CN101505064B - Control method for series connection type active electric power filter - Google Patents

Abstract

The invention relates to the field of gird power optimization and discloses a control method for a series active power filter. The control method comprises the following steps: detecting a three-phase power supply current, adjusting the three-phase power supply current by using three proportional governors respectively, and using the output of the three proportional governors as a harmonic control quantity of a reference value uc<*> of a three-phase compensating voltage; detecting an SAPF direct current side voltage udc, comparing the SAPF direct current side voltage udc with a preset value of the direct current side voltage by using a single subtracter, adjusting the output of the single substracter by using a single proportional integral governor, and using the output, subjected to amplitude limitation of a dynamic limiter, of the single proportional integral governor as a fundamental wave amplitude signal ucf of a reference value uc<*> of the three-phase compensating voltage of theSAPF; detecting a three-phase power supply voltage us, and outputting the three-phase power supply voltage us as three sine wave signals in the same phase as the three-phase power supply voltage after the three-phase power supply voltage us passes through three phase-locked loop and three sine wave generators ; multiplying the three sine wave signals by the fundamental wave amplitude signal ucf respectively by using three multipliers to obtain a fundamental wave control quantity uC-active<*>; and adding the harmonic control quantity to the fundamental wave control quantity uC-active<*> by using three adders and using the output of the three adders as the reference value uc<*> of the three-phase compensating voltage of the SAPF, and controlling the actual three-phase compensating voltage of the SAPF to be uc.

Description

A kind of control method of series connection type active electric power filter

Technical field

The present invention relates to electrical network electric energy quality optimizing field, particularly a kind of control method of series connection type active electric power filter.

Background technology

Popularizing gradually of non-linear equipments such as power electronic equipment produced serious harmonic pollution to electrical network.Particularly in recent years, with frequency converter, UPS and communication switch power supply be representative device development rapidly, they all are the voltage-type harmonic sources, and Passive LC filter and parallel connection type active electric filter all are not suitable for compensating this class voltage-type harmonic source.Series connection type active electric power filter (Series Active Power Filter is called for short SAPF) is a development in recent years class compensation arrangement rapidly, effectively the harmonic problem of bucking voltage type harmonic source initiation.

The main circuit structure of series connection type active electric power filter (SAPF) mainly is made of DC side energy storage device, voltage-source type pwm converter, output filter and coupling transformer.SAPF can produce the voltage of random waveform as required, and therefore, it can be used for simulating a special impedance that shows high impedance for harmonic current and show short circuit for fundamental current.In other words, its circuit model is equivalent to one to the different resistance of the harmonious wave resistance value of first-harmonic.To harmonic wave can equivalence be the resistance of K Ω for resistance, and to first-harmonic, its resistance is 0 Ω.

The control method of series connection type active electric power filter has determined the compensation performance of SAPF, all is the emphasis that people pay close attention to all the time.The core of traditional control method is complicated harmonic wave detection algorithm, the common methods such as fast fourier transform, instantaneous reactive power theory of utilizing detect harmonic wave, but which kind of method no matter, all need complex calculations, and the precision of calculating the time-delay caused and calculating itself all will influence the effect of harmonic compensation.In addition, there is potential destabilizing factor in the voltage control loop of the SAPF DC voltage control loop in the traditional control method.The prerequisite of closed-loop control is the degenerative existence of whole loop, so just may be with system stability a specific balance operating state.And the negative feedback of this DC voltage control loop has ruined possibility.The first harmonic magnitude of the adjuster output control SAPF output voltage of DC voltage control, and the relation of the active power that this first harmonic magnitude and SAPF are absorbed is non-linear, does not possess monotonicity in whole possible interval.In other words, when the first harmonic magnitude of SAPF output voltage increased, it was uncertain specifically can causing dc voltage to rise or descend, and also depends on the work at present state of system.Therefore, after working state of system was transferred in another monotony interval by a monotony interval, the negative feedback of original design just became positive feedback, and system enters labile state.

