Resonance identification suppression method and system for power distribution system under distributed photovoltaic access

Abstract

According to the resonance identification suppression method and system for the power distribution system under distributed photovoltaic access, the frequency corresponding to the maximum modal impedance value is a resonance frequency point, the element corresponding to the maximum total response index value is a resonance key element, and the modal impedance of the resonance key element at the resonance frequency point is resonance impedance; obtaining a current harmonic component and a voltage harmonic component of a grid connection point of the inverter and a filter inductance of the inverter; calculating the equivalent admittance of the inverter based on the control coefficient of the current controller by using the resonant impedance and the filter inductance of the inverter; calculating the harmonic component of the current control instruction value by using the equivalent admittance of the inverter and the voltage harmonic component of the grid-connected point; and the current controller inputs the harmonic component of the bridge arm voltage of the inverter to the driving circuit according to the difference value between the harmonic component of the current control instruction value and the current harmonic component of the grid-connected point of the inverter and the sum of the output voltage instruction value of the grid-connected point and the voltage harmonic component of the grid-connected point so as to obtain a trigger pulse signal and suppress resonance.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics and is applied to active power distribution networks. Specifically, it relates to a method and system for resonance identification and harmonic resonance suppression of a distributed photovoltaic access power distribution system. Background Art

[0002] With the large-scale access of distributed photovoltaic power to the distribution system, there are many possibilities of resonance in the distribution system with a large number of nodes, complex component types, and large source-load power fluctuations, which may cause the modal impedance at the resonant frequency to present a maximum value. Only a small harmonic current excitation will cause a large harmonic voltage, causing the harmonic voltage to exceed the limit, affecting the normal operation of the power grid and even destroying the equipment. When the output impedance of the photovoltaic inverter matches the inductive and capacitive impedance of the power grid under certain conditions, resonance will be caused. Harmonic resonance in the distribution system connected to photovoltaic power needs to be identified and controlled urgently.

[0003] In the prior art, based on the research on the harmonic resonance mechanism of the photovoltaic access distribution system, some control measures and harmonic elimination devices have been proposed. These measures and devices can be divided into two categories: one is to change the network structure parameters to keep the system away from the resonant frequency and harmonic source excitation; the other is to install harmonic filtering devices such as active power filters. However, the two methods have a relatively single application scenario, cannot achieve targeted suppression of resonance, have poor flexibility, and increase the cost of harmonic control, and are not fully applicable to the photovoltaic access distribution network scenario. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a method and system for resonance identification and suppression of a distributed photovoltaic access distribution system, which can identify system harmonic resonance and risk assessment, and has easy operation, clear process, and does not affect the output of photovoltaic power frequency power.

[0005] The present invention adopts the following technical solution.

[0006] The present invention proposes a method for resonance identification and suppression of a power distribution system under distributed photovoltaic access. The components of the power distribution system include: an inverter, an inductive component, a capacitive component, and an active load. The inverter includes: a current controller, a drive circuit, and a filter inductor, including:

[0007] Obtain the resonant admittance matrix of the power distribution system at the resonant frequency, solve the eigenvalues ​​of the resonant admittance matrix, and use the reciprocal of each eigenvalue as the modal impedance of each component; and use the frequency corresponding to the maximum value of the modal impedance as the resonant frequency point;

[0008] The Scobol sensitivity analysis method is used to calculate the total response index of the modal impedance of each component at the resonant frequency point, and the component corresponding to the maximum value of the total response index is used as the resonant key component, and the modal impedance of the resonant key component at the resonant frequency point is used as the resonant impedance;

[0009] The current harmonic component and voltage harmonic component of the inverter grid-connected point, as well as the filter inductance of the inverter are obtained; the equivalent admittance of the inverter is calculated based on the control coefficient of the current controller using the resonant impedance and the filter inductance of the inverter; the harmonic component of the current control command value is calculated using the equivalent admittance of the inverter and the voltage harmonic component of the inverter grid-connected point; the difference between the harmonic component of the current control command value and the current harmonic component of the inverter grid-connected point is used as the input data of the current controller, and the sum of the inverter grid-connected point voltage command value output by the current controller and the voltage harmonic component of the inverter grid-connected point is used as the harmonic component of the inverter bridge arm voltage and is input to the drive circuit to obtain a trigger pulse signal of the inverter switching device, so as to control the inverter to suppress the resonance of the distribution system.

