A boost control method and device for a bipolar direct current grid-connected system of an offshore wind farm

Abstract

The application discloses a kind of offshore wind farm bipolarity direct current grid-connected system boost control method and device, the scheme provided in the present application is calculated by the input side voltage and the output side voltage of boost module in system and the connection relationship of boost module and bipolarity power grid positive and negative pole, the total input voltage of positive pole side boost module and the total input voltage of negative pole side boost module are calculated respectively, according to boost module compensation voltage calculation formula, the input side compensation voltage of boost module is calculated, according to the input side compensation voltage of each boost module corresponding, corresponding input side voltage, output side voltage, input side voltage reference value, output side voltage reference value and positive and negative pole power balance constant are combined, corresponding control signal is generated to carry out boost control to each boost module respectively, the positive and negative pole power balance of bipolarity power grid system is optimized, and the operation stability of offshore wind farm bipolarity direct current grid-connected system is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy, in particular to a control method and device for a bipolar direct current grid-connected system of an offshore wind farm. BACKGROUND

[0002] With the development of offshore wind power gradually moving towards the open sea, the prominent reactive voltage problem of AC cable transmission caused by the long distance of offshore wind farms makes the power gathering and transmission mode of the wind farm change from the original AC gathering-AC transmission to AC gathering-direct current transmission. At the same time, in order to reduce the cost of power generation, offshore wind turbines are developing towards super large size, and the capacity has entered the 10MW level, the area of the wind farm is increasing, and the length of the cable of the power gathering network is also increasing. Under such background, the all-direct-current wind farm of direct current gathering and transmission grid-connected gradually becomes the mainstream of offshore wind farm construction.

[0003] The direct current grid-connected system is divided into single polarity and bipolarity two ways, compared with the single polarity direct current grid-connected way, the bipolarity direct current grid-connected has higher voltage level transformation flexibility, and the power supply reliability is higher, but in the actual application, the current offshore wind farm bipolarity direct current grid-connected still has the technical problem of insufficient stability. SUMMARY

[0004] The present application provides a kind of offshore wind farm bipolarity direct current grid-connected system boost control method and device, for solving the technical problem of insufficient stability of current offshore wind farm bipolarity direct current grid-connected.

[0005] To solve the above technical problems, the first aspect of the present application provides a kind of offshore wind farm bipolarity direct current grid-connected system boost control method, comprising:

[0006] Based on the onshore direct current booster station in the offshore wind farm bipolarity direct current grid-connected system, the input side voltage and the output side voltage of each boost module in the onshore direct current booster station are collected;

[0007] According to the connection relationship of each boost module and the positive and negative poles of the bipolarity direct current grid, the first total input voltage and the second total input voltage are calculated, wherein the first total input voltage is the total input voltage of the positive pole side boost module, and the second total input voltage is the total input voltage of the negative pole side boost module;

[0008] When the gap between the first total input voltage and the second total input voltage exceeds the preset threshold, the input side compensation voltage of the boost module is calculated according to the electrical parameters of the positive and negative poles of the bipolarity direct current grid and the connection relationship, combined with the preset boost module compensation voltage calculation formula;

[0009] Based on the input-side compensation voltage corresponding to each boost module, and in conjunction with the input-side voltage, the output-side voltage, the input-side voltage reference value, the output-side voltage reference value, and the positive and negative power balance constants, boost control is performed on each boost module.

[0010] Preferably, the formula for calculating the compensation voltage of the boost module specifically includes: the formula for calculating the compensation voltage of the boost module on the positive side and the formula for calculating the compensation voltage of the boost module on the negative side.

[0011] Preferably, the calculation of the input-side compensation voltage of the boost module, based on the electrical parameters of the positive and negative poles of the bipolar DC power grid and the connection relationship, combined with the preset formula for calculating the boost module compensation voltage, specifically includes:

[0012] Based on the connection relationship, if the boost module is a positive-side boost module, then based on the electrical parameters of the positive and negative poles of the bipolar DC grid and the calculation formula for the positive-side boost module compensation voltage, the input-side compensation voltage of the boost module is calculated.

[0013] Based on the connection relationship, if the boost module is a negative-side boost module, then the input-side compensation voltage of the boost module is calculated according to the electrical parameters of the positive and negative poles of the bipolar DC power grid and the compensation voltage calculation formula of the negative-side boost module.

[0014] Preferably, the formula for calculating the compensation voltage of the positive electrode boost module is as follows:

[0015]

[0016] In the formula, ΔU1 is the input-side compensation voltage value corresponding to the boost module on the positive side, U P , where k is the positive voltage in the bipolar DC grid, k1 is the number of boost modules connected to the positive side of the bipolar DC grid, I1 is the positive grid-connected current in the bipolar DC grid, P1 is the positive power of the bipolar DC grid, and P2 is the negative power of the bipolar DC grid.

