CN104065077A - Control method of series voltage compensation device - Google Patents

Abstract

The invention discloses a control method of a series voltage compensation device. The control method comprises the following steps: acquiring a reference rated voltage of a three-phase system, a load side three-phase voltage, and a filter inductive current at the AC side of an inverter unit through a data acquiring unit; calculating the difference between the three-phase voltage at the load side and the reference rated voltage of the three-phase system through a first error comparator, and treating the difference as the input of a proportion resonance regulator; calculating the difference between the output of the proportion resonance regulator set and the filter inductive current through a second error comparator, and treating the difference as the input of a proportion controller; accumulating the output of the proportion controller and the front feed of network voltage, and treating the product of the accumulated value and the DC voltage coefficient as IGBT (Insulated Gate Bipolar Translator) input of the inverter unit; accumulating the IGBT output of the inverter unit and the network voltage, and then controlling the load voltage. According to the control method of the series voltage compensation device, the design of combining the series compensation device and the DC voltage coefficient when a network suffers from a fault quickly and effectively ensures the stability of amplitude of the load port voltage.

Description

The control method of series voltage compensation arrangement

Technical field

The present invention relates to electric power neighborhood, more particularly, relate to a kind of control method of series voltage compensation arrangement.

Background technology

Series-type voltage compensation arrangement, be independent of electrical network and load, can be applicable to general energy-dissipating type load and energy feedback type load, when being applied to the low voltage crossing compensation of blower fan, because it is independent of wind-powered electricity generation unit and connecting system, compensation performance does not rely on the self-characteristic of blower fan, payes attention to and be subject to gradually people.This device is series between load and electrical network, in the time that system generation voltage falls, and device output bucking voltage, guarantee that load side voltage is stable, making load not fallen by system voltage affects, and when falling after disappearance, can recover rapidly to send active energy and reactive energy to system.

The inverter control method of series-type voltage compensation arrangement and the quality of control system, be directly connected to the quality of its function realization and the safety and stability of device.For the control algolithm of inverter, what adopt the earliest is simulation control of PID, along with popularizing of digital processing unit, digital PID is used gradually, but due to the impact of digital control middle sampling, computation delay, in a sampling period of control signal lag output, cause the poor stability of system, the complexity of parameter testing simultaneously.Dead beat control is a kind of control method based on circuit model, and the accuracy of its control depends on the accuracy that system model is estimated, therefore the robustness of system is poor.The dynamic property of repetitive controller is poor, and the dynamic responding speed of system is slow, needs the methods such as bonding state FEEDBACK CONTROL to improve its dynamic property.In addition, also have Sliding mode variable structure control, fuzzy control etc., but owing to controlling the factors such as complicated, all in the experimental study stage.

Another subject matter when being applied to the load of blower fan homenergic feedback type and carrying out voltage compensation is the integrity problem of device self.Be different from general power consumption load, blower fan is in the time that low-voltage occurs, and its energy need inject series compensation device, if it is not taked to certain control, and the inherently safe of entail dangers to device.At present, less for the research of tandem type blower fan low voltage devices itself, part document proposes this portion of energy feedback grid, but for larger in short-term rush of current, has proposed higher requirement to controlling, and device reliability is reduced.

Summary of the invention

For the defect existing in prior art, the object of this invention is to provide a kind of control method of series voltage compensation arrangement, it is high that this control method has compensation precision, and fast response time has the ability of harmonic compensation concurrently simultaneously; And in control algolithm, fully ensure the safe and stable operation of device.Particularly, this control method has adopted the double-loop control strategy based on ratio resonant regulator group; And load on the problem of energy flowing backward device between age at failure for energy feedback type, also proposed a kind of method for designing of DC voltage control device, guaranteed the safe and stable operation of series compensation device self.Wherein, the use of fundamental-wave resonator has ensured precision and the steady-state behaviour of load port voltage, for the typical harmonic wave in electrical network and load, by adding harmonic resonator group, can effectively suppress electrical network and the impact of load disturbance on compensation performance.For the fluctuation of DC voltage, introduce direct voltage coefficient and effectively suppressed this fluctuation.

