Institute of Control and Industrial Electronics Warsaw University of Technology Research and Trends in Power Quality Roman Barlik
Institute of Control and Industrial Electronics Warsaw University of Technology Contents 1. Introduction 2. Power quality evaluation - standards 3. Application of power electronics converters in systems designed for power quality improvement 4. Summary
Institute of Control and Industrial Electronics 1.Introduction Warsaw University of Technology Electrical energy is a result of processing as a product should be valued an standardized. The electrical energy quality should be considered on technical categories (physical and technical criteria) and economic categories ( economic and marketing criteria) The term power quality has many different meanings: *A voltage and/or a current or a deviation of frequency from its nominal value, which result in a failure or in the inappropriate operation of energy consumer s equipment, expresses energy quality **Electric energy quality is a set of parameters that describe characteristics of a process of energy delivery to a user under normal operating conditions 1), determine continuity of supply (long and short power interruptions), and describe character of a supply voltage (value, asymmetry, frequency, waveform).- /Advisory Committee on Electromagnetic Compatibility / ***Energy quality is expressed by the degree of user s satisfaction from supply conditions.
Institute of Control and Industrial Electronics 2. Power quality evaluation - standards Warsaw University of Technology Standardization of factors, which characterize particular disturbances, is worked out rather well, and contained in IEC rules of 61000 series, which are systematically developed. The main indices and values determining the power quality are: voltage magnitude frequency voltage and current harmonics voltage fluctuation voltage dips and short interruptions voltage swells transient over voltage voltage unbalance long supply interruption. To describe harmonic distortion the following factors are used: the individual current harmonics voltage ratio - I Ih 100% I 1 U hr = U h hr = 100% U 1 and the total current and voltage harmonic distortion 2 2 - I = RMS I THD 1 100% = 2 i I 100% 2 I 1 h hr U 2 2 = RMS U THD 1 100% = 2 u U 100% 2 hr U 1 h
Institute of Control and Industrial Electronics Warsaw University of Technology a) b) c) One phase rectifier with power factor close to 1: a) converter with unidirectional energy flow; b) circuit with bi-directional energy flow; c) line current and voltage
Three phase line PWM converter with DC voltage type output circuit: a) scheme; b) phasor diagram at ϕ=0; c) output voltage range
Name: Ma x : uai nv i a Ti me 3 1.12 Typical current and voltage waveforms obtained by simulations: a)line side b)dc voltage side Mi n : Ac t : -3-1 8E-2 1. 648. 6596 8E- 2 Name: Ma x : ud i d Ti me 3. 2 1.6.12 Mi n : Ac t : -0.8-0.4 8E-2 2. 472. 6596 8E- 2
Three phase line PWM converter with DC current type output circuit: a) scheme; b) phasor diagram at ϕ=0; c) output voltage range
Typical current and voltage waveforms obtained for current type converter by simulations: a)line side b)dc current side
a) b) 50 0-50 0 100 0.005 0.01 0.015 0.02 50 0-50 -100 0 0.005 0.01 0.015 0.02 Three level 3-phase line converter voltage type with clamping diodes: a) scheme; b) input phase and line voltage waveforms (lab. records)
a) b) Three level 3-phase line converter current type : a)scheme; b) input current line waveforms (lab. records)
a) b) c) d) Power electronic active filters: a) & b) parallel filters obtained using voltage type U-PWM (a) and current type I-PWM (b) converters; c) serial filter; d) parallel-series filter
Power electronic active parallel-series line converter as Flexible AC Transmision Systems (a) and Multi-system energy flow controller
Basic structure of UPS system with electrochemical battery as energy storage
Load power pulse compensation acting in DC link
Three phase universal power compensators with PWM converters and energy storage
Example of supercapacitor battery connection
Dual active bridge as interface for energy storage
Scheme of bi-directional converter with synchronized control of additional DC/DC chopper.
Modified converter with current type inverter and its control
Institute of Control and Industrial Electronics 4. Summary Warsaw University of Technology No internationally accepted definition of power (energy) quality has been worked out. There still exists some disagreement about energy quality and electromagnetic compatibility, To have possibility of effective influence on harmonics the locations of the harmonic sources should be known, A continuous development of distributing generation causes that as well energy sources as loads have dynamic character, The most efficient way to improve the power quality is using different active power conditioners, A natural and perspective way of improving power quality is building receivers with linear character, consisted of a load and integrated with it appropriate converter, Work at searching and improving renewable energy sources and energy storages should be continued.