A distributed energy storage system harmonic electric energy precision metering method

Abstract

The application discloses a kind of distributed energy storage system harmonic electric energy precision metering method, belong to distributed energy storage management technical field, including the following steps: using harmonic analysis method electric signal is decomposed into fundamental component and each harmonic component;The instantaneous power obtained is decomposed into the active power component of the same harmonic number and the cross power component of different harmonic numbers, the active power component of the same harmonic number is integrated in fundamental cycle, to obtain average active power;Based on average active power, the total electric energy and the active and reactive power components corresponding to each harmonic are calculated;Based on the results of the preset dynamic weight and error correction, the electric energy metering is optimized.The application effectively solves the key problems of insufficient accuracy and poor dynamic response of traditional methods in the frequent charging and discharging of energy storage system and high harmonic environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of distributed energy storage management, and more particularly, to a distributed energy storage system harmonic electric energy accurate metering method. BACKGROUND

[0002] With the increasing proportion of new energy access, distributed energy storage systems are increasingly widely used in DC microgrids, becoming a key link for regulating grid load, improving energy utilization rate and system stability. Distributed energy storage devices are usually connected to the grid through bidirectional converters, and their operation has two states of charging and discharging, and the charging and discharging conversion process is frequent. Especially in the scenes of coordinating renewable energy fluctuation compensation, peak clipping and valley filling, and island operation, the energy storage system rapidly switches the charging and discharging mode in a short time, and its output current changes greatly, the rising edge is steep, and obvious high-order harmonics and nonlinear dynamic characteristics are often superimposed.

[0003] Under this background, the traditional electric energy metering method mostly adopts time domain integration method, that is, the instantaneous power is obtained by multiplying the voltage and current signals, and then integrated. However, when facing the dynamic disturbance and complex harmonic background caused by the frequent charging and discharging of the energy storage system, the traditional method often cannot accurately extract the effective power component, resulting in deviation of the electric energy metering result. Especially in the case of power direction reversal in the charging process and current mutation in the discharging process, the traditional method is difficult to distinguish the boundary between active power and invalid harmonic interference, affecting the metering accuracy and the reliability of subsequent energy management and billing settlement.

[0004] Therefore, there is an urgent need for an accurate electric energy metering method that can adapt to the frequent charging and discharging characteristics of distributed energy storage, effectively cope with high-order harmonics and sharp changes in current, to meet the actual needs of intelligent microgrids for high accuracy and high robustness of electric energy metering in complex dynamic operating environments.

[0005] In view of the above problems, the present application provides a solution. SUMMARY

[0006] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present application provide a distributed energy storage system harmonic electric energy accurate metering method, which effectively solves the key problems of insufficient accuracy and poor dynamic response of the traditional method in the frequent charging and discharging of the energy storage system and the high harmonic environment.

[0007] To achieve the above purpose, the present application provides the following technical solutions:

[0008] A kind of distributed energy storage system harmonic electric energy accurate metering method, comprising the following steps: using harmonic analysis method to decompose electric signal into fundamental component and each harmonic component;The instantaneous power obtained is decomposed into active power component of the same harmonic number and cross power component of different harmonic number, the active power component of the same harmonic number is integrated in fundamental cycle, and average active power is obtained;Based on average active power, total electric energy and active and reactive power components corresponding to each harmonic are calculated;Based on the results of preset dynamic weight and error correction, the electric energy metering is optimized.

[0009] In a preferred embodiment, the process of decomposing the obtained instantaneous power specifically includes: multiplying the voltage instantaneous value with the current instantaneous value at each sampling time to obtain the instantaneous power value;The instantaneous power is separated into active power component of the same harmonic number and cross power component of different harmonic number by signal decomposition technology.

[0010] In a preferred embodiment, the process of integrating the active power component of the same harmonic number in fundamental cycle specifically includes: selecting an integer number of complete fundamental cycles as the integration window;The active power component of the same harmonic number in the cycle is integrated and the average value is obtained to obtain the average active power value.

[0011] In a preferred embodiment, the preset dynamic weight is specifically obtained by: calculating the square value of each harmonic voltage amplitude in real time;The obtained square value is subjected to ratio operation with the sum of square values of all harmonic voltage amplitudes, and the ratio is used as the weight coefficient of this harmonic.

