CN115360828A - Flywheel energy storage system active disturbance rejection method based on double-loop optimization feedforward coordination control - Google Patents
Flywheel energy storage system active disturbance rejection method based on double-loop optimization feedforward coordination control Download PDFInfo
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Abstract
The invention provides an active disturbance rejection method of a flywheel energy storage system based on double-loop optimization feedforward coordination control, which comprises the following steps: estimating the current of the machine side converter by using the voltage and current measurement value of the motor and coordinate transformation; introducing the current of the machine side converter as a feedforward term and superposing the current to the output end of the voltage outer ring of the network side converter; a current inner loop of the grid-side converter is additionally provided with a capacitance current control loop, and unbalanced current on a capacitor caused by external disturbance is compensated through direct control of capacitance current. The effectiveness of the control strategy is verified through simulation, the integrated coordination control of the converters on the two sides can be realized, and the dynamic performance of the flywheel energy storage system is integrally improved.
Description
Technical Field
The invention belongs to the technical field of optimization control of power systems, and particularly relates to an active disturbance rejection method of a flywheel energy storage system based on double-loop optimization feedforward coordination control.
Background
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In the process of energy consumption clean and low-carbon, an electric power system necessarily occupies the leading position of an energy system and bears the important task of constructing a clean, low-carbon, safe and efficient energy system, so that the development of new energy needs to be greatly promoted, and a novel electric power system taking the new energy as a main body is constructed. In a novel power system, a high-proportion new energy power generation system and a novel load have strong fluctuation and randomness, and a series of technical challenges such as power and electric quantity balance probability, power grid tide bidirectional, diversified operation modes, complicated stabilization mechanism and the like are brought. The energy storage has bidirectional power characteristics and quick adjustment capability, can realize functions of peak clipping and valley filling, smooth new energy output fluctuation, frequency and voltage support and the like, and is bound to become a basis and a key technology for constructing a novel power system.
Flywheel energy storage is a physical energy storage technology who originates in the aerospace field, compares other traditional energy storage technologies, has characteristics such as minute-second level, high-power, long-life, high efficiency, density are big, and is very low to the requirement and the influence of environment, and the depth of charge-discharge and the prediction of health state are simple relatively, and conveniently realize the modularization and use. With the rapid development of power electronic technology, magnetic suspension technology and physical material technology, the monomer capacity of flywheel energy storage technology will be larger and larger, even megawatt level is realized, the corresponding matching safety and grid-connected control strategy will be more and more advanced, and it will certainly become one of the energy storage technologies of the future novel power system with development potential and application prospect.
The conventional back-to-back frequency converter control strategies are both independent control on two sides, so that for a power grid side converter, a motor side converter and flywheel energy storage can be integrally used as a load of the power grid side converter, and due to the working property of the flywheel energy storage, the load changes frequently, the amplitude is large, and the power grid side converter belongs to strong external disturbance. Load current's change must arouse that direct current bus voltage changes, then net side converter voltage outer loop output changes, just begins to exert the regulating action after the information of voltage outer loop is received to the current inner loop, through the hysteresis of several links, leads to the net to survey the demand that current must not the quick match load, causes the unbalance of both sides electric current, according to kirchhoff's current law, unbalanced current will pass through direct current capacitance to arouse direct current voltage's undulant.
Therefore, research on the aspect of flywheel energy storage grid-connected control technology finds that the system has the problem that the direct-current bus voltage fluctuation is large due to insufficient disturbance resistance in the switching process of different working conditions of flywheel energy storage.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides an active disturbance rejection method of a flywheel energy storage system based on double-loop optimization feedforward coordination control, provides an optimization double-loop feedforward coordination control strategy of a double-side PWM converter, and verifies the accuracy and effectiveness of the optimization double-loop feedforward coordination control strategy based on simulation modeling.
In order to achieve the above object, one or more embodiments of the present invention provide the following technical solutions:
in a first aspect, an active disturbance rejection method of a flywheel energy storage system based on double-loop optimization feedforward coordination control is disclosed, and comprises the following steps:
estimating the current of a machine side converter by using the voltage and current measurement value of the motor and coordinate transformation;
introducing the current of a machine side converter as a feedforward term, and superposing the current to the output end of a voltage outer ring of the network side converter;
a current inner ring of the network side converter is additionally provided with a capacitance current control ring, and unbalanced current on a capacitor caused by external disturbance is compensated through direct control of capacitance current.
