Variable-weight fusion control method based on fusion of voltage source and current source dual sources

Abstract

The application discloses a variable-weighting fusion control method based on voltage source and current source double-source fusion, and belongs to the electrical engineering field.The method is realized through the following steps: firstly, a short-circuit ratio is calculated based on grid impedance to obtain a first initial weighting fusion factor of current source type control; secondly, an inertia ratio is calculated based on grid inertia support demand to obtain a second initial weighting fusion factor; then, local sensitivity weights are obtained by derivation of the two initial factors to obtain an initial double-source fusion factor which is self-adaptively adjusted according to grid state; finally, the initial double-source fusion factor is optimized and corrected in combination with node active regulation capacity and operation economy, safety and other strategy factors.The application can self-adaptively adjust the control fusion proportion of voltage source and current source, realizes smooth transition and stable operation of grid-connected inverters under different grid conditions, and improves the stability and self-adaptability under complex disturbance scenarios.

Description

Technical Field

[0001] This invention relates to the field of electrical engineering, and in particular to a variable weighted fusion control method based on the fusion of voltage and current sources. Background Technology

[0002] With the rapid increase in installed capacity of new energy sources, the proportion of power electronic equipment in the power system has increased significantly, and the inertia and damping provided by traditional synchronous machines have been significantly weakened. Current source inverters that widely adopt phase-locked loop synchronization are highly dependent on grid voltage and frequency in high-penetration operating scenarios. When the grid impedance is large or voltage disturbances are frequent, their control systems are more susceptible to stability problems such as synchronization failure, power oscillation, and wide-band oscillation, resulting in insufficient grid support capabilities.

[0003] To adapt to new system characteristics, voltage source inverters, with their voltage formation and inertia simulation capabilities, are considered an important direction for enhancing the support capacity of new energy power sources. However, voltage source control essentially simulates synchronous machine behavior, with its frequency and voltage dominated by the inverter's internal components. This makes them prone to problems such as power angle deviation and enhanced dynamic interaction in environments with high short-circuit ratios and strong external power grids, potentially even causing the inverter's operating point to deviate from its stable range. Therefore, voltage source inverters exhibit significant performance differences under different grid conditions, making it difficult to guarantee reliability and universality. Consequently, how to coordinate and leverage the advantages of both current source and voltage source control under different grid conditions has become a key research direction.

[0004] 1) Chinese patent document CN 117713200 A, published on March 15, 2024, entitled "A Method and System for Suppressing Wideband Oscillations in Grid-Connected Inverters under Weak Grids," discloses a method and system for suppressing wideband oscillations in grid-connected inverters under weak grids. It mainly addresses the problem that traditional single-synchronous reference frame phase-locked loops (SRF-PLLs) suffer from frequency coupling effects due to asymmetrical control structures and are prone to wideband oscillations due to impedance coupling with weak grids. The proposed solution uses a symmetrical phase-locked loop (SPLL) to eliminate frequency coupling and adds a dual-axis voltage feedforward compensation stage, aiming to improve the operational stability of grid-connected inverters under weak or even extremely weak grids and reduce the risk of subsynchronous / supersynchronous oscillations. However, this scheme still has significant shortcomings in its ability to support the grid. It can only effectively address stability issues in scenarios where the Short-Circuit Ratio (SCR) is greater than 2. When the SCR decreases to 1.7, the system still exhibits harmonic oscillations with a total harmonic distortion rate as high as 22.25%, failing to provide continuous and stable voltage and frequency support for extremely weak grids. Furthermore, this scheme relies on precise iterative calculation of the grid phase dq-axis components and matching of voltage feedforward compensation parameters. Under complex operating conditions such as deep grid voltage drops and multiple inverters in parallel, its reactive power rapid response and collaborative support capabilities are insufficient. Moreover, real-time sampling delay and parameter drift further weaken its grid support reliability.

[0005] 2) Chinese patent document CN 119051134 A, published on November 29, 2024, entitled "A Method for Suppressing Strong Grid Instability of Grid-Type Converters Based on Additional Stabilizers", discloses a targeted suppression scheme for strong grid instability of grid-type converters. It mainly addresses the industry pain point that grid-type converters are prone to instability under high grid intensity conditions. It proposes a control strategy of "additional stabilizer + frequency signal compensation" in order to maintain stable operation under strong grid conditions by offsetting the negative damping of the terminal voltage link and optimizing the system damping characteristics. However, existing grid-connected inverters have significant stability shortcomings in strong grid environments. Their terminal voltage stage introduces negative damping characteristics, which counteracts the system's own positive damping, resulting in a positive root distribution of the system's characteristic roots and causing grid-connected system oscillations and divergence. Furthermore, when the grid reactance drops from 0.4 pu to 0.25 pu (i.e., the grid intensity increases), the inverter's active power will exhibit continuous oscillations and instability, unable to autonomously recover to a steady state. At the same time, traditional control strategies do not compensate for the phase lag problem under strong grid conditions, resulting in extremely low critical stability margins for the grid-connected system under high short-circuit ratio strong grid conditions. This makes it highly susceptible to instability triggered by even a small increase in grid intensity, seriously threatening the safety of the grid-connected system.

