214 results about "Small-signal model" patented technology

Disclosed in the present invention are a method and system for small-signal stability analysis of a power plant containing grid-forming converters. The method comprises: establishing a grid-following converter impedance model; establishing a grid-forming converter impedance model; constructing a new energy power plant grid-connected system model containing grid-following converters and grid-forming converters; establishing a simplified equivalent circuit of a power plant grid-connected system; establishing a small-signal stability Nyquist criterion for a grid-connected new energy power plant containing grid-forming converters; and using a Nyquist plot to analyze the small-signal stability characteristics of the power plant grid-connected system. According to the present invention, the problem in the prior art of lacking quantitative and effective analysis of small-signal stability in new energy power plants containing grid-following converters and grid-forming converters is solved, and establishing a small-signal stability criterion for the power plants on the basis of established small-signal models enables quantitative analysis of the small-signal stability characteristics of a new energy power plant containing grid-forming converters under low grid strength conditions, and compared with conventional impedance modeling methods for new energy power plants, the impact of grid-forming converter integration on the small-signal stability of the new energy power plants is better reflected.

The invention relates to the technical field of simulation verification, in particular to a new energy station grid-connected system stability dual verification simulation method and system. Comprising the following steps: S1, carrying out a sweep frequency test on a controller of a new energy station to obtain frequency domain data; s2, processing the frequency domain data to obtain impedance model parameters of the controller and the new energy device, and fitting equivalent impedance models of the controller and the new energy device based on the combined model parameters; s3, constructing a small signal model based on the equivalent impedance model of the controller, coupling the impedance model of the new energy station with the equivalent impedance of the power grid, and determining a stability boundary; s4, verifying the accuracy of the stability boundary through the combination of frequency domain small signal analysis and time domain large signal simulation; and S5, outputting the stability index map of the new energy station, and determining an optimization measure for stable operation.

The invention belongs to the technical field of new energy active support stability control, and provides a fan power decoupling method based on adaptive virtual impedance and feedforward compensation. According to the method, dynamic characteristics of active power and reactive power in the system are analyzed by combining a topological structure of a doubly-fed fan grid-connected system and fan internal control, and a small signal model is constructed based on power transmission characteristics. A self-adaptive virtual impedance strategy based on power grid impedance characteristic adjustment is introduced for the problem of power coupling caused by high line impedance in a weak power grid environment and dynamic and control loop characteristics of flux linkages in a fan. Meanwhile, through a disturbance component extraction and feedforward control strategy, a disturbance signal in rotor current is introduced into a power ring for adjustment, and power decoupling control is realized. The method overcomes the limitation that an existing decoupling control technology is poor in effect, the control principle is clear, engineering implementation is easy, and the stability and the dynamic response capability of the doubly-fed fan in the weak power grid environment can be improved.

The invention discloses a method and device for restraining shaft system torsional vibration of a net-forming type double-fed fan under the variable wind speed. The method comprises the steps that a mathematical model of the electromagnetic torque-rotating speed difference of the net-forming type double-fed fan is constructed; drawing an electromagnetic torque-rotating speed difference Bode diagram according to the mathematical model; according to the mechanical parameters of the wind turbine and the motor, the shafting natural oscillation frequency of the doubly-fed fan is calculated, and stability analysis is conducted on damping of the shafting natural oscillation frequency in combination with the Bode diagram; drawing a small-signal model block diagram according to the mathematical model; analyzing the small-signal model block diagram to obtain an analysis result that a current loop provides a coupling path for the rotating speed and the active power; according to a stability analysis result and an analysis result of the small-signal model block diagram, negative damping brought by an operation area is weakened by reducing current loop bandwidth, so that the risk of torsional vibration of the shaft system is reduced.

