A three-phase asynchronous motor phase-shifting sampling leading-lagging average power measurement system

Abstract

This invention discloses a three-phase asynchronous motor phase-shift sampling lead-lag average power measurement system, belonging to the field of motor power measurement technology. It includes a signal conditioning module, an ADC sampling module, a dual-state machine module, a lead-lag averaging module, an error compensation module, and a periodic averaging filter module. The signal conditioning module adapts the voltage and current signal levels; the ADC sampling module acquires the conditioned signal at fixed-period time-division multiplexing; the dual-state machine module performs time-division sampling of voltage and current and power pre-calculation; the lead-lag averaging module averages the power values ​​at adjacent sampling times; the error compensation module corrects the system error of the average power value; and the periodic averaging filter module performs full-cycle power averaging filtering based on voltage zero-crossing detection. This invention requires only a single energy metering chip to achieve equivalent synchronous sampling, reducing hardware costs by 40%~50%, controlling system errors within ±0.1%, exhibiting strong harmonic suppression capabilities, and providing good load and frequency adaptability.

Description

Technical Field

[0001] This invention relates to the field of motor power measurement technology, and in particular to a three-phase asynchronous motor phase-shift sampling lead-lag average power measurement system. Background Technology

[0002] Three-phase asynchronous motors are the most important power equipment in industrial production, and their power measurement is of great significance for energy efficiency management, equipment protection, and operation optimization. Accurate measurement of motor power is the foundation for assessing motor operating status and achieving energy-saving control.

[0003] Currently, the following technical solutions are mainly used for power measurement of three-phase asynchronous motors: (1) Synchronous sampling scheme: A multi-channel ADC is used to sample the three-phase voltage and current simultaneously, and the average power is calculated by integrating the instantaneous power (e.g., CN105676125B "Method and device for measuring power of variable frequency motor"). This scheme has high measurement accuracy, but requires a multi-channel synchronous ADC, which is complex and costly, and has strict requirements for sampling synchronization.

[0004] (2) Time-division sampling scheme: Voltage and current signals are collected by a single energy meter in a time-division manner, and the time difference is compensated by software algorithm. This scheme has low hardware cost, but time-division sampling will introduce phase error and jitter, resulting in deviation in power calculation.

[0005] (3) Power metering chip solution: Power measurement is achieved by using a dedicated power metering chip. This solution has high integration, but poor flexibility and difficulty in achieving synchronous sampling of voltage and current signals.

[0006] In summary, existing power measurement technologies mainly suffer from the following technical shortcomings: (1) High hardware cost of synchronous sampling: Traditional synchronous sampling schemes require multiple ADCs to work at the same time and require strict time synchronization between channels, which increases the complexity and cost of hardware design.

[0007] (2) The phase error of time-division sampling is difficult to eliminate: In the time-division sampling scheme, there is a fixed time interval between voltage and current sampling, which leads to a phase difference. Traditional methods are difficult to accurately compensate for this phase error, which affects the accuracy of power measurement.

[0008] (3) Harmonic interference affects measurement accuracy: There are a large number of harmonic components in industrial power grids. Traditional power measurement methods do not effectively filter out harmonic interference, resulting in large fluctuations in power calculation results and a decrease in measurement accuracy.

[0009] (4) Lack of a unified three-phase power calculation model: Existing technologies mostly use the method of simply adding the single-phase power calculations together, without establishing a power calculation method based on the unified ABC three-phase model, making it difficult to accurately analyze system errors. Summary of the Invention

