Active filter resonance suppression method and system based on capacity utilization efficiency

Abstract

The present application discloses a method and system for suppressing resonance of an active filter based on capacity utilization efficiency, the method comprising: obtaining a first relationship between the capacity utilization efficiency of a current-type APF and a resonance deviation coefficient; obtaining a second relationship between the capacity utilization efficiency of a resistance-type APF and the resonance deviation coefficient; obtaining a critical point of the resonance deviation coefficient according to the first relationship and the second relationship; and controlling the switching between the current-type APF and the resistance-type APF according to the comparison result of the real-time resonance deviation coefficient and the critical point. The use of the embodiment of the present application can dynamically select the APF type with better governance effect, effectively improving the resonance suppression capability.

Description

Technical Field

[0001] The present application relates to the field of resonance suppression technology, and in particular to a method and system for suppressing resonance of an active filter based on capacity utilization efficiency. Background Art

[0002] The resonance problem is an important challenge that the power system has faced for a long time. It not only affects the power quality and equipment operation, but also threatens the efficiency and stability of the power grid. With the expansion of the scale of power electronic devices such as wind power, photovoltaics, and DC, the risk of resonance events in new power systems has become more prominent, and the resonance characteristics show strong time-varying characteristics with the operating conditions, making it difficult for traditional passive governance strategies to meet the needs of flexible governance. With the development of power electronics and semiconductor devices, active filters (APF) have played a more important role in the resonance suppression of new power systems. Among them, current-type active power filters (current-type ARF, I-APF) and resistor-type active power filters (resistor-type ARF, R-APF) are the two most common types.

[0003] Existing research focuses on the dynamic performance optimization of APF, but pays less attention to the resonance suppression effect under capacity limitation. For example, I-APF adopts a proportional current limiting control strategy to fully utilize its remaining capacity while avoiding APF overload; R-APF adopts an adaptive damping control strategy to dynamically adjust the virtual impedance parameters according to the system operating conditions to improve the harmonic suppression effect. However, most of these studies focus on the optimization of a single type of APF, and the resonance suppression effect is poor. Summary of the invention

[0004] The present application provides an active filter resonance suppression method and system based on capacity utilization efficiency to solve the problem that the prior art focuses on the optimization of a single type of APF and has a poor resonance suppression effect.

[0005] To achieve the above objectives, an embodiment of the present application provides an active filter resonance suppression method based on capacity utilization efficiency, comprising:

[0006] Obtaining a first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-type APF;

[0007] Obtaining a second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient;

[0008] According to the first relationship and the second relationship, a critical point of the resonance deviation coefficient is obtained;

[0009] According to the comparison result of the real-time resonance deviation coefficient and the critical point, controlling the switching between the current-type APF and the resistance-type APF;

[0010] Among them, the capacity utilization efficiency of the current-type APF is expressed as , is the phase angle of the current flowing into the current-type APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the current-type APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the current-type APF;

[0011] The capacity utilization efficiency of the resistive APF is expressed as , is the phase angle of the current flowing into the resistive APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the resistive APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the resistive APF;

[0012] The resonance deviation coefficient is the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency.

[0013] As an improvement of the above scheme, in the simplified harmonic equivalent circuit of the current-type APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductive reactance, the current transformer, the voltage transformer and the current-type APF are connected end to end in sequence; the current transformer is also connected to the first integrator and the output current tracking controller in sequence; the other end of the output current tracking controller is connected to the current-type APF, the voltage transformer is also connected to the cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source;

[0014] In the simplified harmonic equivalent circuit of the resistive APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductance, the current transformer, the voltage transformer and the resistive APF are connected end to end in sequence; the voltage transformer is also connected to a second integrator and an output current tracking controller in sequence; the other end of the output current tracking controller is connected to the resistive APF, the voltage transformer is also connected to a cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source.

[0015] As an improvement of the above solution, the first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-source APF is obtained, including:

[0016] set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance;

[0017] set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance;

[0018] calculate :

[0019]

[0020] calculate :

[0021]

[0022] right Taking partial derivatives, we get and Relationship:

[0023]

[0024] Using the chain rule of derivation, we get and Relationship:

[0025]

[0026] in, is the current compensation coefficient of the current type APF.

[0027] As an improvement of the above solution, the second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient is obtained, including:

[0028] set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance;

[0029] set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance;

[0030] calculate :

[0031]

[0032] calculate :

[0033]

[0034] make ,right Taking partial derivatives, we get and Relationship:

[0035]

[0036] Using the chain rule of derivation, we get and Relationship:

[0037]

[0038] in, Indicates the current compensation coefficient of the resistive APF.

