Emergency control method and device for transient power angle stability of virtual synchronous network construction power supply

Abstract

The invention discloses a transient power angle stability emergency control method and device for a virtual synchronous network construction power supply, and belongs to the technical field of power systems and automation thereof. The method comprises the following steps: according to a transient process mathematical model of a virtual synchronous machine grid-connected system, determining an acceleration area of the virtual synchronous machine grid-connected system in a power grid fault period considering a damping effect; determining a target deceleration area of the virtual synchronous machine grid-connected system after the power grid fault is cleared by adopting a geometric approximation method; according to the acceleration area, the target deceleration area and a preset critical condition, an objective function is constructed, and the preset critical condition is that the acceleration area is equal to the target deceleration area; solving the target function by using a dichotomy algorithm to obtain an active instruction value critical upper limit; and controlling the transient power angle of the virtual synchronous machine grid-connected system to be stable based on the active instruction value critical upper limit at the moment of power grid fault removal. By using the technical scheme provided by the invention, the transient synchronization stability of the virtual synchronous machine grid-connected system can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power systems and their automation, and in particular to a virtual synchronous grid-forming power transient power angle stability emergency control method and device. BACKGROUND

[0002] With the deepening of the "double carbon" strategy, the power system is showing the characteristics of "double high" of high proportion of new energy and high proportion of power electronic equipment. Under this background, grid-forming converters with voltage source characteristics play an important role. Unlike grid-following converters with current source characteristics, which rely on grid support, grid-forming converters can autonomously establish and stabilize the frequency and amplitude of the AC bus voltage, not only providing good grid active support capability, but also enabling stable operation under islanded conditions, thus becoming an important technical cornerstone for building new power systems dominated by new energy. Among them, the virtual synchronous machine technology simulates the rotor motion equation of the synchronous generator to provide flexible configurable virtual inertia and damping for the system, which is one of the typical control strategies for grid-forming converters.

[0003] However, the synchronous mechanism of grid-forming converters is dominated by fast-response control algorithms, and its transient characteristics differ significantly from those of traditional synchronous generators. When the grid encounters a serious fault, the virtual synchronous machine system may experience power oscillation due to severe energy impact, and even cause the risk of step-out, which poses new challenges to the analysis and control of its transient stability performance. Therefore, it is necessary to provide a more reliable solution to determine the stability mechanism of virtual synchronous machines under large disturbances and develop an emergency control method accordingly, in order to improve the system's ability to withstand serious faults and ensure its safe application at scale. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide a virtual synchronous grid-forming power transient power angle stability emergency control method, device, equipment and storage medium, which can realize quantitative analysis of the stability boundary of virtual synchronous machines under serious grid faults, and further provide key and quantitative power instruction adjustment basis for emergency control decision of virtual synchronous machine grid-connected systems, thereby effectively improving the transient synchronization stability of the system.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] On the one hand, the present application provides a virtual synchronous grid-forming power transient power angle stability emergency control method, which comprises:

[0007] determining the acceleration area of the virtual synchronous machine grid-connected system during the grid fault considering the damping effect according to the transient process mathematical model of the virtual synchronous machine grid-connected system;

[0008] The geometric approximation method is used to determine a target deceleration area of the virtual synchronous machine grid-connected system after the power grid fault is cleared, and the target deceleration area is related to an active instruction value;

[0009] According to the acceleration area, the target deceleration area, and a preset critical condition, a target function is constructed, and the preset critical condition is that the acceleration area is equal to the target deceleration area;

[0010] The target function is solved by using a dichotomy algorithm to obtain a critical upper limit of the active instruction value;

[0011] At the moment when the power grid fault is cleared, based on the critical upper limit of the active instruction value, the transient power angle stability of the virtual synchronous machine grid-connected system is controlled.

[0012] In some possible implementation manners, a transient process mathematical model of the virtual synchronous machine grid-connected system is constructed by using the following formula, as shown in formula (1):

[0013] ; (1)

[0014] wherein, ; ;

[0015] wherein, represents a virtual inertia; represents an instruction value of an angular frequency output by the virtual synchronous machine; represents an equivalent mechanical power; represents an actual value of active power output by the virtual synchronous machine; represents an active instruction value output by the virtual synchronous machine; represents a virtual damping; represents an actual value of an angular frequency output by the virtual synchronous machine; represents an internal electromotive force of the virtual synchronous machine; represents a voltage vector amplitude of the power grid side; represents a line reactance from a virtual synchronous machine port to a grid connection point; represents a virtual control power angle.

[0016] In some possible implementation manners, the determining of the acceleration area of the virtual synchronous machine grid-connected system during the power grid fault in consideration of the damping effect according to the transient process mathematical model of the virtual synchronous machine grid-connected system comprises:

[0017] In the case where the power grid is faulty, the rotor acceleration of the virtual synchronous machine is determined according to the transient process mathematical model;

[0018] The acceleration area accumulated in the rotor acceleration process of the virtual synchronous machine during the power grid fault in consideration of the damping effect is determined, as shown in formula (2):

[0019] ; (2)

[0020] wherein, represents an acceleration area; represents an angle of power at the moment of fault clearance of the virtual synchronous machine; represents an angle of power when the virtual synchronous machine is stably running.

