CN105305454B - A kind of static synchronous compensating device voltage powerless control method suitable for wind power plant - Google Patents

Abstract

The invention relates to the field of static synchronous compensation device control. In order to be suitable for wind farms, a control method for static synchronous compensation devices that takes the voltage of the grid-connected point of the wind farm as the control target and takes into account the reactive power level of the system is specifically a method for wind farms. The static synchronous compensator voltage and reactive power control method. The static synchronous compensation device is installed on the low-voltage bus side of the wind farm to monitor the system voltage U _S and reactive power Q _S at the grid-connected point in real time, and according to the different U _S and Q _S levels, compare the control target selection strategy table, and analyze according to different compensation targets Real-time power status and reactive power demand of the system, so as to determine the adjustment strategy of the passive filter branch and the static synchronous compensation device.

Description

A voltage and reactive power control method for static synchronous compensation devices suitable for wind farms

technical field

The invention relates to the field of static synchronous compensation device control, in particular to a method for controlling voltage and reactive power of a static synchronous compensation device suitable for wind farms.

Background technique

Due to the intermittence and randomness of wind energy, the active and reactive power flows of wind farms often change, and voltage stability accidents are prone to occur. With the increase of wind farm scale, its impact on the power grid will become more and more serious. The power quality problem of wind farm grid-connected operation can be solved by wind farm reactive power compensation to varying degrees. In order to maintain the reactive power balance of wind farms, reactive power compensation must be performed in real time.

The static synchronous compensation device can realize fast, smooth and controllable reactive power compensation by adjusting its own inductive or capacitive current, and is widely used in wind farms. The current research on the voltage control strategy of the static synchronous compensation device mostly determines the required total reactive power output target value according to the rated value of the high-voltage side bus voltage, and then according to the general reactive power distribution principle of the reactive power compensation device, the total reactive power The power is allocated to each group of inductive and capacitive branches, without detailed analysis of the actual operating conditions of reactive power compensation equipment, and lack of consideration for the special requirements of reactive power compensation equipment in actual operation of wind farms. In addition, most of the current wind farm management methods require reactive power compensation devices to adopt voltage control, take the voltage of the grid-connected point of the wind farm as the control target, and be able to quickly respond to abnormal voltage disturbances; Control to achieve the minimum reactive power exchange with the grid, thereby reducing operating costs. However, in the existing control strategies of reactive power compensation devices, voltage control and reactive power control sometimes conflict and cannot be considered at the same time. The traditional control strategy will first adjust the voltage when the voltage does not meet the requirements, and then adjust the reactive power output by the wind farm according to the reactive power command issued by the automatic voltage control system after the voltage meets the requirements. However, at some point, such adjustment may lead to repeated adjustment of voltage and reactive power due to the inconsistency of the regulation properties of voltage and reactive power, causing frequent actions of reactive power compensation equipment. Or it will cause redundant reactive power exchange with the grid when the wind farm meets the voltage requirements, increasing unnecessary operating costs.

Contents of the invention

(1) Technical problems to be solved

Aiming at the above problems, the present invention studies a more detailed and practical control strategy for reactive power compensation devices suitable for wind farms. The present invention considers the real-time level of the system voltage and the real-time working conditions of the static synchronous compensation device in detail, and combines the special requirements of the wind farm system for reactive power compensation, and proposes a voltage reactive power control of the static synchronous compensation device suitable for wind farms Strategy. On the basis of the existing control strategy, the target voltage selection strategy table for different working conditions is given, and the voltage and reactive power coordination control method of the passive filter branch and the static synchronous compensation device is proposed.

The static synchronous compensation device is installed on the low-voltage bus side of the wind farm to monitor the system voltage U _S and reactive power Q _S at the grid-connected point in real time, and according to the different U _S and Q _S levels, compare the control target selection strategy table, and analyze according to different compensation targets Real-time power status and reactive power demand of the system, so as to determine the adjustment strategy of the passive filter branch and the static synchronous compensation device. As shown in Fig. 3, the adjustment strategy of the passive filter branch and the static synchronous compensation device can be divided into the following three situations to confirm the voltage control target: when U _P < U _S , it is judged that the system voltage is abnormal, and at this time the control The voltage is the main target, and the adjustable inductive reactive capacity of the passive filter branch and static synchronous compensation device and the reactive capacity required to compensate the target voltage are analyzed to determine the degree of voltage regulation; when U _S < U _D , Judging that the system voltage is abnormal, at this time, the main goal is to control the voltage, analyze the adjustable capacitive reactive capacity of the passive filter branch, static synchronous compensation device and the reactive capacity required to compensate the target voltage to determine the voltage regulation When U _D ≤ U _S ≤ _UP , it is judged that the system voltage is normal. At this time, the coordinated control of voltage and reactive power is carried out, and priority is given to adjusting the output of the static synchronous compensation device to coordinate the voltage and reactive power.