[0017] The specific formula for calculating the compensation voltage of the negative electrode side boost module is as follows:

[0018]

[0019] In the formula, ΔU2 is the input-side compensation voltage value corresponding to the boost module on the negative side, U N I2 is the negative voltage in the bipolar DC grid, k2 is the number of boost modules connected to the negative side of the bipolar DC grid, I2 is the negative grid-connected current in the bipolar DC grid, P1 is the negative power of the bipolar DC grid, and P2 is the negative power of the bipolar DC grid.

[0020] Preferably, the boosting control of each boosting module according to the input side compensation voltage corresponding to the boosting module, in combination with the input side voltage, the output side voltage, the input side voltage reference value, the output side voltage reference value and the positive and negative electrode power balance constant specifically comprises:

[0021] a first voltage sum value of the input side compensation voltage and a first voltage difference value is calculated according to the input side compensation voltage, the output side voltage and the output side voltage reference value, wherein the first voltage difference value is a voltage difference value between the output side voltage and the output side voltage reference value;

[0022] a first compensation voltage is calculated according to a product of the positive and negative electrode power balance constant and the first voltage sum value;

[0023] a second voltage sum value of the first compensation voltage and a second voltage difference value is calculated according to the first compensation voltage, the input side voltage and the input side voltage reference value, wherein the second voltage difference value is a voltage difference value between the input side voltage and the input side voltage reference value;

[0024] a voltage modulation amount is obtained by PI control according to the second voltage sum value, and the voltage modulation amount is PWM modulated to obtain a control signal of the boosting module, so that the boosting module is controlled based on the control signal.

[0025] Meanwhile, the second aspect of the present application provides a boosting control device for a bipolar DC grid-connected system of offshore wind farms, comprising:

[0026] a boosting module voltage data acquisition unit for acquiring input side voltage and output side voltage of each boosting module in a land DC boosting station in a bipolar DC grid-connected system of offshore wind farms;

[0027] a positive and negative electrode total input voltage calculation unit for calculating a first total input voltage and a second total input voltage according to a connection relationship between each boosting module and positive and negative electrodes of a bipolar DC power grid, wherein the first total input voltage is a total input voltage of positive side boosting modules, and the second total input voltage is a total input voltage of negative side boosting modules;

[0028] a compensation voltage calculation unit for calculating an input side compensation voltage of the boosting module according to electrical parameters of positive and negative electrodes of the bipolar DC power grid and the connection relationship in combination with a preset boosting module compensation voltage calculation formula when a difference between the first total input voltage and the second total input voltage exceeds a preset threshold value;

[0029] The voltage boosting control unit is configured to boost each voltage boosting module according to an input side compensation voltage corresponding to the voltage boosting module, and in combination with the input side voltage, the output side voltage, an input side voltage reference value, an output side voltage reference value, and a positive and negative power balance constant.

[0030] Preferably, the voltage boosting module compensation voltage calculation formula specifically includes a positive side voltage boosting module compensation voltage calculation formula and a negative side voltage boosting module compensation voltage calculation formula.

[0031] Preferably, the compensation voltage calculation unit is specifically configured to:

[0032] According to the connection relationship, if the voltage boosting module belongs to a positive side voltage boosting module, an input side compensation voltage of the voltage boosting module is calculated according to electrical parameters of positive and negative poles of the bipolar direct current power grid, in combination with the positive side voltage boosting module compensation voltage calculation formula.

[0033] According to the connection relationship, if the voltage boosting module belongs to a negative side voltage boosting module, an input side compensation voltage of the voltage boosting module is calculated according to electrical parameters of positive and negative poles of the bipolar direct current power grid, in combination with the negative side voltage boosting module compensation voltage calculation formula.