[0006] To simultaneously leverage the advantages of current-source and voltage-source inverters in different operating scenarios, integrated control strategies have gradually become a research hotspot. This method achieves proportional switching between two control modes based on grid conditions, balancing rapid power response in strong grid scenarios with stable support capabilities in weak grid scenarios. However, existing integrated strategies often rely on single-indicator adjustments or use fixed-weight switching, failing to fully reflect the multi-dimensional state characteristics of the grid. Furthermore, they lack mechanisms for coordinating the joint adjustment of multiple inverters at the plant level, easily leading to control mode oscillations or overall response imbalances.

[0007] 1) Chinese patent document CN 202510804696 A, published on June 17, 2025, entitled "An Adaptive Adjustment Method and System for Inverter Grid-Following and Grid-Building Control Modes," discloses an adaptive adjustment method and system for inverter grid-following and grid-building control modes. It primarily addresses the problem that traditional inverter control relies on fixed parameters and struggles to adapt to grid disturbances across multiple time scales. The proposed method constructs a multi-scale fusion deep evaluation model, training it with massive amounts of historical grid state parameter data to output grid state evaluation indicators, thereby achieving adaptive selection of control modes and parameter optimization to improve the dynamic stability and disturbance response capability of the power system. However, the training and effective operation of the model heavily rely on massive amounts of high-quality historical grid state parameter data and corresponding state evaluation indicators. In actual engineering, data gaps, data noise interference, and scarcity of extreme operating condition data are common. Furthermore, training data often fails to cover all complex disturbance scenarios, leading to model overfitting, insufficient generalization ability under unseen conditions, and potentially exceeding the set threshold for state evaluation indicator prediction errors, thus affecting the accuracy of control decisions.

[0008] 2) Chinese patent document CN 202510555604 A, published on April 29, 2025, entitled "Switching Method, Device, Equipment, Medium, and Product for Grid-Following and Grid-Building Control," discloses a method, device, equipment, medium, and product for switching between grid-following and grid-building control. It primarily addresses the problem of unstable operation of a single control mode in regional power grids under strong, weak, and isolated grid scenarios. The invention proposes to automatically switch between grid-following and grid-building control modes by detecting the operating status of substation busbars and determining grid strength based on the effective short-circuit ratio, aiming to ensure the safe and stable operation of DC projects and the power grid system. However, the preset effective short-circuit ratio threshold is set to a fixed value, without providing a mechanism for dynamic adjustment based on actual operating conditions such as grid topology, load characteristics, and renewable energy penetration. Furthermore, the grid's adaptation threshold for control modes varies significantly under different voltage levels and operating scenarios. A fixed threshold can easily lead to premature or delayed switching of control modes, affecting the flexibility and stability of grid operation.

[0009] 3) The paper "Adaptive Hybrid Grid-Forming and Grid-Following Control of IBRs With Enhanced Small-Signal Stability Under Varying SCRs" published in IEEE Transactions on Power Electronics, Volume 39, Issue 6 in 2024, proposed an adaptive hybrid grid-forming and grid-following inverter control strategy. By integrating phase-locked loop (PLL) and power-based synchronization (PBS) modules, and drawing on the hysteresis loop principle, the ratio of grid-following / grid-following characteristics is adaptively adjusted based on the short-circuit ratio, thereby achieving small-signal stable operation of inverter power supplies in a wide range of grid conditions, from extremely weak grids (SCR=1) to rigid grids (SCR=50). However, the real-time calculation of the hysteresis loop related proportional adjustment formula is computationally complex. In actual deployment, it needs to rely on a pre-set lookup table, making it difficult to respond quickly to dynamic changes in grid strength. At the same time, the phase angle coupling relationship between PLL and PBS in the hybrid synchronization link does not fully consider extreme grid fluctuation scenarios, which may cause instantaneous disturbances in voltage and current during the transition process. Moreover, in a strong grid environment, after the grid-following characteristics are saturated, this strategy is not adaptable to grid impedance changes and is prone to short-term dynamic response lag.

