Receiving end power self-balancing control method and related equipment

Abstract

The invention discloses a receiving end power self-balancing control method and related equipment, which are applied to a multi-end flexible direct current transmission system of new energy. According to the method, a first converter station at a receiving end is set as a constant DC voltage control mode stable voltage reference, and other converter stations are set as a constant active power control mode to flexibly adjust power. And monitoring the active power deviation of the first converter station in real time, and dynamically updating the power reference value of each station according to the adjustment coefficient determined by each station based on the power margin when the active power deviation exceeds a preset power threshold, thereby promoting all receiving end converter stations to jointly bear unbalanced power. Compared with the prior art, the limitation that a single station bears unbalanced power is changed, and overload is avoided; the defect of difference adjustment of droop control is overcome, and the system voltage is accurately stabilized; power is allocated based on the power margin, avoiding imbalance. Through the mechanism, the adaptability of the system to new energy fluctuation is improved, and stable operation of the multi-terminal flexible direct-current power transmission system is guaranteed.

Description

Technical Field

[0001] The present application relates to the technical field of power transmission control, and more specifically, to a receiving-end power self-balancing control method and related equipment. Background Art

[0002] At present, with the deep transformation of the global energy structure, the large-scale grid connection of new energy has become a key challenge in the power field. The multi-terminal flexible DC power transmission system shows great potential in fields such as island power supply and offshore wind power grid connection due to its advantages of flexible power dispatching and low transmission cost. However, its safe and stable operation highly depends on control strategies. Currently, the mainstream master-slave control and voltage droop control cannot achieve receiving-end power self-balancing control, and there are obvious defects.

[0003] In the master-slave control strategy, only one master station in the whole system adopts constant DC voltage control, and other converter stations adopt constant active power control as slave stations. When the master station quits operation due to new energy output fluctuations or faults, it is necessary to send control mode switching instructions to the slave stations. This not only depends on inter-station communication with high switching delays but also causes large fluctuations in the system voltage. In this control method, the unbalanced power is mainly borne by the master station, and the power self-balancing among multiple stations cannot be achieved. Although the droop control strategy can make multiple converter stations jointly bear the unbalanced power, due to its droop regulation characteristics, when the new energy output fluctuates violently, it cannot accurately control the DC voltage and power, resulting in voltage deviation and power distribution imbalance, and it is difficult to achieve reasonable and balanced power distribution.

[0004] In the new energy multi-terminal flexible DC transmission system, the randomness and volatility of the new energy power station power are significant. Since the existing control strategies cannot achieve receiving-end power self-balancing control, the potential of the receiving-end converter station cannot be fully exerted. In the master-slave control strategy, only one master converter station bears the system unbalanced power at any time, which is prone to power over-limit; while the droop control strategy lacks a precise adjustment mechanism, and when the new energy output fluctuates greatly, there will be problems such as DC voltage over-limit and unreasonable power distribution. These defects seriously restrict the stable operation of the multi-terminal flexible DC power transmission system.

[0005] Therefore, it is urgent to innovate control strategies to achieve receiving-end power self-balancing control and ensure the safe and stable operation of the system. Summary of the Invention

[0006] The present application provides a receiving-end power self-balancing control method and related equipment. By setting the first receiving-end converter station to the constant DC voltage control mode and the remaining converter stations to the constant active power control mode, and determining the adjustment coefficient based on the power margin to jointly adjust the power of each station, the multi-station can jointly bear the unbalanced power, stabilize the system voltage, and reasonably distribute the power, effectively improving the system's adaptability to new energy fluctuations and ensuring the safe and stable operation of the multi-terminal flexible DC power transmission system.

[0007] A receiving - end power self - balancing control method is applied to a new - energy multi - terminal flexible DC transmission system. The method includes:

[0008] Set the first converter station at the receiving end to the constant DC voltage control mode, and set the other converter stations except the first converter station at the receiving end to the constant active - power control mode;

[0009] Real - time monitor the actual value of the active power of the first converter station, and calculate the deviation between the actual value of the active power and the calibrated value of the active power;

[0010] When the absolute value of the deviation exceeds a preset power threshold, update the calibrated value of the active power of the first converter station and the reference value of the active power of the other converter stations according to the deviation and the adjustment coefficients of each receiving - end converter station, so that all receiving - end converter stations jointly bear the unbalanced power corresponding to the deviation and maintain the system voltage stable at the rated value, where the adjustment coefficients are determined based on the power margins of each receiving - end converter station.

[0011] Optionally, the calculation formula for updating the calibrated value of the active power of the first converter station is:

[0012] P′ 1n =P 1n +k1ΔP1

[0013] Where, P′ 1n is the updated calibrated value of the active power of the first converter station, P 1n is the calibrated value of the active power of the first converter station, k1 is the adjustment coefficient of the first converter station, and ΔP1 is the deviation.

