VSC-HVDC adaptive inertia setting method and device considering voltage safety

Abstract

The invention discloses a VSC-HVDC adaptive inertia setting method and device considering voltage safety, and the method comprises the steps: carrying out the analysis according to a rotor motion equation of a synchronous machine, and obtaining an influence parameter of a VSC virtual inertia time constant; according to the influence parameters, analyzing and obtaining the relationship between the VSC virtual inertia time constant and the power grid frequency and the direct current voltage; introducing a voltage compensation item and a frequency compensation item according to the relationship between the VSC virtual inertia time constant and the power grid frequency and the DC voltage; a direct-current voltage reference value is adjusted through an HVDC capacitor; and by adjusting the direct-current voltage reference value, the adjustment of the inertia provided by the HVDC capacitor is realized. According to the method, the problem of contradiction between the inertia provided by the HVDC capacitor and the voltage deviation during multi-region interconnection frequency modulation can be solved, and the voltage safety of a sending-end power grid during frequency modulation can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current transmission, and in particular to a method and device for setting a VSC-HVDC adaptive inertia taking voltage safety into consideration. Background Art

[0002] The DC asynchronous interconnected power grid structure has attracted more and more attention at home and abroad. Compared with the traditional LCC-HVDC (Line-Commutated Converter based HVDC) based on grid-commutated converters, the flexible DC transmission based on voltage source converters VSC-HVDC (Voltage Source ConverterbasedHighVoltageDirectCurrent) has the advantages of strong control capability, fast response speed, active and reactive decoupled output, etc., and is not limited by the short-circuit capacity of the AC power grid. It is suitable for transmitting power to passive systems and has the conditions to form a DC power grid. Therefore, it has attracted great attention at home and abroad and has become a research hotspot in the field of electrical engineering.

[0003] In the AC / DC system, the sending-end system has reduced the system inertia level due to the large-scale grid connection of wind power. The sending-end system can participate in the frequency regulation of the receiving-end system. However, when using DC for frequency modulation, the frequency information is transmitted between different regions through voltage changes. In this process, if the voltage changes too much, although it can further promote frequency support in other regions, it will cause voltage collapse. In addition, while the voltage changes, it will also provide inertia support for its own region. When the voltage changes greatly, the inertia provided by the capacitor in the disturbance side area is greater. When the voltage change reaches the voltage safety limit, the inertia it provides is the largest, but the voltage cannot continue to change at this time. It can be seen that there is a contradiction between the size of the inertia provided and the voltage deviation. For this reason, existing research usually hopes to provide a larger inertia when the voltage deviation is small. When the voltage deviation is large, the voltage safety is taken as the standard and no inertia is provided.

[0004] Therefore, how to invent a VSC-HVDC adaptive inertia setting method that takes voltage safety into consideration 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 this end, the present invention provides a VSC-HVDC adaptive inertia setting method and device taking voltage safety into consideration, which solves the contradiction between the inertia size provided by the HVDC capacitor and the voltage deviation during multi-region interconnected frequency modulation, and can ensure the voltage safety of the sending-end power grid itself when participating in frequency modulation.

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

[0007] According to the synchronous machine rotor motion equation, the influencing parameters of the VSC virtual inertia time constant are analyzed and obtained;

[0008] Analyze and obtain the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage according to the influencing parameters;

[0009] According to the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage, a voltage compensation term and a frequency compensation term are introduced;

[0010] The DC voltage reference value is adjusted by the HVDC capacitor; and the inertia size provided by the HVDC capacitor is adjusted by adjusting the DC voltage reference value.

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

[0012]

[0013] Where U dcref (t) is the DC voltage reference value; H vsc is the VSC virtual inertia time constant; S vsc is the capacity of the converter station; C is the DC capacitance; f0 is the rated frequency; f is the actual frequency; U dc0 is the rated DC voltage reference value.

[0014] As a preferred scheme of the VSC-HVDC adaptive inertia setting method considering 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, as the 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;

[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 is the maximum inertia; df max is the maximum frequency deviation allowed for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim is the maximum value of the DC voltage reference value.

[0018] As a preferred solution 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 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 and eventually tends to 1;

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

[0020]

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

[0022] As a preferred scheme of the VSC-HVDC adaptive inertia setting method considering voltage safety, in 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 of the HVDC capacitor; the expression for adjusting the DC voltage reference value by the HVDC capacitor is:

[0023]

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

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

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

[0027] A frequency and voltage relationship analysis module, used for analyzing and obtaining the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage according to the influencing parameters;

[0028] A compensation item introduction module, used for introducing a voltage compensation item and a frequency compensation item according to the relationship between the VSC virtual inertia time constant and the grid frequency and the 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 inertia size provided by the HVDC capacitor is adjusted.

