CN110350602A - Participate in the blower fan control system of power grid frequency modulation - Google Patents

Abstract

The invention provides a fan control system participating in power grid frequency modulation, including: a virtual inertia control unit, whose input is the grid frequency and a frequency reference value, and whose output is an active power command increment; a torque control unit, whose input is the fan output power and the fan The current speed, the output is the fan torque reference value; the active power control unit, the input is the active power command increment, the fan torque reference value, the fan current speed and the fan initial speed, and the output is the active power reference value ; The pitch angle control unit, the input is the deviation of the wind rotor speed and/or the active power deviation of the fan, and the output is the pitch angle of the fan. The wind turbine control system participating in power grid frequency regulation provided by the present invention can adjust the fan speed and pitch angle under the premise of ensuring the stable operation of the wind turbine and not deteriorating the grid frequency, and fully utilizes the kinetic energy of the wind turbine rotation, thereby avoiding The wind turbines operate with reduced output to improve the support effect of the wind turbines on the frequency of the power grid.

Description

Wind turbine control system participating in power grid frequency regulation

technical field

The invention relates to the technical field of wind power generation, in particular to a wind turbine control system participating in power grid frequency regulation.

Background technique

With the increasing penetration of wind power in the power system, especially after large-scale wind farms are directly connected to the high-voltage transmission grid, wind power has brought a non-negligible impact on the dispatching operation, safety and stability of the power system and many other aspects. . One of the key issues is the impact of large-scale wind power on the frequency of the power system and how to control the frequency of the power system including large-scale wind power to maintain the frequency level required by the power system.

Wind power virtual inertia control refers to adding a system frequency response link to the wind turbine control system. When the system frequency changes, it can increase or decrease in a short time by releasing a certain amount of rotational kinetic energy to the grid or converting a certain amount of electrical energy into rotational kinetic energy. The active output of the fan simulates the inertial response and primary frequency modulation response of the traditional synchronous generator set, participates in the frequency control of the power system, and participates in the frequency control of the power system.

Under virtual inertia control, if the frequency of the system drops, the fan will release kinetic energy to increase output. After the virtual inertia control ends, the fan speed will be lower than the optimal speed. In order to return to the optimal speed, the electromagnetic power of the fan needs to be reduced after the power is increased, and the electromagnetic power of the fan needs to be reduced to an operating state that is smaller than the current mechanical power, so that the fan speed increases. Since the current speed deviates from the optimal speed, the mechanical power of the fan is lower than the initial mechanical power, that is, in the speed recovery stage, the output active power of the fan needs to be less than the initial output active power.

In general, the conventional virtual inertia control provides frequency support in the stage of power increase, but in the stage of speed recovery, it needs to reduce the output to operate, and the output active power of the fan is less than the initial output active power, which will deteriorate when the proportion of wind power is high. The recovery of the grid frequency may even lead to a secondary drop in the system frequency, which brings certain risks to the grid operation.

Contents of the invention

The technical problem to be solved by the present invention is to provide a fan control system that participates in power grid frequency regulation, avoiding the operation of the fan with reduced output, so that the whole process of fan virtual inertia control does not deteriorate the grid frequency, eliminates operation risks, and at the same time can increase the frequency of the grid. support capacity.

The invention provides a fan control system participating in power grid frequency regulation, including:

The virtual inertia control unit, the input is the grid frequency f _grid and the frequency reference value f _ref , and the output is the active power command increment ΔP;

The torque control unit, the input is the output power of the fan P _e and the current speed ω _gen of the fan, and the output is the reference value T _ref of the fan torque;

Active power control unit, the input is the active power command increment ΔP, the fan torque reference value T _ref , the current fan speed ω _gen and the fan initial speed ω _gen0 , and the output is the active power reference value _Pre ;

The pitch angle control unit, the input is the deviation of the wind rotor speed and/or the active power deviation of the fan, and the output is the pitch angle of the fan;

The virtual inertia control unit, the torque control unit and the active power control unit are used to increase the active power, and the pitch angle control unit is used to restore the fan speed after the active power is increased.

