Abstract: Proposed produces the SVPWM wave with DSP to realize the entire numerical control one method to the contravariant power source. In has analyzed in the TMS320LF2407A digital signal processor chip characteristic foundation, has given the system design software and hardware structure. The experiment indicated that the system circuit is simple, the reliability is high, but the promotion is strong.
Key word: Invertor; Digital signal processor; Digitization; Space vector pulse-duration modulation
O introduction
Along with information technology’s development, the 400Hz intermediate frequency inversion power source power supply system is getting more and more widespread as various countries applies in the aviation, astronautics, the missile, the radar, the correspondence, the airplane, vehicles’ standard power supply system, generally for high, the essence, point’s electronic installation provides the work power source. At present inverts the power source to use the analogous circuit control perhaps the partial digital circuit control majority, the system maintainability is bad, promotion difficulty. This article unifies the concrete project duty, mainly devotes to the contravariant power source’s entire numerical control technology research, in the original contravariant power source’s foundation, uses DSP to produce the SVPWM wave to substitute the primary circuit supply oscillator as the supply oscillator the technology, improves the contravariant power source’s output performance and the enhancement inversion power source’s reliability.
The contravariant power source uses the numerical control, has the following merit:
1) numerical control (DSP) uses the advanced control method and the intelligent control strategy, causes the contravariant power source’s intellectualized degree to be higher, the performance is more perfect;
2) controls nimbly, the system upgrade is convenient, even may the online revision control algorithm, but does not need to modify the hardware circuit;
3) control system’s reliable enhancement, easy standardization;
4) the system maintenance is convenient. Once the system presents the breakdown, may very conveniently carries on the debugging, the breakdown inquiry, the failure diagnosis, the software repair through the RS232 connection or the USB connection, even controlled variable online revision and debugging;
5) system’s uniformity is good, the cost is low, the manufacturing is convenient.
1 SVPWM principle
Space vector pulse-duration modulation SVPWM (Space Vector Pulse Width Modulation) in fact is regarding three phase voltage source invertor power component’s one kind of special switch triggering order and the pulse width size combination, this kind of switch triggering order and the combination will produce three mutual deviation 120° wave distortion small sinusoidal current in the electrical machinery stator coil. The practice and the theory may prove that compares with the direct sine pulse-duration modulation (sPwM) technology, svPwM will produce less overtones in the output voltage or the electrical machinery coil’s electric current, enhanced to the potential source invertor cocurrent electric power supply’s use factor.
The potential source invertor may 6 switches which by shown in Figure 1 come the equivalent expression. The invertor bridge arm’s about switch in any one time cannot simultaneously the breakover. When does not consider the dead area, the high and low bridge arm’s switch assumes the supplementary condition, therefore the invertor has 8 kind of different switch patterns.
As shown in Figure 1, works as when the bridge arm clear, under the bridge arm shuts off, when namely Sa=1, U=udc/2; Works as the bridge arm to shut off, under the bridge arm clears, when namely Sa=O, U= Udc/2o, Sc also with.
Invertor’s 8 kind of switch pattern correspondence has 8 voltage space vector. Uses 3/2 coordinate transformation, transforms three phase voltages to the d-q shafting.
Substitutes the different switch pattern (Sa, Sb, Sc), through the above 3/2 coordinate transformation, may result in the voltage space vector which shown in Figure 2.
In Figure 2 altogether has 8 vectors, V (O O O) and V (1 1 1) is a null vector, the peak-to-peak value is O; Other 6 vectors are the effective vector, the peak-to-peak value are
the neighboring effective vector included angle are 60°.
May synthesize the new vector through the different vectorial combination, as shown in Figure 2, supposes neighboring two effective vector V1 and Vm, the null vector is Vo, synthesizes new vector Vout, the vector response time respectively is T1, Tm. Tpwm is the PWM pulse width cycle.
Synthesizes the new vector the expression is
2 produce the SVPWM wave based on DSP
2.1 DSP chip TMS320LF2407A
According to the mission requirement and the characteristic, have selected the TMS320LF2407ADSP processor. TMS320LF2407A is TI Corporation specially the serial products which promotes for the industrial control and the motor control. This section of DSP real-time processing ability and controller’s peripheral device function collection in a body. Has the following characteristic: Nimble command system; High speed operational capability; Large capacity memory property; Effective performance price ratio. The main application domain includes: Industry motor-driven; Contravariant power source; Power switch and controller; Automobile system; Measuring appliance and compressor motor control; Robot and computer numerical control machinery.
TMS320LF2407A has 2 event supervisors; 32 central arithmetic logic unit; 32 accumulators; 16 ×16 position multipliers; 3 proportion shifters; The indirect addressing uses 8 16 auxiliary registers and auxiliary arithmetic unit; 4 level of stream line operations; 8 level of hardware operations; 6 maskable interrupts; 544 character internal DARAM and 2K character internal SARAM; 32K character internal FLASH program memory; 64K procedure storage space; 35.5K data storage space; I/0 spatial 64K. In addition also has the function formidable peripheral device: Serial communication connection SCI; Serial periphery connection SPI; CAN bus control unit; Event supervisor EV; A/D switch; Watch-dog WD.
