Multi-level medium voltage data center static synchronous compensator (DCSTATCOM) for active and reactive power control of data centers connected with grid energy storage and smart green distributed energy sources

Patent metadata

Field	Value
Publication number	US-12255458-B2
Application number	US-202218087303-A
Country	US
Kind code	B2
Filing date	Dec 22, 2022
Priority date	Sep 9, 2013
Publication date	Mar 18, 2025
Grant date	Mar 18, 2025

Abstract

Systems and methods for supplying power (both active and reactive) at a medium voltage from a DCSTATCOM to an IT load without using a transformer are disclosed. The DCSTATCOM includes an energy storage device, a two-stage DC-DC converter, and a multi-level inverter, each of which are electrically coupled to a common negative bus. The DC-DC converter may include two stages in a bidirectional configuration. One stage of the DC-DC converter uses a flying capacitor topology. The voltages across the capacitors of the flying capacitor topology are balanced and switching losses are minimized by fixed duty cycle operation. The DC-DC converter generates a high DC voltage from a low or high voltage energy storage device such as batteries and/or ultra-capacitors. The multi-level, neutral point, diode-clamped inverter converts the high DC voltage into a medium AC voltage using a space vector pulse width modulation (SVPWM) technique.

First claim

What is claimed is:

1. A static synchronous compensator for an Information Technology (IT) electrical load, comprising:
a two-stage direct current (DC)-DC converter coupled to an energy storage device;
a multi-level inverter coupled to the two-stage DC-DC converter and configured to output a medium alternating current (AC) inverter voltage; and
a controller configured to control the medium AC inverter voltage of the multi-level inverter to generate or absorb reactive power such that a power factor is substantially one between a utility supply and a transformer, the controller further configured to charge or discharge the energy storage device by adjusting the angle of the medium AC inverter voltage with respect to a medium AC grid voltage,
wherein a negative terminal of the energy storage device, a negative terminal of the two-stage DC-DC converter, and a negative terminal of the multi-level inverter are electrically coupled to a common negative bus.

2. A compensator comprising:
a two-stage direct current (DC)-DC converter coupled to an energy storage device, wherein when the energy storage device is discharged, the two-stage DC-DC converter steps up a voltage, and when the energy storage device is charged, the two-stage DC-DC converter steps down the voltage;
a multi-level inverter coupled to the two-stage DC-DC converter, wherein the multi-level inverter outputs an alternating current (AC) voltage; and
a controller coupled to the multi-level inverter, wherein the controller controls the AC voltage to generate or absorb reactive power such that a power factor is substantially one between a utility supply and a transformer.

3. The compensator according to claim 2 , wherein the AC voltage is between about 3.3 kV and about 18 kV.

4. The compensator according to claim 2 , wherein the two-stage DC-DC converter includes a first stage that generates a first DC voltage and a second stage that generates a second DC voltage greater than the first DC voltage.

5. The compensator according to claim 4 , wherein a positive terminal of the second stage of the two-stage DC-DC converter and a positive terminal of the multi-level inverter are electrically coupled to a common positive bus.

6. The compensator according to claim 4 , wherein the first stage includes two levels and the second stage includes more than two levels.

7. The compensator according to claim 6 , wherein the second stage includes three levels or five levels.

8. The compensator according to claim 6 , wherein the two-stage DC-DC converter includes switches that define the levels of the first and second stages and capacitors coupled together in a flying capacitor topology having a common negative bus.

9. The compensator according to claim 6 , wherein the AC voltage is a three-phase AC voltage,
wherein the multi-level inverter includes three sets of switches,
wherein each set of switches corresponds to one of the three phases of the three-phase AC voltage, and
wherein each set of switches is arranged in a diode-clamped multi-level topology.

10. The compensator according to claim 4 , wherein the multi-level inverter converts the second DC voltage into a third voltage that is an AC voltage less than the second DC voltage.

11. The compensator according to claim 4 , further comprising a DC-DC converter controller that controls the first stage with pulse width modulation control signals and controls the second stage in a flying mode configuration with fixed duty cycle control signals,
wherein the DC-DC controller controls the multi-level inverter using space vector PWM control signals so as to perform neutral point voltage balancing.

12. The compensator according to claim 2 , wherein the two-stage DC-DC converter allows a flow of active and reactive power in a first direction from the energy storage device to the multi-level inverter and in a second direction from the multi-level inverter to the energy storage device.

13. The compensator according to claim 2 , wherein the energy storage device is a low voltage energy storage device.

14. The compensator according to claim 13 , wherein the low voltage is between about 700 V and about 1200 V.

15. The compensator according to claim 2 , wherein the energy storage device is a battery, an ultra-capacitor, or a battery and an ultra-capacitor electrically coupled to one another.

16. The compensator according to claim 2 , wherein the multi-level inverter includes more than two levels.

17. A method comprising:
receiving a first direct current (DC) voltage from an energy storage device;
converting the first DC voltage into a second DC voltage;
generating an alternating current (AC) inverter voltage from the second DC voltage, wherein the AC inverter voltage is a voltage less than the second DC voltage;
providing the AC inverter voltage to a point between a utility supply and a transformer; and
controlling the AC inverter voltage to generate or absorb reactive power.

18. The method according to claim 17 , further comprising:
measuring an AC grid voltage and an AC grid current;
calculating a phase angle between the AC grid voltage and the AC grid current;
calculating reactive power based on the phase angle, the AC grid voltage, and the AC grid current;
determining whether the AC grid current is leading or lagging the AC grid voltage;
when the AC grid current is lagging the AC grid voltage, generating the reactive power by adjusting the AC inverter voltage so that the AC inverter voltage is greater than the AC grid voltage; and
when the AC grid current is leading the AC grid voltage, absorbing the reactive power by adjusting the AC inverter voltage so that the AC inverter voltage is less than the AC grid voltage.

19. The method according to claim 17 , further comprising:
measuring an AC grid voltage, an AC grid current, and a phase angle between the AC grid voltage and the AC grid current;
calculating a power factor based on the phase angle;
calculating active power demand based on the AC grid voltage, the AC grid current, and the power factor;
determining whether to charge or discharge the energy storage device based on the active power demand;
charging the energy storage device by adjusting the angle of the AC inverter voltage so that the AC inverter voltage lags the AC grid voltage; and
discharging the energy storage device by adjusting the angle of the AC inverter voltage so that the AC inverter voltage leads the AC grid voltage.

Assignees

• Inertech Ip Llc

Inventors

• Mondal Subrata K

Classifications

• Y02E40/10

  Flexible AC transmission systems [FACTS] · CPC title

• H02M7/4837

  Flying capacitor converters · CPC title

• H02M1/007

  Plural converter units in cascade (push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826) · CPC title

• Y02E60/13

  Energy storage using capacitors · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title