Fluctuating load power calculation method suitable for electric energy meter and use and acquisition terminal, electric energy meter and use and acquisition terminal

Abstract

The invention discloses a fluctuation load power calculation method suitable for an electric energy meter and an acquisition terminal, the electric energy meter and the acquisition terminal, and belongs to the field of electric energy metering. The method comprises the following steps: continuously and synchronously sampling voltage and current signals of a power grid and filtering high-frequency harmonics; in-phase and orthogonal signals of voltage and current are adaptively estimated on the basis of a state observer under the condition that a direct current component is not removed, and a state estimation vector is obtained; inputting the voltage state estimation vector into a phase-locked loop, and estimating a voltage angular frequency and a phase through dq transformation; and calculating active power and reactive power according to the current state estimation vector, the voltage phase estimation value and the voltage d-axis component. The invention also provides a corresponding electric energy meter and a use and acquisition terminal. According to the method, the power change can be quickly tracked without lag under the fluctuating load working condition, response delay caused by traditional low-pass filtering is avoided, the dynamic metering precision is effectively improved, and the method is suitable for a complex power grid environment containing a direct-current component.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electric energy metering, and particularly relates to a fluctuating load power calculation method suitable for electric energy meters and consumption terminals, an electric energy meter and a consumption terminal. BACKGROUND

[0002] In the field of electric energy metering, the measurement accuracy of active power and reactive power is directly related to the fairness of trade settlement and the reliability of intelligent control of power grids. With the large-scale access of fluctuating and impulsive loads such as electric vehicle charging, distributed photovoltaic, and industrial electric arc furnaces, the load characteristics of power grids are becoming increasingly complex, and the core requirement for electric energy metering equipment has been extended from steady-state accuracy to dynamic accuracy, i.e., it is required to maintain extremely high metering accuracy when the load power changes rapidly.

[0003] Currently, the digital sampling method based on the instantaneous power theory is widely used in electronic electric energy meters, and its technical path is as follows: first, the instantaneous power is calculated, then a low-pass filter is relied on to filter out the two times of the alternating current component and higher frequency components, and finally the direct current component representing the active power is extracted.

[0004] This traditional method exposes its inherent technical defects under fluctuating load conditions, which directly restricts the improvement of dynamic metering accuracy: the inherent large time constant of the narrow-band low-pass filter designed to ensure steady-state accuracy leads to a serious lag in system response. When the load power changes in steps, the power calculation result cannot track the true value immediately, but needs a slow climbing process. This lag will introduce significant electric energy metering errors at the critical moment of load switching, causing undercounting or overcounting of electric energy, so that the electric energy meter loses accuracy at the most dynamic moment when accurate metering is needed. SUMMARY

[0005] The present application proposes a fluctuating load power calculation method suitable for electric energy meters and consumption terminals, an electric energy meter and a consumption terminal, and the purpose is to quickly and non-laggingly track the changes of power signals under fluctuating load conditions, thereby effectively guaranteeing the electric energy metering accuracy at the dynamic moment of load switching.

[0006] The technical solution of the present application is as follows:

[0007] A fluctuating load power calculation method suitable for electric energy meters and consumption terminals, comprising the following steps:

[0008] Step S1: continuously and synchronously sampling the power grid voltage signal and the current signal and filtering out the high-frequency harmonic interference respectively to obtain a voltage channel signal sequence and a current channel signal sequence;

[0009] Step S2: Based on the state observer, without removing the DC component contained in the voltage channel signal sequence and current channel signal sequence obtained in step S1, adaptive estimation of the in-phase and quadrature signals of the voltage and current signals is achieved, and the state estimation vectors of the voltage channel and the current channel are obtained.

[0010] Step S3: Input the state estimation vector of the voltage channel into the phase-locked loop, and estimate the angular frequency and phase of the voltage signal based on the dq transform;

[0011] Step S4: Calculate the active power and reactive power based on the current path state estimation vector obtained in step S2, and the voltage phase estimation value and voltage d-axis component estimated in step S3.

