CONTROL DEVICE FOR CONVERTER

Abstract

A control device for an inverter is provided that can better adjust the control gain even in the presence of a phase error. In a control device (10), a phase correction unit (75) corrects a phase error in an AC power supply (1) detected by a phase detector (5). A current coordinate transformer (74) converts the detected values ​​of the three-phase currents of an inverter (3) into dq-axis currents using the corrected phase. A current control unit (72) calculates a voltage command so that the current commands of the inverter (3) and the dq-axis currents match. A voltage coordinate transformer (73) converts the voltage command into three-phase voltage commands using the corrected phase. An estimation unit (76) estimates the inductance of an inductor (2) based on the voltage commands and the dq-axis currents.The phase correction unit (75) corrects a phase error based on the voltage commands, the dq-axis currents, and the impedance of the choke coil (2). The current control unit (72) updates the current control gain based on the inductance estimated by the estimation unit (76).

Description

Technical area

[0001] The present disclosure relates to a control device for an inverter (or converter). background

[0002] Patent Application Publication No. 1 discloses an example of a current control unit for a three-phase electric motor. Even if the inductance of the three-phase electric motor changes due to magnetic saturation, a control device of the three-phase electric motor increases the stability of current control by identifying the inductance and adjusting a control gain according to the identified value. Citation listPatent literature

[0003] [PTL 1] JP 2003-339183 A Summary of the inventionTask

[0004] The current control of a three-phase PWM (pulse width modulation) inverter and a three-phase electric motor can be performed using similar methods. In other words, the control method described in PTL 1 can also be applied to a three-phase PWM inverter. On the other hand, in PTL 1, an inductance is calculated based on a voltage command. Therefore, a fault in a conductive phase will result in an error between the voltage command and the actual voltage, and an error in the calculated inductance will also occur. Accordingly, the control gain adjustment may not be performed appropriately.

[0005] The present disclosure relates to a solution to such a problem. The present disclosure provides a control device for an inverter capable of more appropriately adjusting a control gain even in the presence of a conducting phase fault. Solution to the problem

[0006] A control device for an inverter according to the present disclosure is a control device for an inverter that receives an input of multi-phase current from a multi-phase power supply and that outputs a DC voltage, the control device comprising a phase detector that detects a phase of the multi-phase power supply; a phase correction transformer that corrects a phase detection error of the phase detector based on a voltage equation of the inverter to calculate a corrected phase; a current coordinate transformer that converts detected values ​​of multi-phase currents of the inverter into DC currents using the corrected phase; a current control unit that exercises control so that current commands of the inverter and the DC currents correspond to each other to calculate a voltage command;a voltage coordinate transformer that converts the voltage command into multi-phase voltage commands using the corrected phase; and an estimation unit that estimates an inductance of a reactor (choke coil) of the converter based on the voltage equation of the converter. The phase correction unit corrects the phase detection error using the voltage command, the direct currents, and an impedance of the reactor, the estimation unit estimates the inductance using the voltage command and the direct currents, and the current control unit updates a current control gain using the inductance estimated by the estimation unit. Advantageous effects of the invention

[0007] With the control device of the inverter according to the present disclosure, a control unit can be set more appropriately even in the case of a conductive phase fault. Brief description of the drawings Fig. 1 is a configuration diagram of an inverter and its control device according to Embodiment 1. Fig. 2 is a diagram showing the relationship between a current flowing through a reactor and an inductance in the inverter according to Embodiment 1. Fig. 3 is a diagram showing the change of a current control band due to a change in the inductance of the reactor in the inverter according to Embodiment 1. Fig. 4 is a block diagram showing a configuration of a power control unit of the control device according to Embodiment 1. Fig. 5 is a block diagram showing a configuration of an estimation unit of the control device according to Embodiment 1. Fig. 6 is a block diagram showing a configuration of a phase correction unit of the control device according to Embodiment 1. Fig. 7 is a flowchart showing an example of the operation of the control device according to Embodiment 1. Fig. 8 is a diagram showing an example of the relationship between an estimated value of inductance and a current control gain in the control device according to Embodiment 1. Fig. 9 is a diagram showing an example of the relationship between an estimated value of inductance and a current control gain in the control device according to Embodiment 1. Fig. 10 is a hardware configuration diagram of essential portions of the control device according to Embodiment 1. Fig. 11 is a block diagram showing a configuration of the power control unit of the control device according to Embodiment 2. Fig. 12 is a flowchart showing, for example, the operation of the control device according to Embodiment 2. Fig. 13 is a configuration diagram of the inverter and its control device according to Embodiment 3. Fig. 14 is a block diagram showing a configuration of the phase correction unit of the control device according to Embodiment 3. Fig. 15 is a flowchart showing, for example, the operation of the control device according to Embodiment 3. Description of the embodiments

[0008] The embodiments for carrying out the subject matter of the present disclosure will be described with reference to the accompanying drawings. Like or corresponding parts in each drawing are denoted by the same symbols, and overlapping descriptions are simplified or omitted where appropriate. It should be understood that the subject matter of the present disclosure is not limited to the following embodiments, and that any components of the embodiments may be modified or any components of the embodiments may be omitted without departing from the spirit of the present disclosure. Embodiment 1

[0009] Fig. 1 is a configuration diagram of an inverter 3 and its control device 10 according to Embodiment 1.

