1、附录附录一：英文文献A 10KV Shunt Hybrid Active Filter for a Power DistributionSystemAbstractthis paper analyzes the compensation performance of a shunt hybrid active power filter. The hybrid active power filter, which combines passive filter and active power filter, has both respective merits, and is an impor
2、tant developing trend of filtering device. The hybrid active power filter can reduce the capacity of active power filter effectively and is more suitable for the engineering application for high voltage nonlinear loads. The compensation performance of hybrid active power filter is analyzed by estima
3、ting the effect of different active power filter gain and parameters change. Then, a conclusion has been obtained that the harmonic attenuation rate is insensitive to the variation of passive parameters when the active power filter with an enough feedback gain is combined. Finally, the feasibility a
4、nd validity of proposed scheme is verified by Simulation using Matlab and a hybrid shunt active power filter prototype. Index Terms:Current harmonics compensation, active power filter, passive filter, generalized integrators.I .INTRODUCTIONIn the development of power electronics brings convenience t
5、o energy conversion and utilization and also causes power quality problems. As one of the key technologies in combating power grid pollution and improving the power quality, active power filter (APF) has become a new research emphasis in power electronics technology1-5. Because of high initial cost,
6、 the further application of active power filter is restricted. The HAPF(Hybrid Active Power Filter), combination of APF and passive filter (PF), can reduce the capacity of Affectively and is more suitable for the engineering application of APF for high voltage nonlinear loads.Traditionally, Passive
7、filter has been used to eliminate the harmonic in power system due to his low cost and high efficiency. A passive filter shows the low impedance at tuned frequency to absorb current harmonic and has a good compensation performance. However, passive filter has the disadvantage of depending on the par
8、ameters of power system, susceptible to the load and power system resonant and the characteristic change due to aging. In addition, passive filter usually is designed with fixed parameters, which can not be lightly adapted for the variation operation condition.Active power filter has been developed
9、to overcome of disadvantages of passive filter and can provide flexible and reliable compensation, but is not a cost-effective solution duet the high operation cost.Because of the drawbacks of passive filter and active power filter, the research on hybrid active power filter has become more attracti
10、ve 6-9. Hybrid active power filter composed of passive filter connected in series to an active power filter improves the compensation performance of passive filter remarkably, give more flexibility and reliability to filter device, and redound to the use of active power filter in high-power system a
11、voiding the expensive initial cost.In this paper, the compensation performance of hybrid active power filter in an industrial power distribution system is analyzed by estimating the effect of different active power filter gain and parameters change. Finally, the compensation of hybrid active power f
12、ilter is verified by simulation and a laboratory prototype. The passive filter of prototype was tuned at the seventh harmonic and the generalized integrators are used to eliminate the 5th, 11th and 13th harmonic current10.II. PRINCIPLES OF CURRENT HARMONIC COMPENSATIONThe hybrid active power filter
13、topology is shown in Fig.1, which consists of a three-phase pulse width modulation(PWM) voltage-source 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 t
14、he harmonic current into the hybrid active power filter. The principle of operation of current harmonic is explained by the single-phase equivalent circuit shown in Fig.2 when the feedback control is applied to the active power filter. In the current harmonic compensation strategy, the active power
15、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 ac
16、tive power filter imposes a voltage signal VAPF that forces load harmonic current flow into the passive filter, thus improving its compensation performance in despite of the variation in the tuned frequency of the passive filter. The voltage reference of active power filter is equal toVAPF = K I sh
17、(1)Where, K is the harmonic compensation 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 resis
