CN107423748B - Method for reducing influence of power grid harmonic waves on non-invasive load identification - Google Patents

Abstract

The application relates to the technical field of power monitoring, in particular to a method for reducing influence of power grid harmonic waves on non-invasive load identification. The method comprises the following steps: acquiring a first current characteristic quantity and a first voltage characteristic quantity at a user power inlet; calculating a second current characteristic quantity according to the first current characteristic quantity and a current weight coefficient; calculating a second voltage characteristic quantity according to the first voltage characteristic quantity and a voltage weight coefficient; obtaining a corrected current characteristic quantity according to the second current characteristic quantity and the second voltage characteristic quantity; and identifying the electric load of the user according to the corrected current characteristic quantity. The corrected current characteristic quantity is closer to the current characteristic quantity generated by equipment and has smaller difference with the current characteristic quantity in the power load characteristic library, so that the corrected current characteristic quantity reduces the influence of power grid harmonic waves on user power load identification and is beneficial to improving the load identification precision.

Description

A method to reduce the influence of grid harmonics on non-intrusive load identification

technical field

The present application relates to the technical field of power monitoring, and in particular, to a method for reducing the influence of power grid harmonics on non-intrusive load identification.

Background technique

Power load monitoring is an important part of the power grid system. It is not only conducive to analyzing the load composition, guiding users to consume reasonably, and reducing the cost of electricity consumption, but also conducive to the optimal allocation of national power resources. Therefore, it is very necessary to build an efficient load monitoring system.

At present, non-intrusive power load monitoring and identification methods mainly include two categories: monitoring and identification technology based on steady state characteristics and monitoring and identification technology based on transient characteristic events. The monitoring and identification technology based on the steady-state feature is to collect the steady-state harmonics, power and other parameters of the load. According to the load feature library, a certain decomposition algorithm is used to identify the working state and power consumption information of each main electrical equipment. When taking the steady-state current harmonics as the load characteristic quantity (or one of the characteristic quantities), the current harmonics in the load characteristic library are only the current harmonics generated by the equipment. However, the collected current harmonics at the user's power inlet not only include the harmonics generated by the equipment, but also include the harmonics generated by the power grid, which are different from the current harmonics in the load signature database.

It can be seen that the power grid harmonics affect the accuracy of the collected harmonics, which in turn affects the accuracy of the user's power load identification. Therefore, how to reduce the influence of power grid harmonics on user power load monitoring has become an urgent problem to be solved.

SUMMARY OF THE INVENTION

The present application provides a method for reducing the influence of power grid harmonics on non-intrusive load identification, so as to solve the problem of low accuracy of user power load identification.

A method of reducing the impact of grid harmonics on non-intrusive load identification, comprising:

obtaining the first current characteristic quantity and the first voltage characteristic quantity at the user's power inlet;

According to the first current feature amount and the current weight coefficient, calculate the second current feature amount; according to the first voltage feature amount and the voltage weight coefficient, calculate the second voltage feature amount;

obtaining a corrected current characteristic quantity according to the second current characteristic quantity and the second voltage characteristic quantity;

According to the corrected current feature quantity, the power consumption load of the user is identified.

Further, the current characteristic quantities are current harmonics, and the voltage characteristic quantities are voltage harmonics.

Further, the current characteristic quantity is the amplitude of the current harmonic, and the voltage characteristic quantity is the amplitude of the voltage harmonic.

Further, the obtaining the corrected current feature amount according to the second current feature amount and the second voltage feature amount includes: calculating the difference between the second current feature amount and the second voltage feature amount to obtain the corrected current feature amount .

Further, the identifying the power consumption load of the user according to the modified current characteristic amount includes: using a load identification algorithm to identify the power consumption load of the user according to the modified current characteristic amount. The load identification algorithm includes, but is not limited to, a pattern identification algorithm, an optimization algorithm for constructing an optimal objective function, a table lookup algorithm, and a clustering algorithm.

The technical solution provided by the present application includes the following beneficial technical effects: the present application obtains a second current feature amount by multiplying the first current feature amount obtained from the user power inlet by a current weight coefficient; The feature quantity is multiplied by the voltage weighting coefficient to obtain the second voltage feature quantity. The corrected current characteristic quantity is obtained by calculating the difference between the second current characteristic quantity and the second voltage characteristic quantity. The difference between the corrected current feature and the current feature in the power load feature library is small. Therefore, the corrected current feature reduces the influence of power grid harmonics on the user's power load identification, which is beneficial to improve the load identification accuracy.

Description of drawings

In order to illustrate the technical solutions of the present application more clearly, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, without creative work, the Additional drawings can be obtained from these drawings.

FIG. 1 is a flowchart of a method for reducing the influence of power grid harmonics on non-intrusive load identification provided by the present application.

Detailed ways

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description serve to explain the principles of the application.

