131 results about "Synchronous coordinates" patented technology

The invention discloses a control method of a three-phase grid-connected inverter based on a modified proportional resonant regulator. The method comprises the following steps of: firstly, computing according to given active and reactive powers of the inverter and a voltage of a power grid to obtain required d-axis and q-axis currents under a synchronous coordinate system, and performing coordinate transformation by combining with phase information which is measured by a phase locking loop and a measured three-phase voltage signal of the power grid to obtain a current reference signal under a stationary alpha-beta coordinate system; secondly, performing coordinate transformation on an output current signal of the inverter to the alpha-beta coordinate system, controlling and tracking the current reference signal by the modified proportional resonant regulator with a harmonic compensator; and finally, returning to an abc coordinate system by coordinate transformation to generate a pulse-width modulation (PWM) pulse-control three-phase full-bridge inverter output, so as to make a distributed generation system grid-connected for power generation. By the method, a large number of complicated computation processes are eliminated, and a control structure is simplified. The control method of the three-phase grid-connected inverter based on the modified proportional resonant regulator is an accurate and high-efficiency novel inverter control method and has a bright development future.

The invention relates to a topological structure of a multi-level photovoltaic power generation system and a control method of the topological structure. The topological structure comprises M photovoltaic arrays, the boost DC / DC (direct current / direct current) converters of the M photovoltaic arrays, 3n isolation flyback DC / DC converters and 3n H-bridge voltage source inverters. The PWM (pulse-width modulation) control signals of the first to nth H-bridge voltage source inverters of the three phases A, B and C of the cascade H-bridge multi-level voltage source inverters are obtained through an active power calculation method of a super-capacitor direct-current bus voltage controller and a photovoltaic array, and current tracking control of a dq synchronous coordinate system; the PWM control signals of the electronic power switches S2 of the wth and kth isolation flyback DC / DC converters are obtained through a control method of the isolation flyback DC / DC converters; the PWM control signals of the electronic power switches S1 of the j boost DC / DC converters are obtained through a control method of the boost DC / DC converters. The topological structure has the benefits that the shortcomings of large volume and high cost of power-frequency boosting transformers used when existing large-scale photovoltaic power generation systems are connected to a power grid are overcome.

The embodiment of the invention discloses a resonance wave detecting and phase-locking method and a resonance wave detecting and phase-locking method for an active power filter. The method comprises the following steps of: carrying out phase shift filtering to a sampled three-phase voltage signal to obtain a first-grade processing signal; substituting the first-grade processing signal into an sequence-dividing formula to obtain a three-phase voltage fundamental positive sequence component; and adopting a dq synchronous coordinate system to lock phase of the three-phase voltage fundamental positive sequence component. The embodiment of the invention extracts the three-phase voltage fundamental positive sequence component in an unbalanced grid by using a way of dividing sequence first and locking phase consequently, locks phase of the positive sequence component by using a dq synchronous coordinate system phase-locking algorithm to obtain a positive sequence fundamental phase angle and eliminate the influence of grid imbalance on the phase locking link, so that the phase locking precision is wholly improved and the technical effect that the real-time and precise phase locking can also be carried out in the situation of unbalanced voltage in the grid is achieved.

The invention discloses an LCL-type single-phase grid-connected inverter power control and active damping optimization method. An equivalent synchronous coordinate PI controller is adopted, a two-phase virtual orthogonal system is constructed by adopting an all-pass filter, the problem that data used in previous construction methods have asynchrony or noise interference is introduced is solved, regulation of grid-connected currents at fundamental frequency in a zero steady state error is achieved, and the stability of the system is improved. According to the LCL-type single-phase grid-connected inverter power control and active damping optimization method, the primary differential and the high-frequency components of the grid-connected currents are fed back in real time, the damping of the system is increased, the resonance peak of the LCL filter is restrained, an optimized parameter selection method is given, single-current feedback factors are reduced to a variable, the defect that parameters are difficult to select in single current high-frequency component feedback is overcome, and the reliability and the dynamic nature of the system are improved.

