Abstract: Based on the analysis of the basic principle of voltage space vector modulation, this paper constructs a single-chip microcomputer control system with TMS320F2812 as the core to realize SVPWM for variable frequency speed regulation of AC motor. Keywords: TMS320F2812; voltage space vector modulation; AC variable frequency speed regulation. Currently, various PWM control methods are applied to AC variable frequency speed regulation systems. Among them, space vector PWM (SVPWM) is widely used in motor speed regulation due to its unique superior performance. This method is simple to control, convenient to implement digitally, and can significantly reduce the harmonic components of inverter output current and motor harmonic losses, reduce pulsating torque, and improve voltage utilization. This paper mainly introduces the real-time control of the variable frequency speed regulation system using TMS320F2812 (hereinafter referred to as F2812). Main features of TMS320F2812: F2812 has a fast operation speed, a working clock frequency of up to 150MHz, an instruction cycle of less than 6.67ns, and low power consumption (core voltage 1.8V, I/O port voltage 3.3V). Employing a Harvard bus architecture, it boasts powerful operational capabilities, rapid interrupt response and processing, and a unified register programming mode. It can implement 16×16-bit and 32×32-bit multiply-accumulate operations, as well as two 16×16-bit multiply-accumulate operations. On-chip memory includes 8K×16-bit Flash memory, 1K×16-bit OTP read-only memory, two 4K×16-bit single-port random access memory (SRAMs), one 8K×16-bit SRAM, and two 1K×16-bit SRAMs. The external memory interface allows for expansion up to 1MB of memory. The External Expansion Module (PIE) supports 96 external interrupts, 45 of which are available. Two enhanced event manager modules (EVA and EVB) provide a complete set of functions and features for motion control and motor control applications. Each event manager module includes a general-purpose timer (GP), a compare unit, a capture unit, and quadrature encoder pulse circuitry. Peripheral devices include three 32-bit CPU timers and a 16-channel 12-bit ADC (single conversion time 200ns, single-channel conversion time 60ns). It not only features a Serial Peripheral Interface (SPI) and two Serial Communication Interfaces (SCI), but also an improved local area network (eCAN), a multi-channel buffered serial interface (McBSP), and a serial peripheral interface mode. The basic principle of space vector control in frequency converters: The main circuit of a frequency converter is typically an AC-DC-AC power electronic conversion circuit. The DC-AC section is a three-phase bridge inverter system. The control strategy that determines its switching signals often determines the performance of the frequency converter. Analyzing the switching states of the three-phase inverter bridge of the frequency converter (the upper bridge arm of the inverter bridge being on is represented by 1, and the corresponding lower bridge arm being off): (000), (001), (010), (100), (101), (110), (111), can be represented as 8 basic space voltage vectors: V1V2V3V4V5V6V7, where V0V7 are zero vectors, and the rest are effective working vectors. Space vector PWM control is achieved by allocating the voltage space vectors, especially the action time of the zero vector, to ultimately form PWM pulse waves of equal amplitude but unequal width, thus tracking the circular trajectory of the magnetic flux. If the magnitude of the reference equivalent composite space vector V on the complex plane is equal to the peak value of the phase voltage, and it rotates counterclockwise at a constant angular frequency, then its projection on the three-phase axis is a symmetrical sinusoidal quantity. Conversely, according to the parallelogram law, these 8 basic vectors can be used to synthesize an equivalent composite vector Vr with arbitrary angle and magnitude. If an equivalent composite vector is emitted at a constant speed and evenly distributed within a circle, a three-phase sinusoidal switching signal is obtained; this is space vector modulation. The more composite vectors emitted in one cycle, the higher the sampling frequency. Speed ​​Control System Design Based on TMS320F2812 The system structure is shown in Figure 1. The system consists of a main circuit, a control circuit, a drive circuit, and auxiliary circuits. The main circuit is an AC-DC-AC frequency converter circuit. The inverter uses the Fuji Electric R-series 7MBP100RA060 intelligent power module (IPM), a complete inverter including a braking unit, comprising 7 IGBTs and 7 fast power diodes. Six IGBTs and six feedback diodes are connected in parallel to form a three-phase bridge arm, and one IGBT is the switching transistor for dynamic braking. It also integrates various IGBT drive circuits and abnormal condition detection units, such as short-circuit detection, overcurrent detection, undervoltage detection, and overtemperature detection. When any of the above-mentioned abnormal signals is detected, the F0 signal of the IPM module can be sent to the power drive protection pin (PDPINT) of the DSP after optocoupler isolation to achieve corresponding protection. The control circuit consists of the F2812 control board, keyboard, and external control terminals. The external control terminals communicate with the F2812 through the RS-485 interface to complete various management functions, such as setting initial parameters and displaying current and frequency status. The main part of the frequency converter is based on the F2812 chip, which completes the core algorithm of voltage space vector control, generates PWM waveforms, and performs relevant voltage/current detection processing. The event management module of the F2812 has a hardware circuit for generating SVPWM, as shown in Figure 2. From the hardware structure, it can be seen that PWM generation is controlled by specific registers: ACTR (12~15) contains the current main vector, and the corresponding value is written according to the position of Vr by looking up the conversion mode table; TICON (11~13) controls the generation of symmetrical or asymmetrical PWM waveforms; the dead time setting is completed by DBTCON; COMCON (9) controls the PWM output or high impedance output, which can protect the system in time when a fault occurs. The three comparison registers CMXP1~3 correspond to when the U, V, and W phases are turned on, respectively. The magnitude of their values ​​is determined by the action time of the main and auxiliary vectors and the zero vector. When the timer value is equal to the value of CMXP13, the output of the control signal corresponding to the space vector will be changed. The drive circuit mainly enables the control input signal to be transmitted through the optocoupler. When designing, optocouplers such as TLP759 and TLP559 can be selected, and the wiring between the optocoupler and the IPM control terminal should be as short as possible and the wiring impedance should be as small as possible. Magnetic balance Hall sensors (CT1, CT2) are used to detect the output two-phase currents iA and iB. The built-in A/D converter of the F2812 is used to sample the stator currents of phases A and B, thus obtaining real-time stator current information. For speed feedback signal detection, an incremental photoelectric encoder is used as the speed detection device. It can output two square wave pulse signals with a 90° phase difference. After Schmitt triggering, the two pulse signals are sent to the quadrature encoder pulse unit (QEP) of the F2812 via optocouplers. After internal frequency multiplication by four, the pulses are counted by the general-purpose timer T3, and the speed feedback value is obtained using the T/M method. System Software Design The system program includes a main program, an SVPWM interrupt subroutine, and a display subroutine. The main program first completes the initialization work, including setting the comparison register COMCON, the full comparison action control register ACTR, the dead-time control register DBTCON, and the control register T1CON of general-purpose timer 1. It also sets the timing period register TIPR of general-purpose timer 1 according to the modulation period (frequency) TS. The interrupt subroutine calculates the values ​​of T1 and T2 based on the given frequency θ and voltage value Vr, and sets them to the full compare registers CMPR1-3 to prepare for the next modulation cycle. Conclusion This paper introduces an AC variable frequency speed control system based on the TMS320F2812 control core. It fully utilizes the high-speed computing performance of the TMS320F2812 to better achieve the speed and real-time performance required by the voltage space vector speed control system, and greatly simplifies the hardware circuitry.