(2) Technical solution

In order to solve the above technical problems, the present invention provides a method for controlling voltage and reactive power of a static synchronous compensation device suitable for wind farms. The method is divided into the following steps:

The static synchronous compensation device is installed on the low-voltage bus side of the wind farm to monitor the system voltage U _S and reactive power Q _S of the grid-connected point in real time;

According to different U _S and Q _S levels, compare the control target selection strategy table, and analyze the real-time power status and reactive power demand of the system according to different compensation targets, so as to determine the adjustment strategy of the passive filter branch and the static synchronous compensation device;

The adjustment strategy of the passive filter branch and the static synchronous compensation device is divided into the following three situations to confirm the voltage control target:

When U _P < U _S : It is judged that the system voltage is abnormal. At this time, with the control voltage as the main goal, analyze the passive filter branch, the adjustable inductive reactive capacity of the static synchronous compensation device and the compensation required to reach the target voltage. Reactive capacity to determine the degree of voltage regulation;

When U _S < U _D , it is judged that the system voltage is abnormal. At this time, with the control voltage as the main goal, analyze the adjustable capacitive reactive power capacity of the passive filter branch and the static synchronous compensation device and the compensation required to reach the target voltage. The reactive capacity to determine the degree of pressure regulation;

When U _D ≤ U _S ≤ _UP , it is judged that the system voltage is normal. At this time, the coordinated control of voltage and reactive power is carried out, and the priority is given to adjusting the output of the static synchronous compensation device to coordinate the voltage and reactive power.

Preferably, when U _P < U _S , the specific operation steps are as follows:

Compare the inductive reactive capacity △Q _L required to adjust the voltage to the target voltage U _T with the remaining inductive reactive capacity Q _S1 of the static synchronous compensation device;

If △Q _L is less than Q _S1 , the inductive reactive power will be added △Q _L , and the adjustment process ends;

If △Q _L is greater than Q _S1 , then priority should be given to cutting off the passive filter branch;

If the capacitor bank is not connected, that is, Q _C0 = 0, the inductive reactive power will be the largest, and the adjustment process is over;

If the capacitor bank is input, that is, Q _C0 >0, calculate the voltage after cutting off a group of passive filter branches;

If the voltage is higher than the target voltage after cutting off a group of passive filter branches, continue to calculate and judge after cutting off until the voltage is within the target area;

If the voltage is lower than the target voltage after cutting off a group of passive filter branches, the passive filter branch will not be cut off, the inductive reactive power will be the largest, and the adjustment process ends.

Preferably, when U _S < U _D , the specific operation steps are as follows:

Compare the capacitive reactive capacity △Q _C required to adjust the voltage to the target voltage U _T with the input inductive reactive capacity Q _S0 ;

If △Q _C is less than Q _S0 , the inductive reactive power is reduced by △Q _C , and the adjustment process ends;

If △Q _C is greater than Q _S0 , then the passive filter branch is given priority;

First judge the operation status of the passive filter branch:

If the passive filter branch has spare capacity, that is, Q _C1 >0, then calculate the voltage rise after putting in a group of passive filter branches;

If the voltage is lower than the target voltage after putting in a group of passive filter branches, continue the above calculation and input process until the voltage is within the target voltage range;

If the passive filter branches are all put into operation, that is, after Q _C1 = 0, the voltage is still lower than the target voltage, so that the static synchronous compensation device will increase the capacitive reactive power;

If the static synchronous compensator reaches the maximum capacity and the voltage is still lower than the target voltage, the adjustment process ends.

Preferably, when U _D ≤ U _S ≤ U _P , the specific operation steps are as follows:

Adjust to U _D ≤ U _S ≤ _UP voltage range and at the same time carry out coordinated control of voltage and reactive power, and indirectly regulate the size of reactive power exchange between the wind farm and the grid by controlling the value of k. The smaller the reactive power exchange capacity, the higher the power factor. higher.