[0021] In some possible embodiments, the geometric approximation method is used to determine a target deceleration area of the virtual synchronous machine grid-connection system after power grid fault clearance, and the method comprises:

[0022] At the moment of power grid fault clearance, the active instruction value of the virtual synchronous machine is reduced, so as to reduce the equivalent mechanical power;

[0023] An initial deceleration area after the active instruction value is reduced is determined, so that the initial deceleration area is determined according to the active instruction value, as shown in formula (3):

[0024] ; (3)

[0025] wherein, represents an initial deceleration area; represents an angle of power at an unstable equilibrium point; represents an angle of power at the moment of fault clearance of the virtual synchronous machine; represents an actual value of active power output by the virtual synchronous machine; represents an equivalent mechanical power; represents a virtual control angle of power, represents a critical upper limit of the active instruction value to be solved;

[0026] wherein, the coordinates of the unstable equilibrium point are ;

[0027] According to the geometric approximation method and the initial deceleration area, a target straight line connecting the fault clearance point and the unstable equilibrium point is determined;

[0028] According to the target straight line, a target deceleration area is determined, and the target deceleration area is the maximum deceleration area provided by the virtual synchronous machine grid-connection system after power grid fault, as shown in formula (4):

[0029] ; (4)

[0030] wherein, represents a target deceleration area; is used to represent a target straight line connecting the fault clearance point and the unstable equilibrium point;

[0031] wherein, the coordinates of the fault clearance point are .

[0032] In some possible implementations, constructing the objective function based on the acceleration area, the target deceleration area, and a preset critical condition includes:

[0033] Based on the acceleration area and the target deceleration area, the preset critical condition is determined as shown in equation (5):

[0034] (5)

[0035] in, Indicates the accelerated area. Indicates the target deceleration area. This represents the critical upper limit of the active power command value to be solved;

[0036] Based on the preset critical conditions, the target equation is determined. The target equation is related to the active power command value, as shown in equation (6):

[0037] (6)

[0038] in, Represents equivalent mechanical power. This represents the actual active power output of the virtual synchronizer. Used to characterize the target straight line connecting the fault clearing point and the unstable equilibrium point; This represents the power angle of the virtual synchronizer at the moment of fault clearing. The power angle represents the angle at which the virtual synchronizer is running stably. This represents the work angle at the unstable equilibrium point. Indicates the virtual control angle;

[0039] Based on the objective equation, the objective function is constructed as shown in equation (7):

[0040] (7)

[0041] in, This represents the objective function.

[0042] In some possible implementations, the step of using a binary search algorithm to solve the objective function to obtain the critical upper limit of the active power command value includes:

[0043] The objective function is solved using a binary search algorithm, and the root that makes the objective function zero is determined as the critical upper limit of the active power command value.

[0044] In some possible implementations, the step of using a binary search algorithm to solve the objective function to obtain the critical upper limit of the active power command value includes:

[0045] determining a left end point value and a right end point value of the current interval, the left end point value and the right end point value satisfying F(a)·F(b)<0, a representing the left end point value, b representing the right end point value, F(a) representing a left end point function value, and F(b) representing a right end point function value;

[0046] determining a current active instruction midpoint value of the current interval according to the left end point value and the right end point value;

[0047] determining whether the left end point value and the current active instruction midpoint value satisfy F(a)·F(m)<0, in a case where the left end point value and the current active instruction midpoint value satisfy F(a)·F(m)<0, updating the right end point value as the current active instruction midpoint value, and determining a first updated interval; in a case where the left end point value and the current interval midpoint do not satisfy F(a)·F(m)<0, updating the left end point value as the current active instruction midpoint value, and determining a second updated interval; wherein F(m) represents a third target function value;

[0048] determining whether |b-a|<ε or F(m)=0 is satisfied, in a case where |b-a|<ε or F(m)=0 is satisfied, determining the current active instruction midpoint value as the active instruction value critical upper limit; in a case where |b-a|<ε or F(m)=0 is not satisfied, taking the first updated interval or the second updated interval as the current interval, and repeating the above determining the current active instruction midpoint value of the current interval according to the left end point value and the right end point value to the determining whether |b-a|<ε or F(m)=0 is satisfied, until |b-a|<ε or F(m)=0 is satisfied, to obtain the active instruction value critical upper limit; wherein ε represents a preset convergence tolerance.

[0049] In another aspect, the present application provides a virtual synchronous type network construction power transient power angle stability emergency control device, the device comprising:

[0050] an acceleration area determination module, configured to determine an acceleration area of the virtual synchronous machine grid-connected system during a power grid fault considering damping effect according to a transient process mathematical model of the virtual synchronous machine grid-connected system;

[0051] a target deceleration area determination module, configured to determine a target deceleration area of the virtual synchronous machine grid-connected system after the power grid fault is cleared by using a geometric approximation method; the target deceleration area is related to an active instruction value;

[0052] The active instruction value critical upper limit determination module is configured to construct a target function according to the acceleration area, the target deceleration area, and a preset critical condition, wherein the preset critical condition is that the acceleration area is equal to the target deceleration area; and the active instruction value critical upper limit is obtained by solving the target function using a dichotomy algorithm.

[0053] The transient power angle stability control module is configured to control transient power angle stability of the virtual synchronous generator grid-connected system based on the active instruction value critical upper limit at the moment of grid fault removal.

[0054] In another aspect, an electronic device is provided, which includes a processor and a memory, the memory storing at least one instruction and at least one program, the at least one instruction and the at least one program being loaded and executed by the processor to implement the virtual synchronous grid-connected power supply transient power angle stability emergency control method as described above.

[0055] In another aspect, a computer readable storage medium is provided, which stores at least one instruction and at least one program, the at least one instruction and the at least one program being loaded and executed by a processor to implement the virtual synchronous grid-connected power supply transient power angle stability emergency control method as described above.

