JPH0334317B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field to Which the Invention Pertains] The present invention relates to an inverter that converts direct current to alternating current, a synchronous motor driven by the alternating current output from the inverter, and a synchronous motor whose rotational frequency matches the output frequency of the inverter. The present invention relates to a commutatorless electric motor comprising an inverter control means for controlling the phase of the inverter so as to control the phase of the inverter, and more particularly, it relates to phase control of the inverter in the inverter control means.

[Prior art and its problems]

FIG. 1 is a block diagram showing the general configuration of a commutatorless motor. In the figure, 1 is a DC power supply, 2 is an inverter, 3 is a synchronous motor, and 4 is an inverter control means.

That is, the inverter 2 converts the DC supplied from the DC power supply 1 into AC to drive the synchronous motor 3. The inverter control means 4 normally detects the position of the rotor of the synchronous motor 3, and generates and outputs a gate signal for starting the thyristor etc. that constitutes the inverter 22. The output frequency of the synchronous motor 3 matches and is synchronized with the rotational frequency of the synchronous motor 3.

Therefore, a commutatorless motor is equivalent to a DC motor in which the mechanical commutation mechanism using brushes and a commutator is replaced with a rotor position detector and thyristor. It is used for various purposes because it combines the advantages of ease of use.

FIG. 2 is a circuit diagram showing a specific example of a commutatorless motor. In this figure, elements corresponding to those in FIG. 1 are given the same reference numerals.

In FIG. 2, the DC power supply 1 consists of a DC power supply device E consisting of a rectifier (not shown) for rectifying a three-phase AC power supply, and a smoothing reactor Li. Inverter 2 receives DC intermediate current from DC power supply 1.
Id and DC intermediate voltage Ed are inputted to create three-phase AC, thereby driving the synchronous motor 3.
The functions of the inverter control means 4 are as described above. _EM is the line-to-line induced voltage of the motor 3.

FIG. 3 is a waveform diagram showing the voltage and current waveforms of the non-commutator motor (directly the synchronous motor 3) as shown in FIG.

That is, in FIG. 3A, the waveform ○A indicated by a dashed line indicates the no-load induced voltage, the waveform ○B indicated by the dotted line indicates the induced voltage under load, and the solid line ○C indicates the terminal voltage. In each case, assuming that the three phases are a, b, and c, this is the line voltage between the a and b phases. The induced voltage ○a during no load and the induced voltage ○b during load form a sine wave, but the terminal voltage ○c has a voltage dip due to commutation between the thyristors in inverter 2. will be recognized.

FIG. 3b shows the current waveform of the a phase.

Now, in Fig. 3a, if the zero cross point of the no-load induced voltage ○a is K ₁ , the firing phase angle β ₀ of the thyristor with respect to K ₁ is called the setting control advance angle, and the induced voltage ○ If the zero cross point of B is K ₂ , then
The firing phase angle β of the thyristor with respect to K ₂ is called the effective control advance angle. Further, γ is called a commutation margin angle, and u is called an overlap angle.

That is, in the DC natural commutation type non-commutator motor as shown in FIG. 2, the effective control advance angle β decreases as the load current increases due to the influence of the armature reaction and the influence of the overlap angle u. Eventually, the voltage necessary for commutation cannot be obtained and operation becomes impossible. In order to complete commutation, commutation voltage must be applied until commutation is completed, and this condition is (β-u)>0. This (β-u)=γ is the commutation margin angle, and the state where β=u is called the commutation limit.

By the way, in the operation of a non-commutator motor, appropriately giving the effective control advance angle β of the inverter 2 secures the margin angle γ of the inverter to the necessary minimum, and therefore operates the motor at a high power factor. This can be said to be an important issue in order to increase the utilization rate of the entire device and to ensure stable commutation in the inverter.

In this sense, when the desired commutation margin angle is γset, and the effective control advance angle required to obtain this γset is βset, there is the following relationship between the two: (1)
It is known that the formula holds true.

βset=u+γset=cos ^-1 (cosγset −√2ωL _c I _d /E _M ) ...(1) where ω; rotational angular velocity L _c ; commutation inductance (included in the synchronous motor) I _d ; DC Intermediate current E _M ; Effective value of induced voltage between motor lines u ; Commutation overlap angle In the above equation (1), ω and I _d are quantities that are easy to detect in a non-commutated motor, and commutation inductance L _c is a quantity uniquely determined by a given synchronous motor. Furthermore, E _M is generally a quantity that can be relatively easily determined by calculation. Therefore, as long as the zero cross point _K2 can be detected, the only thing left to do is to calculate the effective control advance angle βset to obtain the desired commutation margin angle γset according to equation (1) above, and then The firing point of the thyristor can thus be determined. The zero cross point _K2 is
Since the phase of the induced voltage changes depending on the motor load, it is not constant but also changes.

