Copper loss minimum control system and method of variable flux reluctance motor
By optimizing the DC and AC current ratio through a six-phase inverter and current superposition technology, the problem of high copper loss in variable flux reluctance motors is solved, copper loss is reduced and efficiency is improved. It is suitable for minimum copper loss control of variable flux reluctance motors.
Patent Information
- Application Number
- CN202510903664.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-01
- Publication Date
- 2025-09-16
AI Technical Summary
Traditional variable flux reluctance motors have complex winding structures, limited current distribution, and high copper losses, especially when running at high speeds, where efficiency decreases. Existing control methods fail to effectively reduce copper losses and make it difficult to achieve efficient operation over a wide speed range.
It uses a six-phase inverter and space vector PWM technology, optimizes the DC and AC current ratio through the current superposition principle, and combines vector control technology to minimize copper loss.
Copper loss is significantly reduced by 15%-20%, especially in the high-speed weak magnetic field area where efficiency is significantly improved. The motor maintains high efficiency in the range of 0-20000rpm. The simplified structure reduces manufacturing difficulty and cost, and has dynamic response advantages, with copper loss reduced by 18%.
Smart Images
Figure CN120658159A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of motor control, and in particular relates to a copper loss minimization control system and method for a variable flux reluctance motor. Background Art
[0002] In traditional variable flux reluctance motors (VFRMs), the separation of the field winding and the armature winding results in a complex winding structure, limited current distribution, and high copper loss, especially when the efficiency drops significantly at high speeds.
[0003] Existing control methods fail to fully consider the impact of high-order harmonic currents on copper losses, making it difficult to achieve efficient operation over a wide speed range. For example, while field-weakening control can expand the speed range, it increases reactive current, leading to increased copper losses. Based on this, the present invention designs a control system and method for minimizing copper losses in a variable-flux reluctance motor. Summary of the Invention
[0004] The purpose of the present invention is to address the problem of excessive copper loss in variable flux reluctance motors in the prior art due to the winding structure and current control strategy, and to propose a copper loss minimization control method based on the current superposition principle. By optimizing the DC and AC current ratio and combining vector control technology, copper loss reduction and efficiency improvement in the entire operating range can be achieved.
[0005] A copper loss minimization control system for a variable flux reluctance motor includes a six-phase inverter that uses space vector PWM technology to decompose a six-phase command voltage into six H-bridge switching signals. The six-phase inverter includes six windings, and the six-directional winding configuration includes phases A to F, wherein phases A, C, and E are superimposed with a positive DC voltage, and phases B, D, and F are superimposed with a negative DC voltage. Phases A, B, and C are positive three-phase AC, and phases D, E, and F are negative three-phase AC and are 180° out of phase with phases A, B, and C, forming three complementary twin winding structures. The system also includes:
[0006] A current sensor is used to collect the current at the six-phase winding input end or the inverter output end in real time;
[0007] DSP controller, which performs dq transformation to obtain d-axis and q-axis current components
[0008] PI control part, which monitors the current size and waveform to ensure the correct ratio and detects abnormal current to avoid failure;
[0009] The current input of the motor is realized by superimposing the armature current and the field current through hierarchical control of a six-phase inverter.
[0010] In the copper loss minimization control system of the variable flux reluctance motor, the superposition input includes:
[0011] Forward superposition: The auxiliary H-bridge is used to superimpose a positive DC voltage on the A, C, and E phases, which is equivalent to injecting a positive DC component into the AC current of the A, C, and E phases;
[0012] Reverse superposition: Superimpose a negative DC voltage on phases B, D, and F, which is equivalent to injecting a reverse DC component into the AC current of phases B, D, and F;
[0013] Symmetrical control: The DC components of each set of twin windings are equal in magnitude and opposite in direction, ensuring that the superimposed DC components are completely offset when the virtual three-phase is synthesized.
[0014] In the copper loss minimization control system of the variable flux reluctance motor, in the PI control part, PI control is used to generate a command voltage to achieve dynamic adjustment of the amplitudes of the DC and AC current components.
[0015] In the copper loss minimization control system of the variable flux reluctance motor, the PI control part also implements closed-loop control feedback data to adjust the voltage phase.
