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Aggregation Verification: Multiple Loads at the Same Bus

Question

Does pandapower (via midas-powergrid) correctly aggregate the active power (p_mw) of multiple Load elements connected to the same bus into net.res_bus.p_mw?

Method

A minimal pandapower network was created with two buses connected by a line. An external grid was attached to bus 1, and two loads (0.5 MW and 0.3 MW) were attached to bus 2. A power flow calculation was run and the result was inspected.

Test Script

import pandapower as pp

net = pp.create_empty_network()
b1 = pp.create_bus(net, vn_kv=20.0, name="Bus_1")
b2 = pp.create_bus(net, vn_kv=20.0, name="Bus_2")
pp.create_line(net, b1, b2, length_km=1.0, std_type="NAYY 4x50 SE")
pp.create_ext_grid(net, b1)
pp.create_load(net, b2, p_mw=0.5, name="Load_A")
pp.create_load(net, b2, p_mw=0.3, name="Load_B")
pp.runpp(net)

total_load = 0.5 + 0.3
bus_p_mw = net.res_bus.loc[b2, "p_mw"]
assert abs(total_load - bus_p_mw) < 0.001

Result

Bus 1 (Bus_2):
  Loads at bus: 2
  Sum of load p_mw: 0.800000
  res_bus p_mw:     0.800000
  Match: True

pandapower aggregates multiple loads at the same bus correctly. res_bus.p_mw equals the sum of all connected load.p_mw values.

midas-powergrid Behaviour

In PandapowerSimulator.step(), when multiple mosaik entities send inputs to the same Load entity, the simulator sums all source values before calling grid.set_inputs():

for src_id, val in src_ids.items():
    if val is not None:
        setpoint += float(val)

This means multiple EV agents connected to the same Load entity will have their p_mw contributions summed automatically.

Runtime Load Creation

midas-powergrid creates all grid entities (buses, loads, lines, etc.) in PandapowerGrid.__init__ during create(). The entity map is fixed at setup time. New Load entities cannot be created at runtime — all loads must exist when the grid is initialised.

Conclusion

  1. Native aggregation works: pandapower sums multiple loads at the same bus. No generic PowerAggregator simulator is needed.
  2. Runtime load creation is not supported: all loads must be defined at grid setup time.
  3. The LoadRouter approach is still needed — not for aggregation, but because mosaik's topology is static: an EV agent cannot dynamically reconnect to a different Load entity at runtime. The LoadRouterSimulator solves this by routing power to the correct load based on the agent's current bus_id.