CN1477779A - Control system of voltage type pulse-width-modulation converter and its method - Google Patents

Abstract

The present invention relates to a control system of voltage type pulsewidth modulated converter and its method. According to the power factor angle phi solved by phase discriminator the conversion calculation device of said control system can solve the off-set quantity delta alpha of control angle alpha and can solve the off-set quantity delta M of modulated depth M according to D.C. voltage. The control system adopts the current feedforward phasor regulation method to raise the dynamic performance of the system, and the pulsewidth modulator of said system can utilize the alpha value and M value obtained respectively by phase angle control proportional-integral regulator and voltage control proportional-integral regulator to drive main circuit of the converter.

Description

The control system and the method for voltage-type pulse-width modulation current transformer

Technical field

The present invention relates to the control system and the method for voltage-type pulse-width modulation (PWM) current transformer.

Background technology

In the power converter of AC-DC and DC-AC, can the alternating current of electrical network be become the direct current supply load with the PWM current transformer, and the direct current that the outside produces is become alternating current feed back to electrical network.

Though it is multiple that the control method of PWM current transformer has, its purpose all is in order to realize the two-way flow of High Power Factor and energy.The predicted current control (PCFF), the width of cloth that mainly contain current hysteresis ring control (HCC), fixed switching frequency are at present regulated control methods such as (PAC) mutually.Preceding two kinds of methods all adopt the Direct Current Control mode, can follow the tracks of the variation of load current effectively, and dynamic property is good.But the switching frequency of electric current hysteresis control method thereof can change along with the variation of load current, brings additional electric stress to switching device.Predicted current control method more complicated is subjected to influence that parameter changes greatly.Width of cloth phase adjustment control method adopts the indirect current control mode, and it is comparatively easy.The someone proposes to adopt saddle type ripple pulse-width modulation (SAPWM, Saddle PWM) optimizing the width of cloth controls mutually (referring to people such as Chen Guocheng: " in the big output characteristic of optimization PWM pattern control low-converter ", China's speed regualtion of AC motor transmission academic meeting paper collection, Bei Dai River, 1989, the 204-207 page or leaf).But generally speaking, the rapidity of width of cloth phase adjustment control method is not high.

In view of this, need a kind of a kind of like this PWM current transformer, it has the easy and good advantage of dynamic property of control concurrently.The voltage-type pulse-width modulation current transformer that employing of the present invention has the phase amount adjustment method of current feed-forward can meet this requirement.

Summary of the invention

A kind of control system of voltage-type saddle type ripple pulse-width modulation current transformer, this system comprises digital signal processor, this digital signal processor comprises the phase demodulation apparatus that is used to obtain power-factor angle φ, it has two inputs, the voltage and the phase current of detection line wanted in input respectively, and described power-factor angle φ is through its output output; Conversion calculating apparatus, be used for obtaining the offset α of the angle α between the phase voltage that generates after power supply phase voltage and the modulation according to described power-factor angle φ, and the offset M that obtains modulation depth M according to the detection direct voltage, it has two inputs, the output and the direct current pressure side that connect phase demodulation apparatus respectively, it has two outputs, exports Δ α and Δ M respectively; Phase angle control ratio integral controller is used to draw the angle α between the described phasor, and the output Δ α of described conversion calculating apparatus delivers to its input, and described angle α is sent by its output; The voltage control proportional and integral controller is used to draw described modulation depth M, and the output Δ M of described conversion calculating apparatus delivers to its input, and described angle α is sent by its output; The SAPWM modulator is used for the main circuit that comes driving voltage type saddle type ripple pulse-width modulation current transformer according to the described angle α that draws and modulation depth M.

