JPS6315832B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a direct AC/AC converter, i.e., the alternating current output is obtained directly from the alternating current input current without going through any intermediate direct current steps, and the present invention provides a The present invention relates to a converter that can change output characteristics corresponding to characteristics such as frequency, amplitude, and power factor.

In many applications, a power source with characteristics different from those readily available may be required. For example, to control the speed of an induction motor by controlling the frequency and voltage of the power supply, or to reduce the frequency or stabilize the voltage generated by the main synchronous generator coupled to the turbine of a jet machine. It's for the purpose of changing things. In particular, the effect of frequency conversion is useful for all electrical equipment such as motors and transformers. That is, in such cases, higher frequencies than those suitable for supply transmission allow for smaller and cheaper structures.

In addition to changing the voltage and frequency, it would be desirable to be able to change the phase angle of the energy passing through the transducer, and to do this without the use of reactive elements.

Therefore, the desirable features of an AC converter can be summarized as follows.

(1) The amplitude and frequency of the output can be controlled.

(2) The input and output waveforms must be essentially sinusoidal. Or at least a waveform whose unwanted harmonic components are sufficiently separated from the fundamental to have a distinctly higher frequency, and no subharmonics at all.

(3) Allowing bidirectional flow of power (e.g., for regenerative braking of electric motors).

(4) No reactive elements are present. actual,
While it is anticipated that continued advances in semiconductor technology will greatly improve the operation of solid-state switches by reducing their cost and size, similar advances cannot be expected for reactive devices. It will therefore always constitute an obstacle to the technical progress of transducers.

(5) The phase angle of the energy absorbed by the load through the converter group can be controlled.

Various types of AC converters have already been proposed, but
For various reasons, no product has all of the above five features. In principle, existing converters
They can be classified into AC/DC/AC converters and direct converters.

The AC/DC/AC converter includes two stages. In the first stage, the input is converted to a direct current or voltage, and then this current or voltage is transferred to the second
stage where it is converted by producing an alternating current output at the desired frequency. I will not provide a detailed analysis of the various types of AC/DC/AC converters, but they generally have poor output waveforms, require filters, are unidirectional, and have a large number of There are drawbacks such as the need for semiconductors and limitations on input waveforms or output impedance, which impose restrictions on operation and applications.

In contrast, a direct converter directly combines an AC output from an AC input without any intermediate DC steps. The three best known converters of this type are: Part 1
One is the cycloconverter, in which each output essentially constitutes an AC/DC converter. And the UFC recently proposed by Westinghouse
(Unrestricted Frequency Changer) and SFC (Slow Frequency Changer)
There are two converters called Changers (low frequency converters).

In particular, the latter two transducers provide a "configuration" of the output frequency by means of a matrix of switches that are closed according to a predetermined program and function. These converters are excellent with respect to harmonics at the input as well as at the output, but they do not provide phase shift control at the load or output voltage, and require a large number of input phases to reduce the harmonic content at the output. do.

It is therefore an object of the present invention to provide an improved direct AC
A transducer in which undesired harmonic waveforms in its input current and output voltage can be easily shifted to higher frequencies, and which allows bidirectional operation and allows control of frequency, amplitude, and phase angle at the output. The object of the present invention is to provide a converter for

According to the invention, an input conductor for a balanced polyphase AC input voltage system and at least one of the characteristics such as frequency, amplitude, phase angle or phase shift
It seems that the input voltage is different from that of the system.
A direct AC converter comprising an output conductor for an AC output voltage system and a plurality of bidirectional switches individually connecting each input conductor and each output conductor, the direct AC converter comprising:
a controller having timing means for producing a repeating sequence of adjacent width modulated pulses of as many pulses as the number of phases of the AC input voltage system; are closed to connect each phase of said AC input voltage system in turn to each phase of said AC output voltage system, and at any given moment only one of said switches is connected to any one of the output conductors. A direct AC converter is provided, characterized in that it is connected to said switch so as to be closed.

The output voltage system may be single phase or polyphase. The sequence of width modulated pulses, when modulated by equally spaced phases of a sine wave at the modulation frequency, provides a frequency of the output voltage system that differs from the frequency of the input voltage system by the modulation frequency. Preferably, the series of width modulated pulses repeats at a rate of 1,000 to 100,000 times per second, and a filter is provided in the output conductor to absorb high frequency components generated by operation of the switch by the pulse series.

The pulse sequence can be created by analog or digital means. One example of a suitable analog means is a ring of controllable monostable multivibrators, connected such that the reset of one multivibrator triggers the next multivibrator in the ring, producing a modulated oscillation. are provided to control the set time of each multivibrator. Digital means operating on the same principle can also be used for the same purpose by using digital differential analyzer technology or by using a suitably programmed microprocessor.

A converter according to the invention can be configured to produce an output voltage with an apparent negative frequency, i.e., out of phase with the phase shift between current and voltage in the output conductor when the output voltage is applied to a reactive load. A shift is created in the input conductor. The converter also
If the pulses in the sequence are width modulated by a different phase combination of two sinusoidal oscillations of different frequencies (which when used independently produce output voltages of positive and negative frequencies that appear equal in magnitude) If so, it can be used to control the power factor of the input power source. If in such a converter the output and input frequencies are of equal magnitude and the input and output phase numbers are the same, the output conductor can be connected to the input conductor to form a reactive power generator. In this way, the reactive load supplied by the output power can be made to appear to the input power as a purely resistive load. If such an arrangement at some point creates a short circuit for the power supplied by the switch, connect a suitable inductance to the power supply conductor to create the large current that would otherwise flow through the switch. is preferred.

