Isolated DC/DC converter topology structure for fuel cell system

An isolated direct current/direct current (DC/DC) converter for a fuel cell system, comprising:

• a Boost converter topology structure and a bidirectional full-bridge converter topology structure connected in sequence, wherein an input end of the Boost converter topology structure is connected to a fuel cell, and an output end of the Boost converter topology structure is connected to other key components of the fuel cell system and an input end of the bidirectional full-bridge converter topology structure;
• the other key components comprise:
• an air compressor and a hydrogen circulation pump;
• an output end of the bidirectional full-bridge converter topology structure is connected to a power cell;
• and usage of the Boost converter topology structure and usage of the bidirectional full-bridge converter topology structure change under different operating states of the fuel cell system;
• the Boost converter topology structure comprises:
• a power switching transistor Q9, an inductor L2, a filter capacitor Cf2, and a diode D9, one end of the inductor L2 is connected to a positive electrode of the fuel cell, an other end of the inductor L2 is respectively connected to a drain of the power switching transistor Q9 and an anode of the diode D9, a cathode of the diode D9 is respectively connected to one end of the filter capacitor Cf2, the input end of the bidirectional full-bridge converter topology structure, and the other key components of the fuel cell system, and an other end of the filter capacitor Cf2 is connected to a source of the power switching transistor Q9, the input end of the bidirectional full-bridge converter topology structure, and a negative electrode of the fuel cell;
• the bidirectional full-bridge converter topology structure comprises:
• a left topology structure, an inductor L1, a transformer, a right topology structure, and a filter capacitor Cf1;
• an input end of the left topology structure is the input end of the bidirectional full-bridge converter topology structure, and an output end of the right topology structure is the output end of the bidirectional full-bridge converter topology structure;
• the input end of the left topology structure is respectively connected to the cathode of the diode D9 and the other end of the filter capacitor Cf2, an output end of the left topology structure is connected to one end of the inductor L1 and an other end of a primary coil of the transformer, and an other end of the inductor L1 is connected to one end of the primary coil of the transformer;
• a secondary coil of the transformer is connected to an input end of the right topology structure;
• the filter capacitor Cf1 is parallelly connected to the input end of the right topology structure;
• and the power cell is parallelly connected to two sides of the filter capacitor Cf1;
• the isolated DC/DC converter for the fuel cell system prevents a voltage of a bus from surging quickly:
• wherein, when the fuel cell system is integrally started, the fuel cell is not powered on, the power cell is required to supply power to the other key components of the fuel cell system, a pulse width modulation (PWM) duty cycle incremental method is adopted to start the fuel cell system, and a power switching transistor Q5, a power switching transistor Q6, a power switching transistor Q7, and a power switching transistor Q8 on the right topology structure are started preferentially;
• during starting, a voltage change rate and a voltage value of voltage Vdc collected by a voltage sensor are monitored;
• when the voltage change rate of Vdc exceeds a preset threshold, an increase rate of a duty cycle is reduced, and to prevent over-voltage of Vdc, a voltage Vdc limiting protection algorithm is also set, until Vdc reaches a preset voltage;
• and
• after Vac is stabilized and the fuel cell operates normally, the Boost converter topology structure is introduced to the fuel cell, to generate electricity, and a power switching transistor Q1, a power switching transistor Q2, a power switching transistor Q3, and a power switching transistor Q4 in the left topology structure are started while the power switching transistor Q9 is started;
• and
• the isolated DC/DC converter for the fuel cell system sets an energy transfer direction based on an energy flow requirement,
• wherein, when the fuel cell system is started, the power cell supplies power to the other key components of the fuel cell system, and energy of the bidirectional full-bridge converter topology structure flows from the right topology structure to the left topology structure;
• and
• after the fuel cell system operates normally, the fuel cell supplies power to the other key components of the fuel cell system, and the energy of the bidirectional full-bridge converter topology structure flows from the left topology structure to the right topology structure.