A virtual synchronous generator frequency forced constraint control method and system

Abstract

The invention discloses a virtual synchronous generator frequency forced constraint control method and system, belonging to the technical field of distributed power supply operation control; a virtual synchronous generator frequency forced constraint control method comprises: establishing a virtual synchronous generator frequency dynamic control model based on large signal modeling and theory; establishing a forced constraint control model, and reshaping the virtual synchronous generator frequency dynamic control model based on it, and determining the control input items of the virtual synchronous generator; based on the reshaped virtual synchronous generator frequency dynamic control model and control input items, by introducing an activation function, designing a virtual synchronous generator control algorithm with forced frequency operating range constraints; solving the virtual synchronous generator control algorithm with forced frequency operating range constraints by using differential equations, obtaining a forced frequency constraint function analysis model, and theoretically verifying and analyzing the forced frequency constraint function of the virtual synchronous generator to complete closed-loop control.

Description

Technical Field

[0001] The present invention belongs to the technical field of distributed power supply operation control, and in particular relates to a virtual synchronous generator frequency forced constraint control method and system. Background Art

[0002] The high proportion of distributed renewable energy access to the grid has brought about problems such as inertia and damping reduction, which seriously threatens the safe and stable operation of the grid. Therefore, in order to improve the operating characteristics of distributed power sources and enhance the frequency operation stability of the grid, the application of virtual synchronous generator technology has emerged. Compared with distributed power control technologies such as droop and PQ without inertia and weak inertia, the virtual synchronous generator control technology can achieve additional inertia and damping support for the grid by simulating the rotor equation of the synchronous motor, so that the distributed power source has good dynamic operation characteristics. However, considering the time-varying, unknown and multi-dimensional coupling of the inertia of the grid system in practical applications, the application of traditional virtual synchronous generator technology in actual grids is usually difficult to obtain the same frequency fluctuation suppression effect as the theory due to the inability to know the appropriate inertia and damping compensation values. The operating frequency of the grid may still cause unsafe operation conditions such as over-limit and over-limit due to the rapid fluctuation of new energy. Therefore, it is urgent to propose a virtual synchronous generator frequency forced constraint control method and system to improve the accurate control effect of the frequency. Summary of the invention

[0003] In view of the deficiencies in the prior art, an object of the present invention is to provide a virtual synchronous generator frequency forced constraint control method and system, which solves the problems in the prior art.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A virtual synchronous generator frequency forced constraint control method comprises the following steps:

[0006] Based on large signal modeling and theory, a frequency dynamic control model of virtual synchronous generator is established;

[0007] Establish a mandatory constraint control model, and use it to reshape the virtual synchronous generator frequency dynamic control model, and determine the control input items of the virtual synchronous generator;

[0008] Based on the reshaped virtual synchronous generator frequency dynamic control model and control input items, a virtual synchronous generator control algorithm with mandatory frequency operation range constraints is designed by introducing an activation function.

[0009] The virtual synchronous generator control algorithm with forced frequency operating range constraint is solved by differential equations to obtain a theoretical analysis model of forced frequency constraint function, so as to perform theoretical verification and analysis on the forced frequency constraint function of the virtual synchronous generator and complete closed-loop control.

[0010] Furthermore, the virtual synchronous generator frequency dynamic control model is:

[0011]

[0012] Where, ω is the output angular velocity of the virtual synchronous generator; J is the virtual inertia; D is the damping coefficient; ω n is the rated value of angular velocity; △ω ref Input adjustment for angular velocity; P m is the mechanical power; P is the active power output; P ref is the active power reference input; K ω is the angular velocity droop gain coefficient.

[0013] Furthermore, the mandatory constraint control model is:

[0014]

[0015] In the formula, x is the controlled state, The derivative of the controlled state, its initial state should satisfy -x max <x(0)<x max ; K is the control gain; u is the control input, which should satisfy -x max <u<x max ; -x max and x max Indicates the lower and upper limits of the operating range allowed for the controlled state x.

[0016] Furthermore, the reshaped virtual synchronous generator frequency dynamic control model is:

[0017]

[0018] In the formula, u ref Auxiliary control input status, is the derivative of the output angular velocity of the virtual synchronous generator. Further, the control algorithm of the virtual synchronous generator with the forced frequency operating range constraint is:

[0019] u ref =-ω max tanh[K P (ω-ω n )+K I ∫(ω-ω n )dt]

[0020] In the formula, -ω max Indicates the lower limit of the operating range allowed by the virtual synchronous generator controlled state ω; K P and K Iare the proportional and integral control coefficients.