The invention discloses a self-adaptive virtual inertia control and power distribution method of an energy storage converter suitable for a multi-direct-current micro-grid. The method comprises the following steps: establishing a virtual direct-current motor control model; based on the virtual direct current motor control model, designing an adaptive virtual inertial parameter control and power distribution algorithm, so that the energy storage converter can simulate the inertia and damping characteristics of the direct current generator; constructing a small-signal model of the common DC bus of the multi-DC micro-grid, analyzing the influence of inertia and damping parameters on the dynamic performance and stability of the system, and drawing a Nyquist curve based on an impedance ratio criterion to optimize the inertia and damping parameters; and verifying the adaptability of the adaptive virtual inertial parameter control and power distribution algorithm in the multi-direct-current micro-grid, and realizing effective control on the bus voltage stability and the power distribution of the energy storage unit by adjusting the power response characteristic of the energy storage unit. According to the invention, the stability and response speed of the multi-direct-current micro-grid system are improved, the bus voltage fluctuation is effectively slowed down, and the service life of the energy storage unit is prolonged.

The invention relates to a power decoupling control method, device and equipment for a network construction type converter, and the method comprises the steps: introducing virtual impedance into a topological structure of the network construction type converter, and constructing a target small signal model; determining a dynamic gain matrix based on the transfer function of the target small signal model, and obtaining an RGA number according to the dynamic gain matrix; the RGA number is used for representing coupling characteristics of active power and reactive power of the system; determining a virtual value of virtual impedance based on the acquired power grid data by taking the RGA number as a constraint condition; based on the virtual value of the virtual impedance, determining the virtual voltage of the network type converter after the virtual impedance is introduced; according to the virtual voltage, obtaining virtual active power and virtual reactive power of the network-forming converter; the virtual active power and the virtual reactive power have no coupling relation. According to the invention, power decoupling of the new energy power system is realized based on the dynamic gain matrix, and further development of new energy power is promoted.

The embodiment of the invention provides a small-disturbance stability optimization method and device for a single-network converter grid-connected system. The method comprises the following steps: constructing a small-signal model representing dynamic behaviors of the system based on control parameters and network parameters of the single-network converter grid-connected system; performing preprocessing operation on the small signal model to obtain a small signal model only comprising an active synchronization control link; performing order reduction processing on the small signal model to obtain a corresponding equivalent second-order model; determining the dynamic influence of active outer loop control, voltage inner loop control and short-circuit comparison on the stability of the current system according to the equivalent second-order model; adjusting a current system control parameter according to the dynamic influence to meet a small disturbance stability requirement; according to the method, the control parameters of the single-network converter can be optimized based on the small signal model, so that the small disturbance stability of the system is improved, and an optimization strategy is provided for stable operation of the network converter.

The invention discloses a method and a device for suppressing harmonic instability of a new energy grid-connected system, electronic equipment and a storage medium. The method comprises the following steps: acquiring basic data of a diode rectifier in the new energy grid-connected system; constructing a time domain model of the diode rectifier according to the basic data; converting the diode rectifier time domain model into a diode rectifier frequency domain model based on a harmonic linearization algorithm; constructing a frequency domain small signal model according to the diode rectifier frequency domain model and the diode rectifier direct current side filter inductance parameter; constructing an alternating current side impedance model and a direct current side impedance model according to the frequency domain small signal model and the leakage inductance parameters of the diode rectifier transformer; generating the resonant frequency of the new energy grid-connected system according to the AC side impedance model and the DC side impedance model; and adjusting a direct current side filter inductance parameter of the diode rectifier according to the resonant frequency. According to the invention, the harmonic stability of the grid-connected system can be improved.

The invention provides an AC-AC converter control parameter setting method, and belongs to the field of power electronic control. In order to solve the problems that traditional PID control parameters are lagged in adjustment and large in overshoot under the dynamic working condition, an AC-AC converter small-signal model of a single-tube reverse series bidirectional electronic switch topology is established, and the control parameters are optimized in combination with frequency domain characteristics. The method specifically comprises the following steps: establishing a state-space equation by adopting a switching period averaging method, performing linearization processing, and deducing a system dynamic transfer function; introducing duty ratio disturbance based on a steady-state working point to construct a small-signal model, and forming a three-order open-loop system through a serial PI controller; and according to a closed-loop pole configuration matching characteristic equation coefficient, analyzing and solving proportion and integral parameters. By dynamically optimizing the phase margin and the gain margin, the response speed and stability of the converter under input fluctuation and load abrupt change are remarkably improved, and the method has high engineering application value.

