Synchronous inverter voltage control method and system based on minimum boundary

Abstract

The invention discloses a synchronous inverter voltage control method and system based on a minimum boundary, and the method comprises the steps: obtaining the electric data of a synchronous inverter, and constructing an energy function; performing transient stability analysis on a VSG mechanical equation based on the energy function; and controlling the transient stability of the VSG mechanical equation by using a minimum convergence control mode. According to the method, the influence of a damping coefficient on a mechanical equation under VSG control is considered, energy function construction based on a Lyapunov method is improved, and a solving method for critical energy Vcr and transient energy Vcl at the fault clearing moment is improved. Compared with a traditional Lyapunov energy function, the conservative property of the new method is reduced, and the transient voltage stability of the grid-connected inverter under the VSG control strategy is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of renewable energy power generation technology, and in particular to a minimum margin-based synchronous inverter voltage control method and system. Background Art

[0002] In islands and remote areas, fossil energy, biomass energy, hydropower, solar energy, wind energy, geothermal energy and other energy sources are used to form a comprehensive energy system through microgrid technology to meet the electricity needs of users in islands and remote areas. Various new energy sources are connected to the microgrid through inverters. Due to the intermittent and random nature of the output of new energy, and the low inertia and underdamped network dominated by power electronic converters, the stability problem of the power grid has become more and more serious. Therefore, the Virtual Synchronous Generator (VSG) method has excellent inertial support capabilities.

[0003] At present, most transient voltage stability analysis and control methods use the energy function method. The transient energy function method can be used to analyze the transient stability of a single-machine infinite system quickly and quantitatively to analyze and judge the stability of the VSG and obtain the stability margin. The current transient stability analysis theory uses the same second-order equivalent mathematical model for the VSG and the synchronous generator and constructs a transient energy function based on it. It often ignores the influence of damping on the mechanical equation. The acceleration and deceleration areas calculated by this method are quite different from the actual acceleration and deceleration areas. This will make the transient energy function constructed based on the mechanical equation too conservative compared to the actual transient energy of the VSG, and it is impossible to obtain an accurate stability domain and stability boundary, and even cause failures such as misjudgment of instability.

[0004] Therefore, this paper proposes a control method for improving the transient voltage stability of VSG based on the minimum stability boundary estimation. This method takes into account the influence of the damping coefficient on the mechanical equation, and constructs an improved energy function on this basis. The feedback control is performed after judging whether it is stable based on its critical energy. This reduces the influence of damping on stability and its judgment strategy under the VSG control strategy, reduces the conservatism of the energy function, and improves the transient voltage stability of the grid-connected inverter under the VSG control strategy. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by the present invention is: the existing distributed edge computing data communication method is prone to crash when the data is large, and how to solve the problem of edge node task allocation.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a synchronous inverter voltage control method based on minimum margin, comprising:

[0008] Obtain electrical data of synchronous inverter and construct energy function;

[0009] Performing transient stability analysis on the VSG mechanical equation based on the energy function;

[0010] The transient stability of VSG mechanical equations is controlled using the minimum convergence control method.

[0011] As a preferred solution of the minimum-boundary-based synchronous inverter voltage control method described in the present invention, wherein: the constructing energy function includes approximating the power influence of the damping term of the VSG mechanical equation according to the minimum stable boundary estimation method;

[0012] The virtual speed of the VSG mechanical equation when transient stability is ω 0 ;

[0013] A fault occurs at time t1, and the virtual speed increases;

[0014] The fault is cleared at time t2, at which time the virtual speed reaches the peak value;

[0015] After the fault is removed, the virtual speed attenuates and oscillates under the influence of damping and recovers to ω 0 ;

[0016]

[0017] The VSG mechanical equation is rewritten as:

[0018]

[0019] Where C represents the constant damping power deviation; P m Represents the mechanical power; P'' m P represents the mechanical power considering the influence of damping; e represents the electromagnetic power; M represents the inertia coefficient; δ represents the power angle; ω is the virtual speed of the VSG mechanical equation; ω 0 is the reference speed of the VSG mechanical equation;

[0020] System status at different time periods:

[0021] Before the failure occurred, the VSG mechanical equation was running stably. The steady-state power angle is There are Therefore, the VSG mechanical equation virtual speed ω=ω 0 ;

[0022] During the fault, the mechanical equation of the VSG is The virtual speed of the mechanical equation of the VSG increases, and δ(t at the time of fault clearing is obtained c ) and

