Abstract: The present invention relates to a PPG signal quality evaluation method and apparatus and a PPG signal processing method and system. The PPG signal quality evaluation method includes: S1: acquiring an original signal; S2: when an average amplitude difference thereof is within a first preset range, executing S3, and otherwise, executing S11; S3: acquiring a useful signal; S4: when the high-frequency signal-to-noise ratio and the low-frequency signal-to-noise ratio thereof are respectively greater than corresponding first threshold values, executing S5, and otherwise, executing S11; S5: when the kurtosis and the skewness of a power spectrum of the useful signal are respectively greater than second threshold values, executing S6, and otherwise, executing S11; S6: when the average peak period of a correlation function is within a second preset range, executing S7, and otherwise, executing S11.

Abstract: The present invention discloses a stereoscopic DC-DC converter for power transfer between two DC grids, the converter comprises a first converter, a second converter and a third converter, a positive terminal of the first converter is connected to a positive terminal of a second DC grid, a negative terminal of the first converter is connected to a positive terminal of the second converter, a negative terminal of the second converter is connected to a positive terminal of the third converter, a negative terminal of the third converter is connected to a negative terminal of the second DC grid, in the meantime, a positive terminal of the second converter is also connected to a positive terminal of a first DC grid, and the negative terminal of the second converter is also connected to a negative terminal of the first DC grid.

Abstract: The present invention discloses a hybrid converter and a wind power generating system, the hybrid converter including a voltage source converter, a line commutated converter and a line commutated converter, a positive DC terminal of the voltage source converter is connected to a negative DC terminal of the line commutated converter, a positive DC terminal of the line commutated converter is connected to a positive DC transmission line, a negative DC terminal of the voltage source converter is connected to a positive DC terminal of the line commutated converter, and a negative DC terminal of the line commutated converter is connected to a negative DC transmission line. The present invention features a self-commutating capability, can be directly connected to a wind farm to convert wind power to DC power, and is able to improve rated voltage and rated power of the hybrid converter, technology of each component thereof is mature, and system reliability thereof is high.

Abstract: A multiport DC-DC autotransformer for interconnecting three or more DC systems. The autotransformer includes 2N?1 converters sequentially connected in series at a DC side, and connected to an AC transmission line via an AC link at an AC side, and a positive terminal of the ith converter of the 2N?1 sequentially connected converters and a negative terminal of the (2N?i)th converter are respectively connected to a positive terminal of the ith DC system and a negative terminal thereof, where N represents the number of DC systems, and i represents the serial number of converters. Also disclosed are a method for determining power rating of each converter of the multiport DC-DC autotransformer, and a method for controlling the autotransformer. Most power can be transferred between different DC systems via a direct electrical connection without DC-AC-DC conversion.

Abstract: The present invention discloses a stereoscopic DC-DC converter for power transfer between two DC grids, the converter comprises a first converter, a second converter and a third converter, a positive terminal of the first converter is connected to a positive terminal of a second DC grid, a negative terminal of the first converter is connected to a positive terminal of the second converter, a negative terminal of the second converter is connected to a positive terminal of the third converter, a negative terminal of the third converter is connected to a negative terminal of the second DC grid, in the meantime, a positive terminal of the second converter is also connected to a positive terminal of a first DC grid, and the negative terminal of the second converter is also connected to a negative terminal of the first DC grid.

Abstract: A multiport DC-DC autotransformer for interconnecting three or more DC systems. The autotransformer includes 2N?1 converters sequentially connected in series at a DC side, and connected to an AC transmission line via an AC link at an AC side, and a positive terminal of the ith converter of the 2N?1 sequentially connected converters and a negative terminal of the (2N?i)th converter are respectively connected to a positive terminal of the ith DC system and a negative terminal thereof, where N represents the number of DC systems, and i represents the serial number of converters. Also disclosed are a method for determining power rating of each converter of the multiport DC-DC autotransformer, and a method for controlling the autotransformer. Most power can be transferred between different DC systems via a direct electrical connection without DC-AC-DC conversion.

Abstract: The present invention discloses a hybrid converter and a wind power generating system, the hybrid converter comprising a voltage source converter, a line commutated converter and a line commutated converter, a positive DC terminal of the voltage source converter is connected to a negative DC terminal of the line commutated converter, a positive DC terminal of the line commutated converter is connected to a positive DC transmission line, a negative DC terminal of the voltage source converter is connected to a positive DC terminal of the line commutated converter, and a negative DC terminal of the line commutated converter is connected to a negative DC transmission line. The present invention features a self-commutating capability, can be directly connected to a wind farm to convert wind power to DC power, and is able to improve rated voltage and rated power of the hybrid converter, technology of each component thereof is mature, and system reliability thereof is high.