Control system and method for modular centralized direct current energy consuming system

Abstract

This invention provides a control system and method for a modular centralized DC power consumption system. The system includes: a module voltage control module for receiving command and measured values ​​of the average voltage of the modules in the modular centralized DC power consumption system, and outputting a first number of modules; a DC voltage control module for receiving command and measured values ​​of the voltage between the positive and negative terminals of the DC power in the modular centralized DC power consumption system, and outputting a second number of modules; a summation module for summing the first and second number of modules to obtain the total number of modules to be activated; and a sorting and equalizing module for sorting the voltage of all modules and, based on the total number of modules to be activated, determining the modules that need to be activated. This invention can effectively control the DC voltage of the modular centralized DC power consumption system to prevent severe overvoltage problems during AC faults at the shore station, and can also effectively control the average voltage of the modular centralized DC power consumption system.

Description

Technical Field

[0001] This invention relates to the field of power systems, and more particularly to a control system and method for a modular centralized DC power consumption system. Background Technology

[0002] In recent years, the development of offshore wind power has accelerated. Compared with high-voltage AC transmission and grid connection, flexible DC transmission has advantages such as smaller footprint, more flexible control, and no restrictions on transmission distance, making it particularly suitable for transmitting power from large-scale offshore wind farms. For offshore wind power flexible DC systems, when a fault occurs on the AC side of the onshore station, the power of the wind farm cannot be reduced quickly enough, and the DC side voltage will rise due to the surplus power, which may pose a risk of damaging DC submarine cables, converters, and other equipment.

[0003] Therefore, energy dissipation devices are required. For offshore flexible DC transmission systems, due to the limited space available at offshore stations, DC energy dissipation devices are generally installed at onshore stations. Current solutions for DC energy dissipation devices mainly include centralized, distributed, and hybrid types. Centralized energy dissipation devices experience significant system impact during commissioning, and voltage equalization between series-connected components is difficult. Distributed energy dissipation devices have less system impact, lower DC voltage ripple during commissioning, and better voltage equalization across modules; however, because their energy dissipation resistors are distributed across each module, a water-cooling system is required, leading to high costs. Therefore, a modular centralized energy dissipation device is proposed, using centralized resistors and half-bridge or full-bridge modules for the switching section.

[0004] The aforementioned modular centralized energy-consuming device solves the heat dissipation problem of distributed resistors and the problem of large impact of centralized energy consumption. However, since the average current of the energy-consuming device is unidirectional, the equalization problem of the module capacitors needs to be achieved by adopting a new control scheme. Summary of the Invention

[0005] This invention proposes a control system for a modular centralized DC power consumption system. This system effectively prevents severe overvoltage issues during AC faults at onshore stations, and also effectively controls the average voltage of the system. The control system includes: a DC voltage control module, a module voltage control module, a summation module, and a sorting and equalizing module.

[0006] The module voltage control module is used to receive the command value and measured value of the average voltage of the modules in the modular centralized DC power consumption system, and output the first module number;

[0007] The DC voltage control module is used to receive command values ​​and measured values ​​of the voltage between the positive and negative terminals of the DC power consumption system in the modular centralized DC power consumption system, and output the second module number;

[0008] The summation module is used to sum the number of the first module and the number of the second module to obtain the total number of modules that need to be invested.

[0009] The voltage equalization sorting module is used to sort the voltages of all modules and, based on the total number of modules to be put into operation, determine which modules need to be put into operation.

[0010] This invention proposes a control method for a modular centralized DC power consumption system, applied to the control system of the aforementioned modular centralized DC power consumption system. This method effectively prevents severe overvoltage problems in the DC voltage of the modular centralized DC power consumption system during AC faults at the shore station, and also effectively controls the average voltage of the modular centralized DC power consumption system. The method includes:

[0011] The number of modules is obtained based on the commanded and measured values ​​of the average voltage of the modules in the modular centralized DC power consumption system.

[0012] The number of second modules is obtained based on the commanded and measured values ​​of the voltage between the positive and negative terminals of the modular centralized DC energy consumption system.

[0013] Summing the number of modules in the first module and the number of modules in the second module yields the total number of modules that need to be invested.

[0014] Sort all modules by voltage, and determine which modules need to be deployed based on the total number of modules required.

