JP5830484B2 - Reactive power ratio controller, reactive power ratio control method, and power generation system using the same - Google Patents

Description

The present invention relates to reactive power ratio control of a power source that constructs an independent system, and particularly relates to reactive power ratio control of a power source in which the power source is constructed by a storage battery system and renewable energy.

  In recent years, the introduction of renewable energy such as solar power and wind power generation into the power system has been increasing. However, due to the instability of the output, the introduction of the above-mentioned renewable energy brings about fluctuations in the voltage and frequency of the power system, raising new technical issues.

  The fluctuation of active power output from renewable energy can be smoothed by a storage battery system constructed by a cell battery and a frequency conversion inverter. When the inverter is a self-excited inverter, the inverter can control active power and reactive power independently and freely.

  The size of the inverter is determined by the maximum apparent power that can be output. This apparent power is defined by the square root of the square sum of the active power and reactive power output to the power system. If the inverter of the storage battery system is controlled to output a large reactive power while charging / discharging from the storage battery to the system, the semiconductor switching element in the inverter such as an IGBT will be overloaded and may be damaged.

In order to avoid the overload of the IGBT, a method to appropriately control the reactive power output when voltage fluctuation occurs is necessary. One of the above methods is disclosed in Patent Document 1. Patent Document 1 relates to a wind power generation system linked to a large-scale system and a control method and a control device for a storage battery system connected in parallel to the wind power generation system. An integrated control method for suppressing fluctuations and frequency fluctuations is disclosed.

International Publication WO2012 / 070141

  Patent Document 1 is a technique related to a large-scale system. However, the microgrid is operated in a system linkage state or an independent system state. When the renewable energy and the power storage system construct an independent power supply and supply active power and reactive power to the load linked to the independent power system, the independent power supply system always maintains a balance between active power and reactive power. Become. That is, the sum of the renewable energy and the active power output by the storage battery system is equal to the active power consumed by the load. Similarly, the sum of the renewable energy and the reactive power supplied by the storage system is consumed by the load. Equivalent to reactive power.

  When the active power output from the renewable energy is smaller than the active power consumed by the load, the active power is automatically drawn from the storage battery system so as to maintain a balance between supply and demand. At this time, if the apparent power of the inverter in the storage battery system becomes larger than the rated power of the inverter, the inverter is overloaded and the semiconductor switching element may be damaged.

  The control system of Patent Document 1 calculates the charging rate by the storage battery system, transmits the charging rate to the main controller, and the main controller adjusts the reactive power command to the lower-level controller according to the logic of the second operation mode. Has steps. The control method disclosed in Patent Document 1 employs centralized control that requires high-reliability and high-speed communication between a power generation unit such as wind power generation or a storage battery system and a main controller. In particular, the charging rate detection requires a predetermined time for filtering the ripple current.

  The second operation mode described above cannot avoid a time delay, and the time delay imposes an overload on the storage battery system even if it is a short time.

  In order to protect the inverter from overload, it is necessary to issue an inverter output command with a certain margin for the apparent power in consideration of the time delay. This margin reduces the utilization rate of the inverter.

In view of the above, an object of the present invention is to improve the utilization rate of an inverter provided in a storage battery system.

  In order to solve the above problems, the present invention has the following configuration.

A power generation device using renewable energy, a first inverter connected to the power generation device, a storage battery, a second inverter connected to the storage battery, and a controller, the first inverter and the In a power generation system in which a second inverter is connected at a linkage point and the controller controls power supply to a load via the linkage point, the controller converts the effective power output from the second inverter to Based on this, the ratio of the reactive power output from the first inverter and the reactive power output from the second inverter is changed.

ADVANTAGE OF THE INVENTION According to this invention, the utilization factor of the inverter with which a storage battery system is equipped can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS The independent power supply system explanatory drawing constructed | assembled by the photovoltaic power generation system, storage battery system, and main controller which are 1st Example of this invention. FIG. 3 is an explanatory diagram of a control block in the main controller of the first embodiment of the present invention. The drooping characteristic explanatory drawing of the voltage-reactive power which changes according to the output of another inverter of 1st Example of this invention. Calculation block explanatory drawing of voltage-reactive power drooping characteristic control of 1st Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS Main circuit structure explanatory drawing of the self-excitation inverter of 1st Example of this invention. FIG. 3 is an explanatory diagram of a main controller active power and reactive power calculation calculation block according to the first embodiment. Explanatory drawing in case the renewable energy of a present Example 1 is a wind power generation system. The other example of arrangement | positioning of the renewable energy controller of 1st Example of this invention is explanatory drawing.

