CN103107720B - A kind of three inductance dual Buck inverters - Google Patents

Abstract

A kind of three inductance dual Buck inverters, by two switching tubes, two diodes, two DC filtering inductance, an ac filter inductance, two input capacitances, an output filter capacitor composition.This converter is by switching tube S ₁, diode D ₁be followed in series to form the first brachium pontis, by diode D ₂, switching tube S ₂be followed in series to form the second brachium pontis; DC filtering inductance L _dc1, L _dc2be connected across between two brachium pontis mid points, L _dc1, L _dc2public termination ac filter inductance L _ac, L _acanother termination filter capacitor C _fand load R.The advantage of this converter is: the output inductor value substantially reducing traditional dual Buck inverter, and make the volume of converter entirety, weight greatly reduces, the high power density, the high reliability that are conducive to converter are integrated.The present invention is applicable to the Three-Phase Inverter that is made up of above-mentioned three inductance dual Buck inverters and cascaded multilevel inverter and corresponding control mode thereof simultaneously.Involved inverter circuit and control method have good application prospect in occasions such as UPS, airplane power source, wind energy and solar power generations.

Description

A kind of three inductance dual Buck inverters

Technical field

The present invention discloses a kind of three inductance dual Buck inverters, belongs to converters.

Background technology

Along with increasingly sharpening of energy crisis, the new forms of energy such as solar energy, wind energy, fuel cell receive increasing concern.The focus of to be how available alterating and direct current by these energy transformations be current research; Distributed generation system is widely used in such occasion, and distributed system needs to adopt the two-stage type structure of DC/DC+DC/AC usually: prime DC/DC completes inverter input and output voltage coupling and electrical isolation; Rear class DC/AC completes orthogonal conversion and powers to terminate load.And inverter is as the important component part of system, directly decide the output quality of power supply; High reliability, high power density and high efficiency weigh the important indicator of inverter performance.Tradition dual Buck inverter owing to having without bridge arm direct pass, reliability is high, output waveform quality is good, efficiency advantages of higher is widely used in high reliability occasion; But due to needs two independently output inductor and each inductance only works half period, magnetic element utilance is low, and system bulk weight is large, have impact on the application of dual Buck inverter.

At present, have several as follows for the solution that the shortcoming that dual Buck inverter magnetic element utilance is low is main:

(1) magnetic core direct-coupling scheme is shared.This method is by being directly coupled on a magnetic core by two inductor windings.Connect according to Same Name of Ends different, be divided into again two kinds of coupled modes.The advantage of this scheme is that inductance coupling high is fairly simple; But because two inductance exist coupled relation, a voltage corresponding according to the turn ratio relation when winding applying voltage wherein, can be produced on another winding.Inductance due to actual coiling can not ensure the inductance value full symmetric that two windings are corresponding, can produce uncertain circulation at circuit.And loop middle impedance corresponding to circulation is very little, very little voltage difference can produce very large loop current.The existence of circulation will have a strong impact on reliability and the overall efficiency of circuit working.

(2) bimag four winding scheme.By each inductor winding average mark around on two magnetic cores, the inductance value of each inductance is the half of former inductance, is connected by one of them inductor winding Same Name of Ends, and another inductance then different name end is connected.Suppose two magnetic cores whenever parameter all equal (ideal situation), then under the condition of equal turn numbers, two inductance can realize full decoupled, namely on an inductance, apply voltage, and the magnitude of voltage that another inductance is responded to is zero.But, in fact the operating state of two magnetic cores can not ensure identical, as two parameters of magnetic core (magnetic permeability etc.) own just can not be completely equal, cause the two halves winding voltage of an inductance different, on a road inductance of inoperative, induction has voltage, causes the possibility that there is circulation.And the magnetic core parameters such as magnetic permeability are comparatively large along with environmental influences such as temperature, therefore are difficult to ensure that inoperative inductance induced voltage is zero.Therefore also there is the circulation described in scheme (1).

