Introduction

This block is put inside the OPAL Voltage Source Converter (VSC) model to configure the converter and calculate the internal voltages and currents. The calculation is established using a switching function, which is suitable for real-time simulation. The calculated internal voltage will be implemented in the VSC Node Block to interact with other circuit components. The OPAL VSC model is able to simulate a multi-stage and multi-phase VSC that composed of different types of converter units.

The ac/ac converter shown in Figure 1 is an example for the implementation of the OPAL VSC model. The ac/ac converter has three stages, i.e. ac/dc, dc/dc, and dc/ac from left to right. In this model, a single-phase converter unit excluding the capacitor is called a sub-module (SM). Similar to a Modular Multilevel Converter (MMC), a VSC model can have various SM type corresponding to the topology of the converter unit. The OPAL VSC model currently supports SM of half-bridge (HB), full-bridge (FB), T-type, neutral point clamped (NPC), and clamp-double (CD) topologies, as presented in Figure 2. The capacitors can be either calculated inside the OPAL VSC model (as internal capacitors) or simulated with an SPS capacitor block outside the OPAL VSC model (as external capacitors). For some converter topologies, the capacitor unit actually comprises two series-connected capacitors but is deemed as one capacitor in this block. The OPAL VSC model may also include the multiple multi active bridge (MAB) and dual active bridges (DAB), e.g. the middle stage of dc/dc converter in the example.

Figure. 1 Example of VSC with ac-dc, dc-dc and dc/ac conversion stages 

Figure. 2 Types of supported submodules 

Mask and Parameters

Parameters

The VSC Configuration Block allows users to configure the converter flexibly in simulating different VSC topologies, including HB, FB, NPC, T-type, CD, DAB, MAB, MMC, etc. The range of value, data type, and the dimension of parameters in this block must respect certain rules to assure the proper configuration of the converter. This block has an internal Parameter Compatibility Check, which validates the input parameters to the rules. If the Parameter Compatibility Check detects some rules are violated, it will either give an error message, or revise the parameter to its designated limits. For the latter case, a warning will show what has been revised. The user should double check if the revision is the same as intended. If not, please manually revise the parameters following the rules.

nbSM: number of SM

The number of SM in the converter. It should be equal or larger than the total number of SM set in VSC Parameter Block. The difference between the number of SM, indicated in the VSC Configuration Block, and the total number of SM (in group 1, 2, 3) in the VSC Parameter Block are assumed to be the number of SM being disabled.

This number cannot be changed during simulation. It will determine the I/O dimension and calculation burden of this block. Choose the smallest value as possible.

Unit, data type and range: This parameter has no unit and its value is an positive integer between 1 and 50 inclusive.

Parameter Compatibility Check:

• 0< nbSM<=50, otherwise (error message);
• If 1<nbSM<=50 but is not an integer: revised to its floor value. For example, 3.6 =>3 (warning message).

Cap index of SM

An index indicates the connection between the SM and the capacitor. The connections between multiple SM and multiple capacitors are described in a row vector, which has the same dimension as nbSM. The position of a index in the vector identifies the selected SM, and the index value identifies the designated capacitor.

The value of i-th element of the vector being index j, means the i-th SM is connected to j-th capacitor in the converter. Those SMs, the elements of whose positions in the vector have a same value, are connected to the same capacitor.

Unit, data type and range: This parameter has no unit. For a converter with N_cin number of internal capacitors and N_cex number of external capacitors, each index value is a non-0 integer and in the range [-N_cex, -1] or [1, N_cin]. A positive value means that SM is connected to an internal capacitor and a negative value means that SM is connected to an external capacitor.

Example: [1 1 -2 3 -2 -1 2] means the converter has 7 SM & 5 cap (3 internal & 2 external). The connection is indicated as below:

• SM 1 and 2 <=> Cap 1 (int) <=> 1st int Cap
• SM 3 and 5 <=> Cap -2 (ext) <=> 2nd ext Cap
• SM 4           <=> Cap 3 (int) <=> 3rd int Cap
• SM 6           <=> Cap -1 (ext) <=> 1st ext Cap
• SM 7           <=> Cap 2 (int) <=> 2nd int Cap

Parameter Compatibility Check:

• Any 0's in vector will be removed. Example, [1 0 1] => [1 1] (warning message);
• More elements than nbSM: extra elements in the end are removed. Example, if nbSM=3, [1 2 1 2] => [1 2 1], (warning message);
• Less elements than nbSM: missing elements are filled in such a way that each SM missing in the vector is connected to an extra internal capacitor. Example, if nbSM=6, [1 1 -1] => [1 1 -1 2 3 4], (warning message);
• Indexes have skipped number or are out of the range: Re-index capacitor at same order without skipped number. Example, [10 -2 -3 10.5 11 10.5] => [1 -1 -2 2 3 2], (warning message).

