CN103986169B - The control method of a kind of SVC under electrical network asymmetric fault - Google Patents

Abstract

The present invention relates to the control method of SVC under electrical network asymmetric fault, belong to the network stability control technical field of power system; The method considered to connect when the grid-connected point voltage of electrical network is asymmetric three-phase in single-phase bridge SVC produces condition and the influencing characterisitic of circulation to DC capacitor voltage of circulation, adopt the method for setting idle reference current according to the ratio of each phase line voltage, SVC three phase capacitance voltage imbalance and overcurrent while preventing electrical network generation asymmetric fault, guarantee that device moves continually and steadily. The method physical significance is distinct, realization is simple, excellent performance, when the control method of related SVC under electrical network asymmetric fault is applied to large electrical network dynamic passive compensation equipment control, can, in the safe operation scope that improves SVC, improve electrical network Enhancement of Transient Voltage Stability.

Description

The control method of a kind of SVC under electrical network asymmetric fault

Technical field

The network stability control technical field that the invention belongs to power system, particularly a kind of SVC is non-at electrical networkDevice current control method under symmetric fault.

Background technology

SVC (STATCOM) taking turn-off device (IGBT, IGCT) as switching device is modern electricThe typical case of electronic technology in power system application, can help electrical network to realize that dynamic reactive regulates continuously, to improve line voltage steadyDetermining level, limiting circuitry low frequency power oscillation, is that electrical network is realized one of controlledization and intelligentized Main Means. Series connection single-phase bridgeThe circuit structure of formula SVC as shown in Figure 1, is often in series by several single-phase full-bridge inverters head and the tail, canAs required three-phase is connected into triangular form or star-like. Compared with the SVC of traditional structure, series connection single-phase bridgeSVC have harmonic wave little, without transformer, take up an area little, be easy to the advantages such as expansion, in high voltage, large capacity fieldClose, the main circuit of SVC is taking the single-phase bridge architecture of connecting as main.

When electrical network generation unbalanced fault, can cause frequency, the phase place generation disturbance of line voltage, or Voltage unbalance andThe appearance of these unusual service conditions of operating mode such as amplitude bust. Line voltage is easy to cause the overcurrent of static passive compensation device extremely,Harm equipment safety. Tradition STATCOM when especially system voltage is asymmetric, adopts locking pulse in unusual service condition conventionally,Measure out of service, with protective device, drops into when waiting system recovers normal more again. But during electric network fault normallyNeed STATCOM provide dynamic reactive support, when preventing collapse of voltage, the operation of device locking pulse backed off after random is completeCannot provide idle, device is declined greatly to the supporting role of the stabilization of power grids. Research STATCOM when asymmetrical voltageControl strategy, assurance device is operation continually and steadily under unusual service condition, and the security operation zone that can greatly widen device, in systemWhen needing most, provide dynamic reactive to support, give full play to the effectiveness of STATCOM.

The subject matter that when electrical network asymmetric fault, the control of STATCOM and protection will be faced is to fill under unbalanced system voltageThe research of the characteristics and control strategy method of putting. When system voltage is uneven, if the inverter of STATCOM is only exported positive sequence electricityPress, be equivalent to provide the path of a little impedance to system negative sequence voltage, produce the peace of a large amount of negative-sequence current harm devicesEntirely, and on DC capacitor, cause larger voltage ripple, cause the distortion of output voltage and electric current. Chain type STATCOM and manyThe difference of heavily changing structure STATCOM main circuit makes them in operation characteristic, have larger difference: multiple inverter configuration STATCOMConventionally adopt three-phase to share the inverter of electric capacity, the power that injects electric capacity is three phase power sum; And chain type STATCOM three-phaseElectric capacity separates, and injecting the power of electric capacity be only this phase voltage electric current product, originally by three additions with can cancellation somePower composition is retained now and injects respectively three phase capacitance, most importantly reactive power composition. Inhale and send out mutually for suppressing everyA large amount of capacitance voltage ripples that cause when idle, need to choose the electric capacity that capacitance is larger, and this has given chain type STATCOM and has heldBe subject to compared with the ability of large unbalance voltage. But in the time that system voltage is uneven, the power that injects three phase capacitance also may haveThe real component of different sizes, control mode is unreasonable will cause capacitance voltage unstability and even collapse, these characteristics are multiplexesUnexistent in STATCOM. Therefore, can not directly overlap and use chain type for the control method of multiplex STATCOMIn STATCOM. Patent of the present invention takes into full account the difference of chain type STATCOM and multiple inverter configuration STATCOM, from energyThe operation characteristic of the angle Study system Voltage unbalance timer of amount, the condition of the sustainable stable operation of analytical equipment, carries accordinglyGo out the optimal control method of STATCOM under a kind of electrical network asymmetric fault.

