CN113852186A

CN113852186A - A backup power supply of a power generation system and its operation method

Info

Publication number: CN113852186A
Application number: CN202111154203.2A
Authority: CN
Inventors: 张忻庾; 温进; 徐其惠; 胡子晨; 顾伟
Original assignee: Envision Energy Co Ltd
Current assignee: Far East Energy Technology Plc
Priority date: 2021-09-29
Filing date: 2021-09-29
Publication date: 2021-12-28

Abstract

The invention discloses a backup power supply of a power generation system, comprising one or more parallel sub-power supplies and a DC/DC converter. Wherein, each sub-power source includes one or more batteries to provide DC power; and the DC/DC converter is used to convert the DC power of the sub-power source into DC power with different parameters, wherein the output end of the DC/DC converter is connected to the backup The output of the power supply.

Description

Backup power supply of power generation system and operation method thereof

Technical Field

The invention relates to the technical field of wind power generation, in particular to a backup power supply of a power generation system and an operation method thereof.

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 with power from a backup power supply. However, current backup power supplies are difficult to accommodate large power variations of the powered 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.

Disclosure of Invention

Based on part or all of the problems in the prior art, the invention provides a backup power supply which has high reliability and can adapt to the requirements of large power generation power change of a generator and the like and power utilization under extreme conditions, particularly power failure of a power grid, so as to better compensate the power generation fluctuation of a power generation system and provide electric energy when the power grid fails. A backup power source for a power generation system, comprising:

one or more sub-power supplies comprising one or more batteries to provide direct current power; and

a DC/DC converter configured to convert the direct current power of the sub power source into direct current power having different parameters, wherein an output terminal of the DC/DC converter is connected to an output terminal of the backup power source.

Further, the backup power supply further comprises:

a first switch through which an output terminal of the DC/DC converter is connected to an output terminal of a backup power source.

Further, the DC/DC converter is a bidirectional DC/DC converter.

Further, the backup power supply further comprises a frequency converter, including:

the input end of the rectification module is connected with an alternating current power grid and used for converting alternating current electric energy into direct current electric energy;

the input end of the filtering module is connected with the output end of the rectifying module; and

and the input end of the inversion module is connected with the output end of the filtering module and is used for converting the direct current electric energy into the alternating current electric energy.

Further, the backup power supply further comprises a second switch, and an alternating current power grid is connected to the input end of the rectification module through the second switch.

Further, the first switch and/or the second switch comprises one of: power switches, circuit breakers, contactors, and relays.

Further, the inverter module comprises one or more DC/AC converters, the output of which is connected to a control system and/or a load.

Further, the backup power supply further comprises a controller for:

when the voltage of the alternating current power grid connected through the second switch is detected to be lower than a voltage threshold value, the first switch is closed to connect the sub power supply, and the DC/DC converter works in a forward direction to enable the sub power supply to discharge.

Further, the controller is further configured to:

and when the voltage of the alternating current power grid accessed through the second switch is detected to be higher than the voltage threshold and the electric quantity of the sub-power supply is detected to be lower than the electric quantity threshold, the first switch is closed, and the DC/DC converter works reversely, so that the sub-power supply is charged from the alternating current power grid.

In another aspect of the present invention, there is provided a method for operating the backup power supply, including:

determining the grid voltage of the alternating current grid accessed through the second switch;

when the grid voltage is lower than a voltage threshold, closing a first switch to access a sub power supply so that the sub power supply supplies power; and

when the grid voltage is above the voltage threshold and the charge of the sub-power supply is below the charge threshold, the first switch is closed, wherein the DC/DC converter operates in reverse, so that the sub-power supply is charged from the alternating current grid.

Furthermore, the invention relates to a wind power generator with a backup power supply according to the invention, wherein the load connected at the output of the backup power supply comprises one or more of the following: yaw bearing, change oar bearing, and control circuit. Other loads are also contemplated. For example, in the case of a photovoltaic device, the load may be a photovoltaic control circuit, or an active device in the photovoltaic device, or the like.

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 invention has at least the following beneficial effects: the inventor of the invention finds that a direct current backup power source such as a fuel cell has higher response speed, parallel capacity expansion capability and high power density, so that the direct current backup power source can be used as the direct current backup power source to supply electric energy to a load to provide peak power when the power requirement of the load is higher. In addition, the circuit structure is reasonably arranged, so that the backup power supply can be charged from an alternating current power grid when not used, and the availability of the backup power supply at any time is realized. Furthermore, the inventors have unexpectedly found that, with the circuit arrangement of the present invention, the load is connected to the ac power grid through the converter (rectifier, inverter), and thus the load and the preceding grid transformer are isolated from each other, so that the power-consuming unit, i.e., the load, is converted by the converter and then connected to the dc bus, thereby improving the system efficiency of the backup power supply and reducing the operation and maintenance costs and hardware investment.