Cap discharge resistor (ohms)

Resistance of discharge resistor in parallel with the cell capacitor.

In this version, all discharge resistors are the same and this block only takes the first non-0 element as input.

Unit, data type and range: The unit is ohms. This parameter should be positive or 'inf' (for no discharge resistor).

Parameter Compatibility Check:

• Any 0's in vector are removed and the block only takes the first non-0 element. Example, [0 1e5 1e6] => [1e5] (warning message);
• Parameter contains no value or only 0's: revised to 'inf' as if no discharge resistor. Example, [0] => [inf], or [ ]=>[inf] (warning message);

C1 capacitance vector (F)

A row vector has the same dimension as the number of internal capacitors (N_cin) which is implicitly determined by the parameter 'Cap index of SM'.

The value of i-th element being Ci-1 means the capacitance of C1 of i-th capacitor is Ci-1 F. 

For some converter topologies, the capacitor actually comprises two series-connected capacitors, C1 and C2 corresponding to the ones connected to positive and negative dc buses respectively. Other topologies have only one capacitor which is also called C1.

Unit, data type and range: The unit is F. This parameter should be positive.

Parameter Compatibility Check:

• Parameter contains no value or only 0's: Example, [ ] or [0 0] (error message);
• Any 0's in vector are removed: Example, [1e-3 0 1e-2] => [1e-3 1e-2], (warning message);
• Any negative value elements take their absolute value: Example, [-1e-3 1e-2] => [1e-3 1e-2], (warning message);
• More elements than N_cin: extra elements in the end are removed. Example, if N_cin=2, [0.1 0.2 0.2] => [0.1 0.2], (warning message);
• Less elements than N_cin: missing elements are filled with 1st element. Example, if N_cin=5, [0.1 0.2 0.2] => [0.1 0.2 0.2 0.1 0.1], (warning message);

C1/C2 ratio vector

The capacitance ratio of C1 over C2. A row vector has the same dimension as the number of internal capacitors (N_cin) which is implicitly determined by the parameter 'Cap index of SM'.

The value of i-th element being 0 means the i-th capacitor doesn't have C2 (has only C1).

Otherwise if the value of i-th element being r-i means the capacitance of C2 of i-th capacitor is Ci-1/ r-i, where Ci-1 is the capacitance of C1 of i-th capacitor.

Unit, data type and range: This parameter has no unit. This parameter should be non-negative.

Parameter Compatibility Check:

• Any negative value elements take their absolute value: Example, [-1 0] => [1 0], (warning message);
• Parameter contains no value or only 0's: all capacitors have only C1, no C2; (warning message);
• More elements than N_cin: extra elements in the end are removed. Example, if N_cin=2, [1 0 2] => [1 0], (warning message);
• Less elements than N_cin: missing elements are filled with 1st element. Example, if N_cin=3, [0 1] => [0 1 0], (warning message);

Initial capacitor voltage (V)

Initial capacitor voltage. A row vector has the same dimension as the number of internal capacitors (N_cin) which is implicitly determined by the parameter 'Cap index of SM'.

The value of i-th element being Vini-i means the i-th capacitor Ci-1 and Ci-2 (if exists) have same initial capacitor voltage Vini-i.

Unit, data type and range: The unit is Volt. This parameter can be any real value.

Parameter Compatibility Check:

• More elements than N_cin: extra elements in the end are removed. Example, if N_cin=2, [1 0 2] => [1 0], (warning message);
• Less elements than N_cin: missing elements are filled with 0's. Example, if N_cin=3, [2 1] => [2 1 0], (warning message);

DAB/MAB index of SM (same dimension as nbSM; 0 for non-DAB/MAB SM)

A row vector has the same dimension as nbSM.

The value of i-th element being j or -j (j is a positive integer) means the i-th SM is connected to j-th DAB/MAB in the converter. A positive value means that SM is connected to that DAB/MAB positively (positive current of DAB/MAB flows out of the SM's positive terminal), a negative value means that SM is connected to that DAB/MAB negatively (positive current of DAB flows into the SM's positive terminal). As an example in Figure 1, SM4 is positively connected to DAB1 and SM5 is negatively connected to DAB1.

