JPH06101932B2 - Control device for PWM converter - Google Patents

Description

The present invention relates to a PWM control type converter, and more particularly to a converter control device suitable for converting an AC input waveform into a sine wave.

[Conventional technology]

The converter device is widely used in combination with an inverter device for controlling an induction motor, etc., but at this time, it is desirable to prevent distorted current from the AC power source side as much as possible.

By the way, this converter device, for example, as shown in FIG. 2, is a transistor (GTO having a reverse blocking function, a diode and a GTO having a reverse blocking function) as six rectifying elements of a three-phase full-wave rectifying circuit.
Any semiconductor switching element such as TO or a series connection element of transistors may be used) 51 to 56, and a PWM control pulse is supplied to these transistors 51 to 56 to perform a switching operation. The DC power is supplied from the three-phase AC power supply to the load 6. Note that FIG. 2 is an example of a current source converter, and 2 in the figure is a capacitor for suppressing overvoltage.

Then, as a PWM control device for such a converter device, for example, a paper published in the National Congress of the Institute of Electrical Engineers of 1985
502- “Sinusoidal input / output current type GTO inverter system” Headquarters, etc., and 3 others-As proposed by others, etc., a triangular carrier wave signal with a frequency sufficiently higher than the frequency of the AC power supply and the required DC Compare the modulated wave signal whose peak value changes depending on the side output voltage, and
Conventionally, a method of obtaining a pulse pattern for M control has been general.

On the other hand, instead of such an analog method, a method of digitally controlling by using a microcomputer has been proposed.

[Problems to be solved by the invention]

However, of the above-mentioned conventional methods, the former analog method requires a carrier generation circuit, a modulated wave generation circuit, a comparison circuit, etc. in its configuration, which not only complicates the circuit configuration, but also requires such pulse control. If the device is configured by an analog circuit, there is a problem that it is difficult to obtain stable operation because the characteristic changes remarkably due to changes in ambient temperature and changes over time.

On the other hand, even in the latter digital method using a micro computer, like the conventional example, the method of using the carrier wave signal and the modulated wave signal is adopted as in the case of the analog method described above for the operation. Then, the processing of the computer is always bound for the comparison of these signals,
There is a problem that other processing is almost impossible.

In these prior arts, although a sine wave of the input waveform on the side of the AC power supply is considered, the achievement is considered to be sufficient when variations are included. Therefore, these conventional techniques have a problem in that the input waveform of the converter is made sinusoidal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a converter control device which addresses the above-mentioned problems of the conventional example and is capable of sufficiently converting an AC input into a sine wave while using a microcomputer.

[Means for Solving Problems] The purpose of the above is to calculate the pulse width of the PWM control pulse according to the peak value of the polyphase input waveform which the converter is about to receive from the AC power supply. This is accomplished by outputting multiple PWM control pulses during the processing time of.

[Action]

By calculating multiple PWM control pulses during the processing time of the computer, a PWM control pulse with a sufficiently narrow pulse width can be generated without increasing the load on the computer. Sufficient corrugation can be obtained.

〔Example〕

Hereinafter, a control device for a PWM converter according to the present invention will be described in detail with reference to the embodiments shown in the drawings.

FIG. 1 is an embodiment of the present invention, in which 1 is an AC power supply, 3 is a voltage detector for detecting a power supply voltage, 5 is a main switching circuit of a converter device, 7 is a current command input terminal,
Reference numeral 8 is a current detector, 9 is a comparator for obtaining a current deviation, and 10 is a one-chip type microcomputer for control. Capacitor 2, DC reactor 4, transistors 51 to 5
6, load 6, etc. are as described above.

Microcomputer (hereinafter referred to as "microcomputer") 10
Is an input port 101 for various commands, an internal bus 102, a ROM 103 for storing a program, a pulse width data table, etc., a RAM 104 used for temporary storage or a register, an ALU 105 for executing arithmetic operations, a predetermined pulse pattern for an output port 106 ( Event setting register 107 that sets the event necessary to output (event), time setting register 108 that sets the time when this event is enabled, both setting registers
A holding register 109 for connecting and holding the contents of 107 and 108, an associative memory 110 in which several sets of setting data set in the holding register 109 are respectively stored, a timer 111 for outputting the actual time, and an associative memory 110 A comparison unit that compares the set time contents and generates an output when they match
112, and an execution controller 113 for controlling the output of a set event to the output port 106 by receiving a trigger from the comparing unit 112.

