Inverter controller

Abstract

To provide an inverter controller which can correct a steady-state error of an inverter.SOLUTION: A control unit 22 of an inverter controller comprises: a determination unit 32 which determines that fixed engine speed and fixed torque continue in a dynamo 14; an acquisition unit 34 which acquires measurement torque of the dynamo 14 in a steady operation for operating the dynamo at predetermined fixed engine speed; a derivation unit 36 which derives command torque in the steady operation of the dynamo 14; and a correction unit 38 which corrects a preliminarily prepared error compensation map according to an individual dynamo on the basis of difference between the command torque derived by the derivation unit 36 and the measurement torque acquired by the acquisition unit 34.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an inverter control device.

Background Art

[0002] In Patent Document 1, a current detector is provided at the inverter output, the polarity of the current detected by the current detector is discriminated by current polarity discrimination means, and the output voltage of the inverter device set based on the frequency command is corrected by voltage correction means according to the discrimination result, and an output voltage error correction device for an inverter device that sets a threshold value corresponding to the output current in the current polarity discrimination means has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the technique of Patent Document 1 can reduce the output voltage error due to the short-circuit prevention period of the inverter output voltage, there is room for improvement because the correction of the steady-state error is not considered.

[0005] The present invention has been made in consideration of the above facts, and an object thereof is to provide an inverter control device capable of correcting the steady-state error of an inverter.

Means for Solving the Problems

[0006] The inverter control device according to the first aspect includes an acquisition unit that acquires the measured torque of the dynamo in a steady operation in which the dynamo is operated at a predetermined constant rotation by the inverter, a derivation unit that derives a command torque in the steady operation, and a correction unit that corrects an error compensation map created according to the individual dynamo based on the difference between the command torque derived by the derivation unit and the measured torque acquired by the acquisition unit.

[0007] According to the first aspect, in the acquisition unit, the measured torque of the dynamo is acquired in a steady operation in which the dynamo is operated at a predetermined constant rotation by the inverter, and in the derivation unit, the command torque in the steady operation is derived. Then, in the control unit, the error compensation map adapted to the individual dynamo is corrected based on the difference between the command torque derived by the derivation unit and the measured torque acquired by the acquisition unit. In this way, by correcting the error compensation map, it becomes possible to correct the steady error of the inverter.

Advantages of the Invention

[0008] As described above, according to the present invention, it is possible to provide an inverter control device capable of correcting the steady error of the inverter.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0010] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the configuration of the main part of the inverter control device according to the present embodiment.

[0011] The inverter control device 10 according to the present embodiment is applied to an engine bench used for various performance tests and durability tests of the engine 12 and the like.

[0012] The engine 12 as a test specimen is connected to the dynamo 14 via a transmission, a propeller shaft or a drive shaft 13, and various tests are performed by controlling the dynamo 14. In FIG. 1, only the dynamo 14 connected to one drive shaft 13 is shown, and the dynamo connected to the other drive shaft 13 is omitted because it is the same.

[0013] The inverter control device 10 according to the present embodiment includes an encoder 16, a torque meter 18, an inverter 20, and a control unit 22.

[0014] The encoder 16 is provided on the dynamo 14 and outputs the measured rotational speed detecting the actual rotational speed of the dynamo 14 to the control unit 22.

[0015] The torque meter 18 is provided on the output shaft of the dynamo 14, detects the actual shaft torque between the engine 12 and the dynamo 14, and outputs the detected actual measured torque to the control unit 22.

[0016] The inverter 20 drives the dynamo 14 by outputting an execution current corresponding to the final command torque from the control unit 22 to the dynamo 14.

[0017] The control unit 22 calculates the difference between the commanded rotational speed calculated by the ASR (Automatic Speed Regulator) 24 and the measured rotational speed detected by the encoder 16 using a deviation calculator 26 to derive a rotational difference. Then, using the error compensation map 30 created according to the individual dynamo 14 at the time of incorporation of the dynamo 14, feedforward control is performed by a PI control (Proportional-Integral Controller) 28 so as to achieve the commanded rotational speed. The error compensation map 30 is created in advance by connecting the dynamos 14 of both axes to a measuring device, setting one single axis as the rotation command and the other single axis as the torque command, and performing measurements for each rotation-torque.

