A method and system for phase compensation of distributed phase modifier of a photovoltaic system

Abstract

The application discloses a phase compensation method and system of a distributed phase modifier of a photovoltaic system, and the method comprises the following steps: obtaining a linear relationship between a damping torque and a rotating speed provided by an additional damping controller transfer function from a photovoltaic system in which the distributed phase modifier and a photovoltaic power station are connected in parallel; obtaining an expression relationship between the damping torque and the additional damping controller transfer function according to the linear relationship; initializing the additional damping controller transfer function, and performing multiple rounds of iterative calculation on the expression relationship according to a preset iteration condition to obtain an optimal parameter value of the additional damping controller transfer function. The application can solve the problem that the damping provided by the existing distributed phase modifier is weak, enhances the damping value of the photovoltaic system, provides a damping optimization configuration calculation method for the actual safety of a power system, and improves the reliability and controllability of the operation and maintenance of the high-proportion photovoltaic system.

Description

Technical Field

[0001] This invention relates to the field of synchronous condenser control technology, and in particular to a distributed synchronous condenser phase compensation method and system for photovoltaic systems. Background Technology

[0002] The increasing capacity of photovoltaic (PV) grid-connected systems, due to their unique power electronic structure, weakens grid stability and increases the risk of broadband grid oscillations. The stability issue of large-scale PV grid integration has received significant attention from power producers and researchers. To improve voltage stability in areas with large-scale PV grid integration, distributed synchronous condensers are being deployed to enhance grid voltage stability.

[0003] The integration of distributed synchronous condensers (DCSCs) improves the short-circuit capacity ratio and transient voltage stability of high-proportion photovoltaic (PV) systems, but has little effect on low-frequency stability. Existing research on DCSCs mainly falls into two categories: first, improving the system's transient voltage disturbance capability. This research primarily considers the transient reactive power support capability of the DCSCs. Second, optimizing the parameters of the DCSCs, studying the impact of DCSC parameters on stability. Currently, the damping provided by the DCSCs themselves within their operating range is extremely limited, and relying solely on transient q-axis electromotive force changes to provide grid output damping is far from sufficient. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a phase compensation method and system for a photovoltaic system using a distributed synchronous condenser. This method fully utilizes the existing structure of the distributed synchronous condenser and, by analyzing the relationship between the transfer function of the additional damping controller of the distributed synchronous condenser and the damping torque of the photovoltaic system, can achieve phase compensation in a parallel photovoltaic and distributed synchronous condenser system, thereby enhancing the damping value of the photovoltaic system.

[0005] In a first aspect, a first embodiment of the present invention provides a phase compensation method for a distributed synchronous condenser in a photovoltaic system, the method comprising:

[0006] The linearized relationship between damping torque and rotational speed is obtained from the transfer function of the additional damping controller in a photovoltaic system where distributed synchronous condensers and photovoltaic power plants are connected in parallel.

[0007] Based on the linearization relationship, the expression relationship between the damping torque and the transfer function of the additional damping controller is obtained;

[0008] The transfer function of the additional damping controller is initialized, and the expression relationship is iterated multiple times according to the preset iteration conditions to obtain the optimal parameter value of the transfer function of the additional damping controller.

[0009] Furthermore, the specific steps for obtaining the linearized relationship between damping torque and rotational speed provided by the transfer function of the additional damping controller from the photovoltaic system in which the distributed synchronous condenser and the photovoltaic power station are connected in parallel include:

[0010] Obtain the first linearized relationship between the system's active power and the system's equivalent electromotive force;

[0011] Obtain the second linearized relationship between the system's equivalent electromotive force and the transfer function of the additional damping controller;

[0012] Based on the first linearization relationship and the second linearization relationship, the linearization relationship between the damping torque and the rotational speed provided by the transfer function of the additional damping controller is obtained.

[0013] Furthermore, the first linearized relationship is calculated using the following formula:

[0014]

[0015] In the formula, P equ U represents the system's active power. t X is the terminal voltage. equ For internal impedance, δ equ The variable is the system power angle. Variables with a subscript of 0 are the steady-state values ​​of the corresponding variables, and variables with a Δ are the increments of the corresponding variables.

[0016] The second linearization relation is calculated using the following formula:

[0017]

[0018] In the formula, E equ I is the equivalent electromotive force of the system. con For distributed synchronous condenser current, E pv X is the equivalent electromotive force of a photovoltaic power station. equ For internal impedance, δ equ φ is the system power angle. s K is the power factor angle of the photovoltaic power station. A X′ is the amplification factor of the voltage regulator of the distributed synchronous condenser. con For the d-axis transient impedance of the distributed synchronous condenser, x s T is the equivalent reactance of the system. A T′ is the excitation time constant of the distributed synchronous condenser. d0 X is the excitation winding time constant of the distributed synchronous condenser when the stator is open-circuited. con For the d-axis reactance of the distributed synchronous condenser, U t For the terminal voltage, G Eθ (s) is the transfer function of the photovoltaic active power module, G damp(s) is the transfer function of the additional damped controller, s is the Laplace operator, s = jω d j is the imaginary unit, ω d Let Δω be the angular frequency variable, and δ be the angular frequency variable. equ The corresponding virtual rotational speed, a1 is the amplification factor, τ is the delay time constant, and U td For U t The d-axis component, U tq For U t The q-axis component, x d Let x be the equivalent d-axis reactance of the system. q Let U be the system's equivalent q-axis reactance, and U be the infinite bus voltage.

