CN109709428B - High-frequency current source with waveform amplitude-frequency separation real-time control - Google Patents
High-frequency current source with waveform amplitude-frequency separation real-time control Download PDFInfo
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Abstract
According to the high-frequency current source with the waveform amplitude-frequency separation and real-time control functions, imported original sampling data are analyzed through PowerPC, the amplitude and frequency parameters of signals are analyzed, and a direct-current amplitude control signal in a proportional relation with the amplitude of the sampling signals and an alternating-current frequency control signal with the same frequency as the sampling signals are calculated; the coding output and the sending time sequence control of the control signal are finished through the FPGA module; generating a direct-current voltage analog signal through a first digital-to-analog conversion module; generating an alternating voltage analog signal through a second digital-to-analog conversion module; the power electronic current generator outputs a high-frequency current signal. The frequency response test method combines the conventional analog power amplifier test method and the good high-frequency output characteristic of the digital current source, and can be used for developing frequency response precision, filtering cut-off frequency, frequency aliasing and other frequency characteristic tests of the direct-current electronic transformer.
Description
Technical Field
The invention relates to the technical field of current sources, in particular to a high-frequency current source for real-time control of waveform amplitude-frequency separation.
Background
The direct current transformer is important primary equipment for construction and operation of a direct current power transmission system, provides accurate and reliable measurement information for control and protection of the system, and the operation reliability and the measurement accuracy of the direct current transformer are directly related to safe and stable operation of the direct current power transmission system. At the present stage, the direct-current electronic mutual inductor used in the direct-current transmission project in China is imported mainly from abroad, corresponding development and production experience and debugging and calibrating means are lacked in China, and particularly, the mutual inductor and a related measuring system cannot be effectively detected on the site of a converter station, and the operation condition of the direct-current mutual inductor cannot be evaluated. In actual operation, the problems of inaccurate measurement, over-high null shift of output signals, large data difference among channels and the like occur for a part of direct current transformers of the converter station for many times, influence is brought to various aspects of electric energy metering, protection control and the like of the converter station, and the operation stability of a direct current transmission system is seriously influenced.
In engineering application, in order to solve the problems of rapidity and accuracy of step response of a direct-current electronic transformer, the cut-off frequency of a filter loop of the direct-current electronic transformer is often improved, and the transmission and transformation characteristics of the direct-current electronic transformer to high-frequency signals are changed. A large amount of high-frequency signals are accompanied in the actual operation and fault processes of a direct current system, the sampling rate of the direct current electronic transformer is generally 10kHz or 50kHz, and frequency aliasing can be generated on the high-frequency signals which exceed more than half of the sampling rate of the direct current electronic transformer, so that the sampling precision of the direct current transformer is seriously influenced. At present, when a high-frequency current test is carried out on a direct-current electronic transformer, a signal generator is generally adopted to control a current type power amplifier to realize the frequency response test of the direct-current electronic transformer, and a frequency aliasing test is basically not carried out. The current high-frequency current source can be divided into an analog current source and a digital current source;
(1) analog current source
As shown in fig. 1: the analog current source is a push-pull linear power amplifier controlled based on a small voltage signal, and is composed of analog devices, the output current is irrelevant to the load, an adjusting link is formed by using a power tube, stable constant current output and high output impedance can be obtained by utilizing the flat output characteristic of a transistor and a deep negative feedback circuit, and the control of voltage on the current is realized.
The control mode of the analog high-frequency current source is shown in figure 1, a data waveform is introduced through an upper computer to generate real-time data, the waveform real-time data is sent to a main control CPU, the main control CPU generates sampling value data according to a voltage value output proportion and sends the sampling value data to a D/A chip, then the D/A chip is controlled to output a small voltage signal, and a push-pull linear current type power amplifier is controlled to output high-frequency heavy current through the small voltage signal.
(2) Digital current source
The digital current source is realized by adopting a power electronic technology. Based on the PWM modulation technique, a PWM regulator is used to control the on and off of the electronic switch, and the duty cycle of the power switch is controlled to change the voltage across the load, thereby maintaining the current through the load stable and outputting a stable current signal.
The digital high-frequency current source control mode is as shown in fig. 2, the output amplitude and the frequency parameter are set manually, the output modulation signal and the carrier signal of the power electronic current generator are changed, the on-off of the switch tube is controlled, and the large-current analog quantity with variable amplitude and frequency is output.
