An adaptive constant-voltage power supply control method for offshore direct-current wind turbine generator units

Abstract

The application discloses a kind of offshore direct-current wind power unit adaptive constant voltage power supply control methods, it is applied to the offshore direct-current microgrid of carrying hydrogen production load, system configuration permanent magnet synchronous generator, machine side converter MSC and unit dc converter.This method real-time acquisition ac and dc voltage, current and get dq axis component by coordinate transformation;Unit dc converter adopts voltage outer ring PI control, cooperate with current inner ring and SPWM drive signal stable low voltage dc link voltage.Machine side converter d axis adaptive active control relies on dc bus voltage PI regulator to track bus voltage, will regulator output and MPPT power output logic competition to obtain active reference value, realize adaptive power regulation;Q axis closed loop stabilizes generator ac voltage, so as to realize system according to capture wind energy and load power autonomous switching operation, surplus condition unit reduces power to reduce energy storage start-stop loss, power shortage when energy storage energy, improve the reliability and operation economy of microgrid power supply.

Description

Technical Field

[0001] This invention belongs to the field of offshore wind turbine converter control technology, and specifically relates to an adaptive constant voltage power supply control method for offshore DC wind turbines. Background Technology

[0002] Currently, offshore wind power is being developed on a large scale due to its abundant wind energy resources, high utilization hours, and lack of land occupation. However, offshore wind power development is increasingly moving towards deeper waters. The increased distance from shore significantly increases the cost and losses of submarine cables, thus reducing the economic viability of power transmission. In contrast, utilizing offshore wind turbines to supply power to offshore water electrolysis hydrogen production systems or other electrical loads locally reduces reliance on long-distance submarine cables and onshore power grids, while also promoting the local consumption of offshore wind power. This has become an important technological approach for deep-sea wind power development.

[0003] Existing offshore wind-powered hydrogen production systems can be categorized into grid-connected and off-grid types based on their operating mode. Each type can be further divided into AC bus-based and DC bus-based structures. Off-grid systems typically consist of wind turbines, converters, electrolysis hydrogen production units, hydrogen storage units, energy storage, and fuel cells forming an independent microgrid. In this scenario, existing technologies primarily focus on the stability control of offshore AC microgrids composed of offshore AC wind turbines, loads, energy storage, and hydrogen production systems. For DC microgrids, the focus is mainly on photovoltaic power generation. Research on the stability control of offshore DC microgrids composed of offshore DC wind turbines remains relatively limited.

[0004] The fundamental task of DC microgrid operation control is to maintain power balance within the microgrid system. The DC bus is the energy inflow and outflow point of the microgrid. The power from the generation and storage units is collected on the DC bus and connected to the load or grid. Therefore, maintaining stable DC bus voltage is a prerequisite for ensuring load power consumption and internal power balance. Only on this basis can the utilization rate of renewable energy be further considered. Existing DC bus voltage control strategies rely heavily on high-speed communication between units. Once communication is interrupted, system instability is easily caused, making it unable to cope with emergency conditions such as sudden load changes. On the other hand, if relying solely on local information for autonomous operation and automatic power fluctuation sharing, it will cause bus voltage deviation and reduce control accuracy due to differences in line impedance. In addition, wind turbines typically operate in maximum power point tracking (MPPT) mode to pursue maximum wind energy capture. When wind power output exceeds load demand and energy storage absorption capacity, DC bus overvoltage will occur. Existing solutions mostly rely on energy storage and unloading resistors to smooth out power surplus, which not only increases system costs but also fails to fully utilize the power regulation capabilities of the wind turbines themselves.

[0005] Therefore, this invention addresses the application scenario of supplying power from offshore DC wind turbines to offshore hydrogen production platforms or other loads, as shown in the attached diagram. Figure 1As shown, an adaptive constant voltage power supply control method for offshore DC wind turbines is proposed. The machine-side converter (MSC) of the wind turbine adopts the low-voltage DC link voltage control of the wind turbine, and the d-axis of the DC converter adopts the output active power control of the wind turbine. By comparing the output value of the MPPT control loop and the output value of the DC bus voltage control loop, an adaptive reference value for the output active power is generated, as shown in the attached figure. Figure 2 As shown, this ensures the stability of the system's DC bus voltage and reliable power supply to the load under scenarios of wind speed fluctuations and sudden load changes. Summary of the Invention

[0006] The purpose of this invention is to provide an adaptive constant voltage power supply control method for offshore DC wind turbines. This method can overcome the problems of existing technologies, such as reliance on communication and inability to adapt to sudden load changes. It is a simple and easy-to-implement constant voltage power supply control method that can ensure the stability of the system's DC bus voltage and reliable power supply to the load under wind speed fluctuations and sudden load changes.

