CN210074787U

CN210074787U - High-power converter circuit topological structure for offshore wind power

Info

Publication number: CN210074787U
Application number: CN201920454610.7U
Authority: CN
Inventors: 吕怀明
Original assignee: ZHEJIANG HRV ELECTRIC Co Ltd
Current assignee: ZHEJIANG HRV ELECTRIC Co Ltd
Priority date: 2019-04-04
Filing date: 2019-04-04
Publication date: 2020-02-14
Anticipated expiration: 2029-04-04

Abstract

The utility model relates to a high-power converter circuit topological structure for offshore wind power, which comprises a generator, a box transformer substation and a plurality of groups of converter units; the converter units comprise a machine side converter module and a network side converter module, the machine side converter module and the network side converter module both adopt a neutral point clamping type three-level topological structure, a plurality of groups of converter units are connected in parallel, the input end of each group of converter units is connected with one winding of a generator stator, the output end of each group of converter units is connected with a box transformer substation, the output power of the generator is matched with the number of groups of converter units, and the start-stop logic and the regulation power distribution are realized in a power cooperation mode. The utility model discloses converter circuit topology realizes opening through power collaborative mode and stops logic and power distribution, and the group number of the converter unit that decides to drop into according to the power size of generator output, every converter unit can the autonomous working, especially under the fault circumstance, and the converter unit can the work of carrying off, improves the utilization ratio, reduces the generated energy loss.

Description

High-power converter circuit topological structure for offshore wind power

Technical Field

The invention relates to the technical field of wind power generation, in particular to a high-power converter circuit topological structure for offshore wind power.

Background

At present, offshore wind power becomes a research hotspot of global wind power development, offshore wind power is taken as an important direction of renewable energy development in all countries of the world, and China also classifies offshore wind power as an important component of a strategic emerging industry. Different from onshore wind field construction, because offshore wind field construction difficulty is high, infrastructure cost is high, fan equipment only accounts for about 40% of total wind field construction cost, and other costs of offshore construction, hoisting, maintenance, submarine cables and the like account for about 60%, therefore, the offshore wind turbine generator with higher power and high reliability has low relative construction cost, better economy and more obvious trend of large-scale wind turbine generator. Due to the high construction and maintenance cost of offshore wind power, offshore wind power converters are developing towards high power, low cost, high efficiency, high performance, high reliability and high utilization rate. Problems facing offshore wind power converters include: 1) the capacity of a single machine of the offshore converter is increased, so that the high requirement on the bearing of a tower can be brought, and the problem of cable twisting is serious; 2) the offshore wind power construction cost is high, the cost pressure is high, and the cost reduction of the converter is very important; 3) the annual utilization hours of the offshore wind power converter are high, the converter is in high-load power operation, and the utilization rate is higher; 4) and the offshore wind power converter is difficult to maintain, and the reliability of devices is required to be high.

At present, the offshore wind power converter mainly adopts the traditional 690V voltage grade, and partially adopts the improved 3300V medium-voltage converter, and the two schemes have advantages and disadvantages respectively. The traditional offshore wind power converter with the 690V voltage level adopts a two-level topological structure, is simple to control and has mature technology; the parallel connection mode of a plurality of low-voltage converters is adopted, the parallel connection mode is simple, and the power cooperative control is absent without an independent working function; the low-voltage IGBT module and the electric components are adopted, so that the cost of the device is low, and the supply chain is mature; the IGBT device has high switching frequency (the switching frequency of an IGBT module with 1700V voltage grade is more than 2 kHz), good performance indexes such as low-voltage ride through and current harmonic waves and the like, and has operation experience and high technical maturity on land; however, due to the increase of the capacity of the offshore converter, the current can be obviously improved, the number of power cables between the converter and the generator is large, the cables are heavy, the problem of cable twisting exists, cable loss is large, and the efficiency of the whole machine is reduced. The improved offshore wind power converter with 3300V voltage level adopts a three-level topological structure, and is complex to control; a single converter is adopted, the independent operation cannot be realized, the machine is stopped after a fault occurs, and the utilization rate is reduced to a certain extent; the medium-voltage IGCT module and the medium-voltage electrical component are adopted, so that the cost of the device is high and the supply chain is immature; the IGCT device has low switching frequency (4500V IGCT module, switching frequency is about 500 Hz), low-voltage ride through, current harmonic and other properties are difficult to control, the technical difficulty is high, the device insulation requirement is high, the maintenance is inconvenient and the like; by adopting 3300V voltage class, compare 690V voltage class, the current drops to the fourth of low pressure, and the power cable quantity between converter and the generator is few, does not have the cable problem of twisting, and complete machine efficiency is high.

Disclosure of Invention

The invention aims to solve the problem that the cost, technical realization, efficiency and reliability of an offshore converter cannot be considered simultaneously, and provides a high-power converter circuit topological structure for offshore wind power.

