SINUS

Single-Phase Active Filter

Under the SINUS Project were developed two types of Single-Phase Shunt Active Power Filters. The first type was developed in a switch board, with an Integrated Power Quality Monitor. That monitoring system allows the demonstration of the compensation features of the Power ActiveFilter, providing the visualization of the waveform and values of compensated current. That Active Power Filter was installed on the University of Minho, to compensate one of the phase of a switch board from SAPIA (Learning Computer Support Service), in the Azurém campus. Beyond the compensating and monitoring actions, this Single-Phase Shunt Active Power Filter also operates as interface between renewable energy sources (Photovoltaic Solar Panels) and the electrical grid. The Second type of Single-Phase Active Power Filter was developed in an aluminum box, being demonstrated in the Power Electronics Laboratory of the University of Minho.

Usage Importance of Active Power Filters in Single-PhaseSystems

• The broad usage of electronic converters and other non-linear loads, which consume current harmonics, has increased the severity scale of the problems related with power quality in electrical systems. The presence of harmonics results in a rise of losses related with transport and distributionof electrical energy, in interference problems in communications systems, and in degradation of operation in most equipments connected to the electrical grid.
• Even though the necessity of equipments which compensate harmonics is more evident in three-phase systems, more used by industrial consumers, in where production brakes resulting from power quality problems can be very heavy, nowadays, the mass use of computers, printers, copiers and other electronic equipments by service companies, offices and households, which are normally fed by single-phase systems, causes serious power quality problems.
• The continuous growth of harmonics in single phase electrical installations, makes the use of active power filters a viable alternative to enhance the performance of these electrical systems.
• Single-Phase Shunt Active Power Filters allow to dynamically compensate power factor and current harmonics, instantaneously adapting itself to load variations.
• As a result of the operation of Single-Phase Shunt Active Power Filters, the compensated current becomes sinusoidal and in phase with the voltage of the electrical grid. With this, the current amplitude decreases, reducing losses in the conductors. Besides that, sinusoidal currents avoid the distortion of the feeding voltage, enhancing the operation of loads connected to the same electrical system.

Main Features of the developed Single-Phase Power Active Filters

• Easy installation and commissioning equipment, without the need of previous studies about the place where will be connected. Once functioning, theActive Power Filter immediately compensates the current, making it sinusoidal and in phase with the voltage.
• Safe for the electrical grid, once it is shunt connected, and, when occurs an equipment malfunction, it shuts down automatically through a connector and a circuit-breaker, keeping itself isolated from the electrical installation.
• Automatic and instantaneous compensation of all harmonics and power factor. In case of load change, the Control System of the Power Active Filter recalculates the new compensation current values.
• Integrated Power Quality and Consumption Monitoring System. Shows the wave forms and RMS values of currents and voltage, as well as power factor values and total harmonic distortion (THD), onthe load side (before compensation) and on the source side (after compensation). It can also be seen the individual harmonics, as well as the consumed power values. The Monitoring System can operate in a continuous registration mode, in where it detects interruption, sags and swells, RMS values during time, power consumption, etc.
• It can operate as an Interface System for Renewable Energy Sources, injecting the produced energy on the electrical grid simultaneously with thecompensation of harmonics, power factor and unbalances. For that, it is necessary the use of a circuit which adapts the voltage levels of the renewable sources to the ones in the DC side of the Active Power Filter. In the case ofutilization of Photovoltaic Solar Panels as energy source, that circuit as the also the function of optimize the production of energy by the panels, being named as MPPT (Maximum Power Point Tracker) circuit.

Technical features of the developed Single-Phase ShuntActive Power Filters

• Dynamic compensation (automatic and instantaneous) of all current harmonics until the 25th order.
• Dynamic power factor compensation to the unit (adjustable setting).
• Possibility of producing capacitive or inductive reactive power (adjustable setting).
• Possibility of compensating only harmonics or only power factor.
• Dynamic adaptation to load changes, with response timeinferior to 20 ms.
• Does not present overload issues (limited by the Control System to the rated value of compensation current).
• Soft start (while connecting to the grid and starting compensation procedures).
• Power Inverter composed by IGBTs and Control System implemented in DSP (Digital Signal Processor).
• Does not use transformers for electrical grid connection.
• Automatic rearmament after electrical grid failure.
• Low acoustic noise operation.
• Red signalization light indicating the electrical grid connection.
• Integrated Power Quality and Consumption Monitoring System, with 17’’ TFT screen for easy locally visualization of information.
• Possibility of remote access to the Integrated Power Quality and Consumption Monitor System, through Ethernet or 3G board.

Technical Specifications of the developed Single-Phase Active Power Filters

The developed Single-Phase Active Power Filters were put in operation in two sites of the University of Minho, in the Azurém campus, Guimarães: on the Energy and Power Electronics Laboratory of the Industrial Electronics Department, and in a switch board that feeds asingle-phase electrical installation of SAPIA (Learning Computer SupportService). The Active Power Filter connected to the SAPIA switch board, beyond compensating current harmonics and power factor, also works as interface for 16 photovoltaic solar panels (total of 3kW) with the electrical grid.

Results