WO2018089781A1

WO2018089781A1 - Printed circuit board for the electrical system of a wave energy converter

Info

Publication number: WO2018089781A1
Application number: PCT/US2017/061087
Authority: WO
Inventors: Joseph Sarokhan; Michael KALANICK
Original assignee: Ocean Power Technologies, Inc.
Priority date: 2016-11-10
Filing date: 2017-11-10
Publication date: 2018-05-17

Abstract

The electrical system of a Wave Energy Converter is built into a unitary Printed Circuit Board, thereby vastly simplifying the assembly process, reducing cost, and improving reliability. The unitary Printed Circuit Board integrates power electronics that handles power distribution, with sensors and command circuitry that controls battery charging, battery management, and provides protective features.

Description

PRINTED CIRCUIT BOARD FOR THE ELECTRICAL SYSTEM OF A WAVE ENERGY CONVERTER

BACKGROUND

[0001] This disclosure relates to the electrical system of a wave energy converter (WEC).

[0002] The electrical system of a typical WEC includes an electric generator that converts wave energy into an AC voltage. The AC voltage is converted to a high DC voltage (e.g., 325 volts). The high DC voltage is, in turn, converted to one, or more, low DC voltages (e.g., 24 volts and 5 volts). Thus, several AC to DC or DC to DC converters are implemented in the electrical system of a typical WEC. In addition, the electrical system includes a large number of sensors-and-control circuits to sense and control the operation of the WEC. Consequently, the electrical system of a WEC includes several high-power, low-power, high-voltage and/or low-voltage circuits, amounting to hundreds of components that need to be interconnected via hundreds of connectors, cables, and wires.

[0003] While many conventional designs may use a number of small printed circuit boards (PCBs) for control and signal conditioning, most power generation/distribution components and sensors are usually mounted to electrical panels and manually wired together. These electrical panels can take weeks to build, test, and debug due to the large numbers of manual interconnections. This may be illustrated by reference to a highly simplified diagram of the electrical system of a typical WED shown in Figure 1. The electrical system includes a first panel 11 1, which may include circuitry for processing the output of an electric generator driven by the WEC, a second panel 113, which may include drive circuitry of DC to DC converters and power distribution, and a third panel 1 15, which may include circuitry for managing energy storage elements. The interconnections among the panels include numerous cables, wires, and connectors.

[0004] There is a high probability of assembly and wiring errors that can be expensive to identify and correct. The design of a more compact circuit layout and wiring arrangement is contra-indicated because, among other reasons, there are significant interference problems to be overcome. For example, large electrical noise signals and large electrical transients associated with the electrical generator and voltage conversion circuitry normally require that the high-voltage power generation and distribution circuits be located on a separate assembly (e.g., a separate panel) from noise sensitive sensors-and-control circuits.

[0005] Thus, there is a continuing need in the art for improving the manufacture and assembly of the electrical system of WEC, preferably so that the electrical system is compact, reliable and economical to manufacture.

BRIEF SUMMARY OF THE DISCLOSURE

[0006] An electrical system for a wave energy converter, comprises a unitary multi-layered printed circuit board that integrates power electronics that handles power generation and distribution, with sensors and command circuitry that controls battery charging. The power electronics may include a high DC voltage regulator module, and a DC to DC converter having a high-voltage input and a low-voltage output. The sensors and command circuitry may include a current sensor, and circuitry for determining a state of charge of a battery based on a signal generated by the current sensor. The sensors and command circuitry may also include circuitry for selectively activating or deactivating the DC to DC converter. The unitary multi-layered printed circuit board may be partitioned into a high-voltage/high-power section, a low-voltage/high-power section located adjacent to the high-voltage/high-power section, a high-voltage/low-power section located adjacent to the high voltage/high power section, and a sensors-and-control section located remotely from the a high-voltage/high-power section. The unitary multi-layered printed circuit board includes a plurality of layers consisting of conductive traces, each layer being separated from the next layer by a laminated non-conductive substrate traversed by vias. The electrical system may further comprise a generator for converting wave energy into AC voltage, and an AC to DC converter coupled to the generator, wherein the output of the AC to DC converter is connected to the unitary multi-layered printed circuit board. The electrical system may further comprise low voltage and high voltage batteries connected to the unitary multi-layered printed circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] For a more detailed description of the embodiments of the disclosure, reference will now be made to the accompanying drawings, wherein:

[0008] Figure 1 is a simplified block diagram of a prior art WEC electric system;

[0009] Figure 2 is a photograph of a populated PCB in accordance with one embodiment; [0010] Figure 3 is a simplified block diagram of the populated PCB pictured in Figure 2, illustrating the partitioning of the components populating the PCB;

[0011] Figure 4 is a cross-sectional view of the unpopulated PCB pictured in Figure 2, illustrating the multiple layers of the PCB;

[0012] Figure 5 illustrates the partitioning of some of the multiple layers shown in Figure 4;

[0013] Figure 6 is a simplified block diagram of power electronics and sensors and command circuitry with may be integrated onto the PCB pictured in Figure 2; and

[0014] Figure 7 is a simplified block diagram of a WEC electric system in accordance with one embodiment.

DETAILED DESCRIPTION

[0015] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.

[0016] All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. [0017] The disclosure describes electrical systems for a WEC that are implemented onto a unitary PCB. The problems of noises or interferences that may arise from the implementation onto a unitary PCB can be resolved by using a multi-layered PCB with the appropriate partitioning or positioning of circuitry along the outer surfaces of the multi-layered PCB. Also, the different layers of the PCB provide different planes for carrying different voltages and signals. The components of the electrical systems can be interconnected horizontally along the surface of any layer (e.g., with "copper traces") or vertically between the different layers (e.g., with "vias").

[0018] Consequently, in the electrical systems described herein, the control system and the main power distribution circuitry can be implemented onto a unitary multi-layered PCB. For example, the unitary multi-layered PCB may be used for the integration of battery charging functionality, battery management circuitry, and protective features into the same circuit board that handles power distribution. This implementation onto a unitary multi-layered PCB may result in a compact, highly reliable and economical electrical converter system which is much simpler to manufacture.

[0019] The electrical systems of a WEC may be characterized as including the following four types of circuitry: (1) sensors-and-control circuitry; (2) low-voltage/high-power circuitry; (3) a high-voltage/low-power circuitry; and (4) a high-voltage/high-power circuitry. In multi-layered PCBs in accordance with the disclosure, the sensors-and-control circuitry is grouped into a section of the multi-layered PCB that is located the most distantly from the section in which the high- voltage/high-power circuitry is grouped. The low-voltage/high-power circuitry and the high- voltage/low-power circuitry are grouped in sections that are generally positioned around the section grouping the sensors-and-control circuitry. Thus, the high-voltage/high-power circuitry, which is generating the largest noise signals, is the furthest from the sensors-and-control circuitry, which is the most sensitive to noise.

[0020] Further, in the multi-layered PCBs in accordance with a first embodiment of the disclosure, the copper traces conducting high currents may be disposed on the outer layers of the PCB, together with solder pads to mount (e.g., via soldering) the components of the electrical systems and connectors of the electrical system of the WEC. The copper traces conducting measurement signals and command signals may be disposed on the innermost layers of the PCB. The copper traces conducting high DC voltage are separated into two intermediate layers, one for conducting positive high DC voltage, and one for conducting negative high DC voltage. The two intermediate layers are located on either side of the innermost layers, between the innermost layers and the outer layers. The two intermediate layers may also include copper traces used for grounding, in which case, the copper traces used for grounding are compactly grouped in a section, and the copper traces for conducting high DC voltage surround the section having the grounding traces.

[0021] Alternatively, in multi-layered PCBs in accordance with a second embodiment of the disclosure, the solder pads to mount (e.g., via soldering) the components of the electrical systems and connectors of a WEC may be disposed on the outer layers of the PCB, which may also be considered to be multi-purpose. The copper traces conducting high DC voltage, and the copper traces conducting low DC voltage/high-power may be disposed on two of the innermost layers of the PCB. The innermost layers conducting high DC voltage may also include copper traces used for high-power grounding, in which case, the copper traces used for grounding are compactly grouped in a section, and the copper traces for conducting high DC voltage surround the section having the grounding traces. The copper traces conducting low-voltage measurement signals and command signals, and the copper traces for low-power grounding are separated into two intermediate layers. The two intermediate layers are located on either side of the innermost layers, between the innermost layers and the outer layers.

