1002 results about "Voltage vector" patented technology

The invention discloses a control method of a power converter based on subspace predictive control, which is used in the technical field of power converter control, and comprises the following steps: constructing a subspace predictor model of the power converter based on a historical data matrix of the power converter; predicting a linear part of the model and predicting a nonlinear part through a neural network; based on the linear part predicted value and the non-linear part predicted value of the current control period, obtaining a function relational expression of a future predicted output current; determining the optimal input voltage of the current control period based on the target function; and constructing a cost function by using the optimal input voltage of the current control period and the voltage vectors corresponding to the switching states of the power converter, and taking the switching state corresponding to the voltage vector when the value of the cost function is minimum as the optimal switching state of the current control period. The state of the power converter can be accurately predicted, and the negative influence of parameter mismatch on the power converter is reduced.

The invention relates to the technical field of inverter pulse width modulation, in particular to a neutral-point potential balance and low common-mode voltage modulation method and system based on an SVPWM inverter, and the method comprises the steps: determining a basic voltage vector based on different switching states of an NPC three-level inverter; respectively determining the midpoint current of each fundamental voltage vector, and determining the fundamental voltage vector causing midpoint potential deviation; combining with a large vector and a zero vector, and performing mode division of a single vector space region; determining an expected current according to the DC side capacitor voltage of the inverter, and constructing a target function based on the expected current; and performing region judgment according to the output synthesized voltage vector, determining a corresponding optimal division mode, obtaining each basic voltage vector of the synthesized voltage vector and a corresponding duty ratio, and determining a switching sequence to obtain a PWM wave. While the neutral-point potential balance and common-mode voltage suppression of the NPC three-level inverter are realized, the switching frequency of the inverter is effectively reduced, and the switching loss is reduced.

The invention relates to a permanent magnet synchronous motor current control method of an adjustable switching frequency FCS-MPC. Compared with the prior art, the defect that the switching frequency of an inverter is not fixed in current control of an existing FCS-MPC permanent magnet synchronous motor system is overcome. The method comprises the following steps: acquiring data of a driving system; constructing a discrete current prediction control model; determining a cost function and a delay compensation strategy; calculating a current error control band degree; selecting an optimal voltage vector; and outputting the voltage vector. According to the invention, the unique advantages of the FCS-MPC are reserved, and the defect that the inherent switching frequency is not fixed is overcome, so that the FCS-MPC can operate under the specified switching frequency in a wide speed regulation range; by introducing the PI type switching frequency controller, the zero-static-error tracking of the switching frequency reference value can be realized, and the control method realizes the effective regulation and control of the switching frequency on the basis of ensuring the current control performance of the permanent magnet motor.

The present invention provides a method for cooperatively suppressing a common-mode voltage and current harmonics of coupled three-level inverters, comprising: based on amplitude and phase angle of reference voltage vector, determining sector and region in which the reference voltage vector is located; selecting four basic voltage vectors with low common-mode voltage amplitudes to synthesize the reference voltage vector; writing volt-second balance equation based on selected basic voltage vectors, and calculating duty cycles thereof; and based on sector and region in which reference voltage vector is located, set value of voltage difference across capacitors on direct current side, and actual value of voltage difference across capacitors on direct current side, (1) updating duty cycles of basic voltage vectors, to realize separate control of capacitor voltage; and (2) designing and converting switching sequence into PWM drive signal of power switch, to control the coupled three-level inverter to operate.

The invention discloses a frequency conversion vector control method for a digital energy-saving pump station, which belongs to the technical field of vector control and comprises the following steps: constructing a coupling vector model, simulating the running states of a pump unit under different working conditions through a virtual test signal, and automatically correcting the coupling vector model; operating data of a pump set are collected in real time, an operating situation feature set is constructed, predictive vector control is carried out, an optimal voltage vector sequence is generated, and meanwhile load fluctuation of a pipe network is predicted; demand pre-judgment is carried out on the starting and stopping time and the action amplitude of the anti-backflow device, a bidirectional disturbance suppression mechanism is constructed, current vector parameters are pre-adjusted, and calculus correction is carried out based on deviation judgment; when multiple pumps operate in parallel, the instantaneous operation efficiency point of the pump set is calculated in real time, the efficiency change trend is predicted, a load distribution scheme is generated, the comprehensive energy efficiency is evaluated, energy efficiency self-optimization is carried out, the comprehensive energy efficiency of the system is improved, and control experience reuse is achieved.