[0021] Furthermore, the theoretical analysis model of the mandatory frequency constraint function is:

[0022]

[0023] Where ω(t) is the current operating angular frequency; ω(0) is the initial value of the angular frequency, and α is the integration state.

[0024] A virtual synchronous generator frequency forced constraint control system, comprising:

[0025] Model calculation module: Aiming at the demand of short-term frequency dynamic control, a virtual synchronous generator frequency dynamic control model is constructed based on large signal modeling and theory;

[0026] Model reshaping module: Based on the mandatory constraint control model, the dynamic control model of the virtual synchronous generator is reshaped to determine the control input items of the virtual synchronous generator;

[0027] Frequency forced constraint control execution module: Based on the reshaped virtual synchronous generator frequency dynamic control model and control input items, by introducing activation functions, a virtual synchronous generator control algorithm with forced frequency operating range constraints is designed;

[0028] And, verification module: use differential equations to solve the virtual synchronous generator control algorithm with forced frequency operating range constraints, and obtain the theoretical analysis model of the forced frequency constraint function to perform theoretical verification and analysis on the forced frequency constraint function of the virtual synchronous generator to complete closed-loop control.

[0029] A computer storage medium stores a readable program, which can execute the above-mentioned virtual synchronous generator frequency forced constraint control method when the program is running.

[0030] An electronic device, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0031] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the above-mentioned virtual synchronous generator frequency forced constraint control method.

[0032] A computer program product includes computer instructions, wherein the computer instructions instruct a computing device to execute operations corresponding to the above-mentioned virtual synchronous generator frequency forced constraint control method.

[0033] Beneficial effects of the present invention:

[0034] 1. The frequency forced constraint control method of the virtual synchronous generator proposed in the present invention can realize accurate frequency constraint control when the inertia and damping characteristics of the power grid are unknown, avoiding frequency over-limit operation; it can solve the problem that the conventional virtual synchronous generator can only perform inertial support but is difficult to accurately limit the frequency constraint range, and is more suitable for various types of actual power grid engineering practices, especially for areas with rapid power fluctuations where a high proportion of distributed power sources are connected.

[0035] 2. The frequency forced constraint control method provided by the present invention strictly limits the control input of the virtual synchronous generator by constructing a constraint control model and introducing an activation function, thereby realizing accurate and limit-free control of the virtual synchronous generator export frequency; therefore, the provided method can better avoid the frequency overshoot and over-limit operation problems caused by rapid fluctuations in power grid power, and overcome the problem that the virtual synchronous generator control technology can only quantitatively improve inertia and damping but cannot quantitatively limit frequency, and further expand the application flexibility, accuracy and reliability of the virtual synchronous generator technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 It is a control structure diagram of a virtual synchronous generator provided by the present invention;

[0038] Figure 2 is a flow chart of frequency forced constraint control of a virtual synchronous generator of the present invention;

[0039] Figure 3 It is a test simulation system architecture diagram of the present invention;

[0040] Figure 4 This is the comparison result of the simulation test of the forced frequency constraint control of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Example 1

[0043] like Figure 1The figure shows the application scenario of the virtual synchronous generator of the present invention. The virtual synchronous generator control strategy in the figure can achieve auxiliary inertial support for access to the power grid by simulating the second-order rotor dynamics of the traditional synchronous generator. However, due to the unknown nature of the external power grid, the traditional virtual synchronous generator control strategy can only qualitatively compensate for inertia and damping, and when faced with large power changes, there may still be problems of over-limit frequency changes that endanger the safe and stable operation of the power grid. This practical problem will be solved by the strategy of the present invention.

[0044] Example 2

[0045] like Figure 2 As shown, a virtual synchronous generator frequency forced constraint control method comprises the following steps:

[0046] S1, based on large signal modeling and theory, a frequency dynamic control model of virtual synchronous generator is established;

[0047] In order to facilitate full dynamic control and avoid the problem of poor control dynamic performance caused by the lack of small signal modeling modes, the present invention will use large signal modeling and control theory to model and design the control of the virtual synchronous generator.