[0010] To address the aforementioned problems in existing technologies, this invention provides a three-phase asynchronous motor phase-shift sampling lead-lag average power measurement system, comprising a signal conditioning module, an ADC sampling module, a dual-state machine module, a lead-lag averaging module, an error compensation module, and a periodic averaging filtering module. The signal conditioning module adapts the voltage and current signal levels; the ADC sampling module acquires the conditioned signal at a fixed period; the dual-state machine module uses a T0 / T1 dual-state cycle to achieve time-division sampling of voltage and current and power pre-calculation; the lead-lag averaging module averages the power values ​​at adjacent sampling times; the error compensation module calculates a compensation coefficient based on the sampling phase difference to correct system errors; and the periodic averaging filtering module performs full-cycle power averaging filtering based on voltage zero-crossing detection. This invention aims to solve the following technical problems: (1) By using the phase-shift sampling lead-lag averaging algorithm, phase-shift sampling with a fixed phase difference is achieved on a dedicated power metering chip, which significantly reduces hardware costs while ensuring power measurement accuracy. (2) Establish a unified three-phase power calculation model for ABC, quantitatively analyze algorithm errors through rigorous mathematical derivation, and provide accurate error compensation methods to achieve high-precision power measurement; (3) The periodic average filtering method based on the voltage zero crossing point effectively suppresses harmonic interference and power grid fluctuations, and improves the stability and anti-interference capability of power measurement.

[0011] The technical solution of the present invention is as follows: A three-phase asynchronous motor phase-shift sampling lead-lag average power measurement system includes a signal conditioning module, an ADC sampling module, a dual-state machine module, a lead-lag averaging module, an error compensation module, and a periodic averaging filtering module. The signal conditioning module includes a voltage conditioning circuit and a current conditioning circuit; the voltage conditioning circuit converts the voltage of the three-phase asynchronous motor into a low voltage level suitable for ADC sampling, and defines the low voltage level as the original three-phase voltage signal; the current conditioning circuit converts the current of the three-phase asynchronous motor into a low voltage level suitable for ADC sampling, and defines the low voltage level as the original three-phase current signal. The ADC sampling module is constructed using a power metering chip, with a sampling period T. s The raw three-phase voltage and three-phase current signals are acquired in a time-division manner, and the resulting data are defined as three-phase voltage signals and three-phase current signals. The dual-state machine module is connected to the ADC sampling module and uses a dual-state cyclic state machine to control the sampling process of the ADC sampling module; the dual-state cyclic state machine includes a T0 state and a T1 state, and the T0 state and the T1 state follow a sampling period T. sThe process involves cyclic switching; the T0 state control ADC sampling module samples the original three-phase current signal, obtains the three-phase current signal, stores the three-phase current signal in a buffer, and simultaneously reads the three-phase voltage signal from the previous cycle. The total three-phase power is calculated based on the three-phase current signal and the three-phase voltage signal. Similarly, the T1 state control ADC sampling module samples the original three-phase voltage signal, obtains the three-phase voltage signal, stores the three-phase voltage signal in a buffer, and simultaneously reads the three-phase current signal from the previous cycle. The total three-phase power is calculated based on the three-phase current signal and the three-phase voltage signal. The lead-lag averaging module averages the current three-phase total power with the previous cycle's three-phase total power and uses the average value as the current power output value. The error compensation module calculates the error compensation coefficient based on the sampling phase difference, and compensates and corrects the power output value to obtain the power correction value. The periodic average filtering module performs positive zero-crossing detection on the A-phase voltage of the three-phase asynchronous motor, then determines the start and end points of the waveform period of the three-phase asynchronous motor based on adjacent positive zero-crossing points, and finally averages the power correction value within each waveform period to obtain the periodic average power, which is the final measured power of the three-phase asynchronous motor.

[0012] Furthermore, when the dual-state machine module is in state T0, the formula for calculating the total three-phase power is as follows: When the dual-state machine module is in state T1, the formula for calculating the total three-phase power is as follows: in , , Representing the sampling time respectively , , , , , These represent the three-phase voltage signals, , , These represent the three-phase current signals, represent The total three-phase power at any given time. represent The total three-phase power at any given time.

[0013] Furthermore, the lead-lag average module in The power output value at time t is: .

[0014] Furthermore, the compensation coefficient of the error compensation module is: in This is the angular frequency of the power grid.

