SYSTEM, AND METHODS OF OPERATING

POWER CONVERTER SYSTEM

BACKGROUND OF THE INVENTION

[0001] The subject matter described herein relates generally to power systems and, more particularly, to a power converter system, a control system, and methods of operating the power converter system.

[0002] In some known solar power systems, a plurality of photovoltaic panels (also known as solar panels) are logically or physically grouped together to form an array of solar panels. The solar panel array converts solar energy into electrical energy and transmits the energy to an electrical grid or other destination.

[0003] Solar panels generally output direct current (DC) electrical power. To properly couple such solar panels to an electrical grid, the electrical power received from the solar panels must be converted to alternating current (AC). At least some known power systems use a power converter to convert DC power to AC power. Some known power converters use a maximum power point tracking (MPPT) control method to attempt to maximize a power output of the solar panels. However, at least some MPPT control methods do not suitably control a current provided by the solar array. For example, due to a reduced cost of solar panels, some power systems include additional solar panel capacity to increase an average or a total power output of the power system. During certain environmental conditions, such systems can produce more power from the solar panels than the power converter is able to convert to AC power. Accordingly, such power converters may exceed an allowable current limit, thus causing damage to one or more components of the power converter and/or causing the power converter to experience a fault condition.

BRIEF DESCRIPTION OF THE INVENTION

[0004] In one embodiment, a power converter system is provided that includes a converter configured to be coupled to a power generation unit for receiving power from the power generation unit and a control system coupled to the converter. The control system is configured to operate the converter in a current control mode of operation if a current provided to the converter exceeds a predefined current threshold. The control system is configured to generate a current command to facilitate increasing a power output of the power generation unit during the current control mode of operation.

[0005] In another embodiment, a method of operating a power converter system including a converter is provided that includes receiving a current measurement representative of a current received from a solar panel array. The method also includes operating the converter in a current control mode of operation if the current measurement exceeds a predefined current threshold, wherein operating the converter in the current control mode of operation includes generating a current command to facilitate increasing a power output of the solar panel array.

[0006] In yet another embodiment, a control system for a power converter system including a converter is provided that includes a converter controller configured to be coupled to the converter. The converter controller is configured to receive a voltage measurement representative of a voltage received from a power generation unit, and receive a current measurement representative of a current received from the power generation unit. The converter controller is also configured to operate the converter in a current control mode of operation if the current measurement exceeds a predefined current threshold, and operate the converter in a voltage control mode of operation if the voltage measurement exceeds a predefined voltage threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Fig. 1 is a schematic diagram of an exemplary power generation system.

[0008] Fig. 2 is a graphical view of an exemplary power output curve of the solar array shown in Fig. 1. [0009] Fig. 3 is a schematic block diagram of an exemplary power generation system that includes an exemplary converter controller configured in a voltage control mode of operation.

[0010] Fig. 4 is a schematic block diagram of an exemplary power generation system that includes an exemplary converter controller configured in a current control mode of operation.

[0011] Fig. 5 is a flow diagram of an exemplary method of operating a power converter system, such as the power converter systems shown in Figs. 1, 3, and 4.

DETAILED DESCRIPTION OF THE INVENTION

[0012] As described herein, a power generation system includes a power converter and at least one power generation unit, such as a solar array. The power converter includes a boost converter coupled to the solar array, and an inverter coupled to the boost converter by a direct current (DC) bus. The inverter is coupled to an electrical distribution network for supplying electrical energy to the network. A converter controller controls the operation of the boost converter, and an inverter controller controls the operation of the inverter. The converter controller operates the boost converter in a current control mode if a voltage of the solar array exceeds a predefined voltage threshold. If the current supplied by the solar array exceeds a predefined current threshold, the converter controller operates the boost converter in a voltage control mode.

[0013] Fig. 1 is a schematic diagram of an exemplary power generation system 100 that includes a plurality of power generation units, such as a plurality of solar panels (not shown) that form at least one solar array 102. Alternatively, power generation system 100 includes any suitable number and type of power generation units, such as a plurality of wind turbines, fuel cells, geothermal generators, hydropower generators, and/or other devices that generate power from renewable and/or non-renewable energy sources. [0014] In the exemplary embodiment, power generation system 100 and/or solar array 102 includes any number of solar panels to facilitate operating power generation system 100 at a desired power output. In one embodiment, power generation system 100 includes a plurality of solar panels and/or solar arrays 102 coupled together in a series-parallel configuration to facilitate generating a desired current and/or voltage output from power generation system 100. Solar panels include, in one embodiment, one or more of a photovoltaic panel, a solar thermal collector, or any other device that converts solar energy to electrical energy. In the exemplary embodiment, each solar panel is a photovoltaic panel that generates a substantially direct current (DC) power as a result of solar energy striking solar panels.

