MPPT Vs. PWM: Understanding working principles

A solar battery charger is a device that can be used in conjunction with a solar panel to control the charging process between the solar panel/grids and the battery charger. A solar panel and a battery are linked to the device, and this is necessary to guarantee that the battery is fully charged.

The flow of energy between the solar panel and the battery is properly regulated so that neither device malfunctions. A DC(Direct Current) connected solar charger controller was initially employed, which primarily met the needs of small-scale off-grid solar power systems.

MPPT and PWM are the two contemporary and relatively modern technologies that are being used nowadays. However, they differ by the usage, size, characteristics, working principle, voltage regulation, etc.

MPPT (Maximum Power Point Tracking) Technology In Brief

The full form of MPPT is Maximum PowerPoint Tracking. MPPT is a method of monitoring and controlling the energy flow from the solar panel to the batteries. The device is a regulator which converts the high voltage value of DC output into the low voltage required for the electronic battery. However, the name suggests that it is a PowerPoint Tracker, but it is not any panel tracker device that is used to track the sun instead of voltage regulations.

Solar panels produce variable outputs depending on the weather. MPPT charge control devices can match the solar panel voltage with the battery voltage to enhance charge efficiency.

The full power of solar panels may be employed in these systems by balancing voltage and current according to the P = V x I equation (where V stands for the voltage and I stands for the current). When the weather is cloudy, for example, the amount of electricity drawn from the panels is reduced to safeguard the voltage, and it is permitted to draw more current when the weather is sunny.

Maximum Power Point Tracking, or MPPT, is a charge controller technique that extracts the maximum available power from a PV module under particular conditions. Maximum power point refers to the voltage at which a PV module may output the most power (or peak power voltage). Solar radiation, ambient temperature, and solar cell temperature all affect maximum power.

MPPT solar charge controllers are used to detect fluctuations in the current-voltage characteristics of solar cells, as evidenced by the I-V curve, in any application where a PV module is the energy source.

Any solar power system that needs to extract the most power from its PV modules needs an MPPT solar charge controller; it compels the PV module to function at a voltage near the maximum power point to draw possible power.

The MPPT solar charge controller decreases system complexity while increasing system efficiency. It can also be used with various energy sources because the PV output power regulates the DC-DC converter directly.

Other renewable energy sources, such as small water turbines and wind turbines, can also benefit from MPPT solar charge controllers, where similar technologies are used.

PWM (Pulse Width Modulation) Technology In Brief

The full form of PWM is Pulse Width Modulation.PWM is a charge control device that acts as an electrical switch between batteries and the solar panel grid. It can be switched on or off quickly as the battery charges the charge current decreases rapidly.

PWM solar chargers are based on the same technology as other high-quality battery chargers.

When a battery’s voltage reaches the regulatory setpoint, the PWM algorithm gradually reduces the charging current to prevent the battery from overheating and gassing while returning the maximum energy to the battery in the shortest amount of time. The end results are higher charging efficiency, faster recharging, and a healthy battery at full capacity.

Furthermore, the PWM pulsing in this novel solar battery charging promises some fascinating and distinct benefits. These are as follows:

• The ability to restore a battery’s capacity and desulfate it.
• Significantly improve the battery’s charge acceptance.

Key Differences in the Features of MPPT and PWM

The charging capacity is the first notable point of distinction between MPPT and PWM technologies. While MPPT can be utilized for high-capacity charging, PWM is more traditional and thus suitable for charging with lower capacity in terms of voltage output. However, various additional criteria, including site conditions, system components, array load size, and user budget, also influence choosing between the two.

• Temperature as a factor: MPPT technology can be used in both sunny and chilly environments. When the working temperature of the solar module drops, the Vmp1 increases because the peak power point voltage of the solar panels is around 17V at Standard Testing Conditions (STC = 25C°), while the battery voltage is 13.5V, this is the case. The MPPT controller can capture excess module voltage and use it to charge the batteries. As a result, an MPPT controller can give up to 25%-30% more charge than a PWM controller at cold temperatures.