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

A control method for series voltage compensation arrangement, the concrete steps of this control method are:

A. obtain the filter inductance electric current of reference rated voltage, load-side three-phase voltage and the inversion unit AC of three-phase system by data acquisition unit;

B. by after the difference between the first error comparator computational load side three-phase voltage and the reference rated voltage of three-phase system, as the input of ratio resonant regulator group;

Wherein, ratio resonant regulator group is mainly made up of proportional component, fundamental-wave resonator and harmonic resonator group,

The Mathematical Modeling of described ratio resonant regulator group is as follows,

$G_{\mathrm{PR}}\left(s\right)=K_P+\underset{h=\mathrm{1,3,5},...}{\overset{n}{\mathrm{\Σ}}}\frac{{2K}_i{\mathrm{\ω}}_{\mathrm{cut}}s}{s^2+2{\mathrm{\ω}}_{\mathrm{cut}}s+{\left({\mathrm{h\ω}}_0\right)}^2},$

Wherein, K _pfor proportional component gain, its span is between 1～10; K _ifor the gain of resonator, value is between 10～100, and its value is larger, and precision is also just higher, but the stability of system can decrease;

ω _cutfor the shearing frequency of resonator, ω _cutspan is 5～20;

ω ₀for the resonance frequency of system first-harmonic;

H represents in system the waveform of the h time, and wherein, when h=1, corresponding is fundamental-wave resonator, and this resonator is necessary in control system, and object is the following feature of increase system to reference voltage instruction, suppresses the real-time disturbance in electrical network and load simultaneously; H=3,5 ... time, be harmonic resonator group, its number and number of times should add according to the general characteristic of electrical network, and object is to suppress harmonic voltage in electrical network and load or the disturbance of harmonic current;

C. by after the difference between output and the filter inductance electric current of the second error comparator calculating ratio resonant regulator group, as the input of proportional controller;

D. the output of proportional controller and voltage feed-forward control cumulative after with direct voltage coefficient product as the IGBT input in inversion unit, the IGBT output in inversion unit and the cumulative rear control load voltage of line voltage;

Wherein, the introducing of voltage feed-forward control, is that the span of feed-forward coefficients is between 0.5～2 for the response of increase system to voltage fluctuation, and value is larger, and control system is also faster to the response speed of voltage fluctuation, but can reduce the stability of system;

And DC voltage control link is to realize by the design of introducing direct voltage coefficient, object is in order effectively to suppress the impact that DC voltage fluctuates on inverter, improves the compensation precision of compensation waveform.

By introducing direct voltage COEFFICIENT K _dc, follow the tracks of DC voltage and sent into control system with Real-Time Monitoring.The result of itself and step C is made to product calculation, carry out the port voltage of control load, thereby make inverter output voltage can not be subject to the influence of fluctuations of DC voltage.Wherein, K _dcdesign as follows: by the DC voltage value under electrical network rated condition, the direct voltage COEFFICIENT K that it is corresponding _dcget and do 1, in the time of a times of DC voltage rising, K _dcbe reduced to original 1/a; In the time that DC voltage is reduced to original 1/a, K _dcraise as original a times.K _dcpurpose of design be: because DC voltage fluctuation can directly have influence on the output waveform of IGBT, therefore, by introducing DC voltage COEFFICIENT K _dc, because the product of DC voltage and this DC voltage coefficient is 1, and keep constant, therefore, from whole control system, fluctuating with regard to imperceptible DC voltage, thereby effectively increasing the robustness of control system to DC voltage fluctuation.

Described control method is further comprising the steps of:

While judging that according to the direction of load current load characteristic is energy feedback type, detect in real time DC voltage by data acquisition unit, and by stagnant ring controller, it is carried out to stagnant ring control.

The concrete steps of the stagnant ring control of described stagnant ring controller are:

Set DC voltage reference value according to the needed DC voltage value of inverter bucking voltage, on this basis, set stagnant ring higher limit and stagnant ring lower limit;

In the time that DC voltage exceedes the stagnant ring higher limit of its setting, DC side discharge loop switch closure, discharge resistance work, DC voltage starts to reduce;

In the time that DC voltage is reduced to the stagnant ring lower limit of setting, DC side discharge loop switch disconnects, and now direct voltage starts to rise.

