CN102790394A - Control method for active power filter based on double-side voltage information - Google Patents

Abstract

The invention discloses a control method for an active power filter based on double-side voltage information. The control method comprises the following steps of: carrying out phase locking on sampled power supply voltage to obtain a sine value of a phase angle and a starting point of power frequency cyclic waves by a digital phase-locked loop; comparing the sampled APF (Active Power Filter) direct-side capacitance voltage with a set value through a subtracter, sampling and storing and averaging according to the period of power supply voltage; carrying out PI (Proportional Integral) computation on an average value of the direct current side capacitance voltage at a starting point of the power frequency cyclic waves and outputting a fundamental wave active component amplitude of a load; multiplying the fundamental wave active component amplitude of the load with the sine value of voltage phase and outputting fundamental wave active current of the load; and subtracting the fundamental wave active current of the load from total current of the load, outputting compensation current required by the load and directly controlling a converter in a hysteresis comparison mode. According to the control method disclosed by the invention, start from a transmission angle of instantaneous active and reactive energy in the system, troublesome processes of detecting the active and reactive components are avoided and the suppression of harmonic current or compensation of reactive power is realized.

Description

Control method based on the Active Power Filter-APF of bilateral information of voltage

Technical field

The present invention relates to a kind of control method of the Active Power Filter-APF based on the bilateral information of voltage.

Background technology

(Active Power Filter APF) has obtained extensive concern as dynamically suppressing harmonic current and compensating power effective means to Active Power Filter-APF.Its basic principle is the harmonic current that detects in the electrical network; Then through controlled power semiconductor to the electric current that electrical network injects with original harmonic current amplitude equates, phase place is opposite; The total harmonic current that makes power supply is zero, thereby reaches the purpose of real-Time Compensation harmonic current.

The control method of APF has mainly comprised detection method and two parts of offset current control algolithm of harmonic current.In the algorithm research of current APF, mostly be to calculate the harmonic current in the system earlier, and then carry out control corresponding with instantaneous reactive power theory or other detection methods.This method need be carried out a large amount of mathematical operations, and the real-time performance of APF is had certain influence.Compensating Current Control Method mainly contains triangular carrier modulation method, current hysteresis chain rate than modulation method and dead-beat control method, exists such as hardware to realize complicacy, the shortcoming that amount of calculation is big.

Summary of the invention

The present invention is directed to the shortcoming that traditional APF control algolithm operand is big, hardware is realized complicacy; A kind of control method of the Active Power Filter-APF based on the bilateral information of voltage is provided; This method is from the instantaneous meritorious angle of system, transmitting with quadergy, through obtaining the line number calculating of going forward side by side of alternating current-direct current side information of voltage, avoids detecting complicated processes meritorious, idle component; Directly the electric current of output is controlled, fast, dynamically realized suppressing harmonic current or compensating power.

The technical scheme that realizes above-mentioned purpose is:

Based on the control method of the Active Power Filter-APF of bilateral information of voltage, said Active Power Filter-APF is connected in load point in parallel, and said control method comprises the following steps:

Step 1 is sampled and is stored supply voltage, and through digital phase-locked loop supply voltage locked phase, obtains the phase angle of supply voltage, obtains sine value based on this phase angle, and confirms the starting point of power frequency cycle based on the waveform of lock phase;

Step 2 detects the dc capacitor voltage of APF, with itself and set point pass through subtracter relatively after, sample and queue stores, get the mean value of said dc capacitor voltage according to the cycle of said supply voltage;

Step 3 in the starting point of said power frequency cycle, is carried out PI (ratio-integration) with the mean value of said dc capacitor voltage and is calculated, thus the first-harmonic real component amplitude of output load;

Step 4 multiplies each other the fundamental active current of output load with the sine value that obtains in the first-harmonic real component amplitude of said load and the step 1;

Step 5, the total current of sampling load, and pass through the fundamental active current that subtracter deducts said load, and obtaining the reference current of APF, chain rate is directly controlled current transformer than mode through stagnating.

The control method of above-mentioned Active Power Filter-APF, wherein, in the said step 1, the starting point of said power frequency cycle refers to the initial moment of a cycle of supply voltage.