[0022] Referring to Figure 2, there is shown a photograph of the top layer of a PCB 10 containing the vast majority of the control, sensor, and power distribution circuitry forming the electrical system of a WEC.

[0023] Figure 3 is a highly simplified block diagram illustrating the partitioning of the PCB 10 into four general sections, that are relatively convex, compact and have a smooth and regular boundary. Various components (i.e., resistors, capacitors, transistors, connectors) of the electrical system of the WEC may be mechanically adhered to (e.g., soldered) to the top outer layer and the bottom outer layer of the PCB (i.e., layers 1 and 6 shown in Figure 4). The functions carried out by the components are constrained by the section they are mounted in.

[0024] The four sections include: (1) a sensors-and-control section 601; (2) a low-voltage/high- power section 602; (3) a high-voltage/low-power section 603; and (4) a high-voltage/high-power section 604. The sensors-and-control section 601 is located most distant from the high- voltage/high-power section 604. Consequently, the high-voltage/high-power section 604, which is generating the most disturbing noise signals, is the furthest from the most sensitive sensors-and- control section 601. The low- voltage/high-power section 602 and the high-voltage/low-power section 603 are generally positioned around the sensors-and-control section 601.

[0025] As shown in Figure 3, the electrical generator (G) and the drive circuit 612 which converts the AC voltage to raw DC voltage are located off the PCB 10. The raw DC voltage is applied to a regulator module 614 located in the high-voltage/high-power section 604. The output of the regulator module 614 is applied and charges a high-voltage battery 616. The output of regulator module 614 is also shown to be distributed via traces 618 and 619 to the high- voltage/low-power section 603 and via trace 620 to a DC/DC converter 622 located in the low- voltage/high-power section 602. The output of DC/DC converter 622 is applied via trace 624 to a low-voltage battery 626. The output of DC/DC converter 622 is also applied via traces 628 and 630 to the sensors-and-control section 601.

[0026] As noted above, components are only on the top and bottom outer layers of the entire PCB stack. Interconnections between those components and the other parts of the electrical system (see Figure 6) occur primarily with connectors mounted to the top and bottom surfaces (particularly in cases of high current).

[0027] All of the terminal blocks and power distribution blocks shown in Figure 1 have been replaced with copper trace ( e.g., 619, 630) connections on the PCB. Hundreds of connections and cables that would normally connect the processor and data acquisition system to the power electronics have also been eliminated and replaced with copper traces on the PCB.

[0028] Turning to Figure 4, the layers of the PCB are stacked above each other with an insulation laminated substrate 410, 412, 414, 516 and 418 between any two consecutive layers. These copper traces can be extended horizontally along a surface of a layer or vertically thru the layer to the underside (or top) of the layer or to another layer. Not shown in Figure 4 are vias interconnecting copper traces and/or solder pads vertically between the different layers.

[0029] In the exemplary embodiment shown in Figure 4, six conductive layers (e.g., including traces made of copper) are used; however, it should be understood that more, or less, layers may be employed. Each layer, designated as layer 1, layer 2, layer 3, layer 4, layer 5, and layer 6 is insulated from next layer with a laminated non-conductive substrate, such as fiberglass. [0030] Layer 1, which may also be designated as the top outer layer, contains (i) solder pads which may be plated or coated for soldering components or connectors to wires, and (ii) heavy copper traces for conduction of high currents. These copper traces are connected, for example, to the low-voltage/high-power circuitry. This layer permits the mounting of components.

[0031] Layer 2, which may also be designated as the top intermediate layer, is partitioned into two sections, as illustrated in Figure 5. The first section 421 is generally extending from the left edge of the board toward the right over 1/3 of the board width, and from the top edge of the board toward the bottom over 1/9 of the board height. The first section 421 contains (i) copper traces for conduction of negative high-voltage/high-power (i.e., the HVDC Negative net). The second section 423 is occupying the remaining portion of the surface. These copper traces may be connected to the power generation or distribution circuitry. The second section 423 contains (ii) the copper traces used for grounding sensors-and-control circuitry (i.e., the sensor/control ground net).