[0019] in,

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027] K EU =[ΔU t0 -I equ0 X equ cos(δ equ -φ s )0] / E equ0

[0028] K Eφ1 =I equ0 U t0 X equ sin(δ equ -φ s )0 / E equ0

[0029]

[0030] K Eδ1 =I equ0 U t0 X equ sin(δ equ -φ s )0 / E equ0

[0031] Furthermore, the relationship between the damping value and the transfer function of the additional damping controller is calculated using the following formula:

[0032]

[0033]

[0034] In the formula, G damp (s) is the transfer function of the additional damped controller, s is the Laplace operator, and M g The damping value provided by the transfer function, I m To find the imaginary part of the transfer function, I con For distributed synchronous condenser current, E pv X is the equivalent electromotive force of a photovoltaic power station. equ For internal impedance, δ equ φ is the system power angle. s K is the power factor angle of the photovoltaic power station. A X′ is the amplification factor of the voltage regulator of the distributed synchronous condenser. con For the d-axis transient impedance of the distributed synchronous condenser, x s T is the equivalent reactance of the system. A T′ is the excitation time constant of the distributed synchronous condenser. d0 X is the excitation winding time constant of the distributed synchronous condenser when the stator is open-circuited. con The d-axis reactance of the distributed synchronous condenser.

[0035] Furthermore, the specific steps for initializing the transfer function of the additional damping controller include:

[0036] The system active power and system reactive power are initialized according to the preset initial values ​​to obtain the initial values ​​of the transfer function, active power and reactive power.

[0037] Based on the initial values ​​of active power and reactive power, the initial values ​​of distributed synchronous condenser current, equivalent electromotive force of photovoltaic power station, system power angle, and power factor angle of photovoltaic power station are obtained.

[0038] Furthermore, the preset iteration conditions include a preset iteration step size and a preset maximum number of iterations. The maximum number of iterations includes the maximum number of iterations for angular frequency, the maximum number of iterations for system active power, the maximum number of iterations for system reactive power, the maximum number of iterations for delay time constant, and the maximum number of iterations for amplification factor.

[0039] Furthermore, the specific steps for performing multiple rounds of iterative calculations on the expression relationship according to preset iterative conditions include:

[0040] The expression relationship is iteratively calculated based on the preset maximum number of iterations of the angular frequency, and the expression relationship with the minimum damping value is taken as the first expression relationship;

[0041] Based on the preset maximum number of iterations for the system active power and the maximum number of iterations for the system reactive power, the first expression relationship is iteratively calculated, and the first expression relationship with the maximum damping value is taken as the second expression relationship;

[0042] The second expression relationship is iteratively calculated based on the preset maximum number of iterations of the delay time constant, and the second expression relationship with the maximum damping value is taken as the third expression relationship;

[0043] Based on the preset maximum number of iterations for the amplification factor, the third expression relationship is iteratively calculated, and the third expression relationship with the maximum damping value is taken as the fourth expression relationship.

[0044] Furthermore, the specific steps for obtaining the optimal parameter values ​​of the additional damping controller transfer function include:

[0045] Based on the fourth expression relationship, the number of the first iteration and the number of the second iteration corresponding to the delay time constant and the amplification factor are obtained, respectively.

[0046] Based on the preset optimal parameter expression, the first iteration number, and the second iteration number, the optimal value of the delay time constant and the optimal value of the amplification factor are obtained.

[0047] Furthermore, the optimal parameter expression is calculated using the following formula:

[0048] τ opt = 0.05 + (jmax - 1) * 0.01

[0049] a opt = 1 + (imax - 1) * 0.1

[0050] In the formula, τ opt For the optimal value of the delay time constant, a opt To determine the optimal magnification factor, jmax represents the first iteration number, and imax represents the second iteration number.

[0051] Secondly, a second embodiment of the present invention provides a phase compensation system for a distributed synchronous condenser in a photovoltaic system, comprising:

[0052] The linearization relationship acquisition module is used to obtain the linearization relationship between damping torque and rotational speed provided by the transfer function of the additional damping controller from a photovoltaic system in which distributed synchronous condensers and photovoltaic power plants are connected in parallel.

[0053] The expression relationship acquisition module is used to obtain the expression relationship between the damping torque and the transfer function of the additional damping controller based on the linearized relationship;

[0054] The optimal parameter value acquisition module is used to initialize the transfer function of the additional damping controller and perform multiple rounds of iterative calculation on the expression relationship according to preset iterative conditions to obtain the optimal parameter value of the transfer function of the additional damping controller.

