1. A wide frequency single phase power source based on DDS fitting comprising: the device comprises a human-computer interaction module, a DSP controller module, a DDS phase frequency control module, a digital-to-analog conversion module and a power amplifier module; the output end of the human-computer interaction module is connected with the input end of the DSP controller module; the output end of the DSP controller module is connected with the input end of the DDS phase frequency control module; the output end of the DDS phase frequency control module is connected with the input end of the digital-to-analog conversion module; the output end of the digital-analog module is connected with the input end of the power amplification module; and the output end of the power amplification module outputs current and voltage.

2. The DDS fitting-based wide-frequency single-phase power source of claim 1, wherein the DSP controller module comprises a communication module, a gear control logic unit, a signal generator module and a protection unit; the input end of the communication module is connected with the output end of the human-computer interaction module; the output end of the communication module is connected with the input end of the gear control logic unit, the input end of the DDS phase frequency control module and the input end of the protection unit; the output end of the DDS phase frequency control module is connected with the input end of the digital-to-analog conversion module; the output end of the signal generator module is connected with the input end of the DDS phase frequency control module.

3. The DDS fitting based wide-frequency single-phase power source of claim 2, wherein the signal generator module comprises a communication interface, a waveform fitting algorithm module, a waveform data buffer module, a DMA controller, a waveform DAC fitting digital signal module, a magnitude control logic module, a magnitude DAC fitting digital signal module; the output end of the communication interface is connected with the input ends of the waveform fitting algorithm module and the amplitude control logic module; the output end of the waveform fitting algorithm module outputs waveform data to the input end of the waveform data buffer module; the output end of the waveform data buffer module is connected with the input end of the DMA controller; the output end of the DMA controller is connected with the input end of the waveform DAC fitting digital signal module; the output end of the amplitude control logic module is connected with the input end of the amplitude DAC fitting digital signal module; the output end of the amplitude DAC fitting digital signal module and the output end of the waveform DAC fitting digital signal module are connected with the input end of the DDS phase frequency control module.

4. The DDS fitting-based wide-frequency single-phase power source of claim 3, wherein the digital-to-analog conversion module is specifically a dual DA conversion module, and the dual DA conversion module has one path of DA control signal amplitude and one path of DA control signal waveform; and the DDS phase frequency control module is used for converting the digital signal output by the DDS phase frequency control module into an analog signal and outputting the analog signal to the power amplification module.

5. The DDS fitting-based wide-frequency single-phase power source of claim 4, wherein the power amplifier module comprises a power amplifier circuit and a transformer; the input end of the power amplifier circuit is connected with the output end of the DDS phase frequency control module; the output end of the power amplifier circuit is connected with the input end of the transformer.

Background

With the development of the functions and technologies of the new generation of intelligent electric energy meters, the intelligent electric energy meters and the detection standards thereof are changed correspondingly. Compared with the existing detection, the intelligent electric energy meter detection method based on the new standard provides higher requirements. The current GB/T17215 series standards cannot meet the technical requirements of future-oriented intelligent electric energy meters. The current standards comprise GB/T17215.211-2006 general requirements, test and test conditions for AC measuring equipment part 11, GB/T17215.321-2008 special requirements for class 1 and class 2 static active electric energy meters and GB/T17215.322-2008 special requirements for class 0.2S and class 0.5S static active electric energy meters. According to the international suggestion of R46 active electric energy meter and the new requirements of the Chinese electric energy meter under the new situation, a new standard submission is generated: GB/T17215.211-202X "general requirements for Electrical measuring Apparatus (AC), tests and test conditions section 11: measuring equipment and GB/T17215.321-202X Electrical measuring Equipment (AC) Special requirements section 21: static active electric energy meters (class A, class B, class C, class D and class E). The new standard increases the software requirements: the technical characteristics and the management requirements of the electric energy meter in China are combined to put forward software requirements on the electric energy meter, and a verification method is provided. Metering and technical requirements are added and modified: the method is characterized in that spike wave and square wave test items are added, higher harmonic tests, no-load tests (shunt running tests) and the like are added, the test items are added to improve the performance of the intelligent electric energy meter, and meanwhile, the requirements for detection equipment are also increased.

