JP5853644B2 - Line current detection device and power conversion system - Google Patents

Description

  The present invention relates to a line current detecting device and a power conversion system, and more particularly to a technique for estimating a line current by detecting a direct current.

  Patent Document 1 describes a three-phase inverter. The three-phase inverter converts the input DC voltage into an AC voltage. This conversion is realized by appropriately switching conduction / non-conduction of the switching element of the inverter.

  Moreover, in patent document 1, the direct current which flows through the input side of a three-phase inverter is used, The electric current which flows through the output side of a three-phase inverter, ie, a three-phase phase current, is detected. This detection is performed by matching the bus current and the phase current based on the energization pattern adopted by the inverter. For example, in a predetermined cycle (for example, carrier cycle), the bus current is detected in each of the periods in which two different energization patterns are adopted, and these are detected as two-phase phase currents determined based on the two energization patterns. . The remaining one-phase phase current is calculated based on the relationship that the sum of the three-phase phase currents is zero.

  Patent documents 2 to 7 are disclosed as techniques related to the present invention.

Japanese Patent No. 4429338 Japanese Patent No. 4578500 JP 2004-48868 A JP 2011-67023 A JP 2004-64093 A JP 2007-312511 A Japanese Patent No. 3611492

  When the three-phase inverter is controlled so that the phase voltage of the three-phase inverter has, for example, one pulse per cycle, the period during which one switching pattern is maintained is relatively long. The same applies when the phase voltage has a substantially one-pulse waveform. In other words, although the phase voltage includes a pulse having a very short period (pulse width), the period in which one switching pattern is maintained is relatively long even when it has substantially one pulse. The definition of the substantially one-pulse waveform will be described in detail in the embodiment.

  On the other hand, in the technique described in Patent Document 1, a three-phase line current is obtained from a direct current by adopting two switching patterns with a carrier period sufficiently shorter than one period of the phase voltage. Therefore, it has not been studied how to apply the technique in which two switching patterns are employed with a short period as in Patent Document 1 to a substantially one-pulse waveform in which the switching pattern is maintained for a long period. .

  Therefore, an object of the present invention is to provide a line current detection device that can obtain a line current even if the switching pattern is maintained for a long period of time.

A first aspect of the line current detection device according to the present invention includes three AC lines (Pu, Pv, Pw) connected to the inductive load (2), and first and second DC voltages applied between them. A second DC line (LH, LL), a first switching element (S1 to S3) provided between each of the three AC lines and the first DC line, and the three AC lines In a power conversion device including second switching elements (S4 to S6) provided between each and the second DC line, three-phase line currents (iu, iv, iw) flowing through the three AC lines ) To detect the first and second switching elements and to apply an AC three-phase voltage to the three AC lines, each of the three-phase voltages being wherein in one cycle of the AC has a substantially 1 pulse waveform, and the said generally 1 pulse waveform, each of said 3-phase voltage is the first or second The shorter than the first period of time taking continuously potential applied to streamline, waveform ignored from the waveform of each of said three-phase voltage, a waveform having a pulse of a rectangular wave only one, In the first period, the switching control unit (31), which is the minimum time required for detecting the direct current (Idc) flowing through the first or second DC line, and the first or second DC line are connected. A current detection unit (4) that detects a flowing direct current (Idc) and a current detection unit that detects the current detection unit at a first time (t1) before the first timing (t (0)) when the switching pattern changes. The direct current is estimated as a first-phase line current determined by the switching pattern at the first time point, and is detected by the current detection unit at a second time point after the first timing. The DC current is switched on at the second time point. Line current acquisition unit that estimates as a line current of the second phase which is one determined by the pattern (32), and wherein the waveform of the fundamental wave component of the first phase and the second phase line current, the line current Based on the first-phase and second-phase line currents acquired in the acquisition unit (32), at least two-phase of the three-phase line currents at a second timing different from the first timing. A line current estimating unit (33) for estimating a line current , wherein the line current estimating unit sets each of a plurality of timings in a period in which the switching pattern after the first timing is maintained as the second timing, wherein it estimates the line currents of at least two phases.

A second aspect of the line current detection device according to the present invention includes three AC lines (Pu, Pv, Pw) connected to the inductive load (2), and first and second DC voltages applied between them. A second DC line (LH, LL), a first switching element (S1 to S3) provided between each of the three AC lines and the first DC line, and the three AC lines In a power conversion device including second switching elements (S4 to S6) provided between each and the second DC line, three-phase line currents (iu, iv, iw) flowing through the three AC lines ) To detect the first and second switching elements and to apply an AC three-phase voltage to the three AC lines, each of the three-phase voltages being The one cycle of the alternating current has substantially one pulse waveform, and the substantially one pulse waveform means that each of the three-phase voltages is the first or second Among the periods in which the potential applied to the streamline is continuously taken, the waveform shorter than the first period is ignored from each of the three-phase voltage waveforms, and the waveform has only one rectangular wave pulse. In the first period, the switching control unit (31), which is the minimum time required for detecting the direct current (Idc) flowing through the first or second DC line, and the first or second DC line are connected. A current detection unit (4) that detects a flowing direct current (Idc) and a current detection unit that detects the current detection unit at a first time (t1) before the first timing (t (0)) when the switching pattern changes. The direct current is estimated as a first-phase line current determined by the switching pattern at the first time point, and is detected by the current detection unit at a second time point after the first timing. The DC current is switched on at the second time point. A line current acquisition unit (32) for estimating a second-phase line current determined by a pattern, a waveform expression of a fundamental wave component of the first-phase and second-phase line currents, and the line current Based on the first-phase and second-phase line currents acquired in the acquisition unit (32), at least two-phase of the three-phase line currents at a second timing different from the first timing. A line current estimation unit (33) for estimating a line current; and a voltage phase acquisition unit (38) for acquiring a voltage phase (θv) for the three-phase voltage , wherein the line current estimation unit (33) A current amplitude (Im) and a current phase (θi) at the first timing are calculated based on line currents (iu, iv, iw) of the first phase and the second phase, and the current phase at the first timing and A phase difference (Δθ) from the voltage phase is calculated, and the voltage phase at the second timing (t (1), t (n)) is calculated. The current phase at the second timing is calculated based on the phase difference, and the three-phase line current at the second timing is calculated using the current amplitude, the current phase at the second timing, and the waveform equation. wherein estimating the line currents of at least two phases of the.

A third aspect of the line current detection device according to the present invention includes three AC lines (Pu, Pv, Pw) connected to the inductive load (2), and first and second DC voltages applied between them. A second DC line (LH, LL), a first switching element (S1 to S3) provided between each of the three AC lines and the first DC line, and the three AC lines In a power conversion device including second switching elements (S4 to S6) provided between each and the second DC line, three-phase line currents (iu, iv, iw) flowing through the three AC lines ) To detect the first and second switching elements and to apply an AC three-phase voltage to the three AC lines, each of the three-phase voltages being The one cycle of the alternating current has substantially one pulse waveform, and the substantially one pulse waveform means that each of the three-phase voltages is the first or second Among the periods in which the potential applied to the streamline is continuously taken, the waveform shorter than the first period is ignored from each of the three-phase voltage waveforms, and the waveform has only one rectangular wave pulse. In the first period, the switching control unit (31), which is the minimum time required for detecting the direct current (Idc) flowing through the first or second DC line, and the first or second DC line are connected. A current detection unit (4) that detects a flowing direct current (Idc) and a current detection unit that detects the current detection unit at a first time (t1) before the first timing (t (0)) when the switching pattern changes. The direct current is estimated as a first-phase line current determined by the switching pattern at the first time point, and is detected by the current detection unit at a second time point after the first timing. The DC current is switched on at the second time point. A line current acquisition unit (32) for estimating a second-phase line current determined by a pattern, a waveform expression of a fundamental wave component of the first-phase and second-phase line currents, and the line current Based on the first-phase and second-phase line currents acquired in the acquisition unit (32), at least two-phase of the three-phase line currents at a second timing different from the first timing. A line current estimator (33) for estimating a line current, and the line current estimator (33) has a current amplitude based on the line currents (iu, iv, iw) of the first phase and the second phase. (Im) and the current phase (θi) at the first timing are calculated, and the advance of the current phase from the first timing to the second timing (t (1), t (0)) The current phase at the second timing is calculated by adding to the current phase at the timing, and the current amplitude and the previous By using the equation of the current phase and the waveform of the second timing to estimate the line current of the at least two phases of the line current of the three phases in the second timing.

A fourth aspect of the line current detection device according to the present invention includes three AC lines (Pu, Pv, Pw) connected to the inductive load (2), and first and second DC voltages applied between them. A second DC line (LH, LL), a first switching element (S1 to S3) provided between each of the three AC lines and the first DC line, and the three AC lines In a power conversion device including second switching elements (S4 to S6) provided between each and the second DC line, three-phase line currents (iu, iv, iw) flowing through the three AC lines ) To detect the first and second switching elements and to apply an AC three-phase voltage to the three AC lines, each of the three-phase voltages being The one cycle of the alternating current has substantially one pulse waveform, and the substantially one pulse waveform means that each of the three-phase voltages is the first or second Among the periods in which the potential applied to the streamline is continuously taken, the waveform shorter than the first period is ignored from each of the three-phase voltage waveforms, and the waveform has only one rectangular wave pulse. In the first period, the switching control unit (31), which is the minimum time required for detecting the direct current (Idc) flowing through the first or second DC line, and the first or second DC line are connected. A current detection unit (4) that detects a flowing direct current (Idc) and a current detection unit that detects the current detection unit at a first time (t1) before the first timing (t (0)) when the switching pattern changes. The direct current is estimated as a first-phase line current determined by the switching pattern at the first time point, and is detected by the current detection unit at a second time point after the first timing. The DC current is switched on at the second time point. A line current acquisition unit (32) for estimating a second-phase line current determined by a pattern, a waveform expression of a fundamental wave component of the first-phase and second-phase line currents, and the line current Based on the first-phase and second-phase line currents acquired in the acquisition unit (32), at least two-phase of the three-phase line currents at a second timing different from the first timing. A line current estimation unit (33) for estimating a line current and the DC current (Idc) at the second timing (t (1), t (n)) are determined based on the switching pattern at the second timing. e Bei 1 phase line current acquisition unit for acquiring a one-phase line current (iu) (39) that is, the voltage phase acquisition unit that acquires a voltage phase (.theta.v) for the three-phase voltages and (38), The line current estimation unit (33) is configured to perform the first timing based on the line current (iu, iv, iw) of the first phase and the second phase. Current phase (θi) at the time (t (0)), a phase difference (Δθ) between the current phase and the voltage phase at the first timing is calculated, and the voltage phase and the voltage at the second timing are calculated. The current phase at the second timing is calculated based on the phase difference, and the three-phase line current is calculated based on the one-phase line current, the current phase at the second timing, and the waveform equation. Current amplitude (Im) of the remaining two-phase line currents (iv, iw) based on the current amplitude, the current phase at the second timing, and the waveform equation. Estimate the current.