Summary of the invention

While the object of the invention is to solve electrical network generation asymmetric fault, series connection single-phase bridge SVC is owing to controlling notWhen causing the problem of overcurrent and locking. The single-phase bridge static var compensation of connecting in the time having taken into full account that the grid-connected point voltage of electrical network is asymmetricRepay three-phase in device and produce on the condition of circulation and the basis of the influencing characterisitic of circulation to DC capacitor voltage, propose to adopt according to respectivelyThe ratio of phase line voltage is set the method for idle reference current. The method have physical significance distinct, realize simple, performance is excellentThe feature such as different, it is dynamic that the control method of the related SVC of the present invention under electrical network asymmetric fault is applied to large electrical networkWhen reactive-load compensation equipment control, can, in the safe operation scope that improves SVC, improve electrical network Enhancement of Transient Voltage Stability.

The control method of a kind of SVC (STATCOM) that the present invention proposes under electrical network asymmetric fault, its spyLevy and be: for series connection single-phase bridge SVC, in the time of electrical network generation asymmetric fault, SVC connectsThe three-phase voltage that enters electrical network point is asymmetrical state. Control the SVC each reactive current and this phase electrical network electricity of output mutuallyBe pressed into direct ratio, with the three-phase dc capacitance voltage equilibrium of the single-phase bridge SVC of guaranteeing to connect, the inner not ring of deviceStream, can move continually and steadily.

The method specifically comprises the following steps:

1), in the time that a control cycle arrives, measure in real time the three-phase voltage instantaneous value of SVC access electrical network pointv_ab、v_bc、v_ca, calculate three-phase voltage phase place through phaselocked loopCalculate the amplitude of three-phase voltageV_ab、V_bc、V_ca；

2) the reference value U of setting series connection single-phase bridge SVC three phase capacitance voltage_{DC_ab_ref}、U_{DC_bc_ref}、U_{DC_ca_ref}. Measure three phase capacitance voltage U_{DC_ab}、U_{DC_bc}、U_{DC_ca}. The reference value of three phase capacitance voltage and measured valueDifference calculate and control the three-phase phase deviation δ of DC capacitor voltage through a pi regulator_ab、δ_bc、δ_ca. PI adjustsThe transfer function of joint device is:Wherein s is complex frequency, K_vAnd T_vIt is normal to be respectively proportionality coefficient and the time of integrationNumber;

3) the phase angle θ of calculating three-phase current reference value_ab、θ_bc、θ_ca, its computing formula is as follows:

Wherein α is idle merit angle, and value rule is: when needs SVC send perceptual when idle, α=pi/2;In the time that needs SVC sends capacitive reactive power, α=-pi/2;

4) set STATCOM output reactive power Q_ref, the amplitude I of calculating STATCOM three-phase current reference value_{ab_ref}、I_{bc_ref}、I_{ca_ref}, computing formula is as follows:

$I_{\mathrm{ab}\_\mathrm{ref}}=2V_{\mathrm{ab}}{Q}_{\mathrm{ref}}/(V_{\mathrm{ab}}^2+V_{\mathrm{bc}}^2+V_{\mathrm{ca}}^2)$

$I_{\mathrm{bc}\_\mathrm{ref}}=2V_{\mathrm{bc}}{Q}_{\mathrm{ref}}/(V_{\mathrm{ab}}^2+V_{\mathrm{bc}}^2+V_{\mathrm{ca}}^2)$

$I_{\mathrm{ca}\_\mathrm{ref}}=2V_{\mathrm{ca}}{Q}_{\mathrm{ref}}/(V_{\mathrm{ab}}^2+V_{\mathrm{bc}}^2+V_{\mathrm{ca}}^2)$