The invention provides a non-cascade permanent magnet synchronous motor model prediction speed current control system and method, and relates to the technical field of motor control, the system realizes the tracking of the rotating speed and the current in the same loop by introducing a model prediction speed current controller, only needs to set three influence factor parameters, and can realize the tracking of the rotating speed and the current. And the parameter setting workload of the traditional double-PID controller is obviously reduced. By adopting the saturation function type sliding mode load observer, the problem of high-frequency buffeting is effectively relieved, and the accuracy of load torque estimation is improved. The model prediction speed current controller is based on a discretized permanent magnet synchronous motor model, voltage vector output is optimized by constructing a cost function, rapid tracking of current and speed is achieved, and the dynamic performance of the system is improved. The objective of the invention is to solve the problems of limited bandwidth, complex parameter setting and insufficient dynamic performance in a conventional cascade control structure.

The invention relates to the technical field of parallel three-level converter control, and provides a parallel three-level converter model prediction control method and system, and the method comprises the steps: enabling a parallel three-level converter to be modeled as a series connection of an equivalent voltage source and an equivalent filter inductor according to the Thevenin theorem, enabling the parallel three-level converter to be equivalent to a five-level converter, and enabling the parallel three-level converter to be connected in parallel; a three-layer optimization control strategy is adopted; in the first layer, a candidate vector closest to a reference voltage vector is selected as an optimal five-level basic vector so as to track a parallel total output current; in the second layer, a redundant five-level voltage vector is selected to balance the neutral-point voltage; and in the third layer, selecting the candidate switching state which enables the circulating current suppression value function to be the minimum as the optimal redundant three-level switching state so as to suppress the circulating current. The method can effectively reduce output current harmonics under low switching frequency, and balance of neutral-point voltage and effective suppression of circulating current are realized to ensure safe and stable operation of a parallel converter system.

The invention discloses a three-level ANPC converter model prediction control method and device based on Newton iteration method vector optimization, and belongs to the technical field of converter control, and the method comprises the steps: building a mathematical model of a three-level ANPC converter under a three-phase static coordinate system based on the Kirchhoff theorem; performing forward Euler discretization on the mathematical model of the three-level ANPC converter to obtain a current prediction equation model; establishing a cost function according to the control target; performing online search on the optimal voltage vector according to a cost function; voltage vector synthesis is carried out, voltage vectors selected when the optimal voltage vector falls in 36 different small sectors, a voltage vector action sequence and action time distribution are obtained through calculation, and then the action time of a pair of redundant positive and negative small vectors in the voltage vectors is adjusted to carry out neutral point potential balance control. According to the invention, rapid optimal voltage vector search and three-level ANPC converter output current and neutral point potential control are realized.

The application discloses a kind of water electrolysis hydrogen production rectifier transformer harmonic active inhibition optimization method, comprising the following steps: constructing rectifier circuit, rectifier circuit includes switch tube, the voltage vector and zero vector of switch tube output are combined, and combined output voltage vector is obtained;The harmonic amplitude is obtained by processing combined output voltage vector, Levy tangent flight strategy and confidence domain variation strategy are introduced in black-winged kite optimization algorithm to construct improved dynamic search algorithm, the total harmonic distortion is obtained by iterative calculation of harmonic amplitude by improved dynamic search algorithm, i.e. optimal switch tube combination, the switch tube of rectifier circuit is adjusted by optimal switch tube combination, and the total harmonic distortion of rectifier circuit is reduced.The optimal switch tube combination of rectifier circuit is iteratively calculated by improved dynamic search algorithm in the application, effectively reduces resource consumption, and processing speed is accelerated, and the efficiency and accuracy of electrolytic water hydrogen production rectifier are improved.

