CN103187728A - Filter device for controlling harmonic wave of electric power system - Google Patents

Abstract

The invention discloses a filter device for controlling a harmonic wave of an electric power system. The device comprises a passive filter and an active filter, wherein the passive filter comprises a quintic harmonic wave filter branch circuit, a septic harmonic wave filter branch circuit, and an eleventh harmonic wave filter branch circuit, which are connected in parallel; each harmonic wave filter branch circuit comprises a breaker, a current transformer, a fuse protector, an electric reactor, a capacitor and a bidirectional thyristor which are sequentially connected in series; the active filter comprises a first resistor and a second resistor; the first resistor is connected to a low voltage side of a power grid transformer in series; the second resistor is connected to the other side of the first resistor in parallel; the other end of the second resistor is connected with a base of an insulated grid bipolar transistor; the capacitor is connected between a collector and an emitter of the insulated grid bipolar transistor in parallel; each harmonic wave filter branch circuit of the passive filter and the input end of the active filter are connected to the low voltage side of the transformer in parallel; the output end is connected with the load; and the high voltage side of the transformer is connected with the power grid. The device can remove the harmonic wave, and can achieve the targets of saving energy and reducing emission at the same time.

Description

A kind of for administering the filter of Harmonious Waves in Power Systems

Technical field

The present invention relates to a kind of grid supply quality controlling device, be specifically related to a kind of for administering the filter of Harmonious Waves in Power Systems.

Background technology

Pollution problem for natural environment causes already the attention of countries in the world and all formulated corresponding Law on Environmental Protection, and the tolerance of various disposals of pollutants is limited and monitored and manages.Yet, the harmonic wave that various harmonic sources produce in electric power system also pollutes power system environment, have influence on the electric circumstance of whole electric power system, comprise electric power system itself and users, and the scope of its pollution effect is large, distance, may be than a factory is far away apart from going back to the pollution of atmospheric environment, scope is also large.

The electric power system wave distortion is not a new problem, as far back as between 1920 ~ nineteen thirty, the wave distortion problem that Germany produces with regard to proposing passive rectifier, to the development of 50 ~ sixties due to high voltage dc transmission technology, have a large amount of articles to deliver to the research of converter harmonic problem.In recent years more due to the extensive use in each industrial department and electric power system and automatic control thereof of large-capacity power rectification, converter and electronic equipment, countries in the world are all attached great importance to harmonic problem and are concerned about, hold regularly the academic discussion of relevant harmonic problem, International Electrotechnical Commission (IEC) and international conference on large HV electric systems have all formed special working group in succession, and formulated the harmonic standard that comprises electric power system, every electric power and power consumption equipment and household electrical appliance, and within having listed the harmonic wave interference problem in the electromagnetic compatibility scope.

A lot of countries all formulate and have promulgated the standard of restriction Harmonious Waves in Power Systems in succession at present, perhaps by relevant authoritative institution, formulated regulation or the guide rule of restriction harmonic wave, in order to take measures, the harmonic wave in electrical network is controlled in the scope of permission, guarantees electric power netting safe running and user's various consuming device normal operations.

Standard GB/T/T14595-93 " quality of power supply utility network harmonic wave " has been issued in State Bureau of Technical Supervision's approval of China; to impel power department and power consumer, jointly take measures; prevent and treat humorous wave interference as the conservation of nature environment; the harmonics level of electrical network is controlled in the scope of harmonic wave GB permission; improve power supply quality; safeguard electric power netting safe running; ensure the various power consumption equipment normal operations of access electrical network; to obtain good economic results in society, having become those skilled in the art has to be solved and perfect technical problem.

For the harmonic current that guarantees the Harmonics source customer injected system meets the check requirements of GB, just must be administered harmonic wave, at present with regard to the generation reason of harmonic current in network system and to the harm relevant technologies document of various kinds of equipment, carry out detailed analysis, and proposed the technical scheme of harmonic pollution problem in some resolution systems.External Yao Zaoyu China aspect harmonic wave control at present, but because external producer is inadequate because of China's electric power system is understood sometimes when designing, cause harmonic wave to amplify phenomenon, holding at high price of import equipment is difficult to bear for domestic vast medium-sized and small enterprises simultaneously.Therefore, need those skilled in the art to design the harmonic treating apparatus that is applicable to the China Power Grids running status.

Summary of the invention

The object of the invention is to overcome the defect existed in prior art, a kind of filter of administering Harmonious Waves in Power Systems that can be used in is provided, this device can also reach energy-saving and cost-reducing purpose simultaneously.

For achieving the above object, technical scheme of the present invention is that design is a kind of for administering the filter of Harmonious Waves in Power Systems, it is characterized in that, described device comprises passive filter and active filter, described passive filter comprises 5 subharmonic filter branch parallel with one another, 7 subharmonic filter branch, 11 subharmonic filter branch, and described each harmonic filter branch is connected in series successively by circuit breaker, current transformer, fuse, reactor, capacitor and bidirectional triode thyristor; Described active filter comprises the first resistance that is serially connected in the network transformer low-pressure side, be connected in parallel on the second resistance of the first resistance opposite side, the other end of the second resistance is connected with the base stage of insulated gate bipolar transistor npn npn, between the collector electrode of insulated gate bipolar transistor npn npn and emitter, is parallel with capacitor; The input of described passive filter each harmonic filter branch and active filter all is parallel to the low-pressure side of transformer, and its output connects with load, and the high-pressure side of described transformer is connected with electrical network.

In order can effectively to administer for the harmonic wave of different number of times, wherein preferred technical scheme is, in described each harmonic filter branch, the impedance of reactor is identical with the resonance frequency of resonance frequency after the capacitive reactance of capacitor is mated and each filter branch

On the basis that can filter out most of harmonic wave, can make again equipment investment minimum, further preferred technical scheme is, described 5 subharmonic filter branch parallel with one another are 3 tunnels, 7 subharmonic filter branch of described connection parallel with one another are 2 tunnels, and 11 subharmonic filter branch of described connection parallel with one another are 2 tunnels.

For the ease of filter is effectively controlled, further preferred technical scheme also has, and the control signal that described bidirectional triode thyristor is exported by controller is carried out switching, and this signal is d. c. voltage signal.

In order to meet the different filtering demands by electric loading, further preferred technical scheme also has, and the calculation of capacity formula of described each harmonic filter branch is:

The capacitive reactance of filter branch: Xc=U _n ²/ n/Q;

The induction reactance of filter branch: Xl=Xc/h ²;

The practical impedance of filter branch: X=Xc – Xl;

The fundamental current of filter branch: I=U _n/ X;

The rated current of filter branch: Ie=n*Q/ U _n;

the harmonic current surplus of filter branch: I '=√ Ie2-I2;

Compensating fundamental wave capacity: Q '=I ²* X;

In above formula

U _n: the rated voltage of capacitor;

N: the number of single-phase electricity container;

Q: the capacity of single capacitor;

H: be respectively filter times 5,7,11.

Advantage of the present invention and beneficial effect are: the use by said apparatus is significantly improved the power factor of transformer load one side, by 0.65 before administering, brings up to 0.96, and 5 subharmonic, 7 subharmonic, 11 subharmonic are eliminated substantially.And be that this device is due to the filter structure that has adopted active power filtering and passive filtering use, because the passive filtering cost is low and can be by most of harmonic filtration, and then with a road active filter by remaining harmonic wave thoroughly with give filtering, so both can guarantee the leach effect of this device to harmonic wave, can reduce the cost of filter again simultaneously.

