Economic evaluation method of controllable phase shifter access power system

Abstract

The invention discloses an economic evaluation method for accessing controllable phase shifters into a power system, which comprises the following steps of: constructing a power system application scene demand set, acquiring a plurality of controllable phase shifter access schemes and the investment cost of each controllable phase shifter access scheme, and then establishing a power system application scene demand set under each controllable phase shifter access scheme. Obtaining the tail end power of the power system after the controllable phase shifter is connected, and obtaining the electrical stress change range of the source load network after the controllable phase shifter is connected and the transient electrical quantity change characteristic of the power system after the controllable phase shifter is connected based on the tail end power of the power system; and further obtaining the total operation cost and the risk cost of each controllable phase shifter access scheme, and performing economic evaluation on the controllable phase shifter access power system based on the investment cost, the total operation cost and the risk cost of each controllable phase shifter access scheme. The method can comprehensively evaluate the safety and reliability after the phase shifter engineering is accessed, and provides a scientific basis for the investment decision of a power system.

Description

Technical Field

[0001] The invention belongs to the technical field of controllable phase shifters, and in particular relates to an economic evaluation method for connecting a controllable phase shifter to a power system. Background Art

[0002] Engineering economic evaluation can help decision makers choose appropriate engineering projects and maximize the role of resources, thereby avoiding mistakes in investment decisions, ensuring that resources are used reasonably and achieving satisfactory economic results. Engineering economic evaluation methods are widely used in different engineering fields, and phase shifters, as important components in electronic engineering, are widely used in various fields. With the continuous advancement of technology and changes in market demand, the economic evaluation of phase shifter engineering is particularly important.

[0003] In power system decision-making, economic efficiency is an important aspect of evaluating the rationality of decision-making. Commonly used engineering economic evaluation theories mainly include traditional minimum cost evaluation method and benefit-cost evaluation method. Traditional minimum cost evaluation method is a single-attribute economic evaluation method. Its goal is to minimize the cost of the project throughout its life cycle, including maintenance costs, taxes, and investment costs. It is suitable for standard-driven and cost-minimizing scenarios. Since this method only aims to minimize costs and does not consider benefits or other value attributes, it limits the comprehensive evaluation of project economic efficiency. In addition, this method cannot adapt to multi-attribute decision-making needs and lacks corresponding flexibility. Benefit-cost evaluation method is a multi-attribute economic evaluation method. It selects the optimal solution by calculating the ratio of benefits to costs. This method allows the project to exceed the power supply obligation of the power company and only needs to meet the benefit limit. It is particularly suitable for evaluating special maintenance projects and demand-side projects. However, relying solely on the benefit-cost ratio may ignore other important factors, such as risk, project feasibility, and practical operability. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention proposes an economic evaluation method for connecting a controllable phase shifter to a power system.

[0005] The technical solution of the present invention is as follows:

[0006] An economic evaluation method for connecting a controllable phase shifter to a power system, comprising:

[0007] Based on the power system application scenario requirements related to power flow control, harmonic control, reactive power compensation, and voltage and frequency support, a power system application scenario requirement set with several requirement elements is constructed;

[0008] Obtaining a controllable phase shifter access scheme under each demand element in the power system application scenario demand set and an investment cost of each controllable phase shifter access scheme;

[0009] Under each controllable phase shifter access scheme, the terminal power of the power system after the controllable phase shifter is accessed is obtained, and based on the terminal power of the power system, the range of change of electrical stress of the source-load-grid after the controllable phase shifter is accessed and the transient electrical quantity change characteristics of the power system after the controllable phase shifter is accessed are obtained;

[0010] Based on the range of electrical stress variation of the source-load-grid after the controllable phase shifter is connected to each controllable phase shifter access scheme and the transient electrical quantity variation characteristics of the system after the phase shifter is connected, the total operating cost and risk cost of each controllable phase shifter access scheme are obtained;

[0011] The economic feasibility of connecting controllable phase shifters to the power system is evaluated based on the investment cost, total operating cost and risk cost of each controllable phase shifter connection scheme.