[0034] Preferably, the positive side voltage boosting module compensation voltage calculation formula is specifically:

[0035]

[0036] In the formula, ΔU1 is an input side compensation voltage value corresponding to a positive side voltage boosting module, U1 is an input side voltage of the positive side voltage boosting module, U is a positive polarity voltage in the bipolar direct current power grid, k1 is a number of voltage boosting modules connected to the positive side of the bipolar direct current power grid, I1 is a positive grid-connected current in the bipolar direct current power grid, P1 is a positive power of the bipolar direct current power grid, and P2 is a negative power of the bipolar direct current power grid. P

[0037] The negative side voltage boosting module compensation voltage calculation formula is specifically:

[0038]

[0039] In the formula, ΔU2 is an input side compensation voltage value corresponding to a negative side voltage boosting module, U2 is an input side voltage of the negative side voltage boosting module, U is a negative polarity voltage in the bipolar direct current power grid, k2 is a number of voltage boosting modules connected to the negative side of the bipolar direct current power grid, I2 is a negative grid-connected current in the bipolar direct current power grid, P1 is a positive power of the bipolar direct current power grid, and P2 is a negative power of the bipolar direct current power grid. N

[0040] Preferably, the voltage boosting control unit is specifically configured to:

[0041] ​​According to the input side compensation voltage, the output side voltage and the output side voltage reference value, a first voltage sum value of the input side compensation voltage and a first voltage difference value is calculated, wherein the first voltage difference value is a voltage difference value between the output side voltage and the output side voltage reference value;

[0042] According to the positive and negative power balance constant and the first voltage sum value, a product of the positive and negative power balance constant and the first voltage sum value is calculated to obtain a first compensation voltage;

[0043] According to the first compensation voltage, the input side voltage and the input side voltage reference value, a second voltage sum value of the first compensation voltage and a second voltage difference value is calculated, wherein the second voltage difference value is a voltage difference value between the input side voltage and the input side voltage reference value;

[0044] According to the second voltage sum value, PI control is performed to obtain a voltage modulation amount, and the voltage modulation amount is subjected to PWM modulation to obtain a control signal of the boost module, so that the boost module performs boost control based on the control signal.

[0045] From the above technical solutions, the present application has the following advantages:

[0046] The boost control method of the offshore wind farm bipolar DC grid-connected system provided by the present application calculates the total input voltage of the positive side boost module and the total input voltage of the negative side boost module respectively through the input side voltage and the output side voltage of the boost module in the system and the connection relationship between the boost module and the positive and negative poles of the bipolar power grid, judges the power balance state of the positive and negative poles of the bipolar power grid according to the two total input voltages, calculates the input side compensation voltage of the boost module through the preset boost module compensation voltage calculation formula if it is judged that there is positive and negative pole power imbalance, generates corresponding control signals to control the boost modules respectively according to the corresponding input side compensation voltage of each boost module, the corresponding input side voltage, the corresponding output side voltage, the corresponding input side voltage reference value, the corresponding output side voltage reference value and the positive and negative pole power balance constant, optimizes the positive and negative pole power balance of the bipolar power grid system, and ensures the stable operation of the offshore wind farm bipolar DC grid-connected system. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0048] Figure 1A schematic diagram of a system architecture of a bipolar DC grid-connected system of an offshore wind farm.

[0049] Figure 2 A flowchart of an embodiment of a boost control method of a bipolar DC grid-connected system of an offshore wind farm provided by the present application.

[0050] Figure 3 A logic block diagram of boost control logic in a boost control method of a bipolar DC grid-connected system of an offshore wind farm provided by the present application.

[0051] Figure 4 A structural schematic diagram of an embodiment of a boost control device of a bipolar DC grid-connected system of an offshore wind farm provided by the present application. DETAILED DESCRIPTION

[0052] In actual applications, the current bipolar DC grid-connected system of an offshore wind farm still has the problem of insufficient stability, which further causes safety problems. To solve this problem, the applicant has found through research that the reason for this problem is mainly that the positive and negative power of the boost control of the bipolar DC grid-connected system is unbalanced. Each offshore wind farm is connected to the land DC boost station through the same boost station and the bus. If the power difference between the positive and negative poles is large, the ground current of the grounding pole will be large, and the ground current will cause large-scale ground field distortion, thereby affecting the operation stability of the bipolar DC grid-connected system of the offshore wind farm. Therefore, to ensure the operation stability of the bipolar DC grid-connected system of the offshore wind farm, it is necessary to balance the positive and negative power.

[0053] The embodiments of the present application provide a boost control method and device for a bipolar DC grid-connected system of an offshore wind farm, which are used to solve the technical problem of insufficient stability of the current bipolar DC grid-connected system of an offshore wind farm.

[0054] To make the purposes, features, and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the embodiments described below are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0055] As Figure 1As shown, the DC turbine power of each all-DC offshore wind farm is collected via the DC collection bus within the farm, then connected to the collection bus of the onshore booster station via the onshore DC booster converter, and finally integrated into the bipolar DC grid through the onshore booster station. The onshore booster station adopts a modular boost structure, with k boost modules for both positive and negative grid connections, ensuring that both positive and negative poles have the same boost capacity and power transmission capability, providing favorable conditions for achieving power balance between the positive and negative poles.