A PWM controller, on the other hand, cannot capture surplus voltage since pulse width modulation technology charges at the same voltage as the battery. In warm or hot climates, solar panels are employed.

On the other hand, their VMP falls, and the peak power point operates at a voltage that is closer to that of a 12V battery. The MPPT controller isn’t required because there is no surplus voltage to deliver to the battery, negating the MPPT’s benefit over a PWM.

• Size of the system: The size of the solar energy system is important to consider when choosing a charge control device. MPPT charge control devices are the best for professional applications. PWM charge regulators can provide enough performance in simple applications that do not require additional capabilities. The efficiency difference between PWM and MPPT may not be sufficient to justify the price difference in small applications. However, it has a considerable impact on the system’s performance in large projects.

The MPW, on the other hand, is not suitable for low-power systems, and the PWM is far more suitable for this.

This can be explained as follows:

• The PWM operates at a constant efficiency for harvesting, so it operates at the same rate regardless of the array’s size.
• When compared to MPPT technology, PWM is less expensive. Users with a limited budget can opt for this instead of the MPPT.
• When used in low-power appliances, the MPPT is substantially less efficient. The recommended lower bound for using MPPT rather than PWM is around 180 watts in terms of power or 8V in terms of voltage.

The difference in their working principle

MPPT

The primary distinction between an MPPT and a PWM is that the latter simply connects the circuit and reduces the solar panel output to the battery voltage.

MPPT consists of two distinct circuits, allowing whatever is fed in to pass through a computer before being outputted at a different level.

This is a more technologically advanced system, which means your batteries will be charged much more efficiently. 

Assume that we have 200 watts of power going into the input side of your MPPT regulator or controller.

If your battery requires 15 volts to charge, the MPPT will divide 200 watts by the output of 15-volt needed and then output the same amount of power, minus a small degree of inefficiency.

It’ll output 15 volts but at roughly 18 amp, thus utilizing your solar panel’s entire amount of power. Hence the efficiency highly increased.

Another benefit of an MPPT is the term for Maximum Power Point Tracking. 

As a cloud passes overhead, the output will drop significantly, but the MPPT regulator will be able to keep track of it, scanning for the Maximum Power Point and outputting it. That’s something a PWM regulator can’t do.

It’s basically a passive system. If the solar panel warms up or loses efficiency, clouds pass overhead, or you have a small amount of partial shade on your panel, the MPPT can always make the most of it generate the maximum power.

PWM

PWM (Pulse Width Modulation) is a method of generating low-frequency output signals from high-frequency pulses. The low-frequency output is the average voltage throughout a switching time when an inverter leg’s output voltage is rapidly switched between the upper and lower DC rail voltages.

Aside from that, analog approaches, sigma-delta modulation, and direct digital synthesis are also options for generating pulse-width modulated signals.

Comparing two control signals, a carrier signal, and a modulation signal, is one of the easiest ways to generate a PWM signal. Carrier-based PWM is the term for this type of PWM. The carrier signal is a triangle waveform with a high (switching frequency) frequency. Any shape can be used for the modulation signal.

Using this method, the output waveform can be a PWM representation of any desired waveform shape. The most prevalent waveform shapes in machines are sinusoidal and trapezoidal.

Why MPPT is better than the PMW

The MPPT technology has numerous advantages, making it an excellent choice for many.

The following are the details:

• Because they are more modern technology, they are substantially more efficient than PWM regulators.
• They may make full use of the solar panel’s output. Because they are passive devices, they lower the voltage to deliver the maximum amount of current.
• Compared to other technologies, they are equally effective in low light levels, cloudy days, and so on.
• The device was created with a large-scale solar volage in mind. As a result, a much higher voltage solar panel can be used to achieve a lower magnitude of voltage loss.

Which one should one use? 

MPPT controllers are more expensive, but they allow for more panel count flexibility. The PV module’s voltage will drop to match the battery bank, resulting in a rise in current amperage. A faster recharge will be achieved with higher amperage.

These solar charge controllers will be automatically adjusted using the P = V x I equation. As a result, unlike PWM, you’ll get more power to charge the battery with no loss of efficiency.

