Passive damping circuit based on LCC-HVDC system and parameter confirmation method

Abstract

The invention discloses a passive damping circuit based on an LCC-HVDC system and a parameter confirmation method, the passive damping circuit based on the LCC-HVDC system is applied to an LCC-HVDC receiving end system, the circuit comprises a filter capacitor, a resonant capacitor, a resonant inductor and a damping resistor, the resonant inductor and the resonant capacitor are connected in series and then connected with the damping resistor in parallel; one end of the resonant inductor connected with the damping resistor in parallel is grounded, one end of the resonant capacitor connected with the damping resistor in parallel is connected with one end of the filter capacitor, and the other end of the filter capacitor is connected with an alternating-current bus; the receiving end system is connected to an alternating current bus, the amplitude-phase characteristic of the high frequency band can be remodeled on the premise that the low-frequency impedance characteristic in the receiving end system is not affected, the prevention and control effect on high-frequency oscillation is achieved, the passive damping circuit is simple in structure, low in cost and easy to achieve in engineering, meanwhile, the equivalent resistance at the fundamental frequency position is almost zero, and therefore loss is small, and cost is low. And meanwhile, reactive compensation can be provided for a receiving end system.

Description

Technical Field

[0001] The present application relates to the field of ultra-high voltage direct current transmission, and in particular to a passive damping circuit and a parameter confirmation method based on an LCC-HVDC system. Background Art

[0002] With the proposal of dual carbon goals, the transformation of energy structure will be promoted, and renewable energy generation with wind, light and water as the main body will be vigorously utilized. Currently, LCC-HVDC, which has the advantages of long transmission distance and large transmission capacity, is highly favored and has become an important means of long-distance transmission projects.

[0003] In related technologies, as the penetration rate of power electronic equipment in the receiving grid gradually increases, the interaction between it and the grid becomes more prominent, which can easily lead to broadband oscillation problems and threaten the safe and stable operation of the power system. After investigation, it was found that due to unreasonable parameter settings of LCC converter stations, the system may have insufficient damping in the high-frequency band, which is very likely to induce high-frequency harmonic oscillation.

[0004] Therefore, in view of the high-frequency oscillation risk in the LCC-HVDC receiving system, a simple and efficient means is urgently needed to prevent and control oscillation to avoid serious impact of high-frequency harmonics on the power system. Summary of the invention

[0005] In view of the above problems, the present application provides a passive damping circuit and a parameter confirmation method based on an LCC-HVDC system to at least solve the problems existing in the related art.

[0006] In a first aspect, an embodiment of the present application provides a passive damping circuit based on an LCC-HVDC system, which is applied to an LCC-HVDC receiving end system. The passive damping circuit based on the LCC-HVDC system includes:

[0007] Filter capacitor, resonant capacitor, resonant inductor and damping resistor, where:

[0008] The resonant inductor is connected in series with the resonant capacitor and then connected in parallel with the damping resistor;

[0009] One end of the resonant inductor connected in parallel with the damping resistor is grounded, one end of the resonant capacitor connected in parallel with the damping resistor is connected to one end of the filter capacitor, and the other end of the filter capacitor is connected to an AC bus;

[0010] The LCC-HVDC receiving-end system is connected to the AC bus.

[0011] In a second aspect, an embodiment of the present application provides a parameter confirmation method, which is applied to the passive damping circuit based on the LCC-HVDC system proposed in the first aspect, and the parameter confirmation method includes:

[0012] Obtaining a first relational expression between the resonant capacitor and the resonant inductor of the passive damping circuit under fundamental frequency resonance and a reactive power parameter required by the LCC-HVDC receiving-end system;

[0013] Establishing a second relationship based on the reactive power parameter to determine the filter capacitor parameter;

[0014] Based on the impedance output characteristics of the passive damping circuit, a cut-off frequency expression and a purely resistive output frequency expression at high frequency are obtained;

[0015] Based on the first relational expression, the second relational expression, the cutoff frequency expression and the pure resistive output frequency expression at high frequency, the values ​​of the filter capacitor, the resonant capacitor, the resonant inductor and the damping resistor are calculated according to engineering requirements.

[0016] In some embodiments, the first relationship between the resonant capacitor and the resonant inductor of the passive damping circuit under fundamental frequency resonance is obtained, wherein a passive C-type filter is used as the basic topology of the passive damping circuit, and the first relationship is:

[0017]

[0018] In the formula, ω A is the resonant frequency of the passive damping circuit, Cr is the resonant capacitance, and Lr is the resonant inductance.

