A method for suppressing the induced pulsating voltage of the exciting winding based on harmonic current injection

Abstract

The present invention discloses a method for suppressing the induced pulsating voltage of the excitation winding based on harmonic current injection. The suppression method includes the following steps: constructing a model of the armature winding control circuit and the excitation winding control circuit of a synchronous motor including a harmonic current injection module; performing harmonic analysis on the induced pulsating voltage of the excitation winding of the synchronous motor to find out the main voltage harmonic orders therein; qualitatively deriving the corresponding relationship between the harmonic orders of the induced pulsating voltage of the excitation winding and the injected harmonic current orders, considering the influence of the nonlinear factors of the synchronous motor, and optimizing the amplitude and phase of the injected harmonic current of a specified order through a finite element simulation software. The suppression method of the present invention generates an additional magnetic flux component of the excitation winding through the interaction between the injected harmonic current of the armature winding and the mutual inductance between the armature winding and the excitation winding, so as to cancel the original harmonic magnetic flux component in the excitation winding, and further achieve the purpose of suppressing the induced pulsating voltage of the excitation winding.

Description

Technical Field

[0001] The present invention relates to the technical field of motor drive and control, and specifically to a method for suppressing the induced pulsating voltage of an excitation winding based on harmonic current injection. Background Art

[0002] With the development of the motor industry, permanent magnet synchronous motors can provide a sufficient-strength excitation magnetic field for the motor without the need for external energy supply, so they are widely used in fields such as electric vehicles, wind power generation, household appliances, and industrial robots due to their high efficiency. However, rare earth permanent magnet materials are expensive and have unstable supply, and there are also disadvantages such as irreversible demagnetization, poor field weakening speed regulation performance, and difficulty in fault field extinction. Different from permanent magnet synchronous motors, electrically excited synchronous motors use an excitation winding instead of a permanent magnet to provide an excitation magnetic field for the motor, thus avoiding the use of permanent magnet materials and overcoming the inherent defects of permanent magnet synchronous motors. However, when an electrically excited synchronous motor is in operation, a pulsating voltage will be induced in its excitation winding, resulting in fluctuations in the excitation winding current, that is, pulsations in the excitation magnetic field. This will not only affect the motor performance including the sinusoidality of the armature winding voltage, torque pulsation, losses, and efficiency, but also affect the reliability of the excitation power supply.

[0003] Regarding the method for suppressing the induced pulsating voltage of the excitation winding, the traditional method starts from the design of the motor body. By optimizing the motor structure parameters and reducing the magnetic conductance harmonics in the motor air gap, the purpose of suppressing the induced pulsating voltage of the excitation winding is achieved. For example, using a rotor (segmented) skewed pole structure, a rotor axial pairing structure, a rotor non-uniform tooth-slot structure, or a double-three-phase armature winding structure, optimizing the excitation winding type (single-layer / double-layer excitation winding and the number of its parallel branches), optimizing the rotor pole arc angle, optimizing the stator-rotor slot opening size, and optimizing the design of the rotor outer diameter, etc. This type of method for the motor body size parameters will increase the manufacturing cost during the actual industrial production process, so it has certain limitations. Now, a method for suppressing the induced pulsating voltage of the excitation winding based on harmonic current injection is proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for suppressing the induced pulsating voltage of an excitation winding based on harmonic current injection. Starting from the motor control side, without changing the parameters of the motor body, harmonic currents of specified orders are injected into the motor armature winding and the mutual inductance between the armature winding and the excitation winding acts on each other, thereby generating additional magnetic flux components to cancel the original harmonic magnetic flux components in the excitation winding, and further achieving the purpose of suppressing the induced pulsating voltage of the excitation winding. This method is applicable to all electrically excited synchronous motors or hybrid-excited synchronous motors, without the need to change the size parameters of the motor body, and only need to modify the corresponding control software in the motor controller, which is simple and easy to implement.

[0005] The object of the present invention can be achieved by the following technical solutions:

[0006] A method for suppressing the induced pulsating voltage of the excitation winding based on harmonic current injection, the suppression method comprising the following steps:

[0007] Step 1: Construct a two-dimensional electromagnetic finite element model of the synchronous motor based on the size parameters of the motor body.

[0008] Step 2: Construct a control circuit model of the armature winding and an excitation winding control circuit model of the synchronous motor including a harmonic current injection module.

