A method for evaluating harmonic compensation capability of power quality regulation resources

Abstract

The application provides a power quality regulation resource harmonic compensation capacity evaluation method, and belongs to the field of power regulation, and comprises the following steps: step 1: according to the capacity calculation method, the real-time total effective value of the real-time output phase voltage and phase current of the power quality regulation resource is measured and calculated to obtain the real-time compensated output capacity S use and the real-time residual adjustable capacity S surplus ; step 2: based on the real-time residual adjustable capacity S surplus of the power quality regulation resource, considering four limiting factors, the maximum value of each harmonic compensation current and the maximum value of the total harmonic compensation current that can be respectively emitted by the power quality regulation resource in real time are evaluated. The application helps to realize the optimal configuration of a large number of heterogeneous power quality regulation resources in a power grid.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electric energy regulation, and particularly relates to a method for evaluating harmonic compensation capacity of power quality regulation resources. BACKGROUND

[0002] With the accelerated construction of new power systems, the current power grid power quality regulation is facing multiple challenges and urgent needs: on the one hand, the large-scale grid connection of new energy power generation and the rapid development of new types of loads such as electric vehicles and distributed energy storage have led to the characteristics of high proportion of power electronic equipment access in the power system, which has aggravated the problems of voltage fluctuation, harmonic pollution and low power factor; on the other hand, the demand for sensitive industries such as high-end manufacturing and precision medical equipment has surged, and the traditional regulation system dominated by coal-fired power has been unable to adapt to the randomness of new energy output and the complexity of load characteristics. Therefore, distributed power quality regulation resources play an important role in the process of power grid power quality regulation, which can effectively reduce the dependence of power quality regulation on main grid regulation.

[0003] However, the existing evaluation methods of the regulation capacity of power quality regulation resources usually only involve the estimation of the remaining adjustable capacity of specified types of power quality regulation resources, lack of evaluation of harmonic compensation capacity (maximum harmonic compensation current), and are difficult to adapt to complex working conditions and obtain more accurate evaluation results. SUMMARY

[0004] In order to accurately evaluate the real-time harmonic compensation capacity of power quality regulation resources and help realize the optimal allocation of various power quality regulation resources, the present application provides a method for evaluating the harmonic compensation capacity of power quality regulation resources, which accurately calculates the real-time remaining adjustable capacity of power quality regulation resources based on the measured voltage and current effective values, and evaluates the real-time harmonic compensation capacity based on this and considering four limiting factors (including the maximum harmonic compensation current of each harmonic and the maximum total harmonic compensation current that can be respectively emitted in real time), thereby providing a general evaluation method suitable for the harmonic compensation capacity of any type of power quality regulation resource, to help realize the optimal allocation of a large number of heterogeneous power quality regulation resources in the power grid.

[0005] To achieve the above purpose, the present application adopts the following technical solutions:

[0006] A method for evaluating the harmonic compensation capacity of power quality regulation resources, comprising the following steps:

[0007] Step 1, according to the capacity calculation method, the real-time total effective value of the real-time output phase voltage and phase current of the power quality regulation resource is measured and calculated to obtain the real-time compensated output capacity S use and the real-time remaining adjustable capacity S surplus of the power quality regulation resource.

[0008] Step 2, real-time residual adjustable capacity S of the power quality regulation resource based on power quality regulation surplus The maximum value of the harmonic compensation current of each order and the maximum value of the total harmonic compensation current that can be respectively emitted by the power quality regulation resource are evaluated considering four limiting factors.

[0009] Advantages:

[0010] 1. The real-time residual adjustable capacity of the power quality regulation resource is solved according to the real-time measured phase voltage and phase current total effective value, the result is closer to the actual adjustable capacity, and has better applicability, and is not limited to specific power quality regulation resources.

[0011] 2. The real-time harmonic compensation capacity (the maximum value of the harmonic compensation current of each order) is evaluated based on the real-time residual adjustable capacity and considering the limiting factors of the power quality regulation resource itself and the power grid, which can be well applied to the optimal configuration of a large number of heterogeneous power quality regulation resource harmonic current compensation. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 A flowchart of the power quality regulation resource harmonic compensation capacity evaluation method provided by the present application is shown.

[0013] Figure 2 Connection diagrams of three common power quality regulation resources in the power grid are shown. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0015] As shown in Figure 1 , the power quality regulation resource harmonic compensation capacity evaluation method provided by the present application includes the following steps:

[0016] Step 1: According to the capacity calculation method, the voltage and current effective value parameters of the real-time output of the power quality regulation resource are measured and calculated to obtain the real-time compensated output capacity S use and the real-time residual adjustable capacity S surplus .

