CN102508028A - Device and method for detecting and analyzing harmonic - Google Patents

Abstract

The invention discloses a harmonic detection and analysis device and method. One output port of a signal conditioning circuit is respectively connected to a low-pass filter and a delay module, the output of the low-pass filter is connected to a phase-locked loop, and the output of the delay module and the phase-locked loop are respectively connected to each other. The first ADC module has different input ports. The output of the first ADC module is connected to the minimum DSP system. After the detection signal passes through the signal conditioning circuit, the analog signal is filtered by a low-pass filter to obtain the fundamental wave signal, which is synchronously sampled and fixed by the phase-locked loop. Finally, a fixed number of pulse signals is obtained; at the same time, the analog signal is delayed by a delay module to obtain a signal synchronized with the fundamental signal, and the fixed number of pulse signals and the signal synchronized with the fundamental signal are simultaneously input to the first ADC module, and the first ADC After the module converts the analog quantity to the digital quantity, it enters the DSP minimum system. The invention combines a low-pass filter, a phase-locked loop and a delay module to realize high-precision synchronous sampling and effectively improve measurement and analysis precision.

Description

A harmonic detection and analysis device and method

technical field

The invention relates to a harmonic detection and analysis device and method for power systems and electrical equipment. the

Background technique

With the development of power electronics technology, the problem of harmonics is becoming more and more serious, which has become the focus of attention at home and abroad. Many countries and international academic organizations have formulated standards and regulations to limit harmonics in power systems and electrical equipment. The harmonic detection and analysis device has also been extensively researched. Its main function is to detect the current and voltage signals in the power system and conduct harmonic analysis to judge whether the harmonics of the equipment, device or system meet the standard requirements. Analyze the changing relationship between system harmonics and operating loads to provide a basis for improving and ensuring the normal operation of the power system.

The main disadvantage of the existing harmonic detection and analysis device is that the detection accuracy is not high. Since the frequency in the power grid is not fixed, if the sampling process cannot guarantee synchronous sampling and the number of sampling points in a measurement cycle remains constant, the detection and analysis will produce large errors. In the relevant literature that can be retrieved, some harmonic detection and analysis devices do not consider the synchronization of signal sampling; although some consider the synchronization of sampling, they do not consider the error caused by aliasing signals; and anti-aliasing issues, but does not take into account the anti-aliasing circuit errors due to signal attenuation and phase shift.

Contents of the invention

The purpose of the present invention is to solve the problem of poor precision of existing harmonic detection and analysis devices, and provide a high-precision harmonic detection and analysis device and method with display, storage and communication functions.

The technical solution adopted by the harmonic detection and analysis device of the present invention is: comprising a signal conditioning circuit and a low-pass filter, an output port of the signal conditioning circuit is respectively connected to the low-pass filter and a delay module, and the output of the low-pass filter is connected to a phase-locked loop, the output of the delay module and the phase-locked loop are respectively connected to different input ports of the first ADC module, the output of the first ADC module is connected to the DSP minimum system, and the DSP minimum system is respectively connected with an external keyboard, the first storage unit, LCD module, calendar clock chip, communication module; the delay module is composed of the second ADC module, the minimum unit of the microprocessor and the DAC module connected in series in sequence, and the second storage unit is connected with the minimum unit of the microprocessor. the

The technical scheme of the harmonic detection and analysis method of the device of the present invention includes: after the detection signal is passed through the signal conditioning circuit, the analog signal is firstly filtered by a low-pass filter to obtain the fundamental wave signal, and then the phase-locked loop is synchronously sampled and the number of sampling points is fixed. Obtain a fixed number of pulse signals; at the same time, delay the analog signal through a delay module to obtain a signal synchronized with the fundamental signal, and then simultaneously input the fixed number of pulse signals and the signal synchronized with the fundamental signal into the first ADC module, the first ADC module converts the analog quantity to the digital quantity according to the fixed number pulse signal output by the phase-locked loop and the signal synchronized with the fundamental signal output by the delay module; finally, the digital quantity is input to the DSP minimum system, The minimum DSP system performs harmonic analysis based on the read digital quantity and realizes storage, display and human-computer interaction.

