CN104143836A - Alternating-voltage-sensor-free control method for inverter with frequency adaptive characteristic - Google Patents

Abstract

The invention provides an alternating-voltage-sensor-free control method for an inverter with the frequency adaptive characteristic. The method includes the steps that firstly, a quadrature filter with variable frequency is established for the zero-difference following characteristic of specific frequency alternating current signals through a second order generalized integrator, the quadrature filter is utilized to establish a voltage observer of the three-phase grid-connected inverter with the frequency adaptive characteristic, under a two-phase static coordinate system, measured power grid side current signals and inverter controller output bridge terminal voltage reference signals serve as input of the voltage observer, and then power grid voltages are observed; in combination with PR control of the three-phase grid-connected inverter under the two-phase static coordinate system, operational control over the inverter under the alternating-voltage-sensor-free condition is achieved. By the adoption of the method, under the condition that control stability of the inverter is kept, the problems of integral saturation, initial value sensitivity, static errors and the like probably existing in conventional alternating-voltage-sensor-free control are solved, and good adaptability is achieved when power grid voltage frequency changes.

Description

There is the inverter alternating voltage sensorless control method of frequency self-adaption characteristic

Technical field

The present invention relates to a kind of control method of three-phase grid-connected inverter.

Background technology

Regenerative resource grid-connected system development in recent years is rapid, in the time of the comparatively weak power distribution network of its access electrical network end or grid structure, may exist and site capacity of short circuit less, grid stability is poor, and electrical network exists comparatively serious voltage fluctuation, flickering, symmetry or asymmetrical voltage to fall the problems such as fault.The intermittence of regenerative resource self and randomness likely further worsen the voltage stability of the electric power system that accesses, and affect conversely the stable operation of self.In order to realize grid-connected power and the Current Control of renewable energy system, in existing grid-connected converter or inverter, the general phase-locked loop that adopts obtains line voltage information, but this class phase-locked loop control is easily subject to the impact of voltage ripple of power network, easily reduce the quality of power supply of regenerative resource grid-connected system.Therefore, some researchers of recent domestic begin one's study and do not rely on the alternating voltage sensorless control of mains voltage signal, to improve the robustness of grid-connected inverters control.

Voltage sensor control is similar with having, and in Converter Without Voltage Sensor control algolithm, the voltage of reconstruct/virtual magnetic linkage signal can be explicit, the row vector control of going forward side by side; Also can be implicit expression, and carry out direct Power Control.Existing line voltage/virtual magnetic linkage reconstructing method roughly can be divided into two classes, the one, line voltage/virtual magnetic linkage reconstructing method of estimating based on complex power, belongs to open loop method of estimation, and accuracy is not high, and owing to containing current differential item, thereby easily cause interference; The 2nd, the line voltage/virtual magnetic linkage reconstructing method based on current on line side bias adjustment, belongs to closed loop method of estimation, and accuracy is higher.

The people such as T.Noguchi have proposed the direct Power Control method based on Converter Without Voltage Sensor in document " Direct power control of PWM converter without power-source voltage sensors ", first this method is used filter inductance electric current and differential term estimation thereof to obtain the meritorious reactive power of AC, then carries out line voltage reconstruct.The error causing in order to reduce differential term, this method needs larger inductance value and sample frequency; In addition, when electric current hour, voltage estimated accuracy can be a greater impact.The people such as Malinowski propose to use instead integral operation in document " Sensorless control strategies for three-phase PWM rectifiers ", observation electrical network " virtual magnetic linkage "; But pure integrator method exist integration saturated with the problem such as null offset, and comparatively responsive to initial value.

Patent CN201010109338.2 proposes a kind of direct Power Control method of grid-connected inverter without non-AC voltage sensor, solve existing method due to the integrator initial value in the virtual flux observer of voltage on line side vector choose improper, and the problem that causes combining inverter normally to work.Patent CN201010207412.4 proposes a kind of control method of alternating voltage sensorless high voltage direct current transmission converter, by the virtual flux linkage vector of computing system, realizes alternating voltage sensorless control.

Alternating voltage sensorless control method described in above-mentioned document and patent is used the scheme based on flux observer conventionally: under synchronous coordinate system, electric current is carried out to integration, thereby obtain " virtual magnetic linkage ", and indirect calculation goes out line voltage angle.In order to reduce to disturb, improve accuracy of observation, generally need to use low pass filter, but the problems such as low pass filter itself exists that null offset, integration are saturated, steady-state error and initial value sensitivity; In the time that line voltage is asymmetric, the cascade algorithm that flux observation separates with positive-negative sequence has increased time of delay, has reduced the dynamic responding speed of system in addition.