[0009] Step 3: Through the finite element simulation results or measured data, use the Fourier decomposition method to perform harmonic analysis on the induced pulsating voltage of the synchronous motor excitation winding, and find out the main voltage harmonic orders therein;

[0010] Step 4: Qualitatively deduce the corresponding relationship between the harmonic orders of the induced pulsating voltage of the excitation winding and the injected harmonic current orders, and find out the specified injected harmonic current orders.

[0011] Step 5: Considering the influence of the non-linear factors of the synchronous motor, optimize the amplitude and phase of the injected specified order harmonic current through the finite element simulation software.

[0012] Further, the electric excitation synchronous motor is composed of a stator, a rotor and windings. There is an air gap between the stator and the rotor. The armature winding is embedded in the stator slots, and the excitation winding is embedded on the rotor teeth or on the rotor. The winding is energized with a direct current to generate an excitation magnetic field.

[0013] Further, the control circuit model in Step 2 includes a current closed-loop control module, a voltage source type or current source type inverter for supplying power to the armature winding, a converter for supplying power to the excitation winding, and a harmonic current generation and injection module.

[0014] The current closed-loop control modules all adopt series proportional integral regulators, the armature winding is powered by a voltage source type or current source type inverter, the excitation winding is powered by its converter, and the harmonic current generation module generates three-phase symmetrical alternating current.

[0015] Further, for the corresponding relationship between the harmonic orders of the induced pulsating voltage of the excitation winding and the injected harmonic current orders, according to the harmonic orders with larger amplitudes in the results of the harmonic analysis in Step 3, obtain the required injected harmonic current orders, and the expression of the injected harmonic current is as follows:

[0016]

[0017] The interaction of the fundamental mutual inductance between the armature winding and the excitation winding, and the expression of the fundamental mutual inductance is as follows:

[0018]

[0019] Based on the interaction between the injected harmonic current and the fundamental mutual inductance between the armature winding and the field winding, the expression of the order of the additional harmonic magnetic flux linkage can be derived:

[0020]

[0021] Among them, if it is necessary to suppress the k - th harmonic component of the pulsating voltage induced in the field winding of the electric - excitation synchronous motor, k±1 - th harmonic current needs to be injected into the armature winding, where j = 1, 2, 3........, Ψ fk is the magnetic flux linkage generated by the interaction between the k - th harmonic current and the fundamental mutual inductance, M and θ1 are respectively the amplitude and the initial phase of the fundamental mutual inductance, i k and θ k are respectively the amplitude and the initial phase of the k - th harmonic current, and θe is the rotor position angle of the electric - excitation synchronous motor.

[0022] Advantages of the present invention:

[0023] 1. The suppression method of the present invention adopts a method for suppressing the pulsating voltage induced in the field winding of a synchronous motor based on injecting harmonic current into the armature winding, so that the injected harmonic current in the armature winding interacts with the mutual inductance between the armature winding and the field winding to generate an additional magnetic - flux component, which cancels the original harmonic magnetic - flux component in the field winding and is easy to implement;

[0024] 2. The suppression method of the present invention is a method for suppressing the pulsating voltage induced in the field winding of a synchronous motor starting from the design of the motor body. Although it can effectively suppress the pulsating voltage induced in the field winding, it is restricted by the structures of different types of motors, which will increase the manufacturing cost during the actual industrial production process and has certain limitations. After implementing the technology of the present invention, while effectively suppressing the pulsating voltage induced in the field winding, there is no need to increase the system cost, and only the corresponding control software needs to be modified, which is simple and easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below with reference to the drawings.

[0026] Figure 1 is the flow chart of the suppression method of the present invention;

[0027] Figure 2 is the topological diagram of the rotor electric - excitation synchronous motor of the present invention;

[0028] Figure 3 is the control block diagram of suppressing the pulsating voltage induced in the field winding of the synchronous motor of the present invention;

[0029] Figure 4 is the frequency - spectrum diagram of the pulsating voltage induced in the field winding before injecting harmonic current of the present invention;

[0030] Figure 5 It is the expression block diagram of the additional harmonic flux linkage order of the present invention;

[0031] Figure 6 It is the influence diagram of the 6th harmonic amplitude of the induced pulsating voltage in the excitation winding by the 5th harmonic current injected by the present invention under the premise of a fixed amplitude at different phase angles;