The control method of above-mentioned Active Power Filter-APF, wherein, in the said step 2, all index futures power frequency periods of said supply voltage.

The invention has the beneficial effects as follows: the present invention is from the instantaneous meritorious angle of system, transmitting with quadergy; Meritorious energy to regulate the electrical network input is a target, calculates through obtaining the alternating current-direct current side information of voltage line number of going forward side by side, and directly the electric current of exporting is controlled; Can avoid detecting complicated processes meritorious and the reactive current component; Simplify the process that detects harmonic wave, fast, dynamically realize suppressing harmonic current or compensating power, it is simple to have principle; Be easy to realize the characteristics that dynamic property is good.

Description of drawings

Fig. 1 is the structural representation of single-phase shunt active power filter;

Fig. 2 is the schematic diagram of the control method of Active Power Filter-APF of the present invention.

Embodiment

Below in conjunction with accompanying drawing the present invention is described further.

See also Fig. 1, the basic structure of parallel single-phase type APF.P among the figure _LAnd q _LBe respectively the active power and the reactive power of nonlinear load, p _AThe active power that consumes when working for APF, W _SBe the energy of power supply output, W _ABe the energy of APF output, W _LBe the energy that load consumes, W _CBe the dc bus capacitor C energy stored of APF, L _mBe the APF out put reactor, C _mBe APF output HF filtering capacitor, i _CBe the APF output current, i _LBe load current, A1-A4 constitutes 4 controlled tr tubes of current transformer, and AC representes power supply.

In the present embodiment, APF is an example with the parallel single-phase type, and when not adopting APF, nonlinear-load makes system power i _SComprise fundamental active current, fundamental reactive current harmonic current component.If supply voltage (line voltage) u _s(t) be undistorted sine wave, then fundamental active current and fundamental voltage produce active power, and other electric current and fundamental voltage produce reactive power.When adopting shunt voltage type APF, if require the APF active power of output, will consume dc bus capacitor C and go up energy stored, make dc capacitor voltage U _Dc(t) constantly descend.According to PWM current transformer control principle and power-balance principle, dc capacitor voltage U _Dc(t) need remain unchanged, then the offset current i of APF output _CCan not comprise fundamental active current, and only contain reactive current harmonic electric current.

Therefore, from the meritorious angle that among APF, flows with quadergy, control APF only compensates harmonic current and the fundamental reactive current that load produces.Then after the compensation of APF, power supply is only to load power output active power p _LWith loss power p to APF output current transformer _A, and the reactive power q that load needs _LThen, establish supply voltage u by APF output _s(t)=U _sSin (ω t), U _sBe fixed value, then the load total current as shown in the formula:

$i_L\left(t\right)=I_{\mathrm{pL}}\sin \left(\mathrm{\ωt}\right)+I_q\cos \left(\mathrm{\ωt}\right)+\underset{n=2}{\overset{\∞}{\mathrm{\Σ}}}{I}_n\sin (\mathrm{n\ωt}+{\mathrm{\θ}}_n)---\left(\text{1}\right)$

In the formula (1), I _PLIt is the first-harmonic real component amplitude in the load total current; I _qIt is the fundamental reactive component amplitude in the load total current; I _nIt is the nth harmonic component amplitude in the load total current; θ _nIt is the nth harmonic component phase angle in the load total current.

Because fundamental active current and fundamental voltage produce active power, other electric current and fundamental voltage produce reactive power.Therefore, the gross power of load is:

$W_L\left(t\right)=u_s\left(t\right)i_L\left(t\right)p_L+q_L=I_{\mathrm{pL}}{U}_s{\sin }^2\left(\mathrm{\ωt}\right)+I_q{U}_s\sin \left(\mathrm{\ωt}\right)\cos \left(\mathrm{\ωt}\right)+\underset{n=2}{\overset{\∞}{\mathrm{\Σ}}}{U}_s\sin \left(\mathrm{\ωt}\right)I_n\sin (\mathrm{n\ωt}+{\mathrm{\θ}}_n)---\left(2\right)$

The power output of power supply is load active power p _LLoss power p with APF _ASum:

W _S(t)=p _L+p _A=I _pLU _Ssin ²(ωt)+I _pAU _ssin ²(ωt)=(I _pL+I _pA)sin(ωt)u _s(t) （3）

