Grid-connected control method, device and equipment for distributed power supply in power distribution network

Abstract

The application discloses a grid-connected control method for distributed power supply in a power distribution network, comprising the following steps: calculating each harmonic power and / or unbalanced power output by each distributed power supply according to harmonic components and / or negative sequence components in local currents of each distributed power supply and a grid-connected point voltage; calculating reference values corresponding to each inverter respectively based on distributed communication and consistency principles, so as to meet harmonic voltage suppression and / or unbalanced voltage suppression of the grid-connected point, and meet power sharing of each voltage control type inverter and each current control type inverter; performing phase angle pre-synchronization on each voltage control type distributed power supply when a grid-connected condition is met, so as to operate in a grid-connected mode; and suppressing harmonic current and / or unbalanced current by using a dynamic voltage compensator. The application does not need to add a redundant current loop, and improves control performance and power quality. The application also discloses a device, equipment and storage medium, and has corresponding technical effects.

Description

Technical Field

[0001] This invention relates to the field of power distribution network operation and control technology, and in particular to a grid-connected control method, device, equipment, and computer-readable storage medium for distributed power sources in a power distribution network. Background Technology

[0002] With the goals of carbon peaking and carbon neutrality being proposed, key measures for building a new power system with new energy sources as the mainstay have been clearly defined. Distribution networks will face the need for large-scale distributed generation integration, making active distribution networks with high-density distributed generation a development trend.

[0003] Following the principle of local consumption of distributed renewable energy, distributed power sources typically still have local loads. With the increasing application of nonlinear loads, unbalanced loads, and power electronic equipment, the management of harmonics and three-phase imbalance has become an unavoidable issue in the grid connection of distributed power sources. In the distribution network, inverters and local loads are connected to the main grid through the grid connection point. If the voltage at the grid connection point is three-phase unbalanced and distorted, the loads and generators of the distributed power source will be affected by unbalanced currents and / or harmonic currents. Unbalanced currents and / or harmonic currents may cause faults in sensitive loads and motors, increase circuit losses, etc. Furthermore, uneven distribution of harmonic power and / or unbalanced power can also lead to overloading of some inverters, affecting equipment lifespan.

[0004] While various methods have been proposed for harmonic and imbalance control, some are affected by increased voltage and parameter dependence or complex control loops. Furthermore, most existing research on imbalance and harmonics focuses on control strategies for voltage-controlled (VCM) inverters, with limited research on coordinated control in the coexistence of VCM and current-controlled (CCM) inverters. However, distributed grid combinations where VCM inverters provide voltage and frequency support while CCM inverters are used solely for power output are not uncommon. Moreover, extending many harmonic and imbalance control strategies to CCM inverters requires additional current regulation loops. Simultaneously, existing methods rarely consider the suppression of grid-connected harmonics and unbalanced currents caused by grid-side harmonics and imbalances. This results in poor grid-connected power quality for distributed generation systems with both VCM and CCM inverters.

[0005] In summary, how to effectively solve the problem of the need to add an additional current regulation loop when extending the control strategy for harmonics and imbalance to current-controlled inverters, and the problem of poor grid-connected power quality of distributed power sources with both voltage-controlled and current-controlled types, are urgent problems that need to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a grid-connected control method for distributed generation in a power distribution network. This method can be directly used in voltage-controlled and current-controlled distributed generation without adding redundant current loops, thereby improving control performance and power quality. Another purpose of this invention is to provide a grid-connected control device, equipment, and computer-readable storage medium for distributed generation in a power distribution network.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A grid-connected control method for distributed generation in a power distribution network, comprising:

[0009] When each local power grid operates as a system island, the harmonic components and / or negative sequence components in the local current corresponding to the grid connection point voltage and each distributed power source are extracted; wherein, each of the distributed power sources includes each voltage-controlled distributed power source and each current-controlled distributed power source.

[0010] Based on the grid connection point voltage, each of the harmonic components and / or each of the negative sequence components, calculate the harmonic power and / or unbalanced power output of each of the distributed power sources respectively.

[0011] Based on the harmonic power and / or the unbalanced power, the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point are calculated according to the principle of distributed communication and consistency, and the first output reference value and the second output reference value corresponding to each voltage-controlled inverter and each current-controlled inverter are respectively satisfied with the power distribution of each voltage-controlled inverter and each current-controlled inverter.

[0012] Based on each of the first output reference values ​​and each of the second output reference values, harmonic voltage suppression and / or unbalanced voltage suppression operations are performed on the grid connection point, and power sharing operations are performed on each of the voltage-controlled inverters and each of the current-controlled inverters.

[0013] When it is determined from the voltage suppression results that the voltage quality of the grid connection point meets the grid connection conditions, phase angle pre-synchronization is performed on each of the voltage-controlled distributed power sources, and each of the local power grids is controlled to operate in grid-connected mode.

[0014] Dynamic voltage compensators are used to suppress grid-connected harmonic currents and / or grid-connected unbalanced currents.

[0015] In one specific embodiment of the present invention, the method further includes a process of controlling each of the local power grids to operate as a system island, the process of controlling each of the local power grids to operate as a system island includes:

[0016] By using the droop control principle, each voltage-controlled distributed power source in each of the local power grids is controlled to provide voltage and frequency support for each of the local power grids, thereby obtaining each voltage reference value;

[0017] Obtain the preset active power output, preset reactive power output, instantaneous active power output, and instantaneous reactive power output corresponding to each current-controlled distributed power source in each local power grid;

[0018] Based on the preset active power output, preset reactive power output, instantaneous active power output, and instantaneous reactive power output, calculate the current reference value output by each current-controlled distributed power source.

[0019] The voltage reference values ​​are subject to dual-loop voltage and current control, and the current reference values ​​are subject to current loop control, so that each local power grid can operate as a system island.

[0020] In one specific embodiment of the present invention, based on the harmonic power and / or the unbalanced power, harmonic voltage suppression and / or unbalanced voltage suppression that satisfy the grid connection point are calculated according to the distributed communication and consistency principles, and the first output reference value corresponding to each voltage-controlled inverter and the second output reference value corresponding to each current-controlled inverter are calculated based on the power distribution between each voltage-controlled inverter and each current-controlled inverter, including:

[0021] Based on the distributed communication and consistency principle, harmonic power difference and / or unbalanced power difference calculations are performed on adjacent nodes of each voltage-controlled inverter and each current-controlled inverter to obtain the calculation results of each harmonic power difference and / or each unbalanced power difference.

[0022] Based on the calculation results of the harmonic power difference and / or the calculation results of the unbalanced power difference, determine the first virtual impedance corresponding to each of the distributed power sources when the power of each of the voltage-controlled inverters and the current-controlled inverters is evenly distributed;

[0023] Extract each component of the grid connection point voltage;

[0024] Calculate the harmonic distortion and / or unbalance distortion of each harmonic component respectively;

[0025] Calculate the second virtual impedance corresponding to each of the distributed power sources when the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point are satisfied, based on the harmonic distortion and / or unbalanced distortion of each harmonic distortion and / or unbalanced distortion.

[0026] Based on the first virtual impedance and the second virtual impedance, calculate the voltage compensation amount for each voltage-controlled inverter and the current compensation amount for each current-controlled inverter.

[0027] Based on each of the first output reference values ​​and each of the second output reference values, harmonic voltage suppression and / or unbalanced voltage suppression operations are performed on the grid connection point, and power sharing operations are performed on each of the voltage-controlled inverters and each of the current-controlled inverters, including:

[0028] Based on the voltage compensation amount and the current compensation amount, harmonic voltage suppression and / or unbalanced voltage suppression operations are performed on the grid connection point, and power sharing operations are performed on each of the voltage-controlled inverters and each of the current-controlled inverters.