Otherwise, if the value of i-th element being 0 means in the converter, the i-th SM is not connected to any DAB/MAB but connects to an interface node. The user has to define which node it is connected in parameter 'Interface-Node index of SM'.

Unit, data type and range: This parameter has no unit. For a converter with N_MAB number of DAB/MAB (total number of DABs and MABs), each index value is an  integer and in the range [-N_MAB, N_MAB]. A positive value means that SM is connected to that MAB positively, a negative value means that SM is connected to that MAB negatively, and 0 means that SM is not connected to any MAB.

Example: if nbSM=7, [ 0 1 -1 2 -2 0 0 ] means the converter has 4 SM connected to 2 DAB group, and 3 SM connected to the interface nodes. The connection is as below:

• DAB 1 <=> SM [2] positively & SM [3] negatively;
• DAB 2 <=> SM [4] positively & SM [5] negatively;

Parameter Compatibility Check:

• Any DAB contains at least 2 SM, 1 connected positively and 1 connected negatively, otherwise (error message);
• More elements than nbSM: extra elements in the end are removed. Example, if nbSM=3, [1 0 -1 0] => [1 0 -1], (warning message);
• Less elements than nbSM: missing elements are filled with 0's. Example, if nbSM=4, [1 0 -1] => [1 0 -1 0], (warning message);
• Indexes have skipped numbers or are out of the range: Re-index DAB at the same order without skipped number. Example, [ 0 3 -3 2 -2 ] =>[0 2 -2 1 -1], (warning message).

DAB/MAB winding index (same dimension/sequence as non-0 element in DAB/MAB index

Winding number for DAB/MAB. 

A row vector has the same dimension and sequence as the number of DAB/MAB SM in DAB/MAB index.

Elements of this vector can be integers between 1 and 5, inclusive. The i-th element of this vector being j means i-th DAB/MAB SM in DAB/MAB index vector (may NOT be the i-th SM) is connected to j-th winding of corresponding DAB/MAB . Example, DAB/MAB index of SM= [0 1 2 2 2 -1 -2] and DAB/MAB winding index = [1 1 2 3 1 4] means, MAB winding index(1)=1 is winding#1 of DAB/MAB#1, DAB/MAB winding index(2)=1 is winding#1 of DAB/MAB#2, DAB/MAB winding index(3)=2 is winding#2 of DAB/MAB#2, DAB/MAB winding index(4)=3 is the winding#3 of DAB/MAB#2, and so on. As an another example, consider circuit shown in Figure 1. For this topology, DAB/MAB index of SM= [0 0 0 1 -1 0 0 0] and DAB/MAB winding index = [1 2].

Parameter Compatibility Check:

• 0 or negative value: 0s are removed and negative value elements take their absolute value. Example, [0 1 1 2 0 -2 0] => [1 1 2 2] (warning message);
• Extra non-0 elements: if number of non-0 elements is more than number of non-0 elements in DAB/MAB index, extra non-0 elements in the end are removed. Example, DAB/MAB index of SM = [0 0 0 1 -1 0 0 0] and DAB/MAB winding index = [0 0 1 2 0 1 1], then DAB/MAB winding index = [1 2] (warning message);
• Less non-0 elements: if number of non-0 elements is less than number of non-0 elements in DAB/MAB index, missing elements are filled based on DAB/MAB index of SM, considering a default winding connection. Example 1, DAB/MAB index of SM = [1 1 1 1 -1] and DAB/MAB winding index = [1 2], then DAB/MAB winding index = [1 2 3 4 5] (warning message). Example 2, DAB/MAB index of SM = [1 1 1 1 1 1 -1] and DAB/MAB winding index = [1 2], then DAB/MAB winding index =  [1 2 3 4 5 5 5], where winding 5 is considered to have series connection (warning message);
• Skipped indexes : if indexes have skipped numbers, it is re-indexed by considering skipped number(s). Example, DAB/MAB winding = [2 1 4] => [2 1 3] (warning message);
• Putting 0 or [] as a default value: by leaving DAB/MAB winding index as an empty array ([]) or putting 0, all elements are filled based on DAB/MAB index of SM, considering a default winding connection (warning message);
• Values greater than 5: if there is no skipped winding index, any value greater than 5 is replaced by 5 (warning message).

After configuration of DAB/MAB, all connections are shown and user can double check if the revision is the same as intended.

Voltage rating of DAB/MAB SM (V)

Output voltage rating of DAB/MAB SM (SM connected to DAB/MAB), which is usually its nominal capacitor voltage. The total voltage rating of SM connected to the same transformer winding in a DAB/MAB circuit equals the nominal voltage of that winding.  