(3) the full decoupled magnetic Integrated Solution of magnetic core is shared.This scheme is for EE type magnetic core, and the inductance L 1 of traditional dual Buck inverter around on center pillar, inductance L 2 is divided into two parts, respectively around on two lateral columns of magnetic core.When an inductance applying voltage power supply wherein, another one inductance is offset can not produce induced voltage due to magnetic flux, and therefore both can not influence each other, be full decoupled.But in fact the program does not reduce the inductance value needed for dual Buck inverter, although the model that improve the magnetic core needed for utilization rate of magnetic core will increase, the volume and weight of reduction inductance that therefore can not be real.

Summary of the invention

The object of the invention is to, for the shortcoming that traditional double Buck inverter filtering inductance volume weight is large, propose a kind of three inductance dual Buck inverters, do not reducing on the basis of inverter efficiency, effectively reduce the inductance value of dual Buck inverter, improve magnetic element utilance, achieve high power density.

Realize three inductance dual Buck inverters of above-mentioned purpose by two switching tubes, two diodes, two DC filtering inductance, an ac filter inductance, two input capacitances, an output filter capacitor composition.This converter is by switching tube S ₁, diode D ₁be followed in series to form the first brachium pontis, by diode D ₂, switching tube S ₂be followed in series to form the second brachium pontis; DC filtering inductance L _dc1, L _dc2be connected across between two brachium pontis mid points, L _dc1, L _dc2public termination ac filter inductance L _ac, L _acanother termination filter capacitor C _fand load R.It is characterized in that:

Two of traditional dual Buck inverter separate inductors are transformed to two DC filtering inductance L _dc1, L _dc2a profit ac filter inductance L _acsubstitute.Improve the utilance of dual Buck inverter inductance, reduce total inductance value.

The three inductance dual Buck inverters that the present invention proposes have the following advantages:

1) advantage of traditional dual Buck inverter is remained;

2) inductance value of three inductance dual Buck inverters is little, improves magnetic element utilance, alleviates the volume weight of system, reduces the cost of system;

Accompanying drawing explanation

Fig. 1 is that three inductance dual Buck inverters of the present invention implement schematic diagram.

Fig. 2 is the enforcement schematic diagram of traditional dual Buck inverter.

Fig. 3 is three inductance dual Buck inverter operation mode schematic diagrames of the present invention.

Fig. 4 is from the output voltage V being followed successively by three inductance dual Buck inverters in concrete enforcement under upper _out, DC filtering inductance L _dc1, L _dc2current i _l1, i _l2and ac filter inductance L _accurrent i _l.

Fig. 5 is followed successively by three inductance dual Buck inverter switching tube S in concrete enforcement under upper ₁, S ₂duty ratio d ₁, d ₂, switching tube S ₂both end voltage V _{_ ds2}and diode D ₂both end voltage V _{_ d2}.

Three inductance dual Buck inverter switching tube S in concrete enforcement are followed successively by under on Fig. 6 ₁, S ₂duty ratio d ₁, d ₂, flow through diode D ₂current i d2 and switching tube S ₂the current i d4 of body diode.

Fig. 7 is the first brachium pontis switching tube S of three inductance dual Buck inverters of the present invention ₁by switching tube S ₁substitute with the unit of Diode series composition, the second brachium pontis switching tube S ₂by switching tube S ₂with the enforcement schematic diagram that the unit of Diode series composition substitutes.

Fig. 8 be three inductance dual Buck inverters of the present invention when power output is 1kVA applications, DC filtering inductance L _dc1, L _dc2with ac filter inductance L _acpictorial diagram.

Fig. 9 be three tunnel three inductance dual Buck inverters of the present invention respectively as A, B and C three-phase, the three-phase inverter that is combined into implements schematic diagram.