[0029] In one specific embodiment of the present invention, the method further includes a process for determining whether the voltage quality of the grid connection point meets the grid connection conditions based on the voltage suppression result. The process for determining whether the voltage quality of the grid connection point meets the grid connection conditions based on the voltage suppression result includes:

[0030] Obtain the voltage single harmonic, voltage total harmonic, and voltage imbalance at the grid connection point;

[0031] Determine whether the voltage single harmonic, the voltage total harmonic, and the voltage imbalance all meet the preset standard range;

[0032] If so, then the voltage quality of the network point is determined to meet the grid connection conditions;

[0033] If not, then it is determined that the voltage quality of the network point does not meet the grid connection conditions.

[0034] In one specific embodiment of the present invention, obtaining the voltage single harmonic, voltage total harmonic, and voltage imbalance at the grid connection point includes:

[0035] The voltage single harmonic, voltage total harmonic, and voltage imbalance of the grid connection point are obtained at preset time intervals.

[0036] Determining whether the voltage single harmonic, the voltage total harmonic, and the voltage imbalance all meet preset standard ranges includes:

[0037] Determine whether the single harmonic of each voltage, the total harmonic of each voltage, and the voltage imbalance all meet the preset standard range within the preset time interval.

[0038] In one specific embodiment of the present invention, the suppression of grid-connected harmonic current and / or grid-connected unbalanced current using a dynamic voltage compensator includes:

[0039] Extract harmonic components and / or unbalanced components from the grid-connected current;

[0040] Calculate the voltage compensation value of the dynamic voltage compensator based on the harmonic components and / or the unbalanced components;

[0041] The voltage compensation value is converted into the voltage value output by the dynamic voltage compensator through a voltage-current dual loop.

[0042] A grid-connected control device for distributed generation in a power distribution network, comprising:

[0043] The component extraction module is used to extract harmonic components and / or negative sequence components from the grid connection point voltage and the local current corresponding to each distributed power source when each local power grid is operating as a system island; wherein, each of the distributed power sources includes each voltage-controlled distributed power source and each current-controlled distributed power source.

[0044] The power calculation module is used to calculate the harmonic power and / or unbalanced power output by each of the distributed power sources based on the grid connection point voltage, each of the harmonic components and / or each of the negative sequence components.

[0045] The reference value calculation module is used to calculate, based on the harmonic power and / or the unbalanced power, the first output reference value corresponding to each voltage-controlled inverter and the second output reference value corresponding to each current-controlled inverter, respectively, based on the principle of distributed communication and consistency, and satisfying the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point, and satisfying the power distribution of each voltage-controlled inverter and each current-controlled inverter.

[0046] The voltage suppression and power sharing module is used to perform harmonic voltage suppression and / or unbalanced voltage suppression operations on the grid connection point according to each of the first output reference values ​​and each of the second output reference values, and to perform power sharing operations on each of the voltage-controlled inverters and each of the current-controlled inverters.

[0047] The power grid operation control module is used to perform phase angle pre-synchronization on each of the voltage-controlled distributed power sources and control each of the local power grids to operate in grid-connected mode when the voltage quality of the grid connection point is determined to meet the grid connection conditions based on the voltage suppression results.

[0048] The current suppression module is used to suppress grid-connected harmonic currents and / or grid-connected unbalanced currents using a dynamic voltage compensator.

[0049] In one specific embodiment of the present invention, an islanded operation control module is further included, the islanded operation control module comprising:

[0050] The voltage reference value acquisition submodule is used to control each voltage-controlled distributed power source in each of the local power grids to provide voltage and frequency support for each of the local power grids using the droop control principle, thereby obtaining each voltage reference value.

[0051] The power acquisition submodule is used to acquire the preset active power output, preset reactive power output, instantaneous active power output and instantaneous reactive power output corresponding to each current-controlled distributed power source in each local power grid.

[0052] The current reference value calculation submodule is used to calculate the current reference value of each current-controlled distributed power source output based on each preset active power output, each preset reactive power output, each instantaneous active power output, and each instantaneous reactive power output.

[0053] The islanding operation control submodule is used to perform voltage and current dual-loop control on each of the voltage reference values ​​and current loop control on each of the current reference values, so that each of the local power grids can operate in system islanding mode.

[0054] A grid-connected control device for distributed generation in a power distribution network, comprising:

[0055] Memory, used to store computer programs;

[0056] A processor is used to execute the computer program to implement the steps of the grid connection control method for distributed power sources in the distribution network as described above.

[0057] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the grid connection control method for distributed power sources in a power distribution network as described above.

[0058] The grid-connected control method for distributed generation in a distribution network provided by this invention extracts harmonic components and / or negative sequence components from the grid connection point voltage and the local current corresponding to each distributed generation when each local grid operates as a system island. Each distributed generation includes voltage-controlled distributed generation and current-controlled distributed generation. Based on the grid connection point voltage, harmonic components, and / or negative sequence components, the harmonic power and / or unbalanced power output by each distributed generation are calculated. Based on the harmonic power and / or unbalanced power, and based on the principles of distributed communication and consistency, the method calculates the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point, and satisfies the requirements of each voltage-controlled inverter and... The system includes a first output reference value for each voltage-controlled inverter and a second output reference value for each current-controlled inverter, with power shared equally among them. Based on these first and second output reference values, harmonic voltage suppression and / or unbalanced voltage suppression operations are performed at the grid connection point, and power sharing is performed on both the voltage-controlled and current-controlled inverters. When the voltage quality at the grid connection point meets the grid connection conditions based on the voltage suppression results, phase angle pre-synchronization is performed on each voltage-controlled distributed power source, and each local grid is controlled to operate in grid-connected mode. A dynamic voltage compensator is used to suppress grid-connected harmonic current and / or grid-connected unbalanced current.

[0059] As can be seen from the above technical solution, by calculating the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point based on the harmonic components and / or negative sequence components in the local current corresponding to each distributed power source, and by calculating the first output reference value and the second output reference value corresponding to each voltage-controlled inverter and each current-controlled inverter respectively, and performing harmonic voltage suppression and / or unbalanced voltage suppression operations at the grid connection point based on the calculated first output reference value and second output reference value, and performing power sharing operations on each voltage-controlled inverter and each current-controlled inverter, when it is determined from the voltage suppression results that the voltage quality at the grid connection point meets the grid connection conditions, the phase angle pre-synchronization of each voltage-controlled distributed power source is performed, and each local grid is controlled to operate in grid-connected mode, using a dynamic voltage compensator to suppress grid-connected harmonic current and / or grid-connected unbalanced current. This invention considers the coexistence of voltage-controlled and current-controlled distributed power sources. The proposed strategy can be directly applied to the modulated wave and used directly in both voltage-controlled and current-controlled distributed power sources without adding redundant current loops. The proposed strategy addresses the contradiction between grid-connected current control and grid-connected voltage control when the grid side contains harmonics and unbalanced sources. The proposed strategy can simultaneously achieve these two control objectives. This invention adopts a distributed communication method, which facilitates the expansion of the scale of distributed power source combinations and improves control performance and power quality.

[0060] Accordingly, the present invention also provides a grid-connection control device, equipment, and computer-readable storage medium for distributed power sources in a distribution network, which are corresponding to the above-mentioned grid-connection control method for distributed power sources in a distribution network and have the above-mentioned technical effects, which will not be elaborated here. Attached Figure Description

[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0062] Figure 1 This is a flowchart illustrating one implementation of the grid connection control method for distributed power sources in a power distribution network according to an embodiment of the present invention.

[0063] Figure 2 This is a flowchart illustrating another implementation of the grid connection control method for distributed power sources in a power distribution network according to an embodiment of the present invention.

[0064] Figure 3 This is a schematic diagram of the grid-connected control simulation system for distributed power sources in a power distribution network according to an embodiment of the present invention;

[0065] Figure 4 This is a control effect diagram of the grid connection point voltage without any control strategy in an embodiment of the present invention;

[0066] Figure 5 This is a diagram illustrating the control effect of grid connection point voltage after applying harmonic voltage suppression and / or unbalanced voltage suppression and power sharing strategies in an embodiment of the present invention.

[0067] Figure 6 This is a diagram illustrating the control effect of grid-connected current after a harmonic source and / or unbalanced source are added to the grid side 5 seconds later, according to an embodiment of the present invention.

