Multi-voltage differential control method considering overload capacity of static synchronous phase modifier

Abstract

The invention discloses a multi-voltage differential control method considering the overload capacity of a static synchronous phase modifier, and the method comprises the steps: controlling the static synchronous phase modifier to carry out reactive compensation through spontaneous response when the voltage of a grid-connected point of a converter deviates, and obtaining a voltage deviation after reactive compensation; when the voltage deviation exceeds the allowable operation range of the power grid, the static synchronous phase modifier is controlled to carry out reactive power output according to the reactive power compensation requirement; wherein the reactive power required by the power grid is calculated according to the voltage deviation and serves as the reactive compensation requirement. The method comprises spontaneous response control after voltage excursion and simulation excitation control, and compared with an existing method, the method can fully excavate the reactive compensation potential of the static synchronous phase modifier and is beneficial to supporting the voltage level of a power grid.

Description

Technical Field

[0001] The present invention belongs to the technical field of voltage control in power systems, and in particular relates to a multi-voltage differentiation control method considering the overload capacity of a static synchronous condenser. Background Art

[0002] my country's new energy bases and power loads are distributed inversely, and large-scale new energy sources mostly use high-voltage direct current long-distance transmission to absorb new energy. On the one hand, new energy sources themselves contain a large number of power electronic devices, and their own inertia support capacity is insufficient. DC blocking or commutation failures can easily lead to transient overvoltage problems; on the other hand, the DC transmission system converter consumes a lot of reactive power during normal operation, and it is necessary to configure sufficient reactive power reserves on the AC side of the sending system to improve the transient overvoltage problem of the AC side power grid.

[0003] Phase condensers are important equipment for providing reactive power compensation and inertia support in new energy power systems. However, the essence of traditional phase condensers is a synchronous motor that only generates reactive power. It contains a large number of rotating parts, has high operation and maintenance costs, and has large component losses. Compared with reactive power compensation equipment such as SVC (static VAR compensator) and STATCOM (static synchronous compensator), the adjustment speed is slow, and the time from normal reactive power output to maximum forced reactive power output is about 1.2 seconds. Static synchronous phase condensers mainly use static parts, and use the current advanced grid construction technology, supercapacitor short-term energy storage technology, and instantaneous current limiting technology to give them the inertia and reactive power characteristics of traditional phase condensers. However, because they are controlled by electronic devices and have no rotating parts, they are cheaper, more convenient to operate and maintain, and have lower losses under almost the same electrical external characteristics. There are relatively few studies on the reactive power control strategy of static synchronous condensers, which mainly use network control technology to achieve active reactive support. However, this method often does not fully utilize the overload capacity of static synchronous condensers. In fact, static synchronous condensers can operate for a period of time under overload conditions, and the reactive power support capacity of static synchronous condensers has not been fully tapped. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-voltage differentiated control method taking into account the overload capacity of a static synchronous condenser, including spontaneous response control after voltage offset and analog excitation control. Compared with the existing methods, this method can fully tap the reactive power compensation potential of the static synchronous condenser, which is beneficial to supporting the voltage level of the power grid.

[0005] In order to achieve the above object, the solution of the present invention is:

[0006] A multi-voltage differential control method considering the overload capability of a static synchronous condenser, comprising:

[0007] When the voltage at the grid-connected point of the converter 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 static synchronous condenser is controlled to perform reactive power output according to the reactive power compensation demand; wherein the reactive power required by the power grid is calculated according to the voltage deviation as the reactive power compensation demand.

[0009] Wherein, controlling the static synchronous condenser to perform reactive power compensation through spontaneous response includes: the reactive power adjustment amount provided by the static synchronous condenser through spontaneous response is:

[0010]

[0011] Among them, ΔQ sc1 is the reactive power regulation quantity; U PCC is the voltage at the grid-connected point of the converter; ΔU PCC is the voltage deviation of the converter grid connection point; X tr is the simulated equivalent short-circuit reactance of the phase regulator after it is connected to the grid; X d ″ is the simulated direct-axis subtransient reactance; i d0 It is the value of the d-axis current component of the static synchronous condenser before the voltage offset occurs.