[0012] Furthermore, the demand element in the power system application scenario demand set is any one application scenario demand or a combination of multiple application scenario demands.

[0013] Furthermore, the harmonic control in the power system application scenario requirements is used to control the total harmonic distortion, and the calculation method of the total harmonic distortion is as follows:

[0014]

[0015] Where THD is total harmonic distortion; They respectively represent the total effective value, the effective value of the first harmonic, and the square of the effective value of the nth harmonic of a periodic signal; DF is called the distortion index, which represents the ratio of the effective value of the first harmonic to the total effective value.

[0016] Furthermore, the reactive power compensation in the power system application scenario requirement is used to realize reactive power compensation in the power system, and the calculation method of the reactive power compensation amount in the reactive power compensation is as follows:

[0017]

[0018] In the formula, Q c is the reactive power compensation amount; V is the voltage; X c is the capacitive reactance of the capacitor; ω is the system angular frequency.

[0019] Furthermore, the specific method for obtaining the controllable phase shifter access scheme under each demand element in the power system application scenario demand set and the investment cost of each controllable phase shifter access scheme includes:

[0020] For the demand elements of power system application scenarios that include power flow control and / or reactive power compensation, a multi-point distributed access solution is adopted in which controllable phase shifters are connected in a multi-point distributed manner in multiple key load nodes and transmission lines; for the multi-point distributed access solution, the investment cost includes the total equipment cost C device 、Installation cost C install and control the communication system cost C control ;

[0021] For the demand elements of power system application scenarios that include harmonic control, a centralized access solution is adopted in which the controllable phase shifter is centrally accessed at the main substation and load center. For the centralized access solution, the investment cost includes the total equipment cost, the filter cost C filter and installation costs and control communications system costs;

[0022] For the demand elements of the power system application scenario that include voltage and frequency support, a dynamically adjustable access scheme is adopted in the fluctuating load area of ​​the renewable energy access point to dynamically adjust the access controllable phase shifter; for the dynamically adjustable access scheme, the investment cost includes the total equipment cost, the dynamic adjustment module cost C dynamic and installation costs and control communications system costs;

[0023] For demand elements containing multiple power system application scenario requirements, the controllable phase shifter access scheme corresponding to each power system application scenario requirement is used as a sub-scheme, and the sub-schemes are combined to form a controllable phase shifter access scheme, and the investment cost of each sub-scheme is accumulated.

[0024] Furthermore, the method for calculating the terminal power of the power system after the controllable phase shifter is connected is as follows:

[0025]

[0026] Where U s and U r are the voltage at the beginning and end of the controllable phase shifter respectively; X L is the reactance value between the first and last nodes of the phase shifter; α pst is the phase shift angle; δ is the angle between apparent power and active power.

[0027] Furthermore, the source-load-grid electrical stress change includes current stress change and power factor change; the power system transient electrical quantity change includes voltage sag depth and frequency deviation.

[0028] Furthermore, the specific steps of obtaining the range of electrical stress variation of the source-load-grid after the controllable phase shifter is connected and the transient electrical quantity variation characteristics of the power system after the controllable phase shifter is connected based on the terminal power of the power system include:

[0029] Calculate the system current I1 before connecting the controllable phase shifter:

[0030]

[0031] Where, P1 is the terminal power before accessing the controllable phase shifter; is the power factor angle before connection; U1 is the voltage before connection.

[0032] Calculate the system current I2 after connecting the controllable phase shifter:

[0033]

[0034] Where, P2 is the terminal power after connecting to the controllable phase shifter; is the power factor angle after connection; U2 is the voltage after connection.

[0035] Compare the system current I1 before the phase shifter is connected and the system current I2 after the controllable phase shifter is connected to determine the current stress change ΔI=I2-I1;

[0036] Compare the power factor angle before connection And the power factor angle after connection Determine the power factor change

[0037] The voltage sag depth:

[0038]

[0039] Where V initial is the initial voltage; P fault The power injected into the system during a fault; P total is the total system power.

[0040] The frequency offset variation:

[0041]

[0042] Where ΔP is the change in system load; M is the frequency response constant of the system.