[0068] Figure 7 This is an example of the control effect of grid-connected current after the application of a grid-connected current compensation strategy in an embodiment of the present invention.

[0069] Figure 8 This is a diagram illustrating the control effect of unbalanced power output from five distributed power sources in an embodiment of the present invention.

[0070] Figure 9 This is a diagram illustrating the control effect of the fifth harmonic power output from five distributed power sources in an embodiment of the present invention.

[0071] Figure 10This is a diagram illustrating the control effect of the seventh harmonic power output from five distributed power sources in an embodiment of the present invention.

[0072] Figure 11 This is a structural block diagram of a grid-connected control device for distributed power sources in a power distribution network, as described in an embodiment of the present invention.

[0073] Figure 12 This is a structural block diagram of a grid-connected control device for distributed power sources in a power distribution network, as described in an embodiment of the present invention.

[0074] Figure 13 This is a schematic diagram of the specific structure of a grid-connected control device for distributed power sources in a power distribution network, as provided in this embodiment. Detailed Implementation

[0075] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0076] See Figure 1 , Figure 1 This is a flowchart illustrating an implementation of a grid-connected control method for distributed generation in a power distribution network according to an embodiment of the present invention. The method may include the following steps:

[0077] S101: When each local power grid operates as a system island, extract the harmonic components and / or negative sequence components from the grid connection point voltage and the local current corresponding to each distributed power source.

[0078] Among them, each distributed power source includes each voltage-controlled distributed power source and each current-controlled distributed power source.

[0079] A large power grid typically includes multiple local power grids, each of which contains distributed generation sources. These local power grids may contain only voltage-controlled distributed generation sources, only current-controlled distributed generation sources, or both voltage-controlled and current-controlled distributed generation sources.

[0080] Each local power grid is pre-controlled to operate as a system island. When each local power grid operates as a system island, the harmonic components and / or negative sequence components in the local current corresponding to the grid connection point (PCC) voltage and each distributed power source are extracted. If only harmonic components exist in the local current, only the harmonic components in the local current are extracted; if only negative sequence components exist in the local current, only the negative sequence components in the local current are extracted; if both harmonic components and negative sequence components exist in the local current, both harmonic components and negative sequence components in the local current are extracted.

[0081] S102: Calculate the harmonic power and / or unbalanced power output by each distributed power source based on the grid connection point voltage, each harmonic component and / or each negative sequence component.

[0082] After extracting the harmonic components and / or negative sequence components from the grid connection point voltage and the local current corresponding to each distributed power source, the harmonic power and / or unbalanced power output by each distributed power source are calculated based on the grid connection point voltage, each harmonic component, and / or each negative sequence component. When only the grid connection point voltage and each harmonic component are extracted, the harmonic power output by each distributed power source is calculated based on the grid connection point voltage and each harmonic component; when only the grid connection point voltage and each negative sequence component are extracted, the unbalanced power output by each distributed power source is calculated based on the grid connection point voltage and each negative sequence component; when the grid connection point voltage, each harmonic component, and each negative sequence component are extracted, the harmonic power output by each distributed power source is calculated based on the grid connection point voltage and each harmonic component, and the unbalanced power output by each distributed power source is also calculated based on the grid connection point voltage and each negative sequence component.

[0083] S103: Based on the harmonic power and / or unbalanced power, calculate the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point according to the principle of distributed communication and consistency, and satisfy the first output reference value corresponding to each voltage-controlled inverter and the second output reference value corresponding to each current-controlled inverter, respectively, with the power of each voltage-controlled inverter and each current-controlled inverter being equally distributed.

[0084] After calculating the harmonic power and / or unbalanced power output of each distributed power source, based on the harmonic power and / or unbalanced power, and according to the principles of distributed communication and consistency, the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point are calculated, and the first output reference value corresponding to each voltage-controlled inverter and the second output reference value corresponding to each current-controlled inverter are calculated, respectively, to ensure that the power is evenly distributed among each voltage-controlled inverter and each current-controlled inverter.

[0085] The first and second output reference values ​​can be current values, voltage values, etc., obtained through a series of calculations.

[0086] It should be noted that the terms "first" and "second" in the first and second output reference values ​​do not have any order of magnitude or sequence; they are merely used to distinguish the output reference values ​​corresponding to voltage-controlled inverters and current-controlled inverters.

[0087] S104: Based on each first output reference value and each second output reference value, perform harmonic voltage suppression and / or unbalanced voltage suppression operations on the grid connection point, and perform power sharing operations on each voltage-controlled inverter and each current-controlled inverter.

[0088] After calculating the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point, and the first output reference value for each voltage-controlled inverter and the second output reference value for each current-controlled inverter that satisfies the power sharing requirement, harmonic voltage suppression and / or unbalanced voltage suppression operations are performed at the grid connection point based on the first output reference value and the second output reference value, and power sharing operations are performed on each voltage-controlled inverter and each current-controlled inverter. If only the harmonic power is calculated, harmonic voltage suppression is performed on the grid connection point based on the first and second output reference values, and power sharing is performed on each voltage-controlled inverter and each current-controlled inverter. If only the unbalanced power is calculated, unbalanced voltage suppression is performed on the grid connection point based on the first and second output reference values, and power sharing is performed on each voltage-controlled inverter and each current-controlled inverter. If both harmonic power and unbalanced power are calculated simultaneously, harmonic voltage suppression and unbalanced voltage suppression are performed on the grid connection point based on the first and second output reference values, and power sharing is performed on each voltage-controlled inverter and each current-controlled inverter.

[0089] S105: When the voltage quality of the grid connection point is determined to meet the grid connection conditions based on the voltage suppression results, phase angle pre-synchronization is performed on each voltage-controlled distributed power source, and each local power grid is controlled to operate in grid-connected mode.

[0090] After performing harmonic voltage suppression and / or unbalanced voltage suppression operations on the grid connection point based on the first and second output reference values, and performing power sharing operations on each voltage-controlled inverter and each current-controlled inverter, the voltage suppression results can be obtained. Based on these results, it can be determined whether the voltage quality of the grid connection point meets the grid connection conditions. When the voltage suppression results determine that the voltage quality of the grid connection point meets the grid connection conditions, phase angle pre-synchronization is performed on each voltage-controlled distributed power source to eliminate the active power surge caused by the phase angle difference between the grid connection point and the grid side at the moment of grid connection, and to control each local grid to operate in grid-connected mode.

[0091] Grid connection conditions can be set according to international standards as follows: 1) Voltage single harmonic HDh < 3% and total voltage THD < 5%; 2) Maximum allowable voltage imbalance VUF is 2%.

[0092] S106: Suppression of grid-connected harmonic current and / or grid-connected unbalanced current using a dynamic voltage compensator.

[0093] Considering the presence of harmonic sources and / or unbalanced sources on the main power grid side, after controlling each local power grid to operate in grid-connected mode, dynamic voltage compensators are used to suppress grid-connected harmonic currents and / or grid-connected unbalanced currents. For example, if the main power grid side only contains harmonic sources, only dynamic voltage compensators are used to suppress grid-connected harmonic currents; if the main power grid side only contains unbalanced sources, only dynamic voltage compensators are used to suppress grid-connected unbalanced currents; if the main power grid side contains both harmonic sources and unbalanced sources, dynamic voltage compensators are used to suppress both grid-connected harmonic currents and grid-connected unbalanced currents.