[0010] Preferably, the resonant admittance matrix of the power distribution system at the resonant frequency satisfies the following relationship:

[0011] U f =Y f -1 I f

[0012] Where U f is the node voltage vector at the resonant frequency f, I f The node current vector injected at the resonant frequency f, Y f is the resonant admittance matrix at the resonant frequency f;

[0013] The following relationship is obtained:

[0014]

[0015] Where U f1 , U f2 ,……,U fn are the voltages of nodes 1, 2, ..., n at the resonant frequency f, λ f1 , f2 , ..., λ fn are the 1st, 2nd, ..., nth eigenvalues ​​of the resonant admittance matrix, J f1 , J f2 ,……,J fn are the modal currents of nodes 1, 2, ..., n at the resonant frequency f;

[0016] Define each eigenvalue λ f1 , f2 , ..., λfn The reciprocal of is the modal impedance of each component, and the smallest eigenvalue corresponds to the maximum modal impedance.

[0017] Preferably, the modal impedance of each component is used as sample data, the modal impedance at a certain resonant frequency point of the power distribution system is used as the output variable, and the Scobol sensitivity analysis method is used to calculate the total response index of each sample data, satisfying the following relationship:

[0018]

[0019] In the formula, E() is the mathematical expectation function, Var() is the mathematical variance function, y is the output variable, x i is the input variable, x~ i To remove the input variable x i The vector formed by all the remaining variables, ST i is the total response index of the i-th sample data.

[0020] Preferably, the current harmonic component and the voltage harmonic component of the inverter grid connection point and the filter inductance of the inverter are obtained through the harmonic detection link;

[0021] The harmonic detection link includes a trap filter;

[0022] The transfer function of the notch filter satisfies the following relationship:

[0023]

[0024] In the formula, G F is the transfer function of the notch filter, ω n is the central angular frequency of the notch filter, is the fundamental angular frequency, Q is the quality factor of the notch filter, and s is the integration operator.

[0025] Preferably, the equivalent admittance of the inverter is calculated based on the control coefficient of the current controller using the resonant impedance and the filter inductance of the inverter, satisfying the following relationship:

[0026]

[0027] Where Y is the equivalent admittance of the inverter, Z P is the resonant impedance, K p is the proportional coefficient of the current controller, s is the integral operator, and L is the filter inductance of the inverter.

[0028] Preferably, the harmonic component of the current control command value is calculated using the equivalent admittance of the inverter and the voltage harmonic component of the inverter grid connection point; the following relationship is satisfied:

[0029] i ref,H =VB,H Y

[0030] In the formula, i ref,H is the current controller command value i ref The Hth harmonic component, V B,H It is the voltage harmonic component at the inverter grid connection point.

[0031] Preferably, the difference between the harmonic component of the current control command value and the current harmonic component of the inverter grid-connected point is used as the input data of the current controller, and the sum of the voltage command value of the inverter grid-connected point output by the current controller and the voltage harmonic component of the inverter grid-connected point is used as the harmonic component of the inverter bridge arm voltage; the following relationship is satisfied:

[0032] (i ref,H -i H )G i +V B,H =V PWM,H

[0033] In the formula, G i is the transfer function of the current controller, (i ref,H -i H )G i is the voltage command value of the inverter grid connection point output by the current controller, V PWM,H is the Hth harmonic component of the inverter bridge arm voltage, i H It is the harmonic component of the current at the inverter grid connection point.

[0034] The present invention also proposes a resonance identification and suppression system for a distributed photovoltaic access distribution system. The components of the distribution system include: an inverter, an inductive component, a capacitive component, and an active load. The inverter includes: a current controller, a drive circuit, and a filter inductor, including:

[0035] The resonance identification module is used to obtain the resonant admittance matrix of the distribution system at the resonant frequency, solve the eigenvalues ​​of the resonant admittance matrix, and take the reciprocal of each eigenvalue as the modal impedance of each component; take the frequency corresponding to the maximum value of the modal impedance as the resonant frequency point; use the Scobol sensitivity analysis method to calculate the total response index of the modal impedance of each component at the resonant frequency point, take the component corresponding to the maximum value of the total response index as the resonant key component, and take the modal impedance of the resonant key component at the resonant frequency point as the resonant impedance;

[0036] The resonance suppression module is used to obtain the current harmonic component and voltage harmonic component of the inverter grid-connected point, as well as the filter inductance of the inverter; using the resonant impedance and the filter inductance of the inverter, based on the control coefficient of the current controller, the equivalent admittance of the inverter is calculated; using the equivalent admittance of the inverter and the voltage harmonic component of the inverter grid-connected point to calculate the harmonic component of the current control command value; using the difference between the harmonic component of the current control command value and the current harmonic component of the inverter grid-connected point as the input data of the current controller, and the sum of the inverter grid-connected point voltage command value output by the current controller and the voltage harmonic component of the inverter grid-connected point is used as the harmonic component of the inverter bridge arm voltage and input into the drive circuit to obtain the trigger pulse signal of the inverter switch device, so as to control the inverter to suppress the resonance of the distribution system.

[0037] A terminal comprises a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method.

[0038] A computer-readable storage medium stores a computer program, which implements the steps of the method when executed by a processor.

