Multi-converter cooperative networking oscillation suppression method and device and storage medium

Abstract

The invention discloses a multi-converter cooperative network construction oscillation suppression method and device and a storage medium, and belongs to the field of converter network oscillation suppression, and the method comprises the steps: carrying out the calculation based on a power-frequency droop control strategy of active compensation to obtain an active power output value of a converter, so as to achieve the smooth adjustment of the active power of the converter; the mechanical inertia and the damping coefficient of the multi-converter cooperative network construction are calculated through an inertia-damping equation considering the dynamic influence, so that the dynamic adjustment of the mechanical inertia and the damping coefficient is realized; and a reactive power output value of the converter is calculated based on the voltage-reactive droop control strategy of voltage compensation, so that reactive power compensation adjustment of the converter is realized. Through active compensation and consideration of dynamic influence and voltage compensation, multi-converter collaborative networking can quickly respond and keep the stability of a power grid under the conditions of frequency fluctuation, voltage imbalance and load disturbance, and power fluctuation and oscillation are reduced.

Description

Technical Field

[0001] The present invention relates to a method, a device and a storage medium for suppressing oscillation of a multi-converter cooperative network, and belongs to the field of converter network oscillation suppression. Background Art

[0002] With the increasing complexity of power systems and the transformation of energy mix, multi-converter (PC) converters have become an indispensable core component of power grids. They play a particularly critical role in renewable energy generation systems (such as wind power and photovoltaics) and distribution networks. To improve system stability and power quality, PC-based converter coordinated control technology has emerged. In recent years, with the advancement of distributed generation and energy storage technologies, the coordinated operation of PC-based converters has become a hot topic of research. By introducing various control strategies, such as power-frequency droop control and virtual impedance control, PC-based converter coordinated operation can be effectively achieved, maintaining grid stability under disturbances such as load changes and frequency fluctuations. These technologies help reduce oscillations in the power grid and improve the system's dynamic response capabilities. In particular, strategies such as power-frequency droop control and inertia-damping control enable the system to adjust power output in response to changes in grid frequency, further enhancing grid stability.

[0003] However, although the existing technology has made significant progress in the coordinated control of multiple converters, it still faces several problems. Although the existing power-frequency droop control strategy can balance the grid frequency fluctuations to a certain extent, when the grid frequency fluctuates greatly, the power regulation is not smooth enough, which easily leads to excessive power fluctuations and the inability to quickly stabilize the grid frequency. The existing technology usually relies on static or simplified models for the adjustment of inertia and damping coefficients. Therefore, when the frequency changes rapidly, it cannot guarantee the rapid response and stability of the system. Furthermore, although the virtual impedance control strategy has been widely used, the virtual impedance parameter settings in the existing technology are usually fixed and lack adaptability. They cannot be automatically adjusted according to changes in the grid load, resulting in the inability to effectively suppress power oscillations when the load fluctuates greatly. The existing reactive power regulation scheme cannot fully adjust the reactive power output when the frequency fluctuates greatly, resulting in the inability to effectively suppress the fluctuation of the grid voltage. Summary of the Invention

[0004] The purpose of the present invention is to provide a method, device and storage medium for oscillation suppression in a multi-converter collaborative network, so as to solve the problems existing in the prior art, such as insufficient power regulation smoothness, insufficient dynamic adjustment of inertia and damping coefficient, slow response of reactive power regulation and inability to effectively suppress power oscillation.

[0005] To achieve the above objectives, the present invention is implemented by adopting the following technical solutions:

[0006] In a first aspect, the present invention provides a method for suppressing oscillations in a multi-converter collaborative network, comprising:

[0007] After obtaining the target active power, the current frequency of the multi-converter collaborative network, and the nominal frequency, the converter active power output value is calculated based on the power-frequency droop control strategy of active power compensation to achieve smooth regulation of the converter active power.

[0008] The mechanical power of the multi-converter collaborative network is obtained. Based on the mechanical power, current frequency, and active power output of the converters, as well as the inertia-damping equation that considers dynamic effects, the mechanical inertia and damping coefficient of the multi-converter collaborative network are calculated to achieve dynamic adjustment of the mechanical inertia and damping coefficient.

[0009] After obtaining the target reactive power, the current voltage and the nominal voltage of the multi-converter collaborative network, the reactive power output value of the converter is calculated based on the voltage-reactive power droop control strategy of voltage compensation to achieve compensation and regulation of the converter reactive power.

[0010] Furthermore, after obtaining the target active power, the current frequency and the nominal frequency of the multi-converter cooperative network, the converter active power output value is calculated based on the power-frequency droop control strategy of the active compensation, using the following formula:

[0011] ;

[0012] in, Indicates the active power output value of the converter, Indicates the preset target active power, represents the power-frequency droop coefficient, Indicates the preset frequency compensation factor, is the current frequency of the multi-converter collaborative network, represents the nominal frequency, is the active power frequency compensation function, It is the active power compensation term introduced in the power-frequency droop control strategy;

[0013] The active power frequency compensation function is expressed as:

[0014] ;

[0015] in, Represents the width factor used to control the frequency fluctuation response range in the active power frequency compensation function. It represents the sensitivity factor used to control the response speed and amplitude of the active power frequency compensation function, and e represents a natural constant.

[0016] Furthermore, the mechanical inertia and damping coefficient of the multi-converter cooperative network are calculated based on the mechanical power, current frequency, and active power output value of the converter, as well as the inertia-damping equation considering dynamic effects, using the following formula:

[0017] ;

[0018] in, represents the mechanical inertia, represents mechanical power, Indicates the active power output value of the converter, is the damping torque, is the damping coefficient, Indicates time, is the current frequency of the multi-converter collaborative network, is the power error rate of change term introduced in the inertia-damping equation.

