Offshore wind and light same-field sending-out electrical system and control method

Abstract

According to the offshore wind and light same-field sending-out electrical system and the control method, by means of the output complementary characteristic of offshore wind power and photovoltaic power, wind turbine generators and photovoltaic modules are arranged between all sections of alternating current collection submarine cables, the carrying capacity of the submarine cables is utilized to the maximum extent, and according to the operation characteristic of key equipment in an offshore wind power and photovoltaic system, the output power of the offshore wind power and the photovoltaic power is greatly improved. The control method and the power reference value calculation method of the fan converter and the photovoltaic converter are provided, cooperative control of an offshore wind and light same-field sending-out electrical system can be achieved, the utilization rate of submarine cables is fully improved, and the method has great significance in improving the economical efficiency of offshore new energy projects.

Description

Technical Field

[0001] This invention belongs to the field of new energy power generation technology, specifically relating to an offshore wind and solar power transmission system and control method. Background Technology

[0002] With the vigorous development of my country's new energy industry, wind and solar power generation are gradually moving from onshore to offshore. Offshore wind power and offshore solar power have significant advantages such as being close to load centers and not occupying land resources, making them the future development direction of new energy power generation.

[0003] Because the power output of both offshore wind and offshore solar power is highly random and volatile, and submarine cables are designed with rated power capacity, the utilization rate of cable capacity is low during actual operation, leading to higher overall construction costs. In reality, the power output curves of offshore wind and offshore solar power are somewhat complementary, and their site requirements differ, making co-location construction feasible. However, current research on the design scheme of electrical systems for co-location of offshore wind and solar power is very limited. Furthermore, no reports have been published on how to combine the operating characteristics of key equipment in offshore wind and solar power systems to achieve efficient and reliable system operation during actual operation.

[0004] Currently, both wind power and photovoltaic (PV) power generation systems commonly employ maximum power point tracking (MPPT) control strategies. However, in offshore wind and solar co-generation electrical systems, if both the wind turbine converters and PV converters utilize traditional MPPT control strategies, the total power output from the shared submarine cable will fluctuate significantly. This places high demands on the cable's current carrying capacity, leading to excessively high construction costs and hindering the realization of the advantages of co-generation systems. Therefore, it is necessary to propose targeted electrical system design schemes and coordinated control strategies. Summary of the Invention

[0005] The purpose of this invention is to provide a marine wind and solar power simultaneous transmission electrical system and control method, filling the current technological gap in marine wind and solar power simultaneous transmission, realizing coordinated control of the marine wind and solar power simultaneous transmission electrical system, fully improving the utilization rate of submarine cables, and reducing engineering construction costs. To achieve the above-mentioned objective, this invention adopts the following technical solution:

[0006] A marine wind and solar power transmission system, characterized in that it comprises: a marine wind turbine, a wind turbine-side converter, a wind turbine-grid-side converter, a wind turbine step-up transformer, a marine photovoltaic module, a photovoltaic DC / DC converter, a photovoltaic grid-connected converter, a photovoltaic step-up transformer, an AC collection submarine cable, and a marine substation.

[0007] Each offshore wind turbine is connected to a turbine step-up transformer via a turbine-side converter and a grid-side converter. Each photovoltaic module is connected to a photovoltaic step-up transformer via a photovoltaic DC / DC converter and a photovoltaic grid-connected converter. The first wind turbine and the first photovoltaic module are stepped up by their respective step-up transformers and then connected to the far end of the first AC collection submarine cable. The second wind turbine and the second photovoltaic module are stepped up by their respective step-up transformers and then connected to the far end of the second AC collection submarine cable together with the near end of the first AC collection submarine cable. This process continues until the Nth wind turbine and the Nth photovoltaic module are stepped up by their respective step-up transformers and then connected to the far end of the Nth AC collection submarine cable together with the near end of the N-1th AC collection submarine cable. The near end of the Nth AC collection submarine cable is then connected to the offshore substation. This forms a complete incoming line for the offshore wind and solar power transmission system. Multiple complete incoming lines are connected to the offshore substation, where they are stepped up and connected to the onshore power grid.