[0056] Compared with the prior art, the present application has the following beneficial effects:

[0057] In the present application, the acceleration area of the virtual synchronous generator grid-connected system during the grid fault is determined by a transient process mathematical model of the virtual synchronous generator grid-connected system, taking into account the damping effect; the target deceleration area of the virtual synchronous generator grid-connected system after the grid fault is removed is determined using a geometric approximation method, and the target deceleration area is related to the active instruction value; a target function is constructed according to the acceleration area, the target deceleration area, and a preset critical condition, wherein the preset critical condition is that the acceleration area is equal to the target deceleration area; the active instruction value critical upper limit is obtained by solving the target function using a dichotomy algorithm; and the transient power angle stability of the virtual synchronous generator grid-connected system is controlled based on the active instruction value critical upper limit at the moment of grid fault removal, which can determine the active instruction critical value that ensures system stability after the grid fault, realizes quantitative analysis of the stability boundary of the virtual synchronous generator under a serious grid fault, and further provides a key and quantitative power instruction adjustment basis for emergency control decision of the virtual synchronous generator grid-connected system, thereby improving the ability of the system to resist serious faults, and further effectively improving the transient synchronous stability and synchronous support capability of the system, and improving the safety of the system application. BRIEF DESCRIPTION OF DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor.

[0059] Figure 1 is a flowchart of a virtual synchronous type network forming power transient power angle stability emergency control method provided by the embodiments of the present application;

[0060] Figure 2 is a P-δ curve diagram after the active instruction value is reduced at the moment of grid fault removal provided by the embodiments of the present application;

[0061] Figure 3 is a virtual synchronous machine grid-connected system control structure diagram provided by the embodiments of the present application;

[0062] Figure 4 is a simulation curve diagram provided by the embodiments of the present application, wherein (1) is a first simulation curve diagram, including (a) a first power angle-time curve diagram, (b) a first frequency-time curve diagram and (c) a first power-time curve diagram; (2) is a second simulation curve diagram, including (a) a second power angle-time curve diagram, (b) a second frequency-time curve diagram and (c) a second power-time curve diagram;

[0063] Figure 5 is another simulation curve diagram provided by the embodiments of the present application, wherein (a) is a first P-δ curve diagram, (b) is a first phase plane curve diagram;

[0064] Figure 6 is another simulation curve diagram provided by the embodiments of the present application, wherein (a) is a second P-δ curve diagram, (b) is a second phase plane curve diagram;

[0065] Figure 7 is a structure diagram of a virtual synchronous type network forming power transient power angle stability emergency control device provided by the embodiments of the present application. DETAILED DESCRIPTION

[0066] In order to make the technical personnel in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0067] It is to be understood that the terms "first", "second", and the like, used in the description and the claims of the present application as well as above-mentioned drawings of the application merely serve the purpose of differentiating between two or more objects and do not necessarily imply a sequence or order of one object before or after another object. It is to be understood that the data thus distinguished can be interchanged, where appropriate, so that an embodiment of the present application described herein can be carried out in other than the order or sequence described herein. Further, the terms "comprise" and "include" and variations thereof as used in enlisting the features of the application are intended to be open and permit the inclusion of both serial and non-serial steps and / or elements while also encompassing the possibility of reciting features in alternative order.

[0068] In the embodiments of the present application, the term "module" or "unit" refers to a computer program or a part of a computer program having a predetermined function and working together with other related parts to achieve a predetermined target, and can be implemented wholly or partially by using software, hardware (such as a processing circuit or a memory), or a combination thereof. Similarly, one processor (or multiple processors or memories) can be used to implement one or more modules or units. In addition, each module or unit can be a part of an integral module or unit including the function of the module or unit.

[0069] Various exemplary embodiments, features and aspects of the present application will be explained in detail below with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements or features. Although various aspects of embodiments are illustrated in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0070] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations.

[0071] The term "and / or", used in the present document, merely means an association relationship of associated objects, and indicates that three relationships can exist, for example, A and / or B can represent three cases of existence of A alone, existence of A and B simultaneously, and existence of B alone. In addition, the term "at least one" in the present document indicates any one of multiple or any combination of at least two of multiple, for example, including at least one of A, B, and C can indicate including any one or more elements selected from a set consisting of A, B, and C.

[0072] In addition, for a better understanding of the present application, a number of specific details are set forth in the following detailed description. Those skilled in the art will understand that the application can be practiced without certain of the specific details set forth in the following detailed description. In some instances, well-known methods, apparatus, elements and circuits have not been described in detail in order to avoid obscuring the application.

[0073] Figure 1 is a flowchart of a virtual synchronous network power transient angle stability emergency control method provided by an embodiment of the present application. The present specification provides method operation steps as embodiments or flowcharts, but more or fewer operation steps can be included based on conventional or non-creative labor. The order of steps listed in the embodiments is only one of the many execution orders of the steps, and does not represent the only execution order. In actual system or server product execution, the method order shown in the embodiments or the drawings can be executed in sequence or in parallel (for example, in a parallel processor or multi-thread processing environment). Specifically, as shown in Figure 1 The above method can include:

[0074] S101: determining an acceleration area of a virtual synchronous generator grid-connected system during a power grid fault considering a damping effect according to a transient process mathematical model of the virtual synchronous generator grid-connected system;

[0075] In one specific embodiment, the determination of the acceleration area of the virtual synchronous generator grid-connected system during the power grid fault takes into account the damping effect, thereby establishing a transient stability criterion considering the damping effect. Optionally, the virtual synchronous generator (VSG) is a type of grid-connected converter.

