JPS6337594B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device that converts a predetermined DC voltage into a current with a predetermined frequency and waveform. The present invention relates to a power supply device that controls a conversion circuit.

BACKGROUND OF THE INVENTION Due to the recent demand for labor and energy saving in industry, demand for variable speed motors has been increasing from users. Currently, a typical power source for this variable speed drive system is a so-called static frequency converter, which has a converter section that converts power from a commercial AC power source to direct current, and an inverter section that converts the direct current in this converter section to alternating current. There is. This is usually called an inverter device, and has progressed from the rectangular wave output at the time of development to the more recent pulse width modulation control method (PWM). Furthermore, the switching elements in the inverter section are showing a tendency to shift from the original thyristor to high-performance transistors due to their better controllability.

However, the output waveform of many current inverter devices is in the form of a square wave or a combination thereof.
Regarding medium-capacity inverter devices, those whose output waveform is a sine wave have not yet reached the level of practical use. There are various possible reasons for this, but they can be roughly summarized into the following three reasons. One of them is that when generating a sine wave from a DC power supply by class A or class B amplification, a transistor with amplification performance must first be used, but the collector loss of this transistor is large in its unsaturated region. Therefore, it is impractical from the point of view of efficiency. The second reason is that various large capacity transistors currently being developed for power amplification have been developed for switching purposes due to reason 1 above, and the influence of temperature and collector current on the current amplification factor is excessive, and the input signal In order to amplify the original form, it may be impossible to do so in terms of linearity. Third, although it is relatively easy to obtain a single-phase input variable frequency sine wave signal, it is difficult to easily obtain a variable frequency, variable voltage three-phase sine wave signal. .

An object of the present invention is to provide a power supply device that can solve these drawbacks and also meet the above-mentioned variable frequency requirements.

Based on the above object, the power supply device of the present invention stores data of a desired current waveform in advance, reads this stored data sequentially in synchronization with a clock signal of a predetermined frequency, generates a control signal, and generates a control signal using this control signal. The conduction state of the switching element of the conversion circuit is continuously controlled. Here, the desired current waveform data can be set arbitrarily by changing the memory contents, and the frequency of the clock signal can be set arbitrarily, so in the end, the output voltage waveform and its frequency can be set almost freely. Become.

Hereinafter, the present invention will be specifically explained based on an embodiment shown in the drawings.

As shown in FIG. 1, the power supply device of the present invention includes a DC power supply circuit 2, a conversion circuit 3, and a control device 4. The conversion circuit 3 supplies power to a load 5. The DC power supply circuit 2 has a DC voltage
It outputs V _dc and consists of a converter that rectifies and smoothes a commercial AC power supply and outputs it as a DC voltage V _dc . The conversion circuit 3 converts the DC voltage V _dc of the DC power supply circuit 2 into a current with a predetermined waveform using a switching element, and as shown in FIG. _r1 , T _r2 ... T _r6
A separately excited three-phase full-wave inverter ₃₁ is constructed by combining the two in a bridge configuration. Therefore, the conversion circuit 3 of this embodiment generates three-phase output currents I _R , _IS , and _IT with a predetermined waveform, and supplies these to the load 5 . The load 5 is, for example, a three-phase induction motor ₅₁ as shown in FIG. 2, and its Y-connected windings C _R , C _S ,
_CT is connected to the output points of transistors T _r1 , T _r2 . . . _r6 of the three-phase full-wave inverter ₃₁ , respectively.
Of course, this load 5 may be resistive, capacitive or inductive, or may be Δ-connected.

