JP2014217192A - Power converter and control method of power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that a power converter cannot be made compact because the rotational energy due to the moment of inertia of an induction motor and a load is regenerated to the power converter when decelerating the induction motor, and thereby a semiconductor switch, a resistor for control and their control circuit for processing the regenerative energy as thermal energy are required, and to provide a power converter achieving compaction and its control method by solving the problem.SOLUTION: A power converter includes a forward converter for converting the AC voltage of an AC power supply into a DC voltage by rectification, an inverse converter for converting the DC voltage of the forward converter into an AC voltage, and a control unit for operating a slip by using the primary resistance value, secondary resistance value, primary current value i1 and exciting current value of an induction motor, and superposing the output voltage of frequency components lower than the frequency corresponding to the slip thus operated on the variable voltage variable frequency output voltage, during deceleration or regeneration of the induction motor.

Description

  The present invention relates to a power conversion device and a method for controlling the power conversion device.

  Inverters, which are power conversion devices, are widely used as speed control devices for induction motors in industry and home appliances.

  When the induction motor is decelerated and stopped, the rotational energy at the time of deceleration of the induction motor is converted into electric energy and stored as electrostatic energy in the smoothing capacitor in the DC intermediate circuit of the power converter, but the amount of storage that can be processed is Since the voltage is small, the voltage across the smoothing capacitor rises, the voltage detection circuit provided in the DC intermediate circuit of the power converter operates, and the power converter stops when it exceeds a preset overvoltage level.

For this reason, the power converter is equipped with a regenerative braking circuit comprising a semiconductor switch and a braking resistor in the DC intermediate circuit, and the rotational energy during deceleration of the AC machine is converted into thermal energy by the braking resistor. It is configured to consume, and the rise of the voltage across the smoothing capacitor is suppressed so that the voltage detection protection circuit does not operate.

  Paragraph [0007] of Patent Document 1 states that “a series circuit of a braking resistor and a switch connected to both ends of the smoothing capacitor, and the switch when the voltage across the smoothing capacitor exceeds a predetermined value. A voltage detection circuit that closes the circuit, a time during which the switch is closed within a predetermined period (T) based on an external start command, and a totaling circuit that outputs the total time (Σt); A usage rate calculation circuit for calculating the usage rate (X%: X = (Σt / T) * 100) of the braking resistance from the period (T) and the total time (Σt), and the usage rate (X%) And a display circuit for displaying to the outside when the period (T) ends. "

  Further, paragraph [0011] of Patent Document 2 states that “this component is superposed on the main operation command component to cancel the regenerative power of the main component.

FIG. 2 is a T-type equivalent circuit of the induction motor, and the curve of FIG. 1 is created from this equivalent circuit. In FIG. 2, i1 is a primary current, i2 is a secondary current, R1 is a primary resistance, R2 is a secondary resistance, and s is a slip. Considering i2 and ignoring iron loss, when regenerative power becomes 0,
(R1 + R2) · i1 ² + (1-s) · R2 · i1 ² / s = 0 (1)
Solve this for s,
s =-(R2 / R1) (2)
It becomes. Is described.

  Also, paragraph [0006] of Patent Document 2 states that “the present invention consumes regenerative power due to the operating frequency component by superimposing a low frequency component that increases the loss with respect to the normal operating frequency during deceleration. Therefore, it is possible to prevent the inverter from regenerating and to prevent troubles caused by a rise in the voltage of the DC bus.Therefore, it is not necessary to add a regenerative energy processing resistor and control circuit, so the time required for deceleration can be shortened and the size can be reduced. Inverter-driven induction that can be controlled as normal operation by operating at the original operation frequency that does not include superimposed components, and that can be applied to induction motors using sensorless vector control. The object is to provide a braking method for an electric motor and an inverter device. "

Japanese Patent No. 3648932 Patent No. 4300831

  Patent Document 1 describes overload protection and overheat protection based on allowable load time rate% ED management of the regenerative braking resistor, but does not disclose slip control during regeneration of the induction motor.

Patent Document 2 discloses that an operation is performed by superimposing an output voltage having a frequency component lower than a frequency at which slip becomes − (R2 / R1) on the output voltage of the output frequency. That is, it is disclosed that an output voltage (vu_c ^* , vv_c ^* , vw_c ^* ) having a frequency component lower than a frequency at which slip becomes − (R2 / R1) is superimposed on the output voltage of the output frequency.

  Further, as is clear from the T-type equivalent circuit of the induction motor described in FIG. 2 of Patent Document 2, in Patent Document 2, there is no consideration about the exciting current flowing through the exciting impedance Zm, and “where the slip s is large”. However, for the sake of simplicity, it is assumed that “i1 = i2”. However, in reality, in most induction motors, it is impossible to assume that i1 = i2.

  The above objects and means for achieving them are as follows.

  A forward converter that rectifies the alternating voltage of the alternating current power source and converts it into a direct current voltage, an inverse converter that converts the direct current voltage of the forward converter into an alternating current voltage, a primary resistance value R1 and a secondary resistance value R2 of the induction motor The primary current value i1 and the excitation current value im are used to calculate a slip, and when the induction motor is decelerated or regenerated, an output voltage having a frequency component equal to or lower than the frequency corresponding to the calculated slip is output as a variable voltage variable frequency output. And a control unit that superimposes the voltage on the voltage.

