CN110797891B - Flywheel energy storage system of double three-phase brushless direct current motor and control method thereof - Google Patents

Abstract

The invention discloses a flywheel energy storage system of a dual-phase brushless DC motor and a control method thereof. The dual-phase brushless DC motor comprises six windings. The electrical angle differs by 30 degrees; the bidirectional thyristor realizes the connection of a group of three-phase windings and a group of three-phase inverters to form a first inverter circuit and a second inverter circuit; each bridge arm of the three-phase inverter group is connected to A circuit breaker QF and a fuse FU are connected between the first-phase windings, and relays K1 and K2 are respectively set in the DC bus to close the contacts; in the energy feedback, the BOOST circuit is used to control the switch tube to achieve DC side voltage stability, and relays are set in the BOOST circuit. K3 and K4 normally open contacts, when the winding voltage reaches a given value, the normally open contacts of relays K3 and K4 are closed, and the closed contacts of relays K1 and K2 are opened to realize energy switching. The invention is suitable for large-capacity energy storage, has high power, long service life and fast charging and discharging speed.

Description

A flywheel energy storage system of dual-phase brushless DC motor and its control method

technical field

The invention belongs to the technical field of motor control, and in particular relates to a flywheel energy storage system of a dual-phase brushless DC motor and a control method thereof.

Background technique

Energy has always been a major issue for human development. In the process of developing and utilizing traditional energy and new energy, the development of energy storage technology will alleviate the contradiction between energy production and energy consumption. Hydropower is responsible for tasks such as adjusting peak voltage, adjusting frequency and power reserve, reducing overuse of thermal power resources, reducing grid costs, and improving grid reliability. The development of the parallel operation technology of flywheel energy storage units will be applied to the field of large grid energy storage. With the research of power grid, it is imperative to build a distributed energy system based on energy storage technology and develop energy storage technology.

According to the form of energy storage, it is divided into three categories: 1) mechanical energy storage such as flywheel energy storage, compressed air energy storage, pumping energy storage, etc.; 2) supercapacitor energy storage, superconducting energy storage and other electrical energy storage; 3) lead-acid battery , lithium-ion batteries, sodium-sulfur batteries, redox flow batteries and other chemical energy storage.

Among the above energy storage technologies, those applied in engineering are relatively mature, pumped hydro storage and chemical battery storage. Pumped storage has low comprehensive benefits and high requirements. Chemical batteries are widely used, but there are limitations such as charge and discharge times, environmental pollution, and high operating temperature requirements. On the other hand, in recent years, the development of advanced composite materials, high-power power electronics, low-loss advanced bearings, and high-efficiency, long-life flywheel energy storage systems for high-speed permanent magnet motors has injected new vitality. The flywheel energy storage system has high power density, high energy density, convenient installation and maintenance, harmless to the environment, long service life, and almost no limit to the number of charging and discharging, which is superior to chemical battery energy storage technology.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a flywheel energy storage system of a dual-phase brushless DC motor and a control method thereof aiming at the deficiencies in the above-mentioned prior art, so as to improve the charging and discharging efficiency of the flywheel energy storage system.

The present invention adopts following technical scheme:

A flywheel energy storage system of a dual-phase brushless DC motor includes a dual-phase brushless DC motor and a BOOST circuit. The dual-phase brushless DC motor includes six windings, and three windings form a group of three-phase windings; two The three-phase windings are connected by bidirectional thyristors, and the electrical angle between the two groups of windings differs by 30 degrees; the bidirectional thyristor realizes the connection of a group of three-phase windings and a group of three-phase inverters, forming the first inverter circuit and the second inverter circuit. Transformer circuit; each bridge arm of the three-phase inverter group includes two series-connected power MOS switch tubes, the connection point is the midpoint of the bridge arm, and a circuit breaker QF and a fuse are connected between each bridge arm and a phase winding FU, relays K1 and K2 are respectively set in the DC bus to close contacts; in the energy feedback, the BOOST circuit is used to control the switch tube to achieve DC side voltage stability. In the BOOST circuit, relays K3 and K4 are set to normally open contacts. When the value is fixed, the normally open contacts of relays K3 and K4 are closed, and the closed contacts of relays K1 and K2 are disconnected to realize energy switching.

Specifically, in the BOOST circuit, when the switch tube V is turned on, the energy of the power supply flows to the inductor L, and the voltage on the capacitor C supplies power to the grid; when the switch tube V is in the off state, no energy is output; the switch tube V passes through The detected winding terminal voltage is compared with the specified voltage, and the error is adjusted by PI and compared with the triangular wave carrier to generate a PWM signal, which is used to adjust the duty cycle of the switch tube V to achieve a stable DC voltage output.

Specifically, the inverter includes group A and group B, the inverter in group A includes three bridge arms, the bridge arm La of the inverter includes a power switch tube S1 and a power switch tube S2, and a circuit breaker is connected between the bridge arms and the windings QF1 and fuse FU1; inverter bridge arm Lb includes power switch tube S3 and power switch tube S4, and circuit breaker QF2 and fuse FU2 are connected between the bridge arm and the winding; inverter bridge arm Lc includes power switch tube S5 and The power switch tube S6, the circuit breaker QF3 and the fuse FU3 are connected between the bridge arm and the winding;

The inverter of group B includes three bridge arms, the inverter bridge arm Lx includes a power switch tube S7 and a power switch tube S8, and the circuit breaker QF4 and the fuse FU4 are connected between the bridge arm and the winding; the inverter bridge arm Ly includes The power switch tube S9 and the power switch tube S10, the circuit breaker QF5 and the fuse FU5 are connected between the bridge arm and the winding; the inverter bridge arm Lz includes the power switch tube S11 and the power switch tube S12, and the bridge arm and the winding are connected with an open circuit The connection points on both sides of the power switch tube connected in series are connected to the positive and negative poles of the DC power supply respectively.

Further, in the inverters of group A, the three-phase current of the stator is detected, and then the coordinates are transformed into the current value in the two-phase coordinate, the AC-direction axis voltage is obtained through vector control, and the voltage value on the α-β axis is obtained through coordinate transformation. , and output the PWM1 signal through space vector pulse width modulation to generate six signals to control the corresponding six switches respectively;

In group B inverters, the voltage reference signal U _dc ^* is compared with the actual detected U _dc , and the difference is obtained for PI adjustment. The output value of the voltage PI adjustment is the given value of the current loop, which is compared with the current feedback value. After comparison, the obtained difference is adjusted by PI, and then the trigger pulse signal PWM2 is generated by decoupling coordinate transformation and then compared with the triangular wave, and six signals are generated to control the corresponding six switches respectively.

