Parameter design method and system for cross-voltage-level active damping device for suppressing system resonance

Abstract

The invention discloses a method and a system for designing parameters of a cross-voltage-level active damping device for suppressing system resonance. The method comprises the following steps of: collecting resonance system parameters, determining a resonance frequency band range of a system according to a system impedance model, determining a resonance frequency and a corresponding initial harmonic voltage content ratio, and setting a target harmonic voltage content ratio; calculating harmonic current generated by the nonlinear load, and solving a damping value of system suppression resonance; determining the capacity of the active damping device according to the equivalent harmonic impedance, the harmonic current generated by the nonlinear load and the damping value of system suppression resonance, and carrying out cross-voltage grade transformer type selection; and designing a virtual resistance-capacitance value of the active damping device according to the parameters of the selected transformer and the damping value of the system for suppressing resonance. The insulation performance requirement of the active damping device is lowered, and the equipment treatment investment and the occupied area are reduced; and the influence of the cross-voltage level on the resistance-capacitance parameters of the device is fully considered, so that the parameter design result is more accurate, and the resonance suppression effect is further enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of harmonic control, and more specifically, relates to a parameter design method and system for a cross-voltage level active damping device for suppressing system resonance. Background Art

[0002] With the rapid development of power electronics technology, a large number of nonlinear power electronic devices have been put into use, exacerbating grid harmonic distortion and increasing the risk of harmonic resonance. Harmonic resonance can cause overvoltage or overcurrent problems, potentially damaging equipment, triggering protection and automatic devices, and causing control system loss of control, endangering safe and stable system operation. Therefore, effective resonance suppression measures are urgently needed.

[0003] Currently, passive damping is the most common method for suppressing power system resonance. However, the integration of passive damping changes the impedance characteristics of the power grid over a wide frequency range, which may bring new resonance risks. At the same time, there is a problem of reactive power balance when passive damping is connected to the grid, thereby weakening the effect of resonance suppression.

[0004] The existing technology uses active damping to replace passive damping to suppress power system resonances. Active damping resonance suppression has excellent frequency selection characteristics, does not have reactive power balance issues, does not cause secondary resonance risks, and can suppress a wide spectrum of low-frequency resonances. When the power system resonance point shifts, passive damping requires changes in structure and parameters based on the change in the resonance point, while active damping control systems can achieve adaptive adjustment without changing the structure. Therefore, the active damping resonance suppression method has greater flexibility and higher efficiency than the passive damping suppression method.

[0005] However, the active damping and control methods in the existing technology are only used to suppress system resonances at the same voltage level, and have not yet achieved system resonance suppression across voltage levels. When resonance occurs in a high-voltage system, the resonance control at the same voltage level requires high insulation costs for the control equipment, and is accompanied by problems such as high control costs, large control investments, and large equipment footprints. In addition, the better the desired resonance control effect, the larger the capacity of the active damping device required. The existing technology lacks a parameter design method for active damping devices across voltage levels.

[0006] Therefore, how to reasonably design the parameters of the active damping device to effectively suppress system resonance across voltage levels is a key technical problem that urgently needs to be solved. Summary of the Invention

[0007] In order to address the deficiencies in the prior art, the present invention provides a method and system for designing parameters of an active damping device across voltage levels for suppressing system resonance, thereby effectively suppressing system resonance across voltage levels.

[0008] The present invention adopts the following technical solutions.

[0009] A first aspect of the present invention provides a method for designing parameters of a cross-voltage level active damping device for suppressing system resonance, comprising the following steps:

[0010] Step 1: Collect the resonant system parameters, determine the resonant frequency band of the system according to the system impedance model, determine the resonant frequency and the corresponding initial harmonic voltage content within the resonant frequency band, and set the target harmonic voltage content;

[0011] Step 2: Calculate the harmonic current generated by the nonlinear load based on the initial harmonic voltage content and the equivalent harmonic impedance of the system impedance model, and solve the damping value for suppressing system resonance based on the set target harmonic voltage content;

[0012] Step 3: Determine the capacity of the active damping device based on the equivalent harmonic impedance, the harmonic current generated by the nonlinear load, and the damping value of the system to suppress resonance, and select a transformer across voltage levels;

[0013] Step 4: Design a virtual resistance value of the active damping device according to the equivalent resistance of the selected transformer and the damping value of the system to suppress resonance, and design a virtual capacitance value of the active damping device according to the equivalent inductive reactance of the selected transformer.

