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Inverter classification and development trend

Jan 15, 2021

Inverter classification and development trend

Classification of inverters

There are many ways to classify the frequency converter, according to the main circuit working mode, it can be divided into voltage type frequency converter and current type frequency converter; according to the switching mode, it can be divided into PAM control frequency converter, PWM control frequency converter and high carrier frequency PWM control inverter; according to the working principle, it can be divided into V/f control inverter, slip frequency control inverter, vector control inverter, etc.; according to the classification of use, it can be divided into general inverter, high-performance special inverter, High-frequency inverter, single-phase inverter and three-phase inverter, etc.


  VVVF: change voltage, change frequency CVCF: constant voltage, constant frequency. The voltage and frequency of AC power supply used in various countries, whether used in homes or factories, are 400V/50Hz or 200V/60Hz (50Hz), etc. Generally, a device that converts alternating current with a fixed voltage and frequency into alternating current with a variable voltage or frequency is called a "frequency converter." In order to generate variable voltage and frequency, the device first converts the AC power of the power supply into direct current (DC).



  The frequency converter used for motor control can change both the voltage and frequency.


Inverter classification and development trend


   1. Classified according to the link of transformation:

It can be divided into AC-AC frequency converter, that is, the direct conversion of power frequency AC into AC with adjustable frequency and voltage, also known as direct frequency converter; AC-DC-AC frequency converter, which first converts the power frequency AC into DC through the rectifier , And then convert DC into AC with adjustable frequency and voltage, also known as indirect frequency converter, which is a universal frequency converter widely used at present.


   2. According to the nature of DC power supply:

   (1) Current type inverter


The characteristic of the current type inverter is that the intermediate DC link uses a large inductance as the energy storage link to buffer the reactive power, that is, to suppress the change of the current, so that the voltage is close to a sine wave. Because the DC internal resistance is large, it is called a current source inverter ( Current type). The characteristic (advantage) of the current type inverter is that it can restrain the frequent and sharp changes of the load current. Often selected for occasions where the load current changes greatly.


   (2) Voltage type inverter


The characteristic of the voltage type inverter is that the energy storage element of the intermediate DC link adopts a large capacitor, and the reactive power of the load will be buffered by it. The DC voltage is relatively stable, and the internal resistance of the DC power supply is small, which is equivalent to a voltage source, so it is called a voltage type inverter. Often selected for occasions where the load voltage changes greatly.


   In addition, the frequency converter can also be classified according to the output voltage adjustment mode, according to the control mode, according to the main switch components, and according to the input voltage level.


Inverter classification and development trend


  Inverter development trend

   Inverter is a power converter in a motion control system. Today's motion control system is a technical field that includes multiple disciplines. The general development trend is: AC drive, high frequency power converter, digital control, intelligent and networked control. Therefore, the frequency converter, as an important power conversion component of the system, provides a controllable high-performance variable-voltage and variable-frequency AC power source and has developed rapidly.


Today in the 21st century, the substrate of power electronics has been transformed from Si (silicon) to SiC (silicon carbide), enabling new power electronics devices to enter high-voltage large-capacity, high-frequency, module modularization, and miniaturization. In the era of intelligence and low cost, a variety of new electrical equipment suitable for variable frequency speed regulation are under development. With the rapid development of IT technology and the continuous innovation of control theory, these inverter-related technologies will affect its development trend.


   With the expansion of the market and the diversification of user-side needs, the functions of domestic frequency converter products are constantly improving and increasing, the integration and systematization are getting higher and higher, and some special frequency converter products have appeared. It is understood that in recent years, China's frequency converter market has maintained a growth rate of 12-15%, and it is expected to maintain a growth rate of more than 10% for at least the next 5 years. At present, the growth rate of inverter installation capacity (power) in the Chinese market is actually around 20%. It is expected that the inverter market will become saturated and mature gradually after at least 10 years.


  1. Intelligent


   After the intelligent frequency converter is installed in the system, it can be easily operated and used without so many function settings. It has obvious working status display, and can realize fault diagnosis and troubleshooting, and can even perform automatic component conversion. The Internet can be used to remotely monitor and realize the linkage of multiple inverters according to the process program, forming an optimized integrated management and control system for the inverter.


  2. Specialization


   According to the characteristics of a certain type of load, a specialized frequency converter is manufactured in a targeted manner, which is not only conducive to economical and effective control of the load motor, but also reduces manufacturing costs. For example: inverters for fans and water pumps, special inverters for hoisting machinery, special inverters for elevator control, special inverters for tension control, and special inverters for air conditioners.