Advanced periodic control for power harmonics mitigation

The rapidly growing amount of power harmonics injected by power electronic converter interfaced loads and distributed generator systems may cause serious power quality problems in the electrical power systems, such as harmonic losses, resonances, device malfunction, and even entire system instability. Power harmonics induced by power electronics converters usually concentrate on some specific frequencies. For instance, single-phase H-bridge converters mainly produce (4k ± 1) (k = 1, 2, . . . )-order power harmonics, while n-pulse (n = 6, 12, ...) converters, such as in high-voltage direct current (HVDC) transmission systems, mainly produce (nk + 1) (k = 1, 2, .. . )-order power harmonics [1-7], and also diode rectifiers loads used in many applications disturb the grid. As discussed in Chapter 2, the IMP-based fundamental periodic controllers fail to optimally compensate power harmonics with high control accuracy, while maintaining fast dynamic response, guaranteeing robustness, and being feasible for implementation. To address these issues, this chapter will explore advanced IMP-based PC technologies [8] for optimal power harmonics compensation. The general design methodology also comprises an internal model for selective power harmonic signals and synthesis methods for plug-in PC systems. These advanced PC schemes not only exploit the periodicity of reference/disturbance, but also account for its harmonic frequency distribution. The relationship between fundamental periodic controllers and advanced ones will be demonstrated.