Next, the operation in this configuration will be described using a flow chart.

In this embodiment, as shown in FIGS. 3 and 5, it is composed of two large processing systems. First, FIG. 3 shows an event generated at the output port 106, that is, an event calculation for obtaining a pulse pattern. It is a flow chart outlining the processing program F1000.

When the processing of F1000 is started, first, preparation is made for obtaining the total phase θ _{T in} F1100. For the frequency command ω ₁ ^*, the frequency value of the AC power supply is written in advance as data. The phase command θ ^* is a value determined for the current deviation Δi ₁ as shown in the characteristic of FIG. However, when the converter only performs pulse width control and does not use phase control at the same time, that is, when it is not necessary to control the output voltage to near zero, this value may be set to zero.

Next, this frequency command is integrated with ω ₁ ^* at constant time intervals Δt ₁ , and the phase command θ ^* is subtracted to obtain the total phase θ _T in process F1200.

Next, of the six modes obtained by dividing the electrical angle of 360 ° by 60 °, which mode should output the pulse pattern in the total phase θ _T obtained this time, that is, the output event according to this phase θ _T is F1300. Obtained by the process of. Note that the total phase θ _T
The relationship between and the six modes will be described in detail later. Finally, the pulse pattern is changed during the interrupt interval Δt ₁ , but the process of obtaining the time t _En until the change is obtained by referring to the data table of the phase θ _T is F1400.
Done in. By this processing, two items of event content and event change time set in the two registers 107 and 108 are obtained.

Next, the fifth process F2000 for setting the two items thus obtained in the associative memory 110 for output port control
Shown in the figure.

First, in F2100, determine whether the necessary events and time settings for 6 transistors have been completed. If N0, then F220
When 0 is set, the corresponding event is set, and at F2300, the time for event change is set, and the process ends.

Next, FIG. 6 shows how long these two processes F1000 and F2000 are activated. Event setting process F200
0 is activated in synchronization with the timer interrupt 2000 that occurs every Δt ₁ . On the other hand, the event calculation process F1000 is started by the second timer interrupt 1000 that occurs prior to the timer interrupt 2000, and the event calculation process is completed before the F2000 is started. The reason why the event calculation process F1000 is completed immediately before the event setting process F2000 is that the latest data can be used in the F2000. Of course, if a dead time element for the timer interrupt interval may be included, F1000 may be performed subsequently to FF2000. In that case, since the time required for interrupt determination becomes short, the interrupt interval Δt ₁ can be set short and the conversion device can be operated at a high frequency.

Therefore, according to this embodiment, when the setting of the predetermined event and the time is completed, the associative memory unit in the microcomputer takes over the output port control, and the main processor unit is released from the output processing.

Next, the determination of the pulse pattern of the processing F1300 will be described with reference to FIG.

In this embodiment, the pulse pattern is changed for each electrical angle of 60 °, and six sets of modes that make one cycle at 360 ° are repeated. Therefore, 6 sets of mode M1 with 60 ° section
M6 is selected by the total phase θ _T. The flow chart is shown in FIG. If the phase θ _T appears in a region other than 0 ° to 360 °, 360 ° is added / subtracted and θ _T falls within the region.
Go to the top of F1300 to check the area where you want to return.

Next, in FIG. 8, in modes M1 to M6, specifically, during the period Δt ₁ ,
The following shows each combination of a transistor that is normally ignited, a transistor that is ignited and extinguished until an event occurs, and a transistor that is extinguished until an event occurs and then ignited. Therefore, if the phase θ _T is known, the mode can be known and the transistor to be extinguished can be specified. At this point (when the processing of F1300 is finished), it is still unknown when to extinguish. It will only be. Here, for firing, for example, "1" is set in the register when setting an event, and "0" is set for extinguishing, which means that the output is designated for each transistor.