A fifth aspect of the line current detection device according to the present invention includes three AC lines (Pu, Pv, Pw) connected to the inductive load (2), and first and second DC voltages applied between them. A second DC line (LH, LL), a first switching element (S1 to S3) provided between each of the three AC lines and the first DC line, and the three AC lines In a power conversion device including second switching elements (S4 to S6) provided between each and the second DC line, three-phase line currents (iu, iv, iw) flowing through the three AC lines ) To detect the first and second switching elements and to apply an AC three-phase voltage to the three AC lines, each of the three-phase voltages being The one cycle of the alternating current has substantially one pulse waveform, and the substantially one pulse waveform means that each of the three-phase voltages is the first or second Among the periods in which the potential applied to the streamline is continuously taken, the waveform shorter than the first period is ignored from each of the three-phase voltage waveforms, and the waveform has only one rectangular wave pulse. In the first period, the switching control unit (31), which is the minimum time required for detecting the direct current (Idc) flowing through the first or second DC line, and the first or second DC line are connected. A current detection unit (4) that detects a flowing direct current (Idc) and a current detection unit that detects the current detection unit at a first time (t1) before the first timing (t (0)) when the switching pattern changes. The direct current is estimated as a first-phase line current determined by the switching pattern at the first time point, and is detected by the current detection unit at a second time point after the first timing. The DC current is switched on at the second time point. A line current acquisition unit (32) for estimating a second-phase line current determined by a pattern, a waveform expression of a fundamental wave component of the first-phase and second-phase line currents, and the line current Based on the first-phase and second-phase line currents acquired in the acquisition unit (32), at least two-phase of the three-phase line currents at a second timing different from the first timing. A line current estimation unit (33) for estimating a line current and the DC current (Idc) at the second timing (t (1), t (n)) are determined based on the switching pattern at the second timing. A one-phase line current acquisition unit (39) that acquires the one-phase line current (iu), and the line current estimation unit (33) includes the first-phase and second-phase line currents (iu). , iv, iw) based on the first timing (t (0)), and calculates the current phase (θi) from the first timing. The current phase advance up to two timings is added to the current phase at the first timing to calculate the current phase at the second timing, and the one-phase line current and the current phase at the second timing are calculated. And the current amplitude (Im) of the three-phase line current based on the waveform equation, and the remaining amplitude based on the current amplitude, the current phase at the second timing, and the waveform equation. Of the two-phase line currents (iv, iw), at least one phase line current is estimated.

A sixth aspect of the line current detection apparatus according to the present invention is the line current detection apparatus according to the third or fifth aspect, wherein the angular velocity (ω) of the three-phase line currents (iu, iv, iw) is further comprising angular velocity acquiring unit (381) acquires, the line current estimation unit (33), the process proceeds from the first timing of the current phase to the second timing, before Symbol from said first timing second It is calculated as the product of the period (ΔT ′) until timing (t (1), t (0)) and the angular velocity.

A seventh aspect of the line current detection device according to the present invention is the line current detection device according to the third or fifth aspect, wherein the voltage phase acquisition unit acquires the voltage phase (θv) for the three-phase voltage. (38), the line current estimation unit (33), the advance of the current phase from the first timing to the second timing, the first timing and the second timing (t (1), The voltage phase difference is calculated as t (n)).

An eighth aspect of the line current detection device according to the present invention includes three AC lines (Pu, Pv, Pw) connected to the inductive load (2), and first and second DC voltages applied between them. A second DC line (LH, LL), a first switching element (S1 to S3) provided between each of the three AC lines and the first DC line, and the three AC lines In a power conversion device including second switching elements (S4 to S6) provided between each and the second DC line, three-phase line currents (iu, iv, iw) flowing through the three AC lines ) To detect the first and second switching elements and to apply an AC three-phase voltage to the three AC lines, each of the three-phase voltages being The one cycle of the alternating current has substantially one pulse waveform, and the substantially one pulse waveform means that each of the three-phase voltages is the first or second Among the periods in which the potential applied to the streamline is continuously taken, the waveform shorter than the first period is ignored from each of the three-phase voltage waveforms, and the waveform has only one rectangular wave pulse. In the first period, the switching control unit (31), which is the minimum time required for detecting the direct current (Idc) flowing through the first or second DC line, and the first or second DC line are connected. A current detection unit (4) that detects a flowing direct current (Idc) and a current detection unit that detects the current detection unit at a first time (t1) before the first timing (t (0)) when the switching pattern changes. The direct current is estimated as a first-phase line current determined by the switching pattern at the first time point, and is detected by the current detection unit at a second time point after the first timing. The DC current is switched on at the second time point. A line current acquisition unit (32) for estimating a second-phase line current determined by a pattern, a waveform expression of a fundamental wave component of the first-phase and second-phase line currents, and the line current Based on the first-phase and second-phase line currents acquired in the acquisition unit (32), at least two-phase of the three-phase line currents at a second timing different from the first timing. A line current estimation unit (33) for estimating a line current and the DC current (Idc) at the second timing (t (1), t (n)) are determined based on the switching pattern at the second timing. A one-phase line current acquisition unit (39) that acquires the one-phase line current (iu), and the line current estimation unit (33) includes the first-phase and second-phase line currents (iu). , iv, iw) based on the current amplitude, the one-phase line current, and the waveform equation, A current phase (θi) at the second timing is calculated, and at least of the remaining two-phase line currents (iv, iw) based on the current amplitude, the current phase at the second timing, and the waveform equation Estimate one-phase line current.

A ninth aspect of the line current detection device according to the present invention includes three AC lines (Pu, Pv, Pw) connected to the inductive load (2), and first and second DC voltages applied between them. A second DC line (LH, LL), a first switching element (S1 to S3) provided between each of the three AC lines and the first DC line, and the three AC lines In a power conversion device including second switching elements (S4 to S6) provided between each and the second DC line, three-phase line currents (iu, iv, iw) flowing through the three AC lines ) To detect the first and second switching elements and to apply an AC three-phase voltage to the three AC lines, each of the three-phase voltages being The one cycle of the alternating current has substantially one pulse waveform, and the substantially one pulse waveform means that each of the three-phase voltages is the first or second Among the periods in which the potential applied to the streamline is continuously taken, the waveform shorter than the first period is ignored from each of the three-phase voltage waveforms, and the waveform has only one rectangular wave pulse. In the first period, the switching control unit (31), which is the minimum time required for detecting the direct current (Idc) flowing through the first or second DC line, and the first or second DC line are connected. A current detection unit (4) that detects a flowing direct current (Idc) and a current detection unit that detects the current detection unit at a first time (t1) before the first timing (t (0)) when the switching pattern changes. The direct current is estimated as a first-phase line current determined by the switching pattern at the first time point, and is detected by the current detection unit at a second time point after the first timing. The DC current is switched on at the second time point. Line current acquisition unit that estimates as a line current of the second phase which is one determined by the pattern (32) and said inductive voltage equation of the equivalent circuit for a load, has been the first acquired by the line current acquisition unit A line current estimation unit (33) for estimating the line currents of the first phase and the second phase at a second timing different from the first timing based on the phase current and the line current of the second phase; The line current estimation unit includes a two-phase line of the first phase and the second phase, with each of a plurality of timings in a period in which the switching pattern after the first timing is maintained as the second timing. current estimate.

A tenth aspect of the line current detection device according to the present invention is the line current detection device according to the ninth aspect, wherein the inductive load (2) is a motor, and the inductive load is the inductive load in the equivalent circuit. The resistance component (R2) and inductive component (L2) of the load (2) are the first voltage source (E1) by the three-phase voltage applied to the AC line (Pu, Pv, Pw), and the rotation of the motor Accordingly, it is connected in series with the second voltage source (E2) due to the induced voltage generated in the inductive component.

An eleventh aspect of the line current detecting device according to the present invention, the first a line current detecting device according to a tenth or one aspect of, the first timing from the first time point (t1) ( The period (ts1) until t (0)) is longer than the period required to convert the direct current from an analog value to a digital value.

A twelfth aspect of the line current detection device according to the present invention is the line current detection device according to any one of the first to eleventh aspects, wherein the second current from the first timing (t (0)). The period (ts2) until the time (t2) is longer than the period required for the transient fluctuation of the direct current accompanying the change in the switching pattern to fall within a predetermined range.

The first aspect of the power conversion system according to the present invention includes three first and second DC lines (LH, LL) to which a DC voltage is applied, and three inductive loads (2) connected to each other. AC lines (Pu, Pv, Pw), first switching elements (S1 to S3) provided between each of the three AC lines and the first DC line, and each of the three AC lines And a second switching element (S4 to S6) provided between the second DC line and the line current detection device (3) according to any one of the first to twelfth aspects.

According to the first aspect of the line current detection device of the present invention, there is substantially only one pulse in one cycle of the phase voltage (including substantially one pulse waveform). The line current in the vicinity of the first timing can be acquired based on the direct current. In addition, it is possible to obtain the first-phase and second-phase line currents at the second timing different from the first timing at which the pulse rises or falls. In addition, it is possible to estimate the line currents of the first phase and the second phase at the second timing with a simpler calculation than using the voltage equation of the equivalent circuit of the inductive load.

According to the 2nd and 3rd aspect of the line current detection apparatus concerning this invention, it contributes to realization of the line current estimation part concerning a 2nd aspect.

According to the fourth and fifth aspects of the line current detection device according to the present invention, since the one-phase line current at the second timing is detected, the line current according to any of the second and third aspects is detected. The estimation accuracy is higher than that of the estimation unit.

According to the sixth and seventh aspects of the line current detection device of the present invention, it contributes to the realization of the line current estimation unit according to the third or fifth aspect.

According to the eighth aspect of the line current detection apparatus of the present invention, since the one-phase line current at the second timing is detected, the line current estimation unit according to any one of the second to fourth aspects In comparison, the estimation accuracy is high. In addition, it is easy to calculate the current phase at the second timing.

According to the ninth aspect of the line current detection device of the present invention, since the equivalent circuit is used, the estimation accuracy can be improved.

According to the tenth aspect of the line current detection device of the present invention, since a simple equivalent circuit is used, the line current can be estimated by a relatively simple calculation.

According to the eleventh and twelfth aspects of the line current detection device of the present invention, a direct current can be detected more appropriately.

  According to the first aspect of the power conversion system of the present invention, there is substantially only one pulse in one cycle of the phase voltage (including a substantially one-pulse waveform). It is possible to provide a power conversion system that can acquire the line current at the first timing based on the current.