Due to second order improper integral device (Second Order Generalized Integrator, SOGI) can carry out integral operation to the of ac of characteristic frequency, therefore be often used to build the phase-locked loop under rest frame, for grid-connected Synchronization Control single-phase or three-phase voltage source type inverter.In fact, second order improper integral device can be used to build a kind of orthogonal filter (Quadrature Filter, QF), export the orthogonal signalling of an offset of sinusoidal, and for the reconstruct of line voltage, thereby realize alternating voltage sensorless control, its advantage be fast, floating, insensitive to initial value, the voltage observer that this orthogonal filter builds simultaneously can adapt to the variation of mains frequency, thereby has solved well the problem existing in existing alternating voltage sensorless control.In addition, utilize orthogonal signalling can also synchronously realize positive-negative sequence and separate, thereby improve the dynamic property of inverter under asymmetric electrical network condition.

Summary of the invention

The object of the invention is to overcome that null offset, the integration that in the control of existing inverter alternating voltage sensorless, may exist are saturated, the problem such as steady-state error and initial value sensitivity, and make the control of inverter alternating voltage sensorless can adapt to the fluctuation of mains frequency, a kind of three-phase grid-connected inverter alternating voltage sensorless control method with frequency self-adaption characteristic is proposed.The present invention can be in the situation that keeping inverter control stability, avoid the problems such as the integration that may occur in conventional alternating voltage sensorless control is saturated, have fast, floating, to advantages such as initial value are insensitive, line voltage frequency change is had to good adaptability simultaneously.

A kind of inverter alternating voltage sensorless control method with frequency self-adaption characteristic of the present invention, build the orthogonal filter of variable frequency based on second order improper integral device (SOGI), then based on this orthogonal filter and introduce phase-locked loop control and build and there is the line voltage observer of frequency self-adaption characteristic, this voltage observer is applied in the controller of three-phase grid-connected inverter, realizes the alternating voltage sensorless control of inverter.Specifically comprise the following steps:

1, build the variable frequency orthogonal filter (QF) based on second order improper integral device (SOGI), the second order resonance link that this second order improper integral device has comprised sinusoidal signal, can carry out " integration " computing by offset of sinusoidal of ac, can realize floating to the AC signal of characteristic frequency and follow the tracks of control.This variable frequency orthogonal filter comprises the parts such as input/output signal, filter gain coefficient, second order improper integral device, output feedback, and wherein v is filter input signal, with for the output signal of filter, with pair of orthogonal signal, wherein with v same-phase, lag behind 90 ° than v, k is filter gain coefficient; ω _vfor the angular frequency of AC signal to be observed, for variable, obtain by the observation to line voltage frequency information.Ac input signal v enters after filter, with the output signal of feedback deviation, device gain coefficient k after filtering, then enters second order improper integral device, frequency input signal also enter second order improper integral device, the output of second order improper integral device with

2, the variable frequency orthogonal filter based on described in step 1 builds the voltage observer with frequency self-adaption characteristic, and ac grid voltage is observed.Voltage observer be input as i _{α β}and v _{α β}, wherein i _{α β}for the inverter ac-side current that measures is at the component of two-phase rest frame, v _{α β}for the bridge end control voltage of circuit control device output is at the component of two-phase rest frame; Output for the line voltage that obtains of observation is at the component of two-phase rest frame.Inverter ac-side current is at the component i of two-phase rest frame _{α β}with the component v of circuit control device bridge end control voltage in two-phase rest frame _{α β}enter respectively the variable frequency orthogonal filter described in step 1, obtain output with with then the Mathematical Modeling based on three-phase grid-connected inverter $\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=L\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]+R\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]+\left[\begin{array}{c}{v}_{\mathrm{\α}}\\ v_{\mathrm{\β}}\end{array}\right]$ Derivation obtains the component of line voltage in two-phase rest frame

Variable frequency orthogonal filter based on described in step 1, for variable, therefore introduce phase-locked loop (PLL) and control.Voltage observer is exported to the component of line voltage in two-phase rest frame input pll controller, obtain the frequency information of line voltage by phase-locked loop control, input using the frequency information of this line voltage as variable frequency orthogonal filter, thereby follow the tracks of the variation of line voltage frequency, make the voltage observer building based on variable frequency orthogonal filter there is frequency self-adaption characteristic.

