CN105467210A - A harmonic detection method - Google Patents

Abstract

The invention discloses a harmonic detection method comprising the following steps: harmonic waves are detected on the basis of the transient reactive power theory; current sampling is carried out on n points of the harmonic waves to obtain an arithmetic mean value Ihm of the currents; after specific time, current sampling is again carried out on the n points of the harmonic waves to obtain the arithmetic mean value Ihm' of the currents; the difference between the Ihm and the Ihm' is calculated to obtain an absolute value K, wherein when K is in a convergence threshold value, the harmonic wave detection method is converted, and harmonic waves are detected on the basis of a fast Fourier transform method to detect the harmonic waves; and when the k is outside the convergence threshold value, the harmonic waves are further detected on the basis of the transient reactive power theory. The harmonic detection method of the invention solves the problem that higher harmonic waves cannot be detected in harmonic detection on the basis of the transient reactive power theory and accordingly proportions of harmonic components of specific times cannot be known. Besides, the problems of time delay, that is, poor performance in real-time performance, in detection of harmonic waves on the basis of the fast Fourier transform method can be solved.

Description

A kind of harmonic detecting method

Technical field

The present invention relates to a kind of harmonic detecting method.

Background technology

The safe and effective operation of electrical network can improve industrial production efficiency and living standards of the people.Under normal circumstances, the supply target of electric energy will provide the sine voltage signal of standard frequency for user.But in recent years, along with increasing considerably of nonlinear load in commercial production, cause non-linear power electronic equipment to obtain a large amount of application.The actual waveform of voltage and current also exists huge deviation compared with the sinusoidal waveform of standard thus, create huge wave form distortion, we get used to this kind of wave form distortion to be referred to as harmonic wave, the quality of power supply of what these wave form distortions were serious have impact on commercial production and daily life.

In recent years, along with increasing considerably of nonlinear load in commercial production, result in non-linear power electronic equipment and obtain a large amount of application, cause the harmonic pollution in electric power network day by day serious.Active Power Filter-APF (ActivePowerFilter, APF) grew up in recent years, for the major equipment of harmonics restraint.

Control system is extremely important for the one-piece construction of APF, its whether superior effect that directly affects APF improvement harmonic wave.And in the work of Active Power Filter-APF, Harmonic currents detection is the prerequisite of carrying out harmonic compensation accurately and efficiently.At present, existing a variety of harmonic current detecting method tries out, but there is no any one method meet system requirements simultaneously in precision and speed.Harmonic detecting becomes one of bottleneck improving Active Power Filter-APF operating characteristic.

Harmonic Detecting Algorithm, its essence is by sampling power network current or voltage, analyzes and isolate first-harmonic content, obtaining the part of harmonic wave.In detection of grid harmonic wave, the humorous wave method of the detection based on Instantaneous Power Theory, in real-time, effectiveness comparison is good, non-time delay, but is subject to the impact in the sampled point time interval, has omission to higher hamonic wave.Humorous wave method is detected based on Fast Fourier Transform (FFT) method, it is the electric network data first gathering a sampling period, according to fft algorithm, harmonic wave is analyzed again, harmonic wave like this in this sample period time cannot carry out analyzing to it and compensate, and will cause the delay of a generation sample period time.

As shown in Figure 1, suppose that based on the analytical calculation time interval of the method for Instantaneous Power Theory be t1ms, detect from initial point, as can be seen from Figure 1 the amplitude of harmonic wave a is just maximum this moment, in detection, harmonic wave a amplitude is included, but the amplitude of harmonic wave b is now 0, is not included.Being t1ms as schemed sampling period duration, can seeing that the harmonic current detected in figure will fall harmonic wave b to omission, this kind of situation system can be caused to think there is not harmonic wave b in electrical network.Although it can thus be appreciated that this harmonic detecting method can from the initial point time computational analysis total harmonic wave size, ensured the real-time detected.But it, by the impact of analytical calculation time, causes sample frequency cannot reach high, can produce the detection of higher hamonic wave and omit phenomenon, there is certain limitation in this way.

