Oscillation influence analysis method and equipment based on high-voltage direct current system, and medium

Abstract

The invention discloses an oscillation influence analysis method and device based on a high-voltage direct-current system and a medium, and the method comprises the steps: building a state control model of a partition asynchronous interconnection system based on a high-voltage direct-current frequency controller; analyzing direct-current power oscillation based on a state control model of the partition asynchronous interconnection system; the process of analyzing the direct-current power oscillation comprises the following steps of: analyzing an interval oscillation mode of a partitioned power grid without considering direct-current frequency control, and solving an interval oscillation angular frequency; and based on the solved interval oscillation angular frequency, considering a direct current frequency control effect, assuming that the interval oscillation angular frequency of the partitioned power grid is changed in a set threshold range by direct current frequency control, and solving modal damping when high-voltage direct current frequency control is stopped and modal damping when high-voltage direct current frequency control is activated. By considering the influence of the HVDC frequency control parameters on high-voltage direct-current power oscillation and inter-region oscillation in the asynchronous alternating-current power grid, risk control can be carried out on the power grid in time, and the risk of cascading failure increase is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power system dynamic analysis, and in particular to an oscillation influence analysis method, equipment and medium based on a high voltage direct current system. Background Art

[0002] High-voltage direct current (HVDC) systems have high rated power and fast power regulation capabilities. They are often used to connect asynchronous AC grids, such as the North-South Island interconnection of the New Zealand power grid and the China Southern Power Grid. They play an important role in providing grid services for asynchronous interconnected systems and have been proven to be effective in providing power oscillation damping (POD) for AC / DC parallel power systems. In recent years, with the increase in the penetration rate of renewable energy generation and poor frequency support capabilities, the frequency regulation of asynchronous interconnected systems has faced increasing challenges. Therefore, a lot of research has been conducted on the frequency support of high-voltage direct current transmission systems.

[0003] The frequency control methods of HVDC systems found in existing studies are generally similar. In LCC-HVDC systems, additional frequency control modules are usually integrated into the DC current control loop, or in VSC-HVDC, additional frequency control modules are integrated into the active power control loop to adjust the active power or DC current reference value to achieve frequency regulation. Typical examples in actual DC transmission projects include frequency limit control and frequency maintenance control. Due to the long geographical distance between converter stations, there is inevitably a time delay and a risk of communication interruption when the frequency information is transmitted from the inverter side to the rectifier.

[0004] Therefore, DC voltage is used as a medium to transmit the frequency information on the inverter side, and a frequency-DC voltage (f / Vdc) droop loop is introduced and implemented in the inverter DC voltage controller to adjust the DC voltage on the inverter side, thereby transmitting the frequency deviation information. The stability of the LCC-HVDC system using this control method has also been verified. However, the above research did not consider the power oscillation problem in DC transmission frequency control. For power systems, or complex dynamic systems, steady-state operation should be maintained, that is, no periodic oscillations occur. High damping of the system is a necessary condition for stable operation of the system.

[0005] In fact, under dedicated frequency control, the DC power will experience oscillations. In addition, HVDC frequency control also affects inter-regional oscillations within each asynchronous AC grid. Currently, the discussion of HVDC power oscillations caused by the dynamic interaction of DC power with the asynchronous AC grid frequency is insufficient. Insufficient analysis of HVDC power oscillations and inter-regional oscillations caused by the dynamic interaction of DC power with the asynchronous AC grid frequency can easily lead to reduced stability of the High Voltage Direct Current (HVDC) system and the inability to regulate power according to the induced oscillations. If these effects are not analyzed, it may lead to an increased risk of cascading failures. Summary of the invention