However, the analog current source is essentially a voltage-controlled current source, and the implementation principle thereof determines that when the frequency of the output signal is high, the inductive reactance of the output load becomes very high, thereby causing the distortion of the output waveform. Therefore, the high frequency output capability has a certain limit, and the high frequency output and the large current output cannot be simultaneously considered. The digital current source is realized in a power electronic mode, and high-frequency signal output is realized by controlling the quick on-off of an electronic switch. Before output, the amplitude and frequency parameters of an output signal need to be manually controlled, and the amplitude and frequency control of the high-frequency current is realized through feedback regulation. The output signal parameters can not be adjusted in real time in the output process, and the playback output function of the field recording file or the simulation sampling file is not provided. At present, when a high-frequency current test of a direct-current electronic transformer is carried out, the high-frequency current test is generally realized by a control current type power amplifier, a frequency response test is carried out within a range of 3kHZ, a frequency aliasing test for a higher-frequency signal is lacked, and hidden dangers exist in the test content.
Therefore, it is necessary to develop a high-frequency test current source having a frequency output capability in a range of 10kHz to 50kHz in order to develop a study on the high-frequency transmission characteristics of the dc electronic transformer so as to perform frequency characteristic tests such as frequency response accuracy, filter cut-off frequency, and frequency aliasing effect of the dc electronic transformer.
Disclosure of Invention
The invention provides a high-frequency current source with waveform amplitude-frequency separation and real-time control, which has the frequency output capability in the range of 10 kHz-50 kHz and can be used for carrying out frequency characteristic tests of frequency response precision, filtering cut-off frequency, frequency aliasing effect and the like of a direct-current electronic transformer.
The application provides a high frequency current source of wave form amplitude-frequency separation real time control includes: the power PC, the FPGA module, the first digital-to-analog conversion module, the second digital-to-analog conversion module and the power electronic current generator;
the PowerPC is used for analyzing the imported original sampling data, analyzing the amplitude and frequency parameters of the signal, calculating a direct current amplitude control signal in a proportional relation with the amplitude of the sampling signal and an alternating current frequency control signal with the same frequency as the sampling signal, and inputting the direct current amplitude control signal and the alternating current frequency control signal to the FPGA module;
the FPGA module is used for finishing the coding output and sending time sequence control of the direct current amplitude control signal and the alternating current frequency control signal;
the first digital-to-analog conversion module is used for generating a direct-current voltage analog signal in a proportional relation with the amplitude of the sampling signal according to the direct-current amplitude control signal;
the second digital-to-analog conversion module is used for generating an alternating voltage analog signal with the same frequency as the sampling signal;
the power electronic type current generator is used for outputting a high-frequency current signal as a control signal of amplitude and frequency according to the received direct-current voltage analog signal and alternating-current voltage analog signal.
Preferably, the current source further comprises a frequency modulation module;
the frequency modulation module is connected between the second digital-to-analog conversion module and the power electronic current generator;
the frequency modulation module is used for converting the sinusoidal alternating voltage analog signals with the same frequency sent by the second digital-to-analog conversion module into corresponding alternating voltage analog signals with the same frequency of square waves.
Preferably, the PowerPC is specifically configured to:
extracting sampling data of each point from the imported original sampling data, restoring an actual sampling value according to the configuration parameters of the CFG file, and obtaining a sampling discrete signal;
carrying out spectrum analysis on the sampled discrete signal by adopting a fast Fourier transform algorithm to obtain an amplitude parameter and a frequency parameter of the sampled discrete signal;
and adjusting the amplitude parameter according to a preset proportion, outputting a direct current amplitude control signal in a proportional relation with the amplitude of the sampling signal, and generating an alternating current frequency control signal with the same frequency parameter.
Preferably, the actual sampling value is restored according to the CFG file configuration parameter by a first formula to obtain a sampling discrete signal;
the first formula is:
where S' is the actual sample, S is the original sample, CchnIs the channel magnification, OchnFor channel offset, k is the sample ratio.
Preferably, a second formula is used for performing spectrum analysis on the sampled discrete signal by using a fast fourier transform algorithm to obtain a frequency parameter of the sampled discrete signal;
the second formula is:
wherein f isnIs the nth signal frequency, fsIs the sampling frequency, N is the signal serial number, and N is the number of sampling points.
Preferably, a third formula is used for performing spectrum analysis on the sampled discrete signal by using a fast fourier transform algorithm to obtain a frequency parameter of the sampled discrete signal;
the third formula is:
wherein A isnFor the nth time the signal amplitude is,
the modulus of the negative value is calculated for the nth FFT, N being the number of sampling points.
Preferably, the first digital-to-analog conversion module adopts binary complement coding, and the relationship between the output voltage and the input digital signal is as follows:
wherein, VoutFor the output voltage, D is the decimal equivalent of the code loaded by the DAC, VrefIs the reference voltage.
Preferably, the frequency modulation module comprises a low-pass filter circuit and a square wave modulation circuit;
the low-pass filter circuit is specifically a second-order active low-pass filter circuit;
the square wave modulation circuit is specifically an in-phase proportional operation circuit.
