CN203287435U - A micro electrical network harmonic wave and inter-harmonic wave test apparatus based on an STM32F107VCT6 - Google Patents

Abstract

The utility model discloses a micro electrical network harmonic wave and inter-harmonic wave detection apparatus based on an STM32F107VCT6, and belongs to the technical field of electric energy quality test. The apparatus comprises a signal acquisition module, a signal processing module, and a signal display output module. In the signal acquisition module, a Hall voltage current sensor is adopted to be a collector used for collecting three-phase voltages of electrical networks. The signal processing module comprises a converting circuit of voltage currents, an anti-aliasing filter circuit, a level adjusting circuit, a core processor STM32F107VCT6, and a processor peripheral circuit. An output terminal of the level adjusting circuit is connected with an input terminal of an A/D converter of the core processor STM32F107VCT6. The method comprises the processes of signal acquisition and signal processing. The apparatus and the method can satisfy the requirements for the calculating precision and the calculating speed. At the same time, the apparatus and the method can satisfy the requirements for the flexibility and convenience in terms of structure.

Description

A kind of little mains by harmonics based on STM32F107VCT6 and a harmonic measurement device

Technical field

The invention belongs to the Power Quality Detection technical field, specifically, relate to a kind of device and detection method that can detect micro-grid system harmonic wave, a harmonic wave, more particularly, relate to a kind of little mains by harmonics based on STM32F107VCT6 and a harmonic measurement device.

Background technology

At present, known harmonic measurement device is mostly for large electrical network, and is mostly to detect harmonic wave, for the pick-up unit of a harmonic wave and few.IEC6100-4-7 standard and the overwhelming majority have harmonic measurement device now at present, and between pair, FFT(Fast Fourier Transform, fast fourier transform are all adopted in the detection of harmonic wave) algorithm.Yet traditional fft algorithm is more accurately when detecting integral frequency harmonizing wave, but when there was a large amount of non-integer harmonics in electrical network, algorithm just there will be larger error, even can't detect, and caused result of calculation very insincere.Therefore, be badly in need of a kind of more accurate algorithm and improve the detection of harmonic wave and a harmonic wave.

Along with carrying forward vigorously of intelligent grid construction, little electric power network technique development is more and more rapider, and little electrical network power quality problem also more and more causes people's concern.Yet harmonic wave is the key index of weighing the electrical network quality of power supply,, in order to administer harmonic wave, avoids harmonic wave to inject large electrical network, and it is very necessary that the harmonic wave of little electrical network is detected.The frequent throwing of the distributed power source generation harmonic current of withdrawing the membership in little electrical network, the nonlinear characteristic of power electronic equipment also can produce a large amount of harmonic voltages, the unstable meeting of batch (-type) energy output power causes voltage fluctuation and flickering, and the little load of little net capacity is changeable.In addition, because little electrical network has two kinds of steady operational status, namely be incorporated into the power networks state and islet operation state, while being incorporated into the power networks, the fundamental frequency of little electrical network can change along with the change of external power grid fundamental frequency; During islet operation,, if distributed power source is exerted oneself and load power consumption is not mated, also will cause the change of microgrid fundamental frequency.These characteristics of microgrid make the electric current and voltage in microgrid very easily fluctuate, specified fundamental frequency is not a steady state value, making electric current and voltage is the unstable condition amount, also exist except the integral frequency harmonizing wave component a large amount of between harmonic component, totally unfavorable for power grid operation.In little electrical network, power quality problem is to be badly in need of the gordian technique that solves, but the present pick-up unit that does not have effective characteristics for little mains by harmonics and design.Therefore, be badly in need of the harmonic measurement device for microgrid, and along with the continuous popularization of little electrical network, market is also in the urgent need to this harmonic measurement device.

China Patent No.: 200910043655.6, open day on November 25th, 2009, the patent document that a name is called the detection method of a kind of harmonic wave and a harmonic parameters is disclosed, it is the deficiency that overcomes existing harmonic wave, harmonic detection method, this invention provides harmonic wave and a harmonic parameters detection method, its main performing step is: 1), according to characteristic sinusoidal, cosine function, by mathematic(al) manipulation, the fundametal compoment in voltage or current signal and each harmonic component are transformed into respectively DC component; 2) extract DC component with low-pass filtering, the parameters such as the amplitude of calculating fundametal compoment and each harmonic component and phasing degree; 3) deduct first-harmonic and harmonic component from voltage signal, obtain only containing voltage or the current signal of each harmonic wave; 4) search element by the amplitude spectrum maximal value and obtain each harmonic parameters.But the method exists accuracy of detection not high, the practical operation problem such as have difficulties, and be not suitable for the detection of harmonic wave between little electrical network.

