CN103094916A - Three-phase three-wire system interphase balance method based on electric power active power filter - Google Patents

Abstract

The invention relates to a three-phase three-wire system interphase balance method based on an electric power active power filter and belongs to the electric power quality detection and control technical field. The three-phase three-wire system interphase balance method based on an electric power active power filter comprises the following steps: 1,representing each positive sequence, negative sequence and zero sequence of the voltage of the three-phase three-wire system; 2,calculating the amplitude value of a three-phase symmetrical reference current; 3,calculating voltage phase; 4,calculating a three-phase reference current; 5,comparising the three-phase reference current with an actual three-phase system current, then adopting a current tacking type pulse width modulation (PWM) alternating current circuit in a hysteresis comparison mode, and outputting a compensating current. The three-phase three-wire system interphase balance method based on the electric power active power filter has the advantages that a reference phase is controlled independently and corresponding to the system voltage, algorithm structure is simple, and three-phase balance is achieved.

Description

The alternate balance method of three-phase three-wire system based on active power filter

Technical field

The present invention relates to a kind of balance control method for the three-phase three-wire system system, belong to Power Quality Detection, control technology field.

Background technology

Active Power Filter-APF (APF) be as a kind of can dynamically suppress harmonic current and (or) power electronic equipment of compensating power and extensively concerned.The compensation performance of APF is good and bad has much relations with its control computational methods that adopt.Current Compensating Current Control Method to APF has proposed the various control scheme, and its harmonic current detecting method has based on the p of alpha-beta theory, q operation method and ip, iq operation method and based on control computational methods of Cycle Control theory etc.

Load is in the situation that three-phase imbalance, mains side imbalance or distortion, backoff algorithm can not finely accurately detect first-harmonic, and the electric current that floating voltage changes also can't carry out full remuneration to harmonic current in real time due to the impact that is subject to unbalanced factor and distortion.In recent years, reactive power compensation and harmonic detecting method proposed some and be suitable for the new method of supply voltage distortion, uneven situation in improvement, but these methods still need to carry out a large amount of mathematical operations, and the real-time performance of system is had certain impact.Its engineering feasibility is less.

Phase-locked loop (PLL) is to use at present the most general phase synchronization method, and it is used for obtaining accurately real-time phase information, and the calculating benchmark is provided, and its performance is most important for the performance of whole control system.Phase-locked loop commonly used generally adopted the method for zero balancing, calculate phase place by the time of detecting zero crossing, but its dynamic property was relatively poor, and the detection of zero crossing is very responsive to harmonic wave, direct current offset and other interference, and practical application effect is not good.Adopting high-precision single-phase formula Digital Phase-Locked Loop Technology can obtain good dynamic property, solve simultaneously the stationary problem between a plurality of single-phase phase-locked loops, is a kind of good solution.

At present, based on the control algolithm of the single-phase APF of direct voltage feedback and triangular current modulation, can carry out single-phase compensation or the system of center line is arranged for three-phase and four-line, adopt the APF model machine of this algorithm succeed in developing and put into operation.Yet, still there is no a kind of active filter that is used for three-wire system of the practicality compensation technique that balances each other.

Summary of the invention

Technique effect of the present invention can overcome defects, provide a kind of three-phase three-wire system based on active power filter alternate balance method, APF adopts single-phase digital phase-locked loop to obtain voltage-phase information, exist in direct current offset, humorous wave interference equal error situation at input three-phase real-time variable, gather each phase instantaneous value, utilize own sin, cos data to calculate, draw and set the sine value of phase angle, thereby determine the phase place of signal.Have amount of calculation little, three-phase is characteristics independently, can be mutually phase-locked to each separately, take further control.

