有源電力濾波器英文文獻(xiàn)和中文翻譯-展示頁
2025-07-08 02:32本頁面
【正文】 e 5th, 11th and 13th harmonic current[10].II. PRINCIPLES OF CURRENT HARMONIC COMPENSATIONThe hybrid active power filter topology is shown in , which consists of a threephase pulse width modulation(PWM) voltagesource inverter (active power filter, APF)and the passive filter connected in series to APF through coupling transformer. Generally, the active power filter acts as a controlled voltage source and force the harmonic current into the hybrid active power filter. The principle of operation of current harmonic is explained by the singlephase equivalent circuit shown in when the feedback control is applied to the active power filter. In the current harmonic pensation strategy, the active power filter is considered as a controlled voltage source VAPF, and ZF is the impedance of passive filter, ILh is the load harmonic current, ZS is the system impedance.In order to eliminate harmonic of the system current, the active power filter is controlled as a current controlled voltage source. The active power filter imposes a voltage signal VAPF that forces load harmonic current flow into the passive filter, thus improving its pensation performance in despite of the variation in the tuned frequency of the passive filter. The voltage reference of active power filter is equal to VAPF = K ? I sh (1)Where, K is the harmonic pensation gain. Supposing utility voltage is pure sinusoidal, the ration between the utility harmonic current and the load harmonic current is obtained, which can be used to denote the filtering characteristics of hybrid active power filter.Otherwise, K acts as a resistance to damp resonance between ZS and ZF. The larger K is selected, the lower the harmonic contents in the utility current. But this will increase the required power rating of the active power filter. In real condition, K is finite. Otherwise, closed loop control system will bee unstable. Fig. 1 hybrid active power filter configuration.Fig. 2 Singlephase equivalent circuit of the hybrid active power filter scheme.III. ANALYSIS OF THE HYBRID FILTERPERFORMANCE IN A DISTRIBUTION SYSTEMThis section will show the pensation performance of hybrid active power filter through an example. The power distribution energizes the six medium frequency furnace, each of 300KW rate power. The medium frequency furnaces energized by six pulse uncontrolled rectifiers. The single phase diagram of the power distribution is shown in considering hybrid active power filter and medium frequency furnace.Fig. 3 Singlephase line diagram of the power distribution systemThe system harmonic content and harmonic criterion are shown in Table I and the 5th, 7th and 11th frequency harmonics exceed the criterion. So, the passive filters are tuned at the 5th, 7th and 11th frequency harmonic and the rate of reactive power pensation is 500kVar. The system inductance and the parameters of passive filters are shown in Table II.TABLE IPOWER SYSTEM AND PASSIVE FILTER PAREMETERS5th7th11thHarmonic content(A)622814Harmonic criterion(A)TABLE IIPOWER SYSTEM AND PASSIVE FILTER PAREMETERSL(mh)C(uf)R( m Ω)KVARSystem95734821201123826In this case, the rate of active power filter is 25KVA since it would only pensate current harmonic and the coupling transformers turns ratio is equal to 2. (a) shows the harmonic attenuation rate of passive filter and hybrid active power filter. The hybrid active power filter is characterized by using three single resonant filter tuned at the 5th, 7th and 11th harmonic frequency as shown . Therefore, the passive filter presents low impedance at the 5th, 7th and 11th harmonic frequency and their neighborhood. When no active power filter is connected in series with the passive filter, the harmonic amplifying phenomenon appear in the frequency range of 200240Hz,300340Hz and 500640Hz. When the active power filter with a feedback gain of 20 is bined, no harmonic amplifying phenomena occu
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