3, the voltage observer with frequency self-adaption characteristic based on step 1 and step 2 is applied to the PR controller of three-phase grid-connected inverter under α β coordinate system.This PR controller comprises the link such as the power outer shroud based on PI and the current inner loop based on PR, PWM modulation, wherein power outer shroud comprises DC voltage outer shroud and reactive power outer shroud, control respectively DC voltage and reactive power, the meritorious reference current of DC voltage outer shroud output inverter control, the idle reference current of reactive power outer shroud output inverter control; Current inner loop is the PR controller under α β two-phase rest frame.The line voltage of voltage observer output is at the component of two-phase rest frame following aspect for inverter control: 1. for calculating the actual reactive power value of three-phase grid-connected inverter, as the value of feedback of reactive power outer shroud; 2. be tied to the coordinate transform of α β coordinate system for dq coordinate, the current reference value under the dq coordinate system of power outer shroud PI controller output is transformed to the current reference value under α β coordinate system; 3. for the phase-locked loop control of voltage observer, to obtain the frequency information of line voltage.Thereby realize the three-phase grid-connected inverter alternating voltage sensorless control based on the method for the invention.

Brief description of the drawings

Orthogonal filter (QF) structured flowchart of Fig. 1 variable frequency;

Fig. 2 has the voltage observer structured flowchart of frequency self-adaption characteristic;

Fig. 3 has the three-phase grid-connected inverter alternating voltage sensorless control block diagram of frequency self-adaption characteristic;

Fig. 4 uses the simulation result of the line voltage observer with frequency self-adaption characteristic, and wherein Fig. 4 a is actual electric network voltage, and Fig. 4 b is observer output voltage, Fig. 4 c is electric voltage frequency, Fig. 4 d is grid-connected current, and Fig. 4 e is DC voltage, and Fig. 4 f is the instantaneous meritorious and reactive power of input;

Fig. 5 uses the simulation result of fixed frequency line voltage observer, and wherein Fig. 4 a is actual electric network voltage, and Fig. 4 b is observer output voltage, Fig. 4 c is electric voltage frequency, Fig. 4 d is grid-connected current, and Fig. 4 e is DC voltage, and Fig. 4 f is the instantaneous meritorious and reactive power of input.

Embodiment

Further illustrate the present invention below in conjunction with the drawings and specific embodiments.

With the comparison of conventional three-phase grid-connected inverter control method, alternating voltage sensorless control method proposed by the invention is not used AC voltage sensor, and use the voltage observer building based on orthogonal filter to obtain line voltage information, this orthogonal filter has frequency self-adaption simultaneously, thereby realize the operation control of three-phase grid-connected inverter under alternating voltage sensorless condition, and this alternating voltage sensorless control method in the time that changing, mains frequency has good adaptability.

The present invention is based on the orthogonal filter of second order improper integral device (SOGI) structure variable frequency, then based on this orthogonal filter and introduce phase-locked loop control, structure has the line voltage observer of frequency self-adaption characteristic, this voltage observer is applied in the controller of three-phase grid-connected inverter, realizes the alternating voltage sensorless control of inverter.

Described voltage observer can draw according to the model inference of three-phase grid-connected inverter, be shown below:

$\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=L\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]+R\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]+\left[\begin{array}{c}{v}_{\mathrm{\α}}\\ v_{\mathrm{\β}}\end{array}\right]---\left(1\right)$

Wherein, u _αand u _β, i _αand i _β, v _αand v _βbe respectively line voltage, inverter ac-side current and the inverter leg output voltage component in two-phase rest frame, L and R are respectively inverter outlet side equivalent inductance and resistance.

In formula (1), there is the differential term of electric current, in general calculating, easily introduce and disturb.This is also that common alternating voltage sensorless control transfers to adopt integral operation, and calculating electrical network " virtual magnetic linkage " also obtains the reason of line voltage information indirectly; The problems such as but conventional " virtual magnetic linkage " method exists, and null offset, integration are saturated, steady-state error and initial value sensitivity, and dynamic response is slower.The present invention is based on second order improper integral device and propose a kind of orthogonal filter with frequency self-adaption characteristic, use this orthogonal filter to build line voltage observer, can solve preferably current differential operational problem, effectively reduce humorous wave interference, and the three-phase grid-connected inverter alternating voltage sensorless control realizing based on this voltage observer has good dynamic responding speed, and line voltage frequency change is had to good adaptability.