Wherein, the virtual inertia control unit includes:

The first operation module is used to calculate the difference between the grid frequency f _grid and the frequency reference value f _ref to obtain the grid frequency deviation f _err ;

A dead zone module, configured to compare the grid frequency deviation f _err with a specific value f _db , if the grid frequency deviation f _err is smaller than the specific value f _db , the grid frequency deviation f _err is 0; if the The grid frequency deviation f _err is greater than the specified value f _db , and the grid frequency deviation f _err remains unchanged;

A filter module, used for smoothing the grid frequency deviation f _err after the dead zone module;

A gain module, according to the gain coefficient K _D , the grid frequency deviation f _err gain processing after the filtering module;

A DC blocking module, used for DC blocking processing of the power grid frequency deviation f _err after passing through the gain module;

A limiter module, configured to limit the power grid frequency deviation f _err after passing through the DC blocking module, and output the active power command increment ΔP.

Further, in the gain module, the gain coefficient K _D is obtained from the power grid frequency f _grid through a measurement link, a differential link, and a table look-up link in sequence.

Further, in the table look-up link, when the rate of change of the grid frequency f _grid is less than X1, the gain coefficient K _D =Y1; when the rate of change of the grid frequency f _grid is greater than or equal to 0, the gain coefficient K _D =Y0, wherein, the X1, Y1 and Y0 are modifiable parameters.

Further, the torque control unit includes:

The speed parameter value calculation module is used to calculate the fan speed reference value ω _ref according to the fan output power P _e ;

The second computing module is used to calculate the difference between the current speed ω _gen of the fan and the reference value ω _ref of the fan speed to obtain the first speed deviation ω′ _{err_trq} ;

A rotational speed deviation signal processing module, configured to process the first rotational speed deviation ω' _{err_trq} to obtain a second rotational speed deviation ω _{err_trq} ;

The PI control module is configured to process the second rotational speed deviation ω _{err_trq} to obtain the fan torque reference value T _ref .

Further, the calculation method in the calculation module of the rotational speed parameter value is:

Among them, K1, K2, K3, K4 and K5 in the calculation method are modifiable parameters.

Further, in the second calculation module, the fan speed reference value ω _ref is different from the fan current speed ω _gen after a long time inertial link to obtain the first speed deviation ω' _{err_trq} .

Further, in the long-time inertia link, the inertia link time constant Typical value is 60s.

Further, the speed deviation signal processing module processes the first speed deviation _{ω'err_trq} as follows:

When the grid frequency deviation f _err is smaller than the specific value f _db , the second rotational speed deviation ω _{err_trq} is equal to the first rotational speed deviation ω'_{err_trq};

When the grid frequency deviation f _err is greater than or equal to the specific value f _db , the first rotational speed deviation ω′ _{err_trq} needs to go through a dead zone link to obtain the second rotational speed deviation ω _{err_trq} , and the dead zone coefficient is ω _db , namely :

Further, the active power control unit includes:

The fan active power reference value signal processing module obtains the current active power P _{fre_trq} according to the fan torque reference value T _ref , the fan current speed ω _gen and the fan initial speed ω _gen0 ;

The third calculation module sums the current active power P _{fre_trq} and the active power command increment ΔP to obtain the active power reference value P _ref .

Further, in the fan active power reference value signal processing module, when the grid frequency deviation f _err is greater than the specific value f _db , and the second speed deviation ω _{err_trq} is less than or equal to 0, P _{fre_trq} =T _ref *ω _gen0 ; in other cases, P _{fre_trq} =T _ref *ω _gen .

The fan control system participating in power grid frequency regulation provided by the present invention, when the system frequency decreases, the fan releases the moment of inertia of the fan at the initial stage of system frequency drop, provides more active power output, reduces the system frequency drop rate and increases the minimum value of frequency drop, which is powerful The frequency recovery of the support system, in the fan speed recovery stage, by reducing the pitch angle of the fan, releases the backup power of the fan, increases the mechanical power of the fan, restores the fan speed, and avoids the operation of the fan at a reduced output. On the premise of ensuring the stable operation of the fan and not deteriorating the frequency of the grid, the fan speed is adjusted to make full use of the kinetic energy of the fan rotation, and then there is no deterioration of the grid frequency in the whole process of virtual inertia control, eliminating the operation risk and improving the grid frequency at the same time The supporting capacity has certain economic benefits. In addition, the present invention has minor changes to the fan control system, does not affect the normal operation control of the fan, does not need to modify the original fan control parameters, and is easy to implement in engineering.

