JP4697579B2 - Power converter and phase loss detection method - Google Patents

Description

  The present invention relates to a power conversion device having phase loss detection means and a phase loss detection method thereof.

  In the prior art, the current of each output phase of the power conversion device is measured to determine whether each phase current state is normal, and is determined to be a missing phase.

  Patent Document 1 is an example of a power converter having a conventional phase loss detection means. FIG. 3 shows a conventional technique, which is a power conversion apparatus in the case where the output current of each output phase is detected by a CT that is a current detector. In the figure, P and N represent the positive and negative electrodes of the DC power supply, 21, 22 and 23 are semiconductor switching elements connected to the positive electrode side of the DC power supply, and 27, 28 and 29 are connected in reverse parallel to the respective semiconductor switching elements. Freewheeling diode. Reference numerals 24, 25, and 26 denote semiconductor switching elements connected to the negative side of the DC power source, and reference numerals 30, 31, and 32 denote free-wheeling diodes connected in reverse parallel to the respective semiconductor switching elements. Reference numerals 33, 34, and 35 denote CTs for detecting the currents of the respective output phases. The CT output signals are converted into comparison operation circuits 37, 38, 39, polarity operation circuits 40, 41, 42, and AND circuits 43, 44. , 45 is connected to the judgment operation circuit 46 via the phase detection circuit 46, and the pulse widths of the signals generated by the AND circuits 43, 44, 45 in the vicinity of the zero point passing points of the detected values of CT33, 34, 35 are provided. Measurement is performed, and the determination calculation circuit 46 detects that the measured value exceeds a predetermined value, and an open phase signal is output. Reference numeral 36 denotes a load connected to the power converter. Since the CT current detection circuit and the output line of the power converter that penetrates the CT are insulated from each other inside the CT, there is no need to provide a circuit for insulation between the CT and the arithmetic circuit.

FIG. 4 shows a method of detecting the current of each output phase using the voltage drop of the shunt resistor.
4 omits elements and circuits up to 21 to 32 in FIG. 3, 51, 52, and 53 are shunt resistors for detecting the current of each output phase, and 54 is connected to this power converter. 55, 56, 57 are amplifiers that amplify the voltage between both terminals of each shunt resistor, 58, 59, 60 are reference signals for the output signals of the amplifiers 55, 56, 57 based on the potential of each output phase. An insulated voltage converter 61 for transmitting to the computing unit 61 having a different potential is a computing unit that receives the shunt resistance terminal voltage amplification value output from the insulated voltage converter and performs the phase loss determination.
JP 2001-309669 A (page 8, FIG. 1)

  When performing output phase loss detection using a current detector as in the prior art, it is necessary to detect the current of all output phases, and therefore it is necessary to provide an expensive current detector for every phase. For example, in the CT method of FIG. 3, the CT package size is large and the CT component unit price is expensive. In the shunt resistor method of FIG. 4, the number of parts is large due to the circuit configuration, the mounting area is large, the total component price is expensive, and the insulation voltage When a photocoupler is used as a converter, there is a problem in that the lifetime is short and the total unit price is further increased due to the high cost of parts.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a power conversion device equipped with an output phase loss detection means having a small component mounting area and an inexpensive circuit configuration, and a phase loss detection method. To do.

According to the first aspect of the present invention, an arm having an output terminal as a connection portion of a series connection body in which two parallel connection bodies of a semiconductor switching element and a diode connected in reverse parallel are connected in series is defined as an arm. In a power converter that controls on / off of each semiconductor switching element by connecting two or more of them in parallel between the positive and negative electrodes of a DC power supply, the output that is disconnected from the load depending on the state of the output terminal potential Phase loss detection means for determining phase loss is provided.

