High-inertia active / reactive rapid strong compensation and power grid fault stable support equipment based on inductor motor and control method and system

Abstract

The invention discloses high-inertia active / reactive rapid strong compensation and power grid fault stable support equipment based on an inductor motor and a control method and system, and belongs to the technical field of electric power equipment. Comprising a flywheel, a motor system and a boosting transformer which are connected in sequence, and the motor system comprises an inductor motor, a four-quadrant converter, an excitation converter and an excitation transformer. According to the method, the rotating speed of the motor can be increased by means of a high-strength rotor structure of the inductor motor, the energy storage density and the inertia time constant are improved, the energy storage capacity of a long time scale is achieved, and power grid active fluctuation is compensated for for a long time; the pulse power output characteristic of the inductor motor and the large inertia characteristic of the flywheel system can be exerted, a large amount of active power is released or absorbed instantaneously, the frequency instability of the power system is effectively inhibited, and the power grid frequency and inertia support is realized; reactive power regulation and control can be realized through direct-current excitation regulation, and the reactive power fluctuation of a power system can be instantaneously suppressed and compensated.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric power equipment, and more specifically, relates to a high-inertia active / reactive fast and powerful compensation and power grid fault stable support equipment based on an induction motor and a control method and system. Background Art

[0002] Building a new power system with new energy as the main body is a major national development strategy. However, renewable energy sources such as photovoltaic and wind power are highly intermittent and volatile. Their large-scale access and the large-scale withdrawal of traditional thermal power may cause insufficient synchronous inertia level and short-circuit level of the power system, and ultimately lead to voltage and frequency instability. If the corresponding compensation cannot be made in time and quickly, it may cause a major power outage in the power grid.

[0003] Traditional synchronous condensers can only perform reactive power compensation and solve the problem of voltage stability support. They are basically useless for system synchronous inertia and frequency support, and their effect is far less than that of traditional synchronous generator sets. Flywheel energy storage technology has the advantages of high frequency, fast response and long life, and is an effective way to solve the high frequency frequency fluctuations of the power grid. However, traditional flywheel energy storage technology is difficult to provide instantaneous high overload and high power support, and does not have the function of reactive power compensation. It is difficult to smooth the sudden and rapid fluctuations of voltage and frequency in a high-proportion new energy power system.

[0004] Therefore, in order to smooth out the sudden and rapid fluctuations in voltage and frequency in the new energy power system, prevent power outages caused by frequency and voltage instability, and achieve rapid compensation for instantaneous active / reactive power of the new energy power grid, especially to achieve rapid, strong and stable support for frequency / voltage during sudden power grid failures, it is necessary to improve traditional synchronous phase modulation and flywheel energy storage technology. Traditional motors are difficult to combine high energy storage density, high overload strong pulse power output capability, and flexible reactive power regulation capability, and cannot provide the power system with effective system resistance to power fluctuations and stable support capabilities. Summary of the invention

[0005] In response to the gaps, deficiencies or improvement needs in the prior art, the purpose of the present invention is to provide a high-inertia active / reactive fast and powerful compensation and power grid fault stable support equipment and a control method and system based on an induction motor, aiming to achieve fast, strong and stable support for frequency / voltage in the event of sudden power grid failure.

[0006] To achieve the above-mentioned purpose, the present invention provides a high-inertia active / reactive fast and powerful compensation and grid fault stable support equipment based on an induction motor, which realizes fast, strong and stable support for grid frequency and voltage instability faults, including a flywheel, a motor system and a step-up transformer connected in sequence, wherein the motor system includes an induction motor, a four-quadrant converter, an excitation converter and an excitation transformer;

[0007] The flywheel is coaxially connected to the induction motor and is used to increase the rotational inertia of the unit;

[0008] The four-quadrant converter is connected to the stator armature winding of the induction motor, and controls the frequency of the stator rotating magnetic field to change the synchronous speed of the stator armature magnetic field, thereby realizing variable speed operation of the induction motor, so as to send or absorb electric energy to the power grid and release and store active power;

[0009] The excitation transformer is connected to the low voltage side of the step-up transformer and the excitation converter, and is used to provide a three-phase AC excitation power supply for the excitation converter;

[0010] The excitation converter is connected to the stator excitation winding of the induction motor and is used to convert the voltage of the three-phase AC excitation power supply into a DC excitation current to provide DC excitation for the induction motor;

[0011] The step-up transformer is connected to the motor system and the power grid, and is used to achieve voltage conversion and electrical isolation between the motor system and the power grid.