It is a figure which illustrates an example of a notional structure of an inverter. It is a figure which shows an example of a phase voltage typically. It is a figure which shows the electric current which flows through an inverter. It is a figure which shows the electric current which flows through an inverter. It is a figure which shows the electric current which flows through an inverter. It is a figure which shows the electric current which flows through an inverter. It is a figure which shows the electric current which flows through an inverter. It is a figure which shows the electric current which flows through an inverter. It is a figure which shows typically an example of the detection timing of a direct current, and the estimation timing of a phase current. It is a figure which illustrates an example of a notional structure of a control part. It is a figure for demonstrating the method to produce | generate the timing signal of an electric current detection. It is a figure for demonstrating the method to produce | generate the timing signal of an electric current detection. It is a figure for demonstrating the method to produce | generate the timing signal of an electric current detection. It is a figure which illustrates an example of a notional structure of a control part. It is a figure for demonstrating the method of determining the timing of an electric current detection. It is a figure for demonstrating the relationship between the period of a carrier, and the period of a phase voltage. It is a figure for demonstrating the method of determining the timing of an electric current detection. It is a figure for demonstrating the method of determining the timing of an electric current detection. It is a figure which illustrates an example of a notional structure of a control part. It is a figure which illustrates an example of a notional structure of a control part. It is a figure which illustrates an example of a notional structure of a control part. It is a figure which illustrates an example of a notional structure of a control part. It is a figure which shows an example of an equivalent circuit. It is a figure which shows phase difference (delta).

First embodiment.
As illustrated in FIG. 1, the power conversion system includes a power conversion device 1, a control unit 3, and a current detection unit 4. The power converter 1 is connected to DC lines LH and LL and AC lines Pu, Pv and Pw. The power conversion device 1 is, for example, an inverter, converts a DC voltage applied between the DC lines LH and LL into an AC voltage, and outputs the AC voltage to the AC lines Pu, Pv and Pw. Here, the potential applied to the DC line LL is lower than the potential applied to the DC line LH. In the illustration of FIG. 1, a smoothing capacitor C1 is provided. The smoothing capacitor C1 smoothes the DC voltage between the DC lines LH and LL. However, the smoothing capacitor C1 may not be provided.

  The inverter 1 includes switching elements S1 to S6 and diodes D1 to D6. The switching elements S1 to S6 are, for example, insulated gate bipolar transistors or field effect transistors. Switching elements S1 to S3 are provided between each of AC lines Pu, Pv, and Pw and DC line LH. Below, each switching element S1-S3 is also called an upper switching element. The diodes D1 to D3 are connected in parallel with the switching elements S1 to S3, respectively, and the anodes of the diodes D1 to D3 are connected to the AC lines Pu, Pv, and Pw, respectively.

  Each of the switching elements S4 to S6 is provided between each of the AC lines Pu, Pv, Pw and the DC line LL. Hereinafter, the switching elements S4 to S6 are also referred to as lower switching elements. The diodes D4 to D6 are connected in parallel with the switching elements S4 to S6, respectively, and the anodes of the diodes D4 to D6 are connected to the DC line LL. When the switching elements S1 to S6 have parasitic diodes such as MOS field effect transistors, the diodes D1 to D6 may be the parasitic diodes.

  A switching signal S is supplied from the control unit 3 to the switching elements S1 to S6. The switching elements S1 to S6 are turned on by the switching signal S. When the control unit 3 provides the switching signals S to the switching elements S1 to S6 at appropriate timing, the inverter 1 converts the DC voltage into the AC voltage. The control of the inverter 1 will be described in detail later.

  The inverter 1 can drive an inductive load 2, for example. Inductive load 2 is, for example, a motor, and is connected to AC lines Pu, Pv, Pw. When an AC voltage is applied to the inductive load 2, substantially sinusoidal line currents iu, iv, iw flow through the inductive load 2. As a result, the inductive load 2 is driven. Here, the direction of the line current flowing from the inverter 1 to the inductive load 2 is defined as positive, and the direction of the line current flowing from the inductive load 2 to the inverter 1 is defined as negative.

  The direct current Idc flowing through the direct current lines LH and LL is detected by the current detection unit 4 and output to the control unit 3. In the illustration of FIG. 1, the current detection unit 4 is provided on the DC line LL, but may be provided on the DC line LH.

  The current detection unit 4 includes, for example, a shunt resistor R41 and a detection unit 41. In the illustration of FIG. 1, the shunt resistor R41 is provided on the DC line LL. The detection unit 41 detects, for example, a voltage applied to the shunt resistor R41, and obtains a direct current Idc based on the resistance value of the shunt resistor R41 and the detected voltage. The detection unit 41 outputs the value of the direct current Idc to the control unit 3. The detection unit 41 may detect the voltage of the shunt resistor R41 and output the detected voltage to the control unit 3, and the control unit 3 may calculate the direct current Idc. Further, the current detection unit 4 does not need to be detected using a shunt resistor, and any direct current detection sensor can be employed. For example, a current sensor such as Hall CT may be used.

  The control unit 3 includes a switching control unit 31 and a line current acquisition unit 32. The switching control unit 31 outputs the switching signal S to the switching elements S1 to S6 to control the switching pattern of the switching elements S1 to S6. Thereby, the inverter 1 applies an AC phase voltage to the AC lines Pu, Pv, Pw. This switching signal S is generated as follows, for example. That is, for example, phase voltage command values for the phase voltages Vu, Vv, Vw applied to the AC lines Pu, Pv, Pw are generated based on the line currents iu, iv, iw from the line current acquisition unit 32, and the phase voltages A switching signal S is generated by comparing the command value with the carrier waveform. Since the generation of the phase voltage command value based on the line currents iu, iv, iw and the generation of the switching signal S based on the comparison between the phase voltage command value and the carrier waveform are known techniques, detailed description thereof is omitted here.

  The line current acquisition unit 32 acquires line currents iu, iv, and iw. Specific operations will be described in detail later.

  Here, the control unit 3 includes a microcomputer and a storage device. The microcomputer executes each processing step (in other words, a procedure) described in the program. The storage device is composed of one or more of various storage devices such as a ROM (Read Only Memory), a RAM (Random Access Memory), a rewritable nonvolatile memory (EPROM (Erasable Programmable ROM), etc.), and a hard disk device, for example. Is possible. The storage device stores various information, data, and the like, stores a program executed by the microcomputer, and provides a work area for executing the program. It can be understood that the microcomputer functions as various means corresponding to each processing step described in the program, or can realize that various functions corresponding to each processing step are realized. Further, the control unit 3 is not limited to this, and various procedures executed by the control unit 3 or various means or various functions implemented may be realized by hardware.

<Control of inverter 1>
The inverter 1 is controlled by the switching signal S as described below, for example. First, the upper switching element and the lower switching element connected to the same AC line are electrically connected to each other exclusively. That is, the switching elements S1 and S4 conduct exclusively with each other, the switching elements S2 and S5 conduct exclusively with each other, and the switching elements S3 and S6 conduct exclusively with each other. This is to prevent the DC lines LH and LL from being short-circuited and a large current from flowing through the switching elements S1 to S6.

  The switching elements S1 to S6 are controlled so that the phase voltages Vu, Vv, and Vw applied to the AC lines Pu, Pv, and Pw have waveforms illustrated in FIG. In the illustration of FIG. 2, each of the AC phase voltages Vu, Vv, Vw has only one pulse of a rectangular wave per AC cycle. In the example of FIG. 2, the high voltage period in which the phase voltages Vu, Vv, Vw take a high voltage value and the low voltage period in which the low voltage value is taken are substantially equal to each other, and the high voltage period of the phase voltages Vu, Vv, Vw. Are offset from each other by approximately 120 degrees in electrical angle.

  The waveforms of the phase voltages Vu, Vv, and Vw are ideally rectangular waves, and take two values corresponding to the conduction / non-conduction of the switching elements S1 to S3, respectively. For example, if the switching element S1 is conductive, the DC line LH is connected to the AC line Pu and the phase voltage Vu takes a high voltage value. If the switching element S1 is nonconductive, the switching element S4 is conductive, so the DC line LL Is connected to the AC line Pu and the phase voltage Vu takes a low voltage value. In FIG. 2, “Vu (S1)” is described, which also indicates that the high voltage value / low voltage value of the phase voltage Vu is conduction / non-conduction of the switching element S1, respectively.

  Therefore, by making the conduction period and the non-conduction period approximately equal to each other in each of the switching elements S1 to S3, and shifting the conduction periods of the switching elements S1 to S3 by approximately 120 degrees each, the inverter 1 has the phase voltage Vu of FIG. , Vv, Vw can be output.

  Further, according to such control, the switching elements S1 to S6 employ any of the following six switching patterns. Here, when the switching elements of the upper side and the lower side are indicated by “1” and “0”, and the switching patterns of the respective phases are shown side by side, the above-described six switching patterns are (001) (010) ( 011) (100) (101) (110). For example, when the lower switching elements S4 and S5 are turned on and the upper switching element S3 is turned on, the switching pattern (001) is employed (refer to the period from 300 degrees to 360 degrees in FIG. 2).

  In addition, when these switching patterns are adopted, the vectors for the phase voltage output from the inverter 1 are grasped as binary numbers, and the numbers are represented in decimal numbers. This is expressed as V6. Such voltage vectors V1 to V6 are also appended in FIG.

  In the example of FIG. 2, the phase voltages Vu, Vv, and Vw have only one pulse in one cycle of AC (in other words, one cycle of the fundamental component of the phase voltage), but have substantially one pulse waveform. It only has to be. The substantially one pulse waveform will be described in detail later.

<Acquisition method of line current>
Consider the current flowing through the inverter 1 when each switching pattern of FIG. 2 is adopted. Since the switching pattern corresponds to the voltage vector as described above, the following description will be made also using the voltage vector. 3 to 8 show currents flowing through the inverter 1 when the voltage vectors V1 to V6 are employed, respectively.

  As shown in FIG. 3, when the voltage vector V1 is employed, the upper switching element S3 and the lower switching elements S4 and S5 are conducted. Therefore, the DC current Idc flowing through the DC line LH flows through the AC line Pw in the positive direction as the line current iw via the switching element S3. The line current iw branches in the inductive load 2. The two branched currents flow in the negative direction through the AC lines Pu and Pv as line currents iu and iv, respectively. The line currents iu and iv are merged in the DC line LL via the switching elements S4 and S5, respectively, and flow as a DC current Idc. Therefore, when voltage vector V1 is adopted, DC current Idc is equal to line current iw.

  When the voltage vector V3 is employed as shown in FIG. 5, the upper switching elements S2 and S3 and the lower switching element S4 are conducted. Therefore, the DC current Idc flowing through the DC line LH branches and flows through the AC lines Pv and Pw in the positive direction as line currents iv and iw via the switching elements S2 and S3, respectively. The line currents iv and iw are combined in the inductive load 2 and flow in the negative direction through the AC line Pu as the line current iu. The line current iu flows through the DC line LL as the DC current Idc via the switching element S4. Therefore, when voltage vector V3 is employed, DC current Idc is equal to the absolute value -iu of line current iu having a negative value. In the following, when the value of the line current is negative, a negative sign may be added to express the absolute value.

  As shown in FIGS. 4 and 6 to 8, the direct current Idc and the line current are also associated when the other voltage vectors V <b> 2 and V <b> 4 to V <b> 6 are employed. FIG. 2 shows a line current flowing as a direct current Idc corresponding to each voltage vector.