The traditional single-phase power source can only output 2-22 and 2-32 harmonics generally, and the output precision is ensured by adjusting the amplitude and the phase of the output through back extraction based on SPWM modulation output; for the SPWM modulation output scheme, the output frequency is limited by the SPWM carrier frequency, the frequency of a common carrier is dozens of KHz at present, and the carrier frequency is difficult to be improved due to the influence of the switching rate, the later-stage LC filter circuit and the loop stability, so that higher harmonics are difficult to output, and meanwhile, the output stability is poor and is more than one order of magnitude worse than that of a linear power amplifier; meanwhile, the number of waveform fitting points of the existing power source is small, the signal generation is generally a mode of directly generating an embedded CPU + high-speed DA, and the main frequency of the embedded CPU is generally less than 72MHz, so that the number of fitting wave points per week of the general power frequency is not more than 3600, the distortion of high-frequency harmonic waves is large, the accuracy of the harmonic waves is poor, and the stability of the harmonic waves is poor.

The existing detection equipment can not meet the detection requirements of a new generation of intelligent electric energy meter, and particularly the function of the existing power source can not meet the test requirements added in the new detection standard.

Therefore, it is necessary to develop a single-phase power source for wide-frequency IR46 detection suitable for the detection of the new-generation intelligent electric energy meter, and to improve the detection capability of the single-phase power source to the electric energy meter with the IR46 function to be detected.

Disclosure of Invention

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to determine the key or critical elements of the present invention, nor is it intended to limit the scope of the present invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

The invention provides a wide-frequency single-phase power source based on DDS fitting, which comprises: the device comprises a human-computer interaction module, a DSP controller module, a DDS phase frequency control module, a digital-to-analog conversion module and a power amplifier module; the output end of the human-computer interaction module is connected with the input end of the DSP controller module; the output end of the DSP controller module is connected with the input end of the DDS phase frequency control module; the output end of the DDS phase frequency control module is connected with the input end of the digital-to-analog conversion module; the output end of the digital-analog module is connected with the input end of the power amplification module; and the output end of the power amplification module outputs current and voltage.

Preferably, the DSP controller module comprises a communication module, a gear control logic unit, a signal generator module and a protection unit; the input end of the communication module is connected with the output end of the human-computer interaction module; the output end of the communication module is connected with the input end of the gear control logic unit, the input end of the DDS phase frequency control module and the input end of the protection unit; the output end of the DDS phase frequency control module is connected with the input end of the digital-to-analog conversion module; the output end of the signal generator module is connected with the input end of the DDS phase frequency control module.

Preferably, the signal generator module comprises a communication interface, a waveform fitting algorithm module, a waveform data buffer module, a DMA controller, a waveform DAC fitting digital signal module, an amplitude control logic module, and an amplitude DAC fitting digital signal module; the output end of the communication interface is connected with the input ends of the waveform fitting algorithm module and the amplitude control logic module; the output end of the waveform fitting algorithm module outputs waveform data to the input end of the waveform data buffer module; the output end of the waveform data buffer module is connected with the input end of the DMA controller; the output end of the DMA controller is connected with the input end of the waveform DAC fitting digital signal module; the output end of the amplitude control logic module is connected with the input end of the amplitude DAC fitting digital signal module; the output end of the amplitude DAC fitting digital signal module and the output end of the waveform DAC fitting digital signal module are connected with the input end of the DDS phase frequency control module.

Preferably, the digital-to-analog conversion module is a dual DA conversion module, and the dual DA conversion module has an amplitude of a path of DA control signal and a waveform of a path of DA control signal; and the DDS phase frequency control module is used for converting the digital signal output by the DDS phase frequency control module into an analog signal and outputting the analog signal to the power amplification module.

Preferably, the power amplifier module comprises a power amplifier circuit and a transformer; the input end of the power amplifier circuit is connected with the output end of the DDS phase frequency control module; the output end of the power amplifier circuit is connected with the input end of the transformer.

The invention has the following beneficial effects: the invention adopts a DDS (direct digital synthesizer) fitting digital signal mode, can realize high accuracy of frequency and high resolution of phase, simultaneously combines a linear power amplifier technology, realizes the output of low distortion, high accuracy and high stability of high-frequency harmonic signals, and solves the problem that the existing detection equipment can not meet the detection requirement of a new generation of intelligent electric energy meter, especially the function of the existing standard power source can not realize the test requirement added in the new detection standard.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 is a schematic structural diagram according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a signal generator according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a connection structure of a signal generator according to an embodiment of the present invention;

fig. 4 is a schematic diagram of a connection structure of a DDS phase frequency control module according to an embodiment of the invention;

fig. 5 is a schematic diagram of a connection structure of a digital-to-analog conversion module according to an embodiment of the present invention;

fig. 6 is a schematic diagram illustrating a principle of a power amplifier module according to an embodiment of the present invention;

fig. 7 is a schematic diagram illustrating a protection principle of the power amplifier module according to the embodiment of the present invention.