The control device 4 stores data of a predetermined current waveform, for example, a sine waveform, and sequentially reads out the stored data in synchronization with a clock signal So of a predetermined frequency to generate control signals S ₁ , S ₂ , . . . S ₆ Now, the transistors T _r1 , T _r2 ... T _r6 of the above conversion circuit 3
Controls the conduction state of As shown in FIG. 3, the configuration of this control device 4 consists of a ROM or PLC that stores the data of the instantaneous value of the sine wave current Io (see FIG. 5) as a desired voltage waveform by dividing it into 3n equal parts. ―
A memory circuit 7 such as a ROM, a control circuit 8 that reads instantaneous value data from the memory circuit 7 with a phase shift of π/3 electrical angle, and a clock signal of a predetermined frequency for control operation to the control circuit 8. The pulse generation circuit 6 that sends So, temporarily holds the instantaneous value data of the storage circuit 7 that is controlled by the control circuit 8 and read out sequentially, and outputs analog control signals S ₁ , S ₂ ...S ₆ is constructed by combining an output circuit 9 which applies voltage to the bases of the transistors T _r1 , T _r2 . . . T _r6 of the conversion circuit 3. Here, the output circuit 9 includes first latch circuits 11, 12, . . . 16,
The second latch circuit 10 and finally the control signal S ₁ ,
It is constructed by combining a DA converter circuit 17 that generates S ₂ . . . S ₆ . The control circuit 8 is composed of a combination of six address registers, a program memory, a control counter, a decoder that generates control commands for each device, etc., and may be composed of, for example, a central processing unit (CPU). do.

Next, the operation will be explained. The DC power supply circuit 2 always generates a DC voltage V _dc , and the conversion circuit 3 uses the DC voltage V _dc as an input to generate control signals S ₁ ,
S ₂ ...S ₆ is received to generate three-phase alternating currents I _R , I _S , and _IT , which are supplied to the load 5. As shown in the upper part of FIG. 4, these three-phase AC voltages I _R , I _S , and _IT are sinusoidal waves whose phases are shifted by 2/3π electrical angle. The relationship between the DC voltage V _dc and the three-phase AC voltages V _R , V _S , and V _T (effective values) generated in the load 5 can be expressed as follows.

1/2V _dc = √2V _R , √2V _S , √2V _TThe positive half-cycle portion of the three-phase alternating current I _R , I _S , I _T is obtained by the conduction of transistors T _r1 , T _r3 , T _{r5 ,} respectively. The negative half-cycle portion of the three-phase alternating currents I _R , I _S , and I _T are connected to transistors, respectively.
This is obtained by conducting T _r2 , T _r4 , and T _r6 . If the power factor of the load 5 is 1, the waveforms of the three-phase alternating currents I _R , I _S , I _T are simultaneously the three-phase alternating current voltages V _R , V _S , V _T as phase voltages or line voltages. You can also see it. The three-phase alternating currents I _R , I _S , and I _T are windings, respectively.
Assuming that the direction flowing into the connection point of the neutral point N of C _R , C _S , and _CT is positive and the opposite direction is negative, the current waveform is expressed as shown in the lower part of Figure 4. . On the other hand, this three-phase alternating current I _R , I _S ,
Since I _T is also the collector current of transistors T _r1 , T _r2 ... T _r6 at the same time, transistors T _r1 ,
T _r2 ... base voltage of T _r6 , that is, control signal S ₁ ,
S ₂ ...S ₆ are very similar to this half-wave sine wave due to the constant current source characteristics of the transistor. In this way, the control signals S ₁ , S ₂ ...S ₄ are
_The base currents for the transistors T _r1 , T _r2 . This current having the same sinusoidal waveform is transmitted to the control device 5.
The data is stored in the storage circuit 7 as instantaneous value data divided into 3n. That is, the memory circuit 7 divides the sine wave current _I0 into 3n equal parts as shown in FIG. 5, further divides the 3 equal parts into n equal parts, and stores instantaneous value data _i1 , _i2 ... ...i _o , respectively, are stored at predetermined addresses.