[0012] In a preferred embodiment, the error correction is specifically obtained by: continuously monitoring the change of harmonic parameter matrix, calculating error compensation factor according to the parameter change amplitude;The error compensation factor is applied to the electric energy metering result to realize real-time compensation of metering error generated in the dynamic change process.

[0013] The present application is based on the technical effect and advantages of a kind of distributed energy storage system harmonic electric energy accurate metering method:

[0014] 1.The present application constructs multiple harmonic models, separates each harmonic component in voltage and current signals, and eliminates non-synchronous harmonic cross terms, effectively avoiding the errors in the harmonic interference and current fluctuation of the traditional metering method, significantly improving the accuracy and robustness of electric energy metering.

[0015] 2.The present application can track each harmonic power component in real time, dynamically extract active components, and realize accurate response to rapidly changing current, to meet the energy fine monitoring requirements under complex operating conditions.

[0016] 3. By strictly separating active power and reactive power, fundamental wave and harmonic components, the application avoids the pollution of harmonic to the electric energy measurement results, and is particularly suitable for application scenarios with dense power electronic equipment and high harmonic content, such as new energy grid connection and energy storage parallel operation.

[0017] 4. By periodically integrating and averaging the power components, the influence of sampling jitter and instantaneous deviation is effectively suppressed, and the stability and long-term consistency of the measurement system under continuous operation conditions are improved.

[0018] The application realizes accurate active electric energy measurement under harmonic interference and dynamic working conditions by establishing a time-varying multiple harmonic model of voltage and current signals, real-time tracking of harmonic parameter changes based on an adaptive algorithm, accurate decomposition and periodic integration of instantaneous power, and adaptive correction of measurement results combined with preset dynamic weights and error compensation factors. Further, based on the harmonic component separation and error suppression mechanism, the anti-interference ability and robustness of the measurement system are enhanced. By outputting the fundamental wave and each harmonic power component, it is helpful to realize power quality monitoring and fine energy management, and effectively solve the key problems of insufficient accuracy and poor dynamic response of the traditional measurement method in the distributed energy storage system under frequent charging and discharging and high harmonic environment. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A flowchart of a distributed energy storage system harmonic electric energy accurate measurement method according to an embodiment of the application is shown. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0021] Embodiment 1, Figure 1 A distributed energy storage system harmonic electric energy accurate measurement method according to the application is given, including the following steps:

[0022] S1, the electric signal is decomposed into a fundamental wave component and each harmonic component by a harmonic analysis method.

[0023] In this embodiment, the voltage signal of the power grid at the sampling time is expressed as:

[0024]

[0025] ​At the sampling time of the power grid current signal Expressed as:

[0026]

[0027] Among them, the sampling time index in the power system is The maximum harmonic order considered is , Indicates the fundamental angular frequency of the power grid. Indicates the power grid at the sampling time voltage signal, Indicates the power grid at the sampling time The current signal, Indicates the first The voltage amplitude of the second harmonic Indicates the first The amplitude of the subharmonic current. Indicates the first Phase angle of subharmonic voltage Indicates the first Phase angle of the subharmonic current.

[0028] Introducing time-varying harmonic parameter matrix :

[0029] The matrix is ​​in the following form:

[0030] Its update equation is:

[0031] in, Forgetting factor, Let covariance matrix be the variance matrix. For the error term, Indicates transpose. For the power grid at sampling time n, the first... The amplitude of the voltage of the subharmonic. Let be the amplitude of the j-th harmonic current of the power grid at sampling time n. It is a column vector composed of complex exponents corresponding to each harmonic, and its dimension is... Consistency is used to compute predicted outputs and parameter updates in the Recursive Least Squares (RLS) algorithm. for The conjugate transpose of .

[0032] To enhance the accuracy and response speed of electricity metering, an adaptive optimization algorithm is introduced to dynamically adjust the update process of the time-varying harmonic parameter matrix. The specific steps are as follows:

[0033] An update error function for the time-varying harmonic parameter matrix is ​​constructed based on the harmonic voltage and current amplitudes.

[0034] The error function expression is as follows:

[0035] ,

[0036] Where k is the index of the harmonic order;

[0037] The forgetting factor and covariance matrix of the time-varying harmonic parameter matrix are optimized based on the gradient of the error function.

[0038] Specifically, the forgetting factor and covariance matrix are dynamically adjusted using the gradient descent method. The gradient descent formula is as follows:

[0039]

[0040]

[0041] In the formula, The learning rate controls the step size for optimization.