For achieving the above object, the present invention adopts following technical scheme: it comprises the steps:

(1) in the three-phase three-wire system system, each time of voltage positive sequence, negative phase-sequence, zero sequence are expressed as follows:

$,u_{\mathrm{sa}}=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{u}_{\mathrm{ka}}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uka}})=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[u_{k+}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}+})+u_{k-}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}-})]$

$,u_{\mathrm{sb}}=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{u}_{\mathrm{kb}}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{ukb}})=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[u_{k+}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}+}-2\mathrm{\π}/3)+u_{k-}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}-}+2\mathrm{\π}/3)]$

$,u_{\mathrm{sc}}=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{u}_{\mathrm{kc}}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{ukc}})=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[u_{k+}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}+}+2\mathrm{\π}/3)+u_{k-}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}-}-2\mathrm{\π}/3)]$

U wherein _sa,, u _sb, u _scBe three-phase system voltage;

(2) three-phase symmetrical reference current amplitude is calculated: $I_{\mathrm{ref}}=\frac{P_a+P_b+P_c+P_{\mathrm{Loss}}}{3(U_{a1}+U_{b1}+U_{c1})},$

U wherein _a1, U _b1, U _c1Be three-phase positive sequence voltage, P _a, P _b, P _cBe three phase power, P _LossBe load power;

(3) voltage-phase calculates: ${\mathrm{\θ}}_{u1+}=\frac{X_c\·\sin \left(\mathrm{nt}\right)+Y_c\·\cos \left(\mathrm{nt}\right)}{\sqrt{X_c^2+Y_c^2}}$

X wherein _c, Y _cCycle-addition value for transient data and data pool after multiplying each other;

(4) three-phase reference current: $\left\{\begin{array}{c}{i}_{\mathrm{refa}}=I_{\mathrm{ref}}\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u1+})\\ i_{\mathrm{refb}}=I_{\mathrm{ref}}\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u1+}-2\mathrm{\π}/3)\\ i_{\mathrm{refc}}=I_{\mathrm{ref}}\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u1+}+2\mathrm{\π}/3)\end{array}\right.;$

(5) three-phase reference current and actual three-phase system electric current are compared, adopt stagnant chain rate than the Current tracking PWM alternating current circuit of mode, the output offset current.

APF gathers three-phase system voltage, three-phase system electric current, threephase load electric current and current transformer dc capacitor voltage.By the feedback of dc voltage, realize the calculating of the reference current of three-phase symmetrical.The direct voltage amplitude information is to be obtained by dc capacitor voltage information, is single value; And the phase information of three-phase reference current is obtained respectively through three single-phase digital phase-locked loops by its three-phase voltage separately, and the reference current that obtains is that amplitude equates, respectively with the synchronous three-phase current of system voltage.Dc voltage one-period once sampling realizes the smoothly undistorted of reference current.

The stagnant chain rate that system's employing three-phase is controlled separately can take stagnant ring to control to each separately than the Current tracking PWM convertor circuit of mode mutually.Compare with reference to electric current and actual three-phase system electric current, control by PWM, the output offset current realizes controlling target.In sum, as seen the characteristics of this active filter are as follows:

1. the reference current amplitude is unified controls, and guarantees that the three-phase system current amplitude equates all the time.

2. fixed phase is controlled separately, is consistent with system voltage.

3.PWM control signal is controlled separately, relatively the variation that the break-make of a pair of IGBT of phase is separately independently controlled its output current is controlled in output, and the while can guarantee that two IGBT pipes of same phase can not lead directly to.

4. algorithm structure is simple, has the characteristics of three-phase equilibrium.

Description of drawings

Accompanying drawing 1 is APF bucking-out system structure chart;

Accompanying drawing 2 is the active filter three phase algorithm theory diagram of the alternate balance of three-phase three-wire system.

Embodiment

Phase three-wire three without the structure chart of center line bucking-out system as shown in Figure 1.u _sa,, u _sb, u _scBe three-phase system voltage, i _sa, i _sbi _scBe three-phase system electric current, i _La, i _Lb, i _LcBe threephase load electric current, i _ca, i _cbi _ccBe the three-phase offset current of APF output, U _dcBe the current transformer dc capacitor voltage.APF is in parallel with system by inductance L, and it is energy-storage travelling wave tube that its DC side adopts capacitor C.