[0010] An AC power supply 1, for example, is a multi-phase power supply. In this example, the AC power supply 1 is a power supply that supplies three-phase alternating current. The AC power supply 1 supplies alternating current through a reactor 2 to the inverter 3, which is a three-phase voltage PWM inverter. The inverter 3 is a device that converts the AC voltage supplied by the AC power supply 1 into DC voltage and outputs the converted DC voltage. The inverter 3 supplies the converted DC voltage to a smoothing capacitor 4. An intermediate circuit voltage V dc is supplied from the smoothing capacitor 4 to an inverter (not shown) which is used to drive an electric load motor (not shown).

[0011] The control device 10 of the converter 3 comprises a phase control unit 5, a current detection unit 6 and a control unit 7.

[0012] The phase detection unit 5 detects a phase ϕ of the AC power supply 1. It should be noted that the phase detection unit 5 can be arbitrarily configured, regardless of whether it is a part of the hardware or the software, as long as the phase of the AC power supply 1 can be detected.

[0013] Current sensor 6 detects a phase current of inverter 3. In this example, current sensor 6 detects I r and I s as two phases of a current of the inverter 3. Alternatively, the current sensor 6 can also be configured to detect three phases of a current of the inverter 3.

[0014] The control unit 7 calculates on the basis of the phases ϕ of the AC power supply 1 detected by the phase detector 5, the phase currents I detected by the current sensor 6 r and I s of the inverter 3 and the intermediate circuit voltage V d , the voltage commands V r , V s and V t to the converter 3. The control unit 7 comprises a voltage control unit 71, a current control unit 72, a voltage coordinate transformer 73, a current coordinate transformer 74, a phase correction unit 75 and an estimation unit 76.

[0015] The voltage control unit 71 calculates a current command for the q-axis I q * based on a command value V dc * and a recognized value V dcof the intermediate circuit voltage. The voltage control unit 71 can use various methods, such as PID control (P: Proportional, I: Integral, and D: Derivative). While a current command for the d-axis I d * is normally set to 0 to achieve a power factor of 1, field weakening control can be performed taking voltage saturation into account.

[0016] The current control unit 72 calculates the COMMAND VALUES V d * and V q * the voltages of the dq-axes based on the command values ​​I d * and I q * and the detected values ​​I d and I q the currents of the dq-axes. The term dq-axes can be used here for the d-axis and the q-axis. The current control unit 72 can use various methods, such as PID control.

[0017] The voltage coordinate transformer 73 converts the command values ​​of the dq-axis voltages into three-phase voltage commands V r , V s and V e to the inverter 3 using a corrected phase θ. In this case, the corrected phase θ is the phase ϕ detected by the phase detection unit 5 and subsequently corrected by the phase correction unit 75. Details about the phase correction unit 75 will be provided later. Although in Fig. 1 not shown, the three-phase voltage commands are converted into a PWM signal by a carrier comparison and applied as a gate signal to a switching element of the converter 3.

[0018] The current coordinate transformer 74 transforms the phase currents I r and I s of the converter 3 into the dq-axis currents I d and I q. It should be noted that the current coordinate transformer 74 is not limited to a current coordinate transformer to which the currents of two phases are input, but may also be a current coordinate transformer to which the currents of three phases are input.

[0019] The estimation unit 76 estimates an inductance of the choke 2 based on the voltage command V d * the d-axis and the detected values ​​I d and I q of the dq-axis currents. An inductance L^ estimated by the estimation unit 76 is output to the current control unit 72. The current control unit 72 updates a control gain using the input inductance estimate L^. Details of the estimation unit 76 will be provided later.

[0020] Fig. 2 is a diagram showing the relationship between a current flowing through the reactor 2 and an inductance in the inverter 3 according to Embodiment 1.

[0021] An abscissa axis of the Fig. 2 shows a magnitude of the current flowing through the choke 2. The ordinate axis of the diagram shown in Fig. The diagram shown in Figure 2 represents the size of the inductance of choke 2.

[0022] Since the choke 2 is a coil, when a voltage is applied, the current flowing through the choke 2 increases over time, and the magnetic flux density also increases. In other words, the larger the load connected to a DC bus, the larger the current flowing through the choke 2 and the higher the magnetic flux density. On the other hand, the magnetic flux density does not increase infinitely, and a state of magnetic saturation is reached when a maximum magnetic flux density, which is determined by a material, shape, and the like, is exceeded. When magnetic saturation occurs, the inductance of the choke 2 decreases rapidly. This situation is in Fig. 2 shown.

[0023] Fig. 3 is a diagram showing a change in a current control band due to a change in the inductance of the reactor 2 in the inverter 3 according to Embodiment 1.

[0024] Typically, the current control gain in the current control unit 72 is determined based on a design value of the inductance of the choke 2. If the actual inductance of the choke 2 and the design value of the inductance of the current control unit 72 match, the current control characteristic is as shown in Fig. 3 with B and the current control band is ω B . If the actual inductance of the choke 2 is larger than the design value of the inductance of the current control unit 72, the current control band becomes obviously lower and the open loop characteristics are in Fig. 3 is given as A. At this time, the current control unit is ω A which is lower than the design value ω B. On the other hand, if the actual inductance of the reactor 2 is smaller than the design value of the inductance of the current control unit 72, the current control band becomes obviously higher, and the open-loop characteristics are as shown in Fig. 3 under C. At this point, the current control unit ω C which is higher than the design range ω B .

