Impedance monitoring of a modular electrolysis system
An alternating current (AC) impedance spectroscopy method includes providing an AC impedance spectroscopy ripple from power electronics into an electrochemical device, and absorbing the ripple in the power electronics.
1. An alternating current (AC) impedance spectroscopy system, comprising:
a power factor corrected (PFC) rectifier electrically connectable to an AC power source via an AC split bus and to a direct current DC/DC converter via a first DC bus, wherein the PFC rectifier includes:
a plurality of electric power inverters electrically connectable to respective AC busses of the AC split bus;
a first capacitor and a second capacitor electrically connected in parallel to the plurality of electric power inverters via a middle DC bus at a DC-link midpoint; and
an auxiliary electric power converter electrically connected to the DC-link midpoint via the middle DC bus and electrically connectable to the direct current DC/DC converter via the first DC bus, the auxiliary electric power converter configured to draw a reactive power amount from the DC-link to cancel a ripple current drawn by the DC/DC converter and comprising:
a third capacitor electrically connected in parallel to the first capacitor and a fourth capacitor electrically connected in parallel to the second capacitor; and
a filtering inductor electrically connected to the third capacitor and the fourth capacitor in parallel, wherein current from the DC-link midpoint is alternately and controllably drawn through the filtering inductor or the third capacitor and the fourth capacitor.
2. The AC impedance spectroscopy system of claim 1 , wherein the auxiliary electric power converter includes:
the filtering inductor having a first end and a second end, wherein the filtering inductor is electrically connected at the first end to the third capacitor and the fourth capacitor in parallel; and
a half-bridge inverter electrically connected to the second end of the filtering inductor.
3. The AC impedance spectroscopy system of claim 2 , wherein the half-bridge inverter comprises:
a first transistor electrically connected to the second end of the filtering inductor at an emitter end;
a first diode electrically connected to the second end of the filtering inductor at an anode end and in parallel with the first transistor;
a second transistor electrically connected to the second end of the filtering inductor at a collector end; and
a second diode electrically connected to the second end of the filtering inductor at a cathode end and in parallel with the second transistor.
4. The AC impedance spectroscopy system of claim 2 , wherein:
the third capacitor is electrically connected to the first DC bus at a first end and to the middle DC bus and the first end of the filtering inductor at a second end;
the fourth capacitor is electrically connected to the middle DC bus and the first end of the filtering inductor at a first end, and to a return DC bus at a second end; and
the half-bridge inverter comprises:
a first transistor electrically connected to the first DC bus at a collector end;
a first diode electrically connected to the first DC bus at a cathode end and in parallel with the first transistor;
a second transistor electrically connected to the return DC bus at an emitter end; and
a second diode electrically connected to the return DC bus at an anode end and in parallel with the second transistor.
5. The AC impedance spectroscopy system of claim 1 , wherein the plurality of electric power inverters each comprise:
a first diode and a second diode electrically connected to the respective AC bus of the split AC bus in parallel, wherein the first diode is electrically connected to the respective AC bus at an anode end and the second diode is electrically connected to the respective AC bus at a cathode end;
a first transistor comprising a collector end and an emitter end, the collector end electrically connected to the respective AC bus;
a third diode comprising a cathode end and an anode end, the cathode end electrically connected to the respective AC bus at and the anode end electrically connected to the emitter end of the first transistor;
a second transistor comprising a collector end and an emitter end, the collector end electrically connected to the middle DC bus and the emitter end electrically connected to the emitter end of the first transistor; and
a fourth diode comprising a cathode end and an anode end, the cathode end electrically connected to the middle DC bus at a cathode end and the anode end electrically connected to the emitter end of the second transistor.
6. The AC impedance spectroscopy system of claim 1 , comprising a controller configured with controller executable instructions to cause the controller to implement operations comprising:
measuring a ripple voltage of the DC-link based on voltages at the first capacitor and the second capacitor in response to injection of a perturbation to the DC/DC converter; and
injecting a canceling ripple to the DC-link configured to remove the ripple voltage from the DC-link.
7. The AC impedance spectroscopy system of claim 1 , wherein the auxiliary electric power converter includes a third capacitor and a fourth capacitor electrically connected in parallel to the middle DC bus; and
further comprising a controller configured with controller executable instructions to cause the controller to implement operations comprising:
measuring a ripple voltage of the DC-link based on voltages at the third capacitor and the fourth capacitor in response to injection of a perturbation to the DC/DC converter and in response to the first capacitor and the second capacitor being inaccessible; and
injecting a canceling ripple to the DC-link configured to remove the ripple voltage from the DC-link.
8. The AC impedance spectroscopy system of claim 1 further comprising one or more additional power factor corrected (PFC) rectifiers electrically connectable to the AC power source via the AC split bus and to the direct current DC/DC converter via the first DC bus.
9. The AC impedance spectroscopy system of claim 8 , wherein the one or more PFC rectifiers are connected in parallel to the PFC rectifier, the one or more PFC rectifiers configured to cancel one or more additional ripple currents drawn by the DC/DC converter.