A permanent magnet flywheel energy storage phase modifier system and control method thereof

Abstract

The application discloses a permanent magnet flywheel energy storage phase modifier system and a control method thereof. The permanent magnet flywheel energy storage phase modifier system comprises a controller, a converter, a flywheel, a permanent magnet speed regulating motor, a phase modifier and a shaft system. The phase modifier and the permanent magnet speed regulating motor are mounted on a power grid. The controller is used for acquiring the flywheel rotating speed, the active power and the frequency of the power grid, formulating an active power control strategy and sending a control signal. The flywheel and the phase modifier rotor are connected with the permanent magnet rotor and the armature rotor of the permanent magnet speed regulating motor through the shaft system. The converter is connected with the armature winding of the permanent magnet speed regulating motor and changes the power frequency according to the control instruction of the controller. The converter adjusts the rotating speed of the permanent magnet synchronous motor and the flywheel by changing the power frequency, so as to change the flywheel energy storage state. The energy is fed through the phase modifier and the permanent magnet speed regulating motor. The application can actively control the distribution process of the flywheel energy charging and discharging and the active power sending, and improves the inertia support capacity of the phase modifier.

Description

Technical Field

[0001] This invention relates to the field of motor and electrical control technology, specifically to a permanent magnet flywheel energy storage synchronous condenser system and its control method. Background Technology

[0002] Traditional power grid frequency regulation, through the introduction of variable frequency speed control (VFD) generators, utilizes the kinetic energy of generator rotors to increase the output or absorption capacity of the power system's active power. It also provides sufficient active inertia support when the power system frequency oscillates or is about to collapse, effectively ensuring power quality and system stability. However, with the increasing proportion of renewable energy generation within the power system, the frequency and amplitude of grid frequency fluctuations have increased accordingly. The generator's own inertia support capacity and frequency regulation speed are no longer sufficient to meet the frequency regulation requirements of the power system. Furthermore, during the frequency stabilization and speed recovery phase, it can easily cause severe secondary frequency drops in the grid. In addition, traditional methods of reserving backup power also suffer from small energy storage, slow regulation speed, and high energy consumption, placing high demands on the stable output power capacity of the power generation system and failing to match the large power fluctuations of renewable energy generation systems.

[0003] Introducing energy storage devices into high-proportion renewable energy power generation systems can increase the system's short-term active power regulation capability. This involves releasing energy when the system frequency drops and absorbing excess energy from the power generation system when the frequency rises, effectively improving the frequency stability of the power system. However, traditional chemical energy storage for frequency regulation is limited by the short lifespan and low power density of batteries, making it unable to adequately address the grid's needs for short-term high-power and long-term stable frequency regulation. Furthermore, the overly complex control and excitation of battery energy storage hinders its widespread application. Flywheel energy storage, as a type of mechanical energy storage, possesses the capability for instantaneous power response down to the second level. Simultaneously, flywheels themselves offer advantages such as low cost and long lifespan, making them a key research focus in the field of energy storage technology.

[0004] Large synchronous condensers have strong reactive power output capabilities, but their rotational inertia is only 30%-50% of that of generator sets of the same capacity, and their ability to support system inertia is even more insufficient compared to generator sets.

[0005] Existing active power compensation methods based on flywheel energy storage and speed control employ a doubly-fed induction generator (DFIG) directly connected to the grid to regulate the flywheel's energy storage. However, DFIGs are prone to shutdown at low speeds, requiring speed protection algorithms to limit active power output at low rotor speeds, thus losing their frequency regulation capability during large grid frequency fluctuations. Furthermore, this system does not consider the scenario where the flywheel absorbs reactive power from the grid to reduce grid frequency, and it lacks a synchronous condenser, thus lacking strong reactive power regulation capabilities.

[0006] Therefore, utilizing mechanical energy storage systems to expand and enhance the inertia support capacity of large synchronous condenser systems and developing their primary frequency regulation function is crucial for improving power quality. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a permanent magnet flywheel energy storage synchronous condenser system and its control method.

[0008] In a first aspect, the present invention provides a permanent magnet flywheel energy storage synchronous condenser system, which includes a flywheel, a permanent magnet speed-regulating motor, a synchronous condenser, a controller, a converter, a first shaft system and a second shaft system;

[0009] The armature stator of the synchronous condenser is connected to the power grid, and the excitation rotor of the synchronous condenser is connected to one end of the second shaft system; the permanent magnet speed-regulating motor includes an armature rotor and a permanent magnet rotor, and the armature rotor is connected to the other end of the second shaft system, so that the excitation rotor of the synchronous condenser and the armature rotor of the permanent magnet speed-regulating motor can rotate synchronously.

[0010] The permanent magnet rotor is connected to one end of the first shaft system, and the flywheel is connected to the other end of the first shaft system, so that the flywheel and the permanent magnet rotor can rotate synchronously.