In FIG. 9, the process of obtaining the time to change the event (F1400 in FIG. 3) will be described. In conclusion, since it is only necessary to obtain a waveform close to the sine wave output, in this embodiment, sin θ _T and 120 ° phase shift depending on the phase θ _T
Δt ₁ is distributed to the value obtained by multiplying the ratio of the crest values of (θ _T −120 °) and sin (θ _T −240 °) by the conduction ratio γ ^* . That is, the times t _E1n and t _E2n until the first and second events occur (changing the pulse pattern) are defined as a function of θ _T and γ ^* as shown in the following equation.

t _E1n = Δt ₁ · {sin (θ _T −240 °)} · γ ^* t _E2n = Δt ₂ · {sin θ _T } · γ ^* Therefore, as shown in Fig. 10, an example of this pulse pattern As the value of the rate γ ^* decreases, the values of t _E1n and t _E2n both decrease (Δt ₁ −t _E1n −t _E2n ) and increase, and the current flows due to the _extension of the short-circuiting period of the upper and lower arm elements. Rate γ
^* Will be realized.

As a result, a PWM signal in which the same sine wave as the frequency of the AC power supply (for example, 50 Hz) is modulated into a pulse width can be generated, and this will be used for control. Allows you to approach the waves.

This FIG. 10 shows an example of the operation mode and the port output signals S51 to S56 given to the transistors 51 to 56. The mode has a variation in electrical angle because the frequency command ω ₁ ^*
However, this occurs because the timer interrupt interval Δt ₁ is asynchronous, and in order to eliminate this, it is sufficient to set Δt ₁ to ω ₁ ^* such that it is divisible.

Then, next, the flow chart of the event setting process embodied by taking the first part of the mode 1 of this figure as an example will be described.
Shown in Figure 11. As described above, in FIG. 5, the loop configuration has been described for the sake of schematic description, but in reality, the processing is performed in series as shown in FIG. 11.

The flow chart in FIG. 11 is the time point t ₀ to t ₀ + in FIG.
This shows the event setting process for one timer interrupt period up to Δt _1. First, when an interrupt occurs at time t ₀ , F241
At 0, in this mode 1, the event set and the time set are respectively set so that the ignition signal is immediately generated in the transistor 55 (see FIG. 8) that is always fired and the transistor 53 that is fired until the first event occurs. Two sets of transistors are performed. That performs event excisional as to generate a "1" into the port 3 and 5 corresponding to the transistors 55 and 53, then the current time t ₀ as time excisional by adding a predetermined time td to excisional a predetermined register . At this time, since the ignition is performed immediately, it is necessary to select the smallest possible value for this time td. As a result, the event and time are set in the associative memory 110, and thereafter, td
After a lapse of time, the "1" signal is output to the transistors 55 and 53.

The predetermined time td is added here for the following reason. That is, the event is set in the associative memory 110,
Then some time inevitably elapses before being read. Therefore, if the current time t ₀ is set without adding this time td, the coincidence in the comparator 112 can no longer be obtained, and it becomes impossible to give this event to the output port 106. Is.

In F2420, assuming that the operation mode has changed from the previous one due to a sudden change of the phase command θ ^* , in this mode, the extinction confirmation processing of the transistor that should be in the extinguished state is performed. Processing is F2410
The associative memory 110 is used in the same manner as in, but since the event is extinguished here, the event set is performed so as to generate "0" at the ports 1, 2, 4, and 6.

Next, schedule processing is performed by F2430 so that the transistor 53 is extinguished at time t ₀ + t _E1n . Event is “0” on port 3
It is an output, and the time is set to t ₀ + t _E1n . If td has a large value to some extent, it means that a plurality of events for one output port are scheduled at a time within the same timer interrupt.

Further, in the F2440, the schedule setting of the ignition of the transistor 51 is performed instead of the extinction of the transistor 53.

Note here has been the extinguishing the same time the ignition of the transistor 51 of the transistor 53 causes the lap of the "1" period is a current type converter as overvoltage protection, the time t _En for the voltage type making non lap time It is possible to consider changing between F2430 and F2440.

Next, a schedule (F2450) for extinguishing the transistor 51 and a schedule (F2460) for igniting the transistor 52 are continuously _performed at the second event occurrence point t ₀ + t _E2n .

