Rod Pump VFD Capacitor Storage for Regenerative Energy Reuse
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Solution Overview
Problem
Existing methods for managing regenerative energy in reciprocating pump systems, such as using dynamic braking resistors or AC regeneration, are inefficient and can lead to mechanical failures and environmental waste.
Innovation Solution
A variable-frequency drive system with a capacitor-based storage unit and control circuitry that stores and reuses regenerative energy without a dynamic braking resistor, using nickel oxide hydroxide high amperage capacitors and a control circuit to monitor and manage energy flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dynamic braking resistor is used to dissipate regenerative energy, then overvoltage of the DC bus is prevented, but the system experiences short life expectancy and environmental waste
Solution Approach 1:
The patent converts the harmful regenerative energy that needs to be dissipated into a beneficial resource by storing it in a capacitor bank. The capacitor captures the regenerative energy during downstroke operations and provides it during upstroke operations, transforming what was previously wasted energy into a useful asset that improves system efficiency and eliminates environmental waste.
Solution Approach 2:
Instead of discarding the regenerative energy through the braking resistor, the patent recovers and stores this energy in the capacitor bank. The control circuitry manages the energy flow to capture regenerative energy when the motor acts as a generator and reuse it when the motor needs power, thereby recovering energy that would otherwise be lost.
2Reliability
If a dynamic braking resistor is used to handle regenerative energy, then DC bus overvoltage is prevented, but energy is wasted as heat
Solution Approach 1:
The patent transforms the problematic regenerative energy into a beneficial stored resource. The capacitor bank captures the energy that would be wasted as heat in the braking resistor and makes it available for future use, converting energy loss into energy recovery and improving overall system efficiency.
Solution Approach 2:
The system recovers regenerative energy that would otherwise be discarded as heat. The control circuitry directs the regenerative energy to the capacitor bank for storage instead of allowing it to be dissipated through the braking resistor, enabling energy reuse during subsequent motor operations.
3Loss of energy
If AC regeneration is used to convert regenerative energy back to AC power, then energy capture is achieved, but large efficiency loss occurs from conversion
Solution Approach 1:
The patent replaces the complex AC-to-DC-to-AC conversion system with a simpler DC-to-DC storage approach. By keeping the energy in DC form throughout the storage and reuse process, the system eliminates the inefficient AC regeneration conversion step while still achieving energy capture and reuse, thereby significantly improving conversion efficiency.
4Loss of energy
If speed fluctuation is used to handle regenerative energy, then energy management is achieved, but inconsistent downhole performance and mechanical failures occur
Solution Approach 1:
The patent introduces a capacitor bank as an intermediary energy storage device between the motor and the load. This intermediary allows the motor to operate at consistent speeds while the capacitor absorbs or supplies energy as needed, preventing the speed fluctuations that would otherwise cause inconsistent downhole performance and mechanical failures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances operating efficiency and reliability by recycling regenerative energy, eliminating the need for dynamic braking resistors and reducing environmental impact.
Implementation Method 1
the electric motor (M) generates energy during the down-stroke operation of the reciprocating pump unit. When this happens, the electric motor (M) acts as a generator, in which mechanical energy from the electric motor (M) is converted into regenerative energy.
Implementation Method 2
A variable-frequency drive system with a capacitor-based storage unit and control circuitry that stores and reuses regenerative energy
Implementation Method 3
using nickel oxide hydroxide high amperage capacitors
Data Source
AI summary
A variable-frequency drive includes a rectifier, a filter, an inverter, a capacitor bank, and control circuitry. The rectifier converts AC power from a power source to DC power on a DC bus for filtering by the filter. The inverter converts the DC power to three-phase AC power for output to the electric motor. The capacitor bank has one or more capacitors connected to the DC bus. The capacitor bank can store regenerative power on the DC bus from the inverter and can supply the stored DC power to the DC bus for conversion to the three-phase AC power to drive the electric motor. The control circuitry pre-charges the capacitor bank from the AC power of the power source. The control circuitry monitors one or more parameters of the variable-frequency drive and detects one or more fault conditions associated with the one or more monitored parameters.