[0010] 4) The paper "Adaptive Grid-Connection Fusion Control of Converters and Mechanism Analysis for Improving Oscillation Stability," published in the 2024 issue of the *Proceedings of the Chinese Society for Electrical Engineering* (Vol. 45, No. 15), proposes an adaptive grid-connection fusion control strategy based on the short-circuit ratio (SCR). By integrating the characteristics of phase-locked loops and power synchronization control, it dynamically adjusts the grid-connection and grid-connection coefficients, enabling the converter to exhibit good oscillation stability in a wide range of grids where 1 ≤ SCR ≤ 50. However, this strategy only uses SCR as the sole adjustment criterion, without considering requirements such as system inertia ratio. The fusion coefficient adjustment does not fully consider both steady-state stability and transient response, the weight allocation does not incorporate local sensitivity analysis, and its integration compatibility with existing inverter control systems needs further optimization.

[0011] 5) The paper "Stability Control for Grid-Connected Inverters Based on Hybrid-Mode of Grid-Following and Grid-Forming" published in IEEE Transactions on Industrial Electronics, Volume 71, Issue 9 in 2024, proposed a hybrid mode control strategy based on the weighting of modulation signals of grid-following and grid-forming modes. It removed the phase-locked loop of the grid-following mode and adopted the output angle of the droop control loop of the grid-forming mode as the transformation angle. By fixing the optimal weighting factor (n=0.5), it integrated the characteristics of the two modes, which improved the small-signal stability of the grid-connected inverter under large fluctuations in short-circuit ratio. However, this strategy has obvious shortcomings: it only focuses on the single indicator SCR and does not consider the frequency support requirements such as system inertia ratio; the weighting factor is a fixed value and cannot be continuously and dynamically adjusted according to the grid operating conditions; it adopts a simple fixed weighting method and does not combine local sensitivity analysis to reflect the actual impact of the indicator; it is difficult to achieve the coordination of steady-state stability and transient fast response, and its flexible integration and adaptability with the existing inverter control system needs to be optimized.

[0012] 6) Chinese patent document CN 116683528 A, authorized on October 27, 2023, entitled "Integrated Control Method for Grid-Connected Inverters Based on Time-Sharing of Voltage Source and Current Source", discloses an integrated control method for grid-connected inverters based on time-sharing of voltage source and current source. It mainly addresses the problem that it is difficult to operate stably in a single voltage source or current source mode under large fluctuations in short-circuit ratio (SCR). It proposes to divide the control process into N+M control cycles and realize the time-sharing operation of the two modes through counting switching. It integrates the characteristics of the two to ensure the stable operation of the grid-connected inverter without the need for SCR detection and frequent mode switching. However, this method uses a fixed voltage / current source mode with a fixed operating cycle, relies solely on time-sharing rather than dynamic fusion matching, and does not introduce frequency support-related indicators such as system inertia ratio, thus failing to achieve coordinated perception of grid impedance characteristics and frequency support requirements. The fixed fusion cycle, lacking a continuous dynamic adjustment mechanism, makes it difficult to fully balance steady-state stability and transient rapid response capabilities. Furthermore, the absence of a fusion factor based on local sensitivity analysis prevents accurate reflection of the actual impact of different grid indicators on system stability. Fixed-cycle switching may lead to insufficient control smoothness, and the dynamic adaptation flexibility with existing grid-connected inverter control systems needs further improvement.

[0013] In summary, the existing technology has the following problems: 1) In existing technologies, current-source inverters generally rely on phase-locked loops (PLLs) for synchronization. When the grid impedance increases, voltage disturbances become more frequent, or the short-circuit ratio decreases, the PLL is prone to phase drift, frequency coupling, and loss of synchronization, leading to instability phenomena such as wideband oscillations and synchronization failures. In contrast, although voltage-source inverters have voltage forming capabilities and offer better performance under weak grid conditions, their dynamic interaction may be enhanced under strong grid conditions due to the introduction of negative damping in the terminal voltage link, potentially even inducing power angle deviation and power oscillations. Therefore, a single operating mode cannot simultaneously ensure universal adaptability to both strong and weak grids.

[0014] 2) Existing integrated control methods switch control modes by setting a fixed short-circuit ratio threshold or based on a single indicator. However, the actual operating state of the power grid is affected by multiple factors such as grid impedance, inertia level, topology, and renewable energy penetration rate, exhibiting significant time-varying and multi-dimensional characteristics. Fixed thresholds cannot adaptively adjust with changes in operating conditions, easily leading to premature or delayed control mode switching. Furthermore, adjustment based on a single indicator (such as short-circuit ratio SCR) is insufficient to characterize the grid's inertia requirements, damping requirements, and safety margins, resulting in inaccurate integrated ratio settings and even mode oscillations or insufficient support capabilities.