[0056] The system employs a comprehensive coordinated control strategy that decouples the onshore substation control from the onshore booster station control. Each DC-type offshore wind farm independently completes its substation-side control. Each DC-type offshore wind farm can not only independently respond to grid dispatch requirements for power limiting control, but also generate power at its maximum capacity when grid dispatch does not limit power, thus improving the grid integration and absorption of offshore wind power. Boost modules #1 to #2k autonomously adjust the input bus voltage of each boost module, achieving balanced power control between positive and negative poles, and automatically achieving balanced voltage control between the output sides of each boost module. This leverages the advantages of bipolar DC grids, including flexible operation, high redundancy, and high reliability.

[0057] Based on the above system architecture, the following is a detailed description of an embodiment of a boost control method for a bipolar DC grid-connected system for offshore wind farms provided in this application:

[0058] Please see Figure 2 This embodiment provides a boost control method for a bipolar DC grid-connected system in an offshore wind farm, including:

[0059] Step 101: Based on the onshore DC booster station in the bipolar DC grid-connected system of the offshore wind farm, collect the input side voltage and output side voltage of each booster module in the onshore DC booster station.

[0060] Step 102: Calculate the first total input voltage and the second total input voltage according to the connection relationship between each boost module and the positive and negative terminals of the bipolar DC power grid.

[0061] The first total input voltage is the total input voltage of the positive side boost module, and the second total input voltage is the total input voltage of the negative side boost module.

[0062] It should be noted that, firstly, for each modularly configured boost module in the onshore DC boost station of the bipolar DC grid-connected system of the offshore wind farm, the input voltage U of each boost module is collected. L With output voltage U H , among which, U Hm The output voltage of the boost module #m; U Lm This is the input voltage of the boost module #m.

[0063] Then, according to the connection relationship of each boost module and the positive and negative poles of the bipolar DC power grid, the polarity of the bipolar power grid connected by each boost module is determined, that is, each boost module is classified. If the boost module #m is connected to the positive pole side of the bipolar power grid, it is determined that the boost module #m belongs to the positive pole side boost module, such as boost module #1 to boost module #k in Figure 1 On the contrary, if the boost module #m is connected to the negative pole side of the bipolar power grid, it is determined that the boost module #m belongs to the negative pole side boost module, such as boost module #k+1 to boost module #2k in Figure 1 Then, the input side voltage of the boost module collected in the previous step is used to calculate the first total input voltage and the second total input voltage, that is, the positive pole boost module input voltage sum And the negative pole boost module input voltage sum

[0064] Step 103, when the difference between the first total input voltage and the second total input voltage exceeds the preset threshold, the input side compensation voltage of the boost module is calculated according to the electrical parameters and connection relationship of the positive and negative poles of the bipolar DC power grid, and combined with the preset boost module compensation voltage calculation formula.

[0065] Step 104, according to the input side compensation voltage corresponding to each boost module, combined with the input side voltage, the output side voltage, the input side voltage reference value, the output side voltage reference value and the positive and negative pole power balance constant, the boost control is performed on each boost module respectively.

[0066] Then, the first total input voltage and the second total input voltage are compared, and when the difference between the first total input voltage and the second total input voltage exceeds the preset threshold, the power of the positive and negative poles may be unbalanced. At this time, the input side compensation voltage of the boost module is calculated according to the electrical parameters and connection relationship of the positive and negative poles of the bipolar DC power grid, and combined with the preset boost module compensation voltage calculation formula. The input side compensation voltage is introduced into the control logic of the boost module, and the positive and negative pole power balance control is realized by compensating and controlling the input voltage of the positive and negative pole boost module.

[0067] The above is a detailed description of the basic embodiment of the offshore wind farm bipolar DC grid-connected system boost control method provided by the present application. The following is a detailed description of the specific embodiments of the key steps in the embodiments based on the above basic embodiment of the present application, as follows:

[0068] Further, according to the different polarities connected by the boost module, the boost module compensation voltage calculation formula mentioned in the present embodiment can be divided into the following two kinds: positive pole side boost module compensation voltage calculation formula and negative pole side boost module compensation voltage calculation formula.

[0069] Furthermore, based on the electrical parameters and connection relationships of the positive and negative poles of the bipolar DC power grid, and combined with the preset formula for calculating the compensation voltage of the boost module, the calculation of the input-side compensation voltage of the boost module specifically includes:

[0070] Based on the connection relationship, if the boost module is a positive-side boost module, then the input-side compensation voltage of the boost module is calculated according to the electrical parameters of the positive and negative poles of the bipolar DC grid and the calculation formula of the compensation voltage of the positive-side boost module.

