Voltage stability analysis method, system and equipment of new energy grid-connected system and medium

Abstract

The invention discloses a voltage stability analysis method, system and device of a new energy grid-connected system and a medium. At present, the static voltage stability judgment calculation efficiency is low, and the applicability is limited. The method comprises the following steps: constructing an equivalent model of a new energy grid-connected system, wherein an external power grid is equivalent to a single-machine infinite power grid from Thevenin; a Jacobian matrix is obtained through derivation of the power flow equation, and then critical voltage parameters of singular points of the Jacobian matrix are obtained; and deriving an expression form of a static voltage stability criterion through a power circle, calculating a static voltage stability criterion value, and proposing a voltage stability judgment method according to the condition of the static voltage stability criterion value. According to the technical scheme, whether the static voltage is stable or not is effectively judged, safe and stable operation of a high-proportion new energy power grid is accurately supported, and a new method is provided for voltage stability judgment of a new energy station.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and in particular to a voltage stability analysis method, system, equipment and medium for a new energy grid-connected system. Background Art

[0002] With the large-scale access of new energy to the power grid, the proportion of new energy such as wind power and photovoltaics has increased significantly. Their output is characterized by volatility and intermittency, which brings huge challenges to the safe and stable operation of the power grid. It is urgent to establish a static voltage stability criterion that adapts to the characteristics of new energy and improve the identification accuracy and applicability of the stability boundary under complex working conditions. Summary of the Invention

[0003] The technical problem to be solved and the technical task to be addressed by this invention are to improve and enhance existing technical solutions by providing a voltage stability analysis method, system, equipment, and medium for renewable energy grid-connected systems. This method aims to achieve static voltage stability determination that is applicable to renewable energy power supply scenarios, compatible with line resistance effects, and capable of rapid analytical calculation of critical voltages. To this end, this invention employs the following technical solutions.

[0004] A voltage stability analysis method for a new energy grid-connected system includes the following steps: 1) Construct an equivalent model of the new energy grid-connected system, and use Thevenin to equate the external power grid to a single-machine infinite balance node, with a voltage amplitude of E and a phase of 0; 2) Based on the equivalent model, a power flow equation is established, the Jacobian matrix is ​​derived, and the calculation formula for the system critical voltage amplitude is determined by solving the singular points where the Jacobian matrix determinant is zero; 3) Based on the critical voltage amplitude calculation formula and power circle theory, derive the calculation formula for the static voltage stability criterion and calculate the static voltage stability criterion value Δ; 4) Compare the static voltage stability criterion value Δ with the equilibrium node voltage amplitude E. If Δ E, determine that the system is in a stable state; if Δ E, determine that the system is in an unstable risk state.

[0005] This technical solution simplifies the external power grid into a single infinite balancing node using the Thevenin equivalent, effectively reducing the modeling dimensionality of complex power grids. This makes the method applicable to renewable energy grid-connected scenarios with diverse topologies, particularly those in weak grid conditions where resistance is non-negligible. A formula for calculating the critical voltage amplitude is directly determined based on singular points where the Jacobian matrix determinant is zero, overcoming the bottleneck of the traditional PV curve method's reliance on iterative scanning and meeting the requirements for real-time stability assessment under renewable energy power fluctuations. The critical voltage formula is integrated with power circle theory to derive the criterion, improving accuracy in weak grid scenarios. Δ represents the voltage stability margin under the system's current operating conditions; larger values ​​indicate higher stability margins. Directly comparing the criterion value Δ with the node voltage E enables a single-step determination from "numerical calculation to stability output," avoiding the redundant operation of drawing the entire PV curve required in traditional methods. The response speed is as fast as milliseconds, supporting rapid grid control decisions. Traditional methods require repeated iterative calculations of the PV curve. However, this technical solution directly obtains an analytical expression for the critical voltage by ensuring that the determinant of the Jacobian matrix is ​​zero. Combined with the power circle theory, the calculation formula for Δ is derived, completely avoiding the iterative process and increasing the calculation speed by orders of magnitude. This is particularly suitable for real-time monitoring in scenarios with new energy power fluctuations.