[0055] The present invention provides a phase compensation method and system for distributed synchronous condensers in photovoltaic systems. This method fully utilizes the existing structure of distributed synchronous condensers, analyzes the relationship between the transfer function of the additional damping controller of the distributed synchronous condenser and the damping torque of the photovoltaic system. The present invention can solve the problem of weak damping provided by existing distributed synchronous condensers, enhances the damping value of the photovoltaic system, and provides a damping optimization configuration calculation method for the actual safety of power systems. It improves the reliability and controllability of operation and maintenance of high-proportion photovoltaic systems, which is of great significance to the existing field of synchronous condenser control technology. Attached Figure Description

[0056] Figure 1 This is a schematic flowchart of the distributed synchronous condenser phase compensation method for a photovoltaic system provided in an embodiment of the present invention;

[0057] Figure 2 This is a schematic diagram of a photovoltaic power station including a synchronous condenser provided in an embodiment of the present invention;

[0058] Figure 3 yes Figure 2 A schematic diagram of a photovoltaic power station in China;

[0059] Figure 4 yes Figure 2 Equivalent model of distributed synchronous condenser model;

[0060] Figure 5 This is the equivalent model of distributed synchronous condensers and photovoltaic power plants in parallel provided in the embodiments of the present invention;

[0061] Figure 6 yes Figure 1 A flowchart illustrating step S10;

[0062] Figure 7 This is a schematic diagram showing the relationship between the parallel equivalent model, photovoltaic electromotive force, and synchronous condenser stator current provided in the embodiments of the present invention.

[0063] Figure 8 yes Figure 1 A flowchart illustrating step S30;

[0064] Figure 9 yes Figure 1Another flowchart for step S30;

[0065] Figure 10 yes Figure 1 A schematic diagram of the third process in step S30;

[0066] Figure 11 This is a schematic diagram of the structure of the distributed synchronous condenser phase compensation system of the photovoltaic system provided in the embodiment of the present invention. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0068] Please see Figure 1 The present invention provides a phase compensation method for a distributed synchronous condenser in a photovoltaic system, comprising steps S10 to S30:

[0069] Step S10: Obtain the linearized relationship between damping torque and rotational speed provided by the transfer function of the additional damping controller from the photovoltaic system in which the distributed synchronous condenser and the photovoltaic power station are operating in parallel.

[0070] The system and parameters involved in this embodiment will be explained first to facilitate the subsequent calculation and use of the parameters, such as... Figure 2 In the schematic diagram of the photovoltaic power station with synchronous condenser shown, the photovoltaic power generation unit is stepped up to the photovoltaic bus through the box transformer, the photovoltaic bus is stepped up to the common bus through the photovoltaic main transformer, and the synchronous condenser circuit is stepped up to the common bus through the synchronous condenser main transformer. The power of the photovoltaic power station and the synchronous condenser flows to the equivalent system through the common bus and outgoing lines.

[0071] like Figure 3 The following is shown Figure 2 A schematic diagram of the equivalent value of a photovoltaic power station, where photovoltaic power is equivalent to a voltage source E. pv A series circuit driven by a photovoltaic power station, wherein the equivalent electromotive force is E. pv The internal impedance of a photovoltaic cell is X. pv The active power of photovoltaics is P pv The reactive power of photovoltaics is Q. pv The photovoltaic current is I pv The photovoltaic terminal voltage is U t The power angle of a photovoltaic system is δ. pv j is a unit complex number. U is the infinite bus voltage, x s for Figure 2 The reactance of the medium-value system. It should be noted that in this embodiment, the impedances of the photovoltaic step-up transformer and the box-type transformer are included in the internal impedance after being equalized, which is different from the existing power system, which generally excludes the parameters of the step-up transformer from the terminal voltage. This will not be elaborated on in the subsequent calculations.

[0072] like Figure 4 The following is shown Figure 2 The equivalent model of the distributed synchronous condenser model, where the distributed synchronous condenser is equivalent to a voltage source E′. con The driven series circuit, in which the equivalent electromotive force of the distributed synchronous condenser is E′ con The transient impedance of the distributed condenser along the d-axis is X′. con The reactive power of the distributed synchronous condenser is Q. con The current of the distributed synchronous condenser is I. con The terminal voltage of the distributed synchronous condenser is U. t The terminal voltage of the distributed synchronous condenser is the same as that of the photovoltaic system.

[0073] because Figure 2 The text describes the parallel operation structure of distributed synchronous condensers and photovoltaic systems, which will... Figure 3 Photovoltaic power plants and Figure 4 The distributed synchronous condenser model in the model is merged into a hybrid isometry model, resulting in the following: Figure 5 The parallel equivalent model of distributed synchronous condensers and photovoltaics shown represents the combined equivalent voltage source E after the parallel connection of distributed synchronous condensers and photovoltaics. equ The driven series circuit, where the electromotive force of the hybrid equivalent model is E equ The internal impedance of the hybrid equivalent model is X. equ The reactive power of the hybrid equivalent model is Q. equ The active power of the hybrid equivalent model is P. equ The current in the hybrid equivalent model is I. equ The terminal voltage of the hybrid equivalent model is U. t φ s The power factor angle for photovoltaics is δ. The power angle for the hybrid equivalent model is δ. equ Note that the hybrid equivalent model here can be understood as the photovoltaic system in which the distributed synchronous condenser and the photovoltaic power station operate in parallel in this embodiment, which will not be explained in detail later.

