CN117791719A - Control system and method for rapid synchronization grid connection of compressed air energy storage frequency converter - Google Patents
Control system and method for rapid synchronization grid connection of compressed air energy storage frequency converter Download PDFInfo
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Abstract
The invention relates to a control system and a method for fast synchronization grid connection of a compressed air energy storage frequency converter, wherein the control system comprises a 10kV bus, a starting switch, an outgoing switch, n compressors, matched motors and a frequency converter, and all compressors in the same row are connected in series; the starting switch is connected with the 10kV bus and the input end of the frequency converter; the output end of the frequency converter is connected with the motor of each compressor, and the front n-1 motors are also connected to a 10kV bus at the same time; the frequency converter is provided with a controller for controlling the MPC based on model prediction. According to the invention, a rapid synchronization grid-connected control strategy is adopted, and the frequency, amplitude and phase of the output voltage of the frequency converter are rapidly adjusted to be consistent with those of the corresponding power grid voltage through two predictive PI controllers arranged in the controller, so that blindness of control action is eliminated, switching time is effectively shortened, and the purpose of rapid switching is achieved.
Description
Technical Field
The invention belongs to the technical field of compressed air energy storage, and particularly relates to a control system and method for rapid synchronization grid connection of a compressed air energy storage frequency converter.
Background
The compressed air energy storage power station utilizes the electric energy in the electricity consumption valley period to compress air through a compressor, converts the surplus electric energy of the power grid into the internal energy of the air, and stores the internal energy into gas storages such as salt caves, rock caves or other pressure containers; in the electricity consumption peak period, the high-pressure air released from the air storage is heated by the heat stored in the compression stage and then acts through the expander, and the generator is driven to generate electricity, so that the energy is stored and released. The key device in the energy storage stage is a compressor, which is a machine for converting the mechanical energy of a prime mover into gas energy. The compressor in the compression process can adopt a double-row-multi-section configuration scheme, the single-row compressor adopts multi-section compressors which are arranged in series, each section of compressor is driven by an independent motor, and a heat exchanger and a cooler are arranged in the exhaust of the compressor sections, so that compression heat is effectively utilized, the power consumption of the compressor is reduced, and the efficiency of the whole plant is improved. Since the drive motor of each compressor has a large capacity and a large starting current, a large-capacity synchronous motor is often used. The synchronous motor can adopt various starting modes in practical application, including direct starting, series resistance starting, rotor heating starting, star-delta starting, variable frequency starting and the like. Each of these starting modes has a characteristic that an appropriate starting mode is selected according to a specific application scene and requirements. The direct start is realized by directly accessing the power supply, but the impact on the power grid is large, the risk of equipment damage is large, and the use is not extensive. Series resistance starting is to connect resistors in series in the stator coils of the motor, so that the induction voltage and induction current of the motor are reduced during starting, but a part of electric energy is lost, and the efficiency is low. The rotor heating starting is to heat the rotor to expand and contract the rotor to move relative to the rotor and start the motor. Star-delta starting reduces the current and voltage required for starting the motor by converting the stator windings of the motor from a star connection to a delta connection and back to the star connection after starting, but the starting mode has higher requirements on the power supply, large starting current and limited use. The variable frequency starting is to control the rotation speed of the motor through the frequency converter, so that the stable starting of the motor can be realized, the impact is reduced, the energy consumption is reduced, the starting efficiency is improved, and the variable frequency starting device is very widely used. Because the compressor driving motor has large capacity and large starting current, in order to reduce the influence of motor starting on power grid impact and self life, the compressor driving motor is started by adopting a variable-frequency starting mode.
