JPS6070989A - Phase control system of inverter in commutatorless motor - Google Patents

Abstract

PURPOSE:To prevent a commutation from failing by calculating a control leading angle beta in accordance with the prescribed formula, adding a correction amount DELTAbeta depending upon a load thereto, and controlling the phase with beta+DELTAbeta. CONSTITUTION:A correcting calculator 25 for calculating the correcting amount DELTAbeta of a control leading angle beta is provided as a function of a ratio of the magnitude (i) of an armature current to the magnitude (PSI) of a magnetic flux, the calculated correcting amount DELTAbeta is added to the angle beta calculated by a calculator 11, and a firing pulse generator 12 is controlled by the added result of (beta+DELTAbeta). Thus, stable inverter control can be performed without commutation failure even at an overload time or at a field weakening time.

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, and an alternating current output from the inverter; The present invention relates to a commutatorless motor comprising an inverter control means for controlling the phase of the inverter so as to match the phase of the inverter, and more specifically 1. < 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 direct current supplied from the direct current power supply 1 into alternating current to drive the synchronous motor 6. The inverter control means 4 normally detects the position of the rotor of the synchronous motor 30 and generates and outputs a gate signal for starting the thyristor etc. that constitutes the inverter 2. Output frequency and synchronous motor 3
The 0 rotation frequency matches and synchronizes.

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 a thyristor. It is used for a variety of purposes as it combines the advantages of high strength and strength.

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, a DC power supply 1 is comprised of a DC power supply E, which is usually a rectifier (converter) that rectifies a six-phase AC power supply (not shown), and a smoothing reactor Li. The inverter 2 receives the DC intermediate current i and the DC intermediate voltage Ed from the DC power source 1 to create a three-phase AC, and drives the synchronous motor 3 from this Q. Inverter control means 40
The functions are as described above. EM is the line induced voltage of motor B.

FIG. 3 is a waveform diagram of voltage and current in the circuit of FIG. 2. In the figure, the induced voltage eR of each phase of the synchronous motor 3
The waveform of p eS p eT is shown by a broken line, and the DC intermediate voltage Ed is shown as the size of the portion shown by a solid line.

It will also be recognized that a voltage dip occurs due to the commutation in the inverter 2. In this voltage depression, β is the control advance angle of the inverter, U is the overlap angle, and r
is called the margin angle.

That is, in the DC natural commutation type non-commutator motor shown in Fig. 2, the 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, and as the load current increases, the control advance angle β decreases. The voltage required 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 reached is called the commutation limit.

By the way, in the operation of a commutatorless motor, the inverter 20
Appropriate control lead angle β ensures that the margin angle γ of the inverter is kept to the minimum necessary level, which makes it possible to operate the motor at a high power factor, increases the utilization rate of the entire device, and improves the transfer rate of the inverter. This can be said to be an important issue in order to ensure stable flow.

By the way, there is generally a difference between the commutation margin angle γ and the control advance angle β (
1) The relationship of equation holds true.

β = C11s-' (cOsγ-x-i/F)
--(1) However, X: commutation reactance (inside the synchronous motor), i: motor current, F: motor magnetic flux (both are expressed in plJ). FIG. 2 is a block diagram illustrating an example of a conventional system in which a control advance angle β is determined by calculation according to the above equation (1), and the phase control of an inverter is performed based on the advance angle βO.

In the figure, 1F is a control advance angle β calculation circuit, 12 is an ignition pulse generator, 13 is an internal voltage and magnetic flux calculation circuit, and 1
4 is a field weakening pattern generation circuit, 15 is a field control circuit,
16ti converter control circuit, 17 expansion converter, 1B
is an inverter, 19 is a synchronous motor, 20 is a speed setting device,
21 is a field setting device.

In FIG. 4, the synchronous motor 19 is supplied with power from an AC power supply (not shown) via a converter 17 and an inverter 18, and is driven at a variable speed. That is, the motor speed N* set by the speed setting device 20 and the actual value N of the motor speed detected by the tachogenerator TG attached to the motor 19 are compared in the converter control circuit 16,
Converter control circuit 16 generates a control output to control converter 17 to control the speed of electric motor 19 so that both match.

On the other hand, the internal voltage/magnetic flux calculation circuit 16 calculates the motor current detected via the current transformer 6 - Weiyi CT and the voltage transformer PT.
The internal voltage E and magnetic flux V of the motor are calculated by taking in the motor voltage detected through the motor. In the β calculation circuit 11,
The set value γset of the commutation margin angle and the current th given from the converter control circuit 16.

Using the magnetic flux V calculated by the arithmetic circuit 13 and the known commutation reactance X, the control advance angle β is calculated according to the above equation (1) and is provided to the ignition pulse generator 12.

The ignition pulse generator 12 uses the motor internal voltage E given from the arithmetic circuit 13 as a reference, uses β to determine the ignition pulse generation timing, and sends the ignition pulse to the inverter 18 according to the determined timing. A desired control advance angle β is achieved in the inverter 18.