As shown in Figure 2, suppose that based on the humorous wave method of detection of Fast Fourier Transform (FFT) method N number of point (determining according to sequence of calculation length and sample frequency) T.T. of sampling be t ₁ms, and start to carry out fft analysis calculating in the t1 moment.According to sampling thheorem, as long as sample frequency is enough high, meet sampling interval duration t<4 (t here ₂-t ₁), just can analyze harmonic wave a, harmonic wave b.But because this method is after sampling number arrives N number of point, the once calculating carried out, N number of point of sampling (determining according to sequence of calculation length and sample frequency) T.T. is t ₁harmonic components in ms just cannot be known, and has t ₁the delay of ms time.Therefore, this kind of harmonic detecting method also has certain limitation.

Summary of the invention

For this reason, the present invention proposes a kind of new harmonic detecting method at least partially that can solve the problem.

The invention provides a kind of harmonic detecting method, comprising: detect harmonic wave based on Instantaneous Power Theory, to the n on harmonic wave point sampling electric current, obtain the arithmetic mean I of electric current _hm, after special time, puts sample rate current again to the described n on described harmonic wave, obtains the arithmetic mean I of electric current _hm ';

By I _hm and I _hm ' does poor taking absolute value and obtains K, wherein,

When described K value is in convergence threshold, then switching harmonics detection method, selects and detects harmonic wave based on Fast Fourier Transform (FFT) method;

When described K value is when convergence threshold is outer, then continue to detect harmonic wave based on Instantaneous Power Theory.

Alternatively, according to harmonic detecting method of the present invention, wherein, described convergence threshold is 0.3-1.5.

Alternatively, according to harmonic detecting method of the present invention, described Instantaneous Power Theory comprises the Instantaneous Power Theory under α β coordinate and the Instantaneous Power Theory under dq0 coordinate.

Alternatively, according to harmonic detecting method of the present invention, described Fast Fourier Transform (FFT) method comprises time domain Fast Fourier Transform (FFT) method and frequency domain Fast Fourier Transform (FFT) method.

Alternatively, according to harmonic detecting method of the present invention, described detection based on Instantaneous Power Theory comprises pq detection and ip, iq detection.

Alternatively, according to harmonic detecting method of the present invention, the Instantaneous Power Theory under described α β coordinate is utilize α β two phase coordinates to replace a, b, c tri-Instantaneous Power Theory of phase coordinates.

Alternatively, according to harmonic detecting method of the present invention, the Instantaneous Power Theory under described dq0 coordinate is utilize dq0 coordinate to replace a, b, c tri-Instantaneous Power Theory of phase coordinates.

Alternatively, according to harmonic detecting method of the present invention, described pq detects and comprises:

By three-phase current i _a, i _b, i _cthe current component i under α β coordinate system is obtained by α β conversion _α, i _β;

Obtain instantaneous active power p and reactive power q by pq conversion, then through the waveform of low-pass filter filtering high order, obtain fundamental active power and reactive power wherein,

Pq is transformed to: $\left[\begin{array}{c}p\\ q\end{array}\right]=C_{pq}\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right],C_{pq}\left[\begin{array}{cc}{u}_{\mathrm{\&alpha;}}& u_{\mathrm{\&alpha;}}\\ u_{\mathrm{\&beta;}}& -u_{\mathrm{\&alpha;}}\end{array}\right],$ Wherein, u _αand u _βfor voltage;

Obtain three-phase fundamental current by pq inverse transformation and α β inverse transformation, then three-phase fundamental current and three-phase current to be done the current value that subtraction obtains be harmonic current.