[0094] As can be seen from the above technical solution, by calculating the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point based on the harmonic components and / or negative sequence components in the local current corresponding to each distributed power source, and by calculating the first output reference value and the second output reference value corresponding to each voltage-controlled inverter and each current-controlled inverter respectively, and performing harmonic voltage suppression and / or unbalanced voltage suppression operations at the grid connection point based on the calculated first output reference value and second output reference value, and performing power sharing operations on each voltage-controlled inverter and each current-controlled inverter, when it is determined from the voltage suppression results that the voltage quality at the grid connection point meets the grid connection conditions, the phase angle pre-synchronization of each voltage-controlled distributed power source is performed, and each local grid is controlled to operate in grid-connected mode, using a dynamic voltage compensator to suppress grid-connected harmonic current and / or grid-connected unbalanced current. This invention considers the coexistence of voltage-controlled and current-controlled distributed power sources. The proposed strategy can be directly applied to the modulated wave and used directly in both voltage-controlled and current-controlled distributed power sources without adding redundant current loops. The proposed strategy addresses the contradiction between grid-connected current control and grid-connected voltage control when the grid side contains harmonics and unbalanced sources. The proposed strategy can simultaneously achieve these two control objectives. This invention adopts a distributed communication method, which facilitates the expansion of the scale of distributed power source combinations and improves control performance and power quality.

[0095] It should be noted that, based on the above embodiments, the present invention also provides corresponding improvements. In subsequent embodiments, steps identical or corresponding to those in the above embodiments can be referenced interchangeably, and their respective beneficial effects can also be referred to each other. These improvements will not be elaborated upon in the following improved embodiments.

[0096] See Figure 2 , Figure 2This is another implementation flowchart of the grid connection control method for distributed generation in a power distribution network according to an embodiment of the present invention. The method may include the following steps:

[0097] S201: Using the droop control principle, each voltage-controlled distributed power source in each local power grid is controlled to provide voltage and frequency support for each local power grid, and obtains each voltage reference value.

[0098] For local area networks (LANs) within a large power grid, the droop control principle is used to control the voltage-controlled distributed generation sources in each local LAN to provide voltage and frequency support, thus obtaining voltage reference values. For example, the following formula can be used to control the voltage-controlled distributed generation sources in each local LAN to provide voltage and frequency support:

[0099]

[0100] Where the subscript i represents the i-th voltage-controlled distributed power source, ω i This represents the reference value of the angular frequency of the fundamental frequency of the output voltage of the voltage-controlled distributed power source, V. i This represents the reference value for the amplitude of the fundamental frequency of the output voltage of the voltage-controlled distributed power source, ω. ni Indicates the angular frequency of the rated voltage, V ni Indicates the rated voltage amplitude; P i Q represents the active power output of the inverter, calculated using local voltage and current. i This represents the reactive power output of the inverter, calculated using local voltage and current, in m. i The droop factor, n, represents the frequency. i This represents the voltage droop factor.

[0101] S202: Obtain the preset active power output, preset reactive power output, instantaneous active power output, and instantaneous reactive power output corresponding to each current-controlled distributed power source in each local power grid.

[0102] Obtain the preset active power output, preset reactive power output, instantaneous active power output, and instantaneous reactive power output corresponding to each current-controlled distributed power source in each local power grid.

[0103] S203: Calculate the current reference value of each current-controlled distributed power source output based on each preset active power output, each preset reactive power output, each instantaneous active power output, and each instantaneous reactive power output.

[0104] After obtaining the preset active power output, preset reactive power output, instantaneous active power output, and instantaneous reactive power output corresponding to each current-controlled distributed power source in each local power grid, the current reference value output by each current-controlled distributed power source is calculated based on each preset active power output, each preset reactive power output, each instantaneous active power output, and each instantaneous reactive power output.

[0105] The reference current value for the output of each current-controlled distributed power source can be calculated using the following formula:

[0106]

[0107] Among them, i refdi and i refqi P represents the reference value of the output current of this current-controlled distributed power source in the dq coordinate system. avgi Q represents the relatively average active power obtained after the instantaneous output power P of the i-th current-controlled distributed power source passes through a low-pass filter. avgi P represents the reactive power obtained after the instantaneous output power Q of the i-th current-controlled distributed power source passes through a low-pass filter to obtain a more average reactive power. refi This indicates the active power output (Q) set for the distributed power source. refi The reactive power output of this distributed power source is set to k. Cp and k Ci These represent the control coefficients of the proportional and integral links of the PI controller used to calculate the current reference value in a current-controlled inverter, respectively.

[0108] S204: Perform dual-loop control of voltage and current for each voltage reference value, and current loop control for each current reference value, so that each local power grid can operate as a system island.

[0109] After obtaining the voltage reference values ​​and calculating the current reference values ​​of each current-controlled distributed power source, voltage and current dual-loop control is applied to each voltage reference value, and current loop control is applied to each current reference value, thereby enabling each local power grid to operate as a system island.

[0110] S205: When each local power grid operates as a system island, extract the harmonic components and / or negative sequence components from the grid connection point voltage and the local current corresponding to each distributed power source.

[0111] Among them, each distributed power source includes each voltage-controlled distributed power source and each current-controlled distributed power source.

[0112] Harmonics and unbalanced components in grid-connected voltage, distributed generation output voltage, and current can be extracted using a multiple harmonics observer (MHSCO). The unbalanced component, i.e., the negative-sequence component, can be equivalently considered as the -1st harmonic. Harmonic components and / or negative-sequence components can be extracted using the following formula:

[0113]

[0114] in, This represents the k-th iteration estimate of the h-th component of the current or voltage under study. v represents the (k+1)th iteration estimate of the h-th component of the current or voltage under study. k Let represent the original variable, such as voltage or current; ω represent the fundamental frequency; ω represent the cutoff frequency; T represent the sampling period; n is the number of estimated principal harmonics; m is the set of estimated principal components; and h represents the h-th harmonic component. This represents the set of all components estimated by the observer in its k-th iteration.

[0115] S206: Calculate the harmonic power and / or unbalanced power output by each distributed power source based on the grid connection point voltage, each harmonic component and / or each negative sequence component.

[0116] S207: Based on the principles of distributed communication and consistency, calculate the harmonic power difference and / or unbalanced power difference between adjacent nodes for each voltage-controlled inverter and each current-controlled inverter, and obtain the calculation results of each harmonic power difference and / or each unbalanced power difference.

[0117] After calculating the harmonic power and / or unbalanced power output of each distributed power source, based on the principles of distributed communication and consistency, the harmonic power difference and / or unbalanced power difference between adjacent nodes are calculated for each voltage-controlled inverter and each current-controlled inverter, yielding the results of the harmonic power difference calculation and / or the unbalanced power difference calculation. Through continuous iteration, the global harmonic power and / or unbalanced power are indirectly obtained, thereby achieving the goal of power equalization.

[0118] S208: Based on the calculation results of the harmonic power difference and / or the calculation results of the unbalanced power difference, determine the first virtual impedance corresponding to each distributed power source when the power is evenly distributed for each voltage-controlled inverter and each current-controlled inverter.

[0119] After calculating the power differences of each harmonic and / or the power imbalances, the first virtual impedance corresponding to each distributed power source when power is evenly distributed for each voltage-controlled inverter and each current-controlled inverter is determined based on these calculations. The first virtual impedance can be calculated using the following formula:

[0120]

[0121] in, k represents the virtual impedance used to ensure even power distribution. Hpi k represents the proportional term of the power sharing controller. Hii The integral term of the power-sharing controller is represented by S, where c represents the integral. i c represents a coefficient inversely proportional to the rated capacity of the distributed power source i. j H represents a coefficient inversely proportional to the rated capacity of the distributed power source j. i h This represents the h-th harmonic power output by the i-th distributed power source. N represents the h-th harmonic power output by the j-th distributed power source. i Let a represent the set of distributed power sources connected to distributed power source i in the system. ij a represents the adjacency element of a distributed communication topology. ij >0 indicates that distributed source i can receive information from distributed source j; otherwise, a ij =0.

[0122] S209: Extract each component of the grid connection point voltage.

[0123] After extracting the grid connection point voltage, extract each component of the grid connection point voltage.

[0124] S210: Calculate the harmonic distortion and / or unbalance distortion of each component separately.

[0125] After extracting each component of the grid connection point voltage, the harmonic distortion and / or unbalance distortion are calculated separately for each component. When only the harmonic components are extracted, the harmonic distortion is calculated separately for each harmonic component; when only the unbalance components are extracted, the unbalance distortion is calculated separately for each unbalance component; when both harmonic components and unbalance components are extracted, the harmonic distortion is calculated separately for each harmonic component, and the unbalance distortion is calculated separately for each unbalance component.

