A brushless double-fed power generation system

Abstract

The present invention discloses a brushless double-fed power generation system, which belongs to the field of motor power generation, and includes: a brushless double-fed generator including a power winding and a control winding; an AC-DC-AC inverter connected to the control winding, used to establish and maintain the initial DC bus voltage, and adjust the frequency and voltage of the control winding; maintain the power winding frequency constant under the condition of variable speed, and adjust the power distribution relationship between the control winding and the power winding when the power winding capacity is insufficient; an uncontrolled rectifier module connected to the power winding, used to rectify the three-phase AC generated by the power winding into a target DC bus voltage; an inverter module connected to the uncontrolled rectifier module, used to invert the target DC bus voltage into a three-phase AC that meets the power quality standard, so as to supply power to the connected load or connect to the main power grid for grid-connected power supply. The present invention can keep the DC bus voltage stable, improve the dynamic response capability of the system, simplify the system complexity, and reduce the debugging time.

Description

Technical Field

[0001] The present invention belongs to the field of motor power generation, and more specifically, relates to a brushless double-fed power generation system. Background Art

[0002] With the development of human society and the improvement of material level, the problem of energy shortage has become increasingly prominent. Therefore, the development and utilization of clean renewable energy and the improvement of energy conversion equipment to improve energy utilization have become research hotspots in recent years.

[0003] The brushless doubly-fed motor has broad application prospects in variable-speed power generation fields such as wind power, hydropower, and ship shaft belts due to its reliable structure and flexible excitation regulation, and has attracted much attention in recent years.

[0004] At present, the brushless doubly-fed power generation system usually has the power winding directly connected to the load or the power grid, and the control winding connected to the bidirectional inverter. The voltage and frequency of the control winding are changed by the inverter to keep the voltage and frequency of the power winding constant, thereby realizing variable speed constant frequency power generation of the motor.

[0005] However, due to the complexity of the mathematical model of the brushless doubly-fed motor, fully decoupled vector control is difficult to achieve, resulting in the current power generation system still having problems such as poor dynamic response and poor DC bus voltage stability, which can easily cause the entire power generation system to shut down and collapse. Summary of the invention

[0006] In view of the above defects or improvement needs of the prior art, the present invention provides a brushless doubly-fed power generation system, which aims to achieve stable control of the DC bus voltage by using an AC-DC-AC inverter, thereby solving the technical problems of complex regulation, slow dynamic response and poor DC bus voltage stability existing in the current brushless doubly-fed motor power generation system.

[0007] To achieve the above object, according to one aspect of the present invention, a brushless double-fed power generation system is provided, comprising:

[0008] A brushless double-fed generator comprises: a rotor structure and a stator structure, wherein the stator structure comprises: an iron core, a power winding and a control winding, wherein the power winding and the control winding are two sets of three-phase AC windings with different pole pairs;

[0009] an AC-DC-AC inverter, connected to the control winding, for establishing and maintaining an initial DC bus voltage, and for adjusting the frequency and voltage of the control winding; maintaining a constant frequency of the power winding under the condition of variable speed of the brushless double-fed motor, and adjusting the power distribution relationship between the control winding and the power winding when the capacity of the power winding is insufficient;

[0010] an uncontrolled rectifier module, connected to the power winding, and used for rectifying the three-phase alternating current generated by the power winding into a stable target DC bus voltage;

[0011] The inverter module is connected to the uncontrolled rectifier module and is used to invert the target DC bus voltage into three-phase AC power that meets the power quality standard to supply power to the connected load or connect to the main power grid for grid-connected power supply.

[0012] In one embodiment, the DC bus of the AC-DC-AC inverter is connected in parallel with the DC bus of the uncontrolled rectifier module to achieve multi-directional energy flow among the power winding, the control winding, the power grid and the load.

[0013] In one embodiment,

[0014] The power winding is connected to the input side of the uncontrolled rectifier module for feeding energy;

[0015] The control winding is connected to the output end of the AC-DC-AC inverter and is used for bidirectional energy exchange with the brushless double-fed power generation system.

