CN105790295A - Grid fault non-communication ride-through control method for double-end flexible direct current power transmission system - Google Patents

Abstract

The invention discloses a grid fault non-communication ride-through control method for a double-end flexible direct current power transmission system. The method comprises the steps: faults of a Udc/Q end are detected and controlled; when the Udc/Q end has a fault, a P/Q end assists the Udc/Q end to implement fault ride-through detection and control; the faults of the P/Q end are detected and controlled. According to the grid fault non-communication ride-through control method for the double-end flexible direct-current power transmission system, without dependence of a communication line or a fault processing additional circuit, overvoltage of direct current bus voltage, overcurrent of alternating current bus current and the like are suppressed, so that the fault ride-through of the flexible direct current power transmission system is implemented.

Description

A kind of both-end flexible direct current power transmission system electric network fault is without communication traversing control method

Technical field

The invention belongs to Technology of HVDC based Voltage Source Converter field, relate to a kind of both-end flexible direct current power transmission system fault ride-through of power grid control method without communication line.

Background technology

When the joined AC network of flexible direct current power transmission system breaks down (such as single-phase earthing, phase fault and three relative ground circuits), require that flexible direct current power transmission system can continue to run, occur without locking to stop transport, reduce the impact to AC system, ensure equipment of itself safety simultaneously, occur without device over-voltage and over-current, it is achieved fault traversing.Up to the present, existing method is broadly divided into two classes: a class is adjunct circuit in flexible direct current power transmission system, reaches the purpose of release dump power；An other class is the control strategy of amendment system, but the control strategy that can relate to wherein one end uses the information such as associated voltage and the electric current of opposite end, it is therefore desirable to realize the information transmission at two ends by communication line；Above-mentioned two class methods all can relate to the both-end communication of flexible direct current power transmission system, add adjunct circuit, considerably increase the complexity of system, reduce system reliability, break down once communication line, flexible direct current power transmission system unstability can be increased, result even in the situation appearance that locking is stopped transport.

Summary of the invention

For prior art Problems existing, it is an object of the invention to provide a kind of both-end flexible direct current power transmission system electric network fault without communication traversing control method, the present invention needs not rely on communication line or troubleshooting adjunct circuit, thus suppressing DC bus-bar voltage overvoltage and ac bus overcurrent etc., it is achieved that the fault traversing of flexible direct current power transmission system.

The technical solution adopted in the present invention is, a kind of both-end flexible direct current power transmission system electric network fault is without communication traversing control method, at U_dc/ Q end and P/Q end are respectively controlled:

U_dc/ Q end control method is as follows:

Step 11: detection U_dc/ Q end joined AC system three-phase bus voltage v_a1、v_b1、v_c1, do abc-dq conversion, obtain voltage d axle component and q axle component v_d1And v_q1, it is judged that v_d1Size with threshold value: work as v_d1During more than threshold value, Reflector F_aSet to 0, work as v_d1During less than or equal to threshold value, then Reflector F_aPut 1；

Step 12: the Reflector F produced according to step 11_a, it is judged that whether fault occurs, in normal conditions, and U_dc/ Q end current inner loop controller receives original controlled quentity controlled variable C of outer voltage controller output_old；

As Reflector F_aFrom 0 become 1 (i.e. rising edge) time, then fault occur, original controlled quentity controlled variable C_oldValue according to interval T₁(T₁>=0) new controlled quentity controlled variable C is transformed to_new, meanwhile, at elapsed time interval T₁(T₁>=0) after, arranging switching mark a and put 1, now switching mark a is as forbidding signal, stops the work of outer voltage controller, and switching mark a is as switching signal, by original controlled quentity controlled variable C_oldIt is switched to new controlled quentity controlled variable C_new, new controlled quentity controlled variable C_newIt is applied in current inner loop controller；

New controlled quentity controlled variable C_newDefining method is: note fault three-phase busbar voltage d axle component and q axle component are v_d1And v_q1, after note fault, three-phase bus voltage d axle component and q axle component are v'_d1And v'_q1, three phase network most common failure includes single-phase earthing, phase fault and three-phase ground fault, under different faults, and v'_d1And v'_q1Value be different, in consideration of it, new controlled quentity controlled variable is to be multiplied by a proportionality coefficient k on the basis of original controlled quentity controlled variable, this coefficient k is determined according to the following formula,

$k=\frac{\sqrt{{\left(v_{d1}^{\′}\right)}^2+{\left(v_{q1}^{\′}\right)}^2}}{\sqrt{{\left(v_{d1}\right)}^2+{\left(v_{q1}\right)}^2}}$

New controlled quentity controlled variable is C_newIt is C with original controlled quentity controlled variable_oldMeet following relation:

