CN103344825B - Based on the electric energy metered system of AC sampling - Google Patents

Based on the electric energy metered system of AC sampling Download PDF

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CN103344825B
CN103344825B CN201310284687.1A CN201310284687A CN103344825B CN 103344825 B CN103344825 B CN 103344825B CN 201310284687 A CN201310284687 A CN 201310284687A CN 103344825 B CN103344825 B CN 103344825B
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voltage
analog
current
sampling
value
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CN201310284687.1A
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CN103344825A (en
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任家爱
熊皓
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深圳市亚特尔科技有限公司
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Abstract

Based on an electric energy metered system for AC sampling, it comprises voltage sample part, for sampling to obtain voltage analog sampled value to the signal from electrical network of access; Current sample part; For sampling to obtain current-mode analog quantity sampled value to the signal from electrical network of access; Voltage signal processing section; The voltage analog sampled value obtained is nursed one's health and is biased to the voltage analog sampled value in predetermined threshold value; Current signal processing section; The current-mode analog quantity sampled value obtained is nursed one's health and is biased to the current-mode analog quantity sampled value in predetermined threshold value; Zero cross signal processing section, receives the voltage analog sampled value from voltage sample part, carries out Zero-cross comparator and shaping filter to voltage analog sampled value, obtains zero-crossing pulse signal and gives processor section component voltage zero passage detection; Also comprise the processor part based on ARM of band analog to digital converter.Should be that the response time was short based on one of advantage of the electric energy metered system of AC sampling.

Description

Based on the electric energy metered system of AC sampling

Technical field

The utility model belongs to electric energy metrical sampling system, concretely, belongs to the electric energy metered system based on AC sampling.

Background technology

Along with the raising day by day of Automation of Electric Systems level, the acquisition of parameters of electric power and management become more and more important.The popularization and application of microcomputer technology in electric system, makes the measurement and monitoring technology of electric system be developed rapidly.Obtain from conventional instrument various in style the requirement that parameters of electric power can not meet system, development high precision, multiparameter, multi-functional, digitized Modularized power instrument have become a current heat subject.

Usually adopt electric energy computation chip ADE7753 as electric power side control instrument scheme in prior art, the release of ADE7753 is provided convenience to electric energy exploitation, but as electric power observation and control instrument scheme, it also exists response time and harmonic measure and cost aspect and there is certain limitation.

STMicw Electronics releases the Cortex of STM32 series 32 tMthe ARM of-M3 kernel be ST Microelectronics in the industry cycle release at first based on nucleus product in ARMCortex-M3, inherit the excellent blood lineage of Cortex-M3 kernel, add the high performance peripheral hardware resource of ST simultaneously, FLASH, SRAM memory, abundant serial communication interface, as IIC, SPI, USART, CAN, USB etc., and the ADC of 12 and DAC module, support the FSMC of static memory controller flexibly of external memory access.The sampling rate of its 1M, two ADC provides basis for realizing AC synchronization sampling.Powerful peripheral functionality forms a reliable and stable SOC (system on a chip), has good cost performance, develops the electrical measuring instrument platform of AC sampling.

Utility model content

The utility model is intended to solve foregoing problems, and provide a kind of electric energy metered system based on AC sampling, its response time is short.

An aspect of the present utility model provides a kind of electric energy metered system based on AC sampling, and it comprises

Voltage sample part, for sampling to obtain voltage analog sampled value to the signal from electrical network of access;

Current sample part, for sampling to obtain current-mode analog quantity sampled value to the signal from electrical network of access;

Voltage signal processing section, nurses one's health the voltage analog sampled value obtained and is biased to the voltage analog sampled value in predetermined threshold value;

Current signal processing section, nurses one's health the current-mode analog quantity sampled value obtained and is biased to the current-mode analog quantity sampled value in predetermined threshold value;

Zero cross signal processing section, receives the voltage analog sampled value from voltage sample part, carries out Zero-cross comparator and shaping filter to voltage analog sampled value, obtains zero-crossing pulse signal and gives processor section component voltage zero passage detection;

The processor part based on ARM with analog to digital converter: comprise voltage sample value analog to digital converter, current sampling data analog to digital converter, zero passage interrupt unit and parameter arithmetic section; Wherein, voltage sample value analog to digital converter is used for carrying out analog to digital conversion by zero-crossing pulse signal enabling to the voltage analog sampled value in the predetermined threshold value from voltage signal processing section and digitized voltage sample value being kept at a magnitude of voltage storage part; Current sampling data analog to digital converter is used for carrying out analog to digital conversion by zero-crossing pulse signal enabling to the current-mode analog quantity sampled value in the predetermined threshold value from current signal processing section and digitized current sampling data being kept at a current value storage part; This parameter arithmetic section calculates the electric energy metrical parameter for this electrical network according to the digitized voltage sample value obtained and digitized current sampling data according to sampling techniques.