Drawings

To further clarify the above and other advantages and features of embodiments of the present invention, a more particular description of embodiments of the present invention will be rendered by reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings, the same or corresponding parts will be denoted by the same or similar reference numerals for clarity.

Fig. 1 shows a schematic structural view of a wind power generator to which the present invention is applied;

FIG. 2 is a schematic diagram of a backup power source for a power generation system according to an embodiment of the present invention; and

fig. 3 is a flow chart illustrating a method of operating a backup power source of a power generation system according to an embodiment of the present invention.

Detailed Description

In the following description, the present invention is described with reference to examples. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of the specific details, or with other alternative and/or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. Similarly, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the embodiments of the invention. However, the invention is not limited to these specific details. Further, it should be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

Reference in the specification to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

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 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 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.

Furthermore, it should be noted that the invention is not only applicable in the field of wind generators, but also in other fields with electrical loads, such as in the photovoltaic field (for example, for powering components such as control circuits of photovoltaics with the backup power supply of the invention), in the field of meteorological equipment, in lighting installations, and so on.

In the invention, the output end of the backup power supply, the output end of the rectification module and the input end of the inversion module are connected to the direct current bus of the frequency converter.

The principle on which the invention is based is first elucidated. The inventor discovers through long-term research in the field of wind power generators that in the power utilization scene of a wind turbine, due to the influences of wind power, regulation speed, mechanical resistance and other factors, the power of power utilization loads such as a pitch bearing and a yaw bearing can have an instantaneous or short-time jump on the basis of average power, namely peak power can occur, so that under extreme conditions, particularly when a power grid is powered off, a backup power supply needs to be capable of providing instantaneous peak power, otherwise, the situation that the load cannot normally work or even fails can occur; through further research, the inventor finds that a direct-current standby power supply such as a fuel cell has higher response speed (connection, namely power supply), parallel capacity expansion capacity (unlimited parallel battery capacity expansion) and high power density, and is therefore suitable for providing peak power for a load. In addition, the inventor can charge from the alternating current power grid when the backup power supply is not used through reasonably setting a circuit structure, so that the backup power supply can be available at any time. Furthermore, the present inventors have unexpectedly found that, by the circuit arrangement of the present invention, the load is connected to the ac power grid through the converter (rectifier, inverter), and thus the load and the preceding grid transformer are isolated from each other, so that the power-consuming unit, i.e., the load, is converted by the converter and then connected to the dc bus, thereby improving the system efficiency of the backup power supply and reducing the operation and maintenance costs and hardware investment.

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. Normally, the loads of wind turbine 100 are supplied by the ac grid, but in the event of a fault or power outage in the ac grid, a backup power source is required to power these loads, which otherwise would not be operational.

Fig. 2 is a schematic diagram illustrating a backup power source of a power generation system according to an embodiment of the present invention. As shown in fig. 2, the backup power source includes a sub power source 201 and a frequency converter 202.

The sub-power supply 201 is used to provide dc power, which includes, for example, dc current, dc voltage, and dc power. The sub-power supply 201 is connected to the input of a DC-to-DC/DC converter 211 or directly to the output OUT of the backup power supply without a DC/DC converter. In the embodiment of the present invention, a single or more sub power sources 201 may be provided, which are connected in series with the corresponding DC/DC converter 211 and then connected in parallel with each other, and in the embodiment of the present invention, the number of sub power sources connected in parallel may be adjusted according to, for example, the value of the peak power, etc., to achieve the capacity expansion or other requirements. In one embodiment of the present invention, the sub-power supply 201 is a plurality of batteries (e.g., fuel cells or other batteries) connected in series with each other, which may provide multiple times the battery voltage. In other embodiments, the sub-power source 201 may also be a plurality of batteries (e.g., fuel cells or other batteries) connected in parallel to each other to provide multiple times of battery current. The number of cells connected in parallel or in series may be arbitrary, and may be determined, for example, based on the values of the average power and the peak power.