的比较得到双向晶闸管VS的信号F_U，具体为：Specifically, the control of the triac is: detecting the three-phase winding (u _a , u _b , uc ₎ and a given threshold voltage through a voltage sensor

The comparison obtains the signal FU of the triac _VS , specifically:

When the inverter works normally, F _u = 1, the system works in the traditional twelve switching inverter power supply mode, firstly, the triac VS receives the forward voltage signal and conducts, and becomes a dual three-phase motor.

Another technical solution of the present invention is a control method for a flywheel energy storage system of a dual-phase brushless DC motor, comprising:

In the charging state, the external power supply supplies power to the motor/generator through the power electronic converter. The motor/generator operates as a motor, and the flywheel rotor is driven to accelerate. When the rotor speed reaches the maximum working torque, the power electronic device generates a control signal to Control the drive motor, the motor drives the flywheel to run and realize charging;

In the discharge state, the motor/generator operates as a generator, the flywheel rotor decelerates, the mechanical energy is converted into electrical energy by the generator, and the power electronic converter adjusts the bus voltage output by the generator to keep it at a constant voltage all the time;

In the hold state, the flywheel system is in the energy hold phase. It has neither a forward flow of energy nor a reverse flow of energy, and in this mode the system operates with minimal losses;

The detection voltage sensor detects the comparison between the three-phase windings (u _a , _ub , _uc ) and the given voltage value u _o , when u _a , _ub , _uc gradually rise to u _o , it is in the state of charge; when u _o When the value gradually drops to the set value, it is in the discharge state, and the working mode is judged as:

When the current sensor detects the port fault of the armature winding connected to the faulty bridge arm and makes a fault judgment, it controls the six switch tubes of group A/group B of the inverter to turn off at the same time by controlling the control signal of the PWM1/PWM2 module, and stop the Work.

Specifically, during the charging process, six PWM drive signals are sent out by detecting the zero-crossing point of the back electromotive force, and after power amplification, the power switch tube is driven, so that the motor reaches the highest speed and is in the holding stage; the control strategy is to compare the position speed ω ^* with the actual The estimated ω is compared to obtain the difference, and then the difference is obtained through the PI controller to obtain the current signal i _q ^* of the q axis, and the given reference signal of the d axis is set to zero; after the coordinate transformation, it becomes The current components id and i _q are compared with their reference signals _id ^* and i _q ^* . After decoupling through the current controller, the output voltage signals _ud ^* and u _q ^* are output _. After coordinate transformation, the control signal is controlled by SVPWM Generated to realize the charging process.

Further, the specific steps are:

S101. The speed error e _ω is obtained after the mathematical operation of subtraction between the given speed ω* of the motor and the actual speed ω, and the speed error e _ω outputs the given current after the speed PI regulator

以及直流电流、交流电流i_d,i_q计算电流偏差e_d,e_q经两个电流PI调节器后输出参考直流电压

和直流交轴电压

S102, connect the reference DC current signal and the reference AC current signal

And DC current, AC current id , i _q calculate the current deviation _ed , _{e q} output the reference DC voltage after two current PI regulators

and DC AC-axis voltage

计算三相旋转坐标系下的参考电压

S103. Calculate the currents _id and _iq in the two-phase rotating coordinate system according to the stator winding currents _ia and _ib of the motor detected by the current sensor, and compare the calculated reference voltages to the calculated reference voltages.

Calculate the reference voltage in the three-phase rotating coordinate system

S104: Determine the direction of the interval where the reference voltage vector is located, and then synthesize the reference voltage vector by using two adjacent voltage vectors and an appropriate sector-shaped zero vector to realize modulation of the SVPWM signal.

Specifically, in the discharge state, a double closed-loop control system is used, the outer loop is a voltage regulation loop, the quadrature-axis current component i _q ^* is limited in the voltage regulator, and the current inner loop is controlled according to the current output by the voltage loop. After the coupling coordinate is transformed, it is compared with the triangular wave to generate the trigger pulse signal PWM2 module; the discharge process is realized.

Further, the specific steps are as follows:

S201, the PWM2 module transforms the measured three-phase stationary coordinate system into two-phase coordinates of synchronous rotation, and the current value becomes the current components _id and i _q after the coordinate transformation;

S202, adopting the direct current control strategy, the voltage outer loop tracking system controls the given reference signal and the actual value to compare the output current through the PI regulator to achieve a constant DC voltage;

S203, the current inner loop performs current control according to the output current of the voltage loop, and then compares with the triangular wave after decoupling coordinate transformation to generate a trigger pulse signal to control the turn-on and turn-off of the converter;

S204. During the discharge process, the mechanical energy is converted into electrical energy, and the boost circuit after the inverter boosts the voltage to supply power to the DC load, compares the detected winding terminal voltage with the specified voltage, and compares the error with the triangular wave carrier after PI adjustment to generate PWM signal to adjust the duty cycle of V and adjust the output DC voltage.

Compared with the prior art, the present invention at least has the following beneficial effects:

The present invention is a flywheel energy storage system of a dual-phase brushless DC motor. Since the power grid does not supply power during the discharge process of the flywheel energy storage system, the speed of the motor gradually decreases, the required discharge depth is not reached, and the voltage at the motor terminal gradually decreases. Therefore, it is necessary to add a boost circuit before the load, and in order to stabilize the output voltage to the power grid, please supplement the benefits and advantages of the entire energy storage system according to the content of claim 1.

Further, the control signal of the switch tube V in the BOOST circuit is analyzed, and the voltage at the winding terminal is compared with the specified voltage. The error is adjusted by PI and compared with the triangular wave carrier to generate a PWM signal. This method is more than the traditional DC boost. The transformation ratio range is greatly improved, and since there is only one switch tube, the loss of the circuit is effectively reduced, the working efficiency of the inverter is ensured, and the efficiency of the entire flywheel energy storage system is improved.