[0012] The induction motor comprises: a stator structure and a rotor structure, wherein the stator structure comprises: an iron core, a stator armature winding, and a stator excitation winding, wherein the stator iron core can be divided into two left and right parts, each of which is embedded with a stator armature winding, and a ring excitation winding is placed between the two stator iron cores; the rotor structure comprises: a solid rotor, which is usually composed of a whole section of solid steel and is divided into two left and right parts of the same structure, and the axes of the salient poles and magnetic poles of the left and right parts of the rotor are staggered by 180° electrical angle. The integral alloy steel structure of the rotor also helps to enhance the instantaneous damping effect of the rotor when the motor is running with rapid power compensation, thereby further improving the rapid and strong compensation capability of the stator armature winding of the motor. The induction motor provided by the present invention has a special rotor structure, which is generally forged as a whole with solid high-strength alloy steel material, and there are no additional parts or devices on the rotor. The rotor body is a salient pole structure, and the rotor structure has high strength and high reliability, is suitable for high-speed rotation, and is conducive to improving the energy storage density and inertia time constant of the motor rotation system, and is very suitable for application occasions such as flywheel energy storage pulse power generation and active power compensation. At the same time, although the induction motor uses DC excitation on the stator side, the motor still has the operating characteristics of a synchronous motor. The reactive power of the motor can be flexibly controlled by adjusting the excitation current, and it has the reactive power regulation capability of a synchronous phase regulator.

[0013] Beneficial effect: The present invention proposes a high-inertia active / reactive fast and powerful compensation and grid fault stable support equipment based on an induction motor. By adjusting the current amplitude of the excitation converter, or regulating the frequency of the four-quadrant converter, the induction motor is regulated by the electromagnetic torque of the motor, thereby reducing and avoiding large-scale power outages caused by rapid voltage or frequency instability during sudden grid failures. The high energy storage density, high overload strong pulse power output capacity and flexible reactive power regulation capacity of the induction motor are fully utilized, thereby improving the system's ability to resist power fluctuations and stable support, and ensuring the stable operation, power supply quality and reliability of the power system. It is a new type of equipment based on the induction motor that integrates multiple functions such as synchronous phase modulation, flywheel energy storage active compensation, and fast, strong and stable support during grid failures.

[0014] The induction motor can use magnetic bearings according to actual needs to reduce the weight pressure on the bearings and reduce friction losses.

[0015] The flywheel can be an explicit flywheel independent of the motor rotor body, coaxially connected to the motor rotor mechanical transmission, significantly improving the rotational inertia of the motor transmission system; or it can be an implicit flywheel integrated with the rotor body, further improving the overall reliability of the system.

[0016] The four-quadrant converter is connected to the stator armature winding of the induction motor, and is used to change the synchronous speed of the stator armature magnetic field of the motor by controlling the frequency of the stator rotating magnetic field, thereby realizing variable speed operation of the motor, and realizing the motor sending or absorbing electric energy to the power grid, and releasing and storing active power.

[0017] The excitation converter is connected to the stator excitation winding of the induction motor through a rectifier circuit to achieve DC excitation. By adjusting the excitation current of the motor, the nature and size of the reactive power output by the armature winding to the power grid can be regulated to balance the power grid's demand for reactive power.

[0018] The present invention also provides a control method for the high inertia active / reactive fast and powerful compensation and power grid fault stable support equipment based on the induction motor, comprising the following steps:

[0019] When a voltage fluctuation fault occurs in the power grid, the current amplitude of the excitation converter is adjusted to achieve rapid compensation of reactive power and support the stability of the power grid voltage;

[0020] When the grid experiences a sudden frequency drop fault, the frequency of the four-quadrant converter is adjusted to actively reduce it. Through the electromagnetic torque of the motor, the induction motor is adjusted to be in a power generation state, so as to achieve the motor's speed reduction and power generation operation, thus supporting the frequency stability of the grid.

[0021] When a frequency surge occurs in the power grid, the frequency of the four-quadrant converter is adjusted to increase actively. Through the electromagnetic torque of the motor, the induction motor is adjusted to be in an electric state, so as to achieve the speed-up electric energy storage operation of the motor and support the frequency stability of the power grid.

