CN104238362A - Station-level control system modeling method for photovoltaic power station plant - Google Patents

Abstract

The invention relates to a modeling method for a station-level control system of a photovoltaic power station. The system includes a station-level active power control system for a photovoltaic power station and a station-level reactive voltage control system for a photovoltaic power station; The system model determines the reference value of the output active power of the power station according to the maximum output power level of the photovoltaic power station and the active power command issued by the power station, determines the active power adjustment command of the power station through power control, and adds auxiliary grid-connected point frequency droop control; The station-level reactive power and voltage control model of the photovoltaic power station determines the output reactive power reference value according to the voltage level of the grid-connected point, the power factor, or receives the grid dispatching command, and then determines the reactive power adjustment command of the power station through power control. This method can meet the needs of grid-connected analysis of large-scale photovoltaic power plants, and provide a basic model for the analysis of photovoltaic power plant integration systems and auxiliary power grid operation control decisions after photovoltaic power plants are connected.

Description

A Modeling Method for Plant-level Control System of Photovoltaic Power Plant

Technical field:

The invention relates to a modeling method, and more specifically to a modeling method for a station-level control system of a photovoltaic power station.

Background technique:

In recent years, my country's grid-connected solar power generation has developed by leaps and bounds, and the scale of photovoltaic power generation connected to the power system has continued to increase. In the western region of my country, many large-scale photovoltaic power stations of 100 megawatts have been built, and the total installed capacity of grid-connected photovoltaic power stations exceeds one million kilowatts. With the increase in the number and scale of photovoltaic power stations, the unique seasonal and day-night power output fluctuations of photovoltaic power generation will have an impact on the safe and stable operation of the power grid, mainly in the system relay protection after photovoltaic power stations are connected to the grid , security and stability control, power quality, grid frequency and voltage regulation, and economic operation.

Studying the effective model structure is the basis for grid-connected analysis of photovoltaic power generation. By establishing a plant-level control system model of a photovoltaic power station and performing simulation analysis on it, it is possible to fully understand the impact of the photovoltaic power station on the safe and stable operation of the power grid, and deeply analyze the interaction mechanism between the photovoltaic power station and the power grid, so as to provide a basis for the operation of the power grid after the large-scale photovoltaic power station is connected. Control decision-making provides basic models and platform support, which is of great significance for improving the level of grid operation and promoting the development of large-scale photovoltaic power generation. Therefore, a plant-level control system modeling method for photovoltaic power plants is proposed to achieve the above goals.

Invention content:

The purpose of the present invention is to provide a modeling method for the plant-level control system of a photovoltaic power station, which can meet the needs of grid-connected analysis of large-scale photovoltaic power stations, provide system analysis for photovoltaic power stations, and assist in decision-making of grid operation control after photovoltaic power stations are connected. Provides the base model.

In order to achieve the above purpose, the present invention adopts the following technical solutions: a modeling method for a station-level control system of a photovoltaic power station, the system includes a station-level active power control system for a photovoltaic power station and a station-level reactive power and voltage control system for a photovoltaic power station; The method described includes the modeling process of the station-level active power control system of the photovoltaic power station and the modeling process of the station-level reactive power and voltage control system of the photovoltaic power station.

The present invention provides a method for modeling a station-level control system of a photovoltaic power station. The method includes modeling the station-level active power control system of a photovoltaic power station. The process includes the following steps:

(1-1) Determine the active power setting value P _fr ;

(1-2) Determine the set value P _ref of the active output of the photovoltaic power station;

(1-3) Determine the active power regulation command P _ord of the photovoltaic power station and send it to the photovoltaic inverter in the power station.

