An Adaptive Oscillation Suppression Method for New Energy Grid-Connected Systems with High-Inertia Energy Storage Synchronous Condensers

Abstract

This invention discloses an adaptive oscillation suppression method for a new energy grid-connected system with a high-inertia energy storage synchronous condenser. When subsynchronous oscillation occurs in the system, discrete Fourier transform analysis is performed at the grid connection point to determine the subsynchronous oscillation frequency. Based on the measured grid-side branch data and the characteristics of the series resonant circuit, the equivalent series resonant circuit of the system at the oscillation frequency is modeled and its parameters are identified. On this basis, an additional damping control device is connected, and an equivalent state-space model of the system is established. The final compensation phase of the additional damping control device is determined with the maximum damping ratio of the subsynchronous oscillation mode as the target. This invention can achieve adaptive and effective suppression of subsynchronous oscillations in new energy grid-connected systems under multiple oscillation scenarios, thereby better ensuring the safe and stable operation of the power grid.

Description

Technical Field

[0001] This invention relates to an adaptive oscillation suppression method for a new energy grid-connected system with a high-inertia energy storage synchronous condenser. It is applicable to new energy grid-connected systems with compensation equipment such as synchronous condensers. It can optimize the parameters of the additional damping control device for different oscillation scenarios, thereby achieving adaptive suppression of the system's subsynchronous oscillations. It belongs to the field of new energy power generation grid connection technology. Background Technology

[0002] With the large-scale and diversified integration of new energy power generation equipment into the AC power grid, the new power system faces multi-form oscillation problems and power system stability issues with vastly different phenomena. Therefore, in order to ensure that the system can effectively suppress subsynchronous oscillations under different oscillation conditions, it is necessary to establish an adaptive additional damping control system applicable to multiple oscillation scenarios and propose corresponding adaptive oscillation suppression methods.

[0003] Currently, scholars both domestically and internationally have conducted relevant research on adaptive additional damping control technology, as exemplified by the following published literature:

[0004] [1] MA, VSK and JM S. Adaptive Recurrent Neural Network-BasedADRC Supplementary Damping Controller for SSO Mitigation in Type-3 Wind PowerSystems[J]. IEEE Transactions on Power Delivery, 2025, 40(5): 2918-2930

[0005] [2] XUE T, ZHAO MX, KOCAR L, et al. Efficient Deep ReinforcementLearning-Based Supplementary Damping Control with a Coordinated RMS Training and EMT Testing Scheme[J]. IEEE Transactions on Power Delivery, 2025, 40(4):2300-2313.

[0006] Reference [1] proposes a model-free active disturbance rejection additional damping controller using an adaptive recurrent neural network. The adaptive recurrent neural network approximates the total disturbance caused by parameter uncertainty, wind speed variation and nonlinear dynamics in the wind power system. This additional damping control improves the limitations of traditional active disturbance rejection technology. Reference [2] proposes an adaptive additional damping control strategy based on deep reinforcement learning to address the problem that the traditional additional damping control has limited suppression effect in multiple oscillation scenarios. This overcomes the shortcomings of the traditional additional damping control in poor adaptability and limited suppression effect in multiple operating scenarios. However, the above references all use deep reinforcement learning or neural networks to adjust the parameters of the additional damping controller. In practical applications, the training cost is high and the actual implementation in engineering faces great difficulties. Therefore, from the perspective of the subsynchronous oscillation mechanism of the system, it is of great practical significance to propose an adaptive additional damping control method suitable for multiple oscillation scenarios. Summary of the Invention

[0007] To address the aforementioned shortcomings of existing technologies, the present invention aims to propose an adaptive oscillation suppression method for new energy grid-connected systems containing high-inertia energy storage synchronous condensers. This method is based on series resonance theory and state-space methods, combined with the system oscillation mode damping ratio parameter, to analyze the influence of the compensation phase of the additional damping control device on the oscillation mode. This allows for the determination of the optimal compensation phase of the adaptive additional damping control device under different oscillation scenarios, thereby better ensuring the safe and stable operation of the power grid.

[0008] The technical solution of this invention is implemented as follows:

[0009] An adaptive oscillation suppression method for a new energy grid-connected system with a high-inertia energy storage synchronous condenser is proposed, and the specific steps are as follows.

[0010] A1) For direct-drive wind power grid-connected systems with high-inertia energy storage synchronous condensers, the system is considered as a parallel connection of the direct-drive wind farm branch and the synchronous condenser branch before being connected to the grid-side branch. When the system experiences subsynchronous oscillation, a discrete Fourier transform analysis is performed at the grid connection point to determine the subsynchronous oscillation frequency f of the direct-drive wind power grid-connected system. osc Calculate the equivalent impedance of the power grid branch at the oscillation frequency using the following formula;

[0011]

[0012] In the formula, U g I g These are the effective values ​​of voltage and current obtained from the discrete Fourier transform analysis of the power grid branch, φ. u φ i These are the voltage phase angle and the current phase angle, respectively.