In the three-phase three-wire system system, asymmetric harmonic voltage and electric current all can be decomposed into each time positive sequence, negative sequence component.Each time of voltage positive sequence, negative phase-sequence are expressed as follows:

$u_{\mathrm{sa}}=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{u}_{\mathrm{ka}}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uka}})=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[u_{k+}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}+})+u_{k-}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}-})]---\left(1\right)$

$u_{\mathrm{sb}}=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{u}_{\mathrm{kb}}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{ukb}})=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[u_{k+}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}+}-2\mathrm{\π}/3)+u_{k-}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}-}+2\mathrm{\π}/3)]---\left(2\right)$

$u_{\mathrm{sc}}=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{u}_{\mathrm{kc}}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{ukc}})=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[u_{k+}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}+}+2\mathrm{\π}/3)+u_{k-}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}-}-2\mathrm{\π}/3)]---\left(3\right)$

By system's three-phase voltage is carried out phase-locked and normalized, obtain the real-time phase angle θ of voltage _u+, namely obtain the unit positive sequence of fundamental frequency of three-phase voltage:

$\left\{\begin{array}{c}{u}_{1a}=\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u+})\\ u_{1b}=\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u+}-2\mathrm{\π}/3)\\ u_{1c}=\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u+}+2\mathrm{\π}/3)\end{array}\right.---\left(4\right)$

Calculate the amplitude of the reference current of three-phase symmetrical:

$I_{\mathrm{ref}}=\frac{P_a+P_b+P_c+P_{\mathrm{Loss}}}{3(U_{a1}+U_{b1}+U_{c1})}---\left(5\right)$

Three-phase positive sequence voltage and power have been introduced in the calculating of three-phase reference current, have formed single reference current amplitude, and then have reached counterbalance effect when the formation target current compensates.

The relation of dc voltage and load active current size is suc as formula shown in (6):

$I_{\mathrm{ref}}\left(T\right)=\frac{1}{T}\underset{t}{\overset{t+T}{\∫}}\mathrm{\ΔQdt}=\frac{1}{T}\underset{t}{\overset{t+T}{\∫}}C(u_{\mathrm{dc}}-u_{\mathrm{dcf}})\mathrm{dt}---\left(6\right)$

The variation of dc voltage is relevant with the size that load is gained merit.By the feedback of dc voltage, realize the calculating of three-phase reference current.

When utilizing three-phase voltage to obtain phase information, adopt the single-phase digital phase-locked loop that balances each other to carry out phase-locked.Single-phase digital phase-locked loop is by multiplying each other with the sin that sets in advance (t), cos (t) data pool, fetch cycle mean value, more namely obtain voltage-phase information through simple computation:

${\mathrm{\θ}}_{u1+}=\frac{X_c\·\sin \left(\mathrm{nt}\right)+Y_c\·\cos \left(\mathrm{nt}\right)}{\sqrt{X_c^2+Y_c^2}}---\left(7\right)$

X wherein _c, Y _cCycle-addition value for transient data and data pool after multiplying each other.

Active filter three phase algorithm structure chart obtains the reference current amplitude by the feedback of dc voltage as shown in Figure 2, after utilizing three single-phase digital phase-locked loops to obtain voltage-phase, can obtain the three-phase reference current:

$\left\{\begin{array}{c}{i}_{\mathrm{refa}}=I_{\mathrm{ref}}\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u1+})\\ i_{\mathrm{refb}}=I_{\mathrm{ref}}\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u1+}-2\mathrm{\π}/3)\\ i_{\mathrm{refc}}=I_{\mathrm{ref}}\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u1+}+2\mathrm{\π}/3)\end{array}\right.---\left(8\right)$

Compare with reference to electric current and actual three-phase system electric current, adopt stagnant chain rate than the Current tracking PWM convertor circuit of mode, the output offset current.Owing to being that three-phase is controlled separately, for phase three-wire three APF in parallel system, can take mutually stagnant ring to control to each separately.Mutually as example, the mutually stagnant chain rate of relatively input A of A phase reference current and actual current is than controller take A, and the break-make of controlling A phase IGBT is independently controlled the variation of its output current.In such cases, inverter has six kinds of mode of operations, the switching between six kinds of patterns by stagnant chain rate result control.

