WO2022247088A1 - 一种智能电表的无源校准方法 - Google Patents

一种智能电表的无源校准方法 Download PDF

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WO2022247088A1
WO2022247088A1 PCT/CN2021/121549 CN2021121549W WO2022247088A1 WO 2022247088 A1 WO2022247088 A1 WO 2022247088A1 CN 2021121549 W CN2021121549 W CN 2021121549W WO 2022247088 A1 WO2022247088 A1 WO 2022247088A1
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voltage
meter
current
calibration
power
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PCT/CN2021/121549
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French (fr)
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王宜怀
史洪玮
施连敏
喻炳政
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苏州大学
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Publication of WO2022247088A1 publication Critical patent/WO2022247088A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
    • G01R35/04—Testing or calibrating of apparatus covered by the other groups of this subclass of instruments for measuring time integral of power or current

Definitions

  • the invention relates to the technical field of smart meters, in particular to a passive calibration method for smart meters.
  • the sampling circuit of the power quality acquisition terminal is composed of current transformers, sampling resistors, and metering chip ADC modules.
  • the components that make up these parts have precision levels and discreteness.
  • the PCB impedance and the error of the metering chip will lead to differences in accuracy. Due to the existence of these factors, the measurement results of the power grid data will be affected to a certain extent, making the sampling data inaccurate. This problem can be solved by calibrating each terminal.
  • the calibration of power quality terminals is mainly active calibration.
  • Active calibration uses a three-phase standard source to output specified current voltage, phase, etc.
  • the power quality acquisition terminal can be calibrated accurately through the three-phase standard source, but the cost of the three-phase standard source is relatively high, which indirectly increases the development cost.
  • the invention uses passive calibration and cooperates with the calibration program, which can make up for the low efficiency of passive calibration and further improve the calibration accuracy.
  • the invention provides a passive calibration method for a smart meter, comprising:
  • the meter to be calibrated uses an HT7036 metering chip, and the method further includes calibrating the metering chip, including:
  • Parameter settings including mode configuration, channel gain configuration, EMU unit configuration, high-frequency pulse output configuration, voltage loss threshold setting, and startup threshold setting;
  • Phase A correction including power gain correction, voltage correction, current correction
  • the electric energy data includes: voltage, current, power, frequency, and/or harmonics.
  • the meter to be calibrated uses the HT7036 metering chip.
  • the electric energy data is voltage
  • the effective value of the voltage of the standard commercial electric meter is Ur
  • the measured voltage of the electric meter to be calibrated is Urms
  • the voltage calibration coefficient is Ugain
  • INT is a rounding function.
  • the calculation formula of the voltage calibration coefficient is as follows :
  • the electric energy data is current
  • the effective value of the current of the standard commercial electric meter is Ir
  • the measured current of the electric meter to be calibrated is Irms
  • the current calibration coefficient is Igain
  • the calculation formula of the current calibration coefficient is as follows;
  • the active power value of the commercial electric meter is Preal
  • the power value of the electric meter to be calibrated is DataP
  • the power calibration coefficient is Pgain.
  • the calculation formula of the power calibration coefficient is as follows:
  • Ugain', Igain', and Pgain' are a relationship between Ugain', Igain', and Pgain' as shown in the following formula 2-9.
  • the HFconst used in formula 2-9 is a high-frequency pulse constant, and the calculation formula is shown in formula 2-7;
  • U n is the actual access voltage of the meter terminal
  • I b is the actual access current
  • Vu and Vi are the input voltages of the metering chip voltage channel and current channel respectively
  • N used in formula 2-9 is the proportional coefficient , the calculation formula is shown in the following formula 2-8;
  • T A in formula 2-8 is the transformation ratio of the current transformer, and R is the resistance of the current sampling circuit;
  • the registers of the metering chip are divided into two parts, namely metering parameter registers and meter calibration parameter registers.
  • the advantages of the present invention are: compared with the traditional calibration, the cost of the passive calibration method adopted by the present invention is lower, and the current, voltage and power can all meet the requirements of a Class 2 electric energy meter.