  In the illustration of FIG. 2, since the voltage vector is adopted at an arbitrary time, the direct current Idc corresponds to any of the line currents iu, iv, and iw if the positive / negative is ignored at an arbitrary time. Therefore, the direct current Idc at this time can be estimated as a one-phase line current determined based on the switching pattern. For example, the DC current Idc can be detected as the line current iu during the period when the switching pattern (100) is employed (see also FIG. 6).

  Now, as illustrated in FIG. 2, the switching pattern is switched every 60 degrees in electrical angle. As illustrated in FIG. 9, the phases of the line currents detected at two time points t1 and t2 before and after the switching pattern is switched are different from each other. Therefore, the line current acquisition unit 32 estimates the DC current Idc detected by the current detection unit 4 at the time t1 as a line current of a phase determined by the switching pattern at the time t1, and the current detection unit 4 at the time t2. Is estimated as the line current of the phase determined by the switching pattern at time t2.

  For example, referring to FIG. 9, switching pattern (101) (voltage vector V5) is employed at time t1 before timing t (0) when the voltage vector switches from voltage vector V5 to voltage vector V4. Therefore, at this time, the direct current Idc at the time point t1 is estimated as the absolute value −iv of the v-phase line current iv taking a negative value. The value of the line current iv is a value obtained by making the sign of the direct current Idc negative. At time t2 after time t (0), the switching pattern (100) (voltage vector V4) is employed. Therefore, the DC current Idc at time t2 is estimated as the u-phase line current iu.

  This two-phase line current can be approximated to be a line current detected at substantially the same timing. This approximation is more appropriate as the period between the two time points t1 and t2 is shorter. In practice, the period is reasonable if it is about 1 or less of a few tenths of the phase voltage period. Since the sum of the three-phase line currents at the same timing is zero, the line current acquisition unit 32 calculates the remaining one-phase line current from the two-phase line current based on this relationship. For example, the line current iw is calculated based on the line currents iu and iv detected as described above. The calculation of the line current iw is not an essential requirement. For example, when converting the line currents iu, iv, iw into a two-phase fixed coordinate system, it is possible to convert using only the line currents iu, iv in view of the fact that the line current iw = −iu−iv. Because.

  As illustrated in FIG. 1, a direct current Idc and a switching signal S are input to the line current acquisition unit 32. The line current acquisition unit 32 recognizes the switching pattern currently employed by the switching signal S, and estimates the direct current Idc or a current with a negative sign as the line current based on the switching pattern. In other words, the DC current Idc is detected as a line current. Further, the line current acquisition unit 32 can recognize the time points t1 and t2 at which the DC current Idc is detected, for example, as follows. That is, the line current acquisition unit 32 receives the phase voltage command value from the switching control unit 31 and recognizes the schedule of the change of the switching pattern. For example, the time t1, before and after the preset period from the schedule of the change of the switching pattern. t2 is set. When it is determined that the current time point has reached time points t1 and t2, the direct current Idc is detected as a line current. This determination can be realized using, for example, a known timer circuit or counter circuit.

  When the switching pattern changes, for example, as shown in FIGS. This change in the current path is called commutation. Therefore, the timing at which the switching pattern changes can be regarded as the timing at which commutation occurs in the inverter 1.

  With the above-described line current detection method, it is possible to detect a three-phase line current using the DC current Idc every time the switching pattern changes, that is, every 60 degrees in electrical angle.

  Next, consider how long the period between each of the time points t1 and t2 and the timing t (0) at which the switching pattern changes is to be set. Immediately after the switching pattern changes, the direct current Idc fluctuates transiently with the change. It is desirable to detect the DC current Idc in a state where such transient fluctuations are settled, that is, in a state where the transient fluctuations of the DC current Idc are within a predetermined range. Therefore, it is desirable that the period ts2 from the change of the switching pattern to the time point t2 is longer than the transient period required for the transient fluctuation of the direct current Idc to be within the predetermined range. This transient period is determined by circuit conditions such as the power converter 1 and the inductive load 2, the capacitance of the capacitor C1, and the power capacity of the power source that supplies the DC voltage to the capacitor C1, and therefore is determined in advance by design or experiment. can do.

  For example, when the current detection unit 4 needs to convert the detected analog value of the direct current Idc into a digital value, it is desirable that the switching pattern does not change until the conversion period required for the conversion elapses. Therefore, it is desirable that the period ts1 from the time t1 until the switching pattern changes is longer than the period required for the current detection unit 4 to perform this conversion.

  It should be noted that the periods ts1 and ts2 are preferably as short as possible while satisfying the above-described conditions. This is because the remaining one-phase line current is calculated from the two-phase line current using the relationship that the sum of the three-phase line currents at the same timing is zero as described above.

  Here, a substantially one-pulse waveform will be described. The substantially one-pulse waveform here includes the following pulses. For example, in FIG. 2, in the half cycle in which the phase voltage V takes a low voltage value, the phase voltage V may maintain a high voltage value in a very short period. That is, the phase voltage V may include a very thin pulse. The very short period is a period shorter than the minimum period required for detecting the direct current Idc, and the minimum period is, for example, the sum of the above-described transient period, conversion period, and turn-on period of the switching element. However, there are other periods that need to be considered in addition to the transient period, the fluctuation period, and the turn-on period as the period necessary for current detection. Such other periods are common to those skilled in the art and are naturally assumed. Similarly, in the half cycle in which the phase voltage V takes a high voltage value, the phase voltage V may maintain the low voltage value for a very short period. This very short period is a period shorter than the above-mentioned minimum period. In short, a substantially one-pulse waveform is a rectangular wave pulse in which the phase voltage V, which is shorter than the minimum period among the periods in which the high voltage value or the low voltage value is continuously taken, is ignored from the waveform of the phase voltage V. It is sufficient to have only one.

  Next, an example of a method for generating the timing for detecting the direct current Idc (that is, time points t1 and t2) will be described.

<Generation of DC current detection timing 1>
The control unit 3 determines the timing for detecting the direct current Idc using a timer circuit. For example, as shown in FIG. 10, the control unit 3 further includes a periodic signal generation unit 341, a timer value initialization signal generation unit 342, a timer circuit 343, a commutation timing signal generation unit 344, and a current detection timing signal generation unit 345. ing.

  The periodic signal generator 341 generates a periodic signal illustrated in FIG. The activation / inactivation of the periodic signal is switched at a period of 60 electrical degrees. This periodic signal is generated using, for example, a rotational position detector that detects the rotational position (mechanical angle) of the rotor of the motor 2. The rotational position detection unit may be, for example, a sensor (for example, a hall sensor) that detects the rotational position of the rotor. The rotational position may be calculated by a technique. According to this, since it is not necessary to use a Hall sensor, manufacturing cost is suppressed.

  The timer value initialization signal generator 342 outputs a timer initialization signal SA to the timer circuit 343 every time the periodic signal is activated / deactivated.

  The timer circuit 343 increases the timer value CV as time elapses, and initializes the timer value CV every time the timer initialization signal SA is received. Accordingly, as illustrated in FIG. 11, the timer value CV is initialized every time the electrical angle advances by 60 degrees while increasing with the passage of time. Note that the electrical angle advances 60 degrees in a shorter time as the rotational speed of the rotor increases. Therefore, the maximum value of the timer value CV depends on the angular velocity ω of the phase voltage. Since the timer value is initialized in a shorter time as the angular velocity ω is higher, the maximum value of the timer value CV takes a smaller value.

  The commutation timing signal generation unit 344 determines whether the timer value CV is equal to the set value a, generates a commutation timing signal SB when a positive determination is made, and outputs this to the switching control unit 31. To do. In the example of FIG. 11, the timer value CV and the set value a intersect each other at the initialization timing. However, the timer value CV is actually discontinuous before and after the initialization. Therefore, at this timing, the timer value CV is not equal to the set value a, and the commutation timing signal SB is not output.

  When receiving the commutation timing signal SB, the switching control unit 31 changes the switching signal S so as to change the switching pattern of the switching elements S1 to S6. As a result, the switching pattern can be changed every 60 degrees of electrical angle. The switching patterns are employed in the order shown in FIG. 11 (and FIG. 2).

  The current detection timing signal generation unit 345 determines whether the timer value CV is equal to the set value a1 (<set value a) or the set value a2 (> set value a), and detects when a positive determination is made. A timing signal SH is generated and output to the line current acquisition unit 32.

  Each time the detection timing signal SH is input, the line current acquisition unit 32 detects the DC current Idc as a line current as described above.

  For example, the set value a is set to a value smaller than the maximum value of the timer value CV when the rotation speed of the rotor is the maximum speed. Thus, there is a timing at which the timer value CV and the set value a coincide with each other regardless of the rotation speed.

  The set value a1 is set such that the period ts1 is longer than the period required for the analog / digital conversion of the current detection unit 4. If the set value a1 calculated to satisfy this condition is smaller than the minimum value of the timer value CV, the set value a1 is updated as shown in FIG. For example, the set value a1 is updated by adding the timer amplitude that is the difference between the minimum value and the maximum value of the timer value CV to the set value a1. More specifically, when the timer minimum value, the timer maximum value, and the setting value a are 0, 100, and 10, respectively, and the setting value a1 calculated to satisfy the condition is −5, the setting value a1 is set to 95. Update to Then, the current detection timing signal generation unit 345 outputs the detection timing signal SH when the timer value CV is equal to the updated set value a1. Thus, the detection timing signal SH can be output while satisfying the condition. The timer amplitude is the time required for the electrical angle to advance by 60 degrees, and this can be calculated from the angular velocity ω.

  The set value a2 is set such that the period ts2 is longer than the transient period required for the transient fluctuation of the direct current Idc due to the change of the switching pattern to fall within a predetermined range. When the set value a2 calculated to satisfy this condition is larger than the maximum timer value, the set value a2 is updated as shown in FIG. For example, the set value a2 is updated by subtracting the timer amplitude from the set value a2. More specifically, when the timer minimum value, the timer maximum value, and the set value a are 0, 100, and 90, respectively, and the set value a2 calculated to satisfy the condition is 105, the set value a2 is Update to 5. Then, the current detection timing signal generation unit 345 outputs the detection timing signal SH when the timer value CV is equal to the updated set value a2.

  The set value a may be a predetermined value or may be variable. For example, the set value a may be set to a central value between the maximum value and the minimum value of the timer value CV. Thereby, compared with the case where the set value a is set to a value close to the maximum value or the minimum value of the timer value CV, the range in which the set values a1 and a2 are larger than the minimum value of the timer value CV and smaller than the maximum value. Easy to fit in. Therefore, it is possible to reduce the necessity of updating the set values a1 and a2.

<Generation of DC current detection timing 2>
The control unit 3 may determine the timing for detecting the DC current Idc using a carrier for generating the switching signal S. For example, as illustrated in FIG. 14, the switching control unit 31 includes a carrier generation unit 311, a voltage command value generation unit 312, and a comparison unit 313.

