CN1731646A - Separate injection active power filter and frequency-divided self-adaptive control method - Google Patents

Abstract

The invention discloses an active electric filter and frequency division self-adapting control method. Dividing the load harmonic wave into harmonic wave current signal of different phases of frequency; performing harmonic wave phase compensation and controlling its amplitude, and adding it with the feedback signal of the self-adapting control gain, getting the control signal and accumulating each harmonic wave current control signal of different frequency; getting the PWM control signal of active power filter.

Description

Separate injection active power filter and frequency-divided self-adaptive control method

Technical field

The present invention relates to a kind of Active Power Filter-APF, particularly a kind of separate injection active power filter and frequency-divided self-adaptive control method.

Background technology

Along with modern industry development, electric load becomes increasingly complex, the capacity that has formed Harmonious Waves in Power Systems is big, the time characteristics that become.Traditional LC passive filter more and more can not satisfy the requirement of modern industry application and electric power system, along with the appearance of Active Power Filter-APF (APF), for power network harmonic wave management provides a kind of important mode.Active Power Filter-APF is offset the harmonic current that load produces by inject certain offset current to electrical network, its application has overcome some shortcomings of traditional harmonic suppressing method such as LC filter, but it is the high order harmonic component of compensating non-linear load generation both, can adapt to the quick variation of electric network impedance and frequency automatically again, and have high controllability and fast-response.

The APF technical development various topological structures occurred to today: independent type, many current transformers mixed type and APF and PF mixed type.Though the active filter that uses has good filtering performance separately, cost is higher, particularly in the high-power occasion, is difficult to be applied.Equally, many current transformers mixed type of being made up of a plurality of inverters also needs the high initial stage to drop into.Therefore, the hybrid active filter that the low capacity active filter combines with big capacity passive filter becomes the focus and the inevitable choice of current practical application, also is the developing direction of following active power filtering technology.It both can overcome the shortcoming that the APF capacity requirement is big, cost is high, can remedy the deficiency of PF again, made whole filtering system obtain good performance.In existing active filter APF and hybrid active filter that passive filter PF combines, reduce the inverter capacity, reduce cost.Usually the injection circuit that adopts has two kinds: series resonance is pouring-in and parallel resonance is pouring-in.Parallel resonance injection type APF does not possess the reactive power compensation ability; The capacity requirement of serial resonant injection type APF active filter is little, but there is the harmonic wave passage in it between Active Power Filter-APF and passive filter, the offset current that causes Active Power Filter-APF to inject may flow into passive filter and system again, increase the burden of passive filter meaninglessly, and can influence the effect that harmonic wave suppresses.APF is called the parallel connection mixed type active filter with the form that inserts electrical network in parallel again after PF connects, be suitable for high pressure, high-power system application, but generally in order to reduce fundamental voltage that active part bears and the fundamental current that flows through thereof, the impedance of fundamental frequency of PF is very big, cause the PF device volume big, therefore the expense height is not suitable for requiring the occasion of reactive power compensation.

Summary of the invention

The purpose of this invention is to provide a kind of separate injection active power filter, this separate injection active power filter not only can better be administered the harmonic wave in the electrical network, can compensate jumbo reactive power simultaneously.

Another object of the present invention provides a kind of frequency-divided self-adaptive control method of separate injection active power filter.

For realizing above-mentioned purpose, the technical solution adopted in the present invention is: separate injection active power filter comprises Active Power Filter-APF and injection branch, described injection branch composes in series single tuned filter by second electric capacity, first electric capacity, first inductance, first electric capacity, first inductance are formed the first-harmonic resonance circuit, Active Power Filter-APF is connected in parallel by coupling transformer and first-harmonic resonance circuit, inserts electrical network behind second capacitor filtering.

In the above-mentioned separate injection active power filter, the output of described Active Power Filter-APF is connected to the secondary of coupling transformer after ripple filter filtering.

