JP7628071B2 - Power Conversion Equipment - Google Patents

Description

The present invention relates to a power conversion device.

In the conventional technology, as described in Patent Document 1, the direction of the primary current (t-axis) and the direction perpendicular to it (m-axis) are used as the control axes (mt-axis) of a rotating coordinate system, and the induced electromotive force value of the m-axis is estimated from the voltage command value of the m-axis, and the speed estimation value _ωr0 ^{^} is calculated by dividing it by the magnetic flux (Equation 1).

ここに、v_mc ^*：ｍ軸の電圧指令値、ω_s ^*：すべり周波数指令値、ω₁ ^*：一次周波数指令値、i_t ^*：ｔ軸の電流指令値、i_mc：ｍ軸の電流検出値、R₁ ^*：一次抵抗値の設定値、R₂’^*： 一次側に換算した二次抵抗値の設定値、L_σ ^*：漏れインダクタンス値の設定値、Ｍ^*：相互インダクタンス値の設定値、L₂ ^*：二次インダクタンス値の設定値、T_obs：外乱オブザーバ時定数、T_ACR：電流制御遅れ相当の時定数、ｓ：ラプラス演算子

where, v _mc ^* : m-axis voltage command value, ω _s ^* : slip frequency command value, ω ₁ ^* : primary frequency command value, i _t ^* : t-axis current command value, i _mc : m-axis current detection value, R ₁ ^* : primary resistance set value, R ₂ ' ^* : secondary resistance set value converted to the primary side, L _σ ^* : leakage inductance set value, M ^* : mutual inductance set value, L ₂ ^* : secondary inductance set value, T _obs : disturbance observer time constant, T _ACR : time constant equivalent to current control delay, s: Laplace operator

With this technology, even if there is an error between the set value R ₁ ^* used in (Equation 1) and the primary resistance value R ₁ of the induction motor, no estimation error (ω _r0 ^{^} - ω _r ) occurs in the speed estimation value ω _r0 ^{^} , and stable speed control can be performed.

JP 2018-182989 A

The technique of Patent Document 1 has low sensitivity to the error ( _R1 ^* _-R1 ) of the primary resistance value _R1 of the induction motor. However, if there is an error ( _R2 ^* _-R2 ) between the set value _R2 ^* used in (Formula 1) and the secondary resistance value _R2 of the induction motor, an error ( _ωs ^* -ωs ₎ occurs between the slip frequency command value _ωs ^* and the slip frequency _ωs , causing deviation and vibration in the speed estimate value _ωr0 ^{^} of the induction motor. As a result, the motor speed and torque also continue to vibrate.

The objective of the present invention is to provide a power conversion device that can prevent vibration phenomena and achieve speed control without speed deviation even when there is an error in the secondary resistance value.

The present invention includes a power converter that outputs a signal to the induction motor to vary the output frequency, output voltage, and output current of the induction motor, and a control unit that controls the power converter,
The control unit calculates, from the output current, a voltage and a current on a control axis having a direction of the primary current and a direction perpendicular to the primary current as a rotating coordinate system, calculates a first speed estimate value and a second speed estimate value from the voltage and current, calculates speed control from the first speed estimate value, and calculates a primary frequency command value from the second speed estimate value.

According to the present invention, even if there is an error in the secondary resistance value, it is possible to prevent the vibration phenomenon of the speed and torque of the induction motor and realize speed control without speed deviation.

FIG. 1 is a configuration diagram of a first embodiment including a power conversion device and an induction motor. Vector diagram of the d-q axis. FIG. 11 is a vector diagram of the mt axis in Example 1. Load operation characteristics when using conventional technology (R ₁ ^* has some error). Load operating characteristics when using conventional technology ( _R1 ^* and _R2 ^* have errors). FIG. 4 is a configuration diagram of a speed/frequency/phase calculation unit in the first embodiment. FIG. 4 is a configuration diagram of a second speed estimation calculation unit in the first embodiment. FIG. 4 is a configuration diagram of a first speed estimation calculation unit in the first embodiment. Load operation characteristics when Example 1 is used (R ₁ ^* and R ₂ ^* have errors). FIG. 1 is a configuration diagram for verifying the implementation of the present invention. FIG. 11 is a configuration diagram of a second embodiment having a power conversion device and an induction motor. FIG. 11 is a configuration diagram of a third embodiment having a power conversion device and an induction motor. FIG. 11 is a configuration diagram of a speed/frequency/phase calculation unit in the third embodiment. FIG. 13 is a configuration diagram of a second speed estimation calculation unit in the third embodiment. FIG. 11 is a configuration diagram of a first speed estimation calculation unit in the third embodiment. FIG. 11 is a configuration diagram of a fourth embodiment having a power conversion device and an induction motor. FIG. 13 is a configuration diagram of a speed/frequency/phase calculation unit in the fourth embodiment. FIG. 13 is a configuration diagram of a fifth embodiment having a power conversion device, an induction motor, and an IOT controller. FIG. 13 is a configuration diagram of a sixth embodiment having a power conversion device, an induction motor, and an external device.

This embodiment will be explained in detail below with reference to the drawings.

Figure 1 shows a configuration diagram of a first embodiment that includes a power conversion device and an induction motor. This embodiment relates to drive control of a power conversion device that drives an induction motor using speed sensorless vector control that does not use a speed sensor.

This embodiment also relates to a power conversion device that includes stable and highly accurate motor control, suppressing torque pulsation caused by the primary and secondary resistance values that change depending on the winding temperature in an induction motor, and eliminating the speed deviation between the speed command value and the rotation speed.

The induction motor 1 generates a torque _tm by a magnetic flux _φ2d generated by a current of the magnetic flux axis component (d-axis) and a current _iq of a torque axis component (q-axis) perpendicular to the magnetic flux axis.

The power converter 2 includes semiconductor elements as switching elements. The power converter 2 receives three-phase AC voltage command values _vu ^* , _vv ^* , and _vw ^* , and outputs voltage values proportional to the three-phase AC voltage command values _vu ^* , _vv ^* , and _vw ^* . The induction motor 1 is driven based on the output of the power converter 2, and the output voltage, output frequency, and output current of the induction motor 1 are variably controlled. An IGBT (Insulated Gate Bipolar Transistor) may be used as the switching element.

