A grid-connected inverter reactive voltage control method based on structural parameter iteration

Abstract

The application provides a grid-connected inverter reactive voltage control method based on structural parameter iteration, and relates to the technical field of power electronics. The grid-connected inverter reactive voltage control method based on structural parameter iteration comprises the following steps: S1, defining an inverter reactive output model: keeping the grid-connected point voltage at a safe voltage V max The minimum reactive output; S2, defining the inverter output at the previous moment; S3, calculating the target reactive output and recording the real-time voltage; S4, adjusting the inverter reactive output; S5, updating the structural parameters; S6, calculating the target reactive output at the next moment; S7, cyclically iterating the structural parameters and the inverter output. Since the system structural parameter change is small and slow, the system can be approximated as an open-loop system at most moments, the reactive power can follow the active power change more quickly and accurately, and for the moments less than the structural parameter change, since the algorithm adopts the predicted output, the disturbance to the power grid is small, and the power quality is higher.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a reactive voltage control method for grid-connected inverters based on structural parameter iteration. Background Technology

[0002] With the development of new energy technologies, many distributed power sources have emerged in the power grid. The emergence of distributed power sources has changed the original power flow structure of the power grid, causing the voltage at the grid connection point to rise above the safe protection voltage. Moreover, the voltage at the grid connection point will fluctuate with the grid-connected power, which will have an adverse impact on power quality.

[0003] Existing methods rely on the reactive power output of inverters to reduce voltage. However, when active power changes, the reactive power output responds slowly, which has a negative impact on power quality. Traditional grid voltage control methods involve installing additional voltage control equipment, such as dynamic voltage restorers, automatic voltage controllers, and static synchronous compensators, to adjust the voltage. This greatly increases the investment and maintenance costs of the system and cannot achieve the economical and efficient operation of the entire power generation system. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a reactive power and voltage control method for grid-connected inverters based on structural parameter iteration. This method solves the problem that existing methods rely on the reactive power output of the inverter to reduce voltage, but the reactive power output response is slow when active power changes, which adversely affects power quality.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a reactive power and voltage control method for grid-connected inverters based on structural parameter iteration, comprising the following steps:

[0006] S1. Define the inverter reactive power output model:

[0007] First, define the inverter reactive power output model. Based on the inverter's real-time active power output, and assuming the active power output is the inverter's real-time active power output, ensure the grid connection point voltage is maintained at a safe voltage V. max The following is the minimum reactive power output;

[0008] S2, Define the inverter output at the previous moment:

[0009] Define the grid connection point voltage as stable at V max At the previous moment, the inverter's active power output was P(k-1) and reactive power output was Q(k-1);

[0010] S3. Calculate the target reactive power output and record the real-time voltage:

[0011] Record the active power output P(k) of the inverter at the current moment. Based on the structural parameter values ​​b(k-1) and a(k-1) of the previous moment, calculate the target reactive power output Q*(k) at this moment. The calculation of Q*(k) requires that the active power output of the inverter is P(k) while keeping the grid connection point voltage at the safe voltage V. max The following records the real-time grid connection point voltage V. PCC ;

[0012] S4. Adjust the inverter reactive power output:

[0013] The purpose of adjusting the actual reactive power output of the inverter is to stabilize the grid connection point voltage at V. max Record the actual reactive power output Q(k) after adjustment;

[0014] S5. Update structural parameters:

[0015] Based on the current values ​​of active power output P(k) and reactive power output Q(k), calculate and update the values ​​of structural parameters a(k) and b(k). The updated structural parameters a(k) and b(k) will be used for calculation at the next time step.

[0016] S6. Calculate the target reactive power output at the next moment:

[0017] At the next moment, the active power output of the inverter is P(k+1). Based on the updated structural parameters a(k) and b(k), the target reactive power output Q*(k+1) at the next moment is determined. Depending on the grid voltage, ΔQ may need to be adjusted to obtain the actual reactive power output Q(k+1) that is suitable for a stable grid voltage.

[0018] S7. Iteratively calculate structural parameters and inverter output:

[0019] The process involves iterative calculations, starting from step S2 and proceeding to step S6. The structural parameters a and b are calculated sequentially at each time step, and the active power output P and reactive power output Q of the inverter are determined. In each iteration, the structural parameters and inverter output are updated to ensure that the inverter can stabilize the grid-connected voltage and meet the system requirements.