Further, the full-bridge controllability circuit composed of six MOS power switch tubes is analyzed for the bidirectional inverter. The function is to invert the DC current into a 120-degree square wave current to drive the brushless DC motor during charging. When AC/DC conversion is performed, the square wave electromotive force is converted into DC.

Further, it is analyzed that a triac VS is connected between the two sets of three-phase windings of the dual-phase motor to achieve neutral point isolation and effectively improve anti-interference. The electrical angle between the two sets of windings differs by 30 degrees. When the VS is turned on, a group of windings and the inverter perform charging and discharging operations, and another group of windings and the inverter perform charging and discharging operations. When the VS is turned off, the realization system becomes two sets of three-phase motors, one can be charged and discharged normally, and the other can not work. When one group of inverters fails, the other group can achieve normal energy conversion, and when a fault occurs, the system can achieve fault tolerance. To achieve the purpose of replacing the fault group work, to achieve the normal energy storage work of the system.

The present invention is a control method for a flywheel energy storage system of a dual-phase brushless DC motor. By driving the flywheel of the DC motor, the charging and discharging power of the flywheel energy storage system is increased without increasing the voltage and current of the busbar. Reduce the content of low-order harmonics, reduce the loss of the motor rotor, improve the efficiency of the system, realize the combination of multiple motors and the flywheel energy storage system, and the application prospect of the DC motor structure and flywheel energy storage system.

Further, considering the large moment of inertia of the flywheel energy storage system and the relatively long charging time, the PWM control method of current hysteresis tracking reduces the charging time and can eliminate the electromagnetic torque caused by the peak current of the brushless DC motor. fluctuations, reducing the noise of the system during charging.

Further, it is analyzed that vector control is used in the discharge process, and the brushless motor realizes energy feedback through a three-phase inverter. Since the electric energy changes with the speed of the discharge state, it is desirable to have better use of electric energy. , to ensure that the converted DC voltage remains unchanged, a BOOST circuit needs to be added after the inverter to better stabilize the DC bus voltage. The advantage of this method is that the control method is relatively easy.

To sum up, the present invention is suitable for large-capacity energy storage, and has the advantages of high power, long service life, and fast charging and discharging speed, and has very broad prospects. Therefore, research on the charging and discharging control of flywheel energy storage is required.

The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is the winding structure diagram of the brushless DC motor of the present invention;

Fig. 2 is the working principle diagram of the flywheel energy storage system of the present invention;

3 is a diagram of a double closed-loop control system for charging and energy storage of the flywheel system of the present invention;

Fig. 4 is the control system diagram of the flywheel system discharge double closed-loop of the present invention;

Fig. 5 is the circuit schematic diagram of the charging of the energy storage system of the present invention;

Fig. 6 is the main circuit diagram of the energy storage system of the dual-phase motor of the present invention;

Figure 7 is a charging model diagram of the flywheel energy storage system;

Fig. 8 is a charging simulation data diagram, in which (a) is the transformation of the rotational speed N=1000r/min, (b) is the transformation of the electromagnetic torque _Te of N=1000r/min, (c) is the load current of N=1000r/min i _abc , (d) is the transformation of the rotational speed N=2000r/min, ( _e ) is the N=2000r/min load current i _abc , (f) the N=2000r/min electromagnetic torque Te transformation;

Figure 9 is a model diagram of the flywheel energy storage discharge;

Figure 10 is the discharge simulation data diagram, in which (a) is the voltage waveform diagram of the given voltage U=220V on the load side, (b) is the speed waveform diagram of the given voltage U=220V, (c) is the given voltage U= The voltage waveform on the load side in 250V, (d) is the speed waveform in the given voltage U=250V.

Detailed ways

In the description of the present invention, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense, unless otherwise expressly specified and limited, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

The invention provides a flywheel energy storage system of a dual-phase brushless DC motor and a control method thereof. The mathematical model of the DC motor in the natural coordinate system and the rotating coordinate system is analyzed, and double closed-loop control is used to control the charging and discharging of the system. The method includes a motor model, a PI controller model, a coordinate transformation model, and a SVPWM control mathematical model, and then the control models of the charging and discharging systems are obtained; a double closed-loop control method is adopted, the DC brushless motor is connected to the flywheel, and the There are two processes of accelerating energy storage and decelerating discharge to the flywheel.

By establishing the mathematical model of the three-phase brushless DC motor, the coordinate transformation module is needed to obtain the current value and position angle of the dual-phase brushless DC motor. According to the position angle of the motor rotor, the current value of the dual-phase brushless DC motor Perform coordinate transformation to generate the current values of the d-q axes of the two sets of windings in the rotating coordinate system, and generate a module. According to the d-q axis current value of the two windings and the given reference current, the current inner loop value of the energy storage system is generated, and the PWM module obtains the driving signal through the space voltage vector modulation technology to control the conduction and Close short, get the realization of system charge and discharge.

Referring to FIG. 6, the present invention provides a dual-phase brushless DC motor flywheel energy storage system, including a brushless DC motor, a six-phase inverter, a fuse, a circuit breaker, a relay KM, a triac and a BOOST circuit .

Please refer to Figure 1. The dual-phase brushless DC motor includes six windings, and the structure can be divided into three-phase windings to form a set of three-phase windings, and two sets of three-phase windings to form a dual-phase motor winding part; two sets of three-phase windings The windings are connected by a bidirectional thyristor VS to achieve neutral point isolation, and the difference between the two sets of windings is an electrical angle of 30 degrees. The bidirectional thyristor can realize the connection of a group of three-phase windings and a group of three-phase inverters A(B) to form two systems of inverter circuit 1 and inverter circuit 2; each bridge arm in group A(B) inverters A circuit breaker QF and a fuse FU are connected between the first-phase winding. There are relays K1 and K2 closed contacts in the DC bus respectively. At the same time, there are relays K3 and K4 normally open contacts in the BOOST circuit, and the relay action signal The acquisition is by detecting whether the winding voltage reaches the given value. When the given value is reached, the normally open contacts of the relays K3 and K4 are closed, and the closed contacts of the relays K1 and K2 are disconnected, thereby realizing the energy switching process. Its characteristic is that there are only 6 phases at the outlet end, but it can be equivalent to a symmetrical twelve-phase motor system from the inside, which effectively eliminates the 5th and 7th harmonic potential of the traditional three-phase motor, which reduces the requirements of the motor manufacturing process. Improved motor stability.