[0015] In the exemplary embodiment, solar array 102 is coupled to a power converter 104, or a power converter system 104, that converts the DC power to alternating current (AC) power. The AC power is transmitted to an electrical distribution network 106, or "grid." Power converter 104, in the exemplary embodiment, adjusts an amplitude of the voltage and/or current of the converted AC power to an amplitude suitable for electrical distribution network 106, and provides AC power at a frequency and a phase that are substantially equal to the frequency and phase of electrical distribution network 106. Moreover, in the exemplary embodiment, power converter 104 provides three phase AC power to electrical distribution network 106. Alternatively, power converter 104 provides single phase AC power or any other number of phases of AC power to electrical distribution network 106.

[0016] DC power generated by solar array 102, in the exemplary embodiment, is transmitted through a converter conductor 108 coupled to power converter 104. In the exemplary embodiment, a protection device 110 electrically disconnects solar array 102 from power converter 104, for example, if an error or a fault occurs within power generation system 100. As used herein, the terms "disconnect" and "decouple" are used interchangeably, and the terms "connect" and "couple" are used interchangeably. Current protection device 110 is a circuit breaker, a fuse, a contactor, and/or any other device that enables solar array 102 to be controllably disconnected from power converter 104. A DC filter 112 is coupled to converter conductor 108 for use in filtering an input voltage and/or current received from solar array 102.

[0017] Converter conductor 108, in the exemplary embodiment, is coupled to a first input conductor 114, a second input conductor 116, and a third input conductor 118 such that the input current is split between first, second, and third input conductors 114, 116, and 118. Alternatively, the input current may be conducted to a single conductor, such as converter conductor 108, and/or to any other number of conductors that enables power generation system 100 to function as described herein. At least one inductor 120 is coupled to each of first input conductor 114, second input conductor 116, and/or third input conductor 118. Inductors 120 facilitate filtering the input voltage and/or current received from solar array 102.

[0018] In the exemplary embodiment, a first input current sensor 122 is coupled to first input conductor 114, a second input current sensor 124 is coupled to second input conductor 116, and a third input current sensor 126 is coupled to third input conductor 118. First, second, and third input current sensors 122, 124, and 126 measure the current flowing through first, second, and third input conductors 114, 116, and 118, respectively.

[0019] In the exemplary embodiment, power converter 104 includes a DC to DC, or "boost," converter 128 and an inverter 130 coupled together by a DC bus 132. Boost converter 128, in the exemplary embodiment, is coupled to, and receives DC power from, solar array 102 through first, second, and third input conductors 114, 116, and 118. Moreover, boost converter 128 adjusts the voltage and/or current amplitude of the DC power received. In the exemplary embodiment, inverter 130 is a DC- AC inverter that converts DC power received from boost converter 128 into AC power for transmission to electrical distribution network 106. Moreover, in the exemplary embodiment, DC bus 132 includes at least one capacitor 134. Alternatively, DC bus 132 includes a plurality of capacitors 134 and/or any other electrical power storage devices that enable power converter 104 to function as described herein. As current is transmitted through power converter 104, a voltage is generated across DC bus 132 and energy is stored within capacitors 134. [0020] Boost converter 128, in the exemplary embodiment, includes two converter switches 136 coupled together in serial arrangement for each phase of electrical power that power converter 104 produces. In the exemplary embodiment, converter switches 136 are insulated gate bipolar transistors (IGBTs). Alternatively, converter switches 136 are any other suitable transistor or any other suitable switching device. Moreover, each pair of converter switches 136 for each phase is coupled in parallel with each pair of converter switches 136 for each other phase. As such, for a three phase power converter 104, boost converter 128 includes a first converter switch 138 coupled in series with a second converter switch 140, a third converter switch 142 coupled in series with a fourth converter switch 144, and a fifth converter switch 146 coupled in series with a sixth converter switch 148. First and second converter switches 138 and 140 are coupled in parallel with third and fourth converter switches 142 and 144, and with fifth and sixth converter switches 146 and 148. Alternatively, boost converter 128 may include any suitable number of converter switches 136 arranged in any suitable configuration.

[0021] Inverter 130, in the exemplary embodiment, includes two inverter switches 150 coupled together in serial arrangement for each phase of electrical power that power converter 104 produces. In the exemplary embodiment, inverter switches 150 are insulated gate bipolar transistors (IGBTs). Alternatively, inverter switches 150 are any other suitable transistor or any other suitable switching device. Moreover, each pair of inverter switches 150 for each phase is coupled in parallel with each pair of inverter switches 150 for each other phase. As such, for a three phase power converter 104, inverter 130 includes a first inverter switch 152 coupled in series with a second inverter switch 154, a third inverter switch 156 coupled in series with a fourth inverter switch 158, and a fifth inverter switch 160 coupled in series with a sixth inverter switch 162. First and second inverter switches 152 and 154 are coupled in parallel with third and fourth inverter switches 156 and 158, and with fifth and sixth inverter switches 160 and 162. Alternatively, inverter 130 may include any suitable number of inverter switches 150 arranged in any suitable configuration. [0022] Power converter 104 includes a control system 164 that includes a converter controller 166 and an inverter controller 168. Converter controller 166 is coupled to, and controls an operation of, boost converter 128. More specifically, in the exemplary embodiment, converter controller 166 operates boost converter 128 to maximize the power received from solar array 102. Inverter controller 168 is coupled to, and controls the operation of, inverter 130. More specifically, in the exemplary embodiment, inverter controller 168 operates inverter 130 to regulate the voltage across DC bus 132 and/or to adjust the voltage, current, phase, frequency, and/or any other characteristic of the power output from inverter 130 to substantially match the characteristics of electrical distribution network 106.

