A multi-voltage differentiation control method considering overload capability of static synchronous compensator

Abstract

The application discloses a multi-voltage differentiation control method considering overload capacity of a static synchronous compensator, and comprises the following steps: when a grid-connected point voltage of a converter deviates, the static synchronous compensator is controlled to perform reactive power compensation through spontaneous response to obtain a voltage deviation after reactive power compensation; when the voltage deviation exceeds a grid allowed operation range, the static synchronous compensator is controlled to perform reactive power output according to a reactive power compensation demand; wherein the reactive power demand required by the grid is calculated according to the voltage deviation, and is taken as the reactive power compensation demand. The application comprises spontaneous response control and analog excitation control after voltage deviation, and compared with the prior art, the method can fully tap the reactive power compensation potential of the static synchronous compensator, and is favorable to support the grid voltage level.

Description

Technical Field

[0001] This invention belongs to the field of voltage control technology in power systems, specifically relating to a multi-voltage differential control method that considers the overload capacity of a static synchronous condenser. Background Technology

[0002] In my country, the distribution of new energy bases and power loads is inversely related, with large-scale new energy sources often being absorbed through long-distance high-voltage direct current (HVDC) transmission. On the one hand, new energy sources themselves contain a large number of power electronic devices with insufficient inertia support, making them prone to transient overvoltage problems in the event of DC blocking or commutation failure. On the other hand, DC transmission system converters consume a large amount of reactive power during normal operation, requiring sufficient reactive power reserves on the AC side of the sending-end system to mitigate transient overvoltage issues in the AC power grid.

[0003] Synchronous condensers are crucial devices in new energy power systems, providing reactive power compensation and inertia support. However, traditional synchronous condensers are essentially reactive power-generating synchronous motors containing numerous rotating parts, resulting in high maintenance costs and significant component losses. Furthermore, compared to reactive power compensation devices like SVCs (Static Var Compensators) and STATCOMs (Static Synchronous Compensators), their adjustment speed is slower, with approximately 1.2 seconds required to transition from normal reactive power output to maximum forced reactive power output. Static synchronous condensers, primarily using stationary components, leverage advanced grid construction technologies, supercapacitor short-time energy storage technologies, and instantaneous current limiting technologies to achieve the inertia and reactive power characteristics of traditional synchronous condensers. However, because they are electronically controlled and have no rotating parts, they are cheaper to manufacture, easier to maintain and repair, and have lower losses, all while maintaining nearly identical electrical characteristics. There is relatively little research on reactive power control strategies for static synchronous condensers. The main approach is to use grid control technology to achieve active reactive power support. However, this method often fails to fully utilize the overload capacity of static synchronous condensers. In reality, static synchronous condensers can operate under overload conditions for a period of time, thus failing to fully exploit their reactive power support capabilities. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-voltage differential control method that considers the overload capacity of static synchronous condensers, including spontaneous response control after voltage deviation and simulated excitation control. Compared with existing methods, this method can fully tap the reactive power compensation potential of static synchronous condensers, which is beneficial to supporting the grid voltage level.

[0005] To achieve the above objectives, the solution of the present invention is:

[0006] A multi-voltage differential control method considering the overload capacity of a stationary synchronous condenser includes,

[0007] When the voltage at the converter grid connection point deviates, the static synchronous condenser is controlled to perform reactive power compensation through spontaneous response to obtain the voltage deviation after reactive power compensation.

[0008] When the voltage deviation exceeds the allowable operating range of the power grid, the stationary synchronous condenser is controlled to output reactive power according to the reactive power compensation requirement; wherein, the reactive power required by the power grid is calculated based on the voltage deviation as the reactive power compensation requirement.

[0009] Specifically, controlling the static synchronous condenser to perform reactive power compensation through spontaneous response includes the reactive power adjustment provided by the static synchronous condenser through spontaneous response.

