CN1081521A - High-precision AC constant current constant voltage control method and device - Google Patents

Abstract

The present invention relates to a kind of high precision constant current constant voltage control method and device.Under computer management, input requires target output AC current effective value, alternating current integrated value and ac cycle in the sampling load, obtain silicon controlled triggering amount according to the effective value computing formula, by removing to trigger controllable silicon behind flip-flop number accurate timing or the counting, periodic duty so constantly makes constant the requirement on the output quantity of current effective value of load.The invention solves the sampling with high precision of high power AC signal and the problem of control, response frequency is 40Hz～40kHz.Changing the sample rate current mutual inductor into voltage transformer (VT) is exactly constant voltage control.

Description

High-precision AC constant current constant voltage control method and device

The present invention relates to realize high precision constant current or the constant voltage control method and the device of alternating current or voltage effective value by regulating controllable silicon in a kind of robotization control.

The output control signal of most of control instruments and industrial controlling control device able to programme all belongs to low power weak signal scope in automation control area at present, therefore requiring to connect a power converter could realize powerful alternating current equipment is controlled, and existing its conversion accuracy of AC power converter is all very low, they all directly determine controllable silicon triggering amount by the control signal of input, go to finish high-power output by controllable silicon again, the shortcoming of this control method is that conversion accuracy is very low, do not have functions such as output constant current or constant voltage, running into voltage fluctuation, will produce out-of-control phenomenon when frequency drift, the interference of loaded impedance variation etc.The ZK series controllable silicon adjuster that the power converter representative products that manufactures and designs is in this way produced by the automatic synthetic fibre instrument in Shanghai six factories.

The purpose of this invention is to provide a kind of high precision constant current or constant voltage control method and device of realizing alternating current or voltage effective value by the adjusting controllable silicon.

Constant current control is the electric current in the Current Transformer sampling load, and constant voltage control is with the voltage in the load of voltage mutual inductor sample.Other control methods are identical, so following general the method for introducing constant current control.

A kind of high-precision AC constant current control method the steps include:

(1) through amplifying it is transformed into absolute value signal to ac current signal by the current transformer sample detecting, then with the sample integrated value of this absolute value of double integrator A/O, with 2 counters respectively to integration and quadratic integral timing, make the integral multiple n that equals ac cycle for integral time, read the value in these two counters, just obtain AC signal integrated value and ac cycle value;

(2) triggering mode that input requires target alternating current effective value and can select in microcomputer, they are respectively phase shift triggering, zero cross fired, soft-start mode; According to the integrated value that input target and sampling obtain, in microcomputer, calculate to such an extent that silicon controlled triggering amount is phase shifting angle or controllable silicon break-make ratio value according to following formula,

The computing formula that phase shift triggers is:

$\mathrm{Ar\; =}\frac{\mathrm{<figure-callout\; id="2"\; label="ApK"\; filenames="921085079\_DRIMG2.png"\; state="\{\{state\}\}">ApK</figure-callout>}}{\sqrt{2}}\frac{\phi }{\pi }\frac{\mathrm{Sin2\phi }}{\mathrm{2\pi }}{)}^{\mathrm{1/2}}\mathrm{(1)}$

The phase shift time

t _c＝ (φ)/(2π) T （2）

In the formula: the Apk-current peak;

The T-ac cycle;

φ-phase shifting angle;

The Ar-current effective value;

The computing formula of zero cross fired is:

(M)/(M+N) ＝（ (Ao)/(Ai) ） ²（3）

In the formula: M-conducting cycle;

M-closes cycle;

Ao-requires the export target current effective value;

Current effective value in the Ai-load.

Dwindle M and N simultaneously with highest common factor, improve response speed.

Annotate: the various current values in the formula are sent out the mode that the correspondent voltage value is exactly constant voltage control that makes into.

(3) triggering amount t _C1M and N send flip-flop number to remove to trigger controllable silicon respectively behind time-delay or quantitative counting;

Whole constant current process is exactly constantly to repeat above-mentioned steps, and sampling-computing-counting-triggering remains desired steady current desired value.

