CN113725907A - Auxiliary power supply for power generation system and corresponding power generation system - Google Patents

Auxiliary power supply for power generation system and corresponding power generation system Download PDF

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Publication number
CN113725907A
CN113725907A CN202111019782.XA CN202111019782A CN113725907A CN 113725907 A CN113725907 A CN 113725907A CN 202111019782 A CN202111019782 A CN 202111019782A CN 113725907 A CN113725907 A CN 113725907A
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CN
China
Prior art keywords
power
sub
power supply
direct current
generation system
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Pending
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CN202111019782.XA
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Chinese (zh)
Inventor
张忻庾
温进
徐其惠
胡子晨
顾伟
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Envision Energy Co Ltd
Envision Energy Ltd
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Envision Energy Co Ltd
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Priority to CN202111019782.XA priority Critical patent/CN113725907A/en
Publication of CN113725907A publication Critical patent/CN113725907A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/345—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering using capacitors as storage or buffering devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H02J9/062—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems for AC powered loads
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J2207/50—Charging of capacitors, supercapacitors, ultra-capacitors or double layer capacitors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B10/00—Integration of renewable energy sources in buildings
    • Y02B10/70—Hybrid systems, e.g. uninterruptible or back-up power supplies integrating renewable energies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention relates to an auxiliary power supply for a power generation system, comprising: a first sub-power supply including one or more batteries to supply direct current power; a first DC/DC converter configured to convert the direct current power of the first sub power source into direct current power having different parameters, wherein an output terminal of the first DC/DC converter is connected to an output terminal of the auxiliary power source; a second sub-power supply comprising one or more super-capacitors to provide direct current power; and a second DC/DC converter configured to convert the direct-current power of the second sub power source into direct-current power having a different parameter, wherein an output terminal of the second DC/DC converter is connected to an output terminal of the auxiliary power source. The invention also relates to a power generation system and a method for operating an auxiliary power supply. The invention can better compensate the power fluctuation of the power generation system and can provide electric energy when the direct current bus is powered off.

Description

Auxiliary power supply for power generation system and corresponding power generation system
Technical Field
The present invention relates generally to the field of wind power generation, and more particularly to an auxiliary power supply for a power generation system. The invention further relates to a power generation system having such an auxiliary power supply.
Background
In recent years, with the increasing environmental importance of various countries, the field of clean energy has been rapidly developing. The clean energy is a novel energy, and has the advantages of wide distribution, reproducibility, small environmental pollution and the like compared with the traditional fossil fuel. Wind power generators are increasingly used as representatives of clean energy. In addition, in recent years, the advantages of power generation devices such as wind power generators which can be operated for a long period of time without human operation are becoming more prominent due to restrictions on the flow of people caused by new canopy epidemics and other invaluities.
Generators, such as wind generators (or simply wind turbines), have a number of important components that require power supply, such as pitch bearings, yaw bearings, and control circuitry. The stable power supply of these important components directly determines the normal operation and operational safety of the wind turbine. Typically, these components are powered by an ac power grid. However, in the event of a fault in the ac power supply system, these components must be supplied by an auxiliary power supply. However, current backup power supplies are difficult to accommodate for large power variations in the electrical load. In addition, generators such as wind generators, hydroelectric generators and solar cells are subject to natural conditions during normal operation, with large power fluctuations that negatively affect their load. Therefore, there is a need for an auxiliary power supply which has high reliability and can meet the power demand of a generator or the like under extreme conditions, especially when the power grid fails.
Disclosure of Invention
Starting from the prior art, the task of the invention is to provide an auxiliary power supply for a power generation system and a corresponding power generation system, wherein the auxiliary power supply and/or the power generation system can better compensate the power generation fluctuation of the power generation system and can provide electric energy when the power grid is powered off.