[0006] The technical problem to be solved by the present invention is that the high-voltage direct current power oscillation and inter-regional oscillation caused by the dynamic interaction between direct current power and the frequency of an asynchronous alternating current power grid are not considered, resulting in an increased risk of cascading failures. The purpose is to provide an oscillation impact analysis method, device and medium based on a high-voltage direct current system. By constructing a partitioned asynchronous interconnected system state control model, the influence of HVDC frequency control parameters on the power and inter-regional oscillations in the asynchronous alternating current power grid is considered based on the asynchronous interconnected system state control model, and the influence of HVDC power oscillations in the frequency dead zone is analyzed in detail. The high-voltage direct current frequency control with higher proportional gain and lower integral gain can reflect the inhibitory effect on the high-voltage direct current power and inter-regional oscillations under different circumstances. By considering the high-voltage direct current power oscillation and inter-regional oscillation caused by the dynamic interaction between direct current power and the frequency of an asynchronous alternating current power grid, the risk of the power grid can be controlled in time to reduce the risk of increased cascading failures.

[0007] The present invention is achieved through the following technical solutions:

[0008] A first aspect of the present invention provides an oscillation impact analysis method based on a high voltage direct current system, comprising the following specific steps:

[0009] Based on the high-voltage DC frequency controller, a state control model of the partitioned asynchronous interconnected system is constructed;

[0010] Based on the state control model of partitioned asynchronous interconnected system, DC power oscillation is analyzed;

[0011] The process of analyzing the DC power oscillation comprises:

[0012] Perform modal analysis on the interval oscillation of the partitioned power grid without considering DC frequency control and solve the interval oscillation angular frequency;

[0013] Based on the solved interval oscillation angular frequency, the effect of DC frequency control is considered. At the same time, assuming that the DC frequency control changes the interval oscillation angular frequency of the partitioned power grid within the set threshold range, the modal damping when the HVDC frequency control is disabled and the modal damping when the HVDC frequency control is activated are solved.

[0014] Furthermore, the construction of the two-partition asynchronous interconnected system state control model specifically includes:

[0015] Get two asynchronous AC grids, labeled as region 1 and region 2;

[0016] Use lossless LCC-HVDC lines to connect Region 1 and Region 2, transferring active power from Region 1 to Region 2;

[0017] The two asynchronous AC power grids are equivalent to two aggregated units, where each machine represents a group of aggregated synchronous generators, and the electromechanical dynamics of area 1 and area 2 are constructed, and the swing equations of area 1 and area 2 based on each synchronous generator are obtained respectively;

[0018] The active power balance regulation and initial active power and frequency control active power at the high-voltage DC bus are obtained, and the state control model of the two-partition asynchronous interconnected system is constructed based on the swing equation of each synchronous generator in area 1 and area 2.

[0019] Furthermore, the step of obtaining the swing equation of each synchronous generator specifically includes:

[0020]

[0021] sδ i =ω i

[0022] Among them, δ i Represents the motor voltage phase angle, V i Indicates the motor voltage amplitude, δ d Indicates the voltage phase angle at the DC converter bus, V d Indicates the voltage amplitude at the DC converter bus, M i Indicates the motor inertia, P i Indicates motor power; P li Indicates equivalent load; D i Represents the motor damping coefficient, ω i represents the angular frequency, X i represents the equivalent line reactance, which is approximately equal to no power loss, s represents the complex frequency variable in the Laplace transform, s = d / dt.

[0023] Furthermore, the step of obtaining the active power balance regulation at the high-voltage DC bus specifically includes:

[0024]

[0025] Among them, δ i Represents the motor voltage phase angle, V i Indicates the motor voltage amplitude, δ d Indicates the voltage phase angle at the DC converter bus, V d Indicates the voltage amplitude at the DC converter bus, X i Represents the equivalent line reactance, P d Indicates DC power.