The invention discloses a positive-negative sequence voltage feedforward method of three-phase PWM (pulse width modulation) converter which relates to a positive-negative sequence voltage feedforward method and is capable of lowering the influence of lagging and negative sequence voltage of three-phase PWM control on running of a converter caused by. The method comprises the steps of: carrying out phase-sequence separation on an acquired power grid voltage after carrying out Clarke conversion on the acquired power grid voltage so as to obtain a positive sequence voltage component and a negative sequence voltage component; carrying out phase-sequence separation on an acquired current after carrying out Park conversion on the acquired current so as to obtain a positive sequence current component and a negative sequence current component; calculating a positive sequence current loop set value and a negative sequence current loop set value by adopting a PWM control algorithm; carrying outforward-feeding decoupling control on the positive sequence current component and the negative sequence current component to obtain control set voltage of a PWM converter; calculating and respectively carrying out phase angle compensation on a positive sequence synchronous coordinate system and a negative sequence synchronous coordinate system according to angles needed to be compensated in feedforward of positive sequence power grid voltage and negative sequence power grid voltage; synthesizing the control set voltage of the PWM converter and the compensated phase angles after respectively carrying out Park inverse conversion on the control set voltage of the PWM converter and the compensated phase angles to obtain the final control set voltage of the PWM converter. The positive-negativesequence voltage feedforward method of the three-phase PWM converter is suitable for the control process of the three-phase PWM converter.

The invention relates to a method for detecting positive sequence, negative sequence, idle and harmonic currents of a power supply system. The detection method is based on three-phase voltage space vector oriented positive sequence synchronous coordinate rotation transformation, negative sequence synchronous coordinate rotation transformation and low-pass filtering. The method is very effective for detecting various positive sequence, negative sequence, idle and harmonic currents of three-phase four-wire and three-phase three-wire non-linear circuits. The method only transforms the tested current, and does not need to transform voltage. Therefore, the invention has the advantages of simple structure and clear conception. The invention is the simplest engineering method for dynamic and static idle and harmonic compensation.

The invention discloses a control method of a brushless double-fed motor and an application thereof, relating to the field of motor control. In the control method, the observed control-side motor flux linkage and motor torque are used as feedback quantities to be compared with a given value by using the influence of a power-side motor on a control-side motor as the disturbance according to the basic principle of feedback control, a regulator regulates errors to obtain a control quantity under a synchronous coordinate system, and the control quantity is subject to rotation transformation and is converted to a control quantity under a static coordinate system so as to realize the control on the control-side motor flux linkage and motor torque. Flux linkage observer and torque observer models have less dependence on motor parameters; the control algorithm is simple and avoids the difficulty in solving the complicated nonlinear equation; and the invention can realize the effective control on the control-side motor flux linkage and motor torque in the dynamic / static process, thereby being especially applicable to variable-frequency speed-regulating, variable-speed constant-frequency constant-voltage and variable-frequency variable-voltage control systems of the brushless double-fed motor.

The invention relates to a method for tracking and positioning a mobile node of a wireless sensor network, which comprises the following steps: in a measurement positioning period, sending low repeated frequency pulse beacon signals for at least four times at known time intervals by the mobile node approximately keeping uniform speed rectilinear motion, receiving the beacon signals continuously for four times by a main anchoring node, measuring self time difference to acquire three self time difference relation expressions relative to an initial measurement moment, providing two trigonometric function equations from a positioning measurement triangle consisting of a motion locus of the mobile node and a motion radius vector of detection wave by using the cosine theorem, and simultaneously solving the equations so as to determine the relative distance and speed between the mobile node and the anchoring nodes; and further, by adopting the technology of beacon retransmission, retransmitting the beacon signals sent by the mobile node for the last time to the main anchoring node by two auxiliary anchoring nodes so as to achieve asynchronous coordinate positioning of the mobile node. The method can achieve tracking and positioning of a mobile target without time synchronization among the anchoring nodes.

The invention discloses control methods of a two-way converter system connected with an electric network, which comprise a control method of an electric network side converter and a control method of an electric motor side converter. The electric network side converter adopts novel sliding mode control to realize effective control on electric network side control variables including IS, Id and Um. The method plays a full inhibitory action on resonance phenomena of a capacitor loop of a wave filter in a system while ensuring the normal output power of the electric network side converter. The control method of the electric motor side converter cancels a magnetic flux linkage estimator used in the conventional vector control, but adopts a novel electric network voltage-based synchronous coordinate system, and adopts two independent control loops to realize decoupling control on the double-feed electric motor side reactive power Qs and the electric motor rotating speed omega r.