[0023] In the exemplary embodiment control system 164, converter controller 166, and/or inverter controller 168 include and/or are implemented by at least one processor. As used herein, the processor includes any suitable programmable circuit such as, without limitation, one or more systems and microcontrollers, microprocessors, reduced instruction set circuits (RISC), application specific integrated circuits (ASIC), programmable logic circuits (PLC), field programmable gate arrays (FPGA), and/or any other circuit capable of executing the functions described herein. The above examples are exemplary only, and thus are not intended to limit in any way the definition and/or meaning of the term "processor."

[0024] Converter controller 166, in the exemplary embodiment, receives current measurements from first input current sensor 122, second input current sensor 124, and/or third input current sensor 126. Moreover, converter controller 166 receives measurements of a voltage of first input conductor 114, second input conductor 116, and/or third input conductor 118 from a plurality of input voltage sensors (not shown). Inverter controller 168, in the exemplary embodiment, receives current measurements from a first output current sensor 170, a second output current sensor 172, and/or a third output current sensor 174. Moreover, inverter controller 168 receives measurements of a voltage output from inverter 130 from a plurality of output voltage sensors (not shown). In the exemplary embodiment, converter controller 166 and/or inverter controller 168 receive voltage measurements of the voltage of DC bus 132 from a DC bus voltage sensor (not shown). [0025] In the exemplary embodiment, inverter 130 is coupled to electrical distribution network 106 by a first output conductor 176, a second output conductor 178, and a third output conductor 180. Moreover, in the exemplary embodiment, inverter 130 provides a first phase of AC power to electrical distribution network 106 through first output conductor 176, a second phase of AC power to electrical distribution network 106 through second output conductor 178, and a third phase of AC power to electrical distribution network 106 through third output conductor 180. First output current sensor 170 is coupled to first output conductor 176 for measuring the current flowing through first output conductor 176. Second output current sensor 172 is coupled to second output conductor 178 for measuring the current flowing through second output conductor 178, and third output current sensor 174 is coupled to third output conductor 180 for measuring the current flowing through third output conductor 180.

[0026] At least one inductor 182 is coupled to each of first output conductor 176, second output conductor 178, and/or third output conductor 180. Inductors 182 facilitate filtering the output voltage and/or current received from inverter 130. Moreover, in the exemplary embodiment, an AC filter 184 is coupled to first output conductor 176, second output conductor 178, and/or third output conductor 180 for use in filtering an output voltage and/or current received from conductors 176, 178, and 180.

[0027] In the exemplary embodiment, at least one contactor 186 and/or at least one disconnect switch 188 are coupled to first output conductor 176, second output conductor 178, and/or third output conductor 180. Contactors 186 and disconnect switches 188 electrically disconnect inverter 130 from electrical distribution network 106, for example, if an error or a fault occurs within power generation system 100. Moreover, in the exemplary embodiment, protection device 110, contactors 186 and disconnect switches 188 are controlled by control system 164. Alternatively, protection device 110, contactors 186 and/or disconnect switches 188 are controlled by any other system that enables power converter 104 to function as described herein. [0028] Power converter 104 also includes a bus charger 190 that is coupled to first output conductor 176, second output conductor 178, third output conductor 180, and to DC bus 132. In the exemplary embodiment, at least one charger contactor 192 is coupled to bus charger 190 for use in electrically disconnecting bus charger 190 from first output conductor 176, second output conductor 178, and/or third output conductor 180. Moreover, in the exemplary embodiment, bus charger 190 and/or charger contactors 192 are controlled by control system 164 for use in charging DC bus 132 to a predetermined voltage.

[0029] During operation, in the exemplary embodiment, solar array 102 generates DC power and transmits the DC power to boost converter 128. Converter controller 166 controls a switching of converter switches 136 to adjust an output of boost converter 128. More specifically, in the exemplary embodiment, converter controller 166 controls the switching of converter switches 136 to adjust the voltage and/or current received from solar array 102 such that the power received from solar array 102 is increased and/or maximized.

[0030] Inverter controller 168, in the exemplary embodiment, controls a switching of inverter switches 150 to adjust an output of inverter 130. More specifically, in the exemplary embodiment, inverter controller 168 uses a suitable control algorithm, such as pulse width modulation (PWM) and/or any other control algorithm, to transform the DC power received from boost converter 128 into three phase AC power signals. Alternatively, inverter controller 168 causes inverter 130 to transform the DC power into a single phase AC power signal or any other signal that enables power converter 104 to function as described herein.