Preferably, the selection information of the control target selection strategy table is as follows:

When Q _S >0 and U _P <U _S , U _T =U _EXP ;

When Q _S >0 and U _D ≤ U _S ≤ U _P , U _T ＝ U _S -k(U _S -U _D );

When Q _S >0 and U _S < U _D , U _T = U _D ;

When Q _S = 0 and U _P < U _S , U _T = U _P ;

When Q _S =0 and U _D ≤ U _S ≤ U _P , U _T = U _S ;

When Q _S = 0 and U _S < U _D , U _T = U _D ;

When Q _S <0 and U _P <U _S , U _T ＝ U _P ;

When Q _S <0 and U _D ≤ U _S ≤ U _P , U _T = U _S +k _{(UP -U S )} ;

When Q _S <0 and U _S <UD, _{U T =} U _EXD .

(3) Beneficial effects

The invention not only ensures that the voltage is within a qualified range, but also takes into account reasonable reactive power adjustment requirements. On the basis of realizing the control method, the present invention realizes the minimum reactive power exchange with the power grid while the wind farm satisfies the voltage control target, thereby effectively reducing the operating cost of the wind farm. The reactive voltage is adjusted according to the control strategy of the present invention, and when the upper limit or lower limit specified by the standard is approaching, the switching of the capacitor branch is given priority to quickly adjust the voltage. When the deviation from the qualified range is small, the adjustment of the dynamic branch is given priority to avoid the impact of reactive current, and the coordinated adjustment of voltage and reactive power is performed more smoothly and accurately. It not only ensures that the voltage of the wind farm is within the qualified range, but also takes into account the minimum reactive power exchange between the wind farm and the grid, effectively improving the operating efficiency of the wind farm system.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a typical wiring diagram of a wind farm of a dynamic reactive power compensation device according to an embodiment of the voltage and reactive power control method of a static synchronous compensation device suitable for a wind farm;

Fig. 2 is a partition diagram of a voltage control target interval according to an embodiment of a method for controlling voltage and reactive power of a static synchronous compensation device suitable for a wind farm according to the present invention;

Fig. 3 is a flow chart of a wind farm voltage control strategy according to an embodiment of a method for controlling voltage and reactive power of a static synchronous compensation device suitable for a wind farm according to the present invention;

Fig. 4 is a control flow chart when U _P < U _S according to an embodiment of the voltage and reactive power control method of a static synchronous compensation device suitable for wind farms;

Fig. 5 is a control flow chart when U _S < U _D according to an embodiment of the voltage and reactive power control method of a static synchronous compensation device suitable for wind farms;

Fig. 6 is a control flow chart when U _D ≤ U _S ≤ UP according to an embodiment of a method for controlling voltage and reactive power of a static synchronous compensator applicable to a wind farm according to the present invention _.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are only used to illustrate the present invention, but can not be used to limit the scope of the present invention.

The present invention solves the above-mentioned technical problems through the following technical solutions, and the present invention will be further described below in conjunction with the accompanying drawings:

As shown in Figure 1, the static synchronous compensation device is installed on the low-voltage bus side of the wind farm to monitor the system voltage U _S and reactive power Q _S at the grid-connected point in real time, and select the control target according to the levels of U _S and Q _S compared with the static synchronous compensation device In the strategy table, select the control voltage target value _UT of the static synchronous compensation device. Table 1 is the control target selection strategy table for the static synchronous compensation device:

Table 1

U _S is the real-time sampling value of the system voltage at the grid-connected point of the wind farm;

Q _S is the real-time sampling value of the reactive power injected into the grid by the wind farm;

U _EXP , U _EXD are the rated values of the wind farm system voltage limit. It is recommended to choose U _EXP = 107% U _{system voltage} , U _EXD = 97% U _{system voltage} ;

U _T is the control voltage target value of the static synchronous compensation device, which is adjusted by the program itself;

U _P is the upper limit value of the qualified range of the system voltage judged by the static synchronous compensation device, which is manually set according to the on-site working conditions. It is recommended to choose U _P = 106.5% U _{system voltage} ;

U _D is the lower limit value of the qualified range of the system voltage judged by the static synchronous compensation device, which is manually set according to the on-site working conditions. It is recommended to choose UD=97.5% U system voltage;

k is used for the step length of voltage and reactive power coordination of the static synchronous compensation device, which is manually set according to the site working conditions. It is recommended to select k=1%.

According to the calculation formula of the reactive power △Q required to compensate the target voltage, the reactive power demand of the system is calculated, and the reactive power compensation range is determined in combination with the passive filter branch and the static synchronous compensation device in real time, and the corresponding coordination is given Strategy.

△Q＝︱U _S -U _T ︱×(S _D /U _{system voltage} ); where:

△Q is the reactive power required to compensate the target voltage;

U _{system voltage} is the system rated voltage;

S _D is the short-circuit capacity at the busbar of the wind farm.

