Impedance adjusting method, system and equipment for wind-solar direct current sending-out station and medium

Abstract

The invention belongs to the technical field of new energy bundled direct current transmission, and particularly discloses a wind and light direct current transmission station impedance adjusting method, system, equipment and medium, which can configure virtual parallel impedance or virtual series impedance according to wind power and photovoltaic field station impedance and transmission end station input impedance in a wind and light direct current transmission station. The broadband oscillation stability of the wind-solar direct current sending station is optimized, and the influence on the dynamic response performance of the wind-solar direct current sending station is reduced; the virtual impedance configuration-based impedance adjusting device for the wind-light direct-current sending-out station has the advantages of high operability, high engineering applicability, clear physical concept, high visualization degree and the like, so that the virtual impedance configuration-based impedance adjusting device has extremely high practicability in engineering practice and can be applied to improvement of broadband oscillation stability of the wind-light direct-current sending-out station.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy bundled direct current transmission, and in particular to an impedance adjustment method, system, equipment and medium for a wind-solar direct current transmission station. Background Art

[0002] With the transmission of multiple types of power sources such as wind power and photovoltaic power through direct current, the proportion of renewable energy power generation has gradually increased, and UHV DC transmission lines have been continuously connected, posing great challenges to the safe and stable operation of the power grid. In the DC transmission system, although independent sending-end rectifier stations or wind power and photovoltaic stations can operate stably, when wind power, photovoltaic stations and sending-end rectifier stations together form the transmission system, the interaction between the stations may bring broadband oscillation risks to the power system, making the stability and safety of the power system unprecedentedly challenged. Broadband oscillation risks may cause large-scale new energy units to be disconnected from the grid, equipment damage, torsional vibration of thermal power units and other accidents, causing significant economic losses, seriously threatening the safe and stable operation of the power grid, and restricting the efficient consumption of new energy.

[0003] In order to deal with the risk of broadband oscillation in the wind-solar DC transmission station, it is necessary to adjust the impedance of wind power, photovoltaic stations and the sending-end rectifier station. The most common method at present is to adjust the impedance of the wind-solar station by changing the control parameters and output power of the wind-solar station, thereby improving the stability of the system. However, modifying the control parameters of the wind-solar station will inevitably be limited by the stability and dynamic response performance of the station itself, and the output power of the wind-solar station is largely determined by the system operating conditions. Summary of the invention

[0004] In view of this, the present invention provides a method, system, device and medium for adjusting the impedance of a wind-solar DC transmission station, which can connect a virtual impedance in series or in parallel at the input impedance of the sending-end rectifier station of the wind-solar DC transmission system, adjust the input impedance of the receiving-end inverter station within the frequency range where there is a risk of broadband oscillation, and improve the broadband oscillation stability of the system.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A method for adjusting impedance of a wind-solar direct current transmission station comprises the following steps:

[0007] S1. Obtain the wind and solar field impedance of the wind and solar power transmission station and the original input impedance of the sending-end rectifier station by calculation or measurement;

[0008] S2. If the parallel virtual impedance method is adopted, the required parallel virtual impedance is calculated and configured according to the impedance of the wind and light field stations and the original input impedance of the sending-end rectifier station; if the series virtual impedance method is adopted, the required series virtual impedance is calculated and configured according to the impedance of the wind and light field stations and the original input impedance of the sending-end rectifier station.

[0009] Among them, the calculation formula of parallel virtual impedance is:

[0010]

[0011] Among them G Zim_P (s) is the parallel virtual input impedance regulator, V bus is the bus voltage, P o is the active power sent out, e is a natural constant, j is an imaginary unit, θ2 is the given impedance angle of the sending-end inverter, G v (s) is the voltage loop transfer function, G PWM (s) is the transfer function of the modulation link, G id_OL (s) is the transfer function from control to input current, T v (s) is the voltage loop gain, G BPF (s) is a typical second-order bandpass filter.

