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A synchronous bi-directional active power conditioning system (11) suitable for wide variable frequency systems or active loads such as adjustable speed drives which require variable voltage variable frequency power management systems is disclosed. Common power electronics building blocks (100, 200)

A synchronous bi-directional active power conditioning system (11) suitable for wide variable frequency systems or active loads such as adjustable speed drives which require variable voltage variable frequency power management systems is disclosed. Common power electronics building blocks (100, 200) (both hardware and software modular blocks) are presented which can be used for AC-DC, DC-AC individually or cascaded together for AC-DC-AC power conversion suitable for variable voltage and/or wide variable frequency power management systems. A common control software building block (2, 5) includes a digital control strategy/algorithm and digital phase lock loop method and apparatus which are developed and implemented in a digital environment to provide gating patterns for the switching elements (3, 6) of the common power-pass modular power electronics building blocks (100, 200).

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1. A synchronous and bi-directional power conversion module for use in a variable frequency power conversion system, the power conversion module comprising:a digital controller that receives signals from AC and DC voltage and current sensors and generates gating signals to power switching devices to

1. A synchronous and bi-directional power conversion module for use in a variable frequency power conversion system, the power conversion module comprising:a digital controller that receives signals from AC and DC voltage and current sensors and generates gating signals to power switching devices to control power flow between an AC side and a DC side of the power switching devices, wherein the digital controller includes a digital phase lock loop (DPLL) that uses a feed-forward predictive system based on a look-up table to track the system variable frequency, which is a frequency of a variable frequency power source. 2. The synchronous and bi-directional power conversion module according to claim 1, wherein the power conversion module is configurable to operate as a rectifier (AC-DC) or an inverter (DC-AC).3. The synchronous and bi-directional power conversion module according to claim 2, wherein the power conversion module is configured as a rectifier and is combined with another power conversion module configured as an inverter to provide AC-DC-AC power conversion.4. The synchronous and bi-directional power conversion module according to claim 1, wherein the system frequency varies over a ratio of 2 to 1 or more.5. The synchronous and bi-directional power conversion module according to claim 1, wherein a total number of samples in one system fundamental period is continuously monitored and maintained as an even number.6. The synchronous and bi-directional power conversion module according to claim 5, wherein when the system variable frequency varies between 320 to 800 Hz, the total number of samples is adjusted accordingly to achieve a constant switching frequency for the power switching devices.7. The synchronous and bi-directional power conversion module according to claim 1, wherein a substantially constant switching frequency is maintained for the power switching devices.8. The synchronous and bi-directional power conversion module according to claim 7, wherein the power conversion module operates at a switching frequency of approximately 10 kHz for a system frequency range of 320 to 800 Hz.9. The synchronous and bi-directional power conversion module according to claim 8, further comprising:low-pass filters for active rectifiers having cut-off frequencies on the order of 100 Hz for direct and quadrature components of system voltage and current. 10. The synchronous and bi-directional power conversion module according to claim 1, further comprising:a control power supply that internally generates voltages needed for the power conversion module from a single control power source; a DC-link connected to the DC side of the power switching devices; a filter including inductive and capacitive elements connected to the AC side of the power switching devices; and signal conditioning and isolation circuitry for all sensed signals including the sensors for detecting AC voltages and currents on the AC side and DC voltage and current on the DC-link, wherein the digital controller, signal conditioning and isolation circuitry, sensors, filter, DC-link, power switching devices and control power supply are integrated into a common circuit card assembly. 11. A digital phase lock loop (DPLL) for variable frequency power conversion systems comprising:an input section that determines a reference phase angle error signal based on a reference phase angle of a variable frequency input and an estimated phase angle; a PI controller that determines a measured frequency of the variable frequency input based on the phase angle error signal; and a look-up table that, using the measured frequency, determines a phase angle step, a sampling frequency, and a phase angle delay, wherein the estimated phase angle is generated by a discrete integrator using the phase angle step and a prior value of the estimated phase angle, and a compensated phase angle is generated using the estimated phase angle and the phase angle delay. 12. The digital phase lock loop according to claim 11, wherein the phase angle step, the sampling frequency, and the phase angle delay are determined at every sample point and wherein the compensated phase angle is generated at every sample point.13. The digital phase lock loop according to claim 11, wherein the variable frequency input varies over a ratio of 2 to 1 or more.14. The digital phase lock loop according to claim 11, wherein the look-up table is a three-dimensional look-up table.15. The digital phase lock loop according to claim 14, wherein stored values in the look-up table relating to the measured frequency and the phase angle step, the sampling frequency, and the phase angle delay are pre-calculated.16. The digital phase lock loop according to claim 15, wherein the stored values in the look-up table are calculated for discrete intervals of the measured frequency, and wherein the intervals ranges from 1 Hz to 40 Hz.17. The digital phase lock loop according to claim 15, wherein the stored values in the look-up table are calculated for each 20 Hz interval of the measured frequency.18. The digital phase lock loop according to claim 11, wherein the variable frequency input ranges from 320 to 800 Hz.19. The digital phase lock loop according to claim 11, wherein a total number of samples in one system fundamental period is continuously monitored and maintained as an even number.20. The digital phase lock loop according to claim 19, wherein when the variable frequency input varies between 320 to 800 Hz, the total number of samples is adjusted accordingly to achieve a constant switching frequency for the power switching devices.21. A method for implementing a digital phase lock loop (DPLL) for variable frequency power conversion systems, the method comprising:determining a reference phase angle error signal based on a reference phase angle of a variable frequency input and an estimated phase angle; determining a measured frequency of the variable frequency input based on the phase angle error signal; and using the measured frequency as an input to a look-up table that generates a phase angle step, a sampling frequency, and a phase angle delay, wherein the estimated phase angle is generated by a discrete integrator using the phase angle step and a prior value of the estimated phase angle, and a compensated phase angle is generated using the estimated phase angle and the phase angle delay. 22. The method according to claim 21, wherein the phase angle step, the sampling frequency, and the phase angle delay are determined at every sample point and wherein the compensated phase angle is generated at every sample point.23. The method according to claim 21, wherein the variable frequency input varies over a ratio of 2 to 1 or more.24. The method according to claim 21, wherein the look-up table is a three-dimensional look-up table.25. The method according to claim 24, further comprising:pre-calculating stored values in the look-up table relating the measured frequency and the phase angle step, the sampling frequency, and the phase angle delay. 26. The method according to claim 25, wherein the stored values in the look-up table are calculated for discrete intervals of the measured frequency, and wherein the intervals are from 1 Hz to 40 Hz.27. The method according to claim 25, wherein the stored values in the look-up table are calculated for each 20 Hz interval of the measured frequency.28. The method according to claim 21, wherein the variable frequency input ranges from 320 to 800 Hz.29. The method according to claim 21, wherein a total number of samples in one system fundamental period is continuously monitored and maintained as an even number.30. The method according to claim 29, wherein when the variable frequency input varies between 320 to 800 Hz, the total number of samples is adjusted accordingly to achieve a constant switching frequency for the power switching devices.