photovoltaic converters: a review and · pdf filesingle phase pv converters typical ......

April, 2016, Timisoara, Romania 1

Photovoltaic Converters:A Review and Perspective

Emanuel SerbanR&D Chief Engineer, Design Power Electronics

25-28 April 2016Universitatea Politehnica Timisoara


Emanuel Serban� 1994 - B.Sc. E.E. Polytechnic University of Timisoara, Romania� 1995 - M.Sc. E.E. Polytechnic University of Timisoara, Romania� 2016 – PhD EE, University of British Columbia, Vancouver, Canada� 2009 – Registered Professional Engineer, Canada

� 1997-2008 Xantrex Technology Inc.Power Electronics Design Engineer� DC programmable power converters design for industry applications� Solar and battery storage converters, 1-ph and 3-ph (1kVA – 100kVA)

� 2008 - present, Schneider Electric – SolarR&D Chief Engineer, Power Electronics Design� Developed: controls and hardware design in 3-phase PV converters

� 19 years experience in R&D industry for PV and ene rgy storage converters design� opportunity to identify critical issues and provide new design solutions

(power electronics controls and hardware design)� R&D Principal Engineer: developed key-converter platforms for solar applications� Power electronics modeling, control analysis and design of power converters for renewable, storage and distributed energy systems.

� Technical Publications � 4 academic journal papers IEEE Transactions on Power Electronics� 4 conference IEEE proceedings� 2 Patents

Biography


1. Introduction2. Architectures and design requirements for PV grid converters3. Single phase PV converters typical topologies4. Grid-forming converters5. PV-ESS integration6. Three-phase PV converters

6.1 Converter control dynamics6.2 Practical example of 3-phase PV converter performance under LVRT

7. Solar converters for PV plants7.1 PV converter for decentralized PV plants7.2 Power modules selection example for 10-100kVA converter design7.3 Power semiconductors losses evaluation7.4 Thermal performance evaluation7.5 1000V vs. 1500V PV systems performance comparison

8. Applications of PV converters 8.1 Residential PV/Storage for Off-grid systems8.2-8.4 Commercial PV/Storage for Grid-connected systems

Outline


1. Introduction

● The Distributed Power Generation Systems have increased to the point where they represent an important share of the gross electric energy generation●Example: Solar peak power reached 22 GW, equivalent with 20 nuclear power stations into the power grid (Germany).

● Solar converters design requirements● High efficient for a wide operational range (voltage/power/temperature)● Cost-effective, Reliable, Feature enhanced● Standards compliance

● Photovoltaic converters: a review and perspective i s presentedArchitectures and design for 1-ph and 3-ph design in PV and storage for grid-connected and off-grid power systems


• Performance requirements• High efficiency (transformerless, >98%)• High DC input range of operation � higher energy harvesting• Multiple MPPT inputs (boosters) for PV-modules shade-tolerant• Communications (RS485, Ethernet, <5min firmware upgrade)• Ease of installation

• Safety and grid codes compliance• AC disconnects for safety compliance (e.g. IEC 62109), EMC• Resistance Insulation breakdown detection (RISO) for grid codes compliance• Residual Current Detection (RCD) for grid codes compliance (e.g. VDE 4105)• Arc Fault Detection (AFD) for NEC1699 compliance• Rapid Shutdown at the PV module level new requirements• Non-intentional islanding detection (e.g. UL1741)

2. Architectures and design requirements for PV gri d converters


• PV converter with 1 stage power conversion•PV converter T-type Neutral Point Clamped (TNPC) topology in single phase AC systems

3. Single-phase PV converters typical topologies

• PV converter with 2 stage power conversion: boost + inverter


4. Grid-forming (voltage source) converters

• PV and battery energy storage combination in single phase AC systems• Grid-forming (voltage source) - with galvanic isolation (lower efficiency)• Grid forming - transformerless (high efficiency, higher control complexity)


