JP2015192578A - Voltage detection device and voltage/current detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage detection device or the like capable of estimating an input voltage and an input current of an inverter circuit as alternative means of a voltage detection section and a current detection section at an input side of the inverter circuit.SOLUTION: The voltage detection device detects a voltage in an inverter circuit 10 where, in accordance with control of switching elements Q1-Q6, a DC input voltage Vin and an input current Iin are converted into AC output voltages Vu, Vv and Vw and output currents Iu, Iv and Iw and supplied to a load 12. Control states of the plurality of switching elements Q1-Q6 are determined on the basis of voltages of a plurality of wiring Lu, Lv and Lw connected between an output side of the inverter 10 and the load 12, a DC voltage value that is a difference between a high potential and a low potential in the voltages of the plurality of wiring Lu, Lv and Lw is calculated in accordance with a determination result, and a voltage estimate V1 of the input voltage Vin can be estimated on the basis of the DC voltage value.

Description

  The present invention relates to a voltage detection device and a voltage / current detection device added to a power conversion device including an inverter circuit that converts DC input power into AC output power and supplies the output power to a load.

  Generally, when an AC motor is driven, a power conversion device including an inverter circuit that converts DC input power into AC output power is used. For example, when driving a motor mounted on an electric vehicle or a fuel cell vehicle, a configuration in which a battery power source is directly converted into AC power by an inverter circuit, or a DC voltage is boosted by a DC-DC converter and then an inverter circuit is used. The structure etc. which convert into an alternating voltage are assumed.

  A system to which a conventional power converter is applied generally has a function of detecting DC voltage and current on the input side of the inverter circuit for various purposes such as appropriate control according to the driving state of the load. It is. For example, Patent Documents 1 and 2 disclose a configuration in which the DC voltage and current detected by the voltage detection unit and the current detection unit on the input side of the inverter circuit are controlled to have predetermined values. Alternatively, Patent Document 3 discloses a configuration in which an input-side current is estimated by a current estimation unit provided in a control unit that controls an inverter circuit. On the other hand, Patent Document 4 discloses a configuration in which a current detection unit is provided on the output side of an inverter circuit, and input power is estimated from a current value obtained by the current detection unit.

JP-A-2005-251474 JP 2012-106581 A International Publication No. 2013/125320 JP 2012-39883 A

  In the conventional power converter, since an operation for supplying a large amount of power to the load and a state in which internal heat generation increases are expected, it is desirable to take sufficient countermeasures to improve reliability. For example, when the above-described voltage detection unit or current detection unit built in the power conversion device fails, a situation in which the drive of the load cannot be normally controlled is caused. With regard to such countermeasures, for example, Patent Document 2 discloses that three voltage detection units for monitoring the DC voltage of the battery are provided, and the DC voltage is detected by using the downstream voltage detection unit when the upstream voltage detection unit fails. A technique for detecting voltage is shown. Patent Document 1 discloses a method of performing control using an output obtained by the other detection unit that has not failed when one of the voltage detection unit and the current detection unit fails.

  However, the configurations of Patent Documents 1 and 2 only obtain one of the voltage and current on the input side of the inverter circuit by some alternative means when one of the voltage detection unit and the current detection unit fails. In addition, since the configuration of Patent Document 3 estimates the power on the input side of the inverter circuit, it is necessary to devise a method for extracting the current on the input side from the estimated value in order to substitute for the failure of the current detection unit. become. Also, it is clear that the voltage and current on the input side cannot be estimated independently for the configuration of Patent Document 4. Thus, in the conventional power conversion device, even if both the voltage detection unit and the current detection unit fail on the input side of the inverter circuit, both voltage and current are estimated independently as an alternative. Therefore, there was a problem in ensuring the reliability of the power conversion device.

  The present invention has been made to solve these problems, and provides an alternative means for the voltage detection unit and the current detection unit on the input side of the inverter circuit, while minimizing additional devices and inputting the inverter circuit. An object of the present invention is to provide a voltage detection device and the like that can estimate a voltage and an input current independently.

  In order to solve the above-described problem, the voltage detection device of the present invention converts a DC input voltage (Vin) and an input current (Iin) into an AC output voltage (Vu) according to control of a plurality of switching elements (Q1 to Q6). , Vv, Vw) and an output current (Iu, Iv, Iw) and a voltage detecting device for detecting a voltage in the inverter circuit (10) supplied to the load (12), the output side of the inverter circuit being A control state of the plurality of switching elements is determined based on voltages of a plurality of wirings (Lu, Lv, Lw) connected between the loads, and a high of the voltages of the plurality of wirings is determined according to a determination result. A DC voltage value that is a difference between a potential and a low potential is obtained, and the input voltage can be estimated based on the DC voltage value.

  According to the voltage detection device of the present invention, the control state of the plurality of switching elements in the inverter circuit is determined based on the voltages of the plurality of wirings connected between the inverter circuit and the load, and a plurality of the determination results indicate the plurality of switching elements. Since each voltage of the wiring is converted into a DC voltage value, an estimated value of the input voltage of the inverter circuit can be obtained using this DC voltage value. Therefore, without providing a complicated and expensive device, an alternative means when the voltage detection unit on the input side of the inverter circuit fails can be provided, and the reliability of the power converter can be improved.

  The present invention can be realized by various configurations. For example, it is possible to provide a control state determination unit that outputs a plurality of determination signals indicating the timing at which each of the plurality of switching elements is conducted based on the voltages of the plurality of wirings. In this case, there is further provided a voltage monitoring unit that selects a combination of a high potential and a low potential from a plurality of wiring voltages based on a plurality of determination signals and subtracts the low potential from the high potential to output a DC voltage value. May be.

