[FEATURE] Automatic tap changer in step-up transformer support

[Jerry-Jinfeng-Guo]

What need to happen:

• Figure out the maths
• Control side at the node with higher rated voltage
• Tap side and the control side at the same side

[Jerry-Jinfeng-Guo]

Most changes will happen in power_grid_model_c/power_grid_model/include/power_grid_model/optimizer/tap_position_optimizer.hpp

What need to happen:

• validation to check for unsupported scenarios when it comes to enabled tap controllers:
  • more than one enabled tap controller on the same transformer
  • an enabled tap controller is coupled with a not-energized transformer
  • an enabled tap controller is coupled with a two/three winding transformer with disconnected tap side or control side
  • an enabled tap controller is coupled with a two winding transformer which are not fully connected
  • an enabled tap controller is coupled with a three winding transformer with two sides disconnected
  • an enabled tap controller is coupled with a transformer which is not reachable by transformer ranking graph, see logic below (should not happen in the validation, but in the core itself - already implemented after bug report of Steffan BugFix / Handle access violation to unconnected-regulated transformers #703)
• un-regulated transformers given weight of 0 instead of 1:
  in lines

  power-grid-model/power_grid_model_c/power_grid_model/include/power_grid_model/optimizer/tap_position_optimizer.hpp

  Lines 119 to 120 in 5603232

  	add_to_edge(state, edges, edge_props, from_node, to_node, {unregulated_idx, 1});
  	add_to_edge(state, edges, edge_props, to_node, from_node, {unregulated_idx, 1});

  and

  power-grid-model/power_grid_model_c/power_grid_model/include/power_grid_model/optimizer/tap_position_optimizer.hpp

  Lines 157 to 158 in 5603232

  	add_to_edge(state, edges, edge_props, from_node, to_node, {unregulated_idx, 1});
  	add_to_edge(state, edges, edge_props, to_node, from_node, {unregulated_idx, 1});

to

add_to_edge(state, edges, edge_props, from_node, to_node, {unregulated_idx, 0});
add_to_edge(state, edges, edge_props, to_node, from_node, {unregulated_idx, 0});

• logic determining direction of transformer tap/control sides needs update:
  • two winding transformer in lines

    power-grid-model/power_grid_model_c/power_grid_model/include/power_grid_model/optimizer/tap_position_optimizer.hpp

    Lines 151 to 153 in 5603232

    	auto const tap_at_from_side = transformer.tap_side() == BranchSide::from;
    	auto const& tap_side_node = tap_at_from_side ? from_node : to_node;
    	auto const& non_tap_side_node = tap_at_from_side ? to_node : from_node;

  • three winding transformer in lines

    power-grid-model/power_grid_model_c/power_grid_model/include/power_grid_model/optimizer/tap_position_optimizer.hpp

    Lines 107 to 109 in 5603232

    	auto const tap_at_first_side = transformer3w.tap_side() == first_side;
    	auto const single_direction_condition =
    	trafo3w_is_regulated && (tap_at_first_side || transformer3w.tap_side() == second_side);

• after assigning ranks of all regulated transformers, one round of check:

  power-grid-model/power_grid_model_c/power_grid_model/include/power_grid_model/optimizer/tap_position_optimizer.hpp

  Lines 274 to 276 in 5603232

  	}
  	return result;

  • two winding transformers: for every enabled such transformer, rank at the control side (node connected to it) should be 1 greater than the other side, throw exception if not the case.
  • three winding transformers:
    • control side == tap side: rank at the control side (node connected to it) should be 1 greater than any one of the two secondary sides, throw exception if not the case.
    • control side != tap side: rank at the control side (node connected to it) should be 1 greater than the secondary side with tap, throw exception if not the case.
• Adjust control logic

  • power-grid-model/power_grid_model_c/power_grid_model/include/power_grid_model/optimizer/tap_position_optimizer.hpp

    Lines 941 to 950 in 5603232

    	auto const cmp = node_state <=> param;
    	auto new_tap_pos = [&transformer, &cmp] {
    	if (cmp > 0) { // NOLINT(modernize-use-nullptr)
    	return one_step_control_voltage_down(transformer);
    	}
    	if (cmp < 0) { // NOLINT(modernize-use-nullptr)
    	return one_step_control_voltage_up(transformer);
    	}
    	return transformer.tap_pos();
    	}();

    linear search would have to include logic to go the opposite way if control side == tap side

  • power-grid-model/power_grid_model_c/power_grid_model/include/power_grid_model/optimizer/tap_position_optimizer.hpp

    Lines 634 to 667 in 5603232

    	void propose_new_pos(bool strategy_max, bool above_range) {
    	bool const is_down = above_range == tap_reverse_;
    	if (last_check_) {
    	current_ = is_down ? lower_bound_ : upper_bound_;
    	inevitable_run_ = true;
    	} else {
    	last_down_ = is_down;
    	adjust(strategy_max);
    	}
    	}
    	IntS repropose_tap(bool strategy_max, bool previous_down, bool& tap_changed) {
    	// __prefer_higher__ indicates a preference towards higher voltage
    	// that is a result of both the strategy as well as whether the current
    	// transformer has a reversed tap_max and tap_min
    	bool const prefer_higher = strategy_max != tap_reverse_;
    	auto const tap_pos = search(prefer_higher);
    	auto const tap_diff = tap_pos - get_current_tap();
    	if (tap_diff == 0) {
    	if (!inevitable_run_) {
    	inevitable_run_ = true;
    	tap_changed = true;
    	} else {
    	tap_changed = false;
    	}
    	return tap_pos;
    	}
    	if ((tap_diff == 1 && previous_down) || (tap_diff == -1 && !previous_down)) {
    	last_check_ = true;
    	}
    	tap_changed = true;
    	current_ = tap_pos;
    	return tap_pos;
    	}

    binary search would have to add new state control_tap_same_side in the binary logic

[mgovers]

line numbers can change. can you add permalinks? (you can create them using the GitHub viewer)