  ADVANTAGE OF THE INVENTION According to this invention, the control method of the power converter device and power converter device which implement | achieved size reduction can be provided.

It is a block diagram of the power converter device which concerns on this invention. It is a T-type equivalent circuit of an induction motor. It is a simple T-type equivalent circuit of the induction motor in the present invention. It is the figure which showed the state of the electric power transmission / reception at the time of regeneration of the induction motor in this invention. It is a characteristic view of an induction motor. It is a block diagram (1st form) of sensorless vector control of the power converter device which concerns on this invention. It is a block diagram (2nd form) of sensorless vector control of the power converter device which concerns on this invention. It is a block diagram (3rd form) of the power converter device sensorless vector control which concerns on this invention. It is a block diagram (4th form) of the power converter device sensorless vector control which concerns on this invention. It is a block diagram (5th form) of the power converter device sensorless vector control which concerns on this invention. It is a block diagram (6th form) of the power converter device sensorless vector control which concerns on this invention.

  Hereinafter, the present invention will be described with reference to the drawings. In addition, the same reference number is attached | subjected about the common structure in each figure. Further, the present invention is not limited to the illustrated example.

  The form in Example 1 of the power converter device by this invention is demonstrated using figures below.

  FIG. 1 is a configuration diagram of a power converter according to the present invention.

  1 includes a forward converter 1 for supplying power to an induction motor 4, a smoothing capacitor 2, an inverse converter 3, a control circuit 5, a cooling fan 6, a digital operation panel 7, and a driver circuit 8. The current detection circuit 9 is provided. FIG. 1 shows a case where an AC power source is used as an arbitrary input power source.

The forward converter 1 converts AC power into DC power.
The smoothing capacitor 2 is provided in the direct current intermediate circuit.

The inverse converter 3 converts DC power into AC power having an arbitrary frequency. In the inverse converter 3, for example, an IGBT is mounted as a typical switching element. Here, the switching element is not limited to the IGBT, and any element having a form as a switching element may be used.
The cooling fan 6 cools the power modules in the forward converter 1 and the reverse converter 3.
The digital operation panel 7 sets, changes, abnormal states, and monitor displays various control data of the power conversion device. The operation panel 7 is provided with a display unit capable of displaying an abnormality. When an abnormality is detected in the power conversion device, the display is displayed on the display unit. The type of the operation panel 7 of the present embodiment is not particularly limited. However, the operation panel 7 is configured as a digital operation panel so that the operation can be performed while viewing the display on the display unit in consideration of the operability of the apparatus user. .
The display unit is not necessarily configured integrally with the operation panel 7, but it is desirable that the display unit be configured integrally so that an operator of the operation panel 7 can operate while viewing the display.
Various control data of the power converter input from the operation panel 7 is stored in a storage unit (not shown).

The control circuit 5 controls the switching elements of the inverter 3 based on various control data input from the digital operation panel 7 and controls the entire power converter 10. An arithmetic device) is mounted, and is configured to perform necessary control processing in accordance with various control data input from the digital operation panel 7. Although an internal configuration is omitted, a microcomputer (control arithmetic unit) that performs an operation based on information from storage data of a storage unit in which various control data is stored is mounted.
The current detector CT detects the U-phase and W-phase line currents of the induction motor. The V-phase line current is obtained as iv = − (iu + iw) from the AC condition (iu + iv + iw = 0). Although FIG. 1 shows an example in which two CTs are used, three CTs may be used to detect each U-phase, V-phase, and W-phase line current.

  The driver circuit 8 drives the switching element of the inverse converter 3 based on a command from the control circuit 5. A switching regulator circuit (DC / DC converter) is mounted in the driver circuit 8, and each DC voltage necessary for the operation of the power converter is generated and supplied to each component.

The voltage detection circuit 9 detects the DC voltage VPN of the DC intermediate circuit.
Various control data of the power conversion device can be set and changed from the operation panel 7. Further, in the case of supplying a DC power supply instead of an AC power supply as an arbitrary input power supply, the DC power supply + side is connected to the DC terminal P side, and the DC power supply − side is connected to the DC terminal N side. .
Furthermore, the AC terminals R, S, and T may be connected, the DC power source + side may be connected to this connection point, the DC power source N side may be connected to the DC power source negative side, or conversely the DC terminal. The positive side of the DC power source may be connected to the P side, the AC terminals R, S, and T may be connected, and the negative side of the DC power source may be connected to this connection point.

  FIG. 2A is a T-type equivalent circuit of a conventional induction motor.

The induction motor includes a primary side resistance R1, a primary side leakage inductance L1, a secondary side resistance R2, a secondary side leakage inductance L2, an excitation inductance M, and a slip s.
Here, i1 is a primary current flowing to the primary side, i2 is a secondary current flowing to the secondary side, and im is an excitation current flowing to the excitation circuit.

FIG. 2B is a simplified T-type equivalent circuit of the induction motor according to the present invention.
In each constant of the induction motor, the numerical value of the excitation inductance M is extremely larger than the numerical value of the primary leakage inductance L1 and the numerical value of the secondary leakage inductance L2.

M >> L1 (L1 / M≈0)
M >> L2 (L2 / M ≒ 0) ----------------------------- Number (2)
Considering the number (1) and the number (2), the T-type equivalent circuit of the induction motor can be simplified as shown in FIG.

