11

Modular Power Electronics for Modular Power Electronics for Renewable Distributed Energy Renewable Distributed Energy

Dr. Bill KramerDr. Bill KramerDr. Sudipta ChakrabortyDr. Sudipta Chakraborty

IEEE Colorado Symposium on Electronics for Sustainable EnergyMarriot Hotel, Boulder, Colorado

May 17, 2008

22

OutlineOutline

• Background• PE for distributed energy resources (DER)

– PV, fuel Cell– Wind, microturbines, IC engines– Battery, flywheel

• Modular power electronics– Integrated power electronics modules– Topologies for distributed resources– Control requirements

• Conclusions

33

BackgroundBackground

• Increasing importance of distributed resources• Renewable portfolio standards• DER consists of

– Renewable sources (PV, wind) – Non-renewable sources (Fuel cell, microturbines,

IC engines)– Storages (Battery, flywheel)

• Requirements for specific power electronics (PE) for consumer applications and/or grid connection

44

Barriers for PEBarriers for PE

• Addition of PE with distributed resources– Increased cost (up to 40% of capital cost)– Decreased reliability (typically 5 years life)

• Technology challenges– Lack of standardization– Lack of modularity and scalability– Lack of DER system package

• California Energy Commission (CEC) PIER program

55

Power Electronics for DERPower Electronics for DER

• Depends on specific DER– Type of generation (DC or variable AC)– Bidirectional (storages)

• Different PE topologiesDC – DC (Buck, Boost, Isolated)DC – AC (Inverter)AC – DC (Rectifier)AC – AC (Cycloconverter, Matrix converter)Combinations AC-DC-AC, DC-DC-AC

66

PV TopologiesPV TopologiesCentralized PV

Cascaded DC-DC and DC-AC

AC-Module

77

Fuel Cell TopologiesFuel Cell Topologies

UtilityHigh Frequency Inverter

High Frequency AC-AC Converter

High Frequency AC Link

Fuel Cell Stack

Central Inverter

Cascaded DC-DC and DC-AC

Cascaded DC-AC and AC-AC

88

PE for PV and Fuel CellPE for PV and Fuel Cell

3 Phase Transformer Utility

3-Phase Inverter

PVFuel Cell

Single Inverter

Isolated DC-DC Converter and Inverter

99

Wind TopologiesWind Topologies

GearBox G

Blades &Rotor

Synchronous Generator Rectifier Inverter Utility

Partially Rated PE

Full-scale PE

1010

Microturbine TopologiesMicroturbine Topologies

G

High FrequencyGenerator

UtilityRectifier High Frequency Inverter

High Frequency AC-AC Converter

High Frequency Link

Microturbine

DC-link Power Converters

HFAC-link Power Converter

Direct AC-AC converter

1111

IC Engine TopologiesIC Engine Topologies

• IC engines typically connected by fixed speed synchronous generator

• PE offers the advantage of having variable speed operation - optimizes fuel usage for varying loads

Full-scale PE Partially Rated PE

1212

PE for Wind, Microturbine, IC EnginePE for Wind, Microturbine, IC EnginePartially Rated Back-to-back Converters

Full-scale Back-to-back Converters

1313

Controller ExampleController Example

High FrequencyGenerator

Active PWM Rectifier IGBT PWM InverterCommon DC Bus

3 PhaseTransformer Utility

ABCDQ

ABCDQ

uvui

dv qv

θ

θ

di qi

+ -*di

*qi -+

-+

-+

DQ-PLL

PowerRegulator

refP

refQ

outP

outQ

CurrentRegulator

dD

qD

SPWM Modulation

DQABC

G

Microturbine

GatingControl

+

dcV

-*

dcVPI

PWM Modulation

GatingControl

+- *ω

ω

PI++

Load

Fuel Governor(Speed)

Fuel Governor

(Temperature)

+-*T

T

),min( tg FF gF

tF

FuelLimiter

ω

Fuel Valve Actuator

-

*fw

fw

Fuel InputTo

Microturbine

1414

Battery Storage TopologiesBattery Storage Topologies

Single Inverter Cascaded DC-DC and DC-AC

Hybrid System with Battery and Wind

1515

PE for Battery StoragePE for Battery Storage

Battery

Battery

Battery

Battery

Battery

Battery

High Frequency Transformer

DC Bus

Bidirectional DC-DC Converter and Inverter

Isolated Bidirectional DC-DC Converter

1616

Flywheel Storage TopologiesFlywheel Storage Topologies

DC-link Power Converters

HFAC-link Power Converter

1717

PE for Flywheel StoragePE for Flywheel Storage

Back-to-back Converters

Back-to-back PDM Converters

1818

Modular Power ElectronicsModular Power Electronics

• Power Electronics Building Block (PEBB) – Integration of power devices, gate drives, and

other components to functional blocks• Adoption of functional building blocks that can

be used for multiple applications results in – High volume production– Reduced engineering effort

• The value of integration can be enhanced with the standardization of interfaces of the power blocks, control and communications

1919

Integrated PE ModulesIntegrated PE Modules

• Modular design approach revolves around integrated power electronics modules (IPEM)

• IPEM consists of – PE switches– DC-link capacitors– Sensors– Gate drivers– Heat sink – DSP controller

