Peak Lopping Inverter
Peak Lopping Inverter
”Peak Lopping” or “Peak Shaving” are terms used to describe electric power management systems which “lop off” the top of a user’s exceptional peak power consumption curve, either by restricting the amount of power he uses or by supplying the peak requirements from an alternate source. Domestically, peak lopping refers to the first approach where non-critical loads are shed or delayed (dish washers, washing machines) to prioritise the consumers’ preferences (lighting, heating, cooking).
Industrially, peak-shaving invariably refers to the provision of an alternate power source of which there are many choices, depending on the application, as described. In either case, the motivation for this kind of equipment is either economical (the utility penalises consumers who exceed a given rating – sometimes by charging up to 100 times more per kWh) or practical, the normal supply simply cannot provide more power.
A special case of the latter can be found in solar farms not connected to a power grid such that each passing cloud might necessitate the (brief) activation of an alternate source (e.g. a diesel generator-set).
In general terms, whatever the motivation for peak “lopping” or “shaving”, the technology falls into the category of power regulation in networks increasingly supplied by intermittent resources such as wind and solar power.
Principle of Operation
The principle of Thycon power electronics for peak lopping is to invert power from a DC source as required. The battery is the usual storage system but alternatives are also possible. Unlike an Uninterruptible Power Supply (UPS), the full power does not flow through the system but directly to the intended load. The Peak Lopper operates in parallel and assists the source when the demand exceeds its capacity.
Typical Energy Storage Systems
Two or more approaches, generally combined, may be used for the alternate source(s): the storage of electrical energy from the prime supply (e.g. Utility, Solar Panel) and the independent generation of power from a tenable (stored) resource (e.g. diesel). The Power Management System oversees the requirements and switches the alternate sources in and out according to availability and economics.
The economics are partly determined by the nature of the alternate source: where this, typically, is a diesel engine, it is undesireable to make frequent and rapid starts as the life expectancy and service requirements of such machines depends on the number of cold starts that they make, so the activation of stand-by generators is always avaoided for short peak requirements which are best met by battery or other energy stroage systems and offer the added advantage that they can “start” within milliseconds as opposed to the tens of seconds required to bring a diesel engine or gas turbine up to operating speed.
The generator set is thus used for long-duration power peaks or overloads, while the battery system provides short-duration peaks and avoids the more cumbersome starting of the generator sets, except when really needed.