[0015] 3) Existing strategies mostly target the independent adjustment of control modes for a single inverter, lacking a site-wide collaborative mechanism. In scenarios where multiple inverters operate in parallel, each inverter typically relies on its locally measured short-circuit ratio or inertia level for mode switching, easily leading to overall behavioral imbalance. Furthermore, without coordination constraints, some inverters may passively bear higher voltage support or inertia response pressure, resulting in uneven distribution of site-wide support capabilities and reduced overall system stability and reliability. Current technologies have not proposed an effective mechanism to rationally allocate the voltage / current source ratio within the site and achieve smooth collaborative adjustment of the fusion factor for multiple inverters, thus making it difficult to guarantee the continuous stability of the short-circuit ratio and inertia level at the system level. The core idea of ​​traditional multi-model control methods is model switching, i.e., activating a specific sub-model for control under different states. However, different control models cannot be effective simultaneously or superimposed and merged at the same time, making it difficult to simultaneously leverage the advantages of multiple models. Summary of the Invention

[0016] The technical problem this invention aims to solve is to overcome the insufficient adaptability of existing grid-connected inverter control methods under different grid strength conditions. With the increasing penetration rate of new energy sources, the grid short-circuit ratio and equivalent inertia exhibit dynamic changes. Traditional single voltage or current source control modes struggle to simultaneously ensure stability and support capability under both strong and weak grid conditions. Existing fixed-weight or simple-switching fusion control strategies also fail to reflect the multi-dimensional state characteristics of the grid, easily leading to control ratio imbalances or operational instability.

[0017] To overcome this technical bottleneck, this invention proposes a control method based on the weighted fusion of voltage source and current source dual-source converters. By comprehensively considering the changes in grid impedance and the inertia support requirements, the fusion ratio of voltage source and current source control is adaptively adjusted, and further optimized and corrected by combining the active power regulation capability of nodes and operating strategy factors, thereby achieving smooth transition and stable operation of the grid-connected inverter under different grid conditions.

[0018] The technical solution of the present invention is as follows: A variable weighted fusion control method based on the fusion of voltage and current sources is disclosed. The control method involves a circuit including an inverter system, a line inductor, and a three-phase power grid. The inverter system includes multiple inverters, each with its output connected to a line inductor via a node. The other end of the line inductor is connected to the three-phase power grid. The fusion of voltage and current sources refers to the real-time adjustment of the weighting ratio of the voltage and current sources based on changes in grid impedance and the inverter system's inertia requirements. The method includes the following steps: Step 1: Calculate the short-circuit ratio (SCR) of the power grid based on the grid impedance, and adjust the SCR according to the given short-circuit ratio sensitivity coefficient. The initial proportion of current source control in dual-source fusion is determined, and the first initial weighted fusion factor is obtained. ; Step 2: Calculate the grid inertia ratio based on the grid inertia support requirements. And based on the inertia ratio And a given inertia ratio sensitivity adjustment coefficient Determine the initial ratio of the current source control to meet the inertia support requirements, and obtain the second initial weighted fusion factor. ; Step 3: Taking into account the changes in grid impedance and the inertia support requirements, perform dual-source fusion control on voltage source type and current source type to obtain the initial dual-source fusion factor C of voltage source type control and current source type control; Step 4: Denote any one of the inverters in the inverter system as an inverter. Given the active power adjustment factor and the strategy factor, and optimizing the initial dual-source fusion factor C, the dual-source fusion factor is obtained. This dual-source fusion factor For adaptive adjustment of inverter The fusion ratio of voltage and current sources, and the fusion factor of the two sources. Corresponding to inverter The proportion of current source integration, inverter The integration ratio of voltage sources is .

[0019] Preferably, the formula for calculating the short-circuit ratio (SCR) in step 1 is: ; in, This is a reference value for the base power. The equivalent impedance of the power grid. , The equivalent resistance of the power grid. The virtual part, For the equivalent inductive reactance of the power grid; Equivalent impedance of the power grid amplitude, ; First initial weighted fusion factor The expression is: ; in, It is a natural constant. This is the short-circuit ratio sensitivity adjustment coefficient. The current short-circuit ratio of the power grid, The minimum short-circuit ratio threshold required for system stability.