A row vector has the same dimension as the number of DAB/MAB SM (N_smD) which is implicitly determined by the parameter 'DAB/MAB index of SM'.

The value of i-th element being Vb-i means the i-th DAB/MAB SM (may NOT be the i-th SM) has the voltage rating being Vb-i.

Unit, data type and range: The unit is volt. This parameter should be positive.

Example: if nbSM=3 & 'DAB/MAB index of SM' = [-1 0 1], there are 2 DAB SM. DAB SM #1 and #2 corresponds to SM1 and SM3 respectively. Parameter 'Voltage rating of DAB/MAB SM' = [200 400] means voltage rating of DAB SM #1 (i.e. SM1) and DAB SM #2 (i.e. SM3) are 200 V and 400 V respectively. A DAB transformer connects the two SM and the nominal voltages of the windings connected to SM 1 and 3 are 200 V and 400 V respectively.

Parameter Compatibility Check:

• Any 0's in vector are removed and negative value elements take their absolute value. Example, [0 100 -200] => [100 200] (warning message);
• Less elements than N_smD: (error message);
• More elements than N_smD: extra elements in the end are removed. Example, if N_smD=3, [1 0 -1 0] => [1 0 -1], (warning message);

Inductor of DAB/MAB SM (H)

Inductor connected to DAB/MAB SM (SM connected to DAB/MAB), before the DAB/MAB transformer winding. The inductor can be an inductor, the leakage inductance of a transformer, or a combination of the two. If multiple SM connected to one same winding, the inductor can be with any of the SM but should be counted only once.  

A row vector has the same dimension as the number of DAB SM (N_smD) which is implicitly determined by the parameter 'DAB/MAB index of SM'.

The value of i-th element being L-i means the i-th DAB/MAB SM (may NOT be the i-th SM) is connected to an inductor with an inductance of L-i. Note L set in 'Inductor of DAB/MAB SM' and R set in 'Resistor of DAB/MAB SM' are connected in series.

Unit, data type and range: The unit is H. This parameter should be positive.

Example: if nbSM=3 & 'DAB/MAB index of SM' = [-1 0 1], there are 2 DAB SM (N_smD=2), where DAB SM #1 is SM 1 and DAB SM #2 is SM 3. SM 2 is non-DAB SM. Parameter 'Inductor of DAB/MAB SM' = [0 0.01] means a DAB transformer connects the two DAB SM and a 0.01 H inductor is connected between the DAB transformer and DAB SM #2 (i.e. SM 3).

Parameter Compatibility Check:

• Any negative value take their absolute value. Example, [0 -0.02] => [0 0.02] (warning message);
• More elements than N_smD: extra elements in the end are removed. Example, if N_smD=2, [0.01 0 0.1] => [0.01 0], (warning message);
• Less elements than N_smD: missing elements are filled with 0's. Example, if N_smD=2, [0.01 ] => [0.01 0], (warning message);
• There must be at least one inductor in a DAB/MAB circuit. In other words, at least one SM in a DAB/MAB connects to an inductor. Otherwise, (error message).

Resistor of DAB/MAB SM (Ohms)

Resistor connected to DAB/MAB SM (SM connected to DAB/MAB), before the DAB/MAB transformer winding.    

A row vector has the same dimension as the number of DAB/MAB SM (N_smD) which is implicitly determined by the parameter 'DAB/MAB index of SM'.

The value of i-th element being R-i means the i-th DAB/MAB SM (may NOT be the i-th SM) is connected to a resistor with the resistance of R-i. Note L set in 'Inductor of DAB/MAB SM' and R set in 'Resistor of DAB/MAB SM' are connected in series.

Unit, data type and range: The unit is ohms. This parameter should be positive.

Example: if nbSM=3 & 'DAB/MAB index of SM' = [-1 0 1], there are 2 DAB SM. DAB SM #1 and #2 corresponds to SM1 and SM3 respectively. Parameter 'Resistor of DAB/MAB SM' = [0 0.001] means a DAB transformer connects the two SM and a 0.001 Ohm resistor is connected between the DAB transformer and DAB SM #2 (i.e. SM 3).

Parameter Compatibility Check:

• Any negative value take their absolute value. Example, [0 -0.001] => [0 0.001] (warning message);
• More elements than N_smD: extra elements in the end are removed. Example, if N_smD=2, [0.001 0 0.01] => [0.001 0], (warning message);
• Less elements than N_smD: missing elements are filled with 0's. Example, if N_smD=2, [0.001 ] => [0.001 0], (warning message);

DAB/MAB frequency (Hz) (same dimension/sequence as DAB/MAB number)

Nominal operating frequency of each DAB/MAB transformer or switching frequency of each DAB/MAB.

