Fiber Optics in Test Systems: Ensuring Accurate Power Synchronization

In high-power testing applications, parallel operation of AC and DC power supplies is common to increase output capability. However, without precise synchronization, these systems suffer from instability, uneven load sharing, and control loop interference. Fiber optic communication plays a critical role in maintaining accurate, noise-free coordination between units.

Do You Know About Power System Paralleling?

Paralleling power supplies means connecting two or more power sources—AC or DC—in such a way that they work together to deliver higher total current, voltage, or power output than a single unit can provide. This technique is essential when testing high-capacity batteries or systems that exceed the rating of a single power module.

Typical goals of paralleling include:

• Increasing output current (e.g., combining 3 × 100A units for 300A total)
  
  

• Redundancy or modularity in power delivery
  
  

• Load balancing across multiple supplies

Application in Parallel Power Systems

When multiple power supplies are paralleled—either AC sources or DC sources for battery cycling—they must operate with tight coordination. This requires fast, deterministic communication between the control units to synchronize parameters such as:

• Output voltage and current
  
  

• 3 Phase alignment (for AC Power)
  
  

• Load sharing and loop compensation
  
  

Fiber optics is used to:

• Link master controllers to slave power units

• Transmit high-speed, real-time synchronization and control data

• Maintain system-wide timing and phase alignment

• Provide complete galvanic isolation between unit

• EMI and RFI Immunity 

Why Fiber Optics?

Without It, You Could Possibly Cause…

• Desynchronized feedback loops, leading to instability or oscillation
  
  

• Uneven current or power sharing, which can overburden individual units
  
  

• Voltage or phase mismatch in AC systems, damaging equipment or test subjects
  
  

These issues are especially critical in AC systems, where phase misalignment across paralleled sources can create circulating currents or waveform distortion.

How to Parallel Power Systems with Fiber Optics

1. Master-Slave Architecture: Designate one power supply or controller as the master. Use fiber links to transmit synchronization signals to each slave.
   
   

2. Digital Control Bus over Fiber: Implement communication protocols (e.g., proprietary or standard like EtherCAT or CAN over fiber) to carry control loop data.
   
   

3. Phase and Current Feedback: Use fiber to carry precision timing (AC phase sync) and current feedback between units for coordinated operation.
   
   
   

Conclusion

Fiber optics is not just a communication medium—it’s a critical enabler for safe, synchronized, and stable parallel operation of AC and DC power supplies in battery test systems. By ensuring fast, isolated, and interference-free signal transmission, fiber optics eliminates control loop conflicts, improves power sharing accuracy, and enhances overall system reliability.