[0076] In one optional embodiment, the transient process mathematical model of the virtual synchronous generator grid-connected system can be constructed using the following formula, as shown in formula (1):

[0077] ; (1)

[0078] wherein, ; ;

[0079] wherein, represents a virtual inertia; represents an instruction value of an angular frequency of a virtual synchronous generator output; represents an equivalent mechanical power; represents an actual value of active power output by the virtual synchronous generator; represents an active power instruction value of the virtual synchronous generator output; represents a virtual damping; represents an actual value of an angular frequency of the virtual synchronous generator output; represents an internal voltage of the virtual synchronous machine; represents a grid-side voltage vector amplitude; represents a line reactance from a port of the virtual synchronous machine to a point of common coupling; represents a virtual control power angle.

[0080] In one specific embodiment, the active power loop control of the virtual synchronous machine simulates the rotor motion characteristics of a synchronous generator, and a core motion equation thereof can be shown as follows:

[0081] ;

[0082] wherein the virtual control power angle satisfies ;

[0083] According to the core motion equation, it can be determined that the dynamic process of the virtual synchronous machine depends not only on a difference between and but also is affected by a damping term In the process of accurately analyzing the transient stability of a system by using the equal-area criterion, the in the above equation can be defined as an equivalent mechanical power , i.e. , wherein is a time-varying variable varying with the speed, and then the transient process mathematical model of the virtual synchronous machine grid-connected system can be determined according to the defined equivalent mechanical power, as shown in equation (1).

[0084] Alternatively, the actual active power output by the virtual synchronous machine is an actual value of the active power output by the virtual synchronous machine, and the active power instruction value output by the virtual synchronous machine is an instruction value of the active power output by the virtual synchronous machine.

[0085] In one alternative embodiment, the above determining the acceleration area of the virtual synchronous machine grid-connected system during a power grid fault considering the damping effect according to the transient process mathematical model of the virtual synchronous machine grid-connected system can include:

[0086] In the case of a power grid fault, the rotor acceleration of the virtual synchronous machine is determined according to the transient process mathematical model;

[0087] The acceleration area accumulated in the rotor acceleration process of the virtual synchronous machine during the power grid fault considering the damping effect is determined, as shown in equation (2):

[0088] ; (2)

[0089] wherein represents the acceleration area; represents a power angle of the virtual synchronous machine at a fault clearance time; An angle of operation of the virtual synchronous machine.

[0090] In one embodiment, in the case of voltage dip fault of the power grid, the actual active power output of the grid-forming converter drops sharply, while the equivalent mechanical power is basically maintained at the original value. According to the mathematical model of the transient process of the system, the rotor acceleration of the virtual synchronous machine at this time can be determined, and the acceleration area accumulated in the process can be determined by the fault clearing time and other conditions. In addition, the acceleration area accumulated in the rotor acceleration process of the virtual synchronous machine during the grid fault considering the damping effect can be determined by integrating the difference between the equivalent mechanical power and the actual active power during the fault in the acceleration interval [δ0, δ c ].

[0091] S102: The geometric approximation method is used to determine the target deceleration area of the virtual synchronous machine grid-connected system after the power grid fault is cleared.

[0092] In one embodiment, the target deceleration area is related to the active power instruction value, and the relationship between the system deceleration area and the active power instruction value after the power grid fault is cleared can help determine the critical stability point. Optionally, the deceleration area can represent the process in which the actual active power overcomes the work done by the equivalent mechanical power when the system swings from the power angle corresponding to the fault clearing time to the maximum value .

[0093] ;

[0094] wherein, deceleration area, represents the maximum value of the first swing of the power angle when the system is stable.

[0095] In one optional embodiment, the above-mentioned geometric approximation method for determining the target deceleration area of the virtual synchronous machine grid-connected system after the power grid fault is cleared can include:

[0096] At the moment when the power grid fault is cleared, the active power instruction value of the virtual synchronous machine is reduced, so as to reduce the equivalent mechanical power.

[0097] Determine the initial deceleration area after reducing the active power instruction value, so that the initial deceleration area is determined according to the active power instruction value, as shown in formula (3):

[0098] ; (3)

[0099] wherein, initial deceleration area, represents the power angle at the unstable equilibrium point. ​​​represents the power angle of the virtual synchronous machine at the moment of fault clearing; represents the actual active power output of the virtual synchronous machine; represents the equivalent mechanical power; represents the virtual control power angle, represents the critical upper limit of the active power instruction value to be solved;

[0100] wherein the coordinates of the unstable equilibrium point are ;

[0101] According to the geometric approximation method and the initial deceleration area, a target straight line connecting the fault clearing point and the unstable equilibrium point is determined;

[0102] According to the target straight line, a target deceleration area is determined, the target deceleration area being the maximum deceleration area provided by the grid fault post-virtual synchronous machine grid-connected system, as shown in equation (4):

[0103] ; (4)

[0104] wherein, represents the target deceleration area; is used to represent the target straight line connecting the fault clearing point and the unstable equilibrium point;

[0105] wherein the coordinates of the fault clearing point are .

[0106] In a specific embodiment, the emergency control means that can be taken is to reduce the active power instruction value of the virtual synchronous machine at the moment of grid fault clearing, thereby reducing the reference level of the equivalent mechanical power, so as to expand the maximum deceleration area that can be provided by the system after the fault, thereby enhancing the stability margin. Under this emergency control means, the critical stability condition of the system corresponds to the deceleration area reaching the limit value, at this time the integral upper limit is the power angle at the unstable equilibrium point , which is the intersection point between the actual active power and the equivalent mechanical power when the system is unstable, that is, the unstable equilibrium point can be determined by , and is related to the active power instruction value . The initial deceleration area can be the maximum deceleration area that can be provided after the grid fault, and the initial deceleration area is the area surrounded by the actual active power curve and the equivalent mechanical power curve. And according to the deceleration area, the critical value of the active power instruction needs to be solved, so as to determine the initial deceleration area after the active power instruction value of the virtual synchronous machine is reduced, which can be equation (3).