[0012] As a further improvement to the fluctuating load power calculation method applicable to electricity meters and user terminals, in step S2, adaptive estimation is performed for both the voltage channel and the current channel in the following manner:

[0013] Step S2-1: Establish the asymptotic observer equation for the current channel:

[0014] ;

[0015] in, The state estimation vector of the current channel is in the th... The estimated value at each moment, For the state estimation vector at the th The derivative at time n, For the output vector at the th The value at each moment, The state matrix, For the state-output matrix, The observer gain matrix is... The DC correlation matrix is ​​as follows:

[0016] ;

[0017] ;

[0018] ;

[0019] ;

[0020] In the above formula, The voltage channel signal sequence or current channel signal sequence processed in step S1 is in the... The value at each moment, For the first The intermediate state at any given moment. Indicates the first an estimate of the phase angle frequency at the kth moment, and are two elements of the observer gain matrix;

[0021] Step S2-2: initialize the variables in the progressive observer equation;

[0022] Step S2-3: substitute the signal values of the signal sequence obtained in step S1 into the corresponding progressive observer equation in sequence, and perform adaptive update on the intermediate state ;

[0023] Step S2-4: calculate the current observer error:

[0024] ;

[0025] Step S2-5: determine whether the observer error is less than the specified threshold: if it is less than the specified threshold, it is determined that the observer output of the current signal channel is stable at this time, otherwise it is determined that the current signal channel is unstable;

[0026] When the observers of the voltage channel and the current channel are both stable, the corresponding state estimation vector contains the in-phase signal and the quadrature signal of the corresponding channel. The state estimation vector of the voltage channel at the kth moment is denoted as , and the state estimation vector of the current channel is denoted as .

[0027] As a further improvement of the fluctuating load power calculation method applicable to electric energy meters and power consumption terminals, after each new is substituted in step S2-3:

[0028] the current is first calculated;

[0029] then the is calculated based on the current and , and the is calculated according to the current and :

[0030]

[0031] in the above formula, is a parameter affecting the convergence speed;

[0032] the intermediate variable is calculated according to the second element in the current derivative: ​​

[0033] ;

[0034] Then based on and current is calculated ;

[0035] Meanwhile, step S3 updates the estimated value of the angular frequency as .

[0036] As a further improvement of the fluctuation load power calculation method applicable to electric energy meters and load terminals, step S3 specifically comprises:

[0037] Step S3-1: The state estimation vector of the voltage signal is dq-transformed according to the following formula:

[0038] ;

[0039] Wherein, is the phase estimation value of the voltage signal at the th moment obtained by the phase-locked loop.

[0040] As a further improvement of the fluctuation load power calculation method applicable to electric energy meters and load terminals, step S3 further comprises:

[0041] Step S3-2: The voltage q-axis component in step S3-1 is transmitted to a PI controller, and the intermediate quantity is calculated according to the following formula:

[0042] ;

[0043] Wherein, and are PI controller parameters, represents an integrator;

[0044] Step S3-3: The current voltage signal angular frequency estimation value and the phase estimation value are estimated according to the following formula:

[0045] ;

[0046] Wherein, is the angular frequency fixed bias.

[0047] As a further improvement of the fluctuation load power calculation method applicable to electric energy meters and load terminals, step S3 further comprises:

[0048] Step S3-4: The angular frequency estimation value and the phase estimation value feedback to the previous input, updating the variable in the corresponding step; wherein feedback to the voltage channel and the current channel, an observer model, feedback to the voltage channel and the current channel, a dq transformation link.

[0049] As a further improvement of the fluctuating load power calculation method suitable for electric energy meters and load terminals, step S4 specifically comprises:

[0050] Step S4-1: based on the angular frequency estimation value, coordinate transform the state estimation vector of the current channel estimated in step S2 to obtain the current intermediate state vector at the first time :

[0051] ;

[0052] Step S4-2: according to the voltage phase estimation value and the voltage d-axis component estimated in step S3, the active power and the reactive power are calculated according to the following formula:

[0053] ;

[0054] wherein, is the voltage d-axis component calculated in step S3.

[0055] As a further improvement of the fluctuating load power calculation method suitable for electric energy meters and load terminals, step S4 further comprises:

[0056] Step S4-4: determine whether the stability condition of step S2-5 is met; if met, the active power and the reactive power output at this time are the expected power RMS values; otherwise, steps S1 to S4 are continuously executed until the output is stable.