[0126] Distortion can be calculated using the following formula:

[0127]

[0128] in, This represents the amplitude of the h-th harmonic of the grid connection point voltage. It represents the amplitude of the fundamental voltage at the grid connection point.

[0129] S211: Calculate the second virtual impedance corresponding to each distributed power source when the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point are satisfied, based on the harmonic distortion and / or unbalanced distortion of each harmonic distortion and / or unbalanced distortion.

[0130] After calculating the harmonic distortion and / or unbalance distortion, the second virtual impedance corresponding to each distributed power source is calculated based on the harmonic distortion and / or unbalance distortion to meet the harmonic voltage suppression and / or unbalance voltage suppression requirements at the grid connection point. Specifically, if only the harmonic distortion is calculated, the second virtual impedance corresponding to each distributed power source is calculated based on the harmonic distortion to meet the harmonic voltage suppression requirements at the grid connection point; if only the unbalance distortion is calculated, the second virtual impedance corresponding to each distributed power source is calculated based on the unbalance distortion to meet the unbalance voltage suppression requirements at the grid connection point; and if both harmonic distortion and unbalance distortion are calculated, the second virtual impedance corresponding to each distributed power source is calculated based on the harmonic distortion to meet the harmonic voltage suppression and unbalance voltage suppression requirements at the grid connection point.

[0131] The second virtual impedance can be calculated using the following formula:

[0132]

[0133] Where, k Vii This represents the integral term representing the voltage suppression at each distributed power source's grid connection point.

[0134] S212: Based on the first virtual impedance and the second virtual impedance, calculate the voltage compensation amount for each voltage-controlled inverter and the current compensation amount for each current-controlled inverter.

[0135] After calculating the first virtual impedance corresponding to each distributed power source when the power is evenly distributed for each voltage-controlled inverter and each current-controlled inverter, and calculating the second virtual impedance corresponding to each distributed power source when the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point are satisfied, the voltage compensation amount of each voltage-controlled inverter and the current compensation amount corresponding to each current-controlled inverter are calculated based on the first virtual impedance and the second virtual impedance.

[0136] The voltage compensation and current compensation for each iteration can be calculated using the following formulas:

[0137]

[0138] in, This represents the compensation amount for the h-th voltage output of a voltage-controlled inverter. This represents the h-th output current of the voltage-controlled inverter. This represents the compensation amount for the h-th output current of a current-controlled inverter. This represents the h-th output voltage of the current-controlled inverter. It's important to note that the output voltage of a current-controlled inverter is determined by external conditions. Furthermore...

[0139] S213: Based on the voltage compensation and current compensation amounts, perform harmonic voltage suppression and / or unbalanced voltage suppression operations at the grid connection point, and perform power sharing operations on each voltage-controlled inverter and each current-controlled inverter.

[0140] After calculating the voltage compensation for each voltage-controlled inverter and the current compensation for each current-controlled inverter, harmonic voltage suppression and / or unbalanced voltage suppression operations are performed at the grid connection point based on the voltage compensation and current compensation, and power sharing operations are performed on each voltage-controlled inverter and each current-controlled inverter.

[0141] S214: Obtain the voltage single harmonic, voltage total harmonic, and voltage imbalance at the grid connection point.

[0142] After performing harmonic voltage suppression and / or unbalanced voltage suppression operations at the grid connection point, and power sharing operations on each voltage-controlled inverter and each current-controlled inverter, the single harmonic voltage at the grid connection point is obtained. Total Harmonic Discharge (THD) pcc and voltage imbalance VUF pcc .

[0143] S215: Determine whether the voltage single harmonic, voltage total harmonic, and voltage imbalance all meet the preset standard range. If not, proceed to step S216; if yes, proceed to step S217.

[0144] After obtaining the voltage single harmonic, voltage total harmonic, and voltage imbalance at the grid connection point, determine whether the voltage single harmonic, voltage total harmonic, and voltage imbalance all meet the preset standard range. If not, proceed to step S216; if yes, proceed to step S217.

[0145] The following formula can be used to determine whether the voltage single harmonic, voltage total harmonic, and voltage imbalance all meet the preset standard range:

[0146]

[0147] In one specific embodiment of the present invention, step S214 may include the following steps:

[0148] The voltage single harmonic, voltage total harmonic, and voltage imbalance at the grid connection point are obtained at preset time intervals.

[0149] Accordingly, step S215 may include the following steps:

[0150] Determine whether the single harmonic of each voltage, the total harmonic of each voltage, and the unbalance of each voltage all meet the preset standard range within the preset time interval.

[0151] For ease of description, the above steps can be combined for explanation.

[0152] The system pre-sets time intervals for acquiring the single harmonic voltage, total harmonic voltage, and voltage imbalance at the grid connection point. These parameters are acquired at each preset time interval, and it is determined whether each harmonic, total harmonic, and voltage imbalance meets preset standard ranges within the specified time intervals. The fact that harmonic and imbalance indicators consistently meet preset standard ranges over a period of time (e.g., ten cycles acquired at preset time intervals) serves as the basis for determining whether the voltage quality at the grid connection point meets grid connection requirements, thus ensuring stable grid operation and preventing interference.

[0153] S216: The voltage quality of the network point does not meet the grid connection conditions.

[0154] When it is determined that there are indicators in the voltage single harmonic, voltage total harmonic, and voltage imbalance that do not meet the preset standard range, it is determined that the voltage quality of the grid point does not meet the grid connection conditions.

[0155] S217: Determine that the voltage quality of the network point meets the grid connection conditions.

[0156] When the voltage single harmonic, voltage total harmonic, and voltage imbalance all meet the preset standard range, the voltage quality of the grid point is determined to meet the grid connection conditions.

[0157] S218: Perform phase angle pre-synchronization on each voltage-controlled distributed power source and control each local power grid to operate in grid-connected mode.

[0158] After confirming that the voltage quality of the grid points meets the grid connection conditions, phase angle pre-synchronization is performed on each voltage-controlled distributed power source, and each local power grid is controlled to operate in grid-connected mode.

[0159] The following formula can be used to pre-synchronize the phase angle of each voltage-controlled distributed power source:

[0160] Δθ=k θp (θ g -θ pcc )+k θi ∫(θ g -θ pcc );

[0161] Where Δθ represents the adjustment amount of the output phase angle of the voltage-controlled inverter, and k θp k represents the proportional coefficient of the phase angle pre-synchronization controller. θi θ represents the integral coefficient of the phase angle pre-synchronization controller. g θ represents the phase angle on the grid side. pccThis indicates the phase angle at the point of connection (PCC).

[0162] S219: Extract harmonic components and / or unbalanced components from the grid-connected current.

[0163] After controlling each local power grid to operate in grid-connected mode, extract the harmonic components and / or unbalanced components from the grid-connected current. If only harmonic components exist in the grid-connected current, extract the harmonic components; if only unbalanced components exist in the grid-connected current, extract the unbalanced components; if both harmonic and unbalanced components exist in the grid-connected current, extract both harmonic and unbalanced components.

[0164] S220: Calculate the voltage compensation value of the dynamic voltage compensator based on the harmonic components and / or unbalanced components.

[0165] After extracting the harmonic components and / or unbalanced components from the grid-connected current, the voltage compensation value of the dynamic voltage compensator is calculated based on the harmonic components and / or unbalanced components. Specifically, if only the harmonic components of the grid-connected current are extracted, the voltage compensation value of the dynamic voltage compensator is calculated based on the harmonic components; if only the unbalanced components of the grid-connected current are extracted, the voltage compensation value of the dynamic voltage compensator is calculated based on the unbalanced components; and if both harmonic and unbalanced components of the grid-connected current are extracted, the voltage compensation value of the dynamic voltage compensator is calculated based on both harmonic and unbalanced components.

[0166] The voltage compensation value of a dynamic voltage compensator can be calculated using the following formula:

[0167]

[0168] Where, k Dp and k Di This represents the proportional-integral term of the grid-connected current suppressor. This represents the harmonic components and / or unbalanced components extracted from the grid-connected current.