This voltage sample part also comprises phase compensation portion.

This current sample part also comprises phase compensation portion.

AC sample system based on arm processor of the present utility model and method, have employed the arm processor STM32F103RC of ST company, establish the public sample circuit of AC Data Acquisition, software algorithm platform, the powerful peripheral functionality of STM32 and processing speed, conveniently can realize electric power observation and control instrument, multifunctional electric energy meter, the electrical measuring instrument exploitations such as read out instrument and harmonic wave instrument, establish standardized sampling module, realize resource reuse, improve product development speed and development quality.

Accompanying drawing explanation

Fig. 1 is according to the theory diagram based on AC sampling electric energy metered system of the present utility model;

Fig. 2 is according to the circuit diagram based on the voltage sample part of AC sampling electric energy metered system and a kind of embodiment of voltage signal processing section of the present utility model;

Fig. 3 is according to the circuit diagram based on the current sample part of AC sampling electric energy metered system and a kind of embodiment of current signal processing section of the present utility model;

Fig. 4 is the circuit diagram of a kind of embodiment of zero cross signal processing section;

Fig. 5 is according to the process flow diagram based on AC sampling electric energy gauging method of the present utility model.

Fig. 6 is the process flow diagram of the method for sampling one embodiment.

Embodiment

As shown in Figure 1, wherein, the hardware of this AC sample system comprises the sample circuit such as voltage sample part, current sample part to a kind of embodiment of AC sample system of the present utility model; Voltage signal processing section, current signal processing section and zero cross signal handling part grade front-end processing circuit; And the processor part (MCU) based on ARM of band analog to digital converter, can be such as the processor module of the STM32F103RC of STMicw Electronics (TM).

Voltage sample can be obtained by electric resistance partial pressure, as shown in Figure 2.Wherein, example is sampled as with A phase voltage, by resistance R6, R9, R23, R11, R24, R25, R27, R28 dividing potential drop, signal is through VREF bias voltage 1.65VDC, after R24, R25 obtain signal conversion process, again by after filter amplifier U4-B filter and amplification, one tunnel sends the ADC1 sampling of processor calculating part (MCU) to, zero cross signal treatment circuit (Fig. 4) UA_PLUS is passed to through U1-B Zero-cross comparator and shaping filter in another road, obtain the external interrupt I/O port that UA-INT zero-crossing pulse signal gives MCU, carry out A phase voltage zero passage detection.

Fig. 3 shows for a certain phase, such as A phase, current sample part and a kind of circuit diagram of embodiment of current signal processing section.Wherein, for A phase current, A phase current is sampled through current transformer T2, then by after U4-A filter and amplification, sends the ADC2 sampling of MCU to;

Above-mentionedly be described the sample circuit of voltage, electric current for A phase current voltage, B, C phase current voltage sampling circuit principle, realizing can be completely the same with A phase, repeats no more here.

Three-phase voltage and three-phase current become 0V ~ 1.65V ~ 3.3V voltage through signal conditioning circuit and 1.65V reference offset circuit conversion, send into ADC1 and ADC2 converter respectively, realize 6 tunnel simulating signal in-phase sampling and conversions, ensure that every phase voltage, current detecting is same-phase, its precision is 12; For the phase delay that elimination mutual inductor and circuit produce, phase compensation can be provided when circuit design, as the electric capacity C10 in Fig. 2, as the electric capacity C14 in Fig. 3.

The data obtained can shift through DMA queue memory, few to cpu resource occupancy; Voltage signal becomes square wave to send STM32 external interrupt input port to detect through Zero-cross comparator circuit conversion, obtains the cycle of AC signal;

STM32 has powerful peripheral hardware and calculation processing power, easily realizes instrument and measures in real time, analyzes: the parameters of electric power such as U, I, P, Q, S, COS Φ, F, kWh, kvarh.

In system, STM32 processor working procedure completes: control A/D data sampling, carry out FFT computing to sampled result, and the hardware parameter according to sampling techniques coupling system calculates all parameters in electricity, result is sent into RAM for subsequent use.Its flow process is illustrated in fig. 5 shown below.