[0014] Preferably, in step 1, determining the resonant frequency band range of the system includes:

[0015] The harmonic current transfer coefficient is calculated based on the system impedance model and is expressed as follows:

[0016]

[0017] Where: T(h) is the hth harmonic current transfer coefficient, h is the harmonic order, f0 is the system fundamental frequency, R s is the equivalent resistance of the system impedance, L s is the equivalent inductance of the system impedance, U N is the nominal voltage of the resonant system, S0 is the system operating short-circuit capacity, C is the capacitance of the capacitive device, if the system resonance is caused by the line, then C = c × l, c is the capacitance per unit length of the line, l is the line length, if the system resonance is caused by the reactive compensation device, then Q c is the installed capacity of the reactive compensation capacitor, U c is the rated voltage of the reactive compensation capacitor;

[0018] Draw a curve of harmonic current transfer coefficient changing with harmonic order, and set the resonant frequency band range to [h L ,h H], where the upper limit of harmonic order h H The lower limit of harmonic order h L are respectively the maximum and minimum values ​​of the integer harmonic orders whose harmonic current transfer coefficients are greater than or equal to 1 in the curve.

[0019] Preferably, in step 1, determining the resonant frequency and the corresponding initial harmonic voltage content within the resonant frequency band includes:

[0020] When the system's resonant frequency band contains a single harmonic, the harmonic order is used as the system's resonant frequency. When the system's resonant frequency band contains multiple harmonics, the harmonic order with the largest harmonic voltage content is used as the system's resonant frequency. The initial harmonic voltage content is determined to be the harmonic voltage content at the common connection point of the system impedance model at the resonant frequency when no active damping device is added.

[0021] Setting the target harmonic voltage content rate includes:

[0022] The target harmonic voltage content is set according to the harmonic voltage limits in the national standard GB / T 14549-1993 "Power Quality Public Grid Harmonics".

[0023] Preferably, step 2 includes:

[0024] Based on the system impedance model, the equivalent harmonic inductive reactance of the system impedance at the resonant frequency and the equivalent harmonic capacitive reactance of the capacitive device at the resonant frequency are calculated respectively;

[0025] The equivalent harmonic inductive reactance and the equivalent harmonic capacitive reactance at the resonant frequency are connected in parallel to obtain the equivalent harmonic impedance at the resonant frequency;

[0026] Calculate the initial harmonic phase voltage at the common connection point at the resonant frequency according to the initial harmonic voltage content rate;

[0027] The ratio of the initial harmonic phase voltage to the modulus of the equivalent harmonic impedance is the harmonic current at the resonant frequency generated by the nonlinear load;

[0028] According to the set target harmonic voltage content, the harmonic current generated by the nonlinear load, the equivalent harmonic impedance and the nominal voltage of the resonant system are used to calculate the damping value of the system to suppress resonance.

[0029] Preferably, the damping value R of the system to suppress resonance is obtained by solving the following equation:

[0030]

[0031] Where h0 is the resonant frequency, I s (h0) is the harmonic current at the resonant frequency generated by the nonlinear load, Z(h0) is the equivalent harmonic impedance at the resonant frequency, HRUh2 is the target harmonic voltage content rate, U N is the nominal voltage of the resonant system.

[0032] Preferably, step 3 includes:

[0033] Calculate the harmonic current I at the resonant frequency of the damping branch ad (h0), expressed as follows:

[0034]

[0035] Calculate the capacity S of the active damping device using the following formula:

[0036]

[0037] Where U NH is the rated voltage of the high voltage side of the transformer;

[0038] Calculate the capacity S of the transformer T , expressed as follows:

[0039] S T =kS

[0040] Where k is the margin coefficient;

[0041] Select the transformer according to the transformer capacity and high and low voltage side voltages.

