CN102386795B - The harmonic suppression apparatus of inverter - Google Patents

Abstract

The invention discloses the inverter with harmonic suppression apparatus and the harmonic suppressing method for this inverter, inverter includes DC-AC inverter module, harmonic suppression apparatus, PWM mode changer and first arithmetic device, harmonic suppression apparatus receives input voltage and exports corrected parameter, corrected parameter is the ratio between the DC component of input voltage and input voltage, corrected parameter is exported first arithmetic device by harmonic suppression apparatus, first arithmetic device is connected between PWM mode changer and the power supply providing control signal to PWM mode changer, the control signal that power supply is provided by corrected parameter is used to be modified, and provide revised control signal to PWM mode changer, PWM mode changer generates according to revised control signal and drives signal。Inverter disclosed in this invention and harmonic suppressing method avoid the defect that volume is big, cost is high and the life-span is short used caused by large value capacitor。

Description

The harmonic suppression apparatus of inverter

Technical field

The present invention relates to a kind of inverter, more particularly, it relates to have inverter and the harmonic suppressing method thereof of harmonic suppression apparatus。

Background technology

Ideally, the input voltage of inverter only comprises DC component, and the output electric current after conversion is the sine wave not distorted。But, in practical situations both, input voltage is typically subject to the impact of electrical network and comprises AC compounent, so may result in the distortion of output electric current, thus the electrical network that it accesses is polluted。In order to ensure the quality of electric current, for instance for grid-connected voltage source inverter (VSI), generally can be considered as the capacitor of larger capacity。But, the capacity of capacitor is more big, and its size is more big, and cost is more high, and the charging interval also can be more long。Although and the less capacitor size of capacity is little, cost is low, but higher ripple voltage can be caused。Accordingly, it is desirable to provide a kind of bigger capacitor of configuration capacity that can not need when the unidirectional current of input is pressed with more serious distortion is still provided that the inverter of high-quality exchange output。

Summary of the invention

Present invention aims to disadvantages described above and a kind of inverter with harmonic suppression apparatus and harmonic suppressing method are provided。

To achieve these goals, the present invention provides a kind of voltage source inverter, it includes DC-AC (DC-AC) inverter module that input voltage is converted, harmonic suppression apparatus, pulsewidth modulation (PWM) mode converter and first arithmetic device, harmonic suppression apparatus receives input voltage and exports corrected parameter, this corrected parameter is the ratio between the DC component of input voltage and input voltage, this corrected parameter is exported first arithmetic device by harmonic suppression apparatus, first arithmetic device is connected between PWM mode changer and the power supply providing control signal to PWM mode changer, the control signal that this power supply is provided by described corrected parameter is used to be modified, and provide revised control signal to PWM mode changer, PWM mode changer generates the driving signal driving DC-AC inverter module according to revised control signal。

Above-mentioned inverter according to the present invention, it is characterized in that harmonic suppression apparatus includes pressure unit, band filter, low pass filter and second arithmetic device, pressure unit receives the input voltage of inverter, voltage after blood pressure lowering is separately input to band filter and low pass filter, the DC component of the voltage after low pass filter and band filter output buck respectively and AC compounent, second arithmetic device receives DC component and the AC compounent of the voltage after blood pressure lowering, and it is used as corrected parameter to the ratio between the voltage after the DC component and blood pressure lowering of the voltage after first arithmetic device output buck, this ratio is equal to the ratio between DC component and the input voltage of input voltage；First arithmetic device is equal to the DC component of input voltage divided by the product between value and the control signal of input voltage to the revised control signal that PWM mode changer exports。

Above-mentioned inverter according to the present invention, second arithmetic device includes divider and adder, divider receives DC component and the AC compounent of the voltage after blood pressure lowering, export the DC component of post-decompression voltage and the ratio of AC compounent to adder, adder is by the ratio between computing output DC component and input voltage。