[0016] In the copper loss minimization control system of the variable flux reluctance motor, the inverter adopts PWM modulation technology to dynamically adjust the amplitudes of the DC component and the AC component, and realizes frequency and phase control of the AC component and dynamic adjustment of the amplitude of the DC component by adjusting the pulse width.
[0017] A method for minimizing copper loss control system using the variable flux reluctance motor comprises the following steps:
[0018] S1: Current detection: The six-phase current is collected in real time at the six-phase winding input or inverter output by a current sensor. The virtual three-phase current, including the U, V, and W phases, is synthesized according to the rules. After eliminating the DC component, the pure AC U, V, and W phase currents are obtained.
[0019] S2: dq transformation: convert the virtual three-phase current into the d-axis boundary magnetic component and q-axis torque component current i d and i q ;
[0020] S3: Proportional calculation: through i d and i q Calculate the total effective current:
[0021]
[0022] Combined with the winding grouping characteristics, the DC current of a single winding is obtained:
[0023]
[0024] AC current amplitude:
[0025]
[0026] S4: Inverter dynamic adjustment: DSP controller adjusts the inverter according to the calculated I dc and I ac , generate six-phase command voltage, control the switching timing of the inverter H-bridge through PWM signal, and accurately superimpose DC and AC components.
[0027] 7. The method according to claim 6, wherein the command voltage of a single winding is:
[0028] V a =V ac_U +V dc ,V D =V ac_U -V dc
[0029] in:
[0030]
[0031] Where R is the phase resistance, V ac_U is the U-phase AC voltage amplitude.
[0032] In the above method, the command voltage of the single winding is:
[0033] V A =V ac_U +V dc ,V D =V ac_U -V dc
[0034] in:
[0035]
[0036] Where R is the phase resistance, V ac_U is the U-phase AC voltage amplitude.
[0037] In the above method, in step S4, the optimal ratio of DC to AC current is derived with the goal of minimizing the effective value of the phase current. The formula for the effective value of the phase current is:
[0038]
[0039] when When I s To obtain the minimum value, the amplitudes of the DC and AC components are dynamically adjusted to minimize copper loss, namely:
[0040]
[0041] At this time, the effective value of the phase current is:
[0042]
[0043] At this time, I s Minimize copper loss.
[0044] The beneficial effects of the present invention are:
[0045] 1. Copper loss is significantly reduced: Under rated load, copper loss is reduced by 15%-20% compared with traditional methods, especially in the high-speed weak magnetic area, the efficiency is significantly improved, such as Figure 5 As shown in the figure, the copper loss ratio at high speed is reduced from 40% to below 30%.
[0046] 2. Wide range of efficient operation: By dynamically adjusting the DC / AC current ratio, the motor maintains high efficiency in the speed range of 0-20000rpm, such as Figure 6 As shown in Figure 2, the efficiency of CSVFRM is 5%-10% higher than that of IPMSM and SRM).
[0047] 3. Simplified structure: The independent boundary magnetic winding is eliminated, and only one power supply and six-phase inverter are needed to achieve current superposition, which reduces the complexity of the winding, reduces the manufacturing difficulty and cost, and improves the power density of the motor. Figure 7 As shown in the figure, the current superposition type motor has a 20% higher occupancy rate than the boundary magnetic winding type.
[0048] 4. Precise control: The coordinated control of the six-phase inverter achieves decoupling control of "magnetic field regulation" and "drive torque" by grouping and superimposing positive and negative DC components, avoiding mutual interference between the boundary magnetic winding and the armature winding of traditional motors.
[0049] Dynamic response advantage: When the motor speed exceeds 7500rpm and enters the field weakening area, the inverter can quickly reduce I_{dc} and adjust I_{ac} synchronously, and can still maintain I_{ac} at 15000rpm. dc :I ac The optimal ratio reduces copper loss by 18% compared with traditional control. BRIEF DESCRIPTION OF THE DRAWINGS
[0050] Figure 1 It is a schematic diagram of the six-phase winding current superposition structure in the present invention.
[0051] Figure 2 It is the vector control block diagram of the present invention.