The method comprises: sample to obtain voltage analog sampled value to the signal from electrical network of access; Sample to obtain current-mode analog quantity sampled value to the signal from electrical network of access; The voltage analog sampled value obtained is nursed one's health and is biased to the voltage analog sampled value in predetermined threshold value; The current-mode analog quantity sampled value obtained is nursed one's health and is biased to the current-mode analog quantity sampled value in predetermined threshold value; Receive the voltage analog sampled value from voltage sample part, Zero-cross comparator and shaping filter are carried out to voltage analog sampled value, obtain zero-crossing pulse signal and give processor section component voltage zero passage detection; And by zero-crossing pulse signal enabling analog to digital conversion is carried out to the voltage analog sampled value in the predetermined threshold value from voltage signal processing section and digitized voltage sample value is kept at a magnitude of voltage storage part; By zero-crossing pulse signal enabling analog to digital conversion is carried out to the current-mode analog quantity sampled value in the predetermined threshold value from current signal processing section and digitized current sampling data is kept at a current value storage part; The electric energy metrical parameter for this electrical network is calculated according to sampling techniques according to the digitized voltage sample value obtained and digitized current sampling data.

Wherein, the phase differential eliminated and produce in voltage sample process is also comprised.

Wherein, the phase differential eliminated and produce in current sample process is also comprised.

Wherein, also comprise and carry out FFT to through digitized voltage and current sample value.

Wherein, adjust in real time according to the sample frequency of frequency to voltage, current signal of the electrical network detected in real time.

The concrete method of sampling is, as shown in Figure 6:

First, by DMA1 constantly by voltage, the AD value of electric current puts into an array AD_Value [7] S101, then interrupt finding to open an initial point by the outside zero passage of a UA_INT, 128 times are adopted by a timer in one-period, and sample each time 7 data are put in the array of a Tmp_AD_Value [128*7], enable DMA2 when sampling for the 128th time in one-period the data in the array of Tmp_AD_Value [128*7] to be put in Cal_AD_Value [128*7] simultaneously, use during for calculating, complete in interruption at DMA2 and forbid DMA2 and start-up simulation process S103.

Wherein, interrupt finding out T cycle length by the outside zero passage of a UA_INT, then frequency is exactly F=1/T;

The phase angle finding out UA and UC is interrupted by the zero passage of another lower outside interruption U C-INT;

The phase angle finding out U and I is interrupted by the zero passage of another lower external interrupt IA-INT;

Ac cycle detects, and the external hardware that the square-wave signal that voltage transitions becomes sends into STM32 interrupts, and reads the count value of timer, convert the cycle (frequency) to, according to the cycle of period modulation systematic sampling in interrupt service routine.

Adopt AC sampling on hardware circuit basis, by parameters of electric power such as the very convenient acquisition of 1-15 formula U, I, P, Q, S, COS Φ, F, kWh, kvarh

AC sampling is sampled to the instantaneous value of measured signal according to certain rules, then try to achieve measured value with certain numerical algorithm, more accurate relative to the direct current sampling carrying out sampled measurements after DC rectifier again.

In the utility model, can apply STM32F103RC is instrument intelligent kernel parts, adopts the A/D transducer of this chip internal as data acquisition unit, carries out pointwise instantaneous sampling to the electric signal in the electrical network of access, voltage, current effective value is calculated again by single-chip microcomputer, active power, reactive power, applied power, power factor, signal frequency, active energy, reactive energy and frequency analysis etc.

Wherein, the calculation procedure of voltage effective value is as follows:

First, by voltage effective value formula

U = 1 T ∫ 0 T u 2 ( t ) d t - - - ( 1 )

Discretize, replaces continually varying function of voltage value in one-period with limited sampled voltage digital quantity in one-period, then obtains

U c ≈ 1 T Σ m = 1 N u m 2 ΔT m - - - ( 2 )

In formula: Δ Tm is the time interval of adjacent double sampling; u mit is the voltage sample instantaneous value in m-1 the time interval; N is the sampling number in 1 cycle.Make the time interval of adjacent two samplings equal, namely Δ Tm is constant Δ T, considers N=(T/ Δ T)+1, then has

U c = 1 N - 1 Σ m = 1 N u m 2 - - - ( 3 )

Formula (3) is exactly the formula according to each sampled instantaneous value of one-period and each cycle sampling number calculating voltage signal effective value.

In like manner, current effective value computing formula is as follows:

I c = 1 N - 1 Σ m = 1 N i m 2 - - - ( 4 )

Formula (1) is exactly the formula according to each sampled instantaneous value of one-period and each cycle sampling number calculating voltage signal effective value.