[0015] Furthermore, the detection condition for the positive zero-crossing point of the periodic averaging filter module is as follows: Va_norm(k-1)≤0 and Va_norm(k)>0, Where Va_norm is the normalized A-phase voltage signal, which is an array, and k-1 and k represent the index in Va_norm.

[0016] The beneficial technical effects of this invention are as follows: (1) Low hardware cost: The use of a single energy meter in conjunction with a dual-state machine to achieve equivalent synchronous sampling reduces hardware cost by about 40% to 50% compared to the traditional multi-channel synchronous sampling scheme; (2) High measurement accuracy: By establishing a unified power calculation model for three phases ABC, and performing rigorous mathematical derivation and error compensation, the system error can be controlled within ±0.1%; (3) Strong harmonic suppression capability: The periodic averaging filtering method based on zero crossing point utilizes the characteristic that the integral of the harmonic tends to zero within one period to effectively suppress the interference of odd harmonics such as the 5th and 7th order, and the power fluctuation is reduced by about 70% after filtering; (4) The algorithm is simple and efficient: the dual-state machine algorithm has a simple structure, low computational load, is easy to implement in embedded systems, has strong real-time performance, and the output delay is only about 125μs (8kHz sampling). (5) Predictable and compensable error: The algorithm error is quantitatively analyzed through a three-phase unified mathematical model, and a precise compensation method is provided to reduce the system error from -0.077% to near zero; (6) Strong load adaptability: The error magnitude is independent of the power factor angle θ, that is, it is independent of the motor load condition, and can maintain high-precision measurement under various load conditions; (7) Good frequency adaptability: The periodic average filter is based on zero-crossing detection and can automatically adapt to power grid frequency fluctuations (45Hz~65Hz) to ensure measurement stability. Attached Figure Description

[0017] Figure 1 It is a system architecture diagram; Figure 2 It is a time-division sampling waveform of voltage and current; Figure 3 This is a diagram illustrating the principle of leading and lagging averages. Figure 4 This is a diagram showing the effect of error compensation; Figure 5This is a schematic diagram of the effect of periodic averaging filtering; Figure 6 This is a graph showing the relationship between system error and sampling phase difference. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0019] I. System Composition of the Implementation Example like Figure 1 As shown, the embodiment includes a signal conditioning module, an ADC sampling module, a dual-state machine module, a lead-lag averaging module, an error compensation module, and a periodic averaging filter module. The signal conditioning module and the ADC sampling module are hardware modules, while the dual-state machine module, the lead-lag averaging module, the error compensation module, and the periodic averaging filter module are software modules. The software modules are built into a single-chip microcomputer of model STM32G431.

[0020] The signal conditioning module includes a voltage conditioning circuit and a current conditioning circuit. The voltage conditioning circuit converts the 380V three-phase line voltage into a low voltage level suitable for ADC sampling (called the original three-phase voltage signal), with a voltage division ratio of 1000:1. The current conditioning circuit converts the three-phase current into a low voltage level for ADC sampling (called the original three-phase current signal), with a CT ratio of 1000:1.

[0021] The ADC sampling module uses the RN7302 power metering chip, with a sampling period T. s The sampling frequency is set to 125μs (8kHz), and the raw three-phase voltage and three-phase current signals are collected in a time-division manner. The sampled data are called the three-phase voltage signal and the three-phase current signal.

[0022] The dual-state machine module is a dual-state cyclic state machine implemented based on an STM32 embedded microcontroller. State T0 and state T1 alternate, with the switching period varying from the sampling period T. sThe results are consistent. In state T0, the microcontroller controls the ADC sampling module to sample the raw three-phase current signal, obtain the three-phase current signal and store it in a buffer. Simultaneously, it reads the three-phase voltage signal from the previous cycle's buffer and calculates the total three-phase power based on the three-phase current and voltage signals. In state T1, the microcontroller controls the ADC sampling module to sample the raw three-phase voltage signal, obtain the three-phase voltage signal and store it in a buffer. Simultaneously, it reads the three-phase current signal from the previous cycle's buffer and calculates the total three-phase power based on the three-phase current and voltage signals. The voltage and current waveforms obtained from time-division sampling are shown below. Figure 2 As shown.

