Tubular pump power generation grid-connected control system based on three-phase asynchronous electric motor

Abstract

Provided in the present application is tubular pump power generation grid-connected control system based on a three-phase asynchronous electric motor. The system comprises a power generation module, an electric energy control module and a grid-connected module, wherein the power generation module is configured to convert mechanical energy transmitted by a tubular pump into electric energy, and is electrically connected to the electric energy control module; the electric energy control module generates a pulse signal on the basis of a PI controller and by means of ABC-αβ-dq coordinate transformation and flux linkage estimation, so as to drive the control system to operate, and is configured to convert, into direct-current electric energy, three-phase alternating-current electric energy outputted by means of power generation, and process the direct-current electric energy into electric energy consistent with power grid parameters; and the grid-connected module is configured to safeguard grid connection safety and prevent system operation overcurrent, and is electrically connected to the electric energy control module. In the present application, by means of a tubular pump and a three-phase asynchronous electric motor, mechanical energy is converted and processed into electric energy consistent with power grid parameters, thus being incorporated into a power grid. The system has a simple structure, is very suitable for energy-saving modification of wastewater discharged from a wastewater power plant, and meets the requirements of energy saving and emission reduction.

Description

A through-flow pump power generation grid-connected control system based on a three-phase asynchronous motor TECHNICAL FIELD

[0001] The present application relates to the technical field of power generation grid connection, and in particular to a through-flow pump power generation grid-connected control system based on a three-phase asynchronous motor. BACKGROUND

[0002] Under the background of the national double carbon strategy and energy saving and emission reduction, it has become a consensus in the field of power systems to encourage new energy power generation on the power generation side and electrical equipment on the user side. To achieve this goal, enterprises focus on the manufacturing of new energy power generation equipment, such as wind power and photovoltaic power, on the one hand. On the other hand, equipment manufacturers also focus on energy saving and emission reduction technologies for existing systems, such as waste heat power generation and subway flywheel energy storage technologies. The treated wastewater from a sewage power plant is usually directly discharged into the nearby river basin, resulting in energy waste. Therefore, how to utilize the potential energy of the discharged wastewater is an important measure for energy saving and emission reduction in sewage treatment plants. In the prior art, water turbine power generation technology is usually used to utilize the potential energy of the discharged wastewater for power generation. However, the discharged wastewater from a sewage treatment plant generally has the characteristics of large flow and low water head. The water turbine power generation technology utilizes the water head difference to convert potential energy into kinetic energy to drive the water turbine to generate power, which requires a large head difference and cannot well adapt to the power generation demand of the discharged wastewater.

[0003] CONTENT

[0004] The present application is made in view of the above-mentioned problems, and aims to provide a through-flow pump power generation grid-connected control system based on a three-phase asynchronous motor. The system adapts to large flow and low water head conditions through a through-flow pump, controls the three-phase asynchronous motor to convert the mechanical energy of the through-flow pump into electrical energy through a rotor field-oriented control method combining a speed outer loop and a current inner loop, and controls the frequency converter to process the electrical energy into electrical energy consistent with the grid parameters and connect to the grid through a grid voltage vector-oriented control method. The system has a simple structure and is very suitable for energy saving and emission reduction of the discharged wastewater from a sewage power plant, meeting the needs of energy saving and emission reduction.

[0005] Specifically, the first aspect of the present application provides a through-flow pump power generation grid-connected control system based on a three-phase asynchronous motor, comprising a power generation module, an electrical energy control module, and a grid connection module.

[0006] The power generation module is used to convert the mechanical energy transmitted by the through-flow pump into electrical energy, and is electrically connected to the electrical energy control module.

[0007] The electrical energy control module generates a pulse signal to drive the control system to operate through ABC-αβ-dq coordinate transformation and flux estimation based on a plurality of PI controllers, is used to convert the three-phase alternating current electrical energy generated by the power generation module into direct current electrical energy, and process the direct current electrical energy into electrical energy consistent with the grid parameters, and is electrically connected to the power generation module and the grid connection module, respectively.

[0008] The grid-connected module is used to ensure grid-connected safety and prevent system overcurrent, and is electrically connected with the electric energy control module.

[0009] Further, the power generation module is used to convert mechanical energy into electric energy during operation of the through-flow pump by using a three-phase asynchronous motor.

[0010] Further, the electric energy control module comprises a machine-side control part, an intermediate direct-current part and a grid-side control part.

[0011] Further, the machine-side control part is used to control operation of the three-phase asynchronous motor, provide excitation reactive power for the three-phase asynchronous motor and convert three-phase alternating current energy generated by the asynchronous motor into direct-current energy.

