Staggered driving PWM compensating current generator
Technical field
The utility model relates to a kind of PWM compensating current generator, relates in particular to a kind of staggered driving PWM compensating current generator that the harmonic current of electric power system and reactive current are carried out initiatively following the tracks of compensation of being used for.
Background technology
Adopting modern power electronics technology that harmonic current in the electric power system and reactive current are carried out Active Compensation, is development in recent years flexible transmission technology (FACTS) of getting up and the important content in the custom power technology (D-FACTS).For example Active Power Filter-APF (APF) and STATCOM (STATCOM) etc. all belong to the compensating current generator that adopts modern power electronics technology to make.
In order to obtain high efficiency, high-speed effect, this class compensating current generator adopts pulse width modulation (PWM) method to produce required fast-changing high strength offset current usually.The PWM method is that triangular wave (carrier wave) signal that command signal and frequency are significantly higher than the command signal frequency is compared, the time dependent command signal of amplitude is converted to the rectangular pulse signal that a series of width and instruction signal amplitudes are directly proportional, i.e. pwm signal.Pwm signal reflects the variation of command signal amplitude with the variation of pulse duration.Control opening and turn-offing of high power semi-conductor power device with this pwm signal, can obtain jumbo PWM potential pulse,, convert it into the offset current of desirable strength then by the carrier frequency component in the big capacity inductor inhibition pwm pulse.
There are two wretched insufficiencies in known PWM compensating current generator:
1) contains higher-strength carrier frequency ripple current in the offset current that known PWM compensating current generator produces, cause electromagnetic interference.If will reduce the ripple current level, then need the output inductor that adopts inductance value bigger, or improve carrier frequency.But the inductance value that increases output inductor can limit the maximum rate of change of output current, and compensation speed and effect are followed the tracks of in influence, can increase volume, weight and the cost of inductor simultaneously; And improve the switching loss that carrier frequency can increase semiconductor power device, and lower efficiency, and limited by the semiconductor power device switching speed, can not too improve.So the selection of need in several limiting factors, compromising, cause restriction to the compensating current generator technical performance.
2) in compensating current generator when work, also exist than large ripple current in the DC loop of its inverter bridge, causes the DC bus-bar voltage fluctuation and produce than lossy in the dc-link capacitance device.Be the assurance device operate as normal, need bigger dc-link capacitance device, increased volume, weight and the cost of device.
The utility model content
The purpose of this utility model is exactly in order to improve known PWM compensating current generator above shortcomings, a kind of staggered driving PWM compensating current generator is provided, its enough lower carrier frequency of energy and less output inductor, obtain than the significantly reduced output ripple electric current of known technology method, ripple current effective value in the DC loop is also reduced to about 46% of known technology method simultaneously, thereby the indexs such as current tracking speed, output ripple electric current, loss, efficient and cost of PWM compensating current generator are comprehensively improved.
For achieving the above object, the utility model has been taked following technical scheme:
A kind of staggered driving PWM compensating current generator, it is made of dc-link capacitance device, inverter bridge I, inverter bridge II, inductor I, inductor II, drive circuit I, drive circuit II, PWM pulse width modulator I, PWM pulse width modulator II, inverter, triangular-wave generator, computing and control unit, current transformer group I, current transformer group II; Wherein, the dc bus of inverter bridge I and inverter bridge II is connected in parallel, and is connected with shared dc-link capacitance device; The inverting output terminal of inverter bridge I connects the input of inductor I, and the inverting output terminal of inverter bridge II connects the input of inductor II; Be connected with compensated power line after the output parallel connection of inductor I and inductor II; The control end of inverter bridge I is connected with the respective drive output of drive circuit I, and the control end of inverter bridge II is connected with the respective drive output of drive circuit II; The input of drive circuit I is connected with the output of PWM pulse width modulator I, and the input of drive circuit II is connected with the output of PWM pulse width modulator II; Computing and control unit the command signal output be connected with the modulation signal input of PWM pulse width modulator I and the modulation signal input of PWM pulse width modulator II respectively; Computing and control unit synchronous signal output end then after the triangular signal generating means is handled, export two anti-phase triangular signals and send into the triangular wave input of PWM pulse width modulator I and the triangular wave input of PWM pulse width modulator II respectively; Three groups of inputs of computing and control unit connect 2 sides of 2 side summation current transformer group II of compensated power line, current transformer group I respectively; The primary side of current transformer group I is connected on two inductor outputs and compensates in the link circuit of three-phase power circuit with quilt; The primary side of current transformer group II is connected in the compensated power line.
The dc bus of described inverter bridge I and inverter bridge II is public, and the inverting output terminal of inverter bridge I and inverter bridge II is connected respectively one and independently is connected in parallel behind the inductor.
Separate driving between the drive circuit II of the drive circuit I of described inverter bridge I and PWM pulse width modulator I and inverter bridge II and PWM pulse width modulator II.