The accompanying drawing explanation

Fig. 1 is that the present invention is in the circuit theory diagrams of the filter of administering Harmonious Waves in Power Systems;

Fig. 2 is the parallel connection type active electric filter circuit theory diagrams;

Fig. 3 is the series connection type active electric power filter circuit theory diagrams;

Fig. 4 is the single tuned filter circuit theory diagrams;

Fig. 5 is the double-tuned filter circuit theory diagrams;

Fig. 6 is single order amount of decrease mode filter circuit theory diagrams;

Fig. 7 is second order amount of decrease mode filter circuit theory diagrams;

Fig. 8 is three rank amount of decrease mode filter circuit theory diagrams;

Fig. 9 is C mode filter circuit theory diagrams

Figure 10 is serious distorted waveform figure of voltage waveform;

Figure 11 is serious distorted waveform figure of current waveform;

After Figure 12 is 5 branch roads of input, the impedance frequency curve of filter and system;

Figure 13 is after dropping into two 5 branch roads, the impedance frequency curve of filter and system;

Figure 14 is after dropping into two 5 times and 7 branch roads, the impedance frequency curve of filter and system;

Figure 15 is after filter branch all drops into, the impedance frequency curve of filter and system.

In figure: 1, passive filter; 2, active filter; 3,5 subharmonic filter branch; 4,7 subharmonic filter branch; 5,11 subharmonic filter branch; QF, by circuit breaker; TA, current transformer; FU, fuse; L, reactor; C, capacitor; KP, bidirectional triode thyristor; R1, the first resistance; R2, the second resistance; IGBT, insulated gate bipolar transistor npn npn.

Embodiment

Below in conjunction with drawings and Examples, the specific embodiment of the present invention is further described.Following examples are only for technical scheme of the present invention more clearly is described, and can not limit the scope of the invention with this.

The present invention is a kind of for administering the filter of Harmonious Waves in Power Systems, this device comprises passive filter 1 and active filter 2, described passive filter 1 comprises 5 subharmonic filter branch 3,7 subharmonic filter branch 4,11 subharmonic filter branch 5 parallel with one another, and described each harmonic filter branch is connected in series successively by circuit breaker Q F, current transformer TA, fuse FU, reactor L, capacitor C and bidirectional triode thyristor KP; Described active filter 2 comprises the first resistance R 1 that is serially connected in the network transformer low-pressure side, be connected in parallel on the second resistance R 2 of the first resistance R 1 opposite side, the other end of the second resistance R 2 is connected with the base stage of insulated gate bipolar transistor npn npn IGBT, between the collector electrode of insulated gate bipolar transistor npn npn IGBT and emitter, is parallel with capacitor C; The input of described passive filter each harmonic filter branch and active filter all is parallel to the low-pressure side of transformer T, and its output connects with load, and the high-pressure side of described transformer T is connected with electrical network.

In order can effectively to administer for the harmonic wave of different number of times, wherein preferred embodiment is in the present invention, and in described each harmonic filter branch, the capacity of the impedance of reactor and capacitor is ratio with the number of times by the filter harmonic wave.

In the present invention in order to filter out on the basis of most of harmonic wave, can make again equipment investment minimum, further preferred embodiment is, described 5 subharmonic filter branch parallel with one another are 3 tunnels, 7 subharmonic filter branch of described connection parallel with one another are 2 tunnels, and 11 subharmonic filter branch of described connection parallel with one another are 2 tunnels.

In the present invention for the ease of filter is effectively controlled, further preferred embodiment also has, the control utmost point of described bidirectional triode thyristor is connected with the controller for controlling electrical network filtering (figure does not draw), and the control signal of described controller output is d. c. voltage signal.

In order to meet the different filtering demands by electric loading, further preferred embodiment also has in the present invention, and the calculation of capacity formula of described each harmonic filter branch is:

The capacitive reactance of filter branch: Xc=U _n ²/ n/Q;

The induction reactance of filter branch: Xl=Xc/h ²;

The practical impedance of filter branch: X=Xc – Xl;

The fundamental current of filter branch: I=U _n/ X;

The rated current of filter branch: Ie=n*Q/ U _n;

the harmonic current surplus of filter branch: I '=√ Ie2-I2;

Compensating fundamental wave capacity: Q '=I ²* X;

In above formula

U _n: the rated voltage of capacitor;

N: the number of single-phase electricity container;

Q: the capacity of single capacitor;

H: be respectively filter times 5,7,11.

Below the present invention is used for administering the filter of Harmonious Waves in Power Systems, its principle gives detailed introduction:

The implication of harmonic wave and origin

General introduction

Weigh the quality of power supply of electric power system, the permissible variation of only considering frequency and voltage is inadequate, because electric current, voltage waveform distortion degree are also the key factors that affects the quality of power supply.As many pollutions, thus the harmonic wave produced due to a variety of causes in electric power system also form pollution to electrical network worsened whole electrical production environment, to the stage that must adopt an effective measure and be administered.

Generally acknowledged harmonic wave implication is in the world: " harmonic wave is the component sine waves of one-period electric parameters, the integral multiple that its frequency is fundamental frequency ".Because the frequency of harmonic wave is the integer multiple of fundamental frequency, so we also usually claim that it is high order harmonic component.

The reason produced for the harmonic current in current electric power system, the summary for many years through the various countries expert mainly can be divided into three large factors:

(1) household electrical appliance such as the extensive use of great power conversion circuit equipment and regulator etc., television set and frequency conversion is universal.

(2) increase day by day of the nonlinear-load of the electric arc such as arc furnace and electric welding machine type.

(3) change of design philosophy.Tend in the past adopt the larger design of allowance in specified situation, and mainly consider the saturation region close to magnetic material while designing now.

Therefore, administer the harmonic pollution of electric power system and just must first understand the origin of harmonic wave, thereby reach the purpose of taking stopgap measures and effecting a permanent cure.

The origin of harmonic wave

For the origin of harmonic wave, mentioned three factors in above-mentioned, below just respectively three factors are analyzed respectively.

(1) great power conversion circuit equipment produces reason and the principal character harmonic wave of harmonic wave

In the convertor equipment used at present, the main silicon controlled rectifier adopted.According to the inventor, harmonic wave control experience is for many years learnt, general direct current dragging motor or variable-frequency motor are when becoming direct current by interchange, and most of what adopt is three-phase six pulse silicon controlled rectifiers.But the general employing of powerful direct current dragging motor is the rectifying device of six phase twelve-pulses.In addition, the intermediate frequency furnace that current middle-size and small-size steel mill is used is also identical with the rectifier system of direct current machine.

Due to rectifying device, when regulating the power of direct current output, by regulating, the silicon controlled angle of flow completes, and therefore at AC portion, the situation of voltage and current distortion just inevitably occurs.Analysis by the fourier series to the voltage and current waveform can draw in AC portion and contain a large amount of harmonic components.