[0074] Based on the above model, we can derive and calculate the parameter relationships in the model to obtain the relationship between the damping torque provided by the transfer function of the additional damping controller and the rotational speed. The specific steps are as follows: Figure 6 As shown:

[0075] Step S101: Obtain the first linearized relationship between the system's active power and the system's equivalent electromotive force.

[0076] Step S102: Obtain the second linearized relationship between the system's equivalent electromotive force and the transfer function of the additional damping controller.

[0077] Step S103: Based on the first linearization relationship and the second linearization relationship, obtain the linearization relationship between the damping torque and the rotational speed provided by the transfer function of the additional damping controller.

[0078] Below, we will describe the entire derivation and calculation process in detail. It should be noted that the parameters involved in the calculation process can be found in the parameter definitions above, and will not be repeated in subsequent calculations.

[0079] according to Figure 5 As shown, we can obtain the expression relationship of the system's active power as shown in the following formula (1):

[0080]

[0081] Linearizing formula (1) yields formula (2):

[0082]

[0083] Formula (2) is the first linearized relationship between the system's active power and the system's equivalent electromotive force, where the variable with a subscript of 0 is the steady-state value of the corresponding variable, and the variable with Δ is the increment of the corresponding variable.

[0084] As can be seen from equation (2), the damping torque of the hybrid equivalent model is provided by two parts, one part being... This part is determined by the active power characteristics of photovoltaics. In actual photovoltaic power generation, the active power command is given by dispatch and cannot be adjusted, so the damping characteristics of this part are uncontrollable. Another part is... This part can be changed by adjusting reactive power, thus altering ΔE. equ The amplitude.

[0085] Will Figure 5 Model E shown equ Perform dq decomposition, with the q-axis direction parallel to E. equ Since the same relationship exists, and the d-axis is perpendicular to the q-axis, the following relationship can be derived:

[0086] Ucosδ equ =E equ -i d (x d +x s )……(3)

[0087] Usinδ equ =i q (x q +xs )……(4)

[0088] Where: i d For I equ The d-axis component, i q For I equ The q-axis component. d For the d-axis reactance of the hybrid equivalent model, x q The q-axis reactance is a hybrid equivalent model.

[0089] Similarly, regarding the terminal voltage U t Performing dq decomposition yields the corresponding expression:

[0090] U td =i q x q ……(5)

[0091] U tq =E equ -i d x d ……(6)

[0092]

[0093] Among them: U td For U t The d-axis component, U tq For U t The q-axis component.

[0094] Linearizing equations (5), (6), and (7) respectively yields:

[0095] ΔU t =K Uδ Δδ equ +K UE ΔE equ ……(8)

[0096] in:

[0097]

[0098] Define U t The angle between U and U is φ s That is, the power factor angle of photovoltaics, then φ s The expression is as follows:

[0099]

[0100] Assuming U is a constant, linearizing equation (9) yields:

[0101]

[0102] According to formula (10), Δφ can be obtained. s The expression is:

[0103] Δφ s =K Uφ ΔU t +K Iφ ΔI equ ……(11)

[0104] in:

[0105]

[0106] comprehensive Figure 3 , Figure 4 and Figure 5 It is possible to obtain, such as Figure 7 The diagram showing the relationship between the hybrid equivalent model, photovoltaic electromotive force, and synchronous condenser stator current is based on... Figure 7 Using the Law of Cosines, E can be calculated. equ The expression is:

[0107]

[0108] Linearizing equation (12) yields:

[0109] ΔE equ =K EE ΔE pv +K Eδ Δδ equ +K Eφ Δφ s +K EIc ΔI con ……(13)

[0110] in:

[0111] K EE =(E pv0 -I con0 U t0 X′ con cos(δ equ -φ s )0) / E equ0 E Eδ =I con0 E pv0 X′ con sin(δ equ -φ s )0 / E equ0 K Eφ =-I con0 E pv0 X′ con sin(δ equ -φs )0 / E equ0 ,

[0112]

[0113] As can be seen from formula (13), ΔE equ It mainly consists of two parts. The first part mainly consists of the photovoltaic ΔE pv Composition, ΔE pv The first part mainly consists of photovoltaic parameters, structure, and state variables, and is unrelated to distributed synchronous condensers. The second part mainly consists of the ΔI of the distributed synchronous condensers. con The first part is the current of the distributed synchronous condenser. An additional damping controller can be designed in this part. Therefore, this embodiment mainly calculates the second part. However, this part is not related to the power angle of the hybrid isoelectric machine. Therefore, it needs to be converted into the expression of the power angle in order to facilitate the next step of calculating the damping torque.