The invention provides a power distribution network fault section rapid calibration method based on a feeder terminal. According to the method, power distribution network line electrical quantity and distributed power supply output information are collected in real time through a feeder terminal and preprocessed, then fault transient signals are processed through complete set empirical mode decomposition of mean value self-adaptive noise, and intrinsic mode components are obtained to judge fault types. Thirdly, fault section preliminary positioning is carried out, and an approximate area is determined according to a positive sequence voltage vector for a symmetric short-circuit fault, a negative sequence voltage vector for an asymmetric short-circuit fault and a zero sequence current amplitude for a single-phase earth fault; then accurate calibration is carried out, a single-phase earth fault is judged through a filter and correlation coefficients, and short circuit and broken line faults are calibrated through a model or an intelligent algorithm in combination with line topology and electrical parameters. And finally, establishing a target function containing a penalty term, converting the target function into a Markov decision process, solving through an approximate dynamic programming algorithm, realizing rapid and accurate calibration of a fault section, and improving the power supply reliability of the power distribution network.

The invention relates to the technical field of motor control, discloses a direct current brushless motor control method and system based on current prediction, and aims to solve the problems of large torque ripple, low efficiency and poor stability caused by current loop lag in the prior art. The method comprises the following steps: acquiring a motor operation state signal in real time; determining a sector and an electrical angular velocity based on the rotor position and the rotational speed; inputting related parameters into the mixed current prediction model to obtain a three-phase current prediction value of the next period; a prediction error is calculated in combination with a current instruction, and an optimal voltage vector enabling a cost function to be minimum is solved through a model prediction control algorithm; and finally, a space vector pulse width modulation signal is generated to drive an inverter. According to the method, advanced control is realized by fusing a physical model and a data-driven prediction mechanism, the torque ripple is remarkably reduced, and the energy efficiency and robustness are improved.

The invention discloses a predictive control method and system for a network-building type inverter, and belongs to the technical field of power electronics, and the method comprises the steps: building an output voltage prediction model according to the output voltage data and historical control input signals of the network-building type inverter at the current moment; obtaining a current output voltage prediction value through the output voltage prediction model; obtaining a reference voltage vector of the inverter at the next moment according to a preset optimization criterion function and the current output voltage predicted value, and obtaining an optimal control input signal at the next moment; and according to the optimal control input signal at the next moment, regulating and controlling a switch element of the grid-forming inverter. Therefore, by implementing the method and the device, the problems that a traditional output voltage prediction model is easy to generate model mismatch for an actual inverter, and the reliability of a prediction result is greatly reduced when the data of the current sensor is changed due to the fact that a traditional grid-forming inverter model excessively depends on the data of the current sensor in the prior art can be solved.

The invention is suitable for the technical field of flexible power distribution of a power system, and discloses a modular multilevel converter multi-objective optimization method, system and device based on model predictive control and space vector modulation, and a medium. Obtaining an output current reference value and a circulating current reference value; obtaining a reference voltage vector based on the output voltage reference value, and screening out a plurality of groups of redundant voltage vector sequences through a space vector diagram; performing performance evaluation through rolling optimization by combining each redundant voltage vector sequence with a multi-target cost function to obtain an optimal voltage vector sequence; and on the basis of the optimal voltage vector sequence and the corresponding duty ratio, a switching signal for driving each sub-module switching device of the MMC is generated, and multi-target cooperative control is realized. The three targets of reference output current tracking, circulating current suppression and sub-module capacitor voltage balance are met, and the dynamic response capability, efficiency and reliability of MMC system operation are comprehensively improved.