  It is effective to apply the present invention to a configuration in which an inverter circuit drives a load with three-phase AC. In this case, the plurality of wirings for supplying the output voltage and output current of the inverter circuit to the load are configured by three wirings, and the three-phase AC u-phase, v-phase, and w-phase voltages and currents are respectively connected to the three wirings. What is necessary is just to comprise so that it may supply to load via.

  In order to solve the above problems, the voltage / current detection device according to the present invention converts a DC input voltage and an input current into an AC output voltage and an output current and supplies them to a load in accordance with control of a plurality of switching elements. A voltage / current detection device for detecting voltage and current in an inverter circuit, wherein the control state of the plurality of switching elements is determined based on voltages of a plurality of wirings connected between the output side of the inverter circuit and the load. Determining a DC voltage value that is a difference between a high potential and a low potential among the voltages of the plurality of wirings according to the determination result, and a current detection unit that detects the current of the determination results and the plurality of wirings Based on the current detection signal, a direct current value obtained by converting the currents of the plurality of wirings into direct current is obtained, and the input voltage and the input current are calculated based on the direct current voltage value and the direct current value. It is characterized in that it is possible to estimate the.

  According to the voltage / current detection apparatus of the present invention, it is possible to obtain an estimated value of the input current of the inverter circuit using the obtained DC current value in addition to the estimated value of the input voltage of the inverter circuit. Even if both the voltage detection unit and the current detection unit on the input side fail, an alternative means can be provided. A control state determination unit that outputs a plurality of determination signals indicating the timing at which each of the plurality of switching elements is conducted based on the voltages of the plurality of wirings, and a plurality of current detection signals based on the plurality of determination signals You may further provide the current monitor part which outputs the sum of the current value of the direction which flows into a load, or the direction which flows out of a load as a direct current value.

  According to the present invention, even if a failure such as a failure occurs in the voltage detection unit and the current detection unit provided on the input side of the inverter circuit that drives the load, the alternative means provided on the output side of the inverter circuit is effectively used. It is possible to obtain the estimated values of the input voltage and input current of the inverter circuit without using a complicated and expensive device, and the reliability of the power converter can be improved.

It is a figure which shows the structure of the principal part of a power converter device. It is a block diagram which shows the function of an input voltage current estimation part. It is a figure which shows the circuit example of a control state determination part. It is a figure which shows the truth table and switching state in the circuit example of FIG. It is a figure which shows the example of the waveform at the time of operation | movement of a control state determination part. It is a figure which shows the structural example of a voltage monitor part. It is a figure which shows the waveform of a three-phase voltage and a three-phase electric current when a motor is driven on the conditions similar to FIG. It is a figure which shows the structural example of a current monitor part. It is a figure which shows the relationship between the simulation waveform of the voltage of a three-phase alternating current, and the switching control of an inverter circuit. FIG. 10 is a diagram illustrating a correspondence relationship between a control signal and a determination signal in relation to the simulation waveform of FIG. 9. It is a figure which shows the correspondence of the positive / negative DC voltage of the input side of an inverter circuit, the voltage of u phase supplied to a motor, a control signal, and a determination signal. It is a figure which shows the correspondence of the positive / negative DC voltage by the side of the input of an inverter circuit, the v phase voltage supplied to a motor, a control signal, and a determination signal. It is a figure which shows the correspondence of the positive / negative DC voltage of the input side of an inverter circuit, the w-phase voltage supplied to a motor, a control signal, and a determination signal. It is a figure which shows the correspondence of the input current of an inverter circuit, the u-phase current supplied to a motor, a control signal, and a determination signal. It is a figure which shows the correspondence of the input current of an inverter circuit, the v-phase current supplied to a motor, a control signal, and a determination signal. It is a figure which shows the correspondence of the input current of an inverter circuit, the w-phase current supplied to a motor, a control signal, and a determination signal. FIG. 17 is a diagram showing, in a long time range, a simulation waveform of a three-phase current and a simulation waveform of an input current of an inverter circuit in a long time range in relation to FIGS. 14 to 16. It is a figure which shows the correspondence of the input current of an inverter circuit, the sum of the electric current of v phase and w phase supplied to a motor, a control signal, and a determination signal. It is a figure which shows the correspondence of the input current of an inverter circuit, the sum of the current of w phase and u phase supplied to a motor, a control signal, and a determination signal. It is a figure which shows the correspondence of the input current of an inverter circuit, the sum of the current of u phase and v phase supplied to a motor, a control signal, and a determination signal. In relation to FIGS. 18 to 20, each simulation waveform of the sum of the three-phase currents and the simulation waveform of the input current of the inverter circuit are overlapped in a long time range.

  Preferred embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below are examples of forms to which the present invention is applied, and the present invention is not limited by the contents of the present embodiments.

  FIG. 1 is a diagram illustrating a configuration of a main part of a power conversion device according to an embodiment to which the voltage / current detection device of the present invention is applied. FIG. 1 illustrates a range including the inverter circuit 10, the current detection unit 11, the motor 12, the voltage dividing circuit 13, and the input voltage / current estimation unit 14 in the power conversion device of the present embodiment. An actual power converter includes various components such as a DC power source or a battery, various circuits (a booster circuit, a DC / DC converter, etc.) before the inverter circuit 10 and a control circuit. In FIG. 1, this is omitted.

  In the configuration of FIG. 1, the inverter circuit 10 includes six switching elements Q1, Q2, Q3, Q4, Q5, and Q6, and converts DC input power into three-phase AC output power. As the switching elements Q1 to Q6, for example, an IGBT (Insulated Gate Bipolar Transistor) is used. The input side of the inverter circuit 10 is connected to a wiring La to which a positive DC voltage Vd + is applied and a wiring Lb to which a negative DC voltage Vd− is applied. As a result, a DC input voltage Vin (Vin = (Vd +) − (Vd−)) is generated between the pair of wirings La and Lb. For example, if Vd + = 100V and Vd − = − 100V, Vin = 200V. In addition, an input current Iin corresponding to the input voltage Vin flows from one wiring La to the other wiring Lb via the inverter circuit 10 and the motor 12 as a load.