Therefore, conventionally, to find the zero cross point K ₂ ,
The induced voltage of the synchronous motor calculated by the following equation (2) was used.

e _a = v _a −L _c di _a /dt−R _a i _a …(2) where e _a ; One-phase motor induced voltage v _a ; One-phase motor terminal voltage i _a ; Armature current R _a ; The induced voltage _{e a} calculated by the above equation (2) at the child resistance is:
As can be seen from Figure 3a, the terminal voltage v _a used for this calculation is not a clean sine wave but a depressed waveform, and contains many noise components (harmonic components), resulting in an error. There will be a lot of Therefore, in order to remove this noise component, the calculated induced voltage signal is once integrated by an integrator. Although noise is removed from the integration result, the phase is shifted by 90 degrees el due to the integration, so the integrated value becomes an amount equivalent to the magnetic flux of the synchronous motor. Therefore, this integral value is further
By shifting the phase by 90°el and returning it to the original phase, an amount equivalent to the induced voltage was obtained, and the zero crossing point of this was found and defined as K ₂ .

However, as is well known, integrators can become saturated in the positive or negative polarity direction due to input signals, offset characteristics of the integrator itself, temperature drift of the characteristics itself, etc., and generally good performance cannot be obtained. Therefore, the zero-crossing point determined as described above has many errors and is inaccurate, resulting in a disadvantage that the accuracy of the phase control of the inverter in the commutatorless motor becomes low.

[Purpose of the invention]

The present invention has been made to eliminate the drawbacks of the prior art as described above, and an object of the present invention is to solve the problem of inverter commutation margin angle required in inverter phase control in a commutatorless motor. The object of the present invention is to provide a control device that can accurately control the firing phase of a thyristor according to a set control advance angle so as to have a minimum value, thereby improving the power factor (and thus efficiency) of a commutatorless motor. The motor can continue to operate while maintaining the motor in good condition.

[Key points of the invention]

In the present invention, the induced voltage of the synchronous motor is reduced to 2
First, the internal phase difference angle δ of the motor is determined by separating the axial voltage into a component parallel to the magnetic pole and a component perpendicular thereto. On the other hand, the effective control advance angle β is calculated according to equation (1) above. Then, by calculating the sum of δ and β, the set control advance angle β ₀ is obtained, and the zero-crossing point K ₁ of the no-load induced voltage (this position remains unchanged regardless of the load, so it can be easily determined from the magnetic pole position of the motor. ), the thyristor firing signal is sent to the inverter at a phase corresponding to the advance angle β ₀ .

The present invention thus enables highly accurate control of the firing phase of the thyristor in the inverter of a commutatorless motor without using an integrator.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 4 is a block diagram showing one embodiment of the present invention. In the figure, 2 is an inverter, 3 is a synchronous motor, 12 is a voltage and current detector, 13 is a pulse generator, 14 is a magnetic pole position detector that detects when the magnetic pole has come to a specific position (starting point), 15
1 is an induced voltage calculator; 16 is a magnetic pole position calculator that calculates and outputs the position of the rotating magnetic pole from the starting point; 17 is a biaxial induced voltage calculator;
18 is an internal phase difference angle calculator for calculating the internal phase difference angle δ; 19 is a β ₀ calculator for calculating the setting control advance angle β ₀ ; and 20 is an ignition signal generator.

Now, the induced voltage calculator 15 uses the voltage, motor terminal voltage and armature current detected by the current detector 12 to calculate induced voltages e _a , e _b ,
Calculate and output e _c . The magnetic pole position calculator 16 is
A counter that counts pulses from a pulse generator 13 that generates a number of pulses proportional to the amount of rotation of the electric motor 3, and
It is composed of a PROM that stores sin〓, cos θ (where θ is the angle formed between the a-phase winding and the magnetic pole axis) and the count value as an address. The counter is reset every rotation of the electric motor 3 by a reset signal from the magnetic pole position detector 14. Therefore, the magnetic pole position calculator 16 counts the pulses from the pulse generator 13 using a counter, and uses the counted value as an address.
Sinθ and cosθ can be read and output from the PROM.

The two-axis induced voltage calculator 17 calculates induced voltages e _a , e _b ,
Given e _c , sin θ, and cos θ, calculate the voltage e _d parallel to the magnetic pole axis (d axis) and the voltage e _q (q axis induced voltage) perpendicular to it according to the following equation (3). Output.

e _d = e _a cosθ+1/√3 (e _b −e _c ) sinθ e _q = −e _a sinθ+1/√3 (e _b −e _c ) cosθ …(3) where e _a , e _b , e _c ; Induced voltages of each phase e _d , e _q ; d and q axis induced voltages θ ; angle formed by the a-phase winding and the magnetic pole axis. Fig. 5 shows a voltage spectrum diagram of the synchronous machine. In the same figure, Ψ _F is the magnetic flux due to the field current,
Ψ _a represents the magnetic flux due to armature reaction, Ψ represents the resultant magnetic flux, E ₀ represents the no-load induced voltage, and E represents the induced voltage, respectively.

It will be understood from FIG. 5 that the internal phase difference angle δ is given by the following equation (4), and is therefore determined by the internal phase difference angle calculator 18.

δ=tan ^-1 ( _-ed / e _q ) ...(4) In addition, the induced voltages of each phase in the above equation (3) e _a , e _b ,
e _c is obtained by the calculator 15 according to the above equation (2), but due to various errors caused by the calculation, the obtained induced voltage signal generally contains high frequency components and becomes a distorted signal. Become.