Preferably, the circuit of the frequency modulation module includes: the circuit comprises an operational amplifier, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a capacitor CA10, a capacitor CA11, a capacitor CA12 and a diode;
a first end of the resistor R11 is connected with an input end of the frequency modulation module, and a second end of the resistor R11 is connected with a first end of the resistor R12;
the second end of the resistor R12 is connected with the third end of the operational amplifier;
the first end of the resistor R13 is grounded, the second end of the resistor R13 is connected with the first end of the resistor R14, and the second end of the resistor R14 is connected with the output end of the frequency modulation module;
a first end of the capacitor CA10 is connected with a second end of the resistor R11, and a second end of the capacitor CA10 is grounded;
a first end of the capacitor CA11 is connected with a second end of the resistor R11, and a second end of the capacitor CA11 is connected with an output end of the frequency modulation module;
a first end of the capacitor CA12 is connected with a second end of the resistor R12, and a second end of the capacitor CA12 is grounded;
one end of the diode is connected with the input end of the frequency modulation module, and the other end of the diode is grounded;
the second end of the operational amplifier is connected with the second end of the resistor R13, the fourth end of the operational amplifier is connected with a-12V power supply, the sixth end of the operational amplifier is connected with the output end of the frequency modulation module, and the seventh end of the operational amplifier is connected with a +12V power supply.
Preferably, the power electronic current generator is specifically configured to obtain an amplitude of an input dc small voltage signal, and proportionally adjust an amplitude of a self output large current signal; and acquiring a square wave small voltage signal, controlling the on-off of an internal power electronic device, and changing the frequency of an output signal.
According to the technical scheme, the invention has the following advantages:
the application provides a high frequency current source of wave form amplitude-frequency separation real time control includes: the power PC, the FPGA module, the first digital-to-analog conversion module, the second digital-to-analog conversion module and the power electronic current generator; the PowerPC is used for analyzing the imported original sampling data, analyzing the amplitude and frequency parameters of the signal, calculating a direct current amplitude control signal in a proportional relation with the amplitude of the sampling signal and an alternating current frequency control signal with the same frequency as the sampling signal, and inputting the direct current amplitude control signal and the alternating current frequency control signal to the FPGA module; the FPGA module is used for finishing the coding output and sending time sequence control of the direct current amplitude control signal and the alternating current frequency control signal; the first digital-to-analog conversion module is used for generating a direct-current voltage analog signal in a proportional relation with the amplitude of the sampling signal according to the direct-current amplitude control signal; the second digital-to-analog conversion module is used for generating an alternating voltage analog signal with the same frequency as the sampling signal; the power electronic type current generator is used for outputting a high-frequency current signal as a control signal of amplitude and frequency according to the received direct-current voltage analog signal and alternating-current voltage analog signal. The frequency response precision, the filtering cut-off frequency, the frequency aliasing and other frequency characteristic tests of the direct-current electronic transformer can be developed by combining the conventional analog power amplifier testing method and the good high-frequency output characteristic of the digital current source; the rear end output adopts an electronic power current generator, so that the problem of high frequency limitation of output signals of the traditional analog power amplifier is solved in principle, and the power amplifier has the signal output capacity within the range of 50 kHz; the amplitude and frequency separation control technology is adopted, the parameters of output signals do not need to be manually set before output, and the application scenes and the test item types of the digital current source are increased; the high-frequency current source has the capabilities of importing a sampling file and analyzing a signal spectrum, can automatically realize amplitude and frequency matching of an output signal and an original sampling file, and improves the use flexibility of the high-frequency current source on the premise of ensuring the output precision.
Drawings
In order to illustrate the embodiments of the invention more clearly, the drawings that are needed for describing the embodiments or the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained by those skilled in the art without inventive exercise.
FIG. 1 is a schematic diagram illustrating an analog current source in the prior art;
FIG. 2 is a diagram illustrating a digital current source according to the prior art;
FIG. 3 is a schematic diagram of an embodiment of a high-frequency current source for real-time control of amplitude-frequency separation of waveforms provided by the present application;
FIG. 4 is a schematic diagram of another embodiment of a high-frequency current source for real-time control of amplitude-frequency separation of waveforms provided by the present application;
FIG. 5 is a schematic diagram of a high-frequency current source with waveform amplitude-frequency separation real-time control according to the present application;
fig. 6 is a circuit diagram of a frequency modulation module in a high-frequency current source for real-time control of waveform amplitude-frequency separation provided by the present application.
Detailed Description
The invention provides a high-frequency current source with waveform amplitude-frequency separation and real-time control, which has the frequency output capability in the range of 10 kHz-50 kHz and can be used for carrying out frequency characteristic tests of frequency response precision, filtering cut-off frequency, frequency aliasing effect and the like of a direct-current electronic transformer.
