System for stabilising a dc link
The present disclosure relates to a system for stabilising a DC link that supplies power to a load. The system comprises a power converter electrically coupled to the DC link. The power converter is configured to: supply power to or draw power from the DC link; monitor a voltage of the DC link; and control the power supplied to, or drawn from, the DC link based on the monitored voltage of the DC link and an operating voltage setpoint.
1 . A system for stabilising a DC link that supplies power to a load, the system comprising:
a power converter electrically coupled to the DC link;
wherein the power converter is configured to:
supply power to or draw power from the DC link;
monitor a voltage of the DC link; and
control the power supplied to or drawn from the DC link based on the monitored voltage of the DC link and an operating voltage setpoint, the operating voltage setpoint being a value with respect to which the voltage of the DC link is to be stabilized by the system.
2 . The system of claim 1 , wherein the power converter is configured to:
calculate an error value, wherein the error value is a result of subtracting the monitored voltage of the DC link from the operating voltage setpoint;
calculate a target power to supply to or draw from the DC link based on the error value; and
supply power to or draw power from the DC link in accordance with the calculated target power.
3 . The system of claim 2 , wherein the power converter is configured to:
supply power to the DC link if the error value is positive.
4 . The system of claim 3 , wherein the power converter is configured to increase the target power to supply to the DC link in response to an increase in a magnitude of the error value.
5 . The system of claim 2 , wherein the power converter is configured to:
draw power from the DC link if the error value is negative.
6 . The system of claim 2 , wherein:
the power converter is configured to calculate the target power to supply to or draw from the DC link based on a proportional term; and
the proportional term is obtained by multiplying the error value by a proportional coefficient.
7 . The system of claim 6 , wherein
the power converter is configured to calculate the target power to supply to or draw from the DC link based on the proportional term and an integral term; and
the integral term is obtained by multiplying a time-integral of the error value by an integral coefficient.
8 . The system of claim 1 , further comprising the load, wherein the operating voltage setpoint is a first operating voltage setpoint, and wherein
the load is configured to:
draw power from the DC link;
monitor the voltage of the DC link; and
reduce the power drawn from the DC link in response to a determination that the monitored voltage of the DC link is below a second operating voltage setpoint.
9 . The system of claim 8 , wherein
the load is one of a plurality of loads electrically coupled to the DC link; and
each load is configured to:
draw power from the DC link;
monitor the voltage of the DC link; and
reduce the power drawn from the DC link in response to a determination that the monitored voltage of the DC link is below the second operating voltage setpoint.
10 . The system of claim 8 , wherein the or each load is configured to:
calculate an error value, wherein the error value is a result of subtracting the monitored voltage of the DC link from the second operating voltage setpoint;
calculate a target power to draw from the DC link based on the error value; and
draw power from the DC link in accordance with the calculated target power.
11 . The system of claim 10 , wherein
the or each load is configured to calculate the target power to draw from the DC link based on a proportional term; and
the proportional term is obtained by multiplying the error value by a proportional coefficient.
12 . The system of claim 11 , wherein
the or each load is configured to calculate the target power to draw from the DC link based on the proportional term and an integral term; and
the integral term is obtained by multiplying a time-integral of the error value by an integral coefficient.
13 . The system of claim 8 , wherein the or each load includes a further power converter configured to generate an output voltage, and wherein the further power converter is configured to vary the output voltage and/or a frequency of the output voltage to reduce the power drawn from the DC link.
14 . A transport refrigeration system comprising the system of claim 1 and a transport refrigeration unit.
15 . The transport refrigeration system of claim 14 , wherein the or each load includes a further power converter, and wherein the or each further power converter is electrically coupled to a motor, and wherein the motor is configured to drive a compressor, a pump or a fan of the transport refrigeration unit.