[0020] Preferably, the inertia ratio in step 2 The formula for calculation is: ; in, For the system's equivalent inertia, The system requires inertia; Second initial weighted fusion factor The expression is: ; in, It is a natural constant. This is the inertia ratio sensitivity adjustment coefficient. The current inertia ratio is the power grid inertia ratio. The minimum equivalent inertia threshold required for system stability.

[0021] Preferably, the implementation process of step 3 is as follows: Step 3.1, based on the first initial weighted fusion factor and short-circuit ratio sensitivity adjustment coefficient The local sensitivity weights in the short-circuit ratio direction are obtained and denoted as the short-circuit ratio weighting factor. According to the second initial weighted fusion factor Inertia-to-sensitivity adjustment coefficient The local sensitivity weights in the inertia direction are obtained and denoted as the inertia ratio weighting factor. Short-circuit ratio weighting factor Weighting factor for inertia The expression is as follows: ; ; Step 3.2, using the short-circuit ratio weighting factor Weighting factor for inertia For the weighting coefficients, the first initial weighted fusion factor With the second initial weighted fusion factor After performing a weighted summation, the initial dual-source fusion factor C for voltage source control and current source control is obtained, and its expression is: ; The initial dual-source fusion factor C satisfies the adaptive adjustment requirements based on grid impedance and inertia state.

[0022] Preferably, step 4 is implemented as follows: Inverter The common coupling node is denoted as the power grid node. According to the power grid nodes The active power regulation capability, given the active power regulation factor Active regulatory factor For inverter The normalized coefficient for the active power regulation capability provided under current operating conditions ranges from 0 to 1. A stronger active power regulation capability indicates a higher regulation capability. The closer to 1; Given strategy factors , For integrated nodes The economic cost and safety correction coefficients; According to the formula The dual-source fusion factor was obtained. .

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention introduces the grid short-circuit ratio and system inertia ratio as the adjustment basis for dual-source fusion matching, realizing the collaborative perception and unified modeling of grid impedance characteristics and frequency support requirements. It overcomes the problem that existing fusion control methods are not adaptable enough in weak grid or low inertia scenarios because they only adjust based on a single grid index. It significantly improves the comprehensive adaptability of grid-connected inverters to complex grid operating conditions.

[0024] 2. The dual-source variable weighted fusion factor constructed in this invention can continuously change with the grid impedance and inertia state, maintain a relatively stable fusion ratio under the steady-state operation of the grid, and achieve rapid adaptive adjustment when the grid is disturbed or the operating state changes abruptly, thereby taking into account both steady-state operation stability and transient power support performance within the same control framework.

[0025] 3. This invention constructs a weighted mechanism based on the local sensitivity of the fusion factor to the short-circuit ratio parameter and inertia parameter. Compared with the traditional fixed weight or simple arithmetic average method, it can more accurately reflect the actual impact of different power grid parameter changes on system stability and dynamic response, and improve the pertinence and effectiveness of fusion ratio adjustment.

[0026] 4. Under normal operating conditions, the present invention maintains an approximately constant dual-source fusion ratio, effectively suppressing control oscillations and system coupling instability caused by frequent parameter adjustments; at the same time, when the grid impedance or inertia changes abnormally, the fusion factor can quickly respond to the grid demand, thereby improving the smoothness and stability margin of the system operation process.

[0027] 5. The dual-source variable weighted fusion control method proposed in this invention has a clear control structure and a well-defined implementation path. It can be integrated into the existing control system without changing the main circuit topology of the grid-connected inverter, and has good engineering feasibility. It is easy to apply and promote directly in existing new energy grid-connected inverter systems.

[0028] 6. This invention achieves a smooth transition between voltage source control and current source control through a continuously constructed fusion factor, effectively avoiding control abrupt changes, state jumps and transient impacts that are prone to occur during the switching of traditional control modes, thereby expanding the stable operating range of the grid-connected inverter in a wide short-circuit ratio and wide inertia range.

[0029] 7. This invention introduces a strategy factor during the optimization process of the fusion factor, incorporating economic costs and system security constraints into a unified adjustment framework. Without adding extra hardware or changing the main circuit structure, it reduces unnecessary control adjustments and energy losses, lowers system upgrade and operation and maintenance costs, and improves the full life cycle economy of the grid-connected inverter control system.

[0030] 8. This invention is applicable to grid operation scenarios with high penetration of new energy sources. By coordinating the perception of grid short-circuit ratio and system inertia ratio and adaptively adjusting the dual-source fusion control ratio, it enhances the operational robustness of new energy grid-connected inverters under different grid conditions, reduces the risk of power oscillation and grid instability caused by grid parameter fluctuations, and helps improve the power system's ability to accept new energy sources and its overall operational stability. Attached Figure Description

[0031] Figure 1This is a schematic diagram of the control structure of a grid-connected inverter based on dual-source fusion control.