The beneficial effects of the present invention are:

1. The combination of low-pass filter, phase-locked loop and delay module realizes high-precision synchronous sampling and effectively improves the accuracy of measurement and analysis.

2. Use the calendar clock chip to record the time of harmonic generation, and provide accurate research data for the relationship between harmonics and operating loads.

3. The relevant data can be read out through the communication module for further analysis and research.

Description of drawings

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail;

Fig. 1 is the structural block diagram of harmonic detection and analysis device of the present invention;

Fig. 2 is a structural block diagram of delay module 6 in Fig. 1;

Fig. 3 is an embodiment diagram of the sampling method of the device in Fig. 1;

In the figure: 1. DSP minimum system; 2. Power supply module; 3. Signal conditioning; 4. Low-pass filter; 5. Phase-locked loop; 6. Delay module; 7. First ADC module; 8. Keyboard; 9 10. LCD module; 11. Calendar clock chip; 12. Communication module; 13. Microprocessor minimum unit; 14. Second ADC module; 15. DAC module; 16. Second storage unit.

Detailed ways

As shown in Figure 1, it includes signal conditioning circuit 3, low-pass filter 4, ADC module, storage unit, DSP, etc., the detection signal is connected with low-pass filter 4 and delay module 6 through signal conditioning circuit 3, and the signal conditioning circuit 3 One output port is respectively connected to the low-pass filter 4 and the delay module 6, the output of the low-pass filter 4 is connected to the phase-locked loop 5, and the outputs of the delay module 6 and the phase-locked loop 5 are respectively connected to different inputs of the first ADC module 7 Port, the output of the first ADC module 7 is connected to the DSP minimum system 1, and the DSP minimum system 1 is connected to the keyboard 8, the first storage unit 9, the LCD module 10, the calendar clock chip 11, and the communication module 12 respectively with its different ports. The power module 2 is respectively connected to the DSP minimum system 1, the signal conditioning circuit 3, the low-pass filter 4, the phase-locked loop 5, the delay module 6, the first ADC module 7, the keyboard 8, the first storage unit 9, the LCD module 10, Calendar clock chip 11 and communication module 12. Among them, the signal conditioning circuit 3 converts the analog signal at its input end to the allowable range and then outputs it to the low-pass filter 4, and outputs it to the delay module 6; after the low-pass filter 4 filters out the harmonics in the input signal Output the fundamental wave signal, the phase-locked loop 5 outputs the pulse signal to the first ADC module 7 according to the output signal of the low-pass filter 4; the first ADC module 7 according to the fixed number of pulse signals output by the phase-locked loop 5 and the delay module 6 The output analog signal is converted from analog to digital; the DSP minimum system 1 performs harmonic analysis according to the converted value of the first ADC module 7, and realizes functions such as data storage, human-computer interaction, display, and communication. Communication module 12 has RS485 bus and CAN bus in standard configuration.

FIG. 2 illustrates the delay module 6 in FIG. 1 in more detail. The delay module 6 is composed of a second ADC module 14 , a microprocessor minimum unit 13 , a DAC module 15 and a second storage unit 16 . Wherein, the second ADC module 14 , the minimum unit of the microprocessor 13 and the DAC module 15 are sequentially connected in series, and the second storage unit 16 is connected to the minimum unit of the microprocessor 13 . The output of the signal conditioning circuit 3 is connected to the second ADC module 14 , and the output of the DAC module 15 is connected to the second ADC module 14 . The minimum unit 13 of the microprocessor is used to regularly read the conversion value and the precise delay of the second ADC module 14; the second ADC module 14 is used to convert the input analog signal into a digital signal, and the second storage unit 16 is used to store the read The converted value from the second ADC module 14 ; the DAC module 15 converts the digital signal at its input port into an analog signal and outputs it to the input terminal of the first ADC module 17 .