Below describe the implementation step of control method of the present invention in detail:

Step (1): the orthogonal filter (QF) that first builds variable frequency based on second order improper integral device (SOGI).

Second order improper integral device can be realized the tracking to characteristic frequency of ac, is used to the earliest export the of ac of pair of orthogonal, separates to realize positive-negative sequence.According to the feature of its output signal, the filter building based on second order improper integral device is called orthogonal filter (QF) by the present invention, and this orthogonal filter can adapt to the variation of AC signal frequency simultaneously, and its structure as shown in Figure 1.

As shown in Figure 1, v is filter input signal, with for output signal, subscript " ^ " represents observed quantity, for the angular frequency of AC signal to be observed, k is filter gain coefficient.

In practice, line voltage frequency may offrating, and this phenomenon is more prone to occur in the less power distribution network of capacity.When during for fixing mains frequency parameter, after mains frequency is offset, the filter effect of orthogonal filter will sharply decline, thereby be difficult to obtain correct line voltage information.Can expand passband although increase the gain coefficient k of filter, also can increase overshoot, and make control system more responsive to voltage harmonic simultaneously.Therefore, in this orthogonal filter, consider for variable, thereby improve the frequency adaptability of this orthogonal filter.

This orthogonal filter can be followed the tracks of the of ac of frequency change, and its transfer function is:

${\hat{G}}_{\mathrm{QF}1}=\frac{\hat{v}}{v}=\frac{k{\widehat{\mathrm{\ω}}}_{v}s}{s^2+k{\widehat{\mathrm{\ω}}}_{v}s+{\widehat{\mathrm{\ω}}}_v^2}---\left(2\right)$

${\hat{G}}_{\mathrm{QF}2}=\frac{{\hat{v}}^{\⊥}}{v}=\frac{k{\widehat{\mathrm{\ω}}}_v^2}{s^2+k{\widehat{\mathrm{\ω}}}_{v}s+{\widehat{\mathrm{\ω}}}_v^2}---\left(3\right)$

Wherein s is Laplacian.

Can calculate orthogonal filter improve after amplitude-frequency and phase-frequency response as follows:

$\left\{\begin{array}{c}\left|{\hat{G}}_{\mathrm{QF}1}\left({\mathrm{j\ω}}_v\right)\right|=\frac{k{\widehat{\mathrm{\ω}}}_v{\mathrm{\ω}}_v}{\sqrt{{\left(k{\widehat{\mathrm{\ω}}}_v{\mathrm{\ω}}_v\right)}^2+{({\widehat{\mathrm{\ω}}}_v^2-{\mathrm{\ω}}_v^2)}^2}}\\ \∠{\hat{G}}_{\mathrm{QF}1}\left({\mathrm{j\ω}}_v\right)=\arctan \left(\frac{{\widehat{\mathrm{\ω}}}_v^2-{\mathrm{\ω}}_v^2}{k{\widehat{\mathrm{\ω}}}_v{\mathrm{\ω}}_v}\right)\end{array}\right.$

$\left\{\begin{array}{c}\left|{\hat{G}}_{\mathrm{QF}2}\left({\mathrm{j\ω}}_v\right)\right|=\frac{{\widehat{\mathrm{\ω}}}_v}{{\mathrm{\ω}}_v}\left|{\hat{G}}_{\mathrm{QF}1}\left({\mathrm{j\ω}}_v\right)\right|\\ \∠{\hat{G}}_{\mathrm{QF}2}\left({\mathrm{j\ω}}_v\right)=\∠{\hat{G}}_{\mathrm{QF}1}\left({\mathrm{j\ω}}_v\right)-\frac{\mathrm{\π}}{2}\end{array}\right.$

In the time of stable state ${\widehat{\mathrm{\ω}}}_v=\mathrm{\ω},$ Can be obtained by formula (4) and formula (5) $\left|{\hat{G}}_{\mathrm{QF}1}\left({\mathrm{j\ω}}_v\right)\right|=\left|{\hat{G}}_{\mathrm{QF}2}\left({\mathrm{j\ω}}_v\right)\right|=1,$ $\∠{\hat{G}}_{\mathrm{QF}1}\left({\mathrm{j\ω}}_v\right)=0,$ illustrate that filter can carry out floating tracking to the signal of optional frequency, and export the signal of the pair of orthogonal of same frequency with wherein with v same-phase, lag behind 90 ° than v; And controller parameter and frequency input signal are irrelevant, have facilitated adjusting of controller parameter.The quality factor of variable frequency orthogonal filter remain:

$Q=\frac{1}{k}$

Step (2): the variable frequency orthogonal filter based on step (1) builds the voltage observer with frequency self-adaption characteristic.