[0014] Optionally, the calculation formula for updating the reference value of the active power of the other converter stations is:

[0015] P′ xref =P xref +k x ΔP1

[0016] Where, P′ xref is the updated reference value of the active power of the x - th converter station, P xref is the reference value of the active power of the x - th converter station, k x is the adjustment coefficient of the x - th converter station, and ΔP1 is the deviation.

[0017] Optionally, the determination method of the adjustment coefficient is:

[0018]

[0019] Where, k1 is the adjustment coefficient of the first converter station, k xis the adjustment coefficient for the x-th converter station, P 1max is the maximum active power value of the first converter station, P 1n is the rated active power value of the first converter station, P imax is the maximum active power value of the i-th converter station, P iref is the reference active power value of the i-th converter station, P xmax is the maximum active power value of the x-th converter station, P xref is the reference active power value of the x-th converter station, and y is the total number of receiving-end converter stations.

[0020] Optionally, when the absolute value of the deviation does not exceed the preset power threshold, the reference active power values of the other converter stations remain unchanged, and only the first converter station bears the unbalanced power corresponding to the deviation.

[0021] Optionally, the initial rated active power value of the first converter station is the average value of the actual active power values of the first converter station during the steady-state operation of the system.

[0022] A receiving-end power self-balancing control device, comprising:

[0023] A mode setting unit, configured to set the first receiving-end converter station to a constant DC voltage control mode, and set the other receiving-end converter stations except the first converter station to a constant active power control mode;

[0024] A deviation monitoring unit, configured to monitor the actual active power value of the first converter station in real time, and calculate the deviation between the actual active power value and the rated active power value;

[0025] An equilibrium adjustment unit, configured to, when the absolute value of the deviation exceeds the preset power threshold, update the rated active power value of the first converter station and the reference active power values of the other receiving-end converter stations according to the deviation and the adjustment coefficients of the receiving-end converter stations, so that all receiving-end converter stations jointly bear the unbalanced power corresponding to the deviation and maintain the system voltage stable at the rated value, where the adjustment coefficients are determined based on the power margins of the receiving-end converter stations.

[0026] A receiving-end power self-balancing control device, comprising a memory and a processor;

[0027] The memory is configured to store a program;

[0028] The processor is configured to execute the program to implement each step of the receiving-end power self-balancing control method as described in any one of the above.

[0029] A readable storage medium stores a computer program thereon. It is characterized in that when the computer program is executed by a processor, each step of the receiving-end power self-balancing control method described in any one of the above is implemented.

[0030] A computer program product includes a computer program. It is characterized in that when the computer program is run by a processor, each step of the receiving-end power self-balancing control method described in any one of the above is executed.

[0031] As can be seen from the above technical solutions, a receiving-end power self-balancing control method and related devices provided by the embodiments of the present application are directed to a multi-terminal flexible DC transmission system for new energy. The system is optimized through a differential control mode and a dynamic adjustment mechanism. In this method, the first receiving-end converter station is set to a constant DC voltage control mode to ensure the stability of the system voltage reference; the remaining converter stations are set to a constant active power control mode to flexibly adjust the power output. At the same time, the active power deviation of the first converter station is monitored in real time. When the deviation exceeds the preset power threshold, the power reference values of each station are dynamically updated according to the adjustment coefficients determined based on the power margin of each station, so as to prompt all receiving-end converter stations to jointly bear the unbalanced power.

[0032] The present application achieves many beneficial effects: First, by setting the first receiving-end converter station to a constant DC voltage control mode and the remaining converter stations to a constant active power control mode, when it is monitored that the power deviation of the first converter station exceeds the limit, the power is coordinated and adjusted according to the adjustment coefficients of each station, so that multiple stations jointly bear the unbalanced power, effectively avoiding single-station overload; Second, through the constant DC voltage control of the first converter station to provide a stable reference, combined with the precise adjustment of the active power reference values of each converter station, the power fluctuations can be compensated in real time, ensuring that the system voltage is stable at the rated value and solving the problem of DC voltage deviation; Third, the adjustment coefficients are determined based on the power margin of each receiving-end converter station. The converter station with a large power margin can bear more unbalanced power, realizing the reasonable distribution of the unbalanced power and avoiding the power distribution imbalance caused by improper selection of coefficients. Through the above mechanism, this solution effectively improves the system's adaptability to new energy fluctuations and ensures the safe and stable operation of the multi-terminal flexible DC transmission system. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0034] Figure 1 It is a flowchart of a receiving-end power self-balancing control method disclosed in an embodiment of the present application;

[0035] Figure 2 Schematic diagram of a receiving - end power self - balancing control method disclosed in an embodiment of the present application;