[0019] Furthermore, it also includes:

[0020] During the dynamic adjustment of the mechanical inertia and the damping coefficient, in response to detecting a load change of the multi-converter cooperative network, the following steps are performed:

[0021] If the load change ratio is less than the first preset value, the damping torque and the mechanical inertia are kept unchanged, and the adjustment range of the damping coefficient in the inertia-damping equation considering dynamic effects is narrowed;

[0022] If the load change ratio is greater than or equal to the first preset value, the calculated mechanical inertia and damping coefficient are increased, and the damping torque is increased.

[0023] Furthermore, after obtaining the target reactive power, the current voltage and the nominal voltage of the multi-converter cooperative network, the reactive power output value of the converter is calculated based on the voltage-reactive power droop control strategy of the voltage compensation, using the following formula:

[0024] ;

[0025] in, Indicates the reactive power output value of the converter, Indicates the preset target reactive power, Indicates the voltage-reactive power droop coefficient, Indicates the nominal voltage, Indicates the current voltage of the multi-converter collaborative network, represents the nonlinear voltage compensation function;

[0026] The nonlinear voltage compensation function is expressed as:

[0027] ;

[0028] in, represents the shape adjustment coefficient of the nonlinear voltage compensation function, Represents the sensitivity adjustment coefficient of the nonlinear voltage compensation function.

[0029] Furthermore, the method further includes executing the following steps before performing compensation adjustment of the reactive power of the converter:

[0030] After obtaining the d-axis component of voltage, the q-axis component of voltage, the d-axis component of current, and the q-axis component of current, the converter active power output value is calculated based on the virtual impedance control strategy of impedance compensation to achieve even distribution of converter active power in a multi-converter collaborative network.

[0031] The virtual impedance control strategy of the impedance compensation is expressed as:

[0032] ;

[0033] in, is the active power output value of the converter, Indicates voltage Axis component, Indicates voltage Axis component, Indicates current Axis component, Indicates current Axis component, represents the virtual impedance compensation factor, is the virtual impedance compensation term, is the power coupling term.

[0034] Furthermore, in the process of evenly distributing the active power of the converter, in response to detecting a load change, the following steps are performed:

[0035] If the load change ratio is greater than a second preset value, the virtual impedance compensation factor is increased, and the virtual impedance compensation term now dominates the average distribution process of the converter active power;

[0036] If the load change ratio is less than or equal to the second preset value, the virtual impedance compensation factor is kept unchanged, and the power coupling term now dominates the average distribution process of the converter active power.

[0037] Furthermore, the method further includes calculating a voltage phase error between the converter voltage output value and the grid voltage by the following formula before the converter is connected to the grid, so as to achieve phase synchronization before the converter is connected to the grid:

[0038] ;

[0039] in, represents the voltage phase error, Indicates the preset target phase, Indicates the phase of the converter voltage output value, represents the reactive power frequency compensation function;

[0040] The phase of the converter voltage output value is obtained by adjusting the phase-locked loop technology before the converter is connected to the grid;

[0041] The reactive power frequency compensation function is expressed as:

[0042] ;

[0043] in, is the frequency compensation coefficient of the reactive power frequency compensation function, is the current frequency of the multi-converter collaborative network, is the nominal frequency, is the adjustment coefficient of frequency compensation.

[0044] In a second aspect, the present invention provides a multi-converter cooperative network oscillation suppression device, comprising:

[0045] The converter active power smoothing regulation module is configured to obtain the target active power, the current frequency of the multi-converter collaborative network, and the nominal frequency, and then calculate the converter active power output value based on the power-frequency droop control strategy of the active power compensation to achieve smooth regulation of the converter active power;

[0046] The inertia and damping dynamic adjustment module is configured to obtain the mechanical power of the multi-converter collaborative network and calculate the mechanical inertia and damping coefficient of the multi-converter collaborative network based on the mechanical power, current frequency, and active power output value of the converter, as well as the inertia-damping equation considering dynamic effects, so as to achieve dynamic adjustment of the mechanical inertia and damping coefficient.

[0047] The converter reactive power compensation and regulation module is configured to obtain the target reactive power, the current voltage of the multi-converter collaborative network, and the nominal voltage, and then calculate the converter reactive power output value based on the voltage-reactive power droop control strategy of voltage compensation to achieve converter reactive power compensation and regulation.

[0048] In a third aspect, the present invention provides a computer-readable storage medium having a computer program / instruction stored thereon. When the computer program / instruction is executed by a processor, the steps of the multi-converter collaborative network oscillation suppression method described in any one of the first aspects are implemented.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention provides a multi-converter cooperative network oscillation suppression method, device and storage medium, which introduce active power compensation into the power-frequency droop control strategy to smooth the active power regulation process, avoid severe power fluctuations, improve the stability of the multi-converter cooperative network, strengthen the cooperative operation capability between multiple converters, and reduce the oscillation phenomenon during frequency mutations; by considering dynamic effects in the inertia-damping equation, dynamic adjustment of mechanical inertia and damping coefficient is achieved, so that the multi-converter cooperative network can respond quickly to load changes or sudden disturbances and stabilize the frequency. This adjustment process ensures the rapid recovery of the multi-converter cooperative network and reduces the frequency The impact of frequency fluctuations on the power grid; by introducing voltage compensation in the voltage-reactive power droop control strategy, the impact of voltage changes on reactive power is controlled more accurately. This compensation mechanism effectively improves the stability of the power grid voltage, so that the collaborative networking of multiple converters can better adapt to load fluctuations and changes in power grid voltage; through the combination of the above methods, the collaborative networking of multiple converters can quickly respond to and maintain the stability of the power grid under the conditions of frequency fluctuations, voltage imbalance and load disturbances, reduce power fluctuations and oscillations, and improve the collaborative operation capability of multiple converters when connected to the grid and the anti-disturbance capability of the power grid. The present invention achieves better results in terms of stability, reliability and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a flow chart of a multi-converter collaborative network oscillation suppression method corresponding to Example 1 of the present invention;

