CCS/MSP432P401R: expression must be a modifiable lvalue

#include "steer.h

/* Timer_A UpDown Configuration Parameter */
const Timer_A_UpDownModeConfig upDownConfig =
{
TIMER_A_CLOCKSOURCE_SMCLK, // SMCLK Clock SOurce
TIMER_A_CLOCKSOURCE_DIVIDER_8, // SMCLK/1 = 3MHz
30000, // 127 tick period
TIMER_A_TAIE_INTERRUPT_DISABLE, // Disable Timer interrupt
TIMER_A_CCIE_CCR0_INTERRUPT_DISABLE, // Disable CCR0 interrupt
TIMER_A_DO_CLEAR // Clear value

};

/* Timer_A Compare Configuration Parameter (PWM1) */
const Timer_A_CompareModeConfig compareConfig_PWM1 =
{
TIMER_A_CAPTURECOMPARE_REGISTER_1, // Use CCR1
TIMER_A_CAPTURECOMPARE_INTERRUPT_DISABLE, // Disable CCR interrupt
TIMER_A_OUTPUTMODE_TOGGLE_SET, // Toggle output but
29250 // 32 Duty Cycle
};

/* Timer_A Compare Configuration Parameter (PWM2) */
const Timer_A_CompareModeConfig compareConfig_PWM2 =
{
TIMER_A_CAPTURECOMPARE_REGISTER_2, // Use CCR2
TIMER_A_CAPTURECOMPARE_INTERRUPT_DISABLE, // Disable CCR interrupt
TIMER_A_OUTPUTMODE_TOGGLE_SET, // Toggle output but
26250 // 96 Duty Cycle
};
void Servo_TurnAngle(float value)
{
float f_cycle;
f_cycle = (30000-3000/180)*value;//angle
compareConfig_PWM1.compareValue = f_cycle;//new pulse       erro： expression must be a modifiable lvalue
// TIM2_PwmConfig.dutyCycle = (INT16U)f_cycle;//new pulse
MAP_Timer_A_initCompare(TIMER_A1_BASE, &compareConfig_PWM1);
};

timer_a.h 

typedef struct _Timer_A_CompareModeConfig
{
uint_fast16_t compareRegister;
uint_fast16_t compareInterruptEnable;
uint_fast16_t compareOutputMode;
uint_fast16_t compareValue;
} Timer_A_CompareModeConfig;