Two-phase modulation SVPWM signal generation method based on single-resistor sampling

Abstract

The invention relates to the field of PWM (Pulse Width Modulation) control, and provides a two-phase modulation SVPWM (Space Vector Pulse Width Modulation) signal generation method based on single-resistor sampling in order to realize full-range current sampling while reducing switching loss and improving energy efficiency, which comprises the following steps: respectively calculating a three-phase duty ratio according to voltage, judging a maximum phase, an intermediate phase and a minimum phase, calculating half of the duty ratio of the maximum phase as Tmax, and calculating half of the duty ratio of the intermediate phase as Tmax; half of the duty ratio of the intermediate phase is Tmid, and half of the duty ratio of the minimum phase is Tmin; calculating the difference T1 between the Tmax and the Tmid and the difference T2 between the Tmid and the Tmin; whether a sampling blind area exists or not is judged, and if not, the sampling blind area is kept unchanged; if the blind area exists, phase shifting is carried out, and in the all-zero mode, the intermediate phase and / or the maximum phase are / is shifted; in the all-one mode, the intermediate phase and / or the minimum phase are / is moved, and full-range current sampling is realized while a single resistor has no sampling blind area in two-phase modulation, switching loss is reduced and energy efficiency is improved through item shifting.

Description

Technical Field

[0001] The invention relates to the field of PWM control, and in particular to a two-phase modulation SVPWM signal generation method based on single resistor sampling. Background Art

[0002] Current sampling and SVPWM are two important modules in motor FOC control. Current sampling is divided into three sampling methods: three resistors, two resistors and single resistor. Based on cost considerations, the single resistor sampling method is currently widely used.

[0003] The typical circuit of single resistor sampling method is as follows Figure 1 As shown in the figure, the current on the bus is sampled by a single-chip microcomputer, and the three-phase current is decomposed through logical analysis, that is, the current is sampled at two different times in a PWM cycle to obtain two-phase current, and then the third-phase current is reconstructed and calculated based on the sum of the three-phase current being equal to zero. However, there is a sampling blind spot in single-resistance sampling. When the duty ratios of two phases are very close, only one of the two phase currents can be sampled.

[0004] Space vector modulation SVPWM is a process of generating a space vector that meets the needs of any position and a certain amplitude range based on the combined action of a finite number of space vectors at a certain position, that is, changing the distribution of the conduction time of each phase in the entire PWM cycle to form the required arbitrary space vector. SVPWM has three-phase modulation and two-phase modulation. Three-phase modulation divides a cycle into 6 sectors, and obtains 8 vectors including two zero vectors. In each sector, two adjacent non-zero vectors and the corresponding zero vector are used to synthesize any vector in the sector, thereby calculating the action time of two adjacent non-zero vectors and the zero vector. Half of the action time of the zero vector is all "0" and half is all "1", such as Figure 2 The difference between two-phase modulation and three-phase modulation is that in two-phase modulation, only one type of zero vector is used, either all "1" (all 1 mode) or all "0" (all 0 mode), which means that one phase switch in a sector does not operate, thus reducing the switching loss by one third. Figure 3 To use the two-phase modulated SVPWM output in all "0" mode, Figure 4 It is a two-phase modulation SVPWM output using the full "1" mode. Like three-phase modulation, the single resistor sampling of two-phase modulation also has a sampling blind area. Summary of the invention

[0005] In order to achieve full-range current sampling while reducing switching losses and improving energy efficiency, the present application provides a two-phase modulated SVPWM signal generation method based on single resistor sampling.

[0006] The technical solution adopted by the present invention to solve the above problems is:

[0007] The two-phase modulation SVPWM signal generation method based on single resistor sampling includes:

[0008] Calculate the duty cycle of the three phases according to the voltage, determine the maximum phase, the middle phase and the minimum phase, and calculate that half of the duty cycle of the maximum phase is Tmax, half of the duty cycle of the middle phase is Tmid, and half of the duty cycle of the minimum phase is Tmin;

[0009] Calculate the difference △T1 between Tmax and Tmid, and the difference △T2 between Tmid and Tmin;

[0010] Determine whether there is a sampling blind area. If there is no blind area, keep it unchanged; if there is a blind area, shift the phase: in the all-0 mode, move the middle phase and / or the maximum phase; in the all-1 mode, move the middle phase and / or the minimum phase.

