JPH0218035B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a control advance angle control method for an AC non-commutator motor using a cycloconverter as a power converter. Among self-controlled separately excited non-commutator motors that use a synchronous motor as the motor and commutate the power converter using the induced voltage, AC non-commutator motors that use a cycloconverter as the power converter are Even at startup and at low speeds when voltage cannot be obtained, commutation can be performed in synchronization with the motor frequency using the power supply voltage, so there is no need for commutation auxiliary circuits for startup or low speeds, and the circuit configuration It is widely used because of its simplicity. However, in the case of an AC non-commutator motor, the characteristics at high speed are the same as those of other self-controlled separately excited non-commutator motors. greatly influenced by Figure 1 shows the control lead angle β in a non-commutated motor.
and the commutation overlap angle u of the current are shown with the motor output as the horizontal axis. A solid line in FIG. 1 shows a rotor position detector that detects the relative rotational position of the armature and rotor of the motor, and commutates the commutating element of the power converter based on the signal. In other words, it shows the commutation characteristics of the conventional system in which the mechanical control lead angle β ₀ , which is determined by the relative mechanical position of the motor's armature and the field, is fixed. As the child current increases, the phase of the motor voltage shifts due to armature reaction, the effective control advance angle β with respect to the terminal voltage gradually decreases, and the commutation overlap angle u of the armature current increases as the load increases. As a result, the initial commutation value of the current increases, and the reverse bias voltage that contributes to commutation decreases due to the phase shift of the motor voltage due to armature reaction, so it increases rapidly. The point where the effective control advance angle β and the commutation overlap angle u match is the commutation limit, but in reality, operation at that point is impossible, and the commutation overlap angle u is subtracted from the control advance angle β. The point at which the commutation margin angle γ (γ=β−u) reaches a certain value γ _S that takes into account stability and other various margins is the limit of the output that can be guaranteed. Therefore, in the conventional system in which the mechanical control lead angle β is fixed at ₀ , for example, if an overload capacity of 150% is required as shown in Figure 1, the commutation margin angle becomes γ at an output of 150%. It is necessary to set the mechanical control advance angle β ₀ large in advance so that _S is achieved, which has the disadvantage that the power factor at the rated point as well as during overload inevitably becomes low, and torque pulsation is also large. In contrast, it is possible to arbitrarily control the control advance angle according to load conditions and other factors, without fixing the ignition point of the commutating element of the power converter by the relative mechanical position of the armature and the field. Therefore, these drawbacks can be improved. The curves indicated by broken lines β' and u' in Fig. 1 are for the case where the control advance angle is controlled and the commutation margin angle γ is kept at a constant value γ _S regardless of the load. The power output limit can be significantly increased as shown, while improving the engine speed and reducing torque pulsation. FIG. 2 is a block diagram showing a conventional commutatorless motor which is subjected to commutation margin angle control as described above.
In FIG. 2, 1 is an AC power supply, 2 is a cycloconverter, 3 is a synchronous motor driven by the cycloconverter 2, 4 is a rotor position detector that detects the rotational position of the rotor of the synchronous motor 3, and 5 is a rotor position detector. This is a speed detector that detects the rotational speed of the synchronous motor 3. 6 and 6' are current transformers that detect the input current and output current of the cycloconverter 2, respectively; 7 and 7';
8 is a commutation margin angle detector that detects the input voltage and output voltage of the cycloconverter 2, respectively, and 8 is a commutation margin angle detector that measures the period from the commutation end point of the output current of the cycloconverter 2 to the zero point of the terminal voltage of the synchronous motor 3 (transformation margin angle detector). The commutation margin angle is output by detecting the flow margin time), adding the rotational speed element to it, converting it into the electric angle of the motor, and outputting the commutation margin angle. 9, 9', 9'' are comparators, 10, 10' are regulators, 11, 11' are phase shifters for power supply side ignition timing and motor side ignition timing, respectively.