Traditional fft algorithm detect little electrical network between the harmonic wave reason that will certainly produce larger error be: the spectral leakage of fft algorithm can produce harmonic wave between puppet, thereby harmonic wave between flooding really, FFT is only applicable to the detection of fixed cycle amount, but in fact little line voltage current fluctuation does not present the fixed cycle regularity.Therefore, be badly in need of a kind of improved little electrical network harmonic detection method and realize the accurate detection of a harmonic wave.

Defect on above-mentioned algorithm also makes and does not occur for harmonic measurement device between little electrical network, therefore is badly in need of researching and solving.The technical barrier that will solve harmonic wave detects between little electrical network has: how (1) realizes separating of harmonic wave and a harmonic wave; (2) how to suppress between a harmonic spectrum the phase mutual interference and to the interference of harmonic spectrum: how (3) suppress harmonic components floods a harmonic components.In addition, existing harmonic measurement device mostly adopts 8 single-chip microcomputers, and minority with 16 single-chip microcomputers, does not also adopt the pick-up unit of 32 single-chip microcomputers.8 single-chip microcomputer characteristics are that cost is low, use flexibly, but that shortcoming is arithmetic speed are slow, and generally also need expansion RAM and ROM, hardware circuit is more complicated.

Summary of the invention

The problem that 1, will solve

For prior art to the detection of little mains by harmonics exist arithmetic speed slow, need the more complicated problem of expansion RAM and ROM and hardware circuit, the invention provides a kind of little mains by harmonics based on STM32F107VCT6 and a harmonic measurement device, it structurally meets again dirigibility and convenience when meeting computational accuracy, computing velocity.

2, technical scheme

For addressing the above problem, the present invention adopts following technical scheme.

A kind of little mains by harmonics based on STM32F107VCT6 and a harmonic measurement device, the demonstration output module that comprises signal acquisition module, signal processing module and signal, adopt the Hall voltage current sensor as the collector that gathers the electrical network three-phase voltage current in described signal acquisition module; Described signal processing module comprises change-over circuit, Anti-aliasing Filter Circuits, level adjusting circuit, core processor STM32F107VCT6 and the processor peripheral circuit of electric current and voltage; The collection terminal of the Hall voltage current sensor of described signal acquisition module is connected with electrical network, and output termination signal processing module, pass through current-to-voltage converting circuit, Anti-aliasing Filter Circuits and level adjusting circuit successively in signal processing module; The A/D converter input end of the output termination core processor STM32F107VCT6 of described level adjusting circuit, the periphery access LCD display of STM32F107VCT6.

Preferably, described processor peripheral circuit comprises power circuit, reset circuit and crystal oscillating circuit; Described power circuit provides the power supply of the required different voltages of whole system work by voltage transformation; Adopt reset chip hand-reset mode in described reset circuit; Described crystal oscillating circuit provides clock signal for single-chip microcomputer.

Preferably, described output display module comprises LCD display, keyboard, PC communication module.

Preferably, also include keyboard circuit in described output display module, keyboard is to connect by keyboard circuit with being connected of core processor STM32F107VCT6.

In order to be used in conjunction with device of the present invention, harmonic measurement device designed system software of the present invention mainly comprises data sampling, data processing, man-machine interface and communication, mainly adopts Keil development environment C language development instrument.The algorithm aspect proposes the harmonic detection method based on accurate synchronized sampling reconstruction signal on the basis of fft algorithm, this algorithm is by harmonic wave and a harmonic components in separation signal, reach and suppress the purpose that both disturb mutually, can realize simultaneously the Measurement accuracy of harmonic wave and a harmonic parameters.Due to the existence of a harmonic wave, the system voltage current signal is no longer cycle stably, but non-stationary signal.The traditional FFT algorithm has very large error for the analysis of non-stationary signal, and " elimination method " detects harmonic wave and a harmonic wave also there will be larger error in microgrid, between in the reason microgrid, harmonic content is many than electrical network, can not ignore the impact of a harmonic wave on harmonic wave during calculating.The present invention proposes the detection algorithm based on accurate synchronized sampling reconstruction signal, and this method is applicable to the non-synchronous sampling situation, so harmonic measurement device can adopt fixed sampling frequency to sample to electric power signal, thereby guarantees the validity of each sampled data.

