A method and apparatus for adaptive inertia setting of VSC-HVDC considering voltage safety

Abstract

This invention discloses a VSC-HVDC adaptive inertia setting method and apparatus that considers voltage safety. The method analyzes and obtains the influence parameters of the VSC virtual inertia time constant based on the synchronous machine rotor motion equation; based on the influence parameters, it analyzes and obtains the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage; based on the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage, it introduces voltage compensation terms and frequency compensation terms; it adjusts the DC voltage reference value through the HVDC capacitor; and by adjusting the DC voltage reference value, it achieves adjustment of the inertia provided by the HVDC capacitor. This invention can solve the contradiction between the inertia provided by the HVDC capacitor and the voltage deviation during multi-region interconnected frequency regulation, and can ensure the voltage safety of the sending-end grid when participating in frequency regulation.

Description

Technical Field

[0001] This invention relates to the field of DC power transmission technology, and more specifically to a method and apparatus for setting adaptive inertia of VSC-HVDC that takes voltage safety into account. Background Technology

[0002] DC asynchronous interconnected power grid structures have attracted increasing attention both domestically and internationally. Compared with traditional line-commutated converter-based high-voltage direct current (LCC-HVDC), voltage source converter-based flexible direct current (VSC-HVDC) has advantages such as strong control capability, fast response speed, and decoupled active and reactive power output. Furthermore, it is not limited by the short-circuit capacity of the AC power grid, making it suitable for powering passive systems and possessing the conditions to form a DC power grid. Therefore, it has received high attention both domestically and internationally and has become a research hotspot in the field of electrical engineering.

[0003] In AC / DC systems, the inertia level of the sending-end system decreases due to large-scale wind power grid integration. While the sending-end system can participate in frequency regulation of the receiving-end system, when using DC for frequency modulation, frequency information is transmitted between different regions through voltage changes. In this process, if the voltage change is too large, although it can further promote frequency support from other regions, it can lead to voltage collapse. Furthermore, voltage changes also provide inertia support to their own regions. When the voltage change is large, the inertia provided by the capacitor on the disturbance side is greater. When the voltage change reaches the voltage safety limit, the inertia provided is at its maximum; however, at this point, the voltage cannot continue to change. It is evident that there is a contradiction between the magnitude of inertia provided and the voltage deviation. Therefore, current research typically aims to provide a larger inertia when the voltage deviation is small, and when the voltage deviation is large, voltage safety is prioritized, and no further inertia is provided.

[0004] Therefore, how to invent a VSC-HVDC adaptive inertia setting method that takes voltage safety into account to ensure the voltage safety of the sending-end power grid when participating in frequency regulation has become an urgent problem to be solved. Summary of the Invention

[0005] To address this issue, the present invention provides a VSC-HVDC adaptive inertia setting method and apparatus that considers voltage safety, thereby resolving the contradiction between the magnitude of the inertia provided by the HVDC capacitor and the voltage deviation during multi-region interconnected frequency regulation, and ensuring the voltage safety of the sending-end power grid when participating in frequency regulation.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a VSC-HVDC adaptive inertia setting method considering voltage safety, comprising:

[0007] Based on the synchronous machine rotor motion equation, the influence parameters of the VSC virtual inertia time constant are analyzed and obtained;

[0008] Based on the aforementioned influencing parameters, the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage is analyzed and obtained.

[0009] Based on the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage, voltage compensation terms and frequency compensation terms are introduced;

[0010] The DC voltage reference value is adjusted by the HVDC capacitor; by adjusting the DC voltage reference value, the magnitude of the inertia provided by the HVDC capacitor is adjusted.

[0011] As a preferred embodiment of the VSC-HVDC adaptive inertia setting method considering voltage safety, the relationship between the VSC virtual inertia time constant and the influencing parameters is expressed as follows:

[0012]

[0013] In the formula, U dcref (t) represents the DC voltage reference value; H vsc S is the virtual inertial time constant of VSC; vsc U is the converter station capacity; C is the DC capacitor; f0 is the rated frequency; f is the actual frequency; U dc0 This is the reference value for the rated DC voltage.

