How do you use filters and compensators to reduce harmonic resonance and improve power factor?

1 What are harmonics and resonance?

Harmonics are sinusoidal voltages or currents that have frequencies that are multiples of the fundamental frequency of the power system, usually 50 or 60 Hz. Harmonics are generated by nonlinear loads, such as converters, rectifiers, inverters, and electronic devices, that draw nonsinusoidal currents from the source. Harmonics can distort the waveform of the voltage and current, reducing the power quality and efficiency of the system. Resonance is a condition where the impedance of the system becomes very high or very low at a certain frequency, causing a large voltage or current to appear. Resonance can occur when the inductive reactance of the system matches the capacitive reactance of the system or the load at a harmonic frequency. Resonance can amplify the harmonic distortion, create overvoltages or overcurrents, and damage the equipment or the network.

2 What are filters and compensators?

Filters and compensators are devices that can modify the impedance of the system or the load to reduce the harmonic distortion and improve the power factor. Filters are passive elements, such as resistors, capacitors, and inductors, that are connected in series or parallel with the system or the load to block or bypass certain harmonic frequencies. Compensators are active elements, such as power electronic converters, that inject or absorb reactive power or harmonic currents to compensate for the nonlinear behavior of the system or the load. Filters and compensators can be classified into different types, such as series, parallel, shunt, hybrid, passive, active, or adaptive, depending on their configuration, operation, and functionality.

3 How do you use filters to reduce harmonic resonance?

Filters can be used to reduce harmonic resonance by creating a low-impedance path for the harmonic currents to flow, avoiding the resonance condition. For example, a shunt filter is a capacitor bank that is connected in parallel with the system or the load to provide reactive power and improve the power factor. However, if the capacitor bank resonates with the system inductance at a harmonic frequency, it can cause overvoltages and instability. To prevent this, a series filter, such as an inductor or a resistor, can be added to the capacitor bank to form a tuned or detuned filter that shifts the resonance frequency away from the harmonic frequency. Alternatively, a parallel filter, such as an inductor or a resistor, can be connected in series with the system or the load to form a high-pass or a low-pass filter that blocks or bypasses the harmonic currents.

4 How do you use compensators to improve power factor?

Compensators can be used to improve power factor by injecting or absorbing reactive power or harmonic currents to balance the system or the load. For example, a shunt compensator is a power electronic converter that is connected in parallel with the system or the load to generate or consume reactive power and improve the power factor. The shunt compensator can also cancel out the harmonic currents by producing opposite currents that are in phase with the harmonics. A series compensator is a power electronic converter that is connected in series with the system or the load to regulate the voltage and improve the power factor. The series compensator can also mitigate the harmonic distortion by injecting opposite voltages that are in phase with the harmonics.

5 What are the benefits and challenges of using filters and compensators?

Using filters and compensators can have several advantages for your power distribution system, such as reducing harmonic distortion, preventing harmonic resonance and instability, improving power factor, reducing the size and cost of components, and complying with standards and regulations. However, there can be some challenges in choosing the right type, size, location, and tuning of filters and compensators for your system and load characteristics. Additionally, there may be interactions or interferences between different filters and compensators in the system that need to be taken into account. Lastly, you must maintain and monitor the performance and reliability of the filters and compensators while considering environmental and safety aspects.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?