The DC power source 3 supplies DC voltage and DC current to the power converter 2.

The current detector 4 outputs detection values _iuc , _ivc , _iwc of the three-phase AC currents _iu , _iv , _iw of the induction motor 1. The current detector 4 may also detect the phase currents of two of the three phases of the induction motor 1, for example, the U phase and the W phase, and determine the V phase line current as _iv = -(iu + _iw ) from the AC condition ( _iu + _{iv + iw} = 0). In this embodiment, an example has been shown in which the current detector 4 is provided inside the power conversion device, but it may also be provided outside the power conversion device.

The control unit includes a coordinate conversion unit 5, a coordinate conversion unit 6, a speed/frequency/phase calculation unit 7, a reference phase calculation unit 8, an excitation current/magnetic flux setting unit 9, a speed control calculation unit 10, a coordinate conversion unit 11, a coordinate conversion unit 12, an mt-axis vector control calculation unit 13, a coordinate conversion unit 14, and a coordinate conversion unit 15, which are described below. The control unit controls the output of the power converter 2 so as to variably control the output voltage value, the output frequency value, and the output current of the induction motor 1.

The control unit is composed of a semiconductor integrated circuit (arithmetic control means) such as a microcomputer (microcontroller) or a DSP (Digital Signal Processor). Any or all of the control unit can be composed of hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The CPU (Central Processing Unit) of the control unit reads out a program stored in a recording device such as a memory, and executes the processing of each unit such as the coordinate conversion unit 5 described above.

Next, we will explain each component of the control unit.

The coordinate conversion unit 5 outputs d-axis and q-axis current detection values i _dc , i qc from the detection values i _uc , i _vc , i _wc of the three-phase AC currents i _u , _iv , _{i w} and the phase estimate value θ _dc .

The coordinate conversion unit 6 outputs the m-axis and t-axis current detection values i _mc , i _tc from the d-axis and q-axis current detection values i _dc , i _qc and the estimated phase angle θ _mt .

The speed/frequency/phase calculation unit 7 outputs a first speed estimate ωr^, _slip frequency command value _ωs ^* and phase estimate ^θdc of induction motor _{1 based on the m-axis and t-axis voltage command values vmc**, vtc** ,} ^the _m ^- axis and t-axis current command values im ^* , _it ^* , the m-axis and t-axis current detection values imc, itc, the _{m -} axis and t- _axis magnetic flux command values _φm *, φt ^* , the second speed estimate _ωr ^{^} , _{the primary frequency command value ω1 *} ^and the electrical circuit parameters ( _R1 , _R2 ^' , _Lσ , M, _L2 ) of induction motor 1.

A reference phase calculation unit 8 uses the slip frequency command value ω _s ^* to output an estimated phase angle θ _mt from the m-axis to the d-axis.

The excitation current/magnetic flux setting unit 9 outputs an excitation current command value i _d ^* which is positive, a d-axis secondary magnetic flux command value φ _2d ^* which is positive, and a q-axis secondary magnetic flux command value φ _2q ^* which is "0".

The speed control calculation unit 10 outputs a q-axis current command value i _q ^* from the deviation (ω _r ^* - _{ω r} ^{^} ) between the speed command value ω _r ^* and the speed estimate value ω _r ^{^} .

The coordinate conversion unit 11 outputs m-axis and t-axis current command values i _m ^* , i _t ^* from the d-axis and q-axis current command values i _d ^* , i _q ^* and the estimated phase angle θ _mt .

A coordinate conversion unit 12 outputs magnetic flux command values φ _m ^* , φ _t ^* of the m-axis and t-axis from secondary magnetic flux command values φ _2d ^* , φ _2q ^* of the d-axis and q-axis and the estimated phase angle θ _mt .

The m/t-axis vector control calculation unit 13 outputs the m-axis and t-axis voltage command values v _mc ^{* ,} _{v tc} ^* from (i _m ^* - i _mc ), (i _t ^* - i _tc ), which are the deviations between the m-axis and t-axis current command values i m _* , i t ^* and the current detection values i _mc , i _tc .

The coordinate conversion unit 14 outputs d-axis and q-axis voltage command values v _dc ^* , v _qc ^* from the m-axis and t-axis voltage command values v _mc ^* , v _tc ^* and the estimated phase angle θ _mt .

The coordinate conversion unit 15 outputs three-phase AC voltage command values _vu ^* , _vv ^* , _vw ^* from the d-axis and q-axis voltage command values _vdc ^* , _vqc ^* and the phase estimate value _θdc .

First, we will explain the mt axis based on the primary current related to this invention. The mt axis is a rotating coordinate system and is the control axis. Figure 2 is a vector diagram on the dq axis. The direction of the magnetic flux is the d axis, and the direction 90 degrees (π/2) ahead of the d axis is the q axis. Here, the d axis current i _d , the q axis current i _q, and the primary current i ₁ are related by (Equation 2).

In addition, the phase angle _θφ between i _d and i ₁ is calculated from the d-axis current i _d and the q-axis current i _q using (Equation 3).

Fig. 3 is a vector diagram of the mt axis. The direction of the primary current is the t axis, and the direction perpendicular to the t axis is the m axis. Here, the current i _m on the m axis, the current i _t on the t axis, and the primary current i ₁ are related by (Equation 4).

Furthermore, the estimated phase angle θ _mt from the m-axis to the d-axis is given by (Equation 5).

The basic operation of speed sensorless control using the speed estimation calculation shown in (Equation 1), which is a conventional technology, is explained below.

The excitation current/flux setting unit 9 outputs a current command value i _d ^* required to generate a d-axis secondary magnetic flux value φ _2d in the induction motor 1. In addition, the speed control calculation unit 10 calculates a q-axis current command value i _q ^* according to (Equation 6) so that the speed estimate value ω _r0 ^{^} follows the speed command value ω _r ^* .

