CN104269850B - A kind of control method of the active harmonics resistance being applied to shnt capacitor - Google Patents

Abstract

The invention discloses the control method of a kind of active harmonics resistance being applied to shnt capacitor, including: 1) according to electric network impedance Z_sAnd reactive-load compensation network impedance Z_fObtain optimum harmonic wave resistance r_u；2) detection reactive-load compensation branch current I_f, further according to reactive-load compensation branch current I_fHarmonic current I is obtained by detection algorithm_fh, then according to optimum harmonic wave resistance r_uAnd harmonic current I_fhObtain harmonic voltage instruction；3) detection current transformer DC voltage, is then multiplied by the phase place of AC side of converter electric current by the difference of current transformer DC voltage Yu preset voltage value, obtains fundamental voltage instruction；4) result that fundamental voltage instruction is added with harmonic voltage instruction is subtracted each other with AC side of converter voltage feedback signal, again the result subtracted each other is carried out deviation accumulation, and generate harmonic voltage according to the result of deviation accumulation, then suppress resonance according to described harmonic voltage control active harmonics resistance.The present invention is by suppressing the control realization resonance of active harmonics resistance, simple to operate.

Description

A kind of control method of the active harmonics resistance being applied to shnt capacitor

Technical field

The invention belongs to the power quality control technology field of power system, relate to a kind of being applied to having of shnt capacitor The control method of source harmonic wave resistance.

Background technology

In power system, shnt capacitor is usually used to carry out reactive-load compensation.But it is as nonlinear load at electric power Extensive application in system, can produce harmonic current and harmonic voltage, add electrical network background harmonics, all can cause reactive-load compensation electricity Container and power network line inductance generation resonance, trigger the harmonic protection of shnt capacitor and trip, affect normal reactive-load compensation.

Under normal circumstances, current-limiting reactor can be connect to suppress resonance at capacitor.The method for designing of current-limiting reactor is as follows: When low order is 3 times to mains by harmonics content, current-limiting reactor capacity is the 12% of shnt capacitor；When mains by harmonics content When low order is 5 times, current-limiting reactor capacity is the 5% of shnt capacitor.Such effect is that reactive-load compensation branch road is in harmonic wave section Always presenting perception, harmonic current will not be exaggerated.But this method has certain limitation, when mains by harmonics frequency spectrum occurs During change, current-limiting reactor does not ensures that idle branch road always presents perception in all harmonic wave sections, and harmonic wave still has exaggerated Possibility.And the capacity changing current-limiting reactor frequently can be to bringing very burden in practical operation.Another kind of method is to make Carry out resonance suppression with hybrid active electric filter, but compound filter is very sensitive to systematic parameter, the change of systematic parameter Change can make it control effect variation.It addition, in high-pressure system, can set up voltage-current sensor, mutually deserved cost can improve, It is unfavorable for the popularization of compound filter.

Summary of the invention

It is an object of the invention to the shortcoming overcoming above-mentioned prior art, it is provided that a kind of be applied to having of shnt capacitor The control method of source harmonic wave resistance, this control method is by suppressing the control realization resonance of active harmonics resistance, simple to operate, When being applied to bulk power grid reactive-load compensation, active loss can be reduced while effective damping resonance and reduce reactive-load compensation appearance The impact of amount.

For reaching above-mentioned purpose, the control method bag of the active harmonics resistance being applied to shnt capacitor of the present invention Include following steps:

1) electric network impedance Z is obtained_sAnd reactive-load compensation network impedance Z_f, then according to electric network impedance Z_sAnd reactive-load compensation network Impedance Z_fObtain optimum harmonic wave resistance r_u；

2) detection reactive-load compensation branch current I_f, further according to reactive-load compensation branch current I_fHarmonic wave electricity is obtained by detection algorithm Stream I_fh, then according to optimum harmonic wave resistance r_uAnd harmonic current I_fhObtain harmonic voltage instruction (U_ah, U_bh, U_ch)；