[0008] This invention also provides a control method for the above-mentioned marine wind and solar power simultaneous transmission electrical system, which adopts the following technical solution:

[0009] The wind turbine's machine-side converter adopts a maximum power point tracking (MPPT) control strategy. By detecting wind speed in real time and tracking the maximum power generation curve, the wind turbine can operate at the maximum power point under different wind speeds.

[0010] The wind turbine grid-side converter adopts a constant DC bus voltage and reactive power control strategy, with the control objective being to maintain the stability of the wind turbine DC bus voltage.

[0011] The photovoltaic DC / DC converter has a DC voltage reference value given by a photovoltaic output power limit calculation module and a photovoltaic maximum power point tracking module. The photovoltaic maximum power point tracking module controls the active power by adjusting the DC voltage reference value of the photovoltaic module according to the maximum power generation curve, enabling the photovoltaic module to track the maximum power point under different sunshine and temperature environments. The photovoltaic output power limit calculation module calculates the photovoltaic active power limit value based on parameters such as the maximum transmission power of the AC cable and the output power of the wind turbine. When the active power output by the photovoltaic module is less than the limit value output by the photovoltaic output power limit calculation module, the photovoltaic power generation system operates according to the maximum power generation curve. When the active power output by the photovoltaic module is greater than the limit value output by the photovoltaic output power limit calculation module, the photovoltaic power generation system adopts a power limiting control mode, and its active power limit value is given by the photovoltaic output power limit calculation module.

[0012] The photovoltaic grid-connected converter adopts a constant DC bus voltage and reactive power control strategy, with the control objective being to maintain a stable photovoltaic DC bus voltage.

[0013] The photovoltaic output power limiting calculation module calculates the photovoltaic active power limiting value according to the following method:

[0014] In each complete incoming line, the active power limiting value P of the first group of photovoltaic modules slim1 The calculation method is as follows:

[0015]

[0016] Where S1 is the maximum apparent power of the first AC convergence submarine cable, P w1 Q represents the output active power of the first wind turbine. w1 Q represents the output reactive power of the first wind turbine. s1 Q represents the reactive power output of the first group of photovoltaic modules. wT1 Q is the reactive power consumed by the step-up transformer of the first wind turbine. sT1 Q represents the reactive power consumed by the first photovoltaic step-up transformer. L1 Q represents the inductive reactive power consumed by the first AC collection submarine cable. C1 This refers to the capacitive reactive power consumed by the first AC collection submarine cable.

[0017] i is a natural number greater than or equal to 2 and less than or equal to N. In each complete incoming line, the active power limit value P of the i-th group of photovoltaic modules is... slimi The calculation method is as follows:

[0018]

[0019] Among them, S i P represents the maximum apparent power of the i-th segment of the AC convergence submarine cable. i-1 P represents the active power of the near end of the AC collection cable in the (i-1)th segment. wi Let Q be the output active power of the i-th wind turbine. i-1 Q represents the reactive power of the (i-1)th AC collection segment near the submarine cable. wi Let Q be the output reactive power of the i-th wind turbine. si Let Q be the output reactive power of the i-th group of photovoltaic modules. wTi Q represents the reactive power consumed by the step-up transformer of the i-th wind turbine. sTi Q represents the reactive power consumed by the i-th photovoltaic step-up transformer. Li Q represents the inductive reactive power consumed by the i-th segment of the AC collection submarine cable. Ci This represents the capacitive reactive power consumed by the i-th segment of the AC collection submarine cable.

[0020] By adopting the technical solution of this invention, the complementary power output characteristics of offshore wind power and photovoltaics are fully utilized. Wind turbine units and photovoltaic modules are configured between each section of AC convergence submarine cable to maximize the utilization of the submarine cable's current carrying capacity. Furthermore, based on the operating characteristics of key equipment in offshore wind power and photovoltaic systems, control methods and power reference value calculation methods for wind turbine converters and photovoltaic converters are provided. Through the coordinated control of wind turbine converters and photovoltaic converters, the coordinated control of the offshore wind and solar power transmission electrical system can be achieved, significantly improving the utilization rate of the submarine cable. This is of great significance for improving the economic efficiency of offshore new energy projects. Attached Figure Description

[0021] Figure 1 This is a typical topology diagram of the marine wind and solar power transmission system of the present invention.

