A switching method of multi-mode pulse width modulation
A pulse width modulation and multi-mode technology, applied in control systems, control generators, vector control systems, etc., can solve problems such as poor versatility, torque ripple, current impact, etc., and achieve slow response, switching Performance optimization, the effect of improving accuracy
Active Publication Date: 2022-04-29
NORTH CHINA UNIVERSITY OF TECHNOLOGY
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Problems solved by technology
Three-phase independent switching through the analysis of the current transient response equation, choose to switch at the point where the harmonic current transient response is zero, but the harmonic current transient response analysis process used by this method is relatively cumbersome, and the harmonic current in different switching processes The transient response is different, the versatility is not strong, and when the level jump is relatively scattered, independent switching can easily cause pulse disorder, resulting in system overcurrent, which is not meaningful for practical application
[0007] The three-phase synchronous switching method selects the optimal switching point by analyzing and comparing the current characteristics of different switching points or the stator flux characteristics. Among them, the analysis of the current characteristics is based on the current harmonic characteristics of different switching points, considering the harmonics The influence of the current, select the optimal switching point, but the current harmonic analysis is relatively difficult, and the difference is huge under different modulation modes, and the versatility is not strong; the analysis of the stator flux characteristics is based on the stator flux characteristics of different switching points , by analyzing the amplitude of the harmonic flux linkage and the deviation of the amplitude of the harmonic flux linkage to judge whether the stator flux linkage before and after different switching points is continuous, and to select the optimal switching point, this method can only be optimally selected according to the existing switching points , the deviation caused by switching is not dealt with accordingly, and it is necessary to wait for the optimal switching point before switching, and the system is not fast enough
[0008] At present, the existing switching strategy method can only choose among the existing switching points, and it must wait for the optimal switching point to arrive before switching, and even if it is the optimal switching point, due to the optimized flux linkage trajectory There is a fixed deviation, which will still cause a certain flux linkage deviation, which will cause current impact and torque ripple during the switching process, which has certain limitations
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Embodiment 1
[0124] In the process of switching from 5-frequency SHEPWM to 3-frequency SHEPWM, if Figure 7 As shown, the dotted line is the optimized flux linkage trajectory corresponding to the 5-frequency SHEPWM switching sequence at the switching time, and the dotted line is the optimized flux linkage trajectory corresponding to the 3-frequency SHEPWM switching sequence at the switching time. structure, so as to obtain the optimized flux trajectory before and after switching.
[0125] Specifically, the actual stator flux trajectory at the switching instant As follows:
[0126]
[0127] After the working condition changes, the stator flux vector expression is as follows:
[0128]
[0129] Expected stator flux trajectory Can be expressed by the following formula:
[0130]
[0131] Compensate the flux linkage track error before and after switching, through the following formula:
[0132]
[0133] The α-axis flux linkage error component dψ can be obtained α (t) is 0.141...
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The invention discloses a switching method of multi-mode pulse width modulation, which comprises the following steps: obtaining switching sequences of different modulation modes and switching sequences when the number of different switching angles is N; obtaining switching sequences P(m, N 1 ) and switching sequence P(m,N 2 ); Obtain the stator flux error caused by modulation mode switching; Obtain the flux error dψ in the two-phase stationary coordinate system α and dψ β Obtain the compensation time of each phase switching moment; modify the switching sequence after switching to obtain a new switching sequence; generate PWM pulses according to the corrected switching sequence, drive the inverter, and then drive the motor. According to the multi-mode pulse width modulation switching method provided by the present invention, it has many advantages such as not depending on the specific modulation mode and motor parameters, can realize switching at any time, and improves the speed and accuracy of stator flux linkage error elimination.
Description
technical field [0001] The invention relates to a multi-mode pulse width modulation switching method, in particular to a multi-mode pulse width modulation switching method applied in a high-power traction drive system, and belongs to the field of motor control. Background technique [0002] The traction drive system has the characteristics of high voltage, high power, and high current. Its switching frequency is limited by the heat dissipation system. The switching frequency of the locomotive traction converter is only a few hundred hertz. [0003] Compared with ordinary inverters, the lower switching frequency of the locomotive traction system puts forward higher requirements on the modulation algorithm of the inverter, which is manifested in the following two points: first, the speed range is wider during operation, which It will lead to a large change in the carrier ratio, so it is necessary to use a variety of different modulation strategies to meet the requirements of d...
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IPC IPC(8): H02P21/14H02P21/28H02P27/08
CPCH02P21/141H02P21/28H02P27/08
Inventor 苑国锋沈阳
Owner NORTH CHINA UNIVERSITY OF TECHNOLOGY