[0017] As shown in Figure 2As shown, power quality regulation resources are generally connected to the power grid through transformers, reactors, or mechanical switches. u and i represent the instantaneous values ​​of voltage and current output by the power quality regulation resources, respectively. By measuring and calculating these values, the real-time power parameters required by this invention can be obtained. PCC is the common connection point between the power quality regulation resources and the power grid.

[0018] The real-time compensated output capacity S of power quality regulation resources in this invention use and real-time remaining adjustable capacity S surplus The calculation consists of the following two sub-steps:

[0019] Step 11: Measure and calculate the real-time power parameters required for power quality conditioning resource calculation, including:

[0020] The phase voltage (u) output in real time for power quality regulation resources A ,u B ,u C ) and phase current (i A i B i C Sampling is performed, assuming the number of sampling points in each cycle is N, and the instantaneous sampled values ​​of voltage and current corresponding to the k-th sampling point are as follows: u Ak u Bk u Ck i Ak i Bk i Ck The following real-time power parameters were calculated:

[0021] (1)

[0022] Where k is the number of sampling points, N is the total number of periodic sampling points, and U A U B U C I A I B I C These represent the real-time total effective values ​​of the corresponding phase voltage and phase current, respectively.

[0023] Step 12: Calculate the real-time compensated output capacity S of the power quality regulation resources based on the real-time power parameters. use and real-time remaining adjustable capacity S surplus ,include:

[0024] Based on the basic definition of output capacity (apparent power), the real-time compensated output capacity S of the power quality regulation resource can be calculated from the real-time power parameters in equation (1). use for:

[0025] (2)

[0026] Assume the rated capacity of the power quality regulation resources is S. N The working efficiency is η. By combining equations (2), the real-time remaining adjustable capacity S of the power quality regulation resources can be obtained. surplus for:

[0027] (3)

[0028] Step 2: Based on the real-time remaining adjustable capacity S of power quality regulation resources surplus Considering four limiting factors, evaluate the maximum values ​​of each harmonic compensation current and the maximum value of the total harmonic compensation current that power quality regulation resources can still generate in real time, including:

[0029] Step 21: Based on the real-time remaining adjustable capacity S of power quality regulation resources surplus The assessment yielded the maximum values ​​of each harmonic compensation current generated in real time by the power quality regulation resources. :

[0030] In the actual operation of power quality regulation equipment, it can also generate the maximum value of each harmonic compensation current in real time. The main limitations are the following four factors: (1) the remaining output equivalent current of the equipment; (2) the maximum allowable current carrying capacity of the power devices; (3) the peak value of the grid phase voltage; and (4) the DC side voltage and the real-time grid harmonic voltage. These limiting factors will be analyzed in turn below, and the final assessment of the power quality regulation resources will be obtained. :

[0031] (1) The remaining output equivalent current I of the equipment surplus The power quality regulation resources can also separately generate the maximum value of each harmonic compensation current. The restrictions are:

[0032] According to equation (3), the real-time remaining adjustable capacity S of the power quality regulation resources can be obtained. surplus If the effective value of the phase voltage at the power quality regulation resource PCC (point of common coupling) is U at this time PCC The remaining output equivalent current I of the power quality regulation resources can be calculated using the following formula. surplus :

[0033] (4)

[0034] Then, the power quality regulation resources can also generate the maximum values ​​of each harmonic compensation current. It should meet the following requirements:

[0035] (5)

[0036] (2) The maximum allowable current capacity I of the power device Smax The maximum allowable current capacity I of the power device The maximum allowable current capacity I of the power device

[0037] According to formula (2), the real-time compensated output capacity S of the power quality regulation resource can be obtained use The equivalent current I output by the power quality regulation resource can be calculated by the following formula use :

[0038] (6)

[0039] The maximum allowable current capacity I of the power device (such as IGBT) can be obtained by consulting the technical parameters of the power device in the power quality regulation resource specification Smax . Therefore, the maximum allowable current capacity I of the power device (such as IGBT) can be obtained by consulting the technical parameters of the power device in the power quality regulation resource specification should satisfy:

[0040] (7)

[0041] wherein K is a parameter representing the numerical relationship between the effective value of the current borne by the power device and the effective value of the output phase current, and is related to the control mode of the power quality regulation resource.

[0042] (3) The peak value of the grid phase voltage The maximum allowable current capacity I of the power device (such as IGBT) can be obtained by consulting the technical parameters of the power device in the power quality regulation resource specification The maximum allowable current capacity I of the power device (such as IGBT) can be obtained by consulting the technical parameters of the power device in the power quality regulation resource specification

[0043] The output harmonic voltage corresponding to the harmonic current compensation of the power quality regulation resource needs to be coordinated with the grid voltage to avoid overvoltage. Given that the effective value of the phase voltage at the PCC (point of common coupling) of the power quality regulation resource is U PCC , then the harmonic voltage U i corresponding to the i-th harmonic current output by the power quality regulation resource should satisfy the following formula:

[0044] (8)

[0045] wherein represents the maximum value of U i .

