Description of drawings
Fig. 1 is conventional parallel connection type active current filter schematic diagram;
Fig. 2 is the equivalent electric circuit of conventional parallel active filter;
Fig. 3 is for compensating the equivalent electric circuit of the conventional parallel active filter after the side inductance splits;
Fig. 4 is the equivalent electric circuit that only changes the parallel active filter of other circuit equivalents of compensation branch road;
Fig. 5 is the equivalent electric circuit of parallel active filter of the present invention;
Fig. 6 is a parallel connection type active current filter schematic diagram of the present invention;
Fig. 7 is the load current simulation waveform of conventional active current filter in parallel;
Fig. 8 is the current on line side simulation waveform of conventional parallel connection type active current filter;
Fig. 9 is the current on line side simulation waveform of parallel connection type active current filter of the present invention;
Figure 10 is applied to A phase line voltage, power network current and the offset current waveform of a 400Hz electrical network for the present invention.
Designation among the figure:
10-imports filter inductance;
20-three-phase six switching inverters;
30-parallel connection type active electric filter branch road of the present invention;
21-compensation side three pole reactor;
22-three-phase bridge inverter;
23-electric capacity;
U
S-line voltage;
u
Sa, u
Sb, u
Sc-electrical network ABC three-phase voltage;
I
S-current on line side;
I
Sa-A phase electrical network output current;
I
L-load current;
I
C,-offset current;
I
Ca-A phase offset current;
Q
1To Q
6-be respectively first power switch pipe to the, six power switch pipes;
D
1To D
6-be respectively first diode to the, six diodes;
L
Sa, L
Sb, L
Sc-be respectively net side or load front-end A, B, C three-phase filter inductance;
L
S-net side (or load front end) filter inductance;
L
Ca, L
Cb, L
Cc-be respectively inverter to export A, B, C three-phase filter inductance;
L
C, L
C1, L
C2-be respectively inverter output inductor and two to split inductance;
X
S,
-be respectively inductance L
C1Harmonic impedance, inductance L
SImpedance of fundamental frequency and harmonic impedance;
C-inverter direct-flow side electric capacity;
L
f-rectifying and wave-filtering inductance;
C
f-rectifying and wave-filtering electric capacity;
The R-load resistance;
PWM-inverter A manages the PWM drive signal of Q2 mutually down.
Embodiment
Below in conjunction with accompanying drawing technical scheme of the present invention is elaborated:
As shown in Figure 1, be conventional parallel connection type active current filter schematic diagram, control rectifying circuit brings bigger di/dt in order to suppress not, adds three-phase filter inductance 40 in the AC side of control rectifying circuit not, the electric current that flows through this inductance comprises fundamental current and harmonic current, and inductor loss is bigger.The present invention integrates the three-phase filter inductance 40 of conventional shunt active power filter and compensation side three pole reactor 50, constitutes parallel connection type active electric filter of the present invention.
As shown in Figure 2, the desirable equivalent electric circuit of conventional shunt active power filter.Load equivalent is for containing fundamental current i
SAnd harmonic current
Current source I
L, the offset current equivalence is for only containing harmonic current
Current source, power supply U
sOnly provide fundamental current i to load
S
As shown in Figure 3, compensation side three pole reactor L
CMay be split into L
C1And L
C2Two inductance, then B point and the C current potential of ordering is respectively:
Wherein
Be the load harmonic current,
Be three-phase filter inductance L
SHarmonic impedance,
Be inductance L
C1Harmonic impedance.
If harmonic impedance
With
Equate, can be by on the harmonic compensation branch road, increasing harmonic voltage source
With the fundamental voltage source
Make B point and C point current potential equate as shown in Figure 4, that is:
Wherein
Because the compensation branch road is a current source, does not change the state of load-side and grid side by above-mentioned conversion, unique change be the both end voltage of compensating current element, and compensating current element is a controlled source, can be by the control break both end voltage.Thereby change the B point by above-mentioned equivalence and can directly link to each other because of equipotential with the C point, according to external circuit equivalence principle, offset current
Directly move into the injection of B point in Fig. 4 square frame, the circuit in Fig. 4 square frame can equivalence be an inductance L
S
As shown in Figure 5, Fig. 5 is the equivalent electric circuit of parallel connection type active current filter of the present invention.As seen, parallel connection type active current filter of the present invention has been compared following advantage with conventional parallel connection type active current filter:
1), the reducing of compensation side three pole reactor, filter current tracking ability is strengthened; The equivalent inductance value of compensation side three pole reactor increases, and the current ripples of net side is reduced; Therefore the present invention has better compensation effect.