As described above, in the above embodiment, the phase θ _T is calculated, the transistor to be extinguished is determined based on θ _T , and θ
_The time to extinguish is determined by _T , and the process of forming a schedule by pairing the transistor to be extinguished with the time at the end is performed every predetermined time Δt _1. Compared with the conventional method that compares the carrier wave and the modulated wave, a microprocessor (AL
In addition to eliminating the problem that (U) is always bound by comparison, the power supply current waveform is made sinusoidal and a great industrial advantage is obtained in that harmonic components do not flow into the power supply.

In the above explanation, synchronization with the power supply is not particularly mentioned, but a complete synchronization process that synchronizes a series of processing repeated for each Δt ₁ with the zero cross signal of the power supply, Σω ₁ ^* Δt ₁ with the zero cross signal Although resetting synchronization methods and the like are conceivable, this pulse control method is not greatly restricted by these synchronization methods.

Further, in the above description, the method in which the pulse width control and the phase control are used together so that the output voltage can be controlled to 0 is used. However, when that is not necessary, the phase value due to the phase control component is omitted when the total phase θ _{T is} calculated. do it.

Further, in FIG. 9, only 0 ° to 60 ° of the total phase θ _T is provided to reduce the size of the table, but if it is expanded to 0 to 360 ° and held, the phase θ _T is converted to the 0 ° to 60 ° section. This has the effect of simplifying the processing.

In addition, the programmable I / O function in the one-chip microcomputer was used for the schedule processing in the event setting processing F2000 in Fig. 1, but the programmable I / O function in the one-chip microcomputer is used when there are not enough ports or when the port output signal is checked. If / O is not used, it goes without saying that the effects of the present invention are not impaired even if external peripheral I / O having the same function is used.

〔The invention's effect〕

As described above, according to the present invention, the power source current waveform of the current source converter can be made into a sine wave, so that the problems of the prior art can be dealt with and an ideal high-frequency component does not flow to the power source. There is an effect that a converter device can be realized.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of a current source converter device, FIG. 3 is a flow chart showing an event calculation process, and FIG. FIG. 5 is an explanatory diagram showing an example of flow rate characteristics, FIG. 5 is a flow chart showing an event setting process, FIG. 6 is an explanatory diagram of interrupt timing, FIG. 7 is a flow chart showing a mode selection process, and FIG. 8 is a mode chart. Explanatory drawing, FIG. 9 is explanatory drawing of time setting,
Figure 10 shows an example of the PWM control pulse
Figure 1 is a flow chart showing the event setting process. 1 ... AC power supply, 2 ... Overvoltage suppressing capacitor, 3 ...
… Voltage detector, 4 …… DC reactor, 5 …… Main switching circuit, 51 to 56 …… Transistor, 6 …… Load, 7
…… Current command input terminal, 8 …… Current detector, 9 …… Comparator, 10 …… Microcomputer, 101 …… Input port, 102 …… Internal bus, 103 …… ROM, 104 …… RAN, 105 …… ALU, 106 ……
Output port, 107 ... event setting register, 108 ... time setting register, 109 ... holding register, 110 ... associative memory, 111 ... timer, 112 ... comparison section, 113 ... execution controller.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshimitsu Tobita 4026 Kuji-machi, Hitachi City, Ibaraki Prefecture, Hitachi Research Laboratory, Ltd. (72) Hideaki Takahashi 1070 Ige, Katsuta City, Ibaraki Hitachi Ltd., Mito Co., Ltd. In-factory (72) Inventor Shigeta Ueda 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi Co., Ltd. (56) Reference JP 59-63976 (JP, A) JP 62-95973 (JP , A)

Claims (3)

[Claims] 1. A control device for a converter, which takes in a control command at a predetermined almost constant cycle and generates a PWM control pulse for a main switching element of a converter that converts polyphase AC power into DC power. A means for estimating the phase value of the multi-phase AC voltage by integrating the frequency command in the control command at almost constant intervals, and calculating the pulse width of the PWM control pulse according to the phase value and a sine function. And a means for generating a plurality of PWM control pulses in the predetermined substantially constant cycle. 2. The converter according to claim 1, wherein the converter is a current source converter, and the phase value is a phase command obtained corresponding to a deviation between a current command for the converter and an output current. A control device for a PWM converter characterized by being included as. 3. The sine function according to claim 1, wherein the sine function includes, as a coefficient (gain), a conduction ratio defined as a function of a deviation between a current command for the converter and an output current. Control device for PWM converter.