CN203688664U

CN203688664U - Grid efficiency measuring apparatus

Info

Publication number: CN203688664U
Application number: CN201420039317.1U
Authority: CN
Inventors: 潘宇婷
Original assignee: Shanghai University of Engineering Science
Current assignee: Shanghai University of Engineering Science
Priority date: 2014-01-22
Filing date: 2014-01-22
Publication date: 2014-07-02
Anticipated expiration: 2024-01-22

Abstract

The utility model discloses a grid efficiency measuring apparatus which comprises a conditioning circuit, a zero cross detecting circuit, a DSP chip, a time interval measuring module, a high-precision clock, a constant-temperature crystal oscillator, and a DAC and signal conditioning circuit. After a grid high voltage is processed by a mutual inductor, the conditioning circuit and the zero cross circuit, a square wave signal having the same frequency as a grid fundamental wave is obtained and then is transmitted to a capture unit pin of the DSP chip. The DSP chip also receives data of the output frequency of the constant-temperature crystal oscillator, measured by the time interval measuring module based on a GPS clock signal, and after regular samplings and digital filtering, outputs the data to the DAC and signal conditioning circuit to be converted into an analog signal and transformed into a voltage in a receivable voltage range by a voltage control end of the constant-temperature crystal oscillator, and then the analog signal and the voltage are transmitted to the constant-temperature crystal oscillator. The high-precision clock, after calibrating the precision of the output frequency of the constant-temperature oscillator, is transmitted to the DSP chip as an external timer. The DSP chip counts the input square wave signals, and obtains an accurate real-time grid frequency.

Description

A kind of grid frequency measurement device

Technical field

The utility model relates to a kind of grid frequency measurement device.

Background technology

Along with the development of science and technology and national economy, the demand of electric energy is increased day by day, simultaneously also more and more higher to the requirement of the quality of power supply.Mains frequency is an important indicator of the quality of power supply, the quality of the quality of power supply directly affects industrial and agricultural production and the people's life, therefore mains frequency is measured accurately, and guaranteed that it is that operation of power networks regulates the important content of controlling that mains frequency deviation is less than allowable value.

Summary of the invention

Technical problem to be solved in the utility model is to provide a kind of measurement mechanism that accurately measures mains frequency.

In order to solve above technical matters, the utility model adopts following technical scheme.

A kind of grid frequency measurement device, comprise modulate circuit, zero cross detection circuit, digital signal processing (DSP) chip, time interval measurement module, high precision clock, constant-temperature crystal oscillator and DAC and signal conditioning circuit, electrical network high pressure is after mutual inductor becomes small-signal, pass through successively the shaping of amplification, filtering processing and the zero cross detection circuit of modulate circuit, obtain and the square-wave signal of electrical network first-harmonic same frequency, be then sent to the capture unit pin of dsp chip; Dsp chip is the data of the constant-temperature crystal oscillator output frequency of time of reception interval measurement module based on gps clock signal measurement also, after periodic sampling and digital filtering, export to DAC and signal conditioning circuit to be converted into simulating signal and to be transformed to the voltage range that constant-temperature crystal oscillator voltage controling end can receive, then be sent to constant-temperature crystal oscillator, high precision clock, by proofreading and correct after the precision of constant-temperature crystal oscillator output frequency, is sent to dsp chip as outside timer; Dsp chip, by the square-wave signal of input is counted, obtains accurately real-time mains frequency.

As a kind of improvement project, described grid frequency measurement device also comprises GPS receiver module, and described GPS receiver module produces the 1PPS signal that is synchronized with UTC after receiving gps signal, is sent to time interval measurement module.

As further improvement project, described grid frequency measurement device also comprises Clock management frequency division module, and the original frequency signal of the 100MHz that constant-temperature crystal oscillator produces produces the fractional frequency signal of 1MHz through Clock management frequency division module, be sent to time interval measurement module.