[0022] Beneficial effects: By increasing the size of the induction motor rotor or configuring a flywheel to increase the rotational inertia of the rotating system, and by increasing the speed to improve the energy storage density and inertia time constant of the equipment, it is possible to store energy over a longer time scale and to compensate for sudden fluctuations in the active power of the power system, especially rapid and strong power (active / reactive) compensation during power grid failures, which can equivalently improve the synchronous inertia of the new power system, and reduce or avoid the new power system's lack of synchronous inertia and weak transient stability support capacity caused by the withdrawal of thermal power, which leads to the new power system's prone frequency instability during failures. Reactive power control is achieved by adjusting the DC excitation of the motor, so that it has the ability to instantaneously suppress or compensate for reactive power fluctuations in the power system, and maintain the ability of synchronous phase-shifting machine reactive compensation to solve the problems of reactive power imbalance and weak voltage transient support capacity in the new power system. Compared with traditional synchronous phase condensers, the power grid fault fast, strong and stable support equipment based on induction motors has eliminated rotor windings, brush slip rings and other devices. There are no assembled and integrated parts on the rotor, and the structure is reliable and durable. At the same time, it has the comprehensive functions of traditional synchronous phase condensers, active compensation of flywheel energy storage, fast active / reactive compensation and inertia / stability support. It is a fully innovative important key technology and equipment support to break through the problem of voltage and frequency instability in new power systems.

[0023] The present invention also provides a control system for high-inertia active / reactive fast and powerful compensation and power grid fault stable support equipment based on an induction motor, comprising: a computer-readable storage medium and a processor;

[0024] The computer-readable storage medium is used to store executable instructions;

[0025] The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the above control method.

[0026] Compared with the prior art, the above technical solutions conceived by the present invention can achieve the following

[0027] Beneficial effects:

[0028] (1) The high-inertia active / reactive fast and powerful compensation and grid fault stable support equipment based on the induction motor provided by the present invention can give full play to the high-strength rotor structure of the induction motor to increase the motor rotor speed, thereby increasing the energy storage density and inertia time constant of the device, thereby having a longer time scale of energy storage capacity, and achieving longer-term compensation and stable support for grid active fluctuations and frequency faults; by adjusting the current amplitude of the excitation converter, or regulating the frequency of the four-quadrant converter, the induction motor is regulated by the electromagnetic torque of the motor, thereby reducing and avoiding large-scale power outages caused by rapid instability of voltage or frequency during sudden grid faults, and giving full play to the high energy storage density, high overload strong pulse power output capability and flexible reactive power regulation capability of the induction motor, thereby improving the system's ability to resist power fluctuations and stable support, thereby coping with grid faults.

[0029] (2) The high-inertia active / reactive fast and powerful compensation and grid fault stable support equipment based on the induction motor provided by the present invention can give full play to the pulse power output characteristics of the induction motor and the large inertia characteristics of the flywheel system, instantaneously release or absorb a large amount of active power, and realize instantaneous fast and powerful active power compensation, thereby effectively suppressing the frequency instability caused by sudden fluctuations in the active power of the power system, achieving support for the frequency and inertia of the power grid, reducing or avoiding large power outages caused by frequency instability during grid faults, and providing fast, strong and stable support for new power systems;

[0030] (3) The high-inertia active / reactive fast and powerful compensation and grid fault stability support equipment based on the induction motor provided by the present invention can realize reactive power regulation through DC excitation regulation, and has the ability to instantaneously suppress and compensate for reactive power fluctuations in the power system.

[0031] (4) The present invention is a new type of power equipment that integrates multiple functions such as synchronous phase regulator, flywheel energy storage active compensation, and rapid, strong and stable support when the power grid fails. It can increase the synchronous inertia of the power grid, rapidly compensate for active and reactive power, and rapidly, strongly and stably support the power grid when the frequency / voltage fails and becomes unstable. This is crucial for the rapid power compensation and stable and strong support of the new energy power system where thermal power is gradually withdrawn. It is an important key equipment and technical means to suppress and avoid major power outages caused by voltage / frequency instability when the power system fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the topology of the high-inertia active / reactive fast and powerful compensation and grid fault stability support equipment system based on the induction motor provided by the present invention.

