, and 4 is a smoothed DC power. , An inverter for supplying a voltage to a load, 5 an electric motor as a load device, 6 a voltage detecting circuit as voltage detecting means for detecting a voltage _VDC across the smoothing capacitor 3, 8, 9 and 10 for voltage dividing A resistor, 11 is a voltage detection signal line, 12 is a reference potential line, 7 is a calculating means for calculating the frequency of the voltage ripple based on the voltage difference at the time of sampling of the detected voltage signal and determining the phase loss from the calculation result. Arithmetic processing device. The voltage detection circuit 6 is directly connected to a DC bus to which the smoothing capacitor 6 is connected. The detected voltage signal is divided by the voltage dividing resistors 8, 9, and 10 in the voltage detection circuit 6, and is input to the arithmetic processing device 7 through the voltage detection signal line 11 and the reference potential line 12. The signal (analog signal) input to the arithmetic processing unit 7 is A / D converted and converted into a digital signal inside the arithmetic processing unit 7. The arithmetic processing device 7 performs driving of the inverter 4 and information processing therefor by an internal program, and the voltage signal is information for driving the inverter 4. In addition, the arithmetic processing unit 7 processes the signal from the voltage detection circuit 6 at a higher speed than the cycle of the commercial power supply. The arithmetic processing unit 7 is constituted by a microcomputer or the like.
[0007]
FIG. 2 shows an example of a DC voltage waveform when the electric motor 5 as a load device is operated during normal power reception. The amplitude of the ripple voltage is small, and its cycle is t. The voltage waveform divided by the voltage dividing resistors 8, 9, and 10 of the voltage detection circuit 6 is transmitted to the arithmetic processing device 7 and processed.
[0008]
FIG. 3 shows an example of a DC voltage waveform when the electric motor 5 as a load device is operating at the time of phase loss power reception. In the case of three-phase AC power reception, if one phase is lost, single-phase power reception is performed, resulting in a large ripple waveform. The cycle at this time is 3t.
[0009]
4 and 5 are explanatory diagrams of the arithmetic processing device 7. FIG. FIG. 4 is an explanatory diagram of sampling of a voltage signal input from the voltage detection circuit 6, and FIG. 5 is a diagram illustrating an example of a procedure of an open phase detection process by an internally stored open phase detection program. When the execution of the open phase detection program is started, (1) the voltage signal is sampled as shown in FIG. 4, the first time point t _n−2 , the second time point t _n−1 , and the third time point t _n−1 , per time point _{t n,} each of the voltage values _{V n-2, V n-1,} the voltage difference between the _{V n} read, the voltage value _{V n-2} and the voltage value _{V n-1 ΔV n-1} (= V n- ₁₋ V _n−2 ) and a voltage difference ΔV _n between the voltage value V _n and the voltage value V _n−1 (= V _n −V _n−1 ) are calculated (step S51). (2) Based on the calculation result of step S51, whether the voltage difference ΔV _n−1 or ΔV _n is positive or negative is determined. If ΔV _n−1 is positive and ΔV _n is negative, the second time point t _n− It is determined that the voltage value at or near ₁ has reached a local maximum, otherwise, ΔV _n−1 and ΔV _n are both positive, ΔV _n−1 and ΔV _n are both negative, or ΔV _{n -1} negative, if [Delta] V _n is positive, it is determined that the voltage value at the time of the second time point t _n-1 or the vicinity thereof has not reached the maximum. When it is determined that the voltage has reached the maximum point, the voltage maximum point is set as the first voltage maximum point, the time point (second time point t _n−1 ) is stored, and the time point is set as the starting point. While counting, the sampling, the voltage difference calculation, and the voltage difference determination are further performed to obtain the second voltage maximum point and the time point (step S52). (3) If it is determined in step S52 that the voltage has not reached the maximum point, the counting of the time count is started (step S53). (4) When the two voltage maximum points and the time point are obtained in the step S52, the frequency f is converted into a frequency f in which the integrated value of the time counted between the two voltage maximum points is one cycle, This is set as the frequency of the ripple voltage (step S54). (5) The frequency f is compared with an upper limit frequency F which is a reference frequency stored in advance and is an open phase state when the open phase is determined (step S56). ). (6) When the relationship of f> F is satisfied, it is determined that there is no phase loss in a normal state, the time count integration is reset, and the process returns to step S51 (step S57). (7) If the relationship of f> F is not satisfied, it is determined that the phase is open (step S58). (8) A warning is displayed by the display means (step S59), and the program ends. In the present embodiment, the operation of the power converter is continued even after the execution of step S58, and the operation of the electric motor 5 is continued. Thereby, it is possible to prevent the influence of the careless shutdown of the power conversion device on other devices. Further, after the operation is stopped, when the operation is to be started again in the open phase state, a warning is displayed and the restart of the operation is prevented. Thereby, the safety of the power conversion device and the load device and the safety of the user are ensured. Further, the operation from step S51 to step S58 may be repeated a plurality of times, and the open phase state may be determined based on the number of times that the open phase state is determined. In this case, the accuracy of the phase loss detection can be improved.