[0018] Incidentally, the torque accuracy error of the inverter 20 may occur at about ±3% FS. For example, in the case of a 3000 Nm bench, a difference of ±90 Nm may occur. Since the torque accuracy error affects the controllability of the dynamo 14, a technique is generally used in which an error compensation map 30 is created according to the individual dynamo 14 at the time of incorporation of the dynamo 14 and feedforward control is performed to improve the controllability. However, it may not be possible to cope with the increase in error due to the aging deterioration of the inverter, which may significantly impair the equipment performance.

[0019] Therefore, in the control unit 22 of the inverter control device 10 according to the present embodiment, the accuracy error of the inverter 20 in the steady operation of operating the dynamo 14 at a predetermined constant rotation is detected from the difference between the commanded torque and the measured torque, and the error compensation map 30 is corrected.

[0020] Here, the functional configuration of the control unit 22 for detecting the accuracy error of the inverter 20 and correcting the error compensation map 30 will be described. FIG. 2 is a functional block diagram showing the functional configuration of the control unit 22.

[0021] The control unit 22 includes, for example, a general microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). As shown in FIG. 2, for example, the control unit 22 functions as a determination unit 32, an acquisition unit 34, a derivation unit 36, and a correction unit 38 by the CPU expanding and executing a program stored in the ROM in the RAM.

[0022] The determination unit 32 determines whether the dynamo 14 continues to rotate at a constant speed and constant torque based on the rotational difference obtained from the deviation calculator 26 and the measured torque detected by the torque meter 18.

[0023] The acquisition unit 34 acquires the measured torque of the dynamo 14 detected by the torque meter 18 in a steady operation of operating the dynamo 14 at a predetermined constant rotation.

[0024] The derivation unit 36 derives a command torque in the steady operation of the dynamo 14.

[0025] The correction unit 38 corrects the error compensation map 30 created in advance according to the individual dynamo 14 based on the difference between the command torque derived by the derivation unit 36 and the measured torque acquired by the acquisition unit 34. That is, by incorporating the difference between the final command torque calculated in the steady operation of the dynamo 14 and the measured torque measured by the torque meter 18 as the error compensation map 30, the torque accuracy error of the inverter 20 is corrected. By utilizing the test specimen used for evaluation, a dedicated jig is not required and operation at low cost becomes possible. In addition, when the steady state of the indicated rotation speed, measured rotation speed, and measured torque continues for a certain period, the correction value is automatically learned and incorporated into the error compensation map 30, so that it is always possible to create an error compensation map with high accuracy even for aging deterioration (mechanical loss, electrical loss). In addition, by retaining the learning amount, it becomes possible to detect a failure of the inverter 20 in advance. For example, it becomes possible to detect a failure of the inverter 20 in advance by detecting that the correction amount is approaching ±3% of the torque accuracy error of the inverter 20.

[0026] Next, a specific process performed by the control unit 22 of the inverter control device 10 according to the present embodiment configured as described above will be described.

[0027] First, the process performed by the control unit 22 when learning the error of the inverter 20 will be described. FIG. 3 is a flowchart showing an example of the flow of the process performed when learning the error of the inverter 20 in the control unit 22 of the inverter control device 10 according to the present embodiment.

[0028] In step 100, the determination unit 32 determines whether or not the commanded rotational speed is in a constant ASR control state of 1 min or more. If the determination is negative, the series of processes is terminated, and if the determination is positive, the process proceeds to step 102. Note that, as an example, "1 min" is applied as the determination time of the ASR control state, but the present invention is not limited thereto, and a predetermined time other than "1 min" may be applied.