[0016] In one embodiment, the frequency of the control winding and the frequency of the power winding can both be changed;

[0017] Adjusting the frequency of the control winding to maintain a constant frequency of the power winding;

[0018] The power winding frequency is adjusted to adjust the active power distribution of the two sets of three-phase AC windings under overload conditions, thereby increasing the capacity of the brushless double-fed power generation system.

[0019] In one embodiment, the excitation mode of the brushless doubly-fed power generation system is a DC excitation mode or an AC excitation mode.

[0020] In one embodiment,

[0021] When the excitation mode of the brushless doubly-fed power generation system is a DC excitation mode, the brushless doubly-fed power generation system further comprises a battery, which is connected across the DC bus of the AC-DC-AC inverter and the DC bus of the uncontrolled rectifier module; the battery supplies power to the brushless doubly-fed power generation system.

[0022] In one embodiment,

[0023] When the excitation mode of the brushless double-fed power generation system is an AC excitation mode, the main grid is connected to the AC-DC-AC converter via a transformer, and the main grid supplies power to the brushless double-fed power generation system.

[0024] In one of the embodiments, when the main grid and the AC-DC-AC converter are connected via a transformer, the transformer is selected based on a voltage level matching relationship between the AC-DC-AC converter and the main grid.

[0025] In one of the embodiments, the capacity of the AC-DC-AC inverter is smaller than the capacity of the brushless doubly-fed generator; and the difference between the capacity of the inverter module and the capacity of the brushless doubly-fed generator is smaller than a difference threshold.

[0026] In one of the embodiments, the rotor structure includes at least one of a winding, a squirrel cage, and a magnetic resistance.

[0027] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0028] 1. The present invention provides a brushless doubly-fed power generation system including: a brushless doubly-fed motor, an AC-DC-AC inverter, an uncontrolled rectifier module, an inverter module, a transformer, a switch and other electrical components. The brushless doubly-fed generator includes a stator structure and a rotor structure. The stator structure includes an iron core, a power winding and a control winding. Among them, the power winding is directly connected to the uncontrolled rectifier module to feed electric energy into the DC bus, the control winding is connected to the power grid through the AC-DC-AC inverter, the DC bus of the AC-DC-AC inverter is connected in parallel with the DC bus of the rectifier module, and is finally connected to the load or the power grid through the inverter module to realize the generation of electric energy. The present invention can achieve stable operation of the DC bus voltage of the power generation system, improve the dynamic response capability of the system, and can use traditional commercial AC-DC-AC inverters to complete the control by itself, which greatly simplifies the complexity of the brushless doubly-fed power generation system and reduces the debugging time.

[0029] 2. The brushless doubly-fed power generation system provided by the present invention has an innovative topological structure and can achieve stable control of the DC bus voltage using a conventional AC-DC-AC inverter, which can significantly save R&D costs and time, and improve the stability of the DC bus voltage and the dynamic response of the power generation system; at the same time, the power winding frequency of the brushless doubly-fed motor does not need to be maintained at 50Hz, and the power winding frequency can be flexibly changed according to system requirements, which is beneficial to improving the efficiency and overload capacity of the power generation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of a dual-frequency brushless double-fed power generation system provided by the present invention;