[0052] Figure 3 This is a comparison diagram of the current superposition type VFRM in the present invention and the boundary magnetic winding type VFRM in the prior art.
[0053] Figure 4 It is the phase current power spectrum diagram in the present invention.
[0054] Figure 5 2 is a relationship diagram between the rotational speed and the loss in the present invention.
[0055] Figure 6 1 is a graph showing the relationship between the rotational speed and the motor efficiency in the present invention.
[0056] Figure 7 Graph showing the relationship between armature current and torque constant in the present invention.
[0057] Figure 8 It is a curve diagram showing the relationship between DC current and phase current effective value in the present invention.
[0058] Figure 9 This is the FFT analysis diagram of the phase current when the copper loss is minimized in the present invention. DETAILED DESCRIPTION
[0059] Reference Figures 1 to 9 , a copper loss minimum control system and method for a variable flux reluctance motor, wherein,
[0060] The motor structure adopts a six-phase winding configuration (AF phase), in which the A, C, and E phases are superimposed with positive DC voltage, and the B, D, and F phases are superimposed with negative DC voltage, forming a positive and negative symmetrical current superposition structure (such as Figure 1 shown).
[0061] Current superposition: The armature current (3-phase AC) and the field current (DC) are superimposed on the input through hierarchical control of the six-phase inverter:
[0062] (1) AC current generation: The six H-bridges of the inverter (corresponding to the A-F phase) first convert the DC power supply into six-phase AC power (with a phase difference of 60° or 120°), where the A / B / C phases are forward three-phase AC and the D / E / F phases are reverse three-phase AC (with a phase difference of 180° from the A / B / C phases), forming a complementary "twin winding" structure (for example, phase A and phase D are a group responsible for phase U).
[0063] (2) DC component superposition law:
[0064] Forward superposition: A positive DC voltage (+Vdc) is superimposed on the A, C, and E phases through the auxiliary H-bridge, which is equivalent to injecting a positive DC component into the AC current of the A / C / E phases;
[0065] Reverse superposition: Superimpose a negative DC voltage (-Vdc) on the B, D, and F phases, which is equivalent to injecting a reverse DC component into the AC current of the B / D / F phases;
[0066] Symmetrical control: The DC components of each set of "twin windings" (such as A / D phases) are equal in magnitude and opposite in direction, ensuring that the superimposed DC components are completely offset when the virtual three-phase synthesis occurs (such as virtual U phase = A phase + D phase = U phase AC + Vdc + U phase AC - Vdc = 2 times U phase AC).
[0067] (3) Ratio optimization core: Through the PWM modulation technology of the inverter, the amplitude of the DC component and the AC component are dynamically adjusted to make At this time, the effective value of the phase current is: Minimum, to minimize copper loss,
[0068] Copper loss minimization control method:
[0069] Objective function: Minimize the effective value of phase current and derive the optimal ratio of DC to AC current. The formula for the effective value of phase current is:
[0070]
[0071] Therefore, when When I s Obtaining the minimum value corresponds to the minimum copper loss;
[0072] Vector control: The six-phase current is converted into a virtual three-phase current through dq transformation, and the command voltage is generated by PI control to achieve independent regulation of DC and AC current components (control block diagram as shown in Figure 2 shown).
[0073] Voltage distribution: Calculate DC voltage based on the minimum copper loss condition Where R is the phase resistance, which ensures that the winding current meets the torque requirement while minimizing copper losses.
[0074] 3. Implementation steps
[0075] Current detection: The six-phase current is collected in real time at the six-phase winding input or inverter output through a current sensor to synthesize a virtual three-phase current (U, V, and W phases).
[0076] dq transformation: converts the virtual three-phase current into d-axis (boundary magnetic component) and q-axis (torque component) current i d ,i q .
[0077] Proportional calculation:
[0078] (1) Current synthesis and coordinate transformation:
[0079] The six-phase winding current (including AC + DC components) is collected by current sensors, and the virtual three-phase current is synthesized according to the "group addition" rule (for example, virtual U phase = A phase + D phase). After eliminating the DC component, the pure AC U / V / W phase current is obtained.