  • Figure 1 shows a schematic diagram of the principle of passive calibration according to an embodiment of the present invention.
  • Fig. 2 shows a schematic diagram of a metering chip calibration process according to an embodiment of the present invention.
  • Fig. 3 shows a schematic diagram of a single-phase data calibration interface according to an embodiment of the present invention.
  • the invention proposes a passive calibration method, using an ACR330ELH commercial electric meter and a specified power factor load to realize electric meter calibration.
  • the calibration process is combined with special calibration software to calculate the gain coefficient and write to the serial port to improve development efficiency.
  • the cost of passive calibration is lower, and the current, voltage, and power can all meet the requirements of Class 2 electric energy meters.
  • FIG 1 shows the calibration principle, including the following steps:
  • the electric energy data includes: voltage, current, power, frequency, harmonics, etc.
  • the calibration tool in Figure 1 is a WinForm window program, which communicates with the meter to be calibrated through the serial port. According to the input information, the gain value is automatically determined, and it is directly written into the designated sector of the MCU of the meter to be calibrated in a partial update mode to improve development efficiency.
  • the meter to be calibrated in the present invention uses the HT7036 metering chip, and the metering chip also needs to be calibrated before the meter to be calibrated is formally calibrated.
  • the calibration process mainly performs power, current and voltage calibration. When calibrating the power, you only need to calibrate the active power gain register, and write the same coefficient in the reactive power register and apparent power gain register.
  • the metering chip calibration process is shown in Figure 2 below, including:
  • Parameter settings including mode configuration, channel gain configuration, EMU unit configuration, high-frequency pulse output configuration, voltage loss threshold setting, and startup threshold setting;
  • Phase A correction including power gain correction, voltage correction, current correction
  • a stable voltage source is used to output a stable voltage
  • a high-power sliding rheostat with a power factor of 1 is used for calibration to set the specified current, voltage, and power parameters.
  • the calibration tool is used to calculate the error and update the gain parameters of the electric meter to be calibrated.
  • the effective value of the commercial meter voltage is Ur
  • the measured voltage of the meter is Urms
  • the voltage calibration coefficient is Ugain
  • INT is a rounding function.
  • the calculation formula of the voltage calibration coefficient is as follows.
  • the effective value of the commercial electric meter current is Ir
  • the measured current of the electric meter is Irms
  • the current calibration coefficient is Igain.
  • the calculation formula of the current calibration coefficient is as follows.
  • the active power value of the commercial electric meter is Preal
  • the power value is DataP
  • the power calibration coefficient is Pgain.
  • the calculation formula of the power calibration coefficient is as follows.
  • Equation 2-9 there is also a relationship between Ugain', Igain' and Pgain' as shown in the following formula 2-9.
  • HFconst used in Equation 2-9 is the high-frequency pulse constant, and the calculation formula is shown in Equation 2-7.
  • U n is the actual access voltage of the meter terminal
  • I b is the actual access current
  • Vu and Vi are the input voltages of the metering chip voltage channel and current channel, respectively.
  • N used in Equation 2-9 is a proportional coefficient, and the calculation formula is shown in Equation 2-8 below.
  • T A in Formula 2-8 is the transformation ratio of the current transformer
  • R is the resistance of the current sampling circuit.
  • the HT7036 metering chip integrates multiple 19-bit ADC modules inside, and adopts double-ended differential signal input.
  • the ADC input corresponding to the voltage channel of the metering chip should be selected at an effective value of about 0.22V, and the ADC input of the current channel should be selected at an effective value of about 0.05V. In this way, good linearity characteristics can be obtained to ensure measurement accuracy.
  • the voltage sampling circuit adopts the principle of series voltage division.
  • the voltage sampling channel is connected in parallel with a 1.2K ⁇ voltage sampling resistor.
  • the voltage dividing resistor of the voltage sampling circuit is composed of seven 330K ⁇ chip resistors.
  • the voltage data sampled by the voltage channel is positively correlated with the channel gain coefficient.
  • the actual input voltage is about 230V.
  • the gain factor of the voltage channel should be set to 2
  • the input voltage of the voltage sampling channel is about 0.2367V.