[0114] according to Figure 5 We can obtain:

[0115]

[0116] Linearizing equation (14) yields:

[0117] ΔE equ =K EU ΔU t +K Eδ1 Δδ equ +K Eφ1 Δφ s +K EI ΔI equ ……(15)

[0118] in:

[0119] K EU =[ΔU t0 -I equ0 X equ cos(δ equ -φ s )0] / E equ0

[0120] K Eδ1 =I equ0 U t0 X equ sin(δ equ -φ s )0 / E equ0

[0121] K Eφ1 =I equ0 U t0 Xequ sin(δ equ -φ s )0 / E equ0

[0122]

[0123] Substituting formula (11) into formula (15), we can obtain ΔI. equ The expression is as follows:

[0124]

[0125] Substituting formula (8) into formula (16), we get:

[0126]

[0127] According to formulas (8), (11) and (17), Δφ can be obtained. s With Δδ equ ΔE equ Relationship:

[0128] Δφ s =K Uφ ΔU t +K Iφ ΔI equ

[0129] ΔU t =K Uδ Δδ equ +K UE ΔE equ

[0130] Δφ s =K φδ Δδ equ +K φE ΔE equ ……(18)

[0131] in,

[0132]

[0133]

[0134] according to Figure 4 The equivalent model of the distributed synchronous condenser shown can be used to derive I. con The expression:

[0135] I con =(E′) con -U t ) / X′ con ……(19)

[0136] Linearizing equation (19) yields:

[0137] ΔI con =(ΔE′) con -ΔU t ) / X′ con ……(20)

[0138] The dynamic model of the camera can be expressed as follows:

[0139]

[0140] Among them, T′ d0 To adjust the excitation winding time constant of the camera when the stator is open, X con To adjust the camera's d-axis reactance, E fd To adjust the camera's excitation voltage.

[0141] We input the model containing excitation and additional damping into formula (21), and we get:

[0142]

[0143] Among them, G damp (s) is the transfer function of the additional damping controller, where s is the Laplace operator. s can generally be written as s = jω d j is the imaginary unit, ω d Let Δω be the angular frequency variable, and δ be the angular frequency variable. equ The corresponding virtual rotational speed is expressed as follows:

[0144]

[0145] In the formula: a1 is the amplification factor, and τ is the time delay constant.

[0146] Substituting formulas (8) and (22) into formula (20) yields:

[0147]

[0148] Among them, K A T is the amplification factor of the voltage regulator of the distributed synchronous condenser. A This is the excitation time constant of the distributed synchronous condenser.

[0149] Substituting formulas (24) and (18) into formula (14) yields:

[0150]

[0151] According to existing technology, the ΔE of photovoltaics can be... pv Using Δδ equInstead, formula (25) is transformed into:

[0152]

[0153] Among them, G Eθ (s) is the transfer function of the photovoltaic active power module.

[0154] Rearranging formula (26) yields:

[0155]

[0156] Equation (27) is the second linearized relationship between the system's equivalent electromotive force and the damping controller's transfer function. It can be seen from equation (27) that changing G... damp The (s) parameter can change ΔE equ The amplitude and phase of G, combined with formula (2), can be used to deduce that if G is changed... damp The parameters can change ΔP equ The amplitude and phase when ΔP equ When the projection onto the Δω axis is positive, it indicates that ΔP equ Provides positive damping, when ΔP equ When the projection onto the Δω axis is negative, it indicates that ΔP equ By providing negative damping, the system active power and the transfer function G of the additional damped controller can be obtained. damp The relationship between (s) is that, through the above calculations, we can obtain the relationship between damping and G. damp (s) indicates an expressive relation.

[0157] Step S20: Based on the linearization relationship, obtain the expression relationship between the damping value and the transfer function of the additional damping controller.

[0158] G can be obtained from the above formula (27). damp (s) provides the damping value:

[0159]

[0160] From formula (28), it can be seen that when G is changed damp Different damping values ​​will be obtained when the (s) parameter is calculated. Therefore, the damping value can be extracted by... damp The optimal parameters of (s) are used to enhance the damping value of the photovoltaic system.

[0161] Step S30: Initialize the transfer function of the additional damping controller, and perform multiple rounds of iterative calculation on the expression relationship according to the preset iterative conditions to obtain the optimal parameter value of the transfer function of the additional damping controller.

[0162] For G dampThe process of extracting the optimal value of the (s) parameter first requires the analysis of G. damp (s) performs initialization, the specific steps are as follows: Figure 8 As shown:

[0163] Step S301: Initialize the system active power and system reactive power according to the preset initial values ​​to obtain the initial values ​​of the transfer function, active power and reactive power.

[0164] Step S302: Based on the initial values ​​of active power and reactive power, obtain the initial values ​​of distributed synchronous condenser current, equivalent electromotive force of photovoltaic power station, system power angle, and power factor angle of photovoltaic power station.

[0165] In the process of extracting optimal parameters, firstly, G... damp (s), P equ and Q equ When performing initialization, it should be noted that the preset initialization values ​​in this embodiment are only preferred rather than specific. The specific initial values ​​can be flexibly set according to the actual situation, and will not be elaborated here.

