Hydraulic apparatus

Abstract

A closed-loop hydraulic apparatus 200 for converting wave energy comprises a pump 201 for pumping a fluid through the apparatus 200 . The pump 201 includes a body 202 defining a chamber 203 , and a piston 207 that partitions the chamber 203 into a working side 208 and a blind side 209 . A buoyant actuator is connected to the piston 207 . An inlet 64 is connected to the working side 208 of the chamber 203 so that the fluid is able to flow from the inlet 64 and into the working side 208 of the chamber 203 . An outlet 63 is connected to the working side 208 of the chamber 203 so that the fluid is able to flow from the working side 208 of the chamber 203 to the outlet 63 . A hydraulic controller 102 is operable to control the pump 201 by controlling the pressure of the fluid at the inlet 64 and the outlet 63 so as to optimise the output of the pump 201 in response to tidal variations and/or sea state. The pressure of the fluid at the inlet 64 and the outlet 63 is controlled in accordance with a control algorithm.

1 . A closed-loop hydraulic apparatus for converting wave energy, the apparatus comprising: a pump for pumping a fluid through the apparatus, the pump including a body defining a chamber, and a piston that partitions the chamber into a working side and a blind side; a buoyant actuator connected to the piston; an inlet connected to the working side of the chamber so that the fluid is able to flow from the inlet and into the working side of the chamber; an outlet connected to the working side of the chamber so that the fluid is able to flow from the working side of the chamber to the outlet; and a hydraulic controller operable to control the pump by controlling the pressure of the fluid at the inlet and the outlet so as to optimise the output of the pump in response to tidal variations and/or sea state, the pressure of the fluid at the inlet and the outlet being controlled in accordance with a control algorithm, wherein the control algorithm is drawn from an ensemble of algorithms which are generated according to an optimal filter approach, and wherein an optimal filter and the control algorithms are generated by the steps of:
 (i) determining a power matrix;   (ii) determining the most robust spectral model for sea states applicable to a physical location of the apparatus;   (iii) convolving a sea state spectral density with the power matrix to produce a resultant transfer function;   (iv) performing a multi-parameter optimisation of an energy function obtained by integrating the transfer function over time;   (v) defining operating points and stable operating regions within a vector space of the energy function to generate templates;   (vi) applying a control system transfer function to state variables of the apparatus to generate the control algorithm;   (vii) running a simulation of the control algorithm to verify the accuracy and stability of the algorithm and a set point template; and   (viii) repeating steps (i) to (vii) with different sea states as needed to populate the space of required control algorithms.   
     
     
         2 . The closed-loop hydraulic apparatus of  claim 1 , wherein the hydraulic controller includes: an inlet hydraulic accumulator; an input hydraulic control valve connected to the inlet and to the inlet hydraulic accumulator; an outlet hydraulic accumulator; an output hydraulic control valve connected to the outlet and to the outlet hydraulic accumulator; a sequence valve connected to the inlet and to the outlet; a first outlet pressure transducer connected to the outlet; a flow meter connected to the outlet; a proportional throttle connected to the flow meter; and a second outlet pressure transducer connected to the proportional throttle. 
     
     
         3 . The closed-loop hydraulic apparatus of  claim 1 , wherein the hydraulic controller includes: a working side hydraulic accumulator connected to the working side of the chamber; an outlet hydraulic accumulator connected to the outlet; an inlet hydraulic accumulator connected to the inlet; an outlet valve connected to the outlet; an inlet valve connected to the inlet; a pressure relief valve connected to the outlet and to the inlet valve; an intermediate hydraulic accumulator connected to the inlet valve; a control system; and a plurality of sensors, wherein the control system is operable to control the outlet valve and the inlet valve in response to outputs of the sensors. 
     
     
         4 . The closed-loop hydraulic apparatus of  claim 1 , wherein the hydraulic controller includes: a working side hydraulic accumulator connected to the working side of the chamber; an outlet hydraulic accumulator connected to the outlet; an inlet hydraulic accumulator connected to the inlet; a pressure relief valve connected to the outlet and to the inlet; an outlet valve connected to the outlet; an inlet valve connected to the inlet; and an intermediate hydraulic accumulator connected to the inlet valve. 
     