Among the applications of the converter according to the invention is speed control of induction motors achieved by varying the frequency of the power supply supplied to the motor. If necessary, constant speed or constant torque operation of the motor can be achieved by feeding a signal representative of the shaft speed of the motor back to the transducer and measuring the deviation between the drive frequency and the motor speed. Can be done.

BRIEF DESCRIPTION OF THE DRAWINGS In order to enable a thorough understanding and easy implementation of the present invention, reference will now be made to the drawings.

The theoretical basis of the converter according to the invention will be explained with reference to FIGS. 1 to 5.

The 3-phase 3-phase AC converter includes 9 switches, each for connecting between each input line and each output line (Figure 3).
The design problem for this converter can be stated as follows.

A set of input sinusoidal voltages with input frequency 2πω _i and a set of output sinusoidal currents with output frequency 2πω _p When given, the problem is to satisfy the output frequency, input frequency, and amplitude described above, and to calculate the low frequency part of the composite output voltages Vo ₁ , Vo ₂ , Vo ₃ and input currents Ii ₁ , Ii ₂ , Ii ₃ The purpose is to determine the switching times S ₁₁ , S ₁₂ , . . . S ₃₃ so that the signals become sinusoidal waves.
For simplicity, let's first consider the synthesis of only one output line (Figure 1A). The output line is connected to the three inputs by three switches S ₁ , S ₂ , S ₃ . The switch is closed continuously and periodically. In the kth switching series,
The closing time of switches S ₁ , S ₂ , S ₃ is t ₁ ^k , t ₂ ^k ,
Let t ₃ ^k . Here, t ₁ ^k +t ₂ ^k +t ₃ ^k =T _seq =1/f _seq , and T _seq is constant (Figure 1B).

The operation of the converter is determined by these times t ₁ ^k , t ₂ ^k , and t ₃ ^k .

The output voltage waveform Vo is a discontinuous function and is a combination of three input voltage parts. Generally, the Fourier spectrum of the output voltage depends on the input voltage, frequency and switching law of the converter. However, the low frequency part of the output Fourier spectrum mainly depends on the average output voltage in each series, as long as ω _p <<2πf _seq . In other words, if f _seq →∞, then all functions with the same mean value in time T _seq have the same spectrum, regardless of how they are synthesized. If sine waves are to be synthesized, the switching rule must be selected so that the average output value of the series changes in a sine wave manner.

In that case, it is assumed that ω _i , ω _p ≪22πf _seq .

In the above discussion, only series average values were considered.
In the kth series, the average output voltage can be approximated by:

Vo ^k _av = (V ₁ t ₁ ^k + V ₂ t ₂ ^k + V ₃ t ₃ ^k )/T _seg …(3) Here, V ₁ , V ₂ , and V ₃ are measured at the same time in the k-th series. is the input line voltage, and each time
It is assumed that t ₁ ^k , t ₂ ^k and t ₃ ^k are constant.

The output series average Vo ^k _av in equation (3) represents the input voltage, rotates at an angular velocity ω _i , and has a switching time t ₁ ^k ,
It is determined by adding three vectors weighted by t ₂ ^k and t ₃ ^k (Figure 2).

If for all k, e.g. t ₁ ^k = t ₂ ^k = t ₃ ^k
Then the average output voltage will be zero.

If for all k, e.g. t ₁ ^k , t ₂ ^k , t ₃ ^k
If both are constant, the resulting output vector is fixed with respect to the input vector. Therefore, the output voltage becomes a sine wave at the input frequency, and its amplitude and phase can be adjusted by changing t ₁ , t ₂ , and t ₃ .

Finally, if (where q is a constant and ω _n is a constant angular modulation frequency)
, the resulting vector V ^k has a constant amplitude q・
V _i and rotates with an angular frequency ω _n with respect to the input vector as k increases. Therefore, the output voltage is
It becomes a sine wave characterized by an amplitude q·V _i and an angular frequency ω _p =ω _i +ω _n .

It should be noted that ω _n in equation (4) does not need to be a positive value. If ω _n =−ω _i , then
This converter becomes an AC/DC converter. If ω _n <
Even if −ω _i , ω _p <0, there is no difference between positive and negative values of ω _p . This is because both represent sinusoidal changes in the output voltage. Therefore, this converter can synthesize the same output frequency in two operating modes: symmetrical mode: ω _n ＞−ω _i ω _p = ω _i + ω _n antisymmetric mode: ω _n ＜−ω _i ω _p =−(ω _i +ω _n ) Give two possible values of ω _n for the same ω _p .

The simplified converter of Figure 1A can be easily expanded to three output phases (Figure 3). The bidirectional switches of these single-phase converter sets operating according to equation (4) are:
Connected to the input conductor in periodic permutation. Therefore, if the input three-phase system is balanced, then
Naturally, the three output phases will be equidistant. A block diagram of such a converter is shown in FIG.
The overall generation or modulation matrix for this converter is easily derived from equation (4). That is, t _x = [1/T _seq・t−int(1/T _seq・t)]・3 f′(t)=1+q・2・cos[ω _n・T _se
q・int(1/T _seq・t)] f″(t)=1+q・2・cos[ω _n・T _se
q・int(1/T _seq・t)−2/3π], then Here, the symbol 1(t) represents the Dirac step function of t. Note that E= ^ET , so the transducer is completely symmetrical. There is no difference between the input section and the output section. Due to the symmetry of this converter, while the input voltage is converted to a voltage at the output frequency, the same conversion is performed on the output current. Therefore, the converter operation described above is independent of the frequency of the output voltage (even for DC output).
It is characterized by a sinusoidal input current at the input voltage frequency.