[0039] The beneficial effects of the present invention are that, compared with the prior art, at least the method proposed in the present invention can accurately locate the frequency and intensity of the resonance, reduce the risk of harmonic over-limit caused by harmonic source interference, and effectively improve the quality of electric energy.

[0040] The present invention proposes a harmonic suppression strategy based on modal impedance sensitivity analysis. According to the results of the sensitivity analysis, the component with the greatest impact on a certain harmonic resonance is obtained, and then the influence of the non-fundamental component of the component is eliminated through a control strategy, which equivalently changes the capacitive (inductive) characteristics of the component, realizes targeted suppression of harmonic resonance, and has a better suppression effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart of a method for resonance identification and suppression of a power distribution system under distributed photovoltaic access proposed by the present invention;

[0042] Figure 2 is a resonant modal impedance analysis result of a power distribution system in an embodiment of the present invention;

[0043] Figure 3 is a circuit diagram of a power distribution system in an embodiment of the present invention;

[0044] Figure 4 is an equivalent circuit diagram of a power distribution system in an embodiment of the present invention;

[0045] Figure 5 is the Scobol sensitivity analysis result at the resonant frequency of 10.5 pu in the embodiment of the present invention;

[0046] Figure 6 is the Scobol sensitivity analysis result at a resonant frequency of 25 p.u. in an embodiment of the present invention;

[0047] Figure 7 This is a schematic diagram of the control structure of the inverter's harmonic control;

[0048] Figure 8 Schematic diagram of the control structure of the inverter identifying and suppressing resonance in an embodiment of the present invention;

[0049] Fig. 9 It is a comparison diagram of the suppression effect of the suppression method of the present invention and the existing suppression method when there is a 10.5th harmonic source disturbance in the embodiment of the present invention;

[0050] Fig.10 It is a comparison diagram of the suppression effects of the suppression method of the present invention and the existing suppression method when there is a 25.0th harmonic source disturbance in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0052] The present invention proposes a method for resonance identification and suppression of a power distribution system under distributed photovoltaic access. Figure 1 As shown, including:

[0053] Step 1: Obtain the resonant admittance matrix of the distribution system at the resonant frequency, solve the eigenvalues ​​of the resonant admittance matrix, and use the reciprocal of each eigenvalue as the modal impedance of each component; and use the frequency corresponding to the maximum value of the modal impedance as the resonant frequency point.

[0054] Specifically, step 1 includes:

[0055] Step 1.1, obtain the resonant admittance matrix of the distribution system at the parallel resonant frequency.

[0056] When the distribution system resonates, the resonant frequency is f. A small current injected into any node will still produce a large node voltage. The resonant admittance matrix of the distribution system at the resonant frequency satisfies the following relationship:

[0057] U f =Y f -1 I f

[0058] Where U f is the node voltage vector at the resonant frequency f, I f The node current vector injected at the resonant frequency f, Y f is the resonant admittance matrix at the resonant frequency f.

[0059] Step 1.2, solve the eigenvalues ​​of the resonant admittance matrix, and take the reciprocal of each eigenvalue as the modal impedance of each element.

[0060] When the distribution system resonates, an eigenvalue approximately equal to zero appears in the resonant admittance matrix.

[0061] Y f Decomposed into the following relationship:

[0062] Y f =LΛT

[0063] Where Λ is Y f The eigenvalue diagonal matrix of , L is the left eigenvector and T is the right eigenvector.

[0064] Therefore, the node voltage vector satisfies the following relationship:

[0065] U f =LΛ -1 TI f

[0066] Definition U f =TV f , J f =TI f , where V f The voltage vector injected into the node at the resonant frequency f, J f is the modal current vector at the resonant frequency f, and the following relationship is obtained:

[0067]

[0068] Where U f1 , U f2 ,……,U fn are the voltages of nodes 1, 2, ..., n at the resonant frequency f, λ f1 , f2 , ..., λ fn are the 1st, 2nd, ..., nth eigenvalues ​​of the resonant admittance matrix, J f1 , J f2 ,……,J fn They are the modal currents of nodes 1, 2, ..., n at the resonant frequency f.

[0069] Step 1.3, take the frequency corresponding to the maximum value of the modal impedance as the resonant frequency point.

[0070] Define each eigenvalue λ f1 , f2 , ..., λ fn The reciprocal of is the modal impedance, and the smallest eigenvalue corresponds to the modal impedance maximum value. Under the modal impedance maximum value, a small modal current will generate a large modal voltage. Therefore, the present invention proposes to identify the resonant frequency and resonance strength in the power distribution system by judging the characteristics of the broadband modal impedance.

[0071] The modal impedance analysis results of the power distribution system resonance by the method proposed in the present invention are as follows: Figure 2 As shown, Figure 2 It is a waveform diagram based on the results of the resonant modal impedance analysis of the distribution system, in which the maximum values ​​of the modal impedance are approximately 100Ω when the resonant frequencies are 3.6pu and 10.5pu, and the maximum value of the modal impedance exceeds 250Ω when the resonant frequency is 25.0pu.