[0046] If the i-th harmonic output impedance modulus is , and the currently compensated harmonic current is , then the maximum allowable i-th harmonic compensation current should satisfy:

[0047] (9)

[0048] (4) DC side voltage and real-time grid harmonic voltage The limit of the maximum harmonic compensation current that the power quality regulation resource can still issue is:

[0049] The output voltage amplitude of the power quality regulation resource is related to the DC side voltage and the control strategy. According to the PWM modulation principle, in the linear modulation area (modulation ratio ), the maximum fundamental voltage amplitude of the inverter output is . If the i-th harmonic voltage at the PCC (point of common coupling) is , and the i-th harmonic output impedance modulus is , then the maximum i-th harmonic compensation current that the power quality regulation resource can still issue is , which should satisfy:

[0050] (10)

[0051] Considering the above formula (2), formula (3), formula (5), formula (7), formula (9), formula (10), the maximum i-th harmonic compensation current that the power quality regulation resource can still issue is evaluated as:

[0052] (11)

[0053] Step 22: Based on the real-time remaining adjustable capacity S of the power quality regulation resource surplus , the maximum total harmonic compensation current that the power quality regulation resource can still issue is evaluated using the current effective value square relationship:

[0054] Given that the remaining output equivalent current of the power quality regulation resource obtained in step 21 is I surplus . Assuming that different harmonic currents also need to be compensated at the same time, let I ej_need be the j-th harmonic current value that the grid still needs to compensate in real time, and I ej_next be the j-th harmonic current value that the power quality regulation resource can still issue. According to formula (11), I ej_next should satisfy: if , then ; if , then . Accordingly, the total harmonic compensation current that the power quality regulation resource can still issue in real time should satisfy:

[0055] (12) ​​​

[0056] wherein, is the maximum value of the jth harmonic compensation current that the power quality regulation resource can still emit, which is determined by equation (11).

[0057] By combining equation (12) and equation (4), the maximum value of the total harmonic compensation current that the power quality regulation resource can still emit is evaluated as:

[0058] (13)

[0059] wherein, the subscript max represents taking the maximum value.

[0060] Taking an APF (active power filter) with an LCL (inductor-capacitor-inductor) output filter as an example for analysis, the ith harmonic output impedance of the APF with the LCL output filter can be calculated by the following equation:

[0061] (14)

[0062] wherein, L1, C, L2 are the inverter side inductance, filter capacitance, and grid side inductance of the LCL filter, f1 is the fundamental frequency, i is the harmonic number, and j is the imaginary unit.

[0063] Embodiment:

[0064] The phase voltages (u A ,u B ,u C ) and phase currents (i A ,i B ,i C ) output by the APF in real time are sampled, and the number of sampling points per cycle is set to 200 (i.e., N=200). The instantaneous sampling values of the phase voltages and currents corresponding to the kth sampling point are denoted as: u Ak , u Bk , u Ck , i Ak , i Bk , i Ck . The total effective values of the phase voltages and phase currents are calculated as:

[0065] ;

[0066] Taking the 5th and 35th harmonic compensation capability evaluation as an example, the other real-time calculation input parameters of the APF are:

[0067] ;

[0068] wherein, I e5_rt , I​e35_rt U is the effective value of the 5th, 35th harmonic compensation current output by the APF in real time, U e5_rt , e35_rt U is the effective value of the 5th, 35th harmonic voltage at the PCC (point of common coupling) of the APF, U N , I N are respectively the phase rated voltage, current effective value of the APF, and other parameters have been described above.

[0069] The phase voltage effective value U of the power quality regulation resource at the PCC (point of common coupling) PCC The calculation results are as follows by using the real-time equivalent phase voltage:

[0070] ;

[0071] Based on the above parameters, the 5th and 35th harmonic output impedance modulus value of the APF is solved as follows:

[0072] ;

[0073] ;

[0074] First, S use and S surplus are calculated according to formula (2) and formula (3):

[0075] ;

[0076] According to the comprehensive evaluation formula (11), the maximum value of the 5th harmonic compensation current that can be output by the power quality regulation resource in real time is evaluated:

[0077] ;

[0078] The maximum value of the 35th harmonic compensation current that can be output by the power quality regulation resource in real time is evaluated:

[0079] ;

[0080] According to the evaluation formula (12), the maximum value of the total harmonic compensation current that can be output by the power quality regulation resource in real time is evaluated:

[0081] .