[0013] A2) The parallel connection of the direct-drive wind farm branch and the synchronous condenser branch is equivalent to the equivalent resistance R. wh With equivalent capacitance C wh The series connection establishes the oscillation frequency f. osc The equivalent series resonant circuit model of the system is shown below; the equivalent capacitance C is determined based on the series resonance theory using the following formula. wh The equivalent resistance R is determined based on the circuit time constant using the following formula. wh ;

[0014]

[0015]

[0016] In the formula, R g L g These are the equivalent resistance and equivalent inductance of the grid-side branch, respectively; ΔT is the time interval between two adjacent oscillation peaks of the output current of the direct-drive wind farm branch; I 1max I 2max These are two adjacent oscillation peak values ​​of the output current of the direct-drive wind farm branch;

[0017] A3) Connect an additional damping control device at the common grid connection point and form an additional damping branch. Construct the state space matrix A1 corresponding to the system under the additional damping control impedance characteristics. Solve for the damping ratio of the subsynchronous oscillation mode corresponding to the state space matrix A1. Without changing the impedance amplitude of the additional damping branch, iterate the compensation phase φ of the additional damping control device to determine the optimal impedance characteristic compensation phase φ1 corresponding to the maximum damping ratio.

[0018] A4) Construct the state space matrix A2 corresponding to the system under the additional damping control RC characteristics, and solve the damping ratio of the subsynchronous oscillation mode corresponding to the state space matrix A2; without changing the impedance amplitude of the additional damping branch, iterate the compensation phase φ of the additional damping control device to determine the optimal RC characteristic compensation phase φ2 corresponding to the maximum damping ratio.

[0019] A5) Construct the state space matrix A3 corresponding to the system under the pure resistance characteristic of additional damping control, and solve the damping ratio of the subsynchronous oscillation mode corresponding to the state space matrix A3; without changing the impedance amplitude of the additional damping branch, iterate the compensation phase φ of the additional damping control device to determine the optimal pure resistance characteristic compensation phase φ3 corresponding to the maximum damping ratio.

[0020] A6) Compare the damping ratios of the subsynchronous oscillation modes of the system when the compensation phases of the additional damping control device are φ1, φ2, and φ3; take the compensation phase corresponding to the maximum damping ratio as the final compensation phase φ of the additional damping control device. best This means achieving adaptive suppression of subsynchronous oscillations in the system.

[0021] In step A3), the state-space matrix A1 corresponding to the system under the additional damping control impedance characteristic is constructed according to the following formula.

[0022]

[0023] In the formula, R SDC L SDC These are the equivalent resistance and equivalent inductance of the additional damping branch, respectively.

[0024] In step A4), the state-space matrix A2 corresponding to the system under the additional damping control RC characteristics is constructed according to the following formula.

[0025]

[0026] In the formula, R SDC C SDC These are the equivalent resistance and equivalent capacitance of the additional damping branch, R. p =R SDC R wh / (R SDC +R wh ).

[0027] In step A5), the state-space matrix A3 corresponding to the system under the pure resistive characteristic with additional damping control is constructed according to the following formula.

[0028]

[0029] In the formula, R SDC The equivalent resistance of the additional damping branch.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention establishes an equivalent series resonant circuit at the system oscillation frequency based on resonance theory. Building upon this, and combining the state-space method, a method for optimizing the compensation phase parameters of an adaptive additional damping control device is proposed from the perspective of the oscillation mode damping ratio. The adaptive oscillation suppression method proposed in this invention has a clear theory and well-defined concepts, eliminating the need for neural network algorithms to optimize the parameters of the additional damping control device, thus better ensuring the safe and stable operation of the power grid. Attached Figure Description

[0032] Figure 1 This is the equivalent resonant circuit diagram of a new energy grid-connected system containing a high-inertia energy storage synchronous condenser.

[0033] Figure 2 Time-domain simulation waveforms before and after applying this method to suppress subsynchronous oscillations induced by reduced wind speed.