Wherein, I _PABe the active current amplitude that APF consumes, then the power output of APF is active power poor of reactive power and the consumption of its output:

$W_A\left(t\right)q_L-p_A=I_q{U}_s\sin \left(\mathrm{\ωt}\right)\cos \left(\mathrm{\ωt}\right)+\underset{n=2}{\overset{\∞}{\mathrm{\Σ}}}{U}_s\sin \left(\mathrm{\ωt}\right)I_n\sin (\mathrm{n\ωt}+{\mathrm{\θ}}_n)-I_{\mathrm{pA}}{U}_s{\sin }^2\left(\mathrm{\ωt}\right)---\left(4\right)$

Reactive power q _LAt any power frequency period [t ₀, t ₀+ T] in integration be zero, as shown in the formula:

$\underset{t_0}{\overset{t_0+T}{\∫}}{q}_L\mathrm{dt}=\underset{t_0}{\overset{t_0+T}{\∫}}\left(I_q{U}_s\sin \left(\mathrm{\ωt}\right)\cos \left(\mathrm{\ωt}\right)\right)\mathrm{dt}+\underset{n=2}{\overset{\∞}{\mathrm{\Σ}}}{U}_s\sin \left(\mathrm{\ωt}\right)I_n\sin (\mathrm{n\ωt}+{\mathrm{\θ}}_n))\mathrm{dt}=0---\left(5\right)$

The loss power p of APF _ABy AC side power supply input active current p is provided _AEnergy variation with dc bus capacitor in APF embodies p _AIntegration in the one-period is:

Wherein, U _sBe APF access point system voltage amplitude; U _DcBe previous cycle capacitance voltage mean value; Δ U _DcBe this cycle ([t ₀, t ₀+ T] in the time) the capacitance voltage undulate quantity.

Therefore, comprehensive aforementioned derivation is calculated, and the variation that draws the APF dc voltage is caused by two parts: the idle exchange of DC side and AC side and the active loss power of APF, promptly meritorious exchange.Formula (5) has been explained reactive power q _LThrough current transformer and the exchange of dc bus capacitor C produce power, cause dc capacitor voltage U _Dc(t) fluctuation, but its integration in one-period is zero, so its dc capacitor voltage of reactive-load compensation equipment U that ideal is harmless _Dc(t) the cycle mean value in one-period (being 20ms in the present embodiment) is constant.

But in fact cut-off inevitably can consumed energy for power electronic device, and the existence of active power will consume energy stored on the electric capacity, make capacitance voltage constantly descend.Know that by formula (6) integration of loss power in one-period that actual APF exists is non-vanishing, so can cause dc capacitor voltage U _Dc(t) variation of periodic quantity that is to say dc capacitor voltage U _Dc(t) reacting condition of periodic quantity the transmission of APF both sides active power.According to the PWM control law, has only dc capacitor voltage U _Dc(t) must keep constant, could make the APF operate as normal eliminate idle and small echo.If dc capacitor voltage U _Dc(t) fluctuation is bigger, overcompensation or undercompensation will occur, can influence the precision of compensation during undercompensation, can increase the interference harmonic current of APF during overcompensation.For this reason, the present invention adopts and keeps the stable APF control algolithm of dc voltage, by system equipment loss power is provided, and keeps capacitance voltage stable, further realizes effective idle harmonic compensation.

See also Fig. 2, the control method of the Active Power Filter-APF based on the bilateral information of voltage of the present invention, said Active Power Filter-APF (APF) parallel connection insert power supply with load between, said control method comprises the following steps:

Step 1 is to supply voltage u _s(t) sample and queue stores, and through digital phase-locked loop to supply voltage u _s(t) the lock phase obtains supply voltage u _s(t) phase angle obtains sine value sin (ω t) according to this phase angle, and confirms the starting point of power frequency cycle according to the waveform of lock phase, and the starting point of this power frequency cycle refers to supply voltage u _sThe initial moment of a cycle (t);