In addition, the present invention also provides for a kind of current source inverter, it includes the DC-AC inverter module that input current is converted, harmonic suppression apparatus, PWM mode changer and first arithmetic device, harmonic suppression apparatus receives input current, and export corrected parameter, this corrected parameter is equal to the ratio between DC component and the input current of input current, this corrected parameter is exported first arithmetic device by harmonic suppression apparatus, first arithmetic device is connected between PWM mode changer and the power supply providing control signal to PWM mode changer, the control signal that this power supply is provided by corrected parameter is used to be modified, and provide revised control signal to PWM mode changer, PWM mode changer generates the driving signal driving DC-AC inverter module according to revised control signal。

Above-mentioned current source inverter according to the present invention, characterized by further comprising current detecting unit, the DC component of the electric current of the detection of current detecting unit output and the ratio of AC compounent are equal to the DC component of the input current of input inverter and the ratio of AC compounent, harmonic suppression apparatus includes pressure unit, band filter, low pass filter and second arithmetic device, pressure unit receives the output of current detecting unit and to the voltage after band filter and low pass filter output buck, the DC component of the voltage after low pass filter and band filter output buck respectively and AC compounent, wherein the DC component of the voltage after blood pressure lowering and the ratio of AC compounent are equal to the DC component of the electric current of the detection of current detecting unit output and the ratio of AC compounent, described second arithmetic device receives DC component and the AC compounent of the voltage after blood pressure lowering, and to the ratio between the voltage after the DC component and blood pressure lowering of the voltage after first arithmetic device output buck, this ratio is equal to the ratio between DC component and the input current of input current, first arithmetic device is equal to the DC component of input current divided by the product between value and the control signal of input current to the revised control signal that PWM mode changer exports。

Above-mentioned current source inverter according to the present invention, second arithmetic device includes divider and adder, divider receives DC component and the AC compounent of the voltage after blood pressure lowering, to the ratio of the DC component of the voltage after adder output buck and AC compounent, and adder is by the ratio between the voltage after the DC component of the voltage after additive operation output buck and blood pressure lowering。

According to a further aspect in the invention, the present invention provides the harmonic suppressing method of a kind of inverter, the method includes: the input voltage of inverter is carried out blood pressure lowering, and the voltage after blood pressure lowering is separately input to band filter and low pass filter, low pass filter and band filter respectively obtain DC component and the AC compounent of the voltage after blood pressure lowering, the ratio between the voltage after DC component and blood pressure lowering is obtained as corrected parameter by second arithmetic device, and this corrected parameter is inputted first arithmetic device, revised control signal is exported after the control signal of first arithmetic device reception PWM mode generator and corrected parameter, revised control signal equal to the voltage after blood pressure lowering DC component divided by the voltage after blood pressure lowering value again with the product of control signal, revised control signal is imported into PWM mode generator, control PWM mode generator and obtain driving the driving signal of inverter, input voltage is carried out the direct current conversion to exchange according to the signal that drives of input by inverter。

In accordance with a further aspect of the present invention, the present invention also provides for the harmonic suppressing method of a kind of inverter, the method includes: detected the input current of inverter by current detecting unit, and the ratio between DC component and the AC compounent of the electric current after detection is equal to the ratio between DC component and the AC compounent of the input current of inverter；The output of current detecting unit is carried out blood pressure lowering, and the voltage after blood pressure lowering is input to band filter and low pass filter, low pass filter and band filter respectively obtain DC component and the AC compounent of the voltage after this blood pressure lowering, the DC component of the voltage after blood pressure lowering and AC compounent are input to second arithmetic device to the ratio that obtains between the voltage after the DC component of the voltage after blood pressure lowering and blood pressure lowering using as corrected parameter, this ratio is equal to the ratio between DC component and the AC compounent of the electric current after detection, revised control signal is exported after the control signal of first arithmetic device reception PWM mode generator and corrected parameter, revised control signal equal to the voltage after blood pressure lowering DC component divided by the voltage after blood pressure lowering value again with the product of control signal, revised control signal is imported into PWM mode generator, control PWM mode generator to obtain driving the driving signal of inverter, input voltage is carried out the direct current conversion to exchange according to the signal that drives of input by inverter。