5) calculate the instantaneous reference value i of STATCOM three-phase current_{ab_ref}、i_{bc_ref}、i_{ca_ref}, computing formula is as follows:

i_{ab_ref}＝I_{ab_ref}sin(θ_ab)

i_{bc_ref}＝I_{bc_ref}sin(θ_bc)

i_{ca_ref}＝I_{ca_ref}sin(θ_ca)

6) measure STATCOM three-phase current i_ab、i_bc、i_ca, calculate STATCOM three-phase current measured value i_ab、i_bc、i_caWith reference value i_{ab_ref}、i_{bc_ref}、i_{ca_ref}Between difference, through pi regulator calculate STATCOM need defeatedThe voltage increment Δ v going out_ab、Δv_bc、Δv_ca. Wherein the transfer function of pi regulator is:Wherein s is multifrequencyRate, K_iAnd T_iBe respectively proportionality coefficient and integration time constant;

7) calculate according to the three-phase voltage value of STATCOM access electrical network point and the voltage increment that STATCOM need to exportThe three-phase voltage reference value e of STATCOM_ab、e_bc、e_ca, computing formula is as follows:

e_ab＝v_cb-Δv_ab

e_bc＝v_bc-Δv_bc

e_ca＝v_ca-Δv_ca

By the three-phase voltage reference value e of STATCOM_ab、e_bc、e_caDeliver to pwm pulse generator as modulating wave, have PWMImpulse generator calculates and produces the driving pulse that each series connection single-phase bridge of STATCOM needs, and waits for that next control cycle arrivesWhile coming, go to step 1).

Technical characterstic of the present invention is: the related control method of the present invention is positioned in the control system of whole SVCDevice level key-course, its major function is in the time of electrical network generation asymmetric fault, according to the asymmetric feature of line voltage, optimizesThe three-phase current that calculates SVC output, with the assurance device three phase capacitance balance of voltage, prevents overcurrent. Side of the present inventionMethod is the improvement to existing apparatus stage control method, therefore can not need to increase specially hardware and realize. Can be at original static reacanceOn the device level control hardware platform of compensator, realize by change control program, improve series connection single-phase bridge SVCSafe operation scope.

The invention has the beneficial effects as follows: adopt the method can effectively control series connection single-phase bridge SVC non-at electrical networkThree phase capacitance voltage when symmetric fault, prevents the circulation between SVC three-phase and the voltage imbalance causing and dressPut overcurrent, the safe operation scope of expansion instrument, makes can move continually and steadily at the electrical network timer that breaks down, and is electrical networkProvide maximum dynamic electric voltage to support, suppress transient voltage unstability. The method have physical significance distinct, realize simple,The features such as excellent performance, a fault traversing difficult problem for the single-phase bridge SVC of connecting while having solved electrical network asymmetric fault,The related control method of the present invention can effectively be controlled the voltage, electric current of STATCOM all specified in the time of electrical network asymmetric faultIn scope. Can be applicable in the control of large electrical network static passive compensation device.

Brief description of the drawings

Fig. 1 is series connection single-phase bridge SVC;

Fig. 2 is the optimal control block diagram of SVC of the present invention in the time that line voltage is asymmetric.

Detailed description of the invention

The control method of SVC under electrical network asymmetric fault that the present invention proposes by reference to the accompanying drawings and embodiment say in detailBright as follows:

The feature of control method of the present invention is to take into account the control requirement of power system to dynamic stability and voltage stabilization, realizesVoltage and damping are coordinated to control, and it is characterized in that, comprising: for series connection single-phase bridge SVC, when electrical network occursWhen asymmetric fault, the three-phase voltage of SVC access electrical network point is asymmetrical state. Control SVCEach reactive current of output is mutually directly proportional to this phase line voltage, straight with the three-phase of the single-phase bridge SVC of guaranteeing to connectThe equilibrium of stream capacitance voltage, device inside does not have circulation, can move continually and steadily. The related control method of the present invention is whole quietOnly in the control system of reactive-load compensation equipment, be positioned at device level key-course, its major function is the situation of change according to line voltage,Optimize size and the phase place of calculating static reactive equipment three-phase output current, calculate by transient current tracking and controlling methodThe three-phase voltage reference value of static reactive equipment. This reference value is issued to next as the modulating wave of pwm pulse generatorLevel controller (pwm pulse generator), controls static passive compensation device and sends the reactive current of appointment.