[0030] As a preferred solution of a VSC-HVDC adaptive inertia setting device considering voltage safety, in the influencing parameter analysis module, the relationship expression between the VSC virtual inertia time constant and the influencing parameter is:

[0031]

[0032] Where U dcref (t) is the DC voltage reference value; H vsc is the VSC virtual inertia time constant; S vsc is the capacity of the converter station; C is the DC capacitance; f0 is the rated frequency; f is the actual frequency; U dc0 is the rated DC voltage reference value.

[0033] As a preferred solution of a VSC-HVDC adaptive inertia setting device considering voltage safety, in the frequency-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 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 is the maximum inertia; df max is the maximum frequency deviation allowed for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim It is the upper limit of DC voltage reference value.

[0037] As a preferred solution of a VSC-HVDC adaptive inertia setting device considering voltage safety, the compensation term is introduced into the module. 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 and obtained that: when the DC voltage reference value is equal to U dc0 When 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 and eventually tends to 1;

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

[0039]

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

[0041] As a preferred solution of a VSC-HVDC adaptive inertia setting device considering voltage safety, in the inertia adjustment module, in the process of adjusting the DC voltage reference value by the HVDC capacitor, the HVDC capacitor adjusts the DC voltage reference value according to the frequency and voltage of the HVDC capacitor; the expression for adjusting the DC voltage reference value by the HVDC capacitor is:

[0042]

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

[0044] The present invention has the following advantages: the present invention analyzes and obtains the influencing parameters of the VSC virtual inertia time constant based on the synchronous machine rotor motion equation; analyzes and obtains the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage based on the influencing parameters; introduces voltage compensation terms and frequency compensation terms based on the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage; adjusts the DC voltage reference value through the HVDC capacitor; and adjusts the DC voltage reference value to achieve the inertia size adjustment provided by the HVDC capacitor. Compared with the prior art, the present invention first considers voltage safety. On this basis, combined with the voltage safety of the DC frequency controller, a VSC-HVDC adaptive inertia setting method considering voltage safety is formulated. The present invention can optimize the frequency controller parameters and improve the system frequency while ensuring voltage safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0046] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0047] Figure 1 A schematic flow chart of a method for setting a VSC-HVDC adaptive inertia considering voltage safety provided in Embodiment 1 of the present invention;

[0048] Figure 2 A schematic diagram of a specific implementation flow of a VSC-HVDC adaptive inertia setting method considering voltage safety provided in Example 1 of the present invention;

[0049] Figure 3 A schematic diagram of an asynchronous interconnection area of ​​a converter in a VSC-HVDC adaptive inertia setting method considering voltage safety provided in Example 1 of the present invention;

[0050] Figure 4 A schematic diagram of DC modulation power in area 2 in a possible embodiment provided in embodiment 1 of the present invention;

[0051] Figure 5 A schematic diagram of a system frequency change after a disturbance in a possible embodiment provided in Embodiment 1 of the present invention;

[0052] Figure 6 A schematic diagram of actual voltage in region 2 in a 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 considering voltage safety provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0054] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] Example 1

[0056] See also 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. Analyze and obtain the influencing parameters of the VSC virtual inertia time constant based on the synchronous machine rotor motion equation;

[0058] S2. Analyze and obtain the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage according to the influencing parameters;

[0059] S3. Introducing a voltage compensation term and a frequency compensation term according to the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage;

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

[0061] In this embodiment, the asynchronous interconnection area is as follows: Figure 3 As shown in the figure, the connection relationship between the two areas is given. Different areas contain different numbers of units, which are connected through VSC and DC lines. The VSC converters are all double closed-loop controlled and can be controlled by controlling the inner loop current reference value I d_ref Enable power support between different areas.

[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, K f is the frequency-power droop slope, K d is the voltage-power droop slope, P ref0 is the initial power reference value, P ref_h is the actual power reference value, P is the actual power, U is dcref is the voltage reference value, U dc is the actual voltage.

[0063] After each interconnected converter station adopts power-voltage-frequency droop control, when the frequency change of any AC area exceeds the dead zone setting value, it will cause the output power of the converter station to change, directly adjusting the frequency of the AC power grid. At the same time, under the action of the voltage-power droop characteristic, the DC voltage will also be adjusted up and down accordingly and transmitted to other converter stations. These converter stations change the output power according to the change of DC voltage, thereby supporting the AC system with frequency disturbance while realizing the interconnection of various AC systems, and reducing the frequency deviation caused by power shortage as a whole. From the above working principle, it can be seen that droop control also uses DC voltage as a medium to transmit frequency fluctuation information of various asynchronous interconnected systems.

