A method for analyzing operating characteristics of a brushless doubly-fed machine under natural synchronization condition

Abstract

The application discloses a kind of brushless doubly-fed motor natural synchronization operating condition operation characteristic analysis method, comprising: based on the frequency conversion of brushless doubly-fed motor winding, obtain the winding loop voltage equation of brushless doubly-fed motor natural synchronization operating condition;Based on the winding loop voltage equation of brushless doubly-fed motor natural synchronization operating condition, equivalent circuit is deduced and solved;On the basis of equivalent circuit solving result, the power angle of brushless doubly-fed motor is calculated, and then the active output characteristic, electromagnetic torque and excitation characteristic of brushless doubly-fed motor are obtained.The present application can clearly analyze the maximum output power and static performance of brushless doubly-fed motor under the excitation of brushless doubly-fed motor constant voltage source, effectively solve the problem that traditional brushless doubly-fed motor equivalent circuit cannot accurately analyze natural synchronization operating condition operation, and provide a theoretical analysis basis for brushless doubly-fed motor control winding DC excitation control mode.

Description

Technical Field

[0001] This invention belongs to the field of induction motor technology, and more specifically, relates to a method for analyzing the operating characteristics of a brushless doubly fed motor under natural synchronization conditions. Background Technology

[0002] A brushless doubly-fed induction motor is a new type of AC asynchronous motor. It consists of two sets of three-phase stator windings (power winding and control winding) with different pole pairs and a self-enclosed rotor winding. The rotor eliminates brushes and slip rings, making it a novel AC induction motor. The brushless structure of the brushless doubly-fed induction motor makes it more reliable than traditional brushed doubly-fed induction motors and also allows for the use of smaller capacity frequency converters. This gives it great potential in wind power, hydropower generation, and speed regulation of pump and fan loads.

[0003] The equivalent circuit of a conventional brushless doubly-fed motor often uses a Π-type equivalent circuit to analyze its operating characteristics. This circuit typically translates the voltage, current, and impedance of the motor's control winding and rotor winding to the power winding side. The parameters of the Π-type equivalent circuit are relatively well-defined, and even when the motor's technical specifications are unknown, the values ​​of these parameters can be determined experimentally. The Π-type equivalent circuit is established based on the condition that the two sets of stator windings of the motor are connected to AC power. When the control winding of the brushless doubly fed motor adopts the control mode of DC excitation, that is, the brushless doubly fed motor operates under natural synchronous conditions, the operating characteristics of the motor will be different from the conditions for establishing the equivalent circuit. The main manifestations are as follows: (1) When the control winding adopts DC excitation, the spatial magnetic field it generates is a static magnetic field, and the control winding will not generate an induced electromotive force; (2) When the control winding adopts DC excitation, the slip of the rotating magnetic field generated by the rotor relative to the magnetic field generated by the control winding is infinite; (3) When the control winding is connected to DC power, the voltage and current frequency of the control winding are equal to zero. When converting the parameters of the equivalent circuit, there is no need to convert the frequency of the control winding circuit parameters.

[0004] Therefore, accurately analyzing the operating characteristics of a brushless doubly fed motor under natural synchronous conditions is an urgent problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for analyzing the operating characteristics of a brushless doubly-fed motor under natural synchronous conditions, which can accurately analyze the operating characteristics of the brushless doubly-fed motor under natural conditions.

[0006] To achieve the above objectives, this invention provides a method for analyzing the operating characteristics of a brushless doubly-fed induction generator under natural synchronization conditions, comprising the following steps:

[0007] (1) Based on the winding frequency conversion of the brushless doubly fed motor, the winding circuit voltage equation under the natural synchronization condition of the brushless doubly fed motor is obtained.

[0008] (2) Based on the winding circuit voltage equation under the natural synchronous operation of the brushless doubly fed motor, the equivalent circuit is derived and solved.