Alternatively, according to harmonic detecting method of the present invention, described ip, iq detect and comprise:

By three-phase current i _a, i _b, i _cthe current component i under α β coordinate system is obtained by α β conversion _α, i _β;

Instantaneous active current i is obtained by C conversion _pwith reactive current i _q, then through the waveform of low-pass filter filtering high order, obtain fundamental active current and reactive current wherein,

C is transformed to: $\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right],C=\left[\begin{array}{cc}\sin \mathrm{\&omega;}t& -\cos \mathrm{\&omega;}t\\ -\cos \mathrm{\&omega;}t& -\sin \mathrm{\&omega;}t\end{array}\right],$ Wherein, ω is angular velocity;

Obtain three-phase fundamental current by C inverse transformation and α β inverse transformation, then three-phase fundamental current and three-phase current to be done the current value that subtraction obtains be harmonic current.

According to a further aspect in the invention, additionally provide a kind of harmonic detecting equipment, comprising:

For detecting harmonic wave based on Instantaneous Power Theory, to the n on harmonic wave point sampling electric current, obtain the arithmetic mean I of electric current _hm, after special time, puts sample rate current again to the described n on described harmonic wave, obtains the arithmetic mean I of electric current _hthe device of m ';

For by I _hm and I _hm ' does poor taking absolute value and obtains the device of K value, wherein,

When described K value is in convergence threshold, then switching harmonics detection method, selects and detects harmonic wave based on Fast Fourier Transform (FFT) method;

When described K value is when convergence threshold is outer, then continue to detect harmonic wave based on Instantaneous Power Theory.

Harmonic detecting method of the present invention not only solves in Instantaneous Power Theory detection harmonic wave and can't detect higher hamonic wave thus the problem of not knowing the ratio of concrete times harmonic composition, solves again life period in Fast Fourier Transform (FFT) method detection harmonic wave and postpones namely to have in real-time the problem of certain limitation.

Accompanying drawing explanation

By reading hereafter detailed description of the preferred embodiment, various other advantage and benefit will become cheer and bright for those of ordinary skill in the art.Accompanying drawing only for illustrating the object of preferred implementation, and does not think limitation of the present invention.And in whole accompanying drawing, represent identical parts by identical reference symbol.Wherein in the accompanying drawings, the multiple identical parts of alphabetic flag instruction after reference number, when making a general reference these parts, by its last alphabetic flag of omission.In the accompanying drawings:

Fig. 1 is the harmonic detecting method check point graph of a relation based on Instantaneous Power Theory;

Fig. 2 is the harmonic detecting method check point graph of a relation based on Fast Fourier Transform (FFT) method;

Fig. 3 is the structural representation of harmonic detecting method of the present invention;

Fig. 4 is the schematic diagram of the vector in electric current and voltage α β coordinate system;

Fig. 5 is the principle schematic that ip, iq detect harmonic current;

Fig. 6 is that the harmonic detecting method combined with Fast Fourier Transform (FFT) method based on Instantaneous Power Theory emulates;

Fig. 7 detects based on Instantaneous Power Theory to compensate rear power network current oscillogram;

Fig. 8 be the harmonic detecting method combined with Fast Fourier Transform (FFT) method based on Instantaneous Power Theory detect compensate after power network current oscillogram;

Fig. 9 is the block diagram showing the computing equipment that can be used to put into practice embodiments of the present invention.

In the accompanying drawings, use same or similar label to refer to same or similar element.

Embodiment

Under describe illustrative embodiments of the present invention in detail referring now to accompanying drawing.The embodiment that to should be appreciated that shown in accompanying drawing and describe is only exemplary, is intended to explain principle of the present invention and spirit, and not limits the scope of the invention.

Fig. 3 shows the process flow diagram of harmonic detecting method of the present invention.Be appreciated that the process flow diagram shown in Fig. 3 is only schematic, the step wherein recorded can perform according to different order, executed in parallel, omission and/or increase other steps.As shown in Figure 3, described harmonic detecting method comprises based on Instantaneous Power Theory detection harmonic wave, to the n on harmonic wave point sampling electric current, obtains the arithmetic mean I of electric current _hm, after special time, puts sample rate current again to the described n on described harmonic wave, obtains the arithmetic mean I of electric current _hm ' 102; By I _hm and I _hm ' does difference and takes absolute value and obtain K value 104, and judge described K value whether in convergence threshold 106, when described K value is in convergence threshold, then switching harmonics detection method, selects based on Fast Fourier Transform (FFT) method detection harmonic wave 108; When described K value is when convergence threshold is outer, then continue to detect harmonic wave based on Instantaneous Power Theory and namely turn back in step 102.