The DC/DC converter 211 is used to convert the DC power inputted from the sub power supply 201 into DC power having different parameters, wherein an output terminal of the DC/DC converter is connected to an output terminal OUT of the backup power supply through a first switch 212. The first switch 212 may be, for example, a power switch, a circuit breaker, a contactor, or a relay. For example, the DC/DC converter 211 converts the input DC power into DC power having different current or voltage values, which may be determined according to the required power or rated current or rated voltage of the load. In an embodiment of the present invention, a single or more DC/DC converters 211 may be provided, which are connected in series with the respective sub power sources 201 and then connected in parallel with each other. The DC/DC converter 211 is preferably a bidirectional DC/DC converter that can output the converted direct-current power from an input terminal of the bidirectional DC/DC converter (forward operation) and output the converted direct-current power at an output terminal, or can input the direct-current power from an output terminal of the bidirectional DC/DC converter and output the converted direct-current power at an input terminal (reverse operation).

The frequency converter 202 includes a rectifying module 221, a filtering module 222, and an inverting module 223.

The rectifier module 221 is configured to convert ac power into dc power, where an output terminal of the rectifier module 221 is connected to an output terminal OUT of the backup power, and an input terminal of the rectifier module is connected to an ac power grid. In one embodiment of the invention, the input of the rectification module 221 is connected to the ac grid through a second switch 224. The second switch 224 may be, for example, a power switch, a circuit breaker, a contactor, or a relay. By corresponding control, the ac power network 203 can supply both the load and the sub-power supply.

In the present invention, the rectification module 221 may include various devices for converting ac power into dc power, such as diodes, half-wave rectifiers, full-wave rectifiers, thyristors, full-controlled bridges, and so on.

The input end of the filtering module 222 is connected to the output end of the rectifying module 221, and the output end is connected to the input end of the inverting module 223, which is mainly used for suppressing high-frequency noise/harmonic in the electric energy input from the power grid or the sub-power supply, and also absorbing reactive current of inductive loads in the circuit. In an embodiment of the present invention, the filtering module may include a filtering circuit structure commonly used in the art, such as an RC filtering circuit, for example, as shown in the figure, the filtering module 222 includes a capacitor 2221 connected between two input terminals of the inverting module 223 and a resistor 2222 connected between the rectifying module 221 and the inverting module 222, and a third switch 2223 may be further connected in parallel to the resistor 2222.

The inverter module 223 is configured to convert the dc power to ac power to power a load and/or a control system. The input terminal of the inverter module 223 is connected to the output terminal OUT of the backup power source, and the output terminal of the inverter module 223 is connected to a load. The inverter module 223 includes one or more DC/AC converters operating in parallel to supply different AC loads, respectively. Here, the AC loads are, for example, the yaw motor 204 and the control system 205, and the DC/AC converter may be driven one-to-many or one-to-one.

For better power switching, in one embodiment of the invention, the backup power supply further comprises a controller (not shown in the figure). The controller is used for controlling the charging and discharging of the sub power supply 201. Specifically, it is configured to detect the voltage of the ac power grid 203 connected through the second switch 224, and compare the voltage with a voltage threshold, so as to control the operating state of the sub power supply 201:

when detecting that the voltage of the alternating current power grid 203 accessed through the second switch 224 is lower than a voltage threshold (for example, during power failure), closing the first switch 212 to access the sub power supply 201, and controlling the DC/DC converter 211 to work in the forward direction, so that the sub power supply 201 discharges; and

when it is detected that the voltage of the ac power grid 203 accessed through the second switch 224 is higher than the voltage threshold and the power of the sub power source 201 is lower than the power threshold, the first switch 212 is closed and the DC/DC converter 211 is controlled to operate in reverse, so that the sub power source 201 is charged from the ac power grid 203.

The working flow of the backup power according to the invention is explained below.

Grid normal mode

When the alternating current power grid 203 supplies power normally, the second switch 224 is closed, so that the alternating current power of the alternating current power grid 203 supplies power to the alternating current load 204 after being rectified by the rectifying module 221 and inverted by the inverting module 223. Therefore, the alternating current load 204 and the alternating current power grid 203 can be isolated from each other through the converter, harmful electric signals such as higher harmonics and noise generated by a superior transformer are eliminated, and the alternating current load 204 is prevented from being damaged.

Charging mode

When the ac power grid 203 is normally powered and the sub power source 201 needs to be charged (e.g., the amount of power thereof is below the power threshold), the first switch 212 is closed, and the DC/DC converter 211 operates in the reverse mode, so that the sub power source 201 is charged from the ac power grid 203. When charging is not required, the first switch 212 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

In extreme conditions, in particular when the ac power supply system is switched off, i.e. when the ac power supply system 203 is not available, the first switch 212 is closed to access the sub-power supply 201.

The method of operating the backup power supply of the present invention is described below using an offshore wind turbine as an example.