[0015] In this embodiment of the invention, the modular centralized DC energy-consuming system includes multiple modules connected in series and energy-consuming resistors. The modules are half-bridge modules or full-bridge modules. The system includes a DC voltage control module, a module voltage control module, a summation module, and a sorting and equalizing voltage module. The module voltage control module receives the instruction value and measured value of the average voltage of the modules in the modular centralized DC energy-consuming system and outputs a first number of modules. The DC voltage control module receives the instruction value and measured value of the voltage between the positive and negative terminals of the DC power supply in the modular centralized DC energy-consuming system and outputs a second number of modules. The summation module sums the first number of modules and the second number of modules to obtain the total number of modules to be put into operation. The sorting and equalizing voltage module sorts the voltage of all modules and, based on the total number of modules to be put into operation, determines the modules to be put into operation. In this invention, the total number of modules to be deployed is calculated based on the commanded and measured values ​​of the average voltage of the modules in the modular centralized DC power consumption system, as well as the commanded and measured values ​​of the voltage between the positive and negative terminals of the DC power consumption system. This allows for the determination of which modules need to be deployed. By taking into account the average voltage of the modules, the average voltage of the modules can be effectively controlled, and the DC voltage of the system can be effectively controlled to prevent serious overvoltage problems during AC faults at the shore station. Attached Figure Description

[0016] 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. In the drawings:

[0017] Figure 1 This is a schematic diagram of the control system of the modular centralized DC energy consumption system in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of a modular centralized DC power consumption system in an embodiment of the present invention;

[0019] Figure 3 This is an internal structural diagram of the module voltage control module in an embodiment of the present invention;

[0020] Figure 4 This is a flowchart of the control method for a modular centralized DC energy consumption system in an embodiment of the present invention;

[0021] Figure 5 This is a flowchart illustrating the calculation of the number of first modules in an embodiment of the present invention;

[0022] Figure 6 A flowchart for determining the modules that need to be implemented in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0024] In the description of this specification, the terms "comprising," "including," "having," and "containing" are open-ended terms, meaning that they include but are not limited to. The terms "an embodiment," "a specific embodiment," "some embodiments," and "for example," etc., refer to specific features, structures, or characteristics described in connection with that embodiment or example that are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. The order of steps involved in the various embodiments is used to illustrate the implementation of this application, and the order of steps is not limited and can be adjusted appropriately as needed.

[0025] Figure 1 This is a schematic diagram of the control system of the modular centralized DC energy consumption system in an embodiment of the present invention. The control system of the modular centralized DC energy consumption system includes: a DC voltage control module, a module voltage control module, a summation module, and a sorting and equalizing voltage module.

[0026] The module voltage control module is used to receive the instruction value Usm_ref and the measured value Usm of the average voltage of the modules in the modular centralized DC power consumption system, and output the first module number Non_sm;

[0027] The DC voltage control module is used to receive the command value Udc_ref and the measured value Udc of the voltage between the positive and negative terminals of the modular centralized DC energy consumption system, and output the second module number Non_udc;

[0028] The summation module is used to sum the number of the first module and the number of the second module to obtain the total number of modules that need to be invested.

[0029] The voltage equalization sorting module is used to sort the voltages of all modules and, based on the total number of modules to be put into operation, determine which modules need to be put into operation.

[0030] The modular centralized DC energy consumption system includes multiple modules connected in series and energy-consuming resistors, wherein the modules are half-bridge modules or full-bridge modules.

[0031] Figure 2 This is a schematic diagram of a modular centralized DC energy dissipation system in an embodiment of the present invention. The energy dissipation device is generally installed on the DC side of the shore station. When the shore station experiences an AC fault or other fault, resulting in a power surplus transmitted from the offshore station, the DC bus voltage will rise. At this time, the modular centralized DC energy dissipation system will be put into operation to absorb the excess energy, ensure the power balance of the system, and stabilize the DC voltage.

[0032] Figure 3 This is an internal structural diagram of the module voltage control module in an embodiment of the present invention. In one embodiment, the module voltage control module includes a first PI controller and a multiplier calculator.

[0033] The first PI controller is used to perform PI adjustment after subtracting the command value and the measured value of the average voltage of the modules of the received modular centralized DC power consumption system, and outputs the first PI control value LNon_sm.