[0052] Figure 2 This is a flow chart of a multi-converter collaborative network oscillation suppression method corresponding to embodiment 2 of the present invention. DETAILED DESCRIPTION

[0053] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0054] Example 1

[0055] like Figure 1 As shown, this embodiment provides a method for suppressing oscillations in a multi-converter collaborative network, including:

[0056] After obtaining the target active power, the current frequency of the multi-converter collaborative network, and the nominal frequency, the converter active power output value is calculated based on the power-frequency droop control strategy of active power compensation to achieve smooth regulation of the converter active power.

[0057] The mechanical power of the multi-converter collaborative network is obtained. Based on the mechanical power, current frequency, and active power output of the converters, as well as the inertia-damping equation that considers dynamic effects, the mechanical inertia and damping coefficient of the multi-converter collaborative network are calculated to achieve dynamic adjustment of the mechanical inertia and damping coefficient.

[0058] After obtaining the target reactive power, the current voltage and the nominal voltage of the multi-converter collaborative network, the reactive power output value of the converter is calculated based on the voltage-reactive power droop control strategy of voltage compensation to achieve compensation and regulation of the converter reactive power.

[0059] The present invention introduces active power compensation into the power-frequency droop control strategy to smooth the active power regulation process, avoid severe power fluctuations, improve the stability of the multi-converter cooperative network, strengthen the cooperative operation capability between multiple converters, and reduce the oscillation phenomenon during frequency mutations; by considering dynamic effects in the inertia-damping equation, dynamic adjustment of mechanical inertia and damping coefficient is achieved, so that the multi-converter cooperative network can respond quickly to load changes or sudden disturbances and stabilize the frequency. This adjustment process ensures the rapid recovery of the multi-converter cooperative network and reduces the impact of frequency fluctuations on the power grid; Voltage compensation is introduced into the voltage-reactive power droop control strategy to more accurately control the impact of voltage changes on reactive power. This compensation mechanism effectively improves the stability of the grid voltage, enabling the collaborative networking of multiple converters to better adapt to load fluctuations and changes in grid voltage. Through the combination of the above methods, the collaborative networking of multiple converters can quickly respond to and maintain the stability of the grid under conditions of frequency fluctuations, voltage imbalance and load disturbances, reduce power fluctuations and oscillations, and improve the collaborative operation capability of multiple converters when connected to the grid and the anti-disturbance capability of the grid. The present invention achieves better results in terms of stability, reliability and efficiency.

[0060] Example 2

[0061] like Figure 2 As shown, this embodiment provides a method for suppressing oscillations in a multi-converter collaborative network, including:

[0062] S1. Use power-frequency droop control strategy to adjust the active power output of the converter.

[0063] The specific implementation of step S1 includes the following steps:

[0064] The active power output value of the converter is adjusted according to the difference between the current grid frequency and the nominal frequency through the power-frequency droop control strategy, thereby controlling the grid frequency. Based on the power-frequency droop control strategy, an active power frequency compensation function is introduced to dynamically adjust the converter power regulation response according to the fluctuation of the grid frequency to smooth the active power regulation process. The active power frequency compensation function adopts an exponential response model to automatically adjust the amplitude and speed of active power regulation according to the deviation between the current frequency and the nominal frequency. The frequency deviation (the deviation between the current frequency and the nominal frequency) is positively correlated with the influence of the active power frequency compensation function, responding to frequency fluctuations. When the grid frequency fluctuates, the active power frequency compensation function dynamically adjusts the power output according to the preset compensation factor to adjust the active power output of the converter when the frequency fluctuates.

[0065] Maintaining a stable grid frequency is crucial in a multi-converter coordinated grid. Frequency fluctuations directly impact the grid's power balance. Therefore, a power-frequency droop control strategy is employed to regulate the converter's active power output. This control strategy relies on frequency deviation to adjust the power output of the multi-converter coordinated grid. This allows the converters to automatically adjust their active power output based on grid frequency fluctuations, thereby stabilizing the grid frequency.

[0066] The relationship between active power and frequency can be expressed by the power-frequency droop control strategy of active power compensation, which is expressed as:

[0067] ;

[0068] in, Indicates the active power output value of the converter, Indicates the preset target active power, It represents the power-frequency droop coefficient, which determines the sensitivity of the power response. It represents the frequency compensation factor, which is a factor that adjusts the response strength of the active power frequency compensation function. Its function is to adjust the amplitude of frequency fluctuation according to the actual situation to ensure a smooth transition of power adjustment. is the current frequency of the multi-converter collaborative network, represents the nominal frequency, which is usually the ideal frequency for multi-converter coordinated network construction (usually 50 Hz or 60 Hz, 50 Hz is used in this embodiment). is the active power frequency compensation function, which is used to smooth the active power adjustment process according to frequency fluctuations.

