Engee documentation

H-Bridge

H is the bridge motor driver.

blockType: AcausalElectricPowerSystems.Converters.HBridge

h bridge

Path in the library:

/Physical Modeling/Electrical/Semiconductors & Converters/Converters/H-Bridge

Description

Block H-Bridge It is an H-bridge motor driver. The block has the following two simulation mode options:

  • PWM — in this mode, the block output H-Bridge It represents a controlled voltage that depends on the input signal on the PWM (PWM) port. If the value of the input signal exceeds the value of the parameter Enable threshold voltage, then the output voltage H-Bridge has a value equal to the Output voltage amplitude parameter. If the input signal value is less than the value of the Enable threshold voltage parameter, the unit supports the load circuit using one of the following three options Freewheeling mode:

    • Via one semiconductor switch and one freewheeling diode

    • Via two freewheeling diodes

    • Via two semiconductor switches and one freewheeling diode

    The first and third options are sometimes referred to as synchronous operation.

    The signal on the REV port determines the polarity of the output. If the value of the signal on the REV port is less than the value of the Reverse threshold voltage parameter, then the output has a positive polarity, otherwise it has a negative one.

  • Averaged — in this mode, there are two possible load current characteristics:

    • Smoothed

    • Unsmoothed or discontinuous

    In the variant Smoothed It is assumed that the current is almost continuous due to the inductance of the load. In this case, the block output is H-Bridge it has the form:

    where:

    • — the value of the parameter Output voltage amplitude, In.

    • — the value of the voltage at the PWM port, V.

    • — the value of the parameter PWM signal amplitude, In.

    • — the value of the output current, A.

    • — the Bridge on resistance parameter, Ohms.

    The current will be smooth if the PWM frequency is high enough. Synchronous operation mode, in which free oscillation is carried out through the bridge arm back to the power source, also helps to smooth the current. For cases where the current is not smooth or possibly intermittent (i.e. it goes to zero between PWM cycles), use the option Unsmoothed or discontinuous. For this option, you must also specify the values Load total series resistance, Load total series induction and PWM frequency. During the simulation, the unit uses these values to calculate a more accurate value of the output voltage of the H-bridge, which achieves the same average current as in PWM simulation.

To speed up the simulation when controlling the block H-Bridge using the Controlled PWM Voltage block, set the Simulation mode parameter to Averaged. The Simulation mode parameter of the Controlled PWM Voltage block must also be set to Averaged. In this case, the average value of the required PWM voltage is applied to the motor. The accuracy of the simulation results in Averaged it depends on the correctness of your assumption about the load current. If you specify that the current is not smoothed or intermittent, then the accuracy also depends on how demonstrative the load resistance and inductance values are. This mode also makes some simplifying assumptions about the basic equations for the case when the current is intermittent. For typical engine and bridge parameters, the accuracy should be within a few percent. To check the accuracy of the mode Averaged Run the simulation in PWM mode and compare the results with the results obtained in PWM mode. Averaged.

The braking mode is activated when the voltage applied to the BRK port exceeds the Braking threshold voltage. Regardless of the PWM or averaging mode, in braking mode, the H-bridge is modeled by a sequential combination of two resistances. and , where:

  • — the resistance of one bridge arm, that is, half of the value of the parameter Total bridge on resistance.

  • — the resistance of one arm of the bridge is parallel to the resistance of the diode, that is , where — resistance of the diode.

Assumptions and limitations

  • When linearizing the model, set the Simulation mode parameter to Averaged and make sure that you have specified the operating point correctly. Block linearization H-Bridge It is possible only for operating cycles that are greater than zero and less than the amplitude of the PWM signal. If linearization is required at zero duty cycle and if the controller always uses regenerative braking mode, set the Regenerative braking parameter to Always enabled (suitable for linearization).

  • In the mode Averaged and when selecting an option Unsmoothed or Discontinuous To characterize the load current, it is necessary to provide the values of the inductance and resistance of the load. If we are talking about a DC motor, then the resistance is the armature resistance, and the inductance is the sum of the armature inductance and the series smoothing choke (if any). For a universal motor, the total resistance is equal to the sum of the armature and excitation windings, and the total inductance is equal to the sum of the armature and excitation inductors, with the addition of the smoothing inductance of the series winding. For shunt motor Engee It recommends building an equivalent Thevenin circuit to determine the appropriate values.

Ports

Non-directional

+ — positive load connection port
electricity

The electrical port connected to the positive load contact.

− — negative load connection port
electricity

The electrical port connected to the negative load contact.

PWM — Pulse width modulated signal (PWM signal)
electricity

An electrical voltage port connected to a pulse width modulation signal. The voltage is determined relative to the REF port.

REF — pass reference voltage port:q[<br>] electricity

An electrical port connected to a reference zero voltage.

REV — REV
electricity

An electrical port connected to the voltage that controls the reverse polarity of the unit output H-Bridge. The voltage is determined relative to the REF port.

BRK — BRK
electricity

An electrical port connected to the voltage that controls the moment when the output of the unit is closed H-Bridge. The voltage is determined relative to the REF port.

Parameters

Simulation mode and load assumptions

Simulation mode — simulation mode
PWM (default) | Averaged

Select one of the following output voltage type options:

  • PWM — The output voltage is a pulse width modulated signal. This is the default option.

  • Averaged — the output voltage is a constant value, the value of which is equal to the average value of the PWM signal.