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

[0065] Specifically, the generator rotor motion equation can be obtained:

[0066]

[0067] Where P M , P E are the per unit values ​​of mechanical power and electromagnetic power of synchronous generator respectively; H SG is the inertia time constant of the synchronous machine; f0 is the rated frequency; is the rate of change of grid frequency.

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

[0069]

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

[0071] Let equation (1) and equation (2) be equal, and establish a relationship between the DC voltage reference value and the AC frequency, as shown in equation (3):

[0072]

[0073] In the formula, H vsc is the inertia coefficient of virtual inertia control, also known as the VSC virtual inertia time constant, which has the same meaning as the generator inertia time constant, except that it is virtually generated by the flexible DC system; U dcref (t) is the DC voltage reference value; dU dcref (t) is the change in the DC voltage reference value.

[0074] Integrating both ends of equation (3), we can obtain:

[0075]

[0076] Where C1 is the integral constant, and its value can be obtained by substituting the rated frequency f0 and the rated DC voltage reference value U dco Obtained; f is the actual frequency;

[0077] After substituting into C1, we can get:

[0078]

[0079] After solving, we can simplify formula (6):

[0080]

[0081] H VSC The value of measures the ability of the converter to provide inertia. The larger the value, the stronger the stabilization effect on the frequency. Its selection needs to meet the requirement that the DC voltage does not exceed the limit during normal operation.

[0082] In this embodiment, in step S2, the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is analyzed and obtained according to the influencing parameters;

[0083] Specifically, the grid frequency deviation generally does not exceed 0.5 Hz. Assume that the maximum DC voltage deviation allowed by the flexible DC system is ΔU dcmax , let df max =f lim -f0=±0.5,where f lim Corresponding to the highest frequency point, or the lowest frequency point, U dcreflim (t) = U dc0 ±ΔU dcmax , substituting into formula (5) we can get:

[0084]

[0085] In the formula, H VSCmax is the maximum inertia;

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

[0087] From formula (7), we can see that H VSCmax The inertia corresponding to the maximum grid frequency deviation and the maximum DC voltage deviation. In general, equation (5) is further changed to the following equation:

[0088]

[0089] Where, df max is the maximum frequency deviation allowed for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim It is the upper limit of DC voltage reference value.

[0090] From formula (8), we can see that H VSCAffected by frequency and voltage, for the frequency term, after a disturbance event occurs, as the frequency deviation increases, H VSC Gradually decreases, that is, after the disturbance occurs, H VSC Maximum; for the voltage item, as the voltage gradually approaches the voltage limit, H VSC However, when the voltage is close to the critical value, due to the large inertia, the voltage may continue to change, and there is a risk of voltage instability. Therefore, when the voltage is close to 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, a voltage compensation term and a frequency compensation term are introduced according to the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage;

[0092] Specifically, similar to the inertia of a synchronous machine, at the moment of disturbance, a fast component such as a capacitor can quickly provide inertia. At the same time, for voltage safety, the DC voltage ΔU dc Close to the maximum DC voltage ΔU dcmax Keep low H VSC On the contrary, when the DC voltage is far from the limit, a higher H should be maintained. VSC .

[0093] Therefore, H VSC The change trend of voltage is opposite to the demand. VSC , by controlling the DC voltage deviation.

[0094] In order to achieve the above purpose, the compensation coefficient of the voltage compensation term is introduced, as shown in formula (9):

[0095]

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

[0097] From formula (9), we can see that for the voltage compensation term, the voltage reference value is equal to U dco When the voltage reference value is equal to U dcreflim When , the compensation coefficient of 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 and eventually tends to 1.

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

[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 inertia size provided by the HVDC capacitor is adjusted.

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

[0101]

[0102] By rearranging formula (10), we can get formula (11):

[0103]

[0104] in,

[0105] Formula (12) can be obtained through formula (11), so that the VSC reference voltage can be adjusted in real time.

[0106]

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

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

[0109] Use matlab / simulink to build Figure 3 A two-area DC system is shown. In this case, area 1 and area 2 each consist of two 900MW synchronous machines.

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

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

[0112] The DC modulation power in region 2 is as follows: Figure 4 As shown, the system frequency changes after the disturbance as 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 in region 2 is given by Figure 6 It can be seen that the present invention can reduce the variation of actual voltage while improving the system frequency.

