Electric energy quality regulation resource harmonic compensation capability assessment method

Abstract

The invention provides an electric energy quality regulation resource harmonic compensation capability evaluation method, which belongs to the field of electric energy regulation and comprises the following steps of: 1, measuring and calculating a real-time total effective value of phase voltage and phase current output by an electric energy quality regulation resource in real time according to a capacity calculation method; a real-time compensated output capacity Suse and a real-time residual adjustable capacity Ssurplus are obtained; and step 2, based on the real-time residual adjustable capacity Spurplus of the electric energy quality adjusting resource, considering four limiting factors, and evaluating the maximum value of each harmonic compensation current and the maximum value of the total harmonic compensation current which can be respectively sent by the electric energy quality adjusting resource in real time. The method assists in realizing optimal configuration of mass heterogeneous power quality regulation resources in a power grid.

Description

Technical Field

[0001] This invention belongs to the field of power regulation, specifically relating to a method for evaluating the harmonic compensation capability of power quality regulation resources. Background Technology

[0002] With the accelerated construction of new power systems, the current power grid power quality regulation faces 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 loads such as electric vehicles and distributed energy storage have led to a high proportion of power electronic equipment connected to the power system, exacerbating problems such as voltage fluctuations, harmonic pollution, and low power factor. On the other hand, the demand from power quality-sensitive industries such as high-end manufacturing and precision medical equipment is surging, and the traditional coal-fired power-dominated regulation system is no longer able to adapt to the randomness of new energy output and the complexity of load characteristics. Therefore, distributed power quality regulation resources occupy an important position in the process of power grid power quality management, and can effectively reduce the dependence of power quality management on the main grid regulation.

[0003] However, existing methods for assessing the regulation capacity of power quality regulation resources often only involve estimating the remaining adjustable capacity of a specified type of power quality regulation resource, lacking an assessment of harmonic compensation capacity (maximum value of harmonic compensation current), making it difficult to apply to complex operating conditions and obtain assessment results that are closer to the actual output capacity. Summary of the Invention

[0004] To accurately assess the real-time harmonic compensation capability of power quality regulation resources and facilitate the optimal allocation of various power quality regulation resources, this invention provides a method for assessing the harmonic compensation capability of power quality regulation resources. Based on the measured effective values ​​of voltage and current, it accurately calculates the real-time remaining adjustable capacity of power quality regulation resources. Based on this, and considering four limiting factors, it assesses the real-time harmonic compensation capability (including the maximum values ​​of each harmonic compensation current that can be emitted separately in real-time and the maximum value of the total harmonic compensation current). This provides a universal assessment method applicable to the harmonic compensation capability of any type of power quality regulation resource, thereby facilitating the optimal allocation of massive heterogeneous power quality regulation resources in the power grid.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for assessing the harmonic compensation capability of power quality regulation resources includes the following steps:

[0007] Step 1: Based on the capacity calculation method, measure and calculate the real-time total effective values ​​of the phase voltage and phase current output by the power quality regulation resource, and obtain the real-time compensated output capacity S of the power quality regulation resource. use and real-time remaining adjustable capacity S surplus ;

[0008] Step 2: Real-time remaining adjustable capacity S based on power quality regulation resources surplus Considering four limiting factors, the maximum values ​​of each harmonic compensation current and the total harmonic compensation current that can be generated by power quality regulation resources can be evaluated.

[0009] Beneficial effects:

[0010] 1. This invention calculates the real-time remaining adjustable capacity of power quality regulation resources based on the total effective value of the phase voltage and phase current measured in real time. 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. Based on real-time remaining adjustable capacity and considering the limitations of power quality regulation resources themselves and the power grid, this invention evaluates and obtains the real-time harmonic compensation capability (maximum value of each harmonic compensation current), which can be well applied to the optimized configuration of harmonic current compensation for massive heterogeneous power quality regulation resources. Attached Figure Description

[0012] Figure 1 A flowchart of the method for evaluating the harmonic compensation capability of power quality regulation resources provided by the present invention;

[0013] Figure 2 This is a schematic diagram illustrating the connection of three common power quality regulation resources in power grids as shown in this invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0015] like Figure 1 As shown, the method for evaluating the harmonic compensation capability of power quality regulation resources provided by the present invention includes the following steps:

[0016] Step 1: Based on the capacity calculation method, measure and calculate the effective values ​​of voltage and current output from the power quality regulation resources in real time to obtain the real-time compensated output capacity S. use and real-time remaining adjustable capacity S surplus ;

[0017] like 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. Should meet:

[0035] (5)

[0036] (2) Maximum allowable current carrying capacity I of power devices Smax The power quality regulation resources can also separately generate the maximum value of each harmonic compensation current. The restrictions are:

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

[0038] (6)

[0039] Consult the technical parameters of power devices (such as IGBTs) in the power quality conditioning resource manual to obtain their maximum permissible current carrying capacity I. Smax Then, the power quality regulation resources can also separately generate the maximum value of each harmonic compensation current. Should meet:

[0040] (7)

[0041] Wherein, K is a parameter characterizing the numerical relationship between the effective value of the current that the power device can withstand and the effective value of the output phase current, and is related to the control method of power quality regulation resources.

