H bridge inverter control chips for grid tied inverters not available - Page 1
Forum section: electronics / projects

author: ocset
author_rank: Super Contributor
timestamp: July 15, 2018, 08:48:49 am
content: Hello,There are massive numbers of PFC control chips available off the shelf. Why are there not any IC’s available for low power (<300W) H Bridge inverters for putting power back into the mains?All the controllers used for H-bridge inverters seem to be high-end microcontrollers.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 15, 2018, 08:57:20 am
content: Duh, use a PFC with the shunt resistor reversed.(? It might actually work, now I want to try it.)Tim

author: David Hess
author_rank: Super Contributor
timestamp: July 15, 2018, 02:34:56 pm
content: It is not a large enough market and the mixed signal requirements are incompatible with economical integration. If multiple packages are going to be needed anyway, then why bother?UPSes which are a much larger market do not have dedicated ASICs either.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 15, 2018, 05:22:12 pm
content: Quote from: David Hess on July 15, 2018, 02:34:56 pmOne APC I took apart did have an ASIC doing the PWM. It replaced a half dozen or so of discrete logic chips used in a much older APC.

author: David Hess
author_rank: Super Contributor
timestamp: July 15, 2018, 06:56:47 pm
content: Quote from: NiHaoMike on July 15, 2018, 05:22:12 pmSometimes it is difficult to tell if the chip markings have been removed but all of the UPSes I have inspected, Liebert and Powerware mostly, used standard parts including pulse width modulation controllers. There are some microcontroller/DSP ASICs intended for variable frequency motor drives which might be useful but phase locked inverters do not require that kind of performance.APC has enough sales volume though that if anybody has a custom ASIC, I would expect it to be them. Personally I cannot stand their stuff due to their unreliable and deceitful marketing.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 15, 2018, 07:39:47 pm
content: It actually does take quite a bit of logic to get sine wave output. Apparently enough to make designing an ASIC for it worthwhile. That particular UPS was from 1998.I have to agree that APC "doesn't make them like they used to".

author: ahbushnell
author_rank: Frequent Contributor
timestamp: July 15, 2018, 08:00:42 pm
content: Quote from: NiHaoMike on July 15, 2018, 07:39:47 pmTI makes processors like the Piccolo that are designed for this purpose.Sent from my SM-G930V using Tapatalk

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 15, 2018, 08:26:08 pm
content: I would expect microcontrollers with digital power features to be a very popular way of implementing a sine wave inverter nowadays. When exactly did the Piccolo series come out?

author: David Hess
author_rank: Super Contributor
timestamp: July 15, 2018, 08:39:52 pm
content: Quote from: NiHaoMike on July 15, 2018, 07:39:47 pmOr it can be done in the analog domain and any microcontroller even from 1998 can do it with software DDS or even less. I regularly did it with 68HC11s and PICs from that era. Don Lancaster hadsome ideas worth considering.The big advantage of a custom ASIC would be increased integration but I am dubious of the economics unless they were using the same ASIC in a lot of UPSes which of course APC could have done.

author: BrianHG
author_rank: Super Contributor
timestamp: July 15, 2018, 10:44:00 pm
content: Google 'dspic grid tied solar inverter reference design'

author: Phoenix
author_rank: Frequent Contributor
timestamp: July 15, 2018, 11:39:33 pm
content: Quote from: BrianHG on July 15, 2018, 10:44:00 pmThis is the TI Piccolo reference design for a solar micro inverter:http://www.ti.com/tool/TMDSSOLARUINVKIT

author: ocset
author_rank: Super Contributor
timestamp: July 16, 2018, 04:51:37 am
content: Thanks,Its a mystery why all these offtheshelf soltuions for Grid Tied Inverters have so much software in them, after all, GTI's can easily be done very satisfactorily using simple pure analog methods, as the following shows....https://www.eevblog.com/forum/projects/h-bridge-grid-tied-inverter-is-good-despite-non-sinusoidal-current/

author: Phoenix
author_rank: Frequent Contributor
timestamp: July 16, 2018, 05:33:19 am
content: Quote from: treez on July 16, 2018, 04:51:37 amHave you read any standards related to grid tie inverters (E.g. Australia has for solar inverters AS62109 and AS4777)? The requirements are FAR greater and more complex than a load device.

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: July 16, 2018, 05:32:11 pm
content: exactly thisjust to name a few requirements that have to be met by PV grid tied inverters (ymmv, depending the country you live in, though):1) rapid disconnect2) fault-ride-through3) anti-islanding4) 1-fault-safe ac-disconnect, parametrizable on frequency- and voltage-limits5) apparent load delivery, commanded via grid codes6) pv-arcing detection7) panel leakage-testingoften overlooked, but hey, while we are at it: the inverter requires a PLL to cope with the frequency changes. there is simply no public grid that runs on exactly the clock frequency that you have programmed your discrete PWM controller to.coming back to OP's question, well, there is at least one processor that can do all of the above, and also not just for standard push-pull topolgies, but for NPC topologies as well:http://www.analog.com/en/products/processors-dsp/microcontrollers/cm4xx-mixed-signal-control-processors/adsp-cm419f.html(disclaimer: i am working for Analog Devices, Inc. so, yes, this is a shameless plug, SCNR)

author: BrianHG
author_rank: Super Contributor
timestamp: July 16, 2018, 05:44:41 pm
content: Quote from: treez on July 16, 2018, 04:51:37 amPlease stay away and decide to peruse different hardware which has no connection to the grid.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 16, 2018, 06:17:45 pm
content: Quote from: Le_Bassiste on July 16, 2018, 05:32:11 pmNot really, I did a small grid tie inverter as part of my senior design project that worked as a voltage controlled current source.

author: ocset
author_rank: Super Contributor
timestamp: July 16, 2018, 07:33:37 pm
content: Thanks i woudl synch up to the grid by using a sinusoidal reference derived from the grid itself...this way i would not need a PLL.

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: July 16, 2018, 09:05:09 pm
content: understood. that's probably very similar to the "voltage controlled current source" mentioned by NiHaoMike. the "charme" of such a solution is the inherent short-circuit protection (iout = 0 @ vmains= 0). but then you are losing the info about fmains and the "shape" of vmains when mains gets shorted, i.e., in case of f.r.t.. that's why i said that a PLL is required. leaving f.r.t. aside, the VCCS is definitely a viable solution, given that it manages to synthesize a good sine-shape from vmains.you could argue though that using the shape of vmains directly to synthesize the iout waveshape would be sufficient and "ideal" in a sense that your inverter would basically represent a negative resistor to the grid. however, that wouldn't support the grid in terms of reducing harmonic contents in the mains current, as opposed to sine-shaped iout.