Power transmission system for wireless communication systems

• US 10,812,664 B2
• Filed: 01/19/2018
• Issued: 10/20/2020
• Est. Priority Date: 01/20/2017
• Status: Active Grant

• Current Assignee: Raycap S.A.
• Original Assignee: Raycap S.A.
• Inventors: Kostakis, Grigoris, Kolovos, Anestis, Tsakiridis, Nikolaol, Bloxham, Michael C., Warner, Shawn A., Xepapas, Fotis, Politis, Zafiris G.
• Primary Examiner(s): Nguyen, Lee
• Application Number:
  US15/875,795
• Publication Number:
  US 20180213091A1
• Time in Patent Office: 1,005 Days
• Field of Search: 455572
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
• CPC Class Codes: G05F 1/465 Internal voltage generators for integrated circuits, e.g. step down generators
• CPC Class Codes: G05F 1/468 characterised by reference voltage circuitry, e.g. soft start, remote shutdown
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H04B 3/548 the power on the line being DC arrangements for feeding power H04L12/10; extracting feeding power from signals H04L25/02
• CPC Class Codes: H04M 19/008 Using DC/DC converters DC/DC converters per se H02M3/28

Abstract

A power transmission system includes a voltage measurement device located on a tower or rooftop for measuring a voltage (V_RRH) at a top end of a DC cable connected to a remote radio head (RRH). A voltage control system receives an input voltage (V_IN) from a DC power supply and generates an output voltage (V_OUT) at a base end of the DC cable. The voltage control system calculates a voltage drop on the DC cable based on the V_RRH measurement and then adds different voltage steps to V_IN so V_OUT compensates for the voltage drop. Calculating the voltage drop allows the PTS to more efficiently supply power to RRHs without having to increase the size of DC power cables.

Claims

1. A power transmission system, comprising:

a DC-DC converter configured to;

receive a DC input voltage (V_IN) from a power supply and generate an output voltage (V_OUT) to power at least one remote radio head (RRH);

determine a voltage drop on a DC cable connected between the DC-DC converter and the RRH based on a specific configuration of RRH;

apply voltage levels to V_IN so V_OUT compensates for the voltage drop; and

output V_OUT on the DC cable to power the RRH, wherein V_OUT does not change during operation unless there is a reconfiguration of the RRH that changes power consumption of the RRH.

2. The power transmission system of claim 1, wherein the DC-DC converter includes a control unit configured to:

receive a signal from a voltage measurement (VM) device located on a tower or roof where the RRH is located, the signal indicating a voltage (V_RRH) at an input of the RRH;

measure V_OUT and an output current I_OUT at an output of the DC-DC converter;

calculate a resistance of the DC cable (R_CABLE) based on V_RRH, V_OUT, and I_OUT; and

adjust the voltage levels applied to V_IN so V_OUT compensates for the voltage drop associated with R_CABLE.

3. The power transmission system of claim 2, wherein the DC-DC converter includes a current sensor for determining V_RRH based on current pulses transmitted over the DC cable by the VM device.

4. The power transmission system of claim 3, wherein a duration of the current pulses is increased to increase reception accuracy due to capacitance distortion.

5. The power transmission system of claim 3, wherein the control unit is further configured to generate a voltage pulse on the DC cable that causes the VM device to start generating the current pulses.

6. The power transmission system of claim 2, wherein the control unit measures I_OUT during a start-up period of the RRH when a voltage monitor at the RRH generates a current pulse to increase current flow in the cable while calculating R_CABLE.

7. The power transmission system of claim 2, wherein the control unit is further configured to receive the signal indicating V_RRH over a communication link connected between the DC-DC converter and the VM device.

8. The power transmission system of claim 2, wherein the DC-DC converter includes an amplitude shift keying (ASK) demodulator for determining V_RRH based on a modulated ASK pulses transmitted over the DC cable by the VM device.

9. The power transmission system of claim 8, wherein the ASK pulses are generated at 7.5 megahertz (MHz).

10. The power transmission system of claim 1, wherein the DC-DC converter includes:

multiple converter modules coupled between V_IN and V_OUT to add associated voltage steps to V_IN, the converter modules; and

a control circuit configured to enable different combinations of the converter modules to add different combinations of voltage steps to V_IN.

11. The power transmission system of claim 10, including switches connected across outputs for each of the converter modules selectively activated by the control circuit.

12. The power transmission system of claim 11, including a hall effect sensor coupled in series between the switches and V_OUT.

13. The power transmission system of claim 10, including a bypass switch coupled across all of the outputs of the converter modules and selectively activated by the control circuit to reduce or prevent a voltage drop between V_IN and V_OUT.

14. The power transmission system of claim 13, wherein the bypass switch comprises a diode.

15. The power transmission system of claim 13, wherein the bypass switch comprises a metal-oxide semiconductor field effect transistor (MOSFET).

16. The power transmission system of claim 1, wherein the DC-DC converter is further configured to:

calculate a threshold current I_TH for the RRH;

determine a new voltage drop on the DC cable based on detected changes in I_TH;

apply different voltage levels to V_IN so V_OUT compensates for the new voltage drop.

17. The power transmission system of claim 1, wherein the DC-DC converter is further configured to:

select a target voltage for the input of RRH; and

apply the voltage levels to V_IN so V_OUT minus the voltage drop on the DC cable produces the target input voltage.

18. The power transmission system of claim 17, wherein the target voltage is substantially a maximum operating voltage for RRH.

19. The power transmission system of claim 1, wherein the DC-DC converter is further configured to:

monitor a threshold operating current (I_TH) for RRH;

increase the voltage levels applied to V_IN when I_TH increases; and

decrease the voltage levels applied to V_IN when I_TH decreases.

