Electro-magnetic doubly salient generator three-phase asymmetry control method based on minimum loss

Abstract

According to the three-phase asymmetry control method for the doubly salient electro-magnetic generator based on the minimum loss, the influence of the load resistance on the fundamental wave flux density of the iron core and the influence of the conduction angle on the harmonic flux density are analyzed, and a more accurate iron loss calculation method is achieved. According to the method, the influence caused by asymmetry of three-phase magnetic circuits of the doubly salient electro-magnetic generator is considered, and the method for calculating the total loss on line under the condition of three-phase asymmetry is provided. A three-phase conduction angle asymmetry control method is provided, optimal efficiency control is realized based on a copper loss model and an iron loss model, and an optimal conduction angle and an optimal asymmetry conduction angle are determined through a disturbance observation method. According to the invention, the loss is effectively inhibited, and the overall efficiency of the power generation system is improved. The method is suitable for application occasions with strict requirements on efficiency, such as an aviation power generation system.

Description

Technical Field

[0001] The invention belongs to the field of electrical control, and in particular relates to a three-phase asymmetric control method of an electrically excited double-salient-pole generator based on minimum loss. Background Art

[0002] The electrically excited double salient pole generator has strong environmental adaptability and a wide speed range. There is no winding on the rotor of the electrically excited double salient pole generator, and the structure is simple, strong and reliable, which makes the motor structure and manufacturing process very simple, with high reliability and low cost, and is particularly suitable for high-speed operation. The electrically excited double salient pole motor uses an excitation winding instead of the permanent magnet structure of the motor, so it has a flexible magnetic field adjustment capability, which has another advantage over the permanent magnet motor. The electrically excited double salient pole generator has been used in wind power generation systems and aircraft fields. However, the presence of the excitation winding reduces the efficiency of the electrically excited double salient pole generator, and during the power generation operation, the various parameters inside the motor are severely coupled, making the loss analysis more difficult. The generator is the core of the aviation power supply system, and its efficiency directly affects the overall efficiency of the aircraft electrical system. Improving the efficiency of the generator and reducing the loss are the key to improving aircraft performance, reducing fuel consumption and emissions. Therefore, the loss of the electrically excited double salient pole generator must be calculated and analyzed to improve efficiency.

[0003] The controllable rectification control method of the electrically excited double-pole generator is crucial to improving the output voltage and power. The existing angle position control method mainly selects the conduction angle through artificial intelligence algorithm to improve the efficiency of the generator. However, this method requires a lot of data simulation and ignores the three-phase asymmetry problem caused by the parallel teeth of the electrically excited double-pole generator. The three-phase asymmetry problem will lead to uneven distribution of magnetic flux density and local oversaturation problems. The asymmetry of the three-phase magnetic circuit leads to unbalanced output power of the electrically excited double-pole generator, and the three-phase winding cannot be used to the fullest extent.

[0004] The present application is different from the prior art as follows: Technical comparison with patent CN114614725A "An efficiency optimization control method for an electrically excited double-saliency controlled rectifier power generation system" Patent CN114614725A adopts angle position control, mainly through a large amount of data simulation and artificial intelligence algorithm to select the conduction angle. We use the loss model to calculate the loss online to select the pass angle, without a large amount of data, and we use three-phase asymmetric control, fully considering the structural characteristics of the three-phase asymmetry of the electrically excited double-pole generator, so that the three-phase winding is used as much as possible to maximize the efficiency of the generator.

[0005] Technical comparison with patent CN111313779A "A method for controlling the minimum copper loss of controlled rectification of an electrically excited double-salient-pole generator" Patent CN111313779A uses angle position control to minimize copper loss and optimize efficiency. The loss model we use takes into account copper loss and iron loss, because the loss model is more accurate and the optimization effect is better. In addition, we use three-phase asymmetric control to solve the problems of unbalanced three-phase output power and local oversaturation of magnetic flux density of the electrically excited double-pole generator, so that the three-phase winding is used to the maximum extent and the efficiency of the generator is maximized.