[0014] As a preferred embodiment of the VSC-HVDC adaptive inertia setting method that considers voltage safety, the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is as follows: when a disturbance event occurs, the VSC virtual inertia time constant gradually decreases as the grid frequency deviation increases; and the VSC virtual inertia time constant gradually increases as the DC voltage gradually reaches the DC voltage limit.

[0015] The relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is expressed as follows:

[0016]

[0017] In the formula, H VSCmax The maximum inertia; df max The maximum permissible frequency deviation for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim This is the maximum value of the DC voltage reference value.

[0018] As a preferred embodiment of the VSC-HVDC adaptive inertia setting method considering voltage safety, in the process of introducing the voltage compensation term and the frequency compensation term, by introducing the compensation coefficient of the voltage compensation term, it is analyzed that when the DC voltage reference value is equal to U... dc0 When the voltage compensation term has a compensation coefficient of 1, the DC voltage reference value is equal to U. dcreflim When the frequency deviation increases, the compensation coefficient of the voltage compensation term is 0; when the frequency deviation increases, the compensation coefficient of the voltage compensation term increases, eventually tending to 1.

[0019] The compensation coefficient for the voltage compensation term is:

[0020]

[0021] In the formula, k is the compensation coefficient of the voltage compensation term.

[0022] As a preferred scheme for a VSC-HVDC adaptive inertia setting method that considers voltage safety, during the process of adjusting the DC voltage reference value through the HVDC capacitor, the HVDC capacitor adjusts the DC voltage reference value according to the frequency and voltage conditions of the HVDC capacitor; the expression for the adjustment of the DC voltage reference value by the HVDC capacitor is:

[0023]

[0024] In the formula, H VSCmax The maximum inertia; df max The maximum permissible frequency deviation for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim This is the maximum value of the DC voltage reference value.

[0025] The present invention also provides a VSC-HVDC adaptive inertia setting device that considers voltage safety, based on the above-mentioned VSC-HVDC adaptive inertia setting method that considers voltage safety, comprising:

[0026] The influence parameter analysis module is used to analyze and obtain the influence parameters of the VSC virtual inertia time constant based on the synchronous machine rotor motion equation;

[0027] The frequency and voltage relationship analysis module is used to analyze and obtain the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage based on the influencing parameters.

[0028] The compensation term introduction module is used to introduce voltage compensation terms and frequency compensation terms based on the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage.

[0029] The inertia adjustment module is used to adjust the DC voltage reference value through the HVDC capacitor; by adjusting the DC voltage reference value, the magnitude of the inertia provided by the HVDC capacitor is adjusted.

[0030] As a preferred embodiment of a VSC-HVDC adaptive inertia setting device that considers voltage safety, the relationship between the VSC virtual inertia time constant and the influencing parameters in the influencing parameter analysis module is expressed as follows:

[0031]

[0032] In the formula, U dcref (t) represents the DC voltage reference value; H vsc S is the virtual inertial time constant of VSC; vsc U is the converter station capacity; C is the DC capacitor; f0 is the rated frequency; f is the actual frequency; U dc0 This is the reference value for the rated DC voltage.

[0033] As a preferred embodiment of a VSC-HVDC adaptive inertia setting device that considers voltage safety, in the frequency and voltage relationship analysis module, the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage is as follows: when a disturbance event occurs, as the power grid frequency deviation increases, the VSC virtual inertia time constant gradually decreases; as the DC voltage gradually reaches the DC voltage limit value, the VSC virtual inertia time constant gradually increases.

[0034] The relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is expressed as follows:

[0035]

[0036] In the formula, H VSCmax The maximum inertia; df max The maximum permissible frequency deviation for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim This represents the upper limit of the DC voltage reference value.