As further improvement project, time interval measurement module receives after the 1PPS signal of GPS receiver module output and the fractional frequency signal of constant-temperature crystal oscillator output, and the time interval of rising edge is measured and measurement result is sent to dsp chip.

Described modulate circuit comprises amplifying circuit and filtering circuit.

Described dsp chip is selected TMS320F28335 chip.

Described high precision clock is selected the AT8372A/B clock chip with digital calibration function.

Principle of work of the present utility model is: based on gps clock signal calibration constant-temperature crystal oscillator output frequency, the error of bringing to eliminate disturbance, constant-temperature crystal oscillator is compensated, the precision clock obtaining is as the outside input clock of timer, utilize clock accurately to count signal acquisition, thereby obtain mains frequency accurately.

Compared with prior art, superior effect of the present utility model is: the crystal oscillator output frequency after GPS calibration, can improve the precision of dsp chip input clock, thereby can realize accurately real-time grid frequency measurement.

Accompanying drawing explanation

Fig. 1 is the schematic block circuit diagram of a kind of grid frequency measurement device of providing of the utility model.

Embodiment

Below in conjunction with accompanying drawing, the technical solution of the utility model is elaborated further.

As shown in Figure 1, a kind of grid frequency measurement device that the utility model provides, comprise modulate circuit, zero cross detection circuit, digital signal processing (DSP) chip, time interval measurement module, GPS receiver module, Clock management frequency division module, high precision clock, constant-temperature crystal oscillator and DAC and signal conditioning circuit, electrical network high pressure is after mutual inductor becomes small-signal, pass through successively the shaping of amplification, filtering processing and the zero cross detection circuit of modulate circuit, obtain and the square-wave signal of electrical network first-harmonic same frequency, be then sent to the capture unit pin of dsp chip; GPS receiver module receives the 1PPS signal that is synchronized with UTC producing after gps signal and is sent to time interval measurement module; The fractional frequency signal of the 1MHz that the original frequency signal of the 100MHz that constant-temperature crystal oscillator produces produces through Clock management frequency division module is sent to time interval measurement module simultaneously; Described time interval measurement module receives after the 1PPS signal of GPS receiver module output and the fractional frequency signal of constant-temperature crystal oscillator output, and the time interval of rising edge is measured and measurement result is sent to dsp chip; The data that dsp chip is carried time interval measurement module are carried out after periodic sampling and digital filtering, export to DAC and signal conditioning circuit to be converted into simulating signal and to be transformed to the receivable voltage range of constant-temperature crystal oscillator voltage controling end, then be sent to constant-temperature crystal oscillator, high precision clock, by proofreading and correct after the precision of constant-temperature crystal oscillator output frequency, is sent to dsp chip as outside timer; Dsp chip, by the square-wave signal of input is counted, obtains accurately real-time mains frequency.

Described modulate circuit comprises amplifying circuit and filtering circuit.

Described dsp chip is selected TMS320F28335 chip.

Described zero cross detection circuit comprises the elements such as voltage comparator MAX474 and resistance, and function is that the sine wave of electrical network is carried out to shaping, obtains and the square-wave signal of electrical network first-harmonic same frequency, then exports to the capture unit pin of DSP.

The function of described GPS receiver module is to receive gps signal, produces the 1PPS signal that is synchronized with UTC, is then sent to time interval measurement module.

The function of described constant-temperature crystal oscillator is to produce 100MHz original frequency signal.

The function of described Clock management frequency division module is the fractional frequency signal that the 100MHz original frequency signal of constant-temperature crystal oscillator generation is produced to 1MHz, is then sent to time interval measurement module.

The function of described time interval measurement module is the time interval of the rising edge of the frequency division 1Hz signal of 1PPS signal to GPS receiver module output and OCXO output to carry out precision measurement, and sends measurement result to dsp chip.

The function of described dsp chip is sampling and the digital filtering that the data of the time interval measurement module conveying to receiving are carried out some cycles.