Calculate a certain phase active power, the definition of calculating from consecutive periods signal effective value of power and the definition of power, replace continuous integration with numerical integration is approximate.The computing formula of active power is such as formula (5)

P = 1 T ∫ 0 T i u d t - - - ( 5 )

After discretize be

P = 1 N - 1 Σ m = 1 N i m u m - - - ( 6 )

In formula: im, um are electric current, the voltage sample value of synchronization.

Applied power: S=UI

In formula, U, I are the effective value of voltage and current;

Power factor can be tried to achieve by following formula:

cosφ=P/S=P/UI

Calculate reactive power and have many algorithms, adopt digital phase shift Microcomputer Calculation amount less, data processing real-time is good.Because active-power P and reactive power Q only differ from 90 ° in voltage and current phase place, reactive power is write as

Q = 1 N Σ K = 1 N ( u K × i ( K + N 4 ) ) - - - ( 7 )

I in formula (k+N/4)represent the current sampling data (sampled value after phase shift 90 °) that (k+N/4) is secondary, when (k+N/4) is greater than N, (k+N/4) is taken as (k-3N/4).

In three-phase four-wire system, use ternary method, after discrete, ask the expression formula of power as follows:

P = 1 N Σ K = 1 N ( u U K × i U K + u V K × i V K + u W K × i W K ) - - - ( 8 )

Q = 1 N Σ K = 1 N ( u U K × i U ( K + N 4 ) ) + u V K × i V ( K + N 4 ) + u W K × i W ( K + N 4 ) - - - ( 9 )

In formula, Uuk, Uvk, Uwk represent the kth time sampled value of three phase voltages in one-period; i uK, i vK, i wKrepresent the kth time sampled value of three phase currents in one-period.

With two-dimensional method in three-phase three-wire system, after discretize, ask the formula of power as follows:

P = 1 N Σ K = 1 N ( u U V K × i U K + u V W K × i W K ) - - - ( 10 )

Q = 1 N Σ K = 1 N ( u U V K × i U ( K + N 4 ) + u V W K × i W ( K + N 4 ) ) - - - ( 11 )

U in formula uvk, u vwkrepresent the kth time sampled value of two line voltages in 1 cycle respectively.

Applied power S and powerfactorcosφ can be obtained with following formula:

S = P 2 + Q 2 - - - ( 12 )

Active power and reactive power just can be obtained active energy and reactive energy to time integral respectively.

FFT computing:

The cosine signal of the voltage and current in electric power transmission line, by the impact of nonlinear load, the waveform of electrical network can distort, it is still periodic function after distortion, and meet Di Liheli condition, by fourier series decomposition method, voltage and current can be resolved into the superposition of first-harmonic and series of harmonic, namely

u ( t ) = U 0 + Σ n = 1 ∞ U n cos ( n ω t + α n ) - - - ( 14 )

i ( t ) = I 0 + Σ n = 1 ∞ I n c o s ( n ω t + β n ) - - - ( 15 )

U in formula 0, I 0the DC component of-voltage, electric current;

U n, I nthe peak value of-each harmonic amplitude; α n, β ndifference be that harmonic phase is poor.

Real-time sampling is carried out to the continuous time signal of electrical network and obtains discrete sample sequence, with fft algorithm, time-frequency domain conversion is carried out to it, amplitude and the phase condition of first-harmonic and each harmonic can be analyzed, to realize the monitoring of harmonic wave.In addition, in electrical network, between the phase voltage on each road and phase current, there is phase differential, FFT conversion is carried out to voltage and current signal synchronized sampling, just can calculate the phase differential of each harmonic, measure the meritorious of each harmonic and reactive power exactly.

And FFT is calculated, if the end points of sampled data set is discontinuous, just need to introduce window function, thus add the fussy degree of calculating.And meeting correlated sampling principle, when the data point set of sampling is just in time complete cycle, sampled data set two-end-point is continuous, just sampled signal sequence can be similar to and regard infinite periodic signal as, thus FFT calculated amount is reduced.

The determination of sampling number:

According to time-domain samples theorem native system requires to analyze 63 subharmonic, and therefore minimum in one-period sampling number is 78 points, and when FFT butterfly computation itself requires that sampling number is the power of 2, computing velocity is the fastest, and the sample frequency of device is 256 times of fundamental frequency.Due to mains frequency, can fluctuate up and down at about 50Hz, therefore on hardware implementing, cannot sample to voltage, current signal by fixed frequency, and will according to the frequency of electrical network, sampling rate adjusting in real time.