A row vector has the same dimension and sequence as DAB/MAB number.

Unit, data type and range: The unit is Hz (Hz). 

Parameter Compatibility Check:

• There must be at least one value in this vector. Otherwise, (error message);
• Any negative value take its absolute value and if there are less elements than the number of DAB/MAB, missing elements are filled with the absolute value of first element. Example, if there are 4 DAB/MABs and DAB/MAB frequency (Hz)=[-2e3 5e3], then it is revised to [2e3 5e3 2e3 2e3], (warning message).

Magnetization inductor of DAB/MAB (H) (same dimension/sequence as DAB/MAB number)

Magnetization branch inductor of each DAB/MAB transformer.

A row vector has the same dimension and sequence as DAB/MAB number.

To ignore magnetization branch, put either [] or 0.

Unit, data type and range: The unit is Henry (H). 

Parameter Compatibility Check:

• 0 or Negative value: 0s are removed and negative value elements take their absolute value. Example, [0 -2e-3 2e-3 ] =>[2e-3 2e-3], (warning message);
• More elements than the number of DAB/MAB: extra elements in the end are removed. Example, if there are 3 DAB/MAB and Magnetization inductor of DAB/MAB = [2e-3 1e-3 8e-3 5e-3] => [2e-3 1e-3 8e-3], (warning message);
• Less elements than the number of DAB/MAB: missing elements are filled with the first non-0 value of vector. Example, if there are 3 DAB/MAB and Magnetization inductor of DAB/MAB = [2e-3 1e-3] => [2e-3 1e-3 2e-3], (warning message);

Interface-Node index of SM (same dimension as nbSM; 0 for SM connecting to DAB or MAB)

A row vector has the same dimension as nbSM.

The value of i-th element being j (j is a positive integer) means in the converter, the i-th SM is connected to j-th interface-node. An interface node is a node connecting the VSC and external circuit. If several elements (i1, i2, ..., ik) in the vector have the same value j, the corresponding multiple SM (Number i1, i2, ..., ik) are connected in series between the node-j and the reference node and its node voltage is the sum of output voltages of those SM. The reference nodes are defined in the parameters 'Node voltage reference point for SM group 1/2/3'.

Otherwise, i.e. the value of i-th element being 0 means in the converter, the i-th SM is not connected to any interface node but connected to an internal node, i.e. DAB or MAB. The user has to define connected DAB/MAB in parameter 'DAB/MAB index of SM'.

Note, each SM connects to either a DAB/MAB or an interface node. Therefore, internally for i-th element in 'DAB/MAB index of SM' and i-th element in 'Interface-Node index of SM', one of them must be 0 and the other must be non-0 (after the parameter compatibility check).

Unit, data type and range: This parameter has no unit. For a converter has N_node inter-face nodes with an external circuit, each index value is an integer in the range [0, N_node]. 

Example: if nbSM=7, 'DAB/MAB index of SM' = [ 0 1 -1 2 -2 0 0 ], & 'Interface-Node index of SM' = [ 1 0 0 0 0 2 1] means the converter has 4 SM connected to 2 DAB groups, and 3 SM connected to 2 interface nodes. The connection is as below:

• DAB 1 <=> SM [2] positively & SM [3] negatively;
• DAB 2 <=> SM [4] positively & SM [5] negatively;
• Node 1 <=> SM [1 7];
• Node 2 <=> SM [6];

Parameter Compatibility Check:

• Each SM connects to either a DAB/MAB or an interface node, i.e. for i-th element in 'DAB/MAB index of SM' and i-th element in 'Interface-Node index of SM', one of them must be 0 and the other must be non-0. If there are conflicts, this block assumes 'DAB/MAB index of SM' is correct. All non-0 indexes in 'Interface-Node index of SM' are re-mapped to the remaining SM connecting to interface-nodes in order. Example: in case of nbSM=7, 'DAB/MAB index of SM' = [ 0 1 -1 2 -2 0 0 ], & 'Interface-Node index of SM' = [ 1 0 0 0 2 1], conflicts are that SM 5 is connected to both DAB 2 (negatively) and node 2 and SM 7 is connected to neither a DAB nor a node. This block will take non-0 elements of 'Interface-Node index of SM' (i.e. [1 2 1]) and re-map them to remaining non-DAB SM (i.e. SM 1, 6, 7). Thus 'Interface-Node index of SM' is revised to [ 1 0 0 0 0 2 1]. (warning message);
• More non-0 elements than N_node: extra elements in the end are removed. Example, in case of nbSM=7, 'DAB/MAB index of SM' = [ 0 1 -1 2 -2 0 0 ], 'Interface-Node index of SM' = [ 1 0 0 0 0 2 1 2]=> [ 1 0 0 0 0 2 1 ], (warning message);
• Less non-0 elements than N_node: missing elements are filled in such a way that each SM was NOT connected to any DAB/MAB or node will connect to an extra interface node. Example, in case of nbSM=7, 'DAB/MAB index of SM' = [ 0 1 -1 2 -2 0 0 ],   'Interface-Node index of SM' = [ 1 0]=> [ 1 0 0 0 0 2 3 ], (warning message);
• Indexes have skipped number or are out of the range: Re-index nodes at the same order without skipped number. Example, in case of nbSM=7, 'DAB/MAB index of SM' = [ 0 1 -1 2 -2 0 0 ],   'Interface-Node index of SM' = [ 1.1 0 0 0 0 3 1.1 ]=> [ 1 0 0 0 0 2 1 ], (warning message).

Node voltage reference point for SM Group 1/2/3

This parameter sets the reference nodes of the interface-nodes voltages. For the SM belongs to the same group (e.g. group 1/2/3 as defined in VSC Parameter Block), the option must be the same, i.e. the same type of reference node for SM in the same group.

Unit, data type and range: either of the following two options:

• the midpoint of the 2 dc capacitors. Select this option only for the cases of the VSC with 2 dc capacitors and the midpoint being grounded.
• the negative dc bus. Select this option for most cases, including series connected MMC SM,  single capacitor SM, or the negative dc bus being grounded.

Capacitor integration method:

• Discrete integration method for internal capacitor voltage calculation.
• Unit, data type and range: either "Forward Euler" or "Trapezoidal".

Inductor integration method:

• Discrete integration method for DAB/MAB inductor/transformer current calculation.
• Unit, data type and range: either "Forward Euler" or "Trapezoidal".

time step:

Discrete time step of this block.

Unit, data type and range: the unit is second. The value has to be positive real.

Showing warning message by 'Parameter Compatibility Check':

Showing warning message by 'Parameter Compatibility Check' in one of the following 4 options.

• None;
• In a pop-up window;
• In Command Window;
• In both a pop-up and Command windows;

Showing converter config summary message:

Showing converter config summary message in one of the following 4 options.

• None;
• In a pop-up window;
• In block mask;
• In both a pop-up window and block mask;

Summary Message

• Including Capacitor connection summary:

Check or uncheck to set if to include Capacitor connection summary.

• Including DAB connection summary:

Check or uncheck to set if to include DAB connection summary.

• Including node connection summary:

Check or uncheck to set if to include interface-node connection summary.

• Including SM connection summary:

Check or uncheck to set if to include SM connection summary.

Ports, Inputs, Outputs and Signals Available for Monitoring

Ports

No ports.

Input

In (Input)

The Simulink input "In" of the block is a bus with following structure. User can use Bus Creator block to combines the input signals into a bus according to that structure.

g:

gating signals, containing 5 vector signals, g1 ~ g5. Each has a dimension of the number of SM (N_sm). The i-th signal means the gating state for SM-i. Each gating signal takes a value between 0 and 1 inclusive. 0 means the gate is OFF and 1 means the gate is ON. A value between 0 and 1 means the duty cycle, i.e. the ratio of ON time over the time step. For example, g.g1(2) = 0.3 means the g1 of SM 2 has 30% ON time and 70% OFF time during the previous time step.

For definition of g1~g5 of SM, please refer to Figure 2 (a)-(d).

Icint_ext:

This block allows capacitors simulated inside this block (internal capacitors) connect to external circuit. This signal is the charging currents of internal capacitors from external circuits, containing 2 vector signals, Icint1_ext (for the upper capacitor C1) and Icint2_ext (for the lower capacitor C2). Each has a dimension of the number of internal capacitor (N_cin). The i-th signal means the charging current for i-th internal capacitor, Cin-i.

The unit is Amp. The positive direction is charging the capacitor.

For example, Icint_ext.Icint2_ext(5)=0 means no charging current to the lower capacitor of the 5th internal capacitor, C5-2.

Vcext:

External capacitor voltages, containing 2 vector signals, Vc1ext (for the upper capacitor C1) and Vc2ext (for the lower capacitor C2). Each has a dimension of the number of external capacitor (N_cex). The i-th signal means the voltage for i-th external capacitor, Cex-i.