  In the inverter circuit 10, one end of each of the three switching elements Q1, Q2, and Q3 is connected to the wiring La, and one end of each of the three switching elements Q4, Q5, and Q6 is connected to the wiring Lb ( Hereinafter, the switching elements Q1 to Q3 on the plus side and the switching elements Q4 to Q6 on the minus side may be called). Further, a pair of switching elements Q1 and Q4 are connected in series, and the connection point between them is connected to the wiring Lu. Similarly, a pair of switching elements Q2 and Q5 are connected in series, a connection point between them is connected to the wiring Lv, a pair of switching elements Q3 and Q6 are connected in series, and a connection point between them is connected to the wiring Lw. ing. Three-phase (u-phase, v-phase, and w-phase) voltages Vu, Vv, and Vw that are output from the inverter circuit 10 are generated on these three wirings Lu, Lv, and Lw, respectively.

  Control signals S1, S2, S3, S4, S5, and S6 are supplied from the outside to the control terminals of the six switching elements Q1 to Q6 of the inverter circuit 10, respectively. These control signals S1 to S6 are signals for controlling each of the switching elements Q1 to Q6 to be turned on or off, whereby a three-phase alternating current of a rectangular wave or a PWM wave can be created. In the present embodiment, the control state based on the control signals S1 to S6 can be determined based on the waveforms of the three-phase voltages Vu, Vv, and Vw without directly monitoring the control signals S1 to S6. It will be described later.

  Three-phase currents Iu, Iv, and Iw flow from the inverter circuit 10 to the three-phase motor 12 through the output-side wirings Lu, Lv, and Lw, respectively. The current detection unit 11 disposed in the vicinity of the wirings Lu, Lv, and Lw is a sensor that detects the currents Iu, Iv, and Iw. The current detection signals SIu, SIv, and SIw indicating the respective current values are input voltages. Output to the current estimation unit 14. As the current detection unit 11, for example, a current detection signal having an amplitude proportional to the magnitudes of the currents Iu, Iv, and Iw by using a device that detects a magnetic field generated around each of the wirings Lu, Lv, and Lw. SIu, SIv, and SIw can be generated.

  The motor 12 is, for example, a three-phase motor that rotates a rotor having a field according to a rotating magnetic field generated by a stator by three-phase AC. The motor 12 is driven by supplying currents Iu, Iv, and Iw that are 120 ° out of phase with each other through the u-phase, v-phase, and w-phase terminals. The rotational speed of the motor 12 changes in conjunction with the three-phase AC cycle controlled according to the waveforms of the control signals S1 to S6.

  As shown in FIG. 1, the three-phase wirings Lu, Lv, and Lw branch in the middle of being connected to the motor 12 and are also connected to the voltage dividing circuit 13. Since the voltages Vu, Vv, and Vw output from the inverter circuit 10 are high voltages, the voltage dividing circuit 13 has a role of generating relatively small divided voltages VDu, VDv, and VDw by dividing the voltages. . The voltage dividing circuit 13 is also connected to the ground G, and the divided voltages VDu, VDv, and VDw can be generated using the ground G as a reference potential. For example, when a logic circuit or the like subsequent to the voltage dividing circuit 13 operates within a range of 0 to 5 V with respect to high voltage input conditions such as Vd + = 100 V and Vd − = − 100 V, the voltage dividing circuit 13 is Therefore, it is necessary to reduce the voltage amplitude to about 1/40. In this case, the voltage dividing circuit 13 can be configured by, for example, a plurality of resistance elements set to a predetermined resistance ratio and a buffer amplifier using an operational amplifier at the subsequent stage.

  The input voltage / current estimation unit 14 uses the divided voltages VDu, VDv, and VDw received from the voltage dividing circuit 13 and the current detection signals SIu, SIv, and SIw received from the current detection unit 11 to input the inverter circuit 10. The estimated voltage value V1 and estimated current value I1 of the input voltage Vin and input current Iin on the side are output. Although not shown in FIG. 1, in addition to the estimated voltage value V1 and the estimated current value I1, the input voltage / current estimator 14 adds each voltage value on the output side of the inverter circuit 10 (the voltage between the three phases). Etc.), each current value (each three-phase current Iu, Iv, Iw, etc.) and output power may be output.

  Next, a specific configuration and operation of the input voltage / current estimation unit 14 will be described. FIG. 2 is a block diagram illustrating the function of the input voltage / current estimation unit 14. The input voltage / current estimation unit 14 illustrated in FIG. 2 includes a control state determination unit 20, a clock generation unit 21, a voltage monitoring unit 22, a current monitoring unit 23, a voltage correction unit 24, and a current correction unit 25. Consists of.

  In the configuration of FIG. 2, the control state determination unit 20 determines the switching control state of the inverter circuit 10 based on the divided voltages VDu, VDv, and VDw output from the voltage dividing circuit 13 of FIG. The result is output as a determination signal D (determination signals D0 to D7 described later). Here, FIG. 3 shows a circuit example of the control state determination unit 20. 4 shows a truth table and switching control states in the circuit example of FIG. 3, and FIG. 5 shows an example of waveforms during operation of the control state determination unit 20. 3 to 5 will be described on the assumption that the motor 12 is driven by three-phase alternating current of rectangular waves.

  The control state determination unit 20 shown in FIG. 3 includes three comparators 30 and eight AND gates 31. The three comparators 30 compare the divided voltages VDu, VDv, and VDw with the reference voltage Vref, and output a high or low value as a comparison result. The reference voltage Vref may be set to an intermediate potential between high and low of the divided voltages VDu, VDv, and VDw. For example, when the voltage dividing circuit 13 operates at 0 to 5 V, if the motor 12 is driven with a rectangular wave as described above, the maximum is 5 V and the minimum is 0 V. It does not have to be provided. However, since the voltage Vu, Vv, Vw supplied to the motor 12 may be affected by noise or amplitude fluctuation, the voltage waveform is shaped via the comparator 30.