[0010]

[0011] Where, ΔQ sc1 U is the reactive power regulation quantity; PCC The voltage at the converter's grid connection point; ΔU PCC For the voltage deviation at the converter's grid connection point; X tr The simulated equivalent short-circuit reactance after the synchronous condenser is connected to the power grid; X d "To simulate direct-axis subtransient reactance; i" d0 This represents the value of the d-axis current component of the stationary synchronous condenser before the voltage shift occurs.

[0012] Wherein, the voltage deviation exceeds the grid's permissible operating range, wherein the grid's permissible operating range is related to the voltage level and includes,

[0013] At low voltage levels, the permissible deviation of 220V single-phase power supply voltage is +7% to -10% of the rated voltage; at medium voltage levels, the permissible deviation of 10kV and below three-phase power supply voltage is +7% or -7% of the rated voltage; at high voltage levels, the sum of the absolute values ​​of the positive and negative deviations of 35kV and above power supply voltage shall not exceed 10% of the rated voltage, and the permissible voltage deviation of 110kV and above voltage levels is -3% to +7% of the rated voltage; at ultra-high voltage levels, the permissible voltage deviation of 330kV and above and below 1000kV is ±5% of the rated voltage.

[0014] Among these, controlling the stationary synchronous condenser to output reactive power according to reactive power compensation requirements includes:

[0015] The stationary synchronous condenser is controlled to output reactive power at the maximum power level according to the reactive power compensation requirements.

[0016] Real-time judgment of whether the voltage deviation is within the allowable operating range of the power grid; if so, control the static synchronous condenser to stop reactive power output; otherwise, judge whether the working time of the static synchronous condenser has reached the time corresponding to its maximum power level.

[0017] If the working time of the static synchronous condenser reaches the time corresponding to its maximum power level, then the power level of the static synchronous condenser will be reduced by one level to continue reactive power output.

[0018] In real time, it is determined whether the voltage deviation is within the allowable operating range of the power grid. If so, the static synchronous condenser is controlled to stop reactive power output. Otherwise, it is determined whether the working time of the static synchronous condenser has reached the time corresponding to its current power level. If the working time of the static synchronous condenser has reached the time corresponding to its current power level, the power level of the static synchronous condenser is reduced by one level to continue reactive power output. This step is repeated until the voltage deviation is within the allowable operating range of the power grid.

[0019] Specifically, the reactive power required by the power grid is calculated based on the voltage deviation, which serves as the reactive power compensation requirement, including:

[0020] ΔQ sc2 =-U PCC (f(t)*ΔU PCC )+ΔU PCC i d0

[0021]

[0022] Among them, K A K is the simulated excitation amplification factor. B For the simulated impedance ratio; T d ′0 is the simulated direct-axis transient short-circuit time constant; ΔU PCC The voltage deviation at the converter's grid connection point; ΔQ sc2 The reactive power generated by the stationary synchronous condenser; X d X d ′ represents the direct-axis transient and subtransient reactance of a stationary synchronous condenser; X tr To transfer reactance.

[0023] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; the processor executes the computer program to implement the steps of the multi-voltage differential control method considering the overload capacity of a stationary synchronous condenser as described above.

[0024] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the steps of the multi-voltage differential control method considering the overload capacity of a stationary synchronous condenser as described above.

[0025] With the above scheme, this invention includes spontaneous response control and simulated excitation control after voltage deviation. When voltage deviation occurs during normal operation or after a grid fault, the static synchronous condenser first performs reactive power compensation through spontaneous response, but this reactive power capacity will decay over time. If the spontaneous reactive power cannot restore the voltage to normal, the simulated excitation control stage is entered, and the control strategy is determined according to the degree of voltage deviation and the overload capacity of the condenser. Generally speaking, the larger the overcurrent multiple of the condenser, the shorter the operating time. If the voltage deviation value is small, the static synchronous condenser can maintain low-power reactive power compensation for a long time. If the voltage deviation value is large, the static synchronous condenser first outputs reactive power at its maximum capacity according to the reactive power compensation demand (not exceeding the demand value). If the operating time exceeds the maximum time limit corresponding to the reactive power, the reactive power level is reduced to continue supporting compensation. Compared with existing methods, this method can fully tap the reactive power compensation potential of the static synchronous condenser, which is beneficial to supporting the grid voltage level. Attached Figure Description