According to a second aspect of the present invention, there is provided the power converter according to the first aspect, wherein the phase loss detection means is configured such that the output terminal potential is within one cycle of the output frequency, and the negative potential of the direct current power source and the negative potential of the direct current power source. When no potential lower than the first predetermined potential between the potential lower than the forward voltage drop of the diode appears, it is determined that the output phase is missing.

According to a third aspect of the present invention, there is provided the power converter according to the first aspect, wherein the phase loss detecting means is configured such that the output terminal potential is within one cycle of the output frequency and the positive potential of the direct current power supply When no potential higher than the second predetermined potential between the potential higher than the potential by the forward voltage drop of the diode does not appear, it is determined that the output phase is missing.

According to a fourth aspect of the present invention, there is provided the power converter according to the first aspect, wherein the phase loss detecting means includes a diode, a resistor, a capacitor connected in series to the output terminal, and a comparator for comparing the potential of the capacitor with a predetermined potential. It is made up of.

According to a fifth aspect of the present invention, in the power converter according to the fourth aspect , when the pulse output of the comparator is saturated at a low level or a high level during one cycle of the output frequency, or the pulse output When this happens, it is determined that the output phase has been disconnected from the load .

According to a sixth aspect of the present invention, in the power conversion device according to the first aspect, an open phase detecting means is provided in each phase.

According to the seventh aspect of the present invention, an arm that outputs a connection portion of a series connection body formed by connecting two parallel connection bodies of a semiconductor switching element and a diode connected in antiparallel in series is set as one phase, connected in parallel two or more between the positive electrode and the negative electrode of the DC power source and polyphase, in open phase detection method of a power conversion device for controlling on and off the semiconductor switching devices, the time the output terminal potential of the predetermined, the DC power supply That a potential equal to or lower than a first predetermined voltage between the negative electrode potential and a potential lower than the negative electrode potential of the DC power source by a forward voltage drop of the diode appears, and the output terminal potential is set to a predetermined value. time, the potential of the positive electrode of the DC power source, a second predetermined field which is detected that the voltage or potential appearing between the forward voltage drop by high potential of the diode than the potential of the positive electrode of the DC power source Was determined to be normal, the output terminal potential does not appear the first predetermined voltage potential below, and the load when said first high second predetermined voltage or more potential than the predetermined voltage does not appear It is determined that the output phase is disconnected .

  According to the present invention, it is possible to provide an output phase loss detection means and an output phase loss detection method that have a small component mounting area and an inexpensive circuit configuration.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG.

An explanation will be given from the principle that the output phase loss can be determined from the state of the output terminal potential described in claim 1.
FIG. 2 is a diagram in which one circuit of the output phase of FIG. 3 is extracted. When the semiconductor switching element 2 is in the OFF state, 1 is in the ON state, and the current 14 flows from the P pole of the DC power source positive electrode to the output terminal via 1, when 1 is turned off, the inductance characteristic of the load connected to the output terminal A current 15 flows from the N pole of the DC power supply negative electrode to the output terminal via the reflux diode 4. At this time, looking at the output terminal voltage with reference to the N-pole potential, if the forward voltage drop of the freewheeling diode is Vf, it is lower than the N-pole potential by Vf. When the output is lost and the connection with the load is disconnected, the current 14 does not flow, so the current 15 resulting from the inductance characteristics of the load does not flow, and the output terminal voltage based on the N pole potential is an indefinite voltage or 1 When the ON voltage of the semiconductor switching element is Vceon when ON, the P-pole potential Vp−Vceon and 2 when VON is ON, the potential of Vceon appears. In the case of an open phase, almost no current flows in 1 and 2, so that Vceon is minimal, when 1 is ON, near the P pole potential, and when 2 is ON, a potential near zero appears, and the N pole potential. The phenomenon of lowering is eliminated. If this phenomenon is used, output phase loss can be detected. The first predetermined voltage is set to be smaller than 0 V and larger than −Vf with respect to the N pole potential, and the second predetermined voltage is set to be larger than 0 V and smaller than Vf with the P pole potential as a reference.

