NXP Middleware Metering library

The Kinetis-M metering library is used in Kinetis-M series chips and mainly used in metering applications for accurate computation of the active energy, reactive energy, active power, reactive power, apparent power, RMS voltage, and RMS current. Normally this metering library is used for three-phase four-wire, two-phase two-wire or single-phase one-wire applications. This application will guide to use the library in non-standard single-phase multi-channel metering applications. Furthermore, the implementation described in this document can also be extended to other single-phase non-standard meters. The Kinetis-M microcontrollers, e.g. KM34Z128 and KM35Z75M, can offer a high-performance analog front-end (24-bit AFE) combined with an embedded Programmable Gain Amplifier(PGA). Besides high-performance analog peripherals like auxiliary 16-bit SAR ADC, these devices integrate memory, input-output ports, digital blocks, and a variety of communication options. Moreover, on KM35Z75M, the ARM Cortex-M0+ core, with MMAU (Memory Mapped Arithmetic Unit) support for 32-bit and 64-bit math, enables fast execution of metering algorithms. There are two metering libraries provided with Kinetis-M chips, Filter-Based library and FFT library. This application will use Filter-Based library. The Filter-Based Metering Algorithm can be easily integrated into an electronic power meter application. The algorithm requires only instantaneous voltage and current samples to be provided at constant sampling intervals. These instantaneous voltage and current samples are usually measured by an AFE with the help of a resistor divider, in the case of a phase voltage measurement, and a shunt resistor, current transformer or a Rogowski coil in the case of a phase current measurement. All current measurement sensors introduce a phase shift into current measurement. Therefore, it is necessary to align the phases of the instantaneous voltage and current samples prior to their use by the Filter-Based Metering Algorithm using either a digital filter or with the aid of delayed sampling.

Documentation

Documentation is based on application notes, that can be found:

• FFT-Based Algorithm for Metering Applications
• Filter-Based Algorithm for Metering Applications
• Using the FFT on Sigma-Delta ADCs

License

This repository is under LA_OPT_Online Code Hosting NXP_Software_License.

Examples

The examples are placed on the repository mcux-sdk-examples. The example list with description:

• meterlib1ph_test

• This example demonstrates use of the metering library in typical one-phase power meter application.

• meterlib1phkwh_test

• This example demonstrates use of the metering library in active energy one-phase power meter application.

• meterlib1phrc_test

• This example demonstrates use of the metering library in typical one-phase power meter application with Rogowski coil sensor.

• meterlib2ph_test

• This example demonstrates use of the metering library in typical two-phase power meter application.

• meterlib2phkwh_test

• This example demonstrates use of the metering library in active energy two-phase power meter application.

• meterlib2phrc_test

• This example demonstrates use of the metering library in typical two-phase power meter application with Rogowski coil sensor.

• meterlib3ph_test

• This example demonstrates use of the metering library in typical polyphase power meter application.

• meterlib3phkwh_test

• This example demonstrates use of the metering library in active energy polyphase power meter application.

• meterlib3phrc_test

• This example demonstrates use of the metering library in typical polyphase power meter application with Rogowski coil sensor.

• meterlibFFT1ph_test

• This example demonstrates use of the FFT metering library in the typical single-phase power meter application with proportional current sensor and with the S/W phase shift correction. AFE conversion mode (single/continuous) may be selected by the 'AFE_MODE' constant. Number of the FFT samples is set to 32, number of output harmonics is 16 then.

• meterlibFFT2ph_test

• This example demonstrates use of the FFT metering library in the typical two-phase power meter application with derivative current sensor without the S/W phase shift correction. AFE conversion mode (single/continuous) may be selected by the 'AFE_MODE' constant. Number of the FFT samples is set to 64, number of output harmonics is 32 then.

• meterlibFFT3ph_test

• This example demonstrates use of the FFT metering library in the typical three-phase power meter application with proportional current sensor and with the S/W phase shift correction. AFE conversion mode (single/continuous) may be selected by the 'AFE_MODE' constant. Number of the FFT samples is set to 64, number of output harmonics is 32 then. This example allows to measure the sense of rotation of the 3-ph mains.

• meterliblp1ph_test

• This example demonstrates use of the low power metering library in typical one-phase power meter application.

• meterliblp1phkwh_test

• This example demonstrates use of the low power metering library in active energy one-phase power meter application.

• meterliblp2ph_test

• This example demonstrates use of the low power metering library in typical two-phase power meter application.

• meterliblp2phkwh_test

• This example demonstrates use of the low power metering library in active energy two-phase power meter application.

• meterliblp3ph_test

• This example demonstrates use of the low power metering library in typical polyphase power meter application.

• meterliblp3phkwh_test

• This example demonstrates use of the low power metering library in active energy polyphase power meter application.