[0071] Based on the connection relationship, if the boost module is a negative-side boost module, then the input-side compensation voltage of the boost module is calculated according to the electrical parameters of the positive and negative poles of the bipolar DC power grid and the calculation formula for the compensation voltage of the negative-side boost module.

[0072] Furthermore, the specific formula for calculating the compensation voltage of the positive side boost module is as follows:

[0073]

[0074] In the formula, ΔU1 is the input-side compensation voltage value corresponding to the boost module on the positive side, U P , where k is the positive voltage in the bipolar DC grid, k1 is the number of boost modules connected to the positive side of the bipolar DC grid, I1 is the positive grid-connected current in the bipolar DC grid, P1 is the positive power of the bipolar DC grid, and P2 is the negative power of the bipolar DC grid.

[0075] The specific formula for calculating the compensation voltage of the negative side boost module is as follows:

[0076]

[0077] In the formula, ΔU2 is the input-side compensation voltage value corresponding to the boost module on the negative side, U N I2 is the negative voltage in the bipolar DC grid, k2 is the number of boost modules connected to the negative side of the bipolar DC grid, I2 is the negative grid-connected current in the bipolar DC grid, P1 is the negative power of the bipolar DC grid, and P2 is the negative power of the bipolar DC grid.

[0078] Furthermore, based on the input-side compensation voltage corresponding to each boost module, and in conjunction with the input-side voltage, output-side voltage, input-side voltage reference value, output-side voltage reference value, and positive and negative power balance constants, boost control is performed on each boost module, specifically including:

[0079] Based on the input-side compensation voltage, the output-side voltage, and the output-side voltage reference value, calculate the first voltage sum value of the input-side compensation voltage and the first voltage difference, where the first voltage difference is the voltage difference between the output-side voltage and the output voltage reference value;

[0080] Calculate the product of the positive and negative power balance constant and the first voltage sum value to obtain the first compensation voltage according to the positive and negative power balance constant and the first voltage sum value.

[0081] Calculate the second voltage sum value of the difference between the first compensation voltage and the second voltage, where the second voltage difference is the voltage difference between the input-side voltage and the input-side voltage reference value, according to the first compensation voltage, the input-side voltage, and the input-side voltage reference value.

[0082] Perform PI control according to the second voltage sum value to obtain a voltage modulation amount, and then perform PWM modulation on the voltage modulation amount to obtain a control signal for the boost module, so as to perform boost control on the boost module based on the control signal.

[0083] It should be noted that, as Figure 3 shown, the boost module in this embodiment adopts a control strategy for fixing the voltage of the boost station collecting bus that takes into account the positive and negative power and output-side voltage compensation. Among them, U Hm is the output-side voltage of boost module #m; U Lm is the input-side voltage of boost module #m; U L_ref is the reference voltage of the boost station collecting bus; U H_ref is the output-side reference voltage of the boost module. For boost modules #1 to #k, U H_ref is U P / k. For boost modules #k + 1 to #2k, U H_ref is U N / k. U P and U N are the positive and negative voltage values of the bipolar DC power grid respectively. k u is a specified positive number, and it is recommended to take a value of 0.1 to 0.7, which can be comprehensively considered according to the requirements of positive and negative power balance, the voltage equalization requirements of the output side of the boost module, and the requirements for the stability of the collecting bus voltage.

[0084] By converting the power imbalance value between the positive and negative poles into the compensation voltage △U on the input side of the boost module; when the positive power is less than the negative power, that is, P1 < P2, P1 < (P1 + P2) / 2. Because P1 = U p *I1, so U p -(P1 + P2) / 2I1 is less than 0. At this time, △U1 is less than 0, that is, the △U participating in the control of boost modules #1 to #k is less than 0. Correspondingly, the △U participating in the control of boost modules #k + 1 to #2k is greater than 0. The system will reduce the total input voltage of the positive boost module and increase the total input voltage of the negative boost module so as to increase the positive power and reduce the negative power to achieve power balance.

[0085] Similarly, when the positive electrode power is greater than the negative electrode power, the △U controlled by the boost module #1 to the boost module #k is greater than 0, the △U controlled by the boost module #k+1 to the boost module #2k is less than 0, and the system will increase the total input voltage of the positive electrode boost module Reduce the total input voltage of the negative electrode boost module Thus, the positive electrode power is reduced, the negative electrode power is increased, and power balance is achieved.

[0086] If the power output by the wind farm cluster is greater than the grid-connected power, the power collected by the boost station collection bus will increase, causing the boost station collection bus voltage to rise; if the power output by the wind farm cluster is less than the grid-connected power, the power collected by the boost station collection bus will decrease, causing the boost station collection bus to decrease, so that the boost station collection bus voltage stable control can be achieved to realize the timely sending of the power output by the wind farm cluster to the grid.

