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Title:
EFFECTIVE COOLING OF ELECTRIC POWER CONVERTER
Document Type and Number:
WIPO Patent Application WO/2022/063378
Kind Code:
A1
Abstract:
An electric power converter system with an electric power converter, e.g. an AC-DC converter, a DC-AC converter or both. The electric power converter is air cooled by a cooling system having a fluid flow system arranged to force air or liquid through a primary flow path of a heat exchanger. An internal air flow with a fan serves to force air in a loop through a secondary flow path of the heat exchanger and the electric power converter to cool the electric power converter. A controllable bypass inlet opening mechanism provides a controllable opening to allow an inlet of ambient air into the internal air flow, and a control system receives at least one input parameter and being arranged to control the controllable bypass inlet opening mechanism accordingly. A bypass outlet opening, such as having a controllable bypass outlet opening mechanism, is arranged to provide an opening to allow an outlet of air from the internal air flow. The control system is preferably arranged to control the controllable bypass inlet opening mechanism accordingly to at least a temperature sensor sensing a temperature in the internal air flow at a position upstream of the electric power converter. Further, the controllable bypass inlet opening mechanism may be controlled also in response to a sensed humidity in the internal air flow, and a measure of electric power generated by the electric generator.

Inventors:
ANDREASEN MARCIN BLAZNIAK (DK)
PEDERSEN KRISTIAN BONDERUP (DK)
OLESEN ANDERS CHRISTIAN (DK)
Application Number:
PCT/DK2021/050298
Publication Date:
March 31, 2022
Filing Date:
September 24, 2021
Export Citation:
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Assignee:
VESTAS WIND SYS AS (DK)
International Classes:
F03D80/60; H02M1/32; H05K7/20
Domestic Patent References:
WO2019114909A12019-06-20
WO2017114526A12017-07-06
Foreign References:
CN105927482A2016-09-07
CN206555080U2017-10-13
Download PDF:
Claims:
CLAIMS

1. An electric power converter system comprising,

- an electric power converter (P_CNV) arranged to convert the electric power output from a power source into a second electric power output,

- a cooling system arranged to provide air for cooling the electric power converter (P_CNV), wherein the cooling system comprises

- a fluid flow system (II, 01, Fl) arranged to force a fluid through a primary flow path of a heat exchanger (HA),

- an internal air flow (I_L) comprising a fan (F2) arranged to force air in a loop through a secondary flow path of the heat exchanger (HA) and the electric power converter (P_CNV),

- a controllable bypass inlet opening mechanism (BP_I, BI_M) arranged to provide a controllable opening to allow an inlet of ambient air into the internal air flow (I_L),

- a bypass outlet opening (BP_O, BO_M) arranged to provide an opening to allow an outlet of air from the internal air flow (I_L), and

- a control system (CLS) arranged to receive at least one input parameter (T_I, RH_I, P, TL) and to control the controllable bypass inlet opening mechanism (BI_M) to provide an opening accordingly.

2. The electric power converter system according to claim 1, wherein the controllable bypass inlet opening mechanism is arranged to vary an area of said controllable opening in at least one step between a closed state and fully open state.

3. The electric power converter system according to claim 2, wherein the controllable bypass inlet opening mechanism is arranged to vary an area of said controllable opening in a plurality of steps between the closed state and the fully open state.

4. The electric power converter system according to any of the preceding claims, wherein the control system comprises a processor arranged to execute a control algorithm, wherein the control algorithm is arranged to generate an output for controlling the controllable bypass inlet opening mechanism to provide an area of said opening in response to the at least one parameter.

5. The electric power converter system according to claim 4, wherein the control algorithm is arranged to generate the output for controlling the controllable bypass inlet opening mechanism in response to at least a second input parameter.

6. The electric power converter system according to any of the preceding claims, comprising at least one sensor arranged to provide said at least one input parameter.

