What are the consequences of diode short circuit or open circuit on the energy system?

一, Chain reaction of diode short circuit fault
1. Short circuit mechanism and triggering conditions
A diode short circuit is usually caused by chip breakdown, packaging cracking, or poor soldering. In high temperature and high humidity environments, the moisture absorption and expansion of packaging materials may cause the internal metallization layer to break; In overvoltage scenarios, PN junctions may permanently conduct due to avalanche breakdown. For example, a photovoltaic inverter project experienced a short circuit within 10ms due to reverse overvoltage of the diode caused by lightning strikes.

2. System level impact
(1) Change in energy transmission path
Failure of rectifier circuit: In a bridge rectifier circuit, if a diode is short circuited, it will cause direct conduction between the AC and DC sides, leading to transformer or inductor saturation. Due to a short circuit in the rectifier diode of a certain energy storage system project, the input current surged to three times the rated value, and the transformer burned out within 5 seconds.
Short circuit in the freewheeling circuit: In motor drive or inductive energy storage circuits, a short-circuit in the freewheeling diode can damage the energy feedback path. For example, in a certain electric vehicle inverter project, due to a short circuit in the freewheeling diode, the back electromotive force of the motor was directly applied to the power device, causing the IGBT module to explode within 100 μ s.
(2) Protection mechanism failure
Anti reverse protection failure: In DC systems, a short circuit in the anti reverse diode can cause direct damage to the equipment when the power polarity is reversed. The UPS project in a certain data center suffered losses of over 500000 yuan due to a short-circuit of the anti reverse diode, which caused the rectifier module to burn out during maintenance misoperation.
Overvoltage protection bypass: TVS diode short circuit will cause it to lose its clamping function, and overvoltage will be directly transmitted to the subsequent circuit. Due to a TVS diode short circuit in a certain photovoltaic array project, the output voltage of the components soared to 1000V (rated 600V), causing large-scale inverter failures.
(3) Risk of thermal runaway
A short circuit causes a change in the current path, resulting in a significant increase in local current density. A test of a wind power converter project showed that after a diode short circuit, the junction temperature of adjacent power devices rose from 85 ℃ to 200 ℃ within 2 seconds, causing chain thermal runaway.

二, Systemic hazards of diode open circuit faults
1. Open circuit mechanism and typical scenarios
Open circuit is usually caused by welding collapse, chip breakage, or lead breakage. In vibration environments (such as electric vehicles), lead fatigue fracture is a common cause; In high temperature scenarios, the mismatch between the thermal expansion coefficient of packaging and chip may lead to cracking.

2. System level impact
(1) Energy transmission interruption
Rectification output loss: In a three-phase rectification circuit, if a diode is open circuited, it will cause an increase in output voltage ripple. A certain industrial power supply project caused the output voltage ripple to increase from 5% to 30% due to the open circuit of the diode, resulting in the misoperation of the load equipment.
Disconnected freewheeling circuit: In an inductive energy storage circuit, an open freewheeling diode can cause the energy of the inductor to be released nowhere, resulting in high voltage spikes. A certain LED driver project experienced a surge in inductor voltage to 800V (rated 400V) due to an open circuit in the freewheeling diode, resulting in MOSFET breakdown.
(2) Loss of protection function
Overcurrent protection failure: In a parallel diode group, if one of the diodes is open, the remaining diodes need to bear a larger current. A certain energy storage battery balancing circuit project caused overload and burnout of other diodes due to an open circuit of one diode, resulting in overcharging of the battery pack.
Isolation function failure: In photovoltaic module level protection, an open circuit in the bypass diode can exacerbate the hot spot effect. Due to the open circuit of the bypass diode in a certain photovoltaic power station project, the temperature of a certain component rose to 150 ℃ under shadow obstruction, causing glass breakage.
(3) System stability decreases
Open circuit can cause changes in circuit topology, which may lead to resonance or oscillation. A certain electric vehicle charging module project experienced a diode open circuit, causing the LLC resonant circuit to become detuned and the output voltage to fluctuate by more than ± 15%, triggering a protective shutdown.