[0072] Step 2: Use the Scobol sensitivity analysis method to calculate the total response index of the modal impedance of each component at the resonant frequency point, take the component corresponding to the maximum value of the total response index as the resonant key component, and take the modal impedance of the resonant key component at the resonant frequency point as the resonant impedance.

[0073] Specifically, step 2 includes:

[0074] Step 2.1, using the Scobol sensitivity analysis method, calculate the total response index of the parameters in the modal impedance of each component at the resonant frequency point.

[0075] Scobol sensitivity analysis method includes variance-based sensitivity analysis method, which decomposes the variance of modal impedance to obtain the combination of single parameter and multi-parameter sub-function, and uses the variance of single input parameter or collective parameter to quantify the influence of parameter and the interaction between parameters. Scobol sensitivity analysis method is suitable for solving parameter sensitivity of nonlinear model and parameter uncertainty model, and can quantitatively analyze the sensitivity of multiple types of parameters and the influence of multivariate parameter interaction. It is a global sensitivity analysis method, and its calculation results are relatively reliable. It is widely used in sensitivity analysis work in many fields such as power, civil engineering, machinery, etc.

[0076]

[0077] In the formula, E() is the mathematical expectation function, Var() is the mathematical variance function, y is the output variable, and x i is the input variable, x~ i To remove the input variable xi The remaining input variables form a vector, S i is the first-order response index corresponding to the i-th sample data, ST i is the total response index corresponding to the i-th sample data.

[0078] In a non-limiting preferred embodiment, the modal impedance of each component is used as sample data, and the modal impedance at a certain resonant frequency point of the power distribution system is used as the output variable. The Scobol sensitivity analysis method is used to calculate the first-order response index and the total response index corresponding to each sample data as the influence of each component on the resonance of the power distribution system. The first-order response index S i The larger the input variable x is, the i The more significant the effect on modal impedance, the greater the overall response index ST i The larger the input variable x is, the i The greater the degree of influence of the modal impedance on the interaction with other input variables. Therefore, when the modal impedance at a certain resonant frequency point of the distribution system is used as the output variable, Scobol sensitivity analysis is mainly used to determine which input variable has a greater impact on the output variable.

[0079] Step 2.2, taking the component corresponding to the maximum value of the total response index as the resonance key component, and taking the modal impedance of the resonance key component at the resonance frequency point as the resonance impedance.

[0080] The present invention obtains the modal impedance of each component and uses the characteristic that a very small modal current will generate a large modal voltage under the maximum value of the modal impedance to determine the degree of influence of each component on the resonance of the distribution system within a set frequency band. This effectively avoids the influence of the volatility and uncertainty of parameters such as the current and voltage of each node in the distribution system under distributed photovoltaic access on the resonance identification. Therefore, it is more suitable for the resonance identification in the distribution system under the access of new energy, and is in line with the scenario where the parameters of the distribution network system are changeable.

[0081] Figure 3 The invention relates to a power distribution system that implements a resonance identification method and a harmonic resonance suppression strategy for a power distribution system under distributed photovoltaic access. The components of the power distribution system include: an inverter, an inductive component, a capacitive component, and an active load; wherein the inverter includes but is not limited to: a current controller, a PWM drive circuit, and a filtering device.

[0082] Will Figure 3 The power distribution system shown is equivalent to Figure 4 The equivalent circuit of the power distribution system is shown. Figure 4 The power distribution system shown in the figure includes 7 nodes, among which the system equivalent impedance connected to node 1 is R g +jX g, the equivalent resistance of the line between node 1 and node 2 is R = 0.01Ω, and the equivalent inductance is L = 0.1273mH; the equivalent resistance of the line between node 1 and node 3 is R = 0.003Ω, and the equivalent inductance is L = 0.1273mH. The equivalent resistance of the two 2MVA transformers connected in parallel between node 1 and node 2 is R = 0.01Ω, and the equivalent inductance is L = 0.1273mH. The equivalent resistance of one 1MVA and one 3MVA transformer connected in parallel between node 1 and node 3 is R = 0.003Ω, and the equivalent inductance is L = 0.1273mH. Node 2 The equivalent resistance of the 2MVA transformer between node 4 is R = 0.0246Ω, and the equivalent inductance is L = 2.006mH. The equivalent resistance of the 2MVA transformer between node 2 and node 5 is R = 0.0209Ω, and the equivalent inductance is L = 1.667mH. The equivalent resistance of the 1MVA transformer between node 3 and node 6 is R = 0.023Ω, and the equivalent inductance is L = 1.83mH. The equivalent resistance of the 3MVA transformer between node 3 and node 7 is R = 0.0823Ω, and the equivalent inductance is L = 5.27mH. The output impedance of the inverter connected to node 4 is R 0 +jX 0 , the equivalent capacitance of the 150kvar capacitive reactive power supplement device connected to node 4 is C p1 The equivalent resistance of the 100HP motor connected to node 4 is R = 13Ω, the equivalent inductance is L = 9mH, the equivalent resistance of the line between node 4 and node 5 is R = 0.023Ω, the equivalent inductance is L = 0.842mH, and the equivalent capacitance of the 300kvar capacitive reactive power supplement device connected to node 5 is C p2 The equivalent resistance of the 150HP motor connected to node 5 is R=8.67Ω, and the equivalent inductance is L=9mH; the equivalent resistance of the 100HP motor connected to node 6 is R=38Ω, and the equivalent inductance is L=6mH; the equivalent capacitance of the 200kvar capacitive reactive power supplement device connected to node 7 is C p3 , the equivalent inductance is L = 28.5mH, and the equivalent capacitance of the 100kvar capacitive reactive power supplement device connected to node 7 is C p4 , the equivalent inductance is L = 23mH. The parameters in the modal impedance of each node include: equivalent resistance, equivalent reactance, equivalent capacitance and equivalent inductance.