The present invention provides a method for modeling a station-level control system of a photovoltaic power station. The modeling process of the station-level reactive power and voltage control system of a photovoltaic power station includes the following steps:

(2-1) Determine the reactive power set value Q _{PF_ref} of the photovoltaic power station;

(2-2) Determine the reactive power set value Q _ref of the photovoltaic power station;

(2-3) Determine the reactive power adjustment command Q _{q_ord} ;

(2-4) Determine the reactive power adjustment command Q _{v_ord} ;

(2-5) Determine the reactive power adjustment command Q _ord of the photovoltaic power station and send it to the photovoltaic inverter in the power station.

Another preferred method for modeling a plant-level control system of a photovoltaic power station provided by the present invention, in the step (1-1), the active power setting value P _fr is determined by the actual grid frequency;

Compare the grid frequency f of the grid-connected point monitored by the photovoltaic power station with the frequency upper limit value f _up required by the power system security and stability:

A. When f≤f _up , the active power setting value of the photovoltaic power station P _fr =1;

B. When f>f _up , the active power setting value P _fr of the photovoltaic power station is set according to the slope of k _pf ,

Right now

P _fr =k _pf (ff _up ) (1)

k _pf is generally taken as -0.4pu/Hz.

In yet another preferred modeling method of a photovoltaic power plant station-level control system provided by the present invention, the active output set value P _ref in the step (1-2) is obtained by combining the active power set value P _fr with the photovoltaic The smaller value of the active power output command P _{POI_ord} received by the power station from the superior dispatching organization.

In yet another preferred modeling method for a station-level control system of a photovoltaic power station provided by the present invention, the active power adjustment command P _ord in the step (1-3) is the power adjustment command P _{f_ord} of a photovoltaic power station;

The process of determining the power regulation command P _{f_ord} of the power station is as follows:

Pass the active power P _POI actually emitted by the photovoltaic power plant through a first-order filter After comparing with Pre _ref , the active power deviation ΔP=P _ref -P _{POI first order} is obtained;

ΔP determines the power regulation command P _{f_ord} of the power station through an active power proportional-integral controller;

Among them, T _m is the time constant of the first-order filter, and s is the Laplace operator of the station transfer function.

Another preferred modeling method of a photovoltaic power plant station level control system provided by the present invention, the reactive power set value Q _{PF_ref} of the photovoltaic power plant in the step (2-1) is the power factor at the grid-connected point required by the power grid The product of PF _{POI_ref} and the monitored active power P _POI actually emitted by the photovoltaic power plant at the grid connection point;

The power factor PF _{POI_ref} is determined by the following formula:

$\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; PF</span>}}_{\mathrm{<span\; class="notranslate">\; POIs</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; ref</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; PF</span>}}_{\mathrm{<span\; class="notranslate">\; POIs</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; ref</span>}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span>$

In yet another preferred modeling method for a plant-level control system of a photovoltaic power station provided by the present invention, the reactive power setting value Q _ref in the step (2-2) is the Q selected by the power factor switching switch PF _{POI_flag PF_ref} or Q _{POI_ref} .

In yet another preferred modeling method of a photovoltaic power plant station-level control system provided by the present invention, the reactive power adjustment command Q _{q_ord} determination process in the step (2-3) is:

Pass the actual reactive power Q _POI at the grid-connected point of the photovoltaic power station through a first-order filter After comparing with Q _ref , get reactive power deviation ΔQ=Q _ref -Q _{POI first order} ;

ΔQ obtains the reactive power adjustment command Q _{q_ord} based on the reactive power deviation through the reactive proportional integral controller;

Among them, T _m is the time constant of the first-order filter, and s is the Laplace operator of the station transfer function.

Another preferred method for modeling a photovoltaic power plant station-level control system provided by the present invention, the determination process of the reactive power adjustment command _{Qv_ord} in the step (2-4) is:

Determine the voltage droop amount U _qd , that is, the product of the Q _POI and the reactive voltage droop coefficient k _qd ;

Superimpose the voltage droop U _qd on the actual voltage U _POI at the grid-connected point, and then pass through the first-order filter Compared with the voltage setting value U _{POI_ref} at the grid-connected point, the voltage deviation ΔU=U _{POI_ref} -U _{POI first order} -U _{qd first order} is obtained;

The ΔU is passed through a voltage proportional integral controller to obtain a reactive power regulation command Q _{v_ord} based on reactive voltage droop;

Among them, T _m is the time constant of the first-order filter, and s is the Laplace operator of the station transfer function.