The invention relates to the technical field of power electronics and direct current transmission, in particular to a two-level VSC-HVDC minimum direct current capacitance calculation method based on LMI. The method comprises the following steps: establishing a state equation comprising a main circuit and a controller dynamic model, converting a three-phase alternating current quantity into a direct current quantity under a synchronous rotating coordinate system by utilizing Park transformation, and deducing a system state equation in combination with a Kirchhoff's law; performing Taylor expansion and linearization on the nonlinear equation, and constructing a small signal model based on a Lyapunov stability theory; by separating a diagonal matrix and defining a stability criterion in an LMI form, minimum direct-current capacitance solving is converted into a convex optimization problem, a critical value is iteratively searched by adopting a dichotomy method to determine minimum capacitance, and meanwhile, a tolerance mechanism is introduced to improve the robustness of an algorithm. Through combination of mathematical modeling and an optimization algorithm, the calculation efficiency and accuracy are effectively balanced, and a theoretical basis is provided for reducing the cost and the size of the converter.

The invention relates to a power system voltage control technology, in particular to a method and equipment for maintaining grid-connected point voltage three-phase balance under weak power grid unbalanced disturbance, and the method comprises the following steps: firstly, establishing a small signal model of a converter grid-connected system after unbalanced disturbance, and emphatically considering the phasing error influence of a phase-locked loop transient process; then, the fluctuation quantity of the amplitude and phase of the PCC voltage induced by unbalanced disturbance is accurately calculated, the influence is counteracted through a power outer ring feed-forward compensation mode, and three-phase balance of the PCC voltage in the transient state and the steady state process is achieved under the condition that the weak power grid unbalanced disturbance is maintained. According to the method, the influence of the machine-network interaction of the weak power grid on the dynamic characteristics of the PCC voltage is considered, and a better voltage balance maintaining effect is achieved in the weak power grid. Through composite control, according to PCC voltage vector amplitude and phase disturbance compensation, system transient state and steady state whole-process voltage balance maintenance after unbalanced disturbance is realized. The control structure is simple, and the robustness of the system is improved.

The invention discloses a VSG grid-connected system control method based on an improved three-parameter wave trap, and belongs to the technical field of power system control, and the method comprises the steps: firstly building a single-input single-output small signal model based on a VSG grid-connected system containing power coupling, and calculating an active open-loop transfer function; an improved active damping resonance suppression method is introduced, so that the transient stability of the system is improved; the expected system stability margin under the system oscillation frequency is obtained, and the parameter design of the three-parameter wave trap is completed based on the subsynchronous frequency oscillation characteristics; the three-parameter wave trap is remodeled, and active steady-state deviation caused by the virtual damping coefficient under power grid frequency disturbance is eliminated. According to the method, the stability of the system is improved, the system is ensured to have a relatively good stability margin, and active steady-state deviation caused by power grid frequency disturbance of the grid-connected system can be completely eliminated.

The invention discloses a VSG coordinated control method and device based on improved self-adaption and feed-forward compensation, and the method comprises the steps: building a model of a VSG optical storage grid-connected system, and analyzing a power angle characteristic and a frequency oscillation curve; introducing an arc tangent function to optimize a traditional adaptive control strategy, and smoothly adjusting rotational inertia and a damping coefficient; a feed-forward compensation control strategy is added, an active compensation expression and a rotor motion equation are established, a compensation coefficient and a filtering time constant are set in a coordinated mode, and configuration of a small-signal model change zero-pole pair of an active power reference value under disturbance is reconstructed; adjusting virtual rotational inertia and a damping coefficient based on the optimized adaptive control strategy, and correcting a power reference value in advance by predicting frequency fluctuation based on a feed-forward compensation control strategy; according to the method, power overshoot and frequency change deviation are effectively suppressed, smooth adjustment of rotational inertia and VSG dynamic performance optimization are realized, and the system response speed and stability are enhanced.