  When the induction motor is in a regenerative state, the following relational expression is established for each current from the simplified T-type equivalent circuit of FIG.

  That is, the secondary current i2 is represented by the vector sum of the primary current i1 and the excitation current im.

i2 = i1 + jim
∴ i2 ² = i1 ² + im ² ------------------------------ Number (3)

Further, if the output power Pout of the induction motor is consumed as ohmic cross by the primary side resistance R1 and the secondary side resistance R2 in the motor (ignoring iron loss or the like), the following formula is established.

Pout = − (1-s) / s · R2 · i2 ²
= R2 · i2 ² + R1 · i1 ²
∴ (−1 + s) · R2 · i2 ² = s (R2 · i2 ² + R1 · i1 ² ) --- Number (4)
From number (4)
-R2 · i2 ² = s · R1 · i1 ² ----------------------- Number (5)
Substituting the number (3) into the number (5), −R2 · (i1 ² + im ² ) = s · R1 · i1 ² ------------- Number (6)
From the number (6), the slip s is s = −R2 / R1 · (1 + im ² / i1 ² ) ---------------- Number (7)
Here, the number (7) and a comparison of the number (2) in Patent Document 2, accurately model it is an ^{(-R2 / R1 · im 2 /} i1 2) amount corresponding induction motor having the present invention (7) The slip point at which the regenerative power is 0 (zero) can be calculated more accurately.

  Further, the slip obtained from the number (2) in Patent Document 2 is s = − (R2 / R1)> − 1.0 (∵R1> R2) in consideration of the slip sign. This is because, in general, the induction motor has a value of the primary side resistance R1 larger than that of the secondary side resistance R2.

  On the other hand, since the slip determined by the number (7) of the present invention can be applied to the s <−1.0 region, accurate modeling can be performed without being limited by the slip of the induction motor.

In general, in the case of an induction motor, if iron loss or the like is ignored, a part of the output power Pout is consumed as ohmic cross in the primary-side resistor R1 and the secondary-side resistor R2 in the motor, and the power that cannot be consumed is consumed. Input power Pin (Pin = −Pout + R2 · i2 ² + R1 · i1 ² , where Pin> 0 is an electric state, and Pin <0 is a regenerative state) is regenerated to the power converter. For this reason, if the slip s of the induction motor is controlled according to the number (7), the output power Pout of the induction motor (Pout> 0 is an electric state, and Pout <0 is a regenerative state) is equal to the resistance R1 on the primary side inside the motor. All of the ohmic cross can be consumed in the next resistor R2.

  FIG. 3 is a characteristic diagram of the induction motor.

Each characteristic curve is shown with the horizontal axis representing the slip of the induction motor and the vertical axis representing the input power Pin, output power Pout, iron loss, and copper loss.
At the time of regeneration of the characteristic diagram of the induction motor shown in FIG. 3, the point of Pin = 0 can be obtained as a more accurate slip point by the equation (7).
In FIG. 3, the left region where the slip s> 0 is the region operating as the electric side, and the right region where the slip s <0 is the region operating as the regeneration side. Slip s = 0 indicates a case where the slip S = 1 is in a stopped state at the synchronous speed point of the induction motor.
The slip region where the input power Pin is negative indicates that the power is regenerated to the power conversion device. The regenerative power Pin to the power converter is a value obtained by subtracting the loss (mainly W = iron loss + copper loss) consumed internally as an electric motor from the output power Pout.

The region on the right side of the slip s (point A) where the regenerative power becomes 0 (zero) further increases due to the increase in copper loss, and therefore, the region where power is supplied from the power converter to the induction motor also. I understand. This region shows a state in which power is supplied from the power converter to the generator (Pin> 0) even though it operates as a generator (output power Pout <0).
In other words, the loss W in consumption inside the motor becomes larger than the output power Pout, power regeneration to the power converter is not performed, and conversely, the input power Pin is supplied from the power converter to the induction motor, The electric power in the electric motor will be balanced.
That is, if the frequency of the power converter is controlled so that the operating point of the induction motor is in the region on the right side of the slip s (point A), power regeneration from the induction motor to the power converter operates at 0 (zero). Can be made. FIG. 2C shows the state of power transmission / reception.

FIG. 4 is a block diagram (first embodiment) of sensorless vector control of the power converter according to the present invention.
The current detection circuit in FIG. 4 corresponds to the current detection circuit 9 shown in FIG. 1, and the other components in FIG. 4 are detailed configurations of the control circuit 5 in FIG. The sensorless vector control is referred to as direct current control of the induction motor, and the primary side resistance value R1, the primary side leakage inductance value L1, the secondary side resistance value R2, and the secondary side leakage inductance value L2 in the induction motor. Since the excitation inductance value M and the like are electric constant values essential for executing the sensorless vector control, they are generally stored in advance in a memory (not shown) inside the power converter.
If the electrical constants are unknown, the electrical constant value of the induction motor may be measured using the auto tuning function.