2 is a logic circuit that creates gate signals for each commutation element of the cycloconverter 2 from the power supply side firing timing signal and the motor side firing timing signal. In FIG. 2, the speed setting value N and the speed detection value n by the speed detector 5 are compared by a comparator 9,
The speed difference is the regulator 1 as a speed adjustment amplifier.
0 is converted into a current command value I, and furthermore, this current command value I and the current detection value i by the current transformer 6 are matched by a comparator 9', and a phase shifter is used to adjust the input power using this difference signal. 11 has a current minor loop that adjusts the firing phase with respect to the power supply voltage and creates a power supply side firing timing signal. On the other hand, the commutation margin angle detected value γ by the commutation margin angle detector 8 is determined by the commutation margin angle setting value γ _S
The difference signal is converted by the regulator 10' into a phase shift signal with respect to the mechanical reference signal between the armature and the field by the rotor position detector 4, Create the motor side firing timing signal. As described above, the logic circuit 12 receives the power supply side firing timing signal from the phase shifter 11 and the phase shifter 1.
The motor-side ignition timing signals from 1' are synthesized to create a gate signal to each commutating element of the cycloconverter 2, thereby controlling the input and output of the cycloconverter 2. That is, the input adjustment of the cycloconverter 2 consists of a speed control loop and a current minor loop, and the output side adjustment consists of a constant commutation margin angle control loop based on commutation margin angle feedback. However, unlike a power converter that has a DC intermediate circuit between the forward converter and the inverse converter, the cycloconverter 2 does not have independent commutation on the power supply side and motor side, and Since the side commutations are performed in a mixed manner, if the power supply side commutation and the motor side commutation are performed at the same time, they will influence each other. As a result, the commutation margin angle detection value γ varies greatly depending on the power supply side ignition timing, causing unfavorable results in terms of control. FIG. 3 is a configuration diagram of a cycloconverter 2 that outputs three-phase variable AC from a three-phase AC power supply. 1
is a three-phase AC power supply; 3 is a three-phase synchronous motor driven by the cycloconverter 2; 201 to 21;
8 is a commutating element, and a controlled rectifying element such as a thyristor is used. 220 is a smoothing reactor, and the windings of each phase are magnetically coupled. Figure 4 shows the power supply voltages e _R , e _S , e _T and motor voltages e _u ,
The waveforms of e _v and e _w and their respective commutation timings are shown. As shown in the figure, the commutation on the power supply side is fired at the firing angle α, and the commutation ends at overlap u _S. Furthermore, the commutation on the motor side is started at the control advance angle β, and the commutation ends at the overlap u _n . Assuming that the positive commutation from the R phase to the S phase on the power supply side and the positive commutation from the U phase to the V phase on the motor side are performed simultaneously as shown in Figure 4, the operating mode is shown in Figure 5. Shown below. In FIG. 5, 201, 204, 205, and 218 are commutating elements of the cycloconverter 2 shown in FIG. 3, l _n is the motor side commutation inductance, and l _S
is the power supply side commutation inductance. Assuming that commutating element 201 and commutating element 218 are now electrically connected and I ₀ is flowing due to the constant current source, when commutating element 204 is ignited, U as shown in mode I in FIG. 5a.
The phase and V phase are short-circuited by commutation elements 201 and 204, and a commutation current _i1 flows due to the reverse voltage of the motor's induced voltages e _u and e _v , and commutation from the U phase to the V phase occurs. It begins. Next, when the commutation element 205 is fired by the firing command from the R phase to the S phase of the power supply, as shown in the mode of FIG.