[0083] Figure 5 This is the Scobol sensitivity analysis result at the resonant frequency of 10.5 pu. Figure 5 Where S represents the first-order response index, ST represents the total response index, according to Figure 5 It is determined that the maximum value of the total response index at the resonant frequency of 10.5pu is about 0.8, and the parameters corresponding to the maximum value of the total response index are the system equivalent reactance X gand inverter output reactance X 0 , these two parameters are taken as the key parameters of resonance at the resonant frequency of 10.5pu.

[0084] Figure 6 is the Scobol sensitivity analysis result at the resonant frequency of 25p.u., Figure 6 Where S represents the first-order response index, ST represents the total response index, according to Figure 6 It is determined that the maximum value of the total response index under the resonant frequency of 25p.u. is about 1.0. The parameter corresponding to the maximum value of the total response index is the equivalent capacitance C of the 150kvar capacitive reactive power supplement device connected to node 4. p1 , this parameter is used as the key parameter of resonance at the resonant frequency of 25p.u.

[0085] Step 3, obtaining the harmonic current of the grid-connected line and the filter inductance of the inverter; using the resonant impedance and the harmonic current of the grid-connected line to calculate the harmonic component of the inverter grid-connected point voltage; using the resonant impedance and the filter inductance of the inverter, based on the control coefficient of the current controller, calculate the equivalent admittance of the inverter; using the equivalent admittance of the inverter and the harmonic component of the inverter grid-connected point voltage to calculate the harmonic component of the current control command value; using the difference between the harmonic component of the current control command value and the harmonic current of the grid-connected line as the input data of the current controller, the sum of the inverter grid-connected point voltage command value output by the current controller and the voltage harmonic component of the inverter grid-connected point is used as the harmonic component of the inverter bridge arm voltage and is input to the drive circuit to obtain a trigger pulse signal of the inverter switching device, and control the inverter to suppress the resonance of the distribution system.

[0086] Specifically, step 3 includes:

[0087] When using the harmonic control capability of the inverter, its control structure diagram is as follows Figure 7 As shown, the inverter grid-connected voltage V t Perform harmonic detection to obtain the grid-connected voltage harmonic component V t,h , grid voltage harmonic component V t,h Through the virtual harmonic resistor R h Then the harmonic component of the current controller command value is obtained Fundamental component of current controller command value Harmonic components of current controller command value The difference is used as the current controller command value I * In the harmonic control process of the inverter, the inverter is controlled as a virtual harmonic resistor at the harmonic frequency to compensate for the harmonic components emitted by the harmonic source, which is equivalent to providing a part of the damping for the harmonic resonance and plays a certain positive role in resonance suppression. However, considering the stability of the inverter control structure, its virtual harmonic resistor R hThe influence of harmonic sources cannot be completely offset. Figure 7 In, V dc is the DC voltage of the inverter, L is the filter inductance of the inverter, i tabc is the line current, Z g is the equivalent impedance of the power grid system, V g is the grid system voltage, PCC is the grid connection point, S 1～6 is the trigger pulse signal of the inverter switching device, Current Controller is the current controller, and SPWM is the driving circuit.

[0088] Specifically, step 3 includes:

[0089] Step 3.1: Obtain the current harmonic component i at the inverter grid connection point through the harmonic detection link H And voltage harmonic components V B,H , and the filter inductor L of the inverter;

[0090] Specifically, Figure 8 In the embodiment, the harmonic detection link is used to extract the harmonic components. The harmonic detection link includes but is not limited to the notch filter. The central angular frequency of the notch filter is the fundamental angular frequency. The transfer function of the notch filter satisfies the following relationship:

[0091]

[0092] In the formula, G F is the transfer function of the notch filter, ω n is the central angular frequency of the notch filter, and Q is the quality factor of the notch filter.