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 power failure condition of a typhoon power grid, the backup power supply can be 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 startup and shutdown states of the backup power supply are as follows:

1) starting and operating: the method comprises the steps that an offshore wind turbine 400Vac is powered on, a frequency converter is normally closed and soft started to precharge 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 controls a direct current contactor to be closed after being powered on and started to complete the bus voltage establishing process, then the yaw system normally runs in a yaw mode along with a main control instruction, a bidirectional DCDC converter charges according to the voltage of a battery, and a hysteresis control mode can be adopted to avoid repeated charging of the battery.

2) Switching a backup power supply when the power grid is down: when the 400Vac is powered off, the circuit breaker is disconnected after the power grid, and the Udc is reduced to the starting discharge threshold of the bidirectional DCDC converter, the battery and the bidirectional DCDC converter supply power to the bus, and the automatic switching function of the power grid and the backup power supply is completed.

3) Power-off: and (4) 400Vac is powered off, the discharging function of the bidirectional DCDC converter is stopped, the DC loop switch is disconnected, the system is powered off, and the backup power supply is still powered.

Fig. 3 is a flow chart illustrating a method of operating a backup power source of a power generation system according to an embodiment of the present invention. As shown in fig. 3, the method for operating the backup power supply includes:

first, in step 301, the grid voltage is determined. The network voltage of the ac network connected via the second switch is determined. For example, the grid voltage may be measured by a voltage sensor, a voltmeter.

Next, in step 302, the sub power source is discharged. When the grid voltage is lower than a voltage threshold value, closing a first switch to access the sub power supply so that the sub power supply is powered, wherein the DC/DC converter works in a forward direction so that the sub power supply is discharged; and

finally, in step 303, the sub-power supply is charged. When the grid voltage is above the voltage threshold and the charge of the sub-power supply is below the charge threshold, the first switch is closed, wherein the DC/DC converter operates in reverse, so that the sub-power supply is charged from the alternating current grid.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various combinations, modifications, and changes can be made thereto without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention disclosed herein should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A backup power supply of a power generation system, characterized in that, comprising:

one or more parallel sub-power sources, wherein each sub-power source includes one or more batteries to provide DC power; and

The DC/DC converter is configured to be able to convert the direct current power of the sub power supply into direct current power with different parameters, wherein the output terminal of the DC/DC converter is connected to the output terminal of the backup power supply.

2. backup power supply as claimed in claim 1, is characterized in that, also comprises:

A first switch, the output end of the DC/DC converter is connected to the output end of the backup power supply through the first switch.

3. The backup power supply according to claim 2, wherein the DC/DC converter is a bidirectional DC/DC converter.

4. backup power supply as claimed in claim 2, is characterized in that, also comprises frequency converter, it comprises:

a rectifier module, the input end of which is connected to the AC power grid, and is configured to be able to convert the AC electrical energy into the DC electrical energy;

a filter module, the input end of which is connected to the output end of the rectifier module; and

The inverter module, whose input end is connected with the output end of the filtering module, is configured to be able to convert direct current electric energy into alternating current electric energy.

5 . The backup power supply according to claim 4 , further comprising a second switch, and the AC grid is connected to the input end of the rectifier module through the second switch. 6 .

6. The backup power supply of claim 5, wherein the first switch and/or the second switch comprises one of the following: a power switch, a circuit breaker, a contactor, and a relay.

7. The backup power supply according to claim 4, wherein the inverter module comprises one or more DC/AC converters, and the output ends of the one or more DC/AC converters are connected to the control system and/or load.

8. The backup power supply of claim 5, further comprising a controller configured to perform the following actions:

When it is detected that the voltage of the AC grid connected through the second switch is lower than the voltage threshold, the first switch is closed to connect the sub-power supply, and the DC/DC converter is controlled to work in the forward direction, so that the sub-power supply discharges .

9. The backup power supply of claim 8, wherein the controller is further configured to perform the following actions:

When it is detected that the voltage of the AC grid connected through the second switch is higher than the voltage threshold and the power of the sub-power source is lower than the power threshold, the first switch is closed, and the DC/DC converter is controlled to work in reverse, so that the power from the AC The grid charges the sub-sources.

10. A method for operating a backup power supply of a power generation system, comprising the steps of:

determining the grid voltage of the AC grid connected through the second switch;

When the grid voltage is lower than the voltage threshold, closing the first switch to access the sub power source, so that power is supplied by the sub power source; and

When the grid voltage is higher than the voltage threshold and the electric quantity of the sub-power source is lower than the electric quantity threshold, the first switch is closed, so that the sub-power source is charged from the alternating current grid.