[0039] As an improvement of the above scheme, the control of switching between the current-type APF and the resistance-type APF according to the comparison result of the real-time resonance deviation coefficient and the critical point includes:

[0040] When the real-time resonance deviation coefficient is less than the critical point, the control is switched to the current-type APF;

[0041] When the real-time resonance deviation coefficient is greater than the critical point, control is switched to the resistive APF.

[0042] To achieve the above object, an embodiment of the present application further provides an active filter resonance suppression system based on capacity utilization efficiency, including a controller, wherein the controller is configured to:

[0043] Obtaining a first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-type APF;

[0044] Obtaining a second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient;

[0045] According to the first relationship and the second relationship, a critical point of the resonance deviation coefficient is obtained;

[0046] According to the comparison result of the real-time resonance deviation coefficient and the critical point, controlling the switching between the current-type APF and the resistance-type APF;

[0047] Among them, the capacity utilization efficiency of the current-type APF is expressed as , is the phase angle of the current flowing into the current-type APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the current-type APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the current-type APF;

[0048] The capacity utilization efficiency of the resistive APF is expressed as , is the phase angle of the current flowing into the resistive APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the resistive APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the resistive APF;

[0049] The resonance deviation coefficient is the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency.

[0050] As an improvement of the above scheme, in the simplified harmonic equivalent circuit of the current-type APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductive reactance, the current transformer, the voltage transformer and the current-type APF are connected end to end in sequence; the current transformer is also connected to the first integrator and the output current tracking controller in sequence; the other end of the output current tracking controller is connected to the current-type APF, the voltage transformer is also connected to the cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source;

[0051] In the simplified harmonic equivalent circuit of the resistive APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductance, the current transformer, the voltage transformer and the resistive APF are connected end to end in sequence; the voltage transformer is also connected to a second integrator and an output current tracking controller in sequence; the other end of the output current tracking controller is connected to the resistive APF, the voltage transformer is also connected to a cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source.

[0052] As an improvement of the above solution, the first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-source APF is obtained, including:

[0053] set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance;

[0054] set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance;

[0055] calculate :

[0056]

[0057] calculate :

[0058]

[0059] right Taking partial derivatives, we get and Relationship:

[0060]

[0061] Using the chain rule of derivation, we get and Relationship:

[0062]

[0063] in, is the current compensation coefficient of the current type APF.

[0064] As an improvement of the above solution, the second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient is obtained, including:

[0065] set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance;

[0066] set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance;

[0067] calculate :

[0068]

[0069] calculate :

[0070]

[0071] make ,right Taking partial derivatives, we get and Relationship:

[0072]

[0073] Using the chain rule of derivation, we get and Relationship:

[0074]

[0075] in, Indicates the current compensation coefficient of the resistive APF.

[0076] As an improvement of the above scheme, the control of switching between the current-type APF and the resistance-type APF according to the comparison result of the real-time resonance deviation coefficient and the critical point includes:

[0077] When the real-time resonance deviation coefficient is less than the critical point, the control is switched to the current-type APF;

[0078] When the real-time resonance deviation coefficient is greater than the critical point, control is switched to the resistive APF.

[0079] Compared with the prior art, the present application realizes the intelligent selection of active filter types and control strategy switching by introducing the concept of capacity utilization efficiency under the condition of limited capacity. By combining the advantages of current-type APF and resistance-type APF, the present application can dynamically select the APF type with better governance effect according to the actual operating conditions and capacity conditions of the system, effectively improving the resonance suppression capability. Unlike the traditional single-type APF optimization method, the present application not only improves the resonance governance efficiency of the system, but also can achieve more efficient harmonic compensation and damping effects without increasing the equipment capacity, thereby improving the stability and power quality of the power grid. In addition, the control strategy switching mechanism of the present application makes APF more adaptable under different operating conditions, further reducing the probability of system resonance. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 It is a flow chart of an active filter resonance suppression method based on capacity utilization efficiency provided in an embodiment of the present application;

[0081] Figure 2 This is a typical APF resonance suppression system application scenario provided by the embodiment of the present application;

[0082] Figure 3 is a harmonic equivalent circuit diagram of a typical APF resonance suppression system provided in an embodiment of the present application;

[0083] Figure 4 It is a harmonic equivalent circuit of a simplified typical APF resonance suppression system provided in an embodiment of the present application;

[0084] Figure 5 It is a simplified harmonic equivalent circuit of a current-type APF provided in an embodiment of the present application;

[0085] Figure 6 It is a simplified harmonic equivalent circuit of a resistive APF provided in an embodiment of the present application;

[0086] Figure 7is a schematic diagram of capacity utilization efficiency provided by an embodiment of the present application;

[0087] Figure 8 is a schematic diagram of the change trend of capacity utilization efficiency provided by an embodiment of the present application;