[0007] The technical solution of this invention: An adaptive constant voltage power supply control method for offshore DC wind turbines, comprising an offshore DC microgrid composed of offshore DC wind turbines, wherein the DC wind turbines include a wind turbine generator, a turbine-side converter (MSC), and a wind turbine DC converter, characterized in that it includes the following: Step S1, signal acquisition and coordinate transformation, namely: real-time acquisition of the operation data of the offshore DC microgrid composed of offshore DC wind turbines, and sequential coordinate transformation of the acquired voltage and current signals to obtain the d-axis component and q-axis component in the synchronous rotating coordinate system. Step S1 specifically refers to: real-time acquisition of the DC bus voltage U of the offshore DC microgrid. MV Low-voltage DC link voltage U of wind turbine LV The three-phase voltage u on the AC side of the machine-side converter ms With three-phase current i ms The three-phase voltage u in the AC link of the DC-DC converter o Three-phase current i o ; Three-phase voltage u on the AC side of the converter on the machine side ms With three-phase current i ms By applying Clarke transform and Park transform sequentially, the d-axis components u of the three-phase AC voltage on the machine-side converter in the synchronous rotating coordinate system are obtained. msd Three-phase voltage q-axis component u msq d-axis component of three-phase current i msd Three-phase current q-axis component i msq .

[0008] Step S2: Perform DC voltage control on the DC converter of the wind turbine to maintain the stability of the low-voltage DC link voltage of the wind turbine. The wind turbine DC converter in step S2 uses the low-voltage DC voltage U of the wind turbine. LV Control, specifically, refers to: in the outer loop control of the DC-DC converter voltage of the wind turbine generator, adjusting the reference value U of the low-voltage DC link voltage of the wind turbine generator. LV_ref With the low-voltage DC voltage U of the wind turbine LV The difference and the q-axis component U of the DC converter modulation voltage oq By performing PI control as shown in formulas (1) and (2), the reference value I of the inner loop current d-axis component of the wind turbine DC converter current inner loop control is obtained. od_ref and q-axis component reference value I oq_ref ,Right now: #(1) #(2) Among them, K p_od K is the proportional constant for the d-axis control of the DC-DC converter. i_qd K is the integral constant for the d-axis control of the DC-DC converter. p_oq K is the proportional constant for the q-axis control of the DC-DC converter. i_oq Let be the integral constant for the q-axis control of the DC-DC converter, and s be the Laplace operator; I od_ref and I oq_ref The reference value U of the d-axis component of the modulated voltage of the wind turbine DC converter is generated via the inner current loop control. od_ref and q-axis component reference value U oq_ref Then, through sinusoidal pulse width modulation (SPWM), the switching signals of the DC-DC converter of the wind turbine are generated to control the voltage and current of the AC link in the DC-DC converter, so as to maintain the stability of the low-voltage DC link voltage of the wind turbine.

[0009] Step S3: The turbine-side converter MSC adopts adaptive constant voltage power supply control, that is, the turbine-side converter MSC adopts d-axis active power control, and its active power reference value is based on the wind power P captured by the wind turbine. MPPT Power P required for offshore hydrogen production platforms and loads L The magnitude is adaptively adjusted, the q-axis uses PMSG AC voltage control, and reference values ​​I for the inner loop current d-axis component of the machine-side converter MSC are generated respectively. msd_ref and q-axis component reference value I msq_ref The two are controlled by the inner loop current to generate the d-axis component reference value U of the modulated voltage of the machine-side converter. msd _ refand q-axis component reference value U msq_ref Then, through sinusoidal pulse width modulation (SPWM), the switching signals of the wind turbine generator-side converter are generated, thereby controlling the output voltage and current of the MSC, and thus controlling the active power output of the PMSG while maintaining its output AC voltage stability.