The single-row multi-section compressor is characterized in that all the front section compressor driving motors except the tail section compressor motor are sequentially started step by step through a high-voltage frequency converter and then switched to power frequency operation, and the tail section compressor motor is controlled to perform down-conversion operation through the frequency converter after being started. The starting and variable frequency operation of the motors in the same row are controlled by a common high-voltage variable frequency, after the motor of the compressor is started to reach the power frequency rotation speed, the high-voltage frequency converter is withdrawn by controlling the operation switch and the change-over switch to be closed and opened, the motor grid connection of the compressor is operated under the power frequency voltage, and the starting of the compressor is completed. Then the high-voltage frequency converter starts to start the motor of the two-section compressor, and completes the starting of the two-section compressor, and the motors of the following sections of compressors are started section by section in sequence. And after the last section of compressor is started, the frequency converter is not withdrawn any more, and the variable frequency operation of the motor is controlled. As shown in fig. 1. For the previous n-1 sections of compressors, the frequency converter needs to drag the motor to operate to the power frequency rotating speed, synchronous grid-connected control is completed, and the switching of the frequency conversion operation to the power frequency operation is realized. The conventional synchronization grid connection method is as follows: after the rotating speed of the motor reaches 95% of the power frequency rotating speed, the synchronous device starts to operate and enters a synchronous regulation state, and an electronic input and output voltage detection device arranged in the synchronous device of the frequency converter is utilized to continuously detect the phase, the frequency and the amplitude of the output voltage of the frequency converter until the synchronous condition consistent with the phase, the frequency and the amplitude of the voltage of a bus of a power grid is reached, and then synchronous grid connection is completed. The conventional synchronization grid-connected control strategy needs longer switching time, and mainly, the setting of the controller parameters needs repeated iteration or trial-and-error according to a certain experience rule. For the energy storage stage of the compressed air energy storage power station, the low electricity price of the power grid is needed to be utilized, if the grid-connected switching time in the starting process of the motor is too long, the energy storage time length is influenced, and the power consumption cost is increased.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides a control system and a method for fast synchronization grid connection of a compressed air energy storage frequency converter, which are used for solving the technical problems in the prior art.
A control system for fast synchronization of frequency converters, the system comprising: 10kV bus, starting switch, outlet switch, n compressors, matched motor and frequency converter,
n is not less than 1 and is not less than 1,
all compressors in the same row are connected in series, the compressors in the same row are provided with 2 rows, the compressors in the same row are connected in series, and the two rows are respectively provided with 1 frequency converter for controlling n compressors and motors, so that the two rows are provided with 2 frequency converters; the direct connection between the two rows of compressors and the motor does not occur;
one end of the starting switch is connected with the 10kV bus, and the other end of the starting switch is connected with the input end of the frequency converter;
the output end of the frequency converter is connected with a motor of each compressor, and the front n-1 motors are also connected to the 10kV bus at the same time;
the frequency converter is internally provided with a controller for controlling MPC based on model prediction, and the controller is used for rapidly controlling and adjusting the frequency, amplitude and phase of the voltage output by the frequency converter to be consistent with the frequency, amplitude and phase of the 10kV bus voltage.
In the aspect and any possible implementation manner described above, there is further provided an implementation manner, wherein a change-over switch is disposed between an output end of the frequency converter and a motor of each of the compressors.
In the aspect and any possible implementation manner described above, there is further provided an implementation manner, wherein an operation switch is disposed between the motor of the first n-1 compressors and the 10kV bus.
In the aspect and any possible implementation manner as described above, there is further provided an implementation manner, and a bus voltage transformer is disposed between the 10kV bus and the starting switch.
In the aspect and any possible implementation manner described above, there is further provided an implementation manner, and an outlet switch is disposed between an output end of the frequency converter and each of the change-over switches.
In the aspect and any possible implementation manner described above, there is further provided an implementation manner, and a frequency converter outlet voltage transformer is disposed between an output end of the frequency converter and the outlet switch.
In aspects and any possible implementation manner as described above, there is further provided an implementation manner, where the controller based on model predictive control includes a space vector coordinate transformation unit, and an input of the space vector coordinate transformation unit includes voltage signals from a frequency converter outlet voltage signal at a previous time of synchronous control and a voltage signal of a power grid and a frequency converter outlet at a current time of synchronous control, respectively.
The invention also provides a control method for the fast synchronization grid connection of the frequency converter, which is realized by adopting the control system and comprises the following steps:
s1, after a first section of compressor receives a command for starting a motor of the first section of compressor, a frequency converter sends a signal to be combined with a starting switch, an outgoing line switch and a change-over switch corresponding to the compressor, and then the frequency converter accelerates the motor according to an acceleration torque curve until the rated rotation speed of about 95% is reached;
s2, starting operation of a controller in the frequency converter, and entering a synchronous regulation state;
s3, the controller controls an external excitation device to adjust the rotating speed of the motor to gradually reach the rated rotating speed, and then the controller adjusts the output voltage frequency, amplitude and phase of the frequency converter to be consistent with the frequency, amplitude and phase of the 10kV bus voltage;
s4, firstly closing an operation switch connected with the compressor motor by the synchronous frequency converter, and opening a change-over switch connected with the compressor motor, wherein the current of the frequency converter is reduced to zero, and the motor enters a power frequency operation state, so that the motor of the first compressor is started;
s5, repeatedly executing the steps S1-S4 to sequentially start the n-1 motors;
s6, after the nth section of compressor receives a motor starting instruction, the frequency converter sends a signal to control a change-over switch connected with the nth motor to be closed, and then the frequency converter accelerates the motor to drag the nth section of compressor to start and operate at variable speed.