[0088] Fig. 9 is a control structure diagram of a combined active filter based on capacity utilization efficiency provided by an embodiment of the present application;

[0089] Fig.10 This is a diagram of the treatment effect of the combined active filter provided in the embodiment of the present application. DETAILED DESCRIPTION

[0090] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0091] See also Figure 1 , Figure 1 1 is a flow chart of an active filter resonance suppression method based on capacity utilization efficiency provided in an embodiment of the present application, wherein the active filter resonance suppression method based on capacity utilization efficiency comprises:

[0092] S1, obtaining a first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-type APF;

[0093] S2, obtaining a second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient;

[0094] S3. Obtaining a critical point of the resonance deviation coefficient according to the first relationship and the second relationship;

[0095] S4, according to the comparison result of the real-time resonance deviation coefficient and the critical point, controlling the switching between the current-type APF and the resistance-type APF;

[0096] Among them, the capacity utilization efficiency of the current-type APF is expressed as , is the phase angle of the current flowing into the current-type APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the current-type APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the current-type APF;

[0097] The capacity utilization efficiency of the resistive APF is expressed as , is the phase angle of the current flowing into the resistive APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the resistive APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the resistive APF;

[0098] The resonance deviation coefficient is the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency.

[0099] In an embodiment of the present application, a curve can be drawn according to the first relationship, and another curve can be drawn according to the second relationship. The two curves intersect to obtain an intersection point, which is the critical point of the resonance deviation coefficient. Based on the comparison result between the real-time resonance deviation coefficient and the critical point, the switching between the current-type APF and the resistance-type APF is controlled.

[0100] Compared with the prior art, the present application realizes the intelligent selection of active filter types and control strategy switching by introducing the concept of capacity utilization efficiency under the condition of limited capacity. By combining the advantages of current-type APF and resistance-type APF, the present application can dynamically select the APF type with better governance effect according to the actual operating conditions and capacity conditions of the system, effectively improving the resonance suppression capability. Unlike the traditional single-type APF optimization method, the present application not only improves the resonance governance efficiency of the system, but also can achieve more efficient harmonic compensation and damping effects without increasing the equipment capacity, thereby improving the stability and power quality of the power grid. In addition, the control strategy switching mechanism of the present application makes APF more adaptable under different operating conditions, further reducing the probability of system resonance.

[0101] In an optional embodiment, in the simplified harmonic equivalent circuit of the current-type APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductive reactance, the current transformer, the voltage transformer and the current-type APF are connected end to end in sequence; the current transformer is also connected to a first integrator and an output current tracking controller in sequence; the other end of the output current tracking controller is connected to the current-type APF, the voltage transformer is also connected to a cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source;

[0102] In the simplified harmonic equivalent circuit of the resistive APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductance, the current transformer, the voltage transformer and the resistive APF are connected end to end in sequence; the voltage transformer is also connected to a second integrator and an output current tracking controller in sequence; the other end of the output current tracking controller is connected to the resistive APF, the voltage transformer is also connected to a cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source.

[0103] It is worth mentioning that Figure 2A typical APF resonance suppression system application scenario is demonstrated. The system consists of wind turbines, courtyard step-up transformers, long-distance transmission cables, and onshore power grids. Compared with overhead lines, offshore underground cables have stronger capacitive characteristics, which interact with inductive elements on the land side to form resonance, causing the PCC (Point of Common Coupling) harmonic voltage to exceed the standard. In order to suppress the resonance and keep the PCC voltage within the standard range, an APF needs to be installed at the PCC.

[0104] Figure 3 This is the harmonic equivalent circuit diagram of a typical APF resonance suppression system. The background harmonics of the onshore power grid are represented by the Thevenin equivalent circuit, and the hth-order background harmonic is represented by an equivalent harmonic voltage source. Equivalent harmonic impedance R of the series system S and L S The harmonic source of the offshore wind farm is represented by the Norton equivalent circuit, and the hth harmonic source is represented by an equivalent harmonic current source I sh Connect an equivalent harmonic impedance Z in parallel WF Representation; The high-voltage submarine cable is represented by a π-shaped equivalent circuit, where Rc, Lc and C are the series resistance, series inductance and parallel capacitance values ​​of the equivalent circuit respectively.

[0105] In order to analyze the steady-state resonance suppression performance of APF more clearly, I-APF and R-APF are simplified and equivalent to controlled current source models. Among them, I-APF detects the system harmonic current I L Generate I-APF reference current signal:

[0106] I ref.I = k I I L (1)

[0107] In the formula, k I is the current compensation coefficient of I-APF, I L is the system harmonic current.