[0169] S221: Converts the voltage compensation value into the voltage value output by the dynamic voltage compensator through a voltage and current dual loop.

[0170] After calculating the voltage compensation value of the dynamic voltage compensator, the voltage compensation value is converted into the output voltage value of the dynamic voltage compensator through a voltage-current dual loop.

[0171] In a specific application example, see Figure 3 , Figure 3This is a schematic diagram of a grid-connected control simulation system for distributed generation in a distribution network according to an embodiment of the present invention. The distributed generation consists of three voltage-controlled distributed generation sources and two current-controlled distributed generation sources. Each distributed generation source is connected to a common terminal through its own connection impedance. The common terminal has nonlinear loads, linear loads, and unbalanced loads. The rated capacities of the five distributed generation sources are equal. This invention presents a grid-connected coordinated control method for a distribution network with high-density distributed generation access, considering nonlinear and unbalanced loads, according to an embodiment of the present invention. A simulation model is built based on the MATLAB / Simulink platform to verify the control effect of the method.

[0172] like Figures 4 to 10 The figure shows the simulation results of distributed power source control combining voltage-controlled and current-controlled distributed power sources in this embodiment. At the start of operation, only linear loads are connected, and the distributed power sources operate smoothly. At 0.5s, nonlinear and unbalanced loads are connected. Then, at 2s, a control strategy is implemented to suppress harmonics and unbalanced grid connection point voltages, as well as to evenly distribute power among the distributed power sources. At 4s, VCM pre-synchronization for grid connection is performed. At 4.5s, grid connection operation is performed. At 5s, harmonic and unbalanced sources on the grid side are connected. Finally, at 5.5s, a dynamic voltage compensator is added to suppress grid connection current.

[0173] Simulation results are as follows Figures 4 to 10 As shown, where, Figure 4 This is a control effect diagram of the grid connection point voltage without any control strategy in an embodiment of the present invention. The horizontal axis represents time (in seconds), and the vertical axis represents the output voltage (in volts). Figure 4 It can be seen that before the strategy was applied, the voltage distortion at the grid connection point was severe, with the voltage VUF reaching 5.03% and the voltage THD reaching 9.95%, far exceeding the limit standards of VUF<2% and THD<5%. Figure 5 This is a control effect diagram of the grid connection point voltage after applying harmonic voltage suppression and / or unbalanced voltage suppression and power sharing strategies in an embodiment of the present invention. The horizontal axis represents time in seconds, and the vertical axis represents the output voltage in volts. Figure 5 As shown, after the strategy was applied, the voltage imbalance quickly decreased to 0.24%, the voltage THD decreased to 1.89%, and the voltage waveform recovered to a better sine wave. However, in this simulation, only the imbalance and the 5th and 7th harmonics with the highest content were added to the controller, and the higher harmonics were not suppressed. Therefore, theoretically, the harmonics can be reduced to near zero. Figure 6 This diagram illustrates the control effect of grid-connected current after a harmonic source and / or unbalanced source are added to the grid side 5 seconds later, according to an embodiment of the present invention. The horizontal axis represents time (in seconds), and the vertical axis represents grid-connected current (in amperes). Figure 6As shown, the grid-connected current distortion is severe, with VUF reaching as high as 7.83% and current THD reaching as high as 28.83%. Figure 7 This diagram illustrates the control effect of grid-connected current after the application of a grid-connected current compensation strategy in an embodiment of the present invention. The horizontal axis represents time (in seconds), and the vertical axis represents grid-connected current (in amperes). Figure 7 As shown, after the strategy was applied, the grid-connected current quickly recovered to a standard sine wave, with VUF at only 0.19% and THD at only 1.25%. This was because the high-order harmonic control strategy was not applied.

[0174] like Figure 8 , Figure 9 , Figure 10 As shown, Figure 8 This is a diagram illustrating the control effect of unbalanced power output from five distributed power sources in an embodiment of the present invention. Figure 9 This is a diagram illustrating the control effect of the fifth harmonic power output from five distributed power sources in an embodiment of the present invention. Figure 10 This diagram illustrates the control effect of the seventh harmonic power output from five distributed power sources in an embodiment of the present invention. The horizontal axis represents time (in seconds), and the vertical axis represents unbalanced, fifth, and seventh harmonic power (in watts). As can be seen from the diagram, in Step 2, the unbalanced, fifth, and seventh harmonic power are well evenly distributed. In Step 4, the grid connection stage, the unbalanced and harmonic power output from each distributed power source exhibits only minor fluctuations, demonstrating smooth grid connection. In Step 5, even with the addition of grid-side harmonics and unbalanced sources, the corresponding power outputs from the five distributed power sources maintain a good and consistent trend. After the dynamic voltage compensator operates in Step 6, the unbalanced and harmonic power outputs from each distributed power source recover to their original output values ​​after a brief fluctuation. Therefore, the effectiveness of the proposed harmonic control scheme is verified.

[0175] Corresponding to the above method embodiments, the present invention also provides a grid-connected control device for distributed generation in a distribution network. The grid-connected control device for distributed generation in a distribution network described below and the grid-connected control method for distributed generation in a distribution network described above can be referred to in correspondence with each other.

[0176] See Figure 11 , Figure 11 This is a structural block diagram of a grid-connected control device for distributed generation in a power distribution network according to an embodiment of the present invention. The device may include:

[0177] The component extraction module 111 is used to extract the harmonic components and / or negative sequence components in the local current corresponding to the grid connection point voltage and each distributed power source when each local power grid is operating as a system island; wherein, each distributed power source includes each voltage-controlled distributed power source and each current-controlled distributed power source.

[0178] The power calculation module 112 is used to calculate the harmonic power and / or unbalanced power output by each distributed power source based on the grid connection point voltage, each harmonic component and / or each negative sequence component.

[0179] The reference value calculation module 113 is used to calculate, based on the principles of distributed communication and consistency, the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point, and the first output reference value and the second output reference value corresponding to each voltage-controlled inverter and each current-controlled inverter, respectively, based on the power of each harmonic and / or unbalanced power.

[0180] The voltage suppression and power sharing module 114 is used to perform harmonic voltage suppression and / or unbalanced voltage suppression operations on the grid connection point according to each first output reference value and each second output reference value, and to perform power sharing operations on each voltage-controlled inverter and each current-controlled inverter.

[0181] The power grid operation control module 115 is used to perform phase angle pre-synchronization on each voltage-controlled distributed power source and control each local power grid to operate in grid-connected mode when the voltage quality of the grid connection point is determined to meet the grid connection conditions based on the voltage suppression results.

[0182] The current suppression module 116 is used to suppress grid-connected harmonic current and / or grid-connected unbalanced current using a dynamic voltage compensator.

[0183] As can be seen from the above technical solution, by calculating the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point based on the harmonic components and / or negative sequence components in the local current corresponding to each distributed power source, and by calculating the first output reference value and the second output reference value corresponding to each voltage-controlled inverter and each current-controlled inverter respectively, and performing harmonic voltage suppression and / or unbalanced voltage suppression operations at the grid connection point based on the calculated first output reference value and second output reference value, and performing power sharing operations on each voltage-controlled inverter and each current-controlled inverter, when it is determined from the voltage suppression results that the voltage quality at the grid connection point meets the grid connection conditions, the phase angle pre-synchronization of each voltage-controlled distributed power source is performed, and each local grid is controlled to operate in grid-connected mode, using a dynamic voltage compensator to suppress grid-connected harmonic current and / or grid-connected unbalanced current. This invention considers the coexistence of voltage-controlled and current-controlled distributed power sources. The proposed strategy can be directly applied to the modulated wave and used directly in both voltage-controlled and current-controlled distributed power sources without adding redundant current loops. The proposed strategy addresses the contradiction between grid-connected current control and grid-connected voltage control when the grid side contains harmonics and unbalanced sources. The proposed strategy can simultaneously achieve these two control objectives. This invention adopts a distributed communication method, which facilitates the expansion of the scale of distributed power source combinations and improves control performance and power quality.