[0009] (3) Calculate the power angle of the brushless doubly fed motor based on the solution of the equivalent circuit, and then obtain the active power output characteristics, electromagnetic torque and excitation characteristics of the brushless doubly fed motor.

[0010] The present invention provides a method for analyzing the operating characteristics of a brushless doubly-fed motor under natural synchronous conditions. Considering the operating characteristics of the brushless doubly-fed motor at natural synchronous speed, an equivalent circuit similar to that of a traditional synchronous machine is established. The power angle characteristics and excitation characteristics of the brushless doubly-fed motor under natural synchronous conditions are analyzed through the obtained equivalent circuit. In particular, under constant voltage source excitation, the maximum output power and static performance of the brushless doubly-fed motor can be clearly analyzed. This effectively solves the problem that the equivalent circuit of the traditional brushless doubly-fed motor cannot accurately analyze the operation under natural synchronous conditions, and provides a theoretical basis for the DC excitation control mode of the control winding of the brushless doubly-fed motor.

[0011] In one embodiment, in step (2), the equivalent circuit of the brushless doubly fed motor under natural synchronization is a single series loop, including the phase voltage on the power winding side. Natural synchronous impedance Z1 and no-load back EMF related to the DC voltage of the control winding

[0012] The natural synchronous impedance The no-load back electromotive force

[0013]

[0014] In the formula, R1 represents the single-phase resistance of the power winding; X m1 X represents the magnetizing inductance of the power winding; o1 Z represents the leakage inductance and reactance of the power winding; rr Z1 represents the rotor winding impedance; Z2 represents the control winding impedance; R2′ is the calculated single-phase resistance of the control winding. It is the DC voltage source voltage of the control winding after calculation. Voltage multiple, U2′ represents phasor The amplitude; p2 represents the number of pole pairs of the rotating magnetic field of the control winding; θ 120 This indicates the initial position of the rotor winding, with the reference standard being the stationary power winding and control winding.

[0015] In one embodiment, in the equivalent circuit of the brushless doubly fed motor under natural synchronization, the formula for calculating the control winding impedance Z2 is:

[0016]

[0017] The rotor winding impedance Z rr The calculation formula is:

[0018]

[0019] In the formula, s1 represents the slip ratio of the rotating magnetic field of the rotor winding relative to the rotating magnetic field of the power winding under natural synchronous operation. p1 and p2 represent the number of pole pairs of the rotating magnetic field of the power winding and the rotating magnetic field of the control winding, respectively; R3′ is the converted rotor winding resistance; X′ m2 This represents the magnetizing inductance corresponding to the number of pole pairs of the rotor winding and the control winding after conversion; X o ′ r This represents the leakage inductance and reactance of the rotor winding after conversion.

[0020] In one embodiment, the single-phase resistance R1 of the power winding and the leakage inductance X of the power winding are ignored. o1 The converted rotor winding resistance R3′ and the converted rotor winding leakage inductance X o ′ r The simplified equivalent circuit of the brushless doubly-fed induction generator under natural synchronization condition is obtained. This equivalent circuit includes the phase voltage on the power winding side and the natural synchronization reactance X. s and simplified no-load back EMF

[0021] The natural synchronous reactance X s X is the inductive reactance of the excitation inductor for the power winding. m1 The inductance reactance after being connected in parallel with the converted control winding magnetizing inductance reactance is calculated using the following formula:

[0022]

[0023] Simplified no-load back EMF The potential related to the DC voltage of the control winding is calculated using the following formula:

[0024]

[0025] In the formula, This represents the current phasor after coordinate transformation of I2′, where I2′ represents the DC voltage source current of the control winding after conversion. Multiple times the current.

[0026] In one embodiment, the power angle δ of the brushless doubly fed motor under natural synchronization conditions is the sum of the voltage phasor on the power winding side and the no-load back EMF. The electrical angle difference between them is calculated using the following formula:

[0027]

[0028] In the formula, θ 10 θ represents the initial mechanical angle difference between the power winding and the rotor winding; 20 This indicates the initial mechanical angle difference between the control winding and the rotor winding.