[0037] As a preferred embodiment of a VSC-HVDC adaptive inertia setting device that considers voltage safety, in the compensation term introduction module, during the introduction of the voltage compensation term and the frequency compensation term, the compensation coefficient of the voltage compensation term is analyzed to obtain: when the DC voltage reference value is equal to U... dc0 When the voltage compensation term has a compensation coefficient of 1, the DC voltage reference value is equal to U. dcreflim When the frequency deviation increases, the compensation coefficient of the voltage compensation term is 0; when the frequency deviation increases, the compensation coefficient of the voltage compensation term increases, eventually tending to 1.

[0038] The compensation coefficient for the voltage compensation term is:

[0039]

[0040] In the formula, k is the compensation coefficient of the voltage compensation term.

[0041] As a preferred embodiment of a VSC-HVDC adaptive inertia setting device that considers voltage safety, in the inertia adjustment module, during the process of adjusting the DC voltage reference value through the HVDC capacitor, the HVDC capacitor adjusts the DC voltage reference value according to the frequency and voltage conditions of the HVDC capacitor; the expression for the HVDC capacitor's adjustment of the DC voltage reference value is:

[0042]

[0043] In the formula, H VSCmax The maximum inertia; df max The maximum permissible frequency deviation for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim This represents the upper limit of the DC voltage reference value.

[0044] This invention has the following advantages: Based on the synchronous machine rotor motion equation, it analyzes and obtains the influence parameters of the VSC virtual inertia time constant; based on these parameters, it analyzes and obtains the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage; based on this relationship, it introduces voltage compensation terms and frequency compensation terms; it adjusts the DC voltage reference value through the HVDC capacitor; and by adjusting the DC voltage reference value, it adjusts the magnitude of the inertia provided by the HVDC capacitor. Compared to existing technologies, this invention prioritizes voltage safety. Based on this, and considering the voltage safety of the DC frequency controller, it develops a VSC-HVDC adaptive inertia setting method that considers voltage safety. This invention can optimize frequency controller parameters and improve system frequency while ensuring voltage safety. Attached Figure Description

[0045] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0046] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0047] Figure 1 This is a schematic diagram of a VSC-HVDC adaptive inertia setting method considering voltage safety provided in Embodiment 1 of the present invention;

[0048] Figure 2 This is a schematic diagram illustrating the specific implementation process of a VSC-HVDC adaptive inertia setting method considering voltage safety provided in Embodiment 1 of the present invention;

[0049] Figure 3 This is a schematic diagram of the asynchronous interconnection region of the converter in a VSC-HVDC adaptive inertia setting method considering voltage safety provided in Embodiment 1 of the present invention;

[0050] Figure 4 This is a schematic diagram of the DC modulation power in region 2 of a possible embodiment provided in Embodiment 1 of the present invention;

[0051] Figure 5 This is a schematic diagram of the system frequency change after being disturbed in one possible embodiment of Embodiment 1 of the present invention;

[0052] Figure 6 This is a schematic diagram of the actual voltage of region 2 in one possible embodiment provided in Embodiment 1 of the present invention;

[0053] Figure 7 This is a schematic diagram of the architecture of a VSC-HVDC adaptive inertia setting device that considers voltage safety, as provided in Embodiment 2 of the present invention. Detailed Implementation

[0054] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0055] Example 1

[0056] See Figure 1 and Figure 2Embodiment 1 of the present invention provides a VSC-HVDC adaptive inertia setting method considering voltage safety, comprising the following steps:

[0057] S1. Based on the synchronous machine rotor motion equation, analyze and obtain the influence parameters of the VSC virtual inertia time constant;

[0058] S2. Based on the aforementioned influencing parameters, analyze and obtain the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage;

[0059] S3. Based on the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage, introduce voltage compensation terms and frequency compensation terms;

[0060] S4. Adjust the DC voltage reference value through the HVDC capacitor; by adjusting the DC voltage reference value, the magnitude of the inertia provided by the HVDC capacitor is adjusted.