18、tance 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 become unstable. Fig. 1
19、 hybrid active power filter configuration.Fig. 2 Single-phase equivalent circuit of the hybrid active power filter scheme.III. ANALYSIS OF THE HYBRID FILTERPERFORMANCE IN A DISTRIBUTION SYSTEMThis section will show the compensation performance of hybrid active power filter through an example. The po
20、wer 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 Fig.3only considering hybrid active power filter and medium frequency fu
21、rnace.Fig. 3 Single-phase 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 rat
22、e of reactive power compensation is 500kVar. The system inductance and the parameters of passive filters are shown in Table II.TABLE IPOWER SYSTEM AND PASSIVE FILTER PAREMETERS5th 7th 11thHarmonic content(A)62 28 14Harmonic criterion(A)26.5 19.8 12.3TABLE IIPOWER SYSTEM AND PASSIVE FILTER PAREMETERS
23、L(mh) C(uf) R( m ) KVARSystem 2.45thharm.filter36.57 11.08 957 3487thharm.filter57.86 3.57 2120 11211thharm.filter66.46 1.26 3826 39.6In this case, the rate of active power filter is 25KVA since it would only compensate current harmonic and the coupling transformers turns ratio is equal to 2.Fig.4 (
24、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 inFig.3. Therefore, the passive filter presents low impedance at t
25、he 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 200-240Hz,300-340Hz and 500-640Hz. When the active power filter with a feedback gain of 20 i
26、s combined, no harmonic amplifying phenomena occurs. Meanwhile, only adapting the passive filter, the filtering characteristic is unsatisfactory even at the 5th, 7th and 11th harmonic frequency. When the active power filter with a feedback gain of 20 is combined, the harmonic attenuation rate is inc
27、reased and the filter performance of the hybrid active power filter is satisfactory at the 5th, 7th and 11th harmonic frequency.Fig.4 (b) shows the harmonic content of power system indifferent condition. When no filter is connected in parallel with the utility, the 5th, 7th and 11th harmonic current
28、 exceed the criterion seriously. After only adapting the passive filter, the harmonic current of utility is weakened but unsatisfactory adequately. When the active power filter with a feedback gain of 20 is combined, most of 5th, 7th and 11th harmonic current is forced flowing into the hybrid active
29、 power filter.Fig.5 shows how the active power filter gain K changes the harmonic attenuation rate of system current. Large value of K improves the hybrid active power filter compensation performance by increase the harmonic impedance of power system.In addition, Fig.5 shows that the low values of p
30、assive filter quality factor Q will increases the impedance at the resonant frequency and weaken the compensation performance of hybrid active power filter. The passive filter quality factor Q decides the passive filter bandwidth. Though increasing the value of active power filter gain K can compens
31、ate the adverse effect of low value of Q, which would results in the increase of active power filter output voltage required to keep the same compensation performance, thus increasing the active power filter rated power.Fig. 4 Hybrid active power filter frequency response and Harmonic Content.From F
32、ig.5, a conclusion can be received that the quality factor of passive filter and the active power filter gain directly affect the compensation performance of hybrid active power filter when the tuned frequency is fixed. If the quality factor of passive filter is not properly selected, the active pow
33、er filter gain K must been increased to obtain the satisfying compensation performance.Fig. 5 Hybrid active power filter frequency response for different values of passive filter quality factor Q.Fig.6 shows the hybrid active filter frequency response for different values of the system equivalent im
34、pedance. Generally, the system equivalent impedance must be lower to the passive filter equivalent impedance at the resonant frequency; otherwise, the passive can not obtain the favorable compensation performance and most load harmonic current will flow to the power system. When no active power filt
35、er is connected in series with the passive filter, if utility impedance is lower than the passive filter impedance at the tuned frequency, the harmonic attenuation rate is decreased and the filter performance of passive filter is unsatisfactory, as shown in Fig.6 (a). When the active power filter wi