is short-circuited by the commutating element 205, and the power supply voltage e _R
Commutation current _i2 flows due to the voltage difference between and _eS , and commutation from the R phase to the S phase begins. When the motor side commutation current i ₁ and the power supply side commutation current i ₂ become equal and the current flowing through the commutation element 204 becomes zero, the commutation element 204 becomes
OFF and shifts to the mode shown in FIG. 5c, but while commutation element 204 is conducting, motor side commutation and power supply side commutation are performed independently. When the commutation element 204 is turned OFF, as shown in the mode of FIG. 5c, motor side commutation from U phase to V phase and R
Power supply side commutation from phase to S phase is performed in the same circuit. In other words, a common commutation current i ₃ flows due to the sum of the voltage difference between the motor voltages e _u and e _v and the voltage difference between the power supply voltages e _R and e _S , and i ₃ becomes equal to the constant current I ₀ . , when the current in the commutating element 201 becomes zero, the commutating element 201
turns OFF, and commutation on the motor side and commutation on the power supply side end simultaneously. Assuming that the overlap is sufficiently small, the commutation voltage on the motor side (e _u −e _v ) is E _n and the commutation voltage on the power supply side (e _R
−e _S ) by the DC voltage of E _S , each commutation current becomes
i ₁ , i ₂ , i ₃ are as follows. i ₁ = E _n /l _n t+C ₁ , i ₂ = E _S /l _S t + C ₂ , i ₃ = E _n + E _S /
l _n +l _S t + C ₃ where C ₁ , C ₂ and C ₃ are constants. Rated speed N ₀
Let the commutating voltage at E _S =1, E _n =1, and the commutating inductance is l _S =1 on the power supply side and l _n on the motor side.
= 3, at rated speed and 1/2 speed
The slopes of i ₁ , i ₂ , and i ₃ are as shown in the table below.

[Table] Figure 6 shows the commutation current in this case, and Figure 6a shows the commutation current at the rated speed N ₀ ,
Figure 6b shows the commutation current at 1/2 speed and 1/2N ₀ . From now on, in the cycloconverter 2, when power commutation is performed during the motor side commutation period,
It can be seen that the commutation overlap period is shorter than when the motor side commutation is performed alone. That is,
In FIG. 6, the overlapping period is u _n when motor commutation is performed alone, whereas the commutation ends at u _n ' when power commutation is added. This tendency becomes more noticeable as the rotational speed decreases, as can be seen from the comparison of FIGS. 6a and 6b. In this way, in a cycloconverter, commutation characteristics are improved due to the effect of commutation on the power supply side of commutation on the motor side, and it also has a self-recovery function after commutation failure, and furthermore, as mentioned above, the induced voltage of the motor This power supply commutation allows commutation on the motor side even during startup and at low speeds, which is not possible. However, the influence of this power supply commutation becomes a hindrance when attempting to directly detect the commutation end point of the motor current and the zero point of the motor voltage and thereby control the commutation margin angle. In other words, the detected value differs depending on the ignition timing on the power supply side and the motor side, and if commutation on the power supply side is added during the commutation period on the motor side, the value will be different when commutation on the motor side is performed alone. In comparison, the overlapping period of the output currents of the cycloconverter is shorter, so the commutation margin angle is observed to be larger.
Therefore, using this detected value to determine the next ignition point immediately causes commutation failure. In order to avoid this, the conventional method is to take a long sampling period for the commutation margin angle and control using the average value or the minimum value during that time, or to detect the ignition timing on the power supply side and control the commutation margin angle on the motor side. If power side commutation is performed during the commutation period, ignore the sampling value in that commutation mode,
A control method using sampling values in the previous commutation mode is used. However, in the former method, there is a large delay time due to the long sampling period, and in the latter method, the previous sampling value is also used, so a time delay occurs. The delay will become even bigger, etc.