In a first aspect of the invention, the task is solved by an auxiliary power supply for a power generation system, comprising:
a first sub-power supply including one or more batteries to supply direct current power;
a first DC/DC converter configured to convert the direct current power of the first sub power source into direct current power having different parameters, wherein an output terminal of the first DC/DC converter is connected to an output terminal of the auxiliary power source;
a second sub-power supply comprising one or more super-capacitors to provide direct current power; and
a second DC/DC converter configured to convert the direct current power of the second sub power source into direct current power having a different parameter, wherein an output terminal of the second DC/DC converter is connected to an output terminal of the auxiliary power source.
Within the scope of the present invention, the term "alternating electrical energy" covers alternating current, alternating voltage and alternating power, and the term "direct electrical energy" covers direct current, direct voltage and direct power. The term "supercapacitor" refers to a supercapacitor that directly discharges the stored charge of the capacitor without electrochemical reaction. The term "AC/DC converter" encompasses various devices that convert AC electrical energy to DC electrical energy, such as diodes, half-wave rectifiers, full-wave rectifiers, thyristors, fully controlled bridges, and the like. The term "sub-power supply" refers to various electrical devices, such as batteries, generators, etc., capable of providing ac or dc electrical energy, wherein a sub-power supply refers in particular to a power supply outside the grid, i.e. a power supply which can be put into use under extreme conditions, in particular when the grid is powered down. In the present invention, the power generation system may cover various types of generators, especially new energy generators, such as wind generators, hydroelectric generators, solar cells, etc., and also other generators, such as fuel generators, for example, including: diesel generators, hydrogen generators, ethanol generators, fossil fuel generators, and the like.
In a preferred aspect of the invention, it is provided that the auxiliary power supply further comprises a controller configured to perform the following actions:
determining power parameters of a power generation system, wherein the power parameters comprise current power and target power; and
and determining the working modes of the first and second DC/DC converters according to the power parameters so as to access the first and/or second sub power supplies.
In a further preferred embodiment of the invention, it is provided that the auxiliary power supply further comprises:
an engine-side converter configured to convert the electrical energy generated by the generator into direct current electrical energy on a direct current grid; and
a grid converter configured to convert a direct current grid on a direct current grid to alternating current power on an alternating current grid.
Determining a voltage change rate according to the current power, the target power and the power regulation time;
the first DC/DC converter is controlled to operate in a forward mode to switch in the first sub power supply when the voltage change rate is less than the rate threshold, and the first and second DC/DC converters are controlled to operate in the forward mode to switch in the first and second sub power supplies when the voltage change rate is greater than or equal to the rate threshold.
In a preferred aspect of the invention, it is provided that the first and second DC/DC converters are bidirectional DC/DC converters, and that the controller is further configured to perform the following actions:
controlling the first and second DC/DC converters to work in a forward mode to switch in the first sub power supply and/or the second sub power supply when the current power is lower than a power threshold;
when the direct-current bus voltage is lower than a voltage threshold value, controlling the first and/or second DC/DC converter to work in a forward working mode so as to be connected into the first sub power supply and/or the second sub power supply; and
and controlling the first and/or DC/DC converter to work in a reverse operation mode to charge the first sub power supply and/or the second sub power supply when the voltage of the direct current bus is higher than the voltage threshold and the electric quantity of the first sub power supply and/or the second sub power supply is lower than the electric quantity threshold.
In a further preferred embodiment of the invention, it is provided that the power ratio of the first partial power source to the second partial power source is less than 100%, preferably less than 90%; and/or
The speed threshold is a direct current bus voltage change threshold a, and is determined by the following formula:
a＝λx dudtmaxwherein λ is a threshold coefficient, λ is 0 ≦ 1, and dudtmaxThe maximum voltage change rate of the direct current bus is as follows:
dudtmax＝idcmax/Cbuswherein idcmaxIs the maximum DC bus current, CbusAnd supporting the capacitance value of the capacitor for the bus.
λ is preferably 0.4 to 1.0, especially 0.6 to 0.8, where λ is 0.6 to 0.8, taking into account speed and voltage variation tolerance of other devices, makes fault ride-through fast and reliable.
The first sub power supply capacity is larger than the second sub power supply capacity; .
