Inverter is a power converter in motion control system. Motion control system is the development of electrical drive technology as electromechanical energy converter. Today's motion control system is a multi-disciplinary technical field, the general trend of development are: drive communication, high-frequency power converter, control of digital, intelligent and networked. Therefore, the inverter as a system of important power conversion components, to provide controllable high-performance variable frequency AC power and get rapid development.

Experienced about thirty years of research and development and application practices, with the application of new power electronics and high-performance microprocessors and control technology, the inverter cost more and more high performance, smaller and smaller, and manufacturers Still continue to improve the reliability of the inverter to achieve further small and lightweight, high performance and multi-functional and pollution-free and new efforts. The pros and cons of inverter performance, depends on the output of the AC voltage harmonics affect the motor, the second depends on the power grid harmonic pollution and input power factor, three depends on their energy loss (ie efficiency) how? Here only the large amount of AC-DC-AC inverter, for example, from the technical point of view in the following aspects will be further developed:

Pulse Width Modulation Converter control methods: sine wave pulse width modulation (SPWM) control. Eliminate the specified number of harmonic PWM control. Current tracking control. Voltage Space Vector Control (Flux Tracking Control). Advances in AC Motor Frequency Control: From scalar control (V / f control and slip frequency control) to high dynamic performance vector control and direct torque control. Development of speed sensorless vector control and direct torque control system.

Advances in microprocessors have made digital control a trend toward modern controllers . Motion control systems are fast systems, especially AC motors. High performance control requires storing multiple data and rapidly processing large amounts of information in real time. In recent years, major foreign companies have introduced DSP (Digital Signal Processor) -based cores, together with the peripheral functions required for motor control, are integrated in a single chip called DSP monolithic motor controller ADI's ADMC3 × × series, TI's TM320C240 and Motorola's DSP56F8 × × series), the price is greatly reduced, the volume is reduced, compact, easy to use and improve reliability.

The maximum speed of the DSP is 20 ~ 40MIPS, single-cycle instruction execution time of up to tens of nanoseconds, compared with the common microcontroller, digital processing capabilities to enhance 10 to 15 times, to ensure that the system has superior control performance. Digital control makes the hardware simplified and the flexible control algorithm makes the control have great flexibility and can realize the complex control law, make the modern control theory become a reality in the motion control system, easy to connect with the upper system for data transmission, and easy to diagnose the fault Strengthen the protection and monitoring functions to make the system intelligent (such as some frequency converters have self-tuning function).

Main circuit power switching components from the off, modular, integrated, intelligent, increasing switching frequency, switching loss further reduced. Low-voltage small-capacity inverter commonly used power switching devices are: power M OSFET, IG-BT (Insulated Gate Bipolar Transistor) and IPM (Intelligent Power Module).

The medium-voltage high-capacity inverters include GTO (Gate Turn-off Thyristor), IGCT (Integrated Gate Commutated Thyristor), SGCT (Symmetrical Gate Commutated Thyristor), IEGT (Injection Enhancement Gate Transistor) and High Voltage IGBT. Inverter topology of the main circuit: Inverter side of the converter on the low-voltage small capacity often use 6-pulse converter, and the large capacity of the use of multiple 12-pulse multiplexer.

Load-side converters often use two-level bridge inverters for low-voltage and low-capacity small-capacity but multi-level inverters for medium-voltage large-capacity. It is noteworthy that for the four-quadrant drive, in order to achieve the inverter regenerative energy feedback to the grid and save energy, the grid-side converter should be a reversible converter, appeared dual power PWM inverter can flow in both directions, Appropriate control of the grid-side converter can make the input current close to the sine wave, and the system's power factor close to 1, reducing the pollution of the grid.

At present, low, medium voltage frequency converter has such products. The adoption of common DC bus technology enables better utilization of the power of multiple (or multi-axis) drive systems to improve the overall system operating efficiency and reduce the price of the inverter itself. Common DC bus can also be regenerative and non-regenerative. Explore the use of resonant DC ring technology so that the inverter power switch in soft-switching state, the device greatly reduced loss, the switching frequency can be further increased due to voltage and current spikes caused E-MI problems can be suppressed, the buffer circuit can be canceled.

AC synchronous motor has become a new star exchange adjustable transmission, especially permanent magnet synchronous motor, brushless motor access to the structure, high power factor, high efficiency, the rotor speed strictly with the power frequency to keep pace. Synchronous motor frequency control system has his frequency control and automatic control of two major categories.

Self-controlled variable frequency synchronous motor and the DC motor in principle very similar to the use of power electronic converter to replace the DC motor mechanical commutator, such as the use of AC - DC - AC voltage inverter called "DC without commutator motor" Or "brushless DC motor (BLDC)." The traditional self-controlled frequency conversion synchronous machine speed control system has a rotor position sensor, is now developing a rotor-free position sensor system.

He frequency control method of synchronous motor can also be used vector control, the vector control of rotor field oriented by induction motor is simpler than asynchronous motor. Switched Reluctance Motor (SR) is a special type of synchronous motor. The stator is a double-salient pole structure. It has firm brushless and high output torque. Since the SR motor winding needs only unidirectional current, it is supplied with power Just unipolar power converter on it, the circuit is simple.

The traditional SR motor speed control system also needs position detector, and SR speed control system without position sensor is also being developed. The advantage of SR motor is prominent and its application field is expanding day by day. The less obvious is that SR motor power converter outputs irregular current pulses, causing running noise and torque ripple problems to be prominent at low speed. This needs to be further improved.

AC variable frequency speed regulation technology is a combination of strong and weak, mixed, mechatronic technology, it is necessary to deal with the conversion of huge power (rectifier, inverter), but also deal with the collection, transformation and transmission of information, so its common technology must be divided into Power and control two major parts. The former should solve the technical problems related to high voltage high current and the application technology of new power electronic devices. The latter should solve the hardware and software development problems (based on the control theory and intelligent control strategy of modern control theory) Full digital control technology).

Its main development directions are as follows: to achieve a high level of control.

Control strategy based on motor and mechanical model with vector control and magnetic field control

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