  The eight AND gates 31 discriminate among different patterns among the eight patterns of the three comparators 30 of high and low, and, as described above, the determination signals D0 to D7 each including pulses having different timings. Output. Here, in FIG. 4, eight states 0 to 7 are shown as control states for the inverter circuit 10, and the divided voltages VDu and VDv input to the control state determination unit 20 with respect to the respective states 0 to 7. , VDw high (H) and low (L) combination pattern (truth table), determination signals D0 to D7 which become high in response to the pattern, and switching elements Q1 to Q6 in the inverter circuit 10 at that time Are associated with each other (on or off). 4, if the switching elements Q1 to Q6 are on (ON), the corresponding control signals S1 to S6 in FIG. 1 are controlled to be high, and the switching elements Q1 to Q6 are off ( OFF) means that the corresponding control signals S1 to S6 in FIG. 1 are controlled to be low.

  In FIG. 4, for example, when focusing on a pair of switching elements Q1 and Q4 connected in series, it can be seen that one is controlled to be on and the other is controlled to be off. Therefore, the output-side wiring Lu in FIG. 1 is connected to one of the wirings La and Lb via the switching elements Q1 and Q4 on the turned-on side. At this time, if both of the switching elements Q1 and Q4 are simultaneously turned on, a large current flows between the wirings La and Lb. Therefore, at least one of them needs to be kept off. The above control is the same for the pair of switching elements Q2 and Q5 connected in series and the pair of switching elements Q3 and Q6 connected in series.

  FIG. 5 shows the waveforms of the voltages Vu, Vv, and Vw of the wirings Lu, Lv, and Lw in FIG. 1 and the control state determination unit 20 in FIG. The waveforms of determination signals D1 to D6 to be performed are shown. Here, since the determination signals D0 and D7 among the determination signals D0 to D7 in FIG. 3 are not generated in the case of driving by a rectangular wave, only six determination signals D1 to D6 are shown in FIG. The voltages Vu, Vv, and Vw change between a positive high potential + VH and a negative low potential −VL, and have the same waveform although the levels are different from the divided voltages VDu, VDv, and VDw. The absolute values of the high potential + VH and the low potential −VL are slightly smaller than the absolute values of the positive and negative DC voltages Vd + and Vd− in FIG. This is not considered in FIG.

  The upper part of FIG. 5 shows a period T of three-phase alternating current, and the voltages Vu, Vv, and Vw are shifted from each other by a time T / 3 corresponding to a phase of 120 °. And it turns out that the waveform pattern of voltage Vu, Vv, Vw changes with the period T / 6 which divided the period T into six. On the other hand, the determination signals D1 to D6 change corresponding to the truth table on the left side of FIG. 4, and generate pulses with a time width T / 6 at different timings. Within the period T shown in FIG. 5, pulses appear in the order of the determination signals D5, D1, D6, D2, D4, and D3, and continue to change in the same pattern thereafter. Accordingly, in any time zone of the period T in the three-phase alternating current, any one of the determination signals D1 to D6 is always high without overlapping. In other words, the determination signals D1 to D6 that are high can be associated with the waveform patterns of the voltages Vu, Vv, and Vw.

  For example, taking the timing when the determination signal D1 becomes high as an example, Vu = + VH, Vv = −VL, and Vw = −VL at this time. This is the “state 1” (Q1) of the switching control in FIG. , Q5, and Q6 are ON, and Q2, Q3, and Q4 are OFF). Therefore, in the voltage monitor unit 22 to be described later, Vu−Vv (or Vu−) when the determination signal D1 is high using each voltage value corresponding to the voltages Vu, Vv, and Vw obtained by sampling based on the clock CLK. An instantaneous voltage applied to the motor 12 can be determined by performing a calculation corresponding to Vw). In addition, the input voltage Vin of the inverter circuit 10 can be estimated by the above operation, which will be described later in detail.

  Returning to FIG. 2, the clock generation unit 21 generates a clock CLK based on the above-described sampling and supplies the clock CLK to the voltage monitoring unit 22 and the current monitoring unit 23. As can be seen from FIG. 5, the clock CLK generated by the clock generator 21 is set to a frequency high enough to ensure sampling within the time width of each pulse of the determination signals D1 to D6 (T / 6 in FIG. 5). There is a need to. Note that, in the voltage monitor unit 22 and the current monitor unit 23, when the divided voltages VDu, VDv, and VDw are used as analog signals, the clock generation unit 21 may not be provided.

  Next, the voltage monitoring unit 22 in FIG. 2 converts the three-phase alternating current supplied from the inverter circuit 10 to the motor 12 based on the divided voltages VDu, VDv, and VDw output from the voltage dividing circuit 13 in FIG. A DC voltage value V1a converted into a DC voltage is generated by the method shown. Then, the voltage correction unit 24 subsequent to the voltage monitor unit 22 performs a correction operation in consideration of conditions such as loss characteristics of the inverter circuit 10 on the DC voltage value V1a, and estimates the input voltage Vin. Is output.

  Here, FIG. 6 shows a configuration example of the voltage monitor unit 22. The voltage monitoring unit 22 illustrated in FIG. 6 includes three subtracting units 40, three inverting units 41, eight multiplexers 42, and one adding unit 43. In the configuration of FIG. 6, the divided voltages VDu, VDv, and VDw that are input may be either analog signals or digital signals. In order to obtain the divided voltages VDu, VDv, and VDw of the digital signal, three AD converters are inserted in each preceding stage of the subtracting unit 40, and the sampling period according to the clock CLK in FIG. It is necessary to convert the analog divided voltages VDu, VDv, and VDw into digital signals.