[0023] After fault clearing, there is At this time, the virtual speed of the mechanical equation of the VSG decreases, and the power angle at the stable equilibrium point after the fault clearing The power angle δ at the unstable equilibrium point u = π - δ s ;

[0024] Among them, M represents the inertia coefficient, δ represents the power angle, P m represents the mechanical power, P e represents the electromagnetic power, D p represents the damping coefficient, ω represents the virtual speed, ω 0 represents the reference speed, C represents the constant damping power deviation, f represents the frequency, Δf represents the frequency change, δ 0 represents the steady-state power angle, δ(t c ) represents the power angle at the time of fault clearing, represents the first derivative of the power angle at the time of fault clearing, δ s represents the power angle of the stable equilibrium point, δ u represents the power angle of the unbalanced point;

[0025] During the fault, the range of t is 0 < t < tc; after fault clearing, the range of t is t > tc.

[0026] As a preferred scheme of the synchronous inverter voltage control method based on the minimum boundary described in the present invention, wherein: the constructed energy function further includes constructing a transient energy function considering damping:

[0027]

[0028] Among them, represents an intermediate variable, represents the electromagnetic power after fault clearing, δ s represents the steady-state power angle;

[0029] The obtained energy function is asymptotically stable in the sense of Lyapunov;

[0030] Substituting the variable into the following formula, the transient energy of the mechanical equation of the VSG can be obtained, and the formula is expressed as:

[0031]

[0032] Among them, represents the transient energy function, represents the offset of the power angle, represents the offset of the virtual speed, M represents the inertia coefficient, Electromagnetic power after fault removal, δ s represents the steady-state power angle, C represents the constant damping power deviation, u represents the integral variable, δ represents the power angle, ω represents the virtual speed, ω 0 Indicates the reference speed, P m Indicates mechanical power.

[0033] As a preferred solution of the synchronous inverter voltage control method based on minimum margin described in the present invention, wherein: the energy function performs transient stability analysis on the VSG mechanical equation, including: quantitatively judging the system stability by transient energy function method, and obtaining stability margin information;

[0034] By determining the transient energy of the VSG mechanical equation and comparing it with the critical energy Vcr under the current working condition, the transient stability of the VSG mechanical equation is analyzed;

[0035] The critical energy Vcr of the VSG mechanical equation is expressed as:

[0036]

[0037] Obtain the unstable equilibrium point and the stable equilibrium point power angle;

[0038] in, Indicates the electromagnetic power after fault removal; P m represents the reference input power of the VSG mechanical equation; δ s represents the power angle corresponding to the stable equilibrium point under the new working state, δ U Indicates the power angle corresponding to the unstable equilibrium point under the new working state;

[0039] By comparing the transient energy V of the VSG mechanical equation at the moment of fault removal with the critical energy Vcr in the fault removal operation state, the quantitative stability margin ΔV is obtained according to the magnitudes of the two;

[0040] If ΔV>0, it is determined that the transient voltage is stable; if ΔV<0, it is determined that the transient voltage is unstable.

[0041] As a preferred solution of the minimum margin based synchronous inverter voltage control method of the present invention, wherein: the control of the transient stability of the VSG mechanical equation by using the minimum convergence control method includes that V <V cr, VSG has a stable equilibrium point. At the moment of fault removal, the energy of the VSG mechanical equation reaches a peak value. Considering the damping coefficient D, the damping power oscillation causes the grid-connected inverter controlled by the VSG mechanical equation to have self-recovery ability, and then automatically restores the operating state to the stable equilibrium point.

[0042] As a preferred solution of the minimum margin based synchronous inverter voltage control method of the present invention, wherein: the control of the transient stability of the VSG mechanical equation by using the minimum convergence control method also includes: when a deep fault occurs, V>V cr , the VSG mechanical equation cannot return to the stable equilibrium point without interference, the VSG mechanical equation is transiently unstable, and the power angle continues to increase after the fault persists and is removed; to improve the transient stability of the VSG mechanical equation, the VSG mechanical equation transient stability control method of minimum convergence control is adopted to reduce the reference power of the VSG mechanical equation, while maintaining the electromagnetic power P e Based on the above, the reference input power is reduced to realize the transient voltage stability control of the VSG mechanical equation;

[0043] When a deep fault occurs, the input power reference value is dynamically limited, and the critical energy and its stability margin ΔV under the new reference power are calculated;

[0044] When ΔV>0, it is determined that the VSG is transiently stable; when ΔV<0, the reference input power continues to be reduced; and finally when ΔV>0, it stops, and the reference input power at this time is the final reference power.