[0034] The multiplier calculator is used to multiply the received first PI controller and the sine signal Sin(wt) and output the first module number.

[0035] In one embodiment, the DC voltage control module includes a second PI controller.

[0036] The second PI controller is used to perform PI adjustment after subtracting the command value and the measured value of the voltage between the positive and negative terminals of the received modular centralized DC power consumption system, and outputs the second module number.

[0037] like Figure 3 As shown, the first PI controller is further configured to: after receiving an enable signal, perform PI adjustment by subtracting the command value and the measured value of the average voltage;

[0038] The second PI controller is also used to: after receiving the enable signal, perform PI adjustment by subtracting the command value and the measured value of the voltage between the DC positive and negative terminals.

[0039] In one embodiment, the sorting and equalizing voltage module is specifically used for:

[0040] Sort all modules according to the capacitor voltage in the module from smallest to largest;

[0041] When the current moment is the charging moment, based on the total number of modules that need to be put into operation, start with the module with the smallest capacitor voltage to obtain the modules that need to be put into operation;

[0042] When the current moment is the discharge moment, based on the total number of modules that need to be put into operation, start with the module with the largest capacitor voltage to obtain the modules that need to be put into operation.

[0043] In one embodiment, the sorting and equalizing module is further configured to:

[0044] After determining the modules that need to be deployed, the trigger pulses for the modules to be deployed and the modules to be removed are output.

[0045] The trigger pulse can be directly input to a modular centralized DC power consumption system.

[0046] This invention also proposes a control method for a modular centralized DC energy consumption system, applicable to the control system of the aforementioned modular centralized DC energy consumption system. Figure 4 The flowchart of the control method for the modular centralized DC energy consumption system in this embodiment of the invention includes:

[0047] Step 401: Obtain the first number of modules based on the commanded and measured values ​​of the average voltage of the modules in the modular centralized DC power consumption system;

[0048] Step 402: Obtain the number of second modules based on the commanded and measured values ​​of the voltage between the positive and negative terminals of the modular centralized DC power consumption system;

[0049] Step 403: Sum the number of the first module and the number of the second module to obtain the total number of modules that need to be invested;

[0050] Step 404: Sort the voltage of all modules and determine which modules need to be put into operation based on the total number of modules to be put into operation.

[0051] Figure 5 This is a flowchart illustrating the calculation of the first number of modules according to an embodiment of the present invention. In one embodiment, the first number of modules is obtained based on the commanded value and measured value of the average voltage of the modules in the modular centralized DC power consumption system, including:

[0052] Step 501: After subtracting the command value and the measured value of the average voltage of the modules of the received modular centralized DC power consumption system, PI adjustment is performed to obtain the first PI control value.

[0053] Step 502: Multiply the first PI controller and the sine signal to obtain the number of the first modules.

[0054] In one embodiment, the number of second modules is obtained based on the commanded and measured values ​​of the voltage between the positive and negative terminals of the modular centralized DC power consumption system, including:

[0055] The second module number is obtained by subtracting the commanded value and the measured value of the voltage between the positive and negative terminals of the modular centralized DC power consumption system and then performing PI regulation.

[0056] Figure 6 This is a flowchart illustrating the process of determining the modules to be deployed according to an embodiment of the present invention. In one embodiment, the voltages of all modules are sorted, and the modules to be deployed are determined based on the total number of modules required, including:

[0057] Step 601: Sort all modules according to the capacitor voltage in the module from smallest to largest;

[0058] Step 602: When the current time is the charging time, based on the total number of modules that need to be put into operation, start from the module with the smallest capacitor voltage to obtain the modules that need to be put into operation.

[0059] Step 603: When the current time is the discharge time, based on the total number of modules to be put into operation, start from the module with the largest capacitor voltage to obtain the modules to be put into operation.

[0060] The system and method proposed in this invention calculate the total number of modules to be deployed based on the commanded and measured average voltage values ​​of the modules in a modular centralized DC power consumption system, as well as the commanded and measured voltage values ​​between the positive and negative terminals of the DC power consumption system. This determines which modules need to be deployed. By considering the average voltage of the modules, the average voltage of the modules can be effectively controlled, and the DC voltage of the system can be effectively controlled to prevent severe overvoltage problems during AC faults at the shore station. Furthermore, the capacitor voltage within the modules is considered when determining which modules need to be deployed, thus achieving capacitor balancing in the modular centralized DC power consumption system.