A kind of method that is used to control the control system of voltage-type saddle type ripple pulse-width modulation current transformer is comprising following step: obtain the line voltage that will detect and the power-factor angle φ between the phase current by phase demodulation apparatus; Obtain the offset α of the angle α between the phase voltage that generates after power supply phase voltage and the modulation according to described power-factor angle φ by conversion calculating apparatus; Obtain the offset M of modulation depth M by conversion calculating apparatus according to detecting direct voltage; Draw angle α between the described phasor by phase angle control ratio integral controller according to described offset α; Draw described modulation depth M by the voltage control proportional and integral controller according to described offset M; By the main circuit of SAPWM modulator according to described angle α and modulation depth M driving voltage type saddle type ripple pulse-width modulation current transformer.

Description of drawings

Fig. 1 illustrates the main circuit of three-phase voltage type saddle type ripple pulse-width modulation (SAPWM) current transformer;

Fig. 2 illustrates the simple equivalent circuit of R phase;

Fig. 3 a illustrates along the phasor adjusting figure under the change state, and Fig. 3 b illustrates the phasor adjusting figure under the inverter mode;

Fig. 4 illustrates the three-phase voltage type saddle type ripple pulse-width modulation current transformer block diagram of the phasor regulative mode that adopts current feed-forward;

Fig. 5 a illustrates under the Constant Direct Current load from along the experimental waveform that changes to inversion, and Fig. 5 b illustrates under the Constant Direct Current load from inversion to along the experimental waveform that becomes;

Fig. 6 a illustrates load resistance switches to 60 Europe from 100 Europe experimental waveform, and Fig. 6 b load resistance switches to the experimental waveform in 100 Europe from 60 Europe.

Embodiment

1. control principle summary

Present accompanying drawings control principle of the present invention.Fig. 1 illustrates the main circuit of three-phase voltage type saddle type ripple pulse-width modulation (SAPWM) current transformer, and this three phase full bridge circuit is by series inductance L _i(i=R, S, T), power switch component IGBT and filter capacitor form.

Fig. 2 illustrates the simple equivalent circuit of main circuit R phase.Among the figure, phasor E _RIt is the phase voltage of power supply R phase; Phasor U _{R '}It is the first-harmonic composition of the phase voltage of the R ' phase that generates after the current transformer pulse-width modulation; R _NBe distributed resistance,, can omit because of its value is very little; Inductance L _ROn voltage be U _XAccording to above-mentioned document, can release the first-harmonic composition effective value U of R ' phase voltage _{R '}For $U_{R^{\&prime;}}=\frac{{\mathrm{ME}}_d}{\sqrt{6}}----\left(1\right)$ In the formula, E _dBe current transformer DC side busbar voltage, M is a modulation depth.In addition, establish R _dBe the load resistance of current transformer, φ is the power-factor angle of R phase, P _oBe active power of output, by energy relationship $P_o=\frac{E_d^2}{R_d}={3E}_R{I}_R\cos \mathrm{\&phi;}$ Can draw R phase current I _REffective value be $I_R=\frac{{\mathrm{<figure-callout\; id="2"\; label="E\; d"\; filenames="A0311673000101.png,A0311673000121.png"\; state="\{\{state\}\}">E</figure-callout>}}_d^{}}{{3R}_d{E}_d\cos \mathrm{\&phi;}}----\left(2\right)$