[0012] Excitation reactive power refers to reactive current for generating a magnetic field absorbed from a power grid during operation of the three-phase asynchronous motor. The reactive current is mainly used for excitation, i.e. establishing and maintaining a rotating magnetic field inside the motor. Since the excitation current has inductive reactive property, its increase will result in a decrease in power factor of the motor. Excitation reactive power refers to electric power required for establishing an alternating magnetic field and inducing a magnetic flux for the three-phase asynchronous motor.

[0013] Further, the machine-side control part adopts a rotor field-oriented control method combining a speed outer loop with a current inner loop, and specifically comprises:

[0014] Step 1: setting an angular velocity given value ω of the three-phase asynchronous motor according to experience ref , and setting a flux given value Ψ ref ;

[0015] Step 2: converting three-phase stator current of the asynchronous motor into excitation current component and torque current component in a dq synchronous rotating coordinate system through Clark transformation and Park transformation, and obtaining an estimated value of a rotor flux space position angle θ m and an estimated value of a rotor flux Ψ r , and the formulas are as follows:

[0016] Wherein, i ma , i mb and i mc : measured values of three-phase stator current of the motor;

[0017] i md : excitation current component; and i mq : torque current component;

[0018] θ m : estimated value of the rotor flux space position angle; and Ψ r : estimated value of the rotor flux;

[0019] L m : mutual inductance between stator and rotor r : rotor electromagnetic time constant

[0020] ω: actual angular speed of motor; s: complex variable

[0021] The field current component is mainly responsible for establishing the magnetic field of the motor. It interacts with the rotating magnetic field of the rotor to generate magnetic flux. The field current component is the direct-axis current component, whose direction is perpendicular to the voltage vector of the stator winding. By controlling the d-axis current component, the excitation state of the motor can be adjusted, thereby affecting the magnetic field strength and efficiency of the motor.

[0022] The torque current component is mainly responsible for generating electromagnetic torque. It interacts with the rotating magnetic field of the rotor to generate torque. The q-axis current component is the quadrature-axis current component, whose direction is parallel to the voltage vector of the stator winding. By controlling the q-axis current component, the output torque of the motor can be accurately adjusted. When the output torque of the motor is positive, the motor is in motoring state; when the output torque of the motor is negative, the motor is in generating state.

[0023] Step three: rotor flux estimation value Ψ r and the flux given value Ψ ref Subtracting the difference, after the first PI controller on the machine side, the stator field current given value is obtained, the formula is as follows:

[0024] Where: i mdref : stator field current given value; Ψ ref : flux given value

[0025] k pm1 : proportional coefficient of the first PI controller on the machine side; Ψ r : rotor flux estimation value

[0026] k im1 : integral coefficient of the first PI controller on the machine side

[0027] Step four: angular speed given value ω ref and the actual angular speed ω r Subtracting the difference, after the second PI controller on the machine side, the stator torque current given value is obtained, the formula is as follows:

[0028] Where: i mqref : stator torque current given value; ω ref : angular speed given value

[0029] k pm2 : proportional coefficient of the second PI controller on the machine side; ω r : actual angular speed

[0030] k im2 : integral coefficient of the second PI controller on the machine side;

[0031] Step five: stator excitation current given value i mdref Subtract the excitation current component of the three-phase stator current in the dq synchronous rotating coordinate system from the stator voltage d-axis component given value, and process it through the third PI controller on the machine side to obtain the stator voltage q-axis component given value, as follows:

[0032] Wherein: u md : stator voltage d-axis component given value; i mdref : stator excitation current given value;

[0033] k pm3 : proportional coefficient of the third PI controller on the machine side; i md : excitation current component;

[0034] k im3 : integral coefficient of the third PI controller on the machine side;

[0035] Step six: stator torque current given value i mqref Subtract the torque current component of the three-phase stator current in the dq synchronous rotating coordinate system from the stator voltage q-axis component given value, and process it through the fourth PI controller on the machine side to obtain the stator voltage q-axis component given value, as follows:

[0036] Wherein: u mq : stator voltage q-axis component given value; i mqref : stator torque current given value;

[0037] k pm4 : proportional coefficient of the fourth PI controller on the machine side; i mq : torque current component;

[0038] k im4 : integral coefficient of the fourth PI controller on the machine side;

[0039] Step seven: stator voltage d-axis component given value u md and stator voltage q-axis component given value u mq Park inverse transformation to obtain control signals u mα and u mβ , SVPWM modulation to generate pulse signals, control the actual speed and flux to track the given speed and flux, as follows:

[0040] Wherein: u mα , u mβ : control signal component in the αβ coordinate system;

[0041] u md : stator voltage d-axis component given value; u mq : stator voltage q-axis component given value;

[0042] θ m : rotor flux linkage space position angle estimated value.

[0043] The actual speed and flux linkage of the three-phase asynchronous motor are controlled to track the initial given speed and flux linkage, and a closed-loop control system is adopted to detect the actual position, speed and torque of the motor in real time through a feedback device, compare the actual values with the set values, calculate the error and adjust in real time, so as to ensure that the motor operates according to the predetermined speed and flux linkage, and the set values can be adjusted in real time to adjust the system operation.