[0043] Furthermore, the specific steps of obtaining the total operating cost and risk cost of each controllable phase shifter access scheme based on the source-load-grid electrical stress variation range after the controllable phase shifter corresponding to each controllable phase shifter access scheme is connected and the transient electrical quantity variation characteristics of the system after the phase shifter is connected include:

[0044] The total operating cost of the controllable phase shifter access solution is calculated as follows:

[0045]

[0046] In the formula, C run is the total operating cost; k I is the current loss coefficient; is the power factor variation coefficient; k V is the voltage sag coefficient; k f is the frequency shift coefficient; t is the operation time of the controllable phase shifter under consideration;

[0047] The risk cost of the controllable phase shifter access solution is calculated as follows:

[0048] C risk =P I ×C I +P pf ×C pf +P V ×C V +P f ×C f

[0049] Where P I is the ratio of the current stress change to the current safety margin; C I is the equipment damage cost; P pf is the ratio of the power factor change to the given change margin; C pf The cost of additional energy consumption caused by power factor changes; V is the ratio of voltage sag depth to safety margin; C V P is the production loss caused by the depth of voltage sag; f is the ratio of frequency offset to setting margin; C f Cost of equipment damage caused by current surge.

[0050] Furthermore, the specific steps of conducting an economic evaluation of connecting a controllable phase shifter to a power system based on the investment cost, total operating cost and risk cost of each controllable phase shifter connection scheme include:

[0051] Taking the investment cost, total operating cost and risk cost of each controllable phase shifter access scheme as evaluation indicators, an economic evaluation model for the access of controllable phase shifters to the power system is constructed:

[0052]

[0053] Where, E is the economic evaluation result; C in1 , C in2 …C inn is the investment cost of the controllable phase shifter engineering solution in different application scenarios, C run1 , C run2 …C runnis the total operating cost of the controllable phase shifter engineering solution in different application scenarios, W1, W2…W n is the weight of different application scenarios, C risk is the risk cost;

[0054] An economic evaluation result of each controllable phase shifter access scheme corresponding to the economic evaluation model is obtained.

[0055] An electronic device comprises a memory and a processor, wherein the memory stores a computer program, and the processor is used to call and run the computer program stored in the memory to execute any of the methods described above.

[0056] A computer-readable storage medium stores a computer program, wherein the computer program implements the steps of any of the above methods when executed by a processor.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] The present invention proposes an economic evaluation method for accessing a controllable phase shifter to a power system. The method constructs a power system application scenario demand set with a plurality of demand elements, obtains a controllable phase shifter access scheme under each demand element in the power system application scenario demand set and the investment cost of each controllable phase shifter access scheme, and then obtains the terminal power of the power system after accessing the controllable phase shifter under each controllable phase shifter access scheme, and based on the terminal power of the power system, obtains the source-load-grid electrical stress variation range after the controllable phase shifter is accessed and the transient electrical quantity variation characteristics of the power system after the controllable phase shifter is accessed, and finally, based on the source-load-grid electrical stress variation range after the controllable phase shifter is accessed corresponding to each controllable phase shifter access scheme and the transient electrical quantity variation characteristics of the system after the phase shifter is accessed, obtains the total operating cost and risk cost of each controllable phase shifter access scheme, and performs an economic evaluation of accessing the controllable phase shifter to the power system based on the investment cost, total operating cost and risk cost of each controllable phase shifter access scheme. This method can comprehensively evaluate the safety and reliability of the phase shifter project after access, provide a variety of controllable phase shifter access schemes, and conduct economic evaluation of these schemes, providing a scientific basis for power system investment decisions. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 Flow chart of the economic evaluation method of connecting a controllable phase shifter to a power system in an embodiment. DETAILED DESCRIPTION

[0060] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent modifications of the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0061] Embodiment 1:

[0062] The present invention provides an economic evaluation method for connecting a controllable phase shifter to a power system. Figure 1 As shown, including:

[0063] S1. Based on the power system application scenario requirements related to power flow control, harmonic control, reactive power compensation, and voltage and frequency support, a power system application scenario requirement set with several requirement elements is constructed;

