JPH0454872A - Power converter - Google Patents

Abstract

PURPOSE:To decrease instantaneous power pulsation caused by a higher harmonic current by superimposing a voltage component, to cancel the higher harmonic component of an output current generated by a higher harmonic component included in induction voltage, on the output voltage of a power converter. CONSTITUTION:A higher harmonic voltage command eh* equivalent to the higher harmonic component of induction voltage is generated by a higher harmonic voltage command generator 4 and added to a fundamental wave voltage command value ef* by an adder 6. Thereby an inverter 2 transmits fundamental wave voltage ef* and a higher harmonic component eh equivalent to an induction voltage higher harmonic component emh as output voltage (e). Thereby an output voltage command e* becomes a distortion wave but the induction voltage higher harmonic component emh is cancelled by the output voltage higher harmonic component eh; therefore, voltage ec applied to the resistance R and the inductance L of a load 1 is converted into a sine wave.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power conversion device connected to a load having an induced voltage, such as an electric motor.

[Conventional technology]

As a typical conventional technology, “Power Electronics &
C drive J
Translated by Haruo Naito, 1982, Denki Shoin) pages 195 to 19
Examples include the technique described on page 7.

This is related to inverter control.

In this inverter control circuit, the output voltage command is given in the form of a sine wave. This output voltage command is converted into a pulse signal by a PWM control circuit.

The gate amplifier immediately operates each element of the inverter in response to this pulse signal, so that a sine wave voltage is output from the inverter.

[Problems to be Solved by the Invention] However, in a load having an induced voltage such as an electric motor, the induced voltage may contain low-order harmonic components such as third order. In the case of an electric motor, this occurs because the magnetic flux distribution in the air gap deviates from a sine wave shape, and in the case of an electric power system, this occurs due to output fluctuations of the load within the system.

When the induced voltage includes harmonic components, when the power converter outputs a sine wave, the harmonic components included in the induced voltage are directly applied to the main circuit. Therefore, low-order harmonic components are generated in the output current, causing an increase in instantaneous power pulsation.

Instantaneous power pulsations generate torque or thrust pulsations in the electric motor, causing noise and vibration. Furthermore, in power systems, low-order harmonic components cause problems such as increased noise, vibration, and loss in other equipment in the system, and burnout of equipment.

An object of the present invention is to eliminate the influence of induced voltage harmonic components that cause these disturbances.

[Means to solve the problem]

Means for superimposing a voltage corresponding to a harmonic component included in the induced voltage on the output voltage of the power conversion device is provided.

[Operation] A voltage corresponding to a harmonic component of the induced voltage is superimposed on the output voltage by the induced voltage harmonic component superimposition means. As a result, harmonic components in the induced voltage are canceled out, making it possible to reduce harmonic currents and instantaneous power pulsations caused by the harmonic currents.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which a fundamental wave current controller 5 that controls the output current i of the inverter 2, which shows one phase of the load, the power converter, and its control circuit, is A low-pass filter 52 extracts the output current fundamental wave component ir from the output current i detected by the current detector 8, and a subtraction device subtracts the output current fundamental wave component i from the output current command i* to calculate the deviation current i0. 53, and a current control circuit 51 that generates a fundamental wave voltage command e to make the deviation current i, , zero, and a current control circuit 51. The output of a harmonic voltage command generator 4 that generates harmonic voltage commands e, * from the position signal X generated according to the rotation angle of the rotor of the synchronous motor 11 is added to the fundamental voltage command ef* by an adder 6. and generates 0 output voltage commands. From this output voltage command 61, PW
The M control circuit 3 generates a pulse signal, and the inverter 2
is operated to drive the synchronous motor 11.

FIG. 2 shows an embodiment of the harmonic voltage command generator 4. The frequency generator 42 receives the motor position signal X and generates an output frequency f. 41a.

41b and 41c are specific harmonic voltage command generators that generate harmonic voltage commands e1, e-, and e- of the 1st, m-th, and n-th orders, respectively, and are installed according to the order of the harmonic component to be canceled. do it. The explanation will be given by taking as an example 41a which generates the first harmonic voltage command e-. The harmonic voltage amplitude generator 411 stores the characteristics of the amplitude Eel of the first harmonic component of the induced voltage with respect to the output frequency f, and calculates the amplitude E1* of the first harmonic voltage command from the given output frequency f+. Output. The third harmonic amplitude E is an example of the characteristic of the amplitude of the induced voltage harmonic component with respect to the output frequency f6.

The characteristics are shown in Figure 4.