The field control circuit 15 compares the pattern V output from the field weakening pattern generation circuit 14 and the actual value V of the magnetic flux output from the arithmetic circuit 13, and adjusts the field setter 21 so that the two match.

Now, in the conventional inverter phase control method for a non-commutator motor as described above, there is a problem as follows regarding how to set the set value γset of the commutation margin angle.

In other words, the value of the set value γset is generally determined as the sum of the value γm10 required to secure the originally necessary reverse bias time for the thyristor constituting the inverter, and the margin Δγ that takes into account various calculation errors. It is. The problem here is how to take the above-mentioned margin Δγ.

This will be explained below using FIG. 5.

In Fig. 5, the horizontal axis shows the ratio of motor current to magnetic flux (i/
F), and the control advance angle β and commutation margin angle γ are plotted on the vertical axis.

The relationship between β, γ, and (i/F) is defined by equation (1) above, and according to equation (1), (i
As the value of /F) increases from 0, if β follows the course shown by ■ in FIG. 5, it is shown that r also follows the course shown by ■'.

As the value of (i/F) increases from 0, β changes as shown in ■, with a value 1° lower than in the case of ■, and similarly, r also changes as shown in ■'. Similarly, when β changes as shown in ■ with a value 2 degrees lower than in the case of ■, γ also changes as shown in ■'.

In exactly the same way, if β changes as shown in ■ with a value 6 degrees lower than in the case of ■, then γ also changes as shown in ■'. Similarly, ■ corresponds to the case where β is 4° lower than in case ■, and ■' indicates the transition of γ at that time.

The above will be explained below in general terms.

In short, the graph in FIG. 5 shows that the control advance angle β is (i/F
) is the minimum required commutation margin angle γm over the entire range of values.
10 (temporarily denoted by β0 and the corresponding γ is denoted by ro) by Δβ~, i.e., (β0 - Δβ), when the load is within a light range (e.g. (l/F) value is below A), r-C
r0 - Δβ), whereas in the range where the load becomes heavy (for example, the range where the value of (i/F) exceeds A),
γ-(r.

−K・Δβ). However, K>1).

In other words, even if the value of β is apparently 9-ideal, assuming that the actual value is lower than the ideal value due to calculation errors, etc., the minimum required value will be reduced when the load is small. The margin angle γ, which was secured above the commutation margin angle γm10, falls below 1 m10 in a large load range, indicating that commutation failure may occur.

In other words, even in a large load range, the margin lγ is determined so that γ does not fall below 1 m10, and r(-rmin
+Δγ), commutation failure will not occur in the entire load range. However, if this is done, the margin angle γ becomes unnecessarily large in a range of small loads, which is undesirable as it causes a decrease in the power factor and efficiency of the entire device.

[Purpose of the invention]

The present invention has been made in order to improve the problems of the prior art as described above, and an object of the present invention is to prevent the control advance angle β calculated by the arithmetic circuit from being lower than the ideal value due to calculation errors, etc. Even in the case where the load (in detail, i/F) is calculated, commutation failure does not occur in the entire range of 10-100, and even in the small load range, the commutation margin angle γ becomes too large and the entire device is damaged. An object of the present invention is to provide a phase control method for an inverter in a commutatorless motor that does not cause a decrease in power factor and efficiency.

[Key points of the invention]

The gist of the present invention is that, in the inverter phase control method for a non-commutator motor, the control advance angle β is calculated according to a predetermined formula, and a supplementary amount Δβ that depends on the load is added to this. The main feature is that the phase control of the inverter is performed using the .

[Embodiments of the invention]

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

FIG. 6 is a block diagram showing essential parts of an embodiment of the present invention. The difference between the circuit configuration shown in the figure and the conventional circuit configuration shown in FIG. 4 is that the control advance angle β is expressed as a function of (i/F).
A Δβ supplementary calculation circuit 25 is provided to calculate the supplementary amount Δβ of
The calculated supplementary amount lβ is added to the control advance angle β calculated by the β calculation circuit 11, and the ignition pulse generator 12 is controlled based on the addition result of (β+Δβ).

Next, the supplementary amount Δβ calculated by the arithmetic circuit 25 will be explained with reference also to FIG.

FIG. 7 is a graph similar to FIG. 5, and is a graph useful for explaining the effect of the supplementary amount Δβ.

Please refer to FIGS. 6 and 7. The β calculation circuit 11 calculates γset'=γmin+Δγ) in the same manner as in FIG.
An ideal value β corresponding to the above-mentioned βO is calculated according to the equation (1) using the above equation (1). The Δβ supplementary calculation circuit 25 calculates the supplementary amount Δβ according to the load condition (represented by i/F).

In Figure 7, ■ (the right half of β is broken with point A as the border!
corresponds to the above-mentioned ideal value, and the ■ (the right half is also a broken line) of γ indicates the commutation margin angle at that time, and in this case,
This corresponds to the r set value.

Assuming the worst case in which the control advance angle β includes a maximum error of -4° due to various factors such as changes in the motor current and magnetic flux during the commutation period, or calculation errors, In FIG. 7, the true β is indicated by ■, and correspondingly, the margin angle γ is also indicated by ■. If you look at the graph of γ, you can see that this will lead to commutation failure.