That is, for the primary side resistance R1 and the secondary side resistance R2 used for the calculation of the number (7), values stored in advance in the memory inside the power converter are used, or are measured by the auto tuning function. Whether the value is used may be determined by the user of the power conversion device, and in any case, the resistance value is a known value.
Here, the slip s of the induction motor can be expressed by the number (8) according to the definition of the slip.

s = (f1-fr) / f1 ------------------------------ Number (8)
Here, f1 is the primary frequency of the induction motor, and fr is the rotational frequency of the induction motor.

  The slip obtained by the equation (7) is set as sc, and this is substituted into the equation (8), and the frequency f1s corresponding to the slip sc is obtained by the equation (9).

f1s = fr / (1-sc) ----------------------------- Number (9)
Here, in the equation (9), the frequency f1s corresponding to the slip sc may be obtained using the primary frequency f1 of the induction motor instead of the rotation frequency fr of the induction motor.

  When the induction motor is decelerated, the generator s is in a regenerative state and therefore slip s <0. For example, if sc is −1.5 for the slip determined by the equation (7), the frequency f1s corresponding to this slip is the equation (10).

f1s = fr / {1-(− 1.5)} = 0.4 * fr ------------- Number (10)
That is, if the frequency f1s equivalent to 40% is superimposed on the primary frequency f1 with respect to the rotation frequency fr of the electric motor, it means that deceleration can be performed at point A: Pin = 0 during regeneration.

  In an actual induction motor, iron loss and mechanical loss occur in addition to copper loss. However, in the present invention, iron loss and mechanical loss that are not dominant loss (mainly copper loss Wc) are ignored. 7). For this reason, at point A where Pin = 0 at the time of regeneration, which is obtained by Equation (7), not only the copper loss Wc is consumed from the output power Pout, but also the ignored iron loss Wi, mechanical loss Wm, and the like are realistic. Since it is consumed (Pin = −Pout + Wc + Wi + Wm> 0), if it is operated at point A, it will supply the consumption amount such as iron loss Wi and mechanical loss Wm neglected from the power converter to the induction motor. Can be set to 0 (zero).

  Further, if the frequency f1s of 40% or less is superimposed on the primary frequency f1 as the frequency of 40% or less (the slip sc is −1.5 or less, for example, −1.8), the electric power regenerated from the terminal of the induction motor. Can be completely zero, and conversely, power is supplied from the power converter to the induction motor. This operating point is, for example, point B in FIG.

That is, the point B has a larger total power loss including the power loss Wc, the iron loss Wi, and the mechanical loss Wm consumed by the primary side resistance R1 and the secondary side resistance R2 than the output power Pout of the induction motor. Become. For this reason, the input electric power Pin> 0 {Pin = (− Pout + R2 · i2 ² + R1 · i1 ² + iron loss Wi + mechanical loss Wm)> 0}, and the shortage (Pins in FIG. 3) is obtained from the power converter. Supplied to the induction motor.

  The electric power consumed by the primary side resistance R1 and the secondary side resistance R2 and the shortage (Pins) with respect to the total loss including the iron loss Wi and the mechanical loss Wm are supplied.

  Naturally, as a system including an induction motor, when the induction motor is decelerated to operate as a generator, it is desirable to control the regenerative power to 0 (zero), but the power Pins supplied to the induction motor from the power converter is small. Is energy saving.

  However, in the method disclosed in Patent Document 2 (one third of the fundamental frequency), since the region is further to the right of the point B in FIG. 3 of the present invention, a larger amount of power is transferred from the power converter to the induction motor. Will be supplied.

  According to the present invention, since the point A at which the regenerative power becomes 0 (zero) can be accurately obtained, the power regenerated from the terminal of the induction motor can be completely reduced to 0 (zero). The electric power supplied to the induction motor can be minimized.

  The current detector CT detects the line current of the induction motor, converts the current detected by the dq axis conversion unit into orthogonal dq axes, and decomposes it into an excitation current component Id and a torque current component Iq. As shown in FIG. 4A, the dq axis conversion unit performs vector decomposition (i1 = Id + jIq) of the detected current (primary current) i1 into an excitation current component Id and a torque current component Iq orthogonal thereto.

  In this case, in the induction motor, when the torque current component Iq is positive (Iq> 0) is set as the electric mode, it is found that the regeneration mode is set when the torque current component Iq is negative (Iq <0). That is, the sign of the torque current component Iq can determine whether the induction motor is in an electric state (electric motor) or a regenerative state (generator).

  Of course, since the orthogonal dq axes are virtual axes, the names of the dq axes (d axis, q axis) are not limited, and even if they are αβ axes, the axes need only be orthogonal. That is, the intention of the present invention does not change even if the exciting current component Id and the torque current component Iq are replaced with the exciting current component Iα and the torque current component Iβ.

  Here, the excitation current Id corresponds to im in the equation (7), and the torque current Iq corresponds to i2 in the equation (5).

  When the induction motor is brought into an overexcitation state, the Id setting value may be increased. By changing the value of the Id setting, the induction motor can be arbitrarily set to the underexcitation state, the appropriate state, and the overexcitation state. It is also possible to increase the value of Id setting only during regeneration so that an overexcitation state is achieved.

  The slip s is obtained from the primary current i1 of the induction motor and the excitation current im (corresponding to the excitation current Id in the figure), and the frequency corresponding to the slip s is calculated from the estimated speed fr ^ of the induction motor that is the output of the speed estimator. .