[0020] Preferably, in step S1, defining the inverter reactive power output model includes the following:

[0021] Q = a * P + b;

[0022] Where P is the real-time active power output of the inverter (in watts), and Q is the voltage at the grid connection point that can be maintained at the safe voltage V, provided that the active power output is P. max The following minimum reactive power output (in volt-amperes reactive power) is obtained by integrating a large number of structural parameters of the system to obtain the coefficients a and b in the model.

[0023] Preferably, in step S3, the target reactive power output Q*(k) at this moment is calculated using the structural parameter values ​​a(k-1) and b(k-1) from the previous moment, and the specific algorithm follows the formula below:

[0024] Q*(k)=a(k-1)*P(k)+b(k-1).

[0025] Preferably, in step S4, the actual reactive power output is as follows:

[0026] Q(k) = Q*(k) + △Q.

[0027] Preferably, in step S5, the value of a(k) is calculated based on the values ​​of P(k) and Q(k), and the specific algorithm follows the formula below:

[0028] a(k)=[Q(k)–Q(k-1)] / [P(k)–P(k-1)].

[0029] Preferably, in step S5, the value of b(k) is calculated based on the values ​​of P(k) and Q(k), and the specific algorithm follows the formula below:

[0030] b(k)=[Q(k-1)*P(k)–Q(k)*P(k-1)] / [P(k)–P(k-1)].

[0031] This invention provides a reactive power and voltage control method for grid-connected inverters based on structural parameter iteration. It has the following beneficial effects:

[0032] This invention defines an inverter reactive power output model, defines the inverter output at the previous moment, calculates the target reactive power output and records the real-time voltage, adjusts the inverter reactive power output, calculates the target reactive power output at the next moment, and iteratively calculates the structural parameters and inverter output. This ensures that the structural parameters and inverter output are updated in each iteration. Because the changes in the system structural parameters are small and slow, the system can be approximated as an open-loop system most of the time. Reactive power follows active power changes more quickly and accurately. For moments with fewer changes than structural parameters, the algorithm uses the method of predicting the output first and then correcting the parameters, resulting in less disturbance to the power grid and higher power quality. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the specific steps of the present invention;

[0034] Figure 2 This is a detailed flowchart of the method of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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.

[0036] Example:

[0037] Please see the appendix Figure 1 and attached Figure 2 This invention provides a reactive power and voltage control method for grid-connected inverters based on structural parameter iteration, comprising the following steps:

[0038] S1. Define the inverter reactive power output model:

[0039] First, define the inverter reactive power output model, which includes the following:

[0040] Q = a * P + b;

[0041] Where P is the real-time active power output of the inverter (in watts), and Q is the voltage at the grid connection point that can be maintained at the safe voltage V, provided that the active power output is P. max The following minimum reactive power output (unit: volt-ampere reactive power) is obtained by integrating a large number of structural parameters of the system to obtain coefficients a and b in the model. Based on the real-time active power output of the inverter, and under the premise that the active power output is the real-time active power output of the inverter, the grid connection point voltage can be maintained at the safe voltage V. max The following is the minimum reactive power output;

[0042] S2, Define the inverter output at the previous moment:

[0043] Define the grid connection point voltage as stable at V max At the previous moment, the inverter's active power output was P(k-1) and reactive power output was Q(k-1);

[0044] S3. Calculate the target reactive power output and record the real-time voltage:

[0045] Record the active power output P(k) of the inverter at the current moment. Based on the structural parameter values ​​a(k-1) and b(k-1) of the previous moment, calculate the target reactive power output Q*(k) at this moment. The specific algorithm is as follows:

[0046] Q*(k)=a(k-1)*P(k)+b(k-1);

[0047] The calculation of Q*(k) requires that the active power output of the inverter is P(k) while keeping the grid connection point voltage at a safe voltage V.max The following records the real-time grid connection point voltage V. PCC ;

[0048] S4. Adjust the inverter reactive power output:

[0049] Adjust the actual reactive power output of the inverter. The actual reactive power output is as follows:

[0050] Q(k) = Q*(k) + ΔQ;

[0051] The goal is to stabilize the grid connection point voltage at V. max Record the actual reactive power output Q(k) after adjustment;

[0052] S5. Update structural parameters:

[0053] Based on the current active power output P(k) and reactive power output Q(k), calculate and update the values ​​of structural parameters a(k) and b(k). The specific algorithm follows the formula below:

[0054] a(k)=[Q(k)–Q(k-1)] / [P(k)–P(k-1)];

[0055] The updated structure parameters a(k) and b(k) will be used for the calculation in the next time step. The value of b(k) is calculated based on the values ​​of P(k) and Q(k), and the specific algorithm follows the formula below:

[0056] b(k)=[Q(k-1)*P(k)–Q(k)*P(k-1)] / [P(k)–P(k-1)].