Generally, the third harmonics of the induced voltage E, . This depends on the construction and design of the motor. This characteristic can be determined in advance by measurement. In addition, since induced voltage harmonic components of other orders can be found in the same way, it is sufficient to store the harmonic components of the order to be canceled in the harmonic voltage amplitude generator 411.

The frequency multiplier 412 generates a first harmonic signal XI with an amplitude of 1 and a frequency of 1 times from the position signal
* is multiplied by the harmonic signal x1 to generate a first harmonic voltage command 61m. 43 is each specific harmonic voltage command generator 41a,
Adding the commands from 41b and 41c, harmonic voltage command e
This is an adder that generates h*.

The operation of the above configuration will be described.

In FIG. 1, from the output current i to the low-pass filter 52
The output current fundamental wave component if is extracted. Subtractor 53
By subtracting the output current fundamental wave component i from one output current command, the deviation current xar is obtained.

The current control circuit 51 generates a deviation current i, ? A fundamental wave voltage command 611 is generated so as to make the voltage zero. This voltage command ef is pulse width modulated by the PWM control circuit 3 to generate a pulse signal. Inverter 2 outputs a voltage according to this pulse signal.

Next, I will explain the principle.

As shown in FIG. 3(a), when the induced voltage e of the load 1 is only the fundamental wave component ea+f, if the inverter 2 outputs the fundamental wave output voltage e, the output current i becomes a sine wave.

However, as shown in FIG. 3(b), the induced voltage e is the fundamental wave component e. In addition to , a harmonic component emb may be included. The induced voltage harmonic component e1 is composed of relatively low-order components, and the third harmonic often appears particularly large. In this case, if the output voltage e of the inverter 2 is only the fundamental wave component ef, the induced voltage harmonic component e□ is directly applied to the resistance R and inductance of the load 1. FIG. 5 shows each waveform obtained by calculation in this case, and the output current i is a distorted wave and includes harmonic current. Furthermore, the instantaneous output power Pt of the load 1 is the product of the output current i and the induced voltage e, but since the output current i contains harmonic components, the instantaneous output power Pt, as shown in FIG. A pulsation component is superimposed on the , and the instantaneous power pulsation increases. This instantaneous power pulsation is.

This can cause problems such as increased vibration, noise, and loss in equipment.

Therefore, the harmonic voltage command generator 4 in FIG.
is generated and added to the fundamental wave voltage command values ef by an adder 6. As a result, as shown in FIG. 3(c), the inverter 2 has a fundamental wave voltage ef and an induced voltage harmonic component em.
A harmonic component eh corresponding to h is outputted as an output voltage e. As a result, the output voltage command e* becomes a distorted wave as shown in FIG. 6, but the induced voltage harmonic component emb is canceled by the output voltage harmonic component e, so as shown in FIG.
The voltage e6 applied to the resistance R and inductance of the load 1 in c) becomes a sine wave.

Therefore, the output current i becomes a sine wave, and the induced voltage harmonic component e. The harmonic current caused by is eliminated. As a result of calculations by the inventors, even if the compensated induced voltage e□ is a distorted wave, if the output current i is sinusoidal, it is a pulsating component of the instantaneous output power p caused by the induced voltage harmonic component esch. do not appear because they cancel each other out in each phase, and instantaneous power pulsations are reduced.

- As an example, let us consider a case where the induced voltage e1 includes a third harmonic. In FIG. 7, when the induced voltage is only in the basic branch, the current ripple is. [Becomes Al. However, if the third harmonic of the induced voltage is included a[V], the current ripple increases to bi[Al]. Therefore, using the harmonic voltage command generator 4, the inverter 1
When controlled to output a voltage that cancels the harmonics, the current ripple is reduced to b[A].

Similar effects can be obtained with respect to the output current distortion factor shown in FIG. 8 and the instantaneous power pulsation shown in FIG.

Since the third harmonic of the induced voltage often has a larger amplitude than the lower harmonic, the compensation effect when this is canceled out is large.

FIG. 10 shows a configuration diagram showing another embodiment of the fundamental wave current controller 5 in FIG. 1.

The orthogonal coordinate converter 58a generates 18 real axis components, a real axis component, and 18 imaginary axis components from the output current command i*. Cartesian coordinate converter 5
8b generates a real axis component and an imaginary axis component (2) from the output current fundamental wave component if obtained by the low-pass filter 52. The subtractor 57a calculates the deviation current real axis component I tar from the output current command real axis component I,* and the output current basic component I,*.
The subtracter 57b generates a deviation current imaginary axis component Ijar from the output current command imaginary axis component (1), the output current basic component (4), and the output current basic component (4).