$C_{new}=\frac{\sqrt{{\left(v_{d1}^{\′}\right)}^2+{\left(v_{q1}^{\′}\right)}^2}}{\sqrt{{\left(v_{d1}\right)}^2+{\left(v_{q1}\right)}^2}}\×C_{old};$

As Reflector F_aFor from 1 become 0 (i.e. trailing edge) time, then failure vanishes, new controlled quentity controlled variable C_newValue according to interval T₂(T₂>=0) original controlled quentity controlled variable C is transformed to_old, meanwhile, at elapsed time interval T₂(T₂>=0) after, arranging switching mark a and set to 0, now switching mark a is as switching signal, starting the work of outer voltage controller, by new controlled quentity controlled variable C_newIt is switched to original controlled quentity controlled variable C_old, original controlled quentity controlled variable C_oldAgain it is applied in current inner loop controller；

P/Q end control method is as follows:

Step 21:P/Q end assists Udc/Q end to realize detection and the control of fault traversing, detects U in step 11_dcWhile/Q end line voltage, P/Q end detects this side outlet DC bus-bar voltage u_dc, under nominal situation, DC bus-bar voltage u_dcMore than low pressure threshold value and less than high-pressure door limit value, Reflector F_bSet to 0；

As DC bus-bar voltage u_dc>=high-pressure door limit value or DC bus-bar voltage u_dcDuring≤low pressure threshold value, then break down, Reflector F_bPut 1；

Step 22: determine new power command value P₂ ^*, first, the expression formula K according to proportional, integral (PI) link_p×Err+K_i× ∫ Err dt, in formula, K_pIt is proportionality coefficient, K_iBe the input of integral coefficient and proportional, integral (PI) link it is DC bus-bar voltage reference value U_dc* with the DC bus-bar voltage u of actual measurement_dcDifference, i.e. Err=U_dc*-u_dc, it is determined that the output of proportional, integral (PI) link, the output of proportional, integral (PI) link and Reflector F_bIt is multiplied, is power disturbance value P_Δ:

New power command value P₂ ^*=original power command value P₁ ^*+ power disturbance amount P_Δ, by new power command value P₂ ^*Substitute into P/Q end subordinate and control part；

The Detection & Controling of step 31:P/Q end fault, detect U in step 11_dcWhile/Q end line voltage, detect P/Q end joined AC system three-phase bus voltage v_a2、v_b2、v_c2, do abc-dq conversion, obtain voltage d axle and q axle component v_d2、v_q2, it is judged that v_d2Size with threshold value: work as v_d2During more than threshold value, Reflector F_cSet to 0, work as v_d2During less than or equal to threshold value, then Reflector F_cPut 1；

In normal conditions, Reflector F_cIt is that 0, P/Q end current inner loop d axle receives original controlled quentity controlled variable I_d ^*, P/Q end current inner loop q axle receives original controlled quentity controlled variable I_q ^*；

As Reflector F_cFrom 0 become 1 (i.e. rising edge) time, then fault occur, control the P/Q end electric current loop original controlled quentity controlled variable I of d axle_d ^*Become new controlled quentity controlled variableThe original controlled quentity controlled variable I of q axle_q ^*Become new controlled quentity controlled variableNew electric current loop d axle and q axle controlled quentity controlled variable command value are determined by following formula respectively:

$I_{d\_LVRT}^{*}-=\sqrt{{I_{\lim }}^2-{(I_{q\_LVRT}^{*}-)}^2}---\left(1\right)$

$I_{q\_LVRT}^{*}-=I_{qm}\×(V_{dtm}-v_{d2})---\left(2\right)$

In formula, I_lim、I_qm、V_dmIt is total current limit, q shaft current amplitude limit value and voltage amplitude limit value respectively；

As Reflector F_cFor from 1 become 0 (i.e. trailing edge) time, then failure vanishes, control P/Q end electric current loop d axle by new controlled quentity controlled variableBecome original controlled quentity controlled variable I_d ^*, q axle is by new controlled quentity controlled variableBecome original controlled quentity controlled variable I_q ^*。

Further, the determination methods in described step 11 is as follows: in normal conditions, and threshold value takes threshold value 1, works as v_d11During more than threshold value 1, Reflector is 0, proceeds to judge；Work as v_d1During less than or equal to threshold value 1, then Reflector puts 1, and meanwhile, threshold value takes threshold value 2 (threshold value 2 > threshold value 1), namely no longer judges v_d1With the size of threshold value 1, change into and judge v_d1Size with threshold value 2: work as v_d1During less than threshold value 2, Reflector remains unchanged, and proceeds to judge；Work as v_d1During be more than or equal to threshold value 2, then Reflector sets to 0, and meanwhile, threshold value takes threshold value 1, namely no longer judges v_d1With the size of threshold value 2, change into and judge v_d1Size with threshold value 1.