The occasion that alters a great deal at load current, adopting soft-start mode is that phase shift triggering and zero cross fired intersection are used, when sampling full conducting electric current greater than 1.3 times of ratings, the work of employing phase shift system, it can avoid heavy current impact, otherwise just switch to zero trigger mode work, can clean electrical network, also have bigger at Ai/Ao, and frequency of operation is lower, the resolution characteristic of zero cross fired automatically switches to the work of phase shift triggering mode when not reaching precision index, if but the frequency of operation resolution precision that phase shift triggers during greater than 960Hz is too low, at this moment can automatically switch to zero trigger mode work, the frequency of internal clocking is subjected to certain restriction, can select the 1.5MHz clock for use, it is 1/15000 to the phase shift resolution of 50Hz power frequency, and the resolution of zero cross fired is 1/2000 under same power frequency, this is because the total amount of M+N is excessive as obtaining, will make cycle period oversize, the real-time of influence control, but along with increasing of supply frequency, the resolution characteristic of zero cross fired triggers than phase shift conversely becomes better and better, so should select zero cross fired for use greater than 400Hz, just can not trigger with phase shift greater than 960Hz, this zero cross fired and phase shift trigger can automatically switch in device of the present invention.

Designed according to the method described above constant-current control device, it comprises: microprocessor, keyboard, display, storer, double integrator sample circuit, integration counter, quadratic integral counter, an A/O controller, trigger Timer, silicon controlled toggle, multi-way switch, amplifier and absolute value circuit, midget relay; Serial connection curtage mutual inductor in load circuit, its pair limit winding is connected with absolute value circuit with amplification by the contact of midget relay, amplification is connected with multi-way switch with absolute value circuit, by the detected AC signal of mutual inductor through amplifying and being transformed into absolute value signal, sample by double integrator A/O sample circuit through multi-way switch, by integration counter and the timing of quadratic integral counter, microprocessor is connected with A/O controller and triggering Timer by internal bus, trigger Timer output and arrive silicon controlled toggle through photoelectrical coupler, its output triggers high-power silicon controlled rectifier.

The embodiment of the invention elaborates in conjunction with the accompanying drawings.

Fig. 1 is a high-accuracy and constant method of flow control flow chart;

Fig. 2 is a high-accuracy and constant flow control device circuit block diagram;

Fig. 3 is a high-accuracy and constant flow control device schematic circuit.

By Fig. 1, shown in 2, at first initialization, then by current transformer sampling alternating current and periodic signal, signal through amplify and absolute value circuit through multi-way switch, by double integrator A/O this absolute value of sampling, by an integration, the timing of quadratic integral counter, just obtain AC signal integrated value and ac cycle value, whether inquire has fault, fault alarm is arranged, and non-fault is imported effective value and the triggering mode that requires output current in microcomputer with keyboard, according to sampled value and require output valve, according to formula (1), (2), (3) calculate silicon controlled triggering amount by microprocessor.Can accurately phase shift in 3 °～177 ° scopes if trigger the present invention with phase shift, the triggering amount that calculates is to be obtained after to the internal clock signal counting by flip-flop number time delay.If adopt zero cross fired, calculate conducting cycle M and close cycle N, down reduce M and N simultaneously in advance satisfying control accuracy, can accelerate governing speed like this, go to trigger controllable silicon work through behind the counting to synchronizing pulse by triggering amount sending buffer that calculates and flip-flop number.

The constant-current control device that designs according to the high-accuracy and constant method of flow control is by shown in Figure 2, it comprises: microprocessor, keyboard, display, storer, the double integrator sample circuit, an integration counter, the quadratic integral counter, the A/O controller, trigger Timer, silicon controlled toggle, multi-way switch, amplify and absolute value circuit, midget relay, the curtage mutual inductor that in load circuit, is connected in series, its pair limit winding is connected with absolute value circuit with amplification by the contact of midget relay, amplification is connected with multi-way switch with absolute value circuit, by the detected AC signal of mutual inductor through amplifying and being transformed into absolute value signal, sample by double integrator A/O sample circuit through multi-way switch, by an integration counter and the timing of quadratic integral counter, microprocessor is connected with A/O control and triggering Timer by internal bus, trigger Timer output and arrive silicon controlled toggle through photoelectrical coupler, its output triggers high-power silicon controlled rectifier.

Fig. 3 represents the concrete wiring diagram of embodiment, and input sample is partly represented the sampling circuit of three-phase current, and output has only been represented single-phase circuit in Fig. 3, is just combined by a plurality of identical unilines for heterogeneous triggering.