Each inverter bridge arm is composed of two power MOS switch tubes connected in series, and the connection point is the midpoint of the bridge arm. A group of inverters includes three (La, Lb, Lc) bridge arms. The inverter bridge arm La is composed of a power switch tube S1 and a power switch tube S2. A circuit breaker QF1 and a fuse are connected between the bridge arm and the winding. FU1; the inverter bridge arm Lb is composed of a power switch tube S3 and a power switch tube S4, and a circuit breaker QF2 and a fuse FU2 are connected between the bridge arm and the winding; the inverter bridge arm Lc is composed of a power switch tube S5 and a power switch. It is composed of tube S6, and a circuit breaker QF3 and a fuse FU3 are connected between the bridge arm and the winding; the B group inverter includes three (Lx, Ly, Lz) bridge arms, and the inverter bridge arm Lx is composed of power switch tubes S7 and S7 and It consists of a power switch tube S8, and a circuit breaker QF4 and a fuse FU4 are connected between the bridge arm and the winding; the inverter bridge arm Ly consists of a power switch tube S9 and a power switch tube S10, and a circuit breaker is connected between the bridge arm and the winding. QF5 and fuse FU5; inverter bridge arm Lz is composed of power switch tube S11 and power switch tube S12, a circuit breaker QF6 and fuse FU6 are connected between the bridge arm and the winding, and the connection points on both sides of the power switch tube in series are respectively Connect the positive and negative poles of the DC power supply.

A group of inverters includes three (La, Lb, Lc) inverter bridge arms composed of six switch tubes, the control signals of which are generated by the PWM1 controller. The six signals are (S1, S2, S3, S4, S5, S6), the realization process is to detect the three-phase current of the stator, and then transform it into the current value in the two-phase coordinate, obtain the voltage of the AC-direction axis through vector control, and then obtain the voltage on the α-β axis through coordinate transformation value, and output PWM1 signal after space vector pulse width modulation. Group B inverters include three (Lx, Ly, Lz) inverter bridge arms composed of six switch tubes, and the control signals are generated by the PWM2 controller to generate six signals (S7, S8, S9, S410, S11, S12) , and its realization process is to compare the voltage reference signal U _dc ^* with the actual detected U _dc to obtain the difference for PI adjustment. The output of the voltage PI adjustment is used as the given value of the current loop, which is also compared with the current feedback value. The difference obtained is then adjusted by PI, and then compared with the triangular wave through the decoupling coordinate transformation to generate the trigger pulse signal PWM2 signal.

的比较得到双向晶闸管VS的信号F_U，得出不同模式下的1. According to the control of the bidirectional thyristor VS in the double-three-phase motor winding structure, the three-phase winding (u _a , u _b , u _c ) and a given threshold voltage are detected by the voltage sensor

The comparison of the two-way thyristor VS signal _FU is obtained, and the different modes of

The triac _FU is as follows:

When the inverter is working normally, F _u = 1, the system works in the traditional twelve switching inverter power supply mode. First, the triac VS receives the forward voltage signal and turns on, then it becomes a dual three-phase motor. The judgment method of the charging and discharging process is as follows:

The detection voltage sensor detects the comparison of the three-phase winding (u _a , u _b , u _c ) and the given voltage value u _o

When u _a , _ub , _uc gradually rise to u _o , the charging process is realized.

When the value of u _o gradually drops to a certain value, it is the discharge process.

Working mode judgment:

A set of windings and inverters can be used for charging and discharging operations, and another set of windings and inverters can also be used for charging and discharging operations. When a fault occurs, the fault tolerance of the system can be realized. As shown in Figure 6, the main circuit is divided into two parts: inverter circuit 1 and inverter circuit 2. The charging process is that the DC bus voltage passes through the relay K1 (K2) closed contact K3 (K4) normally open contact is disconnected, and after the After the control signal generated by the PWM1 (PWM2) module provided by the above claim 3 controls the six switching tubes of the A (B) group inverter to be turned on at different times, the fuses FU1, FU2, FU3 (FU4, FU5, FU6) is closed, and the circuit breaker contacts QF1, QF2, QF3 (QF4, QF5, QF6) are closed at the same time to realize the charging process of the flywheel. In the discharge circuit part, the discharge process is that the DC motor is in the power generation state, and the energy needs to be fed back to the DC bus, and the feedback energy is controlled by the control signal generated by the PWM2 (PWM1) provided by the above claim 3 to the six switches of the B (A) group of inverters. After the tube is turned on at different times, the fuses FU4, FU5, FU6 (FU1, FU2, FU3) on the three inverter bridge arms are closed, and the circuit breaker closes the contacts QF4, QF5, QF6 (QF1, QF2, QF3) ) is closed, because the actual voltage reaches the given value, the relay operates, the K4 (K3) contacts are disconnected, and the K2 (K1) contacts are closed, and the electric energy can be output stably through the BOOST circuit.

If the voltage of the detection winding is abnormal, _Fu = -1, control the thyristor VS to turn off by giving the reverse voltage signal, when the current or voltage of the detection winding is too large, the fuse contacts (FU1, FU2, FU3, FU4, FU5 , FU6) a certain automatic disconnection. After the current sensor detects the port fault of the armature winding connected to the faulty bridge arm and makes a fault judgment, it controls the six switch tubes of group A (group B) of the inverter to turn off at the same time by controlling the control signal of the PWM1 (PWM2) module. ,stop working. Then the system becomes two sets of three-phase motors, one can be charged and discharged normally, and the other does not work. Assuming that the three bridge arms of group A inverter (La, Lb, Lc) work normally, the normal charging and discharging process can be realized. The group B inverter includes three bridge arms (Lx, Ly, Lz), and a certain bridge When the arm fails, such as a short-circuit fault, the circuit breaker (QF4, QF5 or QF6) connected to the bridge arm will act to cut off the bridge arm, and at the same time, the inverter switch tube will be controlled to be turned off through the PWM2 control signal.