As already pointed out, this converter can synthesize any output frequency in two operating modes. The difference between the two modes can be understood with reference to FIGS. 4 and 5. In Figure 4, Vi ₁ ,
Vi ₂ , Vi ₃ and Vo ₁ , Vo ₂ , Vo ₃ represent input voltage and output voltage, respectively. If the load is resistive, Io ₁ , Io ₂ , Io ₃ and Ii ₁ , Ii ₂ , Ii ₃ represent the output and input currents. If a phase shift is introduced between the current and voltage at the output (Fig. 5),
It becomes the reference rotation in input current synthesis. Therefore, the output phase shift will be found to be unchanged at the input. However, in the symmetric mode, the lagging phase shift at the output is the lagging at the input, while in the antisymmetric mode, the lagging output phase shift is leading the input. According to this result, an inductive load is converted into a capacitive load by this converter. This converter is capable of generating reactive power.

In the above discussion it has been shown that this new converter operation allows all of the previously listed ideal requirements to be satisfied. As a circuit element, a high switching speed converter (HSRC) can be considered a generalized AC converter that can change the frequency, amplitude, and phase of the electrical energy flowing through it. The conversion is determined by three parameters:

S: (+1 or -1); Conversion mode (symmetric or anti-symmetric) q: (0<q<0.5); Output-input amplitude ratio ω _n : (-∞<ω _n <∞); Input-output frequency shift Once these parameters are set, the converter can be modeled as a two-input, conservative, polyphase input-polyphase output circuit element, whose configuration relationships are as follows for sine or DC waveforms: It seems like.

Symmetric mode Antisymmetric mode S=1 S=-1 ω _n >-ω _i ω _n <-ω _i ω _p = ω _i +ω _n ω _p =-(ω _i +ω _n ) φ _p =φ _i φ _p =- φ _i In the above discussion, the operation of this converter is
It was explained under the approximation that ω _i , ω _p ≪2π·f _seq . In practice, this converter switching rate f _seq is limited by device switching efficiency considerations. Therefore, since f _seq is a finite value, the undesirable harmonics that have been ignored so far are to some extent
will be present in the converter waveform. In fact, the Fourier spectrum of the actual transducer waveform contains its undesirable component and the spectrum of other undesirable components at low frequencies. The latter is due to discontinuities in the composite waveform and to approximations introduced when creating the transducer generation matrix. However, if f _seq max(ω _i , ω _p )/2π・8, these undesirable components are significant only in the f1/2 f _seq frequency range, which is equal to or lower than the input and output frequencies. It can be seen that the frequency is 1% or less of the desired component. Unwanted frequency components of the output waveform can be removed by filtering. It has been explained that by using a symmetric mode and an anti-symmetric mode, two phase shifts of opposite meaning can be introduced into the input power supply. When both of these modes are used simultaneously, the effect of a phase shift on the output supply on the input supply can be self-cancelling. In this way, the output supply can be connected to a reactive load, yet the input supply current can be kept in phase with the voltage waveform, allowing the converter and load to be considered as a single resistor. . Other power factor adjustments can also be performed with this converter. If the output frequency is equal to the input frequency, phase shift cancellation can be performed using one transducer as described above.

Although the theory has been developed for most cases of three-phase input supply and one set or three-phase output supply, the present invention converts n-phase input supply (n3) to p-phase output supply (p
It will be understood that the same applies when converting to 1).

In the case of a three-phase input supply, if one is required to realize all possible phase relationships between V _p and V _i , e.g. if the output frequency is different from the input frequency, V _p V _i / 2 and therefore C _i C _p /2. Furthermore, the input power is equal to the output power, i.e., V _p・C _p cosφ _p =V ₁・C _i cosφ _i
Here, φ _p and φ _i are the output phase shift and the input phase shift, respectively.

In the following, actual embodiments of the present invention will be described with reference to FIGS. 6 to 12. FIG. 6 is a block diagram of an example of a three-phase converter according to the present invention. The converter includes a three-phase voltage controlled oscillator 100 whose three outputs are provided to an amplitude-to-pulse length converter 101 from which separate outputs are provided for three dwell times and a drive. The signal is applied to circuits 102, 103, and 104. The output of this circuit 102 is connected to the primary winding of a drive transformer 105. The three secondary windings of this converter are switch modules 106, 107, 108, respectively.
connected to. Similarly, circuit 103 connects three switch modules 1 through drive transformer 109.
10, 111, and 112, circuit 104 connects switch module 11 through drive transformer 113.
4,115,116 are driven. The switch module has three three-phase power source conductors 117, 118,
119 to three three-phase output conductors 120, 121, 1
It forms a matrix of 3 rows and 3 columns connected to 22. Since this switch module is bidirectional, the supply and output conductors may be interchanged.

As can be seen, the circuit of FIG. 6 is symmetrical with respect to the three phases on the supply side, and the output of the amplitude-to-pulse length converter 101 is adjusted to the desired amplitude, phase, and frequency based on the principle already described. is in the form of a signal that is rapidly switched from one output conductor to another to produce a voltage with . Therefore, at any given time, one group of three switch modules is conducting, and the other two groups of switch modules are non-conducting.