By shown in Figure 3, J ₁～J ₆Be midget relay, they are used for switched input signal, P ₁～P ₅Be operational amplifier, P ₆Be comparer, by amplifier P ₁, capacitor C ₁, resistance R ₂～R ₄Form an amplifier, amplifier P ₂, P ₃And resistance R ₅～R ₉Potentiometer M and diode O ₁, O ₂Form absolute value circuit, N is used for regulating the symmetry that positive negative signal amplifies, I ₂And I ₃Composition is to the gating circuit of relay.Multi-way switch I ₁Be used for switching auxiliary signal, by P ₄, P ₅, R ₁₀, C ₂The integrating circuit and the comparer P that form ₆Form the double integrator sample circuit, through R ₁₁, R ₁₂Dividing potential drop produces negative level and is added on the integrator, makes that zero inclined to one side relative integral device of other circuit all is a positive signal, comparer P ₆Be used for detecting the termination of quadratic integral, R ₁₃And R ₁₄Form positive-feedback circuit and quicken comparer counter-rotating, double integrator sample circuit and multi-channel electronic switch I ₄Connect, the selection of integrated signal is by I ₄Switch I ₄By EPROM plate I ₅Control is by I ₅, I ₇And step-by-step counter I ₆Connect into the A/O controller, I ₇In the TIME(Timer) synchronizing pulse is carried out pre-frequency division, deliver to step-by-step counter I then ₆Middle stepping control I ₅I ₅Be an EPROM, it has 12 address wires and 8 output lines, and one group of logical signal is exported in corresponding each address, and these signals are used for controlling I ₄Select integrated signal, control I ₈Count integral time and quadratic integral time respectively, finish quadratic integral after, block I ₆(no longer stepping) and generation A/O look-at-me.

The signal of A/O sampling has two kinds: large-signal: 0～1V, it directly delivers to I ₄Input end, also have a kind of small-signal: 0～70mV, they deliver to I after amplifying ₄Input end, the two kind reference signals corresponding with high low signal are respectively 0.6～0.9V, 50～65mV earlier carries out integration one time to each sampled value (positive level signal) in the sampling, controlled by the A/O controller integral time, it always gets 2 of synchronizing pulse ⁿDoubly, and write down integral time one time, as ledex I with an integration counter ₆Just begun quadratic integral work when stepping to the precalculated position, quadratic integral carries out integration to negative reference signal, and the time of quadratic integral is counted by the quadratic integral counter, I ₈Be 8253 programmable counters it comprised integration counter and quadratic integral counter, as comparer P ₆The sampling task has just been finished in counter-rotating.

For making A/O sampling section high-precision low cost, the present invention adopts the auto zero offset compensation of software, combination of hardware and the automatic calibration of reference signal, and its job step is as follows:

A, midget relay of gating are closed multi-way switch I ₁, measure external signal value Vx one time, obtain integrated value t through integral counting _Xi

B, close all midget relaies, connect multi-way switch I ₁Zero passage partially, measure once zero number of believing one side only Vo, obtain integrated value t through integration counter _o;

C, close all midget relaies, connect and connect I ₁Some internal reference signal, measure the absolute value V of an internal reference signal _E, get its integrated value t through integration counter _E;

D, calculate Vx with following formula,

${\mathrm{Vx\; =\; V}}_E\frac{t_x{\mathrm{-\; t}}_o}{t_E{\mathrm{-\; t}}_o}\mathrm{(4)}$

Find out that from formula (4) all zero partially all obtain full remuneration, so components and parts are required very low, the precision of Vx only depends on V _EPrecision, irrelevant with loop gain, therefore in the A/O loop, only need some fixed resistances, and without potentiometer.Because the stability and the reliability of fixed resistance are all good than potentiometer, improved the quality of complete machine like this.

In order thoroughly to eliminate of the interference of power supply power frequency to A/O, adopted the time of an integration and the method for electrical network cycle synchronisation, and the time of writing down an integration, also be the sampling ac cycle, because the electrical network cycle is a variable, so the integrated value in the formula (4) also will be revised in advance

t _x＝t _x′ (K)/(Tx) （5）

In the formula: a Tx-count value integral time;

T ' _x-quadratic integral time counting value;

The K-constant, desirable 30000(1.5MHz clock, corresponding 20ms);

t _xQuadratic integral value after the-conversion.

By shown in Figure 2, reference generator is by I ₁₅With resistance R ₁₇～R ₁₉Form, reference signal is obtained by the fixed resistance dividing potential drop, by calculating the nominal value V that can obtain reference signal _E', externally connect a signal and measure its exact value Vx with high-precision meter, with calibration command this signal of sampling, use V _E' substitution (4) formula calculates Vx ', and shows at display, if the exact value that this displayed value and high-precision meter measure has error, just revise key and revised with keyboard, make it equal Vx value accurately, revised the notice microprocessor, microprocessor is just according to following formula calibration V _EValue.