[0069] The active power frequency compensation function is expressed as:

[0070] ;

[0071] in, Represents the width factor in the active power frequency compensation function. The width factor affects the response range of frequency fluctuations. A larger The value will make the compensation effect mainly concentrated near the nominal frequency. It represents the sensitivity factor in the active power frequency compensation function. The sensitivity factor is used to control the speed and amplitude of the active power frequency compensation function response. e represents a natural constant. is the current frequency of the multi-converter collaborative network, Indicates the nominal frequency.

[0072] Through the active power frequency compensation function This enables the collaborative networking of multiple converters to smoothly adjust the active power output of the converters in the case of large frequency deviations, avoiding drastic power fluctuations. This not only improves the stability of the system, but also strengthens the collaborative operation capabilities between multiple converters and reduces oscillation phenomena during frequency mutations.

[0073] S2. Dynamically adjust the inertia and damping coefficient of the converter through the inertia-damping equation. Introduce the power error change rate term into the inertia-damping equation to adjust the response speed of the inertia and damping coefficient.

[0074] The specific implementation of step S2 includes the following steps:

[0075] Adjusting the response speed of inertia and damping coefficient includes: dynamically adjusting the mechanical inertia and damping coefficient of the converter through the inertia-damping equation according to the load changes of the multi-converter cooperative network, and the adjustment of the mechanical inertia and damping coefficient is related to the frequency fluctuation of the multi-converter cooperative network; by introducing the power error change rate term, the response speed of the mechanical inertia and damping coefficient is adjusted based on the change rate of the output power of the multi-converter cooperative network; the power error adjustment term adjusts the mechanical inertia and damping coefficient of the multi-converter cooperative network according to the change rate of the power error, and responds to and adjusts to load changes and frequency fluctuations.

[0076] A preferred solution for constructing the inertia-damping equation specifically includes adaptive adjustment of the mechanical inertia and damping coefficient. In a power system (specifically, a multi-converter coordinated network in this embodiment), mechanical inertia and the damping coefficient are important factors determining the dynamic response of the multi-converter coordinated network. Mechanical inertia determines the multi-converter coordinated network's resistance to frequency changes, while the damping coefficient determines the multi-converter coordinated network's ability to suppress frequency fluctuations. To maintain the stability of the multi-converter coordinated network during load changes, an adaptive adjustment strategy is adopted to dynamically adjust the mechanical inertia and damping coefficient based on real-time load disturbances, ensuring that the multi-converter coordinated network can quickly restore stability under any operating conditions.

[0077] The dynamic behavior of the virtual synchronous generator (VSG) is simulated through the inertia-damping equation, and the power error change rate term is introduced. The final inertia-damping equation considering dynamic effects is expressed as:

[0078] ;

[0079] in, Represents mechanical inertia, which affects the frequency response of the multi-converter collaborative network. Represents mechanical power, which represents the mechanical energy input to the multi-converter cooperative network. is the active power output value of the converter, The damping torque is used to suppress the excessive dynamic fluctuation of the multi-converter cooperative network. is the damping coefficient, which adjusts the power response speed of the multi-converter collaborative network to prevent excessive oscillation. Indicates time, is the current frequency of the multi-converter collaborative network.

[0080] By introducing the power error change rate term , realizing dynamic adjustment of the mechanical inertia and damping coefficient of the multi-converter collaborative network, enabling the multi-converter collaborative network to respond quickly to load changes or sudden disturbances and stabilize the frequency of the multi-converter collaborative network. This adaptive adjustment strategy ensures the rapid recovery of the multi-converter collaborative network while reducing the impact of frequency fluctuations on the power grid.

[0081] Low load disturbance: When the load change is small, that is, when the load change ratio is less than 10%, the mechanical inertia and damping torque Will provide sufficient support to alleviate frequency fluctuations, damping coefficient The adjustment range can be kept small, e.g. mechanical inertia The load is 1000kgm², the frequency change rate is controlled within 0.1rad / s², and the multi-converter collaborative network can respond smoothly.

[0082] Large load disturbance: Under large load disturbance, that is, when the load change ratio is greater than or equal to 10%, the multi-converter collaborative network needs a faster response. At this time, the mechanical inertia It can be increased appropriately to enhance the resistance to frequency changes, and the damping torque Can be increased to quickly suppress frequency fluctuations, damping coefficient It will be increased to speed up the response to power fluctuations and ensure that the multi-converter collaborative network returns to a stable state.

[0083] S3. In a multi-converter collaborative network, when multiple converters operate in parallel, power oscillations are reduced by adjusting virtual impedance parameters. Combined with the virtual impedance control strategy, a reactive power adjustment item (reactive power frequency compensation function) is introduced to adjust power output in real time.

[0084] The specific implementation of step S3 includes the following steps:

[0085] The virtual impedance control strategy includes: when multiple converters operate in parallel, based on the d-axis component of voltage, the q-axis component of voltage, the d-axis component of current and the q-axis component of current, the power oscillation is reduced by adjusting the virtual impedance parameters, and the virtual impedance parameters are automatically adjusted according to load fluctuations to balance the power output of multiple converters; in the power output of the multi-converter collaborative network, a virtual impedance compensation term is introduced, and combined with the virtual impedance control strategy, the virtual impedance compensation factor is dynamically adjusted. The virtual impedance compensation factor adjusts the power output in real time according to the load changes, current components and voltage components of the power grid; when the power grid load changes, the effect of the virtual impedance compensation factor is increased to respond to the changes in voltage and current and suppress power fluctuations. When the load is stable, the adjustment of the virtual impedance compensation factor on the power output is reduced to maintain the stability of the power of the multi-converter collaborative network.