  • the current sampling channel is connected in parallel with a 7.8 ⁇ sampling resistor, and the input current is generated by a current transformer, which is 1/1000 of the actual current.
  • the input current is set to 3A, and the gain factor of the current sampling channel is set to 2.
  • the input voltage of the current sampling channel is 0.0468V.
  • the metering chip register is divided into two parts, namely the metering parameter register (read-only memory) and the calibration parameter register. Calibration parameters are stored in the meter calibration parameter register, and grid data are stored in the metering parameter register.
  • the address range of the measurement parameter register is 0x00 ⁇ 0x7F
  • the address range of the calibration parameter register is 0x00 ⁇ 0x71.
  • the SPI communication format of the metering chip is 8-bit command, 24-bit data, and the data transmission adopts the high-order priority system.
  • the highest bit of the command is 0, (Bit7: 0) indicates the read command, which is used for the external MCU to read the metering chip register data, the lower 7 bits (Bit6...0) indicate the register address, and the 24-bit data is a redundant byte (0xFF, 0xFF, 0xFF). After receiving the redundant bytes, the metering chip will reply the corresponding data. If you need to operate the meter calibration parameter register, you need to send a special command, that is, send the command 0xC6, the data is equal to 0x00005A, select SPI to read the parameters of the meter calibration data register, and you cannot read the value of the measurement parameter register at this time.
  • the data is not equal to 0x000005A, and choose to read the parameters of the metering data register at the address 0x0 ⁇ 0x7F through SPI. After power-on reset, the parameters of the metering data register are read out by default.
  • the value read from the 0x00 address is fixed at 0x00AAAA, otherwise the read metering parameter 0x00 address is 0x7122A0.
  • the highest bit of the command is 1, and the lower 7 bits (Bit6...0) indicate the register address, which means writing data to the calibration register.
  • the calibration data needs to be placed in the lower two bytes of the 3 data bytes.
  • the apparent power be S
  • the active power be P
  • the reactive power be Q
  • the measured voltage be Urms
  • the current be Ims
  • the calculation method of S is as follows. Write 0xFD04 to the EMU unit configuration register (0x03 address). Turn off the fundamental wave function, and select the PQS mode for apparent power energy.
  • the terminal described in the present invention stores various calibration parameters and calibration parameter register configuration data in the last sector of the FLASH storage area of the STM32L431 chip. After the terminal is powered on or receives the calibration command, by reading the FLASH sector information, the calibration-related data is read into the calibration structure, and the calibration is performed through the calibration function of the terminal.
  • the user When the user calibrates the metering chip, it needs to calibrate phase by phase. It is necessary to input the measured value of the grid data and the value of the standard meter into the designated area of the calibration program, and then click the start button, and the calibration parameters of the gain register stored in the lower computer will automatically change. The user needs to make an evaluation based on the data obtained after the operation. If there is still a large deviation from the ideal data, it is necessary to repeatedly input the measured value of the grid data and the value of the standard table to perform multiple calibrations. During the calibration process, if it is found that the calibration parameters appear cyclically, but the deviation still exists. The calibration parameters with the smallest error should be selected and written into the development board, and the input power parameters of the experiment should be adjusted.
  • the upper computer calibration program of the present invention is a WinForm form developed by Visual Studio 2019 (VS), and the upper computer communicates with the lower computer through the SCI class.
  • the SCI class inherits the VS system class SerialPort, and the main functions are shown in Table 1 below.
  • the host computer program cannot operate the terminal before it is connected to the terminal. When the upper computer shakes hands with the lower computer, a single thread is used to call the SCIReceiveData function to receive the handshake information. After the connection is successful, the host computer sends commands to read and modify data through the window program button, and calls the SerialDataReceivedEventHandler event to realize asynchronous data reception.
  • the calibration procedure mainly focuses on the single-phase data calibration interface, as shown in Figure 3 below.
  • an AC stabilized voltage source is used to stabilize the voltage at 220V and the current at 2.2A, and then start the calibration.
  • the initial calibration data are shown in Table 2 below.
