Customs container/vehicle inspection systems serve as core technical barriers for border security, anti-smuggling, counter-terrorism and contraband screening. Adopting high-energy X-rays generated by linear accelerators to penetrate containers, trucks and trains, they enable non-intrusive internal imaging without unpacking. Capable of identifying smuggled goods, drugs, explosives, weapons and ammunition rapidly, these systems feature strong penetration, high throughput and clear imaging, becoming standard screening equipment for global customs ports, logistics parks and border checkpoints. The high-voltage DC power supply is an indispensable core component of inspection accelerators, delivering stable high-amplitude DC output and pulse modulation for electron linear accelerators. It converts grid power into high-voltage DC for electron acceleration and precisely controls X-ray energy, dosage and emission status. Its long-term reliability, output stability, environmental adaptability and safety interlock performance directly determine X-ray penetration, imaging clarity, inspection efficiency, continuous operational availability and public safety at ports.
Port application characteristics and radiation safety regulations impose far stricter requirements than conventional industrial high-voltage power supplies: 1.Ultra-high reliability for 24/7 continuous operation: Port inspection runs all year round with annual operating hours exceeding 8,000. Unplanned shutdowns cause cargo backlogs and reduced clearance efficiency. Required MTBF ≥1×10⁵ hours with a 15-year design lifespan, minimal failure rate, online maintainability and redundant architecture for non-stop maintenance. 2.Long-term resistance to intense ionizing radiation: Accelerators continuously emit high-energy X-rays and gamma rays. Power supplies installed close to radiation sources endure total ionizing dose (TID) exposure up to 500 krad(Si), which causes semiconductor drift, insulation aging and high-voltage breakdown. Radiation-hardened performance is mandatory for full-lifetime stability. 3.High stability & fast dynamic response: Stable X-ray energy and dosage guarantee uniform imaging contrast across diverse cargo thicknesses and materials. Output voltage stability ≤±0.5%, current stability ≤±1%, peak-to-peak ripple<1%, and dynamic response <10 ms for rapid adaptive adjustment during scanning. 4.High-power ultra-gain topology challenge: Accelerator output ranges from 1 MeV to 9 MeV (1 MV–9 MV DC) with power 10–100 kW. Based on 380 V three-phase input, the voltage gain can exceed 23,000 times, requiring advanced cascaded insulation, voltage sharing and thermal management impossible with single-stage topologies. 5.Impenetrable multi-level radiation safety interlocks: Class II radiation devices comply with GB 18871 and GBZ 127. Non-bypassable safety cutoffs must instantly terminate high voltage and X-ray emission under abnormal conditions to eliminate accidental radiation exposure. 6.Harsh industrial environmental resilience: Ports often face high temperature & humidity, salt fog corrosion, dust, wide temperature fluctuation (−20 ℃~+55 ℃), unstable grid voltage and severe EMI. Equipment must support triple-proof protection, salt-fog resistance and grid surge immunity. 7.Intelligent health monitoring & remote O&M: Large-scale multi-site port deployments require real-time condition monitoring, early fault warning, remote diagnosis, parameter tuning and firmware updates to minimize on-site maintenance costs.
This methodology establishes a full-process technical framework covering high-reliability topology design, radiation hardening, full-lifetime reliability, mandatory safety interlocks, port environmental adaptation and intelligent remote operation. It supports fixed, vehicle-mounted and mobile container/vehicle inspection accelerators, delivering standardized design guidelines for domestic core-component localization and performance upgrading. Targeting critical challenges including all-weather reliability, radiation tolerance, strict safety compliance and ultra-high voltage gain, the universal three-stage modular architecture is adopted: three-phase PFC rectifier + series multi-module full-bridge LLC resonant isolation + symmetric cascaded Cockcroft-Walton voltage multiplier, integrated with full-chain radiation hardening, non-bypassable multi-level safety interlocks and fully digital intelligent control. It eliminates traditional drawbacks including low efficiency, bulky size, short lifespan, poor radiation resistance and insufficient safety protection.
1.Front-stage three-phase PFC rectifier: A Vienna rectifier achieves high power factor, low switching stress and low EMI. It maintains PF ≥0.99 and THD ≤5% across 20%–120% load complying with GB/T 14549. Wide grid tolerance covers 380 VAC ±30% with 200 ms ride-through capability against voltage sags. Dual parallel N+1 redundancy enables hot swapping and non-stop maintenance. Multi-stage surge, lightning and EMC filtering ensure outdoor port durability.