     
         5 . The closed-loop hydraulic apparatus of  claim 4 , wherein the hydraulic controller also includes another pressure relief valve connected to the outlet and to the inlet. 
     
     
         6 . The closed-loop hydraulic apparatus of  claim 4 , wherein the hydraulic controller also includes: a control system; and a plurality of sensors, wherein the control system is operable to control the outlet valve, inlet valve, and the pressure relief valve in response to outputs of the sensors. 
     
     
         7 . The closed-loop hydraulic apparatus of  claim 6 , wherein the sensors include pressure, temperature, and flow sensors. 
     
     
         8 . The closed-loop hydraulic apparatus of  claim 4 , wherein a gas charge in lines of the working side hydraulic accumulator, outlet hydraulic accumulator, inlet hydraulic accumulator, and the intermediate hydraulic accumulator are able to be varied in accordance with the control algorithm. 
     
     
         9 . The closed-loop hydraulic apparatus of  claim 4 , wherein the outlet valve is a spear valve for a Pelton wheel. 
     
     
         10 . The closed-loop hydraulic apparatus of  claim 4 , wherein the apparatus further comprises: a plurality of pumps for pumping the fluid through the apparatus; a plurality of buoyant actuators connected to the pistons of the pumps; a plurality of inlets connected to the working sides of the pump chambers; and a plurality of outlets connected to the working sides of the pump chambers, and the hydraulic controller includes a plurality of working side hydraulic accumulators connected to the working sides of the pump chambers. 
     
     
         11 . The closed-loop hydraulic apparatus of  claim 10 , wherein the pumps are arranged in an array that is no more than three rows deep. 
     
     
         12 . The closed-loop hydraulic apparatus of  claim 1 , wherein the pumps are identical pumps. 
     
     
         13 . The closed-loop hydraulic apparatus of  claim 1 , wherein the control algorithm is tuned to provide the maximum integrated energy. 
     
     
         14 . The closed-loop hydraulic apparatus of  claim 1 , wherein step (i) is also repeated as part of step (viii) if the ensemble or space of control algorithms includes variations to the state of the machine/apparatus. 
     
     
         15 . The closed-loop hydraulic apparatus of  claim 1 , wherein the generation of the control algorithms is heuristic. 
     
     
         16 . The closed-loop hydraulic apparatus of  claim 1 , wherein optimisation is achieved by:
 (i) determining the power matrix;   (ii) developing and optimising the control system transfer function using the power matrix and a wave model; and   (iii) optimising the transfer function for the particular physical site using a robust physical spectral model for the physical site.   
     
     
         17 . A method for generating an optimal filter and an ensemble of control algorithms for a closed-loop hydraulic apparatus for converting wave energy, the method comprising the steps of:
 (i) determining a power matrix;   (ii) determining the most robust spectral model for sea states applicable to a physical location of the apparatus;   (iii) convolving a sea state spectral density with the power matrix to produce a resultant transfer function;   (iv) performing a multi-parameter optimisation of an energy function obtained by integrating the transfer function over time;   (v) defining operating points and stable operating regions within a vector space of the energy function to generate templates;   (vi) applying a control system transfer function to state variables of the apparatus to generate the control algorithm;   (vii) running a simulation of the control algorithm to verify the accuracy and stability of the algorithm and a set point template; and   (viii) repeating steps (i) to (vii) with different sea states as needed to populate the space of required control algorithms.   
     
     
         18 . The method of  claim 17 , wherein step (i) is also repeated as part of step (viii) if the ensemble or space of control algorithms includes variations to the state of the machine/apparatus. 
     
     
         19 . The method of  claim 17 , wherein the generation of the control algorithms is heuristic. 
     
     
         20 . The method of  claim 17 , wherein optimisation is achieved by:
 (i) determining the power matrix;   (ii) developing and optimising the control system transfer function using the power matrix and a wave model; and   (iii) optimising the transfer function for the particular physical site using a robust physical spectral model for the physical site.   
     
     
         21 . The method of  claim 17 , wherein the closed-loop hydraulic apparatus for converting wave energy comprises the hydraulic apparatus. 
     
     
         22 .- 23 . (canceled)