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. In other words, on the premise of no creative labor, other drawings can also be obtained from these drawings.

The embodiment of the present invention provides a method for reducing the influence of grid harmonics on non _- intrusive load identification, as shown in FIG. It should be noted that this method is also applicable to other types of loads that are not limited to linear loads.

Step 1: Obtain the first current characteristic quantity and the first voltage characteristic quantity at the user's power inlet.

Specifically, the first voltage harmonic at the user's power inlet is obtained as the first voltage feature quantity, and the first current harmonic at the user's power inlet is obtained as the first current feature quantity.

The first voltage harmonic is:

U _Rmains =A ₁ cos(ωt+θ ₁ )+A ₂ cos(2ωt+θ ₂ )+...+A _k cos(kωt+θ _k ) (1)

Among them, A ₁ is the amplitude of the fundamental wave in the voltage harmonic; A ₂ ,...,A _k is the amplitude of each order in the voltage harmonic; ω=2πf is the angular frequency of the fundamental wave, f is the frequency of the fundamental wave; θ ₁ is the initial phase angle of the voltage harmonic fundamental wave, θ ₂ , ......, θ _k is the initial phase angle of each order in the voltage harmonic wave; t is the time.

For the user's linear load R ₁ , according to Ohm's law:

Therefore, the first current harmonic can be expressed as:

为电流谐波中基波的幅值；

为电流谐波中各次波的幅值；ω＝2πf为基波角频率，f为基波频率；θ₁为电流谐波中基波的初相角，θ₂，......，θ_k为电流谐波中各次波的初相角；t为时间。in,

is the amplitude of the fundamental wave in the current harmonic;

is the amplitude of each wave in the current harmonics; ω=2πf is the angular frequency of the fundamental wave, f is the fundamental wave frequency; θ ₁ is the initial phase angle of the fundamental wave in the current harmonic, θ ₂ ,...... , θ _k is the initial phase angle of each wave in the current harmonics; t is the time.

In general, a certain decomposition algorithm is used for the acquired first current harmonic I _RR1 based on the characteristic quantities of the load characteristic library to identify the working states of different electrical appliances of the user.

The current harmonics of the load signature library are the harmonics generated by the equipment. The harmonics of the equipment are measured in the environment where the harmonics of the power grid are extremely small and can be ignored without considering its influence, that is, A ₂ , ......, A The amplitude of each order of _k is 0, and the corresponding voltage harmonics are:

U _Rmains = A ₁ cos(ωt+θ ₁ ) (4)

Without considering the influence of power grid harmonics in harmonics, for the user's linear load R ₁ , the current harmonics of the load signature library are:

And the current harmonic corresponding to the resistance R ₁ actually collected is I _RR1 shown in the formula (3). Comparing the two, it can be found that there is a deviation between I _TR1 and I _RR1 , which will affect the identification accuracy of the final electricity load.

Step 2: Calculate a second current characteristic quantity according to the first current characteristic quantity and the current weighting coefficient; calculate a second voltage characteristic quantity according to the first voltage characteristic quantity and the voltage weighting coefficient.

Due to the complexity of harmonics, in order to simplify the calculation, the amplitude of the current harmonics is used as the current characteristic quantity, and the amplitude of the voltage harmonics is used as the voltage characteristic quantity to represent the changes of the harmonics in the calculation process. Specifically, the amplitude of the first voltage harmonic is denoted as U _HARmains ; the amplitude of the first current harmonic collected under the load of the linear resistance R ₁ is denoted as I _HARR1 ; in the load characteristic library, the load resistance The magnitude of the current harmonic of R ₁ is denoted as I _HATR1 .

For the convenience of expression, U _HARmains , I _HARR1 and I _HATR1 are respectively represented by the per-unit value of their fundamental wave amplitude as the reference. Specifically, the per-unit value of the fundamental wave amplitude is 1, and the per-unit value of each harmonic is is the ratio of its amplitude to the fundamental amplitude.

According to formula (1), we can get:

Wherein, u _HARmains1 is the per-unit value of the amplitude of the fundamental wave in the first voltage harmonic, and u _HARmainsk is the per-unit value of the amplitude of the K-th harmonic in the first voltage harmonic.

According to formula (2), we can get:

Wherein, i _HARR1 is the per-unit value of the amplitude of the fundamental wave in the first current harmonic; i _HARRk is the per-unit value of the amplitude of the K-th harmonic in the first current harmonic.

According to formula (5), we can get:

I _HATR1 =[i _HATR1 , 0, 0, ..., 0] = [1, 0, 0, ..., 0] (8)

Among them, i _HATR1 is the per-unit value of the fundamental wave amplitude in the current harmonics of the load characteristic library.

Further, calculate the second current harmonic amplitude according to the amplitude of the first current harmonic and the current weighting coefficient; calculate the second voltage harmonic according to the amplitude and the voltage weighting coefficient of the first voltage harmonic Amplitude.