[0023] The working principle of the leading-lag averaging module is as follows: Figure 3 As shown, the current time The total three-phase power is averaged with the total three-phase power of the previous cycle, and the average value is used as the power output value at the current moment.

[0024] The error compensation module multiplies the power output value of the lead-lag averaging module by the error compensation coefficient K to obtain the power correction value P_comp. The error compensation effect is as follows: Figure 4 As shown.

[0025] The periodic averaging filter module normalizes, detects positive zero-crossing points, divides the period, and averages the A-phase voltage of the three-phase asynchronous motor within each waveform period. The specific steps are as follows: S1. Normalize the sampled data of the A-phase voltage of the three-phase asynchronous motor to obtain the normalized A-phase voltage signal, i.e., the array Va_norm; S2. Detect positive zero crossings that satisfy Va_norm (k-1)≤0 and Va_norm (k)>0, where k-1 and k represent the indices in Va_norm; S3. Record all the positive zero-crossing points obtained in S2 to obtain a zero-crossing point index array; the interval between two adjacent positive zero-crossing points is one waveform period; S4. Calculate the arithmetic mean of the power correction value P_comp within each waveform period to obtain the periodic average power, which is the final measured power of the three-phase asynchronous motor. The periodic average filtering effect is as follows: Figure 5 As shown.

[0026] II. Three-phase unified power model For a three-phase asynchronous motor, assuming three-phase balance, the effective values ​​of voltage and current are consistent, and considering the power factor angle... To mitigate the impact of these factors, a unified three-phase power model is established: Phase A voltage: Phase A current: Phase B voltage: Phase B current: C-phase voltage: C-phase current: Instantaneous power: III. Sampling Principle of Dual-State Machine The dual-state machine module adopts a dual-state cyclic working mechanism, and its sampling timing is as follows: (1) T0 state (current sampling state): At the current sampling time The three-phase current signals are acquired, and the three-phase voltage signals buffered from the previous cycle are used to calculate the total three-phase power. (2) T1 state (voltage sampling state): At the current sampling time The three-phase voltage signals are acquired, and the three-phase current signals buffered from the previous cycle are used to calculate the total three-phase power. in , , Representing the sampling time respectively , , , , , These represent the three-phase voltage signals, , , These represent the three-phase current signals, represent The total three-phase power at any given time. represent The total three-phase power at any given time.

[0027] IV. Principle of the Lead-Lag Averaging Algorithm The lead-lag averaging module averages the three-phase power values ​​at two adjacent sampling times: Sampling period: Power frequency: Angular frequency: Sampling phase difference: Substituting the three-phase power expressions for states T0 and T1, the power output of phase A can be obtained through mathematical derivation: Using the sum-to-product formula: in , ,but: Substituting, we get: Similarly, the power output of phase B can be obtained: Similarly, the power output of phase C can be obtained: The three-phase algebraic addition yields The algorithm outputs the total power at each time point: V. Three-phase unified error analysis and compensation The error compensation module is based on a three-phase unified power model and undergoes rigorous mathematical derivation and error analysis. (1) Formula for Three-Phase Total Power Error The three-phase instantaneous total power error is calculated using the algorithm. Time output and The difference between the actual values. The actual instantaneous power of phase A at a given time point: so The time-point algorithm outputs the power of phase A: Similarly, we can obtain: , In other words The total three-phase power output by the time-point algorithm: Therefore, the total three-phase power output by the algorithm and the theoretical instantaneous power have an inherent coefficient and an inherent delay, such as Figure 6 As shown.

[0028] (2) Calculation of relative error (3) Numerical calculation (taking 8kHz sampling as an example) Substitution : (4) Error compensation By multiplying by the compensation coefficient K = 1 / cos( ) ≈ 1.00077, which can eliminate systematic errors to near zero.