In a further preferred embodiment of the invention, it is provided that the output of the auxiliary power supply is connected to a dc bus of a power generation system, which dc bus is configured to transmit the electrical energy generated by the power generation system, wherein the power generation system comprises one of a wind power generation system, a solar cell and a hydro power generation system.
In a second aspect of the invention, the aforementioned task is solved by a power generation system comprising:
a direct current bus configured to transmit electric energy generated by the power generation system; and
an auxiliary power supply, comprising:
a first sub-power supply including one or more batteries to supply direct current power;
a first DC/DC converter configured to convert the direct current power of the first sub power source into direct current power having different parameters, wherein an output terminal of the first DC/DC converter is connected to an output terminal of the auxiliary power source;
a second sub-power supply comprising one or more super-capacitors to provide direct current power; and
a second DC/DC converter configured to convert the direct current power of the second sub power source into direct current power having different parameters, wherein an output terminal of the second DC/DC converter is connected to an output terminal of an auxiliary power source, wherein the output terminal of the auxiliary power source is connected to the direct current bus.
In one embodiment of the invention, it is provided that the power generation system further comprises:
an AC/DC converter connected to the DC bus, wherein the AC/DC converter is configured to convert AC power of the DC bus into DC power for charging the first sub power source and/or the second sub power source; and
a DC/AC converter configured to convert the direct current power transmitted on the bus bar into alternating current power to power an alternating current load connected at an output of the auxiliary power supply.
In a further embodiment of the invention, it is provided that the power generation system further comprises a controller, which is configured to carry out the following actions:
determining power parameters of a power generation system, wherein the power parameters comprise current power and target power; and
and determining the working modes of the first and second DC/DC converters according to the power parameters to access the first and/or second sub power sources, so that the output power of the power generation system is not lower than the target power.
In a third aspect of the invention, the aforementioned task is solved by a method for operating an auxiliary power supply according to the invention, comprising the following steps:
determining power parameters of a power generation system, wherein the power parameters comprise current power of the power generation system and target power of the power generation system; and
and when the power difference between the target power and the current power is larger than a power difference threshold value, accessing the first sub-power supply and/or the second sub-power supply, wherein the number of the accessed first sub-power supply and the second sub-power supply is determined according to the power difference.
In a preferred embodiment of the present invention, it is provided that the power parameter further includes a power adjustment time, and the method further includes:
determining a voltage change rate according to the current power, the target power and the power regulation time; and
the first sub-power supply is accessed when the rate of voltage change is less than a rate threshold, and the first sub-power supply and the second sub-power supply are accessed when the rate of voltage change is greater than or equal to the rate threshold.
The invention has at least the following beneficial effects: according to the invention, the direct-current auxiliary power supply formed by the battery pack and the super capacitor is connected to the direct-current bus of the power generation system, so that the power generation power of the power generation system can be compensated in real time, the power generation power is kept stable or reaches a certain power value within a specific time, and the auxiliary unit can also provide a standby power supply when the power generation system is powered off, so that the normal operation of a power utilization assembly of the power generation system is maintained; in addition, the storage energy of the battery pack is large, the power density of the super capacitor is large, and the response speed is high, so that the battery pack and the super capacitor are combined, compensation power which is long in time, high in response speed and large in power density can be provided for the power generation system, and the power output of the power generation system is optimized.
Drawings
The invention is further elucidated with reference to the drawings in conjunction with the detailed description.
Fig. 1 shows a schematic view of a wind power generator to which the present invention is applied;
FIG. 2 shows a circuit diagram of an auxiliary power supply according to the present invention; and
fig. 3 shows a flow of a method for operating an auxiliary power supply according to the invention.
Detailed Description
It should be noted that the components in the figures may be exaggerated and not necessarily to scale for illustrative purposes. In the figures, identical or functionally identical components are provided with the same reference symbols.
In the present invention, "disposed on …", "disposed over …" and "disposed over …" do not exclude the presence of an intermediate therebetween, unless otherwise specified. Further, "disposed on or above …" merely indicates the relative positional relationship between two components, and may also be converted to "disposed below or below …" and vice versa in certain cases, such as after reversing the product direction.