[0022] Figure 2 This is a typical topology diagram of the wind turbine machine-side converter in this invention.

[0023] Figure 3 This is a typical topology diagram of the photovoltaic DC / DC converter in this invention.

[0024] Figure 4 This is a typical topology diagram of the wind turbine grid-side converter and the photovoltaic grid-connected converter in this invention.

[0025] Figure 5 This is a schematic diagram of a specific example system for the wind turbine-side converter control method of the present invention.

[0026] Figure 6 This is a schematic diagram of a specific example system for the control method of wind turbine grid-side converter and photovoltaic grid-connected converter in this invention.

[0027] Figure 7 This is a schematic diagram of a specific example system of the photovoltaic DC / DC converter control method in this invention. Detailed Implementation

[0028] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] In this embodiment of the invention, the offshore solar power system simultaneously transmits electrical signals, such as... Figure 1 As shown, it includes an offshore wind turbine 1, a wind turbine-side converter 2, a wind turbine-grid-side converter 3, a wind turbine step-up transformer 4, an offshore photovoltaic module 5, a photovoltaic DC / DC converter 6, a photovoltaic grid-connected converter 7, a photovoltaic step-up transformer 8, an AC collection submarine cable 9, and an offshore substation 10.

[0030] In this embodiment of the invention, each offshore wind turbine 1 is connected to a wind turbine step-up transformer 4 via a turbine-side converter 2 and a grid-side converter 3. Each photovoltaic module 5 is connected to a photovoltaic step-up transformer 8 via a photovoltaic DC / DC converter 6 and a photovoltaic grid-connected converter 7. The first wind turbine and the first photovoltaic module are stepped up by their respective transformers and then connected to the far end of the first AC collection submarine cable. The second wind turbine and the second photovoltaic module are stepped up by their respective transformers and then connected to the far end of the second AC collection submarine cable together with the near end of the first AC collection submarine cable. This process continues until the Nth wind turbine and the Nth photovoltaic module are stepped up by their respective transformers and then connected to the far end of the Nth AC collection submarine cable together with the near end of the (N-1)th AC collection submarine cable. The near end of the Nth AC collection submarine cable is then connected to the offshore booster station 10. The above system forms a complete incoming line for the offshore wind and solar power transmission system. After multiple complete incoming lines are connected to the offshore substation, the voltage is boosted by the offshore substation and connected to the onshore power grid.

[0031] In this embodiment of the invention, the wind turbine side converter 2 adopts the following... Figure 2 The diagram shows a three-phase six-arm bridge topology. The control strategy for the wind turbine's machine-side converter 2 employs a dual-loop control system: an outer power control loop and an inner current control loop. The output of the outer power control loop, after passing through a limiting circuit, serves as the current reference value for the inner current control loop. The active power reference value is provided by the wind turbine's maximum power point tracking (MPPT) module. By real-time wind speed detection and tracking of the maximum power generation curve, the wind turbine can track its maximum power point at different wind speeds. A specific example system schematic of the wind turbine's machine-side converter control method is shown below. Figure 5 As shown, it includes: rotor position observation module 101, Park transformation module 102, wind turbine maximum power tracking module 103, power control module 104, current control module 105, Park inverse transformation module 106, and modulation module 107.

[0032] The specific implementation method of the power control module 104 of the wind turbine machine-side converter is as follows:

[0033]

[0034] Wherein: F PI1 (s) is the transfer function of the first PI controller, k p1 k is the proportionality coefficient. i1 Let i be the integral coefficient. sdref i sqref Corresponding to the current reference value vector I sdqref d-axis and q-axis components, P mref P is the active power reference value. m For active power, Q mref Q is the reactive power reference value. m This refers to reactive power.