[0006] Technical comparison with patent CN110829939B "A control method for reducing torque ripple of electrically excited double-salient-pole motor" Patent CN110829939B aims to minimize torque pulsation and is mainly applicable to electrically excited double-pole motors. Ours is mainly applicable to electrically excited double-pole generators, with different application scenarios. We take minimizing losses as the optimization goal, use three-phase asymmetric control to improve the efficiency of the power generation system, maximize the efficiency of the generator, and the control method is also different.

[0007] Existing control methods cannot maximize the efficiency of the generator, especially in terms of loss, which still has a lot of room for optimization. Therefore, there is a lack of a method to achieve more efficient operation of the electrically excited double-salient-pole generator, ensure that the generator always operates in a state of optimal loss, use the three-phase winding to the maximum extent, and improve overall performance and efficiency. Summary of the invention

[0008] In order to solve the above technical problems, the present invention proposes a three-phase asymmetric control method for an electrically excited double-pole generator based on minimum loss, which can quickly model the loss of the electrically excited double-pole generator, obtain the optimal loss control parameters, and achieve minimum loss of the generator under the full operating range.

[0009] To achieve the above object, the technical solution adopted by the present invention is: A three-phase asymmetric control method for an electrically excited double-salient-pole generator based on minimum loss comprises the following steps: S1, maintain bus voltage u DC The rated voltage is maintained, the operating condition is maintained unchanged, the conduction angle in the controlled rectifier angle position control of the electrically excited doubly salient generator is maintained unchanged, and the excitation current and armature current under this operating condition are measured; S2. According to the load resistance and conduction angle, the fundamental wave and harmonic wave distribution characteristics of the core magnetic flux density are obtained, and the iron loss model is established to achieve accurate calculation of the iron loss; S3, using the excitation current and the armature current, combined with the internal resistance of the excitation winding and the internal resistance of the armature winding, to calculate the total loss of the electrically excited doubly salient-pole generator, and obtain the total loss corresponding to the controllable rectifier conduction angle under the working condition; S4, changing the controllable rectifier conduction angle, repeating S1 and S2, and obtaining the controllable rectifier conduction angle that minimizes the total loss of the electrically excited double-salient-pole generator under this operating condition through the perturbation observation method; S5. Calculate the effective value of armature current i prms , and sort the effective values ​​of the three-phase armature currents. According to the effective values ​​of the armature currents, the asymmetric conduction angles of the three phases are controlled, and the phase with the maximum effective value of the armature current is p max Multi-conduction β °, for the phase with the minimum armature current effective value p min Less conduction β °, and calculate the mean square error of the three-phase armature current effective values e ; S6, change the three-phase asymmetric conduction angle △ β °, repeat the above S5, take the three-phase current balance as the goal, use the perturbation observation method to perform three-phase asymmetric control, and select the conduction angle with the minimum total loss under this working condition for control, so as to achieve the minimum total loss control.

[0010] As a further improvement of the present invention, keeping the working condition unchanged in step S1 refers to keeping the speed unchanged, the load resistance unchanged, the control parameters and the conduction angle unchanged.

[0011] As a further improvement of the present invention, the iron loss in step S2 P Fe The calculation formula of the model is as follows: ; In the formula, k h , k c , k e They are hysteresis loss coefficient, eddy current loss coefficient and additional loss coefficient, f is the motor operating frequency, B is the magnitude of the magnetic flux density, considering the iron loss generated at different frequencies, M For the highest harmonic order using Fast Fourier Transform, B m For the m The magnetic flux density amplitude of the subharmonic.

[0012] As a further improvement of the present invention, in step S3, the total loss of the electrically excited double-salient-pole generator takes into account copper loss and iron loss, and the copper loss calculation formula is as follows: ; In the formula, P Cu-pis the armature copper loss, P Cu-f is the excitation copper loss, i p is the three-phase armature current, r p is the internal resistance of the armature winding, i f is the excitation current value, r f is the internal resistance of the field winding.