[0025] Combining these results with the Fig. From the relationship shown in Figure 2, it can be seen that the current flowing through the reactor 2 increases as the load connected to the DC bus of the inverter 3 increases and the inductance of the reactor 2 decreases due to the effect of magnetic saturation. At this time, since the actual inductance of the reactor 2 becomes smaller than the design value of the inductance of the current control unit 72, the current control band obviously becomes higher. As the inductance decreases and the current control unit band increases, the current controllability may decrease due to vibrational response, oscillation, or the like. The current control unit 72 according to the present disclosure enables stable current control even when the inductance of the reactor 2 changes by updating a control gain using an estimated value of the inductance.

[0026] Fig. 4 is a block diagram showing a configuration of the power control unit 72 of the control device 10 according to Embodiment 1.

[0027] The current control unit 72 updates the control gain using an estimated value of a changed inductance in order to suppress an effect of the above-described change in the inductance of the reactor 2 on the stability of the current control. The current control unit 72 updates a control gain 721 of the current control unit 72 using the inductance L^ of the reactor 2 estimated by the estimation unit 76. In general, the current control gain 721 of the current control unit 72 is determined using a design value ω I of the current control band and an inductance design value L of the choke coil 2 to ω I L. In this case, the gain ω IL only needs to be multiplied by L^ / L to update a gain using the inductance L^ of the choke coil 2 estimated by the estimation unit 76. In other words, the update of the control unit is done by multiplying the predetermined gain ω I L with the ratio between the value L^ of the inductance estimated by the estimation unit 76 and the design value L.

[0028] Fig. Figure 4 shows an example of using the PI control unit as a current control unit. The current control unit 72 multiplies a current deviation of the dq axes by the control gain 721, multiplies an output of the control gain 721 by an integration time constant 722, and then performs integration by an integrator 723. The current control unit 72 calculates the voltage commands V d * and V q* of the dq-axes by adding an output of the control gain 721, i.e., a proportional term, to an output of the integrator 723. In this way, by estimating the inductance of the choke 2 in real time and adjusting the gain, stable current control can be achieved even when the inductance changes. It should be noted that the Fig. 4 is an example, and the power control unit 72 may use various control methods, such as PID control.

[0029] Fig. 5 is a block diagram showing a configuration of the estimation unit 76 of the control device 10 according to Embodiment 1.

[0030] The estimation unit 76 is a state estimation observation unit that uses the d-axis voltage command V d * and the detected values ​​I d and I qthe dq-axis currents estimate an inductance of the choke coil 2. In this case, a d-axis voltage equation of the converter 3 is represented by the following expression (1). [Math. 1] Vd=−sLId|+ωLIq where L is the inductance of the choke 2, ω is the frequency of the AC power supply 1, and s is a Laplace operator. Replacing the inductance L in Expression 1 by an estimated value L^ yields an estimated value V d ^ the voltage on the d-axis, as shown in expression (2) below. [Math. 2] Vd^=−sL^ld+ωL^lq

[0031] A voltage difference e Vd based on expression (1) and expression (2) is represented by expression (3) below. [Math. 3] evd=Vd−Vd^=−sld(L−L^)+ωlq(L−L^)

[0032] From expression (3) it can be seen that the reduction of a difference (L - L^) between the inductance L of the choke 2 and the estimated value L^ also reduces the voltage difference e Vd reduced to zero. Therefore, the estimation unit 76 estimates the inductance of the choke coil 2 according to a control rule such as that shown in expression (4) below. [Math. 4] L^=K∫(Vd−Vd^)dt=K∫(Vd−ωL^lq)dt+KL^ld

[0033] The estimation unit 76 obtains the estimated value L^ of the inductance by performing an integral control so that a voltage error e Vd between an actual voltage V d and an estimated voltage V d^ becomes zero as in expression (4). In this case, K denotes a control gain of the estimation unit 76. Although the estimated value converges quickly when the control unit K is large, the control unit K is set to an appropriate value in view of the stability of the calculation. While V d in expression (4) is the actual voltage of the inverter 3, the voltage V d by the voltage command value V d * replaced because the voltage command value V d * belongs to the actual voltage of the inverter 3. In other words, the actual inverter voltage V d and the voltage command value V d * must correspond to each other. While the estimation unit 76, which focuses on the d-axis of the converter 3, was shown, a similar inductance estimation can also be performed using the q-axis voltage equation. In addition, the detected values ​​I d and I qthe currents of the dq-axis to be input into the estimation unit 76, the command values ​​I d * and I q * of the currents of the dq-axis. Fig. 5 shows a block diagram of the inductance estimation unit based on expression (4).

[0034] Fig. 6 is a block diagram showing a configuration of the phase correction unit 75 of the control device 10 according to Embodiment 1.

[0035] A phase detection error may occur with respect to the phase ϕ of the AC power supply 1 detected by the phase detection unit 5, for example, depending on the characteristics of a phase detection circuit, a phase calculation method, or the like. Since the estimation unit 76 estimates the inductance of the reactor 2 based on the voltage command V d * estimates, a fault in the conducting phase will result in an error between the voltage command V d* and the actual voltage Vd, and accordingly the estimation accuracy of the estimation unit 76 decreases. In order to suppress such a decrease in the estimation unit, the phase correction unit 75 corrects the phase ϕ detected by the phase detection unit 5.