Aspects and any possible implementation manner as described above, further provide an implementation manner, S3 specifically includes: s31, measuring by using a transducer outlet voltage transformer, and transforming to obtain the transducer outlet direct-axis voltage U of the synchronous control previous moment d_f And quadrature axis voltage U q_f Taking the two values as feedforward quantity, and simultaneously measuring and obtaining the initial value theta of the phase angle at the previous moment _f Accumulating the initial value and the power grid frequency to obtain theta _n ＝θ _f +2pi fT, T is the sampling time interval, f represents the grid voltage frequency;
s32, respectively measuring by adopting a bus voltage transformer and a frequency converter outlet voltage transformer, and obtaining the direct axis voltage U of the power grid bus at the current moment of synchronous control through space vector coordinate transformation d_grid And converter outlet direct axis voltage U d_out Measuring and obtaining the phase angle theta/u of the power grid at the current moment of synchronous control grid And frequency converter outlet phase angle theta/u out ；
S33, outputting the output voltage U of the frequency converter d_out Bus voltage U of power grid d_grid The difference value of the output quantity and the voltage U is input into a first predictive PI controller for closed-loop regulation q_f Accumulating to obtain the quadrature voltage U q_ref A space vector coordinate transformation unit is input; the outlet phase angle theta of the frequency converter _out Phase angle theta with the power grid _grid The difference value of the obtained output quantity and theta is input into a second predictive PI controller for closed-loop adjustment _n Accumulating to obtain a phase angle theta; u is set to d_f As a new U d_ref Theta, U d_ref And U q_ref And the space vector coordinate transformation unit input to the controller performs inverse transformation calculation to obtain signals for controlling the corresponding power devices of the frequency converter to be disconnected.
In the aspect and any possible implementation manner, there is further provided an implementation manner, wherein the initial value theta of the phase angle at the moment before the synchronous control is obtained is measured by adopting a phase angle measurement module built in the frequency converter _f And synchronously controlling the phase angle theta/u of the power grid at the current moment grid And frequency converter outlet phase angle theta/u out 。
The beneficial effects of the invention are that
Compared with the prior art, the invention has the following beneficial effects:
the system of the invention comprises: the system comprises a 10kV bus, a starting switch, an outlet switch, a plurality of compressors, a matched motor and a frequency converter, wherein all compressors in the same row are connected in series; one end of a starting switch is connected with the 10kV bus, and the other end of the starting switch is connected with the input end of the frequency converter; the output end of the frequency converter is connected with a motor of each compressor, and each motor is also connected to the 10kV bus at the same time; the frequency converter is provided with a controller for controlling MPC based on model prediction, and the controller is used for rapidly controlling and adjusting the frequency, amplitude and phase of the voltage output by the frequency converter to be consistent with the frequency, amplitude and phase of the 10kV bus voltage. The controller of the invention adopts a rapid synchronization grid-connected control strategy, and the frequency, amplitude and phase of the output voltage of the frequency converter are rapidly adjusted to be consistent with the frequency, amplitude and phase of the corresponding power grid voltage through predicting the PI controller. The predictive PI controller improves the robustness of the controller and eliminates the blindness of the control action, so that the invention can effectively shorten the switching time and achieve the purpose of quick switching.
Drawings
FIG. 1 is a schematic flow diagram of a prior art single column compressor rack system;
FIG. 2 is a schematic diagram of the internal control logic of the controller according to the present invention;
FIG. 3 is a schematic diagram of a control method of a single column compressor drive motor according to the present invention;
fig. 4 is a schematic diagram of the predictive PI controller structure according to the present invention.