[0080] Perform dq transformation on the virtual three-phase current and decompose it into magnetic field components i d (corresponding to DC regulation requirements) and torque component i q (Corresponding to AC drive requirements).
[0081] (2) Optimal ratio derivation:
[0082] According to the copper loss minimization objective function:
[0083]
[0084] Combined with vector control theory, it is deduced that When I s Minimum.
[0085] In actual control, through i d and i q Calculate the total effective current:
[0086]
[0087] Combined with the winding grouping characteristics, the DC current of a single winding is obtained:
[0088]
[0089] AC current amplitude:
[0090]
[0091] (3) Inverter dynamic adjustment:
[0092] The DSP controller calculates the I dc and I ac , generate six-phase command voltage (such as A phase = U phase AC + Vdc, D phase = U phase AC - Vdc), control the switching timing of the inverter H bridge through PWM signal, and accurately superimpose DC and AC components.
[0093] Voltage generation:
[0094] (1) Calculation of command voltage:
[0095] The command voltage of a single winding (such as phase U) is:
[0096] V A =V ac_U +V dc ,V D =V ac_U -V dc
[0097] in (R is the phase resistance), Vac_U is the U-phase AC voltage amplitude.
[0098] (2) PWM control strategy:
[0099] The inverter uses space vector PWM (SVPWM) technology to decompose the six-phase command voltage into six H-bridge switching signals, and achieves the following by adjusting the pulse width:
[0100] Frequency and phase control of the AC component (driving the rotor to rotate);
[0101] The amplitude of the DC component is dynamically adjusted (regulating the magnetic field strength).
[0102] (3) Closed-loop feedback optimization:
[0103] The current sensor monitors the six-phase current in real time, compares the deviation between the command value and the actual value, and corrects the inverter output through the PI controller to ensure The ratio remains stable when the load changes.
[0104] The PI controller generates a six-phase command voltage with superimposed DC voltage to drive the motor. Innovation point: Current distribution optimization: The square root proportional relationship between DC and AC current is proposed for the first time. Theoretically, it is proved that the effective value of phase current is the smallest under this ratio, which directly reduces copper loss.
[0105] Unbounded magnetic winding design: replace the traditional bounded magnetic winding by current superposition, simplify the winding structure, improve productivity, and realize flexible adjustment of magnetic flux (such as Figure 3 shown).
[0106] Harmonic influence suppression: suppress high-order harmonic current (such as secondary components) through vector control, reduce the loss of non-effective torque current, and improve efficiency (such as Figure 4 As shown in Figure 2, when copper loss is minimized, the high-order harmonic components are significantly reduced).
[0107] Coordinated control of the six-phase inverter: By grouping and superimposing positive and negative DC components, decoupling control of "magnetic field regulation" and "drive torque" is achieved, avoiding mutual interference between the boundary magnetic windings and armature windings in traditional motors.
[0108] Dynamic response advantage: When the motor speed exceeds 7500rpm and enters the field weakening area, the inverter can quickly reduce I_{dc} and adjust I_{ac} synchronously, and can still maintain I_{ac} at 15000rpm. dc :I ac The optimal ratio reduces copper loss by 18% compared with traditional control (such as Figure 6 shown).
[0109] In the control process, the hardware configuration includes a six-phase inverter such as an Infineon IGBT module, paired with a DSP controller such as the TI TMS320F28379D. LEM Hall sensors are used to collect six-phase currents in real time at the winding input. The data is used for closed-loop control and copper loss optimization.
[0110] Software algorithm: A motor model is established in MATLAB / Simulink, and winding parameters (such as inductance and resistance) are determined through finite element analysis (JMAG-Designer).
[0111] Write the DQ transformation and PI control algorithm, set the copper loss minimization objective function, and calculate the optimal DC / AC current ratio in real time.
[0112] Experimental verification: Input DC voltage 48V, set rated torque 8.5Nm, and adjust AC current amplitude (50-200A) to verify the change trend of phase current effective value with DC current (such as Figure 8 Compared with the traditional control method, the copper loss data was measured and confirmed in I dc =84.7A, I ac =120A, the copper loss is minimal and the efficiency reaches over 90%.