[0048] The virtual synchronous generator structure achieves the inertial support effect by simulating the inertial characteristics of the synchronous generator. To achieve the inertial and damping characteristics of the equivalent synchronous generator, the virtual synchronous generator rotor structure is characterized by the second-order inertia relationship equation. Based on the large signal control theory, the frequency dynamic control model of the virtual synchronous generator can be expressed as:

[0049]

[0050] Where, ω is the output angular velocity of the virtual synchronous generator; J is the virtual inertia; D is the damping coefficient; ω n is the rated value of angular velocity; △ω ref Input adjustment for angular velocity; P m is the mechanical power; P is the active power output; P ref is the active power reference input; K ω is the angular velocity droop gain coefficient.

[0051] S2, establishing a mandatory constraint control model, and using it to reshape the virtual synchronous generator frequency dynamic control model, and determine the control input items of the virtual synchronous generator;

[0052] The mandatory constraint control model is:

[0053]

[0054] In the formula, x is the controlled state, The derivative of the controlled state, its initial state should satisfy -xmax <x(0)<x max ; K is the control gain; u is the control input, which should satisfy -x max <u<x max ; -x max and x max Indicates the lower and upper limits of the operating range allowed for the controlled state x.

[0055] To facilitate control design, based on the above forced state control model, the virtual synchronous generator frequency dynamic control model (Formula (1)) is reshaped into the following form:

[0056]

[0057] By defining an auxiliary control input state u ref , the above model can be further simplified as:

[0058]

[0059] In the formula, u ref Auxiliary control input status, is the derivative of the output angular velocity of the virtual synchronous generator.

[0060] At this point, the virtual synchronous generator frequency dynamic control model has been reshaped into a forced state constraint control model.

[0061] And, the angular velocity input adjustment of the virtual synchronous generator can be expressed as:

[0062]

[0063] S3, based on the reshaped virtual synchronous generator frequency dynamic control model and control input items, by introducing an activation function in the input feedback control input loop, a virtual synchronous generator control algorithm with a forced frequency operating range constraint is designed;

[0064] Based on the requirements in the mandatory constraint control model, in order to realize the mandatory state constraint, the auxiliary input state u in the reshaped virtual synchronous generator frequency dynamic control model is ref The following requirements should be met:

[0065] -ω max <u ref <ω max (5)

[0066] Where: -ω max and ω max Indicates the lower and upper limits of the operating range allowed by the controlled state ω of the virtual synchronous generator.

[0067] By utilizing the property of the activation function (hyperbolic tangent function) -1 < tanh(x) < 1, the virtual synchronous generator control algorithm with forced frequency operation range constraint can be designed as follows:

[0068] u ref =-ω max tanh[K P (ω - ω n ) + K I ∫(ω - ω n )dt] (6)

[0069] Where: K P and K I are the proportional and integral control coefficients. This input can meet the requirements in formula (5).

[0070] S4. Solve the virtual synchronous generator control algorithm with forced frequency operation range constraint using differential equations to obtain an analysis model of the forced frequency constraint function, and conduct theoretical verification and analysis on the forced frequency constraint function of the virtual synchronous generator to complete the closed-loop control.

[0071] Based on the virtual synchronous generator reshaping model (3), by solving the algorithm (6) in the time domain, the following theoretical analysis model of the forced frequency constraint function can be obtained:

[0072]

[0073] Where ω(t) is the operating angular frequency at the current moment; ω(0) is the initial value of the angular frequency, and α is the integral state.

[0074] The above solution results satisfy:

[0075]

[0076] By substituting:

[0077]

[0078] The forced frequency operation constraint function proposed in the present invention can be obtained:

[0079] -ω max <ω(t)<ω max (10)

[0080] Embodiment 3

[0081] As Figure 3 shown, the test scenario of the method provided by the present invention is two virtual synchronous generators (the inertia of the virtual synchronous generator #1 is 2 kg / m 2 , and the inertia of the virtual synchronous generator #2 is 4 kg / m 2) grid-connected operation scenario. In this power grid system, some uncontrollable loads #1 (5kW, 5kVar), loads #2 (5kW, 5kVar) and loads #3 (25kW, 25kVar) are additionally connected to facilitate the completion of performance testing. In order to ensure the safe and stable operation of the system, the mandatory frequency operation constraint boundary in the test scenario setting of the present invention is designed to be (49.7Hz, 50.3Hz). In the scenario setting, the low-power load #2 is cut off at t=4s, and the high-power load #3 is connected at t=6s.

