CN103915848B - The regulate and control method of control that double-fed fan motor field is idle - Google Patents

Abstract

The invention provides the regulate and control method of the idle control appliance in a kind of double-fed fan motor field, does one double-fed wind energy turbine set powerless control system comprise an outer ring system, middle loop systems and inner ring system, and sets up following relation: utilize the instruction references value that outer ring system calculating wind energy turbine set adjusts needed for the regulating command of responsive electricity grid control centre ; In setting, the input variable of loop systems is the instruction references value of outer ring system , output variable is the reference value of n platform double-fed fan motor unit reactive power , feedback quantity is the actual reactive power value sum of n platform double-fed fan motor unit: , in formula it is the idle occurrence value of reality of i-th double-fed fan motor unit; Setting inner ring system input variable is the output reference value of middle loop systems , output variable and feedback quantity are the idle occurrence value of reality of each double-fed fan motor unit form a closed-loop system.

Description

Regulation method for reactive power control of doubly-fed wind farm

technical field

The invention belongs to the field of electric power system control, and is especially aimed at adjusting and controlling the reactive power control parameters of a doubly-fed wind farm composed of large-scale doubly-fed wind generators.

Background technique

In today's increasingly depleted resources and increasingly serious environmental problems, in order to maintain the sustainable development of energy economy, wind energy has been developed on a large scale. However, after large-scale wind power is connected to the grid, large-scale off-grid accidents of wind turbines occur frequently. According to the statistics of Gansu Provincial Electric Power Company, from February 24, 2011 to the end of April 2011, there were 43 large-scale off-grid accidents of various wind turbines in the wind farm of Jiuquan Wind Power Base. In Inner Mongolia, Jilin and other places where wind power has developed rapidly, large-scale off-grid accidents of wind turbines have occurred many times. According to preliminary analysis, the main cause of such accidents is the poor quality of the cable heads and other equipment in wind farms that do not have fault ride-through capability. The voltage deteriorates further.

The large-scale integration of wind power without reasonable reactive power control measures directly threatens the safe and economic operation of the power grid. The problem of reactive power and voltage after wind power grid integration has become a bottleneck restricting the development of wind power. Regarding the reactive power and voltage control technology of wind farms, the current research is in its infancy, and a set of systematic theories and methods have not yet been formed, and there are few related engineering applications, which lag far behind the progress of reactive power compensation technology. main obstacle. Therefore, establishing a reactive power control system for wind farms and enhancing the dispatchability and controllability of wind power reactive power are the most important and urgent issues to solve the problem of reactive power and voltage after wind power grid-connected.

Contents of the invention

To sum up, it is indeed necessary to provide a control method for reactive power control parameters that can reasonably control the reactive power voltage of wind farms.

A control method for reactive power control of a doubly-fed wind farm, comprising a doubly-fed wind farm reactive power control system, the doubly-fed wind farm reactive power control system including a wind farm control layer, a cluster control layer, and a doubly-fed wind turbine control layer Layer, the wind power control layer, cluster control layer and doubly-fed wind turbine control layer respectively constitute the outer ring system, middle ring system and inner ring system of the doubly-fed wind farm reactive power control system; the outer ring system, middle ring system The connection relationship with the inner loop system is established in the following way: (a) Use the outer loop system to calculate the command reference value that the wind farm needs to adjust in response to the adjustment command of the grid dispatching center ; (b) Set the input of the middle ring system as the command reference value of the outer ring system , the output is the reference value of the reactive power of n DFIGs , the feedback amount is the sum of the actual reactive power values of n DFIGs: , where is the actual reactive power generation value of the i-th doubly-fed wind turbine; (c) Set the input of the inner loop system as the output reference value of the middle loop system , the output and feedback are the actual reactive power generation values of each doubly-fed wind turbine form a closed loop system.

Compared with the prior art, the regulation method of reactive power control of DFIG wind farm provided by the present invention adopts a three-layer control structure by coordinating control parameters and following the principle of multiple reactive power generation of DFIG wind turbines with large reactive power output. Each layer uses a different control strategy to overcome the current situation of uncoordinated reactive power adjustment, low stability of the control process, and slow response speed in large-scale doubly-fed wind farms.

Description of drawings

Fig. 1 is a schematic structural diagram of a reactive power control system for a doubly-fed wind farm provided by the present invention.

Fig. 2 is a schematic diagram of the relationship between the middle loop system and the inner loop system in the reactive power control system of the double-fed wind farm shown in Fig. 1 .

detailed description

The technical solution of the present invention will be further described in detail according to the accompanying drawings in the description and in conjunction with specific embodiments. For description, the present invention firstly provides a doubly-fed wind farm reactive power control system for controlling wind farm reactive power equipment.

Please refer to FIG. 1 and FIG. 2 together. The reactive power control system of DFIG wind farm provided by the first embodiment of the present invention includes a wind farm control layer, a machine cluster control layer and a DFIG wind turbine control layer. The wind power control layer, the cluster control layer and the doubly-fed wind turbine control layer respectively constitute the outer loop system, the middle loop system and the inner loop system of the reactive power control system of the doubly-fed wind farm. The execution equipment of the control layer of the wind farm and the cluster control layer can be automatic voltage control system software, and the execution equipment of the control layer of the double-fed wind turbine can be a double-fed wind turbine.