The invention realizes the purpose through the following technical scheme: a high-power converter circuit topological structure for offshore wind power comprises a generator, a box transformer substation and a plurality of groups of converter units; the converter units are connected in parallel, the input end of each converter unit is connected with one winding of the stator of the generator, and the output end of each converter unit is connected with the box transformer substation; the converter unit comprises a machine side converter module and a network side converter module, wherein the machine side converter module and the network side converter module both adopt a midpoint clamping type three-level topological structure; the output power of the generator is matched with the number of groups of the converter units, and start-stop logic and power regulation distribution are realized in a power cooperation mode.

Preferably, the machine side converter module and the grid side converter module both adopt a midpoint clamping type three-level topological structure of a low-voltage insulated gate bipolar transistor.

Preferably, the working voltage of the converter unit is 950-1150V.

Preferably, the voltage level of the low-voltage insulated gate bipolar transistor is 1700V.

Preferably, the input end of the machine side converter module is sequentially connected with a machine side reactor, a stator isolating switch and a generator stator winding; the output end of the network side current transformation module is sequentially connected with a network side reactor, a network side circuit breaker and a box transformer substation; the output end of the machine side converter module is connected with the input end of the network side converter module, and a CHOPPER unit is arranged between the output end of the machine side converter module and the input end of the network side converter module.

Preferably, a first filter unit is arranged between the machine side reactor and the stator isolating switch.

Preferably, a second filtering unit is arranged between the network side reactor and the network side breaker.

Preferably, the converter units are all low-voltage devices.

Compared with the prior art, the invention has the following substantial effects: (1) the converter unit adopts devices with low cost and mature supply chain, so that the overall cost of the converter unit is reduced, and the maintenance and the replacement are more convenient; (2) the converter circuit topological structure realizes start-stop logic and power distribution in a power cooperation mode, the number of groups of converter units which are put into the converter circuit topological structure is determined according to the power output by the generator, the range of the output power is greatly widened in the power cooperation mode, and different power consumption requirements are met; each converter unit can also work independently, and particularly under the condition of failure, the converter units can work in a load shedding manner, so that the utilization rate is improved, and the loss of generated energy is reduced; (3) the working voltage of the converter unit is improved, the output current of the converter unit is reduced, compared with a converter with a voltage grade of 690V, the output current is reduced to 60% of the original output current under the same power, the current is reduced, the loss of a tower cylinder cable and the converter is reduced, the efficiency of the whole machine is improved, and the risk of cable twisting is reduced.

Drawings

Fig. 1 is a schematic diagram of a high-power converter topology according to an embodiment of the present invention.

The reference numerals are explained below:

10. stator isolator, 11, machine side reactor, 12, machine side du/dt filter resistance, 13, machine side du/dt filter capacitance, 14, machine side converter, 15, CHOPPER unit, 16, net side converter, 17, net side filter capacitance, 18, net side reactor, 19, net side circuit breaker.

Detailed Description

The invention will be further described with reference to the accompanying drawings in which:

example (b):

a high-power converter circuit topological structure for offshore wind power comprises a generator G1, a box transformer T1 and 4 sets of converter units with the same structure, wherein the converter units 1-4 are connected in parallel as shown in figure 1. The stator of generator G1 contains 4 windings, each winding is connected to a respective converter unit, the 4 converter units are connected in parallel to each other and to the box transformer T1, and generator G1 feeds the electrical energy into the grid via the 4 parallel converter units. The connection mode has the advantages that each converter unit can work independently, particularly, under the condition of failure, the converter units can work in a load shedding mode, the utilization rate is improved, and the loss of generated energy is reduced.

The converter unit 1 comprises a machine side converter module and a network side converter module, wherein the input end of the machine side converter module is sequentially connected with a machine side reactor (11), a stator isolating switch (10) and a generator stator winding; the output end of the grid side current transformation module is sequentially connected with a grid side reactor (18), a grid side circuit breaker (19) and a box transformer substation, and the current transformer unit 1 achieves functions of normal work cut-in, shutdown cut-out and the like through a disconnecting switch (10) and the grid side circuit breaker (19). The output end of the machine side converter module is connected with the input end of the network side converter module, a CHOPPER unit is arranged between the output end of the machine side converter module and the input end of the network side converter module, and the CHOPPER unit (15) is used for preventing the overvoltage problem of the direct-current bus under the fault conditions of low-voltage ride-through, high-voltage ride-through and the like.

Be equipped with first filter unit between machine side reactor (11) and stator isolator (10), first filter unit comprises machine side du/dt filter resistance (12) and machine side du/dt filter capacitance (13) for realize the restriction function who restricts converter exit end du/dt, reduce generator side spike voltage, extension engine life. And a second filtering unit is arranged between the grid-side reactor (18) and the grid-side circuit breaker (19), the second filtering unit is a grid-side filtering capacitor (17), the grid-side filtering capacitor (17) is connected with the grid-side reactor (18) in series, and the grid-side filtering capacitor (17) and the grid-side reactor (18) filter the voltage and current output by the grid-side current transformation module to reduce the current harmonic wave at the grid side.