  • 0xD59A, 0xE38, and 0x1312 are the initial gain parameters of current, voltage, and power set randomly.
  • the current gain parameter is 0xBAAA
  • the active power gain parameter is 0x13EC
  • the voltage gain value is 0xD579.
  • the gain parameters of other phase-splitting reactive power and apparent power are consistent with the gain parameters of active power.
  • the voltage measurement error is large, after recalculation according to formula 2-9, write 0xB4B1.
  • the holding current is 2.1A, and the data measured by adjusting the voltage across the load are shown in Table 3 below.
  • the measurement error of the voltage is less than 2%, and the measurement accuracy reaches the level 2 standard.
  • the gain value After determining the gain value, use a stabilized voltage source to keep the voltage at 220V, and repeatedly adjust the resistance of the sliding rheostat to gradually increase the current and power. Through repeated experiments, the active power error is about 8%, and the current error is between 9% and 15%.
  • the median mean filtering algorithm is used. In order to determine the number of sampling times, the number of continuous reading sampling times of current and power data is changed, and the data rules are found in Table 5 below. The effect of 30 times is the worst, and the effect of 50 and 100 times is the same. In order to reduce energy consumption, the number of continuous sampling is determined to be 50 times.
  • the current measurement and power measurement are compensated by software, and the specific data obtained are shown in Table 6 below.
  • the current error is less than 5%
  • the power error is less than 2%
  • the active power measurement meets the requirements of level 2.

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Abstract

一种智能电表的无源校准方法，包括：通过稳压源生成电压输入指定功率因子的负载；分别使用标准商用电表和待校准电表测量负载的电能数据；根据电能数据计算待校准电表与标准商用电表的误差，作为增益值。校准电表的计量芯片，包括：参数设置，包括模式配置、通道增益配置、EMU单元配置、高频脉冲输出配置、失压阈值设置、启动阈值设置；A相校正，包括功率增益校正、电压校正、电流校正；B相校正和C相校正。相对于传统校准，采用无源校准方式成本更低，且电流、电压、功率均可达到2级电能表要求。