  Prior to the description of the embodiments of the present invention, the technique of Patent Document 1 will be described. Patent Document 1 discloses a control method for a wind power generation system and a storage battery system, and the control method includes two operation modes selected based on a power command required for the storage battery system.

  The power supply system of Patent Document 1 controls a wind power generation controller that receives an active power command and a reactive power command from a main controller, a plurality of wind power generators controlled by the controller, a storage battery, an inverter, and the inverter. And a storage battery controller that inputs an output command from the main controller.

  The first operation mode is an operation mode in which the output command output from the main controller to the wind power generation controller and the storage battery controller is within the rated apparent power of the wind power generation system and the storage system.

  In the second operation mode, when the output command required by the storage battery system exceeds the rated apparent power that changes according to the charging rate of the storage battery system, the wind power generation controller and the storage battery controller, which are subordinate controllers, are used. Then, the reactive power output command from the storage battery system is reduced, and the command is updated to the wind power generation controller so as to increase the reactive power output corresponding to the reduction amount.

  Such a technique of Patent Document 1 has the above-described problems.

Embodiments of the present invention that can solve the above-described problems will be described below with reference to the drawings. When the active power output from the storage battery system approaches the rating of the storage battery system, the renewable energy controller according to the present embodiment adjusts the reactive power ratio of the renewable energy and the reactive power of the storage battery system to adjust the reactive power generated by the renewable energy. It increases the output. As a result, the renewable energy system can avoid overload of the storage battery system and improve the utilization rate of the inverter. This effect changes the ratio of the reactive power derived from the power generation device (natural energy system 1) and the reactive power derived from the storage battery based on the active power derived from the storage battery (storage battery system 2), which will be described in the following examples. This can be achieved by having the main controller 4.

  A power system for an independent system according to the first embodiment of the present invention will be described with reference to FIG. The independent system shown in FIG. 1 includes a renewable energy system 1, a storage battery system 2, a load 3, a system impedance 5, 6, current sensors 81 and 83, voltage sensors 82 and 84, and a main controller 4.

  The renewable energy system 1 supplies power to the load 3. When the power output from the renewable energy 1 is larger than the power consumption of the load 3, the surplus power is charged in the storage battery system 2. Conversely, when the power output from the renewable energy 1 is smaller than the power consumption of the load 3, the sum of the output power from the renewable energy 1 and the output power from the storage battery system 2 matches the power consumption of the load 3. Thus, the storage battery of the storage battery system 2 is discharged.

  In this embodiment, the system impedances 5 and 6 are relatively small in resistance values R_1 and R_2 of the impedances compared to the inductances X_1 and X_2, respectively, and can be ignored.

  The active power P_LOAD consumed by the load 3 is equal to the sum of the active power P_RES output from the renewable energy system 1 and the active power P_BESS output from the storage battery system 2. The effective power P_RES is limited by available energy, and the storage battery system 2 automatically outputs the effective power P_BESS that satisfies the expression P_BESS = P_LOAD−P_RES.

  The storage battery system 2 includes a storage battery unit or storage battery bank 21, a self-excited inverter 22 connected to the storage battery bank, and a controller 23 that receives the voltage (V_PCC) at the load linkage point 7 and controls the self-excited inverter. . The storage battery system 2 is connected to the load linkage point 7 via the system impedance 6. The controller 23 of the storage battery system 2 includes an amplitude calculator that calculates the voltage amplitude V_PCC_AMP at the linkage point 7 from V_PCC, a reactive power controller that controls the reactive power output from the inverter 22 to match the command value, A reactive power drooping characteristic controller is provided. The voltage-reactive power drooping characteristic controller calculates a reactive power command value. The storage battery system is connected to the load linkage point 7 via a system impedance. The controller 23 controls the reactive power output from the inverter 23 based on the command value by the reactive power controller, thereby keeping the voltage at the linkage point 7 within the allowable fluctuation range.

  The drooping characteristic controller calculates a reactive power command value according to Equation 1.

  Here, V_PCC_AMP is a voltage amplitude value at the linkage point 7, V * is a voltage command value at the linkage point 7, k_BESS is a constant, and Q_BESS is a reactive power command value supplied from the storage battery system 2 to the load 3.

  A calculation block of voltage-reactive power drooping characteristic control performed by the controller 23 of the storage battery system 2 is shown in FIG.

  The voltage amplitude V_PCC_AMP calculated from the voltage V_PCC of the linkage point 7 detected by the voltage sensor 84 and the linkage point voltage command value V * are input to the subtractor 101, and the difference is output to the multiplier 102. Multiplier 102 multiplies the output of subtractor 101 by the inverse of k_BESS in Equation 1 to calculate reactive power command value Q_BESS for storage battery system 2. The reactive power command value Q_BESS output from the multiplier 102 is output to a reactive power controller (not shown), and the reactive power output from the inverter 22 is controlled by the reactive power controller so as to match the command value Q_BESS.