Figure 10 is that the cascaded multilevel inverter that three inductance dual Buck inverters of the present invention are formed implements schematic diagram.

Figure 11 is the SPWM control block diagram of the inverter of three inductance dual Buck inverters of the present invention and conversion.

Figure 12 is the Hysteresis control block diagram of the inverter of three inductance dual Buck inverters of the present invention and conversion.

Figure 13 is the control block diagram of the cascaded multilevel inverter that three inductance dual Buck inverters of the present invention are formed.

Embodiment

Contrast accompanying drawing below in conjunction with embodiment, the present invention will be further described.

Fig. 1 is three inductance dual Buck inverter circuit.

As inverter inductor L _dc1electric current is timing, and inverter is divided into following four operation modes, and wherein inductive current direction is as shown in Figure 1:

Mode 1: switching tube S ₁during conducting, due to switching tube S ₂with diode D ₂parasitic capacitance C _s2, C _d2existence, C _s2through input power U _in, DC filtering inductance L _dc1, L _dc2and C _d2charge in loop, C _d2through DC filtering inductance L _dc1, L _dc2and C _s2discharge in loop, i _ldc1, i _ldc2electric current forward resonance rises, C _s2both end voltage rises, C _d2both end voltage declines.Until C _d2when both end voltage drops to zero, this operation mode terminates, due to ac filter inductance L _acvalue is comparatively large, and electric current linearly rises.

Mode 2: work as C _d2after both end voltage drops to zero, D ₂nature conducting; Now, S ₁still conducting, S ₂and D ₁all turn off, i _ldc1, i _lac, forward linearly increases, i _ldc2forward linearly reduces.

Mode 3:D ₁during conducting, S ₁, S ₂and D ₂all turn off, due to switching tube S ₂with diode D ₂parasitic capacitance C _s2, C _d2existence, C _d2through input power U _m, DC filtering inductance L _dc1, L _dc2and D ₁charge in the loop formed, C _s2through DC filtering inductance L _dc1, L _dc2and D ₁discharge in loop, i _ldc1current resonance declines, i _ldc2the reverse resonance of electric current declines, C _d2both end voltage rises, C _s2both end voltage declines.Until C _s2when both end voltage drops to zero, this operation mode terminates.

Mode 4: work as C _s2after both end voltage drops to zero, S ₂body diode D _s2nature conducting; Now, D ₁still conducting, S ₂and S ₁all turn off, C ₂charging, i _ldc1, i _lacforward linearly reduces, i _ldc2reverse linear reduces.

As inverter inductor L _dc2electric current is for time negative, and operation mode is also divided into four mode, identical with during positive half period.

In order to illustrate that three inductance dual Buck inverters can reduce magnetic core size, existing brief analysis is as follows:

If inductance value is L needed for each inductance of traditional dual Buck inverter, the maximum current amplitude flow through is I _p, effective value is I _o, obtaining current density is j _max, maximum functional magnetic is close is B _max, the inductance number of turn is N, and window coefficient is K _u, then the magnetic core size needed for each inductance of traditional dual Buck inverter is:

$S=\frac{L\·I_p}{N\·B_{\max }}$ $Q=\frac{N\·I_o}{j_{\max }\·K_u}$ $\mathrm{SQ}=S\×Q=\frac{L\·I_p\·I_o}{j_{\max }\·K_u\·B_{\max }}$

Owing to needing two identical separate inductors, then required total magnetic core size is:

$\mathrm{SQ}=\frac{2\·L\·I_p\·I}{j_{\max }\·K_u\·B_{\max }}$

If the DC filtering inductance value of three inductance dual Buck inverters is L _dc1=L _dc2=L _dc, ac filter inductance value is L _ac, the maximum current amplitude flowing through DC filtering inductance is I _p, effective value is I _o, the inductance number of turn is N _dc; The maximum current amplitude flowing through ac filter inductance is I _p, effective value is obtaining current density is j _max, maximum functional magnetic is close is B _max, the inductance number of turn is N _ac, then the magnetic core size needed for each DC filtering inductance of three inductance dual Buck inverters is:

$S_{\mathrm{dc}}=\frac{L_{\mathrm{dc}}\·I_p}{N_{\mathrm{dc}}\·B_{\max }}$ $Q_{\mathrm{dc}}=\frac{N_{\mathrm{dc}}\·I_o}{j_{\max }\·K_u}$ $\mathrm{SQ}=S_{\mathrm{dc}}\×Q_{\mathrm{dc}}=\frac{L_{\mathrm{dc}}\·I_p\·I_o}{j_{\max }\·K_u\·B_{\max }}$

Owing to needing two identical DC filtering inductance, then required total magnetic core size is:

$\mathrm{SQ}=\frac{2\·L_{\mathrm{dc}}\·I_p\·I_o}{j_{\max }\·K_u\·B_{\max }}$

Magnetic core size needed for three inductance dual Buck inverter ac filter inductance is:

$S_{\mathrm{ac}}=\frac{L_{\mathrm{ac}}\·I_p}{N_{\mathrm{ac}}\·B_{\max }}$ $Q_{\mathrm{ac}}=\frac{N_{\mathrm{ac}}\·\sqrt{2}{I}_o}{j_{\max }\·K_u}$ $\mathrm{SQ}=S_{\mathrm{ac}}\×Q_{\mathrm{ac}}=\frac{L_{\mathrm{ac}}\·I_p\·\sqrt{2}{I}_o}{j_{\max }\·K_u\·B_{\max }}$

Total magnetic core size then needed for three inductance dual Buck inverters is:

$\mathrm{SQ}=\frac{2\·L_{\mathrm{dc}}\·I_p\·I_o}{j_{\max }\·K_u\·B_{\max }}+\frac{L_{\mathrm{ac}}\·I_p\·\sqrt{2}{I}_o}{j_{\max }\·K_u\·B_{\max }}=\frac{I_p\·I_o\·(2\·L_{\mathrm{dc}}+\sqrt{2}{L}_{\mathrm{ac}})}{j_{\max }\·K_u\·B_{\max }}$

Because inductance value meets L _dc1+ L _acthe condition of≤L, then in two kinds of situations, total inductance value meets all the time relation; So the SQ value perseverance of three inductance dual Buck inverters is less than the SQ value of traditional dual Buck inverter.Therefore adopt three inductance dual Buck inverters can improve magnetic core utilance, realize high power density.

The execution mode of three inductance dual Buck inverters of the present invention can also have:

1. three inductance dual Buck inverters of the present invention, the switching tube S of the first brachium pontis ₁can by switching tube S ₁substitute with the unit of Diode series composition, the switching tube S of the second brachium pontis ₂can by switching tube S ₂substitute with the unit of Diode series composition.

2. the DC filtering inductance L in three inductance dual Buck inverters of the present invention _dc1, L _dc2coupling inductance can be adopted to realize.

3. three inductance dual Buck inverters of the present invention are combined into three-phase inverter, adopt three tunnel three inductance dual Buck inverters respectively as A, B and C three-phase; Three-phase general DC busbar voltage U _in, and three-phase common DC input side two electric capacity C ₁, C ₂common point formed mid point.

4. of the present invention three inductance dual Buck inverters form cascaded multilevel inverter, by the output of N road three inductance dual Buck inverter head and the tail be in turn connected form, N be more than or equal to 2 natural number.