[0031] In the exemplary embodiment, each phase of the AC power is filtered by AC filter 184, and the filtered three phase AC power is transmitted to electrical distribution network 106. In the exemplary embodiment, three phase AC power is also transmitted from electrical distribution network 106 to DC bus 132 by bus charger 190. Bus charger 190 uses the AC power to charge DC bus 132 to a suitable voltage amplitude, for example, during a startup and/or a shutdown sequence of power converter 104. [0032] Fig. 2 is a graphical view of an exemplary power output curve 200 of solar array 102 (shown in Fig. 1). The ordinate axis on the right side of the graph represents a power output 202 of solar array 102, and the abscissa axis represents a voltage output 204 of solar array 102. Fig. 2 also illustrates an exemplary voltage-current (V-I) curve 201 of solar array 102. The ordinate axis on the left side of the graph represents a current output 203 of solar array 102. Accordingly, V-I curve 201 illustrates current output 203 at different voltage outputs 204 of solar array 102, and power output curve 200 illustrates power output 202 at different voltage outputs 204 of solar array 102.

[0033] During normal operation, boost converter 128 (shown in Fig. 1) is operated to control a voltage output 204 and a current output 203 of solar array 102 that facilitate yielding a maximum power level 206 for solar array 102. A first operating region 208 (also known as a left-hand side (LHS) 208 of power output curve 200) defines a low voltage and high current mode of operation with respect to the voltage and current levels at maximum power level 206. A second operating region 210 (also known as a right-hand side (RHS) 210 of power output curve 200) defines a high voltage and low current mode of operation with respect to the voltage and current levels at maximum power level 206.

[0034] During a time period in which solar array 102 is capable of supplying more power than electrical distribution network 106 (both shown in Fig. 1) and/or power converter 104 can accept, solar array 102 is operated within first operating region 208. In addition, in the exemplary embodiment, solar array 102 is operated in, or switched to, second operating region 210 (RHS 210) if voltage output 204 of solar array 102 exceeds a predefined voltage threshold 212. Solar array 102 is operated in, or switched to, first operating region 208 (LHS 208) if a current supplied to boost converter 128 from solar array 102 (i.e., current output 203) exceeds a predefined current threshold 214.

[0035] More specifically, if voltage output 204 of V-I curve 201 exceeds voltage threshold 212, converter controller 166 (shown in Fig. 1) is operated in a voltage control mode of operation (described more fully herein). If current output 203 of V-I curve 201 exceeds current threshold 214, converter controller 166 is operated in a current control mode of operation (described more fully herein). As voltage output 204 is based on, or proportional to, current output 203 within V-I curve 201 (and vice versa), voltage threshold 212 and current threshold 214 can be described with respect to a voltage output 204 or a current output 203 of V-I curve 201. For example, a point 216 at which voltage threshold 212 intersects V-I curve 201 represents a value of current output 203 at which converter controller 166 switches to a voltage control mode of operation if current output 203 is reduced below the current output value at point 216. Accordingly, voltage threshold 212 corresponds to a second (or lower) current threshold 218, and current threshold 214 represents an upper current threshold 214 for V-I curve 201.

[0036] In a similar manner, a point 220 at which current threshold 214 intersects V-I curve 201 represents a value of voltage output 204 at which converter controller 166 switches to a current control mode of operation if voltage output 204 is reduced below the voltage output value at point 220. Accordingly, current threshold 214 corresponds to a second (or lower) voltage threshold 222, and voltage threshold 212 represents an upper voltage threshold 212 for V-I curve 201.

[0037] In the exemplary embodiment, to minimize excessive switching between the current control mode of operation and the voltage control mode of operation, converter controller 166 is not switched until current output 203 exceeds current threshold 214 or voltage output 204 exceeds voltage threshold 212. Accordingly, a hysteresis band 224 of V-I curve 201 is identified for the portion of V- I curve 201 where current output 203 is less than current threshold 214 and where voltage output 204 is less than voltage threshold 212. More specifically, hysteresis band 224 is defined between upper current threshold 214 and lower current threshold 218, and between upper voltage threshold 212 and lower voltage threshold 222. Accordingly, when solar array 102 is operating within hysteresis band 224, converter controller 166 is not switched to a different mode of operation (e.g., to a voltage control mode of operation or to a current control mode of operation). [0038] Fig. 3 is a schematic block diagram of an exemplary power generation system 300 that includes a converter controller 302 configured in a voltage control mode of operation. In the exemplary embodiment, converter controller 302 is substantially similar to converter controller 166 (shown in Fig. 1) when converter controller is operated in the voltage control mode. As used herein, the term "voltage control mode" refers to a mode of operation in which converter controller 302 adjusts or generates a voltage command signal to facilitate increasing or adjusting a power output of solar array 102.

[0039] Unless otherwise specified, power generation system 300 is similar to power generation system 100 (shown in Fig. 1), and similar components are labeled in Fig. 3 with the same reference numerals used in Fig. 1. While boost converter 128 is illustrated as being a two-phase converter (i.e., having two pairs of converter switches 136) that receives power from a first solar array 304 and a second solar array 306, it should be recognized that boost converter 128 may include any number of phases for converting power received from any number of solar arrays 102.