V _E＝V _E′ (Vx)/(V′x) （6）

This accurate V has been arranged _EValue just can calculate accurate Vx value with formula (4), so just obtains the low high A/O sample circuit of precision of cost.

The output triggering part of present embodiment is by integrated circuit I ₉～I ₁₄And photoelectrical coupler, highly sensitive controllable silicon and resistance R ₁₅, R ₁₆Be formed by connecting I ₁₄Be flip-flop number, the startup of counter is by I ₇Control to what amount is counted by I ₁₀Select, it is that internal clocking is counted that phase shift triggers, and zero cross fired is that counting finishes at I to the synchronizing pulse counting ₁₄Output terminal produce a pulse signal and produce once output and interrupt and can trigger I ₁₃Remove to drive photoelectrical coupler after the buffering, I ₁₁Each zero crossing in AC wave shape sends a synchronizing pulse, delivers to I through photoelectrical coupler ₇Deng parts, I ₁₁The trigger pip control that reception is sent here through photoelectrical coupler triggers highly sensitive controllable silicon, and its output triggers high-power silicon controlled rectifier work.I ₁₁Integration module is the TO-2 silicon controlled toggle, its Q end is the synchronizing pulse output terminal, this synchronization pulse is used for the zero-time of synchronous triggering counter in phase shift triggers, in zero cross fired, be used for counting conducting cycle M and close cycle N, this synchronizing signal also is used for integral time of synchronous double integrator A/O, make the integral multiple that always equals power frequency for integral time, suppress the interference of electrical network with this to integration, time to an integration counts, also just recorded sinusoidal wave period the period T in Here it is the formula (3).The TO-2 silicon controlled toggle is provided with two signal input parts, and one is trigger end immediately, and in the phase shift system, delay time is once delivering to this input end to sending a pulse, and TO-2 produces a trigger pip immediately and removes the conducting controllable silicon; Another is the zero cross fired end, and TO-2 is at sinusoidal zero crossing this input end state of sampling, and decision triggers the controllable silicon conducting and still closes.

Zero cross fired is instantaneous in conducting: inductive load≤0.2A;

Resistive load≤3V.

Can guarantee that like this output waveform is still sinusoidal wave basically.

The example of application success of the present invention is a TCP series multifunctional temperature controller, this instrument is mainly used to control the temperature of electric furnace, the temperature signal that its sampling is sent here from thermopair is obtained the magnitude of current that needs control through adaptive algorithm, by the present invention used control method and device electric current is realized constant current control then.

The invention solves the sampling with high precision of AC signal and the problem of control, can accomplish that control accuracy is better than 5 * 10 ^-4; Reference constant current from several amperes to several kiloamperes, frequency is 40Hz～40KHz, working method has phase shift triggering, zero cross fired and soft start, the present invention is applicable to the various occasions that alternating current equipment is accurately controlled.

Claims (7)

1, a kind of high-precision AC constant current constant voltage control method the steps include:

(1) can through amplifying it be transformed into absolute value signal to alternating current or ac voltage signal by current transformer or voltage transformer (VT) sample detecting, then with the sample integrated value of this absolute value of double integration A/D, with 2 counters respectively to integration and quadratic integral timing, make the integral multiple n that equals ac cycle for integral time, read the value in these two counters, just obtain AC signal integrated value and ac cycle value;

(2) input requires target alternating current or voltage effective value and available triggering mode in microcomputer:

They are respectively phase shift triggering mode, zero trigger mode, soft-start mode, the integrated value that obtains surveying alternating current or voltage according to input effective value of target and sampling is calculated to such an extent that silicon controlled triggering amount is phase shifting angle or controllable silicon break-make ratio value in microcomputer according to following formula

The computing formula that phase shift triggers is:

$\mathrm{Ar\; =}\frac{\mathrm{ApK}}{\sqrt{2}}\frac{\phi }{\pi }\frac{\mathrm{Sin2\phi }}{\mathrm{2\pi }}{)}^{\mathrm{1/2}}\mathrm{(1)}$

The phase shift time: t ₀=(Φ)/(2 π) l (2)

In the formula: the Apk-current peak;

φ-phase shifting angle;

The T-ac cycle;

A τ-current effective value;

The computing formula of zero cross fired is:

(N)/(N+N) =( (Ao)/(Ai) ) ²(3)

In the formula: N-conducting cycle;

N-closes cycle;

Ao-requires the export target current effective value;

Current effective value in the Ai-load.