[0019] In some embodiments, a second relational expression is established based on the reactive power compensation value to determine the filter capacitor parameter, wherein the second relational expression is:

[0020]

[0021] In the formula, C f is the filter capacitor, Q is the reactive compensation power required by the LCC-HVDC receiving system, E is the AC voltage amplitude at the grid connection point of the passive damping circuit, and ω0 is the power frequency angular frequency.

[0022] In some embodiments, the parameter confirmation method further includes:

[0023] An impedance expression is determined based on the topological structure of the passive damping circuit, wherein the impedance expression is:

[0024]

[0025] Where s is the Laplace operator, C f is the filter capacitor, Cr is the resonant capacitor, Lr is the resonant inductor, R is the damping resistor, and Zf(s) represents the output impedance of the passive damping circuit under different values ​​of s.

[0026] In some embodiments, the cut-off frequency expression is obtained based on the impedance output characteristic of the passive damping circuit, wherein the cut-off frequency expression is:

[0027]

[0028] In the formula, ω B is the cut-off angular frequency of the passive damping circuit, Cf is the filter capacitor, Cr is the resonant capacitor, and Lr is the resonant inductor.

[0029] In some embodiments, the pure resistive output frequency expression at high frequency is obtained based on the impedance output characteristic of the passive damping circuit, wherein the pure resistive output frequency expression at high frequency is:

[0030]

[0031] In the formula, ω C is the purely resistive output frequency of the passive damping circuit in the high frequency band, Cf is the filter capacitor, Cr is the resonant capacitor, Lr is the resonant inductor, and R is the damping resistor.

[0032] In some embodiments, the calculation of the values ​​of the filter capacitor, the resonant capacitor, the resonant inductor and the damping resistor according to engineering requirements based on the first relational expression, the second relational expression, the cutoff frequency expression and the pure resistive output frequency expression at high frequency includes:

[0033] Obtaining demand parameters in the engineering requirements, wherein the demand parameters include: reactive power compensation requirements, cut-off frequency requirements, and distribution of high-frequency resistance, inductance, and resistance and capacitance;

[0034] Based on the demand parameters, combined with the first relationship, the second relationship, the cutoff frequency expression and the pure resistive output frequency expression at high frequency, calculation is performed to obtain the values ​​of the filter capacitor, resonant capacitor, resonant inductor and damping resistor.

[0035] In a third aspect, an embodiment of the present application provides an electronic device, comprising a memory and a processor, wherein the memory stores a program code that can be executed on the processor, and when the program code is executed by the processor, the parameter confirmation method introduced in any implementation method of the second aspect is implemented.

[0036] In a fourth aspect, an embodiment of the present application provides a computer storage medium storing one or more programs, which can be executed by the electronic device as described in the third aspect to implement the parameter confirmation method as described in any implementation method of the second aspect.

[0037] The embodiment of the present application provides a passive damping circuit based on an LCC-HVDC system and a parameter confirmation method, wherein the passive damping circuit based on the LCC-HVDC system is applied to the LCC-HVDC receiving end system, and the circuit includes: a filter capacitor, a resonant capacitor, a resonant inductor and a damping resistor, wherein: the resonant inductor is connected in series with the resonant capacitor and then connected in parallel with the damping resistor; one end of the resonant inductor connected in parallel with the damping resistor is grounded, one end of the resonant capacitor connected in parallel with the damping resistor is connected to one end of the filter capacitor, and the other end of the filter capacitor is connected to an AC bus; the LCC-HVDC receiving end system is connected to the AC bus, and the amplitude and phase characteristics of the high frequency band can be reshaped without affecting the low-frequency impedance characteristics of the LCC-HVDC receiving end system, thereby playing a role in preventing and controlling high-frequency oscillations, and the passive damping circuit has a simple structure, low cost, and is easy to implement in engineering, and the equivalent resistance at the fundamental frequency is almost 0, so the loss is small, and reactive power compensation can be provided for the LCC-HVDC receiving end system.

[0038] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Hereinafter, the present application will be described in more detail based on embodiments and with reference to the accompanying drawings.

[0040] Figure 1 The electrical topology diagram of a passive damping circuit based on an LCC-HVDC system proposed in an embodiment of the present application is shown;

[0041] Figure 2 A schematic diagram of a parameter confirmation method proposed in an embodiment of the present application is shown;

[0042] Figure 3 An implementation flow chart proposed in an embodiment of the present application is shown;

[0043] Figure 4 The figure shows an amplitude-phase characteristic diagram of the output impedance of a passive damping circuit proposed in one embodiment of the present application;

[0044] Figure 5 A structural block diagram of an electronic device for executing a parameter confirmation method according to an embodiment of the present application is shown;

[0045] Figure 6 A computer-readable storage medium for storing or carrying a parameter confirmation method according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0046] 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.