[0026] Figure 1 This is a flowchart of the present invention;

[0027] Figure 2 This is a topology diagram of a stationary synchronous camera;

[0028] Figure 3 This is the topology diagram of a voltage source converter;

[0029] Figure 4 This is a structural diagram of an ultra-high voltage direct current system in an embodiment of the present invention;

[0030] Figure 5 This is a comparative diagram of the present invention and the prior art. Detailed Implementation

[0031] The technical solution and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] The static synchronous condenser is a dynamic reactive power compensation device that employs a high-voltage cascaded full-bridge topology and supercapacitor short-time energy storage technology. (In conjunction with...) Figure 2 As shown, the power module unit is the core component of the static control system. Its components include AC / DC power units (i.e., H-bridge circuits, PCS), interface units, supercapacitors, bypass switches, etc. The interface unit mainly realizes the monitoring, management, and protection functions of the supercapacitor. The supercapacitor mainly realizes energy storage and provides short-term active power output.

[0033] like Figure 3As shown, the DC / AC power unit connects to conventional thin-film capacitors, supercapacitors, or energy storage batteries on the DC side, and can invert and output AC sinusoidal voltage with adjustable amplitude and phase on the AC side. By adjusting the amplitude and phase angle of the AC voltage output by the static synchronous condenser, reactive and active power exchange between the static condenser and the power system can be realized, achieving four-quadrant operation and following the most basic AC power flow formula.

[0034] When voltage deviation occurs during normal operation or after a grid fault, and the voltage deviation at the converter's grid connection point exceeds the grid's operating range, the static synchronous condenser first performs reactive power compensation through spontaneous response, without additional adjustment, maintaining a constant internal potential and providing reactive power regulation of ΔQ. sc1 This portion of reactive power will decay over time, and the calculation formula is as follows:

[0035]

[0036] In the formula: ΔU PCC X represents the voltage deviation of the converter's grid connection point from the grid's allowable operating range. tr The simulated equivalent short-circuit reactance after the synchronous condenser is connected to the power grid; X d "To simulate direct-axis subtransient reactance; i" d0 The value of the d-axis current component of the camera is adjusted before the voltage shift occurs; U PCC To adjust the voltage at the camera's grid connection point.

[0037] If the spontaneous reactive power decays to a set level (50% in this embodiment), and the voltage still does not meet the allowable fluctuation range of the current voltage level, it is determined that the spontaneous reactive power cannot restore the voltage to normal. Then, the simulation excitation control stage is entered, and the control strategy is determined according to the degree of voltage deviation and the overload capacity of the synchronous condenser.

[0038] Let's assume the overload capacity of a stationary synchronous condenser is as follows: A stationary synchronous condenser can operate for a duration T1 equal to x1 times its overload capacity, for a duration T2 equal to x2 times its overload capacity (x1 > x2), ..., and so on, until the overload capacity reaches x... N (x N >x N-1 ) times overload capacity operating time T N That is, a stationary synchronous condenser can be divided into N levels, where the overcurrent multiple of the k-th level and the maximum operating time of that level are x, respectively. k T k .satisfy:

[0039] x1>x2,>...>x N T1 <T2,<...<T N

[0040] Specifically, the following steps are included:

[0041] Step 1: Determine whether the voltage deviation of the PCC node in the power grid after spontaneous reactive power compensation is within the allowable range for power grid operation;

[0042] Step 2: If the voltage deviation exceeds the allowable operating range of the power grid, calculate the reactive power required by the power grid based on the voltage deviation, and compensate according to the maximum range corresponding to the required reactive power of the synchronous condenser.