[0082] Figure 4 (a) and (b) in the figure respectively give the test results of the traditional synchronous generator control method and the test results of the virtual synchronous generator frequency forced constraint control method proposed by the present invention. From the comparative test results, it can be seen that when dealing with changes in small disturbance load #2, both controls can ensure that the frequency operation does not exceed the safe operating range of the power grid (49.5Hz, 50.5Hz). However, when dealing with larger power disturbance scenarios, that is, when high-power load #3 is connected, the traditional control scheme has an overshoot exceeding the lower limit of 49.5Hz, while the scheme of the present invention can strictly constrain the frequency within the set boundaries (49.7Hz, 50.3Hz). Accurately ensure the safe and stable operation of the overall power grid system.

[0083] Example 4

[0084] In addition, this embodiment discloses a virtual synchronous generator frequency forced constraint control system, including:

[0085] Model calculation module: Aiming at the demand of short-term frequency dynamic control, a virtual synchronous generator frequency dynamic control model is constructed based on large signal modeling and theory;

[0086] Model reshaping module: Based on the mandatory constraint control model, the dynamic control model of the virtual synchronous generator is reshaped to determine the control input items of the virtual synchronous generator;

[0087] Frequency forced constraint control execution module: Based on the reshaped virtual synchronous generator frequency dynamic control model and control input items, the virtual synchronous generator control model with forced frequency operating range constraints is designed by introducing an activation function;

[0088] And, verification module: using differential equations to solve the virtual synchronous generator control model, obtaining a theoretical analysis model of the forced frequency constraint function, to perform theoretical verification analysis on the forced frequency constraint function of the virtual synchronous generator, and complete closed-loop control.

[0089] Example 5

[0090] The present embodiment discloses a virtual synchronous generator frequency forced constraint control terminal device, including a memory, a processor, and an algorithm program or an algorithm module system stored in the memory and capable of running on the processor, wherein the memory stores an algorithm program or an algorithm module system capable of running on the processor, and when the processor loads and executes the algorithm program, the frequency forced constraint control method algorithm or control system described in any one of the above embodiments is adopted.

[0091] Among them, the terminal device can be a desktop computer, workstation, device-side integrated controller or cloud server and other devices that can realize real-time computing, and the terminal device includes but is not limited to a processor and a memory. For example, the terminal device can also include input and output devices, network access devices and buses, etc.

[0092] Among them, the processor can adopt a central processing unit (CPU). Of course, according to actual usage, other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. can also be adopted. The general-purpose processor can adopt a microprocessor or any conventional processor, etc., and this application does not impose any restrictions on this.

[0093] Among them, the memory can be an internal storage unit of the terminal device, such as the hard disk or memory of the terminal device, or it can be an external storage device of the terminal device, such as a plug-in hard disk, smart memory card (SMC), secure digital card (SD) or flash memory card (FC) equipped on the terminal device, etc., and the memory can also be a combination of the internal storage unit and the external storage device of the terminal device. The memory is used to store algorithm programs and other programs and data required by the terminal device. The memory can also be used to temporarily store data that has been output or is to be output, and this application does not impose any restrictions on this.

[0094] Among them, through this terminal device, any one of the virtual synchronous generator frequency forced constraint control algorithms or system modules in the above embodiments is stored in the memory of the terminal device, and is loaded and executed on the processor of the terminal device for easy use.

[0095] This embodiment also discloses a readable storage medium for a virtual synchronous generator frequency forced constraint control method, and the algorithm readable storage medium stores an algorithm or system module program, wherein when the computer program is executed by a processor, any one of the frequency forced constraint control methods in the above embodiments is adopted.

[0096] Among them, the algorithm program can be stored in various algorithm-readable storage media, the algorithm program includes algorithm program code, the algorithm program code can be in source code form, object code form, executable file or certain middleware form, etc. Various algorithm-readable storage media include any entity or device that can carry computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that various algorithm-readable storage media include but are not limited to the above-mentioned components.

[0097] Among them, through the algorithm-readable storage medium, any one of the virtual synchronous generator frequency forced constraint control methods in the above embodiments is stored in the algorithm-readable storage medium, and is loaded and executed on the processor to facilitate the storage and application of the above method.