Native system adopts 128 fft algorithms, namely completes a FFT computing at sampling two all after dates, wherein has one-period to be the result of sampling last time; The time completing 128 FFT computings is about 0.5ms, thus can meet instrument on-line checkingi and analysis.

The frequency of AC network is determined, the method determined is also many, and native system adopts and carrys out measuring period by the method for hardware, send STM32F103RC to carry out timing, thus obtain the frequency of AC network by alternating voltage after conditioning with shaping; Frequency change due to electrical network has larger inertia, and software low-pass filter thus can be adopted to process measured data.

Claims (6)

1. based on an electric energy metered system for AC sampling, it is characterized in that: this system comprises
Voltage sample part, for sampling to obtain voltage analog sampled value with variable voltage sample frequency to the signal from electrical network of access;
Current sample part, for sampling to obtain current-mode analog quantity sampled value with variable current sample frequency to the signal from electrical network of access;
Voltage signal processing section, nurses one's health the voltage analog sampled value obtained and is biased to the voltage analog sampled value in predetermined threshold value;
Current signal processing section, nurses one's health the current-mode analog quantity sampled value obtained and is biased to the current-mode analog quantity sampled value in predetermined threshold value;
Zero cross signal processing section, receives the voltage analog sampled value from voltage sample part, carries out Zero-cross comparator and shaping filter to voltage analog sampled value, obtains zero-crossing pulse signal and gives processor section component voltage zero passage detection; And
The processor part based on ARM with analog to digital converter: comprise voltage sample value analog to digital converter, current sampling data analog to digital converter, zero passage interrupt unit and parameter arithmetic section; Wherein, voltage sample value analog to digital converter is used for carrying out analog to digital conversion by zero-crossing pulse signal enabling to the voltage analog sampled value in the predetermined threshold value from voltage signal processing section and digitized voltage sample value being kept at a magnitude of voltage storage part; Current sampling data analog to digital converter is used for carrying out analog to digital conversion by zero-crossing pulse signal enabling to the current-mode analog quantity sampled value in the predetermined threshold value from current signal processing section and digitized current sampling data being kept at a current value storage part; This parameter arithmetic section calculates the electric energy metrical parameter for this electrical network according to the digitized voltage sample value obtained and digitized current sampling data according to sampling techniques.
2. the electric energy metered system based on AC sampling according to claim 1, is characterized in that: this voltage sample part also comprises phase compensation portion for eliminating the phase differential produced in sampling process.
3. the electric energy metered system based on AC sampling according to claim 1, is characterized in that: this current sample part also comprises phase compensation portion for eliminating the phase differential produced in sampling process.
4. the electric energy metered system based on AC sampling according to claim 1, is characterized in that: sample frequency adjustment part, for the frequency of real-time detection of grid, and adjusts according to the sample frequency of frequency to voltage, electric current of the electrical network recorded.
5. the electric energy metered system based on AC sampling according to claim 1, is characterized in that: this storage part is RAM.
6. based on an electric energy gauging method for AC sampling, it is characterized in that: comprise
Sample to obtain voltage analog sampled value with variable voltage sample frequency to the signal from electrical network of access;
Sample to obtain current-mode analog quantity sampled value with variable current sample frequency to the signal from electrical network of access;
The voltage analog sampled value obtained is nursed one's health and is biased to the voltage analog sampled value in predetermined threshold value;
The current-mode analog quantity sampled value obtained is nursed one's health and is biased to the current-mode analog quantity sampled value in predetermined threshold value;
Receive the voltage analog sampled value from voltage sample part, Zero-cross comparator and shaping filter are carried out to voltage analog sampled value, obtain zero-crossing pulse signal and give processor section component voltage zero passage detection; And
By zero-crossing pulse signal enabling analog to digital conversion is carried out to the voltage analog sampled value in the predetermined threshold value from voltage signal processing section and digitized voltage sample value is kept at a magnitude of voltage storage part;
By zero-crossing pulse signal enabling analog to digital conversion is carried out to the current-mode analog quantity sampled value in the predetermined threshold value from current signal processing section and digitized current sampling data is kept at a current value storage part; And
The electric energy metrical parameter for this electrical network is calculated according to sampling techniques according to the digitized voltage sample value obtained and digitized current sampling data.
CN201310284687.1A 2012-12-28 2013-07-08 Based on the electric energy metered system of AC sampling CN103344825B (en)

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