[0108] The R-APF generates the R-APF reference current signal by detecting the PCC harmonic voltage:

[0109] I ref.R = V pcc / R v (2)

[0110] Where V pcc is the harmonic voltage at the PCC, R v is the virtual impedance set by the R-APF.

[0111] At the same time, offshore wind power system resonance usually occurs at low harmonics (5th -13 th ), at this frequency, the submarine cable mainly exhibits capacitance characteristics, and the equivalent capacitive reactance of the cable is expressed as X C The equivalent impedance Z of an offshore wind farm WF Much larger than X C , and because the low-order harmonics generated by PWM switching are very small, the impact of offshore wind farms can be ignored at the resonant frequency. Figure 4 It is a simplified harmonic equivalent circuit of a typical APF resonance suppression system. is the equivalent harmonic voltage source, R L is the system equivalent impedance, X L is the system equivalent inductance, CT is the current transformer, VT is the voltage transformer, Gc is the output current tracking controller, X C is the equivalent capacitive reactance of the cable, R v is the equivalent virtual resistance of the R-APF branch, Z v is the equivalent virtual impedance of the I-APF branch. Among them, for the current-type APF simplified harmonic equivalent circuit, as shown in Figure 5 As shown, the proportional coefficient of the first integrator is k I , the output current tracks the input current I of the controller Gc ref =I ref.I For the simplified harmonic equivalent circuit of the resistive APF, Figure 6 As shown, the proportional coefficient of the second integrator is , the output current tracks the input current I of the controller Gc ref =I ref.R .

[0112] according to Figure 4 , the harmonic current I flowing to the cable side C = (1- k I ) I L Therefore, Z v It can be expressed as:

[0113] (3)

[0114] In the formula, I A is the current flowing into the APF branch, which is equal to the reference current I of the APF ref I C is the current flowing into the equivalent capacitive reactance of the cable.

[0115] according to Figure 4 Write the corresponding circuit equation:

[0116] (4)

[0117] In the formula, is the total system impedance, , Z APF Represents the equivalent virtual impedance of the active filter branch. When I-APF is used, Z APF =Z v , when using R-APF Z APF =R v .

[0118] The magnitude of the PCC harmonic voltage can be used to measure the APF's suppression effect on system resonance and background harmonic voltage amplification. From formula (4), V pcc The expression is:

[0119] (5)

[0120] According to formula (5), in the same governance scenario (i.e., the impedance Z L , X C And the equivalent harmonic voltage source U sh are the same), V pcc with I A The amplitude and phase of A For two APFs with the same amplitude, according to (1) and (2), we can know their corresponding I A The phases will be different, so the two APFs will have different governance effects under the same capacity. Figure 7 The V is shown in the form of a vector diagram pcc and I A The specific relationship between phases.

[0121] Figure 7 middle, For U sh Leading I A The phase angle, The total impedance of the system is Z L The outermost dotted line represents V pcc Follow The lower area indicates that APF effectively reduces V after it is connected to the system. pcc The upper area represents the V after APF is connected to the system. pcc The added scenario is the invalid governance area. It can be found that V pcc Size and related, The larger the V pcc The smaller it is, the better the governance effect. Therefore, the capacity utilization efficiency CUE is defined to measure the governance effect of APF under the same capacity:

[0122] CUE = (6)

[0123] For the resonance suppression system using current-type APF, The phase angle of the current leading the equivalent harmonic voltage source into the current-type APF is expressed as express;

[0124] For the resonance suppression system using resistive APF, The phase angle of the current flowing into the resistive APF by the equivalent harmonic voltage source is expressed as express.

[0125] According to formula (6), CUE is given by and Determine, where U is obtained by formula (4) sh and I A The relationship between the two can be used to calculate the phase angle between them. .

[0126] (7)

[0127] According to the above formula, U sh Leading I A Phase angle is equal to the phase angle of the impedance Z, which is affected by Figure 4 All impedances Z L , X C , Z APF These impedances vary in different offshore wind power systems. In order to obtain general conclusions, the resonance deviation coefficient η and the damping coefficient λ are introduced to L These impedances are normalized by the magnitude of .

[0128] (8)

[0129] η represents the equivalent capacitive reactance of the submarine cable and the equivalent inductive reactance of the system at the harmonic compensation frequency The closer η is to 1, the higher the resonant frequency. The closer , when η=1, .

[0130] (9)

[0131] Indicates the system equivalent impedance and system equivalent inductance at the harmonic compensation frequency The larger the λ, the greater the system damping.

[0132] In an optional embodiment, obtaining a first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-source APF includes:

[0133] set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance;

[0134] set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance;

[0135] calculate :

[0136]

[0137] calculate :

[0138]

[0139] right Taking partial derivatives, we get and Relationship:

[0140]

[0141] Using the chain rule of derivation, we get and Relationship:

[0142]

[0143] in, is the current compensation coefficient of the current type APF.