Further, the determination methods in described step 31 is as follows: in normal conditions, and threshold value takes threshold value 1, works as v_d21During more than threshold value 1, Reflector is 0, proceeds to judge；Work as v_d2During less than or equal to threshold value 1, then Reflector puts 1, and meanwhile, threshold value takes threshold value 2 (threshold value 2 > threshold value 1), namely no longer judges v_d2With the size of threshold value 1, change into and judge v_d2Size with threshold value 2: work as v_d2During less than threshold value 2, Reflector remains unchanged, and proceeds to judge；Work as v_d2During be more than or equal to threshold value 2, then Reflector sets to 0, and meanwhile, threshold value takes threshold value 1, namely no longer judges v_d2With the size of threshold value 2, change into and judge v_d2Size with threshold value 1.

Further, in described step 21, high-pressure door limit value value has threshold value 3 and threshold value 4, and wherein threshold value 3 is more than threshold value 4, and low pressure threshold value value is by threshold value 5 and threshold value 6, and wherein threshold value 6 is less than threshold value 5；

In normal conditions, Reflector F_bSetting to 0, high pressure thresholding takes threshold value 3, and low pressure threshold value has taken threshold value 6, judges DC bus-bar voltage u in operation_dcSize with threshold value 3 and threshold value 6: when threshold value 3 > DC bus-bar voltage u_dc> threshold value 6 time, Reflector F_bRemain unchanged；

As DC bus-bar voltage u_dc>=threshold value 3 or DC bus-bar voltage u_dcDuring≤threshold value 6, then Reflector F_bPutting 1, meanwhile, high-pressure door limit value value is revised as threshold value 4 by threshold value 3 or low pressure threshold value value is revised as threshold value 5 by threshold value 6, proceeds to judge；When DC bus-bar voltage u occurs_dcMore than threshold value 4 or DC bus-bar voltage u_dcDuring less than the situation of threshold value 5, Reflector F_bRemain 1 not change；When DC bus-bar voltage u occurs_dc≤ threshold value 4 or DC bus-bar voltage u_dcDuring the situation of >=threshold value 5, then Reflector F_bSet to 0, meanwhile, threshold value 4 change high-pressure door limit value value into threshold value 3 or changed low pressure threshold value value into threshold value 6 by threshold value 5.

Further, in described step 31,1.0≤I_lim≤ 1.5,1.0≤I_qm≤ 1.5,1.0≤V_dm≤1.5。

Compared with prior art, the present invention at least has the advantages that

The present invention needs not rely on communication line or troubleshooting adjunct circuit, has following beneficial effect:

(1) faultless communication circuit, greatly reduces the complexity of system, improves system reliability of operation；

(2) meritorious during fault it is not zero, it is ensured that the maximum transmitted of active power；

(3) when symmetric fault or unbalanced fault occur for AC system one end, both sides or two ends simultaneously, it is possible to suppress the DC bus-bar voltage overvoltage thereby resulted in, it is ensured that the safe operation of equipment.

Further, in systems in practice, DC bus-bar voltage u_dcBeing fluctuation, the present invention, by the setting of two-door limit value, effectively prevents DC bus-bar voltage u_dcThe Reflector that fluctuation brings shake back and forth between zero and one, causes subsequent step to repeat, and improves the stability that system is run.

Accompanying drawing explanation

Fig. 1 is both-end flexible direct current power transmission system structural representation；

Fig. 2 is U_dc/ Q end Reflector F_aJudge figure；

Fig. 3 is U_dc/ Q end controlled quentity controlled variable generates schematic diagram；

Fig. 4 is U_dc/ Q end switching mark a generates schematic diagram；

Fig. 5 is U_dc/ Q end Fault Control logical schematic；

Fig. 6 is U_dcDuring/Q end fault, P/Q end assists U_dc/ Q end realizes fault traversing, carries out Reflector judgement figure；

Fig. 7 is U_dcDuring/Q end fault, P/Q end assists U_dc/ Q end realizes fault traversing, and adoption rate-integration generates power disturbance amount P_△Schematic diagram；

Fig. 8 is U_dcDuring/Q end fault, P/Q end assists U_dc/ Q end realizes fault traversing and produces new power instruction schematic diagram.

When Fig. 9 and Figure 10 is P/Q end fault, Fault Control logic chart, wherein, Fig. 9 is P/Q end electric current loop d axle controlled quentity controlled variable switching control schematic diagram, and Figure 10 is P/Q end electric current loop q axle controlled quentity controlled variable switching control schematic diagram.

