CN201173949Y - Three-phase Electric Energy Meter Based on NIOSⅡ Microprocessor - Google Patents

Abstract

The utility model is based on a NIOSII microprocessor-based three-phase electric energy meter, which specifically includes: a sensor, the output end of which is connected with a signal conditioning module; a signal conditioning module, whose input end is connected with the sensor output end; a signal acquisition module, whose input end is connected with a signal conditioning module The output terminal of the module is connected; the energy metering SOPC chip is connected with the signal acquisition module, which is the core of the entire electric energy meter system; the phase-locked frequency multiplier is connected with the signal conditioning module and the signal acquisition module; the universal asynchronous transceiver adopts the RS-232 interface mode Realize the communication between the electric energy meter and the upper computer or meter reading system; LCD display/keyboard module, connected to the electric energy metering SOPC chip; calendar clock module, connected to the electric energy metering SOPC chip; IIC memory, connected to the electric energy metering SOPC chip. The electric energy meter is small in size, high in integration, strong in reliability and reconfigurable.

Description

Three-phase Electric Energy Meter Based on NIOSⅡ Microprocessor

(1) Technical field:

The utility model relates to a three-phase electric energy meter based on a NIOS II microprocessor, which belongs to the technical field of instruments and meters.

(two) background technology:

After the transformation of urban and rural power grids in 2003, the demand for three-phase multi-function meters in the power system increased rapidly. As a result, international and domestic electric meter companies are optimistic about business opportunities, pay close attention to the development of new technologies, and continuously introduce new products of three-phase multi-function meters to meet the application needs of the electric energy meter market. According to incomplete statistics, the State Grid and China Southern Power Grid have a total of 195 million billing electric energy meters. Among them, the two networks directly manage 118 million units for billing, and indirectly manage 77 million units for billing.

In recent years, the domestic demand for electronic energy meters has risen steadily. There are three reasons for the market growth: first, electronic energy meters will gradually replace mechanical energy meters; The third is that the foreign electronic energy meter market has expanded in recent years, which has increased the export volume of domestic enterprises.

Industry insiders analyzed that electronic meters will become the leading role in the future meter market. Some data show that at least 1 billion electric meters (the sum of electronic electric meters and mechanical electric meters) have been installed in the world. In the next 10 years, China's electricity meter market may account for 40% of the global electricity meter market, and this proportion is still rising.

In China's electric energy meter market, electronic electric energy meters account for about 30-40%. Among them, the annual demand for single-phase electronic electric energy meters is stable at about 20 million, and the annual demand for three-phase electronic electric energy meters has increased to more than 6 million. . Electronic energy meters have the advantages of high precision, strong functions, and long life. The remaining 60-70% of traditional mechanical meters are gradually being replaced by electronic energy meters.

At present, in China, the design specifications for single-phase and three-phase electric energy meters are not very strict. Various electric energy meter manufacturers have no clear standards for the functional design of three-phase electric energy meters, basically according to the requirements of customers, select the existing CPU, electric energy metering chip and peripheral hardware modules on the market for specific design. In this way, each design project with different functional requirements needs to make corresponding adjustments to the original software and hardware design scheme. Among them, changes to the hardware design scheme may have a great impact on the safety and reliability of the product, and at the same time bring more investment and inconvenience to the design and manufacturer.

If all the core circuits required by the energy meter (such as microprocessors, energy metering chips, various controllers and communication interfaces, etc.) can be placed on the same chip, the area occupied by the entire system can be greatly reduced. Reduce the signal transmission between the peripheral drive interface unit and the circuit board, speed up the data processing speed of the microprocessor, and the embedded circuit can also avoid the system interference caused by the signal transmission on the external circuit board.

(3) Contents of utility model:

The purpose of this utility model is to provide a kind of three-phase electric energy meter based on NIOS II microprocessor. The energy meter puts all the required core circuits (microprocessor, energy metering chip, various controllers and communication interfaces, etc.) on the same chip, so that the area occupied by the entire system can be greatly reduced, and the energy meter is small. , high reliability. Designers can flexibly construct its hardware structure, functional characteristics, resource occupation, etc. according to user needs, so that the target product can be developed in a relatively short period of time at a very low cost, instead of passively following and using existing products in the market. Some MCUs carry out "rigid hardware connection and assembly".

The utility model is a three-phase electric energy meter based on the NIOS II microprocessor. The electric energy meter adopts the NIOS II soft-core microprocessor released by Altera Company as the CPU, and adopts a three-phase electric energy measurement on-chip programmable system (SOPC, System On Programmable Chip) chip is used as a metering unit, and the corresponding peripheral circuits are externally equipped.