[0144] It is worth noting that the impedance angle of the total impedance of the system can be expressed as:

[0145] (10)

[0146] From equations (3) and (8), it can be seen that the equivalent impedance of I-APF can be expressed as:

[0147] (11)

[0148] Where, j is the imaginary unit;

[0149] According to equations (8), (9) and (11), the impedance in equation (7) is replaced as follows:

[0150] (12)

[0151] According to formula (12), we can calculate :

[0152] (13)

[0153] From formula (13), we can see that Affected by η, λ and The impact on Find the partial derivative to get its changing law, that is, Respectively and , , Relationship:

[0154] (14)

[0155] From formula (14), we can see that , and Always positively correlated. , It is always negatively correlated with η. The relationship with λ is not obvious. We can combine formula (10) and further use the chain rule of derivation to obtain the capacity utilization efficiency of I-APF: Respectively and ,η, Relationship:

[0156] (15)

[0157] According to formula (15), the specific change of capacity utilization efficiency of I-APF is: , With k I There is always a positive correlation. , It is positively and negatively correlated with η. When η = 0, reaches a maximum and is always equal to 1.

[0158] In an optional embodiment, obtaining the second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient includes:

[0159] set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance;

[0160] set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance;

[0161] calculate :

[0162]

[0163] calculate :

[0164]

[0165] make ,right Taking partial derivatives, we get and Relationship:

[0166]

[0167] Using the chain rule of derivation, we get and Relationship:

[0168]

[0169] in, Indicates the current compensation coefficient of the resistive APF.

[0170] It is worth noting that if Figure 6 As shown, the R-APF branch is modeled as an equivalent resistor R v Therefore, I A With voltage V pcc In phase, and I C Advanced V pcc 90°. In order to unify the comparison between R-APF and I-APF, the current compensation coefficient of R-APF is introduced here , defined as = |I A | / |I L |. Its value reflects the degree of harmonic compensation provided by R-APF. Then, R v You can use k R It is expressed as:

[0171] (16)

[0172] Similar to the analysis of I-APF. By substituting equation (8), equation (9) and the above equation into equation (7), after normalizing the impedance, U sh and I A The relationship between them is as follows:

[0173] (17)

[0174] Where, j is the imaginary unit;

[0175] According to the above formula, U sh Ahead I A Phase angle It can be determined as follows:

[0176] (18)

[0177] It can be found By η, λ and Decision. Partial derivative analysis The changing characteristics of , so formula (18) can be expressed as ,right Find the partial derivative to get its changing law, that is, Respectively and , , Relationship:

[0178] (19)

[0179] It can be found that when η<1 + λ², <0, and when η>1 + λ², >0. Therefore, when η<1 + λ², and positive correlation, and when η>1 + λ², and Negatively correlated. In addition, due to is always less than 0, so Positively correlated with η.

[0180] Next, analyze right The impact, specifically, on about Find the partial derivative result. And use the chain rule to analyze and right Impact:

[0181] (20)

[0182] Follow The changing trends of and η are as follows: and Positive correlation. When η<1 + λ², is positively correlated with η; and when η>1 + λ², Negatively correlated with η.

[0183] In the embodiment of the present application, based on the above analysis, the CUE changes of I-APF and R-APF can be summarized as follows:

[0184] 1) Capacity utilization efficiency of I-APF and Positively correlated with η, and negatively correlated with η.

[0185] 2) Capacity utilization efficiency of R-APF and Positive correlation; when η<1 + λ², it is positively correlated with η; when η>1 + λ², it is negatively correlated with η.

[0186] In addition, according to formula (13), when η = 0, Always equal to , for any and λ are both true, then the capacity utilization efficiency of I-APF is is always equal to 1. A similar situation also exists in R-APF, when η = 1+λ 2 hour, Always equal to , for any and λ are both true, then the capacity utilization efficiency of R-APF is Always equal to 1.

[0187] In an optional embodiment, controlling the switching between the current-type APF and the resistance-type APF according to the comparison result between the real-time resonance deviation coefficient and the critical point includes:

[0188] When the real-time resonance deviation coefficient is less than the critical point, the control is switched to the current-type APF;

[0189] When the real-time resonance deviation coefficient is greater than the critical point, control is switched to the resistive APF.

[0190] Based on the above analysis, a schematic diagram of the change trend of the two APF capacity utilization efficiency and the resonance deviation coefficient η can be drawn, as shown in Figure 8 As shown. It can be found that there is a critical point η0 in the capacity utilization efficiency of the two APFs. When η<η0, the capacity utilization efficiency of I-APF is higher and the governance effect is better. At this time, it can be controlled to switch to I-APF; when η>η0, the capacity utilization efficiency of R-APF is higher and the governance effect is better. At this time, it can be controlled to switch to R-APF.