[0031] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0032] Power grid 1, transformers 2 and 14, independent gateway 3, AC / DC converter 4, control winding 5, prime mover 6, brushless double-fed motor 7, power winding 8, uncontrolled rectifier module 9, inverter module 10, main circuit breaker 11, grid-connected switch 12, load 13, battery 15. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] like Figure 1 As shown, the present invention provides a brushless doubly-fed power generation system, comprising: an AC-DC-AC inverter 4 , a brushless doubly-fed generator 7 , an uncontrolled rectifier module 9 and an inverter module 10 . Among them, the AC-DC-AC inverter 4 is used to provide an initial DC bus voltage; the brushless doubly fed generator 7 includes: a rotor structure and a stator structure, the stator structure includes: an iron core, a power winding 8 and a control winding 5, the power winding 8 and the control winding 5 are two sets of three-phase AC windings with different pole pairs; wherein the control winding 5 is connected to the output side of the AC-DC-AC inverter 4, and when the AC-DC-AC inverter 4 outputs a voltage of a preset frequency, the initial bus DC voltage is kept constant and stable, and the active power distribution relationship between the power winding 8 and the control winding 5 is adjusted; the uncontrolled rectifier module 9 is connected to the power winding 8, and is used to rectify the three-phase AC power generated by the power winding 8 into a stable target DC bus voltage; the inverter module 10 is connected to the uncontrolled rectifier module 9, and is used to invert the target DC bus voltage into a three-phase AC power that meets the power quality standard, so as to supply power to the connected load or connect to the main power grid 1 for grid-connected power supply.

[0035] In one embodiment, the DC bus of the AC-DC-AC inverter 4 is connected in parallel with the DC bus of the uncontrolled rectifier module 9 to achieve multi-directional energy flow between the power winding 8, the control winding 5, the power grid 1 and the load. In one embodiment, the rotor structure includes at least one of a winding, a squirrel cage and a magnetic resistance.

[0036] Among them, wind energy, water energy and thermal energy are captured and converted into mechanical energy by the prime mover 6, and the prime mover 6 is directly connected to the brushless double-fed generator 7 coaxially to transfer the mechanical energy to the brushless double-fed generator 7. The brushless double-fed generator 7 includes a stator and a rotor, and the stator includes two independent power windings 8 and a control winding 5. The power winding 8 is directly connected to the uncontrolled rectifier module 9, and the control winding 5 is connected to the output end of the AC-DC-AC inverter 4.

[0037] The present invention relates to a brushless doubly-fed power generation system, which includes a brushless doubly-fed generator 7, an AC / DC converter 4, an uncontrolled rectifier module 9, an inverter module 10, a transformer 2 and a transformer 14, a battery 15 and other electrical transmission components; the brushless doubly-fed generator 7 includes a stator structure and a rotor structure; the rotor structure is composed of a specially designed winding, a squirrel cage, a magnetic resistance or a hybrid structure, and brushes and slip rings are eliminated; the stator structure includes an iron core and two sets of three-phase AC windings with different pole pairs; the three-phase AC windings are respectively a power winding 8 and a control winding 5; the power winding 8 is connected to the input side of the uncontrolled rectifier module 9 to feed energy to the power generation system, and the control winding 5 is connected to the output end of the AC / DC converter 4 to perform a two-way energy exchange flow with the system; the AC / DC converter 4 can input The side is connected to the power grid 1 through the transformer 2 to provide the initial excitation voltage for the system. The output side of the AC-DC-AC inverter 4 is connected to the control winding. By adjusting the voltage of a certain frequency output by the AC-DC-AC inverter 4, the bus DC voltage can be kept constant and the active power distribution relationship between the power winding 8 and the control winding 5 can be adjusted; the battery 15 is connected in parallel to the DC bus to provide the excitation voltage for the system; the uncontrolled rectifier module 9 is connected to the power winding 8 to rectify the three-phase AC power emitted by the power winding 8 into a stable DC bus voltage to provide power for the system and the load. The inverter module 10 inverts the stable DC bus voltage into a three-phase AC power that meets the power quality standard and directly connects to the load 14 for direct power supply or connects to the power grid 1 through the transformer 14 for grid-connected power supply. Among them, a main circuit breaker 11 and a grid-connected switch 12 are provided before the inverter module 10 and the transformer 14.

[0038] The brushless doubly-fed power generation system provided by the present invention improves the performance of the brushless doubly-fed power generation system, has the advantages of high efficiency, strong reliability, simple control, strong versatility, and convenient operation and maintenance, and will effectively promote the application and popularization of brushless doubly-fed power generation.