[0040] In the exemplary embodiment, converter controller 302 includes a first power point tracking (PPT) module 308 and a second PPT module 310 coupled in parallel with each other. First PPT module 308 is coupled to a first output 312 of first solar array 304, and second PPT module 310 is coupled to a second output 314 of second solar array 306. First output 312 is coupled to first input conductor 114, and second output 314 is coupled to second input conductor 116. In the exemplary embodiment, first PPT module 308 facilitates increasing or maximizing the power output of first solar array 304, and second PPT module facilitates increasing or maximizing the power output of second solar array 306.

[0041] First PPT module 308, in the exemplary embodiment, receives a first array voltage measurement 316 at first output 312 from a first input voltage sensor 318, and receives a first array current measurement 320 from first input current sensor 122. First PPT module 308 calculates a current power output of first solar array 304 by multiplying the first array voltage measurement 316 and first array current measurement 320. Module 308 compares the current power output of first solar array 304 to a previous power output of first solar array 304 to determine a direction or trend of the power output. For example, if the comparison yields a negative number (i.e., if the current power output is less than the previous power output), first PPT module 308 determines that the power output is decreasing. Conversely, if the comparison yields a positive number (i.e., if the current power output is greater than the previous power output), first PPT module 308 determines that the power output of first solar array 304 is increasing.

[0042] First PPT module 308 outputs a first voltage command 322 that is expected to increase the power output of first solar array 304. For example, if first PPT module 308 determines that the power output is decreasing, module 308 determines whether the last voltage command was positive or negative with respect to a voltage baseline, or with respect to the voltage command prior to the last command, and switches a "direction" of the last voltage command. Specifically, if the last voltage command was positive such that converter controller 302 commanded boost converter 128 to increase a voltage of first solar array 304, first PPT module 308 outputs a negative value for first voltage command 322. However, if the last voltage command was negative such that converter controller 302 commanded boost converter 128 to decrease a voltage of first solar array 304, first PPT module 308 outputs a positive value for first voltage command 322.

[0043] In another example, if first PPT module 308 determines that the power output is increasing, module 308 determines whether the last voltage command was positive or negative with respect to the voltage baseline, or with respect to the voltage command prior to the last command, and maintains the direction of the last voltage command. If the last voltage command was positive such that converter controller 302 commanded boost converter 128 to increase a voltage of first solar array 304, first PPT module 308 outputs a positive value for first voltage command 322. However, if the last voltage command was negative such that converter controller 302 commanded boost converter 128 to decrease a voltage of first solar array 304, first PPT module 308 outputs a negative value for first voltage command 322. Accordingly, first PPT module 308 outputs first voltage command 322 in a direction (i.e., positive or negative) that is expected to increase the power output of first solar array 304.

[0044] In a similar manner, second PPT module 310 receives a second array voltage measurement 324 at second output 314 from a second input voltage sensor 326, and receives a second array current measurement 328 from second input current sensor 124. Second PPT module 310 calculates a current power output of second solar array 306 by multiplying the second array voltage measurement 324 and second array current measurement 328. Module 310 compares the current power output of second solar array 306 to a previous power output of second solar array 306 to determine a direction or trend of the power output. Second PPT module 310 outputs a second voltage command 330 that is expected to increase the power output of second solar array 306 in a similar manner as described above with respect to first PPT module 308. Moreover, in the exemplary embodiment, first PPT module 308 and second PPT module 310 use real-time sampling to measure or receive the voltage and current measurements from first solar array 304 and second solar array 306, respectively, and to calculate the power outputs of first and second solar arrays 304 and 306.

[0045] First PPT module 308 transmits first voltage command 322 to a first voltage regulator module 332 that adjusts first voltage command 322 if first voltage command 322 exceeds a predetermined voltage threshold. More specifically, in the exemplary embodiment, first voltage regulator module 332 receives first array current measurement 320 from first input current sensor 122, a DC bus voltage measurement 334 from a DC bus voltage sensor 336, and a power limit signal 338 from a power management module 340. Power limit signal 338 is indicative of a power limit for power converter 104. In addition, first voltage regulator module 332 receives, or is programmed with, a voltage maximum value that represents a maximum allowable voltage across DC bus 132.

[0046] First voltage regulator module 332 multiplies first array current measurement 320 and first voltage command 322 to calculate an expected power output of first solar array 304. First voltage regulator module 332 compares the expected power output with the power limit. If the expected power output exceeds the power limit, first voltage regulator module 332 adjusts first voltage command 322 to a value that does not exceed the power limit when multiplied by first array current measurement 320. In addition, first voltage regulator module 332 compares first voltage command 322 to the voltage maximum value. If first voltage command 322 exceeds the voltage maximum value, first voltage regulator module 332 adjusts first voltage command 322 to be equal to the voltage maximum value, or to another value that does not exceed the voltage maximum value. First voltage regulator module 332 outputs a first regulated voltage command 342 that is representative of first voltage command 322 as adjusted as described above. However, if the expected power output does not exceed the power limit, and if first voltage command 322 does not exceed the voltage maximum value, first voltage regulator module 332 outputs first regulated voltage command 342 that is representative of an unchanged first voltage command 322.