Detailed Description
For a better understanding of the present invention, the present disclosure includes, but is not limited to, the following detailed description, and similar techniques and methods should be considered as falling within the scope of the present protection. In order to make the technical problems, technical solutions and advantages to be solved more apparent, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.
It should be understood that the described embodiments of the invention are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
Aiming at the requirement that a power frequency running compressor driving motor needs to be quickly dragged to run to a power frequency rotating speed through a high-voltage frequency converter and synchronization grid-connected control is quickly completed, the invention provides a quick synchronization grid-connected control strategy of a controller in the frequency converter based on Model Predictive Control (MPC).
As shown in fig. 3, the present invention provides a control system for fast synchronization grid connection of frequency converters, the system includes: the system comprises a 10kV bus, a starting switch, an outlet switch, a plurality of compressors, a plurality of matched motors and a frequency converter, wherein the frequency converter adopts a high-voltage frequency converter, and one high-voltage frequency converter controls the motors of all the compressors in the same row to start;
all compressors in the same row are connected in series, and n sections of compressors are arranged in the system, wherein n is greater than or equal to 1;
one end of the starting switch is connected with the 10kV bus, the other end of the starting switch is connected with the input end of the frequency converter, and the starting switch plays a role of switching on and switching off a loop between the frequency converter and the 10kV bus;
the output end of the frequency converter is connected with a motor of each compressor, and the front n-1 motors are simultaneously connected with the 10kV buses;
the frequency converter is internally provided with a controller for controlling MPC based on model prediction, and the controller is used for rapidly controlling and adjusting the frequency, amplitude and phase of the voltage output by the frequency converter to be consistent with the frequency, amplitude and phase of the 10kV bus voltage.
Meanwhile, a change-over switch is arranged between the output end of the frequency converter and each compressor, and the change-over switch plays a role of switching on and off and switching on a loop between the frequency converter and a corresponding motor; an operation switch is arranged between the motor of the n-1 compressor and the 10kV bus, the operation switch plays roles of switching on and off, switching on a loop between the 10kV bus and the corresponding motor, the motor of the n-1 compressor is not connected with the 10kV bus, and a bus voltage transformer PT is arranged between the 10kV bus and the starting switch 1 The bus voltage transformer is used for measuring the voltage on a 10kV bus; an outgoing line switch is arranged between the output end of the frequency converter and each of the change-over switches, the outgoing line switch plays roles of switching on and off, switching on a loop between the frequency converter and the corresponding change-over switch, and a frequency converter outlet voltage transformer PT is arranged between the frequency converter and the outgoing line switch 2 The transformer is used for measuring the outlet voltage of the frequency converter.
Preferably, as shown in fig. 2, the controller based on model predictive control includes a built-in power device trigger signal control algorithm program, namely a fast synchronization grid-connected control program, namely a space vector coordinate transformation unit adopting a synchronization grid-connected control strategy based on Model Predictive Control (MPC), wherein the input ends of the space vector coordinate transformation unit are respectively from the voltage signals (amplitude and phase angle) under the rotation coordinate system of the outlet of the frequency converter at the previous moment of synchronization control, and the voltage signals (amplitude and phase angle) under the rotation coordinate system of the outlet of the frequency converter and the power grid at the current moment of synchronization control.
The first input end of the space vector coordinate transformation unit is connected with the output end of the frequency converter at the moment before synchronous control, the second input end of the space vector coordinate transformation unit is connected with the output end of the first predictive PI controller output signal and the output end of the frequency converter at the moment before synchronous control after superposition of the output voltage signal, the input signal of the first predictive PI controller is the difference value of the output voltage amplitude of the frequency converter at the moment and the voltage amplitude of the power grid at the synchronous control, the third input end of the space vector coordinate transformation unit is connected with the output end of the second predictive PI controller output signal and the output end of the frequency converter at the moment after superposition of the phase angle signal at the synchronous control, and the input signal of the second predictive PI controller is the difference value of the output phase angle signal of the frequency converter at the moment and the phase angle signal of the power grid at the synchronous control.
