1. Introduction

As a critical national infrastructure, the stable operation of control, protection, monitoring, and communication equipment in power systems serves as the cornerstone for ensuring the safety, reliability, and economy of power grids. These key secondary devices (such as relay protection devices, data acquisition and monitoring systems, and power communication equipment) impose far higher requirements on the reliability, stability, and environmental adaptability of power supplies than general industrial standards. As a core device that converts AC power from the grid or backup DC power into precise and stable DC power, the technical performance of switching power supplies is directly related to the safe operation of primary equipment in power systems and the reliability of secondary control systems. This paper aims to conduct an in-depth analysis of the core technical characteristics of dedicated switching power supplies suitable for power systems and their application requirements in typical scenarios.

2. Core Requirements of Power Systems for Switching Power Supplies

The unique operating environment and functional positioning of power systems determine that their dedicated switching power supplies must possess the following key attributes:

Extremely High Reliability and Availability: The Mean Time Between Failures (MTBF) requirement is extremely high, which must meet the strict assessment of power supply equipment specified in power industry standards (e.g., DL/T 856).

Wide Input Voltage Range: Capable of adapting to severe fluctuations in grid voltage and equipped with low-voltage ride-through capability under fault conditions.

Strong Electromagnetic Compatibility (EMC): Operates stably in high electromagnetic interference environments such as substations and switchyards, while strictly controlling its own electromagnetic emissions.

Comprehensive Battery Management Function: Works in synergy with backup battery banks, featuring intelligent charging and discharging management to ensure the DC system can supply power continuously after AC power failure.

Comprehensive Condition Monitoring and Communication Capability: Supports remote monitoring and data upload to meet the management needs of intelligent substations and unattended stations.

3. Core Technical Characteristics

To meet the above requirements, dedicated switching power supplies for power systems adopt a number of special technologies in their design and manufacturing.

3.1 High-Reliability Design

High Redundancy Architecture

Modular N+M Redundancy: The system adopts multiple hot-swappable power modules connected in parallel, configured in an N+M (e.g., N+1, N+2) redundancy mode. Through high-precision active current-sharing technology (with a current-sharing imbalance generally better than 3%), load balancing among modules is achieved. A single faulty module can automatically exit without affecting system operation, enabling online maintenance.

Output Isolation Protection: The output terminal of each module adopts an OR-ing MOSFET circuit to achieve low-loss and fast electrical isolation, preventing faulty modules from adversely affecting the bus in reverse.

Enhanced Protection Mechanisms

Comprehensive Fault Protection: In addition to standard overvoltage, overcurrent, and short-circuit protection, it must be equipped with DC output undervoltage protection, battery reverse connection protection, and anti-backflow protection to ensure the safety of the battery bank as the last line of defense.

Recoverable Protection Modes: It usually adopts Hiccup mode or constant current derating mode to handle continuous overload or short-circuit faults, and can automatically recover after the fault is eliminated, reducing manual intervention.

3.2 Grid Adaptability and Electrical Performance

Ultra-Wide Input Voltage Range: The input voltage range is usually designed to be 85Vac ~ 300Vac (or wider) and can withstand short-term (e.g., 1 cycle) voltage sags or surges.

Excellent Electromagnetic Compatibility

Electromagnetic Immunity: Meets the level requirements for substation environments specified in the IEC 61000-4 series standards, especially surge immunity (Level 4), electrical fast transient (EFT) burst immunity (Level 4), and radiated immunity (e.g., 10V/m).

Low Electromagnetic Emissions: Conducted and radiated emissions must comply with EN 55032 Class B (or more stringent standards) to avoid interfering with sensitive relay protection and communication equipment.

Low Ripple and Noise: The output ripple and noise are generally required to be less than 0.5% ~ 1% of the output voltage to ensure the accuracy of analog sampling and precision control circuits.

3.3 Intelligent Battery Management and System Monitoring

Precise Battery Management

Temperature-Compensated Float Charging: Automatically adjusts the float charging voltage according to the ambient temperature to optimize battery life and capacity.

Automatic Conversion Between Equalizing Charging and Float Charging: Performs equalizing charging to restore battery capacity after battery discharge or at regular intervals, and then automatically switches to float charging.

Battery Capacity Testing and Verification: Supports manual or automatic battery discharge testing to evaluate the actual backup capacity of the battery.

Comprehensive Digital Communication and Condition Monitoring

Standard Communication Interfaces: Generally integrated with RS485/Modbus protocols; in intelligent substations, the IEC 61850 standard can be adopted to achieve seamless integration with the station control system.

Real-Time Data Acquisition: Remotely monitors input/output voltage and current, module status, system load, battery voltage/current/temperature, and fault alarms.

Event Recording and Early Warning: Records historical faults, conducts trend analysis based on operating parameters, and supports predictive maintenance.

4. Analysis of Typical Applications in Power Systems

Intelligent Substations

Core Requirements: Compliance with the IEC 61850 standard, high reliability, and intelligent operation and maintenance.

Key Technical Requirements: Support for the IEC 61850 communication protocol, modular N+M redundancy, and comprehensive condition monitoring and remote diagnosis functions.

Distribution Automation Terminals

Core Requirements: Outdoor environmental adaptability, small size, and low power consumption.

Key Technical Requirements: Wide temperature operation (-40℃ ~ +75℃), high protection level (IP65), compact design, and high efficiency to reduce heat generation and energy consumption.

DC Power Supply Systems

Core Requirements: Power supply for relay protection and operating mechanisms, and battery management.

Key Technical Requirements: Ultra-wide input voltage, intelligent battery management (temperature compensation, equalizing/float charging), low output ripple, and fault ride-through capability.

Power Communication Equipment

Core Requirements: High availability and low electromagnetic interference.

Key Technical Requirements: High MTBF, strict EMC performance (Class B emission limits), redundant configuration, and collaborative management with communication equipment.

Power Plant Auxiliary Power Systems

Core Requirements: Adaptability to high-temperature and high-humidity environments, and anti-interference capability.

Key Technical Requirements: Enhanced heat dissipation design, triple-proof (moisture-proof, mildew-proof, salt spray-proof) coating, and high-level electromagnetic interference suppression capability.

5. Conclusion

In the field of power systems, where safety and reliability requirements are extremely high, switching power supplies have evolved from simple power supply units into key devices integrating power conversion, intelligent management, condition monitoring, and network communication. Their technological development closely aligns with the trends of grid intelligence and unattended operation, and continues to advance toward higher reliability, higher power density, and deeper intelligence. Selecting dedicated switching power supplies that meet the special requirements of power systems is an indispensable key link in building a robust, intelligent, and reliable power grid, and holds important strategic significance for ensuring the overall safe and stable operation of power systems.