Grid Connected and Standalone Mode Operation of PV with Battery System
Grid Connected and Standalone Mode Operation of PV with Battery System
𝐈𝐧𝐭𝐫𝐨𝐝𝐮𝐜𝐭𝐢𝐨𝐧
A PV–battery energy system must supply electrical loads reliably even when solar irradiance changes or the utility grid becomes unavailable. This MATLAB/Simulink model demonstrates how a solar PV system with battery storage operates in both grid-connected and standalone (islanded) modes.
Grid Connected and Standalone Mode Operation of PV with Battery System
A single simulation model is used to study:
Solar PV power generation
Maximum power extraction
Battery charging and discharging
DC-bus voltage regulation
AC and DC load operation
Bidirectional grid power flow
Grid-connected-to-standalone transition
Standalone-to-grid-connected transition
The system automatically selects the required inverter control strategy according to the grid operating condition.
𝐒𝐲𝐬𝐭𝐞𝐦 𝐎𝐯𝐞𝐫𝐯𝐢𝐞𝐰
The proposed configuration combines a solar PV array, boost converter, battery storage, bidirectional converter, DC bus, single-phase inverter, LCL filter, utility grid, and electrical loads.
System component | Purpose |
Solar PV array | Generates electrical power from solar irradiance |
Boost converter | Increases and regulates the PV output voltage |
Incremental Conductance MPPT | Extracts maximum available power from the PV array |
Battery energy storage | Stores surplus energy and supports the loads |
Bidirectional DC–DC converter | Controls battery charging and discharging |
Common DC bus | Connects the PV, battery, DC load, and inverter |
DC load | Receives power directly from the DC bus |
Single-phase inverter | Transfers power between the DC and AC sides |
LCL filter | Reduces inverter switching harmonics |
AC load | Receives regulated AC voltage and power |
Utility grid | Supplies or absorbs power during grid-connected operation |
Circuit breaker | Connects or disconnects the system from the grid |
𝐒𝐲𝐬𝐭𝐞𝐦 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐧𝐠 𝐏𝐚𝐫𝐚𝐦𝐞𝐭𝐞𝐫𝐬
The main operating values and conditions described in the simulation are summarized below.
Parameter | Value or condition |
DC-bus reference voltage | 400 V |
Grid mode command | 1 |
Standalone mode command | 0 |
Example mode-transition time | 0.8 s |
Irradiance change interval | Every 0.3 s |
PV irradiance test levels | 1500, 200, 500, and 1000 W/m² |
Loads supplied | AC load and DC load |
MPPT method | Incremental Conductance |
Battery converter controller | PI voltage controller |
Inverter configuration | Single-phase full-bridge inverter |
Output filter | LCL filter |
𝐖𝐨𝐫𝐤𝐢𝐧𝐠 𝐏𝐫𝐨𝐜𝐞𝐬𝐬
1. Solar PV power generation
The PV array generates voltage and current according to the applied solar irradiance.
PV voltage and current are measured continuously.
The available PV power changes with irradiance.
An MPPT controller determines the suitable operating point.
The boost converter transfers the extracted PV power to the DC bus.
2. DC-bus regulation
The common DC bus connects all major subsystems.
The reference DC-bus voltage is maintained at 400 V.
The battery converter compensates for variations in PV generation and load demand.
The DC load receives power directly from the bus.
The inverter transfers the remaining power to the AC side.
3. Battery operation
The battery supports power balancing under changing operating conditions.
It charges when surplus power is available.
It discharges when PV generation is insufficient.
Its voltage, current, and state of charge are monitored.
Positive and negative battery-current directions indicate different charging and discharging states.
4. Inverter operation
The single-phase inverter has two separate control strategies:
Grid-connected current control
Standalone voltage control
The appropriate control output is selected using the operating-mode command.
𝐆𝐫𝐢𝐝-𝐂𝐨𝐧𝐧𝐞𝐜𝐭𝐞𝐝 𝐌𝐨𝐝𝐞
When the mode command is set to 1, the circuit breaker closes and connects the PV–battery system to the utility grid.
Power flow during grid-connected operation
The PV array supplies available solar power.
The battery charges or discharges according to the power balance.
The AC and DC loads receive continuous power.
Surplus PV power can be supplied to the utility grid.
Grid power can support the loads when PV and battery power are insufficient.
The power-flow direction can be determined using:
PV power
Load demand
Battery state of charge
Battery current
Grid voltage and current
Grid-connected inverter control
The inverter operates mainly as a current-controlled converter in this mode.