[0039] In one of the embodiments, the frequency of the control winding 5 and the frequency of the power winding 8 can both be changed; adjusting the frequency of the control winding 5 is used to maintain the frequency of the power winding 8 constant; adjusting the frequency of the power winding 8 is used to adjust the active power distribution of the two sets of three-phase AC windings under overload conditions, thereby increasing the capacity of the brushless doubly fed power generation system.

[0040] Specifically, the ratio of the active power output by the control winding 5 and the power winding 8 of the brushless double-fed motor 7 is approximately equal to the ratio of the frequencies of the two. When the power winding 8, which is mainly responsible for the output, is overloaded, the frequency of the power winding 8 can be changed by adjusting the frequency of the control winding 5, thereby reducing the capacity of the power winding 8, so that the system has a certain degree of overload capacity.

[0041] After the DC bus is stabilized by the external voltage, the AC-DC-AC inverter 4 outputs a voltage of a certain frequency to the control winding 5, and a symmetrical AC potential and current will be induced in the rotor. In addition to generating a magnetic field with the same number of pole pairs as the control winding, the rotor will also generate a reverse rotating magnetic field with the same number of pole pairs as the power winding, which will induce an AC potential in the power winding 8. The voltage and frequency output by the AC-DC-AC inverter 4 are adjusted respectively, so that the port voltage of the power winding 8 is close to the rated voltage, and the single grid switch 3 or the battery 15 switch is disconnected, and the system is converted from the state of being powered by the external power supply to the state of independent power generation by the brushless double-fed motor 7.

[0042] In the independent power generation state, the AC power generated by the power winding 8 is modulated into stable DC power by the uncontrolled rectifier module 9, the main circuit breaker 11 is closed, a part of the DC power interacts with the control winding 5 through the parallel DC bus structure, and the other part is inverted into three-phase AC power that meets the power quality standards by the inverter module 10 to directly supply power to the load 13 or is connected to the grid 1 directly or through the grid switch 12 or through the transformer 14 for grid-connected power supply.

[0043] When the system is under the working conditions of the prime mover 6 speed changing, the load 13 suddenly increasing or decreasing, etc., the AC-DC-AC inverter 4 adjusts the amplitude and frequency of the current in the control winding 5, so as to keep the power winding 8 emitting a three-phase AC voltage with a constant amplitude, so as to maintain a constant DC bus voltage value, and the inverter module 10 is set to output AC power with a constant frequency and amplitude, so as to complete the variable speed constant frequency power generation process.

[0044] In one of the embodiments, the excitation mode of the brushless doubly-fed power generation system is a DC excitation mode or an AC excitation mode. In one of the embodiments, when the excitation mode of the brushless doubly-fed power generation system is a DC excitation mode, the brushless doubly-fed power generation system further comprises a battery 15, the battery 15 is connected across the DC bus of the AC-DC-AC inverter 4 and the DC bus of the uncontrolled rectifier module 9; the battery 15 supplies power to the brushless doubly-fed power generation system. In one of the embodiments, when the excitation mode of the brushless doubly-fed power generation system is an AC excitation mode, the main grid 1 is connected to the AC-DC-AC inverter 4 through a transformer 2, and the main grid 1 supplies power to the brushless doubly-fed power generation system.

[0045] Specifically, when AC excitation is adopted, the grid 1 is connected to the input side of the AC / DC / AC inverter directly or through the transformer 2 via the independent grid switch 3. The independent grid switch 3 is closed, and the system is powered by the grid 1. When DC excitation is adopted, the switch of the battery 15 is closed, and the battery 15 is used to power the system.

[0046] In one embodiment, when the main grid 1 and the AC-DC-AC converter 4 are connected via the transformer 2, the transformer 2 is selected based on the voltage level matching relationship between the AC-DC-AC converter 4 and the main grid 1. An independent gateway 3 is provided between the transformer 2 and the AC-DC-AC converter 4.

