This article outlines the frequency conversion technology, introduces the relevant knowledge of IRMCF341 and IPM, and then divides IRMCF341
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The application, analysis and practice on the frequency conversion home appliance show that the sensorless vector control technology based on the IRMCF341 microcontroller has many advantages such as high efficiency and low cost, which will be widely used.
1. Overview As international oil prices continue to rise, people are increasingly aware of the importance of energy. How to use energy efficiently and environmentally is a hot issue that governments, academics, and industry all pay attention to. Various measures to encourage energy conservation and emission reduction are also emerging. Energy conservation has become a hot topic in today's society. Reducing the energy consumption of electric motors is another battle of this battle. According to authoritative statistics, the annual consumption of electric energy by electric motors in the world accounts for more than 80% of the global annual energy consumption, and the most influential to us is the motor energy consumption in household appliances. Such as refrigerators, air conditioners, washing machines, etc. Frequency conversion technology is an effective means to reduce motor energy consumption. Frequency conversion appliances have already occupied the mainstream in western developed countries. In 2000, inverter air conditioners accounted for more than 90% of the air conditioner market, inverter refrigerators accounted for 60%, and inverter refrigerators accounted for 30-40. %, and our domestic inverter home appliances started late, but in recent years, the rapid development, domestic major power giants have launched a variety of frequency conversion home appliances, the State Council Development Research Center Market Economy Research Institute predicts: by 2010, inverter air conditioners will occupy More than 85% of the air-conditioning market, 63% of consumers will choose inverter air conditioners.
Frequency conversion control of frequency conversion appliances has various implementation methods, each with its own advantages and disadvantages, but which method is cheaper, more efficient, and better effect is our concern. This paper introduces a sensorless vector control technology based on IRMCF341 microcontroller.
2. Introduction to Frequency Conversion Technology In general, frequency conversion technology is a technology that realizes speed control by changing the frequency of alternating current of the motor. Taking air-conditioner compressors as an example, the motors used in the current mainstream inverter air conditioners are all DC motors, which are divided into square wave motors and sine wave motors according to their driving waveforms. There are two kinds of technologies commonly used for these two motors, namely 120 degree control technology. The 180 degree control technology, which is commonly referred to as square wave drive technology and sine wave drive technology, is a brief comparison of the two technologies.
(1) 120 degree control technology:
The 120-degree control technology means that only two phases of the motor's 3-phase line are turned on at any time, and the phase 1 is turned off. In the driving waveform, that is, in the 180-degree electrical cycle, only one phase line is continuously energized by 120 degrees and turned off by 60 degrees. This technology drives the waveform as a square wave, using the common 6-shot commutation method for commutation control. It has the advantages of simple algorithm and relatively easy implementation, but it also has some disadvantages: It produces a large slip rate when the speed and torque change, resulting in large current, ie energy consumption ratio, low efficiency; poor torque characteristics. When the load is increased, the speed will be lost; the low-speed torque characteristics are poor, and the jitter is easy to occur. The 120-degree control technology was partially adopted in the early frequency conversion home appliances, but due to its low efficiency, poor torque characteristics and other issues have been gradually replaced by 180-degree control technology. The most advanced 180 degree control technology on the market is based on magnetic field oriented vector frequency conversion technology.
(2) Vector frequency conversion control system based on FOC (field orientation):
The control principle is that the magnetic flux and torque can be directly controlled by a certain coordinate conversion, and the double closed loop control of current and speed is realized. The utility model has the advantages of realizing rapid dynamic response without generating a large flow, that is, energy consumption ratio, high efficiency, good torque performance, and ensuring a sufficiently hard torque characteristic without losing the rotational speed. However, its motor control algorithm is relatively complex, with high real-time requirements and high requirements for software personnel. It is mainly used in applications with fast load changes and high dynamic response requirements, such as inverter air conditioners, washing machines, machine tool control systems, etc.