[0036] Figure 3 Control block diagram of the x - th receiving - end converter station in an embodiment of the present application;

[0037] Figure 4 Schematic structural diagram of an offshore wind power multi - terminal flexible DC transmission system disclosed in an embodiment of the present application;

[0038] Figure 5 Curve graph of system response results under power fluctuations disclosed in an embodiment of the present application;

[0039] Figure 6 Schematic diagram of a receiving - end power self - balancing control device disclosed in an embodiment of the present application;

[0040] Figure 7 Hardware structural block diagram of a receiving - end power self - balancing control device disclosed in an embodiment of the present application. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0042] The present application can be used in many general - purpose or special - purpose computing device environments or configurations. For example: personal computers, server computers, handheld devices or portable devices, tablet - type devices, multi - processor devices, distributed computing environments including any of the above devices or equipment, and so on.

[0043] Next, the solutions of the present application will be introduced. The present application proposes the following technical solutions. For details, please refer to the following text.

[0044] Figure 1 Flowchart of a receiving - end power self - balancing control method disclosed in an embodiment of the present application.

[0045] Figure 2 Schematic diagram of a receiving - end power self - balancing control method disclosed in an embodiment of the present application.

[0046] This method can be applied to a new - energy multi - terminal flexible DC transmission system. As shown in Figure 1 and Figure 2 This method may include:

[0047] Step S1: Set the receiving-end first converter station to the constant DC voltage control mode, and set the other converter stations except the first converter station at the receiving end to the constant active power control mode.

[0048] Specifically, at the system startup stage, the mode of the receiving-end converter station is set through the system configuration program. The receiving-end first converter station is set to the constant DC voltage control mode, and the other converter stations except the first converter station at the receiving end are set to the constant active power control mode.

[0049] In the constant DC voltage control mode, the main task of the first converter station is to maintain the stability of the system DC voltage. It is internally equipped with a high-precision voltage sensor to collect the DC bus voltage value in real time. At the same time, there is a voltage controller. This controller compares the collected actual voltage value with the preset rated DC voltage value to obtain the voltage deviation. According to this deviation, the voltage controller generates a corresponding control signal to adjust the trigger pulse of the converter, thereby changing the AC-side output voltage and current of the converter, and further adjusting the power output on the DC side to keep the DC voltage always stable near the rated value.

[0050] For the other converter stations except the first converter station, the constant active power control mode requires them to output power according to the preset active power reference value. These converter stations are equipped with active power sensors to monitor their own active power output in real time. The active power controller compares the actual active power value with the reference value. When there is a deviation, by adjusting the control parameters of the converter, such as the modulation ratio, trigger angle, etc., the active power output is changed to make it track the reference value and achieve precise control of the active power.

[0051] Step S2: Monitor the actual value of the active power of the first converter station in real time, and calculate the deviation between the actual value of the active power and the calibrated value of the active power.

[0052] Specifically, for real-time monitoring, the first converter station is installed with a high-precision power measurement device, which can collect active power data with an extremely short sampling period (such as millisecond level). The collected actual value of the active power will be transmitted to the data processing unit.

[0053] Among them, the initial calibrated value of the active power of the first converter station is the average value of the actual value of the active power of the first converter station during the steady-state operation of the system. After the system starts and enters the steady-state operation stage, the data processing unit continuously records the actual value of the active power of the first converter station. After statistical calculation for a certain period of time, the average value is obtained as the initial calibrated value of the active power. With the change of the system operation conditions, this calibrated value will also be dynamically updated according to the subsequent adjustment strategy.

[0054] As Figure 2 shown, the actual value of the active power P collected in real time1real Perform a subtraction operation with the current active power calibration value P 1n to obtain the deviation ΔP1 between the two. This deviation reflects the difference between the current active power output of the first converter station and the expected value, and is an important basis for subsequent power adjustment.

[0055] Step S3: When the absolute value of the deviation exceeds a preset power threshold, update the active power calibration value of the first converter station and the active power reference values of the other converter stations according to the deviation and the adjustment coefficients of the receiving-end converter stations, so that all receiving-end converter stations jointly bear the unbalanced power corresponding to the deviation and maintain the system voltage stable at the rated value, where the adjustment coefficients are determined based on the power margins of the receiving-end converter stations.

[0056] Specifically, the power threshold P preset in the system dm is an empirical value, and the value range of the preset power threshold is generally 1% to 10% of the maximum active power of the first converter station. The setting of this value range is carefully considered: if the power threshold is lower than 1% of the maximum active power of the first converter station, the system will be too sensitive, and normal small fluctuations in new energy power will frequently trigger power adjustment, resulting in frequent actions of each converter station, increasing the system control complexity and computational load, and even causing unstable system operation; if the power threshold exceeds 10% of the maximum active power of the first converter station, when there is a large power deviation in the first converter station, the system is difficult to respond in time, and the unbalanced power is likely to accumulate in the station, causing power over-limit and then triggering a DC system voltage collapse.