If (i/F) exceeds point A in the figure and the graph of β is raised to ■', then the graph of r will also be ■
As seen in ', it does not need to be lifted up to exceed 1m10. The amount of lift Δ from ■ to ■′ in this β
β is naturally within the range of 4°, which is the maximum error of β, and the idea of the present invention is to output this from the supplementary calculation circuit 25 and add it to the output of the β calculation circuit 11. .

In this way, even if the actual β value output from the β calculation circuit 11 is smaller than the apparent value by 4°, which is the maximum error amount (that is, even if β■ is actually β■ in FIG. ), Δβ is increased, so the margin angle r can be maintained at least 1 m10 as shown in 2'.

Here, the arithmetic expression used by the supplementary calculation circuit 25 to calculate the supplementary amount Δβ is as follows.

In addition, A is a constant consisting of both.

Here, in the range (-<A), Δβ-0 is always set as Δβ-0, as can be seen from the graph of r■ in FIG. If we also raise the margin angle r, even if we do not lift it, γ
ml. Therefore, the margin angle γ is larger than necessary.
This is because this increases the power factor and efficiency of the entire device.

As another embodiment, a method that does not involve addition of the supplementary amount Δβ, that is, an embodiment that does not use the supplementary calculation circuit 25, can be considered. β command value in the above embodiment (β■' in Fig. 7)
Assuming that there is no error and that it is controlled by this, determine r (γ■' in Fig. 7),
Conversely, if this γ is used to calculate β by the calculation of equation (1), this β is equal to the β command value in the above-described embodiment. In other words, the seventh
The present invention can also be realized by performing the β calculation using r■' in the figure in the β calculation circuit 11.

〔Effect of the invention〕

In the phase control of an inverter in a non-commutator motor, the actual value of β may have an error, etc., with respect to the ideal value of the control advance angle β to maintain the commutation margin angle γ to a minimum prescribed value that does not cause commutation failure. Therefore, if it is small, the margin angle γ will also be smaller than the specified value. This tendency becomes more pronounced as (i/F) increases due to overload or flux weakening (assuming that the error between the actual β value and the ideal value remains constant during this period), and when (i/F) exceeds a certain value, commutation The margin angle γ is the minimum value γm10 that does not cause commutation failure.
It becomes impossible to secure

The present invention provides a method for calculating a control advance angle β in order to maintain a commutation margin angle r at a certain specified value (γml.+Δr) from a motor current i and a magnetic flux V, in which (i/F) exceeds the above-mentioned constant value. In the range, a supplementary amount Δβ according to (i/F) is added to the β command value calculated by calculation, so that the minimum required commutation margin angle γm10 can be secured for the error range of the actual β value to be considered. This is what I did.

As a result, stable inverter control without commutation failure is possible even during overload or field weakening, and this supplementary amount Δβ often prevents overload.

It only needs to be applied within a very limited range during field weakening, and the drop in power factor and efficiency caused by this will hardly be a problem.
High power factor and high efficiency operation of commutatorless motors is possible.

[Brief explanation of the drawing]

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. Waveform diagram, Figure 4 is a block diagram showing a conventional example of an inverter phase control method in a non-commutator motor, Figure 5 is a control advance angle β with respect to the ratio of motor current to magnetic flux (i/F),
A graph showing the relationship between the commutation margin angle γ, FIG. 6 is a block diagram showing a main part of an embodiment of the present invention, and FIG. 7 is a graph similar to FIG. 5 for explaining the present invention in detail. , is. Description of symbols 11...β calculation circuit, 12...Ignition pulse generator, 13...Internal voltage, magnetic flux calculation circuit, 14...Field weakening Pattern generation circuit, 15.
...Field control circuit, 16...Converter control circuit, 17...Converter, 18...
...Inverter, 19...Synchronous motor, 20.
... Speed setting device, 21... Field setting device,
25...Δβ supplementary calculation circuit, agent Akio Namiki, patent attorney agent Kiyoshi Matsuzaki 17- 1st, 2nd F! ! J 3rd C72 63eT jlI61i! i1

Claims (1)

[Scope of Claims] 1) An inverter that converts direct current to alternating current, a synchronous motor driven by the alternating current output from the inverter, and an arithmetic function that simulates a predetermined functional expression of the control advance angle with respect to the commutation margin angle. In a commutatorless motor comprising means for calculating a control advance angle corresponding to a commutation margin angle setting value and controlling the phase of an inverter in accordance with this, the inverter phase control means is configured to calculate a control advance angle corresponding to a commutation margin angle setting value and perform phase control of an inverter according to the control lead angle, the inverter phase control means controlling the magnitude of an armature current of a synchronous motor. A supplementary means is provided to additionally increase the control advance angle calculated by the arithmetic function as the ratio i/F increases by inputting a signal representing i and the magnitude V of the magnetic flux. An inverter phase control method for a commutatorless motor characterized by: 2. Phase control method according to claim 1, wherein the signal representing i and V is an actual value signal or a target value signal for control. .