On present detection technique basis, the more superior key problem in technology of this device mainly contains 2 points:

1) effectively limit the leakage of harmonic wave, avoid the loss of harmonic energy.

2), by separating harmonic wave and a harmonic wave, reduce influencing each other between harmonic wave and a harmonic wave.

Above-mentioned key problem in technology point 1 in analyzing large electrical network) put 2 than key problem in technology) even more important, still in view of harmonic content in the middle of little electrical network, increase to some extent key problem in technology point 2) and key problem in technology point 1) be mainly to need the technical barrier that solves equally.

For aforementioned techniques key point 1), because harmonic wave and a harmonic wave after separating are all synchronized samplings, therefore eliminated fence effect and the spectral leakage effect that causes due to the FFT non-synchronous sampling, thereby reached the leakage of effective restriction harmonic wave, as far as possible the technical requirement of harmonic reduction energy loss.

for aforementioned techniques key point 2), proposition is based on the detection algorithm of accurate synchronized sampling reconstruction signal, with the accurate synchronization of non-synchronous sampling signal, reach the purpose that suppresses spectrum leakage and fence effect, at first algorithm adopts the adaptive tracing digital notch filter to carry out pre-service to the signal that obtains under non-synchronous sampling, other frequency component beyond the filtering fundamental frequency, then filtering signal is used with the method for threshold values comparison and utilizes linear interpolation method to obtain the primitive period of signal, according to this primitive period, adopt cubic spline interpolation algorithm reconstruct crude sampling sequence, make reconstruction signal be similar to synchronous sampling signal, reconstruction signal is realized separating of harmonic wave and a harmonic wave by the FIR notch filter subsequently., because spectrum leakage and fence effect have obtained remarkable inhibition, just can obtain the accurate parameter of each harmonic according to the FFT result of reconstruction signal.The method, by harmonic wave and a harmonic components in separation signal, reaches the purpose that suppresses both phase mutual interference, can realize simultaneously the Measurement accuracy of harmonic wave and a harmonic parameters.

3, beneficial effect

Than prior art, the present invention has following beneficial effect:

(1) the present invention is a kind of little mains by harmonics based on STM32F107VCT6 and a harmonic measurement device, taken into full account the impact on microgrid of microgrid self distributed electrical source structure and major network, particularly microgrid and major network off-the-line or microgrid are kept the very large situation of unbalance voltage operation microgrid harmonic content of major network, solve well an above-mentioned difficult problem, it can detection system 51 times with interior harmonic wave, between harmonic wave, and can calculate demonstration single harmonic component aberration rate, total percent harmonic distortion, crest factor, active power, the numerical value such as reactive power, this pick-up unit size is very suitable for hand-held in addition, be easy to carry,

(2) the present invention is a kind of little mains by harmonics based on STM32F107VCT6 and a harmonic measurement device, use on hardware is based on 32 single-chip microcomputer STM32F107VCT6 of Cortex-M3 core, the fast cost of its processing speed is low, in the harmonic wave context of detection, superperformance is arranged.

Description of drawings

Fig. 1 is harmonic measurement device general structure schematic diagram between the present invention;

Fig. 2 is harmonic wave of the present invention and a harmonic wave algorithm flow schematic diagram.

Embodiment

Describe the present invention below in conjunction with accompanying drawing.

As accompanying drawing 1 device workflow be: the present invention adopts following technical scheme.

A kind of little mains by harmonics based on STM32F107VCT6 and a harmonic measurement device, the demonstration output module that comprises signal acquisition module, signal processing module and signal, adopt the Hall voltage current sensor as the collector that gathers the electrical network three-phase voltage current in signal acquisition module; Signal processing module comprises change-over circuit, Anti-aliasing Filter Circuits, level adjusting circuit, core processor STM32F107VCT6 and the processor peripheral circuit of electric current and voltage; The collection terminal of the Hall voltage current sensor of signal acquisition module is connected with electrical network, and output termination signal processing module, pass through current-to-voltage converting circuit, Anti-aliasing Filter Circuits and level adjusting circuit successively in signal processing module; The A/D converter input end of the output termination core processor STM32F107VCT6 of level adjusting circuit, the periphery access LCD display of STM32F107VCT6.Core processor STM32F107VCT6 is produced by group of STMicw Electronics (ST).