Now, the voltage controlled oscillator will be explained with reference to FIGS. 7, 8, and 9. These three drawings together constitute the circuit diagram of this oscillator.

The circuit in Figure 7 has two circuits with the same amplitude but different polarity.
Two output voltages are generated at terminals A1 and A2, respectively. These terminals are connected to the outputs of two operational amplifiers 130, 131, respectively. The variable voltage obtained by sliding potentiometer 132 is applied to the non-inverting input of amplifier 130 and through resistor 133 to the inverting input of amplifier 131. Amplifier 130 has a direct feedback connection from its output to its inverting input so that its output voltage is equal to its input voltage. amplifier 1
31 is a resistor 13 having the same resistance value as the resistor 133.
4, so that its output voltage is the inverse of the slide voltage of potentiometer 132. The sliding portion of the potentiometer is grounded through a capacitor 135 to absorb noise and spurious voltage changes due to sliding.

Terminals A1 and A2 in Figure 7 are connected to terminals A1 and A2 in Figure 8, the latter being, for example,
Two switches like MC14066 140,14
1 input pair. These switches are four devices, but their output connections are in pairs, with each pair of outputs connected to integrators 142 to 14.
5 each. The output voltage of the integrator is coupled to the input of each one of Schmitt trigger circuits 146-149. Trigger circuit 1
The outputs of 46, 147, 148 are the logic circuit 150,
151 and 152, each logic circuit produces two output signals, which are applied to the switch 14.
0,141 to control the progression of the signals applied to terminals A1 and A2 from integrator 142 to 145.

The output of the fourth trigger circuit 149 is applied through an inverter 153 to the input of a counter 154, such as model number 74C164. This counter 154 is a 4-bit counter and has four output lines, which are fed to a logic circuit 155 whose outputs are fed to the inputs of logic circuits 150 to 152 to control those circuits. be done.
The output waveforms of the integrators 142, 143, 144 are also provided to any one of waveform generators 156, 157, 158, typically model name ICL8038.
The functions of the waveform generator are integrators 142, 143, 14
4 to convert the triangular waveform received from terminals B1 and 4 into a sine waveform output, respectively.
Sent to B2 and B3. A potentiometer P is provided to apply a specific voltage level to the generators 156-158 to optimize the sinusoidal shape of the output waveform.

The operation of the circuit of FIG. 8 is as follows. The voltage at terminals A1 and A2 is determined by potentiometer 1 in Figure 7.
32 and is guided from integrators 142 to 145 by switches 140 and 141. The integrator 145 is the integrator 142, 14
3,144, so it has a specific number of one-sixth of the time constant of 3,144;
Six cycles of triangular wave generation are performed within one cycle period in which a triangular wave is generated at the output of 144. Trigger circuit 149 generates a subsequent train of output pulses which are counted by counter 154. As the count value in counter 154 increases, logic circuit 155 provides a control signal to logic circuits 150, 151, 152 to adjust the progression of the voltage at terminals A1 and A2 to integrators 142, 143, 144. , thereby causing the three integrators to produce triangular output waveforms of the same frequency but equidistant from each other in phase. Logic circuits 150, 15
The function of 1,152,155 ensures that the different slopes of the triangular waveform begin at precise times, thereby minimizing frequency differences caused by small variations in the constant values of the components in the integrators 142-144. The goal is to avoid introducing cumulative phase or frequency errors between the two triangular waveforms. As mentioned above, waveform generators 156 to 158 are integrated into integrator 1
Convert the triangular output waveform of 42-144 to the corresponding sine waveform. The sine waves are again equidistant in phase, ie 2π/3 radians apart, and appear at terminals B1, B2, and B3.
Adjustment of potentiometer 132 (FIG. 7) changes the magnitude of the voltage applied to terminals A1 and A2, thus modulating the frequency of both the triangular and sine waves generated in the circuit of FIG. , ie an increase in voltage results in an increase in frequency, and it will become clear that there is an essentially linear proportional relationship between them.

FIG. 9 shows a third portion of voltage controlled oscillator 100, having input terminals B1, B2, B3 connected to terminals B1, B2, B3 of FIG. In FIG. 9, terminals B1 to B3 are connected to non-inverting inputs of operational amplifiers 160, 161, and 162, respectively. These amplifiers have direct negative feedback from their output to their inverting input, so that the output voltage produced by them is equal to the voltage applied to their non-inverting input. The outputs of amplifiers 160, 161, and 162 are respectively connected to terminal 1.
Appears in 63, 164, 165.

As is clear from FIG. 6, the three outputs of the voltage controlled oscillator are applied to an amplitude-to-pulse length converter 101. The circuit of this converter is shown in Figure 10, with the three outputs of the voltage controlled oscillator each connected to terminal 2
00, 201, 202. The converter typically includes three counter/timer circuits 203, 204, 205, model number 555. terminal 20
0, 201, 202 are counter/timer terminals 5
given to. These timers are connected to resistors 206 to 208 and capacitors 209 to 211 to form a monostable circuit. The monostable circuit is connected with capacitors 212, 213, 214 and has 3
A tiered ring is formed so that as each timer is requested, the next timer is set. Here, the time constant is set so that the set state rotates around the ring 5,000 to 25,000 times per second. Transistors 215, 216, 21
A constant current source including 7 is connected to ensure that the time constants of the monostable circuits are essentially the same.
Common amplitude control is provided by a potentiometer 218 which, in conjunction with an emitter follower connected transistor 219, sets a voltage on a conductor 220 connected through a diode to a time constant capacitor 209-211.