[0032] Figure 2 The flowchart shows a variable weighted control method based on the fusion control of voltage and current sources.

[0033] Figure 3 This is a schematic diagram illustrating the voltage support effect of the control method of the present invention under grid voltage disturbance conditions.

[0034] Figure 4 The waveforms of the three-phase voltage and three-phase current of the power grid with a wide range of power grid impedance are obtained by the variable weighted fusion control method based on the dual-source fusion of voltage source and current source proposed in this invention. Detailed Implementation

[0035] The technical solution of the present invention will now be clearly and completely described in conjunction with the accompanying drawings.

[0036] Figure 1 This is a schematic diagram of the control structure of a grid-connected inverter based on dual-source fusion control. Figure 1 The circuit involved in the control method of the present invention is also given, including an inverter system, a line inductor and a three-phase power grid. The inverter system includes multiple inverters, the output terminals of which are respectively connected to the line inductor through their respective nodes, and the other end of the line inductor is connected to the three-phase power grid.

[0037] In addition, from Figure 1 As can be seen, the inverter includes DC power supplies connected in series. Inverter bridge and LCL filter, wherein the LCL filter includes bridge arm side inductors. Filter capacitor Equivalent resistance and grid-side inductor . Figure 1 middle, For line inductance, For power grid nodes .

[0038] exist Figure 1 In the control structure, the current source controls the generated modulation voltage. Modulated voltage generated by voltage source control After fusion factor and After weighting and superimposing, the final debugging reference signal for the inverter is generated.

[0039] Figure 2This is a flowchart of a variable weighted control method based on the fusion control of voltage and current sources. As shown in the diagram, this invention determines the components of the fusion weighting factor through two parallel paths: on the one hand, the short-circuit ratio is calculated based on the grid impedance, and the first initial weighted fusion factor is obtained accordingly. Simultaneously, it incorporates local sensitivity weights in the direction of the short-circuit ratio. The first initial weighted fusion factor is adjusted; on the other hand, the inertia ratio is calculated based on the power grid inertia support requirements. And based on this, the second initial weighted fusion factor is obtained. Simultaneously, the local sensitivity weights in the inertia direction are combined. The second initial weighted fusion factor is adjusted. Based on this, the first initial weighted fusion factor is adjusted... With the second initial weighted fusion factor The initial fusion weighting factor C is obtained by weighting the components according to their corresponding weights, and then an active power adjustment factor is introduced. and strategy factors The initial dual-source fusion factor C is optimized to obtain the optimized dual-source fusion factor. It is used to achieve adaptive fusion between inverters with different control methods.

[0040] Specifically, this invention provides a variable weighted fusion control method based on the fusion of voltage and current sources. The fusion of voltage and current sources refers to the real-time adjustment of the weighting ratio of the voltage and current sources according to changes in grid impedance and the inverter system's inertia requirements, including the following steps: Step 1: Calculate the short-circuit ratio (SCR) of the power grid based on the grid impedance, and adjust the SCR according to the given short-circuit ratio sensitivity coefficient. The initial proportion of current source control in dual-source fusion is determined, and the first initial weighted fusion factor is obtained. .

[0041] In this embodiment, the formula for calculating the short-circuit ratio (SCR) is: ; in, This is a reference value for the base power. The equivalent impedance of the power grid. , The equivalent resistance of the power grid. The virtual part, For the equivalent inductive reactance of the power grid; Equivalent impedance of the power grid amplitude, ; First initial weighted fusion factor The expression is: ; in, It is a natural constant. This is the short-circuit ratio sensitivity adjustment coefficient. The current short-circuit ratio of the power grid, The minimum short-circuit ratio threshold required for system stability.

[0042] Step 2: Calculate the grid inertia ratio based on the grid inertia support requirements. And based on the inertia ratio And a given inertia ratio sensitivity adjustment coefficient Determine the initial ratio of the current source control to meet the inertia support requirements, and obtain the second initial weighted fusion factor. .

[0043] In this embodiment, the inertia ratio The formula for calculation is: ; in, For the system's equivalent inertia, The system requires inertia; Second initial weighted fusion factor The expression is: ; in, It is a natural constant. This is the inertia ratio sensitivity adjustment coefficient. The current inertia ratio is the power grid inertia ratio. The minimum equivalent inertia threshold required for system stability.

[0044] Step 3: Taking into account the changes in grid impedance and the inertia support requirements, perform dual-source fusion control on voltage source type and current source type to obtain the initial dual-source fusion factor C of voltage source type control and current source type control.