3. Introduction to IRMCF341 Chip 3.1 Overview IRMCF341 is a new high-performance, low-cost motor control IC for inverter-less control applications for inverter home appliances. It adopts the most advanced vector control technology based on magnetic field positioning, and realizes three-phase current reconstruction of the motor by single-resistance current sampling, thus achieving double closed-loop vector control of FOC current loop and speed loop. The driving mode is 180-degree sine wave. . The IRMCF341 contains two high-performance processing engines, one is an 8-bit high-speed 8051 core, and the other is a 16-bit motor control engine (MCE) for motor sensorless control. The 8051 core executes at an instruction rate of two system clocks (eg 60MIPS @ 120MHz system clock). 8051 core and MCE processor: Data exchange and command input functions can be realized by exchanging data through dual port RAM. MCE includes all the control resources required to control the motor based on hardware circuitry, such as PI regulators, vector rotation, angle estimator, multiplier/divider, low loss SVPWM, and single resistor current sampling/reconstruction. The key elements of a complex sensorless control algorithm (eg, angle estimator) are all defined control modules, and users can design their own motor control algorithms by using a graphical compiler that seamlessly interfaces with the MATLAB/SIMULINK environment. (Connect to each unit function module and compile in MATLAB/SIMULINK environment). The simulation and debugging of the 8051 code can be done through a third-party debugging tool based on the JTAG port. The 51 program memory in the IRMCF341 is 48K of RAM in a small QFP64 lead-free package.
IRMCF341
The IRMCF341 is a development-oriented version with 48K of program memory in RAM that makes it easy to load 8051 and MCE control code from an external EEPROM. The OTP version or the mask version IRMKK341 with the exact same pin can be used for mass production. Typical applications are as follows:
3.2 Structure and function of IRMCF341
The internal block diagram of IRMCF341 is shown in Figure 2 below:
System block diagram of the FOC algorithm function:
The so-called FOC control algorithm refers to: the stator AC current Ia, Ib, Ic in the three-phase coordinate system, through the three-phase-two-phase transformation (CLARK transformation), equivalent to the alternating current Ia1Ib1 in the two-phase stationary coordinate system And then by the rotor field oriented rotation transformation (PARK transformation), equivalent to the DC current Im1, It1 in the synchronous rotating coordinate system (Im1 is equivalent to the excitation current of the DC motor; It1 is equivalent to the armature current proportional to the torque ), and then imitate the control method of the DC motor to obtain the control amount of the DC motor. Then, using the anti-PARK transform, the inverse CLARK transform converts the DC control amount into the required three-phase AC amount, thereby controlling the motor. Since the 341 adopts the control method of the transmitterless, the start of the first 341 cannot be started in a closed loop manner, and the starting manner is as follows: First, the rotor is moved to the designated position (PARK positioning) by applying a specific vector to the motor. Open loop operation with the electrical angle at the end of the PARK as the starting point. After reaching the threshold speed, it cuts into the closed loop mode. If the flux is successful, the real closed loop control is implemented and the FOC control algorithm is executed.
4 IRMCF341 development environment
Hardware platform:
IRMCS3041 design platform
Software design platform:
Use the built-in EXCEL table to calculate the configuration parameters, and use MCE Designer to debug the motor.
You can use MATLAB for MCE structure design and KEIL uVision2 for 8051 code debugging.
5 Introduction to IPM
IPM (Intelligent Power Module), the intelligent power module, not only integrates the power switching device and the driving circuit. Moreover, fault detection circuits such as overvoltage, overcurrent and overheating are built in, and detection signals can be sent to the CPU. It consists of a high speed, low power die and an optimized gate drive circuit as well as a fast protection circuit. Even if a load accident or improper use occurs, the IPM itself can be guaranteed to be free from damage. IPM generally uses IGBT as a power switching component, and has an integrated structure of a current sensor and a driving circuit. IPM is winning more and more large market with its high reliability and ease of use. It is especially suitable for inverters and various inverter power supplies for driving motors. It is a variable frequency speed control, metallurgical machinery, electric traction, servo drive, and frequency conversion appliances. A very ideal power electronic device.
IRAMS16UP60A PlugNDriveTM Integrated Power Module (IPM) is one of IR's iMOTION integrated design platform series. In addition to integrating six high-voltage power transistors and driver chip IR2136 in a small insulative package, it also has overheating and overcurrent. Undervoltage and built-in deadband control prevent high-side IGBT (insulated gate bipolar transistor) and bottom IGBT short-circuit protection functions to ensure safe operation and system reliability. In addition, it can be supplied with a +15V DC power supply, which simplifies its use in motor drive applications and accelerates the development of the final product.