In the present invention, the embodiments are only intended to illustrate the aspects of the present invention, and should not be construed as limiting.
In the present invention, the terms "a" and "an" do not exclude the presence of a plurality of elements, unless otherwise specified.
In the present invention, the term "connected" may mean either directly connecting the two or indirectly connecting the two through an intermediate member.
It is further noted herein that in embodiments of the present invention, only a portion of the components or assemblies may be shown for clarity and simplicity, but those of ordinary skill in the art will appreciate that, given the teachings of the present invention, required components or assemblies may be added as needed in a particular scenario. Furthermore, features from different embodiments of the invention may be combined with each other, unless otherwise indicated. For example, a feature of the second embodiment may be substituted for a corresponding or functionally equivalent or similar feature of the first embodiment, and the resulting embodiments are likewise within the scope of the disclosure or recitation of the present application.
It is also noted herein that, within the scope of the present invention, the terms "same", "equal", and the like do not mean that the two values are absolutely equal, but allow some reasonable error, that is, the terms also encompass "substantially the same", "substantially equal". By analogy, in the present invention, the terms "perpendicular", "parallel" and the like in the directions of the tables also cover the meanings of "substantially perpendicular", "substantially parallel".
The numbering of the steps of the methods of the present invention does not limit the order of execution of the steps of the methods. Unless specifically stated, the method steps may be performed in a different order.
The principle on which the invention is based is first elucidated. The present inventors found through long-term research in the field of new energy generators that, in a power generation scenario of a generator such as a wind power generator, a hydroelectric generator, a solar cell, the generated power of the generator may fluctuate drastically, e.g., its power may have a very low power level for a certain period of time, which may cause a reduction in power factor or damage to a connected load, due to factors such as weather; the inventor finds out through research that under extreme conditions, especially when a power grid is powered off, the standby power supply also needs to take account of both the average power and the peak power of the load, otherwise, the load can not work normally and even fails; the inventor finds that a direct-current standby power supply such as a battery has high stored energy and parallel capacity expansion capacity (unlimited parallel battery capacity expansion), but the power density and the response speed of the direct-current standby power supply cannot meet the power compensation and fault ride-through requirements of a power generation system, and a super capacitor has the characteristics of high power density and high response speed, so that the battery pack and the super capacitor are combined, compensation power with long time, high response speed and high power density can be provided for the power generation system, and the power output of the power generation system is optimized; at the same time, the combination of the battery pack and the super capacitor is also adapted to provide peak power to a load to which the power generation system is connected. Furthermore, the inventors have found that switching from battery to supercapacitor or battery + supercapacitor is achieved by a reasonable setting of the voltage change rate threshold, so that output power transients are better achieved at a defined speed. In addition, the inventor reasonably sets a circuit structure, so that the battery pack and the super capacitor can be charged from the direct current bus when not in use, and therefore the ready availability of the auxiliary power supply is achieved. The invention has at least the following advantages:
1. an auxiliary power supply: the energy storage battery pack, the bidirectional DCDC converter, the super capacitor and the bidirectional DCDC converter form an auxiliary power supply, and a plurality of groups of auxiliary power supplies are connected to a direct-current bus of the wind power frequency converter in parallel, so that the low starting speed of the diesel generator and the switching failure risk are avoided;
2. by utilizing the characteristics of quick response and ultrahigh power density of the super capacitor and the bidirectional DCDC converter, the bus voltage is supported during the fault ride-through period of the fan, and the performance of the fan is stabilized;
3. in a normal power generation state, the power output of the smooth fan can be stabilized by controlling the charging and discharging of the battery, and the power generation efficiency and controllability of the fan are improved.
The invention is further elucidated with reference to the drawings in conjunction with the detailed description.