The processor peripheral circuit comprises power circuit, reset circuit and crystal oscillating circuit; Power circuit provides the power supply of the required different voltages of whole system work by voltage transformation; Adopt reset chip hand-reset mode in reset circuit; Crystal oscillating circuit provides clock signal for single-chip microcomputer.The output display module comprises LCD display, keyboard, PC communication module.Also include keyboard circuit in the output display module, keyboard is to connect by keyboard circuit with being connected of core processor STM32F107VCT6.

The collection terminal of the Hall voltage current sensor of signal acquisition module is connected with electrical network, output termination signal processing module, at first through current-to-voltage converting circuit, current signal is transformed into voltage signal, this circuit uses adjustable resistance and voltage stabilizing diode to realize conversion and the voltage clamping of electric current and voltage.Signal out enters Anti-aliasing Filter Circuits afterwards by current-to-voltage converting circuit, considering this circuit of filter effect and delay time adopts the second order Butterworth filter to carry out analog filtering, filter cutoff frequency be 2500Hz can elimination higher than the harmonic wave of 51 times, the purpose of this place's filtering is to meet sampling thheorem, frequency of occurrences aliasing while avoiding sampling during for data acquisition in the back.Signal enters level adjusting circuit after Anti-aliasing Filter Circuits, this circuit consists of two amplifiers and resistance, circuit is supplied with the 1.6V reference voltage by outside, signal is after this circuit, the ratio circuit that forms due to amplifier and the adjusting of reference voltage, make signal amplitude become original half and waveform integral raising.In addition, because the effect of two-way amplifier has formed differential signal, signal is sent into the ADC pin of STM32F107VCT6 subsequently, utilizes the A/D converter of STM32F107VCT6 inside to carry out analog to digital conversion.STM32F107VCT6 has two 12 A/D converters, and totally 18 passages, can work by two passages simultaneously.Remove in order to meet the requirement of IEC standard, the width that is analysis window is 200ms, and the frequency resolution of DFT is 5Hz, for accuracy in computation and the harmonic wave frequency resolution that improves the primitive period, the sample frequency of setting device is 10240Hz, and each sample sequence length of processing is 4096 points.Signal carries out analytical calculation in STM32F107VCT6 after sample conversion becomes digital signal.

Concrete performing step such as accompanying drawing 2:

A kind of little mains by harmonics and harmonic detection method, the steps include:

(1) in the situation that meet nyquist sampling theorem, with fixed sampling frequency, power system signal is carried out equal interval sampling, equation is namely arranged

K·T _s=P·T ₀ （1-1）

Set up, wherein T _sFor the sampling period, T ₀Be the signal period, K is the sampled point number, and P is the signal period number, and for non-synchronous sampling, obviously P is not integer;

(2) adopt adaptive tracing digital notch filter elimination sample sequence x (KT _s) in fundametal compoment, obtain new sample sequence x'(KT _s), therefore from x (KT _s) in deduct x'(KT _s), can obtain fundametal compoment x ₀(KT _s); Compare the also accurately filtering owing to combining adaptive filtering mode and make fundamental frequency fluctuate of adaptive tracing digital notch filter near 50Hz with traditional notch filter.The adaptive tracing digital notch filter at this place is for to increase adaptive control on the basis of digital notch filter, its acceptance has the input signal of trap frequency, by the least square adaptive algorithm, obtains a ₁, utilize a ₁Form digital notch filter H (z ^-1) fall into except the signal with this trap frequency.The frequency response of ideal digital notch filter is

$H\left(e^{\mathrm{j\ωt}}\right)=\left\{\begin{array}{cc}1& \mathrm{\ω}\≠{\mathrm{\ω}}_0\\ 0& \mathrm{\ω}={\mathrm{\ω}}_0\end{array}\right.---(1-2)$

Wherein e is natural constant, and j is imaginary unit, and ω is frequency, and t is the time, ω ₀For trap frequency;

For its transfer function H of single trap frequency (z ^-1) have following symmetrical mirror as form