[0010] In step S3, the machine-side converter MSC employs d-axis active power control and q-axis PMSG AC voltage control. The d-axis active power control aims to maintain a stable DC bus voltage, controlled by the DC bus voltage U. MV The control loop adaptively generates a reference value P for the active power of the wind turbine. MV_ref This allows for adaptive matching of the power required by the offshore hydrogen production platform and other loads; the q-axis PMSG AC voltage control maintains a stable output AC voltage.

[0011] The d-axis active power control specifically refers to: ① When the wind turbine captures wind power P MPPT The power P required by the offshore hydrogen production platform and its load is greater than that required by the platform. L That is, P MPPT >P L The energy storage system is not put into operation, so the wind turbines operate in reduced power mode, thereby adaptively matching the power required by the offshore hydrogen production platform and other loads. That is, when the DC bus voltage is controlled at the rated value, the system power will definitely be balanced. The aforementioned power reduction mode specifically refers to: using the maintenance of DC bus voltage stability as the control objective, reducing the DC bus voltage reference value U... MV_ref Compared with the measured value U MV The difference is fed into the PI regulator to obtain the active power reference value output by the DC bus voltage control loop, as shown in formula (3), so as to adaptively match the power required by the offshore hydrogen production platform and other loads. #(3) Among them, K p_MV K is the proportional constant of the DC bus voltage control loop. i_MV This is the integral constant of the DC bus voltage control loop.

[0012] Here, "adaptive" refers to using a PI regulator to adjust the measured DC bus voltage U. MV Track its reference value U MV_ref The output of the PI regulator is used as the active power reference value of the wind turbine. This active power reference value is generated by the DC bus voltage outer loop and logically competes with the MPPT control loop output to select the final active power control reference value. This control structure is... Figure 3 As shown, this is the key to achieving the "adaptive" effect of the present invention, and it is also the core innovation of the present invention.

[0013] ② When the wind turbine captures wind power P MPPT Less than or equal to the power P required by the offshore hydrogen production platform and its load L That is, P MPPT ≤P L Then the wind turbine outputs the maximum captured wind power, and the active power reference value is given as P. MPPT_ref At this time, the energy storage system discharges to provide the shortfall power to maintain the DC bus voltage stability; ③ Reference value of active power P of wind turbine ref After determining it through ① or ②, compare it with the measured value P. o The difference is calculated and input to the PI controller to generate the reference value I of the d-axis component of the inner loop current of the machine-side converter MSC. msd_ref ,Right now: #(4) Among them, K p_msd K is the proportional constant for the d-axis control of the machine-side converter. i_msd This is the integral constant for the d-axis control of the machine-side converter.

[0014] The q-axis PMSG AC voltage control specifically refers to: To maintain stable output AC voltage, that is: to reduce the AC voltage amplitude U of the wind turbine generator's converter. ms and its reference value U ms _ ref The difference is fed into the PI regulator to obtain the reference value I of the q-axis component of the inner loop current of the machine-side converter. msq_ref As shown in formula (5): #(5) Among them, K p_msq K is the proportional constant for the q-axis control of the machine-side converter. i_msq This is a constant for the q-axis control of the machine-side converter.

[0015] In summary, the complete signal flow of this method is as follows: Acquisition U MV u ms i ms u o i o U LV → Coordinate transformation and reference value calculation (P) MPPT_ref P MV_ref → Adaptive generation of P ref → Power / AC voltage outer loop and low-voltage DC voltage outer loop → Current inner loop decoupling → SPWM → Gate signals of switching devices in generator-side converter and DC-DC converter → Unit output power regulation → DC bus power balancing → U MV U LV Ums The three-stage constant voltage ultimately achieves the goal of adaptive constant voltage power supply without relying on communication.

[0016] The adaptive constant voltage power supply control method for offshore DC wind turbines also includes: adjusting the reference value P of the wind turbine output power based on the wind power captured by the wind turbine and the power PL required by the offshore hydrogen production platform and load. ref Specifically, it refers to: When the wind turbine captures wind power P MPPT The power P required by the offshore hydrogen production platform and its load is greater than that required by the platform. L That is, P MPPT >P L If the energy storage system is not activated, the wind turbines need to operate at reduced power to maintain system power balance and DC bus voltage stability. If the energy storage system is activated, the wind turbines can capture wind power, and the surplus power P absorbed by the energy storage system can then be used to achieve this. E = P MPPT -P L ; When the wind turbine captures wind power P MPPT Less than or equal to the power P required by the offshore hydrogen production platform and its load L That is, P MPPT ≤P L At times, wind turbines cannot meet the full power requirements of offshore hydrogen production platforms and loads. In this case, the energy storage system discharges to compensate for the power difference, i.e., P E = P L -P MPPT .

