As both WV (WavePack) and FLAC are lossless audio format, there should be no problem with conversion from one to other or vice versa without risk of lossing audio quality. Many multimedia converters support both .wv and .flac files, so achieving wv to flac conversion should be easy.
Open WV file Open FLAC fileA music library management program - renamed to Helium (version 12) and replaced in 2016
Universal All Purpose Free Media, Audio & Video Converter Player Recorder