[0043] Step 3: If the maximum power setting required exceeds the corresponding duration, reduce the power setting to continue compensation until the voltage deviation is within the allowable range.

[0044] The allowable operating range of voltage deviation is related to the voltage level, as follows: (1) Low voltage (220V and 380V): The allowable deviation of 220V single-phase power supply voltage is +7% to -10% of the rated voltage; (2) Medium voltage (3kV, 6kV, 10kV): The allowable deviation of 10kV and below three-phase power supply voltage is +7% or -7% of the rated voltage; (3) High voltage (35kV, 110kV, 220kV): The sum of the absolute values ​​of the positive and negative deviations of 35kV and above power supply voltage shall not exceed 10% of the rated voltage, and the allowable voltage deviation of 110kV and above voltage levels is generally -3% to +7% of the rated voltage; (4) Ultra-high voltage (330kV, 500kV, 750kV): The allowable voltage deviation of 330kV and above and below 1000kV voltage levels is generally ±5% of the rated voltage.

[0045] The reactive power required by the power grid is calculated based on the voltage deviation. The relationship between the reactive power compensation voltage deviation in the simulated excitation circuit is as follows:

[0046] ΔQ sc2 =-U PCC (f(t)*ΔU PCC )+ΔU PCC i d0

[0047]

[0048] Where: K A K is the simulated excitation amplification factor. B For the simulated impedance ratio; T d ′0 is the simulated direct-axis transient short-circuit time constant; ΔU PCC ΔQ is the voltage deviation of the converter's grid connection point voltage from the grid's allowable operating range. sc2 The reactive power generated during the excitation phase of the synchronous condenser; X d X d ' is used to simulate the direct-axis transient and subtransient reactance of the camera; X tr To transfer reactance.

[0049] The maximum level of the initial compensation is:

[0050]

[0051] In the formula: Q 额定 The rated reactive power of the camera is adjusted.

[0052] This example illustrates a multi-voltage differential control method that considers the overload capacity of a static synchronous condenser. It uses the voltage support during a fault in a real UHVDC system as an example. The system structure is as follows: Figure 4 As shown.

[0053] The converter station has a capacity of 150MW, photovoltaic capacity of 100MW, and a static synchronous condenser capacity of 50MVar. Its short-term overload capacity is 1.2 times the long-term operating capacity, 1.5 times the long-term operating capacity for 30 minutes, and 3 times the long-term operating capacity for 10 seconds. Under the condition of an 8000MW DC system in operation, taking a DC commutation failure at the receiving-end converter station as an example, the simulation of transient overvoltage on the AC side of the sending-end converter station is performed, with a fault duration of 100ms.

[0054] In the simulation, the static synchronous condenser operated at 3 times the overload capacity for 10 seconds, but the voltage still did not recover. It then continued to operate at 1.5 times the overload capacity for 13 minutes, after which the voltage returned to normal.

[0055] from Figure 5 The comparison chart shows that, after considering overload capacity, the voltage can be quickly controlled within a reasonable range.

[0056] This invention also provides another computer device, including a processor and a memory configured to store a computer program capable of running on the processor; wherein, when the processor is configured to run the computer program, it performs the method steps described in the foregoing embodiments.

[0057] In practical applications, the aforementioned processor includes a Field-Programmable Gate Array (FPGA), and the processor can be a Central Processing Unit (CPU) or a Digital Signal Processor (DSP). It is understood that for different devices, the electronic devices used to implement the functions of the aforementioned processor can also be other types, and this embodiment of the invention does not impose specific limitations.

[0058] The aforementioned memory can be volatile memory, such as random-access memory (RAM); or non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid-state drive (SSD); or a combination of the above types of memory, and provides instructions and data to the processor.

[0059] In an exemplary embodiment, the present invention also provides a computer-readable storage medium for storing a computer program.

[0060] Optionally, the computer-readable storage medium can be applied to any of the methods in the embodiments of the present invention, and the computer program causes the computer to execute the corresponding processes implemented by the processor in the various methods of the embodiments of the present invention. For the sake of brevity, these will not be described in detail here.