[0033] Figure 2A topology diagram of a high-inertia active / reactive fast and powerful compensation and grid fault stability support equipment system based on an induction motor provided in Example 1 of the present invention.

[0034] Figure 3 A schematic diagram of the topology of a high-inertia active / reactive fast and powerful compensation and grid fault stability support equipment system based on an induction motor provided in the second embodiment of the present invention. DETAILED DESCRIPTION

[0035] 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.

[0036] like Figure 1As shown, a high-inertia active / reactive fast and powerful compensation and power grid fault stability support equipment based on an induction motor includes: an induction motor, a large-inertia flywheel, a four-quadrant converter, an excitation converter, an excitation transformer, a step-up transformer, etc. The induction motor comprises: a stator structure and a rotor structure, wherein the stator structure comprises: an iron core, a stator armature winding, and a stator excitation winding, wherein the stator iron core can be divided into two left and right parts, each of which is embedded with a stator armature winding, and an annular excitation winding is placed between the two sections of the stator iron core. The stator armature winding of the induction motor can also be connected in series with an external series excitation compensation winding arranged in the same slot as the stator excitation winding after rectification (this series excitation compensation winding can be timely controlled to be connected or short-circuited by a power electronic switch, which is determined according to the needs of different operating states of the motor) to compensate for the effect of the armature reaction magnetomotive force, maintain the basic constancy of the air gap magnetic field or enhance the air gap magnetic field, so as to further improve the rapid and strong compensation capability of the motor power; the rotor structure comprises: a solid rotor, which is usually composed of a whole section of solid steel and is divided into two left and right parts with the same structure, and the salient pole magnetic pole axes of the left and right rotors are staggered by 180° electrical angle; according to actual needs, a magnetic suspension bearing can be selected to reduce the weight pressure on the bearing and reduce friction loss. The large inertia flywheel is a dominant flywheel independent of the motor rotor body, and is coaxially connected to the motor rotor mechanical transmission, which significantly increases the rotational inertia of the motor rotation system. The four-quadrant converter is connected to the stator armature winding of the induction motor, and is used to change the synchronous speed of the motor by controlling the frequency of the stator rotating magnetic field, so as to achieve variable speed operation of the motor, thereby enabling the motor to emit or absorb electrical energy to the power grid, and release and store active power. The step-up transformer is connected to the four-quadrant converter and the power system, and is the total step-down device of the device; the excitation transformer is connected to the low-voltage side of the step-up transformer and the excitation converter of the motor, and is used to provide excitation power for the high-speed induction motor excitation system.

[0037] Embodiment 1

[0038] like Figure 2 As shown, the stator armature winding of the induction motor can also be appropriately connected in series with an external series excitation compensation winding arranged in the same slot as the stator excitation winding after rectification. By optimizing the configuration of the ampere-turn matching of the external series excitation compensation winding and the excitation winding, the effect of the armature reaction magnetomotive force can be compensated, and the air gap magnetic field can be kept basically constant or enhanced during the rapid and strong power compensation of the armature winding, so as to further improve the motor's ability to quickly and strongly compensate for power. This series excitation compensation winding can be timely controlled to be connected or short-circuited by a power electronic switch, which is determined according to the needs of different operating states of the motor.

[0039] Embodiment 2

[0040] like Figure 3As shown, the stator excitation winding of the induction motor can be divided into two parts, namely the first stator excitation winding and the second stator excitation winding. The two parts can be controlled by switches to realize the same direction series connection or reverse series connection of the excitation magnetic field direction or short-circuit one part thereof and optimize the turn ratio of the two parts of the excitation windings, combined with timely and reasonable switch switching control, in different time periods of the motor stator armature winding power compensation operation, through reverse series connection or forward series connection or short-circuit, in order to further enhance the air gap magnetic field of the motor and further enhance the ability of the motor armature winding to quickly and strongly compensate for power. A part of the excitation winding can also be designed as a two-in-one comprehensive design with the external compensation series excitation winding of embodiment one, and its core purpose is to further obtain a stronger air gap magnetic field when the motor stator armature winding power compensation operation is in progress, so as to further enhance the ability of the motor to quickly and strongly compensate for power.