[0011] The controller includes a grid frequency detection unit, a power calculation unit, and a command decision unit. The grid frequency detection unit acquires grid current frequency and power signals and sends the acquired data to the command decision unit. The command decision unit generates command decisions based on the data from the grid frequency detection unit and grid dispatch commands, and sends these decisions to the power calculation unit. The power calculation unit receives the commands from the command decision unit, determines the required system inertia support power, and transmits the frequency conversion signal to the converter. The converter regulates the flywheel speed, ultimately changing the system's energy storage state and smoothing grid frequency fluctuations.

[0012] The permanent magnet speed-regulating motor includes two rotating mechanisms: a permanent magnet rotor and an armature rotor. There is no mechanical connection between the two rotating mechanisms; they are electromagnetically coupled through a rotating magnetic field.

[0013] Furthermore, the armature rotor includes an armature rotor core and an armature rotor winding; the armature rotor winding is installed in the slots of the armature rotor core; the armature rotor winding is connected to the converter, and the armature rotor core is connected to the other end of the second shaft system;

[0014] The permanent magnet rotor includes a permanent magnet and a permanent magnet rotor core; the permanent magnet is attached to the permanent magnet rotor core; the permanent magnet rotor core is connected to one end of the first shaft system.

[0015] Furthermore, the connection between the permanent magnet rotor and one end of the first shaft system is changed to the connection between the permanent magnet rotor and the other end of the second shaft system; the connection between the armature rotor and the other end of the second shaft system is changed to the connection between the armature rotor and one end of the first shaft system; the connection between the armature rotor core and the other end of the second shaft system is changed to the connection between the armature rotor core and one end of the first shaft system, ensuring that the armature rotor and flywheel rotate at the same speed; the connection between the permanent magnet rotor core and one end of the first shaft system is changed to the connection between the permanent magnet rotor core and the other end of the second shaft system, ensuring that the permanent magnet rotor and flywheel rotate at the same speed. This technical solution achieves a mutual interchange of the positions of the permanent magnet rotor and the armature rotor, changing the original system from flywheel-first shaft system-permanent magnet rotor-armature rotor-second shaft system-excitation rotor to a system of flywheel-first shaft system-armature rotor-permanent magnet rotor-second shaft system-excitation rotor.

[0016] Furthermore, the permanent magnet speed-regulating motor achieves variable frequency speed regulation by controlling the armature rotor through a converter and controller, with the converter power source taken from the power grid at the synchronous condenser terminal.

[0017] Secondly, the present invention provides a control method for the above-mentioned permanent magnet flywheel energy storage synchronous condenser system, the specific steps of which are as follows:

[0018] S1: Establish a mathematical model of the permanent magnet flywheel energy storage synchronous condenser system, and use this mathematical model as the control object;

[0019] S2: For the controller and the controlled object, establish a frequency modulation power response control method to realize the control of the grid frequency and the system inertia support power;

[0020] S3: According to the system inertia support power control command of the controller, realize the active power feed control of the permanent magnet flywheel energy storage synchronous condenser system.

[0021] Furthermore, in step S2, the frequency modulation power response control method is implemented by adjusting the flywheel speed. The specific steps are as follows:

[0022] S21: The grid frequency detection unit acquires the grid current frequency signal and power signal, and sends the acquired data to the command decision unit. The command decision unit gives the frequency regulation decision command of the permanent magnet flywheel energy storage synchronous condenser system based on the current power system dispatch command and the current detected grid frequency and feedback active power output information.

[0023] S22: The power calculation unit calculates the active power released or absorbed by the permanent magnet synchronous condenser flywheel energy storage system according to the frequency regulation decision command generated in S21, and gives the active power control command of the permanent magnet flywheel energy storage synchronous condenser system by combining the frequency regulation decision command and the calculated active power.

[0024] S23: The converter receives the active power control command provided by the controller, converts it into a control electrical signal to drive the permanent magnet speed-regulating motor, controls the speed of the permanent magnet rotor of the permanent magnet speed-regulating motor, and enables the permanent magnet flywheel energy storage synchronous condenser system to output the specified active power.

[0025] Furthermore, the mathematical model of the permanent magnet flywheel energy storage synchronous condenser system includes a mathematical model of a permanent magnet speed-regulating motor related to frequency support and active power compensation;

[0026] The mathematical model of the permanent magnet speed-regulating motor is based on the flux linkage equation in a two-phase rotating coordinate system. The derived set of voltage equations for the stator and rotor circuits is as follows:

[0027]

[0028] In the formula, R is the armature rotor resistance, u q and u d These are the d-axis and q-axis components of the armature rotor voltage, i q and i d These are the d-axis and q-axis components of the armature rotor current, respectively, ω e L is the relative electrical angular velocity of the permanent magnet rotor flux linkage relative to the armature rotor flux linkage. d and L d These are the inductance components along the d-axis and q-axis, respectively, ψ f It is a permanent magnet flux linkage, ω re It is the electric angular velocity of the permanent magnet rotor flux linkage, ω se It is the electric angular velocity of the armature rotor flux linkage;

[0029] During the process of the flywheel releasing or absorbing energy, the electromagnetic torque generated by the permanent magnet speed-regulating motor to support the acceleration and deceleration of the flywheel is expressed as:

[0030]

[0031] In the formula, J r ω is the sum of the rotational inertia of the permanent magnet rotor and the flywheel. mr T represents the mechanical rotational speed of the flywheel and the permanent magnet rotor. Lr T is the load torque applied to the permanent magnet rotor. er B is the electromagnetic torque generated by the permanent magnet speed-regulating motor, and B is the air damping coefficient.