[0012] Among them, the calculation formula of series virtual impedance is:

[0013]

[0014] Among them G Zin_S (s) is a series virtual input impedance regulator, is the original bus voltage, P o is the active power sent out, e is a natural constant, j is an imaginary unit, θ2 is the given impedance angle of the sending-end inverter, G id_OL (s) is the transfer function from control to input current, G PWM (s) is the transfer function of the modulation link, Z in_HVDC_ori (s) is the original input impedance of the sending-end rectifier station, T v (s) is the voltage loop gain, G BPF (s) is a typical second-order bandpass filter.

[0015] Among them, G BPF (s) consists of a second-order high-pass filter and a second-order low-pass filter:

[0016]

[0017] Where ω1=2πf1、ω2=2πf2 are the characteristic angular frequencies of high-pass filter and low-pass filter respectively, Q H and Q L are the quality factors of the high-pass filter and the low-pass filter respectively, [f1, f2] are the start and end frequencies where the impedance curves of the sending-end rectifier station and the wind-solar station intersect, and s is the complex variable of the Laplace transform.

[0018] The present invention also provides a wind-solar DC transmission station impedance adjustment system, which is used to implement the wind-solar DC transmission station impedance adjustment method described in the present invention, including an impedance calculation module, an ideal input impedance calculation module and a virtual impedance configuration module;

[0019] The impedance calculation module is used to read the parameters of the wind farm, photovoltaic farm and sending-end rectifier station, and calculate or directly measure the impedance amplitude and phase of the wind farm, photovoltaic farm and sending-end rectifier station;

[0020] Ideal input impedance calculation module, used to calculate the input impedance required for system stability based on the impedance of the rectifier station at the sending end of the wind power and photovoltaic station;

[0021] The virtual impedance configuration module is used to convert the input impedance required for system stability into parallel virtual impedance or series virtual impedance according to the configuration method, and configure the corresponding virtual impedance in the control link of the rectifier station at the sending end of the wind-solar DC transmission station.

[0022] The present invention also provides an electronic device, comprising a processor and a memory for storing executable instructions of the processor; the processor is used to read the executable instructions from the memory and execute the instructions to implement the wind-solar DC transmission station impedance adjustment method described in the present invention.

[0023] The present invention also provides a computer-readable storage medium, wherein the storage medium stores a computer program, and the computer program is used to execute the wind-solar DC transmission station impedance adjustment method described in the present invention.

[0024] Beneficial effects:

[0025] 1. The method of the present invention adjusts the input impedance of the receiving-end inverter station in the frequency range with broadband oscillation risk to improve the broadband oscillation stability of the system. By accurately calculating and configuring virtual impedance, the input impedance of wind farms, photovoltaic power stations and sending-end rectifier stations can be effectively adjusted to ensure that they match other parts of the system, thereby improving the stability and reliability of the entire power system, which is particularly suitable for power grids that contain a large amount of renewable energy generation.

[0026] 2. The method of the present invention is very effective for the safe operation of sensitive loads and precision equipment. Through appropriate impedance configuration, it can reduce harmonic distortion, reduce voltage fluctuations and flicker, and improve the power quality of the access point.

[0027] 3. In the method of the present invention, when a short circuit or other fault occurs, a reasonable virtual impedance setting helps limit the short circuit current, reduces the pressure on the primary equipment, speeds up the protection action, and thus shortens the fault recovery time.

[0028] 4. The system of the present invention supports two virtual impedance configuration modes: parallel and series. It can be flexibly selected or combined according to actual needs to meet the optimal impedance matching requirements under different working conditions. In addition, it can dynamically adjust the virtual impedance value according to real-time monitoring data to maintain the best performance of the system; in addition, by adjusting the impedance to optimize the interaction characteristics between the new energy power source and the power grid, it helps to increase the utilization and penetration of new energy.