  In FIG. 6, three subtracting units 40 subtract predetermined two voltage values from the divided voltages VDu, VDv, and VDw. As the subtraction result, for example, three voltage values of VDu-VDv (VDu-VDw), VDv-VDw (VDv-VDu), and VDw-VDu (VDw-VDv) are obtained. The three inversion units 41 invert the three voltage values output from the three subtraction units 40 (multiply by -1 in the case of a digital value). For example, when VDu-VDv, VDv-VDw, and VDw-VDu are input to three inversion units 41, VDv-VDu, VDw-VDv, and VDu-VDw are output, respectively, and six voltage values are obtained Will be.

  The eight multiplexers 42 selectively output one of the two inputs based on the determination signals D0 to D7. Among the eight multiplexers 42, one of the upper six multiplexers 42 (terminal 1) receives the above six voltage values output from the three subtracting units 40 and the three inverting units 41. An output signal of a signal hold unit 44 described later is input to one end (terminal 1) of the lower two multiplexers 42. Also, the other end (terminal 0) of the eight multiplexers 42 is supplied with a reference potential. The adder 43 adds all the output values of the eight multiplexers 42 and outputs the addition result as the above-described DC voltage value V1a. On the other hand, the signal hold unit 44 receives the DC voltage value V1a output from the adding unit 43, and holds the DC voltage value V1a until the addition result is updated.

  As a specific example of the operation in FIG. 6, it is assumed that the inverter circuit 10 is controlled as shown by the waveform in FIG. 5. In this case, the determination signals D1 to D6 sequentially become high at the cycle T / 6, and in association with this, the six multiplexers 42 are activated one by one. For example, VDu-VDv, VDv-VDw, VDw-VDu, VDv-VDu, VDw-VDv, and VDu-VDw are sequentially output in the order in which the six multiplexers 42 are arranged. These voltage values correspond to the difference between the high potential and the low potential of the three-phase voltage in each cycle T / 6, and become values proportional to the input voltage Vin of the inverter circuit 10. In an arbitrary time zone, only one multiplexer 42 is controlled to the terminal 1 side, and the other seven multiplexers 42 are controlled to the terminal 0 side (a voltage value 0 is output). Therefore, two or more voltage values are not added by the adding unit 43.

  Returning to FIG. 2, the current monitor 23 is based on the current detection signals SIu, SIv, SIw output from the current detector 11, and the three-phase currents Iu, Iv, A direct current value I1a obtained by converting Iw into a direct current is generated. Then, the current correction unit 25 subsequent to the current monitor unit 23 performs a correction operation on the DC current value I1a in consideration of conditions such as loss characteristics of the inverter circuit 10 and estimates the input current Iin. Is output.

  Here, the relationship between the waveforms of the three-phase voltages Vu, Vv, and Vw shown in FIG. 5 and the waveforms of the three-phase currents Iu, Iv, and Iw will be described. FIG. 7 shows waveforms of currents Iu, Iv, and Iw on the same time axis as the waveforms of voltages Vu, Vv, and Vw when the motor 12 is driven under the same conditions as in FIG. The current detection signals SIu, SIv, and SIw are signals that are proportional to the currents Iu, Iv, and Iw, and thus have similar waveforms.

  As shown in FIG. 7, the voltages Vu, Vv, and Vw are rectangular waves, whereas the currents Iu, Iv, and Iw are not rectangular waves but have waveforms that change slowly. This is because the motor 12 has an inductive impedance component. For this reason, in the waveforms of the currents Iu, Iv, and Iw, state changes such as ripple due to switching control of the inverter circuit 10 do not occur. However, in FIG. 7, the waveforms of the currents Iu, Iv, and Iw are shown as sine waves. However, in reality, this is not the case and is represented here as a sine wave for convenience. In addition, each of the currents Iu, Iv, and Iw increases when the corresponding voltages Vu, Vv, and Vw are high potential + VH, and decreases when the corresponding voltages Vu, Vv, and Vw are low potential -VL. I understand that.

  Further, in the lower part of FIG. 7, only one determination signal D1 shown in FIG. 5 is illustrated. When the determination signal D1 is high, the three switching elements Q1, Q5, and Q6 are turned on and the other three switching elements Q2, Q3, and Q4 are turned off, as shown as “state 1” in FIG. It becomes. Accordingly, the input current Iin of the inverter circuit 10 in FIG. 1 flows along the path of the wiring La, the switching element Q1, the wiring Lu, the motor 12, the wirings Lv and Lw, the switching elements Q5 and Q6, and the wiring Lb. In this case, the current Iu flows in the opposite direction to the currents Iv and Iw, and the magnitude of the current Iu should match the sum of the magnitudes of the currents Iv and Iw. Note that the maximum values of the currents Iu, Iv, and Iw are slightly smaller than the absolute value of the input current Iin described above and fluctuate with time due to current leakage in the inverter circuit 10 and the like.

