CN102412590B - Modular direct-current grid connection topology comprising energy storing device for wind power station group - Google Patents

Abstract

The invention discloses a wind farm group modular DC grid-connected system including an energy storage device, comprising a first converter station, a second converter station and a third converter station, wherein the first converter station is located in the wind farm group Nearby, its AC bus end is connected to the wind farm, the AC bus end of the second converter station is connected to an energy storage device, its DC bus end is connected to the first converter station through a DC bus, and the AC bus end of the third converter station is connected to the wind farm. The receiving end grid is connected, and its DC bus end is connected to the DC bus. The first converter station is used to send the power of the wind farm to the DC bus, and the third converter station is used to control the voltage of the DC bus to be constant. The power generated by each wind farm is sent to the receiving end grid, and the energy storage device is used to absorb or generate power to stabilize the fluctuation of wind power. The wind farm in the system of the invention has no AC interconnection with the local power grid and other wind farms, which can limit the influence range of AC faults, stabilize short-term fluctuations of wind power and improve system stability.

Description

A modular DC grid-connected topology of wind farms with energy storage devices

technical field

The invention belongs to the technical field of electric power system transmission, and in particular relates to the grid-connected topology of multiple wind farms and energy storage systems in the form of DC modules.

Background technique

In recent years, my country's wind power generation has developed very rapidly, and its installed capacity reached 44.73 million kilowatts at the end of 2010, surpassing the United States to become the country with the largest wind power installed capacity in the world. However, it is worth noting that most of the seven 10-million-kilowatt-level wind power bases in my country's planned "Three Gorges of Wind Power"—Hami, Jiuquan, Hebei, Jilin, Jiangsu Coastal, Eastern Mongolia, and Western Mongolia—are located at the end of the power grid. Low self-consumption capacity, weak self-consumption capacity, and the reverse distribution of wind energy resources and load centers determine that most wind power generation needs to be consumed in the central and eastern load centers through large-scale long-distance transmission. On the other hand, the grid structure of major wind power bases is not strong enough, and the power supply structure is relatively simple. The strong fluctuation of wind power will have a great impact on the frequency and transient stability of the system, resulting in the limitation of wind farm output. Finally, at present, most wind turbines in my country do not have low voltage ride through (LVRT) capability, and a simple failure of the system will often cause a large area of wind turbines to go off-grid. For example, on April 17, 2011, Gansu Guazhou Xiehe Wind Power Co., Ltd. Ganhekou West Second Wind Farm 35C2-9 box-type transformer high-voltage side cable head breakdown, 35D2-10 box-type transformer cable three-phase connection As a result, 702 wind turbines were disconnected from the grid, and the output loss was 1006.223MW. The frequency of the main grid of the Northwest Power Grid dropped from 50.036Hz before the accident to a minimum of 49.815Hz. The above problems can be summed up in two aspects: limited wind power output and off-grid wind turbines.

Aiming at the problem of limited wind power transmission, Xiao Chuangying et al.’s “Research on Wind Power Regulation Mode in Jiuquan, Gansu Province” (Proceedings of the Chinese Society for Electrical Engineering, 2010, 30(10), 1-7) proposed a method for supporting the construction of thermal power units in Jiuquan, Gansu Province. , through the way of bundling wind power generation and thermal power generation to the eastern load center through the UHV DC line. Among them, the installed capacity of supporting thermal power units is 1.6 to 2.0 times the installed capacity of wind power generation.

In response to the problem of wind turbine off-grid accidents, the State Electricity Regulatory Commission issued the "Notice on Effectively Strengthening the Safety Supervision and Management of Wind Farms and Containing Large-scale Wind Turbine Off-grid Accidents", requiring units that do not have low-voltage ride-through capabilities to formulate practical measures as soon as possible. Feasible low-voltage ride-through capacity transformation plan, and urge equipment manufacturers to cooperate in the implementation.

The plan proposed by Xiao Chuangying and others requires the construction of thermal power units with 1.6 to 2 times the installed capacity of wind power, which deviates from the goal of energy conservation and emission reduction for the development of wind power, and wind power bases such as Jiuquan and Mengxi are located in remote areas short of water. , not suitable for building thermal power units.

In the document "Operation and Control of Multi-terminal HVDC Transmission for Offshore Wind Farms" (IEEE Transactions on Power Delivery, PP(99): 1-1), a voltage source converter-based multi-terminal converter suitable for offshore wind power generation is proposed. DC transmission topology. This topology is aimed at the transmission of offshore wind power to land through DC cables, and considers the cost of offshore wind power construction. This topology does not consider energy storage devices.

Contents of the invention

Aiming at the problems existing in the above-mentioned prior art, the present invention provides a DC modularized wind power grid-connected scheme, the purpose of which is to provide a DC network structure and its operation method suitable for large-scale wind farm group grid-connected, which can realize wind farm Unaffected by external power grid failures, the problem of wind turbine off-grid caused by low voltage is solved to a certain extent; on the other hand, the voltage stability and transient stability inside the wind farm group are improved by rationally configuring energy storage devices.

In order to achieve the above object, the present invention adopts the following technical solutions to achieve:

A wind farm group modular DC grid-connected system including an energy storage device, comprising a first converter station, a second converter station and a third converter station, wherein the first converter station is located near the wind farm group , the AC bus end of which is connected to the wind farm, the AC bus end of the second converter station is connected to an energy storage device, the DC bus end is connected to the first converter station through a DC bus, and the third converter station The AC bus terminal of the wind farm is connected to the receiving grid, and its DC bus terminal is connected to the DC bus. The first converter station is used to control the AC bus voltage of the wind farm to be constant, so as to send the power of the wind farm to the DC bus. , the third converter station is used to control the voltage of the DC bus to be constant, so as to send the power generated by each wind farm to the receiving end grid, and the energy storage device is used to absorb or send power to stabilize the wind power fluctuation.