[0036] Here, an extended model of the induced voltage of an electric motor is presented, where E denotes the induced voltage, R the winding resistance, and Δθ the phase detection error, as shown in Expression (5) and Expression (6) below. [Math. 5] E sin Δθ = Vd−Rld+ωLlq [Math. 6] E cos Δθ = Vq−Rlq−ωLld

[0037] When the expressions are applied to the inverter 3, E corresponds to the voltage of the AC power supply 1. Δθ corresponds to a detected fault of the phase ϕ of the AC power supply 1, as detected by the phase detection unit 5. In addition, the winding resistance R in the inverter 3 is sufficiently small and can be considered zero. Since a current of the inverter 3 can flow in the opposite direction to a current of the electric motor, by reversing the signs of the current, we obtain an extended model of the induced voltage of the inverter 3, as shown in Expression (7) and Expression (8) below. [Math. 7] E sin Δθ = Vd−ωLlq [Math. 8] E cos Δθ= Vq=ωLld

[0038] From expressions (7) and (8), the detected error of the phase detection unit 5 can be determined as shown in expression (9) below. [Math. 9] Δθ = atan Vd−ωLlqVq+ωLld≃Vd−ωLlqVq+ωLld

[0039] Expression (9) is calculated by determining the voltages V d and V q by the command values ​​V d * and V q * In addition, the current values ​​I d and I q by the command values ​​I d * and I q * can be replaced. According to expression (9), the phase correction unit 75 can correct the phase detection error Δθ of the phase detection unit 5 based on the voltage commands V d * and V q *, the currents I d and I q and the impedance ωL of the choke 2.

[0040] The phase correction unit 75 may be configured to remove a high-frequency component from the phase detection error calculated with Expression (9) using various filters, such as a low-pass filter. The phase correction unit 75 calculates the phase error Δθ using Expression (9) and obtains, for example, a phase correction value Δϕ as follows through PLL (Phase Locked Loop) control. The phase correction unit 75 obtains a correction rate by controlling a difference between a phase detection error command = 0 and the phase detection error = Δθ with a PI control unit 752. The phase correction unit 75 obtains the phase correction value Δϕ by integrating the correction rate with an integrator 753. The phase correction unit 75 adds the obtained phase correction value Δϕ to the phase ϕ to calculate a corrected phase θ.By constructing such a PLL control loop, a detected error in the phase ϕ of the AC power supply 1, as detected by the phase detection unit 5, can be corrected, a conducting phase can be improved, and a voltage command and an actual voltage can be matched. Accordingly, a decrease in the estimation accuracy of the inductance by the estimation unit 76 can be suppressed.

[0041] It should be noted that the phase correction unit 75, which performs the correction according to expression (9), requires the inductance L of the reactor 2. Therefore, a case in which a phase detection error ϕ has occurred and a case in which the inductance L changes although no phase detection error ϕ has occurred are inseparable, and in both cases, a calculation is performed under the assumption that the phase detection error Δθ has been generated in the phase detection unit 5. According to the Fig. 2, as the current flowing through the reactor 2 increases, the inductance of the reactor 2 decreases due to the effect of magnetic saturation. On the other hand, when the current flowing through the reactor 2 is small, the inductance of the reactor 2 remains unchanged. Based on this relationship between current and inductance, the control unit 7 suppresses the effect of a change in the inductance L, which is calculated as a phase detection error Δθ, by switching between operations depending on the magnitude of the current. When the current is smaller than a reference value, the phase correction unit 75 corrects or learns a phase error. Specifically, the phase correction unit 75 calculates a phase correction value based on Expression (9) and the like, and corrects the conducting phase using the calculated phase correction value. At this time, the estimation unit 76 does not estimate the inductance.For example, the estimation unit 76 may output a design value of the inductance or an immediately previous estimated value. On the other hand, when the current is equal to or greater than the reference value, the phase correction unit 75 corrects the conduction phase using the phase correction value calculated when the current was smaller than the reference value. At this time, the estimation unit 76 estimates the inductance using a voltage command calculated based on the corrected excitation phase, a current value, and the like. Note that the reference value is a preset current threshold value, such as a current value at which magnetic saturation occurs in the reactor 2, and the like. A current value compared with the reference value is, for example, the dq-axis currents I. d and I q or similar.

[0042] Fig. 7 is a flowchart showing an example of the operation of the control device 10 according to Embodiment 1.

[0043] Fig. Figure 7 shows an example of the processing for phase correction and the inductance estimation unit. Fig. The processing shown in Figure 7 is carried out, for example, when the control of converter 3 is started.

[0044] In step S701, the phase correction unit 75 corrects a phase detection error of the phase detection unit 5 according to a configuration such as shown in the block diagram of Fig. 6. Subsequently, the processing of the control device 10 proceeds to step S702.

[0045] In step S702, the control unit 7 determines whether a current value of the inverter 3 is equal to or greater than a reference value. If the current value is equal to or greater than the reference value, assuming that the inductance of the reactor 2 changes, the processing of the control device 10 proceeds to step S703. On the other hand, if the control value is lower than the reference value, assuming that the inductance of the reactor 2 does not change, the processing of the control device 10 proceeds to step S707 without performing inductance estimation by the estimator 76.

[0046] Since the inductance changes, the phase correction unit 75 stores the correction value Δϕ of the detected phase detection error in step S703. Accordingly, a change in the correction value Δϕ due to a change in the inductance can be suppressed by expression (9). For example, the phase correction unit 75 locks an output of the Fig. 6. By locking the correction value Δϕ, the phase detection error of the phase detection unit 5 is corrected without being influenced by a change in inductance. Subsequently, the processing of the control device 10 proceeds to step S704.

[0047] In step S704, the estimation unit 76 estimates the inductance of the reactor 2 according to a configuration such as shown in the block diagram of Fig. 5. Subsequently, the processing of the control device 10 proceeds to step S705.