[0061] In this embodiment, the asynchronous interconnection region is as follows: Figure 3 The diagram illustrates the connection between two regions, each containing a different number of generator units. These regions are connected via VSC and DC lines. The VSC converters are all dual closed-loop controlled, and the inner loop current reference value I can be controlled. d_ref Enables power support between different regions.

[0062] In this embodiment, the converter adopts power-voltage-frequency control, such as... Figure 3 As shown, f0 is the rated frequency, f is the actual frequency, and K f K is the frequency-power droop slope. d P is the voltage-power droop slope. ref0 As the initial power reference value, P ref_h U is the actual power reference value, where P is the actual power and U is the actual power. dcref U is the voltage reference value. dc This is the actual voltage.

[0063] After each interconnected converter station adopts power-voltage-frequency droop control, when the frequency change in any AC region exceeds the dead zone setting, it will cause a change in the output power of the converter station, directly adjusting the AC grid frequency. Simultaneously, under the influence of the voltage-power droop characteristic, the DC voltage will also be adjusted accordingly and transmitted to other converter stations. These converter stations change their output power based on the DC voltage fluctuations, thereby supporting AC systems experiencing frequency disturbances while achieving interconnection of various AC systems, and reducing frequency deviations caused by power deficits overall. As can be seen from the above working principle, droop control also utilizes DC voltage as a medium to transmit frequency fluctuation information between asynchronous interconnected systems.

[0064] In this embodiment, in step S1, the influence parameters of the VSC virtual inertial time constant are analyzed and obtained according to the synchronous machine rotor motion equation;

[0065] Specifically, from the generator rotor motion equations, we can obtain:

[0066]

[0067] In the formula, P M P E These are the per-unit values ​​of the mechanical power and electromagnetic power of the synchronous generator, respectively; H SG f0 is the inertial time constant of the synchronous machine; f0 is the rated frequency. This represents the rate of change of the power grid frequency.

[0068] From the expression for capacitor charging and discharging power, we can obtain:

[0069]

[0070] In the formula, S vsc C is the converter station capacity; C is the DC voltage; P i and P o These are the per-unit values ​​for input and output power, respectively; U dc This is the actual voltage; The rate of change of DC voltage.

[0071] Equations (1) and (2) are made equal, and the DC voltage reference value is linked to the AC frequency, as shown in equation (3):

[0072]

[0073] In the formula, H vsc This refers to the inertia coefficient of the virtual inertial control, which is also the virtual inertial time constant of the VSC. It has the same meaning as the generator's inertial time constant, except that it is virtually generated by the flexible DC system; U dcref (t) represents the DC voltage reference value; dU dcref (t) represents the change in the DC voltage reference value.

[0074] Integrating both sides of equation (3), we get:

[0075]

[0076] In the formula, C1 is the integration constant, whose value can be obtained by substituting the rated frequency f0 and the rated DC voltage reference value U. dco We obtain f, where f is the actual frequency.

[0077] Substituting C1, we get:

[0078]

[0079] After solving and simplifying, we get equation (6):

[0080]

[0081] H VSC The value of measures the converter's ability to provide inertia; the larger the value, the stronger its effect on frequency stability. Its selection must ensure that the DC voltage does not exceed limits during normal operation.

[0082] In this embodiment, in step S2, the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage is analyzed and obtained based on the influence parameters.

[0083] Specifically, the grid frequency deviation generally does not exceed 0.5Hz, and the maximum allowable DC voltage deviation of the flexible DC system is ΔU. dcmax , let df max =f lim -f0 = ±0.5, where f lim Corresponding to the highest or lowest frequency point, U dcreflim (t)=U dc0 ±ΔU dcmax Substituting into equation (5), we can obtain:

[0084]

[0085] In the formula, H VSCmax Maximum inertia;

[0086] From equation (7), we can see that in(0-U dc0 The voltage deviation ΔU increases monotonically within the range of ) dcmax The larger H is VSC The larger the value, the greater the inertia. Therefore, the value corresponding to equation (7) is the maximum inertia H. VSCmax .