Described Instantaneous Power Theory is by three-phase voltage or current transformation coordinate, simplifies load and gains merit and idle calculating.

Described step 108 is detect harmonic wave based on Fast Fourier Transform (FFT) method.Described higher hamonic wave pace of change is fast, very easily be missed, thus can not be compensated, detect based on Fast Fourier Transform (FFT) method, be that the infinitesimal multiple spot value in employing a period of time interval is analyzed, as long as interval is minimum, count abundant, just can analyze the harmonic wave of very high-frequency section, and frequency accuracy also can be very high.

Harmonic detecting method of the present invention accurately can not only detect higher hamonic wave, and has ensured real-time detection.

In harmonic detecting method of the present invention, described convergence threshold is 0.3-1.5.Because the loadtype of electrical network is different, convergency value has certain change, when described K value drops in described convergence threshold 0.3-1.5, then thinks that now network load harmonic current is stable, switching harmonics detection method, selects and detects harmonic wave based on Fast Fourier Transform (FFT) method.

Harmonic detecting method of the present invention, described Instantaneous Power Theory comprises the Instantaneous Power Theory under α β coordinate and the Instantaneous Power Theory under dq0 coordinate.Instantaneous Power Theory under described α β coordinate utilizes the Instantaneous Power Theory of α β shift theory, below by an embodiment, described α β shift theory is described: if it is in the three-phase windings of the synchronous motor stator of 120 ° that the three phase sine alternating current of time upper difference 120 ° passes into spatially phase differential, it can produce a rotating magnetic field spatially, its angular velocity can be set to ω; As the alternating current differing 90 ° in time through spatially difference be the stator α β winding of 90 °, so just can form the rotating magnetic field be equal to three phase-change pressure windings, and after being replaced by α β two phase winding, the various calculating in three-phase circuit can be simplified.

Fig. 3 is the schematic diagram of the vector in electric current and voltage α β coordinate system.As shown in Figure 3, the angular velocity of rotating magnetic field is ω, a phase axis is made to overlap with α phase axis in figure, the advanced α phase axis of β phase winding axis 90 °, voltage vector rotates with angular velocity omega, just can obtain the meritorious of electric current and idle component by the projection of current phasor on voltage vector, and the projection respectively on α and β axle of electric current and voltage is their component in two-phase coordinate axis.

Suppose that voltage is respectively e mutually respectively with the instantaneous value of electric current in three-phase circuit _a, e _b, e _cwith i _a, i _b, i _c.The voltage of this few phase can be also had electric current respectively through abc-α β coordinate transform, thus the voltage that can obtain under α β coordinate system and electric current are respectively e _α, e _βwith i _α, i _βmeet following relation:

$\left[\begin{array}{c}{e}_{\mathrm{\&alpha;}}\\ e_{\mathrm{\&beta;}}\end{array}\right]=C_{32}\left[\begin{array}{c}{e}_a\\ e_b\\ e_c\end{array}\right],\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right]=C_{32}\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right],$

Wherein, $C_{32}=\sqrt{2/3}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right].$

Instantaneous Power Theory under described dq0 coordinate is utilize dq0 coordinate to replace a, b, c tri-Instantaneous Power Theory of phase coordinates, its principle is all converted to by three phase harmonic electric current on three phase harmonic voltage vector direction, obtain broad sense instantaneous reactive, active current and instantaneous reactive, active power etc., then through the process of inverse transformation, corresponding harmonic current value can just be detected.Instantaneous Power Theory under described dq0 coordinate not only can be used on three-phase voltage and does not occur to distort but also the system of full symmetric, and it can also be used in asymmetric and produce the system of Severe distortion.