As an example disclosed by the invention, the invention also provides a control method for the rapid synchronization grid connection of the frequency converter, the method is realized by adopting the control system, and the method comprises the following steps:
s1, after a first compressor receives a command for starting a motor of the first compressor, a frequency converter sends a signal to be combined with a starting switch, an outgoing line switch and a change-over switch corresponding to the compressor, and then the frequency converter accelerates the motor according to an acceleration torque curve until the rated rotation speed of about 95% is reached;
s2, starting operation of a controller in the frequency converter, and entering a synchronous regulation state;
s3, a controller based on model predictive control MPC of the frequency converter controls an external excitation device to regulate the rotating speed of the motor to gradually reach the rated rotating speed, and then the controller regulates the output voltage frequency, amplitude and phase of the frequency converter to be consistent with the frequency, amplitude and phase of the 10kV bus voltage;
s4, firstly closing an operation switch connected with the compressor motor by the synchronous frequency converter, and opening a change-over switch connected with the compressor motor, wherein the current of the frequency converter is reduced to zero, and the motor enters a power frequency operation state, so that the motor of the first compressor is started;
s5, repeatedly executing the steps S1-S4 to sequentially start the n-1 motors;
s6, after the nth compressor receives a motor starting instruction, the frequency converter sends out a signal to be combined with the nth switch, namely the switch connected with the motor of the nth compressor is closed, and then the frequency converter accelerates the motor according to an acceleration torque curve built in a controller of the frequency converter, drags the nth compressor to start and operate at a variable speed.
Preferably, S3 specifically includes: s31, measuring by using a transducer outlet voltage transformer, and obtaining the transducer outlet direct-axis voltage U of the previous moment of synchronous control through space vector coordinate transformation d_f And quadrature axis voltage U q_f Taking the two values as feedforward quantity, and simultaneously measuring and obtaining the initial value theta of the phase angle at the previous moment _f Accumulating the initial value and the power grid frequency to obtain theta _n ＝θ _f +2pi fT, T is the sampling time interval, f represents the grid voltage frequency;
s32, respectively measuring by adopting a bus voltage transformer and a frequency converter outlet voltage transformer, and obtaining the direct axis voltage U of the power grid bus at the current moment of synchronous control through space vector coordinate transformation d_grid And converter outlet direct axis voltage U d_out Measuring and obtaining the phase angle theta of the power grid at the current moment of synchronous control _grid And frequency converter outlet phase angle theta _out ；
S33, outputting the output voltage U of the frequency converter d_out Bus voltage U of power grid d_grid The difference value of the output quantity and the voltage U is input into a first predictive PI controller for closed-loop regulation q_f Accumulating to obtain the quadrature voltage U q_ref Inputting a control vector coordinate transformation unit; the outlet phase angle theta of the frequency converter _out Phase angle theta with the power grid _grid The difference value of the obtained output quantity and theta is input into a second predictive PI controller for closed-loop adjustment _n Accumulated to obtainTo phase angle θ; u is set to d_f As a new U d_ref Theta, U d_ref And U q_ref And the space vector coordinate conversion module input to the controller performs space vector coordinate inverse conversion calculation, and three output ends output three-phase modulation wave signals which control the on-off of corresponding power devices in the frequency converter.
Preferably, the frequency converter is internally provided with a phase angle measuring module for measuring and obtaining a phase angle initial value theta of the moment before synchronous control _f Synchronously controlling phase angle theta of power grid at current moment _grid And frequency converter outlet phase angle theta _out 。
Specifically, the control process of the present invention is as follows:
the fast synchronization grid-connected control strategy is to quickly adjust the frequency, amplitude and phase of the output voltage of the frequency converter to be consistent with the frequency, amplitude and phase of the corresponding grid voltage through a controller based on model predictive control. After the frequency converter receives the grid-connected signal, the frequency converter can directly adjust the output frequency of the frequency converter to be consistent with the voltage frequency of the power grid in a closed loop mode under the current arbitrary frequency working condition, and meanwhile phase-locking judgment is carried out on the output. After the output frequency of the frequency converter and the frequency error of the power grid bus are within the threshold value, synchronous control is carried out, and the amplitude and the phase of the output voltage are adjusted in an open loop mode during the synchronous control, so that the output frequency and the frequency error of the power grid bus are consistent, and the specific control flow is as follows:
as shown in fig. 2, the controller of the frequency converter synchronously controls the output voltage transformer PT of the frequency converter at the previous moment 2 Collecting three-phase voltage U at output end of frequency converter A_f 、U B_f 、U C_f The direct-axis voltage U is obtained by a space vector coordinate transformation module (3 ABC/2 DQ) (namely, a clarke-park transformation-three-phase static coordinate system is transformed into a two-phase rotating coordinate system) d_f And cross axis U q_f U is set up d_f And U q_f The angle of the moment before the synchronous control is obtained as an initial value theta through a phase angle measuring device arranged in a frequency converter _f Then the power grid frequency is added up to obtain a new angle theta _n (θ _f +2 pi fT, T is the sampling time interval, then the loop is openedLines, i.e. input signals U d_f Directly input to U d_ref Module, bus voltage transformer PT 1 The 10kV bus voltage U of the power grid is measured A_grid 、U B_grid 、U C_grid Likewise, the bus straight axis voltage U is obtained through space vector coordinate transformation d_grid At this time, a transducer outlet voltage transformer PT is adopted 2 Measuring and transforming to obtain the output direct-axis voltage U of the frequency converter synchronously controlling the current moment d_out The method comprises the steps of carrying out a first treatment on the surface of the U for phase locking of power grid d_grid And U out of output phase lock d_out Closed-loop regulation is carried out by adopting a first predictive PI controller, and the obtained output quantity and feedforward quantity U q_f The result of the summation is taken as a new reference quadrature axis voltage U q_ref ，U d_f Directly used as new reference direct-axis voltage U without processing d_ref The method comprises the steps of carrying out a first treatment on the surface of the Obtaining the phase angle theta of the power grid through a phase angle measuring device _grid And frequency converter outlet phase angle theta _out The phase angle theta of the power grid _grid And output phase angle theta _out Closed loop regulation is carried out by adopting a second predictive PI controller, and the obtained output quantity is matched with the new angle theta _n The resultant phase angle theta of the sum is used as the input angle of the space vector coordinate transformation unit, and theta, ud_ref and Uq_ref are input into the space vector coordinate transformation unit to calculate the space vector coordinate inverse transformation (2 DQ/3 ABC), and then three-phase modulation wave signal S is generated A 、S B 、S C Signal S A 、S B 、S C The power device of each corresponding power device in the power module of the frequency converter is controlled to be disconnected respectively, the structural principle of the controller is shown in figure 3, wherein the closed loop regulation adopts two predictive PI controllers, namely a first predictive PI controller 1 and a second predictive PI controller 2, and each predictive PI controller consists of two parts: the standard or phase-change PI control items and the predictive control items are shown in fig. 4, and the two PI control items in each predictive PI controller can improve the robustness of the whole controller, and can keep good control performance when different interferences exist and the model changes; the predictive control term is introduced in the predictive PI controller to overcome the adverse effect of a large net hysteresis on control, which may be predicted based on the control effect over timeAnd measuring future control action and eliminating blindness of the control action. Therefore, the control strategy of the invention can shorten the switching time and achieve the purpose of quick switching.
As shown in fig. 3, the motor starting process for switching the frequency conversion to the power frequency operation for a single (for example, a motor # 1) is as follows:
(1) After the first section of compressor receives the command of starting its No. 1 motor, the frequency converter sends out signal to make the starting switch, outlet switch and correspondent No. 1 change-over switch, then the frequency converter can accelerate the motor according to the built-in accelerating torque curve of its controller until the rated rotating speed is about 95%.
(2) After reaching 95% of the rotating speed, the built-in controller of the frequency converter and the built-in synchronous control algorithm program of the controller start to operate, and enter a synchronous regulation state;
(3) The high-voltage frequency converter sends an analog signal to an external excitation device to regulate the rotating speed of the motor, so that the rotating speed of the synchronous motor gradually reaches the rated rotating speed and gradually approaches to 100% of the rated rotating speed, when the rotating speed is about to reach 100% of the rated rotating speed, the frequency, the amplitude and the phase of the output voltage of the frequency converter are regulated while regulating the rotating speed, the output frequency of the frequency converter is firstly regulated to be consistent with the frequency of the voltage of a power grid, and then a synchronous control program is started to regulate the output voltage of the frequency converter to be consistent with the amplitude and the phase of the voltage of the power grid, and the synchronous control program is realized by adopting the following step (4);
(4) A synchronous control module arranged in the controller is started, and in the synchronous control process, the power grid is phase-locked in real time, the frequency, the amplitude and the phase of the power grid voltage are calculated, after the motor is gradually accelerated to be consistent with the power grid frequency, the angle closed-loop regulation is carried out by using the power grid voltage phase angle and the frequency converter output voltage phase angle, and meanwhile, the voltage closed-loop regulation is carried out by using the power grid voltage amplitude and the frequency converter output voltage amplitude. In the adjusting process, feedforward calculation is carried out by utilizing phase-locked data, meanwhile, P, I parameters of a PI control item transfer function of a predictive PI controller are optimized, the predictive control item has self-adaption and predictive capability, P, I parameters can be quickly set to an optimal value, under the adjustment of the predictive control item of the predictive PI controller, the amplitude and phase deviation between the output voltage of the frequency converter and the 10kV bus voltage are smaller and smaller, quick and accurate synchronous adjusting control is realized, the capability of tracking the change of the voltage at the network side is quickened, the synchronous control time is shortened, and the grid-connected success rate is improved.