The invention relates to a complex-vector-regulator-based low-carrier-ratio control method for a permanent-magnet synchronous motor. The method comprises: constructing a complex vector current regulator and an electric drive control system of a permanent-magnet synchronous motor; according to a speed loop PI regulator, carrying out calculation to obtain d-axis and q-axis reference command currentsin a synchronous coordinate system; difference processing is carried out on the reference command currents in the dq synchronous coordinate system and a current obtained by sampling by a current detecting module to obtain an error current, the error current is inputted into the complex vector current regulator, and the regulator outputs a voltage signal; an average voltage value outputted by thecurrent regulator within a sampling cycle is estimated and an active damping state feedback amount is added at an average voltage output terminal to form a system modulation signal; and the system modulation signal is subjected to SVPWM modulation to generate a PWM pulse wave and thus a three-phase full-bridge inverter is controlled to output an actual voltage, and the SVPWM inverter is connectedto the permanent-magnet synchronous motor to drive the motor.

The invention discloses a method for controlling a DFIG without a phase-locked ring under a synchronous coordinate system. After error adjustment and decoupling compensation are carried out on active power and inactive power outputted by the DFIG, a rotor voltage instruction is automatically generated so that a DFIG rotor current transformer can be controlled. A phase-locked loop link for extracting the positive sequence voltage amplitude by tracking the voltage phase angle is omitted, the designing procedure of a control system is simplified, and the computing burdens on the computer control system are effectively reduced. Meanwhile, the DFIG control method has good adaptability to frequency deviation and inaccurate motor parameters and can still provide good power tracking capability. The method can be applied to PWM converters for grid-connected power generation, alternating-current transmission and the like of new energy sources such as solar energy and biomass energy.

The invention discloses a large soil-underground structure pseudo-static test device and method. The device comprises a bottom plate, a rectangular laminar shearing box body, a lateral limiting framework, a horizontal loading system and a vertical loading system, wherein the rectangular laminar shearing box body comprises a rectangular steel framework and interlaminar rollers; the lateral limiting framework comprises steel stand columns, lateral universal rollers and tie bars; the horizontal loading system comprises horizontal actuators; the vertical loading system comprises vertical actuators, loading plates, top universal rollers and a top pressure-bearing steel plate. The vertical actuators apply vertical loads to the surface of a soil mass uniformly through the loading plate, the top universal rollers and the top pressure-bearing steel plates, and the rectangular laminar shearing box body generates horizontal displacement in a certain distribution form step by step by performing synchronous coordinate control on the horizontal loading system until an underground structure is damaged. The limit that the reduced scale in a test of a traditional underground structure anti-seismic model is small is eliminated, and the anti-seismic property of the underground structure under different vertical seismic motion is researched.

The invention discloses an SOGI based phase-locked loop free photovoltaic inverter control method in the imbalance power grid. The method comprises the following steps that Clark transformation is carried out on three phases of voltage signals Ea, Eb and Ec obtained by a sampling conditioning circuit to obtain components Ealpha and Ebeta in a rest frame; SOGI is used to carry out orthogonal treatment on the Ealpha and Ebeta to obtain a group of orthogonal signals Valpha1 and Valpha2 and another group of orthogonal signals Vbeta1 and Vbeta2; the orthogonal signals are separated to obtain positive-sequence voltage components Valpha+ and Vbeta+ and negative-sequence voltage components Valpha- and Vbeta-; a cosine signal costheta and a sine signal sintheta needed by rotation transformation areneeded according to relation between the phase angle theta of the positive-sequence fundamental wave voltage and the Valpha+ and Vbeta+; and a photovoltaic inverter is controlled in the synchronous coordinate system by using the sine and cosine signals, Valpha- and Vbeta-. Via the method, the photovoltaic inverter in the imbalance power grid can be controlled without a phase-locked loop, and thesystem structure is simple; and positive and negative voltage feedforward is introduced to inhibit grid-connected negative-sequence current, and the waveform quality of the grid-connected current in the imbalance power grid is ensured.

The invention discloses a sliding-mode control method for fuzzy PI parameter self-turning feedback linearization of an active filter. By a fuzzy PI parameter self-turning feedback linearization method, according to actual error in voltage control of the direct-current side of the active filter, fuzzy reasoning is performed according to a preset fuzzy rule so as to realize self-adaptive regulation of feedback linearization control law parameters, and accordingly, stability and adaptability of the voltage of the direct-current side are improved effectively. An integral position tracking sliding-mode controller is capable of effectively reducing harmonic content of supply current after compensation and improving harmonic compensation effect of the active filter. Further, since a synchronous coordinate transformation based unit sinusoidal-signal computing method is utilized, unit synchronous sinusoidal-signals can be computed accurately on the condition of high harmonics of supply voltage, and can be used for computing of reference supply current. The sliding-mode control method has the advantages that the harmonic compensation effect is good, the voltage of the direct-current side of the system has good dynamic and static characteristics, and system performance keeps good even when the power supply contains the harmonic voltage and non-linear loads change.