[0048] In step S705, the control unit 7 determines whether a current value of the inverter 3 is less than the reference value. If the current value is equal to or greater than the reference value, assuming that the inductance of the reactor 2 changes, the processing of the control device 10 proceeds to step S704 to continue estimating the inductance. Conversely, if the control value is less than the reference value, assuming that the inductance of the reactor 2 does not change, the processing of the control device 10 proceeds to step S706.

[0049] In step S706, the estimation unit 76 stops estimating the inductance of the choke coil 2. Since no change in the inductance of the choke coil 2 has occurred at this time, the output of an integrator 761 of the estimation unit 76 can be reset to an initial value, or in other words, to a design value. The processing of the control device 10 then proceeds to step S707.

[0050] In step S707, the control unit 7 determines whether control of the inverter 3 has stopped or not. If control of the inverter 3 has not stopped, the processing of the control device 10 proceeds to step S701 to correct a phase detection error. If, however, control of the inverter 3 has stopped, the processing of the control device 10 ends.

[0051] Fig. 8 and Fig. 9 are diagrams showing, for example, a correspondence between an estimated value of inductance and a current control gain in the control device 10 according to Embodiment 1.

[0052] The abscissa axes of an upper and a lower diagram, which are shown in the Fig. 8 and Fig. 9, represent the course of time. An ordinate axis of the Fig. 8 and Fig. The upper diagram shown in Figure 9 represents an estimated value of the inductance of the choke 2. An ordinate axis of the Fig. 8 and Fig. The lower diagram shown in Figure 9 represents a current control gain that is set in the current control unit 72 according to the estimated value of the inductance. Fig. 8 and Fig. 9 show a situation where the estimated value of inductance decreases due to magnetic saturation.

[0053] Fig. Figure 8 shows an example of a system in which the current control gain is updated stepwise depending on the inductance estimation unit. For example, this system is used in a design in which more flexibility is allowed for the current control gain set for the current control unit 72 in consideration of the stability of a control system or the like.

[0054] Fig. Figure 9 shows an example of a control system in which the current control gain is continuously updated depending on the estimated inductance value. A control system in which the current control gain of the voltage control unit 72 leaves less room for control system stability, or in other words, a system with high gain to suppress current pulsations, bus voltage pulsations, or the like, is used in this case, for example. Continuously changing the control unit further improves control stability.

[0055] As described above, the control unit 10 according to Embodiment 1 is a control device of the converter 3. The converter 3 receives an input of three-phase currents from the AC power supply 1, performs switching, and outputs a DC voltage. The control device 10 includes the phase detector 5, the phase correction unit 75, the current coordinate transformer 74, the current control unit 72, the voltage coordinate transformer 73, and the estimation unit 76. The phase detection unit 5 detects a phase of the AC power supply 1. The phase correction unit 75 corrects a phase detection error of the phase detection unit 5 based on a voltage equation of the converter 3 to calculate a corrected phase. The current coordinate transformer 74 converts detected values ​​of the three-phase currents of the converter 3 into dq-axis currents using the corrected phase.The current control unit 72 controls the current commands of the inverter 3 and the dq-axis currents converted by the current coordinate transformer 74 to calculate a voltage command. The voltage coordinate transformer 73 converts the voltage command into three-phase voltage commands using the corrected phase. The estimation unit 76 estimates an inductance of the reactor 2 of the inverter 3 based on a voltage equation of the inverter 3. The phase correction unit 75 corrects a phase detection error using the voltage commands calculated by the current control unit 72, the dq-axis currents transformed by the current coordinate transformer 74, and an impedance of the reactor 2 estimated by the estimation unit 76. The estimation unit 76 estimates an inductance using the voltage commands calculated by the current control unit 72 and the dq-axis currents transformed by the current coordinate transformer 74.The current control unit 72 updates a current control gain using the inductance estimated by the estimation unit 76.

[0056] With such a configuration, the inductance estimation is performed in a state where a conducting phase error has been corrected. Accordingly, the accuracy of the inductance estimation is further increased, and due to an improvement in the current control band, the stability of the current control is further enhanced. Therefore, the control unit can be adjusted more appropriately even in the case of a conducting phase error.

[0057] If the dq-axis currents transformed by the current coordinate transformer 74 are less than a reference value, the estimation unit 76 stops estimating the inductance. If the dq-axis currents transformed by the current coordinate transformer 74 are equal to or greater than the reference value, the phase correction unit 75 stores a correction value for a phase detection error. If the dq-axis currents transformed by the current coordinate transformer 74 are equal to or greater than the reference value, the estimation unit 76 estimates an inductance with voltage commands calculated using the stored correction value and the converted dq-axis currents.

[0058] According to such a configuration, a conducting phase is corrected under conditions where a change in the inductance of the reactor 2 does not occur. In this case, since the estimation of the inductance is stopped, the conducting phase is effectively corrected. In addition, since a phase correction value is stored and the estimation of the inductance is performed under conditions where a change in the inductance of the reactor 2 occurs, the inductance is accurately estimated. As described above, a more stable current control system is provided even when an inductance change may occur, since the correction of a conducting phase, the estimation of the inductance, and the like are switched according to conditions such as the presence or absence of an inductance change.

[0059] In addition, the phase correction unit 75 calculates a corrected phase by performing feedback control so that the phase detection error of the phase detection unit 5 becomes zero. The phase detection error of the phase detector is calculated based on the voltage commands calculated by the current control unit 72, the dq-axis currents transformed by the current coordinate transformer 74, and an impedance of the reactor 2.