[0013] As a further improvement of the present invention, in step S4, the controllable rectifier conduction angle is changed, and the conduction angle is within the range of 0° to 60°, and is increased by only 5° each time.

[0014] As a further improvement of the present invention, the mean square error of the effective values ​​of the three-phase armature current in step S5 e The calculation formula is as follows: ; In the formula, i rmsmid is the middle value of the three-phase current effective value, i prms is the effective value of the three-phase current, and n is the number of samples.

[0015] As a further improvement of the present invention, in step S6, the changing of the three-phase asymmetric conduction angle Δ β °, the conduction angle is in the range of 0°~20°, and it increases by 1° each time. The three-phase current balance is the goal, that is, if the mean square error exceeds 20%, △ β ° should be further increased if e If it is less than 20%, the output is △ β °, at this time the corresponding conduction angle and the three-phase asymmetric conduction angle are the conduction angles when the total loss is the smallest under this working condition.

[0016] The beneficial effects of the present invention are as follows: The present invention utilizes the inherent controller and sensor of the electrically excited double-pole controlled rectifier power generation system to collect parameters such as the armature current and excitation current of the electrically excited double-pole generator. Based on the influence of load resistance and conduction angle on magnetic flux density, an accurate iron loss calculation model is established. Based on the structural characteristics of the three-phase asymmetry of the electrically excited double-pole generator, the uneven distribution of three-phase losses is fully considered, and a loss model is proposed. Based on the loss model, the optimal conduction angle and asymmetric conduction angle are determined by the perturbation observation method. The present invention can maximize the efficiency of the generator, use the three-phase winding to the maximum extent, and achieve the suppression of total losses and the improvement of efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1It is a flow chart based on the three-phase asymmetric control with minimum loss; Figure 2 It is the overall structure diagram; Figure 3 The iron loss calculated by the proposed iron loss model is compared with the experimentally measured iron loss; Figure 4 It is the efficiency comparison between the proposed method and the traditional method. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments: An embodiment of the present invention provides a three-phase asymmetric control method for an electrically excited doubly salient pole generator based on minimum loss.

[0019] The structure of the electrically excited double-salient-pole generator includes a stator, an excitation winding, an armature winding and a rotor. The flowchart of the three-phase asymmetric control based on minimum loss is as follows: Figure 1 As shown, the overall structure is as follows Figure 2 The output voltage outer loop is controlled by a PI controller according to the feedback DC output voltage. u DC and the reference value of the output voltage u ref Calculate the reference value of the excitation current i fref The excitation current inner loop is calculated by the PID controller to obtain the duty cycle of the excitation controller.

[0020] The iron loss data obtained by the current measurement and iron loss model calculation method of the electrically excited double-pole generator in S1 and S2 is shown in the figure. The iron loss of the electrically excited double-pole generator with a rated power of 3kW and a rated voltage of 270V at 5000 rpm is sampled at 10° intervals within the conduction angle range of 0-60°.

[0021] Figure 3 This is a comparison of the efficiency of an electrically excited double-pole generator using a three-phase asymmetric control method based on minimum loss and an uncontrolled rectifier system, as well as the efficiency of selecting the optimal angle position control through artificial intelligence. Using the controlled rectifier loss model of the electrically excited double-pole generator, the conduction angle and asymmetric conduction angle corresponding to the working point with the minimum loss in any working condition under all working conditions can be found. This patent uses a two-dimensional simulation model instead of a three-dimensional simulation model to save simulation time. The simulation results are shown in Figure 4 When the method proposed in this patent is adopted, the loss of the electrically excited double-salient-pole generator is effectively reduced and the efficiency is effectively improved.

