Design of Variable Frequency Power Supply Measurement System Based on FPGA and DSP

MOS power IC full range

Probe domestic high frequency needle JKT-50L high frequency needle with 3 probes

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Overview:
Starting from the application requirements of the real-time measurement of the variable-frequency power supply parameters, the FPGA and DSP are the hardware cores for the wide frequency range of the variable-frequency power supply. A data acquisition and calculation system based on variable step size adaptive sampling method is designed. The system has the characteristics of strong real-time performance, high integration and flexible expansion.

In the power system, the frequency conversion system is a kind of power electronic equipment, and the voltage and current on the output side are rich in high-order harmonics, and have the characteristics of large adjustable frequency range and high speed. When the harmonic content of the system reaches a certain level To a certain extent, it has certain impacts and hazards to the power system and power users. In the harmonic analysis, if the signal frequency and the sampling period do not match, or the waveform is not periodic during the entire sampling period interval, it will be generated. Spectrum leakage error. If the frequency of the synchronous fundamental wave can be realized, the number of truncated sampling data is exactly an integer multiple of the period of the fundamental signal, which can solve the problem that the sampling of the measured signal is discontinuous at the beginning and the end.

The author uses adaptive real-time adjustment of sampling rate method to track the fundamental frequency of the signal in real time, and adopts the method of soft synchronization to realize the synchronous sampling of AC. The hardware system with FPGA and DSP as the control core implements multi-channel synchronous sampling, which can effectively reduce the spectrum. Measurement error caused by leakage. On the one hand, the three-phase voltage is calculated by this method. The amplitude and phase ratio of the current and the harmonics of each harmonic are calculated according to the calculation method of the power frequency sine. On the one hand, we can use the calculated harmonics as a reference, and add appropriate external filters or algorithms to eliminate the influence of harmonics on the system and measurement.

1 variable frequency power supply measurement system overall design data acquisition system structure shown in Figure 1, three-phase voltage and three-phase current signal after the sensor is sent to the filter circuit, and then through the A / D conversion module for six-way simultaneous sampling, without losing phase information, Finally, the DSP performs parameter calculation and processing. The dual-port RAM is used as the buffer chip for bidirectional communication between the A/D conversion module and the DSP. The dual-port RAM chip has two independent control lines. The address line and the data line can be used for any port. Independent operation. The timing control of the entire data acquisition circuit is completed by the FPGA, which is beneficial to the DSP to perform data operations at full speed, thus ensuring the continuity and real-time of the sampling.

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