Inverter disclosed in this invention and harmonic suppressing method avoid the defect that volume is big, cost is high and the life-span is short used caused by large value capacitor。The present invention adopts the control signal circuit small volume to the mode regulating the output of inverter increase less costly, required of control PWM mode generator, and effectively can regulate its output according to the change of the input of inverter, make when bigger distortion occurs in the input of inverter direct current, it is also possible to obtain mass ratio and export electric current preferably。

Accompanying drawing explanation

The present invention is referred to drawing and description and is better understood。

Fig. 1 illustrates the module frame chart according to one embodiment of the present invention；

Fig. 2 illustrates the circuit diagram according to one embodiment of the present invention；

Fig. 3 illustrates the circuit diagram according to another embodiment of the invention；

Fig. 4 illustrates the circuit diagram of the another embodiment according to the present invention；

The exemplary waveform diagrams of the control signal of the input PWM mode generator before and after what Fig. 5 illustrated that the circuit according to Fig. 3 obtains carry out harmonics restraint and the change of output electric current and voltage。

Detailed description of the invention

The present invention is further described below in association with exemplary embodiment。

The mode of the harmonics restraint of the present invention considers to carry out, according to the AC compounent in input voltage, the driving signal that adjusting pulsewidth modulating mode generator sends to the switch element of inverter, thus regulate the voltage of inverter output, thus reducing or eliminate the harmonic component in inverter output voltage, and then eliminate the distortion of output electric current。And the signal that drives that adjusting pulsewidth modulating mode generator sends can be realized by the control signal (also referred to as reference signal) or carrier signal changing PWM mode generator。The present invention mainly adopts the mode of regulable control signal to realize the elimination of the harmonic component to output voltage。

Generally, for voltage source inverter, output voltage waveforms and input voltage and control signal V_controlRelation can as shown in following equalities (1)。Here control signal refers to the reference signal compared in PWM mode generator with CF signal, and it uses M₁Sin ω t represents。For different types of PWM mode generator, it is possible to express V in a different manner_control。Here adopt M₁Sin ω t is only a kind of example。

V_out=V_inV_control=V_inM₁sinωt(1)

From equation (1) it can be seen that work as V_inWhen only including DC component, V_outOnly comprise fundametal compoment。If input voltage V_inIn except including DC component V_{Dclink, dc}Outside also include AC compounent V_{Dclink, ac}, then the output voltage V according to equation (1)_outAlso will include harmonic component。To input signal V in following equalities (2)_inComprising k AC compounent is the relation being illustrated input with output voltage, and wherein k is the integer more than 0, and ρ is selected from 0 °～360 °。

V_out=[V_{Dclink, dc}+V_{Dclink, ac}sin(kωt+ρ)]M₁sinωt(2)

In order to eliminate output voltage V_outIn harmonic component, the present invention considers to regulate the control signal V in equation (1)_control。By calculating, the present inventor is met the new control signal of below equation (3), and under this control signal, the AC compounent of input voltage the harmonic component of the output voltage caused will be cancelled:

$V_{\mathrm{control}-\mathrm{new}}=V_{\mathrm{control}}\left[\frac{1}{1+\mathrm{\μ}\sin (\mathrm{k\ωt}+\mathrm{\ρ})}\right]=M_1\sin \mathrm{\ωt}\left[\frac{1}{1+\mathrm{\μ}\sin (\mathrm{k\ωt}+\mathrm{\ρ})}\right]---\left(3\right)$

Wherein $\mathrm{\μ}=\frac{V_{\mathrm{dclink},\mathrm{ac}}}{V_{\mathrm{dclink},\mathrm{dc}}}$

Equation (3) can also be transformed to:

$V_{\mathrm{control}-\mathrm{new}}=M_1\sin \mathrm{\ωt}\left[\frac{V_{\mathrm{dclink},\mathrm{dc}}}{V_{\mathrm{dclink},\mathrm{dc}}+V_{\mathrm{dclink},\mathrm{ac}}\sin (\mathrm{k\ωt}+\mathrm{\ρ})}\right]=M_1\sin \mathrm{\ωt}\left[\frac{V_{\mathrm{dclink},\mathrm{dc}}}{V_{\mathrm{in}}}\right]---\left(4\right)$

Can be seen that new control signal and input voltage V from the equation above_inDirect current relevant with AC compounent。

Fig. 1 illustrates the module frame chart according to one embodiment of the present invention。The DC-AC inverter module 110 of voltage source inverter 100 receives the input voltage V with harmonic component_inAnd its output voltage is V_out。As it is shown in figure 1, in order to realize the change to pulse-width modulation control signal, at input voltage V_inAnd between PWM mode generator 120, add harmonic suppression apparatus 130。Harmonic suppression apparatus 130 exports corrected parameter P。The control signal of input PWM mode generator 120 is modified by first arithmetic device 180 according to corrected parameter P, and revised control signal is input to PWM mode generator 120。So, harmonic suppression apparatus 130 is according to input voltage V_inCarrying out the control signal of adjusting pulsewidth modulating mode generator 120, thus changing the driving signal that PWM mode generator 120 sends, and then eliminating the voltage V of inverter module 110 output of inverter 100_outIn harmonic component。

Examples of circuits figure 2 illustrates more specifically。As in figure 2 it is shown, the harmonic suppression apparatus 230 of inverter 200 is mainly made up of pressure unit 240, band filter 250, low pass filter 260, second arithmetic device 270。Comprise DC component V_{Dclink, dc}With AC compounent V_{Dclink, ac}Input voltage V_inIt is input to inverter module 210, and is input simultaneously to harmonic suppression apparatus 230。

Although input voltage V can be directly obtained by low pass filter and band filter_inDC component V_{Dclink, dc}With AC compounent V_{Dclink, ac}Thus come to build the applicable circuit counting corrected parameter to control signal according to equation (4), but in order to building of circuit is simpler and more stable, in this embodiment, introduce the pressure unit 240 input voltage V to being input to harmonic suppression apparatus 230_inCarry out blood pressure lowering, obtain the voltage V after blood pressure lowering_step-down。Voltage after this blood pressure lowering is subsequently inputted into band filter 250 and low pass filter 260。Band filter 250 and low pass filter 260 output AC component V respectively_{Step-down, ac}With DC component V_{Step-down, dc}。The DC component V of the voltage after blood pressure lowering_{Step-down, dc}With AC compounent V_{Step-down, ac}Between ratio and input voltage V_inDC component V_{Dclink, dc}With AC compounent V_{Dclink, ac}Between ratio be of substantially equal。Direct current and the AC compounent of output obtain DC component V by the calculating of second arithmetic device 270_{Step-down, dc}With the voltage V after blood pressure lowering_step-downBetween ratio, this ratio and input voltage V_inIn DC component V_{Dclink, dc}With input voltage V_inBetween ratio of substantially equal, be used as control signal M₁The corrected parameter of sin ω t。

It is imported in first arithmetic device 280 by the output result of the obtained harmonic suppression apparatus of second arithmetic device 270, with to control signal V_controlIt is modified。The computing module that first arithmetic device 280 can be suitable for by multiplier, divider etc. is constituted, and the calculation of corrected parameter can be selected accordingly by it according to the second arithmetic device 270 of harmonic suppression apparatus 230。Such as, if harmonic suppression apparatus 230 calculate obtain 1+ μ sin (k ω t+ ρ) (Namely), then first arithmetic device 280 utilizes divider calculating to obtain $V_{\mathrm{control}-\mathrm{new}}=M_1\sin \mathrm{\ωt}\left[\frac{1}{1+\mathrm{\μ}\sin (\mathrm{k\ωt}+\mathrm{\ρ})}\right].$