[0006] As a preferred technical means: In step 1) in the equivalent model, the new energy grid-connected system serves as a power source and outputs power P+jQ, which is connected to the balance node through an equivalent impedance Z=R+jX, where P is the active power output by the new energy grid-connected system, Q is the reactive power output by the new energy grid-connected system, R is the line resistance, and X is the line reactance; the port voltage amplitude of the new energy grid-connected system is U, and the phase is θ.

[0007] The new energy grid-connected system is defined as a power source role (output P + JQ ), which is essentially different from the traditional load model (absorbed power), and directly fits the engineering reality of wind power, photovoltaic and other new energy sources as power transmission sources, avoiding the misjudgment of stability caused by the traditional load model. Z = R + JX Complex impedance model, including resistance R The impact on power transmission significantly improves the model accuracy of weak power grids and solves the problem of critical voltage calculation deviation caused by ignoring resistance in existing methods. All parameters ( P , Q , R , X , U , θ ) are standard electrical quantities that can be measured or estimated in real time by the power grid (such as PMU data, SCADA system), without relying on historical databases or complex parameter identification.

[0008] As a preferred technical means: in step 2), the Jacobian matrix is ​​constructed by partial derivatives of the active power P and reactive power Q in the power flow equation with respect to the phase angle θ and the voltage amplitude U.

[0009] This construction method directly quantifies the dynamic relationship between active power, reactive power, and key system state variables (phase angle θ, voltage amplitude U), clearly reflecting the coupling characteristics of system power, voltage, and phase angle. Based on this construction, the Jacobian matrix can be directly derived from its singular points (conditions where the determinant is 0) to obtain critical voltage parameters. This eliminates the need for continuous power flow calculations that rely on iteratively solving modified power flow equations, as required by traditional PV curve methods. This simplifies the identification of static voltage stability boundaries and improves computational efficiency and applicability under complex operating conditions characterized by fluctuating and intermittent renewable energy output.

[0010] As a preferred technical means: Step 2) the critical voltage amplitude calculation formula is: the square value of the critical voltage amplitude is equal to the line impedance modulus and new energy output power modulus The product of .

[0011] The formula for calculating the critical voltage amplitude clearly reflects the direct impact of line impedance characteristics and renewable energy output power on the critical state of static voltage stability, breaking through the limitations of traditional methods that only consider active power or pure reactance. This formula is derived based on the singular point conditions of the Jacobian matrix, eliminating the need for the complex continuous power flow iteration calculations used in traditional PV curve methods. The critical voltage amplitude can be directly calculated using only the line impedance modulus and renewable energy output power modulus, significantly simplifying the critical voltage calculation process and improving the ability to quickly identify the static voltage stability boundary. Requiring only four basic parameters (R, X, P, Q) to output the critical voltage, it becomes the core engine of "plug-and-play" stability criteria for renewable energy stations, promptly responding to the impact of renewable energy output changes on the system stability boundary and enhancing its applicability under complex operating conditions.

[0012] As a preferred technical means: in step 3), the calculation formula of the static voltage stability criterion value Δ is:

[0013] The parameters involved in the formula are all parameters that can be directly obtained or measured by the system. Δ can be quickly solved through simple algebraic operations, which greatly simplifies the calculation process of the stability criterion and improves the efficiency of static voltage stability judgment.

[0014] A second technical solution of the present invention is: a voltage stability analysis system for a new energy grid-connected system, which applies the aforementioned voltage stability analysis method for a new energy grid-connected system; the system comprises: Equivalent modeling module: used to simplify the external power grid into a Thevenin equivalent single-machine infinite balance node, whose voltage amplitude is E and phase is 0; Critical voltage calculation module: used to derive the Jacobian matrix based on the power flow equation and determine the calculation formula of the system critical voltage amplitude by solving the singular points where the Jacobian matrix determinant is zero; Criteria generation module: used to derive the calculation formula of the static voltage stability criterion based on the critical voltage amplitude calculation formula and power circle theory, and calculate the static voltage stability criterion value Δ; Stability judgment module: used to compare Δ and E. If Δ>E, it outputs a stable signal; if Δ≤E, it outputs an instability risk signal.

