Sunday, 18 August 2019

Untitled Post

ISLANDS and AREAS of LIGHT - Infrastructure Development  

Electricity Some useful links for ELVDC LED lighting:

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Ultra Bright 1500LM 15W COB LED Light Source 12V DC

48V DC - Mid Power (20W - 50W) COB LED

48V DC - High Power (200W) COB LED

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Suitable lighting units for lensed COB LEDs:

Cobra's up to date post:

Friday, 19 July 2019


ISLANDS and AREAS of LIGHT – Infrastructure Development

Subject: Electricity –

The Indian Standard  'IS 16711 / 2017' – a valuable paper to be followed 
for the firsts Islands of Light (probable even in the early 'post Event era'), we are entitled to consider as an (already in place) standard  of
48 V ELVDC Distribution System

- Guidelines

The same may proper apply for any of-grid community...
Standard: Title IS 16711 / 2017 - "IS 16711 / 2017"

48 V ELVDC Distribution System - Guidelines

[Images are posted for educational purpose only]

Thursday, 18 July 2019


ISLANDS and AREAS of LIGHT Infrastructure Development

Electricity HFAC Microgrid - 

An interesting excerpt from telecommunication system papers, with a good description:

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High-Frequency AC (HFAC) power distribution system was first proposed by NASA for space applications some 45 years ago [14], [15].
The HFAC power distribution approach offers several advantages over the conventional DC power distribution approach, which makes it an attractive solution for many applications such as telecommunications and computers.
The main advantage of HFAC power distribution is that the two main conversion steps are eliminated in the overall power distribution architecture [16].
The advantages of HFAC power distribution over conventional DC power distribution is given as: 
- It is more efficient 
-  It is more reliable 
- It has better heat distribution 
- It has higher power density 
- It also has the potential for connector-less power transfer.

Due to the above-mentioned significant advantages of the HFAC power distribution systems over the DC power distribution systems, HFAC power distribution is also being proposed for high-power density telecommunication as well as computer applications [17]. We have already seen that the conventional power distribution in telecommunication systems is based on the DC power distribution. DC power distribution is usually implemented using either the centralized architecture or distributed architecture. One of the main disadvantages of centralized DC power distribution is that due to the distribution of heavy current through the bus-bar, it creates a lot of losses and also requires a large amount of space on the backplane for tracking.
 Also, remote voltage sensing is required to compensate for the voltage drops along the entire length of the cables. In addition, the heat generated by the DC-DC converters is very high and is mostly concentrated to the converter, which poses a great challenge to the management of thermal energy. Also, few DC-DC converters should also be used to provide redundancy, which can be considered as a necessary evil in the process of communication. Therefore, current sharing is necessary, which also brings complexity to the entire power distribution system [18].
Distributed DC power distribution architecture was introduced to overcome the setbacks due to the centralized DC architecture. This architecture utilizes the point-of-use power supplies (PUPS) in order to locally distribute power to the electronic cards in the telecommunication facility.
The main advantage of this architecture is that, there is a much more efficient thermal management due to the fact that heat is distributed throughout the entire system.
HFAC power distribution opens up a new horizon for telecommunication systems.
 The HFAC distribution system not only combines the advantages of DC power distribution, but also offers newer features, which cannot be implemented in the DC power distribution systems alone. The main features of HFAC power distribution are listed as follows:
- It has excellent transient response since there is no low-pass filter (LPF) and HFAC feedback loop. - The AC power lines can also be used for communication, alarm triggering, etc. 
- It has a very simple current limit circuit for the line feed. 
- There is simplified insertion of electronic cards. 
- It has a simplified ringing generator. 
- It also has the potential for connector-less power distribution.

In this architecture, there is more than one DC-AC inverter in order to produce an HFAC sine-wave output, which is typically 60Vrms, with a carrier frequency of 128 kHz, from the battery voltage of -48V.
Then, the HFAC bus is distributed through the backplane to the electronic cards where AC PUPSs convert it to the required compatible DC voltages [19]. The HFAC bus in telecommunication systems can be of the voltage type or the current type.
The advantages of HF sinusoidal voltage distribution are that it has low electro-magnetic interference (EMI) and overall higher efficiency for a wide variety of loads.