The control periods of the outer loop system, the middle loop system and the inner loop system are respectively , , . In order to avoid oscillations between the control layer of the wind farm, the cluster control layer and the DFIG control layer, the command cycle of each control loop should have a significant difference. , , The relationship between satisfies:

(1)

(2)

In this example, .

Please also refer to Figure 2, the connection relationship between the outer ring system, the middle ring system and the inner ring system is established in the following way:

(a) Use the outer loop system to calculate the command reference value that the wind farm needs to adjust in response to the adjustment command of the grid dispatching center ;

(b) Set the input quantity of the middle loop system as the instruction reference value of the outer loop system , the output is the reference value of the reactive power of n DFIGs (n is the number of wind turbines in the wind farm) , the feedback amount is the sum of the actual reactive power values of n DFIGs, then the reactive power Q _dΣ of the DFIGs is:

(3)

In the formula is the actual reactive power generation value of the i-th DFIG.

Further, by adopting a proportional-integral control strategy (Proportional-Integral, abbreviated as PI), and according to the proportional coefficient ( , ,..., , No. Distribution coefficient of deviation reactive power of a doubly-fed wind turbine (DFIG) ), adjust the reference value of reactive power of each DFIG.

(c) Set the input of the inner loop system as the output reference value of the middle loop system , the output and feedback are the actual reactive power generation values of each doubly-fed wind turbine form a closed loop system.

The outer loop system needs to calculate the instruction reference value Can be calculated by:

(4)

In the formula Indicates the current value of the sum of reactive power output by all doubly-fed wind turbines in the wind farm, in Mvar; Indicates the incremental value that needs to be adjusted based on the current value, and the unit is Mvar.

The incremental value Can be calculated by:

Let the adjustment command of the power grid dispatching center be the voltage increment , the unit is kV, then the incremental value can be calculated according to formula (5);

(5)

In the formula Gather the bus voltage for wind turbines, the unit is kV, which can be obtained through actual measurement; Send out the line impedance for the wind farm, the unit is , is an intrinsic parameter.

Further, the incremental value It can also be calculated by:

Let the adjustment command of the power grid dispatching center be the reactive power increment , then the incremental value Calculate according to formula (6):

(6)

In the formula Gather the bus voltage for wind turbines, the unit is kV; It is the short-circuit voltage of the step-up transformer of the wind farm, in kV, provided by the nameplate of the transformer.

The control parameters of the central ring system include PI control coefficients , and the proportional coefficient of reactive power between multiple doubly-fed wind turbines , ,..., . The control task of the middle loop system is to close-loop track the command reference value of the reactive power of the doubly-fed wind turbine group , and adjust the reference value of the reactive power of each DFIG according to the proportional coefficient. These parameters are dimensionless. The control parameters and proportional coefficients of the central ring system can be set in the following ways:

(1) , Damping coefficient according to type I control system select.

PI controller parameter design is a common-sense method in classical control theory, refer to Dai Zhongda, "Theoretical Basis of Automatic Control", Tsinghua University Press, 1991, first edition, 237-250.

(2) The proportional coefficient is determined according to the principle of multi-generation reactive power of the doubly-fed wind turbine with large adjustable reactive power output.

Specifically, it is assumed that the adjustable reactive power output of the i-th DFIG is , its maximum reactive capacity minus its current reactive output ,which is:

(7)

Then the distribution coefficient of the deviation reactive power of the i-th DFIG is defined as:

(8)

The inner loop system is to track the reactive power reference value of the doubly-fed wind turbine issued by the middle loop system , since the reactive power control of the DFIG is realized based on online measurement, it is possible to eliminate the DFIG by introducing a closed-loop feedback control method based on the deviation between the reference value and the actual value of the reactive power of the DFIG to eliminate the The reactive power control of the unit controls the response rate of the reactive power of the doubly-fed wind turbine due to errors caused by measurement or calculation during the control realization process. The parameter that needs to be determined in the inner loop system is the closed-loop transfer function of the reactive power control of the doubly-fed wind turbine , this parameter can be obtained through experiments, and can also be estimated according to the simplified formula of formula (9):

In the formula is the response time constant of the doubly-fed wind turbine, and the value range is .

The control method for reactive power control of doubly-fed wind farms provided by the present invention, by coordinating various control parameters, according to the principle of multi-generating reactive power of doubly-fed wind turbines with large reactive power output, adopts a three-layer control structure, and each layer adopts a different control strategy, and allocate reactive power control requirements to each DFIG according to the available reactive capacity, and design a single control strategy according to the corresponding external characteristics of the DFIG, which overcomes the uncoordinated reactive power adjustment of large-scale DFIGs , the current situation of low stability of the control process and slow response speed, it provides a reactive power distribution scheme among various reactive power compensation devices in the wind farm, between multiple DFIGs, and within a single DFIG, to achieve The doubly-fed wind farm with online control responds quickly and reliably to the reactive power adjustment requirements after receiving the control instructions.