[0107] In one specific embodiment, the target deceleration area can be the maximum deceleration area that can be provided after a power grid fault, and this target deceleration area is the area enclosed by the actual active power curve and the target straight line, where the target straight line is the straight line connecting the fault clearing point and the unstable equilibrium point. Specifically, Figure 2 This is a schematic diagram of the P-δ curve after the active power command value is reduced instantaneously during grid fault clearing, as provided in an embodiment of the present invention. Figure 2 As shown, This is the output power curve of the virtual synchronizer during stable operation. This is the output power curve of the virtual synchronous machine when a fault occurs. The active power command value is reduced the instant the grid fault is cleared. This expands the maximum deceleration area that the system can provide after a fault, connecting the fault clearing point A. With unstable equilibrium point B Determine the target line AB. Optionally, the target line AB can be approximately represented by... In the interval The trajectory of the change is such that the target deceleration area is approximately the area enclosed by the curve of the actual active power after the fault and the target straight line AB; the equation of the target straight line AB can be assumed to be... ,Should It is about The function, specifically, uses the target line to solve for the critical upper limit of the active power command value. ,so It is about The function of , and the target deceleration area determined therefrom can be expressed as Equation (4).

[0108] S103: Construct an objective function based on the acceleration area, the target deceleration area, and the preset critical condition, where the acceleration area equals the target deceleration area.

[0109] In a specific embodiment, based on the equal area rule, the critical condition for the system to maintain transient power angle stability is that the acceleration area accumulated during the fault is equal to the maximum deceleration area that the system can provide after the fault. Optionally, the preset critical condition that the acceleration area is equal to the target deceleration area is the critical condition for the system to maintain transient power angle stability.

[0110] In an optional embodiment, constructing the objective function based on the acceleration area, the target deceleration area, and the preset critical condition may include:

[0111] Based on the acceleration area and the target deceleration area, the preset critical conditions are determined as shown in equation (5):

[0112] (5)

[0113] in, Indicates the accelerated area. denotes a target deceleration area, denotes a critical upper limit of the active instruction value to be solved;

[0114] According to the preset critical condition, a target equation is determined, the target equation being related to the active instruction value, as shown in formula (6):

[0115] (6)

[0116] wherein, denotes an equivalent mechanical power, denotes an actual active value output by the virtual synchronous machine, is used to represent a target straight line connecting the fault clearance point and the unstable equilibrium point; denotes a power angle of the virtual synchronous machine at the fault clearance time point, denotes a power angle when the virtual synchronous machine is stably running, denotes a power angle at the unstable equilibrium point, denotes a virtual control power angle;

[0117] According to the target equation, a target function is constructed, as shown in formula (7):

[0118] (7)

[0119] wherein, denotes the target function.

[0120] In one specific embodiment, optionally, the target equation can represent a specific active instruction value sought, which can make the work done by the deceleration process of the system from the fault clearance point to the unstable equilibrium point completely offset the accelerating energy accumulated during the fault. Optionally, according to the target equation, the target function is constructed, which can convert the critical stability criterion into a root-finding problem, so as to determine the specific active instruction value.

[0121] S104: The target function is solved by using a dichotomy algorithm, to obtain the critical upper limit of the active instruction value;

[0122] In one specific embodiment, the critical upper limit of the active instruction value is a critical upper limit value corresponding to the instruction value of the active power.

[0123] In one optional embodiment, the above solving the target function by using the dichotomy algorithm to obtain the critical upper limit of the active instruction value can include:

[0124] The root of the target function making the value of the target function zero is determined as the critical upper limit of the active instruction value by using the dichotomy algorithm to solve the target function.

[0125] In an optional embodiment, the above-mentioned solving the objective function by using the dichotomy algorithm to obtain the critical upper limit of the active instruction value can comprise:

[0126] determining a left end point value and a right end point value of the current interval, the left end point value and the right end point value satisfying F(a)·F(b)<0, a representing the left end point value, b representing the right end point value, F(a) representing a left end point function value, and F(b) representing a right end point function value;

[0127] determining a current active instruction midpoint value of the current interval according to the left end point value and the right end point value;

[0128] determining whether the left end point value and the current active instruction midpoint value satisfy F(a)·F(m)<0, updating the right end point value as the current active instruction midpoint value in a case where the left end point value and the current active instruction midpoint value satisfy F(a)·F(m)<0 to determine a first updated interval, and updating the left end point value as the current active instruction midpoint value in a case where the left end point value and the current active instruction midpoint value do not satisfy F(a)·F(m)<0 to determine a second updated interval; wherein F(m) represents a third objective function value;

[0129] determining whether |b-a|<ε or F(m)=0 is satisfied, and determining the current active instruction midpoint value as the critical upper limit of the active instruction value in a case where |b-a|<ε or F(m)=0 is satisfied; and repeating the above-mentioned determining the current active instruction midpoint value of the current interval according to the left end point value and the right end point value to the determining whether |b-a|<ε or F(m)=0 is satisfied until |b-a|<ε or F(m)=0 is satisfied to obtain the critical upper limit of the active instruction value in a case where |b-a|<ε or F(m)=0 is not satisfied; wherein ε represents a preset convergence tolerance.

