CN-121984112-A - Virtual synchronous machine comprehensive control method based on optimal power compensation and inertia damping self-adaption

CN121984112ACN 121984112 ACN121984112 ACN 121984112ACN-121984112-A

Abstract

The invention discloses a virtual synchronous machine comprehensive control method based on optimal power compensation and inertia damping self-adaption, and belongs to the technical field of virtual synchronous machine control in micro-grids. The method comprises the steps of firstly establishing a mathematical model of a virtual synchronous machine (VSG), analyzing the influence of parameters such as virtual inertia, virtual damping and the like on system stability, and realizing on-line self-adaptive adjustment of virtual parameters based on a radial basis function neural network (RBF). Then, a discretization prediction model is constructed according to the active-frequency relation of the VSG, an optimization target is set based on angular frequency deviation and output active power, a corresponding cost function is designed, and an optimal power compensation quantity is solved through quadratic programming so as to adjust an active reference value of the VSG in real time. Compared with the prior art, the invention can effectively inhibit overshoot and oscillation of power and frequency, reduce the frequency change rate and deviation and improve the power frequency response speed.

Inventors

HE SHAN
WANG WEIQING
LING GUO
YUAN JIAWANG
HU SHUAI
HU BING
LI HONGYANG
WANG HAOCHENG
YANG FAN

Assignees

新疆大学

Dates

Publication Date: 20260505
Application Date: 20251224

Claims (6)

1. The utility model provides a virtual synchronous machine integrated control method based on optimum power compensation and inertia damping self-adaptation, the control method adopts VSG control technique to realize the power and the frequency control of grid-connected inverter, is used for the output power and the frequency stability control of renewable energy grid-connected system under load switching and the output fluctuation condition, and is characterized in that includes: s1, establishing a main circuit topology and a control structure of a VSG, wherein the main circuit topology comprises direct-current side voltage, filter inductance and capacitance, line resistance and inductance, a power grid and a load; S2, establishing a function expression between active power and line equivalent impedance, power grid voltage amplitude, output end voltage and system power angle of a virtual synchronous machine input power grid according to the main circuit topology, and combining the function expression with the output power of the virtual synchronous machine and a system power angle equation to obtain a closed loop transfer function of active reference disturbance of the VSG in a grid-connected mode and load switching disturbance of the VSG in an island mode; S3, researching an influence mechanism of dynamic performance of the virtual synchronous machine according to the change condition of the moment of inertia and the damping coefficient and a natural oscillation angular frequency and damping ratio equation to obtain an adaptive principle of the moment of inertia and the damping coefficient in different states, and providing an inertia damping adaptive control method based on an RBF neural network; s4, parameter setting is carried out on the inertia damping self-adaptive control method based on the RBF neural network according to boundary constraints of the phase margin, the amplitude margin and the damping ratio, and a parameter value range is obtained; S5, constructing and discretizing a prediction model according to the self-adaptive control method, designing a cost function taking angular frequency deviation and VSG output power as performance indexes, calculating an optimal power increment through quadratic programming, and adjusting an active reference value of the VSG in real time.
2. The method for comprehensively controlling the virtual synchronous machine based on the optimal power compensation and the inertia damping self-adaption of claim 1 is characterized in that in S2, the functional expression between the active power of the input power grid of the virtual synchronous machine and the equivalent impedance of a circuit, the voltage amplitude of the power grid, the voltage of an output end and the power angle of a system is as follows: In the formula, Is the voltage amplitude of the power grid; The equivalent impedance of the line comprises VSG output impedance, line impedance and grid impedance; ; Is the system power angle.
3. The method for comprehensively controlling the virtual synchronous machine based on the optimal power compensation and the inertia damping self-adaption of claim 1 is characterized in that in S2, a closed loop transfer function of active reference disturbance of VSG in a grid-connected mode and load switching disturbance in an island mode is as follows: In the formula, As a result of the active steady-state deviation, ; In order for the system to be frequency-offset, 。
4. The virtual synchronous machine comprehensive control method based on optimal power compensation and inertia damping self-adaption is characterized in that in S3, the self-adaption principle of the moment of inertia and the damping coefficient in different states is that in a state interval 1, the frequency change rate and the frequency deviation are both larger than 0, the moment of inertia and the damping coefficient are both increased, in a state interval 2, the frequency change rate and the frequency deviation are both smaller than 0, the moment of inertia and the damping coefficient are respectively reduced and slightly larger, in a state interval 3, the frequency change rate and the frequency deviation are respectively smaller than 0 and larger than 0, the moment of inertia and the damping coefficient are respectively increased, in a state interval 4, the frequency change rate and the frequency deviation are respectively larger than 0 and smaller than 0, and the moment of inertia and the damping coefficient are respectively reduced and slightly larger. Based on the method, an inertia damping self-adaptive control method based on an RBF neural network is provided, and the moment of inertia and the damping coefficient can be adjusted in real time according to the frequency change rate and the frequency deviation of the system so as to optimize the dynamic performance of the system.
5. The method for comprehensively controlling the virtual synchronous machine based on optimal power compensation and inertia damping self-adaption according to claim 1, wherein in S4, parameters of the inertia damping self-adaption control method are set, and phase margin is required Amplitude margin Damping ratio Moment of inertia Damping coefficient The following constraint is satisfied. , Wherein: -maximum value of cut-off frequency.
6. The method for comprehensively controlling the virtual synchronous machine based on optimal power compensation and inertia damping adaptation according to claim 1, wherein in S5, angular frequency deviation is designed And VSG output power The cost function for the performance index is: wherein: 、 Respectively a frequency change weighting matrix and an input power change weighting factor; Each given output reference sequence. Constructing a weighting coefficient formula and selecting an exponential function as a weight function. The method has the advantages that the weighting coefficient can be rapidly increased along with the increase of the frequency deviation, so that the frequency recovery is accelerated, and the weighting coefficient is correspondingly reduced when the deviation is gradually reduced, so that the rapid recovery of the system frequency and the priority adjustment of the VSG output cost are realized. Converting the cost function into a standard quadratic programming problem solution, and taking the first term of the control sequence as compensation power Input system scroll optimization.