  Next, FIG. 8 shows a configuration example of the current monitor unit 23. The current monitor unit 23 illustrated in FIG. 8 includes three adders 51, six multiplexers 52, and one adder 53. In the configuration of FIG. 8, the current detection signals SIu, SIv, and SIw are input to one end of the upper three multiplexers 52 and one end of the three adders 51, respectively. The three addition units 51 add two predetermined detection signals among the current detection signals SIu, SIv, and SIw, and, for example, three values of SIv + SIw, SIw + SIu, and SIu + SIv are obtained as an addition result. The addition results of the three adders 51 are input to one end of the lower three multiplexers 52. The six multiplexers 52 selectively output one of the two inputs based on the determination signals D1 to D6. The configuration of the three adders 51 and the eight multiplexers 52 reflects the switching control state of FIG. 4 and flows from the inverter circuit 10 to the motor 12 via the switching elements Q1 to Q3 on the plus side. An operation for obtaining a sum of current values is performed. In FIG. 8, unlike FIG. 6, a configuration corresponding to the two multiplexers 42 and the signal hold unit 44 to which the determination signals D0 and D7 are input is not provided. This is because, as shown in “state 0” and “state 7” in FIG. 4, the determination signal D0 has all the switching elements Q1 to Q3 on the positive side turned off, and the determination signal D7 has the switching elements Q4 to Q6 on the negative side. 1 is turned off, the path through which the input current Iin flows in the inverter circuit 10 of FIG. 1 is cut off, and the currents Iu, Iv, and Iw can be regarded as zero. The role of the adding unit 53 is the same as that of the adding unit 43 in FIG. 6, and the above-described DC current value I1a is output as the addition result of the adding unit 53.

  In the configuration example of FIG. 8, the DC current value I1a is obtained from the sum of the current values flowing in the direction from the wiring La to the motor 12. However, the DC current value is calculated from the sum of the current values flowing in the direction from the motor 12 to the wiring Lb. I1a may be obtained. In this case, in FIG. 8, the determination signals D4, D5, D6, D1, D2, and D3 are connected in order from the upper side to the six multiplexers 52, or each one end (terminal) of the upper three multiplexers 52 is connected. 1), the outputs of the three adders 51 are connected in order from the top, and the current detection signals SIu, SIv, SIw are connected in order from the top to each one end (terminal 1) of the lower three multiplexers 52. That's fine. As a result, six values of SIv + SIw, SIw + SIu, SIu + SIv, SIu, SIv, and SIw are obtained as the addition result of the adding unit 53 in order corresponding to the determination signals D1 to D6.

  Note that the voltage monitoring unit 22 in FIG. 6 and the current monitoring unit 23 in FIG. 8 are both examples, and there are many variations. For example, the three inversion units 41 in FIG. 6 are all arranged on the input side of the multiplexer 42, but these three inversion units 41 are inserted between the output side of the multiplexer 42 and the input side of the addition unit 43. Even in this case, an equivalent operation can be realized. Further, for example, all the multiplexers 42 in FIG. 6 are of the two-input type, but these may be replaced with one 8-input multiplexer. In general, since an 8-input multiplexer is controlled by a 3-bit selection control signal, the eight decision signals D0 to D7 are converted into 3 bits via an 8-to-3 encoder and then selected and controlled. As a signal, it can be supplied to an 8-input multiplexer. On the other hand, the multiplexer 52 of the current monitor unit 23 in FIG. 8 can be similarly replaced with an 8-input multiplexer. However, since two input terminals are left, the two input terminals correspond to a current of zero. Enter a value. In addition to the above modifications, various configurations that can realize the same function can be employed.

  Returning to FIG. 2, the correction calculation in the voltage correction unit 24 and the current correction unit 25 described above is performed, for example, with respect to the input DC voltage value V1a and DC current value I1a. It can be an operation of multiplying by a coefficient. The coefficient used at this time may be controlled so as to reflect a change over time in the switching control state of the inverter circuit 10 or may be controlled so as to use a coefficient appropriately read from a coefficient table provided in advance. Also good. Further, the voltage correction unit 24 and the current correction unit 25 are not limited to the configuration provided integrally with the voltage / current detection unit 14a, and may be provided as components of the control unit in the power conversion device, for example.

  2 includes a control state determination unit 20, a clock generation unit 21, a voltage monitoring unit 22, and a current monitoring unit 23. The portion including the voltage / current detection unit 14a (the present invention) Voltage-current detection device). That is, the present invention can be applied to the power conversion device by attaching a separate voltage / current detection unit 14a in the vicinity of the wirings Lu, Lv, and Lw of the power conversion device. As described above, the voltage / current detection unit 14a outputs each voltage value, current value and output power on the output side of the inverter circuit 10 in addition to the DC voltage value V1a and the DC current value I1a (not shown). May be adopted. Furthermore, in FIG. 2, only the part including the control state determination unit 20, the clock generation unit 21, and the voltage monitoring unit 22 may be configured as a voltage detection unit (voltage detection device of the present invention).

  Next, a simulation is performed on the input voltage / current estimation unit 14 of the present embodiment, and the resulting waveform will be described. In FIGS. 5 and 7 described above, the case where the motor 12 is driven by a rectangular wave three-phase alternating current has been described. However, in this simulation, it is assumed that the motor 12 is driven by a PWM wave three-phase alternating current.

  FIG. 9 is a diagram illustrating the relationship between the simulation waveforms of the three-phase AC voltages Vu, Vv, and Vw and the switching control of the inverter circuit 10. In FIG. 9, when the motor 12 is driven with a PWM wave at a high voltage of about Vin = 400 (V), the voltages Vu, Vv, Vw and the control signals S1, S2, S3 within a short time range (1 ms). Each waveform is shown. Compared with FIG. 5 and FIG. 7 of the rectangular wave, in the drive by the PWM wave, the state of the switching control frequently changes, and the duty ratios of the control signals S1, S2, and S3 are finely controlled. Note that high / low of the control signals S1, S2, and S3 correspond to on / off of the switching elements Q1, Q2, and Q3 on the right side of FIG. In FIG. 9, the control signals S4, S5, S6 are omitted, but when the combination pattern of the control signals S1, S2, S3 is set, the combination pattern of the control signals S4, S5, S6 is correspondingly set. It is clear from FIG. 4 that it is determined uniformly.