7. The electric power converter system according to claim 6, comprising a temperature sensor arranged to sense a temperature (T_I) in the internal air flow at a position upstream of the electric power converter.

8. The electric power converter system according to any of claims 4-7, wherein the control algorithm is arranged to generate the output for controlling the controllable bypass inlet opening mechanism to provide an area of said opening in response to at least one of: a measure of humidity in the internal air flow, and a measure of electric power generated by the electric generator.

9. The electric power converter system according to any of the preceding claims, comprising an external duct system comprising a fan arranged to force ambient air from an inlet, through the primary flow path of the heat exchanger, and to an outlet to ambient air, and wherein the controllable bypass inlet opening mechanism is arranged to provide a controllable opening between the internal air flow and the external duct system upstream of the heat exchanger. 14

10. The electric power converter system according to any of the preceding claims, wherein the internal air flow is formed inside a cabinet, wherein the fluid flow system is arranged to force a liquid through the primary flow path of a heat exchanger, and wherein the controllable bypass inlet opening mechanism provides a controllable opening to allow an inlet of ambient air into the cabinet.

11. The electric power converter system according to any of the preceding claims, comprising a controllable bypass outlet opening mechanism arranged to provide a controllable opening to allow an outlet of air from the internal air flow, wherein the control system is arranged to control the controllable bypass outlet opening mechanism to provide said opening to allow outlet of air from the internal air flow along with controlling the controllable bypass inlet opening mechanism to provide said opening to allow an inlet of ambient air into the internal air flow.

12. The electric power converter system according to any of the preceding claims, wherein the control system is arranged to control the controllable bypass inlet opening mechanism so as to provide ambient air into the internal air flow for lowering air temperature in the internal air flow while keeping a relative humidity in the internal air flow within a predetermined threshold.

13. The electric power converter system according to any of the preceding claims, wherein the controllable opening to allow an inlet of ambient air is arranged in the internal air flow upstream of the fan, and wherein the bypass outlet opening is arranged in the internal air flow between the electric power converter and an inlet of the secondary flow path of the heat exchanger.

14. A wind turbine with an electric power converter system according to any of the preceding claims, wherein the electric power converter and the internal air flow is arranged inside a nacelle (NC) of the wind turbine.

15. A method for cooling an electric power converter arranged to convert a first electric power output from a power source to a second electric power output, the method comprising

- providing (P_HE) a heat exchanger with a first and a secondary flow path, 15

- forcing (F_PP) a fluid through the primary flow path of the heat exchanger, - forcing (F_A_SP) air in a loop through a secondary flow path of the heat exchanger and the electric power converter,

- providing (P_BM) a controllable bypass inlet opening mechanism, and - controlling (C_BM) the controllable bypass inlet opening mechanism to allow ambient air to enter the loop through the secondary flow path of the heat exchanger in response to at least one input parameter.

Description:
EFFECTIVE COOLING OF ELECTRIC POWER CONVERTER

FIELD OF THE INVENTION

The present invention relates to the field of electric power technology, more specifically to the field of electric power converter technology for handling hybrid power plant. More specifically, the invention relates to a modular power converter system for a hybrid power plant, e.g. including connectivity to a wind turbine generator, a photovoltaic power source, an energy storage, and the electric grid.

BACKGROUND

Electric conversion system for hybrid power plants are complicated and typically require a number of separate components at separate locations to handle the different electric demands of electric power sources (e.g. wind turbine and photovoltaic cells, electric storage (e.g. battery), and load (e.g. the electric grid).

Further, e.g. increasing electric power generation of an existing wind turbine installation by means of adding photovoltaic panels and/or battery storage etc. often requires a complicated and costly modification of the power electric installation. Even further, after such modification, maintenance service can be demanding, since such add-on modifications cause the power electric configuration to be complex and often requires addition of a number of auxiliary technical components, e.g. cooling.