The machine side converter module and the network side converter module both adopt a midpoint clamping type three-level topological structure of a low-voltage insulated gate bipolar transistor and adopt a three-level topological structure of a low-voltage device, so that the working voltage of a converter unit is obviously improved; the converter has the advantages of low voltage ride through, faster torque response and the like. The converter units all adopt low-voltage devices, and the machine side converter module and the grid side converter module adopt low-voltage insulated gate bipolar transistors, so that the converter units are low in cost, mature in supply chain, small in device size and convenient to replace and maintain. For example, for a 5.0MW generator G1, the rated working voltage of the converter unit is 1150V, the output power is 1.25MW, the machine side converter module and the grid side converter module adopt IGBT modules with 1700V voltage class, and other electrical devices have corresponding models, so that the cost of the devices selected by the converter is low and the supply chain is mature, the improvement of the working voltage is also beneficial to reducing the output current of the converter unit, compared with the converter with 690V voltage class, the output current is reduced to 60% of the original output current under the same power, the current is reduced, the loss of the tower cable and the converter is reduced, the overall efficiency is improved, and the risk of cable twisting is reduced.

The output power of the generator is matched with the number of groups of converter units, starting and stopping logic and power regulation distribution are realized in a power cooperation mode, the number of groups of the converter units is determined according to the output power of the generator, and when the output power of the generator is 25% of the rated power, one group of converter units is selected to be put into; when the output power of the generator is 50% of the rated power, two groups of converter units are selected to be put into use; when the output power of the generator is 75% of the rated power, selecting to put into three groups of converter units; when the output power of the generator is 100% of the rated power, four groups of converter units are selected to be put into use. The range of the output power is greatly widened by the power cooperation mode, and different power utilization requirements are met.

The converter cell is inefficient at low load, with the highest efficiency at rated load and reduced efficiency at overload, for example, the converter cell efficiency curve is as follows in table 1:

table 1: single converter cell efficiency curve diagram

Load (%)	Efficiency of
		110％	≥96.5％
100％	≥97％
		75％	≥96.7％
50％	≥95％
		25％	≥93％

The converter circuit topological structure is composed of four independent converter units, each converter unit has the same efficiency curve, the converter units realize start-stop logic and power regulation distribution in a power cooperation mode according to the current load, and the improved converter efficiency curve is as the following table 2:

table 2: parallel converter unit efficiency curve diagram

Load (%)	Start-stop logic	Efficiency of
			110％	Four working tables	≥96.5％
100％	Four working tables	≥97％
			75％	Three working tables	≥97％
50％	Two working machines	≥97％
			25％	One working table	≥97％

The characteristic of realizing the start-stop logic and the power distribution regulation in a power cooperation mode is that the overall efficiency of the parallel converter units is improved under the condition that the efficiency of the converter units is not changed. Because the annual generated energy of the offshore wind turbine is about 4000 hours, the operation time of the offshore wind turbine is longer in the low-power section, the efficiency curve of the low-power section of the whole converter is improved, and the generated energy of the offshore wind turbine can be effectively improved.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed.

Claims

1. A high-power converter circuit topological structure for offshore wind power is characterized by comprising a generator, a box transformer substation and a plurality of groups of converter units; the converter units are connected in parallel, the input end of each converter unit is connected with one winding of the stator of the generator, and the output end of each converter unit is connected with the box transformer substation; the converter unit comprises a machine side converter module and a network side converter module, wherein the machine side converter module and the network side converter module both adopt a midpoint clamping type three-level topological structure; the output power of the generator is matched with the number of groups of the converter units, and start-stop logic and power regulation distribution are realized in a power cooperation mode.

2. The circuit topology structure of the high-power converter for offshore wind power as recited in claim 1, wherein said machine side converter module and said grid side converter module both adopt a midpoint clamping type three-level topology structure of a low voltage insulated gate bipolar transistor.

3. The high-power converter circuit topology structure for offshore wind power as claimed in claim 2, wherein the working voltage of the converter unit is 950-1150V.

4. The high power converter circuit topology structure for offshore wind power, according to claim 3, wherein said low voltage IGBT has a voltage level of 1700V.

5. The circuit topology structure of the high-power converter for offshore wind power as claimed in claim 1, wherein the input end of the machine side converter module is connected with a machine side reactor (11), a stator isolating switch (10) and a generator stator winding in sequence; the output end of the network side current transformation module is sequentially connected with a network side reactor (18), a network side circuit breaker (19) and a box transformer substation; the output end of the machine side converter module is connected with the input end of the network side converter module, and a CHOPPER unit is arranged between the output end of the machine side converter module and the input end of the network side converter module.

6. A high power converter circuit topology for offshore wind power according to claim 5, characterized in that a first filtering unit is arranged between the machine side reactor (11) and the stator disconnector (10).

7. A high power converter circuit topology for offshore wind power according to claim 5, characterized in that a second filtering unit is provided between the grid side reactor (18) and the grid side breaker (19).

8. The high power converter circuit topology for offshore wind power as claimed in claim 5, wherein said converter units all use low voltage devices.