[0042] Preferably, the margin coefficient ranges from [1.3, 1.5].

[0043] Preferably, in step 4, the virtual resistance value R of the active damping device at the resonant frequency h0 is designed. v (h0), expressed as follows:

[0044]

[0045] Where n is the ratio of the rated voltage of the transformer high voltage side to the rated voltage of the low voltage side, R T is the resistance equivalent to the high-voltage side of the transformer, and R is the damping value of the system to suppress resonance;

[0046] The transformer is equivalent to the resistance R on the high voltage side. T Calculated by the following formula:

[0047]

[0048] Where, P k is the load loss of the transformer, U NH is the rated voltage of the high voltage side of the transformer, S T is the capacity of the transformer.

[0049] Preferably, in step 4, designing the virtual capacitance value of the active damping device includes:

[0050] Determine the virtual capacitance reactance X of the active damping device at the resonant frequency h0 according to the equivalent inductive reactance of the transformer v (h0), expressed as follows:

[0051]

[0052] Where, X T is the inductive reactance equivalent to the high-voltage side of the transformer, and n is the ratio of the rated voltage of the high-voltage side to the rated voltage of the low-voltage side of the transformer;

[0053] The inductive reactance value of the transformer equivalent to the high voltage side is X T Calculated by the following formula:

[0054]

[0055] Where U k is the percentage of the short-circuit voltage of the selected transformer, U NH is the rated voltage of the high voltage side of the transformer, S T is the capacity of the transformer;

[0056] The virtual capacitance value C of the active damping device at the resonant frequency h0 is v (h0) is calculated by the following formula:

[0057]

[0058] Where f0 is the fundamental frequency of the system.

[0059] A second aspect of the present invention provides a parameter design system for an active damping device across voltage levels for suppressing system resonance, and implements a parameter design method for an active damping device across voltage levels for suppressing system resonance, comprising:

[0060] Parameter acquisition module, used to collect resonant system parameters, obtain resonant frequency band range, determine resonant frequency and corresponding initial harmonic voltage content rate and target harmonic voltage content rate;

[0061] Damping calculation module, used to calculate the damping value of the system to suppress resonance;

[0062] Capacity design module, used to determine the capacity of active damping devices and cross-voltage transformer selection;

[0063] The RC design module is used to design the virtual resistance and capacitance values ​​of the active damping device.

[0064] Compared with the prior art, the beneficial effects of the present invention include at least:

[0065] 1. The present invention provides a parameter design method for an active damping device across voltage levels, which performs parameter design on an active damping device across voltage levels, reduces the insulation performance requirements of the active damping device, and reduces equipment management investment and floor space.

[0066] 2. The present invention rationally designs the resistance and capacitance parameters of the active damping device, fully considering the impact of cross-voltage levels on the resistance and capacitance parameters of the device, making the parameter design results more accurate and further enhancing the resonance suppression effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 Flowchart of the parameter design method of active damping device across voltage levels to suppress system resonance;

[0068] Figure 2 The system impedance model diagram for resonance suppression of active damping devices across voltage levels;

[0069] Figure 3 Schematic diagram of system wiring for cross-voltage level active damping device resonance suppression;

[0070] Figure 4 is a graph showing the harmonic current transfer coefficient changing with the harmonic order;

[0071] Figure 5 This is the harmonic voltage spectrum of the PCC point before the active damping device is added;

[0072] Figure 6 The voltage waveforms at the PCC point before and after the active damping device is added;

[0073] Figure 7 This is the harmonic voltage spectrum of the PCC point after adding the active damping device. DETAILED DESCRIPTION

[0074] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0075] like Figure 1 As shown, embodiment 1 of the present invention provides a parameter design method for an inter-voltage level active damping device for suppressing system resonance, wherein the active damping device is connected to the resonant system via an inter-voltage level transformer, and the active damping device is connected to the low-voltage side of the inter-voltage level transformer to control the harmonics of the resonant system on the high-voltage side of the inter-voltage level transformer, comprising the following steps:

[0076] Step 1: Collect the resonant system parameters, determine the resonant frequency band range of the system according to the system impedance model, determine the resonant frequency and the corresponding initial harmonic voltage content within the resonant frequency band range, and set the target harmonic voltage content rate.