[0010]
In the above embodiment, the arithmetic processing unit 7 determines two voltage maximum points from the voltage difference at the time of voltage sampling, and performs the phase loss detection based on the calculation result of the frequency of the voltage ripple based on this. There is also a method in which two voltage minimum points are obtained from a voltage difference at the time of voltage sampling, and a phase loss is detected from a calculation result of a frequency of a voltage ripple based on the two minimum points. In this case, the missing phase detection program in the arithmetic processing unit 7 executes, for example, the following missing phase detection processing procedure. That is, (1) per voltage signal, to sample as shown in FIG. 4, the first time point _{t n-2,} the second time point _{t n-1,} per third time point _{t n,} each of the voltage values _{V n -2,} reads the _{V n-1, V n,} a voltage difference [Delta] V _n-1 between the voltage value _{V n-2} and the voltage value _{V n-1} and _{(= V n-1 -V n} -2), the voltage value V _n and the voltage difference [Delta] V _n between the voltage value _{V n-1 (= V n} -V n-1) to calculate a. (2) by the calculation result of the (1), the voltage difference [Delta] V _n-1, for each of the [Delta] V _n, determines the sign, if [Delta] V _n-1 is negative, [Delta] V _n is positive, the second time point t It is determined that the voltage value at or near the time point _n−1 has reached the minimum value, otherwise, ΔV _n−1 and ΔV _n are both negative, ΔV _n−1 and ΔV _n are both positive, Alternatively, when ΔV _n−1 is positive and ΔV _n is negative, it is determined that the voltage value at or near the second time point t _n−1 has not reached the minimum value. If it is determined that the voltage has reached the minimum point, the voltage minimum point is set as the first voltage minimum point, the time point (second time point t _n-1 ) is stored, and the time point is used as the starting point. While counting, the sampling, the voltage difference calculation, and the voltage difference determination are further performed to obtain the second voltage minimum point and the time point. (3) In the above (2), when it is determined that the voltage has not reached the minimum point, integration of the time count is started. (4) When the two voltage minimum points and the time point are obtained in the above (2), the frequency is converted into a frequency f having one cycle as an integrated value of the time between the two voltage minimum points counted by time. , And this is the frequency of the ripple voltage. (5) The frequency f is compared with an upper limit frequency F, which is a reference frequency stored in advance and used for determining an open phase and is assumed to be in an open phase state, to determine whether or not the open phase state is present. (6) If the relationship of f> F is satisfied, it is determined that there is no phase loss in a normal state, the time count integration is reset, and the process returns to (1). (7) If the relation of f> F is not satisfied, it is determined that the phase is open. (8) A warning is displayed by the display means, and the program ends.
Also in the above case, the operations from (1) to (6) may be repeated a plurality of times, and the open phase state may be determined based on the number of times the open phase state is determined.
[0011]
Further, in each of the embodiments for obtaining the two voltage maximum points and for obtaining the voltage minimum points, the frequency f is obtained by calculation, and this is used as the reference frequency for phase loss determination stored in advance. Although it is described that the phase loss detection is performed by comparing with the upper limit reference frequency F when the phase loss state is assumed, the present invention is not limited to this. When the two voltage minimum points and the time point are obtained, the integrated value of the time counted between the two voltage maximum points or the time between the two voltage minimum points is defined as one cycle, and this is used for phase loss determination. The phase loss detection may be performed by comparing with a reference cycle T (= 1 / F).