Compared with the prior art, the present invention adopts the voltage source converter station to connect the wind farm, which can give full play to the active and reactive power decoupling control ability of the voltage source converter station and the ability to establish AC side voltage and self-commutation; The modular structure of the converter interconnection can limit the scope of failure and improve the safety and stability of the entire system.

1) Each wind farm is connected to the DC bus using a voltage source converter station instead of directly interconnected with the local AC power grid, which can avoid the problem of wind turbine off-grid caused by the failure of the local AC power grid; there is no AC interconnection between the wind farms, It can avoid the transient disturbance of a certain wind power internal fault to other wind farms;

2) A set of energy storage systems shared by multiple wind farms can not only improve the stability of each wind farm, but also improve the utilization rate of the energy storage system and reduce costs;

3) The use of two grid-side converter stations can improve the operational flexibility of the entire system.

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a schematic diagram of the system topology of the present invention.

Figure 2. Schematic diagram of the connection of two wind power modules in a 220/750kV substation and connected to a 750kV UHV network.

Figure 3 is a connection schematic diagram of eight wind power modules collected and sent to the load center by ±800kV EHVDC transmission.

Detailed ways

As shown in Figure 1, a modular DC grid-connected system for wind farms with energy storage devices mainly consists of a voltage source converter station A connected to wind farms, a voltage source converter station B connected to energy storage devices, and a DC bus C , Two AC grid-side voltage source converter stations D.

Build a voltage source converter based on a fully-controlled device near each wind farm, and connect the wind farm to the AC bus of the voltage source converter; build two voltage sources based on a fully-controlled device in the receiving end power grid type converter, its AC bus is connected to the receiving end grid, and the wind farm side converter station and the AC grid side converter station are connected together through a DC bus; two sets of energy storage devices are connected through two voltage source converter stations connected to the DC bus.

The wind farm side converter station controls the AC bus voltage of the wind farm to be constant, and sends all the power generated by the wind turbines to the DC bus; the AC grid side converter station controls the DC bus voltage to be constant, and sends all the power generated by each wind farm to the AC Power grid; the energy storage device absorbs or sends out power according to the control requirements, which can stabilize short-term fluctuations in wind power and improve system stability.

The aforementioned voltage source converter is based on fully controlled switching devices, and its specific topology can be a three-phase two-level converter, a clamped multi-level voltage source converter, and a cascaded multi-level converter. converters, modular multi-level voltage source converters and multi-pulse voltage source converters, etc.

Taking a single wind farm (100MW) as a unit, build a converter station near the wind farm and connect the wind farm to the AC busbar of the converter station. Considering that the wind farm is not connected to the local AC power grid, the voltage source converter is adopted Station; several converter stations are connected to the DC bus to form a wind power module with a certain rated power (such as 500MW). Inside each module, an energy storage device with appropriate power and capacity (100MW/600MJ) is equipped to smooth the short-term fluctuation of wind power and improve the voltage stability and transient stability of the wind farm.

The grid side also adopts a voltage source converter station. Considering the capacity limitation and operation flexibility of the converter station, each wind power module is equipped with two grid-side converter stations, which are connected to the high-voltage main grid through a step-up transformer.

As shown in Figure 2, two wind power modules can be boosted by a 220/750kV substation and then connected to a 750kV UHV transmission network; as shown in Figure 3, after several wind power modules are assembled, they can be sent to the load center by ±800kV EHV DC transmission.

What enumerated above is only several specific implementation examples of the present invention, the present invention is not limited to above embodiment, also can have many deformations, all deformations that those of ordinary skill in the art can directly derive or think of from the content disclosed in the present invention, All should be considered as protection scope of the present invention.

Claims (3)

1. wind farm group modularized dc grid-connected system that contains energy storage device, comprise the first current conversion station, the second current conversion station and the 3rd current conversion station, and be the voltage-source type current conversion station, wherein, described the first current conversion station is positioned near wind farm group, its ac bus end connects with wind energy turbine set, described the second current conversion station ac bus end is connected with energy storage device, its dc bus end connects with the dc bus end of described the first current conversion station by dc bus, the ac bus end of described the 3rd current conversion station connects with the receiving end electrical network, its dc bus end is connected on described dc bus, described the first current conversion station is used for controlling wind energy turbine set ac bus voltage constant, so that the power of wind energy turbine set is delivered on described dc bus, described the 3rd current conversion station is used for controlling the voltage constant on described dc bus, pass out to the receiving end electrical network with the electric power that each wind energy turbine set is sent, described energy storage device is used for absorbing or sending power, to stabilize the fluctuation of wind power.

2. modularized dc grid-connected system according to claim 1, it is characterized in that, described voltage-source type converter is based on the converter of full-controlled switch device, and its concrete topology is three-phase two level-type converters, clamper type voltage with multiple levels source converter, cascade multi-level converter, modular multi-electrical-level voltage source current converter or many pulse wave electric voltages sources converter.

3. modularized dc grid-connected system according to claim 1 and 2, is characterized in that, described the first current conversion station, the second current conversion station and the 3rd current conversion station are a plurality of.

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