[0077] In a preferred but non-limiting embodiment of the present invention, step 1 specifically comprises:

[0078] Step 1.1, collect the resonant system parameters. Specifically, the resonant system parameters refer to the system voltage level, operating short-circuit capacity, and reactance / resistance ratio. If the system resonance is caused by the line, collect the line parameters, including line length and capacitance per unit length. If the system resonance is caused by the reactive compensation device, collect the reactive compensation device parameters, including the installed capacity of the reactive compensation capacitor and the rated voltage of the capacitor.

[0079] Step 1.2, establish the system impedance model of cross-voltage level active damping device resonance suppression, such as Figure 2 As shown, the system impedance model includes system impedance and capacitive devices, and the capacitance of the capacitive devices, the equivalent inductance and the equivalent resistance of the system impedance are calculated.

[0080] Further preferably, if the system resonance is caused by the line, the capacitance value C (F) of the capacitive device is calculated as follows:

[0081] C=c×l

[0082] Where c (F / km) is the capacitance per unit length of the line, l (km) is the length of the line;

[0083] If the system resonance is caused by the reactive power compensation device, the capacitance value C of the capacitive device is calculated as follows:

[0084]

[0085] Where Q c (Mvar) is the installed capacity of the reactive compensation capacitor, f0 (Hz) is the system fundamental frequency, U c (kV) is the rated voltage of the reactive power compensation capacitor;

[0086] According to the causes of different system resonances, different system parameters are collected and the capacitance values ​​of capacitive devices are calculated using different methods, so that the system impedance model can fully reflect the actual situation of the resonant system, providing a strong guarantee for the accuracy of subsequent parameter design.

[0087] Further preferably, the equivalent inductance L of the system impedance s , equivalent resistance R s The calculation formulas are as follows:

[0088]

[0089] Where U N (kV) is the nominal voltage of the resonant system, S0 (MVA) is the operating short-circuit capacity of the system, and m is the system reactance / resistance ratio;

[0090] Step 1.3: Calculate the resonant frequency point and harmonic current transfer coefficient according to the parameters of the system impedance model in step 1.2, and determine the resonant frequency band range according to the harmonic current transfer coefficient variation curve.

[0091] Further preferably, the resonant frequency point h r The calculation formula is as follows:

[0092]

[0093] Further preferably, the harmonic current transfer coefficient is calculated and expressed as follows:

[0094]

[0095] Where: T(h) is the hth harmonic current transfer coefficient, and h is the harmonic order.

[0096] The curve of harmonic current transfer coefficient changing with harmonic order h is drawn by frequency sweep method, and the boundary harmonic order (integer) corresponding to the curve segment with harmonic current transfer coefficient greater than or equal to 1 is used as the upper limit of harmonic order h of resonant amplification. H The lower limit of harmonic order h L , the resonant frequency band range is set to [h L ,h H ].

[0097] Step 1.4, determine the resonant frequency and the corresponding initial harmonic voltage content rate. Specifically, when the resonant frequency band of the system contains a single harmonic, the harmonic order is the resonant frequency h0 of the system. When the resonant frequency band of the system contains multiple harmonics, the harmonic order with the largest harmonic voltage content rate is used as the resonant frequency h0 of the system; the initial harmonic voltage content rate HRU h1 (%) is the measured value of the harmonic voltage content rate at the resonant frequency at the PCC point (Point of Common Coupling) when no active damping device is added.

[0098] Step 1.5: Set the target harmonic voltage content rate with the goal of suppressing system resonance.

[0099] Further preferably, the target harmonic voltage content rate HRU h2(%) is determined according to the harmonic voltage limit in the national standard GB / T14549-1993 "Power Quality Public Grid Harmonics", and the control target usually does not exceed the limit.

[0100] Step 2: Calculate the harmonic current generated by the nonlinear load based on the initial harmonic voltage content and the equivalent harmonic impedance of the system impedance model, and solve the damping value for suppressing system resonance based on the set target harmonic voltage content.