• PV and Energy Storage Systems (ESS) are complementary solutions for wide applications (e.g. grid support, self-consumption, time-of-use) •System architecture example for single-phase AC systems

• PV converter (input: 150-1000V, output: 400-1000V)• Battery converter (100-400V)• AC converter: 120/240Vac-60Hz or 230V-50Hz

5. PV-ESS (battery) integration


Control of double-stage power conversion: block diagram example

6. Three-phase PV string inverter


6.1 Converter control dynamics● Inverter operation and performance under transient operation

● Inverter start-up, active-reactive power exchange under grid faults (e.g. asymmetrical voltage dip) � stable operation


6.2 Practical example of 3-phase PV converter perfo rmance under LVRT

● Hardware & firmware digital control integration plays a crucial role in converter performance(simulations � experimental evaluation)● Example of PV inverter response to symmetrical voltage sag (Va,Vb,Vc sag 100% to 20%)

● Inverter response to asymmetrical voltage sag (phase Va sags 100% to 50%)


• Typical application: Roof-top, ground mounted solar generators (PV-farms)• Distributed power generators (DPG) candidates: central & string inverters• Modular parallel configuration is preferred

• example 1: •total PV power plant P=2MVA

� use of n=40 string inverters of Pn=50kVA• example 2:

•total PV power plant P=20MVA � use of n=10 central inverters of Pn=2MVA

•Typical LV-MV transformer line voltage (e.g. 400Vrms to 20kVrms)

7. Solar Converters for PV plants


7.1 PV converter for decentralized PV plants

●PV converter topology: single stage conversion● Single MPPT input (Pn>50kVA)● PV converter used in decentralized PV plants


7.2 Power modules selection example for 20-75kVA co nverter design

●Power modules selection example for PV converters


7.3 Power semiconductors losses evaluation

●Power devices (T&D) loss distribution within power module● Design input for thermal design (heatsink, lifetime calculation)● Total power losses on each device (transistor & diode, normalized to %Pn)● Pn=30kVA, Power module used in calculation: Infineon F3L200R● Power devices losses

power factor variation power level variation


7.4 Thermal analysis

● Thermal loading for 3-level power devices● Devices junction temperature (Tj) analysis● Operating conditions: PF=1, 850V/600V


7.5 1000V vs. 1500V PV systems performance comparis on

● DC-Bus voltage range limits design considerations for PV plants● PV Array MPP is in direct relation to the PV modules characteristics, voltage, current and temperature, as shown below.●1000V systems: DC operation range 500V-850V (+/-24%) for 202/350V Inverter DC area of operation does not optimally cover the MPP at low/high temperatures.●1500V systems: DC operation range 750V-1500V (+/-35%) for 277/480V.

Inverter DC area of operation covers the MPP at low/high temps.Note: 1500V represents a better option for ground-mounted PV plants.


• Residential application: real example of energy harvesting• Issues in energy harvesting reduction: PV modules degradation, shading effects, dirt/dust, increased operation temperature.• Commercial available of PV modules with 18-25% the efficiency range

8. Applications of PV Converters


• Residential application: off-grid (e.g. remote areas, islands) • PV 24kW solar panels• Storage lead-acid battery DC: 48V• AC: 24kVA• Typical loads: air conditioning, heating system, home appliances, illumination

8.1 Residential PV/Storage for Off-grid systems


• Small commercial applications•Typical loads: compressors, motors.

8.2 Residential PV/Storage for Off-grid systems


• Commercial applications (e.g. meat processing factory)• PV and storage (lead-acid battery bank)

8.3 PV/Storage Converters for Grid-connected syste ms


• Small commercial application: PV/Storage/Grid• Typical loads: compressors, motors.• Dental clinic example

8.4 PV/Storage Converters for Grid-connected syste ms


Thanks for your attention

Presented by:Emanuel [email protected]

photovoltaic converters: a review and · pdf filesingle phase pv converters typical ......

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