[Diff since v2.21.0](v2.21.0...v2.21.1)

**Merged pull requests:**
- Interpolation with the model macro (#388) (@SebastianM-C)
- Fix initialization for TranslationalPosition and add more tests (#392) (@SebastianM-C)
- Bump version (#393) (@SebastianM-C)

[Diff since v2.20.0](v2.20.0...v2.21.0)

**Merged pull requests:**
- test: fix tests of analytically solved systems (#391) (@AayushSabharwal)

[Diff since v2.19.1](v2.19.1...v2.20.0)

**Merged pull requests:**
- Hydraulic Library Update (#352) (@bradcarman)
- Add NPN and PNP BJT transistor models  (#353) (@jClugstor)
- CompatHelper: bump compat for DataInterpolations to 8 for package docs, (keep existing compat) (#375) (@github-actions[bot])
- Refactor thermal library to use macros (#377) (@matthew-kapp)
- Made PR#349 mergeable (#380) (@matthew-kapp)
- DOCS: Connect the clock in causal direction (#381) (@cstjean)
- RealOutputs for thermal sensors (#385) (@jbatteh)
- test: make test robust to numerical issues (#386) (@AayushSabharwal)
- docs: fix docs (#389) (@AayushSabharwal)

**Closed issues:**
- Thermal.FixedHeatFlow cannot actually model a fixed heat flow rate source (#234)

[Diff since v2.19.0](v2.19.0...v2.19.1)

**Merged pull requests:**
- CompatHelper: bump compat for DataInterpolations to 7 for package docs, (keep existing compat) (#351) (@github-actions[bot])
- fixed SampledData initializaiton (#355) (@bradcarman)
- test: fix several tests (#356) (@AayushSabharwal)
- Adding Power, Modulo, UnaryMinus, Floor and Ceil blocks  (#358) (@shobhitvoleti)
- Connector name edits for Power and Modulo (#359) (@shobhitvoleti)
- Readme updated with new RC circuit example (#361) (@matthew-kapp)
- Hydraulic library updated to use macros (#363) (@matthew-kapp)
- Fixed error of tests failing (#365) (@matthew-kapp)
- test: fix several tests (#368) (@AayushSabharwal)
- Fixes issue #234 using same inputs (#369) (@matthew-kapp)
- Documentation build failure fixed (#370) (@matthew-kapp)
- Drop ref to non-existant `p_int` and fix format (#372) (@ven-k)
- Fix the diode tests + Refactor with `@mtkmodel` (#373) (@ven-k)

**Closed issues:**
- No argument 'p_int' for HydraulicPort (#354)
- ModelingToolkitStandardLibrary: Thermal Components - creating physically representative components (#357)
- QA tests fail due to Unbound Error in VariableResistor (#364)
- Dependency Symbolics from v6.29.2 to v6.30.0 is breaking (#371)

[Diff since v2.18.0](v2.18.0...v2.19.0)

**Merged pull requests:**
- refactor: only load analysis points if not defined in ModelingToolkit (#350) (@AayushSabharwal)

[Diff since v2.17.0](v2.17.0...v2.18.0)

**Merged pull requests:**
- Add capacitor initial voltage to README.md example (#341) (@jaakkor2)
- build(deps): bump codecov/codecov-action from 4 to 5 (#342) (@dependabot[bot])
- Add diode component (#343) (@langestefan)
- test: fix thermal piston test (#344) (@AayushSabharwal)
- Add variable resistor component (#346) (@langestefan)
- fix: change HeatPort to allow changing the guess (#347) (@avinashresearch1)

[Diff since v2.16.0](v2.16.0...v2.17.0)

**Merged pull requests:**
- Add `Interpolation` & `ParametrizedInterpolation` (#314) (@SebastianM-C)

[Diff since v2.15.1](v2.15.1...v2.16.0)

**Merged pull requests:**
- ci: test with `1`, `lts` and `pre` versions of julia (#337) (@thazhemadam)
- Update MTK (#338) (@SebastianM-C)

[Diff since v2.15.0](v2.15.0...v2.15.1)

**Merged pull requests:**
- add parameters to PID controllers (#336) (@baggepinnen)

[Diff since v2.14.0](v2.14.0...v2.15.0)

**Merged pull requests:**
- Remove defaults from Blocks.SISO (#334) (@bradcarman)
- Fix tests (#335) (@ChrisRackauckas)