[0057] The application also discloses an electric energy meter, which comprises a processor and a memory, and a program stored in the memory is configured to be executed by the processor, and when executed, the fluctuating load power calculation method is realized.

[0058] The application also discloses a load terminal, which comprises a processor and a memory, and a program stored in the memory is configured to be executed by the processor, and when executed, the fluctuating load power calculation method is realized.

[0059] Compared with the prior art, the application has the following beneficial effects:

[0060] ​1.The application constructs a system structure capable of quickly and accurately calculating power under fluctuating load conditions by combining a phase-locked loop with a state observer. The phase-locked loop provides dynamic tracking capability for frequency and phase, while the state observer synchronously estimates in-phase and quadrature components in voltage and current signals without pre-DC removal, thereby effectively extracting fundamental components in the presence of DC components and significantly improving the power calculation accuracy under fluctuating load conditions.

[0061] 2.The application adopts an adaptive estimation mechanism based on a state observer, introduces DC-related terms and gradient update strategies in the state equation, and realizes online compensation of DC components in voltage and current signals. This method avoids the problem of occupying multiple cycles in the traditional DC removal calculation step, overcomes the dynamic response delay caused thereby, and is particularly suitable for scenarios with rapid load changes.

[0062] 3.The application utilizes the same frequency characteristics of voltage and current channels, feeds back the frequency and phase information estimated by the voltage channel to the current channel processing process, and realizes power calculation through unified coordinate rotation operation. This structure not only eliminates the low-pass filter link in the traditional power calculation, reducing the computational burden, but also realizes synchronous output of active power and reactive power, further improving the dynamic response speed and real-time performance of the system.

[0063] Through the comprehensive use of the above technical means, the application can realize fast, stable and accurate measurement of power under complex conditions of frequency fluctuation and the presence of DC components in applications such as electric energy meters and consumption terminals that require high real-time performance. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 The figure is a flowchart of the method of the application. DETAILED DESCRIPTION

[0065] The technical solutions of the application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the application, not all embodiments.

[0066] Embodiment one

[0067] As Figure 1 A fluctuating load power calculation method suitable for electric energy meters and consumption terminals, comprising the following steps:

[0068] Step S1: continuously and synchronously sample the grid voltage signal and the current signal, obtain multiple sets of voltage sampling sequences and current sampling sequences and save them to the cache. Perform low-pass filtering on the voltage sampling sequences and current sampling sequences respectively to filter out high-frequency harmonic interference, and obtain voltage channel signal sequences and current channel signal sequences.

[0069] The design of the digital filter is a conventional technical means, and the embodiment does not provide a specific implementation manner. According to engineering experience, a 6th order Butterworth type IIR filter with a passband of 45 Hz to 55 Hz can be used to meet the requirement of -40 dB stopband attenuation. It should be noted that although the IIR filter does not meet the linear phase, since the voltage channel and the current channel pass through the filter at the same time, the influence of the filter on the phase can be offset.

[0070] It should be noted that the low-pass filtering in this step is a basic processing process of the sampled signal, and is different in essence from the low-pass filtering process of filtering out the alternating current components of two times of the power frequency and higher frequencies after obtaining the instantaneous power in the traditional calculation scheme to extract the direct current component. The low-pass filtering of the sampled signal in this step does not require a large time constant, and therefore there is no problem of response lag.

[0071] Suppose that after the processing in step S1, the signal values of the voltage channel signal sequence and the current channel signal sequence at the i th time are represented as V (i) and I (i) respectively. and , and have the following forms:

[0072] ;

[0073] wherein V (i) and I (i) represent the voltage amplitude and the current amplitude respectively, is the signal angular frequency, is the sampling frequency, is the voltage phase, is the current phase, is the voltage signal direct current component, is the current signal direct current component.

[0074] Step S2: Based on the state observer, adaptive estimation of the in-phase signal and the quadrature signal of the voltage signal and the current signal is realized without removing the direct current components contained in the voltage channel signal sequence and the current channel signal sequence obtained in step S1, to obtain a state estimation vector of the voltage channel and a state estimation vector of the current channel.