[0087] The output side of the boost module adopts series control, if the transmission power of a boost module is too large, the output side voltage of the boost module is higher than the output side voltage reference value U H_ref At this time, by using the output side voltage compensation method, the output side voltage change is introduced into the control link of the input boost module, which can simultaneously complete the power balance of each boost module.

[0088] Therefore, by compensating the output side voltage change and the positive and negative electrode power imbalance to the input side voltage control of the boost module, the positive and negative electrode power balance, the positive and negative electrode boost module power balance and the boost station collection bus voltage stability can be realized at the same time, which is suitable for the scenario of large-scale access of offshore wind farm cluster to power system.

[0089] The above is a detailed description of a specific embodiment of the offshore wind farm bipolar DC grid-connected system boost control method provided by the present application, and the following is a detailed description of an offshore wind farm bipolar DC grid-connected system boost control device embodiment provided by the present application.

[0090] Please refer to Figure 4 The offshore wind farm bipolar DC grid-connected system boost control device provided by the embodiment comprises:

[0091] The boost module voltage data acquisition unit 201 is configured to acquire the input side voltage and the output side voltage of each boost module in the onshore DC boost station in the offshore wind farm bipolar DC grid-connected system based on the onshore DC boost station in the offshore wind farm bipolar DC grid-connected system.

[0092] The positive and negative total input voltage calculation unit 202 is configured to calculate a first total input voltage and a second total input voltage according to the connection relationship of each boost module and the positive and negative poles of the bipolar direct-current power grid, wherein the first total input voltage is the total input voltage of the positive-side boost module, and the second total input voltage is the total input voltage of the negative-side boost module.

[0093] The compensation voltage calculation unit 203 is configured to calculate the input-side compensation voltage of the boost module according to the electrical parameters and the connection relationship of the positive and negative poles of the bipolar direct-current power grid and in combination with a preset boost module compensation voltage calculation formula when the difference between the first total input voltage and the second total input voltage exceeds a preset threshold.

[0094] The boost control unit 204 is configured to perform boost control on each boost module according to the corresponding input-side compensation voltage of the boost module and in combination with the input-side voltage, the output-side voltage, the input-side voltage reference value, the output-side voltage reference value, and the positive and negative power balance constant.

[0095] Further, the boost module compensation voltage calculation formula specifically includes a positive-side boost module compensation voltage calculation formula and a negative-side boost module compensation voltage calculation formula.

[0096] Further, the compensation voltage calculation unit 203 is specifically configured to:

[0097] According to the connection relationship, if the boost module belongs to the positive-side boost module, the input-side compensation voltage of the boost module is calculated according to the electrical parameters of the positive and negative poles of the bipolar direct-current power grid and in combination with the positive-side boost module compensation voltage calculation formula.

[0098] According to the connection relationship, if the boost module belongs to the negative-side boost module, the input-side compensation voltage of the boost module is calculated according to the electrical parameters of the positive and negative poles of the bipolar direct-current power grid and in combination with the negative-side boost module compensation voltage calculation formula.

[0099] Further, the positive-side boost module compensation voltage calculation formula is specifically as follows:

[0100]

[0101] In the formula, ΔU1 is the input-side compensation voltage value corresponding to the positive-side boost module, U is the positive polarity voltage in the bipolar direct-current power grid, k1 is the number of boost modules connected to the positive side of the bipolar direct-current power grid, I1 is the positive grid-connected current in the bipolar direct-current power grid, P1 is the positive power of the bipolar direct-current power grid, and P2 is the negative power of the bipolar direct-current power grid. P

[0102] The negative-side boost module compensation voltage calculation formula is specifically as follows:

[0103] ​

[0104] In the formula, ΔU2 is the input side compensation voltage value corresponding to the positive side voltage boosting module, U N is the negative polarity voltage in the bipolar direct current power grid, k2 is the number of voltage boosting modules connected to the negative side of the bipolar direct current power grid, I2 is the negative grid-connected current in the bipolar direct current power grid, P1 is the negative power of the bipolar direct current power grid, and P2 is the negative power of the bipolar direct current power grid.