ここに、Kp__asr：速度制御の比例ゲイン、Ki__asr：速度制御の積分ゲイン

Here, _{Kp_asr} : Proportional gain of speed control, _{Ki_asr} : Integral gain of speed control

The mt-axis vector control calculation unit 13 performs PI (proportional + integral) control so that the current detection values i _mc , i _tc follow the m-axis and t-axis current command values i _m ^* , i _t ^* in accordance with (Equation 7), calculates the m-axis and t-axis voltage command values v _mc ^* , v _tc ^* , and controls the output voltage of the power converter 2. The voltage command values v _mc ^* , v _tc ^* are feedback voltage components for the m-axis and t-axis.

ここに、K_{p_m}：ｍ軸の電流制御の比例ゲイン、K_{i_m}：ｍ軸の電流制御の積分ゲイン、K_{p_t}：ｔ軸の電流制御の比例ゲイン、K_{i_t}：ｔ軸の電流制御の積分ゲイン

Here, K _{p_m} : proportional gain of m-axis current control, K _{i_m} : integral gain of m-axis current control, K _{p_t} : proportional gain of t-axis current control, K _{i_t} : integral gain of t-axis current control.

For the explanation of the basic operation, the speed/frequency/phase calculation unit 7 calculates a speed estimated value _ωr0 ^{^} by (Formula 1) instead of the speed estimated value _ωr ^{^} . Also, the slip frequency calculation unit 71 calculates a slip frequency command value _ωs ^* according to (Formula 8).

ここに、T₂ ^＊＝L₂/R₂：二次時定数値、T_ACR：電流制御遅れ相当の時定数

Here, _T2 ^* = _L2 / _R2 : Secondary time constant value, T _ACR : Time constant equivalent to current control delay

Furthermore, using the speed estimate ω _r0 ^{^} and the slip frequency command value ω _s ^* , the speed/frequency/phase calculation unit 7 calculates a primary frequency command value ω ₁ ^* in accordance with (Equation 9).

The phase estimation calculation unit 75 calculates the phase θ _dc of the magnetic flux axis of the induction motor 1 according to (Equation 10).

The phase estimation value θ _dc , which is an estimation value of the phase θ _d of the magnetic flux axis, is used as the control reference and is calculated by sensorless control.

Figure 4 shows the load operation characteristics when the conventional technology of Patent Document 1 is used for the speed estimation calculation. In this example, the primary resistance value setting _R1 ^* used in (Formula 1) is set to 0.5 times the actual primary resistance value _R1 of the induction motor 1, and the secondary resistance value setting _R2 ^* is set to 1.0 times the actual secondary resistance value _R2 of the induction motor 1. The induction motor 1 is operated at 1 Hz (speed command value _ωr ^* ) in the low speed range. A load torque is applied in a ramp shape from point A to point B in the figure up to 200%.

The rotation speed _ωr of the induction motor 1 and the speed estimate _ωr0 ^{^} are the same, and are insensitive to the primary resistance setting _R1 ^* . However, if there is an error in the secondary resistance setting _R2 ' ^* used in (Equation 1), the sensorless control may become unstable.

FIG. 5 shows the load operation characteristics when the set value R ₂ ^* of the secondary resistance used in the speed estimation calculation (Equation 1) is set to 0.5 times the secondary resistance R ₂ of the induction motor 1 .

The rotational speed _ωr of the induction motor 1 steadily decreases below the estimated speed value _ωr0 ^{^} , and from point B onwards, the vibrations in the torque _τm and rotational speed _ωr of the induction motor 1 gradually increase, creating a problem of such vibration phenomena.

This is because the speed estimation calculation shown in (Formula 1) uses only the voltage information of the m-axis, which causes the torque and rotation speed to vibrate.To solve this problem, two types of speed estimation value are calculated: the speed estimation value _ωr ^ that is fed back to the speed control calculation, and the speed estimation value _ωr ^{^^} that is fed back to the primary frequency command value _ω1 ^* .

Because the above-mentioned vibration is included in both the m-axis and t-axis, the voltage command value (v _mc ^** , v _tc ^** ) and the detected current value (i _mc , i _tc ) are used to calculate the second speed estimate ω _r ^{^^} using the cross product of the power. The second speed estimate ^{^^} is used to calculate the primary frequency command value ω ₁ ^* , thereby canceling the error in the secondary resistance value R ₂ (R ₂ ^* - R ₂ ) and suppressing the vibration phenomenon.

Furthermore, by using the aforementioned primary frequency command value ω ₁ ^* in the first speed estimation calculation, the speed estimation value ω _r ^{^} using the induced electromotive force of the m-axis becomes an appropriate value, and can be fed back to the speed control calculation with high accuracy.

For the reasons described above, the use of the present invention can improve the decrease in rotation speed _ωr and the vibration phenomenon. The speed estimation technique of this embodiment will be described below.

6 shows a block diagram of the speed/frequency/phase calculation unit 7. A slip frequency calculation unit 71 calculates a slip frequency command value ωs ^* in accordance with the above-mentioned (Equation 8) using the q-axis current command value _iq ^* , the d-axis secondary magnetic flux command value _φ2d ^* , the setting value _M ^* of the mutual inductance value M, and the setting value _T2 ^* of the secondary time constant _T2 .

In Patent Document 1, the speed estimate _ωr0 ^{^} is calculated from (Equation 1). In this embodiment, the second speed estimation calculation unit 72 calculates the second speed estimate _ωr ^{^^} using the cross product of power. Also, the first speed estimation calculation unit 73 calculates the first speed estimate _ωr ^{^} using the induced electromotive force of the m-axis.

The adder 74 receives the slip frequency command value ω _s ^* and the second speed estimate value ω _r ^{^^} , and outputs a primary frequency command value ω ₁ ^* according to (Equation 11).

A phase estimation calculation unit 75 receives the primary frequency command value ω ₁ ^* , and outputs a phase estimation value θ _dc according to the above-mentioned (Equation 10).

7 shows the configuration of the second speed estimation calculation unit 72. A power cross product calculation unit 721 calculates a power cross product value E _cp ^{^} in accordance with (Formula 12) using the m-axis and t-axis voltage command values v _mc ^* , v _tc ^* and the m-axis and t-axis current detection values i _mc , i _tc .