[0047] In one embodiment, the capacity of the AC-DC-AC inverter 4 is smaller than the capacity of the brushless double-fed generator 7; the difference between the capacity of the inverter module 10 and the capacity of the brushless double-fed generator 7 is smaller than the difference threshold. Specifically, the capacity of the AC-DC-AC inverter 4 is usually smaller than the capacity of the brushless double-fed generator 7, and the capacity of the inverter module 10 is similar to the capacity of the brushless double-fed generator 7.

[0048] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A brushless double-fed power generation system, characterized in that: include: A brushless double-fed generator comprises: a rotor structure and a stator structure, wherein the stator structure comprises: an iron core, a power winding and a control winding, wherein the power winding and the control winding are two sets of three-phase AC windings with different pole pairs; an AC-DC-AC inverter connected to the control winding, used to establish and maintain an initial DC bus voltage, and also used to adjust the frequency and voltage of the control winding; maintain the power winding frequency constant under the condition of variable speed of the brushless double-fed generator, and adjust the power distribution relationship between the control winding and the power winding when the power winding capacity is insufficient; an uncontrolled rectifier module, connected to the power winding, and used for rectifying the three-phase alternating current generated by the power winding into a stable target DC bus voltage; The inverter module is connected to the uncontrolled rectifier module and is used to invert the target DC bus voltage into three-phase AC power that meets the power quality standard to supply power to the connected load or connect to the main power grid for grid-connected power supply.

2. The brushless double-fed power generation system according to claim 1, characterized in that: The DC bus of the AC-DC-AC inverter is connected in parallel with the DC bus of the uncontrolled rectifier module to achieve multi-directional energy flow among the power winding, the control winding, the power grid and the load.

3. The brushless double-fed power generation system according to claim 1, characterized in that: The power winding is connected to the input side of the uncontrolled rectifier module for feeding energy; The control winding is connected to the output end of the AC-DC-AC inverter and is used for bidirectional energy exchange with the brushless double-fed power generation system.

4. The brushless double-fed power generation system according to claim 3, characterized in that: The frequency of the control winding and the frequency of the power winding can both be changed; Adjusting the frequency of the control winding to maintain a constant frequency of the power winding; The power winding frequency is adjusted to adjust the active power distribution of the two sets of three-phase AC windings under overload conditions, thereby increasing the capacity of the brushless double-fed power generation system.

5. The brushless doubly-fed power generation system according to claim 1, characterized in that: The excitation mode of the brushless double-fed power generation system is a DC excitation mode or an AC excitation mode.

6. The brushless double-fed power generation system according to claim 5, characterized in that: When the excitation mode of the brushless doubly-fed power generation system is a DC excitation mode, the brushless doubly-fed power generation system further comprises a battery, which is connected across the DC bus of the AC-DC-AC inverter and the DC bus of the uncontrolled rectifier module; the battery supplies power to the brushless doubly-fed power generation system.

7. The brushless double-fed power generation system according to claim 5, characterized in that: When the excitation mode of the brushless double-fed power generation system is an AC excitation mode, the main grid is connected to the AC-DC-AC converter via a transformer, and the main grid supplies power to the brushless double-fed power generation system.

8. The brushless double-fed power generation system according to claim 7, characterized in that: When the main grid and the AC-DC-AC converter are connected via a transformer, the transformer is selected based on a voltage level matching relationship between the AC-DC-AC converter and the main grid.

9. The brushless doubly-fed power generation system according to any one of claims 1 to 8, characterized in that: The capacity of the AC-DC-AC inverter is smaller than the capacity of the brushless double-fed generator; and the difference between the capacity of the inverter module and the capacity of the brushless double-fed generator is smaller than a difference threshold.

10. The brushless doubly-fed power generation system according to any one of claims 1 to 8, characterized in that: The rotor structure includes at least one of windings, a squirrel cage, and a reluctance.

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