[0191] In a specific example, I-APF and R-APF have high similarities in topology and control structure, except that the generation method of APF output reference current is different, as shown in equations (1) and (2). Therefore, the two control strategies can be combined and used on an APF to simulate I-APF and R-APF by switching the generation method of reference current. Figure 8 According to the changing trend of APF capacity utilization efficiency, we can select APF control strategy with higher capacity utilization efficiency to achieve better governance effect without changing APF capacity.

[0192] The specific control structure of the combined active filter is as follows: Fig. 9 As shown. After wind power is generated, the electricity is collected by the collection system and transmitted to the onshore power grid through submarine cables after being stepped up at the substation. In order to offset the capacitive effect of the submarine cable, a shunt reactor L is installed at the onshore end. g In the APF control structure, PLL is a phase-locked loop, and θ represents the current voltage phase angle. is the reference current output by APF. When η<η0, current type control is adopted, that is, = I ref.I ; When η>η0, resistance type control is adopted, that is, = I ref.R After the dq coordinate transformation, the signal is decomposed into the active axis (d axis) component and the reactive axis (q axis) component. Then, these components are adjusted by proportional integral (PI) control and proportional resonant (PR) control respectively. At the same time, the DC side voltage of the inverter is detected and the PI controller is used to ensure its voltage is constant. and They are the d-axis and q-axis reference signals of the APF inverter output voltage, which are output after PWM pulse modulation, and finally realize the inverter output current I A control.

[0193] Fig.10 The treatment effect of the combined active filter is demonstrated. When APF is not put into use, the system has serious background harmonic amplification phenomenon, the PCC voltage waveform is obviously distorted, THD=3.87%, which has exceeded the specified harmonic voltage limit. At 2s, the APF is controlled by current mode control, and it can be found that the PCC harmonic voltage content is significantly reduced. At 4s, the APF capacity is kept unchanged, and the APF is switched to resistance mode control. Compared with the current mode control, the PCC harmonic voltage content is reduced again, indicating that there is indeed a difference in the treatment efficiency of the two APFs with the same capacity.

[0194] In addition, an active filter resonance suppression system based on capacity utilization efficiency provided in an embodiment of the present application includes a controller, wherein the controller is configured to:

[0195] Obtaining a first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-type APF;

[0196] Obtaining a second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient;

[0197] According to the first relationship and the second relationship, a critical point of the resonance deviation coefficient is obtained;

[0198] According to the comparison result of the real-time resonance deviation coefficient and the critical point, controlling the switching between the current-type APF and the resistance-type APF;

[0199] Among them, the capacity utilization efficiency of the current-type APF is expressed as , is the phase angle of the current flowing into the current-type APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the current-type APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the current-type APF;

[0200] The capacity utilization efficiency of the resistive APF is expressed as , is the phase angle of the current flowing into the resistive APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the resistive APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the resistive APF;

[0201] The resonance deviation coefficient is the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency.

[0202] Optionally, in the simplified harmonic equivalent circuit of the current-type APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductive reactance, the current transformer, the voltage transformer and the current-type APF are connected end to end in sequence; the current transformer is also connected to a first integrator and an output current tracking controller in sequence; the other end of the output current tracking controller is connected to the current-type APF, the voltage transformer is also connected to a cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source;

[0203] In the simplified harmonic equivalent circuit of the resistive APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductance, the current transformer, the voltage transformer and the resistive APF are connected end to end in sequence; the voltage transformer is also connected to a second integrator and an output current tracking controller in sequence; the other end of the output current tracking controller is connected to the resistive APF, the voltage transformer is also connected to a cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source.

[0204] Optionally, obtaining a first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-source APF includes:

[0205] set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance;

[0206] set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance;

[0207] calculate :

[0208]

[0209] calculate :

[0210]

[0211] right Taking partial derivatives, we get and Relationship:

[0212]

[0213] Using the chain rule of derivation, we get and Relationship:

[0214]

[0215] in, is the current compensation coefficient of the current type APF.

[0216] Optionally, the obtaining of the second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient includes:

[0217] set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance;

[0218] set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance;

[0219] calculate :

[0220]

[0221] calculate :

[0222]

[0223] make ,right Taking partial derivatives, we get and Relationship:

[0224]

[0225] Using the chain rule of derivation, we get and Relationship:

[0226]

[0227] in, Indicates the current compensation coefficient of the resistive APF.

[0228] Optionally, controlling the switching between the current-type APF and the resistance-type APF according to the comparison result between the real-time resonance deviation coefficient and the critical point includes:

[0229] When the real-time resonance deviation coefficient is less than the critical point, the control is switched to the current-type APF;

[0230] When the real-time resonance deviation coefficient is greater than the critical point, control is switched to the resistive APF.