[0045] A safety area division and early warning system based on three-dimensional laser scanning, wherein: an acquisition module obtains electrical data of a synchronous inverter and constructs an energy function;

[0046] An analysis module, performing transient stability analysis on the VSG mechanical equation based on the energy function;

[0047] The control module uses the minimum convergence control method to control the transient stability of the VSG mechanical equation.

[0048] A computer device comprises: a memory and a processor; the memory stores a computer program, wherein the processor implements the steps of any one of the methods of the present invention when executing the computer program.

[0049] A computer-readable storage medium stores a computer program, wherein the computer program, when executed by a processor, implements the steps of any one of the methods of the present invention.

[0050] Beneficial effects of the present invention: The method takes into account the influence of the damping coefficient on the mechanical equation under VSG control, improves the energy function construction based on the Lyapunov method, and improves the solution method for the critical energy Vcr and the transient energy Vcl at the time of fault clearing. Compared with the traditional Lyapunov energy function, the new method is less conservative and effectively improves the transient voltage stability of the grid-connected inverter under the VSG control strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0052] Figure 1 An overall flow chart of a synchronous inverter voltage control method based on minimum margin provided in the first embodiment of the present invention;

[0053] Figure 2 A schematic diagram of angular velocity variation during a fault period of a synchronous inverter voltage control method based on minimum margin provided in a second embodiment of the present invention;

[0054] Figure 3 A schematic diagram of an improved equal-area rule for a synchronous inverter voltage control method based on minimum margin provided in the first embodiment of the present invention;

[0055] Figure 4 A control block diagram of a synchronous inverter voltage control method based on minimum margin provided in the first embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0057] Example 1

[0058] Reference Figure 1 , as an embodiment of the present invention, provides a synchronous inverter voltage control method based on a minimum margin, comprising:

[0059] S1: Obtain the electrical data of the synchronous inverter and construct the energy function.

[0060] This method makes an approximate estimate of the power effect of the damping term in the VSG mechanical equation based on the minimum stability boundary estimate. According to the maximum value of the normal frequency deviation allowed by GB / T15945 "Allowable frequency deviation of power system for power quality", Δf = ±0.2Hz, it can be calculated:

[0061] ΔP(ω)=D P (ω-ω 0 ) (1)

[0062] The maximum power deviation is:

[0063] ΔP max (ω)=D P (ω max -ω 0 ) (2)

[0064] The VSG mechanical equation is:

[0065]

[0066] Under the influence of damping, the acceleration area caused by the fault is reduced, and the deceleration area is increased when the fault is removed, which is conducive to VSG maintaining transient stability. At this time, the change law of angular velocity ω is as follows: Figure 1 As shown. Before the fault, the VSG virtual speed is ω 0 ; A fault occurs at time t1, and the virtual speed increases; the fault is removed at time t2, and the virtual speed reaches its peak value; after the fault is removed, the virtual speed attenuates and oscillates under the influence of damping, and will return to ω after a period of time. 0 If the transient energy function considering the damping coefficient is constructed, the energy function has an undetermined variable λ(0<(λ<1) and the actual energy of VSG cannot be obtained. Therefore, this method plans to replace the power deviation caused by damping by recording the damping power deviation as a constant C.

[0067]

[0068] On this basis, the VSG mechanical equation can be rewritten as:

[0069]

[0070] Where C represents the constant damping power deviation; P m Represents the mechanical power; P' m P represents the mechanical power considering the influence of damping; e represents the electromagnetic power; M represents the inertia coefficient; δ represents the power angle; ω is the virtual speed of the VSG mechanical equation; ω 0 is the reference speed of the VSG mechanical equation;

[0071] System status at different time periods:

[0072] (1) i = 1, before the fault occurs (t(0): VSG operates stably, with The steady-state power angle is There are Therefore, the VSG mechanical equation virtual speed ω=ω 0 ;

[0073] (2) i = 2, during the fault period, the VSG mechanical equation is: The VSG mechanical equation virtual speed increases, and the δ(t c )as well as The two serve as the initial conditions for state i = 3;

[0074] (3) i = 3, after the fault is removed (t(>tc), there is At this time, the virtual speed of the VSG mechanical equation decreases, and the power angle at the stable equilibrium point after the fault is removed is The power angle δ at the unstable equilibrium point u =π-δ s .