Various forms of inverters for three above-mentioned inductance dual Buck inverters and combined transformation thereof provide corresponding control method, and the specific works principle that the control principle block diagram of contrast accompanying drawing provides is as follows:

The specific works principle that the control principle block diagram of accompanying drawing provides is as follows:

1. the SPWM control method of 1,2,3 and 4 inverters in three inductance dual Buck inverters and execution mode, its operation principle is: inverter output voltage compares the error signal of generation as given value of current with voltage reference, Sample AC filter inductance L _acelectric current compare with current reference and obtain current error signal, current error signal and triangular carrier access in-phase end and the end of oppisite phase of comparator 2 respectively; The output of Voltage loop connects the end of oppisite phase of comparator 1, the in-phase end ground connection of comparator 1.The output of comparator 1 and the output of comparator 2 obtain switching tube electricity S through one and door ₂pWM drive.The output of comparator 1 and the output of comparator 2 obtain switching tube electricity S through one and door after negate respectively ₁pWM drive.

2. the hysteresis control method thereof of 1,2,3 and 4 inverters in three inductance dual Buck inverters and execution mode, its operation principle is: inverter output voltage compares the error signal of generation as given value of current with voltage reference; Sample AC filter inductance L _acthe end of oppisite phase of the positive half period input hysteresis comparator 1 of electric current, the in-phase end of given value of current input hysteresis comparator 1, obtains switching tube electricity S ₁pWM drive; Sample AC filter inductance electric current L _acnegative half-cycle input hysteresis comparator 2 in-phase end, given value of current input hysteresis comparator 2 end of oppisite phase, obtain switching tube electricity S ₂pWM drive.

3. the control method of the cascaded multilevel inverter of three inductance dual Buck inverters formations, its operation principle is: the error signal u that inverter output voltage and voltage reference obtain through voltage regulator _eas given value of current; Sample AC filter inductance L _acelectric current and given value of current obtain error signal i through current regulator _e; i _erespectively compared with the triangular wave of phase shift phase angle 2, N road π/N; The output of N road comparator is after logical circuit, and the PWM obtaining each switching tube drives.

It is pointed out that relative to traditional dual Buck inverter, three inductance dual Buck inverters of the present invention carry out by increasing an ac filter inductance output voltage waveforms quality that filtering each harmonic ensures inverter; The filter inductance DC filtering inductance of only half period work is substituted simultaneously, fundamentally reduce the filter inductance value that dual Buck inverter is total, improve the utilance of magnetic element.In its control method, only need Sample AC filter inductance L _acelectric current, simplify control circuit.

Be more than the further description that the present invention is done, can not assert that the concrete enforcement of this aspect is only limitted to these explanations.Concerning the those of ordinary skill of technical field of the present invention, the some conversion made without departing from the inventive concept of the premise and equivalence, and character and utilization is identical, all should be considered as belonging to protection scope of the present invention.

Claims (4)

1. three inductance dual Buck inverters, is characterized in that: by switching tube S ₁, diode D ₁be followed in series to form the first brachium pontis, wherein switching tube S ₁drain electrode meet input power U _inpositive pole, diode D ₁anode meet power supply U _innegative pole; By diode D ₂, switching tube S ₂be followed in series to form the second brachium pontis, wherein switching tube S ₂source electrode meet input power U _innegative pole, diode D ₂negative electrode meet power supply U _inpositive pole; DC filtering inductance L _dc1, L _dc2be connected across between two brachium pontis mid points, L _dc1, L _dc2public termination ac filter inductance L _ac, L _acanother termination filter capacitor C _fand load R.

2. three inductance dual Buck inverters according to claim 1, is characterized in that DC filtering inductance L _dc1, L _dc2employing coupling inductance realizes.

3. the three-phase inverter of three inductance dual Buck inverter compositions according to claim 1, is characterized in that employing three three inductance dual Buck inverters are respectively as A, B and C three-phase, three-phase general DC busbar voltage U _in, and three-phase common DC input side electric capacity C ₁, C ₂common point formed mid point, be combined into three-phase inverter.

4. according to claim 1 three inductance dual Buck inverters form cascaded multilevel inverter, it is characterized in that by the output of N road three inductance dual Buck inverter head and the tail be in turn connected form, N be more than or equal to 2 natural number.