[0011] Furthermore, the method for determining the sampling blind area is:

[0012] If both △T1 and △T2 are greater than or equal to the minimum sampling window Twin, there is no sampling blind area; if either △T1 or △T2 is less than Twin, there is a sampling blind area.

[0013] Furthermore, let the PWM count peak be PERIOD,

[0014] If it is all 0 mode, the phase shift steps are:

[0015] If △T2<Twin, the duty cycle of the middle phase shifts to the right. After the phase shift, △T1=Tmax-Tmidleft is recalculated, and Tmidleft is the duty cycle of the left side of the middle phase.

[0016] If △T1<Twin, calculate the phase shift size △deft=Twin-△T1. When △deft+Tmax≤PERIOD, the duty cycle of the maximum phase shifts to the right; when △deft+Tmax>PERIOD, the duty cycle of the middle phase shifts to the left.

[0017] If it is all 1 mode, the phase shift steps are:

[0018] If △T1<Twin, the duty cycle of the middle phase shifts left; recalculate △T2=Tmidleft-Tmin;

[0019] If △T2<Twin, calculate the phase shift size △deft=Twin-△T2. When Tmin≥△deft, the duty cycle of the minimum phase shifts to the left; when Tmin<△deft, the duty cycle of the middle phase shifts to the right.

[0020] Further, if △T2<Twin, the duty cycle of the middle phase shifts right, specifically: if 2×Tmid≥Twin, after phase shift, the duty cycle of the left side of the middle phase Tmidleft=Twin, and the duty cycle of the right side of the middle phase Tmidright=2×Tmid-Twin; if 2×Tmid<Twin, after phase shift, the duty cycle of the left side of the middle phase Tmidleft=Twin, and the duty cycle of the right side Tmidright=0.

[0021] Further, when △deft+Tmax≤PERIOD, the duty cycle of the maximum phase is shifted to the right, specifically: if 2×Tmax≤Tmid+Twin, after phase shifting, the duty cycle of the left side of the maximum phase Tmaxleft=Tmid+Twin, and the duty cycle of the right side of the maximum phase Tmaxright=0; if 2×Tmax>Tmid+Twin, after phase shifting, the duty cycle of the left side of the maximum phase Tmaxleft=Tmid+Twin, and the duty cycle of the right side of the maximum phase Tmaxright=2×Tmax-Tmaxleft;

[0022] When △deft+Tmax>PERIOD, the duty cycle of the middle phase shifts to the left. Specifically, if Tmid+△deft≤PERIOD, after the phase shift, the duty cycle of the left side of the middle phase Tmidleft=Tmid-△deft, and the duty cycle of the right side of the middle phase Tmidright=2×Tmid-Tmidleft; if Tmid+△deft>PERIOD, after the phase shift, the duty cycle of the left side of the middle phase Tmidleft=Tmid-△deft, and the duty cycle of the right side of the middle phase Tmidright=PERIOD.

[0023] Further, if △T1<Twin, the duty cycle of the middle phase is shifted to the left, specifically: calculate △deft=Twin-△T1, when Tmid+△deft≤PERIOD, after phase shift, the duty cycle of the left side of the middle phase Tmidleft=PERIOD-Twin, and the duty cycle of the right side of the middle phase Tmidright=Tmid+△deft; when Tmid+△deft>PERIOD, after phase shift, the duty cycle of the left side of the middle phase Tmidleft=PERIOD-Twin, and the duty cycle of the right side of the middle phase Tmidright=PERIOD.