The unit is Volt.

For example, Vcext.Vc2ext(5)=100 means the voltage of the lower capacitor of the 5th external capacitor (C5-2) is 100 V.

Ivlv:

Node current with a dimension of the number of interface nodes (N_node). The i-th signal means the measured current of i-th interface node.

The unit is Amp. Please refer to Figure 2 (a)-(d) for positive direction.

For example, Ivlv(2)=100 means the current of the 2nd interface node is 100 A.

Outputs

Out (output)

The Simulink output "Out" of the block is a bus with following structure. User may demultiplex these signals by using the Bus Selector block provided in the Simulink library.

Vs:

Interface-node voltages, containing 2 vector signals, Vsp and Vsn for positive and negative directions. Each has a dimension of the number of interface-nodes. This signal is used by VSC Node Blocks which represent the converter interface nodes connecting to the external circuit.

Vcint:

Voltages of internal capacitors, containing 2 vector signals, Vc1int (for the upper capacitor C1) and Vc2int (for the lower capacitor C2). Each has a dimension of the number of internal capacitor (N_cin).   This signal is used by VSC Internal Capacitor Blocks which represent the internal capacitors and connect to external circuits. The unit is Volt.

Icex:

Charging current from converter to external capacitors, containing 2 vector signals, Ic1ex (for the upper capacitor C1) and Ic2ex (for the lower capacitor C2). Each has a dimension of the number of external capacitor (N_cex). This signal is used by VSC External Capacitor Blocks which represent the external capacitors and connect to external circuits. The unit is Amp. The positive direction is charging the capacitor.

Idab:

Measurement signals of DAB current.

The unit is Amp.

flt:

Indicator signals of capacitor short-circuit fault, containing 2 vector signals, flt1(for the upper capacitor C1) and flt2 (for the lower capacitor C2). Each has a dimension of the number of internal capacitor (N_cin). A value of 1 means fault and 0 means no-fault.

Ismd:

Measurement signals of SM current in dc side, containing 2 vector signals, Ism1d (for the upper capacitor C1) and Ism2d (for the lower capacitor C2). Each has a dimension of the number of SM (N_SM).

The unit is Amp. Positive direction is charging the capacitor.

Ism:

Measurement signals of SM current in ac side, with a dimension of the number of SM (N_SM).

The unit is Amp. Please refer to Figure 2 (a)-(d) for positive direction.

Sensors

Description

As VSC's topology may have many variants, each is made of same basic types of components, which are defined below so the user can flexibly configure them to form different VSC topologies.

SM:

The term Submodule (SM) is borrowed from the modular multi-level converter (MMC) referring to the basic unit consisting of several switches (IGBT/diode) and capacitors. Typical SM include Half-bridge (HB) SM, full-bridge (FB) SM, clamp-double (CD) SM, T-type SM (T-SM), and etc. In this block, SM is defined slightly different than the SM in an MMC. SM in this block only includes the switches part of a converter unit and doesn't include the capacitor. And furthermore, switches of one phase of 2-level converter (similar to HB SM), 3-level NPC converter, T-type converter (similar to T-SM) can also be deemed as an SM. Therefore, SM in this block is a group of switches which converts between ac and dc voltages. Normally, the dc side of SM is connected to a capacitor and the ac side of SM is connected to either a DAB or an interface node.

Capacitor:

The capacitor is excluded from SM because for some converter topologies, such as 2-level, NPC, T-type converters, multiple SM (phases) share the same capacitor. This block is flexible that capacitors can be either simulated inside the block (referred as internal capacitors) or externally using SPS capacitor blocks (referred as external capacitors). Note in this block, a capacitor can be in the form either with one single capacitor or with two (upper C1 and lower C2) capacitors connected in series with or without midpoint grounded.

DAB:

The converter can include Dual Active Bridge (DAB) or, in general, multi active bridge (MAB) converters. A DAB consists of several SM, the inductor/resistor and/or the transformer. In this block, the SM connected to DAB are called a DAB SM.

Interface node:

In this block, an interface node is a node connecting the ac side of SM and the external circuit. For a converter, such as 2-level, NPC, or T-type converter, one interface node represents one ac phase of the converter. For an MMC converter, one interface node represents a single-phase ac output of multiple SM connected in series. In this block, the SM connected to interface node are called an interface-node SM.

How to configure the converter topology in this model?

