Harmonic Measurement And Stochastic Analysis For Residential Harmonic Source Load

As non-linear home appliances propagate in residential load,its harmonic effect on power system becomes more serious.The cost is undoubtedly enormous with installed monitoring tools,for the quantity and regional distribution of the residential loads.Therefore,establishing a model that can effectively evaluate harmonic currents emitted from residential loads is necessary.At present,there are relatively few quantitative studies on residential harmonic source loads.Relavence theories on harmonic is not enough to determine the variation pattern of residential load assembled by kinds of household appliances.This paper,first of all,searches the varying law of each harmonic current through measured data,and analyses the dominat factors influence on harmonic current variation.Then,a bottom-up harmonic evaluation model for residential harmonic source loads is established based on their characteristics found.Main research contents of this paper are listed as followes:(1)The working currents of common non-linear home appliances are sampled and analyzed.The principle components of harmonic current are 3rd?5th?7th.The harmonic amplitude decreases as the harmonic order increses.And the phase distribution difference between harmonic currents of each order is delicate.The frequency-domain model of home appliances show that their harmonic characteristics,influenced by the supply voltage,are relative closely with the topology and parameters of their circuits.In the practical power distribution network,the supply voltage reduces the harmonic emission levels of non-linear household appliances.It also affects the harmonic phase.(2)The current and voltage at four points,one household?one dwelling unit?transformer low-voltage side and high-voltage side,are sampled for series days.The variation laws of active power?the magnitude and phase of harmonic currents are analyzed.The non-linear loads,harmonic source in residential load,determine the harmonic emission level which is less affected by linear home appliances.The linear correlation between each harmonic and active power is different.The 3rd harmonic is most relevant with active power.The main factor affects the 5th harmonic pattern is the THD of voltage,and the 7th harmonic is amplitude of voltage.(3)A bottom-up model,individual home appliance as elementary unit,is established based on harmonic characteristics of residential load.The switch states of home appliances are relative closely with residential activities.Therefore,the activity probability can represent the possibility of switching on the home appliance.Through Monte-Carlo simulation based on corresponding statitics,the switch state of each home appliance is determined.Combining with harmonic current source model of home appliance,the harmonic current emitted by residential load is carried out.The harmonic current source data of diffe'rent brands is provided for each kind of home appliances.The correction factors of each harmonic current,figured out by supply voltage,are used to calibrate the model developed.