(5) After the phase, the frequency and the amplitude are consistent, the high-voltage frequency converter sends a closing command to the motor running switch (firstly closing the 1# running switch and then opening the 1# switching switch), the frequency converter controller controls the power module to be turned off, the current of the high-voltage frequency converter is reduced to zero while the 1# running switch is closed, the power device is blocked, the motor enters a power frequency running state, and the starting of the 1# motor is completed;
(6) The steps and the control program are sequentially implemented until the nth motor is started, and the nth motor is completed in the following manner:
after the nth section of compressor receives the instruction for starting the motor, the frequency converter sends out a signal to be combined with the n# change-over switch, and then the frequency converter accelerates the motor according to the built-in acceleration torque curve of the controller, drags the nth section of compressor to start and operate at variable speed.
While the foregoing description illustrates and describes the preferred embodiments of the present invention, it is to be understood that the invention is not limited to the forms disclosed herein, but is not to be construed as limited to other embodiments, and is capable of numerous other combinations, modifications and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein, either as a result of the foregoing teachings or as a result of the knowledge or technology of the relevant art. And that modifications and variations which do not depart from the spirit and scope of the invention are intended to be within the scope of the appended claims.
Claims (10)
1. A control system for rapid synchronization of compressed air energy storage frequency converters, the system comprising: 10kV bus, starting switch, outlet switch, n compressors, matched motor and frequency converter, n is an integer greater than or equal to 2,
wherein all of the compressors in the same column are connected in series;
one end of the starting switch is connected with the 10kV bus, and the other end of the starting switch is connected with the input end of the frequency converter;
the output end of the frequency converter is connected with a motor of each compressor, and the front n-1 motors are also connected to the 10kV bus at the same time;
the frequency converter is internally provided with a controller for controlling MPC based on model prediction, and the controller is used for rapidly controlling and adjusting the frequency, amplitude and phase of the voltage output by the frequency converter to be consistent with the frequency, amplitude and phase of the 10kV bus voltage.
2. The control system for rapid synchronization of a compressed air energy storage inverter of claim 1, wherein a change-over switch is provided between the output of the inverter and each of the compressor motors.
3. The control system for rapid synchronization of compressed air energy storage frequency converters according to claim 1, wherein an operation switch is arranged between the motor of the first n-1 compressors and the 10kV bus.
4. The control system for rapid synchronization of a compressed air energy storage inverter according to claim 1, wherein a bus voltage transformer is arranged between the 10kV bus and the starting switch.
5. The control system for rapid synchronization of a compressed air energy storage inverter according to claim 2, wherein an outgoing line switch is arranged between the output end of the inverter and each of the change-over switches.
6. The control system for rapid synchronization of a compressed air energy storage inverter of claim 5, wherein an inverter outlet voltage transformer is disposed between the output of the inverter and the outlet switch.
7. The control system for rapid synchronization of a compressed air energy storage inverter according to claim 1, wherein the controller based on model predictive control comprises a space vector coordinate transformation unit, and the input of the space vector coordinate transformation unit comprises voltage signals from the inverter outlet at the previous moment of synchronization control and voltage signals from the power grid and the inverter outlet at the current moment of synchronization control, respectively.