Summary of the invention

The control method that the objective of the invention is to a kind of series connection type active electric power filter, it has abandoned the harmonic wave detection algorithm of the complexity in the conventional method, has significantly reduced soft, the hardware spending of control system, reduces the cost of SAPF control system.

In order to achieve the above object, the present invention is achieved by the following technical solutions.A kind of control method of series connection type active electric power filter is characterized in that, may further comprise the steps:

Step 1 detects the three phase mains current i _s, to adjust by No. three proportional controllers respectively, it is exported as SAPF three-phase compensation voltages reference value u _c* harmonic wave controlled quentity controlled variable;

Step 2 detects SAPF dc voltage u _Dc, and with dc voltage set point u _Dc* compare through the single channel subtracter, its output is adjusted through the single channel proportional and integral controller, and the output of single channel proportional and integral controller is as the three-phase compensation voltages reference value u of SAPF _c* first harmonic magnitude signal u _Cf

Step 3 detects three-phase mains voltage u _s, obtain the three-phase mains voltage phase theta respectively by three road phase-locked loops _Us, and respectively by No. three sine-wave generators, be output as and synchronous three road sine wave signals of three-phase mains voltage, this three road sine wave signals amplitude is identical;

Step 4, with three road sine wave signals by No. three multipliers respectively with the first harmonic magnitude signal u of the three-phase compensation voltages reference value of SAPF _CfMultiply each other, the output of No. three multipliers is as the three-phase compensation voltages reference value u of SAPF _c* first-harmonic controlled quentity controlled variable u _C-active ^*

Step 5 is with the three-phase compensation voltages reference value u of SAPF _c* harmonic wave controlled quentity controlled variable and first-harmonic controlled quentity controlled variable u _C-active ^*After three tunnel adder additions, as the three-phase compensation voltages reference value u of SAPF _c*; The actual three-phase compensation voltages that detects SAPF is u _c, constitute the voltage control closed loop, follow the tracks of the three-phase compensation voltages reference value u of SAPF _c*.

Further improvement of the present invention is:

The first harmonic magnitude signal u of the three-phase compensation voltages reference value of described SAPF _Cf, behind the dynamic limiter amplitude limit, import No. three multipliers; The higher limit U of described dynamic limiter _{Cf up-limit}With lower limit U _{Cf lower-limit}Determine in the following manner: at first, gather the dc voltage u of SAPF _Dc, and ask for its first derivative

And second dervative The second dervative of its current time

Second dervative with previous moment

During jack per line, higher limit U _{Cf up-limit}With lower limit U _{Cf lower-limit}Constant; The second dervative of current time

Second dervative with previous moment

Contrary sign or wherein have one to be zero, and the first derivative of current time

Greater than 0 o'clock, the first harmonic magnitude signal u of the three-phase compensation voltages reference value of current time _Cf(N) as higher limit U _{Cf up-limit}The second dervative of current time

Second dervative with previous moment

Contrary sign or wherein have one to be zero, and the first derivative of current time Smaller or equal to 0 o'clock, the first harmonic magnitude signal u of the three-phase compensation voltages reference value of current time _Cf(N) as lower limit U _{Cf lower-limit}

The control method of series connection type active electric power filter of the present invention, abandoned the harmonic wave detection algorithm of the complexity in the conventional method, saved the checkout gear of three phase mains current harmonics in the control corresponding system, significantly reduce soft, the hardware spending of control system, reduced the cost of SAPF control system.Simultaneously, among the present invention, increased dynamic limiter, the range signal of DC voltage control is u _Cf, behind the dynamic limiter amplitude limit, as SAPF three-phase output voltage reference value u _cThe common range signal of first-harmonic controlled quentity controlled variable has * avoided becoming in some non-linear section negative feedback the risk of positive feedback, makes the SAPF control system always work in stable state.

Description of drawings

Fig. 1 is the main circuit structure figure of series connection type active electric power filter;

Fig. 2 is the control device system diagram among the present invention;

Fig. 3 is the control block diagram among the present invention;

Fig. 4 is the higher limit U of dynamic limiter among the present invention _{Cf up-limit}With lower limit U _{Cf lower-limit}Self adaptation correction FB(flow block);

Fig. 5 is the first harmonic magnitude signal u of the three-phase compensation voltages reference value of SAPF _CfAnd the graph of relation between the active power that SAPF absorbs.