[0042] (3) 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:

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

[0044] (8)

[0045] in, U i The maximum value.

[0046] If the output impedance magnitude of the i-th harmonic is The currently compensated harmonic current output is By combining equations (8), the maximum value of the i-th harmonic compensation current that can still be emitted can be obtained. Should meet:

[0047] (9)

[0048] (4) DC side voltage and real-time power grid harmonic voltage The power quality regulation resources can also separately output the maximum value of each harmonic compensation current. Limitations:

[0049] Output voltage amplitude and DC side voltage of power quality conditioning resources Related to the control strategy, based on the PWM modulation principle, in the linear modulation region (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 at this time... And the output impedance magnitude of the i-th harmonic is Then we can obtain the maximum value of the i-th harmonic compensation current that can still be emitted. Should meet:

[0050] (10)

[0051] Taking into account the above equations (2), (3), (5), (7), (9), and (10), the maximum value of the i-th harmonic compensation current that the power quality regulation resources can still generate is obtained. for:

[0052] (11)

[0053] Step 22: Real-time remaining adjustable capacity S based on power quality regulation resources surplus The maximum total harmonic compensation current that can still be generated by power quality regulation resources can be obtained by evaluating the relationship between the square of the effective value of the current:

[0054] Given that the remaining output equivalent current of the power quality regulation resources obtained from equation (4) in step 21 is I surplus Assuming that compensation for different harmonic currents also needs to be performed simultaneously, let I... ej_need The j-th harmonic current value that the power grid still needs to compensate for in real time, I ej_next The j-th harmonic current value can also be generated as a power quality regulation resource. According to equation (11), I ej_next It should satisfy: If ,but ;like ,but Therefore, the total harmonic compensation current that the power quality regulation resources can generate in real time should meet the following requirements:

[0055] (12)

[0056] in, The maximum value of the jth harmonic compensation current that can be generated in real time for power quality regulation resources is determined by equation (11).

[0057] Combining equations (12) and (4), the maximum value of the total harmonic compensation current that can still be generated by the power quality regulation resources is:

[0058] (13)

[0059] The subscript 'max' indicates taking the maximum value.

[0060] Taking an APF (Active Power Filter) with an LCL (Inductor-Capacitor-Inductor) output filter as an example, the analysis focuses on the i-th harmonic output impedance. For an APF with an LCL output filter, its i-th harmonic output impedance It can be calculated using the following formula:

[0061] (14)

[0062] Where L1, C, and L2 are the inverter-side inductance, filter capacitor, and grid-side inductance of the LCL filter, respectively, f1 is the fundamental frequency, i is the harmonic order, and j is the imaginary unit.

[0063] Example:

[0064] The phase voltage (u) output in real time by the APF A ,u B ,u C ) and phase current (i A i B i C Sampling is performed, with the number of sampling points set to 200 per cycle (i.e., N=200). The instantaneous sampled values ​​of phase voltage and current corresponding to the k-th sampling point are denoted as: u Ak u Bk u Ck i Ak i Bk i Ck The calculated total effective values ​​of phase voltage and phase current are as follows:

[0065] ;

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

[0067] ;

[0068] Among them, I e5_rt Ie35_rt U represents the effective values ​​of the 5th and 35th harmonic compensation currents output by the APF in real time. e5_rt U e35_rt U represents the effective values ​​of the 5th and 35th harmonic voltages at the PCC (point of common coupling) of the APF. N I N These are the phase rated voltage and RMS current values ​​of the APF, respectively; other parameters have been explained previously.

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

[0070] ;

[0071] Based on the above parameters, the magnitudes of the 5th and 35th harmonic output impedances of this APF are calculated as follows:

[0072] ;

[0073] ;

[0074] First, S is calculated according to equations (2) and (3). use and S surplus :

[0075] ;

[0076] According to the comprehensive evaluation formula (11), the maximum value of the 5th harmonic compensation current that can still be generated in real time by the power quality regulation resources is determined. Conduct an assessment:

[0077] ;

[0078] The maximum value of the 35th harmonic compensation current that can be generated in real time by power quality regulation resources. Conduct an assessment:

[0079] ;

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

[0081] .

Claims

1. A method for evaluating the harmonic compensation capability of power quality regulation resources, characterized in that, Includes the following steps: Step 1: Based on the capacity calculation method, measure and calculate the real-time total effective values ​​of the phase voltage and phase current output by the power quality regulation resource, and obtain the real-time compensated output capacity S of the power quality regulation resource. use and real-time remaining adjustable capacity S surplus ,include: 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 real-time total effective values ​​of the corresponding phase voltage and phase current are calculated. Step 2: Real-time remaining adjustable capacity S based on power quality regulation resources surplus Considering four limiting factors, the maximum values ​​of each harmonic compensation current and the total harmonic compensation current that can be generated by power quality regulation resources can be evaluated.