The invention discloses a method for detecting the position of a surface-mounted permanent magnet synchronous motor rotor, belonging to the technical field of motor control. The method comprises the steps of injecting high-frequency current to a d axis of an estimated rotor synchronous coordinate system, and controlling the current under the estimated rotor synchronous coordinate system to be consistent with a given value; when the current under the estimated rotor synchronous coordinate system is controlled to be consistent with the given value, extracting a 1kHz component in the q-axis voltage of the estimated rotor synchronous coordinate system, modulating the extracted 1kHz component and a same-phase high-frequency signal to eliminate 2kHz harmonic, and extracting a direct-current component to obtain an estimated position error signal, thus saving band-pass and low-pass filters, eliminating the delay problem caused by the filters and estimating the position of the rotor more accurately.

The invention provides a virtual synchronous coordinate system-based direct power control method of a grid-connected inverter. The control scheme is implemented in a virtual synchronous coordinate system; a phase angle of a power grid voltage vector does not need to be constantly detected by use of a phase-locked loop; and meanwhile, a current decoupling compensation term related to an inlet inductor is eliminated and the dependency of a control system on inductor parameters is reduced. Meanwhile, the direct power control method has self-adaptive capacity on a power grid frequency deviation, and can be used as supplement and extension of a power grid voltage orientation-based direct power control scheme under the condition that the deviation exists in voltage phase and frequency detection. Furthermore, the virtual synchronous coordinate system-based direct power control method can be used for various forms of PWM power converters of solar energy and biomass energy grid-connected inverters, AC transmission equipment and the like.

The invention discloses a double closed-loop control method and system based on traditional VSR current closed-loop control, belonging to the field of power electronics and its control technology; thesteps of the present invention are as follows: 1. The DC bus voltage of the rectification side is an outer ring, and the PI is passed through the PI. Adjusting to obtain the given value of the outputactive power; 2. Obtaining the given set value and the reactive power set value through the current command calculation module to obtain the active current command value and the reactive current command value; 3. The obtained active current The command value and the reactive current command value are adjusted by the current loop to obtain two values; 4. The two values are converted into a two-phase [alpha][beta] stationary coordinate system by synchronous coordinate transformation, and two other values are obtained; 5. Through SVPWM Generate six PWM signals to control VSR operation. The invention adds a new method for calculating the current command, thereby overcoming the problem that the dynamic response of the vector control strategy of the traditional VSR current closed loop is slow,the total harmonic distortion rate of the grid current is large, and the anti-interference performance to disturbance such as load variation is poor.

The invention discloses a voltage source converter grid-connected system stability analysis method considering the influence of a phase locked loop, The device and the system comprise: acquiring smalldisturbance state equations of an electric main loop unit of an equivalent power network and a grid-connected converter, and small disturbance state equations of a current inner loop, a feedforward link and a converter pulse width modulation link in the control unit; Based on the relationship between the variable increment of synchronous coordinate system of control unit and the variable increment of corresponding actual synchronous coordinate system caused by phase-locked loop detection error under small disturbance, the specific variable relation involving shaft system transformation is obtained. Obtaining a small disturbance state equation of a phase-locked loop in the control unit; Finally, the stability analysis of the grid-connected VSC system is completed by simultaneously establishing the above state equations, substituting the relevant parameters and solving the eigenvalues of the system. The invention can simply and efficiently judge the stability and oscillation characteristics of the grid-connected system of the voltage source converter.

Provided is a shooting aiming track detection method based on live ammunition bullet holes in a target and gun gesture detection. The shooting aiming track detection method based on the live ammunition bullet holes in the target and gun gesture detection comprises the following steps that (1) a gesture track on the target is obtained through a six-dimensional gesture sensor additionally installed on a gun; (2) image acquisition is carried out on the target surface through a camera, and the relative impact point position of the recent bullet on the target surface is determined in real time through image processing and image recognition after live ammunition percussion is accomplished according to images of the target surface and pulse trigger signals generated by live ammunition percussion; (3) the data deviation between a synchronous coordinate point and the relative impact point position is calculated to obtain the drift distance of the gesture track; (4) subtraction between discrete values of points on the gesture track on the target and the drift distance is carried out, a gesture track sequence can be corrected to form an aiming track penetrating through the impact point, and a shooting aiming track can be obtained. According to the shooting aiming track detection method based on the live ammunition bullet holes in the target and gun gesture detection, detection accuracy is effectively improved.