By for many years the statistics of such testing of equipment data being learnt, the harmonic current that three-phase six impulse commutation devices produce mainly be take 5 times, 7 times, 11 times and 13 times as main, wherein 5 subharmonic currents account for the proportion maximum of total current, and 7 subharmonic take second place, 11 times and 13 times smaller.

And the rectifying device of six phase twelve-pulses is general, adopt one three circle to become, adopt the mode of connection of Y/ △ in low-pressure side, direct current component adopts mode in parallel.During normal operation, the rectifying device rectifier system separately of Y and △ both sides is three-phase six impulse commutation modes, produces separately harmonic current and be also to take 5 times, 7 times, 11 times and 13 times as main.But due to the angular differences that 30 degree are arranged between Y and △, so the harmonic current on both sides is by after the stack of magnetic circuit, 5 times and 7 subharmonic currents will significantly descend, and 11 times and the decline of 13 primary currents very little.Therefore, while adopting the mode of connection of this kind, the harmonic current that flows into high-pressure system mainly be take 11 times, 13 times, 23 times and 25 times as main.Under theoretical state, 5 times and 7 subharmonic currents almost do not have.But due to the difference of Y and △ both sides thyristor operating angle, make the harmonic current on both sides can not be fully equal, so in the harmonic current of injected system, 5 times and 7 subharmonic also have certain content.Such mode of connection is mainly reflected in the commonplace of rolling high-speed rod aspect performance at present, and general in the rectifier transformer high-pressure side, Y and the delta connection by many transformers reaches this kind of effect.

(2) arc furnace produces reason and the principal character harmonic wave of harmonic wave

Arc furnace is the important means of making steel in recent years, because it is apparent in view in technology, advantage economically, develops rapider.Along with its proportion in steel industry is increasing, and the capacity of stove also becomes large thereupon, and the harmonic pollution that system is produced is also more and more serious.

Arc furnace is to utilize the electric arc heat produced between its three-phase graphite electrode and furnace charge to carry out metal smelting, and graphite electrode can be done the motion of vertical direction, to adapt to the needs of controlling arc length in fusion process.

Electric-arc furnace steelmaking generally is divided into melting stage and the refining period of furnace charge.Within melting stage, due to factors such as the non-linear and electric arc of electric arc time delay arcing, arc resistance move about, make arc current change very irregular.According to the analytical method of harmonic current relatively more commonly used---Fourier series method is decomposed and can be calculated, and now in system, exists a large amount of 2 times, 3 times, 4 times, 5 times, 6 times and 7 subharmonic currents at present.

In addition, while occurring due to electric arc, AC resistance is very little very little, so the electric current that the ac arc furnace stove becomes is mainly reactive current.This has also caused the sharply variation of system active power and reactive power, thereby has caused the continuous variation of system voltage, and serious distortion will occur voltage waveform.

In refining period, although the impact of load is compared littlely with melting stage, the content of harmonic current is still larger, still more serious to the harm of system.Because the power of this type load is larger, higher level electric substation is generally 110KV or 220KV, and in block supply, 110KV and 220KV are main transmission voltages, so this type load is very serious to the harm of system power quality.

(3) change of design philosophy and produce reason and the principal character harmonic wave of harmonic wave

This is mainly manifested in for core material when designing, for the selection of core sataration degree.It is many that these embody aspect the core design of transformer, approaches the saturated section at magnetization curve while making magnetic material work when design.Once but slightly high at this operation by sections voltage, will cause the exciting curent waveform seriously to distort.

For the iron core of transformer, when disregarding magnetic hysteresis and iron core unsaturation, it is linear basically.But, after core sataration, it is linear with regard to right and wrong, even applied voltage is the pure sine wave under perfect condition, electric current is also wanted distorted.And saturated darker, even if current waveform is more serious.

During due to current distortion, the positive and negative half-wave symmetry of current waveform, only contain odd harmonic in electric current, be mainly wherein triple-frequency harmonics.

Core sataration generally occurs in load to be increased suddenly, surpasses the capacity of main transformer.Perhaps, in the Transformer Close process, the peak value of work magnetic flux is high in the time of will be than normal operation, in the time of seriously, may double.This just makes the iron core degree of depth saturated, and corresponding electric current increases a lot, sometimes can reach 6 ~ 8 times of rated current, and wave distortion simultaneously is also very serious.

Due to core sataration, in electric power system, be the phenomenon often occurred, the proportion that therefore 3 subharmonic currents in current electrical networks at different levels account for is all larger.Those impact loads particularly, the probability that produces 3 subharmonic currents is larger.

The harm of harmonic current

General introduction

Impact and the harm of harmonic current on electrical equipment roughly can be divided into two large classes with regard to its consequence: one: on the impact of power equipment, it can cause device damage, reduce equipment life, increases loss or reduction and exerts oneself etc.; Its two: on the impact of computer, relaying protection, controller or system, instrument and audiovisual facility, it can cause work mistake or the performance degradation of equipment.

The impact how concrete harmonic current produces the said equipment, will describe in detail in several joints below.

The impact of harmonic wave on motor

Harmonic current is the supplementary load loss of aggravation motor to the major effect of motor, makes the ageing of insulation of motor accelerate, and is to produce mechanical shock, noise and harmonic wave overvoltage in addition.

In current low-pressure system, main harmonic source is powerful rectifying installation, and the harmonic current therefore produced is mainly 5 times, 7 times, 11 inferior odd harmonic electric currents.But, 5 times and 11 subharmonic currents are negative-sequence current, and such electric current will produce the magnetic field of negative phase-sequence, hinder the rotation of motor, so motor in power output additionally power output offset the backward power produced because of harmonic current, this has also caused the supplementary load loss aggravation of motor.In the situation that the harmonic current injection motor is arranged, after the fundamental current that total current is motor and the quadratic sum of harmonic current, open root.Be not difficult to find out, in the situation that fundamental current is constant, the larger total current of harmonic current is just larger, and square being directly proportional of the loss of motor and total current, so only have the harmonic current in the reduction motor just can reduce the active loss of motor.

The aggravation of supplementary load loss also makes the caloric value of motor greatly increase, and the Wen Sheng of motor also increases, so the aging aggravation of the insulating barrier of motor.

In addition, the harmonic voltage that harmonic current produces can be superimposed upon the two ends of motor with the rated voltage of system, and at harmonic current, under larger environment, this voltage often is greater than the rated voltage of design of electrical motor, and this has also caused the regular damage of motor.In addition, harmonic current often there will be very high due to voltage spikes value, and impact repeatedly will make the dielectric strength of motor reduce rapidly, and can cause between coil and be short-circuited, and then motor damage.

According to above-mentioned analysis, harmonic current is apparent to the harm of motor.

Interference and the impact of harmonic wave on communication

Harmonic current mainly can be divided into three aspects to the interference of communication:

(1) capacitive coupling.Because cable passage consideration when designing at present is cost-saving, therefore under many occasions, power circuit and telephone wire can use same cable passage simultaneously, and distance each other is also more approaching, therefore the alternating voltage of power network can be coupled on telephone wire by the distributed capacitance between power circuit and telephone line, causes interference.

(2) electromagnetic induction.The alternating current of electric power system fails to be convened for lack of a quorum the producing the magnetic field of alternation on every side of online road and senses on contiguous telephone wire, and affect speech quality, if particularly in system, contain harmonic current, the electric current of system will there will be distortion, instantaneous spike is arranged, and the impact that communication is produced will be more serious.

