High power frequency online UPS (Uninterruptible Power Supply) is the core power supply guarantee equipment for key scenarios such as industrial grade and large data centers. Its design aims to achieve "high reliability, strong stability, and resistance to harsh environments". The following provides a detailed analysis from two aspects: core technology architecture and key features:
1、 Core Technology Architecture
The architecture of high-power power frequency online UPS is designed around "full online power supply+power frequency isolation", forming a closed-loop control from input to output, mainly including 7 core modules (sorted by energy flow direction):
1. Input filtering and surge protection module
Function: Preprocess the AC power input to the grid, suppress harmonics, electromagnetic interference (EMI), and radio frequency interference (RFI) on the grid side, while resisting transient impacts such as surges and lightning strikes, and avoiding grid disturbances that affect subsequent circuits.
Core components:
LC filter composed of inductance and capacitance (suppressing high-frequency harmonics);
Varistors and gas discharge tubes (absorbing surge currents);
EMI/RFI filter (compliant with international electromagnetic compatibility standards such as EN 61000).
2. Rectifier module
Function: Convert alternating current (AC) input into stable direct current (DC), power the inverter, and charge the battery pack (when the power grid is normal).
Core Technology:
Power devices: IGBT (Insulated Gate Bipolar Transistor) or thyristor (SCR) are commonly used as rectifier switching devices in high-power scenarios (IGBT has faster response and is suitable for a wide voltage range); SCR has strong current resistance and is suitable for ultra-high power;
Control strategy: Using PWM (Pulse Width Modulation) or phase controlled rectification technology to achieve input power factor correction (PFC) and reduce harmonic pollution to the power grid (usually input power factor ≥ 0.95, total harmonic distortion THD ≤ 5%);
Wide input range design: Adapts to power grid fluctuations (such as input voltage range of ± 20%~± 30% rated voltage, frequency of ± 5Hz), reducing frequent battery input.
3. Battery pack (energy storage module)
Function: As the only energy source during power grid interruption, it continuously supplies power to the load through the inverter, which is the core guarantee of "uninterrupted" operation.
High power adaptation design:
Capacity configuration: Based on load power and backup time requirements, multiple sets of batteries are connected in series and parallel (such as 2V individual batteries connected in series to form a DC bus voltage, and then expanded in parallel with multiple sets);
Battery type: Valve regulated sealed lead-acid batteries (VRLA) or lithium batteries are commonly used (lithium batteries have higher energy density, but lead-acid batteries have lower cost and mature safety);
Management System (BMS): Real time monitoring of battery voltage, temperature, and capacity to achieve charge and discharge protection, balanced charging, and extend lifespan.
4. Inverter module
Function: Converting direct current (rectified output or battery discharge) into stable alternating current (with the same frequency and phase as the grid) is the core module that determines the quality of the output power supply.
Core Technology:
Topology: Adopting a full bridge inverter circuit (with 4 IGBTs forming the bridge arm), sine wave output is achieved through high-frequency PWM control (switching frequency 10-20kHz);
Output waveform optimization: By using LC filtering or multiple inverters in parallel to cancel out harmonics, ensure that the output waveform distortion rate (THD) is ≤ 3% (linear load), approaching the ideal sine wave;
5. Power frequency isolation transformer
Function: The key component of the inverter output terminal, which is the core difference between "power frequency UPS" and "high-frequency UPS", undertakes three major functions:
Electrical isolation: isolate the load from the UPS internal circuit and power grid, eliminate common mode interference (such as ground potential difference), and protect the safety of the load and personnel;
Voltage regulation: Stabilize the output voltage through the winding turns ratio (to offset the output ripple of the inverter), while supporting different voltage levels of output (such as 380V/220V);
6. Static switch and bypass module
Function: Ensure "uninterrupted switching" - when UPS fails (such as inverter failure), quickly switch to the mains bypass power supply; Switch back to the UPS main circuit after troubleshooting.