[0012] Wherein, the voltage deviation exceeds the allowable operating range of the power grid, wherein the allowable operating range of the power grid is related to the voltage level and includes:

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

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

[0015] Control the static synchronous condenser to output reactive power at the maximum power level according to reactive power compensation requirements;

[0016] Determine in real time whether the voltage deviation is within the allowable operating range of the power grid, if so, control the static synchronous condenser to end reactive power output, otherwise determine whether the working time of the static synchronous condenser reaches the time corresponding to its maximum power gear;

[0017] If the working time of the static synchronous condenser reaches the time corresponding to its maximum power gear, the power gear of the static synchronous condenser is reduced by one gear to continue reactive power output;

[0018] Determine in real time whether the voltage deviation is within the allowable operating range of the power grid. If so, control the static synchronous condenser to end reactive output. Otherwise, determine whether the working time of the static synchronous condenser reaches the time corresponding to its current power level. If the working time of the static synchronous condenser reaches the time corresponding to its current power level, reduce the power level of the static synchronous condenser by one level to continue reactive output. Repeat this step until the voltage deviation is within the allowable operating range of the power grid.

[0019] The reactive power required by the power grid is calculated according to the voltage deviation as the reactive power compensation demand, including:

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

[0021]

[0022] Among them, K A is the simulated excitation gain; K B is the simulated impedance ratio; T d ′0 is the time constant of simulated direct axis transient short circuit; ΔU PCC is the voltage deviation of the converter grid connection point; ΔQ sc2 is the reactive power generated by the static synchronous condenser; X d , X d ′ is the simulated direct-axis transient reactance and sub-transient reactance of the static synchronous condenser; X tr is the transfer reactance.

[0023] A computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, the steps of the multi-voltage differentiation control method considering the overload capacity of a static synchronous condenser as described above are implemented.

[0024] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the steps of the multi-voltage differentiation control method considering the overload capacity of a static synchronous condenser as described above are implemented.

[0025] After adopting the above scheme, the present invention includes spontaneous response control after voltage offset and analog excitation control. When the voltage offset occurs after normal operation or power grid failure, the static synchronous condenser first performs reactive power compensation through spontaneous response, but this part of reactive power capacity will decay over time; if the spontaneous reactive power influence cannot restore the voltage to normal, it enters the analog excitation control stage, and determines the control strategy according to the degree of voltage offset and the overload capacity of the condenser. Generally speaking, the larger the overcurrent multiple of the condenser, the shorter the operation time. If the voltage offset value is small, the static synchronous condenser can maintain low-power reactive power compensation for a long time. If the voltage offset value is large, the static synchronous condenser first outputs reactive power at the 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 to support compensation. Compared with the existing methods, this method can fully tap the reactive power compensation potential of the static synchronous condenser, which is beneficial to supporting the voltage level of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart of the present invention;

[0027] Figure 2 It is the topological diagram of the static synchronous condenser;

[0028] Figure 3 It is the topological diagram of the voltage source converter;

[0029] Figure 4 is a structural diagram of a UHV DC system according to an embodiment of the present invention;

[0030] Figure 5 It is a comparative schematic diagram of the present invention and the prior art. DETAILED DESCRIPTION

[0031] The technical solutions 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 adopts a high-voltage cascade full-bridge topology and supercapacitor short-term energy storage technology. Figure 2 As shown, the power module unit is the core component of the static adjustment, and its components include AC / DC power unit (i.e. H-bridge circuit, PCS), interface unit, supercapacitor, bypass switch, etc.; the interface unit mainly realizes the monitoring, management, protection and other functions of the supercapacitor; the supercapacitor mainly realizes energy storage and provides short-term active energy output.

[0033] like Figure 3As shown, the DC / AC power unit is connected to a voltage source device such as a conventional film capacitor, supercapacitor or energy storage battery on the DC side, which can be inverted and output on the AC side. An AC sinusoidal voltage with adjustable amplitude and phase can be output; by adjusting the amplitude and phase angle of the AC voltage output by the static synchronous phase condenser, the exchange of reactive and active power between the static phase condenser and the power system can be realized, and four-quadrant operation can be achieved, following the most basic AC transmission power flow formula.