In yet another preferred modeling method of a photovoltaic power plant station-level control system provided by the present invention, the reactive power regulation command Q _ord in the step (2-5) is the reactive power regulation command Q _{qv_ord} ;

The reactive power adjustment command Q _{qv_ord} is Q _{q_ord} or Q _{v_ord} selected by the reactive voltage switching switch QV _{POI_flag} .

Another preferred modeling method for the station-level control system of a photovoltaic power station provided by the present invention, in the station-level active power control system model of the photovoltaic power station, if the control system fails, the active power adjustment command can be used to switch the switch P _{POI_flag} To select the empty command, exit the plant-level active power control system.

Yet another preferred modeling method for the station-level control system of a photovoltaic power station provided by the present invention, in the station-level reactive power and voltage control system model of the photovoltaic power station, if the control system fails, it can be switched by a reactive power adjustment command Switch Q _{POI_flag} to select empty command and exit the plant-level reactive power voltage control system.

Compared with the closest prior art, the technical solution provided by the present invention has the following excellent effects

1. Aiming at the station-level operation control problem of photovoltaic power stations, the present invention establishes the station-level active power control and reactive power voltage control system models of photovoltaic power stations, which can meet the needs of grid-connected analysis of large-scale photovoltaic power stations, and provide photovoltaic power station access system analysis and assistance Provide a basic model for grid operation control decision-making after photovoltaic power plants are connected;

2. The plant-level active power control system model of the photovoltaic power station established by the present invention assists the frequency droop control, and introduces the grid frequency as a reference for setting the given value of the active power output of the power station, laying the foundation for large-scale photovoltaic power stations to participate in the system frequency adjustment research Base;

3. The station-level reactive power and voltage control system model of the photovoltaic power station established by the present invention takes into account constant power factor control, constant voltage control and reactive power given control, and meets the requirements of various modes of reactive power and voltage control of the power grid, which is beneficial to Analysis of the safe and stable operation of large-scale photovoltaic power plants in various ways after they are connected to the grid;

4. The plant-level control system model of the photovoltaic power station established by the present invention considers the switching in the case of a control system failure, so that the control system can be exited when the plant-level control system is abnormal, ensuring the safe and stable operation of the photovoltaic power plant;

5. The present invention is of great significance for improving the operation level of the power system connected to large-scale photovoltaic power generation.

Description of drawings

Fig. 1 is the structural diagram of the station-level control system of the photovoltaic power station of the present invention;

Fig. 2 is a model block diagram of the station level active power control system of the present invention;

Fig. 3 is a model diagram of the plant-level reactive voltage control system of the present invention.

Detailed ways

Below in conjunction with embodiment the invention is described in further detail.

Example 1:

As shown in Figures 1-3, the invention of this example is a modeling method for a station-level control system of a photovoltaic power station. The system model includes a station-level active power control system model of a photovoltaic power station and a station-level reactive power and voltage control system model. The method includes a modeling process of a station-level active power control system of a photovoltaic power station and a modeling process of a station-level reactive power and voltage control system of a photovoltaic power station.

The model modeling of the active power control system determines the reference value of the output active power of the photovoltaic power station according to the maximum output power level of the photovoltaic power station and the active power command issued by the dispatching of the power station, and determines the active power adjustment command of the power station through power control. Screen frequency droop control;

The reactive voltage control model modeling determines the output reactive power reference value according to the voltage level of the grid-connected point, the power factor or the grid dispatching command received, and then determines the reactive power adjustment command of the power station through power control.