[0041] Embodiment 3

[0042] For high-speed induction motors, magnetic bearings can be selected according to actual needs to reduce the weight pressure on the bearings and reduce friction losses.

[0043] When the power grid has no faults, the induction motor in the equipment of the present invention runs at the rated synchronous speed of the motor, which is similar to no-load operation, which is equivalent to the idling use of the synchronous phase condenser; when the power grid has a voltage fluctuation fault, the current amplitude of the excitation inverter can be quickly adjusted to achieve rapid compensation of reactive power and support the stability of the power grid voltage; when the power grid has a sudden frequency drop or rise fault, the frequency of the four-quadrant inverter is actively adjusted to be actively reduced or increased, and the induction motor is regulated to be in a power generation or electric state through the action of the electromagnetic torque of the motor, so as to achieve the motor's speed reduction power generation energy release or speed increase electric energy storage operation, balance the active power of the power grid, smooth out the frequency fluctuation of the power grid, and support the frequency stability of the power grid.

[0044] 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 high inertia active / reactive fast and powerful compensation and grid fault stable support equipment based on induction motor, characterized in that: It includes a flywheel, a motor system and a step-up transformer connected in sequence, wherein the motor system includes an induction motor, a four-quadrant converter, an excitation converter and an excitation transformer; The flywheel is coaxially connected to the induction motor and is used to increase the rotational inertia of the unit; The four-quadrant converter is connected to the stator armature winding of the induction motor, and controls the frequency of the stator rotating magnetic field to change the synchronous speed of the stator armature magnetic field, thereby realizing the variable speed operation of the induction motor, so as to send or absorb electric energy to the power grid and release and store active power; The excitation transformer is connected to the low voltage side of the step-up transformer and the excitation converter, and is used to provide a three-phase AC excitation power supply for the excitation converter; The excitation converter is connected to the stator excitation winding of the induction motor and is used to convert the voltage of the three-phase AC excitation power supply into a DC excitation current to provide DC excitation for the induction motor; The step-up transformer is connected to the motor system and the power grid, and is used to achieve voltage conversion and electrical isolation between the motor system and the power grid.

2. The device according to claim 1, characterized in that: The induction motor comprises a rotor structure and a stator structure, wherein the stator structure comprises a stator core, a stator armature winding and a stator excitation winding, wherein the stator armature winding is located at both sides of the stator core, and the stator excitation winding is located in the middle of the stator core; and the rotor structure is a solid steel structure.

3. The device according to claim 2, characterized in that: The stator structure further comprises an external series excitation compensation winding, and the external series excitation compensation winding is arranged in the same slot as the stator excitation winding.

4. The device according to claim 2, characterized in that: The flywheel is independent of the rotor structure of the induction motor, and is coaxially connected to the induction motor through mechanical transmission, or is integrated with the rotor structure of the induction motor.

5. The device according to claim 2, characterized in that: The induction motor adopts a magnetic suspension bearing.

6. The device according to claim 2, characterized in that: The stator excitation winding includes a first stator excitation winding and a second stator excitation winding. The first stator excitation winding and the second stator excitation winding are connected to the excitation circuit according to a preset turns ratio. The first stator excitation winding and the second stator excitation winding are connected in series in the same direction or in reverse direction in the direction of the excitation magnetic field.

7. A control method for high inertia active / reactive fast and powerful compensation and power grid fault stability support equipment based on an induction motor according to any one of claims 1 to 6, characterized in that: The following steps are involved: When a voltage fluctuation fault occurs in the power grid, the current amplitude of the excitation converter is adjusted to achieve rapid compensation of reactive power and support the stability of the power grid voltage; When the grid experiences a sudden frequency drop fault, the frequency of the four-quadrant converter is adjusted to actively reduce it. Through the electromagnetic torque of the motor, the induction motor is adjusted to be in a power generation state, so as to achieve the motor's speed reduction and power generation operation, thus supporting the frequency stability of the grid. When a frequency surge occurs in the power grid, the frequency of the four-quadrant converter is adjusted to increase actively. Through the electromagnetic torque of the motor, the induction motor is adjusted to be in an electric state, so as to achieve the speed-up electric energy storage operation of the motor and support the frequency stability of the power grid.

8. A control system for high inertia active / reactive fast and powerful compensation and grid fault stable support equipment based on induction motor, characterized in that: include: A computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the control method described in claim 7.

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