2), the three-phase filter inductance is in load-side in the conventional topology, all load currents all flow through this inductance, and loss is bigger; The three-phase filter inductance only flows through fundamental current component in the net side among the present invention, and loss reduces.
As shown in Figure 6, shunt active power filter circuit topological structure of the present invention is made up of three-phase filter inductance 10, three-phase six switching inverters 20 and three phase rectifier filter circuit.Wherein: three-phase filter inductance 10 comprises A phase filter inductance L
Sa, B phase filter inductance L
Sb, C phase filter inductance L
Sc, three-phase six switch inversions 20 comprise the first switching tube Q1, second switch pipe Q2, the 3rd switching tube Q3, the 4th switching tube Q4, the 5th switching tube Q5, the 6th switching tube Q6, dc bus capacitor C, inverter AC side A phase output inductor L
Ca, inverter AC side B phase output inductor L
Cb, inverter AC side C phase output inductor L
CcThe three phase rectifier filter circuit is that three-phase diode is not controlled rectification+LC filter circuit.
A phase filter inductance L wherein
SaAn end and A input voltage u mutually
SaConnect A phase filter inductance L
SaThe other end respectively with inverter A output inductor L mutually
CaAn end, rectified load A phase input be connected B phase filter inductance L
SbAn end be connected in B phase input voltage u
Sb, B phase filter inductance L
SbThe other end and inverter B output inductor L mutually
CbAn end link to each other and be connected in rectified load B phase input, C phase filter inductance L simultaneously
ScAn end be connected in C phase input voltage u
Sc, C phase filter inductance L
ScThe other end and inverter C output inductor L mutually
CcAn end link to each other and be connected in rectified load C phase input, inverter AC side A phase output inductor L simultaneously
CaThe other end link to each other with the emitter of the first switching tube Q1 and be connected in the collector electrode of second switch pipe Q2, inverter AC side B phase output inductor L simultaneously
CbThe other end link to each other with the emitter of the 3rd switching tube Q3 and be connected in the collector electrode of the 4th switching tube Q4, inverter C phase output inductor L simultaneously
CcThe other end link to each other with the emitter of the 5th switching tube Q1 and be connected in the collector electrode of the 6th switching tube Q6 simultaneously, the collector electrode of the first switching tube Q1 links to each other with the collector electrode of the 3rd switching tube Q3 and is connected in the collector electrode of the 5th switching tube Q5 and the anode of dc bus capacitor C simultaneously, and the emitter of second switch pipe Q2 links to each other with the emitter of the 4th switching tube Q4 and is connected in the emitter of the 6th switching tube Q6 and the negative terminal of dc bus capacitor C simultaneously.
The present invention includes AC side three-phase filter inductance, three-phase six switching inverters, three-phase and do not control rectification+LC filter circuit.It is the control core device that control system adopts with DSP, electrical network three-phase voltage, load current and offset current and dc voltage signal are delivered to modulate circuit through voltage or current sensor sampling, signal input dsp controller after the processing, dsp controller carries out computing to the signal that sampling obtains then, produce pwm signal, through turning on and off of isolated drive circuit power controlling pipe, thereby realize harmonic compensation.
Below under the MATLAB software environment, the Active Power Filter-APF of conventional Active Power Filter-APF and this paper invention is carried out modeling and simulation.
Fig. 7 is the load current simulation waveform of conventional shunt active power filter.Contain fundamental current and harmonic current in the load current, contain this two current components in the three-phase filter inductance 40 simultaneously.
Fig. 8 is the current on line side simulation waveform of conventional shunt active power filter.At this moment, compensation side three pole reactor is 0.15mH.Current on line side THD%=6.78% after the compensation.
Fig. 9 is the current on line side simulation waveform of the parallel connection type active electric filter of this paper invention.This moment, other parameter of circuit was the same with conventional topology, only compensated the side three pole reactor and was reduced to 0.05mH, the electric current THD%=4.37% after the compensation.As seen, compensation side three pole reactor size is minimized, the current tracking ability strengthens, and compensation performance is improved greatly.And the electric current that flows through three-phase filter inductance 10 only contains fundamental current basically.
Emulation contrast can draw, and this paper inventive circuit topology has good harmonic suppression effect, compensates simultaneously that side three pole reactor size is reduced, the current tracking ability strengthens.
The experimental waveform of A phase line voltage, power network current and offset current when Figure 10 is applied to a 400Hz electrical network for the present invention, current on line side THD reaches 4.6%.
Draw from emulation and experimental result: the parallel connection type active electric filter of this paper invention can be realized power network harmonic wave management preferably, compensates simultaneously that side three pole reactor size is minimized, the current tracking ability strengthens.