Woodward MicroNet ™ Analysis and Application of Simplex and Plus Digital Control Systems

Woodward MicroNet ™  Analysis and Application of Simplex and Plus Digital Control Systems

Introduction

Woodward MicroNet ™  Digital control system is a high-performance and high reliability solution for industrial power control field. This series of products is widely used for precise control and protection of power devices such as gas turbines, steam turbines, diesel engines, and water turbines. The MicroNet Simplex and MicroNet Plus control systems covered in this manual have flexible configuration options that support diverse requirements ranging from simple applications to complex redundant systems. As one of Woodward's core products, the MicroNet platform is renowned in the fields of energy, marine, and industrial automation for its outstanding real-time performance, modular design, and extensive support for industrial communication protocols.

This article is based on the complete content of Woodward's official product manual 26166V1 (revised version V, released in August 2024), aiming to provide in-depth technical analysis, configuration guidelines, and application recommendations to help engineers, technicians, and system integrators fully understand and efficiently apply the control system.

1、 System Overview and Product Architecture

1.1 MicroNet Control System Family

MicroNet Simplex and MicroNet Plus are digital controllers based on 32-bit microprocessors that can be programmed to adapt to various application scenarios. The control system provides comprehensive functions such as high-speed control, system sequence control, auxiliary system control, surge control, monitoring and alarm, and station control. This platform provides Simplex, Redundancy, and Triple Modular Redundancy (TMR) configurations, and this manual mainly covers Simplex and Redundancy configurations.

The system adopts Woodward's unique rate group structure to ensure that control functions can execute deterministically according to the rate group defined by the application engineer. The critical control loop can complete processing within 5 milliseconds, while secondary code is assigned to slower rate groups. This structure ensures that the dynamic characteristics of the system will not change due to the addition of additional code, and the control always has certainty and predictability.

1.2 System Configuration and Compatibility

The MicroNet platform is built around the VME chassis and CPU modules, with the CPU module located in the first active slot of the VME chassis and all I/O modules inserted into the remaining slots. The MicroNet Plus chassis supports single CPU operation and dual CPU redundancy operation, with each chassis capable of accommodating up to 14 VME slots. The system can be expanded to multiple chassis using copper or fiber optic cables to meet additional I/O requirements.

The environmental specifications and compatibility information of the system are detailed in the corresponding appendix of Volume 2 of this manual, while information on non preferred and obsolete modules is included in Volume 3.

2、 Detailed explanation of MicroNet Plus system

2.1 Redundant Configuration

The MicroNet Plus control system provides a complete redundancy solution, achieving high availability through dual CPU modules. In a redundant system, two CPU modules run the same application, share access to I/O modules, and communicate with each other through the VME bus. A CPU module with good health becomes the system controller (SYSCON), while another one serves as a backup (STANDBY). When the main CPU fails, the backup CPU can seamlessly take over control.

The system supports multiple redundant configuration options:

Fully redundant: Both the host rack and expansion rack use redundant CPUs and RTN modules

Partial redundancy: Main CPU redundancy, expansion rack can use single RTN or redundant RTN

Simplex configuration: Single CPU operation, expansion rack using single RTN module

2.2 Power Supply System

The MicroNet Plus chassis uses two load sharing power modules to provide redundant power supply for the motherboard, CPU, and I/O modules. The power module has a dual slot width and is located in the PS1 and PS2 slots at both ends of the chassis. The system supports three power input specifications: low voltage (24 Vdc input), high voltage (110 Vac/dc input), and high voltage 220 Vac input versions.

The power module is equipped with four LED indicator lights, which respectively display information such as power status, input faults, overheating, and power faults, making it easy to diagnose quickly. The system design follows the safety requirements of Class I and Division 2 areas and requires the use of delay fuses or circuit breakers that comply with local regulations.

2.3 I/O module and on-site connection

Each I/O module is connected to the field terminal module (FTM) through a front panel connector, which is used to connect field wiring. For the communication module, there is no need for FTM, and the cable is directly connected to the front panel of the communication module.

The system provides two levels of redundancy:

Sensor level redundancy: Connect two external input devices to two independent input channels