The three-phase electric energy meter specifically includes modules such as sensors, signal conditioning, signal acquisition, electric energy metering SOPC chips, phase-locked frequency multiplication, LCD display/keyboard, universal asynchronous transceiver, IIC memory, and calendar clock.

The output end of the sensor is connected to the signal conditioning module, and the three-phase voltage and three-phase current on the power line are converted into small signals and sent to the signal conditioning module. The three-phase voltage is reduced to a small signal through a resistor divider network, and the three-phase current signal is converted to a small signal through a current transformer.

Signal conditioning module, the input terminal is connected to the output terminal of the sensor. The signal conditioning module specifically includes: anti-aliasing low-pass filter, reference voltage level and A/D conversion module; the small voltage signal sent by the sensor is passed through the anti-aliasing low-pass After the filter is filtered, it is biased to the reference voltage level of the A/D conversion module to supply current to the A/D conversion module.

The input terminal of the signal acquisition module is connected to the output terminal of the signal conditioning module, and the voltage signal sent by the signal conditioning module is converted into a digital signal and then sent to the electric energy metering SOPC chip.

The energy metering SOPC chip, connected with the signal acquisition module, is the core of the entire electric energy meter system. It mainly includes two parts: electric energy metering and NIOS II soft-core microprocessor; the electric energy metering part completes the calculation of voltage and current effective value, active/reactive power /Apparent power calculation, active/reactive power/apparent energy measurement, etc., some functions are realized by hardware; NIOS II soft-core microprocessor completes the scheduling work of the entire electric energy meter, such as realizing the switching of tariff periods, responding to serial port commands, and freezing history Power data, LCD display refresh, fault record alarm and other functions. The electric energy metering SOPC chip is applied for as a separate utility model.

The phase-locked frequency multiplier is connected with the signal conditioning module and the signal acquisition module, and is used to control the sampling frequency of the A/D conversion module. Since the three-phase watt-hour meter has the function of harmonic analysis, FFT transformation (that is, fast Fourier transform) is required for harmonic analysis, and synchronous sampling must be ensured in order to prevent the spectrum from leaking; when the grid voltage frequency fluctuates, each The number of sampling points of the cycle is consistent, so a phase-locked frequency multiplication circuit is designed to control A/D sampling.

Universal Asynchronous Receiver Transmitter, UART (Universal Asynchronous Receiver Transmitter), uses RS-232 interface to realize the communication between the energy meter and the host computer or meter reading system.

LCD display/keyboard module, connected to the energy metering SOPC chip, is the human-computer interaction interface of the entire energy meter system. The LCD display module displays the current effective value of three-phase voltage, effective value of three-phase current, active energy, reactive energy, and apparent energy , the historical power data of the last month, etc.; through the keyboard, you can set the data of the meter, speed up the LCD refresh frequency, etc., and it is also convenient for system debugging.

The calendar clock module is connected with the electric energy metering SOPC chip, and the trickle charging time chip DS1302 from Dallas Company of the United States is selected, which is mainly used to generate a clock including year, month, day, hour, minute and second.

The IIC memory is connected with the electric energy metering SOPC chip, and the two-wire serial EEPROM memory AT24C256 of ATMEL Company of the United States is selected to store program information.

The utility model is a three-phase electric energy meter based on the NIOS II microprocessor. Its advantages and effects are: the electric energy meter adopts the NIOS II soft-core microprocessor released by Altera Company as the CPU, and adopts the three-phase electric energy measurement SOPC ( System On Programmable Chip) chip is used as a metering unit, and the corresponding peripheral circuits are externally equipped. Users can flexibly construct and program the hardware structure, functional characteristics, resource occupation, etc. of the three-phase electric energy metering chip according to their needs, so that the target product can be developed at a very low cost in a relatively short period. Since the three-phase electric energy metering chip integrates all the core circuits (microprocessor, metering chip, various controllers and communication interfaces, etc.) required by the three-phase electric energy meter, it can greatly reduce the volume of the three-phase electric energy meter The signal transmission between the peripheral drive interface unit and the circuit board speeds up the data processing speed of the microprocessor, and the embedded circuit can also avoid the system interference caused by the signal transmission on the external circuit board; the electric energy meter is small in size, highly integrated and reliable Strong and reconfigurable.

(4) Description of drawings:

Figure 1 shows the overall block diagram of the three-phase electric energy meter design.

Figure 2 shows the internal block diagram of the energy metering SOPC chip.

(5) Specific implementation methods:

Below in conjunction with accompanying drawing and embodiment, the technical solution of the present utility model is described further.