[0029] In step 102, the determination unit 32 determines whether or not the difference between the commanded rotational speed and the measured rotational speed continues to be within 3 rpm for 30 sec. If the determination is negative, the series of processes is terminated, and if the determination is positive, the process proceeds to step 104. Note that the rotational speed and the duration are not limited to "3 rpm" and "30 sec", and other values may be applied.

[0030] In step 104, the determination unit 32 determines whether or not the standard deviation of the measured torque within 30 sec is within 3 Nm. If the determination is negative, the series of processes is terminated, and if the determination is positive, the process proceeds to step 106. Note that the standard deviation is not limited to the standard deviation of "30 sec", and the standard deviation of other times may be applied. Also, the threshold value is not limited to "3 Nm", and other values may be applied.

[0031] In step 106, the correction unit 38 calculates the 30-second average value of the difference between the measured torque and the command torque and then proceeds to step 108. That is, the correction (learning) amount of the error compensation map 30 is calculated. Note that the calculation of the average value is not limited to "30 seconds", and other time periods may be used instead.

[0032] In step 108, the correction unit 38 reflects the calculated 30-second average value in the existing correction value and ends a series of processes. That is, the calculated correction amount is reflected in the error compensation map 30.

[0033] Fig. 4 shows the behavior of the dynamo 14 when the error compensation map 30 is corrected by the correction unit 38 and when it is not corrected. Fig. 4 is a diagram showing the behavior of the dynamo 14 in transient operation due to the on / off of the accelerator.

[0034] As shown in Fig. 4, the rotational speed difference of the dynamo 14 shows the ideal rotational speed difference (the difference between the ideal rotational speed and the actual rotational speed) in transient operation. The solid line in Fig. 4 indicates the state with correction of the error compensation map 30, and the dotted line indicates the state without correction. It can be seen that in the state with correction, it can be controlled near 0 and the steady-state error is corrected.

[0035] Next, the processing performed by the control unit 22 when performing early fault detection of the inverter 20 will be described. Fig. 5 is a flowchart showing an example of the processing flow when the control unit 22 of the inverter control device 10 according to the present embodiment performs early fault detection of the inverter 20. Note that the processes common to those in Fig. 3 are denoted by the same reference numerals and the description thereof is omitted.

[0036] That is, after executing the above-mentioned step 108, it proceeds to step 110. In step 110, the correction unit 38 determines whether the new correction value exceeds ±3%FS. If the determination is negative, a series of processes end, and if the determination is positive, it proceeds to step 112. Note that the threshold value is not limited to "±3%FS", and other values may be applied.

[0037] In step 112, the correction unit 38 notifies of the fault detection and ends a series of processes. As a result, it becomes possible to detect and notify in advance the fault of the inverter 20.

[0038] Note that the processes performed by the control unit 22 of the inverter control device 10 in each of the above embodiments have been described as software processes performed by executing a program, but are not limited thereto. For example, the processes may be performed by hardware such as a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), and an FPGA (Field-Programmable Gate Array). Alternatively, the processes may be a combination of both software and hardware. Further, when the processes are software processes, the program may be stored in various storage media and distributed.

[0039] Furthermore, the present invention is not limited to the above, and it goes without saying that various modifications can be made and implemented within the scope not departing from the gist thereof.

Explanation of reference numerals

[0040] 10 Inverter control device 12 Engine 14 Dynamo 16 Encoder 18 Torque meter 20 Inverter 22 Control unit 30 Error compensation map 32 Determination unit 34 Acquisition unit 36 Derivation unit 38 Correction unit

Claims

【Claim 1】 In a steady operation in which a dynamo is operated at a predetermined constant rotation by an inverter, an acquisition unit that acquires a measured torque of the dynamo; A derivation unit that derives a command torque in the steady operation; A correction unit that corrects an error compensation map created for each individual dynamo based on the difference between the command torque derived by the derivation unit and the measured torque acquired by the acquisition unit; An inverter control device comprising the above.

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