The MPPT controller allows a panel array to have a higher voltage than the battery bank. This is critical in areas with low irradiance, especially during the winter when daylight hours are limited.

They provide a 30% increase in charging efficiency when compared to PWM. With additional flexibility, system expansion will be easier. This is critical for commercial establishments. They normally come with a longer warranty than PWM types.

Instead of using PWM, MMPT should be used for high-output battery devices. This improves the device’s efficiency and throughput while making it considerably simpler to use. However, PWM should be prioritized for low-power devices because it is inefficient for such purposes.

Pros and cons of both MPPT and PWM

MPPT

PROS:

• Because they are more modern technology, they are substantially more efficient than PWM regulators.
• They may make full use of the solar panel’s output. Because they are passive devices, they lower the voltage to deliver the maximum amount of current.
• Compared to other technologies, they are equally effective in low light levels, cloudy days, and so on.
• The device was created with a large-scale solar volage in mind. As a result, a much higher voltage solar panel can be used to achieve a lower magnitude of voltage loss.

CONS:

• The MPPT is too costly compared to the PWM technology. Typically they are about 2-3 times more costly compared to the PWM technology.
• Its size is huge in comparison to the PWM technology. As a result, they are very much difficult to handle, transport, and maintain.
• Its lifespan is also significantly less than the PWM because it is associated with much more electrical components than the PWM.
• The MPPT is also not suited for the low-power solar grid. As a thumb rule, it should be used only when the voltage of the solar panel grid is more than 8 V . Otherwise, it is far less efficient compared to PWM. However, they are much more efficient when it comes to high voltage devices.

PWM

PROS:

• It is much more cost-effective compared to the MPPT. They are usually 2-3 times cheaper compared to the MPPT.
• It has much lower power consumption compared to the MPPT.
• For low-power devices, the efficiency of the device is almost 90%.
• At demodulation, the signal can be easily separated. Noise can also be separated easily.
• It has a high-power handling device.
• It can give high-frequency output.
• It does not overheat easily.
• The noise associated with it is far lesser.
• The filtering requirement is far lesser compared to the MPPT.
• The amplitude and the frequency can be controlled independently of each other.

CONS:

• The circuit is quite complex. When compared to its output, it appears to be too vague.
• Voltage spikes regularly are a problem here.
• A semiconductor device is a must for the system to work.
• They generate a radio frequency interface that is not environment-friendly.
• They create electromagnetic noise rapidly.
• For communication purposes, the amount of bandwidth should be large.
• The instantaneous power output varies a lot throughout its operation.

Conclusion 

Charge control devices manage the energy generated by solar panels. It adjusts the current and voltage before delivering it to the batteries. The charge control device prevents the batteries from being overcharged or discharged.

As a result, it safeguards the system. A charge control device is required for all solar energy systems. PWM (Pulse Width Modulation) and MPPT (Maximum Power Point Tracking) are two types of charge control devices.

The way PWM and MPPT controllers handle current and voltage is the major difference between them.

Solar panels generate the most power at a specific voltage when the current is ideal. The panel’s Characteristic Resistance is the internal resistance at this moment.

The most power is produced when the load resistance equals the solar panels’ Characteristic Resistance. Because the battery’s internal resistance does not equal that of the solar panels, less than maximum power is generated.

A PWM controller reduces the panel voltage to the minimum required battery charge. Still, an MPPT controller matches the panel’s resistance, effectively transforming excess voltage into the current for charging.

MPPT can produce up to 30% more charging current from the same solar panel. Another benefit is that they are more efficient in cloudy conditions, extracting as much power as possible from the solar panel array regardless of the weather.

When selecting a charge control device, the size of the solar energy system is critical. MPPT charge control devices are the finest for professional applications, and PWM charge regulators can provide adequate performance in modest applications that do not require additional features.

In modest projects, the efficiency difference between PWM and MPPT may not be sufficient to justify the price difference. However, it has a significant impact on the system’s performance in large projects.

Both MPPT and PWM have their own pros and cons, and you should smartly choose the device depending upon your budget and requirements.