Specifically, the voltage weighting coefficient is ρ _u , the current weighting coefficient is ρ _i , correspondingly, the amplitude of the second voltage harmonic of the fundamental wave and each order wave is ρ _u u _HARmainsn , the fundamental wave and each order wave are The second current harmonic amplitude of is ρ _i i _HATRn .

The magnitude of the second voltage harmonic is:

The magnitude of the second current harmonic is:

Step 3: Obtain a corrected current characteristic quantity according to the second current characteristic quantity and the second voltage characteristic quantity.

Specifically, according to equations (9) and (10), the harmonics of the second order and above in the current characteristic quantity, that is, the power grid harmonics, are corrected according to the difference as shown below: ρ _i i _{HARRk -ρ u} u _HARmainsk , where k≧2.

For different types of loads, the effect of grid harmonics on current harmonics is different, and the values of ρ _i and ρ _u are different. Generally, ρ _i takes _{ρ i} =1; for different types of loads, it is recommended that ρ _u take a value in the range of (0,1]. The resulting current harmonic amplitude I _{HARR1_CAL} is:

I _{HARR1_CAL} = [1, 0, 0, ..., 0]

It can be seen that the amplitudes corresponding to the current harmonics in the corrected current harmonic amplitude I _{HARR1_CAL} and the load characteristic library shown in Equation (8) have a small difference.

In the present application, by correcting the current harmonics, the power grid harmonics in the current harmonics are weakened, and the corrected current characteristic quantity is obtained, and the corrected current characteristic quantity is closer to the reference equipment harmonics in the power load characteristic database. Therefore, the corrected current harmonics reduce the influence of power grid harmonics on user power load identification, which is beneficial to improve the load identification accuracy.

It should be noted that when the fundamental wave and the amplitudes of each order are represented by actual values rather than per unit values, the value range of ρ _u is (0, χ], where χ is the current harmonic amplitude and the voltage harmonic amplitude. For the linear load R1 in the embodiment of the present invention, specifically, χ=1/R ₁ , and ρ _u =1/R ₁ is taken.

Step 4: Identify the user's electricity load according to the corrected current feature quantity.

Specifically, a pattern recognition algorithm, an optimization algorithm for constructing an optimal objective function, a table look-up algorithm, and a clustering algorithm can be used to identify the user's power load.

It should be noted that relational terms such as "first" and "second" etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations are related. any such actual relationship or sequence exists. Furthermore, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that an article or device comprising a list of elements includes not only those elements, but also other elements not expressly listed, Or also include elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

The above descriptions are only specific embodiments of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, this application is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

It should be understood that the present application is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the application is limited only by the appended claims.

Claims (3)

1. A method for reducing the influence of power grid harmonics on non-intrusive load identification, wherein the method comprises: obtaining the first current characteristic quantity and the first voltage characteristic quantity at the user's power inlet; According to the first current feature amount and the current weight coefficient, calculate the second current feature amount; according to the first voltage feature amount and the voltage weight coefficient, calculate the second voltage feature amount; According to the second current feature amount and the second voltage feature amount, a corrected current feature amount is obtained, the difference between the second current feature amount and the second voltage feature amount is calculated, and the quadratic value of the current feature amount is calculated. and harmonics of the second or higher order are corrected according to the difference as shown below: ρ _i i _{HARRk -ρ u} u _HARmainsk In the formula, ρ _i is the current weight coefficient, ρ _u is the voltage weight coefficient, i _HARRk is the per-unit value of the amplitude of the K-th current harmonic, u _HARmainsk is the per-unit value of the amplitude of the K-th voltage harmonic, k ≧2; for different types of loads, the effect of power grid harmonics on current harmonics is different, and the values of ρ _i and ρ _u are different; the corrected current harmonic amplitude I _{HARR1_CAL} is obtained, that is, the corrected current characteristic quantity is obtained; Identify the user's electricity load according to the corrected current feature quantity; Wherein, the current characteristic quantity is the current harmonic, the voltage characteristic quantity is the voltage harmonic; the current characteristic quantity is the amplitude of the current harmonic, and the voltage characteristic quantity is the amplitude of the voltage harmonic value. 2 . The method according to claim 1 , wherein the obtaining a corrected current characteristic quantity according to the second current characteristic quantity and the second voltage characteristic quantity comprises: 2 . Calculate the difference between the second current feature amount and the second voltage feature amount to obtain a corrected current feature amount. 3 . The method according to claim 1 , wherein the identifying the user's electricity load according to the corrected current feature quantity comprises: 3 . According to the corrected current feature quantity, a load identification algorithm is used to identify the user's electricity load; the load identification algorithm adopts, but is not limited to: a pattern identification algorithm, an optimization algorithm for constructing an optimal objective function, a table lookup algorithm, and a clustering algorithm .

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