[0061] In the several embodiments provided by this invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.

[0062] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0063] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0064] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0065] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0066] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0067] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A multi-voltage differential control method considering the overload capacity of a stationary synchronous condenser, characterized in that: include, When the voltage at the converter grid connection point deviates, the static synchronous condenser is controlled to perform reactive power compensation through spontaneous response to obtain the voltage deviation after reactive power compensation. When the voltage deviation exceeds the allowable operating range of the power grid, the stationary synchronous condenser is controlled to output reactive power according to the reactive power compensation requirement; wherein, the reactive power required by the power grid is calculated based on the voltage deviation as the reactive power compensation requirement; Specifically, controlling the static synchronous condenser to perform reactive power compensation through spontaneous response includes the reactive power adjustment provided by the static synchronous condenser through spontaneous response. ， in, This is the reactive power regulation quantity; This refers to the voltage at the converter's grid connection point. This refers to the voltage deviation at the converter's grid connection point. The simulated equivalent short-circuit reactance after the synchronous condenser is connected to the power grid; To simulate direct-axis subtransient reactance; The value of the d-axis current component of the stationary synchronous condenser before the voltage shift occurs; Among these, controlling the stationary synchronous condenser to output reactive power according to reactive power compensation requirements includes: The stationary synchronous condenser is controlled to output reactive power at the maximum power level according to the reactive power compensation requirements. Real-time judgment of whether the voltage deviation is within the allowable operating range of the power grid; if so, control the static synchronous condenser to stop reactive power output; otherwise, judge whether the working time of the static synchronous condenser has reached the time corresponding to its maximum power level. If the working time of the static synchronous condenser reaches the time corresponding to its maximum power level, then the power level of the static synchronous condenser will be reduced by one level to continue reactive power output. In real time, it is determined whether the voltage deviation is within the allowable operating range of the power grid. If it is, the static synchronous condenser is controlled to stop reactive power output. Otherwise, it is determined whether the working time of the static synchronous condenser has reached the time corresponding to its current power level. If the working time of the static synchronous condenser has reached the time corresponding to its current power level, the power level of the static synchronous condenser is reduced by one level to continue reactive power output. This step is repeated until the voltage deviation is within the allowable operating range of the power grid. Specifically, the reactive power required by the power grid is calculated based on the voltage deviation, which serves as the reactive power compensation requirement, including: ， in, This is to simulate the excitation amplification factor; This is to simulate the impedance ratio; To simulate the time constant of a direct-axis transient short circuit; This refers to the voltage deviation at the converter's grid connection point. The reactive power generated by the stationary synchronous condenser; , Simulate direct-axis transient and subtransient reactance for a stationary synchronous condenser; To transfer reactance.

2. The method as described in claim 1, characterized in that: The voltage deviation exceeds the grid's permissible operating range, wherein the grid's permissible operating range is related to the voltage level and includes, At low voltage levels, the permissible deviation of 220V single-phase power supply voltage is +7% to -10% of the rated voltage; at medium voltage levels, the permissible deviation of 10kV and below three-phase power supply voltage is +7% or -7% of the rated voltage; at high voltage levels, the sum of the absolute values ​​of the positive and negative deviations of 35kV and above power supply voltage shall not exceed 10% of the rated voltage, and the permissible voltage deviation of 110kV and above voltage levels is -3% to +7% of the rated voltage; at ultra-high voltage levels, the permissible voltage deviation of 330kV and above and below 1000kV is ±5% of the rated voltage.

3. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, it implements the steps of the multi-voltage differential control method as described in any one of claims 1 to 2, which takes into account the overload capacity of a stationary synchronous condenser.

4. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by the processor, it implements the steps of the multi-voltage differential control method as described in any one of claims 1 to 2, which takes into account the overload capacity of a stationary synchronous condenser.

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