[0029] In one embodiment, the output power P of the brushless doubly-fed motor under natural synchronization is calculated based on the simplified equivalent circuit. em The calculation formula is as follows:

[0030]

[0031] The maximum output power P of the brushless doubly fed motor under natural synchronization conditions max for:

[0032]

[0033] In the formula, E0 represents the phasor. The amplitude; U1 represents the phasor. The amplitude, I2′ represents the phasor. The amplitude.

[0034] In one embodiment, the electromagnetic torque T output by the brushless doubly-fed motor under natural synchronization condition is calculated based on the simplified equivalent circuit. em Under steady-state conditions, the electromagnetic torque T of the motor is... em The calculation formula is:

[0035]

[0036] or:

[0037]

[0038] In the formula, ω r This indicates the mechanical angular velocity of the rotor; Represents voltage phasor amplitude, This represents the back electromotive force phasor generated on the rotor winding by the magnetic field generated by the power winding; Represents voltage phasor amplitude, This represents the back electromotive force generated on the rotor winding by the magnetic field generated by the control winding; |Z rr | represents the impedance Zrr The amplitude, θ Zr Represents impedance Z rr The impedance angle; θ v This represents the torque angle of a brushless doubly-fed motor, which is a voltage phasor. and The angle between them, that is ∠ represents the phasor argument.

[0039] In one embodiment, the no-load excitation characteristics and on-load excitation characteristics of the brushless doubly fed motor under natural synchronous conditions are calculated based on the simplified equivalent circuit.

[0040] The relationship between the power winding current I1 and the control winding voltage under no-load conditions is as follows:

[0041]

[0042] The relationship between the power winding current I1 and the control winding voltage under load is as follows:

[0043]

[0044] In the formula, reactance Reactance This indicates the power factor angle of the power winding of a brushless doubly fed motor. Attached Figure Description

[0045] Figure 1 This is a flowchart of a method for analyzing the operating characteristics of a brushless doubly-fed motor under natural synchronization conditions, provided in an embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram of the reference coordinate system for the power winding and control winding subsystem of the brushless doubly fed motor provided by the present invention;

[0047] Figure 3 This is a schematic diagram of the equivalent circuit of the synchronizing machine under the natural synchronization condition of the brushless doubly fed motor provided by the present invention;

[0048] Figure 4 This is a phasor diagram of the natural synchronization condition of the brushless doubly fed motor provided by the present invention;

[0049] Figure 5 This is a schematic diagram of the power angle characteristics of the brushless doubly fed motor provided by the present invention;

[0050] Figure 6 This is a schematic diagram of the phasor diagram of the brushless doubly fed motor under no-load operation provided by the present invention;

[0051] Figure 7 This is a schematic diagram of the V-shaped curve of the brushless doubly fed motor under no-load operation provided by the present invention;

[0052] Figure 8 This is a schematic diagram of the load-bearing operation vector diagram of the brushless doubly fed motor provided by the present invention;

[0053] Figure 9 This is a schematic diagram of the V-shaped curve of the brushless doubly fed motor under load provided by the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0055] To address the problem that traditional Π-type equivalent circuits cannot accurately analyze the operating characteristics of brushless doubly-fed motors under natural synchronous conditions, such as... Figure 1 As shown, the present invention provides a method for analyzing the operating characteristics of a brushless doubly fed motor under natural synchronous conditions. The method includes the following steps: (1) obtaining the winding circuit voltage equation of the brushless doubly fed motor under natural synchronous conditions based on the winding frequency conversion; (2) deriving and solving the equivalent circuit based on the winding circuit voltage equation of the brushless doubly fed motor under natural synchronous conditions; (3) calculating the power angle of the brushless doubly fed motor based on the solution results of the equivalent circuit, and then obtaining the active power output characteristics, electromagnetic torque and excitation characteristics of the brushless doubly fed motor.