[0086] A preferred virtual impedance control strategy includes adaptive virtual impedance and power coupling. Power oscillations are a common problem when multiple converters operate in parallel, especially when multiple inverters operate collaboratively. Power coupling and phase mismatches can lead to unnecessary energy loss. To mitigate these power oscillations, a virtual impedance control strategy is introduced. By dynamically adjusting the virtual impedance and power coupling terms, it effectively controls the flow of active power, ensuring equal power distribution among multiple converters and avoiding oscillations caused by uneven power distribution. After introducing the virtual impedance compensation term, the virtual impedance control strategy is expressed using the optimized virtual impedance and power coupling formulas.

[0087] The optimized virtual impedance and power coupling formula is expressed as:

[0088] ;

[0089] in, is the actual power, which is the active power output by the converter. Indicates voltage Axis component, Indicates voltage Axis component, Indicates current Axis component, Indicates current Axis component, Indicates the virtual impedance compensation factor.

[0090] Introducing virtual impedance compensation , providing a damping effect to reduce the amplitude of power oscillation. When multiple converters are connected in parallel, the power output of each converter can be effectively balanced by dynamically adjusting the virtual impedance compensation factor, avoiding instability in the multi-converter collaborative network caused by uneven power.

[0091] When the load fluctuation of the power grid is large, that is, when the load change ratio is greater than 10%, if the load changes rapidly, resulting in large voltage fluctuations, the current and voltage Axis components and The axis components also change, in which case the virtual impedance compensation term The effect of the virtual impedance compensation factor will be enhanced. will be increased to better suppress oscillations caused by voltage imbalance.

[0092] When the grid load is stable, that is, when the load change ratio is less than or equal to 10%, the changes in the voltage component and the current component are small, and the virtual impedance compensation term The effect of The dominant power output and the collaborative networking of multiple converters can maintain a relatively stable power output without being greatly affected by voltage fluctuations.

[0093] It should be noted that real-time adjustment of power output includes: adjusting the reactive power output value of the converter through the voltage-reactive power droop control strategy according to the deviation of the grid voltage; introducing a nonlinear voltage compensation function on the basis of the voltage-reactive power droop control strategy to compensate and adjust the reactive power when the grid voltage fluctuates. The nonlinear voltage compensation function adopts a nonlinear model and adjusts according to the deviation between the grid voltage and the nominal voltage.

[0094] It should also be noted that a preferred solution of the voltage-reactive power droop control strategy specifically includes: the regulation of reactive power is crucial to the stability of the grid voltage. The voltage-reactive power droop control strategy is adopted to control the flow of reactive power by adjusting the voltage output of the converter, thereby regulating the grid voltage. In order to improve the accuracy of voltage regulation, a nonlinear voltage compensation function is further introduced to adapt to complex grid conditions.

[0095] The calculation formula of the optimized reactive power is expressed as:

[0096] ;

[0097] in, Indicates the reactive power output value of the converter, Indicates the preset target reactive power, Indicates the voltage-reactive power droop coefficient, Indicates the nominal voltage, Indicates the current voltage of the multi-converter collaborative network, represents the nonlinear voltage compensation function.

[0098] The nonlinear voltage compensation function is expressed as:

[0099] ;

[0100] in, represents the shape adjustment coefficient of the nonlinear voltage compensation function, represents the sensitivity adjustment coefficient of the nonlinear voltage compensation function, Indicates the nominal voltage, Represents the current voltage of the multi-converter cooperative network, by introducing a nonlinear voltage compensation function , which can more accurately control the impact of voltage changes on reactive power. This compensation mechanism effectively improves the stability of grid voltage and enables multi-converter collaborative networking to better adapt to load fluctuations and grid voltage changes.

[0101] According to the voltage fluctuation and reactive power demand of the power grid, the nonlinear voltage compensation function can be divided into the following cases for discussion:

[0102] Case 1: When the current voltage is close to the nominal voltage, , the grid voltage is close to the nominal value, The effect of reactive power is relatively small. The power grid mainly relies on the power-voltage droop control strategy to adjust the reactive power. The calculation formula of reactive power is simplified to:

[0103] ;

[0104] In the case of the multi-converter cooperative network is more sensitive to voltage changes, but the impact of nonlinear voltage compensation function is small. The multi-converter cooperative network is mainly based on the voltage-reactive power droop coefficient. Adjust reactive power.

[0105] When the current voltage is far away from the nominal voltage, or , the grid voltage deviates far from the nominal voltage, and the nonlinear voltage compensation function It will play a key role, for example, when the grid voltage drops below 380V or rises above 420V, The reactive power will be adjusted in a nonlinear way to effectively stabilize the grid voltage. In this case, the nonlinear voltage compensation function It will determine the adjustment range of reactive power to avoid excessive voltage fluctuations affecting grid stability.

[0106] Under high load or fault conditions, when the load of a multi-converter collaborative network suddenly increases or a fault occurs, the voltage will change dramatically. The multi-converter collaborative network will stabilize the voltage by quickly adjusting the reactive power. At this time, the role of the nonlinear voltage compensation function is particularly important to ensure that the multi-converter collaborative network can recover stability in a relatively short time. The fast response can help to dynamically adjust the reactive power, thereby avoiding grid voltage instability.