[0075] For the voltage channel and the current channel, adaptive estimation is performed in the following manner:

[0076] Step S2-1: Establish the progressive observer equation of the current channel:

[0077] ;

[0078] wherein V (i) and I (i) represent the voltage amplitude and the current amplitude respectively, ​​​​The estimated value at each moment, For the state estimation vector at the th The derivative at time n, For the output vector at the th The value at each moment, The state matrix, For the state-output matrix, The observer gain matrix is... The DC correlation matrix is ​​as follows:

[0079] ;

[0080] ;

[0081] ;

[0082] ;

[0083] In the above formula, The voltage channel signal sequence or current channel signal sequence processed in step S1 is in the... The value at each moment, For the first The intermediate state at any given moment. Indicates the first The estimated value of the angular frequency at each moment. and These are two elements of the observer gain matrix. This represents the DC component of the currently estimated signal.

[0084] In this observer, and It is not directly estimated by the observer; the former is updated by subsequent steps, while the latter is... It is part of something that does not need to be explicitly expressed.

[0085] According to the stability condition of the state equation, the matrix The value of needs to satisfy , i.e., matrix Negative determination. Based on engineering experience, Possible values .

[0086] Step S2-2: Initialize the variables in the asymptotic observer equation.

[0087] In this embodiment: , , , There is also an intermediate state. .

[0088] Step S2-3: Substitute the signal values ​​of the signal sequence obtained in step S1 into the corresponding asymptotic observer equations one by one, each time substituting a new value... back:

[0089] First calculate the current ;

[0090] Then based on the current and Calculate ( , (for the sampling period), and also based on the current and Calculate the next moment :

[0091] ;

[0092] In the above formula, The parameter that affects the convergence speed has a value greater than 0, and is generally 100.

[0093] According to the current The second element Calculate intermediate variables Current derivative:

[0094] ;

[0095] Then based on and current Calculate ;

[0096] Meanwhile, we wait for step S3 to update the estimated angular frequency as... .

[0097] According to the Lyapunov stability criterion for nonlinear systems, selecting the gradient update method in step S2-3 can guarantee the asymptotic stability of the nonlinear system.

[0098] Step S2-4: Calculate the current observer error.

[0099] The formula for calculating the observer error is:

[0100] .

[0101] Step S2-5: Determine the observer error Check if it is less than a specified threshold. If it is less than the specified threshold, the observer output of the current signal channel is considered stable; otherwise, the current signal channel is considered unstable.

[0102] Once stabilized, the observer can quickly estimate the DC component, but this invention does not require explicit use of the DC component value. Its purpose is to introduce... The update mechanism can quickly estimate and compensate for DC effects at each sampling point, thus eliminating the need for multiple cycles of averaging in traditional methods to remove DC, and significantly improving the dynamic response speed.

[0103] Once the observers for both the voltage and current channels are stable, the corresponding state estimation vectors will contain the in-phase and quadrature signals for those channels. The state estimation vector of the voltage channel at each time step is denoted as . The state estimation vector of the current channel is denoted as... .

[0104] Step S3: Input the state estimation vector of the voltage channel into the phase-locked loop, and estimate the angular frequency and phase of the voltage signal based on the dq transformation.

[0105] Step S3-1: Perform dq transformation on the state estimation vector of the voltage signal according to the following formula:

[0106] ;

[0107] in, The first phase-locked loop obtained Phase estimate of voltage signal at each moment.

[0108] Step S3-2: Convert the voltage q-axis component from step S3-1. The input is fed into the PI controller, and the intermediate quantity is calculated according to the following formula. :

[0109] ;

[0110] in, and For PI controller parameters, empirical values ​​can be taken as follows: , ; This represents an integrator.

[0111] After the system stabilizes (i.e., after the conditions in step S2-5 are met), there should be , .

[0112] Step S3-3: Estimate the current voltage signal angular frequency using the following formula. and phase estimate :

[0113] ;

[0114] in, A fixed angular frequency bias is used to accelerate convergence; generally, it can be set to a value that is suitable for this purpose. .