(3) electrical conductivity.Acting under normal operation of electrical conductivity generally can be ignored, but will cause that when earth fault occurs dangerous voltage raises, and causes communication apparatus breakdown because of overvoltage.

Harmonic current, except disturbing wire communication, can also disturb other communications.If any the noise frequency that produces of the commutation process of HVDC current conversion station only have 3 ~ 10kHz; but by the coil of interfering carrier trap and the work of tuned cell; make and produce the noise that reaches radio frequency, disturbed carrier communication, and made the locking and the protective relaying device work that utilize carrier wave malfunctioning.

The impact of harmonic wave on Common Instrument

Harmonic wave mainly refers to widely used analog table and digital table in electric power system to the impact of instrument, and this is mainly voltmeter, ammeter, wattmeter, varmeter, electric energy meter and instrument transformer etc.According to national Specification, these instrumentations, under sinusoidal voltage, waveform, only allow to contain a small amount of higher harmonic components.

But the harmonic voltage of many electrical networks and harmonic current all rise to the stage of can not ignore in recent years, as the aberration rate of voltage has reached more than 5%, current distortion rate surpasses 10%.But analog table is different with the principle of digital table in metering, so the impact that harmonic wave produces is also different.

During analogue instrument work, be mainly to rely on voltage or current signal after treatment, the electrodynamic size produced in magnetic field according to it is calculated the size of input signal.Therefore when harmonic content is larger, between the signal meeting after first-harmonic and harmonic wave stack and actual signal, larger difference is arranged, this has also caused measure error.

Digital instrument, when calculating voltage or current signal, is mainly to rely on the size of sampling to be calculated.Due to the existence of harmonic wave, make the signal magnitude of sampling and actual signal that deviation be arranged, the size of therefore calculating also exists more serious error.It is very harmful that this class deviation produces when multiple electric motors is produced continuously, causes the step-out between motor, and then make the Quality Down of product, and defect rate reduces.

Find out thus, the impact that the existence of harmonic wave causes to Common Instrument is apparent in view, eliminate this type of impact and just must carry out harmonic wave control.

The impact of harmonic wave on relaying protection

In the electric power system of China, influence from harmonic and cause in the device of work mistake or performance degradation the proportion maximum of protective relaying device.Analyzing its affected reason must be analyzed from the principle of relay protection.

For mechanical relay equipment, its operating value determines whether action according to the size of input signal effective value often.But, if when containing larger harmonic component in input signal, because the stack of fundametal compoment and harmonic component makes the combined action value of this signal formation surpass setting value, move.

Digital relay equipment is mainly by the sampling of signal, by calculatings gets rid of a part of be considered to the signal of mistake after, remaining calculated signals is gone out to its effective value and judges whether to need to move.Although such judgment mode is higher than the precision of mechanical type relay protection, due to folding of harmonic wave, no matter all error can be arranged at which measurement point of signal, therefore the operation precision of relay protection still had to larger impact.

The probability that such phenomenon occurs in electric power system is still larger; no matter in 220KV, 330KV or the electrical network at 500KV; the serious malignant event that net also can occur to separate in electric power system all occurred, because of harmonic effects route protection or tranformer protection, to make its misoperation or mistrip.

Therefore, the impact of restriction harmonic wave on relaying protection, be vital with safe power supply and the safe operation that guarantees electrical network.

The impact of harmonic wave on reactive power compensator

Because the load in electric power system at present constantly increases, the character of each type load varies, and putting into operation in a large number of those impact loads particularly caused in the system variation of reactive power very rapid, this also makes the voltage fluctuation of system apparent in view, has affected the power supply quality of system.

For addressing this problem, idle work optimization is the major way that current electric power system adopts.But, due to the impact of system harmonics, caused the phenomenon that the regular damage because of fuse or electric capacity of reactive-load compensation capacitor can't bringing normally into operation.Concrete analysis is mainly caused by following reason.

For reduce cost, the reactive power compensator of each electric substation generally is installed in the low-pressure side of transformer, according to the reactive requirement of system, carries out the automatic or manual switching.Because the capacitive reactance of the capacitor rising with frequency reduces, and the induction reactance of transformer raises with frequency, so the harmonic current in system almost all injects and is connected to the capacitor group on bus, cause capacitance current suddenly to increase, capacitor has reduced useful life because of overload.

In addition, the reactive power compensator in electric power system at present can install current limiting reactor additional when design in capacitor loops, and this is mainly that capacitive reactance generally selects 1% or 6% in order to escape the inrush phenomenon of short-circuiting device.The branch road that reactance due to 1% and electric capacity form will have larger amplification to 3 times and 5 subharmonic currents in system, and the harmonic current that therefore flows into system will have obvious increase, cause larger pollution.

In addition, although 6% reactance 5 times are not amplified, to the amplifications of 3 times or apparent in view.In current electric substation, main harmonic source is exactly 3 times and 5 subharmonic, therefore in the situation that higher harmonic current is installed reactive power compensator, can't guarantee its normal operation.

In addition, aspect the selection of condenser voltage, due to the factor of not considering harmonic wave, therefore when harmonic current is injected in capacitor in a large number, just there will be capacitance current higher than rated current, cause the fault of fuse or capacitor.

In addition, through the research to harmonic current for many years, learn, because the caloric value of harmonic current is greater than the fundamental current caloric value of identical numerical value.But common reactive compensation capacitor has larger difference with filtered electrical aspect selection, therefore can't adapt in the situation that higher harmonics content moves, make the capacitor heating and cause the phenomenon of oil impregnate or demolition.

Therefore, changing the reactive power compensator of current each electric substation into filtering compensation device is also the problem that electric power system is being studied.

The harmonic wave management method of electric power system at present

General introduction

In transmission system and power distribution network, the use of a large amount of nonlinear-loads, the problem that make that electrical network exists voltage flicker, fluctuation, frequently floats, three-phase imbalance, harmonic wave etc. affects the quality of power supply and efficiency, especially take a large amount of uses of the various power electronic equipments that Switching Power Supply and AC speed regulating equipment is representative, other users are produced to disturbance, threaten the safe operation of electrical network and power consumption equipment, make reactive power and harmonic compensation in electric power system become problem in the urgent need to address.

How further to improve the quality of power supply, effectively suppress harmonic wave and reactive power in electrical network, this problem has caused widely to be paid close attention to.It is exactly that filter is installed on the pollutant sources of harmonic wave that harmonic carcellation pollutes effective method, is administered on the spot.

The filter of electric power system at present mainly is divided into: active type power filter device and passive power filter device.In China's electric power system, generally adopt the mode of passive filtering for the filter of 10KV and above thereof at present, and, in the system of 10KV electric pressure, due to the price comparison costliness of active filter, the occasion of therefore using not a lot.And active filter (particularly powerful) to develop domestic be not also overripened, at the overseas equipment that domestic used active filter is mainly introduced at present.In China's electric power system, what mainly use is passive filtration unit, so will mainly with regard to the utilization of passive filtration unit, carry out detailed discussion in this paper.

The filter of these two kinds of forms has obvious difference on its design principle, in two joints below, will be described in detail.