[0130] In a specific embodiment, the right end point value is updated as the current active instruction midpoint value in a case where the left end point value and the current active instruction midpoint value satisfy F(a)·F(m)<0 to determine a first updated interval [a,m], and the root is located in the first updated interval [a,m] at this time; the left end point value is updated as the current active instruction midpoint value in a case where the left end point value and the current active instruction midpoint value do not satisfy F(a)·F(m)<0 to determine a second updated interval [m,b], and the root is located in the second updated interval at this time. Optionally, the current active instruction midpoint value is determined as the critical upper limit of the active instruction value, i.e., a specific active instruction value in a case where |b-a|<ε or F(m)=0 is satisfied. Optionally, the preset convergence tolerance can be set in combination with actual application.

[0131] In the above embodiment, the dichotomy can steadily and reliably halve the interval containing the root, so as to accurately locate the critical active instruction value which makes the acceleration area equal to the target deceleration area.

[0132] S105: At the moment of grid fault clearance, based on the critical upper limit of the active instruction value, the virtual synchronous machine grid-connected system transient power angle stability is controlled.

[0133] In one specific embodiment, in the case of grid fault, at the moment of grid fault clearance, the active instruction value is adjusted to the critical upper limit of the active instruction value, so as to restore the transient power angle stability of the virtual synchronous machine grid-connected system, and the transient power angle stability of the virtual synchronous machine grid-connected system can be improved.

[0134] In the above embodiment, the critical value of the obtained active power instruction value has a certain conservatism, so that the control based on the instruction can provide additional safety margin for system stability, and can improve the reliability of the emergency control strategy in application. Further, based on the critical upper limit of the active instruction value, the emergency control is effectively guided, and the transient synchronous stability of the virtual synchronous machine grid-connected system can be improved.

[0135] In one specific embodiment, Figure 3 is a virtual synchronous machine grid-connected system control structure schematic diagram provided by an embodiment of the present application, as Figure 3 shown, is a single-machine infinite system of the virtual synchronous machine grid-connected system built in MATLAB, wherein the main system parameters are set as: virtual damping coefficient D=12000 N·m·s / rad, virtual inertia J=1570 kg / m², the simulation scenario is set as: the grid-side voltage drops to 0.1 p.u. at t=2.0 s, the fault is cleared at t=2.1 s, and the acceleration area A inc =116.739733 of the system under the scenario.

[0136] According to the above-provided virtual synchronous grid-connected power source transient power angle stability emergency control method, the critical upper limit value P ref * of the active reference instruction that can guarantee system stability is obtained.

[0137] Figure 4 is a simulation curve schematic diagram provided by an embodiment of the present application, as Figure 4 shown, in order to verify the result, two groups of comparative simulations are performed, Fig. (1) is a first simulation curve schematic diagram, that is, without taking any emergency control measures (P refis a simulation curve diagram with the critical upper limit value 122.71 MW calculated, and the second simulation curve diagram includes (a) a second power angle-time curve diagram, (b) a second frequency-time curve diagram, and (c) a second power-time curve diagram; ref is a simulation curve diagram with the critical upper limit value 122.71 MW calculated, and the second simulation curve diagram includes (a) a second power angle-time curve diagram, (b) a second frequency-time curve diagram, and (c) a second power-time curve diagram; Figure 5 is another simulation curve diagram provided by an embodiment of the present application, as shown in Figure 5 (a) is a first P-δ curve diagram, and (b) is a first phase plane curve diagram; Figure 6 is another simulation curve diagram provided by an embodiment of the present application, as shown in Figure 6 (a) is a second P-δ curve diagram, and (b) is a second phase plane curve diagram; according to the simulation curve diagrams, when no control measures are taken, the system deceleration area A dec = 101.402921 < A inc , the system power and frequency oscillate, the power angle continuously increases, the power angle- angular velocity phase locus assumes a divergent form, and the system loses synchronization stability; and after the active power command value is reduced to P ref at the moment when the fault is cleared, the deceleration area A dec = 116.740733 is equal to the acceleration area, and each electrical quantity can quickly converge to a new stable state after a period of time, wherein the maximum swing power angle is 151.1590°, the phase locus converges to a stable equilibrium point, and the effectiveness of the critical control value is proved.

[0138] It can be seen from the technical solutions provided by the above embodiments of the present specification that the present specification determines the acceleration area of the virtual synchronous generator grid-connected system during power grid fault considering the damping effect according to the transient process mathematical model of the virtual synchronous generator grid-connected system; the target deceleration area of the virtual synchronous generator grid-connected system after the power grid fault is cleared is determined by using a geometric approximation method, the target deceleration area is related to the active instruction value; a target function is constructed according to the acceleration area, the target deceleration area and a preset critical condition, the preset critical condition is that the acceleration area is equal to the target deceleration area; the active instruction value critical upper limit is obtained by solving the target function by using a dichotomy algorithm; at the moment of the power grid fault clearing, the transient power angle stability of the virtual synchronous generator grid-connected system is controlled based on the active instruction value critical upper limit, the active instruction critical value that ensures the stability of the system after the power grid fault can be determined, the quantitative analysis of the stability boundary of the virtual synchronous generator under the serious fault of the power grid is realized, and then the key and quantitative power instruction adjustment basis for the emergency control decision of the virtual synchronous generator grid-connected system is provided, so that the ability of the system to resist serious faults is improved, and then the transient synchronous stability and the synchronous support ability of the system are effectively improved, and the safety of the system application is improved.

[0139] The present application also provides a virtual synchronous grid-forming power transient power angle stability emergency control device, and correspondingly, Figure 7 is a structural schematic diagram of a virtual synchronous grid-forming power transient power angle stability emergency control device provided by the present application; as Figure 7 indicated above, the device comprises:

[0140] The acceleration area determination module 710 is configured to determine the acceleration area of the virtual synchronous generator grid-connected system during power grid fault considering the damping effect according to the transient process mathematical model of the virtual synchronous generator grid-connected system.