[0113] In summary, the present invention has the following advantages: the present invention analyzes and obtains the influencing parameters of the VSC virtual inertia time constant based on the synchronous machine rotor motion equation; analyzes and obtains the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage based on the influencing parameters; introduces voltage compensation terms and frequency compensation terms based on the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage; adjusts the DC voltage reference value through the HVDC capacitor; and adjusts the DC voltage reference value to achieve the inertia size adjustment provided by the HVDC capacitor. Compared with the prior art, the present invention first considers voltage safety. On this basis, combined with the voltage safety of the DC frequency controller, a VSC-HVDC adaptive inertia setting method considering voltage safety is formulated. The present invention can optimize the frequency controller parameters and improve the system frequency while ensuring voltage safety.

[0114] It should be noted that the method of the embodiment of the present disclosure can be performed by a single device, such as a computer or a server. The method of the present embodiment can also be applied in a distributed scenario and completed by multiple devices cooperating with each other. In the case of such a distributed scenario, one of the multiple devices can only perform one or more steps in the method of the embodiment of the present disclosure, and the multiple devices will interact with each other to complete the described method.

[0115] It should be noted that the above describes some embodiments of the present 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 an order different from that in the above embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0116] Example 2

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

[0118] The influencing parameter analysis module 001 is used to analyze and obtain the influencing parameters of the VSC virtual inertia time constant according to 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 grid frequency and DC voltage according to the influencing parameters;

[0120] A compensation item introduction module 003 is used to introduce a voltage compensation item and a frequency compensation item according to the relationship between the VSC virtual inertia time constant and the 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 inertia size provided by the HVDC capacitor is adjusted.

[0122] In this embodiment, in the influencing parameter analysis module 001, the relationship expression between the VSC virtual inertia time constant and the influencing parameter is:

[0123]

[0124] Where U dcref (t) is the DC voltage reference value; H vsc is the VSC virtual inertia time constant; S vsc is the capacity of the converter station; C is the DC capacitance; f0 is the rated frequency; f is the actual frequency; U dc0 is the rated DC voltage reference value.

[0125] In this embodiment, in the frequency-voltage relationship analysis module 002, 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 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 is the maximum inertia; df max is the maximum frequency deviation allowed for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim It is the upper limit of DC voltage reference value.

[0129] In this embodiment, in the compensation term introduction module 003, 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 and obtained that: when the DC voltage reference value is equal to U dc0 When 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 and eventually tends to 1;

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

[0131]

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

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

[0134]

[0135] In the formula, H VSCmax is the maximum inertia; df max is the maximum frequency deviation allowed for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim It is the upper limit of DC voltage reference value.

[0136] It should be noted that the information interaction, execution process and other contents between the modules of the above-mentioned system are based on the same concept as the method embodiment in Example 1 of the present application, and the technical effects they bring are the same as those of the method embodiment of the present application. For specific contents, please refer to the description in the method embodiment shown above in the present application, and will not be repeated here.

[0137] Example 3

[0138] Embodiment 3 of the present invention provides a non-transitory computer-readable storage medium, in which a program code for a VSC-HVDC adaptive inertia setting method considering voltage safety is stored, and the program code includes instructions for executing embodiment 1 or any possible implementation thereof, a VSC-HVDC adaptive inertia setting method considering voltage safety.

[0139] The computer-readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server or a data center that includes one or more available media. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)).

[0140] Example 4

[0141] Embodiment 4 of the present invention provides an electronic device, including: a memory and a processor;

[0142] The processor and the memory communicate with each other via a bus; the memory stores program instructions executable by the processor, and the processor calls the program instructions to execute a VSC-HVDC adaptive inertia setting method considering voltage safety in embodiment 1 or any possible implementation thereof.

[0143] Specifically, the processor can be implemented by hardware or by software. When implemented by hardware, the processor can be a logic circuit, an integrated circuit, etc.; when implemented by software, the processor can be a general-purpose processor implemented by reading software codes stored in a memory. The memory can be integrated in the processor or can be located outside the processor and exist independently.

[0144] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of 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, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable systems. The computer instructions can be stored in a computer-readable storage medium, or transmitted from a computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions can be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center.