Compared with prior art, adopt the control method of a kind of series voltage compensation arrangement of the present invention to there is following beneficial effect:

1) data acquisition unit detection of grid voltage, through phase-locked loop pll, obtains three-phase A, B, and the amplitude of C system voltage and phase information, phase information, by calculating mutually with set-point, obtains the reference rated voltage of three-phase system.Meanwhile, gather load-side three-phase voltage, current information, using the input variable as control module unit;

2) control unit is realized designed control algolithm by digital processing chip, control algolithm mainly comprises a ratio resonant regulator group, a stagnant ring controller of DC side, wherein, ratio resonant regulator group is defined as: proportional controller+multiple resonant regulator groups form.Wherein, the number of resonant regulator and number of times are determined according to the line voltage operating mode at device place, for example, contain 3,5,7 subharmonic voltage or harmonic currents in electrical network, and this resonator group is by fundamental-wave resonator and 3,5, and 7 harmonic resonator forms.This ratio resonant regulator group is as the outer ring controller of double-loop control strategy, it is input as poor with reference to rated voltage and load virtual voltage, acting as of ratio resonant regulator group makes output follow the tracks of as much as possible given reference, to improve the compensation precision of system.Meanwhile, by adding harmonic resonator group, effectively suppress the typical subharmonic disturbance in electrical network or load.The output of resonator is as the instruction of interior ring controller, and the difference of the current signal that itself and interior ring gather is as the input of interior ring, and output directly acts on inverter.Meanwhile, adding of supply voltage feedforward, can effectively increase the response speed of system.The acting in conjunction of this control strategy, control command is input in controlled device the most at last.

Three, for the model of inversion unit, from document " Xu Dehong. power electronic system modeling and control [M]. Beijing: the .2007:187-200. of China Machine Press ", as the switching frequency f of inversion unit _sbe far longer than the fundamental frequency f of modulation signal ₀, and in the time not there is not ovennodulation, there is fixed proportion relation, i.e. K in the respective components in the fundamental signal in signal wave and low-order harmonic and inverter output voltage _pWM=U _dc/ U _t, wherein, U _dcfor DC voltage, U _tfor the amplitude of triangular wave.In fact, inversion unit is in the time of work, and DC voltage is to fluctuate always, passes through to introduce the COEFFICIENT K relevant to DC voltage in literary composition _dcthereby, the impact of the disturbance that has effectively suppressed DC voltage on inverter output.

Four,, for the problem of the energy injection compensation arrangement of energy feedback type load, it is the voltage of controlling DC side that the stagnant ring controller Main Function of DC side is set, the safe operation of protective device.Specific practice is: detect in real time DC voltage by data acquisition unit, and load current, and be sent in the stagnant ring controller of DC side.Judge according to the direction of load current whether load characteristic is energy feedback type.If so, entering stagnant ring controller controls.While making DC voltage exceed the upper limit threshold of its setting, DC side discharge loop switch closure, discharge resistance work, DC voltage starts to reduce; In the time that DC voltage is reduced to the lower threshold of setting, DC side discharge loop switch disconnects, and now direct voltage starts to rise.And so forth, by with the DC side upper limit, lower threshold is compared, thereby has realized effective control of DC voltage.

In a word, the control method of series voltage compensation arrangement of the present invention, tandem type compensation arrangement during for electric network fault, the control method that a kind of two closed loops based on ratio resonant regulator group add feedforward controller has been proposed, in conjunction with the design of direct voltage coefficient, thus the amplitude of proof load port voltage stable fast and effectively; Meanwhile, inject the excess energy of series compensation device for energy feedback type load, adopt and in device, add electronic switch controlled discharge resistance hardware, by detecting load current steering wheel DC voltage amplitude size, the break-make of electronic switch is controlled.This control system, in series connection low voltage crossing compensating apparatus, had both kept the stable of load terminal voltage, had ensured again the steady safe operation of compensation arrangement.