[0026] Furthermore, the steps of obtaining the initial active power and the frequency controlled active power specifically include:

[0027]

[0028] Among them, P dc0 represents the initial active power of HVDC, ΔP dc represents the frequency controlled active power of HVDC, K P Represents the proportional coefficient of the PI controller, K I represents the integral coefficient of the PI controller, s represents the complex frequency variable in the Laplace transform, s = d / dt, ω d Represents the electrical angular velocity at the DC commutation bus, ω' d Represents the desired electrical angular velocity at the DC commutation bus.

[0029] Furthermore, the process of analyzing the DC power oscillation specifically includes:

[0030] Construct initial conditions, and solve the voltage phase angle at the DC commutation bus and the electrical angular velocity at the DC commutation bus according to the initial conditions;

[0031] The swing equation of each synchronous generator is solved according to the electrical angular velocity at the DC commutation bus, and the state equation of the partitioned asynchronous interconnected system is obtained;

[0032] The modal damping when the HVDC frequency control is deactivated and the modal damping when the HVDC frequency control is activated are solved based on the state equation.

[0033] Furthermore, the process of solving the modal damping when the high voltage DC frequency control is disabled specifically includes:

[0034] Obtaining a characteristic polynomial of an asynchronous AC power grid when an HVDC frequency controller is not started;

[0035] According to the characteristic polynomial of the asynchronous AC power grid when the HVDC frequency controller is not started, the modal damping coefficient of the interval vibration and the modal frequency of the inter-area vibration of the asynchronous AC power grid are calculated.

[0036] Furthermore, the process of solving the modal damping when the high voltage DC frequency control is activated specifically includes:

[0037] Determining a predefined complex conjugate eigenvalue associated with the inter-regional oscillation and a conjugate eigenvalue associated with the high voltage direct current power oscillation based on the modal damping coefficient of the inter-regional oscillation of the asynchronous alternating current power grid and the modal frequency of the inter-regional oscillation obtained by the calculation;

[0038] The characteristic polynomial of the asynchronous AC power grid when the DC frequency control is put into operation is obtained, and the characteristic polynomial of the asynchronous AC power grid when the DC frequency control is put into operation is solved based on the predefined complex conjugate eigenvalues ​​related to the inter-regional oscillation and the conjugate eigenvalues ​​related to the high-voltage DC power oscillation to obtain the modal angular frequency of the DC power oscillation, and determine the influence of the inertia of the asynchronous AC power grid and the integral coefficient of the DC frequency control PI controller on the modal angular frequency of the DC power oscillation.

[0039] A second aspect of the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, an oscillation impact analysis method based on a high voltage direct current system is implemented.

[0040] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements an oscillation impact analysis method based on a high voltage direct current system.

[0041] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0042] By constructing a partitioned asynchronous interconnected system state control model, the influence of HVDC frequency control parameters on power and inter-regional oscillations in asynchronous AC power grids is considered based on the asynchronous interconnected system state control model, and the influence of HVDC power oscillations in frequency dead zone is analyzed in detail. It can reflect the inhibitory effect of HVDC frequency control with higher proportional gain and lower integral gain on HVDC power and inter-regional oscillations under different conditions. By considering the HVDC power oscillations and inter-regional oscillations caused by the dynamic interaction between DC power and asynchronous AC power grid frequency, it is possible to control the risks of the power grid in a timely manner and reduce the risk of increased cascading failures. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0044] Figure 1 is a flow chart of a response analysis method in an embodiment of the present invention;

[0045] Figure 2 A simplified two-region asynchronous interconnection system in an embodiment of the present invention;

[0046] Figure 3 This is a high voltage direct current frequency control process in an embodiment of the present invention;

[0047] Figure 4 An asynchronous interconnection test system in an embodiment of the present invention;

[0048] Figure 5 is the simulation result of Example 1 in the embodiment of the present invention;

[0049] Figure 6 It is the simulation result of Example 2 in the embodiment of the present invention;

[0050] Figure 7 It is the simulation result of Example 3 in the embodiment of the present invention;