[0029] 5. In the system of the present invention, a standardized second-order bandpass filter model is used as the basis, making the system more modular and universal, reducing the development cost and technical threshold. At the same time, the clear functional division is also conducive to the later debugging and maintenance work.

[0030] 6. The present invention reduces the consumption of fossil fuels, reduces carbon emissions and the generation of other pollutants through efficient management and utilization of renewable energy, which is in line with the concept of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the impedance curve diagram of the wind-solar DC transmission station sending-end rectifier station and wind power and photovoltaic stations of the present invention.

[0032] Figure 2 It is a schematic diagram of the parallel virtual impedance configuration method of the present invention.

[0033] Figure 3 Schematic diagram of the parallel virtual impedance control strategy of the present invention.

[0034] Figure 4 It is a schematic diagram of the configuration method of the series virtual impedance of the present invention.

[0035] Figure 5 It is a schematic diagram of the series virtual impedance control strategy of the present invention.

[0036] Figure 6 This is the system structure and configuration method of the present invention.

[0037] Figure 7 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0039] The present invention provides a method for adjusting the impedance of a wind-solar DC transmission station, by connecting a virtual impedance in series or in parallel at the input impedance of a sending-end rectifier station of a wind-solar DC transmission system, to adjust the input impedance of the sending-end rectifier station, thereby reducing the risk of wide-band oscillation of the system while maximally ensuring that the dynamic response performance of the system is not affected.

[0040] The impedance adjustment method of the wind-solar direct current transmission station of the present invention comprises the following steps:

[0041] S1. Obtain the wind and solar field station impedances of the wind and solar power transmission station and the original input impedance of the sending-end rectifier station by calculation or measurement methods; wherein, in the ideal input impedance calculation module, the wind and solar power DC transmission system is divided into a voltage source parallel subsystem and a current source parallel subsystem, wherein the voltage source parallel subsystem is composed of the sending-end rectifier station, and the current source parallel subsystem is composed of the wind and solar field stations;

[0042] Among them, the steps to obtain the ideal input impedance of the sending-end rectifier station are as follows:

[0043] According to the obtained wind and solar field station impedance and the original input impedance of the sending-end rectifier station, the impedance curves of the two are drawn, as shown in Figure 2 As shown, the solid line represents the input impedance of the sending-end rectifier station V bus is the bus voltage, P o To send out active power, the dotted line represents the impedance Z of the wind and solar power stations. o_S , the peak value of its amplitude is Z o_S_peak , f c_L and f c_S are the cut-off frequencies of the voltage loops of the sending-end rectifier station and the wind and solar power station respectively; if the impedance Z o_S and the input impedance Z of the rectifier station at the sending end in_HVDC The impedance curves of c_S Less than f c_L , then the wind-solar DC transmission system is considered unstable.

[0044] The wind-solar direct current transmission system in this embodiment is composed of direct-drive wind turbines, photovoltaic stations and LCC-HVDC sending-end rectifier stations. According to the station networking mode, output characteristics and equipment parameters, the impedance of wind power, photovoltaic stations and sending-end rectifier stations are calculated respectively. Draw the impedance curves of the wind power, photovoltaic stations and sending-end rectifier stations. If the impedance curves of the two intersect, the intersection frequencies are set to f1 and f2 respectively. In addition, set |Z in_HVDC1 |, satisfying |Z in_HVDC1 |Greater than the peak value of the impedance amplitude of the wind and solar power stations.