  The renewable energy system 1 according to the present embodiment is a solar power generation system including a solar panel 11, a self-excited inverter 12 connected to the solar panel 11, and a controller 13 that controls the inverter 12. The renewable energy system 1 is connected to a linkage point 7 via a system impedance 5. The controller 13 mainly has two controllers. The first controller is a maximum power tracking calculator (MPPT) that maximizes the generated power in a predetermined solar radiation, and the second control function keeps the voltage at the linkage point 7 within the allowable fluctuation range. It is a voltage-reactive power droop characteristic controller to maintain.

  MPPT is a technique well known in the art.

  The drooping characteristic controller of the renewable energy system 1 calculates the reactive power command value in accordance with Equation 2.

  Here, V * is the voltage command value at the linkage point 7 and has the same value as the command value shown in Equation 1. Further, k_RES is a variable that changes according to the active power P_BESS output by the storage battery system 2, and Q_RES is a reactive power command value that is supplied from the renewable energy 1 to the load 3. k_RES is calculated by the main controller 4 and output to the controller 13.

  The calculation block of the voltage-invalid droop characteristic controller of the renewable energy system 1 executed by the controller 13 is shown in FIG.

  The voltage amplitude V_PCC_AMP calculated from the voltage V_PCC at the linkage point 7 detected by the voltage sensor 84 and the linkage point voltage command value V * are input to the subtractor 103, and the difference is output to the multiplier 104. The multiplier 104 multiplies the output of the subtracter 103 by the reciprocal of the gain k_RES in Equation 2. k_RES is a value calculated by the main controller 4. The output of the multiplier 104 is a reactive power command value Q_RES of the renewable energy system 1 and is output to a reactive power controller of the renewable energy system 1 (not shown).

The main circuit configuration of the self-excited inverter 22 is shown in FIG. The operation principle of the self-excited inverter will be described with reference to FIG. A DC power source (or power storage element) is connected to the terminals P and N to supply DC power to the inverter. The inverter converts the DC power into AC power by high-frequency switching of a bridge constituted by a semiconductor switching element having a gate signal terminal, and outputs a desired AC voltage or AC current. The gate terminal voltage is calculated and output by the controller 23 so as to drive the semiconductor switching element at an appropriate conduction ratio. The self-excited inverter shown in FIG. 5 uses IGBTs 220m, 220n, 220o, 220p, 220q, and 220r as semiconductor switching elements. However, in the present invention, the semiconductor switching element is not limited to the IGBT, and the same effect can be obtained by using an element such as IGCT, MOS-FET, or GTO. The self-excited inverter 12 has the same configuration as that of the self-excited inverter 22, but the description thereof is omitted to avoid redundant description.
The reactive power output ratio adjustment of the renewable energy system 1 and the storage battery system 2 by the main controller 4, which is one of the features of this embodiment, will be described below.

  FIG. 2 shows a control calculation block of the main controller 4 that controls the inverter 12 via the controller 13. The main controller 4 includes a power calculation unit 41 and a voltage-reactive power drooping characteristic slope calculation unit 42. The power calculation unit 41 calculates active power P_BESS output from the storage battery system 2 from the outputs of the current sensor 81 and voltage sensor 82, and calculates reactive power Q_LOAD consumed by the load from the outputs of the current sensor 83 and voltage sensor 84. .

  The arithmetic unit 42 receives P_BESS and Q_LOAD as outputs of the power calculation unit 41 and calculates a gain k_RES in Equation 2.

  A power calculation calculation block of the power calculation unit 41 is shown in FIG. The power calculation unit 41 inputs line voltage detection values V_BESS_ab and V_BESS_bc from the voltage sensor 82. The line voltage detection values V_BESS_ab and V_BESS_bc are converted into phase voltages by the calculation block 110p. The phase detection calculator (PLL) 113p detects the system voltage phase θ_BESS (at the connection point of the storage battery system 2), and outputs two sine wave signals cos (θ_BESS) and sin (θ_BESS) to the control blocks 111p and 112p. To do.

  The phase voltages V_BESS_a, V_BESS_b, and V_BESS_c, which are outputs of the calculation block 110p, are dq converted by the block 111p. The detected phase current value detected by the current sensor 81 is dq converted by the block 112p. The dq conversion calculation of the phase voltage and the phase current is expressed by the following mathematical formula.