Now, the control circuit 8 reads the data of the instantaneous value of the sine wave current I ₀ with a phase shift of 1/3π in electrical angle and stores it in the first latch circuits 11, 12, . . . , 16 based on a certain control program. Give instructions for what to do. First, in the read mode M=1 during the period t ₁ to _{t 2} in FIG. 4, three transistors T _r1 , T _r5 ,
Read out the control signals S ₁ , S ₅ , and S ₆ as the base current of T _r6 . In this read mode M=1,
As shown in FIG. 5, the control signal S ₁ of the transistor T _r1 is data i ₀ , i ₁ . . . i _o from o to n,
Further, the control signal _S6 of the transistor _Tr6 is the data i _o from n to 2n, i _o +1... _i2o , and the control signal _S5 of the transistor T _r5 is the data from n to 2n.
i _2o +1...i _3o , and the control signals S ₄ , S ₃ , S ₂ of the other transistors T _r4 , T _r3 , T _r2 are all zero. and their instantaneous value data
i ₀ , i ₂ , . . . i _3o and zero are sequentially and independently input to the first latch circuits 11, 12 . all control signals
With the data _{i 0 , i 2 ...} i _3o and zero of S ₁ , S ₂ . i ₂
...Reads i _3o and zero and holds them as they are. Then, the DA conversion circuit 17 converts these data groups into analog quantities, and outputs control signals S ₁ , S ₂
. . . S ₆ is applied to the bases of transistors T ₁ , T _{2 .} . . T ₆ . This operation proceeds sequentially from t ₁ to t ₂ in read mode M=1. This operating speed can be arbitrarily set to the frequency of the clock signal _S0 . Therefore, the control signals S ₁ , S ₂ ...
...The period of S ₆ can be freely selected, and as a result, the frequencies of the three-phase AC voltages V _R , V _S , and V _T can be varied. Also, other read modes M=2, 3...
The state of No. 6 is as shown in each row of FIG. The flow of these operations is as shown in FIG. 6, in which the six control signals S ₁ , S ₂ ...S ₆ are sequentially read out and latched, and then transferred to the second latch circuit 10. After that, the data group is D-
The signal is A-converted and output, and then this operation is repeated as one cycle.

In this way, the control circuit 8 reads out a data group of instantaneous values of the same sine waveform with a phase shift of 1/3π electrical angle, and transfers this data to the transistor T _r1 ,
T _r2 ...Base current or control signal for T _r6
S ₁ , S ₂ . . . S ₆ are generated sequentially, which drives the conversion circuit 3 and finally generates the predetermined three-phase AC voltages V _R , V _S , V _T with a sinusoidal waveform. be.

Here, the contents of the six address designation registers (not shown) of the control circuit 8 are incremented by 1 every time one cycle is completed, and when the address designation of these address designation registers reaches 6n+1, 6n is subtracted. to specify the address. In this way, the data read position returns to the original position and is read out repeatedly.

Incidentally, the transistors T _r1 , T _{r2 . .} . T _r6 of the actual inverter circuit 31 are controlled by the drive circuit 19 shown in FIG. The figure illustrates only the transistor T _r1 . This drive circuit 19 is
Power supply terminal V _cc of operational amplifier A is connected to power supply E for control,
Connect V _EE and connect a resistor to its output terminal.
The Darlington-connected control transistors Q ₁ and _Q 2 operated by the power supply E are connected to the bases of the previous stages through R ₃ and R ₄ , and the collector of the subsequent transistor Q ₂ is connected to the power amplification transistor. The base of T _r1 and the feedback resistor R ₂ are connected to the inverting input terminal. The transistor T _r1 is connected in series with the current transformer CT for detecting the instantaneous value of the output current and a part of the winding C _R of the load 5, and receives the DC voltage V _dc . The control signal S ₁ is applied between the resistor R ₁ on the side of the inverting input end and the common CO _n ,
The output of the current transformer CT is applied to the non-inverting input terminal.

Now, the operational amplifier A inputs the control signal _S1 , the transistor _Tr1 , and the feedback voltage proportional to the collector current _Ic (phase current _IR ), and the difference voltage is _amplified . ₂ and finally controls the power amplifying transistor T _r1 . In this way, the transistor T _r1 reproduces an accurate waveform according to the control signal _S1 . This operation has a time width of approximately 100 [Hz], or a half cycle of 5
Even if instantaneous values of 10 to 50 are inputted in [msec], it will track sufficiently. In particular, the conventionally known circuit forms a rest period of Δt at the time of rise, as shown by the broken line in FIG. It's standing up. This is because one end of the feedback resistor _R2 is connected to the base of the final stage transistor _Tr1 (the emitter of transistor _Q2 ). This function can be obtained in almost the same way by connecting one end of the resistor _R2 to the emitter of the transistor _Tr1 . This useful function was confirmed by the inventor's experiments. In addition, in the conventional type, the signal is taken out directly from the output terminal of the operational amplifier A, as shown by the broken line.