[0051] Figure 8 This is the simulation result of Example 4 in the embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0053] As a possible implementation, Figure 1 As shown, this embodiment provides an oscillation impact analysis method based on a high-voltage direct current system. By constructing a partitioned asynchronous interconnected system state control model, the influence of HVDC frequency control parameters on power and inter-regional oscillations in an asynchronous alternating current power grid is considered based on the asynchronous interconnected system state control model, and the influence of HVDC power oscillations in a frequency dead zone is analyzed in detail. The method can reflect the inhibitory effect of high-voltage direct current frequency control with higher proportional gain and lower integral gain on high-voltage direct current power and inter-regional oscillations under different conditions. By considering the high-voltage direct current power oscillation and inter-regional oscillation caused by the dynamic interaction between direct current power and the frequency of the asynchronous alternating current power grid, the risk of the power grid can be controlled in a timely manner to reduce the risk of increased cascading failures.

[0054] The specific implementation steps of this embodiment are as follows:

[0055] 1. Build the model

[0056] like Figure 2 As shown, in Figure 2In the system shown, a lossless LCC-HVDC line is constructed to connect two asynchronous AC grids, and the two regions are marked as Region 1 and Region 2, respectively, and the active power Pd is transmitted from Region 1 to Region 2. At the same time, the main inter-regional mode of each grid is simplified to two equivalent aggregated units, where each machine represents a group of aggregated synchronous generators (SG). Therefore, based on the equivalent two aggregated units, the electromechanical dynamics of Region 1 (the same as Region 2) can be expressed by the swing equation of each synchronous generator (SG) i = (1,2):

[0057]

[0058] Among them, δ i Represents the motor voltage phase angle, V i Indicates the motor voltage amplitude, δ d Indicates the voltage phase angle at the DC converter bus, V d Indicates the voltage amplitude at the DC converter bus, M i Indicates the motor inertia, P i Indicates motor power; P li Indicates equivalent load; D i Represents the motor damping coefficient, ω i represents the angular frequency, X i represents the equivalent line reactance, which is approximately equal to no power loss, s represents the complex frequency variable in the Laplace transform, s = d / dt.

[0059] At the same time, from Figure 2 It can be seen that the active power balance at the busbar of high-voltage DC satisfies the following relationship:

[0060]

[0061] Among them, δ i Represents the motor voltage phase angle, V i Indicates the motor voltage amplitude, δ d Indicates the voltage phase angle at the DC converter bus, V d Indicates the voltage amplitude at the DC converter bus, X i Represents the equivalent line reactance, P d Indicates DC power.

[0062] Since the structure of region 2 is the same as that of region 1, the equation structure of region 2 is the same as (1) and (2), except for the parameters and variables.

[0063] In a high-voltage DC system, the dynamics of the AC frequency are significantly slower than the dynamics of the high-voltage DC control. Therefore, in this embodiment, the dynamics of the inner control loop can be ignored and only the frequency control mode can be focused on. Figure 3The figure shows the high voltage direct current frequency control used in the high voltage direct current project of the power grid studied in this embodiment. Ignoring the filter and nonlinear elements, the high voltage direct current transmission power can be expressed as follows:

[0064]

[0065] Among them, P dc0 represents the initial active power of HVDC, ΔP dc represents the frequency controlled active power of HVDC, K P Represents the proportional coefficient of the PI controller, K I represents the integral coefficient of the PI controller, s represents the complex frequency variable in the Laplace transform, s = d / dt, ω d Represents the electrical angular velocity at the DC commutation bus, ω' d Represents the desired electrical angular velocity at the DC commutation bus.