[0042] The optimized forgetting factor and covariance matrix are input into the time-varying parameter matrix update equation to obtain the real-time updated time-varying harmonic parameter matrix.

[0043] S2 decomposes the acquired instantaneous power into active power components with the same harmonic order and cross-power components with different harmonic orders. The active power components with the same harmonic order are integrated over the fundamental period to obtain the average active power.

[0044] In this embodiment, the process of obtaining instantaneous power decomposition specifically includes:

[0045] At each sampling moment, the instantaneous voltage value is multiplied by the instantaneous current value to obtain the instantaneous power value;

[0046] The instantaneous power obtained by signal decomposition technology is separated into active power components with the same harmonic order and cross power components with different harmonic orders.

[0047] In this embodiment, the instantaneous power is determined by a voltage signal. and current signal The formula is obtained by multiplying each element one by one, as follows:

[0048]

[0049] In this embodiment, the instantaneous power is decomposed into:

[0050]

[0051] in, This indicates that the harmonic orders of voltage and current are the same. the active power component generated, the voltage and current harmonics are different the cross power component generated;

[0052] In this embodiment, the cross term is expanded using the trigonometric identity, resulting in:

[0053]

[0054] In this embodiment, the process of integrating the active power component with the same harmonic order over the fundamental period, specifically includes:

[0055] Select an integer number of complete fundamental periods as the integration window;

[0056] Integrate the active power component of the same harmonic order over the integration window time period and take the average value to obtain the average active power value.

[0057] In this embodiment, the instantaneous power component with the same harmonic order In the fundamental period is integrated to obtain the average active power:

[0058]

[0059] The power component with different harmonic orders is also integrated, and the result is zero, and the formula is as follows:

[0060]

[0061] where, is the fundamental period, is the sampling time interval.

[0062] S3, calculate the total energy and the active and reactive power components corresponding to each harmonic based on the average active power.

[0063] In this embodiment, the total average active power is:

[0064] ;

[0065] The average active power consumed by the fundamental voltage and current is:

[0066] ;

[0067] The reactive power consumed by each harmonic voltage and current is:

[0068]

[0069] S4, optimizing the electric energy measurement based on the preset dynamic weight and the result of error correction.

[0070] In the embodiment, the preset dynamic weight is specifically obtained in the following method:

[0071] The square value of the amplitude of each harmonic voltage is calculated in real time;

[0072] The square value of the amplitude of each harmonic voltage is subjected to ratio operation with the sum of the square values of all harmonic voltage amplitudes, and the ratio is taken as the weight coefficient of the harmonic.

[0073] In the embodiment, for each harmonic component, the dynamic weight is calculated according to the energy proportion of each harmonic component.

[0074]

[0075] wherein, is the dynamic weight of the nth harmonic at the current time n, is the amplitude of the voltage of the nth harmonic, is the sum of the square values of all harmonic amplitudes, used for normalizing the energy proportion of the nth harmonic. In the embodiment, the error correction is specifically obtained in the following method:

[0076] The change of the harmonic parameter matrix is continuously monitored, and the error compensation factor is calculated according to the parameter change amplitude;

[0077] The error compensation factor is applied to the electric energy measurement result, so as to realize real-time compensation of the measurement error generated in the dynamic change process.

[0078] In the embodiment, the error compensation factor is calculated according to the change amount of the time-varying harmonic parameter :

[0079]

[0080] wherein, is the time-varying harmonic parameter matrix, containing the amplitude and phase information of the voltage and current,

[0081] is the harmonic parameter matrix at the last time, is the two-norm of the matrix. In the embodiment, based on the compensation factor , the compensated electric energy output

[0082] is calculated:

[0083] ​​​

[0084] in, N is the sampling time interval, and N is the number of data collection points.

[0085] This embodiment introduces preset dynamic weights and error compensation factors, which enables the method to adaptively adjust the electricity metering results, effectively reduce metering errors in harmonic environments, and improve the accuracy of electricity metering in distributed energy storage systems.

[0086] This method achieves accurate metering of harmonic energy in distributed energy storage systems by precisely modeling the harmonic components in the power grid, decomposing the power components, and introducing preset dynamic weights and error compensation factors. It effectively solves the problem of insufficient accuracy of traditional metering methods in harmonic environments and provides a reliable basis for energy management and power quality assessment of energy storage systems.