After adopting reduction voltage circuit, the process calculating corrected parameter can also be realized by devices such as MCU (microcontroller) or DSP (digital signal processor) except by analog circuit, thus can improve computational accuracy and stability, and reduce volume and the complexity of circuit。

Control signal V after correction_control-newIt is imported into PWM mode generator, compares as reference signal and carrier signal, thus obtaining driving the driving signal of each switch of inverter 210。

Additionally, the outfan of inverter module can also connect inductance L, it has equivalent resistance R_L。Inductance L can be herein used as low pass filter。

With full-bridge voltage source inventer for the circuit diagram being illustrated inverter in Fig. 2, but it will be appreciated by those skilled in the art that the harmonic suppression apparatus of the present invention can be used for various inverter as required, including three-phase and single-phase inverter。It addition, PWM mode generator can select as required, for instance sinusoidal pulse width modulation (SPWM) can be selected。

In general, output voltage is had the greatest impact by the AC compounent comprised in input signal with the AC compounent of k=2, therefore in actual applications, it is possible to adopt the present invention mainly to eliminate the second harmonic component impact on output voltage and electric current in input signal。

Fig. 3 illustrates the one embodiment more specifically constituting harmonic suppression circuit as described in Figure 2。In the drawings, the pressure unit 340 of harmonic suppression apparatus 330 exports the voltage V after blood pressure lowering_step-down, it is separately input to low pass filter 360 and band filter 350, obtains DC component V_{Step-down, dc}With AC compounent V_{Step-down, ac}。They, through comprising the second arithmetic device 370 of divider 371 and adder 372, obtain the 1+ μ sin (k ω t+ ρ) in equation (3)。The result of second arithmetic device 370 output is as control signal V_controlCorrected parameter and control signal V_controlIt is input in the first arithmetic device 380 including divider 381 together, the control signal V after first arithmetic device 380 output correction_control-newTo PWM mode generator 320, regulate the driving signal of each switch driving inverter module 310, to reach to eliminate the effect of the harmonic wave in inverter module 310 output。

Fig. 5 illustrates the exemplary waveform diagrams of the change of the control signal being input to PWM mode generator before and after the inverter execution harmonics restraint according to Fig. 3 and inverter output voltage and electric current。In this particular example, the voltage V of inverter is inputted_in=400+30sin2 ω t, and V when not adopting harmonics restraint_control=2.5sin ω t。It can be seen that when not adopting harmonic suppression apparatus, there is Severe distortion in the output electric current of inverter, and after carrying out harmonics restraint, along with the change of the control signal of input PWM mode generator, the elimination of the distortion of inverter output current。

Fig. 4 illustrates a kind of embodiment that inverter is full-bridge current source inverter。What receive the difference is that, harmonic suppression apparatus with the embodiment shown in Fig. 2 is the electric current of input inverter of detection, rather than the voltage of input inverter。

For current source inverter, it is possible to obtain the relational expression similar with equation (1)。Output current wave and input current and control signal V_controlRelation such as following equalities (5) shown in:

I_out=I_inV_control=I_inM₁sinωt(5)

In order to offset the harmonic component of the output electric current caused by the AC compounent of input current, thus avoiding the distortion that inverter exports, new control signal is calculated as below:

$V_{\mathrm{control}-\mathrm{new}}=M_1\sin \mathrm{\ωt}\left[\frac{1}{1+\mathrm{\μ}\sin (\mathrm{k\ωt}+\mathrm{\ρ})}\right]---\left(6\right)$

Wherein $\mathrm{\μ}=\frac{V_{\mathrm{dclink},\mathrm{ac}}}{V_{\mathrm{dclink},\mathrm{dc}}}$

K is the integer more than 0, and ρ is selected from 0 °～360 °。

Equation (6) can also be transformed to:

$V_{\mathrm{control}-\mathrm{new}}=M_1\sin \mathrm{\ωt}\left[\frac{I_{\mathrm{dclink},\mathrm{dc}}}{I_{\mathrm{dclink},\mathrm{dc}}+I_{\mathrm{dclink},\mathrm{ac}}\sin (\mathrm{k\ωt}+\mathrm{\ρ})}\right]=M_1\sin \mathrm{\ωt}\left[\frac{I_{\mathrm{dclink},\mathrm{dc}}}{I_{\mathrm{in}}}\right]---\left(7\right)$

Inverter shown in Fig. 4 includes current detecting unit 490。After harmonic suppression apparatus 430 receives the electric current of input inverter of detection, the input that harmonic suppression apparatus 430 receives can be carried out blood pressure lowering, output voltage after blood pressure lowering by pressure unit 440。Voltage after blood pressure lowering through low pass filter 460 and band filter 450, can then respectively obtain DC component and the AC compounent of the voltage after blood pressure lowering, and the ratio between them is equal to the DC component I of the electric current of input inverter_{Dclink, dc}With AC compounent I_{Dclink, ac}Ratio。The second arithmetic device 470 of harmonic suppression apparatus 430 works in the way of identical with reference to the second arithmetic device 370 of the harmonic suppression apparatus 330 described in Fig. 3, obtains the 1+ μ sin (k ω t+ ρ) in equation (6),。The result of second arithmetic device 470 output is as control signal V_controlCorrected parameter and control signal V_controlIt is input in the first arithmetic device 480 including divider 481 together, the control signal after first arithmetic device 480 output correctionTo PWM mode generator 420, regulate the driving signal of each switch driving inverter module 400, to reach to eliminate the effect of the harmonic wave in inverter 410 output。

Additionally, as shown in Figure 4, the outfan of inverter module can connect LC (inductance capacitance) filter circuit, eliminates the harmonic component in the output voltage of inverter module further。

Although oneself is through describing the present invention with reference to many specific detail, but those of ordinary skill in the art is it will be recognized that the present invention can implement without departing from the spirit of the invention in other specific forms。Such as, the inverter of the present invention can select according to actual needs, including various voltage sources and current source inverter。The arithmetic element of harmonic suppression circuit can also select different to build mode as required, for instance adopts analog circuit or is realized by devices such as MCU (microcontroller) or DSP (digital signal processor)。Therefore, it will be understood by those skilled in the art that the present invention is not limited by the foregoing illustrative details, but be defined by the following claims。

Claims (30)

1. a voltage source inverter, it is characterized in that, including the DC-AC inverter module that input voltage is converted, harmonic suppression apparatus, PWM mode changer and first arithmetic device, harmonic suppression apparatus receives input voltage and exports corrected parameter, this corrected parameter is equal to the ratio between DC component and the input voltage of input voltage, this corrected parameter is exported first arithmetic device by harmonic suppression apparatus, first arithmetic device is connected between PWM mode changer and the power supply providing control signal to PWM mode changer, the control signal that this power supply is provided by described corrected parameter is used to be modified, and provide revised control signal to PWM mode changer, PWM mode changer generates the driving signal driving DC-AC inverter module according to revised control signal, the product that revised control signal is multiplied with control signal divided by the value of input voltage equal to the DC component of input voltage again。

2. inverter according to claim 1, it is characterized in that harmonic suppression apparatus includes pressure unit, band filter, low pass filter and second arithmetic device, pressure unit receives described input voltage, voltage after blood pressure lowering is separately input to band filter and low pass filter, the DC component of the voltage after low pass filter and band filter output buck respectively and AC compounent, second arithmetic device receives DC component and the AC compounent of the voltage after blood pressure lowering, and to the ratio between the voltage after the DC component and blood pressure lowering of the voltage after first arithmetic device output buck as corrected parameter, this ratio is equal to the ratio between DC component and the input voltage of input voltage。