36、th an enough feedback gain is combined, the harmonic attenuation rate is insensitive to the variation of utility impedance, as shown in Fig.6 (b).Fig.6 also depicts that the active power filter gain K in bulky utility (small values of Zs) must bigger than that in weak utility (big value of Zs) to ob
37、tain the same compensation performance.Fig. 6 Hybrid active power filter frequency response for different values of the system equivalent impedance.The simulation results are shown in Fig.7-10. Fig.7 shows the phase-a load current and it can be seen that the load current is greatly distorted. Fig.8
38、presents the phase-a supply current when hybrid active power filter is working. Now it can be seen that the hybrid active power filter has improved the quality of supply current markedly and the dominating harmonic current has been eliminated effectively. Fig.9 shows the phase-a hybrid filter curren
39、t. It consists of 5th, 7thand 11th harmonic current mostly.The dynamic compensation performance is studied by load perturbation response and shown in Fig.10. The change in the source current is observed smooth and steady state is reached within 2 cycles.Fig.7. Simulated current waveforms for hybrid
40、filter compensation. Top: simulate load current; bottom: its frequency spectrumFig.8. Simulated current waveforms for hybrid filter compensation. Top: simulate system line current; bottom: its frequency spectrum.Fig.9. Simulated current waveforms for hybrid filter compensation. Top: simulate hybrid
41、filter current; bottom: its frequency spectrum.Fig.10. Dynamic simulated current waveforms for hybrid filter compensation. Top: simulate system line current; middle: simulate load current; bottom: simulate hybrid filter current.IV. EXPERIMENTAL RESULTSA three-phase hybrid shunt active power filter l
42、aboratory prototype using IGBT was implemented and tested in the compensation of a six-pulse uncontrolled rectifier, as shown in Fig.11. The VSI dc-link voltage is composed of a capacitor bank of 6800F for a dc-link voltage 450V. The Eupec 1200V/200A IGBT are used and driven by theM57962L gate drive
43、rs. The digital control system incorporates a double DSP (TMS320C32 and TMS320F240) and CPLD circuit. The sampling period is 200 s . Phase detection and control algorithm are completed byTMS320C32, and sampling and SVPWM program are implemented by TMS320F240. The inverter was operated at5-kHz switch
44、ing frequency and was connected in series to a passive filter directly. The passive filter was tuned at the seventh harmonic (350Hz) and quality factor Q equal to 60.The parameters of the experiment circuit are shown in Table III.Fig.11 PI current controller using generalized integratorsTABLE IIITHE
45、 PARAMETERS OF THE EXPERIMENT CIRCUITUtility impedance 0.5mHUtility phase-phase voltage 380VDc-voltage 200VC7 50uFL7 4mHSince such a single seventh harmonic tuned LC filter issued, a no negligible amount of the 5th, 11th and 13thharmonic current still remains in the supply. Thus, the generalized int
46、egrators are used to eliminate the 5th, 11th and13th harmonic current.The proposed controller based on generalized integrators in stationary frame is depicted in Fig.12, Where, *VAPF is Violate reference， *is is grid current reference.Fig.12 PI current controller using generalized integratorsWhere,
47、Ki is the integral coefficient. The following discrete formula is use to realize the digital generalized integrators.For reducing the computation time, the generalized integrators are implemented by iterative arithmetic.When generalized integrators are used, the harmonic attenuation rate is shown in
48、 Fig.13. Fig.13 illustrates that the5th, 11th, 13th, 17th and 19th harmonic current are eliminated effectively by reason of generalized integrators.Steady-state experimental results are shown in Figs.14-16.Fig.14 (a) shows the experimental waveform of load current; the associate frequency spectrum i
49、s shown in Fig.14 (b).In this case, the load current consists of a mass of harmonic current. As shown in Fig.15, when only proportion controller is used, the elimination of harmonics besides tuned frequency is very limited by hybrid active power filter.With hybrid active power filter compensation using PI controller based on generalized integrators, the 5th, 7th, 11th,13th, 17thand 19th harmonics had been eliminated effectively as shown in Fig.16. When the shunt APF is plunged, the DC linkvoltage can arrive at reference value rapidly, as shown in Fig 7.Fig.14. Experi