Embodiment

With reference to Fig. 1, connect series connection type active electric power filter 2 between three phase mains 1 and the nonlinear load 3.The main circuit structure of series connection type active electric power filter 2 mainly comprises: DC side energy storage device 201, voltage-source type pwm converter 202, output filter 203 and coupling transformer 204 4 parts constitute.DC side energy storage device 202 generally is made of the power capacitor connection in series-parallel.Voltage-source type pwm converter 202 adopts full control device such as compositions such as IGBT, GTO.Output filter 203 employings are connected on the filter inductance of voltage-source type pwm converter 202 AC side and LC filter in parallel is realized; The selection of LC filter parameter depends primarily on the switching frequency of voltage-source type pwm converter, but LC filter additional damping resistance suppress to shake, its parameter request is compromised to select for use between filter effect and damping and is got final product.Coupling transformer 204 is connected between three phase mains 1 and the voltage-source type pwm converter 202, and its effect mainly is that the bucking voltage that voltage-source type pwm converter 202 produces is coupled to three phase mains 1 to offset the harmonic voltage that nonlinear load 3 produces.

In order to narrate conveniently, among the present invention, three-phase mains voltage is designated as u _s, that is: u _Sa, u _Sb, u _ScThe three-phase mains voltage phase theta _Us, that is: θ _Usa, θ _Usb, θ _UscThe three phase mains electric current is designated as i _s, that is: i _Sa, i _Sb, i _ScThe dc voltage of series connection type active electric power filter (SAPF) is designated as u _Dc, the dc voltage set point is designated as u _Dc*.The three-phase compensation voltages of series connection type active electric power filter (SAPF) output is designated as u _c, that is: u _Ca, u _Cb, u _Cc, the three-phase compensation voltages reference value is designated as u _c*; The first harmonic magnitude signal of three-phase compensation voltages reference value is designated as u _Cf, the first-harmonic controlled quentity controlled variable of three-phase compensation voltages reference value is designated as u _C-active ^*

With reference to Fig. 2, Fig. 3, the control method of series connection type active electric power filter of the present invention may further comprise the steps:

Step 1 detects the three phase mains current i _s, to adjust by No. three proportional controllers respectively, it is exported as SAPF three-phase compensation voltages reference value u _c* harmonic wave controlled quentity controlled variable;

Step 2 detects SAPF dc voltage u _Dc, and with dc voltage set point u _Dc* compare through the single channel subtracter, its output is adjusted through the single channel proportional and integral controller, the output of single channel proportional and integral controller through the dynamic limiter amplitude limit after, as the first harmonic magnitude signal u of the three-phase compensation voltages reference value of SAPF _Cf

Step 3 detects three-phase mains voltage u _s, obtain the three-phase mains voltage phase theta respectively by three road phase-locked loops _Us, and respectively by No. three sine-wave generators, be output as and synchronous three road sine wave signals of three-phase mains voltage, this three road sine wave signals amplitude is identical;

Step 4, with three road sine wave signals by No. three multipliers respectively with the first harmonic magnitude signal u of the three-phase compensation voltages reference value of SAPF _CfMultiply each other, the output of No. three multipliers is as the three-phase compensation voltages reference value u of SAPF _c* first-harmonic controlled quentity controlled variable u _C-active ^*

Step 5 is with the three-phase compensation voltages reference value u of SAPF _c* harmonic wave controlled quentity controlled variable and first-harmonic controlled quentity controlled variable u _C-active ^*After three tunnel adder additions, as the three-phase compensation voltages reference value u of SAPF _c*; The actual three-phase compensation voltages that detects SAPF is u _c, constitute the voltage control closed loop, follow the tracks of the three-phase compensation voltages reference value u of SAPF _c*.

The three-phase compensation voltages reference value u of SAPF _c* be u with the actual three-phase compensation voltages that detects SAPF _cCompare, the voltage-source type pwm converter output among the control SAPF, the realization three-phase compensation voltages is u _cControl; In above-mentioned voltage control closed loop, the control mode that relates to the voltage-source type pwm converter can adopt traditional control mode.

