PSS/E Transmission Power Flow (`.raw`)

The @modelscript/psse language package (languages/psse) provides native support for Siemens PSS®E RAW (.raw) transmission grid power flow base cases (Revisions 30 through 35). It delivers streaming parsing, round-trip serialization, pre-flight topological linting (P1001–P4001), sparse nodal admittance matrix ( $Y_{b u s} = G + j B$ ) assembly, in-engine non-linear AC power flow solving (Newton-Raphson & Fast Decoupled), multi-domain projections to Modelica and PSCAD/EMT, interactive Single-Line Diagrams (SLD) via AntV X6, and a dual-mode VS Code custom webview editor.

Supported File Specifications

Revision	Specification	Key Structural Features
PSS/E-30	Legacy Planning Deck	6-character bus names, integer area/zone codes, fixed branch thermal rating blocks
PSS/E-32	Extended Format	12-character alphanumeric bus names, expanded DC line modeling, switched shunt blocks
PSS/E-33	Modern Standard	Canonical 12-character names, multi-section lines, 2-terminal & VSC DC transmission, GIC records
PSS/E-34	Substation-Oriented	Node-breaker topologies, explicit substation IDs, multi-terminal DC grids
PSS/E-35	High-Density Matrix	Extended branch identifiers, expanded transformer winding data, flexible rating vectors

Architecture & Compilation Pipeline

Rendering diagram...

1. Pre-Flight Electrical Diagnostic Rules

@modelscript/psse runs pre-flight static checks across electrical topology, connection consistency, and equipment parameter bounds before simulation or projection:

13 rules6 error7 warning Run with msx psse lint

Code	Rule	Severity	Message
`P1001`	`bus-not-found`	error	`<entityKind>` '`<id>`' references non-existent `<busRole>`bus `<busId>`.
`P1002`	`generator-negative-power`	warning	Generator '`<genId>`' at bus `<busId>` has negative active power output (`<pg>` MW).
`P1003`	`duplicate-equipment-id`	error	Duplicate generator ID '`<genId>`' at bus `<busId>`.
`P2001`	`isolated-bus`	warning	Bus `<busId>` ('`<busName>`') is isolated with 0 in-service connecting branches or transformers.
`P2002`	`missing-slack-bus`	error	Power network base case contains 0 slack/swing buses (Bus Type 3). Power flow solution cannot be anchored.
`P2003`	`multiple-slack-buses`	warning	Power network base case contains `<count>` swing buses without explicit multi-island partitioning.
`P2004`	`voltage-out-of-bounds`	warning	Initial voltage magnitude at bus `<busId>` (`<value>` pu) is outside standard operational limits [0.8, 1.2 pu].
`P3001`	`generator-reactive-limits-inverted`	error	Generator '`<genId>`' at bus `<busId>` has inverted reactive limits: Qmin (`<qMin>` MVAR) > Qmax (`<qMax>` MVAR).
`P3002`	`generator-power-limits-inverted`	error	Generator '`<genId>`' at bus `<busId>` has inverted active power limits: Pmin (`<pMin>` MW) > Pmax (`<pMax>` MW).
`P3003`	`generator-scheduled-voltage-bounds`	warning	Generator '`<genId>`' scheduled voltage Vs = `<vs>` p.u. is outside the typical operating band [0.8, 1.2].
`P4001`	`branch-invalid-reactance`	error	Transmission branch '`<ckt>`' between bus `<fromBus>` and `<toBus>` has zero or negative reactance X = `<x>` p.u.
`P4002`	`branch-base-kv-mismatch`	warning	Branch '`<ckt>`' connects bus `<fromBus>` (`<fromKv>` kV) to bus `<toBus>` (`<toKv>` kV) without a transformer.
`P4003`	`transformer-tap-out-of-bounds`	warning	Transformer '`<ckt>`' between bus `<fromBus>` and `<toBus>` has off-nominal tap ratio `<ratio>` outside typical limits [0.7, 1.3].