In harmonic detecting method of the present invention, described Fast Fourier Transform (FFT) method comprises time domain Fast Fourier Transform (FFT) method and frequency domain Fast Fourier Transform (FFT) method.Finite length sequence can pass through discrete Fourier transformation (DFT) and change into finite length sequence by also discrete for its frequency domain.But its calculated amount is too large, is difficult to process problem in real time, has therefore drawn Fast Fourier Transform (FFT) (FFT).The principle of Fast Fourier Transform (FFT) is original N point sequence, resolves into a series of short data records successively.Make full use of symmetric property and periodic property that the DFT calculating formula Exponential factor has, and then obtain the corresponding DFT of these short data records and carry out appropriately combined, reach deletion double counting, reduce multiplying and simplify the object of structure.The decomposition method of DFT can be divided into two kinds substantially: the first decomposes successively time variable, the fft algorithm that this method obtains is called decimation in time algorithm, another kind decomposes successively transform sequence, make fft algorithm obtained in this way be called decimation in frequency algorithm, and the algorithm of any factor such as base 2, base 4 can be divided into again according to the difference formed by butterfly diagram.

In harmonic detecting method of the present invention, described detection based on Instantaneous Power Theory comprises pq detection and ip, iq detection.

According to an embodiment of the invention, described pq detects and comprises:

By three-phase current i _a, i _b, i _cthe current component i under α β coordinate system is obtained by α β conversion _α, i _β;

Obtain instantaneous active power p and reactive power q by pq conversion, then through the waveform of low-pass filter filtering high order, obtain fundamental active power and reactive power wherein,

Pq is transformed to: $\left[\begin{array}{c}p\\ q\end{array}\right]=C_{pq}\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right],C_{pq}\left[\begin{array}{cc}{u}_{\mathrm{\&alpha;}}& u_{\mathrm{\&alpha;}}\\ u_{\mathrm{\&beta;}}& -u_{\mathrm{\&alpha;}}\end{array}\right],$ Wherein, u _αand u _βfor voltage;

Obtain three-phase fundamental current by pq inverse transformation and α β inverse transformation, then three-phase fundamental current and three-phase current to be done the current value that subtraction obtains be harmonic current.

According to an embodiment of the invention, described ip, iq detect and comprise:

By three-phase current i _a, i _b, i _cthe current component i under α β coordinate system is obtained by α β conversion _α, i _β;

Instantaneous active current i is obtained by C conversion _pwith reactive current i _q, then through the waveform of low-pass filter filtering high order, obtain fundamental active current and reactive current wherein,

C is transformed to: $\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right],C=\left[\begin{array}{cc}\sin \mathrm{\&omega;}t& -\cos \mathrm{\&omega;}t\\ -\cos \mathrm{\&omega;}t& -\sin \mathrm{\&omega;}t\end{array}\right],$ Wherein, ω is angular velocity;

Obtain three-phase fundamental current by C inverse transformation and α β inverse transformation, then three-phase fundamental current and three-phase current to be done the current value that subtraction obtains be harmonic current.

Describe described ip, iq below by specific embodiment to detect:

As shown in Figure 4, three-phase current i _a, i _b, i _cthe current i under α β coordinate system is obtained by α β conversion _α, i _β, and phaselocked loop P passes through a phase line voltage e _aphase-locked sinusoidal signal sin ω t and corresponding cosine signal-cos ω t;

The instantaneous active current i obtained is converted by C _pwith reactive current i _qas follows:

$\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right],C=\left[\begin{array}{cc}\sin \mathrm{\&omega;}t& -\cos \mathrm{\&omega;}t\\ -\cos \mathrm{\&omega;}t& -\sin \mathrm{\&omega;}t\end{array}\right],$ Wherein, ω is angular velocity;

Then through the waveform of low-pass filter filtering high order, fundamental active current is obtained and reactive current three-phase fundamental current i is obtained again by C inverse transformation and α β inverse transformation _af, i _bf, i _cffor: $\left[\begin{array}{c}{i}_{af}\\ i_{bf}\\ i_{cf}\end{array}\right]=C_{23}\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}f}\\ i_{\mathrm{\&beta;}f}\end{array}\right],$ Wherein, $C_{23}=C_{32}^T;$

Again by three-phase fundamental current i _af, i _bf, i _cfwith three-phase current i _a, i _b, i _cdoing the current value that subtraction obtains is harmonic current i _ah, i _bh, i _ch.