通过SVPWM得到PWM1信号对六个开关管进行控制，实现充电过程。If it is the case of state 1, a group of charging assumes inverter circuit 1, and the charging adopts the control strategy of _id ^* = 0, which consists of DC motor, position measurement, speed detection, current control, coordinate transformation, SVPWM, and It is composed of modules such as voltage inverters. The control strategy is to compare the speed ω ^* of the position with the actual estimated ω to obtain the difference e _ω , and then let their difference pass the PI controller to obtain the current of the q axis i _q ^* , while zeroing the given reference signal for the d-axis. After the coordinate transformation, it becomes the current components id and i _q , which are compared with their reference signals _id ^* and i _q ^* _. After decoupling through the current controller, the output voltage signals _ud ^* and u _q ^* are passed through the inverse Park transformation. After u _α ^* and

The PWM1 signal is obtained through SVPWM to control the six switches to realize the charging process.

In the dq two-phase rotating coordinate system, the voltage equation of the sine wave permanent magnet synchronous motor is:

分别为电机定子电压、定子电流、定子磁链在dq两相旋转。Among them, u _sd , u _sq , is _sd , i _sq ,

They are the motor stator voltage, stator current, and stator flux linkage in two-phase rotation of dq.

表示为：The direct axis component and quadrature axis component under the system, ω _r is the angular velocity of the rotor, and the stator flux

Expressed as:

为转子永磁体磁链。Among them, L _d and L _q are the direct-axis inductance and the quadrature-axis inductance of the sine wave permanent magnet synchronous motor, respectively,

is the rotor permanent magnet flux linkage.

Under the synchronous rotation coordinates of the dq two-phase rotor, the motor torque equation is:

in,

Please refer to FIG. 2 , a control method for a flywheel energy storage system of a dual-phase brushless DC motor according to the present invention uses a high-speed rotating flywheel as mechanical energy to realize mutual conversion between electrical energy and mechanical energy by power electronic equipment, including charging , discharge and hold state, the charging state is to use external power supply through the power electronic conversion device to drive the flywheel to rotate, and in the discharge state, the high-speed rotating flywheel rotor is used to drive the motor to rotate, and the working device realizes the conversion of mechanical energy to electrical energy;

In the charging state, the external power source supplies the motor/generator through a power electronic converter, the motor/generator operates as a motor, and the flywheel rotor is driven to accelerate. When the rotational speed of the rotor reaches the maximum working torque, the power electronic device generates a control signal to control the drive motor, and the motor drives the flywheel to run and realize charging.

In the discharge state, the motor/generator operates as a generator, the flywheel rotor decelerates, the mechanical energy is converted into electrical energy by the generator, and the power electronic converter adjusts the bus voltage output by the generator to keep it at a constant voltage all the time.

In the hold state, the flywheel system is in the energy hold phase. It has neither forward nor reverse flow of energy, and in this mode the system operates with minimal losses.

The specific steps for charging are as follows:

S1. For the charging process, please refer to Figure 3 and Figure 5. By detecting the zero-crossing point of the back EMF, six PWM drive signals are sent out, and after power amplification, the power switch tube is driven, so that the motor reaches the maximum speed and is in the holding stage. The control strategy is to compare the speed ω ^* of the position with the actual estimated ω to obtain the difference, and then let their difference pass through the PI controller to obtain the current signal i _q ^* of the q axis, and at the same time, use the given value of the d axis. The reference signal is zero; it becomes the current components _id and i _q after coordinate transformation, and is compared with its reference signals _id ^* , i _q ^* , and after decoupling through the current controller, the output voltage signals _ud ^* and u _q ^* , after the coordinate transformation, the control signal is generated by SVPWM control to realize the charging process; the specific steps are as follows:

S101. The speed error e _ω is obtained after the mathematical operation of subtraction between the given speed ω* of the motor and the actual speed ω, and the speed error e _ω outputs the given current after the speed PI regulator

Define active damping as

_q = i _q ′-B _a ω

Using the control strategy of _id = 0, and assuming that the motor starts under control (T _L = 0), we get:

Coefficient _Ba of active damping:

If the traditional PI regulator is used, the expression of the speed loop controller is shown as

Therefore, the parameters k _pw and k _jw of the PI regulator are set by the following formulas:

Where: β is the desired bandwidth of the speed loop.

以及直流电流、交流电流i_d,i_q计算电流偏差e_d,e_q经两个电流PI调节器后输出参考直流电压

和直流交轴电压

S102, connect the reference DC current signal and the reference AC current signal

And DC current, AC current id , i _q calculate the current deviation _ed , _{e q} output the reference DC voltage after two current PI regulators

and DC AC-axis voltage

Among them, K _pd , K _pq are proportional constant coefficients, K _id , K _iq are integral constant coefficients;

计算三相旋转坐标系下的参考电压

S103. Calculate the currents _id and _iq in the two-phase rotating coordinate system according to the stator winding currents _ia and _ib of the motor detected by the current sensor, and compare the calculated reference voltages to the calculated reference voltages.

Calculate the reference voltage in the three-phase rotating coordinate system

Among them, θ is the electrical angle of the rotor position of the motor;

S104 , to realize the modulation of the SVPWM signal, the direction of the interval where the reference voltage vector is located must be known first, and then the reference voltage vector is synthesized by using two adjacent voltage vectors and an appropriate sector-shaped zero vector.

S1041. Sector judgment of the reference voltage vector

The purpose of determining the sector where the voltage space vector is located is to determine the basic voltage space vector u _out used in this switching cycle, using u _α and u _β to represent the components of the reference voltage vector u _out on the axis in α and β, define The three variables u _ref1 , u _ref2 and u _ref3 are

Then define three variables AB C, through analysis, we can get:

If u _ref1 > 0, then A=1, otherwise A=0;

If u _ref2 > 0, then B=0, otherwise B=0;

If u _ref3 > 0, then C=0, otherwise C=0.

Let N=4C+2B+A, the relationship with the sector can be obtained

S1042, Calculation of non-zero vector and zero vector action time

By simple calculation, it can be

In the same way, the action time of each vector in other sectors can be obtained, let

The time of each sector T ₀ (T ₇ ), T ₄ and T ₆ can be obtained,

If T ₄ +T ₆ >T _S , overmodulation processing is performed, so that

S1043, the sector vector switching point is determined

First define

Then the relationship between the three-phase voltage switching time switching points T _cm1 , T _cm2 , T _cm3 and each sector is as follows:

The determination of the sector of the reference voltage vector, the calculation of the non-zero vector of each sector, the calculation of the action time of the zero vector and the determination of the switching point of each sector vector constitute SVPWM. Finally, a triangular carrier signal with a certain frequency is used. The switching point of each sector vector, through comparison, the PWM pulse signal can be obtained by the converter.