Its control system includes:
Grid-voltage measurement
Orthogonal signal generation
Reference-current generation
Direct- and quadrature-axis current processing
PI current controllers
Reference-frame transformation
PWM signal generation
This strategy enables controlled power transfer between the DC system and the utility grid.
𝐒𝐭𝐚𝐧𝐝𝐚𝐥𝐨𝐧𝐞 𝐨𝐫 𝐈𝐬𝐥𝐚𝐧𝐝𝐞𝐝 𝐌𝐨𝐝𝐞
When the mode command is set to 0, the circuit breaker opens and disconnects the system from the grid.
Power flow during standalone operation
Grid voltage, current, and power become zero.
The PV array and battery supply the complete load demand.
The DC load continues receiving power from the DC bus.
The inverter maintains the voltage required by the AC load.
The battery compensates for differences between PV generation and load demand.
Standalone inverter control
During standalone operation, the inverter becomes a voltage-controlled source.
The controller performs the following tasks:
Measures inverter or load voltage
Generates orthogonal voltage components
Processes voltage quantities in a rotating reference frame
Compares measured voltage with its reference
Uses PI controllers to regulate the voltage
Generates the inverter modulation signal
Maintains stable AC-load voltage
This control strategy allows the system to operate independently when grid power is unavailable.
𝐌𝐨𝐝𝐞 𝐒𝐞𝐥𝐞𝐜𝐭𝐢𝐨𝐧 𝐋𝐨𝐠𝐢𝐜
A common command controls both the grid source and circuit breaker.
Command value | Circuit-breaker state | Grid condition | Inverter control |
0 | Open | Grid disconnected | Standalone voltage control |
1 | Closed | Grid connected | Grid-connected current control |
The switching logic selects the correct inverter modulation signal according to the grid condition.
𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐧𝐠 𝐌𝐨𝐝𝐞 𝐂𝐨𝐦𝐩𝐚𝐫𝐢𝐬𝐨𝐧
Feature | Grid-connected mode | Standalone mode |
Grid availability | Available | Unavailable or disconnected |
Circuit breaker | Closed | Open |
Grid power | Imported or exported | Zero |
Inverter function | Controls current and power exchange | Maintains AC-load voltage |
AC-load supply | PV, battery, and grid | PV and battery |
DC-load supply | PV, battery, and grid support | PV and battery |
Surplus PV power | Battery charging or grid export | Primarily battery charging |
Power deficit | Grid or battery support | Battery support |
Primary control objective | Controlled grid power exchange | Stable load voltage |
𝐂𝐨𝐧𝐭𝐫𝐨𝐥 𝐒𝐭𝐫𝐚𝐭𝐞𝐠𝐲
Incremental Conductance MPPT
The Incremental Conductance algorithm controls the PV boost converter.
Its main functions are to:
Track the maximum-power point
Respond to irradiance variations
Determine the converter control reference
Improve PV energy utilization
Reduce power loss during changing weather conditions
Bidirectional converter control
A PI-based voltage controller regulates the battery converter.
The controller:
Compares the measured DC-bus voltage with the 400 V reference
Determines the required battery power contribution
Controls charging and discharging
Supports DC-bus stability
Balances renewable generation and load demand
Dual-mode inverter control
The inverter control system includes two control paths.
Control path | Activated condition | Main objective |
Grid-connected controller | Grid available | Control inverter current and grid power |
Standalone controller | Grid unavailable | Regulate AC-load voltage |
Mode selector | Based on grid command | Select the correct modulation signal |
PWM generator | Both operating modes | Produce inverter switching pulses |
𝐌𝐞𝐚𝐬𝐮𝐫𝐞𝐝 𝐒𝐲𝐬𝐭𝐞𝐦 𝐐𝐮𝐚𝐧𝐭𝐢𝐭𝐢𝐞𝐬
Several measurement blocks are included for evaluating the system response.
Measurement group | Recorded quantities |
PV measurement | PV voltage, current, and power |
Battery measurement | Battery voltage and current |
DC-bus measurement | DC-bus voltage, current, and power |
DC-load measurement | Load voltage, current, and power |
AC-load measurement | Load voltage, current, and power |
Grid measurement | Grid voltage, current, and power |
Inverter measurement | Inverter voltage and current |
Battery status | State of charge |
These measurements make it easier to analyze power sharing, voltage regulation, and transient behavior.
𝐒𝐢𝐦𝐮𝐥𝐚𝐭𝐢𝐨𝐧 𝐒𝐜𝐞𝐧𝐚𝐫𝐢𝐨𝐬
Scenario 1: Standalone operation
The grid command is set to zero.
Expected response:
The circuit breaker remains open.
Grid voltage, current, and power are zero.