The invention discloses a voltage source inverter control method for decoupling electric current in a virtual synchronous coordinate system. The method comprises the step of conducting error PI adjustment and decoupling compensation calculation on dq axis current outputted by an inverter in a virtual synchronous rotating coordinate system, so that an AC output voltage command can be directly generated. The control method disclosed by the invention can eliminate a phase-locked loop link aiming at detecting the phase and the frequency of the rotating vector of grid voltage, and has obvious self-adaptability to frequency deviation; and furthermore, the control method can also be used for supplement and extension of a vector control method based on grid voltage orientation under the condition of deviation of voltage phase and frequency detection. According to the voltage source inverter control method, a grid voltage phase-locked loop is eliminated, the control design of a voltage source inverter is simplified, and the system computing burden and the realization complexity are reduced.

The invention discloses a magnetic encoder based on double synchronous rotation coordinate systems. The magnetic encoder based on the double synchronous rotation coordinate systems comprises a magneto-electricity signal generator, a signal conditioner, a signal acquisition module and a signal processing unit, wherein the signal processing unit is composed of a forward-direction Parker converter, a reverse-direction Parker converter, a forward-direction decoupling device, a reverse-direction coupling device, low-pass filters and a motion information solver, and is used for carrying out coordinate transformation, decoupling operation, filtering processing and motion information calculation on digital electrical signals input by the signal acquisition module. The signal processing unit which uses the double synchronous coordinate transformation mode carries out coordinate transformation on positive sequence components and negative sequence components of fundamental waves in magneto-electricity signals, and resolves the positive sequence components and the negative sequence components of the fundamental waves into components in a positive sequence dq coordinate system and components in a negative sequence dq coordinate system, calculation of motion information is achieved through a decoupling network and the filtering link, signal distortion components generated due to device difference, installation errors and the like can be eliminated through the decoupling devices and the low-pass filters, and thus calculation accuracy and the anti-interference capacity of the magnetic encoder are greatly improved.

The invention discloses a resonance current suppression method of an LCL type grid connected inverter, without capacitance and current sensors. The resonance current suppression method of an LCL type grid connected inverter, without capacitance and current sensors includes the following concrete steps: 1) obtaining an active component igd and a reactive component igq of the access current through synchronous coordinate conversion of the access current iga, igb and igc of a grid connected inverter, subtracting igd and igq from the given reference value and performing adjustment and control through an improved control adjuster; and 2) processing the active component igd and the reactive component igq of the access current through a feed link without differential, then subtracting igd and igq from the output quantity of the improved control adjuster, obtaining a three phase modulation signal through reverse synchronous coordinate conversion and generating a PWM wave to realize resonance suppression control of the grid connected inverter. The resonance current suppression method of an LCL type grid connected inverter, without capacitance and current sensors does not need sampling of capacitance and current, thus effectively saving the system cost, and eliminating the hidden trouble of amplifying system noise and increasing control risks because of the differential link.

The invention discloses a magnetic suspension rotor harmonic vibration force inhibition method based on a multi-synchronous coordinate transformation method. The method comprises the steps of firstlybuilding a magnetic suspension rotor dynamic model comprising mass imbalance and sensor harmonic waves, and then employing the MSRFT-based magnetic suspension rotor harmonic vibration force inhibitionmethod. The MSRFT can accurately suppress harmonic vibration force, and one controller is used for suppressing vibration in the X direction and the Y direction at the same time, so that hardware computing resources are reduced, and the dynamic process of suppression is accelerated. Meanwhile, the introduction of the phase compensation angle can guarantee the absolute stability of the system in alarger frequency range. The MSRFT controller is simple in structure, convenient to use in practical application, capable of restraining harmonic vibration force in the magnetic suspension rotor, and suitable for restraining harmonic vibration force of a magnetic suspension rotor system with mass imbalance and sensor harmonic waves.