[0107] It should also be noted that real-time adjustment of power output also includes: before grid connection, real-time detection of the grid voltage phase through phase-locked loop technology, and dynamic adjustment of the converter output voltage phase based on the difference between the grid voltage phase and the converter output voltage phase, so that the converter output voltage phase is synchronized with the grid voltage phase; when the grid frequency deviates, the influence of the grid frequency on the converter phase synchronization is corrected through the reactive power frequency compensation function, and the reactive power frequency compensation function is dynamically adjusted according to the change of the grid frequency, so that the converter maintains stable phase synchronization when the frequency fluctuates, so that the frequency between the grid and the converter is matched.

[0108] The reactive power frequency compensation function is based on the deviation between the grid frequency and the nominal frequency. It compensates for the impact of the grid frequency deviation on phase synchronization through adaptive adjustment of the adjustment coefficient. When the grid frequency is stable, the reactive power frequency compensation function has little effect and the converter quickly synchronizes with the grid phase. However, when the grid frequency fluctuates greatly, the reactive power frequency compensation function strengthens its effect according to the frequency change and adjusts the output voltage phase of the converter in real time.

[0109] It should also be noted that in order to ensure a smooth transition of the converter when connected to the grid, pre-synchronization control technology is adopted. Before grid connection, the frequency and phase of the converter's output voltage are synchronized with the grid voltage through phase-locked loop technology (PLL) to avoid surge current caused by voltage asynchrony during parallel connection.

[0110] The pre-synchronization control and phase-locked loop formulas are expressed as:

[0111] ;

[0112] in, represents the voltage phase error, represents the reference phase, Indicates the current output voltage phase of the converter, Represents the reactive power frequency compensation function.

[0113] The reactive power frequency compensation function is expressed as:

[0114] ;

[0115] in, is the frequency compensation coefficient, which is used to adjust the effect of frequency fluctuation on phase synchronization. is the current frequency of the multi-converter collaborative network, is the nominal frequency, which is usually the ideal frequency for multi-converter coordinated network construction (usually 50Hz or 60Hz, 50Hz is used in this embodiment), It is the frequency compensation adjustment coefficient, which is used to control the impact of frequency deviation on phase synchronization. Through pre-synchronization control and phase-locked loop technology, the voltage phase can be accurately synchronized before the converter is connected to the grid, thereby avoiding the impact current caused by phase inconsistency. It provides a smooth transition guarantee for the parallel connection of multiple converters and ensures efficient and stable operation of the system.

[0116] Phase error adjustment: By dynamically calculating the phase difference between the grid and the converter, the output voltage phase of the converter is adjusted based on the phase-locked loop technology. , so that it is in phase with the reference Finally, phase synchronization is achieved. Used to correct the impact of frequency deviation on phase synchronization, assuming that the current frequency of the multi-converter collaborative network Slight fluctuations (such as frequency drop) can be compensated by introducing reactive power frequency compensation function , can smooth the impact of frequency fluctuations on phase synchronization, reduce the impact of frequency fluctuations on phase synchronization in multi-converter collaborative networking, the current frequency of multi-converter collaborative networking Usually in For a 50Hz multi-converter coordinated grid, the frequency fluctuation range is approximately 47.5Hz to 52.5Hz. Therefore, the design of the reactive power frequency compensation function ensures compensation within this range. Phase adjustment range: The value range is usually arrive The range between represents the maximum phase error adjustment range. The larger the phase error, the stronger the influence of the reactive power frequency compensation function will be, resulting in an increase in the phase adjustment amplitude of the converter.

[0117] When the grid frequency is stable, if the grid frequency fluctuation is small, the influence of the reactive power frequency compensation function is small, and the output voltage phase of the converter will quickly stabilize at the reference phase. ,at this time, The value of is close to zero, the phase error adjustment is small, and the converter hardly requires additional adjustment.

[0118] When the grid frequency fluctuates greatly (e.g. load mutation), the reactive power frequency compensation function It will produce a greater correction effect. At this time, the frequency compensation coefficient and frequency compensation adjustment coefficient It will determine the intensity of compensation and ensure that the converter can be stably synchronized. At this time, the increase in frequency compensation effectively avoids the impact of grid frequency fluctuations on the grid connection process.

[0119] In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0120] First, the experiment used six different multi-converter cooperative networks to test their responsiveness to grid frequency, power output, reactive power regulation, and voltage fluctuations under grid load fluctuations. Each multi-converter cooperative network was equipped with the optimized power-frequency droop control strategy, inertia-damping adaptive adjustment strategy, virtual impedance control, voltage-reactive power droop control strategy, and pre-synchronization control technology. The experimental process was carried out according to the following steps: six multi-converter cooperative networks were connected to the experimental grid, and each multi-converter cooperative network was configured with a different control strategy.

[0121] Set the initial conditions to ensure that the grid frequency is the nominal value of 50Hz.

[0122] Record the grid parameters such as voltage, frequency, load and power output at the beginning of the experiment.

[0123] The testing phase includes the following steps 1 to 5:

[0124] Step 1: When the grid frequency fluctuates, a power-frequency droop control strategy is used to adjust the converter's active power output. The active power frequency compensation function smooths the active power regulation process and ensures that the frequency deviation is within an acceptable range.

[0125] Step 2: In the event of load fluctuations or sudden disturbances, dynamically adjust the mechanical inertia and damping coefficient according to the inertia-damping equation to optimize the response speed of the multi-converter collaborative network and reduce the impact of frequency fluctuations.

[0126] Step 3: When multiple converters are running in parallel, adjust the virtual impedance parameters and introduce a virtual impedance compensation term. By dynamically adjusting the virtual impedance compensation factor, power is evenly distributed among the converters, avoiding oscillations caused by uneven power distribution.

[0127] Step 4: Regulate reactive power through voltage-reactive power droop control strategy and further stabilize grid voltage through nonlinear voltage compensation function.