[0066] 2. Modal analysis

[0067] In this embodiment, before analyzing the construction of the partitioned asynchronous interconnected system state control model, the following assumptions are made (i.e., initial conditions are set):

[0068] (1) The dynamics of the synchronous generator (SG) speed governor and prime mover are ignored. Although the speed governor and prime mover will have an impact on HVDC power oscillations and inter-regional oscillations;

[0069] (2) The damping effects of the exciter, load and power system stabilizer (PSS) are integrated into the machine damping coefficient Di;

[0070] (3) All bus voltage amplitudes are equal to V, assuming light load conditions, resulting in a small phase angle difference between the two buses;

[0071] (4) Ignore the reactive power of the HVDC system because the VSC-HVDC system can independently control the reactive power, while the LCC-HVDC system is usually equipped with sufficient reactive power compensation devices on the converter AC bus.

[0072] Based on the above initial conditions, it can be concluded from equation (3) that the voltage phase angle δ at the DC converter bus is d Now it can be expressed as:

[0073]

[0074] By distinguishing the voltage phase angle δ at the DC converter bus d , electrical angular velocity ω at the DC commutation bus d It can be expressed as:

[0075]

[0076] Substituting (4) into (1), the equations of the two SGs in region 1 can be expressed as:

[0077]

[0078] Where X 12 =X1+X2.

[0079] For the HVDC transmission system, by differentiating equation (3), the following relationship can be obtained:

[0080]

[0081] Repeating the analysis of (4)-(7) for region 2, we can obtain a similar set of differential algebraic equations. dc ,ω'1,ω'2,δ'1,δ'2] T As the state vector, we can get Figure 2 The state equation for the system shown is:

[0082]

[0083] in:

[0084]

[0085] Then, we get the state matrix A = T -1 ×J.

[0086] After obtaining the state equation, the DC power oscillation is analyzed by solving the eigenvalues ​​of the established asynchronous interconnection state space model.

[0087] 1) Modal damping when high voltage DC frequency control is disabled (KP = KI = 0)

[0088] For the case where the HVDC frequency controller is not activated, regions 1 and 2 operate independently. This allows the two asynchronous AC grids to be analyzed separately. Therefore, the characteristic polynomial of region 1 can be obtained:

[0089]

[0090] Where a is the modal damping coefficient. ω0 is the modal angular frequency.

[0091] Therefore, the modal damping coefficient and modal angular frequency of the interval vibration of area 1 and area 2 can be calculated as:

[0092]

[0093] The modal frequencies (Hz) of the inter-region vibrations are f0=ω0 / 2π and f'0=ω'0 / 2π, respectively.

[0094] 2) Modal damping when HVDC frequency control is activated

[0095] When DC frequency control is put into use, the characteristic polynomial of the system can be expressed as:

[0096] p(λ)=λ 3 (λ 6 +k5λ 5 +k4λ 4 +k3λ 3 +k2λ 2 +k1λ 1 +k0) (15)

[0097] where the coefficients k5,…,k0 are functions of the system parameters. It is reasonable to assume that HVDC frequency control does not significantly change the modal angular frequencies, i.e. ω0 and ω'0 remain essentially unchanged.

[0098] Based on the analysis of Case 1, two sets of predefined complex conjugate eigenvalues ​​related to inter-regional oscillations can be determined, namely λ=-a±jω0, λ=-a'±jω'0, and one set related to high-voltage DC power oscillations, namely λ=-b±jω1. The above assumptions allow the approximate characteristic polynomials to be as follows:

[0099]

[0100] Formula (16) can be expanded as:

[0101] p(λ)=λ 3 (λ 6 +c5λ 5 +c4λ 4 +c3λ 3 +c2λ 2 +c1λ 1 +c0) (17)

[0102] in:

[0103]

[0104] According to (18), ω0 and ω'0 are defined as constant, and k0 is taken equal to c0, and the modal angular frequency of the DC power oscillation can be calculated. Since k0 is relatively complex, the first-order Taylor expansion is D i =D' i =0 and K P =K i = 0 can be used to obtain a simplified governing expression for ω1:

[0105]

[0106] Among them, M Ξ=M1+M2,M' Ξ =M'1+M'2.