The utility model is a three-phase electric energy meter based on the NIOS II microprocessor, and proposes a complete design scheme for three-phase electric energy measurement. This design scheme can also be applied to the SOPC chip design of the single-phase electric energy meter, only need to modify the corresponding measurement algorithm and adjust the corresponding modules in the system software.

1. The utility model adopts the reason of NIOS II soft-core microprocessor

The main features of the NIOS II soft-core microprocessor launched by Altera include: an efficient and flexible processor module, which can be configured as a 16-bit or 32-bit central processing unit (RISC, Relegate Important Stuff to the Compiler structure) by software, and Different internal memory sizes can be selected, and its maximum execution speed can reach 50MHz; it has a variety of other functional modules to choose from (synchronous dynamic random access memory, UART, PCI interface module, LCD interface module, MAC interface module and other functional modules).

At present, based on FPGA (Field Programmable Gate Array) design system on chip (SOC (System On Chip), there are two schemes: FPGA-based embedding IP hard core and FPGA-based embedding IP soft core. IP hard core (such as ARM core, Power PC core, and microcontroller core), IP soft core (Altera's NIOSII soft core and Xilinx's MicroBlaze soft core).

The advantages of IP soft core implanted in FPGA compared to IP hard core:

(1) Hard cores generally come from third-party companies, and FPGA manufacturers usually cannot directly control their intellectual property costs, resulting in relatively high prices for FPGA devices. Soft cores are non-third-party products launched by FPGA manufacturers, and users generally do not need to pay for intellectual property rights.

(2) The hard core is pre-implanted, and the designer cannot change the structure of the processor according to actual needs. The soft core is an embedded system microprocessor IP core that users can configure and build at will.

(3) The hard core cannot reduce processor hardware resources to reduce FPGA cost. The soft core can be cut at will.

●Comparison between NIOSII soft core and MicroBlaze soft core:

(1) There are almost no restrictions on the implantable FPGA series of NIOSII.

(2) NIOSII is superior to MicroBlaze in terms of completeness of development tools and support for commonly used embedded operating systems.

(3) In terms of cost, NIOSII is a non-third-party product launched by Altera, so users usually do not need to pay for intellectual property rights. The cost of using NIOSII is only the FPGA logic resources it occupies.

2. Design scheme of SOPC chip for electric energy measurement

As shown in Figure 2, the chip includes AD controller, FIFO (First In First Out, first-in-first-out data buffer), energy metering, configuration registers, NIOSII soft-core microprocessor, calendar clock interface, DFC (Digital to Frequency Converter, that is, digital frequency converter), IIC interface, and LCD controller and other parts.

Among them, the input of the AD controller is the three-phase voltage and three-phase current (serial data of 6 channels) collected on the signal acquisition board. The AD controller is based on the 16-bit Σ-ΔA/D chip AD73360 of the American AD company The serial data of the input 6 channels is converted into parallel data and stored in the corresponding FIFO; the 6-channel FIFO saves the AD data of 6 channels and 1 cycle sent by the AD controller for subsequent calculations. Another advantage of doing this is that the electric energy metering module can realize the pipeline structure and speed up the calculation speed; the electric energy metering module mainly uses FPGA to realize the metering of active power, reactive power and apparent power of electric energy. Configuration data, historical power data, frozen data, etc. are saved in the configuration register; the NIOS II soft-core microprocessor completes the scheduling work of the entire electric energy metering chip; the calendar clock interface is connected with the external calendar clock chip to provide clock information for the chip. The NIOS II soft-core microprocessor is used to form a multi-rate electric energy meter. The calendar clock chip selects the trickle charging time chip DS1302 from Dallas Company in the United States; DFC conversion is to convert the measured electric energy value into the number of pulses for output, so as to calibrate the meter; the IIC interface controls the external IIC read-only memory AT24C256, AT24C256 is an American ATMEL's two-wire serial EEPROM memory; LCD controller realizes the driving function of the external LCD, and the LCD uses LCM128645ZK from Beijing Qingyun. 3. Overall design of three-phase electric energy meter

3. The overall block diagram of the design of the three-phase electric energy meter is shown in Figure 1.

Three-phase energy meter based on NIOS II microprocessor, including sensors, signal conditioning, signal acquisition, energy metering SOPC chip, phase-locked frequency multiplier, LCD display/keyboard, universal asynchronous transceiver, IIC memory and calendar clock and other modules.

The output terminal of the sensor is connected with the signal conditioning module, and the three-phase voltage and three-phase current on the power line are converted into small signals and sent to the signal conditioning module. The three-phase voltage is reduced to a small signal through a resistor divider network, and the three-phase current signal is converted to a small signal through a current transformer.