[0022] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A three-phase asymmetric control method for an electrically excited doubly salient generator based on minimum loss, characterized in that: The steps include: S1, maintain bus voltage u DC The rated voltage is maintained, the operating condition is maintained unchanged, the conduction angle in the controlled rectifier angle position control of the electrically excited doubly salient generator is maintained unchanged, and the excitation current and armature current under this operating condition are measured; S2. According to the load resistance and conduction angle, the fundamental wave and harmonic wave distribution characteristics of the core magnetic flux density are obtained, and the iron loss model is established to achieve accurate calculation of the iron loss; S3, using the excitation current and the armature current, combined with the internal resistance of the excitation winding and the internal resistance of the armature winding, to calculate the total loss of the electrically excited doubly salient-pole generator, and obtain the total loss corresponding to the controllable rectifier conduction angle under the working condition; S4, changing the controllable rectifier conduction angle, repeating S1 and S2, and obtaining the controllable rectifier conduction angle that minimizes the total loss of the electrically excited double-salient-pole generator under this working condition through the perturbation observation method; S5. Calculate the effective value of armature current i prms , and sort the effective values ​​of the three-phase armature currents. According to the effective values ​​of the armature currents, the asymmetric conduction angles of the three phases are controlled, and the phase with the maximum effective value of the armature current is p max Multi-conduction β °, for the phase with the minimum armature current effective value p min Less conduction β °, and calculate the mean square error of the three-phase armature current effective values e ; S6, change the three-phase asymmetric conduction angle △ β °, repeat the above S5, take the three-phase current balance as the goal, use the perturbation observation method to perform three-phase asymmetric control, and select the conduction angle with the minimum total loss under this working condition for control, so as to achieve the minimum total loss control.

2. The three-phase asymmetric control method of an electrically excited doubly salient generator based on minimum loss according to claim 1 is characterized in that: Keeping the working condition unchanged in step S1 means keeping the speed unchanged, the load resistance unchanged, the control parameters and the conduction angle unchanged.

3. The three-phase asymmetric control method of an electrically excited doubly salient generator based on minimum loss according to claim 1 is characterized in that: Iron loss in step S2 P Fe The calculation formula of the model is as follows: ； In the formula, k h , k c , k e They are hysteresis loss coefficient, eddy current loss coefficient and additional loss coefficient, f is the motor operating frequency, B is the magnitude of the magnetic flux density, considering the iron loss generated at different frequencies, M For the highest harmonic order using Fast Fourier Transform, B m For the m The magnetic flux density amplitude of the subharmonic.

4. The three-phase asymmetric control method of an electrically excited doubly salient generator based on minimum loss according to claim 1 is characterized in that: In step S3, the total loss of the electrically excited double-salient-pole generator takes into account copper loss and iron loss, and the copper loss calculation formula is as follows: ； In the formula, P Cu-p is the armature copper loss, P Cu-f is the excitation copper loss, i p is the three-phase armature current, r p is the internal resistance of the armature winding, i f is the excitation current value, r f is the internal resistance of the field winding.

5. The three-phase asymmetric control method of an electrically excited doubly salient generator based on minimum loss according to claim 1 is characterized in that: In step S4, the controllable rectifier conduction angle is changed, and the conduction angle is within the range of 0° to 60°, and is increased by only 5° each time.

6. The three-phase asymmetric control method of an electrically excited doubly salient generator based on minimum loss according to claim 1, characterized in that: The mean square error of the effective values ​​of the three-phase armature current in step S5 e The calculation formula is as follows: ； In the formula, i rmsmid is the middle value of the three-phase current effective value, i prms is the effective value of the three-phase current, and n is the number of samples.

7. The three-phase asymmetric control method of an electrically excited doubly salient generator based on minimum loss according to claim 1 is characterized in that: In step S6, the three-phase asymmetric conduction angle Δ is changed. β °, the conduction angle is in the range of 0°~20°, and it increases by 1° each time. The three-phase current balance is the goal, that is, if the mean square error exceeds 20%, △ β ° should be further increased if e If it is less than 20%, the output is △ β °, at this time the corresponding conduction angle and the three-phase asymmetric conduction angle are the conduction angles when the total loss is the smallest under this working condition.

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