[0101] In a preferred but non-limiting embodiment of the present invention, step 2 specifically comprises:

[0102] Step 2.1, based on the system impedance model, calculate the equivalent harmonic inductive reactance X of the system impedance at the resonant frequency h0 Ls (h0) and the equivalent harmonic capacitive reactance X of the capacitive device at the harmonic of the resonant frequency h0 C (h0), respectively expressed as follows:

[0103] X Ls (h0)=2πf0h0L s

[0104]

[0105] Step 2.2, equivalent harmonic inductive reactance X at the resonant frequency Ls (h0) and equivalent harmonic capacitive reactance X C (h0) is connected in parallel to obtain the equivalent harmonic impedance Z(h0) at the resonant frequency h0, which is expressed as the following formula:

[0106]

[0107] Step 2.3, calculate the initial harmonic phase voltage U of the PCC point at the harmonic at the resonant frequency h0 according to the initial harmonic voltage content rate pcc (h0)(kV), expressed as follows:

[0108]

[0109] Step 2.4, initial harmonic phase voltage U pcc The ratio of the modulus of the equivalent harmonic impedance Z(h0) is the harmonic current I at the resonant frequency h0 generated by the nonlinear load. s (h0)(kA), expressed as follows:

[0110]

[0111] In step 2.5, based on the set target harmonic voltage content, the damping value R for suppressing resonance of the system is obtained by solving the following equation:

[0112]

[0113] Step 3: Determine the capacity of the active damping device based on the equivalent harmonic impedance of step 2, the harmonic current generated by the nonlinear load, and the damping value of the system to suppress resonance, and select a transformer across voltage levels.

[0114] In a preferred but non-limiting embodiment of the present invention, step 3 specifically comprises:

[0115] Step 3.1, calculate the harmonic current I at the resonant frequency h0 of the damping branch ad (h0), expressed as follows:

[0116]

[0117] Step 3.2, calculate the capacity S (MVA) of the active damping device, expressed as follows:

[0118]

[0119] Where U NH (kV) is the rated voltage of the high voltage side of the transformer;

[0120] Step 3.3, determine the capacity S of the transformer T (MVA), expressed as follows:

[0121] S T =kS

[0122] Where k is the margin coefficient, which is generally selected as [1.3,1.5].

[0123] In step 3.4, select the transformer based on its capacity and high and low voltage side voltages, and determine the transformer equivalent resistance and equivalent inductive reactance based on the selection results.

[0124] Further preferably, step 3.4 specifically includes:

[0125] In step 3.4.1, the nominal voltage of the resonance generating system is used as the high-voltage side voltage of the transformer, and the rated voltage of the active damping device is used as the low-voltage side voltage of the transformer to select the transformer.

[0126] Step 3.4.2: Obtain the transformer load loss P according to the selected transformer nameplate parameters. k (kW) and short-circuit voltage percentage U k (%), and determine the transformer equivalent to the high voltage side resistance R T and inductive reactance X T , expressed as follows:

[0127]

[0128] Step 4: Design the virtual resistance and capacitance of the active damping device based on the transformer parameters selected in step 3 and the damping value for suppressing the resonance of the system obtained in step 2.

[0129] In a preferred but non-limiting embodiment of the present invention, step 4 specifically comprises:

[0130] Step 4.1: Design the virtual resistance value R of the active damping device at the resonant frequency h0 based on the equivalent resistance of the transformer in step 3 and the damping value of the system to suppress resonance in step 2. v (h0), expressed as follows:

[0131]

[0132] Where n is the ratio of the rated voltage of the high-voltage side to the rated voltage of the low-voltage side of the transformer.

[0133] When designing the parameters of the cross-voltage level active damping device, the present invention fully considers the influence of the transformer itself on the device parameter design when the active damping device is installed at a low voltage level through a cross-voltage level transformer. Through parameter reduction, the parameters of the active damping device are made more reasonable and accurate, thereby enhancing the resonance suppression effect of the active damping device.