[0093] Step 3.2, using the resonant impedance and the filter inductance of the inverter, based on the control coefficient of the current controller, calculate the equivalent admittance of the inverter;

[0094] In the embodiment, the current control method adopted by the current controller includes but is not limited to proportional control, and the control coefficient of the current controller is the proportional coefficient K p , the equivalent admittance of the inverter satisfies the following relationship:

[0095]

[0096] Where Y is the equivalent admittance of the inverter, Z P is the resonant impedance, K p is the proportional coefficient of the current controller, s is the integral operator, and L is the filter inductance of the inverter;

[0097] In the embodiment, Figure 4 Medium Capacitor C p1 is the key resonance component, Z in the above formula P is the capacitance C p1The modal impedance at the resonant frequency of 25 p.u. is the equivalent capacitance of the 150 kvar capacitive reactive power supplement device connected to node 4.

[0098] Step 3.3, using the equivalent admittance of the inverter and the voltage harmonic component of the inverter grid connection point to calculate the harmonic component of the current control command value; satisfying the following relationship:

[0099] i ref,H =V B,H Y

[0100] In the formula, i ref,H is the current controller command value i ref The Hth harmonic component, V B,H is the voltage harmonic component at the inverter grid connection point;

[0101] Step 3.4, the difference between the harmonic component of the current control command value and the current harmonic component of the inverter grid-connected point is used as the input data of the current controller, and the sum of the voltage command value of the inverter grid-connected point output by the current controller and the voltage harmonic component of the inverter grid-connected point is used as the harmonic component of the inverter bridge arm voltage; satisfying the following relationship:

[0102] (i ref,H -i H )G i +V B,H =V PWM,H

[0103] In the formula, G i is the transfer function of the current controller, (i ref,H -i H )G i is the voltage command value of the inverter grid connection point output by the current controller, V PWM,H is the Hth harmonic component of the inverter bridge arm voltage, i H is the current harmonic component at the inverter grid connection point;

[0104] Step 3.5: According to the harmonic component of the inverter bridge arm voltage, the drive circuit sends a trigger pulse signal to the inverter switch device.

[0105] Figure 8 In, V tabc is the line voltage. In the coordinate transformation module, the line voltage V tabc The phase angle θ is obtained through the phase-locked loop PLL, and the current control command value i ref The dq axis component i of the current control command value is obtained by abc / dq coordinate transformation and phase angle θ dref 、i qref , line current i tabc The dq axis component i of the line current is obtained by abc / dq coordinate transformation and phase angle θtd 、i tq , line voltage V tabc The dq axis component V of the line voltage is obtained by abc / dq coordinate transformation and phase angle θ td 、V tq The coordinate transformation module sends data to the current controller. The current controller passes through the transfer function G i The voltage values ​​obtained by and ωL are respectively related to the dq axis components of the line voltage V td 、V tq Calculate the difference and obtain the dq-axis component V of the voltage command value of the inverter grid connection point md 、V mq .

[0106] The present invention further proposes a resonance control strategy for the inverter based on the control architecture for harmonic control of the inverter, and achieves the suppression of harmonic resonance by offsetting the resonance amount of the key resonance components. In the inverter control system, a harmonic detection link is connected in series to extract the current harmonic component and voltage harmonic component of the inverter grid-connected point; the equivalent admittance of the inverter is calculated based on the control coefficient of the current controller using the resonant impedance and the filter inductance of the inverter; the harmonic component of the current control command value is calculated using the equivalent admittance of the inverter and the voltage harmonic component of the inverter grid-connected point. This is actually to obtain the influence component of the key resonant component on the harmonic resonance, and the difference between the harmonic component of the current control command value and the current harmonic component of the inverter grid-connected point is used as the input data of the current controller. The sum of the inverter grid-connected point voltage command value output by the current controller and the harmonic component of the inverter grid-connected point voltage is used as the harmonic component of the inverter bridge arm voltage and input to the drive circuit to eliminate the influence component of the key resonant component on the harmonic resonance. Under the control of the trigger pulse signal, the output impedance characteristics of the inverter and the characteristics of the key resonant component offset each other, thereby achieving more effective suppression of harmonic resonance and having a better suppression effect.

[0107] In the photovoltaic access distribution system, Matlab / Simulink software is used to simulate and analyze the method proposed in the present invention. From the simulation results, it can be seen that the resonance risk identification method and harmonic resonance suppression strategy proposed in the present invention can accurately locate the frequency and intensity of the resonance, reduce the harmonic over-limit risk that may be caused by harmonic source interference, and effectively improve the power quality.