[0141] The target deceleration area determination module 720 is configured to determine the target deceleration area of the virtual synchronous generator grid-connected system after the power grid fault is cleared by using a geometric approximation method; the target deceleration area is related to the active instruction value.

[0142] The active instruction value critical upper limit determination module 730 is configured to construct a target function according to the acceleration area, the target deceleration area and a preset critical condition; the preset critical condition is that the acceleration area is equal to the target deceleration area; the active instruction value critical upper limit is obtained by solving the target function by using a dichotomy algorithm.

[0143] The transient power angle stability control module 740 is configured to control the transient power angle stability of the virtual synchronous generator grid-connected system based on the active instruction value critical upper limit at the moment of the power grid fault clearing.

[0144] The embodiment of the present application also provides an electronic device, which comprises a processor and a memory, wherein the memory stores at least one instruction, at least one program, a code set or an instruction set, and the at least one instruction, the at least one program, the code set or the instruction set is loaded and executed by the processor to realize the virtual synchronous network power transient power angle stability emergency control method according to any one of the method embodiments.

[0145] The embodiment of the present application also provides a computer storage medium, which can be arranged in a server to save at least one instruction, at least one program, a code set or an instruction set for realizing the method embodiment, and the at least one instruction, the at least one program, the code set or the instruction set is loaded and executed by the processor to realize the virtual synchronous network power transient power angle stability emergency control method according to any one of the method embodiments.

[0146] Optionally, in the embodiment of the present application, the storage medium can be located in at least one network server of a plurality of network servers of a computer network. Optionally, in the embodiment of the present application, the storage medium can include but is not limited to a U disk, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk and various storage program codes.

[0147] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can adopt a completely hardware embodiment, a completely software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can adopt a computer program product in the form of being implemented on one or more computer usable storage media containing computer usable program codes, including but not limited to disk storage, CD-ROM, optical storage and the like.

[0148] The present application is described with reference to flowcharts and / or block diagrams of the method, device (system) and computer program product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general purpose computer, a special purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the computer or other programmable data processing device produce a device for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The functions specified in one flow or multiple flows and / or blocks

[0149] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the Figure 1 function specified in the flow or flows of the flowchart Figure 1 block or blocks.

[0150] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that are executed on the computer or other programmable apparatus provide steps for implementing the Figure 1 function specified in the flow or flows of the flowchart Figure 1 block or blocks.

[0151] The flow diagrams and block diagrams in the drawings are presented to illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to the present application. In this regard, each block in the flowchart or block diagrams can represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical functions. In some alternative implementations, the functions noted in the blocks can occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

[0152] Finally, it should be noted that the embodiments of the present application described above are merely exemplary and that a person of ordinary skill in the art can make many changes and modifications without departing from the spirit and scope of the present application, which are defined by the appended claims.

Claims

1. A method for emergency control of transient power angle stability of a virtual synchronous grid-connected power source, characterized in that, The method includes: Based on the transient process mathematical model of the virtual synchronous machine grid-connected system, the acceleration area of ​​the virtual synchronous machine grid-connected system during a grid fault, taking into account the damping effect, is determined. A geometric approximation method is used to determine the target deceleration area of ​​the virtual synchronous machine grid-connected system after the power grid fault is cleared. The target deceleration area is related to the active power command value. Based on the acceleration area, the target deceleration area, and the preset critical condition, an objective function is constructed, wherein the preset critical condition is that the acceleration area is equal to the target deceleration area. The objective function is solved using a binary search algorithm to obtain the critical upper limit of the active power command value; At the instant the grid fault is cleared, the transient power angle of the virtual synchronous machine grid-connected system is stabilized based on the critical upper limit of the active power command value.

2. The emergency control method for transient power angle stability of virtual synchronous grid-connected power sources according to claim 1, characterized in that, The transient process mathematical model of the virtual synchronous machine grid-connected system is constructed using the following formula, as shown in equation (1): ； （1） in, ; ; in, Represents virtual inertia; The instruction value representing the angular frequency output by the virtual synchronizer; Indicates equivalent mechanical power; This represents the actual active power output of the virtual synchronizer; This represents the active power command value output by the virtual synchronizer; Indicates virtual damping; This represents the actual value of the angular frequency output by the virtual synchronizer; This represents the internal potential of the virtual synchronous machine; Indicates the magnitude of the grid-side voltage vector; This represents the line reactance from the virtual synchronous machine port to the grid connection point; This indicates the virtual control angle.

3. The emergency control method for transient power angle stability of virtual synchronous grid power supply according to claim 2, characterized in that, The determination of the acceleration area of ​​the virtual synchronous machine grid-connected system during a grid fault, taking into account the damping effect, based on the transient process mathematical model of the virtual synchronous machine grid-connected system includes: In the event of a power grid failure, the rotor acceleration of the virtual synchronous machine is determined based on the transient process mathematical model. The acceleration area accumulated during the rotor acceleration process of the virtual synchronous machine during a grid fault, taking into account the damping effect, is determined as shown in Equation (2): ；（2） in, Indicates the accelerated area; This represents the power angle of the virtual synchronizer at the moment of fault clearing; This represents the power angle during stable operation of the virtual synchronizer.