2. The method for evaluating the harmonic compensation capability of power quality regulation resources according to claim 1, characterized in that, Step 1 further includes: Based on the definition of output capacity, the real-time compensated output capacity S of the power quality regulation resources is calculated from the real-time total effective value of phase voltage and phase current. use .

3. The method for evaluating the harmonic compensation capability of power quality regulation resources according to claim 2, characterized in that, Assume the rated capacity of the power quality regulation resources is S. N Given an efficiency of η, the real-time remaining adjustable capacity S of the power quality regulation resources is derived. surplus for: (3)。 4. The method for evaluating the harmonic compensation capability of power quality regulation resources according to claim 3, characterized in that, Step 2 includes: Step 21: Based on the real-time remaining adjustable capacity S of power quality regulation resources surplus The assessment yielded the maximum values ​​of the harmonic compensation currents that the power quality regulation resources could generate, respectively. It can also output the maximum value of each harmonic compensation current in real time. It is limited by the following four factors: the remaining output equivalent current of the equipment, the maximum allowable current carrying capacity of the power devices, the peak phase voltage of the grid, the DC side voltage, and the real-time grid harmonic voltage.

5. The method for evaluating the harmonic compensation capability of power quality regulation resources according to claim 4, characterized in that, Remaining output equivalent current I surplus The power quality regulation resources can also separately generate the maximum value of each harmonic compensation current. The restrictions are: Based on the real-time remaining adjustable capacity S of power quality adjustment resources surplus Assume that the effective value of the phase voltage at the point of common coupling corresponding to the power quality regulation resource is U. PCC The remaining output equivalent current I of the power quality regulation resources is calculated. surplus ; Then, the power quality regulation resources can also generate the maximum values ​​of each harmonic compensation current. satisfy: (5)。 6. The method for evaluating the harmonic compensation capability of power quality regulation resources according to claim 5, characterized in that, Maximum permissible current carrying capacity I of power devices Smax The power quality regulation resources can also separately generate the maximum value of each harmonic compensation current. The restrictions are: Based on the real-time compensated output capacity S of power quality regulation resources use The equivalent current I output by the power quality regulation resources was calculated. use ; According to the maximum allowable current carrying capacity I of power devices for power quality regulation resources Smax Then the power quality regulation resources can also generate the maximum value of each harmonic compensation current. satisfy: (7) Wherein, K is a parameter characterizing the numerical relationship between the effective value of the current that the power device can withstand and the effective value of the output phase current, and is related to the control method of power quality regulation resources.

7. The method for evaluating the harmonic compensation capability of power quality regulation resources according to claim 6, characterized in that, 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: The effective value of the phase voltage at the point of common coupling of the power quality regulation resource is known to be U. PCC Obtain the harmonic voltage U corresponding to the i-th harmonic current output by the power quality regulation resource. i Maximum value (U) i ) max ; If the output impedance magnitude of the i-th harmonic is The currently compensated harmonic current output is Then the power quality regulation resources can also generate the maximum value of the i-th harmonic compensation current. satisfy: (9)。 8. The method for evaluating the harmonic compensation capability of power quality regulation resources according to claim 7, characterized in that, DC side voltage and real-time power grid harmonic voltage The power quality regulation resources can also separately generate the maximum value of each harmonic compensation current. The restrictions are: If the output impedance magnitude of the i-th harmonic is Then the power quality regulation resources can also generate the maximum value of the i-th harmonic compensation current. satisfy: (10) Taking into account equations (3), (5), (7), (9), and (10), the maximum value of the i-th harmonic compensation current that the power quality regulation resources can still generate in real time is evaluated and obtained. for: (11)。 9. The method for evaluating the harmonic compensation capability of power quality regulation resources according to claim 8, characterized in that, Step 2 also includes: Step 22: Real-time remaining adjustable capacity S based on power quality regulation resources surplus The maximum total harmonic compensation current that can still be generated by power quality regulation resources is obtained by evaluating the relationship between the effective square of the current and the square of the current, including: Calculate the total harmonic compensation current that can still be generated in real time by power quality regulation resources, which satisfies: (12) Among them, I ej_need The j-th harmonic current value that the power grid still needs to compensate for in real time, I ej_next To adjust the value of the j-th harmonic current that can be emitted in real time, The maximum value of the jth harmonic compensation current that can be generated in real time for power quality regulation resources is determined by equation (11).

10. The method for evaluating the harmonic compensation capability of power quality regulation resources according to claim 9, characterized in that, Combining equations (12) and (4), the maximum value of the total harmonic compensation current that can still be generated by the power quality regulation resources is: (13) The subscript 'max' indicates taking the maximum value.

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