JPS6111548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reference cosine wave derivation device for generating thyristor gate pulses in a static power converter. The cosine cross timing principle is generally known in the static power converter art. For example, in 1976, “Static Power Frequency Changes” by Gyugyi and Pelly, edited by John Wiley, Vol.
I would like to refer to pages 279-298. A known advantage of using a cosine wave as a time reference is that it provides a direct function between the cosine voltage and the output voltage of the thyristor bridge. It is also known to transform a reference sine wave received from a power supply to generate a cosine wave, and to compare the cosine wave with a variable DC control voltage to determine the thyristor conduction angle.
Prior art techniques that handle input sine waves in special ways have had several problems. Therefore, in US Pat. No. 3,983,494, the aim was to convert a sine wave into a cosine wave to make it frequency insensitive.

It is an object of the present invention to generate from a common phase power supply sine wave a series of cosine waves, one after the other, which are combined in sequence with successive phase lines, each cosine wave having a required phase shift in the sequence of firing of the thyristors. and that the ignition takes place under a single and common comparator.

According to one embodiment of the invention, a single line frequency synchronization signal is utilized to derive a plurality of cosine-crossed gate angle reference waves, each of which is coupled to a power transformer in turn associated with several thyristors. It has an additional phase shift to compensate for the phase shift provided by devices such as. A common variable voltage control signal and comparators are used to apply various gating signals to the thyristor multiplexer and drive circuits. A plurality of switches controlled by firing logic sequence the selection between the plurality of cosine reference waves to be generated.

Hereinafter, the present invention will be explained in detail by way of examples with reference to the drawings.

One conventional method to control the gate angle α in a six-thyristor power converter is to generate six independent cosine voltages equally spaced by 60° and compare each cosine voltage to a reference voltage. That's true. When each cosine wave voltage in turn equals the reference voltage, the thyristor associated with the particular cosine wave is fired. The six thyristors are typically
It is in a conventional three-phase rectifying bridge and the average voltage from the bridge is varied by varying the gate angle α. This is done by changing the reference voltage. Such a prior art configuration is shown in FIG. A static power converter 1, typically consisting of a six thyristor bridge, is supplied with alternating current power from a power transformer T. The thyristors are gated via line 2 by a gate pulse generator (GPG) 3 which fires the thyristors in turn at a conduction angle determined by a comparator 4.
As shown in the prior art, a cosine crossed pulse timing method is used to determine the firing angle with reference to a DC reference voltage v _c . In this regard, in 1971 John Willy
“Thyristor Phase-Controlled Converters and Cycloconverters” by B R Pelly, published by Wiley & Sons.
The cosine wave is derived from an auxiliary transformer ^T1 having a triangularly connected primary winding and a secondary winding with six windings equally distributed. The secondary winding generates six reference sine waves on each line 7, spaced π/3 apart from each other, each sine wave being connected to a corresponding wave converter ( wave
converter) 8. Thus, in such a configuration six wave converters and six comparators are required to fire six thyristors. The gate signals GATE1 to GATE6 are thus derived and applied to the gate pulse generator 3 one after another.

U.S. Pat. No. 4,017,744 uses digital technology to generate six time waves by means of a ramp or linear time function, each of which has a proper waveform predetermined by the logic of the gate pulse generator. A method for selecting multiple time references with phase directly from a single wave generator is shown.

According to the invention, as shown in FIG. 2, a single wave converter 8 is used to convert the sine wave from the auxiliary transformer T' into a cosine wave. The cosine wave on one output line 9 is applied to a single comparator 4 together with the reference voltage V _c on line 12, and at the moment the threshold of comparator 4 is exceeded, the gate pulse generator 3
A gate signal for this purpose is generated on line 13. Wave converter 8 is controlled by line 10 according to the logic of gate pulse generator 3. As a result, the wave converter 8 is
One of several unique cosine waves is instantaneously formed with reference to the sine wave input from the auxiliary transformer T' via the line 11.

Referring to FIG. 3, six cosine waves associated with each of the six thyristors are shown in relation to a reference voltage _Vc . Each conduction period is indicated by a solid line on the curve and is indicated by its relationship at the instant of commutation of the "next" thyristor to be fired in turn.
The cosine waves that occur one after another are expressed as follows: Vcos (2πf _L t+φ ₁ ); Vcos (2πf _L t+
φ ₂ )...... Vcos (2πf _L t+φ ₆ ) where φ ₂ = φ ₁ + π/3... These six cosine waves are usually generated individually, i.e. often in a three-phase primary winding. and a secondary winding having six windings for generating six cosine waves. Such a method requires six matched filters, six comparators and a complex transformer. According to this invention, in order to generate all six cosine waves,
Only one single phase sinusoidal synchronization signal is required.
This method inherently has excellent filtering properties.