[0047] In a similar manner, a second voltage regulator module 344 multiplies second array current measurement 328 and second voltage command 330 to calculate an expected power output of second solar array 306. Second voltage regulator module 344 compares the expected power output with the power limit. If the expected power output exceeds the power limit, second voltage regulator module 344 adjusts second voltage command 330 to a value that does not exceed the power limit when multiplied by second array current measurement 328. In addition, second voltage regulator module 344 compares second voltage command 330 to the voltage maximum value. If second voltage command 330 exceeds the voltage maximum value, second voltage regulator module 344 adjusts second voltage command 330 to be equal to the voltage maximum value, or to another value that does not exceed the voltage maximum value. Second voltage regulator module 344 outputs a second regulated voltage command 346 that is representative of second voltage command 330 as adjusted as described above. However, if the expected power output does not exceed the power limit, and if second voltage command 330 does not exceed the voltage maximum value, second voltage regulator module 344 outputs second regulated voltage command 346 that is representative of an unchanged second voltage command 330.

[0048] First voltage regulator module 332 and second voltage regulator module 344 output first regulated voltage command 342 and second regulated voltage command 346, respectively, to a duty cycle calculator module 348. Duty cycle calculator module 348 calculates a duty cycle for converter switches 136. In addition, duty cycle calculator module 348 outputs a first duty cycle command 350 representative of a duty cycle for operating converter switches 136 of the first phase of power received from solar array 102 (hereinafter referred to as first phase converter switches 352). In the exemplary embodiment, first phase converter switches 352 include first converter switch 138 and second converter switch 140 for adjusting the power received from first solar array 304. Duty cycle calculator module 348 also outputs a second duty cycle command 354 representative of a duty cycle for operating converter switches 136 of the second phase of power received from solar array 102, (hereinafter referred to as second phase converter switches 356). In the exemplary embodiment, second phase converter switches 356 include third converter switch 142 and fourth converter switch 144 for adjusting the power received from second solar array 306. First duty cycle command 350 and second duty cycle command 354 are transmitted to a pulse width modulator (PWM) generator 358.

[0049] In the exemplary embodiment, PWM generator 358 outputs a first gating signal 360 for first phase converter switches 352, and a second gating signal 362 for second phase converter switches 356. More specifically, first gating signal 360 controls a switching operation of first converter switch 138 and second converter switch 140. In the exemplary embodiment, first gating signal 360 switches first converter switch 138 and second converter switch 140 in an interleaved fashion, such that first converter switch 138 is in an "off state (i.e., an electrically non- conductive state) when second converter switch 140 is in an "on" state (i.e., an electrically conductive state), and vice versa. In a similar manner, second gating signal 362 controls a switching operation of third converter switch 142 and fourth converter switch 144 such that third and fourth converter switches 142 and 144 are switched in an interleaved fashion. [0050] Power management module 340 receives signals representative of a current, a voltage, and/or a power supplied to electrical distribution network 106, a health or status of electrical distribution network 106 (e.g., whether a low voltage or zero voltage event is occurring within network 106), a current and/or a voltage within electrical distribution network 106, and/or any other signal that enables power generation system 300 to function as described herein. Power management module 340 determines a power limit for power converter 104 and transmits power limit signal 338 that is indicative of the power limit to first and second voltage regulator modules 332 and 344.

[0051] Fig. 4 is a schematic block diagram of an exemplary power generation system 400 that includes a converter controller 402 configured in a current control mode of operation. In the exemplary embodiment, converter controller 402 is substantially similar to converter controller 166 (shown in Fig. 1) when converter controller 166 is operated in the current control mode. As used herein, the term "current control mode" refers to a mode of operation in which converter controller 402 adjusts or generates a current command signal to facilitate increasing or adjusting a power output of solar array 102.

[0052] Unless otherwise specified, power generation system 400 is similar to power generation system 300 (shown in Fig. 3), and similar components are labeled in Fig. 4 with the same reference numerals used in Fig. 3. While boost converter 128 is illustrated as being a two-phase converter (i.e., having two pairs of converter switches 136) that receives power from first solar array 304 and second solar array 306, it should be recognized that boost converter 128 may include any number of phases for converting power received from any number of solar arrays 102.

[0053] In the exemplary embodiment, converter controller 402 includes first PPT module 308 and second PPT module 310 coupled in parallel with each other. First PPT module 308 is coupled to first output 312 of first solar array 304, and second PPT module 310 is coupled to second output 314 of second solar array 306. In the exemplary embodiment, first PPT module 308 facilitates increasing or maximizing the power output of first solar array 304, and second PPT module facilitates increasing or maximizing the power output of second solar array 306.