1. Identify the numbers of SM, Capacitors (internal and external), DAB, DAB SM, interface-node, and interface-node SM in the converter. Assuming:
1. N_sm: number of SM
2. N_c: number of capacitor
3. N_cin: number of internal capacitor
4. N_cex: number of external capacitor
5. N_DAB: number of DAB
6. N_smD: number of DAB SM, i.e. SM connected to DAB
7. N_node: number of interface-node
8. N_smN: number of interface-node SM, i.e. SM connected to interface-node
2. Name each SM, internal Capacitors, external capacitors, DAB, and nodes in numerical order:
1. SM-1, SM-2, … SM-N_sm;
2. Cin-1, Cin-2, …, Cin-N_cin;
3. Cex-1, Cex-2, …, Cex-N_cex;
4. DAB-1, DAB-2, …, DAB-N_DAB;
5. Node-1, Node-2, …, Node-N_node;
3. Connect SM with capacitors using 'Cap index of SM' parameter.
1. A row vector of index with same dimension as number of SM;
2. The i-th element being j or -j (j is a positive integer) means the i-th SM is connected to the j-th capacitor;
3. j means the j-th internal capacitor; and -j means the j-th external capacitor. (Note the j-th internal capacitor and the j-th external capacitor are two different capacitors.)
4. Connect SM with DAB using 'DAB index of SM' parameter.
1. A row vector of index with same dimension as number of SM;
2. i-th element being j or -j (j is a positive integer) means the i-th SM is connected to the j-th DAB;
3. j means positive connection (the positive current of DAB flows into the SM's positive terminal) and -j means negative connection (the positive current of DAB flows into the SM's positive terminal) .
5. Connect SM with interface nodes using 'Interface-Node index of SM' parameter.
1. A row vector of index with same dimension as number of SM;
2. i-th element being j means i-th SM is connected to j-th Interface-Node;
6. Set other parameters properly in the mask.

How to connect to external circuit?

1. Properly configure the converter by setting the right parameters of this block. This block also do calculation for all internal voltages and currents.
2. Converter ac nodes:
1. For each ac interface node, put a VSC Node Block from the library in the same subsystem containing this VSC Configuration Block. The VSC Configuration Block and VSC Node Blocks should be in the same level.
2. Connect input/output signals between the node blocks and the converter config block. The node currents measured in node block are sent to converter config block. And calculated node voltages are sent back in the opposite direction.
3. Set a unique ID in the VSC Node Block corresponding to the interface node ID in this converter config block.
4. Connect the external circuit to the ports of VSC Node Blocks which represent the interface nodes of the converter.
3. External capacitor:
1. For each external capacitor, put a VSC External Capacitor Block from the library in the same subsystem containing this VSC Configuration Block. The VSC Configuration Block and VSC External Capacitor Blocks should be in the same level.
2. Connect input/output signals between the VSC External Capacitor Blocks and the VSC Configuration Block. The capacitor voltages measured in the VSC External Capacitor Block are sent to the VSC Configuration Block. And the currents injecting into the external capacitor are sent back in the opposite direction.
3. Set a unique ID in the VSC External Capacitor Block corresponding to the Cex ID in this VSC Configuration Block.
4. Connect the external circuit to the ports of VSC External Capacitor Blocks.
4. Internal capacitor:
1. For each Internal capacitor that connects to external circuit with extra charging path, put a VSC Internal Capacitor Block from the library in the same subsystem containing this VSC Configuration Block. The VSC Configuration Block and VSC Internal Capacitor Blocks should be in the same level.
2. Connect input/output signals between the VSC Internal Capacitor Blocks and the VSC Configuration Block. The charging currents from external circuit are measured in the VSC Internal Capacitor Block and sent to the VSC Configuration Block. And the capacitor voltage of the internal capacitor are sent back in the opposite direction.
3. Set a unique ID in the VSC Internal Capacitor Block corresponding to the Cin ID in this VSC Configuration Block.
4. Connect the external circuit to the ports of VSC Internal Capacitor Blocks.

Limitations

This block is simulated in CPU with a time step of tens microseconds. Therefore, the switching frequency of converters has a upper limit. If user use PWM Generation Block in the library to generate gating signals, the switching frequency limit can be as high as 1/4 of sampling frequency (reciprocal of the time step). For example, if the model has a time step of 50 microseconds, the converter can have a switching frequency as high as 5 kHz.

The DAB transformer model used in this block is an ideal transformer with leakage inductance and resistance. The transformer magnetizing branch is not considered. 

External capacitor cannot simulate short-circuit fault situation.

References

See Also

VSC Parameter Block, VSC Node Block, VSC External Capacitor Block, VSC Internal Capacitor Block.