Brief description of the drawings

Fig. 1 be embodiments of the invention for the application block diagram of series voltage compensation arrangement;

Fig. 2 is the principle schematic of the control method of series voltage compensation arrangement of the present invention;

Fig. 3 is the transfer function block diagram of the closed-loop control in Fig. 2;

Fig. 4 is the flow chart of the stagnant ring control in Fig. 2;

Fig. 5 is the Bode figure of the frequency characteristic of the control method of the present embodiment, wherein,

Fig. 5 a is G _vref(s) frequency characteristic, closed loop is exported the Bode figure of the tracking characteristics to instruction;

Fig. 5 b is G _vs(s) frequency characteristic, closed loop is exported the Bode figure of the suppression characteristic to supply voltage disturbance;

Fig. 5 c is G _iL(s), closed loop is exported the Bode figure of the suppression characteristic to load disturbance;

The Nyquist figure of open-loop transfer function when Fig. 6 is control system zero load;

Fig. 7 is the compensation waveform that the control method of the present embodiment is applied to blower fan low-voltage problem.

Embodiment

Further illustrate technical scheme of the present invention below in conjunction with drawings and Examples.

Embodiment

Refer to shown in Fig. 1, wherein, in the normal situation of line voltage, load current is flowed into or is flowed out electrical network by the by-pass switch of tandem arrangement, and in the time that low-voltage problem appears in electrical network, by-pass switch disconnects, between compensation arrangement series connection access load and electrical network.Herein designed control system is unloaded and is put unit mainly for the inversion unit in figure and direct current.Wherein, the bucking voltage of the main output inverter of inversion unit, direct current unloads to be put unit and is made up of electronic switch S and discharge resistance, and when S closed loop, discharge resistance and DC side form loop, start electric discharge, and when S disconnects, resistance and DC side disconnection, do not discharge.Wherein, I _sfor system power, I _lfor load current, I _iNfor inverter output filtering reactive current.

Figure 2 shows that the control block diagram of whole control system.Wherein, by elements such as voltage transformer, current transformer, Halls, by the line voltage of three-phase system, load voltage, load current, and the analog signals such as DC side voltage of converter is sent into signal gathering unit, after conditioning, filtering and AD sampling, obtain corresponding digital information.

This digital information is divided into two parts, sends into respectively designed closed loop controller and stagnant ring controller.Wherein, the electric current and voltage of the system that is input as of closed loop controller, the electric current and voltage of load, and the analog quantity such as DC voltage, the IGBT in inverter is directly sent in its output, thus effectively control load port voltage keeps stable.Stagnant ring controller be input as DC voltage, its output is sent into direct current in Fig. 1 and is unloaded and put unit, by controlling the break-make of DC switch S, thereby effectively controls the magnitude of voltage of DC side.

Fig. 3 is the unfolding circuits of closed-loop control part shown in Fig. 2, i.e. the double-loop control strategy based on ratio resonant regulator group proposed by the invention.Wherein, reference voltage is the rated value of the three-phase system voltage obtaining by phase-locked loop, and the outer shroud of this double closed-loop control system is load voltage ring, and controller is ratio resonant regulator; Interior ring is the inductive current ring of inverter, and controller is proportional controller, and meanwhile, controlling unit also combines voltage feed-forward control control, and DC voltage control link.

The object that designs this controller comprises: be load voltage owing to controlling target, therefore particularly important for the control of outer shroud, therefore the detailed design of this place outer ring controller, can effectively ensure to compensate the precision of rear voltage.The introducing of interior ring is the response speed in order to increase system, increase stability margin, therefore only enough meet this control requirement by additional proportion controller, the span of this proportional controller is generally between 2～10, within the scope of this, it is larger that this value is got, and the response speed of system is faster, but unfavorable to the stability of system; Value is less, and effect is contrary.The introducing of voltage feed-forward control, is that the span of feed-forward coefficients is generally between 0.5～2 for the response of increase system to voltage fluctuation, and value is larger, and control system is also faster to the response speed of voltage fluctuation, but can reduce the stability of system.And DC voltage control link is to realize by the design of introducing direct voltage coefficient, object is in order effectively to suppress the impact that DC voltage fluctuates on inverter, improves the compensation precision of compensation waveform.