The invention discloses a flux weakening method of a permanent magnet synchronous motor finite control set model prediction control system based on an expected fundamental wave voltage closed loop, and belongs to the technical field of permanent magnet synchronous motor speed regulation control. According to the method, the problems of voltage saturation and poor robustness of a finite control set model prediction control system in a weak magnetic region are solved. According to the method, one-step delay compensation is carried out on the stator current, the stator current predicted value predicted through delay compensation is substituted into the voltage vector model under current vector dead beat control, and the compensated voltage vector reference value can be calculated. And an expected fundamental wave voltage vector is calculated based on the compensated voltage vector reference value, and finally the expected fundamental wave voltage vector is used as feedback of closed-loop flux-weakening control, so that maximum voltage control can be realized, and voltage saturation of a flux-weakening area is avoided. The method provided by the invention has better current dynamic performance, faster acceleration time and better robustness. The method can be applied to field weakening control of the permanent magnet synchronous motor.

The invention relates to the technical field of flexible power transmission of a power system, in particular to a coordinated optimization method and system of a distributed power flow controller and a medium, and the method comprises the steps: building a layered equivalent coupling model of the distributed power flow controller; taking minimization of the total loss of the flexible power transmission system as an optimization target, and performing global optimization on a parallel side output voltage vector and a series side injection voltage vector of the distributed power flow controller by using a layered equivalent coupling model to obtain an optimal coordinated optimization control strategy; obtaining a target control parameter in a target control mode according to the optimal coordination optimization control strategy; and according to the target control parameter and the real-time voltage and current data of the power transmission line, calculating a voltage compensation amount needing to be injected into the flexible power transmission system, and according to the voltage compensation amount, carrying out coordinated optimization control on the power flow of the power transmission line. According to the method, the parallel side and the series side of the distributed power flow controller are coordinated and optimized by establishing the layered equivalent coupling model, so that the voltage stability and power flow equilibrium distribution of the flexible power transmission system are effectively improved.

The invention discloses a permanent magnet motor model prediction control method and system based on a triangular discrete space, and the method proposes a voltage vector discretization strategy based on a regular triangle, generates as many as 6 * 4 < n-1 > virtual voltage vectors through n times of iterative segmentation, and carries out the current prediction at a next moment through the virtual voltage vectors. And finally, screening out an optimal voltage vector by taking the minimum cost function value as a target, and using the optimal voltage vector for motor control. Besides, on the basis of virtual voltage vectors constructed by relying on midpoints of a regular triangle, under the enlightenment of exploring a specific geometrical relationship between the virtual voltage vector constructed in each layer of iterative segmentation process and the optimal voltage vector, efficient optimal voltage vector search is realized, the number of voltage vectors for online evaluation is effectively reduced, and the efficiency of online evaluation is improved. Therefore, the calculation burden is greatly reduced. According to the technical scheme, accurate control over the permanent magnet motor can be ensured, current harmonics of the motor can be effectively reduced, and thrust fluctuation is reduced.

The invention discloses a two-degree-of-freedom prediction control method of an LCL filtering type three-phase grid-connected inverter system, and belongs to the field of power electronic converter control. A prediction control reference instruction is obtained by sampling parameters of inverter side current, capacitor voltage, network side current and power grid voltage at the moment k, and a continuous and discrete model of an LCL filtering type three-phase grid-connected inverter system is established; designing a control function based on a grid-side current reference tracking error and a gradient thereof, and establishing a prediction model; constructing a prediction cost function based on a control function, and obtaining a prediction control reference instruction by using a minimum value of the prediction cost function; and determining an optimal voltage vector and an action duty ratio according to the prediction control reference instruction, generating a control pulse signal according to a symmetrical five-section pulse mode, and acting on each switching tube in the inverter to realize prediction control of the LCL filtering type three-phase grid-connected inverter system. The method is simple in step, convenient to use, constant in switching frequency and good in stability.