[0015] The equivalent modeling module simplifies the external power grid into a Thevenin-equivalent, single-machine infinite balancing node. While simplifying system complexity, it also captures the key impact of the external power grid on the renewable energy grid-connected system. This provides a concise and effective foundational model for subsequent analysis, avoiding the redundant calculations associated with complex power grid models. The critical voltage calculation module derives the Jacobian matrix based on the power flow equation and determines the critical voltage amplitude formula by solving for singular points where its determinant is zero. This process directly leverages the mathematical relationship between matrix singular points and the system's stability boundary, eliminating the need for continuous power flow iterations required by traditional methods. This allows for rapid and accurate quantification of the voltage characteristics of the system as it enters a critical stability state, resulting in a simpler calculation process and results that better reflect the system's physical nature. The criterion generation module combines the critical voltage amplitude formula with power circle theory to derive the formula for the static voltage stability criterion Δ. This eliminates the need for complex transformations and facilitates rapid criterion value acquisition in engineering practice. The stability assessment module directly compares Δ with E to output a stability or instability risk signal. This allows for rapid response to system state changes and meets the real-time stability assessment requirements under complex operating conditions.

[0016] As an optimal technical means: the criterion generation module obtains the active power P injected by the new energy grid connection point, the reactive power Q injected by the new energy grid connection point, the Thevenin equivalent single-machine infinite voltage source amplitude E of the external power grid, the grid connection point voltage amplitude U, the line equivalent resistance R, and the line equivalent reactance X, through the formula:

[0017] Calculate the static voltage stability criterion value Δ.

[0018] The formula involves parameters such as the active power P and reactive power Q injected by the renewable energy grid connection point, the grid connection point voltage amplitude U, the line equivalent resistance R and reactance X, and the external grid's Thevenin equivalent voltage source amplitude E. These are all directly measurable or known parameters in the renewable energy grid-connected system, eliminating the need for complex models or indirect calculations. The calculation is performed using only basic algebraic operations, avoiding the complex calculations of continuous power flow iterations in traditional PV curve methods. This significantly simplifies the criterion generation process and improves computational efficiency. The formula directly integrates the line impedance characteristics (R, X), the renewable energy output characteristics (P, Q), and the node voltage state (U), clearly quantifying the direct relationship between these core parameters and the static voltage stability criterion Δ. This intuitively reflects the combined impact of line impedance, renewable energy power output, and grid connection point voltage on the system's static voltage stability, making the physical nature of the criterion easier to understand and analyze. In view of the fluctuating and intermittent characteristics of renewable energy output, when parameters such as P, Q or U change in real time with operating conditions, the criterion generation module can quickly recalculate Δ by updating the corresponding parameters in the formula, and promptly respond to the impact of renewable energy output fluctuations on the system stability state, ensuring that the static voltage stability criterion can reflect the current operating conditions of the system in real time, and enhancing its applicability in dynamic and complex scenarios.

[0019] The third technical solution of the present invention is: a computer device, which includes one or more processors and one or more memories, and the one or more memories store at least one program code. When the program code is executed by the one or more processors, it implements the aforementioned voltage stability analysis method for a new energy grid-connected system.

[0020] The fourth technical solution of the present invention is: a storage medium, in which at least one program code is stored, characterized in that when the program code is executed by a processor, the steps of the aforementioned voltage stability analysis method of a new energy grid-connected system are implemented.