[0128] Step 5: Before the converter is connected to the grid, phase-locked loop technology is used to ensure that the converter's output voltage phase is synchronized with the grid voltage phase to avoid surge currents caused by voltage phase inconsistency.

[0129] Test conditions: The nominal frequency of the power grid is 50 Hz. The experiment simulates power grid frequency fluctuations (such as a drop to 49.5 Hz or an increase to 50.5 Hz).

[0130] The load variation range is set to ±5kW, ±8kW, etc. to simulate the load disturbance situation in the actual power grid.

[0131] Measure the grid voltage fluctuation range and the power output of each converter, refer to Table 1, and record some experimental data.

[0132] Table 1 Experimental data table

[0133]

[0134] In Table 1, system 1 to system 6 represent different multi-converter collaborative networks.

[0135] Table 1 shows the performance of different multi-converter collaborative networks under grid frequency fluctuations and load changes. First, the frequency fluctuations of the multi-converter collaborative network reflect its ability to respond to frequency changes. As can be seen from Table 1, when the load changes are small (such as in System 1 and System 5), the frequency response remains around 0.05 Hz / s, showing good stability. However, when the load fluctuates greatly (such as in System 2 and System 6), the frequency response of the multi-converter collaborative network increases, reaching 0.1 Hz / s and 0.08 Hz / s, respectively. This shows that under larger load disturbances, the multi-converter collaborative network can adjust its output more quickly and respond more quickly.

[0136] Secondly, the active and reactive power outputs of the multi-converter collaborative grid demonstrate the converter's regulation capabilities. In the presence of frequency fluctuations, the multi-converter collaborative grid can dynamically adjust the output active power based on the frequency deviation, avoiding excessive power fluctuations. The relatively high power outputs of Systems 3 and 6 demonstrate that the converters are able to adaptively adjust their output active power to smoothly regulate the grid frequency when the frequency deviation is large.

[0137] Table 1 shows that voltage deviations fluctuate around 10V across systems, indicating good voltage stability. The output reactive power fluctuates with load changes, but the multi-converter coordinated grid, through virtual impedance and voltage-reactive power droop control, effectively suppresses voltage fluctuations and maintains stability.

[0138] Example 3

[0139] Based on the same technical concept as Example 1, this embodiment provides a multi-converter cooperative network oscillation suppression device, including:

[0140] The converter active power smoothing regulation module is configured to obtain the target active power, the current frequency of the multi-converter collaborative network, and the nominal frequency, and then calculate the converter active power output value based on the power-frequency droop control strategy of the active power compensation to achieve smooth regulation of the converter active power;

[0141] The inertia and damping dynamic adjustment module is configured to obtain the mechanical power of the multi-converter collaborative network and calculate the mechanical inertia and damping coefficient of the multi-converter collaborative network based on the mechanical power, current frequency, and active power output value of the converter, as well as the inertia-damping equation considering dynamic effects, so as to achieve dynamic adjustment of the mechanical inertia and damping coefficient.

[0142] The converter reactive power compensation and regulation module is configured to obtain the target reactive power, the current voltage of the multi-converter collaborative network, and the nominal voltage, and then calculate the converter reactive power output value based on the voltage-reactive power droop control strategy of voltage compensation to achieve converter reactive power compensation and regulation.

[0143] Example 4

[0144] Based on the same technical concept as Example 1, this embodiment provides a computer-readable storage medium having a computer program / instruction stored thereon. When the computer program / instruction is executed by a processor, the steps of the multi-converter cooperative network oscillation suppression method provided in Example 1 are implemented:

[0145] After obtaining the target active power, the current frequency of the multi-converter collaborative network, and the nominal frequency, the converter active power output value is calculated based on the power-frequency droop control strategy of active power compensation to achieve smooth regulation of the converter active power.

[0146] The mechanical power of the multi-converter collaborative network is obtained. Based on the mechanical power, current frequency, and active power output of the converters, as well as the inertia-damping equation that considers dynamic effects, the mechanical inertia and damping coefficient of the multi-converter collaborative network are calculated to achieve dynamic adjustment of the mechanical inertia and damping coefficient.

[0147] After obtaining the target reactive power, the current voltage and the nominal voltage of the multi-converter collaborative network, the reactive power output value of the converter is calculated based on the voltage-reactive power droop control strategy of voltage compensation to achieve compensation and regulation of the converter reactive power.

[0148] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0149] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0150] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0151] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0152] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for suppressing oscillations in a multi-converter collaborative network, characterized in that: include: After obtaining the target active power, the current frequency of the multi-converter collaborative network, and the nominal frequency, the converter active power output value is calculated based on the power-frequency droop control strategy of active power compensation to achieve smooth regulation of the converter active power. The mechanical power of the multi-converter collaborative network is obtained. Based on the mechanical power, current frequency, and active power output of the converters, as well as the inertia-damping equation that considers dynamic effects, the mechanical inertia and damping coefficient of the multi-converter collaborative network are calculated to achieve dynamic adjustment of the mechanical inertia and damping coefficient. After obtaining the target reactive power, the current voltage and the nominal voltage of the multi-converter collaborative network, the reactive power output value of the converter is calculated based on the voltage-reactive power droop control strategy of voltage compensation to achieve compensation and regulation of the converter reactive power.