[0134] Step 4.2, design the virtual capacitance reactance X of the active damping device at the resonant frequency h0 v (h0), expressed as follows:

[0135]

[0136] Step 4.3, calculate the virtual capacitance C of the active damping device at the resonant frequency h0 v (h0), expressed as follows:

[0137]

[0138] Embodiment 2 of the present invention provides a parameter design system for an active damping device across voltage levels for suppressing system resonance, which implements the parameter design method for an active damping device across voltage levels for suppressing system resonance described in embodiment 1, including:

[0139] Parameter acquisition module, used to collect resonant system parameters, obtain resonant frequency band range, determine resonant frequency and corresponding initial harmonic voltage content rate and target harmonic voltage content rate;

[0140] Damping calculation module, used to calculate the damping value of the system to suppress resonance;

[0141] Capacity design module, used to determine the capacity of active damping devices and cross-voltage transformer selection;

[0142] The RC design module is used to design the virtual resistance and capacitance values ​​of the active damping device.

[0143] In order to better describe the technical solution of the present invention and the beneficial technical effects brought about by it, a specific embodiment is described in detail below:

[0144] A 10kV system has a harmonic overshoot problem due to harmonic resonance amplification caused by the reactive power compensation device. The short-circuit capacity of the system is 159.2MVA, the fundamental frequency of the system is 50Hz, the system reactance / resistance ratio is 4, the installed capacity of the reactive power compensation capacitor is 7.02Mvar, and the rated voltage of the capacitor is 10.5kV. According to the formula in step 1, R s 0.16Ω, L s is 2mH, C is 202.8μF, according to Figure 3 Build a simulation model. The resonant frequency point h of the system r The harmonic current transfer coefficient is 5 times, and the transfer characteristic curve of the harmonic current transfer coefficient as the harmonic order changes is drawn according to the calculation formula of the harmonic current transfer coefficient. Figure 4 As shown, the resonance frequency band is set to [2, 6] times, and the system impedance and the reactive compensation capacitor have 5 parallel resonances, that is, h0 = 5. When the control device is not put into use, the harmonic voltage spectrum of the measured PCC point is as follows: Figure 5 As shown in the figure, the initial harmonic voltage content at the fifth harmonic is 5.07%, exceeding the national harmonic content limit for the 10kV voltage level. Taking the target harmonic voltage content as 2%, the control goal is to reduce the harmonic voltage content at the resonant frequency of the PCC point in the 10kV system to below the target harmonic voltage content.

[0145] According to the formula in step 2, first, the equivalent harmonic impedance at the 5th harmonic is calculated to be (61.6-j3.14)Ω. Then, the initial harmonic phase voltage at the 5th harmonic of the PCC point is calculated to be 0.293kV, and the harmonic current generated by the nonlinear load is 0.0047kA. Finally, based on the set target harmonic voltage content, the damping value for suppressing system resonance is calculated to be approximately 41Ω.

[0146] According to the formulas in steps 3.1 and 3.2, the harmonic current at the fifth harmonic of the damping branch is calculated to be 0.0028 kA, and the capacity of the active damping device is 0.05 MVA. With a margin factor of 1.3, the transformer capacity is calculated to be 0.065 MVA. The transformer ratio is 10 kV / 0.38 kV. Based on the transformer capacity and the high- and low-voltage side voltages, the transformer model is selected as S11-M-80 / 10. Based on the nameplate parameters of the selected transformer, the transformer load loss is calculated to be 1.25 kW and the short-circuit voltage percentage is 4%. According to the formula in step 3.4, the transformer equivalent to the high-voltage side resistance is calculated to be 19.5 Ω, and the transformer equivalent to the high-voltage side inductive reactance is calculated to be 50 Ω.

[0147] According to the formula in step 4, the virtual resistance of the active damping device at the fifth harmonic is calculated to be 0.03Ω, and the virtual capacitance of the active damping device at the fifth harmonic is calculated to be 8.8mF. The virtual resistance and capacitance of the active damping device are carried out through power electronics. A three-loop closed-loop control strategy is employed: an outer voltage loop, a grid-connected current loop, and an inner capacitor current loop. This ensures that the active damping device exhibits resistance-capacitance characteristics within the resonant frequency band.