SUMMARY

Thus, according to the above description, it is an object of the present invention to provide an electric conversion system prepared for a hybrid power plant installation, and which is preferably prepared for scaling of electric power rating with a minimum of installation changes.

In a first aspect, the invention provides an electric power converter system comprising, - an electric power converter (P_CNV) arranged to convert the electric power output from a power source into a second electric power output,

- a cooling system arranged to provide air for cooling the electric power converter, wherein the cooling system comprises

- a fluid flow system arranged to force a fluid, such as ambient air or a liquid, through a primary flow path of a heat exchanger,

- an internal air flow comprising a fan arranged to force air in a loop through a secondary flow path of the heat exchanger and the electric power converter,

- a controllable bypass inlet opening mechanism arranged to provide a controllable opening to allow an inlet of ambient air into the internal air flow,

- a bypass outlet opening arranged to provide an opening to allow an outlet of air from the internal air flow, and

- a control system arranged to receive at least one input parameter and to control the controllable bypass inlet opening mechanism to provide an opening accordingly.

Such system is advantageous, since it allows a cooling system (fans, heat exchanger etc.) with a limited cooling capacity to be used and still provide a high electric power capacity of the converter system. By controlling a bypass to allow ambient air to cool the electric converter, an increase cooling can be obtained, thus allowing a higher electric power capacity of the converter with a cooling system having a given cooling capacity. In preferred embodiments, the bypass inlet is controlled in response to sensor inputs, e.g. sensor inputs indicating internal air flow temperature near the converter, and internal relative humidity. This allows a controlled use of the ambient air bypass to increase cooling, but avoiding problems with too humid air reaching the converter components.

In the following, preferred embodiments and features will be described.

In preferred embodiments, the controllable bypass inlet opening mechanism is arranged to vary an area of said controllable opening in at least one step, e.g. 1- 10 steps, between a closed state and fully open state. Especially, the controllable bypass inlet opening mechanism is arranged to vary an area of said controllable opening in a plurality of steps between the closed state and the fully open state. Alternatively, the bypass inlet opening is controllable only between a closed and an open state.

Preferably, the control system comprises a processor arranged to execute a control algorithm, wherein the control algorithm is arranged to generate an output for controlling the controllable bypass inlet opening mechanism to provide an area of said opening in response to the at least one parameter. Especially, the control algorithm is arranged to generate the output for controlling the controllable bypass inlet opening mechanism in response to two, three, four or even more input parameters, e.g. input parameters provided by one or more sensors. Specifically, an input parameter may be provided by a temperature sensor arranged to sense a temperature in the internal air flow at a position upstream of the electric power converter. The control algorithm may be arranged to generate the output for controlling the controllable bypass inlet opening mechanism to provide an area of said opening in response to at least one of: a measure of humidity in the internal air flow, and a measure of electric power generated by the electric generator.

In some embodiments, an external duct system has a fan arranged to force ambient air from an inlet, through the primary flow path of the heat exchanger, and to an outlet to ambient air, and wherein the controllable bypass inlet opening mechanism is arranged to provide a controllable opening between the internal air flow and the external duct system upstream of the heat exchanger.

In some embodiments, the internal air flow is formed inside a cabinet, wherein the fluid flow system is arranged to force a liquid through the primary flow path of a heat exchanger, and wherein the controllable bypass inlet opening mechanism provides a controllable opening to allow an inlet of ambient air into the cabinet, such as into a main base frame of the cabinet.

Some embodiments comprise a controllable bypass outlet opening mechanism arranged to provide a controllable opening to allow an outlet of air from the internal air flow, wherein the control system is arranged to control the controllable bypass outlet opening mechanism to provide said opening to allow outlet of air from the internal air flow along with controlling the controllable bypass inlet opening mechanism to provide said opening to allow an inlet of ambient air into the internal air flow. Alternatively, the bypass outlet opening is self-adjusting, e.g. by means of a spring mechanism adjusted to at least partially open the bypass outlet opening by means of a valve or a louver or the like, when a predetermined pressure inside the internal air flow is reached.