S2, vector control of the discharge process;

确保其值不大于电机允许的上限。电流内环按电压环的输出的电流进行电流控制，通过解耦坐标变换后再与三角波比较产生触发脉冲信号PWM2模块；实现B组逆变器和绕组的飞轮储能系统放电过程的控制步骤如下：Please refer to FIG. 4 , which is the control system diagram of the flywheel system discharge double closed loop of the present invention. If it is the case of state 1, a group of discharges includes a DC motor, position measurement, voltage detection, current control, Coordinate transformation, SVPWM, and voltage inverter, BOOST circuit and other modules, using double closed-loop control system, the outer loop is a voltage regulation loop, in order to reduce the motor output voltage to maintain voltage stability in the event of external load disturbance or speed drop The size limit of the quadrature-axis current component i _q ^* in the regulator is due to

Make sure its value is not greater than the upper limit allowed by the motor. The current inner loop controls the current according to the output current of the voltage loop, and then compares it with the triangular wave to generate the trigger pulse signal PWM2 module through decoupling coordinate transformation; the control steps to realize the discharge process of the flywheel energy storage system of the inverters and windings of group B are as follows :

The modules S201 and PWM2 transform the measured three-phase stationary coordinate system into two-phase coordinates of synchronous rotation, and the current value becomes the current components _id and i _q after the coordinate transformation;

S202, adopting the direct current control strategy, the voltage outer loop tracking system controls the given reference signal and the actual value to compare the output current through the PI regulator to achieve constant DC voltage, constant power, etc.;

为输入电压。in,

is the input voltage.

S203, the current inner loop performs current control according to the output current of the voltage loop, after decoupling coordinate transformation, and then comparing with the triangular wave to generate a trigger pulse signal to control the turn-on and turn-off of the converter tube;

S204. During the discharge process, the mechanical energy of the system is converted into electrical energy, the permanent magnet brushless current works and the state of the generator. With the conversion of mechanical energy into electrical energy, the speed of the motor gradually decreases, so it is necessary to add a Boost circuit after the inverter. . At the same time, in order to stabilize the output voltage, supply power to the DC load after passing through the Boost boost circuit, compare the voltage at the detection winding end with the specified voltage, and compare the error with the triangular wave carrier after PI adjustment to generate a PWM signal to adjust the duty cycle of V, thus to adjust the output DC voltage.

The boost chopper circuit needs to control a switch tube to control the stability of the DC side voltage. The switch tube V is turned on and off. Assuming that the inductance L and capacitor C in the circuit are large enough, when V is turned on, the energy of the power supply It flows to the inductor L, and the voltage on the capacitor C supplies power to the load; when the capacity of the capacitor C is large enough, the output voltage does not change to U ₀ , when V is in the off state, the power supply E and the inductor L together charge the capacitor C to supply the load. powered by.

The turn-on and turn-off times of V are t _on and t _off respectively. When the circuit works stably, it is considered that the current passing through the inductor L remains basically unchanged as I ₁ . In one cycle T, the energy is constant as:

Among them, A is the duty ratio of the control switch T. It can be seen that as the speed decreases, the back EMF decreases, and the duty cycle of the switch increases, which can maintain the voltage stability.

The critical inductance value of the current continuous mode that the boost circuit can work is:

The size of the capacitor value is:

Among them, ΔU ₀ represents the difference of the required voltage, and reducing the voltage can increase the capacitance value.

After the current sensor detects the port fault of the armature winding connected to the faulty bridge arm and makes a fault judgment, at the same time, it controls the six switches of group A (group B) of the inverter to turn off at the same time by controlling the control signal of the PWM1 (PWM2) module. stop working. Then the system becomes two sets of three-phase motors, one can be charged and discharged normally, and the other does not work. Assuming that the three bridge arms of group A inverter (La, Lb, Lc) work normally, the normal charging and discharging process can be realized. The group B inverter includes three bridge arms (Lx, Ly, Lz), and a certain bridge When an arm fails, such as a short-circuit fault, the circuit breaker (QF4, QF5 or QF6) connected to the bridge arm acts to cut off the bridge arm, and at the same time, the inverter switch tube is controlled to be turned off through the PWM2 control signal.

1. Modeling the charging process

Please refer to Figure 7. The motor speed regulation adopts the closed-loop speed regulation mode, using the inner loop current loop and the outer loop speed loop control mode, in which the outer loop speed reference value is the maximum speed ω required by the flywheel, and the actual value obtained from the permanent magnet synchronous motor side Compare the rotational speed ω to obtain a rotational speed difference and then obtain the current reference i _q through the proportional-integral controller. The q-axis current i _q is adjusted by adjusting the actual rotational speed value to approach the given rotational speed, thereby controlling the electromagnetic torque.

In order to verify the feasibility of building the model, the system consists of the following components, including PID module, speed detection PI, current detection PI, coordinate transformation Plark, Clark module, and SVPWM module, three-phase voltage inverter circuit and three-phase synchronous motor. The simulation setting parameters are: the parameter speed is set to N=1000-3000r/min, the initial load torque T=10N.m, and the simulation result of the load current i _abc within t=0.4.

Simulation result analysis of charging process

The permanent magnet brushless DC motor adopts the d and q coordinate method and uses the PARK transformation to convert the two-phase coordinate system from the three-phase coordinate system to realize the motor current control. Figures 8(a)-(c) are the simulation results when N=1000r/min, and Figures 8(d)-(f) are the simulation results when N=2000r/min.

As can be seen from Figure 8, when the given speed is N=1000r/min, the speed begins to increase with the increase of time, the charging time is very short, the control effect is very good, and there is basically no overshoot, and then it gradually becomes stable. . The electromagnetic torque has harmonic disturbance in the first period of time, and then the torque rises directly from zero to 10N.m. The current switches back and forth between the three phases, and there is no divergence state, and the control effect is very ideal.