[0032] Layer 3, which may also be designated as the top core layer, contains the copper traces for transmitting control and/or measurements signals. These copper traces conduct low currents at both high and/or low DC voltages. These copper traces are connected to the sensors-and-control circuitry.

[0033] Layer 4, which may also be designated as the bottom core layer, also contains the copper traces for transmitting control and/or measurements signals, similarly to layer 3.

[0034] Layer 5, which may also be designated as the bottom intermediate layer is partitioned into two sections, as illustrated in Figure 5. The first section 425 is generally extending from the left edge of the board toward the right over 1/3 of the board width, and from the top edge of the board toward the bottom over 1/9 of the board height. The first section 425 contains (i) copper traces for conduction of positive high-voltage/high-power (i.e., the HVDC Positive net). The second section 427 is occupying the remaining portion of the surface. The second section 427 contains (ii) the copper traces used for grounding power generation or distribution circuitry (i.e., the power ground net). These copper traces may carry high DC currents, at least locally.

[0035] Layer 6, which may also be designated as the bottom outer layer, also contains (i) solder pads which may be plated or coated for soldering components or connectors to wires, and (ii) heavy copper traces for conduction of high currents, similarly to layer 1. [0036] The traces in any of the six layers are constrained to remain in one of the four section shown in Figure 4, with a limited number of traces (e.g., 619, 630) joining components in two different sections.

[0037] Turning to Figure 6, there is shown a simplified block diagram of power electronics which may be integrated with sensors and command circuitry onto the unitary multi-layered PCB 10.

[0038] The power electronics includes a regulator 503 producing a stabilized high voltage DC output. The high voltage DC output (e.g., 325 volts) is supplied to the high voltage bus line 505, and its return is ground line 507. A DC to DC converter 509 that may be part of a battery charger module is shown connected to the output the regulator 503 (i.e., between the high voltage bus line 505 and the ground line 507). The DC to DC converter 509 is designed to be a controllable converter which can be switched on or switched off by a control system 521. The output of DC to DC converter 509 produces the low DC voltage (e.g., 24 volts) which is applied between the low voltage bus line 515 and the ground line 517.

[0039] The sensors and command circuitry includes: (i) a current sensor CS1 that measures the current (i.e., curl) supplied from the regulator 503 to the rest of the PCB, (ii) current sensors CS2 and CS3 that measure the current flowing into and out of high voltage batteries, (iii) a current sensor CS4 that senses a current drawn by high voltage DC, (iv) current sensors CS5 and CS6 that measure the current flowing into and out of low voltage batteries, and (v) a current sensor CS7 that measures the current drawn by the low voltage DC loads. The sensors and command circuitry also includes the control system 521 which applies an on-off command signal (coml) to the DC to DC converter 509. Signals curl-cur7 generated by the corresponding current sensors CS1-CS7 and signal 520 generated by the low voltage DC loads 519 are shown to be fed to the control system 521. These signals are applied to circuitry of the control system 521 (e.g., integrator-operational amplifier, adder—operational amplifier) to determine the state of charge of the low voltage batteries and high voltage batteries, among other parameters used for battery charging and management. The control system 521 may include signal processor(s) and programmed circuitry for determining when the state of charge in the low voltage batteries is below a predetermined threshold, for example, 50%. When the state of charge in the low voltage batteries is determined to be below the predetermined threshold, the control system 521 may generate a command signal to the DC to DC converter 509, turning it fully on. The control system 521 may also include signal processor(s) and programmed circuitry for determining when the state of charge in the low voltage batteries is above another, higher predetermined threshold, for example, 90%. When the state of charge in the low voltage batteries is determined to be above the other, higher predetermined threshold, the control system 521 may generate a command signal to the DC to DC converter 509, turning it fully off. Accordingly, the control system 521 may be programmed to recharge the low voltage batteries after detecting that any of the low voltage batteries is less than 50% charged, and until all batteries are at least 90% charged.

[0040] Rather than running a high power DC to DC converter constantly at low efficiency, the DC to DC converter 509 is only turned on when the state of charge of the voltage batteries gets down to 50% of the full capacity, and, when turned on, the DC to DC converter 509 runs at high efficiency. To use the DC to DC converter 509 close to its maximum efficiency, the current generated by the DC to DC converter 509 is stored in the voltage batteries, which is acting as a buffering "current tank." As such, the DC to DC converter 509 acts as a "pump" which refill the "current tank." Thus, in accordance with an aspect of the disclosure, the DC to DC converter 509 is used on demand (i.e., not running constantly).