(1) Modeling of plant-level active power control system of photovoltaic power station

The active power control system of the photovoltaic power station is to give the active power adjustment command of the photovoltaic power station through the controller, control the photovoltaic inverter in the station, and make the actual output active power of the photovoltaic power station track the active output set value of the photovoltaic power station, and the output set value is determined by the dispatching agency. The output command issued is given by adding frequency droop control, and the specific implementation process is:

①Adopt the frequency drooping control of the grid-connected point, and determine the set value of active power according to the actual grid frequency,

First, compare the grid frequency f of the grid-connected point monitored by the photovoltaic power station with the frequency upper limit value f _up required by the system security and stability:

A. When f≤f _up , give the set value of active power of the photovoltaic power station P _fr =1;

B. When f>f _up , the active power setting value P _fr of the photovoltaic power station is set according to the slope of k _pf ,

Right now

P _fr =k _pf (ff _up ) (1)

k _pf is generally taken as -0.4pu/Hz.

②Compare the P _fr obtained according to the frequency droop algorithm with the active power output command P _{POI_ord} received by the superior dispatching organization received by the photovoltaic power station, and the smaller value of the two is used as the active power output set value P _ref of the photovoltaic power station;

③ Pass the active power P _POI actually emitted by the photovoltaic power plant through a first-order filter After comparing with Pre _ref , the active power deviation ΔP=P _ref -P _{POI first order} is obtained, and ΔP passes through the active power proportional-integral controller ( ) to obtain the power regulation command P _{f_ord} of the power station based on frequency droop control, which is sent to the photovoltaic inverter in the power station as the active power regulation command P _ord of the photovoltaic power station, where T _m is the time constant of the first-order filter, and K _{p_POI} is the station stage active power controller proportional coefficient, T _{p_POI} is the integral time constant of the station-level active power controller, s is the station transfer function Lagrangian operator;

(2) Modeling of plant-level reactive power and voltage control system of photovoltaic power station

The reactive power and voltage control system of the photovoltaic power station is to give the reactive power adjustment command of the photovoltaic power station through the voltage controller or the reactive power controller, and control the photovoltaic inverter in the station, so that the actual output reactive power of the photovoltaic power station can track the reactive power setting of the photovoltaic power station. The fixed value, its reactive power set value can be issued directly by the dispatching organization, or it can be given by the constant power factor control method. The specific implementation process is:

①Adopt the constant power factor control strategy, and pass the power factor PF _{POI_ref} at the grid-connected point required by the grid through the formula Calculation, the result is multiplied by the monitored active power P _POI of the photovoltaic power station actually issued at the grid-connected point, and the reactive power set value Q _{PF_ref} of the photovoltaic power station based on the constant power factor is obtained;

②Q _{PF_ref} and the reactive power setting value Q _{POI_ref} at the grid-connected point set by the dispatching agency, select Q _{PF_ref} or Q _{POI_ref} as the reactive power setting value Q _ref of the photovoltaic power station through the power factor switch PF _{POI_flag} ;

③Adopt the reactive power control method, pass the actual reactive power Q _POI at the grid-connected point of the photovoltaic power station through the first-order filter After comparing with Q _ref , the reactive power deviation ΔQ=Q _ref -Q _{POI first order} is obtained, and ΔQ passes through the reactive power proportional integral controller ( ) to obtain the reactive power adjustment command Q _{q_ord} based on the reactive power deviation, where T _m is the time constant of the first-order filter, K _{q_POI} is the proportional coefficient of the station-level reactive power controller, and T _{q_POI} is the integration time of the station-level reactive power controller constant, s is the station transfer function Laplace operator;

④Using the voltage control method, multiply Q _POI by the reactive voltage droop coefficient k _qd to obtain the voltage droop U _qd , superimpose it to the actual voltage U _POI at the grid-connected point, and pass through the first-order filter Then compare it with the voltage setting value U _{POI_ref} at the grid-connected point, and get the voltage deviation ΔU=U _{POI_ref} -U _{POI first order} -U _{qd first order} , and ΔU passes through the voltage proportional integral controller ( ), get the reactive power regulation command Q _{v_ord} based on reactive voltage droop, where T _m is the time constant of the first-order filter, K _{v_POI} is the proportional coefficient of the station-level voltage controller, and T _{v_POI} is the integral time constant of the station-level voltage controller , s is the station transfer function Laplace operator;