The Mathematical Modeling of designed ratio resonant regulator group is as follows, and this model is made up of proportional component+fundamental-wave resonator+harmonic resonator group:

$G_{\mathrm{PR}}\left(s\right)=K_P+\underset{h=\mathrm{1,3,5},...}{\overset{n}{\mathrm{\Σ}}}\frac{{2K}_i{\mathrm{\ω}}_{\mathrm{cut}}s}{s^2+2{\mathrm{\ω}}_{\mathrm{cut}}s+{\left({\mathrm{h\ω}}_0\right)}^2},$ Wherein,

K _pfor proportional component gain, its span is within 1～10; K _ifor the gain of resonator, general value is tens to hundreds of, and its value is larger, and precision is also just higher, but the stability of system can decrease; ω _cutfor the shearing frequency of resonator, ω _cutgenerally be taken as the number between 5～20; ω ₀for the resonance frequency of system first-harmonic, h represents in system the waveform of the h time, in practical application, should add according to the general characteristic of electrical network, for example, the exemplary voltages that electrical network is contained or current harmonics are 3,5,7 times harmonics, only need to increase the resonator of corresponding 3,5,7 number of times such as grade.

Wherein, when h=1, corresponding is fundamental-wave resonator, and this resonator is necessary in control system, and object is the following feature of increase system to reference voltage instruction, suppresses the real-time disturbance in electrical network and load simultaneously; H=3,5 ... time, be harmonic resonator group, its number and number of times should add according to the general characteristic of electrical network, and object is to suppress harmonic voltage in electrical network and load or the disturbance of harmonic current.

In the present invention, using DC voltage as disturbance quantity processing, by having designed direct voltage COEFFICIENT K _dc, Real-Time Monitoring is followed the tracks of DC voltage and is sent into control system.Concrete steps: by the DC voltage value under electrical network rated condition, the direct voltage COEFFICIENT K that it is corresponding _dcget and do 1, in the time of a times of DC voltage rising, K _dcbe reduced to original 1/a; In the time that DC voltage is reduced to original 1/a, K _dcraise as original a times.K _dcpurpose of design be: because DC voltage fluctuation can directly have influence on the output waveform of IGBT, therefore, by introducing DC voltage COEFFICIENT K _dcbecause the product of DC voltage and this DC voltage coefficient is 1, and keep constant, therefore, from whole control system, it controls output effect just can not feel the fluctuation of DC side, thereby inverter output voltage can not be subject to the influence of fluctuations of DC voltage, has increased the robustness of control system.

Fig. 4 is the detailed description of stagnant ring control in Fig. 2, adopts flowcharting, detects in real time DC voltage, and be sent in the stagnant ring controller of DC side by data acquisition unit.In control system, define load current I _ldirection: it is positive direction that electric current flows into the direction of load from electrical network.Controller is according to the direction of load current, judges that load characteristic is energy-dissipating type (direction for just) or energy feedback type (direction is for negative); If load current direction, for negative, enters stagnant ring controller and carries out DC voltage control.Set direct voltage benchmark U according to the needed DC voltage value of inverter bucking voltage _dc0, then on this basis, set stagnant ring higher limit U _{dc_Upper}with lower limit U _{dc_Lower}.As DC voltage U _dcexceed the upper limit threshold U of its setting _{dc_Upper}time, DC side discharge loop switch S closure, discharge resistance work, DC voltage starts to reduce; As DC voltage U _dcbe reduced to the lower threshold U of setting _{dc_Lower}time, DC side discharge loop switch S disconnects, and now direct voltage starts to rise.During electric network fault, by actual DC voltage and the DC side upper limit, lower threshold recycle ratio, thereby realized the control of DC voltage, ensured the stability of compensation arrangement.

The frequency characteristic of control system that the present invention carries as shown in Figure 5, wherein, is schemed a, b, and c represents respectively load voltage V _lto reference voltage V _ref, load voltage V _lto source voltage V _sand load voltage V _lto load current I _lthe corresponding frequency characteristic of transfer function.Can find out from frequency characteristic shown in figure a, output voltage can well tracing preset instruction (50Hz), steady-state error less (stable state accuracy is 0.99) at first-harmonic place, now the steady-state error of system is 1%, by increasing resonator gain Ki, can further reduce the steady-state error of system.The precision of controlling is higher; Can find out from the frequency characteristic of figure b, system can be good at suppressing the each harmonic (3,5,7) in line voltage; Can find out from the frequency characteristic of figure c, this controller can well suppress the each harmonic (3,5,7) in load current.Thereby reach design effect.