The triangular signal that described triangular-wave generator produces is divided into two-way, and one the tunnel directly supplies with PWM pulse width modulator II, and PWM pulse width modulator I is supplied with by the anti-phase back of inverter in another road; The command signal that computing wherein and control unit produce is supplied with PWM pulse width modulator I and PWM pulse width modulator II simultaneously.
Described triangular signal generating means comprises a triangular-wave generator, and its a triangular wave output signal is directly sent into the triangular wave input of PWM pulse width modulator II; Another triangular wave output signal is sent into the triangular wave input of PWM pulse width modulator I through inverter.
Described triangular signal generating means comprises two anti-phase triangular-wave generators, and their output connects the triangular wave input of PWM pulse width modulator I and the triangular wave input of PWM pulse width modulator II respectively.
In order to last scheme, two inverter bridge are in the offset current of inductor output, and effective offset current component of corresponding command signal is identical, back in parallel mutual superposition, and the output total current is the twice of single inverter bridge output current; And the carrier frequency ripple current component that two inverter bridge produce because of the PWM modulation in the offset current of inductor output is that approximate constant amplitude is anti-phase, can cancel out each other, thereby the ripple component of exporting in the total current is significantly reduced.More deep mathematical analysis proves, the ripple current that flows through the dc-link capacitance device during two inverter bridge work is partial offset each other, and the total current in the dc-link capacitance device is reduced to about 46% of the known PWM compensating current generator of capacity corresponding current.
The beneficial effects of the utility model are:
(1) staggered two PWM inverter bridge that drive output in parallel, efficient output current intensity increase and are twice, and the harmful ripple current content in the output current significantly reduces;
(2) in same carrier frequencies, satisfy under the identical output ripple restrictive condition, can adopt less output inductor, the tracking velocity of the output current that significantly improves, and reducing cost.
(3) satisfying under identical output ripple restriction, the identical output current tracking velocity requirement condition, can adopt lower carrier frequency, reduce requirement, reduce switching loss the semiconductor power device switching speed;
(4) under the condition of the identical offset current of output, the ripple current that flows through the dc-link capacitance device is reduced to about 46% of known PWM compensating current generator corresponding current, can reduce the dc bus ripple voltage, reduce the current stress in the dc-link capacitance, reduce the wastage, improve reliability, and can reduce demand dc-link capacitance device capacity.
Description of drawings
Fig. 1 is the utility model first example structure schematic diagram.
Fig. 2 is the utility model second example structure schematic diagram.
Fig. 3 is the utility model the 3rd example structure schematic diagram.
Wherein: 1. dc-link capacitance device, 2. inverter bridge I, 3. inverter bridge II, 4. inductor I, 5. inductor II, 6. drive circuit I, 7. drive circuit II, 8.PWM pulse width modulator I, 9.PWM pulse width modulator II, 10. inverter, 11. triangular-wave generators, 12. computings and control unit, 13. current transformer group I, 14. current transformer group II.
Embodiment
The utility model is described in further detail below in conjunction with accompanying drawing and embodiment.
Fig. 1 is the embodiment one that described staggered driving PWM compensating current generator is used for the phase three-wire three power circuit.Purpose according to compensation can be used as Active Power Filter-APF or STATCOM, harmonic current in the compensates electric circuit and reactive current.
As shown in Figure 1, a kind of staggered driving PWM compensating current generator, it is made of dc-link capacitance device 1, inverter bridge I 2, inverter bridge II 3, inductor I 4, inductor II 5, drive circuit I 6, drive circuit II 7, PWM pulse width modulator I 8, PWM pulse width modulator II 9, inverter 10, triangular-wave generator 11, computing and control unit 12, current transformer group I 13, current transformer group II 14; Wherein, the dc bus of inverter bridge I 2 and inverter bridge II 3 is connected in parallel, and is connected with shared dc-link capacitance device 1; The inverting output terminal of inverter bridge I 2 connects the input of inductor I 4, and the inverting output terminal of inverter bridge II 3 connects the input of inductor II 5; Be connected with compensated power line after the output parallel connection of inductor I 4 and inductor II 5; The control end of inverter bridge I 2 is connected with the respective drive output of drive circuit I 6, and the control end of inverter bridge II 3 is connected with the respective drive output of drive circuit II 7; The input of drive circuit I 6 is connected with the output of PWM pulse width modulator I 8, and the input of drive circuit II 7 is connected with the output of PWM pulse width modulator II 9; 12 command signal output of computing and control unit is connected with the modulation signal input of PWM pulse width modulator I 8 modulation signal inputs and PWM pulse width modulator II 9 respectively; 12 synchronous signal output end of computing and control unit then after the triangular signal generating means is handled, is exported two anti-phase triangular signals and is sent into the triangular wave input of PWM pulse width modulator I 8 and the triangular wave input of PWM pulse width modulator II9 respectively; Three groups of inputs of computing and control unit 12 connect 2 sides of 2 side summation current transformer group II 14 of compensated power line, current transformer group I 13 respectively; The primary side of current transformer group I 13 is connected on two inductor outputs and compensates in the link circuit of three-phase power circuit with quilt; The primary side of current transformer group II 14 is connected in the compensated power line.