  Further, the slip s is obtained from the primary current i1 and the excitation current im (corresponding to the excitation current Id in the figure) of the induction motor, and the slip is calculated from the frequency f1 that is the output of the frequency control without using the estimated speed fr ^ of the induction motor. A frequency corresponding to s may be calculated.

  Here, the polarity of the torque current Iq in FIG. 4 is regenerative when Iq <0 (electrical state when Iq> 0). Therefore, the slip is calculated according to equation (7) only when Iq <0. Then, the output voltage of the frequency component equal to or lower than the frequency obtained by the equation (10) is superimposed on the output voltage of the variable voltage variable frequency.

  Alternatively, only when the microcomputer (not shown) determines that the induction motor has decelerated, or when the DC voltage VPN of the DC intermediate circuit is detected and the voltage value is determined to have increased, the slip is performed according to Equation (7). An output voltage having a frequency component equal to or lower than the frequency obtained by the calculation (10) may be superimposed on the output voltage of the variable voltage variable frequency.

In the figure, the three-phase output phase voltages Vu ^* , Vv ^* , Vw ^* , which are vector calculation results, are output to the output voltage ΔVuk of a frequency component equal to or lower than the frequency obtained according to equation (10) only when the induction motor is decelerated or regenerated. The speed of the induction motor is controlled based on the PWM calculation result obtained by adding (ie, superimposing) ΔVvk and ΔVwk to each phase.

That is, the AC voltage as a modulated wave of each phase in the PWM arithmetic circuit is expressed by the following equation.
Vu = Vu ^* · sin (ω1 · t) + ΔVuk · sin (ω1s · t)
Vv = Vv ^* · sin (ω1 · t−2π / 3) + ΔVvk · sin (ω1s · t−2π / 3)
Vw = Vw ^* · sin (ω1 · t−4π / 3) + ΔVwk · sin (ω1s · t−4π / 3)
Here, ω1 = 2π · f1 and ω1s = 2π · f1s.

  Further, the magnitudes of the output voltages ΔVuk, ΔVvk, ΔVwk of frequency components equal to or lower than the frequency may be set and adjusted in advance so as not to cause an overcurrent to the power conversion device or the induction motor.

  Alternatively, with gain K (K ≦ 1), ΔVuk = K · ΔVu, ΔVvk = K · ΔVv, ΔVwk = K · ΔVw are obtained, and ΔVuk, ΔVvk, ΔVwk are used as new output voltages of frequency components below the frequency. It may be configured to add (i.e., superimpose) the phases so that the gain K can be changed. If the gain K is set small, the magnitudes of the output voltages ΔVuk, ΔVvk, ΔVwk of frequency components below the frequency added to each phase can be reduced, so that no overcurrent is generated in the power converter or induction motor. Can be controlled.

In this case, the AC voltage as the modulated wave of each phase in the PWM arithmetic circuit is expressed by the following equation.
Vu = Vu ^* · sin (ω1 · t) + ΔVuk · sin (ω1s · t)
= Vu ^* · sin (ω1 · t) + K · ΔVu · sin (ω1s · t)
Vv = Vv ^* · sin (ω1 · t−2π / 3) + ΔVvk · sin (ω1s · t−2π / 3) = Vv ^* · sin (ω1 · t−2π / 3) + K · ΔVv · sin (ω1s · t -2π / 3)
Vw = Vw ^* · sin (ω1 · t-4π / 3) + ΔVwk · sin (ω1s · t-4π / 3) = Vw ^* · sin (ω1 · t-4π / 3) + K · ΔVw · sin (ω1s · t -4π / 3)
Alternatively, the gain K may be a function K (i1) of the primary current i1 of the induction motor, and the gain K may be automatically changed according to the magnitude of the detected primary current i1.

In this case, the AC voltage as the modulated wave of each phase in the PWM arithmetic circuit is expressed by the following equation.
Vu = Vu ^* · sin (ω1 · t) + K (i1) · ΔVu · sin (ω1s · t)
Vv = Vv ^* · sin (ω1 · t−2π / 3) + K (i1) · ΔVv · sin (ω1s · t−2π / 3)
Vw = Vw ^* · sin (ω1 · t−4π / 3) + K (i1) · ΔVw · sin (ω1s · t−4π / 3)
Alternatively, the gain K may be a function K (i2) of the secondary current i2 of the induction motor, and the gain K may be automatically changed according to the magnitude of the secondary current i2.

In this case, the AC voltage as the modulated wave of each phase in the PWM arithmetic circuit is expressed by the following equation.
Vu = Vu ^* · sin (ω1 · t) + K (i2) · ΔVu · sin (ω1s · t)
Vv = Vv ^* · sin (ω1 · t−2π / 3) + K (i2) · ΔVv · sin (ω1s · t−2π / 3)
Vw = Vw ^* · sin (ω1 · t-4π / 3) + K (i2) · ΔVw · sin (ω1s · t-4π / 3)
Furthermore, the gain K is a function K (i1, i2) of the primary current i1 and secondary current i2 of the induction motor, and the gain K is automatically changed according to the magnitudes of the primary current i1 and secondary current i2. May be.