The reactive power control strategy of the doubly-fed wind turbine group proposed by the present invention is easy to operate and has universal applicability, and is not limited to a specific doubly-fed wind turbine group, but is applicable to any doubly-fed wind turbine group directly connected to the public power grid.

In addition, those skilled in the art can also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should be included in the scope of protection claimed by the present invention.

Claims (9)

1. A control method for doubly-fed wind farm reactive power control, comprising a doubly-fed wind farm reactive power control system, said doubly-fed wind farm reactive power control system comprising a wind farm control layer, a cluster control layer and a doubly-fed wind power plant The unit control layer, the wind farm control layer, the cluster control layer and the doubly-fed wind turbine control layer respectively constitute the outer loop system, the middle loop system and the inner loop system of the reactive power control system of the doubly-fed wind farm; The connection relationship between the outer ring system, the middle ring system and the inner ring system is established in the following manner: (a) Use the outer loop system to calculate the command reference value that the wind farm needs to adjust in response to the adjustment command of the grid dispatching center (b) Set the input quantity of the middle ring system as the instruction reference value of the outer ring system The output is the reference value of the reactive power of n double-fed wind turbines The feedback value is the sum of the actual reactive power values of n DFIGs: where Q _di is the actual reactive power generation value of the i-th DFIG; (c) Set the input of the inner ring system as the output reference value of the middle ring system The output and feedback are the actual reactive power generation values Q _d1 , Q _d2 ,...Q _dn of each DFIG to form a closed-loop system; Assuming that the control periods of the outer loop system, the middle loop system and the inner loop system are T ₁ , T ₂ , T ₃ respectively, the relationship between T ₁ , T ₂ , and T ₃ satisfies: T ₁ >5T ₂ (1); T ₂ >5T ₃ (2). 2. The regulating method of doubly-fed wind farm reactive power control as claimed in claim 1, is characterized in that, the instruction reference value that described outer loop system needs to calculate Calculated by: ${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;Q</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; ;</span>$ In the formula, Q ₀ represents the current value of the sum of reactive power output by all DFIGs in the wind farm, and the unit is Mvar; Indicates the incremental value that needs to be adjusted based on the current value, and the unit is Mvar. 3. The regulation and control method of doubly-fed wind farm reactive power control as claimed in claim 2, is characterized in that, described incremental value Calculated by: Assuming that the adjustment command of the power grid dispatching center is the voltage increment ΔU, the unit is kV, then the increment value for: ${\mathrm{<span\; class="notranslate">\; \&Delta;Q</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; ;</span>$ In the formula, U _tur is the collective bus voltage of the doubly-fed wind turbine, in kV; X _trans is the output line impedance of the wind farm, in Ω. 4. the regulation and control method of doubly-fed wind farm reactive power control as claimed in claim 2, is characterized in that, described incremental value Calculated by: Assuming that the adjustment instruction of the power grid dispatching center is the reactive power increment ΔQ, then the incremental value for: ${\mathrm{<span\; class="notranslate">\; \&Delta;Q</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$ In the formula, U _tur is the collective bus voltage of the doubly-fed wind turbine, in kV; X _T is the short-circuit voltage of the step-up transformer of the wind farm, in kV. 5. the regulation and control method of doubly-fed wind farm reactive power control as claimed in claim 1 is characterized in that, by adopting proportional-integral control strategy, and according to the distribution coefficient D of the deviation reactive power of _i -th doubly-fed wind turbine set , to adjust the reference value of the reactive power of each DFIG. 6. The regulating method of reactive power control of doubly-fed wind farm as claimed in claim 1, characterized in that, the control parameters of the central ring system include proportional-integral control strategy control coefficients and the proportional coefficients D ₁ , D ₂ , ..., D _n of reactive power between multiple doubly-fed wind turbines are set in the following way: (1) Select according to damping coefficient ξ=0.707; (2) The proportional coefficient is determined according to the principle of multi-generation reactive power of the doubly-fed wind turbine with large adjustable reactive power output. 7. the regulation and control method of doubly-fed wind farm reactive power control as claimed in claim 6 is characterized in that, the adjustable reactive power output of the ith doubly-fed wind turbine set its maximum reactive capacity Subtract its current reactive output Q _di , namely: $Q_{di}^c=Q_{di}^{\max }-Q_{di};$ Then the distribution coefficient D _i of the deviation reactive power of the i-th DFIG is defined as: ${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; /</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; .</span>$ 8. The regulating method of reactive power control of doubly-fed wind farm as claimed in claim 1, is characterized in that, the closed-loop transfer function of reactive power control of doubly-fed wind turbine in the inner loop system Calculated by: ${\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ;</span>$ In the formula, T _i is the response time constant of the DFIG. 9. The regulating method for reactive power control of doubly-fed wind farms as claimed in claim 1, characterized in that, the execution equipment of the wind farm control layer and the cluster control layer are all automatic voltage control system software, and the doubly-fed wind power The executive device of the unit control layer is a doubly-fed wind turbine.