Fully distributed energy storage system to virtually operate solar plants as a conventional power plant.
Until recently, the typical approach to installing a battery energy storage system has been to set it up downstream of the solar farm. However, a far more reliable and cost-effective solution could be an energy storage system that is distributed across the entire farm.
Pacific Energy has developed a unique and elegant topology that combines a distributed energy storage unit and power boosters. The system is called the GridOptimizer and gives clients the ability to create custom power output profiles, optimized power usage, and maximized monetization of the solar plant while providing high-quality power via smoothing curve output power technology. When compared with a conventional approach, this distributed topology delivers an array of cost and performance advantages.
A Practical and Innovative Storage System Design to EFFICIENTLY and COST EFFECTIVELY Integrate Solar Into the Power Grid
Sun and wind are free and clean energy sources. however, they are intermittent, variable and non-dispatchable. When a cloud passed over an array, the generated power could drop by 50% in less than 30 seconds. This can be extremely disruptive to the stability of a grid. At the solar plant level, this results in variable and intermittent power output, which may cause problems with power quality, power system stability, and supply-demand mismatch.
Grid Optimizer is a Battery Energy Storage System that operates as an add-on to an existing or new solar plant with an inverter and arrays of PV solar panels. By adding advanced power storage capability to the PV plant, Grid Optimizer stabilizes and controls PV solar power output for a highly efficient and robust PV solar integration into the conventional grid and microgrid.
How Does GridOptimizer Compare to a Conventional BESS?
Grid Optimizer is easily integrated into existing or new PV plants.
First, let's take a look at a conventional BESS.
Conventional battery energy storage systems (BESS)are typically installed behind the solar system. Therefore, the inverters are specified to handle the maximum solar generator peak power, which is stored in the batteries. The drawing below shows an example of a microgrid that consists of a 2.5MWp solar plant, a 5.5 kWh BESS and a 1MW diesel generator. Distribution boards are designed to manage the power capacity of the BESS and the solar PV, which amounts in most cases to be twice the capacity of the load it serves.
The distribution hardware rating is also sized concurrently, with oversized feeders needed in order to manage the power coming out of the PV arrays and the BESS, when compared to the actual load being served. Furthermore, a specially engineered area that is designed to support massive weight loads must be allotted to handle the large footprint of the energy storage equipment.
Finally, the failure of a single subsystem of a centralized system can dramatically impact the ability to power the load.
Now, let's take a look at the same place, using Grid Optimizer.
Here is an overview of the same plan but using a distributed GridOptimizer energy storage system topology.
The fundamental design difference between the GridOptimizer and a conventional system is that the sizing of the entire system is based on the maximum power required by the customer and NOT on the maximum peak load delivered by the PV plant.
The cost difference can be quite significant, especially when reserves are factored in for reliance on PV solar only. One of the important benefits is the smaller size and length of wire needed to interconnect the battery system to the PV plant. Another important advantage is the size of the inverters, which are sized for the required power to be supplied and not the total power delivered by the PV plant.
Additionally, GridOptimizer provides hybrid distributed generator control strategies along with configurations for increased efficiency and system optimization. The is no roundtrip necessary as power is stored or injected directly from the PV DC bus.
Because distributed battery energy storage modules are connected via a bi-directional DC/DC converter using existing PV plant combiner boxes; the current flows in both directions. This enables active power electronics to balance the power at the source, with only a very limited loss of efficiency when compared to the centralized system.
DC/DC power management is controlled via the DC/DC converter software that allows multiple operations. These are as follows:
Power Regulation: Power flows to the inverter at a constant level. Batteries are charged when the power flowing from the PV system is higher than the regulated power set point. Likewise, when the PV power is lacking, the battery will discharge to make up the difference. This process is limited by the battery state of charge.
Storage Control: In this mode, the system will automatically control the battery to a specified SoC by taking or injecting power from the PV DC bus. The system is only driven by the SoC and typically used in the preparation of a known discharge event later.
Custom Profile: It allows the user to shape the load profile for the entire day. The system will adjust depending on the actual load and the amount of storage available.
Curve Smoothing: This profile helps counter the fast fluctuation of power sent to the inverter.
Summary of the Key Benefits
GridOptimizer includes 4 main sub-systems:
PV Panel array(s)
PCM/DR2- Buck/ Boost DC/DC Converter(s)
ES-50 Battery Bank(s)