The invention discloses a single-loop droop control method and system for a wind generating set, and the method comprises the following steps: constructing a doubly-fed fan-power converter-power grid three-module coupling model, and completing the dynamic adaptation of the characteristics of a doubly-fed fan of a single-loop droop control architecture without inner-loop current control; based on the input signal-model collaborative integration body and the adaptive architecture, MIMO-GBC is adopted to analyze a phase margin and a resonance peak value of an open-loop transfer function matrix eigenvalue of a dynamic small signal model, and double risks are identified in a full slip rate interval; aiming at the resonance risk, a current induction type virtual impedance strategy is adopted; aiming at insufficient phase margin, adopting a transient phase calibration strategy; and according to the real-time slip ratio of the DFIG and the stator power change, inter-partition linkage optimization is carried out on the virtual resistance and the phase calibration angle so as to minimize a dual-power step response fluctuation square mean value, a parameter setting period and a rotor side converter control period are synchronously matched, and all-working-condition stable control is realized.

The invention belongs to the field of two-level converter small signal and impedance modeling, and discloses a VSC impedance analysis method in a superposition oscillation component scene and a related device. The method comprises the following steps of: superposing an alternating-current voltage oscillation component, and establishing each steady-state quantity frequency domain model; establishing a main circuit steady-state frequency domain model; establishing each small semaphore frequency domain model based on the main circuit steady-state frequency domain model; establishing a main circuit small signal frequency domain model; constructing a PLL controller small signal model, a DC voltage controller small signal model and an AC current controller small signal model; constructing a small signal model of the alternating current modulation signal; and calculating the port impedance of the two-level current converter in the scene of superposition of the oscillation components based on a small signal model of the alternating-current modulation signal. According to the method, the VSC port impedance in the scene of superposition of the oscillation components can be accurately analyzed, and key technical support is provided for oscillation mechanism analysis and stability improvement of new energy access to a weak point network.

The invention discloses a dual-frequency positive-sequence impedance modeling method for a network-building type energy storage converter considering frequency coupling. The method comprises the following steps: 1, injecting a dual-frequency positive-sequence disturbance voltage signal at a grid-connected point of the network-building type energy storage converter based on a virtual synchronous machine; 2, establishing a linearized small signal model for each control link of an active-frequency loop, a reactive-voltage loop, a virtual impedance-containing voltage and current double closed loop and the like to form a multi-frequency signal model; and 3, according to the multi-frequency coupling relationship between the current and the voltage, constructing a frequency coupling impedance matrix, and reducing a coupling term into output impedance to obtain the positive sequence output impedance and the negative sequence output impedance of the converter considering the frequency coupling, thereby simplifying the model stability analysis. According to the method, dual-frequency positive sequence disturbance is introduced, the coupling effect between different frequency components is effectively described, the defect that a traditional single-frequency modeling method cannot reflect the multi-frequency interaction characteristic is overcome, and the accuracy and applicability of the impedance model of the network construction type energy storage converter under the multi-frequency disturbance scene are remarkably improved.

The invention discloses a singular perturbation order reduction method matched with a network construction type wind power plant. The method comprises the following steps: firstly, establishing a small signal model matched with each module of a network construction type wind power plant grid-connected system; constructing a full-order small signal model, solving a broadband oscillation mode, and calculating damping ratios of all modes to obtain an extremely weak damping mode; dividing fast and slow state variables based on the modal participation degree and Hankel singular value weight, and establishing a criterion to supplement the slow state variables based on a singular perturbation method to form a slow state variable set; and determining the order after order reduction, and establishing an order reduction model of the matching network construction type wind power plant grid-connected system in a singular perturbation form. According to the method, the problem that a matched network construction type wind power plant order reduction system of an existing order reduction scheme cannot replace a full-order system to efficiently analyze broadband oscillation can be solved, the order number of the matched network construction type wind power plant can be reduced, and the method has efficient and powerful broadband oscillation analysis capacity while the dynamic characteristics are reserved.