[0060] In addition, the estimation unit 76 estimates an inductance based on the voltage equation of the inverter 3 according to a state estimation observation unit to which the voltage commands calculated by the current control unit 72 and the dq-axis currents transformed by the current coordinate transformer 74 are input.

[0061] Furthermore, the current control unit 72 can gradually update a current control gain using the inductance estimated by the estimation unit 76. In this case, the update of the control unit is simplified according to the estimated value of the inductance.

[0062] Alternatively, the current control unit 72 can continuously update the current control gain based on the inductance estimated by the estimation unit 76. Continuously changing the control unit further improves the stability of the control.

[0063] The following is based on Fig. 10 describes an example of a hardware configuration of the control device 10.

[0064] Fig. 10 is a hardware configuration diagram of essential portions of the control device 10 according to Embodiment 1.

[0065] Each function of the control device 10 can be implemented by a processing circuit. The processing circuit includes at least one processor 100a and at least one memory 100b. The processing circuit may include at least a portion of the associated hardware 200 together with or instead of the processor 100a and the memory 100b.

[0066] When the processing circuit includes processor 100a and memory device 100b, each function of control device 10 is implemented by software, firmware, or a combination of software and firmware. At least one of the software and firmware is described as a program. The program is stored in memory 100b. Processor 100a performs each function of control device 10 by reading and executing the program stored in memory 100b.

[0067] The processor 100a is also referred to as a CPU (central processing unit), processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. The memory 100b is formed, for example, from a non-volatile or volatile semiconductor memory, such as a RAM, a ROM, a flash memory, an EPROM, or an EEPROM.

[0068] For example, if the processing circuit comprises the part of the associated hardware 200, the processing circuit is implemented by a single circuit, a combined circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0069] Each function of the control device 10 can be implemented individually by a processing circuit. Alternatively, the respective functions of the control device 10 can be implemented collectively by a processing circuit. With respect to the respective functions of the control device 10, some of the functions can be implemented by the dedicated hardware 200, while other parts can be implemented by software or firmware. In this way, the processing circuit implements each function of the control device 10 using the dedicated hardware 200, software, firmware, or a combination thereof. Embodiment 2

[0070] In Embodiment 2, points different from the example disclosed in Embodiment 1 are described in detail. Each of the features of the example disclosed in Embodiment 1 can be adopted as features not described in Embodiment 2.

[0071] The control device 10 according to Embodiment 1 stabilizes the current control unit by estimating an inductance of the reactor 2 and updating a gain of the current control unit 72 based on the estimated inductance. Embodiment 2 discloses an example of the control device 10 capable of further increasing the stability of the current control unit 72 by monitoring an estimated value of the inductance.

[0072] Fig. 11 is a block diagram showing a configuration of the power control unit 72 of the control device 10 according to Embodiment 2.

[0073] The control device 10 according to Embodiment 2 is the same as the control device 10 according to Embodiment 1 except for a configuration of the power control unit 72. Compared with the power control unit 72 of the control device 10 according to Embodiment 1, the power control unit 72 of the control device 10 according to Embodiment 2 further includes a determination unit 724.

[0074] The determination unit 724 is a part equipped with the function of monitoring a value of the inductance of the reactor 2 estimated by the estimation unit 76 and determining whether the estimated value is irregular or not. For example, the estimation unit 724 determines whether an estimated value L^ of the inductance deviates from a predetermined range or not. At this time, the determination unit 724 stores a maximum value L max and a minimum value L minthe predetermined inductance. The determination unit 724 determines whether or not the inductance L^ estimated by the estimation unit 76 satisfies a condition known as L min < L^ < L max If the value expressed as L min < L^ < L max is satisfied, the determination unit 724 determines that the estimated value of the inductance is normal. At this time, the current control unit 72 updates the control gain 721 using the estimated value of the inductance determined to be normal. On the other hand, if the condition L min < L^ < L maxis not satisfied, the determination unit 724 determines that the estimated value of the inductance is irregular. In this case, the current control unit 72 does not update the control gain 721. If the current control unit 72 does not update the control gain 721, the current control unit 72 may maintain the value of the control gain 721 that was updated immediately before using the estimated value of the inductance determined to be normal.

[0075] The determination unit 724 may monitor a temporal change of the estimated value L^ of the inductance. For example, the determination unit 724 calculates an amount of temporal change dL^ / dt of L^ for each current control period and compares the calculated amount of temporal change with a predetermined reference value. If the calculated amount of temporal change does not exceed the reference value, the determination unit 724 determines that the estimated value of the inductance is normal. At this time, the current control unit 72 updates the control gain 721 using the estimated value of the inductance determined to be normal. Conversely, if the calculated amount of change over time exceeds the reference value, the calculation unit 724 determines that the estimated value of the inductance is irregular. In this case, the current control unit 72 does not update the control gain 721.

[0076] Since the inductance changes depending on the current, the determination unit 724 may also monitor a current change in the estimated value L^ of the inductance. For example, the determination unit 724 calculates an amount of current change dL^ / dI of L^ for each current control period and compares the calculated amount of current change with a predetermined reference value. If the calculated amount of current change does not exceed the reference value, the calculation unit 724 determines that the estimated value of the inductance is normal. At this time, the current control unit 72 updates the control gain 721 using the estimated value of the inductance determined to be normal. Conversely, if the calculated amount of change in the current exceeds the reference value, the determination unit 724 determines that the estimated value of the inductance is irregular. In this case, the current control unit 72 does not update the control gain 721.