Active filter

One, the development of active filter

Early 1970s, the basic principle of Active Power Filter-APF and circuit structure are just definite, but can not implement owing to being subject to technical conditions restriction at that time.After the eighties, the development of the appearance of novel power transistor, PWM control technology and the proposition of instantaneous reactive power theory, greatly promoted the development of Active Power Filter-APF technology.In AC network, for the Active Power Filter-APF technology that harmonic wave, reactive power and current in middle wire are compensated, reach its maturity.In in the past twenties years, topological structure and the control method of a large amount of relevant Active Power Filter-APFs proposed.Active Power Filter-APF the voltage harmonic in improving the quality of power supply, eliminating three-phase electrical power system, regulate end voltage, suppress voltage fluctuation and improve in the technology such as the balance of voltage to be applied.

The extensive use of power electronic equipment, make power quality problem become more outstanding.The survey report of existing a large amount of relevant power quality problems is paid close attention to the problem of this respect both at home and abroad.In these reports, by harmonic wave and idle measurement, analysis, be familiar with the impact on electrical network and user of harmonic wave and the power quality problem such as idle.According to the use occasion of power consumption equipment, the various ways such as that harmonic source has is single-phase, phase three-wire three and three-phase and four-line.Single-phase load, as family expenses fluorescent lamp, microwave oven, TV, computer switching power supply, air-conditioning, laser printer and photocopier etc., is all nonlinear loads; In threephase load, various RHVC etc. all can cause the generation of power quality problem.

From 1980, existing a large amount of treatises were discussed the research work of Active Power Filter-APF, comprising parallel connection type, tandem type and mixed type.Mixing the tandem type, the parallel connection type active electric filter that use with passive filter is typical device wherein.Many control methods, as instantaneous reactive power theory, synchronous d q coordinate system principle, synchronization detecting method and notch filter method etc. all is used to develop three phase active electric power filter.In three-phase four-wire system, some treatises have mainly been studied by non-linear unbalanced load, the excessive problem of current in middle wire caused as computer power supply, fluorescent lamp etc.Method to various solution currents in middle wire and unbalanced load electric current has also been done trial, and main contents comprise: elimination or minimizing current in middle wire, harmonic compensation, load balance, reactive power compensation etc.

Two, the principle of active filter

Active filter is referred to as APF, specific definition is: contained deleterious current in system (higher harmonic current, reactive current and zero sequence negative-sequence current) is detected, and produce the offset current contrary with it, to offset the semiconductor converter of deleterious current in transmission line.Be that the current waveform that produces of compensation arrangement is just in time identical with the frequency amplitude of deleterious current, and phase place just in time differs 180 °, thereby reached the effect of compensation deleterious current.As a kind of novel electric power electric device for dynamic inhibition harmonic wave, compensating reactive power, the harmonic wave that APF can change big or small and frequency and the idle real-Time Compensation of carrying out of variation.Its main circuit generally consists of the PWM inverter.

Three, the kind of active filter

According to the connected mode of APF and system, generally APF can be divided into to parallel connection type APF, tandem type APF.

Parallel connection type APF

Parallel connection type active electric filter (APF) circuit theory is as shown in 2 figure.APF is by the detection load electric current, and generation equates with the Load harmonic size of current, the harmonic current injection electrical network of single spin-echo, thereby offsets the Load harmonic electric current, the mains side electric current is approached sinusoidal wave.Therefore, parallel connection type APF can regard a harmonic current generator as, is equivalent to a controlled current source in parallel with load.So parallel connection type APF is applicable to offset current type harmonic source.For the voltage-type harmonic source, compensation effect will be subject to the impact of Load harmonic equiva lent impedance.When equiva lent impedance is larger, parallel connection type APF has certain compensating action.But due to the rectifier that generally the actual DC side contains capacitor filtering, though can not equivalence become desirable harmonic voltage source, but still can regard the harmonic voltage source that equiva lent impedance is very little as, parallel connection type APF need to produce very large harmonic current and compensate, this just requires the capacity of filter must be very large, line voltage is directly born in three-phase inverter output, and the requirement of the electric pressure of components and parts is also high.But the components and parts voltage withstand class is limited after all, and the raising of voltage withstand class will certainly increase the cost of APF, and therefore, parallel connection type APF is only suitable for, in offset current type harmonic source, being not suitable for bucking voltage type harmonic source.

Tandem type APF

Series connection type active electric power filter (APF) circuit theory as shown in Figure 3.Series connection APF is connected in power distribution network by a coupling transformer, detects supply voltage, the harmonic voltage of generation and source harmonic voltage equal and opposite in direction, single spin-echo, thus it is sinusoidal wave that load side voltage is approached.Tandem type APF is equivalent to controlled voltage source, the transient state existed in the mode compensation network with voltage source or steady state voltage distortion.Therefore, tandem type APF is suitable for bucking voltage type harmonic source.For the current mode harmonic source, compensation effect will be subject to the impact of load harmonic wave equiva lent impedance.The smaller current mode harmonic source for equiva lent impedance, tandem type APF has certain compensating action.But, due to general actual DC side inductor filter rectifier, equiva lent impedance is quite large.This just requires tandem type APF to produce very large harmonic voltage, and the capacity of filter must be very large.Equally, this is also irrational.Therefore, tandem type APF is only suitable for bucking voltage type harmonic source, is not suitable for offset current type harmonic source.

The function of active filter

Active Power Filter-APF has suitable flexibility on controlling, and it can be used in to some special occasions.Except single-phase, phase three-wire three or three-phase four wire system require, the curtage compensation, the choice criteria of special applications Active Power Filter-APF to be done to one here and discuss.

The current mode compensation can be divided into current harmonics compensation, reactive power compensation, threephase load balance and current in middle wire inhibition etc.These compensation can be carried out separately, also can carry out simultaneously.For harmonic current compensation, Shunt is a desirable selection.And reactive power compensation will divide situation and determine, tunable load is adopted to Shunt, dead load is adopted to AC capacitor.In phase three-wire three or three-phase four wire system, the balance of load is normally completed by parallel connection type active electric filter.

Voltage compensation can be divided into voltage harmonic compensation, improve voltage-regulation, balanced voltage, reduce voltage fluctuation, eliminate voltage ramp and sink etc.Usually adopt series connection type active electric power filter to carry out voltage compensation.At present, Active Power Filter-APF also can be used for revising in the short time instantaneous inclination and the sagging aspect of voltage.

Passive filtration unit

One, the development of passive filtration unit

For the research of passive filtration unit, as far back as last century, the scientist of the '20s Germany is studied with regard to the harmonic current problem started eliminating the rectifying installation generation, and this problem has been proposed to tentative programme.Extensive utilization along with rectifying installation in the industrial enterprise of countries in the world, harmonic problem also more and more causes various countries scientist's extensive attention, to the research of filter also many gradually get up.

Because the principle of passive filtration unit is simple, device is easily chosen, and the mode of connection is relatively succinct, adds its production cost lower, therefore also becomes the Main Means of administering harmonic wave.In China's electric power system, passive filtration unit accounts for the usage ratio more than 80%.

Two, the principle of passive filtration unit

The primary circuit of passive filtration unit is mainly formed by power capacitor, reactor (low pressure is mainly used iron core reactor, and high pressure is mainly used air-core reactor) and resistor appropriate combination.Form different filter branch by the capacitive reactance of electric capacity and the different ratio of induction reactance of reactor, be connected in parallel in system, low impedance path is provided to harmonic current corresponding in system, thereby reaches the effect that filters system harmonics.