The detection and analysis method of the harmonic detection and analysis device of the present invention, the device first detects the analog signal to be detected, and converts the detection signal into the signal type required by the first ADC module 7 and within the allowable measurement range through the signal conditioning circuit, and then After the analog signal is filtered by the low-pass filter 4 to obtain the fundamental wave signal, the anti-aliasing interference function is realized, and then the phase-locked loop 5 is synchronously sampled and the number of sampling points is fixed to obtain a fixed number of pulse signals; at the same time, the analog signal is delayed The time module 6 realizes precise time delay, obtains a signal synchronous with the fundamental wave signal, and simultaneously inputs a fixed number of pulse signals and a signal synchronous with the fundamental wave signal into the first ADC module 7, and the first ADC module 7 outputs the signal according to the phase-locked loop 5 The fixed number of pulse signals and the analog signal output by the delay module 6 are converted from analog to digital; then the digital is input to the DSP minimum system 1, and the DSP minimum system 1 performs harmonic analysis and realizes storage according to the read parameters , display, human-computer interaction and other functions.

Fig. 3 illustrates the accurate sampling method of the present invention with an example. During AD sampling, the phase-locked loop 5 circuit is used to realize the synchronization of sampling and to fix the number of sampling points in a sampling period, but from Figure 3a) is the waveform diagram after the fundamental wave is superimposed on the 7th harmonic, it can be seen that there are mixed The harmonic fundamental wave signal has multiple zero crossing points at the zero crossing point, and the signal zero point is inconsistent with the fundamental wave zero point. The PLL 5 will not be able to obtain the correct fundamental wave frequency due to the variable frequency, resulting in sampling errors; In order to solve the interference caused by frequency mixing, a low-pass filter 4 is used to realize the anti-aliasing interference function. Figure 3b) is the filtered waveform and the original waveform diagram. The sinusoidal signal is the anti-aliasing signal, which can be seen There is a phase shift between the signal and the original signal and the amplitude has a large attenuation, and there is also a sampling error; in order to solve the interference caused by anti-aliasing, the present invention uses the anti-aliasing signal to pass through the phase-locked loop 4 to ensure the sampling error Synchronous and fixed number of sampling points, the original signal is sent to the input terminal of the first ADC module 7 after the phase shift generated by the accurate delay module 6 to compensate the anti-aliasing circuit, so that the input terminal of the first ADC module 7 is and anti-aliasing After the sinusoidal signal is synchronized and has no amplitude attenuation, from Figure 3c) is the delayed waveform and the filtered waveform diagram, it can be seen that the delayed original signal is synchronized with the anti-aliased sinusoidal signal, so that Accurate sampling is achieved.

Claims (2)

1. harmonic wave check and analysis device; Comprise signal conditioning circuit (3) and low-pass filter (4); It is characterized in that: an output port of signal conditioning circuit (3) connects low-pass filter (4) and time delay module (6) respectively; The output of low-pass filter (4) connects phaselocked loop (5); Time delay module (6) and the output of phaselocked loop (5) are connected the different input ports of an ADC module (7) respectively; The output of the one ADC module (7) connects DSP minimum system (1), and DSP minimum system (1) is with its different ports difference external connection keyboard (8), first storage unit (9), LCD module (10), calendar clock chip (11), communication module (12); Serial connection and second storage unit (16) are connected to form with microprocessor minimum unit (13) said time delay module (6) mutually successively by the 2nd ADC module (14), microprocessor minimum unit (13) and DAC module (15).

2. Device Testing analytical approach according to claim 1; It is characterized in that comprising: detection signal is behind signal conditioning circuit (3); Earlier analog signals is obtained fundamental signal through low-pass filter (4) filtering, after phaselocked loop (5) synchronized sampling and fixed sample are counted, obtain the fixed number pulse signal again; Simultaneously analog signals is delayed time through time delay module (6); Obtain and the synchronous signal of said fundamental signal; Import an ADC module (7) simultaneously with the fixed number pulse signal with the synchronous signal of said fundamental signal then, an ADC module (7) is carried out the conversion that analog quantity arrives digital quantity according to the fixed number pulse signal of phaselocked loop (5) output and time delay module (6) output with the synchronous signal of said fundamental signal; At last digital quantity is inputed to DSP minimum system (1), DSP minimum system (1) carries out frequency analysis and realizes storage, demonstration and man-machine interaction according to the digital quantity that reads.

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