[0077] Fig. 12 is a flowchart showing an example of the operation of the control device 10 according to Embodiment 2.

[0078] Fig. Figure 12 shows an example of processing when monitoring an estimated value of inductance.

[0079] In step S1201, the determination unit 724 performs processing to determine whether an estimated value of the inductance estimated by the estimation unit 76 is irregular or not. The determination of whether the estimated value of the inductance is irregular or not is made based on, for example, a magnitude of the estimated value itself, a magnitude of an amount of change in the estimated value over time, a magnitude of an amount of actual change in the estimated value, or the like. At this time, the determination unit 724 performs processing such as reading the estimated value by the estimation unit 76, calculating the amount of change over time, calculating the amount of actual change, or the like. Then, the processing of the control device 10 proceeds to step S1202.

[0080] In step S1202, the determination unit 724 determines whether the estimated inductance value is irregular or not. If the estimated inductance value is determined to be irregular, the processing of the control device 10 proceeds to step S1203. Conversely, if it is determined that the estimated inductance value is not irregular, the processing of the control device 10 proceeds to step S1204.

[0081] Since the estimated value of the inductance is irregular, the current control unit 72 terminates the processing of the control device 10 in step S1203 without updating the current control gain 721. At this time, there is a possibility that a current, voltage, or the like that is an input signal to the estimation unit 76 also has an irregular value. Therefore, the control device 10 can be configured to stop the control of the inverter 3 itself when the estimated value of the inductance is irregular.

[0082] Since the estimated inductance value is normal, the current control unit 72 updates the control gain 721 using the estimated inductance value in step S1204. Then, the processing of the control device 10 is terminated.

[0083] As described above, in the control device 10 according to Embodiment 2, the presence or absence of an abnormality is determined by monitoring the inductance estimated by the estimation unit 76. When the presence of an abnormality is determined, the current control unit 72 does not update the current control gain.

[0084] Due to such a configuration, a more stable control system is provided because it prevents the control unit from being updated to an irregular value. Embodiment 3

[0085] In Embodiment 3, points different from the examples disclosed in Embodiment 1 and Embodiment 2 are described in detail. Each of the features of the examples disclosed in Embodiment 1 and Embodiment 2 can be adopted as features not described in Embodiment 3.

[0086] For example, Embodiment 3 provides a control device 10 capable of further increasing the stability of the current control unit 72 by monitoring a phase correction value of the phase correction unit 75.

[0087] Fig. 13 is a configuration diagram of the inverter 3 and its control device 10 according to Embodiment 3.

[0088] In the control unit 7 of the control device 10 according to Embodiment 3, a signal line from the phase correction unit 75 to the estimation unit 76 is added compared to the control device 10 according to Embodiment 1. In the control device 10 according to this embodiment, the phase correction unit 75 monitors a phase correction value and notifies the estimation unit 76 of the correctness of an inductance estimation based on a result of the monitoring. The estimation unit 76 switches operations based on the inductance estimation characteristic reported by the phase correction unit 75. The estimation unit 76 performs an inductance estimation when it receives a notification from the phase correction unit 75 that an inductance estimation is possible.It should be noted that the estimation unit 76 does not need to estimate the inductance regardless of the content of the notification from the phase correction unit 75 in a situation where, for example, inductance estimation is not performed regardless of the presence or absence of an abnormality, such as when a current of the inverter 3 is small. The estimation unit 76 does not perform inductance estimation if a message is received from the phase correction unit 75 that inductance estimation is not possible.

[0089] Fig. 14 is a block diagram showing a configuration of the phase correction unit 75 of the control device 10 according to Embodiment 3.

[0090] Compared to the phase correction unit 75 of the control device 10 according to Embodiment 1, the phase correction unit 75 of the control device 10 according to Embodiment 3 further includes a determination device 754.

[0091] The determination unit 754 is a part equipped with the function of monitoring a phase correction value calculated by the phase correction unit 75 and determining whether the phase correction value is irregular or not. For example, the determination unit 754 determines whether the phase correction value Δϕ deviates from a predetermined range or not. At this time, the determination unit 754 stores a maximum value Δϕ max and a minimum value Δϕ min of the predetermined phase correction value. The determination unit 754 determines whether or not the phase correction value Δϕ, which is an output of the integrator 753, satisfies a condition defined as Δϕ min <Δϕ < Δϕ max If the value expressed as Δϕ min <Δϕ < Δϕ maxis satisfied, the determination unit 754 determines that the phase correction value is normal. At this time, the phase correction unit 75 sends a message to the estimation unit 76 that an estimation of the inductance is possible. On the other hand, if the condition Δϕ min <Δϕ < Δϕ max is not met, the determination unit 754 determines that the phase correction value is irregular. In this case, the phase correction unit 75 transmits a message to the estimation unit 76 that an estimation of the inductance is not possible.

[0092] The determination unit 754 can monitor a temporal change of the phase correction value Δϕ. For example, the determination unit 754 calculates an amount of temporal change dΔϕ / dt of Δϕ for each current control period and compares the calculated amount of temporal change with a predetermined reference value. If the calculated amount of temporal change does not exceed the reference value, the calculation unit 754 determines that the phase correction value is normal. At this time, the phase correction unit 75 sends a message to the estimation unit 76 that estimation of the inductance is possible. On the other hand, if the calculated amount of temporal change exceeds the reference value, the calculation unit 754 determines that the phase correction value is irregular. In this case, the phase correction unit 75 sends a message to the estimation unit 76 that estimation of the inductance is not possible.