[0064] S2. Obtaining a controllable phase shifter access scheme under each demand element in the power system application scenario demand set and an investment cost of each controllable phase shifter access scheme;

[0065] S3. Under each controllable phase shifter access scheme, obtain the terminal power of the power system after the controllable phase shifter is accessed, and based on the terminal power of the power system, obtain the range of change of electrical stress of the source-load-grid after the controllable phase shifter is accessed and the transient electrical quantity change characteristics of the power system after the controllable phase shifter is accessed;

[0066] S4. Obtain the total operating cost and risk cost of each controllable phase shifter access scheme based on the range of electrical stress variation of the source-load-grid after the controllable phase shifter is connected to each controllable phase shifter access scheme and the transient electrical quantity variation characteristics of the system after the phase shifter is connected;

[0067] S5. An economic evaluation of connecting the controllable phase shifter to the power system is performed based on the investment cost, total operating cost and risk cost of each controllable phase shifter connection scheme.

[0068] Embodiment 2:

[0069] This embodiment is further designed on the basis of the first embodiment in that the demand element in the power system application scenario demand set in this example is any one application scenario demand or a combination of multiple application scenario demands.

[0070] The following example further illustrates the demand elements in the power system application scenario demand set. The power system application scenario demands set in this example are power flow control, harmonic control, reactive power compensation, and voltage and frequency support, which are denoted as a, b, c, and d respectively. The constructed power system application scenario demand set is {a, ab, abc, abd, abcd, ac, acd, ad, b, bc, bcd, bd, c, cd, d}.

[0071] Embodiment three:

[0072] This embodiment is further designed on the basis of the first embodiment in that the harmonic control in the power system application scenario requirement in this embodiment is used to control the total harmonic distortion, and the calculation method of the total harmonic distortion is as follows:

[0073]

[0074] Where THD is total harmonic distortion; They respectively represent the total effective value, the effective value of the first harmonic, and the square of the effective value of the nth harmonic of a periodic signal; DF is called the distortion index, which represents the ratio of the effective value of the first harmonic to the total effective value.

[0075] Embodiment 4:

[0076] This embodiment is further designed on the basis of the first embodiment in that the reactive power compensation in the power system application scenario requirement in this embodiment is used to realize reactive power compensation in the power system, and the calculation method of the reactive power compensation amount in the reactive power compensation is as follows:

[0077]

[0078] In the formula, Q c is the reactive power compensation amount; V is the voltage; X c is the capacitive reactance of the capacitor; ω is the system angular frequency.

[0079] Embodiment five:

[0080] This embodiment is further designed on the basis of the first embodiment in that the specific method of obtaining the controllable phase shifter access scheme under each demand element in the power system application scenario demand set and the investment cost of each controllable phase shifter access scheme in this embodiment includes:

[0081] For the demand elements of power system application scenarios that include power flow control and / or reactive power compensation, a multi-point distributed access solution is adopted in which controllable phase shifters are connected in a multi-point distributed manner in multiple key load nodes and transmission lines; for the multi-point distributed access solution, the investment cost includes the total equipment cost C device 、Installation cost C install and control the communication system cost C control ;

[0082] For the demand elements of power system application scenarios that include harmonic control, a centralized access solution is adopted in which the controllable phase shifter is centrally accessed at the main substation and load center. For the centralized access solution, the investment cost includes the total equipment cost, the filter cost C filter and installation costs and control communications system costs;

[0083] For the demand elements of the power system application scenario that include voltage and frequency support, a dynamically adjustable access solution is adopted in the fluctuating load area of ​​the renewable energy access point to dynamically adjust the access controllable phase shifter. For the dynamically adjustable access solution, the investment cost includes the total equipment cost, the dynamic adjustment module cost C dynamic and installation costs and control communications system costs;

[0084] For demand elements containing multiple power system application scenario requirements, the controllable phase shifter access scheme corresponding to each power system application scenario requirement is used as a sub-scheme, and the sub-schemes are combined to form a controllable phase shifter access scheme, and the investment cost of each sub-scheme is accumulated.