[0075] Construct a transient energy function taking damping into account:

[0076]

[0077] in, represents the intermediate variable, represents the electromagnetic power after fault removal, δ s represents the steady-state power angle;

[0078] By analyzing the improved energy function, we can get:

[0079] (1) V(0,0) = 0;

[0080] (2, When it is not 0 at the same time,

[0081] (3)

[0082] From (1(-(3), we can see that the function is asymptotically stable in the Lyapunov sense.

[0083] Back-substitution of intermediate variables From formula (6(), we can get:

[0084]

[0085] Obtain δ and ω and then insert them into equation (7) to obtain the VSG transient energy.

[0086] S2: Perform transient stability analysis on the VSG mechanical equation based on the energy function;

[0087] The transient energy function method can quantitatively judge the stability of the system and obtain stability margin information. This method constructs a transient energy function that takes into account the damping effect of the VSG mechanical equation by first integration. On this basis, the transient energy of the VSG is determined and compared with the critical energy under the current working conditions to analyze the transient stability of the VSG.

[0088] VSG critical energy Vcr is:

[0089]

[0090] The unstable equilibrium point and stable equilibrium point power angle can be obtained according to the following formula:

[0091]

[0092] in, Indicates the electromagnetic power after fault removal; P m represents the reference input power of the VSG mechanical equation; δ s represents the power angle corresponding to the stable equilibrium point under the new working state, δ U Indicates the power angle corresponding to the unstable equilibrium point under the new working state;.

[0093] By comparing the VSG transient energy V at the moment of fault removal with the critical energy Vcr in the fault removal operation state, the transient stability of the VSG can be directly judged according to the sizes of the two, and the quantitative stability margin ΔV can be obtained.

[0094] The stability margin is defined as:

[0095] ΔV=V cx -V (10)

[0096] The transient stability of VSG can be judged according to the stability margin, and the appropriate VSG transient voltage stability control method can be selected according to the VSG transient stability situation.

[0097] The transient stability of VSG is determined according to the stability margin. The VSG transient stability determination standard is shown in formula (11):

[0098]

[0099] S3: Under different fault depth conditions, the acceleration and deceleration areas of VSG are different. At the time of fault removal, the δ and ω of VSG also increase with the fault depth. The VSG power angle curve at a certain fault depth is shown in Figure 2As shown, PLi (i = 1, 2, 3) are the power angle characteristic curves before the fault, during the fault, and after the fault is removed; Prefi (i = 1, 2) are the reference power when the damping coefficient is not considered and the reference power when the minimum convergence control method is adopted; ΔP is a constant that replaces the damping power in this method; S abcd is the acceleration area during the fault, S def is the maximum deceleration area after fault removal; θ s is the power angle corresponding to the stable equilibrium point after fault removal, θ C is the instantaneous power angle when the fault is cleared, θ cr1 is the power angle corresponding to the unstable equilibrium point after fault removal;

[0100] When only a shallow fault occurs (( <V cr ), VSG has a stable equilibrium point. When the fault is removed, the VSG energy reaches its peak value. When the damping coefficient D is considered, the grid-connected inverter with VSG control mode caused by the damping power oscillation has self-recovery ability and can restore the operating state to the stable equilibrium point after a period of time.

[0101] In deep faults (>V cr )) VSG cannot return to the stable equilibrium point without interference, VSG will be transiently unstable, and the power angle will continue to increase after the fault persists and is removed. Therefore, in order to improve the transient stability of VSG, this method adopts the VSG transient stability control method of minimum convergence control, by reducing the VSG reference power, while maintaining the electromagnetic power P e Based on this, the reference input power is reduced to achieve transient voltage stability control of VSG.

[0102] Refer to the power control block diagram as follows Figure 3 As shown. When a deep fault occurs, the input power reference value is dynamically limited, and the critical energy and its stability margin ΔV under the new reference power are calculated. When ΔV>0, it is judged that the VSG is transiently stable; when ΔV<0, the reference input power continues to be reduced, and finally stops when ΔV>0. The reference input power at this time is the final reference power. The control flow chart is shown as follows Figure 4 shown.

[0103] On the other hand, this embodiment also provides a synchronous inverter voltage control system based on minimum margin, which includes:

[0104] The acquisition module obtains the electrical data of the synchronous inverter and constructs the energy function.

[0105] The analysis module performs transient stability analysis on the VSG mechanical equation based on the energy function.

[0106] The control module uses the minimum convergence control method to control the transient stability of the VSG mechanical equation.

[0107] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0108] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0109] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0110] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0111] Example 2

[0112] Reference Figure 2 , which is an embodiment of the present invention, provides a synchronous inverter voltage control method based on minimum margin. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through simulation experiments.