[0148] Set the switch parameters to activate the active damping device at 0.2s. Figure 6 The voltage waveform of PCC point before and after adding active damping device is shown in Figure 2. Figure 7 This is the harmonic voltage spectrum at the PCC point after the active damping device is deployed. As can be seen, the fifth harmonic voltage content is 1.85% after the active damping device is deployed, which is 2% lower than the target harmonic voltage content and meets the control goal. This verifies the rationality and accuracy of the parameter design method of the present invention.

[0149] Compared with the prior art, the beneficial effects of the present invention include at least:

[0150] 1. The present invention provides a parameter design method for an active damping device across voltage levels, which performs parameter design on an active damping device across voltage levels, reduces the insulation performance requirements of the active damping device, and reduces equipment management investment and floor space.

[0151] 2. The present invention rationally designs the resistance and capacitance parameters of the active damping device, fully considering the impact of cross-voltage levels on the resistance and capacitance parameters of the device, making the parameter design results more accurate and further enhancing the resonance suppression effect.

[0152] The present disclosure may be a system, method and / or computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A parameter design method for a cross-voltage level active damping device for suppressing system resonance, characterized in that: The following steps are involved: Step 1: Collect the resonant system parameters, determine the resonant frequency band of the system according to the system impedance model, determine the resonant frequency and the corresponding initial harmonic voltage content within the resonant frequency band, and set the target harmonic voltage content; Step 2: Calculate the harmonic current generated by the nonlinear load based on the initial harmonic voltage content and the equivalent harmonic impedance of the system impedance model, and solve the damping value for suppressing system resonance based on the set target harmonic voltage content; Step 3: Determine the capacity of the active damping device based on the equivalent harmonic impedance, the harmonic current generated by the nonlinear load, and the damping value of the system to suppress resonance, and select a transformer across voltage levels; Step 4: Design a virtual resistance value of the active damping device according to the equivalent resistance of the selected transformer and the damping value of the system to suppress resonance, and design a virtual capacitance value of the active damping device according to the equivalent inductive reactance of the selected transformer.

2. The method for designing parameters of a cross-voltage active damping device for suppressing system resonance according to claim 1, characterized in that: In step 1, determining the resonant frequency band range of the system includes: The harmonic current transfer coefficient is calculated based on the system impedance model and is expressed as follows: Where: T(h) is the hth harmonic current transfer coefficient, h is the harmonic order, f0 is the system fundamental frequency, R s is the equivalent resistance of the system impedance, L s is the equivalent inductance of the system impedance, U N is the nominal voltage of the resonant system, S0 is the system operating short-circuit capacity, C is the capacitance of the capacitive device, if the system resonance is caused by the line, then C = c × l, c is the capacitance per unit length of the line, l is the line length, if the system resonance is caused by the reactive compensation device, then Q c is the installed capacity of the reactive compensation capacitor, U c is the rated voltage of the reactive compensation capacitor; Draw a curve of harmonic current transfer coefficient changing with harmonic order, and set the resonant frequency band range to [h L ,h H ], where the upper limit of harmonic order h H The lower limit of harmonic order h L are respectively the maximum and minimum values ​​of the integer harmonic orders whose harmonic current transfer coefficients are greater than or equal to 1 in the curve.

3. The method for designing parameters of a cross-voltage level active damping device for suppressing system resonance according to claim 1, characterized in that: In step 1, determining the resonant frequency and the corresponding initial harmonic voltage content within the resonant frequency band includes: When the system's resonant frequency band contains a single harmonic, the harmonic order is used as the system's resonant frequency. When the system's resonant frequency band contains multiple harmonics, the harmonic order with the largest harmonic voltage content is used as the system's resonant frequency. The initial harmonic voltage content is determined to be the harmonic voltage content at the common connection point of the system impedance model at the resonant frequency when no active damping device is added. Setting the target harmonic voltage content rate includes: The target harmonic voltage content is set according to the harmonic voltage limits in the national standard GB / T 14549-1993 "Power Quality Public Grid Harmonics".