[0032] Figure 7 It is the influence diagram of the 6th harmonic amplitude of the induced pulsating voltage in the excitation winding by the 7th harmonic current injected by the present invention under the premise of a fixed amplitude at different phase angles;

[0033] Figure 8 It is to Figure 6 and Figure 7 Combine the best suppression cases in, and it is the waveform diagram of the current in phase A of the three-phase armature winding before and after injecting the 5th and 7th harmonic currents together;

[0034] Figure 9 It is to Figure 6 and Figure 7 Combine the best suppression cases in, and it is the frequency spectrum diagram of the induced pulsating voltage in the excitation winding after injecting the 5th and 7th harmonic currents together. Specific implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0036] Combined with Figures 1-9 shown, a method for suppressing the induced pulsating voltage in the excitation winding based on harmonic current injection, the suppression method includes the following steps:

[0037] Step 1: Construct a two-dimensional electromagnetic finite element model of a synchronous motor based on the size parameters of the motor body;

[0038] As Figure 2 shown, a rotor electrically excited synchronous motor consists of a stator, a rotor and windings. There is an air gap between the stator and the rotor. The armature winding is embedded in the stator slots, and the excitation winding passes through direct current to generate an excitation magnetic field. The excitation winding can be embedded on the stator of the motor or on the rotor of the motor;

[0039] Based on the size parameters of the motor body, a two-dimensional electromagnetic finite element model of a rotor-excited synchronous motor with 12 stator slots and 8 rotor poles is constructed in the finite element software. This excited synchronous motor uses a three-phase symmetrical armature winding. The present invention is applicable not only to the excited synchronous motor with a three-phase armature winding, but also to the excited synchronous motor with a multi-phase armature winding.

[0040] Step 2: Construct a control circuit model of the armature winding and the field winding of the synchronous motor, including a harmonic current injection module;

[0041] As Figure 3 shown, construct a control circuit model of the armature winding and the field winding of the rotor-excited synchronous motor. The control circuit model includes a current closed-loop control module, a three-phase bridge voltage source inverter, a single-phase full-bridge voltage source inverter, and a harmonic current generation and injection module;

[0042] The current closed-loop control module all adopts a series proportional-integral regulator. The armature winding is powered by a voltage source or current source inverter, and the field winding is powered by its converter. And the harmonic current generation module generates three-phase symmetrical alternating current, where i f is the field current, i d is the direct-axis armature current, and i q is the quadrature-axis armature current.

[0043] Step 3: Through the finite element simulation results or measured data, use the Fourier decomposition method to perform harmonic analysis on the induced pulsating voltage of the field winding of the synchronous motor, and find out the main voltage harmonic orders;

[0044] As Figure 4 shown, according to the finite element simulation results, use the Fourier decomposition method to perform harmonic analysis on the induced pulsating voltage of the field winding of this rotor-excited synchronous motor, find out the main voltage harmonic orders, and denote them as k (where k = 1, 2, 3... is used to distinguish different voltage orders). Among the harmonic components with a harmonic order below 15, the amplitude of the 6th harmonic is the largest. Therefore, in this embodiment, the target is to suppress the 6th harmonic component of the induced pulsating voltage of the field winding.

[0045] Step 4: Qualitatively deduce the corresponding relationship between the harmonic order of the induced pulsating voltage of the field winding and the injected harmonic current order, and find out the specified injected harmonic current order;

[0046] As Figure 5 shown, for the corresponding relationship between the harmonic order of the induced pulsating voltage of the field winding and the injected harmonic current order, according to the harmonic order with a larger amplitude in the result of the harmonic analysis in Step 3, obtain the required injected harmonic current order. The expression of the injected harmonic current is as follows:

[0047]

[0048] The interaction of the fundamental mutual inductance between the armature winding and the field winding, and the expression of the fundamental mutual inductance is as follows:

[0049]

[0050] When qualitatively deriving the correspondence between the harmonic order of the pulsating voltage induced in the field winding and the harmonic order of the injected harmonic current, the influence of the higher harmonic components of the mutual inductance between the armature winding and the field winding and the motor saturation factor is ignored. Only considering the interaction between the harmonic current and the fundamental mutual inductance between the armature winding and the field winding, the expression of the additional harmonic flux linkage order generated by the interaction between the injected harmonic current and the fundamental mutual inductance between the armature winding and the field winding is qualitatively derived:

[0051]