[0057] S6. Calculate the target reactive power output at the next moment:

[0058] At the next moment, the active power output of the inverter is P(k+1). Based on the updated structural parameters a(k) and b(k), the target reactive power output Q*(k+1) at the next moment is determined. Depending on the grid voltage, ΔQ may need to be adjusted to obtain the actual reactive power output Q(k+1) that is suitable for a stable grid voltage.

[0059] S7. Iteratively calculate structural parameters and inverter output:

[0060] The process involves iterative calculations, starting from step S2 and proceeding to step S6. The structural parameters a and b are calculated sequentially at each time step, and the active power output P and reactive power output Q of the inverter are determined. In each iteration, the structural parameters and inverter output are updated to ensure that the inverter can stabilize the grid-connected voltage and meet the system requirements.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A reactive power and voltage control method for grid-connected inverters based on structural parameter iteration, characterized in that, Includes the following steps: S1. Define the inverter reactive power output model: First, define the inverter reactive power output model. Based on the inverter's real-time active power output, and assuming the active power output is the inverter's real-time active power output, ensure the grid connection point voltage is maintained at a safe voltage. The following is the minimum reactive power output; S2, Define the inverter output at the previous moment: Define the grid connection point voltage as stable at At the previous moment, the inverter's active power output was The reactive power output is ; S3. Calculate the target reactive power output and record the real-time voltage: Record the active power output of the inverter at the current moment. Based on the structural parameter values ​​of the previous moment and Calculate the target reactive power output at this moment. , The calculation needs to satisfy the requirement that the active power output of the inverter is... At the same time, it keeps the grid connection point voltage at a safe voltage. The following records the real-time grid connection point voltage. ; S4. Adjust the inverter reactive power output: Adjusting the actual reactive power output of the inverter aims to stabilize the grid connection point voltage at a certain level. Record the actual reactive power output after adjustment. ; S5. Update structural parameters: Based on the current active power output and reactive power output The value is used to calculate and update the structure parameters. and The value of the updated structure parameter and It will be used for calculations at the next time step; S6. Calculate the target reactive power output at the next moment: At the next moment, the inverter's active power output is Based on the updated structural parameters and Determine the target reactive power output for the next moment. Depending on the grid connection voltage, adjustments are required. To obtain a suitable actual reactive power output for a stable grid-connected voltage. ; S7. Iteratively calculate structural parameters and inverter output: Perform iterative calculations, starting from step S2 to step S6, to sequentially calculate the structural parameters at each time step. and And determine the active power output of the inverter. and reactive power output Each iteration updates the structural parameters and inverter output to ensure that the inverter can stabilize the grid-connected voltage and meet system requirements. In step S1, the inverter reactive power output model is defined as follows: ； in, This refers to the real-time active power output of the inverter (in watts). For active power output Under the premise of ensuring that the grid connection point voltage is maintained at a safe voltage. The following minimum reactive power output (in volt-amperes) is used to integrate the system's structural parameters to obtain the coefficients in the model. and ; In step S3, the structural parameter values ​​from the previous moment are used. and Calculate the target reactive power output at this moment. The specific algorithm follows the formula below: 。 2. The reactive power and voltage control method for grid-connected inverters based on structural parameter iteration according to claim 1, characterized in that, The actual reactive power output in step S4 is as follows: 。 3. The reactive power and voltage control method for grid-connected inverters based on structural parameter iteration according to claim 1, characterized in that, In step S5, according to and Calculate the value. The value is calculated using the following formula: 。 4. The reactive power and voltage control method for grid-connected inverters based on structural parameter iteration according to claim 1, characterized in that, In step S5, according to and The value, calculate The value is calculated using the following formula: 。

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