[0044] Further, the intermediate DC part provides a stable DC power supply for grid-connected inversion.

[0045] Further, the grid-side control part ensures that the grid-connected power and grid power have the same frequency and phase, and keeps the DC bus voltage stable.

[0046] Further, the grid-side control part adopts a grid voltage vector oriented control method, which specifically includes:

[0047] Step one: the actual voltage of the grid side is subjected to Clark transformation and Park transformation to obtain voltage components u gd and u gq in the dq synchronous rotating coordinate system, and u gq is stabilized near 0 under the action of the first PI controller of the grid side, thereby obtaining the grid voltage space vector angle The formula is as follows:

[0048] Wherein: u gα , u gβ : control signal components in the αβ coordinate system;

[0049] u ga , u gb , u gc : measured values of three-phase stator voltage of the motor;

[0050] u gd , u gd : voltage components in the dq synchronous rotating coordinate system;

[0051] Grid voltage space vector angle;

[0052] k pg1: the proportional coefficient of the first PI controller of the grid side;

[0053] k ig1 : the integral coefficient of the first PI controller of the grid side;

[0054] Step two: the actual current of the grid side is subjected to Clark transformation and Park transformation to obtain active current component i gd and reactive current component i gq in the dq synchronous rotating coordinate system, and the formula is as follows;

[0055] wherein: i gα , i gβ : current component in the αβ coordinate system;

[0056] i ga , i gb , i gc : actual current measurement value of the three-phase stator of the motor of the grid side;

[0057] i gd : active current component in the dq synchronous rotating coordinate system;

[0058] i gq : reactive current component in the dq synchronous rotating coordinate system;

[0059] grid voltage space vector angle;

[0060] Step three: the given value U dc of the DC bus voltage is subtracted from the actual feedback value U ref , and the result is subjected to the second PI regulator of the grid side to obtain the active component reference value i gdref of the current on the d-axis, and the formula is as follows;

[0061] wherein: i gdref : active component reference value of the current on the d-axis;

[0062] k pg2 : the proportional coefficient of the second PI controller of the grid side;

[0063] k ig2 : the integral coefficient of the second PI controller of the grid side;

[0064] U dc : the given value of the DC bus voltage; U ref : the actual feedback value of the voltage;

[0065] Step four: i gdref is subtracted from the active current component i gdThe active voltage in dq rotating coordinate system u is obtained after the third PI regulator of the difference between the active current component i and the active current reference value i gd The formula is as follows:

[0066] Wherein: u gd : the given value of the active voltage in dq rotating coordinate system;

[0067] k pg3 : the proportional coefficient of the third PI controller of the grid side;

[0068] : the integral coefficient of the third PI controller of the grid side; gd : the active current component

[0069] i gdref : the active component reference value of the current in d-axis;

[0070] Step five: the difference between the reactive current component i gqref and i gq is subjected to the fourth PI regulator of the grid side, and the given value of the reactive voltage in dq rotating coordinate system u gq is obtained, and the formula is as follows:

[0071] Wherein: u gq : the given value of the reactive voltage in dq rotating coordinate system;

[0072] k pg4 : the proportional coefficient of the fourth PI controller of the grid side;

[0073] k ig4 : the integral coefficient of the fourth PI controller of the grid side;

[0074] i gqref : the reactive current component in q-axis;

[0075] Step six: the grid side active voltage u gd and the grid side reactive voltage u gq are converted into the given values of α, β axis components in the stationary coordinate system through Park inverse transformation, and the formula is as follows:

[0076] Wherein: u gd : the grid side active voltage; u gq : the grid side reactive voltage;

[0077] u gα : the given value of α axis component in the stationary coordinate system;

[0078] u gβ : the given value of β axis component in the stationary coordinate system;

[0079] Step seven: u gα and u gβ The pulse signal is generated under SVPWM modulation to drive the grid-side converter to work.

[0080] Further, in the step five, to ensure that the grid-side converter works under the condition of unit power factor, the reactive component i gqref of the current on the q-axis is set to 0.

[0081] Further, the grid-connected module includes a fuse, a transformer, a leakage protection circuit breaker, and a power grid.

[0082] In a second aspect, the present application also provides a computing device having the function of implementing the method described in the first aspect, and the beneficial effects can be referred to the description of the first aspect, which will not be repeated here. The function can be realized by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions. In one possible design, the structure of the device includes an acquisition module and a training module, and optionally, a construction module. These modules can realize the function of training the node in the method examples of the first aspect, and the specific description can be referred to the detailed description in the method examples, which will not be repeated here.