The invention belongs to the field of power electronic technology and new energy grid-connected control, and particularly relates to a cooperative control system and method for parallel operation of multiple new energy inverters. The method comprises the following steps: firstly, establishing a small signal model of an inverter parallel system, and analyzing dynamic characteristics of the system under power disturbance; secondly, realizing power decoupling and current sharing control based on a frequency-power droop characteristic; furthermore, coordinated operation of multiple energy sources such as photovoltaic energy and energy storage is realized by monitoring the phase of the direct-current bus voltage and the alternating-current side voltage in real time; the method has high engineering applicability, and high-speed real-time communication between parallel units is not needed; the virtual impedance parameters Rv and Lv have clear physical significance and are easy to preliminarily set according to line parameters; the calculation of the dynamic matching self-adjusting module is linear operation, the requirement for the computing power of a processor is low, and integration and implementation on an existing inverter control platform are facilitated.

The invention relates to the technical field of power systems, and discloses a PID controller parameter adaptive adjustment method and device of a network construction converter. The method comprises the following steps: calculating an output error signal and an output error signal change rate of a small signal model based on the small signal model of the network-forming converter, calculating an error gradient by using the output error signal and the change rate thereof, and dynamically updating PID control parameters based on a gradient descent method. When the PID control parameters are updated, whether selection of the PID control parameters can cause instability of a system where the network construction converter is located or not is checked, if yes, the error gradient calculation parameters are adjusted to recalculate the error gradient of the output error signals, if not, updating of the PID controller parameters is stopped, and by adjusting the PID control parameters in a self-adaptive mode, the network construction converter is updated. And the stability of the network-forming converter in a power grid is effectively ensured. The technical problem that in the prior art, an effective technical means for conducting self-adaptive adjustment on the control parameters of the network building converter to maintain stable operation of a power grid system is lacked is solved.

The invention relates to an impedance modeling method and device and computer equipment. Comprising the steps that disturbance voltage is injected to the alternating current side of a main circuit, a first relation between a modulation small signal and an alternating current small signal is obtained through alternating current control topology, the disturbance voltage and a phase angle small signal are correlated through a phase-locked loop, and a second relation between the modulation small signal and an alternating voltage small signal is determined; injecting disturbance voltage to the direct current side of the main circuit, and determining a third relationship between the modulation small signal and the alternating current small signal and a fourth relationship between the direct current small signals based on the alternating current control topology and the direct current control topology; and finally, impedance modeling is carried out in combination with a frequency small-signal model, so that self-impedance and coupling impedance characteristics of an alternating current side and a direct current side can be accurately reflected, and a basis is provided for analyzing system stability and optimizing a control strategy.

The invention discloses an equipment critical short-circuit ratio calculation method for a large-scale new energy grid-connected system, which is used for solving the technical problem that the equipment critical short-circuit ratio of the large-scale new energy grid-connected system is difficult to solve through an analysis mode in the prior art. The method comprises the following steps: acquiring alternating-current power grid data of the large-scale new energy grid-connected system and critical state data of each grid-following converter; constructing a small signal model of the large-scale new energy grid-connected system according to the AC power grid data and the critical state data, and constructing an equivalent isomorphic small signal model according to the small signal model; and solving the generalized short-circuit ratio of the equivalent isomorphic small signal model when the real part of the dominant pole is zero, and taking the generalized short-circuit ratio as the equipment critical short-circuit ratio when the large-scale new energy grid-connected system is in a critical stable state, thereby successfully solving the equipment critical short-circuit ratio of the large-scale new energy grid-connected system through an analysis mode.