Fig. 6 is that the harmonic detecting method combined with Fast Fourier Transform (FFT) method based on Instantaneous Power Theory emulates.This model based on the three-phase supply frequency of nonlinear load be General Electric Network natural frequency 50HZ, peak value is 380V, between each phase place, differential seat angle is 120 °, inductance value is 10mH, it is 100 Ω that resistive load obtains resistance, RLC parallel branch resistance is 1 Ω, and electronic rectifier load uses IGBT/Diodes.

The design of threshold switch is the key of the harmonic detecting method combined with Fast Fourier Transform (FFT) method based on Instantaneous Power Theory, when described K value hypothesis is greater than 0.5 (according to network load type difference, this value can be adjusted) time, illustrate that now electrical network is not also very stable, therefore also select to detect by the method based on Instantaneous Power Theory.When K is less than 0.5, it has been stable for giving tacit consent to now electrical network, detects harmonic wave, the higher hamonic wave of mechanical periodicity is also detected within it, reaches the object of optimization so transfer to based on Fast Fourier Transform (FFT) method.Fig. 7 detects based on Instantaneous Power Theory to compensate rear power network current oscillogram, and in the model based on instantaneous reactive detection theory, the current waveform after compensating is perfect not enough, the reason that Here it is cannot compensate because higher hamonic wave can not be detected.Fig. 8 be the harmonic detecting method combined with Fast Fourier Transform (FFT) method based on Instantaneous Power Theory detect compensate after power network current oscillogram, compared with Fig. 7, current waveform after being compensated by the harmonic detecting method combined with Fast Fourier Transform (FFT) method based on Instantaneous Power Theory, waveform in figure becomes more smooth, more accurately.The harmonic detecting method combined with Fast Fourier Transform (FFT) method based on Instantaneous Power Theory can be drawn thus, not only have good real-time performance, simultaneously to the higher hamonic wave of electrical network, the particularly higher hamonic wave in cycle, there is good Detection results, and good compensation effect can be obtained, thus improve the quality of power network current.

According to a further aspect in the invention, additionally provide a kind of harmonic detecting equipment, comprising:

For detecting harmonic wave based on Instantaneous Power Theory, to the n on harmonic wave point sampling electric current, obtain the arithmetic mean I of electric current _hm, after special time, puts sample rate current again to the described n on described harmonic wave, obtains the arithmetic mean I of electric current _hthe device of m ';

For by I _hm and I _hm ' does poor taking absolute value and obtains the device of K value, wherein,

When described K value is in convergence threshold, then switching harmonics detection method, selects and detects harmonic wave based on Fast Fourier Transform (FFT) method;

When described K value is when convergence threshold is outer, then continue to detect harmonic wave based on Instantaneous Power Theory.

In harmonic detecting method of the present invention, the higher hamonic wave detected in total harmonic wave based on Fast Fourier Transform (FFT) method comprises: sampled rapidly to electric current by sampling thief, and is kept in data register; Obtain calculating data based on Fast Fourier Transform (FFT) method to the data of sampling; Higher hamonic wave is obtained by calculating data.

Fig. 9 shows the structured flowchart of the example calculation equipment that can be used for putting into practice embodiment of the present invention.Be appreciated that client, agency and/or the server recorded in present disclosure can utilize the computing equipment shown in Fig. 9 to realize.As shown in Figure 9, computing equipment can comprise: CPU (CPU (central processing unit)) 401, RAM (random access memory) 402, ROM (ROM (read-only memory)) 403, system bus 404, hard disk controller 405, keyboard controller 406, serial interface controller 407, parallel interface controller 408, display controller 409, hard disk 410, keyboard 411, serial peripheral equipment 412, concurrent peripheral equipment 413 and display 414.In these parts, what be coupled with system bus 404 has CPU401, RAM402, ROM403, hard disk controller 405, keyboard controller 406, serial interface controller 407, parallel interface controller 408 and display controller 409.Hard disk 410 is coupled with hard disk controller 405, keyboard 411 is coupled with keyboard controller 406, serial peripheral equipment 412 is coupled with serial interface controller 407, and concurrent peripheral equipment 413 is coupled with parallel interface controller 408, and display 414 is coupled with display controller 409.