Core design:
Static switch: using bidirectional thyristors (SCR) or IGBTs as switching devices, with a switching time of ≤ 5ms (far below the allowable power-off threshold of the load);
Bypass synchronization: Controlled by a phase-locked loop (PLL), it ensures that the bypass mains power is completely synchronized with the UPS output voltage, frequency, and phase, avoiding current surges during switching;
7. Control and Protection System
Function: As the "brain" of UPS, it coordinates the work of various modules to achieve intelligent management and fault protection.
Core components:
Main control unit: based on microprocessor (MCU) or multi-core DSP, real-time acquisition of module status (voltage, current, temperature, etc.), controlling the operating parameters of rectification and inversion;
Protection function: including multiple protections such as overvoltage, undervoltage, overcurrent, overload, short circuit, overheating, and battery undervoltage. When triggered, it quickly cuts off the faulty circuit (such as shutting down the inverter or switching to a bypass);
2、 Key features
The characteristics of high-power power frequency online UPS are determined by its architecture, and the core revolves around "reliability, stability, and adaptability":
1. The output power supply has extremely high quality
Pure waveform: Equipped with a power frequency transformer and precision inverter control, the output sine wave distortion rate is low (THD ≤ 3% under linear loads and ≤ 5% under nonlinear loads), suitable for power sensitive loads such as medical equipment, precision instruments, and server clusters;
Parameter stability: The output voltage accuracy is ± 1% (better than ± 2% of high-frequency UPS), the frequency accuracy is ± 0.1Hz, and it can withstand the impact of sudden load changes (such as motor start-up).
2. Strong electrical isolation and anti-interference ability
Power frequency transformers provide physical isolation and completely block common mode interference (such as ground wire noise between the power grid and the load), especially suitable for industrial environments with strong electromagnetic interference (such as factory production lines and substations);
The input filtering module can resist transient interference such as surges (± 2kV/± 4kV) and lightning strikes (10kA/20kA), reducing the impact of power grid anomalies on loads.
3. High reliability and long lifespan
Key components such as power frequency transformers and IGBTs have a long design life (transformer life ≥ 20 years, IGBT cycle times ≥ 100000 times), suitable for continuous operation scenarios (such as uninterrupted power supply in data centers throughout the year);
The static switch has a fast switching speed (≤ 5ms), coupled with multiple protection functions, which can reduce the impact of faults on the load to zero;
Support redundant design (such as N+1 modular configuration), and single module failure does not affect overall operation.
4. Adapt to harsh power grid environments
Wide input range (voltage ± 20%~± 30%, frequency ± 5Hz), capable of stable operation in areas with large voltage fluctuations in the power grid (such as remote industrial plants);
High input power factor (≥ 0.95), low harmonic current (THD ≤ 5%), will not cause pollution to the power grid, and complies with international power grid standards (such as IEEE 519).
5. Volume and efficiency characteristics
Large volume: The volume and weight ratio of the power frequency transformer is relatively high (about 30%~50% of the entire machine), making it more bulky compared to high-frequency UPS. Installation needs to consider load-bearing and space requirements;
Efficiency curve optimization: When fully loaded, the efficiency can reach 92%~95% (close to high-frequency UPS), but at light loads (such as below 30%), the efficiency is slightly lower (about 85%~90%), suitable for long-term full load operation scenarios.
3、 Typical application scenarios
High power frequency online UPS (usually referring to 500kVA or above) is mainly used in scenarios that require extremely high reliability and safety of power supply:
Large data centers (server clusters, cloud computing centers);
Industrial automation (PLC, DCS systems for metallurgical and chemical production lines);
Energy industry (control and protection systems for substations, wind farms, and photovoltaic power plants);
Medical field (precision medical equipment such as MRI, CT, etc.).
In summary, high-power power frequency online UPS forms unique advantages in power quality, reliability, and anti-interference ability through "power frequency isolation transformer+fully online architecture+multiple protections", and is the "power insurance" of critical infrastructure.