[0024] Further, when Tmin≥△deft, the duty cycle of the minimum phase is shifted to the left, specifically: when Tmin+△deft>PERIOD, after the phase shift, the duty cycle of the left side of the minimum phase Tminleft=Tmin-△deft, and the duty cycle of the right side of the minimum phase Tminright=PERIOD; when Tmin+△deft≤PERIOD, after the phase shift, the duty cycle of the left side of the minimum phase Tminleft=Tmin-△deft, and the duty cycle of the right side of the minimum phase Tminright=Tmin+△deft;

[0025] When Tmin<△deft, the duty cycle of the middle phase shifts to the right. Specifically, after the phase shift, the duty cycle of the left side of the middle phase Tmidleft=Tmin+Twin, and the duty cycle of the right side of the middle phase Tmidright=Tmin-Twin.

[0026] Compared with the prior art, the present invention has the following beneficial effects: by shifting terms, a single resistor is free of sampling blind areas in two-phase modulation, switching losses are reduced, energy efficiency is improved, and full-range current sampling is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a typical circuit diagram of a single resistor sampling method;

[0028] Figure 2 It is a schematic diagram of the zero vector action time;

[0029] Figure 3 This is a schematic diagram of a two-phase modulation SVPWM output using the all-0 mode;

[0030] Figure 4 This is a schematic diagram of a two-phase modulation SVPWM output using the all-1 mode;

[0031] Figure 5 The flowchart of the two-phase modulated SVPWM signal generation method based on single resistor sampling is shown in FIG. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] In one PWM cycle, the SVPWM signal can be "low-high-low" or "high-low-high". This embodiment takes the PWM count increasing first and then decreasing as an example, assuming that the PWM count peak is PERIOD, that is, when the PWM count increases from 0 to the duty cycle on the left, the PWM is high; when the PWM count increases from the duty cycle on the left to the peak value PERIOD, and then decreases from the peak value to the duty cycle on the right, the PWM is low; when the count decreases from the duty cycle on the right to 0, the PWM is high.

[0034] like Figure 5 As shown, a two-phase modulation SVPWM signal generation method based on single resistor sampling includes:

[0035] First, calculate the three-phase duty cycle according to the voltage, and then find that half of the duty cycle of the maximum phase is Tmax, half of the duty cycle of the middle phase is Tmid, and half of the duty cycle of the minimum phase is Tmin;

[0036] Then calculate the difference between Tmax and Tmid, △T1, and the difference between Tmid and Tmin, △T2.

[0037] If △T1 and △T2 are both greater than or equal to the minimum sampling window Twin, no phase shift operation is performed, the duty cycle of each phase remains unchanged and the duty cycles of the left and right phases are the same;

[0038] If either △T1 or △T2 is less than the minimum sampling window Twin, a phase shift operation is performed to generate a new waveform. The principle of phase shift in two-phase modulation is that the all-“0” or all-“1” phase of each sector always remains unchanged, and the duty cycle of the other two phases is kept as unchanged as possible during the phase shift operation.

[0039] (1) All 0 mode

[0040] In the all-0 mode, Tmin is always "0". If △T2<Twin, there is a current sampling blind area between the middle phase and the minimum phase, and the phase shift operation is performed to shift the duty cycle on the left side of the middle phase to the right, always ensuring that it moves out of the sampling minimum window Twin, and the duty cycle on the right side of the middle phase is shifted to the right; if 2×Tmid≥Twin, the duty cycle of the middle phase is no longer symmetrical, the duty cycle on the left side of the middle phase Tmidleft=Twin, and the duty cycle on the right side Tmidright=2×Tmid-Twin; if 2×Tmid<Twin, after the phase shift, the duty cycle on the left side of the middle phase Tmidleft=Twin, and the duty cycle on the right side Tmidright=0; that is, between PWM counts 0 and Tmidleft, the PWM level is high, between Tmidleft and Tmidright, the PWM level is low, and between Tmidright and 0, the PWM level is high. After the middle phase phase shift is completed, △T1=Tmax-Tmidleft is recalculated.