The power cross product model calculation unit 722 calculates the cross product model value _{E cp * according to (equation 13) using the m-axis and t-axis current detection values i mc , i tc , the second speed estimation value ω r ^^, the primary frequency command value ω 1} ^* _{, the electrical} ^circuit _parameters ^R ₂ ' ^* , L _σ ^* , M ^* , L ₂ ^* of the induction motor 1, and the m-axis and t-axis magnetic flux command values φ _m ^* , φ _t ^* .

The power cross product value E _cp ^{^} and the cross product model value E _cp ^* are input to the subtraction unit 723, which outputs ΔE _cp, which is their deviation. ΔE _cp , which is output from the subtraction unit 723, is input to a PI control calculation unit 724, which calculates a second speed estimate ω _r ^{^^} by P (proportional) + I (integral) control calculation according to (Equation 14).

ここに、K_{p_omg}：速度推定演算の比例ゲイン、K_{i_omg}：速度推定演算の積分ゲイン

Here, K _{p_omg} : Proportional gain of speed estimation calculation, K _{i_omg} : Integral gain of speed estimation calculation

8 shows the configuration of the first speed estimation calculation unit 73. The t-axis current command value i _t ^* is input to a first-order lag calculation unit 731 with a time constant T _ACR equivalent to the current control delay, and the output i _t ^* _td is multiplied by a gain 732 related to the leakage inductance L _σ and input together with the first-order frequency command value ω ₁ ^* to a multiplication unit 733, which calculates the voltage drop related to the leakage inductance.

The output value of multiplier 733 and m-axis voltage command value v _mc ^* are input to adder 734. The m-axis magnetic flux command value φ _m ^* is multiplied by a gain 735 related to the secondary resistance value R ₂ ' ^* converted to the primary side and the mutual inductance M, and the output of gain 735 is input to adder 736 together with the output of adder 734.

The m-axis current detection value i _mc is multiplied by a gain 737 related to the leakage inductance L _σ , the observer time constant T _obs, and the combined resistance value R _σ ^* (R ₁ ^* + R ₂ ' ^* ), and the output of gain 737 is input to adder 738 together with the output of adder 736.

The output of the adder 738 is input to a first-order lag calculator 739 having an observer time constant T _obs for the speed estimation response. The m-axis current detection value i _mc is multiplied by a gain 7310 related to the leakage inductance L _σ and the observer time constant T _obs . The output of the gain 7310 is input to a subtractor 7311 together with the output of the first-order lag calculator 739.

The t-axis magnetic flux command value φ _t ^* is multiplied by a gain 7312 related to the mutual inductance M and secondary inductance _L2 , and the output of the gain 7312 is input to a divider 7313 together with the output of a subtractor 7311. The output of the divider 7313 is multiplied by a gain 7314 which is -1 to calculate a first speed estimate ω _r ^{^} according to (Equation 15).

Note that Figure 8 is a functional block diagram that has been equivalently converted from (Equation 15).

Figure 9 shows the load operation characteristics in this embodiment (the conditions used in Figure 5 are set). By comparing the load characteristics disclosed in Figure 5 and Figure 9, it can be seen that the first speed estimate _ωr ^{^} coincides with the rotation speed _ωr , and the second speed estimate _ωr ^{^^} > _ωr ^{^} . The primary frequency command value _ω1 ^* and the primary frequency _ω1 are related by (Formula 16).

In (Equation 16), by using the second speed estimate value ω _r ^{^^} , slip frequency command value ω _s ^* , rotation speed ω _r , and slip frequency ω _s , the same equation can be rewritten as (Equation 17).

Equation 17 is rearranged for the second speed estimate value ω _r ^{^^} to obtain Equation 18.

In other words, the error ( _ωs ^* - _ωs ) between the slip frequency command value _ωs ^* and the slip frequency _ωs, which is related to the set value _R2 ^* of the secondary resistance _R2, is included in the second speed estimate _ωr ^{^^} . Since the primary frequency command value _ω1 ^* is calculated using the second speed estimate _ωr ^{^^} , the primary frequency command value _ω1 ^* becomes an appropriate value, and by calculating the first speed estimate _ωr ^{^} from the above-mentioned (Equation 15), the first speed estimate _ωr ^{^} coincides with the rotation speed _ωr .

Although the first speed estimate _ωr ^{^} and the second speed estimate _ωr ^{^^} do not match, the rotational speed _ωr matches the speed command value _ωr ^* (1 Hz in FIG. 9) after point B where the torque stabilizes.

In other words, according to this embodiment, even if there is an error in the secondary resistance value _R2 ( _R2 ^* _{-R2 )} , it is possible to prevent the oscillation phenomenon in the speed and torque of the induction motor, and to achieve highly stable and highly accurate speed control by eliminating the speed deviation, which is the difference between the speed command value and the rotational speed ( _ωr ^* -ωr).

In the above explanation, the calculation of the first speed estimate value or the second speed estimate value has been described using the voltage command value or the current detection value as an example of the output voltage or output current of the induction motor. In the calculation of the first speed estimate value or the second speed estimate value, the voltage detection value may be used as the output voltage, and the current command value may be used as the output current.

Now, with reference to FIG. 10, we will explain the configuration for verifying the implementation of this embodiment. A voltage detector 21 and a current detector 22 are attached to the power conversion device 20 that drives the induction motor 1, and an encoder 23 is attached to the shaft of the induction motor 1.

As a first step, the mt-axis voltage, current, and magnetic flux calculation unit 24 receives the three-phase AC voltage detection values (v _uc , v _vc , v _wc ) and three-phase AC current detection values (i _uc , i _vc , i _wc ) output from the voltage detector 21, and the position θ output from the encoder, and calculates the vector voltage components v _dc ^{^} , v _qc ^{^} , vector current components i _dc ^{^} , i _qc ^{^} , the detection value ω _rc obtained by differentiating the position θ, and an estimated slip frequency value ω _s ^{^} from the vector current components.