[0056] In this embodiment, the voltage equations for each winding circuit of the brushless doubly-fed motor under natural synchronization conditions are as follows:

[0057]

[0058] in,

[0059] In the formula, It is the power winding voltage phasor; It is the DC voltage source voltage of the control winding after calculation. Voltage doubled; It is the back electromotive force phasor generated on the power winding by the magnetic field generated by the rotor winding; It is the back electromotive force phasor generated on the rotor winding by the magnetic field generated by the power winding; It is the back electromotive force generated on the rotor winding by the magnetic field generated by the control winding; It is the power winding current phasor; I2′ is the calculated rotor winding current vector, and I2′ is the calculated control winding DC voltage source current. Double the current; It is the current phasor of I2′ after coordinate transformation; Zrr R1 is the rotor winding impedance; R2' is the single-phase resistance of the power winding; R3' is the calculated single-phase resistance of the control winding; L is the rotor winding resistance. m1 It is the magnetizing inductance of the power winding; L′ mr2 It is the magnetizing inductance corresponding to the number of pole pairs of the rotor winding and the control winding after conversion; L o1 It is the leakage inductance of the power winding; L o ′3 is the converted rotor winding leakage inductance; ω1 is the power winding electrical frequency; s1 is the slip of the rotor winding rotating magnetic field relative to the power winding rotating magnetic field under natural synchronization conditions, and its value is p1 and p2 represent the number of pole pairs of the rotating magnetic field of the power winding and the rotating magnetic field of the control winding, respectively. * This indicates taking the conjugate.

[0060] Based on the voltage equations for each winding circuit mentioned above, the equivalent circuit of the brushless doubly-fed induction generator under natural synchronization can be derived. This equivalent circuit is a single series circuit, including the phase voltages of the power windings. The natural synchronous impedance Z1 and the excitation potential related to the DC voltage of the control winding. The natural synchronous impedance Z1 can be varied according to the required accuracy in the project, and the power winding voltage phasor can be set. With excitation voltage phasor The angle between them is the power angle δ, which characterizes the motor's ability to output active power under natural synchronous conditions.

[0061] The voltage loop equation for this circuit is:

[0062]

[0063] By analyzing the equivalent circuit, the active power output characteristics, electromagnetic torque, and excitation characteristics of the brushless doubly-fed motor under natural synchronization conditions can be obtained. The analysis steps include: establishing the equivalent circuit of the brushless doubly-fed motor under natural synchronization conditions; solving the equivalent circuit to obtain the corresponding physical quantities; and analyzing the corresponding characteristics of the brushless doubly-fed motor under natural synchronization conditions based on the solution results of the equivalent circuit.

[0064] Understandably, the traditional Π-type equivalent circuit converts the control winding to the rotor winding, and then both to the power winding. When DC current flows through the control winding, the slip on the control winding side tends to infinity, which in turn causes the resistance on the control winding side to also tend to infinity, preventing power from flowing through the control winding side and causing the equivalent circuit to fail. This embodiment, however, solves the problem of equivalent circuit failure by pre-setting the preconditions of the brushless doubly-fed motor operating under natural synchronization conditions, thus obtaining the voltage loop equations for the power winding, control winding, and rotor winding.

[0065] The method for analyzing the operating characteristics of a brushless doubly-fed motor under natural synchronous conditions provided in this embodiment takes into account the operating characteristics of the brushless doubly-fed motor at natural synchronous speed. It establishes an equivalent circuit similar to that of a traditional synchronous machine and analyzes the power angle characteristics and excitation characteristics of the brushless doubly-fed motor under natural synchronous conditions through the obtained equivalent circuit. In particular, under constant voltage source excitation, the maximum output power and static performance of the brushless doubly-fed motor can be clearly analyzed. This effectively solves the problem that the equivalent circuit of the traditional brushless doubly-fed motor cannot accurately analyze the operation under natural synchronous conditions, and provides a theoretical basis for the DC excitation control mode of the control winding of the brushless doubly-fed motor.