In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 3, an embodiment of a high-frequency current source for real-time waveform amplitude-frequency separation control according to the present invention includes: the power PC, the FPGA module, the first digital-to-analog conversion module, the second digital-to-analog conversion module and the power electronic current generator;
the PowerPC is used for analyzing the imported original sampling data, analyzing the amplitude and frequency parameters of the signals, calculating a direct current amplitude control signal in a proportional relation with the amplitude of the sampling signals and an alternating current frequency control signal with the same frequency as the sampling signals, and inputting the direct current amplitude control signal and the alternating current frequency control signal to the FPGA module;
the FPGA module is used for finishing the coding output and sending time sequence control of the direct current amplitude control signal and the alternating current frequency control signal;
the first digital-to-analog conversion module is used for generating a direct-current voltage analog signal in a proportional relation with the amplitude of the sampling signal according to the direct-current amplitude control signal;
the second digital-to-analog conversion module is used for generating an alternating voltage analog signal with the same frequency as the sampling signal;
the power electronic type current generator is used for outputting a high-frequency current signal according to the received direct-current voltage analog signal and alternating-current voltage analog signal as control signals of amplitude and frequency.
In this embodiment, the second digital-to-analog conversion module can be used in combination with the electronic power current generator, that is, the second digital-to-analog conversion module can emit a square wave signal or the electronic power current generator can process a sine signal.
The frequency response precision, the filtering cut-off frequency, the frequency aliasing and other frequency characteristic tests of the direct-current electronic transformer can be developed by combining the conventional analog power amplifier testing method and the good high-frequency output characteristic of the digital current source; the rear end output adopts an electronic power current generator, so that the problem of high frequency limitation of output signals of the traditional analog power amplifier is solved in principle, and the power amplifier has the signal output capacity within the range of 50 kHz; the amplitude and frequency separation control technology is adopted, the parameters of output signals do not need to be manually set before output, and the application scenes and the test item types of the digital current source are increased; the high-frequency current source has the capabilities of importing a sampling file and analyzing a signal spectrum, can automatically realize amplitude and frequency matching of an output signal and an original sampling file, and improves the use flexibility of the high-frequency current source on the premise of ensuring the output precision.
The above is a detailed description of an embodiment of a high-frequency current source for real-time waveform amplitude-frequency separation control provided by the present application, and the following is a detailed description of another embodiment of a high-frequency current source for real-time waveform amplitude-frequency separation control provided by the present application.
Referring to fig. 4, another embodiment of a high-frequency current source with waveform amplitude-frequency separation real-time control provided by the present application includes: the power PC, the FPGA module, the first digital-to-analog conversion module, the second digital-to-analog conversion module and the power electronic current generator;
the PowerPC is used for analyzing the imported original sampling data, analyzing the amplitude and frequency parameters of the signals, calculating a direct current amplitude control signal in a proportional relation with the amplitude of the sampling signals and an alternating current frequency control signal with the same frequency as the sampling signals, and inputting the direct current amplitude control signal and the alternating current frequency control signal to the FPGA module;
the FPGA module is used for finishing the coding output of the direct current amplitude control signal and the alternating current frequency control signal and sending time sequence control (used for controlling the first digital-to-analog conversion module and the second digital-to-analog conversion module);
the first digital-to-analog conversion module is used for generating a direct-current voltage analog signal in a proportional relation with the amplitude of the sampling signal according to the direct-current amplitude control signal;
the second digital-to-analog conversion module is used for generating an alternating voltage analog signal with the same frequency as the sampling signal;
the power electronic type current generator is used for outputting a high-frequency current signal according to the received direct-current voltage analog signal and alternating-current voltage analog signal as control signals of amplitude and frequency.
The current source further comprises a frequency modulation module;
the frequency modulation module is connected between the second digital-to-analog conversion module and the power electronic current generator;
the frequency modulation module is used for converting the sinusoidal alternating voltage analog signals with the same frequency sent by the second digital-to-analog conversion module into corresponding alternating voltage analog signals with the same frequency square waves.
Referring to fig. 3, a dashed line frame is a high-frequency current source device with waveform amplitude-frequency separation and real-time control, which is composed of a PowerPC, an FPGA, a digital-to-analog conversion module, a frequency modulation module, and an electronic power current generator. Analyzing the imported original sampling data by the PowerPC, analyzing the amplitude and frequency parameters of the signal, calculating the amplitude scaling-down signal and the instantaneous value of the same-frequency small signal, and inputting the instantaneous values into the FPGA module; the FPGA module controls the digital-to-analog conversion module according to the interactive output signal parameters to respectively generate a direct current small-voltage analog signal which is reduced according to the original sampling amplitude proportion and an alternating current sine small-voltage analog signal which has the same frequency as the original sampling amplitude proportion; the digital-to-analog conversion module is responsible for converting the digital quantity signal output by the FPGA into an analog quantity signal; the frequency modulation module is responsible for converting the same-frequency alternating current sine small-voltage analog quantity into a corresponding square wave small-voltage analog quantity; the power electronic current generator receives the direct current analog quantity and the square wave analog quantity control signal and outputs a final high-frequency large current signal.