[0017] The frequency of start-up and shutdown of energy storage systems should generally be minimized to reduce their impact on lifespan and improve the economic efficiency of microgrid operation. Therefore, when the wind power captured by the wind turbine exceeds the power required by the offshore hydrogen production platform and load, the wind turbine should be controlled to operate in a reduced power mode to reduce the start-up and shutdown coefficient of the energy storage system.

[0018] The working principle of this invention is as follows: The impeller captures wind energy and drives the permanent magnet synchronous generator (PMSG) to rotate through the transmission mechanism. The AC power generated by the PMSG is rectified into a low-voltage DC voltage U for the wind turbine by the turbine-side converter MSC. LV After being boosted by the DC converter of the wind turbine, the power is connected to the DC bus and then supplied to the offshore hydrogen production platform and other electrical loads.

[0019] U MV P is the DC bus voltage. o P is the output power of the wind turbine. L For the power required by offshore hydrogen production platforms and loads, P EFor the energy storage system power, and to maintain DC bus voltage stability, P o P L P E These three factors need to be balanced, and the absorption of wind power should be considered on this basis.

[0020] To fully leverage the power regulation potential of wind turbines, the key lies in determining the wind power captured by the wind turbines and the power P required by the offshore hydrogen production platform and its load. L Adjusting the size of the wind turbine's output power reference value P ref Specifically, it refers to: When the wind turbine captures more wind power than the power required by the offshore hydrogen production platform and its load P L That is, P MPPT >P L If the energy storage system is not activated, the wind turbines need to operate at reduced power to maintain system power balance and DC bus voltage stability. If the energy storage system is activated, the wind turbines can capture wind power, and the surplus power P absorbed by the energy storage system can then be used to achieve this. E = P MPPT - P L ; When the wind power captured by the wind turbine is less than or equal to the power P required by the offshore hydrogen production platform and its load L That is, P MPPT ≤P L At times, wind turbines cannot meet the full power requirements of offshore hydrogen production platforms and loads. In this case, the energy storage system discharges to compensate for the power difference, i.e., P E = P L - P MPPT Generally, the start-up and shutdown frequency of energy storage systems should be minimized to reduce their impact on lifespan and improve the economic efficiency of microgrid operation. Therefore, when the wind power captured by the wind turbine exceeds the power required by the offshore hydrogen production platform and load, the wind turbine should be controlled to operate in a reduced power mode to reduce the start-up and shutdown coefficient of the energy storage system.

[0021] The controller of this invention adopts a dual-loop control structure with an outer power (voltage) loop and an inner current loop, or a triple-loop control structure with an additional voltage control loop.

[0022] Advantages of the present invention: Please summarize the advantages and technical effects of the present invention in conjunction with the technical solution.

[0023] Compared with the prior art, the advantages of the present invention are as follows: (1) It does not rely on communication and has high reliability. The adaptive generation of active power reference value and the switching of operating mode can be completed using only local measurement values. There is no need for high-speed communication between units, which fundamentally eliminates the risk of system instability caused by communication interruption in existing centralized or communication-based DC bus voltage control strategies.

[0024] (2) The mode can be switched automatically and seamlessly, and can easily cope with sudden load changes. By comparing the wind power captured by the wind turbine and the power required by the load, the active power reference value of the wind turbine is adaptively adjusted, and a stable power supply can be maintained under the conditions of sudden load changes and wind speed fluctuations.

[0025] (3) Reduce the frequency of energy storage start-up and shutdown and improve the economic efficiency of operation. Energy storage is not put into operation when there is a power surplus, and is only discharged when there is a power deficit, which significantly reduces the frequency of energy storage system start-up and shutdown, extends its service life, and improves the economic efficiency of offshore DC microgrid operation.