[0087] From equation (7), we can see that H VSCmax The inertia corresponding to the maximum deviation of the power grid frequency and the maximum deviation of the DC voltage. Under normal circumstances, equation (5) is further modified to the following equation:

[0088]

[0089] In the formula, df max The maximum permissible frequency deviation for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim This represents the upper limit of the DC voltage reference value.

[0090] From equation (8), we can see that H VSCAffected by frequency and voltage, for the frequency term, after a disturbance event, as the frequency deviation increases, H... VSC Gradually decrease, that is, H after the disturbance occurs VSC Maximum; for the voltage term, as the voltage gradually approaches the voltage limit, H VSC The voltage gradually increases. However, when the voltage approaches the critical value, it still has a large inertia, which may cause the voltage to continue to change, posing a risk of voltage instability. Therefore, when the voltage approaches the critical safety value, the voltage change should be reduced to ensure the voltage safety of the power system.

[0091] In this embodiment, in step S3, voltage compensation term and frequency compensation term are introduced based on the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage;

[0092] Specifically, similar to the inertia of a synchronous machine, a capacitor, as a fast-acting component, can quickly provide inertia at the moment of disturbance. Simultaneously, for voltage safety, under a DC voltage ΔU... dc Approaching the maximum DC voltage ΔU dcmax Keep H low VSC Conversely, when the DC voltage is far from the limit, a higher H should be maintained. VSC .

[0093] Therefore, H VSC The trend of voltage variation is opposite to that of demand. To control H VSC This can be achieved by controlling the DC voltage deviation.

[0094] To achieve the above objectives, a compensation coefficient for the voltage compensation term is introduced, as shown in equation (9):

[0095]

[0096] In the formula, k is the compensation coefficient of the voltage compensation term.

[0097] From equation (9), it can be seen that for the voltage compensation term, the voltage reference value is equal to U. dco When the voltage term is equal to U, the compensation coefficient is 1; when the voltage reference value is equal to U... dcreflim At this time, the compensation coefficient for the voltage term is 0; therefore, voltage safety can be ensured. For the frequency compensation term, as the frequency deviation increases, the compensation coefficient gradually increases, eventually tending to 1.

[0098] Considering the energy stored in the capacitor Since the voltage is the square of the voltage, the voltage term is introduced in the form of the difference of squares.

[0099] In this embodiment, in step S4, the DC voltage reference value is adjusted by the HVDC capacitor; by adjusting the DC voltage reference value, the magnitude of the inertia provided by the HVDC capacitor is adjusted.

[0100] Specifically, combining equations (8) and (9), we obtain equation (10):

[0101]

[0102] Rearranging equation (10), we obtain equation (11):

[0103]

[0104] in,

[0105] Equation (12) can be obtained from equation (11), thereby allowing the VSC reference voltage to be adjusted in real time.

[0106]

[0107] Equation (12) allows the HVDC capacitor to adjust the voltage reference value according to its own frequency and voltage conditions, thereby adjusting the magnitude of the inertia provided by the capacitor. Considering that voltage changes will drive other regions to provide power support, and in order to maintain the same frequency control logic as its own region, the frequency deviation after the dead zone is introduced as an input.

[0108] In one possible embodiment, a specific inertia setting example is provided as follows:

[0109] A system was built using MATLAB / Simulink, as follows: Figure 3 The diagram shows a two-zone DC system. In this case, Zone 1 and Zone 2 each consist of two 900MW synchronous motors.

[0110] In this embodiment, two calculation examples are provided to verify the effectiveness of the present invention. Case 1 is a traditional control method in which DC does not participate in the frequency response; Case 2 is the control method proposed in this invention.

[0111] In this embodiment, L9 in region 2 is subjected to a load increase disturbance at 1.2 seconds, with a disturbance size of 200MW.