Description of drawings

Fig. 1 is the overall control block diagram of the fan control system participating in power grid frequency regulation in the present invention;

Fig. 2 is the schematic diagram of virtual inertia control unit among the present invention;

Fig. 3 is the schematic diagram of table look-up according to the gain coefficient _K in the gain module in the present invention;

Fig. 4 is a schematic diagram of an active power control unit in the present invention;

Fig. 5 is a schematic diagram of a torque control unit in the present invention;

Fig. 6 is a schematic diagram of a pitch angle control unit in the present invention;

Fig. 7 is a structural diagram of a simulation example in the present invention;

Fig. 8 is a comparison diagram of system frequency response in the present invention;

Fig. 9 is a comparison diagram of fan output power in the present invention;

Fig. 10 is a comparison diagram of fan speeds in the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

A wind turbine control system that participates in power grid frequency modulation, as shown in Figure 1, on the basis of the original wind turbine control system, a virtual inertia control unit is added, and the active power control unit, torque control unit, pitch The corner control unit has been modified, but the modification does not affect the original control function of the fan, which is easy for engineering realization and promotion.

The virtual inertia control unit, the input is the grid frequency f _grid and the frequency reference value f _ref , the output is the active power command increment ΔP; the torque control unit, the input is the fan output power P _e and the fan current speed ω _gen , and the output is the fan speed Torque reference value T _ref ; active power control unit, the input is the active power command increment ΔP, the fan torque reference value T _ref , the current speed of the fan ω _gen and the initial speed of the fan ω _gen0 , and the output is active power Reference value P _ref ; the pitch angle control unit, the input is the deviation of the wind rotor speed and/or the active power deviation of the fan, and the output is the pitch angle of the fan; the virtual inertia control unit, the torque control unit and the active power The control unit is used to increase the active power, and the pitch angle control unit is used to restore the fan speed after the active power is increased.

The virtual inertia control unit is shown in Figure 2, including: a first computing module, used to calculate the difference between the grid frequency f _grid and the frequency reference value f _ref , to obtain the grid frequency deviation f _err ; a dead zone module, used When comparing the grid frequency deviation f _err with a specific value f _db , if the grid frequency deviation f _err is smaller than the specific value f _db , the grid frequency deviation f _err is 0; if the grid frequency deviation f _err is greater than the specified value f _db , the value of the grid frequency deviation f _err remains unchanged; the dead zone module enables the virtual inertia control to respond to a larger frequency deviation to avoid frequent actions of the controller; the filtering module is used to pass through the The grid frequency deviation f _err after the dead zone module is smoothed; the gain module is used to process the grid frequency deviation f _err after the filter module according to the gain coefficient K _D ; the DC blocking module is used to process the gain after the gain The power grid frequency deviation f _err after the module is processed by blocking the direct current; the direct blocking module can make the virtual inertia control of the fan not respond to the steady-state frequency, only respond to the dynamic change process of the frequency, and does not respond to the steady-state frequency; the limiter module is used to control the steady-state frequency The power grid frequency deviation f _err is subjected to limiting processing after the DC blocking module, and the active power command increment ΔP is output. The limiter module can limit the size of the active power command increment ΔP, so as to avoid excessive fan speed reduction caused by too much additional generation of the fan.

In an optional implementation of this embodiment, as shown in FIG. 2 , in the gain module in the virtual inertia control unit, the gain coefficient K _D is sequentially passed through the measurement link, the differential link, and the checking link from the grid frequency f _grid The table link is obtained.

In an optional implementation manner of this embodiment, as shown in FIG. 3 , in the table look-up link, when the rate of change of the grid frequency f _grid is less than X1, the gain coefficient K _D =Y1; the grid frequency When the rate of change of f _grid is greater than or equal to 0, the gain coefficient K _D =Y0, wherein the X1, Y1 and Y0 are modifiable parameters. The gain coefficient K _D is a variable coefficient related to the grid frequency change rate. Its function is to set a larger gain coefficient when the grid frequency drop rate is relatively large, so as to reduce the grid frequency drop rate.