In addition to the well-known advantages (smaller, more reliable, visible as a single component) compared to discrete components, the IRAMS16UP60A module also allows designers to avoid several of the problems often encountered in IGBT inverter design:
(1) The module has a very low circuit inductance, which can reduce the voltage spike, and can work at a higher switching frequency at a lower switching loss;
(2) The transmission delay matching of all low-end and high-end IGBTs can prevent DC current from being applied to the motor;
(3) Built-in dead time control provides sufficient dead time to prevent short circuit of high-end IGBT and low-end IGBT;
(4) Fail-safe operation to ensure shutdown when over-current and over-voltage, so that designers do not need to design over-current and over-voltage protection circuits;
(5) Temperature monitoring and phase current detection pins are provided.
5 IRMCF341 is applied to inverter home appliances
5.1 Application Analysis
The IRMCF341 is used in variable frequency home appliances and is aimed at high functionality and power saving. For example, it is required to have high speed and high output, good control performance, small size and light weight, large capacity, high comfort, long life, safety and reliability, quietness, and power saving.
341 is mainly used in permanent magnet synchronous motor. AC permanent magnet synchronous motor is a kind of motor that can be directly started in 50Hz three-phase AC environment. Its operation mode is: asynchronous start and synchronous operation. The AC permanent magnet synchronous motor is a high-efficiency energy-saving motor made by replacing the traditional electric excitation with rare earth permanent magnet material. It not only has the advantages of simple structure, reliable operation, low heat generation, etc., but also has small volume, light weight and loss. The remarkable features such as small size and high efficiency can achieve high performance that is difficult to achieve with conventional electric excitation motors. In addition, 341 is based on FOC (Field Oriented Direction) vector variable frequency control, and the driving mode is 180 degree sine wave, which makes the performance of this aspect fully exerted. At the same time, 341 adopts electric single resistance current sampling and reconstruction technology, which saves cost. Resistor current sampling reconstruction technology refers to 341 using the current state corresponding to the current PWM,
With the appropriate delay time (avoiding current oscillation), the actual bus current can be obtained, and the currents of many moments can be recombined according to the timing of PWM to obtain the three-phase current of the motor. As shown in the figure:
In the face of permanent magnet synchronous motor, the characteristics of single-resistance current sampling are in line with the characteristics of frequency conversion household appliances, which makes 341 widely used in frequency conversion household appliances. Firstly, it is air-conditioning. After using the variable-modulation control of IRMCF341, it has expanded. The working range of the compressor can achieve cold and warm control without the need for the compressor to operate in the intermittent state, thereby reducing power consumption and eliminating discomfort caused by temperature fluctuations, and the energy saving effect is greatly improved.
Secondly, in terms of washing machines, in the past, variable frequency control was used to achieve variable speed control, and the washing performance was improved. In addition to energy saving and quieting, the IRMCF341 washing machine introduced new control contents in terms of ensuring soft washing of clothes; currently, Beineng launched Based on the 341 inverter washing machine solution, (1) vector control: torque, speed double closed loop control; optimal torque characteristics; lower energy consumption; higher efficiency; (2) simple peripheral circuit: no need for expensive Current sensor; single-resistance sampling does not require complex current detection circuits; it is about 25% lower than similar products. It is the typical and excellent application of 341 in frequency conversion technology.
In terms of air conditioners and washing machines, the 341-based inverter solution has also been applied in some well-known large enterprises in China, and has been mass-produced.
5.2 Hardware Design
(1) Main control circuit
(2) IPM drive circuit design
The IPM (Intelligent Power Module) drive circuit mainly completes the power amplification of the six PWM signals generated by the 341 chip, and drives the internal power tube to drive the motor.
5.3 Software Design
(1) Main control flow (2) Motor control flow
6 Summary This paper briefly describes the market background and frequency conversion technology of inverter household appliances. It mainly introduces the characteristics and functions of the IRMCF341 chip, develops the environment and analyzes its application in the frequency conversion home appliance. Due to the excellent control performance of the IRMCF341 and the humanized development process, it does not stay in the application of home appliances, except Supporting PMSM, BLDC and other DC motors, IR's new code already supports ACIM AC induction asynchronous motors, which greatly expands the application of IRMCF341 in variable frequency control. At present, customers have used IRMCF341 to develop successful variable frequency water pumps and variable frequency treadmills. Frequency treadmill solution: In FOC vector control mode, it provides enough starting torque. In the case of impact load, speed loop and current closed double closed loop vector control, the reaction speed is fast, and the main circuit adopts large capacity. Smoothing capacitor, specially modified for the treadmill load, can effectively and smoothly DC bus voltage, can fully meet the requirements of treadmill load characteristics, achieve 5HZ at low speed, smooth start without jitter load. The effect has been tested to exceed the level of similar foreign products.
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