Maximum Power Point Tracking allows for greater energy production for solar panels and constantly adapts to system changes to maximise output.

For use where the solar panel voltage is greater than the battery voltage. Effectively converting the extra voltage into additional charge current.

Features commonly available hardware components coupled with flexible control to optimise the output over a range of installation conditions.

FEATURES: Up to a 120VDC input, up to 25A output current*.

* Where suitable components are selected.

LB1 ADC limitations:

Current: The ESP32-S3 ADC has a preferred (e.g. relatively linear response) between the voltage ranges at, ADC_ATTEN_DB_11 of 150 mV ~ 2450 mV. Therefore, the ACS71X current sensor resolution can be maximised by acknowledging such limitations. Where the bi-directional ACD outputs a zero voltage at the supply voltage / 2 at the typical 3.3V. However, the current sensor can be supplied by 5V and therefore, the 0 current output voltage will correspond to 2.5V or the upper linear range of the ESP32 ADC. If the circuit is orientated so the typical current flow results in a VCC / 2 - mV*A direction is negative. The response of the current sensor under typical operation will be in the linear and ideal range of the ADC while expanding the typical 45mV/A resolution to 45 * (5/3.3) = 68.2mV/A. As an example: 0A = 2.5V,  5A = 2.16V,  10A = 1.82V,  15A = 1.48V,  20A = 1.13V,  25A = 0.8V.

Voltage: Likewise for input voltage (PV), accuracy can be improved when knowing the applications limitations. For example, a 110V PV OCV, 55V typical battery full SOC voltage can be most accurately measured with a voltage divider of 440k & 10k resistance resulting in an output voltage of 2.44V (with input 110V) and (1.22V at the critical battery voltage full region of 55V).

For the output voltage (for battery monitoring), the resolution can be increased given the maximum expected voltage is under 80V (crowbar circuit protection). The typical output voltage and most important voltages are around 55V for fine control at a high 48V LIFEPO4 SOC. Therefore, the voltage divider can be tweaked to provide greater resolution with a 240k & 10K ohm voltage divider resulting in a 2.2V output at 55V.

Enhanced Thermal Dissipation:

Large areas of copper and large via's have been used to conduct heat away from power components and increase cooling. The large vias promote airflow and connect front and back copper areas to emulate a heatsink.

Enhanced Transient Response through Careful Layout:

• Placement of input and output capacitors next to switch components to minimise transients.

• Compact design enabled by top and bottom placement of large parts and further allows a reduction in the current paths to minimise noise.

• Choice of ultrafast and soft recovery diodes to further reduce transient switching spikes and therefore increasing component life while reducing noise.

• Customisable design that enables easy tuning of gate drive resistance to achieve optimal MOSFET switching while limiting transient causing high switching dV/dt for differing MOSFET characteristics.

Software Enhanced Temperature reduction & noise reduciton

Continuously monitor the temperature of power components and current to adaptively change the switching frequency to maintain Continuous Conduction Mode (CCM) while minimising loss and therefore limit heat production while also minimising electrical noise. Continuous conduction mode is important for future revisions that incorporate synchronous switching for greater efficiency. Additionally, a fallback technique for Bang-Bang control to avoid Discontinuous Conduction Mode when operating outside of the hardware optimal area of control.

Software Enhanced output stability:

• Rate of Change of Current (RoCC) to limit voltage spikes and protect downstream equipment / Battery Management Systems for greater network stability. This is particularly important at:

  • High battery States of Charge (SOC).

  • Where there is intermittent cloud (cloud then full sun).

  • Where the load on the system can be significant and have a high Rate of Change (e.g. a pump turning on / off).

Local MPPT with Remote MPPT Verification:

• A local MPPT algorithm that is robust for a fluctuating output due to the loads of the connected system.

  • Use of the known system parameters (solar panel information, cable length and operating data to calculate deratings).

• Remote verification of the MPPT to avoid local minima / maxima and provide anomaly detection and a device and system level.

  • Change is when a cloud appears or disappears. 

  • Anomaly detection occurs when a single system responds differently to the other local interconnected systems.

Remote Optimised Control:

• With remote data and control available the system can be optimised to:

  • Optimise output (supervision of MPPT).

  • Switching noise reduction by distributing load.

  • Anomaly detection of an underperforming solar array / regulator.

  • Fail safe, protective local operation when system information / state is unavailable.

  • Optimised top balancing (high SOC of lithium batteries with BMS data) and load matching.

  • Periodic performance testing and condition monitoring.

Increased Safety and Availability via hardware design:

• A safe system is one that is under control at all times. If not, it fails gracefully, safely.

• System component choices that generously exceed requirements.

• Data collection at the right places.

• Crowbars & Watchdogs.

• Expectations of problems and self-testing.

TESTING: Found a fluctuating load such as an inverter can greatly influence the operation of the solar regulator due to harmonic AC distortion appearing on the DC Bus. Adjustment of the filtering VIA software filtering on the output side improved the regulators immunity to output noise.

FINDINGS: A noisy DC bus / output connection can cause the ideal diode to frequently activate.

IMPROVEMENTS & NEXT STEPS for v1.X: 

• Holes / mouse bites for breaking away sub-PCBs are not close enough & small enough making it difficult to break.

• Copper fill needs to be ended before PCB breakaway sections.

• Output capacitor is too close to the heatsink screw mount.

• Choice of ideal diode MOSFET should have a much lower RDSon.

• Design a software based Ideal Diode controller for improved DC Bus / output system noise immunity.