These conventional systems have problems with quick response during transients such as rapid load changes, and it is necessary to set the commutation margin angle large in advance to avoid commutation failure during transients. As a result, the power factor of the synchronous motor took into account the safety factor due to these time delays, and commutation margin angle control was not sufficiently effective in improving the power factor and reducing the size of the rotating machine. The present invention solves these drawbacks when controlling the commutation margin angle of an AC non-commutator motor using a cycloconverter. Hereinafter, the present invention will be explained based on the drawings of the embodiments. 7 and 8 are block diagrams showing embodiments of the present invention. In FIGS. 7 and 8, the same reference numerals as in FIG. 2 indicate parts having the same functions. In Fig. 7, 13 is a function generator, which detects the rotor position based on the detected input current of the cycloconverter 2 by the current transformer 6 (or the detected value of the output current of the cycloconverter 2 by the current transformer 6'). The phase shift control amount φ with respect to the reference signal of the device 4 is output. That is, as shown in Fig. 1, the mechanical control advance angle when constant commutation margin angle control is performed is β ₀ ' with respect to the output, that is, the current. The phase shift control amount φ with respect to the reference signal is converted into a function and the phase shift control amount φ corresponding to each current detector is output. Next, a description will be given with reference to FIGS. 9 and 10. 9 is shown to facilitate understanding of the relationship between the phase shift control amount and the phase shift angle, and FIG. 10 is shown to facilitate understanding of the input/output relationship of the function generator 13 and the relationship between the control advance angle. It is something that FIG. 9a shows the operating waveform of the output signal of the rotor position detector 4, and this reference signal _W0 is the output signal of the synchronous motor 3.
The mechanical control advance angle of the armature and field is set to β ₀₀ ′. Figures b and c are from the reference signal W ₀ ,
An example of the general operating principle of a phase shifter 11' which outputs a desired phase shift signal _W3 according to a phase shift control amount φ is shown, in which a sawtooth wave _W1 is created from a reference signal _W0 , The sawtooth wave W ₁ and the phase shift control signal W ₂ are compared and a phase shift signal W ₃ is created from their intersection. Therefore, as shown in FIGS. 10a and 10b, the predicted value of the phase shift control amount φ with respect to the current I is converted into a function so that the control advance angle β with respect to the current I becomes the desired β ₀ '. , the function generator 13 outputs the level of the phase shift control amount φ corresponding to the current. 14 is a signal selector which inputs the output of the function generator 13 and the output of the commutation margin angle control regulator 10', which is the phase shift signal level value from the commutation margin angle feedback circuit, and selects whichever is larger. Select and output the signal. Therefore, when a large commutation margin angle is detected due to the influence of power supply commutation and a command is issued to narrow down the control advance angle by the regulator 10', the function generator 1
Since the signal No. 3 is prioritized and the cycloconverter 2 is controlled by this signal, control is always performed under the severe conditions of either current value or commutation margin angle, resulting in stable and minimum delay. It is possible to drive within the specified time. Further, FIG. 8 shows an example in which the predicted amount is taken as the detected value of the commutation overlap angle, and FIG. 11 shows the input/output relationship of the function generator 13'. In FIG. 8, a commutation overlap angle detector 15 detects a commutation overlap angle u from the output current waveform of the current transformer 6'. (The overlap time is converted into an angle based on the speed signal from the speed detector 5.) Here, when the commutation margin angle is kept constant as shown in FIG. 1, the commutation overlap angle becomes u'. Therefore, as shown in FIG. 11, the predicted value of the commutation overlap angle u with respect to the current I is converted into a function, and the function generator 13' outputs the level of the overlap angle corresponding to the current. 1
Reference numeral 4' denotes a signal selector which outputs the larger signal of the output of the function generator 13' or the output of the commutation overlap angle detector 15 with priority. The commutation margin angle detector 8 detects the commutation margin angle γ from the motor terminal voltage waveform signal from the transformer 7' and the output signal of the signal selector 14'. In the embodiment shown in Fig. 8, the overlap angle is taken as a function of the current, and the commutation margin angle is detected from the larger of the actually measured overlap angle and the predicted value based on the current, thereby determining the influence of power supply commutation. In addition, as in the embodiment of FIG. 7, the stability during transients is significantly improved. As described above, in an AC non-commutator motor using a cycloconverter in which the motor side commutation is affected by the power supply side commutation, the present invention feeds back the detected value of the motor side commutation margin angle to adjust the commutation margin angle. At the same time, from the detected value of the input current or output current of the cycloconverter, the predicted value of the detection signal (for example, commutation overlap angle) or control signal (for example, phase shift control signal) corresponding to the current value is converted into a function. The signal output by the function generator is compared with the corresponding actual signal, and the signal on the safe side with respect to the commutation of the cycloconverter is selected between the actual measured signal and the function generator output signal (predicted value), and the cycloconverter is The ignition timing on the motor side of the converter is adjusted, thereby eliminating erroneous evaluation of detected values due to power supply commutation, which was the biggest difficulty in commutation margin angle feedback control of cycloconverter type non-commutator motors. This enables stable commutation margin angle feedback control in a cycloconverter non-commutator motor. This makes it possible to operate stably and within the minimum delay time by taking advantage of the characteristics of feedback control even under severe load conditions such as sudden load changes and sudden acceleration, and to reduce the response speed in the event of an accident such as a commutation failure. In addition to significantly improving the accuracy of equipment protection, the set value of the commutation margin angle can be reduced to the maximum limit, improving the power factor and reducing the The entire electric motor device can be made smaller.