The invention belongs to the field of electric power, and discloses an equivalent inertia evaluation method and device for an offshore wind power flexible direct-current transmission system, and the method comprises the steps: building a small-signal model of the flexible direct-current transmission system according to the control topology of the flexible direct-current transmission system; establishing a machine-side converter small-signal model according to the control topology of the machine-side converter of the offshore wind plant, and establishing an offshore wind plant small-signal model according to the machine-side converter small-signal model and the control topology of the network-side converter of the offshore wind plant; the flexible direct current power transmission system responds to an analog synchronous machine rotor motion equation, the offshore wind power plant responds to a primary frequency modulation process of an analog synchronous machine, and system class synchronization characteristics are described in the form of the synchronous machine rotor motion equation, so that an offshore wind power flexible direct output system class synchronization supporting model is established; and calculating an equivalent inertia transfer function of the offshore wind power flexible direct output system according to the synchronous support model of the offshore wind power flexible direct output system.

The invention relates to a DC measuring device transmission characteristic MMC impedance modeling method comprising the following steps: constructing a difference and common mode time domain small signal model of an MMC main circuit based on the Kirchhoff voltage law; a coupling rule is obtained according to the frequency coupling characteristic and the phase sequence coupling mechanism of the difference and common mode time domain small signal model; converting the difference and common mode time domain small signal model into an HSS-MMC main circuit model according to a coupling rule; establishing each control HSS model according to the MMC control loop structure; deriving a transfer function model of the DC voltage measurement device to update the DC voltage control HSS model; combining each control HSS model and the modulation wave expression to obtain an MMC control system HSS model; the HSS-MMC main circuit model and the MMC control system HSS model are combined to obtain an MIMO admittance model; obtaining an SISO equivalent impedance model of the MMC according to the power grid impedance expression and the MIMO admittance model; and according to MMC system parameters and different frequency disturbance control gains, an SISO impedance model of the MMC is utilized to solve an impedance analytic value. And the MMC high-band impedance characteristic can be accurately described.

The invention discloses a power distribution network voltage fluctuation control method and device considering communication time lag. The method is applied to a distributed photovoltaic power distribution network, the power distribution network at least comprises a cooperative controller and a plurality of weak branches, each weak branch is connected with an impact load and an energy storage converter, and each energy storage converter corresponds to a local energy storage controller; the method comprises the following steps: uniformly modeling communication time lag between the cooperative controller and each local energy storage controller, and distributing the communication time lag to a power distribution link to obtain a power distribution small signal model containing the time lag; constructing a state space model of the energy storage converter; unifying the power distribution small signal model and the state space model of the energy storage converter to a common reference coordinate system to obtain a whole system state equation; and performing voltage control on the power distribution network based on the full-system state equation. The influence of communication delay on the stability of the power distribution network can be eliminated.

The invention discloses a DC micro-grid power buffer safety control method and device aiming at FDI attack, and relates to the technical field of power electronics and power system control. The method comprises the steps of obtaining a block matrix of a DCmGs system node current equation according to the Kirchhoff's current law; adopting Kron simplification to eliminate internal node voltage, obtaining a relation between a port current vector and a voltage vector, and constructing a small signal model of the port voltage vector; based on a small signal model, a linear mapping relation about disturbance of bus voltage to equivalent input impedance of each power buffer is constructed, modeling and linearization are carried out on energy and adjustable input impedance of each power buffer, a network coupling small signal model is constructed, and a second-order high-gain observer is designed; and if the FDI attack exists in the DCmGs system, an anti-FDI attack elastic control law is designed, so that the closed-loop voltage in the DCmGs system and the energy of a power buffer are quickly converged, and buffeting is inhibited. By adopting the method, the DCmGs system can be prevented from buffeting in an unknown FDI attack scene.