In this case, the AC voltage as the modulated wave of each phase in the PWM arithmetic circuit is expressed by the following equation.
Vu = Vu ^* · sin (ω1 · t) + K (i1, i2) · ΔVu · sin (ω1s · t)
Vv = Vv ^* · sin (ω1 · t−2π / 3) + K (i1, i2) · ΔVv · sin (ω1s · t−2π / 3)
Vw = Vw ^* · sin (ω1 · t-4π / 3) + K (i1, i2) · ΔVw · sin (ω1s · t-4π / 3)
By controlling in this way, the output power Pout of the induction motor is consumed as ohmic crosses by the winding resistances R1 and R2 inside the motor, so that the regenerative power from the induction motor to the power converter is completely zero. Even if the deceleration time of the induction motor is shortened, it is not necessary to add a semiconductor switch for regenerative energy processing, a braking resistor, or its control circuit. Can be achieved.

  In this embodiment, the current s on the excitation side and the current i1 on the primary side are used as the current to calculate the slip s according to the equation (7), and the calculated slip is less than the frequency when the induction motor is decelerated or regenerated. By superimposing the output voltage of the frequency component on the output voltage of the variable voltage and variable frequency, even if the time to decelerate the induction motor is shortened, the semiconductor switch for regenerative energy processing, the resistor for braking, and its control circuit No need to add.

Of course, the same effect can be obtained by obtaining the slip s using the excitation current command Id ^* for instructing the excitation side current instead of the excitation side current im (corresponding to the excitation current Id in the figure) used as the current. Is obtained.
The slip s may be calculated using the excitation current command Id ^* .

  A second embodiment of the power converter according to the present invention will be described with reference to FIG.

  FIG. 5 is a block diagram (second embodiment) of sensorless vector control of the power conversion device according to the present invention.

  Components common to FIG. 4 and the same functions are denoted by the same reference numerals.

From number (5)
-R2 · i2 ² = s · R1 · i1 ²

From the above equation, the slip s is s = −R2 / R1 · i2 ² / i1 ² ---------------------- Number (11)
Here, the secondary current i2 corresponds to the torque current Iq in FIG.
In this embodiment, by controlling the slip of the induction motor according to the number (11), the output power Pout of the induction motor (the electric state when Pout> 0 and the regenerative state when Pout <0) is the resistance R1 on the primary side inside the motor. And can be consumed as ohmic cross by the resistor R2 on the secondary side.

  That is, in the characteristic diagram of the induction motor shown in FIG. 3, the point at which Pin = 0 at the time of regeneration is a slip that satisfies the number (11).

  The difference from FIG. 4 of the first embodiment is that, as the current, the secondary current i2 and the primary current i1 are used to calculate the slip s according to the number (11), and only when the induction motor is decelerated or regenerated, The output voltage of a frequency component equal to or lower than the calculated slip frequency is superimposed on the output voltage of the variable voltage variable frequency.

The same effect can be obtained by obtaining the slip s using the torque current command Iq ^* for commanding the secondary current instead of the secondary current i2 (corresponding to the torque current Iq in the figure) used as the current. can get. The slip s may be calculated using the torque current command Iq ^* .

A third embodiment of the power converter according to the present invention will be described with reference to FIG.
FIG. 6 is a block diagram (third embodiment) of power conversion device sensorless vector control according to the present invention.

  Components common to FIG. 4 and the same functions are denoted by the same reference numerals.

Substituting number (3) into number (5)
-R2 · i2 ² = s · R1 · (i2 ² -im ² )
From the above equation, the slip s is s = −R2 / R1 · i2 ² / (i2 ² -im ² ) ------------ Number (12)
Here, the secondary current i2 corresponds to the torque current Iq in FIG. 6, and the excitation current im corresponds to the excitation current Id in FIG.

  In this embodiment, by controlling the slip of the induction motor according to the number (12), the output power Pout of the induction motor (the electric state when Pout> 0 and the regenerative state when Pout <0) is the resistance R1 on the primary side inside the motor. And can be consumed as ohmic cross by the resistor R2 on the secondary side.

  That is, in the characteristic diagram of the induction motor shown in FIG. 3, during regeneration, the point where Pin = 0 satisfies the number (12).

  The difference from FIG. 4 of the first embodiment is that the slip is calculated according to the number (12) using the current i2 on the secondary side and the current im on the excitation side as the current, and is calculated only when the induction motor is decelerated or regenerated. The output voltage having a frequency component equal to or lower than the frequency that causes the slip is superimposed on the output voltage of the variable voltage and variable frequency.

Instead of the secondary side current i2 (corresponding to the torque current Iq in the figure) used as the current, a torque current command Iq ^* for instructing the secondary side current is used, and the excitation side current im (excitation in the figure) The same effect can be obtained by obtaining the slip s using the excitation current command Id ^* that commands the current on the excitation side instead of the current Id). The slip s may be calculated using the torque current command Iq ^* and the excitation current command Id ^* .

A fourth embodiment of the power converter according to the present invention will be described with reference to FIG.
FIG. 7 is a block diagram (fourth embodiment) of power conversion device sensorless vector control according to the present invention.

Components common to FIG. 4 and the same functions are denoted by the same reference numerals.
The difference from FIG. 4 of the first embodiment is that the actual speed fr is detected by the speed detector SS without using a speed estimator as means for detecting the speed of the induction motor.

  The point that the slip s is calculated according to the number (7) using the current im on the excitation side and the current i1 on the primary side as the current is the same.