Preferably, the control system is arranged to control the controllable bypass inlet opening mechanism so as to provide ambient air into the internal air flow for lowering air temperature in the internal air flow while keeping a relative humidity in the internal air flow within a predetermined threshold. The relative humidity can be monitored by a sensor, or a measure of the relative humidity can be calculated or estimated by input from one or more temperature sensors, e.g. by means of an internal temperature sensor and an ambient air temperature sensor.

Specifically, the controllable opening to allow an inlet of ambient air may be arranged in the internal air flow upstream of the fan, and wherein the bypass outlet opening is arranged in the internal air flow between the electric power converter and an inlet of the secondary flow path of the heat exchanger.

In preferred embodiments, the electric power converter and the internal air flow is arranged inside a nacelle of the wind turbine, e.g. inside a cabinet arranged inside the nacelle of the wind turbine.

The electric converter system may be formed by a plurality of electric power converter modules arranged in racks inside a cabinet.

The total electric power capacity of the electric converter systems may be at least 1 MW, such as 1-12 MW or 10-20 MW.

The controller system may be implemented as a computer or processor system with a processor executing a control algorithm, such as known in the art. Further, an electric output power of the electric power converter may be sensed by a power sensor, such as known in the art. The controllable bypass inlet opening mechanism may be implemented by a valve or louver or door system operated by an actuator, e.g. an electrically controlled actuator. E.g. the actuator may comprise an electric motor, a linear actuator or the like. It is to be understood that the maximum opening area should be designed to match the dimensions of the internal air flow system and/or other parameters.

The electric power converter may in principle be any kind of known electric power converter being arranged for air cooling or being arranged for liquid cooling by a liquid cooler which in turn is arranged for being air cooled.

In a second aspect, the invention provides a method for cooling an electric power converter arranged to converter a first electric power output from a power source to a second electric power output, the method comprising

- providing a heat exchanger with a first and a secondary flow path,

- forcing a fluid through the primary flow path of the heat exchanger,

- forcing air in a loop through a secondary flow path of the heat exchanger and the electric power converter,

- providing a controllable bypass inlet opening mechanism, and

- controlling the controllable bypass inlet opening mechanism to allow ambient air to enter the loop through the secondary flow path of the heat exchanger in response to at least one input parameter.

In a third aspect, the invention provides a computer program comprising a code which, when executed on a processor, such as in a control system of the wind turbine system of the first aspect, performs the method according to the second aspect.

It is to be understood that the same advantages and preferred embodiments and features apply for the second and third aspects, as described for the first aspect, and the aspects may be mixed in any way. BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described in more detail with regard to the accompanying figures of which

FIG. 1 illustrates a wind turbine system embodiment,

FIG. 2 illustrates a block diagram of an electric power converter cooling system according to the prior art,

FIG. 3 illustrates an embodiment with an air to air heat exchanger,

FIG. 4 illustrates an embodiment with a liquid to air heat exchanger,

FIG. 5 illustrates a power versus temperature graph indicating the function of the bypass inlet to maintain a temperature below a predetermined limit temperature, FIG. 6 illustrates elements of a control system embodiments, and

FIG. 7 illustrates steps of a method embodiment.

The figures illustrate specific ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a wind turbine with typically two or three rotor blades BL drives an electric generator located inside the nacelle NC on top of a tower TW. Such wind turbine may generate an electric power of at least 1 MW, such as 2-10 MW, or more. Here, the generator is connected to an electric power converter system housed inside a cabinet inside the nacelle NC. A cooling system serves to cool the converter system inside the cabinet, preferably by forcing ambient air through a heat exchanger with a controllable ambient air bypass inlet to allow ambient air to enter in a cooling air flow forced to cool the electric power converter, as will be further described in the following.

