Grid-tie inverter with active power factor correction

Patent metadata

Field	Value
Publication number	US-9853573-B2
Application number	US-201615082153-A
Country	US
Kind code	B2
Filing date	Mar 28, 2016
Priority date	Mar 28, 2016
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

A grid-tie inverter (the “inverter”) may include a power converter that receives a direct current (DC) output voltage from a DC input power source, and generates an alternating current (AC) output voltage for transmission to a utility power grid. The inverter may also include a system controller that regulates the AC output voltage to efficiently transfer power to the utility power grid while a system AC load may be terminated across the output of the inverter. The inverter may also provide active power factor correction between the utility grid voltage and current. Furthermore, the inverter may also offer harmonic cancellation, which minimizes or eliminates the harmonic content out of the utility power grid voltage and current.

First claim

The invention claimed is:

1. An apparatus, comprising:
a power converter configured to receive a direct current (DC) output voltage from a DC input power source, and generate an alternating current (AC) output voltage for transmission to a utility power grid, a grid-interface circuit, or a set of parallel-connected AC loads; and
a system controller configured to regulate the AC output voltage to efficiently transfer power to the utility power grid and to ensure a zero DC value of an AC output current of the power converter, wherein
the system controller is further configured to
control an AC current of the utility grid to be out-of-phase with respect to a voltage of the utility power grid when a load consumes power exceeding a maximum power of the DC input power source or a rated limiting power of the apparatus, and
control the AC current of the utility grid to be in-phase with respect to the voltage of the utility power grid when the load consumes less power than a delivered output power of the power converter.

2. The apparatus of claim 1 , wherein the power converter comprises a cascaded connection of an input electromagnetic interference filter, an input bulk capacitor, a power switching network, a switching inductor, and an output line-filter.

3. The apparatus of claim 1 , wherein the power converter further comprises an isolation transformer configured to provide a voltage conversion and electrical isolation between the DC input power source and the utility power grid.

4. The apparatus of claim 1 , wherein the utility power grid comprises a series connection of an AC voltage source and a grid-interface inductor.

5. The apparatus of claim 1 , wherein the grid-interface circuit comprises a set of parallel-connected AC loads connected in parallel with the utility grid.

6. The apparatus of claim 1 , wherein the set of parallel-connected AC loads comprise a resistive load, an inductive load, a capacitive load, or any combination thereof.

7. The apparatus of claim 1 , wherein the system controller is further configured to generate an error control voltage signal to regulate a received DC input voltage of the power converter at a level corresponding to a set point reference voltage or a maximum peak power voltage.

8. The apparatus of claim 1 , wherein
the system controller is further configured to control a waveform of the AC output voltage of the power converter to be sinusoidal, and
the waveform comprises a same frequency as a frequency of the utility power grid.

9. The apparatus of claim 1 , wherein the system controller is further configured to control an AC current of the utility power grid to be in-phase or out-of-phase with respect to an AC voltage of the utility power grid.

10. The apparatus of claim 1 , wherein the system controller is further configured to prevent the AC output voltage from exceeding a predetermined threshold value.

11. The apparatus of claim 1 , wherein the system controller is further configured to limit the AC output voltage without exceeding a rated power of the apparatus or a maximum rated output voltage.

12. The apparatus of claim 1 , wherein
the system controller is further configured to control the AC output current of the power converter to have a zero DC content at all times by including a 0-ADC regulation control, and
the 0-ADC regulation control receives the AC output current of the power converter, and delivers an DC offset voltage to provide a counter balance voltage for production of a pulse width modulation duty-ratio,
the pulse width modulation defined as

d
PWM

⁡

(
t
)

=

0.5
+

k
·

V
CON

·

sin
⁡

(

ω
⁢

⁢
t

+
ϕ

)

·

(

1
-

v
INAC

V
IN

)

+

f
⁡

(

V
OFF

)

where f(V OFF ) is a counter balance voltage that is a function of the DC offset voltage produced by the 0-ADC regulation control, V CON is an error voltage control signal delivered by an input voltage regulation controller, an inverter input power limit regulation controller, or an inverter output voltage regulation controller, φ is a phase shift delivered by a phase-controlled reference sine-wave generator, and k is a proper scaling constant such that k·V CON ≦0.5.

13. An apparatus for active power correction, comprising:
a switching network configured to:
produce a positive output voltage for a period that is longer than that of a negative output voltage to cause an inverter to deliver a positive voltage, or
produce the positive output voltage for a period that is shorter than that of the negative output voltage to cause the inverter to deliver a negative voltage;

a steering logic pulse with modulation (PWM) switching driver configured to convert a PWM switching signal to be a set of switching signals that drive the switching network; and
a phase-controlled reference SINE-WAVE generator configured to process a phase control signal and a utility grid voltage and produce a commanding reference signal and a reference co-sinusoidal voltage, wherein
the reference co-sinusoidal voltage possesses a 90 degree phase lead with respect to the utility grid voltage.

14. The apparatus of claim 13 , further comprising:
a SINE-WAVE regulation controller configured to process the commanding reference signal and an error voltage control signal and produce the PWM switching signal.

15. The apparatus of claim 13 , further comprising:
a reactive component detector and integrator further configured to process a utility grid current signal and the reference co-sinusoidal voltage and produce the phase control signal.

16. The apparatus of claim 13 , wherein the phase controlled reference SINE-WAVE generator is further configured to generate a harmonic cancellation voltage derived from an input voltage of the apparatus and to insert the harmonic cancellation voltage into the commanding reference voltage signal with

Assignees

• Aerospace Corp

Inventors

• Siri Kasemsan

Classifications

• H03L7/099

  concerning mainly the controlled oscillator of the loop · CPC title

• H02M7/53871 Primary

  with automatic control of output voltage or current · CPC title

• H02M1/44

  Circuits or arrangements for compensating for electromagnetic interference in converters or inverters · CPC title

• H02M1/42

  Circuits or arrangements for compensating for or adjusting power factor in converters or inverters · CPC title

• H02M1/12

  Arrangements for reducing harmonics from AC input or output · CPC title