• Semikron SKAI• American Superconductor

PM1000 Integrated Heat Sink

Auxiliary Power

Local Controller (Optional)

Coolant In

Coolant Out

DCSide

ACSide

Gate Driver Protection

Measurements

Power Poles

Communications

Auxiliary Power Source

2020

Modular Topologies for DERModular Topologies for DERCascaded DC-DC and DC-AC Converters

Back-to-back Converters

Bidirectional DC-DC and DC-AC Converters

2121

Generalized IPEMGeneralized IPEM--based PEbased PEDG Source DC-Link Generation (IPEM 1) Utility Connection (IPEM 2)

PV, Fuel Cell

Utility

Wind, Microturbine,

IC Engine, Flywheel

+-

Battery

S1 S2

S3 S4

NO*

NO*

* Non-operational

IPEM 1 External Circuits

S1 S2 S3

S4

IPEM 1

S5 S6

S1 S2

S3 S4

NO*

NO*

IPEM 1 External Circuits

* Non-operational

+

-

S1 S2 S3

S4 S5 S6

IPEM 2

I1 I2 I3

SOURCE

INTERFACE

DC

BUS

INTERFACE

UTILITY

INTERFACE

S1 S2

S3 S4

IPEM 2

Single Phase

Three Phase

NO*

NO*

* Non-operational

Single Phase

Three Phase

2222

Controller for Modular PEController for Modular PE

• Dual converters provide flexibility of designing comprehensive control objectives

• In general, the source converters are used for DC bus voltage control

• Grid connected converters are used in constant current control or constant power control

• DC bus voltage regulation is also frequently used for grid converters

• Additionally, for the fuel based systems, such as microturbines, fuel cells and IC engines; external controller can be designed for optimization of fuel

2323

Typical Control FunctionsTypical Control Functions

DE Systems

IPEM 1 IPEM 2 Additional

PV Maximum peak power tracking

Power flow to grid n.a.

Wind Generator speed, current, flux

DC bus voltage, current to utility

n.a.

Microturbines DC bus voltage Power flow to grid Fuel usage

Fuel Cell DC bus voltage Power flow to grid Fuel usage

IC Engine DC bus voltage Power flow to grid Fuel usage

Battery-Charging Battery terminal voltage DC bus voltage Operational mode

Battery-Discharge DC bus voltage Power flow to grid Operational mode

Flywheel Generator torque, speed, DC bus voltage

Power flow to grid n.a.

Control Functions

2424

Standardization RequirementsStandardization Requirements

• Standardization is required for power flow and signal distribution network

• This in turn allows for distributed controller approach

• By using control software that is functionally divided into hierarchical levels and by standardizing interfaces between levels - application software becomes independent of the hardware specifications of power stage

• The standardization of communication interface allows division of PE system into flexible, easy-to-use, multifunctional modules, which can significantly ease the task of system integration

2525

Conceptual Modular PE SystemConceptual Modular PE System

IPEM

(Rectifier)

IPEM

(Inverter)

Heat Sink Heat Sink

Passive Filters and

Transformer

Gate Driver

Heat Sink Heat Sink

Local Controller

Integrated Cooling

DC BusGWind Turbine

GeneratorUtility

Coolant In Coolant Out

Measurements MeasurementsLocal Controller

Gate Driver

EMIFilter

2626

ConclusionsConclusions

• PE adds large installation costs for DER system • PE designs are specific to the DE technology, still

they possess some common functionalities• IPEM based back-to-back converter topologies

- a viable PE interface that can operate with different DE systems with small or no modifications

• However, to reach the goal of modularity, challenges in defining the power and communication interfaces, are to be addressed

2727

AcknowledgementsAcknowledgements

• California Energy Commission (CEC) • National Renewable Energy Laboratory

The National Renewable Energy Laboratory is a national laboratory of the U.S. Department of Energy (DOE) managed by Midwest Research Institute for the U.S. Department of Energy under Contract Number DE-AC26-99GO10337. This report was prepared as an account of the work sponsored by the California Energy Commission and pursuant to the M&O Contract with the United States Department of Energy (DOE). Neither Midwest Research Institute, nor the DOE, nor the California Energy Commission, nor any of their employees, contractors or subcontractors, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacture, or otherwise does not necessarily constitute or imply is endorsement, recommendation, or favoring by Midwest Research Institute, or the DOE, or the California Energy Commission. The views and opinions of authors expressed herein do not necessarily state or reflect those of Midwest Research Institute, the DOE, or the California energy Commission, or any of their employees, or the United States Government, or any agency thereof, or the State of California. This report has not been approved or disapproved by Midwest Research Institute, the DOE, or the California Energy Commission, nor has Midwest Research Institute, the DOE, or the California Energy Commission passed upon the accuracy or adequacy of the information in this report.

2828

Questions ?Questions ?

IPEM

(Rectifier)

IPEM

(Inverter)

Heat Sink Heat Sink

Passive Filters and

Transformer

Gate Driver

Heat Sink Heat Sink

Local Controller

Integrated Cooling

DC BusGWind Turbine

GeneratorUtility

Coolant In Coolant Out

Measurements MeasurementsLocal Controller

Gate Driver

EMIFilter