1 Introduction

The design advantages of distributed power ^[1] have helped it spread to industrial controls, data communication, telecom and every application that uses complex systems with a requirement for multiple power and voltage levels. There was a time when the predominant power supply architecture consisted of a centralized power unit that distributed power throughout the system via a network of cables and supply bus bars, but as power demands have changed, so have system power topologies. Driven by increasing power consumption and a need for better supply performance, in conjunction with the availability of wide bandgap GaN and Sic products, more sophisticated power distribution architectures are being implemented today. The modern distributed power architecture (DPA) can spread the concentration of heat throughout the system, support high currents at different voltage levels and provide excellent transient response to rapidly changing loads. DPA architecture is widely used in AC/DC rectifier application where the front-end AC/DC power supply covers the power needs of the entire system. Then the required DC/DC stages are controlled locally in order to achieve high efficiency and improved static and dynamic performance. This way all the subsystems DC/DC connect to a single DC bus making it easier to design and upgrade the sub-systems.

DPA concept is also being increasingly used today in fast DC charging application because it enables modular design and allows adjusting to a wide range of output voltages. Here again a front-end power factor correction (PFC) stage, such as a three phase Vienna PFC, provides the high voltage DC bus which is then used to power multiple DC/DC stages that finally charge the battery. The modular approach makes it possible to achieve economies of scale for manufacturers, enabling them to reuse existing sub-units and design blocks when addressing new customers. In the event of a failure, the modular approach also simplifies maintenance and repairs. With the push towards shorter charging times the total power that is needed in a DC charger increases significantly. Consequently, the power delivered by each sub-unit and design block in a DC charger goes higher to provide a balance between performance, power, and ease of use. The sub-units themselves are based upon efficient multi-level, multi-phase topologies allowing heat generation to be spread across the available volume, as well as enabling scalability. The modular approach also enables general economies of scale, enabling manufactures to quickly implement a wide array of charger output powers as market demands develop.

Similar DPA approach is also being used today in solar inverter and energy storage systems (ESS), specifically, in solar string inverters with ESS. For the solar string inverter with or without ESS capability, the load-end DC/AC inverter supply covers the power needs of the entire system while achieving high efficiency and improved static and dynamic performance. Then the front-end DC/DC stages are operated locally in order to achieve high efficiency, optimized maximum power point tracking (MPPT) and other features, such as, rapid shutdown control. Common factors that impact energy production in a solar inverter include shading, different module types and orientations or large temperature fluctuations. In this case a distributed architecture can increase energy production largely due to having the maximum power point tracking (MPPT) capability at each dc/dc stage. The DPA architecture also provides obvious advantage of increased uptime for string inverters. Since string inverters are converting less power for fewer panels, if one string fails, the whole array's energy is not lost, just the power from that string. The same applies when inverters need to be disconnected for preventive maintenance of system components. Also, during scheduled maintenance of system components (excluding the inverter stage), the array can be turned off in smaller sections, which further increases uptime.

Thus, with overall goals of cost effectiveness, scalability, modular design, high efficiency, optimize operation and fast static and dynamic performance DPA provides obvious advantages in many AC/DC, DC/DC and DC/AC power conversion applications.

C2000 microcontrollers (MCUs) with its control optimized high speed CPU, flexible control peripherals and fast serial interface (FSI) is a perfect fit for implementing distributed digital control of such DPA systems. Multiple C2000 MCUs can be used to control multiple power conversion stages and then all the MCUs can establish a very fast communication link between them using their FSI ports. This approach essentially implements digitally controlled flexible distributed power control architecture (DPCA) for many DPA systems. The new FSI module is a serial communication peripheral capable of reliable high-speed communication across isolation devices. It provides a higher speed, lower latency, noise tolerant signaling across isolation with built in error detection and correction. It provides variable packet size (2 to 32 bytes, not meant for large data transfer) and so ideal for bytes of data transfer between control loops in a DPCA system. With embedded data robustness checks, data-link integrity checks, skew compensation and integration with control peripherals, the FSI module can enable high-speed, robust communication in any DPA system and thus allows implementation of distributed power control architecture (DPCA).