Generated from languages/psse/src/errors.ts. All languages →

2. Sparse Nodal Admittance Matrix ( $Y_{b u s}$ )

The network admittance matrix $Y_{bus} \in C^{N \times N}$ is extracted via extractPowerFlowNetlist() in languages/psse/src/netlist/powerflow-netlist.ts:

Transmission Lines ( $π$ -Equivalent)

For a branch connecting buses $i$ and $j$ with series impedance $z = r + j x$ and total charging susceptance $b$ :

y_{s} = \frac{1}{r + j x} = \frac{r - j x}{r^{2} + x^{2}} = g_{s} + j b_{s}

Y_{i j} = - y_{s}, Y_{j i} = - y_{s}

Y_{i i} + = y_{s} + j \frac{b}{2}, Y_{j j} + = y_{s} + j \frac{b}{2}

Transformers with Complex Tap Ratio

For a transformer with off-nominal turns ratio magnitude $a$ and phase shift $ϕ$ , the complex tap is $\bar{a} = a e^{j ϕ} = a_{re} + j a_{im}$ :

Y_{i i} + = \frac{y_{s}}{| \bar{a} |^{2}}, Y_{j j} + = y_{s}

Y_{i j} = - \frac{y_{s}}{{\bar{a}}^{*}}, Y_{j i} = - \frac{y_{s}}{\bar{a}}

3. In-Engine Non-Linear AC Power Flow Solver

@modelscript/psse includes an exact, non-linear AC Power Flow engine (solvePowerFlow() in languages/psse/src/solver/ac-powerflow.ts) supporting both Newton-Raphson and Fast Decoupled Power Flow (FDPF):

Mismatch Formulation

For each bus $i \in {1, \dots, N}$ with voltage ${\bar{V}}_{i} = V_{i} e^{j θ_{i}}$ :

P_{i} (V, θ) = V_{i} \sum_{k = 1}^{N} V_{k} (G_{i k} \cos θ_{i k} + B_{i k} \sin θ_{i k})

Q_{i} (V, θ) = V_{i} \sum_{k = 1}^{N} V_{k} (G_{i k} \sin θ_{i k} - B_{i k} \cos θ_{i k})

where $θ_{i k} = θ_{i} - θ_{k}$ . Active and reactive mismatches are:

Δ P_{i} = P_{i}^{spec} - P_{i} (V, θ), Δ Q_{i} = Q_{i}^{spec} - Q_{i} (V, θ)

Analytical Jacobian & Adaptive Damping

The linearized Newton system at each iteration $k$ is:

[\begin{matrix} Δ P \\ Δ Q \end{matrix}] = [\begin{matrix} H & N \\ M & L \end{matrix}] [\begin{matrix} Δ θ \\ Δ V / V \end{matrix}]

$H_{i k} = \frac{\partial P_{i}}{\partial θ_{k}} = V_{i} V_{k} (G_{i k} \sin θ_{i k} - B_{i k} \cos θ_{i k})$ ( $k \neq i$ ), and $H_{i i} = - Q_{i} - B_{i i} V_{i}^{2}$ .
$N_{i k} = V_{k} \frac{\partial P_{i}}{\partial V_{k}} = V_{i} V_{k} (G_{i k} \cos θ_{i k} + B_{i k} \sin θ_{i k})$ ( $k \neq i$ ), and $N_{i i} = P_{i} + G_{i i} V_{i}^{2}$ .
$M_{i k} = \frac{\partial Q_{i}}{\partial θ_{k}} = - V_{i} V_{k} (G_{i k} \cos θ_{i k} + B_{i k} \sin θ_{i k})$ ( $k \neq i$ ), and $M_{i i} = P_{i} - G_{i i} V_{i}^{2}$ .
$L_{i k} = V_{k} \frac{\partial Q_{i}}{\partial V_{k}} = V_{i} V_{k} (G_{i k} \sin θ_{i k} - B_{i k} \cos θ_{i k})$ ( $k \neq i$ ), and $L_{i i} = Q_{i} - B_{i i} V_{i}^{2}$ .