Fig. 1 shows a schematic view of a wind turbine 100 to which the present invention is applied. The wind turbine 100 shown in FIG. 1 includes a tower 101, a nacelle 102 rotatably connected to the tower 101 and supporting a hub 103. Two or more blades 104 are arranged on the hub 103, wherein the blades 104, under the influence of wind, rotate a rotor (not shown) arranged in the hub 108 around an axis (not shown), wherein rotation of the rotor of the generator relative to the stator will generate electrical energy. Wind turbine 100 may include a variety of loads that consume electrical energy, such as pitch bearings, yaw bearings, and control circuitry, among others. It should be noted that although the present invention is illustrated with respect to a wind power generator, the present invention is not limited thereto but is applicable to other power generators such as a wind power generator, a hydro power generator, a solar cell, and the like. The electric energy generated by the wind power generator 100 is transmitted through a direct current bus after being subjected to frequency conversion or current conversion or voltage conversion. However, due to bad weather or wind changes, the power of the energy transmitted on the dc bus varies and therefore needs to be compensated by the auxiliary power supply of the present invention.
Fig. 2 shows a circuit diagram of an auxiliary power supply 200 for a power generation system 209 according to the invention. The power generation system 209 is, for example, a wind power generator, and transmits the generated electrical energy on its dc bus 208. The output OUT of the auxiliary power supply 200 of the present invention is connected to the dc bus 208 to provide the compensation power and is charged from the dc bus. The auxiliary power supply 200 according to the present invention includes the following components, some of which are optional:
a first sub-power supply 201 comprising one or more batteries to provide direct current power, including, for example, direct current, direct voltage, and direct current power. Here, the first sub power supply 201 includes a plurality of battery packs connected in parallel with each other and each including a plurality of batteries connected in series with each other, thereby providing a plurality of times of cell voltages and cell currents. The number of batteries connected in parallel or in series may be arbitrary, and may be determined, for example, according to the value of the current power or the target power.
A first DC/DC converter 203 configured to convert the direct current electrical energy of the first sub-power supply 201 into direct current electrical energy having different parameters (e.g. current, voltage), wherein an output of the first DC/DC converter 203 is connected to an output OUT of the auxiliary power supply 200 through an optional first switch 205. The first switch 205 is optional and not required. The first DC/DC converter 203 is particularly a bidirectional DC/DC converter, in which the bidirectional DC/DC converter is configured to be able to input the DC power from the input terminal of the bidirectional DC/DC converter (forward operation) and output the converted DC power at the output terminal, or to be able to input the DC power from the output terminal of the bidirectional DC/DC converter and output the converted DC power at the input terminal (reverse operation). For example, when the first DC/DC converter 203 is operating in the forward direction, the first sub power source 201 supplies electric energy to the current bus 208 to compensate the power of the power generation system 209; when the first DC/DC converter 203 operates in reverse, the first sub power supply 201 is supplied with power from the DC bus 208 to charge the first sub power supply 201. The batteries of the first sub-power supply 201 are in particular rechargeable batteries, for example lithium ion batteries.
A second sub-power source 202 comprising one or more super-capacitors to provide direct current power, including, for example, direct current, direct voltage, and direct current power. In the present invention, the term "supercapacitor" refers to a supercapacitor that directly discharges a stored charge of a capacitor without electrochemical reaction. A supercapacitor, for example, has two electrodes and an electrolyte between the two electrodes. The capacitance value of the super capacitor is, for example, in the range of several tens to several hundreds of farads (F), e.g., 1-10F, 100-1000F. The second sub power supply 202 may preferably provide a higher power density and response speed than the first sub power supply 204, starting with a large amount of power provided in a short time. The first sub power supply 204 may preferably provide a greater stored energy than the second sub power supply 202, starting with providing power, e.g. average power, for a longer period of time.
A second DC/DC converter 204 configured to convert the DC power of the second sub power source 202 into DC power having different parameters (e.g., current, voltage), wherein an output terminal of the second DC/DC converter 202 is connected to the output terminal OUT of the auxiliary power source through a second switch (not shown). The second switch is optional and not necessary. The second DC/DC converter 204 is particularly a bidirectional DC/DC converter, in which the bidirectional DC/DC converter can either input the DC power from the input terminal of the bidirectional DC/DC converter (forward operation) and output the converted DC power at the output terminal, or input the DC power from the output terminal of the bidirectional DC/DC converter and output the converted DC power at the input terminal (reverse operation). For example, when the second DC/DC converter 204 is operating in the forward direction, the second sub power source 202 supplies electric energy to the current bus 208 to compensate the power of the power generation system 209; when the first DC/DC converter 203 operates in reverse, the second subsidiary power supply 202 is supplied with power from the DC bus 208 to charge the second subsidiary power supply 202.
