How to reduce energy consumption by intelligent motor control

More and more businesses and individuals are looking for ways to reduce their energy footprint and increase their use of renewable resources. Where should we focus in order to have a significant effect?

More than 65% of the world’s electricity is used to power motors and power supplies in industrial settings, commercial buildings, and individual homes. According to Our World in Data, 60% of electricity comes from burning coal and natural gas, and less than 10% comes from renewable energy sources. Intelligent variable frequency digital motor control can reduce energy consumption by more than 25%. Intelligent digital power control can maximize the efficiency of solar and wind power production and minimize power consumption in very high energy-consuming equipment. In this article, we will explore some trends in intelligent control applications and share examples of how intelligent control can reduce energy consumption and improve the efficiency of renewable energy.

Intelligent Motor Control

Air conditioners (Figure 1) are major power consumers on the grid. While specific efficiency standards vary by region, all designs need to implement advanced motor control and power factor correction (PFC) algorithms to achieve target ratings and meet power factor specifications.

Controlling each motor in an air conditioner (compressor, cooling fan) may require a control loop running at frequencies up to 20kHz. On the other hand, PFC typically requires operating frequencies up to 50kHz. Therefore, in order to reliably implement multiple high-frequency control loops, the microcontroller (MCU) must be able to process calculations quickly and efficiently with little latency.

Figure 1: Air conditioning system block diagram

MCUs for air conditioning systems require multiple analog-to-digital (ADC) and pulse-width modulation (PWM) channels to flexibly synchronize with switching events and independently sample and control both inverters and the PFC circuit. Analog comparators and PWM interference cancellation are required for power electronics protection.

The MCU for air conditioners will also provide clock protection in accordance with the International Electrotechnical Commission 60730 requirements, including two on-chip oscillators with better than 1% accuracy, as well as watchdog and clock failure detection circuits.

The Dual Motor Control with Digital Interleaved PFC for Air Conditioners reference design provides hardware and software examples for a single 64-pin C2000Tm TMS320F2800137 MCU that controls compressor and fan motors at >97% efficiency, with a digitally interleaved 72kHz boost PFC stage that delivers >96% power efficiency (Figure 2), along with many common system and communication functions.

Figure 2: Power efficiency of the air conditioner PFC converter reference design

Only 40KB of flash memory and 30% of the central processing unit (CPU) are consumed due to the optimized C2000 real-time MCU architecture designed to reduce latency between sensing (ADC), processing (CPU) and control (PWM). According to TI benchmarks, an Arm? Cortex?-M7F MCU needs to run at 240MHz to provide the same overall performance as our 120MHz device.

The reference design is scalable to single-motor and motor-enhanced PFC applications with the smaller TMS320F2800137 family 48- or 32-pin packages and 64KB to 256KB on-chip non-volatile flash memory options. The reference design can also be used to improve the efficiency of nearly any motor from residential air conditioning system motors to variable speed, variable load systems, from low voltage battery-powered devices in industrial applications to ultra-high power AC drives.

Intelligent digital power supply

For digital power, the goal is to create renewable energy more efficiently, as well as convert and use energy more efficiently. For example, the solar market is trending away from centralized high-power photovoltaic inverters and toward distributed low-power solar systems, such as microinverters and power optimizers. Typically, one such microinverter and power optimizer is installed for every few solar panels to produce lower energy losses and higher efficiency under complex sunlight conditions. When more such module-level power electronics are added to a solar system, a real-time MCU needs to be low-cost but still powerful enough to perform maximum power point tracking for each solar panel under its control.

The growing demand for energy utilization around the world requires efficient, compact and stable power supplies. This requirement has challenged designers of power conversion systems to provide power-dense designs while meeting the efficiency and fast transient response requirements of "small enough but high performance" systems. In addition, the push to digitize existing analog designs to improve scalability has also led to the need for low-cost, high-performance real-time MCU solutions.

New real-time control MCU series

As a new member of the C2000 real-time MCU product family, the TMS320F2800137 helps reduce the cost of real-time technology and expands a long-term software-compatible platform to provide low, medium and high-level options for analog and digital designers. With this new family, engineers in motor control, grid infrastructure and industrial power applications can create products that reduce energy footprints and increase the utilization of renewable resources.