The same effect can be obtained by obtaining the slip s using the excitation current command Id ^* for instructing the excitation side current instead of the excitation side current im (corresponding to the excitation current Id in the figure) used as the current. . The slip s may be calculated using the excitation current command Id ^* .

A fifth embodiment of the power converter according to the present invention will be described with reference to FIG.
FIG. 8 is a block diagram (fifth embodiment) of the power conversion device sensorless vector control according to the present invention.

The components common to FIG. 5 and the same functions are denoted by the same reference numerals.
The difference from FIG. 5 of the second embodiment is that the actual speed fr is detected by the speed detector SS without using a speed estimator as means for detecting the speed of the induction motor.

  The point that the slip s is calculated according to the number (11) using the current i2 on the secondary side and the current i1 on the primary side as the current is the same.

The same effect can be obtained by obtaining the slip s using the torque current command Iq ^* for commanding the secondary current instead of the secondary current i2 (corresponding to the torque current Iq in the figure) used as the current. can get. The slip s may be calculated using the torque current command Iq ^* .

A sixth embodiment of the power converter according to the present invention will be described with reference to FIG.
FIG. 9 is a block diagram (sixth embodiment) of sensorless vector control of the power converter according to the present invention.

The same configuration and the same function as those in FIG. 6 are denoted by the same reference numerals.
The difference from FIG. 6 of the third embodiment is that the actual speed fr is detected by the speed detector SS without using the speed estimator as means for detecting the speed of the induction motor.

  The point that the slip is calculated according to the number (12) using the current i2 on the secondary side and the current im on the excitation side as the current is the same.

Instead of the secondary side current i2 (corresponding to the torque current Iq in the figure) used as the current, a torque current command Iq ^* for instructing the secondary side current is used, and the excitation side current im (excitation in the figure) The same effect can be obtained by obtaining the slip s using the excitation current command Id ^* that commands the current on the excitation side instead of the current Id).
The slip s may be calculated using the torque current command Iq ^* and the excitation current command Id ^* .

  As shown in the above embodiments, the present invention provides a sensorless vector control device or a vector control device for controlling the speed of an induction motor with AC power having a variable voltage and variable frequency. The slip is calculated using one of the value R2, the primary current value i1, the secondary current value i2, and the exciting current value im, and the frequency component of the frequency that is equal to or less than the calculated slip is calculated only when the induction motor is decelerated or regenerated. Even if the time to decelerate the induction motor is shortened by the power converter characterized by superimposing the output voltage on the output voltage of the variable voltage variable frequency, the semiconductor switch for regenerative energy, the resistor for braking, Since it is not necessary to add a control circuit, the power converter can be achieved in a small size.

  In addition, the larger the capacity of the induction motor driven by the power converter, the larger the regenerative power, and the larger the semiconductor switch and brake resistor for regenerative energy processing that must be processed as thermal energy. It is natural that

  In this case, it is difficult to mount a larger semiconductor switch for regenerative energy processing or a resistor for braking inside the power conversion device. Therefore, a semiconductor switch for regenerative energy processing or a resistor for braking is used for power conversion. Must be placed separately from the device.

At this time, especially for the users who use the large-sized regenerative energy processing braking resistor, to secure the installation location, to treat the heat generated from the resistor, and to prevent fire caused by the temperature rise of the resistor due to heat generation. It was a huge burden on a wide variety.
However, according to the present invention, even if the time for decelerating the induction motor is shortened, it is not necessary to add a semiconductor switch for regenerative energy processing, a resistor for braking, or a control circuit thereof, so that the burden on the user side can be reduced. In view of this, the user's merit is extremely large.

DESCRIPTION OF SYMBOLS 1 ... Forward converter, 2 ... Smoothing capacitor, 3 ... Reverse converter, 4 ... Induction motor, 5 ... Control circuit, 6 ... Cooling fan, 7 ... Digital operation panel, 8 ... Power supply circuit, 9 ... DC voltage detection circuit DESCRIPTION OF SYMBOLS 10 ... Power converter, VPN ... DC voltage, R1 ... Primary side resistance of induction motor, R2 ... Secondary side resistance of induction motor, M ... Excitation inductance of induction motor, i1 ... Primary current of induction motor, i2 ... Induction Secondary current of the motor, im ... excitation current of the induction motor, s ... slip of the induction motor, Pin ... input power, Pout ... output power, CT ... current detector, Id ^* ... excitation current command of the induction motor, Iq ^* ... Torque current command of induction motor, fr ^* ... speed setting, fr ^ ... estimated speed,
fr ... detection speed, SS ... speed detector, t ... time, ... multiplication operator, ... division operator, j subscript representing imaginary part, ² square operator

Claims (20)