[0184] In one specific embodiment of the present invention, the device may further include an islanding operation control module, which includes:

[0185] The voltage reference value acquisition submodule is used to control each voltage-controlled distributed power source in each local power grid to provide voltage and frequency support for each local power grid by using the droop control principle, and to obtain each voltage reference value.

[0186] The power acquisition submodule is used to acquire the preset active power output, preset reactive power output, instantaneous active power output, and instantaneous reactive power output corresponding to each current-controlled distributed power source in each local power grid.

[0187] The current reference value calculation submodule is used to calculate the current reference value of each current-controlled distributed power source output based on each preset active power output, each preset reactive power output, each instantaneous active power output, and each instantaneous reactive power output.

[0188] The islanding operation control submodule is used to perform dual-loop voltage and current control on each voltage reference value and current loop control on each current reference value, so that each local power grid can operate as a system island.

[0189] In one specific embodiment of the present invention, the reference value calculation module 113 includes:

[0190] The difference calculation result acquisition submodule is used to perform harmonic power difference calculation and / or unbalanced power difference calculation for adjacent nodes of each voltage-controlled inverter and each current-controlled inverter based on the principle of distributed communication and consistency, and obtain the calculation results of each harmonic power difference and / or each unbalanced power difference.

[0191] The first virtual impedance determination submodule is used to determine the first virtual impedance corresponding to each distributed power source when the power is evenly distributed for each voltage-controlled inverter and each current-controlled inverter, based on the calculation results of each harmonic power difference and / or each unbalanced power difference.

[0192] The first component extraction submodule is used to extract each component of the grid connection point voltage.

[0193] The distortion calculation submodule is used to calculate the harmonic distortion and / or unbalance distortion of each component separately.

[0194] The second virtual impedance determination submodule is used to calculate the second virtual impedance corresponding to each distributed power source when the harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point are satisfied, based on the harmonic distortion and / or unbalanced distortion of each harmonic distortion and / or unbalanced distortion.

[0195] The current compensation calculation submodule is used to calculate the voltage compensation amount of each voltage-controlled inverter and the current compensation amount of each current-controlled inverter based on the first virtual impedance and the second virtual impedance.

[0196] The voltage suppression and power sharing module is specifically designed to perform harmonic voltage suppression and / or unbalanced voltage suppression operations at the grid connection point based on the voltage compensation and current compensation amounts, and to perform power sharing operations on each voltage-controlled inverter and each current-controlled inverter.

[0197] In one specific embodiment of the present invention, the device may further include a grid connection condition determination module, which includes:

[0198] The harmonic and unbalance acquisition submodule is used to acquire the single harmonic voltage, total harmonic voltage, and voltage unbalance at the grid connection point.

[0199] The judgment submodule is used to determine whether the voltage single harmonic, voltage total harmonic, and voltage imbalance all meet the preset standard range.

[0200] The grid connection condition determination submodule is used to determine that the voltage quality of the grid point meets the grid connection conditions when the voltage single harmonic, voltage total harmonic, and voltage imbalance all meet the preset standard range.

[0201] The "Does Not Meet Grid Connection Conditions Determination Submodule" is used to determine that the voltage quality of a grid point does not meet the grid connection conditions when any of the following indicators are found to be outside the preset standard range: voltage single harmonic, voltage total harmonic, and voltage imbalance.

[0202] In one specific embodiment of the present invention, the harmonic and unbalance acquisition submodule is specifically a module that acquires the single harmonic of voltage, the total harmonic of voltage, and the voltage unbalance at the grid connection point according to a preset time interval.

[0203] The judgment submodule is specifically designed to determine whether the single harmonic of each voltage, the total harmonic of each voltage, and the unbalance of each voltage all meet the preset standard range within a preset time interval.

[0204] In one specific embodiment of the present invention, the current suppression module 116 includes:

[0205] The second component extraction submodule is used to extract harmonic components and / or unbalanced components in the grid-connected current.

[0206] The voltage compensation value calculation submodule is used to calculate the voltage compensation value of the dynamic voltage compensator based on harmonic components and / or unbalanced components.

[0207] The voltage value acquisition submodule is used to convert the voltage compensation value into the voltage value output by the dynamic voltage compensator through a voltage and current dual loop.

[0208] For the method embodiments described above, see [link to relevant documentation]. Figure 12 , Figure 12 This is a schematic diagram of the grid-connected control device for distributed power sources in a power distribution network provided by the present invention. The device may include:

[0209] Memory 332 is used to store computer programs;

[0210] The processor 322 is used to execute a computer program to implement the steps of the grid-connected control method for distributed power sources in the power distribution network described in the above method embodiments.

[0211] For details, please refer to Figure 13 , Figure 13This embodiment provides a schematic diagram of the specific structure of a grid-connected control device for distributed power sources in a distribution network. The grid-connected control device for distributed power sources in this distribution network can vary significantly due to differences in configuration or performance. It may include a processor (central processing unit, CPU) 322 (e.g., one or more processors) and a memory 332. The memory 332 stores one or more computer application programs 342 or data 344. The memory 332 can be temporary or persistent storage. The program stored in the memory 332 may include one or more modules (not shown in the diagram), each module may include a series of instruction operations on the data processing device. Furthermore, the processor 322 may be configured to communicate with the memory 332 and execute the series of instruction operations stored in the memory 332 on the grid-connected control device 301 for distributed power sources in the distribution network.

[0212] The grid-connected control device 301 for distributed power sources in the power distribution network may also include one or more power sources 326, one or more wired or wireless network interfaces 350, one or more input / output interfaces 358, and / or one or more operating systems 341.

[0213] The steps in the grid connection control method for distributed generation in the distribution network described above can be implemented by the structure of the grid connection control equipment for distributed generation in the distribution network.

[0214] Corresponding to the above method embodiments, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, can perform the following steps:

[0215] When each local power grid operates as a system island, harmonic components and / or negative sequence components are extracted from the grid connection point voltage and the local current corresponding to each distributed power source. Each distributed power source includes voltage-controlled and current-controlled distributed power sources. Based on the grid connection point voltage, harmonic components, and / or negative sequence components, the harmonic power and / or unbalanced power output of each distributed power source are calculated. Based on the harmonic power and / or unbalanced power, and based on distributed communication and consistency principles, harmonic voltage suppression and / or unbalanced voltage suppression at the grid connection point are calculated, and the power output of each voltage-controlled inverter and each current-controlled inverter is balanced. The system identifies the first output reference value for each voltage-controlled inverter and the second output reference value for each current-controlled inverter. Based on these values, harmonic voltage suppression and / or unbalanced voltage suppression operations are performed at the grid connection point, and power sharing is applied to both voltage-controlled and current-controlled inverters. When the voltage quality at the grid connection point meets the grid connection conditions based on the voltage suppression results, phase angle pre-synchronization is performed on each voltage-controlled distributed power source, and each local grid is controlled to operate in grid-connected mode. A dynamic voltage compensator is used to suppress grid-connected harmonic current and / or grid-connected unbalanced current.

[0216] The computer-readable storage medium may include various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0217] For a description of the computer-readable storage medium provided by the present invention, please refer to the above method embodiments; the present invention will not be described in detail here.

[0218] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatuses, devices, and computer-readable storage media disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0219] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A grid-connected control method for a distributed power source in a power distribution network, characterized by, Comprise: When each local power grid is operated in system island mode, extract the harmonic components and / or negative sequence components in the grid-connected point voltage and the local current corresponding to each distributed power source respectively; wherein each distributed power source comprises each voltage control type distributed power source and each current control type distributed power source; According to the grid-connected point voltage, each harmonic component and / or each negative sequence component, respectively calculate each harmonic power and / or unbalanced power output by each distributed power source; According to the each harmonic power and / or the unbalanced power, based on the distributed communication and consistency principle, calculate the first output reference value corresponding to each voltage control type inverter and the second output reference value corresponding to each current control type inverter respectively, which satisfy the harmonic voltage suppression and / or unbalanced voltage suppression of the grid-connected point, and the power sharing of each voltage control type inverter and each current control type inverter; According to each of the first output reference value and the second output reference value, carry out harmonic voltage suppression and / or unbalanced voltage suppression operation on the grid-connected point, and carry out power sharing operation on each of the voltage control type inverter and the current control type inverter; When the voltage quality of the grid-connected point is determined to satisfy the grid-connected condition according to the voltage suppression result, the phase angle of each voltage control type distributed power source is pre-synchronized, and each local power grid is operated in grid-connected mode; Utilize dynamic voltage compensator to carry out suppression operation on grid-connected harmonic current and / or grid-connected unbalanced current.