[0045] S2. If the parallel virtual impedance method is adopted, the required parallel virtual impedance is calculated and configured according to the impedance of the wind and light field stations and the original input impedance of the sending-end rectifier station; if the series virtual impedance method is adopted, the required series virtual impedance is calculated and configured according to the impedance of the wind and light field stations and the original input impedance of the sending-end rectifier station;

[0046] Specifically, if the impedance of the wind-solar DC transmission station in this embodiment is adjusted by connecting virtual impedance in parallel, its structure is as follows: Figure 3As shown, the wind-solar DC transmission station is divided into a voltage source parallel subsystem and a current source parallel subsystem. The voltage source parallel subsystem is composed of the sending-end rectifier station, and the current source parallel subsystem is composed of the wind and solar field stations. The virtual impedance is connected in parallel with the sending-end rectifier station. Therefore, the input impedance of the sending-end rectifier station is:

[0047]

[0048] Where Z in_HVDC_ori (s) is the original input impedance of the sending-end rectifier station, Z vir_P (s) is the parallel virtual impedance. In order to meet the stability condition of the sending station, the input impedance of the sending-end rectifier station after the parallel virtual impedance is no longer intersected with the impedance amplitude curve of the wind and solar field stations. in_HVDC1 |Substitute into the input impedance regulator transfer function to be configured, where the ideal Z vir_P (s) should read:

[0049]

[0050] Similarly, in order to ensure that the impedance curves of the sending-end rectifier station and the wind-solar station intersect within the start and end frequency range [f1, f2] Required Z vir_P (s) should read:

[0051]

[0052] The control block diagram of the sending end rectifier station is as follows: Figure 4 As shown, is the bus voltage disturbance, is the output voltage disturbance, is the duty cycle disturbance, is the input current disturbance, is the output current disturbance, is the output voltage reference value disturbance, H s (s) is the output voltage sampling parameter, Z in_OL (s) is the open-loop input impedance, G PWM (s) is the transfer function of the modulation link, G v (s) is the voltage loop transfer function, Z o_OL (s) is the open-loop output impedance, G wd_OL (s) is the transfer function from control to output voltage, G vg_OL (s) is the transfer function from open-loop input to output voltage, G id_OL (s) is the transfer function from control to input current, G ii_OL (s) is the open-loop load to input current transfer function.

[0053] Figure 4In the figure, the transfer function of the virtual impedance is represented by a red dotted line, connected between the output voltage reference value and the voltage bus, G Zin_P (s) is a parallel virtual input impedance regulator, and its expression is:

[0054]

[0055] The voltage loop gain T v (s)=H s (s)G v (s)G PWM (s)G vd_OL (s).

[0056] Combined with the above Z vir_P (s) expression, G Zin_P (s) can be further expressed as

[0057]

[0058] Among them, e is a natural constant, j is an imaginary unit, and θ2 is a given impedance angle of the sending-end inverter. It can be seen that G Zin_P The piecewise function characteristics of (s) are close to the characteristics of a bandpass filter, so it can be written as follows:

[0059]

[0060] Among them G BPF (s) is a typical second-order bandpass filter, consisting of a second-order high-pass filter and a second-order low-pass filter:

[0061]

[0062] Where ω1=2πf1、ω2=2πf2 are the characteristic angular frequencies of high-pass filter and low-pass filter respectively, Q H and Q L are the quality factors of the high-pass filter and the low-pass filter respectively, and s is the complex variable of the Laplace transform.

[0063] If the impedance of the wind-solar DC transmission station in this embodiment is adjusted by using the series virtual impedance method, it is necessary to adjust |Z in_HVDC1 Substituting | into the input impedance regulator, we can get the transfer function of the input impedance regulator that needs to be configured. Its structure is as follows Figure 5 As shown, the wind-solar DC transmission station is divided into a voltage source parallel subsystem and a current source parallel subsystem. The voltage source parallel subsystem is composed of the sending-end rectifier station, and the current source parallel subsystem is composed of the wind and solar field stations. The virtual impedance is connected in series with the sending-end rectifier station. Therefore, the input impedance of the sending-end rectifier station is:

[0064] Z in_HVDC(s) = Z in_HVDC_ori (s)+Z vir_S (s)

[0065] In order to meet the stability condition of the sending station, the input impedance of the sending-end rectifier station after the virtual impedance is connected in series no longer intersects with the impedance amplitude curves of the wind and solar field stations. vir_S (s) should read:

[0066]

[0067] is the original bus voltage. Similarly, in order to ensure that the impedance curves of the sending-end rectifier station and the wind-solar station intersect within the range of [f1, f2] Required Z vir_S (s) should read:

[0068]

[0069] The control block diagram of the sending end rectifier station is as follows: Figure 6 As shown, the variables and transfer functions are the same as Figure 4 The same as in. Figure 6 In the figure, the transfer function of the virtual impedance is represented by a red dotted line, connected between the output voltage reference value and the voltage bus, G Zin_S (s) is a series virtual input impedance regulator, and its expression is:

[0070]

[0071] The voltage loop gain T v =H s (s)G v (s)G PWM (s)G vd_OL (s).

[0072] Combined with the above Z vir_S (s) expression, G Zin_S (s) can be further expressed as

[0073]

[0074] It can be seen that the piecewise function characteristics presented are close to the characteristics of the bandpass filter, so it can be written as follows:

[0075]

[0076] Among them G BPF (s) is a typical second-order bandpass filter, consisting of a second-order high-pass filter and a second-order low-pass filter:

[0077]

[0078] Where ω1=2πf1、ω2=2πf2 are the characteristic angular frequencies of high-pass filter and low-pass filter respectively, Q H and Q L are the quality factors of the high-pass filter and the low-pass filter, respectively.

[0079] The present invention also provides a wind-solar DC transmission station impedance adjustment system, the system structure is as follows Figure 1 As shown, it includes an impedance calculation module, an ideal input impedance calculation module and a virtual impedance configuration module; wherein the impedance calculation module is used to read the parameters of the wind farm station, the photovoltaic farm station and the sending-end rectifier station, and calculate or directly measure the impedance amplitude and phase of the wind power, photovoltaic farm station and the sending-end rectifier station; the ideal input impedance calculation module is used to calculate the input impedance required for system stability according to the impedance of the wind power, photovoltaic farm station and the sending-end rectifier station; the virtual impedance configuration module is used to convert the input impedance required for system stability into a parallel virtual impedance or a series virtual impedance according to the configuration method, and configure the corresponding virtual impedance in the control link of the sending-end rectifier station of the wind-solar DC transmission station.

[0080] The wind-solar DC transmission station impedance adjustment system provided in the embodiment of the present invention can execute the wind-solar DC transmission station impedance adjustment method provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

[0081] The embodiment of the present application also provides an electronic device, Figure 7The structure of the electronic device provided by the embodiment of the present invention is shown. For example, the electronic device 70 may include a processor 71, a memory 72 and a transmission device 73. The processor 71 is used to execute the wind-solar DC transmission station impedance adjustment method mentioned in the above embodiment, wherein the processor and the memory may be connected by a bus or other means, taking the bus connection as an example. The transmission device may be connected to the processor and the memory by wire or wirelessly. The memory, as a non-transitory computer-readable storage medium, may be used to store non-transitory software programs, non-transitory computer executable programs and modules, such as program instructions / modules corresponding to the wind-solar DC transmission station impedance adjustment method in the embodiment of the present application. The processor executes various functional applications and data processing of the processor by running the non-transitory software programs, instructions and modules stored in the memory, that is, the wind-solar DC transmission station impedance adjustment method in the above method embodiment is implemented. The memory may include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application required by at least one function; the data storage area may store data created by the processor, etc. In addition, the memory may include a high-speed random access memory, and may also include a non-transitory memory, such as at least one disk storage device, a flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory may optionally include a memory remotely arranged relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof. The one or more modules are stored in the memory, and when executed by the processor, the wind-solar DC transmission station impedance adjustment method in the embodiment is executed.

