Multi-segment and nonlinear droop control for parallel operating active front end power converters

Patent metadata

Field	Value
Publication number	US-10811990-B1
Application number	US-201916370503-A
Country	US
Kind code	B1
Filing date	Mar 29, 2019
Priority date	Mar 29, 2019
Publication date	Oct 20, 2020
Grant date	Oct 20, 2020

Abstract

An active rectifier includes first and second DC nodes, a switching circuit, and a controller configured to compute a voltage reference according to a load signal of the DC output, and a non-linear relationship between a load condition of the DC output and a DC bus voltage at the DC output, and to generate rectifier switching control signals according to the voltage reference to cause the switching circuit to convert AC input power from the AC input to control the DC bus voltage at the DC output.

First claim

The following is claimed:

1. A rectifier, comprising:
an AC input, including AC nodes;
a DC output, including first and second DC nodes;
a switching circuit coupled with the AC input and with the DC output, the switching circuit including switching devices respectively configured to selectively couple one of the AC nodes with a respective one of the first and second DC nodes according to a respective switching control signal; and
a controller configured to:
compute a voltage reference according to:
a load signal of the DC output, and
a non-linear relationship between an electrical load condition of the DC output and a DC bus voltage at the DC output, and
generate the switching control signals according to the voltage reference to cause the switching circuit to convert AC input power from the AC input to control the DC bus voltage at the DC output;

wherein the non-linear relationship is a multi-segment function with multiple segments having different respective slopes that relate the load condition of the DC output to the DC bus voltage at the DC output.

2. The rectifier of claim 1 , wherein the load signal of the DC output is a DC output current signal of the DC output.

3. The rectifier of claim 1 , wherein the multi-segment function includes more than two segments having different respective slopes that relate the load condition of the DC output to the DC bus voltage at the DC output.

4. The rectifier of claim 1 , wherein the multi-segment function is piecewise linear.

5. The rectifier of claim 1 , wherein the multi-segment function includes a curvilinear segment.

6. A rectifier, comprising:
an AC input, including AC nodes;
a DC output, including first and second DC nodes;
a switching circuit coupled with the AC input and with the DC output, the switching circuit including switching devices respectively configured to selectively couple one of the AC nodes with a respective one of the first and second DC nodes according to a respective switching control signal; and
a controller configured to:
compute a voltage reference according to:
a load signal of the DC output, and
a non-linear relationship between an electrical load condition of the DC output and a DC bus voltage at the DC output, and
generate the switching control signals according to the voltage reference to cause the switching circuit to convert AC input power from the AC input to control the DC bus voltage at the DC output;

wherein the non-linear relationship is a second or higher order formula that relates the load condition of the DC output to the DC bus voltage at the DC output.

7. The rectifier of claim 6 , wherein the load signal of the DC output is a DC output current signal of the DC output.

8. The rectifier of claim 6 , wherein the controller includes a lookup table with entries that relate load conditions of the DC output to respective DC bus voltages at the DC output according to the second or higher order formula.

9. The rectifier of claim 6 , wherein the controller is configured to solve the second or higher order formula to compute the voltage reference for a measured load condition of the DC output for a given control cycle.

10. The rectifier of claim 9 , wherein the controller is configured to:
sample a root-mean-square line to line voltage of the AC input for a given control cycle;
compute a minimum DC bus voltage value according to the root-mean-square line to line voltage for the given control cycle;
compute a no load DC bus voltage value according to the minimum DC bus voltage value for the given control cycle; and
compute the voltage reference for the given control cycle according to the load signal, non-linear relationship, and the no load DC bus voltage value.

11. The rectifier of claim 6 , wherein the controller is configured to:
sample a root-mean-square line to line voltage of the AC input for a given control cycle;
compute a minimum DC bus voltage value according to the root-mean-square line to line voltage for the given control cycle;
compute a no load DC bus voltage value according to the minimum DC bus voltage value for the given control cycle; and
compute the voltage reference for the given control cycle according to the load signal, non-linear relationship, and the no load DC bus voltage value.

12. A power conversion system, comprising
a first rectifier, comprising:
a first AC input, including first AC nodes,
a first DC output, including first and second DC nodes,
a first switching circuit coupled with the first AC input and with the first DC output, the first switching circuit including first switching devices respectively configured to selectively couple one of the first AC nodes with a respective one of the first and second DC nodes according to a respective first switching control signal, and
a first controller configured to:
compute a first voltage reference according to:
a first load signal of the first DC output, and
a first non-linear relationship between a first electrical load condition of the first DC output and a DC bus voltage across the first and second DC nodes, and
generate the first switching control signals according to the first voltage reference to cause the first switching circuit to convert AC input power from the first AC input to control the DC bus voltage; and

a second rectifier, comprising:
a second AC input, including second AC nodes,
a second DC output connected to the first and second DC nodes of the first DC output,
a second switching circuit coupled with the second AC input and with the first DC output, the second switching circuit including second switching devices respectively configured to selectively couple one of the second AC nodes with a respective one of the first and second DC nodes according to a respective second switching control signal, and
a second controller configured to:
compute a second voltage reference according to:
a second load signal of the second DC output, and
a second non-linear relationship between a second electrical load condition of the second DC output and the DC bus voltage, and
generate the second switching control signals according to the second voltage reference to cause the second switching circuit to convert AC input power from the second AC input to control the DC bus voltage.

13. The power conversion system of claim 12 , wherein the respective first and second non-linear relationships are multi-segment functions with multiple segments having different respective slopes that relate the load condition of the DC output to the DC bus voltage.

14. The power conversion system of claim 12 , wherein the respective first and second non-linear relationships are second or higher order formulas that relate the respective load conditions of the first and second DC outputs to the DC bus voltage.

15. The power conversion system of claim 12 ,
wherein the first load signal of the first DC output is a first DC output current signal of the first DC output; and
wherein the second load signal of the second DC output is a second DC output current signal of the second DC output.

16. A method, comprising:
computing a voltage reference according to:
a load signal of a DC output of an active rectifier, and
a non-linear relationship between an electrical load condition of the DC output and a DC bus voltage at the DC output; and

generating switching control signals for the active rectifier according to the voltage reference to cause a switching circuit of the active rectifier to convert AC input power from an AC input to control the DC bus voltage;
wherein the non-linear relationship is a

Assignees

• Rockwell Automation Tech Inc

Inventors

• Mohamed Sayed Ahmed Ahmed S
• Wei Lixiang
• Al-Nabi Ehsan
• Patel Nirav
• Nam Sang Woo

Classifications

• H02M1/0095

  Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck · CPC title

• H02M1/0067

  Converter structures employing plural converter units, other than for parallel operation of the units on a single load · CPC title

• H02M1/0019

  the disturbance parameters being load current fluctuations · CPC title

• Y02B70/10

  Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes · CPC title

• H02M7/23 Primary

  arranged for operation in parallel {(H02M7/2176 takes precedence)} · CPC title