The detailed description of the invention of the inventive method is as shown in Figure 2:

Specifically comprise the following steps:

1), in the time that a control cycle arrives, measure in real time the three-phase voltage instantaneous value of SVC access electrical network pointv_ab、v_bc、v_ca, calculate three-phase voltage phase place through phaselocked loopCalculate the amplitude of three-phase voltageV_ab、V_bc、V_ca；

2) the reference value U of setting series connection single-phase bridge SVC three phase capacitance voltage_{DC_ab_ref}、U_{DC_bc_ref}、U_{DC_ca_ref}. Measure three phase capacitance voltage U_{DC_ab}、U_{DC_bc}、U_{DC_ca}. The reference value of three phase capacitance voltage and measured valueDifference calculate and control the three-phase phase deviation δ of DC capacitor voltage through a pi regulator_ab、δ_bc、δ_ca. PI adjustsThe transfer function of joint device is:Wherein s is complex frequency, K_vAnd T_vIt is normal to be respectively proportionality coefficient and the time of integrationNumber, can choose K_v＝4～10，T_v=0.005～0.01 second;

3) the phase angle θ of calculating three-phase current reference value_ab、θ_bc、θ_ca, its computing formula is as follows:

Wherein α is idle merit angle, and value rule is: when needs SVC send perceptual when idle, α=pi/2;In the time that needs SVC sends capacitive reactive power, α=-pi/2;

4) set STATCOM output reactive power Q_ref, the amplitude I of calculating STATCOM three-phase current reference value_{ab_ref}、I_{bc_ref}、I_{ca_ref}, computing formula is as follows:

$I_{\mathrm{ab}\_\mathrm{ref}}=2V_{\mathrm{ab}}{Q}_{\mathrm{ref}}/(V_{\mathrm{ab}}^2+V_{\mathrm{bc}}^2+V_{\mathrm{ca}}^2)$

$I_{\mathrm{bc}\_\mathrm{ref}}=2V_{\mathrm{bc}}{Q}_{\mathrm{ref}}/(V_{\mathrm{ab}}^2+V_{\mathrm{bc}}^2+V_{\mathrm{ca}}^2)$

$I_{\mathrm{ca}\_\mathrm{ref}}=2V_{\mathrm{ca}}{Q}_{\mathrm{ref}}/(V_{\mathrm{ab}}^2+V_{\mathrm{bc}}^2+V_{\mathrm{ca}}^2)$

5) calculate the instantaneous reference value i of STATCOM three-phase current_{ab_ref}、i_{bc_ref}、i_{ca_ref}, computing formula is as follows:

i_{ab_ref}＝I_{ab_ref}sin(θ_ab)

i_{bc_ref}＝I_{bc_ref}sin(θ_bc)

i_{ca_ref}＝I_{ca_ref}sin(θ_ca)

6) measure STATCOM three-phase current i_ab、i_bc、i_ca, calculate STATCOM three-phase current measured value i_ab、i_bc、i_caWith reference value i_{ab_ref}、i_{bc_ref}、i_{ca_ref}Between difference, through pi regulator calculate STATCOM need defeatedThe voltage increment Δ v going out_ab、Δv_bc、Δv_ca. Wherein the transfer function of pi regulator is:Wherein s is multifrequencyRate, K_iAnd T_iBe respectively proportionality coefficient and integration time constant, can choose K_i＝10～20，T_i=O.001～0.004 second;

7) calculate according to the three-phase voltage value of STATCOM access electrical network point and the voltage increment that STATCOM need to exportThe three-phase voltage reference value c of STATCOM_ab、e_bc、e_ca, computing formula is as follows:

e_ab＝v_ab-Δv_ab

e_bc＝v_bc-ΔU_bc

e_ca＝v_ca-Δv_ca

By the three-phase voltage reference value e of STATCOM_ab、e_bc、e_caDeliver to pwm pulse generator as modulating wave,There is pwm pulse generator to calculate and produce the driving pulse that each series connection single-phase bridge of STATCOM needs, and wait for nextWhen individual control cycle arrives, go to step 1).