[0054] First PPT module 308, in the exemplary embodiment, receives first array voltage measurement 316 from first input voltage sensor 318, and receives first array current measurement 320 from first input current sensor 122. First PPT module 308 calculates the current power output of first solar array 304 by multiplying the first array voltage measurement 316 and first array current measurement 320. Module 308 compares the current power output of first solar array 304 to the previous power output of first solar array 304 to determine the direction or trend of the power output. For example, if the comparison yields a negative number (i.e., if the current power output is less than the previous power output), first PPT module 308 determines that the power output is decreasing. Conversely, if the comparison yields a positive number (i.e., if the current power output is greater than the previous power output), first PPT module 308 determines that the power output of first solar array 304 is increasing.

[0055] First PPT module 308 outputs a first current command 404 that is expected to increase the power output of first solar array 304. For example, if first PPT module 308 determines that the power output is decreasing, module 308 determines whether the last current command was positive or negative with respect to a current baseline, or with respect to the current command prior to the last command, and switches a direction of the last current command. Specifically, if the last current command was positive such that converter controller 402 commanded boost converter 128 to increase a current supplied from first solar array 304 to boost converter 128, first PPT module 308 outputs a negative value for first current command 404. However, if the last current command was negative such that converter controller 402 commanded boost converter 128 to decrease a current supplied to boost converter 128, first PPT module 308 outputs a positive value for first current command 404.

[0056] In another example, if first PPT module 308 determines that the power output is increasing, module 308 determines whether the last current command was positive or negative with respect to a current baseline and maintains the direction of the last current command. If the last current command was positive such that converter controller 402 commanded boost converter 128 to increase a current supplied to boost converter 128, first PPT module 308 outputs a positive value for first current command 404. However, if the last current command was negative such that converter controller 402 commanded boost converter 128 to decrease a current supplied to boost converter 128, first PPT module 308 outputs a negative value for first current command 404. Accordingly, first PPT module 308 outputs first current command 404 in a direction (i.e., positive or negative) that is expected to increase the power output of first solar array 304.

[0057] In a similar manner, second PPT module 310 receives second array voltage measurement 324 from second input voltage sensor 326, and receives a second array current measurement 328 from second input current sensor 124. Second PPT module 310 calculates a current power output of second solar array 306 by multiplying the second array voltage measurement 324 and second array current measurement 328. Module 310 compares the current power output of second solar array 306 to a previous power output of second solar array 306 to determine a direction or trend of the power output. Second PPT module 310 outputs a second current command 406 that is expected to increase the power output of second solar array 306 in a similar manner as described above with respect to first PPT module 308. Moreover, in the exemplary embodiment, first PPT module 308 and second PPT module 310 use real-time sampling to measure or receive the voltage and current measurements from first solar array 304 and second solar array 306, respectively, and to calculate the power outputs of first and second solar arrays 304 and 306.

[0058] First current command 404 is transmitted to a first power limiter module 408 that adjusts first current command 404 if first current command 404 will cause the power within power converter 104 to exceed a predetermined power limit. More specifically, in the exemplary embodiment, first power limiter module 408 receives DC bus voltage measurement 334 from DC bus voltage sensor 336, and receives power limit signal 338 from power management module 340. First power limiter module 408 multiplies first current command 404 and DC bus voltage measurement 334 to calculate an expected power within boost converter 128. First voltage regulator module 332 compares the expected power within boost converter 128 with the power limit. If the expected power exceeds the power limit, first power limiter module 408 adjusts first current command 404 to a value that does not exceed the power limit when multiplied by DC bus voltage measurement 334. First power limiter module 408 outputs a first limiter current command 410 that is representative of first current command 404 as adjusted as described above. However, if the expected power within boost converter 128 does not exceed the power limit, first power limiter module 408 outputs first limiter current command 410 that is representative of an unchanged first current command 404.

[0059] In a similar manner, second current command 406 is transmitted to a second power limiter module 412 that adjusts second current command 406 if second current command 406 will cause the power within power converter 104 to exceed a predetermined power limit. More specifically, in the exemplary embodiment, second power limiter module 412 receives DC bus voltage measurement 334 from DC bus voltage sensor 336, and receives power limit signal 338 from power management module 340. Second power limiter module 412 multiplies second current command 406 and DC bus voltage measurement 334 to calculate an expected power within boost converter 128. Second voltage regulator module 344 compares the expected power within boost converter 128 with the power limit. If the expected power exceeds the power limit, second power limiter module 412 adjusts second current command 406 to a value that does not exceed the power limit when multiplied by DC bus voltage measurement 334. Second power limiter module 412 outputs a second limiter current command 414 that is representative of second current command 406 as adjusted as described above. However, if the expected power does not exceed the power limit, second power limiter module 412 outputs second limiter current command 414 that is representative of an unchanged second current command 406.