[0115] Step S3-4: Estimate the angular frequency and phase estimate Feedback is sent to the previous input to update the variables in the corresponding steps. The observer model feeds back to the voltage and current paths. Feedback is provided to the dq transformation stage of the voltage and current channels.

[0116] Step S4: Calculate the active power and reactive power based on the current path state estimation vector obtained in step S2, and the voltage phase estimation value and voltage d-axis component estimated in step S3.

[0117] Step S4-1: Based on the estimated angular frequency, perform coordinate transformation on the state estimation vector of the current path obtained in step S2 to obtain the... Current intermediate state vector at each time step :

[0118] .

[0119] Step S4-2: Based on the voltage phase estimate and voltage d-axis component obtained in step S3, calculate the active power according to the following formula. and reactive power :

[0120] ;

[0121] in, It is the d-axis component of the voltage calculated in step S3.

[0122] For power vector Inverting the second term yields the reactive power. The first term of this vector is the active power. .

[0123] Step S4-4: Determine whether the stability condition of step S2-5 is met. If it is met, then the output active power is... and reactive power This is the desired power RMS value. Otherwise, continue executing steps S1 to S4 until the output stabilizes.

[0124] Since the coordinate transformation has eliminated twice the power frequency AC signal, the resulting , This is a DC signal, specifically the RMS value of the power. In practical engineering applications, a moving average operation can also be performed on the power signal to further stabilize the power estimate.

[0125] It should be noted that steps S1 to S4 are executed synchronously. While continuously sampling through step S1, the state estimation vector needs to be obtained through step S2, the angular frequency and phase need to be estimated through step S3, and the active power and reactive power need to be calculated through step S4 in each sampling period.

[0126] This method combines phase-locked loop (PLL) and observer methods, leveraging the excellent dynamic characteristics of PLLs to simultaneously estimate orthogonal voltage and current signals as well as frequency, achieving high estimation accuracy even under fluctuating load conditions. This invention eliminates the need for explicit DC-DC removal of voltage and current signals, simultaneously estimating orthogonal signals and DC through the observer, resulting in fast dynamic response. Furthermore, this invention utilizes the synchronous frequency characteristics of the voltage and current channels, feeding back the estimated information from the voltage channel to the current channel. Through coordinate rotation, it achieves simultaneous calculation of active and reactive power with low computational complexity, eliminating the need for a low-pass filter and significantly improving response speed.

[0127] Example 2

[0128] This embodiment discloses an energy meter, including a processor and a memory. A program stored in the memory is configured to be executed by the processor, and when executed, it implements the fast power calculation method described in Embodiment 1, which is the fluctuating load power calculation method used by this energy meter.

[0129] Example 3

[0130] This embodiment discloses a data acquisition terminal, including a processor and a memory. A program stored in the memory is configured to be executed by the processor, and when executed, it implements the fast power calculation method described in Embodiment 1, which is the fluctuating load power calculation method used by the energy meter.

[0131] It should be noted that, as will be apparent to those skilled in the art, the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics thereof. The scope of the present invention is defined by the claims rather than the foregoing description.

Claims

1. A method for calculating fluctuating load power applicable to electricity meters and power consumption terminals, characterized in that, Includes the following steps: Step S1: Continuously and synchronously sample the grid voltage signal and current signal and filter out high-frequency harmonic interference respectively to obtain the voltage channel signal sequence and the current channel signal sequence; Step S2: Based on the state observer, without removing the DC component contained in the voltage channel signal sequence and current channel signal sequence obtained in step S1, adaptive estimation of the in-phase and quadrature signals of the voltage and current signals is achieved, and the state estimation vectors of the voltage channel and the current channel are obtained. Step S3: Input the state estimation vector of the voltage channel into the phase-locked loop, and estimate the angular frequency and phase of the voltage signal based on the dq transform; Step S4: Calculate the active power and reactive power based on the current path state estimation vector obtained in step S2, and the voltage phase estimation value and voltage d-axis component estimated in step S3.