[0087] This embodiment establishes a time-varying multiple harmonic model of voltage and current signals, tracks the changes in harmonic parameters in real time based on an adaptive algorithm, and performs precise decomposition and periodic integration of instantaneous power. Combined with preset dynamic weights and error compensation factors, the metering results are adaptively corrected, thereby achieving accurate metering of active power under harmonic interference and dynamic operating conditions. Furthermore, based on harmonic component separation and error suppression mechanisms, the anti-interference capability and robustness of the metering system are enhanced. By outputting the fundamental wave and each harmonic power component, it helps to realize power quality monitoring and refined energy management, effectively solving the key problems of insufficient accuracy and poor dynamic response of traditional metering methods in distributed energy storage systems with frequent charging and discharging and high harmonic environments.

[0088] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0089] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0090] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0091] In addition, each function module in each embodiment of the present application can be integrated in one processing module, or each module can be physically present alone, or two or more modules can be integrated in one module.

[0092] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0093] Finally: the above is only a preferred embodiment of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for accurate metering of harmonic energy in a distributed energy storage system, characterized in that, Includes the following steps: The electrical signal is decomposed into fundamental component and harmonic components using harmonic analysis. The acquired instantaneous power is decomposed into active power components with the same harmonic order and cross-power components with different harmonic orders. The active power components with the same harmonic order are integrated over the fundamental period to obtain the average active power. The total average active power is determined based on the average active power. The error correction result is obtained based on the change of the harmonic parameter matrix, and the system harmonic energy is calculated based on the total average active power, the error correction result and the sampling time interval.

2. The method for accurate metering of harmonic energy based on a distributed energy storage system according to claim 1, characterized in that, The process of obtaining instantaneous power decomposition specifically includes: At each sampling moment, the instantaneous voltage value is multiplied by the instantaneous current value to obtain the instantaneous power value; The instantaneous power obtained by signal decomposition technology is separated into active power components with the same harmonic order and cross power components with different harmonic orders.

3. The method for accurate metering of harmonic energy based on a distributed energy storage system according to claim 2, characterized in that, The process of integrating the active power components with the same harmonic order using the fundamental period specifically includes: Choose an integer number of complete fundamental frequency periods as the integration window; The average active power value is obtained by integrating the active power components of the same harmonic within the integration window time period and calculating the average value.

4. The method for accurate metering of harmonic energy based on a distributed energy storage system according to claim 3, characterized in that, The process of obtaining the error correction result based on the changes in the harmonic parameter matrix is ​​as follows: Continuously monitor the changes in the harmonic parameter matrix and calculate the error compensation factor based on the magnitude of parameter changes; By applying the error compensation factor to the electricity metering results, real-time compensation can be achieved for metering errors generated during dynamic changes.

5. The method for accurate metering of harmonic energy based on a distributed energy storage system according to claim 4, characterized in that, The total average active power The calculation formula is: ； In the formula, BW represents the maximum harmonic order considered. Indicates the first The voltage amplitude of the second harmonic Indicates the first The amplitude of the subharmonic current. Indicates the first Phase angle of subharmonic voltage This represents the phase angle of the i-th harmonic current.

6. The method for accurate metering of harmonic energy based on a distributed energy storage system according to claim 5, characterized in that, The error compensation factor The calculation formula is: ， in, This is a time-varying harmonic parameter matrix, containing amplitude and phase information of voltage and current. It is the harmonic parameter matrix of the previous moment. Let be the amplitude of the j-th harmonic current of the power grid at sampling time n. It is the 2-norm of the matrix.

7. The method for accurate metering of harmonic energy based on a distributed energy storage system according to claim 6, characterized in that, The system's harmonic electrical energy The calculation formula is: ， in, N is the sampling time interval, and N is the number of data collection points.

8. The method for accurate metering of harmonic energy based on a distributed energy storage system according to claim 7, characterized in that, The time-varying harmonic parameter matrix includes an update step, specifically: An update error function for the time-varying harmonic parameter matrix is ​​constructed based on the harmonic voltage and current amplitudes. The forgetting factor and covariance matrix of the time-varying harmonic parameter matrix are optimized based on the gradient of the error function. The optimized forgetting factor and covariance matrix are input into the time-varying harmonic parameter matrix update equation to achieve matrix update.

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