⑤Q _{q_ord} and Q _{v_ord} through the reactive voltage switching switch QV _{POI_flag} , select Q _{q_ord} or Q _{v_ord} as the basis

Reactive power regulation command Q _{qv_ord} for reactive voltage control, this command is used as reactive power of photovoltaic power station

The rate adjustment command Q _ord is sent to the photovoltaic inverter in the power station.

In the plant-level active power control system model of the photovoltaic power station, if the control system fails, the active power adjustment command switching switch P _{POI_flag} can be used to select the empty command and exit the plant-level active power control system.

In the plant-level reactive power and voltage control system model of a photovoltaic power station, if the control system fails, the reactive power adjustment command switching switch Q _{POI_flag} can be used to select an empty command and exit the plant-level reactive power and voltage control system.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Those of ordinary skill in the art should understand with reference to the above embodiments: the specific implementation methods of the present invention can still be modified or equivalent Replacement, any modification or equivalent replacement that does not deviate from the spirit and scope of the present invention is within the protection scope of the claims of the present invention pending application.

Claims (13)

1. a photovoltaic plant plant stand level modeling of control system method, is characterized in that: described system comprises photovoltaic plant plant stand level real power control system and photovoltaic plant plant stand level reactive voltage control system; Described method comprises photovoltaic plant plant stand level real power control system modelling process and photovoltaic plant plant stand level reactive voltage control system modeling process.

2. a kind of photovoltaic plant plant stand level modeling of control system method as claimed in claim 1, is characterized in that: described method comprises photovoltaic plant plant stand level real power control system modelling process and comprises the following steps:

(1-1) meritorious set value of the power P is determined _fr;

(1-2) the meritorious setting value P that exerts oneself of photovoltaic plant is determined _ref;

(1-3) photovoltaic plant active power regulation instruction P is determined _ordand to be issued in power station in photovoltaic DC-to-AC converter.

3. a kind of photovoltaic plant plant stand level modeling of control system method as claimed in claim 1, is characterized in that: described photovoltaic plant plant stand level reactive voltage control system modeling process comprises the following steps:

(2-1) photovoltaic plant reactive power setting value Q is determined _{pF_ref};

(2-2) photovoltaic plant reactive power setting value Q is determined _ref;

(2-3) reactive power regulating command Q is determined _{q_ord};

(2-4) reactive power regulating command Q is determined _{v_ord};

(2-5) photovoltaic plant reactive power regulating command Q is determined _ordand be issued to photovoltaic DC-to-AC converter in power station.

4. a kind of photovoltaic plant plant stand level modeling of control system method as claimed in claim 2, is characterized in that: active power setting value P in described step (1-1) _frdetermined by actual electric network frequency;

The upper frequency limit value f that monitored by photovoltaic plant and site mains frequency f and power system safety and stability require _upcompare:

A, as f≤f _uptime, then photovoltaic plant active power setting value P _fr=1;

B, as f > f _uptime, photovoltaic plant active power setting value P _fraccording to k _pfslope setting, namely

P _fr＝k _pf(f-f _up) (1)

K _pfgenerally be taken as-0.4pu/Hz.

5. a kind of photovoltaic plant plant stand level modeling of control system method as claimed in claim 4, is characterized in that: the meritorious setting value P that exerts oneself in described step (1-2) _refget described active power setting value P _frthe higher level's scheduling institution received with photovoltaic plant issues the meritorious instruction P that exerts oneself _{pOI_ord}smaller value.