In an optional implementation manner of this embodiment, as shown in FIG. 5, the torque control unit includes:

The speed parameter value calculation module is used to calculate the fan speed reference value ω _ref according to the fan output power P _e ;

The second calculation module is used to calculate the difference between the current speed ω _gen of the fan and the reference value ω _ref of the fan speed to obtain the first speed deviation _{ω'err_trq} ;

A rotational speed deviation signal processing module, configured to process the first rotational speed deviation ω' _{err_trq} to obtain a second rotational speed deviation ω _{err_trq} ;

The PI control module is configured to process the second rotational speed deviation ω _{err_trq} to obtain the fan torque reference value T _ref .

Wherein, in an optional implementation of the rotational speed parameter value calculation module, the calculation method is:

Among them, K1, K2, K3, K4 and K5 in the calculation method are modifiable parameters.

In an optional implementation manner, K1=1.2, K2=0.46, K3=-0.75, K4=1.59, K5=0.63, that is, the calculation method is:

In an optional implementation manner of the second computing module, the fan speed reference value ω _ref is different from the fan current speed ω _gen after a long-term inertial link to obtain the first speed deviation ω′ _{err_trq} . In the long-time inertia link, the inertia link time constant Generally larger, preferably, the inertia link time constant for 60s.

In an optional implementation manner of the speed deviation signal processing module, the processing method for the first speed deviation _{ω'err_trq} is as follows:

When the grid frequency deviation f _err is smaller than the specific value f _db , the second rotational speed deviation ω _{err_trq} is equal to the first rotational speed deviation ω'_{err_trq};

When the grid frequency deviation f _err is greater than or equal to the specific value f _db , the first rotational speed deviation ω' _{err_trq} needs to go through a dead zone link to obtain the second rotational speed deviation ω _{err_trq} , and the dead zone coefficient is ω _db , namely :

The role of the dead zone coefficient ω _db is to prevent the fan speed from dropping too much, resulting in failure to recover. The second speed deviation ω _{err_trq} obtains the fan torque reference value T _ref through the PI control module. The purpose is to ensure that the fan speed is not reduced during the power increase. The torque reference value T _ref can output as much active power as possible, and when the speed deviation is too large, the fan torque reference value T _ref can be reduced through the PI control module to reduce the power output and prevent the fan speed from falling continuously and cannot be recovered.

In an optional implementation manner of this embodiment, as shown in FIG. 4, the active power control unit includes:

The fan active power reference value signal processing module obtains the current active power P _{fre_trq} according to the fan torque reference value T _ref , the fan current speed ω _gen and the fan initial speed ω _gen0 ;

The third calculation module sums the current active power P _{fre_trq} and the active power command increment ΔP to obtain the active power reference value P _ref , and after further processing the active power reference value P _ref , the active current control can be obtained instruction

Wherein, in an optional implementation manner of the fan active power reference value signal processing module, as shown in FIG. 4 , when the grid frequency deviation f _err is greater than the specific value f _db , and the second rotational speed deviation When ω _{err_trq} is less than or equal to 0, P _{fre_trq} =T _ref *ω _gen0 ; in other cases, P _{fre_trq} =T _ref *ω _gen . Such processing can keep the current active power P _{fre_trq} unchanged while the virtual inertia control is active, and at the same time, due to the existence of the active power command increment ΔP, the power can be increased for a short time during the system frequency drop to increase the active power output of the fan.

In an optional implementation of this embodiment, as shown in Figure 6, in the pitch angle control unit, the initial pitch angle of the wind turbine is θ ₀ , and the control link includes two parts: speed deviation pitch angle control and power deviation pitch angle control. branches. Among them, the input of the speed deviation pitch angle control is the wind rotor speed ω _t , the wind rotor speed reference value ω _ref ; the input of the power deviation pitch angle control is the current active power P _{fre_trq} of the pitch angle control, the plant level active power command P _ord . The input of the power deviation pitch angle control is set to the current active power P _{fre_trq} of the active power control link, which can avoid the incorrect action of the power deviation pitch angle control when the virtual inertia is active.