[0231] It is worth noting that the working process of each module in the active filter resonance suppression system 10 based on capacity utilization efficiency described in the embodiment of the present application can refer to the working process of the active filter resonance suppression method based on capacity utilization efficiency described in the above embodiment, which will not be repeated here.

[0232] An active filter resonance suppression system 10 based on capacity utilization efficiency provided in an embodiment of the present application realizes intelligent selection of active filter types and control strategy switching by introducing the concept of capacity utilization efficiency when the capacity is limited. By combining the advantages of current-type APF and resistance-type APF, the present application can dynamically select the APF type with better governance effect according to the actual operating conditions and capacity conditions of the system, thereby effectively improving the resonance suppression capability. Unlike the traditional single-type APF optimization method, the present application not only improves the system's resonance governance efficiency, but also can achieve more efficient harmonic compensation and damping effects without increasing the equipment capacity, thereby improving the stability and power quality of the power grid. In addition, the control strategy switching mechanism of the present application enables the APF to have stronger adaptability under different operating conditions, further reducing the probability of system resonance.

[0233] In addition, an embodiment of the present application further provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored computer program; wherein, when the computer program is running, it controls the device where the computer-readable storage medium is located to execute the active filter resonance suppression method based on capacity utilization efficiency as described in any of the above embodiments.

[0234] In addition, an embodiment of the present application further provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the active filter resonance suppression method based on capacity utilization efficiency as described in any of the above embodiments.

[0235] In addition, the embodiment of the present application also provides an active filter resonance suppression device based on capacity utilization efficiency, including: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps in the above-mentioned active filter resonance suppression method embodiment based on capacity utilization efficiency are implemented. Alternatively, when the processor executes the computer program, the functions of each module / unit in the above-mentioned device embodiments are implemented.

[0236] Exemplarily, the computer program may be divided into one or more modules / units, and the one or more modules / units are stored in the memory and executed by the processor to complete the present application. The one or more modules / units may be a series of computer program instruction segments capable of completing specific functions, and the instruction segments are used to describe the execution process of the computer program in the active filter resonance suppression device based on capacity utilization efficiency.

[0237] The active filter resonance suppression device based on capacity utilization efficiency can be a computing device such as a desktop computer, a notebook, a PDA, and a cloud server. The active filter resonance suppression device based on capacity utilization efficiency can include, but is not limited to, a processor and a memory. Those skilled in the art can understand that the schematic diagram is only an example of an active filter resonance suppression device based on capacity utilization efficiency, and does not constitute a limitation on the active filter resonance suppression device based on capacity utilization efficiency. It can include more or less components than shown in the figure, or combine certain components, or different components. For example, the active filter resonance suppression device based on capacity utilization efficiency can also include input and output devices, network access devices, buses, etc.

[0238] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the active filter resonance suppression device based on capacity utilization efficiency, and uses various interfaces and lines to connect various parts of the active filter resonance suppression device based on capacity utilization efficiency.

[0239] The memory can be used to store the computer program and / or module, and the processor realizes various functions of the active filter resonance suppression device based on capacity utilization efficiency by running or executing the computer program and / or module stored in the memory and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area can store data created according to the use of the mobile phone (such as audio data, a phone book, etc.), etc. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0240] Wherein, if the module / unit integrated in the active filter resonance suppression device based on capacity utilization efficiency is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0241] It should be noted that the device embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. In addition, in the accompanying drawings of the device embodiments provided by the present application, the connection relationship between the modules indicates that there is a communication connection between them, which may be specifically implemented as one or more communication buses or signal lines. A person of ordinary skill in the art can understand and implement it without paying any creative work.