[0032] The reverse electromagnetic torque through which the supporting active power generated by the armature rotor is transmitted to the synchronous condenser is expressed as:

[0033]

[0034] In the formula, J s ω is the sum of the moments of inertia of the armature rotor and the excitation rotor of the synchronous condenser. msTo determine the mechanical speeds of the synchronous condenser's excitation rotor and armature rotor, T Ls T is the load torque acting on the second shaft system. es The reverse electromagnetic torque generated for the permanent magnet speed-regulating motor.

[0035] Furthermore, neglecting the switching losses, line losses, and friction losses of the converter, the mechanical energy E of the flywheel, the mechanical power P generated, and the system's own inertia H are respectively:

[0036]

[0037]

[0038]

[0039] In the formula, ω gn p is the rated electrical angular frequency of the power grid. n S represents the number of pole pairs of the permanent magnet in a permanent magnet speed-regulating motor. n The rated capacity of the permanent magnet flywheel energy storage synchronous condenser system.

[0040] Furthermore, in step S3, the active power feed control includes the power distribution relationship related to frequency support and active power compensation.

[0041] The power allocation relationship is as follows:

[0042] The instantaneous power released by the flywheel is input to the power grid through two paths: one via the armature stator of the synchronous condenser, and the other via the armature rotor winding of the permanent magnet speed-regulating motor. Specifically:

[0043] P = P s +P r ;

[0044] The power input to the power grid from the armature stator of the synchronous condenser is expressed as:

[0045]

[0046] This power is controlled by the speed of the synchronous condenser's excitation rotor.

[0047] The power input to the power grid from the armature rotor winding of the permanent magnet speed-regulating motor is expressed as follows:

[0048]

[0049] This part of the power is affected by both the synchronous condenser excitation rotor speed and the converter energizing frequency;

[0050] The instantaneous power released by the flywheel is ultimately expressed in the form of current, as follows:

[0051]

[0052] By controlling i d i q and ω mr Change the power released by the permanent magnet flywheel energy storage synchronous condenser system.

[0053] The present invention has the following beneficial effects:

[0054] (1) In this invention, the flywheel is used as an energy storage module, which enhances the active power regulation capability of the traditional synchronous condenser and expands its own inertia, giving it a function similar to a doubly fed motor, while having a wider speed regulation range and stronger active power output capability than a doubly fed motor.

[0055] (2) In this invention, a novel dual-rotor permanent magnet speed-regulating motor is introduced, which essentially forms a mechanical isolation between the energy storage system and the synchronous condenser. Power is transmitted solely by electromagnetic torque, which enhances system safety. This allows the armature windings of the permanent magnet speed-regulating motor and the armature windings of the synchronous condenser to be connected to the grid simultaneously, avoiding the need for modifications to the rotor winding control method required for doubly fed motors, thus reducing control costs. At the same time, by controlling the output power of the permanent magnet speed-regulating motor instead of controlling the overall output power, a significant reduction in the current in the converter can be achieved, reducing control difficulty and improving control safety.

[0056] (3) The controller introduced in this invention is a controller with active control system inertia. It can further flexibly adjust the system inertia on the basis of expanding the system's own inertia, so that it can make more intelligent active power output decisions for complex power grid environments and enhance the robustness of the power grid. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a structural block diagram of the permanent magnet flywheel energy storage phase-shifting system of the present invention;

[0059] Figure 2 This is a schematic diagram of the magnetic flux distribution of the dual rotors in the permanent magnet speed-regulating motor of the present invention;

[0060] Figure 3 This is a schematic diagram of the force analysis of the permanent magnet speed-regulating motor of the present invention;

[0061] Figure 4This is a schematic diagram illustrating the functional relationships of the permanent magnet flywheel synchronous condenser system of the present invention;

[0062] Figure 5 This is a flowchart of the control method for the permanent magnet flywheel synchronous condenser system of the present invention;

[0063] The attached diagram lists the components represented by each number as follows:

[0064] 1. Flywheel; 2. Permanent magnet speed-regulating motor; 21. Armature rotor; 211. Armature rotor core; 212. Armature rotor winding; 22. Permanent magnet rotor; 221. Permanent magnet; 222. Core; 3. Synchronous condenser; 31. Synchronous condenser armature stator; 32. Synchronous condenser excitation rotor; 4. Controller; 41. Power grid frequency detection unit; 42. Power calculation unit; 43. Command decision unit; 5. Converter; 6. First shaft system; 7. Second shaft system. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0066] like Figure 1 and Figure 2 As shown, this embodiment provides a permanent magnet flywheel energy storage synchronous condenser system, including a flywheel 1, a permanent magnet speed-regulating motor 2, a synchronous condenser 3, a controller 4, a converter 5, a first shaft system 6, and a second shaft system 7.