Resistance can enrich the mode of connection of filter branch, filter branch can be connected into to single tuned filter or high pass filter.To the research of filter, resistance is connected into to the impedance frequency curve that the high-pass filtering branch road not only can adjustment System by recent years, but also can reduces the probability that filter branch and system produce resonance.

Three, the kind of passive filtration unit

As shown in Fig. 4 ~ 9, because the compound mode of capacitor, reactor and resistance is different, the mode of the filter branch produced is also different.Mainly can be divided into: single tuned filter, double-tuned filter, single order amount of decrease mode filter, second order amount of decrease mode filter, three rank amount of decrease mode filters and C mode filter as shown in Figure 9 as shown in Figure 8 as shown in Figure 7 as shown in Figure 6 as shown in Figure 5 as shown in Figure 4.

Below with regard to the operation principle of above-mentioned several filters, do following simple narration.

The operation principle of several passive filters

(1) single tuned filter

Although resistive element is arranged in single tuned filter in Fig. 5, reality in use, only has reactor and capacitor in a filter loop.Resistance is mainly the AC equivalent resistance of reactor, and actual numerical value is less, and this is mainly to be determined by the quality factor of reactor.

And the resistance of capacitor is almost nil, can ignore.This shows, as long as the value of the harmonic wave induction reactance in this loop and harmonic wave capacitive reactance is more approaching, the AC equivalent resistance in reduce loop just can reduce the harmonic impedance of this branch road simultaneously, improves the filter effect of branch road.

In addition, the AC equivalent resistance of branch road is less, also can reduce the A.C.power loss of filter.Because this filter branch mode of connection is simple, the occasion of therefore using in engineering is more.

(2) double-tuned filter

Double-tuned filter is mainly to utilize the parameter between reactor, capacitor and resistor in series connection major loop and shunt circuit to coordinate, and forms two different resonance frequencys.This loop can become the filter transform of two different resonance frequencys a double-tuned filter.

With single tuned filter, compare, this kind of mode of connection more complicated, the device parameter of each branch road is cumbersome when design simultaneously, so this kind of mode of connection almost do not have in engineering design.

(3) second order amount of decrease filter

Second order amount of decrease filter is modal high pass filter, with single tuned filter, compares, and is mainly a resistor in parallel at the reactor two ends.Surpass resistance value because the impedance of reactance after parallel connection and resistance composition is impossible, so it is not as single tuned filter, only a certain frequency is presented to Low ESR, but a lower impedance frequency scope is arranged.

When frequency, during lower than a certain numerical value f, filter induction reactance obviously increases, make the low-order harmonic electric current be difficult to by, this frequency is called cut-off frequency.When frequency is greater than f, impedance is less, changes not quite, is called passband.

During design, the resistance of general resistance will be much larger than the first-harmonic induction reactance of reactor, and therefore, when normal operation, the fundamental current that flows into resistor is very little.Because the resistance of resistance does not change with the variation of frequency, and the induction reactance of reactor rises at double with the number of times of harmonic wave, and the higher induction reactance of number of times and resistance value are just more approaching, and the electric current major part therefore flowed in resistance is harmonic current.

In addition, the small-power concussion current absorption produced between reactor two ends parallel resistance can be by system and filter is fallen, and prevents that this electric current from further amplifying, the safety of harm system.

(4) C mode filter

The C mode filter is a kind of C TYPE FILTER WITH LOWER LOSSES, and the first-harmonic induction reactance of its parallel branch equals the first-harmonic capacitive reactance, makes fundamental current almost all flow in inductance and capacitor loop, and resistance loop does not almost have electric current to flow through, and reaches the purpose that reduces energy consumption.

And the mathematical model of filter is similar to second order high-pass filtering branch road, a cut-off frequency is also arranged.Studies have shown that, harmonic performance and the bivalent high-pass filter of this kind of filter are close, but meritorious power consumption is lower, and when cut-off frequency is lower, and the output of the fundamental wave reactive power of filter adopts the benefit of this filter better when larger.At present, this mode of connection is mainly used in the filter loop of 10KV and above, and the resonance frequency of filter is lower, as 2 times and 3 filter branch.

By the analysis to above-mentioned several passive filtration units relatively, from simplifying the consideration of wiring and design aspect, modal in electric power system at present is single tuned filter and second order amount of decrease filter.

The comparison of passive and active device pluses and minuses

(1) passive filtration unit

From wiring and passive filtration unit is used for many years situation, mainly contain following advantage:

Simple in structure;

Equipment investment is few;

Operational reliability is high;

Operating cost is low;

Easy to maintenance;

Due to passive filter be by system for harmonic wave provides a low impedance path in parallel, to play filter action, its filtering characteristic is that the impedance ratio by system and filter determines, thereby has following shortcoming:

Filtering characteristic is subject to the impact of system parameters larger;

Specific a few subharmonic can only be eliminated, and amplification can be produced to some subharmonic;

Filtering requirements and reactive power compensation, pressure regulation require sometimes to be difficult to coordinate;

When harmonic current increases, the filter burden increases the weight of thereupon, may cause the filter overload;

Effective high material consumption, volume is large.

(2) active filter

With passive filter, compare, the advantage of active filter mainly contain following some:

(1) there is high controllability and fast-response;

(2) can not only compensate each harmonic, also can suppress flickering, compensating reactive power, the characteristics of one-machine-multi-function are arranged, comparatively reasonable on cost performance;

(3) filtering characteristic is not subject to the impact of system impedance, can eliminate the danger with system impedance generation resonance;

(4) there is adaptation function, but the harmonic wave that automatic tracking and compensating is changing.

Shortcoming mainly contains:

With passive filter, compare, the cost of active filter is higher, and the general user is beyond affordability, and this point is to have limited active filter to promote the use of.Simultaneously, due to the impact that is subject to power electronic device, not above active almost not the having of filter of 10KV at present, in electric power system, the filter of 10KV and above is mostly passive.

Although the advantage of active filter is more much more than the advantage of passive filter, its price is far above passive, and in low-pressure system the filter effect of passive filter also close to active.In addition, by quiet benefit and moving being used in conjunction with of mending, also can reducing flickering and suppress voltage fluctuation in the high pressure passive filtration unit.

Therefore, in electric power system, passive filtration unit is still having market widely in the quite a long time at present and later.But compared obvious advantage with passive device due to active filter, along with the decline gradually of power electronic device price, active filter will be a development trend in the filtering field.

The utilization example of passive filtration unit in steel rolling line

General introduction

The effect of using in electric power system in order to understand better filter, below the inventor with regard to filter, at steel rolling production-line, the effect before and after putting into operation compares analysis.

As a steel rolling production-line, mainly take the rolling stainless steel materials as main, the power of milling train is 650KW, there is a transformer to be powered, the capacity of transformer is 1250KVA, voltage becomes 0.4KV by 10KV, can produce harmonic current because the user knows this production line when producing, so the load of this transformer only has a steel rolling production-line.