A kind of frequency-divided self-adaptive control method of separate injection active power filter may further comprise the steps:

With detected load harmonic current I _LhCarry out frequency division, be divided into the harmonic current signal of different frequency section;

Each harmonic current signal behind the frequency division is by corresponding harmonic phase compensator compensates passive part phase deviation;

Feedforward controller is delivered in the output of harmonic phase compensator, utilizes the gain coefficient of adaptive law control feedforward controller, and adder is delivered in feedforward controller output;

The output harmonic wave electric current of Active Power Filter-APF is carried out frequency division, and corresponding feedback controller is delivered in its output respectively;

Utilize the feedback factor of adaptive law Control and Feedback controller, the output addition of the output of feedback controller and same frequency segment feedforward controller obtains the control signal of the harmonic current of this frequency range;

The harmonic current control signal of each frequency range is added up, according to adding up and calculating the pwm control signal of Active Power Filter-APF.

The invention has the beneficial effects as follows:

1) under fundamental frequency resonance takes place owing to the first-harmonic resonance circuit in the separate injection active power filter, therefore injection branch will be born most of line voltage, active filter mainly bears harmonic voltage and does not bear system's fundamental voltage, there is not fundamental current to flow into yet, thereby help reducing the capacity of active filter, reduce cost.

2) separate injection active power filter combines series resonance injection type APF and parallel connection mixed type active filter, the advantage of comprehensive these two kinds of active filters, remedy shortcoming separately again mutually, made separate injection active power filter have the reactive static complementary energy power of larger capacity and less inverter capacity concurrently.

3) in conjunction with the design feature of separate injection active power filter, output frequency characteristic according to active filter, employing is based on the model reference adaptive control of frequency division, simultaneously on the basis of frequency division control, by instantaneous mains by harmonics value, the harmonic value of load harmonic value and active filter output satisfies leg-of-mutton relation, obtain the phase difference of the harmonic value of load harmonic value and active filter output by the cosine law, thereby be used for adjusting phase of input signals, the tracking accuracy of comparing electric current with active power filtering tradition control method is higher, and compensation effect is better.

The invention will be further described below in conjunction with accompanying drawing.

Description of drawings

Fig. 1 is the system configuration of separate injection APF.

Fig. 2 is the active filter adaptive control block diagram based on frequency division.

Embodiment

As shown in Figure 1, separate injection active power filter comprises Active Power Filter-APF and injection branch, and A phase injection branch is by capacitor C ₁, capacitor C ₂, inductance L ₄Compose in series single tuned filter, capacitor C ₂, inductance L ₄Be composed in series A phase first-harmonic resonance circuit, Active Power Filter-APF APF is through LC filter (L ₇, C ₇) after the filtering, be connected in parallel by coupling transformer T and first-harmonic resonance circuit, again through filter capacitor C ₁Insert electrical network, the two-phase injection circuit links identical with A in addition.In the structure of separate injection active power filter, the main effect of injection branch is: provide a low-impedance passage to harmonic wave, intercept certain idle of line voltage and compensation.It is N single tuned filter that the present invention can select injection branch according to the situation of actual harmonic wave output and compensating reactive power.Because the series resonance LC network resonance in the injection branch is tuned in fundamental frequency, its impedance of fundamental frequency is approximately 0, be equivalent to the short-channel of fundamental current, all will flow into this network so flow through the fundamental current of injection branch, and can not flow into coupling transformer and inverter.The effect of active filter mainly contains: the filtering performance and the filter effect that improve whole filtering system, suppress of the influence of electrical network background harmonics voltage to electric voltage, suppress the series parallel resonance that passive filter and electrical network inductance form, remedy defective that passive power filter exists and deficiency etc.The separate injection active power filter operation characteristic is: only by the passive part compensating power, active part and passive part suppress harmonic wave jointly.

Referring to Fig. 2, Fig. 2 is the active filter adaptive control block diagram based on frequency division.Active filter is operated in humorous wave zone, inverter own also is non-linear, harmonic wave output also can produce phase shifts through passive part, therefore consider to adopt frequency division control, utilize model reference adaptive to control amplitude, according to supply harmonic, the vector relations between load harmonic wave and the active filter output harmonic wave is adjusted phase place then.Among the figure, G _Pn(s) expression nth harmonic phase compensator, G _Cn(s) expression nth harmonic feedforward controller, G _Fn(s) expression nth harmonic feedback controller.