Furthermore, in the second step, using the detected vector current components i _dc ^{^} and i _qc ^{^} and the electrical circuit parameters of the induction motor 1 (the results of offline auto-tuning installed in the general-purpose inverter or design values), the estimated phase angle θ _mt ^{^} is derived from (Equation 19), the m-axis and t-axis voltage components v _mc ^{^} and v _mc ^{^} are derived from (Equation 20), the current components i _mc ^{^} and i _tc ^{^} are derived from (Equation 21), and the magnetic flux components φ _m ^{^} and φ _t ^{^} are derived from (Equation 22).

The power cross product calculation unit 25 calculates the power cross product values E _cp ^{^} _ _est and E _cp * _ _est using (Formula 23) and (Formula 24) corresponding to (Formula 12) and (Formula 13), respectively. If E _cp ^{^} _ _est and E _cp ^{* _} _est match, it is clear that the present invention has been adopted. In addition, a second speed estimate ω _r ^{^^} may be calculated and observed using (Formula 25).

Fig. 11 is a configuration diagram of a second embodiment having a power conversion device and an induction motor. In the first embodiment, the mt-axis vector control calculation unit calculates the voltage command values _vmc ^* and _vtc ^* as feedback voltage components of the m-axis and t-axis (feedback calculation). This embodiment is an example of executing a vector control calculation using both feedback calculation and feedforward calculation.

The speed/frequency/phase calculation unit 7a and the mt-axis vector control calculation unit 13a are blocks corresponding to the speed/frequency/phase calculation unit 7 and the mt-axis vector control calculation unit 13 in FIG. 1, respectively. In FIG. 11, the induction motor 1 to the coordinate conversion unit 6, the reference phase calculation unit 8 to the coordinate conversion unit 12, and the coordinate conversion unit 14 to the coordinate conversion unit 15 are the same as in FIG. 1.

The speed/frequency/phase calculation unit 7a outputs the second speed estimate value ω _r ^{^^} and the primary frequency command value ω ₁ ^* calculated by the speed/frequency/phase calculation unit 7 in FIG.

Further, in the mt-axis vector control calculation unit 13a, the m-axis and t-axis current command values i _m ^* , i _t ^* obtained by coordinate transforming the d-axis and q-axis current command values i _d ^* , _{i q} ^* , the electric circuit parameters (R ₁ ^* , R ₂ ' ^* , L _σ ^* , M ^* , L ₂ ^* ) of the induction motor 1, the m-axis and t-axis magnetic flux command values φ _m ^* , φ _t ^* , the second speed estimate ω _r ^{^^} and the primary frequency command value ω ₁ ^* are used to calculate the voltage reference values v _mc0 ^* , v _mt0 ^* as feedforward calculations.

Further, the m-axis current command value i _m ^* , the m-axis current detection value i _mc , the t-axis current command value i _t ^* , and the t-axis current detection value i _tc are input to the mt-axis vector control calculation portion 13 a.

Here, PI (proportional plus integral) control is performed so that the detected current values i _mc , i _tc follow the current command values i _m ^* , i _t ^* according to (Equation 27), and m-axis and t-axis voltage correction values Δv _m ^* , Δv _t ^* are output. The m-axis and t-axis voltage correction values Δv _m ^* , Δv _t ^* are feedback calculations.

Furthermore, after calculating the voltage command values _vmc ^** , _vtc ^** according to (Equation 28), the output voltage of the power converter 2 is controlled by the coordinate-transformed d-axis and q-axis voltage command values _vdc ^* , _vqc ^* .

In this embodiment, by adding a feedforward calculation to the vector control calculation section of the mt axis, more stable speed control can be achieved.

Figure 12 is a configuration diagram of a third embodiment having a power conversion device and an induction motor. In the first embodiment, the speed estimation method uses the induced electromotive force of the m-axis for the first speed estimation calculation, and the cross product of the power for the second speed estimation calculation, particularly in the low speed range.

In this embodiment, in the medium to high speed range, the first speed estimation calculation uses the induced electromotive force of the t-axis, and the second speed estimation calculation uses the inner product of the power. The speed/frequency/phase calculation unit 7b is a block equivalent to the speed/frequency/phase calculation unit 7 in FIG. 1. In FIG. 12, the induction motor 1 to the coordinate conversion unit 6 and the reference phase calculation unit 8 to the coordinate conversion unit 15 are the same as in FIG. 1.

Figure 13 shows the configuration of the speed/frequency/phase calculation unit 7b. The slip frequency calculation unit 7b1, the adder unit 7b4, and the phase estimation calculation unit 7b5 are the same as the slip frequency calculation unit 71, the adder unit 74, and the phase estimation calculation unit 75 in Figure 6.

In this embodiment, the second speed estimation calculation unit 7b2 calculates the second speed estimation value _ωr ^{^^} n using the inner product of the power, and the first speed estimation calculation unit 7b3 calculates _{the first speed estimation value ωr^n using} ^the _induced electromotive force of the t-axis component.

The adder 7b4 receives the slip frequency command value ω _s ^* and the second speed estimate value ω _r ^{^^} _n , and outputs the primary frequency command value ω ₁ ^* according to (Equation 29).

Phase estimation calculation section 7b5 receives primary frequency command value ω ₁ ^* and outputs phase estimate value θ _dc according to the above-mentioned (Equation 10).

14 shows the configuration of a second speed estimation calculation unit 7b2 in Example 3. A power dot product calculation unit 7b21 calculates a power dot product value E _dp ^{^} according to (Formula 30) using the m-axis and t-axis voltage command values v _mc ^* , v _tc ^* and the detected current values i _mc , i _tc .

The power inner product model calculation unit 7b22 calculates the inner product model value E dp * according to (equation 31) using the m-axis and t-axis current detection values i _mc , i _tc , the second speed estimate value ω _r ^{^^} _n , the electrical _circuit parameters R ₁ ^* , R ₂ ^'* , M ^* , L2 ^* of the induction motor 1, and the m-axis and t-axis magnetic flux command values ^φ _m ^* , φ _t ^* .

The subtraction unit 7b23 receives the power dot product value E _dp ^{^} and the dot product model value E _dp ^* , and outputs their deviation, ΔE _dp . The output, ΔE _dp , of the subtraction unit 7b23 is multiplied by a gain 7b24, which is -1, and input to a PI control calculation unit 7b25, which calculates a second speed estimate _ωr ^{^^} _n according to (Equation 32) using P (proportional) + I (integral) control calculation.