  Blocks 114p and 115p are multipliers, and block 116p is an adder. The active power P_BESS is calculated by executing the calculation formula P = V_d × I_d + V_q × I_q using the dq conversion values of the voltage and current calculated by the blocks 114p, 115p, and 116p and the blocks 111p and 112p.

  The line voltage detected values V_PCC_ab and V_PCC_bc at the load linkage point 7 detected by the voltage sensor 84 are converted into phase voltages V_PCC_a, V_PCC_b, and V_PCC_c by the block 110q. The phase detection arithmetic unit (PLL) detects the system voltage phase θ_PCC at the load linkage point 7 and outputs two sine wave signals cos (θ_PCC) and sin (θ_PCC) to the blocks 111q and 112q. The phase voltages V_PCC_a, V_PCC_b, and V_PCC_c are dq converted by the block 111q, and the phase currents I_LOAD_a, I_LOAD_b, and I_LOAD_c detected by the current sensor 83 are dq converted by the block 112q. Here, the blocks 111q and 112q execute dq conversion of the input variables according to Equations 3 to 6.

  Blocks 114q and 115q are multipliers, and 116q is a subtractor. The reactive power Q_LOAD consumed by the load 3 is obtained by executing the arithmetic expression Q = V_q × I_d−Vq_Id using the dq conversion values of the voltage and current calculated by the blocks 114q, 115q, and 116q and the blocks 111q and 112q. It is calculated by doing.

  The operation principle of the voltage-reactive power drooping characteristic controller based on the active power output from the storage battery system 2, which is one of the features of this embodiment, will be described with reference to FIG.

  The drooping characteristic 14 is a characteristic that is fixed by the voltage-reactive power characteristic that is executed by the calculation in the controller 23 according to Equation 1. When the active power output from the storage battery system 2 is small, the storage battery system 2 can output a large reactive power.

  On the other hand, when the storage battery system 2 is large, the reactive power that can be output from the storage battery system 2 is limited to a small value. In order to avoid an overload of the inverter 22 included in the storage battery system 2, the voltage-reactive power drooping characteristic slope calculation unit 42 is calculated based on information from the voltage / current sensors 81, 82, 83, 84. The reactive power ratio Q_BESS / Q_RES is changed according to the active power that 2 supplies to the load 3.

  The drooping characteristic 43 shown in FIG. 3 indicates the voltage-reactive power drooping characteristic calculated by the controller 13 when the active power P_BESS output from the storage battery system 2 is P1, and the drooping characteristic 44 is when P_BESS is P2. The voltage-reactive power drooping characteristic calculated by the controller 13 is shown. Here, P1 is smaller than P2. Even if the reactive power Q_LOAD required by the load 3 is the same value, the reactive power ratio Q_BESS_2 / Q_RES_2 <Q_BESS_1 / Q_RES_1 in the steady state. This is because the drooping characteristic 44 is due to k_RES calculated by the arithmetic unit 42 in the main controller 4 using P_BESS and Q_LOAD as inputs. That is, the main controller 4 includes an arithmetic unit that calculates a proportional constant of the voltage-reactive power drooping characteristic from the active power of the storage battery system 2 and the reactive power required by the load 3, so that the reactive power ratio can be set within an appropriate range. It becomes possible to suppress to. The absolute value of the proportionality constant is a decreasing function with respect to the active power of the storage battery system 2.

  Here, Q_BESS_1 and Q_RES_1 are reactive power output values output from the storage battery system 2 and the renewable energy system 1 when P_BESS is P1, and Q_BESS_2 and Q_RES_2 are the storage battery system 2 and the renewable energy when P_BESS is P2. This is a reactive power output value output from the system 1.

  Next, the slope k_RES calculation process in the voltage-reactive power drooping characteristic slope calculation unit 42 will be described below. In the steady state, the linkage point voltage satisfies the following equation from Equations 1 and 2.

  V_PCC_AMP = V * −k_BESS × Q_BESS = V * −k_RES × Q_RES. Therefore, Equation 7 and Equation 8 hold in the steady state.

  In the present embodiment, the reactive power required for the storage battery system 2 by the load 3 is smaller than the reactive power that can be output from the storage battery system 2 shown in Formula 9.

  The inclination k_RES for avoiding the overload of the inverter 22 and improving the utilization factor of the inverter 22 can be selected using the active power P_BESS output from the storage battery system 2 as shown in Expression 10.

  Here, S_BESS is the rated apparent power of the storage battery system 2. k_RES is a decreasing function with respect to the active power P_BESS.