Detailed Description

In order to make the technical solutions and advantages of the embodiments of the present application more apparent, the following further detailed description of the exemplary embodiments of the present application with reference to the accompanying drawings makes it clear that the described embodiments are only a part of the embodiments of the present application, and are not exhaustive of all embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

First embodiment, the present embodiment is described with reference to fig. 1 to 7, and a single-phase power source with wide frequency based on DDS fitting includes: the device comprises a human-computer interaction module, a DSP controller module, a DDS phase frequency control module, a digital-to-analog conversion module and a power amplifier module; the output end of the human-computer interaction module is connected with the input end of the DSP controller module; the output end of the DSP controller module is connected with the input end of the DDS phase frequency control module; the output end of the DDS phase frequency control module is connected with the input end of the digital-to-analog conversion module; the output end of the digital-analog module is connected with the input end of the power amplification module; and the output end of the power amplification module outputs current and voltage.

The DSP controller module comprises a communication module, a gear control logic unit, a signal generator module and a protection unit; the input end of the communication module is connected with the output end of the human-computer interaction module; the output end of the communication module is connected with the input end of the gear control logic unit, the input end of the DDS phase frequency control module and the input end of the protection unit; the output end of the DDS phase frequency control module is connected with the input end of the digital-to-analog conversion module; the output end of the signal generator module is connected with the input end of the DDS phase frequency control module.

The signal generator module comprises a communication interface, a waveform fitting algorithm module, a waveform data buffer module, a DMA controller, a waveform DAC fitting digital signal module, an amplitude control logic module and an amplitude DAC fitting digital signal module;

the output end of the communication interface is connected with the input end of the waveform fitting algorithm module; the waveform fitting algorithm module receives a control signal of the upper computer and fits and outputs waveform data such as sine waves, square waves, direct currents, triangular waves, harmonic superposition and the like;

an input of the amplitude control logic module; controlling the amplitude output of the dynamic signal waveform;

the output end of the waveform fitting algorithm module outputs waveform data to the input end of the waveform data buffer module;

the output end of the waveform data buffer module is connected with the input end of the DMA controller; the DMA controller reads data from the output waveform buffer area and outputs the data;

the output end of the DMA controller is connected with the input end of the waveform DAC fitting digital signal module; the waveform DAC receives waveform data transmitted by the DMA and controls the shape of an output waveform;

the output end of the amplitude control logic module is connected with the input end of the amplitude DAC fitting digital signal module; controlling the amplitude of the output waveform;

the output end of the amplitude DAC fitting digital signal module and the output end of the waveform DAC fitting digital signal module are connected with the input end of the DDS phase frequency control module.

The waveform fitting algorithm module controls the starting buffer, waveform data in the buffer is transmitted to the DA digital-to-analog conversion module through the SPORT port DMA controller of the DSP controller, namely, the output of a cycle signal is finished, and the DMA controller interrupts and repeats the output of the cycle signal to obtain a periodic continuous signal. The DMA controller transmission mode can ensure that the time delay between every two D/A conversion values is extremely small, the signal distortion is extremely small, the maximum time can reach 5 ten thousand points per cycle of 50Hz frequency signals, the high precision still can obtain the higher points per cycle when the signal frequency is higher, the stability and the precision of the signals are ensured, and the signal distortion is small.

And the gear control logic unit completes the gear control function according to a set value output by a user and the gear control logic value table. The gear control logic value table is a 16-system two-dimensional table of 6x15, wherein 6 represents that the system has 6 phases of output, and 15 represents that each phase can have 15 gears at most. During output, the current driving value is searched in the gear configuration table and is sent to the gear control logic unit to complete the gear control function.

Gear control logic value table

The protection unit is used for protecting the DSP controller, and mainly has voltage overload, current overload and system overheating. When the protection happens, the system stops outputting and gives out prompt tones, and sends alarm signals to a human-computer interface of the upper computer through the communication unit, so that a user is reminded.

The output end of the amplitude DAC fitting digital signal module and the output end of the waveform DAC fitting digital signal module are connected with the input end of the DDS phase frequency control module, the waveform DAC fitting digital signal module outputs digital waveform signals, accurate control over the phase and the frequency of the output digital waveform signals is achieved through the DDS phase frequency control module, the DDS phase frequency control module is connected with the double DA conversion module, digital signals after accurate adjustment of the DDS phase frequency control module output corresponding analog signals through the DA converter, and accurate fitting of the digital signals to the accurate occurrence of the analog signals is achieved.