[0026] (4) Multi-voltage level coordinated stability ensures reliable power supply. The DC bus voltage, the low-voltage DC link voltage of the unit, and the PMSG AC voltage are maintained by dedicated control loops. Under wind speed fluctuations and load changes, the three voltage levels remain stable at their rated values, ensuring reliable power supply to the offshore hydrogen production platform and other loads. The above technical effects have been verified by PSCAD / EMTDC simulation. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of an offshore DC microgrid composed of offshore DC wind turbines, which is part of the adaptive constant voltage power supply control method for offshore DC wind turbines according to the present invention.

[0028] Figure 2 This is a schematic diagram of the overall architecture of an adaptive constant voltage power supply control system for offshore DC wind turbines, as described in this invention.

[0029] Figure 3 This is a schematic diagram of the DC-DC converter control structure of an adaptive constant voltage power supply control method for offshore DC wind turbines, as described in this invention.

[0030] Figure 4 This is a schematic diagram of the wind turbine-side converter control structure for an adaptive constant voltage power supply control method for offshore DC wind turbines, as described in this invention.

[0031] Figure 5 is a waveform diagram of the simulation results of the embodiment of the present invention (wherein, Figure 5-a For wind speed, Figure 5-b 5-c is the reference value of the active power output of the wind turbine, 5-d is the low-voltage DC link voltage of the wind turbine, 5-e is the DC bus voltage of the microgrid, and 5-f is the effective value of the PMSG AC voltage. Detailed Implementation

[0032] Example: The offshore DC microgrid composed of offshore DC wind turbines mainly includes wind turbines, turbine-side converters (MSCs), and wind turbine DC converters, such as... Figure 1 As shown, the overall control architecture of offshore DC wind turbines is as follows: Figure 2As shown, it is characterized by comprising the following: Step S1: Real-time acquisition of the DC bus voltage U of the offshore DC microgrid. MV Low-voltage DC link voltage U of wind turbine LV The three-phase voltage u on the AC side of the machine-side converter ms With three-phase current i ms The three-phase voltage u in the AC link of the DC-DC converter o Three-phase current i o ; Three-phase voltage u on the AC side of the converter on the machine side ms With three-phase current i ms By applying Clarke and Park transformations sequentially, the d-axis and q-axis components u in the synchronously rotating coordinate system are obtained. msd u msq i msd i msq .

[0033] Step S2: Perform DC voltage control on the DC converter of the wind turbine to maintain the stability of the low-voltage DC link voltage of the wind turbine. The wind turbine DC-DC converter uses the low-voltage DC voltage U of the wind turbine. LV Control, the control process is as follows: Figure 3 As shown, specifically, in the outer loop control of the DC-DC converter voltage of the wind turbine, the reference value U of the low-voltage DC link voltage of the wind turbine is adjusted. LV_ref With the low-voltage DC voltage U of the wind turbine LV The difference and the q-axis component U of the DC converter modulation voltage oq By performing PI control as shown in formulas (1) and (2), the reference value I of the inner loop current d-axis component of the wind turbine DC converter current inner loop control is obtained. od_ref and q-axis component reference value I oq_ref ,Right now: #(1) #(2) Among them, K p_od K is the proportional constant for the d-axis control of the DC-DC converter. i_qd K is the integral constant for the d-axis control of the DC-DC converter. p_oq K is the proportional constant for the q-axis control of the DC-DC converter. i_oq Let be the integral constant for the q-axis control of the DC-DC converter, and s be the Laplace operator; I od_ref and I oq_ref The reference value U of the d-axis component of the modulated voltage of the wind turbine DC converter is generated via the inner current loop control. od_ref and q-axis component reference value U oq_refThen, through sinusoidal pulse width modulation (SPWM), the switching signals of the wind turbine DC converter are generated to control the voltage and current of the AC link in the DC converter, so as to maintain the stability of the low-voltage DC link voltage of the wind turbine.

[0034] Step S3: The turbine-side converter MSC adopts adaptive constant voltage power supply control, that is, the turbine-side converter MSC adopts d-axis active power control, and its active power reference value is based on the wind power P captured by the wind turbine. MPPT Power P required for offshore hydrogen production platforms and loads L The magnitude is adaptively adjusted, the q-axis uses PMSG AC voltage control, and reference values ​​I for the inner loop current d-axis component of the machine-side converter MSC are generated respectively. msd_ref and q-axis component reference value I msq_ref The two are controlled by the inner loop current to generate the d-axis component reference value U of the modulated voltage of the machine-side converter. msd _ ref and q-axis component reference value U msq_ref Then, through sinusoidal pulse width modulation (SPWM), the switching signals of the wind turbine generator-side converter are generated, thereby controlling the output voltage and current of the MSC, and thus controlling the active power output of the PMSG while maintaining its output AC voltage stability.