  FIG. 9 shows three consecutive timings tu at which the control signal S1 changes, timing tv at which the control signal S2 changes, and timing tw at which the control signal S3 changes. First, at the timing tu, the voltage Vu changes in conjunction with the control signal S1, the voltage Vu becomes a high potential when S1 = H, and the voltage Vu when S1 = L becomes a low potential. The same applies to the timings tv and tw, and the voltages Vv and Vw change as described above in conjunction with the control signals S2 and S3. This means that the determination signal D corresponding to the switching state of the inverter circuit 10 can be generated based on the high / low of the divided voltages VDu, VDv, VDw proportional to the voltages Vu, Vv, Vw. According to the simulation waveform of FIG. 9, for example, when S1 = H, the high potential of the voltage Vu varies. This is because the relative potential with respect to the ground G changes depending on the state of switching control. The difference between the high potential and the low potential is generally kept constant.

  Next, FIG. 10 is a diagram illustrating a correspondence relationship between the control signals S1 to S6 and the determination signals D1 to D6. The three control signals S1 to S3 in FIG. 10 are the same as the simulation waveforms of the initial time width (0.4 ms) in FIG. 9, and the simulation waveforms of the control signals S4 to S6 and the determination signals D1 to D6 corresponding thereto. Is added. FIG. 10 shows timings tu, tv, and tw at which the control signals S1, S2, and S3 change, respectively, but all coincide with the timings at which the determination signals D1 and D6 change. Also in this case, as shown in FIG. 4, on / off of the switching elements Q1 to Q6 corresponding to the high / low of the control signals S1 to S6 corresponds to the high / low of the determination signals D1 to D6. In FIG. 10, the determination signals D0 and D7 in a state where the current path is interrupted as described above are not shown.

  Next, FIGS. 11 to 13 show positive and negative DC voltages Vd + and Vd− on the input side of the inverter circuit 10 and voltages Vu and Vv supplied to the motor 12 in the same time width (0.4 ms) as FIG. , Vw, the control signals S1 to S3, and the determination signals D1 to D3. Among these, FIG. 11 is a diagram focusing on the relationship between the u-phase voltage Vu and the determination signal D1, and it can be seen that the relationship Vu = Vd + is satisfied in the initial period Ta where D1 = H. At this time, the relationship Vv = Vd− is also satisfied, which means that the input voltage Vin can be estimated based on the calculation of Vu−Vv. The same applies when the voltage Vv is replaced with the voltage Vw.

  FIG. 12 is a diagram focusing on the relationship between the v-phase voltage Vv and the determination signal D2, and it can be seen that the relationship Vv = Vd + is satisfied in the initial period Tb in which D2 = H. At this time, the relationship of Vw = Vd− is also satisfied, which means that the input voltage Vin can be estimated based on the calculation of Vv−Vw. The same applies when the voltage Vw is replaced with the voltage Vu. Further, FIG. 13 is a diagram focusing on the relationship between the w-phase voltage Vw and the determination signal D3, and it can be seen that the relationship of Vw = Vd + is satisfied in the initial period Tc in which D3 = H. At this time, the relationship of Vu = Vd− is also satisfied, which means that the input voltage Vin can be estimated based on the calculation of Vw−Vu. The same applies when the voltage Vu is replaced with the voltage Vv. The validity of the configuration example (particularly the subtraction unit 40) of the voltage monitoring unit 22 in FIG. 6 can be determined from the simulation waveforms in FIGS.

  Next, FIGS. 14 to 16 and FIGS. 18 to 20 show the input current Iin of the inverter circuit 10 and the currents Iu, Iv, Iw supplied to the motor 12 in the same time width (0.4 ms) as FIG. And their sums (Iv + Iw, Iw + Iu, Iu + Iv), the control signals S1 to S6, and the determination signals D1 to D6. 14 to 16 and 18 to 20, the simulation waveform of the input current Iin and the simulation waveforms of the respective currents Iu, Iv, Iw, Iv + Iw, Iw + Iu, and Iu + Iv are shown superimposed. 14, 15, and 16 correspond to states 1, 2, and 3 in FIG. 4 in this order (the three multiplexers 52 on the upper side in FIG. 8), and FIGS. 18, 19, and 20 correspond to FIG. It corresponds to states 4, 5, and 6 (the lower three multiplexers 52 in FIG. 8).

  FIG. 14 is a diagram focusing on the relationship between the u-phase current Iu and the determination signal D1, and it can be seen that the relationship of Iu = Iin is satisfied in the initial period Td in which D1 = H. That is, it means that the input current Iin can be estimated using the value of the current Iu. FIG. 15 is a diagram focusing on the relationship between the v-phase current Iv and the determination signal D2, and it can be seen that the relationship Iv = Iin is satisfied in the initial period Te in which D2 = H. That is, it means that the input current Iin can be estimated using the value of the current Iv. FIG. 16 is a diagram focusing on the relationship between the w-phase current Iw and the determination signal D3, and it can be seen that the relationship of Iw = Iin is satisfied in the initial period Tf in which D3 = H. That is, it means that the input current Iin can be estimated using the value of the current Iw.

  In relation to FIGS. 14 to 16, FIG. 17 shows simulation waveforms of the three-phase currents Iu, Iv, and Iw and a simulation waveform of the input current Iin of the inverter circuit 10 in a longer time range (10 ms). It is shown repeatedly. The currents Iu, Iv, and Iw are close to a slowly changing sine wave, while the input current Iin has short-term fluctuations similar to those shown in FIGS. It can be seen that the short-term fluctuation envelopes are along the sine waves of the currents Iu, Iv, and Iw.