[0021] Beneficial effects: 1. The Thevenin equivalent method simplifies complex external power grids into a single-machine infinite system. This allows accurate identification of voltage instability issues in renewable energy grid-connected systems for load and weak PQ power supply scenarios. 2. Directly solving the critical voltage amplitude based on the singular points of the Jacobian matrix avoids the iterative scanning process of the traditional PV curve method, greatly improving the calculation efficiency and realizing the rapid analytical calculation of the voltage criterion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the equivalent model of new energy grid connection considering resistance.

[0023] Figure 2 It is a flow chart of the present invention.

[0024] Figure 3 1 is a diagram of the simulation results obtained in an example of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings.

[0026] Example 1: like Figure 2 As shown, a voltage stability analysis method for a new energy grid-connected system includes the following steps: S1. Establish a new energy grid-connected system model Considering the integration of new energy systems with resistance into the power grid, a corresponding simplified model is established. Figure 1 As shown, the output power of the new energy side is ; The external grid side is the balance node, and the voltage is The impedance of this model is: (1) S2. Based on the equivalent model, establish the power flow equation, derive the Jacobian matrix, and determine the calculation formula of the system critical voltage amplitude by solving the singular point where the Jacobian matrix determinant is zero. The specific steps are as follows: S2.1 Establishing the tidal flow equation The load side node is the PQ node, and the corresponding power equation is: (2) Where, Active power generated by the new energy grid-connected system, is the reactive power generated by the system, is the voltage amplitude at the grid connection point, is the grid connection point voltage phase, is the resistance value of the line, is the reactance value of the line.

[0027] S2.2 Derivation of static voltage stability criterion The imaginary and real parts of formula (2) are written as (3) (4) Jacobian matrix: (5) (6) Let the determinant of (6) be 0 (7) The above formula shows that at the singular point of the Jacobian matrix, the resistance R cannot work alone, but the impedance mode and power mode / capacity work. Further at the critical point, there is (8) The critical voltage magnitude representing the singular point of the Jacobian matrix.

[0028] S3. Based on the critical voltage amplitude calculation formula and the power circle theory, derive the calculation formula for the static voltage stability criterion and calculate the static voltage stability criterion value Δ; Among them, the power circle is: (9) (10) Square (9) and (10) and add them together to get (11) Substituting (8) into (11), we get (12) New voltage stability criterion: (13) Note: The above derivation process is for load, weak PQ is the power source, that is, new energy is the power source in the weak grid, then , the stability condition is .

[0029] S4. Static voltage stability judgment Calculate the voltage stability criterion , to determine the static voltage stability, if , it indicates that the system static voltage is stable; if , it indicates that the system static voltage is unstable; When the voltage is less than 0.000, the system is in a critical static voltage stability state. This method replaces the consideration of the PV curve (nose curve) with the consideration of the power circle at the Jacobian matrix singular point. This avoids the complex calculation of the PV curve for continuous power flow and simplifies the determination of the system's static voltage stability.

[0030] The present invention will be further described below with reference to specific implementation examples. The impedance used in this example model is:

[0031] The voltage and phase of the corresponding balance node on the infinite grid side are , using the per-unit value .

[0032] Change the active power on the load side, so , t is time (seconds), observe the corresponding terminal voltage changes, the results are shown in Table 1.

[0033] Table 1 Results of the terminal voltage U obtained by changing the active power P

[0034] It can be seen that when other parameters remain unchanged, as the active output of the renewable energy grid-connected system increases, the system terminal voltage U gradually decreases until it collapses. In the case of label 2, the criterion ∆ is approximately close to the grid voltage , which can be used as a critical stability condition. When the criterion ∆ is greater than E, the output system static voltage is stable. When the criterion ∆ is less than E, the output system static voltage is unstable. Weak PQ is the power source, and the direction of the power flow of P and Q should be noted.