Fig. 3 a illustrates along the phasor adjusting figure under the change state, and α is phasor E among the figure _RAnd U _{R '}Angle, be angle of retard.At this moment AC power is exported energy to load.By phasor E _R, U _{R '}And U _XAmong the Δ OAB that constitutes, E is arranged _R=U _{R '}+ U _XUnder the situation of right angle Δ OAB, φ=0, can be drawn this moment by formula (1) and (2): $\cos \mathrm{\&alpha;}=\frac{E_R}{U_{R^{\&prime;}}}=\frac{\sqrt{6}{E}_R}{{\mathrm{ME}}_d}----\left(3\right)$ Again because of U _X=ω LI _R, have $\sin \mathrm{\&alpha;}=\frac{U_X}{U_{R^{\&prime;}}}=\frac{\sqrt{6}\mathrm{\&omega;L}{E}_d}{3{\mathrm{MR}}_d{E}_R}----\left(4\right)$ Thereby draw ${\mathrm{<figure-callout\; id="2"\; label="R\; d\; sin"\; filenames="A0311673000101.png,A0311673000121.png"\; state="\{\{state\}\}">R</figure-callout>}}_d\sin 2\mathrm{\&alpha;}=\frac{4\mathrm{\&omega;L}}{M^2}----\left(5\right)$ Find out that thus when L, M one timing, the product of the left end of formula (3) is a constant.This formula explanation, the load capacity of current transformer is relevant with series electrical sensibility reciprocal and modulation depth.When α＜π/4, along with R _dReduce (that is, load increases the weight of), pilot angle α is dull to be increased.When α=π/4, R _dReach minimum value 4 ω L/M.

Can utilize Fig. 3 a to analyze R _dThe situation of undergoing mutation.Work as R _dWhen reducing suddenly, the working point B from the outset of system approaches the new balance point D point of realizing unity power factor through repeatedly adjusting (for example, along the BCEF curve).Work as R _dWhen increasing suddenly, the working point P from the outset of system approaches new balance point D through repeatedly adjusting (for example, along the PN camber line).In a word, when load was undergone mutation, the working point of system must move up and down along the vertical edges of right-angled triangle, could satisfy the requirement of unity power factor, constant DC voltage and system capacity balance.

Fig. 3 b illustrates the phasor adjusting figure under the inverter mode, and this moment, the energy of external dc power fed back to electrical network.By phasor E _R, U _{R '}And U _XAmong the Δ OAB that constitutes, E is arranged equally _R=U _{R '}+ U _XHere α is an advance angle.Being easy analysis, is current source I with the equivalence of the external dc power among Fig. 1 _sSo, I _d=-(I _s-I _o).Powerfactorcos=-1 in right angle Δ OAB, negative sign represents that electrical power feeds back to electrical network.By the energy relationship under the inverter mode

P _o=E _dI _d=3E _RI _RCos φ and formula (1) can draw $\sin \mathrm{\&alpha;}=\frac{U_X}{U_{R^{\&prime;}}}=\frac{\sqrt{6}\mathrm{\&omega;L}{I}_d}{3{\mathrm{ME}}_R}----\left(6\right)$ Consider formula (3) again, can get $\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="A0311673000101.png,A0311673000121.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&alpha;}=-\frac{4\mathrm{\&omega;L}(I_s-I_o)}{M^2{R}_d{I}_o}----\left(7\right)$ By following formula as seen, as outside direct current I _s＞I _oDuring variation, α increases from 0 to-π/4 negative directions are dull.

Can utilize Fig. 3 b to analyze the situation that outside direct voltage is undergone mutation.When outside direct voltage raises suddenly (is electric current I _sIncrease) time, the working point H from the outset of system approaches the new balance point W that realizes unity power factor through repeatedly adjusting (for example, along the HJKQ curve).When outside direct voltage reduced suddenly, the working point S from the outset of system approached new balance point W through repeatedly adjusting (for example, along the ST camber line).In a word, when outside direct voltage was undergone mutation, the working point of system must move up and down along the vertical edges of right-angled triangle, could satisfy the requirement of unity power factor, constant DC voltage and system capacity balance.