[0108] Fig. 9This is a comparison chart of the suppression effects of the suppression method of the present invention and the existing suppression methods when there is a 10.5th harmonic source disturbance. When the suppression method of the present invention is used, the harmonic voltage distortion rate decreases from 4.39% to 1.90%, and the suppression effect is 56.72%. When the existing suppression method is used, the harmonic voltage distortion rate decreases from 4.39% to 2.85%, and the suppression effect is weaker than that of the suppression method of the present invention, which proves the effectiveness of the suppression strategy.

[0109] Fig.10 This is a comparison chart of the suppression effects of the suppression method of the present invention and the existing suppression method when there is a 25.0th harmonic source disturbance. When the suppression method of the present invention is used, the harmonic voltage distortion rate decreases from 13.48% to 5.34%, and the suppression effect reaches 57.05%. When the existing suppression method is used, the harmonic voltage distortion rate decreases from 4.39% to 7.87%, and the suppression effect is weaker than that of the suppression method of the present invention, which proves the effectiveness of the suppression strategy.

[0110] The present invention also proposes a resonance identification and suppression system for a distributed photovoltaic access distribution system. The components of the distribution system include: an inverter, an inductive component, a capacitive component, and an active load. The inverter includes: a current controller, a drive circuit, and a filter inductor, including:

[0111] The resonance identification module is used to obtain the resonant admittance matrix of the distribution system at the resonant frequency, solve the eigenvalues ​​of the resonant admittance matrix, and take the reciprocal of each eigenvalue as the modal impedance of each component; take the frequency corresponding to the maximum value of the modal impedance as the resonant frequency point; use the Scobol sensitivity analysis method to calculate the total response index of the modal impedance of each component at the resonant frequency point, take the component corresponding to the maximum value of the total response index as the resonant key component, and take the modal impedance of the resonant key component at the resonant frequency point as the resonant impedance;

[0112] The resonance suppression module is used to obtain the current harmonic component and voltage harmonic component of the inverter grid-connected point, as well as the filter inductance of the inverter; using the resonant impedance and the filter inductance of the inverter, based on the control coefficient of the current controller, the equivalent admittance of the inverter is calculated; using the equivalent admittance of the inverter and the voltage harmonic component of the inverter grid-connected point to calculate the harmonic component of the current control command value; using the difference between the harmonic component of the current control command value and the current harmonic component of the inverter grid-connected point as the input data of the current controller, and the sum of the inverter grid-connected point voltage command value output by the current controller and the voltage harmonic component of the inverter grid-connected point is used as the harmonic component of the inverter bridge arm voltage and input into the drive circuit to obtain the trigger pulse signal of the inverter switch device, so as to control the inverter to suppress the resonance of the distribution system.

[0113] The present disclosure may be a system, a method and / or a 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.

[0114] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0115] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0116] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0117] 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 relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for resonance identification and suppression of a power distribution system under distributed photovoltaic access, the components of the power distribution system comprising: Inverter, inductive element, capacitive element, active load, the inverter includes: current controller, drive circuit, filter inductor, characterized in that it includes: Obtain the resonant admittance matrix of the power distribution system at the resonant frequency, solve the eigenvalues ​​of the resonant admittance matrix, and use the reciprocal of each eigenvalue as the modal impedance of each component; and use the frequency corresponding to the maximum value of the modal impedance as the resonant frequency point; The Scobol sensitivity analysis method is used to calculate the total response index of the modal impedance of each component at the resonant frequency point, and the component corresponding to the maximum value of the total response index is used as the resonant key component, and the modal impedance of the resonant key component at the resonant frequency point is used as the resonant impedance; The current harmonic component and voltage harmonic component of the inverter grid-connected point, as well as the filter inductance of the inverter are obtained; the equivalent admittance of the inverter is calculated based on the control coefficient of the current controller using the resonant impedance and the filter inductance of the inverter; the harmonic component of the current control command value is calculated using the equivalent admittance of the inverter and the voltage harmonic component of the inverter grid-connected point; the difference between the harmonic component of the current control command value and the current harmonic component of the inverter grid-connected point is used as the input data of the current controller, and the sum of the inverter grid-connected point voltage command value output by the current controller and the voltage harmonic component of the inverter grid-connected point is used as the harmonic component of the inverter bridge arm voltage and is input to the drive circuit to obtain a trigger pulse signal of the inverter switching device, so as to control the inverter to suppress the resonance of the distribution system.

2. The method for resonance identification and suppression of a distributed photovoltaic access power distribution system according to claim 1, characterized in that: The resonant admittance matrix of the power distribution system at the resonant frequency satisfies the following relationship: Where U f is the node voltage vector at the resonant frequency f, I f The node current vector injected at the resonant frequency f, Y f is the resonant admittance matrix at the resonant frequency f; The following relationship is obtained: Where U f1 , U f2 ,……,U fn are the voltages of nodes 1, 2, ..., n at the resonant frequency f, λ f1 , f2 , ..., λ fn are the 1st, 2nd, ..., nth eigenvalues ​​of the resonant admittance matrix, J f1 , J f2 ,……,J fn are the modal currents of nodes 1, 2, ..., n at the resonant frequency f; Define each eigenvalue λ f1 , f2 , ..., λ fn The reciprocal of is the modal impedance of each component, and the smallest eigenvalue corresponds to the maximum modal impedance.