It is assumed that the wind farm is equipped with a static synchronous compensation device with a capacity of Q _STATCOM (unit: Mvar) and a passive filter branch with a capacity of Q _C (unit: Mvar). The static synchronous compensation device has been put into reactive capacity by Q _S0 , and the remaining reactive capacity is represented by Q _S1 , where the capacitive reactive power is positive and the inductive reactive power is negative. The capacitive reactive capacity of the passive filter branch is represented by Q _C0 , and the remaining capacitive reactive capacity is represented by Q _C1 , and the input, non-action and cut-off of the passive filter branch are respectively represented by "1" and "0 " and "-1". The inductive and capacitive reactive power needed to compensate to the target voltage is represented by △Q _L and △Q _C respectively.

△Q _L ＝△Q _C ＝︱U _S -U _T ︱×(S _D /U _{system voltage} )

As shown in Figure 4, when the system voltage U _P < U _S , the adjustment strategy is as follows:

Specifically:

That is, first compare the inductive reactive capacity △Q _L required to adjust the voltage to the target voltage U _T with the remaining inductive reactive capacity Q _S1 of the static synchronous compensation device;

If △Q _L is less than Q _S1 , the inductive reactive power will be added △Q _L , and the adjustment process ends;

If △Q _L is greater than Q _S1 , then priority should be given to cutting off the passive filter branch;

If the capacitor bank is not put into use (Q _C0 = 0), the inductive reactive power generation is the largest, and the voltage at this time is the value closest to the target voltage that can be achieved, and the adjustment process ends;

If the capacitor bank is input, that is, Q _C0 >0, calculate the voltage after cutting off a group of passive filter branches;

If the voltage is higher than the target voltage after cutting off a group of passive filter branches, continue to calculate and judge after cutting off until the voltage is within the target area;

If the voltage is lower than the target voltage after cutting off a group of passive filter branches, the passive filter branch will not be cut off, the inductive reactive power will be the largest, and the adjustment process ends.

As shown in Figure 5, when the system voltage U _S < U _D , the adjustment strategy is as follows:

Specifically:

First compare the capacitive reactive capacity △Q _C required to adjust the voltage to the target voltage U _T with the input inductive reactive capacity Q _S0 ;

If △Q _C is less than Q _S0 , the inductive reactive power is reduced by △Q _C , and the adjustment process ends;

If △Q _C is greater than Q _S0 , it is preferred to use the passive filter branch, because at this time the voltage drops more, and the passive filter branch can greatly increase the voltage;

First judge the operation status of the passive filter branch:

If the passive filter branch has spare capacity (QC1>0), calculate the voltage rise after putting in a group of passive filter branches;

If the voltage is lower than the target voltage after putting in a group of passive filter branches, continue the above calculation and input process until the voltage is within the target voltage range;

If the voltage of the passive filter branch is still lower than the target voltage after all the passive filter branches are put into use (QC1=0), the static synchronous compensation device will increase the capacitive reactive power;

If the static synchronous compensator reaches the maximum capacity and the voltage is still lower than the target voltage, the adjustment process ends.

As shown in Figure 6, when the system voltage UD≤US≤UP, taking UT≤US≤UP as an example, the adjustment strategy is as follows:

Specifically:

When adjusting to the U _D ≤ U _S ≤ U _P voltage range, the coordinated control of voltage and reactive power should be carried out at the same time, and the reactive power exchange between the wind farm and the grid can be indirectly regulated by controlling the value of k. This reactive power exchange capacity The smaller the value, the higher the power factor.

The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications or equivalent replacements of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all should cover Within the scope of the claims of the present invention.

Claims (5)

1. a kind of static synchronous compensating device voltage powerless control method suitable for wind power plant, the method is divided into following step Suddenly：

Passive filter branch and static synchronous compensating device dress are set to wind farm low voltage bus bar side, monitor grid entry point system in real time Unite voltage U_SWith idle Q_S；

According to U_SAnd Q_SLevel compares static synchronous compensating device control targe selection strategy table, selectes static synchronous compensating device Control targe voltage value U_T, so that it is determined that the adjustable strategies of passive filter branch and static synchronous compensating device；

3 kinds of situations of adjustable strategies point of the passive filter branch and static synchronous compensating device or less confirm that voltage controls mesh Mark：

Work as U_P<U_SWhen：It is abnormal to judge that system voltage occurs, at this time to control voltage as main target, analyzes passive filter branch Road, the adjustable inductive reactive power capacity of static synchronous compensating device and compensation are adjusted to the reactive capability needed for target voltage with determining Pressure degree size；

Work as U_S<U_DWhen, it is abnormal to judge that system voltage occurs, at this time to control voltage as main target, analyzes passive filter branch Road, the adjustable capacitive reactive power capacity of static synchronous compensating device and compensation are adjusted to the reactive capability needed for target voltage with determining Pressure degree size；

Work as U_D≤U_S≤U_PWhen, judge that system voltage is normal, carry out voltage and reactive power coordinated control at this time, pays the utmost attention to adjust static Synchronous compensator plant output makes voltage, idle phase coordinate；

Wherein, U_PFor the upper limit value of system voltage acceptability limit, U_DFor the lower limiting value of system voltage acceptability limit.