[0047] The present application provides a passive damping circuit and parameter confirmation method based on the LCC-HVDC system. The LCC-HVDC receiving system connected to the AC bus can reshape its amplitude and phase characteristics in the high frequency band without affecting the low-frequency impedance characteristics in the LCC-HVDC receiving system, thereby playing a role in preventing and controlling high-frequency oscillations. In addition, the passive damping circuit has a simple structure, low cost, and is easy to implement in engineering. At the same time, its equivalent resistance at the fundamental frequency is almost 0, so the loss is small, and it can provide reactive compensation for the LCC-HVDC receiving system. Among them, the parameter confirmation method is described in detail in the subsequent embodiments.

[0048] The following is an introduction to the application scenarios of the parameter confirmation method provided in the embodiment of the present application:

[0049] See also Figure 1 , Figure 1 This is a flow chart of a parameter confirmation method provided in an embodiment of the present application.

[0050] In this embodiment, the parameter confirmation method can be applied to Figure 1 The electrical topology diagram of the passive damping circuit based on the LCC-HVDC system is shown in FIG. Figure 5 In the electronic device 200 shown, Figure 1 The passive damping circuit is applied to the LCC-HVDC receiving end system, and the circuit includes: filter capacitor, resonant capacitor, resonant inductor and damping resistor, wherein: the resonant inductor is connected in series with the resonant capacitor and then connected in parallel with the damping resistor, one end of the resonant inductor and the damping resistor in parallel is grounded, one end of the resonant capacitor and the damping resistor in parallel is connected to one end of the filter capacitor, and the other end of the filter capacitor is connected to the AC bus. The electronic device 200 may include a mobile terminal, a computer, a tablet, etc., and this application does not limit it. Figure 2 A parameter confirmation method flow chart shown in FIG. 1 is described in detail. The parameter confirmation method may include S110 to S140.

[0051] S110: Obtain a first relational expression between a resonant capacitor and a resonant inductor of a passive damping circuit under fundamental frequency resonance and reactive power parameters required by the LCC-HVDC receiving-end system.

[0052] In the embodiment of the present application, the passive damping circuit can be used to form a passive damping device by selecting a passive C-type filter as a basic topology structure according to specific use, and obtain a first relationship between the resonant capacitance and the resonant inductance of the passive damping circuit under fundamental frequency resonance, wherein the passive C-type filter is used as the basic topology structure of the passive damping circuit, and the first relationship is:

[0053]

[0054] In the formula, ω A is the resonant frequency of the passive damping circuit, Cr is the resonant capacitor, and Lr is the resonant inductor.

[0055] Among them, the reactive power parameters required by the LCC-HVDC receiving-end system can be obtained based on the receiving-end converter.

[0056] Considering that the LCC-HVDC inverter side will consume a large amount of reactive power, the damping device needs to have a certain reactive power compensation capability. In addition, since series resonance occurs at the power frequency, a filter capacitor Cf is connected in parallel at the power frequency.

[0057] S120: Establishing a second relational expression based on the reactive power parameter to determine the filter capacitor parameter, wherein the second relational expression is:

[0058]

[0059] In the formula, C f is the filter capacitor, Q is the reactive compensation power required by the LCC-HVDC receiving system, E is the AC voltage amplitude at the grid connection point of the passive damping circuit, and ω0 is the power frequency angular frequency.

[0060] In some embodiments, the parameter confirmation method further includes: S210 determining an impedance expression based on the topological structure of the passive damping circuit. According to the electrical topological structure of the passive damping device composed of the passive damping circuit, the impedance output expression at different frequencies can be obtained as follows:

[0061]

[0062] Where s is the Laplace operator, C f is the filter capacitor, Cr is the resonant capacitor, Lr is the resonant inductor, R is the damping resistor, and Zf(s) represents the output impedance of the passive damping circuit under different values ​​of s.

[0063] S130: Based on the impedance output characteristics of the passive damping circuit, a cutoff frequency expression and a purely resistive output frequency expression at high frequency are obtained.

[0064] Among them, the impedance output characteristics of the passive damping circuit can be based on the attached Figure 4An amplitude-phase characteristic diagram of the output impedance of a passive damping circuit is provided for determination.