The digital-to-analog conversion module is specifically a double DA conversion module, and one path of the double DA conversion module is the amplitude of a DA control signal and the waveform of the DA control signal; and the DDS phase frequency control module is used for converting the digital signal output by the DDS phase frequency control module into an analog signal and outputting the analog signal to the power amplification module.

Because the magnitude, the precision, the stability of the output current of the V/I conversion power amplifier module are in direct relation with the signal, the digital-to-analog conversion module adopts double DA to realize the output of the signal, the amplitude of one path of DA control signal and the waveform of one path of DA control signal are combined to concentrate the precision of two DA, so that the precision of the DA conversion of the signal is doubled compared with that of a single DA.

And the DDS phase frequency control module strictly and synchronously transmits the amplitude data and the waveform data to the amplitude DAC and the waveform DAC, the output of the amplitude DAC is used as the reference of the waveform DAC, and the waveform DAC outputs an analog quantity signal based on the amplitude DAC.

The ADC is basically under 16 bits, the ADI and TI have a few 18-bit models, the key of high-precision signal generation is that the DAC conversion technology is adopted besides the waveform fitting technology, analog quantity signals are finally needed to be used, digital waveform data are output by the DSP controller module, and therefore a bridge needs to be built between the digital quantity and the analog quantity, the bridge is the DAC converter, and the final output is directly influenced by the quality of the bridge. According to the technical scheme, the double DA signal generation technology can improve the number of the DA bits by a double DA cascade mode, the maximum number can be improved by one time, for example, 16-bit DAC, and the maximum 32-bit signal resolution can be provided by double DA cascade.

The power amplifier module comprises a power amplifier circuit and a transformer; the input end of the power amplifier circuit is connected with the output end of the DDS phase frequency control module; the output end of the power amplifier circuit is connected with the input end of the transformer.

The power amplifier module adopts high accuracy integrated power amplifier and MOS pipe structure to by dual power supply, adopt many pairs of MOS pipe geminate transistors of matching, can realize exchanging output drive back stage transformer and do heavy current output, maximum current exports 120A, and voltage output can reach 264V, and the output bandwidth is high, and the harmonic output can reach 50 times at most.

The power amplifier module has the advantages of simple circuit structure, strong output load capacity, high output precision and good stability by combining a double-loop negative feedback technology, and supports power frequency 2-50 harmonic superposition output.

The power amplification driving chip LME49830 is selected, the LME49830 has low noise, extremely high power supply rejection ratio, extremely low distortion degree and large power bandwidth, 56mA driving current and maximum 16V driving voltage, and almost all MOS can be driven. The LME49830 integrated circuit can support an output power of 1KW with a typical total harmonic distortion plus noise of only 7PPM at 1kHz frequency.

The precision and the accuracy of the amplifier are improved by adopting the precision resistor with the precision of one ten-thousandth and the temperature drift of only 1 ppm.

The power amplification module has the functions of overheating and overload warning. When the temperature on the power amplifier is too high, the current output can be cut off through the stop signal output. Under normal conditions, software limits the output current value and cannot output overload, but when a fault occurs, the output current is possibly overlarge, in order to protect the power amplifier circuit, the overload circuit is required to limit the current, and the current limiting circuit limits the current by limiting the driving voltage of the MOS tube.

In actual use, the power amplifier is often changed due to the measured load, so that the output overload is easily caused due to miswiring or load, and the overload condition of the voltage power amplifier mainly comprises the following steps: the load impedance is too small, the power exceeds the output capability of the power amplifier, and the output is short-circuited to the ground.

The most severe of these is the short circuit of the output to ground, because the high voltage impact is large, it is very easy to cause the power amplifier to burn out.

The overload of the current power amplifier mainly comprises the following steps:

(1) the input impedance of a current loop of the tested device is overlarge, so that the output capacity of the power amplifier is exceeded;

(2) the output is open.

For the current power amplifier, the two conditions do not threaten the safety of the power amplifier. Because the voltage of the output port of the current amplifier is limited (generally, the voltage of the port is only a few volts), the personal safety of a user cannot be threatened due to the open circuit. This is different from a current transformer, which is essentially a transformer, and due to the very high number of secondary windings (relative to the primary windings), it will become a step-up transformer with a very high voltage output if it is open-circuited, thus posing a great threat to human health. The current transformer is therefore strictly forbidden to be open.

The voltage overload protection of the power source adopts a current limiting mode, and the output is stopped quickly after the overcurrent is detected, so that the safety of the power amplifier is protected.