20. A computer program stored in a non-transitory media for controlling voltage at a remote radio head (RRH), the computer program comprising a set of instructions operable to:

identify a specific configuration of the RRH;

read an input voltage (V_IN) received from a DC power supply;

read an output voltage (V_OUT) generated from V_IN at a base of a DC cable;

read an output current (I_OUT) at the base of the DC cable;

receive a voltage measurement (V_RRH) taken at a top of the DC cable at an input of the RRH;

calculate a resistance of the DC cable (R_CABLE) based on V_RRH, V_OUT, and I_OUT;

calculate a voltage drop on the DC cable based on R_CABLE, I_OUT and the specific configuration of the RRH;

identify a target voltage level at the input of the RRH; and

adjust a voltage added to V_IN so V_OUT compensates for the voltage drop on the DC cable and produces the target voltage level at the input of the RRH, wherein V_OUT does not change during operation unless there is a reconfiguration of the RRH that changes power consumption of the RRH.

21. The computer program of claim 20, further comprising instructions operable to:

calculate a boost voltage (V_boost) to compensate for the voltage drop on the DC cable; and

configure converter modules to add V_boost to V_IN.

22. The computer program of claim 20, further comprising instructions operable to:

calculate a current operating threshold (I_TH) for RRH;

calculate a new resistance of the DC cable and a new voltage drop on DC cable based on a detected change in the I_TH; and

readjust the voltage added to V_IN so V_OUT compensates for the new voltage drop on the DC cable and maintains the target voltage level at the input of the RRH.

23. The computer program of claim 20, further comprising instructions operable to:

detect an outage of the DC power supply;

readjust the voltage added to V_IN based on the detected outage to compensate for a new lower value of V_IN provided by a backup battery bank.

24. The computer program of claim 20, comprising instructions operable to:

generate a voltage pulse on the DC cable to activate a voltage measurement device at the top of the DC cable to take the voltage measurement V_RRH; and

determine the V_RRH based on current pulses generated by the voltage measurement device over the DC cable in response to the voltage pulse.

25. The computer program of claim 20, comprising instructions operable to receive the voltage measurement V_RRH over a communication link from a voltage measurement device located at the top end of the DC cable.

26. A voltage monitoring device, comprising:

a hardware processor configured to;

measure a voltage (V_RRH) at a first end of a DC cable on a tower or on a rooftop where an RRH is located; and

transmit V_RRH to a voltage control system at a second end of the DC cable to calculate a voltage drop across the DC cable and generate voltage steps that produce an output voltage V_OUT at the second end of the DC cable that compensate for the voltage drop based on a specific configuration of the RRH, wherein V_OUT does not change during operation unless there is a reconfiguration of the RRH that changes power consumption of the RRH.

27. The voltage monitoring device of claim 26, further comprising a resistor and a transistor coupled to the DC cable, the processor activating the transistor to generate current pulses on the DC cable that indicate V_RRH.

28. The voltage monitoring device of claim 27, wherein the processor is further configured to:

monitor the DC cable for a voltage pulse from the voltage control system; and

generate the current pulses in response to detecting the voltage pulse.

29. The voltage monitoring device of claim 27, further comprising a relay coupled between the resistor and the DC cable, the processor opening the relay to isolate the transistor and the transistor from the DC cable.

30. The voltage monitoring device of claim 26, wherein the processor is further configured to:

monitor the V_RRH for different RRHs located on the tower or on the roof; and

transmit digital signals over a communication link to the voltage control system identifying the V_RRH for the different RRHs.

31. The voltage monitoring device of claim 26, further comprising:

an amplitude shift keying (ASK) modulator coupled to the hardware processor to generate an ASK signal based on a series of encoded bits generated by the hardware processor that identifies V_RRH; and

a transformer coupled between the DC cable and the ASK modulator configured to apply the ASK signal to a DC voltage on the DC cable.

32. A power transmission system, comprising:

a voltage measurement device located on a tower or rooftop for measuring a voltage (V_RRH) at a top end of a DC cable connected a remote radio head (RRH);

a voltage control system connected to a base end of the DC cable, the voltage control system configured to;

receive an input voltage (V_IN) from a DC power supply;

measure an output voltage (V_OUT) at a base end of the DC cable;

receive the measurement for V_RRH from the voltage measurement device;

calculate a voltage drop on the DC cable based on the measurement for V_RRH; and

a specific configuration of the RRH, and

add different voltage steps to V_IN so V_OUT compensates for the voltage drop on the DC cable, wherein V_OUT does not change during operation unless there is a reconfiguration of the RRH that changes power consumption of the RRH.

33. The power transmission system of claim 32, wherein the voltage control system includes a DC-DC converter including an input coupled to the DC power supply and an output coupled to the base end of the DC cable, wherein the DC-DC converter includes:

multiple converter modules coupled between the input and the output of the DC-DC converter to add the different voltage steps to V_IN; and

a control circuit configured to selectively activate the converter modules based on the voltage drop on the DC cable.

34. The power transmission system of claim 32, wherein the DC-DC converter includes a current sensor for detecting current pulses transmitted by the voltage measurement device as the measurement signal for V_RRH.

35. The power transmission system of claim 32, wherein the DC-DC converter includes a coupling transformer and an amplitude shift keying (ASK) demodulator for detecting ASK pulses transmitted by the voltage measurement device as the measurement signal for V_RRH.

36. The power transmission system of claim 32, wherein the DC-DC converter is further configured to:

monitor a current threshold (I_TH) for the RRH;

recalculate the voltage drop on the DC cable based on detected changes in the I_TH; and

readjust the voltage steps added to V_IN so V_OUT compensates for the recalculated voltage drop.