Next, a method for detecting output phase loss will be described.
FIG. 1 is a diagram showing an embodiment in which the output terminal voltage is monitored. By connecting the diode 5 included in the output phase loss detector to the output terminal, it is possible to easily detect the state of the output terminal voltage. If the output phase loss detector is a circuit using the N-pole potential as a reference potential, the potential of Vis in the figure also changes as the output terminal potential changes. Hereinafter, three patterns of the relationship between the output terminal potential and the Vis potential will be described.
Pattern 1 is when a current flows through the semiconductor switching element 2 and an N-pole potential appears in the output terminal voltage. When the forward voltage drop of the diode 5 is Vd and the resistance values of the resistors 7 and 8 are R7 and R8, Vis becomes ((Vceon + Vd) · R8 + 5 · R7)) / (R7 + R8).
Pattern 2 is a case where a current flows through the freewheeling diode 4 and a negative potential −Vf corresponding to the forward voltage of the freewheeling diode 4 appears in the output terminal potential. The Vis potential is further returned as compared with the case where the output terminal voltage is the N-pole potential. Since the voltage drops by the forward voltage of the diode 4, Vis becomes ((−Vf + Vd) · R8 + 5 · R7) / (R7 + R8).
Pattern 3 is a case where a current flows through the semiconductor switching element 1 and a P-pole potential appears at the output terminal potential. Since almost no current flows through the resistor 7 due to the reverse voltage characteristics of the diode 5, Vis passes through the resistor 8. The DC power supply voltage is + 5V.
If the three patterns are arranged in the order of the low Vis potential, pattern 2 → pattern 1 → pattern 3 is obtained. If the intermediate potential (R8 · (−Vf + 2 · Vd + Vceon) + 10 · R7) / 2 · (R7 + R8) between pattern 2 and pattern 1 is input to the negative side of comparison 12 and Vis is input to the positive side, The output of the comparator 12 is a low level output, and the output of the comparator 12 at the time of patterns 1 and 3 is a high level output.
Since noise voltage is generated due to di / dt and wiring inductance when the semiconductor switching element is turned on and off, in order to prevent malfunction of phase loss detection, the charging time constant of the resistor 8 and the capacitor 6 is lengthened, and the resistor 7 and the capacitor 6 The noise voltage is filtered by setting a short discharge time constant. When the output current Iout is a sine wave output, the output Vko of the comparator 12 is a pulse output tuned to the output current frequency as shown in the lower diagram of FIG.
When the output Vko of the comparator 12 is always at a high level and saturated even though the power conversion device is in output operation, it can be determined that the output is in an open phase state.

  FIG. 5 is a simulation when the U phase of the three-phase power converter is lost, and FIG. 6 is an enlarged view of the time axis. Vs is a reference voltage input to the negative terminal of the comparator, and 0.5 V is obtained from the power source 5 V of the comparator by resistance division. Vis is a voltage of a capacitor that receives the output voltage of the power converter with a diode having a forward drop Vf of 0.2 V, a resistance of 330Ω, and a capacitor of 0.01 μF. In the vicinity of the center of FIG. 5, the U phase is lost, and the output of the comparator is saturated to the positive side thereafter. Before the phase loss, the output of the comparator becomes a low level within one output cycle, but does not become a low level after the phase loss.

FIG. 7 is a flowchart showing an output phase loss detection method. In FIG. 7, step ST1 measures a predetermined time, and proceeds to the next step ST2 when the predetermined time has elapsed. In step ST2, it is determined whether or not the output voltage has fallen below a predetermined first voltage within a predetermined time. It is normal if it goes down even once. If not, the process proceeds to the next step ST3. In step ST3, it is determined whether or not the output voltage has risen above a second predetermined voltage. It is normal if it goes up even once. If it does not rise, it is determined that the phase is missing.
In this way, output phase loss can be detected by adding a simple circuit without using a current detector.