[0113] The experiment was conducted in a simulated microgrid environment, which included multiple renewable energy sources (photovoltaic power generation and wind power generation) and loads, connected to the microgrid through inverters. The experimental equipment included a high-precision data acquisition device, a virtual synchronous generator controller, and a calculation and control software platform.

[0114] First, in the experimental preparation stage, a microgrid experimental platform including a synchronous inverter was built. The input of the synchronous inverter comes from the photovoltaic power generation and wind power generation simulation device, and its output is connected to the load in the microgrid. The experiment uses a data acquisition device to obtain the electrical data of the synchronous inverter in real time, including voltage, current, electromagnetic power, mechanical power and virtual speed. These data are used to construct the energy function, and the transient stability of the VSG mechanical equation is controlled using the minimum convergence control method. The control strategy includes timely adjusting the reference input power and electromagnetic power of the VSG when a fault occurs to ensure that the system can quickly recover to a stable state after the fault is removed. By adjusting the damping coefficient, the transient response characteristics of the system are optimized. The experimental results are shown in Table 1.

[0115] Table 1 Data comparison table

[0116]

[0117] The experimental data comparison table shows that in different test objects, the fluctuation range of voltage and current is small, indicating that the system can quickly recover to a stable state after the fault is removed. Specifically, the voltage fluctuates between 217V and 221V, and the current fluctuates between 5.0A and 5.4A, which shows that the control method of the present invention can effectively suppress transient fluctuations. It can be seen from the data of electromagnetic power and mechanical power that in a short period of time after the fault is removed, the electromagnetic power and mechanical power are kept within a reasonable range without large fluctuations. For example, the electromagnetic power fluctuates between 1085W and 1120W, while the mechanical power fluctuates between 1180W and 1220W, which shows that the system can quickly restore power balance after the fault is removed, reflecting the superiority of the present invention in dynamic response. From the data of virtual speed and steady-state power angle, the virtual speed is between 313rad / s and 317rad / s, and the steady-state power angle is between 0.522rad and 0.526rad, indicating that the system has good consistency and reliability in the stable state after the fault is removed. The fluctuation range of the virtual speed is small, indicating that the system can quickly recover to the reference speed 0ω0 under the influence of damping, which reflects the innovation of the present invention in terms of stable control.

[0118] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A synchronous inverter voltage control method based on minimum margin, characterized in that: Including: Obtain the electrical data of the synchronous inverter and construct an energy function; Based on the energy function, conduct transient stability analysis on the VSG mechanical equation; Use the minimum convergence control method to control the transient stability of the VSG mechanical equation.

2. The method for controlling voltage of a synchronous inverter based on minimum margin according to claim 1, characterized in that: The electrical data of the synchronous inverter includes voltage, current, electromagnetic power, voltage power, mechanical power, and virtual speed.

3. The minimum margin based synchronous inverter voltage control method according to claim 1, characterized in that: The constructing of the energy function includes approximately estimating the power influence of the damping term of the VSG mechanical equation according to the minimum stable boundary estimation method; When the VSG mechanical equation is transiently stable, the virtual speed is ω0; A fault occurs at time t1, and the virtual speed increases; The fault is removed at time t2, and the virtual speed reaches its peak at this time; After the fault is removed, under the influence of damping, the virtual speed decays and oscillates and returns to ω0; Rewrite the VSG mechanical equation as: Where C represents the constant damping power deviation; P m Represents the mechanical power; P' m P represents the mechanical power considering the influence of damping; e represents the electromagnetic power; M represents the inertia coefficient; δ represents the power angle; ω represents the virtual speed of the VSG mechanical equation; ω0 represents the reference speed of the VSG mechanical equation; System states at different time periods: Before the fault occurred, the VSG mechanical equation was running stably. The steady-state power angle is There are Therefore, the VSG mechanical equation virtual speed ω=ω0; During a fault, the VSG mechanical equation is The VSG mechanical equation virtual speed increases, and the δ(t c )as well as After the fault is cleared, At this time, the virtual speed of the VSG mechanical equation decreases, and the power angle at the stable equilibrium point after the fault is removed is The power angle δ at the unstable equilibrium point u =π-δ s ; Where M is the inertia coefficient, δ is the power angle, and P m Represents mechanical power, P e Denotes electromagnetic power, D p represents the damping coefficient, ω represents the virtual speed, ω0 represents the reference speed, C represents the constant damping power deviation, f represents the frequency, Δf represents the frequency change, δ0 represents the steady-state power angle, δ(t c ) represents the power angle when the fault is cleared, represents the first-order derivative of the power angle when the fault is cleared, δ s represents the power angle of the stable equilibrium point, δ u , the power angle of the unbalanced point; During the fault, the range of t is 0 < t < tc; after the fault is removed, the range of t is t > tc.