[0066] The specific analysis and implementation process of the present invention will be described below with reference to the accompanying drawings.

[0067] 1. Solve the voltage loop equations for each winding.

[0068] First, assuming the brushless doubly-fed motor operates under natural synchronous conditions, we analyze the operating characteristics of the brushless doubly-fed motor under these conditions.

[0069] In a brushless doubly-fed motor, the stator power winding and control winding cannot be directly coupled due to their different pole pair numbers. Instead, they are indirectly coupled through the modulation effect of the rotor. Therefore, the brushless doubly-fed motor can be divided into two subsystems—the power winding subsystem and the control winding subsystem. The dq-axis reference coordinate systems of the two subsystems are as follows: Figure 2 As shown, initially the power winding and the rotor winding are out of phase by a mechanical angle θ. 10 The mechanical angle θ between the control winding and the rotor winding 20 In the power winding subsystem, the power winding and the rotor winding dq axis are connected at an electrical frequency p1ω. r Rotational motion, ω r It is the mechanical angular velocity of the rotor, and the two reference frames remain relatively stationary; in the control winding subsystem, the control winding and the rotor winding dq axis remain spatially stationary.

[0070] By referring to the relative positions of the windings of the two subsystems of the brushless doubly fed motor, the voltage equations of the power winding, control winding and rotor winding circuits of the brushless doubly fed motor can be obtained respectively, as shown in equation (3):

[0071]

[0072] In the formula, U2 is the unadjusted DC voltage source voltage of the control winding. I2 is the unadjusted DC voltage source current of the control winding. Current multiple; R2 is the uncompensated single-phase resistance of the control winding; L m1 It is the magnetizing inductance of the power winding. Where N s1 =4k w1N1 / π,Λ g1 =μ0τ1l ef / g ef μ0 is the free permeability, k w1 N1 is the fundamental winding coefficient of the power winding, N1 is the number of turns in series per phase of the power winding, τ1 is the pole pitch of the power winding, and l ef g is the effective length of the iron core. ef L is the effective length of the air gap. o1 It is the leakage inductance of the power winding; L 13 It is the mutual inductance between the power winding and the rotor winding. Where, N sr1 =4k wr1 N r1 / π,k wr1 N is the fundamental winding coefficient of the p1 pole rotor winding. r1 L is the number of turns in series per phase of the p1 pole rotor winding; 23 It controls the mutual inductance between the control winding and the rotor winding. Where, N sr2 =4k wr2 N r2 / π,k wr2 N is the fundamental winding coefficient of the p2 pole rotor winding. r2 Λ is the number of turns in series per phase of the p2 pole rotor winding. g2 =μ0τ2l ef / g ef τ2 is the control winding pole pitch; L mr1 p1 is the magnetizing inductance of the rotor winding of the pole pair. L mr2 It is the magnetizing inductance of the p2 pole rotor winding. L o3 It is the leakage inductance of the rotor winding; ω re It is the electrical angular frequency of the rotor winding, and its value under natural synchronous operation is p2ω. r .

[0073] After performing winding and frequency conversion on the winding circuit equation of equation (3), the converted equation (1) can be obtained, and the conversion relationship is as follows:

[0074] In the second term of equation (1), the control winding is DC excitation, so there is no self-inductance or mutual inductance voltage on the control winding. At this time, the rotor rotates at synchronous speed, cutting the spatial static magnetic field generated by the DC current of the control winding, which can generate a corresponding back electromotive force. The interaction between the power winding and the rotor winding magnetic field is similar to other operating conditions of the brushless doubly fed motor.

[0075] 2. Derivation of the equivalent circuit

[0076] In equation (1), let Xm1 =ω1L m1 , X′ m2 =ω1L′ mr2 X o1 =ω1L o1 X o ′ r =ω1L o ′3.