PowerPC is specifically used for:
extracting sampling data of each point from the imported original sampling data, restoring an actual sampling value according to the configuration parameters of the CFG file, and obtaining a sampling discrete signal;
carrying out spectrum analysis on the sampled discrete signal by adopting a fast Fourier transform algorithm to obtain an amplitude parameter and a frequency parameter of the sampled discrete signal;
and adjusting the amplitude parameter according to a preset proportion, outputting a direct current amplitude control signal in a proportional relation with the amplitude of the sampling signal, and generating an alternating current frequency control signal with the same frequency parameter.
Specifically, restoring an actual sampling value according to the configuration parameters of the CFG file through a first formula to obtain a sampling discrete signal;
the first formula is:
where S' is the actual sample, S is the original sample, CchnIs the channel magnification, OchnFor channel offset, k is the sample ratio.
Specifically, a second formula is adopted to perform frequency spectrum analysis on the sampling discrete signal by adopting a fast Fourier transform algorithm to obtain the frequency parameter of the sampling discrete signal;
the second formula is:
wherein f isnIs the nth signal frequency, fsIs the sampling frequency, N is the signal serial number, and N is the number of sampling points.
Specifically, a third formula is adopted to perform frequency spectrum analysis on the sampling discrete signal by adopting a fast Fourier transform algorithm to obtain the frequency parameter of the sampling discrete signal;
the third formula is:
wherein A isnFor the nth time the signal amplitude is,
the modulus of the negative value is calculated for the nth FFT, N being the number of sampling points.
The PowerPC completes the work of system initialization and self-checking, sampling data import, signal spectrum analysis, data preprocessing and the like. Decomposing the amplitude and frequency parameters of the signal according to the imported sampling data file, and generating a direct current amplitude control signal in a proportional relation with the amplitude of the sampling signal and an alternating current frequency control signal with the same frequency as the sampling signal by calculation to realize the preprocessing work of the control data related to the operation of the current source.
PowerPC employs a Freescale MPC8247 embedded microprocessor belonging to the PowerQUICC II family, comprising a kernel based on PowerPC MPC603e, and a communication processing kernel CPM. The method has strong processing capacity and high integration level, reduces the composition overhead of the system, simplifies the design of a circuit board and reduces the power consumption.
The FPGA completes the coding output and sending time sequence control of the direct current amplitude control signal and the alternating current frequency control signal under the control of the high-precision clock module, reproduces the amplitude and frequency information of the original sampling file by matching with the PowerPC module, and drives the digital-to-analog conversion module to output a corresponding small-voltage analog quantity signal.
The FPGA processor adopts Xilinx Spartan3 series products XC3S1500, comprises 150 ten thousand system gates, 32 special multipliers and 4 digital clock management modules, and has rich logic resources and high running speed.
The digital-to-analog conversion module comprises a first digital-to-analog conversion module and a second digital-to-analog conversion module, and is used for receiving the digital driving signal of the FPGA, converting the digital driving signal into a corresponding small-voltage analog signal and realizing a control signal interaction interface of the digital control loop and the analog output loop.
The digital-to-analog conversion module is realized by a special DAC analog-to-digital conversion chip. A16-bit high-precision voltage output type DAC 5764 is adopted. The AD5764 has the advantages of synchronous 4 channels, 16-bit lossless code resolution, integral non-linearity (INL) error of +/-1 LSB, sampling rate of up to 1.26M and the like. The digital part is expressed in a complementary mode, and the analog quantity output voltage ranges from-10 v to +10 v.
The first digital-to-analog conversion module adopts binary complement code, and the relation between the output voltage and the input digital signal is as follows:
wherein, VoutFor the output voltage, D is the decimal equivalent of the code loaded by the DAC, VrefIs the reference voltage.
The principles of the present application will be explained below:
referring to fig. 5, an original sample data file is imported in step one, then fourier analysis is performed on the imported data in step two to obtain amplitude information and frequency information of a sample signal, and in step three, the amplitude and frequency of a current source are controlled by a small voltage. And finally, outputting a high-frequency large-current signal consistent with the original sampling file data through the step four.
The method comprises the following steps: sample file import
The method comprises the steps of importing a high-frequency current sampling file generated by field wave recording or modeling simulation, checking the reasonability of the file, reading configuration information and sampling channel parameter information of the sampling file, analyzing a sampling data file and calculating an actual sampling value of a sampling channel. The sampling file adopts a common format of COMTEADE power system transient data, and comprises a CFG configuration file in an ASCII format and a DAT data file in a binary or ASCII format.