Detailed description of the invention

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

As it is shown in figure 1, in the present embodiment, goal systems is both-end flexible direct current power transmission system, and wherein one end of this system and AC network are connected, and operates in DC bus-bar voltage and controls integrated mode (the i.e. U with Reactive Power Control_dc/ Q mode, U_dcRepresenting and control this end DC bus-bar voltage, Q represents this end reactive power of control), for following convenience, it is defined as U_dc/ Q end；Other end and another AC network are connected, and operate in the integrated mode (i.e. P/Q pattern, P represents this end active power, and Q represents this end reactive power) of active power controller and Reactive Power Control, are defined as P/Q end, U_dc/ Q end and P/Q end are connected by dc bus, are configured without any fault communication or troubleshooting adjunct circuit in system.

Work as U_dcDuring/Q end AC system grid voltage sags, except this end line or device over-voltage and over-current can occur, couple the DC bus-bar voltage u of two end systems_dcAlso can fluctuate, U_dc/ Q end can directly detect voltage ripple of power network, sends Reflector, enables the control strategy of local terminal configuration, it is suppressed that over-voltage and over-current occur in this end line or device, but, couple the DC bus-bar voltage u of two end systems_dcStill fluctuating, this causes due to two ends system power imbalance, now needs P/Q end to assist to be adjusted power to reach the purpose of stable DC busbar voltage, and owing to two ends do not communicate, P/Q end cannot directly obtain U_dc/The Reflector of Q end, but, P/Q end can pass through to detect homonymy DC bus-bar voltage u_dc, and higher limit or lower limit whether is exceeded according to its voltage pulsation, judge whether current system is in malfunction, if it occur that fault, then enable corresponding control strategy, it is suppressed that DC bus-bar voltage fluctuates, and the over-voltage and over-current that this end line or device are likely to occur, namely work as U_dcControl method during/Q end AC system grid voltage sags, including Detection & Controling and the U of Udc/Q end fault_dcDuring/Q end fault, P/Q end assists U_dc/ Q end realizes detection and the control of fault traversing；

When P/Q end AC system grid voltage sags, U_dc/ Q end still continues to use control method in this paper, it is not necessary to make an amendment, and P/Q end is then modified active power command value, two ends power is made to reach balance, meanwhile, to the reactive power that the output of local terminal joined AC system is certain, support line voltage, namely include the Detection & Controling of P/Q end ancient costume.

In present embodiment, both-end flexible direct current power transmission system electric network fault, without communication traversing control method, comprises following concrete steps:

U_dcThe Detection & Controling of/Q end fault:

Step 11: detection U_dc/ Q end joined AC system three-phase bus voltage v_a1、v_b1、v_c1, do abc-dq conversion, obtain voltage d axle and q axle component v_d1、v_q1, as in figure 2 it is shown, under nominal situation, v_d1Near rated value, Reflector F_aSet to 0, operation judges d axle component (i.e. ac bus voltage positive-sequence component) v_d1With the size of threshold value, under nominal situation, threshold value takes threshold value 1, works as v_d1During more than threshold value 1, Reflector F_aIt is 0, proceeds to judge；Work as v_d1During less than or equal to threshold value 1, then Reflector F_aPutting 1, meanwhile, threshold value takes threshold value 2 (threshold value 2 > threshold value 1), namely no longer judges v_d1With the size of threshold value 1, change into and judge v_d1Size with threshold value 2: work as v_d1During less than threshold value 2, Reflector F_aRemain unchanged, proceed to judge；Work as v_d1During be more than or equal to threshold value 2, then Reflector F_aSetting to 0, meanwhile, threshold value takes threshold value 1, namely no longer judges v_d1With the size of threshold value 2, change into and judge v_d1With the size of threshold value 1, repeat aforementioned process afterwards, because of in systems in practice, d axle component v_d1It is fluctuation, therefore the purpose of two threshold values is set, effectively prevent d axle component v_d1The Reflector F that fluctuation brings_aShake back and forth between zero and one, causes subsequent step to repeat；

Step 12: the Reflector F produced according to step 1_a, it is judged that whether fault occurs, as Reflector F_aWhen being 1, then fault occurs, as Reflector F_aWhen being 0, then failure vanishes；As it is shown in figure 5, in normal conditions, U_dc/ Q end current inner loop controller receives original controlled quentity controlled variable C of outer voltage controller output_old, according to Reflector, it is determined that new controlled quentity controlled variable C_new；