[0242] The above is a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A method for suppressing resonance of an active filter based on capacity utilization efficiency, characterized in that: include: Obtaining a first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-type APF; Obtaining a second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient; Obtaining a critical point of the resonance deviation coefficient according to the first relationship and the second relationship; According to the comparison result of the real-time resonance deviation coefficient and the critical point, controlling the switching between the current-type APF and the resistance-type APF; Among them, the capacity utilization efficiency of the current-type APF is expressed as , is the phase angle of the current flowing into the current-type APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the current-type APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the current-type APF; The capacity utilization efficiency of the resistive APF is expressed as , is the phase angle of the current flowing into the resistive APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the resistive APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the resistive APF; The resonance deviation coefficient is the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency; Among them, in the simplified harmonic equivalent circuit of the current-type APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductive reactance, the current transformer, the voltage transformer and the current-type APF are connected end to end in sequence; the current transformer is also connected to the first integrator and the output current tracking controller in sequence; the other end of the output current tracking controller is connected to the current-type APF, the voltage transformer is also connected to the cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source; In the simplified harmonic equivalent circuit of the resistive APF, an equivalent harmonic voltage source, a system equivalent impedance, a system equivalent inductive reactance, a current transformer, a voltage transformer and a resistive APF are connected end to end in sequence; the voltage transformer is also connected to a second integrator and an output current tracking controller in sequence; the other end of the output current tracking controller is connected to the resistive APF, the voltage transformer is also connected to a cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source; The obtaining of the first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-source APF includes: set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance; set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance; calculate : calculate : right Taking partial derivatives, we get and Relationship: Using the chain rule of derivation, we get and Relationship: in, is the current compensation coefficient of the current type APF; The obtaining of the second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient includes: set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance; set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance; calculate : calculate : make ,right Taking partial derivatives, we get and Relationship: Using the chain rule of derivation, we get and Relationship: in, Indicates the current compensation coefficient of the resistive APF.

2. The active filter resonance suppression method based on capacity utilization efficiency according to claim 1, characterized in that: The controlling the switching between the current-type APF and the resistance-type APF according to the comparison result between the real-time resonance deviation coefficient and the critical point comprises: When the real-time resonance deviation coefficient is less than the critical point, the control is switched to the current-type APF; When the real-time resonance deviation coefficient is greater than the critical point, control is switched to the resistive APF.

3. An active filter resonance suppression system based on capacity utilization efficiency, characterized in that: comprising a controller configured to: Obtaining a first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-type APF; Obtaining a second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient; Obtaining a critical point of the resonance deviation coefficient according to the first relationship and the second relationship; According to the comparison result of the real-time resonance deviation coefficient and the critical point, controlling the switching between the current-type APF and the resistance-type APF; Among them, the capacity utilization efficiency of the current-type APF is expressed as , is the phase angle of the current flowing into the current-type APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the current-type APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the current-type APF; The capacity utilization efficiency of the resistive APF is expressed as , is the phase angle of the current flowing into the resistive APF by the equivalent harmonic voltage source in the simplified harmonic equivalent circuit of the resistive APF, is the impedance angle of the total impedance of the system in the simplified harmonic equivalent circuit of the resistive APF; The resonance deviation coefficient is the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency; Among them, in the simplified harmonic equivalent circuit of the current-type APF, the equivalent harmonic voltage source, the system equivalent impedance, the system equivalent inductive reactance, the current transformer, the voltage transformer and the current-type APF are connected end to end in sequence; the current transformer is also connected to the first integrator and the output current tracking controller in sequence; the other end of the output current tracking controller is connected to the current-type APF, the voltage transformer is also connected to the cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source; In the simplified harmonic equivalent circuit of the resistive APF, an equivalent harmonic voltage source, a system equivalent impedance, a system equivalent inductive reactance, a current transformer, a voltage transformer and a resistive APF are connected end to end in sequence; the voltage transformer is also connected to a second integrator and an output current tracking controller in sequence; the other end of the output current tracking controller is connected to the resistive APF, the voltage transformer is also connected to a cable equivalent capacitive reactance, and the other end of the cable equivalent capacitive reactance is connected to the equivalent harmonic voltage source; The obtaining of the first relationship between the capacity utilization efficiency and the resonance deviation coefficient of the current-source APF includes: set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance; set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance; calculate : calculate : right Taking partial derivatives, we get and Relationship: Using the chain rule of derivation, we get and Relationship: in, is the current compensation coefficient of the current type APF; The obtaining of the second relationship between the capacity utilization efficiency of the resistive APF and the resonance deviation coefficient includes: set up , where η represents the ratio of the equivalent capacitive reactance of the submarine cable to the equivalent inductive reactance of the system at the harmonic compensation frequency, represents the equivalent capacitive reactance of the submarine cable, Indicates the system equivalent inductive reactance; set up ,in, It represents the ratio of the system equivalent impedance to the system equivalent inductive reactance at the harmonic compensation frequency. represents the system equivalent impedance, Indicates the system equivalent inductive reactance; calculate : calculate : make ,right Taking partial derivatives, we get and Relationship: Using the chain rule of derivation, we get and Relationship: in, Indicates the current compensation coefficient of the resistive APF.

4. The active filter resonance suppression system based on capacity utilization efficiency as claimed in claim 3, characterized in that: The controlling the switching between the current-type APF and the resistance-type APF according to the comparison result between the real-time resonance deviation coefficient and the critical point comprises: When the real-time resonance deviation coefficient is less than the critical point, the control is switched to the current-type APF; When the real-time resonance deviation coefficient is greater than the critical point, control is switched to the resistive APF.

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