(1) reference model

Active filter will be realized the purpose of filtering harmonic wave, therefore Reference Model Design is a low pass filter., according to the Mathematical Modeling of separate injection APF, the present invention has designed low pass filter with the Butterworth type of system model same order as the reference model, and its transfer function is:

$G_m\left(s\right)=\frac{4.931\×{10}^{10}}{s^4+1231s^3+7.582\×10^5{s}^2+2.735\×{10}^{8}s+4.931\×{10}^{10}}---\left(1\right)$

(2) adaptive law

At separate injection active power filter, plant equation is turned to:

$Y_p\left(s\right)=K_p\frac{N_p\left(s\right)}{D_p\left(s\right)}U\left(s\right)---\left(2\right)$

In the formula

$\left\{\begin{array}{c}{N}_p\left(s\right)=1+a_{1}s+\·\·\·+a_n{s}^n\\ D_p\left(s\right)=b_0+b_{1}s+\·\·\·+b_m{s}^m\end{array}\right.---\left(3\right)$

Kp is a constant gain amplifier.

The reference model equation is

$Y_m\left(s\right)=K_m\frac{1}{D_m\left(s\right)}R\left(s\right)---\left(4\right)$

In the formula

D _m(s)＝ b ₀+ b ₁s+…+ b _ms ^m (5)

Km is a constant gain amplifier.

Can know according to the controller chassis Fig. 2 of system:

U(s)＝G _C(s)·R(s)+G _f(s)·Y _p(s) (6)

When system and reference model coupling, system's feedforward controller and feedback controller are respectively:

$G_C\left(s\right)=\frac{K_m}{K_p{N}_p\left(s\right)}---\left(7\right)$

$G_f\left(s\right)=\frac{D_p\left(s\right)-D_m\left(s\right)}{K_p{N}_p\left(s\right)}---\left(8\right)$

Generalized error:

e(t)＝y(t)-y _m(t) (8)

Target function:

$J=\frac{1}{2}{\∫}_0^1{e}^2\left(t\right)\mathrm{dt}---\left(9\right)$

Design object is sought a exactly _i, b _iThe adjusting rule, make the J minimum.

System's closed loop transfer function, is:

$G\left(s\right)=\frac{Y_p\left(s\right)}{R\left(s\right)}=K\frac{N\left(s\right)}{D\left(s\right)}U\left(s\right)---\left(10\right)$

$\left\{\begin{array}{c}N\left(s\right)=1+{\mathrm{\α}}_{1}s+\·\·\·+{\mathrm{\α}}_n{s}^n\\ D\left(s\right)={\mathrm{\β}}_0+{\mathrm{\β}}_{1}s+\·\·\·+{\mathrm{\β}}_m{s}^m\end{array}\right.---\left(11\right)$

A _i, b _iEach worthwhile parameter of doing, can obtain MIT rule:

${\stackrel{\·}{\mathrm{\α}}}_i=-K_{\mathrm{\αi}}e\frac{\∂e}{{\∂\mathrm{\α}}_i}-K_{\mathrm{\αi}}e\frac{\∂y}{\∂{\mathrm{\α}}_i},K_{\mathrm{\αi}}>\mathrm{0,1}\≤i\≤n---\left(12\right)$

${\stackrel{\·}{\mathrm{\β}}}_i=-K_{\mathrm{\βi}}e\frac{\∂e}{\∂{\mathrm{\β}}_i}-K_{\mathrm{\βi}}e\frac{\∂y}{\∂{\mathrm{\β}}_i},K_{\mathrm{\αi}}>\mathrm{0,1}\≤i\≤m---\left(13\right)$

Formula (12), (13) promptly are the control laws that system asked.