The function of the converter in FIG.
In response to the difference in amplitude of relatively slowly oscillating sinusoidal signals (e.g. 50-200 Hz) applied to the output terminals 1 and 202, the length of time that the monostable circuits are set relative to each other is determined by 221, 222, 22
This is to change the pulse length appearing in 3. The amount of pulse length change can be adjusted by amplitude control potentiometer 218. It will also be clear from the theory discussed above that this adjustment will adjust the amplitude of the AC output voltage.

FIG. 11 shows the circuitry of the rest time and drive circuits to which three outputs of the converter 101 of FIG. 10 are applied. The output signal from the converter is provided to terminal 250 in FIG.
From there, it is connected to the base of a transistor 253 through a parallel connection of a resistor 251 and a diode 252. A capacitor 254 is connected between the base of transistor 253 and ground. The emitter of transistor 253 is also grounded, and its collector is connected in series with resistor 255.
and 256 to the supply power conductor 257. The junction of resistors 255 and 256 is connected to the base of a transistor 258 whose emitter electrode is connected to conductor 257. The collector of transistor 258 is connected to transformer 1
It is connected through a secondary winding 259 to a secondary supply conductor 260, and in parallel with the winding 259 is connected a Zener diode 261 and another diode 262 in series.

The main functions of the circuit of FIG. 11 are three switches SM ₁ -SM ₃ to which the secondary winding of transformer 105 is connected.
The objective is to provide a drive suitable for operating the It also includes resistor 251 and capacitor 254
The effect of the time constant provided by , also serves to slightly delay the rise of the current flowing to primary winding 259 in response to a positive pulse applied to terminal 250 . Typically, resistor 251 is 1KΩ
The capacitor 254 has a resistance value of 0.001 μF.
It is. When the positive pulse at terminal 250 terminates, capacitor 254 rapidly discharges through diode 252. The effect of this part of the circuit is that the switch
For SM rest times, allow the necessary time for the switch to become open circuit, thereby ensuring that no two input conductors are connected to the same output conductor through a continuity switch at any time. , to avoid the generation of large currents that would otherwise result in failure. Zener diode 261 and diode 262 conduct current when transistor 258 becomes non-conducting, thereby preventing relatively high voltages from appearing at the collector of transistor 258, which could destroy the transistor. The primary winding driven by the rest time and drive circuit shown in FIG.
Drive transformers 105, 109, 1 shown in FIG.
It is one part of one of 13. In one example, 1
The secondary winding has 45 turns, each of the three secondary windings has 10 turns, and the size of the pot core is diameter
It was 30mm long and 19mm long. Core void is 0.51
It was millimeter hot.

Each of the three secondary windings on each of the drive transformers are connected to drive a switch module, a typical switch module being shown in FIG. The secondary winding is shown in FIG. 12 and has a reference point 300 and is connected to provide a drive signal across the base-emitter diode of transistor 301. A current limiting resistor 302 is provided in connection to the base electrode, diodes 303, 304, 305 and a Zener to protect the transistor against undesired overloads and limit its hole accumulation time. A diode 306 is provided. The switch itself is a diode 307, 308, 309, 3
10, the switch has terminals 311 and 312. The operation of the switch module is conventional, with diodes 307-310 connected in an opposite pair so that when transistor 301 is non-conducting, current flows from terminal 311 to terminal 312 or vice versa. do not have. However, when the transistor 301 is conductive, the diode 3
07, a current can flow from the terminal 311 to the terminal 312 through the transistor 301 and the diode 310. In addition, the diode 308 transistor 30
1. Current can also flow in the opposite direction through the diode 309.

The circuit configurations described herein with reference to FIGS. 6-12 are capable of adjusting the amplitude, frequency, and phase of the output voltage relative to the input voltage. _However , as _already mentioned with reference _{to FIG .} Modulate it so that ω _p = ω _n + ω _i , or choose ω _n equal to ω _p + ω _i so that ω _p = ω _i −
This is one of the methods of performing modulation so that ω _n . In the first method, the modulation frequency has the same meaning as the input frequency and is therefore added to it.
And in the second method, the modulation frequency is the inverse of the input frequency, so the input frequency is subtracted therefrom. Still referring to FIG. 5, due to the inverse meaning of modulation, the phase angle difference between the current and voltage at the output voltage obtained using the two different methods described above will occur in an inverse manner and thus Tsuteko 2
By combining two voltages, the phase angle difference between current and voltage can be completely canceled out in the supply voltage applied to the input conductor. To obtain a converter using this principle, two voltage-controlled oscillators, one oscillating at a modulation frequency ω _n =−(ω _p +ω _i ) and the other at ω _n =ω _p −ω _i , are required. oscillation) is required. FIG. 13 is a circuit diagram of one example of such a converter. The two voltage controlled oscillators are 400 and 401. Oscillator 400 receives a voltage representing a modulation frequency ω _n =ω _p −ω _i from analog summer 402 . The adder has an input representing ω _p obtained from potentiometer 403;
A second input representing ω _i obtained from a frequency-to-voltage converter 404 is provided. A supply input is also provided to the frequency to voltage converter. Also converter 4
The output ω _i of 04 is doubled and sent to the analog adder 405.
and then inverted by an inverter 406,
The voltage representing ω _n for the oscillator 401 is −(ω _p +
ω _i ). Here, a negative sign indicates that the output phase difference of the oscillator 401 is opposite. The amplitude of the output of oscillators 400 and 401 is
Analog multipliers 407-412 set it to a controllable value q. The value q is realized on potentiometer 413 and doubled in amplifier 414.