FIG. 2 shows a sketch of a prior art electric power converter cooling system with an electric power converter P_CNV, such as an AC-DC converter, a DC-AC converter or both, arranged in a cabinet CB for being cooled by air from a cooling system. The cooling system has a duct system which leads ambient air from an air inlet II via a primary flow path of the air to air heat exchanger HA, driven by a fan Fl, and via the heat exchanger HA primary flow path outlet to an outlet 01 back into ambient air. An internal air flow loop I_L is driven by a fan F2 which forces air to pass through a secondary flow path of the heat exchanger HA and to pass by the electric power converter P_CNV for cooling the electric power converter P_CNV. The large arrows indicate air flow.

FIG. 3 illustrates a sketch of an embodiment of the invention with a number of similarities with the prior art sketch shown in FIG. 2. However, a controllable bypass inlet opening BP_I is arranged to allow ambient air to pass into the internal air flow loop I_L, when controlled to be open. To equalize air flow in the internal air flow loop I_L, a controllable bypass outlet opening BP_O is provided to allow outlet of air from the internal air flow loop I_L back to the ambient air flow duct. As shown, the bypass inlet opening BP_I is arranged to allow ambient air to enter the internal air flow loop I_L in a base frame manifold BFM of the cabinet CB.

A control system (not shown) receives at least one input parameter and controls a controllable mechanism which opens the controllable bypass inlet opening BP_I to provide an opening accordingly. Especially, a temperature inside the internal air flow loop I_L can be used as input for controlling opening of the bypass inlet BP_O, e.g. supplemented by additional sensor inputs regarding relative humidity inside the internal flow loop I_L and further an input indicative of the electric power handled by the electric power converter P_CNV and thus the load of the electric power converter P_CNV. The bypass inlet opening allow ambient air with a relative low temperature to enter the internal air flow loop I_L, thus assisting in cooling the electric power converter P_CNV. In this way, a heat exchanger with a limited capacity can be assisted to provide additional cooling. By a suitable design of a control algorithm using one or more sensor inputs and e.g. a predetermined temperature threshold, humidity causing corrosion problems on the components of the electric power converter P_CNV can be avoided in spite that relative humid ambient air is allowed to enter the internal air flow loop I_L.

The mechanism serving to provide the controllable opening can be such as a valve, a louver, a door or the like which is actuated by an actuator, preferably an electrically controlled actuator. Preferably, the opening area is controllable in a number of steps from fully closed to fully open.

FIG. 4 shows a sketch of another embodiment of the invention. The embodiment has similarities with the one shown in FIG. 3 except that the heat exchanger HA is a liquid to air heat exchanger HA, where a liquid is forced to flow in a pipe P through a primary fluid flow path of the heat exchanger from an inlet L_I to an outlet L_O. The bypass inlet opening BP_I is arranged to allow ambient air to pass into the internal air flow loop I_L, when controlled to be open, and here the controllable bypass inlet opening BP_I is an opening of the cabinet CB directly to ambient air, or via a short pipe to ambient air. The bypass outlet opening BP_O allows air to flow back directly, or via a short pipe, from the internal air flow loop I_L to ambient air.

FIG. 5 shows a graph indicating an example of a relation between air temperature T near an electric power converter as a function of its load, i.e. its produced electric power P for a given electric power converter. A temperature limit TL exists for such converter, here indicated as 40 °C, which sets the limit for the possible power from the electric power converter for safe operation when cooled by a cooling system with a given cooling capacity. The bold straight line W_BP indicates a temperature T versus power P function in the case of a prior art cooling system, i.e. without the proposed bypass inlet opening to ambient air. This relation leads to a maximum power of about 6.0 MW when the temperature limit TL is reached.

The dashed line indicates a temperature T versus power P function in the case of a cooling system with a bypass inlet opening B_OP as proposed by the invention. As seen, the bypass inlet opening is controlled to open, when a temperature of a predetermined threshold temperature is reached, i.e. a threshold temperature which is seen as an example here to be such as 0.5 °C below the temperature limit TL. This is understood to be merely an example of a possible control strategy for control of the bypass inlet opening mechanism.