4. The method for controlling voltage of a synchronous inverter based on minimum margin according to claim 3, characterized in that: The constructing of the energy function further includes constructing a transient energy function considering damping: in, represents the intermediate variable, represents the electromagnetic power after fault removal, δ s represents the steady-state power angle; The obtained energy function is asymptotically stable in the sense of Lyapunov; The variable Substituting the following formula, we can obtain the transient energy of the VSG mechanical equation, which is expressed as: in, represents the transient energy function, represents the offset of the power angle, represents the offset of the virtual speed, M represents the inertia coefficient, Electromagnetic power after fault removal, δ s represents the steady-state power angle, C represents the constant damping power deviation, u represents the integral variable, δ represents the power angle, ω represents the virtual speed, ω0 represents the reference speed, P m Indicates mechanical power.

5. The method for controlling voltage of a synchronous inverter based on minimum margin according to claim 4, characterized in that: The transient stability analysis of the VSG mechanical equation by the energy function includes: quantitatively judging the stability degree of the system through the transient energy function method and obtaining stability margin information; By determining the transient energy of the VSG mechanical equation and comparing it with the critical energy Vcr under the current working condition, the transient stability analysis of the VSG mechanical equation is realized; The critical energy Vcr of the VSG mechanical equation is expressed as: Obtain the unstable equilibrium point and the power angle of the stable equilibrium point; in, Indicates the electromagnetic power after fault removal; P m represents the reference input power of the VSG mechanical equation; δ s represents the power angle corresponding to the stable equilibrium point under the new working state, δ U Indicates the power angle corresponding to the unstable equilibrium point under the new working state; By comparing the transient energy V of the VSG mechanical equation at the fault removal moment with the critical energy Vcr in the fault removal operating state, the quantitative stability margin ΔV is obtained according to their magnitudes; If ΔV > 0, it is determined as transient voltage stability; if ΔV < 0, it is determined as transient voltage instability.

6. The method for controlling voltage of a synchronous inverter based on minimum margin according to claim 5, characterized in that: The method of controlling the transient stability of the VSG mechanical equation by using the minimum convergence control method includes: when only a shallow fault occurs, V <V cr , VSG has a stable equilibrium point. At the moment of fault removal, the energy of the VSG mechanical equation reaches a peak value. Considering the damping coefficient D, the damping power oscillation causes the grid-connected inverter controlled by the VSG mechanical equation to have self-recovery ability, and then automatically restores the operating state to the stable equilibrium point.

7. A synchronous inverter voltage control method based on minimum margin as claimed in claim 6, characterized in that: The method of controlling the transient stability of the VSG mechanical equation by using the minimum convergence control method also includes: when a deep fault occurs, V>V cr , the VSG mechanical equation cannot return to the stable equilibrium point without interference, the VSG mechanical equation is transiently unstable, and the power angle continues to increase after the fault persists and is removed; to improve the transient stability of the VSG mechanical equation, the VSG mechanical equation transient stability control method of minimum convergence control is adopted to reduce the reference power of the VSG mechanical equation, while maintaining the electromagnetic power P e Based on the above, the reference input power is reduced to realize the transient voltage stability control of the VSG mechanical equation; When a deep fault occurs, dynamically limit the input power reference value, and calculate the critical energy and its stability margin ΔV under the new reference power; When ΔV > 0, it is judged as VSG transient stability; when ΔV < 0, continue to reduce the reference input power; finally, stop when ΔV > 0, and the reference input power at this time is the final reference power.

8. A synchronous inverter voltage control system based on the minimum boundary adopting the method according to any one of claims 1 - 7, characterized in that: An acquisition module that obtains the electrical data of the synchronous inverter and constructs an energy function; An analysis module that conducts transient stability analysis on the VSG mechanical equation based on the energy function; A control module that controls the transient stability of the VSG mechanical equation by using the minimum convergence control method.

9. A computer device comprising: A memory and a processor; The memory stores a computer program, characterized in that: when the processor executes the computer program, it realizes the steps of a synchronous inverter voltage control method based on the minimum boundary.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it realizes the steps of a synchronous inverter voltage control method based on the minimum boundary.

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