  The voltage command value generation unit 312 generates phase voltage command values Vu *, Vv *, and Vw * (collectively expressed as “V *” in the drawing) by any known method. For example, the phase voltage command values Vu *, Vv *, and Vw * are generated based on the command value I * for the line current and the line current from the line current acquisition unit 32. Although the command value I * can be generated based on, for example, the command value for the rotational speed of the motor 2 and the rotational speed of the motor 2, detailed description thereof is omitted because it differs from the essence of the present invention. The generated phase voltage command values Vu *, Vv *, Vw * have the same waveform as the phase voltages Vu, Vv, Vw illustrated in FIG.

  The carrier generation unit 311 generates a triangular carrier CW as illustrated in FIG. In the example of FIG. 15, an isosceles triangular wave is shown as the carrier CW. However, the present invention is not limited to this, and an arbitrary triangular wave such as a right-angled triangular wave may be adopted. A plurality of types of triangular waves may be connected to form the carrier CW.

  The comparison unit 313 outputs the switching signal S based on the comparison between the carrier CW and the phase voltage command values Vu *, Vv *, Vw *. For example, the switching element S1 is turned on when the phase voltage command value Vu * is larger than the carrier CW, and the switching element S4 is turned on when the phase voltage command value Vu * is smaller than the carrier CW. The same applies to the other phases. Therefore, as illustrated in FIG. 15, the point in time when one of the phase voltage command values intersects with the carrier CW is the timing at which the switching pattern changes (commutation timing).

  The line current acquisition unit 32 detects the direct current Idc as a line current when the carrier CW takes the minimum value or the maximum value before and after the commutation timing. In the illustration of FIG. 15, these time points are shown as detection timings. For example, the line current acquisition unit 32 detects the direct current Idc as a line current immediately before the commutation timing when the phase voltage command value Vv * becomes equal to the carrier CW, and the commutation is performed. Immediately after the timing, the DC current Idc is detected as a line current when the carrier CW takes the maximum value.

  In the example of FIG. 15, the period ts1 'between the commutation timing at which the phase voltage command value Vu * becomes equal to the carrier CW and the point in time immediately before the carrier CW takes the minimum value is very short. If this period ts1 'is shorter than the period required for analog / digital conversion, the DC current Idc cannot be detected properly. Therefore, as illustrated in FIG. 15, the line current acquisition unit 32 detects the DC current Idc as a line current when the carrier CW takes the maximum value further before. Thereby, the direct current Idc can be detected more appropriately. Similarly, if the time between the commutation timing and the time point at which the carrier CW takes either one of the minimum value and the maximum value immediately after that is short, the DC current Idc is detected at the next time point when the carrier takes the other value. do it. As a result, the DC current Idc can be detected more appropriately while avoiding the transient period of the DC current Idc.

  The half cycle of the carrier CW is set to be shorter than 1/6 of one cycle T1 of the phase voltage. When the half cycle of the carrier CW is longer than one-sixth of one cycle T1 of the phase voltage, the carrier CW has a maximum value and a minimum value in the period in which the switching pattern is maintained, as illustrated in FIG. This is because there is a period during which the DC current Idc cannot be detected during this period.

  If carrier CW is a right triangle wave, one cycle of carrier CW is set to be shorter than one sixth of the phase voltage.

<Generation of DC current detection timing 3>
Again, the control unit 3 determines the timing for detecting the DC current Idc using the carrier CW for generating the switching signal S. This will be described in detail with reference to FIG. In the example of FIG. 17, only the phase voltage command value Vu * is typically shown. The line current acquisition unit 32 first calculates the value of carrier CW (set value a) when any of the phase voltage command values becomes equal to carrier CW. More specifically, the set value a is calculated based on the following equation.

a = (CW2-CW1) · ta / T (1)
Here, CW1 and CW2 indicate a minimum value and a maximum value of the carrier CW, respectively, and T indicates a half cycle of the carrier CW. ta is the time from the start of the half cycle T of the carrier CW including the commutation timing to the commutation timing.

  Next, the line current acquisition unit 32 calculates setting values a1 and a2 using the setting value a calculated by the equation (1). For example, the setting value a1 is calculated by subtracting a predetermined first predetermined value from the setting value a, and the setting value a2 is calculated by adding the predetermined second predetermined value to the setting value a.

  If both of the set values a1 and a2 are not less than the minimum value CW1 and not more than the maximum value CW2, the line current acquisition unit 32 determines that the carrier CW is the set value a1 or the set value in the half cycle of the carrier CW including the commutation timing. When equal to a2, the direct current Idc is detected as a line current.

  In the illustration of FIG. 17, the value of carrier CW (set value a) when phase voltage command value Vu * rises and intersects carrier CW is close to minimum value CW1. For example, if the difference between the set value a and the minimum value CW1 is smaller than the first predetermined value, the calculated set value a1 is smaller than the minimum value CW1. In this case, the line current acquisition unit 32 updates the set value a1 as follows. That is, the set value a1 'is calculated by subtracting the set value a1 from twice the minimum value CW1 of the carrier CW. For example, if the minimum value CW1 is -1 and the set value a1 is -1.2, the set value a1 'is -0.8. Then, the line current acquisition unit 32 performs direct current when the carrier CW is equal to the set value a1 ′ in the half cycle immediately before the half cycle including the time when the phase voltage command value Vu * rises and crosses the carrier CW. The current Idc is detected as a line current.

  As illustrated in FIG. 18, when the set value a2 is larger than the maximum value CW2 of the carrier CW, the set value a2 is updated as follows. That is, the set value a2 'is calculated by subtracting the set value a2 from twice the maximum value CW2 of the carrier CW. For example, when the maximum value CW2 is 1 and the set value a2 is 1.3, the set value a2 'is 0.7. The line current acquisition unit 32 detects the DC current Idc as a line current when the carrier CW is equal to the set value a2 ′ in a half cycle one after the half cycle in which the phase voltage command value and the carrier CW intersect. To do.

  17 and 18, the carrier CW is an isosceles triangular wave, but may be a right triangular wave, for example. In this case, T in equation (1) is not a half cycle of the carrier CW but one cycle.

  When the set value a1 is smaller than the minimum value CW1 of the right-angled triangular wave carrier CW, the set value a1 'is calculated by adding the difference between the maximum value CW2 and the minimum value CW1 of the carrier CW to the set value a1. Then, when the carrier CW is equal to the set value a1 'in one cycle immediately before the cycle in which the phase voltage command value intersects with the carrier CW, the line current acquisition unit 32 detects the DC current Idc as a line current.

  When the set value a2 is larger than the maximum value CW2 of the right-angled triangular wave carrier CW, the set value a2 'is calculated by subtracting the difference between the maximum value CW2 and the minimum value CW1 from the set value a2. The line current acquisition unit 32 detects the direct current Idc as a line current when the carrier CW is equal to the set value a <b> 2 ′ in one cycle after one cycle in which the phase voltage command value intersects the carrier CW.

Second embodiment.
In the first embodiment, three-phase line currents iu, iv, iw can be obtained each time the switching pattern changes. On the other hand, as illustrated in FIG. 9, in the period in which the switching pattern is maintained, one-phase line current can be detected based on the DC current Idc, but three-phase line current is detected based on the DC current Idc. It is difficult. Therefore, in the second embodiment, the three-phase line currents iu, iv, and iw at the timing t (0) at which the switching pattern changes are used for other timings (in FIG. 9, time points t (1) to t ( n) and n are natural numbers), and the three-phase line currents iu, iv and iw are estimated.

  As illustrated in FIG. 19, the control unit 3 further includes a line current estimation unit 33 as compared with the control unit 3 of FIG. 1. The line current estimation unit 33 receives the three-phase line currents iu, iv, and iw from the line current acquisition unit 32. The line current estimation unit 33 uses the three-phase line currents iu, iv, and iw and uses the following equations (2) to (4) to determine the three-phase line current iu at a timing different from the timing t (0). , Iv, iw are estimated.

iu = Im · sin θi (2)
iv = Im · sin (θi−2π / 3) (3)
iw = Im · sin (θi + 2π / 3) (4)
Here, Im is the amplitude of the line currents iu, iv, iw (hereinafter referred to as current amplitude), and θi is the phase of the line currents iu, iv, iw (hereinafter referred to as current phase). These formulas (2) to (4) are waveform formulas for the fundamental wave component of the line current ix (x represents u, v, w, the same applies hereinafter).

  As understood from the equations (2) to (4), the line currents iu, iv, iw at an arbitrary timing are calculated by obtaining the current amplitude Im and the current phase θi at the timing. Therefore, hereinafter, the current amplitude Im and the current phase θi at an arbitrary timing are calculated.

  First, an example of calculating the current amplitude Im will be described. The line current estimation unit 33 calculates the current amplitude Im from the three-phase line currents iu, iv, and iw at time t (0). For example, the line current estimation unit 33 first converts the line currents iu, iv, iw from the line current acquisition unit 32 into an α-axis current iα and a β-axis current iβ in a two-phase fixed coordinate system. As such conversion, for example, a known absolute conversion is adopted. This conversion can be performed using only two-phase line currents. This is because the remaining one phase can be expressed by this two-phase line current. Therefore, the line current acquisition unit 32 does not necessarily need the step of calculating the remaining one-phase line current. Then, the line current estimation unit 33 calculates the current amplitude Im by the following equation based on the currents iα and iβ.

Im = sqrt (2/3) · sqrt (iα ^ 2 + iβ ^ 2) (5)
Here, sqrt () indicates the square root of the value in parentheses, and A ^ B indicates A to the Bth power. The current amplitude Im may be an average value of a plurality of current amplitudes Im calculated each time the switching pattern changes, or the calculated current amplitude Im is input to a low-pass filter, and the output thereof is the current amplitude. It may be used as Im.

  Next, an example of calculating the current phase θi at an arbitrary time point t (k) (k is a natural number from 1 to n) will be described. In calculating the current phase θi at time t (k), the line current estimation unit 33 first calculates the current phase θi at time t (0). The current phase θi at time t (0) can be calculated from the line currents iu, iv, iw detected at time t (0). For example, the line current estimation unit 33 calculates the current phase θi (t0) as the current phase θi at the time point t (0) based on the following equation.

θi (t0) = arctan (iα / iβ) (6)
Here, arctan () indicates the arc tangent of the value in parentheses.

  Now, using the current phase θi at time t (0), the current phase θi at time t (k) is calculated as described below, for example. Here, it is assumed that the phase difference Δθ between the current phase θi and the phase of the phase voltage (hereinafter referred to as voltage phase) is equal to each other at time points t (0) and t (k). This assumption is valid in a steady state where the motor is rotated at a stable speed, particularly if the inductive load 2 is a motor, for example. Therefore, if the phase difference Δθ can be calculated using the current phase θi and the voltage phase θv at the time t (0), the current at the time t (k) using the voltage phase θv and the phase difference Δθ at the time t (k). The phase θi can be calculated.