3. inverter according to claim 2, it is characterized in that second arithmetic device includes divider and adder, divider receives DC component and the AC compounent of the voltage after blood pressure lowering, to the ratio of the DC component of the voltage after adder output buck and AC compounent, adder is by the ratio between the voltage after the DC component of the voltage after computing output buck and blood pressure lowering。

4. inverter according to claim 1, it is characterised in that the outfan of inverter module connects an inductance。

5. inverter according to claim 1, it is characterised in that the AC compounent of input voltage is second harmonic component。

6. inverter according to claim 1, it is characterised in that PWM mode generator is sinusoidal pulse width modulation mode generator。

7. inverter according to claim 1, it is characterised in that first arithmetic device is realized by analog circuit, MCU or DSP。

8. inverter according to claim 2, it is characterised in that second arithmetic device is realized by analog circuit, MCU or DSP。

9. a current source inverter, it includes the DC-AC inverter module that input current is converted, harmonic suppression apparatus, PWM mode changer and first arithmetic device, harmonic suppression apparatus receives input current, and export corrected parameter, this corrected parameter is equal to the ratio between DC component and the input current of input current, this corrected parameter is exported first arithmetic device by harmonic suppression apparatus, first arithmetic device is connected between PWM mode changer and the power supply providing control signal to PWM mode changer, the control signal that this power supply is provided by corrected parameter is used to be modified, and provide revised control signal to PWM mode changer, PWM mode changer generates the driving signal driving DC-AC inverter module according to revised control signal, the product that revised control signal is multiplied with control signal divided by the value of input voltage equal to the DC component of input voltage again。

10. current source inverter according to claim 9, characterized by further comprising current detecting unit, wherein the DC component of the electric current of the detection of current detecting unit output and the ratio of AC compounent are equal to the DC component of the input current of input inverter and the ratio of AC compounent, described harmonic suppression apparatus includes pressure unit, band filter, low pass filter and second arithmetic device, pressure unit receives the output of current detecting unit and to the voltage after band filter and low pass filter output buck, the DC component of the voltage after low pass filter and band filter output buck respectively and AC compounent, wherein the DC component of the voltage after blood pressure lowering and the ratio of AC compounent are equal to the DC component of the electric current of the detection of current detecting unit output and the ratio of AC compounent, second arithmetic device receives DC component and the AC compounent of the voltage after blood pressure lowering, and to the ratio between the voltage after the DC component and blood pressure lowering of the voltage after first arithmetic device output buck, this ratio is equal to the ratio between DC component and the input current of input current。

11. current source inverter according to claim 10, it is characterized in that second arithmetic device includes divider and adder, divider receives DC component and the AC compounent of the voltage after blood pressure lowering, to the ratio of the DC component of the voltage after adder output buck and AC compounent, and adder is by the ratio between the voltage after the DC component of the voltage after additive operation output buck and blood pressure lowering。

12. current source inverter according to claim 9, it is characterised in that the outfan of inverter module connects LC wave filter。

13. inverter according to claim 9, it is characterised in that the AC compounent of input voltage is second harmonic component。

14. inverter according to claim 9, it is characterised in that PWM mode generator is sinusoidal pulse width modulation mode generator。

15. inverter according to claim 9, it is characterised in that first arithmetic device is realized by analog circuit, MCU or DSP。

16. inverter according to claim 9, it is characterised in that second arithmetic device is realized by analog circuit, MCU or DSP。

17. the harmonic suppressing method for inverter, the method includes: the input voltage of inverter is carried out blood pressure lowering, and the voltage after blood pressure lowering is separately input to low pass filter and band filter, thus respectively obtain DC component and the AC compounent of the voltage after blood pressure lowering, second arithmetic device receives DC component and the AC compounent of the voltage after blood pressure lowering, the ratio between voltage after the DC component and blood pressure lowering of the voltage after first arithmetic device output buck is as corrected parameter, revised control signal is exported after the control signal of first arithmetic device reception PWM mode generator and corrected parameter, revised control signal equal to the voltage after blood pressure lowering DC component divided by the voltage after blood pressure lowering value again with the product of control signal；Revised control signal is imported into PWM mode generator, controls PWM mode generator to obtain driving the driving signal of inverter, and input voltage is carried out the direct current conversion to exchange according to the signal that drives of input by inverter。