3) detection current transformer DC voltage, is then multiplied by change by the difference of current transformer DC voltage Yu preset voltage value The phase place of stream device ac-side current, obtains fundamental voltage instruction (U_af, U_bf, U_cf)；

4) fundamental voltage is instructed (U_af, U_bf, U_cf) and harmonic voltage instruction (U_ah, U_bh, U_ch) result that is added and unsteady flow Device AC voltage feedback signal subtracts each other, then the result subtracted each other carries out deviation accumulation, and generates according to the result of deviation accumulation Harmonic voltage, then suppresses resonance according to described harmonic voltage control active harmonics resistance.

Step 1) concrete operations be:

11) electric network impedance Z is obtained_sAnd reactive-load compensation network impedance Z_f, further according to electric network impedance Z_sAnd the resistance of reactive-load compensation network Anti-Z_fObtain grid current harmonic content I_{sh_rms}And reactive current harmonic content I_{fh_rms}Respectively with the functional relationship of harmonic wave resistance r, Then minimum harmonic wave resistance r is obtained according to described functional relationship with Shunt Capacitor Harmonic protection demand_min；

12) when current transformer exists switch time delay and sampling time delay, the transmission function of active harmonics resistance r isWherein, T_wFor switch periods, T_sFor the sampling period, s is continuous frequency domain variable, further according to institute The bode figure of harmonic wave resistance open-loop transfer function is drawn in transmission function r (s) stating active harmonics resistance r, and according to described harmonic wave The bode figure of resistance open-loop transfer function and system stability sexual demand obtain maximum harmonic wave resistance r_max；

13) the energy P that harmonic wave resistance r feeds back in first-harmonic section_rf=P_rh-P_loss, wherein, P_rhFor harmonic wave resistance r in harmonic wave section The energy absorbed, P_lossFor the loss of current transformer, the energy P then fed back in first-harmonic section according to harmonic wave resistance r_rfAnd feedback energy Demand obtains optimum harmonic wave resistance r_u, wherein, optimum harmonic wave resistance r_uResistance be positioned at maximum harmonic wave resistance r_maxResistance with minimum Harmonic wave resistance r_minResistance between.

Step 2) concrete operations be:

Detect idle branch current, obtain a phase current I of idle branch road_a, b phase current I_bAnd c phase current I_c, described idle The a phase current I on road_a, b phase current I_bAnd c phase current I_cSuccessively at CLARKE conversion, PARK conversion, low pass filter filtering First-harmonic composition electric current I is obtained after reason, PARK inverse transformation, CLARKE inverse transformation_af, electric current I_bfAnd electric current I_cf, then by electric current I_af, electricity Stream I_bfAnd electric current I_cfRespectively with a phase current I of idle branch road_a, b phase current I_bAnd c phase current I_cSubtract each other to obtain harmonic components electric current I_ah, electric current I_bhAnd electric current I_ch, then by electric current I_ah, electric current I_bhAnd electric current I_chRespectively with optimum harmonic wave resistance r_uIt is multiplied, obtains humorous Wave voltage instruction (U_ah, U_bh, U_ch)。

Step 11) concrete operations be:

Obtain electric network impedance Z_sAnd reactive-load compensation network impedance Z_f, further according to electric network impedance Z_sAnd reactive-load compensation network impedance Z_fObtain power network current I_sRatio load current I_LGainThen increase than load current according to power network current Benefit G_sAnd each harmonic content I in nonlinear load_LhObtain grid current harmonic content I_{sh_rms}:

$I_{\mathrm{sh}\_\mathrm{rms}}=\sqrt{\mathrm{\Σ}{I}_{\mathrm{sh}}^2}---\left(1\right)$

Wherein, I_shFor mains by harmonics electric current；

Idle branch current is than load current gainAccording to idle branch current than load electricity Flow enhancement G_fAnd each harmonic content I in nonlinear load_LhObtain reactive current harmonic content_{Ifh_rms}:

$I_{\mathrm{fh}\_\mathrm{rms}}=\sqrt{\mathrm{\Σ}{I}_{\mathrm{fh}}^2}---\left(2\right)$

Wherein, I_fhFor idle branch road individual harmonic current；

Demand is protected to obtain minimum harmonic wave resistance r according to formula (1), formula (2) and Shunt Capacitor Harmonic_min。

Step 12) concrete operations be:

When there is switch time delay and sampling time delay in current transformer, harmonic wave resistanceWherein, T_w For switch periods, T_sFor sampling period, then system open loop transmission function $G_o\left(s\right)=\frac{r}{(\frac{T_w}{2}s+1)(\frac{T_s}{2}s+1)(Z_s+Z_f)},$ Draw The bode figure of harmonic wave resistance open-loop transfer function, obtains maximum harmonic wave resistance r according to stability and system stability sexual demand_max。

The energy that described harmonic wave resistance r absorbs in harmonic wave section

The method have the advantages that

The control method of the active harmonics resistance being applied to shnt capacitor of the present invention replaces biography by current transformer The current-limiting reactor of system, controls harmonic voltage by detection harmonic current, enters by controlling active harmonics resistance in harmonic wave section Row resonance suppresses, thus obtains the effect of preferable resonance suppression, and can save energy, meanwhile, relative to traditional series connection Reactor, active harmonics resistance can when mains by harmonics produces change still can effective damping resonance, and to idle benefit Repay and the most do not affect, there is good engineer applied meaning, and when being applied to bulk power grid reactive-load compensation, can be in effective damping Reduce active loss while resonance and reduce the impact on reactive compensation capacity.When concrete operations, current transformer detection is idle The electric current of branch road controls its port voltage, presents resistance characteristic in harmonic wave section, in first-harmonic section to electrical network feedback energy, then chooses Optimum harmonic wave resistance, prevents resonance from causing power network current to exceed standard and shnt capacitor overcurrent, it is achieved damping function.When electricity in parallel During container generation switching, harmonic wave resistance can be optimized and revised accordingly, when in load current, harmonic spectrum changes, Active harmonics resistance remains able to effective must carrying out and damps the resonance between electric network impedance and shnt capacitor.

Accompanying drawing explanation

Fig. 1 is the structural representation of active harmonics resistance of the present invention；

Fig. 2 (a) is that in the present invention, under active harmonics resistor control mode, grid current harmonic content perunit value is electric with harmonic wave Resistance change curve；

Fig. 2 (b) be in the present invention under active harmonics resistor control mode idle branch current harmonic content perunit value with humorous Ripple resistance change curves；

Fig. 3 is the bode figure that in the present invention, active harmonics resistance controls lower open-loop transfer function；

Fig. 4 is active harmonics resistance energy spectrometer in the present invention；

Fig. 5 is that energy that in the present invention, active harmonics resistance feeds back in first-harmonic section is with harmonic wave resistance change curves；

Load current, power network current, idle branch current when Fig. 6 is to add active harmonics resistance in the present invention；

Load current, power network current, idle branch current each harmonic when Fig. 7 is to add active harmonics resistance in the present invention Content block diagram.

Detailed description of the invention

Below in conjunction with the accompanying drawings the present invention is described in further detail:

With reference to Fig. 1, the control method of the active harmonics resistance being applied to shnt capacitor of the present invention includes following Step:

1) electric network impedance Z is obtained_sAnd reactive-load compensation network impedance Z_f, then according to electric network impedance Z_sAnd reactive-load compensation network Impedance Z_fObtain optimum harmonic wave resistance r_u；

2) detection reactive-load compensation branch current I_f, further according to reactive-load compensation branch current I_fHarmonic wave electricity is obtained by detection algorithm Stream I_fh, then according to optimum harmonic wave resistance r_uAnd harmonic current I_fhObtain harmonic voltage instruction (U_ah, U_bh, U_ch)；

3) detection current transformer DC voltage, is then multiplied by change by the difference of current transformer DC voltage Yu preset voltage value The phase place of stream device ac-side current, obtains fundamental voltage instruction (U_af, U_bf, U_cf)；

4) fundamental voltage is instructed (U_af, U_bf, U_cX) with harmonic voltage instruction (U_ah, U_bh, U_ch) result that is added and unsteady flow Device AC voltage feedback signal subtracts each other, then the result subtracted each other carries out deviation accumulation, and generates according to the result of deviation accumulation Harmonic voltage, then suppresses resonance according to described harmonic voltage control active harmonics resistance.