[0166] For G damp The parameters in (s) and P equ and Q equ The initial value is set to:

[0167] a1(0)=1, τ(0)=0.05, s(0)=j1.26, P equ (0) = 0.01, Q equ (0) = 0.01

[0168] Furthermore, for subsequent calculations, initial values ​​for other parameters were set as follows:

[0169] U t =1.02, U=1,x s =0.05, X pv =0.2

[0170] Based on the model and formula described above, the following expression can be obtained:

[0171]

[0172]

[0173]

[0174]

[0175]

[0176]

[0177] Based on the initial values ​​and expressions above, I can be calculated. con (0), E pv0 (0), δ equ (0) and φ s The initial value of (0) is obtained and substituted into formula (28) to calculate G. damp (s) provides the initial damping value:

[0178]

[0179]

[0180] Among them, I m Find the imaginary part of the transfer function.

[0181] After initializing the damping value, iterative calculations are needed on the initialized expression. Here, it is preferable to set the iteration step size to:

[0182] a1(i) = a1(i-1) + 0.1

[0183] τ(j)=τ(j-1)+0.01

[0184] s(n) = s(n-1) + 0.06

[0185] P equ (k)=P equ (k-1)+0.01

[0186] Q equ (k)=Q equ (k-1)+0.01

[0187] Where i, j, n, k are parameters a1, τ, s, P, respectively. equ and Q equ The number of iterations.

[0188] Furthermore, the iterative expression for the damping value can be obtained as follows:

[0189]

[0190]

[0191] Based on the iteration step size and number of iterations mentioned above, the iterative expression above is iteratively calculated, and the specific steps are as follows: Figure 9 As shown:

[0192] Step S303: According to the preset maximum number of iterations of the angular frequency, the expression relationship is iteratively calculated, and the expression relationship with the minimum damping value is taken as the first expression relationship;

[0193] Step S304: Based on the preset maximum number of iterations of the system active power and the maximum number of iterations of the system reactive power, perform iterative calculation on the first expression relationship, and take the first expression relationship with the maximum damping value as the second expression relationship;

[0194] Step S305: According to the preset maximum number of iterations of the delay time constant, the second expression relationship is iteratively calculated, and the second expression relationship with the maximum damping value is taken as the third expression relationship;

[0195] Step S306: According to the preset maximum number of iterations for the amplification factor, the third expression relationship is iteratively calculated, and the third expression relationship with the maximum damping value is taken as the fourth expression relationship.

[0196] The iterative calculation in this embodiment is performed on the parameters a1, τ, s, and P mentioned above. equ and Q equ Each parameter is subjected to iterative calculations, and specific iteration values ​​are set for the number of iterations for each parameter. It should be noted that the specific values ​​in this embodiment are only a preferred scheme and not a specific limitation.

[0197] First, the parameter s is iterated and calculated n times. Since s = jω d In other words, n is actually the angular frequency ω d The number of iterations, n = n + 1, is calculated by looping n from 0 to 24, yielding M. gmin (i,j,k)=min(M g (i,j,k,0),M g (i,j,k,1),…M g The value of (i,j,k,24));

[0198] Secondly, regarding parameter P equ and Q equ Perform k iterations, k = k + 1, and let k cycle from 0 to 100 to obtain M. mmax =max(M gmin (i,j,0),M gmin (i,j,1),…M gmin The value of (i,j,100));

[0199] Third, perform iterative calculations on the parameter τ j times, where j = j + 1, and let j cycle from 0 to 200 to obtain M. taomax =max(Mmmax (i,0),M mmax (i,1),…M mmax The value of (i, 200));

[0200] Finally, the parameter a1 is iterated i times, i = i + 1, and i is looped from 0 to 200 to obtain M. amax =max(M taomax (0),M taomax (1),…M taomax The value of (200)).

[0201] Through the nested iterations described above, we can obtain the iterative expression corresponding to the optimal parameters. Then, we can use this iterative expression to obtain the optimal value of the parameters. The specific steps are as follows: Figure 10 As shown:

[0202] Step S307: Based on the fourth expression relationship, obtain the first iteration number and the second iteration number corresponding to the delay time constant and the amplification factor, respectively;

[0203] Step S308: Based on the preset optimal parameter expression, the first iteration number, and the second iteration number, obtain the optimal value of the delay time constant and the optimal value of the amplification factor.

[0204] M is obtained through the above iterative calculation. amax After that, you can go to M g Find M amax The position, assuming M amax The corresponding positions are (imax, jmax, kmax, nmin). The optimal parameters can be found based on these positions. The expression for the optimal parameters is:

[0205] τ opt = 0.05 + (jmax - 1) * 0.01

[0206] a opt = 1 + (imax - 1) * 0.1

[0207] In the formula, τ opt For the optimal value of the delay time constant, a opt To achieve the optimal magnification, jmax is M. amax The number of iterations for parameter τ, where imax is M. amax The number of iterations for parameter a1.

[0208] By obtaining the optimal values ​​of the parameters mentioned above, the transfer function G is obtained. dampThe value of is obtained by formula (28), and the damping value of the photovoltaic system is obtained. Obviously, the damping value obtained by this embodiment is an enhanced damping value, thereby realizing the phase compensation of the photovoltaic and distributed synchronous condenser parallel system.