[0107] It can be seen from formula (19) that the inertia of the asynchronous interconnected system and the integral coefficient of the DC frequency control PI controller affect the modal angular frequency of the DC power oscillation. Reducing KI can significantly reduce the modal angular frequency.

[0108] Since the modal damping coefficient is generally much smaller than the modal angular frequency, and the modal angular frequency of the DC power oscillation is lower than the modal angular frequency of the inter-regional oscillation, the following simplified relationship can be obtained:

[0109]

[0110] Therefore, by setting and The damping coefficients, i.e., a, a' and b, can be calculated. Similarly, the simplified expressions a, a' and b can be obtained by first-order Taylor expansion D i =D' i =0 and K P =K i =0 as follows:

[0111]

[0112] Where D Ξ =D1+D2,D' Ξ =D1'+D'2.

[0113] It can be seen from equations (22), (23) and (24) that KP is positively correlated with the modal damping coefficient. For the special case where the HVDC commutation bus is located at the electrical midpoint of the asynchronous grid, i.e., M1X1 = M2X2 and M'1X'1 = M'2X'2, DC frequency control does not provide additional damping effect on inter-area oscillations.

[0114] In addition, it should be noted that a and a' are based on the following premise ω0≠ω'0. However, if ω0=ω'0, the calculation results of (23) and (24) do not hold, but in actual power systems, it is basically impossible for ω0=ω'0.

[0115] As a possible implementation method, this embodiment provides a Figure 4 The eight-machine two-zone (8G2A) test system shown. The LCC-HVDC link connects two asynchronous AC grids. The type of HVDC system is not relevant to the analysis because both LCC-HVDC and VSC-HVDC have similar active power control capabilities and the AC voltage remains almost unchanged. Under normal conditions, the HVDC transmits 400MW of active power from zone 1 to zone 2. Figure 4In the table, G1-G4 represent SG. All SGs are equipped with IEEE G1 type governor and turbine, and IEEE DC1A type exciter. Figure 4 The test system shown can be modeled in RSCAD and simulated using RTDS and NovaCorChassisCore. The following four examples are provided to analyze the impact of oscillation:

[0116] like Figure 5 As shown in Figure 1, Example 1 simulates a load increase of 50MW in Region 1 and a load increase of 150MW in Region 2. This example compares HVDC systems with and without frequency control to evaluate whether HVDC frequency control enhances the modal damping of inter-regional oscillations. The HVDC location is Figure 4 In the “Connection 1” shown, the frequency control parameters KP and KI are selected as 3 and 80 respectively.

[0117] Figure 5 The dashed line represents a DC transmission system without frequency control, and the solid line represents a system with frequency control. Figure 5 As shown in (c), when there is no frequency control, the DC transmission power remains relatively constant during the disturbance. The two asynchronous interconnected systems operate independently and inter-regional oscillations can be observed. In contrast, with frequency control enabled, the frequency minimum point in region 2 improves significantly ( Figure 5 (b)), while the lowest frequency point in region 1 decreases due to the increase in DC transmission power ( Figure 5 (a)).

[0118] like Figure 5 As shown in (a), the effect of damping on inter-regional oscillation in region 1 is slightly improved, which is mainly due to the smaller KP, while the effect of damping on inter-regional oscillation in region 2 remains basically unchanged.

[0119] like Figure 6 As shown, Example 2 simulates the 120MW load increase in area 2, compares the impact of two groups of KP and KI: 1) KP = 1.5, KI = 200; 2) KP = 3, KI = 80, and analyzes the impact of the proportional coefficient and the integral coefficient on the DC power oscillation.

[0120] Figure 6 The solid line is the simulation result of KP=1.5 and KI=200, and the dotted line is the simulation result of KP=3.0 and KI=80. Figure 6 (a) It can be seen that selecting a larger KP and a smaller KI can have a better damping effect on the DC power oscillation and effectively reduce the DC power oscillation.