15 shows the configuration of a first speed estimation calculation unit 7b3 in Example 3. The m-axis current command value i _m ^* is input to a first-order lag calculation unit 7b31 with a time constant T _ACR equivalent to a current control delay, and the output i _m ^* _td of the first-order lag calculation unit 7b31 is multiplied by a gain 7b32 related to the leakage inductance L _σ .

The output of the gain 7b32 is input to a multiplier 7b33 together with the primary frequency command value ω ₁ ^* , and the multiplier 7b33 calculates a voltage drop related to the leakage inductance.

The output value of multiplier 7b33 and t-axis voltage command value v _tc ^* are input to subtractor 7b34. The t-axis magnetic flux command value φ _t ^* is multiplied by gain 7b35 related to secondary resistance value R ₂ ' ^* converted to the primary side and mutual inductance M ^* . The output of gain 7b35 is input to adder 7b36 together with the output of subtractor 7b34.

The t-axis current detection value i _tc is multiplied by a gain 7b37 related to the leakage inductance L _σ , the observer time constant T _obs and the combined resistance value R _σ ^* , and the output of the gain 7b37 is input to an adder 7b38 together with the output of an adder 7b36.

The output of the adder 7b38 is input to a first-order lag calculator 7b39 having an observer time constant T _obs of the speed estimation response.

The t-axis current detection value i _tc is multiplied by a gain 7b310 related to the leakage inductance L _σ and the observer time constant T _obs , and the output of the gain 7b310 is input to a first-order lag calculation section 7b39 and a subtraction section 7b311.

The m-axis magnetic flux command value φ _m ^* is multiplied by a gain 7b312 related to the mutual inductance M and secondary inductance _L2 , and the output of the gain 7b312 is input to a divider 7b313 together with the output of the subtractor 7b311, and the output of the divider 7b313 is used to calculate the first speed estimate value _ωr ^{^} _n according to (Equation 33).

Note that Figure 15 is a functional block diagram in which (Equation 33) has been equivalently converted.

In (Equation 31), the second term does not include the leakage inductance value _Lσ and its set value _Lσ ^* , and in (Equation 33), the sensitivity to the leakage inductance value is lower than that of i _m ^* = 0, so the first speed estimate _ωr ^{^} _n and the second speed estimate _ωr ^{^^} _n are robust to leakage inductance errors, enabling stable and highly accurate speed control to be achieved.

16 is a configuration diagram of a fourth embodiment having a power conversion device and an induction motor. In the first embodiment, the first speed estimate _ωr ^{^} is calculated using the electromotive force of the m-axis, and the second speed estimate _ωr ^{^^} is calculated using the cross product of the power, particularly in the low speed range.

In this embodiment, the first speed estimated value ω _r ^{^} and the second speed estimated value ω _r ^{^^} are used in the low speed range, and the first speed estimated value ω _r ^{^} _n and the second speed estimated value ω _r ^{^^} _n are used in the medium to high speed range.

The speed/frequency/phase calculation unit 7c is a block equivalent to the speed/frequency/phase calculation unit 7 in FIG. 1. In FIG. 16, the induction motor 1 to the coordinate conversion unit 6 and the reference phase calculation unit 8 to the coordinate conversion unit 15 are the same as those in FIG. 1.

Figure 17 shows the configuration of the speed/frequency/phase calculation unit 7c. The slip frequency calculation unit 7c1, the addition unit 7c4, and the phase estimation calculation unit 7c5 are the same as 71, 74, and 75 in Figure 6.

In this embodiment, the speed estimation calculation unit 72 using the cross product of power outputs the output value _ωr ^{^^} of the PI control, which is the PI control calculation unit 724 shown in Figure 7, and the speed estimation calculation unit 7b2 using the inner product of power outputs the output value _ωr ^{^^} _n of the PI control calculation unit 7b25 shown in Figure 14.

Switching calculation section 7c10 selects speed estimate _ωr ^{^^} in the low speed range and speed estimate _ωr ^{^^} _n in the medium to high speed range, and outputs one of them as a second speed estimate _ωr ^{^^} _nn .

Moreover, the speed estimation calculation unit 73 using the induced electromotive force of the m-axis calculates the output value _ωr ^{^} of the gain 7314 shown in Fig. 8. Moreover, the speed estimation calculation unit 7b3 using the induced electromotive force of the t-axis outputs the output value _ωr ^{^} _n of the division unit 7b313 shown in Fig. 15.

A switching calculation section 7c11 selects the speed estimate _ωr ^{^} in the low speed range and the speed estimate _ωr ^{^} _n in the medium to high speed range, and outputs one of them as a first speed estimate _ωr ^{^} _nn .

The aforementioned low speed range and medium to high speed range are determined to be the low speed range when the absolute value of the speed command value _ωr ^* is less than approximately 10% of the rated speed, and switching calculation units 7c10, 7c11 switch the speed estimation value to select a speed estimation value corresponding to the low speed range.

When the absolute value of speed command value ω _r ^* is equal to or greater than about 10% of the rated speed, it is determined to be in the medium to high speed range, and switching calculation sections 7c10, 7c11 switch the speed estimate value to select a speed estimate value corresponding to the medium to high speed range.

Alternatively, the control unit may compare the voltage drop related to the sum of the primary resistance value and the converted secondary resistance value with the voltage drop related to the induced electromotive force to determine whether (Formula 34) is satisfied. Specifically, if (Formula 34) is satisfied, the induction motor is in the low-speed range, and the switching calculation units 7c10 and 7c11 select a speed estimation value corresponding to the low-speed range. Otherwise, if (Formula 34) is not satisfied, the induction motor is in the medium-high speed range, and the switching calculation units 7c10 and 7c11 may be controlled to select a speed estimation value corresponding to the medium-high speed range.

As in this embodiment, by switching the speed estimation value between low and high speed ranges, stable and highly accurate speed control can be achieved across the entire speed range.