The further technical scheme also comprises the following steps: and an amplitude limiting link is added in a load current feedforward link so as to maintain the stability of the system while ensuring the improvement of the dynamic performance of the low-rotation-speed working condition.
The technical scheme is further characterized in that the capacitor current is directly controlled, and the method specifically comprises the following steps:
the given value of the capacitance current is set to be zero, the deviation between the given value and the sampling value of the capacitance current is output to a current inner ring terminal through a PI regulator, wherein a differential link is arranged to compensate an integral term in the current inner ring, dynamic time delay is eliminated, and meanwhile, a d-q axis feedforward component of the power grid voltage is added into the current inner ring to compensate the influence of power grid voltage disturbance.
In a further technical scheme, the current inner loop control equation of the grid-side converter is as follows:
in the formula: k pq 、K pd 、K pc As proportional coefficient of PI regulator, K iq 、K id 、K ic For the integral coefficient of the PI regulator, u f * For feedforward summation, K f Is a feedforward coefficient, i cap Is the capacitive current.
According to the further technical scheme, the current of the machine side converter is estimated by utilizing the measured value of a voltage and current sensor of the motor and a coordinate transformation theory according to the outlet power of the machine side converter.
In a second aspect, an active disturbance rejection system of a flywheel energy storage system based on dual-loop optimization feedforward coordination control is disclosed, which includes:
a machine-side controller configured to: estimating the current of the machine side converter by using the voltage and current measurement value of the motor and coordinate transformation;
introducing the current of the machine side converter as a feedforward term and superposing the current to the output end of the voltage outer ring of the network side converter;
a network-side controller configured to: a current inner ring of the network side converter is additionally provided with a capacitance current control ring, and unbalanced current on a capacitor caused by external disturbance is compensated through direct control of capacitance current.
The above one or more technical solutions have the following beneficial effects:
according to the invention, a capacitance current control loop is added in the traditional current inner loop control structure of the network side converter, acts on the output end of the voltage outer loop, simultaneously refers to the estimated value of the load current and the voltage of the power grid as feedforward items, acts on the output end of the current inner loop, and finally verifies the effectiveness of a control strategy through simulation, so that the integrated coordination control of the converters on two sides can be realized, and the dynamic performance of the flywheel energy storage system is integrally improved.
Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
FIG. 1 is a schematic diagram of the flywheel energy storage system;
FIG. 2 is a structural diagram of a flywheel energy storage single grid-connected system;
FIG. 3 is a schematic diagram of a grid-side converter control strategy;
FIG. 4 is a schematic diagram of a grid-side converter control strategy;
FIG. 5 is a diagram of a simulation result of the rotational speed of the flywheel motor;
FIG. 6 is a diagram showing a simulation result of the electromagnetic torque of the flywheel motor;
FIG. 7 is a diagram of a simulation result of q-axis current of a flywheel motor;
FIG. 8 is a diagram of a simulation result of d-axis current of the flywheel motor;
FIG. 9 is a diagram of a three-phase current simulation result of the machine side converter;
FIG. 10 is a diagram of a side converter active power simulation result;
FIG. 11 is a diagram of DC bus voltage simulation results;
FIG. 12 is a partial enlarged analysis diagram of a simulation result of the DC bus voltage;
FIG. 13 is a diagram of a current inner loop control architecture based on a dual loop feedforward control strategy;
FIG. 14 is a result of two-sided current simulation under different control strategies, a) based on a conventional basic control strategy, b) based on an optimized dual-loop feedforward control strategy;
FIG. 15 is a diagram of a simulation result of capacitance current under different control strategies;
fig. 16 is a diagram of simulation results of dc bus voltages under different control strategies.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention.
The embodiments and features of the embodiments of the present invention may be combined with each other without conflict.