[0121] As KP ​​increases, the attenuation of the inter-regional oscillations in regions 1 and 2 is also improved, as shown in Figure 5 (a) and Figure 5The dashed line shown in (b) is more concise.

[0122] like Figure 7 As shown, in Example 3, a load increase of 50MW in region 1 and a load increase of 150MW in region 2 are simulated. The HVDC location at “Connection 1” is compared with the HVDC location at “Connection 2”. The effect of the HVDC system location on inter-regional oscillations is introduced.

[0123] exist Figure 7 In Figure 5, the solid line shows the simulation results of the HVDC system at “connection 1”, while the dashed line shows the results at “connection 2”. Figure 7 This means that the HVDC power oscillation is minimally affected by the location of the HVDC converter busbars, at least in Figure 4 This is the case in the test system shown.

[0124] like Figure 7 From the three graphs, it can be seen from the upper two graphs that the HVDC system at "Connection 1" provides a greater damping effect than the HVDC system at "Connection 2". This is because the HVDC busbar at "Connection 2" is basically located at the electrical midpoint of the two asynchronous AC grids.

[0125] like Figure 8 As shown, in Example 4, a load increase of 120MW in region 2 is simulated to examine the impact of the dead zone of HVDC frequency control on HVDC power oscillation. The frequency dead zone is set to ±0.0Hz and ±0.015Hz for comparison.

[0126] Figure 8 The solid line and dashed line represent HVDC frequency control with and without dead zone, respectively. Figure 8 As shown in (c), the damping and angular frequency of HVDC power oscillations show better performance when HVDC frequency control with dead band is used.

[0127] In addition, if Figure 8 (a) and Figure 8 As shown in (b), the frequency dead zone has a smaller impact on the frequency control performance, but will lead to greater damping of the frequency oscillation. Therefore, setting a reasonable frequency dead zone can have a better damping effect on HVDC power and frequency oscillation.

[0128] As a possible implementation, this embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, an oscillation impact analysis method based on a high-voltage direct current system is implemented.

[0129] As a possible implementation, this embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, an oscillation impact analysis method based on a high-voltage direct current system is implemented.

[0130] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for analyzing oscillation impact based on a high voltage direct current system, characterized in that: The specific steps include: Based on the high-voltage DC frequency controller, a state control model of the partitioned asynchronous interconnected system is constructed; Based on the state control model of partitioned asynchronous interconnected system, DC power oscillation is analyzed; The process of analyzing the DC power oscillation comprises: Perform modal analysis on the interval oscillation of the partitioned power grid without considering DC frequency control and solve the interval oscillation angular frequency; Based on the solved interval oscillation angular frequency, the effect of DC frequency control is considered. At the same time, assuming that the DC frequency control changes the interval oscillation angular frequency of the partitioned power grid within the set threshold range, the modal damping when the HVDC frequency control is disabled and the modal damping when the HVDC frequency control is activated are solved.

2. The oscillation impact analysis method based on the high voltage direct current system according to claim 1 is characterized in that: The construction of the two-partition asynchronous interconnected system state control model specifically includes: Get two asynchronous AC grids, labeled as region 1 and region 2; Use lossless LCC-HVDC lines to connect Region 1 and Region 2, transferring active power from Region 1 to Region 2; The two asynchronous AC power grids are equivalent to two aggregated units, where each machine represents a group of aggregated synchronous generators, and the electromechanical dynamics of area 1 and area 2 are constructed, and the swing equations of area 1 and area 2 based on each synchronous generator are obtained respectively; The active power balance regulation and initial active power and frequency control active power at the high-voltage DC bus are obtained, and the state control model of the two-partition asynchronous interconnected system is constructed based on the swing equation of each synchronous generator in area 1 and area 2.