The invention provides a phase delay error suppression method for a midpoint current sensor of a T-type three-level inverter, and the method comprises the steps: determining a sector and a sub-region where a target voltage vector is located according to the input target voltage vector, selecting a basic voltage vector for synthesis according to the sub-region where the target voltage vector is located, calculating the action time of the voltage vector, and calculating the phase delay error of the midpoint current sensor of the T-type three-level inverter. The switching time of the seven-segment switch is determined, so that a seven-segment PWM switching signal is generated; judging whether the target voltage vector is located in an unobservable area according to the action time of the basic voltage vector; if yes, maintaining the original seven-segment PWM switching signal to send waves; otherwise, adjusting the seven-segment PWM switching signal, and compensating the observable voltage vector which does not meet the minimum sampling time by shifting the PWM signal to obtain a plurality of stable current sampling windows; and phase delay error compensation of the reconstructed three-phase current is realized according to the relationship between the sampling currents. According to the method, the distortion of the reconstruction current is improved, so that the precision of the three-phase reconstruction current is effectively improved.

The invention discloses a double-fan air conditioner and a single-inverter and double-motor control method thereof. The control method comprises the steps that three-phase currents of a master motor and a slave motor which are the same in type and connected to the same inverter are collected, Park conversion is conducted to obtain d-axis components and q-axis components, and the observation angular frequency of the master motor is obtained through a position observer; calculating error angles of the master motor and the slave motor, controlling errors of the error angles through feedback, outputting a product of a motor speed difference reference value and the error angles, and obtaining a d-axis component compensation value idcomp through PI control; inputting a main motor angular frequency reference value in a speed control loop, outputting d-axis and q-axis component reference values of the current of the main motor, and compensating the d-axis component reference value of the current of the main motor with idcomp to obtain a final d-axis component reference value of the current of the main motor; and inputting the q-axis component reference value and the q-axis component reference value into a current control loop, generating a duty ratio signal of pulse width modulation, and controlling a master motor and a slave motor to rotate a voltage vector. According to the invention, through d-axis current injection compensation, system stability is realized.

The invention relates to the field of intelligent medical treatment, in particular to an electrical impedance imaging method and device based on mixed excitation and a program product. Comprising the steps that an initial current vector and an initial boundary voltage vector of mixed excitation are obtained, the mixed excitation comprises L kinds of excitation, and L is a natural number larger than 1; performing weighted fusion on the L excitation initial current vectors to obtain a mixed excitation current vector, and performing weighted fusion on the L excitation initial boundary voltages to obtain a mixed excitation voltage; performing electrical impedance imaging optimization function calculation based on the mixed excitation current vector and the mixed excitation voltage to obtain conductivity change; the optimization function is used for carrying out regularization calculation on regional potential distribution and conductivity variation based on the mixed excitation current vector and the mixed excitation voltage; an electrical impedance distribution image is generated based on the conductivity change. According to the invention, the resolution of EIT imaging is improved, and the method has good clinical value.

The invention provides a permanent magnet synchronous motor control method and device, electronic equipment and a storage medium. The method comprises the following steps: acquiring a sampling rotor electrical angular velocity of the permanent magnet synchronous motor, and determining a first shaft current instruction based on the sampling rotor electrical angular velocity; determining a reference voltage vector according to the first axis current instruction and a preset second axis current instruction; synthesizing a reference voltage vector by using the first preset number of non-zero vectors and the second preset number of zero vectors; determining a candidate voltage vector set by adjusting the number of voltage vectors acting in the control period and the acting time of each voltage vector; constructing a cost function based on the current error, the current harmonic and the switching frequency, and determining an optimal voltage vector combination and action time from the candidate voltage vector set according to the cost function; and determining a driving signal of each switching tube of the inverter based on the optimal voltage vector combination and the action time, and controlling the permanent magnet synchronous motor based on the driving signals.