2. The grid-connected control method of a distributed power source in a power distribution network according to claim 1, characterized by, Also include the process of controlling each local power grid to operate in system island mode, the process of controlling each local power grid to operate in system island mode comprising: Control each voltage control type distributed power source in each local power grid to provide voltage support and frequency support for each local power grid by using droop control principle, to obtain each voltage reference value; Obtain the preset active power output, the preset reactive power output, the instantaneous output active power and the instantaneous output reactive power corresponding to each current control type distributed power source in each local power grid respectively; According to each of the preset active power output, the preset reactive power output, the instantaneous output active power and the instantaneous output reactive power, respectively calculate the current reference value output by each current control type distributed power source; Carry out voltage current double loop control on each voltage reference value, and carry out current loop control on each current reference value, so that each local power grid operates in system island mode.

3. The method of claim 1, wherein the method further comprises: According to the each harmonic power and / or the unbalanced power, based on the distributed communication and consistency principle, calculate the first output reference value corresponding to each voltage control type inverter and the second output reference value corresponding to each current control type inverter respectively, which satisfy the harmonic voltage suppression and / or unbalanced voltage suppression of the grid-connected point, and the power sharing of each voltage control type inverter and each current control type inverter, comprising: Based on the distributed communication and consistency principle, carry out harmonic power difference calculation and / or unbalanced power difference calculation of adjacent nodes on each voltage control type inverter and each current control type inverter, to obtain each harmonic power difference calculation result and / or each unbalanced power difference calculation result; According to each of the harmonic power difference calculation results and / or each of the unbalanced power difference calculation results, determine the first virtual impedance corresponding to each of the distributed power sources when the power of each of the voltage control type inverters and each of the current control type inverters is evenly distributed; Extract each component of the grid-connected point voltage; According to each of the components, calculate each harmonic distortion and / or unbalanced distortion; According to each of the harmonic distortion and / or the unbalanced distortion, calculate the second virtual impedance corresponding to each of the distributed power sources when the harmonic voltage suppression and / or the unbalanced voltage suppression of the grid-connected point is satisfied; According to the first virtual impedance and the second virtual impedance, calculate each voltage compensation of each of the voltage control type inverters and each current compensation corresponding to each of the current control type inverters; According to each of the first output reference value and each of the second output reference value, perform harmonic voltage suppression and / or unbalanced voltage suppression operation on the grid-connected point, and perform power distribution operation on each of the voltage control type inverters and each of the current control type inverters, including: According to each of the voltage compensation and each of the current compensation, perform harmonic voltage suppression and / or unbalanced voltage suppression operation on the grid-connected point, and perform power distribution operation on each of the voltage control type inverters and each of the current control type inverters.

4. The method of claim 1, wherein, It also includes a process of determining whether the voltage quality of the grid-connected point meets the grid-connected condition according to the voltage suppression result, and the process of determining whether the voltage quality of the grid-connected point meets the grid-connected condition according to the voltage suppression result includes: Obtain the voltage single harmonic, voltage total harmonic and voltage unbalance degree of the grid-connected point; Determine whether the voltage single harmonic, the voltage total harmonic and the voltage unbalance degree meet the preset standard range; If yes, it is determined that the voltage quality of the grid point meets the grid-connected condition; If not, it is determined that the voltage quality of the grid point does not meet the grid-connected condition.

5. The grid-connected control method of a distributed power source in a power distribution network according to claim 4, characterized by, Obtaining the voltage single harmonic, the voltage total harmonic and the voltage unbalance degree of the grid-connected point includes: According to the preset time interval, respectively obtain the voltage single harmonic, the voltage total harmonic and the voltage unbalance degree of the grid-connected point; Determine whether the voltage single harmonic, the voltage total harmonic and the voltage unbalance degree meet the preset standard range, including: Determine whether each of the voltage single harmonic, each of the voltage total harmonic and each of the voltage unbalance degree meets the preset standard range within the preset time interval.

6. The method of claim 1, wherein, The suppression operation of the grid-connected harmonic current and / or the grid-connected unbalanced current by the dynamic voltage compensator includes: Extracting the harmonic component and / or the unbalanced component in the grid-connected current; According to the harmonic component and / or the unbalanced component, calculate the voltage compensation value of the dynamic voltage compensator; Convert the voltage compensation value into the voltage value output by the dynamic voltage compensator through the voltage current double loop.

7. A grid-connected control device for distributed generation in a power distribution network, characterized in that, It includes: The component extraction module is configured to extract harmonic components and / or negative sequence components in the grid-connected point voltage and local currents respectively corresponding to the distributed power sources when each local power grid operates in a system island mode; wherein each of the distributed power sources includes a voltage control type distributed power source and a current control type distributed power source; The power calculation module is configured to calculate each harmonic power and / or unbalanced power output by each of the distributed power sources according to the grid-connected point voltage, each of the harmonic components and / or each of the negative sequence components; The reference value calculation module is configured to calculate first output reference values respectively corresponding to each of the voltage control type inverters and second output reference values respectively corresponding to each of the current control type inverters based on a distributed communication and a consistency principle according to each of the harmonic powers and / or the unbalanced powers, so as to satisfy harmonic voltage suppression and / or unbalanced voltage suppression of the grid-connected point and power sharing of each of the voltage control type inverters and each of the current control type inverters; The voltage suppression and power sharing module is configured to perform harmonic voltage suppression and / or unbalanced voltage suppression operation on the grid-connected point and power sharing operation on each of the voltage control type inverters and each of the current control type inverters according to each of the first output reference values and each of the second output reference values; The grid operation control module is configured to perform phase angle pre-synchronization on each of the voltage control type distributed power sources and control each of the local power grids to operate in a grid-connected mode when voltage quality of the grid-connected point determined according to voltage suppression results satisfies a grid-connected condition; The current suppression module is configured to perform suppression operation on grid-connected harmonic current and / or grid-connected unbalanced current by using a dynamic voltage compensator.

8. The apparatus for grid-connected control of distributed power supply in power distribution network according to claim 7, characterized in that, The island operation control module includes: The voltage reference value obtaining submodule is configured to control each of the voltage control type distributed power sources in each of the local power grids to provide voltage support and frequency support for each of the local power grids by using a droop control principle, so as to obtain each voltage reference value; The power acquisition submodule is configured to acquire preset active power output, preset reactive power output, instantaneous output active power and instantaneous output reactive power respectively corresponding to each of the current control type distributed power sources in each of the local power grids; The current reference value calculation submodule is configured to calculate a current reference value output by each of the current control type distributed power sources according to each of the preset active power output, each of the preset reactive power output, each of the instantaneous output active power and each of the instantaneous output reactive power; The island operation control submodule is configured to perform voltage and current double-loop control on each of the voltage reference values and current loop control on each of the current reference values, so as to enable each of the local power grids to operate in a system island mode.

9. A grid-connected control device for a distributed power source in a power distribution network, characterized by, The memory is configured to store a computer program; The processor is configured to implement the steps of the grid-connected control method of the distributed power source in the power distribution grid according to any one of claims 1 to 6 when executing the computer program. The computer program is stored on the computer readable storage medium and is executed by the processor to implement the steps of the grid-connected control method of the distributed power source in the power distribution grid according to any one of claims 1 to 6.

10. A computer-readable storage medium, characterized in that, ​

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