Freewheeling mode — Freewheeling pass mode:q[<br>] Via one semiconductor switch and one freewheeling diode (default) | Via two freewheeling diodes | Via two semiconductor switches and one freewheeling diode

Select one of the following options for the type of H-bridge scattering scheme:

  • Via one semiconductor switch and one freewheeling diode — In this mode, the unit controls the load by keeping one bridge arm on the upper side permanently on and using a PWM signal to modulate the corresponding bridge arm on the lower side. This means that when the bridge is turned off, the unit uses only one of the shunt diodes to complete the scattering circuit. This option is used by default.

  • Via two freewheeling diodes — In this mode, all bridge arms are switched off. This means that the unit dissipates the load current through the power supply using two shunt diodes.

  • Via two semiconductor switches and one freewheeling diode — In this mode, the unit controls the load by keeping one upper arm of the bridge permanently on and using a PWM signal to switch between turning on the corresponding lower arm of the bridge and the opposite upper arm of the bridge. This means that to complete the scattering circuit when the bridge is turned off, a diode connected parallel to the bridge arm is used, as well as another serial bridge arm.

Dependencies

This option is only used when selecting PWM for the Simulation mode parameter or when selecting the value Averaged for the Simulation mode parameter and the values Unsmoothed or discontinuous for the Load current characteristics parameter.

Regenerative braking — regenerative braking
Depends on REV flag and current sign (default) | Always enabled (suitable for lianerization)

Select one of the following options for the type of H-bridge scattering scheme:

  • Depends on REV flag and current sign — this option is used by default.

  • Always enabled (suitable for lianerization) — This option can be used when the controller always sets the REV flag to provide regenerative braking. This is useful if it is necessary to linearize the model for control purposes to ensure that the H-bridge is linearized near the zero duty cycle.

Dependencies

This parameter is used only when selecting a value. Averaged for the Simulation mode parameter.

Load current characteristics — characteristics of the load current
Smoothed (by default) | Unsmoothed or discontinuous

Select one of the following load current type options:

  • Smoothed — it is assumed that the current is almost continuous due to the inductance of the load. This option is used by default.

  • Unsmoothed or discontinuous — this option is used for cases where the current is not smooth or possibly intermittent (that is, it goes to zero between PWM cycles). For this option, you must also set the parameters Load total series resistance, Load total series induction and PWM frequency. During the simulation, the unit uses these values to calculate a more accurate value of the output voltage of the H-bridge, which achieves the same average current as in PWM simulation.

Dependencies

This parameter is used only when selecting a value. Averaged for the Simulation mode parameter.

Load total series resistance — total sequential load resistance
10 Ohms (default)

The total sequential load resistance perceived by the H-bridge.

Dependencies

This parameter is displayed only when a value is selected. Averaged for the Simulation mode parameter and Unsmoothed or discontinuous for the Load current characteristics parameter.

Load total series inductance — total sequential load inductance
1e-5 Gn (default)

The total sequential load inductance perceived by the H-bridge. In addition to the motor inductance, any series inductance added from outside the motor must be turned on to equalize the current.

Dependencies

This parameter is displayed only when a value is selected. Averaged for the Simulation mode parameter and Unsmoothed or discontinuous for the Load current characteristics parameter.

PWM frequency — PWM pass frequency:q[<br>] 10000 Hz (default)

The PWM frequency at which the H-bridge is controlled. For consistency, this value must match the PWM frequency set by the Controlled PWM Voltage control unit of the H-bridge.

Dependencies

This parameter is displayed only when a value is selected. Averaged for the Simulation mode parameter and Unsmoothed or discontinuous for the Load current characteristics parameter.

Freewheeling diode off-state conduction — conductivity of the shunt diode in the off state
1e-6cm (default)

The conductivity of the reverse supply diode.

Dependencies

This parameter is used only when selecting a value. Averaged for the Simulation mode parameter and Depends on REV flag and current sign for the Regenerative braking parameter.

Input thresholds

Enable threshold voltage — threshold switching voltage
2.5V (default)

The threshold above which the voltage on the PWM port must rise in order to turn on the output of the unit H-Bridge.

Dependencies

This parameter is used if the Simulation Mode and Simulation Mode & Load Assumptions parameters are set to PWM.

PWM signal amplitude — amplitude of the PWM signal
5.0 V (default)

The amplitude of the signal at the PWM input.

Dependencies

Block H-Bridge uses this parameter only if the Simulation mode parameter on the Simulation Mode & Load Assumptions tab has the value Averaged.

Reverse threshold voltage — reverse threshold voltage
2.5V (default)

When the voltage at the REV port exceeds this threshold, the output polarity becomes negative.

Braking threshold voltage — threshold braking voltage
2.5V (default)

When the voltage at the BRK port exceeds this threshold, the output terminals of the unit H-Bridge they are closed through the following series of devices:

  • One shoulder of the bridge.

  • One arm of the bridge is parallel to the conductive freewheel diode.

Bridge Parameters

Output voltage amplitude — amplitude of the output voltage
12 V (default)

Voltage amplitude at the output ports of the unit H-Bridge when the output is turned on.

Total bridge on resistance — total bridge resistance
0.1 Ohm (default)

The total effective resistance of two semiconductor collectors connecting the load to two power buses when the voltage at the PWM port exceeds the value of the Enable threshold voltage parameter in the Input Thresholds parameter group.

Freewheeling diode on resistance — resistance of the bypass diode
0.05 Ohms (default)

The total resistance of the shunt diodes that dissipate the current flowing through the motor when the voltage at the PWM port is less than the value of the Enable threshold voltage parameter in the Input Thresholds parameter group.

Examples