[0067] The armature rotor 21 includes an armature rotor core 211 and an armature rotor winding 212; the armature rotor winding 212 is installed in the armature rotor core slot; the armature rotor winding 212 is connected to the converter 5, and the armature rotor core 211 is connected to the other end of the second shaft system 7.

[0068] The permanent magnet rotor 22 includes a permanent magnet 221 and a permanent magnet rotor core 222; the permanent magnet 221 is attached to the permanent magnet rotor core 222; the permanent magnet rotor core 222 is connected to one end of the first shaft system 6.

[0069] The power grid is connected to converter 5 and synchronous condenser 3. One bus of the power grid exchanges power with the permanent magnet speed-regulating motor 2 through the winding of converter 5, and the other bus is connected to the excitation stator winding of synchronous condenser 3 to exchange power with synchronous condenser 3. Controller 4 acquires the power grid frequency signal and active power signal, and generates a frequency conversion signal to control converter 5 in combination with power system dispatch instructions. Converter 5 receives the frequency conversion signal from controller and generates a current of the corresponding frequency, which is injected into permanent magnet speed-regulating motor 2. After being controlled, the speed of permanent magnet rotor 22 of permanent magnet speed-regulating motor 2 is changed. Flywheel 1 is rigidly connected to permanent magnet speed-regulating motor 2 through first shaft system 6. The speed of permanent magnet rotor 22 changes synchronously with flywheel 1. The speed of the flywheel 1 changes with the rotational speed of the permanent magnet speed-regulating motor 2 under the command of the controller 4, and its own energy storage state changes accordingly. When the speed of the flywheel 1 decreases, it feeds power to the grid, and when the speed of the flywheel 1 increases, it absorbs power from the grid. The permanent magnet speed-regulating motor 2 is rigidly connected to the flywheel 1 and the synchronous condenser 3 through the first shaft system 6 and the second shaft system 7, respectively. When the speed of the flywheel 1 changes, the torque generated is transmitted to the synchronous condenser 3 through the electromagnetic conversion relationship of the permanent magnet speed-regulating motor. The synchronous condenser is subjected to torque and transmits the active power generated by the flywheel to the grid through the stator armature 31 winding. At the same time, the permanent magnet speed-regulating motor 2 itself is electrically connected to the grid, and while subjected to torque, it feeds a part of the active power to the grid 1.

[0070] In one specific embodiment of this example, the controller 4 includes a grid frequency detection unit 41, a power calculation unit 42, and a command decision unit 43. The grid frequency detection unit 41 can calculate the current active power output and current and voltage phases of the grid by equipping it with an ammeter, voltmeter, and phase-locked loop. It monitors the grid frequency by detecting the current periodic waveform and calculates the current grid frequency change rate by multiplying the grid frequency detection value by the detection frequency at a specified detection frequency. After receiving the data from the frequency detection unit 41, the command decision unit 43 determines whether the permanent magnet flywheel energy storage synchronous condenser system should perform inertia support and primary frequency regulation based on the grid frequency safety threshold set by the system, and generates a decision command signal. The power calculation unit 42 is controlled by the current decision command signal to perform active power output calculation in response and generates a frequency conversion signal to be transmitted to the converter 5.

[0071] Specifically, the instruction decision unit includes two specific instructions: inertia support and primary frequency regulation. The specific instruction decision is made based on the magnitude of the deviation of the current power grid frequency from the rated value and whether the power grid frequency drop rate exceeds the current threshold.

[0072] When the power grid frequency descent rate exceeds the frequency descent rate threshold When the command decision unit issues an inertial support command, it does so; otherwise, it does not issue a command. The calculation method of the power calculation unit is expressed as follows:

[0073]

[0074] In the formula, P i The permanent magnet flywheel energy storage synchronous condenser system outputs electromagnetic power, P i0 T represents the output electromagnetic power of the permanent magnet flywheel energy storage synchronous condenser system when the system frequency does not drop. J The inertial time constant of the permanent magnet flywheel energy storage synchronous condenser system is... f is the rate of change of the system frequency. g S is the rated frequency of the power grid. n The rated capacity of the permanent magnet flywheel energy storage synchronous condenser system is given by f, where f is the current frequency of the power grid.

[0075] Furthermore, when the difference between the grid frequency and the rated frequency after a frequency drop exceeds a set frequency difference threshold Δf d At that time, the instruction decision unit issues a frequency modulation instruction, and the power calculation unit calculates the power as follows:

[0076]

[0077] In the formula, K p This is the active frequency regulation coefficient for primary frequency regulation.

[0078] The frequency difference threshold judgment decision has a higher priority than the frequency drop rate threshold. That is, when the frequency difference exceeds the difference threshold, a frequency modulation command is given priority; when the frequency difference does not exceed the difference threshold, a command decision is made.

[0079] like Figure 2 As shown, in a specific embodiment of this example, the permanent magnet speed-regulating motor 2 adopts a permanent magnet synchronous motor structure with an internal permanent magnet rotor; the flywheel 1 transmits torque to the permanent magnet rotor 22 through the first shaft system; the permanent magnet rotor 22 generates electromagnetic torque through the interaction of the rotating magnetic field with the rotating magnetic field of the armature rotor 21, and the reverse electromagnetic torque generated on the armature rotor 21 acts on the excitation rotor 32 of the synchronous condenser 3 through the second shaft system, thereby realizing the transmission of torque and the exchange of power.