The current control circuits 56a and 56b respectively generate output voltage commands imaginary axis component E- and real axis component E- so as to make the deviation current real axis component I tar and imaginary axis component I jar zero. 55 is a polar coordinate converter that generates the real axis component E- and imaginary axis component E of the output voltage command, the magnitude IE and phase angle ZE of the output voltage command vector E from the vehicle, and 54 is the magnitude IEI of the output voltage command vector E. This is a coordinate inverse transformer that generates the fundamental wave voltage command e* from the phase angle /E.

When control is performed by a controller using an orthogonal seating system as shown in this figure, the signals handled by the current control circuits 56a and 56b are DC amounts, so there is more leeway in circuit design and control accuracy and responsiveness are improved. do.

FIG. 11 shows another embodiment of the control circuit shown in FIG.

In the control circuit shown in FIG. 1, the waveform of the induced voltage cannot be specified from the load position signal X.

In this case, for example, in an induction motor, there is no position signal X, so this embodiment takes care of this. Hereinafter, only the differences from FIG. 1 will be described.

12 is an induction motor; 45 is a bandpass filter that extracts an output current harmonic component i caused by the induced voltage harmonic component e1 from the output current i; 44 is an output current harmonic component i;
This is a harmonic voltage command generator that generates a harmonic voltage command e- that makes the voltage zero. The current control circuit 51 outputs current i
A harmonic voltage command generator 44 generates an output current harmonic component generated due to the induced voltage harmonic component e1, and generates a fundamental voltage command e, which causes the fundamental wave component if to match the output current command is. A harmonic voltage command of 6 km is generated to suppress i. As a result, a harmonic component e corresponding to the induced voltage harmonic component is superimposed on the output current e, and the first
Effects similar to those of the embodiment shown in the figure can be obtained.

In this embodiment, a current control circuit 51 that controls the fundamental wave component i of the output current i and a harmonic voltage command generator 44 that suppresses the harmonic components are separately provided. It is possible to both control and suppress this with one control circuit.6However, since signals of multiple frequencies are handled simultaneously, designing the control system becomes difficult. By separately controlling the fundamental wave component and suppressing the harmonic component as in this embodiment, there is more leeway in the design of the control system, and control accuracy and responsiveness are improved.

In the above embodiment, the harmonic components of the output current for each phase are detected and compensated for, so in the case of ideal operation, all harmonics disappear and the output current becomes a sine wave. However, there is always a phase lag in the bandpass filter 45, and as the frequency of the harmonic current increases, it is conceivable that the superimposed command values will be superimposed in the positive direction and diverge.

Therefore, in the embodiment shown below, attention is paid to the fact that the harmonic component having a relatively large amplitude is a third harmonic, and the harmonic component is canceled out. In other words, for example, in the case of three phases, the third harmonic and its third harmonic are zero-phase components, and when this harmonic appears, it always appears in the zero-phase as well. Therefore, if control is performed to cancel out the harmonic components appearing in this zero phase, the output current will become sinusoidal without the problem of one phase lag since the zero phase is the sum of each phase.

Fig. 12 shows an example in which the induced voltage harmonic component e is composed of zero-sequence components such as third-order harmonics, and numeral 47 calculates the sum of the output currents of each phase and calculates the output current zero-sequence component. 46 is the output current zero-phase component i. This is a harmonic voltage command generator that generates 01 harmonic voltage commands that suppress .

FIG. 13 shows another embodiment in which the induced voltage harmonic component emk is composed of a zero-phase component. In this embodiment, instead of calculating the output current zero-phase component 10 from the output current of each phase, the neutral line current i is calculated.

Even in this embodiment in which the voltage is detected and inputted to the harmonic voltage command generator 46, the same effect as in the case of using the embodiment shown in FIG. 12 can be obtained.

In the embodiments shown in FIGS. 12 and 13, there is no need for a bandpass filter or the like as seen in the embodiment shown in FIG. Improves sex.

Further, in the embodiments shown in FIGS. 11, 12, and 13, the load is an induction motor, but the above embodiments can of course be applied even if the load is a synchronous motor.

FIG. 14 is a configuration diagram showing a model for one phase when the load is an electric power system. 11 is a power receiving side, 21 is a power transmitting side constituted by a power converter such as a frequency converter or an active power filter, and 7 is a power transmission line. Receiving end voltage eR
contains harmonic components, noise and
This may cause problems such as increased vibration and equipment burnout. By controlling the sending end voltage e using a controller as shown in FIG. 11, 12 or 13, the current i
can be kept as a sine wave to suppress the occurrence of these disturbances.