When the virtual inertia control takes effect, the electromagnetic power of the fan is greater than the mechanical power of the fan, and the speed of the fan decreases. At this time, the speed deviation is negative, and the pitch angle control drives the fan to retract (decrease the pitch angle), thereby increasing the mechanical power of the fan and slowing down the wind speed. The speed of the fan is reduced to achieve the purpose of restoring the speed of the fan. In addition, the transformation of the torque control link and the active power link makes the output active power of the fan within a certain range of fan speed drop. fall.

Beneficial effect verification:

In order to illustrate the feasibility and effectiveness of the wind turbine control system that participates in power grid frequency regulation proposed by the present invention, simulation verification is carried out based on the calculation example shown in Figure 7, where LOAD is the equivalent load of the grid, SYSTEM is the equivalent generator of the grid, and genA is the wind power field. Wind farms are connected to the grid through transformers and transmission lines. Simultaneously, the simulation compares the influence of the wind farm without using the virtual inertia control and enabling the virtual inertia control on the system frequency and other states.

The initial state of the simulation is as follows: the equivalent load active power is 10p.u., the reactive power is 1.5p.u. (the benchmark capacity is 100MW), the equivalent generator active power output is 9p.u., the reactive power is 1.52p.u., the wind power The field active power is 1p.u., and the initial pitch angle is 1.1139°.

Set the power grid to lose 15% of the power supply, and the system frequency dynamic response comparison is shown in Figure 7. Enabling virtual inertia control can effectively reduce the grid frequency drop rate. At the same time, the lowest value of grid frequency drop is 48.76Hz, compared to 48.5Hz without virtual inertia control. , an increase of 0.26Hz. The output power of the wind farm is shown in Figure 8. The wind turbine with virtual inertia control enabled provides a peak value of 1.175p.u. The initial stage of the decline provides a peak active power of 1.05p.u., and the power increment is only 0.05p.u.

The fan speed is shown in Figure 9. During the virtual inertia operation period of the fan with virtual inertia control enabled, the fan speed first decreases, releasing the rotational kinetic energy and improving the active power output of the fan. Compared with Figure 8, during the recovery process of the fan speed, the active power of the fan The output is still greater than the initial active power, avoiding the secondary drop of the system frequency. The comparison diagram of the mechanical power and electromagnetic power of the fan with virtual inertia control enabled is shown in Figure 10. During the power increase of the fan, the mechanical power of the fan is increased by reducing the pitch angle of the fan to avoid the continuous decrease of the fan speed.

It is confirmed by experiments that the fan control system proposed by the present invention that participates in power grid frequency regulation provides more active power output when the system frequency decreases, reduces the system frequency drop rate and increases the minimum value of frequency drop, and strongly supports the system frequency recovery. In the recovery stage, avoid fan operation with reduced output.

The protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention shall be determined by the claims.

Claims (10)

1. a kind of blower fan control system for participating in power grid frequency modulation characterized by comprising

Virtual inertia control unit, inputs as mains frequency f_gridWith frequency reference f_ref, export and instruct increment for active power ΔP；

Torque controlling unit inputs as blower output power P_eWith blower current rotating speed ω_gen, export as blower torque reference value T_ref；

Active power controller unit inputs and instructs increment Delta P, the blower torque reference value T for the active power_ref, it is described Blower current rotating speed ω_genWith blower initial speed ω_gen0, export as active power reference value P_ref；

Award setting unit is inputted as wind speed round deviation and/or blower active power deviation, is exported as blower propeller pitch angle；

The virtual inertia control unit, the torque controlling unit and the active power controller unit are for issuing additional wattful power Rate, the award setting unit, for restoring rotation speed of fan after issuing additional active power.