[0077] Transform the third term of equation (1) into Substituting the first term into equation (1), equation (1) transforms into:

[0078]

[0079] In the formula, Where, θ 120 =θ 10 +θ 20 This angle represents the initial position of the rotor, with the reference standard being the stationary power winding and control winding.

[0080] set up The voltage matrix equation of the power winding circuit can be transformed into:

[0081]

[0082] An equivalent circuit similar to that of a synchronous motor can be established using equation (5). Figure 3 In the picture Depend on From the expression, it can be seen that in the dq-axis coordinate system, its phasor argument is determined by the initial rotor position, and its magnitude is affected by the control winding voltage. After determining the control winding voltage (excitation voltage) and the initial rotor position, the phasor... The voltage will not change regardless of load variations, but will only depend on the DC voltage applied to the control winding excitation. Keeping the voltages of the power winding and control winding constant, when the load changes, the voltage phasor of the power winding will change accordingly. and The relative positional relationship between them reflects the changes in load.

[0083] Figure 3 The equivalent circuit of the synchronizer for a brushless doubly-fed induction generator under natural synchronization is derived. While meeting engineering accuracy requirements, the circuit parameters can be further simplified. Neglecting rotor winding resistance, rotor leakage inductance, power winding resistance, and power winding leakage inductance, Z... rr The expressions for Z1 and Z2 are:

[0084] Z rr =jX′ m2 +jX m1 (6)

[0085]

[0086]

[0087] Assume reactance The synchronous reactance of the brushless doubly-fed motor under natural synchronizing conditions is... Using the reference phasor, the simplified equivalent circuit phasor can be drawn as follows: Figure 4 As shown.

[0088] exist Figure 4 middle, It is the power factor angle of the power winding of a brushless doubly-fed motor. δ is defined as the power angle of a wound-rotor brushless doubly-fed motor under natural synchronization conditions, and its expression is:

[0089] 3. Analysis of active power output characteristics, electromagnetic torque, and excitation characteristics

[0090] Similar to a synchronous machine, the power angle characteristics of a wound-rotor brushless doubly-fed motor under natural synchronous operation can be obtained:

[0091]

[0092] In the formula, E0 is a phasor The amplitude, U1 is the phasor The amplitude, I2′ is the phasor The amplitude. From this, we can also obtain the appropriate... At this time, the brushless doubly-fed motor outputs the maximum electromagnetic power, which is 3I2′U1. Its power angle characteristic curve is as follows: Figure 5 As shown.

[0093] Neglecting rotor winding copper losses, the electromagnetic torque formula for a brushless doubly-fed motor is:

[0094]

[0095] In practice, the power angle of a brushless doubly-fed motor is not easy to obtain, but the power factor angle of the power winding can be measured relatively easily, combined with electromagnetic power... The expression for the power angle of a brushless doubly-fed motor can be obtained as follows:

[0096]

[0097] The electromagnetic torque formula for the output of a brushless doubly-fed motor can also be derived from equation (1):

[0098]

[0099] In the formula, Represents voltage phasor amplitude, Represents voltage phasor The amplitude, |Z rr | represents the impedance Z rr The amplitude, θ Zr Represents impedance Z rr The impedance angle, θ v This represents the torque angle of a brushless doubly-fed motor, which is a voltage phasor. and The angle between them, that is ∠ represents the phasor argument.

[0100] In equation (2), when When θ is at its maximum, the output electromagnetic torque is at its maximum. v =arctanσ 12 At this time, the output electromagnetic torque is at its minimum.