[0083] In a third aspect, the present application also provides a computing device for implementing the function of the method described in the first aspect, and the beneficial effects can be referred to the description of the first aspect, which will not be repeated here. The structure of the computing device includes a processor and a memory, and the memory is used to store instructions and / or data. The memory is coupled to the processor, and the processor can realize the function of training the node in the first aspect examples when executing the program instructions stored in the memory. The structure of the computing device also includes a communication interface for communicating with other devices.

[0084] In a fourth aspect, the present application also provides a computer readable storage medium, which stores instructions, and when the instructions are run on a computer, the computer executes the method in the first aspect and each possible design of the first aspect.

[0085] In a fifth aspect, the present application also provides a computer program product containing instructions, and when the instructions are run on a computer, the computer executes the method in the first aspect and each possible design of the first aspect.

[0086] In a sixth aspect, the present application also provides a computing chip, which is connected to a memory, and the chip is used to read and execute the software program stored in the memory to execute the method in the first aspect and each possible implementation of the first aspect. BRIEF DESCRIPTION OF DRAWINGS

[0087] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from the structures shown in the drawings without creative effort.

[0088] Fig. 1 is a structural block diagram of a control system for a through-flow pump based on a three-phase asynchronous motor;

[0089] Fig. 2 is a flow chart of a rotor field-oriented control method with a speed outer loop and a current inner loop for the machine-side control part;

[0090] Fig. 3 is a flow chart of a grid voltage vector-oriented control method for the grid-side control part;

[0091] Fig. 4 is a structural diagram of the present application;

[0092] Fig. 5 is an implementation schematic diagram of the present application.

[0093] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0094] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be described and explained below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by those skilled in the art without creative effort fall within the scope of the present application.

[0095] Obviously, the drawings in the following description are only some examples or embodiments of the present application, and for those skilled in the art, the present application can be applied to other similar scenarios without creative effort. In addition, it can be understood that although the effort made in this development process can be complex and lengthy, for those skilled in the art related to the content disclosed in the present application, some design, manufacture or production changes based on the technical content disclosed in the present application are only routine technical means and should not be understood as insufficient disclosure of the present application.

[0096] If not specifically stated, all embodiments and optional embodiments of the present application can be combined to form new technical solutions.

[0097] If not particularly specified, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0098] If not particularly specified, all the steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any order. For example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0099] If not particularly specified, the "comprise" and "include" mentioned in the present application are open-ended, and can also be closed. For example, the "comprise" and "include" can mean that other components not listed can also be included, or only the listed components can be included.

[0100] If not particularly specified, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0101] In order to better understand the scheme of the embodiments of the present application, some related terms and concepts that may be involved in the embodiments of the present application are introduced first.

[0102] (1) PI controller is a linear controller, which forms a control deviation according to the given value and the actual output value, and forms a control amount by linear combination of the proportion and integral of the deviation to control the controlled object, mainly used to adjust the difference between the output of the system and the expected value. It combines proportional control (Proportional) and integral control (Integral) two control methods. Proportional control directly converts error into control output through proportional gain (Kp), while integral control accumulates error through integral time constant (Ki) to eliminate system steady-state error and improve control stability.

[0103] (2) Clarke transformation, is a kind of coordinate transformation method for transforming three-phase stationary coordinate system current Ia, Ib, Ic into two-phase stationary coordinate system current Iα, Iβ. Its main purpose is to convert the complex three-phase coordinate system into the two-phase coordinate system that is easy to understand. Clarke transformation can be divided into equal amplitude transformation and equal power transformation. Equal amplitude transformation keeps the amplitude of the current unchanged, while equal power transformation keeps the power of the current unchanged.

[0104] (3) Park transformation, is a kind of coordinate transformation method for further converting two-phase stationary coordinate system current Iα, Iβ into two-phase rotating coordinate system current Id, Iq rotating with the rotor. It projects the three-phase current on the stator onto the direct axis (d-axis) and the quadrature axis (q-axis) rotating with the rotor. Park transformation has important theoretical and practical significance in motor control, because it can convert complex three-phase current into simple two-phase rotating current, thus facilitating motor control.

[0105] (4) SVPWM modulation (Space Vector Pulse Width Modulation), is an advanced power electronic control technology, mainly used in three-phase inverter. Its core principle is to generate pulse width modulation wave through specific switching mode of six power switching elements, so that the output current waveform is as close to the ideal sine waveform as possible, which can improve the performance and efficiency of the motor.

[0106] As shown in FIG. 1, in the embodiment, a three-phase asynchronous motor-based through-flow pump power generation and grid-connected control system is provided, which includes a power generation module, an electric energy control module, and a grid-connected module;

[0107] The power generation module is used to convert the mechanical energy transmitted by the through-flow pump into electric energy, and is electrically connected with the electric energy control module;

[0108] The electric energy control module generates pulse signals to drive the control system to run based on eight PI controllers, through ABC-αβ-dq coordinate transformation and flux estimation, converts the three-phase alternating current energy generated by the power generation module into direct current energy, and processes the direct current energy into electric energy consistent with the grid parameters, and is electrically connected with the power generation module and the grid-connected module;

[0109] The grid-connected module is used to ensure grid-connected safety and prevent system overcurrent, and is electrically connected with the electric energy control module.