4. The emergency control method for transient power angle stability of virtual synchronous grid-connected power sources according to claim 1, characterized in that, The method of using geometric approximation to determine the target deceleration area of ​​the virtual synchronous machine grid-connected system after the power grid fault is cleared includes: At the moment the grid fault is cleared, the active power command value of the virtual synchronous machine is reduced, thereby reducing the equivalent mechanical power. Determine the initial deceleration area after reducing the active power command value, so that the initial deceleration area is determined according to the active power command value, as shown in equation (3): ；（3） in, Indicates the initial deceleration area; This represents the angle of work at an unstable equilibrium point; This represents the power angle of the virtual synchronizer at the moment of fault clearing; This represents the actual active power output of the virtual synchronizer; Indicates equivalent mechanical power; Indicates virtual control power angle, This represents the critical upper limit of the active power command value to be solved; Wherein, the coordinates of the unstable equilibrium point are ; Based on the geometric approximation method and the initial deceleration area, determine the target straight line connecting the fault clearing point and the unstable equilibrium point; Based on the target straight line, the target deceleration area is determined. The target deceleration area is the maximum deceleration area provided by the virtual synchronous machine grid connection system after a grid fault, as shown in equation (4): ；（4） in, Indicates the target deceleration area; The target straight line used to characterize the connection between the fault clearing point and the unstable equilibrium point; Wherein, the coordinates of the fault clearing point are .

5. The emergency control method for transient power angle stability of virtual synchronous grid-connected power sources according to claim 1, characterized in that, The step of constructing an objective function based on the acceleration area, the target deceleration area, and a preset critical condition includes: Based on the acceleration area and the target deceleration area, the preset critical condition is determined as shown in equation (5): ；（5） in, Indicates the accelerated area. Indicates the target deceleration area. This represents the critical upper limit of the active power command value to be solved; Based on the preset critical conditions, the target equation is determined. The target equation is related to the active power command value, as shown in equation (6): ；（6） in, Represents equivalent mechanical power. This represents the actual active power output of the virtual synchronizer. Used to characterize the target straight line connecting the fault clearing point and the unstable equilibrium point; This represents the power angle of the virtual synchronizer at the moment of fault clearing. The power angle represents the angle at which the virtual synchronizer is running stably. This represents the work angle at the unstable equilibrium point. Indicates the virtual control angle; Based on the objective equation, the objective function is constructed as shown in equation (7): ；（7） in, This represents the objective function.

6. The emergency control method for transient power angle stability of virtual synchronous grid power supply according to claim 5, characterized in that, The step of using a binary search algorithm to solve the objective function to obtain the critical upper limit of the active power command value includes: The objective function is solved using a binary search algorithm, and the root that makes the objective function zero is determined as the critical upper limit of the active power command value.

7. The emergency control method for transient power angle stability of virtual synchronous grid power supply according to claim 6, characterized in that, The step of using a binary search algorithm to solve the objective function to obtain the critical upper limit of the active power command value includes: Determine the left and right endpoint values ​​of the current interval, wherein the left and right endpoint values ​​satisfy F(a)⋅F(b)<0, where a represents the left endpoint value, b represents the right endpoint value, F(a) represents the left endpoint function value, and F(b) represents the right endpoint function value; Based on the left endpoint value and the right endpoint value, determine the current active power command midpoint value of the current interval; Determine whether the left endpoint value and the midpoint value of the current active power command satisfy F(a)⋅F(m)<0. If the left endpoint value and the midpoint value of the current active power command satisfy F(a)⋅F(m)<0, update the right endpoint value to the midpoint value of the current active power command, and determine the first update interval; if the left endpoint value and the midpoint of the current interval do not satisfy F(a)⋅F(m)<0, update the left endpoint value to the midpoint value of the current active power command, and determine the second update interval; where F(m) represents the value of the third objective function. Determine whether |ba|<ε or F(m)=0 is satisfied. If |ba|<ε or F(m)=0 is satisfied, the midpoint value of the current active power command is determined as the critical upper limit of the active power command value. If |ba|<ε or F(m)=0 is not satisfied, the first update interval or the second update interval is taken as the current interval, and the above process of determining the midpoint value of the current active power command of the current interval based on the left endpoint value and the right endpoint value is repeated until |ba|<ε or F(m)=0 is satisfied, until |ba|<ε or F(m)=0 is satisfied, and the critical upper limit of the active power command value is obtained. Wherein, ε represents the preset convergence tolerance.

8. A virtual synchronous grid-connected power supply transient power angle stabilization emergency control device, characterized in that, The device includes: The acceleration area determination module is used to determine the acceleration area of ​​the virtual synchronous machine grid-connected system during a grid fault, taking into account the damping effect, based on the transient process mathematical model of the virtual synchronous machine grid-connected system. The target deceleration area determination module is used to determine the target deceleration area of ​​the virtual synchronous machine grid-connected system after the power grid fault is cleared, using a geometric approximation method; the target deceleration area is related to the active power command value. The active power command value critical upper limit determination module is used to construct an objective function based on the acceleration area, the target deceleration area, and a preset critical condition; the preset critical condition is that the acceleration area is equal to the target deceleration area; and the objective function is solved using a binary search algorithm to obtain the active power command value critical upper limit. The transient power angle stabilization control module is used to control the transient power angle stability of the virtual synchronous machine grid-connected system based on the critical upper limit of the active power command value at the moment of grid fault clearing.

9. An electronic device comprising a processor and a memory, the memory storing at least one instruction and at least one program, the at least one instruction and the at least one program being loaded and executed by the processor to implement the virtual synchronous grid power transient power angle stability emergency control method as described in any one of claims 1 to 7.

10. A computer storage medium storing at least one instruction and at least one program, wherein the at least one instruction and the at least one program are loaded and executed by a processor to implement the virtual synchronous grid power transient power angle stability emergency control method as described in any one of claims 1 to 7.

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