[0112] The DC modulation power in region 2 is as follows Figure 4 As shown, the system frequency change after being disturbed is as follows: Figure 5 As shown, by Figure 5 It can be seen that the present invention can effectively improve the system frequency. Figure 6 The actual voltage of region 2 is given, from Figure 6 It can be seen that the present invention can improve the system frequency while reducing the variation in actual voltage.

[0113] In summary, this invention has the following advantages: Based on the synchronous machine rotor motion equation, this invention analyzes and obtains the influence parameters of the VSC virtual inertia time constant; based on these influence parameters, it analyzes and obtains the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage; based on the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage, it introduces voltage compensation terms and frequency compensation terms; it adjusts the DC voltage reference value through the HVDC capacitor; and by adjusting the DC voltage reference value, it achieves adjustment of the inertia provided by the HVDC capacitor. Compared with existing technologies, this invention prioritizes voltage safety. Based on this, and considering the voltage safety of the DC frequency controller, it formulates a VSC-HVDC adaptive inertia setting method that considers voltage safety. This invention can optimize frequency controller parameters and improve system frequency while ensuring voltage safety.

[0114] It should be noted that the method of this disclosure embodiment can be executed by a single device, such as a computer or server. The method of this embodiment can also be applied to a distributed scenario, where multiple devices cooperate to complete the task. In such a distributed scenario, one of these devices may execute only one or more steps of the method of this disclosure embodiment, and the multiple devices will interact with each other to complete the method described.

[0115] It should be noted that the above description describes some embodiments of this disclosure. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in a different order than that shown in the above embodiments and still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0116] Example 2

[0117] See Figure 7 Embodiment 2 of the present invention also provides a VSC-HVDC adaptive inertia setting device that considers voltage safety, comprising:

[0118] The influence parameter analysis module 001 is used to analyze and obtain the influence parameters of the VSC virtual inertia time constant based on the synchronous machine rotor motion equation;

[0119] The frequency and voltage relationship analysis module 002 is used to analyze and obtain the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage based on the influencing parameters.

[0120] The compensation term introduction module 003 is used to introduce voltage compensation terms and frequency compensation terms based on the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage.

[0121] The inertia adjustment module 004 is used to adjust the DC voltage reference value through the HVDC capacitor; by adjusting the DC voltage reference value, the magnitude of the inertia provided by the HVDC capacitor is adjusted.

[0122] In this embodiment, the relationship between the VSC virtual inertial time constant and the influencing parameter in the influencing parameter analysis module 001 is expressed as follows:

[0123]

[0124] In the formula, U dcref (t) represents the DC voltage reference value; H vsc S is the virtual inertial time constant of VSC; vsc U is the converter station capacity; C is the DC capacitor; f0 is the rated frequency; f is the actual frequency; U dc0 This is the reference value for the rated DC voltage.

[0125] In this embodiment, in the frequency and voltage relationship analysis module 002, the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage is as follows: when a disturbance event occurs, as the power grid frequency deviation increases, the VSC virtual inertia time constant gradually decreases; as the DC voltage gradually reaches the DC voltage limit value, the VSC virtual inertia time constant gradually increases.

[0126] The relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is expressed as follows:

[0127]

[0128] In the formula, H VSCmax The maximum inertia; df max The maximum permissible frequency deviation for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim This represents the upper limit of the DC voltage reference value.

[0129] In this embodiment, in the compensation term introduction module 003, during the process of introducing the voltage compensation term and the frequency compensation term, the compensation coefficient of the voltage compensation term is introduced to analyze and obtain: when the DC voltage reference value is equal to U dc0 When the voltage compensation term has a compensation coefficient of 1, the DC voltage reference value is equal to U. dcreflim When the frequency deviation increases, the compensation coefficient of the voltage compensation term is 0; when the frequency deviation increases, the compensation coefficient of the voltage compensation term increases, eventually tending to 1.

[0130] The compensation coefficient for the voltage compensation term is:

[0131]

[0132] In the formula, k is the compensation coefficient of the voltage compensation term.