Referring to FIG. 4, two sets of switches S ₁ -S ₆ and S' ₁ -S' ₆ , the first set and the second set, are connected to the integrator 2, respectively.
2 to line 25 output integrator 24 to line 26
The outputs to the first set of switches have different gains L ₁
-L ₆ to multiple amplifiers with different gains K ₁ -K ₆ for the second set of switches. A 1:1 relationship is established between the gain and the corresponding set of switches. All parallel lines of each set have one connection point, which is (L ₁ −
J ₁ for L ₆ ) and J ₂ for (K ₁ −K ₆ ). The two sets of switches are operated in parallel, and the output from J ₁ to line 27 and the output from J ₂ to line 28 are summed in adder 29 to produce the desired cosine wave signal on line 9. This cosine wave signal is applied to a non-inverting input terminal of an operational amplifier used as a comparator 4. Comparator 4 has a threshold defined by the reference voltage v _c on line 12 applied to its inverting input terminal. The gate signal on line 13 is input to gate pulse generator 3. As is well known, the gate pulse generator 3 includes a ring counter that determines the order of the thyristors and a pulse forming circuit that drives the thyristors. Six gate pulses GP ₁ -GP ₆ are applied by line 2 to each thyristor. Two sets of switches S ₁ −S ₆ and S′ ₁ −S′ ₆
The first set is controlled by lines 10 to 17 and the second set by lines 10 to 18 according to the logic for thyristor firing in gate pulse generator 3.

By simple trigonometry, cos(ωt+φ)=cosω
The relationship tcosφ−sinωtsinφ holds true. From this equation, it can be seen that the adder 29 adds the two trigonometric functions derived from each integrator 22 and 24 as follows. That is, Asin2πf on line 11
_L t is phase-shifted by 90° by the integration of the integrator 22 and becomes -A _I Acos2πf _L t. The integrator 24 once again shifts the phase of this function by 90 degrees and converts it into -A _I ² Asin2πf _L t. In this way, two functions cos ωt and -sin ωt are derived on the lines 25 and 26, cos φ and sin φ, which are functions of a particular phase φ.
It remains to determine the coefficients of . each gain
L ₁ -L ₆ and K ₁ -K ₆ are in a one-to-one relationship to produce six pairs of coefficients that are combined with the signals on lines 25 and 26.

Switches S ₁ -S ₆ , S' ₁ -S' ₆ connect lines 17 and 18
_The required common thyristors are more sequentially controlled so that in each pair L ₁ , K ₁ :L ₂ , L _{2 .} . . A phase shift takes place.

If, at a given time, the exact instantaneous value of the power on the line 11 is known for the associated pair of thyristors, a signal corresponding to one of the curves of FIG. 3 is applied to the comparator 4. Therefore, the curve is followed from t ₀ to time t ₁ when the curve crosses v _c , and at t ₁ the thyristor 1TH is fired by the line 13. The period from t ₁ to t ₂ changes according to a curve on the line 9, and at time t ₂ the thyristor 2TH is fired in response to the gate signal on the line 13. The same operation continues below. v _c changes from REFmin to REFmax and changes the gate angle α in the range from zero to π.

As shown in FIG. 4, the synchronization (SYNC) signal received on line 11 is a sine wave, Asin2πf _L t, at the same frequency as the three-phase AC power supply that powers the thyristor bridge. However, f _L is the power supply frequency. This signal is input to a first integrator 22 which precisely phase shifts the SYNC signal by approximately 0 degrees and waves high frequency voltage spikes and notches that may cause false gating. The output of this integrator 22 is transmitted via a line 23.
A second integrator 2 that further phase-shifts the SYNC signal by 90°
4. A pair of switches are closed,
Introduce gains Kn and Ln, respectively. Signal (−
A・Al ²・Kn) sin2πf _L t and (A・AI・Ln)
cos2πf _L t are obtained and summed to yield one effective cosine wave V cos (2πf _L t+φn), which is compared with the reference voltage v _c to determine when the next thyristor should be fired. When the comparator 4 detects equality, the gating operation is started. When the next switch pair is closed and the previous switch pair is opened, it causes a new cosine wave V cos (2πf _t +
φn ₊₁ )=Vcos(2πf _L +φn+π/3) is sent to comparator 4 to determine when the next thyristor should be fired. Although the sine and cosine values have been explained as voltages, it is important to understand that all sine, cosine and coefficient values are binary numbers taken by one processor.
It is also conceivable that the SYNC signal is immediately and continuously converted to binary. Therefore all additions, multiplications and logic are also handled by that processor.

Again the mathematical relationship asinθ+bcosθ=Ccos(θ+
φ), the constants Ki and Li are such that the desired phase shift φn and amplitude V of the resulting cosine wave are generated6
must be selected in pairs to be the one required for each of the three cosine waves.

Like all analog integrators, numerical integrators with constant sampling frequency tend to have a gain that is inversely proportional to the input frequency. In such a case, the value of A _I will be inversely proportional to the power supply frequency. This would have to be compensated for using a variable power supply frequency.