PV and battery power supply the AC and DC loads.
AC-load voltage remains sinusoidal.
DC-bus voltage remains close to its reference.
Scenario 2: Grid-connected operation
The grid command is set to one.
Expected response:
The circuit breaker closes.
Grid voltage and current become available.
Power flows between the PV–battery system and grid.
AC and DC loads remain supplied.
The battery responds to PV and load variations.
Scenario 3: Grid connected to standalone
The system initially operates with the grid and changes to standalone operation at approximately 0.8 s.
Expected response:
Grid power becomes zero after disconnection.
The standalone inverter controller is activated.
PV and battery continue supplying both loads.
A small transient may occur during changeover.
Load power returns quickly to its normal level.
Scenario 4: Standalone to grid connected
The system starts in islanded mode and is connected to the grid at the selected switching time.
Expected response:
Grid voltage and current appear after reconnection.
The inverter changes from voltage control to current control.
Grid power exchange begins.
The AC and DC loads continue operating.
Battery power adjusts to the new power balance.
𝐒𝐢𝐦𝐮𝐥𝐚𝐭𝐢𝐨𝐧 𝐑𝐞𝐬𝐮𝐥𝐭𝐬
The simulation demonstrates stable operation under PV-power variations and grid-mode transitions.
PV response
PV current and power follow the applied irradiance profile.
The MPPT controller tracks changing operating conditions.
PV voltage remains within the controlled operating region.
Converter ripple is visible but bounded.
Battery response
Battery voltage remains nearly constant.
Battery current changes according to the power imbalance.
Charging and discharging occur during different PV conditions.
State-of-charge variation remains gradual.
DC-bus response
DC-bus voltage is regulated around 400 V.
Short transients occur during irradiance and mode changes.
The battery converter supports voltage recovery.
DC-load power remains available in both modes.
AC-load response
The load receives regulated sinusoidal voltage.
Load current remains continuous.
AC-load power is maintained during grid disconnection.
Only a small temporary deviation appears during mode changeover.
Grid response
Grid voltage, current, and power are zero in standalone mode.
Grid current and power appear after grid connection.
Power import or export depends on PV generation, battery condition, and load demand.
𝐊𝐞𝐲 𝐅𝐞𝐚𝐭𝐮𝐫𝐞𝐬
Combined grid-connected and standalone operation in one model
Automatic selection of inverter control mode
Solar PV system with Incremental Conductance MPPT
Battery energy storage with a bidirectional converter
Regulated 400 V DC bus
Simultaneous AC- and DC-load supply
Bidirectional power exchange with the utility grid
Smooth transition between operating modes
Continuous monitoring of electrical quantities
Suitable for MATLAB/Simulink-based control-system analysis
𝐀𝐝𝐯𝐚𝐧𝐭𝐚𝐠𝐞𝐬
Improves power-supply continuity during grid failure
Increases utilization of available solar energy
Supports battery charging from surplus PV power
Reduces dependence on the utility grid
Enables controlled grid power import and export
Maintains AC- and DC-load operation during transitions
Provides a clear platform for testing energy-management strategies
Helps analyze converter and inverter controller performance
𝐀𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬
This PV–battery system can be applied to:
Residential solar energy systems
Commercial buildings
Smart homes
Grid-interactive renewable-energy systems
Remote and rural power supplies
Solar-powered laboratories
Hybrid AC/DC microgrids
Backup power systems
Telecom power installations
Critical electrical loads
𝐊𝐞𝐲𝐰𝐨𝐫𝐝𝐬
Grid-connected PV system, standalone solar PV system, islanded PV operation, PV system with battery, battery energy storage system, MATLAB Simulink solar model, Incremental Conductance MPPT, bidirectional DC–DC converter, single-phase grid inverter, grid-to-island transition, DC-bus voltage control, solar battery power management, AC/DC microgrid, renewable-energy control, grid power exchange.
𝐂𝐨𝐧𝐜𝐥𝐮𝐬𝐢𝐨𝐧
The grid-connected and standalone PV system with battery storage provides reliable power under different grid conditions. During grid-connected operation, the utility grid can supply deficient power or absorb surplus renewable energy. During standalone operation, the PV array and battery maintain power delivery to both AC and DC loads.
The dual-mode inverter controller allows the system to switch between current-controlled grid operation and voltage-controlled standalone operation. Simulation results show stable DC-bus voltage, effective battery support, continuous load supply, and satisfactory transition between the two operating modes.
This MATLAB/Simulink model is a practical learning and research platform for understanding solar PV integration, battery power management, inverter control, grid synchronization, islanded operation, and hybrid AC/DC power flow.
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