Firstly, analyzing a CFG configuration file line by line, determining a data boundary by taking a byte 0x2c as a data separator, and acquiring a sampling channel parameter, a sampling frequency and a total sampling point number. Then, a DAT data file is configured and analyzed according to the sampling file, if the data file is stored according to a binary format, after the storage space occupied by each point of sampling data is determined, the address offset of each point of data is obtained, and each point of sampling data is read; if the data file is stored according to the ASCII format, the address offset of the first byte of each line in the file is determined according to the line-feed character, and the sampling data of each point is obtained according to the sampling sequence number, the sampling time and the fixed format of the sampling value.
After sampling data of each point is obtained, restoring an actual sampling value according to the configuration parameters of the CFG file, wherein the actual sampling value is as follows:
wherein: s' is the actual sample, S is the original sample, CchnIs the channel magnification, OchnIs the channel offset, k is the sampling transformation ratio;
step two: signal analysis and calculation
And (3) carrying out spectrum analysis on the sampled discrete signal obtained in the step one by adopting a Fast Fourier Transform (FFT) algorithm to obtain the amplitude and the frequency parameter of the sampled discrete signal. Obtaining an N-point complex value through FFT calculation, the nth signal frequency contained in the original signal is:
wherein: f. ofnIs the nth signal frequency, fsIs sampling frequency, N is signal serial number, and N is sampling point number;
the amplitude of the nth signal is:
wherein: a. thenFor the nth time the signal amplitude is,
calculating the modulus of a negative value for the nth FFT, wherein N is the number of sampling points;
after FFT calculation, A is calculatednScaling down to obtain the amplitude A' of the small-voltage direct-current signal, and controlling the amplitude of the output signal of the current source in step three; simultaneous virtual and fnCommon-frequency small-voltage alternating current sinusoidal signal and calculating instantaneous value sequence S thereofnAnd waiting for the step of controlling the frequency of the output signal of the current source.
Step three: frequency-amplitude separation control
And step two, calculating the DC signal data with the original sampling amplitude reduced in proportion, wherein the amplitude is A', and generating small-voltage DC analog quantity signals with the same amplitude through digital-to-analog conversion so as to control the amplitude of the output signal of the rear-end current source.
The binary complement coding is adopted, and the relationship between the output voltage and the digital signal is as follows:
wherein: voutFor the output voltage, D is the decimal equivalent of the code loaded by the DAC, VrefIs a reference voltage;
step two, calculating the original sampling same-frequency small-voltage alternating current sinusoidal signal data with the frequency fnProducing the same frequency of bits by digital-to-analog conversionThe voltage alternating current analog quantity signal is subjected to frequency modulation processing and then converted into a small voltage square wave analog quantity signal with the same frequency, and the frequency of a rear-end current source output signal can be controlled.
The frequency modulation process is based on an in-phase proportional operation circuit, and the proportion of a feedback resistor is adjusted by utilizing the transmission characteristic of data in a saturation area, so that an input sinusoidal signal is quickly saturated, and a square wave signal with the same frequency is output in real time.
Step four: high frequency current output
And synchronously inputting the DC small voltage signal and the square wave small voltage signal generated in the step three into the current generator, and ensuring that the output delay error between two groups of analog quantity signals is less than 1us through output time control and transmission delay compensation to realize amplitude-frequency separation control of the current generator.
The power electronic current generator acquires the amplitude of an input direct current small voltage signal and adjusts the amplitude of a self output large current signal according to the proportion; and acquiring a square wave small voltage signal, controlling the on-off of an internal power electronic device, and changing the frequency of an output signal. The output current characteristic of the current generator can be changed in real time by adjusting and controlling the amplitude and the frequency of the small voltage signal.
Through the steps from the first step to the fourth step, the amplitude information and the frequency information of the original sampling data are separated and respectively converted into the associated small voltage control signals, the output of the power electronic current generator is synchronously driven, and the automatic real-time control of the digital current source is realized.
Referring to fig. 6, the frequency modulation module includes a low-pass filter circuit and a square wave modulation circuit;
the low-pass filter circuit is specifically a second-order active low-pass filter circuit;
the square wave modulation circuit is specifically an in-phase proportional operation circuit.
The circuit of the frequency modulation module comprises: the circuit comprises an operational amplifier, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a capacitor CA10, a capacitor CA11, a capacitor CA12 and a diode;
the first end of the resistor R11 is connected with the input end of the frequency modulation module, and the second end of the resistor R11 is connected with the first end of the resistor R12;
the second end of the resistor R12 is connected with the third end of the operational amplifier;
the first end of the resistor R13 is grounded, the second end of the resistor R13 is connected with the first end of the resistor R14, and the second end of the resistor R14 is connected with the output end of the frequency modulation module;
the first end of the capacitor CA10 is connected with the second end of the resistor R11, and the second end of the capacitor CA10 is grounded;
the first end of the capacitor CA11 is connected with the second end of the resistor R11, and the second end of the capacitor CA11 is connected with the output end of the frequency modulation module;
the first end of the capacitor CA12 is connected with the second end of the resistor R12, and the second end of the capacitor CA12 is grounded;
one end of the diode is connected with the input end of the frequency modulation module, and the other end of the diode is grounded;
the second end of the operational amplifier is connected with the second end of the resistor R13, the fourth end of the operational amplifier is connected with a-12V power supply, the sixth end of the operational amplifier is connected with the output end of the frequency modulation module, and the seventh end of the operational amplifier is connected with a +12V power supply.