With reference to Fig. 4, the higher limit U of dynamic limiter _{Cf up-limit}With lower limit U _{Cf lower-limit}Determine in the following manner: at first, gather the dc voltage u of SAPF _Dc, and ask for its first derivative

And second dervative

The second dervative of its current time

Second dervative with previous moment

During jack per line, promptly $\frac{d^2{u}_{\mathrm{dc}}}{{\mathrm{dt}}^2}\left(N\right)\&CenterDot;\frac{d^2{u}_{\mathrm{dc}}}{{\mathrm{dt}}^2}(N-1)>0$ The time, higher limit U _{Cf up-limit}With lower limit U _{Cf lower-limit}Constant; The second dervative of current time

Second dervative with previous moment

Contrary sign or wherein have one to be zero, and the first derivative of current time

Greater than 0 o'clock, that is: $\frac{d^2{u}_{\mathrm{dc}}}{{\mathrm{dt}}^2}\left(N\right)\&CenterDot;\frac{d^2{u}_{\mathrm{dc}}}{{\mathrm{dt}}^2}(N-1)\&le;0,$ And $\frac{{\mathrm{du}}_{\mathrm{dc}}}{\mathrm{dt}}\left(N\right)>0$ The time, the first harmonic magnitude signal u of the three-phase compensation voltages reference value of current time _Cf(N) as higher limit U _{Cf up-limit}The second dervative of current time

Second dervative with previous moment Contrary sign or wherein have one to be zero, and the first derivative of current time Smaller or equal to 0 o'clock, that is: $\frac{d^2{u}_{\mathrm{dc}}}{{\mathrm{dt}}^2}\left(N\right)\&CenterDot;\frac{d^2{u}_{\mathrm{dc}}}{{\mathrm{dt}}^2}(N-1)\&le;0,$ And $\frac{{\mathrm{du}}_{\mathrm{dc}}}{\mathrm{dt}}\left(N\right)\&le;0$ The time, the first harmonic magnitude signal u of the three-phase compensation voltages reference value of current time _Cf(N) as lower limit U _{Cf lower-limit}

In the practice, lower limit U _{Cf lower-limit}Initial value generally get 0; Higher limit U _{Cf up-limit}Initial value can set a bigger value according to the capacity of system, u when for example making even steady operation _Cf3-5 doubly, purpose is before not calculating amplitude limit value, allows all signals all to pass through, and amplitude limit not.

With reference to Fig. 5, the first harmonic magnitude signal u of the three-phase compensation voltages reference value of SAPF is described _CfAnd the relation between the active power that SAPF absorbs.Among the figure, the active power that the SAPF AC side absorbs is P _C, the active power of SAPF loss is P _LossActive power P when the absorption of SAPF AC side _CActive power P greater than the SAPF loss _LossThe time, as U among the figure ₁To U ₂The interval, the DC side energy storage device absorbs active power, and dc voltage raises.The active power P that the SAPF AC side absorbs _CActive power P less than the SAPF loss _LossThe time, as among the figure 0 to U ₁Interval and U ₂To the Us interval, the DC side energy storage device discharges active power, and dc voltage reduces.As seen from the figure, the first harmonic magnitude signal u of three-phase compensation voltages reference value _CfVariation can be so that SAPF be in different operating states, optimum situation is: when SAPF need absorb active power, improve dc voltage, the active power of absorption is many as far as possible; Need discharge active power and work as SAPF, reduce dc voltage, the active power of release is many as far as possible.