6. a kind of photovoltaic plant plant stand level modeling of control system method as claimed in claim 2, is characterized in that: the active power regulation instruction P in described step (1-3) _ordfor photovoltaic plant power adjustment instruction P _{f_ord};

Described power station power adjustment instruction P _{f_ord}deterministic process is:

By actual for the photovoltaic plant active-power P sent _pOIthrough firstorder filter afterwards with P _refwith compare, obtain meritorious deviation delta P=P _ref-P _{pOI single order};

Δ P determines described power station power adjustment instruction P through meritorious pi controller _{f_ord};

Wherein, T _mfor firstorder filter time constant, s is station transport function laplace operator.

7. a kind of photovoltaic plant plant stand level modeling of control system method as claimed in claim 3, is characterized in that: the photovoltaic plant reactive power setting value Q in described step (2-1) _{pF_ref}for the also site place power factor PF of grid requirements _{pOI_ref}with the photovoltaic plant monitored and the actual active-power P sent in site place _pOIproduct;

Described power factor PF _{pOI_ref}determined by following formula:

$\sqrt{\frac{1-{\mathrm{PF}}_{\mathrm{POI}\_\mathrm{ref}}^2}{{\mathrm{PF}}_{\mathrm{POI}\_\mathrm{ref}}}}---\left(2\right).$

8. a kind of photovoltaic plant plant stand level modeling of control system method as claimed in claim 4, is characterized in that: the reactive power setting value Q in described step (2-2) _reffor passing through power factor change-over switch PF _{pOI_flag}the Q selected _{pF_ref}or Q _{pOI_ref}.

9. a kind of photovoltaic plant plant stand level modeling of control system method as claimed in claim 3, is characterized in that: the reactive power regulating command Q in described step (2-3) _{q_ord}deterministic process is:

By the actual reactive power Q at photovoltaic electric station grid connection point place _pOIthrough firstorder filter afterwards with Q _refwith compare, obtain idle deviation delta Q=Q _ref-Q _{pOI single order};

Δ Q obtains the reactive power regulating command Q based on reactive power deviation through idle pi controller _{q_ord};

Wherein, T _mfor firstorder filter time constant, s is station transport function laplace operator.

10. a kind of photovoltaic plant plant stand level modeling of control system method as claimed in claim 9, is characterized in that: the reactive power regulating command Q in described step (2-4) _{v_ord}deterministic process is:

Determine voltage sag of chain U _qd, namely by described Q _pOIcoefficient k sagging with reactive voltage _qdproduct;

By described voltage sag of chain U _qdbe added to and site place virtual voltage U _pOI, then through firstorder filter with and site place voltage setting value U _{pOI_ref}relatively, voltage deviation Δ U=U is obtained _{pOI_ref}-U _{pOI single order}-U _{qd single order};

Described Δ U, through voltage ratio integral controller, obtains based on the sagging reactive power regulating command Q of reactive voltage _{v_ord};

Wherein, T _mfor firstorder filter time constant, s is station transport function laplace operator.

11. a kind of photovoltaic plant plant stand level modeling of control system methods as claimed in claim 10, is characterized in that: the reactive power regulating command Q in described step (2-5) _ordfor reactive power regulating command Q _{qv_ord};

Described reactive power regulating command Q _{qv_ord}for passing through reactive voltage change-over switch QV _{pOI_flag}the Q selected _{q_ord}or Q _{v_ord}.

12. a kind of photovoltaic plant plant stand level modeling of control system methods as claimed in claim 1, is characterized in that: in described photovoltaic plant plant stand level real power control system model, if control system breaks down, can by meritorious regulating command change-over switch P _{pOI_flag}select dummy instruction, exit plant stand level real power control system.

13. a kind of photovoltaic plant plant stand level modeling of control system methods as claimed in claim 1, is characterized in that: in described photovoltaic plant plant stand level reactive voltage control system model, if control system breaks down, can pass through Reactive-power control instruction change-over switch Q _{pOI_flag}select dummy instruction, exit plant stand level reactive voltage control system.