The frequency modulation module filters high-frequency interference in the original sampling signal, extracts effective data information, generates a square wave modulation voltage signal with the same frequency as the original sinusoidal sampling, and realizes the output frequency control of the rear-end current generator.
The low-pass filter circuit adopts a second-order active low-pass filter circuit, the parameters are adjustable, the cut-off frequency of the output signal of the filter circuit can be adjusted by changing the sizes of the resistors R11 and R12 and the capacitors C11 and C12, and the balance between the interference signal filtering capacity and the signal processing delay is obtained.
The square wave modulation loop adopts an in-phase proportional operation circuit, the proportional relation between an output signal and an input signal can be changed by adjusting the resistance values of the resistors R13 and R14, and the original input sinusoidal signal is subjected to common-frequency squaring by utilizing the working characteristic of a saturation region of the operational amplifier so as to control the frequency of the output signal of the current generator.
The power electronic type current generator is specifically used for acquiring the amplitude of an input direct current small voltage signal and proportionally adjusting the amplitude of a self output large current signal; and acquiring a square wave small voltage signal, controlling the on-off of an internal power electronic device, and changing the frequency of an output signal.
The high-current generator based on the power electronic principle is adopted, and the current generator is synchronously driven to output in real time through the direct-current small-voltage amplitude control signal and the square-wave small-voltage frequency control signal, so that a high-frequency high-current test analog quantity signal is generated.
The current generator adopts a power electronic high-frequency current generator, the output current is 0 to 100A, the frequency range is 10KHZ to 50KHZ, the frequency accuracy is +/-50 ppm, the frequency temperature drifts +/-5 ppm/DEG C, the distortion degree of the output current is better than 0.5 percent, and the stability of the output current is better than 0.02 percent/1 min.
The application has the following technical characteristics:
(1) controlling the amplitude and frequency parameters of output current based on an amplitude-frequency separation technology, controlling the output amplitude of a current source through a direct current voltage signal which is reduced according to the sampling amplitude proportion, and controlling the output frequency of the current source through a square wave voltage signal which is the same as the sampling frequency;
(2) the method supports the import control of a sampling file, can automatically analyze the amplitude-frequency characteristics of original sampling, and controls the analog quantity output of a high-frequency heavy current source in real time;
(3) the digital-to-analog conversion process of the control signal is driven by the FPGA, so that the digital-to-analog conversion process has good time sequence control and concurrent processing capabilities, the synchronism of an amplitude control signal and a frequency control signal is ensured, and the accurate adjustment of the output characteristic of a current source can be realized;
(4) the same-frequency square-wave modulation of the high-frequency sinusoidal signal is realized by utilizing the saturation region working characteristic of the in-phase proportional operation circuit and through a complete analog circuit.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. A high frequency current source with real-time control of waveform amplitude-frequency separation, comprising: the power PC, the FPGA module, the first digital-to-analog conversion module, the second digital-to-analog conversion module, the power electronic current generator and the frequency modulation module;
the PowerPC is used for analyzing the imported original sampling data, analyzing the amplitude and frequency parameters of the signals, calculating a direct current amplitude control signal in a proportional relation with the amplitude of the sampling signals and an alternating current frequency control signal with the same frequency as the sampling signals, and inputting the direct current amplitude control signal and the alternating current frequency control signal to the FPGA module;
the FPGA module is used for finishing the coding output and sending time sequence control of the direct current amplitude control signal and the alternating current frequency control signal;
the first digital-to-analog conversion module is used for generating a direct-current voltage analog signal in a proportional relation with the amplitude of the sampling signal according to the direct-current amplitude control signal;
the second digital-to-analog conversion module is used for generating an alternating voltage analog signal with the same frequency as the sampling signal;
the power electronic current generator is used for outputting a high-frequency current signal as a control signal of amplitude and frequency according to the received direct-current voltage analog signal and alternating-current voltage analog signal;
the frequency modulation module comprises a low-pass filter circuit and a square wave modulation circuit;
the low-pass filter circuit is specifically a second-order active low-pass filter circuit;
the square wave modulation circuit is specifically an in-phase proportional operation circuit;
the frequency modulation module is connected between the second digital-to-analog conversion module and the power electronic current generator;