[0041] If △T1<Twin, there is a current sampling blind area between the maximum phase and the middle phase, and a phase shift operation is performed, and the phase shift size △deft=Twin-△T1,

[0042] When △deft+Tmax≤PERIOD, the middle phase is maintained and the maximum phase is shifted to the right. If 2×Tmax≤Tmid+Twin, the duty cycle after phase shift is Tmaxleft=Tmid+Twin, Tmaxright=0; if 2×Tmax>Tmid+Twin, the duty cycle after phase shift is Tmaxleft=Tmid+Twin, Tmaxright=2×Tmax-Tmaxleft;

[0043] When △deft+Tmax>PERIOD, the maximum phase is maintained, the duty cycle on the left side of the middle phase moves to the left, moves out of the sampling window, and the duty cycle on the right side also moves to the left. When Tmid+△deft≤PERIOD, after phase shifting, Tmidleft=Tmid-△deft, Tmidright=2×Tmid-Tmidleft; when Tmid+△deft>PERIOD, after phase shifting, Tmidleft=Tmid-△deft, Tmidright=PERIOD.

[0044] (2) All 1s mode

[0045] In the all-1 mode, Tmax is always PERIOD, △T1<Twin, the duty cycle on the left side of the middle phase shifts to the left, always ensuring that the sampling minimum window Twin is moved out, and the duty cycle on the right side shifts to the left.

[0046] The phase shift size △deft=Twin-△T1, when Tmid+△deft≤PERIOD, the duty cycle of the left side of the middle phase Tmidleft=PERIOD-Twin, and the duty cycle of the right side Tmidright=Tmid+△deft; when Tmid+△deft>PERIOD, the duty cycle of the left side of the middle phase Tmidleft=PERIOD-Twin, and the duty cycle of the right side Tmidright=PERIOD;

[0047] After the intermediate phase shift is completed, △T2 = Tmidleft-Tmin is recalculated;

[0048] If △T2<Twin, the phase shift size △deft=Twin-△T2,

[0049] When Tmin≥△deft, the duty cycle on the left side of the minimum phase shifts to the left, and the duty cycle on the right side also shifts to the left. When Tmin+△deft>PERIOD, after phase shift, Tminleft=Tmin-△deft, Tminright=PERIOD; when Tmin+△deft≤PERIOD, after phase shift, Tminleft=Tmin-△deft, Tminright=Tmin+△deft;

[0050] When Tmin<△deft, the duty cycle on the left side of the middle phase moves to the right, and the duty cycle on the right side also moves to the right, Tmidleft=Tmin+Twin, Tmidright=Tmin-Twin.

Claims

1. A two-phase modulated SVPWM signal generation method based on single resistor sampling, characterized in that: include: Calculate the duty cycle of the three phases according to the voltage, determine the maximum phase, the middle phase and the minimum phase, and calculate that half of the duty cycle of the maximum phase is Tmax, half of the duty cycle of the middle phase is Tmid, and half of the duty cycle of the minimum phase is Tmin; Calculate the difference △T1 between Tmax and Tmid, and the difference △T2 between Tmid and Tmin; Determine whether there is a sampling blind area. If there is no blind area, keep it unchanged; If a blind area exists, phase shift is performed: in the all-0 mode, the middle phase and / or the maximum phase are shifted; In all 1s mode, move the intermediate phase and / or the minimum phase.

2. The two-phase modulation SVPWM signal generation method based on single resistor sampling according to claim 1 is characterized in that: The method for determining the sampling blind area is: If both △T1 and △T2 are greater than or equal to the minimum sampling window Twin, there is no sampling blind area; if either △T1 or △T2 is less than Twin, there is a sampling blind area.