Generally speaking, the first-harmonic composition of the three-phase compensation voltages of SAPF is big more, the active power that the DC side energy storage device is absorbed is big more, but increase owing to be accompanied by the first-harmonic composition of three-phase compensation voltages, the first-harmonic composition of source current reduces, therefore after the first-harmonic composition of three-phase compensation voltages increases to a certain degree, however the phenomenon that active power that the DC side energy storage device absorbed reduces thereupon can appear, as U among Fig. 5 ₃To the Us interval, this just can cause system to enter labile state.And the active power that the DC side energy storage device of SAPF absorbs and discharges is embodied directly on the rate of change (being the amplitude of the first derivative of dc voltage) of dc voltage, when the first derivative amplitude of dc voltage is in peak (paddy) value, the first harmonic magnitude signal u of the three-phase compensation voltages reference value of current time _CfIt is upward (descending) amplitude limit value of expectation.Therefore, ask for the second dervative of dc voltage earlier, when second dervative equalled zero, first derivative reached extreme value; Judge the positive and negative of first derivative afterwards again, upward (descending) amplitude limit value that can obtain to expect.

Because there is non-linear relation in the active power that the first-harmonic composition of the three-phase compensation voltages of SAPF and SAPF absorb, have potential instability problem, increase dynamic limiter, can effectively avoid potential instability problem in the control method of traditional series connection type active electric power filter, and the function that will suppress current harmonics is realized by harmonic wave controlled quentity controlled variable in the reference value of three-phase compensation voltages mainly.

Claims (1)

1. the control method of a series connection type active electric power filter may further comprise the steps:

Step 1 detects the three phase mains current i _s, to adjust by No. three proportional controllers respectively, its output is as the three-phase compensation voltages reference value u of series connection type active electric power filter _c ^*The harmonic wave controlled quentity controlled variable;

Step 2, the dc voltage u of detection series connection type active electric power filter _Dc, and with dc voltage set point u _Dc ^*Compare through the single channel subtracter, its output is adjusted through the single channel proportional and integral controller, and the output of single channel proportional and integral controller is as the three-phase compensation voltages reference value u of series connection type active electric power filter _c ^*First harmonic magnitude signal u _Cf

Step 3 detects three-phase mains voltage u _s, obtain the three-phase mains voltage phase theta respectively by three road phase-locked loops _Us, and respectively by No. three sine-wave generators, be output as and synchronous three road sine wave signals of three-phase mains voltage, this three road sine wave signals amplitude is identical;

Step 4, with three road sine wave signals by No. three multipliers respectively with the first harmonic magnitude signal u of the three-phase compensation voltages reference value of series connection type active electric power filter _CfMultiply each other, the output of No. three multipliers is as the three-phase compensation voltages reference value u of series connection type active electric power filter _c ^*The first-harmonic controlled quentity controlled variable

Step 5 is with the three-phase compensation voltages reference value u of series connection type active electric power filter _c ^*Harmonic wave controlled quentity controlled variable and first-harmonic controlled quentity controlled variable After three tunnel adder additions, as the three-phase compensation voltages reference value u of series connection type active electric power filter _c ^*The actual three-phase compensation voltages that detects series connection type active electric power filter is u _c, constitute the voltage control closed loop, follow the tracks of the three-phase compensation voltages reference value u of series connection type active electric power filter _c ^*

It is characterized in that,

The first harmonic magnitude signal u of the three-phase compensation voltages reference value of described series connection type active electric power filter _Cf, behind the dynamic limiter amplitude limit, import No. three multipliers; The higher limit U of described dynamic limiter _{Cf up-limit}With lower limit U _{Cf lower-limit}Determine in the following manner: at first, gather the dc voltage u of series connection type active electric power filter _Dc, and ask for its first derivative

And second dervative

The second dervative of its current time

Second dervative with previous moment

Jack per line the time, higher limit U _{Cf up-limit}With lower limit U _{Cf lower-limit}Constant; The second dervative of current time

Second dervative with previous moment

Contrary sign or wherein have one to be zero, and the first derivative of current time

Greater than zero the time, the first harmonic magnitude signal u of the three-phase compensation voltages reference value of current time _Cf(N) as higher limit U _{Cf up-limit}The second dervative of current time

Second dervative with previous moment

Contrary sign or wherein have one to be zero, and the first derivative of current time

Smaller or equal to zero the time, the first harmonic magnitude signal u of the three-phase compensation voltages reference value of current time _Cf(N) as lower limit U _{Cf lower-limit}

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