Step 1) concrete operations be:

11) electric network impedance Z is obtained_sAnd reactive-load compensation network impedance Z_f, further according to electric network impedance Z_sAnd the resistance of reactive-load compensation network Anti-Z_fObtain grid current harmonic content I_{sh_rms}And reactive current harmonic content I_{fh_rms}Respectively with the functional relationship of harmonic wave resistance r, Then minimum harmonic wave resistance r is obtained according to described functional relationship with Shunt Capacitor Harmonic protection demand_min；

12) when current transformer exists switch time delay and sampling time delay, the transmission function of active harmonics resistance r isWherein, T_wFor switch periods, T_sFor the sampling period, s is continuous frequency domain variable, further according to institute The bode figure of harmonic wave resistance open-loop transfer function is drawn in transmission function r (s) stating active harmonics resistance r, and according to described harmonic wave The bode figure of resistance open-loop transfer function and system stability sexual demand obtain maximum harmonic wave resistance r_max；

13) the energy P that harmonic wave resistance r feeds back in first-harmonic section_rf=P_rh-P_loss, wherein, P_rhFor harmonic wave resistance r in harmonic wave section The energy absorbed, P_lossFor the loss of current transformer, the energy P then fed back in first-harmonic section according to harmonic wave resistance r_rfAnd feedback energy Demand obtains optimum harmonic wave resistance r_u, wherein, optimum harmonic wave resistance r_uResistance be positioned at maximum harmonic wave resistance r_maxResistance with minimum Harmonic wave resistance r_minResistance between.

Such as: protect requirement with reference to Fig. 2 (a) and Fig. 2 (b) according to Shunt Capacitor Harmonic, minimum harmonic wave resistance can be drawn It it is 3.5 ohm.When sample frequency and switching frequency all take 10kHz, r take 15 ohm time, draw harmonic wave resistance open-loop transfer function Bode figure, as it is shown on figure 3, now system is in neutrality, i.e. maximum harmonic wave resistance is 15 ohm.As it is shown in figure 5, here Harmonic wave resistance optimal value 6 ohm, and in the interval of harmonic wave resistance；

Step 2) concrete operations be:

Detect idle branch current, obtain a phase current I of idle branch road_a, b phase current I_bAnd c phase current I_c, described idle The a phase current I on road_a, b phase current I_bAnd c phase current I_cSuccessively at CLARKE conversion, PARK conversion, low pass filter filtering First-harmonic composition electric current I is obtained after reason, PARK inverse transformation, CLARKE inverse transformation_af, electric current I_bfAnd electric current I_cf, then by electric current I_af, electricity Stream I_bfAnd electric current I_cfRespectively with a phase current I of idle branch road_a, b phase current I_bAnd c phase current I_cSubtract each other to obtain harmonic components electric current I_ah, electric current I_bhAnd electric current I_ch, then by electric current I_ah, electric current I_bhAnd electric current I_chRespectively with optimum harmonic wave resistance r_uIt is multiplied, obtains humorous Wave voltage instruction (U_ah, U_bh, U_ch)。

Step 11) concrete operations be:

Obtain electric network impedance Z_sAnd reactive-load compensation network impedance Z_f, further according to electric network impedance Z_sAnd reactive-load compensation network impedance Z_fObtain power network current I_sRatio load current I_LGainThen increase than load current according to power network current Benefit G_sAnd each harmonic content I in nonlinear load_LhObtain grid current harmonic content I_{sh_rms}:

$I_{\mathrm{sh}\_\mathrm{rms}}=\sqrt{\mathrm{\Σ}{I}_{\mathrm{sh}}^2}---\left(1\right)$

Wherein, I_shFor mains by harmonics electric current；

Idle branch current is than load current gainAccording to idle branch current than load electricity Flow enhancement G_fAnd each harmonic content I in nonlinear load_LhObtain reactive current harmonic content I_{fh_rms}:

$I_{\mathrm{fh}\_\mathrm{rms}}=\sqrt{\mathrm{\Σ}{I}_{\mathrm{fh}}^2}---\left(2\right)$

Wherein, I_fhFor idle branch road individual harmonic current；

Demand is protected to obtain minimum harmonic wave resistance r according to formula (1), formula (2) and Shunt Capacitor Harmonic_min。

Step 12) concrete operations be:

When there is switch time delay and sampling time delay in current transformer, harmonic wave resistanceWherein, T_w For switch periods, T_sFor sampling period, then system open loop transmission function $G_o\left(s\right)=\frac{r}{(\frac{T_w}{2}s+1)(\frac{T_s}{2}s+1)(Z_s+Z_f)},$ Draw The bode figure of harmonic wave resistance open-loop transfer function, obtains maximum harmonic wave resistance r according to stability and system stability sexual demand_max。

With reference to Fig. 4, the energy that described harmonic wave resistance r absorbs in harmonic wave section

Emulation experiment

Circuit parameter is arranged such as following table:

Us	Zs	Cf	Zf
				380V	0.52mH	200uF	0.25mH

Harmonic source is designed as: according to Utility grid harmonic standard GBT 14549-1993, allows user under 0.38KV The each harmonic content injected is as follows:

Under current electric grid impedance, as shown in the table after harmonic current conversion:

Systematic parameter has set up, and load is chosen as ohmic load 18 ohm under diode uncontrollable rectifier bridge.Observation has Power network current under the harmonic wave resistor control mode of source and the damping situation of idle branch current.

After adding active harmonics resistance, load current, power network current and idle branch current are as shown in Figure 6, it can be seen that Power network current and idle branch current harmonic content substantially reduce, and each harmonic amplifies situation as it is shown in fig. 7, active harmonics resistance Control strategy can be with effective damping resonance.

Claims (4)

1. the control method of the active harmonics resistance being applied to shnt capacitor, it is characterised in that comprise the following steps:

1) electric network impedance Z is obtained_sAnd reactive-load compensation network impedance Z_f, then according to electric network impedance Z_sAnd reactive-load compensation network impedance Z_f Obtain optimum harmonic wave resistance r_u；

2) detection reactive-load compensation branch current I_f, further according to reactive-load compensation branch current I_fHarmonic current I is obtained by detection algorithm_fh, Then according to optimum harmonic wave resistance r_uAnd harmonic current I_fhObtain harmonic voltage instruction (U_ah, U_bh, U_ch)；

3) detection current transformer DC voltage, is then multiplied by current transformer by the difference of current transformer DC voltage Yu preset voltage value The phase place of ac-side current, obtains fundamental voltage instruction (U_af, U_bf, U_cf)；

4) fundamental voltage is instructed (U_af, U_bf, U_cf) and harmonic voltage instruction (U_ah, U_bh, U_ch) result that is added hands over current transformer Stream side voltage feedback signal subtracts each other, then the result subtracted each other carries out deviation accumulation, and generates harmonic wave according to the result of deviation accumulation Voltage, then suppresses resonance according to described harmonic voltage control active harmonics resistance；

Step 1) concrete operations be:

11) electric network impedance Z is obtained_sAnd reactive-load compensation network impedance Z_f, further according to electric network impedance Z_sAnd reactive-load compensation network impedance Z_f Obtain grid current harmonic content I_{sh_rms}And reactive current harmonic content I_{fh_rms}Respectively with the functional relationship of harmonic wave resistance r, then Minimum harmonic wave resistance r is obtained with Shunt Capacitor Harmonic protection demand according to described functional relationship_min；