[0035] The specific implementation method of the current control module 105 of the wind turbine's machine-side converter is as follows:

[0036]

[0037] Wherein: F PI2 (s) is the transfer function of the second PI controller, k p2 k is the proportionality coefficient. i2 U is the integral coefficient. sdref ,u sqref Corresponding to the machine-side modulation voltage vector U sdqref d-axis and q-axis components, i sd i sq Corresponding to the current vector I sdq d-axis and q-axis components, ω r L is the rotor angular frequency. s Ψ represents the stator inductance of the wind turbine, and Ψ represents the rotor permanent magnet flux linkage.

[0038] In this embodiment of the invention, the wind turbine grid-side converter 3 adopts the following... Figure 4 The diagram shows a three-phase six-bridge topology. The control strategy for the wind turbine grid-side converter 3 employs a dual-loop control system: an outer loop for DC bus voltage and reactive power control, and an inner loop for current control. The output of the outer loop for DC bus voltage and reactive power control is used as the current reference value for the inner loop after passing through a limiting circuit. The control objective of the wind turbine grid-side converter 3 is to maintain a stable DC bus voltage for the wind turbine. A specific example system schematic of the wind turbine grid-side converter control method is shown below. Figure 6 As shown, it includes: a phase-locked loop module 201, a Park conversion module 202, a DC bus voltage and reactive power control module 203, a current control module 204, a Park inverse conversion module 205, and a modulation module 206.

[0039] The specific implementation method of the DC bus voltage and reactive power control module 203 of the wind turbine grid-side converter is as follows:

[0040]

[0041] Wherein: F PI3 (s) is the transfer function of the third PI controller, k p3 k is the proportionality coefficient. i3 Let i be the integral coefficient. gdref i gqref Corresponding to the current reference value vector I gdqref d-axis and q-axis components, U dcref U is the reference value for the DC bus voltage. dc Q is the DC bus voltage. wref Q is the reactive power reference value.w This refers to reactive power.

[0042] The specific implementation method of the current control module 204 of the wind turbine grid-side converter is as follows:

[0043]

[0044] Wherein: F PI4 (s) is the transfer function of the fourth PI controller, k p4 k is the proportionality coefficient. i4 U is the integral coefficient. vdref ,u vqref Corresponding to the grid-side modulation voltage vector U vdqref d-axis and q-axis components, u gd ,u gq Corresponding to the grid voltage vector U gdq d-axis and q-axis components, i gd i gq Corresponding to the current vector I gdq d-axis and q-axis components, ω g L is the angular frequency of the grid voltage. g This is a filter inductor.

[0045] In this embodiment of the invention, the photovoltaic DC / DC converter 6 adopts the following... Figure 3 The diagram shows the Boost circuit topology. The control strategy for the photovoltaic DC / DC converter 6 employs a dual-loop control system: an outer loop for DC voltage control and an inner loop for current control. The output of the outer loop, after passing through a limiting circuit, serves as the current reference value for the inner loop. This DC voltage reference value is provided by the photovoltaic output power limiting calculation module and the photovoltaic maximum power point tracking module. The photovoltaic maximum power point tracking module controls the active power by adjusting the DC voltage reference value of the photovoltaic module based on the maximum power generation curve, enabling the photovoltaic module to track the maximum power point under different solar radiation and temperature conditions. The photovoltaic output power limiting calculation module calculates the photovoltaic active power limiting value based on parameters such as the maximum transmission power of the AC cable and the wind turbine output power. When the active power output by the photovoltaic module is less than the limiting value output by the photovoltaic output power limiting calculation module, the photovoltaic power generation system operates according to the maximum power generation curve. When the active power output by the photovoltaic module is greater than the limiting value output by the photovoltaic output power limiting calculation module, the photovoltaic power generation system adopts a power limiting control mode, with the active power limiting value provided by the photovoltaic output power limiting calculation module.

[0046] A specific example system schematic diagram of the photovoltaic DC / DC converter control method is shown below. Figure 7As shown, it includes: a photovoltaic output power limit calculation module 301, a photovoltaic maximum power tracking module 302, a DC voltage control module 303, a current control module 304, and a modulation module 305.