Description

Virtual synchronous machine comprehensive control method based on optimal power compensation and inertia damping self-adaption Technical Field The invention belongs to the technical field of virtual synchronous machine control in micro-grids, and particularly relates to a virtual synchronous machine comprehensive control method based on optimal power compensation and inertia damping self-adaption. Background With the increasing serious problems of energy crisis and environmental deterioration, distributed power generation mainly taking renewable energy sources such as photovoltaic, wind power and the like is widely focused. Renewable energy generation is typically connected to the grid by means of an inverter, but because of its lack of inertial and damping characteristics, the ability to balance and dampen power fluctuations is limited. When external disturbances occur, the risk of voltage and frequency instability is extremely easily induced. To solve this problem, VSGs and control techniques therefor have been developed. The VSG enables the grid-connected inverter to have external characteristics similar to those of the synchronous machine by referring to the swing equation of the synchronous machine, and provides a brand new thought for improving new energy consumption capability and solving the frequency modulation and voltage regulation problems of the distributed generation grid-connected system. However, conventional VSGs have certain disadvantages in terms of applicability and dynamic performance. In the grid-connected mode, the output power is difficult to quickly follow the change of the reference value and has overshoot and oscillation phenomena due to the problem of virtual parameter coupling, and in the island mode, when larger load disturbance occurs, the system frequency can be greatly deviated and even out-of-range. The current common solution is moment of inertia and damping coefficient adaptation, but it improves VSG dynamic response capability and overall stability through a stepwise optimization and long term adjustment mechanism. When a large disturbance occurs in the power system, the self-adaptive algorithm has certain limitation that on one hand, the self-adaptive algorithm has hysteresis and faces the rapid and large-amplitude disturbance, the self-adaptive mechanism cannot fundamentally solve the problem of overlarge frequency change Rate (ROCOF) at the initial stage of disturbance and forms potential threat to the safety and stability of the power system, on the other hand, the self-adaptive strategy is realized by indirectly adjusting the control parameters of the self-adaptive algorithm instead of directly compensating the active deficiency in VSG control, and the non-plug-and-play characteristic is difficult to quickly isolate faults and restore the system to a stable state when the self-adaptive link fails. Therefore, a power frequency control method with strong stability and high response speed is needed to further improve the stability of the system and the response speed of the power frequency. The invention provides a virtual synchronous machine comprehensive control method based on optimal power compensation and inertia damping self-adaption, which comprises the following steps of 1) dynamically adjusting moment of inertia and damping coefficient through detecting angular velocity change rate and frequency deviation of a system in real time based on an inertia damping self-adaption control part of an RBF neural network, so as to inhibit rapid change of output active power and system frequency, shorten time required for system recovery stabilization, and 2) constructing and discretizing a prediction model according to a VSG active-frequency equation by an MPC-VSG power compensation control part, calculating optimal power increment through detecting the frequency deviation and the active deficiency of the system in real time and utilizing the prediction model to conduct rolling optimization, and adjusting active reference value of the VSG in real time so as to improve the active frequency response characteristic in the transient process, further inhibit fluctuation of the active power and reduce frequency deviation in the transient process. Disclosure of Invention Aiming at the problem that the dynamic response capability of the new energy grid-connected inverter is insufficient in a multi-operation mode (grid-connected mode and island mode), the invention provides the virtual synchronous machine comprehensive control method based on optimal power compensation and inertia damping self-adaption, which effectively inhibits overshoot and oscillation of power and frequency, reduces the frequency change rate and deviation and improves the power frequency response speed. In order to achieve the purpose, the invention adopts the following technical scheme that the virtual synchronous machine comprehensive control method based on optimal power compensation and inertia damping self