[0110] Further, the power generation module uses a three-phase asynchronous motor to convert the mechanical energy generated during the operation of the through-flow pump into electric energy.

[0111] In a three-phase asynchronous motor, when three-phase symmetrical alternating current passes through the motor stator winding, a rotating magnetic field will be generated in the air gap. The relationship between the rotating speed n1 of the rotating magnetic field, the alternating current frequency f1 and the pole pair number p0 of the motor is as follows:

[0112] The short-circuit rotor winding of the three-phase asynchronous motor generates an induced electromotive force under the action of the rotating magnetic field, and further generates an induced current. The air gap rotating magnetic field and the current in the rotor winding interact to generate an electromagnetic torque. This makes the motor produce rotary motion. When the motor rotor speed is greater than the rotating speed of the magnetic field, the direction of the electromagnetic torque is opposite to the direction of rotation of the rotor, and the motor is in a power generation state. Specifically to the application scenario of the cross-flow pump power generation, the cross-flow pump is connected with the asynchronous motor shaft through a shaft coupling. When the speed of the cross-flow pump (equivalent to the speed of the motor rotor) is greater than the rotating speed of the air gap magnetic field, the direction of the electromagnetic torque is opposite to the direction of rotation of the rotor. At this time, the asynchronous motor absorbs mechanical power from the cross-flow pump through the shaft, and after overcoming the electromagnetic torque of the asynchronous motor, alternating current energy will be induced in the stator.

[0113] Further, the electric energy control module comprises a machine side control part, an intermediate direct current part and a grid side control part.

[0114] Further, the machine side control part is used for controlling the operation of the three-phase asynchronous motor and providing excitation reactive power for the three-phase asynchronous motor.

[0115] Excitation reactive power refers to the reactive current used to generate a magnetic field absorbed from the power grid during the operation of the three-phase asynchronous motor. This reactive current is mainly used for excitation, i.e. establishing and maintaining the rotating magnetic field inside the motor. Since the excitation current has inductive reactive properties, its increase will cause the power factor of the motor to decrease. Excitation reactive power refers to the electric power required to establish an alternating magnetic field and induce a magnetic flux for the three-phase asynchronous motor.

[0116] Further, in the embodiment, as shown in FIG. 2, the machine side control part adopts a rotor field oriented control method combining a speed outer ring with a current inner ring, which specifically comprises:

[0117] Step one: set the angular velocity given value ω of the three-phase asynchronous motor according to experience ref , and the flux given value Ψ ref ;

[0118] Step two: transform the three-phase stator current of the asynchronous motor into excitation current components and torque current components in the dq synchronous rotating coordinate system through Clark transformation and Park transformation, and obtain the estimated value of the rotor flux space position angle and the estimated value of the rotor flux, as follows:

[0119] The field current component is mainly responsible for establishing the magnetic field of the motor. It interacts with the rotor's rotating magnetic field to produce magnetic flux. The field current component is the direct-axis current component, whose direction is perpendicular to the voltage vector of the stator winding. By controlling the d-axis current component, the excitation state of the motor can be adjusted, thereby affecting the magnetic field strength and efficiency of the motor.

[0120] The torque current component is mainly responsible for generating electromagnetic torque. It interacts with the rotor's rotating magnetic field to produce torque. The q-axis current component is the quadrature-axis current component, whose direction is parallel to the voltage vector of the stator winding. By controlling the q-axis current component, the output torque of the motor can be accurately adjusted

[0121] Step three: rotor flux estimation value Ψ r Subtract the given value of the flux Ψ ref After the first PI controller on the machine side, the given value of the stator field current is obtained, and the formula is as follows:

[0122] Step four: angular velocity given value ω ref Subtract the actual value of the angular velocity ω r After the second PI controller on the machine side, the given value of the stator torque current is obtained, and the formula is as follows:

[0123] Step five: given value of stator field current i mdref After subtracting the field current component of the three-phase stator current in the dq synchronous rotating coordinate system, the given value of the d-axis component of the stator voltage is obtained after processing by the third PI controller on the machine side, and the formula is as follows:

[0124] Step six: given value of stator torque current i mqref After subtracting the torque current component of the three-phase stator current in the dq synchronous rotating coordinate system, the given value of the q-axis component of the stator voltage is obtained after processing by the fourth PI controller on the machine side, and the formula is as follows:

[0125] Step seven: given value of d-axis component of stator voltage u md And the given value of the q-axis component of the stator voltage u mq After Park inverse transformation, the control signal u mα And u mβ After SVPWM modulation, the pulse signal is generated to control the actual speed and flux to track the given speed and flux, and the formula is as follows:

[0126] In this embodiment, the actual speed and flux linkage of the three-phase asynchronous motor are controlled to track the initially given speed and flux linkage. A closed-loop control system is adopted, which uses a feedback device to detect the actual position, speed and torque of the motor in real time, compares these actual values ​​with the set values, calculates the error and adjusts them in real time, thereby ensuring that the motor runs at the predetermined speed and flux linkage, and can adjust the set values ​​in real time to regulate the system operation.