[0057] When the absolute value of the deviation exceeds the preset power threshold, it indicates that there is a large power imbalance in the system, and all receiving-end converter stations need to participate in the adjustment together. At this time, the system will immediately start the power adjustment mechanism.

[0058] First, determine the adjustment coefficients of the receiving-end converter stations. The power margin refers to the additional power that the converter station can safely carry under the current operating state. Its calculation comprehensively considers factors such as the rated capacity of the converter station, the current active power output, the thermal limit of the equipment, and the safety margin. Through a specific algorithm, the corresponding adjustment coefficients are calculated according to the power margins of the converter stations. The larger the power margin of a converter station, the larger its adjustment coefficient, which means it can bear more unbalanced power during the power adjustment process.

[0059] Then, based on the calculated deviation value and the adjustment coefficients of each station, a specific power distribution algorithm is used to update the active power calibration value of the first converter station and the active power reference values of the other converter stations. Specifically, the updated active power calibration value of the first converter station is obtained by adding the product of the adjustment coefficient of the first converter station and the deviation to the original active power calibration value. The updated active power reference value of each of the other converter stations is equal to the original active power reference value of that station plus the product of the adjustment coefficient of that station and the deviation.

[0060] The first converter station adjusts its own active power output according to the new active power calibration value. At the same time, it sends the new active power reference value to the other converter stations. After each converter station receives the new reference value, its active power controller responds quickly. By adjusting the control parameters of the converter, it changes the active power output so that all receiving-end converter stations jointly bear the unbalanced power. During this process, the constant DC voltage control mode of the first converter station continues to play a role, monitoring and regulating the DC voltage in real time to ensure that the system voltage is stably maintained at the rated value and guarantee the safe and stable operation of the system.

[0061] Through this power adjustment strategy based on the comparison of deviation and threshold, the system can flexibly allocate the power sharing tasks of each converter station according to the actual power imbalance situation. It not only ensures the stability of the system during normal fluctuations but also can quickly respond when a large deviation occurs, realizing the power self-equilibrium among the receiving-end converter stations and effectively enhancing the system's adaptability to new energy fluctuations.

[0062] Among them, the updated active power calibration value of the first converter station is obtained by adding the product of the adjustment coefficient of the first converter station and the deviation to the original active power calibration value. The updated active power reference value of each of the other converter stations is equal to the original active power reference value of that station plus the product of the adjustment coefficient of that station and the deviation.

[0063] The calculation formula for updating the active power calibration value of the first converter station is:

[0064] P′ 1n =P 1n +k1ΔP1

[0065] where P′ 1n is the updated active power calibration value of the first converter station, P 1n is the active power calibration value of the first converter station, k1 is the adjustment coefficient of the first converter station, and ΔP1 is the deviation.

[0066] The calculation formula for updating the active power reference values of the other converter stations is:

[0067] P′ xref =P xref +kx ΔP1

[0068] wherein, P′ xref is the active power reference value of the x-th converter station after update, P xref is the active power reference value of the x-th converter station, k x is the adjustment coefficient of the x-th converter station, and ΔP1 is the deviation.

[0069] The determination method of the adjustment coefficient is as follows:

[0070]

[0071] wherein, k1 is the adjustment coefficient of the first converter station, k x is the adjustment coefficient of the x-th converter station, P 1max is the maximum active power value of the first converter station, P 1n is the active power calibration value of the first converter station, P imax is the maximum active power value of the i-th converter station, P iref is the active power reference value of the i-th converter station, P xmax is the maximum active power value of the x-th converter station, P xref is the active power reference value of the x-th converter station, and y is the total number of receiving-end converter stations.

[0072] Figure 3 is the control block diagram of the receiving-end x-th converter station. In the original active power controller of the converter station (inside the virtual box), the active power reference value P xref was originally a fixed value. This value is compared with the actual active power P x of the converter station, and the difference between the two is input to a proportional-integral (PI) controller. The PI controller outputs a reference current value i dref according to the difference. This reference current value will be limited between the maximum reference current i dmax and the minimum reference current i dmin . The limited reference current value is input to the inner-loop current control link, and the inner-loop current control controls and adjusts the current according to the reference current. Finally, through the waveform modulation link, the adjusted signal is converted into a trigger signal for controlling the power output of the converter station, so that the active power output of the converter station is as close as possible to the set fixed value P xref . In the improved control mode, the active power reference value P xref of the x-th converter station is no longer a fixed value, but becomes a variable related to the actual power of the first converter station. This change is crucial. When there is unbalanced power in the system, the actual power of the first converter station will change. At this time, the P xrefIt will be adjusted accordingly according to the correlation with the actual power of the first converter station. In this way, the x-th converter station can adjust its own active power output in real time according to the actual situation of the system power imbalance, and jointly bear the unbalanced power of the system with the first converter station. For example, when the power borne by the first converter station exceeds a certain threshold, the P of the x-th converter station xref will be automatically adjusted to increase its power output, assist the first converter station in sharing the unbalanced power, avoid the power overload of the first converter station, and thus ensure the power balance and stable operation of the entire system.