[0045] In this embodiment, step 3 is implemented as follows: Step 3.1, based on the first initial weighted fusion factor and short-circuit ratio sensitivity adjustment coefficient The local sensitivity weights in the short-circuit ratio direction are obtained and denoted as the short-circuit ratio weighting factor. According to the second initial weighted fusion factor Inertia-to-sensitivity adjustment coefficient The local sensitivity weights in the inertia direction are obtained and denoted as the inertia ratio weighting factor. Short-circuit ratio weighting factor Weighting factor for inertia The expression is as follows: ; ; Step 3.2, using the short-circuit ratio weighting factor Weighting factor for inertia For the weighting coefficients, the first initial weighted fusion factor With the second initial weighted fusion factor After performing a weighted summation, the initial dual-source fusion factor C for voltage source control and current source control is obtained, and its expression is: ; The initial dual-source fusion factor C satisfies the adaptive adjustment requirements based on grid impedance and inertia state.

[0046] Step 4: Denote any one of the inverters in the inverter system as an inverter. Given the active power adjustment factor and the strategy factor, and optimizing the initial dual-source fusion factor C, the dual-source fusion factor is obtained. This dual-source fusion factor For adaptive adjustment of inverter The fusion ratio of voltage and current sources, and the fusion factor of the two sources. Corresponding to inverter The proportion of current source integration, inverter The integration ratio of voltage sources is .

[0047] In this embodiment, step 4 is implemented as follows: Inverter The common coupling node is denoted as the power grid node. According to the power grid nodes The active power regulation capability, given the active power regulation factor Active regulatory factor For inverter The normalized coefficient for the active power regulation capability provided under current operating conditions ranges from 0 to 1. A stronger active power regulation capability indicates a higher regulation capability. The closer to 1; Given strategy factors , For integrated nodes The economic cost and safety correction coefficients; According to the formula The dual-source fusion factor was obtained. .

[0048] To verify the voltage support capability of the proposed fusion control method under grid voltage disturbance conditions, electromagnetic transient simulation analysis was performed on the grid-connected converter. During the simulation, the grid was set to... as well as Maintaining rated voltage operation, while Transient voltage dips in the grid are introduced during the time period, with voltage dip amplitudes set to 10%, 20%, and 30% of the rated value, respectively, to simulate different levels of grid voltage disturbance conditions.

[0049] Figure 3 The grid connection point voltage under the above voltage disturbance conditions is given. Axial components The dynamic response waveform. (By...) Figure 3 It can be seen that when the grid voltage drops, the grid connection point voltage can respond quickly and provide effective support under the proposed integrated control method. Although the voltage amplitude shifts accordingly with different disturbance degrees, the overall change process is smooth, without obvious oscillations or instability. When the grid voltage recovers to its rated value, the grid connection point voltage can quickly return to the steady-state operating level, indicating that the control method has good dynamic adjustment capability and voltage support capability under different voltage drop depths, verifying its effectiveness and robustness in weak grid and voltage disturbance environments.

[0050] Figure 4 The waveforms of the three-phase voltage and three-phase current of the power grid with a wide range of power grid impedance are obtained by the variable weighted fusion control method based on the dual-source fusion of voltage source and current source proposed in this invention.

[0051] In this invention example, to verify the stability and adaptability of the proposed integrated control method under grid impedance fluctuation conditions, electromagnetic transient simulation was performed on the grid-connected converter. This simulation control... Figure 1 power grid During the simulation, the inverter corresponding to the node is used to simulate changes in grid strength by altering the equivalent grid impedance parameters at the grid connection point, thereby affecting the grid short-circuit ratio (SCR). The simulation time is divided into segments according to preset operating conditions. The short-circuit ratio (SCR) is adjusted every 5 seconds, and the corresponding dual-source fusion factor is updated synchronously. .

[0052] like Figure 4 During simulation time SCR=2, ; SCR=3 ; SCR=5 ; SCR=10 ; SCR=20 Specifically, in the initial stage of the simulation, the power grid is under relatively weak grid conditions, and then successively experiences different grid strength ranges, realizing multi-condition switching from weak grid to strong grid. Figure 4 The three-phase grid-connected current waveforms and three-phase grid-connected voltage waveforms recorded during the aforementioned grid impedance fluctuation process are presented. Figure 4 It can be seen that when the grid short-circuit ratio and the fusion weighting factor undergo a step change, both the three-phase grid-connected current and the three-phase grid-connected voltage can converge rapidly, with continuous waveforms and no obvious oscillations or instability. This indicates that the proposed fusion control method can adaptively adjust the control characteristics according to the grid impedance change, and maintain good grid-connected stability and robustness under a wide range of grid strength changes.