  The present invention can be applied to applications in which inverters and servos are used, such as machine tools, robots, and general industrial machines.

Examples of the present invention Principle of phase loss detector of the present invention Conventional phase loss detection circuit (Figure relating to Patent Document 1) Conventional phase loss detection circuit The figure which simulated this invention Figure simulating the present invention Flowchart of output phase loss detection method of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Semiconductor switching element 3, 4 Free-wheeling diode 5 Diode 6 Capacitor 7-11 Resistor 12 Comparator 13 Calculator 14 Output current 15 flowing out from P pole through the semiconductor switching element 1 From N pole through free-wheeling diode 4 Flowing output currents 21 to 26 Semiconductor switching elements 27 to 32 Freewheeling diodes 33 to 35 Current detection CT
36 Load machines 37 to 39 Comparison operation circuits 40 to 42 Polarity operation circuits 43 to 45 AND circuit 46 Determination operation circuits 51 to 53 Shunt resistor 54 Load machines 55 to 57 Amplifier 58 to 60 Insulation type voltage converter 61 A / D converter or Pulse train input function built-in calculator

Claims (7)

An arm having a connection part of a series connection body formed by connecting two parallel connection bodies of a semiconductor switching element and an anti-parallel connected diode in series as an output terminal is defined as one phase, and the arm is connected between a positive electrode and a negative electrode of a DC power source. In a power converter for controlling on / off of each semiconductor switching element by connecting two or more in parallel to form a multi-phase,
During the on / off control of the semiconductor switching element of the arm, it is detected whether or not the output terminal and the load are connected according to the state of the output terminal potential. A power conversion device comprising: a phase loss detection unit for determining. The phase loss detection means is configured such that the output terminal potential is between the negative electrode potential of the DC power supply and a potential lower by the forward voltage drop of the diode than the negative electrode potential of the DC power supply within one cycle of the output frequency. The power conversion device according to claim 1, wherein the output phase loss is determined when a potential equal to or lower than the first predetermined potential does not appear. The phase loss detection means is configured such that the output terminal potential is between a positive electrode potential of the DC power supply and a potential higher than the positive electrode potential of the DC power supply by a forward voltage drop within one cycle of the output frequency. second power converter according to claim 1, characterized in that the output phase and determine the constant time does not appear the predetermined potential above the potential of.   2. The power conversion device according to claim 1, wherein the phase loss detection means includes a diode, a resistor, a capacitor connected in series to the output terminal, and a comparator that compares the potential of the capacitor with a predetermined voltage. . The open phase detection means, when when the low level during one period of the pulse outputs output frequency of the comparator is saturated at a high level, or pulse output becomes toothless state, and said output terminal and the load The power conversion device according to claim 4, wherein it is determined that the output phase is not connected .   The power conversion device according to claim 1, wherein the phase loss detection means is provided for each phase. An arm having a connection part of a series connection body formed by connecting two parallel connection bodies of a semiconductor switching element and an anti-parallel connected diode in series as an output terminal is defined as one phase, and the arm is connected between a positive electrode and a negative electrode of a DC power source. In the method for detecting the phase loss of the power converter for controlling the on / off of each semiconductor switching element by connecting two or more in parallel to each other to form a multi-phase,
The output terminal potential is determined to be normal when it is detected that a potential equal to or higher than the first predetermined voltage appears for a predetermined time, and the output terminal potential is the negative potential of the DC power source and the negative polarity of the DC power source. A potential lower than the first predetermined voltage between the potential of the diode and the potential lower than the potential of the diode by the forward voltage drop does not appear, and the potential of the positive electrode of the DC power supply and the potential of the positive electrode of the DC power supply An open phase detection method comprising: determining that an output open phase is not connected between the output terminal and a load when a potential equal to or higher than a second predetermined voltage between potentials higher by a forward voltage drop of the diode does not appear.

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