When the given speed is set to N=2000r/min, with the increase of time, the speed curve gradually increases, and there is an overshoot of 2%. The charging time is longer than before, and it is probably stable at The rotating speed is 1800r/min. The current is perturbed for a certain period of time, and then the current oscillates back and forth within 10. The electromagnetic torque can be ignored before t=0.03, and then stabilized at 2N.m. When t=0.2s, the torque gradually increased and finally stabilized at about 12N.m.

From the two sets of simulation graphs, it can be concluded that when the parameter value of the given speed is changed, the stability of the speed on the load side decreases with the increase of the speed, and the time required is longer, and the control effect also increases with the increase of the speed. decrease, it will basically remain within a certain value. The change of rotational speed causes the load current to oscillate. The electromagnetic torque is gradually smoothed out.

2. Modeling of the discharge process

The discharge model of the flywheel energy storage system as shown in Figure 9 is built in , the most important thing is to use the Boost DC voltage regulator circuit, the control loop signal is the difference between the load output voltage feedback and its given reference voltage, and the output signal is The required duty cycle signal is compared with the carrier signal, and finally the signal controls the opening and closing of the Mos tube. The motor/generator parameters are as follows: the number of pole pairs is 2, the stator resistance R _S is 0.000233, the stator inductance is 42.24uH, the flux linkage is 0.034Vs, the initial speed is 2000r/s, the friction coefficient is 0.0002Nms, and the moment of inertia is 0.2Kg .M.

(2) Analysis of discharge simulation results

During the discharge process of the system, the flywheel is in the power generation state. Figure 10(a)~(f) shows the simulation results of the load-side voltage and torque waveforms. The discharge simulation control adopts the control method of energy feedback braking. When the speed is reduced, the voltage is always stable at a certain value. The voltage and torque waveforms within 1.5s are provided.

It can be seen from Figure 10(a)~(b) that when the given voltage U=220V, the load voltage gradually increases with the increase of time, and tends to be stable at 230 at about t=0.3s, with a 1% Overshoot, the control effect is better, and the speed is gradually reduced under the given speed N=2000r/min, the curve is relatively smooth, and the speed of reduction is relatively slow.

It can be seen from Figure 10(c)~(d) that when the given voltage is set to U=250V, it can be seen from the voltage waveform diagram that with the increase of time, the voltage gradually increases, and the voltage reaches about 270V when t=0.5s , and finally stabilized at 260V, with an overshoot of 1% to 2%. The speed curve diagram shows that from the given speed of 2000r/min, it gradually decreases, but compared with the given voltage of 220V, the speed of the speed drop is significantly faster. The control effect is ideal.

From the two sets of data, it can be concluded that with the increase of the given voltage, the longer the load-side voltage waveform tends to be stable, and the voltage still has a certain loss, the overshoot is also increasing, and the given speed remains unchanged. In the case of , the speed decreases gradually, the curve becomes steeper, and the control effect decreases.

In the present invention, both the discharge main circuit and the charging main circuit have an inverter circuit. During charging, the conversion process of DC voltage to AC voltage is carried out in an inversion mode, and in discharging, the conversion process from AC voltage to DC voltage is carried out in a rectification mode. . During the discharge process, the DC brushless motor works as a generator. Since the flywheel rotates by inertia to drive the DC brushless motor to generate electricity, the voltage will decrease with the decrease of the speed. The AC voltage is converted into DC voltage, and the stability of the output DC voltage must be ensured.

The above content is only to illustrate the technical idea of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention all fall within the scope of the claims of the present invention. within the scope of protection.

Claims (6)

1. A flywheel energy storage system of a double three-phase brushless direct current motor is characterized by comprising the double three-phase brushless direct current motor and a BOOST circuit, wherein the double three-phase brushless direct current motor comprises six windings, and three windings form a group of three-phase windings; the two groups of three-phase windings are connected through a bidirectional thyristor, and the difference between the two groups of windings is 30 degrees in electrical angle; the bidirectional thyristor realizes the connection of a group of three-phase windings and a group of three-phase inverters to form a first inverter A and a second inverter B;

each bridge arm of the three-phase inverter group comprises two power MOS switching tubes which are connected in series, the connection point is the middle point of the bridge arm, a breaker QF and a fuse FU are connected between each bridge arm and one phase winding, and a relay K1 and a K2 closed contact are respectively arranged in a direct current bus;

the BOOST circuit comprises a first BOOST circuit and a second BOOST circuit, the first BOOST circuit is connected between the first inverter A and the direct-current bus, the second BOOST circuit is connected between the second inverter B and the direct-current bus, the first BOOST circuit comprises a relay K3, an inductor L1, a capacitor C1 and a switch tube V1, and the second BOOST circuit comprises a relay K4, an inductor L2, a capacitor C2 and a switch tube V2; a normally open contact of the relay K3 is connected between the direct current bus and the capacitor C1, and a normally open contact of the relay K4 is connected between the direct current bus and the capacitor C2;

in the energy feedback, a BOOST circuit is adopted to realize the voltage stabilization of a direct current side by controlling a switch tube, when the winding voltage reaches a given value, normally open contacts of relays K3 and K4 are closed, closed contacts of relays K1 and K2 are opened, so that the energy switching is realized, and in the BOOST circuit, when the switch tube is switched on, the energy of a power supply flows to an inductor, and meanwhile, the voltage on a capacitor supplies power to a power grid; when the switching tube is in an off state, energy is not output; the switching tube compares the voltage at the end of the detection winding with the designated voltage, and the error is compared with the triangular wave carrier after being subjected to PI regulation to generate a PWM signal for regulating the duty ratio of the switching tube to realize stable direct-current voltage output;

the control of the bidirectional thyristor is as follows: detection of three-phase winding u by voltage sensor_a,u_b,u_cAnd given a threshold voltage