$H\left(z^{-1}\right)=\frac{1+a_1{z}^{-1}+z^{-2}}{1+a_1{\mathrm{pz}}^{-1}+p^2{z}^{-2}}---(1-3)$

In formula, z is plural variable, p be one near 1 but be slightly less than 1 constant, a ₁For parameter, determined by trap frequency, the trap frequency expression formula is

$f_o=\frac{\arccos ({-a}_1/2)}{2\mathrm{\πT}}---(1-4)$

Wherein T is the sampling period, is obtained a that changes with sampled point by the adaptive least square method ₁(n), its corresponding trap frequency is also time dependent, and in order to realize adaptivity, p changes and is p (n) with sampled point, thus, and x (KT _s) in H (z corresponding to each sampled point signal ^-1) all can be different, realized the self-adaptation adjustment, namely obtain fundamental signal by original signal and filtered signal subtraction;

(3) utilize linear interpolation method to calculate the primitive period of signal, be located at node a=t ₀＜t ₁＜t ₂＜t _nThe functional value at=b place is y ₀, y ₁, y ₂..., y _n, at each minizone [x _j, x _j+1] in replace curve with straight line, signal passes the time t of threshold value a for the i time _iFor

$t_i=\frac{(a-y_j)}{y_{j+1}-y_j}+t_j---(1-5)$

In like manner can obtain the time t that signal passes threshold value a for the i+20 time _I+20, the mean value T* in the sampling time of 20 Cycle Lengths of sample sequence x (n) is:

$T*=\frac{1}{20}[t_{i+20}-t_i]---(1-6)$

T* is the primitive period of signal, and adopting in addition 20 cycles here is in order to calculate the primitive period more accurately;

(4) according to the primitive period of calculating gained, the harmonic component in former sample sequence is carried out accurate synchronization, obtain reproducing sequence x ^*(k λ _s), during non-synchronous sampling, P is not integer, can produce spectral leakage, in order to realize the accurate synchronization of non-synchronous sampling sequence, to sampling period T _sAdjust, utilize T* to calculate accurate synchronized sampling cycle λ _s

${\mathrm{\λ}}_s=\frac{20T^{*}}{L^{*}}---(1-7)$

L wherein ^*, for sampled point number in 20 cycles of new accurate synchronized sampling sequence, but can be similar to, get L ^*=L, to reduce error, L is the sampled point numbers of crude sampling sequence in 20 signal periods, by cubic spline interpolation, obtains each sampled point in accurate synchronized sampling sequence, take the sampled point in former sample sequence as interpolation knot, T _sFor the interpolation knot interval, the starting point that makes a certain signal period is the sampled point starting point simultaneously, due to cubic spline difference functions K (t) at each interval [x _j, x _j+1] on be segmental cubic polynomials, know the second derivative K''(t of cubic spline function K (t)) be an order polynomial on each minizone, establish K''(t _j)=M _j, K''(t _j+1)=M _j+1, K''(t) and expression formula is

$K^{\′\′}\left(t\right)=M_j\frac{t_{j+1}-t}{h_j}+M_{j+1}\frac{t-t_j}{h_j}---(1-8)$

Wherein, h _j=t _j+1-t _j

With K''(t) integration twice, and bring the expression formula that boundary condition obtains K (t) into and be

$K\left(t\right)=M_j\frac{{(t_{j+1}-t)}^3}{{6h}_j}+M_{j+1}\frac{{(t-t_j)}^3}{{6h}_j}+(y_j-\frac{1}{6}{M}_j{h}_j^2)\frac{t_{j+1}-t}{h_j}+(y_{j+1}-\frac{1}{6}{M}_{j+1}{h}_j^2)\frac{t-t_j}{h_j}$

(t∈[t _j,t _j+1];j=0,1,…,n-1) （1-9）

If m accurate synchronous sampling point is between j synchronous sampling point and j+1 synchronous sampling point, this accurate synchronous sampling point can be calculated by following formula

$K\left({\mathrm{m\λ}}_s\right)=M_j\frac{{(t_{j+1}-{\mathrm{m\λ}}_s)}^3}{{6h}_j}+M_{j+1}\frac{{({\mathrm{m\λ}}_s-t_j)}^3}{{6h}_j}+(y_j-\frac{1}{6}{M}_j{h}_j^2)\frac{t_{j+1}-{\mathrm{m\λ}}_s}{h_j}+(y_{j+1}-\frac{1}{6}{M}_{j+1}{h}_j^2)\frac{{\mathrm{m\λ}}_s-t_j}{h_j}$