Wherein, the virtual inertia control unit includes:

First computing module, for calculating the mains frequency f_gridWith the frequency reference f_refDifference, obtain power grid frequency Rate deviation f_err；

Dead zone module is used for the mains frequency deviation f_errWith a particular value f_dbCompare, if the mains frequency deviation f_err Less than the particular value f_db, the mains frequency deviation f_errIt is 0；If the mains frequency deviation f_errGreater than the particular value f_db, the mains frequency deviation f_errNumerical value is constant；

Filter module, for will be by the mains frequency deviation f after the dead zone module_errSmoothing processing；

Gain module, according to gain coefficient K_DTo the mains frequency deviation f after the filter module_errGain process；

Blocking module, for the mains frequency deviation f after the gain module_errBlocking processing；

Clipping module, for the mains frequency deviation f after the blocking module_errAmplitude limiting processing, and described in output Active power instructs increment Delta P.

2. participating in the blower fan control system of power grid frequency modulation as described in claim 1, which is characterized in that in the gain module, The gain coefficient K_DBy the mains frequency f_gridSuccessively obtained by measurement link, differentiation element, link of tabling look-up.

3. participating in the blower fan control system of power grid frequency modulation as claimed in claim 2, which is characterized in that in the link of tabling look-up, The mains frequency f_gridChange rate be less than X1 when, the gain coefficient K_D=Y1；The mains frequency f_gridChange rate it is big When being equal to 0, the gain coefficient K_D=Y0, wherein described X1, Y1 and Y0 are modifiable parameter.

4. participating in the blower fan control system of power grid frequency modulation as described in claim 1, which is characterized in that the torque controlling unit Include:

Rotary speed parameter value computing module, for according to the blower output power P_eRotation speed of fan reference value ω is calculated_ref；

Second computing module, for calculating the blower current rotating speed ω_genWith the rotation speed of fan reference value ω_refDifference, Obtain the first revolving speed deviation ω '_{err_trq}；

Speed error signal processing module, for the first revolving speed deviation ω '_{err_trq}Processing, obtains the second revolving speed deviation ω_{err_trq}；

PI control module, for the second revolving speed deviation ω_{err_trq}Processing, obtains the blower torque reference value T_ref。

5. participating in the blower fan control system of power grid frequency modulation as claimed in claim 4, which is characterized in that the rotary speed parameter value meter Calculate the calculation method in module are as follows:

Wherein, K1, K2, K3, K4 and K5 are modifiable parameter in calculation method.

6. participating in the blower fan control system of power grid frequency modulation as claimed in claim 4, which is characterized in that second computing module In, the rotation speed of fan reference value ω_refBy a long-time inertial element and the blower current rotating speed ω_genIt makes the difference, obtains To the first revolving speed deviation ω '_{err_trq}。

7. participating in the blower fan control system of power grid frequency modulation as claimed in claim 6, which is characterized in that the long-time inertia rings In section, inertial element time constantRepresentative value is 60s.

8. participating in the blower fan control system of power grid frequency modulation as claimed in claim 4, which is characterized in that the speed error signal Processing module, to the first revolving speed deviation ω '_{err_trq}Processing method is as follows:

As the mains frequency deviation f_errLess than the particular value f_dbWhen, the second revolving speed deviation ω_{err_tr}Equal to described One revolving speed deviation ω '_{err_trq}；

As the mains frequency deviation f_errMore than or equal to the particular value f_dbWhen, the first revolving speed deviation ω '_{err_trq}Need through It crosses dead zone link and obtains the second revolving speed deviation ω_{err_trq}, dead zone coefficient is ω_db, it may be assumed that

9. participating in the blower fan control system of power grid frequency modulation as claimed in claim 4, which is characterized in that the active power controller Unit includes:

Blower active power reference value signal processing module, according to the blower torque reference value T_ref, the blower current rotating speed ω_genWith blower initial speed ω_gen0, obtain current active power P_{fre_trq}；

Third computing module, to the current active power P_{fre_trq}With active power instruction increment Delta P summation, institute is obtained State active power reference value P_ref。

10. participating in the blower fan control system of power grid frequency modulation as claimed in claim 9, which is characterized in that the blower wattful power In rate reference value signal processing module, as the mains frequency deviation f_errGreater than the particular value f_dbWhen, and second revolving speed Deviation ω_{err_trq}When less than or equal to 0, P_{fre_trq}=T_ref*ω_gen0；In the case of other, P_{fre_trq}=T_ref*ω_gen。