A forward converter that rectifies the AC voltage of the AC power source and converts it into a DC voltage;
An inverse converter that converts a DC voltage of the forward converter into an AC voltage;
The slip is calculated using the primary resistance value R1, the secondary resistance value R2, the primary current value i1, and the excitation current value im of the induction motor, and when the induction motor is decelerated or regenerated, the slip is less than the frequency corresponding to the calculated slip. A control unit that superimposes the output voltage of the frequency component of the output voltage on the output voltage of the variable voltage variable frequency,
A power conversion device comprising: The power conversion device according to claim 1,
A power conversion characterized in that an output voltage having a frequency component equal to or lower than a frequency at which the slip calculated by the control unit is −R2 / R1 · (1 + im ² / i1 ² ) is superimposed on the output voltage of the variable voltage variable frequency. apparatus. In the power converter device according to claim 1 or 2,
The power conversion device, wherein the excitation current value im is an excitation current command value Id ^* . A forward converter that rectifies the AC voltage of the AC power source and converts it into a DC voltage;
An inverse converter that converts a DC voltage of the forward converter into an AC voltage;
The slip is calculated using the primary resistance value R1, the secondary resistance value R2, the primary current value i1, and the secondary current value i2 of the induction motor, and the frequency corresponding to the calculated slip when the induction motor is decelerated or regenerated. And a control unit that superimposes an output voltage of the following frequency component on an output voltage of a variable voltage variable frequency. The power conversion device according to claim 4, wherein
Power conversion apparatus characterized by superimposing the output voltage of the frequency components below a frequency slip computed by the control unit is ^{-R2 / R1 · i2 2 / i1} 2 to the output voltage of the variable voltage variable frequency. The power conversion device according to claim 4 or 5,
The secondary current value i2 is a torque current command value Iq ^* . A forward converter that rectifies the AC voltage of the AC power source and converts it into a DC voltage;
An inverse converter that converts a DC voltage of the forward converter into an AC voltage;
The slip is calculated using the primary resistance value R1, the secondary resistance value R2, the secondary current value i2, and the exciting current value im of the induction motor, and the frequency corresponding to the calculated slip is reduced or regenerated. And a control unit that superimposes an output voltage of the following frequency component on an output voltage of a variable voltage variable frequency. The power conversion device according to claim 7, wherein
A power converter that superimposes an output voltage having a frequency component equal to or lower than a frequency at which the calculated slip is −R2 / R1 · i2 ² / (i2 ² −im ² ) on the output voltage of the variable voltage variable frequency . The power conversion device according to claim 7 or 8,
The power conversion device characterized in that the secondary current value i2 is a torque current command value Iq ^* , and the excitation current value im is an excitation current command value Id ^* . The power conversion device according to any one of claims 1 to 9,
A power conversion apparatus using the estimated speed estimated by a speed estimator or the detected speed detected by a speed detector when the control unit calculates a frequency corresponding to the calculated slip. Rectifying the AC voltage of the AC power source and converting it to a DC voltage;
Converting the DC voltage converted in the step of converting into the DC voltage into an AC voltage;
The slip is calculated using the primary resistance value R1, the secondary resistance value R2, the primary current value i1, and the excitation current value im of the induction motor, and when the induction motor is decelerated or regenerated, the slip is less than the frequency corresponding to the calculated slip. And a control step of superimposing the output voltage of the frequency component on the output voltage of the variable voltage and variable frequency. In the control method of the induction motor according to claim 11,
A power conversion characterized in that an output voltage having a frequency component equal to or lower than a frequency at which the slip calculated in the control step is −R2 / R1 · (1 + im ² / i1 ² ) is superimposed on the output voltage of the variable voltage variable frequency. Device control method. In the control method of the induction motor according to claim 11 or 12,
The method for controlling a power converter, wherein the excitation current value im is an excitation current command value Id ^* . Rectifying the AC voltage of the AC power source and converting it to a DC voltage;
Converting the DC voltage converted in the step of converting into the DC voltage into an AC voltage;
The slip is calculated using the primary resistance value R1, the secondary resistance value R2, the primary current value i1, and the secondary current value i2 of the induction motor, and the frequency corresponding to the calculated slip when the induction motor is decelerated or regenerated. A control method for controlling a power converter, comprising: superimposing an output voltage of the following frequency component on an output voltage of a variable voltage variable frequency. In the control method of the induction motor according to claim 14,
Power conversion apparatus characterized by superimposing the output voltage of the frequency components below a frequency slip computed by the control step is ^{-R2 / R1 · i2 2 / i1} 2 to the output voltage of the variable voltage variable frequency Control method. In the control method of the induction motor according to claim 14 or 15,
The secondary current value i2 is a torque current command value Iq ^* . Rectifying the AC voltage of the AC power source and converting it to a DC voltage;
A step of converting to a DC voltage in the step of converting to the DC voltage;
The slip is calculated using the primary resistance value R1, the secondary resistance value R2, the secondary current value i2, and the exciting current value im of the induction motor, and the frequency corresponding to the calculated slip is reduced or regenerated. And a control step of superimposing an output voltage having the following frequency component on an output voltage having a variable voltage and a variable frequency. In the control method of the induction motor according to claim 17,
A power converter that superimposes an output voltage having a frequency component equal to or lower than a frequency at which the calculated slip is −R2 / R1 · i2 ² / (i2 ² −im ² ) on the output voltage of the variable voltage variable frequency Control method. The method for controlling an induction motor according to claim 17 or 18,
The method of controlling a power converter, wherein the secondary current value i2 is a torque current command value Iq ^* , and the excitation current value im is an excitation current command value Id ^* . A method for controlling an induction motor according to any one of claims 11 to 19,
A control method for a power converter, wherein the control unit uses an estimated speed estimated by a speed estimator or a detected speed detected by a speed detector when calculating a frequency corresponding to the calculated slip.

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