Description

一种智能电表的无源校准方法 技术领域
本发明涉及智能电表技术领域，具体涉及一种智能电表的无源校准方法。
 背景技术
电能质量采集终端的采样电路由电流互感器、采样电阻、计量芯片ADC模块组成，组成这些部分的元器件有精度等级和离散性。此外，PCB阻抗、计量芯片自身误差均会导致精度差异。电网数据的测量结果会因这些因素的存在，受到一定的影响而使得采样数据不准确，通过对每一个终端进行校准可以解决这个问题。
目前电能质量终端的校准主要是有源校准。有源校准借助三相标准源输出指定电流电压、相位等。通过三相标准源可以对电能质量采集终端进行精确的校准，但三相标准源的造价较高，间接提高了开发成本。
 技术解决方案
本发明的目的是通过以下技术方案实现的。
本发明使用无源校准，配合校准程序，可以弥补无源校准效率低下的缺点，进一步提高校准精度。
本发明提供一种智能电表的无源校准方法，包括：
通过稳压源生成电压输入指定功率因子的负载；
分别使用标准商用电表和待校准电表测量所述负载的电能数据；
根据所述电能数据计算待校准电表与标准商用电表的误差，作为增益值。
将所述增益值写入所述待校准电表的MCU指定扇区，完成校准；
所述待校准电表使用HT7036计量芯片，所述方法进一步包括校准所述计量芯片，包括：
参数设置，包括模式配置、通道增益配置、EMU单元配置、高频脉冲输出配置、失压阈值设置、启动阈值设置；
A相校正，包括功率增益校正、电压校正、电流校正；
B相校正和C相校正。
进一步地，所述电能数据包括：电压、电流、功率、频率、和/或谐波。
进一步地，所述待校准电表使用HT7036计量芯片。
进一步地，当所述电能数据为电压时，假设标准商用电表电压有效值为Ur，待校准电表测量电压为Urms，电压校准系数为Ugain，INT为取整函数，电压校准系数计算公式如下所示：
Figure 296990dest_path_image001
进一步地，当所述电能数据为电流时，假设标准商用电表电流有效值为Ir，待校准电表测量电流为Irms，电流校准系数为Igain，电流校准系数计算公式如下所示；
Figure 157106dest_path_image002
进一步地，当所述电能数据为功率时，设商用电表有功功率值为Preal，待校准电表功率值为DataP，功率校准系数为Pgain，功率校准系数计算公式如下所示：
Figure 961114dest_path_image003
进一步地，Ugain’与Igain’、Pgain’之间存在如下式2-9所示的关系，公式2-9中用到的HFconst为高频脉冲常数，计算公式如式2-7所示；公式2-7中U n为电表终端实际接入电压，I b为实际接入电流，Vu、Vi分别为计量芯片电压通道、电流通道的输入电压；公式2-9中用到的N为比例系数，计算公式如下公式2-8所示；公式2-8中的T A为电流互感器变比，R为电流采样电路电阻；
Figure 158877dest_path_image004
进一步地，所述待校准电表测量所述负载的电能数据时，使用中位均值滤波算法。
进一步地，所述计量芯片的寄存器分为两部分，分别是计量参数寄存器和校表参数寄存器。
 有益效果
本发明的优点在于：相对于传统校准，本发明采用的无源校准方式成本更低，且电流、电压、功率均可达到2级电能表要求。
 附图说明
通过阅读下文优选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本发明的限制。而且在整个附图中，用相同的参考符号表示相同的部件。在附图中：
附图1示出了根据本发明实施方式的无源校准原理示意图。
附图2示出了根据本发明实施方式的计量芯片校准过程示意图。
附图3示出了根据本发明实施方式的单相数据校准界面示意图。
 本发明的实施方式
下面将参照附图更详细地描述本公开的示例性实施方式。虽然附图中显示了本公开的示例性实施方式，然而应当理解，可以以各种形式实现本公开而不应被这里阐述的实施方式所限制。相反，提供这些实施方式是为了能够更透彻地理解本公开，并且能够将本公开的范围完整的传达给本领域的技术人员。
本发明提出无源校准方式，使用ACR330ELH型商用电表与指定功率因子负载实现电表校准。校准过程结合专用校表软件，计算增益系数，串口写入，提高开发效率。相对于传统校准，无源校准方式成本更低，且电流、电压、功率均可达到2级电能表要求。
图1展示了校准原理，具体包括如下步骤：
S1、通过稳压源生成电压输入指定功率因子的负载。