The TMS320LF2407A chip is through 3 main line implementation instruction read, the Ze code, takes operations and so on operand, executive order.
2.2 produce the SVPWM wave the method
In TMS320LF2407A has two event supervisor EVA and EVB, they have a special hardware - - SVPWM state machine component. Therefore 2407A has two SVPWM state machines.
This system uses EVA, state machine cow becomes the profile using 2407The internal bringing SVPWM. Take the effective vector V(100) and V(110) as examples. The plan is V(1OO)-V(11O) one
V(111)-V(11O) one V(1OO), as shown in Figure 3.
This time the power component needs the turn-on frequency
is in the conventional SPWM modulation carrier frequency. Fills to, T1/2 and Tm/2 in EVA, then produces the plan which shown in Figure 3.
So long as after assigning the output frequency, the output line voltage, the direct-current bus bar voltage, may produce SVPWM, the step is as follows.
1) continuously synthesizes the new vector, can produce the electrical machinery the circular magnetic field. The new vector’s angle increasing relations are
In the formula: The angular frequency ω=2π/f, f outputs the frequency.
2) falls according to angle a on 6 different sectors, chooses different effective vector V1 and Vmo
3) effective vector V1 and the Vm function’s priority order, decided that the magnetic field the hand of rotation, decided finally the electrical machinery is the clockwise or the reverse.
4) acts according to the SVPWM production plan, hands over by the SVPWM state machine computation, obtains the computed result.
3 system software and hardware design
3.1 hardware architectures
Through compares each kind of power transfer network, for example the square-wave invertor, the step wave synthesis invertor, the sine pulse-duration modulation invertor and so on good and bad points, determined that still continued to use the product initial models stage use the entire bridge contravariant organization plan, key in improvement control mode, namely uses the entire digital in the control mode the control mode, uses the space vector sine wave pulse-duration modulation (SVPWM) type the control mode. System structure schematic diagram as shown in Figure 4.
This system circuit is three inverts the electric circuit, the main circuit is the typical AC-DC-AC inversion electric circuit, will input three intersection discharges (frequency is 400Hz, voltage 208V) after the rectification, the filter the supplies invertor outputs three intersection discharges, the frequency is 50 Hz, passes through the insulating transformer to turn 380V again the alternating current. Insulating transformer another group output feeds back after a/D transformation to the 2407A chip, the 2407A chip output signal for the driving circuit, controls the invertor output parameter.
The contravariant power source control core electric circuit is the 2407A chip electric circuit, mainly completes the following several aspects the work.
1) accepts the control command, the start, the stop inversion power source;
2) outputs the SVPWM wave control signal to the driving circuit, simultaneously monitors the contravariant power source output voltage, and realizes power source’s closed-loop control through the feedback circuit;
3) momentarily monitors the contravariant power source running status, once breaks down, the closure control output, simultaneously completes the breakdown parameter the memory, the protection.
3.2 softwares realize
Because uses TMS320LF2407A, causes the programming the work load is the reduction greatly. Uses the assembly language programming, the direction overall system’s work, through the system initialization subroutine to various parameters, the register and so on carries on the hypothesis, implements to the main circuit the control, the inversion outputs 50Hz three intersection discharge. The programming uses the smooth structure simply, the transfer subroutine convenient, the subroutine may the voltage, the electric current, the frequency value demonstrate separately through LED. In the entire work process, momentarily to the electric current, the voltage carries on the survey comparison, once presents the overflow, to owe the voltage situation to report to the police promptly, the situation is serious when auto-stop, and storage failure parameter. Master routine flow diagram as shown in Figure 5.
4 result confirmations
According to produces SVPWM the fundamental formula type (6)~ type (7), so long as assigns the output frequency, the output line voltage, the direct-current bus bar voltage, passes through the SVPWM subroutine and TMS320LF24007The SVPWM state machine, produces three invert the bridge which the PWM pulse control (shown in Figure 1), after the contravariant bridge’s out-port will obtain three symmetrical sinusoidal voltage profile (filter).
Figure 6 does not consider the dead area production SVPWM, after PWM base pin filtration carrier base pin profile. In Figure 6, 1 and 2 are Ua and the Ub profile, corresponds in the contravariant bridge’s phase voltage; Middle is the Uab profile, corresponds line voltage which outputs in the contravariant bridge. May see has 1/3 cycle, A or is in high, either is in lowly, therefore cut the turn-on frequency greatly.
5 conclusions
This article studied realizes the SVPWM wave method based on DSP TMS320LE2407A already to obtain the confirmation in the concrete project, and has obtained the good control effect. After the above analysis and the experiment, indicated finally:
1) through the possible arrangement null vector response time, may improve the PWM harmonic characteristic effectively, causes the overtone to reduce, and the voltage use factor is high;
2) may realize the SVPWM algorithm very conveniently, is in the present contravariant power source control the quite ideal choice;
3) uses voltage space vector PWM to take the supply oscillator, the current harmonics are few, the torque pulsation is small, the noise is low, not only the control circuit simplifies, moreover system’s reliability also had the very big enhancement.