2. The multi-converter cooperative network oscillation suppression method according to claim 1, characterized in that: After obtaining the target active power, the current frequency and the nominal frequency of the multi-converter cooperative network, the converter active power output value is calculated based on the power-frequency droop control strategy of active compensation, using the following formula: ； in, Indicates the active power output value of the converter, Indicates the preset target active power, represents the power-frequency droop coefficient, Indicates the preset frequency compensation factor, is the current frequency of the multi-converter collaborative network, represents the nominal frequency, is the active power frequency compensation function, It is the active power compensation term introduced in the power-frequency droop control strategy; The active power frequency compensation function is expressed as: ； in, Represents the width factor used to control the frequency fluctuation response range in the active power frequency compensation function. It represents the sensitivity factor used to control the response speed and amplitude of the active power frequency compensation function, and e represents a natural constant.

3. The multi-converter cooperative network oscillation suppression method according to claim 1, characterized in that: The mechanical inertia and damping coefficient of the multi-converter cooperative network are calculated based on the mechanical power, current frequency, and active power output value of the converter, as well as the inertia-damping equation considering dynamic effects, using the following formula: ； in, represents the mechanical inertia, represents mechanical power, Indicates the active power output value of the converter, is the damping torque, is the damping coefficient, Indicates time, is the current frequency of the multi-converter collaborative network, is the power error rate of change term introduced in the inertia-damping equation.

4. The multi-converter cooperative network oscillation suppression method according to claim 3, characterized in that: Also includes: During the dynamic adjustment of the mechanical inertia and the damping coefficient, in response to detecting a load change of the multi-converter cooperative network, the following steps are performed: If the load change ratio is less than the first preset value, the damping torque and the mechanical inertia are kept unchanged, and the adjustment range of the damping coefficient in the inertia-damping equation considering dynamic effects is narrowed; If the load change ratio is greater than or equal to the first preset value, the calculated mechanical inertia and damping coefficient are increased, and the damping torque is increased.

5. The multi-converter cooperative network oscillation suppression method according to claim 1, characterized in that: After obtaining the target reactive power, the current voltage and the nominal voltage of the multi-converter cooperative network, the reactive power output value of the converter is calculated based on the voltage-reactive power droop control strategy of voltage compensation, using the following formula: ； in, Indicates the reactive power output value of the converter, Indicates the preset target reactive power, Indicates the voltage-reactive power droop coefficient, Indicates the nominal voltage, Indicates the current voltage of the multi-converter collaborative network, represents the nonlinear voltage compensation function; The nonlinear voltage compensation function is expressed as: ； in, represents the shape adjustment coefficient of the nonlinear voltage compensation function, Represents the sensitivity adjustment coefficient of the nonlinear voltage compensation function.

6. The multi-converter cooperative network oscillation suppression method according to claim 1, characterized in that: The method further includes performing the following steps before performing compensation adjustment of the reactive power of the converter: After obtaining the d-axis component of voltage, the q-axis component of voltage, the d-axis component of current, and the q-axis component of current, the converter active power output value is calculated based on the virtual impedance control strategy of impedance compensation to achieve even distribution of converter active power in a multi-converter collaborative network. The virtual impedance control strategy of the impedance compensation is expressed as: ； in, is the active power output value of the converter, Indicates voltage Axis component, Indicates voltage Axis component, Indicates current Axis component, Indicates current Axis component, represents the virtual impedance compensation factor, is the virtual impedance compensation term, is the power coupling term.

7. The multi-converter cooperative network oscillation suppression method according to claim 6, characterized in that: During the average distribution of the converter active power, in response to detecting a load change, the following steps are performed: If the load change ratio is greater than a second preset value, the virtual impedance compensation factor is increased, and the virtual impedance compensation term now dominates the average distribution process of the converter active power; If the load change ratio is less than or equal to the second preset value, the virtual impedance compensation factor is kept unchanged, and the power coupling term now dominates the average distribution process of the converter active power.

8. The multi-converter cooperative network oscillation suppression method according to claim 1, characterized in that: It also includes calculating the voltage phase error between the converter voltage output value and the grid voltage by the following formula before the converter is connected to the grid, so as to achieve phase synchronization before the converter is connected to the grid: ； in, represents the voltage phase error, Indicates the preset target phase, Indicates the phase of the converter voltage output value, represents the reactive power frequency compensation function; The phase of the converter voltage output value is obtained by adjusting the phase-locked loop technology before the converter is connected to the grid; The reactive power frequency compensation function is expressed as: ； in, is the frequency compensation coefficient of the reactive power frequency compensation function, is the current frequency of the multi-converter collaborative network, is the nominal frequency, is the adjustment coefficient of frequency compensation.

9. A multi-converter cooperative network oscillation suppression device, characterized in that: include: The converter active power smoothing regulation module is configured to obtain the target active power, the current frequency of the multi-converter collaborative network, and the nominal frequency, and then calculate the converter active power output value based on the power-frequency droop control strategy of the active power compensation to achieve smooth regulation of the converter active power; The inertia and damping dynamic adjustment module is configured to obtain the mechanical power of the multi-converter collaborative network and calculate the mechanical inertia and damping coefficient of the multi-converter collaborative network based on the mechanical power, current frequency, and active power output value of the converter, as well as the inertia-damping equation considering dynamic effects, so as to achieve dynamic adjustment of the mechanical inertia and damping coefficient. The converter reactive power compensation and regulation module is configured to obtain the target reactive power, the current voltage of the multi-converter collaborative network, and the nominal voltage, and then calculate the converter reactive power output value based on the voltage-reactive power droop control strategy of voltage compensation to achieve converter reactive power compensation and regulation.

10. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instruction is executed by a processor, the steps of the multi-converter cooperative grid oscillation suppression method according to any one of claims 1 to 8 are implemented.

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