In order to improve the dynamic property of system, require the shortest along near the easement curve that changes the vertical line in Fig. 3 a and 3b.For this reason, can adopt current feed-forward control.In Fig. 1, under the condition that keeps unity power factor and constant DC voltage, when the load abrupt change, variation by the output direct current under two controllable state in succession of analytical system, and consider the energy balance relations of AC side of converter and DC side, can derive the expression of additional controlled quentity controlled variable Δ α ' of the angle [alpha] of next poised state.From the expression of deriving as can be seen, Δ α ' is proportional with the rate of change of direct current: $\mathrm{\&Delta;}{\mathrm{\&alpha;}}^{\&prime;}\&Proportional;\frac{{\mathrm{dE}}_d}{\mathrm{dt}}----\left(8\right)$ The derivation of similar Δ α ' can draw the additional controlled quentity controlled variable Δ M ' of modulation depth M.Δ M ' is proportional with the following factor: ${\mathrm{\&Delta;M}}^{\&prime;}\&Proportional;\frac{{\mathrm{\&Delta;\&alpha;}}^{\&prime;}}{\sin (\mathrm{\&alpha;}+{\mathrm{\&Delta;\&alpha;}}^{\&prime;})}----\left(9\right)$ By formula (8) and (9) as can be seen, by detecting the variable quantity of direct voltage, can be converted into the additional controlled quentity controlled variable of next poised state.So the governing equation of system is:

α(n+1)＝α(n)+(kΔα+∫Δαdt)+Δα′ (10)

M (n+1)=M (n)+(k Δ M+ ∫ Δ Mdt)+Δ M ' (11) is the control system of three-phase voltage type saddle type ripple pulse-width modulation current transformer 2.

Fig. 4 illustrates three-phase voltage type saddle type ripple pulse-width modulation (SAPWM) the current transformer block diagram of the phasor regulative mode that adopts current feed-forward.Its control system comprises digital signal processor, drive circuit and keyboard and display unit.Digital signal processor comprises phase demodulation apparatus, conversion calculating apparatus, phase angle control ratio integral controller, voltage control proportional and integral controller and the SAPWM modulator that is made of multiplier.Digital signal processor adopts singlechip chip (for example, the TMS220F2407 of TI company).The line voltage and the phase current of AC side are sent into phase demodulation apparatus, obtain line voltage e by it _STWith phase current i _RBetween power-factor angle φ.Conversion calculating apparatus is obtained the offset α of the angle α between the phase voltage that generates after power supply phase voltage and the modulation on the one hand according to this power-factor angle φ.Conversion calculating apparatus is obtained the offset M of modulation depth M according to detecting direct voltage on the other hand.Phase angle control ratio integral controller draws angle α between the described phasor according to described offset α.The voltage control proportional and integral controller draws described modulation depth M according to described offset M.The SAPWM modulator passes through the main circuit of drive unit driving voltage type saddle type ripple pulse-width modulation current transformer according to described angle α and modulation depth M.According to the variation of direct voltage, keep the constant of DC bus-bar voltage on the one hand, adjust current transformer on the other hand and work in along becoming or inverter mode.3. experimental result for example

Fig. 5 a illustrates under the Constant Direct Current load from along the experimental waveform that changes to inversion, and Fig. 5 b illustrates under the Constant Direct Current load from inversion to along the experimental waveform that becomes.Experiment parameter is: line voltage e _ST=90V, inductance L=14, dc bus capacitor C=2200 μ F, load R=60 Ω, output dc voltage E during along change _d=150V, DC power supply voltage E during inversion _d=165V.Initial several cycles of Fig. 5 a are system works in the waveform along phase voltage under the change state and phase current, and the back is the waveform when entering inversion.Because of the finite capacity of the external dc power of inversion is provided, electric current is less during inversion.The situation of Fig. 5 b in contrast.Stateful switchover process needs 100ms approximately.Under suitable change state, the adjustable extent of output dc voltage is 130V to 180V.By analysis, the fundamental factor of phase current is 99.8%, and the displacement power factor is 1, and the total power input factor is 0.99.Under inverter mode, system is to the electrical network feedback energy, and the displacement power factor is-1.