12) when current transformer exists switch time delay and sampling time delay, the transmission function of active harmonics resistance r isWherein, T_wFor switch periods, T_sFor the sampling period, s is continuous frequency domain variable, further according to described The bode figure of harmonic wave resistance open-loop transfer function is drawn in transmission function r (s) of active harmonics resistance r, and according to described harmonic wave electricity The bode figure of resistance open-loop transfer function and system stability sexual demand obtain maximum harmonic wave resistance r_max；

13) the energy P that harmonic wave resistance r feeds back in first-harmonic section_rf=P_rh-P_loss, wherein, P_rhAbsorb in harmonic wave section for harmonic wave resistance r Energy, P_lossFor the loss of current transformer, the energy P then fed back in first-harmonic section according to harmonic wave resistance r_rfAnd feedback energy demand Obtain optimum harmonic wave resistance r_u, wherein, optimum harmonic wave resistance r_uResistance be positioned at maximum harmonic wave resistance r_maxResistance and minimum harmonic wave Resistance r_minResistance between；

Step 11) concrete operations be:

Obtain electric network impedance Z_sAnd idle branch impedance Z_f, further according to electric network impedance Z_sAnd idle branch impedance Z_fObtain power network current I_s Ratio load current I_LGainThen according to power network current than load current gain G_sAnd it is non-linear negative Each harmonic content I in load_LhObtain grid current harmonic content I_{sh_rms}:

$I_{sh\_rms}=\sqrt{{\mathrm{\ΣI}}_{sh}^2}---\left(1\right)$

Wherein, I_shFor electrical network individual harmonic current；

Idle branch current is than load current gainIncrease than load current according to idle branch current Benefit G_fAnd each harmonic content I in nonlinear load_LhObtain reactive current harmonic content I_{fh_rms}:

$I_{fh\_rms}=\sqrt{{\mathrm{\ΣI}}_{fh}^2}---\left(2\right)$

Wherein, I_fhFor idle branch road individual harmonic current；Demand is protected to obtain according to formula (1), formula (2) and Shunt Capacitor Harmonic Little harmonic wave resistance r_min。

The control method of the active harmonics resistance being applied to shnt capacitor the most according to claim 1, it is characterised in that Step 2) concrete operations be:

Detect idle branch current, obtain a phase current I of idle branch road_a, b phase current I_bAnd c phase current I_c, described idle branch road A phase current I_a, b phase current I_bAnd c phase current I_cSuccessively through CLARKE conversion, PARK conversion, low pass filter Filtering Processing, First-harmonic composition electric current I is obtained after PARK inverse transformation, CLARKE inverse transformation_af, electric current I_bfAnd electric current I_cf, then by electric current I_af, electric current I_bfAnd electric current I_cfRespectively with a phase current I of idle branch road_a, b phase current I_bAnd c phase current I_cSubtract each other to obtain harmonic components electric current I_ah、 Electric current I_bhAnd electric current I_ch, then by electric current I_ah, electric current I_bhAnd electric current I_chRespectively with optimum harmonic wave resistance r_uIt is multiplied, obtains harmonic wave electricity End finger makes (U_ah, U_bh, U_ch)。

The control method of the active harmonics resistance being applied to shnt capacitor the most according to claim 1, it is characterised in that Step 12) concrete operations be:

When there is switch time delay and sampling time delay in current transformer；Harmonic wave resistanceWherein, T_wFor opening The pass cycle, T_sFor sampling period, then system open loop transmission functionDrafting harmonic wave electricity The bode figure of resistance open-loop transfer function, obtains maximum harmonic wave resistance r according to stability and system stability sexual demand_max。

The control method of the active harmonics resistance being applied to shnt capacitor the most according to claim 1, it is characterised in that The energy that described harmonic wave resistance r absorbs in harmonic wave section