[0127] Furthermore, the intermediate DC section serves to provide a stable DC power supply for the grid-connected inverter.

[0128] Furthermore, the role of the grid-side control section is to ensure that the grid-connected electrical energy is in phase and frequency with the grid electrical energy, and to keep the DC bus voltage stable.

[0129] Furthermore, in this embodiment, as shown in Figure 3, the grid-side control section adopts a grid voltage vector orientation control method, specifically including:

[0130] Step 1: Obtain the voltage component u in the dq synchronous rotating coordinate system by performing Clark and Park transformations on the actual voltage on the grid side. gd and u gq u gq Under the action of the first PI controller on the grid side, the voltage stabilizes near 0, thus obtaining the grid voltage space vector angle. The formula is as follows:

[0131] Step 2: The actual current on the grid side is transformed by Clark and Park to obtain the active current component i in the dq synchronous rotating coordinate system. gd and reactive current component i gq The formula is as follows;

[0132] Step 3: The given value U of the DC bus voltage dc With actual feedback value U ref The active component i of the current on the d-axis is obtained by subtracting the second PI regulator on the grid side. gdref The formula is as follows;

[0133] Step 4: i gdref Active current component i in the synchronously rotating coordinate system with dq gd The difference is processed by the third PI regulator on the grid side to obtain the given value u of the active voltage in the dq rotating coordinate system. gd The formula is as follows:

[0134] Step 5: Reactive component i of current on the q-axis gqref with i gq The difference is then processed by the fourth PI regulator on the grid side to obtain the given value u of the reactive voltage in the dq rotating coordinate system. gq The formula is as follows:

[0135] Step Six: Grid-side active voltage u gd and grid-side reactive voltage u gq The values ​​of the α and β axis components in the stationary coordinate system are obtained by the inverse Park transformation, as shown in the following formula:

[0136] Step 7: u gα and u gβ The pulse signal generated under SVPWM modulation drives the grid-side converter to operate.

[0137] Furthermore, in step five, to ensure that the grid-side converter operates under unity power factor conditions, the reactive component i of the current on the q-axis is set. gqref The value is 0.

[0138] Furthermore, the grid-connected module includes fuses, transformers, residual current circuit breakers, and the power grid.

[0139] In this embodiment, as shown in Figure 4, the specific functions of each part in the figure are as follows:

[0140] Axial flow pump: drives an asynchronous motor to rotate.

[0141] Three-phase asynchronous motor: converts the mechanical energy transmitted from the axial flow pump into electrical energy.

[0142] Machine-side converter: provides excitation reactive power for the operation of the three-phase asynchronous generator; outputs the active power generated by the asynchronous motor to the DC bus.

[0143] Intermediate DC section: Provides a stable DC power supply for grid-connected inverters.

[0144] Braking resistor: When the bus voltage is too high, the braking resistor is connected to prevent damage to the bus capacitor and power devices.

[0145] Precharge circuit: to prevent damage or destruction to devices caused by excessive inrush current when the system is first powered on.

[0146] Grid-side converter: During the pre-charging stage, it rectifies the AC power from the grid side into DC power; during grid-connected operation, it converts the DC power into three-phase AC power with the same frequency, amplitude and phase as the grid power.

[0147] LCL filter circuit: suppresses high-frequency harmonic components introduced by pulse width modulation of power devices.

[0148] Leakage protection circuit breaker: prevent system from leakage.

[0149] Fuse: prevent system from over current.

[0150] UPS (Uninterruptible Power Supply): ensure enough power to make control system disconnect from power grid when power grid fails, supply voltage is 380V.

[0151] Grid-connected transformer: make whole system electrically isolated from power grid, ensure grid-connected safety.

[0152] Machine side control board: monitor speed and current of three-phase asynchronous motor, monitor temperature of machine side converter and drive its operation.

[0153] Grid side control board: monitor voltage and current of intermediate DC part and LCL filter circuit, monitor state of pre-charge circuit and leakage protection circuit breaker, monitor temperature of grid side converter and drive its operation.

[0154] The whole system is controlled and driven by host computer, has two modes of generation mode and motor mode, has state indication and emergency stop function.