[0133] In this embodiment, in the inertia adjustment module 004, during the process of adjusting the DC voltage reference value through the HVDC capacitor, the HVDC capacitor adjusts the DC voltage reference value according to its frequency and voltage conditions; the expression for the HVDC capacitor's adjustment of the DC voltage reference value is:

[0134]

[0135]

[0136] In the formula, H VSCmax The maximum inertia; df max The maximum permissible frequency deviation for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim This represents the upper limit of the DC voltage reference value.

[0137] It should be noted that the information interaction and execution process between the modules of the above system are based on the same concept as the method embodiment in Embodiment 1 of this application, and the resulting technical effects are the same as those in the method embodiment of this application. For details, please refer to the description in the method embodiment shown above in this application, and it will not be repeated here.

[0138] Example 3

[0139] Embodiment 3 of the present invention provides a non-transitory computer-readable storage medium storing program code of a voltage-safe VSC-HVDC adaptive inertia setting method. The program code includes instructions for executing the voltage-safe VSC-HVDC adaptive inertia setting method of Embodiment 1 or any possible implementation thereof.

[0140] Computer-readable storage media can be any available medium that a computer can access, or a data storage device such as a server or data center that integrates one or more available media. The available medium can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid-state drives, SSDs).

[0141] Example 4

[0142] Embodiment 4 of the present invention provides an electronic device, including: a memory and a processor;

[0143] The processor and the memory communicate with each other via a bus; the memory stores program instructions that can be executed by the processor, and the processor can call the program instructions to execute a voltage-safe VSC-HVDC adaptive inertia setting method of Embodiment 1 or any possible implementation thereof.

[0144] Specifically, a processor can be implemented in hardware or software. When implemented in hardware, the processor can be a logic circuit, an integrated circuit, etc. When implemented in software, the processor can be a general-purpose processor that reads software code stored in memory. This memory can be integrated into the processor or located outside the processor and exist independently.

[0145] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present invention are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable system. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means.

[0146] It is obvious to those skilled in the art that the modules or steps of the present invention described above can be implemented using general-purpose computing systems. They can be centralized on a single computing system or distributed across a network of multiple computing systems. Optionally, they can be implemented using program code executable by a computing system, thereby storing them in a storage system for execution by the computing system. In some cases, the steps shown or described can be performed in a different order than those presented herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0147] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for setting the adaptive inertia of a VSC-HVDC considering voltage safety, characterized in that, include: Based on the synchronous machine rotor motion equation, the influence parameters of the VSC virtual inertia time constant are analyzed and obtained; Based on the aforementioned influencing parameters, the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage is analyzed and obtained. Based on the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage, voltage compensation terms and frequency compensation terms are introduced; The DC voltage reference value is adjusted by the HVDC capacitor; by adjusting the DC voltage reference value, the magnitude of the inertia provided by the HVDC capacitor is adjusted. The relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is as follows: when a disturbance event occurs, the VSC virtual inertia time constant gradually decreases as the grid frequency deviation increases; and the VSC virtual inertia time constant gradually increases as the DC voltage gradually reaches the DC voltage limit. The relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is expressed as follows: In the formula, H vsc H is the virtual inertial time constant of VSC; VSCmax The maximum inertia; df max U represents the maximum permissible frequency deviation for safe operation of the power grid. dcref (t) represents the DC voltage reference value; U dc0 The rated DC voltage reference value; df is the current frequency deviation of the power grid; U dcreflim This is the upper limit of the DC voltage reference value; In the process of introducing the voltage compensation term and the frequency compensation term, by introducing the compensation coefficient of the voltage compensation term, it is obtained through analysis that: when the DC voltage reference value is equal to U... dc0 At that time, the compensation coefficient of the voltage compensation term is 1; When the DC voltage reference value is equal to U dcreflim At that time, the compensation coefficient of the voltage compensation term is 0; As the frequency deviation increases, the compensation coefficient of the voltage compensation term increases, eventually tending to 1; The compensation coefficient for the voltage compensation term is: In the formula, k is the compensation coefficient of the voltage compensation term.