Claims

1. A method for evaluating harmonic compensation capability of power quality regulation resources, characterized in that, The method comprises the following steps: Step 1, according to the capacity calculation method, the real-time total effective value of the real-time output phase voltage and phase current of the power quality regulation resource is measured and calculated to obtain the real-time compensated output capacity S of the power quality regulation resource use And the real-time remaining adjustable capacity S surplus , comprising: The phase voltage (u A , u B , u C ) and the phase current (i A , i B , i C ) of the real-time output of the power quality regulation resource are sampled, assuming that the number of sampling points per cycle is N, and the voltage and current instantaneous sampling values corresponding to the kth sampling point are u Ak , u Bk , u Ck , i Ak , i Bk , i Ck , respectively, and the real-time total effective values of the corresponding phase voltage and phase current are calculated; According to the definition of the output capacity, the real-time compensated output capacity S of the power quality regulation resource is calculated by the real-time total effective value of the phase voltage and the phase current use ; Step 2, real-time residual adjustable capacity S of power quality regulation resource surplus Considering four limiting factors, the maximum value of each harmonic compensation current and the maximum value of total harmonic compensation current that the power quality regulation resource can respectively issue are also evaluated, including: Step 21: Real-time residual adjustable capacity S of the power quality regulation resource is based surplus The maximum harmonic compensation current that the power quality regulation resource can respectively issue is evaluated The maximum harmonic compensation current that can respectively be issued in real time It is limited by the following four factors: the residual equivalent current that the device can output, the maximum allowable current capacity of the power device, the peak value of the grid phase voltage, the DC side voltage, and the real-time grid harmonic voltage.

2. The method of claim 1, wherein, Assuming that the rated capacity of the power quality regulation resource is S N , the work efficiency is η, the real-time residual adjustable capacity S surplus of the power quality regulation resource is: (3)。 3. The method of claim 2, wherein, the remaining outputtable equivalent current I surplus the maximum value of the harmonic compensation current of each order that can be emitted by the power quality regulation resource is limited by: According to the real-time residual adjustable capacity S of the power quality regulation resource surplus , assuming that the effective value of the phase voltage at the point of common coupling corresponding to the power quality regulation resource at this time is U PCC , the residual output equivalent current I of the power quality regulation resource is calculated surplus ; The maximum value of the compensation current of each harmonic wave respectively emitted by the power quality regulation resource satisfies: (5)。 4. The method of claim 3, wherein, Maximum allowed current flow capability I of the power device Smax Maximum value of the harmonic compensation current that can be emitted by the power quality regulation resource at each harmonic separately is limited by: According to the real-time compensated output capacity S of the power quality regulation resource use , the equivalent current I output by the power quality regulation resource is calculated use ; According to the maximum allowable current capacity I of the power device of the power quality regulation resource Smax The maximum value of the compensation current of each harmonic respectively emitted by the power quality regulation resource Satisfies: (7) K is a parameter representing the numerical relationship between the effective value of the current borne by the power device and the effective value of the output phase current, and is related to the control mode of the power quality regulation resource.

5. The method of claim 4, wherein, Peak phase voltage of the power grid The power quality regulation resources can also separately generate the maximum value of each harmonic compensation current. The restrictions are: It is known that the effective value of the phase voltage at the point of common coupling of the power quality conditioning resource is U PCC , the harmonic voltage U i corresponding to the i-th harmonic current output by the power quality conditioning resource is obtained i ) max ; If the i-th harmonic output impedance modulus is , the current harmonic that has been compensated for the current output is , then the maximum i-th harmonic compensation current that the power quality regulation resource can also issue satisfies: (9)。 6. The method of claim 5, wherein, Direct current side voltage And real-time grid harmonic voltage The limit of the maximum value of each harmonic compensation current that can be respectively issued to the power quality regulation resource is: The limit of the maximum value of each harmonic compensation current that can be respectively issued to the power quality regulation resource is: If the i-th harmonic output impedance modulus is The maximum value of the i-th harmonic compensation current that the power quality regulation resource can also send is Satisfies: (10) In combination with formula (3), formula (5), formula (7), formula (9), and formula (10), the maximum value of the i-th harmonic compensation current that can be output by the real-time power quality regulation resource is evaluated as is: (11)。 7. The method of claim 6, wherein, The step 2 further comprises: Step 22: Real-time residual adjustable capacity S of the power quality regulation resource is based surplus The maximum total harmonic compensation current that the power quality regulation resource can still emit is obtained by evaluating the current effective value square relationship, including: The total harmonic compensation current that can be emitted by the power quality regulation resource in real time is calculated, and the total harmonic compensation current satisfies: (12) Ij= Ij+ Ij ej_need Ij= Ij+ Ij ej_next Ij= Ij+ Ij Ij= Ij+ Ij 8. The method of claim 7, wherein, By simultaneously solving equation (12) and equation (4), the maximum value of the total harmonic compensation current that can be emitted by the power quality regulation resource is evaluated as: (13) Wherein, the subscript max represents the maximum value.

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