Signal conditioning module, the input terminal is connected to the output terminal of the sensor. The signal conditioning module specifically includes: anti-aliasing low-pass filter, reference voltage level and A/D conversion module; the small voltage signal sent by the sensor is passed through the anti-aliasing low-pass After the filter is filtered, it is biased to the reference voltage level of the A/D conversion module to supply current to the A/D conversion module.

The input terminal of the signal acquisition module is connected to the output terminal of the signal conditioning module, and the 6 voltage signals sent by the signal conditioning module are converted into digital signals and then sent to the power metering SOPC chip.

The energy metering SOPC chip, connected with the signal acquisition module, is the core of the entire electric energy meter system. It mainly includes two parts: electric energy metering and NIOS II soft-core microprocessor; the electric energy metering part completes the calculation of voltage and current effective value, active/reactive power /Apparent power calculation, active/reactive power/apparent energy measurement, etc., some functions are realized by hardware; NIOS II soft-core microprocessor completes the scheduling work of the entire electric energy meter, such as realizing the switching of tariff periods, responding to serial port commands, and freezing history Power data, LCD display refresh, fault record alarm and other functions. The electric energy metering SOPC chip is applied for as a separate utility model.

The phase-locked frequency multiplier is connected with the signal conditioning module and the signal acquisition module, and is used to control the sampling frequency of the A/D conversion module. Since the three-phase watt-hour meter has the function of harmonic analysis, FFT transformation (that is, fast Fourier transform) is required for harmonic analysis, and synchronous sampling must be ensured in order to prevent the spectrum from leaking; when the grid voltage frequency fluctuates, each The number of sampling points of the cycle is consistent, so a phase-locked frequency multiplication circuit is designed to control A/D sampling.

Universal Asynchronous Receiver Transmitter, UART (Universal Asynchronous Receiver Transmitter), uses RS-232 interface to realize the communication between the energy meter and the host computer or meter reading system.

LCD display/keyboard module, connected to the energy metering SOPC chip, is the human-computer interaction interface of the entire energy meter system. The LCD display module displays the current effective value of three-phase voltage, effective value of three-phase current, active energy, reactive energy, and apparent energy , the historical power data of the last month, etc.; through the keyboard, you can set the data of the meter, speed up the LCD refresh frequency, etc., and it is also convenient for system debugging.

The calendar clock module is connected with the electric energy metering SOPC chip, and the trickle charging time chip DS1302 from Dallas Company of the United States is selected, which is mainly used to generate a clock including year, month, day, hour, minute and second.

The IIC memory is connected with the electric energy metering SOPC chip, and the two-wire serial EEPROM memory AT24C256 of ATMEL Company of the United States is selected to store program information.

Claims (2)

1, a kind of three-phase electric energy meter based on NIOS II microprocessor is characterized in that: this three-phase electric energy meter specifically comprises programmable chip system, phase locking frequency multiplying, LCD demonstration/keyboard, UART Universal Asynchronous Receiver Transmitter, IIC storer and calendar clock module on sensor, signal condition, signals collecting, the electric energy metrical sheet;

Sensor, output terminal is connected with the signal condition module, transfers the three-phase voltage on the line of electric force and three-phase current to small-signal and gives the signal condition module;

The signal condition module, input end is connected with the sensor output terminal, and this signal condition module specifically comprises: anti-aliasing low-pass filter, reference voltage level and A/D modular converter;

Signal acquisition module, input end links to each other with signal condition module output terminal, gives electric energy metrical SOPC chip after the voltage signal that the signal condition module is sent here transfers digital signal to;

Electric energy metrical SOPC chip is connected with signal acquisition module, is the core of whole electric energy system, mainly comprises the two large divisions: the soft nuclear microprocessor of electric energy metrical and NIOS II;

Phase-locked letter links to each other with signal acquisition module with the signal condition module frequently, is used to control the sample frequency of A/D modular converter.

UART Universal Asynchronous Receiver Transmitter adopts the RS-232 interface mode to realize communicating by letter of electric energy meter and host computer or kilowatt meter reading-out system.

LCD demonstration/Keysheet module connects electric energy metrical SOPC chip, is the interface of whole electric energy system man-machine interaction;

The calendar clock module is connected with electric energy metrical SOPC chip, selects the trickle charge time chip DS1302 of dallas, u.s.a company for use;

The IIC storer is connected with electric energy metrical SOPC chip, and that select for use is the two-wire serial eeprom storer AT24C256 of American ATMEL.

2, the three-phase electric energy meter based on NIOS II microprocessor according to claim 1, it is characterized in that: the small voltage signal that described signal condition module is sent sensor here is biased on the reference voltage level of A/D modular converter through after the anti-aliasing low-pass filter filtering, for A/D modular converter electric current.

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