The invention discloses an automatic generation control-based control method for flexible direct-current transmission to recover a power grid. The method includes the following steps that: 1) the mathematical model of the current converter of a voltage source type flexible direct-current power transmission system in a synchronous coordinate system is established; 2) the control system of the rectifier and inverter of the voltage source type flexible direct-current power transmission system in power grid recovery is established according to a double-closed-loop control principle; 3) an automatic generation control system and a generator speed governor model capable of receiving control signals are established according to a generated output control requirement of the participation of the voltage source type flexible direct-current power transmission system in the power grid recovery; and 4) based on the above model establishment, a control strategy for performing the power grid recoveryby means of the cooperation of the voltage source type flexible direct-current power transmission system and the automatic generation control is provided, so that the power grid system can be recovered. With the control method of the invention adopted, the stability of the power grid system can be maintained, the limitation of the inherent load recovery speed of the system in a black start process can be broken, and the load recovery ratio of the system can be increased once.

The invention discloses a gravity-driven chainless folding-free exercise bicycle with bicycle frame levers, which is characterized in that a front wheel axle is used as a fulcrum to form a front lever with an arc-shaped front beam frame and a steering rod; a back wheel axle is used as a fulcrum to form a back lever with a triangular back wheel fork frame and an adjustable bicycle seat tube; a bicycle head handle and a backrest bicycle seat act as main moving points of the front and back levers; a middle bearing frame and a middle axle act as concentric lifting driving points of the front and back levers; and the middle bearing frame and the middle axle rotate relatively; driving force is transmitted by a sector gear and a flywheel. The gravity-driven chainless folding-free exercise bicycle has the advantages that the bicycle frame is utilized to be manufactured into a labor-saving front-back level telescopic driving device, so the structure is simplified, materials are saved, the weight is lightened, the volume is reduced, the production is easy and the cost is lowed; since the gravity-driven chainless folding-free exercise bicycle self has an telescopic function, a complex structure and troublesome folding procedures of a folding bicycle are saved, so the gravity-driven chainless folding-free exercise bicycle is a small folding-free bicycle; and when the gravity-driven chainless folding-free exercise bicycle is ridden, hand-foot-buttock three-point whole-body synchronous coordinated movement is conducted, so a good exercise effect is achieved, labor is saved, handiness and interestingness are realized, the cost is low, and thus the practical value is high.

The invention discloses an APF (active power filter) harmonic current detection method. On the basis of an ip-iq harmonic current detection method, a phase-locked loop based on a synchronous coordinate system is adopted to replace a traditional phase-locked loop; fundamental wave sine and cosine components are obtained with an adaptive least mean square algorithm; fixed step size is changed into variable step size, a new step size factor and error nonlinear function model is established on the basis of Sigmoid variable step size adaptive filter function, and contradictions of high convergencespeed and small steady-state error are solved; and finally, angular frequency of fundamental wave phase is substituted into the ip-iq harmonic current detection method to obtain a transformational matrix, and three-phase grid current is subjected to a series of transformation to obtain harmonic components.

The invention discloses a grid-voltage-sensor-free vector control method of a synchronous PWM (Pulse Width Modulation) rectifier. The method comprises the following steps: estimating an initial phase angle of grid voltage before a PWM rectifier starts; adopting synchronous coordinate transformation to obtain active current and reactive current under a grid synchronous coordinated system; giving active current through the deviation PI (Proportional Integral) regulation of direct current busbar voltage, and giving reactive current through giving reactive power; adopting active current deviationPI and reactive current deviation PI to obtain a phase angle of grid voltage and output voltage of the rectifier; and controlling switch components through the output voltage of the rectifier. According to the invention, the vector control method has good performance for a three-phase symmetrical / asymmetric grid without a neutral point. The rectifier can work stably under the unit power factor byestimating the initial phase angle of the grid voltage, and the reactive power can be adjusted freely, thus the same control performance when a grid voltage sensor is used is achieved.

The invention relates to a phase locking method based on nonlinear PI and a decoupling double synchronous coordinate system phase-locked loop. Based on the decoupling double synchronous coordinate system phase-locked loop, a nonlinear function is added for changing parameters of a PI controller, so that tracking effect is improved, and rapidity and stability are better; meanwhile, for second harmonics caused by negative sequence voltage, a specific frequency point wave trap is introduced for eliminating the harmonics, so that harmonic eliminating performance is improved on the basis of decoupling and harmonic eliminating. The phase locking method can be used for realizing detection on phases and frequencies of a power grid in different states, is applicable to solar energy and wind power new energy grid-connected power generation systems and can be popularized into a control method for other single phase or three-phase grid-connected inverters.