[0012]
According to the above-described embodiment, even when the power supply voltage changes greatly, stable open-phase detection can be performed without being affected by amplitude fluctuations. Parts such as microcomputers can be shared and low cost can be accommodated. It is also possible to improve the accuracy of phase loss detection.
[0013]
【The invention's effect】
According to the present invention, stable open-phase detection can be realized with a low-cost configuration.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of a power conversion device as an embodiment of the present invention.
FIG. 2 is a diagram showing a full-wave rectified waveform.
FIG. 3 is a diagram showing a DC voltage waveform in an open phase state.
FIG. 4 is an explanatory diagram of a voltage signal sampling operation.
FIG. 5 is a diagram showing an example of a procedure of an open phase detection process according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Polyphase AC power supply, 2 ... Converter, 3 ... Smoothing capacitor, 4 ... Inverter, 5 ... Electric motor, 6 ... Voltage detection circuit, 7 ... Arithmetic processing unit, 8, 9, 10 ... Resistor for voltage division, 11 ... Voltage detection Signal line, 12 ... Reference potential line.

Claims (5)

In a power converter that supplies full-wave rectified and smoothed AC power of multiple phases to the load side,
Voltage detection means for detecting the voltage of the smoothed power,
From the voltage difference between the first time point and the second time point of the detected voltage and the voltage difference between the second time point and the third time point, two voltage maximum points at time positions adjacent to each other or A voltage minimum point is obtained, a period or frequency of a voltage ripple is obtained based on a time between the two voltage maximum points or a time between the two voltage minimum points, and the period or the frequency is determined by a predetermined reference period or reference. Calculating means for determining an open phase by comparing with the frequency;
Means for displaying the determination result;
A power converter characterized by comprising: In a power converter that supplies full-wave rectified and smoothed AC power of multiple phases to the load side,
A converter for full-wave rectification of AC power,
Smoothing means for smoothing the full-wave rectified power using a smoothing capacitor;
Voltage detection means for detecting the voltage across the smoothing capacitor;
For the detected voltage, a first voltage difference as a difference between the voltage value at the first time point and the voltage value at the second time point, and a difference between the voltage value at the second time point and the voltage value at the third time point Means for determining the second voltage difference as the first voltage difference, and two voltage maximum points where the first voltage difference is positive and the second voltage difference is negative, or the first voltage difference is negative, Means for determining two voltage minimum points at which the second voltage difference is positive at positions adjacent to each other; and determining a voltage ripple based on the time between the two voltage maximum points or the time between the two voltage minimum points. Means for determining a cycle or frequency, and arithmetic means comprising means for comparing the determined cycle or frequency with a preset reference cycle or reference frequency to determine phase loss,
Means for displaying the determination result;
A power converter characterized by comprising: The calculating means starts time counting from the time when the first voltage maximum point of the two voltage maximum points or the first voltage minimum point of the two voltage minimum points is detected. The power converter according to claim 1 or 2, wherein a time between two voltage maximum points or a time between the two voltage minimum points is obtained. The power converter according to claim 1, wherein the voltage detection unit is configured to divide a voltage. An open-phase detection program used in a power converter that supplies full-wave rectified and smoothed multi-phase AC power to a load side,
On the computer,
A first procedure for obtaining a voltage difference between the first time point and the second time point of the smoothed voltage and a voltage difference between the second time point and the third time point;
Two voltage maximum points where the voltage difference between the first time point and the second time point in the first procedure is positive, and the voltage difference between the second time point and the third time point is negative, or A second procedure for determining two voltage minimum points at which the voltage difference between the first time point and the second time point is negative and the voltage difference between the second time point and the third time point is positive at time positions adjacent to each other; ,
A third procedure for determining the period or frequency of the voltage ripple from the time between the two voltage maximum points or the time between the two voltage minimum points;
A fourth procedure of comparing the determined cycle or frequency with a preset reference cycle or frequency to determine phase loss;
A fifth procedure for instructing display of the determination result,
The program for detecting an open phase, wherein the program is executed.

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