Optional grid-side converter 206, optional machine-side converter 207 and auxiliary transformer 207, wherein grid-side converter 206 is configured to convert the dc electrical energy transmitted on dc bus 208 into ac electrical energy, and auxiliary transformer 207 is configured to transform the converted ac electrical energy for transmission to a load; the machine side converter 207 is configured to convert ac power generated by the generator of the power generation system into dc power (which is transmitted through the dc bus 208). That is, the electrical energy (e.g. ac or dc) of the generator is converted into dc electrical energy on the dc bus by the generator-side converter 207, and the dc electrical energy on the dc bus is converted into ac electrical energy on the ac grid 210 by the grid converter 206, optionally with voltage conversion by the auxiliary transformer 207.
An optional controller (not shown), wherein the controller is configured to perform the following actions:
determining power parameters of the power generation system, the power parameters including a current power, a target power, and optionally a power change time.
Determining an operation mode of the first and second DC/DC converters to switch in the first and/or second sub power sources according to the power parameter such that the output power of the power generation system is not lower than the target power. For example, a voltage change rate is determined from the current power, the target power, and the power adjustment time, and the first sub-power supply is accessed when the voltage change rate is less than a rate threshold, and the first sub-power supply and the second sub-power supply are accessed when the voltage change rate is greater than or equal to the rate threshold. The rate threshold is determined by an equation that can be:
the speed threshold is a direct current bus voltage change threshold a, and is determined by the following formula:
a＝λx dudtmaxwherein λ is a threshold coefficient, λ is 0 ≦ 1, and dudtmaxThe maximum voltage change rate of the direct current bus is as follows:
dudtmax＝idcmax/Cbuswherein idcmaxIs the maximum DC bus current, CbusAnd supporting the capacitance value of the capacitor for the bus.
The access sub-supply accesses the first sub-supply and/or the second sub-supply when the grid voltage is above a voltage threshold and the dc bus voltage change is above a ripple threshold.
The first partial source and/or the second partial source are switched in when the dc bus voltage is below a voltage threshold (for example, when the ac mains is switched off).
And charging the first sub power supply and/or the second sub power supply when the voltage of the dc bus is higher than the voltage threshold and the power of the first sub power supply and/or the second sub power supply is lower than the power threshold.
The operation of the auxiliary power supply 200 is explained below.
Normal mode of power generation system
The first switch 205 is open or not connected to the first and second sub-sources when the power generation system 209 is operating normally. The electrical energy generated by the power generation system 209 is transferred by conversion to an ac power grid 210.
Charging mode
When the DC bus voltage is normal and the first or second sub power source 201 and/or 202 needs to be charged (for example, the charge amount thereof is lower than the charge amount threshold), the first switch 205 is closed, and the first DC/DC converter 203 and/or the second DC/DC converter 204 operates in the reverse mode, so that the first or second sub power source 201 and/or 202 is charged from the DC bus. When charging is not required, the first switch 205 may be opened. This reverse charging allows the sub-power supply to be charged at all times and to be available at all times.
Discharge mode
Under extreme conditions, in particular when the power generation system is not stable in power or when the ac grid is not able to supply power, the first switch 205 is closed to switch in the first sub power source 201 and/or the second sub power source 202. When the required power conversion speed is less than or equal to the speed threshold, only the first sub power supply 201 may be accessed. Both the first and second sub-power supplies 201 and 202 may be accessed when the required power conversion speed is greater than a rate threshold.
The method of operating the auxiliary power supply of the present invention is described below by way of example of an offshore wind turbine.