The invention discloses a three-level converter two-dimensional optimization model prediction control method and device. The method comprises the following steps: calculating a reference voltage vector and a phase angle of an inverter at a moment k through a dead-beat principle; the method comprises the following steps: dividing a voltage vector region of a three-level converter into six large sectors based on a two-dimensional optimization principle, and dividing each large sector into six small sectors; taking the optimal voltage vectors corresponding to the small and medium sectors in each large sector as preparatory optimal voltage vectors, and making a preparatory optimal voltage vector corresponding table of each sector; selecting a preparatory optimal voltage vector corresponding to the reference voltage vector at the k moment by using the preparatory optimal voltage vector corresponding table of each sector; determining an optimal voltage vector according to the prepared optimal voltage vector and the neutral-point voltage; according to the invention, on the premise of realizing neutral-point voltage balance and stable operation of the three-level converter, current ripples and calculation burden can be reduced.

The invention provides a permanent magnet motor continuous set model-free predictive control method based on Bayesian optimization, and relates to the field of permanent magnet synchronous motor control. The method comprises the following steps: acquiring a hyper-local model and an extended state observer; determining the bandwidth and the input gain as optimization variables, and obtaining a training set and a test set for Bayesian optimization; joint probability distribution of the training set and the test set is calculated through a kernel function, and a prediction mean value and a prediction variance of optimization variables are determined; an optimization variable combination is screened based on the expected value collection function, and the bandwidth and the input gain are updated based on the optimization variable combination; based on the updated extended state observer and the hyper-local model, calculating the reference voltage of the next control period by using a dead-beat control principle; the reference voltage is decomposed into basic voltage vectors through space vector modulation, and the switching sequence of the basic voltage vectors is executed according to the minimum switching times to drive the permanent magnet motor. The method is not affected by motor parameter changes, and the current prediction control steady-state performance can be improved.

The invention relates to the field of three-level inverters, and particularly discloses a model-free strong-robustness predictive control method and system for a three-level SNPC inverter, and the method comprises the steps: carrying out the real-time sampling and coordinate transformation of the inverter, and obtaining the current and voltage components under a two-phase static coordinate system; establishing a hyper-local model, enabling the system parameter deviation and the external disturbance to be uniformly equivalent to lumped disturbance, and designing a full-order sliding-mode observer for real-time estimation; calculating a reference voltage vector based on the disturbance estimation value and the extrapolated reference current; and an optimal double-vector combination is selected through space vector optimization, action time is solved, redundant small vectors are selected according to midpoint voltage deviation, and PWM driving signals are generated. According to the method, excellent current tracking performance and low harmonic distortion can still be kept under the conditions of parameter mismatch and working condition change, meanwhile, neutral-point potential balance on the direct-current side is achieved, and the method has the advantages of being small in calculation amount, high in robustness, easy to achieve in engineering and the like.

The invention discloses a single-stage interconnection converter port power distribution method based on a multilayer space vector modulation strategy. The method comprises the following steps: firstly, obtaining a single-stage interconnection converter alternating current side reference voltage vector through an energy management strategy, a power control loop and a current and voltage double closed loop of a hybrid alternating current and direct current micro-grid; then, the single-stage interconnection converter is subjected to equivalent decoupling modeling to form four virtual two-level converters, a four-layer space vector diagram is obtained, scaling factors for decomposing reference voltage vectors are calculated according to given reference power, and therefore the two reference voltage vectors on the alternating current side are decomposed into four independent voltage vectors; and synthesizing the four voltage vectors in a four-layer space vector diagram to obtain the duty ratio of each phase of the four two-level converters so as to obtain the switching sequence of the single-stage interconnection converter.

The invention discloses a high-robustness deadbeat predictive current control method which is suitable for current control of a dual three-phase permanent magnet motor driving system, and belongs to the technical field of permanent magnet motor control. The method mainly comprises the following steps: reconstructing a motor mathematical model by adopting a space vector decoupling matrix and Park transformation to obtain a motor voltage equation under a dqxy axis; designing a linear expansion state observer; a reference value of an output voltage vector is obtained in combination with deadbeat predictive current control; time delay in the digital control system is calculated, and angle delay is compensated; and designing a closed-loop Smith predictor for compensating a time delay link to complete high-robustness dead-beat predictive current control of the dual three-phase permanent magnet motor. The current loop design in the method does not depend on motor parameters, and the method has high parameter change robustness. By introducing the closed-loop Smith predictor, large delay of the system can be effectively compensated, and high-precision current tracking is realized under low switching frequency.