Figure 18 is a configuration diagram of Example 5 having a power conversion device, an induction motor, and an IOT (Internet of Things) controller. In Examples 1 to 4, the configuration is such that the electrical circuit parameters of the induction motor 1 are set in the power converter controller (such as a microcomputer).

In this embodiment, the state of the control is fed back to an IOT controller, which is a higher-level external device, and the machine-learned electrical circuit parameters are reset to the controller, which is the control unit of the power converter.

The induction motor 1 to the coordinate conversion unit 15 in Figure 18 are the same as those in Figure 1. 16 is an IOT controller that performs machine learning.

In this embodiment, the voltage command values _vmc ^* , _vtc ^* , the current detection values _imc , _itc , the first speed estimate _ωr ^{^} and the second speed estimate _ωr ^{^^} , and the slip frequency command value _ωs ^* are fed back to a higher-level IOT controller 16. The IOT controller 16 performs machine learning from the current detection waveform and the like. The electric circuit parameters ( _R1 ^* , _R2 ^* , _Lσ ^* , M ^* , _L2 ^* ) that the IOT controller 16 has learned by machine learning are reset in the controller that is the control unit of the power converter 2.

Even with this embodiment, it is possible to achieve more stable and highly accurate control characteristics than in embodiment 1.

Figure 19 is a configuration diagram of Example 6 having a power conversion device, an induction motor, and an external device. This example is applied to an induction motor drive system. In Figure 19, software 20a is the same as the control unit in Figure 1.

The induction motor 1, which is a component of FIG. 1, is driven by a power conversion device 20. In the power conversion device 20, the coordinate conversion unit 5, coordinate conversion unit 6, speed/frequency/phase calculation unit 7, and reference phase calculation unit 8 to coordinate conversion unit 15 of FIG. 1 are implemented as software 20a. In addition, the power converter 2, DC power supply 3, and current detector 4 of FIG. 1 are implemented as hardware.

In addition, the software 20a's "ω _chg 26, which is the switching frequency between low speed range and medium to high speed range," and "ω _c 27, which is the observer time constant that calculates the speed estimate and the control response that is set for proportional control or integral control" can be set or changed using a higher-level external device such as a digital operator 20b, a personal computer 28, a tablet 29, or a smartphone 30.

By applying this embodiment to an induction motor drive system, stable and highly accurate control characteristics can be achieved in speed sensorless vector control. In addition, "ω _chg , which is the low speed range/medium-high speed range switching frequency 26," and "ω _c , which is the speed estimation control response 27" may be set on a field bus such as a programmable logic controller, a local area network connected to a computer, or an IOT controller.

Furthermore, although this embodiment discloses using Example 1, Examples 2 to 5 may also be used.

In the above embodiments 1 to 6, the power cross product value E _cp ^{^} (Formula 12), the power cross product model value E _cp ^* (Formula 13), and the speed estimation calculation formula using the m-axis induced electromotive force (Formula 15) use the current detection values i _mc , i _mc for calculation, but the current command values i _m ^* , i _t ^* may be used instead.

In addition, in the power dot product value E _dp ^{^} (Equation 30), the power dot product model value E _dp ^* (Equation 31), and the speed estimation calculation equation using the induced electromotive force of the t-axis (Equation 33), the current detection values i _mc , i _mc are used in the calculation, but the current command values i _m ^* , i _t ^* may be used instead.

Furthermore, in the first to sixth embodiments, the m-axis and t-axis voltage command values are calculated as _vmc ^* , _vtc ^* (Formula 7) or _vmc ^** , _vtc ^** (Formula 28). Without being limited thereto, intermediate current command values i _m **, i t** shown in (Formula 35) used for vector control calculation may be created from ^the current command values i _m ^* , i _t ^* and the current detection values i _mc , i _{tc ,} ^and the vector control calculation shown in (Formula 36) may be performed using the second speed estimate ω _r ^{^^} , the primary frequency command value ω ₁ ^* and the electric circuit parameters of the induction motor 1.

ここに、K_{p_m2}：ｍ軸の電流制御の比例ゲイン、K_{im_2}：m軸の電流制御の積分ゲイン、K_{p_t2}：ｔ軸の電流制御の比例ゲイン、K_{it_2}：ｔ軸の電流制御の積分ゲイン

Here, K _{p_m2} : proportional gain of m-axis current control, K _{im_2} : integral gain of m-axis current control, K _{p_t2} : proportional gain of t-axis current control, K _{it_2} : integral gain of t-axis current control.

ここに、T_m：m軸の電気時定数(L_σ/R^*)、T_t：ｔ軸の電気時定数(L_σ/R^*)、R^*：＝R₁ ^*+ R₂ ^’*

Here, T _m : Electrical time constant of m axis (L _σ /R ^* ), T _t : Electrical time constant of t axis (L _σ /R ^* ), R ^* : = R ₁ ^* + R ₂ ^'*

Alternatively, the mt-axis vector control calculation unit may use the current command values i _m ^* , i _t ^* and current detection values i _mc , i _tc to create the voltage correction value Δv _{m_p} ^* of the proportional calculation component of the m axis, the voltage correction value Δv _{m_i} ^* of the integral calculation component of the m axis, the voltage correction value Δv _{t_p} ^* of the proportional calculation component of the t axis, and the voltage correction value Δv _{t_i} ^* of the integral calculation component of the t axis, using (Equation 37), and perform the vector control calculation shown in (Equation 38) using the second speed value estimate ω _r ^{^^} , the primary frequency command value ω ₁ ^* and the electrical circuit parameters of the induction motor 1.

ここに、K_{p_m3}：ｍ軸の電流制御の比例ゲイン、K_{im_3}：m軸の電流制御の積分ゲイン、K_{p_t3}：ｔ軸の電流制御の比例ゲイン、K_{it_3}：ｔ軸の電流制御の積分ゲイン

Here, K _{p_m3} : proportional gain of m-axis current control, K _{im_3} : integral gain of m-axis current control, K _{p_t3} : proportional gain of t-axis current control, K _{it_3} : integral gain of t-axis current control.

