Publication of TPC Information
This paper discusses the publication of information relating to the Temporary Price Cap (TPC) mechanism in the Singapore Wholesale Electricity Market (SWEM). Information on certain product prices that are not subject to lower TPC limits when the TPC is activated was not available when the Energy Market Authority (EMA) introduced the TPC in the SWEM.
The Rules Change Panel (RCP) discussed and unanimously supported publishing the historical and real-time prices for Primary Reserve, Contingency Reserve, Regulation and Market Network Nodes that are unaffected by the TPC.
The EMA approved the Market Rules on 5 June 2025 to implement the RCP’s decision.
For more details on the rule changes mentioned and for future updates, please visit our website.
Modelling of Energy Storage Systems
This paper proposed amending the market clearing engine (MCE) formulation so that dispatch schedules can better reflect the physical capabilities of energy storage systems (ESS).
Currently, the MCE assumes that generators can only inject energy into the grid, without withdrawing any. As such, generator offer quantities are only allowed to be positive (to inject into the grid). However, when an ESS intends to charge from the grid, this should be reflected as a negative offer quantity (to withdraw from the grid).
Furthermore, existing MCE constraints related to scheduling of reserve and regulation quantities are largely based on the physical constraints of gas generators. However, these constraints do not apply to ESS which can ramp up or down rapidly and provide reserves and/or regulation even while charging.
EMC proposed rule modifications to:
- allow ESS to submit energy storage offers which can include both positive and negative offer quantities to indicate its willingness to discharge and charge, respectively; and
- introduce a different set of (relatively simplified) constraints for ESS’ provision of reserve and regulation, to account for ESS’ fast-ramping capability and ability to provide reserves and regulation when charging.
The Rules Change Panel (RCP) unanimously supported EMC’s recommendations.
The Energy Market Authority (EMA) approved the Market Rules reflecting the RCP’s decision, and the rule change proposal took effect on 12 August 2025.
For more details on the rule changes mentioned and for future updates, please visit our website.
Incorporation of State-of-Charge in MCE modelling of ESS
State-of-Charge (SoC) refers to the percentage of stored energy in an energy storage facility.
As a follow up to RC383 on the Modelling of Energy Storage Systems (ESS), this paper proposed incorporating SoC data into the Market Clearing Engine (MCE), thus constraining ESS dispatch schedules and improving the deliverability of scheduled quantities for ESS.
There are currently no SoC-related constraints within the MCE. Existing modelling constraints largely reflect physical constraints applicable to gas generators; gas generators do not have SoC concerns. Thus, there is a risk that ESS facilities may not be able to deliver when scheduled, depending on their actual SoC levels in real-time.
EMC proposed rule modifications to:
- require the Power System Operator (PSO) to provide real-time SoC data for each ESS to EMC before each dispatch period; and
- constrain ESS dispatch schedules based on the real-time SoC data received.
The Rules Change Panel (RCP) unanimously supported EMC’s recommendations.
The Energy Market Authority (EMA) approved the Market Rules reflecting the RCP’s decision, and the rule change proposal took effect on 12 August 2025.
For more details on the rule changes mentioned and for future updates, please visit our website.
Enhancement to Fallback Mechanisms for StartGeneration and PriorScheduledPurchase
The market clearing engine’s (MCE) input parameters, StartGeneration and PriorScheduledPurchase, may affect dispatch schedules:
- StartGeneration values reflect the megawatt (MW) generation level of each generator ten minutes before each period.
- PriorScheduledPurchase values reflect the MW consumption level of each load at the start of each period.
Values for these two parameters are always required to generate dispatch schedules. If the usual data sources for the two parameters are unavailable, fallback values for StartGeneration and PriorScheduledPurchase are needed. Ideally, those fallback values should still reasonably reflect physical conditions (i.e., actual generation or consumption levels).
As such, EMC proposed enhancing the fallback mechanism for both parameters, StartGeneration and PriorScheduledPurchase, to provide more fallback values for each parameter based on previously generated schedules, thereby improving scheduling resiliency.
The Rules Change Panel (RCP) unanimously supported EMC’s recommendations.
The Energy Market Authority (EMA) approved the Market Rules reflecting the RCP’s decision, and the rule change proposal took effect on 12 August 2025.
For more details on the rule changes mentioned and for future updates, please visit our website.
Market Clearing and Offers for Energy Storage Systems
At its 139th Rules Change Panel (RCP) meeting, the RCP unanimously supported the proposals in RC383: Modelling of Energy Storage Systems and RC386: Incorporation of State-of-Charge in MCE modelling of ESS.
While working on system changes to implement these changes, EMC discovered that further rule modifications are required.
This paper therefore proposes Market Rule and Market Manual modifications, related to:
- market clearing formulation of energy storage systems (ESS); and
- requirements for standing offers and offer variations by ESS.
These modifications are intended to increase market clearing formulation accuracy for ESS and clarify requirements for ESS energy storage offers. They have been reviewed and endorsed by the Technical Working Group as requested by the RCP.
The RCP unanimously supported the EMC’s recommendations.
The Energy Market Authority (EMA) approved the Market Rules reflecting the RCP’s decision, and the rule change proposal took effect on 12 August 2025.
For more details on the rule changes mentioned and for future updates, please visit our website.