[0098] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A virtual synchronous generator frequency forced constraint control method, characterized in that: The following steps are involved: Based on large signal modeling and theory, a frequency dynamic control model of virtual synchronous generator is established; Establish a mandatory constraint control model, and use it to reshape the virtual synchronous generator frequency dynamic control model, and determine the control input items of the virtual synchronous generator; Based on the reshaped virtual synchronous generator frequency dynamic control model and control input items, a virtual synchronous generator control algorithm with mandatory frequency operation range constraints is designed by introducing an activation function. The virtual synchronous generator control algorithm with forced frequency operating range constraint is solved by differential equations to obtain a theoretical analysis model of forced frequency constraint function, so as to perform theoretical verification and analysis on the forced frequency constraint function of the virtual synchronous generator and complete closed-loop control; The reshaped virtual synchronous generator frequency dynamic control model is: In the formula, u ref Auxiliary control input status, is the derivative of the output angular velocity of the virtual synchronous generator; ω is the output angular velocity of the virtual synchronous generator; J is the virtual inertia; D is the damping coefficient; ω n is the rated value of angular velocity; △ω ref is the angular velocity input adjustment; P is the active power output; P ref is the active power reference input; K ω is the angular velocity droop gain coefficient; The control algorithm of the virtual synchronous generator with forced frequency operating range constraint is: u ref =-ω max tanh[K P (ω-ω n )+K I ∫(ω-ω n )dt] In the formula, -ω max Indicates the lower limit of the operating range allowed by the virtual synchronous generator controlled state ω; K P and K I are the proportional and integral control coefficients.

2. A virtual synchronous generator frequency forced constraint control method according to claim 1, characterized in that: The virtual synchronous generator frequency dynamic control model is: Where P m is the mechanical power.

3. A virtual synchronous generator frequency forced constraint control method according to claim 2, characterized in that: The mandatory constraint control model is: In the formula, x is the controlled state, The derivative of the controlled state, its initial state should satisfy -x max <x(0)<x max ; K is the control gain; u is the control input and should satisfy -x max <u<x max ; -x max and x max Indicates the lower and upper limits of the operating range allowed for the controlled state x.

4. A virtual synchronous generator frequency forced constraint control method according to claim 3, characterized in that: The theoretical analysis model of the mandatory frequency constraint function is: Where ω(t) is the current operating angular frequency; ω(0) is the initial value of the angular frequency, and α is the integration state.

5. A virtual synchronous generator frequency forced constraint control system, characterized in that: include: Model calculation module: Aiming at the demand of short-term frequency dynamic control, a virtual synchronous generator frequency dynamic control model is constructed based on large signal modeling and theory; Model reshaping module: Based on the mandatory constraint control model, the dynamic control model of the virtual synchronous generator is reshaped to determine the control input items of the virtual synchronous generator; Frequency forced constraint control execution module: Based on the reshaped virtual synchronous generator frequency dynamic control model and control input items, by introducing activation functions, a virtual synchronous generator control algorithm with forced frequency operating range constraints is designed; And, verification module: using differential equations to solve the virtual synchronous generator control algorithm with forced frequency operating range constraints, obtaining a theoretical analysis model of forced frequency constraint function, to perform theoretical verification analysis on the forced frequency constraint function of the virtual synchronous generator and complete closed-loop control; The reshaped virtual synchronous generator frequency dynamic control model is: In the formula, u ref Auxiliary control input status, is the derivative of the output angular velocity of the virtual synchronous generator; ω is the output angular velocity of the virtual synchronous generator; J is the virtual inertia; D is the damping coefficient; ω n is the rated value of angular velocity; △ω ref is the angular velocity input adjustment; P is the active power output; P ref is the active power reference input; K ω is the angular velocity droop gain coefficient; The control algorithm of the virtual synchronous generator with forced frequency operating range constraint is: u ref =-ω max tanh[K P (ω-ω n )+K I ∫(ω-ω n )dt] In the formula, -ω max Indicates the lower limit of the operating range allowed by the virtual synchronous generator controlled state ω; K P and K I are the proportional and integral control coefficients.

6. A computer storage medium storing a readable program, characterized in that: When the program is running, it can execute the virtual synchronous generator frequency forced constraint control method described in any one of claims 1 to 4.

7. An electronic device comprising: A processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to a virtual synchronous generator frequency forced constraint control method according to any one of claims 1-4.

8. A computer program product, comprising computer instructions, wherein the computer instructions instruct a computing device to execute operations corresponding to a virtual synchronous generator frequency forced constraint control method as claimed in any one of claims 1 to 4.

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