[0034] Figure 3Time-domain simulation waveforms before and after applying this method to suppress subsynchronous oscillations induced by reduced grid strength. Detailed Implementation

[0035] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0036] The present invention proposes an adaptive oscillation suppression method for new energy grid-connected systems with high-inertia energy storage synchronous condensers, which can adaptively suppress subsynchronous oscillations in different scenarios of new energy grid-connected systems. Figure 1 This is the equivalent resonant circuit diagram of a high-inertia energy storage synchronous condenser, an additional damping control device, and a direct-drive wind power grid-connected system. Figure 2 The time-domain simulation waveforms of each unit in the system before and after adopting the suppression strategy of this method are shown when the wind speed decreases at 3s in the direct-drive wind farm to induce subsynchronous oscillation. Figure 3 The time-domain simulation waveforms of each unit in the system before and after applying the suppression strategy of this method are shown when the power grid intensity decreases at 10s, inducing subsynchronous oscillations in the system.

[0037] The specific implementation steps of this invention are as follows:

[0038] A1) For direct-drive wind power grid-connected systems with high-inertia energy storage synchronous condensers, the system is considered as a parallel connection of the direct-drive wind farm branch and the synchronous condenser branch before being connected to the grid-side branch. When the system experiences subsynchronous oscillation, a discrete Fourier transform (DFT) analysis is performed at the grid connection point to determine the subsynchronous oscillation frequency f of the direct-drive wind power grid-connected system. osc Calculate the equivalent impedance of the power grid branch at the oscillation frequency using the following formula;

[0039]

[0040] In the formula, U g I g These are the effective values ​​of voltage and current obtained from the discrete Fourier transform analysis of the power grid branch, φ. u φ i These are the voltage phase angle and the current phase angle, respectively.

[0041] A2) The parallel connection of the direct-drive wind farm branch and the synchronous condenser branch is equivalent to the equivalent resistance R. wh With equivalent capacitance C wh The series connection establishes the oscillation frequency f. osc The equivalent series resonant circuit model of the system is shown below; the equivalent capacitance C is determined based on the series resonance theory using the following formula. wh The equivalent resistance R is determined based on the circuit time constant using the following formula. wh ;

[0042]

[0043]

[0044] In the formula, R g L g These are the equivalent resistance and equivalent inductance of the grid-side branch, respectively; ΔT is the time interval between two adjacent oscillation peaks of the output current of the direct-drive wind farm branch; I 1max I 2max These are two adjacent oscillation peaks of the output current of the direct-drive wind farm branch.

[0045] A3) Connect an additional damping control device at the common grid connection point and form an additional damping branch. Construct the state space matrix A1 corresponding to the system under the additional damping control impedance characteristics according to the following formula, and solve the damping ratio of the subsynchronous oscillation mode corresponding to the state space matrix A1. Without changing the impedance amplitude of the additional damping branch, iterate the compensation phase φ of the additional damping control device to determine the optimal impedance characteristic compensation phase φ1 corresponding to the maximum damping ratio.

[0046]

[0047] In the formula, R SDC L SDC These are the equivalent resistance and equivalent inductance of the additional damping branch, respectively.

[0048] A4) Construct the state space matrix A2 corresponding to the system under the additional damping control RC characteristics according to the following formula, and solve the damping ratio of the subsynchronous oscillation mode corresponding to the state space matrix A2; without changing the impedance amplitude of the additional damping branch, iterate the compensation phase φ of the additional damping control device to determine the optimal RC characteristic compensation phase φ2 corresponding to the maximum damping ratio.

[0049]

[0050] In the formula, C SDC R is the equivalent capacitance of the additional damping branch. p =R SDC R wh / (R SDC + R wh ).

[0051] A5) Construct the state space matrix A3 corresponding to the system under the pure resistance characteristic of additional damping control according to the following formula, and solve the damping ratio of the subsynchronous oscillation mode corresponding to the state space matrix A3; without changing the impedance amplitude of the additional damping branch, iterate the compensation phase φ of the additional damping control device to determine the optimal pure resistance characteristic compensation phase φ3 corresponding to the maximum damping ratio.

[0052]

[0053] A6) Compare the damping ratios of the subsynchronous oscillation modes of the system when the compensation phases of the additional damping control device are φ1, φ2, and φ3; take the compensation phase corresponding to the maximum damping ratio as the final compensation phase φ of the additional damping control device. best This means achieving adaptive suppression of subsynchronous oscillations in the system.

[0054] Description of the effects of this invention:

[0055] Figure 2 and Figure 3 Time-domain simulation results are presented before and after applying the suppression strategy described in this paper when subsynchronous oscillations of the system are induced by reduced wind speed and reduced grid strength. DFT analysis shows that... Figure 2 , Figure 3 The system's subsynchronous oscillation frequencies are 42Hz and 30Hz, respectively. According to this method, the following can be established: Figure 1 The equivalent series resonant circuit model and state-space model of the system shown are used to calculate the optimal compensation phases of the additional damping control device as 113.4° and 49.3° respectively, with the goal of maximizing the damping ratio of the oscillation mode. After the additional damping control device is put into use ( Figure 2 It was put into use at 8 seconds. Figure 3 (When put into use at 13s), the subsynchronous oscillation of the system was effectively suppressed. It is evident that the method proposed in this invention can achieve adaptive suppression of subsynchronous oscillations in different oscillation scenarios.