  Now, the current phase θi at time t (0) is calculated using equation (6). On the other hand, the voltage phase θv at the time point t (0) can be obtained as follows. That is, as shown in FIG. 19, the control unit 3 includes a voltage phase acquisition unit 38. For example, the voltage phase acquisition unit 38 receives the phase voltage command value V * from the switching control unit 31 and acquires the voltage phase θv based on the phase voltage command value V *. Since the phase voltage command value V * has the same waveform as the phase voltage in FIG. 2, the fundamental wave component may be extracted and the voltage phase θv may be calculated in the same manner as the current phase θi. Alternatively, a voltage detector that detects a phase voltage applied to the AC lines Pu, Pv, and Pw may be provided, and the voltage phase θv may be calculated from the detected phase voltage.

  The line current estimation unit 33 calculates the phase difference Δθ (= θi−θv) between the current phase θi and the voltage phase θv at time t (0). The phase difference Δθ may be an average value of a plurality of phase differences Δθ calculated each time the switching pattern changes. The calculated phase difference Δ is input to a low-pass filter, and an output thereof is converted into a phase difference. It may be used as Δθ.

  The voltage phase θv at the time point t (k) is acquired by the voltage phase acquisition unit 38 in the same manner as the voltage phase θv at the time point t (0). The line current estimation unit 33 calculates the current phase θi at the time t (k) using the phase difference Δθ and the voltage phase θv at the time t (k) according to the following equation.

θi = θv + Δθ (7)
Then, the line current estimation unit 33 calculates the line current ix at the time t (k) based on the equations (2) to (4) using the calculated current amplitude Im and the current phase θi at the time t (k). calculate. Thereby, the line currents iu, iv, iw can be estimated even at an arbitrary time point t (k) during which the switching pattern is maintained. Note that it is not always necessary to estimate the line currents iu, iv, iw, and any two-phase line currents may be estimated. This is because, for example, in the case of conversion to a line coordinate iu, iv, iw two-phase fixed coordinate system, a two-phase line current is sufficient in view of the fact that the line current iw = −iu−iv.

  Next, another example of calculation of the current phase θi at time t (k) will be described. Note that the calculation of the current amplitude Im and the calculation of the line current at the time t (k) based on the current amplitude Im and the current phase θi at the time t (k) are the same as the above-described calculation, so that repeated description is avoided. . As illustrated in FIG. 20, the control unit 3 further includes an angular velocity acquisition unit 381 instead of the voltage phase acquisition unit 38 as compared with the control unit 3 of FIG. 19. The angular velocity acquisition unit 381 will be described later.

  The current phase θi satisfies the following formula.

θi (tk) = θi (t0) + ωΔt ′ (8)
Here, θi (tk) represents the current phase θi at time t (k), θi (t0) represents the current phase θi at time t (0), and Δt ′ represents time t (0) from time t (0). The elapsed time up to k) is known and known. Since the current phase θi (t0) at the time point t (0) can be calculated as described above, the current phase θi (tk) at the time point tk can be calculated if the angular velocity ω can be obtained.

  The angular velocity ω is acquired by the angular velocity acquisition unit 381. Hereinafter, calculation of the angular velocity ω will be described in detail. Since the angular velocity of the phase voltage Vx and the angular velocity of the line current ix are equal to each other, the angular velocity ω may be calculated from the current phase θi or may be calculated from the voltage phase θv. Here, the case where it calculates from current phase (theta) i first is demonstrated. The angular velocity ω is expressed by the following equation.

ω = (θi1−θi2) / ΔT (9)
Here, θi1 and θi2 are current phases θi at two different points in time among the current phases θi of the line currents iu, iv, and iw detected at every electrical angle of 60 degrees. For example, the current phase θi at two time points t (0) closest to the time point t (k) among the time points t (0) at every 60 degrees of electrical angle. ΔT is a period between the two time points. The period ΔT can be obtained using any time measuring means (for example, a timer circuit). Therefore, the angular velocity ω in the period between the two time points can be calculated based on the equation (9).

  Then, assuming that the angular velocity ω is substantially constant, it is assumed that the angular velocity ω in the period between the two time points is equal to the angular speed ω in the period from the time point t (0) to the time point t (k). This assumption is valid in a steady state where the motor is rotated at a constant speed, particularly if the inductive load 2 is a motor, for example.

  Therefore, the line current estimation unit 33 uses the angular velocity ω, the period Δt ′ from the time t (0) to the time t (k), and the current phase θi at the time t (0) to formula (8). Based on this, the current phase θi at time t (k) can be calculated. In other words, the line current estimation unit 33 adds the advance of the current phase θi based on the angular velocity ω and the period Δt ′ from the time t (0) to the time t (k) to the current phase θi at the time t (0). Then, the current phase θi at the time point t (k) is calculated.

  As described above, the angular velocity ω is also the angular velocity with respect to the phase voltage Vx. Therefore, the angular velocity ω can be calculated using the voltage phase θv. For example, the angular velocity ω can be calculated based on the following equation using the voltage phases θv1 and θv2 that are the voltage phases θv at two arbitrary time points and the period ΔT ′ between these two time points.

ω = (θv2−θv1) / ΔT ′ (10)
Therefore, using the angular velocity ω calculated based on the voltage phase θv, the current phase θi at the time point t (k) is calculated based on the equation (8), and then based on the equations (2) to (4). The line currents iu, iv, iw at time t (k) may be calculated.

  Note that the angular velocity ω may be calculated at an arbitrary plurality of times (for example, every time the switching pattern changes), and the average value may be used as the angular velocity ω. Alternatively, the angular velocity ω may be input to a low-pass filter and the output thereof may be You may use as angular velocity (omega).

  If the time points t (0) and t (k) are adopted as the two time points, the period ΔT ′ in the equation (10) coincides with the period Δt ′. Substituting Equation (10) at this time into Equation (8) yields the following equation.

θi (tk) = θi (t0) + θv (tk) −θv (t0) (11)
The line current estimation unit 33 may calculate the current phase θi at the time point t (k) based on the equation (11). In other words, the current phase θi at time t (k) can be calculated by adding the difference between the voltage phases θv at time t (k) and time t (0) to the current phase θi at time t (0). Good. According to this, the current phase θi can be calculated without calculating the angular velocity ω. Therefore, in this case, the voltage phase acquisition unit 38 is provided instead of the angular velocity acquisition unit 381.

  If the inductive load 2 is a motor, a rotational speed detection sensor for detecting the mechanical angular speed of the motor (angular speed of the rotor) may be provided, and the angular speed acquisition unit 381 may calculate the angular speed ω based on the mechanical angular speed. The value obtained by dividing the mechanical angular velocity by the number of pole pairs of the rotor of the motor is the angular velocity ω. The mechanical angular velocity of the motor may be calculated by a known sensorless technique.

  Now, all of the above examples calculate at least two-phase line currents among the line currents iu, iv, and iw at time t (k). Hereinafter, a case will be described in which one-phase line current at time t (k) is detected and at least one-phase line current is calculated from the remaining two-phase line currents.

  In the illustration of FIG. 21, the control unit 3 further includes a one-phase line current acquisition unit 39 as compared with the control unit 3 of FIGS. The one-phase line current acquisition unit 39 estimates the DC current Idc detected at time t (k) as a one-phase line current determined based on the switching pattern at time t (k). For example, when the switching pattern at time t (k) is (100), the DC current Idc is estimated as the u-phase line current iu.

  As described above, the one-phase line current acquisition unit 39 detects one-phase line current among the line currents iu, iv, and iw at the time point t (k).

  The line current estimation unit 33 calculates the current phase θi at the time point t (k) based on any of the methods described above. The line current estimation unit 33 then calculates the one-phase line current at the time point t (k), the current phase θi at the time point t (k), and the line current waveform formulas (formulas (2) to (4)). Based on the above, current amplitude Im is calculated. For example, when the u-phase line current iu is detected as the one-phase line current at time t (k), the current amplitude Im is calculated based on the equation (2).

  Next, the line current estimation unit 33 uses the current amplitude Im and the current phase θi at the time t (k) to calculate the remaining two-phase line currents based on the waveform equation of the fundamental component of the line current. calculate. For example, the line current of at least one phase among the line currents iv and iw is calculated based on the expressions (3) and (4).

  According to this estimation method, since the one-phase line current at time t (k) is detected, the estimation accuracy can be improved.

  Further, the line current estimation unit 33 may calculate at least one phase line current among the remaining two phase line currents as follows. That is, first, the line current estimation unit 33 calculates the current amplitude Im based on the line currents iu, iv, iw detected at time t (0). The current amplitude Im is calculated based on, for example, the equation (5). Then, based on the one-phase line current detected at time t (k), the current amplitude Im, and the equation of the waveform of the line current, the current phase θi at time t (k) is calculated. For example, when the u-phase line current iu is detected as the one-phase line current, the current phase θi at the time point t (k) is calculated based on the equation (2).

  Next, the line current estimation unit 33 uses the current amplitude Im and the current phase θi at the time point t (k), based on the line current waveform equations (formulas (2) to (4)), Of the two-phase line currents, at least one phase line current is calculated. For example, the line currents iv and iw are calculated based on the equations (2) and (4).

  Even in this estimation method, since the one-phase line current at the time point t (k) is detected, the estimation accuracy can be improved. In addition, the current phase θi at the time point t (k) can be calculated relatively easily, and thus the calculation of the line current can be simplified.

Third embodiment.
In the second embodiment, the line current estimation unit 33 calculates the line current at an arbitrary timing using the waveform formula of the fundamental wave component of the line current. In the present embodiment, the line current estimation unit 33 calculates the line current at an arbitrary timing using the voltage equation in the equivalent circuit of the inductive load 2. Below, the case where a motor is employ | adopted as the inductive load 2 is demonstrated. For example, the motor here is a synchronous motor including a motor having a permanent magnet.

  As illustrated in FIG. 22, the control unit 3 further includes an angular velocity acquisition unit 381, an interlinkage magnetic flux acquisition unit 382, and a phase voltage acquisition unit 383 compared to the control unit 3 of FIG. 19.

  Further, as illustrated in FIG. 23, in this equivalent circuit, the induction component L2 and the resistance component R2 of the motor 2 include an AC voltage source E1 indicating a phase voltage, and an induced voltage generated in the induction component L2 by the rotation of the motor 2. Is connected in series with an AC voltage source E2. In such an equivalent circuit, a simple equivalent circuit is employed as the inductive load 2, so that the voltage equation is simplified as shown by the following equation. Therefore, the arithmetic processing can be simplified.

  Here, L represents the inductance of the inductive component L2, R represents the resistance value of the resistance component R2, ω represents the angular velocity of the line current, and φx represents the x-phase armature flux linkage by the permanent magnet. The induced voltage is represented by multiplication of the angular velocity ω and the flux linkage φx.

  When Expression (12) is transformed, Expression (13) is derived.