The application of the typhoon-resistant yaw backup power supply of the offshore wind power generator is as follows:
when the offshore wind driven generator is in a condition of power failure of a typhoon power grid, the auxiliary power supply system is switched to drive the yaw system to normally operate, the load of the whole wind driven generator is reduced, and the reliability of the offshore wind driven generator set is greatly improved. The starting and stopping states of the backup power supply are as follows:
1) starting and operating: the method comprises the steps that an alternating current power grid is electrified, a wind power frequency converter is normally closed and soft started to pre-charge bus voltage Udc, an inverter power supply is automatically started to supply power to a control system after the Udc is established, the control system is electrified and started to control a direct current contactor to be connected with a direct current bus and a backup power supply in a closed mode, the bus voltage establishing process is completed, a yaw system normally performs yaw operation along with a main control instruction, a bidirectional DCDC converter is charged according to super-junction capacitance/battery voltage, a hysteresis control mode can be adopted, and repeated charging is avoided.
2) Switching a backup power supply when the power grid is down: when the alternating current power grid is powered off and the Udc is reduced to a starting discharge threshold value of the bidirectional DCDC converter, the super capacitor/battery and the bidirectional DCDC converter supply power to the bus, and the power is supplied to a control system, a yaw system and the like through the transformation of the grid-side inverter and the transformation of the auxiliary transformer, so that the automatic switching function of the power grid and the backup power supply is completed.
3) Power-off: and (3) the alternating current power grid is powered off, the discharging function of the bidirectional DCDC converter is stopped at the same time, the DC loop switch is disconnected, the system is powered off, and the backup power supply is noticed to be still powered on.
Fig. 3 shows a flow of a method for operating an auxiliary power supply according to the invention, wherein the dashed boxes show optional steps.
In step 301, power parameters of the power generation system are determined, the power parameters including a current power of the power generation system and a target power of the power generation system.
In step 302, when the power difference between the target power and the current power is larger than the power difference threshold, the first sub power source and/or the second sub power source are/is accessed, wherein the number of the accessed first sub power source and the second sub power source is determined according to the power difference.
In optional step 303, a voltage rate of change is determined based on the current power, the target power, and the power adjustment time.
In optional step 304, the first sub-power supply is accessed when the rate of voltage change is less than the rate threshold, and the first sub-power supply and the second sub-power supply are accessed when the rate of voltage change is greater than or equal to the rate threshold.
Although some embodiments of the present invention have been described herein, those skilled in the art will appreciate that they have been presented by way of example only. Numerous variations, substitutions and modifications will occur to those skilled in the art in light of the teachings of the present invention without departing from the scope thereof. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims (12)

1. An auxiliary power supply for a power generation system, comprising:
a first sub-power supply including one or more batteries to supply direct current power;
a first DC/DC converter configured to convert the direct current power of the first sub power source into direct current power having different parameters, wherein an output terminal of the first DC/DC converter is connected to an output terminal of the auxiliary power source;
a second sub-power supply comprising one or more super-capacitors to provide direct current power; and
a second DC/DC converter configured to convert the direct current power of the second sub power source into direct current power having a different parameter, wherein an output terminal of the second DC/DC converter is connected to an output terminal of the auxiliary power source.
2. The auxiliary power supply of claim 1, further comprising a controller configured to perform the following acts:
determining power parameters of a power generation system, wherein the power parameters comprise current power and target power; and
and determining the working modes of the first and second DC/DC converters according to the power parameters so as to access the first and/or second sub power supplies.
3. The auxiliary power supply of claim 2, further comprising:
an engine-side converter configured to convert the electrical energy generated by the generator into direct current electrical energy on a direct current grid; and
a grid converter configured to convert a direct current grid on a direct current grid to alternating current power on an alternating current grid.
4. The auxiliary power supply of claim 2, wherein the power parameter further comprises a power adjustment time, wherein the controller is further configured to perform the following acts:
determining a voltage change rate according to the current power, the target power and the power regulation time;
the first DC/DC converter is controlled to operate in a forward mode to switch in the first sub power supply when the voltage change rate is less than the rate threshold, and the first and second DC/DC converters are controlled to operate in the forward mode to switch in the first and second sub power supplies when the voltage change rate is greater than or equal to the rate threshold.