In this algorithm, the reference current amplitude information is to be obtained by dc capacitor voltage information, is single value; And the phase information of three-phase reference current is obtained respectively through three single-phase phase-locked loops by three-phase voltage, and the final reference electric current is that amplitude equates, respectively with the synchronous three-phase current of system voltage.If system side three-phase voltage phase place is symmetrical, reference current three-phase complete equipilibrium.In the unbalanced situation of three-phase system, still can effectively compensate.

It should be understood that multiple modification, modification and additional embodiment are all possible, so within the embodiment of all modification, modification will regard the protection range that is in the present patent application as.

Before this method, system and material description should be understood the disclosure and be not limited to described ad hoc approach opinion, system and material, because these may change.Be understood that equally the term that uses in specification just for specific scheme and embodiment are described, does not limit to the limited field of this explanation.

Claims (1)

1. the alternate balance method of the three-phase three-wire system based on active power filter, is characterized in that, comprises the steps:

(1) in the three-phase three-wire system system, each time of voltage positive sequence, negative phase-sequence, zero sequence are expressed as follows:

$,u_{\mathrm{sa}}=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{u}_{\mathrm{ka}}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uka}})=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[u_{k+}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}+})+u_{k-}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}-})]$

$,u_{\mathrm{sb}}=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{u}_{\mathrm{kb}}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{ukb}})=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[u_{k+}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}+}-2\mathrm{\π}/3)+u_{k-}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}-}+2\mathrm{\π}/3)]$

$,u_{\mathrm{sc}}=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{u}_{\mathrm{kc}}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{ukc}})=\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}[u_{k+}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}+}+2\mathrm{\π}/3)+u_{k-}\sin (\mathrm{k\ωt}+{\mathrm{\θ}}_{\mathrm{uk}-}-2\mathrm{\π}/3)]$

U wherein _sa,, u _sb, u _scBe three-phase system voltage;

(2) three-phase symmetrical reference current amplitude is calculated: $I_{\mathrm{ref}}=\frac{P_a+P_b+P_c+P_{\mathrm{Loss}}}{3(U_{a1}+U_{b1}+U_{c1})},$

U wherein _a1, U _b1, U _c1Be three-phase positive sequence voltage, P _a, P _b, P _cBe three phase power, P _LossBe load power;

(3) voltage-phase calculates: ${\mathrm{\θ}}_{u1+}=\frac{X_c\·\sin \left(\mathrm{nt}\right)+Y_c\·\cos \left(\mathrm{nt}\right)}{\sqrt{X_c^2+Y_c^2}}$

X wherein _c, Y _cCycle-addition value for transient data and data pool after multiplying each other;

(4) three-phase reference current: $\left\{\begin{array}{c}{i}_{\mathrm{refa}}=I_{\mathrm{ref}}\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u1+})\\ i_{\mathrm{refb}}=I_{\mathrm{ref}}\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u1+}-2\mathrm{\π}/3)\\ i_{\mathrm{refc}}=I_{\mathrm{ref}}\sin (\mathrm{\ωt}+{\mathrm{\θ}}_{u1+}+2\mathrm{\π}/3)\end{array}\right.;$

(5) three-phase reference current and actual three-phase system electric current are compared, adopt stagnant chain rate than the Current tracking PWM alternating current circuit of mode, the output offset current.

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