4. The method for designing parameters of a cross-voltage level active damping device for suppressing system resonance according to claim 3, characterized in that: Step 2 includes: Based on the system impedance model, the equivalent harmonic inductive reactance of the system impedance at the resonant frequency and the equivalent harmonic capacitive reactance of the capacitive device at the resonant frequency are calculated respectively; The equivalent harmonic inductive reactance and the equivalent harmonic capacitive reactance at the resonant frequency are connected in parallel to obtain the equivalent harmonic impedance at the resonant frequency; Calculate the initial harmonic phase voltage at the common connection point at the resonant frequency according to the initial harmonic voltage content rate; The ratio of the initial harmonic phase voltage to the modulus of the equivalent harmonic impedance is the harmonic current at the resonant frequency generated by the nonlinear load; According to the set target harmonic voltage content, the harmonic current generated by the nonlinear load, the equivalent harmonic impedance and the nominal voltage of the resonant system are used to calculate the damping value of the system to suppress resonance.

5. The method for designing parameters of a cross-voltage level active damping device for suppressing system resonance according to claim 4, characterized in that: The damping value R of the system to suppress resonance is obtained by solving the following equation: Where h0 is the resonant frequency, I s (h0) is the harmonic current at the resonant frequency generated by the nonlinear load, Z(h0) is the equivalent harmonic impedance at the resonant frequency, HRU h2 is the target harmonic voltage content rate, U N is the nominal voltage of the resonant system.

6. The method for designing parameters of a cross-voltage active damping device for suppressing system resonance according to claim 5, characterized in that: Step 3 includes: Calculate the harmonic current I at the resonant frequency of the damping branch ad (h0), expressed as follows: Calculate the capacity S of the active damping device using the following formula: Where U NH is the rated voltage of the high voltage side of the transformer; Calculate the capacity S of the transformer T , expressed as follows: S T =kS Where k is the margin coefficient; Select the transformer according to the transformer capacity and high and low voltage side voltages.

7. The method for designing parameters of a cross-voltage level active damping device for suppressing system resonance according to claim 6, characterized in that: The margin coefficient value range is [1.3,1.5].

8. The method for designing parameters of a cross-voltage active damping device for suppressing system resonance according to claim 1, wherein: In step 4, the virtual resistance value R of the active damping device at the resonant frequency h0 is designed. v (h0), expressed as follows: Where n is the ratio of the rated voltage of the transformer high voltage side to the rated voltage of the low voltage side, R T is the resistance equivalent to the high-voltage side of the transformer, and R is the damping value of the system to suppress resonance; The transformer is equivalent to the resistance R on the high voltage side. T Calculated by the following formula: Where, P k is the load loss of the transformer, U NH is the rated voltage of the high voltage side of the transformer, S T is the capacity of the transformer.

9. The method for designing parameters of a cross-voltage level active damping device for suppressing system resonance according to claim 1, wherein: In step 4, the virtual capacitance value of the active damping device is designed by: Determine the virtual capacitance reactance X of the active damping device at the resonant frequency h0 according to the equivalent inductive reactance of the transformer v (h0), expressed as follows: Where, X T is the inductive reactance equivalent to the high-voltage side of the transformer, and n is the ratio of the rated voltage of the high-voltage side to the rated voltage of the low-voltage side of the transformer; The inductive reactance value of the transformer equivalent to the high voltage side is X T Calculated by the following formula: Where U k is the percentage of the short-circuit voltage of the selected transformer, U NH is the rated voltage of the high voltage side of the transformer, S T is the capacity of the transformer; The virtual capacitance value C of the active damping device at the resonant frequency h0 is v (h0) is calculated by the following formula: Where f0 is the fundamental frequency of the system.

10. A system for designing parameters of an active damping device across voltage levels for suppressing system resonance, which implements the method for designing parameters of an active damping device across voltage levels for suppressing system resonance as claimed in any one of claims 1 to 9, characterized in that: include: Parameter acquisition module, used to collect resonant system parameters, obtain resonant frequency band range, determine resonant frequency and corresponding initial harmonic voltage content rate and target harmonic voltage content rate; Damping calculation module, used to calculate the damping value of the system to suppress resonance; Capacity design module, used to determine the capacity of active damping devices and cross-voltage transformer selection; The RC design module is used to design the virtual resistance and capacitance values ​​of the active damping device.

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