  When the equation (13) is transformed by the forward difference using the time points t (k + 1) and t (k), the following equation is derived. Note that a backward difference or a center difference may be used regardless of the forward difference. Here, a method using forward difference will be described.

ix (tk + 1) = ix (tk) + {Vx (tk) -R ・ ix (tk) -ω ・ φx (tk)} (t (k + 1) -t (k)) / L ... (14)
Here, ix (tk + 1) indicates the line current ix at time t (k + 1), ix (tk) indicates the line current ix at time t (k), and Vx (tk) indicates the phase voltage Vx at time tk. , Φx (tk) indicates the x-phase flux linkage at time tk.

  In equation (14), the phase voltage Vx (tk) is acquired by the phase voltage acquisition unit 383. For example, the phase voltage acquisition unit 383 may detect the phase voltage Vx at the time tk, or may adopt the phase voltage command value at the time tk as the phase voltage Vx. The inductance L and the resistance value R are values inherent to the motor 2 and are known. Therefore, if the induced voltage at the time point tk (multiplication of the angular velocity ω and the linkage flux φx (tk)) is known, the relationship between the line current ix (tk + 1) and the line current ix (tk) is obtained by the equation (14). Become known.

  Now, the induced voltage of each phase is expressed by the following equation.

ω · φu = ω · φa · sqrt (2/3) · sin (θv-δ) (15)
ω · φv = ω · φa · sqrt (2/3) · sin (θv-δ-2π / 3) (16)
ω · φw = ω · φa · sqrt (2/3) · sin (θv−δ + 2π / 3) (17)
Here, φa is the magnitude of the flux linkage vector for the flux linkage. The magnitude φa of the flux linkage vector is a value inherent to the motor 2 and is known. δ is the phase difference between the induced voltage vector and the voltage vector V for the fundamental component of the phase voltage. The induced voltage vector is along the q axis in a rotary coordinate system having a d axis corresponding to the magnetic pole center of the rotor of the motor 2 and a q axis orthogonal to the d axis and corresponding to the poles of the rotor. Therefore, as illustrated in FIG. 24, the phase difference δ is a phase difference between the q axis and the voltage vector V in the rotating coordinate system.

  The rotational position (phase) of the q axis can be detected by any known method. For example, it is detected by providing a rotational position detector that detects the rotational position of the rotor of the motor 2. The rotational position detection unit may be, for example, a hall sensor that detects the rotational position of the rotor. Alternatively, for example, the rotational position may be calculated by a known sensorless technique based on an induced voltage generated in the winding of the motor 2 or a line current flowing in the motor 2. According to this, since it is not necessary to use a Hall sensor, manufacturing cost is suppressed.

  The voltage phase θv is detected by the voltage phase acquisition unit 38 as described above. As described above, since the rotation position (phase) of the q axis and the voltage phase θv can be detected, the phase difference δ can be obtained. The calculation of the phase difference δ is executed by the interlinkage magnetic flux acquisition unit 382, and the interlinkage magnetic flux φx is calculated based on the equations (15) to (17).

  The angular velocity ω is acquired by the angular velocity acquisition unit 381 as described above. Therefore, the induced voltage at the time tk can be obtained by multiplying the flux linkage φx and the angular velocity ω.

  As described above, parameters other than the line currents ix (tk + 1) and ix (tk) can be obtained in Expression (14). The line current ix (t0) at the time point t (0) is acquired by the line current acquisition unit 32. Therefore, the line current ix (t1) at the time t (1) can be calculated using the line current ix (t0) at the time t (0). Similarly, the line current ix (t1) at the time t (1) is calculated. Can be used to calculate the line current ix (t2) at time t (2). Thereafter, the line current ix (tk + 1) at time t (k + 1) can be sequentially calculated using the line current ix (tk) at time t (k).

  Moreover, in the third embodiment, the estimation accuracy of the line currents iu, iv, iw can be improved as compared with the second embodiment. This will be described below. The line currents iu, iv, iw actually have harmonic components as well as fundamental components having an angular velocity ω. This harmonic component does not satisfy the equations (2) to (4). Therefore, an error may occur in the estimation of the line current using the equations (2) to (4). On the other hand, even the harmonic component of the line current satisfies the formula (14). Therefore, if the line current is estimated using the voltage equation of the equivalent circuit, the estimation accuracy of the line current can be improved as compared with the second embodiment.

  Also in the third embodiment, the DC current Idc detected at time t (k + 1) is detected as a one-phase line current determined by the switching pattern at time t (k + 1), and the other 1 The line current of the phase may be estimated based on the equation (14), and the remaining one phase may be calculated based on the relationship that the sum of the line currents is zero. Thereby, the estimation accuracy of the line current at the time point t (k + 1) can be improved.

  Also in the third embodiment, as in the first and second embodiments, it is not necessary to estimate all of the line currents iu, iv, and iw. For example, the line current acquisition unit 32 acquires the line currents. Only the two-phase line current may be estimated using equation (14).

DESCRIPTION OF SYMBOLS 1 Inverter 4 Current detection part 31 Switching control part 32 Line current acquisition part 33 Line current estimation part 38 Voltage phase acquisition part 381 Angular velocity acquisition part 39 Single phase line current acquisition part LH, LL Input line Pu, Pv, Pw AC line S1- S6 Switching element

Claims (13)