S2、分别使用标准商用电表和待校准电表测量所述负载的电能数据；所述电能数据包括：电压、电流、功率、频率、谐波等。
S3、根据所述电能数据计算待校准电表与标准商用电表的误差，作为增益值。
S4、将所述增益值写入所述待校准电表的MCU指定扇区，完成校准。
图1中校准工具为WinForm窗体程序，通过串口与待校准电表通信。根据输入信息，自动确定增益值，并以局部更新方式，直接写入待校准电表MCU指定扇区，提高开发效率。
本发明的待校准电表使用HT7036计量芯片，在正式校准所述待校准电表之前，计量芯片也均需要进行校准。校准过程，主要进行功率、电流、电压校准。对功率进行校准时，只需校准有功功率增益寄存器，无功功率寄存器、视在功率增益寄存器写入相同系数即可。计量芯片校准过程如下图2所示，包括：
参数设置，包括模式配置、通道增益配置、EMU单元配置、高频脉冲输出配置、失压阈值设置、启动阈值设置；
A相校正，包括功率增益校正、电压校正、电流校正；
B相校正和C相校正。
在实际校准时，使用稳压源输出稳定的电压，使用功率因子为1的高功率滑动变阻器进行校准，以设置指定电流、电压、功率参数。实际测量时，根据商用电表、待校准电表数据，使用校准工具，进行误差计算，并更新待校准电表的增益参数。进行无源校准时，假设商用电表电压有效值为Ur，电表测量电压为Urms，电压校准系数为Ugain，INT为取整函数，电压校准系数计算公式如下所示。
Figure 706533dest_path_image001
假设商用电表电流有效值为Ir，电表测量电流为Irms，电流校准系数为Igain，电流校准系数计算公式如下所示。
Figure 938931dest_path_image002
设商用电表有功功率值为Preal，功率值为DataP，功率校准系数为Pgain，功率校准系数计算公式如下所示。
Figure 694266dest_path_image003
此外，Ugain’与Igain’、Pgain’之间还存在如下式2-9所示的关系。公式2-9中用到的HFconst为高频脉冲常数，计算公式如式2-7所示。公式2-7中U n为电表终端实际接入电压，I b为实际接入电流，Vu、Vi分别为计量芯片电压通道、电流通道的输入电压。公式2-9中用到的N为比例系数，计算公式如下公式2-8所示。公式2-8中的T A为电流互感器变比，R为电流采样电路电阻。
Figure 379325dest_path_image004
 具体实施例
1 准备工作
HT7036计量芯片内部集成多路19位ADC模块，采用双端差分信号输入。在校准时，应将计量芯片电压通道对应的ADC输入选在有效值0.22V左右，电流通道ADC输入选在有效值0.05V左右。这样，可以获得良好的线性特性，保证计量精度。电压采样电路采用串连分压原理，电压采样通道与1.2KΩ电压采样电阻并联，电压采样电路的分压电阻由7个330KΩ的贴片电阻组成，电压通道采样电压数据与通道增益系数正相关。使用市电进行校准时，实际接入电压约为230V，为使电压通道尽可能的接近0.22V，电压通道增益系数应设为2，电压采样通道输入电压约为0.2367V。电流采样通道与7.8Ω的采样电阻并联，输入电流由电流互感器产生，是实际电流的1/1000，为使电流通道采样电压接近0.05V，输入电流设置为3A，电流采样通道增益系数设为2，电流采样通道输入电压为0.0468V。
计量芯片寄存器分为两部分，分别是计量参数寄存器（只读存储器）和校表参数寄存器。校准参数存储在校表参数寄存器中，电网数据存储在计量参数寄存器中。计量参数寄存器的地址范围为0x00~0x7F，校表参数寄存器地址范围为0x00~0x71。计量芯片的SPI通讯格式为8位命令，24位数据，数据发送采用高位优先制。命令的最高位为0，（Bit7：0）表示读命令，用于外部MCU读取计量芯片寄存器数据，低7位（Bit6…0）表示寄存器地址，24位数据为冗余字节（0xFF、0xFF、0xFF）。计量芯片在收到冗余字节后，回复相应数据。若需对校表参数寄存器进行操作，需发送特殊命令，即发送命令0xC6，数据等于0x00005A，选择SPI读出校表数据寄存器的参数，此时不可读出计量参数寄存器的值。发送命令0xC6，数据不等于0x000005A，选择通过SPI读出0x0～0x7F地址的计量数据寄存器的参数。上电复位后默认读出计量数据寄存器的参数。选择读出校表数据寄存器的参数时，从0x00地址读出的值固定为0x00AAAA，否则读取计量参数0x00地址为0x7122A0。