Specifically, referring to fig. 7, the voltage overload protection is implemented by a current limiting circuit formed by a resistor R9, a resistor R110 and a MOS transistor T6, when the output is overloaded, the current flowing through the resistor R9 will increase sharply and generate a voltage drop on the resistor R9, the voltage drop is applied to the base of the MOS transistor T6 to cause the transistor T6 to conduct, and the voltage at the base of the MOS transistor T5 will be pulled down by the MOS transistor T6 as the MOS transistor T6 is turned on, so that the current on the transistor T5 will be limited.

The resistor R10 is used to protect the MOS transistor T6 from damage due to transient voltage spikes applied to the MOS transistor T6.

For the current power amplifier, the current power amplifier is not afraid of overload because most of the voltage is loaded on the load when the current power amplifier is overloaded, which is the lightest load for the output power tube.

The overload protection of the current power amplifier has no significance to the reliability of the power amplifier, but is useful for reminding a user of the state of the power amplifier. When the current power amplifier is overloaded, the driving output reaches the maximum value, and when the current power amplifier is serious, the driving output is in a square wave form, and according to the characteristic, a comparator is generally arranged at a driving stage to judge whether the current power amplifier is overloaded or not.

The man-machine interaction module realizes man-machine interaction through the embedded screen, and has the advantages of simple structure, stability, reliability, high starting speed and instant use. DSP can also be through serial ports connection, and this interface is used for communicating with outside host computer, can make things convenient for outside host computer directly to control the source through serial ports communication.

The DSP controller module uses a dual-core DSP processor, expands a 128M DDR synchronous memory and a 32M asynchronous access Flash, and has very strong signal processing capability.

The working principle of the invention is as follows:

parameters (amplitude, phase, frequency and the like) are input to a waveform fitting algorithm module, fitting data points of signal waveforms are calculated in real time and stored in a DSP buffer.

The DSP controller module is composed of an ADI high-speed dual-core DSP (BF609) + DDR + high-capacity FLASH, waveform data fitting with large data volume is carried out through the high-speed DSP, hundreds of megas of SDRAM are arranged in the DSP, the fitted waveform can be directly stored in a system memory (SDRAM), is controlled through the DMA controller module, is sent to the DDS phase frequency control module at a fixed speed under the condition that a CPU does not interfere, and is output to the digital-to-analog conversion module through the accurate adjustment of the DDS phase frequency control module. Therefore, the digital waveform data directly determines the restored analog signal waveform, and the waveform fitting algorithm module is the key of the signal generator. The waveform fitting algorithm is embodied as follows, and comprises a fundamental formula of harmonic sine waveform fitting:n represents the harmonic order. And taking the discretized numerical sequence at certain intervals in a cycle time by the formula to be used for the output of the DAC, wherein the number of the value taking points is matched with the rate of the DAC. Assuming that the transmission rate of the DAC is m 50Mbit/s, the frequency of the wave f to be output is 50Hz, and one point is data of 16 bits, the number of required values is N,points, that is, data of 62500 points per cycle, where the 62500 point data is waveform data generated by the waveform fitting algorithm module.

Common standard sources within the power system are typically 360 to 3600 points per cycle; in fact, accurate and fine waveform output can be performed when each cycle reaches more than 1 ten thousand points, even if 20-order harmonics are output, the waveform of the 20-order harmonics has a data volume of 500 points per cycle, which exceeds the existing waveform of each cycle from 360 points to 3600 points, and the signal generator can be ensured to accurately output an IR46 waveform signal. Since the DMA output rate is known, the sampling rate of the formula waveform is known, and the number of waveform data points of the output frequency can be obtained by operation. If the waveform is a periodic waveform, only one piece of periodic data is buffered, and a desired waveform signal can be obtained through cyclic output. By adopting a high-speed 16-bit DAC (the communication speed is 50MBit/s), the invention can realize the waveform fitting capability of 3-5 ten thousand points per cycle wave at 50Hz, thereby outputting high-precision higher harmonics and having extremely low waveform distortion. The invention adopts the DAC supporting the multiplication reference input function, thereby supporting the dynamic reference voltage input and realizing the double-DAC framework: a waveform DAC and an amplitude DAC. The waveform DAC is used for outputting a waveform signal, the amplitude is controlled through the amplitude DAC, and the two DACs are both 16 bits, so that the highest 32-bit signal resolution is provided on the premise of not sacrificing the speed.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this description, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as described herein. Furthermore, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. The present invention has been disclosed in an illustrative rather than a restrictive sense, and the scope of the present invention is defined by the appended claims.