CN201269907Y - Harmonic detector used between electrical power systems - Google Patents

Abstract

The utility model relates to an interharmonic detector for power systems, which comprises a data analysis module, a switching power supply and a liquid crystal display, the input end of the data analysis module is connected to a signal acquisition circuit, and the output end is connected to a liquid crystal display circuit and a communication circuit; the data analysis module also Connect the clock hold circuit. The signal acquisition circuit is composed of PT or CT and the operational amplifier circuit connected to it; the data analysis module is composed of a digital signal processor DSP, a 6M crystal oscillator connected to the XTAL1 terminal of the DSP and an oscillation capacitor; the clock holding module is composed of a clock chip, It consists of a 3.6V button battery connected to the clock chip, an oscillation capacitor and a 32.768K crystal oscillator. This device is used for interharmonic detection of equipment such as substations. It can collect the voltage and current signals of the power system online and analyze the data, display the components of the intermediate harmonics of the signal on the LCD screen, and communicate with the computer through the communication circuit for data transmission. , to achieve the function of real-time detection of harmonics in the power system.

Description

A Harmonic Detector for Power System

technical field

The utility model relates to an electric energy quality detection device of an electric power system, in particular to a device for detecting inter-harmonic waves of electric energy systems in substations and the like.

Background technique

Usually, people define the voltage or current that contains non-integer multiples of the power supply system design operating frequency (50HZ in my country) as inter-harmonics; the root cause of harmonics in power systems is due to nonlinear loads. Harmonics and interharmonics widely exist in the power system, and have a serious impact on the safe and stable operation of the power grid, the normal power consumption of users, and industrial and agricultural production. Therefore, the problem of harmonics and interharmonics in power system has aroused people's great attention. At present, online detection can already be realized for the harmonic detection of power system, and there are many harmonic detection devices. However, for interharmonics in power systems, due to the characteristics of interharmonics that are sensitive to spectrum leakage and obvious interference by noise, there are few detection methods for interharmonics, and due to the complexity of calculation methods, generally only It is difficult to collect data for analysis, but it is difficult to implement online detection. At present, there is still a lack of on-line power system interharmonic detectors with high measurement accuracy and fast detection.

Chinese patent (CN2932397) discloses a power harmonic and inter-harmonic monitoring device, which includes an instrument voltage transformer group, an instrument current transformer group, an A/D converter, and a digital signal processor (DSP) , a microcontroller (MCU), 2 program memories (program memory 1, program memory 2), I/O controller, data memory, communication control unit, display and keyboard, touch screen and mouse, instrument voltage transformer group Heyi uses a current transformer group to form a three-phase voltage and current sampling circuit. The A/D converter is connected between the sampling circuit and the DSP. The communication between the DSP and the MCU uses the HPI data bus. The two program memories communicate with the DSP respectively through the bus. , MCU connection, the data memory is connected to the MCU through the bus, and the display, keyboard, touch screen and mouse are all connected to the corresponding ports of the I/O controller of the MCU. Although this device has realized the monitoring work of harmonics and inter-harmonics, it has the following deficiencies: first: it adopts windowed FFT operation, which has the problem of spectrum leakage, and inter-harmonic components have a high impact on spectrum leakage. Sensitivity, the spectral leakage of harmonic components may submerge the real interharmonics, or generate false interharmonic planes that are difficult to distinguish, which seriously affects the accurate detection of interharmonics; second: the communication between DSP and MCU The HPI data bus is adopted, and the circuit is complicated; thirdly, the monitoring device is too bulky and not easy to carry.

Utility model content

Aiming at the shortcomings of the existing detection technology, the purpose of the utility model is to provide a power system interharmonic detector with high measurement accuracy, fast detection and reliable detection results.

The purpose of this utility model is achieved like this: a kind of interharmonic detector of electric power system, comprises data analysis module, switching power supply and liquid crystal display, is characterized in that: the input end of data analysis module is connected with signal acquisition circuit, and output end is connected with liquid crystal Display circuit and communication circuit; the data analysis module is also connected to the clock holding circuit;

The signal acquisition circuit is composed of PT or CT and the operational amplifier circuit connected to it; the data analysis module is composed of a digital signal processor DSP, a 6M crystal oscillator connected to the XTAL1 terminal of the DSP and an oscillation capacitor;

The clock holding circuit is mainly composed of a clock chip, a 3.6V button battery connected to the clock chip, an oscillation capacitor and a 32.768K crystal oscillator.