This invention belongs to the field of linear periodic time-varying system modeling and analysis technology, and discloses a small-signal modeling method and application for LCC-HVDC systems. The method includes: constructing mathematical models of the segmented and continuous parts of the LCC-HVDC system based on its circuit topology within each operating interval, and integrating these models as the mathematical model of the LCC-HVDC system; linearizing the trajectory of this mathematical model to obtain its small-signal model within each operating interval; designing a small-signal model of the LCC-HVDC system during switching between adjacent operating intervals using the Filippov method; and combining the small-signal models of the LCC-HVDC system within each operating interval and the small-signal models at the switching time to constitute the small-signal model of the LCC-HVDC system, thus completing the small-signal modeling. This invention can accurately characterize the switching dynamics of the LCC-HVDC system, achieving accurate and low-complexity small-signal modeling of the LCC-HVDC system.

The invention provides an online identification and input design method and device for a wireless power transmission system, and the method comprises the steps: carrying out the online estimation of a transfer function parameter of a target system, and building an initial small signal model; constructing a full-order model corresponding to the target system, and performing order adaptive order reduction processing; determining a loss function of the target system by taking minimization of disturbance of the excitation signal to the target system as a target; on the basis of defining the loss function, constructing an optimization problem of the target system under disturbance constraint, and performing optimal excitation input design; and constructing a robust controller of the target system by adopting a robust control method in combination with the initial small signal model. According to the method, the system modal change can be tracked in real time under the closed-loop working condition, the modeling precision and the real-time performance are improved, and the problem that the identification precision is poor in the prior art is solved.

The present invention discloses a power impedance modeling method based on virtual synchronous control, which performs dq impedance modeling for port shore power supply in frequency bands based on virtual synchronous control, including: respectively constructing each small-signal dq model required for dq impedance modeling; according to the constructed small-signal dq models, using different dynamic links for modeling in different frequency bands, where in the low-frequency region, the dynamic links used are the power controller and the voltage controller; in the medium-low frequency region, the dynamic links used are the voltage-current loop and the power loop; in the intermediate frequency region, the dynamic link used is the voltage-current loop; in the high-frequency region, the dynamic links used are the current loop, the sampling low-pass filter, the control delay, and the voltage loop. The present invention can accurately characterize the differences in impedance characteristics of port shore power supply in each frequency band, construct an accurate impedance model based on virtual synchronous control in frequency bands, and effectively realize the small-signal stability assessment of the port shore power supply system.

The invention provides a converter power ripple suppression method and device under unbalanced disturbance, and relates to the technical field of power electronics and new energy grid connection. The method comprises the following steps: constructing a small signal model of a grid-connected converter of a weak alternating current system under unbalanced disturbance, wherein the small signal model comprises PCC voltage vector dynamic modeling, physical process modeling of phase orientation errors caused by PLL slow dynamic, converter control loop dynamic modeling and weak alternating current system line transmission characteristic modeling; based on a small signal model, considering and considering the control characteristics of the converter, and constructing a power transmission model of machine-network closed-loop interaction; and designing a feed-forward decoupling compensation branch, and carrying out dynamic feed-forward power compensation on the power ripples of the converter under unbalanced disturbance according to a power transmission model of machine-network closed-loop interaction. According to the invention, suppression of power ripples can be well realized in the transient process and the steady-state process of the system, and the electric energy quality and the stability of the grid-connected system are effectively improved.

The invention provides a stability judgment method for a direct-current bus of a full-power pumped storage unit, and relates to the technical field of hydroelectric power generation. The method comprises the steps that a direct-current bus capacitor is equivalent to two parallel equivalent capacitors, and the pumped storage unit is split into a unit side and a network side with a parallel connection point as a boundary; respectively constructing small signal models of the electrical devices of the two parts; based on each small signal model, respectively constructing a corresponding admittance model, and then constructing a corresponding impedance model; substituting the electrical parameters and the control parameters into the impedance model, and drawing a corresponding Bode diagram; and under the same working condition, if the phase difference at the amplitude intersection point of the two Bode diagrams is less than 90 degrees, the direct current bus does not generate interactive instability under the corresponding working condition, otherwise, the interactive instability occurs. According to the method, the modeling difficulty and model complexity of the full-power pumped storage unit can be effectively reduced, the characteristics of the pumped storage unit can be accurately reflected, and the interaction stability of a power system on a direct-current bus can be judged.