18. as claimed in claim 17 for the harmonic suppressing method of inverter, it is characterized in that second arithmetic device includes adder and divider, obtain the ratio that the step of corrected parameter includes the DC component of the voltage after by blood pressure lowering and AC compounent obtains between them by divider, this ratio is processed the ratio between the value of the voltage after the DC component of the voltage after obtaining blood pressure lowering and blood pressure lowering by adder, and this ratio is equal to the ratio between DC component and the input voltage of inverter of the input voltage of inverter。

19. as claimed in claim 17 for the harmonic suppressing method of inverter, it is characterised in that the outfan of inverter connects an inductance, for the output voltage of inverter is filtered。

20. as claimed in claim 17 for the harmonic suppressing method of inverter, it is characterised in that the AC compounent of input voltage is second harmonic component。

21. as claimed in claim 17 for the harmonic suppressing method of inverter, it is characterised in that PWM mode generator is sinusoidal pulse width modulation mode generator。

22. as claimed in claim 17 for the harmonic suppressing method of inverter, it is characterised in that first arithmetic device is realized by analog circuit, MCU or DSP。

23. as claimed in claim 18 for the harmonic suppressing method of inverter, it is characterised in that second arithmetic device is realized by analog circuit, MCU or DSP。

24. the harmonic suppressing method for inverter, the method includes: detected the input current of inverter by current detecting unit, and the ratio between DC component and the AC compounent of the electric current after detection is equal to the ratio between DC component and the AC compounent of the input current of inverter；The output of current detecting unit is carried out blood pressure lowering, and the voltage after blood pressure lowering is input to band filter and low pass filter, low pass filter and band filter respectively obtains DC component and the AC compounent of the voltage after this blood pressure lowering；Second arithmetic device receives DC component and the AC compounent of the voltage after blood pressure lowering, and the ratio of the DC component of the voltage after output buck and AC compounent is as corrected parameter, this ratio is equal to the ratio between the electric current after the DC component of the electric current after detection and detection；First arithmetic device exports revised control signal after receiving control signal and the corrected parameter of PWM mode generator, revised control signal equal to revised control signal equal to the voltage after blood pressure lowering DC component divided by the voltage after blood pressure lowering value again with the product of control signal；Revised control signal is imported into PWM mode generator, controls PWM mode generator to obtain driving the driving signal of inverter；Input voltage is carried out the direct current conversion to exchange according to the signal that drives of input by inverter。

25. as claimed in claim 24 for the harmonic suppressing method of inverter, it is characterized in that second arithmetic device includes adder and divider, obtain the ratio that the step of corrected parameter includes the DC component of the voltage after by blood pressure lowering and AC compounent obtains between them by divider, by adder this ratio processed the ratio between the value of the voltage after the DC component of the voltage after obtaining blood pressure lowering and blood pressure lowering, this ratio equal to detection after electric current DC component and detection after electric current between ratio, namely equal to the ratio between DC component and the input current of inverter of the input current of inverter。

26. as claimed in claim 24 for the harmonic suppressing method of inverter, it is characterised in that the outfan of inverter connects LC wave filter, for the output voltage of inverter is filtered。

27. as claimed in claim 24 for the harmonic suppressing method of inverter, it is characterised in that the AC compounent of input voltage is second harmonic component。

28. as claimed in claim 24 for the harmonic suppressing method of inverter, it is characterised in that PWM mode generator is sinusoidal pulse width modulation mode generator。

29. as claimed in claim 24 for the harmonic suppressing method of inverter, it is characterised in that first arithmetic device is realized by analog circuit, MCU or DSP。

30. as claimed in claim 25 for the harmonic suppressing method of inverter, it is characterised in that second arithmetic device is realized by analog circuit, MCU or DSP。