[0041] In Figure 6, the state of charge of the batteries is calculated from measurements of current flows supplied to and drained from the batteries or other components. A state of charge may then be estimated by continuously summing the instantaneous current flows over time. For example, the current flowing into a battery is a positive contribution that charges the battery, while current flowing from the battery is a negative contribution that discharges the battery. Accordingly, integration circuitry or an algorithm programmed in a processor in the control system 521 may be used to continually sum the measurements signals generated by the current sensors CS1-CS7, and thus determine the state of charge of the batteries. Other means may be used for sensing or tracking the state of charge. For example, an external sensor attached to the batteries may be used to measure the state of charge.

[0042] Turning to Figure 7, a WEC electric system in accordance with this disclosure includes the electrical generator (G) and the drive circuit 612 which converts the AC voltage to raw DC voltage, the populated multi -layered PCB 10, and payloads, batteries, and sensors connected to the populated multi -layered PCB 10. The battery charging functionality, battery management circuitry, and protective features are integrated into the same PCB 10 that handles power distribution. Because it is based on a unitary PCB 10, the WEC electrical system requires minimal labor to assemble and can be built by automatic assembly machines. The simplified assembly process and reduction in connection count also vastly reduces the probability of wiring and assembly errors. The reduction in wiring and connection count also improves overall reliability.

[0043] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and description. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the claims to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the claims.

Claims

What is claimed is:

1. An electrical system for a wave energy converter, comprising:

a unitary multi-layered printed circuit board that integrates power electronics that handles power generation and distribution, with sensors and command circuitry that controls battery charging.

2. The electrical system of claim 1, wherein the power electronics include a high DC voltage regulator module, and a DC to DC converter having a high-voltage input and a low-voltage output.

3. The electrical system of claim 2, wherein the sensors and command circuitry includes a current sensor, and circuitry for determining a state of charge of a battery based on a signal generated by the current sensor.

4. The electrical system of claim 3, wherein the sensors and command circuitry includes circuitry for selectively activating or deactivating the DC to DC converter.

5. The electrical system of claim 1, 2, 3 or 4, wherein the unitary multi -layered printed circuit board is partitioned into a high-voltage/high-power section, a low-voltage/high-power section located adjacent to the high-voltage/high-power section, a high-voltage/low-power section located adjacent to the high voltage/high power section, and a sensors-and-control section located remotely from the a high-voltage/high-power section.

6. The electrical system of claim 5, wherein the unitary multi-layered printed circuit board includes a plurality of layers consisting of conductive traces, each layer being separated from the next layer by a laminated non-conductive substrate traversed by vias, wherein the innermost core layers have only traces for conducting both high-voltage and low-voltage signals used for measurement and control.

7. The electrical system of claim 6, wherein intermediate layers located between the innermost core layers and outer layers have only traces for conducting high-voltage/high-power or traces for conducting grounding.

8. The electrical system of claim 7, wherein the traces for conducting grounding are located in a compact section, and wherein the traces for conducting high-voltage/high-power are located around the compact section.

9. The electrical system of claim 8, wherein the outer layers have traces for conducting high current and solder pads.

10. The electrical system of claim 5, wherein the unitary multi -layered printed circuit board includes a plurality of layers consisting of conductive traces, each layer being separated from the next layer by a laminated non-conductive substrate, wherein the innermost core layers have only traces for conducting both high-voltage/high-power grounding or high-power.

11. The electrical system of claim 10, wherein the traces for conducting high-power grounding are located in a compact section, and wherein the traces for conducting high-voltage are located around the compact section.

12. The electrical system of claim 10 or 11, wherein intermediate layers located between the innermost core layers and outer layers have only traces for conducting low-voltage or low- voltage grounding.

13. The electrical system of any of claims 1 to 12, further comprising a generator for converting wave energy into AC voltage, and an AC to DC converter coupled to the generator, wherein the output of the AC to DC converter is connected to the unitary multi-layered printed circuit board.

14. The electrical system of any of claim 13, further comprising low voltage and high voltage batteries connected to the unitary multi-layered printed circuit board.