[0080] The expression for the mechanical model (dynamic equation) of the permanent magnet flywheel synchronous condenser system is as follows:

[0081]

[0082] In the formula, J r ω is the sum of the rotational inertia of the permanent magnet rotor and the flywheel. mr T represents the mechanical rotational speed of the flywheel and the permanent magnet rotor. Lr T is the load torque applied to the permanent magnet rotor. er The electromagnetic torque generated by the permanent magnet speed-regulating motor, T esT is the reverse electromagnetic torque generated by the permanent magnet speed-regulating motor. er With T es Equal in magnitude but opposite in direction, B is the air damping coefficient, J s ω is the sum of the moments of inertia of the armature rotor and the synchronous condenser rotor. ms To synchronize the mechanical speeds of the synchronous condenser rotor and armature rotor, T Ls This is the load torque acting on the shaft system.

[0083] like Figure 3 As shown, the permanent magnet rotor 22 generates electromagnetic torque through the interaction of its rotating magnetic field with the rotating magnetic field of the armature rotor 21. Specifically, the torque generation process involves the three-phase flux linkage vector of the armature rotor winding moving in space at an angle of ω. es The electric angular velocity of rotation is given by the known electric angular velocity of the permanent magnet flux linkage, which is ω. er The difference in rotational speed between the two flux linkages is the steady-state current frequency in converter 5. After transforming the three-phase coordinate system of the permanent magnet speed-regulating motor armature rotor to the synchronous rotating coordinate system dq, the synchronous speed of the new synchronous rotating coordinate system is equivalent to the difference between the rotational speed of the armature winding three-phase flux linkage vector in space and the rotational electric angular velocity of the permanent magnet flux linkage.

[0084] Based on the fundamental characteristics of the equivalent synchronous rotating coordinate system, the electromagnetic model of the system can be established as shown below:

[0085]

[0086] In the formula, R is the armature rotor resistance, u q and u d These are the d-axis and q-axis components of the armature rotor voltage, i q and i d These are the d-axis and q-axis components of the armature rotor current, respectively, ω e L is the relative electrical angular velocity of the permanent magnet rotor flux linkage relative to the armature rotor flux linkage. d and L d These are the inductance components along the d-axis and q-axis, respectively, ψ f It is a permanent magnet flux linkage, ω re It is the electric angular velocity of the permanent magnet rotor flux linkage, ω se It is the electric angular velocity of the armature rotor flux linkage.

[0087] To ensure that the speed of the permanent magnet speed-regulating motor is stable and controllable, the frequency of the current flowing through the converter needs to be equal to the difference between the electric angular frequencies of the armature rotor and the permanent magnet rotor flux linkage.

[0088] When the system is connected to the grid, the stator winding of the synchronous condenser is connected to the power grid with a frequency of f1, and the current in the three-phase stator windings forms a magnetomotive force that rotates relative to the stator at a synchronous speed ω1. Simultaneously, a three-phase symmetrical current with a frequency of f2 is injected into the three-phase windings of the armature rotor, generating a rotating magnetomotive force with an angular frequency of ω2 relative to the armature rotor. Given that the electric angular velocity of the phase converter rotor is ω se Then the armature rotor magnetomotive force The electrical angular frequency relative to the phase converter stator is ω2+ω se According to the working principle of AC motors, the armature rotor magnetomotive force... With adjusting the stator magnetomotive force of the camera In electrical angular space, relative stillness is required for electromechanical energy conversion to occur. Therefore, the electrical angular frequency of the power grid, the electrical angular frequency of the armature rotor rotation, and the electrical angular frequency of the combined rotating magnetomotive force of the AC variable frequency speed regulation within the armature satisfy the following:

[0089] ω se +ω2=ω1.

[0090] For a permanent magnet speed-regulating motor, the permanent magnet rotor forms an electrical angular frequency ω relative to the stationary coordinate space. re The rotating magnetomotive force F3, the angular frequency of the permanent magnet rotation, the electric angular frequency of the armature rotor rotation, and the electric angular frequency of the combined rotating magnetomotive force of the AC variable frequency speed regulation within the armature satisfy the following:

[0091] ω se +ω2=ω re

[0092] By changing the frequency ω2 of the alternating current in the converter, the rotational speed of the permanent magnet rotor of the permanent magnet speed-regulating motor can be changed, thereby achieving flywheel speed regulation and realizing the mutual conversion of mechanical energy and electrical energy.

[0093] In one specific embodiment of this example, the stored energy E, instantaneous output power P, and inertia coefficient H in the system are represented as follows:

[0094]

[0095]

[0096]

[0097] In the formula, ω gn p is the rated electrical angular frequency of the power grid. n S represents the number of pole pairs of the permanent magnet in a permanent magnet speed-regulating motor. n The rated capacity of the permanent magnet flywheel energy storage synchronous condenser system.