写数据时命令的最高位为1，低7位（Bit6…0）表示寄存器地址，表示向校表寄存器写入数据。用户在通过SPI方式进行通信，配置校表寄存器时，需将校表数据放在3个数据字节的低两个字节。
在正式校表时，需要先向校表参数寄存器写入相应参数，具体命令如下。
（1）配置模式寄存器（0x01地址），写入推荐值0xB9EF。开启vref chopper功能，以获取更稳定的参考电压。开启功率有效值慢速模式，减小跳动；配置仿真器（Emulator，EMU）时钟为921.6kHz，降低功耗；开启A、B、C三相电压、电流通道数据采样功能。
（2）视在功率的计算有两种选择方式，分别是PQS方式，RMS视在方式。令视在功率为S，为有功功率为P，无功功率为Q，测量得到的电压为Urms，电流为Ims，则S计算方式如下所示。向EMU单元配置寄存器（0x03地址）写入0xFD04。关闭基波功能，视在功率能量选择PQS方式。
Figure 996252dest_path_image005
（3）向模拟模块使能寄存器（0x31地址）写入0x3437，开启高通滤波器；开启欠压复位（Brown-out Reset，BOR）电源监测电路。
（4）向ADC增益配置寄存器（0x02地址）写入0x154，将三相电压，电流通道增益设为2倍增益，使校准时，电流通道输入电压接近0.05V，电压通道输入电压接近0.5V 。
（5）向高频脉冲常数寄存器（0x1E地址）写入HFconst。
（6）向算法控制寄存器（0x70地址）写入0x8，芯片启动自动补偿机制，自动计算全部通道的增益值，并写入0x5C地址，将测量模式设为三相四线制。
2 校准程序
计量芯片校准时，需要根据标准表的读数，电表终端的测量值，计算计量芯片增益寄存器的校准参数。取得校准参数时，需将校准参数写入终端中。若采用重新烧录的方式，所需时间较长。本发明中所述的终端，将各项校准参数、校表参数寄存器配置数据存储在STM32L431芯片FLASH存储区域的最后一个扇区中。在终端上电或接收到校准指令后，通过读取FLASH扇区信息，将校表相关数据读取到校表结构体中，并通过终端的校准函数进行校准。
校准程序在终端电压通道、电流通道的采样电压达到额定电压时，会获得较好的校准效果。若无法为采样通道提供额定电压，则应修改实际入板电压、实际入板电流和电压、电流通道输入电压。针对上述情况，开发人员可通过改变校准程序界面图中计量参数操作区域的相应参数，以对下位机内存储的参数进行修改。而且，用户在操作时，只需输入入板电压、入板电流，再点选更新按钮，即可自动更新电压、电压通道输入文本框数据。
用户进行计量芯片校准时，需逐相进行校准，需将电网数据测量值、标准表数值输入校表程序指定区域，再点击开始按钮，下位机内存储的增益寄存器校准参数即会自动改变。用户需根据操作后获得的数据进行评估，若与理想数据仍存在较大偏差，则需重复输入电网数据测量值、标准表数值，进行多次校准。在校准过程中若发现校准参数循环出现，但偏差依然存在。应选取误差最小的校准参数写入开发板，调整实验输入电力参数，若误差保持恒定，可使用软件进行弥补；否则，需对开发板进行检修。在校准某相增益寄存器时，若开发板测出的电压、电流数据已经达到要求精度，只需对功率进行校准时，勾选电压、电流校准参数文本框前的按钮，后续的校准过程便只改变功率校准参数。
本发明的上位机校准程序是由Visual Studio 2019（VS）开发的WinForm窗体，上位机通过SCI类与下位机进行通讯。SCI类继承VS的***类SerialPort，主要函数如下表1所示。上位机程序在连接终端前，无法对终端操作。上位机与下位机握手时，采用单线程，调用SCIReceiveData函数接收握手信息。在连接成功后，上位机通过窗体程序按钮发送读取、修改数据命令，调用SerialDataReceivedEventHandler事件，实现异步接收数据。
Figure 817577dest_path_image006
使用本发明中提到的校准程序，在校准过程中，会将新的校准参数存入FLASH指定扇区中，终端再次上电后，该数据依然会存留。相对于手动计算校准参数，重新烧录程序，使用本发明提供的校准程序进行校准，效率、准确性都得到了大幅度提升。校准程序主要集中在单相数据校准界面，具体如下图3所示。
3 校准过程
硬件电路搭建完毕，打开交流稳压源开关，输出稳定电压、电流。记录电表终端、标准表读数，将相应参数输入单相数据校准界面指定位置，进行校准，直至电表终端测试数据稳定，且误差较小。然后，重新搭建校准电路，改变电表终端的接入电压、电流，验证是否需要重新校准。