A hybrid HFAC power distribution architecture was also proposed for the telecommunication systems in order to combine the advantages of both sinusoidal voltage and sinusoidal current distribution [20]. This hybrid HFAC architecture can provide the following features:
- It can be used for connector-less power transfer. 
- It has fuse-less protection. 
-There is sinusoidal voltage and current distribution. 
- It has high overall system efficiency.
- In HFAC power distribution for telecommunication systems, several inverter modules are generally configured in parallel to provide reliable power distribution for several reasons, such as better heat dissipation, lower cost, elimination of short-time overload, provision of redundancy, better reliability, and designing of a modular structure. Even sharing of the power results in better thermal management, optimized component ratings, and thus, the overall cost is minimized [21], [22].

[posted for educational purpose only]

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If you put together the above described system with those ones linked from our blog, and of course if you are 'awakened' and in knowledge, you will find it also as a neat path for application in other areas of interest, particularly in our Islands and Areas of Light.

Useful Links:

Control and Design of High Frequency Power Distribution System

Friday, 5 July 2019


ISLANDS and AREAS of LIGHT Infrastructure Development

Electricity – UHFAC Microgrid Papers - an Incunabulum of a real high frequency AC power distribution

UHFAC Microgrids:
Summary of the Work:
"This dissertation presents a framework for the proposed novel Ultra-High-Frequency-AC (UHFAC) Microgrids.
The bus frequency and the power transmission frequency of the UHFAC Microgrids is pushed to 54 kHz. 

The bus voltage waveform is quasi-square (trapezoidal) and the peak value is 400 V. 
Compared to traditional Low-Frequency-AC (LFAC) Microgrids, the size and weight of the transformer and passive component in UHFAC Microgrids are significantly smaller; the distributed source interface and load interface converters are greatly simplified; the acoustic noise is eliminated; and wireless connection of power electronics interfaces is enabled.
Compare to traditional DC Microgrids, huge DC capacitors are eliminated since there is no DC bus to stabilize. 
In addition, the proposed UHFAC Microgrids get rid of DC-arcing flash since the bus has current zero crossing points.
The circuit breaker therefore is much easier to develop than those in DC Microgrids.
Furthermore, short-circuit protection is possible to respond as fast as 9.26 ยตs,
which is the time interval between two nearest zero-crossing point.
Chapter 1 gives a review on the traditional LFAC Microgrids and DC Microgrids.
Existing 500 Hz HFAC Microgrids is also included for comparison.
Chapter 2 presents an in-depth analysis on the advantages of the proposed UHFAC Microgrids." 

A novel distributed PV system with ultra-high-frequncy-AC bus for residential applications
"In this paper, three existing distributed PV system configurations are reviewed and compared in depth. A novel ultra-high-frequency-AC (UHFAC) PV system for residential application is proposed. Compared with traditional DC parallel PV systems, this new approach eliminates the high voltage DC bus by replacing it with UHFAC bus, which avoids the DC arcing fault and enables ultra-fast short circuit protection as well. Resonance is utilized in this system to help UHFAC power transfer and realize soft-switching. Cable modeling is conducted to extract AC parameters, which helps validate the UHFAC power transmission (i.e., 100 kHz) in 30 to 40-feet-distance. Cable parameters also participate in the resonant intervals which demonstrates full utilization of system components. Simulation and experimental results are provided to verify the proposed approach."
"Renewable energy resources, especially solar power, has drawn tremendous interest in recent decades. Distributed and centralized PV systems are two main architectures, while distributed system is favorable for both industry and academic research. Because of radiation mismatch, centralized PV system can expect a power loss of about 30% for lacking of individual MPPT [1]. Power electronic technologies for conditioning PV panel power fall into two big categories: panel series solution and panel parallel solution."

[posted for educational purpose only]