[0093] Fig. 15 is a flowchart showing an example of the operation of the control device 10 according to Embodiment 3.

[0094] Fig. Figure 15 shows an example of processing when monitoring a phase correction value.

[0095] In step S1501, the determination unit 754 performs processing to determine whether a phase correction value calculated by the phase correction unit 75 is irregular or not. The determination of whether the phase correction value is irregular or not is made based on, for example, a magnitude of the phase correction value itself, a magnitude of a temporal change amount of the phase correction value, or the like. At this point, the determination unit 754 performs processing such as reading the calculated phase correction value, calculating a temporal change amount, or the like. Then, the processing of the control device 10 proceeds to step S1502.

[0096] In step S1502, the determination unit 754 determines whether the phase correction value is irregular or not. If it is determined that the phase correction value is irregular, the processing of the control device 10 proceeds to step S1503. Conversely, if it is determined that the phase correction value is not irregular, the processing of the control device 10 proceeds to step S1505.

[0097] Since the phase correction value is irregular, the phase correction unit 75 does not correct any phase in step S1503. Then, the processing of the control device 10 proceeds to step S1504. If the phase correction value is irregular, there is a possibility that a current, voltage, or the like that is an input signal to the phase correction unit 75 also has an irregular value. Therefore, the control device 10 can be configured to stop controlling the inverter 3 itself when the phase correction value is irregular.

[0098] In step S1504, the phase correction unit 75 transmits a message to the estimation unit 76 indicating that an estimation of the inductance is not possible. The processing of the control device 10 is then terminated.

[0099] Since the phase correction value is normal, the phase correction unit 75 corrects a phase using the correction value in step S1505. Then, the processing of the control device 10 proceeds to step S1506.

[0100] In step S1506, the phase correction unit 75 sends a message to the estimation unit 76 that an estimation of the inductance is possible. The processing of the control device 10 is then terminated.

[0101] As described above, in the control device 10 according to Embodiment 3, the presence or absence of an abnormality is detected by monitoring a correction value of the phase detection error calculated by the phase correction unit 75. If the presence of an abnormality is determined, the phase correction unit 75 does not correct a phase detected by the phase detection unit 5. In this case, the estimation unit 76 does not estimate an inductance.

[0102] A control system with more stable current control unit is provided due to such a configuration since an irregular value of inductance cannot be estimated. Industrial applicability

[0103] The control device according to the present disclosure can be used for controlling an inverter. List of reference symbols 1 AC power supply, 2 throttle, 3 inverters, 4 smoothing capacitor, 5 phase detector, 6 current sensor, 7 control unit, 10 control device, 71 voltage control unit, 72 power control unit, 73 voltage coordinate transformer, 74 current coordinate transformer, 75 phase correction unit, 76 estimation unit, 100a processor, 100b memory, 200 Assigned Hardware QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2003-339183 A

[0003]

Claims

[1] A control device for an inverter that receives an input of multi-phase currents from a multi-phase power supply and outputs a direct current (DC) voltage, the control device comprising: a phase detector that detects a phase of the multi-phase power supply; a phase correction unit that corrects a phase detection error of the phase detector based on a voltage equation of the inverter to calculate a corrected phase; a current coordinate transformer that converts detected values ​​of multi-phase currents of the converter into direct currents using the corrected phase; a current control unit that performs control so that current commands of the inverter and the DC currents correspond to each other to calculate a voltage command; a voltage coordinate transformer that converts the voltage command into multi-phase voltage commands using the corrected phase; and an estimation unit that estimates an inductance of a reactor of the converter based on the voltage equation of the converter, where the phase correction unit corrects the phase detection error using the voltage command, the direct currents and an impedance of the choke, the estimation unit estimates the inductance using the voltage command and the DC currents, and the current control unit updates a current control gain using the inductance estimated by the estimation unit. [2] The control device for the converter according to claim 1, wherein, when the direct currents are smaller than a reference value, the estimation unit stops estimating the inductance, when the direct currents are equal to or greater than the reference value, the phase correction unit maintains a correction value of the phase detection error, and when the DC currents are equal to or greater than the reference value, the estimation unit estimates the inductance with the voltage command calculated using the held correction value and the DC currents. [3] The control device for the inverter according to claim 1 or 2, wherein the phase correction unit calculates the corrected phase by performing feedback control so that the phase detection error of the phase detector calculated using the voltage command, the DC currents and the impedance of the reactor becomes zero. [4] The control device for the inverter according to any one of claims 1 to 3, wherein the estimation unit estimates the inductance according to a state estimation observation unit to which the voltage command and the DC currents are input based on the voltage equation of the inverter. [5] The control device for the inverter according to any one of claims 1 to 4, wherein the current control unit updates the current control gain in stages using the inductance estimated by the estimation unit. [6] The control device for the inverter according to any one of claims 1 to 4, wherein the current control unit continuously updates the current control gain using the inductance estimated by the estimation unit. [7] The control device for the inverter according to any one of claims 1 to 6, wherein, when an abnormality is detected by monitoring the inductance estimated by the estimation unit, the current control unit does not update the current control gain. [8] The control device for the inverter according to any one of claims 1 to 7, wherein when an abnormality is detected by monitoring the correction value of the phase detection error calculated by the phase correction unit, the phase correction unit does not correct a phase detected by the phase detector, and the estimation unit does not estimate the inductance.

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