In the embodiment shown in Fig. 1, a rotary synchronous motor is used as the load, and in Figs. 11, 12, and 13, a rotary induction motor is used as an example, but the control of linear synchronous motors and linear induction motors is also possible. Furthermore, the present invention can of course be applied even when the load is not an electric motor, as in the embodiment in the power system shown in FIG.

〔Effect of the invention〕

According to the present invention, instantaneous power pulsations caused by the induced voltage of the load can be suppressed, so that torque fluctuations, noise, etc. can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing an embodiment of a harmonic voltage command generator, Fig. 3 is a diagram showing a model of the main circuit, and Fig. 4 is a block diagram showing an embodiment of the harmonic voltage command generator. Figure 5 shows the characteristics of the third harmonic as an example of the relationship between the amplitude of the harmonic component of the induced voltage and the output frequency. Figure 6 shows the calculated waveforms of each part when the output voltage is output by adding a voltage corresponding to the induced voltage harmonic component, and Figure 7 shows the output current ripple with respect to the effective value of the third harmonic of the induced voltage. Figure 8 shows the characteristics of the output current distortion rate with respect to the effective value of the third harmonic of the induced voltage, and Figure 9 shows the characteristics of instantaneous power pulsation with respect to the effective value of the third harmonic of the induced voltage. 10 is a block diagram showing another embodiment of the current control circuit in FIG. 1, and FIGS. 11, 12, and 13 are block diagrams showing other embodiments of the inverter control circuit. 1st
Figure 4 is a diagram showing a model of the power system. DESCRIPTION OF SYMBOLS 1... Load, 2... Inverter, 3... PWM control circuit, 11... Synchronous motor, 12... Induction motor, 13... Power receiving side in power system, 21... Power system power transmission side, 4... harmonic voltage command generator,
41... Specific harmonic voltage command generator, 411... Harmonic voltage amplitude generator, 412... Frequency multiplier, 4
13... Multiplier, 42... Frequency generator, 43...
-Adder, 44...Harmonic voltage command generator, 45...
-Band pass filter, 46...Harmonic voltage command generator, 47...Adder, 48...Harmonic voltage command generator, 5...Fundamental wave current controller, 51...Current control Circuit, 52...Low pass filter, 53...Subtractor,
54... Coordinate inverse transformer, 55... Polar coordinate transformer, 5
6... Current control circuit, 57... Subtractor, 58...
Orthogonal coordinate converter, 6... Adder, 7... Fig. 1 M3WA Fig. 4 Output frequency 1. N 1113 Fig. a1 (b) Fig. 7 Induced voltage 3rd order tllJ Effective value Induced voltage 3rd order j Effective value Atsushi 9 Fig. 10rIA 1111 Fig. 12g

Claims (1)

[Claims] 1. In a power conversion device that supplies power to a load having an induced voltage, a voltage component that cancels out harmonic components of an output current generated due to harmonic components included in this induced voltage is provided. A power conversion device comprising means for superimposing an output voltage on the output voltage of the power conversion device. 2. A power conversion device that supplies power to a load having an induced voltage, which is equipped with means for superimposing a voltage component equal to a harmonic component included in the induced voltage on the output voltage of the power conversion device in an opposite phase. conversion device. 3. In a power conversion device that supplies power to a synchronous motor, means for creating a voltage command corresponding to a harmonic component of an induced voltage generated in this synchronous motor from a position signal of this synchronous motor, and creating this voltage command. A power conversion device comprising means for adding an output of the device to an output voltage command value of the power conversion device. 4. In a power conversion device that supplies power to an induction motor, means for detecting harmonic components of an output current caused by harmonic components of an induced voltage generated in the induction motor, and a voltage that cancels the harmonic components of the output current. A power conversion device comprising means for superimposing a component on an output voltage of the power conversion device. 5. In a power conversion device that supplies power to general equipment such as the power receiving end of a power system, harmonic components of the output current caused by induced voltage harmonic components generated in general equipment such as the power receiving end of this power system. and means for superimposing a voltage component that cancels a harmonic component of the output current on the output voltage of the pre-electromotive force converter. 6. The power converter according to claim 1, 2, 4, or 5, wherein the harmonic component of the output current to be canceled is a zero-phase component. 7. In the power conversion device according to claim 1, 2, 4, 5, or 6, the means for detecting harmonic components of the output current detects a current in a neutral line. A power conversion device that is a means. 8. The power converter according to claim 1, 2, 3, 4, or 5, wherein the harmonic voltage component to be canceled is a third harmonic.