[0035] The mechanism of voltage collapse at the generator end: the output system's active power output continues to increase, leading to an increase in line current. The line reactive power loss is proportional to the square of the current, while the reactive power support of the renewable energy grid-connected system is insufficient, causing the generator end voltage to drop. This, in turn, requires a larger current to transmit the same active power, triggering a vicious cycle and eventually leading to voltage collapse. Figure 3 As shown in the figure, according to the technical solution's criterion logic: when voltage U (red) is less than 0.9E, the system is stable when Δ>E and unstable when Δ≤E. Considering the curve trend: 2 seconds ago, the active power output of the renewable energy grid-connected system was low, and voltage U was slightly higher than E (black), causing Δ (cyan) to approach E. 2 seconds later, the system was operating normally, and the active power output of the renewable energy grid-connected system continued to increase. At this point, Δ>E, indicating that the system meets the stability conditions and has not entered an unstable state. Although the grid connection point voltage U gradually decreased later, the increase in P exceeded the impact of the decrease in U (the dominant effect of the increase in P outweighed the weakening effect of the decrease in U), so the system remained stable. As P continued to increase, the line voltage loss (PR + QX) increased significantly, reducing the system voltage margin. Later, P continued to increase, and after 9 seconds, U further decreased to below 0.9E. At the same time, the growth of Δ slowed down. This requires vigilance against the approaching stability boundary (Δ=E), and proactive voltage regulation or power limiting measures should be implemented. After 11 seconds, Δ drops rapidly below E, and voltage U also drops rapidly, at which point voltage collapse occurs. In summary, during the observation period, the renewable energy grid-connected system established normal operation within 2 seconds. From 2 to 11 seconds, the system met the static voltage stability criterion (Δ>E) and remained stable. However, the grid connection point voltage continued to decline as active power increased, shrinking the voltage margin. Attention should be paid to stability risks with further power growth. After 11 seconds, the system no longer met the static voltage stability criterion (Δ≤E), and voltage collapse occurred.

[0036] Example 2: This embodiment provides a voltage stability analysis system for a new energy grid-connected system, which applies the aforementioned voltage stability analysis method for a new energy grid-connected system. The system includes: Equivalent modeling module: used to simplify the external power grid into a Thevenin equivalent single-machine infinite balance node, whose voltage amplitude is E and phase is 0; Critical voltage calculation module: used to derive the Jacobian matrix based on the power flow equation and determine the calculation formula of the system critical voltage amplitude by solving the singular points where the Jacobian matrix determinant is zero; Criteria generation module: used to derive the calculation formula of the static voltage stability criterion based on the critical voltage amplitude calculation formula and power circle theory, and calculate the static voltage stability criterion value Δ; Stability judgment module: used to compare Δ and E. If Δ>E, it outputs a stable signal; if Δ≤E, it outputs an instability risk signal.

[0037] Among them, the criterion generation module obtains the active power P injected by the new energy grid connection point, the reactive power Q injected by the new energy grid connection point, the Thevenin equivalent single-machine infinite voltage source amplitude E of the external power grid, the grid connection point voltage amplitude U, the line equivalent resistance R, and the line equivalent reactance X, through the formula:

[0038] Calculate the static voltage stability criterion value Δ.

[0039] It is understandable that the detailed functional implementation of each of the above modules can be found in the introduction of the aforementioned method embodiment, and no further details are given here.

[0040] Example 3 This embodiment provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the voltage stability analysis method for a new energy grid-connected system as described in any embodiment of the present invention is implemented.

[0041] Example 4 This embodiment provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the voltage stability analysis method for a new energy grid-connected system according to any embodiment of the present invention is implemented.

[0042] Those skilled in the art will appreciate that the various units and algorithm steps described in the embodiments disclosed in the present invention can be implemented by a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0043] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0044] In the several embodiments provided in this application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of this application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory; hereinafter referred to as: ROM), random access memory (Random Access Memory; hereinafter referred to as: RAM), magnetic disk or optical disk, and other media that can store program code.

[0045] The voltage stability analysis method, system, device and medium for a new energy grid-connected system shown above are specific embodiments of the present invention, which have embodied the substantial features and progress of the present invention. Based on actual usage needs and under the guidance of the present invention, equivalent modifications in shape, structure, etc. can be made to them, which are all within the scope of protection of this solution.

