Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
Reactive Power-Voltage Control of Inverter Based ResourcesDouglas Brown, Siemens PTI
Unrestricted © Siemens 2020
Unrestricted © Siemens 2020November 2020Page 2
Overview
Discussion of reactive power and voltage control of Inverter Based Resources
• Reactive Power Requirements
• Implementation
• Performance Targets
• Modeling of reactive power-voltage controls for planning and operating studies
• Examples
See companion paper for references.
Unrestricted © Siemens 2020November 2020Page 3
Active and Reactive Power
Active power is the power transmitted to loads and transformed into mechanical energy, heat, or light.
Reactive power is used to establish and maintain the magnetic field in electrical equipment.
The active and reactive power supplied must equal demand plus losses. • Shortage of active power will cause frequency to decline. • Shortage of reactive power will cause voltage to decline.
Unrestricted © Siemens 2020November 2020Page 4
Inverter Based Resources
• Wind turbines, solar PV inverters and battery energy storage inverters are asynchronously connected to the grid
• Partially or completely interfaced through power electronics• Non-synchronous generators are also referred to as Inverter-Based Resources
Unrestricted © Siemens 2020November 2020Page 5
Reactive Power Requirements for Non-Synchronous Generators
FERC Order No. 2003 (2003)• Established standard procedures for interconnecting generators larger than 20 MW• Generators required to provide ±0.95 power factor at POI• Exempted wind plants from reactive power requirement
FERC Order No. 661 (2005)• Established standards for interconnection of large wind plants• Preserved reactive power exemption for wind plants unless system impact study
showed capability was required for reliability• Exemption did not apply to non-wind technologies
FERC Order No. 827 (2016)• Newly interconnecting non-synchronous generators required to provide dynamic
reactive power within the power factor range of ±0.95
Unrestricted © Siemens 2020November 2020Page 6
FERC Order 827 Requirements for Non-Synchronous Generators
Power Factor Range• Dynamic reactive power within the power factor range of 0.95 leading to 0.95 lagging
Point of Measurement• Reactive power requirement is measured at the high side of the generator substation
Dynamic Reactive Power Capability• Dynamic reactive power capability of the inverter or other dynamic reactive power
devices• Static reactive power devices to make up for losses
Real Power Output Level• Generating Facility is required to meet the reactive power requirements at all levels
of real power output
Unrestricted © Siemens 2020November 2020Page 7
Plant Controls
• Plant-level controller
• Inverter-level controllers
• OLTC or DETC on the main power transformer
• Plant-level capacitors and/or reactors
Unrestricted © Siemens 2020November 2020Page 8
Plant-Level and Inverter-Level Controllers
Plant-level controller• Controls voltage at POI or POM• Distributes voltage or reactive power setpoints to each inverter
Inverter-level controllers• Inverters inject reactive current in response to command from plant controller• Many inverters also provide fast control of terminal voltage
Unrestricted © Siemens 2020November 2020Page 9
Performance Requirements: Plant Capability Curve
Order 827 requires plant provide reactive power within the power factor range of 0.95 leading to 0.95 lagging at all levels of real power output
Critical test points are usually at rated output and near 0 MW output.
Plant shown at right requires switched capacitors when operating above 90% of rated output.
Many wind turbines and solar inverters cannot control voltage at zero active power output unless this option is purchased by the Generator Owner.
Plant Reactive Power Capability at POM
Unrestricted © Siemens 2020November 2020Page 10
Reactive Power Requirement as a Function of Voltage
Order No. 827 does not specify a voltage range for the reactive power requirement.
Consider power factor requirements at different system voltages.
System voltage affects the reactive capability of the inverter as well as the need for reactive power from the plant.
Pay special attention to capability within VAR-002-4.1 voltage schedule tolerance band.