三, Consequences of faults in typical energy systems
1. Photovoltaic power generation system
Component level impact: An open circuit in the bypass diode can cause the thermal spot temperature of the component to exceed the limit when partially obstructed, accelerating the aging of the packaging material; Short circuit may cause DC side arc fault. According to statistics from a 5MW photovoltaic power station, diode failures account for 18% of component failures, resulting in an annual loss of over 500000 kWh of power generation.
Inverter level impact: Short circuit of rectifier diode can cause uncontrolled DC bus voltage, leading to IGBT module explosion; Open circuit leads to intermittent input current, causing transformer noise and vibration.
2. Energy storage system
Battery balancing impact: An open circuit in the balancing circuit diode can lead to increased inconsistency in the battery pack and shorten the cycle life; A short circuit may cause overcharging/overdischarging. Due to a fault in the balancing diode of a certain energy storage power station project, the capacity degradation rate of the battery pack has increased from 3%/year to 8%/year.
DC/DC conversion impact: Open circuit of synchronous rectifier diode can lead to a decrease in efficiency of more than 10%; Short circuit may cause output voltage overshoot.
3. Electric vehicle charging system
Charging module impact: PFC circuit diode short circuit can cause input current distortion rate to exceed the standard, triggering grid protection; An open circuit will cause the power factor to drop below 0.7 and result in a fine from the power grid.
Impact of car charger: Open circuit of output rectifier diode will cause charging interruption; A short circuit may cause overvoltage in the battery. In a certain vehicle recall incident, over 20000 vehicles were recalled due to the risk of output diode short circuit.
四, Fault diagnosis and protection strategy
1. Online monitoring technology
Voltage/current monitoring: Real time monitoring of the voltage and current across the diode through Hall sensors, triggering an alarm if there is an abnormal fluctuation exceeding 10%.
Infrared temperature measurement: Infrared thermal imager is used to monitor the surface temperature of the diode. When the junction temperature exceeds the limit (such as SiC diode>175 ℃), it will automatically shut down.
Impedance spectrum analysis: By injecting high-frequency signals to detect the equivalent series resistance of diodes, the impedance approaches infinity in open circuit and zero in short circuit.
2. Redundant design
Parallel redundancy: Multiple diodes are connected in parallel in critical circuits, and the system can still operate in the event of a single fault. For example, a certain wind power inverter uses 4 parallel SiC diodes, and the system efficiency only decreases by 2% after a single open circuit.
Backup path: Install a mechanical switch in parallel with a diode in the anti reverse circuit, and automatically switch to the switch path when the diode fails.
3. Material and process upgrades
Moisture resistant packaging: ceramic or airtight packaging is used to verify reliability through double 85 testing (85 ℃/85% RH/1000h).
Low stress soldering: Use lead-free solder and elastic leads to verify fatigue resistance through vibration testing (such as 5-2000Hz/10g).
五, Case Study: Diode Fault in Offshore Wind Power Converter
A certain offshore wind power project is located in a typhoon prone area, and the original design used ordinary silicon-based diodes. After 2 years of operation, multiple diode leads were broken (open circuit) due to vibration, and 3 diodes were short circuited due to salt spray corrosion. Malfunction causing:

Energy transmission interruption: 12 inverters shut down, resulting in a daily loss of over 50MWh of power generation per inverter;
Equipment chain damage: IGBT module explosion caused by short circuit, repair cost exceeds 2 million yuan;
System stability degradation: Open circuit leads to intermittent input current, and transformer noise reaches 85dB (design<65dB).
The improvement plan includes:

Device upgrade: Replace with SiC diodes and ceramic packaging;
Structural reinforcement: using vibration reduction brackets and three proof coatings;
Monitoring upgrade: Deploy infrared temperature and vibration sensors.
After improvement, the system has been running continuously for 3 years without any diode failures, with an annual power generation increase of 12% and a maintenance cost reduction of 70%.