the frequency modulation module is used for converting the sinusoidal alternating voltage analog signals with the same frequency sent by the second digital-to-analog conversion module into corresponding alternating voltage analog signals with the same frequency of square waves;
the circuit of the frequency modulation module comprises: the circuit comprises an operational amplifier, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a capacitor CA10, a capacitor CA11, a capacitor CA12 and a diode;
a first end of the resistor R11 is connected with an input end of the frequency modulation module, and a second end of the resistor R11 is connected with a first end of the resistor R12;
the second end of the resistor R12 is connected with the third end of the operational amplifier;
the first end of the resistor R13 is grounded, the second end of the resistor R13 is connected with the first end of the resistor R14, and the second end of the resistor R14 is connected with the output end of the frequency modulation module;
a first end of the capacitor CA10 is connected with a second end of the resistor R11, and a second end of the capacitor CA10 is grounded;
a first end of the capacitor CA11 is connected with a second end of the resistor R11, and a second end of the capacitor CA11 is connected with an output end of the frequency modulation module;
a first end of the capacitor CA12 is connected with a second end of the resistor R12, and a second end of the capacitor CA12 is grounded;
one end of the diode is connected with the input end of the frequency modulation module, and the other end of the diode is grounded;
the second end of the operational amplifier is connected with the second end of the resistor R13, the fourth end of the operational amplifier is connected with a-12V power supply, the sixth end of the operational amplifier is connected with the output end of the frequency modulation module, and the seventh end of the operational amplifier is connected with a +12V power supply.
2. The waveform amplitude-frequency separation real-time control high-frequency current source as claimed in claim 1, wherein said PowerPC is specifically configured to:
extracting sampling data of each point from the imported original sampling data, restoring an actual sampling value according to the configuration parameters of the CFG file, and obtaining a sampling discrete signal;
carrying out spectrum analysis on the sampled discrete signal by adopting a fast Fourier transform algorithm to obtain an amplitude parameter and a frequency parameter of the sampled discrete signal;
and adjusting the amplitude parameter according to a preset proportion, outputting a direct current amplitude control signal in a proportional relation with the amplitude of the sampling signal, and generating an alternating current frequency control signal with the same frequency parameter.
3. The high-frequency current source for waveform amplitude-frequency separation real-time control according to claim 2, wherein a sampling discrete signal is obtained by restoring an actual sampling value according to a CFG file configuration parameter by a first formula;
the first formula is:
where S' is the actual sample, S is the original sample, CchnIs the channel magnification, OchnFor channel offset, k is the sample ratio.
4. The high-frequency current source for real-time control of waveform amplitude-frequency separation according to claim 2, wherein a second formula is used to perform spectrum analysis on the sampled discrete signal by using a fast fourier transform algorithm to obtain frequency parameters of the sampled discrete signal;
the second formula is:
wherein f isnIs the nth signal frequency, fsIs the sampling frequency, N is the signal serial number, and N is the number of sampling points.
5. The high-frequency current source for real-time control of waveform amplitude-frequency separation according to claim 2, wherein a third formula is used to perform spectrum analysis on the sampled discrete signal by using a fast fourier transform algorithm to obtain an amplitude parameter of the sampled discrete signal;
the third formula is:
wherein A isnFor the nth time the signal amplitude is,
the modulus of the negative value is calculated for the nth FFT, N being the number of sampling points.
6. The waveform amplitude-frequency separation real-time control high-frequency current source of claim 1, wherein the first digital-to-analog conversion module adopts binary complement coding, and the relationship between the output voltage and the input digital signal is as follows:
wherein, VoutFor the output voltage, D is the decimal equivalent of the code loaded by the DAC, VrefIs the reference voltage.
7. The high-frequency current source for real-time control of amplitude-frequency separation of waveform according to claim 1,
the power electronic type current generator is specifically used for acquiring the amplitude of an input direct current small voltage signal and proportionally adjusting the amplitude of a self output large current signal; and acquiring a square wave small voltage signal, controlling the on-off of an internal power electronic device, and changing the frequency of an output signal.
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| CN113468837B (en) * | 2021-05-10 | 2023-11-03 | 浙江大学 | Method and system for estimating current of chip power supply network bump |
| CN113960364A (en) * | 2021-09-30 | 2022-01-21 | 陕西航空电气有限责任公司 | Frequency determination method and device suitable for wide-frequency-conversion alternating-current power generation system |
| CN114221527B (en) * | 2022-02-22 | 2022-05-20 | 深圳市深澳视觉科技有限公司 | Alternating current-direct current energy conversion control circuit and high-frequency medical equipment |
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| CN102525456A (en) * | 2012-01-11 | 2012-07-04 | 中国人民解放军国防科学技术大学 | Voltage control current source for electrical impedance tomography |
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