[0073] In addition, as Figure 2 shown, when the absolute value of the deviation does not exceed the preset power threshold, the active power reference values of the remaining converter stations remain unchanged, and only the first converter station bears the unbalanced power corresponding to the deviation.

[0074] Specifically, when the absolute value of the deviation does not exceed the preset power threshold, it means that the current power deviation is within the normal fluctuation range tolerable by the system. At this time, the active power reference values of the remaining converter stations remain unchanged, and only the first converter station bears the unbalanced power corresponding to the deviation. With the characteristics of its constant DC voltage control mode, the first converter station adjusts its active power output through its own adjustment mechanism to balance this part of the deviation. Since the first converter station can monitor and adjust the DC voltage in real time under the constant DC voltage control mode, it can also maintain the system voltage stable at the rated value during the process of bearing the unbalanced power. This strategy can avoid unnecessary power adjustment operations, reduce the adjustment times of the system, and improve the stability and reliability of the system operation.

[0075] As can be seen from the above technical solutions, a receiving-end power self-balancing control method and related equipment provided by the embodiments of the present application are directed to a multi-terminal flexible DC transmission system for new energy, and realize system optimization through a differential control mode and a dynamic adjustment mechanism. This method sets the first receiving-end converter station to the constant DC voltage control mode to ensure the stability of the system voltage reference; the remaining converter stations are set to the constant active power control mode to flexibly adjust the power output. At the same time, the active power deviation of the first converter station is monitored in real time. When the deviation exceeds the preset power threshold, the power reference values of each station are dynamically updated according to the adjustment coefficients determined by each station based on the power margin, so as to prompt all receiving-end converter stations to jointly bear the unbalanced power.

[0076] The present application achieves many beneficial effects: First, by setting the receiving-end first converter station to the constant DC voltage control mode and the other converter stations to the constant active power control mode, when it is detected that the power deviation of the first converter station exceeds the limit, the power is coordinated and adjusted according to the adjustment coefficients of each station, enabling multiple stations to jointly bear the unbalanced power and effectively avoiding single-station overload; Second, by providing a stable reference through the constant DC voltage control of the first converter station and combining with the precise adjustment of the active power reference values of each converter station, the power fluctuations can be compensated in real time, ensuring that the system voltage is stabilized at the rated value and solving the problem of DC voltage deviation; Third, the adjustment coefficients are determined based on the power margins of each receiving-end converter station. The converter station with a large power margin can bear more unbalanced power, realizing the reasonable distribution of unbalanced power and avoiding power distribution imbalance caused by improper selection of coefficients. Through the above mechanism, this solution effectively and fully improves the system's adaptability to new energy fluctuations and ensures the safe and stable operation of the multi-terminal flexible DC transmission system.

[0077] The following uses an example to verify the technical solution of the present application.

[0078] Build the offshore wind power multi-terminal flexible DC transmission system as shown in Figure 4 on the PSCAD / EMTDC simulation platform. Since the wind turbines have no grid-forming ability, the sending-end converter stations WFMMC1, WFMMC2, and WFMMC3 adopt the island control mode to provide grid-connected voltage for the wind farms.

[0079] Figure 5 is the curve graph of the system response results under power fluctuations. Among them Figure 5 (a) is the curve graph of the active power provided by the sending-end converter stations. The red line corresponds to WFMMC1, the green line corresponds to WFMMC2, and the blue line corresponds to WFMMC3. Figure 5 (b) is the curve graph of the active power borne by the receiving-end converter stations. The purple line corresponds to GSMMC1, and the orange line corresponds to GSMMC2. Figure 5 (c) is the DC system voltage fluctuation graph.

[0080] As shown in Figure 5 (a), during normal operation, the sending-end converter stations WFMMC1, WFMMC2, and WFMMC3 provide active powers of 1500MW, 1600MW, and 1700MW to the DC system respectively. The two onshore receiving-end converter stations GSMMC1 and GSMMC2 both have a maximum active power of 3000MW. Among them, GSMMC1 is the first converter station and GSMMC2 is the second converter station. The basic simulation parameters of the system are shown in Table 1.