2.Middle-stage series full-bridge LLC resonant converters: Standardized identical modules adopt parallel input and series output to flexibly scale from 1 MV to 9 MV. All modules operate at optimal resonant points with ZVS/ZCS to minimize losses, achieving overall efficiency ≥95%. Master-slave voltage sharing ensures deviation ≤±1%. Radiation-resistant high-frequency low-loss ferrite transformers with interleaved winding reduce leakage inductance. N+1 module redundancy enables fast bypass isolation without shutdown. Vacuum epoxy potting enhances insulation, thermal conduction and radiation resistance.
3.Rear-stage symmetric cascaded voltage multiplier: The dual-input Cockcroft-Walton topology reduces ripple by over 50% and evenly distributes voltage stress across stages, simplifying ultra-high-voltage insulation. Radiation-hardened fast-recovery HV diodes/SiC Schottky devices and low-dispersion polypropylene film capacitors maintain stable parameters under prolonged irradiation. Grading rings and shielding optimize electric field distribution to suppress corona discharge. Integrated oil/SF6 insulation shortens HV paths and minimizes parasitic effects.
4.Full-chain radiation hardening system: A three-layer strategy ensures TID resilience up to 500 krad(Si): —Component-level screening: Radiation-tolerant SiC power devices, rad-hard ICs (≥100 krad(Si), LET ≥60 MeV·cm²/mg), non-electrolytic capacitors and radiation-resistant insulation materials with double derating margins. —Circuit-level reinforcement: Real-time adaptive compensation offsets parameter drift caused by total dose effects; triple modular redundancy (TMR) and ECC eliminate single-event upsets; fast current limiting prevents single-event latchup burnout; strict electrical thermal derating reduces aging acceleration. —System-level shielding: Thick steel main shielding attenuates primary radiation; independent tungsten/lead alloy shielded cavities protect sensitive control circuits; optimized mechanical layout places low-voltage electronics far from radiation sources for additional structural shielding.
5.Non-bypassable four-tier safety interlock system: Fully compliant with national radiation regulations: —Hardware emergency cutoff: Purely hardwired normally closed interlocks connect all emergency stops, instantly disconnecting main power and discharging residual high voltage without software bypass. —Device physical interlocks: Door, shield, key switch, X-ray shutter, vacuum and cooling interlocks disable HV within 1 μs if any safety barrier opens; dual redundant interlock loops prevent single-point failure. —System radiation linkage: Area dose monitoring, access control and human body infrared detection terminate emission immediately upon unauthorized entry or excessive environmental radiation. —Operational authority management: Three-level user permission prevents unauthorized parameter modification or interlock bypass; mandatory acoustic-optical warning before startup enforces standardized operation. Redundant high-voltage discharge circuits fully release residual energy within 100 ms for personnel safety during shutdown or emergencies.
6.Full-lifetime high-reliability engineering: Strict derating for all components (voltage ≤50%, current ≤40%, temperature ≤70% of ratings); water cooling with uniform thermal distribution maintains stable junction temperatures and eliminates hotspots; dual redundant cooling, control, drive and sampling circuits ensure seamless switchover during faults; IP55 fully sealed enclosure with conformal coating, salt-fog corrosion resistance and wide-temperature (−20 ℃~+55 ℃) adaptability; embedded AI health management predicts lifespan, analyzes degradation and issues early failure alerts.
7.Intelligent monitoring & remote O&M: Full real-time data acquisition covers voltage, current, temperature, cooling status, interlock signals and radiation dosage via Ethernet/5G for centralized port management. Expert diagnosis and machine learning achieve precise fault localization; remote tuning, upgrades and troubleshooting reduce on-site labor; automated operational statistics support long-term asset planning.
8.Imaging-oriented performance optimization: Dual-loop digital control ensures voltage stability ≤±0.3%, beam stability ≤±0.8% and ultra-low ripple for consistent X-ray dosage and high-contrast imaging. Feedforward dynamic adjustment achieves response<10 ms adapting to variable cargo thickness. Switchable continuous/pulse modes optimize energy efficiency for mobile inspection systems while extending service lifespan.
In summary, this integrated framework resolves core weaknesses of conventional high-voltage supplies under port radiation and 24/7 operation. The three-stage modular topology delivers ≥95% efficiency and MV-class ultra-high output; comprehensive radiation hardening guarantees over 15 years of stable service; mandatory non-bypassable interlocks fully satisfy national radiation safety laws; full-lifetime reliability enables uninterrupted port screening. Widely applicable to fixed, vehicle-mounted and mobile container/vehicle inspection accelerators and large-scale baggage scanners, it provides core independent technologies for domestic substitution and performance breakthroughs in China’s customs security equipment.