Inverter-filter non-linearity blanking time and zero current clamping compensation system and method
View Patent ↗Inverter-filter non-linearity blanking time and zero current clamping compensation is accomplished by comparing the average output current with the discontinuous current mode threshold values to determine when the average output current is entering a discontinuous current mode and introducing a compensation voltage to the inverter drive voltage in response to the average output current entering a discontinuous current mode to compensate for discontinuous current mode distortion of the inverter output voltage.
1. An inverter-filter non-linearity blanking time and zero current clamping compensation system comprising:
a current measurement circuit for measuring an average output current of an inverter;
a comparator circuit for comparing said average output current with discontinuous current mode threshold values for determining when said average output current is entering a discontinuous current mode; and
a compensation circuit, responsive to said average output current entering a discontinuous current mode, for introducing a compensation voltage to the inverter reference voltage to compensate for discontinuous current mode distortion of the inverter output voltage.
2. The inverter-filter non-linearity compensation system of claim 1 in which said compensation circuit includes a waveform generator for generating a compensation waveform.
3. The inverter-filter non-linearity compensation system of claim 2 in which said compensation waveform includes a sinusoidal waveform.
4. The inverter-filter non-linearity compensation system of claim 3 in which said compensation current includes a start ramp generator and a finish ramp generator for generating start and finish ramps.
5. The inverter-filter non-linearity compensation system of claim 4 in which said compensation circuit includes a ramp control circuit for combining said start and finish ramps with said compensation waveform to form said compensation voltage.
6. The inverter-filter non-linearity compensation system of claim 1 in which said comparator circuit includes a storage device for storing the discontinuous current mode threshold values.
7. The inverter-filter non-linearity compensation system of claim 1 in which said discontinuous current mode threshold values are generated from
I
av
(
ω
t
)
=
[
Vdc
2
]
2
-
[
V
·
sin
ω
t
]
2
L
·
2
·
T
S
·
Vdc
where V is a predetermined nominal voltage, Vdc is a DC voltage, L is a filter inductor, and T s is a switching period.
8. The inverter-filter non-linearity compensation system of claim 7 in which, for one part of each output voltage cycle, V is a predetermined nominal voltage and, for an other part of each output voltage cycle, V is a predetermined distorted voltage.
9. The inverter-filter non-linearity compensation system of claim 1 in which said compensation voltage for said inverter reference voltage is a scaled function of the difference between a nominal inverter output voltage and a distorted inverter output voltage.
10. An inverter-filter non-linearity blanking time and zero current clamping compensation method comprising:
comparing an average output current with discontinuous current mode threshold values to determine when the average output current is entering a discontinuous current mode; and
introducing a compensation voltage to an inverter reference voltage, in response to the average output current entering a discontinuous current mode, to compensate for discontinuous current mode distortion of the inverter output voltage.
11. The inverter-filter non-linearity compensation method of claim 10 further including generating discontinuous current mode threshold values.
12. The inverter-filter non-linearity compensation method of claim 10 in which introducing a compensation voltage includes generating a compensation waveform.
13. The inverter-filter non-linearity compensation method of claim 12 in which said waveform is sinusoidal.
14. The inverter-filter non-linearity compensation method of claim 12 in which introducing the compensation voltage includes providing a start ramp and a finish ramp.
15. The inverter-filter non-linearity compensation method of claim 12 in which introducing the compensation voltage includes providing a start ramp and a finish ramp and combining said ramps with said compensation waveform to form said compensation voltage.
16. The inverter-filter non-linearity compensation method of claim 11 in which generating discontinuous current mode threshold values includes retrieving them from a look-up table.
17. The inverter-filter non-linearity compensation method of claim 11 in which generating discontinuous current mode threshold values includes calculating them from the expression:
I
av
(
ω
t
)
=
[
Vdc
2
]
2
-
[
V
·
sin
ω
t
]
2
L
·
2
·
T
S
·
Vdc
where V is a predetermined nominal values, Vdc is a DC voltage, L is a filter inductor, and T s is a switching period.
18. The inverter-filter non-linearity compensation method of claim 17 in which, for one part of each output voltage cycle, V is a predetermined nominal valve and, for an other part of said output voltage cycle, V is a predetermined distorted voltage.
19. The inverter-filter non-linearity compensation method of claim 10 in which said compensation voltage for said converter drive voltage is a scaled function of the difference between a nominal inverter output voltage and a distorted inverter output voltage.