Step 2, the dc capacitor voltage U of detection APF _Dc(t), with itself and set point V _RefProcess subtracter relatively back (is dc capacitor voltage U _Dc(t) deduct the reference value V of setting _Ref), sample and store, and according to supply voltage u _s(t) cycle (power frequency period) cut-off stream lateral capacitance voltage U _Dc(t) mean value;

Step 3 is in the starting point of described power frequency cycle, with dc capacitor voltage U _Dc(t) mean value carries out PI (ratio-integration) and calculates, thus the first-harmonic real component amplitude I of output load _PL, wherein proportional component makes dc capacitor voltage U _Dc(t) fast near set-point, integral element is used for regulating static difference, makes dc capacitor voltage U _Dc(t) near given reference voltage level, fluctuate, improve the steady-state behaviour of system; The dc capacitor voltage U that passing ratio integral element obtains sampling _Dc(t) can obtain the amplitude size of reference current after the comparison value correction; Described PI calculates, and is meant what strict calculating of process and reasoning drew, through this specific calculation procedure, obtains described load first-harmonic real component amplitude I _PL

Step 4 is with the first-harmonic real component amplitude I of load _PLMultiply each other the fundamental active current i of output load with the sine value sin that obtains in the step 1 (ω t) _PL(t);

Step 5, the total current i of sampling load _L(t), and through subtracter deduct the fundamental active current i of load _PL(t), obtain the reference current of APF, this reference current has little, the consuming time weak point of amount of calculation, characteristics that dynamic property is good, controls the current transformer that is made up of A1-A4 through the chain rate that stagnates than mode is direct then, and A1-A4 is controlled tr tube, among Fig. 2,

Cycle on average is illustrated in the carrier cycle input value is removed mean value, and Δ I representes as the electric current difference of input of chain rate that stagnates.

Above-mentioned load is a nonlinear-load.

In sum, the present invention is provided with suitable dc capacitor voltage reference value from the instantaneous meritorious angle of system, transmitting with quadergy, and it is stable in the cycle to be with this value that benchmark is kept capacitance voltage; The dc voltage of being gathered carries out proportional integral according to specific mathematical relationship and calculates, the amplitude of the real component that obtains loading; Gather AC side voltage and draw three-phase current numerical value according to specific mathematical relationship, with the difference of this electric current and active current as a reference electric current carry out Direct Current Control, can avoid detecting simultaneously idle harmonic; Significantly reduce amount of calculation; Simplify the process that detects harmonic wave, fast, dynamically realize suppressing harmonic current or compensating power, it is simple to have principle; Be easy to realize the characteristics that dynamic property is good.

Above embodiment only supplies to explain the present invention's usefulness; But not limitation of the present invention; The technical staff in relevant technologies field under the situation that does not break away from the spirit and scope of the present invention, can also make various conversion or modification; Therefore all technical schemes that are equal to also should belong to category of the present invention, should be limited each claim.

Claims (3)

1. based on the control method of the Active Power Filter-APF of bilateral information of voltage, said Active Power Filter-APF is connected in load point in parallel, it is characterized in that, said control method comprises the following steps:

Step 1 is sampled and is stored supply voltage, and through digital phase-locked loop supply voltage locked phase, obtains the phase angle of supply voltage, obtains sine value based on this phase angle, and confirms the starting point of power frequency cycle based on the waveform of lock phase;

Step 2 detects the dc capacitor voltage of APF, with itself and set point pass through subtracter relatively after, sample and queue stores, get the mean value of said dc capacitor voltage according to the cycle of said supply voltage;

Step 3 in the starting point of said power frequency cycle, is carried out PI with the mean value of said dc capacitor voltage and is calculated, thus the first-harmonic real component amplitude of output load;

Step 4 multiplies each other the fundamental active current of output load with the sine value that obtains in the first-harmonic real component amplitude of said load and the step 1;

Step 5, the total current of sampling load, and pass through the fundamental active current that subtracter deducts said load, and obtaining the reference current of APF, chain rate is directly controlled current transformer than mode through stagnating.

2. the control method of Active Power Filter-APF according to claim 1 is characterized in that, in the said step 1, the starting point of said power frequency cycle refers to the initial moment of a cycle of supply voltage.

3. the control method of Active Power Filter-APF according to claim 1 is characterized in that, in the said step 2, and all index futures power frequency periods of said supply voltage.

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