Three AC lines (Pu, Pv, Pw) connected to the inductive load (2), first and second DC lines (LH, LL) to which a DC voltage is applied between them, and the three A first switching element (S1 to S3) provided between each AC line and the first DC line, and a first switching element (S1 to S3) provided between each of the three AC lines and the second DC line. In a power conversion device comprising two switching elements (S4 to S6), a line current detection device for detecting a three-phase line current (iu, iv, iw) flowing through the three AC lines,
The switching pattern of the first and second switching elements is controlled to apply an AC three-phase voltage to the three AC lines, and each of the three-phase voltages has a substantially one pulse waveform in one cycle of the AC. The substantially one-pulse waveform means that each of the three-phase voltages is shorter than a first period among periods in which potentials applied to the first or second DC line are continuously taken. The waveform neglected from the waveform of the phase voltage is a waveform having only one rectangular wave pulse, and the first period is necessary for detecting the direct current (Idc) flowing through the first or second DC line. Switching control unit (31) which is a minimum time,
A current detector (4) for detecting the direct current (Idc);
The DC current detected by the current detection unit at the first time (t1) before the first timing (t (0)) at which the switching pattern changes is changed according to the switching pattern at the first time. And the DC current detected by the current detector at the second time after the first timing is determined by the switching pattern at the second time. A line current acquisition unit (32) that estimates the line current of the second phase to be determined ;
Based on the equation of the waveform of the fundamental wave component of the line current of the first phase and the second phase, and the line current of the first phase and the second phase acquired in the line current acquisition unit (32). A line current estimation unit (33) for estimating at least two phase line currents of the three phase line currents at a second timing different from the first timing ;
The line current estimation unit, each of the plurality of timing in the period in which the switching pattern is maintained after the first timing as said second timing, you estimate the line current of the at least two phases, the line current detecting device . Three AC lines (Pu, Pv, Pw) connected to the inductive load (2), first and second DC lines (LH, LL) to which a DC voltage is applied between them, and the three A first switching element (S1 to S3) provided between each AC line and the first DC line, and a first switching element (S1 to S3) provided between each of the three AC lines and the second DC line. In a power conversion device comprising two switching elements (S4 to S6), a line current detection device for detecting a three-phase line current (iu, iv, iw) flowing through the three AC lines,
The switching pattern of the first and second switching elements is controlled to apply an AC three-phase voltage to the three AC lines, and each of the three-phase voltages has a substantially one pulse waveform in one cycle of the AC. The substantially one-pulse waveform means that each of the three-phase voltages is shorter than a first period among periods in which potentials applied to the first or second DC line are continuously taken. The waveform neglected from the waveform of the phase voltage is a waveform having only one rectangular wave pulse, and the first period is necessary for detecting the direct current (Idc) flowing through the first or second DC line. Switching control unit (31) which is a minimum time,
A current detector (4) for detecting the direct current (Idc);
The DC current detected by the current detection unit at the first time (t1) before the first timing (t (0)) at which the switching pattern changes is changed according to the switching pattern at the first time. And the DC current detected by the current detector at the second time after the first timing is determined by the switching pattern at the second time. A line current acquisition unit (32) that estimates the line current of the second phase to be determined;
Based on the equation of the waveform of the fundamental wave component of the line current of the first phase and the second phase, and the line current of the first phase and the second phase acquired in the line current acquisition unit (32). A line current estimating unit (33) for estimating at least two phase line currents of the three phase line currents at a second timing different from the first timing;
A voltage phase acquisition unit (38) for acquiring a voltage phase (θv) for the three-phase voltage;
With
The line current estimation unit (33)
Based on the line current (iu, iv, iw) of the first phase and the second phase, a current amplitude (Im) and a current phase (θi) at the first timing are calculated,
Calculating a phase difference (Δθ) between the current phase and the voltage phase at the first timing;
Calculating the current phase at the second timing by adding the phase difference to the voltage phase at the second timing (t (1), t (n));
A line current detection apparatus that estimates the at least two-phase line currents of the three-phase line currents at the second timing using the current amplitude, the current phase at the second timing, and the waveform equation . Three AC lines (Pu, Pv, Pw) connected to the inductive load (2), first and second DC lines (LH, LL) to which a DC voltage is applied between them, and the three A first switching element (S1 to S3) provided between each AC line and the first DC line, and a first switching element (S1 to S3) provided between each of the three AC lines and the second DC line. In a power conversion device comprising two switching elements (S4 to S6), a line current detection device for detecting a three-phase line current (iu, iv, iw) flowing through the three AC lines,
The switching pattern of the first and second switching elements is controlled to apply an AC three-phase voltage to the three AC lines, and each of the three-phase voltages has a substantially one pulse waveform in one cycle of the AC. The substantially one-pulse waveform means that each of the three-phase voltages is shorter than a first period among periods in which potentials applied to the first or second DC line are continuously taken. The waveform neglected from the waveform of the phase voltage is a waveform having only one rectangular wave pulse, and the first period is necessary for detecting the direct current (Idc) flowing through the first or second DC line. Switching control unit (31) which is a minimum time,
A current detector (4) for detecting the direct current (Idc);
The DC current detected by the current detection unit at the first time (t1) before the first timing (t (0)) at which the switching pattern changes is changed according to the switching pattern at the first time. And the DC current detected by the current detector at the second time after the first timing is determined by the switching pattern at the second time. A line current acquisition unit (32) that estimates the line current of the second phase to be determined;
Based on the equation of the waveform of the fundamental wave component of the line current of the first phase and the second phase, and the line current of the first phase and the second phase acquired in the line current acquisition unit (32). A line current estimation unit (33) for estimating at least two phase line currents of the three phase line currents at a second timing different from the first timing;
With
The line current estimation unit (33)
Based on the line current (iu, iv, iw) of the first phase and the second phase, a current amplitude (Im) and a current phase (θi) at the first timing are calculated,
The advance of the current phase from the first timing to the second timing (t (1), t (0)) is added to the current phase at the first timing to obtain the current phase at the second timing. Calculate
A line current detection apparatus that estimates the at least two-phase line currents of the three-phase line currents at the second timing using the current amplitude, the current phase at the second timing, and the waveform equation . Three AC lines (Pu, Pv, Pw) connected to the inductive load (2), first and second DC lines (LH, LL) to which a DC voltage is applied between them, and the three A first switching element (S1 to S3) provided between each AC line and the first DC line, and a first switching element (S1 to S3) provided between each of the three AC lines and the second DC line. In a power conversion device comprising two switching elements (S4 to S6), a line current detection device for detecting a three-phase line current (iu, iv, iw) flowing through the three AC lines,
The switching pattern of the first and second switching elements is controlled to apply an AC three-phase voltage to the three AC lines, and each of the three-phase voltages has a substantially one pulse waveform in one cycle of the AC. The substantially one-pulse waveform means that each of the three-phase voltages is shorter than a first period among periods in which potentials applied to the first or second DC line are continuously taken. The waveform neglected from the waveform of the phase voltage is a waveform having only one rectangular wave pulse, and the first period is necessary for detecting the direct current (Idc) flowing through the first or second DC line. Switching control unit (31) which is a minimum time,
A current detector (4) for detecting the direct current (Idc);
The DC current detected by the current detection unit at the first time (t1) before the first timing (t (0)) at which the switching pattern changes is changed according to the switching pattern at the first time. And the DC current detected by the current detector at the second time after the first timing is determined by the switching pattern at the second time. A line current acquisition unit (32) that estimates the line current of the second phase to be determined;
Based on the equation of the waveform of the fundamental wave component of the line current of the first phase and the second phase, and the line current of the first phase and the second phase acquired in the line current acquisition unit (32). A line current estimating unit (33) for estimating at least two phase line currents of the three phase line currents at a second timing different from the first timing;
The DC current (Idc) at the second timing (t (1), t (n)) is acquired as a one-phase line current (iu) determined based on the switching pattern at the second timing 1 Phase wire current acquisition unit (39),
A voltage phase acquisition unit (38) for acquiring a voltage phase (θv) for the three-phase voltage;
With
The line current estimation unit (33)
Calculating a current phase (θi) at the first timing (t (0)) based on the line currents (iu, iv, iw) of the first phase and the second phase;
Calculating a phase difference (Δθ) between the current phase and the voltage phase at the first timing;
Adding the phase difference to the voltage phase at the second timing to calculate the current phase at the second timing;
Based on the one-phase line current, the current phase at the second timing, and the waveform equation, the current amplitude (Im) of the three-phase line current is calculated,
A line current detection apparatus that estimates at least one line current of the remaining two-phase line currents (iv, iw) based on the current amplitude, the current phase at the second timing, and the waveform equation . Three AC lines (Pu, Pv, Pw) connected to the inductive load (2), first and second DC lines (LH, LL) to which a DC voltage is applied between them, and the three A first switching element (S1 to S3) provided between each AC line and the first DC line, and a first switching element (S1 to S3) provided between each of the three AC lines and the second DC line. In a power conversion device comprising two switching elements (S4 to S6), a line current detection device for detecting a three-phase line current (iu, iv, iw) flowing through the three AC lines,
The switching pattern of the first and second switching elements is controlled to apply an AC three-phase voltage to the three AC lines, and each of the three-phase voltages has a substantially one pulse waveform in one cycle of the AC. The substantially one-pulse waveform means that each of the three-phase voltages is shorter than a first period among periods in which potentials applied to the first or second DC line are continuously taken. The waveform neglected from the waveform of the phase voltage is a waveform having only one rectangular wave pulse, and the first period is necessary for detecting the direct current (Idc) flowing through the first or second DC line. Switching control unit (31) which is a minimum time,
A current detector (4) for detecting the direct current (Idc);
The DC current detected by the current detection unit at the first time (t1) before the first timing (t (0)) at which the switching pattern changes is changed according to the switching pattern at the first time. And the DC current detected by the current detector at the second time after the first timing is determined by the switching pattern at the second time. A line current acquisition unit (32) that estimates the line current of the second phase to be determined;
Based on the equation of the waveform of the fundamental wave component of the line current of the first phase and the second phase, and the line current of the first phase and the second phase acquired in the line current acquisition unit (32). A line current estimating unit (33) for estimating at least two phase line currents of the three phase line currents at a second timing different from the first timing;
The DC current (Idc) at the second timing (t (1), t (n)) is acquired as a one-phase line current (iu) determined based on the switching pattern at the second timing 1 Phase wire current acquisition unit (39) and
With
The line current estimation unit (33)
Calculating a current phase (θi) at the first timing (t (0)) based on the line currents (iu, iv, iw) of the first phase and the second phase;
The current phase advance from the first timing to the second timing is added to the current phase at the first timing to calculate the current phase at the second timing,
Based on the one-phase line current, the current phase at the second timing, and the waveform equation, the current amplitude (Im) of the three-phase line current is calculated,
A line current detection apparatus that estimates at least one line current of the remaining two-phase line currents (iv, iw) based on the current amplitude, the current phase at the second timing, and the waveform equation . An angular velocity acquisition unit (381) for acquiring an angular velocity (ω) of the three-phase line current (iu, iv, iw);
The line current estimation unit (33) advances the current phase from the first timing to the second timing, from the first timing to the second timing (t (1), t (0)). The line current detection device according to claim 3 , wherein the line current detection device is calculated as a product of a period (ΔT ′) and the angular velocity . A voltage phase acquisition unit (38) for acquiring a voltage phase (θv) for the three-phase voltage;
The line current estimation unit (33) determines the advance of the current phase from the first timing to the second timing at the first timing and the second timing (t (1), t (n)). is calculated as the difference between the voltage phase, the line current detecting device according to claim 3 or 5. Three AC lines (Pu, Pv, Pw) connected to the inductive load (2), first and second DC lines (LH, LL) to which a DC voltage is applied between them, and the three A first switching element (S1 to S3) provided between each AC line and the first DC line, and a first switching element (S1 to S3) provided between each of the three AC lines and the second DC line. In a power conversion device comprising two switching elements (S4 to S6), a line current detection device for detecting a three-phase line current (iu, iv, iw) flowing through the three AC lines,
The switching pattern of the first and second switching elements is controlled to apply an AC three-phase voltage to the three AC lines, and each of the three-phase voltages has a substantially one pulse waveform in one cycle of the AC. The substantially one-pulse waveform means that each of the three-phase voltages is shorter than a first period among periods in which potentials applied to the first or second DC line are continuously taken. The waveform neglected from the waveform of the phase voltage is a waveform having only one rectangular wave pulse, and the first period is necessary for detecting the direct current (Idc) flowing through the first or second DC line. Switching control unit (31) which is a minimum time,
A current detector (4) for detecting the direct current (Idc);
The DC current detected by the current detection unit at the first time (t1) before the first timing (t (0)) at which the switching pattern changes is changed according to the switching pattern at the first time. And the DC current detected by the current detector at the second time after the first timing is determined by the switching pattern at the second time. A line current acquisition unit (32) that estimates the line current of the second phase to be determined;
Based on the equation of the waveform of the fundamental wave component of the line current of the first phase and the second phase, and the line current of the first phase and the second phase acquired in the line current acquisition unit (32). A line current estimating unit (33) for estimating at least two phase line currents of the three phase line currents at a second timing different from the first timing;
The DC current (Idc) at the second timing (t (1), t (n)) is acquired as a one-phase line current (iu) determined based on the switching pattern at the second timing 1 Phase wire current acquisition unit (39) and
With
The line current estimation unit (33)
A current amplitude (Im) is calculated based on the line current (iu, iv, iw) of the first phase and the second phase;
Based on the current amplitude, the one-phase line current, and the waveform equation, a current phase (θi) at the second timing is calculated,
A line current detection apparatus that estimates at least one line current of the remaining two-phase line currents (iv, iw) based on the current amplitude, the current phase at the second timing, and the waveform equation . Three AC lines (Pu, Pv, Pw) connected to the inductive load (2), first and second DC lines (LH, LL) to which a DC voltage is applied between them, and the three A first switching element (S1 to S3) provided between each AC line and the first DC line, and a first switching element (S1 to S3) provided between each of the three AC lines and the second DC line. In a power conversion device comprising two switching elements (S4 to S6), a line current detection device for detecting a three-phase line current (iu, iv, iw) flowing through the three AC lines,
The switching pattern of the first and second switching elements is controlled to apply an AC three-phase voltage to the three AC lines, and each of the three-phase voltages has a substantially one pulse waveform in one cycle of the AC. The substantially one-pulse waveform means that each of the three-phase voltages is shorter than a first period among periods in which potentials applied to the first or second DC line are continuously taken. The waveform neglected from the waveform of the phase voltage is a waveform having only one rectangular wave pulse, and the first period is necessary for detecting the direct current (Idc) flowing through the first or second DC line. Switching control unit (31) which is a minimum time,
A current detector (4) for detecting the direct current (Idc);
The DC current detected by the current detection unit at the first time (t1) before the first timing (t (0)) at which the switching pattern changes is changed according to the switching pattern at the first time. And the DC current detected by the current detector at the second time after the first timing is determined by the switching pattern at the second time. A line current acquisition unit (32) that estimates the line current of the second phase to be determined;
Based on the voltage equation of the equivalent circuit for the inductive load and the line currents of the first phase and the second phase acquired by the line current acquisition unit, at a second timing different from the first timing. A line current estimation unit (33) for estimating a line current of the first phase and the second phase of
With
The line current estimation unit estimates the line currents of the first phase and the second phase, with each of a plurality of timings in a period in which the switching pattern after the first timing is maintained as the second timing, Line current detector. The inductive load (2) is a motor,
In the equivalent circuit, a resistance component (R2) and an inductive component (L2) of the inductive load (2) are applied to the AC line (Pu, Pv, Pw) by the first voltage source (the three-phase voltage) ( 10. The line current detection device according to claim 9 , wherein the line current detection device is connected in series to E1) and a second voltage source (E2) based on an induced voltage generated in the inductive component as the motor rotates . The period of the first from time (t1) to said first timing (t (0)) (ts1 ) is greater than the time required for the DC current to convert from an analog value to a digital value, claim 1 To 10. The line current detection device according to any one of 10 to 10 . A period (ts2) from the first timing (t (0)) to the second time point (t2) is required for the transient fluctuation of the DC current accompanying the change of the switching pattern to be within a predetermined range. The line current detection device according to claim 1, wherein the line current detection device is longer than the period . A line current detection device (3) according to any one of claims 1 to 12,
The first and second DC lines (LH, LL);
The three AC lines (Pu, Pv, Pw);
The first and second switching elements;
A power conversion system comprising:

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