[0101] Equations (11) and (12) are results obtained by neglecting the rotor winding leakage inductance. Due to the stator and rotor winding design of some brushless doubly-fed motors, the calculated rotor leakage inductance is relatively large and cannot be ignored. rr The expressions for Z1 and Z2 should be:

[0102] Z″ rr =jX′ m2 +jX m1 +jX′ or (13)

[0103]

[0104]

[0105] To obtain more accurate results, the leakage reactance of the power winding can also be taken into account, let the reactance X s1 With reactance X s2 They are respectively:

[0106]

[0107]

[0108] The voltage loop equation for the power winding is then:

[0109]

[0110] The excitation characteristics of a synchronous motor are commonly characterized by its V-curve. The V-curve of a synchronous motor refers to the relationship between the stator current and the excitation current when the stator voltage is kept at its rated value and the electromagnetic power is constant. For a brushless doubly-fed motor operating under natural synchronous conditions, the excitation characteristics can also be characterized by a V-curve. This is expressed as the relationship between the control winding voltage or current and the power winding current when the power winding voltage is kept constant and the electromagnetic torque output by the brushless doubly-fed motor is constant.

[0111] When the brushless doubly-fed motor is running under no-load, Figure 4 As shown in equation (9), the power angle of the brushless doubly fed motor is 0 at this time, and the power winding voltage phasor... With excitation voltage phasor On the same straight line, the power winding current phasor is perpendicular to the two voltage phasors. Considering the rotor leakage reactance and the power winding leakage inductance, its phasor diagram is as follows: Figure 6 As shown.

[0112] like Figure 6 As shown, combining equations (16) and (17), the relationship between the power winding current I1 and the control winding voltage or current is as follows:

[0113]

[0114] The relationship between the power winding current I1 and the control winding voltage curve is as follows: Figure 7 As shown.

[0115] When operating under load, the power angle of the brushless doubly-fed motor is not 0, and its phasor diagram is as follows. Figure 8 As shown.

[0116] Figure 8 The relationship between the power winding current I1 and the control winding voltage can be obtained as follows:

[0117]

[0118] Combining equation (20), the V-curve of the brushless doubly fed motor under load can be obtained as follows: Figure 9 As shown.

[0119] In summary, compared with the prior art, the present invention has the following advantages:

[0120] The equivalent circuit structure of the brushless doubly-fed induction generator (DFIG) under natural synchronous operation constructed in this invention is simple and easy to analyze. It solves the problem of failure in the analysis of traditional equivalent circuits under natural synchronous operation. Furthermore, it combines the analysis methods of traditional synchronous motors to accurately calculate the power angle of the DFIG under natural synchronous operation. For DFIGs with constant voltage source excitation, the constructed equivalent circuit can be used to conveniently analyze the output power limit of the DFIG under this operation. The excitation characteristics of the DFIG under this operation can also be obtained by analogy with the analysis methods of synchronous motors.

[0121] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for analyzing the operating characteristics of a brushless doubly-fed induction generator under natural synchronization conditions, characterized in that, Includes the following steps: (1) Based on the winding frequency conversion of the brushless doubly fed motor, the winding circuit voltage equation under the natural synchronization condition of the brushless doubly fed motor is obtained; (2) Based on the winding circuit voltage equation under the natural synchronous operation of the brushless doubly fed motor, the equivalent circuit is derived and solved; (3) Calculate the power angle of the brushless doubly fed motor based on the solution of the equivalent circuit, and then obtain the active power output characteristics, electromagnetic torque and excitation characteristics of the brushless doubly fed motor. In step (2), the equivalent circuit of the brushless doubly fed motor under natural synchronization is a single series circuit, including the phase voltage on the power winding side. Natural synchronous impedance and the no-load back EMF related to the DC voltage of the control winding ; The natural synchronous impedance The no-load back electromotive force ; In the formula, This indicates the single-phase resistance of the power winding; This represents the magnetizing inductance reactance of the power winding; Indicates the leakage inductance and reactance of the power winding; Indicates the rotor winding impedance; Indicates the control winding impedance; It is the single-phase resistance of the control winding after conversion; It is the DC voltage source voltage of the control winding after calculation. Double voltage, express The amplitude; Indicates the number of pole pairs of the rotating magnetic field controlling the winding; This indicates the initial position of the rotor winding, with the reference standard being the stationary power winding and control winding; In the equivalent circuit of the brushless doubly-fed motor under natural synchronization, the control winding impedance The calculation formula is: rotor winding impedance The calculation formula is: In the formula, This represents the slip ratio of the rotating magnetic field of the rotor winding relative to the rotating magnetic field of the power winding under natural synchronous operation. , , These represent the number of pole pairs of the rotating magnetic field of the power winding and the rotating magnetic field of the control winding, respectively. This is the rotor winding resistance after conversion; This represents the magnetizing inductance corresponding to the number of pole pairs of the rotor winding and the control winding after conversion; This represents the leakage inductance and reactance of the rotor winding after conversion. Power angle of a brushless doubly fed motor under natural synchronization conditions The calculation formula is: In the formula, This represents the initial mechanical angle difference between the power winding and the rotor winding; This indicates the initial mechanical angle difference between the control winding and the rotor winding.