  FIG. 18 is a diagram focusing on the relationship between the sum Iv + Iw of the v-phase current Iv and the w-phase current Iw and the determination signal D4. In the initial period Tg where D4 = H, the relationship of Iv + Iw = Iin You can see that it meets. That is, it means that the input current Iin can be estimated using the value of the current sum Iv + Iw. FIG. 19 is a diagram focusing on the relationship between the sum Iw + Iu of the w-phase current Iw and the u-phase current Iu and the determination signal D5. In the initial period Th in which D5 = H, the relationship of Iw + Iu = Iin You can see that it meets. That is, it means that the input current Iin can be estimated using the value of the sum of currents Iw + Iu. FIG. 20 is a diagram focusing on the relationship between the sum Iu + Iv of the u-phase current Iu and the v-phase current Iv and the determination signal D6. In the initial period Ti where D6 = H, the relationship of Iu + Iv = Iin is shown. You can see that it meets. That is, it means that the input current Iin can be estimated using the value of the current sum Iu + Iv.

  In relation to FIGS. 18 to 20, FIG. 21 shows simulation waveforms of the sums Iv + Iw, Iw + Iu, and Iu + Iv of the three-phase currents and the input current of the inverter circuit 10 in the long time range (10 ms) similar to FIG. The simulation waveform of Iin is shown superimposed. In this case, it can be seen that the states of the waveforms of the current sums Iv + Iw, Iw + Iu, Iu + Iv, and input current Iin are as described in FIG. As described above, the validity of the configuration example of the current monitor unit 23 in FIG. 8 can be determined from the simulation waveforms in FIGS. 14 to 21.

  As described above, the configuration of the present embodiment is an effective alternative as a countermeasure against a failure of the voltage detection unit and the current detection unit provided on the input side of the inverter circuit 10. In this case, since the input voltage / current estimation unit 14 of FIG. 1 can independently generate the voltage estimation value V1 and the current estimation value I1, among the voltage detection unit and the current detection unit on the input side of the inverter circuit 10, It is possible to cope with either one of the failure or both failure. Even if the voltage detection unit and the current detection unit are not provided on the input side of the inverter circuit 10, the input side of the inverter circuit 10 can be provided in the power converter by attaching the voltage / current detection device of this embodiment. It is possible to add a voltage detection function and a current detection function.

  As mentioned above, although preferred embodiment of this invention was described, the power converter device (and voltage current detection apparatus, voltage detection apparatus) to which this invention is applied can be utilized for various uses. For example, a power conversion device having a configuration that compensates for fluctuations in magnetic flux in industrial fields such as electric vehicles, electric motorcycles, trains, etc., industrial applications such as blowers, FA devices, processing devices, elevators, air conditioners, etc. In addition, the present invention can be applied to various other voltage / current detection devices and voltage detection devices.

DESCRIPTION OF SYMBOLS 10 ... Inverter circuit 11 ... Current detection part 12 ... Motor 13 ... Voltage dividing circuit 14 ... Input voltage current estimation part 20 ... Control state determination part 21 ... Clock generation part 22 ... Voltage monitor part 23 ... Current monitor part 24 ... Voltage correction part 25 ... Current correction unit 30 ... Comparator 31 ... AND gate 40 ... Subtraction unit 41 ... Inversion unit 42, 52 ... Multiplexer 43, 51, 53 ... Addition unit 44 ... Signal hold unit La, Lb ... Wiring (input side of inverter)
Lu, Lv, Lw ... wiring (inverter output side)
Vin ... Input voltage Vd + ... Positive DC voltage Vd -... Negative DC voltage Iin ... Input currents Vu, Vv, Vw ... Three-phase AC voltages Iu, Iv, Iw ... Three-phase AC currents VDu, VDv, VDw ... min Voltage V1 ... Voltage estimation value V1a ... DC voltage value I1 ... Current estimation value I1a ... DC current values Q1-Q6 ... Switching elements S1-S6 ... Control signals D0-D7 ... Determination signals SIu, SIv, SIw ... Current detection signal

Claims (6)

A voltage detection device that detects a voltage in an inverter circuit that converts a DC input voltage and input current into an AC output voltage and output current and supplies the load to a load in accordance with control of a plurality of switching elements,
The control state of the plurality of switching elements is determined based on the voltages of the plurality of wirings connected between the output side of the inverter circuit and the load, and the higher of the voltages of the plurality of wirings according to the determination result A voltage detection apparatus characterized in that a DC voltage value which is a difference between a potential and a low potential is obtained, and the input voltage can be estimated based on the DC voltage value.   The voltage detection device according to claim 1, further comprising: a control state determination unit that outputs a plurality of determination signals indicating timings at which the plurality of switching elements are turned on based on voltages of the plurality of wirings. .   A voltage monitor that selects a combination of the high potential and the low potential from the voltages of the plurality of wirings based on the plurality of determination signals and subtracts the low potential from the high potential to output the DC voltage value The voltage detection apparatus according to claim 2, further comprising a unit.   The inverter circuit supplies the output voltage and the output current of a three-phase AC to the load, and the plurality of wirings are three wirings to which a voltage and a current of each phase of the three-phase AC are supplied. The voltage detection device according to any one of claims 1 to 3. A voltage / current detection device that detects a voltage and a current in an inverter circuit that converts a DC input voltage and an input current into an AC output voltage and an output current and supplies them to a load according to control of a plurality of switching elements,
The control state of the plurality of switching elements is determined based on the voltages of the plurality of wirings connected between the output side of the inverter circuit and the load, and the higher of the voltages of the plurality of wirings according to the determination result A DC voltage value that is a difference between a potential and a low potential is obtained, and the currents of the plurality of wirings are converted to direct current based on the determination result and a current detection signal of a current detection unit that detects currents of the plurality of wirings. A voltage-current detection device characterized in that a DC current value can be obtained and the input voltage and the input current can be estimated based on the DC voltage value and the DC current value. Based on the voltages of the plurality of wirings, a control state determination unit that outputs a plurality of determination signals indicating the timing at which each of the plurality of switching elements is conducted,
Based on the plurality of determination signals, a current monitoring unit that outputs a sum of current values in a direction flowing into the load or a direction flowing out from the load among the plurality of current detection signals as the DC current value;
The voltage / current detection device according to claim 5, further comprising:

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