So far the control task of the SVC that, the present invention proposes under electrical network asymmetric fault all completes.

Claims (1)

1. the control method of SVC (STATCOM) under electrical network asymmetric fault, is characterized in that: forSeries connection single-phase bridge SVC, in the time of electrical network generation asymmetric fault, three of SVC access electrical network pointPhase voltage is asymmetrical state; Control the each reactive current of output mutually of SVC and be directly proportional to this phase line voltage, withGuarantee the to connect three-phase dc capacitance voltage equilibrium of single-phase bridge SVC, device inside does not have circulation, can continueStable operation; The method specifically comprises the following steps:

1), in the time that a control cycle arrives, measure in real time the three-phase voltage instantaneous value v of SVC access electrical network point_ab、v_bc、v_ca, calculate three-phase voltage phase place through phaselocked loopCalculate the amplitude V of three-phase voltage_ab、V_bc、V_ca；

2) the reference value U of setting series connection single-phase bridge SVC three phase capacitance voltage_{DC_ab_ref}、U_{DC_bc_ref}、U_{DC_ca_ref}; Measure three phase capacitance voltage U_{DC_ab}、U_{DC_bc}、U_{DC_ca}; The reference value of three phase capacitance voltage and measured value poorCalculate the three-phase phase deviation δ that controls DC capacitor voltage through a pi regulator_ab、δ_bc、δ_ca; Pi regulatorTransfer function is:Wherein s is complex frequency, K_vAnd T_vBe respectively proportionality coefficient and integration time constant;

3) the phase angle θ of calculating three-phase current reference value_ab、θ_bc、θ_ca, its computing formula is as follows:

Wherein α is idle merit angle, and value rule is: when needs SVC send perceptual when idle, α=pi/2; Work as needWhile wanting SVC to send capacitive reactive power, α=-pi/2;

4) set SVC (STATCOM) output reactive power Q_ref, calculate SVC (STATCOM)The amplitude I of three-phase current reference value_{ab_ref}、I_{bc_ref}、I_{ca_ref}, computing formula is as follows:

$I_{ab\_ref}=2V_{ab}{Q}_{ref}/(V_{ab}^2+V_{bc}^2+V_{ca}^2)$

$I_{bc\_ref}=2V_{bc}{Q}_{ref}/(V_{ab}^2+V_{bc}^2+V_{ca}^2)$

$I_{ca\_ref}=2V_{ca}{Q}_{ref}/(V_{ab}^2+V_{bc}^2+V_{ca}^2)$

5) calculate the instantaneous reference value i of SVC (STATCOM) three-phase current_{ab_ref}、i_{bc_ref}、i_{ca_ref}, computing formula asUnder:

i_{ab_ref}＝I_{ab_ref}sin(θ_ab)

i_{bc_ref}＝I_bcrefsin(θ_bc)

i_{ca_ref}＝I_{ca_ref}sin(θ_ca)

6) measure SVC (STATCOM) three-phase current i_ab、i_bc、i_ca, calculate SVC (STATCOM)Three-phase current measured value i_ab、i_bc、i_caWith reference value i_{ab_ref}、i_{bc_ref}、i_{ca_ref}Between difference, calculate through pi regulatorSVC (STATCOM) needs the voltage increment Δ v of output_ab、Δv_bc、Δv_ca; The wherein transmission of pi regulatorFunction is:Wherein s is complex frequency, K_iAnd T_iBe respectively proportionality coefficient and integration time constant;

7) according to three-phase voltage instantaneous value and the SVC of SVC (STATCOM) access electrical network point(STATCOM) need the voltage increment of output to calculate the three-phase voltage reference value e of SVC (STATCOM)_ab、e_bc、e_ca, computing formula is as follows:

e_ab＝v_ab-Δv_ab

e_bc＝v_bc-Δv_bc

e_ca＝v_ca-Δv_ca

By the three-phase voltage reference value e of SVC (STATCOM)_ab、e_bc、e_caDeliver to pwm pulse as modulating waveGenerator, has pwm pulse generator to calculate and produces driving of each series connection single-phase bridge needs of SVC (STATCOM)Artery punching, and wait for when next control cycle arrives, go to step 1).