The dc bus of described inverter bridge I 2 and inverter bridge II3 is public, and the inverting output terminal of inverter bridge I 2 and inverter bridge II 3 is connected respectively one and independently is connected in parallel behind inductor I 4 and the inductor II 5.
The drive circuit II 7 of the drive circuit I 6 of described inverter bridge I 2 and PWM pulse width modulator I 8 and inverter bridge II 3 and 9 separate drivings of PWM pulse width modulator II.
The triangular signal that described triangular-wave generator 11 produces is divided into two-way, and one the tunnel directly supplies with PWM pulse width modulator II 9, and PWM pulse width modulator I 8 is supplied with by inverter 10 anti-phase backs in another road; The command signal that computing wherein and control unit 12 produce is supplied with PWM pulse width modulator I 8 and PWM pulse width modulator II 9 simultaneously.
Described triangular signal generating means comprises a triangular-wave generator 11, and its a triangular wave output signal is directly sent into the triangular wave input of PWM pulse width modulator II 9; Another triangular wave output signal is sent into the triangular wave input of PWM pulse width modulator I 8 through inverter 10.
Described triangular signal generating means comprises two anti-phase triangular-wave generators 11, and their output connects the triangular wave input of PWM pulse width modulator I 8 and the triangular wave input of PWM pulse width modulator II 9 respectively.
A kind of staggered driving PWM compensating current generator control method:
(1) presses known method by computing and control unit and analyze current compensation demand in the compensated power line, and produce the command adapted thereto signal;
(2) command signal is sent into simultaneously two identical PWM pulse width modulators;
(3) under the synchronizing signal control that computing and control unit provide, produce the carrier frequency triangular wave by a triangular-wave generator, and triangular wave is sent into an inverter, obtain with frequency, constant amplitude, anti-phase triangular wave;
(4) will be inverting each other by two kinds that step (3) obtain, the same frequency that phase difference is 180 °, constant amplitude triangular wave are sent into two PWM pulse width modulators in the step (2) respectively, respectively command signal is carried out the PWM modulation, obtain two groups of pwm signals that carrier phase is interlaced with each other 180 °;
(5) above-mentioned two groups of carrier phases pwm signal interlaced with each other 180 ° is sent into two cover drive circuits respectively, driven two identical inverter bridge respectively;
(6) send into compensated power line after the offset current stack that two inverter bridge is produced.
Described in the step (4) two kinds inverting each other, the same frequency that phase difference is 180 °, constant amplitude triangular wave are produced synchronously by computing and two triangular-wave generators inverting each other of control unit Synchronization Control.
Computing in the described staggered driving PWM compensating current generator and control unit, detect voltage and current value in the compensated power line by input that connects compensated power line and the input that is connected current transformer group II, after by the sequential operation of setting, can draw the current value that need compensate.Computing simultaneously and the input of control unit through being connected current transformer group I detect the actual output current of this compensating current generator, and the current value that the needs that this actual current value and computing are drawn compensate compares, and can obtain error signal.Computing and control unit produce command signal according to error signal, give two PWM pulse width modulators, produce the PWM drive signal.The PWM drive signal drives two inverter bridge through drive circuit, can change output current by demand, makes it meet the compensation needs.
The all available known technology of drive circuit I in the described staggered driving PWM compensating current generator, drive circuit II, PWM pulse width modulator I, PWM pulse width modulator II, inverter, triangular-wave generator, computing and control unit is realized.For example drive circuit can adopt driver formations such as EXB841, the PWM pulse width modulator can adopt voltage comparator formations such as LM339, triangular-wave generator and inverter can adopt operational amplifier formations such as TL074, computing and control unit can adopt digital signal processor formation digital controllers such as TMS320F2812, adopt methods such as instantaneous reactive theory, fast Fourier transform to finish the analysis computing, and finish control according to the control program that weaves in advance.PWM pulse width modulator I wherein, PWM pulse width modulator II, inverter and triangular-wave generator can constitute with hardware circuit, also can directly finish its identical function by digital control chip with the digital operation method.
Fig. 2 is used for the embodiment two of three-phase and four-line power circuit for described staggered driving PWM compensating current generator.For satisfying the compensation demand of center line electric current in the three-phase four wire system, the dc-link capacitance device need be with two capacitors in series, and it is connected in series a little and being connected of the neutral line of power circuit.Other parts are all identical with embodiment one, and working method is identical with embodiment one.
Fig. 3 is used for the embodiment three of Monophase electric power circuit for described staggered driving PWM compensating current generator.This moment, inverter bridge I and inverter bridge II all were reduced to single-phase bridge, inductor I and inductor II all are reduced to phase structure, current transformer group I summation current transformer group II all is reduced to single current transformer, drive circuit I, drive circuit II, PWM pulse width modulator I, PWM pulse width modulator II and computing and control unit also only need to handle single-phase signal, and working method is still identical with embodiment one, embodiment two.