5. The auxiliary power supply of claim 3, wherein the first and second DC/DC converters are bi-directional DC/DC converters, and the controller is further configured to perform the following acts:
controlling the first and second DC/DC converters to work in a forward mode to switch in the first sub power supply and/or the second sub power supply when the current power is lower than a power threshold;
when the direct-current bus voltage is lower than a voltage threshold value, controlling the first and/or second DC/DC converter to work in a forward working mode so as to be connected into the first sub power supply and/or the second sub power supply; and
and controlling the first and/or DC/DC converter to work in a reverse operation mode to charge the first sub power supply and/or the second sub power supply when the voltage of the direct current bus is higher than the voltage threshold and the electric quantity of the first sub power supply and/or the second sub power supply is lower than the electric quantity threshold.
6. The auxiliary power supply of claim 4 or 5, wherein the power ratio of the first sub-power supply to the second sub-power supply is less than 100%; and/or
The speed threshold is a direct current bus voltage change threshold a, and is determined by the following formula:
a＝λx dudtmaxwherein λ is a threshold coefficient, λ is 0 ≦ 1, and dudtmaxThe maximum voltage change rate of the direct current bus is as follows:
dudtmax＝idcmax/Cbuswherein idcmaxIs the maximum DC bus current, CbusAnd supporting the capacitance value of the capacitor for the bus.
7. The auxiliary power source of claim 3, wherein an output of the auxiliary power source is connected to a DC bus of a power generation system, the DC bus configured to transmit electrical energy generated by the power generation system, wherein the power generation system comprises one of a wind power generation system, a solar cell, and a hydro power generation system.
8. A power generation system, comprising:
a direct current bus configured to transmit electric energy generated by the power generation system; and
an auxiliary power supply, comprising:
a first sub-power supply including one or more batteries to supply direct current power;
a first DC/DC converter configured to convert the direct current power of the first sub power source into direct current power having different parameters, wherein an output terminal of the first DC/DC converter is connected to an output terminal of the auxiliary power source;
a second sub-power supply comprising one or more super-capacitors to provide direct current power; and
a second DC/DC converter configured to convert the direct current power of the second sub power source into direct current power having different parameters, wherein an output terminal of the second DC/DC converter is connected to an output terminal of an auxiliary power source, wherein the output terminal of the auxiliary power source is connected to the direct current bus.
9. The power generation system of claim 8, further comprising:
an AC/DC converter connected to the DC bus, wherein the AC/DC converter is configured to convert AC power of the DC bus into DC power for charging the first sub power source and/or the second sub power source; and
a DC/AC converter configured to convert the direct current power transmitted on the bus bar into alternating current power to power an alternating current load connected at an output of the auxiliary power supply.
10. The power generation system of claim 9, further comprising a controller configured to perform the following acts:
determining power parameters of a power generation system, wherein the power parameters comprise current power and target power; and
and determining the working modes of the first and second DC/DC converters according to the power parameters to access the first and/or second sub power sources, so that the output power of the power generation system is not lower than the target power.
11. Method for operating an auxiliary power supply according to one of claims 1 to 7, comprising the following steps:
determining power parameters of a power generation system, wherein the power parameters comprise current power of the power generation system and target power of the power generation system; and
and when the power difference between the target power and the current power is larger than a power difference threshold value, accessing the first sub-power supply and/or the second sub-power supply, wherein the number of the accessed first sub-power supply and the second sub-power supply is determined according to the power difference.
12. The method of claim 11, wherein the power parameter further comprises a power adjustment time, the method further comprising:
determining a voltage change rate according to the current power, the target power and the power regulation time; and
the first sub-power supply is accessed when the rate of voltage change is less than a rate threshold, and the first sub-power supply and the second sub-power supply are accessed when the rate of voltage change is greater than or equal to the rate threshold.
CN202111019782.XA 2021-09-01 2021-09-01 Auxiliary power supply for power generation system and corresponding power generation system Pending CN113725907A (en)

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