[0047] In the photovoltaic output power limiting calculation module 301, the photovoltaic active power limiting value is calculated according to the following method:

[0048] In each complete incoming line, the active power limiting value P of the first group of photovoltaic modules slim1 The calculation method is as follows:

[0049]

[0050] Where S1 is the maximum apparent power of the first AC convergence submarine cable, P w1 Q represents the output active power of the first wind turbine. w1 Q represents the output reactive power of the first wind turbine. s1 Q represents the reactive power output of the first group of photovoltaic modules. wT1 Q is the reactive power consumed by the step-up transformer of the first wind turbine. sT1 Q represents the reactive power consumed by the first photovoltaic step-up transformer. L1 Q represents the inductive reactive power consumed by the first AC collection submarine cable. C1 This refers to the capacitive reactive power consumed by the first AC collection submarine cable.

[0051] i is a natural number greater than or equal to 2 and less than or equal to N. In each complete incoming line, the active power limit value P of the i-th group of photovoltaic modules is... slimi The calculation method is as follows:

[0052]

[0053] Among them, S i P represents the maximum apparent power of the i-th segment of the AC convergence submarine cable. i-1 P represents the active power of the near end of the AC collection cable in the (i-1)th segment. wi Let Q be the output active power of the i-th wind turbine. i-1 Q represents the reactive power of the (i-1)th AC collection segment near the submarine cable. wi Let Q be the output reactive power of the i-th wind turbine. si Let Q be the output reactive power of the i-th group of photovoltaic modules. wTi Q represents the reactive power consumed by the step-up transformer of the i-th wind turbine. sTi Q represents the reactive power consumed by the i-th photovoltaic step-up transformer. Li Q represents the inductive reactive power consumed by the i-th segment of the AC collection submarine cable. Ci This represents the capacitive reactive power consumed by the i-th segment of the AC collection submarine cable.

[0054] The specific implementation method of the DC voltage control module 303 of the photovoltaic DC / DC converter is as follows:

[0055] I bref =F PI5 (s)(U dcsref -U dcs )

[0056]

[0057] Wherein: F PI5 (s) is the transfer function of the fifth PI controller, k p5 k is the proportionality coefficient. i5 I is the integral coefficient. bref U is the reference value for DC current. dcsref U is the reference value for DC voltage. dcs It is a DC voltage.

[0058] The specific implementation method of the current control module 304 of the photovoltaic DC / DC converter is as follows:

[0059] U bref =F PI6 (s)(I bref -I b )

[0060]

[0061] Wherein: F PI6 (s) is the transfer function of the sixth PI controller, k p6 k is the proportionality coefficient. i6 I is the integral coefficient. b For direct current, U bref This is the reference value for the modulation voltage.

[0062] In this embodiment of the invention, the photovoltaic grid-connected converter 7 adopts the following... Figure 4 The diagram shows a three-phase, six-arm bridge topology. The control strategy for the photovoltaic grid-connected converter 7 employs a dual-loop control system: an outer loop for DC bus voltage and reactive power control, and an inner loop for current control. The output of the outer loop for DC bus voltage and reactive power control, after passing through a limiting circuit, serves as the current reference value for the inner loop. The control objective is to maintain a stable photovoltaic DC bus voltage. The specific implementation of the photovoltaic grid-connected converter control strategy is the same as that of the wind turbine grid-side converter.