Referring to Fig. 3 and Fig. 4, as Reflector F_aFrom 0 become 1 (i.e. rising edge) time, then fault occur, original controlled quentity controlled variable C_oldValue according to interval T₁(T₁>=0) new controlled quentity controlled variable C is transformed to_new, meanwhile, at elapsed time interval T₁(T₁>=0) after, arranging switching mark a and put 1, now switching mark a is as forbidding signal, stops the work of outer voltage controller, and switching mark a is as switching signal, by original controlled quentity controlled variable C_oldIt is switched to new controlled quentity controlled variable C_new, new controlled quentity controlled variable C_newIt is applied in current inner loop controller, in this step, first by original controlled quentity controlled variable C_oldValue to new controlled quentity controlled variable C_newConversion, says original controlled quentity controlled variable C after having converted_oldTo new controlled quentity controlled variable C_newSwitching, it is to avoid switching bringing fluctuation that electrical network impacted；

New controlled quentity controlled variable C_newDefining method is: note fault three-phase busbar voltage d axle component and q axle component are v_d1And v_q1, after note fault, three-phase bus voltage d axle component and q axle component are v'_d1And v'_q1, three phase network most common failure includes single-phase earthing, phase fault and three-phase ground fault, under different faults, and v'_d1And v'_q1Value be different, in consideration of it, new controlled quentity controlled variable is to be multiplied by a proportionality coefficient k on the basis of original controlled quentity controlled variable, this coefficient k is determined according to the following formula,

$k=\frac{\sqrt{{\left(v_{d1}^{\′}\right)}^2+{\left(v_{q1}^{\′}\right)}^2}}{\sqrt{{\left(v_{d1}\right)}^2+{\left(v_{q1}\right)}^2}}$

New controlled quentity controlled variable is C_newIt is C with original controlled quentity controlled variable_oldMeet following relation:

$C_{new}=\frac{\sqrt{{\left(v_{d1}^{\′}\right)}^2+{\left(v_{q1}^{\′}\right)}^2}}{\sqrt{{\left(v_{d1}\right)}^2+{\left(v_{q1}\right)}^2}}\×C_{old}$

With reference to Fig. 3 and Fig. 4, as Reflector F_aFor from 1 become 0 (i.e. trailing edge) time, then failure vanishes, new controlled quentity controlled variable C_newValue according to interval T₂(T₂>=0) original controlled quentity controlled variable C is transformed to_old, meanwhile, at elapsed time interval T₂(T₂>=0) after, arranging switching mark a and set to 0, now switching mark a is as switching signal, starting the work of outer voltage controller, by new controlled quentity controlled variable C_newIt is switched to original controlled quentity controlled variable C_old, original controlled quentity controlled variable C_oldAgain being applied in current inner loop controller, this step effectively prevent equally and is made directly the impact that electrical network is brought by controlled quentity controlled variable switching；

U_dcDuring/Q end fault, P/Q end assists U_dc/ Q end realizes detection and the control of fault traversing:

Step 21: detect U in step 11_dcWhile/Q end line voltage, P/Q end detects this side outlet DC bus-bar voltage u_dc, under nominal situation, DC bus-bar voltage u_dcMore than low pressure threshold value and less than high-pressure door limit value, Reflector F_bSet to 0；

As DC bus-bar voltage u_dc>=high-pressure door limit value or DC bus-bar voltage u_dcDuring≤low pressure threshold value, then break down, Reflector F_bPut 1；

Referring to Fig. 6, high-pressure door limit value value has threshold value 3 and threshold value 4, and wherein threshold value 3 is more than threshold value 4, and low pressure threshold value value is by threshold value 5 and threshold value 6, and wherein threshold value 6 is less than threshold value 5；

In normal conditions, Reflector F_bSetting to 0, high pressure thresholding takes threshold value 3, and low pressure threshold value has taken threshold value 6, judges DC bus-bar voltage u in operation_dcSize with threshold value 3 and threshold value 6: when threshold value 3 > DC bus-bar voltage u_dc> threshold value 6 time, Reflector F_bRemain unchanged；

As DC bus-bar voltage u_dc>=threshold value 3 or DC bus-bar voltage u_dcDuring≤threshold value 6, then Reflector F_bPutting 1, meanwhile, high-pressure door limit value value is revised as threshold value 4 by threshold value 3 or low pressure threshold value value is revised as threshold value 5 by threshold value 6, proceeds to judge；When DC bus-bar voltage u occurs_dcMore than threshold value 4 or DC bus-bar voltage u_dcDuring less than the situation of threshold value 5, Reflector F_bRemain 1 not change；When DC bus-bar voltage u occurs_dc≤ threshold value 4 or DC bus-bar voltage u_dcDuring the situation of >=threshold value 5, then Reflector F_bSet to 0, meanwhile, threshold value 4 change high-pressure door limit value value into threshold value 3 or changed low pressure threshold value value into threshold value 6 by threshold value 5, repeating aforementioned process afterwards, because of in systems in practice, DC bus-bar voltage u_dcIt is fluctuation, two threshold values is set, can effectively prevent DC bus-bar voltage u_dcThe Reflector F that fluctuation brings_bShake back and forth between zero and one, causes subsequent step to repeat；