For full phase control it is necessary to differentially multiply the outputs of oscillators 400 and 401. And this means that the value representing α1 can be changed to potentiometer 4.
This is achieved by setting it above 15. The value is then multiplied by 1/3 in the amplifier, and the analog multiplier 4 is fed with the output of the oscillator 400.
17,418,419. This value α1
is inverted in inverter 420 and added to 1 volt in analog adder 421 to produce a signal equal to 1-α1. This signal is then multiplied by 1/3 in amplifier 422 and applied to analog multipliers 423, 424, and 425 as a signal representing 1/3 (1-.alpha.1). These analog multipliers include an oscillator 41
An output of 0 is given. Nine analog adders 426-434 are provided to which the outputs from each of the three multipliers 417, 418, 419 are applied, and which are combined with the outputs of multipliers 423, 424, 425 in nine different combinations. It is then combined. The combinations are made by taking one output from each set of three multipliers. Additionally, a constant input equal to 1/3 volt is provided to all of the adders 426-434, and their outputs are provided to switch modules SM1-SM9, respectively (see FIGS. 10-12), which switches Three input conductors 435, 436, 437 are connected to three output conductors 43
It is connected to 8,439,440. switch
SM1-SM9 are an amplitude-pulse length converter 101, a pause time and drive circuit 10 as shown in FIG.
2-104, and are connected to drive transformers 105 and 109. The monostable circuits in switches SM1-SM9 are connected to form three separate rings which operate as described above in connection with FIG. Since each ring is connected to a different output conductor, it can be stepped constructively without fear of shorting out the supplies.

Circuits suitable for inverters, analog adders, and analog multipliers are described, for example, in "Electronic Computer Technology" by NR Scott, published by McGraw-Hill Books in 1970.

FIG. 14 shows a high switching speed converter 500.
By applying this, the induction motor 5 can be
01 speed control is performed. A rotary generator 503 is connected to the output shaft 504 of the motor, which generates a voltage on a conductor 505, which is applied to a processing circuit 506 to generate a polyphase sinusoidal output with an angular frequency ω _n and an amplitude control signal q. occurs. These signals are used to control the switches in converter 500 to stabilize the frequency of the power supplied to electric motor 501, as described above. This configuration can be operated in two modes. In the first mode, the speed of the motor remains constant regardless of the load applied to it, in which case conductor 5
The voltage set on 05 is compared with a reference and used to increase its amplitude, which depends on the frequency and q of the power supply applied to the motor 501. Thus, as the deviation between supply frequency and motor speed increases with load, the supply frequency is increased to keep the motor speed more constant. In the second mode, it is a constant torque mode, in which the deviation between the motor speed and the supply frequency is measured and set to a constant value to ensure that the torque provided by the motor is constant. It is maintained.

The circuit configuration shown in Figure 14 allows a generator operated at variable speed to be used by adjusting the angular frequency ω _n of the modulation signal to compensate for fluctuations in the output frequency due to fluctuations in the shaft speed of the generator. It can also be used to stabilize the frequency of the supply voltage that is generated. This configuration can also be used to synchronize the generated power with existing power so that the former is added to the latter.

FIG. 15 illustrates how microprocessor 520 is used to generate the width modulated pulses required to operate switches S1-S9. This microprocessor has clock 521
address output lines 522,
Data input/output line 523, scanning output line 52
4, has a data output line 525. Keyboard 526 receives scan pulses from line 524 and generates corresponding input pulses on conductor 523. ROM527 is microprocessor 520
RAM 528 stores data input from keyboard 526 and data obtained during calculation. A four-digit seven-segment display 529 is provided, driven by scan pulses from the address bus on line 524, to display data entered by keyboard 526 and other information required by the operator. Display. Address bus 522 is also connected to operate selector 530. selector 53
0 directs data received on line 525 to nine latches 531, each storing the required conduction state for switches S1-S9. In operation, microprocessor 520 determines which latch 5
Determine which latch should be in the ``1'' state to indicate that the corresponding switch is conducting, and which latch should be in the ``0'' state to indicate that the corresponding switch is non-conducting. perform the necessary calculations to This calculation is based on the theory already mentioned.

FIG. 16 is a modification of the switch module shown in FIG. 12, in which an inductor L is provided in the collector lead of the transistor, and a diode D and a resistor R are connected in series in parallel with it. These components act as voltage snubbers to limit the rate of switch current rise to a safe value during transients.

FIG. 17 shows an example of the use of a current type snubber consisting of a current path defined by a diode D in series with a capacitor C connected in parallel to the emitter-collector path of a transistor. A resistor R is connected in parallel to the diode D.

FIG. 18 is an example of using a power FET F in a diode bridge of the same type as used in FIGS. 12, 16, and 17. Such transistors can provide very high switching frequencies and thus reduce the need for input and output filters. At present, power FET
Its rating is limited to a few kilowatts, but it is expected that devices that can handle larger amounts of power will be put into practical use in the near future.

Another form of switch module uses a thyristor, which is connected in antiparallel with a forced commutation drive circuit to ensure its conduction at the beginning of each half cycle. In the present invention, since all switches operate simultaneously, a single forced commutation circuit can be used for all power elements using transformer coupling.