8. A control method for fast synchronization grid connection of compressed air energy storage frequency converter, characterized in that the method is realized by adopting the control system of any one of claims 1-7, comprising the following steps:
s1, after a first compressor receives a command for starting a motor of the first compressor, a frequency converter sends a signal to be combined with a starting switch, an outgoing line switch and a change-over switch corresponding to the compressor, and then the frequency converter accelerates the motor according to an acceleration torque curve until the rated rotation speed of about 95% is reached;
s2, starting operation of a controller in the frequency converter, and entering a synchronous regulation state;
s3, the controller controls an external excitation device to adjust the rotating speed of the motor to gradually reach the rated rotating speed, and then the controller adjusts the output voltage frequency, amplitude and phase of the frequency converter to be consistent with the frequency, amplitude and phase of the 10kV bus voltage;
s4, firstly closing an operation switch connected with the compressor motor by the synchronous frequency converter, and opening a change-over switch connected with the compressor motor, wherein the current of the frequency converter is reduced to zero, and the motor enters a power frequency operation state, so that the motor of the first compressor is started;
s5, repeatedly executing the steps S1-S4 to sequentially start the n-1 motors;
s6, after the nth compressor receives a motor starting instruction, the frequency converter sends a signal to control a change-over switch connected with the nth motor to be closed, and then the frequency converter accelerates the motor to drag the nth compressor to start and operate at a variable speed.
9. The control method for rapid synchronization grid connection of the compressed air energy storage frequency converter according to claim 8, wherein S3 specifically comprises: s31, measuring by using a transducer outlet voltage transformer, and transforming to obtain the transducer outlet direct-axis voltage U of the synchronous control previous moment d_f And quadrature axis voltage U q_f Taking the two values as feedforward quantity, and simultaneously measuring and obtaining the initial value theta of the phase angle at the previous moment _f Accumulating the initial value and the power grid frequency to obtain theta _n ＝θ _f +2pi fT, T is the sampling time interval, f represents the grid voltage frequency;
s32, respectively measuring by adopting a bus voltage transformer and a frequency converter outlet voltage transformer, and obtaining the direct axis voltage U of the power grid bus at the current moment of synchronous control through space vector coordinate transformation d_grid And converter outlet direct axis voltage U d_out Measuring and obtaining the phase angle theta/u of the power grid at the current moment of synchronous control grid And frequency converter outlet phase angle theta/u out ；
S33, outputting the direct-axis voltage U of the frequency converter d_out Direct axis voltage U of bus of power grid d_grid The difference value of the output quantity and the output direct-axis voltage U of the frequency converter are input into a first predictive PI controller for closed-loop adjustment q_f Accumulating to obtain the quadrature voltage U q_ref A space vector coordinate transformation unit is input; the outlet phase angle theta of the frequency converter _out Phase angle theta with the power grid _grid The difference value of the obtained output quantity and theta is input into a second predictive PI controller for closed-loop adjustment _n Accumulating to obtain a phase angle theta; the output direct-axis voltage U of the frequency converter d_f U d_f As a new U d_ref Theta, U d_ref And U q_ref And the space vector coordinate transformation unit input to the controller performs inverse transformation calculation to obtain a signal for controlling the frequency converter to be switched on and off.
10. The method for controlling rapid synchronization of a compressed air energy storage inverter according to claim 9, wherein a phase angle measurement module built in the inverter is used for measuring and obtaining a phase at a previous moment of synchronization controlInitial value of angle theta _f And synchronously controlling the phase angle theta/u of the power grid at the current moment grid And frequency converter outlet phase angle theta/u out 。
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103644095A (en) * | 2013-12-03 | 2014-03-19 | 中国科学院工程热物理研究所 | Compressed air energy storage method and device suitable for variable working condition operation |
| US20190305555A1 (en) * | 2018-03-28 | 2019-10-03 | State Grid Jiangsu Electric Power Co., Ltd | Power grid adjustment method based on loads of variable frequency air conditioner |
| CN114400951A (en) * | 2022-01-12 | 2022-04-26 | 中冶赛迪电气技术有限公司 | Synchronous switching method of frequency converter based on vector control mode |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103644095A (en) * | 2013-12-03 | 2014-03-19 | 中国科学院工程热物理研究所 | Compressed air energy storage method and device suitable for variable working condition operation |
| US20190305555A1 (en) * | 2018-03-28 | 2019-10-03 | State Grid Jiangsu Electric Power Co., Ltd | Power grid adjustment method based on loads of variable frequency air conditioner |
| CN114400951A (en) * | 2022-01-12 | 2022-04-26 | 中冶赛迪电气技术有限公司 | Synchronous switching method of frequency converter based on vector control mode |
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