Because the orthogonal signalling of sinusoidal signal are equivalent to homophase or the inversion signal of its differential, therefore can derive and obtain following formula based on formula (1):

$\begin{array}{c}\left[\begin{array}{c}{\hat{u}}_{\mathrm{\α}}\\ {\hat{u}}_{\mathrm{\β}}\end{array}\right]=L\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{\hat{i}}_{\mathrm{\α}}\\ {\hat{i}}_{\mathrm{\β}}\end{array}\right]+R\left[\begin{array}{c}{\hat{i}}_{\mathrm{\α}}\\ {\hat{i}}_{\mathrm{\β}}\end{array}\right]+\left[\begin{array}{c}{\hat{v}}_{\mathrm{\α}}\\ {\hat{v}}_{\mathrm{\β}}\end{array}\right]\\ =-L\left[\begin{array}{c}{\hat{i}}_{\mathrm{\α}}^{\⊥}\\ {\hat{i}}_{\mathrm{\β}}^{\⊥}\end{array}\right]+R\left[\begin{array}{c}{\hat{i}}_{\mathrm{\α}}\\ {\hat{i}}_{\mathrm{\β}}\end{array}\right]+\left[\begin{array}{c}{\hat{v}}_{\mathrm{\α}}\\ {\hat{v}}_{\mathrm{\β}}\end{array}\right]\\ =-G_{\mathrm{QF}2}L\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]+G_{\mathrm{QF}1}(R\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]+\left[\begin{array}{c}{v}_{\mathrm{\α}}\\ v_{\mathrm{\β}}\end{array}\right])\\ =G_{\mathrm{VO}}{\left[\begin{array}{cccc}{i}_{\mathrm{\α}}& i_{\mathrm{\β}}& v_{\mathrm{\α}}& v_{\mathrm{\β}}\end{array}\right]}^T\end{array}---\left(7\right)$

Wherein i _α, i _βfor the inverter ac-side current that measures is at the component of two-phase rest frame, v _α, v _βfor the bridge end control voltage of circuit control device output is at the component of two-phase rest frame; Output for the line voltage that obtains of observation is at the component of two-phase rest frame. with with for i _α, i _βoutput variable after the described orthogonal filter of step (1), subscript " ^ " represents observed quantity, wherein with with orthogonal signalling each other; with with for v _α, v _βoutput variable after the described orthogonal filter of step (1) respectively, wherein with with orthogonal signalling each other; G _vOfor the transfer function of line voltage observer.

Variable frequency orthogonal filter described in integrating step (1) simultaneously, for variable, therefore introduce phase-locked loop (PLL) and control, the component by the line voltage of voltage observer output in two-phase rest frame input pll controller, obtain the frequency information of line voltage by phase-locked loop control, input using the frequency information of this line voltage as variable frequency orthogonal filter, thereby follow the tracks of the variation of line voltage frequency, make the voltage observer building based on variable frequency orthogonal filter there is frequency self-adaption characteristic.

Based on formula (7) and introduce the control block diagram of the voltage observer after phase-locked loop, as shown in Figure 2, can realize the observation to ac grid voltage, there is certain adaptability for line voltage frequency change simultaneously.

Step (3): the voltage observer with frequency self-adaption characteristic of step (2) is applied in the PR controller of three-phase grid-connected inverter under two-phase rest frame, realizes the alternating voltage sensorless control of inverter.

Control block diagram by voltage observer substitution three-phase grid-connected inverter under α β coordinate system, can realize the alternating voltage sensorless control of three-phase grid-connected inverter, as shown in Figure 3.Voltage observer FAVO wherein for step (2) propose a kind of novel have frequency self-adaption characteristic voltage observer, under two-phase rest frame, the bridge end reference voltage signal of the grid side current signal that utilization measures and circuit control device output, observes line voltage information.As shown in Figure 3, K _cfor current controller, the present invention uses conventional PR controller.

For verifying the validity of control method of the present invention, in MATLAB, carry out emulation comparison, use respectively line voltage observer and the fixed frequency line voltage observer with frequency self-adaption characteristic.Use have frequency self-adaption characteristic line voltage observer control block diagram as shown in Figure 3, simulation result is as shown in Figure 4; While using fixed frequency line voltage observer, for rated frequency value, simulation result as shown in Figure 5.