Example one
The embodiment discloses an active disturbance rejection method of a flywheel energy storage system based on double-loop optimization feedforward coordination control, and in order to better explain the technical scheme of the application, the following contents are introduced firstly:
regarding flywheel energy storage grid-connected system and mathematical model:
wherein, flywheel energy storage grid-connected system structure:
the basic working principle of the flywheel energy storage system is shown in fig. 1, and the flywheel energy storage system can be continuously switched among a charging working condition, a discharging working condition and a keeping working condition according to scene requirements after being connected to the power grid. Under the charging working condition, the electric energy conversion device absorbs the energy of the power grid to drive the flywheel motor and drive the flywheel body to rotate in an accelerating way, and the electric energy of the power grid is converted into the kinetic energy of the flywheel; under the discharging working condition, the flywheel motor decelerates and rotates to drive the flywheel body to transmit energy to the power grid through the electric energy conversion device, and the kinetic energy of the flywheel is converted into the electric energy of the power grid; under the working condition, the flywheel motor keeps rotating at a constant speed, and because the flywheel device is positioned in the vacuum chamber, almost no friction loss exists between the flywheel motor and air, and almost no energy exchange exists between the flywheel energy storage system and a power grid.
It can be seen that there are two key aspects to flywheel energy storage systems: firstly, a flywheel motor is rapidly controlled to continuously accelerate and decelerate so as to ensure energy conversion; and secondly, the flywheel motor and the electric energy conversion device can flexibly convert between two quadrants with energy flowing in forward and reverse directions. Therefore, from the viewpoints of operating efficiency, hardware reliability, control difficulty and the like, the simulation modeling research is carried out on the flywheel energy storage single body grid-connected system based on the permanent magnet synchronous motor and the back-to-back double PWM frequency converters, and the overall structure is shown in FIG. 2.
Flywheel energy storage grid-connected system mathematical model:
mathematical models for the flywheel and its motor:
flywheel energy storage systems rely on a flywheel rotor rotating at high speed to store energy, which can be expressed as:
in the formula: e is energy of the energy storage system, J is rotational inertia of the flywheel rotor, and omega is the angular speed of the flywheel rotor. Because the flywheel rotor and the flywheel motor are coaxial, and no air friction can be considered in the vacuum chamber, the rotational inertia of the flywheel rotor and the shafting can be superposed into the parameters of the permanent magnet synchronous motor during simulation modeling, and a mass block model of the flywheel rotor does not need to be established.
The structure of the permanent magnet synchronous motor is basically the same as that of a general induction motor, and the magnetic circuit structure of the rotor of the permanent magnet synchronous motor is the main difference from other types of motors. For grid-connected control of the three-phase PWM converter, control strategy design is very convenient and fast based on a synchronous rotating coordinate system, three-phase time variables can be converted into direct current quantities, and active and reactive component decoupling can be achieved. Therefore, only the mathematical model in the d-q coordinate system is described based on the coordinate transformation theory. In the coordinate system, a stator voltage equation of the permanent magnet synchronous motor can be expressed as follows:
in the formula: u. u d 、u q Is the d-q axis component of the stator voltage，i d 、i q Is the d-q component of the stator current, R is the stator resistance, # d 、ψ q Is the d-q component of the stator flux linkage, ω e Is the rotor electrical angular velocity. The stator flux linkage equation can be expressed as:
in the formula: l is d 、L q Is the d-q component of the stator inductance,. Psi f Representing a permanent magnet flux linkage. Substituting equation (3) into equation (1) can obtain the stator voltage equation as:
electromagnetic torque T only considering fundamental magnetic motive force of motor stator e Under the rotating coordinate system, there are:
mathematical model of the PWM converter:
according to kirchhoff's law and a coordinate transformation theory, a mathematical model of the three-phase PWM converter in a d-q coordinate system is obtained as follows:
in the formula: e.g. of the type d ′、e q ' is the d-q component of the grid electromotive force, v d 、v q Being the d-q axis component of the AC side voltage of the converter, i d ′、i q The method comprises the following steps that a component of a d-q axis of current on an alternating current side of a converter is obtained, R' is a resistance component of power grid impedance, L is an inductance component of the power grid impedance, omega is a reference angular frequency of the power grid, and p is a differential operator. According to the instantaneous power theory, the PWM converter outlet power can be expressed as:
in the formula: p is converter output active power, and Q is converter output reactive power.
Basic control strategy and simulation modeling of the system:
analyzing a system control strategy:
the key technology of the flywheel energy storage system in the electrical angle is to realize the rapid and accurate control of the rotating speed of a flywheel motor through the control of a frequency converter, and a control strategy of the flywheel energy storage system is also a core part of simulation modeling.