[0085] Embodiment six:

[0086] This embodiment is further designed on the basis of the first embodiment in that the method for calculating the terminal power of the power system after the controllable phase shifter is connected in this embodiment is as follows:

[0087]

[0088] Where U s and U r are the voltage at the beginning and end of the controllable phase shifter respectively; X L is the reactance value between the first and last nodes of the phase shifter; α pst is the phase shift angle; δ is the angle between apparent power and active power.

[0089] Embodiment seven:

[0090] This embodiment is further designed on the basis of the first embodiment in that the source-load-grid electrical stress change in this example includes the current stress change and the power factor change; the power system transient electrical quantity change includes the voltage sag depth and the frequency deviation.

[0091] Embodiment eight:

[0092] This embodiment is further designed on the basis of the seventh embodiment in that, in this embodiment, based on the terminal power of the power system, the specific steps of obtaining the range of change of the electrical stress of the source-load-grid after the controllable phase shifter is connected and the transient electrical quantity change characteristics of the power system after the controllable phase shifter is connected include:

[0093] Calculate the system current I1 before connecting the controllable phase shifter:

[0094]

[0095] Where, P1 is the terminal power before accessing the controllable phase shifter; is the power factor angle before connection; U1 is the voltage before connection.

[0096] Calculate the system current I2 after connecting the controllable phase shifter:

[0097]

[0098] Where, P2 is the terminal power after connecting to the controllable phase shifter; is the power factor angle after connection; U2 is the voltage after connection.

[0099] Compare the system current I1 before the phase shifter is connected and the system current I2 after the controllable phase shifter is connected to determine the current stress change ΔI=I2-I1;

[0100] Compare the power factor angle before connection And the power factor angle after connection Determine the power factor change

[0101] The voltage sag depth:

[0102]

[0103] Where V initial is the initial voltage; P fault The power injected into the system during a fault; P total is the total system power.

[0104] The frequency offset variation:

[0105]

[0106] Where ΔP is the change in system load; M is the frequency response constant of the system.

[0107] Embodiment nine:

[0108] This embodiment is further designed on the basis of the eighth embodiment in that the specific steps of obtaining the total operating cost and risk cost of each controllable phase shifter access scheme based on the source-load-grid electrical stress variation range after the controllable phase shifter access scheme corresponding to each controllable phase shifter access scheme and the transient electrical quantity variation characteristics of the system after the phase shifter access comprises:

[0109] The total operating cost of the controllable phase shifter access solution is calculated as follows:

[0110]

[0111] In the formula, C run is the total operating cost; k I is the current loss coefficient; is the power factor variation coefficient; k V is the voltage sag coefficient; kf is the frequency shift coefficient; t is the operation time of the controllable phase shifter under consideration;

[0112] The risk cost of the controllable phase shifter access solution is calculated as follows:

[0113] C risk =P I ×C I +P pf ×C pf +P V ×C V +P f ×C f

[0114] Where P I is the ratio of the current stress change to the current safety margin; C I is the equipment damage cost; P pf is the ratio of the power factor change to the given change margin; C pf The cost of additional energy consumption caused by power factor changes; V is the ratio of voltage sag depth to safety margin; C V P is the production loss caused by the depth of voltage sag; f is the ratio of frequency offset to setting margin; C f Cost of equipment damage caused by current surge.

[0115] Embodiment ten:

[0116] This embodiment is further designed on the basis of the ninth embodiment in that the specific steps of evaluating the economic feasibility of connecting the controllable phase shifter to the power system based on the investment cost, total operation cost and risk cost of each controllable phase shifter connection scheme in this embodiment include:

[0117] Taking the investment cost, total operating cost and risk cost of each controllable phase shifter access scheme as evaluation indicators, an economic evaluation model for the access of controllable phase shifters to the power system is constructed:

[0118]

[0119] Where, E is the economic evaluation result. The closer the value of E is to 1, the better the economic efficiency of the phase shifter engineering solution. in1 , C in2 …C inn is the investment cost of the controllable phase shifter engineering solution in different application scenarios, C run1 , C run2 …C runn is the total operating cost of the controllable phase shifter engineering solution in different application scenarios, W1, W2…W n is the weight of different application scenarios, Crisk is the risk cost;

[0120] An economic evaluation result of each controllable phase shifter access scheme corresponding to the economic evaluation model is obtained.