Step 22: determine new power command value P₂ ^*, first, as it is shown in fig. 7, the expression formula K according to proportional, integral (PI) link_p× Err+ ∫ Err dt, in formula, K_pIt is proportionality coefficient, K_iIt is integral coefficient, and the input of proportional, integral (PI) link is DC bus-bar voltage reference value U_dc* with the DC bus-bar voltage u of actual measurement_dcDifference, i.e. Err=U_dc*-u_dc, it is determined that the output of proportional, integral (PI) link, the output of proportional, integral (PI) link and Reflector F_bIt is multiplied, is power disturbance value P_Δ, as shown in Figure 8 be the control part of P/Q end fault, by original power command value P₁ ^*With power disturbance amount P_ΔIt is overlapped obtaining new power command value P₂ ^*, by new power command value P₂ ^*Substitute into P/Q end subordinate and control part, (the Reflector F when not having fault_bBeing 0, now power disturbance amount P Δ is zero, new power command value P₂ ^*It is original command value P₁ ^*；

During P/Q end fault, the Detection & Controling of fault:

Step 31: detect U in step 11_dcWhile/Q end line voltage, detect P/Q end joined AC system three-phase bus voltage v_a2、v_b2、v_c2, do abc-dq conversion, obtain voltage d axle and q axle component v_d2、v_q2, shown in step 11, method generates P/Q end Reflector F_c, as shown in Figure 9 and Figure 10, according to Reflector F_c, control P/Q end electric current loop d axle and q axle command value, in normal conditions, Reflector F_cIt is that 0, P/Q end current inner loop d axle receives original controlled quentity controlled variable I_d ^*, P/Q end current inner loop q axle receives original controlled quentity controlled variable I_q ^*；

As Reflector F_cFrom 0 become 1 (i.e. rising edge) time, then fault occur, control the P/Q end electric current loop original controlled quentity controlled variable I of d axle_d ^*Become new controlled quentity controlled variableThe original controlled quentity controlled variable I of q axle_q ^*Become new controlled quentity controlled variableNew electric current loop d axle and q axle controlled quentity controlled variable command value are determined by following formula respectively:

$I_{d\_LVRT}^{*}-=\sqrt{{I_{\lim }}^2-{\left(I_{q\_LVRT}^{*}\right)}^2}---\left(1\right)$

$I_{q\_LVRT}^{*}-=I_{qm}\×(V_{dtm}-v_{d2})---\left(2\right)$

In formula, I_lim、I_qm、V_dmBeing total current limit, q shaft current amplitude limit value and voltage amplitude limit value respectively, concrete value is relevant with systematic parameter, generally, and I_limBetween 1.0～1.5, I_qmBetween 1.0～1.5, V_dmBetween 1.0～1.5；

As Reflector F_cFrom 1 become 0 (i.e. trailing edge) time, then failure vanishes, the controlled quentity controlled variable of P/Q end electric current loop d axle is by new controlled quentity controlled variableBecome original controlled quentity controlled variable I_d ^*, the controlled quentity controlled variable of q axle is by new controlled quentity controlled variableBecome original controlled quentity controlled variable I_q ^*。

The present invention needs not rely on communication line or troubleshooting adjunct circuit, achieve the fault traversing of both-end flexible direct current power transmission system electrical network, greatly reduce the complexity of system, improve system reliability of operation, and gain merit during fault and be not zero, it is ensured that the maximum transmitted of active power；When there is symmetric fault or unbalanced fault in AC system one end, both sides or two ends simultaneously, the DC bus-bar voltage overvoltage thereby resulted in can be suppressed, it is ensured that the safe operation of equipment, present invention employs double threshold simultaneously and set up calmly, in systems in practice, DC bus-bar voltage u_dcBeing fluctuation, the present invention, by the setting of two-door limit value, effectively prevents DC bus-bar voltage u_dcThe Reflector that fluctuation brings shake back and forth between zero and one, causes subsequent step to repeat, and improves the stability that system is run.