  In Example 1 demonstrated above, the solar panel 11 which is a power generator using renewable energy, the self-excited inverter 12 which is a 1st inverter connected to the solar panel 11, and the storage battery bank 21 which has a storage battery. And a self-excited inverter 22 that is a second inverter connected to the storage battery bank 21 and the main controller 4, the self-excited inverter 12 and the self-excited inverter 22 are connected at the linkage point 7, and the main controller 4 In the power generation system that controls the power supply to the load 3 via the linkage point 7, the main controller 4 is based on the active power output from the self-excited inverter 22 and the reactive power output from the self-excited inverter 12. The ratio of the reactive power output from the self-excited inverter 22 is changed. The ratio of the reactive power is changed based on the voltage-reactive power drooping characteristic. The main controller 4 reduces the reactive power output from the storage battery system 2 by increasing the reactive power output from the renewable energy 1 when the storage battery system 2 outputs a large amount of active power. It is possible to avoid the overload of the two grid linking inverters 22.

By avoiding the overload of the inverter 22, it is possible to reduce the control margin as compared with the method of Patent Document 1, and it is possible to improve the utilization rate of the inverter 22. )
The power generation system according to the first embodiment further includes a voltage sensor 84 that is a first voltage measurement device that measures the voltage at the linkage point 7, and a current sensor 83 that is a first current measurement device that measures the current at the linkage point 7. A voltage sensor 82 which is a second voltage measuring device for measuring the voltage on the linkage point 7 side of the self-excited inverter 22, and a second current measuring instrument for measuring the current on the linkage point 7 side of the self-excited inverter 22. A current sensor 81 is provided. Therefore, the active power of the storage battery system 2 can be calculated based on the voltage detection value and the current detection value detected by the voltage sensor and the current sensor, and the reactive power required by the load 3 can be calculated. This calculation is performed by the power calculation unit of the main controller 4.

  FIG. 7 shows another embodiment. FIG. 7 is another example of a power generation system using the renewable energy system 1. FIG. 7 differs from FIG. 1 only in that a wind turbine power generation system 11 is used instead of the solar power generation system. FIG. 8 also shows another embodiment. The only difference from FIG. 1 of FIG. 8 is that the main controller 4 is one of the components of the renewable energy system 1.

  The present invention is not limited to the configuration described in the first embodiment. The renewable energy system 1 is not limited to a photovoltaic power generation system. For example, a wind power generation system as shown in FIG. 7 may be used. Further, the position of the main controller 4 can be changed as appropriate, and for example, it may be incorporated in the controller of the renewable energy system 1 as shown in FIG.

Claims (7)

A power generator using renewable energy, a first inverter connected to the power generator,
A storage battery and a second inverter connected to the storage battery;
Equipped with a controller,
In the power generation system in which the first inverter and the second inverter are connected at a linkage point, and the controller controls power supply to a load via the linkage point.
A first voltage measuring instrument that measures the voltage at the linkage point; a first current measuring instrument that measures the current at the linkage point; and a second voltage measuring instrument that measures the outlet voltage of the second inverter; A second current measuring device for measuring the outlet current of the second inverter,
The controller changes the ratio of the reactive power output from the first inverter and the reactive power output from the second inverter based on the active power output from the second inverter. Power generation system characterized by The power generation system of claim 1 ,
The power generation system, wherein the controller changes the ratio of reactive power based on a voltage-reactive power drooping characteristic. The power generation system according to claim 2 ,
The power generation system, wherein the controller includes an arithmetic unit that calculates a proportional constant of the voltage-reactive power drooping characteristic based on the active power derived from the storage battery and the reactive power required by the load. In a controller for power generation equipment having a power generation device and a storage battery using renewable energy,
Based on the active power from the storage battery,
Change the ratio of reactive power derived from the power generator and reactive power derived from the storage battery ,
The active power is calculated from the current and voltage derived from the storage battery,
Controller The reactive power, wherein Rukoto is calculated from the current and voltage from storage battery and associated point. 5. The controller according to claim 4 , wherein the ratio of the reactive power is changed based on a voltage-reactive power drooping characteristic. 6. The controller according to claim 5 , further comprising an arithmetic unit that calculates a proportionality constant of the voltage-reactive power drooping characteristic based on the active power derived from the storage battery and the reactive power required by the load. A power generator using renewable energy, a first inverter connected to the power generator,
A storage battery and a second inverter connected to the storage battery;
In the control method of the system in which the first inverter and the second inverter are connected at a linkage point, and power is supplied to the load via the linkage point.
A control method for a system, characterized in that a ratio of reactive power output from the first inverter and reactive power output from the second inverter is changed based on a voltage-reactive power drooping characteristic.