The result of opening the bypass inlet is seen as another temperature T versus power P relation, namely the not bold straight line which has a lower rate of inclination. Thus, as seen with the bypass inlet opening in the open state, a power of about 6.1-6,2 MW can be handled before the temperature limit TL is reached. Thus, with the same cooling capacity, the bypass inlet opening according to the invention allows the same electric power converter has an increased power handling capacity. This effect is obtained due to the intake of ambient air with a rather low temperature, and due to the increased air flow rate due to the air flow between bypass inlet and bypass outlet which is preferably opened along with opening of the bypass inlet.

FIG. 6 illustrates an example of a control system CLS for controlling a bypass inlet opening mechanism BI_M and a bypass outlet opening mechanism BO_M. The control system has a processor which executes a control algorithm CA which outputs control signal for controlling opening and closing of the bypass inlet and outlet opening mechanisms BI_M, BO_M. The control algorithm CA operates on a number of inputs, here illustrated as an air flow temperature T_I from a temperature sensor internal air flow, near the electric power converter. Further, an input indicative of a relative humidity RH_I in the internal air flow is provided by a humidity sensor placed in the internal air flow, near the electric power converter. Further, the control algorithm receives a signal indicating actual power P handled by electric power converter. Finally, the control algorithm receives an input regarding the predetermine temperature limit TL for the actual cooling system and electric power converter design.

The control algorithm CA is understood, most preferably, to be designed as a balanced strategy to provide a graduated opening of both bypass inlet and openings BI_M, BO_M to obtain increased cooling, thereby providing a high power handling capacity without reaching the temperature limit, but also without accepting a relative humidity being above a certain value to avoid any problems with corrosion etc. on the electric power converter components.

FIG. 7 illustrates steps of an embodiment for a method for cooling an electric power converter arranged to converter a first electric power output from a power source, e.g. a wind turbine generator, a photovoltaic power source, or an energy storage source, to a second electric power output, e.g. the electric grid. First, providing P_HE a heat exchanger with a first and a secondary flow path. Forcing F_PP a fluid, air or liquid, through the primary flow path of the heat exchanger, and forcing F_A_SP air in a loop through a secondary flow path of the heat exchanger and the electric power converter. Next, providing P_BM a controllable bypass inlet opening mechanism, and controlling C_BM the controllable bypass inlet opening mechanism to allow ambient air to enter the loop through the secondary flow path of the heat exchanger in response to at least one input parameter, such as in response to one or more sensor inputs.

To sum up, the invention provides a wind turbine comprising an electric generator connected to be driven by a rotor blade system (BL) and to generate a power electric output which is converted by an electric power converter system with an electric power converter, e.g. an AC-DC converter, a DC-AC converter or both. The electric power converter is air cooled by a cooling system having a fluid flow system arranged to force air or liquid through a primary flow path of a heat exchanger. An internal air flow with a fan serves to force air in a loop through a secondary flow path of the heat exchanger and the electric power converter to cool the electric power converter. A controllable bypass inlet opening mechanism provides a controllable opening to allow an inlet of ambient air into the internal air flow, and a control system receives at least one input parameter and being arranged to control the controllable bypass inlet opening mechanism accordingly. A bypass outlet opening, such as having a controllable bypass outlet opening mechanism, is arranged to provide an opening to allow an outlet of air from the internal air flow. The control system is preferably arranged to control the controllable bypass inlet opening mechanism accordingly to at least a temperature sensor sensing a temperature (TJn) in the internal air flow at a position upstream of the electric power converter. Further, the controllable bypass inlet opening mechanism may be controlled also in response to a sensed humidity in the internal air flow, and a measure of electric power generated by the electric generator.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is to be interpreted in the light of the accompanying claim set. In the context of the claims, the terms "including" or "includes" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.