Compared with the traditional power system harmonic detection device, the utility model has the following advantages:

(1) The harmonic detector in this room has high reliability, high measurement accuracy, and can detect online in real time;

(2) The inter-harmonic detector adopts advanced data analysis methods, which can test non-integer harmonics in the system; and there is no spectrum leakage problem;

(3) The harmonic detector in this room can display data and waveform in real time, and has data storage function, which is convenient for operation and management;

(4) The inter-harmonic detector has the advantages of wide measurement range, high cost performance, and good real-time performance. It solves the current problem of inter-harmonic detection in power systems, and can accurately and timely report inter-system harmonic components and characteristics, ensuring power supply security;

(5) This inter-harmonic detector only needs one DSP to complete the task, and no longer uses MCU. Compared with the power harmonic and inter-harmonic monitoring device, it is simpler and more reliable; it is also small in size, easy to carry and easy to install specialty.

Description of drawings

Fig. 1 is a schematic block diagram of the utility model;

Fig. 2 is the signal acquisition circuit of the present utility model;

Fig. 3 is the utility model data analysis module and communication circuit;

Fig. 4 is the clock holding circuit of the present utility model;

Fig. 5 is the software flowchart of the utility model.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment, the utility model is further described.

As shown in Figure 1, the utility model relates to a power system interharmonic detector, which mainly includes a signal acquisition circuit 1, a data analysis module 2, a switching power supply 3, a clock holding circuit 4, a display screen 5 and a communication circuit 6; it It is a DSP processor-based power system interharmonic detector. External structures such as housing and key switch are omitted in the figure.

Referring to Fig. 2, the signal acquisition circuit (1) is composed of PT or CT and its operational amplifier circuit; Circuit processing, sent to the AD conversion port of DSP.

Referring to Fig. 3, be the data analysis module of a kind of embodiment and communication circuit, data analysis module (2) is made up of DSP, the 6M crystal oscillator and the oscillating capacitance that are connected at the XTAL1 end of this DSP; Data analysis module (2) is based on The DSP of TMS320LF2407 is the core, and CY7C1021 off-chip program memory and peripheral circuits. The DSP of the utility model adopts TMS320LF2407 of TI series, which has the advantages of strong computing power, large capacity and high precision. The actual voltage and current value of each phase is obtained through DSP operation processing, and at the same time enters the inter-harmonic detection processing, adopts digital signal processing technology, and obtains the inter-harmonic component parameters existing in the signal through interpolation FFT calculation and other methods from the measured data , and store the sampling data and analysis results into the EEPROM of the DSP at the same time. Its communication circuit is composed of DSP, MAX202 communication chip connected to the RX and TX ends of the DSP, MAX485 communication chip and its peripheral circuits.

The DSP and operational amplifier circuits in this design are powered by +3.3V and ±12V power switches.

Referring to Fig. 4, clock holding circuit (4) is made up of clock chip PCF8583 and the 3.6V button cell battery that is connected on the clock chip, oscillating capacitor and 32.768K crystal oscillator, to guarantee still have clock holding function when power supply is interrupted.

Referring to Fig. 5, using the utility model, after the analysis data is obtained, the waveform and parameters of the measured signal can be displayed in real time on the LCD screen by pressing the buttons, or only the waveform and parameters of the inter-harmonic components can be selected to be displayed through synchronous Clock, you can choose to save the measured data and analysis results at regular intervals. If the communication interface is connected to the computer, the real-time measured data and analysis results can be processed and transmitted to the computer through the communication chip MAX202 and MAX485, and processed by the background software to make a report form and publish it on the Internet.

This device is used for interharmonic detection of equipment such as substations. It can collect the voltage and current signals of the power system online and analyze the data, display the components of the intermediate harmonics of the signal on the LCD screen, and communicate with the computer through the communication circuit for data transmission. , to achieve the function of real-time detection of harmonics in the power system. This device has the advantages of wide measurement range, high reliability, high cost performance, and good real-time performance. It solves the current problem of inter-harmonic detection in power systems, and can accurately and timely report inter-system harmonic components and characteristics to ensure power supply safety. Moreover, the inter-harmonic detection device adopts power spectrum estimation and uses the PRONY method to detect the amplitude and phase of the inter-harmonic, and this detection method does not have the problem of spectrum leakage.

Claims (2)

1, a kind of electric system interharmonic detector, comprise data analysis module (2), switching power supply (3) and liquid crystal display, it is characterized in that: the input end of data analysis module (2) connects signal acquisition circuit (1), The output terminal is connected to the liquid crystal display circuit (5) and the communication circuit (6); the data analysis module (2) is also connected to the clock holding circuit (4); The signal acquisition circuit (1) is made up of PT or CT and the operational amplifier circuit connected with it; the data analysis module (2) is made up of digital signal processor DSP, the 6M crystal oscillator and the oscillating capacitor connected to the XTAL1 end on the DSP; The clock holding module (4) is composed of a clock chip, a 3.6V button battery connected to the clock chip, an oscillation capacitor and a 32.768K crystal oscillator. 2. The power system interharmonic detector according to claim 1, characterized in that said digital signal processor DSP adopts TMS320LF2407 chip.

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