The invention discloses an induction motor model predictive current control method based on a generalized flux linkage error and a closed-loop flux weakening strategy, and belongs to the field of induction motor speed regulation control. According to the method, the problem that the existing control method cannot simultaneously meet the requirements of not adding extra flux weakening weight factors in a value function, not depending on motor parameters, carrying out closed-loop control and not causing current following error increase under single-vector model predictive current control is solved. The method specifically comprises the steps of 1, defining a generalized flux linkage vector reference value and a generalized flux linkage predicted value, and obtaining a relation between a basic generalized flux linkage vector and a basic voltage vector according to the generalized flux linkage predicted value; step 2, obtaining a value function of single vector model predictive current control of the induction motor according to a result of the step 1; and step 3, obtaining an optimal voltage vector according to the value function, and generating a flux weakening current component for compensation according to the basic generalized flux linkage vector corresponding to the optimal voltage vector. The method can be applied to model predictive current control of the induction motor.

The invention provides a motor vibration noise control method and system based on modal resonance frequency prediction, and belongs to the field of motor control. The method comprises the following steps: acquiring each order of intrinsic mode frequency of the permanent magnet motor; a cost function parameter, a current constraint condition and a control target are set, and a model prediction control method is adopted to drive an inverter to operate, specifically, the current operation state quantity of the permanent magnet motor is collected; predicting a state response in a future finite time domain based on the operation state quantity; constructing a value function, and evaluating and optimizing a state change result; and selecting an optimal voltage vector, generating a pulse signal to drive an inverter to execute, obtaining a motor high-frequency electromagnetic force wave distribution condition, comparing the motor high-frequency electromagnetic force wave distribution condition with the intrinsic mode frequency of the permanent magnet motor, and optimizing an optimal voltage vector selection logic. The problems that harmonic waves are concentrated and resonance is easily caused by a fixed switching frequency modulation method in the prior art, and a passive suppression method is high in cost and poor in flexibility are solved.

The invention belongs to the field of inverter transient synchronous stability analysis, and discloses a coupling-considered parallel power supply system large disturbance stability analysis method, and the topological structure of a parallel power supply system comprises a network-constructing inverter, a network-following inverter, a line impedance and a power grid. The method specifically comprises the following steps: simplifying a topological structure of the parallel power supply system, constructing an equivalent circuit mathematical model of the parallel power supply system, and constructing a voltage vector expression at a common bus for analyzing a coupling interaction relationship between a network-constructing inverter and a network-following inverter; based on the control block diagram of the network-constructing type inverter, constructing a network-constructing type control ring mathematical model in the large-disturbance transient process of the network-constructing type inverter; the method solves the problems that in the prior art, the coupling influence of a grid-forming inverter and a grid-following inverter parallel power supply system is not considered sufficiently, and the transient stability under large disturbance is difficult to analyze accurately.

The invention discloses an optimized virtual vector modulation strategy of a T-type three-level inverter, which is characterized in that a sector is re-divided based on the virtual vector modulation strategy, a synthesis mode of a virtual vector is optimized, a low-amplitude common-mode voltage vector is adopted to synthesize the virtual vector, on one hand, common-mode voltage generated by the inverter can be inhibited, and on the other hand, the common-mode voltage generated by the inverter can be inhibited; and on the other hand, the optimized modulation method does not influence the neutral point potential, the smoothness of the direct output voltage of the inverter is improved, the voltage quality is improved, and the method has the advantages of low harmonic content of the output current and the like. In addition, the method solves the problems of inverter output voltage distortion, common-mode voltage spike and the like caused by a dead zone effect through a voltage vector compensation method, and has guiding significance for improving the reliability of a photovoltaic system and a micro-grid system.