[0056] Finally, it should be noted that the above examples of the present invention are merely illustrative and not intended to limit the implementation of the invention. Although the applicant has described the present invention in detail with reference to preferred embodiments, those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An adaptive oscillation suppression method for a new energy grid-connected system containing a high-inertia energy storage synchronous condenser, characterized in that: The specific steps are as follows: A1) For direct-drive wind power grid-connected systems with high-inertia energy storage synchronous condensers, the system is considered as a parallel connection of the direct-drive wind farm branch and the synchronous condenser branch before being connected to the grid-side branch. When the system experiences subsynchronous oscillation, a discrete Fourier transform analysis is performed at the grid connection point to determine the subsynchronous oscillation frequency f of the direct-drive wind power grid-connected system. osc Calculate the equivalent impedance of the power grid branch at the oscillation frequency using the following formula; In the formula, U g I g These are the effective values ​​of voltage and current obtained from the discrete Fourier transform analysis of the power grid branch, φ. u φ i These are the voltage phase angle and the current phase angle, respectively. A2) The parallel connection of the direct-drive wind farm branch and the synchronous condenser branch is equivalent to the equivalent resistance R. wh With equivalent capacitance C wh Serial series connection, to establish oscillation frequency f osc The equivalent series resonant circuit model of the system is shown below; the equivalent capacitance C is determined based on the series resonance theory using the following formula. wh The equivalent resistance R is determined based on the circuit time constant using the following formula. wh ; In the formula, R g L g These are the equivalent resistance and equivalent inductance of the grid-side branch, respectively; ΔT is the time interval between two adjacent oscillation peaks of the output current of the direct-drive wind farm branch; I 1max I 2max These are two adjacent oscillation peak values ​​of the output current of the direct-drive wind farm branch; A3) Connect an additional damping control device at the common grid connection point and form an additional damping branch. Construct the state space matrix A1 corresponding to the system under the additional damping control impedance characteristics. Solve for the damping ratio of the subsynchronous oscillation mode corresponding to the state space matrix A1. Without changing the impedance amplitude of the additional damping branch, iterate the compensation phase φ of the additional damping control device to determine the optimal impedance characteristic compensation phase φ1 corresponding to the maximum damping ratio. A4) Construct the state space matrix A2 corresponding to the system under the additional damping control RC characteristics, and solve the damping ratio of the subsynchronous oscillation mode corresponding to the state space matrix A2; without changing the impedance amplitude of the additional damping branch, iterate the compensation phase φ of the additional damping control device to determine the optimal RC characteristic compensation phase φ2 corresponding to the maximum damping ratio. A5) Construct the state space matrix A3 corresponding to the system under the pure resistance characteristic of additional damping control, and solve the damping ratio of the subsynchronous oscillation mode corresponding to the state space matrix A3; without changing the impedance amplitude of the additional damping branch, iterate the compensation phase φ of the additional damping control device to determine the optimal pure resistance characteristic compensation phase φ3 corresponding to the maximum damping ratio. A6) Compare the damping ratios of the subsynchronous oscillation modes of the system when the compensation phases of the additional damping control device are φ1, φ2, and φ3; take the compensation phase corresponding to the maximum damping ratio as the final compensation phase φ of the additional damping control device. best This means achieving adaptive suppression of subsynchronous oscillations in the system.

2. The adaptive oscillation suppression method for a new energy grid-connected system with a high-inertia energy storage synchronous condenser according to claim 1, characterized in that: In step A3), the state-space matrix A1 corresponding to the system under the additional damping control impedance characteristic is constructed according to the following formula. In the formula, R SDC L SDC These are the equivalent resistance and equivalent inductance of the additional damping branch, respectively.

3. The adaptive oscillation suppression method for a new energy grid-connected system with a high-inertia energy storage synchronous condenser according to claim 1, characterized in that: In step A4), the state-space matrix A2 corresponding to the system under the additional damping control RC characteristics is constructed according to the following formula. In the formula, R SDC C SDC These are the equivalent resistance and equivalent capacitance of the additional damping branch, R. p =R SDC R wh / (R SDC + R wh ).

4. The adaptive oscillation suppression method for a new energy grid-connected system with a high-inertia energy storage synchronous condenser according to claim 1, characterized in that: In step A5), the state-space matrix A3 corresponding to the system under the pure resistive characteristic with additional damping control is constructed according to the following formula. In the formula, R SDC The equivalent resistance of the additional damping branch.

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