Because milling train has adopted the rectification speed governing, therefore natural power factor is lower, for fear of the monthly average power factor that causes charging point after putting equipment in service lower than 0.9 by idle fine, so the user has installed two reactive power compensators in low-pressure side, total first-harmonic is 700KVAR.

But milling train has produced a large amount of harmonic currents while producing, just caused the regular phenomenon of burning of fuse, thermal relay, A.C. contactor and capacitor in the reactive power compensator in one month after putting equipment in service, still can not guarantee normal operation after changing the element damaged, finally can only stop transport.And, because a large amount of harmonic currents in system have also caused main switch generation misoperation, brought serious threat to user's normal production.

Because the interference effect of harmonic wave also makes the product defect rate produced high, although this user has also asked the manufacturer of milling train to analyze and transform, DeGrain in this process.

Test and the analysis of inventor to steel rolling production-line

For understanding the quality of power supply situation of this milling train when normally producing, the inventor has carried out field measurement in the low-pressure side time master switch side of this transformer, three-phase voltage and current signal have been selected during test, the PQPT1000 that tester is Switzerland lime company, this equipment is with automatically recording the function of ripple, and test is continuous measurement in 24 hours.

In order to reduce production costs, utilize the electricity price of peak valley poor, this user generally produces at night, and part throttle characteristics when therefore we have adopted normal production when power quality analysis is as the foundation of analyzing.

According to test data, we find the seriously distortion (referring to Figure 10,11) of voltage and current waveform.Voltage waveform and current waveform

Can be found out by Figure 10,11 oscillogram, contain a large amount of harmonic currents in system, the analysis software carried according to testing equipment can analyze the value (specifically seeing the following form) of each main harmonic voltage and electric current in system.

?	Maximum	Minimum value	95% value	Mean value	State's scale value	Judgement
							H1(V)	246.505	216.661	244.388	233.346	---	---
H5(%)	13.084	1.344	11.324	6.144	4.000	Exceed standard
							H7(%)	3.606	0.17	3.188	1.85	4.000	Normally
H11(%)	4.61	0.032	3.509	1.737	4.000	Normally
							H13(%)	1.961	0.03	1.555	0.814	4.000	Normally
THD(%)	14.619	1.713	12.636	7.111	5.000	Exceed standard

The statistical value of voltage

?	Maximum	Minimum value	95% value	Mean value	State's scale value	Judgement
							H 1 (A)	1738.77	58.735	1571.21	903.823	---	---
H 5 (A)	615.977	0.603	519.813	336.341	74.400	Exceed standard
							H 7 (A)	196.093	0.616	178.055	101.27	52.800	Exceed standard
H11 (A)	147.543	0.039	109.886	54.76	33.600	Exceed standard
							H13 (A)	53.59	0.085	43.744	28.08	23.038	Exceed standard

The statistical value of electric current

From top data, can find out, the voltage distortion rate of steel rolling production-line 400V side of transformer when normal production and the harmonic current of injected system have seriously surpassed the limit value of GB, to the harm of system, are apparent.Make the harmonic current of the busbar voltage aberration rate of 400V and injected system can meet the check requirements of GB, just must be administered harmonic wave, filtering compensation device is installed.

Control measures

(1) the compensating fundamental wave capacity determines

At first the design of filtering compensation device will determine the compensating fundamental wave capacity, because what user first was concerned about is the problem of power factor, after putting into operation, filtering compensation device to guarantee that the steel rolling production equipment is under any operating mode, the monthly average power factor of charging point at least will reach more than 0.9, because power supply department maximum when power factor is examined is preferential, be 0.95, certain power factor surpasses 0.95 words except can being rewarded the electricity charge, can also reduce the inlet wire current of transformer, reduce active loss.

Before administering, the power factor of the low-pressure side of transformer is very low, probably only has 0.65 left and right, guarantee power factor to reach more than 0.95, and compensating fundamental wave 700KVAR left and right gets final product.

(2) filter branch determines

Because the harmonic current of system mainly be take 5 times, 7 times, 11 times and 13 times as main and all exceed standard, 5 primary current maximums wherein.

The experience of according to the inventor, for many years this kind equipment being carried out to harmonic wave control is learnt, as long as arrange 5 times, 7 times and 11 filter branch for this kind equipment filtering compensation device, need not separately establish branch road 13 times.Reason is that the impedance of system is multiplied along with the increase of frequency, and the impedance phase of the impedance of filter branch and system 13 times or smaller, therefore 13 subharmonic currents mostly flow in filter, and therefore need not separately establish 13 filter branch also can guarantee that 13 subharmonic currents of injected system meet the check requirements of GB.

(3) each filter branch parameter determines

The parameter of each branch road, when calculating, must be considered three aspects:

1) total fundamental wave reactive power of filter branch need reach the 700KVAR left and right;

2) the harmonic current surplus of filter branch must guarantee to be not less than the maximum of system harmonics electric current, the normal load operation state of electric capacity in 90% left and right, and harmonic wave calculates according to 95% probable value;

3) first-harmonic and harmonic resonance can not occur after putting into operation in filter;

Therefore, can calculate the parameter of each filter branch according to top requirement, as shown in the table:

?

Capacitance voltage

The separate unit capacitance

The single-phase capacitance number

The first-harmonic capacity

Installed capacity

5 times

350V

50KVAR

3

202KVAR

450KVAR

5 times

350V

50KVAR

3

202KVAR

450KVAR

7 times

350V

60KVAR

2

158KVAR

360KVAR

11 times

350V

20KVAR

2

130KVAR

300KVAR

Amount to

?

?

?

692KVAR

1560KVAR

(4) simulation calculation of filter branch

1) calculating of harmonic wave capacity

The capacitive reactance of filter branch: Xc=U _n ²/ n/Q

The induction reactance of filter branch: Xl=Xc/h ²

The practical impedance of filter branch: X=Xc-Xl

The fundamental current of filter branch: I=U _n/ X

The rated current of filter branch: Ie=n*Q/ UN

the harmonic current surplus of filter branch: I '=√ Ie2-I2

Compensating fundamental wave capacity: Q '=I2*X

In above formula

UN: the rated voltage of capacitor

N: the number of single-phase electricity container

Q: the capacity of single capacitor

H: be respectively filter times 5,7,11 .

Therefore can calculate respectively the electric current of each filter branch while normally moving and the maximum harmonic wave current value while occurring according to above formula.

?	5 branch roads	7 branch roads	11 branch roads
				First-harmonic (A)	586.73	230.00	189.32
Harmonic wave (A)	520.00	178.00	110.00
				Total current (A)	784.00	290.83	218.96
Rated current (A)	857.14	342.86	285.71
				Filter load rate (%)	0.91	0.85	0.77

Electric current during normal operation

?	5 branch roads	7 branch roads	11 branch roads
				First-harmonic (A)	586.73	230.00	189.32
Harmonic wave (A)	616.00	196.00	148.00
				Total current (A)	850.71	302.19	240.30
Rated current (A)	857.14	342.86	285.71
				Filter load rate (%)	0.99	0.88	0.84

Electric current when harmonic wave is maximum

No matter from top data, can find out, be work or maximum harmonic current occurs, and filter branch can meet instructions for use.