The power grid side converter adopts a vector control strategy based on power grid voltage orientation, and a control system of the power grid side converter consists of an inner closed-loop structure and an outer closed-loop structure. Because the flywheel motor is accelerated and decelerated continuously in the running process of the flywheel energy storage system, energy is transmitted bidirectionally between a power grid and a flywheel continuously, a network side converter is equivalent to a continuously changing load, and frequent changes of the load can be borne only by ensuring the stability of the voltage of a direct-current bus, so that the control target of an outer ring is the voltage of the direct-current bus. The control strategy employed herein is d-axis voltage orientation, e q And =0, according to equation (7), active power and reactive power are decoupled, so that the output quantity of the direct-current bus voltage outer ring can be used as a reference value of a d-axis current inner ring, and meanwhile, in order to ensure energy conversion efficiency and power quality of a power grid, a converter needs to operate in a unit power factor state, so that the reference value of the q-axis current inner ring is set to be 0. The control strategy of the grid side converter is shown in fig. 3.
The machine side converter adopts a vector control strategy based on stator flux linkage orientation, and a control system of the machine side converter consists of an inner closed-loop structure and an outer closed-loop structure. Because the network side converter is responsible for controlling the voltage of the direct current bus, the control target of the outer ring is set as the rotating speed of the motor, and the flywheel can be rapidly switched among different working conditions through direct adjustment of the rotating speed. The control strategy adopted by the inner ring is zero d-axis control method, i.e. i d * =0, the motor electromagnetic torque will be only equal to i according to equation (5) q In connection with this, decoupling of the magnetic field and the torque is achieved, and the alternating current motor is treated as a direct current motor in an approximate manner. Thus, it is possible to provideThe output quantity of the rotating speed outer ring can be used as a reference value of the q-axis current inner ring, and the d-axis current inner ring reference value is set to be 0. The control strategy of the machine side converter is shown in fig. 4.
Analyzing a system simulation result:
based on the control strategy, a flywheel energy storage single machine grid-connected system simulation model is built in MATLAB/Simulink, and key parameter settings are shown in table 1.
TABLE 1 simulation model Key parameter settings
Tab.1 Key parameter setting of simulation model
In order to research the response characteristics and the dynamic performance of the flywheel energy storage system under different working conditions, a relatively complex scene is set during simulation, as shown in table 2.
TABLE 2 simulation model scene settings
The rotating speed simulation result of the flywheel motor is shown in fig. 5, the rotating speed instruction of the motor can be quickly and accurately tracked by setting the control parameters of the machine side converter, and the flywheel energy storage system can be seamlessly switched among different working conditions. The simulation results of the electromagnetic torque of the flywheel motor, the d-q axis current of the stator, the three-phase current of the machine side converter and the active power (the positive direction is power grid-flywheel) are shown in fig. 6-10. According to the above results, under the charging working condition, the energy of the flywheel energy storage system built herein flows from the power grid side to the flywheel side, and the electromagnetic torque of the motor is positive; under the working condition, almost no energy flows between the power grid and the flywheel, and the electromagnetic torque of the motor is almost zero; under the discharge working condition, energy flows from the flywheel side to the power grid side, and the electromagnetic torque of the motor is negative; in the simulation process, the q-axis current of the motor is in a proportional relation with the electromagnetic torque, the q-axis current is kept to be zero, the higher the change rate of the rotating speed of the motor is, the larger the electromagnetic torque is, the larger the current and power interacted with the system are, and the method is consistent with theoretical analysis.
The simulation result of the direct-current bus voltage is shown in fig. 11, although the direct-current bus voltage can be generally stabilized at a given value, the amplification analysis shows that the direct-current bus voltage fluctuates to different degrees every time the working condition of the flywheel energy storage system is switched, as shown in fig. 12.
Optimally designing a system control strategy:
analyzing fluctuation reasons of the direct-current bus voltage:
the conventional back-to-back frequency converter control strategies are both independent control on two sides, so that for a power grid side converter, a motor side converter and flywheel energy storage can be integrally used as a load of the power grid side converter, and due to the working property of the flywheel energy storage, the load changes frequently, the amplitude is large, and the power grid side converter belongs to strong external disturbance. Load current's change must arouse that direct current bus voltage changes, then net side converter voltage outer loop output changes, just begins to exert the regulating action after the information of voltage outer loop is received to the current inner loop, through the hysteresis of several links, leads to the net to survey the demand that current must not the quick match load, causes the unbalance of both sides electric current, according to kirchhoff's current law, unbalanced current will pass through direct current capacitance to arouse direct current voltage's undulant.