In literary composition, the stability of designed control system is determined by system open-loop transfer function, the open loop Nyquist (Nyquist) of system figure when Fig. 6 is zero load, as can be seen from the figure Nyquist curve does not surround (1,0j) point, and system is without the right limit of open loop, thereby in proof literary composition, designed control system is stable.

The control method of Fig. 7 for adopting the present invention to carry, for the compensation effect of tandem type blower fan low voltage ride through device, wherein, passage 1 is line voltage, passage 2 is the blower fan port voltage after compensating, and passage 3 is the bucking voltage of inverter output, and passage 4 is the DC voltage of stagnant ring control.Can find out from compensation result, this control strategy can effectively be controlled the port voltage of blower fan, makes its impact that not fallen by line voltage, and meanwhile, stagnant ring controller can effectively be restrained DC voltage, has ensured the stable operation of compensation arrangement.The results show the control method that proposes and the validity of control system.

Those of ordinary skill in the art will be appreciated that, above embodiment is only for object of the present invention is described, and not as limitation of the invention, as long as in essential scope of the present invention, variation, modification to the above embodiment all will drop in the scope of claim of the present invention.

Claims (3)

1. a control method for series voltage compensation arrangement, is characterized in that:

The concrete steps of this control method are:

A. obtain the filter inductance electric current of reference rated voltage, load-side three-phase voltage and the inversion unit AC of three-phase system by data acquisition unit;

B. by after the difference between the first error comparator computational load side three-phase voltage and the reference rated voltage of three-phase system, as the input of ratio resonant regulator group;

Wherein, ratio resonant regulator group is mainly made up of proportional component, fundamental-wave resonator and harmonic resonator group,

The Mathematical Modeling of described ratio resonant regulator group is as follows,

$G_{\mathrm{PR}}\left(s\right)=K_P+\underset{h=\mathrm{1,3,5},...}{\overset{n}{\mathrm{\Σ}}}\frac{{2K}_i{\mathrm{\ω}}_{\mathrm{cut}}s}{s^2+2{\mathrm{\ω}}_{\mathrm{cut}}s+{\left({\mathrm{h\ω}}_0\right)}^2},$

Wherein, K _pfor proportional component gain, its span is between 1～10; K _ifor the gain of resonator, value is between 10～100, and its value is larger, and precision is also just higher, but the stability of system can decrease;

ω _cutfor the shearing frequency of resonator, ω _cutspan is 5～20;

ω ₀for the resonance frequency of system first-harmonic;

H represents in system the waveform of the h time, and wherein, when h=1, corresponding is fundamental-wave resonator; H=3,5 ... time, be harmonic resonator group, its number and number of times should add according to the general characteristic of electrical network, and object is to suppress harmonic voltage in electrical network and load or the disturbance of harmonic current;

C. by after the difference between output and the filter inductance electric current of the second error comparator calculating ratio resonant regulator group, as the input of proportional controller;

D. the output of proportional controller and voltage feed-forward control cumulative after with direct voltage coefficient product as the IGBT input in inversion unit, the IGBT output in inversion unit and the cumulative rear control load voltage of line voltage;

Wherein, the span of feed-forward coefficients is between 0.5～2.

2. control method according to claim 1, is characterized in that:

Described control method is further comprising the steps of:

While judging that according to the direction of load current load characteristic is energy feedback type, detect in real time DC voltage by data acquisition unit, and by stagnant ring controller, it is carried out to stagnant ring control.

3. control method according to claim 2, is characterized in that:

The concrete steps of the stagnant ring control of described stagnant ring controller are:

Set DC voltage reference value according to the needed DC voltage value of inverter bucking voltage, on this basis, set stagnant ring higher limit and stagnant ring lower limit;

In the time that DC voltage exceedes the stagnant ring higher limit of its setting, DC side discharge loop switch closure, discharge resistance work, DC voltage starts to reduce;

In the time that DC voltage is reduced to the stagnant ring lower limit of setting, DC side discharge loop switch disconnects, and now direct voltage starts to rise.