Claims (5)

1. a both-end flexible direct current power transmission system electric network fault is without communication traversing control method, it is characterised in that at U_dc/ Q end and P/Q end are respectively controlled:

U_dc/ Q end control method is as follows:

Step 11: detection U_dc/ Q end joined AC system three-phase bus voltage v_a1、v_b1、v_c1, do abc-dq conversion, obtain voltage d axle component and q axle component v_d1And v_q1, it is judged that v_d1Size with threshold value: work as v_d1During more than threshold value, Reflector F_aSet to 0, work as v_d1During less than or equal to threshold value, then Reflector F_aPut 1；

Step 12: the Reflector F produced according to step 11_a, it is judged that whether fault occurs, in normal conditions, and U_dc/ Q end current inner loop controller receives original controlled quentity controlled variable C of outer voltage controller output_old；

As Reflector F_aFrom 0 become 1 (i.e. rising edge) time, then fault occur, original controlled quentity controlled variable C_oldValue according to interval T₁(T₁>=0) new controlled quentity controlled variable C is transformed to_new, meanwhile, at elapsed time interval T₁(T₁>=0) after, arranging switching mark a and put 1, now switching mark a is as forbidding signal, stops the work of outer voltage controller, and switching mark a is as switching signal, by original controlled quentity controlled variable C_oldIt is switched to new controlled quentity controlled variable C_new, new controlled quentity controlled variable C_newIt is applied in current inner loop controller；

New controlled quentity controlled variable C_newDefining method is: note fault three-phase busbar voltage d axle component and q axle component are v_d1And v_q1, after note fault, three-phase bus voltage d axle component and q axle component are v'_d1And v'_q1, three phase network most common failure includes single-phase earthing, phase fault and three-phase ground fault, under different faults, and v'_d1And v'_q1Value be different, in consideration of it, new controlled quentity controlled variable is to be multiplied by a proportionality coefficient k on the basis of original controlled quentity controlled variable, this coefficient k is determined according to the following formula,

$k=\frac{\sqrt{{\left(v_{d1}^{\′}\right)}^2+{\left(v_{q1}^{\′}\right)}^2}}{\sqrt{{\left(v_{d1}\right)}^2+{\left(v_{q1}\right)}^2}}$

New controlled quentity controlled variable is C_newIt is C with original controlled quentity controlled variable_oldMeet following relation:

$C_{new}=\frac{\sqrt{{\left(v_{d1}^{\′}\right)}^2+{\left(v_{q1}^{\′}\right)}^2}}{\sqrt{{\left(v_{d1}\right)}^2+{\left(v_{q1}\right)}^2}}\×C_{old};$

As Reflector F_aFor from 1 become 0 (i.e. trailing edge) time, then failure vanishes, new controlled quentity controlled variable C_newValue according to interval T₂(T₂>=0) original controlled quentity controlled variable C is transformed to_old, meanwhile, at elapsed time interval T₂(T₂>=0) after, arranging switching mark a and set to 0, now switching mark a is as switching signal, starting the work of outer voltage controller, by new controlled quentity controlled variable C_newIt is switched to original controlled quentity controlled variable C_old, original controlled quentity controlled variable C_oldAgain it is applied in current inner loop controller；

P/Q end control method is as follows:

Step 21:P/Q end assists Udc/Q end to realize detection and the control of fault traversing, detects U in step 11_dcWhile/Q end line voltage, P/Q end detects this side outlet DC bus-bar voltage u_dc, under nominal situation, DC bus-bar voltage u_dcMore than low pressure threshold value and less than high-pressure door limit value, Reflector F_bSet to 0；

As DC bus-bar voltage u_dc>=high-pressure door limit value or DC bus-bar voltage u_dcDuring≤low pressure threshold value, then break down, Reflector F_bPut 1；

Step 22: determine new power command value P₂ ^*, first, the expression formula K according to proportional, integral (PI) link_p×Err+K_i× ∫ Err dt, in formula, K_pIt is proportionality coefficient, K_iBe the input of integral coefficient and proportional, integral (PI) link it is DC bus-bar voltage reference value U_dc* with the DC bus-bar voltage u of actual measurement_dcDifference, i.e. Err=U_dc*-u_dc, it is determined that the output of proportional, integral (PI) link, the output of proportional, integral (PI) link and Reflector F_bIt is multiplied, is power disturbance value P_Δ:

New power command value P₂ ^*=original power command value P₁ ^*+ power disturbance amount P_Δ, by new power command value P₂ ^*Substitute into P/Q end subordinate and control part；

The Detection & Controling of step 31:P/Q end fault, detect U in step 11_dcWhile/Q end line voltage, detect P/Q end joined AC system three-phase bus voltage v_a2、v_b2、v_c2, do abc-dq conversion, obtain voltage d axle and q axle component v_d2、v_q2, it is judged that v_d2Size with threshold value: work as v_d2During more than threshold value, Reflector F_cSet to 0, work as v_d2During less than or equal to threshold value, then Reflector F_cPut 1；

In normal conditions, Reflector F_cIt is that 0, P/Q end current inner loop d axle receives original controlled quentity controlled variable I_d ^*, P/Q end current inner loop q axle receives original controlled quentity controlled variable I_q ^*；