3. The resonance identification and suppression method for a distributed photovoltaic access power distribution system according to claim 1, characterized in that: Taking the modal impedance of each component as sample data and the modal impedance at a certain resonant frequency point of the power distribution system as the output variable, the Scobol sensitivity analysis method is used to calculate the total response index of each sample data, which satisfies the following relationship: In the formula, E() is the mathematical expectation function, Var() is the mathematical variance function, y is the output variable, and x i is the input variable, x~ i To remove the input variable x i The vector formed by all the remaining variables, ST i is the total response index of the i-th sample data.

4. The method for resonance identification and suppression of a distributed photovoltaic access power distribution system according to claim 1, characterized in that: The harmonic detection link is used to obtain the current harmonic components and voltage harmonic components of the inverter grid connection point and the filter inductance of the inverter; The harmonic detection link includes a trap filter; The transfer function of the notch filter satisfies the following relationship: In the formula, G F is the transfer function of the notch filter, ω n is the central angular frequency of the notch filter, is the fundamental angular frequency, Q is the quality factor of the notch filter, and s is the integration operator.

5. The method for resonance identification and suppression of a distributed photovoltaic access power distribution system according to claim 4, characterized in that: Using the resonant impedance and the filter inductance of the inverter, the equivalent admittance of the inverter is calculated based on the control coefficient of the current controller, satisfying the following relationship: Where Y is the equivalent admittance of the inverter, Z P is the resonant impedance, K p is the proportional coefficient of the current controller, s is the integral operator, and L is the filter inductance of the inverter.

6. The method for resonance identification and suppression of a distributed photovoltaic access power distribution system according to claim 5, characterized in that: The harmonic component of the current control command value is calculated using the equivalent admittance of the inverter and the voltage harmonic component of the inverter grid connection point; the following relationship is satisfied: i ref,H =V B,H Y In the formula, i ref,H is the current controller command value i ref The Hth harmonic component, V B,H It is the voltage harmonic component at the inverter grid-connected point.

7. The method for resonance identification and suppression of a distributed photovoltaic access power distribution system according to claim 6, characterized in that: The difference between the harmonic component of the current control command value and the current harmonic component of the inverter grid-connected point is used as the input data of the current controller, and the sum of the voltage command value of the inverter grid-connected point output by the current controller and the voltage harmonic component of the inverter grid-connected point is used as the harmonic component of the inverter bridge arm voltage; the following relationship is satisfied: (i ref,H -i H )G i +V B,H =V PWM,H In the formula, G i is the transfer function of the current controller, (i ref,H -i H )G i is the voltage command value of the inverter grid connection point output by the current controller, V PWM,H is the Hth harmonic component of the inverter bridge arm voltage, i H It is the harmonic component of the current at the inverter grid connection point.

8. A resonance identification and suppression system for a distributed photovoltaic access power distribution system, the components of the power distribution system comprising: Inverter, inductive element, capacitive element, active load, the inverter includes: current controller, drive circuit, filter inductor, characterized in that it includes: The resonance identification module is used to obtain the resonant admittance matrix of the distribution system at the resonant frequency, solve the eigenvalues ​​of the resonant admittance matrix, and take the reciprocal of each eigenvalue as the modal impedance of each component; take the frequency corresponding to the maximum value of the modal impedance as the resonant frequency point; use the Scobol sensitivity analysis method to calculate the total response index of the modal impedance of each component at the resonant frequency point, take the component corresponding to the maximum value of the total response index as the resonant key component, and take the modal impedance of the resonant key component at the resonant frequency point as the resonant impedance; The resonance suppression module is used to obtain the current harmonic component and voltage harmonic component of the inverter grid-connected point, as well as the filter inductance of the inverter; using the resonant impedance and the filter inductance of the inverter, based on the control coefficient of the current controller, the equivalent admittance of the inverter is calculated; using the equivalent admittance of the inverter and the voltage harmonic component of the inverter grid-connected point to calculate the harmonic component of the current control command value; using the difference between the harmonic component of the current control command value and the current harmonic component of the inverter grid-connected point as the input data of the current controller, and the sum of the inverter grid-connected point voltage command value output by the current controller and the voltage harmonic component of the inverter grid-connected point is used as the harmonic component of the inverter bridge arm voltage and input into the drive circuit to obtain the trigger pulse signal of the inverter switch device, so as to control the inverter to suppress the resonance of the distribution system.

9. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

Images