The comparison of (A) to (B) yields the signal F of the triac_UThe method specifically comprises the following steps:

when the inverter is operating normally, F_u1, the system works in a 12-phase switching inverter power supply mode, firstly, a bidirectional thyristor receives a forward voltage signal to be conducted, and the bidirectional thyristor becomes a double three-phase motor;

the first inverter A comprises three bridge arms, the bridge arm La of the inverter comprises a power switch tube S1 and a power switch tube S2, and a circuit breaker QF1 and a fuse FU1 are connected between the bridge arms and windings; the inverter bridge arm Lb comprises a power switch tube S3 and a power switch tube S4, and a circuit breaker QF2 and a fuse FU2 are connected between the bridge arm and the winding; the inverter bridge arm Lc comprises a power switch tube S5 and a power switch tube S6, a breaker QF3 and a fuse FU3 are connected between the bridge arm and a winding, three-phase current of a stator is detected in an A-group inverter, then a coordinate is converted into a current value under a two-phase coordinate, quadrature-direct axis voltage is obtained through vector control, a voltage value on an alpha-beta axis is obtained through coordinate conversion, and a PWM1 signal is output after space vector pulse width modulation to generate six paths of signals to respectively control the corresponding six switch tubes;

the second inverter B comprises three bridge arms, the bridge arm Lx of the inverter comprises a power switch tube S7 and a power switch tube S8, and a circuit breaker QF4 and a fuse FU4 are connected between the bridge arms and the windings; the inverter bridge arm Ly comprises a power switch tube S9 and a power switch tube S10, and a circuit breaker QF5 and a fuse FU5 are connected between the bridge arm and the winding; the inverter bridge arm Lz comprises a power switch tube S11 and a power switch tube S12, a circuit breaker QF6 and a fuse FU6 are connected between the bridge arm and the winding, and connection points on two sides of the power switch tube after being connected in series are respectively connected with the positive electrode and the negative electrode of a direct-current power supply; in the B-group inverter, the reference signal U is passed_dc ^*And actual detected U_dcAnd comparing to obtain a difference value for PI regulation, wherein the output quantity of the voltage PI regulation is a given value of a current loop, comparing with a current feedback value, performing PI regulation on the obtained difference value, converting decoupling coordinates, comparing with a triangular wave to generate a trigger pulse signal PWM2 signal, and generating six paths of signals to respectively control the corresponding six switching tubes.

2. The method for controlling the flywheel energy storage system of the dual three-phase brushless DC motor according to claim 1, comprising:

in a charging state, an external power supply supplies power to the motor/generator through the power electronic converter, the motor/generator operates as a motor, the flywheel rotor is driven to accelerate, when the rotating speed of the rotor reaches the maximum working torque, the power electronic device generates a control signal to control the driving motor, and the motor drives the flywheel to operate and realize charging;

in a discharging state, the motor/generator operates as a generator, the flywheel rotor decelerates, mechanical energy is converted into electric energy by the generator, and the power electronic converter adjusts the bus voltage output by the generator to keep the bus voltage constant all the time;

a hold state, in which the flywheel system is in an energy hold phase with neither forward nor reverse flow of energy, in which mode the system operates with minimal losses;

detection three-phase winding u by detection voltage sensor_a,u_b,u_cWith a given voltage value u_oWhen u is compared with_a,u_b,u_cGradually rise to u_oWhen the battery is in a charging state; when u is_oWhen the value gradually drops to a set value, the discharge state is realized, and the working mode is judged as follows:

when the current sensor detects that the port of the armature winding connected with the fault bridge arm has fault and makes fault judgment, the six switching tubes of the first inverter A and the second inverter B are controlled to be simultaneously turned off by controlling control signals of the PWM1 module and the PWM2 module, and the operation is stopped.

3. The method according to claim 2, characterized in that in the charging process, six PWM driving signals are sent out by detecting the zero crossing point of the back electromotive force, and the power switching tube is driven after power amplification, so that the motor reaches the highest rotating speed and is in a holding stage; the control strategy is to compare the given rotating speed of the motor with the actual rotating speed to obtain a difference value, then obtain a reference current signal of a q axis through a PI controller by the difference value, and simultaneously set the given reference signal of a d axis to be zero; the actually detected stator winding current is transformed into a d-axis current component and a q-axis current component through coordinate transformation, the d-axis current component and the q-axis current component are compared with reference signals of the d-axis current component and the q-axis current component, the d-axis current component and the q-axis current component are decoupled through a current controller, reference voltage signals are output, and control signals are generated through SVPWM control after the coordinate transformation, so that the charging process is realized.

4. The method according to claim 3, characterized by the specific steps of:

s101, subtracting the given rotating speed omega of the motor from the actual rotating speed omega to obtain a speed error e_ωVelocity error e_ωOutputting a reference current signal of a q axis after passing through a rotating speed PI regulator

S102, comparing the d-axis reference current signal with the q-axis reference current signal

With d-axis current component, q-axis current component i_d,i_qCalculating to obtain a current deviation e_d,e_qOutputs d-axis reference voltage after passing through two current PI regulators

And q-axis reference voltage

S103, detecting the stator winding current i of the motor according to the current sensor_a,i_bCalculating current component i under two-phase rotating coordinate system_d,i_qFor the calculated reference voltage

Calculating reference voltage under three-phase rotating coordinate system

And S104, determining the direction of the interval where the reference voltage vector is located, and synthesizing the reference voltage vector by using two adjacent voltage vectors and a proper sector zero vector to realize the modulation of the SVPWM signal.

5. The method of claim 2, wherein in the discharging state, a double closed loop control system is used, the outer loop is a voltage regulation loop, and the q-axis reference current signal i is referenced in the voltage regulator_q ^*Limiting, wherein the current inner ring performs current control according to the current output by the voltage ring, and generates a trigger pulse signal PWM2 module by comparing the current with a triangular wave after the decoupling coordinate transformation; the discharge process is realized.

6. The method according to claim 5, characterized by the following specific steps:

s201 and PWM2 modules convert the measured three-phase stationary coordinate system into synchronously rotating two-phase coordinates, and the current value is converted into a current component i after coordinate conversion_dAnd i_q；

S202, adopting a direct current control strategy, and controlling a given reference signal to be compared with an actual value by a voltage outer ring tracking system to realize constant direct current voltage through the output current of a PI regulator;

s203, current control is carried out on the current output by the current inner ring according to the voltage ring, and the current is subjected to decoupling coordinate transformation and then is compared with a triangular wave to generate a trigger pulse signal to control the on and off of the converter;

and S204, in the discharging process, converting mechanical energy into electric energy, boosting the BOOST circuit behind the inverter to supply power to the direct current load, comparing the voltage at the end of the detection winding with the specified voltage, comparing the error with a triangular wave carrier after PI regulation to generate a PWM signal to regulate the duty ratio, and regulating the duty ratio of a switching tube of the BOOST circuit to output direct current voltage.

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