2. The method for calculating fluctuating load power applicable to electricity meters and power consumption terminals as described in claim 1, characterized in that, In step S2, adaptive estimation is performed for both the voltage path and the current path using the following method: Step S2-1: Establish the asymptotic observer equation for the current channel: ； in, The state estimation vector of the current channel is in the th... The estimated value at each moment, For the state estimation vector at the th The derivative at time n, For the output vector at the th The value at each moment, The state matrix, For the state-output matrix, The observer gain matrix is... The DC correlation matrix is ​​as follows: ； ； ； ； In the above formula, The voltage channel signal sequence or current channel signal sequence processed in step S1 is in the... The value at each moment, For the first The intermediate state at any given moment. Indicates the first The estimated value of the angular frequency at each moment. and These are two elements of the observer gain matrix; Step S2-2: Initialize the variables in the asymptotic observer equation; Step S2-3: Substitute the signal values ​​of the signal sequence obtained in step S1 into the corresponding asymptotic observer equations, and process the intermediate states. Perform adaptive updates; Step S2-4: Calculate the current observer error: ； Step S2-5: Determine the observer error Is it less than a specified threshold? If it is less than a specified threshold, the observer output of the current signal channel is determined to be stable; otherwise, the current signal channel is determined to be unstable. Once the observers for both the voltage and current channels are stable, the corresponding state estimation vectors will contain the in-phase and quadrature signals for those channels. The state estimation vector of the voltage channel at each time step is denoted as . The state estimation vector of the current channel is denoted as .

3. The method for calculating fluctuating load power applicable to electricity meters and power consumption terminals as described in claim 2, characterized in that, In steps S2-3, each time a new... back: First calculate the current ; Then based on the current and Calculate At the same time, according to the current and Calculate the next moment : ； In the above formula, These are parameters that affect the convergence speed; According to the current The second element Calculate intermediate variables Current derivative: ； Then based on and current Calculate ; Meanwhile, we wait for step S3 to update the estimated angular frequency as... .

4. The method for calculating fluctuating load power applicable to electricity meters and power consumption terminals as described in claim 2, characterized in that, Step S3 specifically includes: Step S3-1: Perform dq transformation on the state estimation vector of the voltage signal according to the following formula: ； in, The first phase-locked loop obtained Phase estimate of voltage signal at each moment.

5. The method for calculating fluctuating load power applicable to electricity meters and power consumption terminals as described in claim 4, characterized in that, Step S3 also includes: Step S3-2: Convert the voltage q-axis component from step S3-1. The input is fed into the PI controller, and the intermediate quantity is calculated according to the following formula. : ； in, and For PI controller parameters, Indicates an integrator; Step S3-3: Estimate the current voltage signal angular frequency using the following formula. and phase estimate : ； in, The angular frequency is fixed by bias.

6. The method for calculating fluctuating load power applicable to electricity meters and power consumption terminals as described in claim 5, characterized in that, Step S3 also includes: Step S3-4: Estimate the angular frequency and phase estimate Feedback is sent to the preceding input to update the variables in the corresponding steps; where The observer model feeds back to the voltage and current paths. Feedback is provided to the dq transformation stage of the voltage and current channels.

7. The method for calculating fluctuating load power applicable to electricity meters and power consumption terminals as described in claim 4, characterized in that, Step S4 specifically includes: Step S4-1: Based on the estimated angular frequency, perform coordinate transformation on the state estimation vector of the current path obtained in step S2 to obtain the... Current intermediate state vector at each time step : ； Step S4-2: Based on the voltage phase estimate and voltage d-axis component obtained in step S3, calculate the active power according to the following formula. and reactive power : ； in, It is the d-axis component of the voltage calculated in step S3.

8. The method for calculating fluctuating load power applicable to electricity meters and power consumption terminals as described in claim 7, characterized in that, Step S4 also includes: Step S4-4: Determine whether the stability condition of step S2-5 is met; if it is met, then the output active power is... and reactive power This is the desired power RMS value; otherwise, continue executing steps S1 to S4 until the output stabilizes.

9. An electricity meter, characterized in that: It includes a processor and a memory, wherein a program stored in the memory is configured to be executed by the processor, and when executed, implements the fluctuating load power calculation method as described in any one of claims 1 to 8.

10. A terminal for data acquisition, characterized in that: It includes a processor and a memory, wherein a program stored in the memory is configured to be executed by the processor, and when executed, implements the fluctuating load power calculation method as described in any one of claims 1 to 8.

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