[0052] Among them, if it is necessary to suppress the k - th harmonic component of the pulsating voltage induced in the field winding of this brushless excitation synchronous motor, it is necessary to inject k±1 - th harmonic current into the armature winding. In this embodiment, 5 - th or 7 - th harmonic current will be injected into the armature winding, where j = 1, 2, 3........, Ψ fk is the flux linkage generated by the interaction between the k - th harmonic current and the fundamental mutual inductance, M and θ1 are respectively the amplitude and initial phase of the fundamental mutual inductance, i k and θ k are respectively the amplitude and initial phase of the k - th harmonic current, and θe is the rotor position angle of this brushless excitation synchronous motor.

[0053] Step Five: Considering the influence of the non - linear factors of the synchronous motor, optimize the amplitude and phase of the injected harmonic current of a specified order through finite - element simulation software.

[0054] Injecting 5 - th or 7 - th harmonic current into the armature winding can significantly suppress the amplitude of the 6 - th harmonic of the pulsating voltage induced in the field winding, and has little influence on the sinusoidality of the armature current. On the premise that the amplitude of the injected 5 - th or 7 - th harmonic current into the armature winding is fixed, by traversing the change of the harmonic current phase angle from 0° to 360°, there is a certain phase angle that makes the effect of suppressing the amplitude of the 6 - th harmonic of the pulsating voltage induced in the field winding the best.

[0055] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above - mentioned terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0056] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A method for suppressing the induced pulsating voltage of the excitation winding based on harmonic current injection, characterized in that, The suppression method includes the following steps: Step 1: Construct a two-dimensional electromagnetic finite element model of a synchronous motor based on the size parameters of the motor body; Step 2: Construct a model of the armature winding control circuit and the field winding control circuit of the synchronous motor, including a harmonic current injection module; Step 3: Through the finite element simulation results or measured data, use the Fourier decomposition method to perform harmonic analysis on the induced pulsating voltage of the field winding of the synchronous motor to find out the main voltage harmonic orders; Step 4: Qualitatively deduce the corresponding relationship between the harmonic orders of the induced pulsating voltage of the field winding and the injected harmonic current orders to find out the specified injected harmonic current orders; Step 5: Considering the influence of the non-linear factors of the synchronous motor, optimize the amplitude and phase of the injected harmonic current of the specified order through finite element simulation software; Regarding the corresponding relationship between the harmonic orders of the induced pulsating voltage of the field winding and the injected harmonic current orders, according to the harmonic orders with larger amplitudes in the results of the harmonic analysis in Step 3, obtain the required injected harmonic current orders. The expression of the injected harmonic current is as follows: Regarding the interaction of the fundamental mutual inductance between the armature winding and the field winding, the expression of the fundamental mutual inductance is as follows: According to the injected harmonic current and the interaction of the fundamental mutual inductance between the armature winding and the field winding, deduce the expression of the additional harmonic flux linkage order: Among them, if it is necessary to suppress the k-th harmonic component of the induced pulsating voltage in the excitation winding of the synchronous motor, it is necessary to inject the (k±1)-th harmonic current into the armature winding, where j = 1, 2, 3........, Ψ fk is the magnetic flux generated by the interaction between the k-th harmonic current and the fundamental mutual inductance, M and θ1 are respectively the amplitude and initial phase of the fundamental mutual inductance, i k and θ k are respectively the amplitude and initial phase of the k-th harmonic current, θ e is the rotor position angle of the synchronous motor.

2. The method for suppressing the induced pulsating voltage of the excitation winding based on harmonic current injection according to claim 1, wherein The synchronous motor consists of a stator, a rotor and windings. There is an air gap between the stator and the rotor. The armature winding is embedded in the stator slots, and the field winding is embedded on the rotor teeth or on the rotor. The windings are energized with direct current to generate an excitation magnetic field.

3. A method for suppressing the induced pulsating voltage of an excitation winding based on harmonic current injection according to claim 1, characterized in that, The control circuit model in Step 2 includes a current closed-loop control module, a voltage source type or current source type inverter for supplying power to the armature winding, a converter for supplying power to the field winding, and a harmonic current generation and injection module; The current closed-loop control modules all adopt series proportional-integral regulators. The armature winding is powered by a voltage source type or current source type inverter, the field winding is powered by its converter, and the harmonic current generation module generates three-phase symmetrical alternating current.

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