[0121] Embodiment eleven:

[0122] An electronic device includes a memory and a processor, wherein the memory stores a computer program, and the processor is used to call and run the computer program stored in the memory to execute the method described in any of the above embodiments.

[0123] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method described in any of the above embodiments are implemented.

[0124] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for evaluating the economic performance of a controllable phase shifter connected to a power system, characterized in that: include: Based on the power system application scenario requirements related to power flow control, harmonic control, reactive power compensation, and voltage and frequency support, a power system application scenario requirement set with several requirement elements is constructed; Obtaining a controllable phase shifter access scheme under each demand element in a power system application scenario demand set and an investment cost of each controllable phase shifter access scheme; Under each controllable phase shifter access scheme, the terminal power of the power system after the controllable phase shifter is accessed is obtained, and based on the terminal power of the power system, the range of change of electrical stress of the source-load-grid after the controllable phase shifter is accessed and the transient electrical quantity change characteristics of the power system after the controllable phase shifter is accessed are obtained; Based on the range of electrical stress variation of the source-load-grid after the controllable phase shifter is connected to each controllable phase shifter access scheme and the transient electrical quantity variation characteristics of the system after the phase shifter is connected, the total operating cost and risk cost of each controllable phase shifter access scheme are obtained; The economic feasibility of connecting controllable phase shifters to the power system is evaluated based on the investment cost, total operating cost and risk cost of each controllable phase shifter connection scheme.

2. The economic evaluation method for connecting a controllable phase shifter to a power system according to claim 1, characterized in that: The demand element in the power system application scenario demand set is any one application scenario demand or a combination of multiple application scenario demands.

3. The economic evaluation method for connecting a controllable phase shifter to a power system according to claim 1, characterized in that: The harmonic control in the power system application scenario requirements is used to control the total harmonic distortion. The calculation method of the total harmonic distortion is as follows: Where THD is total harmonic distortion; They respectively represent the total effective value, the effective value of the first harmonic, and the square of the effective value of the nth harmonic of a periodic signal; DF is called the distortion index, which represents the ratio of the effective value of the first harmonic to the total effective value.

4. The economic evaluation method for connecting a controllable phase shifter to a power system according to claim 1, characterized in that: The reactive power compensation in the power system application scenario requirement is used to realize reactive power compensation in the power system. The calculation method of the reactive power compensation amount in the reactive power compensation is as follows: In the formula, Q c is the reactive power compensation amount; V is the voltage; X c is the capacitive reactance of the capacitor; ω is the system angular frequency.

5. The economic evaluation method for connecting a controllable phase shifter to a power system according to claim 1, characterized in that: The specific method for obtaining the controllable phase shifter access scheme under each demand element in the power system application scenario demand set and the investment cost of each controllable phase shifter access scheme includes: For the demand elements of power system application scenarios that include power flow control and / or reactive power compensation, a multi-point distributed access solution is adopted in which controllable phase shifters are connected in a multi-point distributed manner in multiple key load nodes and transmission lines; for the multi-point distributed access solution, the investment cost includes the total equipment cost C device 、Installation cost C install and control the communication system cost C control ; For the demand elements of power system application scenarios that include harmonic control, a centralized access solution is adopted in which the controllable phase shifter is centrally accessed at the main substation and load center. For the centralized access solution, the investment cost includes the total equipment cost, the filter cost C filter and installation costs and control communications system costs; For the demand elements of the power system application scenario that include voltage and frequency support, a dynamically adjustable access scheme is adopted in the fluctuating load area of ​​the renewable energy access point to dynamically adjust the access controllable phase shifter; for the dynamically adjustable access scheme, the investment cost includes the total equipment cost, the dynamic adjustment module cost C dynamic and installation costs and control communications system costs; For demand elements containing multiple power system application scenario requirements, the controllable phase shifter access scheme corresponding to each power system application scenario requirement is used as a sub-scheme, and the sub-schemes are combined to form a controllable phase shifter access scheme, and the investment cost of each sub-scheme is accumulated.