[0034] When the voltage shifts during normal operation or after a grid fault, when the voltage shift at the grid connection point of the converter exceeds the grid operation range, the static synchronous condenser first performs reactive power compensation through spontaneous response without additional adjustment, keeping the internal potential unchanged, and providing reactive power adjustment of ΔQ sc1 , this part of reactive power will decay over time, and the calculation formula is:

[0035]

[0036] Where: ΔU PCC The voltage deviation of the grid-connected point voltage of the converter within the allowable operating range of the grid; X tr is the simulated equivalent short-circuit reactance of the phase regulator after it is connected to the grid; X d ″ is the simulated direct-axis subtransient reactance; i d0 is the value of the d-axis current component of the phase regulator before the voltage offset occurs; U PCC The voltage at the grid-connected point of the condenser.

[0037] If the spontaneous reactive power decays to the set level (set to 50% in this embodiment), the voltage still does not meet the fluctuation range allowed by the current voltage level, and it is determined that the spontaneous reactive power cannot restore the voltage to normal, the analog excitation control stage is entered, and the control strategy is determined according to the degree of voltage offset and the overload capacity of the phase regulator.

[0038] Suppose the overload capacity of the static synchronous condenser is as follows: the static synchronous condenser can operate for a duration of T1 at an overload capacity of x1 times, and for a duration of T2 at an overload capacity of x2 (x1>x2), ..., and for a duration of T3 at an overload capacity of x1 times. N (x N >x N-1 ) times overload capacity running time T N That is, the static synchronous condenser can be divided into N gears, and the overcurrent multiple of the kth gear and the maximum operating time of the gear are x k , T k .satisfy:

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

[0040] The specific steps include:

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

[0042] Step 2: If the voltage deviation exceeds the allowable operating range of the power grid, the reactive power required by the power grid is calculated based on the voltage deviation, and compensation is performed according to the maximum gear corresponding to the phase regulator not exceeding the required reactive power;

[0043] Step 3: If the maximum gear corresponding to the required reactive power runs for more than the corresponding time, the power gear is reduced 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 three-phase power supply voltage of 10kV and below 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 the power supply voltage of 35kV and above shall not exceed 10% of the rated voltage. The allowable voltage deviation of voltage levels of 110kV and above is generally -3% to +7% of the rated voltage; (4) Extra-high voltage (330kV, 500kV, 750kV): The allowable voltage deviation of voltage levels of 330kV and above and below 1000kV 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 of the simulated excitation link is:

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

[0047]

[0048] Where: K A is the simulated excitation gain; K B is the simulated impedance ratio; T d ′0 is the time constant of simulated direct axis transient short circuit; ΔU PCC The voltage deviation of the grid-connected point voltage of the converter within the allowable operating range of the grid; ΔQ sc2 is the reactive power generated during the excitation phase of the phase regulator; X d , X d ′ is the simulated direct-axis transient reactance and sub-transient reactance of the phase regulator; X tr is the transfer reactance.

[0049] The maximum range of initial compensation is:

[0050]

[0051] Where: Q 额定 is the rated reactive power of the phase regulator.

[0052] This example is a multi-voltage differential control method considering the overload capacity of static synchronous condenser. The voltage support when a fault occurs in an actual UHV DC system is used as an example to illustrate the system structure. Figure 4 shown.

[0053] The capacity of the converter station is 150MW, the photovoltaic installed capacity is 100MW, the installed capacity of the static synchronous phase condenser is 50MVar, and the short-term overload capacity is 1.2 times the long-term operation, 1.5 times the operation for 30 minutes, and 3 times the operation for 10s. In the operation state of the DC system 8000MW, taking the DC commutation failure fault at the receiving end converter station as an example, the transient overvoltage on the AC side of the sending end converter station is simulated, and the fault duration is 100ms.