[0098] In one specific embodiment of this example, the dual-path power feed can be described as follows:

[0099] The flywheel uses the electromagnetic torque transmitted by the permanent magnet speed-regulating motor as the driving torque for the synchronous condenser. A portion of the power (called stator power) is input into the power grid through the stator armature of the synchronous condenser.

[0100]

[0101] The flywheel acts as a prime mover, driving a permanent magnet variable speed motor to rotate. This induces a current in the armature rotor windings, and a portion of the power (called slip power) is input into the power grid through the armature rotor.

[0102]

[0103] The stator power in steady state is only related to the synchronous speed of the synchronous condenser rotor; the slip power is related to the difference in speed between the flywheel and the synchronous condenser; the sum of the stator power and the flywheel power, after ignoring the effects of losses and friction, is equal to the instantaneous output power of the flywheel.

[0104] The sign of the slip power is related to the difference in speed between the flywheel and the synchronous condenser under steady state. When the flywheel speed is lower than the synchronous condenser speed, the slip power is negative, and the permanent magnet speed-regulating motor sends power to the grid. When the flywheel speed is higher than the synchronous condenser speed, the slip power is positive, and the permanent magnet speed-regulating motor absorbs power from the grid.

[0105] The output power of the flywheel in steady state depends only on the flywheel's own rotational speed. When the flywheel decelerates, the flywheel power is negative, and the flywheel permanent magnet energy storage synchronous condenser system sends power to the grid. When the flywheel accelerates, the flywheel power is positive, and the flywheel permanent magnet energy storage synchronous condenser system absorbs power from the grid.

[0106] like Figure 4 As shown, there exists another analysis method equivalent to the system model in this embodiment, namely... Figure 2 The permanent magnet regulating motor shown has its armature rotor and synchronous condenser excitation rotor combined into a first rotor, and its flywheel and permanent magnet rotor combined into a second rotor. The synchronous condenser armature stator is considered as the stator, forming a dual-rotor motor structure of first rotor-second rotor-stator. In the figure, P mec P is the mechanical power input to the flywheel. s P is the active power generated on the stator side. c P represents the active power obtained by the grid-side converter from the grid. g P is the active power fed into the grid by the permanent magnet flywheel synchronous condenser system. r This refers to the active power absorbed by the armature rotor side. Based on... Figure 3Based on the force analysis results, in the equivalent system, the equivalent motor stator is the synchronous condenser armature stator, directly connected to the power grid. The first rotor is an equivalent structure of synchronous condenser excitation rotor-shaft system-armature rotor, connected to the power grid via an AC-DC-AC converter. The AC-DC-AC converter consists of two back-to-back voltage-type PWM converters; the side closer to the first rotor is called the rotor-side converter, and the side closer to the power grid is called the grid-side converter. The grid-side converter generally operates in high power factor rectification mode, providing a constant DC bus voltage to the rotor-side converter. The rotor-side converter achieves variable speed constant frequency operation of the permanent magnet speed-regulating motor by controlling the rotor current and voltage. The second rotor is the permanent magnet rotor of the permanent magnet speed-regulating motor. This part is mechanically connected to the flywheel shaft system (i.e., the first shaft system), receiving power exchange from the flywheel. Without external torque exchange and ignoring air resistance and winding losses, the relationship between the mechanical power output by the flywheel and the active power output by the stator and rotor is:

[0107] P g =P s +P c =P s +P r =P mec .

[0108] Based on the functional relationship of synchronous motors, it can be seen that due to the speed difference between the stator and rotor flux linkages in a speed-regulating motor, the speed-regulating motor needs to absorb additional slip power to maintain its stable speed operation. The relationship between the active power supplied to the grid by the permanent magnet flywheel synchronous condenser system and the active power of the armature rotor is as follows:

[0109]

[0110] The direction of the active power flow on the armature rotor side is related to the direction of the speed difference between the permanent magnet rotor and the armature rotor. Power is defined as positive when flowing into the grid; when the flywheel speed decreases, the first derivative of the flywheel speed is negative, P... s The current is positive, the stator armature of the synchronous condenser outputs active power to the grid, and the slip becomes negative after the permanent magnet rotor speed decreases. r If the value is negative, the armature rotor absorbs active power from the power grid.

[0111] In one specific embodiment of this example, the system's frequency modulation power response control method is expressed as follows:

[0112] Step 1: The controller issues a frequency regulation decision command to the permanent magnet flywheel energy storage synchronous condenser system based on the current power system dispatch instructions, the current detected grid frequency, and the feedback active power output information. Specifically, the system frequency regulation decision command in Step 1 is as follows: when the detected grid frequency deviation is too large, the decision module generates a primary frequency regulation command; when the detected grid frequency deviation is less than a set threshold and the grid frequency change rate deviation is too large, the decision module generates an inertia response command; when the detected grid frequency deviation is less than a set threshold and the grid frequency change rate deviation is less than a set threshold, the decision module switches to power dispatch operation and generates a controllable output power command.

[0113] Step 2: The controller calculates the active power released or absorbed by the permanent magnet synchronous condenser flywheel energy storage system according to the frequency regulation decision command generated in Step 1, and in combination with the collected grid frequency and voltage and current information. Based on the frequency regulation decision command and the calculated power, the controller gives the active power control command of the flywheel energy storage synchronous condenser.