[0155] In this embodiment, as shown in Figures 4-5, when the system starts, the circuit breaker is closed, the three-phase 380V power of the power grid enters the pre-charge resistor, passes through the LCL filter circuit and the grid side converter, and charges the DC bus. When the DC bus voltage is charged to about 90% of the rated voltage, the pre-charge main contactor is closed, and the power grid continues to charge the DC bus until the rated voltage. Start the machine side converter, the energy flows from the DC bus to the machine side, and the excitation magnetic field is established in the asynchronous motor. When the motor operates in the generation mode, the crossflow pump drives the asynchronous motor to rotate, and the rotor speed nr> Synchronous speed n0, the slip S is negative, at this time the asynchronous motor converts the input mechanical energy into electrical energy, the energy flows from the machine side to the bus through the machine side converter, and the energy is finally connected to the power grid through the processing of the grid-connected inverter.

[0156] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments, combination of part of the components in the embodiments to construct other ways can also be included in the scope of the present application.

Claims

1. A three-phase asynchronous motor-based through-flow pump grid-connected control system, characterized in that, The power generation module, the electric energy control module, and the grid-connected module are electrically connected. The power generation module is used for converting mechanical energy transmitted by the tubular pump into electric energy and is electrically connected with the electric energy control module. The electric energy control module is electrically connected with the power generation module and the grid-connected module, and is used for generating a pulse signal to drive the control system to run, converting three-phase alternating current electric energy output by the power generation module into direct current electric energy, and processing the direct current electric energy into electric energy consistent with grid parameters, based on a plurality of PI controllers, through ABC-αβ-dq coordinate transformation and flux estimation. The grid-connected module is electrically connected with the electric energy control module and is used for guaranteeing grid-connected safety and preventing system overcurrent.

2. The control system for a three-phase induction motor based through-flow pump grid-connected system according to claim 1, characterized in that, The power generation module is used for converting mechanical energy into electric energy during operation of the tubular pump by using a three-phase asynchronous motor.

3. The control system for a three-phase induction motor based through-flow pump grid-connected system according to claim 1, characterized in that, The electric energy control module includes a machine-side control part, an intermediate direct current part, and a grid-side control part.

4. The control system for a three-phase induction motor based through-flow pump grid-connected system according to claim 3, characterized in that, The machine-side control part is used for controlling operation of the three-phase asynchronous motor, providing excitation reactive power for the three-phase asynchronous motor, and converting alternating current electric energy output by the three-phase asynchronous motor into direct current electric energy.

5. The control system for a three-phase induction motor based through-flow pump grid-connected system according to claim 4, characterized in that, The machine-side control part adopts a rotor field-oriented control method combining a speed outer ring with a current inner ring, and specifically includes: Step one: Set the angular velocity given value ω of the three-phase asynchronous motor according to experience ref , flux linkage given value Ψ ref ; Step two: the three-phase stator current of asynchronous motor is converted into excitation current component and torque current component in dq synchronous rotating coordinate system through Clark conversion and Park conversion, and the rotor flux space position angle estimation value and rotor flux estimation value are obtained, the formula is as follows: wherein: i ma , i mb , i mc : motor three-phase stator current measurement values; i md : excitation current component; i mq : torque current component; θ m : estimated value of the rotor flux linkage spatial position angle; Ψ r : estimated value of the rotor flux linkage L m : mutual inductance between stator and rotor r : electromagnetic time constant of rotor ω: actual angular velocity of the motor; s: complex variable; Step three: rotor flux estimation value Ψ r and the flux given value Ψ ref Subtracting, through the machine side of the first PI controller to get the stator excitation current given value, the formula is as follows; wherein: i mdref : stator excitation current given value; Ψ ref : flux linkage given value; k pm1 : Proportional coefficient of the machine-side first PI controller; Ψ r : Rotor flux estimation value; k im1 : integral coefficient of the first PI controller on the motor side Step four: angular velocity given value ω ref Subtracting the angular velocity actual value ω r Subtracting the angular velocity actual value ω wherein: i mqref : stator torque current given value; ω ref : angular velocity given value; k pm2 : Proportional coefficient of the second PI controller on the machine side; ω r : Actual value of the angular velocity; k im2 : integral coefficient of the second PI controller on the motor side Step five: stator excitation current given value i mdref The difference between the three-phase stator current and the excitation current component in the dq synchronous rotating coordinate system is processed by the third PI controller on the machine side to obtain the stator voltage d-axis component given value, and the formula is as follows: wherein: u md : stator voltage d-axis component given value; i mdref : stator excitation current given value; k pm3 : Proportional coefficient of the third PI controller on the machine side; i md : Excitation current component; k im3 : integral coefficient of the third PI controller on the motor side Step six: stator torque current given value i mqref The difference between the three-phase stator current and the torque current component in the dq synchronous rotating coordinate system is processed by the fourth PI controller on the machine side to obtain the stator voltage q-axis component given value, and the formula is as follows: wherein: u mq : stator voltage q-axis component given value; i mqref : stator torque current given value; k pm4 : proportional coefficient of the fourth PI controller on the motor side; i mq : torque current component; k im4 : integral coefficient of the fourth PI controller on the motor side Step seven: stator voltage d-axis component given value u md and stator voltage q-axis component given value u mq Park inverse transformation to get control signal u mα and u mβ , SVPWM modulation to produce pulse signal, control actual speed, flux to track given speed and flux, formula as follows: where: u mα , u mβ : control signal component in αβ coordinate system; u md : stator voltage d-axis component given value; u mq : stator voltage q-axis component given value; θ m : estimated value of the rotor flux linkage spatial position angle.