[0035] like Figure 4 As shown, the machine-side converter MSC employs d-axis active power control and q-axis PMSG AC voltage control. Particularly in the d-axis active power control, the goal is to maintain a stable DC bus voltage, which is controlled by the DC bus voltage U. MV The control loop adaptively generates a reference value P for the active power of the wind turbine. MV_ref This allows for adaptive matching of the power requirements of offshore hydrogen production platforms and other loads, specifically: ① When the wind turbine captures wind power P MPPT The power P required by the offshore hydrogen production platform and its load is greater than that required by the platform. L That is, P MPPT >P L When the energy storage system is not engaged, the wind turbines operate in reduced-power mode, thus adaptively matching the power requirements of the offshore hydrogen production platform and other loads. In other words, when the DC bus voltage is controlled at its rated value, the system power is always balanced. If the energy storage system is engaged, the wind turbines can capture wind power, and the surplus power P absorbed by the energy storage system in this case... E = P MPPT - P L ; like Figure 4 As shown, the power reduction mode specifically refers to: maintaining the stability of the DC bus voltage as the control objective, and reducing the DC bus voltage reference value U... MV_ref Compared with the measured value U MVThe difference is fed into the PI regulator to obtain the active power reference value output by the DC bus voltage control loop, as shown in formula (3), so as to adaptively match the power required by the offshore hydrogen production platform and other loads. #(3) Among them, K p_MV K is the proportional constant of the DC bus voltage control loop. i_MV This is the integral constant of the DC bus voltage control loop.

[0036] ② When the wind turbine captures wind power P MPPT Less than or equal to the power P required by the offshore hydrogen production platform and its load L That is, P MPPT ≤P L If the wind turbine cannot meet the full power requirements of the offshore hydrogen production platform and its load, then the wind turbine will output the maximum captured wind power. In this case, the active power reference value is given as P. MPPT_ref At this time, the energy storage system discharges to compensate for the power deficit in order to maintain the stability of the DC bus voltage, i.e., P E = P L -P MPPT ; ③ Reference value of active power P of wind turbine ref After determining it through ① or ②, compare it with the measured value P. o The difference is calculated and input to the PI controller to generate the reference value I of the d-axis component of the inner loop current of the machine-side converter MSC. msd_ref ,Right now: #(4) Among them, K p_msd K is the proportional constant for the d-axis control of the machine-side converter. i_msd This is the integral constant for the d-axis control of the machine-side converter.

[0037] In addition, the q-axis PMSG AC voltage control to maintain stable output AC voltage specifically refers to: To maintain stable output AC voltage, that is: to reduce the AC voltage amplitude U of the wind turbine generator's converter. ms and its reference value U ms _ ref The difference is fed into the PI regulator to obtain the reference value I of the q-axis component of the inner loop current of the machine-side converter. msq_ref As shown in formula (5): #(5) Among them, K p_msq K is the proportional constant for the q-axis control of the machine-side converter. i_msq This is a constant for the q-axis control of the machine-side converter.

[0038] To verify the effectiveness of the control method proposed in this invention, the following system was built in PSCAD / EMTDC. Figure 1 The offshore DC microgrid system shown is composed of offshore DC wind turbines. The rated wind speed of the offshore DC wind turbines is 15 m / s, the rated active power is 6 MW, the rated output AC voltage of the PMSG is 0.98 kV, the rated low-voltage DC link voltage of the wind turbines is 2 kV, and the rated DC bus voltage of the system is ±50 kV. A load abrupt change scenario is set up under wind speed fluctuations. At 5 seconds, the power required by the offshore hydrogen production platform and other loads suddenly increases from 3.3 MW to 4 MW. The total simulation time is 10 seconds. The simulation results are shown in Figure 5. Using random fluctuating wind speeds as shown in Figure 5(a), in this scenario, whether the wind turbines are supplying power to a constant power load or experiencing a load abrupt change, they can adaptively adjust the given active power reference value P of the wind turbines based on the maximum wind power they capture and the power required by the offshore hydrogen production platform and other loads. ref To meet load demands, as shown in Figures 5(b) and (c), the DC bus voltage is kept stable while minimizing the start-up and shutdown frequency of the energy storage system, as shown in Figure 5(e). During this process, the low-voltage DC link voltage of the wind turbine and the output AC voltage of the PMSG are both kept stable at their rated values, as shown in Figures 5(d) and 5(f), verifying the effectiveness of the proposed method.