(5) Calculation of Reliability of filter branch and system

Due to passive filtration unit put into operation after possibly with system generation first-harmonic resonance or harmonic resonance, four kinds of operating modes that therefore must put into operation to filter are calculated respectively, specifically are calculated as follows:

Figure 12: after dropping into 5 branch roads, the impedance frequency curve of filter and system;

Figure 13: after dropping into two 5 branch roads, the impedance frequency curve of filter and system;

Figure 14: after dropping into two 5 times and 7 branch roads, the impedance frequency curve of filter and system;

Figure 15: after filter branch all drops into, the impedance frequency curve of filter and system;

Can find out from top simulation calculation, under the various operating modes that filter branch drops into, first-harmonic resonance and harmonic resonance all do not occur, so the design of filter be rational.

In addition aspect the filter switching, due to the combination switch switching technology that has adopted the controllable silicon parallel contactor.Adopt controllable silicon can realize the zero current automatic switching, without any inrush current, can not produce harmful spike, thereby guarantee the safe operation of other power consumption equipments, active loss when parallel contactor can reduce controlled silicon conducting simultaneously.When switching, first controllable silicon is put into operation, after five cycles, after (being 0.01S), again contactor is dropped into, after contactor drops into, because contact resistance is less, so the voltage between contact is almost nil, and under this operating mode, controllable silicon is in closed condition.When needs excise, first, by the contactor excision, after time delay 0.01S, again controllable silicon is turn-offed.The controllable silicon two ends only produce heat in moment of conducting and excision like this, so power consumption almost can ignore, and not only can reduce the area of radiator for thyristors, remove cooling device, can also reduce power consumption.

(6) effect of filter before and after putting into operation relatively

1) the release capacity of transformer

Total first-harmonic: I=1738 A before administering

Administer forward sight at power: S=1204 KVA

Power factor before administering: COS ∮=0.65

Active power: P before administering=782 KW

Reactive power: Q before administering=915 KVAR

The reactive power of compensation: Q '=692 KVAR

Reactive power after improvement: Q "=223 KVAR

Apparent power after improvement: S '=814 KVA

Power factor after administering: COS ∮ '=0.96

From above calculating, can find out, after harmonic wave control, the capacity of transformer has discharged closely 1/3, and power factor has brought up to 0.96 simultaneously, and compensation effect is fairly obvious.

2) drop-out current of transformer end of incoming cables

Inlet wire current before administering: I=69.5 A

Inlet wire current after improvement: I=47 A

Inlet wire current after improvement is nearlyer 30% than having descended before administering, and active loss has almost descended half, and effect is fairly obvious.

3) voltage distortion rate and the harmonic wave current value after improvement

After filtering compensation device is installed, the inventor has carried out again field measurement to the quality of power supply of this step down side, from statistics, with administer before compared significantly and descended, effect is fairly obvious:

?	Maximum	Minimum value	95% value	Mean value	State's scale value	Judgement
							H1(V)	249.319	217.452	246.457	236.748	---	---
H5(%)	4.967	0.937	3.534	2.022	4.000	Normally
							H7(%)	1.606	0.182	0.923	0.822	4.000	Normally
H11(%)	1.61	0.032	1.241	0.624	4.000	Normally
							H13(%)	0.974	0.022	0.857	0.515	4.000	Normally
THD(%)	5.456	1.254	4.217	3.213	5.000	Normally

The statistical value of voltage

?	Maximum	Minimum value	95% value	Mean value	State's scale value	Judgement
							H 1 (A)	1181.54	54.579	937.34	746.573	---	---
H 5 (A)	79.854	0.552	49.563	61.673	74.400	Normally
							H 7 (A)	47.659	0.472	32.465	28.342	52.800	Normally
H11 (A)	34.533	0.027	19.664	14.73	33.600	Normally
							H13 (A)	19.343	0.045	16.577	12.064	23.038	Normally

The statistical value of electric current

As can be seen here, at steel rolling production-line low-pressure side installing static compensation device, the effect of carrying out harmonic wave control and reactive power compensation is fairly obvious, and the expense of administering is lower than the cost of active device, therefore has wide market.

Due to passive filtration unit self, although main harmonic current has had apparent in view decline after filter puts into operation, power factor also is greatly improved.But, because this kind equipment is impact load, the variation of active power and reactive power is larger, and the capacity of single filter branch is larger, can't reach the requirement of quick compensation when switching, therefore passive filtration unit can't be eliminated the voltage oscillation caused because of reactive power impact, and directly performance is exactly that the voltage flicker value does not significantly descend before and after filter puts into operation.

In addition, the switching of filter carries out according to idle demand often, and have load on reactive requirement hour, harmonic current is larger, now widely used frequency control equipment particularly, filter effect now inevitably produces larger impact.Therefore,, owing to being according to the big or small automatic switching of harmonic wave, there is not the problem of filter effect in active device.So active filter is only the development trend of the industry of filtering in the future.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the technology of the present invention principle; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (5)

1. one kind for administering the filter of Harmonious Waves in Power Systems, it is characterized in that, described device comprises passive filter and active filter, described passive filter comprises 5 subharmonic filter branch parallel with one another, 7 subharmonic filter branch, 11 subharmonic filter branch, and described each harmonic filter branch is connected in series successively by circuit breaker, current transformer, fuse, reactor, capacitor and bidirectional triode thyristor; Described active filter comprises the first resistance that is serially connected in the network transformer low-pressure side, be connected in parallel on the second resistance of the first resistance opposite side, the other end of the second resistance is connected with the base stage of insulated gate bipolar transistor npn npn, between the collector electrode of insulated gate bipolar transistor npn npn and emitter, is parallel with capacitor; The input of described passive filter each harmonic filter branch and active filter all is parallel to the low-pressure side of transformer, and its output connects with load, and the high-pressure side of described transformer is connected with electrical network.

2. as claimed in claim 1ly for administering the filter of Harmonious Waves in Power Systems, it is characterized in that, the resonance frequency in described each harmonic filter branch after the capacitive reactance coupling of the impedance of reactor and capacitor is identical with the resonance frequency of each filter branch.

3. as claimed in claim 2 for administering the filter of Harmonious Waves in Power Systems, it is characterized in that, 5 subharmonic filter branch of described connection parallel with one another are 3 tunnels, 7 subharmonic filter branch of described connection parallel with one another are 2 tunnels, and 11 subharmonic filter branch of described connection parallel with one another are 2 tunnels.

4. as claimed in claim 3ly for administering the filter of Harmonious Waves in Power Systems, it is characterized in that, the control signal that described bidirectional triode thyristor is exported by controller is carried out switching, and this signal is d. c. voltage signal.

5. as claimed in claim 2ly for administering the filter of Harmonious Waves in Power Systems, it is characterized in that, the calculation of capacity formula of described each harmonic filter branch is:

The capacitive reactance of filter branch: Xc=U _n ²/ n/Q;

The induction reactance of filter branch: Xl=Xc/h ²;

The practical impedance of filter branch: X=Xc – Xl;

The fundamental current of filter branch: I=U _n/ X;

The rated current of filter branch: Ie=n*Q/ U _n;

the harmonic current surplus of filter branch: I '=√ Ie2-I2;

Compensating fundamental wave capacity: Q '=I ²* X;

In above formula

U _n: the rated voltage of capacitor;

N: the number of single-phase electricity container;

Q: the capacity of single capacitor;

H: be respectively filter times 5,7,11.

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