6. The control system for a three-phase induction motor based through-flow pump grid-connected system according to claim 3, characterized in that, The intermediate direct current part is used for providing stable direct current power for grid-connected inversion.

7. The control system for a pump-generator grid-connected based on a three-phase asynchronous motor according to claim 3, characterized in that, The grid-side control part is used for ensuring that electric energy connected with the grid has the same frequency and phase as grid electric energy and keeping the direct current bus voltage stable.

8. The control system for a three-phase induction motor based through-flow pump grid-connected system according to claim 7, characterized in that, The grid-side control part adopts a grid voltage vector-oriented control method, and specifically includes: Step one: the actual voltage of the grid side is transformed by Clark transformation and Park transformation to get the voltage component u in dq synchronous rotating coordinate system gd and u gq , u gq is stabilized near 0 under the action of the first PI controller of the grid side, and the grid voltage space vector angle is obtained The formula is as follows: where: u gα , u gβ : control signal component in αβ coordinate system; u ga , u gb , u gc : motor three-phase stator voltage measurement values; u gd , u gd : dq voltage components in the synchronous rotating coordinate system; Grid voltage space vector angle; k pg1 : proportional coefficient of the grid-side first PI controller; k ig1 : integral coefficient of the grid-side first PI controller; Step two: the actual current on the grid side is transformed by Clark transformation and Park transformation to get the active current component i gd and the reactive current component i gq , as follows; where: i gα , i gβ : current component in αβ coordinate system; i ga , i gb , i gc : actual three-phase stator current measurement of the grid-side motor i gd : dq active current component in the synchronous rotating coordinate system; i gq : dq reactive current component in the dq synchronous rotating coordinate system; Grid voltage space vector angle; Step three: the given value of the DC bus voltage U dc with the actual feedback value U ref The difference is obtained after the second PI regulator on the grid side, and the active component reference value of the current on the d-axis i gdref , the formula is as follows; wherein: i gdref : active component of current on d-axis reference value; k pg2 : proportional coefficient of the grid-side second PI controller; k ig2 : integral coefficient of the grid-side second PI controller; U dc : given value of the DC bus voltage; U ref : actual feedback value of the voltage; Step four: i gdref Active current component i in dq synchronous rotating coordinate system gd Subtracting the third PI regulator on the grid side to get the given value of active voltage in dq rotating coordinate system u gd The formula is as follows: where: u gd : given value of the active voltage in the dq rotating coordinate system; k pg3 : proportional coefficient of the third grid-side PI controller; k ig3 : integral coefficient of the third grid-side PI controller; i gd : active current component; i gdref : active component of current on d-axis reference value; Step five: reactive component of current in q-axis i gqref The difference between i gq and i gq is regulated by the fourth grid-side PI regulator to obtain the given value of reactive voltage in dq rotating coordinate system u gq , which is as follows: where: u gq : given value of reactive voltage in dq rotating coordinate system; k pg4 : proportional coefficient of the fourth grid-side PI controller k ig4 : integral coefficient of the fourth grid-side PI controller i gqref : reactive component of current on q-axis; Step six: grid-side active voltage u gd and grid-side reactive voltage u gq Convert into given values of α, β axis components in the stationary coordinate system by Park inverse transformation, the formula is as follows: wherein: u gd : grid-side active voltage; u gq : grid-side reactive voltage; u gα : given value of the alpha-axis component in the stationary coordinate system; u gβ : given value of the beta-axis component in the stationary coordinate system; Step seven: u gα and u gβ The pulse signal is generated under SVPWM modulation to drive the control of the grid-side converter.

9. The control system for a three-phase induction motor based through-flow pump grid-connected system according to claim 8, characterized in that, In the fifth step, to ensure that the grid-side converter operates under the condition of unity power factor, the reactive component of the current in the q-axis is set as i gqref = 0.

10. The control system for a three-phase induction motor based through-flow pump grid-connected system according to claim 1, characterized in that, The grid-connected module includes a fuse, a transformer, a leakage protection circuit breaker, and a grid.

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