Renesas Electronics RAMDA algorithm variable frequency drive solution

As green environmental protection, energy conservation and emission reduction have gradually become the themes of the Chinese market and society, government supervision has been increasing year by year, and the requirements for low energy consumption of various products have become stricter. From small home appliances such as razors and hair dryers to industrial automation production lines, a wide variety of motors play a central role in various consumer products and industrial products. In order to achieve the goal of energy saving and environmental protection, motor control technology has become particularly important. For the Chinese market, while actively promoting high-performance, low-power RX microcontrollers, Renesas also developed the RAMDA algorithm, an advanced motor control solution with completely independent intellectual property rights, to build high-performance, high-reliability permanent magnet synchronous motors Drive solutions to help customers develop a new generation of green and environmentally friendly new products.

The possession of household appliances is huge, and the total energy consumption is also very considerable, which is the focus of national attention. In particular, the energy efficiency requirements of air conditioners, a large energy consumer in household appliances, are increasing year by year, and the driving technology of the air conditioner compressor is the key technology to improve energy efficiency.

By combining the RAMDA algorithm on the RX microcontroller, customers can quickly develop a high-performance, high-reliability air conditioner outdoor unit system.

The RAMDA algorithm is an advanced Variable Frequency Drive solution provided by Renesas Electronics, and Renesas Electronics has completely independent intellectual property rights.

The RAMDA algorithm integrates motor control and single-phase AC power factor correction technology, and cooperates with the RAMDA program framework to provide a solid foundation platform and a friendly user interface for the development of the user's overall system.

The RAMDA algorithm has two core technologies: A-PAM function for adjusting the power factor of the power supply and advanced compressor driving technology. Such an algorithm does not increase hardware costs. On the contrary, the two core technologies provide streamlined hardware requirements.

After long-term market verification, it has been fully recognized by customers.

The following figure shows the RAMDA control logic block diagram:

A-PAM technology for power factor correction

• Variable DC bus voltage • Adjustable overall efficiency of the frequency conversion system

Based on A-PAM, users can accurately control the output value of the DC bus voltage, and provide sufficient DC bus voltage on the premise of ensuring the overall efficiency of the system. Compared with traditional PFC, A-PAM can limit the output value of the DC bus voltage, and the efficiency of the PFC circuit is relatively high.

By limiting the DC bus voltage, customers can choose filter capacitors with lower withstand voltage levels to achieve lower system costs. For example, in a single-phase 220V power supply system, the output DC voltage of a traditional PFC is generally 350[V]-390[V], and the system designer will choose a 450[V] withstand voltage filter capacitor. After adopting A-PAM technology, the DC bus voltage can be limited to a maximum of 340[V]±1[V] according to load changes in real time, and the system design can select 400[V] withstand voltage filter capacitors, which reduces the system Hardware costs.

In addition, the A-PAM technology does not require a hardware circuit to detect the zero-crossing point or amplitude of the AC voltage, which further reduces the system cost.

RAMDA algorithm provides basic permanent magnet synchronous motor drive function, based on the basic parameters of the motor (number of poles, winding resistance, synchronous inductance, maximum magnetic flux, moment of inertia) to make the motor run efficiently and stably.

The RAMDA algorithm is unique in its original torque control algorithm.

Single-rotor motors are commonly used in home appliances, such as air-conditioning compressors. Driven by ordinary algorithms, a motor with a single rotor structure will cause system vibration. This kind of vibration is harmful. Take the air conditioning system as an example. In the case of low speed (below 30[rps]), system resonance will be formed, system noise will increase, and in severe cases, stress concentration points of the air conditioning system will be damaged. In high-speed operation, the peak value of the motor phase current is high, the harmonics are large, and the high frequency noise is high, and it limits the output capacity of the inverter. In response to such market requirements, RAMDA algorithm includes the following two torque fluctuation compensation technologies:

Under the action of G-type torque control, the system vibration reaches the lowest level, thus ensuring the stable and normal operation of the system at low speed, and expanding the low frequency range of the actual operation of the system. It can be seen from the figure below that G-type torque control can greatly reduce system vibration when it is lower than 30 [rps].

The comparison chart of the vibration amplitude of the system at various speeds under various torque controls.