[Brief explanation of drawings]

Figure 1 shows the control advance angle and current commutation overlapping angle in a non-commutated motor with the motor output as the horizontal axis, and Figure 2 shows a conventional non-commutated motor device with commutation margin angle control. 3 is a block diagram showing the configuration of a cycloconverter that outputs 3-phase variable AC from a 3-phase AC power source, and FIG. 4 is a diagram showing the waveforms of the power supply voltage and motor voltage and their commutation timings. Figures 5a, b, and c show the operating modes in Figure 4, Figures 6a and b show commutation currents at rated speed and 1/2 speed, and Figures 7 and 8 respectively. FIGS. 9, 10 and 11, which are block diagrams showing one embodiment of the present invention, are explanatory diagrams shown to facilitate understanding of FIGS. 7 and 8. 1...AC power supply, 2...cycloconverter,
3... Same machine electric motor, 4... Rotor position detector, 5
...Speed detector, 6,6'...Current transformer, 7,7'...
...Transformer, 8...Commutation margin angle detector, 9,9',
9'', 9... comparator, 10, 10', 10...
Adjuster, 11, 11'... Phase shifter, 12... Logic circuit, 13, 13'... Function generator, 14, 1
4'... Signal selector, 15... Commutation overlap angle detector, 201-208... Commutation element.

Claims (1)

[Scope of Claims] 1. An AC power source, a cycloconverter that outputs variable AC power using the AC power source as input, a synchronous motor driven by the cycloconverter, and a commutation end point of the output current of the cycloconverter. means for detecting an electrical phase angle (commutation margin angle) formed by the voltage zero point of the terminal voltage of the synchronous motor; and a motor-side firing timing synchronized with the frequency of the commutation element of the cycloconverter on the synchronous motor side. means for adjusting the input current or output current of the cycloconverter;
a function generator that outputs a predicted amount of at least one of a detection signal and a control signal for adjusting the motor-side firing timing of the cycloconverter in accordance with the current value, the output of the function generator; It is equipped with a priority circuit that selects a signal on the safe side with respect to the commutation of the cycloconverter from among the signal (predicted amount) and the detection signal or control signal (actual measured amount) corresponding to the output signal (predicted amount), A control advance angle control method for a commutatorless motor, characterized in that a motor-side firing timing of the cycloconverter is adjusted based on the safe side signal. 2. The function generator is configured to operate based on the detected value of the input current or output current of the cycloconverter and output a phase shift amount level corresponding to the current value, and the priority circuit is configured to operate based on the detected value of the input current or output current of the cycloconverter, and the priority circuit is configured to operate based on the detected value of the input current or output current of the cycloconverter, and to output a phase shift amount level corresponding to the current value. 2. A control advance angle control method for a commutatorless motor according to claim 1, wherein the larger one of the control signal and the control signal by the means for detecting the commutation margin angle is selected. 3. The function generator is operated by the detected value of the input current or output current of the cycloconverter and outputs a commutation overlap angle level corresponding to the current value, and the commutation overlap angle of the output current of the cycloconverter is The non-commutated motor according to claim 1, wherein the priority circuit selects the larger of the detected value of the commutation overlap angle and the output signal of the function generator. Control advance angle control method.