This distortion is undesirable in terms of control, so if an attempt is made to remove the distortion by passing a signal through a filter circuit, for example, since this signal is an alternating current, a phase lag will occur, causing problems. Generally, this signal is led to an integrating circuit to remove the distortion caused by the high frequency mentioned above, and then the integrated output is phase shifted by 90°el to obtain a sine wave signal without distortion. As mentioned above, there are problems such as characteristic drift of the integrator.

Therefore, in this embodiment, the distortion can be removed without using an integrator by the following method. In other words, the biaxial induced voltage obtained by the above equation (3)
e _d and e _q are DC amounts in steady state. Therefore
Even if the e _d and e _q signals are passed through a filter, the phase lag that was a problem in the case of alternating current does not occur. Therefore, in this embodiment, when calculating the internal phase difference angle δ in the calculator 18 according to equation (4), the distortion caused by the calculation as described above is eliminated by passing the e _d and e _q signals through a filter. is removed to obtain error-free δ.

Next, the setting control advance angle β ₀ of the inverter is determined by the calculator 19 using the following equation (5).

β ₀ = δ + u + γset = tan ^-1 (-e _d / e _q ) + cos ^-1 (cos γ set - √2ωL _c I _d /E _M ) ...(5) The zero-crossing point of the no-load induced voltage is the reference
K ₁ is determined by the magnetic pole position detector 14 attached to the rotating shaft of the motor, and the pulses from the pulse generator 13 are counted, and the count value matches the value of β ₀ determined by calculation. At times, a firing pulse is output to the thyristor in the inverter 2 via the firing signal generator 20.

As explained above, in the calculation method according to the present invention, each instantaneous value is used as each quantity, and the desired commutation margin angle γset can be obtained not only statically but also transiently, and the motor can be It becomes possible to drive in a state with good efficiency.

In addition, in the embodiment of the present invention, two
Although the explanation has been made using the magnetic pole axis as the reference coordinate axis when determining the shaft voltage, this reference coordinate axis may be set at any arbitrary position, and the phase angle δ' of the induced voltage with respect to the reference coordinate axis set at any position can be calculated by If calculated using a calculation similar to the above equation (3), the set control advance angle β ₀ ' with respect to the reference axis can be given by the following equation (6).

β ₀ ′=δ′+u+γset=δ′+cos ^-1 (cos γset−√2ωL _c I _d /E _M ...(6) [Effects of the Invention] According to the present invention, the induced voltage of the synchronous motor can be converted into two-axis voltage, For example, the internal phase difference angle δ of a synchronous machine is determined by separating the component parallel to the magnetic pole and the component perpendicular to it (two-axis voltage), and the setting control lead angle β ₀ of the inverter of a non-commutated motor is determined. , is realized by shifting the phase from the easily determined reference point _K1 by an amount corresponding to the sum of this δ, the commutation overlap angle u, and the desired commutation margin angle γ, so the commutation margin angle is always maintained. This has the advantage that the electric motor can be operated with a good power factor while maintaining the necessary minimum precision.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the general configuration of a non-commutator motor, Fig. 2 is a circuit diagram showing a specific example of a non-commutator motor, and Fig. 3 shows voltage and current waveforms in the circuit of Fig. 2. FIG. 4 is a block diagram showing an embodiment of the present invention, and FIG. 5 is a voltage vector diagram of a synchronous machine. Explanation of symbols, 1... DC power supply, 2... Inverter, 3... Synchronous motor, 4... Inverter control means, 12... Voltage detection circuit, 13... Pulse generator, 14... Magnetic pole position detector, 15 ...Induced voltage calculation circuit, 16...Magnetic pole position calculation circuit, 1
7...Two-axis induced voltage calculator, 18...Internal phase difference angle calculator, 19... _β0 calculator, 20...Ignition signal generator.

Claims (1)

[Claims] 1. An inverter that converts direct current to alternating current, a synchronous motor driven by an alternating current output from the inverter, and an inverter that is operated so that the rotational frequency of the synchronous motor and the output frequency of the inverter match. In a commutatorless motor comprising an inverter control means for sending an ignition signal to the constituent switch elements, the induced voltage of the synchronous motor is applied and divided into two components: a component parallel to the magnetic poles and a component orthogonal thereto.
a first calculating means that separates the axial voltage into axial voltages, passes each of them through a filter to remove distortion, and calculates an internal phase difference angle of the motor from the two axial voltages after the distortion has been removed; and a load current of the synchronous motor. a second calculation means for calculating the sum of the commutation overlap angle and the commutation margin angle target value of the switch elements in the inverter given the induced voltage, rotation speed, and commutation inductance; and the calculated internal phase difference angle; third calculating means for summing the sums and outputting a setting control advance angle of the switch element; means for detecting the phase of a zero-crossing point of no-load induced power of the synchronous motor; A commutatorless electric motor characterized in that the inverter control means comprises at least the following: means for outputting an ignition signal to the switch element at a timing when a time corresponding to the set control advance angle has elapsed from time of day. Inverter phase control device.