[0029] (5) Load independence From the error formula, we can see that the systematic error... Only with the sampling phase difference Related to the power factor angle It is independent of the motor load, meaning the error magnitude is independent of the motor load condition, and it has good load adaptability.

[0030] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, and for those of ordinary skill in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. Therefore, the present invention is not limited to the specific details without departing from the general concept defined by the claims and their equivalents.

Claims

1. A three-phase asynchronous motor phase-shift sampling lead-lag average power measurement system, characterized in that: It includes a signal conditioning module, an ADC sampling module, a dual-state machine module, a lead-lag averaging module, an error compensation module, and a periodic averaging filter module; The signal conditioning module includes a voltage conditioning circuit and a current conditioning circuit; the voltage conditioning circuit converts the voltage of the three-phase asynchronous motor into a low voltage level suitable for ADC sampling, and defines the low voltage level as the original three-phase voltage signal; the current conditioning circuit converts the current of the three-phase asynchronous motor into a low voltage level suitable for ADC sampling, and defines the low voltage level as the original three-phase current signal. The ADC sampling module is constructed using a power metering chip, with a sampling period T. s The raw three-phase voltage and three-phase current signals are acquired in a time-division manner, and the resulting data are defined as three-phase voltage signals and three-phase current signals. The dual-state machine module is connected to the ADC sampling module, and a dual-state cyclic state machine is used to control the sampling process of the ADC sampling module. The dual-state cyclic state machine includes a T0 state and a T1 state, and the T0 state and the T1 state are configured according to a sampling period T. s The process involves cyclic switching; the T0 state control ADC sampling module samples the original three-phase current signal, obtains the three-phase current signal, stores the three-phase current signal in a buffer, and simultaneously reads the three-phase voltage signal from the previous cycle. The total three-phase power is calculated based on the three-phase current signal and the three-phase voltage signal. Similarly, the T1 state control ADC sampling module samples the original three-phase voltage signal, obtains the three-phase voltage signal, stores the three-phase voltage signal in a buffer, and simultaneously reads the three-phase current signal from the previous cycle. The total three-phase power is calculated based on the three-phase current signal and the three-phase voltage signal. The lead-lag averaging module averages the current three-phase total power with the previous cycle's three-phase total power and uses the average value as the current power output value. The error compensation module calculates the error compensation coefficient based on the sampling phase difference, and compensates and corrects the power output value to obtain the power correction value. The periodic average filtering module performs positive zero-crossing detection on the A-phase voltage of the three-phase asynchronous motor, then determines the start and end points of the waveform period of the three-phase asynchronous motor based on adjacent positive zero-crossing points, and finally averages the power correction value within each waveform period to obtain the periodic average power, which is the final measured power of the three-phase asynchronous motor.

2. The three-phase asynchronous motor phase-shift sampling lead-lag average power measurement system according to claim 1, characterized in that: When the dual-state machine module is in state T0, the formula for calculating the total three-phase power is as follows: When the dual-state machine module is in state T1, the formula for calculating the total three-phase power is as follows: in , , Representing the sampling time respectively , , , , , These represent the three-phase voltage signals, , , These represent the three-phase current signals, represent The total three-phase power at a given moment. represent The total three-phase power at any given time.

3. The three-phase asynchronous motor phase-shift sampling lead-lag average power measurement system according to claim 2, characterized in that, The leading-lag averaging module is in The power output value at time t is: .

4. The three-phase asynchronous motor phase-shift sampling lead-lag average power measurement system according to claim 1, characterized in that: The compensation coefficient of the error compensation module is: in This is the angular frequency of the power grid.

5. The three-phase asynchronous motor phase-shift sampling lead-lag average power measurement system according to claim 1, characterized in that: The detection condition for the positive zero-crossing point of the periodic averaging filter module is as follows: Va_norm(k-1)≤0 and Va_norm(k)>0, Where Va_norm is the normalized A-phase voltage signal, which is an array, and k-1 and k represent the index in Va_norm.

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