Distributed Frequency Converters: A Comprehensive Guide

Distributed frequency converter (DFC), as a new type of power electronic device, is gradually emerging in the fields of industrial automation and new energy. Compared with traditional centralized frequency converters, DFC has higher flexibility and reliability, and can better adapt to the diverse demands of modern industry for power systems. This article aims to deeply explore the working principle, technical characteristics and advantages of DFC in practical applications, and provide readers with a comprehensive understanding. Through in-depth analysis of DFC technology, it is helpful to promote its widespread application in the industrial field, improve production efficiency and reduce energy consumption.

The core idea of ​​distributed frequency converter (DFC) is to decompose the traditional centralized high-power inverter into multiple small power modules, and achieve high-power output through parallel or series connection. Each power module has an independent control unit and can be flexibly configured according to load requirements.

The main technical features of DFC include:

Modular design: The power module adopts a standardized design, which is easy to replace and maintain, and improves the reliability of the system.

Parallel/series topology: Through parallel or series connection, the output power and voltage can be flexibly adjusted to meet the needs of different loads.

Vector control: Advanced vector control technology is used to achieve high-performance control of the motor and improve the dynamic response speed of the system.
Fault diagnosis: Each power module has a self-diagnosis function, which can detect faults in time and take corresponding protection measures to ensure the safe operation of the system.
Compared with traditional centralized frequency converters, DFC has higher flexibility and reliability. The modular design makes the system easier to expand and maintain, and the parallel/series topology improves the redundancy of the system and reduces the risk of failure. In addition, DFC's vector control technology can achieve high-precision control of the motor and improve the efficiency of the system.

The control strategy of DFC is the core of its efficient operation. Common control algorithms are mainly the following

1. Vector Control

Principle: Decompose the three-phase stator current into flux component and torque component, and control these two components to achieve independent control of the motor torque and magnetic field.

Advantages: Fast dynamic response, high accuracy, insensitive to changes in motor parameters.

Disadvantages: The control algorithm is complex and requires precise motor parameters.

JCF and JCME distributed converter, with independent intellectual property rights, is featured with compact structure, convenient operation, and flexible expansion. It provides customers with a full range of control methods such as open loop vector control, /F control, and closed loop vector control.

2. Direct Torque Control (DTC)

Principle: By directly comparing the deviation between the actual torque and flux and the given value, select the appropriate voltage vector to achieve direct control of the motor torque and flux.
Advantages: Fast dynamic response and simple structure.
Disadvantages: Large torque and flux fluctuations, requiring complex switch tables.
3. Model Predictive Control (MPC)
Principle: Based on the motor model, predict the motor state in the future, and select the optimal control input through the optimization algorithm to achieve high-performance control of the motor.
Advantages: It has multivariable coupling control capabilities and is robust to model uncertainty.
Disadvantages: Large amount of calculation and high real-time requirements.
The following factors should be considered comprehensively when selecting a suitable control algorithm:

Motor type: asynchronous motor, synchronous motor, etc.
Load characteristics: variable load, constant load, etc.
Control performance requirements: dynamic response, accuracy, stability, etc.
Hardware platform: DSP, FPGA, etc.

DFC communication technology

The communication between DFC modules is the key to achieving system coordinated control. Common communication methods are:

CAN bus:
Advantages: High real-time performance, strong anti-interference ability, and low cost.
Application: Data exchange between modules, fault diagnosis, etc.
PROFINET:
Advantages: High real-time performance, flexibility, and strong scalability.
Application: Industrial automation field, communication with PLC and other devices.
Ethernet:
Advantages: High bandwidth and long transmission distance.
Application: Data acquisition, remote monitoring, etc.
The following factors should be considered when choosing a communication protocol:

Communication rate: Meet the needs of real-time control.
Reliability: Ensure the accuracy of data transmission.
Cost: Choose a cost-effective communication method.
Network topology: Choose a suitable network topology according to the system structure.

DFC heat dissipation design

DFC power modules are dense and generate a lot of heat. Heat dissipation design is the key to ensure stable operation of the system. Common heat dissipation methods are:

Natural cooling: Use air convection for heat dissipation, suitable for low power density systems.
Air cooling: Use fans for forced cooling, suitable for medium power density systems.
Liquid cooling: Use liquid as the cooling medium, suitable for high power density systems.
Heat pipe: Use heat pipes to transfer heat to the radiator to improve heat dissipation efficiency.
Optimization measures for heat dissipation design:

Reasonable layout: The layout of the power module should take into account the airflow organization to avoid heat accumulation.
Heat dissipation material: Select materials with good thermal conductivity, such as aluminum alloy, copper, etc.
Heat dissipation area: Increase the heat dissipation area to improve heat dissipation efficiency.
Temperature monitoring: Real-time monitoring of the power module temperature to prevent overheating.