Claims

1. A variable-weighted fusion control method based on the fusion of voltage and current sources, the control method involving a circuit including an inverter system, a line inductor, and a three-phase power grid, wherein the inverter system includes multiple inverters, the output terminals of the multiple inverters are respectively connected to the line inductor through their respective nodes, and the other end of the line inductor is connected to the three-phase power grid; the fusion of voltage and current sources refers to the real-time adjustment of the weighting ratio of the voltage and current sources according to the changes in grid impedance and the inertia requirements of the inverter system, characterized in that... Includes the following steps: Step 1: Calculate the short-circuit ratio (SCR) of the power grid based on the grid impedance, and adjust the SCR according to the given short-circuit ratio sensitivity coefficient. The initial proportion of current source control in dual-source fusion is determined, and the first initial weighted fusion factor is obtained. ; Step 2: Calculate the grid inertia ratio based on the grid inertia support requirements. And based on the inertia ratio And a given inertia ratio sensitivity adjustment coefficient Determine the initial ratio of the current source control to meet the inertia support requirements, and obtain the second initial weighted fusion factor. ; Step 3: Taking into account the changes in grid impedance and the inertia support requirements, perform dual-source fusion control on voltage source type and current source type to obtain the initial dual-source fusion factor C of voltage source type control and current source type control; Step 4: Denote any one of the inverters in the inverter system as an inverter. Given the active power adjustment factor and the strategy factor, and optimizing the initial dual-source fusion factor C, the dual-source fusion factor is obtained. This dual-source fusion factor For adaptive adjustment of inverter The fusion ratio of voltage and current sources, and the fusion factor of the two sources. Corresponding to inverter The proportion of current source integration, inverter The integration ratio of voltage sources is .

2. The variable weighted fusion control method based on the fusion of voltage and current sources according to claim 1, characterized in that, The formula for calculating the short-circuit ratio (SCR) in step 1 is as follows: in, This is a reference value for the base power. The equivalent impedance of the power grid. , The equivalent resistance of the power grid. The virtual part, For the equivalent inductive reactance of the power grid; Equivalent impedance of the power grid amplitude, ; First initial weighted fusion factor The expression is: in, It is a natural constant. This is the short-circuit ratio sensitivity adjustment coefficient. The current short-circuit ratio of the power grid. The minimum short-circuit ratio threshold required for system stability.

3. The variable weighted fusion control method based on the fusion of voltage and current sources according to claim 1, characterized in that, The inertia ratio mentioned in step 2 The formula for calculation is: in, For the system's equivalent inertia, The system requires inertia; Second initial weighted fusion factor The expression is: in, It is a natural constant. This is the inertia ratio sensitivity adjustment coefficient. The current inertia ratio is the power grid inertia ratio. The minimum equivalent inertia threshold required for system stability.

4. The variable weighted fusion control method based on the fusion of voltage and current sources according to claim 1, characterized in that, The implementation process of step 3 is as follows: Step 3.1, based on the first initial weighted fusion factor and short-circuit ratio sensitivity adjustment coefficient The local sensitivity weights in the short-circuit ratio direction are obtained and denoted as the short-circuit ratio weighting factor. According to the second initial weighted fusion factor Inertia-to-sensitivity adjustment coefficient The local sensitivity weights in the inertia direction are obtained and denoted as the inertia ratio weighting factor. Short-circuit ratio weighting factor Weighting factor for inertia The expression is as follows: Step 3.2, using the short-circuit ratio weighting factor Weighting factor for inertia For the weighting coefficients, the first initial weighted fusion factor With the second initial weighted fusion factor After performing a weighted summation, the initial dual-source fusion factor C for voltage source control and current source control is obtained, and its expression is: The initial dual-source fusion factor C satisfies the adaptive adjustment requirements based on grid impedance and inertia state.

5. The variable weighted fusion control method based on the fusion of voltage and current sources according to claim 1, characterized in that, The implementation process of step 4 is as follows: Inverter The common coupling node is denoted as the power grid node. According to the power grid nodes The active power regulation capability, given the active power regulation factor Active regulatory factor For inverter The normalized coefficient for the active power regulation capability provided under current operating conditions ranges from 0 to 1. A stronger active power regulation capability indicates a higher regulation capability. The closer to 1; Given strategy factors , For integrated nodes The economic cost and safety correction factor; According to the formula The dual-source fusion factor was obtained. .

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