[0081] System parameters Value Rated DC voltage 1000 kV DC submarine cable parameters per unit length 0.0072 Ω / km + 0.36 mH / km DC overhead line parameters per unit length 0.0313 Ω / km + 0.16 mH / km DC submarine cable length 115 km DC overhead line length from terminal conversion station to collection station 35 km DC overhead line length from collection station to receiving converter station 150 km Power change threshold Pdm 300 MW

[0082] Table 1

[0083] As Figure 5 shown in (b), at the moment of t = 0, the system is in a steady state. The calibrated active power value (P 1n ) of GSMMC1 is 2300MW, and the reference active power value (P 2ref ) of GSMMC2 is 2500MW. The corresponding adjustment coefficients k1 and k2 can be calculated as 7 / 12 and 5 / 12 respectively.

[0084] As Figure 5 shown in (a) and 5(b), at t = 1.5s, the output of the wind farm increases. The active power provided by WFMMC1 to the system increases from 1500MW to 1650MW. The active power borne by GSMMC1 increases from 2300MW to 2450MW, and the power increment is 2450 - 2300 = 150MW, which does not exceed the set power threshold Pdm = 300MW. According to the proposed strategy, in this case, P 1n and P 2ref both remain unchanged, that is, GSMMC1 alone bears the power fluctuation. The results show that when the output of the wind farm has small fluctuations, GSMMC1 can handle it independently and there will be no power over - limit problem, verifying the effectiveness of the strategy in the small - fluctuation scenario, that is, the power balance of the system can be maintained through the self - regulation of the first converter station (GSMMC1).

[0085] At t = 4.5s, at this time, the input active power of the wind farm further increases. The active power output of WFMMC1 increases from 1650MW to 1950MW, and the active power output of WFMMC3 increases from 1700MW to 2000MW. If the receiving - end active - power self - balancing strategy is not adopted, only GSMMC1 bears the power increment, and its active power will reach 3050MW, exceeding the power limit of 3000MW. When the proposed strategy is adopted, as the active power of GSMMC1 increases, GSMMC2 will adjust its own reference active - power value according to the strategy.

[0086] After t = 5s, the active power of GSMMC1 is 2737MW, and the active power of GSMMC2 increases from 2500MW to 2813MW. And as Figure 5 shown in (c), during the above - mentioned whole process, the DC system voltage remains basically stable. This shows that the proposed strategy can enable GSMMC1 and GSMMC2 to jointly bear the unbalanced power, avoiding the power over - limit of GSMMC1, verifying that in the large - fluctuation scenario, the strategy can adjust the power through multi - station coordination to ensure the stable operation of the system and prevent the power over - limit of the converter station.

[0087] Next, a receiving - end power self - balancing control device provided by an embodiment of the present application will be described. The receiving - end power self - balancing control device described below can be correspondingly referred to with the receiving - end power self - balancing control method described above.

[0088] SeeFigure 6 , Figure 6 Schematic diagram of a receiving - end power self - balancing control device disclosed in an embodiment of the present application.

[0089] As Figure 6 shown, the receiving - end power self - balancing control device may include:

[0090] A mode - setting unit 110, configured to set the first receiving - end converter station to a constant DC voltage control mode, and set each of the remaining converter stations except the first receiving - end converter station to a constant active - power control mode;

[0091] A deviation - monitoring unit 120, configured to monitor the actual value of the active power of the first converter station in real time, and calculate the deviation between the actual value of the active power and the calibrated value of the active power;

[0092] An equalization - adjustment unit 130, configured to, when the absolute value of the deviation exceeds a preset power threshold, update the calibrated value of the active power of the first converter station and the reference values of the active powers of the remaining converter stations according to the deviation and the adjustment coefficients of each receiving - end converter station, so that all receiving - end converter stations jointly bear the unbalanced power corresponding to the deviation and maintain the system voltage stable at the rated value, where the adjustment coefficients are determined based on the power margins of each receiving - end converter station.

[0093] It can be seen from the above technical solutions that a receiving - end power self - balancing control method and related devices provided by the embodiments of the present application are directed at a multi - terminal flexible DC transmission system for new energy, and realize system optimization through a differential control mode and a dynamic adjustment mechanism. This method sets the first receiving - end converter station to a constant DC voltage control mode to ensure the stability of the system voltage reference; the remaining converter stations are set to a constant active - power control mode to flexibly adjust the power output. At the same time, the active - power deviation of the first converter station is monitored in real time. When the deviation exceeds the preset power threshold, the reference values of the powers of each station are dynamically updated according to the adjustment coefficients determined based on the power margins of each station, so as to prompt all receiving - end converter stations to jointly bear the unbalanced power.