In the above embodiment, the sinusoidal three-phase AC voltage V _R ,
Although it is explained that V _S and V _T are generated,
The waveform of this output voltage is determined by the memory circuit 7 of the control device 4.
By changing the data of the waveform current I ₀ to be stored in order to generate an arbitrary waveform, it is possible to obtain a predetermined waveform, that is, an arbitrary waveform other than a sine wave. Further, the conversion circuit 3 is not limited to a three-phase type. Further, it is particularly effective if the load 5 is a three-phase induction motor 3 ₁ , but as already mentioned, other types may be used, and therefore, the present invention is not limited to that of the embodiment.

According to the present invention, a voltage of a predetermined output waveform can be obtained by appropriately changing the content of waveform data to be stored in the control device, and this control operation can be performed with high precision using a control means such as a computer. Moreover, because it can be performed at high speed, a stable output voltage that is not influenced by external conditions can be obtained, and by changing the frequency of the pulse signal of the control device, the frequency of any output waveform can be increased or decreased accordingly. For example, speed control of motors and the like becomes easier.

Note that when the output voltage is a sine wave,
Since a regular sine wave voltage with few harmonic components can be obtained, problems such as decrease in motor efficiency, especially temperature rise, noise, and vibration caused by harmonic components can be solved.
In addition, since a sine waveform can be generated without harmonic components, when applied to precision machine tools, there is no mechanical loss, stable machining accuracy can be obtained at all speeds, and harmonic components are reduced. This makes it possible to wire the motor with less noise to surrounding electronic equipment.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the power supply device of the present invention, Fig. 2 is a circuit diagram of the conversion circuit and load, Fig. 3 is a block diagram of the control device, and Fig. 4 shows the AC voltage waveform and the collector current of the transistor. FIG. 5 is a waveform diagram showing the relationship between control signals, FIG. 5 is a waveform diagram showing the relationship between the sine wave voltage as stored data and the phase of the transistor, FIG. 6 is a flowchart during operation, and FIG.
The figure is a circuit diagram of the drive circuit, and FIG. 8 is an output waveform diagram. 1...Power supply device, 2...DC power supply circuit, 3...
Conversion circuit, 4...control device, 5...load, 6...
Pulse generation circuit, 7...memory circuit, 8...control circuit, 9...output circuit.

Claims (1)

[Scope of Claims] 1. A DC power supply circuit that outputs a DC voltage, a conversion circuit that converts the DC voltage of this DC power supply circuit into a predetermined current using a switching element, and a circuit that stores data of a desired current waveform and stores this stored data. 1. A power supply device comprising: a control device which sequentially reads out the signals in synchronization with a clock signal of a predetermined frequency to generate a control signal, and controls the conduction state of a switching element of the conversion circuit with the control signal. 2. The conversion circuit is a three-phase full-wave inverter with six transistors as switching elements, and the control device generates a corresponding control signal to the base of each transistor, as set forth in claim 1. power supply. 3. The control device includes a memory circuit that stores instantaneous value data of a sine waveform, a control circuit that reads out the data in this memory circuit in a phase-shifted state based on a predetermined control program, and a control circuit that performs control operations on this control circuit. a pulse generation circuit that generates a periodic clock signal for the purpose of the clock, and a conversion circuit that temporarily holds the data in the storage circuit that is controlled by the control circuit and sequentially read out and converts it into an analog control signal. and an output circuit for applying voltage to the base of each transistor.
The power supply device according to item 1 or 2. 4. The power supply device according to claim 3, wherein the pulse generation circuit of the control device is of a variable frequency type.