[0065] In an embodiment of the present application, in one implementation, a cutoff frequency expression is obtained based on the impedance output characteristics of the passive damping circuit, wherein the cutoff frequency expression is:

[0066]

[0067] In the formula, ω B is the cut-off angular frequency of the passive damping circuit, Cf is the filter capacitor, Cr is the resonant capacitor, and Lr is the resonant inductor.

[0068] In another embodiment, a purely resistive output frequency expression at high frequency is obtained based on the impedance output characteristics of the passive damping circuit, wherein the purely resistive output frequency expression at high frequency is:

[0069]

[0070] In the formula, ω C is the purely resistive output frequency of the passive damping circuit in the high frequency band, Cf is the filter capacitor, Cr is the resonant capacitor, Lr is the resonant inductor, and R is the damping resistor.

[0071] It should be noted that, see Figure 4 The output impedance of a passive damping circuit is shown in the figure. According to the figure, in this passive damping circuit, ω C The passive damping device formed by the passive damping circuit has a purely resistive output frequency in the high frequency band. When the frequency is lower than this frequency, the passive damping device exhibits resistance-capacitance, and when the frequency is higher than this frequency, the passive damping device exhibits resistance-inductance.

[0072] S140: Based on the first relationship, the second relationship, the cutoff frequency expression and the pure resistive output frequency expression at high frequency, the values ​​of the filter capacitor, the resonant capacitor, the resonant inductor and the damping resistor are calculated according to engineering requirements.

[0073] In the embodiment of the present application, S140 may include S141 to S142, wherein:

[0074] S141: Obtaining demand parameters in engineering requirements, wherein the demand parameters include: reactive power compensation demand, cut-off frequency demand, and distribution of high-frequency resistance-inductance and resistance-capacitance.

[0075] S142: Based on the required parameters, the first relational expression, the second relational expression, the cutoff frequency expression and the pure resistive output frequency expression at high frequency are calculated to obtain the values ​​of the filter capacitor, the resonant capacitor, the resonant inductor and the damping resistor.

[0076] In this embodiment, a passive C-type filter can be selected as the basic topology structure, including a filter capacitor Cf, a resonant capacitor Cr, a resonant inductor Lr and a damping resistor R. The amplitude-frequency curve of the passive damping device is obtained according to the passive damping circuit, and the impedance output characteristics of the passive damping device at the cutoff frequency and the high frequency are determined to obtain two sets of variable equations. In combination with steps S2 and S3, the values ​​of the filter capacitor Cf, the resonant capacitor Cr, the resonant inductor Lr and the damping resistor R are obtained.

[0077] For example, the embodiments of the present application can be found in Figure 3 The implementation flow chart shown includes S1 to S4.

[0078] S1: A passive C-type filter is selected as the basic topology, which includes a filter capacitor Cf, a resonant capacitor Cr, a resonant inductor Lr and a damping resistor R.

[0079] S2: In order to reduce the fundamental frequency loss of the passive damping device, the passive damping circuit needs to be constructed so that the passive damping device resonates at the fundamental frequency, thereby obtaining a set of equations about the quantitative relationship between the resonant capacitor Cr and the resonant inductor Lr.

[0080] S3: According to the reactive power compensation value required by the receiving end converter, a set of filter capacitor C is obtained. f The equation confirms that C f Get the value.

[0081] S4: According to the amplitude-frequency curve of the passive damping device, determine the impedance output characteristics of the passive damping device at the cutoff frequency and the high frequency, obtain two sets of variable equations, and combine steps S2 and S3 to obtain the filter capacitor C f , the values ​​of resonant capacitor Cr, resonant inductor Lr and damping resistor R.

[0082] See also Figure 5 , Figure 5 The present application provides a structural block diagram of an electronic device 200 that can execute the above-mentioned parameter confirmation method. The electronic device 200 can be a smart phone, a tablet computer, a computer, a portable computer or other devices.

[0083] The electronic device 200 further includes a processor 202 and a memory 204. The memory 204 stores a program that can execute the contents of the aforementioned embodiments, and the processor 202 can execute the program stored in the memory 204.

[0084] Please refer to Figure 6 , Figure 6The structure block diagram of a computer-readable storage medium provided in an embodiment of the present application is shown. The computer-readable storage medium 400 stores a program code 410, and the program code 410 can be called by a processor to execute the parameter confirmation method described in the above method embodiment.

[0085] The embodiment of the present application also provides a computer program product or a computer program, which includes a computer instruction stored in a computer-readable storage medium. The processor of the computer device reads the computer instruction from the computer-readable storage medium, and the processor executes the computer instruction, so that the computer device executes the parameter confirmation method described in the above various optional implementations.