Yet another form of switch module is shown in FIG. An advanced fast switching Darlington circuit is used here which uses diodes to limit and discharge the holes stored in the base of the transistor.

The switching frequency of the switch used in the converter is, for example, between 1000 and 100000 Hz, which is significantly higher than the supply frequency and output frequency of the converter. Undesirable harmonics inevitably appear in the input and output waveforms due to switching, and such harmonics can be classified into two types. First, the harmonics resulting from the discontinuity in the switched waveform are of the same magnitude as the harmonics generated by the pulse width modulation converter, and are clustered around frequencies that are multiples of the switching frequency. Since they are significantly higher than the supply frequency, they are not a significant drawback for inductive loads and can in any case be removed from the supply supply, for example by using a conventional series inductor and parallel capacitor. be able to. The second group of harmonics arises from the assumption that the switching frequency is infinitely large so that neither the input nor the output waveform changes within a cycle of the switching frequency. This harmonic has a frequency that is the sum and difference of the input and output frequencies with respect to the switching frequency, and is therefore also sufficiently high frequency to interfere with the operation of the load applied through the converter. Never. Also, there are no fractional harmonics at the input or output of the converter.

The polyphase input required for the converter according to the invention can be obtained, for example, from a single-phase AC power supply by means of suitable reactive elements.

The converter according to the invention is reversible in that the input and output are interchangeable, except that a reference frequency is derived from the input power supply and a transfer switch is then provided to take that frequency from the output conductor. It will be understood that similar operations are possible.
This means that the input power can be derived from the output power despite the fact that a step-up of the voltage is required. An inductor connected to the output conductor for the purpose of smoothing the output waveform provides a step increase in this voltage as a result of the current interruption by the switch. Obviously, such an inductor can also be provided in the input conductor to remove the restriction that the maximum output voltage is half the input voltage.

If a converter of the type shown in Figure 13 is configured to give an output with the same input and frequency and the same number of phases, the input and output conductors will be connected together such that the converter is a reactive power generator. can be connected to. It is desirable to connect an inductor in series with the switches to limit the current through the switches S1-S9.

Although the invention has been described with respect to a particular example, particularly one having three inputs and three outputs, it is understood that the invention is also equally applicable to desirable modifications of the configuration described herein and to any polyphase power supply. It will be clear to those skilled in the art.

In connection with the above description, the following sections are further disclosed.

(1) Input conductors for balanced polyphase AC input voltage systems and AC output voltage systems whose at least one characteristic, such as frequency, amplitude, phase angle, or phase shift, differs from that of the AC input voltage system. A direct AC converter comprising an output conductor and a plurality of bidirectional switches individually connecting each input conductor to each output conductor, the direct AC converter comprising:
a controller having timing means for producing a repeating sequence of adjacent width modulated pulses of as many pulses as the number of phases of the input voltage system; Each phase of the input voltage system is closed in turn to connect each phase of the AC output voltage system, and at any given moment only one of the switches connected to any one of the output conductors is closed. , and further connected to said switch such that each input conductor is always connected to at least one output conductor.

(2) A converter according to paragraph 1, wherein the AC output voltage system is a single-phase system.

(3) The converter of item 1, wherein the AC output voltage system is a polyphase system.

(4) A converter according to item 3, in which a series of pulses is given to each output conductor to each switch connected to the output conductor, and the series of pulses and the input conductor are The correspondence with the transducer is now shifted periodically for different output conductors.

(5) A converter according to clause 4, wherein the timing means comprises a ring of monostable circuits connected in such a way that resetting one circuit sets the next circuit. A converter in which each monostable circuit has an input for a width modulation signal that determines the set time of the circuit, and the sequence of width modulation pulses is taken from the monostable circuit.

(6) A converter according to paragraph 5, which includes means for providing a variable voltage to a monostable circuit and thereby adjusting the response of that circuit to a width modulated signal.

(7) Any converter from paragraphs 1 to 6, including a polyphase sine waveform generator that generates sine waves shifted by equal phase angles, the same number as the number of phases of the input voltage system; A transducer in which each sine wave is applied to a modulator for modulation within the width of the corresponding pulse in the sequence.

(8) A converter according to paragraph 7, including means for adjusting the amplitude of the sine wave generated by the generator.

(9) Any converter from items 1 to 8, which has a pulse sequence of 1000 to 100000 per second.
A repeatable converter.

(10) The converter of paragraph 1, wherein the controller uses digital differential analyzer technology to generate a repeating sequence of width modulated pulses.

(11) A linear AC converter having an input conductor for a balanced N-phase AC input voltage system, and a frequency, amplitude,
At least one of phase angle or phase shift, etc.
an output conductor for a balanced multiphase AC output voltage system having characteristics that differ from those of the input voltage system in one characteristic, and a plurality of bidirectional electronic switches individually connecting each input conductor to each output conductor; A control system comprising two frequency controllable sine wave oscillators, each producing a sinusoidal output with an equal phase angle, the frequency of one oscillator being determined by subtracting the frequency of the input system from the desired output frequency. two oscillators in common, such that the frequency of the other oscillator is equal to the sum of the frequencies of the input and output systems, but the out-of-phase output is opposite to the output of the latter oscillator, Apparatus for controlling the output amplitude of an oscillator in response to a signal; Apparatus for differentially controlling the output amplitude of one oscillator relative to the output of another; A converter characterized in that it includes a control system including a summing device for separately combining each output of the oscillator, and means for connecting the summing device to an electronic switch.