Dynamic analysis of a traditional control strategy:
because the change range of the rotating speed of the motor of the flywheel energy storage system is large, the energy flow direction is changed frequently, the fluctuation of the direct current bus voltage is more obvious, and the inconvenience is brought to the hardware design and the dynamic performance of the system, so that a back-to-back frequency converter integrated coordination control strategy with excellent performance is necessary to be provided. Firstly, a small signal analysis method is introduced to carry out dynamic analysis on a traditional basic control strategy, and the influence of which factors in a system on the direct-current voltage is confirmed.
The grid-side converter operates in a unit power factor state, neglects switching loss and power grid impedance loss, and has the following relation:
in the formula: v is the effective value of the network voltage, I is the effective value of the network voltage, V dc Is a DC bus voltage, I L Is the effective value of the load current, I C Effective value of capacitance current, I dc Is the direct current of the grid-side converter. The variables are now decomposed into steady-state quantities and disturbance quantities, see equation (9).
In the formula: v, i, v dc 、i L 、i dc In order to be a steady-state quantity,
v dc 、i L 、i dc is the amount of turbulence. In steady state I L ＝I dc Further, combining the formula (8) and the formula (9) gives:
since the two disturbance quantities are multiplied by a second order minor component, they are small relative to the other variables and are ignored [13]. On the basis of the above, the formula (10) is transformed to obtain:
let the transfer function of the outer ring of the network side converter voltage be G u (s) an active current inner loop transfer function of G i (s) the machine side converter and the flywheel are equivalent to a load R L Equation (11) can be written as:
substituting equation (12) into equation (11) can yield:
in the formula: v. of dc * For a given value disturbance for the dc voltage, the remaining transfer functions are defined as follows:
from equation (13), it is clear that the fluctuation of the dc bus voltage has a direct relationship with the voltage set value, the grid voltage, and the load current.
Research of optimization feedforward control strategy:
according to the automatic control theory, the feedforward control method can enable the controlled quantity to predict the state of the disturbance quantity in advance, thereby achieving the purpose of rapid tracking and improving the dynamic performance of the system. The invention considers the current introduced into the machine side converter as a feedforward term, and the feedforward term is added to the output end of the voltage outer ring of the network side converter after being amplified in proportion, but the method has the following problems:
1) In reality, an extra current sensor needs to be installed on a machine-side converter, so that the cost is increased;
2) For a flywheel energy storage system, the change degree of the rotating speed is large and small, the stability of the system is damaged by an excessively large proportionality coefficient, and the effect of an excessively small proportionality coefficient on the condition that the change amplitude of the rotating speed is small is not obvious;
3) After the feedforward term is added, the current still needs to pass through the current inner loop regulator, so that certain hysteresis exists, and the improvement on the dynamic performance of the system is limited;
aiming at the problems, the invention provides an optimized feedforward control strategy which acts on an internal and external double-ring control system of a network side converter simultaneously.
Firstly, according to the formula (7), the current of the machine side converter can be estimated by utilizing the measured value of a voltage and current sensor of the motor and the coordinate transformation theory, and meanwhile, a limit is added in a load current feedforward linkAnd the amplitude link maintains the stability of the system while ensuring the improvement of the dynamic performance of the low-rotation-speed working condition. Aiming at the problem of current inner loop hysteresis, a capacitance current control loop is added to the current inner loop, and unbalanced current on a capacitor caused by external disturbance is compensated through direct control of capacitance current. The specific method is to set the capacitance current given value i cap * And setting the sampling value to be zero, and outputting the deviation of the sampling value of the capacitance current to a current inner ring terminal through a PI regulator, wherein a differential link is arranged to compensate an integral term in the current inner ring and eliminate dynamic time delay. Meanwhile, a d-q axis feedforward component of the power grid voltage is added into the current inner ring to compensate the influence of power grid voltage disturbance. Based on the double-loop feedforward coordination control strategy provided by the invention, the current inner loop control equation of the network side converter is as follows:
in the formula: k pq 、K pd 、K pc As proportional coefficient of PI regulator, K iq 、K id 、K ic For the integral coefficient of the PI regulator, u f * For feedforward summation, K f As a feedforward coefficient, i cap Is a capacitive current.