Claims

1. A voltage stability analysis method for a new energy grid-connected system, characterized by: The following steps are involved: 1) Construct an equivalent model of the new energy grid-connected system, and use Thevenin to equate the external power grid to a single-machine infinite balance node, with a voltage amplitude of E and a phase of 0; 2) Based on the equivalent model, a power flow equation is established, the Jacobian matrix is ​​derived, and the calculation formula for the system critical voltage amplitude is determined by solving the singular points where the Jacobian matrix determinant is zero; 3) Based on the critical voltage amplitude calculation formula and power circle theory, derive the calculation formula for the static voltage stability criterion and calculate the static voltage stability criterion value Δ; 4) Compare the static voltage stability criterion value Δ with the equilibrium node voltage amplitude E. If Δ E, determine that the system is in a stable state; if Δ E, determine that the system is in an unstable risk state.

2. The voltage stability analysis method for a new energy grid-connected system according to claim 1, characterized in that: In the equivalent model of step 1), the renewable energy grid-connected system outputs power P+jQ as a power source and is connected to the balancing node through an equivalent impedance Z=R+jX, where P is the active power output by the renewable energy grid-connected system, Q is the reactive power output by the renewable energy grid-connected system, R is the line resistance, and X is the line reactance. The port voltage amplitude of the renewable energy grid-connected system is U, and the phase is θ.

3. The voltage stability analysis method for a new energy grid-connected system according to claim 2, characterized in that: In step 2), the Jacobian matrix is ​​constructed by the partial derivatives of the active power P and reactive power Q in the power flow equation with respect to the phase angle θ and the voltage amplitude U.

4. The voltage stability analysis method for a new energy grid-connected system according to claim 3, characterized in that: Step 2) The critical voltage amplitude is calculated as follows: The square of the critical voltage amplitude is equal to the line impedance modulus and new energy output power modulus The product of .

5. The voltage stability analysis method for a new energy grid-connected system according to claim 4, characterized in that: In step 3), the calculation formula of the static voltage stability criterion value Δ is: 。 6. A voltage stability analysis system for a new energy grid-connected system, characterized in that: A voltage stability analysis method for a new energy grid-connected system according to any one of claims 1 to 5 is applied; the system comprises: Equivalent modeling module: used to simplify the external power grid into a Thevenin equivalent single-machine infinite balance node, whose voltage amplitude is E and phase is 0; Critical voltage calculation module: used to derive the Jacobian matrix based on the power flow equation and determine the calculation formula of the system critical voltage amplitude by solving the singular points where the Jacobian matrix determinant is zero; Criteria generation module: used to derive the calculation formula of the static voltage stability criterion based on the critical voltage amplitude calculation formula and power circle theory, and calculate the static voltage stability criterion value Δ; Stability judgment module: used to compare Δ and E. If Δ>E, it outputs a stable signal; if Δ≤E, it outputs an instability risk signal.

7. The voltage stability analysis system for a new energy grid-connected system according to claim 6, characterized in that: The criterion generation module obtains the active power P injected by the renewable energy grid connection point, the reactive power Q injected by the renewable energy grid connection point, the Thevenin equivalent single-machine infinite voltage source amplitude E of the external power grid, the grid connection point voltage amplitude U, the line equivalent resistance R, and the line equivalent reactance X, through the formula: Calculate the static voltage stability criterion value Δ.

8. A computer device, characterized in that: The device includes one or more processors and one or more memories, and at least one program code is stored in the one or more memories. When the program code is executed by the one or more processors, a voltage stability analysis method for a new energy grid-connected system as described in any one of claims 1 to 5 is implemented.

9. A storage medium storing at least one program code, characterized in that: When the program code is executed by a processor, the steps of the voltage stability analysis method of a new energy grid-connected system as claimed in any one of claims 1 to 5 are implemented.

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