(12) Any converter according to paragraphs 1 to 11, wherein the control system includes a microprocessor and a plurality of output latches, each corresponding to a switch, and the microprocessor A transducer that is programmed to set or reset a latch at the times when the corresponding switch is to be closed or opened.

(13) Any converter among items 1 to 12, which delays the response of each switch to a signal that causes each switch to close, and transmits a signal that causes the other switch to open without delay. , a converter including means for compensating for delays in opening of the switch in response to a control signal.

(14) Any converter according to paragraphs 1 to 13, wherein each switch includes a four-diode bridge circuit and a controllable semiconductor device connected diagonally to the bridge; A converter whose diagonal is connected in the middle of the current path connecting the input conductor and output conductor.

(15) The converter according to item 14, wherein the controllable semiconductor device is a bipolar transistor.

(16) The converter according to item 14, wherein the controllable semiconductor device is a Darlington pair of bipolar transistors.

(17) A converter according to paragraph 15 or 16,
A converter containing a diode device connected to reduce the hole accumulation time of the transistor when switched off.

(18) The converter according to item 14, wherein the controllable semiconductor device is a power field effect transistor.

(19) A converter according to paragraph 14, in which the controllable semiconductor device is connected in anti-parallel configuration with a forced commutation drive circuit for ensuring continuity during each half-cycle when the switch is closed. A converter that is a thyristor pair.

(20) A converter according to any of paragraphs 14 to 19, which includes means for protecting the controllable semiconductor device from high voltage transients when switched.

(21) A circuit configuration including any of the converters set forth in paragraphs 1 to 20, which is connected between a multiphase main power supply and an induction motor, and includes a tachometer connected to the shaft of the motor, and a tachometer that measures the motor speed. A circuit arrangement including a control system connected to compare to a reference speed or output frequency of the transducer and to control the transducer to maintain the motor at either constant speed or constant torque.

(22) A circuit configuration including any of the converters of paragraphs 14 to 21, connected between the multi-layer power supply system and the multi-phase generator, connected to the shaft of the generator and connected to the shaft of the generator. A tachometer that generates a voltage representative of the speed; a control for the converter that, depending on the output of the tachometer, acts on the converter to provide a constant frequency supply to the supply conductor regardless of variations in the shaft speed of the generator; Circuit configuration included in the system.

[Brief explanation of the drawing]

FIG. 1A is a circuit diagram used to explain the operation of a three-phase input single-phase output converter. FIG. 1B shows the switching time of the converter of FIG. 1A. Second
The figure is a vector diagram showing the output voltage combination of the converter of FIG. 1A. FIG. 3 shows the principle of a three-phase input three-phase output converter. 4 and 5 are vector diagrams used to explain the operation of the converter of FIG. 3. FIG. 6 is a block diagram of an actual embodiment of a three-phase input three-phase output converter. Figures 7 and 8
Figures 8a, 8b and 9 together constitute detailed drawings of a three-phase voltage controlled oscillator suitable for the converter of figure 6. FIG. 10 is a drawing of an amplitude to pulse length converter suitable for use in the converter of FIG. FIG. 11 is a dwell time and drive circuit suitable for use in the converter of FIG. FIG. 12 is an example of a switch module suitable for use in FIG. Figures 13a and 13
Figure b shows a transducer capable of performing phase shift control. FIG. 14 shows a motor speed control circuit using a converter according to the invention. FIG. 15 shows an embodiment of the invention that employs a microprocessor to control switching time. 16, 17, 18 and 19 show alternative forms of switches that can be employed in a converter according to the invention.

Claims (1)

[Scope of Claims] 1. A plurality of input phase conductors for a balanced multiphase AC input voltage system and characteristics that differ from those of the input voltage system in at least one characteristic of frequency, amplitude, phase angle or phase shift, etc. a plurality of output phase conductors for a multiphase AC output voltage system having a plurality of adjacent non-overlapping width modulation conductors and a plurality of bidirectional switch means for individually connecting each input phase conductor to each output phase conductor operating said bidirectional switch means at a frequency substantially higher than the frequencies of both said input and output voltage systems, said bidirectional switch means comprising means for producing a repeating series of driven pulses, once for each output phase conductor to said output phase conductor; and connecting all of said input phase conductors to at least one output phase conductor multiple times during any cycle of said input voltage system or said output voltage system. AC converter. 2. A plurality of input phase conductors for a balanced polyphase AC input voltage system and a polyphase AC output having characteristics that differ from those of the input voltage system in at least one of the following characteristics: frequency, amplitude, phase angle, or phase shift. including a plurality of output phase conductors for the voltage system and a plurality of bidirectional switch means individually connecting each input phase conductor to each output phase conductor for repeating adjacent, non-overlapping, width-modulated drive pulses; operating said bidirectional switch means at a frequency substantially higher than the frequencies of both said input and output voltage systems, with means for producing a series of voltages of only one input phase at a time to that output phase conductor for each output phase conductor; an AC converter characterized in that the conductors are connected directly and all of the input phase conductors are connected to at least one output phase conductor multiple times during any cycle of the input voltage system or the output voltage system. An engine speed control system, comprising: means for coupling either the input phase conductor or the output phase conductor to the engine; and means connected to receive an output signal indicative of shaft speed from a tachometer means, an output of the tachometer means; An engine speed control system for controlling the speed of the engine by adjusting width modulated drive pulses produced by the timing means using signals.