[0082] As another aspect, the present application also provides a computer-readable storage medium, which may be a computer-readable storage medium included in the device described in the above embodiment; or it may be a computer-readable storage medium that exists independently and is not assembled into the device. The computer-readable storage medium may be a tangible storage medium, such as a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a floppy disk, a hard disk, a removable storage disk, a CD-ROM, or any other form of storage medium known in the technical field. The computer-readable storage medium stores one or more programs, and the programs are used by one or more processors to execute the wind-solar DC transmission station impedance adjustment method described in the present application.

[0083] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for adjusting impedance of a wind-solar DC transmission station, characterized in that: The following steps are involved: S1. Obtain the wind and solar field impedance of the wind and solar power transmission station and the original input impedance of the sending-end rectifier station by calculation or measurement; S2. If the parallel virtual impedance method is adopted, the required parallel virtual impedance is calculated and configured according to the impedance of the wind and light field stations and the original input impedance of the sending-end rectifier station; if the series virtual impedance method is adopted, the required series virtual impedance is calculated and configured according to the impedance of the wind and light field stations and the original input impedance of the sending-end rectifier station.

2. The method according to claim 1, characterized in that The calculation formula of parallel virtual impedance is: Among them G Zin_P (s) is the parallel virtual input impedance regulator, V bus is the bus voltage, P o is the active power sent out, e is a natural constant, j is an imaginary unit, θ2 is the given impedance angle of the sending-end inverter, G v (s) is the voltage loop transfer function, G PWM (s) is the transfer function of the modulation link, G id_OL (s) is the transfer function from control to input current, T v (s) is the voltage loop gain, G BPF (s) is a typical second-order bandpass filter.

3. The method according to claim 1, characterized in that The series virtual impedance calculation formula is: Among them G Zin_s (s) is a series virtual input impedance regulator, is the original bus voltage, P o is the active power sent out, e is a natural constant, j is an imaginary unit, θ2 is the given impedance angle of the sending-end inverter, G id_OL (s) is the transfer function from control to input current, G PWM (s) is the transfer function of the modulation link, Z in_HVDC_ori (s) is the original input impedance of the sending-end rectifier station, T v (s) is the voltage loop gain, G BPF (s) is a typical second-order bandpass filter.

4. The method according to claim 2 or 3, characterized in that G BPF (s) consists of a second-order high-pass filter and a second-order low-pass filter: Where ω1=2πf1、ω2=2πf2 are the characteristic angular frequencies of high-pass filter and low-pass filter respectively, Q H and Q L are the quality factors of the high-pass filter and the low-pass filter respectively, [f1, f2] are the start and end frequencies where the impedance curves of the sending-end rectifier station and the wind-solar station intersect, and s is the complex variable of the Laplace transform.

5. A wind-solar DC transmission station impedance adjustment system, characterized in that: Used to implement the wind-solar DC transmission station impedance adjustment method as described in any one of claims 1 to 4, comprising an impedance calculation module, an ideal input impedance calculation module and a virtual impedance configuration module; The impedance calculation module is used to read the parameters of the wind farm, photovoltaic farm and sending-end rectifier station, and calculate or directly measure the impedance amplitude and phase of the wind farm, photovoltaic farm and sending-end rectifier station; Ideal input impedance calculation module, used to calculate the input impedance required for system stability based on the impedance of the rectifier station at the sending end of the wind power and photovoltaic station; The virtual impedance configuration module is used to convert the input impedance required for system stability into parallel virtual impedance or series virtual impedance according to the configuration method, and configure the corresponding virtual impedance in the control link of the rectifier station at the sending end of the wind-solar DC transmission station.

6. An electronic device, characterized in that: The electronic device includes a processor and a memory for storing executable instructions of the processor; the processor is used to read the executable instructions from the memory and execute the instructions to implement the wind-solar DC transmission station impedance adjustment method as described in any one of claims 1-4 above.

7. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and the computer program is used to execute the wind-solar direct current transmission station impedance adjustment method as described in any one of claims 1-4 above.

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