3. The oscillation impact analysis method based on the high voltage direct current system according to claim 2 is characterized in that: The step of obtaining the swing equation of each synchronous generator specifically includes: sd i =ω i Among them, δ i Represents the motor voltage phase angle, V i Indicates the motor voltage amplitude, δ d Indicates the voltage phase angle at the DC converter bus, V d Indicates the voltage amplitude at the DC converter bus, M i Indicates the motor inertia, P i Indicates motor power; P li Indicates equivalent load; D i Represents the motor damping coefficient, ω i represents the angular frequency, X i represents the equivalent line reactance, which is approximately equal to no power loss, s represents the complex frequency variable in the Laplace transform, s = d / dt.

4. The oscillation impact analysis method based on a high voltage direct current system according to claim 2, characterized in that: The step of obtaining the active power balance regulation at the high-voltage DC bus specifically includes: Among them, δ i Represents the motor voltage phase angle, V i Indicates the motor voltage amplitude, δ d Indicates the voltage phase angle at the DC converter bus, V d Indicates the voltage amplitude at the DC converter bus, X i Represents the equivalent line reactance, P d Indicates DC power.

5. The oscillation impact analysis method based on a high voltage direct current system according to claim 2, characterized in that: The steps of obtaining the initial active power and the frequency controlled active power specifically include: Among them, P dc0 represents the initial active power of HVDC, ΔP dc represents the frequency controlled active power of HVDC, K P Represents the proportional coefficient of the PI controller, K I represents the integral coefficient of the PI controller, s represents the complex frequency variable in the Laplace transform, s = d / dt, ω d Represents the electrical angular velocity at the DC commutation bus, ω' d Represents the desired electrical angular velocity at the DC commutation bus.

6. The oscillation impact analysis method based on a high voltage direct current system according to claim 1, characterized in that: The process of analyzing the DC power oscillation specifically includes: Construct initial conditions, and solve the voltage phase angle at the DC commutation bus and the electrical angular velocity at the DC commutation bus according to the initial conditions; The swing equation of each synchronous generator is solved according to the electrical angular velocity at the DC commutation bus, and the state equation of the partitioned asynchronous interconnected system is obtained; The modal damping when the HVDC frequency control is deactivated and the modal damping when the HVDC frequency control is activated are solved based on the state equation.

7. The oscillation impact analysis method based on a high voltage direct current system according to claim 6, characterized in that: The process of solving the modal damping when the high voltage DC frequency control is disabled specifically includes: Obtaining a characteristic polynomial of an asynchronous AC power grid when an HVDC frequency controller is not started; According to the characteristic polynomial of the asynchronous AC power grid when the HVDC frequency controller is not started, the modal damping coefficient of the interval vibration and the modal frequency of the inter-area vibration of the asynchronous AC power grid are calculated.

8. The oscillation impact analysis method based on a high voltage direct current system according to claim 7, characterized in that: The process of solving the modal damping when the high voltage DC frequency control is activated specifically includes: Determining a predefined complex conjugate eigenvalue associated with the inter-regional oscillation and a conjugate eigenvalue associated with the high voltage direct current power oscillation based on the modal damping coefficient of the inter-regional oscillation of the asynchronous alternating current power grid and the modal frequency of the inter-regional oscillation obtained by the calculation; The characteristic polynomial of the asynchronous AC power grid when the DC frequency control is put into operation is obtained, and the characteristic polynomial of the asynchronous AC power grid when the DC frequency control is put into operation is solved based on the predefined complex conjugate eigenvalues ​​related to the inter-regional oscillation and the conjugate eigenvalues ​​related to the high-voltage DC power oscillation, so as to obtain the modal angular frequency of the DC power oscillation, and determine the influence of the inertia of the asynchronous AC power grid and the integral coefficient of the DC frequency control PI controller on the modal angular frequency of the DC power oscillation.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the oscillation impact analysis method based on the high voltage direct current system according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the oscillation impact analysis method based on a high voltage direct current system as claimed in any one of claims 1 to 8 is implemented.

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