Australian Energy Market Operator Reactive Power Requirement
Unrestricted © Siemens 2020November 2020Page 11
Disturbance Performance Targets
• Response of non-synchronous generators is determined by the controls programmed into the inverters and plant level controller
• NERC Reliability Guideline1 provides performance targets for small and large disturbances
• Plant-level controller provides primary response to small disturbances
1. NERC Reliability Guideline: BPS-Connected Inverter-Based Resource Performance
Unrestricted © Siemens 2020November 2020Page 12
Disturbance Performance Targets
• Inverter-level controllers provide primary response to large disturbances
Unrestricted © Siemens 2020November 2020Page 13
Generic Models for Positive Sequence Stability Analysis
Generic models for renewable energy plants are available as standard library models in commercial planning software platforms• Intended to provide a representation of dynamic electrical performance at POI• Intended for analyzing electrical phenomena in the frequency range of zero to 10 Hz• Applicable for systems with a short circuit ratio of 3 or higher at POI
Unrestricted © Siemens 2020November 2020Page 14
REGC Renewable Energy Generator/Converter Model
Represents the generator/converter interface with the grid
Inputs• Real and reactive current command from
REEC model
Outputs• Real and reactive current
injection
Unrestricted © Siemens 2020November 2020Page 15
REEC Renewable Energy Electrical Control Model
Represents the electrical controls of the inverters
Variety of REEC models to represent controls associatedwith different prime movers
Inputs• Active and reactive power reference
from REPC model• Terminal voltage and inverter output power
Outputs• Real and reactive current command to REGC model
Operating modes selected using the flags PfFlag, VFlag and Qflag
REEC_A Reactive Current Control (Active Current Control not Shown)
Unrestricted © Siemens 2020November 2020Page 16
REPC Renewable Energy Plant Control Model
Represents the plant controller
Inputs• Voltage• Frequency• Plant output
Outputs• Active and reactive power
reference to REEC model
Operating modes selected using the flag VCFlag, RefFlag
Model PLNTB is similar and includes constant power factor mode
Reactive Power Control (Active Power Control not Shown)
Unrestricted © Siemens 2020November 2020Page 17
REPC Voltage Regulation
In voltage control mode, VCFlag used to select line drop compensation or droop response.
Reactive droop provides a reactive power setpoint based on the voltage error
• Ensures coordinated control among resources in close electrical proximity
• Droop is the voltage error that causes the reactive power output to go to the maximum value
• Graph shows 3% reactive droop on 0.95 power factor base
3% Reactive Droop, Qmax = 33% of Prated
Unrestricted © Siemens 2020November 2020Page 18
Reactive Power Control Options
Flags in the REEC and REPC models can be used to simulate various combinations of plant-level and inverter-level controls
Common combination are shown below
Unrestricted © Siemens 2020November 2020Page 19
Wind Power Plant Example
• 100 MW power plant
• POM connected to POI by short 161 kV transmission line
• Plant controller set to regulate voltage at POM to 1.02 per unit
• WTG have local coordinated Q/V control
Unrestricted © Siemens 2020November 2020Page 20
Wind Power PlantSwitching 21 MVAr Reactor at POI
Terminal voltage falls and local V control quickly increases WTG reactive power output.
Local Q control starts to reset WTG reactive power
Around 2 seconds, WTG starts to increase reactive power output as a result of the plant controller changing the REEC reactive power reference to restore POM voltage
Plant-Level V Control & Local Coordinated Q/V Control
Unrestricted © Siemens 2020November 2020Page 21
Wind Power PlantSmall Disturbance Reactive Power-Voltage Performance
• Small disturbance performance evaluated using techniques similar to those for MOD-026-1
• Wind plant model checked by applying a 2% step to the plant reference voltage
• Performance exceeds NERC Guideline targets
2% Step Applied to Reference Voltage
Unrestricted © Siemens 2020November 2020Page 22
Wind Power PlantLarge Disturbance Reactive Current-Voltage Performance
• Wind plant model checked by applying a permanent fault at POI to drive voltage at WTG terminals to 0.50 per unit
• Performance exceeds NERC Guideline targets
Response to Fault at POI
Unrestricted © Siemens 2020November 2020Page 23
Solar PV Power PlantSmall Disturbance Reactive Power-Voltage Performance
• 100 MW solar PV power plant• Plant controller set to regulate voltage• Inverters have local coordinated Q/V control
• Model checked by applying a 2% step to the plant reference voltage
• Performance does not meet NERC Guideline targets
2% Step Applied to Reference Voltage
Unrestricted © Siemens 2020November 2020Page 24
Conclusions
Reactive power-voltage control requirements relevant to inverter based resources• FERC Order No. 827 reactive power requirement• NERC VAR-002-4.1 requires that generating facility operate in automatic voltage control
mode and maintain the voltage schedule provided by the Transmission Operator
Performance requirements and guidelines• IEEE working group P2800 is drafting a standard that will establish recommended
interconnection capability and performance criteria for inverter-based resources• NERC Reliability Guideline: BPS-Connected Inverter-Based Resource Performance
Plant models should be verified• Ensure that FERC Order No. 827 requirements are implemented correctly by the
Generator Owner• Check dynamic performance using NERC guideline
Unrestricted © Siemens 2020November 2020Page 25
Douglas BrownSenior Manager, Power System ConsultingSiemens Power Technologies International
10900 Wayzata BoulevardMinnetonka, MN 55305
952.818.2227