为保证电能数据的稳定性，采用交流稳压源，将电压稳定在220V，电流稳定在2.2A，然后开始校准。初始校准数据如下表2所示。0xD59A、0xE38、0x1312为随机设置的电流、电压、功率初始增益参数，后续校准过程中确认电流增益参数为0xBAAA，有功增益参数为0x13EC，电压增益值为0xD579。其它分相无功功率、视在功率的增益参数，与有功功率增益参数保持一致。
Figure 494546dest_path_image007
电压测量误差较大，根据公式2-9重新计算后，写入0xB4B1。保持电流为2.1A，调整负载两端电压测得的数据如下表3所示。电压的测量误差小于2%，测量精度达到2级标准。
Figure 666901dest_path_image008
调整点电表终端输入电流参数，观察计量芯片测得的电流、功率的变化规律。功率误差集中在8%左右，电流功率误差在10%~15%之间，具体数据如下表4所示。
Figure 307092dest_path_image009
确定增益值后，使用稳压源将电压保持在220V，反复调整滑动变阻器的阻值，使电流逐渐升高，功率也随之增大。通过反复实验，有功功率误差在8%左右，电流误差在9%~15%之间。电网数据采样时，均使用了中位均值滤波算法。为确定采样次数，改变电流、功率数据的连续读取采样次数，发现数据规律如下表5所示。30次效果最差，50、100次效果一致，为降低能量消耗，将连续采样次数确定为50次。
Figure 514083dest_path_image010
确定采样次数后，对电流测量、功率测量进行软件弥补，所得的具体数据如下表6所示。经软件弥补后电流误差小于5%，功率误差小于2%，有功功率测量达到2级要求。
Figure 361953dest_path_image011
以上所述，仅为本发明较佳的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应以所述权利要求的保护范围为准。

Claims (8)

  1. 一种智能电表的无源校准方法，其特征在于，包括：通过稳压源生成电压输入指定功率因子的负载；分别使用标准商用电表和待校准电表测量所述负载的电能数据；根据所述电能数据计算待校准电表与标准商用电表的误差，作为增益值。将所述增益值写入所述待校准电表的MCU指定扇区，完成校准；所述待校准电表使用HT7036计量芯片，所述方法进一步包括校准所述计量芯片，包括：参数设置，包括模式配置、通道增益配置、EMU单元配置、高频脉冲输出配置、失压阈值设置、启动阈值设置；A相校正，包括功率增益校正、电压校正、电流校正；B相校正和C相校正。
  2. 根据权利要求1所述的方法，其特征在于，所述电能数据包括：电压、电流、功率、频率、和/或谐波。
  3. 根据权利要求2所述的方法，其特征在于，当所述电能数据为电压时，假设标准商用电表电压有效值为Ur，待校准电表测量电压为Urms，电压校准系数为Ugain，INT为取整函数，电压校准系数计算公式如下所示：
    Figure 379402dest_path_image001
    。
  4. 根据权利要求3所述的方法，其特征在于，当所述电能数据为电流时，假设标准商用电表电流有效值为Ir，待校准电表测量电流为Irms，电流校准系数为Igain，电流校准系数计算公式如下所示：
    Figure 543142dest_path_image002
    。
  5. 根据权利要求4所述的方法，其特征在于，当所述电能数据为功率时，设商用电表有功功率值为Preal，待校准电表功率值为DataP，功率校准系数为Pgain，功率校准系数计算公式如下所示：
    Figure 544596dest_path_image003
    。
  6. 根据权利要求5所述的方法，其特征在于，Ugain’与Igain’、Pgain’之间存在如下式2-9所示的关系，公式2-9中用到的HFconst为高频脉冲常数，计算公式如式2-7所示；公式2-7中U n为电表终端实际接入电压，I b为实际接入电流，Vu、Vi分别为计量芯片电压通道、电流通道的输入电压；公式2-9中用到的N为比例系数，计算公式如下公式2-8所示；公式2-8中的T A为电流互感器变比，R为电流采样电路电阻；
    Figure 477917dest_path_image004
    。
  7. 根据权利要求5所述的方法，其特征在于，所述待校准电表测量所述负载的电能数据时，使用中位均值滤波算法。
  8. 根据权利要求1所述的方法，其特征在于，所述计量芯片的寄存器分为两部分，分别是计量参数寄存器和校表参数寄存器。
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