As Reflector F_cFrom 0 become 1 (i.e. rising edge) time, then fault occur, control the P/Q end electric current loop original controlled quentity controlled variable I of d axle_d ^*Become new controlled quentity controlled variableThe original controlled quentity controlled variable I of q axle_q ^*Become new controlled quentity controlled variableNew electric current loop d axle and q axle controlled quentity controlled variable command value are determined by following formula respectively:

$I_{d\_LVRT}^{*}=\sqrt{{I_{\lim }}^2-{\left(I_{q\_LVRT}^{*}\right)}^2}---\left(1\right)$

$I_{q\_LVRT}^{*}=I_{qm}\×(V_{dtm}-v_{d2})---\left(2\right)$

In formula, I_lim、I_qm、V_dmIt is total current limit, q shaft current amplitude limit value and voltage amplitude limit value respectively；

As Reflector F_cFor from 1 become 0 (i.e. trailing edge) time, then failure vanishes, control P/Q end electric current loop d axle by new controlled quentity controlled variableBecome original controlled quentity controlled variable I_d ^*, q axle is by new controlled quentity controlled variableBecome original controlled quentity controlled variable I_q ^*。

2. a kind of both-end flexible direct current power transmission system electric network fault according to claim 1 is without communication traversing control method, it is characterised in that the determination methods in described step 11 is as follows: in normal conditions, and threshold value takes threshold value 1, works as v_d11During more than threshold value 1, Reflector is 0, proceeds to judge；Work as v_d1During less than or equal to threshold value 1, then Reflector puts 1, and meanwhile, threshold value takes threshold value 2 (threshold value 2 > threshold value 1), namely no longer judges v_d1With the size of threshold value 1, change into and judge v_d1Size with threshold value 2: work as v_d1During less than threshold value 2, Reflector remains unchanged, and proceeds to judge；Work as v_d1During be more than or equal to threshold value 2, then Reflector sets to 0, and meanwhile, threshold value takes threshold value 1, namely no longer judges v_d1With the size of threshold value 2, change into and judge v_d1Size with threshold value 1.

3. a kind of both-end flexible direct current power transmission system electric network fault according to claim 1 is without communication traversing control method, it is characterised in that the determination methods in described step 31 is as follows: in normal conditions, and threshold value takes threshold value 1, works as v_d21During more than threshold value 1, Reflector is 0, proceeds to judge；Work as v_d2During less than or equal to threshold value 1, then Reflector puts 1, and meanwhile, threshold value takes threshold value 2 (threshold value 2 > threshold value 1), namely no longer judges v_d2With the size of threshold value 1, change into and judge v_d2Size with threshold value 2: work as v_d2During less than threshold value 2, Reflector remains unchanged, and proceeds to judge；Work as v_d2During be more than or equal to threshold value 2, then Reflector sets to 0, and meanwhile, threshold value takes threshold value 1, namely no longer judges v_d2With the size of threshold value 2, change into and judge v_d2Size with threshold value 1.

4. a kind of both-end flexible direct current power transmission system electric network fault according to claim 1 is without communication traversing control method, it is characterized in that, in described step 21, high-pressure door limit value value has threshold value 3 and threshold value 4, wherein threshold value 3 is more than threshold value 4, low pressure threshold value value is by threshold value 5 and threshold value 6, and wherein threshold value 6 is less than threshold value 5；

In normal conditions, Reflector F_bSetting to 0, high pressure thresholding takes threshold value 3, and low pressure threshold value has taken threshold value 6, judges DC bus-bar voltage u in operation_dcSize with threshold value 3 and threshold value 6: when threshold value 3 > DC bus-bar voltage u_dc> threshold value 6 time, Reflector F_bRemain unchanged；

As DC bus-bar voltage u_dc>=threshold value 3 or DC bus-bar voltage u_dcDuring≤threshold value 6, then Reflector F_bPutting 1, meanwhile, high-pressure door limit value value is revised as threshold value 4 by threshold value 3 or low pressure threshold value value is revised as threshold value 5 by threshold value 6, proceeds to judge；When DC bus-bar voltage u occurs_dcMore than threshold value 4 or DC bus-bar voltage u_dcDuring less than the situation of threshold value 5, Reflector F_bRemain 1 not change；When DC bus-bar voltage u occurs_dc≤ threshold value 4 or DC bus-bar voltage u_dcDuring the situation of >=threshold value 5, then Reflector F_bSet to 0, meanwhile, threshold value 4 change high-pressure door limit value value into threshold value 3 or changed low pressure threshold value value into threshold value 6 by threshold value 5.

5. a kind of both-end flexible direct current power transmission system electric network fault according to claim 1 is without communication traversing control method, it is characterised in that in described step 31,1.0≤I_lim≤ 1.5,1.0≤I_qm≤ 1.5,1.0≤V_dm≤1.5。