[0145] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing system, they can be concentrated on a single computing system, or distributed on a network composed of multiple computing systems, and optionally, they can be implemented by a program code executable by a computing system, so that they can be stored in a storage system and executed by the computing system, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0146] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A VSC-HVDC adaptive inertia setting method considering voltage safety, characterized in that: include: According to the synchronous machine rotor motion equation, the influencing parameters of the VSC virtual inertia time constant are analyzed and obtained; According to the influencing parameters, the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage is analyzed and obtained; According to the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage, a voltage compensation term and a frequency compensation term are introduced; The DC voltage reference value is adjusted by the HVDC capacitor; and the inertia size provided by the HVDC capacitor is adjusted by adjusting the DC voltage reference value.

2. A VSC-HVDC adaptive inertia setting method considering voltage safety according to claim 1, characterized in that: The relationship between the VSC virtual inertia time constant and the influencing parameter is expressed as follows: Where U dcref (t) is the DC voltage reference value; H vsc is the VSC virtual inertia time constant; S vsc is the capacity of the converter station; C is the DC capacitance; f0 is the rated frequency; f is the actual frequency; U dc0 is the rated DC voltage reference value.

3. A VSC-HVDC adaptive inertia setting method considering voltage safety according to claim 2, characterized in that: 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 value, 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 is the maximum inertia; df max Indicates the maximum frequency deviation allowed for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim It is the upper limit of DC voltage reference value.

4. A VSC-HVDC adaptive inertia setting method considering voltage safety according to claim 3, characterized in that: 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 compensation coefficient of the voltage compensation term is 1; When the DC voltage reference value is equal to U dcreflim When , the compensation coefficient of the voltage compensation item is 0; When the frequency deviation increases, the compensation coefficient of the voltage compensation term increases and eventually tends to 1; The compensation coefficient of the voltage compensation term is: Wherein, k is the compensation coefficient of the voltage compensation term.

5. A VSC-HVDC adaptive inertia setting method considering voltage safety according to claim 4, characterized in that: In 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 of the HVDC capacitor; the expression for adjusting the DC voltage reference value by the HVDC capacitor is: In the formula, H VSCmax is the maximum inertia; df max is the maximum frequency deviation allowed for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim It is the upper limit of DC voltage reference value.

6. A VSC-HVDC adaptive inertia setting device considering voltage safety, adopting a VSC-HVDC adaptive inertia setting method considering voltage safety as described in any one of claims 1 to 5, characterized in that: include: The influencing parameter analysis module is used to analyze and obtain the influencing parameters of the VSC virtual inertia time constant based on the synchronous machine rotor motion equation; A frequency and voltage relationship analysis module, used for analyzing and obtaining the relationship between the VSC virtual inertia time constant and the grid frequency and DC voltage according to the influencing parameters; A compensation item introduction module, used for introducing a voltage compensation item and a frequency compensation item according to the relationship between the VSC virtual inertia time constant and the grid frequency and the 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 inertia size provided by the HVDC capacitor is adjusted.

7. A VSC-HVDC adaptive inertia setting device considering voltage safety according to claim 6, characterized in that: In the influencing parameter analysis module, the relationship between the VSC virtual inertia time constant and the influencing parameter is expressed as follows: Where U dcref (t) is the DC voltage reference value; H vsc is the VSC virtual inertia time constant; S vsc is the capacity of the converter station; C is the DC capacitance; f0 is the rated frequency; f is the actual frequency; U dc0 is the rated DC voltage reference value.

8. A VSC-HVDC adaptive inertia setting device considering voltage safety according to claim 7, characterized in that: In the frequency-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 value, 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 is the maximum inertia; df max Indicates the maximum frequency deviation allowed for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim It is the upper limit of DC voltage reference value.

9. A VSC-HVDC adaptive inertia setting device considering voltage safety according to claim 8, characterized in that: In the compensation term introduction module, 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 and obtained that: when the DC voltage reference value is equal to U dc0 When , the compensation coefficient of the voltage compensation term is 1; When the DC voltage reference value is equal to U dcreflim When , the compensation coefficient of the voltage compensation item is 0; When the frequency deviation increases, the compensation coefficient of the voltage compensation term increases and eventually tends to 1; The compensation coefficient of the voltage compensation term is: Wherein, k is the compensation coefficient of the voltage compensation term.

10. A VSC-HVDC adaptive inertia setting device considering voltage safety according to claim 9, characterized in that: In the inertia adjustment module, in 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 of the HVDC capacitor; the expression for adjusting the DC voltage reference value by the HVDC capacitor is: In the formula, H VSCmax is the maximum inertia; df max is the maximum frequency deviation allowed for safe operation of the power grid; df is the current frequency deviation of the power grid; U dcreflim It is the upper limit of DC voltage reference value.

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