[0105] Further, the voltage boosting control unit 204 is specifically configured to:

[0106] According to the input side compensation voltage, the output side voltage, and the output side voltage reference value, a first voltage sum value of the input side compensation voltage and a first voltage difference value is calculated, wherein the first voltage difference value is a voltage difference value of the output side voltage and the output side voltage reference value;

[0107] According to the positive and negative power balance constant and the first voltage sum value, a product of the positive and negative power balance constant and the first voltage sum value is calculated to obtain a first compensation voltage;

[0108] According to the first compensation voltage, the input side voltage, and the input side voltage reference value, a second voltage sum value of the first compensation voltage and a second voltage difference value is calculated, wherein the second voltage difference value is a voltage difference value of the input side voltage and the input side voltage reference value;

[0109] According to the second voltage sum value, PI control is performed to obtain a voltage modulation amount, and then the voltage modulation amount is subjected to PWM modulation to obtain a control signal of the voltage boosting module, so that the voltage boosting module is controlled to boost based on the control signal.

[0110] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices and units can refer to the corresponding processes in the foregoing method embodiments, which will not be described herein.

[0111] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0112] The terms "first", "second", "third", "fourth" and the like in the description of the application and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the use of these terms herein is to be construed to cover a changeable order, sequence or arrangement, for example, unless otherwise stated or unless it is clear from the context. Furthermore, the beginning of the terms "comprising", "having", "including", and the like, are to be construed open- ended (meaning that "comprising", "having", and "including" will be given their broadest interpretation to include even one) unless otherwise noted or unless it is clear from the context. It is to be understood that even though a number of embodiments of the application have been described specifically, various omissions and substitutions and changes of the methods and systems described herein can be made by those skilled in the art without departing from the spirit of the application as defined by the appended claims. For example, the specification can be implemented with both hardware and software, or software only, or hardware only, depending on the application.

[0113] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e. may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0114] In addition, the functional units in each embodiment of the application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0115] The integrated unit, if implemented in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the application essentially or the part of the prior art that contributes to the technical solutions or all or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the embodiments of the application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0116] The above-described embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A boost control method for a bipolar DC grid-connected system in an offshore wind farm, characterized in that, include: Based on the onshore DC booster station in the bipolar DC grid-connected system of offshore wind farm, the input side voltage and output side voltage of each booster module in the onshore DC booster station are collected; Based on the connection relationship between each boost module and the positive and negative poles of the bipolar DC grid, the first total input voltage and the second total input voltage are calculated respectively, wherein the first total input voltage is the total input voltage of the boost module on the positive side, and the second total input voltage is the total input voltage of the boost module on the negative side; When the difference between the first total input voltage and the second total input voltage exceeds a preset threshold, the input-side compensation voltage of the boost module is calculated based on the electrical parameters of the positive and negative poles of the bipolar DC grid and the connection relationship, combined with the preset boost module compensation voltage calculation formula. Based on the input-side compensation voltage, the output-side voltage, and the output-side voltage reference value, calculate the first voltage sum value of the input-side compensation voltage and the first voltage difference, wherein the first voltage difference is the voltage difference between the output-side voltage and the output voltage reference value; Based on the sum of the positive and negative power balance constants and the first voltage, calculate the product of the positive and negative power balance constants and the first voltage to obtain the first compensation voltage; Based on the first compensation voltage, the input side voltage, and the input side voltage reference value, calculate the second voltage sum value of the first compensation voltage and the second voltage difference, wherein the second voltage difference is the voltage difference between the input side voltage and the input voltage reference value; PI control is performed based on the second voltage and value to obtain a voltage modulation amount. Then, PWM modulation is performed on the voltage modulation amount to obtain a control signal for the boost module, so that the boost module can perform boost control based on the control signal.

2. The boost control method for a bipolar DC grid-connected system in an offshore wind farm according to claim 1, characterized in that, The calculation formulas for the compensation voltage of the boost module specifically include: the calculation formula for the compensation voltage of the boost module on the positive side and the calculation formula for the compensation voltage of the boost module on the negative side.

3. The boost control method for a bipolar DC grid-connected system in an offshore wind farm according to claim 2, characterized in that, Based on the electrical parameters of the positive and negative poles of the bipolar DC power grid and the aforementioned connection relationship, and in conjunction with the preset formula for calculating the compensation voltage of the boost module, the calculation of the input-side compensation voltage of the boost module specifically includes: Based on the connection relationship, if the boost module is a positive-side boost module, then based on the electrical parameters of the positive and negative poles of the bipolar DC grid and the calculation formula for the positive-side boost module compensation voltage, the input-side compensation voltage of the boost module is calculated. Based on the connection relationship, if the boost module is a negative-side boost module, then the input-side compensation voltage of the boost module is calculated according to the electrical parameters of the positive and negative poles of the bipolar DC power grid and the compensation voltage calculation formula of the negative-side boost module.