(3) triggering amount t _C1N and N send flip-flop number to remove to trigger controllable silicon respectively behind time-delay or quantitative counting;

Whole constant current constant voltage process is exactly constantly must repeat above-mentioned steps, and sampling-computing-counting-triggering remains desired steady current, voltage-target.

2, high precision constant current according to claim 1, constant voltage control method, its soft-start mode are that phase shift triggering and zero cross fired intersection are used.

3, a kind of application rights requires 1 described method and the constant-current control device that designs, it comprises: microprocessor, keyboard, display, storer, the double integrator sample circuit, an integration counter, the quadratic integral counter, the A/O controller, trigger Timer, silicon controlled toggle, multi-way switch, amplify and absolute value circuit, midget relay, the curtage mutual inductor that in load circuit, is connected in series, its pair limit winding is connected with absolute value circuit with amplification by the contact of midget relay, amplification is connected with multi-way switch with absolute value circuit, by the detected AC signal of mutual inductor through amplifying and being transformed into absolute value signal, sample by double integrator A/O sample circuit through multi-way switch, by integration counter and the timing of quadratic integral counter, microprocessor is connected with A/O controller and triggering Timer by internal bus, trigger Timer output and arrive silicon controlled toggle through photo-coupler, its output triggers high-power silicon controlled rectifier.

4, constant-current control device according to claim 3 is characterized in that, J ₁～J ₆Be midget relay, be used for switched input signal, by being transported into P ₁, capacitor C ₁, resistance R ₂～R ₄Form an amplifier, amplifier P ₂, P ₃And resistance R ₅～R ₉, potentiometer M and diode D ₁, D ₂Form absolute value circuit.

5, constant-current control device according to claim 3 is characterized in that, by multi-way switch I ₁, midget relay J ₁～J ₆, by P ₄, P ₅, R ₁₀, C ₂The integrating circuit and the comparer P that form ₆Form the double integrator sample circuit, through R ₁₁, R ₁₂Dividing potential drop produces negative level and is added on the integrator, makes that zero inclined to one side relative integral device of other circuit all is a positive signal, comparer P ₆Be used for detecting the termination of quadratic integral, R ₁₃And R ₁₄Form positive-feedback circuit and quicken comparer counter-rotating, double integrator sample circuit and multi-way switch I ₄Connect, the selection of integrated signal is by I ₄Switch I ₄By EPROM plate I ₅Control is by I ₅, I ₇And step-by-step counter I ₆Connect into the A/O controller, I ₇In the TIME(Timer) synchronizing pulse is carried out pre-frequency division, deliver to I then ₆Middle step-by-step counting.

6, constant-current control device according to claim 3.It is characterized in that the output triggering part is by integrated circuit I ₉～I ₁₄And photoelectrical coupler, highly sensitive controllable silicon and resistance R ₁₅, R ₁₆Be formed by connecting I ₁₄Be flip-flop number, the startup of counter is by I ₇Control to what amount is counted by I ₁₀Select, it is that internal clocking is counted that phase shift triggers, and zero cross fired is counted synchronizing pulse, and counting finishes at I ₁₄Output terminal produce a pulse signal and produce once output and interrupt and can trigger I ₁₃Through I ₁₂Remove to drive photoelectrical coupler after the buffering, I ₁₁Each zero crossing in AC wave shape sends a synchronizing pulse, delivers to I through photoelectrical coupler ₇Deng parts, I ₁₁The trigger pip control that reception is sent here through photoelectrical coupler triggers highly sensitive controllable silicon, and its output triggers high-power silicon controlled rectifier work.

7,3,6 described constant-current control devices as requested is characterized in that I ₁₁Be the TO-2 silicon controlled toggle, its Q end is the synchronizing pulse output terminal, other is provided with two signal input parts, one is trigger end immediately, and in the phase shift system, delay time is once delivering to this input end to sending pulse, TO-2 produces a trigger pip immediately and removes the conducting controllable silicon, another is the zero cross fired end, and TO-2 is at sinusoidal wave zero crossing this input end state of sampling, and decision triggers the controllable silicon conducting and still closes.

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