[0054] Under the simulation, the static synchronous condenser operated at 3 times the overload capacity for 10 seconds, and the voltage still did not recover. It was switched to 1.5 times the overload capacity and continued to operate for 13 minutes, and the voltage returned to normal.

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

[0056] An embodiment of the present invention further provides another computer device, including a processor and a memory configured to store a computer program that can be run on the processor; wherein, when the processor is configured to run the computer program, the method steps in the aforementioned embodiment are executed.

[0057] In practical applications, the processor includes a field programmable gate array (FPGA), and the processor may be a central processing unit (CPU) or a digital signal processor (DSP). It is understandable that for different devices, the electronic device used to implement the function of the processor may be other, and the embodiment of the present invention does not specifically limit it.

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

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

[0060] Optionally, the computer-readable storage medium can be applied to any one of the methods in the embodiments of the present invention, and the computer program enables the computer to execute the corresponding processes implemented by the processor in each method in the embodiments of the present invention. For the sake of brevity, they are not described here.

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

[0062] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may 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 codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0063] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0064] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0065] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0066] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0067] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A multi-voltage differential control method considering the overload capacity of a static synchronous condenser, characterized in that: include, When the voltage at the grid-connected point of the converter 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 static synchronous condenser is controlled to perform reactive power output according to the reactive power compensation demand; wherein the reactive power required by the power grid is calculated according to the voltage deviation as the reactive power compensation demand.

2. The method according to claim 1, characterized in that: Controlling the static synchronous condenser to perform reactive power compensation through spontaneous response includes: the reactive power regulation amount provided by the static synchronous condenser through spontaneous response is: Among them, ΔQ sc1 is the reactive power regulation quantity; U PCC is the voltage at the grid-connected point of the converter; ΔU PCC is the voltage deviation of the converter grid connection point; X tr is the simulated equivalent short-circuit reactance of the phase regulator after it is connected to the grid; X d ″ is the simulated direct-axis subtransient reactance; i d0 It is the value of the d-axis current component of the static synchronous condenser before the voltage offset occurs.

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

4. The method according to claim 1, characterized in that: Control the static synchronous condenser to output reactive power according to reactive power compensation requirements, including: Control the static synchronous condenser to output reactive power at the maximum power level according to reactive power compensation requirements; Determine in real time whether the voltage deviation is within the allowable operating range of the power grid, if so, control the static synchronous condenser to end reactive power output, otherwise determine whether the working time of the static synchronous condenser reaches the time corresponding to its maximum power gear; If the working time of the static synchronous condenser reaches the time corresponding to its maximum power gear, the power gear of the static synchronous condenser is reduced by one gear to continue reactive power output; Determine in real time whether the voltage deviation is within the allowable operating range of the power grid. If so, control the static synchronous condenser to end reactive output. Otherwise, determine whether the working time of the static synchronous condenser reaches the time corresponding to its current power level. If the working time of the static synchronous condenser reaches the time corresponding to its current power level, reduce the power level of the static synchronous condenser by one level to continue reactive output. Repeat this step until the voltage deviation is within the allowable operating range of the power grid.

5. The method according to claim 1, characterized in that: Calculating the reactive power required by the power grid according to the voltage deviation as reactive power compensation demand, including: ΔQ sc2 =-U PCC (f(t)*ΔU PCC )+ΔU PCC i d0 Among them, K A is the simulated excitation gain; K B is the simulated impedance ratio; T d ′0 is the time constant of simulated direct axis transient short circuit; ΔU PCC is the voltage deviation of the converter grid connection point; ΔQ sc2 is the reactive power generated by the static synchronous condenser; X d , X d ′ is the simulated direct-axis transient reactance and sub-transient reactance of the static synchronous condenser; X tr is the transfer reactance.

6. 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, the steps of the multi-voltage differentiation control method considering the overload capacity of the static synchronous condenser according to any one of claims 1 to 5 are implemented.

7. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by a processor, the steps of the multi-voltage differentiation control method considering the overload capacity of the static synchronous condenser according to any one of claims 1 to 5 are implemented.

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