[0094] This application achieves many beneficial effects: First, by setting the receiving-end first converter station to the constant DC voltage control mode and the other converter stations to the constant active power control mode, when the power deviation of the first converter station is detected to exceed the limit, the power is coordinated and adjusted according to the adjustment coefficients of each station, enabling multiple stations to jointly bear the unbalanced power and effectively avoiding single-station overload; Second, by providing a stable reference through the constant DC voltage control of the first converter station and combining with the precise adjustment of the active power reference values of each converter station, the power fluctuations can be compensated in real time to ensure that the system voltage is stable at the rated value, solving the problem of DC voltage deviation; Third, the adjustment coefficients are determined based on the power margins of each receiving-end converter station. Converter stations with larger power margins can bear more unbalanced power, realizing the reasonable distribution of unbalanced power and avoiding power distribution imbalance caused by improper coefficient selection. Through the above mechanism, this solution effectively improves the system's adaptability to new energy fluctuations and ensures the safe and stable operation of the multi-terminal flexible DC transmission system.

[0095] Optionally, the calculation formula for updating the active power calibration value of the first converter station is:

[0096] P′ 1n =P 1n +k1ΔP1

[0097] Where, P′ 1n is the updated active power calibration value of the first converter station, P 1n is the active power calibration value of the first converter station, k1 is the adjustment coefficient of the first converter station, and ΔP1 is the deviation.

[0098] Optionally, the calculation formula for updating the active power reference values of the other converter stations is:

[0099] P′ xref =P xref +k x ΔP1

[0100] Where, P′ xref is the updated active power reference value of the x-th converter station, P xref is the active power reference value of the x-th converter station, k x is the adjustment coefficient of the x-th converter station, and ΔP1 is the deviation.

[0101] Optionally, the determination method of the adjustment coefficient is:

[0102]

[0103] Where, k1 is the adjustment coefficient of the first converter station, k x is the adjustment coefficient of the x-th converter station, P 1max is the maximum active power value of the first converter station, P 1nis the rated active power value of the first converter station, P imax is the maximum active power value of the i-th converter station, P iref is the reference active power value of the i-th converter station, P xmax is the maximum active power value of the x-th converter station, P xref is the reference active power value of the x-th converter station, and y is the total number of receiving-end converter stations.

[0104] Optionally, when the absolute value of the deviation does not exceed the preset power threshold, the reference active power values of the other converter stations remain unchanged, and only the first converter station bears the unbalanced power corresponding to the deviation.

[0105] Optionally, the initial rated active power value of the first converter station is the average value of the actual active power values of the first converter station during the steady-state operation of the system.

[0106] The receiving-end power self-balancing control device provided by the embodiments of the present application can be applied to the receiving-end power self-balancing control equipment. Figure 7 shows the hardware structure block diagram of the receiving-end power self-balancing control equipment. Refer to Figure 7 , the hardware structure of the receiving-end power self-balancing control equipment may include: at least one processor 1, at least one communication interface 2, at least one memory 3, and at least one communication bus 4;

[0107] In the embodiments of the present application, the number of the processor 1, the communication interface 2, the memory 3, and the communication bus 4 is at least one, and the processor 1, the communication interface 2, and the memory 3 complete mutual communication through the communication bus 4;

[0108] The processor 1 may be a central processing unit CPU, or a specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present invention, etc.;

[0109] The memory 3 may include a high-speed RAM memory, and may also include a non-volatile memory, such as at least one disk memory;

[0110] Among them, the memory stores a program, and the processor can call the program stored in the memory. The program is used for:

[0111] Set the receiving-end first converter station to the constant DC voltage control mode, and set the other converter stations except the first converter station at the receiving end to the constant active power control mode;

[0112] Real-time monitor the actual value of the active power of the first converter station, and calculate the deviation between the actual value of the active power and the calibrated value of the active power;

[0113] When the absolute value of the deviation exceeds a preset power threshold, update the calibrated value of the active power of the first converter station and the reference values of the active power of the other converter stations according to the deviation and the adjustment coefficients of the receiving-end converter stations, so that all receiving-end converter stations jointly bear the unbalanced power corresponding to the deviation and maintain the system voltage stable at the rated value, where the adjustment coefficients are determined based on the power margins of the receiving-end converter stations.

[0114] Optionally, the refinement functions and extension functions of the program can be referred to the above description.

[0115] The embodiment of the present application further provides a readable storage medium, which can store a program suitable for being executed by a processor, and the program is used for:

[0116] Set the first receiving-end converter station to the constant DC voltage control mode, and set the other receiving-end converter stations except the first converter station to the constant active power control mode;

[0117] Real-time monitor the actual value of the active power of the first converter station, and calculate the deviation between the actual value of the active power and the calibrated value of the active power;

[0118] When the absolute value of the deviation exceeds a preset power threshold, update the calibrated value of the active power of the first converter station and the reference values of the active power of the other converter stations according to the deviation and the adjustment coefficients of the receiving-end converter stations, so that all receiving-end converter stations jointly bear the unbalanced power corresponding to the deviation and maintain the system voltage stable at the rated value, where the adjustment coefficients are determined based on the power margins of the receiving-end converter stations.