Line voltage (U.abc) and frequency (f.U) thereof, observer output voltage (Uob.abc) and frequency (f.Uob) thereof, three-phase grid electric current (Iabc), direct voltage (Udc) and instantaneous input power (PQ) in simulation result figure, are provided.

As can be seen from Figure 4, in the t=0.3s moment, mains frequency jumps to 55Hz, and frequency self-adaption voltage observer can comparatively promptly be followed the tracks of grid voltage change, and observes correct line voltage, and transient process is about 0.15s.And as can be seen from Figure 5, in the time using the observer of fixed frequency, excessive due to mains frequency variation, cause observer cannot correctly follow the tracks of line voltage, control system starts to disperse after approximately 0.1 second in mains frequency saltus step.Above emulation comparative descriptions, the voltage observer with frequency self-adaption characteristic of the present invention makes the alternating voltage sensorless control of inverter can adapt to wider frequency change.

Claims (5)

1. one kind has the inverter alternating voltage sensorless control method of frequency self-adaption characteristic, it is characterized in that, first described control method builds the orthogonal filter of variable frequency based on second order improper integral device (SOGI), then build the line voltage observer with frequency self-adaption characteristic based on this orthogonal filter, described voltage observer is applied in the PR controller of three-phase grid-connected inverter under two-phase rest frame, realizes the alternating voltage sensorless control of inverter.

2. inverter alternating voltage sensorless control method according to claim 1, it is characterized in that, the second order resonance link that described second order improper integral device comprises sinusoidal signal, can carry out " integration " computing by offset of sinusoidal of ac, can realize floating to the AC signal of characteristic frequency and follow the tracks of control.

3. inverter alternating voltage sensorless control method according to claim 1, is characterized in that, the orthogonal filter of described variable frequency comprises input/output signal, filter gain coefficient, second order improper integral device and output feedback; Ac input signal v enters after the orthogonal filter of variable frequency, with the output signal of feedback deviation, device gain coefficient k after filtering, then enters second order improper integral device, frequency input signal also enter second order improper integral device, the output of second order improper integral device with frequency input signal for the angular frequency of AC signal to be observed, be variable, obtain by the observation to line voltage frequency information.

4. according to the inverter alternating voltage sensorless control method described in claim 1 or 3, it is characterized in that, the variable frequency orthogonal filter structure based on described has the voltage observer of frequency self-adaption characteristic to be observed ac grid voltage; Voltage observer be input as i _{α β}and v _{α β}, wherein i _{α β}for the inverter ac-side current that measures is at the component of two-phase rest frame, v _{α β}for the bridge end control voltage of circuit control device output is at the component of two-phase rest frame; for the line voltage of voltage observer output is at the component of two-phase rest frame;

I _{α β}and v _{α β}by described variable frequency orthogonal filter, obtain exporting respectively with with then the Mathematical Modeling based on three-phase grid-connected inverter $\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=L\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]+R\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]+\left[\begin{array}{c}{v}_{\mathrm{\α}}\\ v_{\mathrm{\β}}\end{array}\right]$ Derivation obtains the component of line voltage in two-phase rest frame variable frequency orthogonal filter based on described, introduces phase-locked loop (PLL) and controls, the component by the line voltage of voltage observer output in two-phase rest frame input pll controller, obtain the frequency information of line voltage by phase-locked loop control, input using the frequency information of this line voltage as this variable frequency orthogonal filter, thereby follow the tracks of the variation of line voltage frequency, make the voltage observer building based on variable frequency orthogonal filter there is frequency self-adaption characteristic.

5. inverter alternating voltage sensorless control method according to claim 1, it is characterized in that, the described voltage observer with frequency self-adaption characteristic is applied in the PR controller of three-phase grid-connected inverter under α β coordinate system, and this controller comprises the power outer shroud based on PI and the current inner loop based on PR; Voltage observer output following aspect for inverter control: 1. for calculating the actual reactive power value of three-phase grid-connected inverter, as the value of feedback of reactive power outer shroud; 2. be tied to the coordinate transform of α β coordinate system for dq coordinate, the current reference value under the dq coordinate system of power outer shroud PI controller output is transformed to the current reference value under α β coordinate system; 3. for the phase-locked loop control of voltage observer, to obtain the frequency information of line voltage, thereby realize the alternating voltage sensorless control to three-phase grid-connected inverter.