[0114] Step 3: The converter receives the active power control command provided by the controller, converts it into a corresponding control signal to drive the permanent magnet speed-regulating motor, controls the speed of the permanent magnet rotor of the permanent magnet motor, and enables the permanent magnet flywheel synchronous condenser system to output the specified active power.

[0115] The system outputs a specified active power consisting of two parts: slip power and stator power. By adjusting the converter's energizing frequency, the distribution of active power from the dual feeders and the regulation of the flywheel speed can be achieved.

[0116] In one specific embodiment of this example, the controller's instruction unit further includes, for example: Figure 5 The decision-making and active power calculation process shown herein enables power control of the permanent magnet flywheel energy storage synchronous condenser system. The specific control method is as follows:

[0117] Step 1: Determine the maximum tolerance limit and safety threshold for the frequency change rate and frequency change value of the grid connected to the system.

[0118] Step 2: Determine whether the output power is controllable based on external dispatch instructions. If there is a clear output power instruction from the outside, directly decide to output the specified active power value; otherwise, enter the frequency regulation decision mode.

[0119] Step 3: When the controller selects to enter the frequency regulation decision mode, the specific mode is as follows: First, it determines whether the current grid frequency has dropped or risen above the safety threshold. If so, it enters the primary frequency regulation decision mode and outputs an active power command using the combined effect of the droop control coefficient and inertia regulation.

[0120]

[0121] If not, proceed to inertia-supported decision-making;

[0122] Step four: When the controller enters the inertia support decision, the output power of the system is only affected by the current grid frequency change rate. The faster the grid frequency changes, the larger the specified inertia power value. First, it determines whether the current grid frequency change rate has fallen or risen above the safety threshold. If so, it enters the inertia support decision and outputs the active power command as follows:

[0123]

[0124] If not, the decision is to output 0 active power at the current moment;

[0125] Step 5: Add a proportional-integral term to the output active power command to ensure zero steady-state error in the output power and guarantee output power accuracy.

[0126]

[0127] In the formula, P out K is the final output power command of the controller. p1 K is the power loop proportional coefficient. i1 This represents the power loop integral coefficient.

Claims

1. A permanent magnet flywheel energy storage synchronous condenser system, characterized in that, It includes a flywheel (1), a permanent magnet speed-regulating motor (2), a synchronous condenser (3), a controller (4), a converter (5), a first shaft system (6), and a second shaft system (7); The armature stator (31) of the synchronous condenser (3) is connected to the power grid, and the excitation rotor (32) of the synchronous condenser is connected to one end of the second shaft system (7); the permanent magnet speed-regulating motor (2) includes an armature rotor (21) and a permanent magnet rotor (22), and the armature rotor (21) is connected to the other end of the second shaft system (7), so that the excitation rotor (32) of the synchronous condenser and the armature rotor (21) of the permanent magnet speed-regulating motor rotate synchronously; The permanent magnet rotor (22) is connected to one end of the first shaft system (6), and the flywheel (1) is connected to the other end of the first shaft system (6), so that the flywheel (1) and the permanent magnet rotor (22) rotate synchronously; The controller (4) includes a power grid frequency detection unit (41), a power calculation unit (42), and an instruction decision unit (43). The power grid frequency detection unit (41) is used to acquire the power grid current frequency signal and power signal, and send the acquired data to the instruction decision unit (43). The instruction decision unit (43) generates an instruction decision based on the data from the power grid frequency detection unit (41) and the power grid's dispatch instructions, and sends it to the power calculation unit (42). The power calculation unit (42) receives the instruction from the instruction decision unit (43), determines the required system inertia support power, and transmits the frequency conversion signal to the converter (5). The armature rotor (21) includes an armature rotor core (211) and an armature rotor winding (212); the armature rotor winding (212) is installed in the slot of the armature rotor core; the armature rotor winding (212) is connected to the converter (5), and the armature rotor core (211) is connected to the other end of the second shaft system (7); The permanent magnet rotor (22) includes a permanent magnet (221) and a permanent magnet rotor core (222); the permanent magnet (221) is attached to the permanent magnet rotor core (222); the permanent magnet rotor core (222) is connected to one end of the first shaft system (6); The connection between the permanent magnet rotor (22) and one end of the first shaft system (6) is changed to the connection between the permanent magnet rotor (22) and the other end of the second shaft system (7), and the connection between the armature rotor (21) and the other end of the second shaft system (7) is changed to the connection between the armature rotor (21) and one end of the first shaft system (6); The connection between the armature rotor core (211) and the other end of the second shaft system (7) is changed to the connection between the armature rotor core (211) and one end of the first shaft system (6), so that the armature rotor and the flywheel rotate at the same speed; the connection between the permanent magnet rotor core (222) and one end of the first shaft system (6) is changed to the connection between the permanent magnet rotor core (222) and the other end of the second shaft system (7), so that the permanent magnet rotor and the flywheel rotate at the same speed.

2. The permanent magnet flywheel energy storage synchronous condenser system according to claim 1, characterized in that, The permanent magnet speed-regulating motor achieves variable frequency speed regulation by controlling the armature rotor through a converter and controller. The power supply of the converter is taken from the power grid at the end of the synchronous condenser.