Generator $Q$ -Limit Clamping & PV-to-PQ Switching

When $Q_{g} > Q_{max}$ or $Q_{g} < Q_{min}$ , the generator bus is clamped at its reactive limit and dynamically converted to a PQ bus for remaining iterations, preventing unrealistic voltage regulation.

4. Multi-Domain Interoperability Projections

Projection to Modelica (`psseToModelica`)

Projects a .raw case into a clean, strongly-typed Modelica physical system model:

Buses mapped to equipotential AC pins.
Generators mapped to sinusoidal voltage sources (Modelica.Electrical.Analog.Sources.SineVoltage).
Branches mapped to series R-L models (Modelica.Electrical.Analog.Basic.Resistor + Inductor).
Loads mapped to constant active and reactive impedance networks.

modelica

model Ieee14Test
  Modelica.Electrical.Analog.Basic.Ground ground;
  Modelica.Electrical.Analog.Sources.SineVoltage gen_1_1(V = 106.0, f = 60.0);
  Modelica.Electrical.Analog.Basic.Resistor line_1_2_r(R = 0.01938);
  Modelica.Electrical.Analog.Basic.Inductor line_1_2_l(L = 0.0001569);
equation
  connect(gen_1_1.n, ground.p);
  connect(gen_1_1.p, line_1_2_r.p);
  connect(line_1_2_r.n, line_1_2_l.p);
end Ieee14Test;

Projection to PSCAD / EMT Netlist (`psseToEmtNetlist`)

Generates multi-bus companion-circuit netlists compatible with ModelScript's Dommel EMT solver (@modelscript/simulate) for transient stability and electromagnetic switching studies.

5. Command-Line Interface (`msx psse`)

ModelScript's CLI provides headless inspection, linting, diagram rendering, and power flow solving:

bash

# Display summary of buses, generators, loads, branches, and MW totals
msx psse summary case.raw

# Run pre-flight electrical topology and bounds linter
msx psse lint case.raw

# Solve non-linear AC power flow with Newton-Raphson (default)
msx psse solve case.raw

# Solve with Fast Decoupled algorithm and custom tolerance
msx psse solve case.raw --algorithm=fdpf --tol=1e-5 --max-iter=30

# Export publication-quality Single-Line Diagram SVG
msx psse diagram case.raw --out=grid.svg

# Inspect sparse Ybus non-zero entry metrics
msx psse netlist case.raw

6. Custom Visual Webview Editor (`modelscript.rawEditor`)

Opening any .raw file in the ModelScript IDE or VS Code launches the custom dual-mode editor:

Single-Line Diagram View: Interactive pan/zoom SVG canvas with voltage-tier color coding (345 kV red, 138 kV blue, 69 kV green), power flow overlays, and generator/transformer glyphs.
High-Density Tabular Grid: Live-filterable tables for Buses, Generators, Branches, Transformers, and Loads with search.
Overload & Violation Badges: Automatic highlight of under-voltage ( $V < 0.95 pu$ ), over-voltage ( $V > 1.05 pu$ ), and thermal line overloads ( $S_{i j} > Rate A$ ).
Export Toolbar: Export to SVG diagrams, Modelica .mo packages, and PSCAD/EMT netlists.

PSS/E Transmission Power Flow (.raw) ​

Supported File Specifications ​

Architecture & Compilation Pipeline ​

1. Pre-Flight Electrical Diagnostic Rules ​

2. Sparse Nodal Admittance Matrix (Ybus) ​

Transmission Lines (π-Equivalent) ​

Transformers with Complex Tap Ratio ​

3. In-Engine Non-Linear AC Power Flow Solver ​

Mismatch Formulation ​

Analytical Jacobian & Adaptive Damping ​

Generator Q-Limit Clamping & PV-to-PQ Switching ​

4. Multi-Domain Interoperability Projections ​

Projection to Modelica (psseToModelica) ​

Projection to PSCAD / EMT Netlist (psseToEmtNetlist) ​

5. Command-Line Interface (msx psse) ​

6. Custom Visual Webview Editor (modelscript.rawEditor) ​