Grid-Connected System Definitions
Grid-connected systems integrate solar power with the electrical grid, enabling bidirectional energy flow and reliable power supply for residential use.
Grid-Connected System Definitions establish the terminology and essential concepts related to solar power systems that interface directly with the utility electrical grid. These definitions clarify the operational and technical characteristics of systems designed to both consume and export electricity in coordination with the utility grid, ensuring safe, reliable, and efficient integration.
Utility-Interactive Operation Definition
Utility-interactive operation refers to the mode of a solar power system that allows it to operate in parallel with the utility grid. In this mode, the system can supply power to meet local loads, export excess power to the grid, and draw power from the grid when solar generation is insufficient. This operation requires synchronization with grid voltage, frequency, and phase to maintain safety and power quality standards.
Point of Common Coupling Definition
The point of common coupling (PCC) is the electrical node where the customer’s solar power system connects to the utility grid. It represents the boundary between the utility’s electrical distribution system and the customer’s premises wiring. The PCC is the reference point for measuring power flow, voltage, frequency, and for applying grid interconnection standards and protections.
Bidirectional Meter Definition
A bidirectional meter is an electrical meter capable of measuring energy flow in two directions: energy consumed from the utility grid and energy exported back to the grid by the solar power system. This meter is essential for net metering and net billing arrangements, providing accurate accounting of the energy exchanged between the customer and the utility.
Net Metering Definition
Net metering is a billing arrangement where the customer’s electricity meter records the net difference between electricity consumed from the grid and electricity exported to the grid over a billing period. If the customer exports more energy than consumed, the net excess may be credited or carried forward, depending on local policies. Net metering incentivizes on-site generation by offsetting consumption with generation.
Net Billing Definition
Net billing is a tariff mechanism where exported electricity is compensated at a predefined rate, which may differ from the retail electricity rate charged for consumption. Unlike net metering, net billing separately accounts for energy consumed and energy exported, providing payments or credits for exports at specific rates that reflect market or utility policies.
Feed-in Tariff Definition
A feed-in tariff (FIT) is a policy mechanism that guarantees fixed payments to renewable energy producers for the electricity they generate and feed into the utility grid over a specified period. FITs are designed to promote investment in renewable energy by providing predictable and stable financial returns independent of the customer’s electricity consumption.
Volt-Watt Control Definition
Volt-watt control is a grid support function implemented in photovoltaic inverters that reduces active power output when the local voltage exceeds predefined thresholds. This control helps mitigate overvoltage conditions by curtailing power injection into the grid, maintaining voltage within acceptable limits and enhancing grid stability.
Volt-Var Control Definition
Volt-var control is an inverter function that dynamically adjusts reactive power output based on local voltage measurements. By injecting or absorbing reactive power, the inverter helps regulate voltage levels on the distribution system, improving power quality and reducing losses without necessarily curtailing active power generation.
Frequency-Watt Control Definition
Frequency-watt control is a grid support feature where the inverter adjusts its active power output in response to changes in grid frequency. When the frequency deviates from nominal values, indicating imbalance between generation and load, the inverter can reduce or increase power output to aid in frequency regulation and maintain grid stability.
This diagram displays a grid-connected solar power system where solar panels supply DC power to an inverter that converts it to AC. The inverter interacts with the utility grid at the Point of Common Coupling (PCC) through a bidirectional meter, enabling both consumption and export of electricity. Control functions such as volt-watt, volt-var, and frequency-watt support grid stability and power quality.
Net energy flow over a billing period is calculated as the difference between energy exported to the grid and energy imported from the grid, serving as the basis for net metering settlements.
Volt-Watt control reduces inverter active power output when the local voltage exceeds
These definitions form the foundation for understanding and designing residential grid-connected solar power systems, ensuring compliance with electrical codes, interconnection standards, and utility requirements, while promoting efficient and stable integration of distributed solar generation.