The solid line in Figure 3 indicates the (+) of the comparator at each moment.
It shows the actual value going to the input terminal. The thyristor is fired as shown. The gate angle can be varied from 0° to 180° by changing v _c . The voltage from a converter bridge operating with continuous current is approximately proportional to cos α. Gate angle α is proportional to arc cos(v _c ). Therefore, the DC voltage from the bridge is linearly proportional to v _c , which is a typical advantage of a cosine-cross gate pulse generator, as discussed above.

Constant coefficients Ki and Li are calculated to account for the additional phase shift between the SYNC signal and the bridge AC voltage due to the power transformer T and auxiliary transformer T' or other factors. However, the phase shift must be constant over the range of power supply frequencies over which the gate circuit must operate.

When implemented with analog technology, inexpensive amplifiers and analog switches exist. Analog switches can be used to continuously vary the gain of the amplifier to provide six gain constants Ln. The same applies to various values of Kn. 2
one integrating amplifier, two gain amplifiers (Kn and Ln
(for constants), one summing amplifier and one comparator, a minimum of six amplifiers would be required to meet the circuit requirements. This compares favorably to the six comparators used in conventional methods. Therefore, the gain switching logic can be handled by a single programmable read only memory (PROM). This method is the fifth
As shown in the figure.

FIG. 5 may be understood with reference to FIG. Three solid-state devices, e.g. model IH4019, are connected to a switch (S ₁ -
S ₆ ) and (S′ ₁ −S′ ₆ ). Each of these solid-state devices has four FET switches, which according to the logic of the decoding logic circuit 30, of type IM5600, arranged in the gate pulse generator 3, connect the lines C ₁ -C ₄ ; C ₅ , C ₆ ,
Controlled by _C1 , _C2 and _C3 - _C6 . Comparator 4
provides a clock pulse to a 3-bit counter 31, which in turn provides a clock pulse to a 3-bit counter 31, which is in turn connected to a decoding logic circuit 30 and another
one decoding logic circuit 32 (this is a gate pulse GP
1-Generates GP6). The control signals from the decoding logic circuit 30 are C ₁ -C ₆ as well as the signal PS
(sine wave selection, e.g. for lines 26 and 28) and PC
(cosine wave selection eg for lines 25 and 27). Signals PS and PC control FET and 34.
As shown in FIG. 5, operational amplifier 35 is associated with switches S' ₁ -S' ₆ on the sine wave side, while operational amplifier 36 is associated with switches S ₁ -S ₆ on the cosine wave side. These operational amplifiers are inserted in the circuit with resistors R _x and R _s to give a gain depending on the value of eg R _x with selection by C ₁ -C ₆ . In this way, the line 2 on the output side of the operational amplifier 35
On the output side of the operational amplifier 36, a wave V representing ±R _S /R _{X ·} SIN is derived.
A wave representing R _x COS is derived.

In the above discussion a signal in the form of a cosine wave has been described assuming that it determines when the "next" thyristor is to be fired. However, within the scope of this invention, the signal may be directly and continuously converted to binary numbers such that all sine, cosine and coefficient values are binary. This can be accomplished by data processing within a microprocessor that handles addition, multiplication, and other logical operations as described above.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional thyristor gate pulse generator, Fig. 2 is a block diagram of a thyristor gate pulse generator using the present invention, and Fig. 3 shows the firing sequence using the present invention. FIG. 4 is a schematic circuit diagram of a thyristor gate pulse generator for controlling the firing angle of a thyristor using the cosine wave generator of the present invention, and FIG. 5 is a preferred curve diagram of the present invention. FIG. 2 is a schematic circuit diagram showing an example. 3... Gate pulse generator, 4... Comparator, 2
2, 24... Integrator, 29... Adder, v _c ...
Reference voltage, S ₁ −S ₆ , S′ ₁ −S′ ₆ ... switch, L ₁ −
L ₆ , K ₁ −K ₆ ...amplifier gain, 35, 36...
operational amplifier.

Claims (1)

[Claims] 1. In order to convert one single-phase sine wave signal into a plurality of polyphase cosine waves in which phase shifts are equally distributed sequentially from one cosine wave to the next cosine wave, the sine wave means for responsive to a signal and integrating the sinusoidal signal to form a cosine-shaped first signal; responsive to the first signal, means for integrating the first signal to form a sinusoidal second signal; means for, responsive to said first signal;
means for amplifying the first signal by a selected amount to generate a first periodic signal at the frequency of the sinusoidal signal; means for adding the first periodic signal and the second periodic signal to generate a second periodic signal at the frequency of the sine wave signal, and adding the first periodic signal and the second periodic signal to generate one of the plurality of cosine waves. a cosine wave generator comprising means for generating a cosine wave, the selected quantity being varied in predetermined steps to generate the plurality of cosine waves; the cosine wave generator and a reference control; a comparator responsive to voltage; and a gate circuit operated by the comparator to sequentially fire a plurality of thyristors, the cosine wave generator being controlled by the gate circuit and then firing a plurality of thyristors. A thyristor gate pulse generator adapted to select a corresponding predetermined amount of gain in the cosine wave generator in relation to the thyristor to be arced.