{"id":272,"date":"2013-11-09T22:15:21","date_gmt":"2013-11-09T21:15:21","guid":{"rendered":"http:\/\/lukasz.kocewiak.eu\/blog\/?p=272"},"modified":"2013-11-09T22:13:18","modified_gmt":"2013-11-09T21:13:18","slug":"harmonic-mitigation-methods-in-wind-power-plants","status":"publish","type":"post","link":"https:\/\/lukasz.kocewiak.eu\/blog\/2013\/11\/09\/harmonic-mitigation-methods-in-wind-power-plants\/","title":{"rendered":"Harmonic mitigation methods in wind power plants"},"content":{"rendered":"

There are various techniques for dealing with the harmonic problem in large wind power plants (WPPs) depending upon the nature and source of the problem.
\nLarge offshore WPPs are characterized by complex structures including wide application of power electronic devices in wind turbines, FACTS devices and\/or HVDC transmission. Moreover, there is a large amount of passive components such as filters, cable arrays, transformers, transmission cables, and shunt compensation equipment. Consequently, there are many potential sources of harmonic problems, and simultaneously many ways of dealing with them [1].
\nPrimarily there are two methods of harmonic mitigation in a WPP: (i) avoiding harmonic resonance by design and (ii) design and use of filters [2]. A good design involves system layout, component selection and controller tuning with the aim of avoiding potential resonance conditions in the WPP.<\/p>\n

\"Harmonic<\/a>
Fig. 1 Harmonic mitigation methods in wind power plants.<\/figcaption><\/figure>\n

Both passive and active filtering could be used for harmonic mitigation. It is recognized that passive filtering is the state-of-the-art technology. However, it requires extensive knowledge of the system during the WPP design phase. In many cases information about the system is uncertain and over-sizing of passive filters may take place to cover uncertainties and risks.
\nDue to the fact that more and more power electronic equipment (e.g. wind turbines with grid connected converter, STATCOMs, HVDC, etc.) is being utilised in WPPs, active filtering appears to be an interesting solution.
\nActive filtering can be implemented at the converter control level, thereby avoiding or reducing the need for installing expensive passive filters. Moreover, active filter controllers could be tuned and re-tuned, sometimes adaptively, to overcome the uncertainties faced during the WPP design phase [3].
\nA comparison between passive and active filters including major factors is presented in Table 1. It can be easily seen that there is a potential in active filtering and the technology is improving.<\/p>\n

\nTable 1 Comparison between passive and active filtering technology.<\/em><\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Indices<\/b><\/td>\nPassive filters<\/b><\/td>\nActive filters<\/b><\/td>\n<\/tr>\n
Technology<\/em><\/td>\nKnown<\/td>\nImproving<\/td>\n<\/tr>\n
Reliability<\/em><\/td>\nHigh<\/td>\nMedium<\/td>\n<\/tr>\n
Effectiveness<\/em><\/td>\nMedium<\/td>\nGood<\/td>\n<\/tr>\n
Engineering time<\/em><\/td>\nLarge<\/td>\nMedium<\/td>\n<\/tr>\n
Power electronics<\/em><\/td>\nNo<\/td>\nYes<\/td>\n<\/tr>\n
Energy storage<\/em><\/td>\nLarge<\/td>\nSmall<\/td>\n<\/tr>\n
EMI<\/em><\/td>\nNo<\/td>\nYes<\/td>\n<\/tr>\n
Control circuit<\/em><\/td>\nNo<\/td>\nYes<\/td>\n<\/tr>\n
Voltage regulation<\/em><\/td>\nNo<\/td>\nYes<\/td>\n<\/tr>\n
Dynamic response<\/em><\/td>\nSlow<\/td>\nFast<\/td>\n<\/tr>\n
Cost<\/em><\/td>\nLow<\/td>\nHigh<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Considering the different attributes, probably hybrid solutions involving both the passive and the active filters at various locations, as shown in Fig. 1, would be the most beneficial for effective harmonic mitigation scheme. In order to optimize the WPP design from harmonic emission and stability perspective some more studies and research is required [4]. The hybrid solutions would comprise of:<\/p>\n

    \n
  1. Passive filtering at the wind turbine level:\n