Power Grid Harmonic Pollution and Reactive Power Compensation

Power grid harmonic pollution

When a sine wave voltage is applied to a nonlinear load, the current becomes a non-sinusoidal wave, and the non-sinusoidal current causes a voltage drop on the grid impedance.

The voltage waveform will also become a non-sinusoidal wave. Perform Fourier series decomposition for non-sinusoidal waves, in which the component with the same frequency as the power frequency is called the fundamental wave.

Components with frequencies greater than the fundamental are called harmonics.

Most of the loads widely used today are non-linear, such as rectifiers, frequency converters, UPS, elevators, air conditioners, fluorescent lamps, copiers, home appliances, etc.

Electrical appliances, etc., these nonlinear loads will generate a large amount of harmonic current and inject it into the power grid, causing distortion of the grid voltage. This harmonic

Pollution can cause serious harm to the power grid and users.

Harmonic pollution and reactive power compensation capacitors

Harmonic pollution in a wide frequency range is common in power distribution systems. The impedance characteristics of reactive power compensation capacitors in the power grid are consistent with the frequency of the power grid.

Therefore, directly using pure capacitive reactive power compensation in harmonic pollution situations can easily cause various electrical faults:

◎ Causes the capacitor to overload, generate heat, and shorten its service life.

◎ Causes resonance in the power grid and causes electrical accidents

◎ Capacitors cause harmonic amplification, aggravate harmonic pollution, and reduce power factor

◎Unable to reach target value

Resonance and harmonic amplification caused by capacitors

In the power grid, various different devices are connected together, such as transformers, transmission lines, capacitors, and loads. resistance at any point in the power grid

Immunity depends on frequency, device and network topology.

Capacitors and inductors connected in series have very low impedance in a specific frequency range close to the resonant frequency, which is called series resonance; capacitors and inductors connected in parallel have very high impedance in a specific frequency range close to the resonant frequency, which is called series resonance. It is parallel resonance.

Within a wide frequency range, both series resonance and parallel resonance may exist in the same power grid. If harmonic voltages or harmonic currents excite these resonant circuits, it may cause amplification of voltage and current, interfering with systems and equipment. overload it or even damage it.

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