2. The method for analyzing the operating characteristics of a brushless doubly-fed motor under natural synchronization conditions according to claim 1, characterized in that, Ignore the single-phase resistance of the power winding Leakage inductance and reactance of power winding Rotor winding resistance after conversion and the calculated rotor winding leakage inductance and reactance The simplified equivalent circuit of the brushless doubly-fed induction generator under natural synchronization condition is obtained. This equivalent circuit includes the phase voltage on the power winding side and the natural synchronization reactance. and simplified no-load back EMF ; The natural synchronous reactance Inductive reactance of the excitation inductor for the power winding The inductance reactance after being connected in parallel with the converted control winding magnetizing inductance reactance is calculated using the following formula: Simplified no-load back EMF The potential related to the DC voltage of the control winding is calculated using the following formula: In the formula, express After coordinate transformation, the current phasor This indicates the DC voltage source current of the control winding after conversion. Multiple times the current.

3. The method for analyzing the operating characteristics of a brushless doubly-fed induction generator under natural synchronization conditions according to claim 2, calculates the output power of the brushless doubly-fed induction generator under natural synchronization conditions based on the simplified equivalent circuit. The calculation formula is as follows: Maximum output power of brushless doubly-fed motor under natural synchronization conditions for: In the formula, Represents phasor The amplitude; Represents phasor amplitude, Represents phasor The amplitude.

4. The method for analyzing the operating characteristics of a brushless doubly-fed induction generator under natural synchronization conditions according to claim 2, calculates the electromagnetic torque output by the brushless doubly-fed induction generator under natural synchronization conditions based on the simplified equivalent circuit. Under steady-state conditions, the electromagnetic torque of the motor is The calculation formula is: or: In the formula, This indicates the mechanical angular velocity of the rotor; Represents voltage phasor amplitude, This represents the back electromotive force phasor generated on the rotor winding by the magnetic field generated by the power winding; Represents voltage phasor amplitude, This represents the back electromotive force generated on the rotor winding by the magnetic field generated by the control winding; Represents impedance amplitude, Represents impedance The impedance angle; This represents the torque angle of a brushless doubly-fed motor, which is a voltage phasor. and The angle between them, that is , Indicates the phasor argument. .

5. The method for analyzing the operating characteristics of a brushless doubly-fed motor under natural synchronization conditions according to claim 2, based on the simplified equivalent circuit, calculates the no-load excitation characteristics and on-load excitation characteristics of the brushless doubly-fed motor under natural synchronization conditions. in, Magnitude of power winding current under no-load conditions The relationship between the voltage of the control winding and the voltage of the control winding is as follows: Power winding current under load The relationship between the voltage of the control winding and the voltage of the control winding is as follows: In the formula, reactance Reactance ; This indicates the power factor angle of the power winding of a brushless doubly fed motor.

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