2. a kind of static synchronous compensating device voltage powerless control method suitable for wind power plant according to claim 1, It is characterized in that, working as U_P<U_SWhen concrete operation step it is as follows：

Compare and voltage is transferred to target voltage U_TRequired inductive reactive power capacity △ Q_LWith static synchronous compensating device residue inductive reactive power Capacity Q_S1Size；

If △ Q_LLess than Q_S1, then inductive reactive power additional issue △ Q_L, adjustment process terminates；

If △ Q_LMore than Q_S1, then excision passive filter branch is paid the utmost attention to；

If it is Q that capacitor group, which is not put into,_C0=0, then inductive reactive power hair is maximum, and adjustment process terminates；

If capacitor group has the i.e. Q of input_C0>0, calculate voltage after one group of passive filter branch of excision；

If cutting off voltage after one group of passive filter branch is higher than target voltage, continue to calculate judgement after excision, until voltage In target area；

If cutting off voltage after one group of passive filter branch is less than target voltage, passive filter branch is not cut off, perceptual nothing Work(hair is maximum, and adjustment process terminates.

3. a kind of static synchronous compensating device voltage powerless control method suitable for wind power plant according to claim 2, It is characterized in that, working as U_S<U_DWhen concrete operation step it is as follows：

Compare and voltage is transferred to target voltage U_TRequired capacitive reactive power capacity △ Q_CWith put into inductive reactive power capacity Q_S0Size；

If △ Q_CLess than Q_S0, then inductive reactive power, which subtracts, sends out △ Q_C, adjustment process terminates；

If △ Q_CMore than Q_S0, then input passive filter branch is paid the utmost attention to；

First judge the situation that puts into operation of passive filter branch：

If passive filter branch has spare capacity i.e. Q_C1>0, then calculate the voltage liter after one group of passive filter branch of input High situation；

If putting into voltage after one group of passive filter branch is less than target voltage, continue above-mentioned calculating and input process, directly It is in target voltage region to voltage；

If all input is Q to passive filter branch_C1After=0, voltage is still below target voltage, makes static synchronous compensating device Issue additional capacitive reactive power；

If static synchronous compensating device is sent to maximum capacity, voltage is still below target voltage, then adjusts process and terminate.

4. a kind of static synchronous compensating device voltage powerless control method suitable for wind power plant according to claim 3, It is characterized in that, working as U_D≤U_S≤U_PWhen concrete operation step it is as follows：

It is adjusted to U_D≤U_S≤U_PVoltage and reactive power coordinated control is carried out while voltage range, by k value sizes controlled come The size that indirect adjustments and controls wind power plant is exchanged with electric network reactive-load, reactive power exchange capacity is smaller, and power factor is higher.

5. according to a kind of static synchronous compensating device voltage suitable for wind power plant of Claims 1 to 4 item any one of them without Work(control method, which is characterized in that the control targe selection strategy table selection information is as follows：

Work as Q_S>0 and U_P<U_SWhen, U_T=U_EXP；Wherein U_TFor target voltage values, U_EXPFor windfarm system upper voltage limit value rated value；

Work as Q_S>0 and U_D≤U_S≤U_PWhen, U_T=U_S-k(U_S-U_D)；Wherein, k is that static synchronous compensating device carries out voltage power-less association The step-length of tune；

Work as Q_S>0 and U_S<U_DWhen, U_T=U_D；

Work as Q_S=0 and U_P<U_SWhen, U_T=U_P；

Work as Q_S=0 and U_D≤U_S≤U_PWhen, U_T=U_S；

Work as Q_S=0 and U_S<U_DWhen, U_T=U_D；

Work as Q_S<0 and U_P<U_SWhen, U_T=U_P；

Work as Q_S<0 and U_D≤U_S≤U_PWhen, U_T=U_S+k(U_P-U_S)；

Work as Q_S<0 and U_S<U_DWhen, U_T=U_EXD；Wherein, U_EXDFor windfarm system voltage lower limit value rated value.