6. The economic evaluation method for connecting a controllable phase shifter to a power system according to claim 1, characterized in that: The calculation method of the terminal power of the power system after the controllable phase shifter is connected is as follows: Where U s and U r are the voltage at the beginning and end of the controllable phase shifter respectively; X L is the reactance value between the first and last nodes of the phase shifter; α pst is the phase shift angle; δ is the angle between apparent power and active power.

7. The economic evaluation method for connecting a controllable phase shifter to a power system according to claim 1, characterized in that: The source-load-grid electrical stress variation includes current stress variation and power factor variation; the power system transient electrical quantity variation includes voltage sag depth and frequency deviation.

8. The economic evaluation method for connecting a controllable phase shifter to a power system according to claim 7, characterized in that: The specific steps of obtaining the range of electrical stress variation of the source-load-grid after the controllable phase shifter is connected and the transient electrical quantity variation characteristics of the power system after the controllable phase shifter is connected based on the power system terminal power include: Calculate the system current I1 before connecting to the controllable phase shifter: Where, P1 is the terminal power before accessing the controllable phase shifter; is the power factor angle before connection; U1 is the voltage before connection. Calculate the system current I2 after connecting the controllable phase shifter: Where, P2 is the terminal power after connecting to the controllable phase shifter; is the power factor angle after connection; U2 is the voltage after connection. Compare the system current I1 before the phase shifter is connected and the system current I2 after the controllable phase shifter is connected to determine the current stress change ΔI=I2-i1; Compare the power factor angle before connection And the power factor angle after connection Determine the power factor change The voltage sag depth: Where V initial is the initial voltage; P fault The power injected into the system during a fault; P total is the total system power. The frequency offset variation: Where ΔP is the change in system load; M is the frequency response constant of the system.

9. The economic evaluation method for connecting a controllable phase shifter to a power system according to claim 8, characterized in that: The specific steps of obtaining the total operating cost and risk cost of each controllable phase shifter access scheme based on the range of electrical stress variation of the source-load-grid after the controllable phase shifter corresponding to each controllable phase shifter access scheme is connected and the transient electrical quantity variation characteristics of the system after the phase shifter is connected include: The total operating cost of the controllable phase shifter access solution is calculated as follows: In the formula, C run is the total operating cost; k I is the current loss coefficient; is the power factor variation coefficient; k V is the voltage sag coefficient; k f is the frequency shift coefficient; t is the operation time of the controllable phase shifter under consideration; The risk cost of the controllable phase shifter access solution is calculated as follows: C risk =P I ×C I +P pf ×C pf +P V ×C V +P f ×C f Where P I is the ratio of the current stress change to the current safety margin; C I is the equipment damage cost; P pf is the ratio of the power factor change to the given change margin; C pf The cost of additional energy consumption caused by power factor changes; V is the ratio of voltage sag depth to safety margin; C V P is the production loss caused by the depth of voltage sag; f is the ratio of frequency deviation to setting margin; C f Cost of equipment damage caused by current surge.

10. The economic evaluation method for connecting a controllable phase shifter to a power system according to claim 9, characterized in that: The specific steps of conducting an economic evaluation of the controllable phase shifter access to the power system based on the investment cost, total operating cost and risk cost of each controllable phase shifter access scheme include: Taking the investment cost, total operating cost and risk cost of each controllable phase shifter access scheme as evaluation indicators, an economic evaluation model for the access of controllable phase shifters to the power system is constructed: Where, E is the economic evaluation result; C in1 , C in2 …C inn is the investment cost of the controllable phase shifter engineering solution in different application scenarios, C run1 , C run2 …C runn is the total operating cost of the controllable phase shifter engineering solution in different application scenarios, W1, W2…W n is the weight of different application scenarios, C risk is the risk cost; An economic evaluation result of each controllable phase shifter access scheme corresponding to the economic evaluation model is obtained.

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