Harmonic detecting method of the present invention not only solves in Instantaneous Power Theory detection harmonic wave and can't detect higher hamonic wave thus the problem of not knowing the ratio of concrete times harmonic composition, solves again life period in Fast Fourier Transform (FFT) method detection harmonic wave and postpones namely to have in real-time the problem of certain limitation.

Some embodiments of the present invention are described by way of example above.Above-mentioned different masses, can being performed at least partially of operation and technology, by using hardware, processor performs firmware instructions, the instruction of processor executive software, or and combination in any.When adopting the processor performing firmware and software instruction to perform, software or firmware instructions can be stored in the storage of any computer-readable, such as disk, CD or other storage mediums, at RAM or ROM or flash storer, processor, hard disk, CD, disk etc.Similarly, software and firmware instructions can be transferred to user or system, are comprised by transmission mode that is known or that expect arbitrarily, such as, at computer readable diskette or other portable computer memory mechanisms or pass through telecommunication media.Telecommunication media typically specifically talks about computer-readable instruction, data structure, program module or other data in modulated message signal such as carrier wave or other transmission mechanisms.By example, and unrestricted, and communication media comprises wire medium such as cable network or single line and connects, and wireless medium, such as sound, wireless frequency, infrared and other wireless medium.Thus, software and firmware instructions can be transferred to user or system, by communication channel, such as telephone wire, DSL line, cable television line, optical fiber cable, wireless channel, the Internet, etc. (provide such software by portable storage media, it is counted as identical or interchangeable).Software or firmware instructions can comprise and instructions, and it causes processor to perform different action when being executed by a processor.

It should be noted that embodiments of the present invention can be realized by the combination of software, hardware or software and hardware.Hardware components can utilize special logic to realize; Software section can store in memory, and by suitable instruction execution system, such as microprocessor or special designs hardware perform.Those having ordinary skill in the art will appreciate that above-mentioned method and system and computer executable instructions can be used and/or be included in processor control routine and realize, such as, on the programmable memory of mounting medium, such as ROM (read-only memory) (firmware) or the data carrier of such as optics or electrical signal carrier of such as disk, CD or DVD-ROM, provide such code.The equipment of present embodiment and module thereof can be realized by the hardware circuit of the programmable hardware device of the semiconductor of such as VLSI (very large scale integrated circuit) or gate array, such as logic chip, transistor etc. or such as field programmable gate array, programmable logic device etc., also with the software simulating performed by various types of processor, also can be realized by the combination such as firmware of above-mentioned hardware circuit and software.

The communication network mentioned in instructions can comprise disparate networks, include but not limited to LAN (Local Area Network) (" LAN "), wide area network (" WAN "), based on IP agreement network (such as, the Internet) and ad-hoc network (such as, adhoc peer-to-peer network).

In addition, although describe the operation of the inventive method in the accompanying drawings with particular order, this is not that requirement or hint must perform these operations according to this particular order, or must perform the result that all shown operation could realize expectation.On the contrary, the step described in process flow diagram can change execution sequence.Additionally or alternatively, some step can be omitted, multiple step is merged into a step, or a step is decomposed into multiple step.

Though describe the present invention with reference to some embodiments, should be appreciated that, the present invention is not limited to disclosed embodiment.The present invention is intended to contain the interior included various amendment of spirit and scope and the equivalent arrangements of claims.The scope of claims meets the most wide in range explanation, thus comprises all such amendments and equivalent structure and function.

