Interfacing with the MNA Solver

The various solver classes based on MNASolver are used to perform Nodal Analysis during a DPsim simulation. For components to be able to influence the input variables of the MNA, they have to implement certain methods defined in the MNAInterface interface class. While it is possible to individually implement MNAInterface for every component, the behavior of many components can be unified in a common base class. This base class is called MNASimPowerComp<T>. Currently, it is the only class which directly implements MNAInterface and in turn all MNA components inherit from this class. Much like the CompositePowerComp class for Composite Components, the MNASimPowerComp class provides some common behavior for all MNA components, e.g. the creation and registration of the MNAPreStep and MNAPostStep tasks. Additionally, MNASimPowerComp provides a set of virtual methods prefixed mnaComp... which can be implemented by the child component classes to provide their own MNA behavior. These methods are:

virtual void mnaCompInitialize(Real omega, Real timeStep, Attribute<Matrix>::Ptr leftVector);
virtual void mnaCompApplySystemMatrixStamp(SparseMatrixRow& systemMatrix);
virtual void mnaCompApplyRightSideVectorStamp(Matrix& rightVector);
virtual void mnaCompUpdateVoltage(const Matrix& leftVector);
virtual void mnaCompUpdateCurrent(const Matrix& leftVector);
virtual void mnaCompPreStep(Real time, Int timeStepCount);
virtual void mnaCompPostStep(Real time, Int timeStepCount, Attribute<Matrix>::Ptr &leftVector);
virtual void mnaCompAddPreStepDependencies(AttributeBase::List &prevStepDependencies, AttributeBase::List &attributeDependencies, AttributeBase::List &modifiedAttributes);
virtual void mnaCompAddPostStepDependencies(AttributeBase::List &prevStepDependencies, AttributeBase::List &attributeDependencies, AttributeBase::List &modifiedAttributes, Attribute<Matrix>::Ptr &leftVector);
virtual void mnaCompInitializeHarm(Real omega, Real timeStep, std::vector<Attribute<Matrix>::Ptr> leftVector);
virtual void mnaCompApplySystemMatrixStampHarm(SparseMatrixRow& systemMatrix, Int freqIdx);
virtual void mnaCompApplyRightSideVectorStampHarm(Matrix& sourceVector);
virtual void mnaCompApplyRightSideVectorStampHarm(Matrix& sourceVector, Int freqIdx);

MNASimPowerComp provides empty default implementations for all of these methods, so component classes are not forced to implement any of them.

Controlling Common Base Class Behavior

Child component classes can control the behavior of the base class through the constructor arguments of MNASimPowerComp. The two boolean variables hasPreStep and hasPostStep can be used to control whether the MNAPreStep and MNAPostStep tasks will be created and registered. If these tasks are created, the mnaCompPreStep / mnaCompPostStep and mnaCompAddPreStepDependencies / mnaCompAddPostStepDependencies methods will be called during the component’s lifecycle. If the tasks are not created, these methods are superfluous and should not be implemented in the child class.

Currently, the MNASimPowerComp base class only exhibits additional behavior over the mnaComp... methods in the mnaInitialize method. In this method, the list of MNA tasks is cleared, and the new tasks are added according to the hasPreStep and hasPostStep parameters. Additionally, the right vector attribute mRightVector required by MNAInterface is set to a zero-vector with its length equal to that of the system leftVector. If this behavior is not desired, e.g. for resistors which have no influence on the system right vector, the right vector can be re-set to have zero size in the mnaCompInitialize method:

void DP::Ph1::Resistor::mnaCompInitialize(Real omega, Real timeStep, Attribute<Matrix>::Ptr leftVector) {

	**mRightVector = Matrix::Zero(0, 0);

For all other MNA methods, the MNASimPowerComp base class will just call the associated mnaComp... method. For more details, take a look at the implementations in MNASimPowerComp.cpp.