[0061] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control system for a modular centralized DC energy consuming system, characterized in that, include: The module includes a DC voltage control module, a module voltage control module, a summation module, and a sorting and equalizing module. The module voltage control module is used to receive the command value and measured value of the average voltage of the modules in the modular centralized DC power consumption system, and output the first module number; The DC voltage control module is used to receive command values ​​and measured values ​​of the voltage between the positive and negative terminals of the DC power consumption system in the modular centralized DC power consumption system, and output the second module number; The summation module is used to sum the number of the first module and the number of the second module to obtain the total number of modules that need to be invested. The voltage equalization sorting module is used to sort the voltage of all modules and, based on the total number of modules to be put into operation, determine which modules need to be put into operation. The voltage control module includes a first PI controller and a multiplier calculator. The first PI controller is used to perform PI adjustment after subtracting the command value and the measured value of the average voltage of the modules of the received modular centralized DC power consumption system, and outputs the first PI control value. The multiplier calculator is used to multiply the received first PI controller and sine signal, and output the first module number.

2. The system as described in claim 1, characterized in that, The DC voltage control module includes a second PI controller. The second PI controller is used to perform PI adjustment after subtracting the command value and the measured value of the voltage between the positive and negative terminals of the received modular centralized DC power consumption system, and outputs the second module number.

3. The system as described in claim 2, characterized in that, The first PI controller is also used to: after receiving the enable signal, perform PI adjustment by subtracting the command value and the measured value of the average voltage; The second PI controller is also used to: after receiving the enable signal, perform PI adjustment by subtracting the command value and the measured value of the voltage between the DC positive and negative terminals.

4. The system as described in claim 1, characterized in that, The sorting and equalizing voltage module is specifically used for: Sort all modules according to the capacitor voltage in the module from smallest to largest; When the current moment is the charging moment, based on the total number of modules that need to be put into operation, start with the module with the smallest capacitor voltage to obtain the modules that need to be put into operation; When the current moment is the discharge moment, based on the total number of modules that need to be put into operation, start with the module with the largest capacitor voltage to obtain the modules that need to be put into operation.

5. The system as described in claim 1, characterized in that, The sorting and equalizing voltage module is also used for: After determining the modules that need to be deployed, the trigger pulses for the modules to be deployed and the modules to be removed are output.

6. A control method for a modular centralized DC energy consumption system, characterized in that, The control system applied to the modular centralized DC power consumption system according to any one of claims 1 to 5 includes: The number of modules is obtained based on the commanded and measured values ​​of the average voltage of the modules in the modular centralized DC power consumption system. The number of second modules is obtained based on the commanded and measured values ​​of the voltage between the positive and negative terminals of the modular centralized DC energy consumption system. Summing the number of modules in the first module and the number of modules in the second module yields the total number of modules that need to be invested. Sort all modules by voltage, and determine which modules need to be deployed based on the total number of modules required.

7. The method as described in claim 6, characterized in that, Based on the commanded and measured average voltage values ​​of the modules in the modular centralized DC power consumption system, the first module number is obtained, including: The first PI control value is obtained by subtracting the command value and the measured value of the average voltage of the modules of the received modular centralized DC power consumption system. The first PI controller and the sine signal are multiplied to obtain the number of the first module.

8. The method as described in claim 6, characterized in that, Based on the commanded and measured values ​​of the voltage between the positive and negative terminals of the modular centralized DC power consumption system, the number of the second module is obtained, including: The second module number is obtained by subtracting the commanded value and the measured value of the voltage between the positive and negative terminals of the modular centralized DC power consumption system and then performing PI regulation.

9. The method as described in claim 6, characterized in that, Sort all modules by voltage, and based on the total number of modules required, determine which modules need to be deployed, including: Sort all modules according to the capacitor voltage in the module from smallest to largest; When the current moment is the charging moment, based on the total number of modules that need to be put into operation, start with the module with the smallest capacitor voltage to obtain the modules that need to be put into operation; When the current moment is the discharge moment, based on the total number of modules that need to be put into operation, start with the module with the largest capacitor voltage to obtain the modules that need to be put into operation.

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