Claims (10)

1. a harmonic detecting method, comprising:

Detect harmonic wave based on Instantaneous Power Theory, to the n on harmonic wave point sampling electric current, obtain the arithmetic mean I of electric current _hm, after special time, puts sample rate current again to the described n on described harmonic wave, obtains the arithmetic mean I of electric current _hm ';

By I _hm and I _hm ' does poor taking absolute value and obtains K value, wherein,

When described K value is in convergence threshold, then switching harmonics detection method, selects and detects harmonic wave based on Fast Fourier Transform (FFT) method;

When described K value is when convergence threshold is outer, then continue to detect harmonic wave based on Instantaneous Power Theory.

2. method according to claim 1, wherein, described convergence threshold is 0.3-1.5.

3. method according to claim 1, wherein, described Instantaneous Power Theory comprises the Instantaneous Power Theory under α β coordinate and the Instantaneous Power Theory under dq0 coordinate.

4. method according to claim 1, wherein, described Fast Fourier Transform (FFT) method comprises time domain Fast Fourier Transform (FFT) method and frequency domain Fast Fourier Transform (FFT) method.

5. method according to claim 1, wherein, described detection based on Instantaneous Power Theory comprises pq detection and ip, iq detection.

6. method according to claim 3, wherein, the Instantaneous Power Theory under described α β coordinate is utilize α β two phase coordinates to replace a, b, c tri-Instantaneous Power Theory of phase coordinates.

7. method according to claim 3, wherein, the Instantaneous Power Theory under described dq0 coordinate is utilize dq0 coordinate to replace a, b, c tri-Instantaneous Power Theory of phase coordinates.

8. method according to claim 5, wherein, described pq detects and comprises:

By three-phase current i _a, i _b, i _cthe current component i under α β coordinate system is obtained by α β conversion _α, i _β;

Obtain instantaneous active power p and reactive power q by pq conversion, then through the waveform of low-pass filter filtering high order, obtain fundamental active power and reactive power wherein,

Pq is transformed to: $\left[\begin{array}{c}p\\ q\end{array}\right]=C_{pq}\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right],C_{pq}=\left[\begin{array}{cc}{u}_{\mathrm{\&alpha;}}& u_{\mathrm{\&beta;}}\\ u_{\mathrm{\&beta;}}& -u_{\mathrm{\&alpha;}}\end{array}\right],$ Wherein, u _αand u _βfor voltage;

Obtain three-phase fundamental current by pq inverse transformation and α β inverse transformation, then three-phase fundamental current and three-phase current to be done the current value that subtraction obtains be harmonic current.

9. method according to claim 5, wherein, described ip, iq detect and comprise:

By three-phase current i _a, i _b, i _cthe current component i under α β coordinate system is obtained by α β conversion _α, i _β;

Instantaneous active current i is obtained by C conversion _pwith reactive current i _q, then through the waveform of low-pass filter filtering high order, obtain fundamental active current and reactive current wherein,

C is transformed to: $\left[\begin{array}{c}{i}_p\\ i_q\end{array}\right]=C\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right],C=\left[\begin{array}{cc}sin\mathrm{\&omega;}t& -cos\mathrm{\&omega;}t\\ -cos\mathrm{\&omega;}t& -\sin \mathrm{\&omega;}t\end{array}\right],$ Wherein, ω is angular velocity;

Obtain three-phase fundamental current by C inverse transformation and α β inverse transformation, then three-phase fundamental current and three-phase current to be done the current value that subtraction obtains be harmonic current.

10. a harmonic detecting equipment, comprising:

For detecting harmonic wave based on Instantaneous Power Theory, to the n on harmonic wave point sampling electric current, obtain the arithmetic mean I of electric current _hm, after special time, puts sample rate current again to the described n on described harmonic wave, obtains the arithmetic mean I of electric current _hthe device of m ';

For by I _hm and I _hm ' does poor taking absolute value and obtains the device of K value, wherein,

When described K value is in convergence threshold, then switching harmonics detection method, selects and detects harmonic wave based on Fast Fourier Transform (FFT) method;

When described K value is when convergence threshold is outer, then continue to detect harmonic wave based on Instantaneous Power Theory.