In the first to fifth embodiments, the switching elements constituting the power converter 2 may be Si (silicon) semiconductor elements or wide band gap semiconductor elements such as SiC (silicon carbide) and GaN (gallium nitride).

1...induction motor, 2...power converter, 3...DC power supply, 4...current detector, 5...coordinate conversion section, 6...coordinate conversion section, 7, 7a, 7b, 7c...speed/frequency/phase calculation section, 71...slip frequency calculation section, 72, 7b2...second speed estimation calculation section, 73, 7b3...first speed estimation calculation section, 7c10, 7c11...switching calculation section, 8...reference phase calculation section, 9...excitation current/magnetic flux setting section, 10...speed control calculation section, 11...coordinate conversion section, 12...coordinate conversion section, 13...mt-axis vector control calculation unit, 14...coordinate conversion unit, 15...coordinate conversion unit, 20...power conversion device, 20a...software for power conversion device, 20b...digital operator for power conversion device, 21...voltage detector, 22...current detector, 23...encoder, 24...mt-axis voltage, current, and magnetic flux calculation unit, 25...power cross product calculation unit, 26...predetermined low-speed range/medium-high-speed range switching frequency, 27...control response of speed estimation calculation, 28...personal computer, 29...tablet, 30...smartphone, i _d ^* ...d-axis current command value, i _q ^* ...q-axis current command value, i _dc ...d-axis detected current value, i _qc ...q-axis detected current value, v _dc ^* , v _dc ^** ...d-axis voltage command value, v _qc ^* , v _qc ^** ...q-axis voltage command value, φ _2d ^* ...d-axis secondary magnetic flux command value, φ _2q ^* ...q-axis secondary magnetic flux command value, i _m ^* ...m-axis current command value, i _t ^* ...t-axis current command value, i _mc ...m-axis detected current value, i _tc ...t-axis detected current value, v _mc ^** , v _mc ^** , v _mc ^*** , v _mc ^**** ...m-axis voltage command value, v _tc ^* , v _tc ^** , v _tc ^*** , v _mc ^**** ...t-axis voltage command value, φ _m ^* ... magnetic flux command value of the m-axis, _φt ^* ... magnetic flux command value of the t-axis, _ωr ^* ... speed command value, _ωr ... rotation speed of the induction motor, _ωr ^{^} , _ωr ^{^} _n , _ωr ^{^} _nn ... first speed estimate value, _ωr ^{^^} , _ωr ^{^^} _n , _ωr ^{^^} _nn ... second speed estimate value, _ωs ^* ... slip frequency command value, _ω1 ^* ... primary frequency command value, _θmt ... estimated phase angle which is the phase angle between the d-axis and m-axis, _θdc ... estimated phase value, _Ecp ^ ... cross product value of power, _Ecp * ... cross product model value of power, _Edp ^ ... dot product value of power, _Edp * ... dot product model value of power, _vu , _vv , _vv ... three-phase AC voltage command values, _iu , _iv , _iv ... three-phase AC currents, _iuc , _ivc , i _vc …Three-phase AC current detection value

Claims (12)

a power converter that outputs a signal to the induction motor to vary an output frequency, an output voltage, and an output current of the induction motor;
A control unit that controls the power converter,
The control unit is
Calculating a voltage and a current on a control axis having a primary current direction and a direction perpendicular thereto as a rotating coordinate system from the output current;
calculating a first speed estimate and a second speed estimate from the voltage and current;
calculating a speed control from the first speed estimate;
a power conversion device that calculates a primary frequency command value from the second speed estimate value,
the first speed estimation value is calculated using an induced electromotive force on the m-axis in a low speed range, and is calculated using an induced electromotive force on the t-axis in a medium to high speed range;
A power conversion device in which the second speed estimate is calculated using a cross product of power in a low speed range and is calculated using an inner product of power in a medium to high speed range . 2. The power conversion device according to claim 1,
The control unit is
A power conversion device that performs a vector control calculation from the second speed estimate value. 2. The power conversion device according to claim 1,
The control unit is
a power conversion device that calculates the first speed estimation value from an m-axis voltage command value, a current detection value, a t-axis current command value, m-axis and t-axis magnetic flux command values, electric circuit parameters of the induction motor, and the primary frequency command value. 2. The power conversion device according to claim 1,
The control unit is
a power conversion device that calculates the first speed estimation value from a t-axis voltage command value, a current detection value, an m-axis current command value, m-axis and t-axis magnetic flux command values, electric circuit parameters of the induction motor, and the primary frequency command value. 2. The power conversion device according to claim 1,
The control unit is
Calculate the cross product of the power from the m-axis and t-axis voltage command values and the current detection values;
calculating a cross product model of power from m-axis and t-axis current detection values, electrical circuit parameters of the induction motor, the second speed estimate, and the primary frequency command value;
A power conversion device that calculates the second speed estimate from a cross product of power and a cross product model of power. 2. The power conversion device according to claim 1,
The control unit is
Calculate the inner product of power from the m-axis and t-axis voltage command values and the current detection values;
calculating an inner product model of power from m-axis and t-axis current detection values, electrical circuit parameters of the induction motor, the second speed estimate value, and the primary frequency command value;
A power conversion device that calculates the second speed estimate from a power dot product and a power dot product model. The power conversion device according to claim 3,
The control unit is
The power conversion device determines that the induction motor is in a low speed range. The power conversion device according to claim 4,
The control unit is
A power conversion device that determines that the induction motor is in the medium to high speed range. 6. The power conversion device according to claim 5,
The control unit is
The power conversion device determines that the induction motor is in a low speed range. 7. The power conversion device according to claim 6,
The control unit is
A power conversion device that determines that the induction motor is in the medium to high speed range. 2. The power conversion device according to claim 1,
The control unit is
A power conversion device that feeds back the voltage and current, the first speed estimate value, and the second speed estimate value to an external device for analysis, and corrects the resistance value and inductance value of the induction motor in accordance with the analysis. 2. The power conversion device according to claim 1,
The control unit is
The switching frequency value for switching between low-speed and medium-high-speed control,
A power conversion device that sets or changes, from an external device, the observer time constant that calculates the speed estimate value and the control response that is set in proportional control or integral control.

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