Described DAC and the function of signal conditioning circuit are that the digital signal of dsp processor output is converted into simulating signal, and are transformed to the receivable voltage range of constant-temperature crystal oscillator voltage controling end, thereby realize the adjustment to constant-temperature crystal oscillator output frequency.

The function of described high precision clock is the external clock input as DSP timer.

ECAP module by DSP is caught the rising edge of input square-wave signal, and utilizes the triggered time of two rising edges of timer record of outside precisely input clock, obtains the real-time and precise frequency of electrical network.

The 1PPS signal that the utility model provides take GPS receiver is reference source, in conjunction with gps clock signal and complementary this characteristic of constant-temperature crystal oscillator clock signal precision, by the voltage-controlled end of regulation and control constant-temperature crystal oscillator, its output frequency is changed thereupon, to maintain short-term and long-term clock accuracy and stability, then this clock is offered to the timer of DSP, by the eCAP module of DSP, the rising edge of input signal is caught, the triggered time of two rising edges of record obtains the real-time frequency of electrical network.

Visible in sum, the crystal oscillator output frequency of the utility model after GPS calibration, can improve the precision of dsp chip input clock, accurately measures in real time mains frequency thereby realized, and has conspicuousness practical value.

Finally be necessary described herein: above embodiment, only for the technical solution of the utility model is described in more detail, can not be interpreted as the restriction to the utility model protection domain; Some nonessential improvement that those skilled in the art makes according to foregoing of the present utility model and adjustment all belong to protection domain of the present utility model.

Claims

1. a grid frequency measurement device, it is characterized in that: comprise modulate circuit, zero cross detection circuit, digital signal processing dsp chip, time interval measurement module, high precision clock, constant-temperature crystal oscillator and DAC and signal conditioning circuit, electrical network high pressure is after mutual inductor becomes small-signal, pass through successively the shaping of amplification, filtering processing and the zero cross detection circuit of modulate circuit, obtain and the square-wave signal of electrical network first-harmonic same frequency, be then sent to the capture unit pin of dsp chip; Dsp chip is the data of the constant-temperature crystal oscillator output frequency of time of reception interval measurement module based on gps clock signal measurement also, after periodic sampling and digital filtering, export to DAC and signal conditioning circuit to be converted into simulating signal and to be transformed to the voltage range that constant-temperature crystal oscillator voltage controling end can receive, then be sent to constant-temperature crystal oscillator, high precision clock, by proofreading and correct after the precision of constant-temperature crystal oscillator output frequency, is sent to dsp chip as outside timer; Dsp chip, by the square-wave signal of input is counted, obtains accurately real-time mains frequency.

2. grid frequency measurement device as claimed in claim 1, is characterized in that: also comprise GPS receiver module, described GPS receiver module produces the 1PPS signal that is synchronized with UTC after receiving gps signal, is sent to time interval measurement module.

3. grid frequency measurement device as claimed in claim 2, it is characterized in that: also comprise Clock management frequency division module, the original frequency signal of the 100MHz that constant-temperature crystal oscillator produces produces the fractional frequency signal of 1MHz through Clock management frequency division module, be sent to time interval measurement module.

4. grid frequency measurement device as claimed in claim 3, it is characterized in that: time interval measurement module receives after the 1PPS signal of GPS receiver module output and the fractional frequency signal of constant-temperature crystal oscillator output, the time interval of rising edge is measured and measurement result is sent to dsp chip.

5. grid frequency measurement device as claimed in claim 1, is characterized in that: described modulate circuit comprises amplifying circuit and filtering circuit.

6. grid frequency measurement device as claimed in claim 1, is characterized in that: described dsp chip is selected TMS320F28335 chip.

7. grid frequency measurement device as claimed in claim 1, is characterized in that: described high precision clock is selected the AT8372A/B clock chip with digital calibration function.