3. The two-phase modulation SVPWM signal generation method based on single resistor sampling according to claim 2 is characterized in that: Assume the PWM count peak value is PERIOD, If it is all 0 mode, the phase shift steps are: If △T2<Twin, the duty cycle of the middle phase shifts to the right. After the phase shift, △T1=Tmax-Tmidleft is recalculated, and Tmidleft is the duty cycle of the left side of the middle phase. If △T1<Twin, calculate the phase shift size △deft=Twin-△T1. When △deft+Tmax≤PERIOD, the duty cycle of the maximum phase shifts to the right; when △deft+Tmax>PERIOD, the duty cycle of the middle phase shifts to the left. If it is all 1 mode, the phase shift steps are: If △T1<Twin, the duty cycle of the middle phase shifts left; recalculate △T2=Tmidleft-Tmin; If △T2<Twin, calculate the phase shift size △deft=Twin-△T2, when Tmin≥△deft, the duty cycle of the minimum phase shifts left; When Tmin<△deft, the intermediate phase duty cycle shifts to the right.

4. The two-phase modulation SVPWM signal generation method based on single resistor sampling according to claim 3 is characterized in that: If △T2<Twin, the duty cycle of the middle phase shifts right, specifically: if 2×Tmid≥Twin, after the phase shift, the duty cycle of the left side of the middle phase Tmidleft=Twin, and the duty cycle of the right side of the middle phase Tmidright=2×Tmid-Twin; If 2×Tmid<Twin, after phase shifting, the duty cycle on the left side of the middle phase Tmidleft=Twin, and the duty cycle on the right side Tmidright=0.

5. The two-phase modulation SVPWM signal generation method based on single resistor sampling according to claim 3 is characterized in that: When △deft+Tmax≤PERIOD, the duty cycle of the maximum phase shifts right, specifically: if 2×Tmax≤Tmid+Twin, after phase shifting, the duty cycle of the left side of the maximum phase Tmaxleft=Tmid+Twin, and the duty cycle of the right side of the maximum phase Tmaxright=0; If 2×Tmax>Tmid+Twin, after phase shifting, the duty cycle on the left side of the maximum phase Tmaxleft=Tmid+Twin, and the duty cycle on the right side of the maximum phase Tmaxright=2×Tmax-Tmaxleft; When △deft+Tmax>PERIOD, the duty cycle of the middle phase shifts left, specifically: if Tmid+△deft≤PERIOD, after the phase shift, the duty cycle of the left side of the middle phase is Tmidleft=Tmid-△deft, and the duty cycle of the right side of the middle phase is Tmidright=2×Tmid-Tmidleft; If Tmid+△deft>PERIOD, after phase shift, the duty cycle on the left side of the middle phase Tmidleft=Tmid-△deft, and the duty cycle on the right side of the middle phase Tmidright=PERIOD.

6. The two-phase modulation SVPWM signal generation method based on single resistor sampling according to claim 3 is characterized in that: If △T1<Twin, the duty cycle of the middle phase is shifted to the left, specifically: calculate △deft=Twin-△T1, when Tmid+△deft≤PERIOD, after phase shift, the duty cycle of the left side of the middle phase Tmidleft=PERIOD-Twin, and the duty cycle of the right side of the middle phase Tmidright=Tmid+△deft; when Tmid+△deft>PERIOD, after phase shift, the duty cycle of the left side of the middle phase Tmidleft=PERIOD-Twin, and the duty cycle of the right side of the middle phase Tmidright=PERIOD.

7. The two-phase modulation SVPWM signal generation method based on single resistor sampling according to claim 3 is characterized in that: When Tmin≥△deft, the duty cycle of the minimum phase shifts left, specifically: when Tmin+△deft>PERIOD, after the phase shift, the duty cycle of the left side of the minimum phase Tminleft=Tmin-△deft, and the duty cycle of the right side of the minimum phase Tminright=PERIOD; When Tmin+△deft≤PERIOD, after phase shift, the duty ratio of the left side of the minimum phase Tminleft=Tmin-△deft, and the duty ratio of the right side of the minimum phase Tminright=Tmin+△deft; When Tmin<△deft, the duty cycle of the middle phase shifts to the right. Specifically, after the phase shift, the duty cycle of the left side of the middle phase Tmidleft=Tmin+Twin, and the duty cycle of the right side of the middle phase Tmidright=Tmin-Twin.

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