[0086] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A passive damping circuit based on an LCC-HVDC system, characterized in that: Applied to the LCC-HVDC receiving end system, the circuit includes: a filter capacitor, a resonant capacitor, a resonant inductor and a damping resistor, wherein: The resonant inductor is connected in series with the resonant capacitor and then connected in parallel with the damping resistor; One end of the resonant inductor connected in parallel with the damping resistor is grounded, one end of the resonant capacitor connected in parallel with the damping resistor is connected to one end of the filter capacitor, and the other end of the filter capacitor is connected to an AC bus; The LCC-HVDC receiving-end system is connected to the AC bus.

2. A parameter confirmation method, characterized in that: Applied to the passive damping circuit based on the LCC-HVDC system according to claim 1, the parameter confirmation method comprises: Obtaining a first relational expression between the resonant capacitor and the resonant inductor of the passive damping circuit under fundamental frequency resonance and a reactive power parameter required by the LCC-HVDC receiving-end system; Establishing a second relationship based on the reactive power parameter to determine the filter capacitor parameter; Based on the impedance output characteristics of the passive damping circuit, a cut-off frequency expression and a purely resistive output frequency expression at high frequency are obtained; Based on the first relational expression, the second relational expression, the cutoff frequency expression and the pure resistive output frequency expression at high frequency, the values ​​of the filter capacitor, the resonant capacitor, the resonant inductor and the damping resistor are calculated according to engineering requirements.

3. The parameter confirmation method according to claim 2, characterized in that: The first relationship between the resonant capacitor and the resonant inductor of the passive damping circuit is obtained under fundamental frequency resonance, wherein a passive C-type filter is used as the basic topology structure of the passive damping circuit, and the first relationship is: In the formula, ω A is the resonant frequency of the passive damping circuit, Cr is the resonant capacitance, and Lr is the resonant inductance.

4. The parameter confirmation method according to claim 2, characterized in that: The second relational expression is established based on the reactive power compensation value to determine the filter capacitor parameter, wherein the second relational expression is: In the formula, C f is the filter capacitor, Q is the reactive compensation power required by the LCC-HVDC receiving system, E is the AC voltage amplitude at the grid connection point of the passive damping circuit, and ω0 is the power frequency angular frequency.

5. The parameter confirmation method according to claim 2, characterized in that: The parameter confirmation method further includes: An impedance expression is determined based on the topological structure of the passive damping circuit, wherein the impedance expression is: Where s is the Laplace operator, C f is the filter capacitor, Cr is the resonant capacitor, Lr is the resonant inductor, R is the damping resistor, and Zf(s) represents the output impedance of the passive damping circuit under different values ​​of s.

6. The parameter confirmation method according to claim 2, characterized in that: The cut-off frequency expression is obtained based on the impedance output characteristic of the passive damping circuit, wherein the cut-off frequency expression is: In the formula, ω B is the cut-off angular frequency of the passive damping circuit, Cf is the filter capacitor, Cr is the resonant capacitor, and Lr is the resonant inductor.

7. The parameter confirmation method according to claim 2, characterized in that: The pure resistive output frequency expression at high frequency is obtained based on the impedance output characteristic of the passive damping circuit, wherein the pure resistive output frequency expression at high frequency is: In the formula, ω C is the purely resistive output frequency of the passive damping circuit in the high frequency band, Cf is the filter capacitor, Cr is the resonant capacitor, Lr is the resonant inductor, and R is the damping resistor.

8. The parameter confirmation method according to claim 2, characterized in that: The calculation of the values ​​of the filter capacitor, the resonant capacitor, the resonant inductor and the damping resistor according to engineering requirements based on the first relational expression, the second relational expression, the cutoff frequency expression and the pure resistive output frequency expression at high frequency includes: Obtaining demand parameters in the engineering requirements, wherein the demand parameters include: reactive power compensation requirements, cut-off frequency requirements, and distribution of high-frequency resistance, inductance, and resistance and capacitance; Based on the demand parameters, combined with the first relationship, the second relationship, the cutoff frequency expression and the pure resistive output frequency expression at high frequency, calculation is performed to obtain the values ​​of the filter capacitor, resonant capacitor, resonant inductor and damping resistor.

9. An electronic device, characterized in that: The electronic device includes a memory and a processor, wherein the memory stores program codes that can be run on the processor, and when the program codes are executed by the processor, the parameter confirmation method according to any one of claims 2 to 8 is implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores program codes, and the program codes can be called by one or more processors to execute the parameter confirmation method according to any one of claims 2 to 8.

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