(t∈[t _j,t _j+1];j=0,1,…,n-1) （1-10）

Repeat K (m λ _s) computation process, can obtain L ^*-1 calculated value, this L ^*It is T that-1 accurate synchronous sampling point and starting point have formed length jointly ^*Accurate synchronized sampling sequence, so far, obtained reconstructed sample sequence x ^*(k λ _s) full detail, i.e. the position of reconstruction signal and sampled value;

(5) utilize the FIR notch filter to separate x ^*(k λ _s) in harmonic wave and a harmonic component, wave filter arranges a plurality of trap frequencies and forms pectinations; Be the integral multiple of this wave filter between cog spacing frequency due to sample frequency, so the FIR notch filter have good effect for synchronized sampling, can the produce power loss, be applicable to accurate synchronized sampling sequence; Because the trap frequency of wave filter is the integral multiple of first-harmonic, therefore can filtering first-harmonic and all integral frequency harmonizing waves;

(6) to harmonic components x between obtaining after the filtering of FIR notch filter ^{* I}(k λ _s), use the parameter of harmonic wave between the two interpolation FFT algorithms calculating add the Hanning window;

(7) from accurate synchronized sampling sequence x ^*(k λ _s) in deduct a harmonic components x ^{* I}(k λ _s), obtain harmonic component x ^{* H}(k λ _s);

(8) to x ^{* H}(k λ _s) carry out DFT or FFT computing, calculate the each harmonic parameter by its result.

Can find out that by embodiment the present invention has following advantage:

1) between, the design of harmonic measurement device has taken into full account the characteristics of little mains by harmonics.

2) simple in structure, overall cost is lower, is easy to realize,, owing to adopting the signal reconstruction technology on algorithm, has saved the phase lock circuitry on hardware, not only makes the testing result of a harmonic wave more accurate, has also saved simultaneously cost.

3) selected 32 interconnection type single-chip microcomputer STM32F107 based on Cortex-M3 core on core processor, the high computing velocity of this processor can be given full play to the superiority of signal reconstruction algorithm, and implementation algorithm coordinates with the effective of hardware.

4) adopt the method for signal reconstruction on detection method, overcome the phase mutual interference of harmonic wave and a harmonic wave and the spectral leakage of traditional FFT algorithm.

5) carry out separating of harmonic wave and a harmonic wave by design FIR wave filter, harmonic wave and a harmonic wave can be calculated separately, avoid the phase mutual interference to improve computational accuracy.

Claims (4)

1. the little mains by harmonics based on STM32F107VCT6 and a harmonic measurement device, comprise the demonstration output module of signal acquisition module, signal processing module and signal, it is characterized in that: adopt the Hall voltage current sensor as the collector that gathers the electrical network three-phase voltage current in described signal acquisition module; Described signal processing module comprises change-over circuit, Anti-aliasing Filter Circuits, level adjusting circuit, core processor STM32F107VCT6 and the processor peripheral circuit of electric current and voltage; The collection terminal of the Hall voltage current sensor of described signal acquisition module is connected with electrical network, and output termination signal processing module, pass through current-to-voltage converting circuit, Anti-aliasing Filter Circuits and level adjusting circuit successively in signal processing module; The A/D converter input end of the output termination core processor STM32F107VCT6 of described level adjusting circuit, the periphery access LCD display of STM32F107VCT6.

2. a kind of little mains by harmonics based on STM32F107VCT6 according to claim 1 and a harmonic measurement device, it is characterized in that: described processor peripheral circuit comprises power circuit, reset circuit and crystal oscillating circuit; Described power circuit provides the power supply of the required different voltages of whole system work by voltage transformation; Adopt reset chip hand-reset mode in described reset circuit; Described crystal oscillating circuit provides clock signal for single-chip microcomputer.

3. a kind of little mains by harmonics based on STM32F107VCT6 according to claim 1 and 2 and a harmonic measurement device, it is characterized in that: described output display module comprises LCD display, keyboard, PC communication module.

4. a kind of little mains by harmonics based on STM32F107VCT6 according to claim 3 and a harmonic measurement device, it is characterized in that: also include keyboard circuit in described output display module, keyboard is to connect by keyboard circuit with being connected of core processor STM32F107VCT6.

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