The current inner frame control structure based on the dual-loop feedforward control strategy is shown in fig. 13.
The method comprises the steps of firstly sampling three-phase current at the power grid side, three-phase voltage at the power grid side and direct-current voltage through a Hall sensor and a hardware phase-locked circuit, estimating load current iL at the motor side, obtaining a feedforward item id through a proportion link Kf and an amplitude limiting link, and superposing the feedforward item id and a d-axis current instruction value id to serve as a new d-axis current instruction value.
Secondly, the sampled capacitance current sampling value icap is compared with a given reference current value icap, which is set to 0. And sending the comparison result to a PI regulator, eliminating time delay through a differential term sL to obtain a d-axis potential feedforward term ed, and acting the d-axis potential feedforward term ed on the output end of the current inner ring.
And finally, comparing the d-axis current and the q-axis current with the command value, obtaining voltage command values vd and vq through the combined action of a decoupling term wL, the grid potentials ed and eq and a feedforward term ed, sending the voltage command values vd and vq to the SVPWM controller, outputting six paths of pulse signals to control the on-off of a switch of the PWM converter, and controlling the power flow direction and the power magnitude between the flywheel energy storage system and the grid.
And (3) optimizing a feedforward control strategy simulation verification:
the method is based on an optimized double-loop feedforward control strategy, a simulation model is improved in MATLAB/Simulink, and the strategy is verified.
Under the basic control strategy and the dual-loop feedforward coordinated control strategy proposed herein, the current simulation results of the converters on both sides are shown in fig. 14 (the positive direction is the grid-flywheel), and the capacitance current and dc bus voltage simulation results under the two strategies are shown in fig. 15 and fig. 16. According to simulation results, the optimized double-loop feedforward coordination control strategy provided by the method greatly improves the tracking capability of the current on the network side, has an obvious inhibiting effect on the fluctuation of the direct current bus voltage in the transition stage of the flywheel energy storage working condition, improves the voltage regulation speed, can fully integrate the dynamic change information of the flywheel energy storage to the network side, and integrally improves the dynamic performance of the flywheel energy storage system.
The invention is based on the mathematical models of the back-to-back double PWM frequency converters and the permanent magnet synchronous motor, a single-machine grid-connected simulation model of the flywheel energy storage system is built in the MALAB/Simulink, and the problem of large fluctuation of the direct-current bus voltage is found by analyzing the simulation result under the complex working condition. By theoretically analyzing and establishing a small-signal model, the main reason for the fluctuation of the direct-current bus voltage is clear from the disturbance of the power grid voltage and the load current.
Aiming at the problems, the invention provides an optimized double-loop feedforward coordination control strategy of a back-to-back frequency converter, and the method is characterized in that a capacitance current control loop is added in a current inner loop control structure of a traditional network side converter to act on a voltage outer loop output end, meanwhile, a load current estimated value and a power grid voltage are quoted as feedforward items to act on the current inner loop output end, and finally, the effectiveness of the control strategy is verified through simulation, so that the integrated coordination control of the converters at two sides can be realized, and the dynamic performance of a flywheel energy storage system is integrally improved. In the aspect of grid-connected control of a flywheel energy storage system, technologies such as permanent magnet motor sensorless control based on a fundamental wave mathematical model, network coordination control of a flywheel energy storage array, combined frequency modulation control applied to new energy power generation and the like are planned to be continuously developed.
Example two
The embodiment aims to provide an active disturbance rejection system of a flywheel energy storage system based on double-loop optimization feedforward coordination control, and the active disturbance rejection system comprises:
a machine-side controller configured to: estimating the current of the machine side converter by using the voltage and current measurement value of the motor and coordinate transformation;
introducing the current of a machine side converter as a feedforward term, and superposing the current to the output end of a voltage outer ring of the network side converter;
a network-side controller configured to: a current inner ring of the network side converter is additionally provided with a capacitance current control ring, and unbalanced current on a capacitor caused by external disturbance is compensated through direct control of capacitance current.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (10)
1. The flywheel energy storage system active disturbance rejection method based on double-loop optimization feedforward coordination control is characterized by comprising the following steps:
estimating the current of the machine side converter by using the voltage and current measurement value of the motor and coordinate transformation;
introducing the current of a machine side converter as a feedforward term, and superposing the current to the output end of a voltage outer ring of the network side converter;
a current inner ring of the network side converter is additionally provided with a capacitance current control ring, and unbalanced current on a capacitor caused by external disturbance is compensated through direct control of capacitance current.