[0113] Example 2: High-speed weak magnetic field application
[0114] Control adjustment: When the speed exceeds 7500rpm, the field weakening control is activated, the DC current is reduced to reduce the magnetic flux, and the AC current is dynamically adjusted according to the minimum copper loss condition.
[0115] Effect verification: At 15000rpm, copper loss is reduced by 18% compared with traditional weak magnetic control, and motor efficiency remains above 85% (such as Figure 6 shown).
[0116] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.
Claims
1. A copper loss minimization control system for a variable flux reluctance motor, characterized in that: The system comprises a six-phase inverter, which uses space vector PWM technology to decompose the six-phase command voltage into six H-bridge switching signals. The six-phase inverter includes six-directional windings, and the configuration of the six-directional windings includes phases A to F, wherein phases A, C, and E are superimposed with positive DC voltages, and phases B, D, and F are superimposed with negative DC voltages. Phases A, B, and C are positive three-phase AC, and phases D, E, and F are negative three-phase AC and are 180° out of phase with phases A, B, and C, forming three complementary twin winding structures. The system also includes: A current sensor is used to collect the current at the six-phase winding input end or the inverter output end in real time; DSP controller, which performs dq transformation to obtain d-axis and q-axis current components PI control part, which monitors the current size and waveform to ensure the correct ratio and detects abnormal current to avoid failure; The current input of the motor is realized by superimposing the armature current and the field current through hierarchical control of a six-phase inverter.
2. The copper loss minimization control system of the variable flux reluctance motor according to claim 1, characterized in that: The superposition input includes: Forward superposition: The auxiliary H-bridge is used to superimpose a positive DC voltage on the A, C, and E phases, which is equivalent to injecting a positive DC component into the AC current of the A, C, and E phases; Reverse superposition: Superimpose a negative DC voltage on phases B, D, and F, which is equivalent to injecting a reverse DC component into the AC current of phases B, D, and F; Symmetrical control: The DC components of each set of twin windings are equal in magnitude and opposite in direction, ensuring that the superimposed DC components are completely offset when the virtual three-phase is synthesized.
3. The copper loss minimization control system of the variable flux reluctance motor according to claim 1, characterized in that: In the PI control part, PI control is adopted to generate a command voltage to achieve dynamic adjustment of the amplitudes of the DC and AC current components.
4. The copper loss minimization control system of the variable flux reluctance motor according to claim 1, characterized in that: The PI control part also implements closed-loop control feedback data to adjust the voltage phase.
5. The copper loss minimization control system of the variable flux reluctance motor according to claim 1, characterized in that: The inverter adopts PWM modulation technology to dynamically adjust the amplitudes of the DC component and the AC component, and realizes frequency and phase control of the AC component and dynamic adjustment of the amplitude of the DC component by adjusting the pulse width.
6. A method for minimizing copper loss control system of a variable flux reluctance motor using any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Current detection: The six-phase current is collected in real time at the six-phase winding input or inverter output by a current sensor. The virtual three-phase current, including the U, V, and W phases, is synthesized according to the rules. After eliminating the DC component, the pure AC U, V, and W phase currents are obtained. S2: dq transformation: convert the virtual three-phase current into the d-axis boundary magnetic component and q-axis torque component current i d and i q ; S3: Proportional calculation: through i d and i q Calculate the total effective current: Combined with the winding grouping characteristics, the DC current of a single winding is obtained: AC current amplitude: S4: Inverter dynamic adjustment: DSP controller adjusts the inverter according to the calculated I dc and I ac , generate six-phase command voltage, control the switching timing of the inverter H-bridge through PWM signal, and accurately superimpose DC and AC components.
7. The method according to claim 6, characterized in that The command voltage of the single winding is: V A =V ac_U +V dc ,V D =V ac_U -V dc in: Where R is the phase resistance, V ac_U is the U-phase AC voltage amplitude.
8. The method according to claim 6, characterized in that In step S4, the optimal ratio of DC to AC current is derived with the goal of minimizing the effective value of the phase current. The formula for the effective value of the phase current is: when When I s To obtain the minimum value, the amplitudes of the DC and AC components are dynamically adjusted to minimize copper loss, namely: At this time, the effective value of the phase current is: At this time, I s Minimize copper loss.