(3) phase compensation control

Employing detects the instantaneous value of supply harmonic, load harmonic wave and the separate injection active filter output harmonic wave in a certain moment based on the harmonic wave frequency division detection method of instantaneous power theory, and any moment has:

${\stackrel{\·}{I}}_{\mathrm{Sh}}={\stackrel{\·}{I}}_{\mathrm{Fh}}+{\stackrel{\·}{I}}_{\mathrm{Lh}}---\left(14\right)$

Wherein Be the supply harmonic electric current,

Be the load harmonic current,

Flow into the harmonic current of active filter.

When certain subharmonic is analyzed, just have:

${\stackrel{\·}{I}}_{\mathrm{Sn}}={\stackrel{\·}{I}}_{\mathrm{Fn}}+{\stackrel{\·}{I}}_{\mathrm{Ln}},n=\mathrm{2,3},\·\·\·---\left(15\right)$

Just can know by formula (15), Constitute three sides of a triangle, just have by the cosine law:

$\cos \mathrm{\θ}=-\frac{I_{\mathrm{Ln}}^2+I_{\mathrm{Fn}}^2-I_{\mathrm{Sn}}^2}{2I_{\mathrm{Ln}}{I}_{\mathrm{Fn}}}---\left(16\right)$

Wherein θ is a vector

Between angle, just instantaneous

Between phase difference,

Control by PI and to adjust harmonic phase compensating controller G _Pn(s).

The frequency-divided self-adaptive control procedure of this Active Power Filter-APF is as follows:

1. with detected load harmonic current I _LhCarry out frequency division, the controller different according to different Frequency Band Selection;

2. the I behind the frequency division _LhAt first by harmonic phase compensator G _Pn(s) compensation passive part phase deviation, and then by feedforward control of harmonic device G _Cn(s), G _Cn(s) output and harmonic wave feedback controller G _Fn(s) output adds up, and will add up and send into the controlled signal I of controlled device _Sh

3. the actual output I of controller _ShWith load harmonic current I _LhIdeal output I by reference model _ShSubtract each other, obtain error signal e (t), e (t) is as the input that adapts to mechanism, the system parameters that is used to regulate feedforward controller and feedback controller;

4. the continuous regulating system parameter of adaptive law makes that error e (t) is more and more littler, levels off to zero.The ideal output of reference model is followed the tracks of in the actual output that is controller fully, thereby realizes the complete filtering of harmonic wave.

Claims (4)

1, a kind of separate injection active power filter, comprise Active Power Filter-APF and injection branch, it is characterized in that: described injection branch composes in series single tuned filter by second electric capacity, first electric capacity, first inductance, first electric capacity, first inductance are formed the first-harmonic resonance circuit, Active Power Filter-APF is connected in parallel by coupling transformer and first-harmonic resonance circuit, inserts electrical network behind second capacitor filtering.

2, separate injection active power filter according to claim 1 is characterized in that: the output of described Active Power Filter-APF is connected to the secondary of coupling transformer after ripple filter filtering.

3, a kind of frequency-divided self-adaptive control method of separate injection active power filter may further comprise the steps:

Ilh carries out frequency division with the load harmonic current, is divided into the harmonic current signal of different frequency section;

Each harmonic current signal behind the frequency division is by corresponding harmonic phase compensator compensates passive part phase deviation;

Feedforward controller is delivered in the output of harmonic phase compensator, utilizes the gain coefficient of adaptive law control feedforward controller, and adder is delivered in feedforward controller output;

The output harmonic wave electric current of Active Power Filter-APF is carried out frequency division, and corresponding feedback controller is delivered in its output respectively;

Utilize the gain coefficient of adaptive law Control and Feedback controller, the output addition of the output of feedback controller and same frequency segment feedforward controller obtains the control signal of the harmonic current of this frequency range;

The harmonic current control signal of each frequency range is added up, according to adding up and calculating the pwm control signal of Active Power Filter-APF.

4, the frequency-divided self-adaptive control method of separate injection active power filter according to claim 3, the input signal of described adaptive law are e (t), and e (t) is the actual output I of Active Power Filter-APF _ShWith load harmonic current I _LhIdeal output I by reference model _Sh' subtract each other the error signal that obtains.

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