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Electric vehicle integration’s impacts on power quality in distribution

Electric vehicle integration’s impacts on power quality in distribution


The integration of electric vehicles (EVs) into power distribution systems can have significant impacts on power quality. Here are the key points:

- EVs and Power Quality: The increasing use of EVs can lead to power quality issues such as voltage imbalance, transformer failure, and harmonic distortion due to their grid-to-vehicle (G2V) and vehicle-to-grid (V2G) charging and discharging capabilities.

- Research on Impact: Several studies have been conducted to analyze the impact of EVs on power quality. These studies have looked at aspects like harmonic distortion caused by EV charging stations and the random operating characteristics of EVs.

- Mitigation Techniques: Various mitigation techniques have been discussed to eliminate the harmonics and minimize the adverse impacts of EVs on power quality in power distribution systems.

- Future Implications: The integration of EVs poses challenges for electrical networks. Understanding these challenges and developing solutions is crucial for the future of EV integration.

The integration of electric vehicles (EVs) into the power grid can lead to transformer failures due to several reasons:

1. Overloading: The growth in plug-in electric vehicles (EVs) can put strain on nearby transformers, causing overloads, premature aging, and potential failures⁴. EV charging may cause prolonged transformer overload condition, that may in turn result in transformer loss of life and increased hazard of failure.

2. Temperature Rise: Due to the nonlinear nature of the load, the temperature of the transformer and its associated loss rise during EV battery charging, reducing the transformer's lifetime.

3. Harmonic Distortion: The non-linear nature of some loads during EV charging induces total harmonic distortion (THD) in the charging current, i.e., the THD of the current influences the power quality of the distribution network³.

To mitigate these issues, several strategies have been proposed:

- Battery Energy Storage Systems (BESS): Installation of battery energy storage systems (BESS), especially when paired with solar photovoltaic (PV) panels, can help mitigate transformer loss of life.

- Active Power Filters and FACTS Devices: Active power filters and FACTS devices such as shunt and series active power filters, dynamic voltage restorers, and unified power quality conditioners (UPQC), etc. are utilized to overcome these issues.

Remember, it's important to understand these challenges and develop solutions for the future of EV integration.

A Dynamic Voltage Restorer (DVR) is a method of overcoming voltage sags and swells that occur in electrical power distribution³. These are a problem because spikes consume power and sags reduce the efficiency of some devices. DVR saves energy through voltage injections that can affect the phase and wave-shape of the power being supplied.

The basic principle of dynamic voltage restoration is to inject a voltage of the magnitude and frequency necessary to restore the load side voltage to the desired amplitude and waveform, even when the source voltage is unbalanced or distorted.

Devices used for DVR include static var devices, which are series compensation devices that use voltage source converters (VSC)³. The DVR can generate or absorb independently controllable real and reactive power at the load side³. In other words, the DVR is a solid state DC to AC switching power converter that injects a set of three-phase AC output voltages in series and synchronicity with the distribution and transmission line voltages.

The source of the injected voltage is the commutation process for reactive power demand and an energy source for the real power demand³. The energy source may vary according to the design and manufacturer of the DVR, but DC capacitors and batteries drawn from the line through a rectifier are frequently used. The energy source is typically connected to the DVR through its DC input terminal.

The amplitude and phase angle of the injected voltages are variable, thereby allowing control of the real and reactive power exchange between the dynamic voltage restorer and the distribution system³. As the reactive power exchange between the DVR and the distribution system is internally generated by the DVR without the AC passive reactive components.

Practically, DVR systems can inject up to 50% of nominal voltage, but only for a short time (up to 0.1 seconds). However, most voltage sags are much less than 50 percent, so this is not typically an issue.

Source: Microsoft Bing


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