3. A control method for a permanent magnet flywheel energy storage synchronous condenser system, used to control the permanent magnet flywheel energy storage synchronous condenser system as described in claim 1 or 2, characterized in that, Including the following steps: S1: Establish a mathematical model of the permanent magnet flywheel energy storage synchronous condenser system, and use this mathematical model as the control object; S2: For the controller and the controlled object, establish a frequency modulation power response control method to realize the control of the grid frequency and the system inertia support power; S3: According to the system inertia support power control command of the controller, realize the active power feed control of the permanent magnet flywheel energy storage synchronous condenser system.

4. The control method for the permanent magnet flywheel energy storage synchronous condenser system according to claim 3, characterized in that, In step S2, the frequency modulation power response control method is implemented by adjusting the flywheel speed. The specific steps are as follows: S21: The grid frequency detection unit acquires the grid current frequency signal and power signal, and sends the acquired data to the command decision unit. The command decision unit gives the frequency regulation decision command of the permanent magnet flywheel energy storage synchronous condenser system based on the current power system dispatch command and the current detected grid frequency and feedback active power output information. S22: The power calculation unit calculates the active power released or absorbed by the permanent magnet synchronous condenser flywheel energy storage system according to the frequency regulation decision command generated in S21, and gives the active power control command of the permanent magnet flywheel energy storage synchronous condenser system by combining the frequency regulation decision command and the calculated active power. S23: The converter receives the active power control command provided by the controller, converts it into a control electrical signal to drive the permanent magnet speed-regulating motor, controls the speed of the permanent magnet rotor of the permanent magnet speed-regulating motor, and enables the permanent magnet flywheel energy storage synchronous condenser system to output the specified active power.

5. The control method for the permanent magnet flywheel energy storage synchronous condenser system according to claim 3, characterized in that, The mathematical model of the permanent magnet flywheel energy storage synchronous condenser system includes a mathematical model of a permanent magnet speed-regulating motor related to frequency support and active power compensation. The mathematical model of the permanent magnet speed-regulating motor is based on the flux linkage equation in a two-phase rotating coordinate system. The derived set of voltage equations for the stator and rotor circuits is as follows: In the formula, For armature rotor resistance, and These are the d-axis and q-axis components of the armature rotor voltage, respectively. and These are the d-axis and q-axis components of the armature rotor current, respectively. It is the relative electrical angular velocity of the permanent magnet rotor flux linkage relative to the armature rotor flux linkage. and These are the inductance components along the d-axis and q-axis, respectively. It is a permanent magnet flux chain. It is the electric angular velocity of the permanent magnet rotor flux linkage. It is the electric angular velocity of the armature rotor flux linkage; During the process of the flywheel releasing or absorbing energy, the electromagnetic torque generated by the permanent magnet speed-regulating motor to support the acceleration and deceleration of the flywheel is expressed as: In the formula, This is the sum of the rotational inertia of the permanent magnet rotor and the flywheel. The mechanical rotational speeds of the flywheel and permanent magnet rotor. The load torque applied to the permanent magnet rotor. The electromagnetic torque generated by the permanent magnet speed-regulating motor This refers to the air damping coefficient; The reverse electromagnetic torque through which the supporting active power generated by the armature rotor is transmitted to the synchronous condenser is expressed as: In the formula, This is the sum of the moments of inertia of the armature rotor and the excitation rotor of the synchronous condenser. To synchronize the mechanical speeds of the excitation rotor and armature rotor of the synchronous condenser, The load torque acting on the second shaft system, The reverse electromagnetic torque generated for the permanent magnet speed-regulating motor.

6. The control method for the permanent magnet flywheel energy storage synchronous condenser system according to claim 5, characterized in that, Ignoring converter switching losses, line losses, and friction losses, the flywheel's mechanical energy E, the generated mechanical power P, and the system's own inertia H are respectively: In the formula, The rated electrical angular frequency of the power grid. This refers to the number of pole pairs of the permanent magnet in a permanent magnet speed-regulating motor. The rated capacity of the permanent magnet flywheel energy storage synchronous condenser system.

7. The control method for the permanent magnet flywheel energy storage synchronous condenser system according to claim 6, characterized in that, In step S3, active power feed control includes the power distribution relationship related to frequency support and active power compensation. The power allocation relationship is as follows: The instantaneous power released by the flywheel is input to the power grid through two paths: one via the armature stator of the synchronous condenser, and the other via the armature rotor winding of the permanent magnet speed-regulating motor. Specifically: ； The power input to the power grid from the armature stator of the synchronous condenser is expressed as: This power is controlled by the speed of the synchronous condenser's excitation rotor. The power input to the power grid from the armature rotor winding of the permanent magnet speed-regulating motor is expressed as follows: This part of the power is affected by both the synchronous condenser excitation rotor speed and the converter energizing frequency; The instantaneous power released by the flywheel is ultimately expressed in the form of current, as follows: ， By controlling and Change the power released by the permanent magnet flywheel energy storage synchronous condenser system.

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