2. The flywheel energy storage system active disturbance rejection method based on double-loop optimization feedforward coordination control as claimed in claim 1, further comprising: and an amplitude limiting link is added in a load current feedforward link so as to maintain the stability of the system while ensuring the improvement of the dynamic performance of the low-rotation-speed working condition.
3. The flywheel energy storage system active disturbance rejection method based on the double-loop optimization feedforward coordination control as claimed in claim 1, characterized by directly controlling the capacitance current, comprising the following specific steps:
setting the given value of the capacitance current to be zero, outputting the deviation of the sampling value of the capacitance current to a current inner ring terminal through a PI regulator, wherein a differential link is arranged to compensate an integral term in the current inner ring, eliminating dynamic time delay, and simultaneously adding a d-q axis feedforward component of the power grid voltage into the current inner ring to compensate the influence of the power grid voltage disturbance.
4. The flywheel energy storage system active disturbance rejection method based on the double-loop optimization feedforward coordination control as claimed in claim 1, wherein the current inner loop control equation of the network side converter is as follows:
in the formula: k is pq 、K pd 、K pc As proportional coefficient of PI regulator, K iq 、K id 、K ic For the integral coefficient of the PI regulator, u f * For feedforward summation, K f As a feedforward coefficient, i cap Is the capacitive current.
5. The flywheel energy storage system active disturbance rejection method based on double loop optimization feedforward coordination control as claimed in claim 1, characterized in that the machine side converter current is estimated by using the voltage and current sensor measurement value of the motor and the coordinate transformation theory according to the machine side converter outlet power.
6. Flywheel energy storage system auto-disturbance rejection system based on two return circuits optimize feedforward coordinated control, characterized by includes:
a machine-side controller configured to: estimating the current of a machine side converter by using the voltage and current measurement value of the motor and coordinate transformation;
introducing the current of the machine side converter as a feedforward term and superposing the current to the output end of the voltage outer ring of the network side converter;
a network-side controller configured to: a current inner ring of the network side converter is additionally provided with a capacitance current control ring, and unbalanced current on a capacitor caused by external disturbance is compensated through direct control of capacitance current.
7. The flywheel energy storage system active disturbance rejection system based on double-loop optimization feedforward coordination control as claimed in claim 6, further comprising a sampling circuit for sampling grid side three-phase current, grid side three-phase voltage and direct current voltage, and a transmitter side controller.
8. The flywheel energy storage system active disturbance rejection system based on double-loop optimization feedforward coordination control as claimed in claim 6, wherein after the machine side controller estimates the machine side converter current, a feedforward term is obtained through a proportion link and an amplitude limiting link and is superposed with the d-axis current command value to serve as a new d-axis current command value, so that the grid side converter can predict the state change of the machine side converter in advance, the grid current matches the change of the load current, and the unbalance degree of the currents at two sides is reduced.
9. The flywheel energy storage system active disturbance rejection system based on the double-loop optimization feedforward coordination control as claimed in claim 7, wherein the sampling circuit further samples a sampled capacitance current sampling value, the machine side controller compares the sampled capacitance current sampling value with a given reference current value, sends a comparison result to the PI regulator, and obtains a d-axis potential feedforward term ed after a differential term sL is delayed and removed, the d-axis potential feedforward term ed is applied to an output end of the current inner loop, and unbalanced current on a capacitor caused by external disturbance is compensated through direct control of capacitance current, and direct current voltage fluctuation is suppressed.
10. The flywheel energy storage system active disturbance rejection system based on double loop optimization feedforward coordination control as claimed in claim 7, further comprising: the machine side controller compares the d-axis current and the q-axis current with the command value, obtains voltage command values vd and vq through the combined action of a decoupling term wL, a power grid potential ed, eq and a feedforward term ed, sends the voltage command values vd and vq to the SVPWM controller, outputs six pulse signals to control the on-off of a switch of the PWM converter, and controls the power flow direction and the power magnitude between the flywheel energy storage system and the power grid.
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