2. The VSC-HVDC adaptive inertia setting method considering voltage safety according to claim 1, characterized in that, The relationship between the VSC virtual inertial time constant and the influencing parameters is expressed as follows: In the formula, S vsc C is the converter station capacity; f0 is the DC capacitor; f is the rated frequency; f is the actual frequency.

3. The VSC-HVDC adaptive inertia setting method considering voltage safety according to claim 1, characterized in that, During the process of adjusting the DC voltage reference value through the HVDC capacitor, the HVDC capacitor adjusts the DC voltage reference value according to its frequency and voltage characteristics; the expression for the adjustment of the DC voltage reference value by the HVDC capacitor is as follows: In the formula, H VSCmax The maximum inertia; df max U represents the maximum permissible frequency deviation for safe operation of the power grid; df represents the current frequency deviation of the power grid; U dcreflim This represents the upper limit of the DC voltage reference value.

4. A VSC-HVDC adaptive inertia setting device considering voltage safety, employing the VSC-HVDC adaptive inertia setting method considering voltage safety as described in any one of claims 1-3, characterized in that, include: The influence parameter analysis module is used to analyze and obtain the influence parameters of the VSC virtual inertia time constant based on the synchronous machine rotor motion equation; The frequency and voltage relationship analysis module is used to analyze and obtain the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage based on the influencing parameters. The compensation term introduction module is used to introduce voltage compensation terms and frequency compensation terms based on the relationship between the VSC virtual inertia time constant and the power grid frequency and DC voltage. The inertia adjustment module is used to adjust the DC voltage reference value through the HVDC capacitor; by adjusting the DC voltage reference value, the magnitude of the inertia provided by the HVDC capacitor is adjusted.

5. The VSC-HVDC adaptive inertia setting device considering voltage safety according to claim 4, characterized in that, In the influence parameter analysis module, the relationship between the VSC virtual inertia time constant and the influence parameter is expressed as follows: In the formula, U dcref (t) represents the DC voltage reference value; H vsc S is the virtual inertial time constant of VSC; vsc U is the converter station capacity; C is the DC capacitor; f0 is the rated frequency; f is the actual frequency; U dc0 This is the reference value for the rated DC voltage.

6. The VSC-HVDC adaptive inertia setting device considering voltage safety according to claim 5, characterized in that, In the frequency and voltage relationship analysis module, the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is as follows: when a disturbance event occurs, as the grid frequency deviation increases, the VSC virtual inertia time constant gradually decreases; as the DC voltage gradually reaches the DC voltage limit, the VSC virtual inertia time constant gradually increases. The relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is expressed as follows: In the formula, H VSCmax The maximum inertia; df max This represents the maximum permissible frequency deviation for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim This represents the upper limit of the DC voltage reference value.

7. A VSC-HVDC adaptive inertia setting device considering voltage safety according to claim 6, characterized in that, In the compensation term introduction module, during the introduction of the voltage compensation term and the frequency compensation term, the compensation coefficient of the voltage compensation term is introduced to analyze and obtain: when the DC voltage reference value is equal to U... dc0 At that time, the compensation coefficient of the voltage compensation term is 1; When the DC voltage reference value is equal to U dcreflim At that time, the compensation coefficient of the voltage compensation term is 0; As the frequency deviation increases, the compensation coefficient of the voltage compensation term increases, eventually tending to 1; The compensation coefficient for the voltage compensation term is: In the formula, k is the compensation coefficient of the voltage compensation term.

8. The VSC-HVDC adaptive inertia setting device considering voltage safety according to claim 7, characterized in that, In the inertia adjustment module, during the adjustment of the DC voltage reference value via the HVDC capacitor, the HVDC capacitor adjusts the DC voltage reference value according to its frequency and voltage characteristics; the expression for the HVDC capacitor's adjustment of the DC voltage reference value is: In the formula, H VSCmax The maximum inertia; df max The maximum permissible frequency deviation for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim This represents the upper limit of the DC voltage reference value.

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