4. The boost control method for a bipolar DC grid-connected system in an offshore wind farm according to claim 3, characterized in that, The specific formula for calculating the compensation voltage of the positive electrode side boost module is as follows: ； In the formula, This is the input-side compensation voltage value corresponding to the boost module on the positive side. This is the positive voltage in a bipolar DC power grid. This refers to the number of boost modules connected to the positive side of a bipolar DC power grid. This refers to the positive grid-connected current in a bipolar DC power grid. For bipolar DC grid positive power, This is the negative power of a bipolar DC power grid; The specific formula for calculating the compensation voltage of the negative electrode side boost module is as follows: ； In the formula, This is the input-side compensation voltage value corresponding to the boost module on the negative side. This is the negative voltage in a bipolar DC power grid. This refers to the number of boost modules connected to the negative side of a bipolar DC power grid. This refers to the negative pole grid-connected current in a bipolar DC power grid. For the negative power of a bipolar DC power grid, It represents the negative power of a bipolar DC power grid.

5. A boost control device for a bipolar DC grid-connected system in an offshore wind farm, characterized in that, include: The voltage data acquisition unit for the boost module is used to acquire the input and output voltages of each boost module in the onshore DC boost station based on the onshore DC boost station in the bipolar DC grid-connected system of the offshore wind farm. The positive and negative total input voltage calculation unit is used to calculate the first total input voltage and the second total input voltage according to the connection relationship between each boost module and the positive and negative poles of the bipolar DC grid, wherein the first total input voltage is the total input voltage of the positive side boost module and the second total input voltage is the total input voltage of the negative side boost module; The compensation voltage calculation unit is used to calculate the input-side compensation voltage of the boost module when the difference between the first total input voltage and the second total input voltage exceeds a preset threshold, based on the electrical parameters of the positive and negative poles of the bipolar DC grid and the connection relationship, combined with a preset boost module compensation voltage calculation formula. The boost control unit is configured to: calculate a first voltage sum value between the input-side compensation voltage and a first voltage difference, based on the input-side compensation voltage, the output-side voltage, and the output-side voltage reference value, wherein the first voltage difference is the voltage difference between the output-side voltage and the output-side voltage reference value; calculate a first compensation voltage by multiplying the positive and negative power balance constants with the first voltage sum value; calculate a second voltage sum value between the first compensation voltage and a second voltage difference, based on the first compensation voltage, the input-side voltage, and the input-side voltage reference value, wherein the second voltage difference is the voltage difference between the input-side voltage and the input-side voltage reference value; perform PI control based on the second voltage sum value to obtain a voltage modulation amount, and then perform PWM modulation on the voltage modulation amount to obtain a control signal for the boost module, so that the boost module can perform boost control based on the control signal.

6. The boost control device for a bipolar DC grid-connected system in an offshore wind farm according to claim 5, characterized in that, The calculation formulas for the compensation voltage of the boost module specifically include: the calculation formula for the compensation voltage of the boost module on the positive side and the calculation formula for the compensation voltage of the boost module on the negative side.

7. The boost control device for a bipolar DC grid-connected system in an offshore wind farm according to claim 6, characterized in that, The compensation voltage calculation unit is specifically used for: Based on the connection relationship, if the boost module is a positive-side boost module, then based on the electrical parameters of the positive and negative poles of the bipolar DC grid and the calculation formula for the positive-side boost module compensation voltage, the input-side compensation voltage of the boost module is calculated. Based on the connection relationship, if the boost module is a negative-side boost module, then the input-side compensation voltage of the boost module is calculated according to the electrical parameters of the positive and negative poles of the bipolar DC power grid and the compensation voltage calculation formula of the negative-side boost module.

8. The boost control device for a bipolar DC grid-connected system in an offshore wind farm according to claim 7, characterized in that, The specific formula for calculating the compensation voltage of the positive electrode side boost module is as follows: ； In the formula, This is the input-side compensation voltage value corresponding to the boost module on the positive side. This is the positive voltage in a bipolar DC power grid. This refers to the number of boost modules connected to the positive side of a bipolar DC power grid. This refers to the positive grid-connected current in a bipolar DC power grid. For bipolar DC grid positive power, This is the negative power of a bipolar DC power grid; The specific formula for calculating the compensation voltage of the negative electrode side boost module is as follows: ； In the formula, This is the input-side compensation voltage value corresponding to the boost module on the negative side. This is the negative voltage in a bipolar DC power grid. This refers to the number of boost modules connected to the negative side of a bipolar DC power grid. This refers to the negative pole grid-connected current in a bipolar DC power grid. For the negative power of a bipolar DC power grid, It represents the negative power of a bipolar DC power grid.

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