[0209] Please see Figure 11 Based on the same inventive concept, the second embodiment of this invention proposes a phase compensation system for a distributed synchronous condenser in a photovoltaic system, comprising:

[0210] The linearization relationship acquisition module 10 is used to obtain the linearization relationship between damping torque and speed provided by the transfer function of the additional damping controller from the photovoltaic system in which the distributed synchronous condenser and the photovoltaic power station are connected in parallel.

[0211] The expression relationship acquisition module 20 is used to obtain the expression relationship between the damping torque and the transfer function of the additional damping controller based on the linearized relationship;

[0212] The optimal parameter value acquisition module 30 is used to initialize the transfer function of the additional damping controller and perform multiple rounds of iterative calculation on the expression relationship according to preset iterative conditions to obtain the optimal parameter value of the transfer function of the additional damping controller.

[0213] The technical features and effects of the phase compensation system for a distributed synchronous condenser in a photovoltaic system proposed in this embodiment are the same as those of the method proposed in this embodiment, and will not be repeated here. Each module in the aforementioned phase compensation system for a distributed synchronous condenser in a photovoltaic system can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0214] In summary, the present invention proposes a phase compensation method for a distributed synchronous condenser (SSC) in a photovoltaic system. This method obtains a linearized relationship between damping torque and rotational speed provided by the transfer function of an additional damping controller in a photovoltaic system operating in parallel with the SSC and the photovoltaic power station. Based on this linearized relationship, an expression relationship between the damping torque and the additional damping controller transfer function is obtained. The additional damping controller transfer function is initialized, and the expression relationship is iteratively calculated multiple times according to preset iteration conditions to obtain the optimal parameter values ​​of the additional damping controller transfer function. This invention fully utilizes the existing structure of distributed synchronous condensers, analyzes the relationship between the additional damping controller transfer function of the distributed synchronous condenser and the damping torque of the photovoltaic system, and can solve the problem of weak damping provided by existing distributed synchronous condensers. It enhances the damping value of the photovoltaic system, provides a damping optimization configuration calculation method for the actual safety of power systems, and improves the reliability and controllability of operation and maintenance of high-proportion photovoltaic systems.

[0215] The various embodiments in this specification are described in a progressive manner. For directly identical or similar parts of the embodiments, refer to each other. Each embodiment focuses on its differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0216] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this invention, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A phase compensation method for a distributed synchronous condenser in a photovoltaic system, characterized in that, include: The linearized relationship between damping torque and rotational speed is obtained from the transfer function of the additional damping controller in a photovoltaic system where distributed synchronous condensers and photovoltaic power plants are connected in parallel. Based on the linearization relationship, the expression relationship between the damping torque and the transfer function of the additional damping controller is obtained; The transfer function of the additional damping controller is initialized, and the expression relationship is iterated multiple times according to the preset iteration conditions to obtain the optimal parameter value of the transfer function of the additional damping controller.

2. The phase compensation method for distributed synchronous condensers in a photovoltaic system according to claim 1, characterized in that, The specific steps for obtaining the linearized relationship between damping torque and rotational speed provided by the transfer function of the additional damping controller from the photovoltaic system in which the distributed synchronous condenser and the photovoltaic power station are connected in parallel include: Obtain the first linearized relationship between the system's active power and the system's equivalent electromotive force; Obtain the second linearized relationship between the system's equivalent electromotive force and the transfer function of the additional damping controller; Based on the first linearization relationship and the second linearization relationship, the linearization relationship between the damping torque and the rotational speed provided by the transfer function of the additional damping controller is obtained.