Claims

1. An adaptive constant voltage power supply control method for offshore DC wind turbines, comprising an offshore DC microgrid composed of offshore DC wind turbines, wherein the DC wind turbines include a wind turbine generator, a turbine-side converter (MSC), and a wind turbine DC converter, characterized in that... It includes the following: Step S1, signal acquisition and coordinate transformation, namely: real-time acquisition of the operation data of the offshore DC microgrid composed of offshore DC wind turbines, and sequential coordinate transformation of the acquired voltage and current signals to obtain the d-axis component and q-axis component in the synchronous rotating coordinate system. Step S2: Perform DC voltage control on the DC converter of the wind turbine to maintain the stability of the low-voltage DC link voltage of the wind turbine. Step S3: The turbine-side converter MSC adopts adaptive constant voltage power supply control, that is, the turbine-side converter MSC adopts d-axis active power control, and its active power reference value is based on the wind power P captured by the wind turbine. MPPT Power P required for offshore hydrogen production platforms and loads L The magnitude is adaptively adjusted, the q-axis uses PMSG AC voltage control, and reference values ​​I for the inner loop current d-axis component of the machine-side converter MSC are generated respectively. msd_ref and q-axis component reference value I msq_ref The two are controlled by the inner loop current to generate the d-axis component reference value U of the modulated voltage of the machine-side converter. msd _ ref and q-axis component reference value U msq_ref Then, through sinusoidal pulse width modulation (SPWM), the switching signals of the wind turbine generator-side converter are generated, thereby controlling the output voltage and current of the MSC, and thus controlling the active power output of the PMSG while maintaining its output AC voltage stability.

2. The adaptive constant voltage power supply control method for offshore DC wind turbines according to claim 1, characterized in that... Step S1 specifically refers to: real-time acquisition of the DC bus voltage U of the offshore DC microgrid. MV Low-voltage DC link voltage U of wind turbine LV The three-phase voltage u on the AC side of the machine-side converter ms With three-phase current i ms The three-phase voltage u in the AC link of the DC-DC converter o Three-phase current i o ; Three-phase voltage u on the AC side of the converter on the machine side ms With three-phase current i ms By applying Clarke transform and Park transform sequentially, the d-axis components u of the three-phase AC voltage on the machine-side converter in the synchronous rotating coordinate system are obtained. msd Three-phase voltage q-axis component u msq d-axis component of three-phase current i msd Three-phase current q-axis component i msq .

3. The adaptive constant voltage power supply control method for offshore DC wind turbines according to claim 1, characterized in that... The wind turbine DC converter in step S2 uses the low-voltage DC voltage U of the wind turbine. LV Control, specifically, refers to: in the outer loop control of the DC-DC converter voltage of the wind turbine generator, adjusting the reference value U of the low-voltage DC link voltage of the wind turbine generator. LV_ref With the low-voltage DC voltage U of the wind turbine LV The difference and the q-axis component U of the DC converter modulation voltage oq By performing PI control as shown in formulas (1) and (2), the reference value I of the inner loop current d-axis component of the wind turbine DC converter current inner loop control is obtained. od_ref and q-axis component reference value I oq_ref ,Right now: #(1) #(2) Among them, K p_od K is the proportional constant for the d-axis control of the DC-DC converter. i_qd K is the integral constant for the d-axis control of the DC-DC converter. p_oq K is the proportional constant for the q-axis control of the DC-DC converter. i_oq Let be the integral constant for the q-axis control of the DC-DC converter, and s be the Laplace operator; The reference value I of the d-axis component of the inner loop current od_ref and q-axis component reference value I oq_ref The reference value U of the d-axis component of the modulated voltage of the wind turbine DC converter is generated via the inner current loop control. od_ref and q-axis component reference value U oq_ref Then, the on / off signals of the switching devices of the wind turbine DC converter are generated through sinusoidal pulse width modulation.