[0063] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to the above embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A marine solar and wind power transmission system, characterized in that, include: Offshore wind turbines, wind turbine generator-side converters, wind turbine grid-side converters, wind turbine step-up transformers, offshore photovoltaic modules, photovoltaic DC / DC converters, photovoltaic grid-connected converters, photovoltaic step-up transformers, AC collection submarine cables, and offshore substations; Each offshore wind turbine is connected to a turbine step-up transformer via a turbine-side converter and a grid-side converter. Each photovoltaic module is connected to a photovoltaic step-up transformer via a photovoltaic DC / DC converter and a photovoltaic grid-connected converter. The first wind turbine and the first photovoltaic module are stepped up by their respective step-up transformers and then connected to the far end of the first AC collection submarine cable. The second wind turbine and the second photovoltaic module are stepped up by their respective step-up transformers and then connected to the far end of the second AC collection submarine cable together with the near end of the first AC collection submarine cable. This process continues until the Nth wind turbine and the Nth photovoltaic module are stepped up by their respective step-up transformers and then connected to the far end of the Nth AC collection submarine cable together with the near end of the N-1th AC collection submarine cable. The near end of the Nth AC collection submarine cable is then connected to the offshore substation. This forms a complete incoming line for the offshore wind and solar power transmission system. Multiple complete incoming lines are connected to the offshore substation, where the voltage is stepped up and connected to the onshore power grid. The control method for the marine wind and solar power simultaneous transmission electrical system is characterized by: The wind turbine's machine-side converter adopts a maximum power point tracking (MPPT) control strategy. By detecting wind speed in real time and tracking the maximum power generation curve, the wind turbine can track the maximum power point at different wind speeds. The wind turbine grid-side converter adopts a constant DC bus voltage and reactive power control strategy, with the control objective being to maintain the stability of the wind turbine DC bus voltage. The photovoltaic DC / DC converter has a DC voltage reference value given by a photovoltaic output power limit calculation module and a photovoltaic maximum power point tracking module. The photovoltaic maximum power point tracking module controls the active power by adjusting the DC voltage reference value of the photovoltaic module according to the maximum power generation curve, enabling the photovoltaic module to track the maximum power point under different sunshine and temperature environments. The photovoltaic output power limit calculation module calculates the photovoltaic active power limit value based on parameters such as the maximum transmission power of the AC cable and the output power of the wind turbine. When the active power output by the photovoltaic module is less than the limit value output by the photovoltaic output power limit calculation module, the photovoltaic power generation system operates according to the maximum power generation curve. When the active power output by the photovoltaic module is greater than the limit value output by the photovoltaic output power limit calculation module, the photovoltaic power generation system adopts a power limiting control mode, and its active power limit value is given by the photovoltaic output power limit calculation module. The photovoltaic grid-connected converter adopts a constant DC bus voltage and reactive power control strategy, with the control objective being to maintain a stable photovoltaic DC bus voltage.

2. The control method for the marine wind and solar power simultaneous transmission electrical system according to claim 1, characterized in that, The photovoltaic output power limiting calculation module calculates the photovoltaic active power limiting value according to the following method: In each complete incoming line, the active power limiting value P of the first group of photovoltaic modules slim1 The calculation method is as follows: Where S1 is the maximum apparent power of the first AC convergence submarine cable, P w1 Q represents the output active power of the first wind turbine. w1 Q represents the output reactive power of the first wind turbine. s1 Q represents the reactive power output of the first group of photovoltaic modules. wT1 Q is the reactive power consumed by the step-up transformer of the first wind turbine. sT1 Q represents the reactive power consumed by the first photovoltaic step-up transformer. L1 Q represents the inductive reactive power consumed by the first AC collection submarine cable. C1 This refers to the capacitive reactive power consumed by the first AC collection submarine cable. i is a natural number greater than or equal to 2 and less than or equal to N. In each complete incoming line, the active power limit value P of the i-th group of photovoltaic modules is... slimi The calculation method is as follows: Among them, S i P represents the maximum apparent power of the i-th segment of the AC convergence submarine cable. i-1 P represents the active power of the near end of the AC collection cable in the (i-1)th segment. wi Let Q be the output active power of the i-th wind turbine. i-1 Q represents the reactive power of the (i-1)th AC collection segment near the submarine cable. wi Let Q be the output reactive power of the i-th wind turbine. si Let Q be the output reactive power of the i-th group of photovoltaic modules. wTi Q represents the reactive power consumed by the step-up transformer of the i-th wind turbine. sTi Q represents the reactive power consumed by the i-th photovoltaic step-up transformer. Li Q represents the inductive reactive power consumed by the i-th segment of the AC collection submarine cable. Ci This represents the capacitive reactive power consumed by the i-th segment of the AC collection submarine cable.

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