[0060] First array current measurement 320 is subtracted from first limiter current command 410 to obtain a first current error signal 416 that is transmitted to a first current regulator module 418. In the exemplary embodiment, first current regulator module 418 is a proportional-integral (PI) regulator that translates first current error signal 416 into a voltage command, and outputs first regulated voltage command 342 to facilitate reducing first current error signal 416. First regulated voltage command 342 is transmitted to duty cycle calculator module 348.

[0061] Second array current measurement 328 is subtracted from second limiter current command 414 to obtain a second current error signal 420 that is transmitted to a second current regulator module 422. In the exemplary embodiment, second current regulator module 422 is a proportional-integral (PI) regulator that translates second current error signal 420 into a voltage command, and outputs second regulated voltage command 346 to facilitate reducing second current error signal 420. Second regulated voltage command 346 is transmitted to duty cycle calculator module 348.

[0062] In the exemplary embodiment, duty cycle calculator module 348 operates substantially as described above in Fig. 3 to calculate the duty cycle for converter switches 136. Duty cycle calculator module 348 outputs first duty cycle command 350 representative of the duty cycle for operating first phase converter switches 352, and second duty cycle command 354 representative of the duty cycle for operating second phase converter switches 356. First duty cycle command 350 and second duty cycle command 354 are transmitted to PWM generator 358 for generating first and second gating signals 360 and 362, as described above with reference to Fig. 3.

[0063] Fig. 5 is a flow diagram illustrating an exemplary method 500 of operating a power converter, such as power converter 104 (shown in Fig. 1). In the exemplary embodiment, method 500 is executed by converter controller 166 (shown in Fig. 1), that is configured to operate in a similar manner as converter controller 302 (shown in Fig. 3) and/or converter controller 402 (shown in Fig. 4).

[0064] In one embodiment, an initial operating mode may be set for boost converter 128 (shown in Fig. 1). For example, boost converter 128 may be configured by a user, by configuration settings in boost converter 128, or by another device to initially operate in the voltage control mode of operation or in the current control mode of operation. In such an embodiment, method 500 is executed while boost converter 128 is in the initial mode of operation defined by the user, the configuration settings, or the remote device.

[0065] Method 500 includes receiving 502 a measurement of a power generation unit voltage. More specifically, in the exemplary embodiment, first array voltage measurement 316 is received 502 from first input voltage sensor 318 (both shown in Fig. 3). One or more additional voltage measurements may be received 502, such as second array voltage measurement 324 and/or any other voltage measurement. Converter controller 166 determines 504 whether the voltage measurement (or at least one of the voltage measurements, if boost converter 128 includes more than one phase) exceeds a predefined voltage threshold, such as voltage threshold 212 described above with reference to Fig. 2. If the voltage measurement exceeds the voltage threshold, converter controller 166 operates 506 boost converter 128 in the voltage control mode of operation. In one embodiment, if boost converter 128 is operating in the current control mode of operation, converter controller 166 switches boost converter 128 to operate 506 in the voltage control mode. In other words, converter controller 166 switches boost converter 128 from operating solar array 102 in LHS 208 of power output curve 200 to operating solar array 102 in RHS 210 of curve 200 (shown in Fig. 2). Converter controller 166 returns to receiving 502 a measurement of a power generation unit voltage as described above.

[0066] If the voltage measurement is determined 504 to not exceed the voltage threshold, converter controller 166 operates 508 boost converter 128 in the current control mode of operation. In one embodiment, if boost converter 128 is operating 506 in the voltage control mode of operation, converter controller 166 switches boost converter 128 to operate 508 in the current control mode. In other words, converter controller 166 switches boost converter 128 from operating solar array 102 in RHS 210 of power output curve 200 to operating solar array 102 in LHS 208 of curve 200. [0067] Converter controller 166 receives 510 a measurement of a power generation unit current, such as first and/or second array current measurement 320 and/or 328. Converter controller 166 determines 512 whether the current measurement (or at least one of the current measurements, if boost converter 128 includes more than one phase) exceeds a predefined current threshold, such as current threshold 214 described above with reference to Fig. 2. If the current measurement exceeds the current threshold, converter controller 166 continues to operate 508 in the current control mode. However, if the current measurement does not exceed the current threshold, converter controller 166 operates 506 in the voltage control mode as described above. In the exemplary embodiment, converter controller 166 is not switched to a different mode of operation (e.g., to the voltage control mode of operation or to the current control mode of operation) while solar array 102 is operating within hysteresis band 224 (shown in Fig. 2).

[0068] A technical effect of the systems and methods described herein includes at least one of: (a) receiving a current measurement representative of a current received from a solar panel array; and (b) operating a converter in a current control mode of operation if a current measurement exceeds a predefined current threshold, wherein operating the converter in the current control mode of operation includes generating a current command to facilitate increasing a power output of a solar panel array.

[0069] Exemplary embodiments of a power converter system, a control system, and methods of operating a power converter system are described above in detail. The power converter system, control system, and methods are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the power converter system may also be used in combination with other power generation systems and methods, and is not limited to practice with only the solar power system as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other renewable energy and/or power generation applications. [0070] Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

[0071] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.