[0119] Optionally, the refinement functions and extension functions of the program can be referred to the above description.

[0120] The embodiment of the present application further provides a computer program product, including a computer program, and the method executed when the computer program is run by a processor is:

[0121] Set the first receiving-end converter station to the constant DC voltage control mode, and set the other receiving-end converter stations except the first converter station to the constant active power control mode;

[0122] Real-time monitor the actual value of the active power of the first converter station, and calculate the deviation between the actual value of the active power and the calibrated value of the active power;

[0123] When the absolute value of the deviation exceeds a preset power threshold, update the calibrated active power value of the first converter station and the reference active power values of the other converter stations according to the deviation and the adjustment coefficients of the receiving converter stations, so that all the receiving converter stations jointly bear the unbalanced power corresponding to the deviation and maintain the system voltage stable at the rated value, where the adjustment coefficients are determined based on the power margins of the receiving converter stations.

[0124] Optionally, the refinement function and the expansion function of the program can be referred to the above description.

[0125] Finally, it should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0126] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A receiving-end power self-balancing control method, characterized in that Applied to a multi-terminal flexible DC transmission system for new energy, the method includes: Set the first converter station at the receiving end to the constant DC voltage control mode, and set the other converter stations at the receiving end except the first converter station to the constant active power control mode; Monitor the actual value of the active power of the first converter station in real time, and calculate the deviation between the actual value of the active power and the calibrated value of the active power; When the absolute value of the deviation exceeds the preset power threshold, update the calibrated value of the active power of the first converter station and the reference values of the active powers of the other converter stations according to the deviation and the adjustment coefficients of the converter stations at the receiving end, so that all converter stations at the receiving end jointly bear the unbalanced power corresponding to the deviation and maintain the system voltage stable at the rated value, where the adjustment coefficients are determined based on the power margins of the converter stations at the receiving end.

2. The method according to claim 1, wherein The calculation formula for updating the calibrated value of the active power of the first converter station is: Wherein, is the rated active power value of the updated first converter station, is the rated active power value of the first converter station, is the adjustment coefficient of the first converter station, is the deviation.

3. The method according to claim 1, characterized in that, The calculation formula for updating the reference values of the active powers of the other converter stations is: Among them, is the reference value of the active power of the updated xth converter station, is the reference value of the active power of the xth converter station, is the adjustment coefficient of the xth converter station, is the deviation.

4. The method according to claim 2 or 3, characterized in that The determination method of the adjustment coefficients is: Among them, is the adjustment coefficient of the first converter station, is the adjustment coefficient of the x-th converter station, is the maximum active power value of the first converter station, is the rated active power value of the first converter station, is the maximum active power value of the i-th converter station, is the reference active power value of the i-th converter station, is the maximum active power value of the x-th converter station, is the reference active power value of the x-th converter station, and y is the total number of receiving-end converter stations.

5. The method according to claim 1, wherein When the absolute value of the deviation does not exceed the preset power threshold, the reference values of the active powers of the other converter stations remain unchanged, and only the first converter station bears the unbalanced power corresponding to the deviation.

6. The method according to claim 1, characterized in that, The initial calibrated value of the active power of the first converter station is the average value of the actual value of the active power of the first converter station during the steady-state operation of the system.

7. A receiving-end power self-balancing control device, characterized in that, It includes: A mode setting unit for setting the first converter station at the receiving end to the constant DC voltage control mode and setting the other converter stations at the receiving end except the first converter station to the constant active power control mode; A deviation monitoring unit for monitoring the actual value of the active power of the first converter station in real time and calculating the deviation between the actual value of the active power and the calibrated value of the active power; An equilibrium adjustment unit for, when the absolute value of the deviation exceeds the preset power threshold, updating the calibrated value of the active power of the first converter station and the reference values of the active powers of the other converter stations according to the deviation and the adjustment coefficients of the converter stations at the receiving end, so that all converter stations at the receiving end jointly bear the unbalanced power corresponding to the deviation and maintain the system voltage stable at the rated value, where the adjustment coefficients are determined based on the power margins of the converter stations at the receiving end.

8. A receiving-end power self-balancing control device, characterized in that, It includes a memory and a processor; The memory is used for storing programs; The processor is used for executing the programs to implement each step of the receiving-end power self-equilibrium control method as described in any one of claims 1-6.

9. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements each step of the receiving-end power self-equilibrium control method as described in any one of claims 1-6.

10. A computer program product comprising a computer program, characterized in that, When the computer program is run by the processor, it executes each step of the receiving-end power self-equilibrium control method as described in any one of claims 1-6.

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