4. The adaptive constant voltage power supply control method for offshore DC wind turbines according to claim 1, characterized in that... In step S3, the machine-side converter MSC employs d-axis active power control and q-axis PMSG AC voltage control. The d-axis active power control aims to maintain a stable DC bus voltage, controlled by the DC bus voltage U. MV The control loop adaptively generates a reference value P for the active power of the wind turbine. MV_ref This allows for adaptive matching of the power required by the offshore hydrogen production platform and other loads; the q-axis PMSG AC voltage control maintains a stable output AC voltage.

5. The adaptive constant voltage power supply control method for offshore DC wind turbines according to claim 4, characterized in that... The d-axis active power control specifically refers to: ① When the wind turbine captures wind power P MPPT The power P required by the offshore hydrogen production platform and its load is greater than that required by the platform. L That is, P MPPT >P L The energy storage system is not put into operation, allowing the wind turbines to operate in reduced power mode, thereby adaptively matching the power required by the offshore hydrogen production platform and other loads; ② When the wind turbine captures wind power P MPPT Less than or equal to the power P required by the offshore hydrogen production platform and its load L That is, P MPPT ≤P L Then the wind turbine outputs the maximum captured wind power, and the active power reference value is given as P. MPPT_ref At this time, the energy storage system discharges to provide the shortfall power to maintain the DC bus voltage stability; ③ Reference value of active power P of wind turbine ref After determining it through ① or ②, compare it with the measured value P. o The difference is calculated and input to the PI controller to generate the reference value I of the d-axis component of the inner loop current of the machine-side converter MSC. msd_ref ,Right now: #(4) Among them, K p_msd K is the proportional constant for the d-axis control of the machine-side converter. i_msd This is the integral constant for the d-axis control of the machine-side converter.

6. The adaptive constant voltage power supply control method for offshore DC wind turbines according to claim 5, characterized in that... The power reduction mode in step ① specifically refers to: taking the maintenance of DC bus voltage stability as the control objective, reducing the DC bus voltage reference value U... MV_ref Compared with the measured value U MV The difference is fed into the PI regulator to obtain the active power reference value output by the DC bus voltage control loop, as shown in formula (3), so as to adaptively match the power required by the offshore hydrogen production platform and other loads. #(3) Among them, K p_MV K is the proportional constant of the DC bus voltage control loop. i_MV This is the integral constant of the DC bus voltage control loop.

7. The adaptive constant voltage power supply control method for offshore DC wind turbines according to claim 4, characterized in that... The q-axis PMSG AC voltage control specifically refers to: To maintain stable output AC voltage, that is: to reduce the AC voltage amplitude U of the wind turbine generator's converter. ms and its reference value U ms _ ref The difference is fed into the PI regulator to obtain the reference value I of the q-axis component of the inner loop current of the machine-side converter. msq_ref As shown in formula (5): #(5) Among them, K p_msq K is the proportional constant for the q-axis control of the machine-side converter. i_msq This is a constant for the q-axis control of the machine-side converter.

8. The adaptive constant voltage power supply control method for offshore DC wind turbines according to claim 1, characterized in that... The adaptive constant voltage power supply control method for offshore DC wind turbines also includes: adjusting the reference value P of the wind turbine output power based on the wind power captured by the wind turbine and the power PL required by the offshore hydrogen production platform and load. ref Specifically, it refers to: When the wind turbine captures wind power P MPPT The power P required by the offshore hydrogen production platform and its load is greater than that required by the platform. L That is, P MPPT >P L If the energy storage system is not activated, the wind turbines need to operate at reduced power to maintain system power balance and DC bus voltage stability. If the energy storage system is activated, the wind turbines can capture wind power, and the surplus power P absorbed by the energy storage system can then be used to achieve this. E = P MPPT - P L ; When the wind turbine captures wind power P MPPT Less than or equal to the power P required by the offshore hydrogen production platform and its load L That is, P MPPT ≤P L At times, wind turbines cannot meet the full power requirements of offshore hydrogen production platforms and loads. In this case, the energy storage system discharges to compensate for the power difference, i.e., P E = P L -P MPPT .

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