Hybrid power system for transport refrigeration systems
A transport refrigeration system includes a compressor, condenser and evaporator; an inverter providing a multiphase, AC output voltage to the compressor; and a DC power system having an output coupled to the inverter, the DC power system including: a primary power source; a DC-AC converter connected to the primary power source; a transformer connected to the DC-AC converter; an AC-DC converter connected to the transformer, the AC-DC converter outputting a primary DC voltage; a secondary power source; and a DC-DC converter connected to the secondary power source, the DC-DC converter outputting a secondary DC voltage; a combination of the primary DC voltage and the secondary DC voltage provides the output of the DC power system.
1. A transport refrigeration system comprising:
a compressor, condenser and evaporator;
an inverter providing a multiphase, AC output voltage to the compressor; and
a DC power system having an output coupled to the inverter, the DC power system including:
a primary DC power source;
a DC-AC converter connected to receive an output of the primary DC power source;
a transformer connected to receive an output of the DC-AC converter;
an AC-DC converter connected to receive an output of the transformer, the AC-DC converter outputting a primary DC voltage;
a secondary DC power source; and
a DC-DC converter connected to receive an output of the secondary DC power source, the DC-DC converter outputting a secondary DC voltage;
wherein a combination of the primary DC voltage and the secondary DC voltage provides the output of the DC power system to the inverter;
a controller coupled to the DC-DC converter, wherein the controller is configured to compare the primary DC voltage to a reference;
wherein the controller is configured to control the DC-DC converter to supply a positive secondary DC voltage when the primary DC voltage is less than the reference; and
wherein the controller is configured to control the DC-DC converter to supply a negative secondary DC voltage when the primary DC voltage is greater than the reference.
2. The transport refrigeration system of claim 1 , wherein the primary DC power source includes a fuel cell.
3. The transport refrigeration system of claim 1 , wherein the primary DC power source includes a battery.
4. The transport refrigeration system of claim 1 , wherein the secondary DC power source includes a battery.
5. The transport refrigeration system of claim 1 , wherein the DC-DC converter is connected in electrical series with the AC-DC converter.
6. The transport refrigeration system of claim 1 , wherein the DC-DC converter is connected in electrical parallel with the AC-DC converter.
7. The transport refrigeration system of claim 1 , further comprising a sensor in communication with the controller, the sensor configured to detect the primary DC voltage.
8. The transport refrigeration system of claim 1 , wherein the DC-AC converter includes SiC switches, the AC-DC converter includes GaN switches, and the DC-DC converter includes GaN switches.
9. The transport refrigeration system of claim 1 , wherein the DC-AC converter includes SiC switches, the AC-DC converter includes GaN switches, and the DC-DC converter includes SiC switches.
10. The transport refrigeration system of claim 1 , wherein the transformer is a high switching frequency transformer with zero voltage switching.