Hybrid Power Plants
Hybrid power systems combine two or more energy conversion devices, or two or more fuels for the same device, that when integrated, overcome limitations inherent in either, and provide increased system efficiency and greater balance in energy supply. Hybrid systems can address limitations in terms of fuel flexibility, efficiency, reliability, emissions and / or economics. UtiliCell specializes in designing hybrid systems that maximize the use of renewables, resulting in a system with lower emissions than traditional fossil-fueled technologies. We help customers achieve the desired attributes at the lowest acceptable cost.
The Hybrid Power Plant is:
- a system capable to generate electricity
- combines multiple renewable energy sources (PV, wind, CAES, flywheel, mini hydro...)
- includes a LiFePO4 Battery Energy Storage System
- can operate in stand-alone mode (off-grid)
- implements the Distributed Generation principle
- Hybrid Power Plants have a power range from 35 kW up to several MWs
- Hybrid Power Plants are modularly extensible
Electricity from different renewable energy sources
The Hybrid Power Plant (HPP) is a system capable to generate electricity from different renewable energy sources, typically photovoltaic (PV) and wind turbines. The HPP is equipped with LiFEPO4 Battery Energy Storage.
The HPP can operate parallel connected to the main grid (on-grid operation), stand alone (off-grid operation) or connected to a micro grid, with other generators working in parallel (grid supporting mode, with droop control).
It is practical that the same HPP can function in these three different modes of operation and that the suitable control strategy is either automatically selected by an Energy Management System (EMS), or by the operator. The HPP inverter control allows to implement all these different modes of operation. Power control and energy conversion units are suitable for operation in enclosed housings (control and energy conversion cabinets).
Hybrid Power Plant combinations
UtiliCell offers three series of Hybrid Power Plants: the DC series with DC inputs for the connection of photovoltaic solar power plants (PV), the second series to the connection with an AC energy source (e.g. mini hydro or wind turbine), and the third series for inter-modal connections, DC and AC energy sources. The control and conversation cabinets have been conceptualized for indoor use, air-conditioning is available upon request. Thermal containers with control, conversation and battery subdivisions, and doors for service personnel are available in sizes from 20‘- 30‘ – 40‘ with nominal capacities from 20, 35, 70, 125, 250 kVA.
Hybrid Power Plant Applications
- Village Power
- Commercial Power Parks
- Industrial Power Quality
- Integrated Building Efficiency (CHP+)
- Remote (Off-Grid) Power
- Distribution (Grid) Support
- Water Resource Management
- Green Power
- Brownfields (to Brightfields)
- Power Price Stabilization
AC Bus Configuration
The AC bus configuration is preferred for High Power Hybrid power plants, with rated power more than 250kVA. It is suitable for on-grid and off-grid operation. The renewable sources are connected to bus through their power converters. In absence of grid, the battery bi-directional inverter can be operated by a “grid forming control”, which imposes voltage and frequency. The Diesel genset has a synchronizing controller which follows the (V, f) existing on the AC bus.
DC bus Configuration
The DC bus configuration is more indicated for HPP with lower performance. The HPP unit, with single phase 230V 50/60Hz output voltage, adopts the DC bus. A HPP can connect a small Diesel genset to the AC inlet normally dedicated to the wind generator, so that a fully DC bus solution is created. A fully DC bus configuration of HPP, with an inverter at the output, can work both on-grid or off-grid, using a “grid following” or “grid forming” control, respectively.
The Hybrid Power Plant Conversion and Control Systems with DC power input include:
- Power static converters (DC-DC and DC-AC)
- AC filters, for harmonic components reduction at inverter output
- Low frequency (50Hz) output power transformer
- EMI filters, both on DC side and AC side Battery pre-charge circuit
- Digital controllers
- Insulation Resistance
- Monitoring Device on DC side
- Protections (DC over-voltage, over-current, over-temperature, grids against direct contact hazard)
- Grid Interface Protection, including voltage-frequency relay and electromechanical contactor
- Terminal blocks for power connections Accessories (power supplies, fans, data communication interfaces)
- Operator panel on cabinet front door
- Communication interfaces (RS 485 with CAN bus and Modbus protocols )
- Master Control system (MS), Energy Management System (EMS)
- Remote Monitoring System
The HPP Conversion and Control Cabinets (C- H-PVW-xxx- DC) are based on a configuration with common DC bus at nominal 650V (see block diagram) and provide input/output power connections, with adequate protections, to the following items:
- External battery bank
- Photovoltaic field
- Main grid
- User load
- Windturbine, Diesel Generating set
Operation modes and Control
The HPP inverter control allows the following operating modes, which can be selected by the operator:
The HPP is either connected to an isolated micro grid or it operates stand alone. It works as a Voltage Generator, the inverter control provides regulation of voltage and frequency, maintaining their values equal to the relative set-points, ensuring the power balance in the system. (Off grid operation).
The HPP is connected to the main grid or to an isolated micro grid and it works as a Current Generator. The inverter control provides active power P and reactive power Q regulation. The inverter operates in synchronism to the micro grid voltage (which is established by the main grid, or by an inverter functioning in grid forming mode, or by a windturbine or diesel generating set) and it regulates the generated current to follow the P and Q set points (On grid operation).
The generator is connected to the micro grid in parallel with other generators, its inverter control assures active and reactive power sharing through voltage and frequency regulation, by “droop control” (Micro grid operation).
PV control by MPPT and RPPT:
The PV generator can be operated in MPPT (Max Power Point Tracking) or in RPPT (Requested Power Point Tracking) mode. In MPPT mode the PV generator injects into the DC bus the maximum power available from the solar source; in RPPT mode it limits the solar generated power following the set point received from the EMS.
Energy Management System:
A simplified Energy Management System (EMS) is resident in the HPP controller and it governs the power flows in the HPP, optimizing the HPP operation according to general control functions. It can select automatically the mode of operation of the inverter and it controls the transitions between the on grid and the off grid states. In off grid operation it continuously matches power generation with load demand and controls the state of charge of battery. The HPP systems can operate in connection with an external controller, where a more complex EMS can be implemented, capable to manage applications involving more generators.