After adding current feed-forward, the experimental waveform under step load is shown in Fig. 6 a and Fig. 6 b.Among the figure, the amplitude of phase voltage waveform is big than the amplitude of the waveform of phase current.Experiment parameter is: line voltage e _ST=220V, dc bus capacitor C=1100 μ F, output dc voltage E _d=385V, load R _d=100 Ω and R _d=60 Ω.In Fig. 6 a, load resistance R _dSuddenly reduce, phase current lags behind phase voltage.The situation of Fig. 6 b in contrast.Do not adding under the situation of current feed-forward, it is more than the 200ms that system reaches the synchronous response time of phase current and phase voltage, and after adding current feed-forward, then is reduced to 60ms.

Experiment has reached the requirement of unity power factor and energy two-way flow, and output dc voltage is constant adjustable.The harmonic content of phase current is 6.1%, and waveform almost approaches sine wave.Owing to added current feed-forward control, improved the dynamic property of width of cloth phase control mode effectively.

It should be noted that and in system, to add phase-locked loop control, the variation of tracking power supply voltage so in time, the operate as normal of safeguards system.

In the phase adjusted control mode, modulation depth M and pilot angle α are two controlled quentity controlled variables that intercouple.α is bigger to the weight of control, does not regulate α, and system can't work.Do not regulate M, then cause direct voltage E _dFluctuation, thereby have influence on control for power-factor angle φ.

Though implemented this method at the three-phase pulse width modulated current transformer, also can adopt similar method for single-phase pulse-width modulation current transformer.

Though in pulse-width modulation current transformer of the present invention, used the saddle type modulating wave, also can use sinusoidal modulation wave.

Claims (4)

1. a control system that is used for voltage-type pulse-width modulation current transformer is characterized in that, described control system comprises digital signal processor, and described digital signal processor comprises:

Phase demodulation apparatus is made of multiplier, is used to obtain power-factor angle φ, and described phase demodulation apparatus has two inputs, imports detection line voltage and phase current respectively, and described power-factor angle φ is through the output output of described phase demodulation apparatus;

Conversion calculating apparatus, be used for obtaining the offset α of the angle α between the phase voltage that generates after power supply phase voltage and the modulation according to described power-factor angle φ, and the offset M that obtains modulation depth M according to the detection direct voltage, described conversion calculating apparatus has two inputs, the direct current pressure side that connects the output and the described current transformer of described phase demodulation apparatus respectively, described conversion calculating apparatus has two outputs, exports described offset α and described offset M respectively;

Phase angle control ratio integral controller is used to draw the angle α between the described phasor, and the output Δ α of described conversion calculating apparatus delivers to its input, and described angle α is sent by its output;

The voltage control proportional and integral controller is used to draw described modulation depth M, and the output Δ M of described conversion calculating apparatus delivers to its input, and described angle α is sent by its output; And

The pulse-width modulation modulator is used for the main circuit that drives described voltage-type pulse-width modulation current transformer according to the described angle α that draws and modulation depth M.

2. control system as claimed in claim 1 is characterized in that described control system also comprises drive circuit, and described drive circuit links to each other with the main circuit of described digital signal processor and described current transformer, is used to drive the main circuit of described current transformer.

3. control system as claimed in claim 1 is characterized in that described control system also comprises keyboard and display unit, and described keyboard links to each other with described digital signal processor with display unit.

4. a method that is used to control the control system of voltage-type pulse-width modulation current transformer is characterized in that described method comprises the steps:

Obtain power-factor angle φ between line voltage and the phase current by phase demodulation apparatus;

Obtain the offset α of the angle α between the phase voltage that generates after power supply phase voltage and the modulation according to described power-factor angle φ by conversion calculating apparatus;

Obtain the offset M of modulation depth M by conversion calculating apparatus according to detecting direct voltage;

Draw angle α between the described phasor by phase angle control ratio integral controller according to described offset α;

Draw described modulation depth M by the voltage control proportional and integral controller according to described offset M;

There is the variable quantity that detects direct voltage to be converted into the additional controlled quentity controlled variable Δ α ' and the Δ M ' of the next poised state of system;

By the main circuit of pulse width modulator according to described angle α and modulation depth M driving voltage type pulse-width modulation current transformer.

Images