3. The phase compensation method for a distributed synchronous condenser in a photovoltaic system according to claim 2, characterized in that, The first linearized relation is calculated using the following formula: In the formula, P equ U represents the system's active power. t X is the terminal voltage. equ For internal impedance, δ equ The variable is the system power angle. Variables with a subscript of 0 are the steady-state values ​​of the corresponding variables, and variables with a Δ are the increments of the corresponding variables. The second linearization relation is calculated using the following formula: In the formula, E equ I is the equivalent electromotive force of the system. con For distributed synchronous condenser current, E pv X is the equivalent electromotive force of a photovoltaic power station. equ For internal impedance, δ equ φ is the system power angle. s K is the power factor angle of the photovoltaic power station. A X′ is the amplification factor of the voltage regulator of the distributed synchronous condenser. con For the d-axis transient impedance of the distributed synchronous condenser, x s T is the equivalent reactance of the system. A T′ is the excitation time constant of the distributed synchronous condenser. d0 X is the excitation winding time constant of the distributed synchronous condenser when the stator is open-circuited. con For the d-axis reactance of the distributed synchronous condenser, U t For the terminal voltage, G Eθ (s) is the transfer function of the photovoltaic active power module, G damp (s) is the transfer function of the additional damped controller, s is the Laplace operator, s = jω d j is the imaginary unit, ω d Let Δω be the angular frequency variable, and δ be the angular frequency variable. equ The corresponding virtual rotational speed, a1 is the amplification factor, τ is the delay time constant, and U td For U t The d-axis component, U tq For U t The q-axis component, x d Let x be the equivalent d-axis reactance of the system. q Let U be the system's equivalent q-axis reactance, and U be the infinite bus voltage. in, K EU =[ΔU t0 -I equ0 X equ cos(δ equ -f s )0] / E equ0 K Eφ1 =I equ0 U t0 X equ sin(δ equ -f s )0 / E equ0 K Eδ1 =I equ0 U t0 X equ sin(δ equ -f s )0 / E equ0。 4. The phase compensation method for distributed synchronous condensers in a photovoltaic system according to claim 1, characterized in that, The relationship between the damping torque and the transfer function of the additional damping controller is calculated using the following formula: In the formula, G damp (s) is the transfer function of the additional damped controller, s is the Laplace operator, and M g The damping value provided by the transfer function, I m To find the imaginary part of the transfer function, I con For distributed synchronous condenser current, E pv X is the equivalent electromotive force of a photovoltaic power station. equ For internal impedance, δ equ φ is the system power angle. s K is the power factor angle of the photovoltaic power station. A X′ is the amplification factor of the voltage regulator of the distributed synchronous condenser. con For the d-axis transient impedance of the distributed synchronous condenser, x s T is the equivalent reactance of the system. A T′ is the excitation time constant of the distributed synchronous condenser. d0 X is the excitation winding time constant of the distributed synchronous condenser when the stator is open-circuited. con The d-axis reactance of the distributed synchronous condenser.

5. The phase compensation method for a distributed synchronous condenser in a photovoltaic system according to claim 1, characterized in that, The specific steps for initializing the transfer function of the additional damping controller include: The system active power and system reactive power are initialized according to the preset initial values ​​to obtain the initial values ​​of the transfer function, active power and reactive power. Based on the initial values ​​of active power and reactive power, the initial values ​​of distributed synchronous condenser current, equivalent electromotive force of photovoltaic power station, system power angle, and power factor angle of photovoltaic power station are obtained.

6. The phase compensation method for a distributed synchronous condenser in a photovoltaic system according to claim 1, characterized in that, The preset iteration conditions include a preset iteration step size and a preset maximum number of iterations. The maximum number of iterations includes the maximum number of iterations for angular frequency, the maximum number of iterations for system active power, the maximum number of iterations for system reactive power, the maximum number of iterations for delay time constant, and the maximum number of iterations for amplification factor.

7. The phase compensation method for a distributed synchronous condenser in a photovoltaic system according to claim 6, characterized in that, The specific steps for performing multiple rounds of iterative calculations on the expression relationship according to preset iterative conditions include: The expression relationship is iteratively calculated based on the preset maximum number of iterations of the angular frequency, and the expression relationship with the minimum damping value is taken as the first expression relationship; Based on the preset maximum number of iterations for the system active power and the maximum number of iterations for the system reactive power, the first expression relationship is iteratively calculated, and the first expression relationship with the maximum damping value is taken as the second expression relationship; The second expression relationship is iteratively calculated based on the preset maximum number of iterations of the delay time constant, and the second expression relationship with the maximum damping value is taken as the third expression relationship; Based on the preset maximum number of iterations for the amplification factor, the third expression relationship is iteratively calculated, and the third expression relationship with the maximum damping value is taken as the fourth expression relationship.

8. The phase compensation method for a distributed synchronous condenser in a photovoltaic system according to claim 7, characterized in that, The specific steps for obtaining the optimal parameter values ​​of the additional damping controller transfer function include: Based on the fourth expression relationship, the number of the first iteration and the number of the second iteration corresponding to the delay time constant and the amplification factor are obtained, respectively. Based on the preset optimal parameter expression, the first iteration number, and the second iteration number, the optimal value of the delay time constant and the optimal value of the amplification factor are obtained.

9. The phase compensation method for a distributed synchronous condenser in a photovoltaic system according to claim 8, characterized in that, The optimal parameter expression is calculated using the following formula: t opt =0.05+(jmax-1)*0.01 a opt =1+(imax-1)*0.1 In the formula, τ opt For the optimal value of the delay time constant, a opt To determine the optimal magnification factor, jmax represents the first iteration number, and imax represents the second iteration number.

10. A phase compensation system for a distributed synchronous condenser in a photovoltaic system, characterized in that, include: The linearization relationship acquisition module is used to obtain the linearization relationship between damping torque and rotational speed provided by the transfer function of the additional damping controller from a photovoltaic system in which distributed synchronous condensers and photovoltaic power plants are connected in parallel. The expression relationship acquisition module is used to obtain the expression relationship between the damping torque and the transfer function of the additional damping controller based on the linearized relationship; The optimal parameter value acquisition module is used to initialize the transfer function of the additional damping controller and perform multiple rounds of iterative calculation on the expression relationship according to preset iterative conditions to obtain the optimal parameter value of the transfer function of the additional damping controller.

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