Assessing the impact of green certificate market transformation on China's carbon market under a multi-market coupling framework

China's 2023 revision of its green-certificate policy marks a new phase for tradable green certificates (TGCs), but its implications for national carbon emission trading (CET) remain unclear. The reform turns TGCs into an accounting basis for renewable-electricity environmental attributes, whereas current CET compliance remains centered on direct emissions. We construct a system dynamics model coupling China's TGC, power, and CET markets to examine how this accounting reform could affect carbon-market outcomes as policy boundaries expand. A mechanism-separated scenario ladder distinguishes TGC issuance expansion, tiered industrial CET expansion, indirect-emission accounting under compensating free allocation, and bundled green-power deduction. Monthly simulations over a January 2022 to January 2035 horizon, with 2022 used for base-year initialization and the post-reform policy transition evaluated from January 2023 onward, show that TGC issuance expansion alone has limited direct carbon-market effects: the 2035 carbon price rises by 5.24% while allowance demand remains broadly stable. Scarcity is reshaped mainly by CET design: the two industrial-expansion steps raise the carbon price by 7.85% and 3.53%, and adding electricity-related indirect emissions increases gross allowance demand by 22.29% and the carbon price by 10.41%. Once this boundary is active, bundled green-power deduction credits 56.94 million MWh/month by 2035, equal to 15.33% of covered purchased electricity, reducing electricity-related allowance demand by 6.06%, total allowance demand by 1.63%, and the carbon price by 6.07%. The reform therefore functions first as renewable-attribute accounting infrastructure; its carbon-market role emerges only when explicit, double-counting-safe linkage rules convert those attributes into bounded compliance flexibility.